Abstract:
A closure cap and method of making the same wherein an annular or ring-shaped gasket is injection molded onto the inner surface of a cap shell formed of plastic or metal. The annular or ring-shaped gasket includes at least one radially extending tab integrally formed therewith. A channel in the working surface of a mold core cooperates with the inside surface of the cap to form a mold cavity having the shape of the gasket to be formed therein. The cavity includes a melt inlet and a melt outlet which is in flow communication with a cold well through a connecting portion of reduced cross-sectional area with respect to the cross-sectional areas of both the gasket-defining mold cavity and the cold well.

Description:
This application is a continuation of U.S. patent application Ser. No. 11/217,989, filed Sep. 1, 2005 (now U.S. Pat. No. 7,367,465) which, in turn, was a continuation of U.S. patent application Ser. No. 09/634,182, filed on Aug. 9, 2000 (now U.S. Pat. No. 6,964,346). 

   BACKGROUND OF THE INVENTION 
   The present invention generally relates to new and useful improvements in closure caps for glass and plastic containers and, more particularly, to a closure cap having an improved injection molded annular gasket and method of making the same. In this regard, an important aspect of the present invention is directed to a closure cap having a one-piece or unitary cap shell formed of a polyolefin such as, for example, polypropylene, in which an annular or ring-shaped gasket characterized by improved uniformity, definition and consistency which is composed of a moldable resin such as, for example, a thermoplastic elastomer, is injection molded onto the inner surface of the closure cap shell via an insert molding procedure. 
   Closure caps having full disks formed by compression or injection molding the same in a closure shell are known. For example, U.S. Pat. No. 4,398,874 describes a molding tool for forming a full disk liner in a closure shell which includes a central punch or molding member and a shell positioning sleeve disposed externally of the molding member that is received within a cap shell. Liner material deposited within the shell is contacted by the punch and forms a full disk liner with the cap shell. Correspondingly, U.S. Pat. No. 4,803,031 describes a closure cap and method wherein an injection molded full disk gasket is formed followed by injection molding the closure cap shell around the thus formed gasket. These full disk closure caps while providing generally satisfactory sealing on containers are characterized by higher manufacturing costs associated with using greater amounts of gasket-forming resin and also by the disadvantages of having the entire inside surface of the cap shell fully covered thereby increasing the possible migration of gasket components into product (particularly food products) in the container sealed therewith and also making the inner surface of the cap shell unavailable for displaying labels or other message-conveying indicia. 
   U.S. Pat. No. 5,685,443 describes a composite closure cap where an annular gasket providing a top and side seal is injection molded onto a metal disk followed by injection molding a plastic skirt around the disk in surrounding and capturing relation therewith. This composite closure while utilizing an injection molded annular gasket requires the presence of a separate disk which adds to the cost of the closure and to the complexity of manufacturing the same. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the foregoing disadvantages of these prior art closures by providing a novel closure utilizing a plastic or metal cap shell and an injection molded annular or ring-shaped gasket wherein the central portion of the inner surface of the cap shell is free of gasket material. 
   In accordance with an important aspect of the present invention, an improved closure cap is provided which includes a unitary or one-piece plastic or metal shell and an annular ring-shaped gasket having inwardly radially extending tabs integrally formed therewith, one of said tabs being formed at the location wherein plastic melt is fed to an annular gasket-forming channel in a mold core and the other of said tabs being formed at the location wherein plastic melt is discharged from said channel. The latter of said tabs, in accordance with a preferred embodiment of the present invention, includes a cold well which communicates with the annular gasket forming channel through a passageway of reduced cross-sectional area with respect to the cross-sectional areas of both the gasket forming channel and the cold well. 
   It is, therefore, an object of the present invention to provide an improved closure cap having a novel injection molded annular gasket and method of making the same. 
   Another object of the present invention is to provide a closure cap having a one-piece plastic or metal shell and an injection molded top seal annular gasket which utilizes a cost-effective amount of moldable, gasket-forming material and which provides an efficient seal with the end finish of a container to which the closure cap is applied. 
