Patent ID: 7524171

Claim:
A high pressure radial piston fuel pump comprising: an hydraulic head defining a central cavity for receiving a rotatable drive shaft longitudinally disposed along a drive axis passing through the cavity; a cylindrical drive member rigidly carried by and offset from the drive shaft for eccentric rotation in the cavity about the drive axis as the drive shaft rotates; a pair of axially side by side, substantially cylindrical piston actuation rings annularly mounted around the drive member; bearing means between the drive member and the actuation rings, whereby each actuating ring is supported for freely rotating about the drive member; two piston bores associated with each actuation ring, extending in the housing to the cavity in substantial opposition to each other, each piston bore having a centerline that intersects the actuation ring but is offset (x) from the drive axis as viewed along the drive axis; a piston situated respectively in each piston bore for reciprocation therein, said piston having an actuated end in the cavity and a pumping end remote from the cavity, wherein the pumping end cooperates with the piston bore to define a pumping chamber, said actuated end and said pumping end of the piston disposed at opposite ends of a rigid piston stem of nominal cross sectional area, said actuated end forming a flared enlargement of the stem toward the cavity and terminating in a substantially flat actuation surface for maintaining contact with the actuation ring during rotation of the drive shaft; a substantially “C” shaped band situated in the cavity around one side of each actuation ring, having opposite ends which respectively engage the enlargement of the piston and maintain a substantially constant distance between the actuation surfaces of the shoes; a feed fuel valve train for delivering charging fuel through an inlet passage in the head at a feed pressure to the pumping chamber; a high pressure valve train for delivering pumped fuel to a discharge passage in the head at a high pressure from the pumping chamber; whereby during one complete rotation of the drive shaft, each pumping chamber undergoes a charging phase wherein the associated piston is retracted toward the cavity by the band, thereby increasing the volume of the pumping chamber to accommodate feed fuel from the inlet valve train, and a discharging phase wherein said associated piston is actuated away from the cavity by the actuation ring, thereby decreasing the volume of the pumping chamber and pressurizing the fuel therein for discharge through said discharge valve train.