Rotary fluid displacement machine with revolving working chambers of periodically varying volume

A rotary fluid machine of the kind comprising

• (a) a rotor supported for rotation about a stationary axis and with
• (a1) a rotor ring placed coaxially with said axis and having a number of at least partially radially extending vane slots substantially equally angularly distributed about said stationary axis, and
• (a2) slidably supported in each vane slot a vane,
• (b) a machine housing with a housing chamber of a non-circular cross-sectional shape, a part of which is situated outside of said rotor ring and is divided into a number of working chambers of periodically varying volume by said vanes, which for this purpose are in substantially fluid tight engagement with the inner wall of the housing, said working chambers following the rotor ring during its rotary movement and passing in succession at least one inlet port and at least one outlet port, as well as
• (c) a substantially rigid cam member situated non-rotatably within said rotor ring and shaped with a non-circular cross-section guiding surface, against which the vanes may abut with their radially innermost ends and thereby be kept in said substantially fluid tight engagement with said inner wall of said housing, wherein
• (d) the cam member is supported concentrically with said rotor ring and in a floating manner between the radially innermost ends of said vanes, and wherein
• (e) said vanes are present in a number of at least four.