Priming piston pump piston check valve

In a reciprocating piston displacement pump having a displacment rod in a cylinder having upper and lower chambers and valve means for controlling the flow between said chambers, said valve means comprising:

• a valve seat attached to said rod, said valve seat comprising:
• seating area first and second ends, each of said valve seat seating area first and second ends having diameters;
• and
• a center section having a reduced diameter relative to said valve seat seating area first and second ends, said valve seat center section being smooth and free of grooves;
• an annular piston having a circumference and first and second piston ends and being slidably mounted coaxially about said seat, said piston having a conical seating area on said piston first end and a plurality of spaced guides extending toward said piston second end, said piston being slidably located in said cylinder;
• and
• seal means mounted between said piston and said cylinder wherein said seat is attached to the lower end of said displacement rod, the length of said piston being less than the distance between said first valve seat seating area and said displacement rod and said seat has a tapered first end and smooth contours over the remainder of said seat to allow fluid to flow from said lower chamber between said seat seating area and said piston seating area when said piston in contacting said displacement rod and thence between the center section of said seat and the interior of said piston first end and thence between said guides into said upper chamber, said seal means extending over only a relatively small fraction of said piston length.