JP3837593B2

JP3837593B2 - Biaxial stretch blow molding method, mold apparatus and housing

Info

Publication number: JP3837593B2
Application number: JP2000354978A
Authority: JP
Inventors: 高雄飯塚; 則之田中; 栄大久保
Original assignee: Yoshino Kogyosho Co Ltd
Current assignee: Yoshino Kogyosho Co Ltd
Priority date: 2000-11-21
Filing date: 2000-11-21
Publication date: 2006-10-25
Anticipated expiration: 2020-11-21
Also published as: JP2002160286A

Description

【０００１】
【発明の属する技術分野】
本発明は、合成樹脂製壜体の２軸延伸ブロー成形方法と、この２軸延伸ブロー成形方法を実施するための金型装置と、そしてこの２軸延伸ブロー成形方法により成形された壜体の構造に関するものである。
【０００２】
【従来の技術】
飽和ポリエステル樹脂、特にポリエチレンテレフタレート樹脂（以下、ＰＥＴと称する）製の２軸延伸ブロー成形壜体は、有底筒状のプリフォームをブロー成形温度に加熱して延伸ブロー金型に組付けた状態で、延伸ピンにより軸方向に強制的に延伸させると共に、プリフォーム内にブロー流体を圧入してブロー延伸させて、所望の形状に成形されるが、延伸成形の最後まで延伸ピンの先端部が接触している底部中心部分は、延伸ピンとの接触により延伸しないので、成形された壜体の底部中心部分に肉厚な未延伸部分が形成されると云う不都合があった。
【０００３】
このように、壜体の底部中心部分に残留形成された未延伸部分は、壜体の他の延伸された延伸部分に比べてその物性が大幅に劣り、このため底部の耐衝撃性等の機械的強度が不足すると共に、耐熱性が劣って熱変形し易く、さらにアルコール等との接触によりクレージングが発生すると云う不都合を生じる。
【０００４】
この不都合を解消する従来技術として、２ステージブロー成形（ダブルブロー成形）が知られており、この技術は、中間成形品であるプリフォームを、延伸ピンを使用した通常の２軸延伸ブロー成形手段により準成形品に成形した後、この準成形品を再度ブロー成形温度まで加熱し、最終形状に延伸ブロー成形するものであり、この二度目のブロー成形操作の際に、未延伸部分であった底部中心部分に延伸が集中するようにし、これにより底部中心部分の延伸不足を解消するものとなっている。
【０００５】
【発明が解決しようとする課題】
しかしながら、上記したダブルブロー成形技術にあっては、底部中心部分を充分に延伸させることができるのであるが、高延伸倍率の成形であるので、成形された壜体は全体的に肉薄となり、これによりガラス壜の様な高級感をもたせるべく、肉厚として質感がでるようにした壜体の成形には不向きである、と云う問題があった。
【０００６】
なお、通常の２軸延伸ブロー成形手段により、低延伸倍率で肉厚壜体をブロー成形し、この壜体の未延伸部分である底部中心部分を熱結晶化させて、この底部中心部分の物性を高める手法もあるが、この場合、耐熱性および硬度が高められるものの、耐衝撃性が低下し、壜体の座としての底部の機械的強度に不安が生じる、と云う問題があった。
【０００７】
そこで、本発明は、上記した従来技術における問題点を解消すべく創案されたもので、一回の低延伸倍率での２軸延伸ブロー成形操作により、底部中心部分を充分に延伸させることを技術的課題とし、もって底部を含めた胴部全体を不足なく延伸させた肉厚壜体を得ることを目的とする。
【０００８】
【課題を解決するための手段】
上記技術的課題を解決する本発明の内、請求項１記載の発明の手段は、
延伸ピンの前進限を、この延伸ピンの前進限までの前進と、圧力流体の圧入とにより、プリフォームから主に軸方向にブロー延伸された一次延伸プリフォームの、延伸ピンの先端部に接触している未延伸部に、充分な延伸を与えることのできる型空間を残した位置に設定すること、
延伸ピンを前進限まで前進させること、
また一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分をブロー金型の型面に接触させること、
一次延伸プリフォームの未延伸部間近の延伸部部分をブロー金型の型面に接触させたまま、継続しているブロー延伸により、一次延伸プリフォームを壜体にブロー成形すること、にある。
【０００９】
延伸ピンが前進限まで前進した状態で、一次延伸プリフォームの未延伸部間近の延伸部部分が、ブロー金型の型面に接触すると、一次延伸プリフォームは、このブロー金型の型面に接触した延伸部部分でブロー金型に固定されることになる。
【００１０】
この状態でブロー延伸を継続すると、ブロー金型の型面に接触した延伸部部分を除く延伸部が径方向にだけ延伸するのに対して、未延伸部全体は、延伸ピンの先端部から離れて、軸方向と径方向の両方向に延伸して壜底部に成形される。
【００１１】
一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分を、ブロー金型の型面に、略そのままの状態で接触させる必要があるので、プリフォームの径寸法に対してブロー金型の型面の径寸法を充分に大きくすることができず、これにより壜底部を延伸させた、低延伸倍率の壜体が成形されることになる。
【００１２】
請求項２記載の発明は、請求項１記載の発明における、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分のブロー金型の型面への接触を、延伸ピンと一緒となった一次延伸プリフォームのブロー金型の前記した型面部分への進入により達成する、こととしたものである。
【００１３】
