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For Clare-Pendar patents, see the Clare-Pendar page.

Some patents of yet-to-be-seen switches that are not matched to a known series are listed visually under unmatched patents.

General switch patents

Known switch types that are yet to be documented anywhere are indicated in bold.

Note that there seems to be a strong tendency for Taiwanese companies to file patents abroad to an individual instead of an organisation, meaning that a number of patents from Taiwanese organisations cannot be tied down to a particular company or product. This is especially frustrating with Win-Join Chen’s patent for the de-facto early 1990s Alps clone design, as it cannot be traced back to either Himake or Tai-Hao, and it could be either company’s product.

Note that I do not pretend to understand the mess that is European patent practice.

Company Patent Title Filed Published Notes
Willcox US 3290439 A Data encoding keyboard 1963-04-29 1966-12-06 A flat keyboard that in some ways was a precursor to Datanetics elastic diaphragm array
Angelo De Falco US 3283274 A Push button reed switch 1963-10-04 1966-11-01 This patent was found on a GRI reed switch (similar to KB series but taller, possibly a forerunner) attached to a Mostek/Fairchild F8 Evaluation Kit; curiously, there is no discernible connection between Angelo De Falco and GRI
Cherry Electrical Products US 3644855 A Keyboard reed switch 1970-07-10 1972-02-22 A tactile double-pole reed switch that has never observed in the wild; the external design is fairly similar to Cherry M7
Controls Research Corp US 3773996 A Pushbutton switch with coil spring contacts 1971-05-20 1973-11-20 CRC concentric spring: a block-assembly system outwardly very similar to Key Tronic and Maxi Switch assemblies, but using two concentric springs
Cherry Electrical Products US 3739127 A Keyboard pulse switch 1972-02-17 1973-06-12 A variant of M5 or M6 Series that causes the contacts to re-open immediately after closing, generating a pulse of current; not known to be in any catalogues
Illinois Tool Works Inc US 3824362 A Alternate action switch mechanism 1973-05-23 1974-07-16 ITW first-generation alternate action switch, as seen in the HP 02645-60023 ca. 1978 as magnetic valve
Illinois Tool Works Inc US 3882295 A Tactile feedback switch mechanism 1973-10-04 1975-05-06 Tactile feedback mechanism for ITW first-generation switches
Cherry Electrical Products US 3849621 A Illuminated push-button switch 1974-05-09 1974-11-19 Cherry M41 corner-illuminated (this design was omitted from Serie M7)
Illinois Tool Works Inc US 3902032 A Electrical switch with improved contact structure 1974-06-07 1975-08-26 ITW first-generation switch, metal contact system (which references Hi-Tek’s patent filed two years earlier)
Tokai Communication Ind JP S5276687 A Push button switch 1975-12-23 1977-06-28 Tokai MM9 series
Illinois Tool Works Inc US 4028696 A Double depression magnetic keyswitch 1976-01-26 1977-06-07 Magnetic valve double action switch; from the drawings it’s not clear which series this is from as it does not match any known type
Alps Electric Co., Ltd. US 4153829 A Pushbutton switch assembly 1977-02-16 1979-05-08 Never observed in the wild; the patent depicts an older design of switchplate before SKCC series, suggesting that SKCC series was introduced in 1977 or later (and as later patents cite this one, this appears to be only patent for the vertical switchplate design itself)
