Hairspring for clock movement

Abstract

The invention relates to a spiral spring (2) formed from a spiral strip of a determined length for a watch movement, at least a portion of the strip being provided with a scale (40) comprising a plurality of graduations each of which corresponds to a fraction of time of an advance or a delay of the watch movement.

Description

Technical field of the invention

[0001] The present invention relates to a spiral spring for a watch movement. Technological background

[0002] In all that follows, by convention, the term "component" will be used to designate a spare part forming part of the device for pinning and adjusting the active length of a spiral spring according to the invention, and the term "part" will be used to designate an assembly of two or more "components".

[0003] In a mechanically-moved timepiece, the regulating organ is the balance-spring assembly in conjunction with the escapement. These various elements are set in motion by the mechanical energy supplied by a barrel spring and carry out the counting and division of time into seconds. It is therefore understood that the precision of the time indication provided by the mechanically-moved timepiece depends on the precision of the adjustment of the operation of the balance-spring assembly and the escapement.

[0004] A first known technique for ensuring the precision of the operation of a balance-spring assembly is to equip the balance with a plurality of weights, for example, fixed in an adjustable manner on the rim of the balance. By adjusting the position of these weights, the inertia of the balance is influenced, which has the effect of modifying the pivoting frequency of this balance-spring assembly.

[0005] Another known technique for ensuring the accuracy of the operation of a balance-spring assembly consists of equipping this balance-spring assembly with an index assembly comprising at least one index and an index key which is carried by the index and which is provided with a slot through which the hairspring passes. The index key can be pivoted on itself, while the index can be pivoted around the pivot axis of the balance-spring assembly, on a bearing of a bridge, or around a shock-absorbing bearing.

[0006] The portion of the spiral spring that extends from the racket key to the center of that spiral spring defined by the free end of the last coil inside that spiral spring determines the active length of the spiral spring.

[0007] The portion of the spiral spring that extends between a stud on which the free end of the last coil outside the spiral spring is fixed and the racket key is considered mechanically rigid and does not participate in the oscillations of the balance wheel.

[0008] The position of the racket key defines a so-called counting point. The position of this counting point can be changed by pivoting the racket. By changing the position of the counting point, the useful length of the balance spring and therefore the beat frequency of the balance-spring assembly are changed. By pivoting the racket key on itself, the travel of the balance spring is limited inside the slot made in this racket key, taking care not to completely block this balance spring of course. This has the effect of improving the precision of the adjustment of the beat frequency of the balance-spring assembly and therefore the rate precision of this assembly.

[0009] As will be understood from the above, in a certain number of mechanical movements for timepieces, equipping a balance-spring assembly with means for adjusting its frequency requires a significant number of components (stud for studding the free end of the last coil outside the balance spring, possibly a stud holder, index, index tail and eccentric screw for fine adjustment of the position of the index, index key), which is expensive and requires a fairly long adjustment time in order to precisely adjust the pivoting frequency. The other solution consisting of adjusting the inertia of the balance by means of adjustment screws is even more expensive in terms of machining operations and adjustment time of the pivoting frequency of the balance-spring assembly. Summary of the invention

[0010] The present invention aims to overcome the drawbacks mentioned above and others by proposing a spiral spring for an improved watch movement.

[0011] To this end, the present invention relates to a spiral spring formed from a spiral strip of a determined length for a watch movement, at least a portion of the strip being provided with a scale comprising a plurality of graduations, each of which corresponds to a fraction of time of an advance or a delay of the watch movement.

