JP4290807B2

JP4290807B2 - Insulating paper container

Info

Publication number: JP4290807B2
Application number: JP09834599A
Authority: JP
Inventors: 貢一稲葉
Original assignee: 日本ストロー株式会社
Priority date: 1999-04-06
Filing date: 1999-04-06
Publication date: 2009-07-08
Anticipated expiration: 2019-04-06
Also published as: JP2000289733A

Description

【０００１】
【発明の属する技術分野】
本発明は、即席食品のための包装用容器であって断熱性紙製容器に関する。
【０００２】
【従来の技術】
カップ状の紙製容器本体の外側に上方及び下方共に開口した筒状の外筒を被せ、紙製容器本体と外筒との間に空隙を形成して断熱性をもたせた断熱性紙製容器は、例えば特開平８−１１３２７４号公報並びに登録実用新案第２５７１７９７号公報に開示されて知られている。
上記特開平８−１１３２７４号公報に開示の断熱性紙製容器は、出願人が開発したもので、現在実用化され、市場に多数出回っている。しかし、この断熱性紙製容器は外筒に多数の縦溝を設けてあるから、外筒の表面が平面でなく、容器表面の印刷効果に多少の難がある。
一方、登録実用新案２５７１７９７号公報に開示の断熱性紙製容器は、外筒開口縁に内向きカール部を設け、このカール部を紙製容器本体の下方の側壁外周に接触させてあり、外筒の上方開口内面を紙製容器本体の上部の外向きカール部直下の側壁外周に接触させて構成してある。この断熱性紙製容器は、外筒表面に何らの凹凸も有さないから、印刷効果に優れている。
【０００３】
【発明が解決しようとする課題】
前者の断熱性紙製容器は、上記したように現在実用化され市場に多数出回っているから、この断熱性紙製容器を使っての内容物充填、シール蓋のシール作業等の自動機が稼働している。特にこの自動機に使用されるリテーナーは、前者の断熱性紙製容器即ち紙製容器本体の外側に多数の縦溝を有する外筒を被せて構成してある断熱性紙製容器に適応させてあるから、このリテーナーの寸法は、上記外筒の上部の外径に合わせて決定されている。
従って、この現在稼働している自動機を使用して後者の断熱性紙製容器に内容物を充填し、シール蓋をシールすると、外筒の外径が僅かに小径であるから、リテーナーの寸法に合わないという問題点が生ずる。その結果、リテーナーの位置でガタツキを生じたり、リテーナーの位置で断熱性紙製容器が傾いたりしてリテーナーからの円滑な供給が行われず、シール蓋のシール位置で位置合わせが円滑になされないという問題点がある。
【０００４】
本発明は上記問題点に鑑み、断熱性があることは勿論、外筒表面に凹凸部がなく印刷効果が上がるようにするとともに、現在実際に前者の断熱性紙製容器の内容物充填、シール蓋のシール作業に稼働している自動機に適格に適用できる断熱性紙製容器を提供する。
【０００５】
【課題を解決するための手段】
そのために、本発明では、上方開口縁に外向きフランジを有する紙製容器本体と、上方及び下方を開口させてあって、該容器本体の側面に被せる紙製の外筒とからなり、該外筒の上方及び下方の開口縁に内向きの折り曲げ部を設け、上方開口縁の折り曲げ部を容器本体の上方の側面外周に接触させ、下方開口縁の折り曲げ部を容器本体の下方の側面外周に接触させて、紙製容器本体と外筒との間に空隙を設けてある断熱性紙製容器を提供する。
外筒の上方開口縁の内向き折り曲げ部の厚みの寸法より下方開口縁の内向き折り曲げ部の厚み寸法を大きく形成して、容器本体と外筒との間の上部の空隙より下部の空隙の寸法を大きくしてあるとよい。
また、上記外筒の上方開口縁と下方開口縁の内向き折り曲げ部の何れか一方を容器本体の側面外周に接着してある。
上記外筒の上方開口縁と下方開口縁の内向き折り曲げ部の両方を容器本体の側面外周に接着してあるとよい。
さらに、紙製容器本体の上部に外向きのピーター線を設けてある。
上記ピーター線を外筒内面に接着してあるとよい。
紙製容器本体の中間部に外向きのピーター線を設けてあるとよい。
上記中間部の外向きのピーター線を外筒内面に接着してあるとよい。
上記外筒の上方及び下方の開口縁の内向き折り曲げ部に変えて内向きカール部としてあってもよい。
【０００６】
また、本発明では、上方開口縁に外向きフランジを有する紙製容器本体と、上方及び下方を開口させてあって、該容器本体の側面に被せる紙製の外筒とからなり、該外筒の上方開口縁に内向き折り曲げ部を設け、この上方開口縁の内向き折り曲げ部を容器本体の上方の側面外周に接触させ、下方の開口縁を容器本体の下方の側面外周に接触させて、紙製容器本体と外筒との間に空隙を設けてある断熱性紙製容器を提供する。
容器本体の底の周壁を垂直または下方が僅かに外向きに広がる構成として、この底部においても外筒との間に空隙を設けてあるとよい。
上記外筒の上方開口縁の内向きの折り曲げ部と外筒の下方開口縁の何れか一方を容器本体の側面外周に接着してある。
上記外筒の上方開口縁の内向きの折り曲げ部と外筒の下方開口縁の両方を容器本体の側面外周に接着してあるとよい。
紙製容器本体に外向きのピーター線を設けてある。
上記ピーター線を外筒内面に接着してあるとよい。
上記外筒の上方開口縁の内向き折り曲げ部に変えて内向きカール部としてあってもよい。
【０００７】
【発明の実施の形態】
本発明の実施の形態を図面に基づいて説明する。
図１乃至図４に外筒の上方及び下方の両方の開口縁に内向きの折り曲げ部を設けた実施例を示してあり、図５乃至図７に外筒の上方の開口縁にのみ内向きの折り曲げ部を設けた実施例を示してある。
【０００８】
図中１がカップ形状の紙製容器本体で、胴部２の上方開口縁にカールした外向きフランジ３を設け、底４を有する。この紙製容器本体１の上部には、即席食品の食用時に入れる湯量の目安となる水域にピーター線５を外向き突条によって形成してある。また、胴部２はカップ形状であるから上方が広がるテーパー状となっているが、底４の周壁６は傾斜がなく垂直としてある。
後述する外筒に厚い紙を用い強度がある場合は必要ないが、外筒に薄い紙を用いる場合には、図４に示すように紙製容器本体の高さの中間位置に上記ピーター線５とは別のピーター線７を設けるとよい。
この紙製容器本体１の胴部２には、坪量２００ｇ／ｍ² の原紙に内面にポリエチレンあ押し出しラミネートした紙が用いられる。
また、底４には坪量２００ｇ／ｍ² 〜３００ｇ／ｍ² の原紙に内面又は両面にポリエチレンを押し出しラミネートした紙が用いられる。
【０００９】
図中１０が、上方及び下方を開口させてあって、上方に向けて僅かに広がる略中空円筒状からなり、上記紙製容器本体１の側面に被せてある外筒で、胴部１１の上方及び下方の開口縁に、内向きの折り曲げ部１２及び１３を設けて構成してある。この内向きの折り曲げ部は、上方の内向き折り曲げ部１２の厚みの寸法より下方の内向き折り曲げ部１３の厚みの寸法を大きく形成してある。この内向きの折り曲げ部１２，１３に変えて内向きのカール部にしてもよい。
この外筒１０には、表面の印刷適性を良好とするために、片面コートしたコート紙、コートボール紙、アート紙が好ましく、坪量１６０ｇ／ｍ² 〜４５０ｇ／ｍ² の原紙が用いられる。
【００１０】
本発明断熱性紙製容器は、上記紙製容器本体１の側面に上記外筒１０を被せてあり、上方の開口縁の内向き折り曲げ部１２を容器本体１の上方の側面外周に接触させ、下方の開口縁の折り曲げ部１３を容器本体１の下方の側面外周に接触させてあって、紙製容器本体１と外筒１０との間に空隙１５を設けてある。
外筒１０を容器本体１に一体化させるために、上記上方及び下方の開口縁の内向き折り曲げ部１２と１３の何れか一方を容器本体１の側面外周に接着剤により接着してもよいし、両方を接着してもよい。
同様に、容器本体１のピーター線５と７の何れか一方又は両方を外筒１０内面に接着させてもよい。
上記上方の内向き折り曲げ部１２の厚み寸法より下方の内向き折り曲げ部１３の厚み寸法を大きくしてあるから、容器本体１と外筒１０との間に形成される空隙１５は、その上方より下方の方が幅が大きく構成されている。
【００１１】
図５〜図７で示した実施例で図１〜図４に示した実施例と同じ符号を付したものは同じものである。この実施例では、外筒１０を構成する胴部１１の下方には折り曲げ部を設けてなく、この折り曲げ部のない開口縁１７を容器本体の下部の外周面に接触させてあり、この部分を接着させてもよい。この実施例では、空隙１５において下方より上方の方が空隙の幅が大きく構成されるが、図６に示すように容器本体１の底４の周壁６を垂直又は下方が僅かに外向きに広がる構成とすれば、下方においてもある程度の幅の空隙１５をもてる上で効果的である。
【００１２】
【実施例】
