Principle Of Operation; Hydraulic Circuit; Travel, Scissors Lift; Steering / Stabilisation - Haulotte H12 SD Operating And Maintenance Instructions Manual

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.
ADJUSTMENT MUST ONLY BE PERFORMED BY SPECIALIST PERSONNEL.

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.

Two hydraulic motors drive the fixed-axle wheels via epicloidal reducing gears.
The two speeds (high, low) are controlled by a switch.
4 x 2 version:
• 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.
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-
4 x 4 version:
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.
3.

PRINCIPLE OF OPERATION.

Misadjustment may disable the machine's safety devices,
and thus cause a risk of serious accident.
WARNING.
Motors alimentation.
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