Screw compressor with involute profiled teeth

A screw compressor for the compression and axial displacement of a gas, said compressor comprising:

• a housing formed with an axially extending passage having at one axial end a gas inlet and at the other axial end a gas outlet;
• a one-piece main rotor extending axially in said passage and formed with a plurality of helical ribs having generally convex flanks and root regions formed at least partially as involutes in cross section, said ribs being asymmetrical with respect to the centers of said ribs, each rib of said main rotor having a profile consisting of a leading flank formed as an involute (1-2) from a point (1) at its junction with the respective root region to an intermediate location (2) along said leading flank and a circular arc (23/4) from said intermediate location (2) to a circular arc apex (3,4) of the rib, and a trailing flank (3/4-5) formed as an involute from said apex (3,4) to the junction point (5) of said trailing flank with a respective root portion;
• a one-piece auxiliary rotor extending axially in said passage and formed with a respective plurality of helical ribs meshing with said ribs of said main rotor and having opposite flanks, the leading flank of each rib of said auxiliary rotor being formed as a concave cycloid (8-9/7-8) from the root point (8) to an intermediate location (7,9) along the leading flank, the trailing flank being formed as a circular arc from said root point to an intermediate location along the trailing flank, and both flanks further being formed as convex involutes (6-7/9-10) from the latter intermediate locations (7,9) to the crown (6,10) of each rib at the auxiliary rotor;
• and
• drive means connected only to said main rotor for rotating same and thereby rotating said auxiliary rotor in mesh therewith, said flanks being of arcuate shape adjacent their regions shaped as involutes, relative to a rotation direction of the respective rotor the front flanks of said ribs having a different pressure angle from the back flanks.