JP3708445B2 - Powder coating material supply device - Google Patents

Description

ここで、Ｆv₁＝サイズが０．５〜１．９μの未使用粉体塗装材料の粒子の体積百分率、Ｆv₂＝サイズが１．９〜２．４μの未使用粉体塗装材料の粒子の体積百分率、・・・・である。
【００５５】
【数２】

ここで、Ｆr₁＝０．５〜１．９μの１パス再生粉体塗装材料の粒子の体積百分率、Ｆr₂＝１．９〜２．４μの１パス再生粉体塗装材料の粒子の体積百分率、
・・・・である。
【００５６】
測定した粒子サイズ分布ＦvおよびＦrを、制御装置１０８に入力し、これは以下のように粒子サイズ分布の商を計算することができる。
【００５７】
【数３】

上述の式（３）から得られた商を、次に下記の関係に従って正規化する。
【００５８】
【数４】

これは、２段階のプロセスで達成されるが、まずＦv／Ｆr₁の商、つまりＳを求める。
【００５９】
【数５】

その後、図１２および１３のグラフで示した１６の粒子サイズ範囲のそれぞれについて、様々な商を「正規化した」値を、次のように計算する。
【００６０】
【数６】

制御装置１０８のソフトウェアが実行する計算の次のシーケンスによって、たとえば各粒子サイズ範囲のＰ₁〜₁₆などの、確率係数Ｐの解が得られる。確率係数Ｐ₁〜₁₆は、図１２および１３に示した１６のサイズ範囲のそれぞれで、粒子がシステム５００内に残る、つまりブース１２内の車体３２に引き寄せられず、したがって過剰吹付け粉体として再生される確率を表す。この情報が重要なのは、上述したように、システムの安定性が、混合ホッパー５０２内の微粉の体積百分率を、３０％などの所定レベルより下に維持することにかかっているからである。確率係数Ｐ₁〜₁₆を求めるのに用いる式は、以下のように与えられる。
【００６１】
【数７】

ここでＦ_A＝調整係数 ｘ＝整数１〜１６ Ｐ＝確率係数Ｐ₁、Ｐ₂・・・Ｐ₁₆式（７）のＦ_A項より後の部分は、次の２段階の計算で求める。まず、係数Ｚを次のように計算する。
【００６２】
【数８】

次に、式（８）に基づく計算から得られた商を、１に正規化する。
【００６３】
【数９】

式（９）に基づく計算から得られた商はそれぞれ、図１２および１３のグラフの１６の粒子サイズ範囲それぞれについて、正規化した値を表す。次に、この値を式（７）に用いて、各粒子サイズ範囲の確率係数Ｐ、つまり各サイズ範囲が特定の塗装作業の後にシステム内に残る（部品に付着しない）確率を表す。
たとえば、式（７）を書いて、０．５〜１．９ミクロンという第１グループの粒子のサイズを有する粉体粒子について、次のように、確率係数Ｐ₁を求めることができる。
【００６４】
【数１０】

１６グループの粒子サイズのそれぞれについて、試行錯誤によって経験的に「調整係数」Ｆ_Aを求めることができるので、次の式は、未使用粒子および１パス再生粒子の実際の測定値より正確である。
【００６５】
【数１１】

【００６６】
【数１２】

【００６７】
【数１３】

つまり、式（１）および（２）で述べたように、レーザ回折粒子サイズ分析器で最初に得た粒子サイズ分布ＦvおよびＦrの実際の測定値を用いて、適切な調整値Ｆ_Aを導き、Ｆr₁₆の最終的な数学的計算値が可能な限り正確になることを保証する。上述した粉体塗装材料のタイプが与えられたとすると、０．５〜１．９μから８７．２〜１８８μに増加する粒子サイズ範囲の実際の調整係数Ｆ_A1〜₁₆は、それぞれ１．０、０．９５、０．９０・・・０．２５であることが好ましい。
【００６８】
上記のように確率係数Ｐ₁〜₁₆がそれぞれ計算されたら、この値も、上記と同じ方法で１．０に正規化しなければならない。これで、その結果得られたＰ₁〜₁₆の正規化した値を、たとえば未使用粉体の粒子サイズ分布にかけるなど、乗数として用いて、装置１０を通る各サイクルの過剰吹付け粒子サイズ分布を数学的に予測することができる。
【００６９】
以上の検討は、単純に言うと、システムにこれ以外の未使用粉体材料が追加されず、元の量の粉体材料が連続的な塗装作業中にリサイクルされる、ということを前提とした数学的モデルに基づくものであった。粉体塗装材料は、通常の運転状態では、ブース１２内の車体３２などの物体に付着し、絶えず交換しなければならないので、システム５００の実際の動作を近似するには、所定の分率の未使用粉体材料がシステムに追加されるという数学的モデルが必要である。
【００７０】
上記で、式（１）〜（１３）で与えられた計算を繰り返さず、以下の関係式を用いて、式（１１）〜（１３）から１パス再生の粒子サイズ分布を表す。
【００７１】
【数１４】

したがって、項Ｆrは、式（１）〜（１３）の数学的モデルを用いて計算したように、第１パス再生粉体内の粒子サイズ分布を表す。
式（１４）で１．０に正規化して、第１パスまたは塗装運転の後に再生粉体に追加される新しい未使用粉体の体積分率ｙの追加を考慮すると、次の関係式が導かれる。
【００７２】
【数１５】

ここで、ｙ＝１パス再生粉体の収集後にシステムに追加される未使用粉体塗装材料の体積分率、Ｆr_iy＝分率ｙの未使用粉体塗装材料を含む１パス再生粉体の粒子サイズ分布、ｉ＝未使用粉体塗装材料から始まるパス数の指数、である。
Ｆr_iyの値を計算すると、その後の「パス」または塗装作業の粒子分布を、次のように表現することができる。
【００７３】
【数１６】

式（１６）を１．０に正規化してから、次の計算を実行する。
【００７４】
【数１７】

項Ｆr_i+1yは、分率ｙの未使用粉体を含む第２パス再生粉体（ｉ＋１）内の粒子分布を表す。
【００７５】
図１４のグラフに描かれたタイプの曲線を生成できるよう、この同じ計算のシリーズを、サイクル数だけ繰り返す。図１４は、未使用粉体の分率または体積百分率を変化させて、Ferro 158E 114粉体塗装材料を吹き付けたときに存在する微粉の体積百分率を表す。図１４のグラフの各曲線は、再生粉体中の未使用粉体ｙの様々な体積百分率を表し、粉体の体積百分率がサイクル数または連続的な塗装作業とともに変化する様子を描く。式（１５）および（１７）からの計算、および全粒子サイズ（ｉ＋１６）に関するこれの逐次反復法に基づき、１６の粒子サイズ範囲の全範囲にわたる粒子サイズ分布の計算値が得られる。制御装置１０８のソフトウェアが作動して、１６のサイズ範囲のそれぞれにおいて、１０ミクロン以下の全粒子の体積百分率の計算値を合計し、連続的サイクルまたは塗装作業のそれぞれについて、図１４のグラフの縦座標上の値が得られる。微粉の体積百分率が、連続するサイクルとともに変化し、再生粉体に対する未使用粉体の分率の変化とともに変化する様子を示すため、例証として、幾つかの異なつたｙの値の計算値を、図１４に含めた。
【００７６】
図１４の曲線は、粒子サイズの中央値が約２２ミクロンのFerro 158E114未使用粉体塗装材料を使用して、上記の式から数学的に導かれた。このタイプの材料の場合、上記の過剰な微粉の蓄積という問題を回避するため、微粉の体積百分率を約３０％未満に維持するとよいことが分かっている。図１４のグラフから、３０％未満という微粉の体積百分率を維持するためには、定常運転中に、システム５００に６５％を超える、あるいは約７０％のオーダーの分率ｙの未使用粉体を追加するとよいことが観察される。これは、制御装置１０８の操作によって実行され、これは、１次ホッパー６０から混合ホッパー５０２への各ライン５０４、５０５のゲート弁５０８、および再生ホッパー８０と混合ホッパー５０２との間に延びる各ライン５０６、５０７のゲート弁５０９を選択的に開閉する。
【００７７】
上述したように、本明細書で用いる数学的モデルは、様々な体積百分率の未使用粉体を含む粉体塗装材料について、混合ホッパー５０２内の微粉の百分率を示すのに有用である。こうすると、システム５００の定常運転中、混合ホッパー５０２内に過剰な微粉が蓄積しないよう、適切な体積分率の未使用粉体を混合ホッパー５０２に追加することができる。安全対策として、本発明のシステム５００は、混合ホッパー５０２内の粒子サイズ分布を監視して、混合チャンバ５０２内の実際の微粉の百分率を数学的モデルで予想された値と確実に一致させるソフトウェアも、制御装置１０８内に含まれている。
【００７８】
図１５を参照すると、上記のモニタ機能を実行する操作のシーケンスを図によって示した流れ図がある。最初に、サンプルを手動で混合ホッパー５０２から抜き取り、ブロック５２８で概略的に描いているように、上記と同じレーザ回折粒子サイズ分析器を使用して、混合ホッパー５０２内の実際の粒子サイズ分布Ｆ_Mを測定する。粒子サイズ分布の情報を、手作業または電子的にブロック５２８からライン５３０を介して制御装置１０８に入力する。その後、図１５に描かれた作業はすべて、制御装置１０８のソフトウェアが電子的に実行する。制御装置１０８が作動して、混合ホッパー５０２に含まれる、たとえば約１０ミクロン未満の粒子などの微粉の体積百分率を計算する。
【００７９】
ブロック５３２を参照のこと。このような体積百分率の計算値を代表する１つの値を、ライン５３４によってブロック５３６に入力し、ここで、システム５００が塗布する特定タイプの粉体塗装材料について、微粉の体積百分率の計算値と所定の最大体積百分率とを比較する。図１５に示した例証的な実施形態では、ブロック５３６に３０％という所望の最大体積百分率が名目上示されているが、他のタイプの塗装材料では、他の最小体積百分率の微粉の方が適切な場合もあることが理解される。微粉の百分率の計算値が３０％以下の場合は、ライン５３８によってブロック５２８に「ＮＯ」の信号が送り返され、次のモニタ期間が開始するまで、たとえば１日、１週間または他の所望の期間、モニタ・シーケンスは終了している。
【００８０】
ブロック５３６で、微粉の百分率の計算値が、混合チャンバ５０２内の粉体を重量で３０％上回っていると判断されると、ライン５４０を通ってブロック５３からブロック５４２に信号が送られる。ブロック５４２で示すように制御装置１０８が実行する計算は、重量分率Ｗ、つまり２０％、３０％などの分率を経験的に選択する。次に、制御装置１０８は、選択した重量分率Ｗを用いて、次の式を解く。
【００８１】
【数１８】

ここで、Ｆf＝混合ホッパー内の微粉の所望の体積百分率で、たとえば＜３０％、Ｗ＝未使用粉体の重量分率、Ｆm＝混合ホッパー内の粉体の粒子サイズ分布、Ｆv＝未使用粉体の粒子サイズ分布、である。
【００８２】
選択した重量分率Ｗで、Ｆfの値が３０％より大きくなった場合は、別の、これより大きい重量分率Ｗを選択し、式（１８）を用いた計算を繰り返す。
【００８３】
図１５に示したモニタ・シーケンスの次のステップは、図１に関連して上述したタイプのロード・セル１０６を使用して、混合ホッパー５０２内の粉体を計量することである。ボックス５４４を参照のこと。次に、ブロック５４６で概略的に示すように、混合ホッパー５０２内の粉体の実際の重量を、混合ホッパー５０２の総重量容量と比較し、その計算を表す信号を、ライン５４８を介してブロック５５０に入力する。ブロック５５０で示すように、混合ホッパー５０２内の粉体のレベルが１−Ｗ以下の場合は、制御装置１０２が作動して、未使用粉体塗装材料を混合ホッパー５０２に入れる（ブロック５５２）。混合ホッパー５０２が満杯で、微粉の体積分率を所望のレベル、つまり＞（１−Ｗ）に下げるのに必要な体積分率Ｗの未使用粉体塗装材料を受け取れない場合は、制御装置１０８は、ブロック５５４で示すように混合ホッパー５０２から十分な量の粉体を放出してから、未使用粉体塗装材料を加える。未使用の粒子状粉体塗装材料を加えるための余地をとるよう、混合ホッパー５０２から放出または除去しなければならない粉体の量は、次の関係式から求めることができる。
【００８４】
【数１９】

