JPH0232138B2 - - Google Patents

Description

Detailed Description of the Invention <Technical Field> The present invention relates to a container lid made of synthetic resin having pilfer-proof properties, and more specifically, to a container lid made of a synthetic resin having a pilfer-proof property, and more specifically, a male thread on the outer peripheral surface and a locking jaw located below the male thread. Applicable to containers with a mouth and neck formed with a
The present invention relates to a method of manufacturing a synthetic resin container lid having pilfer-proof properties. <Prior Art> Recently, container lids with pilfer-proof properties for containers such as beverage bottles have been developed.
Synthetic resin container lids have been proposed and put into practical use in place of metal container lids. A typical example of such a synthetic resin container lid is disclosed in Japanese Patent Application Laid-open No. 1983-
Publication No. 74445, Japanese Patent Application Publication No. 58-30949, and Japanese Patent Application Publication No. 1987-30949
The container lid disclosed in Japanese Patent No. 58-51116 can be mentioned. The container lid disclosed in the above publication has a top wall and a cylindrical skirt wall that hangs down from the periphery of the top wall. A weakened line extending in the circumferential direction is formed on the skirt wall, and the skirt wall is divided into a main portion above the weakened line and a pilfer-proof hem below the weakened line. A female thread is formed on the inner surface of the main portion, and a plurality of locking flap pieces protruding radially inward are formed on the inner surface of the pilfer-proof hem at intervals in the circumferential direction. . The synthetic resin container lid as described above is applied to a container having a neck portion in which a male thread and a locking jaw portion located below the male thread are formed on the outer peripheral surface. When closing the mouth and neck of a container with a container lid, the container lid is fitted onto the mouth and neck and rotated in a predetermined direction, that is, the closing direction, and the female thread on the container lid is screwed into the male thread on the mouth and neck. Match. As a result, the container lid rotates in the closing direction relative to the mouth and neck and moves downward in the axial direction. At this time, the locking flap piece formed on the inner surface of the pilfer-proof hem is interfered with by the locking jaw formed on the outer surface of the mouth and neck, and is elastically bent radially outward. . When it completely passes through the locking jaw, it elastically returns radially inward and locks onto the lower surface of the locking jaw. When opening the neck of the container, the container lid is rotated in the opposite direction to the closing direction, that is, in the opening direction. In this way, the female thread of the container lid is moved along the male thread of the mouth and neck, so that the container lid rotates in the opening direction and moves upward in the axial direction. However, the pilfer-proof hem of the container lid cannot move upward in the axial direction because the locking flap piece formed on its inner surface engages with the lower surface of the locking jaw of the mouth and neck. Therefore, considerable stress is generated in the line of weakness formed in the skirt wall of the container lid. Thus,
The weakened line is completely broken and the skirt wall is separated into the main part and the pilfer-proof hem, or the weakened line is broken leaving only a part and the skirt wall is attached to the pilfer-proof hem in the axial direction. The weakened line extending from the bottom is broken, and the pilfer-proof hem is opened from an endless ring to an edged band. Thereafter, the other parts of the container lid leaving the separated pilf-proof hem, or the entire container lid including the pilf-proof hem, are separated from the neck and neck, and the mouth and neck are opened. Therefore, it is important for the container lid as described above to satisfy the following two requirements. 1st
Furthermore, when the neck of the container is closed with the container lid, the locking flap piece can be elastically deflected radially outwards with sufficient ease to pass through the locking jaw; It is important to be able to apply the container lid to the mouth and neck with a relatively small rotational torque, thus ensuring that excessive stresses are not created in the line of weakness and the line of weakness is ruptured. Second, when opening the neck of the container, the locking flap piece locks sufficiently securely in the locking jaw, thus allowing the so-called snap-off to occur without causing the intended breakage of the line of weakness. If the container lid comes off (the locking flap bends radially outward and passes through the locking jaw), the container lid will separate from the mouth and neck (thus, the pill-proof property will be impaired). ) is important to ensure that this is avoided. In order to satisfy these two requirements, the necessary downward rotational torque that must be applied to the container lid when the locking flap piece is passed through the locking jaw from axially upward to downward is sufficiently small; If the locking flap piece is to be passed through the locking jaw from axially downward to upward, the necessary upward rotational torque that must be applied to the container lid is sufficiently large and the weakening line is ruptured in the desired manner. Therefore, it is necessary to set the necessary breaking rotational torque that must be applied to the container lid between the above-mentioned necessary downward rotational torque and the above-mentioned necessary upward rotational torque. However, in conventional container lids, it is not possible to create a sufficient difference between the required downward rotational torque and the required upward rotational torque, and therefore,