胴部２に坪量２８０ｇ／ｍ² の原紙に内面に厚さ２５ミクロンのポリエチレンを押し出しラミネートした紙を使用し、底に坪量２５０ｇ／ｍ² の原紙に外面に厚さ１５ミクロンのポリエチレンを押し出しラミネートし、また原紙の内面に厚さ３０ミクロンのポリエチレンを押し出しラミネートした紙を使用して紙容器本体１を作成し、外筒１０に外面印刷した坪量３５０ｇ／ｍ² で紙厚が０．４５ｍｍのコートボール紙を使用し、上方の開口縁の内向き折り曲げ部の厚みを１．２ｍｍとし、下方の開口縁の内向き折り曲げ部の厚みを２．０５ｍｍにして断熱性紙製容器を作成した。
この構成の紙製容器に即席ラーメンを収め、熱湯を上方ピーター線まで注入したところ、手で把持することができるだけの断熱性を発揮した。
そしてこの断熱性紙製容器の実施例を現在稼働している自動機で充填、蓋シール作業をしたが、そのリテーナーに充分適格に適合し、良好な作業性を得た。
【００１３】
【発明の効果】
叙上の如く、本発明断熱性紙製容器では、紙製容器本体と外筒とからなり、該外筒の少なくとも上方開口縁に内向きの折り曲げ部を設け、この折り曲げ部を紙製容器本体の上方の側面外周に接触させて、紙製容器本体と外筒との間に空隙を設けてあるから、印刷効果がよく、しかも断熱性のある紙製容器を得ることができた。
しかも、外筒上方開口縁に内向きの折り曲げ部を設けてあるから、現在既に稼働している自動機のリテーナーにも適格に適合し、リテーナーの寸法を変えることなく適用できる効果を有する。
【図面の簡単な説明】
【図１】外筒の上方及び下方開口縁に内向きの折り曲げ部を設けた本発明断熱性紙製容器の実施例の断面図
【図２】図１上Ａ部の拡大断面図
【図３】図１上Ｂ部の拡大断面図
【図４】紙製容器本体の中間部にピーター線を設けた実施例の断面図
【図５】外筒の上方開口縁のみに内向き折り曲げ部を設けた本発明断熱性紙製容器の実施例の断面図
【図６】図５上Ｃ部の拡大断面図
【図７】図５に示した本発明断熱性紙製容器の紙製容器本体の中間部にピーター線を設けた実施例の断面図
【符号の説明】
１紙製容器本体
２胴部
３外向きフランジ
４底
５ピーター線
６底の周壁
７ピーター線
１０外筒
１１胴部
１２折り曲げ部
１３折り曲げ部
１５空隙[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a packaging container for instant foods and to a heat insulating paper container.
[0002]
[Prior art]
A heat-insulating paper container having a heat insulating property by covering the outer side of the cup-shaped paper container body with a cylindrical outer cylinder that opens both upward and downward, and forming a gap between the paper container body and the outer cylinder. Are disclosed in, for example, Japanese Patent Laid-Open No. 8-113274 and Registered Utility Model No. 2571797.
The heat insulating paper container disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-113274 has been developed by the applicant, and is currently put into practical use and is widely available on the market. However, since this heat insulating paper container is provided with a large number of longitudinal grooves in the outer cylinder, the surface of the outer cylinder is not flat and there is some difficulty in the printing effect on the container surface.
On the other hand, the heat insulating paper container disclosed in the registered utility model No. 2571797 has an inwardly curled portion at the opening edge of the outer cylinder, and this curled portion is brought into contact with the outer periphery of the lower side wall of the paper container main body. The inner surface of the upper opening of the cylinder is configured to be in contact with the outer periphery of the side wall immediately below the outwardly curled portion at the top of the paper container body. This heat insulating paper container is excellent in printing effect because it does not have any irregularities on the outer cylinder surface.
[0003]
[Problems to be solved by the invention]
As mentioned above, the former heat-insulating paper containers are currently put into practical use and are on the market, so automatic machines such as filling the contents using the heat-insulating paper containers and sealing the seal lid are in operation. is doing. In particular, the retainer used in this automatic machine is adapted to the former heat-insulating paper container, that is, the heat-insulating paper container which is configured by covering an outer cylinder having a number of vertical grooves on the outside of the paper container body. Therefore, the dimensions of the retainer are determined in accordance with the outer diameter of the upper portion of the outer cylinder.
Therefore, if the automatic machine that is currently in operation is used to fill the latter heat-insulating paper container with the contents and seal the seal lid, the outer diameter of the outer cylinder is slightly smaller. The problem that it does not fit is caused. As a result, rattling occurs at the position of the retainer, or the insulating paper container is tilted at the position of the retainer, and smooth supply from the retainer is not performed, and alignment is not smoothly performed at the seal position of the seal lid. There is a problem.