ここで、Ｑ_D＝混合ホッパーから放出される粉体の分率、ＭＨw＝混合ホッパーの重量測定値、ＭＨc＝混合ホッパーの容量、である。
したがって、上記の一連の重量計算は、混合ホッパー５０２内には新しい未使用粉体塗装材料を受け入れるだけ十分な容量があり、したがって混合ホッパー５０２が溢れることなく、微粉の全体的な体積分率が下がるのを保証することである。未使用粉体塗装材料を追加した後（ブロック５５２）、次のモニタ期間までモニタ操作は終了している。
【００８５】
したがって、混合ホッパー５０２内で再生粉体塗装材料と未使用粉体塗装材料との所望の割合を維持する上記の方法は、塗装作業が進行するにつれて、混合ホッパー５０２内の重量損失を測定することに依存する。あるいは、重量測定値ではなく流量測定値に基づいて、混合ホッパー５０２に適切な量の再生および未使用粉体塗装材料を供給できる、と考えられる。この実施の形態では、混合ホッパー５０２から放出される粉体塗装材料の流量を、時間の経過とともに監視し、スクリュー供給装置（図示せず）などの流量制御装置を使用して、それぞれ再生ホッパー８０および１次ホッパー６０から、所定の量の再生粉体塗装材料および未使用粉体塗装材料の両方を、混合ホッパー５０２に追加する。１次ホッパー６０に関連付けられたスクリュー供給装置または同様の装置、および再生ホッパー８０に関連付けられた別個のスクリュー供給装置は、混合ホッパー５０２からの信号に応じて、または追加の未使用粉体塗装材料と再生粉体塗装材料とを混合ホッパー５０２に導入する所定の作業期間の後、あるいはその両方で、制御装置１０８によって起動されることが好ましい。
【００８６】
粉体受け
図２を参照すると、図１のシステム１０の検討に関連して上述した粉体受け５８が、詳細に図示されている。その他の粉体受け６６、８２および９４はそれぞれ、構造的にも機能的にも粉体受け５８に等しく、したがって本明細書では粉体受けのうち１個のみを詳細に検討することを理解されたい。また、粉体受け６００の代替実施形態については、図１１に関連して以下で開示する。
粉体受け５８は、板１３４でカートリッジ・フィルタ１３２を取り付けた中空の内部１３０を有するコレクタ筐体１２８を含む。コレクタ筐体１２８の一方側に沿って、掛け金１３８により開放可能な状態でアクセス・パネル１３６が固定されているので、カートリッジ・フィルタ１３２にアクセスすることができる。
コレクタ筐体１２８の内部１３０は、通気孔１４０によって通気され、その上端は、掛け金１４４によって固定されたキャップ１４３で閉じている。キャップ１４２は、板１３４に接続したカートリッジ・フィルタ１３２の開放端と整列した逆エア・ジェット弁１４６を搭載する。逆エア・ジェット弁１４６は、ライン１４８によってアキュムレータ１５０に接続され、それは図２で概略的に示す加圧空気の供給源７３に接続される。キャップ１４２は、第１真空ポンプ６２からの吸込みホースまたはライン６１に接続された取付具１５４を担持する。コレクタ筐体１２８の下部は、未使用粉体塗装材料を担持する容器からのライン５６に接続された粉体入口１５８を含む。コレクタ筐体１２８は、図２で示すように、粉体入口１５８から下方向に放射状内側に先細りになり、外部フランジ１６２を含む先細りの基部１６０を形成する。
【００８７】
上記で検討したように、１次ホッパー６０に関連付けられたロード・セル１０６Ａが適切に機能するためには、１次ホッパー６０に完全に粉体塗装材料がない状態で、これを「ゼロ設定」つまり重量の読取値をゼロに設定しなければならない。この方法により、ロード・セル１０６Ａは、実際に１次ホッパー６０に入る粉体塗装材料のみを計量する。１次ホッパー６０内で確実に粉体の重量を正確に読み取るために、第１粉体受けユニット５８に関連付けられたすべての要素を、１次ホッパー６０とは独立して、図２に示す枠１６４上で支持する。この枠１６４は、垂直の脚１６８上に支持された上板１６６、上板１６６と垂直脚１６８との間に延びる傾斜した筋交い１７０、および垂直脚１６８間の中間位置にある１個以上の水平支持体１７２を含む。
【００８８】
コレクタ筐体１２８は、コレクタ筐体１２８の外部フランジ１６２と上板１６６との間に延びるボルト１７４によって、枠１６４の上板１６６に取り付けられる。コレクタ筐体１２８の先細りの基部１６０から下方向に延びるのは、コレクタ筐体１２８を、カンザス州サリーナのプライマー ニューマティックス インコーポレーテッド（Premier Pneumatics，Inc.）が型番MDR-F-G-76-10NH-2-RT-CHE-T3で市販しているタイプの回転エア・ロック計量装置１７８に連結するフレキシブル・スリーブ１７６である。計量装置１７８は、１本の垂直脚１６８に接続した支持板１８４上に担持されたモータ１８２の出力部に、ベルト（図示せず）によって駆動接続される。モータ１８２が作動して、計量装置１７８内の一連の内部翼１８６を回転させ、計量した量の粉体塗装材料を、コレクタ筐体１２８の先細りの基部１６０から水平支持体１７２上に取り付けられた回転式篩１９６に移送する。回転式篩１９６は、ドイツのAzo Incorporatedが型式Ｅ−２４０で製造販売しているタイプの市販の商品である。回転式篩１９６は、粉体塗装材料を、第２フレキシブル・スリーブ１９８を通って１次ホッパー６０の粉体入口２００に移送する。これについては、図３でさらに詳細に図示し、以下で述べる。
運転時には、第１真空ポンプ６２が、制御装置１０８によって起動され、吸込みホースまたはライン６１に沿って真空を生成し、コレクタ筐体１２８の中空の内部１３０に負圧を生成する。これによって、未使用粉体塗装材料が、供給用容器５４からライン５６および粉体入口１５８を通って、コレクタ筐体１２８の中空の内部１３０に引き込まれる。粉体塗装材料の一部が、重力によってコレクタ筐体１２８の先細りの基部１６０に落下し、粉体塗装材料のある一部は、カートリッジ・フィルタ１３２の壁に溜まる。アキュムレータ１６０から定期的に供給された加圧空気が、カートリッジ・フィルタ１３２と整列した逆エア・ジェット弁１４７を通って、パルス状に搬送される。この空気のジェットによって、フィルタ１３２の壁に溜まった粉体塗装材料が離れ、コレクタ筐体１２８の先細りの基部１６０へと下方向に落下することができる。
【００８９】
粉体塗装材料は、モータ１８２の動作に応じて、エア・ロック計量装置１７８によってコレクタ筐体１２８から移送されるので、計量された量の粉体塗装材料が、回転式篩１９６に入る。粉体塗装材料は、回転式篩１９６を通過した後、重力によってフレキシブル・スリーブ１９８を通過し、１次ホッパー６０の粉体入口２００へと落下する。所定量の粉体塗装材料が１次ホッパー６０内に溜まったら、それに関連付けられたロード・セル１０６Ａが制御装置１０８に信号を送信し、これが第１真空ポンプ６２の操作を停止する。上述したように、図１の粉体移送システムのその他の粉体受けユニット６６、８２および９４はすべて、構造的にも機能的にも同一である。
【００９０】
図１１を参照すると、粉体受け６００の別の実施形態が、詳細に図示されている。粉体受け６００は、図２の検討に関連して上述した粉体受け５８、６６、８２および９４と部分的に類似し、図１１では、図２と共通の構造を特定するために同じ参照番号を使用する。粉体受け６００と粉体受け５８との１つの違いは、粉体塗装材料をコレクタ筐体１２８から１次ホッパー６０に移送するための構造である。特定のタイプの粉体材料を用いる用途では、粉体受け５８の先細りの基部１６０の領域で塗装材料がアーチ状またはブリッジ状になるので、中間で流れが停止することがあるのが分かっている。先細りの基部１６０が閉塞すると、粉体塗装材料は、エアロック計量装置１７８を通って図２で図示した構造の回転式篩１９６に入ることができない。また、図１１の粉体受け６００は、篩１９６を含まないが、ホッパー６０の上に配置して、ホッパー６０に導入する前に粒子状の粉体塗装材料を篩にかけることができると考えられる。少なくとも、たとえば受け５８および８２などの、システムに粉体塗装材料を最初に導入する箇所で、篩１９６を使用することが好ましい。図１を参照のこと。
【００９１】
図１１の粉体受け６００は、基本的に図２の粉体受け６８の上部で構成され、下部はコレクタ筐体１２８に向かう粉体塗装材料を流動化する構造を含むので、１次ホッパー６０に滑らかに移送することができる。コレクタ筐体１２８の底部は、流動床６０２を含む内部を規定し、これはキャップ１４２と、コレクタ筐体１２８の側壁から外側に延びて側壁にブラケット（図示せず）で支持された有孔板６０４との間に延びる。コレクタ筐体１２８の基部内の第２区域は、コレクタ筐体１２８の側壁１２９に取り付けられたブラケットによって担持された円形の取付板６１０と有孔板６０４との間に延びるエア・プレナム６０８である。コレクタ筐体内部の基部内の第３区域は、コレクタ筐体１２８の底壁６１４と取付板６１０との間に延びるモータ・チャンバ６１２である。以下で明白になる目的のために、粉体受け６００全体を、支持スタンド６１５の頂部に、１次ホッパー６０またはその他のホッパーの垂直方向上部の位置に取り付けることが好ましい。
【００９２】
供給ホッパー６００の基部には撹拌器６１６が設けられ、これは取付板６１０に接続されたモータ・マウントによってモータ・チャンバ６１２内に担持されたモータ６１８を含む。モータ６１８の出力は、軸受６２４内に回転可能な方法で担持された軸６２２に駆動接続される。軸受６２４は、軸受マウントによって取付板６１０に取り付けられ、エア・プレナム６０８を通って有孔板６０４のすぐ上の箇所まで、垂直上方向に延びる。軸受６２４を通って延びる軸６２２の頂部には、ロック・ナット６３０によって少なくとも２本のエントレインメント・アーム６２８が固定されるので、モータ６１８の動作に応じて、エントレインメント・アーム６２８が有孔板６０４に対して、その上の位置で回転する。
【００９３】
モータ・チャンバ６１２の片側に入る空気供給ライン６３６に、少なくとも２個の空気入口６３２が、管によって図示していない方法で接続される。この空気供給ラインは、加圧空気の供給源７３に接続される。
【００９４】
上方向に向く空気の流れが、空気入口６３２を通ってエア・プレナム６０８に入り、ここで空気は、軸受け６２４に取り付けられたバッフル６３８によって偏向する。このバッフルの目的は、本発明の譲受人の所有する米国特許第5,018,909号で詳細に開示され、その開示を、参照によって本明細書にそっくりそのまま組み込む。
【００９５】
移送管６４０は、一方端が、有孔板６０４の上かつ流動床６０２の内部で、コレクタ筐体１２８に接続される。移送管６４０の他方端は、１次ホッパー６０の入口６４２に取り付けられる。回転式エア・ロック１７８は、モータ１８２によって駆動され、いずれも粉体受け５８の検討に関連して上述したのと同じタイプであるが、移送管６４０内で接続される。図１１で概略的に示すように、モータ１８２の動作は制御装置１０８によって制御され、従って回転式エア・ロック１７８の動作もこれに制御される。粉体受け６００内の流動床６０２からの粉体塗装材料は、回転式エア・ロック１７８の動作に応じて、重力によって下方向に流れ、移送管６４０を通過してから１次ホッパー６０の内部に入る。モータ１８２が停止して、所望通りに回転式エア・ロック１７８の動作を停止し、移送管６４０を通る粉体塗装材料の流れを留める。粉体受け６００のこの構成が、１次ホッパー６０への粉体の滑らかな移送を提供し、このような粉体受け６００は、図１および１０双方の実施形態の代替品として利用できると考えられる。その他では、粉体受け６００は上述した粉体受け５８と同じ方法で機能し、そのような動作についての検討を、ここで繰り返すことはしない。
【００９６】
１次および再生ホッパー
１次ホッパー６０および再生ホッパー８０は、基本的に相互に等しく、検討するためには、１次ホッパー６０についてのみ図示し、詳細に述べる。図３および４を参照すると、１次ホッパー６０は、おおむね「８の字」の形状の内壁２０４を有する筐体２０２を含む。したがって、内壁２０４は、２つの円形部２０６および２０８を含み、これはそれぞれが筐体２０２の片側に接続された対向する三角形のバッフル２１２および２１４によって規定され、筐体２０２の中心にある直径減少区域２１０で合う。バッフル２１２、２１４はそれぞれ、筐体２０２の壁から内側に延びて合い、筐体内部２０３の中心に向かって頂部２２０を形成する１対のサイド・パネル２１６、２１８を有する。
図４で最もよく分かるように、有孔板２２２は、筐体２０２の基部付近のマウント２２４によって担持され、筐体内部２０３を、有孔板２２２と筐体２０２の上壁２２９との間にある流動床２２６と、有孔板２２２と筐体２０２の底壁２３２との間に位置するエア・プレナム２３０とに分離する。エア・プレナム２３０は、幾つかのバッフル２７０およびおおむねＵ字形の有孔空気管２７２を含む。
底壁２３２は、本発明の粉体移送システムに関連して上記で検討したロード・セル１０６Ａの頂部に配置される。
【００９７】
筐体２０２の上壁２２８は、第１撹拌器２３４と、第２撹拌器２３６と、ハンドル２４０および掛け金機構２４２を有して上壁２２８の開口部２４４に蝶番２４３によって取り付けられるアクセス・カバー２３８とを支持する。この開口部２４４は、１次ホッパー６０の粉体入口２００からずれるので、保守などのために、粉体入口２００と干渉することなく、筐体内部２０３にアクセスすることができる。第１撹拌器２３４は、軸２４８によってギア・ボックス２５０に接続されるモータ２４６を含む。ギア・ボックス２５０の出力は、管２５４内に収納された軸２５２に駆動接続される。軸２５２の下端には、少なくとも２個の撹拌器の櫂２５６が取り付けられ、これは内壁２０４によって形成された筐体内部２０３の円形部２０６の内部で、有孔板２２２の垂直上方の位置で回転する。第２撹拌器２３６は、第１撹拌器２３４と同様の構造を有する。第２撹拌器２３６は、ギア・ボックス２６２に接続された軸２６０を有するモータ２５８を含み、ギア・ボックスの出力は、管２６６内に収納された軸２６４に駆動接続される。２個以上の櫂２６８が、内壁２０４によって形成された筐体内部２０３の他方の円形部２０８内で、軸２６４の基部に取り付けられる。図４で示すように、第２撹拌器２４６に関連付けられた軸２６４および管２６６は、第１撹拌器２３４のそれよりわずかに長いので、第２撹拌器２３６の櫂２６８は、第１撹拌器２３４より有孔板２２２に近い位置にある。櫂２５６、２６８は重なるが、垂直方向にずれているので、互いに干渉することはない。
【００９８】
上述したように、本発明の一つの態様は、たとえば１時間当たり１３６．２キログラム（３００ポンド）以上などの大量の粉体塗装材料を、１秒当たり０．４５４ないし０．９０８キログラム（１ないし２ポンド）などの流量で移送しながら、粉体塗装材料の流れで所望の密度および粒子分布を維持することである。上述したように、「密度」という用語は、粉体と空気との相対的な混合または割合を指し、「粒子分布」という用語は、粉体塗装材料の流れの中の様々なサイズの粉体粒子の分布を指す。１次ホッパー６０および再生ホッパー８０は、粉体塗装材料の高いスループットにおいて、所望の密度および粒子分布の要件を満たすよう設計されている。
【００９９】
運転時には、エア・プレナム２３０内の有孔空気管２７２に加圧空気が導入されて、空気の上向きの流れを生成し、これがバッフル２７０によって有孔板２２２の底部全体にむらなく分布する。粉体塗装材料は、粉体入口２０を通って筐体内部２０３に導入され、流動化用の上向きの空気の流れによって、および第１および第２撹拌器２３４、２３６の動作によって、有孔板２２２に沿って分布する。撹拌器の櫂２５６、２６８が、有孔板２２２に対して動くにつれ、内壁２０４によって規定された筐体内部２０３の「８の字」形によって、内部の「死点」がほぼなくなるので、粉体塗装材料は有孔板２２２の表面全域に沿ってむらなく分布し、粉体材料の凝集または蓄積がほぼなくなる。これによって、流動床２２６内に粉体がむらなく均一に分布し、所望の粒子分布および密度になる。第２真空ポンプ６９が起動すると、空気に混入した粉体塗装材料が、１次ホッパー６０の筐体２０２から吸い出され、筐体内部２０３に挿入された吸込み管２７４を通り、筐体内部は、上述した移送ライン６４に接続されている。
【０１００】
供給ホッパー
第１および第２供給ホッパー６８および９６は、基本的に構造が等しいので、ここでは第１供給ホッパー６８についてのみ詳細に検討する。図５を参照すると、供給ホッパー６８は、カバー２７９で閉じられた開口部を付けて形成された上壁２７８と、ほぼ円筒形の側壁２８０と、ロード・セル１０６Ｂに担持された底壁２８２とを備える。筐体２７６は、基本的に３つの別個の区域に分離した内部を規定する。１つの区域は、筐体の側壁２８０から外方向に延びてブラケット２８８によって側壁に支持された有孔板２８６と上壁２７８との間に延びる流動床２８４である。筐体２７６内の第２の区域は、側壁２８０に取り付けられたブラケット２９４によって担持された円形の取付板２９２と有孔板２８６との間に延びるエア・プレナム２９０である。筐体２７６の内部の第３の区域は、取付板２２９２と底壁２８２との間に延びるモータ・チャンバ２９６である。
【０１０１】
供給ホッパー６８には、取付板２９２に接続されたモータ・マウント３０２によってモータ・チャンバ２９６内に担持されたモータ３００を含む撹拌器２９８が設けられている。モータ３００の出力は、軸受３０６内に回転可能な状態で担持された軸３０４に、駆動接続される。軸受３０６は、軸受マウント３０８によって取付板２９２に取り付けられ、エア・プレナム２９０を通って垂直上方向に延び、有孔板２８６のすぐ上の箇所に至る。軸受２０６を通って延びる軸３０４に頂部には、ロック・ナット３１０によって少なくとも２つの櫂３０８が固定されているので、モータ３００の動作に応じて、櫂３０８は有孔板２８６に対し、そのすぐ上の位置で回転する。
【０１０２】
少なくとも２個の空気入口３１２が、取付板２９２に担持され、管３１４によって、モータ・チャンバ２９６の片側に入る空気供給ライン３１６に図示していない方法で接続される。この空気供給ライン３１６は、粉体受けに関して上述した加圧空気供給源７３に接続される。空気入口３１３を通ってエア・プレナム２９０に、上方向の空気の流れが提供され、ここで空気は、軸受３０６に取り付けられたバッフル３１８によって偏向する。このバッフル３１８は、粉体受け６００に使用したものと同じタイプで、上述した米国特許第5,018,909号で開示されている。
【０１０３】
運転時には、粉体塗装材料が、筐体２７６の側壁２８０に沿って取り付けられた先細りの粉体入口２７６を通って、筐体２７６の流動床２８４内に導入される。モータ３００が作動して、櫂３０８を回転するので、粉体塗装材料は死点なく有孔板２８６に沿ってむらなく分布する。粉体塗装材料は、空気供給ライン３１６および空気入口３１２からの上方向の空気の流れによって、有孔板２８６に沿って流動化される。粉体塗装材料を筐体２７６から取り出すために、ポンプ７４などの１個以上の粉体ポンプを操作し、有孔板２８６のすぐ上で筐体内部へと延びる吸込み管３２２を通って、粉体塗装材料を吸い出す。供給ホッパー６８から粉体を吸い出すために、複数の粉体ポンプ７４を使用できることを例証するため、図５に幾つかの吸込み管３２２を示す。
【０１０４】
ロボット・ホッパー
図１に概略的に示したロボット・ホッパー７８を、図６にさらに詳細に示す。
【０１０５】
本発明の好ましい実施形態では、ロボット・ホッパー７８は、上端に１つ以上の櫂３３０が取り付けられている軸３２８に駆動接続されたモータ３２６を収容するモータ・チャンバとエア・プレナムとの混合３２４を形成する円筒形の基部を含む。ロボット・ホッパー７８の頂部は、エア・プレナムおよびモータ・チャンバ３２４と連絡する有孔板３３６によって形成された底壁と上壁３３４とを有する円筒形の筐体３３２を含む。円筒形の筐体３３２は、流動床３３８を規定し、その中には長方形の板またはバッフル３４０が取り付けられている。バッフル３４０は、有孔板３３６の上に垂直に間隔をおき、流動床３３８を２つの区画に分割する。バッフル３４０の一方の区画または側では、供給ホッパー６８からの粉体塗装材料が、円筒形筐体３３２の頂部に概略的に図示された粉体入口３４２に通って導入される。粉体ポンプ７９に関連付けられた吸込み管３４４が、バッフル３４０の反対側で円筒形筐体３３２に取り付けられ、この吸込み管３４４は、有孔板３３６のすぐ上で終了している。
【０１０６】
ロボット・ホッパー７８は、供給ホッパー６８に関連付けられた粉体ポンプ７４から、ライン７６を介して粉体塗装材料を受け取る。粉体塗装材料は、円筒形筐体３３２の粉体入口３４２に入り、バッフル３４０の一方側に沿って下方向に向かい、有孔板３３６に至る。モータ３２６が作動して、有孔板３３６のすぐ上の櫂３３０を回転するので、空気に混入した粉体材料の均一な流れが、吸込み管３４４を通って粉体ポンプ７９から引き出され、ロボット４０およびそれに関連付けられたスプレー・ガン４２に送られる。円筒形筐体３３２の内部にバッフル３４０があると、有孔板３３６にわたる粉体塗装材料の流動化を安定させるのに役立ち、粉体ポンプ７９によって引き出される粉体塗装材料の流れに、確実に所望の密度および粉体分布が維持される。
【０１０７】
粉体収集回収システム
図１および７ないし９を参照すると、粉体収集回収システム１６が、さらに詳細に図示されている。このシステム１６は、全体としてShuticその他に帰される米国特許第5,078,084号で開示されたシステムに関係があり、その開示は、参照により本明細書にそっくりそのまま組み込む。上述したように、粉体収集回収システム１６は、粉体吹付けブース１２の床２０の下で、車体３２がコンベヤ３４によって移送されるブース１２の中心部３６のいずれかの側に位置する。図７の左側の部分で示すように、格子３８がブースの床２０を覆うので、過剰に吹き付けた空気混入の粉体塗装材料は、ブース室内３０のいかなる区域からもシステム１６内へと下方向に吸い込むことができる。
【０１０８】
粉体収集回収装置１６は、構造がモジュール式で、全体として、ブース１２の全長に沿って縦方向に延び並んで取り付けられた一連の粉体収集ユニット３４６を備える。図７の中央を参照のこと。図１および図４の右側で示すように、粉体収集ユニット３４６は、たとえば３つか４つのグループで、粉体収集ユニット３４６の下に位置する個々のファンまたはブロワ・ユニット３４８に接続される。
【０１０９】
各粉体収集ユニット３４６は、対向する側壁３５４、３５６、対向する端壁３５８、３６０、および傾斜した底壁３６２を有するコレクタ筐体３５０を含む。クリーン・エア・チャンバ３６４がコレクタ筐体３５０の頂部に位置し、内側に傾斜してそれぞれが幾つかの間隔をあけた開口部３６８を有する１対の支持板３６６、３６７、対向する側板３６９、３９０、およびそれぞれ側板３６９、３７０に蝶番で留められた１対のアクセス・ドア３７１、３７２によって形成される。
【０１１０】
クリーン・エア・チャンバ３６４は、コレクタ筐体３５０の長さにわたって延び、延長部３７３に接続するが、その目的については以下で述べる。コレクタ筐体３５０の下部は、有孔板３７６で規定された底壁および先細りの側壁を有する粉体収集チャンバ３７４を形成する。有孔板３７６は、コレクタ筐体３５０の基部３６２に、水平に対して約５度の角度で取り付けられ、その間にエア・プレナム３７７を形成する。入口（図示せず）を通って、有孔板３７６の下のエア・プレナム３７７に、上方向の空気の流れが導入されるので、粉体収集チャンバ３７４に入る粉体塗装材料は、有孔板３７６の頂部で流動化する。
本発明の好ましい実施形態では、２グループすなわち２列のカートリッジ・フィルタ３７８が、粉体収集チャンバ３７４内に位置し、図８で分かるように、逆Ｖ字形に配置される。各カートリッジ・フィルタ３７８の開放された頂部は、クリーン・エア・チャンバ３６４の支持板３６６、３６７の一方によって、この板３６６、３６７の開口部３６８の上の位置に担持される。各カートリッジ・フィルタ３７８は、上端にねじ込んだ中心棒３８２を有し、棒３８２に締め付けられたマウント３８４を受けるので、支持板３６６または３６７の一方が、マウント３８４とカートリッジ・フィルタ３７８の頂部との間に挟まれる。コレクタ筐体３５０の端壁３５８、３６０間に延びるフィルタ取付板３８６のうち１枚以上が、各カートリッジ・フィルタ３７８に追加の支持を提供することが好ましい。
上記で検討したようにコレクタ筐体３５０に入る粉体塗装材料を、カートリッジ・フィルタ３７８の壁から除去するために、カートリッジ・フィルタ３７８の各バンクに、１組または１グループのエア・ジェット・ノズル３９２が設けられる。１組のエア・ジェット・ノズル３９２が、クリーン・エア・チャンバ３６４内に取り付けられたノズル支持体３９４上に担持され、第２組のエア・ジェット・ノズル３９２が、クリーン・エア・チャンバ３６４内のノズル支持体３９６上に担持される。図８で示すように、各組のエア・ジェット・ノズル３９２は、１グループすなわち１列のカートリッジ・フィルタ３７８の開放された頂部に向けられている。各列のカートリッジ・フィルタ３７８に関連付けられたエア・ジェット・ノズル３９２は、空気ライン３９８によって油圧弁４００に接続され、これは加圧空気供給源７３に接続される。システム制御装置１０８からの信号に応じて、油圧弁４００が作動し、加圧空気のジェットがエア・ジェット・ノズル３９２から一方または両方の列のカートリッジ・フィルタ３７８へと放出されるよう、空気ライン３９８を通って加圧空気を選択的に方向づける。このパルス状の空気ジェットが、粉体塗装材料をカートリッジ・フィルタ３７８の壁から取り除くので、粉体塗装材料は、重力によって粉体収集チャンバ３７４へ、さらに有孔板３７６へと落下することができる。
【０１１１】
図１および７を参照すると、空気に混入した粉体塗装材料は、上述したブロワ・ユニット３４８によって生成された負圧がかかると、ブース内部３０から粉体収集ユニット３４６のそれぞれに吸い込まれる。各ブロワ・ユニット３４８は、ファンまたはブロワ４０４を収容するファン・プレナム４０２、および図１で概略的に示す幾つかの最終フィルタ４０６を含む。ファン・プレナム４０２は、幾つかの開口部４０８が形成され、その上に排気ダクト４１０が固定される。各排気ダクト４１０は、垂直上方向に延び、各粉体収集ユニット３４６に関連付けられたクリーン・エア・チャンバ３６４の１つの基部に位置する軸継手４１２と係合する。ファン・プレナム４０２内のブロワ４０４の作動に応じて、排気ダクト４１０内に負圧が生成され、各粉体収集ユニット３４６に関連付けられたクリーン・エア・チャンバ３６４内にも生成する。この負圧は、ブース室内３０に下向きの空気の流れを生じ、それに過剰に吹き付けた粉体塗装材料が混入する。空気に混入した粉体塗装材料は、吹付けブース１２の床２０にある格子３８を通過して、各粉体収集ユニット３４６に入り、ここで粉体塗装材料は、カートリッジ・フィルタ３７８の壁に沿って溜まるか、コレクタ筐体３５０の基部にある有孔板３７６上に落下する。
【０１１２】
本発明の粉体収集回収システム１６の重要な態様は、１つのブロワ・ユニット３４８が限られた数の粉体収集ユニット３４６に対応することである。たとえば、図７の右側部分に示したブロワ・ユニット３４８Ａには、それぞれが１つの粉体収集ユニット３４６に接続された排気ダクト４１０を受ける４つの開口部４０８で形成されたファン・プレナム４０２を有する。したがって、４つの粉体収集ユニット３４６に、１つのブロワ・ユニット３４８Ａが対応している。他のブロワ・ユニット３４８は、比較的小さいグループの隣接する粉体収集ユニット３４６に関連付けられ、その結果、ブース室内３０全体に均一な下向きの空気の流れが与えられる。さらに、各粉体収集ユニット３４６のクリーン・エア・チャンバ延長部３７３の構成によって、吹付けブース１２の一方側にある粉体収集ユニット３４６は、ブース１２の反対側にある粉体収集ユニット３４６に「あり継ぎ」つまり嵌合することができる。図７の中央を参照のこと。これによってスペースが節約され、ブース１２の全体的寸法が小さくなる。
【０１１３】
本発明の粉体収集回収システム１６の別の態様は、収集した過剰吹付け粉体を粉体収集ユニット３４６から回収して、粉体キッチン１４に再循環して戻すことである。上述したように、ブース室内３０からの空気に混入した粉体材料は、各粉体収集ユニット３４６に吸い込まれ、重力によって基部にある有孔板３７６上に落下するか、エア・ジェット・ノズル３９２から放出した加圧空気の定期的な噴射により、カートリッジ・フィルタ３７８の壁から取り除かれる。本発明の好ましい実施形態では、有孔板３７６への粉体の移動は、エア・ジェット・ノズル２９３から逆の加圧空気ジェットが放出されると振動するように、各粉体収集ユニットのコレクタ筐体３５０の壁３５４〜３６２を、たとえば１８〜２０ケージのＮｏ．３０４ステンレス鋼などの比較的薄手の金属で形成することによって助けられる。有孔板３７６は、水平に対して約５度の角度がついているので、その上の流動化した粉体塗装材料は、有孔板３７６の下端にあるコレクタ筐体３５０の一方側の出口４２２に向かって流れる。粉体収集ユニット３４６の各出口４２２は、分岐ライン４２４によって共通のヘッダ・パイプ４２６と接続され、これは粉体ブース１２の長さに沿って、その両側を縦方向に延びる。ヘッダ・パイプ４２６は、粉体キッチン１４内の第３粉体受け８２につながる再生ライン８６に接続される。各分岐ライン４２４内にギロチン型のゲート弁４２８を担持し、この弁が、粉体塗装材料が流れることができる開位置とこのような流れを妨げる閉位置との間で移動できることが好ましい。
【０１１４】
粉体キッチン１４内の第３真空ポンプ８４は、上述したように第３粉体受け８２および再生ホッパー８０に関連付けられるが、この起動に応じて、ヘッダ・パイプ４２６内に負圧が生成される。粉体移送システムに関連して上述したシステム制御装置１０８が作動して、各粉体収集ユニット３４６に関連付けられたゲート弁４２８を選択的に開放するので、その中の粉体はそれぞれの分岐ライン４２４を通ってヘッダ・パイプ４２６に吸い込まれる。多数の粉体収集ユニット３４６があるので、所与の時間には所定の数のゲート弁４２８しか開放されず、第３粉体受け８２および１次ホッパー８０につながる再生ライン８６に移送するためにヘッダ・パイプ４２６に入ることができる粉体材料の総量を制限する。
【０１１５】
図１を参照すると、圧力センサ４３０が、ブロワ・ユニット３４８のファン・プレナム４０２に接続されるよう、概略的に図示されている。圧力センサ４３０の目的は、ブロワ・ユニット３４８内の最終フィルタ４０６での圧力低下を感知し、それを表す信号を制御装置１０８に送信することである。所与のブロワ・ユニット３４８と関連付けられた粉体収集ユニット３４６内で１つ以上のカートリッジ・フィルタ３４８に故障またはその他の問題が生じた場合は、粉体塗装材料がクリーン・エア・チャンバ３６４を通過して、最終フィルタ４０６に至り、最終フィルタ４０６で圧力が低下する。この圧力低下は、圧力センサ４３０によって感知され、この時点で、このような圧力低下を表す信号が制御装置１０８に送信され、オペレータにこのような粉体収集ユニット３４６内に問題があることを警告する。幾つかのブロワ・ユニット３４６があるので、粉体収集回収システム１６内の故障を正確に指摘し、１つのブロワ・ユニット３４８および関連の粉体収集ユニット３４６のグループに帰することができる。これはシステムの保守を容易にし、オペレータは、このような問題が生じた時に、ブロワ・ユニット３４８のそれぞれを検査する必要がない。
【０１１６】
本発明は、好ましい実施形態に関連して述べてきたが、当業者には、本発明の範囲から逸脱することなく、その要素に様々な変更ができ、同等品で置換できることが理解される。また、本発明の基本的な範囲から逸脱することなく、本発明の教示に対して、多くの修正を特定の状態または材料に加えることができる。
たとえば、本発明のシステム１０は、単一の１次ホッパー６０、単一の再生ホッパー８０、ロボット・ホッパーおよびロボット４０に関連付けられた供給ホッパー６８、および頭上ガン・マニピュレータ４４に関連付けられた供給ホッパー９６があると述べてきた。図面で示し上述したシステム１０の実施形態は、本発明の主題となる事項を例証することを目的とし、システム１０は特定の用途の要件に応じて修正できることが理解される。複数の１次ホッパー６０および再生ホッパー８０を使用することができ、様々な組合せの供給ホッパーやロボット・ホッパーで供給した自動操作および手動操作のガンを含む、様々なスプレー・ガンの構成を使用することができる。
【０１１７】
したがって、本発明は、本発明を実行すると企画される最善のモードとして、開示した特定の実施形態に限定されるものではなく、本発明は添付の請求の範囲に入るすべての実施形態を含むもとのする。
【図面の簡単な説明】
【図１】粉体収集回収システムの一部および供給ホッパーを含む粉体吹付けブースの一方端部を描き、粉体キッチンの概略図を含む、本発明の１つの実施形態の部分概略図である。
【図２】粉体キッチンに含まれる１次ホッパーと粉体受けユニットとの立面図である。
【図３】図１に示す１次ホッパーの平面図である。
【図４】おおむね図３の線４−４に沿って切り取った断面図である。
【図５】本発明の供給ホッパーの１つの実施例の部分断面図の立面図である。
【図６】本発明のロボット・ホッパーの概略部分切断図である。
【図７】粉体収集回収システムの概略部分切断図である。
【図８】粉体収集チャンバの端面図である。
【図９】図８で描いた粉体収集チャンバの側面図である。
【図１０】本発明の粉体塗装システムの別の実施形態を除き、図１に類似の図である。
【図１１】図５に示した供給ホッパーの別の実施形態の部分断面図の立面図である。
【図１２】未使用の粒状粉体塗装材料の粒子サイズ分布を体積百分率で示したグラフである。
【図１３】再生した粒状粉体塗装材料の粒子サイズ分布を体積百分率で示したグラフである。
【図１４】所定数の再生サイクルの後に様々な百分率の未使用粉体を有する粉体塗装材料内に存在する、１０ミクロン未満の粒子サイズの粒状粉体塗装材料の百分率をグラフで示す、計算値の曲線の組である。
【図１５】図１０に示した本発明の実施形態で使用する制御装置が実施する測定および制御機能を描くブロック図である。
【符号の説明】
１２ 粉体吹付けブース
４２、４６ スプレー・ガン
８０ 再生ホッパー
８２ 第３粉体受け
８４ 第３真空ポンプ
１３０ 中空の内部
１３２ フィルタ
１４６ 逆エア・ジェット弁
１７８ 回転エア・ロック計量装置
１９６ 回転式篩[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder coating system, in particular, a powder spray booth, a powder collection and recovery system, and a mixture of unused powder coating material and unused and recycled or oversprayed powder coating material. TECHNICAL FIELD The present invention relates to a powder coating system used in a vehicle manufacturing facility including a powder supply device that transports to a coating dispenser associated with a spraying booth.
[0002]
[Prior art]
The process of applying coating materials to large objects such as automobiles and other car bodies has traditionally been in the form of elongated tunnels formed at the entrance where the car body enters, the paint application area, depending on the design, the curing or drying area, and the exit where the car body exits. Has been carried out in a spray booth having the structure of In many systems, “conditioned” air, ie humidified and filtered air, is introduced by a blower or blower fan into the plenum chamber at the top of the blowing booth and then directed to the vehicle passing through the booth. To the bottom. The conditioned air picks up overspray coating material in the booth chamber, and this oversprayed material that is conveyed by air is exhausted downward by one or more exhaust fans through the floor or side of the booth. Filters are provided to capture oversprayed coating material and the resulting filtered or clean air is drawn from the booth and vented to the atmosphere or recirculated and reused in the system.
[0003]
[Problems to be solved by the invention]
The most commonly used coating material for vehicles such as automobiles and trucks is a high-solid resin coating material having a relatively high proportion of liquid solvent component that facilitates atomization of the resin material. There are detailed records of the problems associated with the recovery of excessively sprayed resin coating materials, which continue to be an environmental issue in the paint and finish industries. See U.S. Pat. No. 4,247,591 attributed to Cobbs and 4,553,701 attributed to Rehman et al.
[0004]
