JPS6244893Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a bottle made of synthetic resin such as polyethylene terephthalate resin by biaxial stretch blow molding, in which a larger amount of stretching is applied to the bottom of the bottle. The purpose is to mold the bottle and ensure a stable self-supporting function of the bottle.

[Conventional technology]

Biaxially stretched blow-molded bottles made of synthetic resin have the disadvantage that the bottom part cannot undergo sufficient stretching, resulting in poor heat resistance.

In other words, in this type of bottle, the liquid content is heated and filled depending on the purpose, but if the bottom part is not stretched sufficiently, the amount of thermal deformation will increase and the bottle will become useless as a bottle. It was done.

As is well known, when a bottle is stretch-molded, the density of the bottle-forming material formed by this stretching increases, which improves the heat resistance of the bottle. It is known that the stretching magnification that can be achieved is at least 3 times or more in terms of area magnification, and preferably 7 times or more in area.

In this way, the density of a synthetic resin material can be increased by applying stretching, but in many cases, the stretched material becomes aligned and crystallized, increasing its density, but the amount of stretching is insufficient. The portions with a low crystallinity are stretched and deformed, causing distortion. That is, stretching results in areas with sufficient crystallinity and areas with insufficient crystallinity, and the smaller the total amount of stretching, the more areas are distorted due to insufficient stretching.

This generated strain can be removed by subjecting the stretch-molded bottle to heat treatment, that is, by heating the bottle to around the glass transition point temperature of the molding material, but if the amount of stretching is insufficient, Since the density is not sufficiently large, heat resistance cannot be improved even if heat treatment is performed to remove strain.

In addition, the stretching deformation to increase density is set based on the area magnification, and even if the stretching magnification in one fixed direction is large, it will not lead to an increase in density. When stretching the bottom of the bottle, consideration must be given to increasing the amount of stretching in the circumferential direction in addition to the stretching in the radial direction.

As a means of increasing the stretching amount of the bottom of a biaxially stretched blow-molded bottle, as shown in Japanese Patent Application Laid-open No. 55-79235, the bottom of the bottle was divided into an odd number of equal parts at equal central angles, and The bottom structure is such that the diameter lines are inclined and each diameter line is connected by a wavy inclined wall along the circumferential direction, so that the amount of extension in the radial direction and the circumferential direction at the bottom is three times or more as described above. The area magnification of is shown.

The device disclosed in JP-A No. 55-79235 can certainly increase the area stretching ratio of the bottom part to 3 times or more, but the ratio of the slope of each inclined wall constituting the bottom wall is However, there were disadvantages in that it was not always possible to obtain a sufficient amount of stretching, and it was not possible to obtain a larger area magnification.

Furthermore, the bottom structure shown in JP-A No. 55-79235 has a self-supporting function through independently protruding leg pieces, so it is not necessarily necessary for the self-supporting function of the bottle to be achieved. It had not turned out to be satisfactory. That is, each leg piece is individually formed by stretch molding, and the amount of protrusion and elongation of each leg piece must be completely equal, but in this way, the elongation of the protrusions that are completely independent of each other It is difficult to equalize the amount by taking into account the amount of cooling shrinkage, and in situations where heat that causes deformation acts on the bottom due to hot filling, etc., it is necessary to uniformly control the amount of thermal deformation of each leg piece. This was even more difficult, and as a result, there remained concerns about their ability to function independently.

Looking at the bottom structure of the bottle in JP-A-55-79235, the amount of stretching in the circumferential direction is much greater than that of previous bottles of this type due to the combination of numerous inclined walls. However, while the leg section, which is the lower end of the slanted diameter line, is formed with sufficient stretching in the radial direction, the diameter of the opposite side is smaller than this leg section. The amount of stretching in this direction was significantly small, and as a result, the stretching ratio of the entire bottom portion could not be sufficiently increased, and the resulting heat resistance was by no means satisfactory.

In this way, conventional bottles of this type have a general structure in which the central part of the bottom is recessed inward, but instead of having insufficient stretching in the circumferential direction over the entire bottom, , it is possible to form a leg part that has a sufficient amount of stretching in the radial direction and exhibits a stable self-supporting function. The advantages and disadvantages of the legs are mutually interchanged, such that although a sufficient amount of stretching can be obtained, there is insufficient stretching in the radial direction in some areas, and there is a sense of anxiety about the self-sustaining function that the leg parts exert. It's summery.

Therefore, by combining this bottom structure in which the center portion of the bottom is depressed inward with the bottom structure shown in Japanese Patent Application Laid-open No. 55-79235, a bottom configured as shown in FIG. 3 can be obtained. Therefore, it should be possible to mold a bottom with stable legs that have a high area magnification and have a self-supporting function.

