CH706913B1 - A spring-balance regulating device for a mechanical watch and a method of thermal stabilization of such a regulating device. - Google Patents

Abstract

The invention relates to a spiral balance-adjusting device for a mechanical watch, this regulating device comprising a balance (1) associated with a spiral spring (10), the axis (2) on which is mounted the balance (1) being pivoted between a plate and a cock (14), the spiral spring (10), formed of a plurality of concentric blades (24), having a curve inside (8) which is rigidly fixed on the axis (2). ) of the balance (1), and a last outer turn (16) which is fixed rigidly directly or indirectly to the cock (14) at a point of stud (18), characterized in that the regulating device is without racket and in that a portion of the last outer turn (16) of the hairspring (10) preceding the pinning point (18) is twisted helically, the pitch (P) of the twisting being between 0.5 and 10 times the height of the blades (24). The invention also relates to a method of thermal stabilization of such a regulating device.

Description

Technical area

The present invention relates to a regulating member for a mechanical watch of the type comprising a balance associated with a spiral spring. More precisely, the present invention relates to a regulating member in which the spiral spring, formed of a plurality of concentric turns, has a first inner free end which is rigidly fixed on an axis of the balance pivoted between a plate and a cock, and a second outer free end which is rigidly fixed directly or indirectly at an attachment point on the rooster.

In particular, the present invention relates to a regulating member of the type mentioned above in which the hairspring has an active length defined and stable over time, in particular in the event of shocks.

Technological background

[0003] The quality of a regulating member of the spring balance type for a mechanical watch lies in its ability to produce isochronous oscillations. To tend towards this operating ideal, each element making up the regulating organ must be optimized to withstand on the one hand external factors such as connection with the escapement, temperature variations or even mechanical shocks to which the regulating organ is subjected. , and on the other hand to resist wear due to time.

[0004] To compensate for or reduce the influence of these various parameters on the isochronism of the regulating organ, many solutions have already been proposed in the prior art.

[0005] By way of example, patent CH 327 796 describes a flat hairspring intended for use in a regulating system comprising a racket and of which an area of the inner curve and an area of the outer curve of the hairspring each have a section line different from the section of the rest of the hairspring. These zones of different sections are thus rigidified and allow the hairspring to develop concentrically. This decreases, or even eliminates, the lateral pressure exerted by the axis of the balance on its pivots during the contraction and expansion of the hairspring. The stiffened zone of the outer curve is located at least partly before the racket pins, starting from the center of the hairspring. Conventionally, the last turn also has a deformation in a radial direction which forms a step, also arranged before the racket pins. The purpose of this terminal curve is to separate the end part of the last turn of the preceding turn and thus to facilitate the fixing of the hairspring on the peak. In an exemplary embodiment, the stiffness of the section of said zones of the inner curve and of the outer curve is obtained from the normal profile of the blade by bending over an angle of approximately 70 °. This folding does not modify the counting point of the hairspring which is conventionally defined by the racket pins. However, the deformed areas of the hairspring have the drawback of tending to resume their initial shape before deformation in the event of an impact.

[0006] Patent EP 1,612,626 attempts to remedy the problems posed by the aging of the glue which is usually used to fix the last turn of the hairspring of the hairspring of a regulating system with a racket to the peak. To this end, patent EP 1 612 626 teaches to twist at 90 ° a portion of the last turn of the hairspring between the racket pins and the eyebolt in order to define a fixed count point in the twisted zone. The hairspring also includes a step obtained by deformation of the last turn and located before the racket pins. However, this document does not specify the pitch of the spiral helix to define the counting point with certainty and precision. This is understandable as the count point is primarily defined by the racquet pins. In fact, the active length of the hairspring which cooperates with the racket pins is defined by these pins during the 90% of the time that an oscillation of the balance lasts and where the hairspring blade is resting against one or the other of the balance. pins during the alternating cycles of expansion and contraction of the balance spring. As in the case of patent CH 327 796, the deformation by folding of the blade of the hairspring remains sensitive to shocks, the latter having the consequence of modifying the geometry of the bent zones of the hairspring by bringing them closer to their geometry before bending. Thus, in the event of an impact, the portion of the terminal curve may tend to approach its initial geometry, in which case this portion of the last turn may come into contact with the peak at rest, so that the active length of the balance spring is modified. The same goes for the twist which, following an impact, can be modified, which leads the hairspring to appear flat. In both cases, the chronometric properties of the regulating system are altered.

[0007] To reinforce the impact resistance of the deformed zones of the hairspring, patent EP 0 911 707 A1 proposes to heat treat these areas of the hairspring in order to stabilize them.

