FIELD OF THE INVENTION
The invention pertains to a closure for sealing the opening of a container and a package comprising the closure assembled onto a container.
BACKGROUND OF THE INVENTION
Closures for sealing a container comprising a top wall, depending therefrom a skirt having a threaded portion and attached thereto a tamper-evident device are well known in the art. In particular, closures having a sealing means comprising an annular sealing member depending from the top wall of the closure which is coaxial with the closure skirt are known also. An example of one such closure is described in U.S. Pat. No. 6,235,226 to Krautkramer, which employs an annular member defining a sealing “olive” which enters the neck of a container onto which it is applied and has a portion that seals with the internal surface of the container neck. In addition to the sealing olive, the Krautkramer closure has a second sealing member in the form of a ring which depends from the top wall of the closure, coaxial with the closure skirt and located between the closure skirt and sealing olive. This second sealing member impinges the opening of the container, making contact with the outer lip portion of the container opening, forming a second seal as the closure is screwed onto the container. This arrangement produces two seals on the container, an inner seal in which the inner wall of the container opening places the sealing olive in compression, and an outer seal in which the sealing flap is placed in tension by the outer lip of the container opening.
As is known in the art, such closures are subject to over-torquing on application, making it difficult to remove the closure. In addition, such closures are subjected to loss of seal between the closure and the container when a package comprising the closure assembled to a container is subjected to shock, for example, dropping, or sudden changes in pressure which result in “bulging” of the closure (increases in pressure), or drawing the closure into the container (decrease in pressure). These events, termed herein for convenience as “doming” effect the manner in which both the inner and outer seals impinge the container and can cause the seal to break and the container to leak. In addition, with these prior art closures, forces applied to the center of the closure during storage and handling after filling, for example, stacking of cases of bottles, are translated to the sealing means of the closure with similar breaking of the seal and loss of sealing.
SUMMARY OF THE INVENTION
These and other deficiencies are met by the present invention. The present invention provides a container closure having a top wall which has a base cross-sectional thickness and depending from the periphery thereof, an annular skirt having an internally threaded portion and frangibly attached to the free edge of said annular skirt, a tamper-evident means which includes means for engaging a feature on a container to which the closure is applied to facilitate separating said tamper-evident means from said annular skirt at said frangible connection, and wherein the closure is further characterized by:
- (a) a filled shoulder region between the top wall and said annular skirt forming a substantially conical profile having a face oriented toward the radial axis of the closure;
- (b) an annular sealing means depending from said top wall and centered on the radial axis of the closure, comprising:
- (i) a stiffening block in the form of a ring of material depending from said top wall coaxially with said annular skirt, having an inner and outer periphery, the stiffening block being characterized in having a cross-section thicker than said top wall base thickness;
- (ii) an annular outer seal depending from the stiffening block proximal to said closure shoulder, having an outer wall defining the outer periphery of said stiffening block and an inner wall facing the radial axis of the closure, and which is further characterized in having at least a portion of the free end thereof which projects toward said annular skirt;
- (iii) an annular inner seal having an inner and an outer wall depending from said stiffening block, said inner wall defining a point of attachment to the stiffening block at a point outboard of the edge of the inner periphery of said stiffening block, said outer wall defining a point of attachment to the stiffening block inboard of said inner wall of the annular outer seal, the inner seal being further characterized in projecting toward said annular skirt, wherein said annular inner seal has a face directed toward the radial axis of the closure which is substantially conical and is further characterized by the outer wall defining a surface having an outermost diameter greater than the opening of a container to which the closure is applied which enters into sealing engagement with the opening of said container; and
- (iv) an annular groove in said stiffening block which defines the point of attachment of the inner wall of the outer seal with the stiffening block and which is further characterized by having a depth yielding a cross-sectional thickness to the stiffening block which is at least as great as the base thickness of the closure top wall and which is disposed in the stiffening block to provide a step between the point at which the outer wall of the inner annular seal is attached to the stiffening block and the groove, the step being positioned to impinge a portion of the inner edge of the opening of a container to which the closure is attached,
wherein the diameter and length of said inner and outer seal and the spacing between them are selected to accommodate a container opening and place said outer seal in a biaxial stretching condition against the lip of the container opening.
In one embodiment of the present invention closure, the base thickness of the top wall, and the cross-sectional thickness of the stiffening block and annular groove are selected such that doming of the cap due to stress is confined to the central region of the cap within the inner periphery of said stiffening block.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional representation of a bisected portion of one embodiment of a closure of the invention.
FIG. 2 details various cross-sectional features of the top wall and sealing means of one embodiment of a closure of the invention.
FIG. 3 further details various cross-sectional features of the stiffening block and inner and outer seals of one embodiment of a closure of the invention.
The figures utilize numbers pointing out various features of the inventive closures wherein like numbers in different figures represent like features in the closure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
European patent no. 0810951 to Thompson, and published International Application no. WO 03/074380 and the priority documents claimed therein describe several molded plastic closures, the details of which are incorporated in their entirety herein by reference. As illustrated in FIG. 1, the present invention improves on these molded plastic closures by providing a closure which contains both a plug seal and an external seal along with a closure top wall profile which decouples flexing in the cap due to stacking or internal pressure changes in the container to which the closure is applied from the sealing region of the cap.
The following description employs terms utilizing structural description, for example, “point of attachment”. It is to be understood that no limitation regarding methods of forming the subject closures are inherent therein. Accordingly, it is contemplated that the closures of the invention will be prepared by any known means, including injection molding of plastics forming the closure as a single, monolithic structure. It is to be understood that the term “closure” refers to molded plastic closures as that term is understood by those of ordinary skill in the art.
