Difference between revisions of "RAFI RS 74 M"

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(Fixed warning from the infobox (parameter "actuation force" used twice).)
 
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{{TODO photo|more=true|not all variants are covered yet}}
 +
 
{{infobox dswitch
 
{{infobox dswitch
−
| image name        = RAFI RS74M -- infobox.jpg
+
| image name        = RAFI RS 74 M.jpg
 
| manufacturer      = [[RAFI]]
 
| manufacturer      = [[RAFI]]
 
| product code      =  
 
| product code      =  
−
| contact mechanism = [[Contact mechanism#Metal leaf|Metal leaf]]
+
| contact mechanism = [[Metal leaf]]
−
| switch type      = Linear, latching lock
+
| switch type      = Linear, alternate action, changeover
−
| actuation force  =
+
| introduced        = 1975<ref name="Intro" />
−
| introduced        = 1975
 
 
| discontinued      = 2005
 
| discontinued      = 2005
−
| family            = [[RAFI Full-Travel Keyswitch]]
+
| family            = [[RAFI full-travel key switch]]
−
| keycap mount      = RAFI
+
| keycap mount      = [[RAFI mount]]
−
| switch mount      = PCB
+
| switch mount      = [[PCB mount]]
 
| travel            = 2.5 mm
 
| travel            = 2.5 mm
 
| actuation force  = 80 cN
 
| actuation force  = 80 cN
 +
| patents          = [https://google.com/patents/DE2504091 DE2504091] (1975)<br>GB1533154 (1976)<br>[http://www.google.com/patents/DE2914954 DE2914954] (1979)
 
}}
 
}}
  
−
'''RAFI RS 74M''' is a low-travel switch in the [[RAFI Full-Travel Keyswitch]] family.
+
'''RAFI RS 74 M''' is a low-travel switch in the [[RAFI Full-Travel Keyswitch]] family. It is the mechanical counterpart to the Hall effect [[RAFI RS 74 C|RS 74 C]].  
  
 
==Description==
 
==Description==
−
RS 74M switches share the same overall design as the 4 mm [[RAFI RS 76M]] switch, but have a reduced travel of 2.5 mm. They are targeted at a [[unit]] of 0.75", or 19.05 mm, and the switch shells are themselves this exact width.
+
RS 74 M switches share the same overall design as the 4 mm [[RAFI RS 76 M]] switch, but have a reduced travel of 2.5 mm. They are targeted at a [[unit]] of 0.75", or 19.05 mm, and the switch shells are themselves this exact width.
  
 
The switch uses a square loop of sprung metal that is kept away from a metal contact by the slider. When the slider is depressed, the metal loop lowers until it reaches the static contact. The switch has two solder points, and the slider recess appears to form the single PCB fixing pin. Actuation is at 1.5±0.5 mm; the lug on the slider which raises the loop travels further than the loop drops.
 
The switch uses a square loop of sprung metal that is kept away from a metal contact by the slider. When the slider is depressed, the metal loop lowers until it reaches the static contact. The switch has two solder points, and the slider recess appears to form the single PCB fixing pin. Actuation is at 1.5±0.5 mm; the lug on the slider which raises the loop travels further than the loop drops.
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The switches are available in several forms: linear, linear (illuminated), latching, and latching (illuminated). So-called "illuminated" switches simply have room for an [[LED]] in the top-right corner; they are not intended to provide backlit keycaps.
 
The switches are available in several forms: linear, linear (illuminated), latching, and latching (illuminated). So-called "illuminated" switches simply have room for an [[LED]] in the top-right corner; they are not intended to provide backlit keycaps.
  
−
==Keyfeel==
+
RS 74 M was patented together with RS 74 C in [https://google.com/patents/DE2504091A German patent DE2504091A], filed in 1975.
−
RS 74M switches appear to be intended for keypads, not desktop keyboards (for which, you would use the [[RAFI RS 76M|RS 76M]] or [[RAFI RS 76C|RS 76C]]); they have an actuation force of 80 cN within a pretravel distance of 2.5 mm, which makes them quite stiff. Based on a 1984 keyboard, they can also suffer from binding when struck at the corner.
+
 
 +
According to RAFI, RS 74 M was discontinued in July 2005.<ref>Conversation with RAFI, July 2013</ref>
 +
 
 +
==Key feel==
 +
RS 74 M switches appear to be intended for keypads, not desktop keyboards (for which, you would use the [[RAFI RS 76 M|RS 76 M]] or [[RAFI RS 76 C|RS 76 C]]); they have an actuation force of 80 cN within a pretravel distance of 1.5 mm, which makes them quite stiff. Based on a 1984 keyboard, they can also suffer from binding when struck at the corner.
  