[0012] According to another embodiment of the invention, the scale comprises graduations which each represent 0.1 s. Brief description of the figures

[0013] Other special embodiments and advantages of the present invention will emerge more clearly from the following detailed description of an embodiment of a device for pinning and adjusting the active length of a spiral spring using a spiral spring according to the invention, this example being given purely for illustrative and non-limiting purposes only, in conjunction with the appended drawing in which: there figure 1 is a top view of the device for pinning and adjusting the active length of a spiral spring for a watch movement according to the invention; figure 2 is a sectional view along section line II-II of the figure 1 ; there figure 3 is a perspective view of a particular embodiment of the terminal curve of a spiral spring according to the invention; figure 4is a perspective view from below showing the arrangement between the push button of the device according to the invention and the spiral spring of the figure 3 ; there Figure 5 is a schematic representation of the device according to the invention fixed to a bridge of the watch movement by means of a screw. Detailed description of the invention

[0014] The present invention relates to a device which consists of combining in a single piece at least some of the functions relating to a spiral spring intended to ensure the isochronous beats of a balance of a balance-spring assembly of a watch movement. The device firstly comprises a push button arranged so as to immobilize a spiral spring of a watch movement at a point along its length without it being necessary to use glue. From this, it follows that the watch manufacturer enjoys complete freedom in terms of the choice of material from which the spiral spring is made and that, in addition, given that the spiral spring is not glued, the device can be dismantled at any time, for example when returning the timepiece to the factory. Consequently, the device already allows, initially, the repositionable pinning of the spiral spring.Furthermore, by using a push button, the spiral spring can be immobilized at any point along its length, which allows the active length of this spiral spring to be adjusted, i.e. the distance between the point where the spiral spring is immobilized by the push button and the free end of the first coil inside this spiral spring. The device therefore also allows the pivoting frequency of the balance-spring assembly equipped with the device to be adjusted at will. Finally, in one embodiment, the device is equipped with a push-button holder which allows it to be fixedly mounted, for example, on a bridge of the watch movement, or else to be pivotally mounted on a support such as a balance bridge or a bearing carried by this bridge.In this embodiment, the device thus fulfills four distinct functions: the repositionable stud of the balance spring, the mounting of the stud holder on its support, the adjustment of the active length of this same balance spring, and the adjustment of the balance reference. The device, consisting of a single part formed, in a simplified variant, of a tube, a button and an elastic member, therefore advantageously replaces the assembly of components such as stud, stud holder, index, index key, index tail and eccentric, which makes it possible to reduce the number of components necessary for fixing the balance spring and for adjusting the pivoting frequency of the balance-spring assembly, and facilitates the assembly of the device in the watch movement due to its reduced size. Another advantage of this device lies in the fact that it eliminates the need for glue.

[0015] Designated as a whole by the general numerical reference 1, the device is shown in top view at figure 1 , and in section along line II-II of the figure 1 to the figure 2 .

[0016] In a simplified form of execution, the device 1 allows the winding of a spiral spring 2 for a watch movement, as well as the adjustment of an active length of this spiral spring 2.

[0017] The spiral spring 2, arranged in turns, has a determined length between a free end of a first turn on the inside and a free end of a last turn on the outside 3. By way of example only, the spiral spring 2 can be shaped as a flat strip delimited by first and second faces which extend parallel to and at a distance from each other.

[0018] More precisely, the device 1 makes it possible to immobilize, advantageously in a removable manner as described below, the spiral spring 2 at any point along its length, and to adjust the length which separates a point 4 where this spiral spring 2 is immobilized from the free end of the first turn inside this same spiral spring 2.

[0019] For this purpose, the device 1 firstly comprises a push button 6 arranged to releasably hold the spiral spring 2 at a location along the length of the band of this spiral spring 2.

[0020] As visible on the figure 2 , the push button 6 essentially comprises a button 8 and a tube 10 in which the button 8 is able to slide. Advantageously, the button 8 is elastically returned to a rest position by an elastic member 12 of the spring or elastic blade type (see, in particular, the figure 1 ).

[0021] The button 8 is, in a service position, kept away from its rest position by interposition of a portion of the spiral spring 2 between the button 8 and the tube 10, which ensures the mechanical immobilization of the spiral spring 2.

[0022] It is easily understood that the spiral spring 2 can be released at any time from its grip with the push button 6. To do this, it is sufficient to exert pressure on the button 8 that counteracts the return force of the elastic member 12 in order to make it come out further from the tube 10. On the other hand, it is understood that by an appropriate choice of the stiffness coefficient of the elastic member 12, it is possible to precisely control the pinching force that is exerted on the spiral spring 2 when the latter is held stationary between the button 8 and the tube 10 of the push button 6. Consequently, the risks of breaking the spiral spring 2, in particular when it is made of silicon, are limited.

