PISTON 3330058 - Caterpillar

Hydraulic Control Group
Illustration 1 g00294215
(1) Cab floorplate (2) Pedal assembly (3) Pilot control valveThe hydraulic control group is bolted to cab floorplate (1) on the right side of the travel levers/pedal. The hydraulic control group consists of pedal assembly (2) and pilot control valve (3) .The auxiliary pedal is operated by depressing the pedal forward and backward. Depressing the pedal forward causes the machine to travel straight forward. Depressing the pedal backward causes the machine to travel in straight reverse.Operation of Pilot System
Illustration 2 g00294213
(3) Pilot control valve (third pedal) (4) Hydraulic activation control valve (5) Shuttle valve (6) Main control valve (7) Pilot control valve (left travel) (8) Pilot control valve (right travel)
Illustration 3 g00294229
Pilot Control Valve (9) Pilot oil supply port (10) Passage (11) Rod (12) Seat (13) Spring (14) Spring (15) Stem (16) Passage (17) PortWhen hydraulic activation control valve (4) is activated, pilot oil is supplied to port (9) of pilot control valve (3) . The pilot oil at port (9) goes into passage (10) .When pedal (2) is depressed forward, rod (11) and seat (12) are pushed down against the force of springs (13) and (14) . When stem (15) moves down, passage (16) is opened to passage (10) .As passage (16) is opened, the pilot oil in passage (10) goes through passage (16) and then out port (17) . The pilot oil goes to shuttle valve (5) .
Illustration 4 g00294181
Shuttle Valve (18) Inlet port (straight travel) (19) Inlet port (right travel) (20) Inlet port (left travel) (21) Outlet port (22) Outlet port (23) Check ball (24) Check ballThe pilot oil from pilot control valve (3) goes to shuttle valve (5) . The shuttle valve gives priority to the pilot oil with the highest pressure. The shuttle valve prevents more than one pilot control valve from sending a pilot oil pressure to the main control valve.The pilot oil goes in port (18) . The pilot oil pressure pushes check ball (23) and check ball (24) against port (19) and port (20) . The check balls prevent pilot oil to flow from port (19) and port (20) . The pilot oil flows out of port (21) and port (22) .The pilot oil goes to the main control valve. The pilot oil shifts the travel control valve which allows main pump oil to go to the travel motors.