Automatic non-return valve

Claim 1

A check valve for ensuring both the flow of a fluid in one direction under a very slight pressure differentials and simultaneously a hermetic seal in the opposite direction under very slight pressure differentials, comprising an outer casing of rigid moldable material, a valve member of elastomeric moldable material, said valve member including a thin mobile wall having a central port and enlarged stiffened outer and inner edges, the wall having a first annular portion of undulated cross section adjacent the inner edge, and a second substantially annular portion connecting the first annular portion with the outer edge, said second portion being shaped to form a loop having its convexity outwardly facing with respect to the valve member, said casing being provided with an inner circumferential groove in which the outer edge of the valve member is seated, said casing having an inner wall provIded with an abutment for the inner edge of the mobile wall of the valve member to seat against, the valve member being mounted in the casing such that an elastic pre-load causes the inner and outer edges of the mobile wall to adhere tightly to the casing surfaces, the casing having a hole providing communication between the cavity provided between the mobile wall of the valve member and the casing and the space from which the fluid is required to be discharged.