JPH10181734A - Bottom structure of container such as thin synthetic resin bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent flexion due to load from occurring to the lowermost step part of a container even though the lowermost step part is formed broadly in width by providing hollow ribs alternately from the inside and the outside at a circumferential wall of a domelike bottom wall. SOLUTION: The structure of bottom of the container is composed of a thin grounding periphery 2 connecting to a circumferential side wall 1 being integral with a drum part, and a bottom wall 3 of a domelike shape surrounded by the grounding periphery 2 and comprising of a plurality of steps formed at the circumferential wall. The top part 7 of the bottom wall 3 is formed in a thickness the same as that of an uppermost step part 4. The circumferential wall extending from the uppermost step part 4 to the grounding inner edge is formed by drawing thin, approximately same as that of the grounding periphery 2. At least three hollow outer ribs 8 relatively narrow in width are provided radially at equal intervals at parts extending from the top part 7 to an inner edge 6a of a lowermost step part 6. Hollow inner ribs 9, bigger in width than the outer ribs, extending from the uppermost step part 4 to the in-plane 6b of the lowermost step part 6 are provided between the outer ribs 8, and flexion of the lowermost step part 6 due to load can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom structure of a thin synthetic resin container such as a PET bottle formed by stretch blow molding.

[0002]

In a thin synthetic resin container such as a bottle manufactured by stretch blow molding, it is said that the strength increases as the thickness is reduced by stretching. However, it is necessary to form the entire bottom wall into a thin wall. Is technically difficult. Further, even if it can be formed to be thin, it has flexibility, so that it is deflected by the load of the contents on a flat surface, making it difficult to sit and becoming unstable.

Therefore, the bottom wall is pushed into the container in a dome shape to form an annular grounding surface, and the load of the contents applied to the bottom wall is dispersed around the bottom surface.
Increasing the height of the dome reduces the inner volume of the bottom, and the narrowing between the peripheral side wall and the bottom wall makes it difficult to form a thin wall around the bottom from the ground contact to the bottom wall. The bottom wall is made as small as possible so that the peripheral portion of the bottom surface can be stretched to be thin.

In order to reduce the thickness of the bottom wall, the peripheral wall is formed in multiple steps, and longitudinal ribs are integrally formed on the thin peripheral wall to reinforce the thin peripheral wall to prevent bending due to a load. It is said that this rib also prevents the lowermost portion of the bottom wall formed flat from bending, but the reinforcing ribs so far are formed from the inner edge of the lowermost portion to the uppermost portion, so the width is Even if it is effective in preventing the bending of the lowermost step, which is narrow and has a short span between the inner edge of the ground, the effect is limited by the length of the span,
In many cases, the lowermost portion of the bottom wall surface protrudes downward from the ground contact surface without supporting the deflection at the wide lowermost portion. Even if the deflection is within the range of the ground contact surface, since the internal volume increases by the amount of the deflection, the water level of the contents in the container falls below the set water level, and the apparent impression on the consumer that the capacity is insufficient. It is said that it is not preferable because it will be attached.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the invention is to form a lowermost step portion wide by alternately providing hollow ribs on the peripheral wall of a dome-shaped bottom wall from inside and outside. Even so, it is an object of the present invention to provide a new bottom structure of a container such as a thin synthetic resin bottle which can prevent bending due to a load by those ribs.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a thin ground contacting edge connected to a peripheral side wall integral with a body,
The bottom wall surrounded by the grounding edge is pushed into the container, and the bottom wall is formed in a dome shape and the peripheral wall is formed in a plurality of steps, and the top wall of the bottom wall is formed thick to the uppermost step, A peripheral wall extending from the uppermost portion to the inner peripheral edge of the ground is formed to be thin and substantially the same as the peripheral edge of the ground, and at least three relatively narrow hollow outer ribs are radially arranged at equal intervals from the top to the inner edge of the lowermost portion. On the other hand, hollow inner ribs, which are wider than the outer ribs and extend from the uppermost portion to the plane of the lowermost portion, are provided on the intermediate peripheral wall between the outer ribs.

In such a structure, the bending strength of the thin peripheral wall of the bottom wall is strengthened by the alternately arranged inner and outer ribs, and the load of the content applied to the thick top is reduced by the inner edge of the lowermost step and the in-plane. And the load is prevented from concentrating on the inner edge of the lowermost portion, so that outward bending of the lowermost portion due to the load is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, reference numeral 1 denotes a peripheral side wall at the bottom integrated with a body, and 2 denotes an annular grounding edge connected to the peripheral side wall.
Are flat and they are 0.2-0.3 mm
It is stretched to a small thickness.

