JPH11115953A - Synthetic resin cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably mount a cap so that contents may not leak outside and to allow the cap to be easily separated manually from a container opening at the time of opening by placing a plurality of weakened lines comprising two stages of thin parts at a distance in a circumferential direction of a skirt wall. SOLUTION: A circular seal protrusion 8 extending downward is formed on an internal face of a top wall 4 of the synthetic resin cap 2, a locking protrusion 10 is formed on an inner peripheral face of a skirt wall 6, and a tab 12 protruding outward is formed at a lower opening end of the skirt wall 6. Further, a plurality of weakened lines (a to j) are formed at a distance in a circumferential direction on the skirt wall 6. At least two of the weakened lines 20 are placed on a region X toward the tab at 180 deg. on the skirt wall 6 and at least one is placed in a region Y opposite to the tab at 180 deg., wherein each weakened line 2.0 comprises a first thin part 22 and a second thin part 24. Thus at least a part of the weakened lines is broken at the time of opening a cap, thereby easily separating the cap from a bottle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cap made of synthetic resin which is applied to a glass or synthetic resin container containing contents such as a liquid without pressurizing or depressurizing the inside of the container, especially milk. The present invention relates to a cap made of a synthetic resin applied to a milk bottle containing therein.

[0002]

2. Description of the Related Art As a conventional example of a synthetic resin cap applied to a container containing contents such as a liquid, for example,
The one disclosed in Japanese Utility Model Publication No. 47-13109 can be mentioned. The synthetic resin cap disclosed in the above publication includes a top wall and a skirt wall extending downward from the periphery of the top wall. At the center of the top wall, an inner plug (recess) projecting downward is formed. The inner plug portion includes an annular side wall hanging down from the center of the top wall and a bottom wall closing the lower end of the side wall, and the upper surface of the side wall and the inner peripheral surface of the bottom wall form part of the upper surface of the top wall. The outer peripheral surface of the side wall of the inner plug formed as described above forms an annular seal ridge (inner seal) fitted to the inner peripheral surface of the container opening. Locking ridges (thick ridges and thick ridges) are formed on the inner peripheral surface of the skirt wall to be locked by an annular locked jaw formed on the outer peripheral surface of the container opening. ing. On the outer peripheral surface at the open end of the skirt wall, a knob portion protruding radially outward is formed over a part of the circumferential direction. Breakable thin grooves are formed on both side edges of the skirt wall in the circumferential direction of the knob. In the cap, the outer peripheral surface of the seal ridge is fitted to the inner peripheral surface of the container opening, and the locking ridge is locked to the locked jaw formed on the outer peripheral surface of the container opening by stoppering. , Attached to the container opening. When the knob is opened, the skirt wall is broken along the thin groove by pulling the knob away from the container opening, and the cap is detached from the container opening.

[0003]

However, when the conventional synthetic resin cap constructed as described above is applied to a milk bottle as a container, the following problems exist. That is, milk is generally filled in a milk bottle while being cooled to 5 ° C. Then, the opening of the milk bottle filled with milk is closed by closing the cap. Such milk bottles have an external temperature in summer, for example 40
When the milk bottle is exposed to the temperature, the internal pressure of the milk bottle is increased, whereby the cap is lifted and the sealing function of the sealing ridge is reduced. When the sealing function of the sealing ridge is reduced, problems such as milk seeping out from the opening of the milk bottle to wet the opening or completely leaking out from the opening occur. In order to solve this problem, if the degree of fitting of the seal ridge is excessively increased, the sealing function is improved, but opening the plug becomes extremely difficult.

[0004] In the case of milk, in particular, consumers are often weak children or sick people, so that the difficulty of opening the bottle must be avoided. Therefore, when the above-mentioned conventional synthetic resin cap is applied to a milk bottle, opening of the cap is restricted by restricting the degree of fitting of the sealing ridge within a range in which the sealing property (sealing state) is sufficiently ensured. In order to prevent the difficulty, it is possible to sufficiently counter the rise in the internal pressure of the milk bottle by the locking force of the locking projection on the inner peripheral surface of the skirt wall against the locked jaw of the outer peripheral surface of the milk bottle opening. At least, it is necessary to surely prevent the seepage or leakage of milk as described above.

Accordingly, it is an object of the present invention to securely attach the container to the container opening so as to prevent the contents from leaking to the outside, and to easily mount the container from the container opening when the container is manually opened. An object of the present invention is to provide a novel synthetic resin cap which can be detached.

Another object of the present invention is to provide a novel synthetic resin cap which has a simple structure, is easy to mold, and can be mass-produced at low cost.

Other objects and features of the present invention will become apparent from the following description of embodiments of a synthetic resin cap constructed in accordance with the present invention, with reference to the accompanying drawings.

[0008]

According to one aspect of the present invention, there is provided a top wall, and a skirt wall extending downward from a periphery of the top wall, and a downwardly extending container opening is formed on an inner surface of the top wall. An annular seal ridge is formed on the inner peripheral surface of the container, and is engaged with a locked jaw formed on the outer peripheral surface of the container opening on the inner peripheral surface of the skirt wall. A synthetic resin cap formed with a stop ridge and having a tab projecting radially outward on an outer peripheral surface at an open end of the skirt wall over a partial area in the circumferential direction. A plurality of circumferentially spaced weakening lines are formed extending from the open end toward the top wall and the tab is substantially centered circumferentially when the skirt wall is viewed axially. 180 ° tab side area X of skirt wall
And the other 180 ° anti-tab side area Y of the skirt wall, at least two weakening lines are provided in the tab side area X, and at least two weakening lines are provided in the anti-tab side area Y. One of the weakening lines is provided, and each of the weakening lines is formed of a thin portion, and the thin portion is formed in an upper region near the top wall and has a relatively thick first thin portion having a residual thickness and the opening end. And a second thin portion formed in a lower region closer to the first thin portion and having a smaller remaining thickness than the first thin portion.

