Johnson has used a fixed-displacement pump
and variable speed control to change the control model from temperature control to actual energy control, by constantly controlling the rate of energy exchange with the mold.
"Our original hydraulic cooling system used a fixed-displacement pump
and motor," Buchanan said, "and we controlled fan speed by dumping part of the flow back to the reservoir.
To control speed, the students had to settle for a fixed-displacement pump
and pressure-compensated flow control valves.
Injection machines using fixed-speed electric motors progressed from simple hydraulic drives, using a fixed-displacement pump
, to the more modern and efficient variable-displacement pump.
For moderate fan outputs of up to 27 hp, systems incorporating a hydraulic fixed-displacement pump
with bypass control represent the most economical solution, the company said.
The Sunlab dual-flow pump is a fixed-displacement pump
similar in design to the Sunlab S-series, with the exception that it can deliver a hydraulic pressure and an oil flow from two separate outputs on the same pump.
of Kadant Inc., Queensbury, N.Y., comprises a fixed-displacement pump
, servo motor, and pump-modeling hydraulic drive.
This circuit has a fixed-displacement pump
protected by a relief valve, a design frequently used in fluid power systems.
In cases where a hydraulic pump must be changed, fixed-displacement pumps
that need no calibration are faster and easier to change than variable-displacement pumps.
Other than accounting for displacement at any operating point, the questions to be answered are the same as when dealing with fixed-displacement pumps
are quieter, less costly, and less maintenance intensive than variable-volume pumps.
It is equipped with a Power Match system that reportedly can cut energy consumption 40-60% compared with fixed-displacement pumps
. It also features proportional hydraulics and six steps each of injection speed and pressure.