Screw rotor machine with hollow thread rotor enclosing a screw cam rotor

In a screw rotor machine for compressible working medium including a screw cam rotor provided with gudgeons, a hollow screw thread rotor provided with bearing surfaces and enclosing the screw cam rotor, the rotors being journalled in a housing for respective rotation around parallel mutually displaced rotation axes, the rotors forming chambers for the working medium between their screw cam and screw threads which chambers move from end to end of the rotors during their rotation while changing their volumes, the improvement enabling high working loads with short sealing lengths and small leakage losses while maintaining simple rotor screw profiles comprising:

• a circularly profiled single-thread-screw cam rotor having two parts with different lead angles,
• the single-thread-screw being generated in relation to an inner base cylinder formed by the centers of the circular rotor cross sections taken along the screw cam rotor axis and having a diameter amounting to two times the distance between the rotation axes,
• the single-thread-screw cam rotor circular profile enclosing, in each cross section, both the inner base cylinder and cylindrical extensions of the gudgeons the relation between the distance between the rotation axes and the radices of the cam rotor profile amounting to a value between 0.2 and 0.4.