TRACK GP 2495288 - Caterpillar

Main Control Valve Operation in NEUTRAL Position
Illustration 6 g00803968
Main control valve (neutral position) (1) Stick II control valve (2) Boom I control valve (3) Heel 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 right 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 left 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, right 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. Left 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 right pump oil. One path flows through center bypass passage (20) to right travel control valve (5). The other path flows through the following passages:parallel feeder passage (6), attachment control valve (4), heel control valve (3) and boom I control valve (2). Activation of any joystick and/or travel levers/pedals also provides two paths for left pump oil. 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
Heel control valve (NEUTRAL position) (1) Line relief valve (heel cylinder rod end) (2) Port (3) Parallel feeder passage (4) Load check valve (5) Passage (6) Port (7) Line relief valve (heel cylinder head end) (8) Pilot port (9) Pilot port (10) Return passage (11) Spool (12) Center bypass passage (13) SpringThe heel 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 right pump oil flows through center bypass passage (12) to the hydraulic tank.
Illustration 8 g00747318
Heel control valve (HEEL CLOSE) (2) Port (3) Parallel feeder passage (4) Load check valve (5) Passage (6) Port (8) Pilot port (10) Return passage (11) Spool (12) Center bypass passage (14) Passage