Fujitsu Leaf Spring

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Fujitsu
Leaf Spring Switch
(1st Gen)
FLS-1stGen-SwitchActuation.png
Manufacturer Fujitsu
Inventor Seisuke Kamei
Hideo Nabetani
Ryohei Kinoshita
Switch type Linear, clicky
Sense method Metal dome
Peak force 80 g
Patents US4370533
Fujitsu
Leaf Spring Switch
(2nd/3rd Gen)
FLS-2nd3rdGen-SwitchActuation.png
FLS-2nd3rdGen-LinearForceCurve.png
Manufacturer Fujitsu
Inventor Seisuke Kamei
Toshiaki Tanaka
Kazutoshi Hayashi
Akira Tanaka
Ryohei Kinoshita
Switch type Linear
Clicky (Rare)
Sense method Metal dome
Peak force 40 g, 45 g
Patents US4529849

History

The Fujitsu Leaf Spring switch seems to have been developed in the late 1970's as a way to reduce manufacturing costs for contact-based keyboard switch mechanisms (as opposed to sense-based mechanisms such as Hall Effect). The first iteration of the switch design used individual housings, and could be used individually, provided the switch is inserted into a stabilizing plate. The second design still used individual barrels for the switches, but it relied on the plate to suspend them over the leaf spring, similar to how IBM Model F capacitive buckling spring keyboards were designed. There is one confirmed keyboard that uses a one piece slider assembly, similar to the way the IBM Model M keyboard is designed.[Citation needed]

There is also a known tactile version of the 3rd generation of the Fujitsu Leaf Spring switch. Though due to the design (the mechanism is inside the slider barrel), this newer design could be used in 2nd generation housings. Unfortunately, keyboards with this tactile switch are much more rare than the linear variants.

These switches are most famously used in the FM Towns line of keyboards as well as the Tandy 1000 keyboards.

1st Generation

Individually housed leaf spring with corresponding button spring for actuation in each switch. Could be used individually. It used a cruciform slider with part of the leaf spring mechanism embedded into the slider, going through it and poking of the top of the cross.

The keycap mount dimensions are a fraction of a millimetre too large to fit Cherry keycaps; keycap insertion is very stiff. Testing with a modern Signature Keycaps novelty keycap yielded borderline success, while testing with a 2009 Filco keycap resulted in what appeared to be whitening of the plastic from stretching. Attempting to use Cherry MX mount keycaps is liable to lead to split keycap stems.

Key feel

The linear version is extremely smooth (even when dirty). Much heavier than the later generation switches. One of the best examples of well designed linear switches.

Keycaps

All known keycaps are spherical double-shot, some nearly solid plastic. It uses a cruciform slider, as do many of the switches from the late 1970's through the 1980's.

  • 1st Generation clicky switch; note the tiny metal tip at the top of the stem

  • 1st Generation clicky switch top; note the letter "F" at the base

  • 1st Generation clicky switches

  • 1st Generation keycaps

  • 1st Generation keycaps

  • 1st Generation keycaps

  • 1st Generation keycaps; the rightmost keycap is actually from a Fujitsu vertical reed switch, the other two could possibly be from a 1st generation or vertical reed switch, as the keycaps are compatible.[Citation needed]

Linear switch module

The following switch is NOS purchased through AliExpress.

  • Top, with Fujitsu branding

  • Bottom

  • Base, showing interesting cutout pattern in the plastic

  • Opened; unlike the patent image, the contact assembly is a flat discrete module

  • Partial disassembly

  • Slider with moulded-in actuator

  • Slider rear

  • Slider, showing where actuator leaf enters into the stem

2nd Generation

Individual barrels attached to a metal plate. Leaf spring and button spring attached to PCB below the plate. The slider is separate from the barrel and the keycap. It uses rubber gaskets/stoppers at the bottom of keys to slow the keys down in case the user is bottoming out.

Key feel

Very smooth linear actuation, with a rubber stopper at the bottom of each key.

Keycaps

All known keycaps are spherical double-shots, some double shots also have filled engravings. They fit directly onto the slider, similar to how the legends fit onto the two piece IBM buckling spring keycaps. Thick plastic is used. Keycaps are not compatible with the 1st Generation.

