JP2004042965A

JP2004042965A - Bottle-shaped can

Info

Publication number: JP2004042965A
Application number: JP2002203569A
Authority: JP
Inventors: Shigeru Noto; 野戸　滋; Minoru Kanehara; 兼原　稔; Yasushi Enoki; 榎木　泰史
Original assignee: Daiwa Can Co Ltd
Current assignee: Daiwa Can Co Ltd
Priority date: 2002-07-12
Filing date: 2002-07-12
Publication date: 2004-02-12
Anticipated expiration: 2022-07-12
Also published as: JP4229650B2

Abstract

<P>PROBLEM TO BE SOLVED: To effectively strengthen a trunk, whose wall thickness is made thinner than that of a shoulder and a neck, using less metal, of a bottle-shaped can of which a mouth, shoulder, trunk, and neck (and flange) are formed integrally. <P>SOLUTION: An intermediate molded product of the bottle-shaped can is a bottom-attached cylindrical can whose trunk has a wall thickness thinned by a ironing process. On the bottom-attached cylindrical can, a mouth having a small diameter and a sloped shoulder are formed on the bottom side of the can, a neck is formed near the opening end of the trunk, and a separate bottom lid is wound-tightened and fixed to a flange formed on the opening edge of the neck. A part near the upper end, close to the shoulder, of the cylindrical trunk, whose wall thickness is thinner than that of the shoulder and neck, the wall thickness of the can is not reduced sharply from the lower end of the shoulder to a certain point, beyond which the wall thickness is reduced sharply until it becomes identical with that of the thinner part. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、しごき加工により胴部が薄肉化された有底円筒缶の中間成形品から、その缶底側が小径の口頸部と傾斜した肩部に成形され、その胴部の開口端付近がネック部に成形され、ネック部の開口端縁に成形されたフランジ部に別体の底蓋が巻締め固着されるボトル型缶に関し、特に、そのようなボトル型缶における胴部の壁厚構造に関する。
【０００２】
【従来の技術】
近年、絞りしごき加工等により胴部が薄肉化されたシームレス缶（側面無継目缶）による飲料用の缶容器として、リシール（再封鎖）が可能なようにキャップが装着されるネジ付きで小径の口頸部を有し、口頸部と胴部の間が滑らかなドーム状の肩部に成形されて、胴部の下端側（即ち、胴部の下端開口付近をネック部に成形し、ネック部の下端開口縁をフランジ部に成形した、そのフランジ部）に別体の底蓋が巻締め固着されたボトル型缶が、本出願人により既に商品化されて市場を賑わすようになっている。
【０００３】
そのようなボトル型缶の製造については、例えば、予め金属板（アルミニウム合金板）の両面に保護被膜となる熱可塑性樹脂層をラミネートした樹脂被覆金属板を材料として、樹脂被覆金属板のブランクからカップ状を経て側壁部（胴部）が薄肉化された有底円筒缶の中間成形品に一体成形してから、その缶底側を小径の口頸部と傾斜した肩部に一体成形し、更に、口頸部にカール部やネジ部を成形すると共に、その胴部（中間成形品の側壁部）の開口端付近にネックイン加工とフランジ加工を施してネック部とフランジ部を成形した後、別体の底蓋をフランジ部に巻締め固着することで、キャップが装着される前のボトル型缶を形成している（特開２００１−１５８４３６号公報，特開２００１−１６２３４４号公報等参照）。
【０００４】
【発明が解決しようとする課題】
ところで、上記のように製造されるボトル型缶では、ネック・フランジ加工（ネックイン加工とフランジ加工）を施したり、底蓋を巻締め固着する際に、缶体に対して垂直方向（軸方向）で大きな荷重が作用することになる。すなわち、口頸部や肩部が成形された後で、胴部（中間成形品の側壁部）の開口端付近にネック・フランジ加工を施したり、フランジ部と底蓋を巻締め固着したりするためには、口頸部の側を下にして保持部材により肩部を保持した状態で行わなければならないが、その際に、具体的には、ネック・フランジ加工を施す際には約１２００Ｎの成形荷重が缶体の軸方向に作用し、底蓋を巻締める際には約８００Ｎの巻締め荷重が缶体の軸方向に作用することとなる。
【０００５】
そのため、そのような口頸部の側を下にした加工の際に、図４に示すように、傾斜面となっている肩部を保持部材６０により保持した状態では、荷重が作用する方向に対して缶体の軸線Ｘを垂直に保持することが難しく、缶体の芯ずれを起こし易くなって、その結果、荷重方向に対して缶体が垂直方向からずれていると、偏荷重が作用して、胴部と肩部の間の変曲部で挫屈したり、缶体が傾いて保持部材が胴部に接触した部分でデント（凹み）が発生したりする虞がある。
【０００６】
また、多数のボトル型缶を連続的に搬送するような際に、缶体同士が接触することによって、胴部の上端付近（肩部に近接する部分）でデントが発生する虞があって、そのように缶体の胴部にデントが発生していると、内容物を充填してからキャップを装着する際に、口頸部の側を上にした状態で上方から約１１００Ｎの軸方向荷重が作用することから、デントが発生している部分で挫屈が起きる虞がある。なお、デントの発生については、それが挫屈にまで至らなくても、缶の美観を損ねることで商品価値を落とす要因となっている。
【０００７】
缶体同士の接触により胴部の上端付近でデントが発生する理由について説明すると、絞りしごき加工により胴部を引き伸ばして薄肉化したＤＩ缶では、一般的に、引き伸ばされた胴部の中央部が内方に収縮して外径が小さくなる（円筒状に極めて近い鼓状になる）傾向があることが判っており、ボトル型缶の場合にも同様の現象が見られることから、多数のボトル型缶を連続的に搬送するような際には、円筒状の胴部の上下両端付近（肩部やネック部の近傍）で缶体同士が接触することとなる。
【０００８】
その結果、口頸部や肩部が成形された後で、底蓋が巻締められる前の缶体の搬送時には、缶体の下端部は未だ開口された状態にあるため、この付近で缶体同士が接触しても、缶体が撓んで弾性変形するためにデントは発生し難いが、胴部上端の肩部近傍では、肩部が成形を受けて剛性を有しているため、缶体同士が接触するとデントが発生する虞がある。なお、底蓋を巻締めた後の缶体の搬送時では、缶体の下端部付近で撓み変形ができなくなるため、胴部下端のネック部近傍でも、缶体同士の接触によってデントが発生する虞がある。
【０００９】
また、底蓋が巻締められる前の缶体の搬送時では、底蓋を巻締めた後の搬送時と比較して、缶体の重心が高い位置にあって缶体が傾き易いため、一方の缶体の肩部と他方の缶体の胴部上端の肩部近傍とが接触し易く、それが胴部の上端付近でデントが発生し易い要因にもなっており、特に、肩部が半球面状のドーム形状に成形されている場合には、接触部が略点状となって接触面積が小さいため、部分的に缶体が受ける応力が大きくなってデントが発生し易くなる。
【００１０】
なお、搬送時の缶体の傾きについて、従来の２ピース缶では、缶体を直立状態で搬送する場合に、缶体が傾いて転倒することを防止する目的で、缶体の上端開口部の上方に平板状のガイドを設けることがあって、そのように開口部の直上に所定の隙間を空けて平板状のガイドを設けた場合、開口部の直径が大きいため、比較的僅かな傾きで、傾いた缶体の開口部がガイドに接触して、傾いた缶体は直立状態に戻るため、缶体の転倒が防止される。
【００１１】
これに対して、ボトル型缶の場合には、上端開口部（口頸部上端）の直径が小さく、傾きによる高さの変化が小さいため、缶体の上方に平板状のガイドを設けて傾いた缶体をガイドに接触させようとすると、ガイドと口頸部上端との隙間を非常に小さくすることが必要となることから、ガイドを設置する際の高さの管理が難しく、しかも、ボトル型缶では缶体の重心が高い位置にあるため、缶体が傾いた状態で口頸部がガイドに接触すると、逆に缶体の転倒を誘発することになる。そのため、従来から２ピース缶で使用されているような転倒防止用のガイドは、設置が難しく且つ効果も薄いことから使用されないことが多く、従って、ボトル型缶の場合には、搬送中に傾いた缶体がそのまま周囲の缶体に接触することが多くなり、このこともボトル型缶においてデントの発生を増加させる一因となっている。
【００１２】
上記のようなデントや挫屈の発生に対して、材料として使用する金属板を厚くしてボトル型缶の成形を行えば、成形された缶体の胴部の壁厚が一様に増加して強度が向上することから、デントや挫屈の発生を防止できるものの、壁厚の変更によって一缶当たりに必要な金属量が増加するため、製造コストが高くなるという新たな問題が生じることになる。
【００１３】
この点に関して、通常、大量に消費される飲料用の容器では、一缶当たりで数グラム、金額にして数十銭の材料コスト削減は、大きな製造費用の合理化となるため、缶体としての性能を維持しながら、できるだけ少ない金属量で缶体を製造することが要求されており、ボトル型缶においても、その製造工程や求められる性能を充分に考慮した上で、缶体の壁厚を適正化し、経済性の高い製品を製造することが求められている。
【００１４】
本発明は、上記のような問題の解消を課題とするものであり、具体的には、口頸部と肩部と胴部とネック部（及びフランジ部）が一体成形されるボトル型缶において、肩部やネック部よりも薄肉化される胴部を、少ない金属量で効果的に強化できるようにすることを課題とするものである。
【００１５】
