HOSE 7W4850 - Caterpillar

Illustration 1 g00300639
Cab (1) Pilot control valve (stick and swing) (2) Pilot control valve (boom)
Illustration 2 g00474248
Main control valve compartment (top view) (3) Stick II (drain) (4) Boom I BOOM RAISE (6) Right travel (backward travel) (7) Left travel (backward travel) (8) Swing SWING RIGHT (9) Stick I STICK OUT (10) Boom II BOOM RAISEPilot control valve (1) and pilot control valve (2) send pilot pump oil to the main control valve through the following pilot lines:
Stick I STICK OUT (9)
Stick II (drain) (3)
Boom I BOOM RAISE (4)
Boom II BOOM RAISE (10)
Swing SWING RIGHT (8)
Right travel (backward travel) (6)
Left travel (backward travel) (7) A pilot line is connected to the main control valve on the opposite side of the following ports.
Stick I STICK IN
Stick II STICK IN
Stick II STICK OUT
Boom I BOOM LOWER
Swing SWING LEFT
Right travel (forward travel)
Left travel (forward travel)
Illustration 3 g00373712
Pilot control valve (implement and swing) (11) Spool (12) Passage (13) Return passage (14) Spring (15) Spring (16) Seat (17) Rod (18) Plate (19) Rod (20) Spring (21) Seat (22) Spring (23) Spring (24) Return chamber (25) Passage (26) Spool (27) Port (28) PortWhen the pilot control lever is moved to the right side, plate (18) tilts to the right side. Plate (18) pushes down on rod (19). Seat (21) pushes against the force of metering spring (22) and spring (23). The force of metering spring (22) shifts spool (26). Passage (25) opens. The oil flows through passage (25) and port (27) to the main control valve. The oil pressure shifts the stem of the main control valve. This enables the implement operation or swing operation.The oil at the opposite end of the stem flows back through port (28). The oil next flows through return passage (13) and into return chamber (24). The oil then flows back to the tank.When rod (17) is not forced down, return passage (13) is open and passage (12) is blocked.The control levers will return to the NEUTRAL position due to the force of spring (23) and spring (14) .When the pilot control lever is moved to the left, plate (18) tilts to the left. Plate (18) pushes down on rod (17). Seat (16) pushes against the force of metering spring (15) and spring (14). Metering spring (15) forces spool (11) to move down. Movement of spool (11) controls the amount of pilot oil that flows through passage (12). The pilot oil flows through passage (12) to the main control valve.The pilot oil that flows to the main control valve changes proportionally to the travel distance of the pilot control lever. Movement of the stem of the main control valve causes a change in the oil flow to the cylinders and/or motors. Fine movement of the pilot control lever allows fine control of the operation of the cylinders and/or motors.When the control lever is moved a little, spring (22) controls spool (26). The change in the pilot pressure is small and fine control of the machine is accomplished. When the control lever is moved