In the above cap according to the present invention, each of the weakening lines formed on the skirt wall is formed of a thin portion, and the thin portion is formed in the upper region near the top wall and has a relatively thick residual wall thickness. It is composed of one thin portion and a second thin portion formed in a lower region near the opening end and having a thinner residual thickness than the first thin portion, particularly due to the presence of the first thin portion. Then, the weakening line can be easily and reliably plugged into the container opening without breaking,
After stoppering, a predetermined locking force (holding force) of the locking ridge against the locked jaw formed on the outer peripheral surface of the container opening is secured, so that the locking ridge is firmly attached and the internal pressure rises. The cap is reliably prevented from lifting, and the sealing function of the sealing ridge on the inner peripheral surface of the container opening is sufficiently ensured. As a result, seepage or leakage of the liquid from the container opening is sufficiently and reliably prevented. Further, as described above, at least two weakening lines composed of thin portions are provided in the tab side area X and at least one weakening line is provided in the opposite tab side area Y. When a force is applied (lifted) in a direction away from the container opening, at least a part of the weakened line of the tab-side region X is first broken, and when a further force is applied (lifted), the anti-tab-side region is broken. Due to the presence of the weakening line of Y,
The cap is easily separated from the bottle, and the cap is easily detached from the container opening. In particular, when the above-described force is applied to the tab due to the presence of the second thin portion, the weakening line is easily broken from the lower end on the opening end side, so that the opening is easily performed. As a result, without excessively increasing the degree of fitting of the sealing ridge to the inner peripheral surface of the container opening, it is possible to limit the sealing property to a range in which the sealing property is sufficiently ensured. Easy to carry out. Furthermore, the structure as a whole is simple, molding (integral molding by injection molding or compression molding) is easy, and mass production can be performed at low cost. As can be easily understood from the above description, the cap according to the present invention can be suitably used particularly for a milk bottle containing milk.

[0010] According to another aspect of the present invention, there is provided a top wall, and a skirt wall extending downward from the periphery of the top wall, and the inner surface of the top wall extends downward and has an inner peripheral surface of the container opening. Is formed on the inner peripheral surface of the skirt wall, and a locking ridge is formed on an inner peripheral surface of the skirt wall to be engaged with a locked jaw formed on an outer peripheral surface of the container opening. In the synthetic resin cap, a tab protruding radially outward is formed on an outer peripheral surface at an open end of the skirt wall over a partial area in the circumferential direction. A plurality of weakening lines extending from the open end toward the top wall, wherein the skirt wall is viewed axially and the tabs are substantially 180 ° of the circumferentially centered skirt wall. Tab area X of the skirt wall and another 180 ° When divided into the tab side area Y, at least two weakening lines are provided in the tab side area X, and at least one weakening line is provided in the opposite tab side area Y. The weakening line disposed in the upper region near the top wall is formed in a first thin portion having a relatively thick residual wall thickness and the first thin portion formed in a lower region near the opening end. A plurality of thin portions composed of a second thin portion having a smaller residual thickness than the thin portion, and at most three slits, and the weakening portion disposed in the anti-tab side region Y. A synthetic resin cap is provided, wherein the line is made of the thin portion.

In the above-mentioned cap according to the present invention, substantially the same operation and effect as those of the first-mentioned cap according to the present invention are achieved, but the tab side region X in the above-mentioned cap is obtained.
Since the weakening line includes at most three (one or two or three) slits in addition to a plurality of thin portions, it is easier to open than the cap according to the present invention described first. Will be performed. It should be noted that forming four or more slits is not desirable because the sealing function is reduced, as will be easily understood from the following description.

[0012] According to still another aspect of the present invention, there is provided a top wall, and a skirt wall extending downward from the periphery of the top wall, and the inner surface of the top wall extends downward and has an inner periphery of the container opening. An annular seal ridge is formed on the inner surface of the skirt wall, and a locking ridge locked on a locked jaw formed on the outer peripheral surface of the container opening is formed on the inner peripheral surface of the skirt wall. A synthetic resin cap formed on the outer peripheral surface at the open end of the skirt wall and having a radially outwardly projecting tab formed over a partial area in the circumferential direction. A plurality of weakening lines are formed extending from the open end toward the top wall at an angle, and the skirt wall is viewed axially and the tab is positioned substantially centrally in the circumferential direction. ° tab side area X and another 180 ° of the skirt wall. When divided into the non-tab side area Y,
At least two weakening lines are provided in the tab side region X, and at least one weakening line is provided in the opposite tab side region Y, and the weakening line provided in the tab side region X is A first thin portion having a relatively large residual thickness formed in an upper region near the top wall and a second thin portion having a smaller residual thickness than the first thin portion formed in a lower region near the opening end. A plurality of thin portions composed of two thin portions; a first thin portion formed in the upper region near the top wall; and a slit formed in the lower region near the opening end. Characterized in that the weakening line disposed in the anti-tab side area Y is formed of the thin portion. ,
Is provided.

[0013] In the above cap according to the present invention, substantially the same operation and effect as those of the cap according to the first aspect of the invention are achieved, but the weakening line of the tab side region X in the cap is formed by a plurality of thin portions. In addition, since at most three (one or two or three) thin-wall / slit combination means are included, opening is easier than in the cap according to the invention described first. Further, as compared with the cap according to the second aspect of the present invention (including at most three slits), the above-mentioned locking force with respect to the container opening is smaller due to the thin portion / slit combination means including the thin portion. Somewhat superior. It is not desirable to form four or more thin-walled / slit combination means, as in the case of the slit described above, since the sealing function is reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a synthetic resin cap constructed according to the present invention will be described below in more detail with reference to the accompanying drawings. The embodiment described below is a synthetic resin cap applied to, but not limited to, a milk bottle as a container. 1 to 5
Referring to FIG. 1, the synthetic resin cap generally designated by reference numeral 2 includes a top wall 4 having a substantially disk shape, and a skirt wall 6 extending downward from the periphery of the top wall 4. An annular seal ridge (inner ring) 8 extending downward is formed on the inner surface of the top wall 4. The outer peripheral surface of the seal ridge 8 is detachably fitted to the inner peripheral surface 102 of the opening of the milk bottle 100 shown in FIGS. A locking ridge 10 is formed on the inner peripheral surface of the skirt wall 6. Locking ridge 10
Is detachably locked to a locked jaw 104 (see FIGS. 7 and 8) formed on the outer peripheral surface of the opening of the milk bottle 100. A lower surface of the top wall 4 and a radially outward position of the sealing ridge 8; and a corner portion 11 having a curved cross section where the lower surface of the top wall 4 and the inner peripheral surface of the skirt wall 6 are connected. Has annular ribs 4a and 4b, respectively. A tab 12 protruding radially outward is formed on the outer peripheral surface of the open end of the skirt wall 6 over a part of the circumferential direction.