[0004]
In view of the above problems, the present invention has heat insulation as well as the surface of the outer cylinder so that the printing effect is improved and the contents of the former heat insulating paper container are actually filled and sealed. To provide a heat-insulating paper container that can be properly applied to an automatic machine operating for lid sealing.
[0005]
[Means for Solving the Problems]
For this purpose, the present invention comprises a paper container main body having an outward flange at the upper opening edge, and a paper outer cylinder that is open on the upper and lower sides and covers the side surface of the container main body. Inwardly bent portions are provided at the upper and lower opening edges of the cylinder, the bent portion of the upper opening edge is brought into contact with the outer periphery of the upper side of the container body, and the bent portion of the lower opening edge is set at the outer periphery of the lower surface of the container body. Provided is a heat-insulating paper container in which a space is provided between the paper container main body and the outer cylinder.
The thickness dimension of the inward bent portion of the lower opening edge is made larger than the thickness dimension of the inward bent portion of the upper opening edge of the outer cylinder, and the lower gap of the upper gap between the container body and the outer cylinder is formed. The dimensions should be large.
In addition, either one of the upper opening edge and the inward bent portion of the lower opening edge of the outer cylinder is bonded to the outer periphery of the side surface of the container body.
Both the upper opening edge of the outer cylinder and the inwardly bent portion of the lower opening edge may be bonded to the outer periphery of the side surface of the container body.
Furthermore, an outwardly facing Peter line is provided at the upper part of the paper container main body.
The Peter wire may be bonded to the inner surface of the outer cylinder.
An outwardly facing Peter line may be provided in the middle part of the paper container body.
It is preferable that the outwardly facing Peter wire of the intermediate portion is bonded to the inner surface of the outer cylinder.
Instead of the inwardly bent portions of the upper and lower opening edges of the outer cylinder, an inwardly curled portion may be provided.
[0006]
Further, the present invention comprises a paper container main body having an outward flange at the upper opening edge, and a paper outer cylinder that is open on the upper and lower sides and covers the side surface of the container main body. An inwardly bent portion is provided at the upper opening edge of the upper opening edge, the inwardly bent portion of the upper opening edge is brought into contact with the outer periphery of the upper side of the container body, and the lower opening edge is brought into contact with the outer periphery of the lower side surface of the container body, Provided is a heat insulating paper container in which a gap is provided between a paper container main body and an outer cylinder.
As a configuration in which the peripheral wall at the bottom of the container main body extends vertically or slightly outwardly, a gap may be provided between the bottom portion and the outer cylinder.
One of the inwardly bent portion of the upper opening edge of the outer cylinder and the lower opening edge of the outer cylinder is bonded to the outer periphery of the side surface of the container body.
Both the inwardly bent portion of the upper opening edge of the outer cylinder and the lower opening edge of the outer cylinder may be bonded to the outer periphery of the side surface of the container body.
An outwardly facing Peter wire is provided on the paper container body.
