Fluid motor or pump

A rotodynamic fluid machine comprising a plurality of separate co-axial cylindrical chambers, each chamber having a drive rotor mounted therein, said drive rotors being fixedly mounted on a common shaft to provide a drive rotor assembly, each drive rotor having a plurality of spiral blades formed thereon, the blades on the respective drive rotors being arranged so that if the rotors were to be placed in end-to-end abutting relationship the blades would be contiguous with the contiguous blades having an angle of wrap exceeding 360/n where n is the number of blades on each drive rotor so that neighboring contiguous blades overlap in the longitudinal direction of the rotor axis, each drive rotor mating with a pair of sealing rotors located in lateral chambers positioned parallel to the respective cylindrical chamber and intersecting the respective cylindrical chamber, said sealing rotors being fixedly mounted in pairs on respective common shafts to provide a pair of respective sealing rotor assemblies, said sealing rotors being provided with spiral recesses to receive said spiral blades of said driving rotors to provide continuous meshing engagement between the drive rotor assembly and each sealing rotor assembly, each said central cylindrical chamber being divided into two working chambers by the drive rotor and the two sealing rotors therein, the two working chambers being disposed one to each side of the line of centres of the drive rotor and the two sealing rotors, each working chamber having an inlet port and an outlet port circumferentially spaced from the inlet port.