【０００１】
【発明の属する技術分野】
この発明は、胴部が前後壁が両側壁よりも幅広の角筒形で薄肉の周壁に環状リブを凹設した延伸ブローボトルに関するものである。
【０００２】
【従来の技術】
従来の周壁を角筒形状に形成した延伸ブロー成形によるボトルでは、薄肉の胴部の剛性を高める手段として、胴部の周壁を周方向に凹設した環状溝部により上下部に区画している。またその環状溝部の中央部に補強用の突部を設けているものもある（例えば、特許文献１参照）。
【０００３】
【特許文献１】
特開平９−１９３９１８号公報（第２−３頁、図１、図２）。
【０００４】
【発明が解決しようとする課題】
前後壁が両側壁よりも幅広の角筒形で隅部を斜面に形成し、その隅部を除く周壁を外側に緩曲面に形成した胴部に、該周壁を上下部に区画する環状リブを、周方向に連続して凹設した平断面形状が長方形の周知の延伸ブローボトルでは、前後壁のスパン（両端間の長さ）が両側壁のスパンよりも長いことから、内容物の充填時や段ボール箱に入れて積み重ねた時に、上方からボトル口部に押圧力（トップロード）が加わると、胴隅部に次いでスパンが長い前後壁の方に押圧力が強く作用し、前後壁のどちらかの環状リブの上壁側が座屈するようになって、ボトルが環状リブから屈曲変形し易いとされている。
【０００５】
このためボトルの軽量化を目的として、通常５７〜７０ｇを要する２リットルの飲料水用の包装用ボトルを、これまでより胴部を薄肉に形成して、ボトル重量を５５ｇ以下に軽くするには、環状リブの部位における変形を何らかの手段により防止することが必要となる。
【０００６】
上記特許文献１に記載されているように、正方形の胴部の周壁に連続形成した環状溝部の内部中央に、補強リブを横長に設けることは知られている。しかし、その補強リブは内容物の加熱充填後の冷却時に生ずる内部負圧により、環状溝部が折れるのを防止するためのもので、これを上方からの押圧力に対する環状リブの補強リブに採用すると、環状リブ内が二重溝となって圧縮され易くなり、さらに変形し易くなる。また環状リブ内に複数の縦リブを設けて補強することも考えられるが、それはスパンの短い両側壁の環状リブには有効であっても、スパンの長い前後面側では効果が殆どなく、ボトルデザインの上からも好ましいものではない。
【０００７】
この発明は、上記事情から考えられたものであって、その目的は、スパンが長い前後壁側の環状リブの両端を、ボトル隅部の隅リブと関連づけて補強リブに形成することにより、胴部肉厚を薄減してボトル重量を節減しても、押圧力によりボトルが屈曲変形し難い新たな延伸ブローボトルを提供することにある。
【０００８】
【課題を解決するための手段】
上記目的によるこの発明は、前後壁が両側壁よりも幅広の角筒形で隅部を斜面に形成し、その隅部を除く周壁を外側に緩曲面に形成した胴部に、該周壁を上下部に区画する環状リブを連続して凹設した延伸ブローボトルであって、上記環状リブを上下リブ面が弯曲斜面でリブ底面が垂直な台状形に形成するとともに、前後壁のリブ底面を真直に形成して中央部を両端部よりも深く形成し、その環状リブの隅部斜面に位置する部位にリブ底面を膨出して隅リブを設ける一方、両側壁の環状リブ内に一対の側面リブをリブ底面を膨出して対設し、前後壁の環状リブの隅部斜面に隣位する両端に、リブ底面の膨出による補強リブを隅リブと連続して設けてなり、上記各リブは環状リブの上下リブ面の中程までリブ底面を平面台状形に膨出して形成してなるというものである。
【０００９】
【発明の実施の形態】
図中１は重量５０〜５５ｇの飲料水用のボトルで、射出成形したポリエチレンテレフタレート（ＰＥＴ）のプリフォームを、延伸ブロー成形して製造した胴部２が薄肉のものからなる。この胴部２は前後壁３が両側壁４よりも１５〜２０％ほど幅広の平断面形状が長方形の角筒形で、四方の隅部５を斜面に隅取り形成した周壁に、該周壁を上下部２ａ，２ｂに区画する環状リブ６を連続して凹設したものからなる。
【００１０】
この周壁の上下部２ａ，２ｂの壁面には、内容物の加熱充填後の冷却により生ずる内部負圧に耐えるリブが、正方形又は長方形に形成してある。また上記隅部５を除く周壁は、予め外側に緩曲面に膨出形成して、内容物の荷重により周壁が外側に膨らみ変形しないようにしてある。
