Haulotte H12 SD, Operating And Maintenance Instructions Manual

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3. PRINCIPLE OF OPERATION.
3.1. HYDRAULIC CIRCUIT.
All machine movements, except travel, are performed by hydraulic power.
This power is supplied by an engine-driven gear pump.
In the bi-energy version, the hydraulic power can be provided by two gear pumps powered by drive batteries.
If a fault occurs, the scissors can be lowered by performing a manual emergency action.
A high-pressure filter fitted at the pump discharge protects the circuit from pollution.
3.1.1. Travel, scissors lift.
These functions are performed by all-or-nothing spool valves via a proportional-control spool valve, which
allows progressive movement.
Only one movement can be performed at a time.
3.1.2. Steering / stabilisation.
These functions are performed by an all-or-nothing solenoid valve supplied by the small pump stage.
In the bi-energy version, only one motor pump supplies this movement.
3.1.3. Scissors lift cylinder
This is equipped with a flanged check valve on its casing.
WARNING.
ADJUSTMENT MUST ONLY BE PERFORMED BY SPECIALIST PERSONNEL.
Misadjustment may disable the machine's safety devices,
and thus cause a risk of serious accident.
3.1.4. Brake release of reducing gears during travel.
Each time a travel movement is performed, the brake-disengage circuit of the reducing gears mounted on
the fixed axle is pressurised.
When the movement stops, or if there is a lack of pressure, the brake is reactuated.
3.1.5. Travel.
Motors alimentation.
4 x 2 version:
Two hydraulic motors drive the fixed-axle wheels via epicloidal reducing gears.
The two speeds (high, low) are controlled by a switch.
•
High speed - 4 x 2 and bi-energy: The two motors are fed in series: the pump discharge
flows into one motor, then the other.
•
Low speed - 4 x 2 and bi-energy: The two motors are fed in parallel: each receives half the
pump flow.
4 x 4 version:
Four hydraulic motors drive the wheels via epicloidal reducing gears.
The three speeds (high, medium, low) are controlled by a switch.
•
High speed - 4 x 4: The two fixed-axle motors are fed in series: the steer axle free-wheels.
•
Medium speed - 4 x 4: The two fixed-axle motors are fed in parallel: the steer axle free-
wheels.
•
Low speed - 4 x 4: Each axle receives half the pump flow. The motor on each axle is fed in
parallel.
At low and medium speed, a hydraulic differential lock can be used on each axle.