この請求項２記載の発明においては、延伸ピンの前進限までの前進により、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分の固定を達成するので、延伸ピンの前進停止後における未延伸部の２軸延伸ブロー成形に際して、未延伸部先端に位置する延伸中心点の変位が発生することは殆どない。
【００１４】
請求項３記載の発明は、請求項１記載の発明における、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分のブロー金型の型面への接触を、延伸ピンの前進停止後、未延伸部が延伸ピンの先端から離れるのに先立って、継続しているブロー延伸により達成する、こととしたものである。
【００１５】
この請求項３記載の発明においては、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分とブロー金型の型面との間に隙間が形成されることになるので、軸方向に延伸成形される一次延伸プリフォームとブロー金型との間に、寸法上の余裕をもたせることができ、その分、ブロー金型の型面およびプリフォームの許容寸法範囲を広くすることができる。
【００１６】
本発明の内、請求項４記載の発明の手段は、
２軸延伸ブロー成形用の金型装置を、
延伸ピンの前進限までの前進と、圧力流体の圧入とにより、プリフォームから主に軸方向にブロー延伸された一次延伸プリフォームの、延伸ピンの先端部に接触している未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分に対向するブロー金型の型面部分に、延伸ピンの前進限までの前進により、この未延伸部間近の延伸部部分が接触する程度に縮径してシボリ部を形成して構成した、
ことにある。
【００１７】
この請求項４記載の発明においては、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分に接触するブロー金型の型面部分として、縮径したシボリ部を設けたので、この未延伸部間近の延伸部部分のブロー金型による接触固定が簡単にかつ確実に達成される。
【００１８】
請求項５記載の発明は、請求項４記載の発明における、シボリ部を、このシボリ部部分への延伸ピンと一緒となった一次延伸プリフォームの進入により、未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分に接触する径寸法とした、ものである。
【００１９】
この請求項５記載の発明においては、延伸ピンの前進動作により、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分を接触固定して未延伸部の支持を達成することになるので、未延伸部先端に位置する延伸中心点の変位が発生することのない、安定したブロー成形操作を実施することになる。
【００２０】
請求項６記載の発明は、請求項４記載の発明における、シボリ部を、延伸ピンの前進停止後のブロー延伸時に、延伸ピンの先端部から未延伸部が離れるのに先立って、未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分が接触する径寸法とした、ものである。
【００２１】
この請求項６記載の発明においては、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分とシボリ部との間に隙間が形成されることになるので、一次延伸プリフォームに対してシボリ部の許容寸法範囲を広くすることができ、ブロー金型の設計の自由度が大きくなる。
【００２２】
本発明の内、請求項７記載の発明の手段は、
プリフォームの胴部から成形される壜胴部と、プリフォームの底部から成形される壜底部との境界部の外径を、２軸延伸ブロー成形時に、延伸ピンの前進限まで前進と、圧力流体の圧入とにより、プリフォームから主に軸方向にブロー延伸された一次延伸プリフォームの、延伸ピンの先端部に接触している未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分の外径と略等しい値としたこと、
壜底部を一次延伸プリフォームの未延伸部からブロー延伸成形されたものとしたこと、
にある。
【００２３】
この請求項７記載の発明においては、壜胴部と壜底部との境界部の外径が、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部との境界部分であった延伸部部分の外径と略等しいので、この部分は、小さい延伸倍率で成形されて肉厚となり、また壜底部が、一次延伸プリフォームの未延伸部からブロー延伸成形されるので、底部を含めた胴部全体に延伸を与えた、肉厚な合成樹脂製２軸延伸ブロー成形壜体となる。
【００２４】
【発明の実施の形態】
以下、本発明の実施例を、図面を参照しながら説明する。
プリフォーム１は、半球殻状に膨出させた底部５と、筒形状をした胴部２とを有し、外周面に螺条を刻設した口筒部３と胴部２との境界部分の外周面に、外鍔状の鍔部４を周設して構成され、ＰＥＴ製の射出成形品となっている。
【００２５】
このプリフォーム１は、延伸ピン１７を有する延伸治具１６の保持部１８に、逆立姿勢で嵌入保持され、この延伸治具１６に組付けられたまま、ブロー温度に加熱されると共に、ブロー金型１４に組付けられる。
【００２６】
図示実施例の場合、ブロー金型１４は、一対の割り金型で構成されているが、一対の割り金型と一つの底部金型との組合せで構成しても良い。
【００２７】
ブロー金型１４の型締めが完了した後、延伸ピン１７が前進（図においては、上昇）して、プリフォーム１の底部５を含む胴部２を、前進限まで軸方向に延伸させるが、この際、延伸ピン１７による軸方向の延伸と同時またはやや遅れて、圧力流体のプリフォーム１内への圧入によりブロー延伸をする。
【００２８】
延伸ピン１７が前進限まで前進して、プリフォーム１が一次延伸プリフォーム６にブロー延伸されると、図３に示すように、延伸ピン１７の先端部に接触している底部５部分は未延伸部９となり、残りの底部５および胴部２は、軸方向の延伸を受けて延伸部８となる。
【００２９】
