JPH11115923A - Bottom part structure of plastic bottle body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bottom part structure of a plastic bottle body reducing the strain generated in the bottom part of the bottle body at a time of molding at proper temp. and hard to generate deformation with the elapse of time and thermal deformation. SOLUTION: The bottom part 2 of a plastic bottle body 1 molded from a primary molded product preform by biaxial stretch blow molding is equipped with the annular bottom wall part 4 continuing to a body part 3, the projected bottom wall part 5 projected into the body part 3 in a semisphirical shape from the inner peripheral edge of the annular bottom wall part 4 along the center axial line 1a of the bottle body and a recessed bottom wall part 6 formed by depressing the top wall part of the projected bottom wall part 5 in a semispherical shape. The shape of the recessed bottom wall part 6 is allowed to substantially coincide with that of the leading end part of the bottom part of the preform. The state at a time of the molding of the preform is left in the bottom part of the bottle body easiest to generate thermal deformation of the plastic bottle body 1 as it is and the strain of the bottle bottom part at a time of blow molding is also reduced. Therefore, thermal deformation or deformation with the elapse of time is hard to generate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic bottle formed by biaxially stretching and blowing a preform of a primary molded product. More specifically, the present invention relates to a bottom structure of a Placig bottle which is unlikely to undergo thermal deformation and temporal deformation.

[0002]

2. Description of the Related Art A plastic bottle represented by a PET bottle is biaxially stretch blow-molded from a preform as a primary molded product. The preform is injection molded by an injection molding machine and heated to a temperature suitable for blow molding while being transported to the blow molding machine for biaxial stretch blow molding. Alternatively, the preform after injection molding is conveyed into a blow mold while being kept at a temperature suitable for biaxial stretch blow molding. In a blow molding machine, a preform is blow molded while being stretched vertically and horizontally. Therefore, in general, distortion generated during the blow molding process remains in the plastic bottle after the blow molding.

[0003] For example, in the case of a PET bottle, a preform made of PET resin has a temperature of 250 ° C to 2 ° C.
It is injection molded by an injection molding machine in a state of being melted at 80 degrees. The biaxial stretch blow molding is performed in a state where the PET resin preform is heated to about 90 to 110 degrees Celsius. Although distortion generated during injection molding performed at a high temperature is extremely small, distortion generated during blow molding performed at a relatively low temperature tends to be large.

[0004]

When the residual distortion during blow molding of a plastic bottle is large, the plastic bottle is easily deformed with time, and may shrink or deform even at room temperature. In particular, a PET bottle or the like may be filled with high-temperature contents of about 85 to 92 degrees Celsius. In this case, the filling of the hot contents is performed in a state where the filling nozzle is inserted to a position near the bottom of the bottle. As a result, heat and filling pressure act on the bottom of the bottle at the time of filling, so that the bottle is easily deformed. Such deformation due to heat and pressure during the filling of the high-temperature contents is more likely to occur as the blow molding temperature of the bottle is closer to the temperature of the contents to be filled.

Therefore, in order to prevent such deformation, the temperature of the preform at the time of blow molding should be set to a temperature sufficiently higher than the temperature of the filler. However, when the temperature of the preform is increased, for example, when the temperature of the PET resin preform is increased to 130 ° C. to 150 ° C., the viscosity of the resin is reduced, or the resin is crystallized. There is a possibility that blow molding cannot be performed properly.

[0006] The object of the present invention is to solve the above problems.
An object of the present invention is to propose a bottom structure of a plastic bottle that generates little distortion at the bottom of the bottle during blow molding at an appropriate temperature and is unlikely to undergo temporal deformation and thermal deformation.

[0007]

In order to solve the above-mentioned problems, the present invention adopts the following structure in a bottom structure of a plastic bottle which is biaxially stretch blow-molded from a primary molded product preform. ing.

Referring to FIG. 1, the bottom portion 2 of the plastic bottle 1 has an annular bottom wall portion 4 which is continuous with the body 3 of the plastic bottle 1, and A convex bottom wall portion 5 protruding hemispherically from the inner peripheral edge 4a into the body 3 along the central axis 1a of the bottle, and a top wall portion of the convex bottom wall portion 5 is depressed hemispherically. And a concave bottom wall portion 6 in a state.

Here, the shape of the concave bottom wall portion 6 substantially matches the shape of the tip portion 12 of the bottom portion 11 of the primary molded product preform 10 shown in FIG.

In order to achieve this, the concave bottom wall portion 6
The radius R (6a) of the inner peripheral surface 6a of the inner peripheral surface 12a of the bottom end portion 12 of the primary molded product preform 10
What is necessary is just to make it substantially equal to (12a).

Instead, the outer peripheral surface 6 of the recess bottom wall portion 6
b of the outer peripheral surface 12b of the tip portion 12 of the bottom 11 of the primary molded product preform 10
What is necessary is just to make it substantially equal to b).

Further, the radius R (6b) of the outer peripheral surface 6b of the concave bottom wall portion 6 is set to the bottom 11 of the primary molded product preform 10.
Is substantially equal to the radius r (12a) of the inner peripheral surface 12a of the distal end portion 12 of the preform 10, so that the volume of the bottom 11 of the primary molded product preform 10 is slightly extended and the original shape of the preform bottom is substantially maintained. A concave bottom wall portion 6 can be formed.

