JP2014061918A - Mouth sealing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mouth sealing mechanism which has a simple structure, which has high sealability against a plug member having a pour-out hole at a center and covering an upper surface opening portion of a container mouth and is capable of releasing gas reliably at an internal pressure rising time while keeping stable sealability without depending upon the threading strength of a cap even at the recapping time, thereby to prevent the burst of the container reliably.SOLUTION: A mouth sealing mechanism 100 comprises a plug member 120 and a cap body 130. The plug member 120 includes a sealing ring portion 123 on the outer circumference side of a pour-out hole 121. The cap body 130 includes an inner contact ring portion 141 to contact closely with the inner circumference of the sealing ring portion 123, and an outer contact ring portion 142 to contact closely with the upper face of the plug member 120. The sealing ring portion 123 has a radially thin wall portion 124 in at least one portion of the circumferential direction.

Description

  The present invention is a mechanism that is provided in a container mouth portion that pours out contents such as a stored liquid and is configured to be openable and closable and sealable. The present invention relates to a mouth sealing mechanism having an inner plug member that covers an opening and a detachable cap body that covers a container mouth together with the inner stopper member.

In containers that contain contents such as liquids, the contents are preserved so that they are sterilized, for example, hot packs, when the contents are filled, and in order to prevent the entry of external bacteria into the containers during storage, A mouth-sealing mechanism is required which has a sealing property during the first capping.
In addition, the opening sealing mechanism needs to have a sealing property at the time of recapping from the viewpoint of hygiene and prevention of leakage of contents even after being opened by the user.

For example, a mouth sealing mechanism 500 as shown in FIG. 7 has been proposed as a mouth sealing mechanism for a plastic container that contains concentrated fruit juice or the like.
The mouth portion sealing mechanism 500 has an outlet hole 521 at the center and an inner stopper member 520 that covers the upper surface opening of the container mouth portion 511 of the container 510, and is detachable that covers the container mouth portion 511 together with the inner stopper member 520. A cap body 530.
The inner plug member 520 has an insertion cylinder part 526 inserted inside the container mouth part 511 and a fitting cylinder part 527 fitted from the outside of the container mouth part 511, and from above the container mouth part 511. It is formed so as to be in close contact with the upper surface opening.
The cap body 530 includes a side wall portion 550 having a female screw portion 551 that is screwed into a male screw portion 512 provided on the outer periphery of the container mouth portion 511, and a top plate portion 540 that covers the upper portion of the container mouth portion 511. On the lower surface side of the top plate portion 540, an inner contact ring portion 541 that protrudes in an annular shape and adheres closely to the inner peripheral surface of the outlet hole 521 of the inner plug member 520, and an inner plug that protrudes in an annular shape toward the outer peripheral side from the inner contact ring portion 541 And an outer contact ring portion 542 in close contact with the upper surface 522 of the member 520.

After the container 510 is filled with the contents, the cap body 530 is screwed into the container mouth 511 so that the outer peripheral surface of the inner contact ring portion 541 is in close contact with the inner peripheral surface of the outlet hole 521 of the inner plug member 520. At the same time, the end edge 543 of the outer contact ring portion 542 is tightly sealed with the upper surface 522 of the inner plug member 520 to prevent entry of external bacteria into the container during storage.
In addition, even when the cap is once opened by the user, the user can similarly seal the sealing performance by screwing the cap main body 530 into the container mouth portion 511.

However, since such a mouth-sealing mechanism 500 has high sealing performance even at the time of recapping, for example, when contents are rotted and fermented by bacteria or yeast that have invaded by opening, the gas is generated in the container 510. There was a risk that the gas pressure of the container 510 would rise and the container 510 could not withstand the gas pressure and burst.
In order to solve such problems, various types of mouth sealing mechanisms have been proposed that have a function of allowing gas to escape from the container mouth when the gas pressure in the container increases (see Patent Documents 1-6, etc.). .)

JP 09-95348 A JP 07-277353 A JP 2006-69574 A Japanese Patent Laid-Open No. 2003-237813 JP 2003-170952 A Japanese Utility Model Publication No. 60-25409

However, the known mouth sealing mechanism described in the above-mentioned Patent Document 1 is provided with a clogging plate 19 on the top plate 17 of the cap C, a closing portion 19 at the center portion that engages with the mouth portion 14 of the dispensing cylinder 8, and an annular shape that is thinner than the center portion. The closed portion 19 of the top plate 17 is movable due to the thin flexible portion 20, so that at the time of initial capping, after uncapping once opened In both cases, there is a problem that it is difficult to obtain high sealing performance.
Further, at the time of recapping, there is a problem that both the sealing performance and the pressure for releasing the gas are not constant depending on the strength of screwing of the cap C.

