Check valve

Claim 1

A check valve, comprising: a single integral body of an elastomeric material having an externally shaped portion substantially that of a hemisphere of given radius R, and an inlet passage passing into the base of the hemisphere and terminating in a normally closed inner end to define a wall thickness to the exterior of said hemisphere of a given value T, said inner end being cut through to the outer forward periphery of the hemisphere to define a slit at a given acute angle A to a plane normal to the axis of the inlet passage, said slit having a given transverse dimension D and a given length L measured from the interior to the outer periphery of said hemisphere, the inner end of said inlet passage terminating in a V-shape, the vertex of the V defining an angle equal to said given acute angle, said Slit initiating at the vertex of said V, and wherein: .125R<T<.75R 20°<A<50° .25R<D<1.25R, and .0625R<L<.375R whereby when fluid pressure across the hemisphere between said inlet passage and the exterior exceeds a given differential value, said slit will be opened to pass fluid from the interior to the exterior, said slit closing when the differential pressure reverses to block any reverse flow of fluid through said body.