Clock movement provided with a device for adjusting the frequency of a mechanical resonator

Abstract

The watch movement includes a mechanical resonator, formed by a balance wheel and a balance spring (6), a device for adjusting the oscillation frequency of the mechanical resonator, and means for setting the mechanical resonator to its reference point. A movable part (16) of the adjusting device includes means for securing an outer end portion (8) of the balance spring and means for defining the active length of the balance spring. Means for varying the active length of the balance spring include a first toothed wheel (22), carried by the movable part, and a first set of teeth (10), arranged along the outer end portion of the balance spring, with which the first toothed wheel meshes. The securing means hold the outer end portion by friction so as to allow the first toothed wheel to drive this outer end portion via the first set of teeth and thus vary the active length of the balance spring.The first toothed wheel is in mesh relationship with a second toothed wheel, fixed to the support of the resonator, so that when the outer end part undergoes an angular displacement in a selected direction relative to the moving part, this moving part is simultaneously displaced angularly by a corresponding angular distance in the opposite direction.

Description

Technical field of the invention

[0001] The invention relates to a watch movement comprising a mechanical resonator and a device for adjusting the frequency of this resonator. The invention also relates to a device for setting the timing of the escapement associated with the mechanical resonator.

[0002] In particular, the invention relates to a device for adjusting the frequency of a mechanical watch resonator which does not disrupt a previously established alignment of the 'balance & anchor' system. Technological background

[0003] Patent application BE 483992 A describes various embodiments for a device for adjusting the frequency of the balance wheel and hairspring forming a mechanical watch resonator. With reference to Figures 50 to 54, this document describes such an adjusting device, which has the advantage of allowing the resonator's frequency to be adjusted from outside a watch case designed to allow a user to perform this frequency adjustment. This adjusting device comprises a sophisticated system that allows correction of the mechanical resonator's frequency while keeping the balance wheel and anchor system in alignment. The adjusting device is complex.It comprises, on the one hand, a clamp that firmly holds the outermost coil of the balance spring at a given angular position on a support, called a 'sector', which rotates around the axis of rotation of the balance wheel. This clamping of the outermost coil defines the active length of the balance spring and thus the oscillation frequency of the balance wheel and hairspring. The clamping of the outermost coil is achieved by a slide arranged within the watch case, which includes an internal projecting portion designed to act on an elastic arm of the clamp. The slide can be actuated substantially tangentially to the axis of rotation of the balance wheel by an actuating mechanism accessible from outside the case.The elastic arm is configured so that, in a first angular position of the slide, the slide presses laterally against the elastic arm, pinching the outer coil and closing an access opening to an adjusting wheel machined into the watch case. In a second angular position, the slide releases the access opening while ceasing to exert lateral force on the elastic arm, so that the outer coil is no longer held by the clamp. The adjusting device includes a stud mounted on a second elastic arm of the support and two interlocking wheels, each carrying a spiral cam. The cam of the first wheel presses against the second elastic arm to define an angular position of the stud and also an angular distance to the clamp.The cam of the second wheel presses against a third spiral cam which is fixed but whose angular position can be adjusted by a watchmaker during an initial setting, the cam of the second wheel being held in contact against the fixed cam by elastic means of rotational actuation of said support.

[0004] To adjust the resonator frequency, the second wheel is actuated using a tool while the slide is in its second angular position and the clamp has thus released the outer coil of the balance spring. This actuation causes the first wheel and its cam to rotate, so that the second elastic arm moves, varying the angular position of the pin and thus the angular distance between this pin and the clamp. Once the clamp is closed, the active distance has changed, and therefore so has the active length of the balance spring, resulting in a change in the oscillation frequency.An interesting feature in this complex adjustment device is the following: The rotation of the second wheel not only causes a variation in the angular position of the stud and thus in the active length of the balance spring, but also an angular displacement of said support in a direction opposite to that of the stud and over a substantially identical angular distance, so that the initial setting is not disturbed, but remains.

