Patents

This is a partial list of patents. Newly-discovered patents are generally added to the manufacturer page rather than to this page. The fate of this page is uncertain.

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.

Also note that the priority dates are not listed below; some designs are older than the filing date suggests when you take into account earlier patents filed in different countries.

Company	Patent	Title	Filed	Published	Notes
Trans Lux Corp	US 3290439 A	Selector	1945-06-16	1948-03-30	Photoelectric encoder mechanism for devices such as teleprinters
Monroe Calculating Machine Co	US 2641753 A	Photoelectric keyboard	1951-07-14	1953-06-09	Optoelectric keypad (identical in concept to full-size keyboards using this principle)
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
Xerox Corp	US 3340401 A	Motionless data input key	1963-12-26	1967-09-05	Keyboard with photoelectric switches with combined plunger-keycaps
Kokusai Denshin Denwa KK	US 3363737 A	Pulse generating key board	1967-04-05	1968-01-16	Some type of electromagnetic sensing implementation
Friden Inc	US 3465099 A	Optical encoder	1967-09-05	1969-09-02	Optoelectric keyboard; note that Friden were by this time owned by Singer
Singer Co	US 3767022 A	Return spring key stem boot	1970-04-24	1973-10-23	Optoelectric keyboard arrangement, with buckling rubber sleeves
Texas Instruments Inc	US 3668407 A	Optical switching for keyboard encoder	1970-05-28	1972-06-06	Optoelectric calculator keyboard
Cherry Electrical Products	US 3644855 A	Keyboard reed switch	1970-07-10	1972-02-22	A tactile double-pole reed switch that was briefly advertised around 1971
Controls Research Corp	US 3773996 A	Pushbutton switch with coil spring contacts	1971-05-20	1973-11-20	Controls Research Corp BI-PAC
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
Controls Research Corp	GB 1345831 A	Electrical switch	1972-05-11	1974-02-06	Controls Research Corp BI-PAC
International Standard Electric Corp (ISEC)	US 3750150 A	Photoelectric keyboard for data input devices or the like	1972-07-21	1973-07-31	Optoelectric keyboard arrangement
U Halfon, M Niv	US 3856127 A	Photo-optical keyboard	1972-11-24	1974-12-24	Optoelectric keyboard arrangement
Alps Electric Co Ltd	US 3823292 A	Push-button switch with conductive coil spring contact	1973-03-16	1974-07-09	Alps spring bridge
Western Digital Systems Inc	US 3818485 A	Keyboard apparatus	1973-03-30	1974-06-18	Optoelectric keyboard (this is the patent on the Collimation D40.592)
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
J. & J. Marquardt	DE 2360168 A1	Schalter, insbesondere Taster (“Switch, in particular pushbutton”)	1973-12-03	1975-06-05	Possibly precursors to the Marquardt “Butterfly” switch
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	Early Ⅲ Cortron (ITW) ferrite core double action switch
Illinois Tool Works Inc	US 4017850 A	Magnetic keyswitch with two-piece support assembly	1976-02-02	1977-04-12	Early Ⅲ Cortron (ITW) ferrite core switches
Alps Electric Co., Ltd.	US 4123641 A	Pushbutton switch	1977-02-16	1978-10-31	Priority date 1976-02-27 to the Japanese patent; this patent covers the Hirose keycap mount, only it was filed by Alps instead
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 1982-01-06	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, whatever that means …)
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
Unisys Corp (originally Burroughs Corp)	US 4278965 A	Photo-optical keyboard having n-key rollover	1979-09-14	1981-07-14	Opto-electric keyboard
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	DE 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
アルプス電気株式会社 (Alps Electric Co., Ltd.)	JP S58150232 U	Push-button switch	1982-03-31	1983-10-08	This is a “switchplate”-based double-action switch, possibly related to the type used in some Canon typewriters.
Thomas H Gifft	US 4529967 A	Non contacting inductive keyboard	1982-07-15	1985-07-16	This is an inductive arrangement with the “windings” as PCB tracks, similar to IMS and ADI keyboards
General Instrument Corporation	US 4453198 A	Linear feel keyswitch with hysteresis	1982-09-15	1984-06-05	General Instrument S700 Series
General Instrument Corp	US 4454562 A	Keyswitch with telescoping plunger	1982-09-15	1984-06-12	General Instrument S700 Series
Digital Equipment Corp	US 4467150 A	Electronic keyboard	1982-02-24	1984-08-21	DEC membrane system, as used with the LK201
Ing.C.Olivetti E C. SPA	IT 1155954 B	Tastiera a contatti (Contact keyboard)	1982-09-28	1987-01-28	Olivetti semi-discrete conductive dome
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
Rudolf Schadow GmbH	DE 3324253 A1	Tastenschalter	1983-07-06	1985-01-17	Never seen in the wild; not confirmed to be keyboard-suitable (more details on the switch contacts in adjacent patent 3324254 A1)
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 FES-370
Fujitsu Ltd	JP H0615373 Y2	Pushbutton switch	1987-08-11	1994-04-20	Fujitsu FES-370 (a different variant to the 1986 US patent)
立石電機株式会社 (Tateishi Electric Co., Ltd.)	H 01109148 U	Switch	1988-01-15	1989-07-24	Contact assembly from Omron “Alps-style” switches
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	US 5124514 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)
ZF Electronics GmbH	EP 2979289 B1	Key push rod for a key module of a key for a keyboard, key module of one key for a keyboard and method of key module assembly for a key of a keyboard	2014-02-28	2018-02-14	Damped Cherry MX

