DRIVE G-FINAL 8Z7463 - Caterpillar

Illustration 1 g00857009
Tandem Pump Arrangement (Implement)The implement pump is two pumps in tandem. Each pump is a fixed displacement axial piston pump. Each pump produces an equal amount of displacement. Both pumps receive hydraulic oil from the same hydraulic tank and both pumps supply oil to the same port on the main control valve. The tandem pump rotates in the counterclockwise direction when the pump is viewed from the drive end.
Illustration 2 g00857010
Cross Section View of the Fixed Displacement Axial Piston Pump (1) Head. (2) Port plate. (3) Pump housing. (4) Barrel assembly. (5) Bearing. (6) Piston. (7) Cam. (8) Shaft. (9) Spacer. (10) Spring. (11) Bearing. (12) Shoe plate. (13) Thrust plate.The pump rotates when the engine is activated. The pump drive rotates shaft (8). Pistons (6), barrel assembly (4), and shoe plate (12) rotate at the same speed as the shaft. Cam (7), and port plate (2) do not rotate. Oil from the hydraulic oil tank flows into pump head (1) at the inlet passage. The oil flows through inlet passages in port plate (2). As drive shaft (8) turns, the openings of the cylinder barrel move by the inlet passages of port plate (2) .Each piston (6) inside cylinder barrel (4) is held against swashplate (13) by shoe plate (12). Swashplate (13) is attached to cam (7) and the angle of swashplate (13) is fixed by the angle of the cam.As pistons (6) follow the angle of swashplate (13), the pistons move in and out of cylinder barrel (4). When a piston (6) moves out of cylinder barrel (4), oil is pulled in behind the piston.The angle of swashplate (13) determines the amount of oil that is drawn into each cylinder barrel (4). As the barrel assembly continues to rotate the swashplate angle pushes the pistons into the barrel.The pistons push oil out of cylinder barrel (4) through the outlet passages in port plate (2). The angle of the swashplate determines the amount of oil that is pumped out of each cylinder barrel (4) for each drive shaft rotation.The force of spring (10) holds the barrel assembly against port plate (2). The smooth surfaces of barrel (4), head (1), and port plate (2) create a metal-to-metal seal between the port plate and the barrel assembly. This seals the inlet port from the outlet port. Any wear to the surfaces will decrease the efficiency of the pump.