IBM buckling sleeve

IBM Quiet Touch buckling rubber sleeves (or simply IBM buckling sleeves) is the provisional name for a tactile keyswitch used by IBM as a quiet, low-profile alternative to IBM buckling springs for IBM's flagship keyboards (Model M family) outside the buckling spring keyboards' primary domains. It first saw use on IBM portable computers, which by the early 1990s had become too thin to use standard keyswitches. The Model M3 with the original IBM buckling sleeve implementation was introduced as the keyboard assembly for the IBM Personal System/2 L40SX notebook and its optional numeric keypad in March 1991^[1][1]
IBM - The IBM PS/2 Model L40 SX System and Features Announcement Letter (#191-030) [accessed 2024-12-04].. Later that year, IBM and Lexmark decided to port the M3 keyboard and keypad assemblies to desktop usage as the Model M4-family Space Saving Keyboards and Numeric Keypads. The M3 design was then modified to become the Model M6-family PS/note, PS/55note and ThinkPad keyboard assemblies. Its use on portable computers was phased out by the late 1990s as even buckling sleeves were too tall for the ever decreasing typical laptop thickness, however, Unicomp continued to produce the M4-based Mighty Mouse keyboards until the late 2000s^[2][2]
Sharktastica - Revealed: The Story of the Model M4 family [accessed 2021-11-01].. IBM buckling sleeves still survives in the point-of-sale industry thanks to the Retail POS (Models M7, M7-1, M8, M9 and M11), "pre-Modular POS", and Modular POS ("Model M-e") keyboard families. After Toshiba TEC acquired IBM Retail Store Solutions in 2012, Toshiba Global Commerce Solutions continues to make buckling-sleeve Model M derivatives to this day. The variants M3/M4/M4-1 type, M6/M6-1 type, early POS type, and late POS type are recognised. Whilst they have not achieved the same fame buckling springs have, IBM buckling sleeves can be considered as "IBM's last stand" in making a unique, in-house keyswitch design before eventually following the wider PC industry from mid-1990s onwards with employing third-party designed standard rubber dome keyboards.

Contents

Specifications

Design

IBM buckling sleeve keyswitches are membrane driven and were seemingly derived from the same patents and/or copyright as IBM membrane buckling springs as their host devices often cite "1984" as the copyright date. However, patents relating directly to IBM buckling sleeves are presently unknown. They have been spotted as prior art for a patent Lexmark filled in 1992 for an attempted replacement to using buckling sleeves as a low-profile keyswitch^[4][4]
Lexmark - Low profile tactile keyswitch [accessed 2024-12-04]. License/note: provided by Google Patents.. In that patent and in marketing from Lexmark and Unicomp, IBM buckling sleeves have been referred to generically as "rubber domes" but its design is quite different from a standard rubber dome keyswitch design.

For a typical membrane-driven rubber dome keyswitch, the titular dome is typically housed inside a keyboard assembly and is used for actuation (compressing on top of membrane assembly contact points to register a key press), for tactility and for providing a return force so the keycap returns to its rest position after a press. "Buckling rubber sleeve" elements in general are recognised as such for sitting outside a keyboard assembly and are divorced from actuation. They are also not traditionally dome shaped, as they may appear upside-down and/or sport an opening to allow a keycap plunger or mount to go through it.

IBM buckling sleeves do not part-way actuate (register a key before bottoming-out) like buckling-spring keyswitches, but crucially since the sleeve element is not what compresses on bottoming out to actuate, they retain uniqueness and a more solid key feel over membrane-drive rubber dome keyswitch designs. Depending on exact variant, the keycap itself or sliders fixed in the keyboard's frame are used and give a solid press on the keyboard's membrane assembly. The sleeve elements themselves are outwardly-expanding conical-shaped, sculpted so that the thick top rim rests besides the bottom one when fully pressed. Conceptually, IBM buckling sleeves also appears similar to Mitsumi KPQ-type keyswitches, but IBM's design lacks the conductive rubber foot on the bottom of its actuation element, eliminating another possible element that could dampen a solid bottoming out feel. IBM buckling sleeves can be described as tactile, snappy, and are of medium-heavy weighting (slightly less than buckling springs).

