JP3835366B2

JP3835366B2 - Mold for injection molding of resin molded products

Info

Publication number: JP3835366B2
Application number: JP2002207852A
Authority: JP
Inventors: 義明上尾
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Resonac Corp
Priority date: 2002-07-17
Filing date: 2002-07-17
Publication date: 2006-10-18
Anticipated expiration: 2022-07-17
Also published as: JP2004050465A

Description

【０００１】
【発明に属する技術分野】
本発明は、樹脂成形品の射出成形用金型であって、成形品の離型を、金型の一部を回転させることにより行なう仕様の金型に関する。この金型は、殊に、フェノール樹脂等、成形時の流動性が良い樹脂の射出成形に適したものである。
【０００２】
【従来の技術】
例えば、図３に示すようなアンダーカット形状のポンプ用羽根車を射出成形する場合は、成形品の離型を、金型の一部を回転させることにより行なう仕様の金型を用いる必要がある。
この成形品は、中央部１と円環状の周縁部２の間の円環状空隙に、断面「く」の字形のアンダーカット形状部３が円環に沿って配列され、中央部１と円環状の周縁部２がアンダーカット形状部３で連結された一体成形品である。また、この成形品は、中央部１の中心に非円形の貫通穴４（図面ではＤ穴）を備えている。従って、このような成形品の離型は、金型を一軸方向に型開きするだけでは行なえず、アンダーカット形状部３を成形するための金型部材を、型開き方向と直角をなす面で回転させながら、型開き方向に後退させる必要がある。
【０００３】
図４は、射出成形のためのこのような金型を示す要部断面図である。この金型は、パーティングライン１０で型開きする可動側金型２０と固定側金型３０からなっている。
可動側金型２０は、成形品に貫通穴４を形成するための入れ子ピン２１と入れ子型（可動側）２２を含む。入れ子型（可動側）２２は、入れ子ピン２１を軸として回転しながら型開き方向に前進・後退する。
一方、固定側金型３０は、可動側金型２０と協働して成形空間を構成し、固定入れ子型３１と入れ子型（固定側）３２を含む。入れ子型（固定側）３２は、固定入れ子型３１を軸として回転しながら型開き方向に前進・後退する。型締めした状態では、入れ子ピン２１の先端面は固定入れ子型３１に当接するので、固定入れ子型３１には、前記当接面を避けてゲート部３３とこれに連なるスプル部３４を配置している。
入れ子ピン２１と固定入れ子型３１は、主として成形品の中央部１を成形する成形空間を構成し、入れ子型（可動側）２２と入れ子型（固定側）３２は、主としてアンダーカット形状部３と周縁部２を成形する成形空間を構成する。
【０００４】
上記金型を用いて成形品を射出成形し、然る後に、金型から取出すときは、まず、金型を閉じた状態のまま、入れ子ピン２１、入れ子型（可動側）２２、固定入れ子型３１、入れ子型（固定側）３２を含む部分を、射出成形機から離れる方向にわずかに移動させる。これによって、ゲートが切断される。次に、固定入れ子型３１を軸として入れ子型（固定側）３２を回転しながら型開き方向に後退させる。この操作で、成形品が固定側金型３０から離型される。さらに、可動側金型２０を型開き方向に後退させ、入れ子ピン２１を軸として入れ子型（可動側）２２を回転しながら型開き方向に後退させる。これで、成形品は入れ子ピン２１だけに保持され、容易に取出せる状態となる。
【０００５】
上記のように、金型の一部を回転させることにより樹脂成形品の離型を行なう仕様の金型では、金型の回転摺動面のクリアランスを４０μｍ程度に設定している。一般的な熱可塑性樹脂の場合、金型に射出した樹脂が流動状態にある時間は比較的短いので、クリアランスを前記程度に設定しておいても、流動した樹脂がクリアランスに入り込む心配は殆どない。そして、クリアランスを前記程度に設定しておくことにより、金型の回転摺動は滑らかに行なわれるし、流動した樹脂がクリアランスに入り込むこともないので、クリアランスの清掃をしなくても成形を連続して繰返すことができる。
【０００６】
それに対し、フェノール樹脂やポリフェニレンサルファイドは、金型内で流動状態にある時間が長い。上記のように、金型の一部を回転させることにより離型を行なう仕様の金型を用いてこのような樹脂の射出成形を行なうと、流動した樹脂が回転摺動面のクリアランスに入りやすい。このため、成形を繰り返すと早い段階でクリアランスが樹脂で埋まって金型の回転摺動ができなくなり、成形不可となる。そして、可動側金型と固定側金型の両方を、クリアランス清掃のために解体し再び組立てなければならず、清掃作業が面倒である。
【０００７】