The skirt wall 6 is formed with a plurality of weakening lines 20 (a to j) extending from the open ends toward the top wall 4 at intervals in the circumferential direction. Looking at the skirt wall 6 in the axial direction of the cap 2, the 180 ° tab side region X of the skirt wall 6 where the tab 12 is located substantially at the center in the circumferential direction, and the other 180 ° anti-tab side of the skirt wall 6. When divided into the region Y, it is important that at least two weakening lines 20 are provided in the tab side region X and at least one weakening line 20 is provided in the non-tab side region Y. In this embodiment, a total of ten weakening lines 20 are provided. That is, five (20a to 20a)
20e) are arranged, and five (20)
f to 20j). One of the weakening lines 20a arranged in the tab side area X is arranged at a circumferential central position in a part of the circumferential direction where the tab 12 is formed. Further, one of the weakening lines 20j arranged in the non-tab side area Y is opposite to the tub 12 in the diametrical direction (in this embodiment, the weakening line 20).
a substantially on the opposite side in the diametrical direction). A plurality of ribs 14 extending in the axial direction at intervals in the circumferential direction are formed in the outer peripheral surface of the skirt wall 6 where the weakening line 20 does not exist. In FIG. 3, reference numeral L1 denotes a line that separates the tab side region X and the opposite tab side region Y (a line passing through the axis of the cap 2), and reference numeral L2 denotes a line passing through the axis of the cap 2 and orthogonal to the line L1. . As is clear from the above description, the weakened lines 20a and 20j are located on the line L2.

Each of the weakening lines 20 (a to j) is composed of a thin portion. As shown in FIG. 5, the thin portion includes a first thin portion 22 having a relatively thick residual thickness and formed in an upper region S1 of the skirt wall 6 near the top wall 4, and a portion near the opening end. And a second thin portion 24 having a smaller remaining thickness than the first thin portion 22 formed in the lower region S2. Each of the weakening lines 20 (a to j) formed of a thin portion includes a groove 26 formed to extend linearly over the entire outer circumferential surface of the skirt wall 6 in the axial direction. The groove 26 has a predetermined circumferential width and depth. That is, in this embodiment, the groove 26 extending in the axial direction is formed on the outer peripheral surface of the skirt wall 6.
Forming a weakening line 20 that is thinner than the thickness of the skirt wall 6. The first thin portion 22 is formed to be thinner than the thickness of the skirt wall 6 by the depth of the groove 26. The radially outer surfaces of the first thin portion 22 and the second thin portion 24 are on the same plane (on the bottom surface of the groove 26), and the inner peripheral surface of the first thin portion 22 (of course, locking) Since the inner peripheral surface excluding the ridge 10 is on the same plane as the corresponding inner peripheral surface of the skirt wall 6 (on the same inner peripheral surface), the radially inner surface of the second thin portion 24 is The first thin portion 22 is positioned radially outward from a radially inner surface of the first thin portion 22. The lower end inner peripheral surface 24a of the second thin portion 24 below the locking ridge 10 and the lower end inner peripheral surface 24a on the opening end side (of course, the inner peripheral surface excluding the locking ridge 10) is It is positioned on the same plane (on the same inner peripheral surface) as the corresponding inner peripheral surface of the lower end. Therefore, the second thin portion 2 of the skirt wall 6
The inner diameter of the inner peripheral surface 24a at the lower end where 4 is located is larger than the inner diameter of the inner peripheral surface of the skirt wall 6 where the first thin portion 22 exists.

The locking ridge 10 is connected to a weakening line 20 (a
To j) are substantially separated into a plurality in the circumferential direction at each formation site. As shown in FIG. 2, each circumferential end of each of the locking projections 10 separated from each other has a curved shape, not a linear shape extending at least in the axial direction when viewed in the radial direction from the axis. No. The locking ridge 10 has a substantially parabolic mountain shape in the axial direction cross section with respect to the inner peripheral surface of the skirt wall 6. The first thin portion 22 includes:
It is important that the lower end extends at least down to the axial area where the locking ridge 10 is present, but in an embodiment the axial position 10a corresponding to the radial top of the locking ridge 10 Extending downward to a position beyond.

The cap 2 constructed as described above has a simple structure as a whole, and is injection-molded or compression-molded from an appropriate synthetic resin, for example, low-density polyethylene (LDPE) (in practice, injection molding is preferable). Thus, it can be easily formed integrally. Therefore, it can be mass-produced at low cost. Then, the cap 2 configured as described above is stoppered as shown in FIGS. 7 and 8.
The outer peripheral surface of the seal ridge 8 is removably fitted to the inner peripheral surface 102 of the opening of the milk bottle 100, and the locking ridge 10 is detached from the locked jaw 104 formed on the outer peripheral surface of the opening. By being freely locked, it is attached to the opening of the milk bottle 100.

The weakening line 20 (a to
Each of j) is the first thin portion 2 formed in the upper region S1.
2 and the second thin portion 24 formed in the lower region S2 near the opening end. In particular, the presence of the first thin portion 22 in the upper region S1 facilitates the weakening line 20 without breaking. And the plug can be reliably plugged into the opening. Further, due to the presence of the first thin portion 22,
After stoppering, a predetermined locking force (holding force) of the locking ridge 10 with respect to the locked jaw 104 formed on the outer peripheral surface of the opening is secured, so that the locking ridge 10 is firmly attached and the internal pressure is reduced. Lifting of the cap 2 due to the rise is reliably prevented, and the sealing function of the sealing ridge 8 with respect to the inner peripheral surface 102 of the opening is sufficiently ensured. As a result, milk bottle 10
Occurrence of milk seepage or leakage from the opening 0 is sufficiently and reliably prevented.

As described above, five weakening lines 20 each having a thin portion are provided in the tab side area X and five in the opposite tab side area Y. When a force is applied to the tab 12 in a direction away from the opening, at least one of the weakening lines 20a to 20e in the tab side region X is first broken (particularly, the weakening lines 20d and 20e apply a large load). (There is a strong tendency to be broken first upon receipt), so that the cap 2 is easily detached from the opening. In particular, when the above-described force is applied to the tab 12 due to the presence of the second thin portion 24 in the lower region S2, the weakened line 20 is easily broken from the lower end on the opening end side (the initial opening of the tab). The opening is easily performed because the rupture is easy). As a result, without excessively strengthening the degree of fitting of the opening of the seal ridge 8 to the inner peripheral surface 102, the seal ridge 8 can be limited to a range where the sealing property is sufficiently ensured. But it can be done easily. It is important that at least two weakening lines 20 are provided in the tab side area X and at least one weakening line 20 is provided in the opposite tab side area Y. This is the first tab 12
Is lifted, the weakening line 2 existing in the tab side area X
This is because if at least a part of the “0” is broken and the tab 12 is further lifted, the cap 2 is easily separated from the bottle by the presence of the weakening line 20 in the non-tab side area Y.