Gauges

IBM buckling sleeves exist in five distinct sizes and forms (referred to as gauges) suited for different key sizes.

Colours

IBM buckling sleeves were manufactured in various colours, which could vary based on many factors such as year of production, OEM, sleeve gauge and the colour of the host keyboard. The following sleeve colours are known:

Grey

Grey was the first prominent colour of buckling sleeve element used from the beginning, in 1991. They were typically found in most pearl white Model M3s and pre-Unicomp Model M4s and M4-1s, but can also be found in early Model M7 to M11 keyboards made by Lexmark and Maxi Switch as late as 1996. They have only been seen in standard gauge.

Black

The black buckling sleeve element was an alternative to the grey sleeves, used for most raven black buckling sleeve keyboards. They were first found on Model M6 ThinkPad and PS/55note C52 keyboard assemblies introduced in 1992 in alt-standard and medium gauge. The following year, raven black Model M4-1s appeared with standard gauge black sleeves. By the 2000s, Unicomp Mighty Mouse keyboards regardless of host keyboard colour may use black sleeves. This colour of sleeve can notably vary, with some examples becoming greyish and powdery, likely due to age and/or wear.

Grey-pink

Grey-pink coloured buckling sleeve elements can be found as the alt-standard gauge buckling sleeves used on a number of buckling sleeve keyboards' spacebars. They appeared as early as 1993 on the spacebars for Model M6 for Lexmark's OEM laptops and most pre-Unicomp Model M4 and M4-1 keyboards. For Models M4 and M4-1, grey-pink sleeves were eventually replaced by the blue translucent standard gauge sleeve.

Blue translucent

The blue translucent sleeve element was a spacebar-only standard gauge sleeve that served as either an alternative or outright replacement for grey-pink alt-standard sleeves. It has been spotted as early as 1995 on Lexmark-made Model M4-1s but is primarily associated with Unicomp after they took over Model M4/M4-1 production from Key Tronic in 1998.

Clear translucent

Clear translucent sleeve elements first began appearing as Model M6 and M6-1 keyboard assemblies' small gauge sleeves and Apple Newton X0044 keyboard's medium gauge sleeves. As early as 2000, Maxi Switch had introduced clear translucent standard gauge sleeves on IBM POS keyboards too. Afterwards, all buckling sleeve elements would be of this colour. In 2001, the IBM Model "M-e" CANPOS Keyboard introduced the final sleeve gauge - medium-tall - in clear translucent.

Variants

Model M3/M4/M4-1 type (1991-2010)

The original implementation of IBM buckling sleeves was introduced with the March 1991-launched^[1][1]
IBM - The IBM PS/2 Model L40 SX System and Features Announcement Letter (#191-030) [accessed 2024-12-04]. IBM PS/2 L40SX notebook computer and its numeric keypad and manufactured by IBM United States as the Model M3 family. Later that year, Lexmark adapted the L40SX keyboard and keypad assemblies into a desktop keyboard and keypad respectively designated Model M4. IBM formally branded them as the IBM Space Saver Keyboard, who additionally marketed a Model M4-1 as a version with a TrackPoint II pointing stick. Lexmark exclusively produced M4s until Lexmark's keyboard exit in 1996, with Key Tronic taking over immediate production albeit briefly. Unicomp took over sometime in 1998, producing them for IBM into the 2000s, and for themselves under the "Mighty Mouse" name until 2010.

During the 19 years of production and sale, the keyswitch design remained unchanged and exclusively uses standard gauge sleeves (even for the smaller-sized keys). The principal feature of this seminal version of IBM buckling sleeves is the keycap mount, which features two plastic clips on either side of the keycap that retains the keycap on the keyboard frame. The M3/M4/M4-1 type design, being the earliest, is potentially subject to some nuances later IBM buckling sleeve implementation do not suffer from. The aforementioned clips may cause some scratchiness depending on the keyboard's condition or potential plastic degradation/warping over time. In such cases, cleaning the keyboard frame and potentially lubing the clips may remedy this. The spacebar stabiliser may also struggle to register a key press if pressed in certain ways such as across the front face or on their extreme corners (if this issue is experienced, ensuring the spacebar is pressed towards its middle and on its top face will typically avoid it).

