PIPE 0862507 - Caterpillar

Illustration 3 g03313200
Propel Pump
(35) Servo springs
(36) Swashplate
(37) Slipper pad
(38) Feedback link
(39) EDC
(40) Servo piston
(41) Servo piston
(42) Feedback link
(43) EDC
(44) Servo springs
(45) Swashplate
(46) Slipper pad
(47) Piston
(48) Rotating group
(49) Piston
(50) Rotating group
(51) Input shaft Engine rotation turns pump input shaft (51), which then rotates two rotating groups (48) and (50). Each rotating group contains a multi bore cylinder and pistons. Pistons (47) and (49) in the groups rotate with the cylinder assembly.Piston slipper pads (37) and (46) cause the pistons to follow the angle of swashplates (36) and (45). The rotating groups only generate flow when the swashplates are not at zero angle. When the machine electronic control system sends an output signal to EDC (39) or (44), corresponding servo piston (40) or (41) moves. As the servo piston moves, the action of the control linkage causes the angle of swashplates (36) or (45) to change. The swashplate angle is proportional to the signal from the machine electronic control system.Slipper pads (37) and (46) in each rotating group (48) and (50) follow the angle of swashplates (36) and (45). This action causes pistons (47) and (49) to move in and out of the barrel assembly as input shaft (51) rotates. As a piston moves out of the barrel assembly, oil in the low-pressure circuit is drawn into the piston chamber. As a piston moves into the barrel assembly, oil is forced out of the piston chamber and into the high-pressure circuit.
Illustration 4 g03313240
Makeup and Relief Valves
(52) Relief poppet
(53) Check valve
(54) Relief spring
(55) Makeup spring Note: In the illustration above, the left image shows low-pressure operation while the right image, shows high-pressure operation.These combination valves provide two primary functions make-up and relief. Oil in the high-pressure side of the closed circuit loops acts to close check valve (53). Oil in the low pressure (return) side of the closed circuit loop acts to open the check valve. Flushing and internal leakage cause pressure in the return side of the closed circuit to decrease. This decrease causes charge pressure to unseat the check valve. When the pressure in the return circuit is low enough, the check valve moves the main relief cartridge against the force of makeup spring (55). The check valve opens a passage for charge oil to flow into the return side of the circuit. Charge oil replenishes the oil that the circuit looses from flushing and internal leakage.Pressure in the high-pressure circuit acts to open relief poppet (52). The combined force from the oil in the charge circuit and relief spring (54) acts to close the relief poppet. When the pressure in the high-pressure circuit reaches the relief setting, the relief poppet compresses the relief spring. In this case, oil from the high-pressure circuit is directed into the charge circuit.