APPENDIX
GLOSSARY
Accumulator--device for storing liquid under pressure, usually consisting of a chamber separated into a
gas compartment and a liquid compartment by a bladder, piston, or diaphragm. An accumulator also
smooths out pressure surges in a hydraulic system.
Actuating cylinder--device that converts fluid power into linear mechanical force and motion.
Actuating cylinder, double-action--actuating cylinder in which both strokes are produced by pressurized
fluid.
Actuating cylinder, single-action--actuating cylinder in which one stroke is produced by pressurized
fluid and the other stroke is produced by some other force, such as gravity or spring tension.
Angular piston pump--hydraulic pump that has the cylinder block placed at an angle to the drive shaft
plate where the pistons are attached. The angular configuration causes the pistons to stroke as the pump
shaft is turned.
Baffle--metal plate installed in a reservoir to keep the fluid from swirling and surging.
Bladder--synthetic rubber bag inserted in an accumulator to hold the air charge.
Bypass valve--valve used to allow fluid to go around a filtering element if the element becomes clogged.
Cam pump--type of hydraulic pump that utilizes a cam to cause stroking of the pistons.
Check valve--valve that permits fluid flow in one direction, but prevents flow in the reverse direction.
Closed-center valve--type of valve that has its pressure passage blocked to fluid flow when the valve is
in the OFF position.
Cracking pressure--pounds per square inch pressure at which the valving device of a pressure relief
valve clears its seat just enough to permit fluid to seep through.
Diaphragm--synthetic rubber device that divides an accumulator into two separate compartments, one
for air and the other for
fluid.
Displacement--volume of fluid that can pass through a pump, motor, or cylinder in a single revolution or
stroke.
Double-action actuating cylinder--See Actuating cylinder, double-action.
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