Rotary machines

A rotary machine comprising:

• a rotary drive member;
• a rotary piston block having portions which define an open piston-reciprocation chamber having a central chamber axis along which the chamber extends with the uniform cross-sectional diameter into the block;
• bearing means mounting the rotary drive member for rotation about a first axis, fixed relative to the bearing means;
• mounting means mounting the rotary piston block for rotation about a second axis which is oblique to the said first axis and is spaced from the said central chamber axis;
• and a piston member having an end portion articulated to the said rotary drive member at a location spaced from the said first axis and having a main portion received in the said piston-reciprocation chamber for reciprocation therein, the said main portion comprising:
• a first piston length of part-spherical shape for sliding exclusively sealingly in the said piston-reciprocation chamber, so as to form an articulatedly movable sealing location, said part-spherical shape having a cross-sectional plane at which it has a maximum cross-sectional diameter corresponding to the said uniform cross-sectional diameter, the said first piston length decreasing in cross-sectional diameter with increasing distance in opposite directions from the said cross-sectional plane,
• and a second piston length of frusto-conical shape being located to one end of the said first piston length and having a cross-sectional diameter decreasing with increasing distance from the said first piston length, for engaging with the said rotary piston block in the said piston-reciprocation chamber to transmit rotary drive between the said drive member and the block.