Product Manual

Table of Contents Rev. 9/13/2019 LL-PMPS MANUAL
Table of Contents Copyright 2019 Vestil Manufacturing Corp. Page 17 of 22
HYDRAULIC CIRCUIT DIAGRAM: ELECTRICALLY POWERED UNITS
OPERATING THE LIFTER: ELECTRIC UNITS (MODULAR POWER UNIT)
If your unit was manufactured on or after Dec. 1, 2018, see the NOTE in the Table of Contents on the cover page.
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, first make sure that
power is turned on (on/off switch points to ON); then press either the RAISE or LOWER button. When either button is
released, the carriage will maintain position until the RAISE or LOWER button is pressed.
OPERATION
To raise the forks, press the RAISE 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 RAISE button is pressed. 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 LOWER 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 LOWER 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. 6 on p. 4 & 5; item no. 5 on p. 6), refer to the solutions presented in Troubleshooting on p. 21. 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