JP6005965B2 - Plastic cap - Google Patents

Description

  The present invention relates to a synthetic resin cap for sealing a container mouth.

  As a synthetic resin cap for sealing the mouth of a container such as a plastic bottle, a cap having a middle leg that hangs down from the inner surface of the top wall of the cap and is inserted inside the container mouth is well known. In such a cap, it is important that the middle foot is in close contact (seal) over the entire circumference of the inner peripheral surface of the container mouth portion in a closed state in order to hermetically seal the container.

JP 2009-29498 A (particularly FIG. 7, [0041])

  By the way, as one method for improving the sealing performance of the cap, as disclosed in Patent Document 1, in the natural state, the middle part of the middle foot is outward from the upper part (base part) and the lower part (tip part). It is conceivable to make it approach. In this case, the center part of the middle leg inserted into the container mouth part comes into strong contact with the container mouth part. However, as the protrusion width of the middle foot increases, the sealing performance improves, but the so-called undercut amount increases, and it becomes difficult to remove the middle foot from the mold in the manufacturing process.

  If only considering avoiding the problem of excessive punching due to excessive undercutting, the mold used for molding the cap is divided as appropriate, and the mold located inside the middle foot is pulled out first when punching. However, since such a mold becomes too expensive due to the complicated structure, such a countermeasure is not realistic.

  Of course, if the amount of protrusion of the center part of the middle foot to the outside is suppressed in order to surely prevent the mold release failure, there is a possibility that sufficient sealing performance cannot be secured.

  That is, the improvement of the sealing performance of the cap, the prevention of mold release failure, and the cost limitation are in a so-called trilemma relationship. As a result of intensive studies, the present inventors have invented an epoch-making cap that breaks down this trilemma.

  The present invention has been made in consideration of the above-described matters, and an object of the present invention is to provide a synthetic resin cap capable of improving the sealing performance while avoiding defective mold release and cost increase.

In order to achieve the above object, a synthetic resin cap according to the present invention is provided with a top wall and a skirt wall hanging from the outer periphery of the top wall, and is screwed into a container mouth. The inner wall of the top wall is provided with an annular middle leg that is in close contact with the inner circumferential surface of the container mouth, and the middle leg is configured to have a maximum outer diameter at the center. In addition, a bulging portion that bulges inward is formed in the upper part of the middle foot, and the portion above the bulging portion in the middle foot is thicker toward the upper side , The outer peripheral surface of the upper part of the middle foot expands downward, the outer peripheral surface of the lower part of the middle foot decreases in diameter, and the outer peripheral surface of the central part of the middle foot becomes a sealing surface, The upper and lower parts of the middle leg do not adhere to the container mouth part, and the bulging part is not provided at the middle part and the lower part of the middle leg. The lower surface of the portion immediately communicating with the inside of the metatarsal in the top wall has a feature that you have to immediately lower than the lower surface of the portion occupied outside of the metatarsal (claim 1).

In the above synthetic resin cap, an outer peripheral surface of the front Symbol central portion of the metatarsal, either hanging, or may be reduced in diameter downward a smaller extent than the outer peripheral surface of the lower (claim 2) .

  In the synthetic resin cap, the degree to which the portion forming the lower surface of the bulging portion on the inner peripheral surface of the middle foot expands downward is determined by the lower surface of the bulging portion on the inner peripheral surface of the middle foot. It can be assumed that it is larger than the same degree of the part connected to the upper side and the lower side of the above (claim 3).

  In the synthetic resin cap, the thickness of the central portion may be 0.85 to 0.95 mm.

  In the synthetic resin cap, the width of the bulging portion in the bulging direction may be 0.1 mm or more.

  In the synthetic resin cap, the minimum outer diameter of the upper part of the middle foot is not more than the inner diameter of the container mouth part, and the radius difference between the maximum outer diameter of the central part and the minimum outer diameter of the upper part is 0.8 mm or less. (Claim 6).

  In this invention, the synthetic resin cap which can aim at the improvement of sealing performance, avoiding a mold release defect and a cost increase is obtained.

  That is, in the synthetic resin cap of the invention according to each claim of the present application, by providing a bulging portion at the upper part (root part) of the middle foot, the portion where the bulging part is provided at the upper part of the middle foot If it is thicker and more rigid than the lower part, especially if the thickness of the middle foot is smaller on the lower side as a whole, as a result, in the middle and lower molds of the middle foot Since the deformation space at the time of mold release and the flexibility higher than the upper part are ensured, the mold release property is improved. Moreover, since the upper part of the middle leg after cooling and solidification is hardly bent by the bulging part, the sealing performance can be improved. Therefore, it is not necessary to increase the undercut amount so much in order to improve the sealing performance, and even if the undercut amount is large to some extent, it has an excellent mold releasability as described above, so that there is an extra mold for molding. Therefore, the cap can be formed and manufactured at a low cost.

