Sealing gaskets for container closures

Claim 1

A roll-on cap blank destined to closing and sealing a bottle, which comprises an end panel, a depending peripheral skirt and a liner affixed to said end panel, said liner having (a) a flat central panel occupying from 50 to 94% of the internal radius of the cap blank and (b) an adjoining peripheral portion occupying the remaining 6 to 50% of the radius, the configuration of the peripheral portion being as follows, namely; considering the cap blank in an up-turned position relative to that which the cap occupies on the container and considering the peripheral portion in a radially outward direction, it comprises consecutively: (i) a first part (AB) of relatively steep gradient upwards from the edge of the central panel which makes an angle (β) with the plane of the central panel of from 25 to 90° and which has a radial length of from 5 to 30% of the radial length (AW) of the whole peripheral portion (AE); (ii) an adjoining relatively flat step part (BC) of constant gradient which makes an angle (α) with the plane of the central panel of from 0 to 25° and which has a radial length of from 10 to 70% of the radial length (AW) of the whole peripheral portion (AE); (iii) an adjoining corner part (CD) sloping upwardly, the height (DX) of which above the plane of the step part is from 20 to 65% of the height (DY) of the top of the corner part above the plane of the central panel, and (iv) an adjoining final marginal part (DE) which extends to the skirt at a level not below that of the corner part and which has a radial length of from 2 to 15% of the radial length (AW) of the whole peripheral portion (AE).