Hitachi ZW180, Technical Manual

Page: 98 / 374

SYSTEM / Control System
T2-1-56
Lift Arm Float Control
Purpose: Free to raise and lower the lift arm in re-
sponse to the external force in order to re-
move snow and clean road.
Operation:
1. When the lift arm control on lever is moved to the
floating position (farther position than the lift arm
lowering position), the lift arm control lever is re-
tained by the electromagnet on the lift arm lower-
ing side, and pressure oil from the pilot valve
moves the lift arm spool in the control valve to the
floating position (farthest right position).
NOTE: When the engine is running, the electro-
magnet on the lift arm lowering side is al-
ways excited by current from fuse #6 of
fuse box B.
2. Pressure oil from the main pump is blocked by the
lift arm spool, and the ports on the rod side and
the bottom side of the lift arm cylinder are con-
nected, to the tank port through the lift arm spool.
As the both ports of the lift arm cylinder have the
same pressure as the hydraulic oil tank, the lift
arm cylinder is not restricted and the lift arm can
move in response to the external force.
3. The lift arm control lever returns to neutral if
pulled more strongly than the magnetic force of
the electromagnet. As the lift arm spool in the
control valve also returns to neutral, the lift arm
float control is released.