プリフォーム１が一次延伸プリフォーム６に延伸成形された時点では、未延伸部９間近の、プリフォーム１の胴部２と底部５の境界部分であった延伸部８部分が、図示のように、ブロー金型１４のシボリ部１５に、小さい隙間Ｓを介して対向するか、シボリ部１５に軽く接触する。
【００３０】
一次延伸プリフォーム６は、延伸ピン１７が前進限に停止後に継続しているブロー延伸により二次延伸プリフォーム７に延伸されるが、この際、隙間Ｓがある場合には、図３に示すように、未延伸部９が延伸ピン１７の先端部から離れるに先立って、未延伸部９間近の、プリフォーム１の胴部２と底部５の境界部分であった延伸部８部分が、拡径方向への延伸によりシボリ部１５に接触するように、プリフォーム１およびシボリ部１５の径寸法関係を設定しておくことが必要である。
【００３１】
なお、一次延伸プリフォーム６の成形と同時に、未延伸部９間近の、プリフォーム１の胴部２と底部５の境界部分であった延伸部８部分がシボリ部１５に軽く接触する構成の場合は、この未延伸部９間近の延伸部８部分の外径と、シボリ部１５の内径を等しくするだけで良い。
【００３２】
未延伸部９間近の、プリフォーム１の胴部２と底部５の境界部分であった延伸部８部分がシボリ部１５に接触した後の二次延伸プリフォーム７の延伸は、シボリ部１５に接触した部分の下側全域、すなわち延伸部８は、単純な拡径変形となるのに対し、シボリ部１５に接触した部分の上側全域、すなわち未延伸部９全域は、図３に点線で図示したように、軸方向と径方向への２軸延伸変形となる。
【００３３】
このように、未延伸部９全域は、プリフォーム１の胴部２と底部５の境界部分であった延伸部８部分で固定支持された状態で２軸延伸されるので、未延伸部９の先端に位置する延伸中心が偏心することは殆どなく、これにより肉厚の偏りは殆ど発生しない。
【００３４】
図１は、壜胴部１１と壜底部１２の全体が雫状となって、尖塔状の壜底部１２を有する壜体１０を成形した実施例を示したもので、ブロー金型１４のシボリ部１５は、上方に縮径したテーパー面状となった型面の一部が、そのまま形成している。
【００３５】
これに対して、図２は、壜底部１２に自立機能を付与したもので、直線筒状をした壜胴部１１と壜底部１２との境界部に、縮径したくびれ部１３を形成した構造となっている。
【００３６】
【発明の効果】
本発明は、上記した構成となっているので、以下に示す効果を奏する。
請求項１記載の発明にあっては、プリフォームから、主に軸方向に延伸された一次延伸プリフォームの未延伸部を、この未延伸部間近の、プリフォームの胴部と底部の境界部分であった延伸部部分で固定支持して壜底部に２軸延伸成形するので、２軸延伸ブロー成形壜体の底部を、その全体に延伸を与えて成形することができる。
【００３７】
また、主に軸方向に延伸された一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部の境界部分であった延伸部部分をブロー金型の型面に接触させるので、当然のこととして、その延伸倍率は小さく抑えられることになり、これにより底部を延伸成形したにもかかわらず、肉厚な壜体を得ることができる。
【００３８】
請求項２記載の発明にあっては、軸方向の延伸の完了と同時に、延伸中心が位置する未延伸部に対する固定支持が確立されるので、延伸中心を偏心させることなく未延伸部の２軸延伸を達成でき、これにより壜底部を偏肉発生のない状態で延伸成形することができる。
【００３９】
請求項３記載の発明にあっては、プリフォームとブロー金型との相互寸法関係に余裕を与えることができるので、実施するブロー金型装置の製作、およびプリフォームの成形が容易となる。
【００４０】
請求項４記載の発明にあっては、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部の境界部分であった延伸部部分のブロー金型の型面への接触を、確実にかつ安全にそして簡単に達成することができるので、一次延伸プリフォームの未延伸部の壜底部への２軸延伸成形を安定して確実に達成することができる。
【００４１】
請求項５記載の発明にあっては、シボリ部による一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部の境界部分であった延伸部部分の接触固定を、軸方向延伸の終了と同時に、確実にかつ安定して達成するので、未延伸部を寸法精度良く壜底部に２軸延伸成形することができる。
【００４２】
請求項６記載の発明にあっては、一次延伸プリフォームに対するシボリ部の許容寸法範囲が大きいので、ブロー金型の製作が容易となる。
【００４３】
請求項７記載の発明にあっては、壜体のくびれ部の外径が、一次延伸プリフォームの未延伸部間近の、プリフォームの胴部と底部の境界部分であった延伸部部分の外径と略等しいので、壜底部全体を延伸成形した低延伸倍率の肉厚な合成樹脂製２軸延伸ブロー成形壜体を成形するのが容易である。
【図面の簡単な説明】
【図１】本発明の第一の実施例を示す、半縦断した説明図。
【図２】本発明の第二の実施例を示す、半縦断した説明図。
【図３】本発明の詳細な動作説明に供する、要部拡大説明図。
【符号の説明】
１；プリフォーム
２；胴部
３；口筒部
４；鍔部
５；底部
６；一次延伸プリフォーム
７；二次延伸プリフォーム
８；延伸部
９；未延伸部
１０；壜体
１１；壜胴部
１２；壜底部
１３；くびれ部
１４；ブロー金型
１５；シボリ部
１６；延伸治具
１７；延伸ピン
１８；保持部
Ｓ；隙間[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxial stretch blow molding method for a synthetic resin casing, a mold apparatus for carrying out the biaxial stretch blow molding method, and a casing molded by the biaxial stretch blow molding method. Concerning structure.
