Product Manual

02/05 03-126-121.doc
VESTIL MFG. CO. 11
THE POWER UNIT’S OPERATION -- UNI
The electric / hydraulic Uni-tilt utilizes an electric motor directly coupled to a gear-type hydraulic pump to produce the needed
fluid pressure and flow to allow the cylinders to perform the work of tilting a container or pallet.
A hydraulic manifold houses the hydraulic control components, and is bolted directly onto the gear pump.
The power unit’s hydraulic components are all rated for 3,000 psi working pressure.
o Important parts of the power unit include:
• The electric motor. Motors are available for operation on single- or three-phase AC supplies (all are dual-voltage capable).
• The gear pump. Its shaft is coupled directly to the shaft of the electric motor. Several displacements are available, depending
on the motor horsepower used.
• The check valve. Its purpose is to prevent the backflow of fluid through the pump. In this way it allows the platform to be held
at a given elevation indefinitely.
• The pressure relief valve. Its job is to open a path for fluid to flow back to the reservoir in the event that the fluid pressure
built up by the pump exceeds 3,000 psi. Thus the system cannot see more than 3,000 psi.
• The lowering solenoid valve. This is an electrically-operated cartridge valve. It contains a screen to keep contaminants from
entering the valve.
• The pressure-compensated flow control spool. This regulates the fluid flow back to the reservoir when the valve opens. It
allows the platform to always lower at the same rate regardless of whether there is a load on the platform or not. Several sizes
are available.
• The hydraulic lifting cylinder(s). This is a displacement style cylinder. The cylinder has a bleeder valve located at the blind
end to allow air to be bled from the hydraulic system. See the note below to bleed air from the cylinder.
• The safety velocity fuse. This is a device that is installed in the cylinder’s hose port. It closes quickly in the event of a
catastrophic hose failure to prevent the platform from collapsing down. The platform will remain stationary until pressure is
reapplied to the system.
• The hydraulic fluid. The system uses HO150 hydraulic fluid. Any anti-wear hydraulic fluid with a viscosity grade of 150 SUS at
100°F (ISO 32 @ 40°C) such as AW-32 or Dexron transmission fluid are acceptable.
o When the platform is to be tilted, press the “RAISE” pushbutton. The motor turns, and in turning it spins the hydraulic gear
pump. Oil is drawn from the reservoir through the suction filter and into the pump.
♦ The pump pushes the pressurized oil through the check valve and out to the lift cylinder(s).
Releasing the pushbutton at any point will stop the motion, and the platform will hold at that height and angle.
An upper travel limit switch turns off the motor when the platform is at its full lift height or tilt angle.
o When the platform is to be lowered, press one of the “LOWER” pushbuttons.
♦
The lowering valve opens, bypassing the check valve and allowing the oil in the cylinder to return back to the reservoir through
the return hose. The rate at which the platform lowers is regulated by the internal pressure-compensated flow spool.
Releasing the pushbutton at any point will stop the motion, and the platform will hold at that height and angle.
o In the event that the platform creeps down slowly after releasing a “LOWER” control, it will be necessary to remove the
lowering cartridge valve for inspection and cleaning, as follows:
♦ Remove any load from the platform.
♦ Raise the platform, install the maintenance prop, and lower the platform until the unit rests on the prop.
♦ Remove the nut holding the solenoid coil on the valve stem, then remove the coil, and then unscrew the valve from the
manifold.
♦ Inspect the valve for contaminants, and the valve’s o-rings and back-up washers for cuts, tears, or other damage.
♦ With the valve immersed in mineral spirits or kerosene, use a thin tool such as a small screwdriver or a small hex wrench to
push the poppet in and out several times from the bottom end of the valve. The valve should move freely, about 1/16” from
closed to open position. If it sticks in, the valve stem could be bent and will need to be replaced if it doesn’t free up after
cleaning. Blow the valve off with a compressed-air gun while again pushing the poppet in and out.
♦ Inspect the bottom of the manifold’s valve cavity for contaminants.
♦ Again with the thin tool, press on the middle of the flow control spool located in the bottom of the cavity. It should move down
and back up freely.
♦ Reinstall the valve into the manifold, tightening the valve with approximately 20 lb-ft of torque.
o If the platform lowers extremely slowly, or not at all, the cylinder’s velocity fuse could be closing. This can be caused by
air in the hydraulic cylinder. To bleed the air from the system:
♦ Remove any load from the platform.
♦ Raise the platform, install the maintenance prop, and lower the platform until the unit rests on the prop.
♦ Drop the rod end of the cylinder down out of its push cup, hold a rag over the cylinder’s bleeder valve (it looks like a grease
zirk) and open the valve about ½ turn with a 5/16” wrench. Push the cylinder rod in. Oil and air will sputter from the valve –
once no air is observed, close the bleeder valve and reinstall the cylinder rod into its push cup.