PISTON 9T0805 - Caterpillar

Illustration 1 g02420477
Hydraulic schematic for GRAPPLE CLOSE
(1) Grapple cylinders
(2) Line
(3) Line
(4) Pilot line
(5) Main control valve
(6) Return passage
(7) Parallel feeder passage
(8) Load check valve
(9) Center bypass passage
(10) Grapple control valve OPEN/CLOSE
(11) Pilot line
(12) Proportional reducing valves (grapple control)
(13) Negative flow control line
(14) Pilot line
(15) Control valve (grapple rotate)
(16) Pilot line
(17) Line
(18) Grapple rotate motor
(19) Line
(20) Crossover relief valve (rotate counterclockwise)
(21) Spool
(22) Dump valve
(23) Main relief valve
(24) Crossover relief valve (rotate clockwise)
(25) Spring
(26) Passage
(27) Passage
(28) Return line
(29) Passage
(30) Supply line
(31) Pilot line
(32) Spring
(33) Proportional reducing valves (negative flow control)
(34) Negative flow control line
(35) Pilot line
(36) Auxiliary pump
(37) Drive pump
(38) Idler pump
(39) Pilot pump
(40) Hydraulic tank
(41) Line
(42) Pilot oil manifold Grapple Open/Close Operation
Illustration 2 g02420678
Main control valve
(10) Grapple control valve OPEN/CLOSE
Illustration 3 g02423662
Located in pump compartment
(12) Proportional reducing valves (grapple control) The oil delivery for the open/close operation is supplied by drive pump (37) only.The oil delivery from drive pump (37) flows through line (41) and center bypass passage (9) in main control valve (5) to grapple control valve (10).When the hydraulic activation control lever is in the UNLOCKED position, the oil delivery from pilot pump (39) flows through pilot oil manifold (42) and pilot line (35) to proportional reducing valves (grapple control) (12). When the switch for the grapple is activated to the GRAPPLE CLOSE position, pilot oil flows through proportional reducing valves (12) and pilot line (4) to grapple control valve (10). The pilot oil pressure shifts the spool in the grapple control valve to the left. The pilot oil on the other end of the spool in the grapple control valve flows through pilot line (11) and proportional reducing valves (12) to hydraulic tank (40).Since the spool in the grapple control valve is fully shifted, center bypass passage (9) is blocked. None of the oil delivery from the drive pump flows to the negative flow control orifice and no negative flow control pressure is created in center bypass passage (9). Proportional reducing valve (33) is energized when proportional reducing valve (12) is activated. Pilot oil line (14) supplies pilot oil pressure to proportional reducing valves (33). The machine ECM controls proportional reducing valves (33) in order to control the negative flow control pressure to the idler pump and the drive pump. The output flow rate of the pumps is adjusted. Oil flows through parallel feeder passage (7), load check valve (8), grapple control valve (10) and line (3) to the head end of grapple cylinders (1).Reference: For more information concerning the negative flow control operation, refer to Systems Operation, "Negative Flow Control System".The return oil from grapple cylinders (1) flows through line (2), the passage