 
==Keycaps==
 
==Keycaps==
Line 33: Line 39:
  
 
==Variants==
 
==Variants==
−
===Linear===
+
RS 74 M was covered in the 2001 Electromechanical Components catalogue, allowing some part numbers to be retrieved. Some switches have been discovered however were already end-of-life when that catalogue was published.
−
The basic linear switch has a clear plastic top.
+
 
 +
Tentatively, the series appears to be divided as follows:
 +
 
 +
*3.12960.nnnn — alternate action
 +
*3.12961.nnnn — momentary
 +
*3.17960.nnnn — illuminated
 +
 
 +
{| class="wikitable variants-table"
 +
! !! Part !! IP rating !! Type
 +
|-
 +
| [[File:RAFI RS 74 M SPST uncovered.jpg|175px]] ||            || IP40 || Momentary
 +
|-
 +
| [[File:No photograph.svg|175px]]              ||            || IP40 || Momentary, illuminated
 +
|-
 +
| [[File:RAFI RS 74 M 3.12961.001.jpg|175px]]    || 3.12961.001 || IP40 || Momentary, with increased ESD strength
 +
|-
 +
| [[File:RAFI RS 74 M red.jpg|175px]]            ||            || IP40 || Momentary (red cover)
 +
|-
 +
| [[File:RAFI RS 74 M 3.12960.101.jpg|175px]]    || 3.12960.101 || IP40 || Alternate action
 +
|-
 +
| [[File:No photograph.svg|175px]]              || 3.17960.101 || IP40 || Alternate action, illuminated
 +
|-
 +
| [[File:RAFI RS 74 M SPDT latching.jpg|175px]]  ||            || IP40 || [[RAFI RS 74 M SPDT latching|Alternate action changeover]]
 +
|-
 +
| [[File:No photograph.svg|175px]]              || 3.12961.211 || IP54 || Momentary
 +
|-
 +
| [[File:No photograph.svg|175px]]              || 3.12960.311 || IP54 || Alternate action
 +
|-
 +
| [[File:No photograph.svg|175px]]              || 3.17960.351 || IP54 || Alternate action, illuminated
 +
|}
  
−
===Linear (illuminated)===
+
===IP40===
−
The illuminated linear variant has space at the top-right for an LED, and the clear plastic top to the switch is absent. There is a recessed area at the rear of the shell which appears to be designed to support the latching mechanism in the latching variety.
+
Standard momentary switches can be found with and without a clear plastic cover. The clear cover is depicted on type 3.12961.001, which has [[sealed terminals]] and is described as having
 +
"increased ESD-strength". The cover is non-conductive and appears simply to insulate the contacts. A variant with a transparent red cover has also been discovered; nothing is known about this version.
  
−
The slider on the linear version has two lugs that sit above and below the sprung loop; when the switch is fully depressed, the loop is forcibly deformed, unlike the non-illuminated version where the loop is only raised by the slider on the return.
+
The exact number of configurations is not clear. The basic unsealed momentary type supports two stationary contacts; a DPST/SPDT version has yet to be seen. Curiously, the SPST alternate action and SPDT alternate action variants have different part numbers moulded into the the bases (".374" and ".512" respectively) but these bases appear to be identical, supporting two stationary contacts. The momentary illuminated switch uses a different base where the top-right accepts an LED; this base also accepts a latching mechanism and will be shared with alternate action illuminated.
  
−
===Latching lock===
+
All known sliders are white; the cream slider of the alternate action version depicted above is due to yellowing of the plastic.
−
===Latching lock (illuminated)===
+
 
 +
<gallery widths=250 heights=187>
 +
File:RAFI RS 74 M 3.12960.101 -- base.jpg    | SPST alternate action base marked ".374"
 +
File:RAFI RS 74 M SPDT latching -- bottom.jpg | SPDT alternate action base marked ".512"
 +
</gallery>
 +
 
 +
===IP54===
 +
The IP54 splash-proof variant was introduced in 1980.{{citation needed}} Instead of the clear top, it sports a diaphragm between the switch and its cap. An insert punches through the foil and connects the keycap with the slider.<ref name="Sealing" />
 +
 
 +
Illumination and alternate action are available in the IP54 sub-series.
  