The known mouth sealing mechanism described in Patent Document 2 has a complicated structure with a large number of parts because the inner plug 14 incorporates the movable valve 15, increases the number of assembly steps, and increases the overall mechanism. There was a problem that.
Further, the inner plug 14 is a member used for sealing and gas escape, and is removed together with the cap body 11 when used. Therefore, the container 14 has a pouring hole 521 at the center as in the mouth sealing mechanism 500 described above. There is a problem that it cannot be applied to the structure having the inner stopper member 520 that covers the upper surface opening of the container mouth portion 511 of 510.

The known mouth sealing mechanism described in Patent Document 3 has a structure in which the seal member 5 provided on the cap is in close contact with the inner plug 2 from above when recapping, and elastically displaces as the internal pressure rises to release gas. For this reason, there is a problem that the sealing performance and the pressure for releasing the gas are not constant depending on the strength of screwing of the cap.
The known mouth sealing mechanism described in Patent Documents 4 and 5 seals the packing with the cap in close contact with the mouth, and the internal pressure is abnormally increased by devising the shape and structure of the cap or packing. In this case, the packing is deformed and gas is released, so that the outlet hole 521 is provided at the center and covers the upper surface opening of the container mouth 511 of the container 510 as in the mouth sealing mechanism 500 described above. There was a problem that it could not be applied to a structure having a plug member 520.
Further, there is a problem that the sealing performance and the pressure for releasing the gas are not constant depending on the strength of screwing of the cap.

The known mouth sealing mechanism described in Patent Document 6 has a problem in that the valve body 3 is built in between the inner plug 1 and the cap 2, so that the number of parts is complicated and the number of assembly steps increases. there were.
Further, in the aspect in which the ring portion 14 of the inner plug 1 is separated from the main body portion 1a, the main body portion 1a of the inner plug 1 corresponds to the inner plug member 520 of the mouth sealing mechanism 500 described above, but the number of parts is further increased. At the time of recap, there is a problem that both the sealing performance and the pressure for releasing the gas are not constant depending on the strength of screwing of the cap 2.

  The present invention solves the above-mentioned problems, has a simple structure, has a high sealing performance with respect to an inner plug member that has a pouring hole in the center and covers the upper surface opening of the container mouth, and Another object of the present invention is to provide a mouth sealing mechanism that reliably releases gas when a predetermined internal pressure rises while maintaining a stable sealing performance even during recap, and that reliably prevents the container from bursting.

  The invention according to claim 1 is a mouth having an inner stopper member that has a pouring hole in the center and covers the upper opening of the container mouth, and a removable cap body that covers the container mouth with the inner stopper A sealing ring portion that protrudes annularly upward from the outlet hole of the inner plug member, and the cap body is a male screw provided on the outer periphery of the container mouth portion A side wall portion having a female screw portion to be screwed to the portion, and a top plate portion covering the upper portion of the container mouth portion, and projecting annularly on the lower surface side of the top plate portion, the sealing ring portion of the inner plug member An inner contact ring portion that is in close contact with the inner peripheral surface of the inner contact ring portion, and an outer contact ring portion that protrudes annularly from the inner contact ring portion toward the outer peripheral side and is in close contact with the upper surface of the inner plug member. Have a thin portion with a small radial thickness at least in one direction. Accordingly, it is intended to solve the above problems.

In the invention according to claim 2, in addition to the structure of the mouth portion sealing mechanism described in claim 1, the thin portion of the sealing ring portion is formed with a recess in the radial direction from the outer peripheral side. Thus, the problem is solved.
In the invention according to claim 3, in addition to the structure of the mouth sealing mechanism described in claim 1 or claim 2, the edge closely contacting the upper surface of the inner plug member of the outer contact ring portion is By having a high end edge formed with a high height from the lower surface of the top plate portion and a low end edge formed lower than the high end edge, the above problem is solved.
In addition to the structure of the mouth sealing mechanism described in claim 3, the invention according to claim 4 solves the above problem by forming the high end edge at three or more locations in the circumferential direction. It is.

