A horological instrument includes an oscillator assembly and a hairspring. The hairspring is fastened at one end to the oscillator assembly and is anchored to the frame or bridge at its opposite end. A regulator includes two spaced apart arms having slots which surround the hairspring. The regulator is designed to impart a positive isochronism characteristic to the hairspring in order to permit synchronizing of the balance wheel motor. The frequency of balance oscillation is thus made dependent on amplitude of oscillation.
A one-piece regulator key for watch movements includes two spaced apart prongs projecting from and integral with a common support, each prong has an inward plane surface facing and substantially parallel to a like inward plane surface on the other prong and is provided at its free end with an inwardly projecting protuberance for decreasing the spacing between the prongs at their free ends.
A precision regulating device for the regulator pointer of a timepiece includes a balance cock and an index regulator mounted on the balance cock such that the index regulator is pivotable about a regulator axis. A hairspring key arranged on the index regulator at a radial distance from the regulator axis allows changing the active length of a hairspring of the oscillating system of the timepiece in response to pivoting of the index regulator. The index regulator also includes a radially directed regulator pointer. A counterpressure spring including a resilient arm has one end region fastened on the balance cock and another free end region arranged so that it forces the regulator pointer, under prestressing, in the pivoting direction and holds it in abutment against a regulating screw arranged in a rotatable manner in a threaded bore of the balance cock or a component connected to the balance cock. The resilient arm has a holding-down region which can be positioned on an axial side of the regulator pointer relative to the regulator axis.
A mechanical timepiece movement has a mainspring serving as a power source, a wheel train rotated by a rotational force produced by the mainspring for driving a display, and an escapement and speed control apparatus for controlling rotation of the wheel train and having a balance with hairspring, an escape wheel and pinion and a pallet fork. A stud holder is rotatably mounted with respect to a central axis of the balance with hairspring and a hairspring holder is attached to the stud holder to undergo movement in a direction orthogonal to the central axis of the balance with hairspring. A hairspring has a central portion fixed to the balance with hairspring and an outer portion fixed to the hairspring holder. The hairspring is adjustable by pivoting the hairspring holder.
