ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES

**Definition:** This place covers:

Positive displacement machines, i.e. devices which could be equally an engine or pump, with rotary or oscillating pistons for elastic fluids or for combination of liquid and elastic fluid.

**Limiting references (this place does not cover):** - Internal-combustion aspects of rotary-piston or oscillating-piston engines -> F02B53/00 , F02B55/00 - Engines with reciprocating pistons or rotary or oscillating pistons wherein the working fluid is a liquid. -> F03C - Positive displacement machines for liquids, or pumps in which the working-fluid is displaced by one or more reciprocating pistons or by flexible working members -> F04B

**Glossary:** - Cooperating members: means the "oscillating piston" or "rotary piston" and another member, e.g., the working-chamber wall, which assists in the pumping action or machine's action - Internal axis type: means that the rotational axes of the inner and outer co-operating members remain at all times within the outer member, e.g., in a similar manner to that of a pinion meshing with the internal teeth of a ring gear - Machine: means a device that could equally be both an engine and a pump and not a device which is restricted to an engine or one which is restricted to a pump - Movement of the cooperating members: is to be interpreted as relative, so that one of the "cooperating members" may be stationary, even though reference may be made to its rotational axis, or both may move - Oscillating piston machine: means a positive-displacement machine in which a fluid-engaging, work-transmitting member oscillates, e.g. a vane piston swinging back and forth about a fixed axis - Positive displacement engines: the energy of a working fluid is transformed into mechanical energy, in which variations of volume created by the working fluid in a working chamber produce equivalent movement of mechanical members, e.g. pistons transmitting the energy, the dynamic effect of the fluid being of minor importance - Positive displacement pumps: pumps using pistons or other mechanical members to displace a working fluid in a working chamber, the dynamic effect on the fluid being of minor importance - Pump: means a device for continuously raising, forcing, compressing, or exhausting fluid by mechanical means - Reciprocating piston: means a fluid-engaging, work-transmitting member of an reciprocating-piston type machine or pump that slides alternately back and forth usually along a straight line or path - Rotary piston: means a fluid engaging, work-transmitting member of a rotary-piston machine or pump that can completely rotate about a fixed axis or about an axis moving along a circular or similar orbit when operating, e.g. rotor having vanes or teeth - Rotary piston machine: means a positive-displacement machine in which a liquid-engaging, work-transmitting member rotates about a fixed axis or about an axis moving along a circular or similar orbit, e.g. machine with a rotor having vanes or teeth - Teeth or tooth equivalents: include lobes, projections or abutments - Working fluid: means the driven fluid in a pump or driving or driven liquid in a machine. The working fluid can be in a compressible, gaseous state, e.g. steam, called elastic fluid, a liquid state, or a state where there is coexistence of elastic fluid and liquid state