Plastic closure with enhanced performance

Abstract

A plastic closure embodying the principles of the present invention comprises a closure cap having a top wall portion, and an annular skirt portion depending from the top wall portion. The skirt portion includes an internal thread formation for threaded engagement with the external thread formation of an associated container. In order to facilitate high-speed application, and minimize the use of polymeric material, the closure is configured to exhibit a variation in retention force which decreases in a direction away from the top wall portion of the closure cap.

Claims

1. A plastic closure, comprising: a closure cap having a top wall portion, and an annular skirt portion depending from said top wall portion and extending around an axis, said skirt portion of said closure cap having an internal thread formation for threaded engagement with an external thread formation of an associated container, wherein said internal thread formation is configured to exhibit a variation in retention force which decreases in a direction away from said top wall portion of said closure cap when engaged with an external thread formation of an associated container, said internal thread formation being configured to define a plurality of thread profiles, including a thread profile having a relatively large cross-sectional area viewed in a plane containing the axis positioned closer to said top wall portion than another one of said thread profiles having a relatively small cross-sectional area, wherein at least a portion of said thread formation has a continuously varying thread profile cross section, including a continuously varying depth in said thread profile extending at least 180 about a circumference of said closure cap over which the depth in said thread profile decreases in a direction away from said top wall portion.

2. The plastic closure of claim 1, wherein said internal thread formation is continuous and wherein said continuously varying thread profile cross section varies continuously throughout the length of the thread.

3. The plastic closure of claim 1 further including a tamper-evident pilfer band at least partially detachably connected to said skirt portion.

4. The plastic closure of claim 1, wherein said internal thread formation includes one or more discontinuities therein to facilitate gas venting.

5. The plastic closure of claim 1, wherein said internal thread formation includes a helical engagement surface.

6. A package including a container and a plastic closure, the package comprising: said container with an external threaded portion for threaded engagement with an internal thread formation of said closure; and said plastic closure including a closure cap and an annular skirt portion, said closure cap having a top wall portion, and said annular skirt portion depending from said top wall portion and extending around an axis, said skirt portion of said closure cap having said internal thread formation for threaded engagement with said external thread formation of said container, wherein said internal thread formation is configured to exhibit a variation in retention force which decreases in a direction away from said top wall portion of said closure cap when engaged with said external thread formation of said container, said internal thread formation being configured to define a plurality of thread profiles, including a thread profile having a relatively large cross-sectional area viewed in a plane containing the axis positioned closer to said top wall portion than another one of said thread profiles having a relatively small cross-sectional area, wherein at least a portion of said thread formation has a continuously varying thread profile cross section, including a continuously varying depth in said thread profile extending at least 180 about a circumference of said closure cap over which the depth in said thread profile decreases in a direction away from said top wall portion.

7. The package of claim 6, wherein said internal thread formation of said closure is continuous and wherein said continuously varying thread profile cross section varies continuously throughout the length of the thread.

8. The package of claim 6 further including a tamper-evident pilfer band at least partially detachably connected to said skirt portion.

9. The package of claim 6, wherein said internal thread formation of said closure includes one or more discontinuous in therein to facilitate gas venting.

10. The package of claim 6, wherein said internal thread formation of said closure includes a helical engagement surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagrammatic view of a plastic closure having an internal thread formation having a substantially uniform cross-sectional area, and a plurality of axially extending gas-venting grooves;

(2) FIG. 2 is a diagrammatic view similar to FIG. 1 illustrating a plastic closure embodying the principles of the present invention, wherein the internal thread formation comprises a plurality of thread segments having non-helical centerlines;

(3) FIG. 3 is a diagrammatic view of a plastic closure illustrating a further aspect of the present invention, wherein a portion of the internal thread formation is provided with a plurality of reinforcing elements;

(4) FIG. 4 is a further diagrammatic view illustrating an embodiment of the present closure, wherein the retention force of portions of the internal thread formation are reduced by the provision of regions having a reduced cross-sectional area;

