HYDRAULIC SYSTEMTM 5-3805-258-24-1SYSTEMS OPERATIONis held in passage (19)]. Lift stem (13) is now pushedoff of retainer (6) and is held (floating) in a pressuremodulating position. The lift stem keeps a balancebetween the pressure in passage (19) and the force ofspring (7).When the lift control lever is released, spring (9)pushes up on plunger (4). Actuator (1) turns shaft(2) and the lever moves back to HOLD position. Liftstem (13) moves up because retainer (6) has movedup (with the plunger) and the force of spring (7) isless. The oil in passage (19) can now go through holes(15) and tank passage (11). The centering springs onthe lift valve spool in the lift and tilt control valvemove the valve spool back to HOLD position. Theextra oil from the end of the lift valve spool also goesthrough holes (15) and tank passage (11).NOTE: The farther the lift control lever is movedinto RAISE position, the more plunger (4) and liftstem (13) move. Thus there is more compression onspring (7) and the pressure in passage (19) increases.The lift valve spool now moves farther and lets moreoil go to the head end of the lift cylinders. So thebucket lifts faster.LOWER PositionLower stem (12) has two purposes: to send pres-sure oil to the lift valve spool and provide exactmovement of the valve spool during LOWER opera-tions; to release pressure (vent) in the spring passageof the make-up valve for the rod end of the liftcylinders during FLOAT operations.When the lift control lever is moved into LOWERposition, shaft (2) and actuator (1) turn in the direc-tion shown. The actuator pushes plunger (3) downagainst the force of spring (8). Lower stem (12)moles down with the plunger. The oil from pumppassage (20) now goes through holes (14) and outpassage (18) to one end of the lift valve spool. Thepressure of this oil, controlled by the force of spring(8). moves the lift valve spool into LOWER position.The oil from the chamber at the opposite end of thelift valve spool comes back through passage ( 19).This oil goes through holes (15) of lift stem (13) intotank passage (11).Oil pressure in passage (18) pushes up againstlower stem (12) and spring (8). A small pressureincrease in passage (18) pushes lower stem (12) upagainst the force of spring (8). The flow of pressureoil through holes ( 14) and passage ( 18) is stopped[the pressure is held in passage (18)]. Lower stem(12) is now pushed off of retainer (5) and is held(floating) in a pressure modulating position. Thelower stem keeps a balance between the pressure inpassage ( 18) and the force of spring (8).3-97As the lift control lever [and actuator (1) andplunger (3)] is moved farther into LOWER position,plunger (3) comes in contact with lower stem (12).Holes (14) now become fully open to oil from pumppassage (20). This now moves the lift valve spoolcompletely to LOWER or full “power down” posi-tion. The maximum amount of oil now goes to the rodend of the lift cylinders. So the bucket lowers faster.When the lift control lever is released, spring (10)pushes up on plunger (3). Actuator (1) turns shaft(2) and the lever moves back to HOLD position,Lower stem (12) moves up because retainer (5) hasmoved up (with the plunger) and the force of spring(8) is less. The oil in passage (18) can now go throughholes (14) and tank passage (11). The centeringsprings on the lift valve spool in the lift and tiltcontrol valve move the valve spool back to HOLDposition. The extra oil from the end of the lift valvespool also goes through holes (14) and tank passage(11).
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