cap

Abstract

Provided is a cap capable of improving airtightness without an increase in opening torque and closing torque. The cap is provided with: a shell 1 having a top wall 3, a sidewall 4 extending downward from the peripheral edge of the top wall 3, and a female thread 5 formed on the sidewall 4 and to be screwably engaged to a male thread M1 of a container mouth part M; and a gasket 2 held inside the shell 1 and sealing the container mouth part M. The gasket 2 is provided with a top plate 10 for covering the container mouth part M and a shank 11 disposed continuing from the lower surface of the top plate 10 and coming into close contact with the inner peripheral surface of the container mouth part M, and the center portion of the top plate 10 is displaced downward more significantly than the peripheral edge portion thereof as the top plate 10 elastically deforms when being pushed downward by the top wall 4 during closing.

Description

Technical Field

[0001] The present invention relates to a two-piece cap having, for example, a shell and a packing separate therefrom.

Background Art

[0002] A two-piece cap having a shell and a packing (so-called two-piece cap) generally has a structure as shown in FIG. 3 (see, for example, Patent Document 1). That is, the cap shown in FIG. 3 includes a shell 1 and a packing 2 held in the shell 1 and sealing the container opening M. The packing 2 is provided with a middle foot 11 that is fitted into the container opening M when the cap is closed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a cap, it is important for maintaining a high airtightness of the container that the outer peripheral surface of the middle foot 11 adheres strongly to the inner peripheral surface of the container opening M when the cap is closed. Therefore, conventionally, the adhesion of the outer peripheral surface of the middle foot 11 to the inner peripheral surface of the container opening M has been adjusted mainly by adjusting the amount of bulging of the outer peripheral surface of the middle foot 11 outward. However, when the amount of bulging is increased, although the adhesion and thus the airtightness are improved, there is a problem that an increase in the closing torque leading to problems such as poor capping and an increase in the opening torque directly resulting in a decrease in usability are also caused.

[0005] The present invention has been made in view of the above matters, and an object thereof is to provide a cap capable of improving airtightness while suppressing an increase in the opening torque and the closing torque.

Means for Solving the Problems

[0006] To achieve the above objective, the cap according to the present invention comprises a shell having a top wall and side walls hanging down from the periphery of the top wall, with a female thread formed on the side wall that screws onto a male thread of the container opening, and a resin packing held within the shell to seal the container opening, wherein the packing has a top plate covering the container opening, a middle foot connected to the lower surface of the top plate and in close contact with the inner circumferential surface of the container opening, and a bent portion that bends downward from the periphery of the top plate and in close contact with the outer circumferential surface of the container opening, and when closed, the top plate, which is pressed downward by the top wall, elastically deforms, and the central part of the top plate is displaced significantly lower than the peripheral part, and the middle foot is configured to elastically deform so that its lower end expands in diameter in conjunction with this elastic deformation, and in the closed state, the portion of the top plate between the middle foot and the bent portion is sandwiched between the upper end of the container opening and the top wall of the shell. Furthermore, the lower surface of the top wall is formed as a curved surface that is convex downwards as a whole, and the upper surface of the top plate is formed as a curved surface that is convex upwards as a whole. (Claim 1).

[0007]

[0008] In the cap described above, a biasing portion protruding inward toward the shell may be provided near the boundary between the top wall and the side wall of the shell, or a biasing portion protruding outward toward the outer surface of the packing may be provided (claim) Section 2 ). [Effects of the Invention]

[0009] The present invention provides a cap that can improve airtightness while suppressing an increase in both opening and closing torque.

[0010] In other words, in the cap of the present invention as claimed in each claim, when closing, the center of the top plate of the packing undergoes elastic deformation that displaces significantly lower than the peripheral edge, and the middle foot attempts to elastically deform so that its lower end (open end) expands in diameter. As a result, the outer surface of the middle foot adheres strongly to the inner surface of the container opening, thereby improving airtightness. Moreover, since it is not necessary to increase the outward bulge of the outer surface of the middle foot as in the conventional method, it is possible to suppress an increase in closing torque and opening torque, and in fact contribute to reducing them.

[0011] Claim Item 1 The cap of the invention described herein can ensure the effectiveness of the aforementioned improvements in airtightness and other effects.

[0012] In caps with a biasing portion, there is a concern that during closing, as the container opening enters between the middle foot and the bent portion, the bent portion, which is biased by the biasing portion, will come into contact with the outer circumference of the upper end of the container opening, making it difficult to close. Section 2 In the cap of the invention described herein, when the cap is closed, the central part of the top plate of the packing undergoes elastic deformation that displaces significantly lower than the peripheral part, causing the lower end (tip) of the bent portion to expand in diameter, which is expected to make it easier to close. [Brief explanation of the drawing]

[0013] [Figure 1] A perspective view showing the configuration of a cap according to one embodiment of the present invention and the container opening to which it is attached. [Figure 2] (A) and (B) are semi-longitudinal end views showing the configuration of the main parts of the cap shell and packing. [Figure 3] This is a semi-vertical cross-sectional view showing the configuration of the aforementioned cap. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings.