Omron Tateisi Electronics Co JP S53136680 A Keyboard Switch 1977-05-04 1978-11-29 Magnetic tactile and click system within a compact reed switch; the switch depicted is not known, but the magnet system has been found in B2H-F7W which is very similar in shape
Omron Tateisi Electronics Co JP S57136719 A Method of Producing Illumination Keyboard Switch 1979-02-16
1982-08-23 Covers the internally-sprung centre illumination system found in B2R and B2H, depicted in a Hall effect switch largely identical to B2R; the alternate action mechanism is also covered, although it seems not to match up with the provisions made on B2R, and this arrangement is seemingly also extendable to tactility (based on a fragmentary translation) (The 1979 application date is 「前実用新案出願日援用」 while the application itself is dated 1982; don’t ask me …)
Omron Tateisi Electronics Co JP S55105916 A Contactless Keyboard Switch 1979-02-06 1980-08-14 Covers the Hall effect arrangement in B2H and the Hall equivalent to B2R
Omron Tateisi Electronics Co JP S5743324 A Electrostatic Capacitance Type Keyboard Switch 1980-08-26 1982-03-11 Some kind of foam and foil arrangement, with an optional spring-over-foam arrangement to get a more linear feel
Omron Tateisi Electronics Co JP S5746418 A Electrostatic Capacitive Keyboard Switch 1980-09-02 1982-03-16 A revision of the previous patent to include Topre-like springs, possibly over some kind of rubber mat (a translation would make things clearer)
Omron Tateisi Electronics Co JP S5750721 A Electrostatic Capacitive Keyboard Switch 1980-09-12 1982-03-25 A revision of JP S5743324 A (some kind of foam and foil including spring over foam); a translation would reveal the specifics
Omron Tateisi Electronics Co JP S5755014 A Electrostatic Capacitance Type Keyboard Switch 1980-09-19 1982-04-01 A revision of JP S5746418 A (foam and foil, and Topre-like springs)
Rafi & Co Elektrotechnische Spezialfabrik JP 3037448 A1 Pushbutton switch assembly - has leads of diode connected directly to internal contact and external contact pin 1980-10-03 1983-10-27 (B1) Internal diode arrangement for RAFI RS 76 M; Google Patents lists C2 as the grant, but only A1 from 1982-05-13 has the complete set of drawings
Oak Industries Inc US 4559426 A Membrane switch and components having means for preventing creep 1980-11-03 1985-12-17 Oak Full-Travel Membrane alternate action switch
Digital Equipment Corp US 4467150 A Electronic keyboard 1982-02-24 1984-08-21 DEC membrane system, as used with the LK201
Oak Industries Inc US 4479040 A Tactile feel switch with positive switch actuation 1983-03-07 1984-10-23 Implementation of tactile feel for what appears to be a derivative of Oak Full-Travel Membrane
SMK KK JP S6017 A Switch Element and Method of Producing the Same 1983-06-15 1985-01-05 Mitsumi/Hosiden–style contact assembly fitted to a J-M0404–style switch; never seen in the wild
Mitsumi Electric Co JP S6063832 A Pushbutton switch 1983-09-17 1985-04-12 Some sort of parabolic rate spring arrangement, including a horizontal spring version of Mitsumi miniature mechanical, but without the spring-over-nub arrangement seen in KLT-11 (note that this patent pre-dates the patent on miniature mechanical, below)
Mitsumi Electric Co JP S60230317 A Pushbutton switch 1984-04-27 1985-11-15 Mitsumi miniature mechanical, linear version (KLM)
SMK KK JP S60243912 A Method of Producing Switch Element 1984-05-17 1985-12-03 Mitsumi/Hosiden–style contact assembly fitted to a proto–second generation switch; never seen in the wild
Siemens AG EP 0164446 B1 Device for fixing a diode in a push-button housing 1984-12-14 1988-04-27 Diode fitment to STB 21; for some reason they felt that the diode had to have its legs removed and separate legs used!
