The invention comprises an improved hairspring arrangement having a hairspring fixed in a groove of the hub in such a way that the hairspring protrudes from the groove, and furthermore, the protruding part of the hairspring should carry the electric conductor. The basic conception of the invention makes it possible to fix the hairspring, which has the customary shape of an upright standing metal strip, to the hub in the usual way. Normally one of the front surfaces of the hub is equipped with a straight or ring-shaped notch which reaches to the peripheral area of the hub and into which the inner end of the hairspring is inserted and then is fastened in the hub by deforming the notch-rims. Up to now the chosen depth of the notch was at least equal to the height of the metal strip forming the hairspring. According to the present invention, however, the height of the upright standing and hairspring-forming metal band is chosen larger than the depth of the notch arranged on one of the front surfaces of the hub, so that one longitudinal edge of the hairspring protrudes from the hub. If the electric conductor is then arranged on this longitudinal edge of the hairspring--naturally by inter positioning of an insulation layer, e.g. an insulating adhesive--then only the actual hairspring is contacted by the hub, but not the electric conductor carried by the hairspring.
A method for manufacturing a balance-spring for a clockwork movement wherein a spring is formed by winding, from a wire or metal strip, said spring including an inner end intended to be fixed to a balance and a outer end zone intended to be fixed to the balance-spring stud and wherein the whole spring is subjected to a first heat treatment subsequent to the winding step of said wire. The method of the invention is characterized in that it further includes an additional step consisting in subjecting at least said outer end zone to a second heat treatment. This method improves in particular the shock resistance of the balance-spring.
The anti-trip device is for a detent escapement mounted on a wristwatch. It includes a finger fixed to the arm of the balance, two columns between which the finger can pass, said columns being secured to the balance bridge, and a locking arm fixed to the outer coil of the balance spring, said locking arm being able to be inserted between said columns and said finger to prevent the balance from rotating beyond an angle exceeding its normal operating angle. The locking arm is a clamp hooked onto the outer coil of the balance spring.
