JPH0825566B2 - Synthetic resin container lid - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a synthetic resin container lid, and more particularly to a synthetic resin container lid in which a so-called doming phenomenon due to an increase in internal pressure of the container is suppressed.

<Prior Art> As a container lid for a container such as a soft drink bottle, a synthetic resin container lid molded from an appropriate synthetic resin such as polypropylene or polyethylene has recently been proposed and put into practical use. Came. Such a synthetic resin container lid has a circular top wall, a cylindrical skirt wall, and a shoulder wall extending from the peripheral edge of the top wall to the upper end of the skirt wall in an arc shape over an angle range of about 90 degrees. Separately molded sealing liner material is provided on the inner surface of the top wall or the shoulder wall, or an annular sealing ridge is integrally formed.

<Problems of Prior Art> However, the conventional synthetic resin container lid has the following problems to be solved. For example, when the content of the container is a soft drink containing carbon dioxide, when the container is exposed to direct sunlight in summer, the temperature inside the container is raised to about 40 to 50 degrees and the pressure inside the container is 6 to 8 kg / cm ² It can be increased to some extent. Thus, in the conventional synthetic resin container lid, the so-called doming phenomenon in which the top wall or the shoulder wall bulges upward to the dome line due to the increased internal pressure is excessively generated, which causes the container mouth and neck by the container lid. The seal of the part is damaged. Such a problem is the diameter of the neck of the container,
Therefore, the larger the diameter of the container lid, the more remarkable.

As a solution to the above problems existing in conventional synthetic resin container lids, it is possible to increase the wall thickness of the top wall or the shoulder wall to increase the rigidity of the top wall or the shoulder wall, and thus suppress the doming phenomenon. Conceivable. However, if such a solution is adopted, the amount of synthetic resin material required for molding the container lid is significantly increased, and thus the manufacturing cost is increased.

<Problems to be Solved by the Invention> The present invention has been made in view of the above facts, and a problem to be solved is to avoid or suppress an increase in the amount of synthetic resin material required for molding a container lid, thereby increasing the pressure inside the container Is to sufficiently suppress the above-mentioned doming phenomenon.

<Means for Solving the Invention> As a result of earnest research and experimentation, the inventors of the present invention have made the radius r of the center line of the shoulder wall considerably larger than in the conventional case, and the outer diameter of the container lid is set to 0.07R ≦ r. While setting ≦ 0.15R,
The top wall and the upper half of the shoulder wall over an angle range of about 45 degrees are made to have substantially the same thickness, and the lower half of the shoulder wall is gradually reduced in thickness downward to solve the above problem. We have found that we can achieve the task.

That is, according to the present invention, as a synthetic resin container lid that achieves the above-mentioned problem, a circular top wall, a cylindrical skirt wall,
And a synthetic resin container lid having a shoulder wall extending in an arc shape over an angle range of approximately 90 degrees from the peripheral edge of the top wall to the upper end of the skirt wall; the radius r of the center line of the shoulder wall is the container lid. Let the outer diameter be R
0.07R ≦ r ≦ 0.15R, approximately 45 of the top wall and the shoulder wall
The upper half over the angular range of degrees is made to have substantially the same thickness, and the lower half of the shoulder wall is gradually reduced in thickness downward. A resin container lid is provided.

The lower half of the shoulder _{wall, 0.3t 1 ≦ t 2 ≦ 0.9t} 1 thick and substantially the same thickness t ₁ of the upper half of the shoulder wall, especially 0.4t ₁ ≦ t ₂ ≦ 0.6
It is preferably gradually reduced to a thickness t ₂ which is t ₁ .

