The advent of the self-winding watch ushered in a new age of design in watches. It also increased the thickness of watches. In most designs, the rotor was concentric with the movement, and stacked below the gears. But there was a way to limit the increase in thickness, as Universal Perret Freres (later Universal Geneve) said eloquently in their 1956 patent application:
According to a primary feature of our invention, the rocking weight has its axis arranged eccentrically with that of the watch and it is arranged in superposition with the winding mechanism above the watch plate within the space left free on the latter by the mainspring, the movement and the balance wheel while the total height of said weight and winding mechanism is at least approximately equal to that of the movement.
This concept, of having the rotor co-planar with (at least part of) the movement, is what we now know as a micro-rotor. This patent (really, this one is worth a read) goes into some depth as the problems with alternative low-height winding mechanisms.
The micro-rotor is still something of a niche item, but it's very interesting to see a patent describing it as early as the mid 50s.
I love this 1921 patent granted to Zenith for a couple of reasons.
First, the drawings are just a wonderfully straightforward depiction of a stem and crown that could be used for setting the hands (pushed in) or winding (pulled out). Second, it's always interesting to see an early version of something that's become such an integral part of watches today, and mores to see it in a slightly different light.
In the drawing above you can see the stem in the winding position, meshing with the top gear which would go to the power train. When pushed in, another set of gears on the stem mesh the hand setting mechanism. The leaf shapes help hold the gears together, and maintain the stem in a particular position.
In this 2013 patent, Tudor discloses a fine adjustable watch bracelet that has both fine adjustment and elastic adjustment capabilities. While I try not to get too judgmental about these patents, I'm very surprised that this was issued.
The patent discloses two ways to adjust the fit of a bracelet, each at opposite ends of a wristband or clasp.
The first is to attach springs in the bracelet. The springs allow the bracelet to stretch and return to its original position. This is something that was well-known in the art.
The second is a series of grooves in the clasp, along with a bar which snaps into the grooves, also well-known in the art of fine-adjustment of bracelets.
It's axiomatic that you can't combine two things, get the expected result, and obtain a patent on that. If already erasers existed, and pencils already existed, you usually can't get a patent on sticking an erase on a pencil. Here, I'm struggling to see what the point of novelty was, other than maybe the adjustments being at opposite ends of the clasp.
Regardless, it's an interesting, if not likely redundant, mechanism, that I don't believe we've seen in Tudors.
This is a patent that's very interesting for its historical context, and how clear the specification is about the problem it seeks to solve and how it solves it. This was filed in 1929 and issued in 1933 (don't let anyone tell you that long delays in getting a patent are a new thing).
The patent specification succinctly sums up what the problem was in the prior art, "As is well-known, a watch mechanism, or movement, containing parts of magnetic material, or which are sensitive to magnetism, or a magnetic field to which the movement is exposed, may have its accuracy impaired, or indeed under some conditions, its running may be stopped."
Steel was commonly used in the escape wheel to withstand the repeated hits from the pallet fork (pictured above) which may hit the escape wheel teeth three or more times a second. But steel wheels could easily be magnetized, and was susceptible to magnets.
The most common anti-magnetic metal for use in gears was brass, but, "it is not hard enough to resist wear so that while its use for an escape wheel would eliminate the effect of magnetic influences, it would fail for want of wear resisting properties."
So, the inventor came up with a rather elegant solution. "I construct the escape wheel so that it has a main or body part of wheel-form, that is to say, a hub, spokes and rim or circumference, of a non-magnetic material, such as brass, and teeth of steel." There is a small enough amount of steel that it is largely unaffected by magnets, and the brass is just immune to its effects. Further, the combination of the metals, and their different coefficients of expansion as they heat are counteracted by the movement in the plates on which they are mounted.
This Gruen Patent from 1972 is featured not because it's particularly groundbreaking, but because it does such a great job at showing one common way to implement day-date mechanisms.
The day indicator is linked to the seven-sided star gear shown in the center, and it's advanced by the wheel to its left with a single finger. That wheel rotates once a day, and once a day rotates the star gear by 1/7th of a rotation, advancing a day wheel that shows the day of the week on the face of the watch.
Meanwhile in this implementation, the finger in the lower left will connect with the spurs on the date wheel around the edge. As it completes its rotation, it will advance the date wheel just like the date wheel does.
This particular implementation has a couple of interesting tweaks. The date cam is in a groove, so as it rotates around it also extends out a bit to better engage the spur. It also keeps the two wheels (day star wheel, and date wheel) in place with springs, that aid in limiting the movement to once a day when engaged by their respective cams.
In 2003, Chopard was granted a patent on a clever system for adjusting a balance wheel on a watch.
The most common ways of adjusting a balance wheel are a bit clunky. There are weights held on by pins. Screws that can be moved in and out, or removed entirely. Monochrome has a great article about this. All of these are to adjust the balance wheel's moment of inertia.
