JPH0648433A - Self-standing hollow container - Google Patents

Abstract

PURPOSE:To provide the bottom part which does not generate crack even during a long period of storage by a method wherein a valley-shaped part consisting of a valley bottom surface which equally divides the bottom surface by an equal central angle, and leg part side walls which are located across the valley bottom surface is provided, and a plurality of leg parts consisting of the body lower end part which is divided by the valley-shaped parts, leg part side walls and leg part top surface are provided. CONSTITUTION:For a self-standing hollow container consisting of a mouth neck part 9, body part 10 and bottom part, the bottom surface is equally divided by equal central angles. A valley-shaped part, which consists of a valley bottom surface 2 that is a part of the common semi-spherical surface being rise-tilted toward the outside from the bottom center 1, and leg part side walls 4 being located across the valley bottom surface 2, is provided. Also, a divided bottom surface part, which consists of the leg part side walls 4 and a leg part top surface being extended from the bottom central part peripheral edge that is equally divided by equal central angles by the valley-shaped parts, is provided. At the same time, a leg part which is formed of a body lower end part 11 being divided by the valley-shaped parts, and divided bottom surface part is provided, and the outer circumferential part of the leg part top surface is made to be a ground part 6. The leg part side wall 4 is formed of a curved surface protruding to the inside of the container, and the diameter is made to be approximately 1/2-3/2 of the diameter of the body lower end part, and is provided in such a manner that the leg part side wall 4 becomes an obtuse angle at a connecting part 7 with the bottom central part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-supporting container formed by stretch blow molding without using a base cup. More specifically, the invention relates to an internal pressure resistant self-supporting container suitable for a gas-containing component.

[0002]

2. Description of the Related Art Conventionally, as a self-supporting container which is stretch-molded without using a base cup, Japanese Patent Publication Nos. 48-5708, 61-9170 and 61-2671 are available.
A container described in Japanese Patent No. 46, etc. is known. Each of these containers has legs formed at the bottom of the container so that it can stand by itself. The problem with these conventional containers is that there is a valley bottom that divides the bottom of the container and a bottom that has a valley that radially extends toward the peripheral edge and is divided by the boundary line between the side walls that sandwich the valley bottom, that is, the side walls of the legs. Indicates that the stress concentration near the center of the bottom is large and the occurrence of cracks cannot be prevented. If the angle of the side wall of the leg from the valley bottom to the top of the leg at the boundary is small, the formability deteriorates, and molding strain remains and cracks also occur here.

[0003]

The present inventor has conducted a study to prevent the occurrence of cracks at the bottom and found that the concentration of stress near the center of the bottom must be prevented. However, if the legs are made thin for that reason, the ground contact area of the legs, more precisely, the ground contact portion consisting of the outer circumferential portion of the top surface of the legs is shortened, which causes a drawback that the self-sustaining stability is deteriorated.

On the other hand, as described in JP-B-48-5708, attempts have been made to widen the leg gaps to prevent stress concentration. However, if the number of legs is reduced, independence is deteriorated. Become. Therefore, simply widening the space between the legs cannot solve all problems. The present invention provides a container which prevents the occurrence of such cracks and has improved self-standing stability and moldability.

[0005]