<Preferred Specific Examples of the Invention> Hereinafter, preferred specific examples of a synthetic resin container lid configured according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a container lid, generally designated 2, which can be injection molded or compression molded from a suitable synthetic resin material such as polypropylene or polyethylene comprises a circular top wall 4, a shoulder wall 6, And a cylindrical skirt wall 8. The shoulder wall 6 extends in an arc shape from the peripheral edge of the top wall 4 to the upper end of the skirt wall 8 over an angle range of approximately 90 degrees. A weakening line 10 extending in the circumferential direction is formed in the lower part of the skirt wall 8, and the skirt wall 8 has a main portion 12 above the weakening line 10 and a pilfer proof hem 14 below the weakening line 10. It is partitioned. Weakening line 10
Is composed of a plurality of slits (cutting grooves) 16 formed at intervals in the circumferential direction and extending in the circumferential direction, and a plurality of bridging portions 18 left between the slits 16. The far proof skirt 14 is connected to the main portion 12 by a plurality of bridging portions 18. In the illustrated example, one specific bridging portion 18A of the plurality of bridging portions 18 is used.
Has a larger width in the circumferential direction than the other bridging portions 18, and therefore has increased strength. A weakening line 20 extending in the axial direction is formed in the pill-proof skirt 14 at a position adjacent to one side edge of the specific bridging portion 18A in the circumferential direction. This weakened line 20 may be a score or a perforation.

A female screw thread 22 is formed on the inner surface of the upper portion 12 of the skirt wall 8, and an unevenness or knurled shape 24 is formed on the outer surface thereof to prevent the sliding of fingers applied thereto. On the other hand, a plurality of locking flap pieces 26, which may be of any suitable shape, are formed on the inner surface of the thin pilfer proof skirt 14 at circumferential intervals. Further, on the inner surface of the shoulder wall 6, there is formed an annular ridge 28 which projects inward in the radial direction, and in a region surrounded by the annular ridge 28, a separately formed substantially disc-shaped member is formed. A sealing liner material 30 is provided. The sealing liner material 30 can be formed at a required position by a known embossing molding method from an appropriate synthetic resin material after molding the container lid body. If desired, instead of the sealing liner material 30, an appropriate shape of sealing ridges may be integrally formed on the inner surfaces of the top wall 4 to the shoulder wall 6.

The synthetic resin container lid 2 as described above is applied to a container provided with the mouth / neck portion 32 having the form as shown in FIG. The mouth-neck portion 32, which is known per se, has a cylindrical outer peripheral surface, and on the outer peripheral surface, a male screw thread 34 and a locking jaw portion 36 located below the male screw thread 34 are formed.

When closing the mouth / neck 32 with the container lid 2,
The container lid 2 is fitted in 32, and the container lid 2 is rotated in the closing rotation direction, that is, in the clockwise direction when viewed from above in FIG. As a result, the female screw thread 22 formed on the container lid 2 becomes
It is screwed into a male thread 34 formed on 32, whereby the container lid 2 is moved downward with rotation. When the container lid 2 is moved downward, each of the locking flap pieces 26 formed on the container lid 2 passes through the male thread 34 formed on the mouth / neck portion 32, and further the locking jaws. Although it will pass through the part 36, when passing through the locking jaw part 36,
By being interfered with by 36, each of the locking flap pieces 26 is elastically bent outward in the radial direction. Female thread of container lid 2
When 22 is fully screwed into male thread 34 of mouth and neck 32,
As shown in the figure, each of the locking flap pieces 26 completely passes through the locking jaws 36 and is not interfered with by the locking jaws 36, and each of the locking flap pieces 36 returns to its original state. It is elastically restored and locked on the lower surface of the locking jaw 36. Further, the sealing liner material 30 is brought into close contact with the end face portion of the mouth / neck portion 32, and thus the mouth / neck portion 32 is sealed.

As described above, the container lid 2 attached to the mouth / neck 32 is
When opening the mouth and neck 32 by detaching it from the mouth and neck 32,
The direction opposite to the closing rotation direction when the container lid 2 is attached,
That is, when viewed from above in FIG. 2, it is rotated counterclockwise. Thus, the female thread formed on the container lid 2
Since the container 22 is moved along the male screw thread 34 formed on the mouth / neck portion 32, the container lid 2 does not move upward. However, since the locking flap piece 26 formed on the inner surface of the pill-proof skirt 14 of the container lid 2 is locked to the lower surface of the locking jaw 36 of the mouth / neck 32, the pill-proof skirt. The upward movement of the part 14 is prevented. Thus, a considerable amount of stress is generated in the weakening line 10 formed on the container lid 2, and the bridging portion 18 in the weakening line 10 has a large circumferential width and is increased in strength.
Except for 18A, a considerable amount of stress is also generated in the weakening line 20 formed in the pilfer proof hem 14 and also the weakening line 20 is ruptured so that the pilfer proof hem 14 has an endless annular shape. It is opened like an end strip. Thus, the engagement of the engagement flap piece 26 with respect to the lower surface of the engagement jaw 36 is released, and after that, it is connected to the main portion 12 by the specific bridging portion 18A which is maintained without being broken. The entire container lid 2 including the pill-proof skirt 14 is moved upward with rotation, thus the entire container lid 2 is separated from the mouth / neck portion 32, and the mouth / neck portion 32 is opened.

