FR2767205A1 - Measuring balance wheel amplitude on mechanical watch - Google Patents

Abstract

A light source and photoelectric cell (10,12) detect the movement of the balance wheel arms (3',3'') and this data is used to determine the amplitude and other parameters. The time between the first and fourth escapement clicks is measured by a microphone (8,9) and the corresponding balance wheel angle is calculated. Subsequently the same escapement time measurement enables the then current amplitude to be checked.

Description

METHOD FOR MEASURING PARAMETERS OF A WATCH
MECHANICAL AND DEVICE FOR ITS IMPLEMENTATION
The present invention relates to a method for measuring certain parameters of a mechanical watch, more particularly the angle traveled by its sprung balance between two shocks of the exhaust, in order to allow an accurate measurement of its amplitude. The invention also relates to a device for implementing this method.

Numerous devices and methods are known for measuring parameters of the mechanical watch and in particular methods in which the amplitude is defined by an optical measurement of the movement of the sprung balance, also referred to simply as a pendulum. After the walk,
Amplitude is the most significant and interesting parameter. His knowledge can interpret a number of defects and take action to address them. An amplitude that is too small or too strong may, in fact, affect the accuracy of the watch when it is in a vertical position, whereas amplitude fluctuations over time may show defects in the gear train or the spring barrel. Finally, a loss of amplitude in the medium term can be interpreted as an indicator of oil aging.

A device for measuring the amplitude of the pendulum by an optical analysis of its movement is described in communication No. 18 of the 52nd Congress of the Swiss Chronometry Society (1977) under the title of "LE
MICROFONTOCINQ: Apparatus for measuring and calculating both the gait and amplitude of movements of spring-balance watches. "In order for the measurement to be carried out with this device, the rocker must be visible and have two streaks inscribed on its serge. The device comprises an electro-optical system with a light source which sends a ray to the serge The shape of the streaks is such that when one of them reflects the light beam, it is directed towards a photocell. The information relating in particular to the amplitude is obtained by calculation from the time elapsed between two successive pulses collected by the photocell As the measurement can only be made if the pendulum is visible, this solution is not not usable with a nested watch.

There is also known a method, described in patent CH 596,600, which makes it possible to measure the amplitude of the balance when the case of the watch is closed. The device includes an electroacoustic measuring system that collects and analyzes the noise generated by the escapement when it gives a pulse to the pendulum. To obtain the amplitude of the balance on the basis of this signal, it is necessary to introduce a value corresponding substantially to its lifting angle. This angle is likened to the angle traveled by the balance between the first and fourth shock of the exhaust. It should first be noted that the lifting angle is known only approximately for a given size and that it can vary from one room to another. In addition, the angle traveled by the balance between the first and fourth shocks does not exactly match the lifting angle. The information obtained by means of the device described in the patent cited above therefore allow only interpretations on the basis of comparisons, but the measured amplitude can in no case be considered as a significant quantitative measure.

One of the aims of the present invention is to define precisely the angle traveled by the balance between two shocks of the exhaust in a given watch, to then allow, at a different place and at a different time, a precise measurement. amplitude of the balance by analyzing the noise emitted by the exhaust.

More specifically, the invention relates to a method for measuring the angle traveled by the balance of a mechanical watch between two shocks of its exhaust, characterized in that it comprises the following operations: measuring the amplitude of the pendulum by analysis of his movement at
means of a radiation sent by a source in the form of a beam
in the direction of said balance, a part of the latter modifying
momentarily the path of the radiation, - measurement of the time that the pendulum takes to traverse the said angle by a
analyzing the sounds emitted by the escapement during said shocks, and then determining said angle by calculation, on the basis of the amplitude and
measured time.

Another object of the invention is to allow accurate measurement of the amplitude of a beam, for a given piece, even nested, from the angle traveled by said balance between two shocks of the exhaust. For this purpose, the method is characterized in that it comprises the steps of measuring the time elapsed between two shocks of the escapement and then calculating the amplitude from said previously measured angle.

