JP2022176541A - screw cap - Google Patents

Abstract

To provide a screw cap capable of being formed by thermoforming from a sheet of resin, having resealability by screw engagement, and capable of developing liquid-tightness.SOLUTION: A drop-lid-shaped screw cap includes a skirt part. The skirt part includes a top surface, an inner side wall extending upward from the outer circumferential edge of the top surface, and a screw part connecting to the inner side wall through an annular part extending outwardly from the upper edge of the inner side wall. The inner side wall has an annular protruding part whose outer diameter is larger than the inner diameter of a mouth of a container part to be applied and is capable of elastic deformation in the radial direction of the cap.SELECTED DRAWING: Figure 2

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw cap, and more particularly to a screw cap that can be formed by thermoforming from a resin sheet, is lightweight, and can reliably exhibit liquid-tightness.

2. Description of the Related Art As screw caps applied to containers such as polyester bottles, resin screw caps are widely used, which are formed by integral molding of plastic and can exhibit liquid-tightness without using a liner or packing.
As such a cap made of resin, for example, Patent Document 1 below discloses a substantially cylindrical cap side wall portion having an inner thread and a sealing effect in the region of the mouth of the container by contacting the outside of the mouth of the container. A closure cap made of a plastic material used for closing the mouth of a container consisting of a cap top with a ring-shaped sealing lip that performs the inner diameter (A) of the lip (5) being sized larger than the outer diameter (B) of the container (2) and the cap top (4) being provided with retaining means for engaging the mouth of the container; When the closure cap is screwed on, the top of the container exerts a concentric pressing action, and at least the top of the cap is made elastic to press the top of the container as the retaining means is inserted into the mouth of the container. However, closure caps have been proposed in which the outer diameter of the top of the container is reduced so that the sealing lip can press against the outside of the mouth of the container.

Further, Patent Document 2 below discloses a resin screw cap in which a top surface and a skirt hanging down from the periphery of the top surface are integrally molded with plastic, and a screw thread is provided on the inner peripheral surface of the skirt. A screw cap is disclosed in which liquid-tightness is ensured by an inner ring and an outer ring hanging down from the inner surface and in close contact with the inner and outer surfaces of the mouth of the container.

JP-A-58-216552 Japanese Patent No. 3872546

The screw caps described in Patent Documents 1 and 2 above have high sealing performance and reliable liquid tightness, but because of their complicated structure, they are molded by injection molding or compression molding. Therefore, it has been difficult to easily form a thin and lightweight screw cap.
Further, when molding a multi-layered cap by injection molding or compression molding, it is not easy to spread the intermediate layer uniformly over the entire cap. Therefore, in such a conventional screw cap, it is difficult to improve the gas barrier properties of the cap by providing the gas barrier intermediate layer to reduce the thickness of the cap, and it is difficult to further reduce the weight of the cap. .
Furthermore, since the conventional screw cap has an inner ring and the like, if the top surface is made thin, the sealing performance is inevitably lowered, and it is difficult to further reduce the weight of the cap.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a screw cap that can be thermoformed from a resin sheet, has resealing properties due to screw engagement, and can exhibit liquid tightness. Another object of the present invention is to provide a screw cap that can be thinned and lightened even when molded by injection molding or compression molding.

According to the present invention, the top surface, the inner wall extending upward from the outer peripheral edge of the top surface, and the skirt portion provided with the screw portion are connected to the inner wall via the annular portion extending outward from the upper end of the inner wall. In a drop-lid-shaped screw cap consisting of A screw cap is provided.

In the screw cap of the present invention,
(1) the inner wall has a dogleg shape that is bent outward in the radial direction of the cap, and the annular protruding portion is a bent portion of the dogleg;
(2) a countersink portion is formed on the outer peripheral edge of the top surface;
(3) the top surface has an upper dome shape or a lower dome shape;
(4) A seal portion is formed on the upper portion of the skirt portion so as to be in close contact with the outer surface of the mouth portion of the container.
(5) made of synthetic resin;
(6) be applied to the bottle;
(7) molding by thermoforming using a synthetic resin sheet;
is preferred.

In the screw cap of the present invention, the inner wall has an annular protrusion with an outer diameter larger than the inner diameter of the mouth of the container to which it is applied, and is elastically deformable in the radial direction of the cap. Secondly, the annular protrusion presses the inner surface of the mouth of the container radially outward due to elastic deformation, so excellent sealing performance can be achieved.
In addition, by making the top surface dome-shaped, pressure resistance can be imparted, and deterioration of sealing performance due to deformation can be suppressed. Furthermore, it is possible to reduce the head space by adopting a drop-lid shape.
Further, by thermoforming the resin sheet, it becomes possible to easily form a thin and lightweight screw cap. In addition, by using a thin screw cap, the flexibility of the cap is improved, and the elastic deformation of the annular protrusion and the countersink is facilitated.