[0002]
[Prior art]
A biaxial stretch blow molded casing made of a saturated polyester resin, particularly polyethylene terephthalate resin (hereinafter referred to as PET), is a state where a bottomed cylindrical preform is heated to a blow molding temperature and assembled to a stretch blow mold. Then, the drawing pin is forcibly drawn in the axial direction by the drawing pin, and the blow fluid is press-fitted into the preform to be blow-drawn to be formed into a desired shape. Since the bottom center portion in contact is not stretched by contact with the stretching pin, there is a disadvantage that a thick unstretched portion is formed at the bottom center portion of the molded casing.
[0003]
In this way, the unstretched portion remaining in the central portion of the bottom of the housing is significantly inferior in physical properties to other stretched portions of the housing. In addition to insufficient mechanical strength, heat resistance is inferior and heat deformation tends to occur, and in addition, crazing occurs due to contact with alcohol or the like.
[0004]
As a conventional technique for solving this inconvenience, two-stage blow molding (double blow molding) is known. This technique is a conventional biaxial stretch blow molding means that uses a preform as an intermediate molded product. After being molded into a semi-molded product, the semi-molded product is heated again to the blow molding temperature and stretch blow molded to the final shape, which was an unstretched part during this second blow molding operation. Stretching is concentrated on the bottom center portion, thereby eliminating the stretch shortage at the bottom center portion.
[0005]
[Problems to be solved by the invention]
However, in the double blow molding technique described above, the center part of the bottom can be sufficiently stretched, but since the molding is performed at a high stretch ratio, the molded casing is thin overall, Therefore, there is a problem that it is unsuitable for forming a casing having a texture as a thick wall to give a high-class feeling like a glass bowl.
[0006]
In addition, by a normal biaxial stretch blow molding means, a thick casing is blow-molded at a low stretch ratio, and the bottom center portion which is an unstretched portion of the casing is thermally crystallized, and the physical properties of the bottom center portion However, in this case, although the heat resistance and the hardness are improved, there is a problem that the impact resistance is lowered and the mechanical strength of the bottom portion as the seat of the housing is uneasy.
