resin cap

Abstract

In a resin cap with a so-called one-piece structure in which the cap body and the sealing part are integrally molded, the localized increase in wall thickness around the sealing part is suppressed. [Solution] A resin cap has a structure in which a cap body 2 having a top plate portion 4 and a side wall portion 5 connected to the peripheral edge portion 4c of the top plate portion 4 and a sealing portion 3 provided on the back surface 4b side of the top plate portion 4 are integrally molded, and is attached to the mouth of a container so as to cover the mouth with the top plate portion 4 and the side wall portion 5, and the sealing portion 3 is in close contact with the mouth when attached to the mouth, and the peripheral edge portion 4c of the top plate portion 4 is provided with a stepped portion 15 that is recessed toward the sealing portion 3 side in the axial direction of the cap 1 when compared with the radially central region R on the surface 4a of the top plate portion 4.

Description

Technical Field

[0001] The present invention relates to a resin cap used for sealing the mouth of a beverage container or the like.

Background Art

[0002] As a resin cap used for sealing the mouth of a beverage container or the like, there is known a resin cap having a so-called two-piece structure in which a seal member called an inner stopper is combined on the back side of the top plate portion of a cap body in which the top plate portion and the side wall portion are integrally formed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As an alternative to two-piece resin caps, a one-piece resin cap in which the cap body and seal are integrally molded is being considered. When designing such a one-piece cap, it becomes necessary to match the external dimensions of the cap to those of the two-piece cap, as existing manufacturing lines for beverage products and the like are configured to accommodate two-piece resin caps. However, simply integrating the cap body and seal can result in a thicker section around the seal where the wall thickness increases. In this case, the time required to cool the thicker section after molding increases, and consequently, the time required to demold the molded product also increases, worsening molding efficiency. In addition, the wall thickness of the inner and outer rings of the seal is relatively small, and these inner and outer rings cool down faster than the thicker section. Therefore, if the inner or outer ring has an undercut section that engages with the mold in the demolding direction, when the thicker section has cooled to the required extent, the undercut section may cool and harden excessively, potentially making it difficult to remove the undercut section from the mold.

[0005] Therefore, the present invention aims to provide a resin cap that can suppress a localized increase in wall thickness around the sealing portion, even when employing a so-called one-piece structure in which the cap body and the sealing portion are integrally molded. [Means for solving the problem]

[0006] A resin cap according to one aspect of the present invention has a structure in which a cap body portion having a top plate portion and a side wall portion connected to the peripheral edge of the top plate portion and a sealing portion provided on the back side of the top plate portion are integrally molded, and is attached to the opening of a container so as to cover the opening with the top plate portion and the side wall portion, and the sealing portion is in close contact with the opening when attached to the opening, and the peripheral edge of the top plate portion is provided with a stepped portion that is set back toward the sealing portion in the axial direction of the cap when compared with the area on the radial center side of the surface of the top plate portion. [Brief explanation of the drawing]

[0007] [Figure 1] A half-cross-sectional view of a cap according to one embodiment of the present invention. [Figure 2] Plan view of the cap in Figure 1. [Figure 3] A diagram showing an example of a two-piece cap, as shown in the reference example, attached to the mouth of a container. [Figure 4] A plan view of the cap according to a modified example shown in Figure 2. [Modes for carrying out the invention]

[0008] Figures 1 and 2 show a resin cap according to one embodiment of the present invention. The illustrated cap 1 is constructed as a so-called one-piece cap, in which the cap body 2 and the sealing part 3 are integrally molded. The material of the cap 1 is the same as that of existing resin caps. For example, polypropylene resin or polyethylene resin can be used as the material for the cap 1. Figure 1 is drawn as a half-cross-sectional view, with the right side showing the external appearance of the cap 1 and the left side showing the cross-section of the cap 1, separated by the axis AX of the cap 1. The axis AX is an axis that passes through the center of the top surface 1a of the cap 1 and is perpendicular to the top surface 1a. Hereinafter, the direction of the axis AX will be referred to as the axial direction of the cap 1, the upper part of Figure 1 will be referred to as the upper part of the cap 1, and the lower part of Figure 1 will be referred to as the lower part of the cap 1.