Think of the balance wheel like a figure skater. The skater takes a big push off, and starts spinning. At this point, the skater has some energy in the spin that is not going to increase. But, if the skater brings their arms closer to their body, they will spin faster. That's because by doing this they are reducing their moment of inertia - the energy it takes to spin - and spinner faster with the same amount of energy in the spin.
Similarly, the balance wheel is always getting a set amount of energy from the watch's power train. So to adjust its oscillation, you need to vary the balance wheel's moment of inertia.
Enter the Chopard patent. It discloses small u-shaped weights that slot into holes in the outer rim of the balance wheel. By turning the weight at particular angles, you can adjust whether there is more weight toward the outside of the balance wheel (extending the skater's arms and increasing the moment of inertia) or closer to the center of the balance wheel (bringing the skater's arms in).
In a seeming rare case for this site, we can actually see that this patent is in use in a current Chopard watch.
This is one of those patent's that is so simple and obvious that I was a little surprised not to have seen it before. I think this could be useful on watches with a million little complications, but then the question becomes where do you put the function indicator?
In this patent, the crown is connected to an indicator dial on the face of the watch. When the crown is pulled out to its first position, a finger engaged with the sleeve of the crown pulls a rack attached to the function dial. This rack and pinion connects the function dial on the face to the crown.
One thing this doesn't account for is indicating how to turn the crown to adjust it when a given position on the crown controls two functions on the watch. I admit that every time I grab a day-date or a GMT watch with a date function I almost always rotate the crown the wrong way to adjust it first. As a result, my GMT watches are perpetually on some random timezone that I don't care a wick about.
In the 1970s, Certina had a problem. There were already watches that were sealed and at low pressure to minimize oxidation of the gears and lubricating oils, but they were less accurate than other watches. Moreover, they were impossible to adjust while they were still sealed.
So, Certina sought a way to adjust a fully sealed watch. And this is what they came up with.
Certina put two bimetallic strips on either side of a regulation point, when heated, the bi-metaltic strips would push on the regulation point, adjusting the speed of oscillation.
You may be familiar with bimetallic strips from older-style thermostats. They are exactly what they sound like. A strip of two metals, joined together. Because they are not the same, the metals expand differently when heat is applied, and the metal curves. For a thermostat, it typically has a mercury switch on one side, so when it bends too much in one direction (or unbends) it will turn the heater on or off.
Similarly here, these two bimetallic strips are able to be heated from the outside of the case, and then bend to adjust the oscillation of the movement and make a more accurate timekeeping device.
You probably don't think too often that you need slightly different moon phase mechanisms for a watch in the northern hemisphere compared to the southern. In fact, all you need is for the moon phase wheel, the wheel that has the moon on it, to rotate in the opposite direction: right to left on most watches.
In most watches, this would just be a matter of adding a gear, or assembling the mechanism differently. But what, Breguet asks, what do you do for someone who travels from the northern hemisphere to the southern, or vice versa?
Well, for that world traveler, who only wants to bring one watch with them, Breguet has an answer: a moon phase mechanism with counterrotating wheels, two heart cams, and a selection mechanism to engage one or the other.
This is an interesting patent in that it may do fewer new things than any other modern patent we've featured here. It's basically two moon phases, with a selector between them. The heart cams allow the selection lever to engage one wheel or the other.
Like many of the patents here, this one is unlikely to see manufacture. It's not a really meaningful improvement on the existing mechanisms, and has incredibly limited real world use.
This is a delightfully over the top patent. Granted in December, 2017, this patent describes an adjustable mechanical snooze function on a watch with an alarm.
I say this is over the top because watches with alarms are rare enough. It seems unlikely that anyone would actually manufacture one with a snooze feature (prove me wrong if they exist already), let alone an adjustable snooze.
The mechanism by which the snooze is achieved is pretty straight froward. There's a rack and cam (pictured above). The angle of the rack determines the duration of the snooze, and the cam has multiple points where it can set the angle of the cam.
This is really one of those patents that would make an absurdly high-end watch. Would I use this if I had it on a watch? Of course I would. Would I ever buy one? I cannot imagine a world where I would.
Here's the thing with moon phase complications: they're popular, they're mechanically simple, and they're very bad at accurately displaying anything other than full and crescent moons.
The way most work is to have a semicircular opening with a smaller semicircle, or occulation disk on either end of the semicircle. As the moon emerges over left side, it starts as a tight crescent, and slowly grows to a full moon, before waxing. But the middle areas between the full moon and crescents are poor representations of the moon. If you check your moon phase at a half moon, it will look like a moon cookie with a bite taken out of it more than a half moon.
