Closure Cap

Abstract

A metal cap for closing a container, e.g. a glass container for foodstuffs, of the kind comprising a cap base extending over the container mouth and beyond its outer edge and a separate encircling cap skirt secured to the container by a screw or bayonet connection and engaging over the edge of the cap base; the cap base being originally curved inwards, but being forced into an outward curve by the anchoring forces acting on its edge when the skirt is secured over it and subsequently being curved inwards again by reduced pressure formed in the container. Loss of pressure is thus indicated by a return to the outwardly curved condition. The region of the cap base projecting beyond the outer edge of the container mouth has a downwardly widening conical edge portion engaged by a rolled-in bead on the upper end of the cap skirt. The adjacent portion of the cap skirt may be conically tapered, and the conical edge portion of the cap base may terminate in an out-turned stiffening flange. The circle of contact preferably lies slightly below the plane of the container mouth. Good engagement and sealing are thereby obtained as well as reliable inward and outward curving of the cap base.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to metal caps for closing containers, particularly glass containers.

2. Description of the Prior Art

More specifically it relates to caps of the kind comprisng a cap base which is adapted to extend over the container mouth and beyond the edge thereof, and which in the unstressed condition, that is to say before the cap is secured on the container, is originally curved inwards, is adapted to be first resiliently curved outwards through anchoring forces acting on its periphery when the cap is secured on the container, and is then adapted to be curved inwards again by reduced pressure in the container, and an encircling cap skirt which is adapted to be secured on the container by a screw or bayonet connection, is separate from the base of the cap, and engages over an edge portion of the latter.

Metal caps of this kind are known from U.S. Pat. No. 2,194,004, and are used mainly for the airtight sealing of containers which contain foodstuffs or other substances which have to be stored with the exclusion of air and in which a reduced pressure prevails. The cap base, which is curved inwards before the cap is fastened on the container and is adapted to be curved outwards by the anchoring forces acting on its periphery on securing the cap to the container and to be curved inwards again by the reduced pressure in the container, serves as an external visible sign of the effective sealing of the container closure. When a container is sealed completely tightly with the aid of the metal cap and consequently the reduced pressure is maintained unchanged in the interior of the container, the cap base is in fact curved inwards and through its concave shape indicates that the container closure is effectively sealed. If on the other hand the container closure is inadequately sealed when the metal cap is fitted or if it should subsequently leak during storage so that the reduced pressure is not produced in the vessel or is lost, that is to say the internal pressure in the container retains or assumes approximately the same value as the external pressure, the base of the cap curves outwards and through its convex shape indicates that the container closure is leaking.

SUMMARY

The invention seeks to improve upon the known construction and to provide a metal cap of the kind first mentioned above, for the purpose of closing containers, wherein the outward curvature of the originally inwardly curved cap base is produced, on securing the cap on the container with the application of only a small force and without permanent deformation of the parts of the encircling cap skirt cooperating with the cap base, while at the same time effective sealing of the container closure is obtained. It should thus also be made possible to manufacture the encircling cap skirt or the cap base of weaker or thinner sheet metal, particularly of sheet aluminum, with the economic and manufacturing advantages resulting therefrom.

According to the invention, in its region projecting beyond the outer edge of the container mouth, the cap base has a downwardly directed conical edge portion which widens in the downward direction and on which rests a rolled-in bead provided on the upper end of the encircling cap skirt at a distance from the outer edge of the container mouth.

When the metal cap according to the invention is secured on the container which is to be closed, the upper rolled-in bead provided on the encircling cap skirt and resting on the conical edge portion of the cap base applies not only a downwardly directed compressive force but also a compressive force directed radially inwards to the cap base, which was originally curved inwards. Since the downwardly directed compressive force acts outside the edge of the container mouth, it applies with a considerably greater lever arm a correspondingly greater outward curving action to the cap base, the top edge of the container mouth acting as pivot support. At the same time the cap base is compressed in the radial direction by the compressive force directed radially inwards, and is thereby likewise forced to curve outwards. Consequently the originally inwardly curved cap base is curved outwards through the combined action of these two compressive forces with greater reliability and in particular even if the total pressure applied by the encircling cap skirt to the conical edge portion of the cap base is relatively slight. It is therefore possible to make the encircling cap skirt and the cap base of correspondingly weaker or thinner sheet metal, in particular of sheet aluminum. The danger of permanent deformation of the upper rolled-in bead provided on the encircling cap skirt and engaging over the cap base is then practically eliminated, because a rolled-in bead of this kind has particularly great strength or resistance to deformation.