[0023] We see on the figure 2 that the button 8 extends between a head 14 and a foot 16 in which a groove 18 is formed which goes at least partially around the foot 16. Consequently, the spiral spring 2 is passed around the foot 16 of the button 8 in its portion where it is desired that it be immobilized by the push button 6 by pinching between the foot 16 of the button 8 and the opposite end of the tube 10. The spiral spring 2 is thus pinched between the foot 16 of the button 8 and the opposite end of the tube 10 at two points, which allows the push button 6 to transmit a holding torque to the spiral spring 2 so that this spiral spring 2 does not slip or rotate around its fixing point during the life of the timepiece.

[0024] According to a simplified form illustrated in the Figure 5 , the device 1 and its push button 6 are simply fixed on a bridge 20 of a plate of the watch movement, typically by means of a screw 21.

[0025] According to another form, the device 1 for the pitonnage and the adjustment of the active length of the spiral spring 2 further comprises a push-button holder 22 which carries the push-button 6, as well as a balance 24 forming part of a balance-spiral assembly 26. The push-button holder 22 is arranged to be able to pivot about a pivot axis. D of the balance-spring assembly 26 of the watch movement.

[0026] For this purpose, the pusher holder 22 is provided with an opening 28 whose inner diameter is adjusted to the outer diameter of the pivot axis. D of the balance-spring assembly 26. The device 1 thus advantageously fulfills both the function of stud and stud holder.

[0027] As shown in the figures 1 And 2, the balance-spring assembly 26 is preferably pivoted in a shock-absorbing bearing 30 conventionally comprising a setting 32, a holed jewel 34, a counter-pivot jewel 36 and a spring 38.

[0028] According to the invention, the spiral spring 2 comprises, on at least a portion of the spiral band forming this spiral spring 2, a scale 40, each graduation of which represents, for example, a variation of 0.1 s as is visible on the Figures 3 and 4. To adjust the active length of the spiral spring 2, it is sufficient to press the button 8 of the push-button 6 to momentarily release the spiral spring 2, then to pivot the balance 24 by the desired angle to correct a known advance or delay. For example, if the watch movement advances by 1 second per day, the balance-spring assembly 26 is moved to induce a delay by passing 10 graduations of 0.1 s in front of an index 42. Then the pressure on the button 8 of the push-button 6 is released to once again immobilize the spiral spring 2. The pivoting of the balance 24 will also cause the displacement of the marker which can then be realigned by rotating the device 1 which is composed of the push-button 6 and the push-holder 22 carrying the push-button 6. It will of course be understood that this operation is not possible in the case of the simplified embodiment of the invention illustrated in Figure 5. It will also be noted that by push button we mean an assembly formed of a cylinder and a tube inside which the cylinder is able to slide against the elastic restoring force of a spring. It will also be noted that, as already mentioned above, the immobilization of the spiral spring 2 is done at two points located for one on the terminal curve and the other in the region where the scale can be provided. Nomenclature

[0029] 1. Device 2. Spiral spring 3. Last coil on the outside 4. Point 6. Push button 8. Button 10. Tube 12. Elastic member 14. Head 16. Foot 18. Groove 21. Screw 22. Push button holder 24. Balance wheel D . Pivot axis 26. Balance-spring assembly 28. Opening 30. Shock-absorbing bearing 32. Chaton 34. Jewel with hole 36. Counter-pivot jewel 38. Spring 40. Scale 42. Index

Claims

1. Spiral spring (2) formed from a spiral strip of a determined length for a watch movement, at least a portion of the strip being provided with a scale (40) comprising a plurality of graduations each of which corresponds to a fraction of time of an advance or a delay of the watch movement.

2. Spiral spring (2) according to claim 1, characterized in that the scale (40) includes graduations which each represent 0.1 s.

Images