Vestil HBD series - Manual (Page 4)

4
POWER UNIT'S OPERATION
The electric / hydraulic box dumper utilizes an electric motor directly coupled to gear-type hydraulic pump to produce the
needed fluid pressure and flow to allow the cylinders to perform the work of dumping a box container.
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.
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 (1-4K). 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 counterbalance valves (6K). These valves allow for smooth motion in double-acting hydraulic circuits.
• The pressure-compensated flow control spool (1-4K). This rests under the lowering valve, and regulates the fluid flow
back to the reservoir when the valve opens. It allows the table 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 lift cylinder(s). Displacement-style (1-4K), or double-acting (6K) cylinders. The displacement style have
a bleeder valve located at their top end to allow air to be bled from the hydraulic system.
• 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
claustrophobic hose failure to prevent the chute from collapsing down. The chute remains stationary until pressure is
reapplied to the system.
• They 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.
WHEN THE CHUTE IS TO BE TILTED, PRESS THE "UP" PUSH-BUTTON. 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:
•
For 2K & 4K capacities. The pump pushes the pressurized oil through the check valve and out to the lift cylinders.
• For 6K capacity: The pump pushes the pressurized oil through the energized directional valve RT and into the blind end
of the lift cylinders. Oil is pushed out to the cylinders' rod end and through counterbalance valve 2CB, which prevents the
chute from jumping when it nears the highest point of its rotation.
Releasing the push-button at any point will stop the rotation, and the chute will hold at that tilt angle.
An upper travel limit switch turns off the motor when the chute is at its full tilt angle.
WHEN THE CHUTE IS TO BE LOWERED, PRESS THE "DOWN" PUSH-BUTTON:
•
For 2K & 4K capacities. The lowering valve opens, bypassing the check valve and allowing the oil in the cylinders 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.
• For 6K capacity: The motor turns the pump pushes the pressurized oil through the energized directional valve LT and into
the rod end of the lift cylinder. Oil is pushed out of the cylinders' blind end and through counterbalance valve 1CB, which
regulates the speed and smoothness with which the chute lowers. A limit switch turns off the motor when the chute is fully
lowered. Releasing the push-button at any point will stop the rotation, and the chute will hold at that tilt angle.
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