The invention also relates to a device for implementing the method of measuring the angle traveled by the balance between two shocks of the exhaust. It comprises, in combination: - a support intended to receive a watch movement to be measured, - a measurement unit which comprises a radiation source, a sensor of said radiation and an electronic circuit for processing the signal coming from said sensor, - a unit electroacoustic device associated with said support, comprising a microphone and an electronic circuit for processing the signal coming from the microphone, and - a computing unit processing the signals from said circuits and programmed so that it calculates at least the amplitude of the balance on the base signal from said sensor, that it measures a time, between two shocks of
The escape, based on the signal from said microphone, and that it establishes a correlation between the measured time and the amplitude of the balance, thus defining an angle traveled by the balance between the two shocks.

The device according to the invention, for the implementation of the method for defining the amplitude of the balance, is characterized in that it comprises a device for entering and memorizing the value of the angle traveled by the balance between two shocks of the escapement, an electroacoustic device for measuring the time between these two shocks and a calculation unit for calculating the amplitude of the balance from said angle and said time.

The correlation thus established between the information coming from the unit of measurement, preferably electro-optical, and from the electroacoustic unit makes it possible to have an accurate value of the amplitude of the balance, even if the box is closed. It suffices for this to memorize the angle traveled by the balance between the two noises, this parameter does not vary in time, and then calculate the amplitude by analyzing the noise of the exhaust.

The invention will be better understood on reading the description which follows, given with reference to the appended drawings in which:
- Figure 1 shows schematically a device according to the invention;
FIG. 2 shows at "a" the sinusoid of the movement of the balance, with the indication of the significant moments, and in "b" the appearance of the signals generated by the electro-optical unit and their interpretation;
- Figure 3 shows in "a" the sinusoid of the movement of the balance and in "b" an image of the signals obtained at the terminals of the microphone;
- Figure 4 shows the exhaust in the five positions in which constituent parts collide and generate a shock; and
- Figure 5 illustrates the procedure applied by the calculation unit to determine the angle traveled by the balance between two shocks of the exhaust.

The device shown in Figure 1 comprises a support 1 for stably positioning a clockwork movement 2 whose base is a plate 2 '. The movement has a balance-spring 3, which is provided with two arms 3 'and 3 "and an exhaust (not shown) .The support 1 comprises four pins 7, at least two of which are movable laterally, to grip the movement 2 thanks to a mechanism well known to those skilled in the art.

The device further comprises an electroacoustic unit 4, an electro-optical unit 5 and a computing unit 6. The electroacoustic unit 4 comprises a microphone 8 and an electronic circuit 9. The electro-optical unit 5 comprises a light source 10, a cell 12 and an electronic circuit 13. The computing unit 6, schematically represented in the drawing, is constituted by a computer. It comprises input and output information means, such as electrical connections, a keyboard and a screen, which have not been represented in the drawing. The microphone 8 is acoustically connected to at least one of the pins 7 for capturing the sounds generated by the shocks of the constituents of the escapement during the impulse given to the pendulum. The signals from the microphone 8 are applied to the electronic circuit 9 which shapes them and calculates the time between two signals that it identifies. The operation of this circuit will be discussed in more detail with reference to Figure 3.

The support 1 also carries the light source 10 emitting a light beam schematically represented by the mixed line 11 and the photocell 12 used to capture the beam 11. This is emitted towards the watch movement 2, in the The space occupied by the balance 3. The cell 12 is electrically connected to the electronic circuit 13 which transforms the analog signal from the cell 12 into a binary signal. The calculation unit 6 is connected to the circuits 9 and 13, and processes the signals that they generate to calculate, according to a procedure that will be described below, the operation of the watch, the amplitude of the balance and a angle traveled by the latter between two shocks of the exhaust.

Figure 2 has two parts, identified by the letters "a" and "b". On the part "a", one can see the sinusoid representing schematically in abscissa the elongation of the balance 3 during its oscillation and the time t in ordinate. It is clear that when considering the amplitude of a pendulum, this curve is not known. Part "b" represents the signal from the electronic circuit 13. On part "a" of FIG. 2, the following symbol is used:
: Amplitude of the pendulum
: Extend the balance
ss: Angle in degrees during which a balance arm hides the
Ray of light
Angle in degrees during which the light ray is not hidden.