Summary of the invention

[0008] The present invention therefore aims to overcome the drawbacks of the aforementioned prior art by providing a regulating device for a mechanical watch of the sprung-balance type without a racket which has a geometry of the hairspring determined precisely in order to guarantee the stability of the hairspring. in time.

[0009] The invention also aims to provide a regulating device for a mechanical watch of the spring balance type, the active length of which does not undergo any modification over time, even in the event of an impact.

[0010] The invention also aims to provide a method of thermal stabilization of an improved regulating device to enhance the impact stability of said regulating device.

[0011] The aim of the invention is also to provide a thermal process for stabilizing a regulating device which is reliable and easy to implement.

[0012] To this end, the invention relates to an adjusting device for a mechanical watch, this adjusting device comprising a balance associated with a spiral spring, the axis on which the balance is mounted being pivoted between a plate and a cock, the spiral spring, formed of a plurality of concentric turns, having an inside curve which is rigidly fixed to the axis of the balance, and an end curve which is rigidly fixed directly or indirectly to the cock at a point of 'attachment, characterized in that the regulating device is without snowshoe and in that a portion of the end curve of the balance spring preceding the attachment point is helically twisted, the twist pitch being between 0.5 and 10 times the height of the turns.

[0013] According to a first embodiment, the end of the terminal curve is twisted at an angle substantially equal to 90 °, so as to bring said end of the terminal curve into a plane perpendicular to the height of the turns, preferably in the extension of the median axis of the turns.

[0014] By recommending a geometry of the hairspring which favors high plastic deformations to the detriment of areas with low plastic deformations such as low radial deformation of the last outer turn of the hairspring, the stability of the hairspring is guaranteed over time. When the fixing is carried out for example by gluing in the slot of a stud attached to the cock or of a stud holder, it will be observed that the twisting of the end of the terminal curve does not modify the dimensions of the blade of the balance spring. , so that no modification of the eyebolt is necessary except that the width of the slit of the eyebolt must be provided slightly greater than the height of the blade of the hairspring. Thus, the embedding point no longer depends on the way in which the glue is applied, nor on the aging of the latter, but only on the point stiffened by the twisting of the end of the hairspring.

[0015] The invention also relates to a method of heat treatment of the balance spring according to the invention. In accordance with this method, the last outer turn is locally heated in order to induce the relaxation of the residual stresses and to stabilize the geometry of the hairspring over time. We have indeed realized that, despite the care taken in the manufacture of the balance-spring, shocks applied to the balance-spring could induce a modification of the mark of the balance-spring. The term "mark" is understood to mean the difference between the durations of the two consecutive alternations of an oscillation of the regulating device.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge more clearly from the following detailed description of an embodiment of the hairspring according to the invention, this example being given for purely illustrative and non-limiting purposes only, in conjunction with the accompanying drawing in which: FIG. 1 is a perspective view partially cut away of a sprung balance regulating device provided with a hairspring according to the invention; fig. 2 is a top view of the hairspring according to the invention and of the pinning point of the end curve of the hairspring, and FIG. 3 is an enlarged perspective representation of the end of the terminal curve of the hairspring of FIG. 1.

Detailed description of the invention

The present invention proceeds from the general inventive idea which consists, in a regulating device of the sprung balance type without a racket, in helically deforming the end portion of the last turn of the hairspring so as to define a count point perfectly rigid balance spring. More specifically, the present invention teaches that the pitch of the twist must be between 0.5 and 10 times the height of the blades to ensure good definition of the count point. In fact, in the known regulating devices without a snowshoe, the pinning point which defines the active length of the hairspring is usually obtained by pinning or gluing the end portion of the last turn of the hairspring either directly or via a peg on the cock. . However, such fixing techniques, either because of slight displacements, or because of the aging of the adhesive or its crumbling, have the drawback of not guaranteeing the correct positioning of the pinning point over time, which has the effect of effect of altering the rate and isochronism of the regulating device. To remedy this problem, it has already been proposed to twist at 90 ° a portion of the last turn of the hairspring without further precision and without specifying, in particular, the value of the pitch of the helical helix. This is very understandable insofar as this proposal was made in conjunction with a sprung balance regulating device of the racket type. However, in such a case, the counting point is essentially determined by the portion of the last turn of the hairspring which is between the racket pins. Indeed, it is the racquet pins that define the active length of the hairspring and with one or the other of which the end curve is in contact during the 90% of the time that an oscillation lasts. Therefore, the twisted portion of the last turn of the hairspring has very little influence on the definition of the count point and no further efforts have been made to improve the characteristics of this count point. However, we realized that shocks applied to the hairspring could also induce an alteration of the hairspring mark. To remedy this problem, it is therefore proposed to give the hairspring a geometry which favors high plastic deformations insofar as such a geometry seems to guarantee the stability of the hairspring over time whereas, on the contrary, the balance-springs of the art front whose last turn is slightly deformed plastically tends to approach its original shape in the event of impact, which is as detrimental to the isochronism of the balance spring as to its reference mark.

