H Y D R A U L I C
S Y S T E M
S Y S T E M S O P E R A T I O N
LIFT AND TILT CONTROL
Tilt Valve Spool
LIFT AND TILT CONTROL VALVE
(Lift Valve Spool in HOLD and Tilt Valve Spool in TILT BACK)
1. Chamber for pilot oil.
6. Passage to head end of
10. Inlet paaaage for
11. Tilt valve apool.
4. Make-up valve for rod
12. Chamber for pilot
end of tilt cylinder.
9. Load check valve for tilt
5. Paasage to rod end of
Oil from the implement pump section goes
TILT BACK Operation
15. Outlet paasage to
16. Lift valve spool.
through inlet passage (10) to tilt valve spool (11). On
machines with an attachment (three spool) control
valve, the pump flow goes to the attachment valve
spool before it goes to the lift and tilt valve spools.
The tilt valve spool is a spring-centered, open center,
pilot operated spool with three positions: TILT
BACK, HOLD and DUMP. Springs (2) keep the
spool in HOLD position when there is no pilot pres-
sure oil in chambers (1) and (12). Movement of the
spool is controlled by pilot pressure oil from the lift
and tilt pilot valve in chambers (1) and (12).
When the tilt control lever is moved to TILT
BACK position, pilot oil is sent to chamber (1) and
tilt valve spool (11) moves to the right. Implement oil
is sent from inlet passage (10) to load check valve (9).
The load check valve prevents reverse oil flow which
can cause cylinder drift or load loss. Load check valve
(9) does not open until the oil pressure becomes
greater than the force of spring (8) and the head end
pressure of the tilt cylinder. The oil opens the load
check valve, goes through passage (7) and out pas-
sage (6) to the head end of the tilt cylinder. This
When tilt valve spool (11) is in HOLD position,
causes the bucket to tilt back.
implement oil goes from inlet passage (10), through
passage (14) and outlet passage (15) to the hydraulic
Oil from the rod end of the tilt cylinder comes
tank. The position of the spool holds (blocks) the oil
through passage (5), around tilt valve spool (11),
in both ends of the tilt cylinder and keeps the cylinder
through passage (13), around lift valve spool (16)
and through outlet passage (15) to the hydraulic