JPH06270929A - Self-standing bottle - Google Patents

Abstract

PURPOSE:To prevent breakage or the like of a bottom from occurring by providing a peripheral rib contiguous in a peripheral direction on a bottom summit region which is shaped like a downward protrusion and setting a radius from a center of the bottom to the peripheral rib in a specific relation. CONSTITUTION:A blow mold 10 for detecting a self-standing bottle forms respectively opposing cavity faces 10A, 10B at bottle body and a bottom with a plurality of radii S1, S2. A ring-like protrusion 10D forming a peripheral rib is provided on the cavity face 10B. A position where the ring-like protrusion 10D is formed is set as R2<R<=R1, wherein a radius from the center of the bottom to inside of the ring-like protrusion 10D is R between an inversion point P and a gate trace, a radius from the center of the bottom to a shape inverting point P at a border for transferring toward a leg forming cavity face 10C is R1, and a radius of the gate trace remaining on the bottom is R2. Thus withstanding internal pressure property can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-supporting bottle, and in particular,
The present invention relates to a structure of a self-supporting bottle in which a container itself and legs for making it self-supporting are integrally molded.

[0002]

2. Description of the Related Art Generally, a thin-walled container made of synthetic resin called a biaxially stretch blow molded container (hereinafter referred to as a molded product).
Is a bottomed parison obtained by, for example, injection molding, located in a blow mold cavity, longitudinally extended in the axial direction of the container, and expanded in a direction perpendicular to the axial direction by the pressure of gas blown into the container. Is done.

By the way, there is a container called a self-supporting bottle as a container to be biaxially stretch blow molded. As one of the configurations of this container, there is a configuration having a container main body whose bottom is set to a hemispherical shape by biaxial stretch blow molding, and a base cup attached to the bottom to make the main body self-supporting.

The bottom of the container body is formed in a hemispherical shape so that the internal pressure due to the vaporized gas from the filled contents, for example, the filler such as carbonic acid, acts uniformly on the inner surface of the bottom. Also, the legs are used for supporting the container body or for coloring in a decorative sense,
The container body may be made of a material different from that of the container body. For example, the container body may be made of poly ethylene terephthalate (P
When it is formed of ET), a material different from PET may be used.

However, in the case of a container using parts made of different materials, that is, a so-called self-supporting bottle, it is necessary to sort each part for recycling. Therefore, there is a problem that it is difficult to easily execute the reprocessing step when recycling, and the number of parts to be reprocessed increases.

Therefore, conventionally, it has been put into practical use that the container body and the legs are integrally molded to form a so-called one-piece bottle without being constituted by a plurality of parts.

That is, FIG. 5 shows the one-piece bottle 100 described above. In this one-piece bottle 100, a plurality of leg portions 120 forming a grounding portion are radially arranged at equal intervals in the circumferential direction of the bottom portion 110, for example. , An odd number of books are formed.

[0008]

By the way, internal pressure resistance is a mechanical property required for this type of self-supporting bottle.
As a specific characteristic value relating to the internal pressure resistance, for example, when the content to be filled is carbonic acid, 10.5 kg /
cm ² or more is required. As a matter of course, this value is set in consideration of a safety factor that anticipates foaming due to impact during transportation and rise in internal pressure due to foaming when the outside temperature rises.

However, when the self-supporting bottle was examined from the viewpoint of such mechanical characteristics, there were the following problems.

That is, when a self-supporting bottle is blow-molded, the center position of the bottom of the bottle is cooled by coming into contact with a stretch rod used for longitudinal stretching, so-called a non-stretched portion. Therefore, if such an unstretched portion exists, it is difficult to obtain mechanical strength because the orientation in that portion is low. However, in the case of a so-called two-piece bottle in which the container main body and the leg are configured separately, the bottom of the container main body has a hemispherical shape, so if the wall thickness due to unstretching is sufficiently thick, it bursts from the bottom. The situation is that it does not happen that much.

On the other hand, in the case of a one-piece bottle, there is a risk of bursting at the bottom for the following reasons.

