JP2004122457A - Bottle body made of synthetic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bottle body made of a synthetic resin having sufficient rigidity even with respect to a large container reaching several L in its volume and excellent in handleability and appearance in consideration of a technical subject for suppressing the bottom falling of the depressed part forming part of the bottom part of the bottle body. <P>SOLUTION: The bottle body is obtained from a preform being a primary molded product by biaxial stretching blow molding. The bottom part of the bottle body has an annular flat part becoming an earthing part provided to its peripheral edge and the depressed part formed from the inner peripheral edge of the annular flat part and the central part thereof. A gentle recessed part is formed to the undersurface of the central part of the depressed part by a support pin, which has a gentle projected shape formed to the leading end surface thereof, for supporting the bottom part of the preform from the outside in a state grasping the bottom part from the inside along with a stretching rod at the time of biaxial stretching blow molding. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention particularly relates to a synthetic resin bottle having a bottom formed by biaxial stretch blow molding and depressed into a substantially arc-shaped shell.
[0002]
[Prior art]
In recent years, bottles formed by biaxial stretching blow molding of polyethylene terephthalate resin (hereinafter referred to as PET), which is synthetic resin, particularly transparent and excellent in mechanical strength and gas barrier properties, have been frequently used. .
[0003]
In order to make PET or other thermoplastic resin into a bottle by biaxial stretching blow molding, a preform as a primary molded product is molded by injection molding, and this preform is biaxially oriented in a blow molding die. Stretch blow molding is performed. In many cases, the neck portion of the opening of the preform is attached to a blow mold, heated to a temperature at which stretch molding is possible, and then blow molded while being stretched in the longitudinal direction by a stretching rod. (See Patent Document 1)
[0004]
When the blow molding is performed by such a method, there is a drawback that the preform is liable to be laterally shaken due to a vibration phenomenon caused by air pressure blown into the preform to easily cause uneven thickness in the bottle. In Patent Document 2, an opening neck of a preform is attached to a blow molding die, and a bottom portion is supported while being sandwiched between a tip surface of an inner extending rod and a tip surface of an outer support pin. There is a description of a method of performing blow molding while retracting the support pin while stretching in the direction.
[0005]
Also, in many cases, the bottom of these bottles has an annular flat portion on the peripheral edge that serves as a ground contact portion,
In addition to ensuring a stable ground contact surface, the central portion has a depression formed in the body inward, and has sufficient rigidity to resist deformation due to the weight of the content liquid. In addition, the shape of the depressed portion is made suitable for the application by, for example, providing a rib in the radial direction so as to withstand a reduced pressure state at the time of filling the content liquid at a high temperature.
[0006]
[Patent Document 1]
JP-A-57-12617 [Patent Document 2]
JP-A-10-71641
[Problems to be solved by the invention]
However, in order to ensure high productivity, the bottle is usually taken out of the mold at a high temperature after molding, so when the molded product is released, the surface rigidity of the depression is insufficient and the depression Is pulled down below the bottle, and the depression height becomes lower than the design value, so-called a bottom-down deformation state may occur. This deformation is caused by the shape of the annular flat portion located at the periphery of the depression. In addition, there is a problem such as poor contact with the ground, and there is also a problem from the viewpoint of appearance.The shape of the bottom can be released more smoothly and the bottom can be prevented from falling down. Creation is an issue.
[0008]
In view of the above, the present invention has been made to solve the above-described problems in the prior art, and has a technical problem of suppressing the bottom of the depression of the bottom of the bottle book from falling. It is an object of the present invention to provide a synthetic resin bottle excellent in quality.
[0009]
[Means for Solving the Problems]
In the present invention for solving the above technical problems, the means of the invention described in claim 1 is:
It is biaxially stretch blow-molded from a preform, which is a primary molded product, and has an annular flat portion serving as a ground contact portion at a peripheral portion of the bottom portion, and a depression formed in the body inward from the inner peripheral edge to the center of the annular flat portion. Having a depressed portion,
At the bottom of the center of the depression, the bottom surface of the preform is clamped together with the extension rod from the inside during the secondary stretch blow molding, and the tip end surface supported from the outside is formed by a gently convex support pin. Having a configuration having a concave portion,
It is in.
[0010]
The bottle having the above configuration according to claim 1, wherein the opening neck portion of the preform is attached to the blow mold, and the bottom portion is stretched in the longitudinal direction by the stretching rod from a state where the bottom portion is sandwiched between the inner stretching rod and the outer support pin. At the same time, it is molded by a method of blow molding while retracting the support pin, and is taken out as a product through a mold opening process such as opening of a main body split die, retraction of a blow core die and a stretch rod, and a release process.
[0011]
In the mold opening and releasing steps, the support pin is slightly protruded by the resilient force of a spring installed at the base end thereof and presses the lower surface of the center of the depression of the bottle by pressing the bottom mold surface. Demonstrates the function of smoothly releasing from the mold.