1 is a side sectional view of an example of a screw cap of the present invention; FIG. 2 is a partially enlarged side cross-sectional view showing a state in which the screw cap of FIG. 1 is applied to the mouth of a container; FIG. FIG. 4 is a partially enlarged side cross-sectional view showing another example of the screw cap of the present invention; FIG. 11 is a partially enlarged side cross-sectional view for explaining another aspect of the annular protrusion in the screw cap of the present invention; 3 is a partially enlarged side cross-sectional view showing a mode in which a countersink portion is not formed in the mode shown in FIG. 2; FIG.

The screw cap of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a side cross-sectional view of an example of the screw cap of the present invention. The screw cap, which is generally indicated by 1, roughly speaking, includes a top surface 2 that covers the opening of a container, and an outer peripheral edge of the top surface 2. an inner wall 3 extending upwardly from the inner wall 3 and a skirt portion 6 provided with a threaded portion 5 connected to the inner wall via an annular portion 4 extending outwardly from the upper end of the inner wall 3 .
In the screw cap shown in FIGS. 1 and 2, the inner wall 3 has a V shape, that is, an upper inner wall 3a having an inverted tapered shape in which the outer diameter of the inner wall increases as it goes downward, and an outer diameter as it goes downward. A tapered lower inner wall 3b with a decreasing diameter is formed as an annular projection 7 at a bend at the boundary between the upper inner wall 3a and the lower inner wall 3b. The vertex is elastically deformable radially inward.
That is, as shown in FIG. 2, the maximum outer diameter L1 of the annular projecting portion 7 when not applied to the container is formed to be larger than the inner diameter L2 of the container mouth portion 20 to which the screw cap is applied. 1 is applied to the container opening 20, and in a sealing state in which the cap is screwed to the bottom dead center, the annular protrusion 7 is in a state of being pressed against the inner surface 20 of the container opening in the radial direction to achieve excellent liquid tightness. can be expressed.

In the specific example shown in FIGS. 1 and 2, the top surface 2 is in a so-called drop-lid shape with the top surface 2 downward with respect to the annular portion 4, and the head space is small, so that when it is cooled after hot filling, it is not deformed under reduced pressure. can be suppressed.
FIG. 3 is a diagram for explaining another aspect of the top surface 2 in the screw cap of the present invention. In the mode shown in FIG. 3A, the top surface 2 is dome-shaped upward. In the embodiment shown in FIG. 3B, on the contrary, the top surface 2 is dome-shaped downward. For example, when applied to a container filled with a content such as a carbonated drink having an autogenous pressure, the annular projection 7 presses the inner surface of the mouth of the container more strongly due to the upward pressure applied to the top surface 2. Therefore, the hermetic sealability can be improved. Further, by devising the shape, even if the internal pressure increases, it is possible to keep the pressing force exerted by the annular protrusion 7 on the inner surface of the mouth of the container unchanged. In that case, the ease of opening is not impaired while the hermetic sealability is maintained. When the top surface 2 has a flat shape as in the specific examples shown in FIGS. 1 and 2, the top surface 2 deforms into a dome shape when the internal pressure increases, and the pressure force exerted by the annular discharge portion 7 on the inner surface of the mouth of the container. can be provided with a vent function that can lower the pressure and release the internal pressure. In this way, the shape of the top surface 2 makes it possible to impart functions according to the contents.

Further, in the specific example shown in FIGS. 1 and 2, a contact ring 9 is formed on the inner surface of the annular portion 4 so as to come into pressure contact with the tip of the container mouth portion 20 when the cap reaches the bottom dead center due to screw engagement. Therefore, the sealing performance of the cap is further enhanced.
Furthermore, the portion of the skirt portion 6 above the threaded portion 5 and connected to the annular portion 4 (hereinafter referred to as the "upper skirt portion 10") is formed in a reverse tapered shape in which the outer diameter of the skirt portion decreases downward. By doing so, the vicinity of the tip of the container mouth portion 20 is hooped from the outside in the radial direction, a seal portion is formed between the outer surface of the container mouth portion and the inner surface of the upper skirt portion 10, and the sealing performance of the cap can be further improved. becomes.

FIG. 4 is a partially enlarged view for explaining another aspect of the inner wall and the annular protrusion in the screw cap of the present invention.
In the embodiment shown in FIGS. 1 and 2, the inner wall 3 is composed of a reverse tapered upper inner wall 3a whose outer diameter increases downward and a tapered lower inner wall 3b whose outer diameter decreases downward. 4(A), the upper inner wall 3a is reversed in the same manner as in FIGS. The lower inner wall 3b is tapered, and the lower inner wall 3b is formed in an arc shape with the apex of the arc facing obliquely downward. In this embodiment, liquid-tightness is ensured by radially outward elastic deformation of the annular projection 7 by the reverse tapered upper inner wall 3a.

In the embodiment shown in FIG. 4(B), the upper inner wall 3a is a straight wall without inclination, and the lower inner wall 3b is arranged so that the apex of the arc faces radially outward and is radially wider than the upper inner wall 3a. In this mode, the circular arc is positioned outward, and the contact point of this circular arc with the container mouth portion is the annular projecting portion 7 . In this embodiment, the liquid-tightness is ensured by elastic deformation of the annular projecting portion 7 radially outward by the arc-shaped lower inner wall 3b.

