JPH0764348B2 - Bottom wall structure of synthetic resin container - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the bottom wall structure of a synthetic resin container which is biaxially stretch blow-molded.

[0002]

2. Description of the Related Art The bottom of a biaxially stretch blow-molded synthetic resin container has a lower stretch ratio than that of a body or the like, but the self-weight of the contents to be filled at high temperature acts on the bottom of the container. In the case of carbonic acid or the like, the internal pressure also acts, so mechanical strength to withstand this is required and heat resistance is also required. Therefore, various improvements have been made to increase the mechanical strength of the bottom portion and improve the heat resistance.

This type of improvement is a so-called "champagne bottom" type improvement in which a convex portion is provided when the bottom portion is convex toward the inside of the bottle.
As proposals of this type, JP-A-62-251335 and JP-A-63-17893
2, Japanese Patent Publication No. 2-365456, Japanese Patent Application Laid-Open No. 2-85143, and the like.

[0004]

By the way, the convex portion on the bottom portion disclosed in each of the above publications forms a bottle bottom portion having a mechanical strength and heat resistance which does not cause deformation by increasing the stretching ratio at the bottom portion. However, this convex portion projects inward of the bottle, which reduces the volume of the bottle. Then, the wider the surface area of the convex portion protruding inward of the bottle, the higher the stretching rate and the bottle excellent in strength can be provided, but on the other hand, the bottle capacity decreases at a higher rate.

Actually, the bottle is molded to a size capable of containing a specified amount of contents. However, the convex portion formed on the bottom of the bottle in this manner has a remarkable protrusion amount, and the like. It impresses a bad image that gives consumers the illusion that there is little content.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and to improve the draw ratio of the bottom of a biaxially stretch-blown container to ensure mechanical strength and the like. It is an object of the present invention to provide a bottom wall structure for a synthetic resin container that can minimize the reduction in the capacity of the container caused by the shape of the container while adopting the above.

[0007]

A bottom wall structure of a synthetic resin container according to the present invention is a bottom wall structure of a biaxially stretch-blown synthetic resin container, wherein a height H is higher than a ground plane at a peripheral edge of the bottom wall.
₁ to project inward of the container so that the projecting surface is parallel to the grounding surface.
And a first convex portion having an outer edge diameter D ₁ and the first convex portion
A second convex portion that protrudes from the central region of the convex portion of the inside of the container to a position of height H ₂ above the ground contact surface and has an outer edge diameter of D _2, and is formed in two stages. The convex part of 1 is
Ribs convex or concave along the radial direction of the vessel
The a, the height _H 1, _{H 2} and a diameter _D 1, _{D 2} relationship, and in _{H 1 ≦ H 2/2,} , characterized in that a _{D 2} ≦ _{D 1/2.}

[0008]

According to the above construction, since the second convex portion has the height H ₂ which projects maximum inward of the container, the stretching ratio is high,
Moreover, since the outer edge diameter D ₂ thereof is relatively small, the strength against buckling load becomes high and the heat resistance is secured. On the other hand, the first convex portion around the second convex portion has a relatively low projecting height H ₁ toward the inside of the container, so the stretching ratio is not so high,
Since the reinforcing ribs are formed, the strength against buckling load can be secured and thermal deformation can be prevented. Moreover, the present invention has a second one-half of the outer diameter D ₁ of the outer diameter D ₂ of the convex portion is first convex portion below the most protruding into the container inwardly, a large outer diameter D ₁ Since the height H _{1 of} the first convex portion is less than or equal to ½ of the maximum protruding height H ₂ , the container is reduced by protruding the first and second convex portions inward of the container. The volume volume of can be kept to a minimum.

[0009]

EXAMPLE An example in which the present invention is applied to a bottle made of poly (ethylene terephthalate) will be specifically described below with reference to the drawings.

FIG. 1 is a sectional view showing a bottom region of a bottle to which the present invention is applied and a blow mold for molding the bottle, and FIG. 2 is a cut perspective view of the bottom region of the bottle.

In each of the drawings, a bottle having a body portion 10 and a bottom portion 12 for closing one end thereof is obtained by biaxially stretch-blow molding a preform (not shown) with a blow molding die shown in FIG. The blow mold is, as shown in FIG. 1, two blow cavity molds 14a and 14b which are movable in the horizontal direction in FIG. 1 and a bottom mold 1 which defines the bottom portion 12.
6 and 6. By forming the cavity surface of the bottom mold 16 as shown in FIG. 1, the mechanical strength of the bottom portion 12 is improved and the bottle consumer is not given the bad image that the content is small. I have to.

