Remontoir d’Égalité, a constant force mechanism
For the first time in a wristwatch, Andreas Strehler offers a mechanical solution which filters nearly all technical and mechanical factors impeding the escapement.
The constant and linear supply of energy to the balance is ideal in watchmaking. It is the basis for precision.
To achieve this aim and to get at the same time a solid basis for future complications, Andreas Strehler was looking for a solution to completely uncouple the escapement from the gear train.
To do this would ensure that the escapement is not influenced by what is happening upstream, i.e. in the gear train.The intended device should be of compact dimensions, guarantee a permanent (i.e. long-lasting) constant amplitude. Further, the solution to be found should be a universal one; this means it ideally should work independently of the frequency of the escapement. This would enable Andreas Strehler to use the device on any future movement he would be designing.
The mechanism functions in the following way:
One tooth of the star shaped satellite wheel rests against the stopping jewel. This blocks the satellite arm. This satellite arm in its centre sits on the pinion of the seconds wheel and is thus linked via the gear train to the mainspring barrel and kept under tension. Hence, the stopping jewel keeps the satellite wheel and the satellite arm from moving clockwise and consequently the whole gear train from running down. The seconds wheel is not riveted to its pinion (the second pinion) but rotates independently. The seconds wheel is linked to the hairspring of the intermediary winding mechanism and actuated by a tube in its centre. On the other side, the seconds wheel is checked by the escapement. Hence, the seconds wheel continuously rotates clockwise, once per minute. In doing so, it moves the stopping lever fixed to the top of the tube by 6 degrees per second, also clockwise. Before the hairspring of the intermediary winding mechanism has lost too much energy, the stopping lever with its stopping jewel has moved far enough in a clockwise direction so that the stopping jew-el releases the star wheel.
The star wheel now starts to turn anticlockwise, powered by the satellite arm.
Once the star wheel has caught up with the stopping lever – and therefore with the stopping jewel – it is being stopped. The star wheel has rotated anticlockwise by one tooth; the satellite arm has moved clockwise by 6 degrees and thus caught the stopping lever which had hurried ahead in small increments of 6 degrees.
Now the cycle starts again, offset clockwise by 6 degrees and one tooth of the star wheel: The seconds wheel again moves the stopping lever by 6 degrees, the star wheel is being released, turns by one tooth and, moved by its satellite arm, again catches up with the stopping lever.
This movement of the stopping lever has re-tensioned the hairspring and resupplied the seconds wheel with energy.
The energy supplied to the seconds wheel thus only depends on the hairspring in the intermediary winding mechanism. This is being retensioned in the course of each second by the satellite arm. It is therefore for all practical purposes independent from the power delivered by the barrel.
The force of the star wheel on the stopping jewel is at a right angle to the axis of the mechanism. Thus, fluctuations in the driving power have no effect on the tension of the hairspring.