[0007]
Therefore, the present invention was devised to solve the above-described problems in the prior art, and is a technique for sufficiently stretching the central portion of the bottom portion by a biaxial stretch blow molding operation at a single low stretch ratio. Therefore, an object of the present invention is to obtain a thick-walled body in which the entire body including the bottom is stretched without a shortage.
[0008]
[Means for Solving the Problems]
Among the present invention for solving the above technical problems, the means of the invention according to claim 1 is:
The advance limit of the draw pin is brought into contact with the tip end of the draw pin of the primary draw preform blown mainly in the axial direction from the preform by the advance to the advance limit of the draw pin and the press-fitting of the pressure fluid. To set the position in the mold space that can give sufficient stretching to the unstretched part,
Rukoto to before advancing the stretching pin advance limit or in,
In addition, the stretched part near the unstretched part of the primary stretched preform , which is the boundary part between the body part and the bottom part of the preform, is brought into contact with the mold surface of the blow mold,
The primary stretch preform is blow-molded into a casing by continuous blow stretching while the stretched portion near the unstretched portion of the primary stretch preform is in contact with the mold surface of the blow mold.
[0009]
In a state where the drawing pin is advanced to the advance limit, unstretched portions close stretching portions of the primary stretching preform in contact with the mold surface of the blow mold, primary stretching preform, the mold surface of the blow mold It will be fixed to the blow mold at the stretched portion in contact with.
[0010]
If blow-stretching is continued in this state, the stretched portion excluding the stretched portion contacting the mold surface of the blow mold stretches only in the radial direction, whereas the entire unstretched portion is separated from the tip of the stretch pin. Thus, it is stretched in both the axial direction and the radial direction to be formed at the bottom of the heel.
[0011]
Since it is necessary to bring the stretched part near the unstretched part of the primary stretched preform , which is the boundary part between the body part and the bottom part of the preform , into contact with the mold surface of the blow mold as it is, The diameter dimension of the mold surface of the blow mold cannot be sufficiently increased with respect to the diameter dimension of the preform, and as a result, a low-stretch ratio casing having the bottom portion stretched is formed.
[0012]
The invention according to claim 2 is the blow mold of the stretched part in the invention according to claim 1 , which is the boundary part between the body part and the bottom part of the preform, near the unstretched part of the primary stretched preform. Contact to the surface is achieved by entering the blow mold of the primary stretch preform together with the stretch pin into the mold surface portion described above.
[0013]
In the second aspect of the present invention, the stretched portion fixed at the boundary between the body portion and the bottom portion of the preform is close to the unstretched portion of the primary stretched preform by the advancement of the stretch pin to the advance limit. Therefore, in the biaxial stretch blow molding of the unstretched portion after the advancement of the stretch pin is stopped, the stretch center point located at the tip of the unstretched portion hardly occurs.
[0014]
The invention according to claim 3 is the blow mold of the stretched part in the invention according to claim 1 , which is the boundary part between the body part and the bottom part of the preform, near the unstretched part of the primary stretched preform. Contact with the surface is achieved by continuous blow-drawing after the forward movement of the drawing pin is stopped and before the unstretched portion is separated from the tip of the drawing pin.
[0015]
In the invention according to claim 3 , there is a gap between the stretched portion near the unstretched portion of the primary stretched preform and the boundary between the body portion and the bottom portion of the preform and the mold surface of the blow mold. Therefore, a dimensional allowance can be provided between the primary stretched preform stretched in the axial direction and the blow mold, and accordingly, the mold surface and the mold of the blow mold can be provided. The allowable dimension range of the reform can be widened.
[0016]
Among the present inventions, the means of the invention according to claim 4 is:
A mold device for biaxial stretch blow molding,
The primary stretch preform blown from the preform mainly in the axial direction by the advance to the advance limit of the stretch pin and the press-fitting of the pressure fluid, close to the unstretched portion in contact with the tip of the stretch pin. , the mold surface portion of the blow mold which faces the extending portion was boundary portion between the body portion and the bottom portion of the preform, by advancing to the forward limit of the stretching pin, this unstretched portion close stretching portion The diameter was reduced to the extent of contact, and a sharp part was formed.
There is.
[0017]
In the invention of claim 4, as the mold surface portion of the blow mold that comes into contact with the stretched portion that was the boundary portion between the body portion and the bottom portion of the preform, near the unstretched portion of the primary stretched preform, is provided with the reduced diameter aperture portion, the contact fixing by the blow mold of the unstretched portion close stretching portions are easily and surely achieved.
