JPH0123936Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to the bottom structure of a plastic bottle, and more specifically, the bottom structure of a blow-molded or stretch-blow-molded plastic bottle that has excellent internal pressure resistance and upright stability. Regarding.

(Prior art) In order to achieve both internal pressure resistance and upright stability for plastic bottles used for filling and sealing with positive internal pressure (that is, the internal pressure after sealing is higher than atmospheric pressure) contents such as carbonated drinks, various conventional techniques have been developed. A bottom structure has been proposed. For example, there is a system in which the bottom is made into an outwardly convex hemispherical shape, and the hemispherical part is provided with a plurality of protrusions or bulges, and the bottom surface is used as a grounding surface (Japanese Patent Publication No. 1983-5708). In this case, the distance between the center bottom edge of the hemispherical part and the ground plane is generally short, and as a result, the internal pressure after sealing causes the center bottom edge of the hemispherical part to protrude outside the ground plane, impairing upright stability. The problem is that it is easy. In an attempt to solve this problem,
In Publication No. 110415 and Japanese Utility Model Application Publication No. 56-91210, the bottom is basically a hemispherical shape convex outward, a cap-shaped or spherical recess is formed in the center of the hemispherical part, and a plurality of concave parts are formed on the outside of the hemispherical part. Synthetic resin bottles have been proposed that are provided with an overhang or a bulging protrusion. However, in this case, there is a problem in that the recessed portion is likely to buckle, that is, bulge outward due to the internal pressure after sealing.

(Problems to be Solved by the Invention) The object of the present invention is to provide a bottom structure for a plastic bottle that has both erect stability and internal pressure resistance.

(Means for Solving the Problems) The bottom structure of the plastic bottle of the present invention is a bottom structure of a blow-molded or stretch-blow-molded plastic bottle having a body with a circular cross section,
The bottom structure is coaxial with the body and has a structure at the lower end of the body, in which at least three hollow hemispheres are connected through intersections between the hemispheres to form a central recess. The diameter of each hemisphere is approximately equal to the radius of the circumscribed circle of the body at the lower end of the body, and the hemispheres are arranged at equal intervals in the circumferential direction. , the hemispherical connecting body is inscribed in the circumscribed circle at the lower end of the body, and the bottom end of each hemispherical body forms a grounding point or ground plane.

(Function) The hemispherical connecting body which is the main part of the bottom structure of the plastic bottle of the present invention has at least three hollow hemispherical bodies connected through the intersection line of each hemispherical body,
It is formed by forming a central recess. This central concave portion is substantially larger than the inner part of the hemispherical body, which itself has excellent internal pressure resistance, and the intersection line functions as a reinforcing rib, so even if high positive internal pressure is applied, it will not move outward. It is difficult to cause backlash.

The hemispherical connectors are connected to the lower end of the barrel, and the diameter of each hemisphere is approximately equal to the radius of the circumscribed circle of the barrel at the lower end of the barrel. If the diameter of each hemisphere is smaller than the radius of the circumscribed circle, the vicinity of the center of the hemisphere connecting body will not be formed by a hemisphere, and as a result, the central recess will have a portion that is not reinforced at the intersection line, reducing buckling resistance. do.

On the other hand, if the diameter of each hemisphere is larger than the radius of the circumscribed circle, the bottom end of each hemisphere approaches the center of the hemispherical connector. This bottom end forms a grounding point or a grounding surface, but in this case, the ratio of the diameter of the circle connecting each grounding point or the ring connecting each grounding surface to the diameter of the body becomes small, resulting in a decrease in upright stability. If the diameter is approximately equal to the radius, this disadvantage does not occur.

There are three or more hemispheres, and each hemisphere is arranged at equal intervals in the circumferential direction, so the three or more grounding points or ground surfaces formed by the bottom ends are also circumferential. Evenly spaced in the direction. Therefore, each grounding point or surface receives the load equally, so the bottle has excellent upright stability. Further, the lengths of the intersection line portions of the central recessed portion are equal. Therefore, a central recess due to the eccentric application of positive internal pressure occurs when the hemispheres are not arranged at equal intervals and, for example, extremely short or extremely long intersections alternate. Deterioration of buckling resistance is unlikely to occur. Furthermore, since the hemispherical bodies are arranged symmetrically with respect to the center, the bottle has an excellent appearance.

The hemispherical connectors are coaxial with the barrel, and each hemisphere is inscribed in the circumcircle of the barrel at the lower end of the barrel. Therefore, there is no risk that the hemispherical connector would protrude laterally eccentrically with respect to the body, spoiling the appearance of the bottle or reducing the stability of the bottle when it is erected.

(Example) The present invention will be described below with reference to drawings showing examples.