[0018] FIG. 1 is a perspective view with partial cutaway of a sprung balance regulating device without a racket on which only the parts useful for understanding the invention are shown.

The regulating device comprises a balance 1 which conventionally consists of a balance axis 2 connected to a rim 4 by means of four radial arms 6 equidistant. The curve inside 8 of the hairspring 10 is fixed to the balance 1 by means of a ferrule 12 fixed to the balance shaft 2. This fixing can obviously be carried out by any other means known to those skilled in the art. . Conventionally, the axis 2 of the balance 1 is pivoted between the movement plate and the cock 14.

The last outer turn 16 is made integral with the cock 14. In the example shown, this fixing is obtained by pinning the last outer turn 16 at an attachment point 18 formed by a stud fixed in a stud holder 20, said embedding being effected by gluing. For this purpose, the eyebolt 18 comprises (see fig. 3) a groove 22, the width L of which is slightly greater than the height H of the blades 24 of the hairspring 10. A drop of glue 26 is deposited in the groove 22 to allow the immobilization of the last outer coil 16 in the piton 18.

The terminal curve 28 of the last outer turn 16 is of section H * E generally rectangular, where H is the height of the blades and E the thickness thereof. Usually, the end curve 28 of the last outer turn 16 is found in the extension of the blades 24. On the contrary, according to the present invention, the end curve 28 of the last outer turn 16 is deformed, so that the count point of the hairspring 10 is no longer defined by the peg 18, but by the hairspring 10 itself, at the place where the latter has been stiffened by deformation.

For this purpose, and as shown in FIGS. 2 and 3, to create the count point, the end curve 28 of the last outer turn 16 is helically twisted, for example a 90 ° twist can be applied to the end curve 28 of the last outer turn 16, so as to bring this terminal curve 28 into a plane perpendicular to the height H of the blades 24. The median line 30a of the blades 24 before the deformation is then located in the extension of the median line 30b of the twisted part 32. More generally, a torsion between 10 ° and 180 ° can be applied to the end curve 28 of the last outer turn 16.

[0023] Furthermore, still in accordance with the invention, the pitch P of the twist is between 0.5 and 10 times the height H of the blades. In other words, the length of the portion of the last outer turn 16 which is necessary to pass this last outer turn 16 from its position in which it extends vertically to its position in which it is found in a perpendicular plane at the height H of the blades 24 is between 0.5 and 10 times the height H of said blades 24. It has in fact been determined that this range of lengths, defined as a multiple of the height of the blades 24, made it possible to obtain optimum from the point of view of the rigidity of the counting point and therefore guarantee excellent maintenance of the isochronism over time of the sprung balance regulating device without a racket according to the invention.

The twisted portion 32 of the last outer turn 16 is connected to the previous turn 34 by a transition zone 36 forming a fold 38 extending radially outwards. The angle between the tangent to the preceding turn 34 and the transition zone 36 is called α. This angle α is between 0 and 160 °, preferably between 0 and 90 °. The length I of the transition zone 36 is between 0 and the outside diameter D of the hairspring 10 before modification of the last outer turn 16. Finally, the length d of the portion of the last outer turn 16 which leads from the twisted part 32 at peak 18 is between 0 and 10 times the height H of slats 24.

[0025] According to another aspect, the present invention relates to a method of thermal stabilization of the metering point.

[0026] During the manufacture of a watch balance spring, a very fine metal wire wound in the shape of a coil is conventionally subjected to a first heat treatment in order to fix its shape. In the past, it has already been proposed to subject the same balance spring to two successive heat treatments. Such a hairspring comprises a transition zone forming a staircase or step between the last outer coil and the coil which precedes it. The purpose of this curve opening is to separate the last outer coil from the preceding coil in order to facilitate the installation of this last outer coil between the racquet pins and to facilitate the pinning. The step, obtained by radial deformation of the last outer turn of the hairspring subsequent to the heat treatment of the hairspring as a whole, is heated locally to cause relaxation of the stresses induced by the bending. In fact, any shock to the watch can cause the hairspring to return to a shape close to its original shape which, let us remember, was frozen during the first heat treatment, which causes significant disturbances to the rate and performance. the amplitude of the balance and, consequently, a loss of its chronometric qualities. By locally heating the step, the residual stresses are relaxed and the hairspring tends less to return to its original shape.