[0009] The cap body 2 has a top plate portion 4 and a side wall portion 5 connected to the peripheral edge portion 4c of the top plate portion 4. As is clear from Figure 2, the top plate portion 4 is generally a circular flat plate. The surface 4a of the top plate portion 4 constitutes the top surface 1a of the cap 1. The underside 4b of the top plate portion 4 faces the mouth of the container when the cap 1 is attached to the mouth of the container. The side wall portion 5 is cylindrical and encircles the top plate portion 4. As shown in Figure 1, the outer circumference of the side wall portion 5 is provided with a so-called knurled shape, in which protrusions and grooves extending in the axial direction of the cap 1 are alternately arranged in the circumferential direction of the cap 1 for the purpose of preventing slippage, etc. On the inner circumference of the side wall portion 5, there is a female screw portion 6 that engages with the male screw portion formed on the mouth of the container to be sealed. Below the side wall portion 5, there is a TE ring 7 for checking whether or not it has been opened. The TE ring 7 is molded to be connected to the side wall portion 5 via a plurality of connecting portions 8. When the cap 1 is opened, the connecting portion 8 breaks, separating the TE ring 7 from the side wall portion 5. The outer diameter of the TE ring 7 gradually increases as it moves away from the side connected to the cap body portion 2.

[0010] The sealing portion 3 is provided on the underside 4b of the top plate portion 4. The sealing portion 3 has an inner ring 10 extending downward from the underside 4b of the top plate portion 4, an outer ring 11 extending downward at a position outside the inner ring 10, and a sealing surface 12 extending generally horizontally between the inner ring 10 and the outer ring 11. The inner ring 10, the outer ring 11, and the sealing surface 12 form a space that receives the mouth of the container, and the sealing portion 3 is configured to seal the mouth by making close contact with the mouth that fits into this space. Specifically, when the cap 1 is attached to the mouth of the container, the inner ring 10 makes close contact with the inner circumferential surface of the mouth, the outer ring 11 makes close contact with the outer circumferential surface of the mouth, and the sealing surface 12 makes close contact with the top surface of the mouth.

[0011] The inner ring 10 has an enlarged diameter portion 10a formed at its tip, that is, at the lower end of Figure 1, which bulges outward in the outer diameter direction. When the mold is removed from the cap 1 in the direction shown below Figure 1, that is, when the mold is removed downward in Figure 1 with the cap 1 as the reference point, the enlarged diameter portion 10a becomes a so-called undercut portion. Therefore, in order to remove the cap 1, it is necessary to elastically deform the inner ring 10 so that the enlarged diameter portion 10a can be removed from the mold.

[0012] The peripheral edge 4c of the top plate portion 4 is provided with a stepped portion 15 that recedes toward the seal portion 3 in the axial direction of the cap 1, compared to the central region R of the surface 4a of the top plate portion 4. Furthermore, with respect to the radial direction of the cap 1 (left-right direction in Figure 1), at least a portion of the stepped portion 15 is provided so that it is located on the outer circumference side of the cap 1, i.e., on the side of the side wall portion 5, rather than on the inner circumference of the seal portion 3, i.e., the inner surface of the inner ring 10. As an example, the stepped portion 15 is formed to have a cross-sectional shape that combines an inclined surface 15a that gradually recedes downward as it approaches the outer circumference of the cap 1, starting from approximately the same position as the seal surface 12 in the radial direction of the cap 1, and a flat surface 15b that extends roughly horizontally from the inclined surface 15a and connects to the rounded radius portion 5a at the upper end of the side wall portion 5. In Figure 1, the range of the stepped portion 15 is indicated by the symbol S. As is clear from Figure 2, the stepped portion 15 is provided to encircle the peripheral edge 4c of the top plate portion 4. The cross-sectional shape of the stepped portion 15 is approximately constant regardless of its position in the circumferential direction. However, it is not necessarily required that the cross-sectional shape of the stepped portion 15 be constant. The cross-sectional shape of the stepped portion 15 may be appropriately changed according to its position in the circumferential direction.