In the cap 2, the first thin portion 2
Preferably, the lower end 2 extends downward at least to the axial region where the locking ridge 10 is present, but the lower end thereof corresponds to at least the axial position 10 a corresponding to the radial top of the locking ridge 10. More preferably, it extends downward to a position beyond (see FIG. 5). Since the lower end of the first thin portion 22 extends downward to the axial region where the locking ridge 10 exists, the locking force of the locking ridge 10 on the locked jaw 104 is increased, Sufficient holding force (maintaining sealing properties) is secured against an increase in internal pressure in milk bottle 100. Therefore, when the lower end of the first thin portion 22 extends downward to a position beyond the axial position 10a corresponding to the radial top of the locking ridge 10, the holding force is further increased.

In the cap 2, it is preferable that the locking ridge 10 is not provided in at least a part of the tab-side region X in the circumferential direction where the tab 12 is formed. In the above-described embodiment, as shown in FIG. 3, the skirt wall 6 is configured such that the locking ridge 10 does not exist in a region other than both ends in a part of the circumferential direction where the tab 12 is formed. ing. With such a configuration, the portion of the tub 12 having relatively high rigidity at the beginning of opening is easily lifted, and opening is facilitated. Furthermore, skirt wall 6
Since the strength in the entire circumferential direction is balanced, detachment from the mold described later is also smoothly performed. One of the weakened lines 20a in the tab side area X is the tab 12
Is formed at a circumferential center position (a region where the locking ridge 10 does not exist) in a part of the circumferential region where the ridges are formed, so that the above-described operation and effect can be more reliably obtained. Furthermore, one of the weakening lines 20j disposed in the non-tab side region Y is substantially diametrically opposite to the circumferential center position of the tub 12 (in this embodiment, the weakening line 2).
0a). With this configuration, the tab 12 is raised in the early stage of opening, and in a state where one or more of the weakening lines in the tab-side region X are broken, the circumferential direction with respect to the weakening line 20j in the anti-tab-side region Y. Because the load tends to expand
The weakening line 20j is elastically extended, so that opening is significantly facilitated. Also, at least two weakening lines 20h located at equal intervals on both sides in the circumferential direction of the weakening line 20j.
And 20i (four weakening lines 20 in this embodiment)
h, 20f, 20i and 20g), the elastic deformation on the side opposite to the tab side region Y at the time of opening is performed in a well-balanced manner, and opening becomes easier.

In the cap 2, the first thin portion 2
Preferably, 2 has a thickness of 0.35 mm to 0.6 mm, and the second thin portion 24 has a thickness of 0.15 mm to 0.3 mm. If the first thin portion 22 is excessively thick, it becomes extremely difficult to open the plug. If the first thin portion 22 is excessively thin, the above-mentioned locking force is reduced and a desired sealing function cannot be obtained. The first thin portion 22 has a thickness of 0.6 mm or less, particularly 0.35 mm or more.
When the thickness is 0.6 mm, a desired sealing function can be obtained and the plug can be easily opened. If the second thin portion 24 is excessively thick, the opening becomes extremely difficult. If the second thin portion 24 is excessively thin, the possibility of breaking at the time of tapping increases. The second thin portion 24 has a thickness of 0.3 mm or less, particularly 0.15 mm to
When the thickness is 0.3 mm, opening can be easily performed and breakage at the time of tapping can be prevented.

In the cap 2, the lower surface of the top wall 4, which is located radially outward of the seal ridge 8, and the top wall 4
Are connected to the inner peripheral surface of the skirt wall 6 and the corner portion 11 having a curved cross section is provided with an annular rib 4
a and 4b are formed. As shown in FIGS. 7 and 8, with the cap 2 attached to the opening of the milk bottle 100 as described above, the rib 4a is brought into close contact with the upper end surface of the opening, and the rib 4b is a cross section of the opening. Is brought into close contact with the surface of the peripheral portion that forms a curved surface. In this state, the milk bottle 100 is stored in the refrigerator, and when the temperature of the milk drops to a temperature lower than the filling temperature of 5 ° C., for example, 4 ° C., the inside of the milk bottle 100 becomes negative pressure and tries to suck the outside air. However, the ribs 4a and 4b are more strongly adhered to the surface of the opening to improve the sealing function, and the suction of the outside air is reliably prevented.

The cap 2 has a simple structure as a whole, is easy to mold (integral molding by injection molding or compression molding), and can be mass-produced at low cost. Referring to FIG. 6, which schematically shows the relationship between the molding die and the molded cap 2, a first male mold 30 is positioned coaxially with the axis of the cap 2 not shown. First Male 3
A second male mold 32 is positioned on the outer side in the radial direction of “0” so as to be relatively movable. A stripper 34 is positioned at a position radially outward and axially below the second male mold 32 so as to be relatively movable with respect to the second male mold 32. A female mold 36 is positioned at the upper end of the stripper 34. The female mold 36 has its lower end positioned at the upper end of the stripper 34, and radially outside the second male mold 32 and above each of the second male mold 32 and the first male mold 30.
Each is positioned with a predetermined gap (space). As can be easily understood from FIG. 6, the first male mold 30 and the second male mold 3 positioned at the molding positions as described above.
2. The surface shape of the stripper 34 and the female mold 36 facing each other with a gap therebetween is formed so that the cap 2 can be molded. In FIG. 6, an axis (not shown) of the cap 2 is positioned so as to extend in the vertical direction. However, in practical use, generally, the axis of the cap 2 is positioned so as to extend substantially in the horizontal direction. Molded.

After the integral molding of the cap 2 by injection molding or compression molding using the molding die as described above, the die is removed in the following order. That is, first, the female mold 36 is moved upward in FIG. 6 and is detached above the cap 2. Next, the first male mold 30 is moved downward in FIG. 6 while relatively moving with respect to the second male mold 32, and is detached below the cap 2. Next, the second male mold 32 is moved relative to each other at the bottom of FIG. 6 and the stripper 34 is moved at the top of FIG. The cap 2 is formed with a seal ridge 8 having a shape such that a part thereof projects radially outward and a locking ridge 10 having a shape such that a part thereof projects radially inward. Therefore, the so-called forcing is performed. Already the first male 3
0 is not present at the molding position, the sealing ridge 8 is elastically deformed inward in the radial direction, thereby forcibly removing the sealing ridge 8. Further, since the female die 36 is not present at the molding position, the locking ridge 10 is formed. The skirt wall 6 is elastically deformed so as to bulge outward in the radial direction, thereby forcibly removing the skirt wall 6.

In the cap 2, a plurality of ribs 14 extending in the axial direction are formed on the outer peripheral surface of the skirt wall 6 at intervals in the circumferential direction, and the skirt wall 6 is reinforced by each of the ribs 14. Is done. For this reason, when performing the above-described forcible removal, the skirt wall 6
Is slightly reduced, and the reduced amount of the swelling is absorbed by the elastic deformation of the locking ridge 10 itself. As a result, breakage of the weakening line 20 during forcible removal is reliably avoided.