MEANS FOR SOLVING THE PROBLEMS The present invention provides: 1. A self-standing hollow container having a split bottom portion equally divided by a valley bottom surface, wherein A. The bottom surface of a biaxially stretched pressure-resistant container is equicentered. A valley portion that is equally divided, and includes a valley bottom that is a part of a common hemisphere that is inclined upward from the bottom center toward the outside, and a leg sidewall that sandwiches the valley bottom; Sectioned bottom part consisting of leg tops that are equally divided by the center part and extended from the peripheral edge of the bottom center part, C. Lower end of the trunk defined by valleys, and a square formed by the divided bottom part A leg portion having a trapezoidal side surface, and D. a ground contact portion composed of an outer circumferential portion of the top surface of the leg portion, and E. a boundary line between the valley bottom surface and the leg sidewall extends toward the center line of the valley bottom surface. And a curved curve in a convex shape, F. Rise of the side wall of the leg rising from the bottom of the valley toward the top of the leg near the center of the bottom. A biaxially stretched, self-supporting hollow container in which the rising angle near the starting point is larger than the rising angle of the leg side wall rising from the valley bottom near the connecting portion with the trunk toward the leg top surface. The biaxially stretched, self-supporting hollow container according to item 1, wherein the top surface of the leg is a curved surface that is convex toward the inside of the container 3. The boundary line between the bottom of the valley and the side wall of the leg is the lower end of the body. The biaxially stretched self-supporting hollow container described in item 1 or 2 which is an arc shape having a diameter of 2 to 6 times the diameter of 4. The ground contact portion formed by the outer circumferential portion of the top surface of the leg. The biaxially stretched self-standing hollow container according to any one of items 1 to 3, wherein the diameter of the arc is 0.5 to 0.85 times the diameter of the lower end of the body. Any one of 1 to 4 wherein the diameter of the arc of the top surface of the leg which is a convex curved surface is 1/2 to 3/2 of the diameter of the lower end of the trunk 6. The self-supporting biaxially stretch-molded hollow container described in 6. The self-supporting self-supporting biaxially stretch-molded product according to any one of items 1 to 5, in which the bottom surface is divided into equal parts at equal center angles. Hollow container 7. Even numbered division of the bottom surface by equal center angle is 4 or 6
The biaxially stretch-molded self-supporting hollow container according to any one of items 1 to 6, which is equally divided. 8. Item 1 to 7 in which the center of the bottom is convex inward of the container
Item 2. A self-supporting hollow container formed by biaxial stretching according to any one of items. 9. The biaxially stretched, self-supporting hollow container according to any one of items 1 to 8, wherein the center of the bottom is thermally crystallized. Regarding

In the self-supporting hollow container of the present invention, the bottom is equally divided by the valley bottom. The valley is formed by the bottom of the valley and the side wall of the leg that sandwiches the bottom of the valley, and the bottom of the divided container is formed by the side wall of the leg and the top surface of the leg. The rising angle of the present invention is the rising angle of the leg side wall extending from the valley bottom to the leg top surface, and the inclination of the leg side wall having a large angle is gentle. Polyethylene terephthalate resin is used as the resin forming the container. In addition to these, blends of polyester resins such as isophthalic acid and nylon are also used. Biaxial stretch blow molding may be performed using these resins.

[0007]

As a result of research, the present inventor has found that in order to eliminate stress concentration near the center of the bottom, the leg that rises from the bottom of the valley toward the top of the leg near the center of the bottom to form the side surface of the leg. It was clarified that the rising angle near the starting point of the side wall needs to be larger than the rising angle near the joint between the bottom and the body. This is the first feature of the present invention. Specifically, the rising angle in the vicinity of the starting point of the leg side wall is about 1.5 times or more the rising angle in the vicinity of the connecting portion between the bottom and the body. With this structure, the side wall near the starting point of the leg side wall has a larger rising angle than the side wall near the connecting portion with the trunk, so the slope of the side wall of the leg side near the starting point becomes gentle and stress concentration is eliminated. You can

The second feature is that the leg top surface of each divided bottom surface portion is directed toward the inside of the container, and is 1/2 to 3 / of the diameter of the lower end portion of the trunk.
Since it is an arc-shaped curved surface with a diameter of 2, the connecting portion between the leg top surface of the split bottom portion and the vicinity of the center of the bottom is connected at a gentle angle to prevent concentration of stress in this portion, and in the vicinity of this connecting portion. Is the rising start point of the side wall of the leg, so the rising angle of the rising start point becomes large. Since stretching is performed during molding, the strength is high and cracks do not occur. If the top surface of the leg is a curved surface that is convex toward the inside of the container, the pressure resistance will be good, but it is preferably 1/2 to 3/2 of the diameter of the lower end of the trunk. If it is ½ or less, the center of the bottom tends to bulge outward of the container. If it is 3/2 or more, it does not become arcuate and approaches a flat surface and is not sufficiently stretched, the rise angle near the rise start point of the leg side wall becomes small, and stress concentration occurs. In this way, the two features act synergistically in association with each other to prevent stress concentration near the center of the bottom and prevent cracks from occurring.