Thus, the above-described configuration and operation of the illustrated synthetic resin container lid 2 are already known, and also merely show one example of the synthetic resin container lid to which the present invention is applied.

In the container lid 2 described above, a so-called doming phenomenon in which the top wall 4 to the shoulder wall 6 bulge upward to a dome line is generated when the internal pressure of the container is increased. In No. 2, in order to sufficiently suppress the doming phenomenon, the following improvements are added.

Referring to FIG. 3 together with FIG. 1, the radius of curvature of the shoulder wall 6 is set to be considerably larger than that of a conventional container lid, and the radius r of the central axis 38 of the shoulder wall 6 is equal to that of the conventional container lid. The outer diameter R of the container lid 2 is considerably larger than that of the container lid.
It is set to 0.07R ≦ r ≦ 0.15R. Central axis of shoulder wall 6
When the radius r of 38 is set to a large value as described above, the change in the radius of curvature at the boundary between the top wall 4 and the shoulder wall 6 and the boundary between the shoulder wall 6 and the skirt wall 8 becomes small, and therefore, will be mentioned later. As can be understood from the description of Examples and Comparative Examples, the occurrence of the doming phenomenon can be effectively suppressed. On the other hand, if the radius r of the central axis 38 of the shoulder wall 6 is set too large beyond the above range, the appearance of the container lid is disturbed and it becomes difficult to secure an appropriate accommodation space for the sealing liner agent 30. .

Continuing the description with reference to FIGS. 1 and 3, the circular top wall 4 is made to have substantially the same thickness t ₁ over the entire surface. Further, the upper half portion of the shoulder wall 6 extending in an arc shape over an angle range of approximately 90 degrees, that is, the upper half portion 6a extending over an angle range of approximately 45 degrees from the peripheral edge of the top wall 4 also has the thickness of the top wall 4. The thickness t ₁ is substantially the same as t ₁ . On the other hand, the thickness of the lower half portion 6b of the shoulder wall 6 which extends over an angle range of about 45 degrees is gradually reduced from the thickness t ₁ downward. The thickness t ₂ of the lower end of the lower half 6b of the wall shoulder _{6, 0.3t 1 ≦ t 2 ≦ 0.9t} 1, is preferably particularly _{0.4t 1 ≦ t 2 ≦ 0.6t 1} . When the thicknesses of the top wall 4 and the shoulder wall 6 are made to be as described above, there is a sudden change in wall thickness in the range from the top wall 4 through the shoulder wall 6 to the upper end of the skirt wall 8. It does not exist, hence
As will be understood from the description of Examples and Comparative Examples mentioned later, the doming phenomenon can be effectively suppressed.

<Example and Comparative Example> Example polypropylene (melt index 2.0, density 0.9
0) is used to injection mold a container lid body having a shape as shown in FIGS. 1 and 3, and a vinyl acetate resin is further used to place the first container lid body at a predetermined position. A sealing liner agent having a shape as shown in the drawings and FIG. 3 was embossed and molded.

The main dimensions of the container lid were as follows (3rd
See figure).

