Flexure-type symmetrical oscillator

Claim 1

In a flexutre-type symmetrical oscillator for an electric timepiece comprising: a U-shaped part including two flexible limbs adapted to flex in the fashion of a tuning fork, two rigid arms serving as counterbalances for the flexible limbs, the rigid arms being connected to respective flexible limbs adjacent the free ends of the latter and projecting therefrom parallel to the limbs along the complete length thereof and beyond the closed end of the U-shpaed part to form arm and limb units in a symmetrical arrangement, each arm and limb unit having an instantaneous center of rotation during flexure and being dimensioned to define a center of gravity substantially coincident with the instantaneous center of rotation whereby the frequency of the oscillator is substantially independent of changes of position and orientation of the oscillator with respect to the field of gravity, at least one of the two rigid arms mounting in the area of its free extremity an inertia-block fitted for occupying a plurality of angular positions around an axis out of coincidence with its center of gravity, with displacement of the inertiablock about the axis producing variations of the kinetic moment of the oscillator for modifying the frequency thereof, the frequency-regulating inertia-block being constituted by a washer frictionally fitted on a trunnion carried by the rigid arm with the washer having a recess such that its center of gravity is situated outside of its axis.