【課題を解決するための手段】
本発明は、上記のような課題を解決するために、しごき加工により胴部が薄肉化された有底円筒缶の中間成形品から、その缶底側が小径の口頸部と傾斜した肩部に成形され、その胴部の開口端付近がネック部に成形され、ネック部の開口端縁に成形されたフランジ部に別体の底蓋が巻締め固着されるボトル型缶において、肩部やネック部よりも壁厚が薄くなっている円筒状の胴部の肩部に近い上端近傍部分で、肩部の下端から所定の範囲までは壁厚を大きく減少させることなく、その範囲を過ぎてから壁厚を急激に薄壁部分にまで減少させていることを特徴とするものである。
【００１６】
上記のような構成によれば、胴部の全体を一様に厚肉化するのではなく、肩部に近い胴部の上端近傍部分で、特にデントや挫屈が発生し易い所定の範囲だけを厚肉化して、その他をできる限り薄壁部分としているため、胴部の肩部近傍でのデントや挫屈の発生を防止できると共に、胴部の上端近傍部分で厚肉化のために使用する金属量をできる限り削減することができる。
【００１７】
【発明の実施の形態】
以下、本発明のボトル型缶の実施形態について、図面に基づいて詳細に説明する。なお、本発明の一実施形態に係るボトル型缶について、図１は、外観形状を示し、図２は、製造工程の全体を概略的に示し、図３は、トップドーム成形工程で口頸部と肩部を成形する状態を示し、図４は、ネック・フランジ成形工程や缶蓋巻締工程での缶体の保持状態を示し、図５は、実施例での壁厚分布を示し、図６は、カップから中間成形品（有底円筒缶）を成形する際に使用するパンチの形状を示し、図７は、実施例の中間成形品（有底円筒缶）での壁厚分布を示すものである。また、図８は、ボトル型缶の従来例での壁厚分布を示し、図９は、従来例の中間成形品（有底円筒缶）での壁厚分布を示すものである。
【００１８】
本実施形態のボトル型缶１では、図１に示すように、大径円筒状の胴部４から上方に、縦断面が円弧状のドーム形状（外方に突出する半球面状）の肩部３を介して、小径円筒状の口頸部２が一体的に成形されており、胴部４の円筒下端部に続くネック部５の下端（ネック部５の下端開口縁に形成されたフランジ部）には、金属製で別部材の底蓋６が巻き締め固着されていて、ネジが形成された口頸部２には、図示していないが、缶内に飲料が充填された後で、周知のキャップ装着装置（キャッパー）によって、金属製で別部品のキャップがリシール（再封鎖）可能なように装着される。
【００１９】
このボトル型缶１の口頸部２と肩部３と胴部４とネック部５（及びフランジ部）は、金属板の両面に保護被膜となる熱可塑性樹脂層が形成された樹脂被覆金属板から一体成形されており、そのような樹脂被覆金属板としては、厚さが０．２２〜０．３５ｍｍのアルミニウム合金板の両面に、厚さが８〜３０μｍのポリエステル樹脂，ポリプロピレン樹脂等の熱可塑性樹脂フィルムが予めラミネートされた樹脂被覆アルミニウム合金板を使用することができる。
【００２０】
なお、樹脂被覆金属板の基材となるアルミニウム合金板としては、通常の缶の製造に用いるものであれば特に限定されるものではなく、例えば、日本工業規格（ＪＩＳ）に規定する３００４系アルミ合金，３１０４系アルミ合金等を使用することができる。また、金属板の両面で保護被膜となる熱可塑性樹脂についても、通常の缶体の製造に用いるものであれば特に限定されるものではなく、例えば、耐熱性，耐内容物性が良好で、缶の用途に適した熱可塑性ポリエステル樹脂フィルムを使用することができる。
【００２１】
樹脂被覆金属板の基材となるアルミニウム合金板の板厚については、０．３５ｍｍ以上にしても、必要以上に無駄な材料コストが増えるだけであり、一方、０．２２ｍｍ以下にすると、缶体を成形する段階での肩部のシワや胴部のデント等による不良缶の発生が増加して逆にコストの増加に繋がってしまうことから、０．２２〜０．３５ｍｍの範囲内とするのが適当である。また、金属板の両面で保護被膜となる熱可塑性樹脂層の厚さについては、材料コストの点からは薄いほど好ましいが、その厚さが８μｍを下回ると被覆性能が低下して、特に、缶内面側では、内容物を充填した際に、内容物が樹脂層に浸透して金属板を腐食させる虞があることから、コスト面を考慮すると、８〜３０μｍの範囲内とするのが適当である。
【００２２】
そのような観点から、ボトル型缶の製造に好適に使用される樹脂被覆金属板について、その具体的な一例を挙げると、厚さ０．３２ｍｍのアルミニウム合金板に対して、その缶外面側に厚さ１２μｍの熱可塑性樹脂フィルムをラミネートし、その缶内面側に厚さ２５μｍの熱可塑性樹脂フィルムをラミネートした樹脂被覆アルミニウム合金板がある。
【００２３】
そのような樹脂被覆金属板からボトル型缶を製造するための製造工程の一例について説明すると、先ず、缶の成形に入る前に、樹脂被覆金属板の両面に熱可塑性樹脂層の上から、例えば、ノルマルブチルステアレート，流動パラフィン，ペトロラタム，ポリエチレンワックス等の適宜の潤滑剤を予め塗布しておいてから、図２に示すように、カップ成形工程で、樹脂被覆金属板を円板状に打ち抜いたブランクを絞り加工してカップ形状に成形し、缶胴成形工程で、カップに絞りしごき加工を施す（少なくとも一回以上の再絞り加工やストレッチ加工の後でしごき加工を施す、或いは、２回の再絞り加工のうちの１回でストレッチ加工を施し、その後、しごき加工を施す）ことで、カップよりも胴部が小径で薄肉化された有底円筒状の缶を中間成形品として製造する。
【００２４】
次いで、中間成形品である有底円筒缶に対して、トップドーム成形工程で、その缶底側を複数回の絞り加工によって肩部と未開口の口頸部に成形する。このトップドーム成形工程について詳しく説明すると、本実施形態では、図３に示すように、中間成形品の有底円筒缶に対して、その缶底側を上にした状態で、先ず、缶底コーナー部を肩部曲面（肩部の下部となる曲面）３１に予備成形してから、この肩部曲面をダイ５１とプッシャー５２によるシワ押さえ工具によってシワ押さえした状態で、平坦な缶底２１をパンチ５３により有底円筒缶の側壁部（胴部４）よりも小径の有底円筒状に絞り成形する。
【００２５】
なお、缶底コーナー部を肩部曲面（肩部の下部）に予備成形する方法としては、缶胴成形工程で有底円筒缶の中間成形品に成形した後で、その缶底コーナー部をトップドーム成形工程の前に再成形するようにしても良く、また、缶胴成形工程で有底円筒缶を成形する際に、缶胴成形用パンチの先端の周辺形状を縦断面円弧状とすることで、缶胴成形と同時に成形するようにしても良い。更には、肩部の成形性に問題がなければ、そのような予備成形を行うことなく、トップドーム成形工程で、ダイとプッシャーによるシワ押さえ工具によって肩部曲面を成形すると共に、そのままの状態でパンチにより缶底を小径の有底円筒状に絞り成形するようにしても良い。
【００２６】
次いで、新たに絞り成形された有底円筒部２２について、予備成形された肩部曲面（肩部の下部）３１に続く仮想曲面の断面円弧に近似した断面直線形状のテーパー面を持つシワ押さえ工具（ダイ５４とプッシャー５５）により、有底円筒部の底コーナー部をシワ押さえした状態で、パンチ５６により更に小径の有底円筒状に絞り成形し、そのような絞り加工をもう１度繰り返すことで、有底円筒部２３の径を口頸部２の径と略同じになるまで縮径してから、絞り加工の繰り返しにより当初の肩部曲面（肩部の下部）３１に続いて形成された肩部の複数のテーパー面３２，３３を、肩部曲面３１から延びる仮想曲面の形状を持つ一対の成形工具（ダイ５７とプッシャー５８）により押し延ばしすることで、連続した滑らかな曲面に再成形（リフォーム）する。
【００２７】
更に、図２に示すように、肩部を再成形（リフォーム）した後のトップドーム成形工程の最終段階で、有底円筒状に成形された口頸部に対して２回の口絞り成形を施した後、潤滑剤除去工程で、口頸部が未開口で胴部下端が開口された缶の少なくとも外面から潤滑剤を除去し、トリミング工程で、口頸部とは反対側の胴部の開口端側をトリミングして缶を所定の長さにしてから、印刷・塗装工程で、円筒状の胴部に対して所望のデザイン（文字や装飾模様等）を印刷した上からトップコートを塗布し、乾燥工程で、印刷インキ層やトップコート層を充分に乾燥させると共に、保護被膜の熱可塑性樹脂層を非晶質化しておく。
【００２８】
なお、ボトル型缶の円筒状の胴部に対して所望のデザイン（文字や装飾模様等）を付与するための工程については、上記のような胴部の外面に直接に印刷と塗装を順次に施すような印刷・塗装工程に限らず、予め印刷インキ層やトップコート層が形成された印刷済みの樹脂フィルムを熱接着による貼着で胴部外面にラミネートするような印刷済み樹脂フィルム貼着工程としても良い。
【００２９】
次いで、ネジ・カール成形工程において、先ず、未開口の口頸部の先端閉鎖部をトリミングすることで口頸部を開口させてから、その開口端部を外巻きで環状のカール部に成形し、その円筒状周壁にキャップ螺合用のネジを成形し、ネジ形成部分の下方にビード部を形成する。次いで、図４に示すように、口頸部の側を下にして肩部を保持部材６０により保持した状態で、ネック・フランジ成形工程において、図示していないが、口頸部とは反対側となる胴部（中間成形品の側壁部）の開口端付近に対してネック・フランジ加工（ネックイン加工とフランジ加工）を施すことで、胴部の円筒下端部に続くようにネック部（図１に示した形状に限らず、多段形状のネック部に形成しても良い）とフランジ部を形成する。
【００３０】
そして、底蓋巻締工程において、図示していないが、シーマー（缶蓋巻締機）により、ネック・フランジ成形の場合と同様に、口頸部の側を下にして肩部を保持した状態で、樹脂被覆金属板からなる別部材の底蓋を、胴部の円筒下端部に続くネック部の下端開口縁に成形されたフランジ部に対して、二重巻き締め法により一体的に固着することで、図１に示すようなキャップ（図示せず）が装着される前のボトル型缶（胴部の印刷デザインは省略）が製造される。
【００３１】
なお、上記のように製造されたボトル型缶では、通常、缶内に飲料を充填した後で、周知のキャップ装着装置（キャッパー）により、金属製で別部品のキャップを口頸部に装着しているが、このキャップ装着（キャッピング）については、一般的には、キャップを口頸部に被せて上から押さえ付けながらキャップの側壁を口頸部のネジ部にロールで半径方向に押し付けて変形させることでキャップにネジ部を成形しながら装着している。（そのようなキャップの装着時には、口頸部の上方から最大で約１１００Ｎ程度の垂直荷重が作用することになる。）
【００３２】
ところで、上記のように製造されるボトル型缶については、製造時の成形性という観点から、缶体の各部分の壁厚を元板厚（成形前の樹脂被覆金属板の板厚）からどの程度まで薄くできるかということが検討されており、その結果、以下のようなことが既に判っている。
【００３３】
口頸部については、中間成形品である有底円筒缶の缶底部（元板厚と略同じ厚さ）から複数回の絞り加工により縮径されているため、口頸部の壁厚は、縮径により壁厚が増加する効果と、パンチで軸方向に引き伸ばされて壁厚が減少する効果との両方によって決まることになるが、縮径による壁厚増加の効果の方が比較的大きいため、中間成形品である有底円筒缶の缶底部の壁厚（元板厚と略同じ）と略等しくなるか、又は、それよりも少し厚くなる。