  In the synthetic resin cap according to the second aspect of the present invention, the middle foot can be smoothly inserted into the container mouth portion when the cap is closed by the middle foot lower portion whose outer peripheral surface is reduced in diameter downward, and the middle portion of the middle foot. A seal surface that adheres well to the inner peripheral surface of the container mouth is obtained by the outer peripheral surface.

  In the synthetic resin cap according to the third and fifth aspects of the present invention, the bulge portion can be projected to the inside of the middle leg to further improve the releasability, and the bulge portion can be enlarged. The inside space of the middle foot that has no other use can be effectively used without causing any particular adverse effects caused by the protrusion.

  In the synthetic resin cap according to the fourth aspect of the present invention, it is possible to improve the operability by reducing the opening torque of the cap body by reducing the thickness of the central portion closely contacting the container mouth.

  In the synthetic resin cap of the invention according to claim 6, there is no large resistance when the cap is completely tightened with respect to the container mouth, and an increase in the closing torque and the opening torque can be prevented, and the undercut By suppressing the amount, it is possible to reliably prevent the mold from becoming difficult.

It is sectional drawing which shows schematically the structure of the synthetic resin caps which concern on one embodiment of this invention. FIG. 2 is a detailed view of part A in FIG. 1. It is sectional drawing which shows schematically the structure of the said synthetic resin cap of the state fitted to the container opening part. It is sectional drawing which overlaps and shows the said synthetic resin cap of a natural state on a container opening part.

  Embodiments of the present invention will be described below with reference to the drawings.

  A cap according to an embodiment of the present invention has an annular band via a plurality of bridges 2 at the lower end of a cap body 1 screwed into a mouth M (see FIGS. 3 and 4) of a container such as a PET bottle. (Tamper-evidence band) A synthetic resin pilfer-proof cap to which 3 is connected, and the cap body 1 and the band 3 are integrally formed, and the so-called one-piece cap has no other packing. (See FIG. 1).

  In order to prevent the band 3 from detaching from the container mouth M when opening the cap body 1 from the container mouth M (screwing), an annular protrusion M1 of the container mouth M is provided inside the band 3. A flap 4 is provided to engage the. Therefore, the bridge 2 that connects the cap body 1 that is detached from the container mouth M and the band 3 that is not detached is broken when the cap is opened. Note that a slit (not shown) is provided at the outer peripheral portion of the boundary between the cap body 1 and the band 3 so that the bridge 2 is appropriately broken.

  The cap body 1 has a top wall 5 having a substantially circular shape in plan view, and a substantially cylindrical skirt wall 6 hangs down from the outer peripheral portion of the top wall 5. Further, on the inner surface of the top wall 5, when the cap body 1 is screwed into the container mouth portion M, an annular middle leg 7 that is inserted into the container mouth portion M and is in close contact with the inner peripheral surface of the container mouth portion M; An annular rib 8 that is in close contact with the annular upper end surface of the container mouth portion M and an annular outer leg 9 that is in close contact with the outer peripheral surface of the container mouth portion M are connected (see FIGS. 3 and 4).

  In FIG. 2, the hatched portion (a portion or a lump portion in close contact with the inner peripheral surface of the container mouth M among the portions protruding downward from the lower surface of the top wall 5) is the middle foot 7 and is natural (nothing). In the (load) state, the outer peripheral surface of the upper portion 11 of the middle foot 7 increases in diameter downward and the outer peripheral surface of the lower portion 12 of the middle foot 7 so that the outer diameter of the middle foot 7 becomes maximum at the central portion 10. The diameter is reduced downward. Moreover, the outer diameter from the upper end of this center part 10 to a lower end is the same, and the outer peripheral surface of the center part 10 becomes a sealing surface. By providing such a sealing surface, the sealing performance can be improved, and the upper part 11 and the lower part 12 of the middle foot 7 are not in close contact with the container opening M, so that the opening torque (the cap body 1 is rotated when opening). The torque required to do this does not increase excessively, and a feeling that the cap body 1 is closed at the time of closing is obtained.

