USE - This control system is used to operate two double
acting cylinders where a "jogging" action, possibly remotely controlled, is
desired. Since the cylinders may operate at different pressures, a metering
valve is required to maintain nearly equal speeds.
TYPICAL APPLICATIONS-This
system is used principally to raise or push a load using two double acting
hydraulic jacking cylinders. The metering valve is used to keep the load level
by maintaining equal cylinder speeds.
OPERATION-The jog button controls
the solenoid operating venting valve. When the jog button is pushed, the venting
valve will block the relief valve's vent line. This will cause the relief valve
to function and will permit pressure buildup to the relief valve's setting. When
the jog button is released, the relief valve's vent line will be connected to
tank. This will cause the relief valve to "dump" the combined delivery of the
pumps back to the reservoir at low pressure. The jog button will be mounted on
15 feet of cable for remote control. The metering valve and 4-way valve,
however, will remain on the pump unit. To raise or lower the cylinder rams, the
operator:
- Moves the 4-way valve handle.
- Pushes the jog button
The metering valve can be used to control ram speeds when
raising or lowering by rotating the valve handle to "meter" or split the flow.
When lowering, there may be some tendency for the low pressure pump to remain
unloaded continuously. If the capability for "locking" the cylinders
hydraulically is desired, the "fail-safe" globe valve and check valve
arrangement shown on the hydraulic schematic should be added for each cylinder.
The "fail-safe" valves can be mounted on the pump unit or on the cylinders. The
globe valves and check valves hold the cylinders in position whenever the power
is shut off. The globe valves must be opened to retract the rams.
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