[0012]
In addition, the lower surface of the depressed portion at the bottom of the bottle is pressed against the tip surface of the support pin due to the force acting during the longitudinal stretching by the stretching rod and the air blowing step, and the bottle is in a state of being in close contact with the bottle. Since the adhesive force is considerably large, the depressed portion is pulled down below the bottle by this separating operation, causing a so-called bottom-down deformation.
[0013]
Here, as in the configuration of claim 1, the shape formed by the support pins on the center lower surface of the depressed portion of the bottle is formed into a gentle concave shape, that is, the tip end surface of the support pin is formed into a gentle convex shape. By doing so, at the peripheral edge of the contact portion between the depression center central lower surface and the support pin, the action of the pressing force generated at the time of the above-described stretching step can be reduced, so that the adhesive force between the two at the peripheral edge is reduced. The separation between the two can be easily and smoothly achieved while starting from the peripheral portion and smoothly progressing toward the central portion, so that the so-called bottom-down deformation of the depression is suppressed to a small extent. be able to.
[0014]
Considering the mechanism for separating the contact portion as described above, it is preferable that the tip surface of the support pin rises at a gentle angle from the peripheral edge, has no step on the way, and has a shape that is not too high in overall height.
[0015]
On the other hand, if the shape formed by the support pin on the center lower surface of the depression of the bottle is convex or substantially flat, that is, if the tip surface of the support pin is concave or substantially flat, The action of the mutual pressing force at the time of molding tends to be equal to or greater than the central part, and a large force is required to separate the peripheral part, and the center of the depressed part is closer to the lower part of the bottle due to the adhesion force , Causing a large bottom-down condition.
[0016]
According to a second aspect of the present invention, the concave portion has a concave depth in a range of 0.5 to 2.5 mm.
[0017]
If the concave depth is less than 0.5 mm, the effect on bottom drop is small, and if the concave depth is too large, that is, if the inclination at the tip end surface of the support pin becomes too large, the contact area increases. In the vicinity of the peripheral portion of the close contact portion, smooth separation is difficult due to factors such as a force not effectively acting in a direction in which the two are separated from each other. Thereby, the effect of suppressing bottom falling in a bottle having a capacity of about 0.5 to 5 liters is sufficiently exhibited.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings (FIGS. 1 to 5).
The bottle 1 according to the present embodiment is a biaxial stretch blow-molded product made of PET having a capacity of 4 liters, and includes a mouth portion 2, a shoulder portion 3, a body portion 4 and a bottom portion 5.
[0019]
The bottom portion 5 has an annular flat portion 6 serving as a ground contact portion at a peripheral portion, and is formed in a substantially arcuate shell shape from the inner peripheral edge to the center inward of the body portion 4 to secure sufficient surface rigidity of the bottom surface. A tip surface 16a for supporting the center of the bottom surface of the preform P from below at the time of the second stretch blow molding at the center axis position of the bottle 1 at the center lower surface of the recess 7 Has a gentle concave portion 8 formed by a convex support pin 15.
[0020]
3 to 5 show an example of a method for molding the bottle 1 of the present embodiment, and FIG. 3 shows a state in which a preform P is attached to a molding apparatus, and is used for blow molding. The mold is composed of a main body split mold 11, a blow core mold 12, and a bottom mold 13. The blow core mold 12 has a mouth-neck portion 12a that fits into the opening neck portion of the preform P, An air hole for blowing (omitted in the figure) and an extension rod 14 are provided concentrically at the center thereof, and the mouth and neck 12a and the upper end of the main body split mold 11 hold the opening neck of the preform P.
[0021]
In addition, the bottom mold 13 has a support pin 15 which can be advanced and retracted at the center, and a distal end face 16a of the support pin 15 has a gentle convex shape. The convex height of the distal end face 16a is 1. It is 5 mm.
[0022]
A preform P having a shape of a cylinder with a bottom and a test tube by injection molding of PET is preformed as a primary molded product, and an opening neck portion of the preform P is, as shown in FIG. It is fitted into the mouth and neck portion 12a of the blow core mold 12 of the molding die, clamped by the main body split die 11, and has a stretching rod 14 provided with the bottom of the preform P inside and a support pin 15 provided outside. Between them so that the center of the stretching is not displaced.
[0023]
From the above state, the preform P is stretched in the longitudinal direction by advancing the stretching rod 14 and, at the same time, the support pin 15 is retracted and the pressurized air is injected into the preform P to expand it, thereby stretching in the biaxial direction. The bottle 1 is blow-molded.
[0024]
FIG. 4 shows the state of the bottle 1 stretch blow-molded as described above in the molding die. From this state, the bottle 1 is subjected to a predetermined heat in the molding die. After a heat treatment operation such as setting and cooling, the main body split mold 11 is opened, the blow core mold 12 and the stretching rod 14 are retracted, and the mold is opened, and the product is taken out through a release process.
