HAMMER AR-HYDRAULIC 2030924 - Caterpillar

Illustration 1 g00455648
Pilot Valve (Boom) (1) Pivot plate (2) RAISE plunger (3) LOWER plunger (4) Retainer (5) Retainer (6) Centering springs (7) Centering springs (8) Metering spring (9) Metering spring (10) Metering stem (11) Metering stem (12) Port to main control valve (13) Port to main control valve (14) Port to hydraulic tank (15) Inlet (pilot oil) (A) RAISE position (B) SWING RIGHT position (C) LOWER position (D) SWING LEFT position
Illustration 2 g00533379
Pressure reducing valve for pilot circuit (16) Port to hydraulic tank (17) Port to pilot control valve (18) Pressure reducing valveWith a running engine, oil flows from the swing boom control valve to pressure reducing valve (18) . The oil flows through the valve (18) and to the pilot accumulator and the pilot control valve.The oil flows into the valve (18) and the pressure is reduced. Reduced pressure oil flows out of port (17) and the oil flows to the pilot accumulator and the pilot control valve.If the engine stops running or the hydraulic pump fails, the pilot accumulator provides pilot oil to the system. This allows the boom to be lowered, as required.When the control lever is in the HOLD position, centering springs (6) and (7) keep pivot plate (1) in the centered position. Pump oil flows through port (15) to metering stems (10) and (11) . In this position, the metering stems block the flow of oil to the main control valve.When the operator places the control lever in the RAISE position, pivot plate (1) causes plunger (3) to move downward. As plunger (3) moves downward, the force on retainer (4) overcomes springs (6) . This allows plunger (3) to contact