【００３４】
胴部については、カップ形状から有底円筒缶の中間成形品に成形される際に、しごき加工によって薄肉化されるが、両面に熱可塑性樹脂層がラミネートされた樹脂被覆金属板をしごき加工する場合、しごき加工による加工率を高くして一定の壁厚以下に薄肉化すると、表面にラミネートされた熱可塑性樹脂層が損傷してしまう虞がある。使用する熱可塑性樹脂の種類にもよるが、一般的には、胴部の壁厚を元板厚に対して３２％以下に薄くすると、熱可塑性樹脂層の損傷が激しくなって製品として不適当なものとなる。
【００３５】
肩部については、中間成形品である有底円筒缶において、しごき加工を受けて薄肉化された側壁部（有底円筒缶の胴部）のうちの缶底部に近い部分を肩部曲面（その後の工程で肩部の下部となる部分）に予備成形しているが、この部分の壁厚は、缶底部の壁厚（元板厚と略同じ厚さ）の６０％以上の厚さを有することが必要であって、元板厚の６０％以上の厚みがないとシワが発生するということが本発明者らの研究により判っている。
【００３６】
すなわち、肩部は、ダイとプッシャーによるシワ押さえ工具によりシワ押さえした状態で、再絞り用ポンチによる絞り加工と再絞り加工を繰り返すことにより成形されることから、そのような絞り加工を受ける前の中間成形品の有底円筒缶において、缶底部に近い部分の側壁部（肩部曲面に成形される部分）の壁厚と缶底部の板厚との差が大きい場合、ダイとプッシャーは板厚の大きい缶底部のみを押さえつけることとなり、シワ押さえが有効に働かず、板厚の薄い側壁部でシワが発生し易くなる。
【００３７】
ネック部（及びフランジ部）については、しごき加工を受けて薄肉化された中間成形品の側壁部（有底円筒缶の胴部）の開口端付近にネックイン加工（及びフランジ加工）を施すことにより成形されるものであり、中間成形品の側壁部（有底円筒缶の胴部）において、その開口端付近のネック成形部（ネックイン加工とフランジ加工が施される部分）は、その後に施されるネックイン加工やフランジ加工の際にシワや割れが発生しない壁厚が必要である。
【００３８】
そのため、中間成形品の側壁部（有底円筒缶の胴部）のうちのネック成形部については、その他の部分（ボトル型缶で円筒状の胴部として残る部分）と比べて、薄肉化の程度を小さくする（壁厚を厚くする）ことが必要である。このネック成形部の壁厚は、０．１６ｍｍ以上の厚さがあれば、ネック・フランジ加工の際にシワや割れが発生しないような良好な成形性が得られる。
【００３９】
上記のように製造時の成形性の観点から各部分の壁厚が検討された上で製造されるボトル型缶について、従来のボトル型缶では、ネック・フランジ加工が施される前の状態で、各部分の壁厚分布は、図８に示すように、元板厚と同じ（又は僅かに厚い）壁厚の口頸部から下方に続く肩部では、その壁厚が肩部の上端（口頸部との接続部）から下端（胴部との接続部）に向けて徐々に薄くなり、肩部の下端に続く胴部では、肩部の下端から急激に壁厚が減少して薄壁部分になってからネック成形部まで壁厚が殆ど変わることなく、ネック成形部では、壁厚が漸増する部分を経てから肩部の下端よりも僅かに厚い壁厚となっている。
【００４０】
なお、図８に示した従来例は、具体的には、厚さが０．３２ｍｍのアルミニウム合金板の内外両面に、外面で厚さが１２μｍとなり内面で厚さが２５μｍとなるように、それぞれ熱可塑性樹脂層をラミネートした樹脂被覆アルミニウム合金板（元板厚は０．３５７ｍｍ）から缶体（底蓋の部分を除く）が一体成形された、内容量が５００ｍｌのボトル型缶によるものである。
【００４１】
そのような壁厚分布を有する従来のボトル型缶では、既に述べたように、ネック・フランジ加工や底蓋巻締めの際に、胴部の肩部に近い部分でデントや挫屈が発生したり、或いは、底蓋巻締め前の缶体の搬送中に、缶体同士の接触によって胴部の肩部に近い部分でデントが発生したりする虞があり、更に、底蓋巻締め後の缶体の搬送中には、胴部のネック部に近い部分でもデントが発生するという問題がある。
【００４２】
これに対して、本実施形態のボトル型缶では、上記の従来例と同じ材料で同じ大きさに製造されるボトル型缶による実施例において、ネック・フランジ加工が施される前の状態で、各部分の壁厚分布は、図５に示すようなものとなっている。すなわち、胴部の肩部に近い上端近傍部分において、図８に示した従来例のボトル型缶では、肩部の下端から直ちに薄壁部分にまで急激に壁厚が減少しているのに対して、図５に示した実施例のボトル型缶では、肩部の下端から下方に所定の範囲までは壁厚が大きく減少することなく、その範囲を過ぎてから壁厚が急激に薄壁部分にまで減少している。
【００４３】
また、胴部の中央付近から下方の部分において、図８に示した従来例のボトル型缶では、ネック成形部（ネック・フランジ加工が施される部分）まで壁厚が殆ど変わることなく薄壁部分が続いていて、ネック成形部に入ってから壁厚が急激に増加しているのに対して、図５に示した実施例のボトル型缶では、薄壁部分からネック成形部に向けて壁厚が徐々に厚くなっている。
【００４４】
なお、上記のようにボトル型缶の各部分を所定の壁厚分布とするための手段については、例えば、中間成形品である有底円筒缶をカップから成形するための絞りしごき加工において、各部分の壁厚分布に対応した形状を備えたパンチを使用することで、その後の成形を経て製造されるボトル型缶の各部分を所定の壁厚分布とすることができる。
【００４５】
すなわち、本実施形態のボトル型缶を製造する場合には、カップから中間成形品の有底円筒缶を成形する際に使用するパンチを、図６に示すような形状としており（図示した形状は、実際の寸法関係に基づくものではなく、極端な形で模式的に示すものである）、そのような形状のパンチを使用して、図７に示すような壁厚分布を有する中間成形品（有底円筒缶）を製造すれば、その後の成形加工（トップドーム成形加工）を施すことで、図５に示すような壁厚分布を有する実施例のボトル型缶を製造することができる。なお、図８に示すような壁厚分布を有する従来例のボトル型缶では、その中間成形品（有底円筒缶）の壁厚分布は、図９に示すようなものとなっている。
【００４６】
上記のような壁厚分布を有する本実施形態のボトル型缶によれば、肩部に近い胴部の上端近傍部分で、特にデントや挫屈が発生し易い所定の範囲だけを厚肉化して、それ以外の部分を直ちに薄壁部分としていることから、胴部の全体を一様に厚肉化する場合と比べて、胴部で使用する金属量を削減することができるのは勿論のこと、例えば、肩部の下端から胴部の中央に向けて壁厚を徐々に薄くするような場合と比べても、胴部の上端近傍部分で厚肉化のために使用する金属量をできる限り削減することができて、しかも、胴部の肩部近傍でデントや挫屈が発生するのを防止するのに充分な強度を得ることができる。
【００４７】
また、本実施形態のボトル型缶によれば、中間成形品の側壁部のうちの底部に近い部分における板厚を元板厚に対して６０％以上に維持することで、肩部の成形性を良好に保っていると共に、外方に突出する半球面状のドーム形状に形成された肩部の壁厚を、口頸部との接続部分で最大となり、胴部との接続部分で最小となり、その中間の領域では最大壁厚部から最小壁厚部へ向けて徐々に壁厚が薄くなるようにしていることから、少ない材料で経済的に効率良く肩部の強度を維持することができる。
【００４８】
また、本実施形態のボトル型缶によれば、胴部の中央付近から下方で、胴部の薄壁部分からネック部に向けて徐々に壁厚を厚くしていることで、胴部のネック部近傍が厚肉化されていることから、底蓋巻締め後の缶体の搬送中に缶体同士が接触しても、缶体同士の接触による胴部のネック部近傍でのデントの発生を経済的且つ効果的に防止することができる。
【００４９】
この点について、肩部に近い胴部の上端近傍部分では、剛性の高い肩部との接触によるデントの発生を防止するために比較的厚い壁厚が必要であり、しかも、デントの発生箇所が比較的狭い範囲であるため、胴部上端側（肩部から下方）の厚肉部をなだらかなテーパー状に形成すると、不必要な部分まで壁厚を増加させることになり、また、肩部近傍でのデントは、底蓋が巻締められる前の不安定な状態で搬送された時に発生することが多く、できるだけ缶体上部の重量を増加させないようにする必要があることから、胴部の上端近傍部分（肩部近傍）の厚肉部については、なだらかなテーパー状に形成するのは適切でなく、既に述べたように、デントや挫屈が発生し易い所定の範囲だけを厚肉化して、それ以外の部分を直ちに薄壁部分とするのが効果的である。
【００５０】
これに対して、底蓋巻締め後には、缶体下部の開口端が底蓋の巻締めにより固定されるため、缶体下部が剛性を有するようになり、そのような状態では、缶体の安定性が増すため、搬送時に胴部の上端近傍部分（肩部近傍）におけるデントの発生は少なくなり、逆に、缶体下部が剛性を有するようになることで、缶体同士の接触や搬送経路のガイド等との接触により、胴部の中央付近から下方の比較的広い領域でデントが発生し易くなる。
【００５１】
そのような胴部の中央付近から下方の領域において、胴部の下端付近（ネック部近傍）では、巻締められた底蓋との接触によりデントが発生するため、その防止のために比較的壁厚を厚くする必要があるが、それから上方に胴部中央付近までは、底蓋との接触は殆どなく、缶体の胴部同士が互いに接触したり、搬送経路のガイドと接触したりすることでデントが発生するため、その発生を防止するために必要な壁厚は比較的小さくて良いことから、本実施形態では、上記のように胴部の中央付近から下方で、胴部の薄壁部分からネック部に向けて徐々に壁厚を厚くしており、そのようにすることが、缶重量の軽減や缶体成形の容易さを考慮すると、デントの発生を防止する上で最も経済的且つ効果的であると言える。
【００５２】
ところで、上記のような本実施形態のボトル型缶について、胴部の肩部近傍でデントが発生するのを防止できるという点に関して、具体的な実施例と従来例とにより効果の違いを確認するための実験を行った。
【００５３】
すなわち、ボトル型缶の缶体材料となる樹脂被覆アルミニウム合金板については、製缶上の問題や耐腐食性や材料コスト等の観点から、アルミニウム合金板の厚さは０．２２〜０．３５ｍｍの範囲が適当であり、また、保護被膜として被覆する熱可塑性樹脂層の厚さは８〜３０μｍの範囲が適当であることは既に述べた通りであるが、そのような樹脂被覆アルミニウム合金板の範囲内で、アルミニウム合金板の厚さが異なる材料から製造された各実施例（１〜３）と各従来例（１〜３）のボトル型缶（缶容量５００ｍｌ）のそれぞれ（各例毎に５００缶ずつ）について実験を行った。
【００５４】
各実施例（１〜３）については、図５に示すようなパターン（各実施例で壁厚の具体的な数値は異なる）の壁厚分布を有するものであって、各実施例（１〜３）の何れにおいても、肩部の下端（肩部と胴部の境界位置）での壁厚が、成形前の樹脂被覆金属板の板厚の５３％の厚さとなり、肩部の下端から下方に１０ｍｍまでの範囲の壁厚の平均値が、成形前の樹脂被覆金属板の板厚の５０％となっていて、その範囲を過ぎてから壁厚が急激に減少して、胴部の薄壁部分での壁厚は、成形前の樹脂被覆金属板の板厚の３８％の厚さとなっている。
【００５５】
