Variable displacement rotary pump and displacement regulation method

A variable displacement rotary positive displacement pump for fluids, comprising a rotor arranged to rotate within an eccentric cavity of a stator ring in turn arranged to be rotated within a predetermined angular interval, as operating conditions of the pump vary, in order to vary a relative eccentricity between the cavity and the rotor and hence the displacement of the pump, characterised in that the stator ring is configured as a multistage rotary piston for displacement regulation, arranged to be directly driven by a fluid under pressure.

A method of regulating the displacement of a rotary positive displacement pump of a kind comprising a rotor arranged to rotate within an eccentric cavity of a stator ring, the method comprising the step of making the stator ring rotate within a predetermined angular interval in order to vary the eccentricity between the cavity and the rotor as operating conditions of the pump vary, and being characterised in that it further comprises the steps of:

• configuring the ring as a multistage rotary piston;
• directly driving the rotation of the piston by means of a fluid under pressure.