Model M6/M6-1 type (1992-1999)

IBM buckling sleeves received its first and largest revision in February 1992 when the IBM PS/2 CL57SX was announced^[7][7]
Ardent Tool - IBM PS/2 Model CL57 SX System 8554-A45 and Features Announcement Letter (#ZG92-0165) [accessed 2023-07-13]., sporting a Model M6 based keyboard (made by IBM United States^[8][8]
ASK - Revealed: IBM Model M3 & M6 laptop buckling sleeves keyboards#CL57SX [accessed 2022-06-19]. and later Lexmark^[9][9]
Ardent Tool - PS/2 Model CL57 SX [accessed 2022-06-19].) that despite resembling the L40SX's featured a radical change in the switch's actuator design. Namely, the membrane assembly's contact points are now pressed on by a barrel-fixed slider instead of a rod on the keycap, and the keycap itself now has a more traditional form of mounting (cross-style) that doesn't require clips on the edges. The barrel slider colour was at first brown, a defining feature of early Model M6s. Along with the keyboards used for the ThinkPads 700, 720 and 350 series, PS/note 182 and 425 series and PS/55note N27sx and C52, these keyboard assemblies were usually designated Model M6 by IBM. Lexmark itself also used the M6 design for a number of its own laptop (Lexbook) keyboard assemblies and some laptop keyboards it made for other companies. All known M6 keyboards were produced by IBM United States (typically early, pre-October 1992) or Lexmark.

M6 was later supplanted by the Model M6-1 introduced in June 1993^[10][10]
ThinkWiki - ThinkPad History [accessed 2021-11-18]. with the IBM ThinkPad 500 series. The actual distinction between M6 and M6-1 is blurry as both keyboards use interchangeable sleeve gauges and keycaps (depending on unit size), but over time, the barrel slider colour was first changed to black then its keycap stem mounting socket was altered to appear more solid. M6-1 was made widespread by what followed the ThinkPad 500, such as the ThinkPads 750 series, 360 series, 370C, 355 series, 755C series, Power Series 850, 365 series and RS/6000 Notebook 860. There are some other non-ThinkPad IBM laptops and Lexmark OEM designs that were M6-1 based too. M6-1 was produced by Lexmark and later Key Tronic^[2][2]
Sharktastica - Revealed: The Story of the Model M4 family [accessed 2021-11-01]. starting 1995 Q4, however, these should not be confused with Key Tronic's own take on the buckling rubber sleeves design used on the ThinkPad 701C/701CS TrackWrite keyboard^[11][11]
micrex22 - ThinkPad Keyboards and Switches [accessed 2021-11-18].. Several lineages of M6 family keyboards have appeared that use different layouts and/or key sizes which have been described into six types. For the alphanumeric and modifiers keys, the M6 family typically used standard or alt-standard gauge sleeves (all M6/M6-1 types except 4) that are fully interchangeable with M3/M4/M4-1 type. However, for the smaller function and navigation keys, medium gauge sleeves are now employed. Type 4 Model M6-1s use medium gauge sleeves for the alphanumeric and modifier keys, and Types 4 and 6 also use small gauge sleeves and a different keycap mount for their function and navigation keys. The latest observed production year for a keyboard with M6/M6-1 type buckling sleeves was 1999^[12][12]
u/themavery - A NOS IBM Model M6-1 ThinkPad 365 Keyboard Assembly [accessed 2023-06-27]..

Possible inverted sleeves

M6/M6-1 type IBM buckling sleeves at standard key-size positions are uniquely capable of supporting their sleeves inverted (upside-down, to resemble a traditional rubber dome shape) thanks to recesses in M6/M6-1 keyboards' frame. It is presently unknown why these are present and if M6/M6-1 keyswitches were ever practically deployed like this. One can flip the sleeves themselves, though it can lead to a mushy key feel.