The first requirement or the second requirement is often not satisfied due to manufacturing errors or the like. <Object of the Invention> The present invention has been made in view of the above facts, and its main purpose is to provide a system in which the necessary downward rotational torque is sufficiently small and the necessary upward rotational torque is sufficiently large so that there is a sufficient difference between the two. An object of the present invention is to provide a method for manufacturing a synthetic resin container lid having pilfer-proof properties, which is improved so that the first and second requirements described above can be reliably satisfied. <Summary of the Invention> As a result of intensive studies and experiments, the present inventors have found that by making the following improvements in the production of container lids, a container lid that reliably satisfies the first and second requirements above can be obtained. I discovered that it can be done. That is, the container lid body of the above configuration is molded from a synthetic resin material by an appropriate molding method such as injection molding or compression molding. The angle α ₁ that each of them forms with the inner surface of the pilfer-proof hem when viewed in the opposite direction to the closing rotation direction of the container lid when the container lid is attached to the mouth and neck is made relatively large. Thereafter, each of the locking flap pieces is tilted with respect to the closing rotation direction by heating and mechanical force, so that the locking flap pieces each have the above-mentioned shape against the inner surface of the pilfer-proof hem. The angle seen in the opposite direction is reduced to an angle α ₂ smaller than the above angle α ₁ . According to the above-mentioned improvements, in particular, the required upward rotational torque is considerably increased, and thus a sufficient difference is created between the required downward rotational torque and the required upward rotational torque. The reason why the required upward rotational torque is considerably increased is that each of the locking flap pieces has a so-called memory characteristic that allows it to return to the state at the time of molding, and this causes the locking of the locking flap piece to the locking jaw of the mouth and neck. It is presumed that this is because the locking of the flap pieces is strengthened. Therefore, according to the present invention, the pilfer-proof property is achieved for a container having a neck portion in which a male thread and a locking jaw portion located below the male thread are formed on the outer circumferential surface. A method for manufacturing a synthetic resin container lid comprising: a top wall surface and a cylindrical skirt wall hanging down from the periphery of the top wall surface, the inner surface of a pilfer-proof hem defined at the bottom of the skirt wall is formed with a plurality of locking flap pieces projecting radially inward, and at least the base of each of the locking flap pieces is in contact with the neck portion against the inner surface of the pill-proof hem. a container lid body forming step of molding a container lid body extending from a synthetic resin material at an angle α ₁ when viewed in the opposite direction to the closing rotation direction of the container lid when the container lid is attached; After the container lid body forming process, at least the pilfer-proof hem and the locking flap pieces of the container lid body are heated to a temperature that does not exceed the melting point, and each of the locking flap pieces is rotated in the closing rotation direction. mechanically forced to tilt in the opposite direction, such that the angle that the base of each of the locking flap pieces makes with the inner surface of the pilfer-proof hem when viewed in the opposite direction to the direction of closing rotation. The method is characterized in that it comprises the step of: forcing the locking flap piece to tilt to an angle α ₂ smaller than the angle α ₁ . <Preferred Specific Examples of the Invention> Hereinafter, preferred specific examples of the method of the present invention will be described in detail with reference to the accompanying drawings. In a preferred embodiment of the method of the present invention, a container lid body 2 as shown in FIG. 1 is first molded from a suitable synthetic resin material such as a polyolefin resin by compression molding or injection molding. 1st
To explain with reference to the drawings, the illustrated container lid main body 2
has a circular top wall 4 and a cylindrical skirt wall 6 that hangs down from the periphery of the top wall 4. The skirt wall 6 has a relatively thick upper part 8, a relatively thin lower part 10, and an intermediate part 12 of intermediate thickness located therebetween. And the middle part 12
A weakened line 14 extending in the circumferential direction is formed in the skirt wall 6, and the skirt wall 6 is divided into a main portion 16 above the weakened line 14 and a pilfer-proof hem portion 18 below the weakened line 14. . The weakened line 14 may be a so-called score formed by reducing the thickness of the material, but in the illustrated example, the weakened line 14 is formed by a plurality of circumferentially extending slits ( Cut groove) 2
0 and a plurality of bridging portions 22 remaining between the slits 20, and the pilfer-proof hem portion 18 is composed of a plurality of bridging portions 22 remaining between the slits 20.
