PISTON 3166234 - Caterpillar

Main Control Valve Operation in NEUTRAL Position
Illustration 6 g01239950
Main control valve (neutral position)
(1) Stick II control valve
(2) Boom l control valve
(3) Bucket control valve
(4) Attachment control valve
(5) Right travel control valve
(6) Parallel feeder passage
(7) Inlet port
(8) Straight travel control valve
(9) Left travel control valve
(10) Parallel feeder passage
(11) Swing control valve
(12) Stick l control valve
(13) Boom II control valve
(14) Right body
(15) Left body
(16) Negative flow control orifice
(17) Return port
(18) Negative flow control orifice
(19) Return passage
(20) Center bypass passage
(21) Inlet port
(22) Center bypass passage
(23) Return passageThe drive pump supplies oil to right body (14) through inlet port (7). The oil then flows through center bypass passage (20) and parallel feeder passage (6). The idler pump supplies oil to left body (15) through inlet port (21). The oil then flows through center bypass passage (22) and parallel feeder passage (10).When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, drive pump oil flows through center bypass passage (20), negative flow control orifice (18), return passage (19), return passage (23) and return port (17) back to the hydraulic tank. Idler pump oil from inlet port (21) flows through center bypass passage (22), negative flow control orifice (16) and return port (17) back to the hydraulic tank. Oil in parallel feeder passages (6) and (10) remains blocked by each control valve spool.Activation of any joystick and/or travel levers/pedals provides two paths for drive pump oil. One path flows through center bypass passage (20) to right travel control valve (5). The other path flows through parallel feeder passage (6), attachment control valve (4), bucket control valve (3) and boom l control valve (2). Activation of any joystick and/or travel levers/pedals also provides two paths for idler pump oil. One path flows through center bypass passage (22) to left travel control valve (9) and stick l control valve (12). The other path flows through parallel feeder passage (10) to swing control valve (11).Individual Valve Operation
Illustration 7 g00747317
Bucket control valve (NEUTRAL position)
(1) Line relief valve (bucket cylinder rod end)
(2) Port
(3) Parallel feeder passage
(4) Load check valve
(5) Passage
(6) Port
(7) Line relief valve (bucket cylinder head end)
(8) Pilot port
(9) Pilot port
(10) Return passage
(11) Spool
(12) Center bypass passage
(13) SpringThe bucket control valve is used as a typical example for describing the operation of individual control valves.When the joysticks and/or travel levers/pedals are in the NEUTRAL position, pilot oil does not flow to port (8) and port (9). Spool (11) is centered in the NEUTRAL position by the force of spring (13). The drive pump oil flows through center bypass passage (12) to the hydraulic tank.
Illustration 8 g00747318
Bucket control valve BUCKET CLOSE
(2) Port
(3) Parallel feeder passage
(4) Load check valve
(5) Passage
(6) Port
(7) Line relief valve (bucket cylinder head end)
(8) Pilot port
(10) Return passage
(11) Spool
(12) Center bypass passage
(14) Passage
(15) PassageWhen the joystick for the bucket is moved to the BUCKET CLOSE position, pilot oil is supplied to pilot port (8). Spool (11) moves to the left. Center bypass passage (12) is closed and passage (15) becomes opened. Port (14) is now connected