(5) FIG. 5 is a further diagrammatic view illustrating a plastic closure embodying the principles of the present invention, wherein the internal thread formation of the closure cap has a portion of relatively large cross-sectional area, provided by a relatively deep thread profile;

(6) FIG. 6 is a further diagrammatic view of the closure embodying the principles of the present invention, wherein the internal thread formation as a portion of relatively large cross-sectional area provided by a relatively wide thread profile;

(7) FIG. 7 is a diagrammatic view of a closure embodying the principles of the present invention, wherein a thread formation having a non-uniform cross-sectional area comprises thread segments which collectively define a non-helical engagement surface;

(8) FIG. 8 is a further diagrammatic view of a closure embodying the principles of the present invention, wherein the retention force provided by the internal thread formation of the closure is varied by decreasing the thickness of the skirt portion of the closure cap in a direction away from the top wall portion; and

(9) FIG. 9 is a relatively large, diagrammatic view illustrating an axially extending projection or rib provided in an axially extending gas-venting groove of the skirt portion of the closure cap; and

(10) FIG. 10 is a further diagrammatic of a further embodiment of a closure embodying the principle of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(11) While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described presently preferred embodiments, with the understanding that the present disclosure is to be considered as an exemplification of the invention, and is not intended to limit the invention to the specific embodiments illustrated.

(12) With reference first to FIG. 1, therein is illustrated a closure C showing typical features of a closure formed from polymeric material. Closure C includes a top wall portion T, and an annular, depending skirt portion S, having an internal thread formation F configured for threaded cooperation with an external thread formation on the neck of an associated container to which the closure is applied. In order to facilitate venting of gas pressure from within a container such as containing carbonated contents, the closure C is configured to include a plurality of axially extending gas-venting grooves V, which interrupt the thread formation F, such as illustrated.

(13) Features of this typical closure construction will be noted, including the skirt portion S having a substantially uniform thickness, and the thread formation F having a substantially uniform thread depth, and a substantially uniform thread width, as indicated at A, B and C.

(14) With reference now to FIG. 2, there is illustrated a closure 10 embodying the principles of the present invention. As discussed hereinabove, closure 10 can be efficiently formed from polymeric materials, such as by injection molding or compression molding. It is contemplated that closure 10 is configured to provide the desired sealing cooperation with an associated container, while at the same time being configured to minimize the use of polymeric material, while facilitating high-speed application to an associated container.

(15) Closure 10 includes a closure cap including a top wall portion 12, and an annular skirt portion 14 depending from top wall portion 12. The closure can be provided with a separate sealing liner adjacent the inside surface of top wall portion 12, or may otherwise be configured as a linerless closure, including one or more sealing features formed integrally with the inside surface of top wall portion 12 for sealing cooperation with the neck portion of an associated container.

(16) In accordance with the present invention, the closure 10 has been configured to exhibit a variation in the retention force on the associated container, which decreases in a direction away from top wall portion 12 of the closure cap. In this embodiment, this variation in retention force is achieved by configuring the internal thread formation 16 of the closure cap such that the retention force created by the thread formation decreases in a direction away from top wall portion 12.

(17) In particular, the internal thread formation 16 is defined by a plurality of thread profiles, including a thread profile having a relatively large cross-sectional area positioned closer to top wall portion 12, then another one of the thread profiles having a relatively small cross-sectional area. This is evident from FIG. 2, where it will be observed that segments of the thread formation 16, interrupted by axially extending gas-venting grooves 18, decrease in cross-sectional area in a direction away from top wall portion 12. Thus, the material required for formation of the closure is desirably reduced, at the same time reducing the retention force of the thread formation in a direction away from the top wall portion. This configuration has been found to desirably facilitate high-speed application to an associated container, with those portions of the thread formation closest to the top wall portion 12 exhibiting the necessary hoop strength and retention force so that the closure exhibits the desired strip torque attendant to threaded application to an associated container.

