Patent Publication Number: US-11397410-B2

Title: Device for autonomous adjustment of the active length of a balance spring

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to European Patent Application No. 17208988.0 filed on Dec. 20, 2017, the entire disclosure of which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention concerns a device for autonomous adjustment of the active length of a balance spring, for an oscillator of the balance/balance spring type. 
     The invention also concerns a timepiece movement comprising the device for autonomous adjustment of the active length of a balance spring, for an oscillator of the balance/balance spring type. 
     The invention also concerns a timepiece, particularly a watch, including the timepiece movement. 
     BACKGROUND OF THE INVENTION 
     In the field of watches provided with mechanical oscillators of the balance/balance spring type, there are known manual devices for adjusting the active length of the balance spring. 
     For example, in ordinary manual adjustment mechanisms, the outer end of the balance spring is immobilised by a stud fixed to a stud holder integral with a cock. A regulator that is movable in rotation with respect to the stud holder is provided for adjusting the active length of the balance spring, thereby allowing the frequency of the balance/balance spring to be adjusted. The regulator is a pivoting lever, generally with two arms, centred on the axis of the balance staff. A first arm of the regulator carries, for example, two pins, between which the balance spring is free. A second arm of the regulator can be actuated manually to rotate the regulator through a certain angle about the balance staff. This allows the real position of the counting point to be changed. When the regulator pivots, the active length of the spring is reduced or increased. However, one drawback of such a manual adjustment device is that terrestrial gravity affects the oscillation frequency of the balance/balance spring as a function of the orientation of the corresponding timepiece movement. Thus, the rate of the watch may have a significant deviation of rate, especially between its horizontal and vertical positions. Further, when the balance spring moves between the pins because of play between the spring and the pins, the oscillations of the balance disturb its active length and thus cause a slight variation in the oscillation frequency of the balance/balance spring assembly. 
     To limit the negative effects of gravity a solution is known, in particular from Swiss Patent No CH70560561, which implements a device for adjusting the active length of the balance spring, wherein the regulator carries clamping means intended to clamp an end portion of the spring to define its active length. The outer end of the spring is also integral with an attachment system movably mounted relative to the regulator and arranged to cooperate therewith. The clamping means, formed for example of a pin/cam clamping system wherein the end portion of the spring is clamped, can be loosened or tightened at will by a watchmaker. When the watchmaker has loosened the pin/cam clamping system, he can move the attachment system using a tool, thereby moving the spring relative to the regulator, which remains fixed, and thus relative to the pin, which allows the active length of the spring to be changed. The watchmaker can then clamp the spring against the pin by tightening up the clamping system, to place the adjustment device in the operating position again. However, this solution remains a manual adjustment solution, which has the drawback of considerably limiting adjustment precision in compensating for the effects of gravity. Further, such a solution is tedious to implement, due to the various manual adjustment steps to be performed by a watchmaker for the adjustment. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a device for adjusting the active length of a balance spring, for an oscillator of the balance/balance spring type, which makes it possible to offset, in a simple, precise and autonomous manner, the effects of gravity, particularly disturbances to the isochronism of the balance of the oscillator, and overcomes the aforementioned drawbacks of the state of the art. 
     To this end, the invention concerns a device for adjusting the active length of a balance spring, for an oscillator of the balance/balance spring type, which includes the features mentioned in the independent claim  1 . 
     Specific embodiments of the adjustment device are defined in the dependent claims  2  to  13 . 
     One advantage of the adjustment device according to the invention lies in the fact that it includes elastic stress means configured to exert on the regulator an elastic, return-to-position action, and an inertia block mounted for free rotation on the cock and connected to the pivot arm of the regulator. A rotation of the inertia block, subject to gravity, thus causes a displacement of the pivot arm of the regulator, between a position of rest and a correction position of the device, and simultaneously acts on the means for changing the active length of the balance spring, allowing the spring to be adjusted to offset disturbances to the isochronism of the balance caused by gravity. Consequently, the adjustment device according to the invention makes it possible to precisely adjust the operation of the oscillator as a function of its position in space, by offsetting disturbances to the isochronism of the balance caused by gravity, in an autonomous manner. 
     According to a preferred embodiment of the invention, the adjustment device further includes a cam driving the pivot arm of the regulator, said cam being integral with the inertia block and in contact with the pivot arm. 
     Advantageously, the cam is in contact with the pivot arm of the regulator regardless of the position of the inertia block. This makes it possible to permanently adjust the operation of the oscillator according to its position in space, and to further improve correction precision. 
     According to a particular embodiment of the invention, the elastic stress means include an elastically deformable arm, with a first end of the arm resting against a part integral with the cock and a second end of the arm being attached to the regulator. 
     Advantageously, the regulator, the pivot arm and the elastically deformable arm together form one piece. This both reduces the space required and improves the reliability of the adjustment device. 
     Advantageously, the adjustment device further includes means for adjusting the elastic stress defined by the elastic stress means. This allows a user to adjust the intensity of the elastic return action exerted on the regulator, according, for example, to the type of use desired for the watch provided with the adjustment device. 