  • 2nd Generation spherical doubleshot keycaps.

  • 2nd Generation stopper, slider/housing, and reverse side of keycap.

  • 2nd Generation leaf springs, and Caps Lock LED.

  • 2nd Generation housing/slider underside, attached to metal plate.

3rd Generation

Individual barrels attached to a metal plate. Leaf spring and button spring attached to PCB below the plate. The slider is separate from the barrel and the keycap. It does not use rubber gaskets/stoppers in the switches. Linear and clicky versions of the switch exist; the clicky version uses a mechanism within the slider, while the rest of the switch remains identical to the linear variety. The FMV77AV keyboard is known to use a single piece housing for all of the sliders, similar to the IBM Model M keyboard.

Key feel

Linear

Very smooth linear actuation.

Clicky

Weak tactile event, and a quiet clicking sound.

There is no known patent, a measured force curve is available elsewhere.[1]

Keycaps

All known keycaps are cylindrical double shots, with a slightly unusual shape bearing no texture on the top. Keycaps are made of thick plastic and they are compatible with the 2nd Generation.

  • 3rd Generation slider and housing attached to metal plate.

  • 3rd Generation leaf springs attached to PCB and LED.

  • 3rd Generation cylindrical keycaps with and without snap-in slider.

  • 3rd Generation switch, dismantled.[2]

  • 3rd Generation switch underside, separate housing and plate construction, linear slider.

  • 3rd Generation switches dismantled, linear (top) vs. clicky (bottom).[3]

Keyboards

It is believed that production of keyboards with these switches stopped in the late 1990s or perhaps early 2000s. Fujitsu later pushed its Peerless switch.

1st Generation Keyboards

  • DK'tronics ZX81/ZX Spectrum keyboard Mk1 [4][5]
  • Fujitsu Micro 8 (FM-8)[6]
  • Olympia People keyboard (Linear) [7]
  • Sanyo MBC-2000/3000 keyboard (Clicky)[8]

2nd Generation Keyboards

3rd Generation Keyboards

  • Data General 6246-A (Clicky)
  • Data General 6348-A Terminal Keyboard (Clicky)
  • Epson Q503A[10] (Linear)
  • Fujitsu F8113KB13[11]
  • Fujitsu FACOM6130KC1[12] (Clicky)
  • Fujitsu FACOM6130KF1[13]
  • Fujitsu FACOM6140KA1[14]
  • Fujitsu FACOM6684KC3[15] (Linear)
  • Fujitsu FMR30KB501[16]
  • Fujitsu FMR50AKB31 (N860-2279-V003 02B)[17]
  • Fujitsu FMR60KB101 (N860-2882-T001)[18]
  • Fujitsu FMR60KB201 (N860-2881-T001)[18]
  • Fujitsu FMR60KB211 (N860-2335-T001)[18]
  • Fujitsu FMT-KB205 (FM Towns)[19] (Linear)
  • Fujitsu FMT-KB207[18]
  • Fujitsu FMV-KB211[20] (Linear)
  • Fujitsu FMV-KB611 (N860-2367-T022)[18]
  • Fujitsu M5053KB14[21]
  • Fujitsu Micro 7 (FM-7)[22]
  • Fujitsu OAKB-201 (N860-2987-T011)[18]
  • Fujitsu N860-2322-T002 01A[23]
  • Fujitsu N860-2500-T101 03A[18]
  • Fujitsu N860-2500-T111[24]
  • Fujitsu N860-2505-T00201A[25]
  • Fujitsu N860-2531-T001 "Sanyo"[26] (Linear)
  • Fujitsu N860-2880-T101 03A[27]
  • Hatsuko HEKB01 Data Entry Machine EM988 (N860-2368-T001 01A)[28]
  • HP 46010A (Clicky)
  • HP 46020 (Clicky)
  • Mai Basic Four[29]
  • Omron F-300K[30]
  • Sanyo MBC-885[31]
  • Tandy 1000 (Linear)
  • Tandy 3000 (Linear)
  • Toshiba N860-2503-T021[32]
  • Toshiba T300[33]