That is, in a bottle having an odd number of legs,
As shown by the reference symbol P in FIG. 6, there is a boundary shape reversal point P that shifts from the center position of the bottom toward the leg. The reversal point P has a low stretching rate in relation to the above-mentioned stretch rod, and is present in a so-called unstretched portion.

At the reversal point P where the strength due to such unstretching is relatively low, stress concentration is likely to occur due to internal pressure.

On the other hand, since the leg portion having the above-mentioned shape reversal point P is formed toward the center of the bottle, the center of the bottom portion bears the stress concentration generated in all the leg portions.

However, at the center of the bottom, a crack is more likely to occur than at the above-mentioned shape reversal point P, and the presence of this crack may cause the bottom to burst.

That is, the bottom of the bottomed parison has a gate formed at the time of injection molding.
There are many microcrystalline parts and strains due to the generation of shear heat (heat due to the shearing force generated in the material that passes through the injection gate), which is a so-called heterogeneous part that does not have a stable molecular structure. .

Regarding this molecular structure, at the shape reversal point P,
Since it is an amorphous structure, so-called amorphous, it has a relatively stable structure. On the other hand, since the center of the bottom is an inhomogeneous portion, it can be said microscopically where stress concentration is likely to occur, and cracks and cracks are likely to occur around it.

The defect at the gate located at the bottom is not limited to the one-stage system, but is a so-called two-stage system in which the injection molding unit and the final blow molding unit are installed on different bases. The same applies to the parison in the case.

When molding a self-supporting bottle by this type of blow molding, the gate remaining in the injection-molded parison may be removed. That is, as shown in FIG. 7, after injection molding, the gate which is still soft may be crushed by the nippers 130 or the like and then cut and removed. In addition, in FIG. 7, a nipper 13 shown by a chain double-dashed line
Reference numeral 0 and reference numeral 140 respectively represent the state at the time of cutting and the removed gate.

However, depending on the type of blade of the nipper 130, it is difficult to completely remove even the root of the crushed gate so that there is no trace of the gate, and it is often the root of the gate. However, as shown in FIG. 8, it remains in an edge shape or a ring shape, and becomes a so-called gate trace 150. Note that FIG. 9 shows a state of the gate trace 150 seen from the direction indicated by the symbol X in FIG. Particularly, in the so-called two-stage method, it is possible to provide a processing time for completely eliminating the trace of the gate when the gate is removed after the injection molding, but in the one-stage method, the molding is performed on the same base. Due to the limited product transfer cycle time, it is difficult to completely eliminate the gate traces.

By the way, the gate trace 150, in particular, the edge existing as the trace has a shape slightly protruding from the surface of the bottom of the bottle and has a relatively small heat capacity, so that it is likely to cool and solidify early. Therefore, when the bottom of the bottle is pressed against the cavity surface by the blow pressure during blow molding, the solidified edge has a larger heat capacity than this, and there is still some softness during blow molding. May be buried in. Originally, it is ideal that the buried gate trace 150 and the flesh of the bottom 110 are integrated, but as described above, the solidification speed is different due to the difference in heat capacity between each other, and thus it is difficult to integrate them. Is. Therefore, as shown in FIG. 10 (A) or (B), the edge may remain on the bottom surface without being adhered to the bottom when crushed. Therefore, after the final blow molding, as shown in FIG. 10 (C) or (D), the unbonded portion between the bottom and the edge is in the same state as the crack 160, and stress concentration occurs around this. However, cracks may occur.
As a matter of course, since the thickness of the bottom portion where the unbonded portion is present is smaller than that of the other portions of the bottom portion, the durability when the internal pressure acts becomes low. In FIG. 10, (C) shows the gate trace shown in (A) after deformation, and (D) shows the gate trace shown in (B) after deformation.

Such a problem is particularly noticeable in the self-standing bottle in which the gate is cut as described above, and even in the case of a gateless structure or one with a gate, the so-called bottom portion where the gate mark remains remains The same is true for the freestanding bottles we have.

In view of the above-mentioned problems in the conventional self-supporting bottle, the purpose of the present invention is to provide a self-supporting bottle having a structure that is resistant to internal pressure and does not cause rupture of the bottom. To provide.