     To this end, the invention also concerns a timepiece movement including the adjustment device described above, and which includes the features defined in the dependent claim  14 . 
     To this end, the invention also concerns a timepiece comprising the timepiece movement described above, and which includes the features mentioned in the dependent claim  15 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, advantages and features of the device for adjusting the active length of a balance spring and of a timepiece comprising the same will appear more clearly in the following description based on at least one non-limiting embodiment, illustrated by the drawings, in which: 
         FIG. 1  is a perspective view of a timepiece movement of a watch including a mechanism for adjusting the active length of the balance spring according to the invention. 
         FIG. 2  is an exploded perspective view of the adjustment device of  FIG. 1 . 
         FIG. 3  is a top view of the adjustment device of  FIG. 1  in a rest position of the device. 
         FIG. 4  is a similar view to that of  FIG. 3 , in a correction position of the device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, reference is made to a timepiece movement provided with a device for adjusting the active length of a balance spring, for an oscillator of the balance/balance spring type. The ordinary components of the timepiece movement, which are well known to those skilled in the art in this technical field, will be described only in a simplified manner or not described at all. Those skilled in the art will know how to adapt these different components and make them work together for the timepiece movement to operate. In particular, there will be no description below of anything relating to the escapement mechanism of the timepiece movement, although an escapement mechanism can advantageously cooperate with the adjustment device according to the invention. 
       FIG. 1  represents part of a timepiece  1  which includes a timepiece movement  2 . In the particular example embodiment of  FIG. 1 , timepiece movement  1  is a watch. Timepiece movement  2  includes an oscillator with a balance  4  and a balance spring  5 , and a device  6  for autonomous adjustment of the active length of balance spring  5 . In a conventional manner, balance spring  5  is attached to a staff  7  of balance  4  by its inner end (not visible). Staff  7  of balance  4  has one end pivotally mounted in a balance bar (the latter is not visible in the Figures for the sake of clarity). The outer end of balance spring  5  is attached in a conventional manner to a stud  8  fixed to a stud holder  10 , stud holder  10  being lightly clamped to a cock  12 . More precisely, stud holder  10  is pivotally mounted on cock  12  concentrically to staff  7  of balance  4 , as illustrated in  FIG. 2 . Staff  7  of balance  4  is pivotally mounted in cock  12 . 
     Adjustment device  6  is mounted on a frame  13  of timepiece movement  2  via cock  12  and includes a regulator  14 . As represented in  FIG. 2 , regulator  14  is pivotally mounted on stud holder  10  concentrically to staff  7  of balance  4 . Regulator  14  includes a pivot arm  16  and means  18  for changing the active length of balance spring  5 . 
     Means  18  for changing the active length of balance spring  5  are capable of changing the active length of balance spring  5  by pivoting regulator  14 . In the particular example embodiment illustrated in  FIG. 2 , means  18  for adjusting the active length of balance spring  5  include two pins  19  fixed to regulator  14 . Balance spring  5  is arranged such that an outer coil  21  of balance spring  5  passes between the two pins  19 . The two pins  19  act like a vice for outer coil  21  and are oriented along a plane substantially perpendicular to frame  13  of timepiece movement  2 , in other words along a substantially vertical plane when timepiece movement  2  extends in a horizontal plane. As illustrated in  FIG. 2 , the upper ends of the two pins  19  are, for example, pressed into a slot  23  arranged in regulator  14 , which allows pins  19  to be attached to regulator  14 . Lower main portions of pins  19  thus extend from a lower face  14   a  of regulator  14 , allowing outer coil  21  of balance spring  5  to be arranged between said lower main portions. In the particular example represented in  FIG. 2 , pins  19  have a substantially parallelepiped shape. However, any shape other than the parallelepiped shape could be envisaged for pins  19  within the scope of the present invention. 
     Adjustment device  6  further includes elastic stress means  20  and an inertia block  22 . In a preferred example embodiment, adjustment device  6  further includes a cam  24  for driving pivot arm  16  of regulator  14 . Preferably, adjustment device  6  may also include means  26  for adjusting the elastic stress defined by elastic stress means  20 , and shock absorption means  28 . 
     Elastic stress means  20  are configured to exert an elastic, return-to-position action on regulator  14 . More precisely, elastic stress means  20  are configured to exert on regulator  14  an elastic return action to a rest position of adjustment device  6  illustrated in  FIG. 3 . According to a particular example embodiment, elastic stress means  20  include an elastically deformable arm  30 . A first end  32   a  of arm  30  abuts against a part  34  integral with cock  12 , placing arm  30  under elastic stress. To facilitate this elastic stress arrangement, cock  12  can, for example, be provided with a support and guide rim  36  for deformable arm  30  on a lateral surface  12   a . Part  34  is, for example, formed of elastic stress adjusting means  26 , as will be described in detail below, but may, in a variant, be formed of a pin integral with cock  12 . A second end  32   b  of arm  30  is attached to regulator  14 . Preferably, as represented in  FIGS. 1 to 4 , regulator  14 , pivot arm  16  and elastically deformable arm  30  together form one piece. The one-piece part formed by regulator  14 , pivot arm  16  and elastically deformable arm  30  substantially defines a U-shape, for example, with pivot arm  16  and elastically deformable arm  30  forming the two arms of the U. 
