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Unmatched patents

The images below are used to help identify switches in interesting patents. None of these have been found in keyboards at the time of writing. For other patents, see patents.

US 3725625 A

“Mechanical pushbutton switch with pointed end coil spring contact”

Raytheon, filed 1971-08-25, granted 1973-04-03

US 3946181 A

“Push button-type switch”

Koji Takamizawa, Shitiro Shimizuhata, Akinori Shinonaga and Masaru Tsuruta, filed 1974-06-11, granted 1976-03-23

US 4418252 A

“Key switch assembly”

Phillip R. Daigle, filed 1982-04-05, granted 1983-11-29

Remarkably similar to an unidentified Alps switch.

US 4473727 A

“Electric switch having helical spring bridging element”

C and K Components Inc, filed 1982-03-22, granted 1984-09-25

Not to be mistaken with Stackpole torsion spring.