[0005] The regulating device described above is complex and presents several drawbacks. First, it comprises a large number of parts that require adjustment. Machining some of these parts is complex, as is assembling the regulating device. Second, a significant problem arises from the fact that the oscillation frequency cannot be adjusted once the watch movement is complete, but only after it has been mounted in the case, and then only through an access opening in the side of the case. The fact that the regulating device includes a component mounted on the watch case, which is necessary for any frequency adjustment, is a major issue. Furthermore, this regulating device requires several elastic elements, namely two elastically deformable arms and a spring, which must be correctly dimensioned and may experience fatigue over time.Finally, the end of the outer spiral of the balance spring is held in the conventional way in a stud, either by a lateral screw or more often by gluing, these means of fixing can generate stress on the spiral at its end, which has an influence on the accuracy of the frequency adjustment. Summary of the invention

[0006] The present invention aims to solve the problems of the prior art mentioned in the technological background, by providing a watch movement equipped with a mechanical resonator, formed of a balance wheel and hairspring, and a device for adjusting the frequency of this mechanical resonator which is less complex, reliable and autonomous relative to the watch case, and which allows an efficient adjustment of the frequency without changing an initial setting.

[0007] To this end, the invention relates to a watch movement comprising: a mechanical resonator consisting of a balance wheel, mounted to rotate in a support, and a balance spring, an escapement comprising an anchor arranged to oscillate synchronously with the balance wheel, and a device for adjusting the oscillation frequency of the mechanical resonator, called the adjusting device, the adjustment device comprising a movable part rotating about the axis of rotation of the balance wheel, called the movable part, this movable part comprising means for fixing an outer end part of the spiral, called the fixing means, and means for defining the active length of the spiral, called the defining means, which define an extreme point of the active part of the spiral in a fixed point of the movable part once the spiral is fixed to this movable part by the fixing means.The adjustment device further includes means for varying the active length of the spiral, called the variation means, allowing the oscillation frequency to be adjusted by an angular displacement, relative to said axis of rotation and in a selected direction, of the outer end part relative to the moving part, and thus to said fixed point of this moving part, the adjustment of the oscillation frequency being combined with a rotation of the moving part over an angular distance corresponding substantially to said angular displacement and in a direction opposite to the selected direction.

[0008] The watch movement further includes means for aligning the mechanical resonator with the anchor, referred to as the alignment means. These adjustment means comprise a first toothed wheel, carried by the moving part, and a first set of teeth, arranged along the outer end portion of the balance spring, with which the first toothed wheel meshes. This first toothed wheel can be driven in rotation to perform the angular displacement. The fixing means hold the outer end portion by friction so as to allow the first toothed wheel to drive this outer end portion via the first set of teeth and thus to angularly displace the outer end portion relative to the moving part and the setting means, so as to vary the active length of the balance spring.Finally, the first gear meshes with a second gear, which is fixed to the resonator support, such that when the outer end undergoes the selected angular displacement relative to the moving part, this moving part is simultaneously displaced angularly by the same distance in the opposite direction. Thus, the outer end undergoes no angular displacement, and the previous alignment is maintained.

[0009] The adjustment device of the invention does not require a spring. It is then sufficient to provide a means of actuating the first toothed wheel or the moving part to adjust the resonator's frequency without displacing a previously established timing mark. Although this adjustment device, which allows for frequency adjustment while automatically maintaining the timing mark established in a preliminary step, could be designed for a watch allowing such adjustment once the watch is fully assembled, it is independent of the watch case, so such a watch movement can also be mounted in a case that does not allow adjustment from the outside. Admittedly, the device may appear complex at the outer end of the balance spring, which includes teeth.Such teeth can be formed in a piece initially separate from the balance spring and glued, welded, or otherwise attached to the end of the outer coil of a conventional balance spring. Since balance springs are now increasingly made of silicon and using micromachining techniques borrowed from the field of microtechnology, obtaining an outer end section of the balance spring with lateral teeth—that is, with a cut profile of the balance spring featuring teeth—presents no particular problem. The same applies to balance springs made of glass or similar materials. It should be noted that alignment can be achieved simply by pre-positioning the first set of teeth relative to the first toothed wheel with the moving part in a given initial position. Brief description of the figures

