Explanation of the operation
The capstone a is under pressure of the spring b. For a vertical impact this jewel can lift as far as the stop c abuts a fixed part. To damp lateral shocks the jewel is mounted in a chuck that is provided with an inclined surface d, which allows a slight shift; this is limited by the shaft stopper e, which abuts against a fixed part of the frame.
The first shock protection devices integrated into a watch movement appeared in the early 19th century. Abraham-Louis Breguet is known to have created a device called the "pare-chute" which protected the pivots of the balance from shock. It used a cone-shaped cup for the pivot which was itself mounted in a bearing on a spring. This allowed it to shift in the event of a shock but then to re-center itself after. Breguet famously demonstrated this invention by dropping his watch in front of bystanders and picking it up to show that it was still working.
Although so-called "pare-choc" anti-shock devices were widely seen in the late 19th and early 20th century, it is the 1933 invention of Incabloc by Frédéric "Fritz" Marti that brought these to the masses. Marti's company, Portescap, developed a shock proofing mechanism that could easily be adapted to any existing watch movement. These were pioneered by Election, Marti's former employer, until its 1931 bankruptcy. After this, Marti and Georges Braunschweig founded "La Porte-Echappement Universel SA" across the street from the Election factory in La Chaux-de-Fonds and began producing his innovative devices. The term "incassable" ("unbreakable") was widely used on these durable watches, so Incabloc and many other technologies included "inca" in their name.
Other companies also developed shock protection in the 1930s. Wyler's Incaflex balance, patented in 1927, had flexible arms unlike anything else on offer. Helvetia (from General Watch Co. offered mass-produced pare-choc watches by 1930 and Reconvilier Watch Co. offered pare-choc on Roskopf movements in 1932. Even Marti's own patent, which passed to the Neuchâtel bank after Election was liquidated, was offered to other companies before being sold to Doxa in 1933 and then to Zodiac in 1935. But these were integrated with specific movements and were not generally available to other manufacturers.
Portescap's success with Incabloc as a universal shock protection quickly brought competitors. Grenier Erismann-Schniz introduced Shock-Resist by 1935, which used a spiral-shaped spring. Another competitor after 1952 was Emo SA. Ernest Morf, former director of Wyler, produced Vibrax, which used a straight leaf spring and a long flexible shaft. But it was Parechoc of Le Sentier that would become Portescap's true competitor for Incabloc. Under the brand name Kif, Parechoc would be the primary alternative.
By the 1950s, anti-shock devices were a strong selling point for watches. The Kif or Incabloc logo became a key differentiator, even as over 50 different shock protection devices were available by the 1960s. But by the 1970s such devices were commonplace, with Seiko and Citizen designing their own Diashoc and Parashoc.
Today every watch includes shock protection similar in concept to Incabloc or Kif. Nivarox FAR produces Nivachoc, which is claimed to be more precise in resetting the proper positioning of the balance staff after a shock. This is used on many ETA movements, including those for Breguet and Omega. And Rolex, which had long relied on Kif anti-shock, created its own Paraflex system in 2005.