FILTER A OIL 1M4794 - Caterpillar

Illustration 1 g00776535
Simplified Hydraulic Schematic (1) Boom cylinder (2) Boom lowering control valve (3) Supply line to rod end of boom cylinder (4) Line (5) Solenoid valve (6) Drain line (7) Supply line (pilot oil) (8) Supply line (pilot oil) (9) Drain line (10) Proportional valve for boom cylinder rod end (11) Supply line to head end of boom cylinder (12) Flow compensator valve (13) Load check valve (14) Boom control valve (15) Passage (pump delivery flow) (16) Passage (pump delivery flow) (17) Passage (oil flow to boom lowering control valve) (18) Relief valve (boom cylinder rod end) (19) Proportional valve for boom cylinder head end (20) Pilot manifold (21) Hydraulic tank (22) Front pump (23) Rear pump (24) Pilot pump (25) Drain line (26) Pilot supply line (35) Return passage (36) Return line
Illustration 2 g00776641
Boom lowering control valve (11) Supply line to head end of boom cylinder (25) Drain line (26) Pilot supply line (27) Spool valve (28) Check valve (29) Spool valve (30) Drain line (31) Manual purge valve (32) Supply line to head end of boom cylinder (33) Check valve (34) Relief valve (head end)Boom Raise Operation
Illustration 3 g00776670
Boom Cylinders (2) Boom lowering control valvesDuring a boom operation, boom control valve (14) is activated. The oil delivery from front pump (22) and rear pump (23) are combined in the main control valve. Pilot pump (24) sends pilot system oil to pilot manifold (20). The pilot system oil then flows through line (8) to the proportional valve for boom cylinder head end (19) and the proportional valve for boom cylinder rod end (10) .When the boom control lever is operated, an electrical signal from the control lever is sent to the machine electronic control module. The machine electronic control module energizes the proportional valve for boom cylinder head end (19) .When the proportional valve for boom cylinder head end (19) is energized, the spool in boom control valve (14) shifts. The oil delivery from the main pumps flows from passage (15) through control valve (14), load check valve (13), flow compensator valve (12), passage (16) and passage (17). The oil delivery from the main pumps in passage (17) now flows through line (11) to boom lowering control valves (2). The oil flows from boom lowering control valves (2) through check valve (33) to the head end of boom cylinders (1) .The oil from the rod end of boom cylinders (1) flows through line (3), boom control valve (14) and passage (35) to return line (36). The return oil now flows back to the hydraulic filters and the hydraulic tank.If a line breaks, the boom will not fall because check valve (33) prevents the oil in the head end of the boom cylinders from flowing out of the boom cylinders.Boom Lower Operation
The BOOM LOWER operation is similar to the BOOM RAISE operation. The operation of boom lowering control valves (2) during a BOOM LOWER operation is described below.When the boom control lever is operated in order to perform a BOOM