Helvetia Shock Protection
Helvetia applied for a patent for their shock protection system in 1929 and used it through to the 1950s.
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Helvetia’s patent for a shock protection system for the balance of its movements was granted on October 31, 1930 (patent number 143073). Shock protection was needed as the ends of the balance staff of mechanical watches are extremely small, fractions of a millimetre in size and a sudden movement could cause one or both ends of the balance staff to break off. Before this they appear to have used a variation on the Depollier/Brun cross shaped system for several years. See my blog post on Depollier and Helvetia here.
Helvetia’s system consisted of a flat 3 legged spring held in place over the end of the balance staff cap stone by a boss. The boss had a flange around the edge which the legs of the spring slotted under to keep the spring in place. A small notch was pierced in the edge of the boss and while two legs of the spring were placed under the flange the third would be placed into the notch to allow the easy removal and replacement of the spring. Once in place the spring could be rotated to stop it coming loose. (Fig 2). This easy removal system was developed years before Incabloc's, supposedly revolutionary, removal system. You could say Incabloc stole the idea from Helvetia!
The bottom of the balance was protected by a spring in the form of a flat blade attached to the bottom plate by a screw.
Once their patent was granted Helvetia used their shock protection system on almost all of their men's watch movements from 1930 onward. They were almost the only company to do this and marketed themselves as a specialist 'Sports' watch manufacturer.
Though the basic idea of their shock protection did not change a great deal Helvetia did make numerous changes and improvements over the years of its use before completely replacing it with the Incabloc system in the early 1950s.
Below is a brief guide to the main differences introduced during the life of Helvetia’s shock protection system.
This is the first shock protection system seen in Helvetia watches. It appears to be a variation of the Depollier/Brun shock system and appear in Helvetia watches from the mid 1920s through to about 1935, mainly in their pilot watches with the caibre 51S movement. See my blog post on Depollier and Helvetia here and Helvetia Pilot's watches here.
This is the shock protection introduced in about 1930 pretty much as described in the patent document. Note the notch to help insert the three legged spring.
The main difference is the addition of a hole in the middle of the spring, this could be for decorative purposes as the patent makes mention of the spring not having too many legs covering the jewel as it has a decorative purpose as well as practical.
It looks as if there may have been issues with the spring staying fitted with only the pressure of the boss itself to keep it in place and quite quickly, by the mid 1930s at the latest, the fitting had been adapted by changing the notch for a screw to hold the boss and spring securely.
By 1940 however the design had been adapted again to give a much more secure fitting. The boss was now held in place by two screws which were tightened from below and three indentations were cut in the underside to seat the three legs of the spring (note the bottom of the screws visible protruding from the boss either side of the spring).
The spring itself was also redesigned having narrower legs and losing the central hole.
(Disassembled image by kind permission of watchguy.co.uk)
There are examples of the old screw fitting with the newer springs, these could be an intermediate step or replacement springs fitted to older movements.
The next step, in the mid 1940s was a complete redesign and simplification.
The whole assembly was replaced with a single annular spring in the shape of a circle with three tongues protruding inwards to its centre but not quite meeting.
The outside circle was then screwed directly onto the balance cock as the boss had been previously but from above. I have only seen this version fitted to a few early 1940s watches.
By the late 1940s a slightly amended version seems to have been the standard design for the 'D' variant of movements.
The last change Helvetia made before deciding to adopt Incabloc shock protection was patented in September 1952, the patent having been applied for in 1950.
This consisted of adapting their flat circular spring design by cutting a slot in it which sat above a slot in the balance cock. The balance cock also had graduations marked on it that could be seen through slot in the spring.
This enabled you to see the balance through the slot and help make accurate adjustments with the aid of the graduations.
Early calibre 830 movement introduced by Helvetia in about 1953 used Helvetia's own shock protection system but soon they were being produced with the Incabloc system instead, as did some late 800C movements and all the movements that followed.