References

  1. ↑ Atelier Silencium — Force curves for various 3rd Generation keyboards Last updated 2010-02-20. Retrieved 2015-07-25.
  2. ↑ MouseFan — FUJITSU　テンキーボード　FMR30KB501 JAPAN — Uses 3rd Generation switches. Retrieved 2015-07-25.
  3. ↑ MouseFan — FUJITSU　オアシス　OAKB-406　JAPAN — Uses 3rd Generation switches, click variant. Retrieved 2015-07-25.
  4. ↑ k1.spdns.de — dK'tronics Keyboard for the ZX81
  5. ↑ World of Spectrum — DK'Tronics Keyboard
  6. ↑ park10.wakwak - [1]
  7. ↑ Deskthority — Olympia People Microcomputer keyboard
  8. ↑ Deskthority — Sanyo MBC-2000 / 3000 keyboard
  9. ↑ YouTube - Epson Q703A keyboard review (Fujitsu leaf spring 2nd generation) Uploaded 2019-10-18.
  10. ↑ Geekhack — Espson Q503A Keyboard Posted 2013-12-09. Retrieved 2015-07-25.
  11. ↑ Imgur - Fujitsu F8113KB13 (Credits to Haata) Uploaded 2023-02-23.
  12. ↑ Imgur - Fujitsu Oasys FACOM6130KC1 (Fujitsu Leaf Spring Clicky) Uploaded 2024-09-15.
  13. ↑ Imgur - Fujitsu FACOM 6130KF1 (Fujitsu Leaf Spring) Uploaded 2024-09-15.
  14. ↑ YouTube - Fujitsu Leaf Spring 3rd Gen typing test (OASYS FACOM6140KA1) Uploaded 2021-11-23.
  15. ↑ Deskthority - FACOM 6684KC3 Keyboard + Terminal Posted 2013-01-10.
  16. ↑ Twitter - Fujitsu FMR30KB501 Posted 2024-09-21.
  17. ↑ Twitter - FMR50AKB31 Posted 2024-05-12.
  18. ↑ 18.0 18.1 18.2 18.3 18.4 18.5 18.6 Kiyoto-y - Summary page about Fujitsu's leaf spring mechanical keyboards -- Product database
  19. ↑ YouTube - Fujitsu FM Towns FMT-KB205 review (Fujitsu leaf spring 3rd generation) Uploaded 2023-01-23.
  20. ↑ YouTube - Fujitsu FMV-KB211 Brief Typing (Fujitsu Leaf Spring Linear 3rd Generation) Uploaded 2022-11-17.
  21. ↑ Imgur - Fujitsu M5053KB14 Uploaded 2024-09-15.
  22. ↑ Deskthority - FM-7 ("Fujitsu Micro 7") info request Posted 2016-01-19.
  23. ↑ Flickr - Fujitsu N860-2322-T002 01A
  24. ↑ Deskthority - Fujitsu 3rd Gen Leafspring Teensy Wired Posted 2017-07-29.
  25. ↑ Deskthority - Fujitsu Limited N860-2505-T00201A Posted 2016-05-08.
  26. ↑ YouTube - Fujitsu N860 "Sanyo" review (Fujitsu leaf spring 3rd gen.) Uploaded 2016-06-11.
  27. ↑ Imgur - Old ass Fujitsu Mechanical Keyboard Posted 2020-01-30.
  28. ↑ Imgur - N860-2368-T001 (Credit to techbreezin) Posted 2023-06-23.
  29. ↑ Deskthority - Mai Basic Four Keyboard Conversion Posted 2019-06-29.
  30. ↑ Deskthority - Ohaimark's Collection Posted 2016-10-16.
  31. ↑ Deskthority - Fujitsu Leafspring keyboard - converted! Posted 2020-09-13.
  32. ↑ Twitter - TOSHIBA Unknown Keyboard (N860-2503-T021) Posted 2024-09-01.
  33. ↑ Imgur - Toshiba T300 Posted 2023-03-31.
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