   Another object of the present invention is to provide an injection molded annular gasket formed by insert molding the same in a one-piece closure cap shell wherein the uniformity and consistency of the gasket is enhanced which gasket is characterized by integral radially extending tabs at locations along the periphery of the gasket corresponding to the locations wherein the melt is supplied to and from a gasket defining channel. 
   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: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view, partially broken away, of a closure cap embodying the present invention and a portion of a container on which the closure is fitted; 
       FIG. 2  is a bottom plan view of the closure cap shown in  FIG. 1 ; 
       FIG. 3  is a sectional view of the closure cap shown in  FIGS. 1 and 2  taken along the line  3 - 3  of  FIG. 2 ; 
       FIG. 4  is a sectional view of the closure cap shown in  FIGS. 1 and 2  taken along the line  4 - 4  of  FIG. 2 ; 
       FIG. 5  is a schematic side elevation view of a mold apparatus which can be used to manufacture the closure cap of the present invention; 
       FIG. 6  is a schematic perspective view of a portion of the moving platen of the mold apparatus shown in  FIG. 5  which is separated from a core plate of the stationary platen; 
       FIG. 7  is a schematic perspective view of the moving platen of the bold apparatus of the present invention with the stripper plate thereof removed; 
       FIG. 8  is a partial top plan view of the mold core of the present invention; 
       FIG. 9  is a sectional view taken along the line  9 - 9  of  FIG. 8 ; 
       FIG. 10  is a schematic sectional view of the core head of the mold apparatus shown in  FIGS. 8 and 9 ; 
       FIG. 11  is an enlarged sectional view of the melt discharge side of the core head shown in  FIG. 10 ; 
       FIG. 12  is an enlarged sectional view of the melt inlet side of the core head shown in  FIG. 10 ; 
       FIG. 13  is a fragmentary perspective view, partially broken away, of the closure cap of another embodiment of the present invention and a portion of a container on which the closure cap is fitted; and, 
       FIGS. 14-18  are schematic views of a mold apparatus for manufacturing the closure cap shown in  FIG. 13  with each of the views showing successive phases of the closure shell manufacturing process. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings and with particular reference to  FIGS. 1-4 , a closure cap embodying the present invention is generally designated by the reference numeral  20 . As shown, closure cap  20  is applied to a container  21  and includes an end panel  22  having an inner or bottom surface  23 , a skirt  24  which terminates in an enlarged axially extending cylindrical section  25 . 
   As best shown in  FIGS. 1 ,  3  and  4 , bottom cylindrical section  25  is, in the illustrated embodiment, connected to a tamper indicating band  26  by a plurality of frangible bridges which includes an upper band portion  27  and a lower band portion  28  which are connected by a flexible hinge  29 . Closure cap  20  is provided with a spiral thread  31  on the interior surface of skirt  24 , however, it will be appreciated that other container engaging securement systems such as, for example, conventional lugs and the like may be used without departing from the present invention. Correspondingly, the closure cap can be made with other forms of tamper indicating bands or, if desired, without any such band. 
   In accordance with an important aspect of the present invention, closure cap  20  includes an injection molded annular or ring-shaped gasket  32  positioned around the outer periphery of the inner or bottom surface  23  for top-seal engagement with an end finish or top edge  33  of container  21  which defines an open mouth  34  of the container. As shown in  FIG. 1 , container  21  includes a spiral thread  35  sized to matingly engage thread  31  on closure cap  20  and also includes a retainer bead  36  for engagement with the bottom edge of lower tamper indicating band portion  26  in a manner which is well known in the art. 
   Annular or ring-shaped injection molded gasket  32  is provided with an integral radially inwardly extending tab  37  corresponding to the location at which inlet melt feed is supplied to the mold cavity during the injection molding process and a cold well tab  38  and connector portion  39  which also are integral with the gasket  32  and which correspond to the location at which melt is discharged from the mold cavity defining the gasket. The precise manner in which these respective tabs are formed will be more fully described in connection with the mold apparatus. 
   In accordance with another aspect of the described embodiment of the present invention, the top surface  40  of gasket  32  is provided with a plurality of V-shaped ribs that provide improved seal-forming contact with the closure finish. It is important to note that the formation of these V-shaped ribs via injection molding gives them significantly better definition than that attainable by other manufacturing procedures, such as, for example, compression molding. In this regard, however, it will be appreciated that, if desired, the top surface  40  of gasket  32  can be flat or of other configurations. 