Another object of the present invention is to:
An object of the present invention is to provide a self-supporting bottle having a structure capable of suppressing a decrease in wall thickness of the bottom when the bottom has internal pressure resistance.

[0025]

In order to achieve this object, the invention according to claim 1 is such that the bottom of a downwardly convex, generally hemispherical bottom portion is provided at three or more locations at equal intervals in the circumferential direction, and In a self-supporting bottle having legs protruding radially toward,
A circumferential rib that is continuous in the circumferential direction is provided in the downwardly convex top portion region, and the radius from the center of the bottom portion to the circumferential rib is R.
When the radius from the top region to the shape reversal point of the boundary transitioning to the legs is R1 and the radius of the gate trace remaining in the top region is R2, the relation of R2 <R ≦ R1 is set. It is characterized by being.

According to a second aspect of the present invention, a bottomed parison having a gate trace on the bottom is formed by biaxial stretch blow molding, and the bottom is convex downward and has a substantially hemispherical shape. In the above-mentioned location, in a self-supporting bottle having legs protruding radially downward, in the top region of the bottom of the downward convex, the central portion of the top region is formed by bulging below the peripheral portion. And a radius of the bulging portion is r, a protruding height from the peripheral portion is h, a radius of a gate trace remaining on the bottom of the parison is r1, and a protruding height thereof is h1. At this time, the relationship is set such that r> r1 and h> h1.

According to a third aspect of the present invention, a bottomed parison having a gate trace on the bottom is formed by biaxial stretch blow molding, and the bottom is formed in a substantially hemispherical shape having a downward convex shape. In the above-mentioned location, in a self-supporting bottle having legs protruding radially downward, a circumferential rib continuous in the circumferential direction is provided in the top region of the downwardly convex bottom portion, and the radius from the center of the bottom portion to the circumferential rib is provided. Where R is R, the radius from the top region to the shape reversal point of the boundary transitioning to the leg is R1, and the radius of the gate trace remaining in the top region is R2, the relationship of R2 <R ≦ R1 is set. Further, a bulge portion formed by bulging the center portion of the top region below the peripheral portion is provided in the top region inside the peripheral rib, and the radius of the bulge portion is r. , The projection height from the peripheral portion is h, Serial radius of the gate trace r1 remaining parison bottom, when the protrusion height was set to h1, are characterized by being set in relation r> r1 a and h> h1.

[0028]

In a self-supporting bottle, in particular, in a self-supporting bottle having a shape-inverted portion, stress concentration is likely to occur around the microcrystal portion and the bottom gate portion where many distortions exist during injection molding,
Cracks and cracks are more likely to occur.

In addition to this, one of the factors that makes it impossible to ensure the internal pressure resistance of the bottom is the change in wall thickness. When the trace of the gate remaining on the bottom surface is crushed by the blow pressure, an unbonded portion may be formed between the bottom surface and the bottom portion, and this portion may form a crack after molding. Therefore, if there is a crack, the thickness of that portion also becomes thin, and stress concentration is likely to occur in this portion, so cracking is likely to occur.

Therefore, in the present invention, the peripheral rib forming another shape reversal portion is formed outside the trace of the gate and inside the reversal point. This makes it possible to disperse the stress concentration in the center of the bottom, which tends to lower the mechanical strength in the non-uniform portion, particularly in the periphery of the gate. In particular, the gate trace and its surroundings are likely to crack due to microcrystals and strain due to shear heat, and stress concentration is not preferable from the viewpoint of rupture at the bottom, but due to the dispersion of stress concentration described above. It is possible to prevent the bottom from bursting.

Further, in the present invention, it is possible to prevent the thickness of the bottom portion from being thinned by the trace of the gate remaining in the bottomed parison. That is, when the gate trace is crushed and collapsed, an unbonded portion may remain between the gate trace and the bottom portion, and this unbonded portion corresponds to a crack in the bottom portion. Therefore, in the present invention, the bulge portion is formed at the center of the bottom portion. The bulging portion is formed by a cavity surface having a shape and a size that has a volume capable of accommodating the gate trace, so that the gate trace can be shaped according to the shape of the bulging portion during blow molding. . For this reason, the gate trace is always formed in a constant shape as a part of the bottom portion, so that the gate trace is not crushed.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing a mold used to mold the bottom of a self-supporting bottle according to the present invention.

