TUBE AS 2887173 - Caterpillar

Main Control Valve Operation in NEUTRAL Position
Illustration 6 g00747315
Main control valve (neutral position) (1) Stick II control valve (2) Boom I 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 I 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 idler 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 drive 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, hydraulic oil from the idler pump 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. Hydraulic oil from the drive pump 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 hydraulic oil from the idler pump. 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 I control valve (2). Activation of any joystick and/or travel levers/pedals also provides two paths for hydraulic oil from the drive pump. One path flows through center bypass passage (22) to left travel control valve (9) and stick I 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)