Patent ID: 6257841
Filing Date: 2001-07-10
Classification: F04C

Abstract:
A positive displacement pump for a fluid comprising:a pressure chamber for the pumped fluid;an outlet duct for the pumped fluid of said pressure chamber;a bypass flow control valve which controls a useful flow of the pumped fluid; anda regulating device which regulates a delivery flow of the pumped fluid to said outlet duct includinga) a spring chamber having a first portion and a second portion,b) a regulating piston disposed in said first portion of said spring chamber with a first end subject to a pressure of said pressure chamber and a second end facing said second portion of said spring chamber,c) a spring disposed in said spring chamber which acts on the second end of said regulating piston and against the pressure exerted on the first end of said regulating piston,d) a bypass duct which connects said pressure chamber with said second portion of said spring chamber,e) a throttle duct which connects said second portion of said spring chamber with said outlet duct, said throttle duct having an open cross-sectional surface which opens into said second portion of said spring chamber and which is adjacent to said second end of said regulating piston, andf) a first control edge and a second control edge on said second end of said regulating piston such that as said regulating piston moves by an increasing pressure exerted on the first end of said regulating piston against said spring,(i) said first control edge of said second end is initially moved over said throttle duct causing a reduction of said open cross-sectional surface thereof which in turn limits fluid flow through said throttle duct and hence through said outlet duct, and(ii) said second control edge of said second end is thereafter moved over said throttle duct causing an increase of said open cross-sectional surface thereof which in turn increases fluid flow through said throttle duct and hence through said outlet duct relative to when only said first control edge was moved over said throttle duct.