BOLT 1536881 - Caterpillar

Lowering Devise
NEUTRAL Condition
Illustration 1 g02402616
Lowering Device Valve
(A) Passage
(B) Passage
(1) Set screw
(2) Relief valve
(3) Spring
(4) Pin
(5) Check valve
(6) Line from control valve
(7) Manual lowering screw
(8) Control piston
(9) Line from pilot valve
(10) Spring
(11) Line from control valve
(12) Rod
(13) Line to parallel cylinder
(14) Tapered piston
(15) Spring
(16) Spring chamber
(17) Retainer
(18) spring
(19) Poppet
(20) Flow control LOWER Condition
Illustration 2 g02402977
Lowering Device Valve
(A) Passage
(B) Passage
(1) Set screw
(2) Relief valve
(3) Spring
(4) Pin
(5) Check valve
(6) Line from control valve
(7) Manual lowering screw
(8) Control piston
(9) Line from pilot valve
(10) Spring
(11) Line from control valve
(12) Rod
(13) Line to parallel cylinder
(14) Tapered piston
(15) Spring
(16) Spring chamber
(20) Flow control 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 (5). 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 line (9). The pressure pushes control piston (8) against spring (10). When pilot pressure increases, control piston (8) pushes the ball. The ball then pushes rod (12). Rod (12) lifts poppet (19) off the seat. This action allows spring chamber (16) to release pressure to the tank. Now, piston (14) can be pushed against spring force (15). Oil can flow from passage (B) to passage (A) through orifices of piston (14). Increased pilot pressure allows the opening between passage (A) and passage (B) to be increased. When pilot pressure is decreased, forces of springs (10) and (15) push piston (8) backward. Spring (18) closes poppet (19). Piston (14) comes back on the seat. This action closes the opening between passage (A) and passage (B). Oil leaks between piston (14) and the housing in order to refill chamber (16) with oil. This locks piston (14) on the seat and the boom lowering control valve is locked again.
Illustration 3 g00932518
Flow Control Valve (20)
( A) Passage
(B) Passage
(C) Orifice
(21) Nipple
(22) Stop nut
(23) Spring
(24) Washer
(25) Bolt Parallel Cylinders
If two cylinders are working in parallel mode, flow control valve (20) is installed in parallel cylinder port (13) of the boom lowering control valve. Flow control valve (20) restricts oil leakage if a connecting hose breaks.Normal Operation (Open Valve)
Spring (23) pushes washer (24) open. Stop nut (22) determines the length of bolt (25), which determines the amount of flow from passage (B) to passage (A).Broken Line
A high flow from passage (B) to passage (A) raises the pressure in chamber (B). This pressure closes washer (24) against the seat and flow is restricted through orifice (C).