[0027] In the prior art, we are therefore limited to the heat treatment of the step and, more generally, areas with low plastic deformation. Indeed, the step is obtained by simple radial deformation of the outer curve of the hairspring, so that the plastic deformations involved are relatively low. However, in the event of an impact, these areas with low plastic deformations tend to easily return to their original shape, hence the idea of heat treating these areas in order to cause stress relaxation.

[0028] The same does not apply in the case of the present invention where the twisting of the last outer turn 16 of the hairspring 10 to define the count point induces very high plastic deformations. Until now, no one had thought of thermally treating areas with high plastic deformations, considering that, even in the event of an impact, these areas with high plastic deformations would not tend to resume a shape close to their initial shape due to even the existence of high plastic deformations and would therefore not negatively influence the isochronism of the regulating devices.

However, the applicant, by subjecting batches of balance springs according to the invention to series of shocks, realized that these shocks had not only an influence on the geometry of the balance springs, but also significantly affected the mark of these balance springs. The term "mark" is understood to mean the difference between the durations of the two consecutive alternations of an oscillation of the regulating device. The closer the durations of the two vibrations of an oscillation, the better the quality of the balance spring. In other words, despite the presence of a twisted portion with strong plastic deformations in the end part of the last outer turn of the springs according to the invention, the shocks have a very unfavorable influence on the reference mark of the balance-sprung assemblies comprising such springs. .

On the other hand, it has always been considered that the presence of strong plastic deformations in the last outer turn 16 of the hairspring 10 considerably weakened this hairspring 10. However, in this case too, it was surprisingly found that a heat treatment of the twisted portion 32 of the hairspring 10, not only did not result in the destruction of the hairspring 10, but also allowed the relaxation of the residual stresses in the twisted part 32 so as to freeze the shape of the counting point.

These observations are confirmed by a series of tests carried out on spiral spirals and heat treated in accordance with the present invention and the details of which are given in the table below:

[0032] It will be noted that the variation of the mark of a regulating device induced by shocks varies substantially from one to two depending on whether the hairspring according to the invention is heat treated or not.

[0033] The tests were first carried out on a batch A of ten hairsprings, the last outer coil of which was twisted and then heat treated in accordance with the invention. The same tests were carried out on a batch A1 of balance springs of the same composition as the balance springs in batch A, but the last outer coil of which was twisted, but was not heat treated. The values shown in the table are average values expressed in milliseconds.

The first column marked "Entry" indicates the average value of the mark for the batch of balance springs considered upon receipt of this batch. For example, the average value of the mark upon receipt of the batch of balance springs A is 0.24 ms. The second column indicates the mean value of the mark of a batch of hairspring which has undergone the Chappuis test. By way of example, the mean value of the mark for the batch of balance springs A is 0.75 ms after the Chappuis test. The third column indicates the mean value of the mark of a batch of hairspring which has undergone an acceleration of 100 g. By way of example, the mean value of the mark of the batch of balance springs A is 0.70 ms after acceleration 100 g. The fourth column indicates the average value of the mark of a batch of hairspring which has undergone an acceleration of 500g. By way of example, the average value of the mark of the batch of balance springs A is 0.62 ms after acceleration 500 g. The fifth column indicates the average value of the mark of a batch of hairspring which has undergone rotary shocks. By way of example, the average value of the mark of the batch of balance springs A is 0.62 ms after the rotary shocks. The sixth column indicates the mean value of the mark of a batch of hairspring which has undergone an acceleration of 5000g. For example, the average value of the mark of the batch of balance springs A is 0.53 ms after acceleration 5000g. The seventh and last column indicates the average for all the hairsprings in batch A of the maximum variation in the value of the mark according to the tests undergone. Thus, the average for all ten balance springs of batch A which were heat treated of the maximum variation of the value of the mark is 0.87 ms, while the maximum variation of the value of the mark of the balance springs of batch A1 which n have not been heat treated is 1.50 ms. The amplitude of the variation of the benchmark under the effect of shocks therefore drops significantly from single to double depending on whether the balance springs have been heat treated or not. These results show two things: firstly, that the shocks have an influence on the value of the mark of the hairsprings whose curve on the outside has been twisted, but has not been heat treated; secondly, that the heat treatment makes it possible to limit the influence of shocks on the value of the mark of the balance springs by preventing the folded portions from resuming a shape close to their original shape.

