A general need exists for devices to prevent return flow of fluid, for instance under conditions of under pressure, in order to prevent the penetration of air into a fluid supply line, or the return to the supply duct of a fluid which has already passed therethrough. In water supply applications, there is significant interest in preventing a return flow of water into the supply line, since the water quality may degrade due to the return flow. CHECK VALVESIn order to prevent return flow, it is known to use check valves whose moveable valve closing members are subjected to spring action in the direction of a valve seat which is provided in the housing of the check valve. Examples of check valves are provided in U.S. Pat. Nos. 3,378,030; 3,612,097; 4,605,041; 5,482,080; and 5,664,602, as well as the patents referenced therein.

Despite the existence of a large number of Check Valves designs, there is a continuing need for enhanced, simple, reliable check valve designs. The present invention is thus directed to providing an enhancement to the existing state of check valve designs.

Briefly summarized, the invention comprises in one aspect a Check Valves which includes a valve housing having a pair of opposite end faces comprising an upstream end face and a downstream end face with a fluid passage extending axially through the valve housing between the upstream end face and the downstream end face. A first seating surface is formed within the valve housing around the fluid passageway and adjacent to the upstream end face. A seating ring is provided having a second seating surface adapted to engage the first seating surface, and an o-ring is sized to reside between the first seating surface and the second seating surface when the seating ring and the valve housing are placed in engagement to seal fluid from passing between the first seating surface and the second seating surface and to maintain the seating ring and valve housing in fixed relation to each other, notwithstanding the existence of an outward axial biasing force against the seating ring imparted by a spring mechanism which resides within the valve housing.

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