Machines inducing a flow of a pumped fluid wherein the displaced fluid is directly in contact with an inducing fluid different from said displaced fluid.

Related subclasses F04B, F04C and F04D cover the same type of machines using reciprocating, rotary or non-positive displacement means for pumping fluids.

Where combinations of pumps covered by this subclass with other pumps are defined, such combinations shall be classified in this subclass if such a system of pumps is characterised by an interaction or a specific combination of these pumps.

In patent documents the words "gas", "steam" and "elastic fluid" are often used as synonyms.

Machines in which the displacing power comprises a pressurising force subjected upon a fluid other than the fluid to be pumped. The fluids may e.g. be a liquid, or a gas, e.g. steam, or also a mixture of a liquid with solids.

Machines where the delivery outlet for evacuation is exposed to negative fluid pressure inside a working chamber.

Jet-pumps, injectors, ejectors, or thermocompressors using the Venturi effect of a converging-diverging nozzle to convert the pressure energy of an inducing fluid to velocity energy which creates a low pressure zone that draws in and displaces a suction fluid. The inducing fluid may be a liquid, or a gas, e.g. steam. The displaced suction fluid may be a gas,e.g. steam, or a liquid, a slurry, or a dust-laden gas stream.

Machines inducing a flow of fluid by generating vibration in a resonatable fluid, e.g. by acoustic energy.

Machines using the fluid hammer effect to develop pressure that allows a portion of the input fluid to reach a higher pressure or to be moved. The fluid hammer effect is a pressure surge or wave resulting when a fluid in motion is forced to stop or change direction suddenly, i.e. momentum change.

Momentum transfer pumps using a high speed jet of vapour to direct gas molecules in the pump down into the bottom of the pump and out through an exhaust, e.g. to obtain a high vacuum.

Combinations of pumps covered by this group with other pumps are only classified in this group if such other pumps are intended for preliminary pumping for diffusion pumps.

Machines which cause a liquid to flow above the surface of a reservoir, without pumps, powered by the fall of the liquid as it flows down a tube under the pull of gravity, and is discharged at a level lower than the surface of the reservoir.

Machines for exchanging pressure energy between relatively high and relatively low pressure fluid systems, wherein the fluid being may include gases (steam), liquids and pumpable mixtures of liquids and solids. The exchange of pressure energy is used for transfer of energy from one fluid stream to another.

Machines inducing a flow of fluid by means not provided for in other groups of this subclass, e.g. by magnetohydrodynamic effects, by electrostatic effects, or by electro-osmotic flow effects.