Patent ID: 6938641

Claim:
A check valve comprising: a pair of body elements ( 1 , 4 ) through which a fluid passes; a cylindrical valve element ( 7 ), which is slidably engaged inside one ( 1 ) of said pair of body element ( 1 , 4 ), constantly subjected to a fluid pressure and biased toward its closed position under the influence of a resilient force exerted by a compression coil spring ( 10 ) having a diameter substantially equal to an inside diameter of a recess within the cylindrical valve element in which the compress on coil spring is engaged, said compression coil spring coated with a tubular element; and, a stopper element ( 24 ) disposed inside another one ( 4 ) of said pair of body elements ( 1 , 4 ), wherein at least one of said cylindrical valve element ( 7 ) or said stopper element ( 24 ) is provided with a spiral seat portion ( 11 ) having a spiral surface which is brought into press-contact with a terminal turn of said compression coil spring ( 10 ) to support said compression coil spring ( 10 ) in said cylindrical valve element ( 7 ), and wherein said compression coil spring ( 10 ) is constrained to move within said pair of body elements only in the direction of the longitudinal axis of the check valve without fear of buckling.