尚、図５に示すように、入れ子型（固定側）３２に、入れ子ピン２１の先端との当接面を避けてゲート部３３とこれに連なるスプル部３４を配置する構成、すなわち、図３における固定入れ子型３１を入れ子型（固定側）３２と一体にして両者の摺動面をなくした構成が考えられる。しかし、この場合、入れ子型（固定側）３２を回転して成形品の固定側金型の離型を行なうためには、スプルが入れ子型（固定側）３２から完全に抜けきる位置まで、金型を閉じた状態のまま、入れ子ピン２１、入れ子型（可動側）２２、入れ子型（固定側）３２を含む部分を、射出成形機から離れる方向に長いストロークで移動させなければならない。何故なら、スプル部３４が、入れ子型（固定側）３２の回転軸線上に位置していないからである。スプルの基部側にはランナさらには射出成形機射出部からのスプル（１次スプル）が連なっており、スプル部３４の軸線が入れ子型（固定側）３２の回転中心と一致していないので、スプルが入れ子型（固定側）３２から完全に抜けきるまでは前記ランナ及び１次スプルが障害となって、入れ子型（固定側）３２を回転できないのである。
【０００８】
このように、入れ子型（固定側）３２を長いストロークで移動させる（実際は、入れ子型（固定側）３２を嵌め込んだ中間板を移動させる）ことは、成形サイクルを長くするだけでなく、中間板を保持する支持ピンの強度も十分に大きくしておくことが必要となる。中間板を長い移動ストロークに亘って支持しなければならないからである。そうすると、装置が大型になり実用的でなくなる。
【０００９】
【発明が解決しようとする課題】
本発明が解決しようとする課題は、金型の一部を回転させることにより樹脂成形品の離型を行なう仕様の射出成形用金型において、殊に、固定側金型の回転摺動面への溶融樹脂の侵入を防いで、固定側金型の清掃保守の手数を省き、装置も大型にならないようにすることである。
【００１０】
【課題を解決するための手段】
本発明が対象とする金型は、可動側金型と固定側金型からなり、金型内で成形した樹脂成形品の離型を、型開き方向と直角をなす面で金型の一部を回転させながら型開き方向に後退させることにより行なう仕様の射出成形用金型である。
【００１１】
上記課題を解決するために、第１の発明に係る樹脂成形品の射出成形用金型は、次のような構成を備える。
まず、可動側金型は、成形品に貫通穴を形成するための入れ子ピンと当該入れ子ピンを軸として回転しながら型開き方向に前進・後退する入れ子型（可動側）を含む。
一方、固定側金型は、上記可動側金型と協働して成形空間を構成し回転しながら型開き方向に前進・後退する入れ子型（固定側）を含む。当該入れ子型（固定側）の固定側金型との回転摺動部（図示せず）を成形空間の外側の離れた位置に配置するとともに、当該入れ子型（固定側）には、上記入れ子ピンの先端に所定の間隙をもって相対する凹陥部と凹陥部に開口するゲート部とゲート部に連なるスプル部を配置する。そして、入れ子型（固定側）の回転中心を前記ゲート部とスプル部の軸線上とする。
【００１２】
上記金型は、入れ子型（固定側）の回転中心がゲート部とゲート部に連なるスプル部の軸線と一致する。従って、射出成形後、入れ子ピン、入れ子型（可動側）、入れ子型（固定側）を含む部分を、射出成形機から離れる方向にわずかに移動させゲートを成形品から切断すれば、入れ子型（固定側）をゲート部とスプル部の軸線上で回転しながら移動させて、成形品を固定側金型より離型することができる。スプルが入れ子型（固定側）に残っていても入れ子型（固定側）の回転には何ら支障はない。また、入れ子型（固定側）の回転摺動部は、成形空間の外側の離れた位置にあるので、溶融樹脂が侵入することはない。入れ子型（固定側）は、スプルが入れ子型（固定側）３２から完全に抜けきるまで移動させなくて済み、これを保持するするための支持部材の強度アップの必要もない。
次に、可動側金型を型開き方向に後退させ、入れ子ピンを軸として入れ子型（可動側）を回転しながら型開き方向に後退させる。これで、成形品は入れ子ピンだけに保持された状態となり、容易に取出すことができる。
尚、成形品には、入れ子ピンと入れ子型（固定側）の凹陥部によって、成形品の貫通穴を塞ぐ空洞の突出部が成形される。しかし、この突出部は成形品の平面研磨により容易に除去することができるので、問題とはならない。
【００１３】
第２の発明に係る射出成形用金型は、可動側金型は、成形品に貫通穴を形成するための入れ子ピンと当該入れ子ピンに沿って回転することなく相対的に前進・後退する入れ子型（可動側）と成形品の突出しピンを含む。固定側金型は、上記第１の発明における射出成形用金型と同様の構成である。
【００１４】
この金型を使用する場合、固定側金型における成形品の離型は、第１の発明における金型と同様の操作で実施する。一方、可動側金型の離型は、入れ子型（可動側）の回転を伴わずに、入れ子ピンと入れ子型（可動側）を相対的に移動させて、入れ子ピンを成形品から抜く。そして、突出しピンにより成形品を突出すと、入れ子型（可動側）に規制された成形品は回転するしかなく、回転しながら入れ子型（可動側）から抜け離脱する。
【００１５】
【発明の実施の形態】
図３に示したポンプ用羽根車の成形に適用する射出成形用金型について、発明の実施の形態を説明する。
【００１６】
まず、第１の発明に係る発明の実施の形態を、図１を参照して説明する。
可動側金型２０と固定側金型３０は、協働して成形空間を構成する。両者のパーティングライン１０は、成形品のアンダーカット形状部３を成形する部分では成形品の厚さ方向中央部（断面「く」の字形の屈曲部）に、中央部１と円環状の周縁部２を成形する部分では成形品の片側表面部にある。
【００１７】