なお、肩部の下端から下方に１０ｍｍまでの範囲（壁厚の平均値が成形前の樹脂被覆金属板の板厚の５０％となっている厚肉部）では、壁厚が僅かずつ徐々に薄くなっているが、この範囲の開始位置での壁厚が、樹脂被覆金属板の板厚の５３％であり、この範囲の終了位置での壁厚が、樹脂被覆金属板の板厚の４９％であって、この範囲の缶体高さ方向の距離が１０ｍｍであることから、壁厚減少率（％）を、〔（範囲開始位置での壁厚−範囲終了位置の壁厚）／範囲の缶体高さ方向の距離〕×１００の式によって求めると、壁厚減少率は約０．１％となっている。
【００５６】
これに対して、肩部下端から下方に１０ｍｍの位置から薄壁部分までの急激に壁厚が減少する範囲では、この範囲の開始位置での壁厚が、樹脂被覆金属板の板厚の４９％であり、この範囲の終了位置での壁厚が、樹脂被覆金属板の板厚の３８％であって、この範囲の缶体高さ方向の距離が８ｍｍであることから、上記のような式によって求められる壁厚減少率（％）は約０．５％となっており、肩部の下端から下方に１０ｍｍまでの範囲（厚肉部）での壁厚減少率（約０．１％）と比較して約５倍の大きさとなっていて、壁厚の減少が急激になっている。
【００５７】
各従来例（１〜３）については、図８に示すようなパターン（各従来例で壁厚の具体的な数値は異なる）の壁厚分布を有するものであって、各従来例（１〜３）の何れにおいても、肩部の下端（肩部と胴部の境界位置）での壁厚が、成形前の樹脂被覆金属板の板厚の４９％の厚さとなり、肩部の下端から直接的に壁厚が急激に減少して、胴部の薄壁部分での壁厚は、成形前の樹脂被覆金属板の板厚の３８％の厚さとなっている。そのため、肩部の下端から下方に７ｍｍまでの範囲の壁厚の平均値は、成形前の樹脂被覆金属板の板厚の４２％となっている。
【００５８】
上記のように壁厚分布のパターンが異なる実施例と従来例の、成形前の樹脂被覆金属板のアルミニウム合金板の厚さが異なる１〜３の各例のそれぞれ（各例毎に５００缶）について、実際に製造ライン上で搬送させて、胴部の肩部近傍でデントが発生した缶（不良缶）の有無を調べた結果、以下の表１に示すように、各従来例（１〜３）では、胴部の肩部近傍でデントが発生した缶（不良缶）が見られたのに対して、各実施例（１〜３）では、胴部の肩部近傍でデントが発生した缶（不良缶）は全く見られなかった。なお、表１において、（Ａ）は、アルミニウム合金板の厚さを示し、（Ｂ）は、熱可塑性樹脂層の厚さを示し、（Ａ＋Ｂ）は、樹脂被覆アルミニウム合金板の板厚を示すものである。
【００５９】
【表１】

【００６０】
上記の表１に示した各実施例（１〜３）については、成形前の樹脂被覆金属板のアルミニウム合金板の厚さ（０．２５〜０．３５ｍｍ）がそれぞれ異なっているものの、それぞれの樹脂被覆金属板の板厚（元板厚）に対して、肩部の下端（肩部と胴部の境界位置）から下方に１０ｍｍまでの範囲の壁厚の平均値を元板厚の５０％としていることによって、何れの実施例（１〜３）においても、従来例（１〜３）と比べて僅かに缶質量を大きくするだけで、胴部の肩部近傍が充分に強化されて当該部分でデントが発生しないものとなっている。
【００６１】
さらに、上記のようなボトル型アルミ缶だけでなく、ボトル型スチール缶についても、以下のような実施例と従来例のそれぞれ（各例毎に５００缶ずつ）について、上記のアルミ缶の場合と同様の実験を行った（なお、何れも缶容量５００ｍｌで、樹脂被膜の厚さや、実施例における肩部の下端から下方に続く厚肉部の範囲については上記のアルミ缶の場合と同様である）。
【００６２】
〔実施例〕
成形前の樹脂被覆金属板の元板厚が０．２６６ｍｍ、肩部下端（肩部と胴部の境界位置）での壁厚が１４１μｍ（元板厚の５３％）、肩部の下端から下方に続く厚肉部での壁厚の平均値が１３３μｍ（元板厚の５０％）、胴部の薄壁部分での壁厚が１０３μｍ（元板厚の３９％）、缶質量が４３．９ｇ。
〔比較例〕
成形前の樹脂被覆金属板の元板厚が０．２６６ｍｍ、肩部下端（肩部と胴部の境界位置）での壁厚が１１２μｍ（元板厚の４２％）、胴部の薄壁部分での壁厚が１０３μｍ（元板厚の３９％）、缶質量が４２．６ｇ。
上記のような実施例と従来例による実験の結果、実施例では不良缶の発生がなかったのに対して、従来例では、３缶の不良缶が発生した。
【００６３】
なお、肩部の下端の壁厚を元板厚に対してどの程度の割合にするか、胴部の上端近傍部分で、肩部の下端から下方にどれだけの範囲を厚肉部にするか、また、その範囲（厚肉部）での壁厚を元板厚に対してどの程度の割合にするか等については、上記の具体的な数値が一応の目安になるものの、それに限定されるものではなく、若干の幅があるものであって、その幅についても、成形前の樹脂被覆金属板の板厚（金属板の厚さ）や金属材質の違いによって、若干の相違があるものと考えられる。
【００６４】
この点に関して、例えば、厚さが０．３２ｍｍのアルミニウム合金板の内外両面に、外面で厚さが１２μｍとなり内面で厚さが２５μｍとなるように、それぞれ熱可塑性樹脂層をラミネートした樹脂被覆アルミニウム合金板（従来から広く使用されている元板厚が０．３５７ｍｍの樹脂被覆アルミニウム合金板）から製造されるボトル型缶について、更に詳しく検討した結果、そのようなボトル型缶に限っては以下のようなことが判った。
【００６５】
すなわち、肩部の下端から下方に２０ｍｍの範囲で、肩部下端からの壁厚の平均値が元板厚の４５％以上（コスト上からは４５〜５５％）であれば問題はないが、肩部下端からの壁厚の平均値が元板厚の４５％以下（具体的な実験例では４３％）であると、胴部の肩部近傍でデントが発生する虞があることが判った。
【００６６】
また、肩部の下端から下方に続く厚肉部（肩部下端から下方に所定の範囲の胴部）の壁厚平均値が元板厚の５０％となるようにした場合でも、肩部の下端から下方に７ｍｍ以上（コスト上からは７〜２０ｍｍ）の範囲まで厚肉部となっていれば問題はないが、厚肉部の範囲が肩部の下端から６ｍｍ以下（具体的な実験例では６ｍｍ）であると、胴部の肩部近傍でデントが発生する虞があることが判った。
【００６７】
また、肩部の下端から下方に７ｍｍ以上の範囲まで厚肉部となるようにした場合でも、肩部下端から下方に続く厚肉部（肩部下端から下方に所定の範囲の胴部）の壁厚の平均値が元板厚の４５％以上となっていれば問題はないが、この厚肉部の壁厚の平均値が元板厚の４５％以下（具体的な実験例では４３％）であると、胴部の肩部近傍でデントが発生する虞があることが判った。
【００６８】
そのようなことから、厚さが０．３２ｍｍのアルミニウム合金板に対して、その外面で厚さが１２μｍとなり、その内面で厚さが２５μｍとなるように熱可塑性樹脂層をラミネートした樹脂被覆アルミニウム合金板（元板厚が０．３５７ｍｍ）から製造されるボトル型缶、或いは、これに近い板厚の樹脂被覆アルミニウム合金板から製造されるボトル型缶については、肩部の下端から下方に７〜２０ｍｍまでの範囲で、その壁厚の平均値を元板厚の４５％以上として、その範囲を過ぎてから壁厚を急激に薄壁部分にまで減少させることで、材料コストをできるだけ削減した上で、胴部の肩部近傍でデントが発生するのを確実に防止することができるものと考えられる。
【００６９】
なお、胴部における肩部近傍の厚肉部（肩部下端から下方に続く厚肉部）と薄肉部分との間の、壁厚が急激に減少する範囲においては、壁厚減少率が小さすぎる（壁厚の減少が緩やかである）と、デントの発生し易い部分のみを厚肉化することで缶体に使用する金属量をできる限り減らすという本発明の目的からして、その作用効果が小さくなることから、この範囲における壁厚減少率（％）、即ち、〔（範囲開始位置での壁厚−範囲終了位置の壁厚）／範囲の缶体高さ方向の距離〕×１００については、０．２％以上であることが望ましい。
【００７０】
以上、本発明のボトル型缶の一実施形態について説明したが、本発明は、上記の実施形態に限られるものではなく、例えば、材料となる金属板材については、上記の実施形態に示したような樹脂被覆アルミニウム合金板に限らず、従来から知られた製缶用の適宜の金属板材による場合でも適用可能であり、肩部の形状や成形方法についても、上記の実施形態に示したような肩部全体を半球面状のドーム形状に成形するような場合に限らず、適宜の成形方法により適宜の形状（例えば、肩部に段部が形成された形状等）に成形して実施することも可能である等、適宜設計変更可能なものであることは言うまでもない。
【００７１】
【発明の効果】
以上説明したような本発明のボトル型缶によれば、缶体の製造時や搬送時に、薄肉化された胴部の肩部近傍でデントや挫屈が発生するのを、胴部に使用する金属量をできるだけ削減した上で、効果的に防止することができる。
【図面の簡単な説明】
【図１】ボトル型缶の外観形状を示す部分切欠き側面図。
【図２】図１に示したボトル型缶を製造するための製造工程の一例を概略的に示す説明図。
【図３】図２に示した製造工程のトップドーム成形工程での口頸部と肩部の成形状態を示す側面と断面による説明図。
【図４】図２に示した製造工程のネック・フランジ成形工程や缶蓋巻締工程での缶体の保持状態を示す部分断面側面図。
【図５】本発明のボトル型缶の一実施例について、ネック・フランジ加工が施される前の状態での各部分の壁厚分布を示すグラフ。
【図６】本発明のボトル型缶について、カップから中間成形品（有底円筒缶）を成形する際に使用するパンチの形状を模式的に示す側面図。
【図７】図５に示した壁厚分布を有する実施例のボトル型缶について、その中間成形品（有底円筒缶）での各部分の壁厚分布を示すグラフ。
【図８】ボトル型缶の従来例について、ネック・フランジ加工が施される前の状態での各部分の壁厚分布を示すグラフ。
【図９】図８に示した壁厚分布を有する従来例のボトル型缶について、その中間成形品（有底円筒缶）での各部分の壁厚分布を示すグラフ。
【符号の説明】
１　　　ボトル型缶
２　　　口頸部
３　　　肩部
４　　　胴部
５　　　ネック部[0001]
BACKGROUND OF THE INVENTION
The present invention is an intermediate molded product of a bottomed cylindrical can whose body has been thinned by ironing, and the bottom of the can is molded into a small-diameter mouth neck and an inclined shoulder, and the vicinity of the opening end of the trunk is The present invention relates to a bottle-shaped can that is molded into a neck portion, and a separate bottom lid is fastened and fixed to a flange portion that is formed at the opening edge of the neck portion. In particular, the wall thickness structure of the trunk portion in such a bottle-shaped can About.