     According to a preferred embodiment, inertia block  22  is mounted for free rotation on cock  12  and is connected to pivot arm  16  of regulator  14  such that a rotation of inertia block  22  causes a displacement of pivot arm  16  of regulator  14  and simultaneously acts on means  18  for adjusting the active length of balance spring  5 . The displacement of pivot arm  16  of regulator  14  caused by the rotation of inertia block  22 , which is itself subject to gravity, is carried out between a rest position of device  6 , illustrated in  FIG. 3 , and a correction position of device  6 , illustrated in  FIG. 4 . As illustrated in  FIGS. 1 to 4 , inertia block  22  is, for example, formed of a half-solid disc. In a variant not represented in the Figures, inertia block  22  is formed of a bimaterial solid disc, wherein the two materials of the disc have distinct densities. 
     According to another embodiment, inertia block  22  is mounted for free rotation on plate  13 . 
     In the preferred example embodiment, wherein device  6  includes a cam  24  driving pivot arm  16  of regulator  14 , cam  24  is integral with inertia block  22  and is in contact with pivot arm  16 . In a variant of this preferred example, illustrated in  FIGS. 1 to 4 , inertia block  22  is mounted for free rotation on cock  12  via an arbor  38  integral with inertia block  22 . Cam  24  is mounted on inertia block  22  concentrically to arbor  38  and is integral with arbor  38 . 
     Preferably, cam  24  is a radial cam with a shaped outer circumference. Although a radial cam  24  with a substantially rectangular outer circumference is represented in  FIGS. 1 to 4 , in practice any type of shape can be envisaged for the outer circumference of cam  24 , depending on the type of balance spring  5  used. For example, a radial cam with a triangular, oblong or oval outer circumference can also be used within the scope of the present invention. Preferably, and as represented in  FIGS. 3 and 4 , in the rest position of adjustment device  6 , a flat portion  40  of cam  24  is in contact with pivot arm  16  of regulator  14 , whereas in the correction position of device  6 , a corner or an angle  42  of cam  24  is in contact with pivot arm  16 . Also, preferably, as seen in  FIGS. 1, 3 and 4 , cam  24  is in contact with pivot arm  16  of regulator  14 , regardless of the position of inertia block  22 . 
     In the particular example embodiment illustrated in  FIGS. 1 to 4 , wherein the one-piece part formed by regulator  14 , pivot arm  16  and elastically deformable arm  30  substantially defines a U shape, cam  24  is arranged between pivot arm  16  and elastically deformable arm  30  such that cam  24  acts as support for pivot arm  16  and thus participates in subjecting elastically deformable arm  30  to elastic stress. In this particular example embodiment, support part  34  for elastically deformable arm  30  is also arranged between pivot arm  16  and elastically deformable arm  30 , in the hollow between the two arms of the U. 
     Elastic stress adjusting means  26  can serve as support part  34  for elastic deformable arm  30 . In a particular example embodiment, illustrated in  FIGS. 1 to 4 , elastic stress adjusting means  26  include an elastic stress adjustment button  44 , which can move between several adjustment positions. Adjustment button  44  is preferably actuatable from outside timepiece  1  by a user, by any means known to those skilled in the art, such as, in particular, a push button or a bezel. 
     Elastic stress adjustment button  44  has, for example, an outer profile defining a radial contour of variable radius. In the illustrative example of  FIGS. 1 to 4 , wherein adjustment button  44  acts as support piece  34  for elastically deformable arm  30 , this allows the position of arm  30  to be changed relative to pivot arm  16 , and thus the intensity of the elastic stress exerted on regulator  14 , according to the position of adjustment button  44 . The threshold for releasing the cam  24 /inertia block  22  assembly is thus changed as a function of the position of adjustment button  44 , which allows adjustment device  6  to be adapted according to user&#39;s desired use. For example, in the case where timepiece  1  is a watch, adjustment button  44  may be movable between three adjustment positions corresponding to use in the sedentary mode, normal mode or sports mode of the watch. 
     Shock absorption means  28  are arranged on regulator  14  and at least partially rest on staff  7  of balance  4 . Shock absorption means  28  include, for example, an ordinary shock absorber  46  into which a clover spring  48  is driven. 
     It is therefore envisaged that, according to the position of timepiece movement  2  in space, inertia block  22  which is subject to gravity, can rotate about its axis of rotation and thus cause a displacement of pivot arm  16  of regulator  14 , as illustrated in  FIGS. 3 and 4 . This rotation of inertia block  22  thus simultaneously acts on means  18  for adjusting the active length of balance spring  5 , allowing the active length of the spring to be continuously adjusted to offset disturbances to the isochronism of the balance caused by gravity.