As disclosed in US Pat.No. 5,078,084, attributed to Shutic et al. And owned by the assignee of the present invention, powder coating materials are an alternative to solvent-based liquid paint materials for painting large objects such as car bodies. Has been proposed. In practice of powder coating, when the powdered resin is applied to the substrate and then the substrate and the powder are heated, the powder is melted, and then cooled to form a continuous solid film on the substrate. In most powder spray applications, the amount of powder that adheres to the substrate increases and imparts a static charge to the spray powder directed toward the grounded object to be applied to help hold the powder to the substrate. The operation of applying powder material to the body of an automobile or truck is carried out in a spray booth that provides a management area where excess spray powder that does not adhere to the vehicle body can be collected. The containment of the oversprayed powder in the booth is assisted by a discharge system that generates a negative pressure in the booth chamber and sucks out the oversprayed powder from the booth and puts it in the powder collection and recovery system. The recovered oversprayed powder can be stored for future use or immediately recirculated to the powder spray gun associated with the powder spray booth.
[0005]
There are some inherent problems in painting automobiles and other car bodies with powder coating materials. Due to the design of the vehicle manufacturing facility, the source of coating material is usually far from the spray booth, that is, hundreds of feet. In addition, a large amount of powder coating material, such as 136.2 kilograms per hour (300 pounds) or more, can be applied at a relatively high flow rate such as 0.454 to 0.908 kilograms per second (1 to 2 pounds). Long distances must be transferred from the source to the spray booth. Also, in order to properly coat the powder material on the vehicle body, the powder coating material must be transferred with an appropriate density and particle distribution. The term “density” refers to the relative mixing or proportion of powder and air, and the term “particle distribution” is conveyed by air, sent to a spray gun associated with the powder spray booth Refers to the distribution of powder particles of various sizes in the flow of powder material. Currently available powder coating systems have been found to be unable or insufficient to maintain the desired density and particle distribution while transferring large amounts of powder material over long distances at high flow rates. .
[0006]
As described above, the powder coating material released in the powder spray booth does not all adhere to the vehicle body passing through the booth. This oversprayed powder material is collected in a powder collection and recovery system at the base of the booth as disclosed, for example, in US Pat. No. 5,078,084 attributed to Shutic et al. In this type of system, the powder collection and recovery system includes individual groups or banks of individually contained cartridge filters in a series of powder collection chambers mounted side by side under the spray booth floor. A single exhaust fan or blower creates a negative pressure in the booth chamber, and the negative pressure sucks into the individual powder collection chambers the powder material that is over-blasted and conveyed by air, where the powder is Collected on the wall of the cartridge filter, "clean air" passes through it and is then released to the atmosphere.
[0007]
When the reversed air jet is operated to remove the collected powder from the wall of the cartridge filter, the powder falls to the base of the powder collection chamber where the spray spray associated with the powder spray booth. Removed for collection or recirculation back to the gun.
[0008]
In large-scale applications such as painting of automobile bodies, the practicality of the powder collection and recovery system and the application of uniform negative pressure in the booth room are particularly problematic. Using a single exhaust fan or blower fan to achieve a uniform negative pressure in the booth chamber is somewhat difficult in some cases, which negatively affects the efficiency with which powder coating material can be collected and It has been found that the pattern of powder coating material emitted from the spray gun on the passing vehicle body may be disrupted. In this type of system, there is also a need to improve the practicality of the reverse air jet valve contained within each powder recovery chamber.
[0009]
There are other problems with powder coating systems of the type described above, which are related to the recovery of excess spray powder for recirculation back to the spray gun associated with the powder spray booth. . The unused powder coating material includes powder particles having a wide particle size distribution, that is, various sizes. Larger powder particles tend to adhere to objects to be painted in the spray booth. This is because, due to its size, the electrostatic charge is higher than the smaller particles, and the larger and heavier particles have a greater moment than the smaller particles when released from the spray gun towards the painted object. . As a result, the powder that is oversprayed and collected to recirculate back to the spray gun without adhering to the object has a higher percentage of particles that are smaller than the unused powder. This is because the larger particles adhere to the object more than the smaller particles.
[0010]
The stability of the operation of the powder coating system depends, at least in part, on how to avoid the deposition or accumulation of “fine powder”, eg, particles having a size of less than about 10 microns. As used herein, the term “stability” refers to the ability of a system to fluidize, transport and spray powder coating materials without the problems caused by excessive levels of fines. Excessive levels of fines in the powder coating material will reduce powder fluidization, impact fusion, clogging of filter cartridges and sieves, powder spray booth interior and powder to spray gun May result in an increase in adhesion and a decrease in coating efficiency. The term “impact fusion” refers to the attachment of powder particles to the surface as a result of particle velocity relative to electrostatic attraction, and “coating efficiency” refers to the amount of powder sprayed toward an object. It is a measure of the proportion of adhering powder material.
[0011]
Powder coating systems of the type described above have essentially no measures to ensure system stability when the oversprayed powder material is recycled to the spray gun after collection. Ventilation units are used to remove fines from supply hoppers, etc., but such units have limited effectiveness and control the level or proportion of fines in a given supply hopper with the desired accuracy You can't rely on this to do it.
[0012]
[Means for Solving the Problems]
Therefore, the desired density and particle distribution can be maintained while conveying a large amount of powder material at a relatively large flow rate over a long distance, and the appropriate amount of powder coating material in the system is maintained regardless of the required amount. , Large amounts of excessively sprayed powder is collected and recovered efficiently for recirculation, avoiding the accumulation of excessive levels of fines, relatively easy to maintain, such as large cars and other car bodies It is part of the object of the present invention to provide a powder spray system for applying a powder coating material to an object.
[0013]
These objectives include a powder spray booth that defines a control area where powder coating material is applied to the car body, and powder coating material to apply the powder coating material to large objects such as cars, trucks or other car bodies, "Powder kitchen" located far from the spray booth and the powder coating material from the powder kitchen located in the vicinity of the booth and associated with the booth and operated automatically or manually This is accomplished in an instrument that includes several supply hoppers that feed a powder spray gun. The excessively sprayed powder coating material is removed from the booth room by a powder collection and recovery system that recirculates the excessively sprayed powder to the powder spray gun. Return to one or more mixing hoppers.
[0014]
One aspect of the present invention is based on the concept of providing an effective means for transferring powder coating material from a remote location, that is, from a powder kitchen location to a supply hopper located near the spray booth. is expected. This is accomplished with the instrument of the present invention by a powder transfer system operating at vacuum or negative pressure rather than positive pressure. The powder kitchen includes one or more primary hoppers, each coupled to a powder receiver unit, connected to a source of unused powder coating material in the powder kitchen. The transfer line interconnects the primary hopper with a powder receiver unit associated with each supply hopper of the spray booth. The first vacuum pump is operated to generate a negative pressure in the powder receiving unit associated with the primary hopper, and the unused powder material is sucked into the powder receiving unit from the supply source to obtain the primary powder. Can be supplied to the hopper. A second vacuum pump applies negative pressure in each powder receiving unit associated with the supply hopper so that unused powder material from the primary hopper located in the powder kitchen passes through a long transfer line. And sucked into the powder receiving unit associated with the supply hopper in the vicinity of the spray booth. The powder receiving unit in the spray booth fills individual supply hoppers with powder, and the powder is transferred from the supply hopper to the powder spray gun in the spray booth by a powder pump.
[0015]
This same principle of powder transfer with negative pressure applied is used to collect the oversprayed powder material from the spray booth. A regeneration hopper located in the powder kitchen is coupled to a powder receiving unit, which is connected by a regeneration line to a powder collection and recovery system associated with the powder spray booth. The vacuum pump generates a negative pressure in a powder receiving unit associated with a regeneration hopper that receives excessively sprayed powder from the booth, and transfers such excessively sprayed powder to the regeneration hopper. In one preferred embodiment of the invention, this regenerated oversprayed powder is then transported from the regenerative hopper under a negative pressure by another vacuum pump and connected to a supply hopper located near the booth. Supply excess spray powder to the receiving unit. The supply hopper then supplies excess spray powder to a spray gun associated with the spray booth, which operates to apply the powder to other parts of the vehicle body to be painted.
[0016]
In another embodiment, the regeneration hopper and the primary hopper are each connected to a mixing hopper located in the powder kitchen. A powder pump in the primary and regenerative hoppers transfers a selected proportion of unused powder and regenerated or oversprayed powder to the mixing hopper, such powder being associated with the spray booth. Here it is mixed in preparation for transfer to a spray gun. According to the method of the present invention in which the particle size distribution of the powder contained in the mixing hopper is mathematically predicted, the supply of unused powder and recycled powder introduced into the mixing hopper is included in the mixing hopper. The volume percentage of the fines is controlled so that it does not exceed a predetermined maximum percentage. This ensures a stable operation of the powder coating system when reclaimed or oversprayed powder is applied to objects in the booth.
[0017]
For example, a large amount of powder coating material of about 136.2 kilograms (300 pounds) per hour is efficiently and effectively conveyed by the vacuum transfer system described above, and the source of the powder coating material is powder blowing. It has been found that the specific demands of an automobile manufacturing facility located far from the attached booth can be satisfied. Using negative pressure instead of positive pressure would reduce air usage and therefore reduce the overall energy requirements of the system. Also, if any one of the transfer lines extending between the powder kitchen and the spray booth leaks, the powder material will be forced out in the case of a positive pressure powder transfer system. In such a transfer line, a vacuum is drawn inside the line. This reduces the risk of contaminating the facility with powder if a leakage problem occurs.
[0018]
Another aspect of the powder transfer aspect of the present invention relates to automatically monitoring and replenishing unused powder coating material and oversprayed powder material as the coating operation proceeds. The primary hopper, regeneration hopper and feed hopper are each carried by a load cell connected to a programmable logic controller. This load cell is effective in measuring the weight of powder material entering each individual hopper during system operation, with each hopper set to zero reference with an empty weight. For example, considering a primary hopper, the load cell associated with it sends a signal to the controller indicating the weight of the powder in such primary hopper during system operation. When the amount of powder material in the primary hopper falls below a predetermined minimum value, the controller receives a signal from the load cell and connects to the powder receiver unit associated with such primary hopper. As a result, additional unused powder coating material is conveyed from the supply source to the powder receiver unit and then to the primary hopper. When the primary hopper receives a sufficient level of powder coating material, the supply of further powder is stopped. The regeneration hopper and feed hopper operate in a similar manner, so that appropriate levels of powder coating material are maintained during the powder coating operation. In one embodiment, a connection line is provided between each primary hopper and regeneration hopper so that the amount of excess spray powder material collected in the spray booth powder collection and recovery system is reduced in the regeneration hopper. If the amount of powder material is insufficient to maintain the desired level, unused powder coating material can be fed from the primary hopper to the regeneration hopper.
[0019]
In another embodiment, a programmable controller transfers the unused powder coating material from each primary hopper and the associated hopper according to a selection ratio determined by the method described above and discussed in detail below. Governs regeneration or transfer of oversprayed powder to the mixing hopper. The mixing hopper supplies a mixture of unused powder and regenerated powder to one or more spray guns.
[0020]
Another aspect of the present invention is that the structure for each of the primary hopper, regeneration hopper and feed hopper ensures that the powder coating material is transported through the system at the desired density and particle distribution and fed to the spray gun. Regarding measures. In this embodiment, the same operating principle used in the powder feed hopper disclosed in U.S. Pat.No. 5,018,909 owned by the assignee of the present invention and attributed to Crum et al. It is used. In general, each hopper herein includes a perforated plate that receives an upward flow of air passing through a baffle disposed in the base space of such hopper. A stirrer containing a rotary spear or wing is placed on the perforated plate, which ensures proper fluidization of powder material, even distribution of powder particles, and appropriate before discharging from individual hoppers High density or air to particle ratio is ensured.
[0021]
Yet another aspect of the invention is based on the concept that a powder spray booth provides an efficient and easily maintainable powder collection and recovery system that produces a homogeneous, downward air flow in the booth chamber. Based. The powder collection and recovery system has a modular structure and includes several powder collection units mounted alongside the floor along the length of the powder spray booth. Each powder collection unit includes a powder collection chamber, which is arranged in two groups or two rows mounted in an inverted V shape on an angled fluidization plate located at the base of the powder collection chamber. Of cartridge cartridges. A limited number of individual powder collection units are connected to separate exhaust fans or blower units by a common duct. Each exhaust fan creates a negative pressure in the associated powder collection unit and sucks in over-powdered powder material conveyed by air from the booth chamber down through the booth floor and then into each powder collection chamber. It is effective to put. Excess blown powder material accumulates on the wall of the cartridge filter, and “clean” air passes through it and enters the clean air chamber associated with each powder collection unit. When a pulsed air jet is periodically introduced into the cartridge filter from an air jet valve located above the cartridge filter, the powder is then removed from the filter wall. Drops onto an angled fluidization plate at the base of each powder collection chamber and is removed. Each powder collection chamber has an outlet connected to a common header pipe, and a gate valve is disposed at each of the outlet lines. The system controller is effective to open and close the valves sequentially so that the collected powder material is removed from the various powder collection units in the order in which it is transferred to the regeneration hopper associated with the powder kitchen. .
