JP2013203419A - Synthetic resin cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic resin cap capable of reducing plug opening torque, while keeping high sealing performance.SOLUTION: A synthetic resin cap is provided with a top wall 5, and a skirt wall 6 suspended from the outer circumferential part of the top wall 5, and is threadedly fitted to a container opening portion, annular inner legs 7 contacting closely with an inner circumferential face of the container opening portion are adjacently provided in an inner face of the top wall 5, an outer circumferential face of an upper part 11 of the inner leg 7 is expanded diameter toward a lower side and an outer circumferential face of a lower part 12 of the inner leg 7 is contracted diameter toward the lower side, to make an outside diameter of the inner leg 7 maximum in the central part 10 of the inner leg 7, and an outer circumferential face of the central part 10 is suspended downwards, is expanded diameter toward the lower side at a degree more moderate than the outer circumferential face of the upper part 11, or is contracted diameter toward the lower side at a degree more moderate than the outer circumferential face of the lower part 12.

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, the outer peripheral surface of the middle foot in the natural state is from the upper part (base part) and the lower part (tip part) to the central part. It is possible to make a large squeeze outward as you 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, in such a cap, the tendency that the improvement in the sealing performance is directly reflected in the increase in the opening torque becomes remarkable. Therefore, in this cap, the amount of protrusion of the middle part of the middle foot to the outside is suppressed, and the opening torque is reduced by reducing the area of the middle part of the middle foot that is in close contact with the container mouth in the closed state. If it tries to do so, the deterioration of the sealing performance will become large, and considering the manufacturing error and the like, the range of the amount of protrusion that satisfies both the sealing performance and the opening torque has been extremely limited.

  That is, the cap has little room for further reducing the opening torque within a range where high sealing performance can be maintained due to its structure.

  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 reducing the opening torque while maintaining high sealing performance.

  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 outer diameter of the middle leg is maximized at the center of the middle leg. In addition, the outer peripheral surface of the upper part of the middle leg is expanded in diameter downward, and the outer peripheral surface of the lower part of the middle leg is decreased in diameter, and the outer peripheral surface of the central part is suspended, It is characterized in that the diameter is increased downward with a gentler degree than the outer peripheral surface of the upper part, or the diameter is reduced downward with a gentler degree than the outer peripheral surface of the lower part (Claim 1).

  In the synthetic resin cap, the thickness of the upper part and the lower part of the middle foot decreases downward, and the thickness of the central part is the same up and down, or the thickness of the upper part and the lower part It may be smaller in the downward direction at a slower degree (Claim 2).

  In the synthetic resin cap, 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 difference between the maximum outer diameter of the central part and the minimum outer diameter of the upper part of the middle foot is 0. It can be 8 mm or less (claim 3).

  In the synthetic resin cap, the vertical length of the central portion can be 0.5 to 2.0 mm.

  The said synthetic resin cap WHEREIN: The bulging part which bulges inward may be formed in the upper part of the said middle leg (Claim 5).

  In the present invention, a synthetic resin cap capable of reducing the opening torque while maintaining high sealing performance is obtained.

  That is, in the synthetic resin cap of the invention according to each claim of the present application, a seal surface that adheres well to the inner peripheral surface of the container mouth portion is obtained by the outer peripheral surface of the middle portion of the middle foot, and the seal surface is used to seal The performance can be improved. In addition, since the upper and lower portions of the middle foot are not in close contact with the container mouth, the opening torque does not increase excessively, and consequently the opening torque can be reduced. Further, the lower part of the middle leg whose outer peripheral surface is reduced in diameter downwards allows the middle leg to be smoothly inserted into the container mouth part at the time of closing.

  Under the closed condition, the middle leg is subjected to strong stress due to its own elastic restoring force. However, in the synthetic resin cap of the invention according to claim 2, since the thickness of the central portion forming the sealing surface of the middle leg does not change greatly in the vertical direction, the strain force is distributed substantially uniformly throughout. The container mouth can be satisfactorily sealed over the entire sealing surface (outer peripheral surface).

  In the synthetic resin cap of the invention according to claim 3, there is no large resistance when the cap is completely tightened with respect to the container mouth, and it is possible to prevent an increase in the closing torque and the opening torque, and an undercut By suppressing the amount, it is possible to reliably prevent the mold from becoming difficult.