In the cap 2, the weakened lines 20 (a to j) each formed of a thin portion include a groove 26 formed so as to extend linearly over the entire outer peripheral surface of the skirt wall 6 in the axial direction. The lower end inner peripheral surface 24a of the thin portion 24 of the skirt wall 6 at a position below the locking ridge 10 and on the open end side of the skirt wall 6 is positioned on the same plane as the corresponding lower end inner peripheral surface of the skirt wall 6. ing. Due to this configuration, the outer peripheral surface of the second male mold 32 from which the forcible removal is performed, which is lower than the portion corresponding to the inner peripheral surface 24a of the lower end portion of the skirt wall 6, can have a circular shape. 2
The inner peripheral surface of the fitting hole of the stripper 34 into which the outer peripheral surface of the male mold 32 is relatively movably fitted can also be circular. As a result, the configuration of the mold is significantly simplified.
This makes it easier to position the male mold 32 and the stripper 34, reduces the wear between the second male mold 32 and the stripper 34, and reduces the molding cost of the cap 2. . As a result, the productivity of the cap 2 is improved, and the molding cost of the cap 2 is significantly reduced.

In the cap 2, a thin portion is formed in the upper region S1 and a first thin portion 22 having a relatively large remaining thickness and a first thin portion 22 formed in the lower region S2. Formability is improved due to the configuration including the second thin portion 24 having a smaller remaining thickness. That is, when the thin portion is constituted only by the second thin portion 24, the flowability of the synthetic resin in the gap of the mold corresponding to the second thin portion 24 of the skirt wall 6 during molding is It is significantly worse than the gap in the mold corresponding to the other part of the skirt wall 6. This is because the gap of the mold corresponding to the second thin portion 24 is considerably narrower than the gap of the mold corresponding to the other part of the skirt wall 6, so that at the time of molding, the synthetic resin first flows into the wide gap, This is because there is a tendency to flow into the next narrow gap. Specifically, in general, in the case of injection molding, the synthetic resin is injected into the gap from a portion corresponding to the axis of the top wall 4 of the cap 2. The injected synthetic resin is first removed from the gap corresponding to the top wall 4 by the second thin portion 2 of the skirt wall 6.
After flowing into the wide gap corresponding to the portion other than the portion 4 and reaching the portion corresponding to the opening end, then, there is a strong tendency to flow into the narrow gap corresponding to the second thin portion 24 from the gap on the opening end side. . At this time, the synthetic resin passes through a gap corresponding to the top wall 4,
It hardly flows directly into the narrow gap corresponding to the second thin portion 24. For this reason, the synthetic resin may not be completely filled in the upper part of the narrow gap corresponding to the second thin part 24, and a part lacking in the upper part of the second thin part 24 of the molded cap 2 may be generated. Become.

On the other hand, the cap 2 according to the present invention
In the above, since the thin portion is composed of the first thin portion 22 and the second thin portion 24, the synthetic resin is completely and reliably filled in the entire gap corresponding to the thin portion, and the moldability is improved. Therefore, the problem that a portion missing at the upper portion of the second thin portion 24 of the formed cap 2 is reliably prevented. To explain the reason specifically,
As described above, the synthetic resin injected into the gap corresponding to the top wall 4 is first removed from the gap corresponding to the top wall 4 except for the first thin portion 22 and the second thin portion 24 of the skirt wall 6. After flowing into the wide gap corresponding to the portion of the opening portion and reaching the portion corresponding to the opening end, then, from the gap on the opening end side, flows into the narrow gap corresponding to the second thin portion 24. This is because the length of the gap corresponding to the thin portion 24 is shorter than in the related art, so that the gap can be filled relatively easily. Furthermore, part of the synthetic resin injected into the gap corresponding to the top wall 4
This is because it is presumed that the gas flows into the gap corresponding to the first thin portion 22 which is wider than the gap corresponding to the second thin portion 24.

Next, referring mainly to FIGS. 9 and 10,
Another embodiment of the synthetic resin cap configured according to the present invention will be described. 9 and 10, substantially the same parts as those in FIGS. The cap 40, which is partially shown in FIG. 9 and FIG. 10 and not shown in its entirety, is similar to the synthetic resin cap 2 described with reference to FIGS.
A total of ten unillustrated weakening lines 42 (a to j) are formed, and their circumferential positions are the same as those of the cap 2 (see FIG. 3). Note that the weakening line 42 (a to j)
Means a weakened line formed at a position corresponding to the weakened lines 20 (a to j). Referring also to FIG. 3, the cap 40 is different from the cap 2 in that the weakening lines 20 (a to j) of the cap 2 are all formed of thin portions, whereas the cap 40 has a weakening line. 42 (a to j), tab side area X
Are formed of slits, and the other weakening lines 42 (a to c and f
To j) are composed of thin portions, and the configurations of the thin portions are different.

The thin portion is formed in an upper region S near the top wall 4.
1, the first thin portion 22 having a relatively large residual thickness.
And a second thin portion 24 formed in the lower region S2 near the opening end and having a smaller remaining thickness than the first thin portion 22 (this basic configuration is a weakening line of the cap 2). 20). Each of the weakening lines 42 (a to c and f to j) formed of a thin portion includes a groove 44 formed to extend linearly over a part of the inner peripheral surface of the skirt wall 6 in the axial direction. . The groove 44 has a predetermined circumferential width and a predetermined depth, and is formed so as to extend from the open end of the skirt wall 6 toward the top wall 4 by a predetermined length S1 + S2. That is, in this embodiment, the groove 4 extending in the axial direction is formed in the inner peripheral surface of the skirt wall 6.
By forming 4, a weakening line 42 that is thinner than the thickness of the skirt wall 6 is formed. The first thin portion 22 is formed to be thinner than the thickness of the skirt wall 6 by the depth of the groove 44. Since the radially outer surfaces of the first thin portion 22 and the second thin portion 24 are on the same plane (on the outer peripheral surface of the skirt wall 6), the radially inner surface of the second thin portion 24 is located on the radially inner side. In terms of
The first thin portion 22 is positioned radially outward from a radially inner surface of the first thin portion 22.

The slits 46 forming the weakening lines 42d and 42e are linearly formed by a predetermined length S2 + S1 (the length of the lower region S2 + the length of the upper region S1) from the open end of the skirt wall 6 toward the top wall 4. Is formed so as to extend. The slits 46 have a predetermined circumferential interval. It is preferable that the length of the slit 46 and the interval be determined not to be cut but to be a size that can be formed by a mold. As a result, the cap 40 can be completed by a single molding step as in the case of the cap 2. In the illustrated embodiment, the cross section of the slit 46 has a shape that penetrates the bottom of the groove 44. Therefore, the mold at the slit 46 can be a mold similar to the thin portion.