It is connected to the main part 16 by. In the illustrated example, one specific bridge portion 22A among the plurality of bridge portions 22 has a larger width in the circumferential direction than the other bridge portions 22, and therefore has increased strength. ing. A weakened line 24 extending in the axial direction is formed in the pilfer-proof hem 18 at a position adjacent to one edge in the circumferential direction of the specific bridging portion 22A. This weakened line 24 is
Scores or perforations may be used. The slit 20 in the weakened line 14 and the weakened line 24 may be formed by a suitable cutting device after forming the container lid body 2, if desired, instead of being formed directly during the molding of the container lid body 2. It can also be formed by, for example, making the necessary cuts. An annular protrusion 26 is formed at the upper end of the inner surface of the main portion 16 of the skirt wall 6 and projects radially inward therefrom. The inner surface of the main portion 16 has a female thread 28.
is also formed. The outer surface of the main portion 16 has an uneven or knurled shape 30 to prevent the fingers from slipping when rotating the container lid body 2 by placing the fingers thereon.
It is convenient that . On the other hand, on the inner surface of the pilfer-proof hem 18, more specifically on the inner surface of the relatively thin lower part 10, there are a plurality of pieces (30 pieces in the illustrated case) spaced apart in the circumferential direction.
A locking flap piece 32 is formed. Each of the locking flap pieces 32 may extend in a straight line radially inward from the base edge 34 connected to the inner surface of the pilfer-proof hem 18, but as shown in FIGS. As clearly shown, the first portion or base portion 38 is bent along the fold line 36 and extends from the base edge 34 to the fold line 36, and the second portion extends from the fold line 36 to the free end.
Preferably, it is defined by a portion or a tip 40. The base edge 34 extends substantially parallel to the central axis of the container lid body 2, and therefore substantially vertically. However, if desired, the base edge 34 may be moved in a suitable direction with respect to the central axis of the container lid body 2, i.e., during the closing rotation of the container lid when the container lid is attached to the neck of the container as described below. Direction (clockwise when viewed from above in Figure 1, Figures 2 and 3)
It can also be made to extend downward at an appropriate angle (in the direction indicated by arrow 42 in the figure) or in the opposite direction. Referring to FIGS. 2 and 3, the base portion 38 of each of the locking flap pieces 32 is connected to the inner surface of the pilfer-proof hem 18 when viewed in a direction opposite to the closing rotation direction 42. It extends radially inwardly from the base edge 34 at an angle α ₁ . The above angle α ₁ during molding is relatively large, 30 degrees ≦ α ₁
≦135 degrees, especially 45 degrees≦α ₁ ≦120 degrees, especially 60 degrees≦α ₁ ≦
Preferably it is 100 degrees. A distal end portion 40 extending from the folding line 36 extends at an angle β ₁ with respect to the base portion 38 in the closing rotation direction 42 . The above angle β ₁ during molding is also relatively large,
5 degrees≦β ₁ ≦150 degrees, especially 10 degrees≦β ₁ ≦120 degrees, especially 30 degrees
It is preferable that degrees≦β ₁ ≦90 degrees. Above folding line 3
6 itself can extend substantially parallel to the central axis of the container lid body 2, thus substantially vertically, or inclined downwardly toward the inner surface of the pilfer-proof hem 18. , preferably extends downwardly and away from the inner surface of the pilfer-proof hem 18 at an angle. Folding line 36
The inclination angle γ of the downward direction away from the inner surface of the pilfer-proof hem 18 is 5 degrees≦γ.