[0022]
The structure of the powder collection and recovery system described herein has several advantages. Since several exhaust or blower units are used, each associated with a limited number of powder collection units, a more even and evenly distributed downward air flow is present in the powder spray booth room. And along its entire length. This is an improvement over systems with a single exhaust fan or blower. This is because it is difficult to obtain a uniform negative pressure with only one blower unit in a spray booth that has the extreme length necessary to apply large objects such as car bodies. Because it is. Maintenance of the powder collection and recovery system described herein is also much easier than that of conventional designs. For ease of access, a reverse air jet valve is placed at the top of the powder collection unit, allowing a single operator to easily remove the cartridge filter from the powder collection chamber. Removing the powder material from each powder collection chamber is also facilitated by an angled fluidizing plate at its base, which helps to smoothly transfer the powder from the chamber. Also, the walls of the powder collection chamber are made thin enough to help vibrate and deliver the powder onto the perforated plate when the reverse jet of air is activated.
[0023]
The operation and advantages of the structure of the presently preferred embodiment of the present invention will become more apparent when the following description is considered in conjunction with the accompanying drawings.
[0024]
【Example】
Referring now to the drawings, one embodiment of the powder coating system 10 of the present invention includes a powder spray booth 12, an apparatus for transferring powder coating material from the powder kitchen 14 to the booth 12, and the booth 12. A powder collection and recovery system 16 associated with the. These system elements are described separately below and their operation is discussed.
[0025]
Powder spray booth
With reference to FIGS. 1 and 2, the powder spray booth 12 includes a ceiling 18, a floor 20, opposing sidewalls 22, 24, and opposing end walls that define a booth inlet 26 and a booth outlet 28. See also FIG. The structure of the spray booth 12 includes a room 30 that forms a control area in which a powder coating material is applied to an object such as a vehicle body 32 that is moved by a conveyor 34 through a central portion 36 that extends in the longitudinal direction of the spray booth 12. Stipulate. Excess spray powder material that does not adhere to the vehicle body 32 passes through a grid 38 disposed along the floor 20 of the spray booth 12 and enters the powder collection and recovery system 16 described in detail below.
[0026]
The powder spray booth 12 extends a considerable distance in the vertical direction, and in the process of passing through the booth room 30, the powder coating material is applied to the entire area of the vehicle body 32 so that various powders can be applied at various positions along the powder coating booth 12. A body spray gun can be placed. For illustration, the robot 40 carrying the spray gun 42 is depicted on one side of the spray booth 12 and the overhead gun manipulator 44 is shown carrying the spray gun 47 at a position above the vehicle body 32. ing. Depending on the size of the car body 32, the type of powder coating material to be applied, the desired coating area on the car body 32 and other factors, an automatic or manual operation is performed to coat the car body 32 with the powder coating material. Basically any number of spray guns can be provided along the length of the spray booth 12. The specific position and operation of such a spray gun is not considered here as it does not form part of the present invention in itself.
[0027]
In the preferred embodiment of the present invention, the vehicle body 32 is maintained at ground potential by the conveyor 34 and the spray coatings 42 and 46 provide an electrostatic charge to the powder coating material. The electrostatic charge imparted to the powder material increases the amount of powder adhering to the car body 32 and helps retain the powder on it, but still a relatively large amount of powder material is “oversprayed”. That is, it does not adhere to the vehicle body 32. This oversprayed powder must be collected and collected during the powder coating operation as described below.
[0028]
Fig. 1 Powder coating system
An important aspect of the present invention relates to the structure of the system 10 for transferring powder coating material from the powder kitchen 14 to the spray booth 12. In many vehicle manufacturing facilities, the powder kitchen 14 is located far from the spray booth 12, for example, several tens to hundreds of meters (hundreds of feet), and a large amount of powder coating material is quickly passed between them. Must be transported. A powder flow rate of 0.454 to 0.908 kilograms (1-2 pounds) per second and a total demand of 136.2 kilograms (300 pounds) per hour is not uncommon. The overall configuration of the powder transfer system of the present invention that can satisfy such parameters efficiently and economically is first described, and then the various individual elements that make up such a transfer system. Consider in detail.
[0029]
In the embodiment of FIG. 1, the powder kitchen 14 is essentially a closed enclosure (not shown) and is “conditioned” supplied from a conventionally designed air house (not shown). Air, ie, air that has been filtered and humidified, is provided. Within the powder kitchen 14 is a supply source 54 that contains unused powder coating material, which is connected by a line 56 to a first powder receiver unit 58 that will be described in detail below. The powder receiving unit 58 is connected to the primary hopper 60 and also connected to the first vacuum pump 62 by a suction hose 61, both of which are accommodated in the powder kitchen 14. The primary hopper 60 is connected to a second powder receiver 66 coupled to the first supply hopper 68 by a transfer line 64. This transfer line 64 carries a first gate valve 70 and is connected to a first make-up air valve 72, both located in the powder kitchen 14 downstream of the primary hopper 60. The makeup air valve 72 is connected to a pressurized air supply source 73 schematically depicted in FIG. As illustrated at the top of FIG. 1, the second powder receiver 66 and the first supply hopper 68 are located in the vicinity of the powder spraying booth 12, but the primary hopper 60 and the second powder receiver 66 are connected to each other. The interconnecting transfer lines 64 may be tens to hundreds of meters (hundreds of feet) long. The supply hopper 68 is connected by a line 67 to a third vacuum pump 69 housed in the powder kitchen 14 and carries a powder pump 74 (see FIG. 5), which is connected to the robot hopper 78 by a line 76. Connected. Robot hopper 78 is connected by line 79 to spray gun 42 associated with robot 40.
[0030]
As illustrated in FIG. 1, the right portion of the powder kitchen 14 includes a structure similar to that described above with respect to the primary hopper 60. Instead of receiving unused powder coating material from the container 54, this portion of the powder kitchen 14 is primarily supplied with collected oversprayed powder from the collection and recovery system 16 of the powder spray booth 12. Is done. In a preferred embodiment of the present invention, the powder kitchen 14 contains a regenerative hopper 80 coupled to a third powder receiving unit 82 of the same type as the receiving units 58 and 66. The third powder receiving unit 82 is connected by a line 83 to a third vacuum pump 84 disposed in the powder kitchen 14 and, as will be discussed below, by a regenerative suction line 86 by a powder collection and recovery system 16. To be joined. The second transfer line 88 carries the replenishing air valve 92 and the gate valve 90 connected to the air supply source 73 and interconnects the regeneration hopper 80 with the fourth powder receiving unit 94. The fourth powder receiving unit 94 is coupled to a second supply hopper 96 located in the vicinity of the powder spray booth 12. As schematically illustrated in FIGS. 1 and 5, a second supply hopper 96 is a positive pressure powder pump that supplies powder material through line 100 to a spray gun 46 associated with the overhead gun manipulator 44. 98 is included. The fourth powder receiving unit 94 is connected to the fourth vacuum pump 102 located in the powder kitchen 14 by a line 104.
[0031]
In a preferred embodiment of the present invention, primary hopper 60, first supply hopper 68, robot hopper 78, regeneration hopper 80 and second supply hopper 96 are each manufactured by Hardy Instruments Company, part number FLB-3672- Supported on individual load cells 116A-E of the type commercially available in 1K and H1242 PS-C500. Load cells 106A-E are “zeroed” or adjusted to reflect zero weight when there is no powder coating material in each associated hopper. As discussed below, each load cell 106A-E operates to measure the weight or amount of powder coating material accumulated in the associated hopper and generate a signal representative of such weight readings. The signal is sent to the programmable logic controller 108 (PLC), which is preferably of the type sold by Allen Bradley, Cleveland, Ohio, under model number PLC-5. The control device 108 operates the vacuum pumps 62, 71, 84, and 102 and the valves 70, 72, 90, and 92, respectively, in response to signals from the load cells 106A to 106E.
[0032]
FIG.Of the powder coating system shown in Fig.
The structure and operation of each individual element of the powder coating system 10 will be discussed in detail below, and the overall operation of one embodiment thereof can be described with reference to the schematic diagram of FIG. Unlike many prior systems, the powder coating system 10 of the present invention conveys powder coating material from the powder kitchen 14 to the powder spray booth 12 using negative pressure. In addition, powder supply and transfer are basically automatically performed as the powder coating operation proceeds.
Referring first to the left side of the powder kitchen 14, when the controller 108 activates the first vacuum pump 62, unused powder coating material is transferred from the supply source 54. The first vacuum pump 62 generates a negative pressure in the first powder receiver 58, whereby unused powder coating material is drawn from the supply 54 into the first powder receiver 58 through the line 56. As will be described below, the first powder receiver 58 releases powder coating material into the primary hopper 60 and the amount of such powder coating material received is a load cell associated with the primary hopper 60. Monitored at 106A. When a predetermined level or amount of powder coating material is in the primary hopper 60, the load cell 106A sends a signal representative of this condition to the controller 108, which stops the first vacuum pump 62.
[0033]
The operation of transferring the powder coating material from the primary hopper 60 to the first supply hopper 68 is also performed by applying a negative pressure. The control device 108 activates the second vacuum pump 69 to generate a negative pressure in the second powder receiver 66 associated with the first supply hopper 68. This negative pressure sucks the powder coating material from the primary hopper 60 into the transfer line 64 and passes it through the gate valve 70 which is opened simultaneously with the start of the second vacuum pump 69 by the control device 108. The transfer of powder from the primary hopper 60 is monitored by its load cell 116A, which sends a signal to the controller 108 when a predetermined amount or weight of powder is discharged from the primary hopper 60. The controller 108 closes the gate valve 70 in the transfer line 64, stops the flow of powder through it, and switches off the second vacuum pump 69. The operation of filling the first supply hopper 68 with the powder from the primary hopper 60 is performed by the load cell 106B associated therewith monitoring the weight or amount of the powder. When the amount of powder in the first supply hopper 68 falls below a predetermined level, the load cell 106B sends a signal to the controller 108, as will be discussed in detail below, as described in detail below. Start the weighing device included in. Next, the powder transferred from the primary hopper 60 to the second powder receiver 66 is directed to the first supply hopper 68, and when a predetermined weight is obtained, a signal is sent from the load cell 106B to the control device 108. As a result, the measuring device in the second powder receiver 66 stops operating.
[0034]
As schematically shown at the top of FIG. 1, the powder coating material in the first supply hopper 68 is removed by the powder pump 74 under positive pressure (see also FIG. 5), via line 76, It is transported to a robot hopper 78 carried on its own load cell 106C. When the robot hopper 78 receives a sufficient amount of powder coating material, the load cell 106C monitors, the controller 108 stops the powder pump 74, and the second powder pump 77 passes through line 79. Then, the powder coating material is transferred from the robot hopper 78 to the spray gun 42 associated with the robot 40 and applied to the vehicle body 32.
[0035]
The purpose of the load cells 106A-E is to ensure that the flow rate and total amount of powder coating material transported through the system meets the requirements when a predetermined number of vehicle bodies 32 pass through the powder spray booth 12. Is basically automatic operation. Each of the load cells 106A-C associated with the primary hopper 60, the first supply hopper 68 and the robot hopper 78 monitors the amount or weight of the powder coating material, respectively, and the amount of powder falls below a predetermined level. Once activated, the controller 108 is activated to provide a signal. When the controller 108 receives such a signal, an appropriate vacuum pump or metering device is activated to transfer the powder coating material to a hopper that has been depleted of the supplied coating material. In this way, the hoppers 60, 68 and 78 all supply sufficient powder coating material continuously.
[0036]
Due to the extreme length of the transfer line 64, it remains in the transfer line 64 when the second vacuum pump 69 stops and stops the flow of powder coating material from the primary hopper 60 to the second powder receiver 66. The powder kitchen 14 includes a valve action arrangement so that no powder coating material is present. As described above, the controller 108 opens the gate valve 70 in the transfer line 64 during the transfer operation from the primary hopper 60 through the second powder receiver 66.
[0037]
When the load cell 106A associated with the primary hopper 60 indicates that a predetermined amount has been released from the primary hopper, the controller 108 stops the second vacuum pump 69 in the powder kitchen 14, The gate valve 70 is closed and the replenishment air valve 72 is opened. Next, pressurized air from the air supply source 73 passes through the replenishment air valve 72 and enters the transfer line 64, and the coating material remaining upstream of the transfer line 64 is received from the powder kitchen 14 by the second powder receiver. “Pursue” to 66, that is, positively forced transfer. As a result, accumulation of the powder coating material in the transfer line 64 is substantially prevented, so that the subsequent powder transfer operation from the primary hopper 60 to the first supply hopper 68 is performed quickly and efficiently. be able to.
[0038]
Referring to the right portion of the powder kitchen 14 and the upper right portion of FIG. 1, the components of the powder transfer system that supply the powder coating material to the spray gun 46 are depicted. As discussed above, such elements are located near the regeneration hopper 80, the third powder receiver 82 and the third and fourth vacuum pumps 84, 102, and the powder spray booth 12 in the powder kitchen 14. 4 includes a fourth powder receiver 94, a second supply hopper 96 and a third powder pump 98. The structure and operation of these elements are essentially the same as the corresponding elements in the left part of FIG. 1, but instead of conveying only unused powder coating material from the powder kitchen 14 to the spray booth 12, Such elements primarily convey the collected oversprayed powder coating material received from the collection and recovery system 16.
