Positive-displacement machine for compressible media

A positive-displacement machine for compressible media is described, with at least one displacer chamber (8) located in a stationary casing and designed like a spiral slot, and with a band-like or tongue-like displacer (9), also of spiral shape, allocated to each displacer chamber and held on a disc-shaped rotor (3) that can be driven eccentrically with respect to the casing. The eccentric mounting of the rotor is such that, during operation, each point on the rotor performs a circular motion restricted by the peripheral walls of the displacer chamber, with its eccentricity as the radius. The casing comprises two parts (2a, 2b) divided essentially in the plane of the disc-shaped rotor (3), which are connected to each other by axially aligned retaining means. In order to reduce the radial dimensions of the displacer machine, the retaining means are to be formed of at least one retaining element (10), connecting the two parts (2a, 2b) of the casing and running essentially axially, which is located in a peripheral plane radially adjacent to a central guide bearing (6) of the rotor (3) and engages through a through-hole (14) made on the rotor and connecting the two working chambers (15, 16) formed on either side of the rotor.