A float chamber is a device for automatically regulating the supply of a liquid to a system. It is most typically found in the

carburettor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meterin ...

of an

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...

, where it automatically meters the fuel supply to the engine. However, this arrangement is found in many automatic liquid systems, for example the

cistern A cistern (Middle English ', from Latin ', from ', "box", from Greek ', "basket") is a waterproof receptacle for holding liquids, usually water. Cisterns are often built to catch and store rainwater. Cisterns are distinguished from wells by ...

of most

toilet A toilet is a piece of sanitary hardware that collects human urine and feces, and sometimes toilet paper, usually for disposal. Flush toilets use water, while dry or non-flush toilets do not. They can be designed for a sitting position popu ...

s could be said to be a type of float chamber. A float chamber works by allowing liquid within the chamber to lift a float which is linked to a

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

which regulates the liquid intake. When the level is low, the float drops and opens the valve, allowing in liquid until the float rises sufficiently to close off the valve again. This is identical in principle to the

ballcock A ballcock (also balltap or float valve) is a mechanism or machine for filling water tanks, such as those found in flush toilets, while avoiding overflow and (in the event of low water pressure) backflow. The modern ballcock was invented by J ...

valve.

Carburettors

Carburettor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meterin ...

s are provided with a float chamber to provide a constant hydrostatic head of fuel above the carburettor's metering jets, thus a constant pressure. The float chamber itself does not vary the pressure according to demand, but it does vary the supply flowrate with demand, to keep this pressure constant. The valve is often described as a

needle valve A needle valve is a type of valve with a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates. Construction and operation An instrument ne ...

, although this is a misnomer. A true needle valve uses a tapered needle in a tapered seat, so as to provide fine control over flow rate. The float valve uses a pointed needle against a square-edged seat, to give a positive shut-off. As the float relies on gravity, the chamber must be mounted vertically. Some designs, such as the SU, may allow a separate float chamber body to be adjusted relative to the carburettor to compensate for this. Acceleration effects may also apply a forwards force on the float and so the float hinges often have to be mounted across the car to avoid surging. Some designs, such as the Stromberg use wide, shallow floats to reduce surging. One drawback of the basic type of float chamber described is that it only operates correctly when it is the right way up, so more sophisticated solutions are needed in

aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...

Carburettors

See also