Fujitsu Ltd US 4803316 A Push button switch using dome spring and switch element thereof 1986-10-16 1989-02-07 Fujitsu lever action
Alps Electric Co Ltd US 4920245 A A push-button switch with uniform on and off timings 1988-06-30 1990-04-24 This patent covers a portion of the Mk II Alps switchplate, specifically a way to improve the injection moulding to get a more consistent pretravel distance (the change from large to small foil, or large to small dimensions, are not included)
Omron Tateisi Electronics Co. US 5015811 A Snap-action pushbutton switch with click sound 1989-06-13 1991-05-14 Inverted, moving click leaf design for Omron B3G-S switches; never observed in the wild
Alps Electric Co Ltd US 5120923 A Push button switch 1990-09-18 1992-06-09 Unnamed membrane type; later discovered in the Toshiba T4600C
Alps Electric Co Ltd JP H04220915 A Push-button switch 1990-12-21 1992-08-11 Alps ultra low profile
Win-Join Chen JP H04220915 A Structure of mechanical key switch 1991-07-08 1992-06-23 Either Himake AK series or Tai-Hao APC series
Silitek Corporation US 5310973 A Structure of key switch 1991-10-08 1994-05-10 Alternative patent for Silitek (MX mount) dome with slider
Alps Electric Co Ltd US 5201824 A Push button switch 1992-01-13 1993-04-13 A “division” of US 5120923 A, above
Monterey International Corp US5406277A Structure of the keypad for keyboard 1993-04-12 1995-04-11 Monterey 0/180° Alps dome with slider (not the same as the well-known 0/90/180/270° version); no spring, dome, contacts or membranes are shown
Sen-Cheng Wang US 5380969 A Computer key 1993-04-28 1995-01-10 The drawings bear a strong resemblance to Monterey dome with slider
Daw Shen Chen GB 2282703 A Mechanical key switch 1993-10-05 1995-04-12 Quite possibly Can Technology buckling spring
Tokai Communication Ind JP H07220561 A Contactless switch 1994-02-01 1995-08-18 Optoelectronic adaptation of Tokai MM9 series, never observed in the wild; patent filed ten months before that of Tokai SPT-0101
Liao Ching-Shui US 5456541 B1 Key unit of a keyboard 1994-03-23 1995-10-10 Unrecognised spring-over-membrane type; curiously it depicts ATW Alps clone (as found in the Oriental Tech OK-100 from ca. 1992) as the prior art
Silitek Corporation US 6184481 B1 Key switches for computer keyboards 1994-03-30 2001-02-06 (!) Silitek (Alps mount) dome with slider
Mitsumi Electric Co JP H07326257 A Pushbutton switch 1994-05-31 1995-12-12 This is some kind of redesign of KPQ series with what appears to be a single rubber dome sheet (クリックラパーコート) instead of separate buckling rubber sleeves; existing KPQ series is shown as 「別の従来のキーボードスイッチ」 (“another conventional keyboard switch”)
Focus Electronic Co Ltd US 5442152 A Computer key switch 1994-09-28 1995-08-15 Focus spring over dome — a clicky dome switch similar to Fujitsu Peerless; the click sound is attributed to “barbs” within the spring tube hitting some part of the tube within the slider in which it fits
Tokai Communication Ind JP H08167361 A Semiconductor photocoupling switch 1994-12-12 1996-06-25 Tokai SPT-0101
Silitek Corp US 5938009 A Key switch for a keyboard 1998-08-24 1999-08-17 Silitek spring over dome — a clicky dome switch similar to Fujitsu Peerless (the sudden extension of the coil spring is said to generate the click sound)
Jing Mold Enterprise Co Ltd US 6156986 A Computer key switch 1999-12-30 2000-12-05 A fairly typical rubber dome switch; notable only as it is from Jing Mold, whose FCC ID is on the Tulip 9151B (also rubber dome)