[0010] The invention will be described below in more detail with the aid of the appended drawings, given as non-limiting examples, in which: There Figure 1 is a perspective view, from above, of an embodiment of a watch movement according to the invention, this Figure 1 showing a complete watch movement including the regulating device and an outer end portion of the balance spring. Figure 2 is a top view of the entire clockwork mechanism shown in the Figure 1 , with a transparent top plate whose outlines are dashed lines (except for its teeth). The Figure 3 is a perspective view, from above, of the entire clockwork mechanism of the Figure 1 from which the top plate has been removed. The Figure 4 is a partial perspective view, from below, of the whole and the outer end part of the spiral shown in the Figure 1 . THE Figures 5A and 5B are partial views from below of the entire assembly and the outer end portion of the spiral shown in the Figure 1 with the moving part in two different positions corresponding to two different active lengths of the spiral. Detailed description of the invention

[0011] With reference to the figures, we will describe below an embodiment of a watch movement according to the invention.

[0012] The watch movement 2 includes: a mechanical resonator consisting of a balance wheel, mounted to rotate in a support (only the balance bridge 14 forming this support is shown in the figures), and a balance spring 6 (only a portion of the outer coil 7 and the outer end part 8 of the balance spring are shown in the figures), an escapement comprising an anchor arranged to oscillate synchronously with the balance wheel (the escapement is not shown in the figures, in particular a classic watch escapement with a Swiss-type anchor), and a device 4 for adjusting the frequency of the mechanical resonator, called the 'adjustment device'.

[0013] The balance wheel is, in particular, a conventional balance wheel with a plate carrying a pin that serves as a periodic coupling element between the pallet fork and the oscillating balance, resulting in a back-and-forth motion of the pallet fork, which thus oscillates synchronously with the balance wheel. The regulating device 4 comprises a movable part 16 that rotates about the axis of rotation 50 of the balance wheel, called the 'moving part'. This movable part 16 has the function of fixing the outer end portion 8 of the balance spring 6 and defining the active length of this spring. Subsequently, the movable part 16 and the outer end portion 8 are arranged to allow the mechanical resonator to be aligned with the escapement pallet fork.Furthermore, as will become clearer later, the moving part 16 is arranged so that, once the resonator and the regulating device 4 are mounted in the watch movement 2, a variation in the active length of the balance spring, to regulate the oscillation frequency of the mechanical resonator, is achieved while maintaining the angular position of the outer end portion as determined during its fixing, and thus a stable angular position of the balance wheel and balance spring at rest, so as not to lose any previously established alignment. In particular, a variation in the active length of the balance spring is achieved while maintaining correct alignment of the balance wheel's pivot at rest, namely radial alignment with the balance wheel's axis of rotation and the pallet fork's axis of rotation.

[0014] Thus, in general, the moving part 16 includes means for fixing the outer end part 8 of the spiral 6, called 'fixing means', and means for defining the active length of the spiral 6, called 'defining means', which define an extreme point PE of the active part of the spiral 6 in a fixed point PF of the moving part 16 once the spiral is fixed to this moving part by the fixing means.The adjustment device 4 further includes means for varying the active length of the spiral, called 'variation means', allowing the oscillation frequency to be adjusted by an angular displacement, relative to the axis of rotation 50 and in a selected direction, of the outer end part 8 relative to the moving part 16, and thus to said fixed point PF of this moving part, combined with a rotation of the moving part around said axis of rotation over an angular distance corresponding substantially to said angular displacement and in a direction opposite to the selected direction (See . Fig. 5A and 5BThe watch movement also includes means for aligning the mechanical resonator with the escapement anchor, called 'alignment means', in a preliminary step. This preliminary step is either a step occurring during the assembly of the resonator in the watch movement, or a step occurring during a watchmaker's overhaul of the watch movement.

[0015] According to the invention, the variation means consist of a first toothed wheel 22, carried by a plate 18 of the movable part 16, and a first set of teeth 10, arranged along the outer end portion 8 of the balance spring, with which the first toothed wheel meshes and which can be driven in rotation to perform the aforementioned angular displacement. Preferably, the balance spring is made of silicon or glass and obtained by a micromachining technique. Thus, the first set of teeth can be easily produced during the manufacture of the balance spring 6.

