Abstract: The twin screw rotors for axis-parallel installation in displacement machines for compressible media have asymmetrical transverse profiles and numbers of wraps that are ≧2. Depending upon the wrapping angle (&agr;), the pitch (L) varies, which pitch increases in a first subdivision (T1) from the suction-side screw end, reaches a maximal value (Lmax) after one wrap, decreases in a second subdivision (T2) until a minimal value (Lmin), and is constant in a third subdivision (T3). The pitch course in the first subdivision (T1) is preferably mirror-symmetrical to that in the second subdivision (T2), within the subdivisions T1 to T2, it is point-symmetrical to the mean values in almost all cases. Compact screw rotors, completely free of imbalance, can thereby be achieved with compression rates of 1.0 . . . 10.0, also without profile variation.

Abstract: The twin screw rotors for axis-parallel installation in displacement machines for compressible media have asymmetrical transverse profiles and numbers of wraps that are ≧2. Depending upon the wrapping angle (&agr;), the pitch (L) varies, which pitch increases in a first subdivision (T1) from the suction-side screw end, reaches a maximal value (Lmax) after one wrap, decreases in a second subdivision (T2) until a minimal value (Lmin), and is constant in a third subdivision (T3). The pitch course in the first subdivision (T1) is preferably mirror-symmetrical to that in the second subdivision (T2), within the subdivisions T1 to T2, it is point-symmetrical to the mean values in almost all cases. Compact screw rotors, completely free of imbalance, can thereby be achieved with compression rates of 1.0 . . . 10.0, also without profile variation.