MANITOWOC ENGINEERING, CO.
Division of The Manitowoc Company, /nc. Manitowoc, Wisconsin 54220
GANTRY LIFTING DEVICE
2900 -- 4100W
M
Sol
Motor
Solenoid
ting
wer
ylinder
Fill/Bn
P
Res
Power Unit, Inside Machinery Cab
Relief Valve B
(2500 psi)
Solenoid Valve Orifice
l ~--'] / /~--'J X¢/'~', Filter
Check Motor A199
Valve
Hydraulic Schematic of Power vnit
Figure 1. Gantry Lifting Device with Power Unit (Typical Arrangement)
DESCRIPTION
The gantry lifting device consists of a lever, a hydraulic
cylinder, and an electrically operated pump and reser-
voir unit (see Figure 1).
OPERATION
Raising Gantry
When the"U P" button of the gantry lifting device control
is depressed, electric current energizes the motor sole-
noid, and the motor drives the pump in the reservoir. Oil
flows past the check valve into the head end of the
gantry cylinder, and the cylinder rod extends to raise the
lever and gantry.
NOTE
When the gantry is raised, there is no electric
current to the solenoid valve, and the solenoid
valve remains closed.
When the "uP" button is released, the motor solenoid is
deenergized, and the motor stops driving the pump. The
check valve then closes to hold the lever in any position
it is raised to.
NOTE
Relief valve (A) protects the system from high
pressure when the pump is running.
Lowering Gantry
When the "DOWN" button on the gantry lifting device
control is depressed, electric current energizes the
solenoid valve, and the valve opens. There is no electric
current to the motor solenoid, so the motor does not
drive the pump. The weight of the gantry causes the
gantry cylinder to retract, and the oil flows back to the
reservoir through the solenoid valve and orifice. The
preset orifice restricts the oil flow, thus controlling the
rate of speed that the gantry lowers.
When the "DOWN" button is released, the solenoid valve
closes to block oil flow.
NOTE
Relief valve (B) protects the system from shock
loads when the gantry is lowered onto the lever
(system off).
© Manitowoc 1984
f Continued]
10-3-69 (Rev. 1-6-84) GANTRY LIFTING DEVICE FOLIO 655-1
395143
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