In the invention according to claim 5, in addition to the structure of the mouth sealing mechanism described in claim 3 or claim 4, the edge closely contacting the upper surface of the inner plug member of the outer contact ring portion is The above-mentioned problem is solved by having an inclined edge whose height changes with a predetermined length in the circumferential direction between the high edge and the low edge.
In the invention according to claim 6, in addition to the structure of the mouth sealing mechanism according to any one of claims 1 to 5, the boundary surfaces at both ends in the circumferential direction of the thin portion are in a radial direction. The said subject is solved by being formed in the inclined surface.
In the invention according to claim 7, in addition to the structure of the mouth sealing mechanism according to any one of claims 1 to 6, the cap body is made of polypropylene, and the inner plug member is made of polyethylene. Thus, the problem is solved.

According to the mouth portion sealing mechanism of the invention according to claim 1, the inner contact ring portion that is in close contact with the inner peripheral surface of the seal ring portion, and the outer contact ring portion that is in close contact with the upper surface of the inner plug member from the inner contact ring portion; The cap body has a simple structure and can ensure extremely high sealing performance against the inner plug member, and the inner contact ring portion is in close contact with the inner peripheral surface of the sealing ring portion even during recapping. Stable sealing performance can be obtained regardless of the screwing strength.
In addition, since the sealing ring portion has a thin portion with a thin radial thickness at at least one place in the circumferential direction, the thin portion when a certain force is applied outwardly in the radial direction of the sealing ring portion when the internal pressure is increased. Is deformed outward from the other parts and the circular shape becomes a distorted annular shape, and a gap is generated between the inner contact ring part that is deformed in a circular shape, and gas is released to reliably prevent the container from bursting. Is possible.
In addition, when the internal pressure rises, the sealing ring part is deformed by the radial force and hardly depends on the vertical pressing force of the cap body. Therefore, when the cap is recaptured, the constant internal pressure rises regardless of the strength of the cap body screwing. It is possible to reliably deform and escape the gas.
Furthermore, since no member contacts the pouring hole in the center, and the pouring hole is not involved in the sealing performance or the function of escaping gas, if it is inside the sealing ring part, its size, shape, There is no restriction on the position and number, and it can be set freely according to the contents.

According to the structure of Claim 2, the inner peripheral surface of a sealing ring part becomes circular, an inner contact ring part is closely_contact | adhered reliably, and a sealing performance improves.
According to the structure of Claim 3, when the outer contact ring part has a high end edge and a low end edge and the height difference is set appropriately, the cap body is strongly screwed at the time of the first capping. The upper surface of the inner plug member that is in close contact with the high end edge is greatly deformed, and the lower end edge is also in close contact with the upper surface of the inner plug member. A gap is formed between the lower edge and the upper surface of the inner plug member.
As a result, a high sealing performance can be ensured at the time of the first capping, and a flow path for escaping gas when the internal pressure rises can be secured at the time of recapping, and the container can be reliably prevented from rupturing.
According to the configuration described in claim 4, since the high end edge is formed at three or more locations in the circumferential direction, even if the cap body is screwed slightly diagonally during recapping, any one of the circumferential directions A gap is reliably formed between the lower end edge of the outer contact ring portion and the upper surface of the inner plug member, and a flow path for releasing gas can be secured.

According to the configuration of the fifth aspect, the edge closely contacting the upper surface of the inner plug member of the outer contact ring portion has a predetermined length in the circumferential direction between the high end edge and the low end edge. By having the inclined edge that changes, the outer contact ring portion and the inner plug member can be more closely adhered to each other when the cap body is screwed and tightened.
According to the structure of claim 6, when the thin portion of the sealing ring portion is deformed outwardly from other portions to become a distorted annular shape, the deformation concentrates on the boundary surface, and plastic deformation, cracks, etc. Is prevented, and the sealing performance when the pressure drops again is not impaired.
According to the structure of claim 7, the cap main body is made of polypropylene and the inner plug member is made of polyethylene, so that the high end edge of the outer contact ring portion of the hard cap main body is soft when capping after filling the contents. Since the upper surface of the member is deformed, the adhesion between the cap body and the inner plug member is further improved, the sealing performance is further improved, and the sealing ring portion is easily deformed and reliably deformed when the internal pressure rises. Gas can be released.

