TRIM-HAND HOLD 1548847 - Caterpillar

Lowering Devise
NEUTRAL Condition
Illustration 1 g06067151
Lowering Device Valve
(A) Passage
(B) Passage
(1) Set screw
(2) Pilot valve
(3) Spring
(4) Pilot spool
(5) Control piston
(6) Pilot port
(7) Passage from control valve
(8) Relief valve adjusting screw
(9) Spring
(10) Relief valve spool
(11) Manual lowering valve
(12) Poppet
(13) Load port
(14) Spring
(15) Control spool
(16) Balancing valve
(17) Line from control valve
(18) Line to main control valve (port "A5")LOWER Condition
Illustration 2 g06067156
Lowering Device Valve
(A) Passage
(B) Passage
(1) Set screw
(2) Pilot valve
(3) Spring
(4) Pilot spool
(5) Control piston
(6) Pilot port
(7) Passage from control valve
(8) Relief valve adjusting screw
(9) Spring
(10) Relief valve spool
(11) Manual lowering valve
(12) Poppet
(13) Load port
(14) Spring
(15) Check valve
(16) Balancing valve
(17) Line from control valve
(18) Line to main control valve (port "A5")The boom lowering control valve is used to prevent the cylinder from falling, if a hose breaks. One valve is on the head end of each cylinder. During the boom raise operation, the valve operates as a load check valve.Boom Raise
As the joystick is moved to the BOOM RAISE position, pump oil flows from passage (A) through passage (B) after pushing check valve (15). The control valve works as a standard check valve. When the joystick returns to the NEUTRAL position, the load will be held by all valve elements in a sealed condition.Boom Lower
Pilot pressure comes in the control valve from the pilot valve through port (6). The pressure pushes control piston (5) against spring (3). When pilot pressure increases above the set pressure of the spring (3), the pilot spool (4) opens.Parallel Cylinders
If two cylinders are working in parallel mode, flow control valve (16) is installed in the parallel cylinder port of the boom lowering control valve. Flow control valve (16) restricts oil leakage if a connecting hose is broken.Broken Line
A high flow from passage (13) to passage (7) raises the pressure in the chamber, and closes check valve (15).