PISTON MOTOR GROUP 9J0688 - Caterpillar

The Cushion-Hitch Switch Is Turned On While The Engine Is Running.
Illustration 2 g00275771
The Cushion-Hitch Switch Is Turned On. The Cushion Ride Mode is Activated. The Engine Is Running. (1) Check valve (2) Manifold (3) Solenoid valve (4) Leveling stem (5) Oil passage for the cushion-hitch pump (6) Passage to the cushion-hitch accumulator (7) Inlet passage for the pressure oil from the cushion-hitch piston pump (8) Detent ball (9) Nitrogen gas (10) Drain to the hydraulic oil tank (11) Supply drain for the cushion-hitch accumulator (12) Directional spool (13) Passage to the head end of the load cylinder (14) Outlet to the hydraulic oil tank (15) Passage to the rod end of the load cylinder (16) Inner spring (17) Outer spring (18) Cover (19) Hydraulic oil end of the cushion-hitch accumulator (20) Piston of the cushion-hitch accumulator (21) Passage for pilot pressure oil (22) Cushion-hitch piston pump (23) Pressure compensator valve (24) Accumulator valve stem (25) Rod end of the load cylinder (26) Load cylinder (27) Head end of the load cylinder (28) Hydraulic oil tank (29) Line to the bail valve on the push-pull machines only (30) Leveling valve (31) Rod (A) Pump oil (B) Return oilWhen the engine is operating, cushion-hitch piston pump (22) pumps pilot pressure oil upward through passage (5) into manifold (2). When the cushion-hitch switch is turned on and the cushion ride mode is activated, solenoid valve (3) directs pilot pressure oil into passage (21). The pilot oil that is flowing into passage (21) exerts a downward pressure on directional spool (12) .When the hydraulic pressure that is pushing directional spool (12) downward becomes greater than the upward forces of inner spring (16) and outer spring (17), directional spool (12) moves downward. Directional spool (12) is pushed downward against cover (18) .The oil from cushion-hitch piston pump (22) at leveling stem (4) flows around directional spool (12) into head end (27) of load cylinder (26). As the hydraulic oil pressure to head end (27) of load cylinder (26) increases, rod (31) of load cylinder (26) extends. Hydraulic oil from leveling stem (4) flows to hydraulic oil end (19) of cushion-hitch accumulator. This hydraulic flow charges hydraulic oil end (19) of cushion-hitch accumulator.Rod (31) of load cylinder (26) extends. The extension of rod (31) lifts the front of the scraper off the tractor. The cushion-hitch is now in the cushion ride mode. A leaf spring that is attached to the lower link assembly pulls leveling stem (4) downward. Leveling stem (4) stops the flow of hydraulic oil to hydraulic oil end (19) of cushion-hitch accumulator. Leveling stem (4) stops the flow of hydraulic oil to head end (27) of load cylinder (26). The pressure of the hydraulic oil in the hydraulic oil end of cushion-hitch accumulator (19) is equal to the pressure