Pulsation causing check valve assembly for a plural piston pump system

Abstract

The fluid pump has a casing defining an inlet manifold, an outlet manifold and a plurality of piston chambers between the inlet manifold and the outlet manifold, each piston chamber having a piston therein for drawing fluid into the piston chamber from the inlet manifold and for pumping fluid out of the piston chamber into the outlet manifold, and a spring biased check valve associated with each piston chamber wherein a spring biases each valve toward the piston chamber and seals the piston chamber from the outlet manifold, the improvement comprises: at least one of the check valves having a hole therethrough which provides open communication between the outlet manifold and the piston chamber, blocking and sealing structure associated with the check valve for blocking and sealing the opening, and a mechanism for moving the blocking and sealing structure between a first position wherein the hole is blocked and sealed and a second position whereby the hole is not blocked or sealed, such that when the blocking and sealing structure is in the first position, liquid is prevented from flowing from the outlet manifold back into the piston cylinder and thereby causes fluid to exit the pump in a continuous flow and when the blocking and sealing structure is in the second position fluid can flow from the outlet manifold into the piston cylinder and fluid exits the pump in a pulsed or vibratory flow.