【００１１】
上記環状リブ６は、図４に示すように、上下リブ面６ａが弯曲斜面でリブ底面６ｂが垂直な台状形の横溝に形成されており、両側壁４では壁面と並行にリブ底面を緩曲形成しているが、前後壁３ではリブ底面６ｂを横方向に真直に形成して中央部を両端部よりも深くしてある。
【００１２】
この環状リブ６の隅部５の斜面に位置する部位には、リブ底面６ｂを膨出して突出形成した隅リブ７が設けてある。また両側壁４の環状リブ６内の対称位置には、一対の側面リブ８がリブ底面６ｂを膨出して対設してあり、さらに前後壁３の環状リブ６の隅部斜面に隣位する両端には、リブ底面６ｂの膨出による補強リブ９が隅リブ７と連続して設けてある。この補強リブ分だけ前後壁３の環状リブ６は、スパンが実質的に短くなって押圧力により沈み難くなる。
【００１３】
これらの隅リブ７、側面リブ８、補強リブ９は、図に示すように、環状リブ６の上下リブ面６ａの中程まで突出形成するのが好ましく、また平面断面が台状形になるように形成しているが、隅リブ７はコーナーに向けて膨出形成されることから角が丸く成形されて弧状となり易い。しかし、その何れにおいても中程までの膨出形成によって全体的に肉厚が均等な縦リブとして機能する。
【００１４】
上記構造のボトル１では、ボトル口部に上方から押圧力が加わると、環状リブ６の四隅の隅リブ７により押圧力を受けることになるが、前後壁３のスパンが両側壁４のスパンよりも長く形成された長方形の胴部２では、前後壁３の方が物理的に押圧力に弱いので、緩曲面の前後壁３に対し真直で垂直なリブ底面６ｂからなる環状リブ６でも、上面側が歪んで沈みがちとなる。
【００１５】
また環状リブ６の強度は、僅かな肉厚分布の差などから同一ではないことと、押圧力の掛かり方にも偏りがあることから、前後壁３の何れか一方に大きく沈みが生じて、片側の環状リブ６が内側に潜り込んで沈み、反対側の環状リブ６が上側に引っ張られるようになるが、前後壁３の環状リブ６の両端を、隅リブ７と連続した補強リブ９に形成したので、環状リブ６の端部が補強リブ９により支えられるとともに、隅リブ７と相俟って隅部５から前後壁３の端部にかけての圧縮又は引張り抵抗が増すという相乗作用により、前後壁側の環状リブ６の沈みが小さく抑制されて、前後壁３における環状リブ６から上壁面２ａにかけての座屈が阻止され、前後壁側の環状リブ６からボトル１が屈曲変形するのが防止されるようになる。
【００１６】
この結果、胴部２が薄肉で軽量化されたボトル１であっても、大きな押圧力に十分に耐えるものとなる。また環状リングは内部の各リブにより側方に対しても補強された状態となるので、内容物の荷重により胴部２が環状リング６の部位から膨らみ変形すことも防止されて、全体的に剛性を有するようになり、使用樹脂量の節減から胴部肉厚をこれまでより薄肉に形成しても、飲料水等の包装用ボトルとして、十分に使用可能な経済性を有するボトルを提供することができる。
【００１７】
【実施例】
【図面の簡単な説明】
【図１】この発明に係わる延伸ブローボトルの前面図である。
【図２】同じく側面図である。
【図３】環状リブ部分の平断面図である。
【図４】図３Ａ−Ａ断面図である。
【図５】各リブの寸法を示す環状リングの隅部平断面図である。
【符号の説明】
１ ボトル
２ 胴部
３ 前後壁
４ 両側壁
５ 隅部
６ 環状リブ
６ａ 上下リブ面
６ｂ リブ底面
７ 隅リブ
８ 側面リブ
９ 補強リブ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stretch blow bottle in which a body portion has a rectangular cylindrical shape whose front and rear walls are wider than both side walls and an annular rib is recessed in a thin peripheral wall.