[0002]
[Prior art]
In recent years, as a beverage can container with a seamless can (side seamless joint) whose body has been thinned by squeezing and ironing, etc., it has a small diameter with a screw attached to a cap so that it can be resealed (resealed) It has a mouth and neck and is molded into a smooth dome-shaped shoulder between the mouth and neck and the torso. The lower end of the torso (that is, the vicinity of the lower end opening of the torso is formed in the neck, A bottle-shaped can with a separate bottom lid is fastened and fastened to the flange part) with the lower end opening edge of the part formed into a flange part. .
[0003]
For manufacturing such a bottle-shaped can, for example, a resin-coated metal plate in which a thermoplastic resin layer as a protective coating is laminated on both surfaces of a metal plate (aluminum alloy plate) in advance is used as a material. After integrally molding into an intermediate molded product of a bottomed cylindrical can whose side wall (trunk) has been thinned through a cup shape, the bottom of the can is integrally molded with a small-diameter neck and neck and an inclined shoulder, Furthermore, after molding the curled part and the threaded part in the mouth and neck part, and forming the neck part and the flange part by performing neck-in processing and flange processing in the vicinity of the opening end of the trunk part (side wall part of the intermediate molded product) The bottle-shaped can before the cap is mounted is formed by winding and fixing the separate bottom lid to the flange portion (see JP 2001-158436 A, JP 2001-162344 A, etc.). ).
[0004]
[Problems to be solved by the invention]
By the way, in the bottle-type can manufactured as described above, when the neck / flange processing (neck-in processing and flange processing) is performed or the bottom lid is wound and fixed, the vertical direction (axial direction) with respect to the can body ) Will cause a large load. In other words, after the mouth and neck and shoulders are molded, neck flange processing is performed near the open end of the body (side wall portion of the intermediate molded product), and the flange portion and the bottom lid are wound and fixed. In order to achieve this, the shoulder and neck must be held by the holding member with the mouth-and-neck side facing down. In this case, specifically, when performing neck and flange processing, about 1200 N is required. The forming load acts in the axial direction of the can body, and when the bottom lid is wound, a winding load of about 800 N acts in the axial direction of the can body.
[0005]
Therefore, in the state where the shoulder portion which is the inclined surface is held by the holding member 60, as shown in FIG. On the other hand, it is difficult to hold the axis X of the can body vertically, and the can body is easily misaligned. As a result, if the can body is deviated from the vertical direction with respect to the load direction, an unbalanced load acts. Then, there is a possibility that the inflection portion between the trunk portion and the shoulder portion may be bent, or a dent (dent) may be generated at a portion where the can body is inclined and the holding member is in contact with the trunk portion.
[0006]
In addition, when continuously transporting a large number of bottle-shaped cans, there is a risk that dents may occur near the upper end of the trunk (portion close to the shoulder) by contacting the cans, When dents are generated in the body of the can, the axial load of about 1100 N from above with the mouth and neck side up when the cap is mounted after filling the contents. Because of this, there is a possibility that buckling may occur in the portion where the dent is generated. In addition, the occurrence of dents is a factor that reduces the value of products by deteriorating the beauty of cans, even if they do not become cramped.
[0007]
The reason why dents are generated near the upper end of the barrel due to contact between the cans will be explained. In a DI can that has been thinned by drawing and squeezing and squeezing, generally, the center of the stretched barrel is It is known that the outer diameter tends to shrink and the outer diameter tends to be small (it becomes a drum shape very close to a cylindrical shape), and the same phenomenon can be seen in the case of bottle-shaped cans. When the mold cans are continuously conveyed, the cans come into contact with each other in the vicinity of the upper and lower ends of the cylindrical body (near the shoulder and the neck).
[0008]
As a result, the bottom end of the can is still open when the can is transported after the mouth neck and shoulders are molded and before the bottom lid is wound, so the can Even if they are in contact with each other, the can body is bent and elastically deformed, so it is difficult for dents to occur, but in the vicinity of the shoulder portion at the upper end of the body portion, the shoulder portion is molded and has rigidity, so the can body If they come into contact with each other, dents may occur. In addition, when the can body is transported after the bottom lid is wound, dents are generated due to contact between the can bodies even near the neck portion at the lower end of the body portion because it becomes impossible to bend and deform near the lower end portion of the can body. There is a fear.
[0009]
Also, when the can body is transported before the bottom lid is wound, the can body is easy to tilt because the center of gravity of the can body is at a higher position than when transporting after the bottom lid is wound. The shoulder of the can body and the vicinity of the shoulder at the upper end of the body of the other can easily come into contact with each other. In the case of being formed into a hemispherical dome shape, the contact portion is substantially dot-shaped and the contact area is small, so that the stress received by the can partially increases and dents are likely to occur.
[0010]
In addition, about the inclination of the can body at the time of conveyance, in the case of the conventional two-piece can, when the can body is conveyed in an upright state, for the purpose of preventing the can body from tilting and falling, There is a case where a flat guide is provided above, and when the flat guide is provided with a predetermined gap just above the opening, the diameter of the opening is large, so that the inclination is relatively slight. Since the tilted can body comes into contact with the guide and the tilted can body returns to the upright state, the can body is prevented from falling.
[0011]
On the other hand, in the case of a bottle-type can, since the diameter of the upper end opening (mouth neck upper end) is small and the change in height due to the tilt is small, a flat guide is provided above the can body and tilted. When the can body is brought into contact with the guide, it is necessary to make the gap between the guide and the upper end of the mouth and neck part very small, so it is difficult to manage the height when installing the guide, and the bottle Since the center of gravity of the can body is high in the mold can, if the can and the neck portion comes into contact with the guide while the can body is tilted, the can body may be inverted. For this reason, the guide for preventing overturn, which has been conventionally used in a two-piece can, is often not used because it is difficult to install and has a low effect. Therefore, in the case of a bottle-type can, it is inclined during conveyance. The can body often comes into contact with the surrounding can body as it is, and this also contributes to an increase in the generation of dents in the bottle-type can.
[0012]
If the metal plate used as a material is made thicker and the bottle-shaped can is molded against the occurrence of dents and buckling as described above, the wall thickness of the body of the molded can body increases uniformly. Although the strength is improved, the occurrence of dents and buckling can be prevented, but the amount of metal required per can increases by changing the wall thickness, resulting in a new problem of increased manufacturing costs. Become.
[0013]
In this regard, in the case of containers for beverages that are usually consumed in large quantities, the material cost reduction of several grams per can, and several tens of thousands of dollars, can rationalize the manufacturing cost, so the performance as a can body It is required to produce cans with as little metal as possible while maintaining the same, and even for bottle-shaped cans, the wall thickness of the cans is set appropriately after fully considering the production process and required performance. There is a need to manufacture products that are economical and highly economical.
[0014]
An object of the present invention is to eliminate the above-described problems. Specifically, in a bottle-type can in which a mouth-and-neck portion, a shoulder portion, a trunk portion, and a neck portion (and a flange portion) are integrally formed. It is an object of the present invention to make it possible to effectively reinforce a body portion that is thinner than a shoulder portion or a neck portion with a small amount of metal.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an intermediate molded product of a bottomed cylindrical can whose body has been thinned by ironing, and the bottom of the can has a small diameter neck and neck and an inclined shoulder. In a bottle-shaped can, the shoulder part or neck of the bottle part can be molded, the vicinity of the opening end of the body part is formed in the neck part, and a separate bottom lid is wound and fixed to the flange part formed on the opening edge of the neck part In the vicinity of the upper end near the shoulder of the cylindrical body that is thinner than the wall thickness, the wall thickness is not greatly reduced from the lower end of the shoulder to the predetermined range, and after that range is exceeded. The wall thickness is rapidly reduced to a thin wall portion.
[0016]
According to the above configuration, the entire body portion is not uniformly thickened, but only in a predetermined range where dents and buckling are likely to occur particularly in the vicinity of the upper end of the body portion near the shoulder portion. , And other parts are made as thin as possible, preventing dents and buckling from occurring in the vicinity of the shoulder of the torso and being used for increasing the thickness in the vicinity of the upper end of the torso The amount of metal to be reduced can be reduced as much as possible.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the bottle-shaped can of the present invention will be described in detail with reference to the drawings. In addition, about the bottle-shaped can which concerns on one Embodiment of this invention, FIG. 1 shows external appearance shape, FIG. 2 shows the whole manufacturing process schematically, FIG. 4 shows the state of molding the shoulder, FIG. 4 shows the holding state of the can body in the neck flange forming process and the can lid winding process, and FIG. 5 shows the wall thickness distribution in the embodiment. 6 shows the shape of the punch used when forming the intermediate molded product (bottom cylindrical can) from the cup, and FIG. 7 shows the wall thickness distribution in the intermediate molded product (bottom cylindrical can) of the example. Is. FIG. 8 shows the wall thickness distribution in the conventional example of the bottle-type can, and FIG. 9 shows the wall thickness distribution in the intermediate molded product (bottom cylindrical can) of the conventional example.
[0018]
In the bottle-type can 1 of the present embodiment, as shown in FIG. 1, a shoulder portion having a dome shape (hemispherical shape projecting outward) having an arcuate longitudinal section upward from the large-diameter cylindrical trunk portion 4. 3, a small-diameter cylindrical mouth-and-neck portion 2 is integrally formed, and a lower end of the neck portion 5 following the cylindrical lower end portion of the trunk portion 4 (a flange portion formed at a lower end opening edge of the neck portion 5 ), The bottom lid 6 made of metal is tightened and fixed, and the mouth-and-neck portion 2 on which the screw is formed is not shown, but after the beverage is filled in the can, With a known cap mounting device (capper), a cap made of metal is mounted so that it can be resealed (resealed).
