PIN AS 2136709 - Caterpillar

Illustration 2 g00296739
Main Control Valve (Tilt Valve Spool in the HOLD Position and Lift Valve Spool in the RAISE Position) (10) Inlet passage for implement pump oil (11) Tilt valve spool (13) Passage (14) Passage (15) Outlet passage to the hydraulic oil tank (16) Lift valve spool (17) Chamber for pilot oil (18) Springs (19) Makeup valve for the rod end of the lift cylinders (20) Vent passage to the pilot valve (oil manifold) (21) Spring (22) Passage to the rod end of the lift cylinders (23) Passage to the head end of the lift cylinders (24) Passage (25) Check valve for the lift circuit (26) Spring (27) ChamberOil from the implement pump flows through inlet passage (10) and around tilt valve spool (11) before the oil reaches lift valve spool (16). On machines with an auxiliary control valve, pump oil flows to the auxiliary valve spool before the oil flows to the main control valve. Lift valve spool (16) is spring centered. The lift valve spool is controlled by pilot pressure oil. The lift valve spool has an open center.HOLD Position
Springs (18) keep lift valve spool (16) in the HOLD position when there is no pilot pressure oil in chambers (17) and (27). Spool movement is controlled by pilot pressure oil in chambers (17) and (27) .When lift valve spool (16) is in the HOLD position, implement pump oil flows from inlet passage (10) to passage (14). The oil then flows through outlet passage (15) to the hydraulic oil tank. The position of the lift valve spool prevents the flow of oil to passages (22) and (23). The lift valve spool blocks the oil in both ends of the lift cylinder. This prevents the lift cylinder from moving.RAISE Position
When the lift control lever is moved to the RAISE position, pilot oil flows to chamber (17). This causes lift valve spool (16) to move to the right. Oil from the implement pump flows into inlet passage (10). The oil then flows through passage (14) to check valve (25) .Check valve (25) does not open until the oil pressure becomes greater than the combined force of spring (26) and the oil pressure in passage (24). When check valve