The Peter wire may be bonded to the inner surface of the outer cylinder.
Instead of the inwardly bent portion of the upper opening edge of the outer cylinder, an inwardly curled portion may be provided.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIGS. 1 to 4 show an embodiment in which inwardly bent portions are provided at both upper and lower opening edges of the outer cylinder, and FIGS. 5 to 7 show inward directions only at the upper opening edge of the outer cylinder. The example which provided the bending part of this is shown.
[0008]
In the figure, reference numeral 1 denotes a cup-shaped paper container main body, which is provided with an outward flange 3 curled on the upper opening edge of the body portion 2 and has a bottom 4. On the upper part of the paper container main body 1, a Peter wire 5 is formed by outward protrusions in a water area that serves as a measure of the amount of hot water to be put into the instant food. Moreover, since the trunk | drum 2 is a cup shape and becomes the taper shape which upper direction spreads, the surrounding wall 6 of the bottom 4 is not inclined and is vertical.
This is not necessary when thick paper is used for the outer cylinder, which will be described later, and there is strength. However, when thin paper is used for the outer cylinder, the Peter line 5 is placed at the middle position of the paper container body as shown in FIG. A different Peter line 7 may be provided.
The body 2 of the paper container body 1 is made of paper obtained by extruding and laminating polyethylene on the inner surface of a base paper having a basis weight of 200 g / m ² .
Also, paper laminated with extruded polyethylene on the inner surface or both surfaces of a base paper having a basis weight of 200g / m ^² ~300g / m ² is used for the bottom 4.
[0009]
In the figure, reference numeral 10 denotes an outer cylinder that has an open top and bottom and has a substantially hollow cylindrical shape that slightly extends upward, and is placed on the side surface of the paper container body 1. Further, inwardly bent portions 12 and 13 are provided at the lower opening edge. The inward bent portion is formed so that the thickness dimension of the lower inward bent portion 13 is larger than the thickness dimension of the upper inward bent portion 12. Instead of the inward bent portions 12 and 13, an inwardly curled portion may be used.
This outer cylinder 10, in order to improve the printability of the surface, coated paper was one-side coated, coated cardboard, art paper is preferred, the base paper having a basis weight of 160g / m ^² ~450g / m ² is used.
[0010]
The heat-insulating paper container of the present invention covers the outer cylinder 10 on the side surface of the paper container main body 1, the inwardly bent portion 12 of the upper opening edge is brought into contact with the outer peripheral surface of the upper side of the container main body 1, A bent portion 13 at the lower opening edge is brought into contact with the outer periphery of the lower side surface of the container body 1, and a gap 15 is provided between the paper container body 1 and the outer cylinder 10.
In order to integrate the outer cylinder 10 into the container body 1, either one of the inwardly bent portions 12 and 13 of the upper and lower opening edges may be adhered to the outer periphery of the side surface of the container body 1 with an adhesive. Both may be glued together.
Similarly, either or both of the Peter wires 5 and 7 of the container body 1 may be bonded to the inner surface of the outer cylinder 10.
Since the thickness dimension of the inward bent portion 13 below is larger than the thickness dimension of the upper inward bent portion 12, the gap 15 formed between the container body 1 and the outer cylinder 10 is from above. The lower part has a larger width.
[0011]