≦80 degrees, especially 10 degrees≦γ≦60 degrees, especially 20 degrees≦γ≦50
It is preferable that the As shown in FIGS. 1 and 2, the upper edge 44 of the base portion 38 extends radially inwardly and downwardly in a smooth curve, and the upper edge 46 of the tip portion 40 is approximately Advantageously, it extends horizontally or radially inwardly and downwardly at a slight angle. On the other hand, the lower edge 48 of the base 38 and the tip 40
Advantageously, the lower edge 50 extends radially inwardly and upwardly. Generally, the base 3
The inclination angle δ of the lower edge 48 of the tip part 40 is 10 degrees≦δ≦30 degrees, and the inclination angle ε ₁ of the lower edge 50 of the tip portion 40 is somewhat larger than the above-mentioned inclination angle δ, 20 degrees≦ε ₁ ≦ A convenient angle is 60 degrees. FIG. 4 illustrates an example of a mold that can be used to compression mold the container lid body 2 as described above. Briefly describing such a mold, the mold, generally designated by the numeral 52, is comprised of a lower mold assembly 54 and an upper mold assembly 56. The lower mold assembly 54 has a centrally located cylindrical member 58 and a cylindrical member 60 located outside of the member 58 . The upper mold assembly 56 is
Ejection pin member 62 and member 62 located in the center
It has a substantially cylindrical member 64, a substantially cylindrical member 66, a substantially cylindrical member 68, a hollow truncated cone-shaped member 70, and an annular member 72, which are located in order on the outside. Before starting molding, the member 5 in the lower mold assembly 54
8, the member 60 in the lower mold assembly 54
are located below the position shown, and members 62, 64, 66, 68, 70 in the upper mold assembly 56
and 72 are located above the illustrated position. In this state, a molten synthetic resin material is supplied onto the member 58 of the lower mold assembly 54. After that, the lower mold assembly 54
The member 60 in the upper mold assembly 56 is raised to the position shown, and the member 60 in the upper mold assembly 56 is raised to the position shown.
2, 64, 66, 68, 70 and 72 are lowered to the positions shown. In this way, the container lid main body 2 is compression molded in an inverted state (that is, a state in which the skirt wall 6 extends upward from the top wall 4). Each of the locking flap pieces 32 formed on the inner surface of the pill-proof hem 18 of the container lid body 2 is formed at the lower end of the members 66 and 68 in the upper mold assembly 56 at intervals in the circumferential direction. Defined by grooves 74 and 76. More specifically, the base 38 of each locking flap piece 32 is defined by a groove 76 formed in the lower end of member 68, and the distal end 40 is defined by a groove 74 formed in the lower end of member 66 (such The radially outer end of groove 74 is defined by a radially inner end of groove 74 (located in alignment with the radially inner end of groove 76 formed in the lower end of member 66). When the container lid main body 2 is molded as described above, the member 60 in the lower mold assembly 54 is lowered, and the member 62 in the upper mold assembly 56,
64, 66, 68, 70 and 72 are raised together and the container lid body 2 is raised accordingly, thus removing member 58 in the lower mold assembly 54.
Then, the container lid main body 2 is removed from 60. Next, the member 70 of the upper mold assembly 56 is raised and removed from the container lid body 2, and then the members 66 and 68 are raised and removed from the container lid body 2. Next, the member 64 is raised and the member 62 is lowered, so that the members 62, 64 and 72 are also separated from the container lid body 2, and the container lid body 2 is taken out from the mold 52. Therefore, when molding the container lid main body 2 using the mold 52 as described above and then removing the container lid main body 2 from the mold 52, refer to FIGS. 2 and 3 together with FIG. 4. 64 of the upper mold assembly 56 relative to the container lid body 2, as understood by
is raised to a temperature below the melting point but still considerably high (e.g. 100
The outer circumferential surface of the member 64 interferes with the locking flap piece 32 of the container lid main body 2, which has a temperature of approximately C). Due to such interference, the locking flap piece 32
is from the state at the time of molding to the closing rotation direction 42 (second
and FIG. 3). After the container lid main body 2 is removed from the mold 52, the locking flap piece 32 is moved to the third position, which has been tilted somewhat in the closing rotation direction 42 from the state at the time of molding, as shown by the solid line in FIG. The state is as shown by the two-dot chain line 32A in the figure. In a preferred embodiment of the method of the invention, a seal liner forming step is performed after the container lid body forming step as described above. In this sealing liner forming step, which is carried out in a manner known per se, a molten liner material, which may be a suitable synthetic resin material, is applied to the inner surface of the top wall 4 of the container lid body 2, which is held in an inverted position. Then, a stamping tool is inserted into the container lid body 2 to stamp the liner material into the desired shape, thus forming the fifth liner material.