(18) Notably, the desired sealing cooperation with an associated container is achieved in this embodiment by configuring the centerlines of the segments of the thread formation 16 to be non-helical, or staggered, as illustrated by the offset relationship of the centerlines, as seen in FIG. 2, with the thread segments collectively defining a helical engagement surface for engagement with the external thread formation of the associated container. It is believed if the diameter of thread formation is varied, from a large diameter at the open end of the closure (for better application), to a small diameter at the closed end (for better strip torque performance), without changing the centerline, the natural contact between the closure and container thread will tend to cock the closure once fully applied. To resolve this, the centerlines are non-helical and staggered for the different thread profiles, so that at the closed end of the thread there is even contact with the container thread, without cocking.

(19) As noted, a closure embodying the principles of the present invention is configured such that the retention force created by the internal thread formation of the closure cap decreases in a direction away from the top wall portion of the closure. FIG. 3 illustrates an embodiment of the present invention which achieves this variation in a thread formation comprised of a plurality of segments, wherein the cross-sectional area and configuration of the thread segments is substantially uniform. In particular the thread formation 16 of closure 10 illustrated in FIG. 3 has the desired variation in retention force by the provision of at least one reinforcing element, which in the illustrated embodiment comprises one or more reinforcing ribs 19 which extend between an inside surface of skirt portion 14 and the thread formation 16, beneath an engagement surface of the thread formation.

(20) FIG. 4 illustrates an embodiment of the present closure, wherein the desired variation in retention force is provided by configuring the thread formation 16 to include a region of relatively reduced thread cross-sectional area. As illustrated, each region of reduced thread cross-sectional area is defined by a recess 21 in the thread formation, beneath an engagement surface of the thread formation.

(21) In each of the embodiments of FIGS. 3 and 4, axially extending gas-venting grooves 18 are provided, thus facilitating the release of gas pressure from within an associated container, such as containing carbonated contents, during closure removal.

(22) FIGS. 5 and 6 illustrate embodiments of the present invention, wherein the desired variation and the retention force created by internal thread formation 16 is achieved by the thread formation being defined by a plurality of thread profiles, including a thread profile having a relatively large cross-sectional area positioned closer to the top wall portion 12 than another one of the thread profiles having a relatively small cross-sectional area. In the embodiment of FIG. 5, this difference in the cross-sectional areas of the thread formation 16 is provided by providing at least one portion of the thread profile closer to top wall portion 14 with a relatively deeper thread profile, to define a relatively reduced inside diameter for the thread formation at that region. In FIG. 5, dimensions A, B and C illustrate the constant width of the profile, while dimensions D, E and F show the decreasing depth of the thread profile. In the embodiment of FIG. 6, the portion of the thread profile having a relatively large cross-sectional area is provided by a relatively wide thread profile, so that the retention force provided by the internal thread formation decreases in a direction from the top wall portion. In FIG. 6, the variation in dimensions A, B and C show the decreasing width of the thread profile.

(23) In each of the embodiments of FIGS. 5 and 6, axially extending gas-venting grooves 18 are provided, including in an uppermost portion of each illustrated internal thread formation, positioned most closely adjacent to top wall portion 12, which is interrupted where the gas-venting groove 18 intersects the thread formation 16.

(24) The embodiment of FIG. 7 of the present invention contemplates the desired variation in the retention force of the closure cap by decreasing the cross-sectional area of the internal thread formation 16 in a direction away from the top wall portion 12. In this embodiment, contact with the associated container is optimized such as by configuring the segments of the thread formation 16 to collectively define a non-helical, or staggered, engagement surface, as illustrated by the offset in successive ones of the thread segments, arranged so that the centerlines of the thread segments are helical.

