Hydraulic pumps are used for hydraulic drive systems,function of hydraulic pumps . Hydraulic pump is a mechanical power source that transforms mechanical power into hydraulic power. It generates flow with enough power to overcome the pressure caused by the pump outlet load. When the hydraulic pump is running, it produces a vacuum at the pump inlet, forcing the liquid from the reservoir into the pump inlet pipeline, and through mechanical action the liquid is conveyed to the pump outlet and pressed into the hydraulic system. Hydrostatic pumps are volumetric pumps and hydrodynamic pumps can be fixed displacement pumps in which displacement can not be adjusted or have more complex structures allowing displacement adjustment variable displacement pumps. Although fluid pumps are more frequent in daily life.

Gear Pump
Gear pumps are simple and economical pumps. The displacement or displacement of the hydraulic gear pump is about 1 to 200 milliliters. For lubrication, the gear pump uses a small amount of oil from the pressure side of the gear, which is discharged through a hydrodynamic bearing, and the same oil is discharged to the low-pressure side of the gear, or through the port on the pump housing of the special discharge port. Compared with other types of gear pumps, some gear pumps are noisy, but modern gear pumps are more reliable and quieter than older ones.

Rotary Vane Pump
Rotary vane pumps are more efficient than gear pumps, but can also be used at moderate pressure, typically up to 18,000 kPa. These adjustable vane pumps are usually constant-pressure or constant-power pumps: increase the displacement until the required pressure or power is reached, then decrease the displacement or displacement until equilibrium is reached function of hydraulic pumps.

Screw Pump
The screw pump is made up of two Archimedes screws. They are intermeshed and sealed in the same chamber.
The main problem of screw pump is that the hydraulic reaction force is transmitted in the direction opposite to the direction of flow.

Curved Shaft Pump
Bending shaft pump, axial piston pump and motor use bending shaft principle, fixed or adjustable displacement, there are two different basic design.