As shown in the figure, a sealing liner 78 is provided in the area defined by the inner surface of the top wall 4, more specifically, the annular protrusion 26 formed at the upper end of the inner surface of the skirt wall 6 and the inner surface of the top wall 4. It is formed. If desired, instead of stamping the sealing liner 78 on the inner surface of the top wall 4, a separately molded sealing liner of the desired shape can be inserted into the container lid body 2 and positioned on the inner surface of the top wall 4. You can also do it. Further, instead of molding the sealing liner 78 separately from the container lid body 2, a sealing protrusion of an appropriate shape may be integrally formed on the inner surface of the top wall 4 in the container lid body molding process. . In the method of the present invention, it is further important to carry out the step of forcibly tilting the locking flap piece after the step of forming the container lid body. This step of forcing the locking flap piece to tilt can be performed before, after, or simultaneously with the sealing liner forming step. Referring to FIGS. 2 and 3, in the forcible tilting step of the locking flap piece, each of the locking flap pieces 32 in the state shown by the two-dot chain line 32A in FIG. It is forcibly tilted in a direction opposite to direction 42, resulting in the state shown by the two-dot chain line 32B in FIGS. 2 and 3. Thus, the angle between the base 38 of each locking flap piece 32 and the inner surface of the pilfer-proof hem 18 when viewed in the opposite direction to the closing rotation direction 42 is smaller than the angle α ₁ during molding. is also forced to a small angle α ₂ . It is important that such angle α ₂ is smaller than 90 degrees, 5 degrees ≦ α ₂ ≦ 85 degrees, especially 20 degrees ≦ α ₂ ≦ 80
degree, in particular 30 degrees≦α ₂ ≦70 degrees. Further, the base portion 38 of each of the locking flap pieces 32
The angle between the end portion 40 and the closing rotation direction 42 is also made to be an angle β ₂ smaller than the angle β ₁ during molding. Such an angle β ₂ is such that 0 degrees < β ₂ ≦90 degrees, in particular 0 degrees < β ₂ ≦70 degrees, in particular 5 degrees ≦ β ₂
Preferably, the temperature is ≦45 degrees. Locking flap piece 32
Since the base edge 34 of the base portion 38 extends substantially parallel to the central axis of the container lid body 2, and therefore substantially vertically, the angle of inclination of the upper edge 44 and the lower edge 48 of the base portion 38 does not change. However, since the folding line 36 is inclined at an inclination angle γ and the angle between the base 38 and the tip 40 is reduced to an angle β ₂ , the upper edge 46 and the lower edge of the tip 40 The angle of inclination of the edge 50 is varied somewhat. Preferably, the upper edge 46 of the tip 40 extends substantially horizontally, and the inclination angle ε ₂ of the lower edge 50 of the tip 40 is preferably 20 degrees≦ε ₁ ≦50 degrees. Each time. In the method of the present invention, at least the pilfer-proof hem 18 and the locking flap piece 32 of the container lid body 2 are heated at a temperature that does not exceed the melting point (for example, if the container lid body 2 is made of polypropylene) In some cases, heat to a temperature of about 50 degrees C to 80 degrees C). Such heating can be conveniently achieved, for example, by moving the container lid body 2 through a heating furnace or by blowing hot air onto the container lid body 2. The forcible tilting step of the locking flap piece is preferably carried out by using a forcible tilting tool 80 shown in FIG. Referring to FIG. 6, the forced inclination tool 80 formed at the lower end of the support shaft 82 has a cylindrical upper part 84 and a truncated conical lower part 86.
has. And such upper part 84 and lower part 86
A plurality of blades 88 (four blades in the illustrated case) are formed at intervals in the circumferential direction on the outer peripheral surface of the blade 88 and project outward in the radial direction. Locking flap piece 3
2 in a direction opposite to the closing rotation direction 42, as shown in FIGS. 7 and 8, a forced tilting tool 80 is used to
Insert inside. Next, the forced tilting tool 80 is rotated in a direction opposite to the closing rotation direction 42 .
If desired, instead of or in addition to rotating the forced tilting tool 80, the container lid body 2 can be rotated in the closing rotation direction 42. In this way, the blade 88 is attached to the locking flap piece 32.
and is forced to tilt in the opposite direction to the closing rotation direction 42. The container lid main body 2 shown in FIGS. 1 to 3 is subjected to the sealing liner forming process and the locking flap piece forced tilting process, and thus is shown as a whole in FIG.
The container lid shown in is completed. The container lid 90 is applied to a container having a neck portion 92 as shown in FIG. The neck portion 92, which is known per se, has a cylindrical outer circumferential surface on which a male thread 94 and a locking jaw 96 located below the male thread 94 are formed. When closing the mouth and neck part 92 with the container lid 90, the container lid 90 is fitted onto the mouth and neck part 92, and the container lid 9 is closed.
