TM 5-3805-290-23-1
THEORY OF OPERATION - CONTINUED
0003 00
HYDRAULIC SYSTEM - CONTINUED
d.
FLOAT Position.
(1)
When the lift circuit is the only hydraulic circuit in operation, the lift circuit will have the highest signal oil
pressure in the hydraulic system. When the pilot valve is moved to the FLOAT position, pilot oil enters the
control valve through port (24). The pilot oil flows through the shock reducing check valve (23). The
shock reducing check valve moves to the right.
(2)
The pilot oil flows into chamber (25) and passage (28). As the pilot oil moves spool (27) to the right,
spring (9) is compressed. The pilot oil also opens the pilot operated check valve (12).
(3)
No hydraulic oil flows from passage (16) to the pressure compensator valve (6) and passage (29). No
hydraulic oil flows into the internal passages in the compensator valve and to passage (4). No hydraulic oil
flows around the pressure compensator valve to spring (3).
(4)
No signal oil enters passage (4) or flows to the pressure compensator valve in each control valve. No sig-
nal oil flows to the pressure and flow compensator valve on the hydraulic pump. The signal oil controls the
output of the hydraulic pump. The hydraulic pump is at standby pressure. No hydraulic oil flows to load
check valve (21) or to passages (14 and 19).
(5)
The hydraulic oil from the rod end of the lift cylinders flows through port (2) to passage (20). Then, the oil
flows through passage (19) to passage (14). The hydraulic oil flows around the spool into passage (13).
(6)
In passage (13), hydraulic oil flows from the head end of the lift cylinders to port (5). The hydraulic oil
flows to the pilot operated check valve (12). The hydraulic oil flows through the pilot operated check valve
to passage. The hydraulic oil flows around the spool to passages (8 and 15). The hydraulic oil flows
through passage (30) to the back pressure check valve (1). The back pressure check valve builds up the
hydraulic oil pressure in passages so that regeneration check valve (18) can activate.
(7)
In passage (15), the flow of oil is blocked by the regeneration check valve (18). When the hydraulic oil
pressure overcomes the force of the spring in regeneration check valve, the regeneration check valve
opens. The hydraulic oil flows through the regeneration check valve to passage (19). The hydraulic oil
combines with the hydraulic oil in passage (29). Then, the hydraulic oil flows to passage (14). The hydrau-
lic oil flows around the spool into passage (13). The hydraulic oil flows around the spool to passages (8
and 15).
(8)
The hydraulic oil in passage (8) flows through passage (30) to back pressure check valve (1). The hydrau-
lic oil in passage flows to other control valves as makeup oil. When the oil pressure overcomes the force of
the spring in the back pressure check valve, the back pressure check valve opens. The hydraulic oil flows
through the valve. Then, the hydraulic oil flows to the tank.
0003 00-182