ENGINE AR-COMPLETE 3899982 - Caterpillar

Illustration 1 g03496464
Pressure circuit for SWING RIGHT operation (partial schematic)
(1) Passage
(2) Relief valve
(3) Check valve
(4) Makeup port
(5) Passage (supply oil)
(6) Swing motor
(7) Motor rotary group
(8) Passage (return oil)
(9) Check valve
(10) Relief valve
(11) Passage
(12) Swing control valve
(13) Port (return oil)
(14) Return line
(15) Makeup line
(16) Port (supply oil)
(17) Check valve
(18) Slow return check valve
(19) Return line
Illustration 2 g03496461
Swing motor
(2) Relief valve
(4) Makeup port
(6) Swing motor
(10) Relief valve
(15) Makeup line
Illustration 3 g01231050
Swing relief valve
(4) Return passage
(7) Passage
(20) Orifice
(21) Spring
(22) Stem
(23) Piston chamber
(24) Passage
(25) Piston
(26) Passage
(27) Piston chamber
(28) Orifice
(29) Passage
(30) Adjustment plug Relief valves (2) and (10) are located in the head of swing motor (6). These relief valves limit the pressure in the left and right swing circuits to the swing relief valve setting. This pressure limit provides a cushion effect at a start or stop of the swing operation.When the swing joystick is returned to the NEUTRAL position during the swing right operation, the swing control valve shifts to the NEUTRAL position. Since the swing control valve is in the NEUTRAL position, the oil delivery through port (16) to the motor rotary group (7) is now blocked at the swing control valve. The return oil from the motor rotary group through port (13) is also blocked at the swing control valve.The mass (weight and size) of the upper structure causes the upper structure to attempt to continue to rotate after the swing joystick is returned to the NEUTRAL position. The motor rotary group is also attempting to continue to rotate. The motor rotary group attempts to draw oil through port (16) and attempts to displace the oil through port (13).The oil supply to motor rotary group (7) is insufficient. A vacuum condition occurs in passage (5). Return oil is supplied to the motor rotary group as makeup oil in order to prevent the vacuum condition. For more information concerning the makeup operation, refer to Systems Operation, "Oil Makeup (Swing System)". Since the flow of return oil from the motor rotary group through port (13) is blocked at the swing control valve, the pressure of the blocked oil in passage (8) increases. The increased oil pressure in passage (8) acts on swing relief valve (10). The increased pressure oil forces stem (22) of relief valve (10) to the right (open position)