可動側金型２０は、成形品に貫通穴４（Ｄ穴）を形成するための入れ子ピン２１と当該入れ子ピン２１を軸として回転しながら型開き方向に前進・後退する入れ子型（可動側）２２を含む。
一方、固定側金型３０は、回転しながら型開き方向に前進・後退する入れ子型（固定側）３２を含む。当該入れ子型（固定側）３２には、上記入れ子ピン２１の先端に所定の間隙をもって相対する凹陥部３５と凹陥部３５に開口するゲート部３３とゲート部３３に連なるスプル部３４を配置する。入れ子型（固定側）３２の回転中心を前記ゲート部３３とスプル部３４の軸線上とする。入れ子型（固定側）３２は、中間板（図示せず）に嵌め込んで保持するが、入れ子型（固定側）３２の円柱体の周面からはピンを突出させておく。前記ピンは、中間板の移動から独立し型開き方向に対して平行部と傾斜部をもったガイドレールに係合させる。ガイドレールとピンの係合状態を保ったまま中間板を型開き方向に移動させると、入れ子型（固定側）３２は、前記ガイドレールの傾斜部区間で回転する。さらに、入れ子型（固定側）３２の円柱体の周面からは別のピンを突出させておき、入れ子型（固定側）３２を嵌め込む中間板の嵌め込み穴周壁には前記別のピンが係合する螺旋（又は螺旋の一部をなす）溝を切って、両者の係合関係を保持しておく。これによって、回転する入れ子型（固定側）３２は、後退又は前進をする。この原理は、入れ子型（可動側）２２の回転にも適用できるが、入れ子型（可動側）２２に対しては、種々の回転手段を設置する空間的自由度が十分にある。
【００１８】
上記のような射出成形用金型を用いて、例えばフェノール樹脂を射出成形した後、成形品の離型を次のように実施する。
まず、金型を閉じた状態のまま、入れ子ピン２１、入れ子型（可動側）２２、入れ子型（固定側）３２を含む部分を、ゲートが切断されるわずかなストローク（１mm程度）だけ、射出成形機から離れる方向に移動させる。しかる後、入れ子型（固定側）３２を回転しながら型開き方向に後退させる。この操作で、成形品は固定側金型３０から離型される。スプルは入れ子型（固定側）３２に残っているが、ゲート部３３とスプル部３４の軸線と入れ子型（固定側）３２の回転中心が一致しているので、スプルが入れ子型（固定側）３２の回転に支障をもたらすことはない。
次に、可動側金型２０を型開き方向に後退させ、入れ子ピン２１を軸として入れ子型（可動側）２２を回転しながら型開き方向に後退させる。これで、成形品は入れ子ピン２１だけに保持され、容易に取出せる状態となる。
【００１９】
上記の金型は、入れ子型（固定側）３２の回転摺動面は、成形空間の外側の離れた位置、すなわち、中間板（図示せず）への嵌め込部にある。従って、成形空間に射出した溶融樹脂がパーティングライン１０に侵入し、さらに前記嵌め込部まで侵入する心配はない。
入れ子ピン２１と入れ子型（可動側）２２の回転摺動面には少なくとも一方の面にフッ素系樹脂の被膜を形成し、回転摺動面のクリアランスを５μｍ〜３０μｍにしておくことが好ましい。通常より狭いクリアランスに設定して溶融樹脂のクリアランスへの侵入を抑えつつ、フッ素系樹脂の被膜の存在により円滑な回転摺動が確保される。クリアランスが５μｍ未満になると金型への嵌め込みが困難になるので、５μｍ以上のクリアランスを確保する。フッ素系樹脂の被膜は、入れ子ピン２１の外周面と入れ子型（可動側）２２の内周面のいずれか一方に形成してもよいし、両方に形成してもよい。しかし、回転摺動面の少なくとも一方の周面に形成しておけば、円滑な摺動性を確保できる。また、フッ素系樹脂の被膜は、入れ子型（可動側）２２の内周面に形成するより、入れ子ピン２１の外周面に形成する方が寸法精度確保の上で都合がよい。
【００２０】
上記成形金型は、ゲート部３３が開口する入れ子型（固定側）３２の凹陥部３５が、入れ子ピン２１の先端に所定の間隙をもって相対している。溶融樹脂は、成形空間の中心位置に射出され周縁に向かって充填されるので、ウエルドのない寸法精度に優れた成形品を製造することができる。入れ子ピン２１と入れ子型（固定側）３２の凹陥部３５によって、成形品にはその貫通穴４を塞ぐ空洞の突出部が成形されることになる。しかし、この突出部は成形品の平面研磨により除去できる方向の突出であり、その除去作業は容易で問題とはならない。
【００２１】
次に、第２の発明に係る発明の実施の形態を図２を参照して説明する。
可動側金型２０は、成形品に貫通穴４を形成するための入れ子ピン２１と入れ子ピン２１に沿って回転することなく相対的に前進・後退する入れ子型（可動側）２２と成形品の突出しピン２３を含む。固定側金型３０は、上述した第１の発明に係る発明の実施の形態における射出成形用金型と同様の構成である。
【００２２】
この金型を使用する場合、固定側金型２０における成形品の離型は、第１の発明に係る発明の実施の形態で説明した操作と同様の操作で実施する。一方、可動側金型２０の離型は、入れ子型（可動側）２２の回転を伴わずに、入れ子ピン２１と入れ子型（可動側）２２を型開き方向に相対的に移動させて、入れ子ピン２１を成形品から抜く。そして、突出しピン２３により成形品を突出すと、入れ子型（可動側）２２に規制された成形品は回転するしかなく、回転しながら入れ子型（可動側）２２から抜け離脱する。
第２の発明に係る発明の実施の形態では、入れ子型（可動側）２２に、その回転手段を付加する必要がなく、型開き方向に進出・後退する突出しピン２３を配置するだけでよいので、構造が簡単になる。
【００２３】
