Method of adjusting the oscillation frequency of a timepiece sub-assembly

A method of adjusting oscillation frequency of a timepiece regulating assembly with no index assembly, formed solely of a balance and a balance spring assembly including at least one balance spring with at least one twist, to a predetermined oscillation frequency, only movable members of the regulating assembly being formed by the balance and by the balance spring assembly, the method comprising:

• taking a particular balance spring assembly from a production of toleranced products;
• measuring return torque of the particular balance spring assembly;
• taking a particular balance from a production of toleranced products;
• calculating a theoretical inertia of the particular balance at which said regulating assembly oscillates at said predetermined oscillation frequency, according to the measured return torque of the taken particular balance spring assembly;
• measuring an actual inertia of the particular balance;
• correcting inertia of the particular balance when assembled to the particular balance spring assembly, by direct action on a felloe or at least one arm of the particular balance, to the calculated theoretical inertia to obtain the predetermined oscillation frequency for the regulating assembly formed by the particular balance and by the particular balance spring assembly, wherein the inertia of the particular balance is locally corrected upwards or downwards by displacement of material of the particular balance, by local melting and displacing of a liquid phase of the material resulting from the melting;
• determining parameters for correcting inertia of the particular balance when assembled to the particular balance spring assembly, by determining an unbalance axis and an unbalance value of the particular balance and a position of an unbalance on the unbalance axis to define, on either side of a pivot axis of the particular balance:
• a first domain on a side of the unbalance;
• and
• a second domain on an opposite side to the unbalance;
• wherein the correcting the inertia of the particular balance symmetrically relative to the pivot axis of the particular balance includes creating at least one zone, each zone located in the first domain being a first zone and corresponding to a first algebraic variation of mass, each zone located in the second domain being a second zone and corresponding to a second algebraic variation of mass,
• so that:
• a difference between (a) an integrated sum of moments of inertia with respect to the unbalance axis of the second algebraic variation of mass and (b) an integrated sum of moments of inertia with respect to the unbalance axis of the first algebraic variation of mass, is equal to the unbalance value,
• and so that:
• a difference between (c) an integrated sum of moments of inertia with respect to an axis perpendicular to the unbalance axis and passing through the pivot axis of the second algebraic variation of mass and (d) an integrated sum of moments of inertia with respect to an axis perpendicular to the unbalance axis and passing through the pivot axis of the first algebraic variation of mass, is equal to zero;
• and so that:
• a sum between (e) the integrated sum of moments of inertia with respect to the unbalance axis of the second algebraic variation of mass and (f) the integrated sum of moments of inertia with respect to the unbalance axis of the first algebraic variation of mass, is equal to a difference between the actual inertia and the theoretical inertia.

A timepiece comprising:

• at least one regulating mechanism, wherein the at least one regulating mechanism is a timepiece regulating mechanism with no index assembly, formed solely of an adjusted balance and of a balance spring assembly including at least one balance spring with at least one twist, only movable members of the regulating mechanism being formed by the adjusted balance and by the balance spring assembly,
• the adjusted balance, which has zero unbalance and a theoretical inertia at which said regulating mechanism oscillates at a predetermined oscillation frequency, includes a particular balance and material of the particular balance that is melted and displaced in a liquid phase resulting from local melting, the melted and displaced material locally corrects an inertia of the particular balance upwards or downwards, and wherein, on either side of a pivot axis of the particular balance, the particular balance includes:
• a first domain on a side of an unbalance;
• and
• a second domain on an opposite side to the unbalance;
• wherein the particular balance includes zones, each zone located in the first domain being a first zone and corresponding to a first algebraic variation of mass, each zone located in the second domain being a second zone and corresponding to a second algebraic variation of mass;
• wherein a difference between:
• (a) an integrated sum of moments of inertia with respect to an axis perpendicular to an unbalance axis and passing through the pivot axis of the second algebraic variation of mass and (b) an integrated sum of moments of inertia with respect to an axis perpendicular to the unbalance axis and passing through the pivot axis of the first algebraic variation of mass, is equal to zero, and
• wherein a difference between:
• (c) an integrated sum of moments of inertia with respect to the unbalance axis of the second algebraic variation of mass and (d) an integrated sum of moments of inertia with respect to the unbalance axis of the first algebraic variation of mass, is equal to an unbalance value;
• and
• a sum between:
• (e) an integrated sum of moments of inertia with respect to the unbalance axis of the second algebraic variation of mass and (f) an integrated sum of moments of inertia with respect to the unbalance axis of the first algebraic variation of mass, is equal to a difference between an actual inertia of said particular balance and the theoretical inertia.

A method of adjusting oscillation frequency of a timepiece regulating assembly with no index assembly, formed solely of a first component being a balance and a second component being a balance spring assembly including at least one balance spring with at least one twist, to a predetermined oscillation frequency, only movable members of the regulating assembly being formed by the balance and by the balance spring assembly, the method comprising:

• without classifying the first and second components into grades, taking a particular balance spring assembly and a particular balance from a production of toleranced products;
• measuring return torque of the particular balance spring assembly;
• measuring an actual inertia of the particular balance;
• correcting inertia of the particular balance locally upwards or downwards by displacement of material of the particular balance, by local melting and displacing of a liquid phase of the material resulting from the melting;
• and
• modifying the return torque of said particular balance spring assembly by a local or total heat treatment, without removing material, at an assembled stage of the particular balance that is sprung.