Rev. 7/14/2016
PMPS, MANUAL
Copyright 2016 Vestil Manufacturing Corp.
Page 17 of 22
Electric PMPS Operation Instructions:
Pushbutton controls are standard equipment on PMPS series pallet handlers, i.e. a handheld controller as well as
control buttons on the housing of the modular power unit. To raise or lower the fork carriage, press the appropriately
marked button. When either button is released, the carriage will maintain position until the
UP
or
DOWN
button is
pressed.
OPERATION:
To raise the forks, press the
UP
button on the pushbutton controller. This starts the electric motor which turns the
hydraulic pump. Oil from the reservoir (inside the modular power unit) flows through the suction filter and into the pump.
The pump delivers pressurized oil to the hydraulic cylinder through a check valve. The check valve allows oil to flow only
in one direction, i.e. to the cylinders, and prevents oil from flowing back into the pump circuit when the pump stops. This
traps oil in the cylinder, which allows the forks to maintain elevation after the control button is released.
If a load exceeds the capacity of the lifter, pressure will build up in the circuit between the pump and the cylinders
when the
UP
button is pressed. This pressure forces the relief valve to unseat which in turn allows oil to circulate back to
the reservoir instead of to the cylinder. This pressure relief mechanism prevents damage to the hydraulic system.
To lower the forks, press the
DOWN
button. This energizes the lowering solenoid valve coil, which unseats the poppet
valve and allows oil to return to the reservoir from the cylinders through the pressure-compensated flow control valve.
Releasing the
DOWN
button de-energizes the solenoid and closes the valve poppet. The poppet valve and check valve
together prevent oil from returning to the reservoir and cause the cylinders to stop retracting. The forks remain elevated
until the operator presses a button on the pushbutton controller again.
LOWERING SOLENOID VALVE:
The pallet handler is equipped with a cartridge lowering valve. If a malfunction occurs while lowering the fork carriage
(item no. 3; p. 4 & 5), refer to the solutions presented in “Troubleshooting” on p. 19.
If a malfunction of this valve occurs, clean it by applying the following procedure:
1. Completely lower the forks.
2. Use a thin tool to press the poppet in from the bottom and open the valve.
3. Repeat several times while immersing the valve in kerosene or mineral spirits; then blow dry the cleaned valve.
4. Blow compressed air through the valve while holding the valve open as described in step 2.
1
1
/
2
in. x 18in.
displacement
cylinder with
internal
velocity fuse
Motor
Hydraulic
pump
LC/TC
LC/TC
LY/FC
Pressure
check
valve
Lowering valve
Pressure
compensated
flow control
Adjustable
pressure
relief valve
100 micron
suction filter
10 micron
return filter
FIG. 11: Hydraulic circuit diagram (electrically powered units)
