COUPLING 4785666 - Caterpillar

Illustration 1 g00762084
Cross Section of the Elevator Pump (1) Drive shaft (2) Swashplate (3) Retainer (4) Pistons (nine) (5) Pump control valve (6) Actuator piston (7) Barrel (8) Port plate (9) Bearing (two) (10) Spring (11) Bias piston (12) HeadWhen the engine is running, pump drive shaft (1) turns at engine speed. Shaft (1) rotates barrel (7) with nine pistons (4). The ends of the pistons are in the shape of a ball that fits into the slipper. The slipper is held against the swashplate by retainer (3). The slipper slides on a thin film of oil on swashplate (2). Swashplate (2) does not turn. There are bearings (9) on each side of swashplate (2). Swashplate (2) rests on these bearings. This allows the swashplate to pivot in the pump housing. By pivoting, swashplate (2) changes angles. This change in the angle results in a change of the pump displacement.The elevator pump has one bias piston (11) and one actuator piston (6) with spring (10). Bias piston (11) works against actuator piston (6) and spring (10). Actuator piston (6) keeps the pump angled toward the maximum angle. Bias piston (11) is used to destroke the pump. Pump control valve (5) changes the pump displacement by regulating the oil pressure behind bias piston (11). This regulated pressure is supplied by pump discharge pressure or pilot pressure. When pump control valve (5) allows oil pressure to bias piston (11), the oil pressure overcomes actuator piston (6) and spring (10). This will destroke the pump.Pump drive shaft (1) turns barrel (7). When swashplate (2) is at an angle, pistons (4) move in and out of the barrel. Pistons (4) move in and out of the barrel as the pistons follow the angle of the swashplate. Swashplate (2) is shown at the maximum angle. As piston (4) moves out of barrel (7), the piston pulls oil from the hydraulic tank. The oil flows from the hydraulic tank through the pump inlet and port plate (8) into the piston cylinder. As the barrel continues to turn, the piston is moved into the barrel. This compresses the oil. The piston pushes the oil from the piston cylinder through the port plate to the pump outlet. Then, the oil flows to the elevator motor.A shuttle valve is located in head (12). The oil supply for the pump control is selected by the shuttle valve. The shuttle valve will select oil from the internal discharge pressure or the pilot pressure for the main control valve. This shuttle valve is not shown. This shuttle valve has a passage that is common to the control valve. During normal pump operation, the shuttle valve connects pump discharge pressure to the common passage. The discharge oil from the elevator pump flows through the common passage to the control of the elevator pump. When the output pressure from the elevator pump drops below 3450 kPa (500 psi), the higher oil pressure from the pilot system connects the pilot pressure to the common