That is, in the blow mold 10 for forming the self-supporting bottle according to the present invention, cavity surfaces 10A and 10B facing the bottle body and the bottom are formed by a plurality of radii S1 and S2. Even if the bottom of the self-supporting bottle expands to the radius of the bottle body, the bottom does not reach below the grounding surface of the leg formed by the cavity surface shown by reference numeral 10C in FIG. This is because. By setting such a radius, even if the bottom portion is deformed by internal pressure or when receiving a drop impact force, the bottom portion does not project downward from the ground contact surface of the leg portion. Therefore, it is possible to prevent the deterioration of the self-supporting property of the self-supporting bottle, which is caused when the bottom part pops out, that is, the deterioration of the self-supporting stability.

On the other hand, a ring-shaped projection 10D is formed on the cavity surface 10B facing the bottom of the self-supporting bottle which is a molded product. The ring-shaped protrusion 10D is a characteristic configuration of this embodiment, and is provided for stress diffusion in the self-standing bottle.

That is, the ring-shaped projection 10D is formed by setting a height of, for example, 1 mm or more, preferably about 1 to 2 mm from the cavity surface facing the bottom of the self-standing bottle toward the inside of the cavity. There is.

The formation position of the ring-shaped projection 10D is set to have the following relationship with the inversion point P and the trace of the gate. In addition, in the following positional relationship, the bottom means the name of the self-standing bottle to be molded, and in FIG. 1, the cavity surface 10B facing the bottom corresponds.

Now, let R be the radius from the center position of the bottom portion (the position intersecting the center line indicated by the reference symbol L) to the inside of the ring-shaped projection 10D, and direct it from the center position of the bottom portion toward the cavity surface 10C for leg formation. When the radius to the shape reversal point P of the transitional boundary is R1 and the radius of the gate trace remaining at the bottom is R2, the relation of R2 <R ≦ R1 is set.

Therefore, the ring-shaped projection 10D is located outside the center of the bottom of the gate trace and is at the reverse position P.
At a position closer to the center of the bottom than that of the bottom, for example, it is projected inward in the self-standing bottle.

Since this embodiment has the configuration as described above,
The freestanding bottle molded using the blow mold 10 shown in FIG. 1 has the shape of the bottom portion 20 shown in FIG.

That is, the bottom portion 20 of the self-supporting bottle comes into contact with the cavity surfaces 10A, 10B and 10C of the blow mold 10 by stretching in a biaxial direction of the vertical axis and the horizontal axis by a stretch rod (not shown) and blow pressure, respectively. Will be done. The self-supporting bottle has its side wall formed by contacting the cavity surface 10A facing the side wall by blow pressure while being stretched in the longitudinal direction by the stretch rod, and has a bottom portion before the cavity surface 10C facing the leg. By contacting the cavity surface 10B opposed to, the thickness of the bottom portion in the unstretched state is set.

On the other hand, when the bottom portion 20 contacts the cavity surface 10B facing the bottom portion 20, the ring-shaped projection 10D formed on the cavity surface 10B causes a part of the bottom portion, that is, the gate indicated by a double-dot chain line in FIG. A circumferential rib 22 is formed at a position outside the trace and at a position inside the reversal point P so as to project into the space.

The peripheral rib 22 constitutes a deformed portion near the periphery of the gate trace remaining on the bottom portion 20, and is a portion where stress concentration occurs. Therefore, the stress concentration is dispersed in the bottom portion 20. For this reason, cracks and cracks are likely to occur at locations where gate traces exist when stress concentration occurs in this portion, but by dispersing the stress concentration, stress concentration around the gate traces can be weakened. It is possible to suppress the generation of cracks and cracks. The action of dispersing the stress concentration at the bottom by forming the circumferential rib 22 also affects the shape reversal point P, and the stress concentration at this portion is also reduced. Moreover, since the circumferential rib 22 also exerts an effect on the bending moment at the bottom portion, from this point also, the rupture of the bottom portion can be efficiently avoided.