Reference numeral 3 denotes a bottom wall surrounded by the grounding peripheral edge 2, which is formed in a dome shape by pushing the bottom surface into a container. The peripheral wall of the uppermost step part 4, the middle step part 5, and the lowermost step part 6 is formed. It is formed in three steps.

The top 7 of the bottom wall 3 extends from the top
The peripheral wall extending from the uppermost step portion 4 to the inner peripheral edge of the ground is formed to extend thinly in substantially the same manner as the peripheral edge 2 of the ground. On the thin peripheral wall, from the top 7 to the inner edge 6a of the lowermost step 6 connected to the inner edge of the ground, four hollow outer ribs 8, 8 having a relatively narrow width (about 4 mm) are radially arranged at equal intervals. The inner bottom wall of each of the outer ribs 8 has a width (about 5 mm) wider than the outer ribs 8 and extends from the uppermost step 4 to the in-plane 6b of the lowermost step 6. Are provided respectively.

The rib surface of the inner rib 9 facing the inside of the container and the rib surface of the outer rib 8 facing the outside of the container are formed as flat surfaces.
As a result, the inner and outer ribs 8 and 9 are alternately positioned with respect to the peripheral wall of the bottom wall 3 to partition the peripheral wall vertically at regular intervals, thereby enhancing the bending strength of the thin peripheral wall from the uppermost step portion 4 to the lower side. On the other hand, the load of the contents applied to the top 7 is changed to the inner edge 6 of the lowermost step 6.
a and the in-plane 6b, and the inner edge 6 of the lowermost step 6 is transmitted.
The concentration of the load on a is prevented.

The load of the contents applied to the dome-shaped bottom wall concentrates on the inner edge 6 a of the lowermost portion 6. Due to the concentration of the load on the inner edge 6a, the projecting surface of the lowermost portion 6 bends downward about the connection boundary with the inner edge of the ground. When the overhang surface is short, in other words, when the overhang surface is narrow, even if the overhang surface is bent, the warp does not protrude downward from the ground surface 2a. The wide lowermost portion 6 is easily bent and the amount of bending is increased, so that it protrudes below the ground contact surface 2a and the sitting of the container becomes worse. Also, even if there is no bending so that it pops out, the amount of bending causes a large change in the internal volume at the bottom,
This causes a decrease in the water level of the contents in the container.

However, in the present invention, the load of the contents applied to the bottom wall, particularly the load applied to the top 7, is dispersed and transmitted to the inner edge 6a and the in-plane 6b of the lowermost step 6 by the inner and outer ribs 8,9. The concentration of the load on the inner edge 6b is reduced, and the lower end of the inner rib 9 is supported near the boundary between the inner rib 9 and the grounding inner edge serving as a bending fulcrum. Therefore, the lowermost part 6
Is formed wider, the lowermost portion 6 protrudes due to bending, and also deformation that causes a significant drop in water level hardly occurs.

Therefore, the distance between the peripheral side wall 1 and the dome-shaped bottom wall 3 is set to be wide, and the lowermost portion 6 of the bottom wall 3 is formed wide, so that the bottom from the grounding periphery 2 to the bottom wall 3 is made thin. Even if it is stretched and formed, the bottom wall does not protrude due to the load of the lowermost portion 6 and can sufficiently withstand an impact. In addition, at least three hollow ribs 8 and 9 each have a structure.
Are simply formed alternately on the inside and outside of the peripheral wall, and the structure of the mold used for molding does not become particularly complicated.

[Brief description of the drawings]

FIG. 1 is a bottom view of a bottom structure of a container such as a thin synthetic resin bottle according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 peripheral side wall 2 ground peripheral edge 2a ground plane 3 bottom wall 4 uppermost step 6 lowermost step 5 middle step 6a inner edge of lowermost step 6b in-plane of lowermost step 7 top 8 outer rib 9 inner rib

Claims (1)

[Claims] 1. A thin-walled grounding rim connected to a peripheral side wall integral with a trunk, and a bottom wall formed by pushing a bottom surface surrounded by the grounding rim into a container and forming a dome-shaped and peripheral wall in a plurality of steps. The top wall thickness of the bottom wall is formed thick up to the uppermost portion, and the peripheral wall extending from the uppermost portion to the inner peripheral edge of the ground is formed to be thinner almost in the same manner as the above-mentioned grounding edge, and the lowermost portion from the top portion is formed. At least three relatively narrow inner edges
While the hollow outer ribs of the book are provided radially at equal intervals, hollow inner ribs which are wider than the outer ribs and extend from the uppermost portion to the lowermost portion are provided on the intermediate peripheral wall of each outer rib. The bottom structure of containers such as thin synthetic resin bottles.