(25) FIG. 8 illustrates an embodiment of the present invention wherein the desired variation in the retention force of the closure cap is achieved by decreasing the thickness of skirt portion 14 in a direction away from top wall portion 12, in order to provide the closure with the retention force which decreases in a direction away from the top wall portion. In this embodiment, the exterior of the skirt portion 16 is provided with a substantially cylindrical configuration, dimensioned for cooperation with conventional capping heads or trucks.

(26) The decrease in the thickness of the skirt portion 14 is illustrated by comparison of dimensions G and H in FIG. 8, while dimensions A, B and C illustrate the constant width of the thread formation. Dimensions D, E and F show that notwithstanding the substantially constant thread depth, the effective inside diameter of the thread formation increases in a direction away from top wall portion 12, thus achieving the desired variation in the retention force in a direction away from the top wall portion.

(27) FIG. 9 illustrates a feature of the present invention to facilitate high-speed application of the present closure to an associated container. In particular, FIG. 9 illustrates the provision of an axially extending projection 22 respectively positioned in one of the gas-venting grooves 18 defined by the skirt portion 14 of the present closure. Notably, projection 22 is configured to engage and cooperate with the external thread formation of an associated container, attendant to closure application, thereby desirably stabilizing the closure and preventing undesired cocking or cross-threading of the closure as it is applied to the associated container.

(28) FIG. 10 is a diagrammatic view of a further embodiment of a closure embodiment of the principles of the present invention, wherein the closure 10 includes a closure cap having a top portion 12 and an annular skirt portion 14 depending from the top wall portion 12. In this illustrated embodiment, the closure 10 includes a tamper-evident pilfer band 15 at least partially detachably connected to the skirt portion 14.

(29) As in previous embodiments, the skirt portion 14 of the closure 10 includes an internal thread formation 16 for threaded engagement with an external thread portion of an associated container. In accordance with the present invention, the internal thread formation 16 is configured to exhibit a variation in retention force which decreases in a direction away from top wall portion 12, with the thread formation being configured to define a plurality of thread profiles, including a thread profile having a relatively large cross-sectional area positioned closer to the top wall portion and another one of the thread profiles having a relatively small cross-sectional area.

(30) In this embodiment, at least a portion of the thread formation 16 has a continuously varying thread profile cross section, which in the illustrated embodiment varies continuously throughout the length of the thread formation. The centerlines of a plurality of the thread profiles may be either helical, or smoothly, non-helical, with the plurality of thread profiles collectively defining a helical engagement surface for engagement with the external thread formation of the associated container. As illustrated in FIG. 10, the upper engagement surface can be configured at an angle beta, which is equal to a lower engagement surface angle lambda. In this embodiment, the cross-sectional area of the thread formation 16 gradually decreases in a direction away from top wall portion 12, in that dimension A is greater than dimension B, which is greater than dimension C, with the thread formation thus gradually decreasing in width in a direction away from top wall portion 14. In addition, thread formation 16 is configured with a decreasing depth in that dimension D is greater than dimension F.

(31) The thread width and height continuously vary from a wide/tall cross section at the closed end of the closure, proximal to top wall portion 12, to a narrow/thin cross section at the open end of closure, distal from the top wall portion. By this arrangement, wherein the thread formation may have a helical centerline, or a smoothly varying centerlines, the retention characteristics of the closure can be infinitely varied, thus permitting the closure to be configured for any desired application. As in previous embodiments, one or more discontinuities in the thread formation may be provided to facilitate gas venting, such as for use on containers having carbonated beverages, however, for containers having non-carbonated contents, a continuous thread formation can be advantageously employed. By this configuration, it is within the purview of the present invention to provide the thread formation with a helical engagement surface, with the centerline of the thread formation also being helically configured, but at a pitch different from that of the helical engagement surface.

(32) From the foregoing, it will be observed that numerous modifications and variations can be affected without departing from the true spirit and scope of the novel concept of the present invention. It will be understood that no limitation with respect to the specific embodiments illustrated herein is intended or should be inferred. The disclosure is intended to cover, by the appended claims, all such modifications as fall within the scope of the claims.