[0016] According to the invention, the fastening means hold the outer end part 8 by friction so as to allow the first toothed wheel 22 to drive this outer end part via the first toothing 10 and thus to displace the outer end part angularly relative to the movable part 16 and to said defining means, so as to vary the active length of the spiral 6. The first toothed wheel 22 is in meshing relationship with a fixed toothing 30 which comprises an upper plate 28 which is fixed to the support of the resonator, more generally with a second toothing 30 integral with this support, so that, when the outer end part undergoes said angular displacement in the selected direction relative to the movable part 16, this movable part is simultaneously displaced angularly by said angular distance in the opposite direction.

[0017] In the advantageous variant shown in the figures, said fixing means further comprise a first eccentric 32 and a second eccentric 33 which are arranged respectively on one side and the other of the outer end part 8 of the spiral 6.These first and second eccentrics can each be rotated by a tool so that, when the balance spring is mounted in the movement 2, they are in contact respectively with the first and second lateral sides of the outer end portion 8, while the balance spring 6 is in an unconstrained state and thus in its own rest position. This ensures that the portion of the outer end portion located between the first and second eccentrics 32 and 33 has a spatial position corresponding to the balance spring's own rest position for any adjustment of the oscillation frequency within a useful range, and that this portion can maintain this spatial positioning during an oscillation of the mechanical resonator after the outer end portion is fixed. This feature is highly advantageous for ensuring that, during the operation of the watch movement, the balance spring oscillates precisely around the axis of rotation 50.This increases the accuracy of the watch movement. The second eccentric 33 is positioned opposite the wheel 22, which is located on the other side of this second eccentric relative to the outer end portion 8. The second eccentric 33 thus also serves to ensure that the first toothing remains engaged in the first toothed wheel 22, and therefore that they mesh together. The various parts involved in the radial positioning of the outer end portion of the balance spring 6, the radial positioning of the first toothed wheel, and the first toothed wheel itself are preferably machined with sufficiently tight tolerances so that, in the balance spring's rest position (unconstrained state of the balance spring), the first toothing 10 meshes with the first toothed wheel 22 with a certain amount of play.Indeed, if this were not the case, it would be impossible to have meshing between the first gear and the first tooth of the balance spring while maintaining the portion of the outer end piece 8 between the first and second eccentrics 32, 33 with a spatial positioning corresponding to the balance spring's own rest position. It should be noted that the first and second eccentrics advantageously feature a circular groove in which the outer end piece 8 is placed. Such a groove allows for axial positioning of this outer end piece.

[0018] The means for defining the active length of the spiral 6 consist of the first eccentric 32, against which a first part 9a of the outer end portion 8 bears. The point of contact of this first part 9a against the first eccentric defines the end of the active portion of the spiral and therefore the extreme point PE of its active length. This extreme point is located at the point of contact which is fixed relative to the moving portion, so that the extreme point is always located at a determined fixed point PF, that is to say, at an invariable point of the moving portion.

[0019] The means of setting the reference are formed by the first toothing 10 of the spiral 6, arranged along a median part of the outer end part 8 of this spiral, and the first toothed wheel 22, the setting of the reference being carried out by a preliminary angular positioning of the first toothing relative to the first toothed wheel while the moving part 16 is in a given initial angular position, which can be any in the angular stroke of the moving part, but preferably substantially in the middle of this angular stroke.

[0020] In the variant described, said fixing means include a third eccentric 34 which is arranged on the same side of the outer end part of the spiral as the first eccentric 32, the second eccentric 33 being situated between the first and third eccentrics along the outer end part, the first eccentric 32 being situated on the side of the outer coil 7 of the spiral 6 relative to the second eccentric.The third eccentric is arranged so that it can be rotated by a tool to exert a third lateral force F3 against the outer end part 8, so that the first and second eccentrics react in reaction to exert respectively a first lateral force F1 and a second lateral force F2 against the outer end part 8 which is thus held in place, in the absence of rotation of the first toothed wheel 22, by friction forces between this outer end part and the first, second and third eccentrics.

