Abstract: A rotary machine, particularly a planetary gear motor, has a control plate 4, two annular channels (18, 19) which are arranged on the inner circumference of a cup-shaped housing section 7 and stationary commutators (8, 9) which are arranged side by side adjacent the annular channels. The control channels are coupled together when the transit channel 15 and when the plate and one of the annular channels are aligned with an open corner channel 16 and alternately with the annular channels. A simply shaped and simply manufactured commutator includes two like-formed disk-shaped commutators, which completely intersect alternately with each other. Transit channels 15 are provided and, with the plate cam and one of the annular channels, open into corner channels 16. Both commutators are arranged in such a way that at times a transit channel of a commutator adjoins a corner channel of the other commutator and vice versa.