[0015] The cap in this example is to be mounted on the container mouth M as shown in FIGS. 1 and 3, and includes a shell 1 made of a polypropylene-based resin and formed by injection molding or the like, and a packing 2 made of a polyethylene-based resin and formed by injection molding or the like. The container having the container mouth M is, for example, a PET bottle and contains contents such as carbonated beverages and soft drinks.

[0016] As shown in FIGS. 1 and 3, the shell 1 has a top wall 3 circular in plan view and a substantially cylindrical side wall 4 hanging down from the periphery of the top wall 3, and a female thread 5 that screws into the male thread M1 of the container mouth M is formed on the side wall 4.

[0017] Further, the cap in this example is a pilfer-proof cap, and an annular band (tamper evidence band) 8 is connected to the lower side of the side wall 4 via a plurality of breakable bridges 7, and a locking piece (flap) 9 that engages with an annular projection (bead portion) M2 of the container mouth M is provided on the band 8.

[0018] On the other hand, the packing 2 has a top plate 10 circular in plan view that covers the container mouth M in a closed state, a substantially cylindrical middle leg 11 that is concentrically connected to the lower surface of the top plate 10 and adheres to the inner peripheral surface of the container mouth M, and a bent portion 12 that bends downward from the periphery of the top plate 10 and adheres to the outer peripheral surface of the container mouth M, and is configured to be able to seal the container mouth M (see FIG. 3).

[0019] And this packing 2 is used while being held in the shell 1. Specifically, the uppermost part of the female thread 5 of the shell 1 is used as a packing retention prevention part, and when the bent portion 12 of the packing 2 is pushed between this packing retention prevention part and the top wall 3, the packing 2 is held in a state where it can move relative to the shell 1 in the direction of the central axis of the shell 1 and around the central axis.

[0020] In the cap with such a structure, during the closing process, the locking piece 9 of the shell 1 gets over the annular protrusion M2, and in the closed state where the closing operation is completed, the locking piece 9 elastically returns to a posture where it can be locked below the annular protrusion M2. Also, in the closed state, the middle leg 11 of the packing 2 is fitted into the opening of the container mouth part M, and the part (connection part) 13 between the middle leg 11 and the bent part 12 on the top plate 10 is in a state of being sandwiched between the upper end of the container mouth part M and the top wall 3 of the shell 1.

[0021] Furthermore, in this example, in order to firmly adhere the bent part 12 to the outer peripheral surface of the container mouth part M in the closed state, an annular biasing part 14 (see FIG. 3) that protrudes toward the inside of the shell 1 is provided near the boundary between the top wall 3 and the side wall 4 of the shell 1. In the closed state, the biasing part 14 biases the bent part 12 downward, and this biasing force is surely and efficiently converted into a force that presses the bent part 12 against the outer peripheral surface of the container mouth part M.

[0022] And in this example, as shown in FIGS. 2(A) and (B), the lower surface of the top wall 3 of the shell 1 is formed into a "curved surface that is convex downward as a whole", and the upper surface of the top plate 10 of the packing 2 is formed into a "curved surface that is convex upward as a whole". Thereby, when closing, the top plate 10 of the packing 2 whose upper surface is pressed downward by the lower surface of the top wall 3 of the shell 1 elastically deform, and the central part of the top plate 10 is configured to be displaced downward more greatly than the peripheral part. Note that "curved surface that is convex downward as a whole" and "curved surface that is convex upward as a whole" respectively mean allowing there to be partially regions that do not form a "curved surface that is convex downward" and a "curved surface that is convex upward", and specific examples of the regions that do not form a "curved surface that is convex downward" and a "curved surface that is convex upward" can include the concave parts 15 shown in FIGS. 2(B) and FIG. 3.

[0023] In the cap configured in this example, when the cap is closed, the center of the top plate 10 of the packing 2 undergoes elastic deformation, displacing significantly lower than the peripheral edge. As a result, the middle foot 11 attempts to elastically deform so that its lower end (open end) expands in diameter. This causes the outer surface of the middle foot 11 to adhere tightly to the inner surface of the container opening M, thereby improving airtightness. Moreover, since it is not necessary to increase the outward bulge of the outer surface of the middle foot 11 as in the conventional method, it is possible to suppress increases in closing torque and opening torque, and in fact contribute to reducing them.

[0024] Furthermore, in caps with the biasing portion 14 described above, there is a concern that when closing the cap, the biased bending portion 12 will come into contact with the outer circumference of the upper end of the container opening M as the container opening M enters between the middle foot 11 and the bending portion 12, making it difficult to close. However, in this example, when closing the cap, the center of the top plate 10 of the packing 2 undergoes elastic deformation, displacing significantly lower than the peripheral edge. As a result, the lower end (tip) of the bending portion 12 attempts to undergo elastic deformation to expand in diameter, which is expected to make it easier to close. Of course, in the closed state, the biasing of the biasing portion 14 causes the bending portion 12 to be in close contact with the outer circumference of the container opening M.

