TUBE AS 8Y8517 - Caterpillar

Illustration 1 g00448443
The HOLD Position is Shown. (3) Pivot plate (4) Detent balls (5) Plunger assembly (6) Plunger assembly (7) Plunger (8) Nut (9) Centering springs (10) Washer (11) Spring (12) Plunger (13) Metering springs (14) Passage to tank (15) Springs (16) Metering stem (17) Metering stem (18) Work port (19) Pressure oil port (20) Work port (A) LOWER position (B) HOLD position (C) RAISE positionWhen the pilot valve is in HOLD position (B) , centering springs (9) , (15) and detent balls (4) keep pivot plate (3) in the center position. Springs (15) hold up metering stems (16) and (17) . This allows work ports (18) and (20) to vent to the oil tank. There are orifices in work ports (18) and (20) in order to provide stability in the valve group. When the pilot valve is in RAISE position (C) , pivot plate (3) causes plunger assembly (6) to move down. Plunger assembly (6) will force down plunger (12) , collapsing metering spring (13) and spring (15) . This will allow metering stem (16) to shift. Also, this will allow oil from pressure oil port (19) to flow out of work port (20) .When the pilot valve is in LOWER position (A) , pivot plate (3) causes plunger assembly (5) to move down. Plunger assembly (5) will force down plunger (7) , collapsing metering spring (13) and spring (15) . This will allow metering stem (17) to shift. Also, this will allow oil from pressure oil port (19) to flow out of work port (18) .