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A buckling spring is a type of keyswitch
mechanism Mechanism may refer to: * Mechanism (engineering), rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission * Mechanism (biology), explaining how a feature is created * Mechanism (philosophy), a theory tha ...
, popularized by IBM's keyboards for the PC, PC/AT, 5250/3270 terminals, PS/2, and other systems. It was used by IBM's
Model F keyboard The Model F was a series of computer keyboards produced mainly from 1981–1985 and in reduced volume until 1994 by IBM and later Lexmark. Its mechanical-key design consisted of a buckling spring over a capacitive PCB, similar to the later Model ...
s (for instance the AT keyboard), and the more common
Model M Model M designates a group of computer keyboards designed and manufactured by IBM starting in 1985, and later by Lexmark International, Maxi Switch, and Unicomp. The keyboard's many variations have their own distinct characteristics, wit ...
. It is described in (Model F) and (Model M), both now expired.


Operation

The
coil spring A selection of conical coil springs The most common type of spring is the coil spring, which is made out of a long piece of metal that is wound around itself. Coil springs were in use in Roman times, evidence of this can be found in bronze Fi ...
tensed between the
keycap A keycap is a small cover of plastic, metal, or other material placed over the keyswitch of a computer keyboard. Keycaps are often illustrated to indicate the key function or alphanumeric character they correspond to. Early keyboards were manu ...
and a pivoting hammer buckles (i.e. kinks or collapses) at a certain point in its downward traverse, providing auditory and tactile feedback to the keyboard operator. Upon buckling, the hammer is pivoted forward by the spring and strikes an electrical contact which registers the key press. In a Model M, the electrical contact is a membrane sheet similar to that of a modern dome switch keyboard.


Gallery

File:Bucklingspring-animation-300ms.gif, Buckling spring on key press and release File:Bucklingspring1-o.svg, Illustration from the original buckling spring , issued to IBM in 1978 File:IBM buckling spring.svg, A drawing included in the patent for the buckling spring mechanism File:Fig 2 harris keyforce-o.svg, Graph of key force over key travel for a buckling spring key. Visible in graph position 1C the fast force drop when the spring buckles. , issued to IBM in 1978.


See also

* Collapse action *
Euler's critical load Euler's critical load is the compressive load at which a slender column will suddenly bend or buckle. It is given by the formula: P_ = \frac where *P_, Euler's critical load (longitudinal compression load on column), *E, Young's modulus of the ...
*
List of mechanical keyboards Mechanical keyboards (or mechanical-switch keyboards) are computer keyboard A computer keyboard is a peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or keys to act as mechanical levers or ...


References


External links


Wiki article on the various buckling spring mechanisms
– From deskthority.net {{Compu-hardware-stub Computer keyboards