Adjustable check valve

Claim 1

A check valve comprising a valve housing having an inlet and an outlet, a valve seating in the housing defining a passage between inlet and outlet chambers defined in said housing, a ball valve seatable on the seating on the outlet side thereof, a compression spring urging the ball onto the seat, a spring abutment adjustably mounted in the housing, the spring acting between the ball and the abutment to apply an adjustable bias to said ball tending to retain it on said valve seat, a cylinder defined in the housing between the inlet and the valve seat, a piston having a path of movement in said cylinder and having a stem extending into and substantially closing the passage defined by the valve seating, leakage path means placing in communication the portions of the cylinder on either side of the piston, and passageway means defined by the piston and extending from an inlet on the side of the piston nearest the inlet through the stem to at least one outlet in the side of the stem and so positioned that at one end of the path of movement of the piston the outlet is within the passage in the valve seating and at the other end of the travel of the piston is on the outlet side of the valve seat, the end of the stem being engageable with the ball valve member.