 
==Keyboards==
 
==Keyboards==
 +
*Gercom portable unit (illuminated switches minus the LEDs)<ref>Reddit — [https://www.reddit.com/r/MechanicalKeyboards/comments/2duwxw/help_identify_switch_old_terminal_keyboard_project/ Help identify switch, old terminal keyboard *PROJECT*]</ref>
 
*[[Neve Necam 96]] audio workstation keyboard
 
*[[Neve Necam 96]] audio workstation keyboard
 +
*[[Siemens]] field programming unit 670&nbsp;C (has the splash-proof variant){{citation needed}}
 +
*Thorn EMI Liberator keyboard<ref name="Liberator" />
  
−
==Status==
+
==Availability==
−
RS 74M switches were discontinued from production in 2005, but they are still available as replacement parts with a minimum order quantity (MOQ) of 25 pieces.
+
RS 74 M switches were discontinued from production in 2005 but old stock was still available in 2013; in April 2015, RAFI confirmed that spare switches are no longer available.
  
 
==Gallery==
 
==Gallery==
 
<gallery widths=250 heights=187>
 
<gallery widths=250 heights=187>
−
File:Neve Necam 96 -- RAFI switches.jpg|RAFI RS 74M switches
+
File:Neve Necam 96 -- RAFI switches.jpg                               | RAFI RS 74 switches
−
File:Neve Necam 96 -- RAFI switches angled.jpg|RAFI RS 74M switches
+
File:Neve Necam 96 -- RAFI switches angled.jpg                       | RAFI RS 74 switches
−
File:RAFI RS 74M -- PCB traces.jpg|PCB traces
+
File:RAFI RS 74 M -- PCB traces.jpg                                   | PCB traces
−
File:RAFI RS 74M linear -- opened.jpg|Opened switch
+
File:RAFI RS 74 M linear -- opened.jpg                               | Opened switch
−
File:RAFI RS 74M linear -- opened, rear.jpg|Opened switch viewed from the rear
+
File:RAFI RS 74 M linear -- opened, rear.jpg                         | Opened switch viewed from the rear
−
File:RAFI RS 74M -- slider, spring, upper shell.jpg|Slider, spring, upper shell
+
File:RAFI RS 74 M -- slider, spring, upper shell.jpg                 | Slider, spring, upper shell
−
File:RAFI RS 74M -- upper shell is hard to remove without damage.jpg|Upper shell is hard to remove without damage
+
File:RAFI RS 74 M -- upper shell is hard to remove without damage.jpg | Upper shell is hard to remove without damage
−
File:RAFI RS 74M -- gold crosspoint prism on the static contact.jpg|Gold crosspoint prism on the static contact
+
File:RAFI RS 74 M -- gold crosspoint prism on the static contact.jpg | Gold crosspoint prism on the static contact
−
File:RAFI RS 74M -- gold crosspoint prism on the sprung contact.jpg|Gold crosspoint prism on the sprung contact
+
File:RAFI RS 74 M -- gold crosspoint prism on the sprung contact.jpg | Gold crosspoint prism on the sprung contact
−
File:RAFI RS 74M linear -- slider fully depressed.jpg|Slider fully depressed
+
File:RAFI RS 74 M linear -- slider fully depressed.jpg               | Slider fully depressed
−
File:RAFI RS 74M linear illuminated.jpg|Linear illuminated variant; the switch design is open and has no transparent top
+
File:RAFI RS 74 M linear illuminated.jpg                             | Linear illuminated variant; the switch design is open and has no transparent top
−
File:RAFI RS 74M linear illuminated -- slider removed.jpg|Slider removed
+
File:RAFI RS 74 M linear illuminated -- slider removed.jpg           | Slider removed
−
File:RAFI RS 74M linear illuminated -- spring removed.jpg|Spring removed from the slider
+
File:RAFI RS 74 M linear illuminated -- spring removed.jpg           | Spring removed from the slider
−
File:RAFI keycaps -- lasered vs double-shot.jpg|RAFI keycaps targeted at the RS 74M
+
File:RAFI keycaps -- engraved vs double-shot.jpg                     | RAFI keycaps targeted at the RS 74
 
