Patent ID: 9690260
Date: 2017-06-27
CPC Classifications: G04B,G04D,Y10T

Claim:
1. A method for adjustment of an oscillation frequency of a timepiece sprung balance assembly formed at random from among a total output of balance springs and an output of balance wheels to obviate a need for any grading of the balance wheels and balance springs: wherein a predetermined mean value is set to produce said balance springs, and in order to limit a sample standard deviation of said output of said balance springs to a predetermined maximum value, wherein a predetermined mean value is set to produce balances, and in order to limit a sample standard deviation of said output of said balances to a predetermined maximum value and within a given unbalance tolerance for a total population of said balances, wherein: a mean of a single batch of balance springs of a given type produces a given oscillation frequency for a predetermined balance wheel inertia, each of said balance springs being finished, cut to be pinned up to a stud and ready for assembly, and forming a single population of balance springs whose sample standard deviation is peculiar to an output of said single batch of balance springs, and a mean of a single batch of balances of a given type produces a given oscillation frequency for a predetermined balance spring torque and forming a single population of balances whose sample standard deviation is peculiar to an output of said single batch of balances, the method comprising: determining manufacturing parameters for said balances and said balance springs in order to classify said mean of the population of the balances according to said mean of the population of the balance springs, so that there exists a difference corresponding to a maximum allowable value of a decrease in inertia for each said balance, between extreme values of: a gaussian distribution of theoretical frequency values for each balance as a function of said reference balance spring torque, a gaussian distribution of theoretical frequency values for each balance spring as a function of said reference inertia of the balance; taking a random balance spring sample from said single balance spring batch, and taking a random balance sample from said single batch of balances, measuring a torque value of said balance spring sample, machining said balance sample to adjust the unbalance of said balance sample to bring the unbalance within a given unbalance tolerance, and carrying out a complementary inertia adjustment operation of said balance sample taking into account the torque value of said balance spring sample, in order to form a sprung balance assembly oscillating at said oscillation frequency after said inertia adjustment operation has been performed on said balance.