ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS

**Definition:** This place covers:

Pumps with rotary or oscillating pistons for liquids, for elastic fluids, or for combination of liquid and elastic fluid.

Positive displacement machines, i.e. devices which could be equally an engine or pump, with rotary or oscillating pistons for liquids only.

**Limiting references (this place does not cover):** - Positive displacement engines for liquids -> 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:** - Pump: means a device for continuously raising, forcing, compressing, or exhausting fluid by mechanical means - 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 - 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 - 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 - 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 - 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 - 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 - 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 - Teeth or tooth equivalents: include lobes, projections or abutments - 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 - 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