第２の発明に係る発明の実施の形態においても、第１の発明に係る発明の実施の形態に準じて、入れ子型（可動側）２２と入れ子ピン２１及び突出しピン２３との摺動面にフッ素系樹脂の被膜を形成し、摺動面のクリアランスを５μｍ〜３０μｍにしておくことが好ましい。
【００２４】
上記各発明の実施の形態で説明した金型は、隣合うアンダーカット形状部３の間に「く」の字形に屈曲した貫通穴を有するフェノール樹脂成形品の成形を対象としているが、そのほか、前記屈曲した貫通穴の代わりに傾斜した貫通穴や傾斜した凹陥部が円環に沿って配列された樹脂成形品の成形を対象としたものであってもよい。
【００２５】
【実施例】
上記発明の実施の形態で図１を参照して説明した金型を用い、フェノール樹脂成形品の射出成形を実施した（実施例１〜３）。可動側金型２０における摺動面のフッ素系樹脂被膜形成の有無ならびに摺動面のクリアランスを表１に示すとおりとした。固定側金型３０における入れ子型（固定側）３２の回転摺動面のクリアランスは、４０μｍに設定した。
【００２６】
上記発明の実施の形態で図２を参照して説明した金型を用い、フェノール樹脂成形品の射出成形を実施した（実施例４〜６）。可動側金型２０における摺動面のフッ素系樹脂被膜形成の有無ならびに摺動面のクリアランスを表１に示すとおりとした。固定側金型３０における入れ子型（固定側）３２の回転摺動面のクリアランスは、４０μｍに設定した。
【００２７】
また、図４に示した従来の金型を用い、フェノール樹脂成形品の射出成形を実施した（従来例１、２）。固定側金型３０における固定入れ子型３１と入れ子型（固定側）３２の回転摺動面のクリアランスは、表１に示すとおりとした。
【００２８】
さらに、図４に示した従来の金型において、固定側金型の摺動面にフッ素系樹脂被膜を形成した金型を用い、フェノール樹脂成形品の射出成形を実施した（参考例１、２）。固定側金型３０における固定入れ子型３１と入れ子型（固定側）３２の回転摺動面のクリアランスは、表１に示すとおりとした。
【００２９】
金型の摺動面の清掃を行なわずに、射出成形を連続繰返しできる回数（ショット数）を、可動側金型と固定側金型のそれぞれについて調査した。その結果を表１に示す。
【００３０】
【表１】

【００３１】
表１から明らかなように、本発明の実施例の金型は、固定側金型の連続ショット回数を飛躍的に延ばして、その清掃作業工数を低減することができる。実施例１〜３は、可動側金型の摺動が回転運動であるので、大きな力をかけるとねじれによる破損が心配される。一方、実施例４〜６は、可動側金型の摺動が直線運動であるので、金型の破損を心配せずに摺動に大きな力をかけることができる。実施例４〜６においては、可動側金型の連続ショット回数も延ばせる。
【００３２】
【発明の効果】
従来、金型の一部を回転させることにより成形品の離型を行なう仕様の金型を用いて樹脂成形品の射出成形を実施しようとすると、連続繰返し成形が不可能であったところ、上述のように、本発明に係る金型を用いることにより、固定側金型の回転摺動面への溶融樹脂の侵入を長期に亘り防ぐことができる。金型摺動面の清掃は、可動側金型を重点的に実施すればよいので、その清掃作業工数を著しく低減することができる。。
【図面の簡単な説明】
【図１】本発明に係る樹脂成形品の射出成形用金型の発明の実施の形態を示す要部断面図である。
【図２】本発明に係る樹脂成形品の射出成形用金型の他の発明の実施の形態を示す要部断面図である。
【図３】本発明に係る射出成形用金型が成形対象とする成形品の一例を示す一部欠截斜視図である。
【図４】従来の射出成形用金型を示す要部断面図である。
【図５】従来の他の射出成形用金型を示す要部断面図である。
【符号の説明】
１は中央部
２は周縁部
３はアンダーカット形状部
１０はパーティングライン
２０は可動側金型
２１は入れ子ピン
２２は入れ子型（可動側）
２３は突出しピン
３０は固定側金型
３１は固定入れ子型
３２は入れ子型（固定側）
３３はゲート部
３４はスプル部
３５は凹陥部[0001]
[Technical field belonging to the invention]
The present invention relates to a mold for injection molding of a resin molded product, and relates to a mold having specifications for releasing a molded product by rotating a part of the mold. This mold is particularly suitable for injection molding of a resin having good fluidity during molding, such as a phenol resin.
[0002]
[Prior art]
For example, when an undercut pump impeller as shown in FIG. 3 is injection-molded, it is necessary to use a mold having a specification for releasing a molded product by rotating a part of the mold. .
