The mechanical device that is used to convert mechanical power into hydraulic energy is known as a hydraulic pump. This pump are two type:
Fixed Pumps
A fixed-displacement pump has a set flow rate — every stroke of the motor moves the same amount of fluid. Fixed-displacement pumps are
The simplest type of fixed-displacement pump is the gear pump, in which the hydraulic fluid is pushed by rotating gears. In some models, the gears are sequential; in the quieter and more efficient version, the gears are interlocking. Another common variation is the screw pump, which uses the classic Archimedes screw, which looks much like a drill bit, to move the fluid. They have the advantage of providing a high rate of flow at relatively low pressures.
In a variable-displacement pump, the flow rate and outlet pressure can be changed as the pump operates. This results in pumps that are
The most common type of variable-displacement pump is the rotary vane pump, which is a variation of the gear pump in which the 'gear' is offset and the 'cogs' aren't fixed, but rather extend and retract as the gear turns, allowing the pump to increase the pressure of the fluid by compacting it as it pushes the fluid through. The top-tier pumps, however, are bent-axis piston-and-cylinder pumps, much like the ones that are used in an internal combustion engine.
