Alps KFL Series
KFL is a compact, PCB-mount keyboard switch series from Alps. The earliest known mention of it is from magazines in 1982, as (in one instance) “KFL Series” and “Model KFL” simultaneously; this material is partially accessible on Google Books. Advertisements placed in magazines in 1983, including Electronic Engineers Master 83–84, are however fully accessible. Here, it is advertised as “Series KFL Low Profile Keyboards”, which covers both the switches and completed keyboards (prior to Alps putting keyboards into separate series). The utility models filed by Alps are contemporary with this, suggesting that the switches entered production around 1983.
The legs protrude out from the sides of the switch, entering the shell high up. This strange design characteristic may be intended to prevent fouling of the switch contacts by the ingress of solder, flux or cleaning fluids during the wave soldering process, without the need to apply terminal sealant (as was used with KCC, KCM and KCL series in some cases).
The specifications given in the Alps Low-Profile Keyboard Switches sample pack are indicated to apply to both the standard momentary (SKFLAC and SKFLFB) and alternate action (SKFLJB) types, but this is unlikely to be true as it is definitely not true in the case of SKCL; thus, the force specifications below likely apply only to SKFLAC. The “operating force” is given as 60 gf, while the official force curve shows 60 gf to be the total travel force. If the operating point is taken to be half travel at 2 mm, this would correspond to roughly 50 gf, and the preload appears to be around 40 gf. There is no indication of a date with these specifications.
|Operating force||ca. 50 gf|
|Total travel force||60 gf|
|Preload||ca. 40 gf|
|Total travel||4.0 mm|
|Lifetime||10 million cycles|
|Contact resistance||1 Ω maximum|
The older part numbers come from Roland service literature, and cover just the standard momentary switches (non-illuminated, and illuminated with a red LED). The newer part numbers are taken from the Alps Low-Profile Keyboard Switches sample pack.
|Type||KFL model||SKFL model||Colour|
|Momentary, standard weight||KFL10903||SKFLAC||Pale grey|
|Momentary, standard weight, red LED||KFL11904||SKFLFB|
|Momentary, heavy weight||Pale cyan|
|Alternate action||SKFLJB||Pale yellow|
Patents and utility models
The following patents (“A”) and utility models (“U1”) were located by a search for “スイッチ” (switch) and “キーボード” (keyboard) from Alps Electric (アルプス電気) on J-PlatPat (the Japanese Patent Platform). J-PlatPat does not provide inbound links to documents.
|S57-095717, U1||1982||Contact assembly, a little bit like that of KFL|
|S58-174821, U1||1982-05-18||1983-11-22||KFL alternate action|
|S58-188928, U1||1983||KFL momentary, possibly unused variation|
|S58-193428, U1||1982-06-15||1983-12-22||KFL momentary, actual implementation|
|S59-161227, U1||1984||KFL keycap mount|
|S59-161226, U1||1984||KFL keycap mount, production version|
|S59-162729, U1||1984||KFL keycap mount|
|S59-162727, U1||1984||KFL keycap mount|
|S60-107528, U1||1985||KFL compact|
|S60-131925, U1||1985||KFL LED and KFL compact|
|S63-141219, A||1988||KFL switch contact manufacturing process|
- Alps Electric (USA) advertisement, Electronic Engineers Master catalogue 1983–1984 extract
- Alps Low-Profile Keyboard Switches sample pack (no date specified)
- Alps SKFL series on the Deskthority wiki for photos and keyboard listings