The weakened lines 42 (a to e) in the tab side region X in the cap 40 are two in addition to the thin portions.
Weakening lines 42d and 42e composed of two slits 46
The opening is more easily performed as compared with the cap 2. That is, as described above, when a force is applied to the tab 12 by a finger in a direction away from the opening for opening the cap, first of all the weakening lines 42a to 42e of the tab side area X. Weakening lines 42d and 42
Although e has a strong tendency to break first under a large load, the weakening lines 42d and 42e comprise the slits 46, so that the cap 40 can be more easily detached from the opening. The cap 40 is provided with the slit 4
Except for the presence of 6, the cap 2 has substantially the same configuration as the cap 2, so that substantially the same operation and effects as those of the cap 2 described in detail above are achieved. However, the cap 2 is more excellent in moldability due to the difference in the configuration of the thin portion. Further, the cap 2 is more excellent in terms of the holding power of the cap, the stability at the time of supplying the cap, and the tamper-evident property. However, after the cap 40 is plugged into the milk bottle 100, the cap 40 can be covered with a shrink film or the like and sealed to improve the holding power and tamper-evident property of the cap. The number of the slits 46 is preferably at most three in order to secure the sealing function of the seal ridge 8.

The weakening line 42 in the cap 40
d and 42e consist of a slit 46, and the slit 46
The skirt wall 6 is formed so as to extend linearly from the opening end of the skirt wall 6 toward the top wall 4 by the predetermined length S2 + S1. Instead, the slit 46 extends linearly only in the lower region S2. There is also an embodiment in which a thin portion / slit combination means (not shown) formed as described above is used. Also in this embodiment, the cap 4 shown in FIGS.
It is possible to obtain the same operation and effect as 0. It is preferable that the number of the thin portion / slit combination means is at most three in order to secure the sealing function of the sealing ridge 8.

As described above, in the cap 40, among the weakening lines 42 (a to j), the weakening lines 42d and 42e existing in the tab side region X are formed of slits, and the other weakening lines 42 (a to 42) are formed. c and f ~ j)
Is constituted by a thin portion, but there is also an embodiment in which all the weakened lines 42 (a to j) of the cap 40 are constituted by a thin portion as shown in FIGS. Also in this embodiment, the same operational effects as those of the cap 2 can be obtained except for the problem of moldability.

It should be noted that the weakening lines 20 (a to e) in the tab side region X in the cap 2 described above are all formed of thin portions, but, similarly to the cap 40, two weakening lines 20d and 20d. In some embodiments, the slit 20e is constituted by a slit. Then, slit the cap 40
Similarly to the above embodiment, the skirt wall 6 is formed so as to extend linearly from the open end toward the top wall 4 by the predetermined length S2 + S1, and only the lower region S2 is extended linearly. There is an embodiment in which a thin portion / slit combination means is formed. In any of these embodiments,
Opening is easier than with the above-mentioned all-thin-wall-shaped cap 2. Also in this embodiment, it is preferable that the number of slits and the combination of the thin portion and the slit are at most three for the same reason as described above.

Next, another embodiment of the synthetic resin cap constructed according to the present invention will be described with reference to FIG. In FIG. 11, substantially the same parts as those in FIGS. 1 to 10 are denoted by the same reference numerals, and description thereof will be omitted. The cap 50 shown in FIG. 11 has a total of nine weakening lines 52 (a to i) formed on the skirt wall 6. Five weakening lines 52a to 52e are formed in the tab side area X, and four weakening lines 52f to 52i are formed in the opposite tab side area Y. The weakening lines 52 (a to i) of the cap 50 are all formed of thin portions. The substantial configuration of the thin portion is the same as that shown in FIGS. However, the shape of the locking ridge 10 is such that both ends in the circumferential direction are not curved when viewed from the axis, but extend linearly in the axial direction. Further, as shown in the drawing, the locking ridge 10 between the weakening lines 52b and 52d is cut out in such a manner that its height decreases from the weakening line 52d to 52b,
Similarly, the locking ridge 1 between the weakening lines 52c and 52e
0 is cut out in such a manner that its height decreases from the weakening lines 52e to 52c. Tab 1
The locking ridges 10 are formed over the entire area between the weakening lines 52a and 52b and between the weakening lines 52a and 52c in the two circumferential regions. The cap 5
Even at 0, the same operational effects as those of the cap 2 can be obtained except for the problem of moldability. In the above-described cap 2 and cap 40, there is naturally an embodiment in which nine weakening lines 20 and 42 are provided as shown in FIG. Of course, there is no reason why the total number of weakening lines is not limited to any of the above embodiments.

[0039]