In the example of FIG. 2, the amplitude c of the balance 3 is 250 and the angle D is equal to 30. As the balance 3 comprises two arms, the angle Y is equal to 1500. These values are Illustrative data and to better understand the invention will be defined by the calculation unit 6 by analyzing the signals from the electronic circuit 13, as will be described later.

In an instant, the pendulum 3 passes through its equilibrium position. It moves in a rotational movement whose direction corresponds to that of the needles of a watch. The position of the arms 3 'and 3 "is such that they do not cut the light beam 11. The latter is reflected by the underlying plate 2', towards the photocell 12. The signal from the circuit 13 is at the logic 1. It can be noted that the orientation of the arms 3 'and 3 "is any.

In an instant t1, the elongation of the rocker 3 is 50 ° C. The ray 11 is cut by the arm 3 'and is thus deflected from the photocell 12.

The signal from the circuit 13 goes from level 1 to level 0 and remains there until an elongation of 80, at a time t2. The spoke 11 is then no longer cut by the arm 3 '. It is reflected by the plate 2 'to the cell 12.

When the elongation # of the balance 3 reaches 230, at a time t3, it is the arm 3 "which cuts the light beam Il and deflects it from the cell 12. The signal then goes back to level 0.

At 250, at a time t, the balance 3 has reached its maximum elongation Q> o, corresponding to the amplitude of the balance. He then returns to his point of equilibrium, in a movement whose meaning is this time counterclockwise. The spoke 11 is deflected from the cell 12 by the arm 3 "until the balance 3 has reached an extension of 230 again at a time t5, and the signal then goes from level 0 to level 1.

When the elongation # of the balance 3 reaches 80, at a time t6, the arm 3 'again cuts the radius 11 and deflects it from the cell 12. The signal passes from level 1 to level 0 and this until the balance 3 reaches, at a time t7, an elongation O of 50.

At one point you, the balance 3 goes into neutral. It continues its course up to an elongation of 100, at a time tg, where the arm 3 "intersects the radius 11 and deflects it from the cell 12, which makes the level 1 signal go to the level 0. II remains until a time t10, for an elongation O of 1300. The radius is then no longer deflected by the arm 3 ", the signal passes from level 0 to level 1. The balance 3 continues its oscillation until its elongation maximum o, in a moment t11. The balance 3 returns in a clockwise motion.

In an instant t12, the elongation O is equal to 1300. The spoke 11 is then cut by the arm 3 "and deflected from the cell 12. The signal again passes from level 1 to level 0. It remains there until a moment t13, corresponding to an elongation of 100. The balance 3 ends its oscillation until reaching the dead point at a time t14
The balance 3 has thus made a complete oscillation in a period whose duration T is equal to t14 - to. When we examine the "b" part of Figure 2, we see that the signals have a symmetrical structure with respect to the instants t4 and tu 1.

The curve shown in FIG. 3 in "a" illustrates the sinusoidal movement of the balance while the portion "b" presents the signal coming from the microphone 8 corresponding to the shocks between the constituents of the escapement. This signal is applied to the input terminals of the electronic circuit 9 which analyzes it and shapes it. This figure will be commented parallel to the description of Figure 4 which shows an exhaust in the five different positions occupied by its components, during shocks generating noise of the watch, commonly called the "ticking".

 The exhaust shown in Figure 4 is anchor type. It comprises a wheel 16 provided with teeth 17 at its periphery, an anchor 18 with pallets 19 and 20 and a fork 21 with two horns 22 and 23 defining an opening 24, a peg 25 integral with the balance 3 and two stops 26 and 27 integral with the plate 2 'of the watch and limiting the movement of the anchor. Each pallet 19 and 20 includes a rest plane 19a and 20a and a pulse plane 19b and 20b. When the exhaust is at rest, the tooth 17a bears against the rest plane 20a of the pallet 20. The shapes of the tooth 17a and of the pallet 20 are such that the torque applied by the wheel 17 to the anchor 18 keeps it in abutment against the stop 27.

