Method for adjusting the oscillation frequency of a sprung balance assembly

Patent metadata

Field	Value
Publication number	US-9690260-B2
Application number	US-201214239965-A
Country	US
Kind code	B2
Filing date	Sep 5, 2012
Priority date	Sep 5, 2011
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

A method adjusting oscillation frequency of a sprung balance assembly formed at random from balance springs and balance wheels. A production mechanism is set to limit a sample standard deviation of a single batch of balance springs to a predetermined maximum value, and to limit a sample standard deviation of a single batch of balance wheels to a predetermined maximum value within a given unbalance tolerance. The mean of the balance population is classified according to the mean of the balance springs, to obtain a difference corresponding to a maximum inertia decrease value of the balances, between extreme gaussian distribution values of balances and of balance springs. A random balance spring sample is taken from the single batch of balance springs and a random balance from among the single batch of balances. The inertia of the balance is adjusted according to a torque value of the balance spring sample.

First claim

The invention claimed is:

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.

2. The method according to claim 1 , wherein said inertia adjustment operation comprises carrying out:
a complementary machining operation to adjust the inertia of said balance, as a function of the torque, measured earlier, of said balance spring sample, simultaneously or in series with the machining when the unbalance of said sample is greater than the given unbalance tolerance,
so as to form a sprung balance assembly oscillating at said oscillation frequency after said inertia adjustment operation.

3. The method according to claim 2 , wherein the volume of material to be removed from each machining area is calculated and the flow of material is distributed over a sufficient surface area to respect predefined minimum sections in the various areas of said balance.

4. The method according to claim 2 , wherein the volume of material to be removed from each machining area is calculated so as not to exceed a certain predefined mass flow relative to the total mass of said balance, and the flow of material on the surfaces is distributed sufficiently far away from the pivot axis of said balance to attain the inertia value calculated for said balance.

5. The method according to claim 2 , wherein, after the final inertia adjustment of said balance to form a sprung balance assembly with said oscillation frequency, according to the measured torque of said balance spring, said balance spring and said balance are driven onto each other up to a mark.

6. The method according to claim 1 , wherein the difference corresponding to an allowable decrease in inertia for each balance is limited to said maximum unbalance tolerance value.

7. The method according to claim 1 , wherein the machining includes a material-removal machining process that is carried out on said balance for a first implementation without poising, and further includes, after measuring the unbalance of said balance and calculating the machining definition, a machining operation to poise and set the inertia a second time to a value calculated so that said sprung balance assembly oscillates at said oscillation frequency.

8. The method according to claim 7 , wherein the material-removal machining operation is performed on said balance by reserving certain first surfaces of said balance for said material-removal machining process, and reserving certain second surfaces of said balance for said machining operation.

9. The method according to claim 8 , wherein said first surfaces are determined as being distinct from said second surfaces of said balance.

10. The method according to claim 8 , wherein said first surfaces and said second surfaces of said balance are defined by at least prohibiting any machining in certain third areas of said balance reserved for areas of reduction or for receiving unbalance inertia blocks or additional components.

11. The method according to claim 8 , wherein said first surfaces and said second surfaces of said balance are defined by at least prohibiting any machining on the arms of said balance.

12. The method according to claim 8 , wherein at least said first inertia setting machining operation is performed symmetrically relative to the pivot axis of said balance.

13. The method according to claim 1 , wherein said unbalance adjustment machining operation is performed symmetrically relative to a plane passing through the pivot axis of said balance and in proximity to said plane.

14. The method according to claim 1 , wherein a primary elementary frequency amplitude is defined, corresponding to a reference relative period variation, and a tolerance is attributed to:
said balance spring population as regards said balance spring torque in a first amplitude such that said first amplitude is a multiple by a first factor of said primary amplitude,
said balance population as regards the inertia of said balances in a second amplitude such that said second amplitude is a multiple by a second factor of said primary amplitude,
the second range of distribution of the relative period variations of which said balances are capable extending beyond the first range of distribution of relative period variations of which the balance springs are capable, with, between said second range and said first range, a difference which is a multiple by a third factor of said primary amplitude, and, between the balance and the balance spring theoretically the furthest apart as regards the category of relative period variation thereof, a difference which is a multiple by a factor of said primary amplitude.

15. The method according to claim 14 , wherein said fourth factor is defined to be close to double the value of said first factor, which is in turn close to double the value of said second factor, which is close to four times the value of said third factor.

16. The method according to claim 14 , wherein said third factor is defined with a value of two.

Assignees

• Verardo Marco
• Graf Emmanuel
• Barthoulot Philippe
• Giusto Nicola
• Vorpe Sacha
• Nivarox Far Sa

Inventors

• Verardo Marco
• Graf Emmanuel
• Barthoulot Philippe
• Giusto Nicola
• Vorpe Sacha

Classifications

• Y10T29/49581

  having arbor, pinion, or balance · CPC title

• G04D7/1292 Primary

  whereby the adjustment device works on the balance wheel · CPC title

• G04B18/006

  by adjusting the devices fixed on the balance (construction of the pendulum G04B17/063; balancing G04B17/28) · CPC title

• G04B17/06

  Oscillators with hairsprings, e.g. balance {(electrically driven balances G04C3/04; contacts actuated by a balance G04C13/065)} · CPC title

• G04D7/085 Primary

  by removing material from the balance wheel itself · CPC title