The screw cap of the present invention is not limited to the above-described specific examples, and can take various forms as long as the inner wall is formed with an annular projection having an outer diameter larger than the inner diameter of the container opening to which it is applied. be able to.
For example, in the specific example shown in FIG. 1, by forming the countersink portion 8, the countersink portion is also elastically deformable in the radial direction of the cap when applied to a container as described above. As a result, the radially outward pressing force on the inner surface of the mouth of the container due to the elastic deformation of the annular projecting portion is increased, so that excellent sealing performance can be achieved. Depending on the size of the top surface, etc., even if the countersink portion is not formed, excellent hermetic sealing performance can be exhibited. That is, as shown in FIG. 5, excellent sealing performance can be realized only by the radially outward pressing force of the annular projection 7 without forming a countersink portion.

In the screw cap of the present invention, the relationship between the outer diameter (L1) of the annular protruding portion and the inner diameter (L2) of the container opening to be applied depends on the diameter of the container, the thickness of the cap, the presence or absence of a countersink portion, and the like. Although it can be appropriately changed depending on the degree of elastic deformation of the projecting portion, it is preferable that the difference of L1-L2 is in the range of 0.1 to 1.0 mm.
When the upper inner wall is formed in a reverse tapered shape, the taper angle can be appropriately changed depending on the length of the upper inner wall, the difference between L1-L2, etc., but is 0.1 to 45 with respect to the axial direction of the cap. It is preferable to form it in the range of °.
Similarly, when forming the upper skirt portion in a reverse tapered shape, the length of the upper skirt portion can be appropriately changed, but it is preferable to form the upper skirt portion in the range of 0.1 to 45° with respect to the axial direction of the cap. be.

The screw cap of the present invention may be made of resin or metal as long as it can be molded into the above-described shape in which the annular projection can be elastically deformed. A resin cap is preferable because it can exhibit elastic deformation.
In the case of the resin cap, conventionally known thermoplastic resins such as olefin resins and polyester resins, which have been conventionally used for molding resin caps, can be used, but olefin resins are particularly preferred. be. In the case of a metal cap, a metal such as aluminum that has been conventionally used for molding metal caps can be used.

As for the molding method, in the case of a resin cap, it can be molded by a conventionally known molding method such as compression molding or injection molding. Molding by thermoforming such as air pressure molding is desirable. As a result, a thin screw cap can be easily molded, and weight reduction can be achieved. Further, by using a multilayer sheet having a gas barrier resin such as an ethylene-vinyl alcohol copolymer or a gas barrier intermediate layer made of an aluminum foil or the like, it is possible to provide a resin cap which is thin but has excellent gas barrier properties. is also possible.
When the screw cap of the present invention is formed by thermoforming, a sheet having a thickness of 0.1 to 1.5 mm is used when a sheet made of an olefin resin such as polyethylene or polypropylene is used, although it depends on the type of resin. is preferably used.
In the case of a metal cap, it can be formed by press-molding a metal sheet. In the case of a metal cap, conventionally known shapes can be adopted, such as forming a liner material on the annular portion, or forming a tamper-evident band via a breakable weakened portion at the lower end of the skirt portion. .

As the container to which the screw cap of the present invention can be applied, all conventionally known containers such as those made of metal, glass, and resin can be used. It is particularly suitable for application to containers of 15 to 50 mm. If the diameter is larger than the above range, it may not be possible to obtain sufficient sealing performance due to a drop impact compared to the above range, and the amount of elastic deformation of the top surface is small. It may become difficult to further improve the liquid-tightness.

INDUSTRIAL APPLICABILITY The screw cap of the present invention can be molded by thermoforming from a resin sheet, has resealability due to screw engagement, and can exhibit liquid-tightness. Available as a cap.

1 screw cap, 2 top surface, 3 inner wall, 4 annular portion, 5 screw portion, 6 skirt portion, 7 annular projecting portion, 8 countersink portion, 9 contact ring, 10 upper skirt portion, 20 container mouth portion.

Claims (8)

A drop-lid shape comprising a top surface, an inner wall extending upward from the outer peripheral edge of the top surface, and a skirt portion having a screw portion connected to the inner wall via an annular portion extending outward from the upper end of the inner wall. in the screw cap,
A screw cap, wherein the inner wall has an annular protrusion whose outer diameter is larger than the inner diameter of the container opening to which it is applied, and which is elastically deformable in the radial direction of the cap. 2. A screw cap according to claim 1, wherein said inner wall is doglegged and bent outward in the radial direction of the cap, and said annular protrusion is a bent portion of said dogleg. 3. The screw cap according to claim 1, wherein a countersink portion is formed on the outer peripheral edge of the top surface. 3. The screw cap according to claim 1, wherein said top surface has an upper dome shape or a lower dome shape. 3. The screw cap according to claim 1, wherein the upper portion of the skirt portion is formed with a sealing portion that is in close contact with the outer surface of the mouth portion of the container. The screw cap according to any one of claims 1 to 5, which is made of synthetic resin. A screw cap according to any one of claims 1 to 6 applied to bottles. 8. The method for producing a screw cap according to any one of claims 1 to 7, wherein a synthetic resin sheet is used for molding by thermoforming.

Images