[0039]
In order to fill the regeneration hopper 80 with the oversprayed powder material, the control device 108 activates the third vacuum pump 84 to generate a negative pressure in the third powder receiver 82, and passes through the regeneration line 84. The powder coating material is sucked from the collection and recovery system 16 into the third powder receiver 82. The third powder receiver 82 places the oversprayed powder material into the regeneration hopper 80 in a manner that will be discussed in detail below. The amount of powder entering the regeneration hopper 80 is monitored in its associated load cell 106D. When the control device 108 activates the fourth vacuum pump 102, the powder material is transferred from the regeneration hopper 80 to the fourth powder receiver 94 and the second supply hopper 96. The negative pressure generated in the fourth powder receiver 94 sucks the powder from the regeneration hopper 80 through the gate valve 90 opened by the control device 108 into the second transfer line 88, and the fourth powder receiver In 94. The second supply hopper 96 receives such powder from the fourth powder receiver 94, the amount of which is monitored by the load cell 106E associated with it, and the positive pressure powder pump 98 then Is transferred from the second supply hopper 96 through the line 100 to the spray gun 46 carried by the manipulator 44. The operation of the metering device associated with the vacuum pumps 84 and 102 and the fourth powder receiver 94 is the same as discussed above, namely the load cell 106D and the load cell 106D associated with the regeneration hopper 80 and the second supply hopper 96, respectively. In response to the signal from 106E, it is governed by the controller 108. The operation of the positive pressure powder pump 98 is also controlled by the control device 108 depending on whether or not the vehicle body 32 exists in the powder spray booth 12. The valves 90 and 92 in the powder kitchen 14 function in the same manner as the valves 70 and 72 described above.
[0040]
Before discussing each of the individual elements associated with the powder transfer system in detail, two further features of the powder transfer system should be mentioned. Depending on the application, the total amount of powder coating material required for the regeneration hopper 80 may exceed the amount of oversprayed powder coating material supplied from the collection and recovery system 16. In order to ensure that there is always a sufficient amount of powder coating material in the regeneration hopper 80, the primary hopper 60 containing unused powder coating material is line 112 to the mini cyclone 114 carried by the regeneration hopper 80. A powder pump 110 connected by This minicyclone 114 is commercially available from Nordson Corporation, Amherst, Ohio, under model number PC-4-2. If the load cell 106D associated with the regeneration hopper 80 senses that the powder material in the regeneration hopper 80 is below the required weight and the powder cannot be sufficiently supplied from the collection and recovery system 16, the controller 108 will The body pump 110 is activated, and unused powder coating material is transferred to the regeneration hopper 80 via the line 112 and the mini cyclone 114 to replenish the total amount of the powder. If such transfer is necessary, both unused powder coating material and powder coating material from booth 12 collected by overspraying are mixed in the regenerative hopper 80 and then described above. To the spray gun 46 in the same manner.
[0041]
Yet another embodiment of the powder transfer system shown in FIG. 1 uses an aeration utility collector 116 located in the powder kitchen 14 and connected by a line 118 to a vent 120 at the top of the primary hopper 60. To do. Similarly, the second ventilation utility collector 122, which is also included in the powder kitchen 14, is connected to the ventilation hole 126 of the regeneration hopper 80 by a line 124. The ventilation utility collectors 116, 122 vent the interior of the primary and regenerative hoppers 60, 82, respectively, and remove "fines" from above the interior of such hoppers 60, 82. As used herein, the term “fine powder” is typically concentrated near the upper portion of the powder feed hopper and does not charge static electricity when discharged from a spray gun, such as spray guns 42 and 46, It refers to particles of powder material of very small diameter of less than 10μ that do not have enough moment to reach the object to be applied. Such small particles are usually not attracted to the surface of the object to be applied and therefore tend to accumulate in the system, reducing the coating efficiency, ie the proportion of particles adhering to the object to be applied. Accordingly, these small particles or fines are advantageously removed by the aeration utility collectors 116 and 112 in the powder kitchen 14 and then disposed of.
[0042]
FIG.Powder coating system and operating method
Referring to FIG. 10, another embodiment of a powder coating system 500 according to the present invention is schematically illustrated. Since the powder coating system 500 includes several of the elements shown in FIG. 1 and described above, the same reference numerals are used in FIG. 10 to identify structures common to FIG.
The distinction between the system 500 of FIG. 10 and the system 10 of FIG. 1 avoids excessive accumulation of “fines” primarily in certain spraying applications using various types of unused powder coating materials. Based on the recognition that you need to be careful. The term “fine powder” refers to powder particles that are less than about 10 microns in size. As mentioned above, excessive accumulation of fines reduces fluidization in the hoppers 60, 68, impact fusion on the parts to be painted, filter cartridge and sieve clogging, spray booth 12 and various It has been found that there are problems of increased powder accumulation in the coating dispensers 42, 46 and reduced coating efficiency. With many types of powder coating materials, if more than 30% of the total amount of powder coating material accumulates, one or more of the problems listed above may occur, but depending on the type of powder coating material, The proportion of fines that cause problems is different.
[0043]
In addition to concerns about the accumulation of excessive amounts of fine powder in the powder coating material supplied to the spray guns 42, 46, the appearance of the finished product should be taken into account when painting the coating material with particles in powder form. It is a power element. For example, as the proportion of relatively large or coarse particles increases, the surface finish tends to deteriorate. For example, particles larger than about 70 microns do not flow on the surface of the part to be painted as much as particles of about 10 microns, and therefore have a rough surface finish. On the other hand, the smaller the particles, the better the surface finish, but the above problem becomes dominant when the relative proportion of such small particles exceeds a predetermined level.
[0044]
To address the problem of maintaining an acceptable surface finish while limiting excessive fines accumulation, the system 500 shown in FIG. 10 includes unused particulate powder material by a pair of supply lines 504, 505. It connects with the mixing hopper 502 connected to the primary hopper 60, and connects with the reproduction | regeneration hopper 80 which receives the excessive spraying powder from the booth 12 by one pair of supply lines 506 and 507 as mentioned above. A gate valve 508 is disposed in each of supply lines 504 and 505 extending from the primary hopper 60 to the mixing hopper 502, and a gate valve 509 is provided in each line 506 and 507 between the regeneration hopper 80 and the mixing hopper 502. It is attached. The mixing hopper 502 was connected to the fourth powder receiving unit 94 by a transfer line 512, which was connected to the regeneration hopper 80 by a line 88 in the embodiment of FIG.
[0045]
In addition to the above, other structural differences between the coating system 10 and the system 500 illustrated in FIG. 1 are that a single vacuum pump 514 connected to each powder receiver 66 and 94 by a line 516 is used. is there. As described above, in the embodiment of FIG. 1, two vacuum pumps 69 and 102 were used to provide a negative pressure to transfer the coating material to the powder receivers 66 and 94, respectively. Also, in FIG. 10, one aeration utility collector 518 is used instead of the two aeration utility collectors 116, 122 depicted in FIG. The aeration utility collector 518 has a larger capacity than that described above and is connected to the filter unit 522 by a line 520 as shown in the right portion of the powder kitchen 14 of FIG. Filter unit 522 is connected to fan 526 by duct 524. The aeration utility collector 518 is connected to the primary hopper 60 by line 519, to the regeneration hopper 80 by line 521, and to the mixing hopper 502 by line 523.
[0046]
As described above in connection with the discussion of the ventilation utility collectors 116, 122 of FIG. 1, the purpose of the ventilation utility collector 518 is to provide at least one of the fines present in the primary hopper 60, the regeneration hopper 80, and the mixing hopper 502. To avoid excessive fines accumulation and to avoid the same attendant problems described above. Nevertheless, the aeration utility collectors 116, 112, and 518, as such, are an overall mixture of unused powder coating material and recycled powder coating material supplied to at least a portion of the spray gun. The relative volume percentage of fines in is not sufficient to properly control.
[0047]
The powder coating system 500 of FIG. 10 operates in the same manner as described above with respect to FIG. 1, except that a mixture of unused powder coating material and regenerated or oversprayed powder coating material is It is supplied to the coating dispenser 46. As shown in FIG. 1 and described above, rather than supplying oversprayed powder material directly from the regenerative hopper 80 to the gun 46, the system 500 of the present invention has overspread unused powder coating material. Mixing with the regenerated powder coating material in an appropriate volume percentage, no excess fines accumulate in the mixing hopper 502, and with such a mixture fed to the coating dispenser 46, an appropriate particle size distribution is achieved. Methods and means of operation are provided to ensure acquisition. The gate valve 508 associated with the unused powder supply lines 504, 505 and the gate valve 509 associated with the regenerated powder supply lines 506, 507 are in accordance with the mathematical model executed by the software in the controller 108, and are controlled by the controller. 108 operates. The purpose of the mathematical model is to predict the particle size distribution in the mixing hopper 502 in steady state operation, which will make it “stable”, that is, without excessive fines and easily fluidized. From the supply hopper 60 to the mixing hopper 502 for combination with regenerated or oversprayed powder fed from the regeneration hopper 80 to the hopper 502 so as to obtain a powder mixture that can be pumped and sprayed onto the parts to be painted. It can be determined how much unused powder coating material should be added.
[0048]
Referring first to FIGS. 12 and 13, the particle size distribution within the powder coating material is depicted graphically. The term “particle size distribution” refers to the volume percentage of powder particles in a particular size range of a given powder coating material sample. FIG. 12 shows the particle size distribution of an unused powder coating material sold by Ferro, Cleveland, Ohio and sold as No. 158E114. This unused powder coating material has a median particle size of 22 microns and the graphed data points represent the total volume percentage of the 16 particle size range within this type of unused powder coating material. It is physically measured and represented by a laser diffraction particle size analyzer such as the Malvern PSD analyzer commercially available from Malvern Instruments, Inc., Southborough, Massachusetts. The range of 16 particle sizes is, for example, 0.5 to 1.9 μ, 1.9 to 2.4 μ, etc., and is a range selected for easy illustration. In the following description of the method of the invention, various It is believed that other particle size ranges can be used.
[0049]
FIG. 13 is a graph similar to FIG. 12, but the particulate powder regenerated or collected from the powder spraying booth 12 after applying an unused powder coating material to a predetermined vehicle body 32 in the booth 12. It represents the particle size distribution within the coating material. That is, FIG. 13 shows the particle size distribution of the powder coating material that did not adhere to the vehicle body 32 in the spray booth 12 after spraying once with the unused powder coating material shown in FIG. Show. The particle size distribution of the powder shown in FIG. 13 was also measured with a Malvern PSD analyzer, and as shown, the oversprayed powder sample after one pass in FIG. The proportion of smaller particles is larger than the coating material. This is because, in general, large powder particles are easily and efficiently charged with static electricity by the coating dispenser 42 or 46 before being deposited on the object, and such large particles have a larger mass. This is because the moment for flowing to the vehicle body 32 in the attached booth 12 is large.
[0050]
The purpose of the mathematical model of the present invention is to accumulate a sufficient amount of unused powder coating material from the primary hopper 60 continuously into the mixing hopper 502 during the steady operation of the system 500 to accumulate excess fines. Is to mathematically predict the particle size distribution of the powder that remains in the system, i.e. does not adhere to the vehicle body 32 in the booth 12, so that an acceptable overall particle size distribution can be maintained.
[0051]
In order to calculate the change in particle size distribution over time, the probability that particles will remain in the system must be determined. A method for obtaining the probability coefficient for each size range of the distribution will be briefly described below, and then mathematically detailed. The purpose is to find a set of numbers (probability coefficients) that, when multiplied by the unused particle size distribution, yields an oversprayed particle size distribution.
(i) First, for each size range, the ratio of the size distribution of unused particles to the size distribution of regenerated particles is obtained. This percentage is a measure of the relative tendency that various particle sizes are attracted to the part. Particle sizes having a ratio of 1 or more are more likely to be attracted to the part than particle sizes with a ratio of less than 1. This latter particle tends to remain in the system.
(ii) Next, normalize the cumulative sum of data from paragraph (i) to 1.00 to ensure that the probability distribution still reflects 100% of all particles.
(iii) The probability that the powder remains in the system is calculated by subtracting the probability distribution of each particle size from the value of “1” and normalizing it. However, this mathematical operation still does not provide the necessary probability distribution. What we are looking for is a set of numbers that, when multiplied by the size distribution of unused particles, yields a size distribution of oversprayed particles.
(iv) To obtain a good match between the calculated particle size distribution and the particle size distribution of the oversprayed powder, use the appropriate multiplier for each particle size in the distribution of paragraph (iii) above. . When this new set of numbers is also normalized, the resulting value is the particle size distribution of each cycle through the system multiplied by a probability factor.
[0052]
The first step of the method outlined above physically measures the particle size distribution Fv of the unused powder coating material used for a given coating application using the above-described Malvern PSD analyzer. Next, this material is sprayed into a spray booth 12 of a predetermined configuration where a specific vehicle body 32 to be painted exists, and then the oversprayed or recycled powder coating material is collected. For the purposes of this specification, such excessively sprayed powder material is referred to as “one pass regeneration”, ie, a powder that has been regenerated after one “pass” or spraying operation. Next, the particle size distribution of one-pass regeneration is physically measured to determine Fr.
[0053]
As can be seen in FIGS. 12 and 13, the particle size “distribution” refers to the volume percentage summed of 16 distinct particle size ranges from 0.5 microns to 188 microns. Therefore, the terms Fv and Fr are expressed as follows:
[0054]
[Expression 1]

