TUBE AS 3041792 - Caterpillar

HOLD Position
Note: Detailed oil flow is not shown for the HOLD position. Refer to Illustration 1 for references to components.When the engine is running, the charge pump (not shown) sends pilot oil to pressure accumulator (29) through line (31) . Pilot oil is available to the electrohydraulic pilot solenoids.At the same time, implement pump (9) sends oil to margin relief valve (20) and to the control valves. The margin relief valve controls the maximum pressure in the implement hydraulic system. When all the control valve spools are in the HOLD position, the oil flows through the valve bank. The oil is sent to hydraulic tank (4) .The valve spools in the HOLD position block the passages to the rod end and to the head end of the hydraulic cylinders. The oil is trapped and the implements do not move. In the HOLD position, the spring centers the valve spool.OPEN Operation
Illustration 1 g01668893
Multipurpose bucket circuit (OPEN) (4) Hydraulic oil tank (6) Multipurpose bucket cylinders (9) Implement pump (16) Pilot control solenoid (18) Anti-drift valve (20) Margin relief valve (22) Relief valve (tilt head end, multipurpose bucket, and ripper) (26) Multipurpose bucket control spool (27) Implement pump compensator valve (29) Accumulator (31) Flow from the charge circuit of the left drive pumpWhen the multipurpose bucket control is moved to the OPEN position, the solenoids allow pilot oil to flow to the left end of multipurpose bucket valve spool (26) . This causes the valve spool to move to the right.The movement of multipurpose bucket valve spool (26) stops the flow of oil through the attachment