In this molded product, undercut portions 3 having a cross-section “<” shape are arranged along an annular shape in an annular space between the central portion 1 and the annular peripheral edge portion 2, and the central portion 1 and the annular shape are formed. This is an integrally molded product in which the peripheral edge portion 2 is connected by the undercut shape portion 3. Further, this molded product is provided with a non-circular through hole 4 (D hole in the drawing) at the center of the central portion 1. Therefore, the mold release of such a molded product cannot be performed only by opening the mold in a uniaxial direction, and the mold member for forming the undercut shape portion 3 is formed on a surface perpendicular to the mold opening direction. It is necessary to retreat in the mold opening direction while rotating.
[0003]
FIG. 4 is a cross-sectional view of an essential part showing such a mold for injection molding. This mold is composed of a movable mold 20 and a fixed mold 30 which are opened by a parting line 10.
The movable mold 20 includes a nested pin 21 and a nested mold (movable side) 22 for forming the through hole 4 in the molded product. The nesting die (movable side) 22 moves forward and backward in the mold opening direction while rotating around the nesting pin 21.
On the other hand, the fixed side mold 30 forms a molding space in cooperation with the movable side mold 20, and includes a fixed nested mold 31 and a nested mold (fixed side) 32. The nested mold (fixed side) 32 moves forward and backward in the mold opening direction while rotating around the fixed nested mold 31. In the clamped state, the tip surface of the nesting pin 21 abuts against the fixed nesting die 31. Therefore, the fixed nesting die 31 has a gate portion 33 and a sprue portion 34 connected to the gate portion 33 avoiding the abutting surface. Yes.
The nesting pin 21 and the fixed nesting die 31 mainly constitute a molding space for molding the central portion 1 of the molded product, and the nesting die (movable side) 22 and the nesting die (fixed side) 32 are mainly formed with the undercut shape portion 3. A molding space for molding the peripheral edge 2 is formed.
[0004]
When a molded product is injection-molded using the above-mentioned mold, and then taken out from the mold, first, with the mold closed, the nested pin 21, the nested mold (movable side) 22, the fixed nested mold 31. The part including the nesting die (fixed side) 32 is slightly moved away from the injection molding machine. As a result, the gate is cut. Next, the insert mold (fixed side) 32 is rotated in the mold opening direction while rotating around the fixed insert mold 31 as an axis. With this operation, the molded product is released from the fixed mold 30. Further, the movable side mold 20 is retracted in the mold opening direction, and the nest mold (movable side) 22 is rotated around the nest pin 21 as the axis while being retracted in the mold opening direction. Thus, the molded product is held only by the insert pin 21 and can be easily taken out.
[0005]
As described above, in a mold in which the resin molded product is released by rotating a part of the mold, the clearance of the rotational sliding surface of the mold is set to about 40 μm. In the case of a general thermoplastic resin, since the time when the resin injected into the mold is in a fluid state is relatively short, even if the clearance is set to the above level, there is almost no fear that the fluidized resin enters the clearance. . By setting the clearance to the above level, the mold can rotate and slide smoothly, and the resin that has flowed will not enter the clearance. Therefore, molding can be continued without cleaning the clearance. Can be repeated.
[0006]
On the other hand, phenol resin and polyphenylene sulfide are long in the fluid state in the mold. As described above, when such a resin is injection-molded using a mold whose mold is released by rotating a part of the mold, the fluidized resin easily enters the clearance of the rotating sliding surface. . For this reason, if molding is repeated, the clearance is filled with resin at an early stage, and the mold cannot be rotated and slid, and the molding becomes impossible. Then, both the movable side mold and the fixed side mold must be disassembled and reassembled for clearance cleaning, and the cleaning work is troublesome.
[0007]
As shown in FIG. 5, the gate portion 33 and the sprue portion 34 connected to the nest die (fixed side) 32 avoiding the contact surface with the tip of the insert pin 21 are arranged, that is, FIG. A configuration in which the fixed nesting die 31 is integrated with the nesting die (fixed side) 32 and the sliding surfaces of both are eliminated is conceivable. However, in this case, in order to rotate the insert mold (fixed side) 32 to release the fixed mold of the molded product, the mold is moved to a position where the sprue is completely removed from the insert mold (fixed side) 32. The portion including the nesting pin 21, the nesting die (movable side) 22, and the nesting die (fixed side) 32 must be moved with a long stroke in a direction away from the injection molding machine while the die is closed. This is because the sprue portion 34 is not positioned on the rotation axis of the nesting type (fixed side) 32. Since the sprue (primary sprue) from the runner and further the injection molding machine injection part is connected to the base side of the sprue, the axis of the sprue part 34 does not coincide with the rotation center of the nesting type (fixed side) 32. Until the sprue is completely removed from the nesting die (fixed side) 32, the runner and the primary sprue become obstacles, and the nesting die (fixed side) 32 cannot be rotated.
[0008]
In this way, moving the nested die (fixed side) 32 with a long stroke (actually, moving the intermediate plate fitted with the nested die (fixed side) 32) not only lengthens the molding cycle, It is necessary to sufficiently increase the strength of the support pins that hold the plate. This is because the intermediate plate must be supported over a long movement stroke. If it does so, an apparatus will become large and will become impractical.
[0009]
[Problems to be solved by the invention]
A problem to be solved by the present invention is an injection mold having a specification in which a resin molded product is released by rotating a part of a mold, particularly to a rotational sliding surface of a fixed mold. It is to prevent the molten resin from entering, to save the trouble of cleaning and fixing the fixed mold, and to prevent the apparatus from becoming large.
