One-piece thermoplastic closure having press-on screw off structure including spaced vertical ribs in the skirt of the closure

Claim 2

A closure for a container having generally helical threads on the neck finish, the closure comprising a one-piece molded cap shell of non-heat shrunk thermoplastic including a top wall and a peripheral skirt, the skirt having means thereon for engaging threads of the neck of a container, the means including a plurality of spaced, flexible generally vertical non-heat shrunk thermoplastic ribs integral with the skirt, each rib being so constructed and arranged that it has sufficient resistance to coald flow that the rib only slightly bends around the thread to form a slight indentation on the rib when the rib is forced into contact with the thread, the slight indentation being sufficient to provide purchase on the threads for removing the closure, there being a resilient deformable gasket liner inside the cap shell for a top seal, the liner located between the top cap wall and the top of the finish of the container, the cap shell being made of high density polyethylene and the gasket of foamed polyvinyl chloride.

Claim 3

A closure for a container having generally helical threads on the neck finish, the closure comprising a one-piece molded cap shell of non-heat shrunk thermoplastic material including a top wall and a peripheral skirt, the skirt having means thereon for engaging threads of the neck of a container, the means including a plurality of spaced, flexible generally vertical non-heat shrunk thermoplastic ribs integral with the skirt, each rib being so constructed and arranged that it has sufficient resistance to cold flow that the rib only slightly bends around the thread to form a slight indentation on the rib at the crest of the rib when the rib is forced into contact with the thread, the slight identation being sufficient to provide purchase on the threads for removing the closure, there being limited contact between the rib and threads amounting to less than 50% of the area at the crest of the rib, the thermoplastic of the rib having a modulus and resistance to cold flow at least about equivalent to that of polyethylene having a specific gravity of 0.942 to 0.965, a melt flow index of about 0.2 to 8 and a melt viscosity at 190° C. of about 7,000 to 120,000 poises, there being a resilient deformable gasket liner inside the cap shell for a top seal, the liner located between the top cap wall and the top of the finish of the container, the cap shell being high density polyethylene, the gasket being a foamed polyvinyl chloride, and each rib has a length about 3 to 4 times the width, the width being about 3/4 to 11/4 times the height of the rib.

Claim 4

A closure for a container having generally helical threads on the neck finish, the closure comprising a one-piece molded cap shell of non-heat shrunk thermoplastic material including a top wall and a peripheral skirt, the skirt having means thereon for engaging threads of the neck of a container, the means including a plurality of spaced, flexible generally vertical non-heat shrunk thermoplastic ribs integral with the skirt, each rib being so constructed and arranged that it has sufficient resistance to cold flow that the rib only slightly bends around the thread to form a slight indentation on the rib at the crest of the rib when the rib is forced into contact with the thread, the slight identation being sufficient to provide purchase on the threads for removing the closure, there being limited contact between the rib and threads amounting to less than 50% of the area at the crest of the rib, the thermoplastic of the rib having a modulus and resistance to cold flow at least about equivalent to that of polyethylene having a specific gravity of 0.942 to 0.965, a melt flow index of about 0.2 to 8 and a melt viscosity at 190° C. of about 7,000 to 120,000 poises, there being a resilient deformable gasket liner inside the cap shell for a top seal, the liner located between the top cap wall and the top of the finish of the container, the cap shell being high density polyethylene, the gasket being a foamed polyvinyl chloride, and each rib has a length about 3 to 4 times the width, the width being about 3/4 to 11/4 times the height of the rib.