The plastic bottle 1 shown in FIG. 1 is formed by blow molding or stretch-blow molding, and the body 2 has a circular cross section. In the case of bottles for filling and sealing positive internal pressure contents such as carbonated drinks, stretch-blow molded bottles made of polyethylene terephthalate, for example, have excellent container performance such as strength, impact resistance, gas barrier properties, and transparency. It is desirable that The bottom 3 of the bottle 1 is
It has a structure as shown in FIG. 3, FIG. 4, and FIG. 5. The bottom part 3 includes a hemispherical connecting body 6 in which four hollow hemispherical bodies 4 are connected via intersection lines 5 between the hemispherical bodies 4, and a central flat part 7 located at the center upper end of the hemispherical connecting body 6. It's summery. The diameter 2d of the hemispherical body 4 is determined by the circumcircle of the body 2 at the lower end 8 of the body where the hemisphere connecting body 6 and the body 2 are connected (the diameter 2d of the body 2 in FIG.
is equal to 1/2 the diameter (or radius) of the circle (corresponding to the circle shown in Figure 5). and hemispherical body 4
are arranged at equal intervals in the circumferential direction, that is, so that the intersection lines 5 are orthogonal to each other. Further, each hemispherical body 4 is inscribed in the circumscribed circle at its outer end 4a, and therefore, near the outer end 4a, the body 2 and the hemispherical body 4 are continuously connected on a smooth surface. There is. On the other hand, the part near the outer end of the intersection line 5 of the hemispherical connector 6 is the lower end 8 of the body 2 (near the intersection line 5).
It is slightly discontinuously connected to the recess 9 formed nearby. Furthermore, the bottom end 4b of the hemispherical body 4 is chamfered into a planar shape to improve the upright stability.

The central flat portion 7 is unavoidably formed during stretch-blow molding because the stretch rod hits this portion as described later, and its side length is approximately equal to the diameter of the stretch rod, usually about 10 mm. ~15mm and does not change depending on the diameter of the body. Therefore, in the case of the blow-molded bottle 11, as shown in FIG. 6, the bottom portion 13 consists only of the hemispherical connecting body 16, and the center portion 16a of the hemispherical connecting body 16 has a spire shape with no flat part. In the embodiment shown in FIG. 6, the bottom end 14b of the hemispherical body 14 is not chamfered;
b forms the ground point.

The bottle 1 is manufactured, for example, as follows.
As shown in FIG. 7, a neck mold 21, a body mold 22, which have a cavity shaped like the bottle 1,
The inside of the mold 20 includes a bottom mold 23 and a pin 24 that slides vertically through a central hole 23a of the bottom mold 23 and whose upper surface 24a has a shape corresponding to the central flat part 7 of the bottle bottom 3 and its vicinity. Then, with the pin 24 in the lowered position as shown in FIG. 7a, the parison (not shown) is stretched in the axial direction with a stretching rod 25. Then, by blowing, the bottom of the molded body 26 is connected to the pin 24 as shown in FIG. 7a.
When the pin 24 comes into contact with the upper surface 24a of the seventh
The molded body 26 is raised to the position shown in FIG.
Blow until it comes into close contact with the inner surface of the cavity. In this way, a stretched and blown plastic bottle 1 having a central flat part 7 on the bottom part 3 can be formed.

The present invention is not limited to the above embodiments, and the number of hemispherical bodies 4 may be three. Two pieces are not preferable from the viewpoint of erecting stability. It should be noted that even if the number of hemispherical bodies 4 exceeds four, the upright stability and buckling resistance will not particularly improve, but rather the shape will become complicated and the mold cost will increase.
Usually the number of hemispheres 4 is three to four.

A specific example will be described below.

Specific Example A bottomed parison 17 (FIG. 7a) made of polyethylene terephthalate was formed by injection molding.

Connect the threaded portion 17c of this parison 17 with the neck mold 2.
1 (FIG. 7a) and in a vertical position with the threaded portion 17c facing down, rotate it around the axis and pass it between the infrared heaters to remove the body wall portion 17.
a and bottom 17b were heated substantially uniformly to about 100°C. Immediately thereafter, the parison 17 and the neck mold 21 were placed in the mold 20 (mold temperature approximately 50° C.) with the body mold 22 (FIG. 7a) open, and the body mold 22 was immediately closed. At this time, the pin 24 was in the lowered position as shown in FIG. 7a, and the bottom of the stretching rod 25 was in the position shown by the dashed line in FIG. 7a.