   Closure cap  20 , in accordance with the present invention, is made of suitable moldable polyolefin such as, for example, polypropylene and homopolymers and copolymers thereof. In this regard, however, it will be appreciated that other suitable moldable plastic resins may be used in forming the closure cap. Alternatively, if desired, the injection molded annular gasket of the present invention may also be incorporated in metal closures. 
   Annular or ring-shaped gasket  32  may likewise be formed of any resilient or elastomeric materials which provide the desired seal with a container finish, however, vinyl chloride-free resins or non-PVC materials are preferred. If desired, suitable additives such as those providing improved oxygen barrier and/or oxygen scavenger properties, as well as those which facilitate torque release may be incorporated into the gasket composition. 
   These non-PVC materials include rubbery block copolymers dispersed in a matrix of polyolefin as the continuous phase, with a moldable thermoplastic elastomer being especially preferred since they possess a number of processing advantages. Gasket compositions which can be effectively used include those composed of a thermoplastic elastomeric material selected from a moldable-saturated ABA-type block copolymer based on styrene and butadiene such as styrene-ethylene-butylene styrene (SEBS) type block copolymers containing from about 20% to about 40% styrene and about 60% to 80% ethylene-butylene co-monomers such as Kraton® G-2705, available from Shell Chemical Corporation. Preferred thermoplastic elastomers also include the EPDM (ethylene-propylene-dicyclopentadiene) elastomers such as those commercially available under the trade name Santropene® from Monsanto Company. Other suitable thermoplastic elastomers are those which are available from Advanced Elastomer Systems, L.P. of Akron, Ohio. 
   A suitable apparatus for manufacture of the closures of the present invention is generally depicted in  FIGS. 5-12 .  FIGS. 5-9  schematically depict a mold apparatus having a feed system for supplying preformed closure cap shells to the molding station wherein the injection molded gasket is formed via insert molding procedures. It will be appreciated that while a specific transport mechanism is described herein for supplying closure cap shells to the mold apparatus and for transportation of such closure caps through and from that apparatus, other transport feeding systems such as, for example, belt and/or robotic closure cap transportation arrangements, could be used if desired. A common feature of all molding systems which is important to the present invention, however, concerns the precise insert molding arrangement by which annular or ring-shaped gaskets are formed with exceptional preciseness in their configuration and without air entrapment. 
   As generally shown in  FIG. 5 , the molding apparatus includes a moving platen  45 , and a stationary platen  46  which comprises a core section  47 . Moving platen  45  includes a transfer drive  48 , a transfer dial  49 , a stripper plate  50  and feed chute  51  which will be more fully described in conjunction with  FIGS. 6 and 7 . Correspondingly, the core section  47  schematically shown in  FIG. 5  includes individual mold cores  52  and  53 . Melt is supplied to the core section  47  from an injection unit  54  which feeds melt to a manifold section  56  that, in turn, supplies pressurized melt feed via line  57  and  58 . 
   As best shown in  FIG. 7 , moving platen  45  includes a rotatable star wheel transfer mechanism generally depicted by the reference numeral  60  which has ten cap-receiving pockets, each of which is generally designated by the reference numeral  61 . As shown, caps are supplied from feed chute  51  into each of the individual pockets  61  until the star wheel is fully loaded. Individual mold cores on mold core section  47  are respectively received within each of the cap shells. After the gasket-forming operation is completed, the mold is opened and the completed closure caps discharge from the moving platen via discharge chute  63 . If desired, pressurized air may be used to facilitate loading and removal of the cap shells in the star wheel transfer mechanism. In this regard, it will be appreciated that the number of cap-receiving pockets located in the star wheel can be varied. For example, in the arrangement illustratively depicted in  FIG. 7 , ten cap-receiving pockets are shown, while eight such pockets are shown in  FIG. 6 . 
