Rotary positive displacement machine

A rotary positive displacement machine comprising:

• a stator having a circular cylindrical internal surface delimiting an operating chamber, the stator having fluid inlet/outlet ports;
• a rotor in the operating chamber, the rotor being mounted so as to be rotatable relative to the stator about the axis of the said internal surface, the rotor having a cylindrical external surface, the said axis passing through the rotor, a generatrix of the external surface being adjacent to the said internal surface, and a diametrically opposite generatrix being spaced from the said internal surface;
• a sealing member projecting substantially radially through a slot in the stator into the operating chamber and being movable substantially radially, the sealing member extending parallel to the said axis and having a length substantially equal to that of the rotor;
• means for keeping the radially inner end of the sealing member adjacent the external surface of the rotor;
• and
• a shutter at one end of the rotor, the shutter rotating with the rotor and covering one of the said ports, the shutter having a through-hole with a first end remote from the operating chamber and a second end opening into the operating chamber, the first end periodically overlapping the said one port as the rotor rotates relative to the stator.