[0002]
[Prior art]
In a conventional bottle formed by stretch blow molding in which a peripheral wall is formed in a rectangular cylindrical shape, the peripheral wall of the body is divided into upper and lower portions by an annular groove recessed in a circumferential direction as means for increasing rigidity of a thin body. In some cases, a reinforcing projection is provided at the center of the annular groove (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-9-193918 (pages 2-3, FIGS. 1 and 2).
[0004]
[Problems to be solved by the invention]
An annular rib that partitions the peripheral wall into upper and lower portions is formed on a body portion in which the front and rear walls are formed in a rectangular cylindrical shape wider than both side walls and the corners are formed on the slopes, and the peripheral wall excluding the corners is formed with a gentle curved surface on the outside. In the case of a well-known stretch blow bottle having a rectangular cross-sectional shape that is continuously recessed in the circumferential direction, the span of the front and rear walls (the length between both ends) is longer than the span of both side walls. When the bottles are stacked in a box or cardboard box, if a pressing force (top load) is applied to the bottle mouth from above, the pressing force acts strongly on the front and rear walls, which have a longer span next to the body corner, and It is said that the upper wall side of the annular rib buckles, and the bottle is easily bent and deformed from the annular rib.
[0005]
For this reason, in order to reduce the weight of the bottle, it is necessary to reduce the bottle weight to 55 g or less by forming a 2 liter bottle for drinking water, which usually requires 57 to 70 g, into a thinner body than ever before. In addition, it is necessary to prevent deformation at the portion of the annular rib by some means.
[0006]
As described in Patent Literature 1, it is known that a reinforcing rib is provided horizontally long at an inner center of an annular groove formed continuously on a peripheral wall of a square body. However, the reinforcing rib is for preventing the annular groove portion from being broken due to an internal negative pressure generated at the time of cooling after heating and filling of the contents, and if this is used as a reinforcing rib for the annular rib against a pressing force from above. In addition, the inside of the annular rib becomes a double groove, which is easily compressed and further deformed. It is also conceivable to provide a plurality of vertical ribs in the annular ribs to reinforce them, but this is effective for the annular ribs on both side walls with a short span, but has little effect on the front and rear sides with a long span. It is not desirable from the viewpoint of design.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to form a body rib by forming both ends of an annular rib on the front and rear walls having a long span in association with a corner rib at a corner of a bottle. It is an object of the present invention to provide a new stretch blow bottle in which the bottle is hardly bent and deformed by the pressing force even when the bottle thickness is reduced by reducing the wall thickness.
[0008]
[Means for Solving the Problems]
The present invention according to the above object has a front and rear wall which is formed in a rectangular cylindrical shape wider than both side walls and has a corner formed on an inclined surface, and a peripheral wall excluding the corner formed with a gentle curved surface on the outer side. A stretch blow bottle in which annular ribs partitioned into sections are continuously recessed, wherein the annular ribs are formed in a trapezoidal shape in which the upper and lower rib surfaces are curved slopes and the rib bottom surface is vertical, and the rib bottom surfaces of the front and rear walls are A straight portion is formed so that the central portion is formed deeper than both end portions, and a rib bottom is bulged at a portion located on a corner slope of the annular rib, and a pair of side surfaces are provided in the annular ribs on both side walls. The ribs are bulged at the bottoms of the ribs and opposed to each other, and reinforcing ribs formed by bulging the rib bottoms are provided at both ends of the front and rear walls adjacent to the corner slopes of the annular ribs. Is formed by bulging the rib bottom into a flat trapezoidal shape to the middle of the upper and lower rib surfaces of the annular rib. It is intended to become.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
In the figure, reference numeral 1 denotes a bottle for drinking water having a weight of 50 to 55 g, and a body 2 made by stretch-blowing an injection-molded polyethylene terephthalate (PET) preform is made of a thin wall. The body 2 has a front and rear wall 3 that is 15 to 20% wider than the side walls 4 and has a rectangular cross section with a rectangular cross section, and a four-sided corner 5 formed on a slope to form a peripheral wall. The annular rib 6 is divided into upper and lower portions 2a and 2b, and is continuously formed in a concave shape.