In the plastic bottle 1 according to the present invention, as can be seen from FIG. 3, the concave bottom wall portion 6 located at the center of the bottom portion 2 corresponds to the shape of the tip portion 12 at the bottom of the preform 10. ing. Accordingly, in the concave bottom portion 6, the shape of the bottom tip portion 12 of the preform 10 hardly changes during blow molding. As a result, the concave bottom wall portion 6 forms a bottle bottom portion in which the molding memory at the high temperature during injection molding of the preform 10 (the molding memory at 250 to 280 degrees Celsius in the case of PET resin) remains as it is. Become.

As described above, according to the present invention, the state at the time of preform molding is left as it is in the bottom portion of the plastic bottle 1 where the thermal deformation is most likely to occur.
Little distortion of the bottle bottom during blow molding. Therefore, it is possible to realize a bottom structure of the plastic bottle that is less likely to undergo thermal deformation and temporal deformation.

On the other hand, in a conventional plastic bottle 20 having a bottom having a cross-sectional shape as shown in FIG. 4, an intersection line XX with the preform 10 drawn on the plastic bottle 20 is drawn. On the basis of the reference, the bottle bottom end portion 12 is formed to fall down during blow molding. A large distortion is likely to occur in the portion formed in this manner.
According to the present invention, such adverse effects can be avoided.

Referring again to FIG. 1, in the present invention, in addition to the above-described structure, a circular shape in which the convex bottom wall portion 5 and the concave bottom wall portion 6 of the plastic bottle 1 intersect. Are formed at a plurality of locations along the boundary line 7 of FIG. Generally, they are formed at equal angular intervals.
These reinforcing ribs 8 are desirably set at a height not exceeding the apex 6c of the outer peripheral surface 6b of the concave bottom wall portion 6 when viewed in the direction of the bottle center axis 1a.

By forming the reinforcing ribs 8 connecting the convex bottom wall portion 5 and the concave bottom wall portion 6 as described above, the mechanical strength and rigidity of the bottom portion 2 can be increased. It can be further suppressed.

[0018]

As described above, in the bottom structure of the plastic bottle according to the present invention, the bottom wall of the concave portion having a shape corresponding to the shape of the bottom end portion of the preform is formed in a part of the bottom. . Therefore, the state at the time of injection molding of the preform is maintained as it is, and distortion during blow molding is small. Therefore, a plastic bottle having a bottom portion that is unlikely to undergo thermal deformation and temporal deformation can be realized.

Further, in the present invention, in addition to this configuration, the reinforcing ribs at the bottom are arranged to increase the mechanical strength and rigidity of the portions, so that thermal deformation and temporal deformation can be further suppressed. .

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing the bottom of a plastic bottle to which the present invention is applied.

FIG. 2 is a longitudinal sectional view showing a preform used for molding the plastic bottle of FIG.

FIG. 3 is an explanatory view showing that the shape of a concave bottom wall portion at the bottom of the plastic bottle body of FIG. 1 matches the shape of the bottom end portion of the preform;

FIG. 4 is an explanatory diagram showing a cross-sectional shape of a bottom portion of a conventional plastic bottle together with a cross-sectional shape of a bottom end portion of a preform.

[Explanation of symbols]

 Reference Signs List 1 plastic bottle 1a bottle center axis 2 bottom 3 trunk 4 annular bottom wall 5 convex bottom wall 6 concave bottom wall 6a inner peripheral surface of concave bottom wall 6b outer peripheral surface of concave bottom wall 7 convex Circular boundary line between the bottom wall portion and the concave bottom wall portion 8 Reinforcement rib 10 Preform 11 Bottom portion 12 Bottom tip portion 12a Inner peripheral surface of bottom tip portion 12b Outer peripheral surface of bottom tip portion

Claims (6)

[Claims] 1. A bottom structure of a plastic bottle that is biaxially stretch blow-molded from a primary molded product preform, wherein the bottom of the plastic bottle is an annular shape that is continuous with the body of the plastic bottle. A bottom wall portion, a convex bottom wall portion which is hemispherically protruded into the body from an inner peripheral edge of the annular bottom wall portion, and a top wall portion of the convex bottom wall portion which is depressed into a hemisphere. A concave bottom wall portion, wherein the shape of the concave bottom wall portion substantially conforms to the shape of the tip portion of the bottom of the primary molded product preform. Bottom structure. 2. The method according to claim 1, wherein the radius of the inner peripheral surface of the concave bottom wall portion is substantially equal to the radius of the inner peripheral surface of the tip portion of the bottom of the primary molded product preform. Bottom structure of plastic bottle. 3. The plastic material according to claim 1, wherein a radius of an outer peripheral surface of the concave bottom wall portion is substantially equal to a radius of an outer peripheral surface of a front end portion of a bottom portion of the primary molded product preform. The bottom structure of the bottle. 4. The plastic according to claim 1, wherein a radius of an outer peripheral surface of the concave bottom wall portion is substantially equal to a radius of an inner peripheral surface of a front end portion of a bottom of the primary molded product preform. The bottom structure of the bottle. 5. The method according to claim 1, wherein a plurality of protruding reinforcing ribs are formed along a circular boundary line where the convex bottom wall portion and the concave bottom wall portion intersect. Characteristic plastic bottle bottom structure. 6. The method according to claim 5, wherein each reinforcing rib is set at a height not exceeding a vertex of an outer peripheral surface of the concave bottom wall portion when viewed in a direction of a bottle central axis. Plastic bottle bottom structure.