[0013] The cap 1, configured as described above, is attached to the mouth of the container by screwing the female thread portion 6 on the inner circumference of the side wall portion 5 onto the male thread portion provided at the mouth of the container, thereby covering the mouth of the container with the top plate portion 4 and the side wall portion 5. When attached to the mouth, the inner ring 10, outer ring 11, and sealing surface 12 of the sealing portion 3 each make close contact with the mouth of the container, thereby sealing the mouth of the container.

[0014] The stepped portion 15 of the cap 1 is provided to reduce the thickness of the cap 1 at the peripheral edge 4c of the top plate portion 4 located above the sealing portion 3, compared to the case where the stepped portion 15 is not provided. The stepped portion 15 is intended to solve the problems that arise when ensuring compatibility with conventional two-piece resin caps. The significance of the stepped portion 15 will be explained below with reference to Figure 3.

[0015] Figure 3 shows an example of a two-piece resin cap 100, which is a reference example of a cap 1 according to this embodiment that can be replaced, attached to the mouth 201 of the container 200. The resin cap 100 has a structure that combines a cap body 110 and a sealing member 120. Both the cap body 110 and the sealing member 120 are resin molded products, but they are separate parts manufactured in different processes. The sealing member 120 is positioned on the underside of the top plate portion 111 of the cap body 110. The female thread portion 113 of the side wall portion 112 of the cap body 110 is screwed into the male thread portion 202 provided on the mouth 201 of the container 200, thereby attaching the cap 100 to the mouth 201. In this state, the inner ring 121 of the sealing member 120 is in close contact with the inner circumferential surface 203 of the opening 201, the outer ring 122 is in close contact with the outer circumferential surface 204 of the opening 201, and the sealing surface 123 is in close contact with the top surface 205 of the opening 201. The sealing structure of the opening is the same for cap 100 in Figure 3 and cap 1 in Figure 1. Therefore, when cap 1 is attached to the opening 201, the inner ring 10 of the sealing part 3 is in close contact with the inner circumferential surface 203 of the opening 201, the outer ring 11 is in close contact with the outer circumferential surface 204 of the opening 201, and the sealing surface 12 is in close contact with the top surface 205 of the opening 201.

[0016] On the other hand, in order to replace the two-piece cap 100 in Figure 3 with the cap 1 in Figure 1, it is necessary to set the female thread portion 6 of cap 1 to be the same shape and size as the female thread portion 113 of cap 100, and to set the seal portion 3 to a shape that can ensure the same sealing function as the seal member 120. In addition, the dimensions of each part of cap 1 must be matched with those of the two-piece cap 100 from which it will be replaced. For example, the outer diameter of the cap body portion 2, the maximum diameter of the TE ring 7, and the total height of cap 1 including the TE ring 7 must be matched with cap 100. If these dimensions do not match, it will be difficult to share equipment used for transporting and handling the cap itself or the container sealed by the cap, and equipment upgrades will be necessary.

[0017] Furthermore, it is necessary to ensure that the position of the top surface 1a of cap 1 when it is attached to the container matches the position of the top surface of the two-piece cap 100 when it is attached. To achieve this, the thickness Ta from the top surface 1a of cap 1 to the sealing surface 12 of the sealing portion 3 must match the thickness Tb from the top surface 100a of cap 100 to the sealing surface 123 of sealing member 120 in Figure 3. In other words, the thickness Ta of cap 1 in Figure 1 must be set to the sum of the thickness of the top plate portion 111 of the cap body 110 in cap 100 in Figure 3 and the thickness of the portion of sealing member 120 excluding the inner ring 121 and outer ring 122. As a result, the wall thickness of cap 1 increases relatively around the sealing portion 3. Such problems arise specifically when attempting to replace a two-piece cap with a one-piece cap.