That is, as shown in FIG. 3, the bottom wall 2 of the main body 1 having an elongated cylindrical shape has a generally truncated conical cylinder whose central portion excluding the leg wall 6, which is the outer peripheral edge portion of the bottom wall 2, is depressed inward. A tapered wall 3 having a shape is provided, and this tapered wall 3 is divided into an odd number of equal central angles, with a ridgeline 4a extending from the lower end periphery to the center O, and a valley extending this ridgeline 4a to the upper end periphery of the opposing tapered wall 3. line 4b
The structure is such that an inclined bent straight line 4 is provided, and an inclined wall 5 surrounded by the adjacent ridge line 4a and valley line 4b is formed (this structure is hereinafter referred to as the [combined bottom wall structure]). The inclined wall 5 allows a sufficient amount of stretching in the circumferential direction, and the tapered wall 3 allows a sufficient amount of stretching in the radial direction. It should also be possible to obtain it on the outer peripheral edge of the wall 2.

[Problem that the invention attempts to solve]

However, as shown in Figure 3, a combined bottom wall structure in which the two are simply combined is
Due to the unevenness of strain due to the uneven amount of stretching of the structural part shown in Publication No. 79235, that is, the central part of the bottom wall 2 consisting of the bent straight line 4, the inclined wall 5, and the separated tapered wall 3, and the stretching molding. The difference between the amount of distortion that occurs in the central portion of the bottom wall 2 and the amount of distortion in the main body 1 including the leg wall 6 directly affects the leg wall 6, causing deformation of the leg wall 6. The self-supporting function of the leg wall 6 is impaired.

That is, due to the non-uniform strain generated in the central portion of the bottom wall 2, the central portion of the bottom wall 2 itself is slightly deformed, and a deforming force accompanying this strain acts on the leg wall 6. Although the slight deformation of the central portion of the bottom wall 2 itself does not cause any inconvenience,
This deforming force acting on the leg wall 6 from the center portion of the bottom wall 2 causes the disadvantage that the leg wall 6 is deformed and its self-supporting function is reduced. The deforming force due to strain acting on the leg wall 6 from the center of the bottom wall 2 acts on the entire leg wall 6 along the circumferential direction, but the deforming force generated on the inclined wall 5 is concentrated on the bending straight line 4. , tends to act on the leg wall 6 through this bending straight line 4, and therefore deforming force tends to concentrate at the connection portion of the bending straight line 4 to the leg wall 6. In addition, due to the difference in the amount of strain occurring in the main body 1 portion and the strain occurring in the center portion of the bottom wall 2 (the amount of strain is greater in the bottom wall portion), the difference between the main body 1 portion and the center portion of the bottom wall 2. The difference in the amount of strain causes the leg wall 6, which is the boundary between the main body 1 portion and the center portion of the bottom wall 2, to wrinkle and generate a deforming force. In this case as well, this deforming force tends to concentrate and act on the connection portion between the bending straight line 4 and the leg wall 6. like this,
Uneven deformation occurs in the leg wall 6 due to the deformation force due to uneven strain among the wall parts of the bottom wall 2 and the deformation force due to the difference in the amount of strain between the main body 1 portion and the center portion of the bottom wall 2. Become.

Therefore, the present invention is based on this [combined bottom wall structure]
In, the deformation force generated due to the unevenness of strain among the wall parts in the center part of the bottom wall 2 and the difference between the amount of shrinkage strain in the center part of the bottom wall 2 and the amount of shrinkage strain in the main body 1 part including the leg wall 6, The technical problem is to eliminate the influence of this deformation force on the leg wall 6 by applying it to parts other than the leg wall 6.

[Means for solving problems]

The means of the present invention is the above-mentioned [combined bottom wall structure]
, a cylindrical wall 7 having a short cylindrical shape concentric with the central axis of the main body 1 is provided between a leg wall 6 which is a peripheral portion of the bottom wall 2 and a central portion of the bottom wall 2.

In addition, by providing the cylindrical wall 7 between the leg wall 6 and the center portion of the bottom wall 2, the space between the leg wall 6 and the center portion of the bottom wall 2 is reversely bent along the radial direction to provide flexibility. They are connected with each other with a cylindrical wall structure.

[Effect]

In this way, the central portion of the bottom wall 2 is formed into a complicatedly curved wall structure with a plurality of tapered walls 3, inclined walls 5, and bent straight lines 4.
This means that the strain that occurs in each part of the central part is never uniform, but rather non-uniform, and this non-uniform strain produces a deforming force, and this deforming force is applied to the peripheral part of the central part of the bottom wall 2. It also acts on the cylindrical wall 7. Even if the cylindrical wall 7 is deformed due to the deformation force generated in the central portion of the bottom wall 2, the boundary between the cylindrical wall 7 and the central portion of the bottom wall 2 and the boundary between the cylindrical wall 7 and the leg wall 6 Since the portions are bent and have flexibility, the deformation that occurs in the cylindrical wall 7 is limited to the cylindrical wall 7 and does not extend to the leg wall 6. That is, even if the center portion of the bottom wall 2 is deformed due to the deformation force generated in the center portion of the bottom wall 2, the action of the cylindrical wall 7 prevents this deformation from reaching the leg wall 6. It is.