[0018]
According to a fifth aspect of the present invention, in the invention according to the fourth aspect , the body portion of the preform in the vicinity of the unstretched portion is formed by the entrance of the primary stretched preform combined with the stretched pin into the portion of the sharp portion. It is set as the diameter dimension which contacts the extending | stretching part part which was the boundary part of a part and a bottom part .
[0019]
In this invention of Claim 5, the extending part which was the boundary part of the trunk | drum and bottom part of a preform near the unstretched part of a primary extending preform is contact-fixed by advance operation | movement of a extending | stretching pin. Since support of the unstretched portion is achieved, a stable blow molding operation is performed without causing displacement of the stretch center point located at the tip of the unstretched portion.
[0020]
The invention according to claim 6 is the unstretched portion of the invention according to claim 4, in which the unstretched portion is separated from the unstretched portion from the tip portion of the stretched pin during blow stretching after the forward stop of the stretched pin. The diameter is such that the stretched part which is the boundary part between the body part and the bottom part of the preform is in contact with the diameter.
[0021]
In the invention according to claim 6, a gap is formed between the stretched portion and the sharp portion, which is a boundary portion between the body portion and the bottom portion of the preform, near the unstretched portion of the primary stretched preform. Therefore, the allowable dimension range of the hollow portion can be widened with respect to the primary stretched preform, and the degree of freedom in designing the blow mold is increased.
[0022]
Of the present invention, the means of the invention according to claim 7 is:
When the biaxial stretch blow molding is performed, the outer diameter of the boundary between the collar body molded from the preform body and the collar bottom molded from the bottom of the preform is advanced to the advance limit of the stretching pin , pressure The boundary between the preform and the bottom of the primary stretch preform blown from the preform mainly in the axial direction due to fluid injection , close to the unstretched portion in contact with the tip of the stretch pin. It was a value substantially equal to the outer diameter of the stretched part that was part ,
That the bottom of the heel was blow-stretched from the unstretched portion of the primary stretch preform,
It is in.
[0023]
In the invention according to claim 7, the outer diameter of the boundary portion between the heel trunk portion and the heel bottom portion is the boundary portion between the preform body portion and the bottom portion in the vicinity of the unstretched portion of the primary stretch preform . Since this part is approximately equal to the outer diameter of the stretched part, this part is molded with a small stretch ratio to be thick, and the bottom of the heel is blow-stretched from the unstretched part of the primary stretch preform. Thus, a thick synthetic resin biaxially stretched blow-molded casing is obtained by stretching the entire body.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
The preform 1, the boundary between the bottom 5 which is bulged in the semi-ball-shell, and a body portion 2 having a cylindrical shape, a mouth tube portion 3 and the body 2 which is engraved the screw thread on the outer peripheral surface The outer peripheral surface of the portion is formed by surrounding the outer flange-shaped flange portion 4 to form an injection molded product made of PET.
[0025]
The preform 1 is fitted and held in an inverted position on the holding portion 18 of the drawing jig 16 having the drawing pins 17, and is heated to the blow temperature while being attached to the drawing jig 16. It is assembled to the mold 14.
[0026]
In the case of the illustrated embodiment, the blow mold 14 is configured by a pair of split molds, but may be configured by a combination of a pair of split molds and one bottom mold.
[0027]
After the mold clamping of the blow mold 14 is completed, the stretching pin 17 moves forward (in the figure, rises), and the body 2 including the bottom 5 of the preform 1 is stretched in the axial direction to the forward limit. At this time, the axial stretching simultaneously with or slightly later by stretching pin 17, to the I Ri blow stretching the pressed to the pressure fluid of the preform 1.
[0028]
When the stretching pin 17 advances to the forward limit and the preform 1 is blow- stretched to the primary stretching preform 6, the bottom 5 portion that is in contact with the tip of the stretching pin 17 is not yet formed as shown in FIG. The stretched portion 9 is formed, and the remaining bottom portion 5 and body portion 2 are stretched in the axial direction to become the stretched portion 8.
[0029]
When the preform 1 is stretch-molded into the primary stretched preform 6, the stretched portion 8 portion that is the boundary portion between the body portion 2 and the bottom portion 5 of the preform 1 near the unstretched portion 9 is as shown in the figure. It faces the crevice part 15 of the blow mold 14 through a small gap S or lightly contacts the crevice part 15.
