Linerless closure with crushable seal

Claim 1

A linerless closure for sealing a glass finish on a glass container having an external screw thread for threadably receiving said closure, said closure comprising a one piece body of polypropylene having a top end wall for extending across the open top of a container, a dependent skirt wall integrally joined to said top end wall about the outer circumference of said top end wall, an integral screw thread formed on the inner side of said skirt wall for threading engagement with the external screw thread on a glass container, a rigid V-shaped sealing fin projecting downwardly from said top end wall, said V-shaped sealing fin being substantially triangular shaped in cross section and being rigid to transmit closure torque loading forces applied thereto to said top end wall, said V-shaped sealing fin having a lower sealing end for sealing engagement with the container finish, said end having a radius of 0.005 inch or less than 0.005 inch and having upwardly extending walls defining an apex angle within the range of 40° to 60° and having a cross-sectional width in the range of 0.04 to 0.06 inch at the juncture of the fin of said top end wall, and being formed of polypropylene having a compressive strength of less than about 15,000 psig to define a crushable end to flatten and to cold flow and to permanently deform into a width at least several times greater than 0.005 inch with conventional closure torques and thereby to seal with imperfections in said finish, said top end wall having a thickness of at least about 0.070 inch from the juncture of said skirt wall and top end wall to at least the sealing ring diameter and said skirt wall having a thickness of at least 0.048 inch to withstand compressive forces in the range of 18,000 to 24,000 psig generated during the crushing and permanently deforming of the sealing fin by automatic capping machines, said crushable end being rigid and non-bending, said threads and said skirt wall being formed of polypropylene having a flexural stiffness of at least 175,000 psi to prevent flaring of the skirt wall when permanently deforming said crushable end against said container finish, said V-shaped annular sealing ring being the only sealing surface on said closure for sealing with said container finish.