Patent ID: 7237694

Claim:
A pump apparatus comprising: a cylinder for containing a piston and for forming a product chamber, said cylinder having a longitudinal axis, an inlet for receiving a product into said product chamber and an outlet for allowing said product chamber to be evacuated; a piston mounted in said cylinder and movable in a direction parallel to the longitudinal axis, said piston having a first longitudinally directed internal aperture, a second longitudinally directed internal aperture spaced from said first longitudinally directed internal aperture, a third longitudinally directed internal aperture spaced from said first and said second longitudinally directed internal apertures, and a laterally directed aperture, said laterally directed aperture being elongated in the direction of the longitudinal axis, said second and said third longitudinally directed internal apertures having communication with said first longitudinally directed internal aperture, said second longitudinally directed internal aperture also having communication with said inlet, and said third longitudinally directed internal aperture also having communication with said outlet; a valve mounted to reciprocate in said first longitudinally directed internal aperture of said piston, said valve having a first structure for engaging a source of motion to move said valve in a reciprocating manner, a second structure for connecting to said piston to selectively move said piston, and a third structure for providing communication with said second and said third longitudinally directed internal apertures of said piston, wherein during a cycle of movement of said piston and said valve, said valve moves together with said piston during a part of the cycle and said valve moves when said piston is stationary during another part of the cycle.