The side sectional view of the mouth part sealing mechanism of one embodiment of the present invention. The top view and partial enlarged view of the inside plug member of the opening part sealing mechanism of FIG. The (a) side sectional view and (b) side view of the cap main body of the mouth part sealing mechanism of FIG. The bottom view of the cap main body of the opening part sealing mechanism of FIG. The deformation | transformation explanatory top view of the sealing ring part of this invention. Operation | movement explanatory sectional drawing at the time of gas escape of this invention. Side surface sectional drawing of the conventional opening part sealing mechanism.

Below, the opening part sealing mechanism which is one Embodiment of this invention is demonstrated based on drawing.
As shown in the side sectional view of FIG. 1, the mouth sealing mechanism 100 according to one embodiment of the present invention has a pouring hole 121 at the center and covers the upper opening of the container mouth 111 of the container 110. It has a stopper member 120 and a detachable cap body 130 that covers the container opening 111 together with the inner stopper member 120.
The inner plug member 120 has an insertion cylinder part 126 inserted inside the container mouth part 111 and a fitting cylinder part 127 fitted from the outside of the container mouth part 111, and from above the container mouth part 111. It is formed so as to be in close contact with the upper surface opening.
Further, on the outer peripheral side of the top surface 122 of the inner plug member 120 from the outlet hole 121, there is a sealing ring portion 123 projecting upward in an annular shape.

As shown in FIG. 2, the sealing ring portion 123 of the inner plug member 120 has a pouring hole 121 at the center of the upper surface 122, and the sealing ring portion that projects annularly upward from the pouring hole 121 to the outer peripheral side. 123.
Thin portions 124 having a small radial thickness formed by providing concave portions in the radial direction from the outer peripheral side are provided at three circumferentially equidistant intervals on the sealing ring portion 123. As shown in the enlarged view of FIG. 2, the boundary surface 125 is formed by a surface inclined by a ° with respect to the radial direction.
The inclination of the boundary surface 125 with respect to the radial direction is preferably 5 ° to 60 °, and is about 30 ° in this embodiment.

As shown in FIGS. 1 and 3A and 3B, the cap main body 130 includes a side wall portion 150 having a female screw portion 151 screwed into a male screw portion 112 provided on the outer periphery of the container mouth portion 111. The top plate part 140 covers the upper part of the container mouth part 111.
On the lower surface side of the top plate portion 140, an inner contact ring portion 141 protruding in an annular shape and closely contacting the inner peripheral surface of the sealing ring portion 123 of the inner plug member 120, and an inner plug protruding in an annular shape outward from the inner contact ring portion 141. And an outer contact ring portion 142 that is in close contact with the upper surface 122 of the member 120.
Further, on the outer peripheral side of the side wall portion 150, there is a concavo-convex shape anti-slip portion 152 so that the user can easily open and recap.

As shown in FIG. 4, the end edge 143 closely contacting the upper surface 122 of the inner plug member 120 of the outer contact ring portion 142 includes a high end edge 144 formed with a height from the lower surface of the top plate portion 140, and the high end A lower end edge 145 formed lower than the edge 144, and an inclined end edge having a predetermined length in the circumferential direction between the high end edge 144 and the low end edge 145, respectively. 146.
In the present embodiment, three high end edges 144 and three low end edges 145 are provided at equal intervals in the circumferential direction, and inclined end edges 146 are provided at six positions therebetween.

An operation of the mouth sealing mechanism 100 that is one embodiment of the present invention configured as described above will be described.
First, the container 110 is filled with contents heated to a high temperature, the inner plug member 120 is attached to the container mouth portion 111, the cap body 130 is screwed to the container mouth portion 111, and the first capping is performed. .
At this time, the outer peripheral surface of the inner contact ring portion 141 is in close contact with the inner peripheral surface of the sealing ring portion 123 of the inner plug member 120, and the edge 143 of the outer contact ring portion 142 is in close contact with the upper surface 122 of the inner plug member 120. .
The end edge 143 of the outer contact ring portion 142 has a high end edge 144 and a low end edge 145. However, since the initial capping is performed with a strong force by the machine, the portion in contact with the high end edge 144 is greatly deformed and the low end edge 145 also securely adheres to the upper surface of the inner plug member 120.