In the embodiment shown in FIGS. 5 to 7, the same reference numerals as those in the embodiment shown in FIGS. In this embodiment, a bent portion is not provided below the trunk portion 11 constituting the outer cylinder 10, and the opening edge 17 without the bent portion is brought into contact with the outer peripheral surface of the lower portion of the container body, and this portion is It may be adhered. In this embodiment, the gap 15 is configured to have a larger width at the upper side than the lower side. However, as shown in FIG. 6, the peripheral wall 6 of the bottom 4 of the container body 1 is spread vertically or slightly outward. This configuration is effective in providing a gap 15 having a certain width even in the lower part.
[0012]
【Example】
The base ^{2 is} a base paper with a basis weight of 280 g / m ^{2 and} a laminate of polyethylene with a thickness of 25 microns is used on the inner surface. The bottom is a base paper with a basis weight of 250 g / m ² and a polyethylene with a thickness of 15 microns on the outer surface. The paper container body 1 was made using paper that was extruded and laminated with polyethylene having a thickness of 30 microns on the inner surface of the base paper, and the paper thickness was 0 at a basis weight of 350 g / m ² printed on the outer cylinder 10. Using a 45 mm coated cardboard, the thickness of the inwardly bent portion of the upper opening edge is 1.2 mm, and the thickness of the inwardly bent portion of the lower opening edge is 2.05 mm. Created.
Immediate ramen was placed in a paper container of this configuration, and hot water was poured up to the upper Peter line. As a result, heat insulation that could be grasped by hand was exhibited.
The embodiment of the heat insulating paper container was filled and covered with an automatic machine that is currently in operation. The container was adequately qualified for the retainer, and good workability was obtained.
[0013]
【The invention's effect】
As described above, the heat insulating paper container of the present invention comprises a paper container main body and an outer cylinder, and is provided with an inwardly bent portion at least at the upper opening edge of the outer cylinder. Since a space is provided between the paper container main body and the outer cylinder in contact with the upper outer periphery of the paper, a paper container having good printing effect and heat insulation could be obtained.
In addition, since an inwardly bent portion is provided at the upper opening edge of the outer cylinder, it can be applied to a retainer of an automatic machine that is already in operation and can be applied without changing the dimensions of the retainer.
[Brief description of the drawings]
1 is a cross-sectional view of an embodiment of the heat-insulating paper container according to the present invention in which an inward bent portion is provided at the upper and lower opening edges of an outer cylinder. FIG. 2 is an enlarged cross-sectional view of an upper portion A in FIG. 1 is an enlarged cross-sectional view of the upper B portion of FIG. 1. FIG. 4 is a cross-sectional view of an embodiment in which a Peter wire is provided in the middle of the paper container body. FIG. 5 is provided with an inward bent portion only at the upper opening edge of the outer cylinder. FIG. 6 is an enlarged cross-sectional view of the upper part C of FIG. 5. FIG. 7 is an intermediate view of the paper container body of the heat-insulating paper container of the present invention shown in FIG. Sectional view of an embodiment in which a Peter wire is provided in the section [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Paper container main body 2 trunk | drum 3 outward flange 4 bottom 5 Peter wire 6 bottom peripheral wall 7 Peter line 10 outer cylinder 11 trunk | drum 12 bending part 13 bending part 15 space | gap

