Buckling spring
Provided by the ASK Keyboard Dictionary
A buckling spring is a keyswitch actuator design where a metal coil spring characteristically buckles into a kink instead of compressing in a straight column, which pivots something that can be registered by a pad card or membrane assembly underneath (depending on exact implementation). Various keyswitches that use such a design are referred to as "buckling springs", including IBM's famous buckling spring keyswitches originally designed by Richard Hunter Harris. Buckling springs allow a keyswitch to provide actuation, tactility, auditory feedback and a keycap return force all with just one spring, with the actuation and "click" events occurring at the same time. IBM used versions of buckling springs on all Model F (capacitive) and many Model M (membrane) family keyboards.
