air cushion


Also found in: Dictionary, Thesaurus.

air cushion

1. the pocket of air that supports a hovercraft
2. a form of pneumatic suspension consisting of a constricted volume of air

Air Cushion

 

a region of increased air pressure between the base of a machine and a supporting surface or between the movable and fixed elements of mechanisms in instruments and machine tools. It is used in transportation equipment (hovercraft, ram-wing craft, and other flying vehicles), various instruments (gyroscopes), and mechanisms as an”air bearing” to reduce the friction between contiguous surfaces .

Static and dynamic methods of forming an air cushion exist. In the static method, pressure is created in the air cushion by a fan or compressor, and in the dynamic method it is developed by the relative velocity of an airflow. Of the many known methods for producing an air cushion, the principal ones are the chamber, nozzle, slot, and wing types.

In the chamber method, the lifting force is produced by the static air pressure forced under the base of the chamber by a fan. Owing to the lifting force, the chamber is raised, and the air then escapes through the gap formed between the chamber rim and the supporting surface. Since the leakage area is fairly large, a substantial air flow rate is needed even with relatively small gaps. In the nozzle method, the air cushion is created by an airflow from an orifice located around the perimeter of the nozzle assembly. The lifting force is made up of the static pressure force on the base of the nozzle assembly and the reaction forces from the outflow of air through the nozzle. This method permits larger gaps between the base of the nozzle assembly and the supporting surface with lower airflow rates. In the slot method, the air cushion is created in a thin, slotlike cavity from which the air flows out in all directions. This cavity is located between specially shaped carrying and supporting surfaces in the case of transportation equipment and between the movable and fixed elements of mechanisms in machine tools. The increased pressure of the air cushion is maintained as a result of relative motion between the surfaces and because of the viscosity of the air passing through the slot. In the wing method an air cushion is formed by the increased air pressure under the wing of a flying vehicle (such as a ram-wing craft) as it moves with a certain angle of attack close to a supporting surface.

REFERENCE

Stepanov, G. lu. Gidrodinamicheskaia teoriia apparatov na vozdushnoi podushke. Moscow, 1963.

K. P. VASHKEVICH

air cushion

[′er ‚ku̇sh·ən]
(mechanical engineering)
A mechanical device using trapped air to arrest motion without shock.
References in periodicals archive ?
With air cushions, it is easy and convenient to reapply makeup several times a day, for a fresh look all day.
This new five-year cost-plus-fixed-fee contract, awarded in Q2, encompasses legacy work Engility is delivering on the Landing Craft Air Cushion (LCAC)-1 Class and broadens work into the new Ship-to-Shore Connector LCAC-100 Class.
The Air Cushion Vehicle H-191 will be based at Okha under the Administrative and Operational Control of the Commander Coast Guard Region (North-West).
The air cushion material is free from any toxic, hazardous or heavy metals and from manufacturing through usage to disposal, Green Family products are designed with the smallest possible carbon footprint in mind.
The air cushion enables seat weight reduction, leading to lower fuel consumption for the A330-300.
1955 The hovercraft, or air cushion vehicle, was patented by British engineer Christopher Cockerell.
The 55-year-old, wanted over the slaying of his mum-in-law, son and a pal of his ex-wife, landed on a giant air cushion and was arrested.
Omipa SpA in Italy, well known for dies and extrusion systems to produce hollow profile sheet used in glazing panels and packaging, has patented a calibrator that creates an air cushion on which the profile floats.
Model K394A31's suspension system virtually eliminates transverse lateral motion, providing an air cushion, and adjusts to calibrate a range of accelerometer sizes.
A separate air cushion softens impact of every footfall.
JR West staff carried on bowling competition after fatal crash accident (Yomiuri, Mainichi) Train's air cushion developed unusual vibrations before getting derailed.