Enter Audemars. Their stated goal with this patent was to create a complication that did not add substantially to the complexity of the movement, while providing a more accurate representation of the moon at any given phase. What they've come up with is a really clever mechanism that was patented in the United States on July 30, 2013.
They maintain a few staples of more common moon phase complications. As shown in the patent, it keeps the semicircular opening for the complication, a moon disk with two moons opposed at 180 degrees from one another, and the traditional rotation rate of 29.5 days per half-turn. That is where the similarities end.
Instead of having semicircular occulation disks, the patented complication has two rotatable occulation disks that look vaguely like those three winged boomerangs. The disks can be calibrated to provide more accurate occulation of the moon at particular parts of its orbit. As the moon disk rotates it engages gears that move the occulation disks, typically in one quick movement, like with a date change.
In the end, this is a very interesting, but very high end complication. It adds a lot of pieces to what is typically a simple and inexpensive addition to a watch. I would really love to see this make its way into a watch, either by AP or licensed by someone else.
In late November, 2016, Rolex was granted a patent for a complication that would serve a similar purpose to a chronograph, but with fewer parts, thereby making it more reliable, smaller, and lighter than traditional mechanical chronograph movements.
The basic premise is to have a your normal hour, minute, and second hands (shown as a small seconds in the patent drawings), and then "stored" hours, minutes, and seconds hands. Both sets move in sync until you freeze the "stored" time hands. Then, instead of having a readout of how much time has elapsed as with a typical chronograph, you simply have a display of when you stopped the clock.
Two heart cams then serve to resynchronize the seconds with seconds, and hours and minutes with the actual time. Heart cams are routinely used to zero out chronographs, so they have a long history in watchmaking.
I feel that it's unlikely this makes it into a Rolex watch. (The discussion of why you patent something if you're never going to sell it is for another day.) It's not clear where it would fit in their line, and it seems like most people would correctly view it as a cheaper, less convenient version of a chronograph. It's easy to read elapsed time. It's harder to do watch-math -- It's 8:37 now and I stopped the watch at 7:18. . . It's an hour and nineteen minutes, but it took you longer to get there than looking at a chronograph.
One thing that's notable about this patent is that it relates to a new complication, rather than improvements in materials or reliability to existing components. It's a little out of the ordinary for Rolex.
We don't plan to cover much of Rolex's materials patent portfolio here. It's not because it's not interesting; it really is. It's just that ceramic chemistry and metallurgy aren't as easily understood by the typical watch nerd as a bunch of gears and some simple drawings. And, if I'm being honest, aren't as easily understood by me either. When we do cover them, it's more likely going to be a "what does this mean," rather than getting too far into the "how."
This recently issued Rolex patent is a decent example.
The abstract reads:
Watch component made of a persistent phosphorescent ceramic composite material which is a sintered dense body comprising two or more phases, a first phase consisting of at least one metal oxide and a second phase consisting of a metal oxide containing at least one activating element in a reduced oxidation state, the watch component having a surface which comprises an area which shows phosphorescent emission and an area which does not show phosphorescent emission or which shows phosphorescent emission with an intensity which is lower than that of the emission of the other area.
The patent covers a ceramic element of a watch that is either partially phosphorescent, or has elements that have different phosphorescent properties. Like hour indices that look like one piece in day light, but only the tips glow. Or a solid ceramic bezel where indices on the bezel are luminescent. It's potentially pretty cool.
These patents are dense. Like fruitcake dense. Flourless chocolate cake dense. While most mechanical watch patents are pretty brief, and explain the relevant gearing and positions in relation to other gears in the train, these patents go into great detail (see the image) above regarding how the ceramic was manufactured, and which temperatures and concentrations of metals provided what results. It's good technique for getting a broad patent, but it's not easy for me to post a picture of ceramic crystals and have the implications of that be apparent for watch fans.
All of which isn't to say we will never cover them, but my feeling is that these will be of less general interest to readers than a day-night complication where the moon also displays the moon phase.
From time to time we will revisit some much older patents. They show us some ideas that either never caught on, or did but have since been improved upon or gone out of style.
This Benrus patent was issued in 1952 and expired in 1969.
This patent disclosed a simpler way to adjust watch bracelets. The bracelet features a traditional tri-fold clasp, but also allows quick adjustment to make the bracelet tighter or looser. An internal spring bar and several notches allow the user to easily adjust the fit of the bracelet while it is still on their arm, all invisible to the user.
The patent suggests that on hot days you may want a little more room in the bracelet, or to quickly push it up your arm while washing your hands.
It's a clever idea, though I don't know that it was ever mass produced. And certainly the spring bar would loose resilience over time and the bracelet would begin to slip, which is a major downside.
Meanwhile, we have seen some quick fine adjust mechanisms on bracelet clasps lately, but none that I'm aware of that let you adjust the fit while it's on your arm.