A third feature is that the boundary line between the bottom of the valley and the side wall of the leg is a curved curve which is convex toward the center line of the bottom of the valley. The reason why the rising boundary line is a convex curve toward the center line side of the valley bottom is to lengthen the ground contact portion.
In this way, when protruding in a curved shape toward the valley bottom side, the width of the leg portion becomes wider than that of a linear boundary. If the legs are widened, the ground contact portion is also lengthened, which has the effect of increasing the self-sustaining stability. The boundary line between the valley bottom and both side walls of the leg is curved, but the curve of the present invention is called a curved line including a true circular arc, an elliptic arc, a parabola, a hyperbolic conical curve, and the like. A true circular arc is most preferable from the viewpoint of action and effect. When the boundary line is an arc of 2 to 6 times the diameter of the lower end of the trunk, the self-sustaining effect is the best. If it is 2 times or less, the bottom of the valley disappears before approaching the vicinity of the center of the bottom. On the other hand, if it is 6 times or more, it becomes a straight line and there is no effect of an arc.

The diameter of a virtual arc connecting the ground contact portion formed by the outer circumferential portion of the leg top surface of the divided bottom surface portion is 0.5 to 0.85 of the diameter of the lower end portion of the trunk. If it is 0.5 or less, the self-sustaining stability is poor, and if it is 0.85 or more, the wall thickness of the grounding portion becomes small and the pressure resistance deteriorates. Note that this virtual arc may be a polygon.

Another feature of the present invention is that the bottom surface is divided into even numbers at equal center angles by valleys. Since blow molding is performed uniformly and symmetrically, there is a high probability that improper deformation will also occur symmetrically. If the bottom surface is divided into odd numbers at equal center angles by the valleys, the deformation occurs asymmetrically, so that the container frequently tilts and there is a tendency that the container falls over during transportation. Therefore, when the bottom surface was divided into even numbers, the number of falls fell sharply. Most preferably, it is divided into 6 or 4. The odd-numbered division of the bottom surface is somewhat inferior to the even-numbered division in stability effect, but is similarly excellent in the effect of preventing cracks and the like.

When the contents having a large internal pressure such as a beverage containing gas are stored, the central portion of the bottom may bulge outward due to pressure. Since the present invention is a leg portion having a special structure, the vicinity of the center of the bottom is also stretched and the pressure resistance is large. However, in such a bulging state, there is a risk that the center of the bottom will come into contact with the ground and will be damaged by a drop impact. Or the independence stability deteriorates. In order to solve this problem, the present invention also includes a structure in which the center of the bottom is convex inward of the container. With this structure, outward bulging of the center of the bottom is completely prevented. Also, the center of the bottom can be thermally crystallized. In this case, the bottom of the preform may be thermally crystallized and biaxially stretch blow molded.

[0013]

The present invention will be described in detail below.

FIG. 1 shows a side view of the self-supporting hollow container of the present invention. The container is composed of a mouth / neck portion 9, a body portion 10 and a bottom portion, and a leg portion is formed by a body lower end portion 11 partitioned by a valley portion, a leg side wall 4 and a leg top surface. In addition, 6 is a grounding portion on the top surface of the leg portion.

FIG. 2 shows the bottom of the container of the present invention. 1 is the center of the bottom. A valley bottom 2 extends from the vicinity of 1 in the peripheral direction. In this embodiment, the bottom surface is divided into four by four valley bottom surfaces. Reference numeral 3 denotes a leg top surface forming a divided bottom surface portion. Reference numeral 4 denotes a side wall of the leg portion, which forms a divided bottom surface portion together with the top surface of the leg portion. Reference numeral 5 denotes a boundary line between the valley bottom surface and the leg side wall 4, which is a convex curve toward the center line of the valley bottom surface.
The leg sidewalls 4 that sandwich the valley bottom are formed so as to rise from the valley bottom and have a rising angle with the valley bottom.
If this angle is small, stress strain remains and cracks occur.
Reference numeral 6 denotes a grounding portion, and the long length of this portion indicates that the self-sustaining stability is high. Therefore, it is desirable that the width of the valley bottom of this portion is narrow. Reference numeral 8 is a virtual arc connecting the outer circumferences of the grounded portions.

