Cannula pierceable self-sealing closure

Claim 1

A cannula pierceable, self-sealing, gas proof closure for sealing an open end of an air evacuated blood collection tube, which comprises: (a) a tubular elastomeric body having (i) flexible, elastic sidewalls; (ii) an open first end; and (iii) a closed second end formed by a cannula pierceable, flexible, elastic end wall integral with said sidewalls; (b) a flange disposed radially about the periphery of said sidewalls adjacent to said first end; and (c) a removable sheet selected from either a pressure sensitive tape or a polymeric resin closing the open first end; said end wall having a convex inner surface and a concave outer surface when pressure on inner and on outer surfaces is equal, said tubular body having a diameter which bears a ratio to the height of the body of about 0.8:1 and to thickness of the second end of from 5.4:1 to 12.1:1; whereby when the closure is emplaced in and sealing an open end of an air evacuated tube, the higher pressure on the convex inner surface of the end wall as compared to the lower pressure (vacuum) exerting itself on the concave outer surface creates a pressure differential on the end wall, flexing and flattening the concave-convex configuration and creating a radial force directed toward the periphery of the end wall, said force effecting a restraining and sealing force between the closed second end of the elastomeric body and the air evacuated tube.