[0021] According to an advantageous feature, the first lateral force F1 can have such a magnitude, and the first portion 9a of the outer end portion 8, located opposite the first eccentric 32, has a selected rigidity such that this first portion can remain in contact with the first eccentric when the mechanical resonator oscillates. Thus, once adjusted, it is ensured that the active length of the spiral remains constant during the oscillation of the resonator, despite the fact that the first portion 9a is in contact on only one side with the means for defining the active length of the spiral, which consist solely of the eccentric 32. In particular, the rigidity of the first portion 9a is selected to allow fine adjustment of the oscillation frequency.

[0022] According to a particular feature of the fastening means, the outer end portion 8 has a terminal portion 9b located after the first toothed portion 10, which occupies an intermediate part of this outer end portion. The terminal portion 9b is provided to be more flexible than the first portion 9a and is located opposite the third eccentric 34, which can exert the third lateral force F3 against this terminal portion. Preferably, the terminal portion 9b has a width that increases towards its free end, so that the third lateral force F3 remains substantially constant for any frequency setting and therefore for any active length within the intended adjustment range.

[0023] In the described embodiment, the moving part 16 comprises a second gear 24 mounted coaxially with the first gear 22, these first and second gears being fixed on the same shaft 20 so that they are rotationally fixed. The second gear 24 meshes with the fixed teeth 30 of the upper plate 28, which is fixed to the balance bridge 14 that forms part of the support for the mechanical resonator.

[0024] According to a particular variant, the moving part 16 comprises a third toothing 38 carried by an arm 18a of the plate 18, and the mechanical movement 2 includes a drive device for rotating the moving part about said axis of rotation 50 via the third toothing. The plate 18 further comprises two elastic arms 18b and 18c which form a split ring surrounding the support of the shock-absorbing bearing 46, which thus guides the rotating part 16. The drive device is arranged so that it can be actuated from the lateral periphery of the movement to rotate the moving part 16, thereby causing a variation in the active length of the balance spring 6 from this lateral periphery via the first and second toothed wheels 22, 24.The drive device includes a third gear 40 which meshes with an Archimedes screw 42. The Archimedes screw has an end 42a accessible from the lateral periphery of the mechanical movement and features a non-cylindrical coupling portion designed to allow its coupling to an actuation member for the Archimedes screw. It should be noted that the upper plate 28 has a tab 28a which maintains the Archimedes screw in a fixed longitudinal position, so that when the Archimedes screw is rotated, the gear 40 is driven in rotation even in the absence of longitudinal pressure exerted on the Archimedes screw.

[0025] The invention also relates to a watch comprising a mechanical movement according to the invention. This watch includes a case (not shown) incorporating the mechanical movement 2 and is arranged to allow the drive device of the moving part to be actuated by the aforementioned actuating member (not shown) which can be manipulated from outside the watch.

Claims

1. Watch movement (2) comprising: - a mechanical resonator formed of a balance wheel, rotatably mounted in a support, and a balance spring (6), - an escapement comprising an anchor arranged to oscillate synchronously with the balance wheel, and - a device (4) for adjusting the oscillation frequency of the mechanical resonator, called the adjustment device, the adjustment device (4) comprising a part (16) movable in rotation about the axis of rotation (50) of the balance wheel, called the movable part, this movable part comprising means for fixing an outer end part (8) of the balance spring, called the fixing means, and means for defining the active length of the balance spring, called the definition means, which define an extreme point (P E ) of the active part of the spiral at a fixed point (P F) of the moving part (16) once the spiral is fixed to this moving part by the fixing means, the adjustment device further comprising means for varying the active length of the spiral (6), called the variation means, making it possible to adjust the oscillation frequency by an angular displacement, relative to said axis of rotation and in a selected direction, of the outer end part (8) relative to the moving part, and thus to said fixed point of this moving part, the adjustment of the oscillation frequency being combined with a rotation of the moving part (16) over an angular distance corresponding substantially to said angular displacement and in a direction opposite to the selected direction; the watch movement further comprising means for setting the mechanical resonator relative to said anchor, called the setting means; characterized in thatthe variation means comprise a first toothed wheel (22), carried by the movable part, and a first toothing (10), arranged along the outer end part of the hairspring, with which meshes the first toothed wheel which can be driven in rotation to carry out said angular displacement, said fixing means holding the outer end part (8) by friction so as to allow the first toothed wheel to drive this outer end part via the first toothing and thus to angularly move the outer end part relative to the movable part and to said defining means, so as to vary the active length of the hairspring; and in thatthe first toothed wheel (22) is in meshing relationship with a second toothing (30), integral with the support of the resonator, so that, when the outer end part undergoes said angular displacement in the selected direction relative to the movable part, this movable part is simultaneously angularly displaced by said angular distance in the opposite direction.