The self-sustaining stability is a delicate performance, and it greatly fluctuates even if the length of the grounding portion is slightly changed. For example, if the spread angle of the leg from the center of the bottom is increased by 4 °, 10
% Stability increases. Therefore, only by making the boundary line 5 between the bottom of the valley and the side wall of the leg arc-shaped, the spread angle of the leg is increased, and the self-standing stability is greatly improved. Since the effect of a common hemispherical shell appears in the connecting portion between the valley bottom and the body, increasing the width of the valley bottom tends to improve the strength but deteriorate the formability. Therefore, it is desired to increase the width of the valley bottom of this portion as long as molding is possible, but the grounding portion 6 must be widened. In that case, there is the contradictory problem that the width of the valley bottom of the grounding part must be reduced, but if the boundary line between the valley bottom and the side wall of the leg is a straight line, the width of the valley bottom of the grounding part should be narrowed to It is not possible to increase the width of the valley bottom of the connecting part of. In other words, adjustment is impossible. The present invention solves this contradictory problem by forming the boundary line between the valley bottom and the side wall of the leg in a curved shape toward the center line of the valley bottom. Since the bottom surface of the valley spreads at the peripheral portion due to the curved shape, even if the width of the bottom surface of the ground portion is reduced, the width of the bottom surface of the connecting portion with the trunk portion can be made sufficient. Therefore, the width of the valley bottom of the ground contact portion can be freely selected, and the width of the valley bottom of the connecting portion with the body can be the same as that of the conventional one or wider. Figure 3
As is apparent from the above, the leg top surface 4 of each divided bottom surface is a curved surface that is convex inward of the container, and the diameter is 1/2 to the diameter of the lower end portion of the body.
Since it is 3/2, unlike the plane, it is a connecting part 7 with the center of the bottom.
Is a gentle angle. The vicinity of this joint is the starting point of the rise from the valley bottom of the side wall of the leg, but the joint between the top surface of the leg and the center of the bottom is joined at a gentle angle, that is, there is no sudden change, so the rise angle is Inevitably grows. When the rising angle becomes large, the inclination of the side wall of the leg portion becomes gentle and the leg portion is stretched so that molding strain does not remain, so-called meat accumulation does not occur, and the generation of cracks is advantageous.
The leg top surface 4, which is the top surface of the divided bottom surface, is a curved surface that is convexly deformed inward of the container, and therefore has high internal pressure resistance.

FIG. 4 and FIG. 5 are conventional examples for comparison.
The valley bottom 2 spreads in a linear fan shape from the vicinity of the center 1 of the bottom toward the peripheral edge, and the boundary line 5 with the side wall of the leg is linear. Therefore, the width of the valley bottom of the ground contact portion is not so narrow as compared with the width of the valley bottom of the joint with the trunk. Therefore, the length of the grounding portion 6 does not become long, and the self-sustaining stability is poor.

As is apparent from FIG. 5, the leg top surface of the divided bottom surface of the conventional example is a flat surface, and the connecting portion with the central portion of the bottom is connected at a sharp angle to cause a sharp change. Therefore, not only the molding strain remains, but also this portion is the starting point of the rising of the side wall of the leg portion, the rising angle becomes small and the sharp rising occurs, so that stress concentration occurs and the meat accumulation increases and cracks occur. Further, since the leg top surface 4 of the divided bottom surface is a flat surface, there is a drawback that it tends to bulge outward due to internal pressure.

FIG. 6 is the same embodiment of the present invention as FIG. 1, but FIG. 7 is a sectional view taken along the line AA of FIG. Figure 7
12 is the rising angle of the side wall of the leg, and it is clear that the rising angle in the vicinity of the center 1 of the bottom is larger than the rising angle on the peripheral side. Next, the effects of the present invention will be clarified by showing performance tests of the container of the present invention and the conventional container.

(Performance test) (1) Cracking occurrence test of the present invention 50 g of resin having 49 g of resin having a bottom shown in FIG. 1 and FIG. Was filled in a prescribed amount, Lubricant (P-200 manufactured by Daisan Kogyo Co., Ltd.) was applied to the bottom as a stock solution, and the state of cracking was observed by storing in a constant temperature and humidity chamber at a temperature of 40 ° C. and a humidity of 90%. For the evaluation of the state of cracking, the number of cracking per 1 cm ^{2 at} the most occurrence site on the bottom was counted, and the average number was calculated. Conventional Example Same as the present invention except that it has a bottom portion shown in FIGS. 3 and 4. The test results are shown in Table 1.

[0021]

[Table 1]

(2) Bottom bulge test In the cracking test, bottom bulge was observed in parallel.
The number of bulges at the center of the bottom from the ground contact portion was counted. The results are shown in Table 2.