In the following, the structure of the bottom wall of the bottle will be described. In this embodiment, the bottom 12 of the bottle is convex toward the inside of the bottle, for example, the two first and second convex portions 20,
30 is formed, and the grounding surface 18 formed of a flat surface is formed on the outer edge portion of the bottom portion 12 which is the outer side thereof. The first convex portion 20 is, for example, a flat first convex flat surface 22 projecting inward of the bottle at a height H ₁ from the ground contact surface 18, and a first convex surface 22 that rises upward from the ground contact surface 18. The outer edge diameter of the first peripheral wall 24 at the position where the first peripheral wall 24 is joined to the ground contact surface 18 is D ₁ . The first convex flat surface 22 does not necessarily have to be parallel to the ground contact surface 18, and may be, for example, an inclined surface or a curved surface whose protruding height increases or decreases toward the center. Further, the angle formed by the first peripheral wall 24 and the ground contact surface 18 is θ ₁ .

The second convex portion 30 is the first convex portion 2
A second convex flat surface 32, which is formed in the central region of 0 and which projects further inward of the bottle than the first convex flat surface 22, and a flat second convex flat surface 32, and rises above the first convex flat surface 22. And a second peripheral wall 34. The second convex flat surface 32
Is not necessarily limited to a horizontal plane, and may be curved or inclined convexly or concavely toward the inside of the bottle. Second convex plane 32
Of the second peripheral wall 34 from the ground plane 18 is H _2.
The outer edge diameter at the position where intersects the first convex plane 22 is D ₂
Has become. The angle formed by the second peripheral wall 34 and the first convex flat surface 22 is θ ₂ . Further, ribs 26 extending in the radial direction from the center side to the outer edge side on the first convex plane 22 are formed at substantially equal intervals in the circumferential direction, and the ribs 26 have the first convex shape. For example, it is formed in a convex shape toward the inside of the bottle rather than the flat surface 22. The ribs 26 are formed on the first convex flat surface 2 having a relatively large area.
2 is to improve the mechanical strength, and may be concave toward the inside of the bottle, and the arrangement pattern thereof may be continuous in the circumferential direction or scattered at equal intervals, or along the concentric circles. It may be formed in a plurality of rings.

In the present embodiment, the heights H ₁ and H ₂ of the first and second convex portions 20 and 30 and the outer edge diameters D ₁ and
The relationship between _{D 2, H 1 ≦ H 2} /2 preferably _{H 1 ≦ H 2/3 ...} (1) D 2 ≦ D 1/2 preferably set to _{D 2 ≦ D 1/3 ...} (2) There is.

Further, the inclination angles θ ₁ and θ ₂ of the first and second peripheral walls 24 and 34 are preferably set to θ ₁ ≧ 60 degrees, θ ₂ ≧ 70 degrees (3). The larger the angles of θ ₁ and θ ₂ are, the higher the reinforcing effect is. However, the rising height H ₁ of the first peripheral wall 24 is equal to the rising height (H ₂ −H 2) of the second peripheral wall 34.
_Since it is smaller than ₁ ), an angle as large as the angle θ ₂ is not always necessary, and for example, θ ₁ ≧ 45 degrees may be used.

Further, the inclination angles θ _{1 of} the peripheral walls 24 and 34,
θ ₂ is the inclination angle of the flat surface when the peripheral wall is a flat surface as shown in FIG. 1, and means the maximum inclination angle of the tangent that is in contact with the curved surface when the peripheral wall is a curved surface.
Therefore, when the radius for connecting the upper and lower ends of the peripheral walls 24, 34 is large and the peripheral wall itself does not have an obvious inclined plane, the maximum angle of the tangent line may be set as in the above formula (3). .

Furthermore, the relationship between the maximum protruding height H _{2 of} the second convex portion 30 and the outer edge diameter D _{1 of} the first convex portion 20 is as follows.
Preferably, it is set to _{H 2 ≦ D 1/3 ...} (4), the outer edge diameter D ₁ of the first convex portion 20, the relationship between the maximum outer diameter D of the bottle body portion, preferably, D ₁ ≧ 0.65 × D (5) is set. The outer edge diameter D _{1 of} the first convex portion 20
The maximum value of is determined in consideration of at least ensuring the ground plane 18 having a minimum area for stabilizing the bottle to be self-supporting.

Next, the operation of the bottle having such a bottom wall structure will be described.

First, considering the second convex portion 30, this portion has the largest height H ₂ protruding toward the inside of the bottle, so that the vertical axis stretching rate is particularly large.
Therefore, the mechanical strength of the second convex portion 30 is improved,
Moreover, heat resistance is also improved. In addition, this second convex portion 3
Since the outer edge diameter D _{2 of} 0 is relatively small according to the equation (2),
Mechanical strength against a buckling load on the second convex flat surface 32 is guaranteed.

Further, by setting the rising angle θ ₂ of the second peripheral wall 34 of the second convex portion 30 according to the equation (3), the vertical axis stretching ratio can be further increased, and The buckling strength of the second convex portion 30 can be improved. Therefore, even if this bottle is filled with contents that have been sterilized at a high temperature and the self-weight of the contents acts perpendicularly on the second convex flat surface 32, the buckling deformation of the second convex portion 30 will occur. Can be reliably prevented.

