TM 5-3805-261-20
PRINCIPLES OF OPERATION.
1-31.
BLADE SYSTEM.
e.
Blade Float Hydraulic System. The purpose of this circuit is to allow blade lift cylinder rods along with the
blade to move freely up and down over uneven surfaces when moving snow, gravel, and other loose materials.
The system consists of: a manual switch at the Monitor System panel, one blade float pilot valve assembly, one blade float
check valve for each cylinder, and a limit switch at each of the blade lift lever linkages. Refer to hydraulic system for lift
cylinder above.
When moved to the ON position, the switch at the Monitor System panel opens a normally closed solenoid valve and
closes a normally open solenoid valve in the blade float pilot valve assembly. The opened valve sends pump pressure oil
to actuate the blade float check valves and the closed valve prevents pressure oil from returning to the tank from the blade
float check valves.
Pistons within the blade float check valves then move check balls off their seats which allows free movement of oil between
the head and rod ends of the lift cylinders. This allows the blade to move freely up and down over uneven surfaces.
The limit switches on the blade lift lever linkage allow raising and lowering of the blade lever even when the blade float
system is on. If the lift lever is moved, the limit switch turns off the current to the solenoids in the blade float pilot valve.
This turns off the blade float system until the lever is returned to its NEUTRAL position.
When moved to the OFF position, the blade float pilot valve assembly returns to normal which now prevents free circulation
of oil between upper and lower ends of the cylinders. It also allows any pressure remaining in the check valve to return to
the tank.
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