[0010]
[Means for Solving the Problems]
The mold targeted by the present invention is composed of a movable mold and a fixed mold, and a part of the mold is formed on the surface perpendicular to the mold opening direction for releasing the resin molded product molded in the mold. This is a mold for injection molding with a specification that is performed by retreating in the mold opening direction while rotating.
[0011]
In order to solve the above-mentioned problems, an injection molding die for a resin molded product according to the first invention has the following configuration.
First, the movable mold includes a nested pin for forming a through hole in the molded product and a nested mold (movable side) that moves forward and backward in the mold opening direction while rotating around the nested pin.
On the other hand, the fixed side mold includes a nested mold (fixed side) that forms a molding space in cooperation with the movable side mold and moves forward and backward in the mold opening direction while rotating. A rotating sliding portion (not shown) of the nesting die (fixed side) with the fixed side mold is arranged at a position away from the outside of the molding space, and the nesting pin (fixed side) includes the nesting pin. A concave portion opposed to each other with a predetermined gap, a gate portion opening in the concave portion, and a sprue portion connected to the gate portion are arranged at the tip of the gate. The center of rotation of the nesting type (fixed side) is on the axis of the gate portion and the sprue portion.
[0012]
In the mold, the rotation center of the nested mold (fixed side) coincides with the axis of the gate section and the sprue section connected to the gate section. Therefore, after injection molding, if the part including the nesting pin, nesting die (movable side), nesting die (fixed side) is moved slightly away from the injection molding machine and the gate is cut from the molded product, the nesting die ( The molded product can be released from the fixed side mold by moving the fixed side) while rotating on the axis of the gate portion and the sprue portion. Even if the sprue remains in the nesting type (fixed side), there is no problem with the rotation of the nesting type (fixed side). Further, since the rotary sliding portion of the nesting type (fixed side) is located at a position apart from the outside of the molding space, the molten resin does not enter. The nesting type (fixed side) does not need to be moved until the sprue is completely removed from the nesting type (fixed side) 32, and there is no need to increase the strength of the support member for holding it.
Next, the movable mold is retracted in the mold opening direction, and the insert mold (movable side) is rotated in the mold opening direction with the insert pin as an axis. Thus, the molded product is held only by the insert pin and can be easily taken out.
In addition, the protrusion of the cavity which closes the through-hole of a molded article is shape | molded by the nest pin and the recessed part of a nested mold (fixed side) in a molded article. However, this protrusion is not a problem because it can be easily removed by surface polishing of the molded product.
[0013]
The injection mold according to the second invention is such that the movable side mold is a nested pin for forming a through hole in the molded product and a nested mold that moves forward and backward relatively without rotating along the nested pin. (Movable side) and projecting pin of molded product. The fixed side mold has the same configuration as the injection mold in the first invention.
[0014]
When this mold is used, the molded product is released from the fixed mold by the same operation as the mold in the first invention. On the other hand, in the mold release of the movable mold, the insert pin and the insert mold (movable side) are relatively moved without rotating the insert mold (movable side), and the insert pin is removed from the molded product. When the molded product is projected by the projecting pin, the molded product restricted to the nested mold (movable side) can only be rotated, and is detached from the nested mold (movable side) while rotating.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention will be described with respect to an injection mold applied to the molding of the impeller for a pump shown in FIG.
[0016]
First, an embodiment of the invention according to the first invention will be described with reference to FIG.
The movable mold 20 and the fixed mold 30 cooperate to form a molding space. Both parting lines 10 have a central portion 1 and a ring-shaped peripheral edge at the central portion in the thickness direction of the molded product (bent portion having a cross-section "<") at the portion where the undercut shape portion 3 of the molded product is molded. In the part which shape | molds the part 2, it exists in the one-side surface part of a molded article.
[0017]
The movable side mold 20 includes a nested pin 21 for forming the through hole 4 (D hole) in the molded product and a nested mold (movable side) that moves forward and backward in the mold opening direction while rotating around the nested pin 21 as an axis. 22 is included.
On the other hand, the fixed mold 30 includes a nested mold (fixed side) 32 that moves forward and backward in the mold opening direction while rotating. In the nesting die (fixed side) 32, a recessed portion 35 facing the tip of the nesting pin 21 with a predetermined gap, a gate portion 33 opening in the recessed portion 35, and a sprue portion 34 connected to the gate portion 33 are arranged. The center of rotation of the nesting type (fixed side) 32 is on the axis of the gate part 33 and the sprue part 34. The nesting die (fixed side) 32 is fitted and held in an intermediate plate (not shown), but a pin protrudes from the peripheral surface of the cylindrical body of the nesting die (fixed side) 32. The pin is engaged with a guide rail having a parallel part and an inclined part with respect to the mold opening direction independently of the movement of the intermediate plate. When the intermediate plate is moved in the mold opening direction while maintaining the engagement state between the guide rail and the pin, the nesting die (fixed side) 32 rotates in the inclined portion section of the guide rail. Further, another pin is projected from the peripheral surface of the cylindrical body of the nesting die (fixed side) 32, and the other pin is engaged with the peripheral wall of the fitting hole of the intermediate plate into which the nesting die (fixed side) 32 is fitted. The mating spiral (or part of the spiral) is cut to keep the engagement relationship between them. Accordingly, the rotating nested type (fixed side) 32 moves backward or forward. This principle can be applied to the rotation of the nested type (movable side) 22, but the nested type (movable side) 22 has a sufficient degree of spatial freedom to install various rotating means.
