In developing our new crown two general weak points of screw-lock type crowns were taken into account:
Many crowns that decouple while screwing often become defective after only a short time. This is partly due to the positive-fit coupling or connection elements usually only having a hexagon bolt with 1mm width across flats for the positive fit for space reasons, as well as due to the materials used, such as brass, German silver or soft, unhardened stainless steel. As a consequence, the outer edges of the hexagon bolt become chamfered very rapidly and the watch movement can no longer be wound, or the hands can no longer be set, as the required form-fit no longer exists in the crown. Watch Manufacturers often resort to using inferior coupling crowns which no longer disengage – during the screwing down onto the crown shaft the movement has be wound along with it.
The second approach focuses on the materials used since the crowns are usually made of the same stainless steel as the case, and thus are relatively soft. Through possible canting or incorrect positioning of the crown body onto the shaft during the screwing, the beginning of the thread of the shaft or crown body, or under certain circumstances the threads as a whole, can very easily be destroyed, making a new screwing, which is important for the tightness of the watch, no longer possible.
Our company developed a crown which decouples from the crown tube during screwing, i.e. the crown body separates from the setting stem and can be gently screwed onto the crown shaft without the movement having to be wound up. An adequate dimensioning of the internal mechanics and choosing the right materials enabled us to offer a crown with unprecedented longevity.
In our newly developed crown mechanics a hexagon bolt with a width across flats of 2mm for the positive fit in coupling and decoupling is employed. Since our crowns and the mechanics contained therein as well as our case are hardened to approximately 60 HRC, we expect a hitherto unattained longevity for these crowns. The use of Viton gaskets (a material that is many times more chemically resistant than nitrile for example) in the crown shaft and on the plane surface in the crown body also contributes to this.
Of course our crown shaft as well as our pushers are equipped with the lubricant cell patented by our company, which ensures a soft gliding of the crown setting stem and the pushers and reduces the amount of consequent friction to a minimum and tending close to zero.
The crown tube is screwed into the case by means of a special key in the case, and thus not pressed in as other manufacturers do. A Viton gasket between case and tube ensures the required degree of sealing.
Our newly developed crown is legally protected and patented.