  In addition, the width (length) w of the center part 10 in the up-down direction can be set to 0.5 mm to 2.0 mm, for example, and is 1 mm in this example. Moreover, the distance h from the upper end of the middle leg 7 to the upper end of the center part 10 can be 0.8 mm-2.5 mm, and is 1.6 mm in this example. On the other hand, when the inner diameter of the container mouth portion M is 21.74 mm, the outer diameter (maximum outer diameter) D1 of the central portion 10 can be set to 22.0 mm to 22.5 mm, for example, and is 22.2 mm in this example. .

  The outer peripheral surface of the upper part 11 of the middle foot 7 is configured to gradually reduce from the lower end of the upper part 11 toward the minimum outer diameter part of the upper part 11 on the upper side, and the minimum outer diameter D2 on the upper side of the upper part 11 is It is smaller than the inner diameter of the container mouth M. The radius difference d between the minimum outer diameter D2 of the upper portion 11 and the outer diameter (maximum outer diameter) D1 of the central portion 10 is set to 0.8 mm or less (preferably 0.2 mm to 0.5 mm). If the radius difference d exceeds 0.8 mm, a large resistance is generated when the cap body 1 is completely tightened with respect to the container mouth M, and the closing torque and opening torque are increased, and an excessive undercut is caused. This is because the tendency of demolding becomes remarkable. In addition, the width | variety of the up-down direction of the upper part 11 can be 1.6 mm, for example. When the inner diameter of the container mouth M is 21.74 mm, the minimum outer diameter D2 of the upper portion 11 can be set to 21.4 mm to 21.7 mm, for example, and is 21.6 mm in this example.

  The outer peripheral surface of the lower part 12 of the middle leg 7 is reduced in diameter toward the lower side so that the middle leg 7 can be smoothly inserted into the container mouth part M when closed. The vertical width of the lower portion 12 can be set to 1.4 mm, for example.

  On the other hand, a bulging portion 13 bulging inward is formed in the upper portion 11 of the middle leg 7. Here, the thickness of the portion below the bulging portion 13 in the central portion 10 and the upper portion 11 can be 0.85 to 0.95 mm (0.85 mm in this example). The width e of the protruding portion 13 in the bulging direction can be 0.1 mm to 0.4 mm (0.4 mm in this example). Further, in the middle leg 7, the portion above the bulging portion 13 (or the lower surface 13 a of the bulging portion 13) is thicker toward the upper side.

  The inner peripheral surface of the middle foot 7 gradually increases in diameter downward except for the lower surface 13 a of the bulging portion 13, and forms the lower surface 13 a of the bulging portion 13 on the inner peripheral surface of the middle foot 7. The degree to which the part expands downward is greater than the degree to which the part connected to the upper side and the lower side of the lower surface 13a of the bulging part 13 on the inner peripheral surface of the middle leg 7. In this example, the bulging part 13 An area extending horizontally is included in the lower surface 13a.

  By providing such a bulging portion 13, the portion where the bulging portion 13 is provided in the upper portion 11 of the middle foot 7 becomes thicker and more rigid as much as it bulges than the portion below it. Since the thickness of the foot 7 is generally smaller on the lower side, as a result, the deformed space in the mold of the central portion 10 and the lower portion 12 of the middle foot 7 and the flexibility higher than the upper portion 11 are obtained. Is secured and the releasability is improved. Moreover, since the upper part 11 of the middle leg 7 after cooling solidification becomes difficult to bend by the bulging part 13, the sealing performance can be improved. Therefore, it is not necessary to increase the undercut amount so much in order to improve the sealing performance, and even if the undercut amount is large to some extent, it has an excellent mold releasability as described above, so that there is an extra mold for molding. Therefore, the cap can be formed and manufactured at a low cost.

  In addition, in this cap, the central portion 10 that is in close contact with the container mouth M is thinned, and this thinning increases the flexibility of the central portion 10 and improves the operability by reducing the cap opening torque of the cap body 1. It is also possible to make it.

  Further, in the closed state, the middle foot 7 is subjected to strong stress due to its own elastic restoring force, but the central portion 10 that forms the sealing surface of the middle foot 7 has an outer peripheral surface with a straight cross section and downward. The inner peripheral surface gradually decreases in diameter, and the wall thickness does not change greatly from top to bottom, so that the strain force is distributed almost uniformly over the entire surface and the container mouth M is excellent over the entire sealing surface (outer peripheral surface). Can be sealed.

  The cap only needs to be configured to exhibit the above functions (actions). For example, the cap can be made of, for example, polypropylene (homo, block) having excellent flexibility and low frictional resistance. , Random, etc.), polyethylene (high density (HD), LL (Linear Low Density), low density (LD), etc.) can be used as a base resin, and can be molded by ordinary injection molding or compression molding.