On the other hand, as shown in FIG. 3, in this embodiment,
As described in FIG. 10, when the gate trace is crushed by the blow pressure used during molding, that is, when the gate trace is buried in the bottom meat portion,
A structure is provided for solving the problem that the unbonded portion becomes a crack and the thickness of the bottom portion becomes thin and stress concentration on that portion is caused.

That is, FIG. 3 is a sectional view of the blow mold 10 showing the above-mentioned structure, which has a recess 10E formed in the cavity surface 10B facing the bottom of the self-standing bottle.
It is composed by. The concave portion 10E is a top region formed in a downward convex shape on the bottom portion 20 of the self-supporting bottle,
The central portion is provided to form a bulging portion 24 that bulges below the peripheral portion.

When the radius of the gate trace of the parison 30 shown by the chain double-dashed line in the drawing is r1 and the radius of the recess 10E is r from the center position of the bottom of the parison 30, r> r1. The relationship is set, and the outer peripheral portion of the recess 10E is located outside the trace of the gate.

Further, in FIG. 3, the depth (h) of the recess 10E is h> h1 with respect to the protruding height (h1) of the gate trace of the parison 30 so as to obtain a space volume capable of accommodating the gate trace. The relationship is set.

The depth of the concave portion 10E (h) is (h).
With respect to the above, it is preferable that the bulging portion 24 of the self-standing bottle is set to a size that does not deviate from the radius S2 of the bottom portion shown in FIG. This is because the self-standing stability is not deteriorated when the bottom of the self-supporting bottle is popped out. Furthermore, in FIG.
It is preferable that the side wall surface 10F continuing from the outer peripheral portion of the recess 10E has a rising angle set to a substantially right angle. This is because when blow molding is performed, the edge portion of the gate trace accommodated inside the recess 10E has the recess 10E.
This is to prevent it from being crushed by E.

Since the outer peripheral portion of the recess 10E having such a structure is located outside the gate trace, the gate trace can be shaped as the bottom of the self-standing bottle. That is, as shown by the chain double-dashed line in FIG. 3, the gate traces remaining at the tip of the parison are not crushed by the cavity surface as in the conventional case after being located in the recess 10E, but the shape of the recess 10E. Will be modeled after. Therefore, even if the shape of the gate trace of the parison 30 is divided by cutting, the gate trace after blow molding into a self-supporting bottle is formed as a part of the bottom of a uniform shape as shown by the solid line in FIG. Will be put out. For this reason, since the gate trace does not form an unbonded portion with the bottom portion, the change in wall thickness at the bottom portion, that is,
The situation of thinning is avoided.

When such a gate trace is used for shaping the bottom portion, the hot parison method, in which a relatively large amount of heat is retained for deformation, is effective.

[0051]

As described above, according to the present invention,
By providing the peripheral ribs, it is possible to disperse the stress concentration parts at the bottom of the self-supporting bottle into a plurality of parts. Therefore, it is possible to suppress the stress concentration on the gate trace and its surroundings where cracks and cracks are likely to occur due to strain in the microcrystalline portion.

Further, according to the present invention, by preventing the trace of the gate from being crushed to form an unbonded portion between itself and the bottom, it is possible to avoid leaving the unbonded portion as a crack, and to this portion. It is possible to prevent stress concentration. That is,
The bottom is provided with a bulge formed in the downwardly convex top region by a cavity surface having a volume capable of accommodating a gate trace. Therefore, the gate trace is shaped in accordance with the cavity surface for forming the bulging portion when the blow molding is performed. For this reason, the gate trace formed as a part of the bottom portion having a constant shape is not crushed by the cavity surface, and therefore an unbonded portion with the bottom portion, that is, a crack is not left. This allows
Since no cracks occur, stress concentration on this portion can be avoided.

In this way, by preventing the dispersion of stress concentration points at the bottom and the occurrence of cracks where stress concentration is likely to occur, the strength at the bottom corresponding to the unstretched portion is improved and internal pressure resistance is secured. It becomes possible to do.