[0030]
The primary stretched preform 6 is stretched to the secondary stretched preform 7 by blow stretching which continues after the stretching pin 17 stops at the forward limit. In this case, when there is a gap S, it is shown in FIG. Thus, before the unstretched portion 9 moves away from the tip of the stretch pin 17, the stretched portion 8 portion, which is the boundary portion between the body portion 2 and the bottom portion 5 of the preform 1, near the unstretched portion 9 is expanded. It is necessary to set the dimensional relationship between the preform 1 and the flexible portion 15 so as to come into contact with the flexible portion 15 by stretching in the radial direction.
[0031]
When the primary stretched preform 6 is formed, the stretched portion 8 portion, which is the boundary portion between the body portion 2 and the bottom portion 5 of the preform 1, which is close to the unstretched portion 9 , is in light contact with the sharp portion 15. Therefore, it is only necessary to make the outer diameter of the stretched portion 8 near the unstretched portion 9 equal to the inner diameter of the sharp portion 15.
[0032]
Stretching of the secondary stretched preform 7 after the stretched portion 8 portion , which is the boundary portion between the body portion 2 and the bottom portion 5 of the preform 1 in the vicinity of the unstretched portion 9, contacts the sharpened portion 15, The entire lower side of the contacted portion, that is, the extending portion 8 is simply expanded in diameter, whereas the entire upper portion of the portion in contact with the sharp portion 15, that is, the entire unextended portion 9 is illustrated by a dotted line in FIG. As described above, the biaxial stretching deformation is performed in the axial direction and the radial direction.
[0033]
In this way, the entire unstretched portion 9 is biaxially stretched in a state of being fixedly supported by the stretched portion 8 portion that was the boundary portion between the body portion 2 and the bottom portion 5 of the preform 1 . The stretching center located at the tip is hardly decentered, so that the thickness deviation hardly occurs.
[0034]
FIG. 1 shows an embodiment in which a casing body 11 and a bowl bottom 12 are entirely shaped like a bowl, and a casing 10 having a spire-like bowl bottom 12 is formed. No. 15, a part of the mold surface having a tapered surface with a reduced diameter is formed as it is.
[0035]
In contrast, FIG. 2 is obtained by imparting a self-supporting function Binsoko portion 12, the boundary between the Bindo portion 11 and the bottle bottom 12 in which the straight tubular, to form a constricted portion 13 which is reduced in diameter It has a structure.
[0036]
【The invention's effect】
Since the present invention has the above-described configuration, the following effects can be obtained.
In the first aspect of the invention, the unstretched portion of the primary stretched preform stretched mainly in the axial direction from the preform is the boundary portion between the trunk portion and the bottom portion of the preform in the vicinity of the unstretched portion. since biaxial stretching fixedly supported to the bottle bottom at a stretching portion was, the bottom of the biaxial stretch blow molding the bottle, can be formed by applying a stretching across it.
[0037]
In addition, since the stretched portion that was the boundary portion between the body portion and the bottom portion of the preform is brought into contact with the mold surface of the blow mold , which is close to the unstretched portion of the primary stretched preform stretched mainly in the axial direction. As a matter of fact, the stretch ratio can be kept small, whereby a thick casing can be obtained despite the bottom being stretch-molded.
[0038]
In the invention according to claim 2, since the fixed support for the unstretched portion where the stretching center is located is established simultaneously with the completion of the stretching in the axial direction, the two axes of the unstretched portion are not decentered. Stretching can be achieved, whereby the bottom portion can be stretch-molded without occurrence of uneven thickness.
[0039]
In the invention described in claim 3, since it is possible to give a margin to the mutual dimensional relationship between the preform and the blow mold, it is easy to manufacture the blow mold apparatus to be implemented and to mold the preform.
[0040]
In the invention of claim 4 , the contact of the stretched portion portion that was the boundary portion between the body portion and the bottom portion of the preform near the unstretched portion of the primary stretched preform, to the mold surface of the blow mold, Since it can be reliably, safely and easily achieved, biaxial stretch molding of the unstretched portion of the primary stretch preform to the bottom of the base can be stably and reliably achieved.
[0041]
In the invention according to claim 5, the contact fixing of the stretched portion portion that is the boundary portion between the body portion and the bottom portion of the preform in the vicinity of the unstretched portion of the primary stretch preform by the sharp portion is performed in the axial stretch. At the same time as the completion, it is reliably and stably achieved, so that the unstretched portion can be biaxially stretched to the bottom portion with high dimensional accuracy.
[0042]
In the invention according to the sixth aspect, since the allowable dimension range of the recess portion with respect to the primary stretch preform is large, the blow mold can be easily manufactured.