  In addition, this invention is not limited to said embodiment at all, Of course, it can change and implement variously in the range which does not deviate from the summary of this invention. For example, the following modifications can be given.

  The cap of the above embodiment has a three-point seal structure with the middle foot 7, the annular rib 8 and the outer foot 9, but is not limited thereto, for example, either the annular rib 8 or the outer foot 9 or You may make it not provide both.

  In the above-described embodiment, the outer peripheral surface of the central portion 10 of the middle foot 7 hangs down. However, the present invention is not limited thereto. For example, the outer peripheral surface of the upper portion 11 of the middle foot 7 has a lower degree than the outer peripheral surface. The diameter may be increased toward the lower side, or the diameter may be reduced toward the lower side at a moderate (smaller) degree than the outer peripheral surface of the lower part 12 of the middle foot 7.

  In the above embodiment, the bulging portion 13 is provided in the central portion of the upper portion 11 of the middle foot 7. However, the embodiment is not limited thereto, and for example, the bulging portion 13 is provided at the lower end portion of the upper portion 11 of the middle foot 7. Also good. In addition, the upper portion 11 of the middle leg 7 may be provided with two or more bulging portions 13, and in this case also, the inner peripheral surface of the upper portion 11 is configured to have a diameter decreasing upward. From the point of view, it is preferable.

  In the above embodiment, in order to improve the sealing performance, the inner surface (lower surface) of the top wall 5 connected to the inner side of the middle foot 7 is formed so that the middle foot 7 after being cooled and solidified is not easily bent inward. The inner wall (lower surface) occupying between the middle foot 7 and the annular rib 8 is, for example, about 0.1 mm lower (in other words, the portion occupying the inner side of the middle foot 7 in the ceiling wall 5). (Thickness is made to be about 0.1 mm thicker than the thickness of the portion occupying just outside the middle foot 7), but not limited to this, for example, the above height difference (thickness difference) is not provided. May be.

  In the above embodiment, the thickness of the upper portion 11 and the lower portion 12 of the middle foot 7 decreases downward, whereas the thickness of the central portion 10 is gentler than the thickness of the upper portion 11 and the lower portion 12. However, the present invention is not limited to this, and the wall thickness of the central portion 10 may be the same up and down.

  Needless to say, the above modifications may be combined as appropriate.

DESCRIPTION OF SYMBOLS 1 Cap main body 2 Bridge 3 Band 4 Flap 5 Top wall 6 Skirt wall 7 Middle foot 8 Annular rib 9 Outer foot 10 Center part 11 Upper part 12 Lower part 13 Swelling part 13a Lower surface d Radius difference e Width M Container mouth part M1 Annular protrusion w width

Claims (6)

A synthetic resin cap provided with a top wall and a skirt wall hanging from the outer periphery of the top wall, and screwed into the container mouth;
On the inner surface of the top wall, an annular middle leg that is in close contact with the inner peripheral surface of the container mouth is continuously provided, and the middle leg is configured to have a maximum outer diameter at the center, and A bulging portion that bulges inward is formed at the upper part of the middle leg, and the portion above the bulging part in the middle leg is thicker toward the upper side ,
The outer peripheral surface of the upper part of the middle foot expands downward, and the outer peripheral surface of the lower part of the middle foot shrinks downward, and the outer peripheral surface of the central part of the middle foot becomes a sealing surface, The upper and lower parts of the middle leg do not adhere to the container mouth,
In addition, the bulging portion is not provided in the middle portion and the lower portion of the middle foot
Furthermore, a synthetic resin cap characterized in that a lower surface of a portion of the top wall that is connected immediately inside the middle foot is lower than a lower surface of a portion that occupies just outside the middle foot . The outer peripheral surface, drooping either, or synthetic resin cap according to claim 1 which diameter is downwardly a smaller extent than the outer peripheral surface of the lower portion of the front Symbol central portion of the metatarsal.   The degree to which the portion forming the lower surface of the bulging portion on the inner circumferential surface of the middle foot expands downward is continuous with the upper and lower sides of the lower surface of the bulging portion on the inner circumferential surface of the middle foot. The synthetic resin cap according to claim 1 or 2, wherein the cap is larger than the same degree of parts.   The synthetic resin cap according to claim 1, wherein a thickness of the central portion is 0.85 to 0.95 mm.   The synthetic resin cap according to claim 1, wherein a width of the bulging portion in the bulging direction is 0.1 mm or more. The minimum outer diameter of the upper part of the middle foot is equal to or smaller than the inner diameter of the container mouth part, and the radius difference between the maximum outer diameter of the central part and the minimum outer diameter of the upper part is 0.8 mm or less. Synthetic resin cap.