SNOW AR-MOTOR GRADER 2429549 - Caterpillar

Introduction
Illustration 1 g03815691
Swing motor
(1) Swing motor
(4) Relief valve
(7) Relief valve
(10) Makeup port Relief valves (4) and (7) are located in the top of swing motor (1). The relief valves limit the pressure in the swing circuit to the relief valve pressure setting. This action provides a cushion effect at a start or stop of the swing operation.Swing Stop
Illustration 2 g03813938
Partial schematic of swing circuit (Stopping state)
(1) Swing motor
(2) Motor rotary group of the swing motor
(3) Passage
(4) Relief valve
(5) Check valve
(6) Passage
(7) Relief valve
(8) Check valve
(9) Port
(10) Makeup port
(11) Port
(12) Passage
(13) Makeup line
(14) Bypass check valve
(15) Hydraulic tank
Illustration 3 g03350010
Relief valve
(6) Passage
(7) Relief valve
(12) Passage
(18) Passage
(19) Spring chamber
(20) Piston
(21) Passage
(22) Sleeve
(23) Spring
(24) Valve When the swing control lever is moved back to the NEUTRAL position from the SWING LEFT position, both the inlet and outlet ports of swing motor (1) are closed. No oil flow is supplied to port (9). This blocks the oil flow from port (11) to swing motor (1). The mass (weight and size) of the upper structure causes swing motor (1) to rotate after the control lever is in the NEUTRAL position. Swing motor (1) attempts to draw oil from port (9) and attempts to force the oil out of port (11). Since port (11) is closed, the pressure of the blocked oil in passage (6) increases. The increased pressure oil in passage (6) shifts valve (24) to the right (open position). Valve (24) shifts against the forces of spring (23) in relief valve (7). When valve (24) shifts, oil flows through passage (12) and check valve (5) to passage (3). From passage (3), oil enters the motor rotary group (2). The force of the rotating upper structure is absorbed at a stop of swing movement.The oil in passage (6) goes through passage (21) of valve (24) and spring chamber (19) to passage (18). The force of spring (23) is less than the relief valve pressure setting. Valve (24) opens just before the oil pressure in passage (6) reaches the relief valve pressure setting. When valve (24) opens, the oil in passage (6) is allowed to vent. At the same time, the pressure oil in passage (18) moves piston (20) to the left. This compresses spring (23) until the left face of piston (20) comes in contact with sleeve (22). For a very small amount of time during the piston movement, the oil pressure in passage (18) is lower than the relief valve pressure setting. When piston (20) stops movement to the left, the oil pressure in passage (6) increases the relief valve pressure setting. All of the oil is allowed to flow from relief valve (24) to passage (12) when the relief valve pressure setting is reached.The two-stage relief action prevents a peak pressure buildup when relief valve (24) opens. This action produces less shock load when swing motor (1) comes to a stop. The force of the rotating upper structure is absorbed as swing motor (1) comes to a stop.After the start of a SWING RIGHT