Pump/Structure Movements; Lift Up/Down; Hydraulic Pump Electric Schematic; Mast Lift System - Basic Schematic - JLG TOUCAN 10E Service And Maintenance Manual

SECTION 3 - THEORY OF OPERATION

3.6 PUMP/STRUCTURE MOVEMENTS

An electrically driven hydraulic pump provides hydraulic
pressure to actuate the steering and superstructure move-
ments.
The Power Module is essentially a "low-side" switch for the
pump motor. The positive terminal of the pump is tied to
Battery Positive (+B) after the Line Contactor. The nega-
tive terminal of the pump connects to the (-P) Terminal of
the Master Power Module, which switches current through
MOSFET transistors to the Battery Negative.
For variable speed pump operation, the MOSFET transis-
tors switch On and Off at high frequencies. The Duty
Cycle is varied to control the voltage applied to the pump
motor. When the MOSFET's spend 50% of the period On
and 50% Off, approximately half of the available Battery
power will be applied to the pump motor. Similarly, the
MOSFET are On continuously (100% Duty Cycle) to apply
all available Battery power to the pump motor (i.e. Mast
Lift Up at full speed from Platform Mode).
Figure 3-3. Hydraulic Pump Electric Schematic
When the Control System is energized, the voltage at the
(- P) Terminal will be approximately +24V (referenced to -
B) when the pump is static.
The (-P) Terminal will be approximately at +1V (refer-
enced to -B) when the pump is running at full speed (i.e.
Mast Lift Up from Platform Mode).

Lift Up/Down

The lift actuators are single acting hydraulic cylinders. Cyl-
inders do not have sealed pistons but only rod guides.
The area of the guide that fluid touches on both sides
does not provide lift because the forces on both sides
cancel each other. Only the area of the rod provides the
lifting.
Lift down is "powered" by gravity.
3-4
To lift the mast, the pump is run and an appropriate signal
is sent to the proportional relief valve. Then, after a short
delay, the solenoid energizes and opens the mast valve.
The pump speed is set proportional to joystick position.
Fluid flows into the mast cylinder and extend the rod. As
mast sections are linked to each others by lifting chains,
all mast sections elevate simultaneously.
To bring down the mast, an appropriate electric signal is
sent for the proportional relief valve to close and the pump
is run for a short period of time to pressurize the circuit.
Once the circuit is pressurized, the mast valve opens and
the load is held by the proportional pressure relief valve.
Then, the pressure relief valve opens proportional to joy-
stick position, and allows fluid back to the tank, allowing
the mast to retract by gravity.
Figure 3-4. Mast Lift System - Basic Schematic
– JLG Lift – 31210090