HARNESS AS-PANEL 1228486 - Caterpillar

HOLD Position
Illustration 1 g00859825
HOLD position for the boom valve (1) Head end line relief valve, (2) Spool, (3) Chamber for pilot oil, (4) Spring, (5) Passage to tank, (6) Signal passage, (7) Chamber, (8) Load check valve, (9) Passage, (10) Pump passage, (11) Hole, (12) Passage, (13) Hole, (14) Spring, (15) Chamber, (16) Signal passage, (17) Passage to tank, (18) Spring, (19) Chamber for pilot oil, (20) Line to the next valve, (21) Secondary resolver, (22) Line from the previous valve, (23) Signal line from the previous valve, (24) Line relief valve, (25) Port to the head end of the boom cylinder, (26) Port to the rod end of the boom cylinder, (A) Pump oil, (B) Return oil, (C) Blocked oil and (D) Pilot oil The boom control valve is between the auxiliary control valve and the swing control valve.Pilot oil in chamber (3) and chamber (19) is vented back to the tank through the pilot valve in the HOLD position. Springs (4) and (18) hold spool (2) in the HOLD position.In the HOLD position, spool (2) blocks pressure oil in passage (12) from flowing to ports (25) and (26). Spool (2) is centered by spring (4) and spring (18) .Supply oil from the pump flows in the valve through passage (10). Passage (10) is common in all sections of the valves and the passage has no outlet. Oil flows into passage (9) through hole (11) in load check valve (8). The oil then flows into chamber (7) .Pressure in chamber (7) rises and the pressure acts against load check valve (8). When the pressure overcomes the force of spring (14) and the pressure in chamber (15), the pressure causes load check valve (8) to move down. As the load check valve (8) moves down, oil flows from passage (10) into passage (12). The oil in passage (12) is blocked by spool (2) until the operator moves the control lever.The oil in passage (12) enters hole (13). The