In Figure 4, the shocks are schematically represented by broken arrows. In the position shown at "a", the pin 25 has penetrated into the opening 24 and comes into contact with the blank of the horn 23. This results in a first shock, generating a noise picked up by the microphone 8. The signal It generates is identified by the indication "shock 1" on the part "b" of Figure 3.

The electric signal generated by this shock is shaped by the circuit 9 and sent to the calculation unit 6.

Under the effect of the shock, the anchor 18 pivots and the pallet 20 recoils the tooth 17a.

The motor torque drives the wheel 17 which rotates clockwise.

The end of the tooth 17a comes into contact with the pulse plane 20b of the pallet 20 and generates a second shock. The electrical signal from the microphone 8 is not taken into account by the circuit 9. The position of the exhaust relative to this shock is illustrated in "b" in FIG. 4. Under the effect of the engine torque, L Anchor 18 is driven not by the rocker pin 25, but by the wheel 17. The anchor 18 then begins its driving function, the horn 23 coming into contact with the pin 25 and generates a third shock. This occurs directly after the second and the signal it generates is weaker. As a result, it is substantially flooded in the damping of the noise of the second shock. The signal from the microphone 8 is not identified as interesting by the circuit 9. The position of the exhaust at the moment of the third shock is represented at "c" in FIG.

When the tooth 17a of the escape wheel has traveled the pulse plane 20b of the pallet 20 over its entire length, the anchor 18 continues its movement in synchronism with the balance 3 until it hits the stop 28 and generates a fourth shock. The electrical signal from the microphone 8 is shaped by the circuit 9 and sent to the calculation unit 6. This position is represented at "d" in FIG. 4.

Finally, the tooth 17b comes into contact with the rest plane 19a of the pallet 19.

 This results in a fifth shock whose noise immediately follows that generated by the fourth shock. It follows that it is difficult to identify by the electronic circuit 9. This noise is not taken into account by the electronic circuit. The position corresponding to the fifth shock is represented in "e" in FIG.

The balance 3 can then continue its oscillation freely. The first and fourth shocks having generated signals at the output of the electronic circuit 9, the computing unit 6 can then define instants ta and td respectively corresponding to the first and fourth shocks.

Note by the symbol 6 the angle traveled by the balance 3 between the first and fourth shocks. More precisely, the rocker 3 travels the angle 6 from the moment when the pin 25 comes into contact with one of the horns 22 or 23 and the moment when the tooth 17b comes into contact with the rest plane 19a of the pallet 19. In other words, the beginning of this angle 6 corresponds to the first shock, the position of the various constituents of the exhaust being represented in FIG. 4a. The end of this angle corresponds to the fourth shock, the position of the various components of the exhaust being shown in Figure 4d. The time elapsing between the first and the fourth shock is equal to the difference between the instants td and ta.

The mathematical bases used by the calculation unit 6 to determine the angle 6 will now be specified with reference to FIG. 5, the left part of which presents the processing of the data supplied by the electro-optical unit, while its right part describes the processing of data from the electroacoustic unit.

To define the amplitude of the balance 3, we start by analyzing the information from the electrooptical device 5 This corresponds to the operation I of Figure 5. It is assumed that the oscillation movement of the balance is sinusoidal. Given the great freedom of oscillation and the small amount of energy supplied to the pendulum at each impulse, this hypothesis can be considered as realistic and has little effect on the precision of the measurement. Under these conditions, the amplitude of the pendulum can be expressed by the formula: O (ti csinoe (trto) (1)
The symbolic used in this formula is the same as that used in Figure 2. In addition, where is the pulsation of the pendulum. As has been seen above, the device according to the invention has recorded the values of the instants tj.