[0043]
In the invention according to claim 7, the outer diameter of the constricted portion of the housing is outside the stretched portion portion that is the boundary portion between the body portion and the bottom portion of the preform in the vicinity of the unstretched portion of the primary stretch preform. Since it is substantially equal to the diameter, it is easy to form a thick synthetic resin biaxially stretched blow-molded casing having a low stretch ratio, which is formed by stretch-molding the entire bottom portion.
[Brief description of the drawings]
FIG. 1 is a semi-longitudinal explanatory view showing a first embodiment of the present invention.
FIG. 2 is a semi-longitudinal explanatory view showing a second embodiment of the present invention.
FIG. 3 is a main part enlarged explanatory view for explaining the detailed operation of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Preform 2; Body part 3; Mouth part 4; Gutter part 5; Bottom part 6; Primary stretch preform 7; Secondary stretch preform 8; Stretch part 9; Unstretched part 10; part 12; Binsoko section 13; Ku beauty is 14; the blow mold 15; the throttle unit 16; stretching jig 17; stretching pin 18; holder S; gap

Claims

Primary stretch preform mainly blown in the axial direction from the preform (1) by the advance limit of the stretch pin (17) to the advance limit of the stretch pin (17) and the press-fitting of pressure fluid. In (6), the unstretched portion (9) in contact with the tip of the stretching pin (17) is set at a position leaving a mold space capable of giving sufficient stretching, and the stretching pin (17 ) forward limit or in to pre advances and also the undrawn portion (9) close by, the body portion of the preform (1) (2) and the bottom (5) and the stretching unit has a boundary portion (8) A biaxial stretch blow molding method in which the primary stretch preform (6) is blow-molded into a casing (10) by blow stretching which is continued as it is, with the portion brought into contact with the mold surface of the blow mold (14).

To the mold surface of the blow mold (14) in the stretched portion (8) portion, which was the boundary portion between the body portion (2) and the bottom portion (5) of the preform (1), near the unstretched portion (9). 2. The biaxial stretch blow molding method according to claim 1, wherein the contact of the first stretch preform (6) together with the stretch pin (17) is made to enter the mold surface portion of the blow mold (14). .

To the mold surface of the blow mold (14) in the stretched portion (8) portion, which was the boundary portion between the body portion (2) and the bottom portion (5) of the preform (1), near the unstretched portion (9). 2. The contact according to claim 1 is achieved by continuous blow stretching before the unstretched portion (9) leaves the tip of the stretching pin (17) after stopping the advancement of the stretching pin (17). Biaxial stretch blow molding method.

The stretching pin (17) of the primary stretching preform (6) blown and stretched mainly in the axial direction from the preform (1) by the advancement of the stretching pin (17) to the advance limit and the press-fitting of the pressure fluid. The stretched portion (8) , which is the boundary portion between the body portion (2) and the bottom portion (5) of the preform (1), is close to the unstretched portion (9) in contact with the tip portion of the preform. The diameter of the blow mold (14) is reduced to the extent that the stretched portion (8) near the unstretched portion (9) comes into contact with the mold surface portion of the blow mold (14) by the advance to the advance limit of the stretched pin (17). A die device for biaxial stretch blow molding formed by forming a sharp portion (15).

Squeezing unit (15), the entry of which the squeezing unit (15) stretching pin (17) and the primary stretching preform became together to part (6), unstretched portion (9) close the preform (1 The die device for biaxial stretch blow molding according to claim 4, wherein the die size is in contact with a stretched portion (8) portion which was a boundary portion between the body portion (2) and the bottom portion (5) .

Prior to the unstretched portion (9) moving away from the tip of the stretch pin (17), the unstretched portion (9) The biaxial stretch blow molding according to claim 4, wherein the stretched portion (8) , which is the boundary portion between the body portion (2) and the bottom portion (5) of the preform (1), is brought into contact with the diameter. Mold equipment.

壜 body part (11) formed from the body part (2) of the preform (1 )
And the outer diameter of the boundary between the bottom (5) formed from the bottom (5) of the preform (1) and the advancement to the advance limit of the stretching pin (17) during biaxial stretch blow molding , by press-fitting of the pressure fluid, the preform (1) from the main blow drawn primary stretching preform in the axial direction (6), unstretched portions in contact with the tip of the stretching pin (17) ( 9) It is set to a value substantially equal to the outer diameter of the extending portion (8) which was the boundary portion between the body (2) and the bottom (5) of the preform (1), and the heel bottom (12) A biaxially stretched blow-molded casing made of synthetic resin, which is blow-stretched from the unstretched portion (9).