Plastic lid for an open topped container

Abstract

A plastic lid is provided for an open topped generally circular container having an outwardly directed lip encircling the open top of the container. The lid comprises a rim of generally annular shape to cooperate with the outwardly directed lip of the container and a squat generally cylindrical section extending from an inner periphery of the rim to a closure wall at its operatively inner end to form a plug type of closure adapted to form a seal with an inner periphery of the container. The lid has at least one locking member that is an endless locking ring connected to the rim by way of one or more integral frangible connecting elements. The locking member is adapted to operatively cooperate with the lip of the container such that fracturing of one or more of said integral frangible connecting elements occur attempted removal of the lid from the container.

1 . A plastic lid for an open topped generally circular container of the type having an outwardly directed lip encircling the operatively upper open end of the container, the plastic lid comprising:
 a rim of generally annular shape and configured to cooperate with the outwardly directed lip of the container, in use; and   a squat generally cylindrical section formed integral at its operatively outer end with the inner periphery of the rim and having formed integral therewith at its operatively inner end a closure wall such that the cylindrical section and closure wall together form a plug type of closure adapted to form a seal with the inner periphery of a the container,   wherein at least one locking member is connected to the rim by way of one or more integral frangible connecting elements,   and wherein the locking member is adapted to operatively cooperate with the lip of the container such that fracturing of one or more of said integral frangible connecting elements occurs during removal or attempted removal of the lid from the container.   
     
     
         2 . The plastic lid as claimed in  claim 1  in which the locking ring carries on its outer surface, a retainer ridge or groove. 
     
     
         3 . The plastic lid as claimed in  claim 11  in which a single retaining connecting element of more robust proportions attaches the locking ring to the rim of the lid to hold the ring captive unless the ring and lid are more firmly torn away from each other. 
     
     
         4 . The plastic lid as claimed in  claim 1  in which the frangible connecting elements are located radially inwards of the outer periphery of the rim. 
     
     
         5 . The plastic lid as claimed in  claim 1  in which the outer periphery of the rim has a downturned return flange. 
     
     
         6 . The plastic lid as claimed in  claim 1  in combination with a thermoformed container that inherently has an inwardly directed endless bead formed immediately adjacent the open end and that is of smoothly rounded shape in cross-section. 
     
     
         7 . An injection moulding process for producing a plastic lid as claimed in  claim 1  in which a mould cavity is formed by
 a primary outer mould member contoured to mould the outer top surface of the lid and movable coaxially between its operative and inoperative positions;   a sliding core mould member contoured to mould the inside surface of the closure wall of the lid and movable in the same axial direction;   a sliding sleeve slidable coaxially on the core mould member and having an edge configured to mould the outside surface of the squat cylindrical section, the inside surface of the locking ring, and undersurface of the rim between the locking ring and squat cylindrical section;   a coaxial stripper ring also movable coaxially and configured to mould the outer surface of the part of the locking ring adjoining the rim and, together with the end region of the sliding sleeve, to form a multitude of frangible connecting webs or bridges between the locking ring and rim; and   a concentric collar coaxially slidable on the sliding sleeve for forming the balance of the outer surface of the locking ring of the lid,   wherein movement of said parts of the mould is arranged such that the end of the sliding sleeve is withdrawn from a moulded component prior to it being released by the stripper ring.   
     
     
         8 . An injection mould assembly for producing a plastic lid as claimed in  claim 1  in which a mould cavity is formed by
 a primary outer mould member contoured to mould the outer top surface of the lid and movable coaxially between its operative and inoperative positions and   a sliding core mould member contoured to mould the inside surface of the closure wall of the lid and movable in the same axial direction, wherein the mould assembly further comprises:   a sliding sleeve slidable coaxially on the core mould member and having an edge configured to mould the outside surface of the squat cylindrical section, the inside surface of the locking ring, and undersurface of the rim between the locking ring and squat cylindrical section;   a coaxial stripper ring also movable coaxially and configured to mould the outer surface of the part of the locking ring adjoining the rim and, together with the end region of the sliding sleeve, to form a multitude of frangible connecting webs or bridges between the locking ring and rim; and   a concentric collar coaxially slidable on the sliding sleeve for forming the balance of the outer surface of the locking ring of the lid,   wherein axial movement of said parts of the mould may be arranged such that the end of the sliding sleeve is withdrawn from a moulded component prior to it being released by the stripper ring.   
     
     
         9 . The injection mould assembly as claimed in  claim 8  in which the stripper ring has a groove or ridge for moulding a retainer ridge or groove in the outer surface of the locking ring for ensuring removal of the sliding sleeve from a moulded lid prior to disengagement of the lid from the stripper ring. 
     
     
         10 . The injection mould assembly as claimed in  claim 8  in which cooperating surfaces of the stripper ring and collar are bevelled to enable a relatively small operative mould surface to be provided on the stripper ring. 
     
     
         11 . The plastic lid as claimed in  claim 1  in which the locking member is an endless locking ring having an endless latch formation for engaging the underside of the outwardly directed lip of the container. 
     
     
         12 . The plastic lid as claimed in  claim 1  in which the said one or more frangible connecting elements are a multitude of frangible webs or bridges formed integral with the rim and locking ring and spaced apart equally and angularly relative to each other. 
     
     
         13 . A plastic lid for an open topped generally circular container of the type having an outwardly directed lip encircling the operatively upper open end of the container, the plastic lid comprising:
 a rim of generally annular shape and configured to cooperate with the outwardly directed lip of the container, in use; and   a squat generally cylindrical section formed integral at its operatively outer end with the inner periphery of the rim and having formed integral therewith at its operatively inner end a closure wall such that the cylindrical section and closure wall together form a plug type of closure adapted to form a seal with the inner periphery of the container,   wherein at least one locking member in the form of an endless locking ring having an endless latch formation for engaging the underside of the outwardly directed lip of the container is connected to the rim by way of one or more integral frangible connecting elements in the form of a multitude of frangible webs or bridges formed integral with the rim and locking ring and spaced apart equally and angularly relative to each other,   and wherein the locking member is adapted to operatively cooperate with the lip of the container such that fracturing of one or more of said integral frangible connecting elements occurs during removal or attempted removal of the lid from the container.   
     
     
         14 . The plastic lid as claimed in  claim 13  in which the locking ring carries on its outer surface, a retainer ridge or groove. 
     
     
         15 . The plastic lid as claimed in  claim 13  in which a single retaining connecting element of more robust proportions attaches the locking ring to the rim of the lid to hold the ring captive unless the ring and lid are more firmly torn away from each other. 
     
     
         16 . The plastic lid as claimed in  claim 13  in which the frangible connecting elements are located radially inwards of the outer periphery of the rim. 
     
     
         17 . The plastic lid as claimed in  claim 13  in which the outer periphery of the rim has a downturned return flange. 
     
     
         18 . The plastic lid as claimed in  claim 13  in combination with a thermoformed container that inherently has an inwardly directed endless bead formed immediately adjacent the open end and that is of smoothly rounded shape in cross-section.