As described above, in the first capping, the inner contact ring portion 141 and the sealing ring portion 123, and the outer contact ring portion 142 and the upper surface 122 of the inner plug member 120 are in close contact with each other, and are securely sealed and stored in the container during storage. Invasion of external bacteria into the is prevented.
At this time, even when the inside of the container 110 becomes a negative pressure due to cooling after capping, the adhesion between the inner contact ring portion 141 and the sealing ring portion 123 does not deteriorate, and the container 110 can be reliably sealed. it can.

At the time of recapping after being opened once by the user, the user screws the cap body 130 into the container mouth portion 111 so that the outer peripheral surface of the inner contact ring portion 141 is inside the sealing ring portion 123 of the inner plug member 120. Adhering to the peripheral surface, sealing performance is ensured.
The end edge 143 of the outer contact ring part 142 has a high end edge 144 and a lower end edge 145, and the user's force is slightly between the lower end edge 145 of the outer contact ring part 142 and the upper surface 122 of the inner plug member 120. However, the practical sealability is sufficiently ensured only by the close contact between the inner contact ring portion 141 and the seal ring portion 123.

Next, the operation when the contents are spoiled and fermented by the bacteria or yeast that have invaded by opening and gas is generated will be described.
Even during recapping, the inner contact ring portion 141 and the sealing ring portion 123 are highly sealed, so that the internal pressure of the container 110 is increased by the generated gas. Each of them tries to deform in the direction that its diameter increases.
At this time, the sealing ring portion 123 is provided with thin portions 124 having a small radial thickness formed by providing concave portions in the radial direction from the outer peripheral side at three locations at equal intervals in the circumferential direction. Thus, the inner peripheral surface of the sealing ring portion 123 is deformed so as to become a distorted non-circular shape (indicated by a solid line) from a circular shape (indicated by a dotted line) (note that the drawings are emphasized for explanation). And does not accurately represent the actual shape.)

Due to the deformation caused by the internal pressure of the sealing ring portion 123, a gap is generated between the inner peripheral surface of the thin portion 124 and the inner contact ring portion 141, and as shown in FIG. It flows out to the outer peripheral part of the sealing ring part 123 from the said clearance gap.
When the sealing ring portion 123 does not have the thin wall portion 124 and has a uniform thickness, the seal ring portion 123 is deformed in the direction in which the diameter expands together with the inner contact ring portion 141, so that a gas outflow gap is generated. Be inhibited.

Since there is a slight gap between the lower end edge 145 of the outer contact ring portion 142 and the upper surface 122 of the inner plug member 120, the gas that has flowed to the outer periphery of the sealing ring portion 123 further flows toward the female screw portion 151. To do.
In addition, when the female threaded portion 151 (or the male threaded portion 112 of the container mouth portion 111) is provided with a vertically cut groove (not shown), it flows more reliably through the cut groove. The released gas can be released into the atmosphere.

As described above, when the contents are spoiled and fermented by the bacteria or yeast that have invaded by opening and gas is generated, and the internal pressure of the container 110 rises above a predetermined pressure, the sealing ring portion 123 is deformed and sealed. Is released, and the escape of gas from the inside of the container 110 and the rupture of the container can be reliably prevented.
Further, when the gas is released and the internal pressure is reduced, the sealing ring portion 123 returns to its original shape due to elasticity, so that the inner contact ring portion 141 and the sealing ring portion 123 come into close contact with each other to restore the sealing performance.

  In this embodiment, the tightening torque when the user recaps is at most about 50 N · cm, and this torque slightly increases the space between the lower edge 145 of the outer contact ring portion 142 and the upper surface 122 of the inner plug member 120. There is a gap, the tightening torque of the first capping is 200 N · cm, and both the inner contact ring portion 141 and the sealing ring portion 123, and the outer contact ring portion 142 and the upper surface 122 of the inner plug member 120 are sufficiently in close contact. Was set to obtain a good sealing property.

The specifications of each component are set so that the internal pressure at which the sealing ring portion 123 is deformed to release the sealing is smaller than the internal pressure at which the container 110 bursts.
In addition, the internal pressure at which the sealing ring 123 is deformed to release the seal is smaller than the internal pressure at which the container 110 ruptures, so that it can be visually observed that the contents have been spoiled and fermented by bacteria and yeast, and the gas is generated. You may set so that it may become larger than the internal pressure which the container 110 expand | swells.
In the present embodiment, the specifications of each component are set so that the internal pressure at which the internal pressure for bursting is about 650 kpa and the internal pressure at which the sealing ring portion 123 is deformed to release the sealing is 350 to 450 kpa. .

