COVER 2700335 - Caterpillar

HOLD Position
Illustration 1 g02963381
(1) Control spool
(2) Load sense
(3) Make up valve
(4) Passage to workport (A) to the head end of the lift cylinder
(5) Compensator
(6) Passage to workport (B) to the rod end of the lift cylinder
(7) From pilot valve
(8) Spring
(9) Passage to tank
(10) Bridge passage
(11) Pump supply passage
(12) Feeder passage
(13) Spring
(14) From pilot valve In the HOLD position, spring (8) and spring (13) hold spool (1) in the centered position. No pilot oil enters the control valve through the supply ports. Any pilot oil in the pilot lines drains through the pilot valve to the tank. The spool (1) blocks the flow of pump supply oil in passage (11).Passage (11) is common to all control valves in the bank valve. The passage has no outlet. The spool blocks the flow of pump supply oil until the operator moves the control lever.The lift control valve includes a rod end makeup valve.RAISE Position
Illustration 2 g02963759
(1) Control spool
(2) Load sense
(3) Make up valve
(4) Passage to workport (A) to the head end of the lift cylinder
(5) Compensator
(6) Passage to workport (B) to the rod end of the lift cylinder
(7) From pilot valve
(8) Spring
(9) Passage to tank
(10) Bridge passage
(11) Pump supply passage
(12) Feeder passage
(13) Spring
(14) From pilot valve When the lift circuit is the only hydraulic circuit in operation, the lift circuit will have the highest signal oil pressure in the hydraulic system. When the pilot valve is moved to the RAISE position, pilot oil enters the control valve. The pilot oil flows into passage (14). When the pilot oil and spring (13) overcome the force of spring (8), spool (1) moves to the right.Pump supply oil flows from passage (11) over the spool to passage (12). The hydraulic oil from passage (12) flows to the pressure compensator valve (5). In the pressure compensator valve, the hydraulic oil flows into internal passages. The pressure compensator valve moves up. As the pressure compensator valve moves up, some of the hydraulic oil flows around the pressure compensator valve to chamber (2). The hydraulic oil that flows to chamber (2) is signal oil. The signal oil balances the pressure compensator valve against the hydraulic oil pressure in passage (12). This pressure balance controls the flow across spool (1).The signal oil flows to the pressure compensator valve in each control valve. The signal oil also flows to the pump control valve on the hydraulic pump. The signal oil helps to control the output of the hydraulic pump. When the pressure compensator moves up, oil flows from passage (12) to bridge passage (10). Hydraulic oil flows from passage (10), around the spool to passage (4). Oil in passage (4) flows through port (A) to the head end of the lift cylinders.Hydraulic oil flows from the rod end of the lift cylinder flows through port (B) into passage (6). The hydraulic oil flows around spool (1) into passage (9). Then, the hydraulic oil flows to the tank.When the operator releases the pilot valve, the pilot oil flow to the valve is