[0025]
In the releasing step, the support pin 15 has its tip end surface 16a slightly protruding due to the resilience of a spring installed below and presses the lower surface of the center of the depression 7 of the bottle 1 to push the support pin 15 from the bottom mold 13 surface. The function to smoothly release the mold is exhibited.
[0026]
Further, after the bottom 5 is released, it is necessary to separate the distal end surface 16a of the support pin 15 and the lower surface of the center of the depressed portion 7 from each other, but by making the distal end surface 16a of the support pin 15 a gently convex shape, This separation can be achieved smoothly, and the center of the recessed portion 7 is pulled downward at the time of this separation, so that the so-called bottom-down state can be suppressed.
[0027]
FIG. 5 shows a state in which the bottom 5 of the bottle 1 of the present embodiment is sandwiched between the stretching rod 14 and the support pin 15 in the molding die after the stretching blow. A concave portion 8 was formed on the lower surface at the center of the concave portion 7, and the concave depth was approximately 1.5 mm.
[0028]
FIG. 6 shows a comparative example, in which the other shape is the same as that of the above-mentioned one example, and is a bottle 1 having a bottom portion 5 having a convex portion 9 on the center lower surface of a depression 7. FIG. 7 shows a state similar to that of FIG. 5 of the above-described embodiment when the bottle 1 of the comparative example is formed. I have.
[0029]
With respect to the bottles 1 of the above example and the comparative example, the state of falling down after the molding was measured.
When the height of the center of the depression 7 was measured from the bottom surface of the mold (refer to the height H of the depression in FIGS. 1 and 6), it was 9.5 mm in one example, and 7.5 mm in the comparative example. The so-called bottom drop was 1.5 mm and 3.5 mm, respectively, as compared with 11 mm which is the dimension of the molding die, and the bottom drop of the bottle 1 of the present invention was small and suppressed.
[0030]
In the above-described embodiment, for example, the entire wall at the center of the recess 7 is formed to be recessed upward from the lower surface of the recess 7. By making the shape to be formed into a gentle concave shape, the separation of the support pin 15 is smoothly achieved, and the so-called bottom drop is suppressed. This is generally exhibited by the bottle 1 having the depression 7.
[0031]
【The invention's effect】
The present invention has the above-described configuration, and has the following effects.
According to the first aspect of the present invention, the shape formed by the support pins on the center lower surface of the depression is formed into a gentle concave shape, so that the lower surface of the center of the depression at the bottom of the bottle can be removed from the molding die. The separation of the support pin from the distal end surface is smoothly achieved, and the so-called bottom fall of the bottom recessed portion can be suppressed to be small.
[0032]
According to the second aspect of the present invention, by setting the depth of the concave portion in the range of 0.5 to 2.5 mm, the effect of suppressing bottom dropping in a bottle having a capacity of about 0.5 to 5 liters can be obtained. It is fully demonstrated.
[Brief description of the drawings]
FIG. 1 is a front view showing one embodiment of a synthetic resin bottle of the present invention.
FIG. 2 is a bottom view of the embodiment of FIG.
FIG. 3 is a longitudinal sectional view showing a state in which a preform is held in a molding apparatus for molding an embodiment of the synthetic resin bottle of the present invention.
FIG. 4 is a longitudinal sectional view showing a state in which a preform is formed into a bottle in FIG. 3;
FIG. 5 is an explanatory longitudinal sectional view showing an enlarged main part of a state in which a bottle is held at the center of a depressed portion in FIG. 4;
FIG. 6 is a front view showing a comparative example of a synthetic resin bottle.
FIG. 7 is an explanatory longitudinal sectional view showing an enlarged main part of a state in which the center of the depressed portion of the bottle of the comparative example is sandwiched.
[Explanation of symbols]
1; Bottle body 2; Mouth 3; Shoulder 4; Body 5; Bottom 6; Annular flat portion 7; Depressed portion 8; Depressed portion 9; Convex portion 11; Body split mold 12; Mouth and neck 13; Bottom mold 14; Stretching rod 15; Support pin 16a; Tip surface 16b; Tip surface P; Preform H;

Claims (2)

The preform (P), which is a primary molded product, is biaxially stretched and blow-molded, and has a bottom portion (5) and an annular flat portion (6) serving as a ground contact portion at a peripheral portion. A body (4) has a depression (7) which is depressed inward from the inner peripheral edge to the center, and the bottom of the preform (P) is formed on the lower surface of the depression (7) at the time of the second stretch blow molding. Having a moderately concave portion (8) formed by a support pin (15) having a moderately convex tip end surface, which is supported from the outside while being sandwiched with a stretching rod (14) from the inside. Bottle made of synthetic resin. 2. The synthetic resin bottle according to claim 1, wherein the concave portion has a concave depth in the range of 0.5 to 2.5 mm.

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