[0018] To solve the above-mentioned problems, in this embodiment of the cap 1, a stepped portion 15 is provided on the peripheral edge 4c of the top plate portion 4, thereby relatively reducing the wall thickness around the seal portion 3 compared to the case where the stepped portion 15 is not provided, and thereby suppressing the localized increase in wall thickness around the seal portion 3. In particular, with respect to the radial direction of the cap 1, by providing the stepped portion 15 on the outer circumference side of the cap 1 beyond the lower end of the inner ring 10 of the seal portion 3, it is possible to effectively suppress the increase in wall thickness associated with the addition of the seal portion 3. However, with respect to the radial direction of the cap 1, the stepped portion 15 does not necessarily have to be limited to the area on the outer circumference side of the cap 1 beyond the inner circumferential surface of the inner ring 10 of the seal portion 3. As long as at least a part of the stepped portion 15 is located in the area on the outer circumference side of the inner circumferential surface of the inner ring 10, the stepped portion 15 may be provided so as to extend radially towards the center beyond the inner circumferential surface of the inner ring 10.

[0019] As described above, by providing the stepped portion 15, the time required for the temperature around the seal portion 3 to decrease to a level necessary for demolding the cap 1 after molding can be relatively shortened. This shortens the waiting time until the molded cap 1 is demolded, improving the manufacturing efficiency of the cap 1. When the enlarged diameter portion 10a of the inner ring 10 becomes a so-called undercut portion, shortening the waiting time until demolding ensures adequate flexibility of the inner ring 10 during demolding, reducing or eliminating the risk of the inner ring 10 becoming too cold and difficult to remove from the mold. Easier removal of the inner ring 10 also has the effect of improving dimensional accuracy by suppressing irreversible deformation of the inner ring 10 during mold removal.

[0020] In the above-described cap 1, not only the inner ring 10 but also the female screw portion 6 becomes an undercut portion during mold extraction. When the seal portion 3 is molded integrally with the cap body portion 2, the resistance exerted by the female screw portion 6 when extracting the mold is such that the vicinity of the seal portion 3 has a complex shape, so that the upper region closer to the seal portion 3 in the axial direction of the cap 1 becomes relatively larger than the lower region farther from the seal portion 3. Depending on the degree of resistance during mold extraction, so-called screw sag may occur, in which the female screw portion 6 is deformed so as to hang down in the extraction direction (downward in FIG. 1), and the possibility of this is relatively high in the region where the female screw portion 6 is close to the seal portion 3. In order to suppress the occurrence of such screw sag, it is effective to set the height of the thread of the female screw portion 6, that is, the amount of protrusion of the thread from the thread bottom toward the radial center side when the inner peripheral surface of the side wall portion 5 is the thread bottom of the female screw portion 6, to be smaller in the region closer to the seal portion 3 than in the region farther from the seal portion 6. For example, by gradually reducing the height of the thread of the female screw portion 6 as it approaches the seal portion 3, it is possible to suppress the occurrence of screw sag in the range close to the seal portion 3. Alternatively, the height of the thread within a certain range in the axial direction from the seal portion 3 may be set to be smaller by a certain value than the height of the thread in the portion farther from the seal portion 3 beyond that range. By suppressing the screw sag of the female screw portion 6, it is also possible to improve the dimensional accuracy of the female screw portion 6.

[0021] In the above-described embodiment, since the step portion 15 is provided so as to go around the peripheral edge portion 4c of the top plate portion 4, it is possible to uniformly exhibit the effect of reducing the wall thickness by the step portion 15 in the circumferential direction of the cap 1. However, the step portion 15 does not necessarily have to be provided so as to go around the peripheral edge portion 4c of the top plate portion 4. For example, as shown in FIG. 4, a plurality of step portions 15 may be arranged along the circumferential direction. In this case, even if the boundary portion 16 sandwiched between the step portions 15 is formed flush with the surface 4a of the top plate portion 4, if the circumferential width of the boundary portion 16 is set small enough not to substantially affect the time required for cooling the periphery of the seal portion 3, the effects of the present invention can be achieved.

[0022] The present invention is not limited to the above-described forms and may be implemented in appropriately modified or changed forms. For example, the shape and size of the step portion 15 may be appropriately changed as long as the thickness around the seal portion 3 can be reduced to a necessary extent. The seal portion 3 is not necessarily limited to the example having the inner ring 10, the outer ring 11, and the seal surface 12. As long as the above-described thickness Ta matches the thickness Tb of the original cap 100 and the mouth of the container can be sealed to a necessary extent, the shape of the seal portion may be appropriately set.