[0023]

[Table 2]

(3) Fall Test The present invention has a bottom portion shown in FIGS. 1 and 2. Fill a bottle with a specified amount of 4.0 gas volume of carbonated water at 25 ° C, Dry
The sample is stored in a constant temperature and humidity chamber under the condition of 24 hours for 24 hours, and then the fall angle is measured. 4 on the ramp to stop the bottle from slipping
A No. 00 sandpaper was fixed, a bottle was placed on the sandpaper, and the angle when the bottle fell down was measured. The measurement angle measures an angle with the horizontal plane. Valley direction: Place the bottom of the valley parallel to the tilting direction of the tilting table and measure. Leg direction: Place the leg parallel to the tilt direction of the tilt table and measure. Conventional Example Same as the present invention except that it has a bottom portion shown in FIGS. 3 and 4. The test results are shown in Table 3.

[0025]

[Table 3]

[0026]

EFFECTS OF THE INVENTION The self-supporting container of the present invention has the effect that no cracks are generated at the bottom even during long-term storage and the self-sustaining stability is very excellent.

[Brief description of drawings]

FIG. 1 is a side view of a container of the present invention.

FIG. 2 is an explanatory view of a bottom surface portion of the container of the present invention.

FIG. 3 is a vertical cross-sectional view of the bottom of the container of the present invention cut along the axis.

FIG. 4 is an explanatory diagram of a bottom surface portion of a conventional container.

FIG. 5 is a vertical cross-sectional view of the bottom of a conventional container cut along the axis.

FIG. 6 is an explanatory view showing a cutting direction of a bottom surface portion of the container of the present invention.

7 is a cross-sectional view of the bottom surface of the container of the present invention cut in the direction shown in FIG.

[Explanation of symbols]

 1 Bottom center part 2 Valley bottom 3 Leg top surface 4 Leg side wall 5 Border line between valley bottom and leg side wall 6 Grounding part 7 Connection part near leg top surface and bottom center 8 Grounding part virtual line 9 Mouth neck 10 Trunk 11 Lower end 12 Trunk side wall rise angle

Claims (9)

[Claims] 1. A self-supporting hollow container having a divided bottom portion that is evenly divided by a valley bottom. A valley bottom that is a part of a common hemispherical surface that rises outward from the center of the bottom that equally divides the bottom of the biaxially stretched pressure-resistant container at an equal center angle, and a leg sidewall that sandwiches the valley bottom. Tanibe consisting of B. C. a divided bottom surface consisting of a leg side wall and a leg top surface equally divided by a valley portion at an equal central angle and extending from a bottom central portion peripheral edge; D. a lower end of the trunk defined by valleys, legs having square trapezoidal side surfaces formed by divided bottom surfaces, and D. A ground contact portion formed of an outer circumferential portion of the top surface of the leg portion, and E. The boundary line between the bottom of the valley and the side wall of the leg is a curve that is convexly curved toward the center line of the bottom of the valley, and F. The leg that rises from the bottom of the valley toward the top of the leg near the center of the bottom The leg that rises near the starting point of the side wall of the leg from the bottom of the valley near the joint with the trunk toward the top of the leg A biaxially stretched, self-supporting hollow container with a rising angle greater than the side wall. 2. The biaxially stretch-molded self-supporting hollow container according to claim 1, wherein the top surface of each leg is a curved surface that is convex toward the inside of the container. 3. The biaxially stretch-molded self-supporting type according to claim 1 or 2, wherein the boundary line between the valley bottom surface and the leg side wall is an arc shape having a diameter of 2 to 6 times the diameter of the trunk lower end portion. Hollow container. 4. The diameter of an arc connecting the ground contact portion formed by the outer circumferential portion of the top surface of the leg portion is 0.5 to 0.85 of the diameter of the lower end portion of the trunk.
The biaxially stretch-molded self-supporting hollow container according to any one of claims 1 to 3, which is double. 5. The diameter of the arc of the top surface of the leg, which is a convex curved surface inside the container, is 1/2 to 3/2 of the diameter of the lower end of the body, and the diameter is 1/2 to 3/2. Biaxially stretched self-supporting hollow container. 6. The biaxially stretch-molded self-supporting hollow container according to claim 1, wherein the bottom surface is divided into equal parts at equal center angles. 7. Even-numbered even division of the bottom surface by an equal center angle is 4
Or any one of claims 1 to 6, which is equally divided into six.
The biaxially stretch-molded self-supporting hollow container described in the item. 8. The biaxially stretch-molded self-standing hollow container according to claim 1, wherein the center of the bottom has a convex shape inward of the container. 9. The biaxially stretch-molded self-standing hollow container according to claim 1, wherein the center of the bottom is thermally crystallized.