Mouse button type (1992-1996)

The mouse button type IBM buckling sleeve is a subtype of Model M6/M6-1 type used for the mouse buttons on Lexmark Lexbook AR10 (16mm trackball) and GS20 (pointing stick) series laptop keyboard assemblies. Thanks to the AR10, they appeared as early as March 1992^[13][13]
PC Mag - 31 Mar 1992 [accessed 2023-05-11]. License/note: accessed via Google Books.. The two buttons are positioned in between the left-side Ctrl and Alt keys and are labelled "M1" and "M2". The sleeve and keycap design are the same as M6's, with the only observed sleeve used being standard gauge. The barrel slider is clearly raised compared to its standard counterpart and is white compared to M6 (brown) and M6-1 (black). This reduces the possible travel, creating a more "binary" feel that one might expect from a mouse button switch.

Early POS type (1993-2002)

In June 1993, IBM introduced the Retail POS (RPOS) series Model M keyboards - designations M7, M7-1, M8, M9 and M11 - for IBM 4690-family POS terminals^[14][14]
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-04-23].. IBM originally ported M6/M6-1 type IBM buckling sleeves for them, resulting in essentially the same design but with minor modifications. This version (dubbed "early POS type") used a black 'skeletal' barrel slider similar to that found on early Model M6-1 keyboard assemblies but with a more curved rim. The mount itself is unchanged, thus it's possible to mount Model M6 and M6-1 sourced keycaps onto RPOS keyboards with this implementation. RPOS keyboards only ever used standard gauge sleeves. RPOS keyboards produced in the Americas by Lexmark (United States of America) and Maxi Switch (Mexico) sported early POS type from launch to approximately 2002. After that, RPOS production was transferred to Asia and subsequently used late POS type IBM buckling sleeves instead.

Late POS type (2002-present)

Sometime in 2002, production of the IBM RPOS series Model M keyboards was transferred from the Americas to Asia. Coinciding with this event, IBM introduced the latest revision of IBM buckling sleeves, which is also the only one left in production. Dubbed "late POS type", the design was simplified over early POS type by eliminating the barrel slider first added by M6/M6-1 type and replacing it with an integrated-style mount where each keycap has an elongated bottom that acts as the keyswitch mechanism's slider and actuator. This is also different to M3/M4/M4-1 type that also used two clips to hold the keycap in place rather than having the mount integrated onto their rod actuators. Keyboards with late POS type IBM buckling sleeves were produced by XAC (Taiwan) and XSZ (China) during the IBM era.

In June 2008, IBM introduced the Modular POS (MPOS) series Model M extended family ("M-e") keyboards^[15][15]
IBM - IBM SurePOS 300 machine type 4810 offer new point-of-sale keyboards [accessed 2022-06-19]. that were an evolution of the RPOS designs with more keys and removable major components, but also retained the use of late POS type. The IBM Modular CANPOS II (MCANPOS) and IBM Modular ANPOS II (MANPOS) Keyboards were notable amongst them. In between RPOS and MPOS, a few other IBM POS keyboards and keypads appeared, such as the original IBM CANPOS Keyboard and the IBM 4820 SurePoint Monitor Keypads that also made use of late POS type. As with early POS type, RPOS keyboards only used standard gauge sleeves, however, CANPOS and MCANPOS keyboards also use medium-tall gauge sleeves for their half-height keys. In 2012, Toshiba TEC bought IBM Retail Stores Solutions^[16][16]
IBM - Toshiba TEC to Acquire IBM’s Retail Store Point-of-Sale Solutions Business; Agreement Allows Both to Tap Growing Smarter Commerce Opportunity [accessed 2021-06-17]., forming Toshiba Global Commerce Solutions (TGCS) who continued to produce and market IBM-related POS equipment including Model M keyboards with buckling sleeves. TGCS-made RPOS and MPOS keyboard rear labels state Toshiba TEC themselves were hereon responsible for production. After RPOS vanished at some point in the mid 2010s, MPOS remains the last IBM buckling sleeve bearing keyboards in production.

