Jump to page content

Alps KCP Series

Overview

KCP is a keyboard switch series from Alps. Several types are depicted in an Alps Low-Profile Keyboard Switches sample pack of unknown age. From this sample pack, we can see that CP (KCP) series has several specific characteristics:

A hysteresis mechanism was created for SCK switches, and it is not clear why a very different design was created here. Alphabetically, KCP follows both KCL and KCM, but far too little information exists at present to determine the order in which each series was created. Hysteresis appears to act as a differentiating factor between KCP and KCM.

There are three known variants of this design. The photos in the sample pack are not clear but they are consistent with the standard plate-mount version. The SKCP name was originally derived from a Canon AP 560 typewriter, whose keyboard module is model KFCPAA011A. The switches in that typewriter are also plate-mount, meaning that no data presently exists to indicate whether the two different PCB-mount types are the same series or a different series. There is some evidence to suggest that the square PCB-mounted type is SKCR series, but this is not confirmed yet, and there is contradictory evidence in the form of an article or advertisment “Low-Profile Keyboard Switches CP Series” from JEE (Journal of Electronic Engineering), somewhere within Volume 22, 1985. A poor-quality (1 bpp) scan on Google Books shows switches that appear to be the square PCB-mount type. All that can be read of the article is the following:

Low-profile keyboard switches are now born. They will meet the future business use requirements by performing sharp and stable operations.

The CP Series Tactile Low-Profile Keyboard Switches are newly designed to be used in electronic typewriters, office computers …

Specifications

Curiously, the rated lifetime is half of that of KCL/KCM, at only 10 million cycles; it is equal to that of KFL, yet KCP uses the more complex metal foil switching sandwich.

Operating force Unclear
Total travel force 70 gf
Tactile force ca. 70 gf
Preload 20 gf
Total travel 3.5 mm
Lifetime 10 million cycles
Contact resistance 1 Ω maximum

Models

All known models are taken from the Low-Profile Keyboard Switches sample pack.

Type KCP model SKCP model
Momentary, standard weight SKCPAB
Momentary, standard weight, red LED SKCPFB
Alternate action SKCPJB
Double action SKCPKB

SKCPJB appears identical to SKCLJB from KCL Series; it appears that, since neither tactile feedback nor hysteresis were meaningful to an alternate action switch, Alps found it more practical to repurpose an existing switch.

The utility model that covers the double action model depicts the force curve, and puts the second stage force at 500 gf.

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. Only a person who can read Japanese could understand the scope of these documents. Not every one is confirmed to be KCP/SKCP, and the older patents appear to be for a much taller design than KCP.

Document Filed Granted Description
S60-054121, A 1983-09-01 1985-03-28 Tall design, plate mount, with force curve
S61-135426, U1 1985-02-13 1986-08-23 Double action, with force curve (tall design)
S61-139528, U1 1985-02-20 1986-08-29 LED (tall design)
S61-146828, U1 1985-03-05 1986-09-10 KCP lower profile?
S61-149231, U1 1985-03-07 1986-09-13 Unknown changes
S61-153942, U1 1985-03-15 1986-09-24 Variation of the previous utility model
S62-002128, U1 1985-06-20 1987-01-08 Space bar assembly, and double-action switch (the latter per S61-135426, U1)
S62-165621, U1 1986-04-11 1987-10-21 Unclear variation
S63-041821, U1 1988-03-18 1986-09-04 Unclear variation

References

See also