Where Fv₁= Volume percentage of particles of unused powder coating material of size 0.5-1.9μ, Fv₂= Volume percentage of particles of unused powder coating material having a size of 1.9 to 2.4 μ, and so on.
[0055]
[Expression 2]

Where Fr₁= Volume percentage of particles of 1-pass recycled powder coating material of 0.5-1.9μ, Fr₂= Volume percentage of particles of 1-pass recycled powder coating material of 1.9 to 2.4 μ,
....
[0056]
The measured particle size distributions Fv and Fr are input to the controller 108, which can calculate the quotient of the particle size distribution as follows.
[0057]
[Equation 3]

The quotient obtained from Equation (3) above is then normalized according to the following relationship:
[0058]
[Expression 4]

This is accomplished in a two-stage process, but first Fv / Fr₁Is obtained, that is, S.
[0059]
[Equation 5]

Then, for each of the 16 particle size ranges shown in the graphs of FIGS. 12 and 13, various quotient “normalized” values are calculated as follows.
[0060]
[Formula 6]

The next sequence of calculations performed by the software of the controller 108, for example, for each particle size range P₁~₁₆A solution of the probability coefficient P is obtained. Probability coefficient P₁~₁₆Represents the probability that in each of the 16 size ranges shown in FIGS. 12 and 13, the particles remain in the system 500, i.e. not attracted to the car body 32 in the booth 12, and thus regenerated as overspray . This information is important because, as mentioned above, the stability of the system depends on maintaining the volume percentage of fines in the mixing hopper 502 below a predetermined level, such as 30%. Probability coefficient P₁~₁₆The equation used to determine is given as:
[0061]
[Expression 7]

Where F_A= Adjustment factor x = integer 1 to 16 P = probability factor P₁, P₂... P₁₆F in equation (7)_AThe part after the term is obtained by the following two-stage calculation. First, the coefficient Z is calculated as follows.
[0062]
[Equation 8]

Next, the quotient obtained from the calculation based on Expression (8) is normalized to 1.
[0063]
[Equation 9]

The quotient obtained from the calculation based on equation (9) represents the normalized value for each of the 16 particle size ranges in the graphs of FIGS. This value is then used in equation (7) to represent the probability factor P for each particle size range, that is, the probability that each size range will remain in the system (do not adhere to the part) after a particular painting operation.
For example, for a powder particle having the size of a first group of particles of 0.5 to 1.9 microns, writing equation (7), the probability coefficient P₁Can be requested.
[0064]
[Expression 10]

For each of the 16 groups of particle sizes, the “adjustment factor” F empirically by trial and error._AIs more accurate than actual measurements of unused particles and 1-pass regenerated particles.
[0065]
## EQU11 ##

[0066]
[Expression 12]

[0067]
[Formula 13]

That is, as described in the equations (1) and (2), an appropriate adjustment value F is used by using the actual measurement values of the particle size distributions Fv and Fr first obtained by the laser diffraction particle size analyzer._AFr₁₆To ensure that the final mathematical calculation of is as accurate as possible. Given the type of powder coating material described above, the actual adjustment factor F for the particle size range increasing from 0.5 to 1.9 microns to 87.2 to 188 microns._A1~₁₆Are preferably 1.0, 0.95, 0.90... 0.25, respectively.
[0068]
Probability coefficient P as above₁~₁₆Once each is calculated, this value must also be normalized to 1.0 in the same manner as above. Now the resulting P₁~₁₆Can be used as a multiplier, such as by multiplying the particle size distribution of the unused powder, for example, to mathematically predict the oversprayed particle size distribution for each cycle through the apparatus 10.
[0069]
The above discussion is based on the premise that, to put it simply, no other unused powder material is added to the system and the original amount of powder material is recycled during continuous painting operations. It was based on a mathematical model. Since the powder coating material adheres to objects such as the car body 32 in the booth 12 under normal operating conditions and must be constantly replaced, to approximate the actual operation of the system 500, a predetermined fraction of A mathematical model is needed in which unused powder material is added to the system.
[0070]
In the above, the calculation given by the equations (1) to (13) is not repeated, and the particle size distribution of one-pass regeneration is expressed from the equations (11) to (13) using the following relational expressions.
[0071]
[Expression 14]

Therefore, the term Fr represents the particle size distribution in the first pass regenerated powder as calculated using the mathematical models of equations (1) to (13).
Considering the addition of the volume fraction y of new unused powder added to the recycled powder after the first pass or painting operation, normalized to 1.0 in equation (14), the following relationship is derived: It is burned.
[0072]
[Expression 15]

Here, the volume fraction of unused powder coating material added to the system after collecting y = 1 pass recycled powder, Fr_iy = particle size distribution of one-pass recycled powder containing unused powder coating material of fraction y, i = index of the number of passes starting from unused powder coating material.
Fr_iOnce the value of y is calculated, the subsequent “pass” or particle distribution of the painting operation can be expressed as:
[0073]
[Expression 16]

After normalizing equation (16) to 1.0, the following calculation is executed.
[0074]
[Expression 17]

The term Fr_{i + 1}y represents the particle distribution in the second pass regenerated powder (i + 1) containing the unused powder of fraction y.
[0075]
This same series of calculations is repeated for the number of cycles so that a curve of the type depicted in the graph of FIG. 14 can be generated. FIG. 14 represents the volume percentage of fines present when the Ferro 158E 114 powder coating material is sprayed with varying percentage or volume percentage of unused powder. Each curve in the graph of FIG. 14 represents various volume percentages of the unused powder y in the recycled powder and depicts how the volume percentage of the powder changes with the number of cycles or continuous painting operations. Based on the calculations from equations (15) and (17) and its iterative iteration over the total particle size (i + 16), a calculated particle size distribution over the entire range of 16 particle size ranges is obtained. The controller 108 software operates to sum the calculated volume percentages for all particles below 10 microns in each of the 16 size ranges, and for each continuous cycle or painting operation, A coordinate value is obtained. To illustrate how the volume percentage of fines changes with successive cycles and changes with changes in the percentage of the unused powder relative to the reclaimed powder, by way of example, the calculated values for several different y values are: It was included in FIG.
[0076]
The curve in FIG. 14 was mathematically derived from the above equation using Ferro 158E114 virgin powder coating material with a median particle size of about 22 microns. For this type of material, it has been found that the volume percentage of fines should be kept below about 30% in order to avoid the problem of excessive fines accumulation described above. From the graph of FIG. 14, in order to maintain a fine powder volume percentage of less than 30%, during steady state operation, the system 500 can be filled with unused powder with a fraction y on the order of more than 65% or about 70%. It is observed that it can be added. This is performed by the operation of the controller 108, which includes the gate valve 508 of each line 504, 505 from the primary hopper 60 to the mixing hopper 502, and each line extending between the regeneration hopper 80 and the mixing hopper 502. The gate valves 509 of 506 and 507 are selectively opened and closed.
[0077]
As discussed above, the mathematical model used herein is useful for indicating the percentage of fines in the mixing hopper 502 for powder coating materials containing various volume percentages of unused powder. In this way, it is possible to add unused powder having an appropriate volume fraction to the mixing hopper 502 so that excessive fine powder does not accumulate in the mixing hopper 502 during the steady operation of the system 500. As a safety measure, the system 500 of the present invention also includes software that monitors the particle size distribution in the mixing hopper 502 to ensure that the actual fines percentage in the mixing chamber 502 matches the value expected in the mathematical model. , Included in the control device 108.
[0078]
Referring to FIG. 15, there is a flowchart illustrating a sequence of operations for executing the above monitoring function. First, the sample is manually extracted from the mixing hopper 502 and the actual particle size distribution F in the mixing hopper 502 is used using the same laser diffraction particle size analyzer as described above, as schematically depicted at block 528._MMeasure. Information on the particle size distribution is input manually or electronically from block 528 to controller 108 via line 530. Thereafter, all the operations depicted in FIG. 15 are performed electronically by the software of the control device 108. Controller 108 operates to calculate the volume percentage of fines, such as particles less than about 10 microns, contained in mixing hopper 502.
[0079]
See block 532. One value representative of such a calculated volume percentage is entered into block 536 by line 534, where for a particular type of powder coating material to be applied by system 500, the calculated volume percentage of fines and Compare with a predetermined maximum volume percentage. In the illustrative embodiment shown in FIG. 15, the desired maximum volume percentage of 30% is nominally indicated in block 536, but for other types of coating materials, other minimum volume percentage fines are better. It is understood that this may be appropriate. If the calculated fines percentage is less than or equal to 30%, a “NO” signal is sent back to block 528 by line 538 until the next monitoring period begins, eg, 1 day, 1 week or other desired period The monitor sequence is complete.
[0080]
If it is determined at block 536 that the calculated fines percentage is 30% by weight above the powder in the mixing chamber 502, a signal is sent from block 53 to block 542 via line 540. The calculation performed by the controller 108, as indicated by block 542, empirically selects a weight fraction W, ie, a 20%, 30%, etc. fraction. Next, the control device 108 solves the following equation using the selected weight fraction W.
[0081]
[Expression 18]

Where Ff = desired volume percentage of fines in the mixing hopper, eg <30%, W = weight fraction of unused powder, Fm = particle size distribution of powder in the mixing hopper, Fv = unused The particle size distribution of the powder.
[0082]
When the value of Ff becomes larger than 30% at the selected weight fraction W, another larger weight fraction W is selected, and the calculation using the equation (18) is repeated.
[0083]
The next step in the monitoring sequence shown in FIG. 15 is to weigh the powder in the mixing hopper 502 using a load cell 106 of the type described above in connection with FIG. See box 544. Next, as shown schematically at block 546, the actual weight of the powder in the mixing hopper 502 is compared to the total weight capacity of the mixing hopper 502, and a signal representing the calculation is blocked via line 548. Enter in 550. As indicated by block 550, if the powder level in the mixing hopper 502 is 1-W or less, the controller 102 is activated to place unused powder coating material into the mixing hopper 502 (block 552). If the mixing hopper 502 is full and does not receive the unused powder coating material with the volume fraction W required to reduce the volume fraction of fines to the desired level, ie> (1-W), the controller 108. Release a sufficient amount of powder from the mixing hopper 502 as indicated by block 554 and then add the unused powder coating material. The amount of powder that must be discharged or removed from the mixing hopper 502 to allow room for adding unused particulate powder coating material can be determined from the following relationship:
[0084]
[Equation 19]

