When the spool is shifted from the HOLD to the RAISE
position, the spool is moved to the right. Pressure oil is sent
from inlet passage (8) to passage (3) through internal passage
(10). This causes the blade to raise.
With spool (6) in the RAISE position, cylinder head end
passage (5) is open to outlet passage (4).
Centering spring (2) is compressed in this position.
When the blade control lever is released, centering spring (2)
returns to the normal position. This pulls the blade control
lever back into the HOLD position.
When the spool is shifted from the HOLD position to the
LOWER position, the spool is moved to the left. Pressure oil
flows through the spool. The LOWER position on the spool is
the second valve setting from the bottom. Pressure oil acts on
the cylinder head end and the cylinder moves down. With
spool (6) in the LOWER position, passage (3) is open to
Leveling Blade Control Valve in FLOAT
(1) Detent. (2) Centering springs. (3) Passage to rod end of
cylinder. (4) Outlet passage. (5) Passage to head end of
cylinder. (6) Spool. (7) Relief valve. (8) Inlet passage. (9)
Leveling Blade Hydraulic System in the FLOAT position
(3) Passage to rod end of cylinder. (4) Outlet passage. (5)
Passage to head end of cylinder. (6) Spool. (7) Relief valve.
(8) Inlet passage. (9) Valve body. (10) Leveling blade
cylinder. (11) Blocked passage. (12) Line from gear pump.
(13) Line to charge circuit.
When spool (6) is shifted from the HOLD position to the
FLOAT position the spool is moved all the way to the left.
Centering spring (2) is fully compressed, and detent (1) is
located in the groove of the detent sleeve. Centering spring (2)
does not have enough force in order to pull the detent past the
groove in the detent sleeve. Spool (6) is held in the FLOAT
position until the operator moves the blade control lever out of
the FLOAT position.
With the control valve in the FLOAT position, spool (6) blocks
pressure oil in inlet passage (8) and internal passages (10) and
(11). Passage (3) and passage (5) are open to outlet passage
(4). When the cylinder rod and the head ends are open to the
charge circuit, the blade follows the shape of the ground.