The iconic Pallweber pocket watches launched in the late 19th century are one of the most significant milestones in the history of IWC Schaffhausen: instead of hands, they had a digital display that showed the hours and minutes in large numerals. To mark its 150th jubilee, the luxury watch manufacturer unveils the first wristwatches to feature a jumping-numeral display. The in-house 94200 calibre developed specially for this watch via a separate wheel train with its own barrel to advance the display discs.
In Schaffhausen, the digital age began early, back in 1884. That was the year IWC manufactured its first Pallweber pocket watches. "These were avant-garde watches and displayed the hours and minutes using large numerals on rotating discs," explains Christian Satzke, project manager for movement development with IWC Schaffhausen. A watchmaker in Salzburg, Josef Pallweber, was the inventor of the jumping-numeral timepiece. Johannes Rauschenbach-Schenk, head of IWC at the time, was captivated by the modern form of time display and secured the patent for the innovative technology behind it. During the period up to 1890, IWC made about 20,000 of these watches.
The first wristwatch with a jumping-numeral display
As part of its jubilee collection, the Company is proud to present the IWC Tribute to Pallweber Edition "150 Years" with a jumping-numeral display for the hours and minutes. The design of the watch, which is available in limited editions in platinum, 18-carat 5N gold or stainless steel, leans heavily on the historic original. The dials are painstakingly coated with up to twelve layers of high-quality lacquer and were inspired by the enamel dials featured in the original Pallweber watches. And just as back then, the windows for the digital display are inscribed with the words "Hours" and "Minutes".
The case conceals a new technical feature: "We developed a brand-new solution from scratch for the technically demanding job of moving the display discs," confides Satzke, "which we've registered for patent." In the original Pallweber movements, the display discs were advanced by cogwheels with unequally spaced teeth. When a gap between the teeth occurred, the power from the mainspring was transferred directly to the starwheel on the one-minute disc. This design, however, led to fluctuations in balance amplitude and made the movements susceptible to wear and tear. And the fact the energy required to advance the display discs was tapped from the barrel meant that the power reserve was somewhat limited.
We developed an entirely new solution from scratch for the energy-sapping job of moving the display discs.
A separate wheel train advances the display discs
The IWC-manufactured 94200 calibre, which comprises 290 individual parts and took five years to develop, now disengages the display discs from the train driving the watch. It is made possible by two separate wheel trains, each with a barrel of its own. The first of these supplies the movement with power while the second takes care of the display discs. A release mechanism connects the two barrels. Every 60 seconds, it releases the wheel train and then locks it again immediately. Compared with the original Pallweber movements, it is a distinct improvement: "The fact that advancing the display discs has practically no more influence on the flow of power to the balance means we can guarantee a precise rate and a 60-hour power reserve," says Satzke, summing up the movement's principal advantages.
The release mechanism is mounted on the third wheel, which rotates around its axis once every four minutes and is part of the watch's regular wheel train. A cam fixed to the pinion raises the release lever from one side. After every completed minute, the lever jumps up and releases the unlocking wheel connected to the wheel train of the display discs. It jumps forward and advances the one-minute disc by a single position. The procedure is repeated nine times. After the tenth switching sequence, a runner on the one-minute disc engages with the Geneva drive on the ten-minute disc and advances it. A pin located on the underside rotates with the intermediate Geneva wheel. When the ten-minute disc is on "5" and the one-minute disc on "9", the intermediate Geneva wheel advances the hour ring to the next position.
A Geneva drive makes the connection
As in the original Pallweber watches, a Geneva mechanism with an unusual geometric shape links the components. This arrangement prevents the display discs from moving out of line and keeps them perfectly synchronized. One of the advantages of the design is that the digital displays can conveniently be moved forwards and backwards using just the crown. However, it calls for the highest possible quality during production. The permissible tolerances are extremely low, and the surfaces must be absolutely flat. The shape of the Geneva mechanism was calculated using CAD and precision-adjusted until the frictional losses had been noticeably reduced. The design engineers also made significant improvements to the precision of the actual release. Advancing the discs takes just one-tenth of a second.
Switching the hour discs requires an enormous amount of energy because four wheels have to be advanced simultaneously. The components therefore need to be as light as possible. The hour ring, for instance, is made of aluminium and weighs just 0.41 grams. To prevent the relatively light metal alloy from wearing, it is specially tempered. Both barrels are wound via the same gear chain. The barrels and gear chains were designed to rotate at different speeds. "This ensures that the barrel driving the display discs always has enough energy to advance the mechanism, even when the watch's power reserve is running low," explains Satzke.
The in-house 94200 calibre disengages the display discs from the watch drive.
Clicking sounds from the watch signal the jumps
Although the Pallweber mechanism is based on an invention made 130 years ago, it has lost none of its fascination. The arrival of a new hour on the dial is a spectacular sight, 24 times a day. While a "59" in the minute window instantaneously turns into a "00", the hour likewise advances by one position. The jumps are accompanied by audible clicking sounds from within the watch. "They're a reminder that the mechanism at work is highly complex. And a mechanical digital watch without a battery is no less incredible than a watch without hands in 1884," notes Satzke.
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