OPTION AR-PRECLEANER 3534292 - Caterpillar

Illustration 1 g00780439
Swing circuit (partial schematic) (1) Swing motor (2) Motor rotary group (3) Passage (4) Passage (5) Port (6) Relief valve (7) Check valve (8) Passage (9) Makeup port (10) Check valve (11) Relief valve (12) Port (13) Makeup line (14) Main control valve (15) Slow return check valve (16) Return line
Illustration 2 g00780440
Relief valve (4) Passage (8) Passage (17) Valve (18) Spring (19) Passage (20) Sleeve (21) Piston (22) Piston chamberRelief valve (6) and relief valve (11) are located in the head of swing motor (1). These relief valves limit the pressure in the swing circuit to a specified setting. The relief valves provide a cushion effect at the start of a swing operation or at the end of a swing operation.When the oil supply to the swing motor is insufficient at the end of a swing operation, a portion of the return oil from main control valve (14) is sent to the swing motor as makeup oil. The makeup oil removes the vacuum condition.When the swing control lever is moved back to the NEUTRAL position from the SWING RIGHT position, the inlet port and the outlet port of the swing control valve are closed. Oil flow is now blocked at port (5) and at port (12). The inertia of the upper structure causes the swing motor to rotate after the stop operation is made. The continued operation attempts to draw oil from port (5) and the continued operation attempts to force oil out of port (13). Since port (12) is closed, the pressure of the blocked oil in passage (4) increases. The increased pressure oil in passage (4) forces valve (17) in relief valve (11) to the right against the force of spring (18). Oil now flows through passage (8) and through check valve (7) to passage (3). The oil in passage (3) enters motor rotary group (2). The swing motor comes to a stop after the inertia of the upper structure is absorbed by the relief valve.The oil in passage (4) flows through passage (19) of valve (17) to piston chamber (22). Since the force of spring (18) is less than the pressure setting of the relief valve, valve (17) opens before the oil pressure in passage (4) reaches the relief setting and the oil is allowed to vent. At the same time, the pressure oil in piston chamber (22) moves piston (21) to the left. The piston compresses spring (18) until the left face of the piston contacts sleeve (20). For approximately 0.1 second of the piston movement, The oil pressure in piston chamber (22) is lower than the relief setting. When the movement of piston (21) stops, the oil pressure in passage (4) increases to the relief setting and the oil is allowed to flow out of relief valve (17) to passage (8) .Because of the two-stage relief action, no peak pressure builds up when relief valve (11) opens. Less of a shock load occurs when the swing motor stops.When the swing control lever