PISTON AS 3234017 - Caterpillar

Illustration 2 g00635976
Hydraulic Retrieval Device Valve (HOLD Position) (8) Pilot oil chamber (9) Spring (10) Passage to tank (11) Signal passage (12) Port (B) to hydraulic motor (reel in) (13) Control spool (14) Port (A) to hydraulic motor (reel out) (15) Signal passage (16) Passage to tank (17) Spring (18) Pilot oil chamber (19) Solenoid valve (20) Port (21) Spring (22) Spring cavity (23) Passage (24) Passage (25) Pump passage (26) Spool (27) Chamber (28) Solenoid valveWhen the HRD control valve is used as a separate attachment on either machine, the control valve section will be located between the decking blade valve section and the arch valve section. Pump oil flows from the decking blade valve section to the HRD valve through passage (25). The location of passage (25) in the valve is common in all valve sections. The passage has no outlet.When the operator places the control switch in the HOLD position, solenoids (19) and (28) block pilot oil from flowing into both chambers (8) or (18). Centering springs (9) and (17) keep control spool (13) in the HOLD position.Oil flows into passage (24) through openings in spool (26). The oil then flows into chamber (27) .Oil pressure in chamber (27) increases. This acts against spool (26) until the oil pressure overcomes the force of spring (21). This causes spool (26) to move to the left. As spool (26) moves left, oil flows from passage (25) into passage (23). The oil in passage (23) is blocked by spool (13) .As spool (26) moves left, slots in the spool begin to close. When the slots close, oil flow from passage (25) to passage (23) is restricted. Oil then flows from signal passage (11) into spring cavity (22) through port (20) .Oil is now metered through the slots in spool (26) in order to maintain pressure in chamber (27) and passage (25) above the pressure in signal cavity (11). This pressure is lower than pump pressure in passage (25) .In the HOLD position, spool (13) blocks the oil in passage (23) from flowing into either ports (12) or (14). The oil in the hydraulic motor and oil lines are also blocked at ports (12) and (14) .Since no oil flows to the hydraulic motor, oil in passages (10), (11), (15), (16), and (20) will return to the hydraulic oil tank.Hydraulic Retrieval Device Valve in the REEL IN Position
Illustration 3 g00635976
Hydraulic Retrieval Device Valve (REEL IN Position) (8) Pilot oil chamber (9) Spring (10) Passage to tank (11) Signal passage (12) Port (B) to hydraulic motor (reel in) (13) Control spool (14) Port (A) to hydraulic motor (reel out) (15) Signal passage (16) Passage to tank (17) Spring (18) Pilot oil chamber (19) Solenoid valve (20) Port (21) Spring (22) Spring cavity (23) Passage (24) Passage (25) Pump passage (26) Spool (27) Chamber (28) Solenoid valveWhen the operator places the control switch in the REEL IN position, solenoid valve (19) energizes. Solenoid valve (19) shifts and routes pilot oil into chamber (8)