【Example】

Example 1 A cap 2 shown in FIGS. 1 to 5 was formed from low-density polyethylene by injection molding. The main dimensions of the formed cap 2 are as follows (see FIGS. 4 and 5). 40.6 mm Minimum inner diameter d1 of skirt wall 6 Lower inner diameter d2 of skirt wall 6 41.0 mm Central inner diameter d3 of locking ridge 10 ... 39.0mm inner diameter d4 at the lower end of the seal ridge 8 ... 27.4mm inner diameter d5 at the upper end of the seal ridge 8 ... 27.0mm Maximum of the seal ridge 8 Outer diameter d6 29.7mm Upper end outer diameter d7 of seal ridge 8 28.7mm Lower end outer diameter D1 of skirt wall 6 42.8 mm Lower end outer diameter D2 of rib 14 43.4 mm Upper end outer diameter D3 of skirt wall 6 42.4 mm Height h1 of cap 2 11.5 mm Height h2 from the open end of the rib 14 7.0 mm Locking ridge 10 Distance between the center of the skirt wall 6 and the lower surface of the skirt wall 6... 6.65 mm Distance h4 between the center of the seal ridge 8 and the lower surface of the skirt wall 6. ············································································ 0 mm Thickness t1 of first thin portion 22... 0.45 mm Thickness of second thin portion 24... 0.25 mm Thickness of top wall 4 1.6 mm The width W1 at the bottom of the groove 26 of the weakening line 20... 1.2 mm The width W2 on the outer diameter side of the groove 26 of the weakening line 20. 2.0 mm In addition, referring to FIG. 3, the circumferential angle between each of the weakening lines 20 (a to j) is set between the weakening lines 20a and 20b and the weakening line 20a. 20c between are 40 ° each other are all 35 °. The main dimensions of the milk bottle 100 to which the cap 2 is attached are as follows (see FIGS. 7 and 8). Inner diameter d8 of the opening 29.0 mm Outer diameter D4 of the opening 41.0 mm The distance h6 from the lower surface of the jaw 104 to 7.0 mm The capacity of the milk bottle 100 is 213.5 ml. Milk cooled to 5 ° C in the milk bottle 100
After injecting 00 ml and capping the cap 2 (all thin portions), the milk bottle 100 was placed in a temperature space maintained at 5 ° C., a temperature space maintained at room temperature, and a temperature maintained at 40 ° C. Put each side down in the space, 24
After leaving it for a while, an experiment was conducted to confirm the presence or absence of milk leakage. The results were as shown in Table 1 below. Embodiment 2: The weakening lines 20d and 20e of the weakening lines 20 (a to j) are slit as shown in FIG. 9 (inner side width W3... 1.5 mm, outer side width W4. .7
mm), the same cap (two slits) as the cap 2 of Example 1 was formed, and the same experiment as in Example 1 was performed. The results were as shown in Table 1 below. Comparative Example 1: For comparison, the weakening lines 20d, 20e, 20b, and 20c of the weakening lines 20 (a to j) are slit as shown in FIG. 9 (inner width W3... 1.5 m).
m, the same cap (four slits) as the cap 2 of Example 1 was formed except that the width W4 on the outer diameter side was W4... 0.7 mm, and was the same as Example 1 and Example 2. Was performed. The results were as shown in Table 1 below. Comparative Example 2: For comparison, the weakening lines 20 (a to
j) are all slits (width W3 on the inner diameter side) as shown in FIG.
... 1.5mm, outer diameter side width W4 ... 0.7mm)
The same cap (all slits) as the cap 2 of Example 1 was formed except that
The same experiment was performed. The results were as shown in Table 1 below. Embodiment 3 In the cap 40 shown in FIGS. 9 and 10, the number of the weakening lines 42 is nine, and the weakening lines 42 are formed at the same circumferential position as the skirt wall 6 shown in FIG. 42a to 42i) were formed by injection molding the low-density polyethylene into the cap 40 composed of the thin portions shown in FIGS. In addition, weakening line 4
The angles in the circumferential direction between each of 2 (a to i) are all 40 °. The main dimensions of the formed cap 40 are as follows (see FIGS. 9 and 10). Minimum inner diameter d1 of skirt wall 6 40.6 mm Central inner diameter d3 of locking ridge 10 39.0 mm Lower end inner diameter d4 of sealing ridge 8 · · · · 27.4 mm Upper end inner diameter d5 of seal ridge 8 · · · · · 27.0 mm Maximum outer diameter d6 of seal ridge 8 · · · 29.6 mm Seal ridge 8 28.7 mm Lower end outer diameter D1 of skirt wall 6 42.8 mm Lower end outer diameter D2 of rib 14 43.4mm Upper end outer diameter D3 of skirt wall 6 ... 42.4mm Height h1 of cap 2 ... 11.3mm From opening end of rib 14 Height h2 7.0 mm Distance h3 between the center of the locking ridge 10 and the lower surface of the skirt wall 6. ········· 6.65 mm Distance h4 between the center of the seal ridge 8 and the lower surface of the skirt wall 6 ··· 2.0 mm Seal ridge 8 Distance h5 between the lower end of the skirt wall 6 and the lower surface of the skirt wall 6... 4.0 mm Thickness t1 of the first thin portion 22. 0.35 mm Thickness of the second thin portion 24 t2... 0.2 mm Thickness of the top surface wall 4... 1.4 mm Weakening line The width W5 on the inner diameter side of the groove 44 of 42 ... 1.5 mm The width W6 at the bottom of the groove 44 of the weakening line 42 ... 0.7 mm The main dimensions and capacity of the milk bottle 100 to which the cap 40 is attached are: It is the same as the milk bottle 100 to which the cap 2 is attached in the first embodiment. 200 ml of milk cooled to 5 ° C. was poured into the milk bottle 100, and the cap 40 (all thin portions) was stoppered.
Into the temperature space maintained at 5 ° C., the temperature space maintained at room temperature, and the temperature space maintained at 40 ° C., respectively, and left standing for 24 hours. An experiment for confirming (an experiment similar to Example 1 and Example 2) was performed. The results were as shown in Table 1 below. Embodiment 4: The weakening lines 40d and 40e of the weakening lines 40 (a to i) are slit as shown in FIG. 9 (inner side width W3... 1.5 mm, outer side width W4. .7
mm), the same cap (two slits) as the cap 40 of Example 3 was formed, and the same experiment as in Example 3 was performed. The results were as shown in Table 1 below. Comparative Example 3: For comparison, the weakening lines 40d, 40e, 40b, and 40c among the weakening lines 40 (a to i) are slit as shown in FIG. 9 (inner width W3... 1.5 m).
m, and the same cap (four slits) as the cap 40 of the third embodiment except that the width W4 on the outer diameter side is W4... 0.7 mm. Was performed. The results were as shown in Table 1 below.

[0040]

[Table 1] When comparing the experiments of Examples 1 and 2 and Comparative Examples 1 and 2 and Examples 3 and 4 and Comparative Example 3 with each other to confirm the presence or absence of milk leakage, it was found that the synthesis composed according to the present invention. Milk bottle with resin cap
Even when left sideways in a 40 ° C temperature space for 24 hours in a state of lying down, no milk seepage or leakage from the opening was observed, and it was confirmed that there was no practical problem at all.

The preferred embodiment of the synthetic resin cap constructed according to the present invention has been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiment, and the scope of the present invention is not limited thereto. Various changes or modifications are possible without departing from the invention.

[0042]

The synthetic resin cap according to the present invention is firmly attached to the container opening while maintaining a sufficiently secure sealing state so as to prevent the contents from leaking to the outside, and the container is opened when opened manually. It can be easily detached from the opening. The synthetic resin cap according to the present invention has a simple structure and is easy to mold, and therefore can be mass-produced at low cost.

[Brief description of the drawings]

FIG. 1 is a top view of an embodiment of a synthetic resin cap configured according to the present invention as viewed from a top wall side.

FIG. 2 is a front view of the cap shown in FIG. 1, with one side in the radial direction cut away from the axis.

FIG. 3 is a bottom view of the cap shown in FIG. 1 as viewed from an opening end side.

FIG. 4 is an enlarged view of a portion A in FIG. 3;

FIG. 5 is an enlarged cross-sectional view taken along the line BB of FIG. 4;

FIG. 6 is a diagram in which a part of a mold is illustrated in FIG. 5;

FIG. 7 is a partially cutaway front view showing a state in which the cap shown in FIGS. 1 to 5 is attached to a milk bottle.

