Tooth profile for rotors of positive displacement external gear pumps

摘要

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 (εt) comprised in the range from 0.4 to 0.45, helical teeth with helical contact ratio (εβ) 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 ζ in the range from 1.1 to 1.6.

主权项

1. A tooth profile for rotors of a positive displacement gear pump with external helical teeth gear wheels, comprising:
an inactive tooth top profile, an inactive tooth bottom profile, an active right-handed tooth flank profile and an active left-handed flank profile, wherein said active right and left-handed tooth flank profiles are stub-tooth involute profiles and said inactive tooth top and bottom profiles are defined by circular arcs wherein the active stub-tooth involute profile has a transverse contact ratio or continuity (εt) from 0.4 to 0.45, and the helical teeth gear has an helical contact ratio or continuity (εβ) from 0.6 to 0.85, said circular arches of inactive tooth top and bottom profiles have a centre (Of, Ot) and radius (rf, rt) defined by the following equations:{Of=Hf+(Hf-O)·Δ⁢⁢RHf-Orf=Pf-Of⁢⁢and⁢⁢{Ot=Ht+(O-Ht)·ζ·Δ⁢⁢RHt-Ort=Pt-Ot with (ζ=[1.1÷1.6])
ΔR=0.5*(|Ht−Kt|+|Hf−Kf|) wherein O is the centre of the primitive circumference (p) of the gear; Hf is a point on the primitive circumference on the radial direction (r-v) of the centre line of the space between two contiguous teeth; Pf is a point at the end of the involute segment near the beginning of the tooth root section; Kf is a point identified by the intersection of the normal and the involute profile in point Pf and the radial direction (r-v) of the centre line of the space between two contiguous teeth, Ht is a point on the primitive circumference on the radial direction (r-v) of the centre line of the tooth; Pt is a point at the end of the involute segment near the beginning of the tooth top section; Kt is a point identified by the intersection between the normal and the involute profile in point Pt of the segment and the radial direction (r-d) of the centre line of the tooth.