0 in the closing rotation direction, that is, in the clockwise direction when viewed from above in FIG. In this way, the female thread 28 formed on the container lid 90 is screwed into the male thread 94 formed on the neck portion 92, thereby causing the container lid 90 to move downward as it rotates. When the container lid 90 is moved downward,
Locking flap piece 32 formed on the container lid 90
Each of the male threads 9 formed in the mouth and neck part 92
4, and further passes through the locking jaw 96. When passing through the locking jaw 96, each of the locking flap pieces 32 is interfered with by the locking jaw 96. is elastically deflected radially outward. When the female threads 28 of the container lid 90 are fully screwed into the male threads 94 of the neck portion 92, each of the locking flap pieces 32 completely passes through the locking jaws 96, as shown in FIG. As a result, the locking jaws 96 no longer interfere with each other, and each of the locking flap pieces 32 elastically returns to its original state. As will be clearly understood from the description of Examples and Comparative Examples to be mentioned later, in the container lid 90 manufactured according to the method of the present invention, the locking flap piece 32 is elastically bent and locked. The required downward rotational torque that must be applied to the container lid 90 when it is passed through the stop jaw 96 is substantially the same as that of conventional container lids and is sufficiently small. Therefore, the mouth and neck 92
When attaching container lid 90 to the container, excessive stress is created in weakened lines 14 and 24 and
and 24 are reliably prevented from being broken. When each of the locking flap pieces 32 is fully restored to its original state, each of the locking flap pieces 32 locks onto the underside of the locking jaw 96, as clearly shown in FIG. It will be done. Further, when the female thread 28 of the container lid 90 is fully screwed into the male thread 94 of the neck part 92, the sealing liner 78 seals the end surface of the neck part 92, as shown in FIG. The mouth and neck region 92 is thus sealed. The container lid 90 attached to the mouth and neck part 92 as described above is removed from the mouth and neck part 92, and the mouth and neck part 9
When opening 2, the container lid 90 is rotated in the opposite direction to the closing rotation direction at the time of attachment, that is, in the counterclockwise direction when viewed from above in FIG. In this way, the female thread 28 formed on the container lid 90
is moved along the male thread 94 formed in the neck portion 92, so that the container lid 90 does not move upward. However, the locking flap piece 32 formed on the inner surface of the pilfer-proof hem 18 of the container lid 90 is
6, upward movement of the pilfer-proof hem 18 is prevented. In this way, considerable stress is generated in the weakened line 14 formed in the container lid 90, and the bridge portion 22 at the weakened line 14 has a specific bridge portion 22A having a large circumferential width and increased strength. The weakened line 24 formed in the pilfer-proof hem 18 is also ruptured, and the weakened line 24 is ruptured, causing the pilfer-proof hem 18 to change from an endless ring shape to an edged band shape. It will be opened in In this way, the locking jaw portion 96
The locking flap piece 32 is released from the lower surface of the main portion 1, and thereafter the main portion 1
Pilfer-proof hem 18 connected to 6
The entire container lid 90 including the parts is rotated and moved upward, and thus the entire container lid 90 is separated from the neck part 92, and the neck part 92 is opened (the above-mentioned specific bridging part 22 in the weakened line 14).
A also has substantially the same strength as the other bridge parts 22,
When the weakened line 24 is not formed in the pilfer-proof hem 18, the weakened line 14 is completely broken and the pilfer-proof hem 18 is completely separated from the main portion 16, and the pilfer-proof hem 18 is completely separated. (The rest of the container lid 90 is removed from the mouth and neck part 92, leaving the remaining parts intact.) Therefore, as will be clearly understood from the description of Examples and Comparative Examples to be mentioned later, when removing the container lid 2 from the mouth and neck part 92, the method of the present invention is more effective than in the case of conventional container lids. Container lid 90 manufactured by
In this case, the locking flap piece 32 locks considerably firmly against the lower surface of the locking jaw 96. In other words, the required upward rotational torque that must be applied to the container lid 90 in order to elastically deflect the locking flap piece 32 from below to above the locking jaw 96 is reduced by the method of the present invention. Container lid 90 manufactured according to
The size of the lid is considerably increased compared to conventional container lids. Therefore, detachment of the container lid 90 from the mouth and neck portion 92 without the weakened lines 14 and 24 breaking as expected is reliably avoided, thus ensuring pilfer-proof properties. The reason why the required rotational torque is considerably increased in the container lid 90 manufactured according to the present invention is presumed to be as follows. That is, according to the method of the present invention, each of the locking flap pieces 32:
During molding, the two-dot chain line 32 is shown in Figures 2 and 3.