Next, considering the first convex portion 20, this portion has a relatively small height H ₁ from the ground plane 18, and the vertical axis stretching ratio is lower than that of the second convex portion 32. For,
Improvement in mechanical strength due to stretch crystallization cannot be expected so much. However, in the present embodiment, a plurality of ribs 26 extending in the radial direction from the center to the outer edge are formed on the second convex flat surface 32 of the second convex portion 30 at substantially equal intervals in the circumferential direction. Since the ribs 26 are formed, the reinforcing effect of the ribs 26 makes the first convex flat surface 22 of the second convex portion 30 relatively large in area.
The mechanical strength of can be secured. Further, in the outer edge portion of the first convex portion 20, by setting the rising angle θ ₁ of the first peripheral wall 24 as in the formula (3), the strength of this portion against the buckling load can be improved. You can Further, from the viewpoint of guaranteeing the strength of the entire bottom wall, the first convex portion 20
It is desirable to set the outer edge diameter D ₁ of the above in the range of the formula (5).

As described above, according to this embodiment, the mechanical strength of the bottom 12 of the bottle can be improved without making the shape of the cavity surface of the bottom mold 16 relatively complicated. Moreover, in this embodiment, while improving the mechanical strength of such a bottom wall, the volume volume of the bottle that is reduced by raising the bottom of the bottom is kept to a minimum, so that the consumer of this bottle has little content. I can suppress receiving a bad image. In other words, the outer edge diameter D _{2 of} the second convex portion 30 having the highest height H _{1 that} is discharged toward the innermost side of the bottle from the ground contact surface 18 is set as in equation (2). The decrease in the bottle capacity due to the raised bottom of the convex portion 30 is relatively small. On the other hand, the height H ₁ from the ground contact surface 18 of the first convex portion 20 having a relatively large outer edge diameter D ₁ is set as in the formula (1), and the bottom convex portion 20 is raised by the first convex portion 20. The decrease in bottle capacity due to is also relatively small. In the case of setting the dimensions outside the ranges of the above formulas (1) and (2), the mechanical strength of the bottom wall is improved, but the reduction rate of the bottle capacity becomes remarkable, so that the excessive strength is guaranteed and the reduction rate of the bottle capacity increases. It deteriorates the consumer image. Thus, the first and second convex portions 20, 30
Each reduction in bottle capacity that results in the formation of a bottle is set to a minimum so that the consumer does not have the illusion that the bottle contents are low.

From the viewpoint of guaranteeing the mechanical strength when the dimensions of equations (1) and (2) are set, equation (3)
It is preferable to apply the condition of (1) and / or the condition of expression (5) together, and from the viewpoint of suppressing the reduction rate of the bottle capacity, the expression (4) that further defines the upper limit of the maximum protruding height H ₂ is given.
It is desirable to apply the conditions of.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist of the present invention.

[0025]

[0026]

[0027]

As described above, according to the present invention,
By improving the mechanical strength of the bottom wall of the biaxially stretch-blown container from its center to the periphery, it is possible to prevent buckling or thermal deformation due to the self-weight of the contents, etc. By minimizing the reduction of the internal volume, it is possible to reduce the bottle consumers from having a bad image based on the illusion that the contents are small.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a bottom wall structure of a bottle and a blow molding die for molding the bottle according to an embodiment of the present invention, in the vicinity of a bottom portion thereof.

2 is a cross-sectional perspective view of the bottom wall region of the bottle shown in FIG.

[Explanation of symbols]

10 Body 12 Bottom 18 Ground plane 20 1st convex part 22 1st convex plane 24 1st peripheral wall 26 Rib 30 2nd convex part 32 2nd convex plane 34 2nd peripheral wall 40th Convex part 3
NS007801

Claims (2)

[Claims] 1. A bottom wall structure of a biaxially stretch-blown synthetic resin container, wherein the container protrudes inward at a height H ₁ from a grounding surface at the periphery of the bottom wall ,
A first convex portion whose protruding surface is parallel to the ground contact surface and has an outer edge diameter of D _1, and a height H ₂ higher than the ground contact surface from the central region of the first convex portion to the inside of the container. projecting up position, and a second convex portion that the outer diameter and D _2, in which formed in two stages, the first convex portion is convex or concave in the radial direction of the container
Having a reinforcing rib formed into a shape, the relationship between the heights H ₁ and H ₂ and the diameters D ₁ and D ₂ is H ₁
≦ _H 2/2, in and bottom wall structure of synthetic resin container, characterized in that a _{D 2} ≦ _{D 1/2.} 2. The peripheral walls of the first and second convex portions according to claim 1, wherein inclination angles θ ₁ and θ ₂ with respect to a plane parallel to the ground contact surface are θ ₁ ≧ 60 °, and , Θ ₂ ≧ 70 °, a bottom wall structure of a synthetic resin container having a steep inclination.