Scissor switch patents

Just listing the priority dates for these as the new Google Patents site doesn’t want to make filing dates easy to access when exploring patents. Note that non-crossed designs (where the two arms are not attached to each other and do not scissor) are also included, and are marked “non-cross”.

This list also covers stabiliser arrangements with scissor arms, as these appear to be precursors to modern scissor switches.

Company Patent Title Priority Notes
General Instrument Corporation US 4433225 A Keytop levelling mechanism 1983-02-22 This is a stabiliser design in the form of scissor arms
Brother Industries Ltd US 5278371 A Keyswitch assembly with support mechanism coupled to support plate beneath printed circuit board 1992-02-14
Brother Industries Ltd US 5278374 A Assembly with an asymmetrical resilient spring 1992-02-14
Brother Industries Ltd US 5463195 A Key switch 1993-01-06
Mitsumi Electric Co JP H07296673 A Keyboard switch 1994-04-22 Some kind of four-arm non-cross arrangement; figures 5 through 7 show “conventional” keyboard switches for comparison
Mitsumi Electric Co JP H08124456 A Keyboard switch 1994-10-26 Some kind of non-cross arrangement; figures 4 and 5 show “conventional” keyboard switches for comparison
Alps Electric Co Ltd US 5488210 A Push button switch 1992-06-11
Nagano Fujitsu Component Ltd US 5874696 A Key switch, keyboard and portable information processing unit with keyboard 1996-08-12 Non-cross
Fujitsu Ltd JP H11185564 A Key switch, keyboard and information processor using these 1997-12-22 Non-cross
Nagano Fujitsu Component Ltd US 6118092 A Key switch for keyboard 1998-09-22 Non-cross
Fujitsu Ltd, Nagano Fujitsu Component Ltd US 6257782 B1 Key switch with sliding mechanism and keyboard 1998-06-18 Suggested to be spring-over-membrane
SMK Corp US 6297461 B1 Key switches for computer keyboards 1999-12-17 Both leaf spring and dome actuators are implied
Behavior Technical Computer Corp US 6572289 B2 Pushbutton structure of keyboard 2001-06-28
Minebea Co Ltd US 6759614 B2 Keyboard switch 2002-02-27
Fujitsu Component Ltd US 7138587 B2 Key switch, keyboard and key-switch assembling jig 2004-07-01 Non-cross
Fujitsu Component Ltd US 8624140 B2 Key switch and keyboard 2006-07-10 Non-cross

Other keyboard-related patents

The following table covers patents for aspects of keyboards other than keystroke sensing. In particular, it lists patents for mechanical shift lock mechanisms. These do not use alternate action switches. Instead, pressing shift lock causes a special mechanism (external to the switch) to hold the key down, and pressing either shift key (or just left shift, if right shift is not connected) releases shift lock. Mechanical shift lock mimiced the shift lock mechanism on manual typewriters, where the shift mechanism could be locked in place for convenient entry of capitalised text.

Also covered are stabiliser mechanisms that do not use scissor arms; those types with scissor arms are covered above alongside scissor switches.

Company Patent Title Filed Published Notes
CLARE PENDAR Co US 3626120 A Key-locking assembly 1970-09-30 1971-12-07 Mechanical shift lock mechanism; here, the keycap itself operates the release mechanism
Cherry Electrical Products US 3678255 A Mechanical key lock-in 1971-06-18 1972-07-18 Mechanical shift lock mechanism, used by M61-0300/0310/0500/0510 (early 1970s) and later M61-0025/0026/0027/0028 (by the late 70s)
Cherry Electrical Products US 3711685 A Keyboard switch actuator 1971-12-27 1973-01-16 Cherry paddle-type stabiliser, as seen in B70-05AB; replaced with the wire-type stabiliser
Burroughs Corp US 4010838 A Spacer bar mechanism 1975-01-17 1977-03-08 Space bar stabiliser
Illinois Tool Works Inc US 4071719 A Keyboard switch assembly having actuator interlocking keyboard shift and shift lock and release mechanism 1976-07-22 1978-01-31 Mechanical shift lock for ITW first-generation switches
Cherry Electrical Productsucts Corp US 4188136 A Keyboard switch actuator and locking assembly 1978-01-19 1980-02-12 The Cherry stabiliser arrangement (wire-type), plus a mechanical shift lock mechanism (unclear switch types)
Illinois Tool Works Inc US 4295012 A Secretarial shift mechanism for an electric keyboard 1980-02-04 1981-10-13 Mechanical shift lock for ITW second-generation switchces (both magnetic valve and metal contact are depicted here)

Funny terminology

membrane sheet
“plunger” according to Omron
Another term for scissors
spacer bar
An old term for space bar

Other patents

The following patents are not for keyboards, but they are notable in relation to keyboards.

Company Patent Title Filed Published Notes
Olympia Werke AG DE 3330624 A1 Push-button switch 1983-08-25 1985-03-14 This is notable for being a Western example of the folded-plate contact module, akin to that of Mitsumi KAM and Hosiden switches