Check valve cartridge for fluid pump

A check valve cartridge for a fluid pump, the check valve cartridge comprising:

• a) a valve seat;
• b) a flap valve member seated on the valve seat, the flap valve member having a first portion movable toward and away from the valve seat;
• c) a bumper seated on the flap valve member, said bumper member for biasing the first portion of the flap valve member toward the valve seat;
• d) a stop member located on the bumper, said bumper located between the stop member and the flap valve member, said stop member for limiting the movement of the flap valve member first portion away from the valve seat;
• and
• e) fastening means for joining the valve seat, flap valve member, bumper, and stop member to form the integral valve cartridge, said fastening means comprising
• a compression inducing shoulder portion having a first lateral dimension,
• a threaded Portion having a second lateral dimension,
• said first lateral dimension being greater than said second lateral dimension to form a preload face joining the shoulder and threaded portions, and
• said shoulder portion having a length which is less than a combined thickness of said flap valve member, bumper, and stop member, such that upon tightening said fastening means, said preload face seats against said valve seat to cause said bumper and said flap valve member to be compressed between said stop member and said valve seat to sealingly engage said flap valve member with said valve seat.