[0010]
On the wall surfaces of the upper and lower portions 2a and 2b of the peripheral wall, ribs are formed in a square or rectangular shape to withstand internal negative pressure generated by cooling after heating and filling of the contents. The peripheral wall excluding the corners 5 is formed to bulge outward in advance into a gentle curved surface so that the peripheral wall does not bulge outward and deform due to the load of the contents.
[0011]
As shown in FIG. 4, the annular rib 6 is formed in a trapezoidal horizontal groove in which the upper and lower rib surfaces 6a are curved slopes and the rib bottom surface 6b is vertical. Although it is curved, the rib bottom surface 6b of the front and rear walls 3 is formed to be straight in the lateral direction, and the center portion is deeper than both end portions.
[0012]
A corner rib 7 is formed on a portion of the annular rib 6 located on the slope of the corner 5 so as to protrude and protrude from the rib bottom surface 6b. A pair of side ribs 8 bulge out from the rib bottom surface 6b at symmetrical positions in the annular ribs 6 of the side walls 4, and are adjacent to the corner slopes of the annular ribs 6 of the front and rear walls 3. At both ends, reinforcing ribs 9 formed by bulging of the rib bottom surface 6b are provided continuously with the corner ribs 7. The span of the annular rib 6 of the front and rear walls 3 is substantially shortened by the amount of the reinforcing rib, and the annular rib 6 is unlikely to sink due to the pressing force.
[0013]
These corner ribs 7, side ribs 8, and reinforcing ribs 9 are preferably formed so as to protrude to the middle of the upper and lower rib surfaces 6a of the annular rib 6 as shown in the figure, and have a trapezoidal planar cross section. However, since the corner ribs 7 are formed to bulge toward the corners, the corners are formed to have rounded corners, which tends to be arcuate. However, in any case, the bulges formed to a middle extent function as vertical ribs having a uniform thickness as a whole.
[0014]
In the bottle 1 having the above structure, when a pressing force is applied to the bottle mouth from above, the pressing force is applied by the corner ribs 7 at the four corners of the annular rib 6. Since the front and rear walls 3 are physically weaker in the pressing force in the rectangular body portion 2 which is also formed long, even the annular ribs 6 having the rib bottom surfaces 6b which are straight and perpendicular to the front and rear walls 3 having a gentle curved surface, have the upper surface. The sides are distorted and tend to sink.
[0015]
Further, the strength of the annular rib 6 is not the same due to a slight difference in thickness distribution and the like, and there is also a bias in the manner in which the pressing force is applied, so that one of the front and rear walls 3 greatly sinks, The annular rib 6 on one side sinks down and sinks inward, and the annular rib 6 on the opposite side is pulled upward. However, both ends of the annular rib 6 of the front and rear walls 3 are formed as reinforcing ribs 9 continuous with the corner ribs 7. As a result, the end of the annular rib 6 is supported by the reinforcing rib 9, and the compression or tensile resistance from the corner 5 to the end of the front and rear wall 3 is increased in cooperation with the corner rib 7, whereby the front and rear ends are increased. The sinking of the annular rib 6 on the wall side is suppressed to a small extent, so that buckling from the annular rib 6 on the front and rear walls 3 to the upper wall surface 2a is prevented, and the bottle 1 is prevented from being bent and deformed from the annular rib 6 on the front and rear walls. Will be done.
[0016]
As a result, even if the body 2 is a thin and lightweight bottle 1, it can sufficiently withstand a large pressing force. Further, since the annular ring is reinforced by the ribs on the sides thereof, the body 2 is prevented from bulging and deforming from the annular ring 6 due to the load of the contents. The present invention provides a bottle having sufficient economical efficiency that can be sufficiently used as a packaging bottle for drinking water, even if it has rigidity and can be formed to be thinner than ever before due to reduction in the amount of resin used. be able to.
[0017]
【Example】
[Brief description of the drawings]
FIG. 1 is a front view of a stretch blow bottle according to the present invention.
FIG. 2 is a side view of the same.
FIG. 3 is a plan sectional view of an annular rib portion.
FIG. 4 is a cross-sectional view of FIG. 3A-A.
FIG. 5 is a plan sectional view of a corner of an annular ring showing dimensions of each rib.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 bottle 2 body 3 front and rear wall 4 both side walls 5 corner 6 annular rib 6 a upper and lower rib surfaces 6 b rib bottom 7 corner rib 8 side rib 9 reinforcing rib