Immediately lower the stretching rod 25 to stretch the parison 17 in the axial direction, and then open the center hole 27 of the stretching rod 25.
Then, the parison 17 was blown by blowing out pressurized air of 25 kgf/cm from the blowing hole 27a. When the bottom 26a of the molded body 26 under stretch blow molding comes into contact with the upper surface 24a of the pin 24, as shown in FIG. 7a, the pin 24 is raised to the raised position shown in FIG. 7b, and the molded body 26 Blow is performed until it comes into close contact with the inner surface of the cavity of the mold 20 to produce a drawn-blow bottle having a bottom portion 33 consisting of a hemispherical connecting body 36 having six hemispherical bodies 34 in the shape shown in FIGS. 8 and 9. 31 was created.

The weight of the bottle 31 is 30 gr, the height is 180 mm, the outer diameter of the main body part 32a is 72 mm, the outer diameter D of the lower end part 38 of the body is 74 mm, and the diameter (outer diameter) 2d of the hemispherical body 34 is 34 mm.
mm, the diagonal length of the central flat part 37 is 15 mm, the bottom end 3
The height from 4b to the central flat part 37 is 5.5 mm, the average thickness of the body main part 32a is 0.35 mm, and the hemispherical body 34
The average wall thickness of is 0.35 mm, and the average wall thickness of hemispherical body 34 is
It was 0.6mm.

The properties of bottle 31 were as follows.

(a) Transparency: It was 98% when measured using a haze meter, which was the same transparency as glass.

(b) Impact drop strength: 120cm after filling with carbonated water and sealing
It was tested by being dropped 10 times from a height of 100, but it did not break.

(c) Gas barrier property: Oxygen gas permeability is 2.0ml.
mm/M ²・24Hr・ATM・25℃.

(d) Internal pressure resistance: After filling and sealing Coke 4GV (gas volume), no buckling occurred at the bottom even when the container was kept at 37°C. Note that 1 GV is the unit of pressurizing 1 liter of carbon dioxide gas to 1 liter of water at 15°C, and 4 GV is the unit of pressurizing 4 liters of carbon dioxide gas.
4GV, 37℃ corresponds to 7Kgf/cm ² .

(e) Upright stability: When stored under the conditions (d), the bottle 31 has a height of 1.5 to 2 mm and a diameter of 0.3 to 0.5 mm.
mm, and the volume expanded to 15 to 20 ml, but the bottom did not wobble.

(Effects of the Invention) The bottom structure of the plastic bottle of the present invention has excellent upright stability and internal pressure resistance, and has the effect of being difficult to cause buckling even when the normal internal pressure is relatively high.

[Brief explanation of the drawing]

Fig. 1 is a front view of the bottle of the first embodiment of the present invention, Fig. 2 is a bottom view of the bottle of Fig. 1, and Fig. 3 shows the vicinity of the bottom of the bottle of Fig. 1 along the - line in Fig. 2. 4 is a longitudinal sectional view of the main part taken along the - line in Fig. 2, Fig. 5 is a longitudinal sectional view of the main part taken along the - line in Fig. 2, and Fig. 6 is a longitudinal sectional view of the main part taken along the - line in Fig. FIG. 7 is a vertical cross-sectional view of the main part corresponding to FIG. 5 of the bottle of the example, and FIG. 7 is a longitudinal cross-sectional view for explaining the bottle manufacturing method of FIG. 1, and FIG. Figure 7b is a diagram showing the state of the bottle after molding is completed, Figure 8 is a front view of the bottle of the third embodiment of the present invention, and Figure 9 is a diagram showing the bottle of Figure 8. It is a bottom view. 1...Plastic bottle, 2...Body part, 3...
...bottom, 4...hemisphere, 4b...bottom end, 5...
Intersection part, 6... Hemisphere connector, 7... Central flat part,
8... lower end of trunk, 12... trunk, 13... bottom, 14... hemispherical body, 14b... bottom end, 16...
...hemisphere connective body.

Claims (1)

[Claims for Utility Model Registration] (1) A bottom structure of a blow-molded or stretch-blow-molded plastic bottle having a body with a circular cross-section, the bottom structure comprising at least three hollow hemispheres in each hemisphere. It mainly consists of a hemispherical connecting body that is coaxial with the torso and connected to the lower end of the torso, which is connected via the intersection line between the bodies to form a central recess, and the diameter of each hemispherical body is equal to the diameter of the torso. Approximately equal to the radius of the circumscribed circle of the body at the lower end,
Each hemisphere is arranged at equal intervals in the circumferential direction, and the hemisphere connecting body is inscribed in the circumscribed circle at the lower end of the body, and the bottom end of each hemisphere forms a grounding point or ground plane. The bottom structure of the plastic bottle is characterized by: (2) The bottom structure of a plastic bottle according to claim 1, wherein each hemisphere has a flat bottom end. (3) The bottom structure of a plastic bottle according to claim 1, wherein the upper end of the central recess is substantially flat.