</gallery>
 
</gallery>
 +
 +
==Documentation==
 +
*[[:File:RAFI Electromechanical Components 2001, section 5, excerpt RS 74 and 76.pdf|RS 74 and 76 excerpt from Electromechanical Components 2001]]
 +
 +
==References==
 +
<references>
 +
<ref name="Intro">''Engineering Materials and Design'' '''19''' (1975) p.&nbsp;77: ''The new Rafi RS74 keyboard system from Cole Electronics consists only of key switches and a printed circuit board — a matrix frame is not needed — giving low profile with an overall height of 15 mm.''</ref>
 +
<ref name="Liberator">The Register — [http://www.theregister.co.uk/2012/11/12/the_secret_history_of_liberator_the_first_british_laptop_part_one/?page=4 Liberator: the untold story of the first British laptop part 1] (page 4) Dated 2012-11-12. Retrieved 2015-08-01.</ref>
 +
<ref name="Sealing">Patent {{cite patent|country=DE|number=2914954}}. For a photo of the sealed switch, see "Rafi-System RS74, spritzwassergeschützt IP 54" in ''Konstruktion im Maschinen-, Apparate- und Gerätebau'' (1981), p.&nbsp;169.</ref>
 +
</references>
  
 
[[Category:RAFI switches]]
 
[[Category:RAFI switches]]
 +
[[Category:Keyboard switches with a RAFI mount]]
 +
[[Category:Low travel switches]]
 
[[Category:Linear switches]]
 
[[Category:Linear switches]]
−
[[Category:Latching action switches]]
+
[[Category:Alternate action switches]]
 +
[[Category:Illuminated switches]]
 
[[Category:Metal contact switches]]
 
[[Category:Metal contact switches]]
−
[[Category:Low travel switches]]
+
[[Category:List of all keyboard switches]]

Latest revision as of 20:45, 23 January 2018

Template icon--Illustration.png This article requires additional photographic illustration
RAFI RS 74 M
RAFI RS 74 M.jpg
Manufacturer RAFI
Family RAFI full-travel key switch
Introduced 1975[1]
Discontinued 2005
Switch type Linear, alternate action, changeover
Sense method Metal leaf
Actuation force 80 cN
Total travel 2.5 mm
Keycap mount RAFI mount
Switch mount PCB mount
Patents DE2504091 (1975)
GB1533154 (1976)
DE2914954 (1979)

RAFI RS 74 M is a low-travel switch in the RAFI Full-Travel Keyswitch family. It is the mechanical counterpart to the Hall effect RS 74 C.

Description

RS 74 M switches share the same overall design as the 4 mm RAFI RS 76 M switch, but have a reduced travel of 2.5 mm. They are targeted at a unit of 0.75", or 19.05 mm, and the switch shells are themselves this exact width.

The switch uses a square loop of sprung metal that is kept away from a metal contact by the slider. When the slider is depressed, the metal loop lowers until it reaches the static contact. The switch has two solder points, and the slider recess appears to form the single PCB fixing pin. Actuation is at 1.5±0.5 mm; the lug on the slider which raises the loop travels further than the loop drops.

The sprung loop and the static contact both feature gold crosspoint contacts, as with most Cherry switches.

The switches are available in several forms: linear, linear (illuminated), latching, and latching (illuminated). So-called "illuminated" switches simply have room for an LED in the top-right corner; they are not intended to provide backlit keycaps.

RS 74 M was patented together with RS 74 C in German patent DE2504091A, filed in 1975.

According to RAFI, RS 74 M was discontinued in July 2005.[2]

Key feel

RS 74 M switches appear to be intended for keypads, not desktop keyboards (for which, you would use the RS 76 M or RS 76 C); they have an actuation force of 80 cN within a pretravel distance of 1.5 mm, which makes them quite stiff. Based on a 1984 keyboard, they can also suffer from binding when struck at the corner.

Keycaps

QWERTY keycaps are double-shot; other legended keycaps are engraved and painted; RAFI's catalogue suggests that the engraving is not performed with a laser, as the infill process is not stated as being applied to lasered keycaps, only the "labour intensive" low volume engraving process. Relegendable keycaps are also available.