[0023] Various aspects of the present invention derived from each of the above-described embodiments and modification examples will be described below. In the following description, corresponding components illustrated in the accompanying drawings are appended in parentheses to facilitate understanding of each aspect of the present invention, but the present invention is not limited to the illustrated forms thereby.

[0024] A resin cap (1) according to one aspect of the present invention has a cap main body portion (2) having a top plate portion (4) and a side wall portion (5) continuous with a peripheral edge portion (4c) of the top plate portion, and a seal portion (3) provided on the back surface (4b) side of the top plate portion are integrally molded, and is mounted on the mouth of the container so as to cover the mouth with the top plate portion and the side wall portion, and when mounted on the mouth, the seal portion adheres closely to the mouth, and a step portion (15) that retreats toward the seal portion side in the axial direction of the cap is provided at the peripheral edge portion of the top plate portion when compared with a region (R) on the radially central side of the surface (4a) of the top plate portion.

[0025] According to the above embodiment, the wall thickness around the seal portion is relatively reduced compared to the case where no step portion is provided, thereby suppressing the localized increase in wall thickness around the seal portion. Therefore, the time required for the temperature around the seal portion to decrease to a level necessary for demolding the cap after molding can be relatively shortened. This shortens the waiting time until the molded cap is demolded, improving the manufacturing efficiency of the cap. When at least a part of the seal portion is a so-called undercut portion, shortening the waiting time until demolding ensures adequate flexibility of the seal portion during demolding, reducing or eliminating the risk of the seal portion becoming too cold and difficult to remove from the mold. By making it easier to remove the seal portion, it is also possible to suppress irreversible deformation of the seal portion during mold removal and improve dimensional accuracy.

[0026] In the above embodiment, the stepped portion may be provided so as to encircle the peripheral edge. In this case, the thickness reduction effect of the stepped portion can be evenly exerted in the circumferential direction of the cap.

[0027] In the above embodiment, at least a portion of the stepped portion may be located on the outer periphery of the top plate portion with respect to the radial direction, rather than on the inner periphery of the seal portion. This makes it possible to effectively suppress the increase in thickness that occurs when adding the seal portion.

[0028] A female thread portion (6) is provided on the inner circumference of the side wall portion, and the height of the threads of the female thread portion in the radial direction may be set to be smaller in the region closer to the seal portion with respect to the axial direction compared to the region further from the seal portion. The threads of the female thread portion become an undercut portion when the mold is removed, and when the seal portion is integrally molded, the area near the seal portion has an intricate shape, so the mold removal resistance in the region closer to the seal portion is relatively greater than in the region further from the seal portion. As a result, there is a risk of screw drooping, in which the threads of the female thread portion deform to droop in the direction of mold removal. In contrast, by setting the height of the threads as described above, it is possible to reduce the removal resistance of the thread portion in the region closer to the seal portion and suppress the risk of screw drooping. [Explanation of Symbols]

[0029] 1 cap 2. Cap body 3. Sealing part 4. Top panel 4a Surface of the top panel 4b Underside of the top panel 4c Peripheral edge of the top panel 5 Side wall section 15 Stepped section 200 containers 201 Mouth

Claims

1. A resin cap having a cap body having a top plate portion and a side wall portion connected to the peripheral edge of the top plate portion, and a sealing portion provided on the back side of the top plate portion, which are integrally molded, and which is attached to the opening of a container so as to cover the opening with the top plate portion and the side wall portion, and the sealing portion is in close contact with the opening when attached to the opening, A resin cap having a stepped portion on the peripheral edge of the top plate portion that recedes toward the sealing portion side in the axial direction of the cap compared to the radially central region of the surface of the top plate portion.

2. The resin cap according to claim 1, wherein the stepped portion is provided so as to encircle the peripheral edge.

3. The resin cap according to claim 1 or 2, wherein at least a portion of the stepped portion is located on the outer circumference side of the top plate portion with respect to the radial direction, compared to the inner circumference of the sealing portion.

4. A resin cap according to claim 1 or 2, wherein a female threaded portion is provided on the inner circumference of the side wall portion, and the height of the threads of the female threaded portion in the radial direction is set to be smaller in the region closer to the seal portion with respect to the axial direction compared to the region further from the seal portion.

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