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
Preh GmbH	US 4580022 A	Keyboard key with means for supporting large key surface	1983-08-17	This is a stabiliser design in the form of scissor arms (referred to as “shears”)
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
Alps Electric Co Ltd	US 5488210 A	Push button switch	1992-06-11
Brother Industries Ltd	US 5463195 A	Key switch	1993-01-06
Charles E. Emmons	US 5424516 A	Low profile pushbutton switch	1993-09-23	A spring-over-membrane design, with a telescoping scissor slider; the scissor arms are arranged such that the coil spring can run down the middle from under the keycap, to the membranes.
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
Lite-On Singapore Pte Ltd (originally Minebea Co Ltd)	US 5597067 A	Pushbutton switch	1994-08-03
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
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
Western Electric Co Inc	US 1907930 A	Process of manufacturing electrical contact members	1930-11-24	1933-05-09	Costruction of crosspoint switch contacts (first of three simultaneously-filed patents on the subject)
Western Electric Co Inc	US 1907931 A	Process of manufacturing electrical contact members	1930-11-24	1933-05-09	Costruction of crosspoint switch contacts
Western Electric Co Inc	US 1907932 A	Process of manufacturing electrical contact members	1930-11-24	1933-05-09	Costruction of crosspoint switch contacts
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 Products 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)
Honeywell Inc	US 4421432 A	Key switch cap mounting arrangement	1981-09-04	1983-12-20	Honeywell keycap mount
IBM	US 4460534 A	Two-shot injection molding	1982-09-07	1984-07-17
アルプス電気株式会社 (Alps Electric Co., Ltd.)	JP S6234723U	キーボードのキートップ取付構造 (“Key top mounting structure for keyboard”)	1985-08-19	1987-02-28	Stabiliser assembly found in the Zenith Supersport
Alps Electric Co Ltd	US 4771146 A	Keyboard key top mounting structure	1987-11-30	1988-09-13	Stabiliser assembly found in the Zenith Supersport
Key-Tech Inc (later Poly-Flex Circuits Inc.)	US 4960614 A	Printed circuit board	1989-06-14	1990-10-02	Improved silver ink for producing tracks on printed circuit boards

Funny terminology

film: membrane sheet
pushbutton: “plunger” according to Omron
shears: 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.