[0018]
After injection molding of, for example, a phenol resin using the injection mold as described above, the molded product is released as follows.
First, with the mold closed, the portion including the nesting pin 21, the nesting die (movable side) 22, and the nesting die (fixed side) 32 is injected by a slight stroke (about 1 mm) at which the gate is cut. Move away from the molding machine. Thereafter, the nested mold (fixed side) 32 is rotated in the mold opening direction while rotating. By this operation, the molded product is released from the fixed mold 30. Although the sprue remains in the nesting type (fixed side) 32, the axis of the gate part 33 and the sprue part 34 coincides with the rotation center of the nesting type (fixed side) 32, so the sprue is nesting type (fixed side). The rotation of 32 is not hindered.
Next, the movable mold 20 is retracted in the mold opening direction, and the nested mold (movable side) 22 is rotated around the nesting pin 21 while being retracted in the mold opening direction. Thus, the molded product is held only by the insert pin 21 and can be easily taken out.
[0019]
In the mold described above, the rotational sliding surface of the insert mold (fixed side) 32 is located at a position outside the molding space, that is, at a fitting portion into an intermediate plate (not shown). Therefore, there is no fear that the molten resin injected into the molding space enters the parting line 10 and further enters the fitting portion.
It is preferable that a fluorine resin film is formed on at least one surface of the rotational sliding surfaces of the nesting pin 21 and the nested mold (movable side) 22 so that the clearance of the rotational sliding surface is 5 μm to 30 μm. Smooth rotation sliding is ensured by the presence of the fluororesin coating, while setting the clearance to be narrower than usual to suppress the penetration of the molten resin into the clearance. If the clearance is less than 5 μm, it is difficult to fit into the mold, so a clearance of 5 μm or more is ensured. The fluororesin coating may be formed on either the outer peripheral surface of the nesting pin 21 or the inner peripheral surface of the nesting die (movable side) 22, or may be formed on both. However, if it is formed on at least one peripheral surface of the rotational sliding surface, smooth slidability can be ensured. In addition, it is more convenient for securing the dimensional accuracy to form the fluororesin film on the outer peripheral surface of the nesting pin 21 than on the inner peripheral surface of the nesting die (movable side) 22.
[0020]
In the molding die, the recessed portion 35 of the nesting die (fixed side) 32 where the gate portion 33 opens is opposed to the tip of the nesting pin 21 with a predetermined gap. Since the molten resin is injected into the center position of the molding space and filled toward the periphery, it is possible to manufacture a molded product having no dimensional accuracy and no weld. Due to the nesting pin 21 and the recessed portion 35 of the nesting die (fixed side) 32, a hollow projecting portion that closes the through hole 4 is formed in the molded product. However, this protrusion is a protrusion in a direction that can be removed by surface polishing of the molded product, and the removal operation is easy and does not cause a problem.
[0021]
Next, an embodiment of the invention according to the second invention will be described with reference to FIG.
The movable mold 20 includes a nested pin 21 for forming the through hole 4 in the molded product, a nested mold (movable side) 22 that moves relatively forward and backward without rotating along the nested pin 21, and the molded product. A protruding pin 23 is included. The fixed-side mold 30 has the same configuration as the injection mold in the embodiment of the invention according to the first invention described above.
[0022]
When this mold is used, mold release of the fixed-side mold 20 is performed by the same operation as that described in the embodiment of the invention according to the first invention. On the other hand, the mold release of the movable mold 20 is performed by moving the nesting pin 21 and the nesting mold (movable side) 22 relatively in the mold opening direction without rotating the nesting mold (movable side) 22. The pin 21 is removed from the molded product. When the molded product is projected by the projecting pin 23, the molded product restricted by the nesting die (movable side) 22 can only be rotated, and is detached from the nesting die (movable side) 22 while rotating.
In the embodiment of the invention according to the second invention, it is not necessary to add the rotating means to the nested mold (movable side) 22, and it is only necessary to arrange the protruding pin 23 that advances and retracts in the mold opening direction. , The structure becomes simple.
[0023]
Also in the embodiment of the invention according to the second invention, according to the embodiment of the invention according to the first invention, the sliding surface of the nesting die (movable side) 22, the nesting pin 21 and the protruding pin 23 is provided. It is preferable to form a fluororesin film and keep the sliding surface clearance between 5 μm and 30 μm.
[0024]
The molds described in the embodiments of the above inventions are intended for the molding of a phenol resin molded product having a through hole bent in a “<” shape between adjacent undercut shape portions 3, Instead of the bent through hole, an inclined through hole or an inclined recessed portion may be intended for molding of a resin molded product arranged along an annular ring.
[0025]
【Example】
Using the mold described with reference to FIG. 1 in the embodiment of the present invention, injection molding of a phenol resin molded product was performed (Examples 1 to 3). Table 1 shows the presence / absence of the fluororesin coating on the sliding surface of the movable mold 20 and the clearance of the sliding surface. The clearance of the rotational sliding surface of the nested mold (fixed side) 32 in the fixed mold 30 was set to 40 μm.
