Radial piston machine having working fluid passing through the crankcase

Piston machine, capable of operating either as an engine (such as an expansion motor operated with compressed gas) or as a working machine (such as a compressor), the piston machine comprising:

• two pistons connected via connecting rods to a single eccentric crank pin of a centrally located crankshaft,
• the pistons forming first and second working chambers in two cylinders, arranged 180.degree. apart so that when one piston is at top deadcenter the other is at bottom deadcenter,
• said crank pin and connecting rod assembly being located in a crankcase,
• the machine further comprising a slide valve and control passages through which a working medium is conducted to and from the first and second working chambers,
• wherein the slide valve and control passages are so arranged that the working medium, at high pressure, passes through the crankcase regardless of whether the piston machine is operated as an engine or as a working machine,
• and wherein the crankcase acts as a third working chamber by virtue of the pressure from the working medium acting on the underside of the pistons.