[Brief description of drawings]

1 is a cross-sectional view showing the bottom structure of a blow mold used to form a freestanding bottle according to the present invention.

FIG. 2 is a cross-sectional view showing a bottom structure of a self-standing bottle molded by the blow mold shown in FIG.

FIG. 3 is a cross-sectional view showing a bottom structure of a blow mold used for molding another portion of the bottom of the self-supporting bottle according to the present invention.

4 is a cross-sectional view corresponding to FIG. 3 for explaining a partial structure of another portion of the self-standing bottle shown in FIG.

FIG. 5 is a perspective view showing an example of a self-standing bottle.

FIG. 6 is a cross-sectional view showing a structure of a portion indicated by reference numeral Z in FIG.

FIG. 7 is a schematic view showing a structure for removing a gate trace of a parison used for molding a self-standing bottle.

8 is a schematic cross-sectional view showing a bottom structure of the parison shown in FIG. 7, particularly a structure of a gate trace.

9 is a view taken in the direction of the arrow X in FIG.

10 is a cross-sectional view showing a state of the gate trace shown in FIG. 8 during molding, (A) and (B) showing a form of the gate trace remaining before molding, and (C) and (D). () Shows the form after the gate traces of the forms shown in (A) and (B) have been formed.

[Explanation of symbols]

 10 Blow Mold for Molding Self-Standing Bottle 10A Cavity Surface Facing Side Wall of Self-Standing Bottle 10B Cavity Surface Facing Bottom of Self-Standing Bottle 10C Cavity Surface Facing Leg of Self-Standing Bottle 10D Forming Peripheral Rib of Self-Standing Bottle Circumferential projection 10E for forming a recess for forming a bulging portion of the self-supporting bottle 20 Self-supporting bottle 22 Circumferential rib 24 Swelling portion

Claims (3)

[Claims] 1. A self-supporting bottle having downwardly protruding substantially hemispherical bottom portions equidistantly in the circumferential direction at three or more locations with radially projecting downwardly directed legs, wherein the downwardly convex bottom top portion is provided. A circumferential rib that is continuous in the circumferential direction is provided in the region, and the radius from the center of the bottom to the circumferential rib is R.
When the radius from the top region to the shape reversal point of the boundary transitioning to the legs is R1 and the radius of the gate trace remaining in the top region is R2, the relation of R2 <R ≦ R1 is set. A free-standing bottle characterized by being 2. A bottomed parison having a gate trace on the bottom is formed by biaxial stretch blow molding, and is formed at three or more locations at equal intervals in the circumferential direction of the bottom of the downward convex convex hemisphere. In a self-supporting bottle having legs protruding radially toward, a downwardly convex top region of the bottom portion is provided with a bulge portion formed by bulging a central portion of the top region below a peripheral portion. Let r be the radius of this bulge, h be the protrusion height from the peripheral edge, r1 be the radius of the gate trace remaining on the bottom of the parison, and h1 be the protrusion height, then r> r1 And a freestanding bottle characterized by being set in a relationship of h> h1. 3. A bottomed parison having a gate trace on the bottom is formed by biaxial stretch blow molding, and is formed at three or more locations at equal intervals in the circumferential direction on the bottom of a downward convex, substantially hemispherical shape. In a self-supporting bottle having legs protruding radially toward, a circumferential rib that is continuous in the circumferential direction is provided in the top region of the downwardly convex bottom portion, and the radius from the center of the bottom portion to the circumferential rib is R, and the top portion When the radius from the region to the leg shape reversal point at the transition to the leg is R1 and the radius of the gate trace remaining in the top region is R2, the relation of R2 <R ≦ R1 is set. In the apex region inside the rib, a bulge portion formed by bulging the central portion of the apex region below the peripheral portion is provided, and the radius of the bulge portion is defined as r, Remaining at the bottom of the parison, where the protruding height is h The free-standing bottle is characterized in that the relation of r> r1 and h> h1 is set, where r1 is the radius of the gate trace and r1 is the protruding height.