Closure cap with injection molded annular gasket and method of making same

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 radially extending tabs integrally formed therewith, one of said tabs being formed at a location wherein the plastic melt is fed to an annular gasket-forming channel in a mold core and another of said tabs being formed at the location wherein plastic melt is discharged from said channel. Preferably, said other tab includes a cold well formation which communicates with the annular gasket through a connecting portion of reduced cross-sectional area with respect to the cross-sectional areas of both the gasket and the cold well formation.

What is claimed:  
     
         1 . A closure cap comprising: 
 a shell which includes an end panel and an integral skirt downwardly extending therefrom, said end panel having a generally circular inside surface of a given outer diameter; and,    an injection molded annular gasket having a ring-shaped body which includes an outer edge and an inner edge, said outer edge having a diameter which is less than the outer diameter of said end panel inner surface whereby said outer edge of said gasket body is inwardly spaced from the outer periphery of said end panel inside surface to define a substantially gasket-free annular border which surrounds said ring-shaped gasket body, said gasket having a width sufficient to provide a top seal with an end finish of a container mouth to which said closure is applied, said inner edge of said ring-shaped gasket body surrounding a substantially gasket-free interior portion of said inside surface of said end panel, said gasket also including a first inwardly extending tab of generally uniform cross section formed therewith and a second inwardly extending tab integrally formed therewith, said second tab including an inner-most and an outer-most portion, said inner-most portion having a relatively small cross section with respect to the cross section of said outer-most portion.    
     
     
         2 . The closure of  claim 1  wherein said first and second tabs extend radially inwardly from the inner edge of said ring-shaped gasket body.  
     
     
         3 . The closure cap of  claim 2  wherein said first and second tabs are oppositely disposed along the circumference of said ring-shaped gasket body.  
     
     
         4 . The closure cap of  claim 1  wherein said ring-shaped gasket body includes a top seal-forming surface defined by a plurality of concentric ribs.  
     
     
         5 . The closure cap of  claim 4  wherein said concentric ribs are conically shaped.  
     
     
         6 . The closure cap of  claim 1  wherein said gasket is composed of a moldable resin which is substantially free of vinyl chloride.  
     
     
         7 . The closure cap of  claim 1  wherein said gasket is composed of a thermoplastic elastomer.  
     
     
         8 . The closure cap of  claim 1  wherein said shell is formed of a moldable thermoplastic resin.  
     
     
         9 . The closure cap of  claim 8  wherein said thermoplastic resin is a polyolefin.  
     
     
         10 . The closure cap of  claim 9  wherein said thermoplastic resin is polypropylene.  
     
     
         11 . The closure cap of  claim 8  wherein said end panel of said shell includes a layer of an oxygen barrier film.  
     
     
         12 . The closure cap os  claim 11  wherein said layer of oxygen barrier film is adhered to the inside race or said end panel.  
     
     
         13 . The closure cap of  claim 1  wherein said shell is composed of a metal.  
     
     
         14 . A closure cap comprising: 
 a shell which includes an end panel and an integral skirt downwardly extending therefrom, said end panel having a generally flat, circular inside surface of a given outer diameter; and,    an injection molded annular gasket having a ring-shaped body which includes an outer edge and an inner edge, said outer edge having a diameter which is less than the outer diameter of the end panel inner surface thereby providing a substantially gasket-free annular border which surrounds said ring-shaped gasket body, said gasket body having a width sufficient to provide a top seal with an end finish of a container mouth to which said closure is applied, said inner edge of the ring-shaped gasket body surrounding a substantially gasket-free interior portion of the inside surface of said end panel inner surface; said gasket also including first and second tabs extending radially inwardly from the inner edge of said ring shaped gasket body, said second tab including an inner-most portion adjacent said inner edge of said ring-shaped gasket and an outer-most portion,    
     
     
         15 . The closure cap of  claim 14  wherein said first and second tabs are oppositely disposed along the circumference of said ring-shaped gasket body.  
     
     
         16 . The closure cap of  claim 14  wherein said ring-shaped gasket body includes a top seal-forming surface defined by a plurality of concentric ribs.  
     
     
         17 . The closure cap of  claim 14  wherein said concentric ribs are conically-shaped.  
     
     
         18 . The closure cap of  claim 14  wherein said gasket is composed of a thermoplastic elastomer.  
     
     
         19 . The closure cap of  claim 14  wherein said shell is formed of a moldable thermoplastic resin.  
     
     
         20 . The closure cap of  claim 14  wherein said thermoplastic resin is a polyolefin.  
     
     
         21 . The closure cap of  claim 20  wherein said thermoplastic resin is polypropylene.  
     
     
         22 . The closure cap of  claim 19  wherein said end panel of said shell includes a layer of an oxygen barrier film.  
     
     
         23 . The closure cap of  claim 22  wherein said layer of oxygen barrier film is adhered to the inside face of said end panel.  
     
     
         24 . The closure cap of  claim 14  wherein said shell is composed of a metal.  
     
