Screw-rotor machine with an ellipse as a part of its male rotor

A screw rotor machine having a female rotor meshing with a male rotor, helical lands and intervening grooves and adapted for rotation around parallel axis in a working space of the machine, the profile of the rotors comprising:

• a first curve of the male rotor having an arc of a first circle tangent externally to the dedendum circle of the male rotor and with a center outside the pitch circle of the male rotor,
• a second curve of the male rotor being part of an ellipse with a long axis laid on a line segment connecting the central axis of the male rotor and female rotor, the second curve intersecting the line segment and tangent externally to the dedendum circle of the female rotor and internally to the addendum circle of the male rotor, wherein the second curve of the male rotor is between the first curve of the male rotor, and the point where the line segment connecting the central axis of the male and female rotor intersects with the dedendum circle of the female rotor and the addendum circle of the male rotor,
• a first curve of a female rotor being an arc of a second circle tangent internally to the addendum circle of the female rotor, the center of which lies on a line which forms a modulated angle with the line segment connecting the central axis of the male rotor and female rotor, wherein the radius of curvature of the first circle is within the range of 2 to 5 times the radius of curvature of the second circle,
• a second curve of the female rotor internally tangent to the addendum circle of the female rotor at one end, internally tangent to the second curve of the male rotor and externally tangent to the dedendum circle of the female rotor at a point where the dedendum circle of the female rotor intersects the line segment connecting the central axis of the male rotor and female rotor at the other end, wherein the second curve of the female rotor is generated by the second curve of the male rotor.