[0019]
The mouth-and-neck part 2, the shoulder part 3, the trunk part 4, and the neck part 5 (and the flange part) of the bottle-shaped can 1 are resin-coated metal plates in which a thermoplastic resin layer serving as a protective coating is formed on both surfaces of the metal plate. As such a resin-coated metal plate, heat of a polyester resin, a polypropylene resin or the like having a thickness of 8 to 30 μm is formed on both surfaces of an aluminum alloy plate having a thickness of 0.22 to 0.35 mm. A resin-coated aluminum alloy plate on which a plastic resin film is previously laminated can be used.
[0020]
In addition, as an aluminum alloy plate used as the base material of the resin-coated metal plate, it is not particularly limited as long as it is used for manufacturing a normal can. For example, 3004 series aluminum specified in Japanese Industrial Standard (JIS) An alloy, 3104 series aluminum alloy, etc. can be used. In addition, the thermoplastic resin that forms the protective coating on both sides of the metal plate is not particularly limited as long as it is used for the production of a normal can body. For example, the can has good heat resistance and content resistance, It is possible to use a thermoplastic polyester resin film suitable for the above-mentioned use.
[0021]
As for the thickness of the aluminum alloy plate used as the base material of the resin-coated metal plate, even if it is 0.35 mm or more, only the unnecessary material cost is increased. On the other hand, if the thickness is 0.22 mm or less, the can body Since the generation of defective cans due to wrinkles on the shoulders and dents on the body at the stage of molding the mold will lead to an increase in cost, the range of 0.22 to 0.35 mm is used. Is appropriate. In addition, the thickness of the thermoplastic resin layer serving as a protective coating on both surfaces of the metal plate is preferably as thin as possible from the viewpoint of material cost. However, when the thickness is less than 8 μm, the coating performance is deteriorated. On the inner surface side, when the contents are filled, the contents may permeate into the resin layer and corrode the metal plate. Therefore, considering the cost, it is appropriate that the content is in the range of 8 to 30 μm. is there.
[0022]
From such a viewpoint, when a specific example is given about the resin-coated metal plate suitably used for the production of the bottle-shaped can, the outer surface side of the aluminum alloy plate having a thickness of 0.32 mm There is a resin-coated aluminum alloy plate in which a thermoplastic resin film having a thickness of 12 μm is laminated and a thermoplastic resin film having a thickness of 25 μm is laminated on the inner surface side of the can.
[0023]
An example of a manufacturing process for manufacturing a bottle-shaped can from such a resin-coated metal plate will be described. First, before entering the molding of the can, from the thermoplastic resin layer on both sides of the resin-coated metal plate, for example, After applying an appropriate lubricant such as normal butyl stearate, liquid paraffin, petrolatum, polyethylene wax, etc., as shown in FIG. 2, the resin-coated metal plate is punched into a disk shape in the cup forming process. The blank is drawn and formed into a cup shape, and the cup is drawn and ironed in the can body forming process (at least one redrawing and stretching after ironing, or twice Of the bottomed cylindrical can with a smaller diameter and thinner wall than the cup. Manufactured as a molded article.
[0024]
Next, the bottomed cylindrical can which is an intermediate molded product is formed into a shoulder portion and an unopened mouth-and-neck portion by a plurality of drawing processes in the top dome forming step. This top dome molding process will be described in detail. In the present embodiment, as shown in FIG. 3, first, the bottom corner of the intermediate molded product with the bottom side facing up, Punch the flat can bottom 21 in a state where the shoulder curved surface is preliminarily formed into a shoulder curved surface (curved surface which becomes the lower part of the shoulder) 31 and then the shoulder curved surface is wrinkled by a wrinkle pressing tool by a die 51 and a pusher 52. 53 is drawn into a bottomed cylindrical shape having a smaller diameter than the side wall portion (body portion 4) of the bottomed cylindrical can.
[0025]
In addition, as a method of pre-molding the bottom corner of the can into a curved shoulder (under the shoulder), the can bottom corner is topped after being molded into an intermediate molded product of a bottomed cylindrical can in the can body molding process. It may be possible to re-form before the dome forming process, and when forming a bottomed cylindrical can in the can body forming process, the peripheral shape of the tip of the can body forming punch should be an arc of vertical section Thus, it may be formed simultaneously with the can body forming. Furthermore, if there is no problem in the formability of the shoulder portion, without performing such preliminary molding, in the top dome molding process, the curved surface of the shoulder portion is formed with a wrinkle pressing tool with a die and a pusher, and the state is left as it is. The bottom of the can may be drawn and formed into a small bottomed cylindrical shape by punching.
[0026]
Next, a wrinkle pressing tool having a taper surface having a linear cross-sectional shape that approximates a cross-sectional arc of a virtual curved surface following a preformed shoulder curved surface (lower portion of the shoulder) 31 with respect to the newly drawn bottomed cylindrical portion 22 (Die 54 and pusher 55) With the bottom corner of the bottomed cylindrical portion being wrinkled, the punch 56 is drawn into a smaller bottomed cylindrical shape, and such drawing is repeated once more. Then, after the diameter of the bottomed cylindrical portion 23 is reduced until it becomes substantially the same as the diameter of the neck 2, it is formed following the initial curved shoulder surface (lower portion of the shoulder) 31 by repeated drawing. The plurality of tapered

surfaces

32, 33 of the shoulder portion are extended by a pair of forming tools (die 57 and pusher 58) having a virtual curved surface shape extending from the shoulder curved surface 31, so that a continuous smooth curved surface is obtained again. Molding Omu) to.
[0027]
Further, as shown in FIG. 2, in the final stage of the top dome molding process after the shoulder is reshaped (reformed), the mouth-and-neck molding is performed twice on the mouth-and-neck formed in the bottomed cylindrical shape. After applying the lubricant, the lubricant is removed from at least the outer surface of the can whose neck and neck are not open and the lower end of the trunk is opened in the lubricant removing process, and in the trimming process, the trunk on the side opposite to the mouth and neck is removed. After trimming the opening end side to make the can a predetermined length, the top coat is applied after printing the desired design (characters, decorative patterns, etc.) on the cylindrical body in the printing and painting process In the drying step, the printing ink layer and the top coat layer are sufficiently dried, and the thermoplastic resin layer of the protective film is made amorphous.
[0028]
In addition, about the process for giving a desired design (a character, a decoration pattern, etc.) to the cylindrical body part of a bottle type can, printing and painting are performed directly on the outer surface of the body part as described above. Not only the printing and painting processes to be applied, but also the printed resin film sticking process in which a printed resin film on which a printing ink layer or topcoat layer has been formed in advance is laminated on the outer surface of the body part by sticking by thermal bonding It is also good.
[0029]
Next, in the screw / curl forming process, first, the mouth / neck portion is opened by trimming the front end closing portion of the unopened mouth / neck portion, and then the opening end portion is formed into an annular curled portion by external winding. Then, a screw for screwing the cap is formed on the cylindrical peripheral wall, and a bead portion is formed below the screw forming portion. Next, as shown in FIG. 4, with the shoulder and neck held by the holding member 60 with the mouth and neck side down, in the neck and flange forming process, the side opposite to the mouth and neck is not shown. Neck flange processing (neck-in processing and flange processing) is applied to the vicinity of the opening end of the body portion (side wall portion of the intermediate molded product), so that the neck portion (Fig. 1), and a flange portion may be formed.
[0030]
And in the bottom lid winding process, although not shown, the shoulder is held with the neck and neck side down by a seamer (can lid clamping machine) as in the case of neck and flange molding Then, the bottom cover of another member made of a resin-coated metal plate is integrally fixed to the flange portion formed at the lower end opening edge of the neck portion following the cylindrical lower end portion of the body portion by a double winding method. Thus, a bottle-shaped can (not shown in the print design of the body part) before the cap (not shown) as shown in FIG. 1 is mounted is manufactured.
[0031]
In the case of a bottle-type can manufactured as described above, usually, after filling a beverage in the can, a cap made of a metal and attached to the mouth and neck portion by a well-known cap mounting device (capper). However, this cap attachment (capping) is generally deformed by pressing the side wall of the cap against the threaded portion of the mouth and neck with a roll in the radial direction while covering the mouth and neck with the cap and pressing it from above. By attaching it, the cap is mounted while forming the screw part. (When such a cap is attached, a vertical load of about 1100 N at the maximum acts from above the mouth and neck.)
[0032]
By the way, about the bottle-shaped can manufactured as mentioned above, from the viewpoint of moldability at the time of manufacture, the wall thickness of each part of the can body is determined from the original plate thickness (plate thickness of the resin-coated metal plate before forming). Whether it can be made as thin as possible has been studied, and as a result, the following has already been found.
[0033]
For the neck and neck, the wall thickness of the mouth and neck is reduced by multiple drawing operations from the bottom of the bottomed cylindrical can that is an intermediate molded product (substantially the same thickness as the original plate thickness). This is determined by both the effect of increasing the wall thickness due to the reduced diameter and the effect of reducing the wall thickness by being stretched in the axial direction by the punch, but the effect of increasing the wall thickness due to the reduced diameter is relatively greater. The wall thickness (substantially the same as the original plate thickness) of the bottom of the bottomed cylindrical can, which is an intermediate molded product, is approximately equal to or slightly thicker.
[0034]
The body is thinned by ironing when it is molded from a cup shape to an intermediate molded product of a bottomed cylindrical can, but the resin-coated metal plate with a thermoplastic resin layer laminated on both sides is ironed. In this case, when the processing rate by the ironing process is increased and the wall thickness is reduced below a certain wall thickness, the thermoplastic resin layer laminated on the surface may be damaged. Although it depends on the type of thermoplastic resin used, generally, if the wall thickness of the body is reduced to 32% or less of the original plate thickness, the thermoplastic resin layer will be severely damaged and unsuitable as a product. It will be something.
[0035]
As for the shoulder portion, in the bottomed cylindrical can which is an intermediate molded product, a portion near the bottom of the side wall portion (the body portion of the bottomed cylindrical can) subjected to the ironing process is thinned to the shoulder curved surface (after that In this process, it is preformed on the lower part of the shoulder), and the wall thickness of this part is 60% or more of the wall thickness of the can bottom (substantially the same thickness as the original plate thickness). The present inventors have found that wrinkles are generated unless the thickness is 60% or more of the original plate thickness.
[0036]
In other words, the shoulder is formed by repeating drawing and redrawing with a redrawing punch in a state where it is wrinkled with a wrinkle holding tool with a die and a pusher. In the case of intermediate-shaped bottomed cylindrical cans, if the difference between the wall thickness of the side wall near the bottom of the can (the part that is molded into the curved shoulder) and the thickness of the bottom of the can is large, Only the bottom of the can having a large thickness is pressed down, so that the wrinkle pressing does not work effectively, and wrinkles are likely to occur in the side wall portion having a thin plate thickness.
[0037]
About neck part (and flange part), we perform neck-in processing (and flange processing) near the opening end of side wall part (body part of bottomed cylindrical can) of intermediate molding product that was thinned by ironing In the side wall part of the intermediate molded product (the barrel part of the bottomed cylindrical can), the neck molding part (the part where neck-in processing and flange processing are performed) near the opening end is A wall thickness that does not cause wrinkles or cracks during neck-in or flange processing is required.