In addition, the deformation force as wrinkling due to the difference between the shrinkage strain generated in the main body 1 portion including the leg wall 6 and the shrinkage strain generated in the center portion of the bottom wall 2 is also applied to the main body 1 portion including the leg wall 6. Since it acts concentratedly on the cylindrical wall 7, which is the boundary between the bottom wall 2 and the center part of the bottom wall 2, and does not act on the leg wall 6, the leg wall 6 is not deformed.
As described above, since the cylindrical wall 7 is formed to have a flexible structure, the leg wall 6 will not be deformed due to the deformation that occurs in the cylindrical wall 7.

Therefore, even if deformation force is generated in the bottom wall 2 due to strain, the difference between the amount of strain caused by contraction in the main body 1 including the leg walls 6 and the amount of contraction strain generated in the center portion of the bottom wall 2 will be Even if deformation force is generated as wrinkling, the leg wall 6 is not deformed by this deformation force, and the stable self-supporting function of the leg wall 6 is reliably maintained.

Furthermore, since the cylindrical wall 7 is located adjacent to the leg wall 6 on the side of the center O, which is the center of stretching, the entire area of the leg wall 6 is uniformly stretched due to the action of the cylindrical wall 7. Therefore, the leg wall 6 is formed as a part that is unlikely to be deformed.

Note that the larger the height of the cylindrical wall 7, the greater the amount of deformation absorbed.
Unnecessarily increasing the height of this cylindrical wall 7
Since the amount of extension of the leg wall 6 will be extremely large, causing local thinning of the leg wall 6, the height of the cylindrical wall 7 should be set to sufficiently absorb the expected amount of deformation. It is desirable to set it to a smaller value within the possible range. Further, since the cylindrical wall 7 only needs to be able to absorb the amount of deformation, it is not necessarily specified to have a straight cylindrical shape, but may have a cylindrical shape with a taper angle slightly expanding downward. .

〔Example〕

The illustrated embodiment shows the case of a bottle with a capacity of 1, in which five bent straight lines 4 are provided, the thickness of the body 1 is 88 mm, the opening diameter of the lower end of the tapered wall 3 is 57 mm, The diameter of the upper end is 26 mm, the height is 17 mm, the height of the cylindrical wall 7 is 1.5 mm, the inclination angle of the tapered wall 3 is about 44 degrees, and the inclination angle of the bent straight line 4 is about 19 degrees. There is.

In the bottom wall 2 of this embodiment, the wall thickness of the ridgeline 4a portion is somewhat large because the inclination angle of the ridgeline 4a is not large, but the wall thickness of the connection portion between the valley line 4b and the tapered wall 3 and between the tapered wall 3 and the cylindrical wall 7 The wall thickness of the connecting part was appropriate.

When this bottle is actually used as a heat-resistant bottle filled at 90°C, the ridge line 4a will be slightly pushed downward and curved due to the action of internal pressure, but it will not be significantly displaced, and the displacement at this ridge line 4a will be It was confirmed that the bottom wall 2 exhibits extremely high heat resistance without causing thermal deformation, since it disappears when the effect of the internal pressure of the bottle disappears.

[Effects of the invention] As is clear from the above explanation, although the synthetic resin bottle of the present invention can be stretch-molded over the entire bottom wall at a sufficient areal stretching ratio,
Even if the deformation is Even if it happens,
The deformation occurs only in the cylindrical wall and not at all in the leg wall, so the stable self-supporting function of the leg wall can be ensured, and since it can be molded using the same molding operations as conventional methods, it is easy to mold. It exhibits many excellent effects such as.

[Brief explanation of drawings]

FIG. 1 is an explanatory view of the configuration of the present invention, and is a vertical sectional view taken along the line - in FIG. Figure 2 shows
FIG. 2 is a bottom view of the configuration of the present invention shown in FIG. 1; FIG. 3 is an explanatory diagram showing a [combined bottom wall structure] of a bottle that can be considered by combining the conventional techniques. Explanation of symbols, 1; Main body, 2; Bottom wall, 3; Tapered wall, 4; Bent straight line, 4a; Ridge line, 4b; Valley line,
5; Slanted wall; 6; Leg wall; 7; Cylindrical wall; O; Center point.

Claims (1)

[Scope of utility model registration request] In a synthetic resin biaxially stretched blow molded bottle,
A bottom wall 2 connected to the lower end of the main body 1 having an elongated cylindrical shape
is a tapered wall having a generally truncated conical shape that is depressed inward from the inner circumferential edge of the leg wall 6, which is the peripheral edge portion, through a short cylindrical cylindrical wall 7 that is concentric with the central axis of the main body 1. 3 is provided, and the tapered wall 3 is divided into an odd number of equal central angles from the lower end periphery to the center O.
An inclined bent straight line 4 is provided, which is composed of a ridge line 4a extending to the ridge line 4a and a valley line 4b extending the ridge line 4a to the upper end periphery of the opposing tapered wall 3, and the adjacent ridge line 4a and valley line 4b are tapered A synthetic resin bottle comprising a sloped wall 5 surrounded by a wall 3.