FIG. 8 is an enlarged sectional view showing a broken portion of FIG. 7;

FIG. 9 is a partial view showing another embodiment of the synthetic resin cap constituted according to the present invention, and is a view corresponding to FIG. 4;

10 is an enlarged cross-sectional view taken along the line CC of FIG. 9;

FIG. 11 is a partial view showing another embodiment of the synthetic resin cap configured according to the present invention, corresponding to FIG. 3;

[Explanation of symbols]

 2 Cap made of synthetic resin 4 Top wall 6 Skirt wall 8 Seal ridge 10 Locking ridge 12 Tab 14 Rib 20 (a to j) Weakening line 22 First thin portion 24 Second thin portion 24a Second thin portion Inner peripheral surface 26 at the lower end 26 groove 40 synthetic resin cap 42 (a to j) weakening line 44 groove 46 slit 50 synthetic resin cap 52 (a to i) weakening line 100 milk bottle 102 opening 104 locked jaw S1 Upper area S2 Lower area X Tab side area Y Anti-tab side area

Claims (11)

[Claims] 1. An annular seal comprising: a top wall; and a skirt wall extending downward from a periphery of the top wall, and an annular seal extending downward on an inner surface of the top wall and fitted to an inner peripheral surface of the container opening. A ridge is formed on the inner peripheral surface of the skirt wall, and a locking ridge is formed on an inner peripheral surface of the container opening to be locked by a locked jaw formed on an outer peripheral surface of the container opening. Wherein a tab protruding radially outward is formed over a part of the circumferential direction on the outer peripheral surface of the synthetic resin cap. The skirt wall is circumferentially spaced from the opening end from the opening end. A plurality of weakening lines extending toward the face wall, and a 180 ° tab-side area X of the skirt wall and the skirt where the tabs are located substantially centrally in the circumferential direction when the skirt wall is viewed axially; When divided into the other 180 ° anti-tab side area Y of the wall , At least two weakening lines are provided in the tab side area X, and at least one weakening line is provided in the anti-tab side area Y. Each of the weakening lines comprises a thin part, Are formed in the upper region near the top wall, the first thin portion having a relatively thick residual thickness, and formed in the lower region near the opening end, the first thin portion has a residual thickness greater than the first thin portion. A synthetic resin cap comprising a thin second thin portion. 2. An annular seal, comprising: a top wall; and a skirt wall extending downward from a periphery of the top wall. An annular seal extends downward on an inner surface of the top wall and fitted to an inner peripheral surface of the container opening. A ridge is formed on the inner peripheral surface of the skirt wall, and a locking ridge is formed on an inner peripheral surface of the container opening to be locked by a locked jaw formed on an outer peripheral surface of the container opening. Wherein a tab protruding radially outward is formed over a part of the circumferential direction on the outer peripheral surface of the synthetic resin cap. The skirt wall is circumferentially spaced from the opening end from the opening end. A plurality of weakening lines extending toward the face wall, and a 180 ° tab-side area X of the skirt wall and the skirt where the tabs are located substantially centrally in the circumferential direction when the skirt wall is viewed axially; When divided into the other 180 ° anti-tab side area Y of the wall The at least two weakening lines are provided in the tab side area X, and at least one weakening line is provided in the opposite tab side area Y. A first thin portion having a relatively thick residual thickness formed in an upper region near the top wall and a thinner residual thickness than the first thin portion formed in a lower region near the opening end; A plurality of thin portions composed of a second thin portion and at most three slits, and the weakening line disposed in the anti-tab side region Y comprises the thin portion. A synthetic resin cap characterized by the following. 3. An annular seal comprising a top wall, and a skirt wall extending downward from a periphery of the top wall, and an annular seal extending downward on an inner surface of the top wall and fitted to an inner peripheral surface of the container opening. A ridge is formed on the inner peripheral surface of the skirt wall, and a locking ridge is formed on an inner peripheral surface of the container opening to be locked by a locked jaw formed on an outer peripheral surface of the container opening. Wherein a tab protruding radially outward is formed over a part of the circumferential direction on the outer peripheral surface of the synthetic resin cap. The skirt wall is circumferentially spaced from the opening end from the opening end. A plurality of weakening lines extending toward the face wall, and a 180 ° tab-side area X of the skirt wall and the skirt where the tabs are located substantially centrally in the circumferential direction when the skirt wall is viewed axially; When divided into the other 180 ° anti-tab side area Y of the wall The at least two weakening lines are provided in the tab side area X, and at least one weakening line is provided in the opposite tab side area Y. A first thin portion having a relatively thick residual thickness formed in an upper region near the top wall and a thinner residual thickness than the first thin portion formed in a lower region near the opening end; A plurality of thin portions comprising a second thin portion; a first thin portion formed in the upper region near the top wall; and a slit formed in the lower region near the opening end. And at least three thin-walled / slit combining means comprising: a weakening line provided in the anti-tab side region Y is formed by the thin-walled portion. cap. 4. The method according to claim 1, wherein each of the first thin portions has a lower end extending downward at least to an axial region where the locking ridge is present. Synthetic resin cap. 5. The method according to claim 4, wherein each of said first thin portions extends downward at least to a position beyond an axial position corresponding to a radial top of said locking ridge. Synthetic resin cap. 6. The tab-side region X according to any one of claims 1 to 5, wherein a locking ridge is not provided on at least a part of the circumferential region where the tab is formed. The cap made of synthetic resin according to 4. 7. One of the weakening lines disposed in the non-tab side area Y is positioned substantially diametrically opposite to the circumferential center position of the tab. The synthetic resin cap according to any one of claims 1 to 6. 8. At least two weakening lines located at equal intervals on both sides in the circumferential direction of the one of the weakening lines disposed in the non-tab side area Y. 7. The synthetic resin cap according to 7. 9. The synthetic resin according to claim 1, wherein a plurality of ribs extending in the axial direction are formed on the outer peripheral surface of the skirt wall at intervals in the circumferential direction. Made cap. 10. Each of the thin portions includes a groove formed to extend linearly over the entire area of the outer peripheral surface of the skirt wall in the axial direction, and the locking ridge of the second thin portion is provided. The lower end inner peripheral surface at a lower position on the open end side is located flush with a corresponding lower end inner peripheral surface of the skirt wall. Synthetic resin cap. 11. The first thin portion has a thickness of 0.35 mm to 0.1 mm.
6 mm thick, and the second thin portion is 0.15 mm-
The synthetic resin cap according to any one of claims 1 to 10, which has a thickness of 0.3 mm.