[0038]
Therefore, the neck molding part of the side wall part of the intermediate molded product (the body part of the bottomed cylindrical can) is thinner than the other part (the part that remains as a cylindrical body part in the bottle-shaped can). It is necessary to reduce the degree (increase the wall thickness). As long as the wall thickness of the neck forming portion is 0.16 mm or more, a good formability that prevents wrinkles and cracks during neck / flange processing can be obtained.
[0039]
For bottle-shaped cans manufactured after considering the wall thickness of each part from the viewpoint of moldability at the time of manufacturing as described above, in the conventional bottle-shaped cans, the state before the neck flange processing is performed As shown in FIG. 8, the wall thickness distribution of each portion is the same as (or slightly thicker) the thickness of the shoulder portion that extends downward from the mouth and neck of the wall thickness. The thickness gradually decreases from the neck and neck to the lower end (joint to the torso), and in the torso following the lower end of the shoulder, the wall thickness decreases rapidly from the lower end of the shoulder. The wall thickness hardly changes from the wall portion to the neck forming portion, and the neck forming portion has a wall thickness slightly thicker than the lower end of the shoulder portion after passing through the portion where the wall thickness gradually increases.
[0040]
In addition, the conventional example shown in FIG. 8 specifically has a thickness of 12 μm on the outer surface and a thickness of 25 μm on the inner surface on the inner and outer surfaces of the 0.32 mm thick aluminum alloy plate, respectively. A can body (excluding the bottom cover portion) is integrally formed from a resin-coated aluminum alloy plate (original plate thickness is 0.357 mm) laminated with a thermoplastic resin layer, and is a bottle-shaped can having an internal capacity of 500 ml. .
[0041]
In a conventional bottle-shaped can with such a wall thickness distribution, as already mentioned, dents and buckling occur near the shoulder of the trunk when necking and flange processing and bottom lid tightening. Or during transport of the can body before tightening the bottom lid, there is a risk that dents may occur near the shoulder of the trunk due to contact between the can bodies. During the transportation of the can body, there is a problem that dents are generated even in a portion near the neck portion of the trunk portion.
[0042]
On the other hand, in the bottle type can of the present embodiment, in the example of the bottle type can manufactured in the same size with the same material as the conventional example, in a state before the neck flange processing is performed, The wall thickness distribution of each part is as shown in FIG. That is, in the bottle-shaped can of the conventional example shown in FIG. 8 in the vicinity of the upper end near the shoulder portion of the trunk portion, the wall thickness decreases rapidly from the lower end of the shoulder portion to the thin wall portion immediately. In the bottle-type can of the embodiment shown in FIG. 5, the wall thickness does not decrease greatly from the lower end of the shoulder portion to the predetermined range, and the wall thickness rapidly decreases after passing the range. It has decreased to.
[0043]
Further, in the bottle-shaped can of the conventional example shown in FIG. 8 in the lower part from the vicinity of the center of the body part, the wall thickness hardly changes up to the neck forming part (the part where the neck and the flange are processed). In the bottle-shaped can of the embodiment shown in FIG. 5, the thin wall portion is directed toward the neck forming portion, whereas the portion continues and the wall thickness increases rapidly after entering the neck forming portion. The wall thickness gradually increases.
[0044]
As described above, the means for making each part of the bottle-shaped can have a predetermined wall thickness distribution, for example, in the drawing and ironing process for forming a bottomed cylindrical can, which is an intermediate molded product, from each cup, By using a punch having a shape corresponding to the wall thickness distribution of the part, each part of the bottle-shaped can manufactured through subsequent molding can have a predetermined wall thickness distribution.
[0045]
That is, when manufacturing the bottle type can of this embodiment, the punch used when forming the bottomed cylindrical can of the intermediate molded product from the cup has a shape as shown in FIG. The intermediate molded product having a wall thickness distribution as shown in FIG. 7 using a punch having such a shape (not schematically based on an actual dimension relationship but schematically shown in an extreme form) If a bottomed cylindrical can is manufactured, the bottle-shaped can of the Example which has wall thickness distribution as shown in FIG. 5 can be manufactured by performing subsequent shaping | molding process (top dome shaping | molding process). In addition, in the bottle type can of the conventional example which has wall thickness distribution as shown in FIG. 8, the wall thickness distribution of the intermediate molded product (bottom cylindrical can) is as shown in FIG.
[0046]
According to the bottle-shaped can of the present embodiment having the wall thickness distribution as described above, only a predetermined range where dents and buckling are likely to occur is thickened in the vicinity of the upper end of the trunk portion close to the shoulder portion. Since the other parts are immediately thin walled, the amount of metal used in the body can be reduced compared to the case where the entire body is uniformly thickened. For example, even if the wall thickness is gradually reduced from the lower end of the shoulder portion toward the center of the torso, the amount of metal used for thickening in the vicinity of the upper end of the torso is as much as possible In addition, it is possible to obtain a sufficient strength to prevent dents and buckling from occurring in the vicinity of the shoulder portion of the trunk portion.
[0047]
Moreover, according to the bottle type can of this embodiment, the moldability of the shoulder portion is maintained by maintaining the plate thickness in the portion near the bottom portion of the side wall portion of the intermediate molded product at 60% or more with respect to the original plate thickness. The wall thickness of the shoulder part formed in a hemispherical dome shape protruding outward is maximized at the connection with the mouth and neck, and minimized at the connection with the trunk. In the middle region, the wall thickness gradually decreases from the maximum wall thickness portion toward the minimum wall thickness portion, so that the shoulder strength can be maintained economically and efficiently with a small amount of material. .
[0048]
Further, according to the bottle-shaped can of the present embodiment, the wall neck is gradually increased from the vicinity of the center of the body part toward the neck part from the thin wall part of the body part to the neck part. Since the area near the head is thickened, even if the cans come into contact with each other during transportation of the cans after tightening the bottom lid, dents are generated near the neck of the trunk due to contact between the cans. Can be economically and effectively prevented.
[0049]
In this regard, in the vicinity of the upper end of the body portion close to the shoulder portion, a relatively thick wall thickness is necessary to prevent the occurrence of dent due to contact with the shoulder portion having high rigidity. Because it is a relatively narrow range, if the thick part on the upper end of the trunk (downward from the shoulder) is formed into a gentle taper, the wall thickness will increase to unnecessary parts, and the vicinity of the shoulder Dent at the top of the body is often generated when the bottom lid is transported in an unstable state before being tightened, and it is necessary to avoid increasing the weight of the top of the can as much as possible. It is not appropriate to form a thick taper in the vicinity (near the shoulder) with a gentle taper. As already mentioned, thicken only the specified area where dents and buckling are likely to occur. Immediately turn the other part into a thin wall part The is effective.
[0050]
On the other hand, after the bottom lid is tightened, the opening end of the lower portion of the can body is fixed by tightening the bottom lid, so that the lower portion of the can body has rigidity. In such a state, Due to increased stability, the occurrence of dents in the vicinity of the upper end of the trunk (near the shoulder) during transportation is reduced, and conversely, the lower part of the can body has rigidity, so that contact between can bodies and transportation Due to the contact with the guide or the like of the path, dents are likely to be generated in a relatively wide area below the center of the trunk.
[0051]
In such a region from the vicinity of the center of the body part to the lower part, a dent is generated near the lower end of the body part (near the neck part) due to contact with the wound bottom cover. Although it is necessary to increase the thickness, there is almost no contact with the bottom cover up to the vicinity of the center of the barrel, and the barrels of the cans contact each other or contact with the guide of the transport path. In this embodiment, as described above, the thin wall of the trunk portion is formed downward from the vicinity of the center of the trunk portion. The wall thickness is gradually increased from the part to the neck part, and this is the most economical in preventing the occurrence of dents, considering the reduction of the weight of the can and the ease of forming the can body. And it can be said that it is effective.
[0052]
By the way, regarding the bottle-shaped can of the present embodiment as described above, the difference in effect between the specific example and the conventional example is confirmed with respect to the point that dents can be prevented from being generated near the shoulder part of the trunk part. An experiment was conducted.
[0053]
That is, for the resin-coated aluminum alloy plate that becomes the can body material of the bottle-shaped can, the thickness of the aluminum alloy plate is 0.22 to 0.35 mm from the viewpoint of can manufacturing problems, corrosion resistance, material cost, etc. As described above, the thickness of the thermoplastic resin layer to be coated as a protective coating is suitably in the range of 8 to 30 μm. Within each range, each of the bottle-shaped cans (can capacity 500 ml) of each of the examples (1 to 3) and the conventional examples (1 to 3) manufactured from materials having different thicknesses of the aluminum alloy plate (for each example) Experiments were conducted on 500 cans each).
[0054]
About each Example (1-3), it has wall thickness distribution of the pattern (The concrete numerical value of wall thickness differs in each Example) as shown in FIG. In any of 3), the wall thickness at the lower end of the shoulder (boundary position between the shoulder and the trunk) is 53% of the thickness of the resin-coated metal plate before molding, and from the lower end of the shoulder The average value of the wall thickness in the range up to 10 mm is 50% of the plate thickness of the resin-coated metal plate before molding, and after passing the range, the wall thickness decreases rapidly, The wall thickness at the thin wall portion is 38% of the thickness of the resin-coated metal plate before molding.
[0055]
In the range from the lower end of the shoulder portion to 10 mm downward (thick wall portion where the average value of the wall thickness is 50% of the thickness of the resin-coated metal plate before forming), the wall thickness is gradually increased little by little. Although it is thin, the wall thickness at the start position of this range is 53% of the plate thickness of the resin-coated metal plate, and the wall thickness at the end position of this range is 49% of the plate thickness of the resin-coated metal plate. Since the distance in the height direction of the can body in this range is 10 mm, the wall thickness reduction rate (%) is expressed as [(wall thickness at range start position−wall thickness at range end position) / range When the distance in the can body height direction] × 100 is determined, the wall thickness reduction rate is about 0.1%.
[0056]
On the other hand, in the range where the wall thickness suddenly decreases from the position of 10 mm downward from the lower end of the shoulder to the thin wall portion, the wall thickness at the start position of this range is 49 of the thickness of the resin-coated metal plate. The wall thickness at the end position of this range is 38% of the plate thickness of the resin-coated metal plate, and the distance in the can body height direction in this range is 8 mm. The wall thickness reduction rate (%) obtained by the above is about 0.5%, and the wall thickness reduction rate (about 0.1%) in the range (thick part) from the lower end of the shoulder to 10 mm downward. The wall thickness is rapidly decreasing.
