CARRIER-PLANETARY 2634903 - Caterpillar

Illustration 1 g00555893
Pilot valve for a machine that is equipped with STIC steering (1) Handle. (2) Link. (3) Link. (4) Plunger. (5) Plunger. (6) Spring. (7) Spring. (8) Cap. (9) Cap. (10) Spring seat. (11) Spring seat. (12) Spring. (13) Spring. (14) Outlet port to tank. (15) Spring. (16) Spring. (17) Passage. (18) Passage. (19) Spool valve. (20) Spool valve. (21) Port to the steering neutralizer valve for a right turn. (22) Inlet port. (23) Port to the steering neutralizer valve for a left turn.When the machine engine is running, oil is drawn from the hydraulic tank by the pilot oil pump. The pilot oil pump sends pilot oil through the hydraulic oil filter to the pilot valve. Pilot oil enters the pilot valve at inlet port (22) .The STIC steering control lever is attached to handle (1) . When the STIC steering control lever is in the STRAIGHT AHEAD position, centering springs (6) , (7) , (12) , (13) , (15) and (16) keep the pivot plate in the CENTERED position. Pilot oil flows through inlet (22) to metering spool valves (19) and (20) . In this position, the spool valves block the flow of oil to the steering control valve. This action causes the oil to flow back to the hydraulic tank. Ports (21) and (23) are also open to the hydraulic tank.When the STIC steering control lever is moved to the LEFT TURN position, the pivot plate causes link (2) to move plunger (4) downward. As the plunger moves downward, the plunger overcomes the force of spring (6) . This action causes the spring to move downward. As the plunger moves downward through cap (8) , the plunger also causes spring seat (10) , spring (12) , spring (15) , and spool valve (19) to move downward. The other plunger remains stationary.When spool valve (19) moves downward, passage (17) opens. Oil can now flow from inlet port (22) into passage (17) . The oil then flows through passage (17) and past spool valve (19) . The oil then moves out of port (21) .The oil flows from port (21) to the steering neutralizer valve for right turns. Next, the oil flows to the steering quad check valve and to the steering control valve.Oil that flows from the steering control valve flows through the steering neutralizer valve for left turns. The oil then flows from the steering neutralizer valve for left turns to port (23) .When the control lever for the steering transmission integrated control (STIC) is moved to the RIGHT TURN position, the pivot plate causes link (3) to move plunger (5) downward. As the plunger moves downward, spring (7) moves downward. As the plunger moves downward through cap (9) , the plunger causes spring seat (11) , spring (13) , spring (16) , and spool valve (20) to move downward.When spool valve (20) moves down, passage (18) opens. Oil can now flow from inlet port (22) into passage (18) . The oil then flows through