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I Think My Switch Is Stuck! - The Tale of Cherry MX Locks

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Over the years of collecting mechanical keyboard switches, I’ve been lucky enough to have encountered dozens upon dozens of rare and unique ones that have stuck in my mind to this day. Prototypes, factory errors, and even a few switches so rare that there is literally zero documentation about them anywhere in the world all fill that personal list from top to bottom. However, I realize that talking about switches so far outside of most people’s reaches, and even sometimes my own grasp, doesn’t make for the most exciting of articles about switches. To this newest generation of keyboard enthusiasts, though, there is one pretty rare MX-style switch which has made its way to the top of everyone’s “must try” lists – Cherry MX Locks. These often undiscussed and even more rarely seen switches are something that few people have seen and even fewer have had the chance to try at a meetup before. However, the list of people who really know how these unique Cherry switches work is even shorter than either of those aforementioned lists. Knowing full well from my own firsthand experience that you’ll absolutely find these switches fascinating too, let’s take a brief look into some of the most unique and rarest of Cherry’s switches.
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Figure 1: My personal 3- and 5-Pin Cherry MX Lock switches.
Cherry MX Locks are a ‘latching mechanism’ style switch that operates differently from all other MX-style switches that Cherry has made over the years in that they physically ‘lock’ about halfway through their upstroke upon being pressed inwards. Much like with how Caps Lock and Num Lock keys work on modern keyboards, simply pressing a locked MX Lock switch will ‘unlock’ it again and return it back to its full upright position after completing its upstroke. In spite of this sounding like a concept that is pretty advanced by today’s switch standards, the MX Lock is actually quite old, first making its debut in Hirose Cherry keyboards as far back as 1984! Originally, Cherry’s MX Lock switches came in entirely black housings in those Hirose-made keyboards, though they didn’t necessarily appear in all Hirose made boards. (Frustratingly, they only seem to appear in the rarest and hardest to find of those Hirose keyboards, as well.) At some point between 1984 and the early 2000’s, Cherry moved on from the original all-black housing design of MX Locks and introduced the “NOS Grey” housings that are what most people today recognize as true Cherry MX Locks. Produced in both 3-Pin and 5-Pin configurations, these MX Locks were produced all the way up to 2015 until Cherry ended their production reportedly due to the material used in the grey colored housings reaching its end of life. In spite of this, documentation and one now sold out sales page from MechanicalKeyboards.co.id suggests that Cherry produced at least one final round of MX Locks featuring black housings and clear sliders. To date, though, I can’t say I’ve ever recalled seeing these switches loose in collections nor in prebuilt keyboards.
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Figure 2: Cherry MX Lock and their components from Deskthority.
While linears, tactiles, and even the occasional clicky switch are easy enough for me to explain via the typed word, Cherry’s MX Lock switch is perhaps one of the hardest I’ve ever had to attempt to put into words. This isn’t just because of the simple fact that they lock, rather it has to do with the fact that the style of mechanism used to physically lock the stems in Cherry MX Locks is particularly exclusive to Cherry and their switches. This mechanism, which uses a “star wheel” to lock the stem in place, was first patented all the way back in 1972 for Cherry’s M6 switches, and titled most affectionately as an “Alternate-Action Switch Actuator With Pawl Stop Plate Also Providing A Guide For Stroke-Control Means” (US 3,770,923). (Try saying that one three times fast.) Looking below to the two figures used in the original patent, and trying to avoid all the numbers labeling the various parts, we can actually pretty easily see how these work with a touch of color coding on my part. As can be seen, the star wheels each have three spokes (pink, yellow, and blue) which have mouth-like grooves in the ends of them. On the left hand side in Figure 5, notice that the pink spoke is facing straight up with a piece of the internal housing construction wedged between it and the yellow spoke. When the stem is pressed downwards, the curved left part of the pink spoke will contact this housing lip and be pushed to the right, causing the entire star wheel to rotate clockwise about its center axis. As this wheel rotates clockwise and the stem is released to carry out the upstroke, the yellow spoke’s mouth opens up to the ledge and ‘chomps’ down on this ledge on return, effectively locking the stem halfway up. Once pressed again, the star wheel will continue its clockwise rotation due to the blue spoke hitting the bottom of the housing, which will return it from the state of Figure 6 back to that of Figure 5, but with the yellow spoke in the air and the blue spoke staged up for the next actuation. All in all, the fact that this not only works so cleanly but consistently is quite an impressive feat of engineering!
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Figure 3: Cherry's 'Star Wheel' locking mechanism as seen in US Patent 3,770,923.
In spite of the fact that I could probably spend at least two thousand more words talking about all my personal stories and anecdotes tied up with Cherry MX Lock switches, or at the least talking about other locking style mechanisms used in keyboard switches, I think that this article will have to stay at about this length for brevity’s sake. As I sat down to write this, I realized that there aren't all that many great explanations out there about how these switches work, and I am glad I get to share with you all the same mechanism that amazes me every time I look over the patent. While I’m uncertain if Cherry will ever revive these switches for production at some time in the future, we can only hope that recent efforts in reviving the Ergo Clears, ‘New Nixies’, and Hirose Oranges means that these are a short while away! In the meantime, though, consider checking out some of my other articles here on Drop such as ‘Not All Linears Are The Same!’ or ‘The Vintage Switch Conundrum'. 
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Figure 4: Also enjoy the strange force curve for the MX Locks that I collected as well!
(Edited)
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This is really cool. What an intriguing design for unique purpose! Love it.
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