EXTENSION AS. 2093307 - Caterpillar

Illustration 1 g00907229
Pilot Valve (Oil Manifold)The pilot valve (oil manifold) is part of the valve group that is located in the front frame. The pilot valve (oil manifold) controls the flow of pilot oil to the main control valve. Illustration 1 shows a main control valve without an auxiliary function.
Illustration 2 g00818898
Section View of the Pilot Valve (Oil Manifold) (1) Shuttle valve (2) Port to the steering system (3) Passage (primary pilot pressure) (4) Supply port from the pilot/brake pump (5) Primary pressure reducing valve (6) Secondary pressure reducing valve (7) Passage to hydraulic oil tank (8) Proportional solenoid valve (DUMP) (9) Proportional solenoid valve (LOWER) (10) Port to the main control valve (LOWER) (11) Port to the main control valve (DUMP) (12) Passage (pilot pressure) (13) Port from the lift cylinder (14) Port to the lowering control valve (15) Passage (secondary pilot pressure) (16) Passage from the lift valve spool (17) Vent port from the makeup valve (18) Supply port to the ride control solenoid valve (19) Solenoid valve (hydraulic lockout) (20) Port to the main control valve (TILT BACK) (21) Proportional solenoid valve (TILT BACK) (22) Return port to the hydraulic oil tank (23) Proportional solenoid valve (RAISE) (24) Port to the main control valve (RAISE) (25) Float valveOil enters the pilot valve (oil manifold) at port (4) from the pilot/brake pump. Primary pressure reducing valve (5) reduces the pressure of the pilot oil to 3450 200 kPa (500 30 psi). The oil then flows through passage (3) to shuttle valve (1). Pilot pressure oil for the steering system flows through passage (3) to port (2) .Secondary pressure reducing valve (6) supplies pilot oil when the engine is stopped. The secondary pilot oil allows an operator to lower the lift arms when the engine is stopped. In order to lower the lift arms with the lift control lever, the engine start switch key must be in the ON position.If there is an electrical failure the lift arms can be lowered manually. The engine start switch key does not need to be in the ON position. Opening the lowering control valve causes the lift arms to slowly lower.When the lowering control valve is open, hydraulic oil from the lift cylinders flows through port (14) to the lowering control valve. The oil then returns to the hydraulic oil tank.Secondary pressure reducing valve (6) receives high pressure oil from the lift cylinder through port (13). A check valve allows the oil to flow from the end of the lift cylinder with higher pressure. The check valve is located in the manifold that is attached to the main control valve.The pressure of the oil is reduced to 2070 200 kPa (300 30 psi) by secondary pressure reducing valve (6). The pilot pressure oil then flows through passage (15) to shuttle valve (1) .Excess oil from pressure reducing valves (5) and (6) flows to port (22). The oil then flows to the hydraulic oil tank. Shuttle valve (1) senses