In the present embodiment, the thin-walled portions 124 are provided at three places at equal intervals in the circumferential direction of the sealing ring portion 123, but may be two places or less or four places or more.
However, depending on conditions such as dimensions and materials, there is a possibility that the deformation of the sealing ring portion 123 becomes uneven and the internal pressure at which the sealing is released may vary in the case of one place, and in the case of six places or more, the sealing is performed. Since the deformation of the ring portion 123 is close to a circle and there is a risk that it is difficult to effectively create a gap, it is preferable to use two to five locations.
Moreover, although the high end edge 144 of the outer contact ring part 142 was provided in three places of the circumferential direction, it is good also as two places or less or four places or more.
Further, in the present embodiment, the case where the inner plug member is formed separately from the container mouth portion and formed to be closely fitted to the upper surface opening of the container mouth portion has been described. The present invention can also be applied when formed integrally with the mouth portion.

The mouth-sealing mechanism of the present invention can be applied to a container such as plastic that has a risk of deformation or breakage, such as concentrated fruit juice that may spoil, ferment and produce gas due to bacteria and yeast that have invaded by opening. Although it is suitable for being employed in the mouth portion when accommodated, it can be applied to any contents, containers of any material and shape.
In addition, the mouth sealing mechanism of the present invention is suitable for the one having a relatively small outlet hole at the center, but the size, shape, position and number of the outlet holes can be freely set as long as they are inside the sealing ring part. Can be set.

100, 500 ... Mouth sealing mechanism 110, 510 ... Container 111, 511 ... Container mouth 112, 512 ... Male thread 120, 520 ... Inside plug member 121, 521 ... Extraction holes 122, 522 ... Upper surface 123 ... Sealing ring portion 124 ... Thin wall portion 125 ... Interface surface 126, 526 ... Insertion tube portion 127, 527 ... Fitting tube portion 130, 530 ... Cap body 140, 540 ... Top plate parts 141, 541 ... Inner contact ring parts 142, 542 ... Outer contact ring parts 143, 543 ... Edge 144 ... High edge 145・ ・ ・ Low edge 146 ・ ・ ・ Inclined edge 150, 550 ・ ・ ・ Side wall parts 151, 551 ・ ・ ・ Female thread part 152 ・ ・ ・ Slip stopper

Claims (7)

A mouth sealing mechanism having an inner stopper member that has a pouring hole in the center and covers the upper opening of the container mouth, and a removable cap body that covers the container mouth together with the inner stopper member,
On the outer peripheral side from the outlet hole of the inner plug member, it has a sealing ring portion that protrudes annularly upward,
The cap body is composed of a side wall portion having a female screw portion screwed into a male screw portion provided on the outer periphery of the container mouth portion, and a top plate portion covering the upper portion of the container mouth portion,
An inner contact ring portion projecting annularly and closely contacting an inner peripheral surface of the sealing ring portion of the inner plug member, and an inner plug member projecting annularly from the inner contact ring portion to the outer peripheral side on the lower surface side of the top plate portion And an outer contact ring portion closely contacting the upper surface of
The mouth sealing mechanism, wherein the sealing ring part has a thin part with a small radial thickness at least at one place in the circumferential direction.   The mouth sealing mechanism according to claim 1, wherein the thin portion of the sealing ring portion is formed by providing a concave portion in a radial direction from the outer peripheral side.   An end edge of the outer contact ring portion that is in close contact with the upper surface of the inner plug member has a high end edge formed with a height higher than the lower surface of the top plate portion, and a low end edge formed lower than the high end edge. The mouth portion sealing mechanism according to claim 1, wherein the mouth portion sealing mechanism is provided.   The mouth sealing mechanism according to claim 3, wherein the high edge is formed at three or more locations in the circumferential direction.   The edge of the outer contact ring portion that is in close contact with the upper surface of the inner plug member has an inclined edge whose height changes with a predetermined length in the circumferential direction between the high edge and the low edge. The mouth portion sealing mechanism according to claim 3 or 4, characterized in that:   The mouth sealing mechanism according to any one of claims 1 to 5, wherein boundary surfaces at both ends in the circumferential direction of the thin portion are formed with surfaces inclined with respect to a radial direction.   The mouth sealing mechanism according to any one of claims 1 to 6, wherein the cap body is made of polypropylene and the inner plug member is made of polyethylene.

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