2. Watch movement according to claim 1, characterized in that the spiral (6) is made of silicon or glass and obtained by a micro-machining technique.

3. Watch movement according to claim 1 or 2, characterized in thatsaid fixing means comprise a first eccentric (32) and a second eccentric (33) which are arranged respectively on one side and the other of the outer end portion (8) of the hairspring and each capable of being rotated by a tool so as to be placed, during assembly of the hairspring (6) in the watch movement, in contact respectively against first and second lateral flanks of the outer end portion (8), while the hairspring is unstressed and thus in its own rest position, so that the portion of the outer end portion between the first and second eccentrics (32, 33) has a spatial positioning corresponding substantially to that of the hairspring's own rest position for any adjustment of the oscillation frequency within a useful range, said fixing means maintaining this spatial positioning of said portion of the outer end portion once fixed,the first eccentric (32) constituting said definition means., 4. Watch movement according to claim 3, characterized in thatsaid fixing means comprise a third eccentric (34) which is arranged on the same side of the outer end portion (8) of the hairspring as the first eccentric (32), the second eccentric (33) being located between the first and third eccentrics along the outer end portion, the first eccentric being located on the side of the outer coil (7) of the hairspring relative to the second eccentric and the third eccentric (34) being arranged so as to be rotatable by a tool to exert a third lateral force against the outer end portion (8) so that the first and second eccentrics exert in reaction respectively a first lateral force and a second lateral force against the outer end portion which is thus held in place, in the absence of rotation of the first toothed wheel, by friction forces between this outer end portion and the first, second and third eccentrics.

5. Watch movement according to claim 4, characterized in that said first lateral force may have such an intensity and a first part of the outer end part, located opposite the first eccentric, has a selected rigidity such that this first part can remain in contact with the first eccentric when the mechanical resonator oscillates.

6. Watch movement according to claim 5, characterized in that said stiffness is selected to allow fine adjustment of the oscillation frequency.

7. Watch movement according to claim 5 or 6, characterized in that the outer end portion has an end portion, following the first toothing, which is more flexible than said first portion and located opposite the third eccentric, which can exert said third lateral force against this end portion.

8. Watch movement according to any one of the preceding claims, characterized in that said reference setting means are formed by the first toothing of the hairspring and the first toothed wheel, the reference setting being carried out by a preliminary positioning of the first toothing relative to the first toothed wheel while the moving part is in a given angular position.

9. Watch movement according to any one of the preceding claims, characterized in that the movable part (16) comprises a second toothed wheel (24) mounted coaxially with the first toothed wheel (22), the first and second toothed wheels being arranged on the same shaft (20) so as to be integral in rotation, the second toothed wheel (24) meshing with the second toothing (30).

10. Watch movement according to any one of the preceding claims, characterized in thatthe movable part (16) comprises a third toothing (38) and the movement comprises a device for driving the movable part in rotation, around said axis of rotation (50), via the second toothing (30); and in that the drive device is arranged so as to be able to be actuated from the lateral periphery of the movement to effect a rotational drive of the moving part (16), so as to generate a variation in the active length of the balance spring from this lateral periphery via the first and second toothed wheels.

11. Watch movement according to claim 10, characterized in that the drive device comprises an Archimedes screw (42) one end of which is accessible from the lateral periphery of the movement and which has a non-cylindrical coupling part, to allow its coupling to an actuating member of this Archimedes screw.

12. Watch comprising a movement according to claim 10 or 11, characterized in that the watch comprises a case incorporating the movement (2) and arranged so as to allow the actuation of the device for driving the moving part (16) by the actuation member which can be manipulated from outside the watch.

Images