The present disclosure is directed to plastic closures for beverage, food, juice, pharmaceutical and like applications, and more particularly to a closure, package and method of manufacture that are particularly well suited for high-temperature (e.g., pasteurization, hot-fill and retort) applications.
It heretofore has been proposed to provide a plastic closure for a container, which includes a plastic cap or shell with an interior liner for sealing engagement with a sealing surface of the container finish. For example, U.S. Pat. No. 4,984,703 discloses a plastic closure that comprises a shell having a base wall with a peripheral skirt and at least one internal thread or bead for securing the closure to a container finish, and a sealing liner compression molded in situ on the interior of the shell base wall. U.S. Pat. No. 5,451,360 discloses a method and apparatus for compression molding the liner in situ within the closure shell. It also has been proposed to provide plastic resin barrier materials within the sealing liner for resisting transmission of gases (e.g., carbon dioxide and oxygen), water vapor and/or flavorants through the liner. For example, U.S. Pat. No. 6,371,318 discloses a plastic closure and method of manufacture in which the liner is compression molded in situ on the interior surface of the closure base wall, and includes a multiplicity of alternating layers of matrix polymer such as EVA and barrier polymer such as EVOH. U.S. Pat. No. 6,399,170 discloses a plastic closure and method of manufacture in which the liner is compression molded in situ on the interior surface of the closure base wall, and includes a dispersion of barrier polymer platelets, such as EVOH, in a matrix polymer such as EVA.
It is desirable to provide a closure and liner construction, a method of closure manufacture, and a closure and container package that are particularly well adapted for high-temperature applications. Such high-temperature applications include, for example, applications in which the container is filled with product while the product is hot, such as so-called hot fill applications. High-temperature applications also include applications in which the filled package is subjected to pasteurization or retort after filling. During retort applications, for example, the filled package may be subjected to a temperature of 265° F. for fifteen minutes or more. High-temperature situations can also occur when a package is filled with a carbonated beverage and stored or transported under high-temperature conditions in which the internal pressure within the container can increase dramatically. In all of such high-temperature situations, the container closure is subjected to elevated internal pressure, which tends to distort or dome the closure base wall and lift the sealing liner away from sealing engagement with the container finish.
U.S. Patent document 2003/0098286 discloses a plastic closure that has particular utility for such high temperature and retort applications. The closure includes a shell having a base wall and a skirt with one or more internal threads for securing the closure to a container finish. In some embodiments, a plastic disk is loosely captured within the closure shell. An annular ring extends axially from the disk adjacent to but spaced from the periphery of the disk. A resilient liner is molded onto the disk over at least the central portion of the disk and over the ring on the disk. The ring urges the liner into sealing engagement with the radially inner edge and the axial end of the container finish when the closure is secured to the container finish. In some embodiments of the closure, the disk includes an annular rib around the periphery of the disk, with the liner extending around the inner periphery of the rib. The disk thus urges the liner into sealing engagement with the inner and outer edges of the container finish as well as the axial end of the container finish. When a filled package that includes such a closure is subjected to elevated temperatures, during retort applications for example, the liner is maintained in sealing contact with the container finish.
U.S. Patent document 2004/0108294 discloses a plastic closure, package and method of manufacture that are particularly well suited for high-temperature and retort applications. The closure includes a plastic closure shell having a base wall with a central opening and a skirt with at least one internal thread or bead for securing the closure to a container neck finish. A plastic disk is retained within the shell parallel to but spaced from the base wall. The disk includes a plurality of axially extending spacer elements around the disk to engage the undersurface of the base wall and space the disk from the base wall of the shell. A plurality of angularly spaced fingers preferably extend from the disk through the central opening of the shell base wall to retain the disk within the shell. A resilient liner is disposed on an underside of the disk, preferably by being compression molded in situ, for sealing engagement with the container neck finish.
It is a general object of the present disclosure to provide a closure, package and method of manufacture of the general type disclosed in the above-noted U.S. Patent documents, in which the sealing liner is economically molded in situ onto the undersurface of the disk.
The present disclosure embodies a number of aspects or inventions that can be implemented separately from or in combination with each other.
A method of making a closure that includes an end panel and a sealing liner on one face of the end panel, in accordance with a first aspect of the present disclosure, includes providing an injection mold having at least first and second mold elements, at least one of which is movable with respect to the other. The first and second mold elements are positioned to form a first mold cavity, and the end panel is injection molded within the first mold cavity. At least one of the first and second mold elements then is moved to form a second mold cavity in which a face of the end panel forms at least one mold cavity wall, and the sealing liner is injection molded onto the face of the end panel. The end panel and liner are then removed from the second mold cavity. The liner/panel subassembly thus is provided more easily and economically than if the liner were compression molded in situ onto the undersurface of a separately formed panel. The closure preferably is a two-piece closure, and the method preferably includes the step of assembling the end panel to a separately formed closure shell. The closure may be a one-piece closure in which the liner is molded to the undersurface of the end panel that forms the base wall of a closure shell.
A two-piece plastic closure in accordance with another aspect of the present disclosure includes a plastic closure shell having a base wall with a skirt for securing the closure to a container neck finish. A plastic disk is loosely retained within the shell parallel to but separate from the base wall. The disk includes a plurality of axially extending spacer elements around the disk to engage an undersurface of the base wall and space the disk from the base wall of the shell. A resilient sealing liner is molded in situ on an underside of the disk in a two-material molding operation for sealing engagement with a container neck finish. There preferably are angular gaps between the spacer elements to permit flow of fluid through a central opening on the closure shell, between the base wall and the disk, and through the gaps to flush debris from between the closure shell and disk. The disk preferably includes angularly spaced fingers that extend from the disk through the central opening of the shell base wall to retain the disk within the shell.
The disclosure, together with additional objects, features, advantages and aspects thereof, will best be understood from the following description, the appended claims and the accompanying drawings, in which:
The disclosures of above-noted U.S. Patent documents 2003/0098286 and 2004/0108294 are incorporated herein by reference.
In accordance with the illustrated embodiments of the present disclosure, liner 32 is molded onto the undersurface of end-panel disk 30 or 52 in a multi-material or a multi-component injection molding operation, preferably a two-material injection molding operation. A multi-material injection molding operation is one in which multiple material parts or components are molded in a single machine cycle. An exemplary mold 60 is illustrated schematically in
The method of manufacture and the mold schematically illustrated in
There thus have been disclosed a closure, a package and a method of manufacture that fully satisfies all of the objects and aims previously set forth. The disclosure has been presented in conjunction with presently preferred exemplary embodiments, and additional modifications and variations have been discussed. Other modifications and variations readily will suggest themselves to persons of ordinary skill in the art in view of the foregoing discussion. For example, mold 60 could be configured to mold a one-piece closure shell and a sealing liner onto the undersurface of the shell base wall. Mold 60 preferably is configured to mold multiple disk/liner subassemblies in a single operation. The disclosure is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.