Claims

A paper container main body having an outward flange at an upper opening edge, and a paper outer cylinder that opens on the upper and lower sides and covers the side surface of the container main body. The upper and lower openings of the outer cylinder An inwardly bent portion is provided at the edge, the bent portion of the upper opening edge is brought into contact with the outer peripheral surface of the upper side of the container body, and the bent portion of the lower opening edge is brought into contact with the outer peripheral surface of the lower side of the container main body. A gap is provided between the main body and the outer cylinder, and the thickness dimension of the inwardly bent portion of the lower opening edge is larger than the thickness dimension of the inwardly bent portion of the upper opening edge of the outer cylinder, A heat insulating paper container characterized in that the size of the lower gap is larger than the upper gap between the outer cylinder .

The heat-insulating paper container according to claim 1, wherein either one of the upper opening edge and the inward bent portion of the lower opening edge of the outer cylinder is bonded to the outer periphery of the side surface of the container body.

The heat-insulating paper container according to claim 1, wherein both the upper opening edge and the inward bent portion of the lower opening edge of the outer cylinder are bonded to the outer periphery of the side surface of the container body.

The heat insulating paper container according to any one of claims 1 to 3 , wherein an outwardly facing Peter wire is provided on an upper portion of the paper container main body.

The heat insulating paper container according to claim 4, wherein the Peter wire is bonded to the inner surface of the outer cylinder.

The heat insulating paper container according to any one of claims 1 to 5 , wherein an outward Peter wire is provided in an intermediate portion of the paper container main body.

The heat insulating paper container according to claim 6 , wherein an outwardly facing Peter wire of the intermediate portion is bonded to the inner surface of the outer cylinder.

The heat-insulating paper container according to any one of claims 1 to 7 , wherein the inwardly curled portion is formed as an inwardly curled portion instead of the inwardly bent portion of the upper and lower opening edges of the outer cylinder.