Abstract: A gear pump has a toothed driving wheel, a toothed driven wheel, a front flange from which a projecting portion of the shaft protrudes, being connected to the shaft of the driving wheel, a back lid fixed to the case, and an intermediate flange between the case and the front flange. The intermediate flange has first and second chambers connected by a connection duct to the inlet or outlet fluid duct of the pump. A compensating ring is mounted in the first chamber and inserted on the shaft of the driving wheel to compensate the axial forces of the driving wheel and transmit the motion on the shaft of the driving wheel. A piston is mounted in the second chamber in order to stop against one end of the shaft of the driven wheel, in such manner to compensate the axial forces imposed on the toothed driven wheel.

Abstract: The present invention deals with the analytical definition of a tooth profile for rotors used in gear pumps. The purpose is to obtain a pump characterized by noiseless operation, minimization of vibrations and pressure overoscillations generated in operating conditions at the beginning and end of life, and high specific displacement, in such a way to increase the delivery of the pump in given volume conditions. This profile is characterized by an active profile of the tooth flanks with involute stub-tooth with transverse contact ratio (?t) comprised in the range from 0.4 to 0.45, helical teeth with helical contact ratio (??) comprised in the range from 0.6 to 0.85, circular inactive tooth bottom and top profiles, with center (Of, Ot) and radius (rf, rt) defined by a non-dimensional parameter ? in the range from 1.1 to 1.6.