Drive coupling--device that transmits torque from a driving unit to a hydraulic pump drive shaft.
Efficiency--ratio of output power to input power, generally expressed as a percentage.
Energy--ability or capacity to do work.
Filter--device used to remove contaminants from hydraulic fluid.
Fixed-displacement pump--pump in which the volume of fluid per cycle cannot be varied.
Fluid--any liquid, gas, or mixture thereof.
Hydraulics--that branch of mechanics or engineering that deals with the action or use of liquids forced
through tubes or lines under pressure to operate various mechanisms.
Irreversible valve--device used in conjunction with a servo to block feedback.
Land--smooth machined surface on the spool of a spool selector valve.
Micron--millionth of a meter, or about 0.00004 inch.
Open-center valve--type of valve that has its pressure passage open to return when the valve is in the
Orifice--device used to restrict the flow of fluid in order to slow the operation of a component.
Pilot valve--valve used to control the operation of another valve, the spool in a selector valve.
Piston--that part of an actuating cylinder, servo, or motor that the hydraulic fluid works against. In a
pump, the pistons work against the fluid.
Poppet--valving device similar to the valves found in an automobile engine.
Port--opening for the intake or exhaust of fluid.
Power--rate of doing work or expending energy.
Pressure--amount of force distributed over each unit area expressed in pounds per square inch (psi).
Pressure reducer--device for lowering the pressure in a hydraulic system to allow a component to
operate at a lower pressure than the rest of the system.