Patent ID: 6254358
Filing Date: 2001-07-03
Classification: F04B

Abstract:
A positive displacement pump for conveying a pressure medium from a container to a consumer comprising:a pump package including a housing having a suction chamber and a pressure chamber, a rotor, a cam ring located radially about the rotor, several operating slides inserted into an interior of the housing between the rotor and the cam ring, and control plates located on respective axial sides of operating slides such that work chambers are formed between the cam ring and the rotor, the work chamber being (a) divided by the operating slides, (b) limited in an axial direction by the control plates, and (c) pumping the medium from the suction chamber to the pressure chamber;a bypass flow control valve which is used for controlling a bypass flow of the medium from the pressure chamber to the suction chamber, the flow control valve having a bypass piston with a proximal end open to the pressure chamber; anda throttle for the bypass flow control valve includinga) a throttle opening between the pressure and suction chambers, the throttle having a cross-sectional surface,b) a throttle chamber,c) a throttle member movable in the throttle chamber and having a distal end and a proximal end which adjustably closes the cross-sectional surface of the throttle opening and against which a pressure of the medium in the pressure chamber acts,d) a spring in the throttle chamber which urges the proximal end of the throttle member towards the throttle opening and which opposes the pressure in the pressure chamber, ande) a conduit which connects a side of the throttle chamber adjacent the distal end of the throttle member with the suction chamber,whereby the cross-sectional surface of the throttle opening is varied as a function of the pressure present in the pressure chamber.