Where Q_D= Fraction of powder discharged from the mixing hopper, MHw = weight measurement of the mixing hopper, MHc = volume of the mixing hopper.
Thus, the series of weight calculations described above has sufficient capacity in the mixing hopper 502 to accept the new unused powder coating material, so that the total volume fraction of fines is reduced without overflowing the mixing hopper 502. It is guaranteed to go down. After the unused powder coating material is added (block 552), the monitoring operation is completed until the next monitoring period.
[0085]
Thus, the above method of maintaining the desired ratio of recycled powder coating material to unused powder coating material in the mixing hopper 502 measures the weight loss in the mixing hopper 502 as the coating operation proceeds. Depends on. Alternatively, it is believed that an appropriate amount of recycled and unused powder coating material can be supplied to the mixing hopper 502 based on flow rate measurements rather than weight measurements. In this embodiment, the flow rate of the powder coating material discharged from the mixing hopper 502 is monitored over time, and a regenerative hopper 80 is respectively used by using a flow rate control device such as a screw supply device (not shown). And from the primary hopper 60, a predetermined amount of both recycled powder coating material and unused powder coating material is added to the mixing hopper 502. A screw supply device or similar device associated with the primary hopper 60 and a separate screw supply device associated with the regeneration hopper 80 may be responsive to signals from the mixing hopper 502 or additional unused powder coating material. And / or after a predetermined period of time during which the recycled powder coating material is introduced into the mixing hopper 502, or both.
[0086]
Powder receiver
Referring to FIG. 2, the powder receiver 58 described above in connection with the discussion of the system 10 of FIG. 1 is illustrated in detail. It is understood that each of the other powder receivers 66, 82 and 94 is structurally and functionally equivalent to the powder receiver 58, so that only one of the powder receivers will be discussed in detail herein. I want. An alternative embodiment of the powder receiver 600 is also disclosed below in connection with FIG.
The powder receiver 58 includes a collector housing 128 having a hollow interior 130 with a cartridge filter 132 attached by a plate 134. Since the access panel 136 is fixed along one side of the collector housing 128 so as to be opened by a latch 138, the cartridge filter 132 can be accessed.
The interior 130 of the collector casing 128 is vented by the vent hole 140, and the upper end thereof is closed by a cap 143 fixed by a latch 144. The cap 142 carries a reverse air jet valve 146 aligned with the open end of the cartridge filter 132 connected to the plate 134. The reverse air jet valve 146 is connected to the accumulator 150 by line 148, which is connected to a source 73 of pressurized air, schematically shown in FIG. The cap 142 carries a fitting 154 connected to a suction hose or line 61 from the first vacuum pump 62. The lower portion of the collector housing 128 includes a powder inlet 158 connected to a line 56 from a container carrying unused powder coating material. The collector housing 128 tapers radially inwardly downward from the powder inlet 158 and forms a tapered base 160 that includes an external flange 162, as shown in FIG.
[0087]
As discussed above, in order for the load cell 106A associated with the primary hopper 60 to function properly, it is “zeroed” with the primary hopper 60 completely free of powder coating material. That is, the weight reading must be set to zero. In this way, the load cell 106A only weighs the powder coating material that actually enters the primary hopper 60. In order to reliably read the weight of the powder in the primary hopper 60, all the elements associated with the first powder receiving unit 58 are independent of the primary hopper 60 and shown in FIG. Support on 164. The frame 164 includes an upper plate 166 supported on the vertical legs 168, an inclined brace 170 extending between the upper plate 166 and the vertical legs 168, and one or more horizontal positions intermediate the vertical legs 168. A support 172 is included.
[0088]
The collector housing 128 is attached to the upper plate 166 of the frame 164 by bolts 174 extending between the outer flange 162 of the collector housing 128 and the upper plate 166. Extending downward from the tapered base 160 of the collector housing 128 is the collector housing 128 manufactured by Primer Pneumatics, Inc. of Salina, Kansas, model number MDR-FG-76-10NH- A flexible sleeve 176 connected to a rotary air lock metering device 178 of the type commercially available in 2-RT-CHE-T3. The weighing device 178 is drivingly connected to the output portion of the motor 182 carried on the support plate 184 connected to one vertical leg 168 by a belt (not shown). The motor 182 was activated to rotate a series of inner wings 186 in the metering device 178 and a metered amount of powder coating material was mounted on the horizontal support 172 from the tapered base 160 of the collector housing 128. Transfer to rotary sieve 196. The rotary sieve 196 is a commercially available product of the type manufactured and sold by Azo Incorporated, Germany, with model E-240. The rotary sieve 196 transfers the powder coating material through the second flexible sleeve 198 to the powder inlet 200 of the primary hopper 60. This is illustrated in more detail in FIG. 3 and described below.
In operation, the first vacuum pump 62 is activated by the controller 108 to generate a vacuum along the suction hose or line 61 and to generate a negative pressure in the hollow interior 130 of the collector housing 128. Thereby, unused powder coating material is drawn from the supply container 54 through the line 56 and the powder inlet 158 into the hollow interior 130 of the collector housing 128. Part of the powder coating material falls onto the tapered base 160 of the collector housing 128 by gravity, and some part of the powder coating material collects on the wall of the cartridge filter 132. Pressurized air periodically supplied from the accumulator 160 is conveyed in pulses through a reverse air jet valve 147 aligned with the cartridge filter 132. This air jet allows the powder coating material that accumulates on the walls of the filter 132 to separate and fall downwardly onto the tapered base 160 of the collector housing 128.
[0089]
The powder coating material is transferred from the collector housing 128 by the air lock metering device 178 in response to the operation of the motor 182, so that a metered amount of the powder coating material enters the rotary sieve 196. After passing through the rotary sieve 196, the powder coating material passes through the flexible sleeve 198 by gravity and falls to the powder inlet 200 of the primary hopper 60. When a predetermined amount of powder coating material has accumulated in the primary hopper 60, the associated load cell 106A sends a signal to the controller 108, which stops the operation of the first vacuum pump 62. As noted above, all other powder receiver units 66, 82 and 94 of the powder transfer system of FIG. 1 are all structurally and functionally identical.
[0090]
Referring to FIG. 11, another embodiment of the powder receiver 600 is illustrated in detail. The powder receiver 600 is partially similar to the powder receivers 58, 66, 82 and 94 described above in connection with the discussion of FIG. 2, and in FIG. 11, the same references are used to identify structures common to FIG. Use numbers. One difference between the powder receiver 600 and the powder receiver 58 is the structure for transferring the powder coating material from the collector housing 128 to the primary hopper 60. In applications using certain types of powder material, it has been found that the flow may stop in the middle as the coating material becomes arched or bridged in the region of the tapered base 160 of the powder receiver 58. . When the tapered base 160 is occluded, the powder coating material cannot pass through the airlock metering device 178 and enter the rotary sieve 196 having the structure shown in FIG. 11 does not include the sieve 196, but is considered to be arranged on the hopper 60 so that the particulate powder coating material can be sieved before being introduced into the hopper 60. It is done. It is preferred to use a sieve 196 at least where the powder coating material is first introduced into the system, such as receivers 58 and 82, for example. See FIG.
[0091]
The powder receiver 600 of FIG. 11 is basically composed of the upper part of the powder receiver 68 of FIG. 2, and the lower part includes a structure for fluidizing the powder coating material toward the collector housing 128. Can be transported smoothly. The bottom of the collector housing 128 defines an interior that includes a fluidized bed 602, which includes a cap 142 and a perforated plate that extends outwardly from the sidewall of the collector housing 128 and is supported by a bracket (not shown) on the sidewall. 604. A second area within the base of the collector housing 128 is an air plenum 608 that extends between a circular mounting plate 610 and a perforated plate 604 carried by brackets attached to the side wall 129 of the collector housing 128. . A third area within the base within the collector housing is a motor chamber 612 that extends between the bottom wall 614 of the collector housing 128 and the mounting plate 610. For purposes that will become apparent below, the entire powder receiver 600 is preferably attached to the top of the support stand 615 in the vertical upper position of the primary hopper 60 or other hopper.
[0092]
A stirrer 616 is provided at the base of the supply hopper 600 and includes a motor 618 carried in a motor chamber 612 by a motor mount connected to a mounting plate 610. The output of the motor 618 is drivingly connected to a shaft 622 carried in a rotatable manner within the bearing 624. The bearing 624 is attached to the mounting plate 610 by a bearing mount and extends vertically upward through the air plenum 608 to a location just above the perforated plate 604. At least two entrainment arms 628 are secured to the top of the shaft 622 extending through the bearings 624 by lock nuts 630 so that the entrainment arms 628 are perforated in response to the operation of the motor 618. Rotate relative to 604 at a position above it.
[0093]
At least two air inlets 632 are connected to the air supply line 636 entering one side of the motor chamber 612 by a tube in a manner not shown. The air supply line is connected to a pressurized air supply source 73.
[0094]
Upward air flow enters the air plenum 608 through the air inlet 632, where the air is deflected by a baffle 638 attached to the bearing 624. The purpose of this baffle is disclosed in detail in US Pat. No. 5,018,909 owned by the assignee of the present invention, the disclosure of which is hereby incorporated by reference in its entirety.
[0095]
One end of the transfer pipe 640 is connected to the collector housing 128 on the perforated plate 604 and inside the fluidized bed 602. The other end of the transfer pipe 640 is attached to the inlet 642 of the primary hopper 60. The rotary air lock 178 is driven by a motor 182, both of the same type as described above in connection with the study of the powder receiver 58, but connected within the transfer tube 640. As shown schematically in FIG. 11, the operation of the motor 182 is controlled by the controller 108, and thus the operation of the rotary air lock 178 is also controlled thereby. The powder coating material from the fluidized bed 602 in the powder receiver 600 flows downward by gravity according to the operation of the rotary air lock 178, passes through the transfer pipe 640, and then enters the interior of the primary hopper 60. to go into. The motor 182 stops and stops the operation of the rotary air lock 178 as desired, stopping the flow of powder coating material through the transfer tube 640. This configuration of the powder receiver 600 provides a smooth transfer of powder to the primary hopper 60, and such powder receiver 600 is considered to be usable as an alternative to both the embodiments of FIGS. It is done. Otherwise, the powder receiver 600 functions in the same manner as the powder receiver 58 described above, and the discussion of such operation will not be repeated here.
[0096]
Primary and regenerative hopper
The primary hopper 60 and the regeneration hopper 80 are basically equal to each other, and only the primary hopper 60 is illustrated and described in detail for consideration. Referring to FIGS. 3 and 4, the primary hopper 60 includes a housing 202 having an inner wall 204 that is generally “eight-shaped”. Thus, the inner wall 204 includes two circular portions 206 and 208, each defined by opposing triangular baffles 212 and 214 connected to one side of the housing 202, with a reduced diameter at the center of the housing 202. Fit in area 210. Each of the baffles 212, 214 has a pair of side panels 216, 218 that extend inwardly from the wall of the housing 202 and form a top 220 toward the center of the housing interior 203.
As best seen in FIG. 4, the perforated plate 222 is carried by a mount 224 near the base of the housing 202, and the housing interior 203 is placed between the perforated plate 222 and the upper wall 229 of the housing 202. It separates into a fluidized bed 226 and an air plenum 230 located between the perforated plate 222 and the bottom wall 232 of the housing 202. The air plenum 230 includes a number of baffles 270 and a generally U-shaped perforated air tube 272.
The bottom wall 232 is located at the top of the load cell 106A discussed above in connection with the powder transfer system of the present invention.
[0097]
The upper wall 228 of the housing 202 has a first stirrer 234, a second stirrer 236, a handle 240 and a latch mechanism 242 and is attached to the opening 244 of the upper wall 228 by a hinge 243. And support. Since the opening 244 is displaced from the powder inlet 200 of the primary hopper 60, the inside of the housing 203 can be accessed without interfering with the powder inlet 200 for maintenance or the like. First agitator 234 includes a motor 246 connected to gear box 250 by shaft 248. The output of the gear box 250 is drivingly connected to a shaft 252 housed in the tube 254. At least two stirrer troughs 256 are attached to the lower end of the shaft 252, inside the circular portion 206 of the housing interior 203 formed by the inner wall 204, at a position vertically above the perforated plate 222. Rotate. The second stirrer 236 has the same structure as the first stirrer 234. The second agitator 236 includes a motor 258 having a shaft 260 connected to a gear box 262, and the output of the gear box is drivingly connected to a shaft 264 housed in a tube 266. Two or more ridges 268 are attached to the base of the shaft 264 within the other circular portion 208 of the housing interior 203 formed by the inner wall 204. As shown in FIG. 4, the shaft 264 and the tube 266 associated with the second stirrer 246 are slightly longer than that of the first stirrer 234, so that the trough 268 of the second stirrer 236 is It is in a position closer to the perforated plate 222 than 234. Although the ridges 256 and 268 overlap, they are displaced in the vertical direction and do not interfere with each other.
[0098]
As noted above, one aspect of the present invention is to provide a large amount of powder coating material, such as 136.2 kilograms per hour (300 pounds) or more, from 0.454 to 0.908 kilograms per second (1 to Maintaining the desired density and particle distribution in the powder coating material flow while transferring at a flow rate such as 2 pounds). As mentioned above, the term “density” refers to the relative mixing or proportion of powder and air, and the term “particle distribution” refers to various sizes of powder in the flow of powder coating material. Refers to particle distribution. Primary hopper 60 and regenerative hopper 80 are designed to meet the desired density and particle distribution requirements at high throughput of powder coating materials.
[0099]
In operation, pressurized air is introduced into the perforated air tube 272 in the air plenum 230 to create an upward flow of air that is evenly distributed by the baffle 270 across the bottom of the perforated plate 222. The powder coating material is introduced into the housing interior 203 through the powder inlet 20 and is perforated by the upward air flow for fluidization and by the operation of the first and second agitators 234, 236. Distributed along the line 222. As the stirrer troughs 256, 268 move relative to the perforated plate 222, the "eight" shape of the housing interior 203 defined by the inner wall 204 substantially eliminates the "dead point" inside. The body coating material is evenly distributed along the entire surface of the perforated plate 222, and the aggregation or accumulation of the powder material is almost eliminated. As a result, the powder is uniformly distributed in the fluidized bed 226, and a desired particle distribution and density are obtained. When the second vacuum pump 69 is activated, the powder coating material mixed in the air is sucked out from the casing 202 of the primary hopper 60 and passes through the suction pipe 274 inserted into the casing interior 203. , Connected to the transfer line 64 described above.
[0100]
Supply hopper
Since the first and second supply hoppers 68 and 96 are basically identical in structure, only the first supply hopper 68 will be discussed in detail here. Referring to FIG. 5, the supply hopper 68 includes a top wall 278 formed with an opening closed by a cover 279, a substantially cylindrical side wall 280, and a bottom wall 282 carried by the load cell 106B. Is provided. The housing 276 basically defines a separate interior into three distinct areas. One area is a fluidized bed 284 that extends outwardly from the side wall 280 of the housing and extends between a perforated plate 286 supported on the side wall by a bracket 288 and an upper wall 278. A second area within the housing 276 is an air plenum 290 that extends between a circular mounting plate 292 and a perforated plate 286 carried by a bracket 294 mounted to the side wall 280. A third area inside the housing 276 is a motor chamber 296 that extends between the mounting plate 2292 and the bottom wall 282.
[0101]
The supply hopper 68 is provided with a stirrer 298 that includes a motor 300 carried in a motor chamber 296 by a motor mount 302 connected to a mounting plate 292. The output of the motor 300 is drivingly connected to a shaft 304 that is rotatably supported in the bearing 306. The bearing 306 is attached to the mounting plate 292 by a bearing mount 308 and extends vertically upward through the air plenum 290 to a location just above the perforated plate 286. At least two hooks 308 are secured to the top of the shaft 304 that extends through the bearing 206 by a lock nut 310 so that, depending on the operation of the motor 300, the hooks 308 are immediately against the perforated plate 286. Rotates in the upper position.
[0102]
At least two air inlets 312 are carried on the mounting plate 292 and connected by a tube 314 to an air supply line 316 that enters one side of the motor chamber 296 in a manner not shown. This air supply line 316 is connected to the pressurized air supply source 73 described above with respect to the powder receiver. An upward air flow is provided to the air plenum 290 through the air inlet 313, where the air is deflected by a baffle 318 attached to the bearing 306. This baffle 318 is the same type used for the powder receiver 600 and is disclosed in the aforementioned US Pat. No. 5,018,909.
[0103]
In operation, powder coating material is introduced into the fluidized bed 284 of the housing 276 through a tapered powder inlet 276 attached along the side wall 280 of the housing 276. Since the motor 300 operates and rotates the basket 308, the powder coating material is evenly distributed along the perforated plate 286 without dead center. The powder coating material is fluidized along the perforated plate 286 by the upward air flow from the air supply line 316 and the air inlet 312. In order to remove the powder coating material from the housing 276, one or more powder pumps, such as the pump 74, are operated and passed through a suction pipe 322 extending directly into the housing just above the perforated plate 286, Suction body paint material. To illustrate that multiple powder pumps 74 can be used to draw powder from the supply hopper 68, several suction tubes 322 are shown in FIG.
[0104]
Robot hopper
The robot hopper 78 shown schematically in FIG. 1 is shown in more detail in FIG.
[0105]
In a preferred embodiment of the present invention, the robot hopper 78 has a motor chamber and air plenum mix 324 that houses a motor 326 that is drivingly connected to a shaft 328 with one or more rods 330 attached to the upper end. Including a cylindrical base. The top of the robot hopper 78 includes a cylindrical housing 332 having a bottom wall and a top wall 334 formed by a perforated plate 336 communicating with the air plenum and motor chamber 324. A cylindrical housing 332 defines a fluidized bed 338, in which a rectangular plate or baffle 340 is mounted. The baffle 340 is vertically spaced above the perforated plate 336 and divides the fluidized bed 338 into two compartments. In one compartment or side of the baffle 340, powder coating material from the supply hopper 68 is introduced through a powder inlet 342 schematically illustrated at the top of the cylindrical housing 332. A suction pipe 344 associated with the powder pump 79 is attached to the cylindrical housing 332 on the opposite side of the baffle 340, and the suction pipe 344 terminates just above the perforated plate 336.
[0106]
Robot hopper 78 receives powder coating material via line 76 from powder pump 74 associated with supply hopper 68. The powder coating material enters the powder inlet 342 of the cylindrical housing 332, travels downward along one side of the baffle 340, and reaches the perforated plate 336. Since the motor 326 operates and rotates the bowl 330 just above the perforated plate 336, a uniform flow of powder material mixed in the air is drawn from the powder pump 79 through the suction pipe 344, and the robot 40 and its associated spray gun 42. The presence of the baffle 340 inside the cylindrical housing 332 helps stabilize the fluidization of the powder coating material across the perforated plate 336 and ensures that the flow of powder coating material drawn by the powder pump 79 is The desired density and powder distribution is maintained.
[0107]
Powder collection and recovery system
Referring to FIGS. 1 and 7-9, the powder collection and recovery system 16 is illustrated in further detail. This system 16 is generally related to the system disclosed in US Pat. No. 5,078,084 attributed to Shutic et al., The disclosure of which is hereby incorporated by reference in its entirety. As described above, the powder collection and recovery system 16 is located on either side of the center 36 of the booth 12 where the vehicle body 32 is transferred by the conveyor 34 under the floor 20 of the powder spraying booth 12. As shown in the left portion of FIG. 7, the grid 38 covers the booth floor 20 so that oversprayed aerated powder coating material can flow downward into the system 16 from any area of the booth chamber 30. Can inhale.
[0108]
The powder collection and recovery apparatus 16 has a modular structure, and includes a series of powder collection units 346 attached as a whole extending in the vertical direction along the entire length of the booth 12. See the center of FIG. As shown on the right side of FIGS. 1 and 4, the powder collection units 346 are connected to individual fans or blower units 348 located under the powder collection unit 346, for example in groups of three or four.
[0109]
Each powder collection unit 346 includes a collector housing 350 having opposed side walls 354, 356, opposed end walls 358, 360, and an inclined bottom wall 362. A pair of support plates 366, 367, opposite side plates 369, with a clean air chamber 364 located at the top of the collector housing 350 and having inwardly inclined openings 368 that are spaced apart from each other; 390 and a pair of access doors 371, 372 hinged to side plates 369, 370, respectively.
[0110]
The clean air chamber 364 extends over the length of the collector housing 350 and connects to the extension 373, the purpose of which will be described below. The lower portion of the collector housing 350 forms a powder collection chamber 374 having a bottom wall defined by a perforated plate 376 and a tapered side wall. The perforated plate 376 is attached to the base 362 of the collector housing 350 at an angle of about 5 degrees with respect to the horizontal, forming an air plenum 377 therebetween. The upward flow of air is introduced through the inlet (not shown) into the air plenum 377 below the perforated plate 376 so that the powder coating material entering the powder collection chamber 374 is perforated. Fluidize at the top of plate 376.
In a preferred embodiment of the present invention, two groups or two rows of cartridge filters 378 are located in the powder collection chamber 374 and are arranged in an inverted V shape, as can be seen in FIG. The open top of each cartridge filter 378 is carried by the one of the support plates 366, 367 of the clean air chamber 364 at a position above the opening 368 of this plate 366, 367. Each cartridge filter 378 has a central bar 382 threaded at the top and receives a mount 384 clamped to the bar 382 so that one of the support plates 366 or 367 is mounted between the mount 384 and the top of the cartridge filter 378. Sandwiched between them. One or more of the filter mounting plates 386 extending between the end walls 358, 360 of the collector housing 350 preferably provide additional support for each cartridge filter 378.
A set or group of air jet nozzles in each bank of cartridge filters 378 for removing the powder coating material entering the collector housing 350 as discussed above from the walls of the cartridge filters 378. 392 is provided. A set of air jet nozzles 392 is carried on a nozzle support 394 mounted in a clean air chamber 364, and a second set of air jet nozzles 392 is in the clean air chamber 364. Is supported on a nozzle support 396. As shown in FIG. 8, each set of air jet nozzles 392 is directed to the open top of a group or row of cartridge filters 378. An air jet nozzle 392 associated with each row of cartridge filters 378 is connected to a hydraulic valve 400 by an air line 398, which is connected to a pressurized air supply 73. In response to a signal from the system controller 108, the hydraulic valve 400 is actuated so that a jet of pressurized air is discharged from the air jet nozzle 392 to one or both rows of cartridge filters 378. Selectively direct the pressurized air through 398. This pulsed air jet removes the powder coating material from the wall of the cartridge filter 378 so that the powder coating material can fall by gravity into the powder collection chamber 374 and further into the perforated plate 376. .
[0111]
Referring to FIGS. 1 and 7, the powder coating material mixed in the air is sucked from the booth interior 30 into each of the powder collecting units 346 when the negative pressure generated by the blower unit 348 described above is applied. Each blower unit 348 includes a fan plenum 402 that houses a fan or blower 404 and a number of final filters 406 shown schematically in FIG. The fan plenum 402 is formed with several openings 408 on which the exhaust duct 410 is secured. Each exhaust duct 410 extends vertically upward and engages a shaft coupling 412 located at one base of a clean air chamber 364 associated with each powder collection unit 346. In response to operation of the blower 404 in the fan plenum 402, negative pressure is generated in the exhaust duct 410 and also in the clean air chamber 364 associated with each powder collection unit 346. This negative pressure generates a downward air flow in the booth chamber 30 and the powder coating material sprayed excessively is mixed therein. The powder coating material entrained in the air passes through the grid 38 on the floor 20 of the spray booth 12 and enters each powder collection unit 346 where the powder coating material is applied to the wall of the cartridge filter 378. It collects along or falls onto the perforated plate 376 at the base of the collector housing 350.
[0112]
An important aspect of the powder collection and recovery system 16 of the present invention is that one blower unit 348 corresponds to a limited number of powder collection units 346. For example, the blower unit 348A shown in the right portion of FIG. 7 has a fan plenum 402 formed with four openings 408 each receiving an exhaust duct 410 connected to one powder collection unit 346. . Therefore, one blower unit 348A corresponds to four powder collecting units 346. The other blower unit 348 is associated with a relatively small group of adjacent powder collection units 346 so that a uniform downward air flow is provided throughout the booth chamber 30. Further, due to the configuration of the clean air chamber extension 373 of each powder collection unit 346, the powder collection unit 346 on one side of the spray booth 12 is replaced with the powder collection unit 346 on the opposite side of the booth 12. Can be "joint" or mated. See the center of FIG. This saves space and reduces the overall size of the booth 12.
[0113]
Another aspect of the powder collection and recovery system 16 of the present invention is to collect the collected oversprayed powder from the powder collection unit 346 and recirculate it back to the powder kitchen 14. As described above, the powder material mixed in the air from the booth chamber 30 is sucked into each powder collecting unit 346 and falls on the perforated plate 376 in the base by gravity, or the air jet nozzle 392. Is removed from the wall of the cartridge filter 378 by periodic jets of pressurized air released from it. In a preferred embodiment of the invention, the movement of the powder to the perforated plate 376 oscillates when the opposite pressurized air jet is discharged from the air jet nozzle 293 so that the collector of each powder collection unit. For example, the walls 354 to 362 of the housing 350 are connected to the No. 18 cage of 18-20 cage. Helped by forming with a relatively thin metal such as 304 stainless steel. Since the perforated plate 376 has an angle of about 5 degrees with respect to the horizontal, the fluidized powder coating material on the perforated plate 376 has an outlet 422 on one side of the collector housing 350 at the lower end of the perforated plate 376. It flows toward. Each outlet 422 of the powder collection unit 346 is connected by a branch line 424 to a common header pipe 426 that extends longitudinally on both sides along the length of the powder booth 12. The header pipe 426 is connected to a regeneration line 86 connected to the third powder receiver 82 in the powder kitchen 14. A guillotine-type gate valve 428 is preferably carried within each branch line 424 and is movable between an open position where powder coating material can flow and a closed position which prevents such flow.
[0114]
As described above, the third vacuum pump 84 in the powder kitchen 14 is associated with the third powder receiver 82 and the regeneration hopper 80. In response to this activation, a negative pressure is generated in the header pipe 426. . The system controller 108 described above in connection with the powder transfer system is activated to selectively open the gate valve 428 associated with each powder collection unit 346 so that the powder therein is in its respective branch line. It is sucked through 424 into the header pipe 426. Since there are a large number of powder collection units 346, only a predetermined number of gate valves 428 are open at a given time for transfer to the regeneration line 86 leading to the third powder receiver 82 and the primary hopper 80. Limit the total amount of powder material that can enter the header pipe 426.
[0115]
Referring to FIG. 1, a pressure sensor 430 is schematically illustrated as being connected to a fan plenum 402 of a blower unit 348. The purpose of the pressure sensor 430 is to sense a pressure drop at the final filter 406 in the blower unit 348 and send a signal representative thereof to the controller 108. If one or more cartridge filters 348 fail or have other problems within the powder collection unit 346 associated with a given blower unit 348, the powder coating material will cause the clean air chamber 364 to Passes through to the final filter 406 where the pressure drops. This pressure drop is sensed by the pressure sensor 430, at which point a signal representing such a pressure drop is sent to the controller 108 to alert the operator that there is a problem in such a powder collection unit 346. To do. Since there are several blower units 346, faults within the powder collection and recovery system 16 can be pinpointed and attributed to a group of one blower unit 348 and associated powder collection unit 346. This facilitates system maintenance and the operator does not need to inspect each of the blower units 348 when such problems occur.
[0116]
Although the present invention has been described in connection with a preferred embodiment, those skilled in the art will recognize that various modifications can be made to the elements and that equivalents can be substituted without departing from the scope of the invention. In addition, many modifications may be made to a particular condition or material to the teachings of the invention without departing from the basic scope thereof.
For example, the system 10 of the present invention includes a single primary hopper 60, a single regeneration hopper 80, a supply hopper 68 associated with the robot hopper and robot 40, and a supply hopper associated with the overhead gun manipulator 44. There have been 96. It is understood that the embodiment of the system 10 shown in the drawings and described above is intended to illustrate subject matter of the present invention, and that the system 10 can be modified according to the requirements of a particular application. Multiple primary hoppers 60 and regenerative hoppers 80 can be used, using a variety of spray gun configurations, including automatic and manually operated guns supplied by various combinations of feed hoppers and robot hoppers. be able to.
[0117]
Accordingly, the present invention is not limited to the particular embodiments disclosed as the best mode contemplated for carrying out the invention, and the invention includes all embodiments that fall within the scope of the appended claims. To do.
[Brief description of the drawings]
1 is a partial schematic diagram of one embodiment of the present invention depicting one end of a powder spray booth including a portion of a powder collection and recovery system and a supply hopper, including a schematic diagram of a powder kitchen. is there.
FIG. 2 is an elevation view of a primary hopper and a powder receiving unit included in the powder kitchen.
3 is a plan view of the primary hopper shown in FIG. 1. FIG.
4 is a cross-sectional view taken generally along line 4-4 of FIG.
FIG. 5 is an elevation view of a partial cross-sectional view of one embodiment of a feed hopper of the present invention.
FIG. 6 is a schematic partial cutaway view of the robot hopper of the present invention.
FIG. 7 is a schematic partial cutaway view of a powder collection and recovery system.
FIG. 8 is an end view of the powder collection chamber.
9 is a side view of the powder collection chamber depicted in FIG. 8. FIG.
10 is a view similar to FIG. 1 except for another embodiment of the powder coating system of the present invention.
11 is an elevational view of a partial cross-sectional view of another embodiment of the supply hopper shown in FIG.
FIG. 12 is a graph showing the particle size distribution of an unused granular powder coating material as a percentage by volume.
FIG. 13 is a graph showing the particle size distribution of the regenerated granular powder coating material as a percentage by volume.
FIG. 14 graphically illustrates the percentage of granular powder coating material having a particle size of less than 10 microns present in a powder coating material having various percentages of unused powder after a predetermined number of regeneration cycles. A set of value curves.
15 is a block diagram depicting measurement and control functions performed by the control device used in the embodiment of the present invention shown in FIG.
[Explanation of symbols]
12 Powder spray booth
42, 46 spray gun
80 Reproduction hopper
82 Third powder receiver
84 Third vacuum pump
130 Hollow interior
132 Filter
146 Reverse Air Jet Valve
178 Rotating air lock metering device
196 Rotating sieve