[0026]
Using the mold described with reference to FIG. 2 in the embodiment of the present invention, injection molding of a phenol resin molded article was performed (Examples 4 to 6). Table 1 shows the presence / absence of the fluororesin coating on the sliding surface of the movable mold 20 and the clearance of the sliding surface. The clearance of the rotational sliding surface of the nested mold (fixed side) 32 in the fixed mold 30 was set to 40 μm.
[0027]
Moreover, the injection molding of the phenol resin molded product was implemented using the conventional metal mold | die shown in FIG. 4 (conventional examples 1 and 2). The clearances of the rotational sliding surfaces of the fixed nesting die 31 and the nesting die (fixed side) 32 in the fixed die 30 were as shown in Table 1.
[0028]
Furthermore, in the conventional mold shown in FIG. 4, a phenol resin molded product was injection-molded using a mold having a fluororesin film formed on the sliding surface of the stationary mold (Reference Examples 1 and 2). ). The clearances of the rotational sliding surfaces of the fixed nesting die 31 and the nesting die (fixed side) 32 in the fixed die 30 were as shown in Table 1.
[0029]
The number of times that injection molding can be repeated continuously (number of shots) without cleaning the sliding surface of the mold was investigated for each of the movable mold and the fixed mold. The results are shown in Table 1.
[0030]
[Table 1]

[0031]
As is apparent from Table 1, the mold of the embodiment of the present invention can drastically extend the number of continuous shots of the fixed side mold and reduce the number of cleaning work steps. In Examples 1 to 3, since sliding of the movable side mold is a rotational motion, if a large force is applied, damage due to torsion is a concern. On the other hand, in Examples 4 to 6, since the sliding of the movable mold is a linear motion, a large force can be applied to the sliding without worrying about damage to the mold. In Examples 4 to 6, the number of continuous shots of the movable mold can be extended.
[0032]
【The invention's effect】
Conventionally, when it is attempted to perform injection molding of a resin molded product using a mold having a specification for releasing a molded product by rotating a part of the mold, continuous repeated molding is impossible. Thus, by using the metal mold | die which concerns on this invention, the penetration | invasion of the molten resin to the rotation sliding surface of a stationary-side metal mold | die can be prevented over a long period of time. The cleaning of the mold sliding surface may be carried out with emphasis on the movable mold, so that the number of cleaning work steps can be significantly reduced. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a principal part showing an embodiment of an injection mold for a resin molded product according to the present invention.
FIG. 2 is a cross-sectional view of an essential part showing another embodiment of an injection mold for a resin molded product according to the present invention.
FIG. 3 is a partially broken perspective view showing an example of a molded product to be molded by the injection mold according to the present invention.
FIG. 4 is a cross-sectional view of a main part showing a conventional injection mold.
FIG. 5 is a cross-sectional view of a main part showing another conventional injection mold.
[Explanation of symbols]
1 is a central portion 2 is a peripheral portion 3 is an undercut shape portion 10 is a parting line 20 is a movable mold 21 is a nested pin 22 is a nested shape (movable side)
23 is a protruding pin 30 is a fixed mold 31 is a fixed insert mold 32 is a insert mold (fixed side)
33 is a gate part 34 is a sprue part 35 is a concave part

Claims

It consists of a movable side mold and a fixed side mold, and the mold release of the resin molded product molded in the mold is retreated in the mold opening direction while rotating a part of the mold on a plane perpendicular to the mold opening direction. A mold for injection molding with specifications,
The movable side mold includes a nesting pin for forming a through hole in the molded product and a nesting die (movable side) that moves forward and backward while rotating around the nesting pin.
Stationary die includes a nested (fixed side) to move forward and backward while rotating constitute a molding space in cooperation with the movable mold, a fixed mold of the nested (fixed side) The rotary sliding portion is arranged at a position apart from the outside of the molding space, and the nest mold (fixed side) has a recessed portion and a gate opening to the recessed portion facing the tip of the nest pin with a predetermined gap. An injection mold for a resin molded product, characterized in that a sprue portion connected to the gate portion and the gate portion is arranged, and the rotation center of the nesting die (fixed side) is on the axis of the gate portion and the sprue portion.

It consists of a movable side mold and a fixed side mold, and the mold release of the resin molded product molded in the mold is retreated in the mold opening direction while rotating a part of the mold on a plane perpendicular to the mold opening direction. A mold for injection molding with specifications,
The movable mold includes a nested pin for forming a through hole in the molded product, a nested mold (movable side) that relatively moves forward and backward without rotating along the nested pin, and a protruding pin of the molded product.
Stationary die includes a nested (fixed side) to move forward and backward while rotating constitute a molding space in cooperation with the movable mold, a fixed mold of the nested (fixed side) The rotary sliding portion is arranged at a position apart from the outside of the molding space, and the nest mold (fixed side) has a recessed portion and a gate opening to the recessed portion facing the tip of the nest pin with a predetermined gap. An injection mold for a resin molded product, characterized in that a sprue portion connected to the gate portion and the gate portion is arranged, and the rotation center of the nesting die (fixed side) is on the axis of the gate portion and the sprue portion.

The sliding surface of the nesting pin and the nesting type (movable side) is formed with a fluorine resin coating on at least one surface thereof, and the clearance of the sliding surface is set to 5 μm to 30 μm. 2. A mold for injection molding of a resin molded product according to 2.

The mold for injection molding of a resin molded product according to any one of claims 1 to 3, which is used for injection molding of a phenol resin molded product.