Variants

RS 74 M was covered in the 2001 Electromechanical Components catalogue, allowing some part numbers to be retrieved. Some switches have been discovered however were already end-of-life when that catalogue was published.

Tentatively, the series appears to be divided as follows:

  • 3.12960.nnnn — alternate action
  • 3.12961.nnnn — momentary
  • 3.17960.nnnn — illuminated
Part IP rating Type
RAFI RS 74 M SPST uncovered.jpg IP40 Momentary
No photograph.svg IP40 Momentary, illuminated
RAFI RS 74 M 3.12961.001.jpg 3.12961.001 IP40 Momentary, with increased ESD strength
RAFI RS 74 M red.jpg IP40 Momentary (red cover)
RAFI RS 74 M 3.12960.101.jpg 3.12960.101 IP40 Alternate action
No photograph.svg 3.17960.101 IP40 Alternate action, illuminated
RAFI RS 74 M SPDT latching.jpg IP40 Alternate action changeover
No photograph.svg 3.12961.211 IP54 Momentary
No photograph.svg 3.12960.311 IP54 Alternate action
No photograph.svg 3.17960.351 IP54 Alternate action, illuminated

IP40

Standard momentary switches can be found with and without a clear plastic cover. The clear cover is depicted on type 3.12961.001, which has sealed terminals and is described as having "increased ESD-strength". The cover is non-conductive and appears simply to insulate the contacts. A variant with a transparent red cover has also been discovered; nothing is known about this version.

The exact number of configurations is not clear. The basic unsealed momentary type supports two stationary contacts; a DPST/SPDT version has yet to be seen. Curiously, the SPST alternate action and SPDT alternate action variants have different part numbers moulded into the the bases (".374" and ".512" respectively) but these bases appear to be identical, supporting two stationary contacts. The momentary illuminated switch uses a different base where the top-right accepts an LED; this base also accepts a latching mechanism and will be shared with alternate action illuminated.

All known sliders are white; the cream slider of the alternate action version depicted above is due to yellowing of the plastic.

  • SPST alternate action base marked ".374"

  • SPDT alternate action base marked ".512"

IP54

The IP54 splash-proof variant was introduced in 1980.[Citation needed] Instead of the clear top, it sports a diaphragm between the switch and its cap. An insert punches through the foil and connects the keycap with the slider.[3]

Illumination and alternate action are available in the IP54 sub-series.

Keyboards

  • Gercom portable unit (illuminated switches minus the LEDs)[4]
  • Neve Necam 96 audio workstation keyboard
  • Siemens field programming unit 670 C (has the splash-proof variant)[Citation needed]
  • Thorn EMI Liberator keyboard[5]

Availability

RS 74 M switches were discontinued from production in 2005 but old stock was still available in 2013; in April 2015, RAFI confirmed that spare switches are no longer available.

Gallery

  • RAFI RS 74 switches

  • RAFI RS 74 switches

  • PCB traces

  • Opened switch

  • Opened switch viewed from the rear

  • Slider, spring, upper shell

  • Upper shell is hard to remove without damage

  • Gold crosspoint prism on the static contact

  • Gold crosspoint prism on the sprung contact

  • Slider fully depressed

  • Linear illuminated variant; the switch design is open and has no transparent top

  • Slider removed

  • Spring removed from the slider

  • RAFI keycaps targeted at the RS 74

Documentation

References

  1. ↑ Engineering Materials and Design 19 (1975) p. 77: The new Rafi RS74 keyboard system from Cole Electronics consists only of key switches and a printed circuit board — a matrix frame is not needed — giving low profile with an overall height of 15 mm.
  2. ↑ Conversation with RAFI, July 2013
  3. ↑ Patent DE 2914954 . For a photo of the sealed switch, see "Rafi-System RS74, spritzwassergeschützt IP 54" in Konstruktion im Maschinen-, Apparate- und Gerätebau (1981), p. 169.
  4. ↑ Reddit — Help identify switch, old terminal keyboard *PROJECT*
  5. ↑ The Register — Liberator: the untold story of the first British laptop part 1 (page 4) Dated 2012-11-12. Retrieved 2015-08-01.
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