The present invention relates generally to closures for containers and, more particularly, to a gasketed closure for thin-walled, flexible containers having a multi-lead threaded neck. In this regard, an important aspect of the present invention is directed to a gasketed closure and thin-walled, blow molded bottle combination, wherein the closure and bottle neck have multi-lead threaded constructions and the gasket includes a thermoplastic elastomer and has a profile that resists mouth-distorting forces produced by the mating engagement of overlapping end portions of the multi-lead threads on the closure and bottle neck.
Plastic closures for containers having a thin wall construction, such as, for example, extrusion blow molded bottles, desirably must be capable of high speed application and also of accommodating imperfections in the shape of the neck finish to provide effective sealing of the container. Unlike conventional metal caps, these plastic closures often do not employ a sealing gasket or liner, but instead rely upon the properties of the plastic and the interior cap geometry to effect a seal with the container or bottle to which the closure is applied.
U.S. Pat. No. 3,901,404 describes a typical linerless plastic closure which utilizes three sealing surfaces which are integrally formed with the cap shell. These sealing surfaces engage the neck of a bottle to which the closure is applied along its inside surface, top surface and outside surface. The closure and bottle neck are of a single-lead, threaded construction. During tightening of the closure onto the bottle neck, the cap deforms or flexes to cause the sealing surface to move into flush sealing engagement with a bottle neck at both its top surface and outside surface. This closure, while suitable in many applications, suffers from the lower capping speeds associated with single-lead threaded constructions and can exhibit a potential for a less than satisfactory leakage rate particularly where there are significant imperfections in the neck finish of the blow molded bottle.
A relatively recently introduced dairy closure has found success in overcoming some of the problems associated with the closure of U.S. Pat. No. 3,901,404 by employing a thermoplastic elastomer top-seal gasket on the inside of a single-lead threaded closure. As such, this dairy closure provides improved sealing, however, it does not enjoy the higher capping speed rates and other advantages associated with multi-lead threaded closures/container neck finished constructions.
The utilization of multi-lead threaded constructions, however, while affording increased capping speeds produces mouth-distorting forces on the container neck. In particular, at locations wherein the ends of the multiple individual threads on each of the closure and the container bottle neck are in axially-spaced, overlapping relation, increased forces are imparted to the container neck in comparison to the forces imparted along the periphery of the neck wherein the individual threads are in axially-spaced, non-overlapping relation. This causes the container neck and mouth to ovalize or otherwise distort by exerting forces thereon which urge the non-overlapped thread sections outward and thereby creates a potential for increased leakage sites wherein the out-of-round container mouth does not seal with the circular, non-deformed liner or gasket.
The present invention overcomes the above-mentioned problems and disadvantages by providing a novel closure/thin-walled container combination wherein both the closure and neck of the thin-walled container are of multi-lead threaded construction and the closure includes a resilient gasket that both forms a top seal with a generally flat annular sealing surface that surrounds the open mouth of the container and resists mouth-distorting forces produced by the mating engagement of overlapping end portions of a multi-lead threads on the closure and bottle neck when the closure is applied to the container.
It is, therefore, a general object of the present invention to provide a new and improved gasketed closure cap and thin-walled container combination.
Another object of the present invention is to provide a novel gasketed closure cap which is particularly suited for use with a blow molded, thin-walled container or bottle that both accommodate irregularities and imperfections associated with the end finish of such container or bottle and also allows for high speed capping rates associated with multi-lead threaded constructions on both the interior of the cap skirt and exterior of the neck of the container.
Another object of the present invention is to provide a thermoplastic elastomer gasketed closure which is especially suitable with use for a blow molded, thin-walled container or bottle composed of high density polyethylene or polyethylene terephthalate wherein both the closure and neck of the container or bottle have a multi-lead threaded construction.
These and other objects of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings wherein like reference numerals refer to like parts and in which:
Referring to the drawings and with particular reference to
Closure cap 10 is in overlying relation to a bottle 17 having a neck portion 18, the exterior surface of which is provided with a pair of multi-lead threads 19, 20 which are adapted for mating engagement with the threads 15, 16 on the cap 10. A retaining bead 21 is axially-spaced below the threads 19, 20 for cooperative relation with the tamper-indicating band 14 when the closure cap 10 is fully seated on the bottle 10. As shown, the end portions of multi-lead threads 19, 20 are in axially-spaced, overlapping relation to each other and the neck 17 terminates in a generally flat annular sealing surface 22 which surrounds an open mouth 23.
While bottle 17 can be formed by any suitable method of construction, it is preferably formed by extrusion blow molding from thermoplastic materials such as, for example, high density polyethylene, polypropylene or polyethylene terephthalate. As such, the neck 18 and annular sealing surface 22 exhibit flexibility and are subject to minor variations which are characteristic of and inherent in the extrusion blow molding process.
In accordance with an important aspect of the present invention, gasket 13 is composed of a thermoplastic elastomer which possesses easy processability and rubbery mechanical performance. Typically, the gasket or liner composition comprises a thermoplastic component and a torque release modifier component with the thermoplastic component consisting essentially of a moldable, saturated A-B-A thermoplastic elastomer block copolymer. The torque release component can be selected from a variety of well known suitable materials such as, for example, fatty acid amides and mixtures of fatty acid amides.
A particularly suitable thermoplastic elastomer comprises a saturated A-B-A block copolymer derived from styrene and butadiene units such as, for example, a styrene-butylene-styrene (SBS) block copolymer or a styrene-ethylene-butylene-styrene (SEBS) type block copolymer which possesses about twenty to forty percent styrene and sixty to eighty percent ethylene-butylene co-monomers monomers. These SEBS polymers have polystyrene endblocks and ethylene-butylene midblocks. As such, these materials possess excellent direct bonding performance, as well as high temperature hermetic sealing characteristics, even under pasteurization, hot fill, and retort processing conditions. Additionally, they provide a desirable balance of mechanical properties combined with odorless and tasteless performance which is important in food packaging applications.
As best shown in
Referring to
As best shown in
As shown in both
In accordance with the present invention, the inclined surface 27 of rim 26 of liner or gasket 13 engages with the inner edge 24 of the sealing surface 22 of container 17 and imparts a stabilizing force on the edge 24 which resists distortion of the container mouth caused by full application of the closure cap to the container. Additionally, the support provided by inclined surface 27 of gasket 13 on the edge 24 allows a capping machine to apply increased torque during application and allows improved control of the final position of the closure as well as improved cap application torque control.
As best shown in
The present invention has been described in the context of a preferred embodiment with various modifications thereof. It will be apparent to those skilled in this art, however, that modifications and variations therefrom can be made without departing from the spirit and scope of this invention. Accordingly, this invention is to be construed and limited only by the scope of the appended claims.
Number | Date | Country | |
---|---|---|---|
Parent | 09435892 | Nov 1999 | US |
Child | 10852805 | May 2004 | US |