Deformation, particularly outwardly directed bending, of the upper rolled-in bead of the encircling cap skirt can additionally be particularly effectively avoided, even in the case of heavy pressures applied to the conical edge portion of the cap base, if the upper portion of the encircling cap skirt adjoining the rolled-in bead is conically tapered. In this construction the upper rolled-in bead of the encircling cap skirt engages over the conical edge portion of the cap base without sharp bends in the encircling cap skirt. Consequently, the bending forces acting on the rolled-in bead are diverted more easily, or without deformation, into the vertical portion of the encircling cap skirt or into its securing on the container.

Particularly reliable outward curving of the originally inwardly curved cap base, in conjunction with particularly good sealing of the container closure, can be achieved by locating the circle of contact between the rolled-in bead of the encircling cap skirt and the conical edge portion of the cap base, when the cap is fully secured on the container, approximately in the plane of the container mouth, or preferably slightly below that plane.

The conical edge portion of the cap base preferably terminates at the bottom in an outwardly-bent stiffening flange. The conical edge portion of the cap base is thereby in particular given greater ability to resist the pressure applied by the rolled-in bead of the encircling cap skirt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section through half of a metal cap according to the invention, before the cap is finally secured on the container which is to be closed,

FIG. 2 shows the metal cap of FIG. 1 after its final securing on the container but before a reduced pressure has been formed in the interior of the container, and

FIG. 3 shows the metal cap of FIG. 2 with effective sealing of the container closure and after reduced pressure has formed in the interior of the container.

DETAILED DESCRIPTION OF THE INVENTION

The metal cap illustrated, which is intended for closing containers, particularly glass containers, consists of a cap base 2 and of an encircling cap skirt 1 separate from the cap base. For the purpose of securing the cap on the container 3, a screw connection is provided between the encircling cap skirt 1 and the container 3, this screw connection consisting of screw threads 4 formed on the outside of the container 3 and of inwardly projecting anchoring projections 5 which are disposed on the bottom edge of the encircling cap skirt 1 and are in the form of rolled-in beads and which cooperate with the said screw threads.

The diameter of the cap base 2 is such that at its periphery it projects beyond the outer edge of the container mouth 103. The edge portion 102 of the cap base 2 which projects beyond the outer edge of the container mouth at its periphery is bent downwards and widens conically in the downward direction. The cap base 2 is originally, that is to say in its unstressed position before the cap is secured on the container 3, curved inwards in its entire middle portion 202 covering the opening of the container, as can be seen particularly in FIG. 1. The annular transition portion 302, intended for resting on the container mouth 103, of the cap base 2 between the middle, inwardly curved portion 202 of the cap base and the outer conical edge portion 102 is originally, that is to say before the cap is secured on the container, inclined inwards and downwards in relation to the axis of the container mouth, and forms an approximately tangential outer extension of the inwardly curved middle portion 202 of the cap base. This annular transition portion 202 of the cap base is provided with a sealing gasket 6 on its lower side.

The upper portion of the encircling cap skirt 1 is tapered conically and at its upper edge terminates in an inwardly projecting rolled-in bead 7, which engages over and rests on the outer conical edge portion 102 of the cap base 2. The outer conical edge portion 102 of the cap base 2 terminates at a bent-over, outwardly projecting stiffening and centring flange 402.

When the metal cap described is secured on the container 3 which is to be closed, that is to say when the encircling cap skirt 1 is screwed on to the external screw threads 4 on the container 3, the top inwardly rolled-in bead 7 of the encircling cap skirt 1 applies a vertical pressure, that is to say a pressure directed downwards parallel to the axis of the container mouth, to the conical edge portion 102 of the cap base 2. This vertical pressure has a force component directed downwards parallel to the surface of the conical edge portion 102 of the cap base and a force component directed radially inwards. The downwardly directed force component effects the anchoring of the cap base 2 on the container 3 and presses the cap base 2 sealingly against the top edge of the container mouth 103. More specifically, the downwardly directed force component pivots the annular transition portion 302 of the cap base 2 outwards around the edge of the container mouth 103 serving as pivot support, so that the aforesaid transition portion 302 of the cap base assumes a position inclined outwards and downwards in relation to the axis of the container mouth, as illustrated in FIG. 2. At the same time the gasket 6 is pressed against the upper, outer edge of the container mouth 103 and simultaneously an upwardly directed lever action is applied to the middle, inwardly curved portion 202 of the cap base, which is thus curved outwards. The force component directed radially inwards and acting on the entire periphery of the cap base 2 compresses the latter in the radial direction and consequently applies an additional outward curving action to the middle, inwardly turned portion 202 of the cap base. Through the combined action of these two force components applied by the encircling cap skirt 1 to the outer conical edge portion 102 of the cap base, the middle portion 202 of the cap base, which was originally curved inwards, is curved out resiliently, as illustrated in FIG. 2. When the cap is finally secured on the container, the circle of contact between the upper rolled-in bead 7 of the encircling cap skirt 1 and the outer conical edge portion 102 of the cap base 2 preferably lies slightly below the plane of the container mouth 103.

