Editing Scissor switch

[[File:Scissor switch (RM).jpg|thumb|250px|right|Scissor switch on an RM notebook]]

A '''scissor switch''' (also '''pantograph switch''') is a form of [[stabiliser|stabilised]] switch. The scissor mechanism functions like a pair of opposed stabilisers joined by a hinge. The scissor mechanism allows for a stable key with a low profile.

A typical scissor switch uses a small [[rubber dome]] over [[membrane]]s but many other solutions for return force and sensing exist.

Key travel is usually in the 1.0-2.5 mm range. In the upper range, the [[Mitsumi KGL Type]] has 2.5-3.0 mm and the original [[Logitech PerfectStroke]] had 3.2 mm key travel.

Scissor switch keyboards were likely introduced for the constrained dimensions of notebook computers. For reasons of familiarity and preference, scissor switch keyboards are becoming increasingly common in desktop keyboards. For instance, all current [[:Category:Apple keyboards|Apple desktop keyboards]] use scissor switches.

==Internals==
A traditional scissor-switch has two cross-arms, one of which pivots on the baseplate, the other pivoting on the keycap. The opposite ends of each cross-arm slide within guides. The cross-arm mechanism replaces the need for an upper shell with guide shafts for [[slider]]s, reducing both the height and weight of the board. The flat base of the keycap rests directly on the rubber dome.

[[File:Scissor switch mechanism.svg|center]]

The exact design of the mechanism varies between manufacturers.

On ''butterfly''-type scissor switches the legs don't extend below past the hinge, and each leg pivots and/or slides against the bottom on its own side.
Butterfly switches typically have very low key travel, often below 1 mm.

==History==
The origin of scissor switches has yet to be identified. In 1983, [[General Instrument]] filed a patent ([https://www.google.com/patents/US4433225 US4433225] "Keytop levelling mechanism") for a scissor-like mechanism for stabilising L-shaped keycaps. A narrow scissor arrangement occupies the side of the keycap opposite to the switch. Comparing the patents it cites, with the patents citing it, it would not be a stretch for this design to be the origin of the scissor mechanism.

===Patents===
There are a great many patents relating to scissor switches from many different manufacturers; examples:

{| class="wikitable"
! Manufacturer !! Patent !! Filed !! Notes
|-
| [[General Instrument]]
| [https://www.google.com/patents/US4433225 US 4433225]
| 1983
| Keycap levelling mechanism patent, that appears to be a forerunner of the scissor switch
|-
| [[SMK]]
| [http://www.google.com/patents/US5894117 US 5894117]
| 1997
| 
|-
| SMK
| [http://www.google.com/patents/EP1164463 EP 1164463]
| 1999
| 
|-
| [[Alps Electric]]
| [http://www.google.com/patents/US6312176 US 6312176]
| 1999
| 
|-
| SMK
| [http://www.google.com/patents/US6297461 US 6297461]
| 2000
| 
|-
| Alps Electric
| [http://www.google.com/patents/US7238907 US 7238907]
| 2003
| 
|-
| [[Mitsumi]]
| [https://www.google.co.uk/patents/EP1458000B1 EP 1458000]
| 2004
| 
|-
| Mitsumi
| [https://www.google.co.uk/patents/US7199320 US 7199320]
| 2006
| 
|}

==Gallery==
<gallery widths=250 heights=187>
File:Scissor switch (Compal).jpg               | Scissor switch on a Compal notebook
File:Apple MB110BA -- scissor switch sizes.jpg | Normal and compact switches from an [[Apple Aluminium Keyboard]]
</gallery>

==See also==
*[[Elecom rack and pinion]] — an alternative approach to scissor switches
*[[:Category:Scissor switches|Category:Scissor switches]]

==References==
<references />

[[Category:Keyboard terms]]
[[Category:Low travel switches]]
[[Category:Rubber dome over membrane switches]]
[[Category:List of all keyboard switches]]