Rather than being molded into the state shown in B, at the time of molding, it is molded into the state shown in solid lines in FIGS. 2 and 3.
It is forcibly tilted to the state shown by the two-dot chain line 32B in the figure. Therefore, each of the locking flap pieces 32 retains a so-called memory characteristic that allows it to be restored to the state at the time of molding, that is, the state shown by solid lines in FIGS. It is presumed that the locking of each of the locking flap pieces 32 to the locking jaws 96 is strengthened. If desired, a gripping tab may be provided on the outer surface of the pilfer-proof hem 18, preferably adjacent the right side of the line of weakness 24, to remove the container lid 90 from the neck 92 and to open the neck 92. By pulling the gripping protrusion, the weakened line 24 is broken and the weakened line 14 is broken over its entirety, and then the container lid 90 is rotated counterclockwise when viewed from above in FIG. It can also be made to rotate. <Example> Using polypropylene (melt index 2.0, density 0.90), the container lid main body 2 shown in FIGS. Ten container lid bodies having substantially the same shape were molded by compression molding. Internal thread diameter d of the formed container lid body =
25.4 mm, upper outer diameter D = 30.0 mm, and total height H = 19.0 mm. In each of the locking flap pieces 32 formed on the inner surface of the pilfer-proof hem 18, the thickness t=0.35 mm, the length l ₁ of the lower edge 48 of the base 38 = 1.9 mm, and the length l 1 of the lower edge 48 of the base 38 is 1.9 mm. Length of the lower edge 50 l ₂ =
2.0 mm, angle when forming α ₁ = 70 degrees, angle when forming β ₁ = 80 degrees, angle γ = 30 degrees, tilt angle δ
= 20 degrees, inclination angle ε ₁ during molding = 30 degrees, the upper edge 44 of the base 38 is an arc with a radius of 0.5 mm, the tip 40
The upper edge was approximately horizontal. Next, the entire container lid body is heated to approximately 70 degrees Celsius by moving it through a heating furnace, and then the locking flap piece is removed by the method described with reference to FIGS. 6 to 8. 32 is forcibly tilted, and the angle α ₂ = 50
degree, the angle β ₂ =10 degrees, and the inclination angle ε ₂ =45 degrees. Such a container lid main body was attached to the mouth and neck part 92 of a glass container having a nominal diameter of 28 mm in the form shown in FIG. 9, and the required rotational torque at this time, that is, the required downward rotational torque was measured. In addition, the mouth and neck 92
The container lid body attached to the container was forcibly removed from the mouth and neck part 92, and the required rotational torque at this time, that is, the required upward rotational torque was measured. The results were as shown in Table 1 below. <Comparative example> For comparison, angle α ₁ = 50 degrees during molding,
A container lid similar to the example, except that the angle β ₁ during molding is 10 degrees, and the tilt angle ε ₁ = 45 degrees during molding (therefore, the state is the same as the state after the forced tilting operation in the example). Ten bodies were molded by compression molding. Then, the required downward rotational torque and the required upward rotational torque of the container lid body were measured in the same manner as in the example. The results were as shown in Table 1 below. 【table】

[Brief explanation of drawings]

FIG. 1 is a side view, partially in cross section, of a specific example of a molded container lid body. 2 is a partial perspective view showing a locking flap piece in the container lid body of FIG. 1; FIG. 3 is a partial bottom view showing the locking flap piece of the container lid body of FIG. 1; FIG. FIG. 4 is a partial sectional view showing a specific example of a mold used for compression molding the container lid body shown in FIG. 1. Figure 5 shows
FIG. 2 is a side view, partially in cross section, of a container lid completed by subjecting the container lid body of FIG. 1 to a sealing liner forming process and a locking flap piece forced tilting process; Figure 6 shows
FIG. 3 is a side view showing a specific example of a forced inclination tool used in the locking flap piece forced inclination process. Figure 7 shows the first
FIG. 7 is a side view, partially in cross section, of the forced tilting tool of FIG. 6 inserted into the container lid body of the figure; FIG. 8 is a sectional view taken along the line - in FIG. 7. FIG. 9 is a side view, partially in section, showing a state in which the container lid of FIG. 5 is attached to the mouth and neck of the container to close the mouth and neck. 2... Container lid main body, 4... Top wall, 6... Skirt wall, 14... Weakening line, 16... Main part of skirt wall, 18... Pilfer-proof hem, 2
8... Female thread, 32... Locking flap piece, 36...
