Machine for transforming pressure or potential energy of a fluid into mechanical work

A machine for transforming pressure or potential energy of a fluid into mechanical work, comprising

• a working chamber (27,28) the volume of which is cyclically variable in response to reciprocatory motion of a wall (20) which partially defines the working chamber,
• a reciprocatory power member (15,16) which is displaceable by said wall under action of the pressure of the fluid on the wall during expansion of the working chamber,
• an inlet conduit (12) communicating with the working chamber,
• an outlet conduit (13) communicating with the working chamber,
• an outlet valve (22) which is closable to prevent fluid flow in the outlet conduit int he direction away from the working chamber, and
• a driven member (17) operatively connected with the power member (15,16),
• characterized in that
• the outlet conduit (13) comprises a gap-like passage (26) which substantially surrounds the working chamber (27,28) and extends along the periphery thereof and which is openable by means of the outlet valve (22) to permit fluid flow therethrough from the working chamber substantially without any pressure drop, and further characterized by a second valve (21) which is disposed in a circumferentially extending gap-like passage (25) between radially inner (27) and radially outer (28) portions of the working chamber and which is openable by means of the second valve (21) to permit fluid flow between the inner and outer portions of the working chamber substantially without any pressure drop.