Claims (7)

  Powder coating material supply for supplying powder coating material to at least one coating dispenser (42, 46) to adhere the powder coating material to an object moving through the powder spray booth (12) In the apparatus, in the powder spray booth (12), a part of the powder coating material does not adhere to the object but becomes an excessive spray powder coating material, and the excessive spray powder coating material is recovered. Are provided with a plurality of powder collecting units (346) disposed under the powder spraying booth (12), and each of the plurality of powder collecting units (346) includes an excessively sprayed powder. One or more filters (378) for collecting the coating material, and a collection chamber (374) for temporarily holding the powder removed from the filter (378), the collection chamber (374) ) Is connected And an outlet (422) connected to a transfer conduit (86) by a data line (424), which is connected to a transfer device (82, 84). 82, 84) operate under application of negative pressure to transfer the oversprayed powder coating material from the collection chamber (374) to the regeneration hopper (80).   The transfer device includes a powder receiving unit (82) coupled to the regeneration hopper (80) and a vacuum device (84) connected to the powder receiving unit (82). (82) receives the powder coating material from the powder spray booth (12) and transfers a prescribed amount of the powder coating material to the regeneration hopper (80), and the vacuum device (84) 2. The powder coating material supply device according to claim 1, wherein the powder coating material is transferred into the powder receiving unit (82) under the application of.   The powder receiving unit (82) includes a powder recovery chamber (130) for receiving a powder coating material, and the powder recovery chamber (130) includes a cartridge filter (132). A clean air chamber disposed away from the recovery chamber (130), an air jet device (146) for removing the powder coating material from the cartridge filter (132), and a prescribed amount of the powder coating material. The powder coating material supply device according to claim 2, further comprising a device (178) for transferring the powder from the powder recovery chamber (130) to the regeneration hopper (80).   The apparatus for transferring a specified amount of powder coating material comprises a metering air lock (178) connected to the powder recovery chamber (130), the metering air lock and the regeneration hopper (80). The powder coating material supply device according to claim 3, further comprising a sieve (196) connected between the two.   Each of the connector lines (424) is connected to a valve (428) operable between an open position and a closed position, and the powder coating material supply device comprises the powder collection unit (346) The powder coating material supply device according to claim 1, further comprising a control means (108) for sequentially opening and closing the valves (428) associated with each of the valves.   Each collection chamber (374) of each of the powder collection units (346) is mounted at an angle with respect to the horizontal to receive powder coating material from the powder spray booth (12). A perforated plate (376) and an air plenum (underneath the perforated plate (376) for fluidizing the received powder coating material and for passing an air flow through the perforated plate (376)) 377), the perforated plate (376) has one lower end lower than the other end, and the outlet (422) is arranged at the lower end. The powder coating material supply apparatus according to claim 1.   Each collection chamber (374) of each of the powder collection units (346) is mounted at an angle with respect to the horizontal to receive powder coating material from the powder spray booth (12). A perforated plate (376) and an air plenum (underneath the perforated plate (376) for fluidizing the received powder coating material and for passing an air flow through the perforated plate (376)) 377), the perforated plate (376) has one lower end lower than the other end, and the outlet (422) is arranged at the lower end. The powder coating material supply apparatus according to claim 5.

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