Patent ID: 8702409

Claim:
A screw compressor ( 1 ) comprising at least a male rotor ( 2 ) and at least a female rotor ( 3 ) rotating respectively around a first axis (O 1 ) and second axis (O 2 ) of rotation, said male rotor ( 2 ) showing, in cross section, lobes ( 4 ) and valleys ( 6 ) meshing with corresponding valleys ( 5 ) and lobes ( 7 ) of the female rotor ( 3 ), said lobes ( 4 ) of the male rotor ( 2 ) and said valleys ( 5 ) of the female rotor ( 3 ) having profiles at least partially generated by enveloping a rack profile (p), wherein said profiles of the lobes ( 4 ) of the male rotor ( 2 ) and of the valleys ( 5 ) of the female rotor ( 3 ) have portions generated by enveloping a first curve (z 1 ) of the rack profile (p), said first curve (z 1 ) extending, in a Cartesian reference frame (X, Y), between a first point (H) and a second point (Q) and having a convexity in the positive direction of the axis of abscissa (X), said first point (H) lying on the axis of abscissa (X) at a distance from an origin (O) of the Cartesian reference frame (X, Y) equal to an addendum (h 1 ) of the male rotor ( 2 ), and wherein said first curve (z 1 ) is a branch of hyperbola in which a generic point has coordinates (XS, YS) defined by the following equations: XS =( h 1 +RA )− RA /cos φ YS=−HB tg φ, said equations being parametric and dependant upon a first parameter (RA), a second parameter (HB) and a third parameter (φ), said first parameter (RA) being the measure of a radius of an auxiliary circumference (u) tangent to the rack profile (p) in said first point (H) and having its centre (C) lying upon the axis of abscissa (X), said second parameter (HB) being the distance from the centre (C) of the auxiliary circumference (u) of an auxiliary line (r) parallel to the axis of ordinates (Y) and passing through the axis of abscissa (X) between said first point (H) and said centre (C) of the auxiliary circumference (u), said third parameter (φ) indicating an auxiliary acute angle delimited by the axis of abscissa (X) and by a radius of said auxiliary circumference (u) passing through an auxiliary point (T) lying on said auxiliary line (r) and having an ordinate (YT) equal to the ordinate (YS) of said generic point (S) lying on said branch of hyperbola.