CONTROL GP-SERVICE BRAKE 2061638 - Caterpillar

Lowering the Apron
Illustration 1 g00363352
The Apron Circuit in the LOWER Position (1) Control lever (2) Pilot valve (3) Line from the pilot valve to the control valve (4) Line to the filter and the hydraulic tank (5) Oil from cushion-hitch pump to the pilot valve (6) Solenoid valve (7) Pressure reducing valve (8) Valve spool for the ejector cylinders (9) Cushion-hitch pump (10) Pilot oil to the control valve (11) Valve spool for the apron cylinder (12) Apron cylinder (13) Sequence valve (14) Passage to sequence valve for the apron (15) Bumper spring (16) Valve spool for the bowl cylinder (17) Control valve (18) Hydraulic tank (19) Filter in the hydraulic tank (20) Line from small section of the hydraulic pump to the steering system (21) Hydraulic pump (22) Relief valve (23) Line to head end of apron cylinder (24) Line to rod end of apron cylinder (25) Passage (six) (27) Pressure reducing valve (28) Dead engine pressure to the pilot valve (29) Shuttle valve (A) FLOAT position (B) LOWER position (C) HOLD position (D) RAISE position (AA) Pressure oil from the pump (BB) Pilot oil (CC) Blocked oil (DD) Oil at tank pressureWhen control lever (1) is moved to the LOWER position (B) , pilot valve (2) sends a pressure signal to spool (11) through line (10) . This shifts spool (11) until spool (11) contacts bumper spring (15) . The pump oil flows around valve spool (11) and through a passage to sequence valve (13) . Then, the pump oil flows through line (24) to the rod end of apron cylinder (12) . The hydraulic oil in the rod end moves the piston downward. When the piston moves down, the piston pushes the oil in the head end of the cylinder through line (23) . Then, the oil flows through sequence valve (13) and a passage to control valve (17) . Then, the return oil flows through line (4) into filter (19) and hydraulic oil tank (18) .
Illustration 2 g00363452
Scraper Control Levers (1) Apron control lever (24) Electric switch for lowering the apron (25) Control for the scraper bowl (26) Ejector controlValve spool (11) can be moved to the LOWER position by solenoid valve (6) . Solenoid valve (6) is activated by electrical switch (24) . Electrical switch (24) is located in the handle of control (25) .When switch (24) is depressed, solenoid valve (6) opens a path of oil from line (23) through main reducing valve (7) . This reduces the main pilot valve pressure from 3500 kPa (508 psi) to 1500 kPa (218 psi). This pressure is directed to valve spool (11) through line (10) . Valve spool (11) shifts until the valve spool contacts bumper spring (15) .Apron Float
When control lever (1) is moved to FLOAT position (A) , a magnet in pilot valve (2) holds the lever in FLOAT position (A) . In the