Keycaps

Plastics & printing

Keycaps for IBM buckling sleeve keyboards outside the majority of Model M6 and M6-1 keyboard assemblies appear to be PBT. Pearl white M3/M4/M4-1 type and early POS type IBM buckling sleeve hosts have durable dye-sublimated legends, which would preclude the use of ABS as it is less porous than PBT (and PBT's porosity is what allows dye-sublimation to work with it compared to ABS^[17][17]
fanf @ KeebTalk - Reply on "Does Thick ABS perform the same as Thick PBT?" thread [accessed 2024-12-07]. License/note: quoting Melissa Petersen of Signature Plastics.). Pearl-coloured IBM buckling sleeve keycaps in general do not appear to yellow. With the advent of late POS type, IBM POS keyboard keycaps began using lasered legends for pearl white keyboards and silk-screened legends for iron grey keyboards. However, it appears the keycaps are still made with PBT, as they do not yellow even when their host keyboards have yellowed.

The relatively few Model M6 and M6-1 keyboards that are pearl white also appear to use PBT keycaps, regardless of whether the legends are dye-sublimated or pad-printed. Raven black (PS/2 CL57SX, most ThinkPads, etc.) or Newton blue-tinted black keycaps appear to be ABS though, as they have been demonstrated to dissolve in acetone when PBT would not.

Mounts

M3/M4/M4-1 type & M6/M6-1 small gauge

The IBM buckling sleeve variant mounted via two plastic clips on either side of the keycap that clip into the host keyboard's frame, retaining it in place and preventing it from significantly rotating in its place. The nature of this design makes removing the keycap by hand difficult, so a wire puller is recommended for them.

For Type 4 and 6 Model M6-1 keyboard assemblies that have a function-key row and/or half-height navigation keys that make use of small gauge sleeves, the mount for those keys in particular differs to the expected M6/M6-1 & early POS types mount and its design somewhat resembles that of the M3/M4/M4-1 style mount in that it is a dual-clip design (although they are not compatible with each other).

M6/M6-1, mouse button & early POS types

M6/M6-1 type IBM buckling sleeves introduced a more elegant keycap mount for IBM buckling sleeve keyswitches using medium or larger gauge sleeve elements. The barrel sliders in the keyboard frame introduced for actuation have a form of cross-shaped hole, and the keycaps have a cross-shaped stem underneath. The keycaps are much easier to remove than the other mount styles and can usually be removed with fingers alone by grabbing from any two opposite sides, though a wire puller is still advised. M6/M6-1 style single-unit keycaps will easily mount to an early POS type IBM buckling sleeve keyswitch if attempted. However, the reverse is generally not feasible since early POS style keycaps are taller. During the M6-1 lifecycle, the barrel slider hole shape was altered, but despite appearances, it does not break compatibility with M6 or older M6-1 keycaps.

Late POS type

The final (and now solely produced) mount is exclusive to late POS type IBM buckling sleeves, simplifying the mount to a single stem through barrel (integrated-style) design. Whilst the design is functional, it breaks full keycap compatibility with earlier versions of the same POS Model M keyboards that use early POS type IBM buckling sleeves. Keycaps with this mount are also the most difficult to remove, and pulling straight up with a wire puller has been known to break the keycap's top face from its stem. For single-unit keystems used by relegendable keys, it's possible to remove them with the following instructions:

Other keys such as alphanumeric, modifiers and the spacebar can only be safely removed by opening up the keyboard assembly and pushing them out from the other side of the keyboard frame. To put a keycap back in, you simply push it back in with the two protrusions on the keystem's plug facing left and right relative to the keyboard. If the key doesn't press properly or stays stuck at the bottom, you should be able to rotate the keystem until it starts pressing normally again.

Host devices

M3/M4/M4-1 type host devices

More information: Model M3 PS/2 L40SX Numeric Keypad, Model M4 & M4-1 Space Saver Keyboard & Numeric Keypad

M6/M6-1 type host devices

More information: Model M6 & M6-1 ThinkPad Laptop Keyboard Assemblies

Early POS type host keyboards

More information: Model M7, M7-1, M8, M9 & M11 Retail POS Keyboards

Late POS type host keyboards

More information: Model M-e Modular 67-Key POS, MANPOS & MCANPOS Keyboards

Gallery

Further reading & resources

Internal

Articles

Wiki pages

Sources

ASK. Admiral Shark's Keyboards original content. License/note: CC BY-NC-SA 4.0.

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