Diaphragm pump

A diaphragm pump having a piston adapted for reciprocal movement from a first to a second position defining a power stroke and from the second to the first position defining a return stroke, a diaphragm moveable between first and second positions, a pumping chamber on one side of the diaphragm, a piston chamber on the other side of the diaphragm having a volume defined, in part, by the relative positions of the piston and diaphragm, a source of hydraulic fluid connected with the piston chamber to allow hydraulic fluid into the piston chamber, the hydraulic fluid in the piston chamber serving to transfer motion of the piston to the diaphragm, and means for reciprocating the piston, said diaphragm pump comprising:

• a plurality of piston inlets connecting the hydraulic fluid source with the piston chamber;
• check valve means for permitting the flow of hydraulic fluid from the hydraulic fluid source to the piston chamber when the pressure in the piston chamber is less than the pressure in the hydraulic fluid source and for preventing the flow of hydraulic fluid when the pressure in the piston chamber is greater than the pressure in the hydraulic fluid source, said check valve means including a plurality of ball valves, each having a ball and valve seat, which are disposed within the plurality of inlets connecting the hydraulic fluid source with the piston chamber, said ball valves movable between a closed position and an open position such that the ball is disposed in contacting relationship against the valve seat when the ball valve is in the closed position, said valve seat including a conical section sloped inward toward the hydraulic fluid inlet and having an inner edge adjacent the inlet, wherein the slope of the conical section is such that the tangential contact point between the ball and valve seat when the ball valve is in the closed position is located at a position on the conical section outward from the inner edge of the valve seat, and wherein the distance the ball is permitted to move between the open and closed positions is such that the ball valve closes substantially in conjunction with the piston beginning its power stroke and the ball is not able to generate a high closure velocity when moving from the open to the closed position;
• a diaphragm stop for limiting movement of the diaphragm away from the pumping chamber, said diaphragm stop having an inner edge;
• a diaphragm plunger connected to the diaphragm which contacts the diaphragm stop during the return stroke of the piston under a pressure feed condition, said plunger having an outer edge and including a spherical surface portion wherein the spherical surface portion contacts the diaphragm stop at a position outward from the inner edge of the diaphragm stop and inward from the outer edge of the plunger when the plunger contacts the diaphragm stop;
• a piston reciprocating chamber adjacent the piston such that the hydraulic fluid source is located within the piston reciprocating chamber;
• an isolation reservoir adjacent and connected to said piston reciprocating chamber such that hydraulic fluid completely fills the piston reciprocating chamber and further flows into the isolation reservoir to form an upper surface of hydraulic fluid within the isolation reservoir;
• and
• sliding valve means responsive to the relative movement between the diaphragm and piston for controlling the flow of hydraulic fluid from the hydraulic fluid source into the piston chamber, wherein the sliding valve means includes a cylinder valve connected to the diaphragm and a cylinder valve housing connected to the piston and adapted to receive the cylinder valve therein, said cylinder valve housing including at least one elongated slot disposed adjacent said cylinder valve to permit the flow of hydraulic fluid into the piston chamber.