Screw cap core seal structure

Abstract

A screw cap for containers comprises a screw cap body ( 10 ) and an expandable core seal ( 24 ) with an annular sealing element ( 30 ). A peripheral part ( 36 ) of a seal energizing clement ( 38 ) expands radially as the screw cap body ( 10 ) is screwed onto a container. The peripheral part ( 36 ) is joined to a backing ( 34 ) of the annular scaling element ( 30 ) which comprises a plurality of separate, axially extending segments ( 42, FIG. 4 ). The axial compression of the seal energising clement ( 38 ) thereby not only makes the adjacent part of the scaling element ( 30 ) tend to expand radially, but also makes the axially extending segments ( 42 ) tend to rotate upwardly and outwardly. A more evenly distributed sealing pressure of the annular sealing element ( 30 ) results.

1 . A screw cap comprising:
 a cap body comprising an end wall and an internally threaded, annular side wall depending from the end wall;   an annular sealing element disposed concentrically within and spaced from the annular side wall so as to be receivable within an externally threaded container neck when the screw cap is screwed onto the container neck;   the annular sealing element comprising a detent engageable with the container neck so as to support the annular sealing element within the container neck as the screw cap is screwed onto the container neck;   a resiliently deformable seal energizing element comprising a central part braced against the cap body end wall and a peripheral part joined to the annular sealing element; the seal energizing element being constructed and operatively arranged within the cap body so that axial compression of the seal energizing element between central part and the peripheral part as the cap body is screwed onto the container neck causes radial expansion of the seal energizing element at the peripheral part, thereby radially expanding the annular sealing element towards the inner surface of the container neck;   the annular sealing element comprising a backing formed from a relatively stiff but resilient material and a radially outer facing of a relatively more yielding material, wherein the backing extends in a direction away from the cap body end wall to below the level of the detent;   characterised in that:   the peripheral part of the seal energizing element is joined to the backing at a level at or below the detent, and the backing below this level comprises a plurality of separate, axially extending segments.   
     
     
         2 . The screw cap of  claim 1 , in which the seal energising element and the annular sealing element comprise parts of an expandable plug seal subassembly positionable within the screw cap. 
     
     
         3 . The screw cap of  claim 2 , in which the plug seal subassembly and cap body comprise a snap-fit connection by which plug seal subassembly is held in the cap body even when the screw cap is not screwed onto the container neck. 
     
     
         4 . The screw cap of  claim 3 , in which the snap-fit connection comprises a recess at the central part of the seal energizing element, into which a projection extending from the cap body end wall is snap-fittingly received. 
     
     
         5 . The screw cap of  claim 4 , in which the projection comprises a plurality of axially extending fingers or segments. 
     
     
         6 . The screw cap of  claim 4 , in which the projection comprises an enlarged end which is snap-fittingly received in an undercut portion of the recess at the central part of the seal energizing element. 
     
     
         7 . The screw cap of  claim 3 , in which the snap-fit connection allows relative rotation between the seal energizing element and the cap body, whereby normally there is substantially no relative rotation between the annular sealing element and the container neck as the screw cap is screwed on or unscrewed. 
     
     
         8 . The screw cap of  claim 2 , in which the detent is integrally formed with the expandable plug seal subassembly as an annular flange extending radially from an upper portion of the backing. 
     
     
         9 . The screw cap of  claim 1 , in which the backing and seal energizing element comprise through-going slots extending radially in the seal energizing element and axially in the annular sealing element, and in which the axially extending through-going slots serve to define the plurality of separate, axially extending segments of the backing. 
     
     
         10 . The screw cap of  claim 9 , in which the axially extending through-going slots continue into an annular flange which forms the detent. 
     
     
         11 . The screw cap of  claim 9 , in which the axially extending through-going slots are united with, run into, or become, the radial through-going slots in the seal energizing element. 
     
     
         12 . The screw cap of  claim 9 , in which a bottom surface of the seal energizing element has a covering of a softer and more compliant material to seal the slots therein. 
     
     
         13 . The screw cap of  claim 12 , in which the covering is continuous with the facing. 
     
     
         14 . The screw cap of  claim 1 , in which the seal energizing element comprises a domed shape which becomes flatter and expands radially as the detent engages the container neck, the cap body is screwed onto the container neck and the cap body end wall presses down on the central part of the seal energizing element. 
     
     
         15 . The screw cap of  claim 2 , in which the expandable plug seal subassembly comprises a through-going aperture, over which a gas permeable, liquid impermeable membrane is secured, to provide a gas venting path. 
     
     
         16 . The screw cap of  claim 15 , in which the through-going aperture is formed in the seal energizing element. 
     
     
         17 . The screw cap of  claim 16 , in which the through-going aperture is formed in a recess at the central part of the seal energizing element. 
     
     
         18 . The screw cap of  claim 17 , in which the recess comprises the recess of the snap-fit connection as defined in  claim 4 . 
     
     
         19 . The screw cap of  claim 15 , in which the detent and/or the inside surface of the cap body end wall are provided with grooves or projections which space the detent away from the inside surface of the cap body end wall when the screw cap is fully tightened.