[0025] It should be noted that the present invention is not limited in any way to the embodiments described above, and can be implemented in various ways without departing from the spirit of the invention. For example, the following modifications can be given.

[0026] In the above embodiment, as shown in Figures 2(A) and (B), the lower surface of the top wall 3 of the shell 1 is formed as a "curved surface that is convex downward overall," and the upper surface of the top plate 10 of the packing 2 is formed as a "curved surface that is convex upward overall." This configuration causes the top plate 10 of the packing 2 to elastically deform when its upper surface is pressed downward by the lower surface of the top wall 3 of the shell 1 during closing, causing the central part of the top plate 10 to displace significantly lower than the peripheral part. However, the point is that when closing, the top plate 10 of the packing 2 is elastically deformed when its upper surface is pressed downward by the lower surface of the top wall 3 of the shell 1, causing the central part of the top plate 10 to displace significantly lower than the peripheral part, and the means to achieve this are not limited to the configurations shown in Figures 2(A) and (B).

[0027] For example, as shown in Figure 2(B), the upper surface of the top plate 10 of the packing 2 may be formed as an "overall upward-convex curved surface", while the lower surface of the top wall 3 of the shell 1 may be flat (planar), or it may be formed as an "overall upward-convex curved surface" that is gentler than the upper surface of the top plate 10 of the packing 2.

[0028] Alternatively, as shown in Figure 2(A), the lower surface of the top wall 3 of the shell 1 may be formed as a "curved surface that is convex downward overall," while the upper surface of the top plate 10 of the packing 2 may be flat (planar), or it may be formed as a "curved surface that is convex downward overall" that is gentler than the lower surface of the top wall 3 of the shell 1.

[0029] Alternatively, a downward-facing protrusion may be provided in the center of the lower surface of the top wall 3 of the shell 1, or an upward-facing protrusion may be provided in the center of the upper surface of the top plate 10 of the packing 2. In these cases, the size (height and width), position, number, and shape of the protrusions can be appropriately determined within a range in which, when the plug is closed, the top plate 10 of the packing 2, whose upper surface is pressed downward by the lower surface of the top wall 3 of the shell 1, elastically deforms, and the center of the top plate 10 is displaced significantly lower than the peripheral edge.

[0030] Alternatively, the outer diameter and angle of the intermediate leg 11 may be adjusted so that when the intermediate leg 11 is fitted into the opening of the container mouth M, the central part of the top plate 10 protrudes above the peripheral part (outside the opening), and when this protruding central part is pressed against the lower surface of the top wall 3 during closing, the elastically deformed central part of the top plate 10 is displaced significantly below the peripheral part. In this case, both the lower surface of the top wall 3 and the upper surface of the top plate 10 can be made flat (planar).

[0031] Furthermore, in the above embodiment, a biasing portion 14 is provided near the boundary between the top wall 3 and the side wall 4 of the shell 1, projecting inward in a wedge shape in a vertical cross-section view. However, the invention is not limited to this, and a biasing portion 14 projecting outward may be provided on the outer circumferential surface of the packing 2. In this case, the biasing portion 14 can be omitted from the shell 1, and the inner diameter near the boundary between the top wall 3 and the side wall 4 can be configured to gradually increase downward.

[0032] Needless to say, the above variations can be combined as appropriate. [Explanation of Symbols]

[0033] 1 Shell 2. Packing 3. Ceiling Wall 4 side wall 5 Female thread 7 Bridge 8 bands 9 Locking piece 10 Top plate 11 Midfoot 12 Bend section 13 Liaison Department 14. Encouraging part 15 recesses M Container opening M1 male screw M2 Annular process

Claims

1. A cap comprising a shell having a top wall and side walls hanging down from the periphery of the top wall, with female threads formed on the side walls that screw into male threads of the container opening, and a resin packing held within the shell and sealing the container opening, The packing comprises a top plate that covers the container opening, a middle leg connected to the underside of the top plate and in close contact with the inner circumferential surface of the container opening, and a bent portion that bends downward from the periphery of the top plate and in close contact with the outer circumferential surface of the container opening. When the cap is closed, the top plate, which is pressed downward by the top wall, undergoes elastic deformation, causing the central part of the top plate to be displaced significantly lower than the peripheral part. In conjunction with this elastic deformation, the middle foot is configured to attempt to undergo elastic deformation so that its lower end expands in diameter. In the closed state, the portion of the top plate between the middle leg and the bent portion is sandwiched between the upper end of the container opening and the top wall of the shell. The cap has a downwardly convex curved surface on the lower surface of the top wall and an upwardly convex curved surface on the upper surface of the top plate.

2. The cap according to claim 1, wherein a biasing portion is provided near the boundary between the top wall and the side wall of the shell, projecting inward toward the inside of the shell, or a biasing portion is provided on the outer circumferential surface of the packing, projecting outward toward the outside.

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