SECTION 3 - THEORY OF OPERATION - 1230ES
3121222
– JLG Lift –
3-5
3.6
PUMP/LIFT/MAST
An electrically driven hydraulic pump provides hydraulic
pressure to actuate the steering and lift up. Lift down is
"powered" by gravity. The lift actuator is a three stage
hydraulic cylinder. The cylinder pistons are not sealed so
fluid can flow from one cylinder to the next. The area of
the piston that fluid touches on both sides does not pro-
vide lift because the forces on both sides cancel each
other. The area of the piston with the rod behind it pro-
vides the lifting force necessary because no pressure is
there to cancel the force applied by the pressure on the
other side.
To lift the platform, the solenoid energizes and opens the
lift up valve. The pump speed is set proportional to joy-
stick position. Fluid flows into the first cylinder, through
the hollow rod. This extends the barrel of the first cylinder.
The rod to the second cylinder is attached to the barrel of
the first cylinder. Fluid is passed by a port in the first cylin-
der to the hollow rod of the second cylinder. That extends
the second cylinder. The barrel of the second cylinder is
attached to the barrel of the third cylinder. A port in the
barrel of the second cylinder passes fluid to the third cylin-
der. This extends the third cylinder, and lifts the platform.
To bring down the platform, the lift down valve opens,
proportional to joystick position, and allows fluid out of
the cylinder, allowing it to retract by gravity.
Figure 3-4. LIFT SYSTEM
The Power Module is essentially a "low-side" switch for the
pump motor. The positive terminal of the pump is tied to
Battery Positive after the Line Contactor. The negative ter-
minal of the pump connects to the P Terminal of the
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 (16kHz). 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 ½ of the available
Battery power will be applied to the pump motor. Simi-
PLATFORM
ATTACHMENT
CHASSIS
Summary of Contents for 1230ES
Page 1: ...AS NZS Service and Maintenance Manual Model s 1230ES P N 3121222 June 22 2017 ...
Page 2: ...NOTES ...
Page 24: ...SECTION 1 MACHINE SPECIFICATIONS 1 12 JLG Lift 3121222 NOTES ...
Page 32: ...SECTION 2 GENERAL SERVICE INFORMATION 2 8 JLG Lift 3121222 NOTES ...
Page 78: ...SECTION 4 BASE COMPONENTS 4 40 JLG Lift 3121222 NOTES ...
Page 104: ...SECTION 5 CONTROL COMPONENTS 5 26 JLG Lift 3121222 NOTES ...
Page 158: ...SECTION 8 DIAGNOSTIC TROUBLE CODES 8 22 JLG Lift 3121222 NOTES ...
Page 198: ...SECTION 9 GENERAL ELECTRICAL INFORMATION SCHEMATICS 9 40 JLG Lift 3121222 ...
Page 199: ...SECTION 9 GENERAL ELECTRICAL INFORMATION SCHEMATICS 3121222 JLG Lift 9 41 ...
Page 200: ...SECTION 9 GENERAL ELECTRICAL INFORMATION SCHEMATICS 9 42 JLG Lift 3121222 ...
Page 202: ...SECTION 9 GENERAL ELECTRICAL INFORMATION SCHEMATICS 9 44 JLG Lift 3121222 NOTES ...