According to the method of the invention, the end curve 28 is heat treated in a subsequent step of the method, after the initial heat treatment step to which is conventionally subjected the hairspring 10 in its entirety once the wire or the metal strip in which it is made has been rolled up. The metal can be a ferronickel steel, a paramagnetic steel, for example Nb-Zr, or else an antiferromagnetic steel, for example Fe-Mn-Ni-Cr.

[0036] For the subsequent heat treatment step, an energy source is used which produces an energy beam directed in a direction of energy supply. It can, for example, be a micro-torch whose flame heat is typically of the order of 2700 ° C and which briefly carries the outer curve of the balance-spring at high temperature. The microchalumeau passes close to the point where the hairspring 10 has been deformed by twisting to constitute the counting point, causing localized heating of the hairspring 10 at this point. This leads to a relaxation of the residual stresses in the twisted zone 32 and to the solidification of the shape of the counting point which tends less to cover its initial shape in the event of an impact.

It goes without saying that the present invention is not limited to the embodiment which has just been described, and that various modifications and simple variants can be envisaged without departing from the scope of the invention as defined by the appended claims. It will be understood in particular that other heat sources can be used. By way of nonlimiting example, mention may be made of laser beams, infrared beams or else induction heating devices. The heat treatment can also be done by diffusing heat into the hairspring or by the Joule effect by means of an electrical resistance. To do this, the end of the hairspring is heated and the heat travels along the hairspring. The thermal input at the end of the hairspring is done so that the thermal propagation is limited to the folded areas.

Claims (13)

1. Spiral balance adjusting device for a mechanical watch, this adjusting device comprising a balance (1) associated with a spiral spring (10), the axis (2) on which is mounted the balance (1) being pivoted between a plate and a cock (14), the spiral spring (10), formed of a plurality of concentric blades (24), having a curve inside (8) which is fixed rigidly on the axis (2) of the balance (1), and a last outer turn (16) which is fixed rigidly directly or indirectly to the cock (14) at a point of stud (18), characterized in that the regulating device is without racket and in that a part (32) of the end curve (28) of the last outer turn (16) of the hairspring (10) preceding the pegging point (18) is twisted helically, the pitch (P) of the twisting being between 0.5 and 10 times the height (H) of the blades (24). 2. A regulating device according to claim 1, characterized in that the portion (32) of the end curve (28) of the last outer turn (16) has a twist at 90 °. 3. Adjusting device according to claim 1 or 2, characterized in that the twisted portion (32) is connected to the preceding turn (34) by a transition zone (36) forming a fold (38) extending radially towards the outside, the angle (α) between the tangent to the previous turn (34) and the transition zone (36) being between 0 and 160 °, and preferably between 0 and 90 °. 4. Adjusting device according to claim 3, characterized in that the length (I) of the transition zone (36) is between 0 and the outer diameter (D) of the spiral (10) before modification of the last outer turn ( 16). 5. Device according to one of claims 1 to 4, characterized in that the length (d) of the portion of the last outer turn (16) which leads from the twisted portion (32) to the point of pitonnage (18) is between 0 and 10 times the height (H) of the blades (24). 6. Adjusting device according to one of claims 1 to 5, characterized in that the center line (30b) of the twisted portion (32) of the last outer turn (16) is in the extension of the center line (30a) blades (24) located before the deformation. 7. Adjusting device according to one of claims 1 to 6, characterized in that the section of the spiral spring (10) is identical in the twisted portion (32) and in the non-twisted portion of the spiral spring (10). 8. Adjusting device according to one of claims 1 to 7, characterized in that the spiral is made of a ferronickel steel, a paramagnetic steel or antiferromagnetic steel. 9. A method of thermal stabilization of a regulating device according to one of claims 1 to 8, characterized in that after a first heat treatment step to which is subjected the spiral (10) in its entirety once the wire or the metal strip in which it is made has been rolled up, the twisted portion (32) is locally heated in a helical manner with the last outer turn (16) of the hairspring (10) which precedes the pegging point (18) to cause a relaxation of the residual mechanical stresses in this twisted portion (32). 10. Thermal stabilization method according to claim 9, characterized in that, to heat the twisted portion (32) of the last outer turn (16), using a power source producing a beam of energy directed in one direction of energy supply. 11. Thermal stabilization method according to claim 10, characterized in that the energy source is a micro-torch, a laser beam or an infrared beam. 12. stabilization method according to claim 11, characterized in that, in the case where the energy source is a micro-torch, the flame is directed in a direction of energy supply substantially perpendicular to the plane in which s 'extends the balance-spiral regulating device. 13. Thermal stabilization method according to claim 9, characterized in that the energy source is an induction heating device or by diffusion of heat in the spiral (10), or even a heating device by Joule effect .