   Referring to  FIG. 6 , it will be observed that a core plate  64  is depicted in space-away relationship to the moving platen  46 . As will be apparent from the description of  FIGS. 8 and 9 , the portion of core plate  64  facing moving platen  45  includes a plurality of standoff posts (shown in  FIG. 8  and designated by reference numeral  65 ) which control the depth of penetration of the individual mold cores into each of the closure cap shells. 
   Referring now to  FIGS. 8-12 , each of the mold cores (designated by reference numeral  52 ) is sized to be received within the closure cap shell for direct contact with the inner or bottom surface  23  of end panel  22  of a given closure cap. Melt supplied from manifold  56  and melt feed line  57  is discharged through a gate  66  into an inlet melt feed line  68  and from there into an annular channel  67  which, together with the inner or bottom surface  23  of the closure cap forms a gasket-defining mold cavity. Typically, with plastic enclosure cap shells, the mold cores will penetrate the end panel surface to a limited and controlled extent, while with metal closure cap shells no such penetration is needed in order to achieve effective melt flow shut-off for containment of the melt within the gasket-defining mold cavity. The melt flow from inlet  68  passes in clockwise and counterclockwise directions through the annular channel  67  and is discharged into a cold well portion  73  of the core via a connecting passage  74 . In accordance of an important aspect of the present invention, the connecting passage  74  has a reduced cross-sectional configuration to ensure that the meeting melt streams will knit at that location and, additionally, eliminates or at least greatly minimize the trapping of any air in the gasket itself. This reduced size passageway results in a lower pressure on the inside portion of the cold well than is present in the annular gasket-defining portion  67  causing any air present in the melt to be readily discharged into the cold well. 
   As shown, a vent line  71  can be provided to draw a vacuum on the system to further facilitate air removal during the feed of melt. Also, as shown, an air line  72  can be provided to facilitate removal of the finished closure after the injection molding of the gasket has been accomplished and the mold opened. If desired, vent line  71  and air line  72  can be coupled to further facilitate removal of the finished closure when the molding operation is complete. 
   Heat built up during the injection molding process can be dissipated through the use of water cooling, which can be accomplished by an outlet water line  70  which is in flow communication with an inlet water line (not shown). 
   As best shown in  FIGS. 11 and 12 , the bottom surface  75  of annular channel  67  is provided with a plurality of V-shaped grooves which form a plurality of concentric V-shaped ribs that impart improve seal-forming contact with the closure finish. As previously noted, the formation of these V-shaped ribs by injection molding process gives them significantly better definition than is achievable by other molding procedures. 
     FIG. 13  generally designates a further embodiment of the present invention in the form of a modified closure cap  80  having a layer of metallic foil or other suitable material bonded to the inner surface  23  of end panel  22  and to which the annular or ring-shaped injection molded gasket is bonded. This construction is particularly suitable for applications wherein improved oxygen barrier properties are required and/or where it is desirable to provide a visible display on the interior of the closure cap. As such, the annular injection molded gasket is particularly suitable for such applications, since it leaves the central portion of the panel exposed, enabling use of such area for the display of printed matter and the like. 
     FIGS. 14-18  illustrate one procedure for manufacturing this closure shell. As shown in  FIG. 14 , a mold apparatus is provided which includes an upper mold component  83  having a melt feed line  84  and gate  85 , a lower mold component  86  and a core  87 . A sheet or strip of foil or other suitable material which is to be laminated to the interior surface  23  of the closure cap shell is positioned between upper and lower mold components  83 ,  86 . As shown in  FIG. 15 , these mold components are closed, thereby trapping and securely holding the strip  82  in place. 
   Core  87  is then positioned within lower mold component  86  in direct contact with the strip  82  and defines a mold cavity  88  which corresponds to the configuration of the closure cap to be formed therewith. A supply of melt  89  is then fed into the cavity which, as shown in  FIG. 17 , forms closure portion  90  and, at the same time, due to the high pressure of the melt feed, breaks the marginal portions of the foil strip and continues to flow as shown in  FIG. 18  to form the finished closure shell. The mold portions are then opened and the formed closure cap shell removed therefrom. 
   While the present invention has been described in connection with the context of various embodiments, it will be apparent to those skilled in this art that modifications and variations may be made therefrom 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.