...Folding line in the locking flap piece, 38...Base of the locking flap piece, 40...Tip of the locking flap piece, 52...Mold, 80...Forced tilting tool,
88... Feather, 90... Container lid, 92... Container neck and neck, 94... Male thread, 96... Locking jaw.

Claims (1)

[Scope of Claims] 1. A composition having pilfer-proof properties for a container having a neck portion in which a male thread and a locking jaw portion located below the male thread are formed on the outer peripheral surface. A method for manufacturing a resin container lid; comprising a top wall and a cylindrical skirt wall hanging down from the periphery of the top wall, the inner surface of a pilfer-proof hem defined at the bottom of the skirt wall; A plurality of locking flap pieces projecting radially inwardly are formed, and at least a base of each of the locking flap pieces is positioned at the neck of the container lid against an inner surface of the pilfer-proof hem. a container lid body molding step of molding a container lid body extending from a synthetic resin material at an angle α ₁ when viewed in the opposite direction to the closing rotation direction of the container lid when the container lid is attached; After the forming process, at least the pilfer-proof hem and the locking flap pieces of the container body are heated to a temperature that does not exceed the melting point, and each of the locking flap pieces is heated in a direction opposite to the closing rotation direction. The angle α, which is mechanically forced to tilt, and thus the angle that the base of each of the locking flap pieces makes with the inner surface of the pilfer-proof hem, viewed in a direction opposite to the direction of closing rotation, is defined as the angle α. A method characterized in that it comprises the step of: forcibly tilting the locking flap piece to reduce the angle α to ₂ which is less than ₁ . 2. The angle α ₁ is 30 degrees≦α ₁ ≦135 degrees, and the angle α ₂ is 5 degrees≦α ₂ ≦85 degrees.
The method described in section. 3 The angle α ₁ is 45 degrees≦α ₁ ≦120 degrees, and the angle α ₂ is 20 degrees≦α ₂ ≦80 degrees.
The method described in section. 4. The method of claim 3, wherein the angle α ₁ is 60 degrees≦α ₁ ≦100 degrees and the angle α ₂ is 30 degrees≦α ₂ 70 degrees. 5. In the container lid body formed in the container lid body molding step, each of the locking flap pieces has a base extending at the angle α ₁ with respect to the inner surface of the pilfer-proof hem, and and a tip extending obliquely at an angle β ₁ in the closing rotation direction, and in the forced tilting step of the locking flap piece, the angle β ₁ is reduced to an angle β ₂ . The method according to any one of items 1 to 5. 6. Claim 5, wherein the angle β ₁ is 5 degrees≦β ₁ ≦150 degrees, and the angle β ₂ is 0 degrees<β ₂ ≦90 degrees.
The method described in section. 7. The angle β ₁ is 10 degrees≦β ₁ ≦120 degrees, and the angle β ₂ is 0 degrees<β ₂ ≦70 degrees.
The method described in section. 8 The angle β ₁ is 30 degrees≦β ₁ ≦90 degrees, and the angle β ₂
8. The method according to claim 7, wherein 5 degrees≦β ₂ ≦45 degrees. 9. The folding line between the base and the tip of each of the locking flap pieces extends downwardly away from the inner surface of the pilfer-proof hem at an angle γ.
9. A method according to any one of claims 1 to 8, wherein the method extends obliquely. 10. The method according to claim 9, wherein the angle γ is 5 degrees≦γ≦80 degrees. 11. The method according to claim 10, wherein the angle γ is 20 degrees≦γ≦60 degrees. 12. The method of claim 11, wherein the angle γ is 20 degrees≦γ≦50 degrees. 13. In the locking flap piece forced tilting step, a forced tilting step in which a plurality of blades projecting outward in the radial direction are arranged at intervals in the circumferential direction is inserted into the container lid body, and causing a forced tilting step to rotate relative to the container lid body in a direction opposite to the closing rotational direction, thus mechanically forcing the locking flap by the vane in a direction opposite to the closing rotational direction; The method according to any one of claims 1 to 12, wherein the mouth and neck are tilted.