All other values are unknown. In this formula, two parameters are interesting, the pulsation co and the amplitude o. The pulse o is connected to the period T of the pendulum by the formula:
T = 2nlo (2)
As noted previously, there are points of symmetry in the signal reading from the circuit 13. These are the instants t4 and t11, on the sinusoid shown on the part "a" of Figure 2. These points of symmetry correspond to the moments for which the balance has reached its maximum elongation. The time that elapses between these two instants is therefore equal to half a period T / 2. The time t4 is not for itself identifiable in the signals of the part "a" of FIG. 2. However, because of the symmetrical structure of the signals, it is found that the instant t can be expressed by the formula
t4 = (tr + t7) / 2 (3)
This operation is denoted by the reference II in FIG. 5. The procedure is the same to obtain the instant titi.

Applying then formula (2), we obtain the period T of the balance by the operation III.

To know the running of the watch, we then compare the period T with a period To, corresponding to a perfect walk of the watch. The watches are generally arranged so that a second hand performs an integer number of jumps between two seconds index. As a result, the frequency (equal to the inverse of the period) is a semi-integer, the needle jumping at each half-period. In watches, this number is generally equal to 2.5, 3, 4 or 5. To can therefore be defined by the unit of calculation as the inverse of the semi-integer number closest to 1, T. This operation is represented in IV in FIG.

The step M of the watch, expressed in seconds per day can then be calculated, during the operation V, from the following formula:
M [s / j] = 86'400. (To-T) / TB (4)
The computation of the amplitude of the balance is then carried out considering that the arms which it comprises are in a finite number, in general 2, 3 or 4, distributed symmetrically. In the example given, the balance has 2 arms.

If we look at Figure 2, we can see that the balance has made a shift of 1800 between instants t1 and t3. This is so for all the successive instants generating a rise, respectively a descent, of the signal from the circuit 13 between two maximum elongations. This observation can be expressed by the following formula:
P (ta = (t3) + 1800 (5)
If the pendulum had three arms, the angle would then be 1200.

Assuming that to is zero and combining the formulas (1) and (5), we find: # 0 sin # (t1-t0) = 180 + # 0 sin # (t3-t0) (6)
By developing this formula, we obtain:
# 0 = 180 / (sin # t1 - sin # t3) (7)
On the basis of this formula, the calculation unit can define the amplitude of the balance by the operation VI of FIG.

The processing of the data from the electroacoustic unit 4 is illustrated on the right half of FIG. 5. As explained above, the electroacoustic unit 4 sends to the calculation unit 6 the values of the instants ta and td via the electronic circuit 9. This operation is designated by the reference VII.

On the basis of the information obtained after the operations VI and VII, it is then possible to calculate the angle 8 by the operation VIII.

As has been shown with reference to FIG. 4, the angle 6 traveled by the balance between the first and fourth sounds of the escapement can be considered constant. This angle can be defined as follows: # = #d - # a 8)
In this formula, d and a respectively correspond to the elongation of the balance 3 when it is in the positions illustrated in Figure 4, in "d" and "a". From formula (1) and assuming that to is equal to zero, we can ask:
6 = t0 (sin Otd -sin (Dta) (9) It is thus possible to calculate the angle 6 on the basis of the formula (9), all the terms of the right part being known.

This value 6 can then be stored either in written form, for example on the manufacturing sheet of the movement, or by introduction into a computer, for example the one serving as a computing unit, by identifying the movement that takes place therein. reports by number.

Alternatively, the light source 10 and the photocell 12 could be replaced by an ultrasonic source and an acoustic sensor respectively.

In another variant, it would be possible to work with other exhaust noise than the first and fourth.

To measure the amplitude of the balance when the watch is nested, using a device comparable to that of Figure 1, but which has no electro-optical unit. In this case, the magnitude c can be calculated from the following formula: # 0 = # / (sin # (td - t0) - sin # (ta - t0)) (10)
In this formula, 6 is the value of the angle defined above and which has been memorized. The instants td and ta are measured by the device. To get cDo, it is still necessary to know you.

