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Tuesday, 13 November 2018 20:21

Zenith's 1921 Patent on a Winding/Setting Stem

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. 

Published in Patents
Wednesday, 07 November 2018 18:01

Tudor's Two-Way Adjustable Bracelet

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. 

Published in Patents
Thursday, 01 November 2018 20:58

Hamilton's 1930s Antimagnetic Escape Wheel

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.

 

 

Published in Patents
Thursday, 18 October 2018 16:37

Chopard's Clever Balance Wheel Adjustment

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.

Published in Patents

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.

Published in Patents