Video animation by Bob Tascione
Incabloc Shock Absorber System
Prior to the arrival of floating jewel shock absorbers such as the Incabloc Shock absorbing system shown in the above animation most balance hole and cap jewels were press fit into settings. These settings were then inserted into the plate and balance cock and held rigidly in place with screws so that no movement or buffer was present between staff pivot and hole or cap jewel. A significant impact delivered to a watch case would send a wave of energy through the movement passing into the sensitive escapement. Lacking any capability for the jewels to ‘give’ a little a strong enough jolt could easily damage one or both of the delicate balance staff pivots as well as the balance jewels.
The transition from the somewhat protected pocket watch to the exposed, much more vulnerable Wrist Watch caused concern for watch manufacturers leading to a large number of clever anti shock designs. Some companies developed their own proprietary designs which they used regularly. Most of these devices are now obsolete giving way to a group of popular systems.
Today only a handful from this group of anti-shock systems are being used with Incabloc and KIF leading the way.
These floating jewel bearing devices function by allowing the balance to move a little if a sudden shock takes place. The balance jewels sit in a precisely machined bushing which in turn sets loosely in the bearing block. The bushing accepts first the hole jewel and then the cap jewel which is kept at a fixed distance from the face of the hole jewel by means of a ledge machined in the upper portion of the bushing – see diagram. When at rest the bushing and jewels are held in position by the tension of a lyre shaped anti-shock spring which is fitted above them. When a shock occurs the bushing can move in any direction and if its limit of travel is reached the dimensions between balance staff and block – labeled ‘Setting’ in the above diagram – are such that impact between the staff and block occur on the shank of the staff rather than the delicate pivot and the jewel transferring the remainder of the impact energy into the stronger much larger shank sections of the staff – labeled “Shock or Impact Surfaces” in the above diagram. After this action the bushing with its jewels is immediately returned to its original position by the spring as shown in the animation above.
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