As a first approximation, one could consider that the moment to is in the middle of the interval ta - td. This is not the case, however, unless the watch is perfectly at the mark. On the other hand, it can be seen in FIG. 3 that, for two successive pulses, n and n + 1, the instants td (n) and ta (n + 1), on the one hand, and the instants ta (n) and td (n + 1), on the other hand, correspond to equal values of the pendulum elongation. In other words, these moments are distributed symmetrically with respect to the moment when the balance reaches its maximum elongation. We can therefore say that 2 (to + T / 4) = ta (n + 1) - td (n) = td (n + 1) - ta (n) (11)
The period T is equal to the time that elapses between two instants corresponding to the same shock, for example the first, for the same direction of rotation of the balance, or between two pulses of the same parity. This can be expressed by the following formula:
T = td (n + 2) - td (n) = ta (n + 2) - ta (n) (12)
All the terms of the right-hand side of equation (10) are thus definable by the calculation unit 6. This can therefore calculate the value of the left-hand term, ie the amplitude of the balance.
By applying the procedure defined in FIG. 5 by the calculation unit, it is then possible to precisely define the angle traveled by the pendulum. As can be seen in this figure, the computing unit analyzes, on the one hand, the information coming from the electro-optical unit in order to define the amplitude of the pendulum and, on the other hand, the information coming from the electroacoustic unit, by measuring the elapsed time between the first and fourth noises. From these two pieces of information, the computing unit determines the angle 8 traveled by the balance between the two shocks, on the basis of the formula (9).

As has been shown above, it is possible, thanks to the measurement of the angle 8 traveled by a balance between two sounds of the exhaust to measure the amplitude of the pendulum of a watch accurately, even when the box is closed. The means to be implemented are limited and can be easily used in the companies, for the management of the stocks or the ser

Claims (10)

1. Method for measuring the angle traveled by the pendulum of a watch  between two shocks of its exhaust, characterized in that  includes the operations:  measuring the amplitude of the pendulum by an analysis of its  movement by means of radiation sent from a source under  beam shape towards said beam, part of the latter  temporarily modifying the path of said radiation,  measuring the time the pendulum has to traverse the said angle by a  analysis of the sounds emitted by the exhaust during said shocks,  - then determining said angle by calculation, on the basis of said  amplitude and said time. 2. Method according to claim 1, characterized in that said source of  radiation emits a beam of light. 3. Method according to claim 2, characterized in that said source of  radiation emits light in the infrared. 4. Method for measuring the amplitude of the balance of a mechanical watch  provided with an exhaust, characterized in that it comprises the operations  measuring the time elapsed between two shocks from the exhaust and then  calculating said amplitude from said time and angle, previously  measured, traversed by the pendulum between said shocks. 5. Method according to one of claims 1 to 4, applied to a watch  provided with an anchor escapement, characterized in that said shocks are  the first and fourth shocks of the exhaust. 6. Device for implementing the method according to one of the  Claims 1 to 3, characterized in that it comprises, in combination:  a support intended to receive a watch movement to be measured,  - a unit of measure that includes a source of radiation, a  said radiation sensor and an electronic circuit for processing the  signal from said sensor,  an electroacoustic unit associated with said support, comprising a  microphone and an electronic circuit for processing the signal from the  microphone, and  a computing unit processing the signals from said circuits and  programmed so that it calculates at least the amplitude of the  pendulum on the basis of the signal from said sensor, that it measures a  time, between two shocks of the exhaust, based on the signal from  said microphone and establish a correlation between time  measured and the amplitude of the pendulum, thus defining an angle traveled  by the pendulum between the two shocks. 7. Device according to claim 6, characterized in that said unit of  measurement is of the electro-optical type. 8. Device according to one of claims 6 and 7, characterized in that  the calculation unit is programmed to calculate the  of the watch. 9. Device for carrying out the process of claim 4,  characterized in that it comprises an input and storage device  of the value of said angle, an electroacoustic device for measuring the  time between said shocks and a calculation unit for calculating the amplitude  balance from said angle and said time. 10.Device according to claim 9, characterized in that the device  input and storage is arranged in such a way as to be able to  memorize an identification number of the watch to be analyzed.