With reference to FIG. 1, one embodiment of the closure of the invention provides a closure having a top wall (1) from which an annular skirt (2) depends. Annular skirt (2) has an internally threaded portion (3) and frangibly attached to the free edge of said annular skirt, a tamper-evident means (4) which includes means (5) for engaging a feature on a container to which the closure is applied, thereby separating said tamper-evident means from said annular skirt at said frangible connection (6) when the closure is removed from the container.
With reference to FIG. 2, the top wall of the closure (2) has a base cross-sectional thickness 21, and is further characterized by a filled shoulder region between said top wall and said annular skirt (22) forming a substantially conical profile having a face (23) oriented toward the radial axis of the closure (24). With further reference to FIG. 1, depending from the top wall and centered on the radial axis of the closure is a stiffening block, a portion of the cross-section is designated as region (11) in the Figure. The stiffening block has the form of a ring of material having an inner (12) and outer periphery (13) depending from said top wall coaxially with said annular skirt. In cross-section (25), the stiffening block is thicker than said top wall base thickness
With further reference to FIG. 2, integrally formed with and depending from the stiffening block are an annular outer seal (26) and annular inner seal 27. Annular outer seal (26) has an outer wall (28), an inner wall (29) and a bulbous free end (30). The outer wall (28) of outer seal (26) defines the outer periphery of stiffening block (11) and is proximal to conical face 23 of the closure shoulder. Outer seal (26) is also characterized by having a portion of the free end of the seal (200) projecting toward the annular skirt of the closure. Preferably, the projection has the form of a bulbous section or bead appended to the edge of the outer wall of the seal. In use, when the closure is applied to a container, a portion of the outer wall of the opening of the container impinges the annular inner wall of the outer seal, forcing projection (200) to contact face (23) of the closure shoulder. Upon contact, and with continued tightening of the closure, the seal is expanded axially by the impinging container opening and is stretched radially by the bulbous feature rolling in contact with face (26) of the closure shoulder region. Accordingly, the outer seal is placed in tension in two directions, and thus is biaxially stressed in sealing the container. This imparts improved resistance to breach the seal due to dimensional changes in the container during storage or to shock and sudden pressure changes in handling and storage of the filled container.
With reference to FIG. 3, annular inner seal (27) has an inner (30) and an outer (31) wall depending from said stiffening block and projects in the direction of the annular skirt. The point at which the inner wall attaches to the stiffening block (32) is outboard (radially) from the edge (33) of the inner periphery of said stiffening block. As mentioned above, the inner seal is further characterized in projecting toward the annular skirt. This is shown in FIG. 3 as a line bisecting the cross-section of said inner seal (34) forms an obtuse angle (a) with a line (35) bisecting the cross-section of said top wall and passing through the radial axis (24) of the closure. In this manner, face 30, which is directed toward the radial axis of the closure, is substantially conical. The cross-section of the free end of the inner seal may be reverse tapered or rounded such that upon initial contact with a container opening, the inner seal presents a cross-sectional diameter which is smaller than the container opening, and thus presents little resistance to passing into the container opening. With reference to FIG. 2, the maximum cross-sectional diameter presented to the container opening (201) is selected to exceed the container opening, thus axially compressing the outer wall (31) of the inner seal and sealing it to the inner wall of a container opening to which the closure is applied.
With further reference to FIG. 3, the stiffening block contains also an annular groove (36) which is placed in the stiffening block in a location defining the point at which the inner wall (29) of the outer seal joins the sealing block. The groove also defines a step (37) in the stiffening block between the inner edge of the groove and the point (38) at which the outer wall (31) of the inner seal joins the sealing block. The depth of groove 36 is selected to provide a minimum thickness in the groove region which is at least as thick as the base thickness of the closure top wall. The thickness of step (37) is selected to impinge the inner portion of the edge of the opening of a container to which the closure is applied, acting as a stop which insures a satisfactory seal between the outer annular seal and the container without over tightening the closure. Accordingly, the diameter and length of said inner and outer seal and the spacing between them are selected to accommodate a container opening. The shape and length of the outer seal is selected to insure that when the closure is applied to a container, the container opening forces the bulbous projection of the outer seal to contact the conical face of the should region of the closure, placing the outer seal in a biaxial stretching condition against the lip of the container opening. It is preferred if the length of the seals and the spacing between the seal and the threaded portion of the closure are selected such that the seals are broken from engagement with a container to which the closure is applied before the threaded portions of the container and closure disengage.
The cross-section thickness of the stiffening block in the various regions described above relative to the base thickness of the cap itself, permits the central portion of the cap to be relatively thin, permitting overall weight and materials savings, and allows the sealing region to remain relatively free of the stresses effecting sealing during handling and storage of a filled container. Accordingly, the base thickness of the closures top wall, and the cross-sectional thickness of the stiffening block and its attendant integral stop block and annular groove are selected such that the comparatively thinner central top wall portion of the closure can be subjected to doming forces due to product stacking and pressure changes internally in the filled container, which are decoupled from the periphery of the closure, and thus from straining or impinging on the sealing features of the closure. Thus, permitting longer storage and handling life to packages sealed with the closure.
Numerous tamper-evident means are known in the industry and cited in the publications incorporated herein by reference. These publications are incorporated herein for illustration of tamper-evident means as well. It is preferred if tamper-evident means include a ribbed frangible region and include also a “winged” or “claw-like” radially projecting array of features directed to the radial axis of the closure. The dimensions and configuration of these projections will be selected for engagement with a feature on the finish of a container to which the closure is applied. As is known, such engagement promotes immobilization of the tamper-evident band when the closure is removed from the container, assisting in rupture of the frangible connection between the closure and the tamper-evident band and retention of the band (as an indication of container breach) on the container.
Having described the presently preferred embodiments, it is to be understood that the invention may be otherwise embodied within the scope of the appended claims.
Patent Application
20060163193