Outer diameter of container lid R …………………… 39.0mm Radius of center line of shoulder wall r ……………… 3.6mm Thickness of top wall and upper half of shoulder wall t ₁ … 1.8mm Thickness of lower end of shoulder wall T ₂ ……………… 1.1mm Then, as shown in Fig. 4, the mouth and neck A of a commercially available polyethylene terephthalate container with a nominal neck of 38mm is cut, and the neck of the mouth and neck A is cut. The ring B was placed on the steel support D via the annular rubber ring C, and fixed on the support D by the tightening nut E. After that, the container lid F as described above was mounted as required, and nitrogen gas was pressure-injected through the hole G formed in the bottom wall of the support base D to increase the pressure in the mouth / neck portion A. Thus, the top wall or the shoulder wall of the container lid was swollen as shown by the chain double-dashed line in FIG. Then, as a result of measuring the relationship between the pressure in the mouth / neck portion A and the amount of upward change of the center of the top wall, it was as shown in FIG.

Comparative Example 1 For comparison, a conventional container lid whose shoulder wall and its vicinity are as shown in FIG. 6 was used. The main dimensions of this conventional container lid were as follows (see FIG. 6).

Outer diameter of container lid R …………………… 39.0mm Radius of center line of shoulder wall r ……………… 1.2mm Top surface wall thickness t ₁ …………………… 1.8mm Shoulder wall bottom thickness t ₃ ……………… 1.5 mm Thickness of skirt wall upper end t ₄ ………… 1.0 mm Then, in the same manner as in the example, the pressure in the mouth and neck A and the amount of upward displacement of the top wall center. As a result of measuring the relationship of, it was as illustrated in FIG.

Comparative Example 2 For comparison, the shape of the shoulder and its vicinity is as shown in FIG. 7, and (1) the radius r of the central axis of the shoulder wall is 1.2 mm, which is the same as in Comparative Example 1. And (2) The thickness t ₁ (in the area b from the middle position of the shoulder wall (angle position of about 45 degrees from the top wall) downward to the position vertically separated by 4.0 mm from the top surface of the top wall. = 1.8 mm) to t ₂ (=
The same container lid as in the example was manufactured except that it gradually decreased to 1.1 mm).

Then, in the same manner as in the example, the relationship between the pressure in the mouth / neck portion A and the upward displacement of the center of the top wall was measured, and the result was as shown in FIG.

Discussion From the measurement results in Examples and Comparative Examples 1 and 2,
According to the container lid improved in accordance with the present invention, the amount of upward displacement of the top wall center due to the increase in the pressure in the mouth / neck portion A is significantly suppressed, and thus the doming phenomenon that causes the damage to the seal is significantly reduced. It is understood that it is suppressed by.

[Brief description of drawings]

FIG. 1 is a side view, partly in section, of a container lid improved according to the present invention. FIG. 2 is a side view showing a state in which a part of the container lid of FIG. 1 is attached to the container neck portion. FIG. 3 is a sectional view showing a part of the container lid of FIG. 1 in an enlarged manner. FIG. 4 is a simplified cross-sectional view showing a measuring method in Examples and Comparative Examples. FIG. 5 is a diagram showing the measurement results in Examples and Comparative Examples. FIG. 6 is an enlarged sectional view showing a part of the container lid used in Comparative Example 1. FIG. 7 is an enlarged sectional view showing a part of the container lid used in Comparative Example 2. 2 ... Container lid 4 ... Top wall 6 ... Shoulder wall 6a ... Upper half of shoulder wall 6b ... Lower half of lower wall 8 ... Skirt wall

Claims (3)

[Claims] 1. A synthetic resin container lid having a circular top wall, a cylindrical skirt wall, and a shoulder wall extending in an arc shape over an angle range of approximately 90 degrees from the peripheral edge of the top wall to the upper end of the skirt wall. The radius r of the center line of the shoulder wall is 0, where R is the outer diameter of the container lid.
07R ≦ r ≦ 0.15R, the top wall and the upper half of the shoulder wall over an angle range of about 45 degrees are made to have substantially the same thickness, and the lower half of the shoulder wall is A synthetic resin container lid, characterized in that its thickness is gradually reduced downward. Lower half of 2. A shoulder wall thickness the thickness of the upper half of the shoulder wall of substantially the same thickness from t ₁ is 0.3t ₁ ≦ t ₂ ≦ 0.9t ₁ of
Claim 1 which is gradually reduced to t ₂ .
The synthetic resin container lid according to the item. Wherein said thickness t ₂ is _{0.4t 1 ≦ t 2 ≦ 0.6t 1} , plastic container closure of the second term recited in the claims.