TUBE AS 2520332 - Caterpillar

Illustration 1 g00857319
Pilot ValveThe pilot valve is a closed center type valve. The pilot valve consists of two sections that are bolted together. The sections have a common pilot pressure and a common return to the hydraulic tank.
Illustration 2 g00857214
Cross Section View of the Pilot Valve (1) Control lever. (2) Plate. (3) Plunger. (4) Coil assembly. (5) Plate. (6) Spring. (7) Plunger. (8) Valve inlet. (9) Valve outlet. (10) Seat. (11) Capsule assembly.When the pilot valves are in the HOLD position, the pilot oil enters the inlet port and the pilot oil is blocked. The pilot oil will continue to be blocked until one of the control levers is actuated.
Illustration 3 g00857352
Typical Example of a Control Lever that is ActuatedAs the lift control lever (1) is moved to the RAISE position, plate (2) rotates toward coil assembly (4). Rotating the plate will push plunger (3) into coil assembly (4). The plunger pushes on plate (5). Plate (5) pushes plunger (7) against seat (10). As seat (10) is moved inside the capsule assembly the port in seat (10) will line up with the passage from inlet port (9). A proportional amount of oil, that is determined by the amount of actuation of the control lever will flow through the hole in the middle of seat (10). The pilot oil will flow through port (B) to the main control valve. The spool in the main control valve will move proportionally to the amount of flow through the pilot valve. Refer to Illustration 4 in order to view the path of pilot oil through the pilot valve.When the control lever is activated to the RAISE position, the trappped oil in the chamber for the opposite end of the spool will be forced out of the valve through port (A). The oil will flow through the center of the seat and out of the pilot valve through outlet port (8). The oil will then flow to the hydraulic tank.
Illustration 4 g00857258
Oil Flow in the Pilot ValveWhen the control lever is positioned in the HOLD position, plate (2) will go back to the HOLD position. The force of spring (6) will move plate (5) and plunger (3) to the HOLD position. This will allow plunger (7) to move up and the spring in the capsule assembly will move seat (10) to the HOLD position. This will block the pilot oil from traveling through seat (10). The pilot oil that is trapped between the main control valve and the pilot valve can release to port (8) and flow back to the hydraulic tank. This will allow the shifted spool in the main control valve back to the HOLD position.If the switch for the kickouts is activated and the magnet has passed over the control switch, coil assembly (4) is energized. When the control lever is fully activated, the magnetic force will hold plate (2) to the coil assembly. Coil assembly (4) will continue to be energized until the magnet for the kickouts passes over the control switch.