Flow controller for vane pumps

The controller regulates the flow of liquid from a pump to a user. The controller incorporates a piston (5) against which the pump pressure act from one side while a spring (13) acts against the other side. The piston has a control edge which acts with an edge in the outlet bore of the controller. The piston has an extension which passes through an opening (29) and forms a choke for the liquid flow by an amount which depends on the travel of the piston. The piston extension has sections (35,37) of different diameter which are separated by a sharp edged step (39). The step and the opening are so correlated, that the step only reaches the opening when the control edge (21) of the piston has passed an edge (45) in the outlet bore.