  In the synthetic resin cap of the invention according to claim 4, the area of the sealing surface necessary for exhibiting the sealing performance is secured, and as a result, high sealing performance is secured.

  In the synthetic resin cap of the invention according to claim 5, by providing a bulging portion at the upper part (root part) of the middle foot, the part where the bulging part is provided at the upper part of the middle foot is lower than the part below it. If the wall thickness of the middle foot is smaller on the lower side as a whole, as a result, the mold will be released in the middle and lower molds of the middle foot. Since the flexibility higher than the deformation space and the upper part is ensured, the releasability 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.

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. It is sectional drawing which shows schematically the structure of the synthetic resin caps which concern on the modification of this invention. FIG. 6 is a detailed view of part A in FIG. 5.

  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 S 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) R of the central portion 10 can be set to 22.0 mm to 22.5 mm, for example, 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 r on the upper side of the upper part 11 is It is smaller than the inner diameter of the container mouth M. The difference d between the minimum outer diameter r of the upper part 11 and the outer diameter (maximum outer diameter) R of the central part 10 is 0.8 mm or less (preferably 0.2 mm to 0.5 mm). When the 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, the plugging torque and the opening torque are increased, and the undercut is excessively separated. This is because the tendency to make the mold difficult is remarkable. In addition, the width | variety of the up-down direction of the upper part 11 can be 1.6 mm, for example. Further, when the inner diameter of the container mouth M is 21.74 mm, the minimum outer diameter r 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, the inner peripheral surface of the middle leg 7 gradually increases in diameter toward the lower side. And the thickness of the center part 10 and the upper part 11 can be 0.85-0.95 mm (0.85 mm in this example), the root part (upper part of the upper part 11) of the middle leg 7, and the lower part 12 While the wall thickness decreases downward, the wall thickness of the central portion 10 decreases downward with a gentler degree than the thickness of the base portion of the middle foot 7 and the lower portion 12. .

  The cap configured as described above has the following effects. That is, in the closed state, the middle foot 7 is subjected to strong stress due to its elastic restoring force, but the central portion 10 that forms the sealing surface of the middle foot 7 is directed downward from the outer peripheral surface having a straight section. 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.

  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.

  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.

  As shown in FIGS. 5 and 6, a bulging portion 13 that bulges inward may be formed in the upper portion 11 of the middle foot 7. For example, 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 the illustrated example). The width e in the bulging direction of the portion 13 can be 0.1 mm to 0.4 mm (0.4 mm in the illustrated example). Further, in this case, the thickness of the portion above the bulging portion 13 (or the lower surface 13a of the bulging portion 13) in the middle leg 7 can be increased 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 the example shown in FIGS. 5 and 6, the bulging portion 13 is provided in the central portion of the upper portion 11 of the middle foot 7, but the bulging portion is not limited to this, for example, at the lower end portion of the upper portion 11 of the middle foot 7. 13 may be provided. 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 The bulging part 13a Lower surface d Difference e Width M Container mouth part M1 Annular protrusion w Width

Claims (5)

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,
The outer peripheral surface of the upper part of the middle foot is expanded downward, and the outer peripheral surface of the lower part of the middle foot is downward so that the outer diameter of the middle foot is maximized at the center part of the middle foot. The diameter is reduced toward
The outer peripheral surface of the central portion hangs down or increases in diameter downward at a gentler degree than the outer peripheral surface of the upper part, or decreases in diameter downward at a gentler degree than the outer peripheral surface of the lower part. A synthetic resin cap.   The thickness of the upper part and the lower part of the middle foot decreases downward, and the thickness of the central part is the same in the upper and lower parts, or lower than the thicknesses of the upper part and the lower part. The synthetic resin cap according to claim 1, which becomes smaller toward.   The minimum outer diameter of the upper part of the middle leg is equal to or smaller than the inner diameter of the container mouth part, and the difference between the maximum outer diameter of the central part and the minimum outer diameter of the upper part of the middle leg is 0.8 mm or less. The synthetic resin cap described in 1.   The synthetic resin cap according to claim 1, wherein a length of the central portion in the vertical direction is 0.5 to 2.0 mm.   The synthetic resin cap according to claim 1, wherein a bulging portion that bulges inward is formed at an upper portion of the middle foot.