[0057]
Each of the conventional examples (1 to 3) has a wall thickness distribution having a pattern as shown in FIG. 8 (specific values of wall thickness are different in each conventional example). In any of 3), the wall thickness at the lower end of the shoulder (boundary position between the shoulder and the torso) is 49% of the thickness of the resin-coated metal plate before molding, and from the lower end of the shoulder The wall thickness directly decreases sharply, and the wall thickness at the thin wall portion of the barrel is 38% of the thickness of the resin-coated metal plate before molding. Therefore, the average value of the wall thickness in the range from the lower end of the shoulder portion to 7 mm downward is 42% of the plate thickness of the resin-coated metal plate before forming.
[0058]
Examples 1 to 3 in which the thickness of the aluminum alloy plate of the resin-coated metal plate before molding is different between the example and the conventional example having different wall thickness distribution patterns as described above (500 cans for each example) As shown in Table 1 below, as a result of examining the presence or absence of a can (defective can) that was actually conveyed on the production line and dented in the vicinity of the shoulder of the trunk, In 3), a dent was generated in the vicinity of the shoulder of the trunk (defective can), whereas in each of the examples (1 to 3), dent was generated in the vicinity of the shoulder of the trunk. No cans (bad cans) were found. In Table 1, (A) shows the thickness of the aluminum alloy plate, (B) shows the thickness of the thermoplastic resin layer, and (A + B) shows the plate thickness of the resin-coated aluminum alloy plate. Is.
[0059]
[Table 1]

[0060]
About each Example (1-3) shown in said Table 1, although the thickness (0.25-0.35 mm) of the aluminum alloy plate of the resin coating metal plate before shaping | molding differs, respectively, The average value of the wall thickness in the range from the lower end of the shoulder (boundary position of the shoulder to the trunk) to 10 mm below the thickness of the resin-coated metal plate (original thickness) is 50% of the original thickness. In any of the embodiments (1-3), the shoulder portion of the trunk is sufficiently strengthened by merely slightly increasing the can mass compared to the conventional examples (1-3). Dent does not occur in the part.
[0061]
Furthermore, not only the bottle type aluminum can as described above, but also the bottle type steel can, each of the following examples and conventional examples (500 cans for each example) The same experiment was conducted (in all cases, the capacity of the can is 500 ml, the thickness of the resin film, and the range of the thick part continuing downward from the lower end of the shoulder in the example is the same as in the case of the above aluminum can. ).
[0062]
〔Example〕
The original thickness of the resin-coated metal plate before molding is 0.266 mm, the wall thickness at the lower end of the shoulder (boundary position of the shoulder and the trunk) is 141 μm (53% of the original thickness), and downward from the lower end of the shoulder The average value of the wall thickness at the thick part following is 133 μm (50% of the original plate thickness), the wall thickness at the thin wall part of the trunk is 103 μm (39% of the original plate thickness), and the can mass is 43.9 g. .
[Comparative Example]
The original thickness of the resin-coated metal plate before molding is 0.266 mm, the wall thickness at the lower end of the shoulder (boundary position between the shoulder and the trunk) is 112 μm (42% of the original thickness), and the thin wall portion of the trunk The wall thickness is 103 μm (39% of the original plate thickness), and the can mass is 42.6 g.
As a result of the experiments according to the example and the conventional example as described above, no defective can was generated in the example, whereas three cans were generated in the conventional example.
[0063]
In addition, the ratio of the wall thickness at the lower end of the shoulder part to the original plate thickness, how much of the range near the upper end of the trunk part from the lower end of the shoulder part to the thick part In addition, the ratio of the wall thickness in the range (thick part) to the original plate thickness is limited to that, although the above specific numerical values can be used as a guide. It is not a thing, but there is a slight width, and the width is also slightly different depending on the thickness of the resin-coated metal plate before molding (the thickness of the metal plate) and the metal material Conceivable.
[0064]
In this regard, for example, resin-coated aluminum in which a thermoplastic resin layer is laminated on both the inner and outer surfaces of an aluminum alloy plate having a thickness of 0.32 mm so that the outer surface has a thickness of 12 μm and the inner surface has a thickness of 25 μm. As a result of a more detailed examination of a bottle-shaped can manufactured from an alloy plate (a resin-coated aluminum alloy plate having a thickness of 0.357 mm which has been widely used in the past), the following is limited to such a bottle-shaped can. I found out.
[0065]
That is, there is no problem if the average value of the wall thickness from the lower end of the shoulder is 45% or more (45 to 55% from the cost) in the range of 20 mm downward from the lower end of the shoulder, It has been found that if the average value of the wall thickness from the lower end of the shoulder is 45% or less of the original plate thickness (43% in a specific experimental example), dents may occur near the shoulder of the trunk. .
[0066]
Moreover, even when the wall thickness average value of the thick wall portion continuing downward from the lower end of the shoulder portion (the body portion of the predetermined range downward from the lower end of the shoulder portion) is 50% of the original plate thickness, There is no problem as long as it is a thick part from the lower end to the range of 7 mm or more (7 to 20 mm from the viewpoint of cost), but the range of the thick part is 6 mm or less from the lower end of the shoulder (specific experimental example) 6 mm), it has been found that there is a possibility that dents are generated in the vicinity of the shoulder of the trunk.
[0067]
In addition, even when the thick portion extends from the lower end of the shoulder portion to the range of 7 mm or more downward, the thick portion continuing from the lower end of the shoulder portion downward (the body portion of the predetermined range downward from the lower end of the shoulder portion). If the average value of the wall thickness is 45% or more of the original plate thickness, there is no problem, but the average value of the wall thickness of this thick part is 45% or less of the original plate thickness (43% in a specific experimental example). ), It has been found that there is a possibility that dents may occur in the vicinity of the shoulder of the trunk.
[0068]
Therefore, a resin-coated aluminum obtained by laminating a thermoplastic resin layer to an aluminum alloy plate having a thickness of 0.32 mm so that the outer surface has a thickness of 12 μm and the inner surface has a thickness of 25 μm. For a bottle-shaped can manufactured from an alloy plate (original plate thickness is 0.357 mm), or a bottle-shaped can manufactured from a resin-coated aluminum alloy plate having a plate thickness close to this, 7 In the range up to 20mm, the average value of the wall thickness is 45% or more of the original plate thickness, and after passing the range, the wall thickness is sharply reduced to the thin wall part, thereby reducing the material cost as much as possible. From the above, it is considered that dents can be reliably prevented from occurring near the shoulders of the trunk.
[0069]
Note that the wall thickness reduction rate is too small in the range where the wall thickness rapidly decreases between the thick part (thick part continuing downward from the lower end of the shoulder part) and the thin part in the trunk part. For the purpose of the present invention to reduce the amount of metal used in the can as much as possible by thickening only the portion where the dent is likely to occur, the effect of the operation is as follows. Since the wall thickness decrease rate in this range (%), that is, [(wall thickness at the start position of the range−wall thickness at the end position of the range) / distance in the height direction of the can body] × 100, It is desirable that it is 0.2% or more.
[0070]
As mentioned above, although one embodiment of the bottle-shaped can of the present invention has been described, the present invention is not limited to the above-described embodiment. For example, the metal plate material used as the material is as described in the above-described embodiment. The present invention is not limited to a resin-coated aluminum alloy plate, but can be applied to a conventionally known metal plate material for can making, and the shape of the shoulder and the forming method are also shown in the above embodiment. Not only in the case where the entire shoulder portion is formed into a hemispherical dome shape, but in a suitable shape (for example, a shape in which a shoulder is formed on the shoulder portion) is performed by an appropriate forming method. Needless to say, the design can be changed as appropriate.
[0071]
【The invention's effect】
According to the bottle-shaped can of the present invention as described above, dents and buckling are generated in the vicinity of the shoulder portion of the thinned barrel portion at the time of manufacturing and transporting the can body. This can be effectively prevented while reducing the amount of metal as much as possible.
[Brief description of the drawings]
FIG. 1 is a partially cutaway side view showing the external shape of a bottle-type can.
FIG. 2 is an explanatory view schematically showing an example of a manufacturing process for manufacturing the bottle-shaped can shown in FIG. 1;
3 is a side view and a cross-sectional view showing a molded state of the mouth neck portion and the shoulder portion in the top dome forming step of the manufacturing step shown in FIG. 2. FIG.
4 is a partial cross-sectional side view showing a holding state of a can body in a neck / flange forming process and a can lid winding process of the manufacturing process shown in FIG. 2;
FIG. 5 is a graph showing the wall thickness distribution of each part in a state before neck / flange processing is performed on an example of the bottle-type can according to the present invention.
FIG. 6 is a side view schematically showing the shape of a punch used when forming an intermediate molded product (bottomed cylindrical can) from a cup in the bottle-shaped can of the present invention.
7 is a graph showing the wall thickness distribution of each part in the intermediate molded product (bottom cylindrical can) of the bottle-shaped can of the example having the wall thickness distribution shown in FIG. 5;
FIG. 8 is a graph showing a wall thickness distribution of each part in a state before a neck flange processing is performed for a conventional example of a bottle-type can.
9 is a graph showing the wall thickness distribution of each part of an intermediate molded product (bottomed cylindrical can) of the conventional bottle-type can having the wall thickness distribution shown in FIG. 8;
[Explanation of symbols]
1 Bottle-shaped can
2 mouth and neck
3 shoulder
4 trunk
5 Neck

Claims

From the intermediate molded product of a bottomed cylindrical can whose body has been thinned by ironing, the bottom of the can is molded into a small diameter neck and neck and an inclined shoulder, and the vicinity of the open end of the barrel is molded into the neck. In a bottle-shaped can where a separate bottom lid is wound and fixed to a flange portion formed at the opening edge of the neck portion, a cylindrical body portion whose wall thickness is thinner than the shoulder portion and neck portion In the vicinity of the upper end near the shoulder of the wall, the wall thickness does not decrease significantly from the lower end of the shoulder to the specified range, but after that range, the wall thickness decreases rapidly to a thin wall portion. Bottle type can characterized by.

The shoulder is formed in a hemispherical dome shape that protrudes outward, and the wall thickness of the shoulder is maximized at the upper end connected to the mouth and neck, and is minimized at the lower end connected to the trunk. The bottle-shaped can according to claim 1, wherein the bottle-shaped can is gradually thinned from an upper end toward a lower end in an intermediate region.

The part of the can except for the bottom lid is integrally formed from a resin-coated metal plate with a thermoplastic resin layer laminated on both sides of the metal plate. The bottle-shaped can according to claim 1 or 2, wherein the wall thickness gradually increases toward the portion.

The portion of the can except for the bottom lid is integrally formed from a resin-coated metal plate obtained by laminating a thermoplastic resin layer having a thickness of 8 to 30 μm on each side of an aluminum alloy plate having a thickness of 0.22 to 0.35 mm. The wall thickness in the thin wall portion of the body portion is 32 to 44% of the thickness of the resin-coated metal plate before molding, and the wall thickness in the range of at least 7 mm downward from the lower end of the shoulder portion. The bottle-shaped can according to any one of claims 1 to 3, wherein an average value of is a thickness of 45 to 55% of a thickness of the resin-coated metal plate before molding.