     
         25 . A method of making a closure cap having an injection molded ring-shaped gasket, said method comprising: 
 providing an injection mold having first and second mold components which are moveable with respect to each other between an open position and a closed position, said first mold component having a cap shell-receiving portion, said second mold component including a core: 
 positioning said first and second mold components into an open position;  
 inserting a preformed cap shell which includes a circular end panel having a given diameter, a circular inside surface and an integral skirt in surrounding relation thereto;  
 closing said mold to position said core within the cap shell, a working surface on said core being in contact with said inside surface of said cap shell end panel, said core working surface having a ring-shaped channel formed therein which is defined by outer and inner peripheral edges, said channel forming a gasket defining mold cavity with said inside surface of said cap shell, said core working surface including peripherally-spaced and inwardly-extending melt inlet and outlet channels in flow communication with said ring-shaped channel, said outlet channel including a pressure reducing flow restriction, said inner and outer peripheral edges of said channel being sealingly engageable with the inside surface of said cap shell where said mold is in said closed position to provide melt-flow shut-off barriers therewith;  
 supplying a melt flow under pressure into said melt inlet channel to feed melt through said gasket defining cavity;  
 continuing said supply of pressurized melt flow until a lead portion of said flow is received in said outlet channel and a complete gasket is formed in said cavity; and,  
 opening said mold and removing said closure cap shell with the injection molded gasket formed therein.  
   
     
     
         26 . The method of  claim 25  wherein said outlet channel includes a cold well which communicates with said ring-shaped channel through a passageway having a reduced cross-sectional area with respect to the cross-sectional areas of each of said ring-shaped channel and said cold well.  
     
     
         27 . The method of  claim 25  wherein said ring-shaped channel has a bottom surface defined by a plurality of concentric rings to provide the molded gasket formed therein with a top seal-forming surface defined by a plurality of sharply-defined concentric ribs.  
     
     
         28 . The method of  claim 27  wherein said concentric rings have a V-shaped cross-section which produce a conically-shaped cross section on the corresponding concentric ribs in the seal-forming surface of the molded gasket.  
     
     
         29 . The method of  claim 25  wherein at least one of said mold components includes a stand-off post which contacts the other of said mold components when said first and second mold components are in a closed position to precisely control the position of said core in said cap shell.  
     
     
         30 . The method of  claim 29  wherein said second mold component includes said stand-off post.  
     
     
         31 . The method of  claim 25  wherein said inlet and outlet channels are oppositely disposed with respect to each other along the inner circumference of said ring-shaped channel.  
     
     
         32 . The method of  claim 25  wherein said cap shell is composed of a moldable thermoplastic resin and said inner and outer peripheral edges of said channel penetrate said inside surface of said cap shell to produce said melt-flow shut-off barriers.  
     
     
         33 . A method of making a closure cap having an injection molded ring-shaped gasket, said method comprising: 
 providing an injection mold having first and second mold components which are moveable with respect to each other between an open position and a closed position, said first mold component having a cap shell-receiving portion, said second mold component including a core;    positioning said first and second mold components into an open position;    inserting a preformed shell composed of a moldable thermoplastic resin which includes a circular end panel having a given diameter, a circular inside surface and an integral skirt in surrounding relation thereto;    closing said mold to position said core within the cap shell, a working surface on said core being in contact with said inside surface of said cap shell end panel, said core working surface having a ring-shaped channel formed therein which is defined by outer and inner peripheral edges, said channel forming a gasket defining mold cavity with said inside surface of said cap shell, said core working surface including peripherally-spaced and inwardly-extending melt inlet and outlet channels in flow communication with said ring-shaped channel, said outlet channel including a cold well which communicates with said ring-shaped channel through a passageway having a reduced cross-sectional area with respect to the cross-sectional areas of each of said ring-shaped channel and said cold well, said inner and outer peripheral edges of said channel penetrating the inside surface of said cap shell when said mold is in said closed position to provide melt-flow shut-off barriers therewith;    supplying a melt flow under pressure into said melt inlet channel to feed melt through said gasket defining cavity;    continuing said supply of pressurized melt flow until a lead portion of said flow is received in said outlet channel and a complete gasket is formed in said cavity; and,    opening said mold and removing said closure cap shell with the injection molded gasket formed therein.    
     
     
         34 . The method of  claim 33  wherein said ring-shaped channel has a bottom surface defined by a plurality of concentric rings to provide the molded gasket formed therein with a top seal-forming surface defined by a plurality of sharply-defined concentric ribs.  
     
     
         35 . The method of  claim 34  wherein said concentric rings have a V-shaped cross-section which produce a conically-shaped cross section on the corresponding concentric ribs in the seal-forming surface of the molded gasket.  
     
     
         36 . The method of  claim 33  wherein at least one of said mold components includes a stand-off post which contacts the other of said mold components when said first and second mold components are in a closed position to precisely control the position of said core in said cap shell.  
     
     
         37 . The method of  claim 36  wherein said second mold component includes said stand-off post.  
     
     
         38 . The method of  claim 33  wherein said inlet and outlet channels are oppositely disposed with respect to each other along the inner circumference of said ring-shaped channel.