Thereupon, when reduced pressure has been formed in the interior of the container, the outwardly curved middle portion 202 of the cap base 2 is curved inward again, as illustrated in FIG. 3. The annular transition portion 302 of the cap base 2 is thus once again partly pivoted inwards, to such an extend that it assumes an approximately horizontal position, that is a position at right angles to the axis of the container mouth. The gasket 6 is thereby also pressed against the inner edge of the container mouth 103, as can be seen in FIG. 3.

The inwardly curved or concave shape of the middle portion 202 of the cap base indicates the effective sealing of the container closure and the maintenance of the reduced pressure in the interior of the container, and is retained unchanged as long as reduced pressure prevails in the interior of the container. If the sealing of the container closure should fail, and consequently the reduced pressure in the interior of the container should be lost, the middle portion 202 of the cap base 2 will resume its outwardly curved shape, illustrated in FIG. 2, as a result of the anchoring pressure of the encircling cap skirt 1. This outwardly curved or convex shape of the cap base 2 indicates the leaking of the container closure.

The pivoting of the annular portion 302 of the cap base about the top edge of the container mouth 103, firstly outwardly from a starting position in which it is inclined inwards and downwards (FIG. 1) into a temporary position in which it is inclined outwards and downwards (FIG. 2), and then again partly inwards into an approximately horizontal end position (FIG. 3) supports the corresponding resilient outward and inward curving movements of the cap base 2 and not only ensures reliable pressing of the entire gasket 6 against the container mouth 103, but also brings about a stretching and consequently an easier adaptation of the portion 302 of the cap base lying above the seal to any irregularities in the container mouth 103. The thickness of the gasket 6 can consequently be considerably reduced. The conical shape of the edge portion 102 of the cap base which projects beyond the outer edge of the container mouth 103 and over which the upper rolled-in bead 7 of the encircling cap skirt 1 engages additionally reduces the pressure required for the outward curving of the cap base in consequence of the radial compression of the latter, which was originally curved inwards, and also reduces resistance when the encircling cap skirt is screwed on and off.

Claims

I claim:

1. A metal cap for closing a container, particularly a glass container, comprising a cap base which is adapted to extend over the container mouth and beyond the outer edge thereof and which, in the unstressed condition, that is to say before the cap is secured on the container, is originally curved inwards and is adapted to be first resiliently curved outwards by anchoring forces acting on its periphery when the cap is secured to the container, and then to be curved inwards again by reduced pressure in the container, and an encircling cap skirt which is adapted to be secured to the container by a screw or bayonet connection, is separate from the cap base, and engages over an edge portion of the latter, wherein in its region which projects beyond the outer edge of the container mouth the cap base has a downwardly directed conical edge portion which widens in the downward direction and on which rests a rolled-in bead provided on the upper end of the encircling cap skirt at a distance from the outer edge of the container mouth.

2. A metal cap according to claim 1, wherein the portion of the encircling cap skirt adjoining the rolled-in bead is tapered conically.

3. A metal cap according to claim 1, wherein the circle of contact between the rolled-in bead of the encircling cap skirt and the outer conical edge portion of the cap base, over which the said skirt engages, lies approximately in the plane of the container mouth or preferably slightly below this plane, when the cap is fully secured on the container.

4. A metal cap according to claim 1, wherein the conical edge portion of the cap base terminates at the bottom in a stiffening flange bent over in the outward direction.

5. A metal cap according to claim 1, wherein the cap base has an annular transition portion in its region intended to rest on the container mouth between the middle portion of the cap base, which is orginally curved inwards and which is adapted to be curved outwards, and the conical edge portion of the cap base, this transition portion being originally, that is to say before the securing of the cap on the container, inclined inwards and downwards in relation to the axis of the container mouth and on the securing of the cap on the container this transition portion is adapted to pivot about the edge of the container mouth, first through the action of the anchoring pressure applied by the encircling cap skirt, into a position in which it is inclined outwards and downwards in relation to the axis of the container mouth and then, through the action of the reduced pressure in the container and of the consequent inward curving of the cap base, into an end position which is approximately horizontal or perpendicular to the axis of the container mouth.