Non-return valve

A non-return valve including a valve body having a fluid inlet, a fluid outlet, and an annular valve seat disposed in the body between the inlet and outlet;

• an enclosed hollow valve member, and a valve guide bush mounted in the valve body on one side of and coaxial with the valve seat, the valve guide bush having an elongated imperforate casing with an open end directed toward the valve seat and being closed at the other end, and the valve member having a portion disposed within said guide bush for axial displacement between a valve shut position in which the valve member makes sealing contact with the valve seat and a valve open position in which the valve member is axially spaced from the valve seat, wherein the improvement comprises:
• means for forming a constricted space between the inner wall of the valve guide bush casing and the outer wall of the portion of the valve member disposed within the guide bush for a limited axial range adjacent to the valve shut position for damping the movement of the valve member as it approaches the shut position and
• means for limiting the entry of the valve member into the guide bush such that a chamber is disposed between the closed end of the valve guide bush casing and the valve member even when the valve member extends the greatest admissible distance into the guide bush, whereby the withdrawal of the valve member from the guide bush is not impeded by adhesion forces therebetween.