Radial piston pump

A radial piston pump is a form of hydraulic pump. The working pistons extend in a radial direction symmetrically around the drive shaft, in contrast to the axial piston pump.

Construction

The stroke of each piston is caused by an eccentric drive shaft or an external eccentric tappet.
When filling the workspace of the pumping pistons from "inside" it is called an inside impinged radial piston pump '. If the workspace is filled from "outside" it's called an outside impinged radial piston pump '.

Function

The general mode of operation will be explained at the movement of one pumping piston by means of picture 1:
The outer ring for bracing of the pumping pistons is in eccentric position to the hollow shaft in the center. This eccentricity determines the stroke of the pumping piston.
The piston starts in the inner dead center with suction process. After a rotation angle of 180° it is finished and the workspace of the piston is filled with the moved medium. The piston is now in the outer dead center. From this point on the piston displaces the previously sucked medium in the pressure channel of the pump.

Attributes

These kinds of piston pumps are characterized by the following advantages:

high efficiency
high pressure
low flow and pressure ripple
low noise level
very high load at lowest speed due to the hydrostatically balanced parts possible
no axial internal forces at the drive shaft bearing
high reliability

A disadvantage is the bigger radial dimensions in comparison to the axial piston pump, but it could be compensated with the shorter construction in axial direction.

Applications

Due to the hydrostatically balanced parts it is possible to use the pump with various hydraulic fluids like mineral oil, biodegradable oil, HFA, HFC, HFD or cutting emulsion. That implies the following main applications for a radial piston pump: