CH720867A1 - Torque limiting mobile, winding gear and watch movement - Google Patents

Abstract

The invention relates to a torque limiting wheel set (19) comprising a first wheel (21) in a disengageable kinematic connection with a second wheel (29), the first wheel (21) being rotationally secured to a tube (23) housing a number N of elastic disengagement elements each comprising an inner part cooperating with a rod rotationally secured to the second wheel (29), as well as at least one elastic arm, the end of which cooperates with the inner wall of the tube (23), in which the tube (23) is arranged to house a maximum number N max of elastic disengagement elements, N max being at least three and the number N of elastic disengagement elements housed in the tube (23) is between 1 and N max . The invention also relates to a winding gear and a watch movement (1) comprising such a wheel set. The invention also relates to a timepiece movement (1) comprising a barrel (7), an oscillator driven by the barrel, a power reserve device arranged to control the position of a rack as a function of the power reserve, a brake arranged to stop the oscillator at a predetermined minimum power reserve level as a function of said position of said rack. The brake is carried by a first elastic arm of an elastic fork pivotally mounted on a lever arranged to move between a first position, in which the brake is distant from said oscillator, and a second position, in which it is in contact with it. The rack comprises an actuating member cooperating with a tab carried by the end of a second elastic arm that said elastic fork comprises, allowing the lever to move towards said second position when said actuating member cooperates with said tab.

Description

Technical field

[0001] The present invention relates to the field of watchmaking. It relates, more particularly, to a torque limiting wheel set for a winding train of a watch movement, as well as a watch movement arranged to stop when a predetermined minimum power reserve is reached.

State of the art

[0002] In order to optimize the operation of a watch movement, it is desirable that the torque available to the escapement wheel remains within reasonable limits. An excess of torque increases the amplitude of the oscillator, which impairs its operation by advancing it, and even creates a risk of galloping or rebating, while an insufficient torque results in an insufficient amplitude, which also impairs its operation by delaying it. In the absence of compensation measures, a standard mainspring risks providing too much torque when it is fully wound, and will, in any case, provide insufficient torque when it approaches the end of its power reserve. Furthermore, in the case where the movement includes additional mechanisms (for example a chronograph, striking, animation or similar mechanism), insufficient torque will not allow it to operate correctly.

[0003] A constant force device, or an equality winder, is a solution which makes it possible to ensure that a quasi-constant torque is provided to the oscillator, and therefore a quasi-constant amplitude of the latter, but at the cost of a significant increase in complexity.

[0004] Among the simpler solutions, sliding flanges and disengagement devices between the winding crown or the oscillating weight and the barrel ratchet are known to limit the maximum torque of the barrel. These systems comprise a torque limiting element, such as a spring, which ensures that the user, or the oscillating weight, can no longer wind the mainspring when a torque threshold has been reached. For this purpose, mention may be made of documents EP3705949 and FR1207713, which disclose two devices of this type arranged to limit the winding torque, which in turn limits the maximum torque that the mainspring can provide to the going train and therefore to the oscillator.

[0005] With regard to the situation in which the torque provided by the mainspring is insufficient to ensure the proper functioning of the movement, whether at the level of the oscillation amplitude of the oscillator or the operation of an additional mechanism, various devices for stopping the movement under the control of a power reserve device have been proposed. For this purpose, mention may be made of document EP2503405, which discloses a mechanism arranged to block the operation of a striking mechanism when the mainspring is not in a condition to provide sufficient torque to ensure its proper operation. For the remainder, document CH716841 describes a watch movement in which a power reserve device controls a balance stop of an oscillator dedicated to a chronograph, in order to stop it when the mainspring does not provide sufficient torque.

[0006] The aim of the invention is therefore to propose a new torque limiting mobile for a winding train of a watch movement, as well as a new watch movement arranged to stop when a predetermined minimum power reserve is reached.

Disclosure of the invention

[0007] More specifically, a first aspect of the invention relates to a torque limiting wheel set, in particular for a winding train of a watch movement. This torque limiting wheel set comprises a first wheel in disengageable kinematic connection with a second wheel, said first wheel being integral in rotation with a tube housing a number N of elastic disengagement elements each comprising an inner part cooperating (in particular by blocking shapes) with a rod integral in rotation with the second wheel, as well as at least one elastic arm whose end cooperates with the inner wall of said tube.

[0008] Said tube is arranged to accommodate a maximum number Nmax of elastic disengagement elements, Nmax being at least three and the number N of elastic disengagement elements accommodated in said tube is between one and Nmax, preferably between 2 and Nmax, more preferably between 3 and Nmax.

[0009] Such a torque limiting mobile makes it possible to limit the winding of a mainspring so that the latter is prevented from providing too much torque to the finishing gear, eliminating the risk that excess torque increases the oscillation amplitude of the oscillator and causes a risk of galloping, and, secondarily, eliminating the need to provide a sliding flange or other means of protection against excessive winding of the mainspring.

[0010] Furthermore, by choosing the number N of elastic disengagement elements, the torque generating a disengagement can be easily determined, either for the optimization of a particular winding train, or to be able to use the same torque limiting wheel set for different series of movements having motor springs of different stiffnesses, instead of having to provide different torque limiting wheels and/or elastic disengagement elements for each series. Indeed, it is simply necessary to provide a batch of substantially identical elastic disengagement elements, and to choose the number N according to the manufacturer's needs.

[0011] Advantageously, the inner wall of said tube has at least one notch arranged to cooperate with said at least one end of each elastic disengagement element.

[0012] This torque limiting mobile is advantageously integrated into a winding gear for a watch movement, this gear comprising a winding stem in connection with a member arranged for winding a barrel (typically a ratchet wheel but which could be the teeth of the drum in the reverse arrangement of the usual), said torque limiting mobile being kinematically arranged between said winding stem and said member arranged for winding a barrel.

[0013] Advantageously, the axis of rotation of said torque limiting mobile is perpendicular to the axis of rotation of said rod.

[0014] Advantageously, said torque limiting wheel set is arranged laterally relative to said barrel, considered in the plane of the movement. Ideally, this arrangement is without any superposition with the barrel, but a partial superposition of at least one of said wheels of said torque limiting wheel set is also possible.

[0015] According to a second aspect, the invention relates to a watch movement comprising: – a barrel housing a mainspring; – an oscillator arranged to be driven by said barrel, typically via a conventional finishing gear train; – a power reserve device arranged to control the position of a rack as a function of the power reserve of said mainspring; – a brake arranged to stop said oscillator at a predetermined minimum power reserve level (typically by contact with the periphery of the balance wheel), as a function of said position of said rack, i.e. when the power reserve is reduced to a level insufficient to guarantee good chronometry and/or the proper functioning of an additional mechanism such as a chronograph, a chime, an animation or the like.

[0016] Said brake is carried by a first elastic arm of an elastic fork pivotally mounted on a rocker arranged to move between a first position, typically stable, in which said brake is distant from said oscillator and does not cooperate with the latter, and a second position, in which said brake is in contact with said oscillator to stop it.

[0017] Said rack comprises an actuating member cooperating with a tab carried by the end of a second elastic arm which said elastic fork comprises, such as to allow said rocker to move towards said second position when said actuating member cooperates with said tab.

[0018] In doing so, the brake is actuated to stop the oscillator at a predetermined power reserve level reliably and efficiently, while minimizing the risk of the brake rubbing against the oscillator without stopping it. Chronometric and/or operational problems of an additional mechanism related to an insufficient power reserve are thus overcome.

[0019] Advantageously, said tab has an oblique flank arranged so as to cooperate with said actuating member to retain said second elastic arm against the effect of an elastic actuating element acting directly or indirectly on said rocker and arranged to be flexed by a stop secured to said rack, said tab further comprising a flat end face, the transition between said oblique flank and said flat end face being arranged so as to release said second elastic arm so that said rocker can adopt its second position under the effect of said elastic actuating element, in particular when the actuating member crosses the peak between the oblique flank and the flat end face. In doing so, the movement of the brake is abrupt, quickly stopping the oscillations of the balance.

[0020] Advantageously, an elastic return element is provided and is arranged to push said rocker towards its first position in a direct or indirect manner.

[0021] Advantageously, said elastic return element is arranged to act on a lever pivotally mounted and articulated to said rocker. This lever can also be arranged to be actuated by a winding stem, for example by means of a pull tab, in order to provide a conventional balance stop operation when the user sets the time or controls another mechanism of the movement.

[0022] Advantageously, said brake is arranged at a free end of a shaft fixed to the free end of said first elastic arm.

[0023] Of course, the two aspects of the invention can be implemented in combination, in order to maintain the torque provided by the drive member between two predetermined terminals.

Brief description of the drawings

[0024] Other details of the invention will appear more clearly on reading the description which follows, made with reference to the appended drawings in which: - Figure 1 is an isometric view of a part of a clockwork movement according to a first aspect of the invention; - Figure 2 is an exploded view as well as an isometric view of the torque limiting wheel set of Figure 1; - Figure 3 is an isometric view of a part of a clockwork movement according to a second aspect of the invention; - Figure 4 is a view similar to that of Figure 3, the actuating member beginning to cooperate with a lug carried by an elastic fork; - Figure 5 is a view similar to that of Figure 4, the actuating member having actuated the fork; - Figure 6 is an isometric view of a part of the movement of Figures 3 to 5, the brake not cooperating with the balance; and – Figure 7 is a view similar to Figure 6, the brake cooperating with the balance.

Embodiments of the invention

[0025] Figure 1 illustrates a part of a watch movement 1 according to a first aspect of the invention. This movement comprises a winding train 3, which is used to kinematically connect a winding stem 5 to a barrel 7, in particular to its member 9 arranged for winding the mainspring housed in the barrel. In the illustrated embodiment, the configuration of the barrel 7 is conventional, that is to say that said member is a ratchet wheel 9 integral in rotation with the barrel shaft 11, the teeth 13 of the drum being used to drive the finishing gear train (not illustrated). However, the reverse configuration is also possible, in which case the necessary modifications are within the reach of those skilled in the art and do not need to be detailed.

[0026] The winding gear train 3 comprises a pinion 15 integral in rotation with the stem 5, this rotational connection being permanent or disengageable, as is generally known. A first intermediate wheel 17 meshes on the one hand with the pinion 15 and on the other hand with a torque limiting wheel set 19, the latter being positioned next to the barrel 7 and meshing in turn with a second intermediate wheel 20 which is engaged with the ratchet wheel 9. It should be noted that all of the elements 17, 19, 20 pivot about axes which extend parallel to each other and perpendicular to the plane of the movement 1 and the axis of rotation of the stem 5.

[0027] Of course, other configurations of the winding gear train 3 are possible and the illustrated configuration is in no way limiting, insofar as it includes the torque limiting wheel set 19, which will be described in more detail below.

[0028] As clearly illustrated in FIG. 2, the torque limiting mobile 19 comprises a first wheel 21 integral in rotation with a tube 23 which is adapted to house a maximum number Nmax of elastic disengagement elements 25. The inner parts 25a of the latter are integral in rotation with a shaft 27 which comprises a flange 27a arranged to position the shaft 27 axially relative to the first wheel 21 and to allow rotation between these two elements. In other words, the first wheel 21 and the tube 23 are mounted loosely on the shaft 27. The free end of the shaft 27 is also integral in rotation with a second wheel 29, the latter as well as said internal parts 25a having a non-circular opening which cooperates with a complementary non-circular section of the shaft 27 in order to make them integral in rotation by locking of shapes, but a driving, gluing, welding or similar of the internal parts 25a on a section of the shaft 27 of any section is also possible.

[0029] Each elastic disengagement element 25 comprises at least one elastic arm 25b (here, there are two per elastic disengagement element 25, but the number can vary between 1 and 6) which cooperates with a respective notch 23a provided in the inner wall of the tube 23.

[0030] The first wheel 21 cooperates with the first return 17, and the second wheel 29 cooperates with the second return 20, but in the alternative, the second wheel 29 can cooperate directly with the ratchet wheel 9. When the resistance torque, to which the first wheel 21 is subjected, is less than a predetermined threshold value, each of the ends of the elastic arms 25b remains in the corresponding notch 23a. However, when said resistance torque reaches said threshold, the elastic arms 25b flex sufficiently so that the ends come out of their notches 23a, thereby disengaging the first wheel 21 from the second wheel 29, and consequently also disengaging the rod 5 from the member 9 arranged for winding the barrel 7 (i.e. the ratchet wheel 9 in the illustrated configuration, but which could alternatively be the teeth of the drum in a reverse configuration of the barrel 7).

[0031] Of course, the configuration of the torque limiting wheel 19 can be reversed, that is to say that the second wheel 29 can mesh with the first return 17 while the first wheel 21 meshes with the second return 20.

[0032] In order to determine the threshold value of the torque that will cause the aforementioned disengagement, the number of elastic elements 25 can vary according to the needs of the manufacturer. In doing so, the maximum torque, up to which the mainspring can be wound, can be determined, by choosing a number N of elastic elements 25 between 1 and Nmax, where Nmax is at least 3, preferably 3, 4, 5 or 6. The number N is preferably 2, 3, 4, 5 or 6. This torque can thus easily be determined either to optimize each movement 1, or for each series of movements, the same torque limiting mobile 19 can thus find an application in different series of movements having different mainsprings with different stiffnesses.

[0033] Not only is the maximum torque limited by the torque limiting mobile 19 according to the invention, but also the use of a sliding flange, which has a defect in terms of wear, can be avoided, since the use of the torque limiting mobile 19 makes it impossible to overload the mainspring.

[0034] As regards the positioning of the torque limiting wheel set 19, the whole of this wheel set 19 is located next to the barrel 7, considered in the plane of the movement 1 and perpendicular to the axis of rotation of the wheel set 19, in the illustrated configuration. There is therefore no overlap or superposition of the wheel set 19 relative to the barrel 7. However, in the case where the second wheel 29 meshes directly with the ratchet wheel 9, or with a second intermediate wheel 20 of reduced diameter, it is possible for the second wheel 29 to be superimposed on the barrel 7.

[0035] Finally, it is noted that a reverse construction is also possible, in which the elastic elements 25 are rotationally integral with the wheel 21, for example with pins, or with the tube 23 and cooperate elastically with notches or equivalent structures provided on the shaft 27.

[0036] Figures 3 to 7 partially illustrate a movement 1 according to a second aspect of the invention, the barrel 7 housing a mainspring in a conventional manner as well as the finishing gear train not having been illustrated. This movement 1 comprises a power reserve device 31, of which only the output wheel set 33 is visible, arranged to move a rack 35 according to the winding state of the mainspring. Various types of power reserve devices are known to those skilled in the art, and typically comprise a differential gear whose output wheel set 33 pivots in one direction during winding, and in another direction when the mainspring unwinds, the two inputs of the differential cooperating respectively with the teeth of the drum 13 of the barrel 7 and its ratchet wheel 9 directly or indirectly. In doing so, the rack 35 travels a curved path, defined by a cam path 37 secured to the frame. Alternatively, this cam path 37 may be straight.

[0037] In order to indicate the power reserve to the user, an indicator member 39 is mounted integrally with the rack 35, but other types of indicator members 39 are possible.

[0038] In order to stop the oscillator 41, a brake 43 (typically called a “balance stop”) is arranged to rest against the periphery of the balance 45 that the oscillator 41 comprises. In the illustrated embodiment, the brake 43 is a domed-head stud, but other shapes are possible (for example a disk, cylinder, etc.).

[0039] The brake 43 is carried at the free end of a shaft 47, the latter passing through the plate 49 inside a slot 49a made in the latter. The other end of the shaft 47 is fixed to the free end of a first elastic arm 51a of an elastic fork 51 which is pivotally mounted on a rocker 52, which is, in turn, pivotally mounted on a frame element, the two elastic arms 51a, 51b of said fork 51 extending from the pivot point 52a on the rocker 52 in similar directions, but the direction of extension of the elastic arms 51a, 51b is not important insofar as the operation described is produced. The rocker 52 is held in its first position, as illustrated in FIG. 3, by means of an ad hoc elastic return element 54, which is, in the case of the illustrated embodiment, a leaf spring 54 cooperating with a lever 63 which is pivotally mounted on a frame element and articulated to the rocker 52, these elements being arranged in such a way as to urge the rocker 52 in the counterclockwise direction (according to the orientation of the figures) under the effect of the elastic return element 54.

[0040] The rocker 52 is also integral with an elastic actuating element 57, which cooperates with a stop 53c integral with the rack 35, as described below. In the state of FIG. 3, the free end of the elastic actuating element 57 is not in contact with the stop 53c, which is also the case over the greater part of the travel of the latter, and the elastic actuating element 57 is therefore not stressed.

[0041] In this first position, the brake 43 is distant from the oscillator 41 and therefore does not cooperate with the latter. The lever 63 can also have another operation, as described below, and other arrangements of ad-hoc elastic elements are also possible.

[0042] The free end of the second elastic arm 51b of the fork 51 carries a tab 53 which cooperates with an actuating member 55 carried by the rack 35. In the illustrated embodiment, this actuating member 55 is a pin extending perpendicular to the plane of movement 1, but alternatively it may be a stud, a bump, a stop, a shoulder or the like carried by the rack 35.

[0043] For most of the travel of the actuating member 35, the latter is out of reach of the tab 53, FIG. 3 illustrating the situation just before these two elements come into contact. The brake 43 is remote from the balance 45, as illustrated in FIG. 6.

[0044] In Figures 4 and 5, only the reference signs mentioned in connection with a particular figure have been reproduced, so as not to overload the figures.

[0045] Figure 4 illustrates the situation some time after that illustrated in Figure 3, the actuating member 55 having come into contact with the oblique flank 53a of the tab 53, which begins to flex the second arm 51b by cam effect. At the same time, the stop 53c comes into contact with the free end of the elastic actuating element 57 and begins to flex it, the cooperation between the oblique flank 53a of the tab 53 and the actuating member 55 retaining the rocker 52 against the effect of the elastic actuating element 57. It should be noted that a limitation of the drawing software, used to prepare the figures, did not allow the flexion of the second arm 51b, of the elastic actuating element 57, or of the elastic return element 54 to be illustrated correctly, and the designer chose to break the latter. However, these elements are to be understood as being unitary elements in deflection, without discontinuity.

[0046] Figure 5 illustrates the situation some time after that illustrated in Figure 4. In the meantime, since the situation of Figure 4, the rack has continued to move such that the elastic actuating element 57 has been stressed even more by the stop 53c, the actuating member 55 having at the same time crossed the top of the oblique flank 53a of the lug 53 and is therefore no longer retained by the latter. In doing so, the lever 52 has been released to pivot to its second position under the effect of the elastic actuating element 57 against the effect of the elastic return element 54, which has the consequence of pulling the brake 43 towards the balance 45 so as to generate an abrupt contact between these two elements. The latter now have the relationship illustrated in Figure 7.

[0047] This abrupt movement of the brake 43 when the lever 52 pivots ensures an almost instantaneous stopping of the balance 45, without the friction that would be generated in the case where the brake 43 gradually approaches the balance 45. This friction partially slows down the oscillations, harming the operation of the movement and causing wear on the balance 45 and the brake 43. However, if this functionality is not desired, other shapes of lugs 53 are also possible, which allow a progressive pivoting of the lever 52 and thus a progressive approach of the brake 43 towards the balance 45.

[0048] When the mainspring is wound, the sequence of movements is reversed. The actuating member 55 moves away from the lug 53, the stop 53c moves away from the elastic actuating element 57, and the elastic return element 54 is thus free to return the lever 52 and the fork 51 to their initial positions, which has the consequence of moving the brake 43 away from the rim of the balance 45 in an abrupt manner. The movement is thus restarted.

[0049] The lever 52 may also be arranged to be actuated when the user pulls on the time-setting stem 59 in order to set the time or to control another function of the movement. For this purpose, the stem 59 cooperates in a known manner with a pull-out piece 61 which carries a pin 61a arranged to pivot the lever 63 in the counterclockwise direction (according to the orientation of the figures), the latter consequently pivoting the lever clockwise (according to the orientation of the figures) to its second position. In this position, the brake 43 is in contact with the periphery of the balance 45 to stop the oscillations of the latter, as described above. However, this functionality is not mandatory and can be omitted.

[0050] Although the invention has been described with reference to particular embodiments, other variations are possible without departing from the scope of the appended claims.

Claims (13)

1. Torque limiting mobile (19), in particular for a winding train (3) of a watch movement (1), said torque limiting mobile (19) comprising a first wheel (21) in disengageable kinematic connection with a second wheel (29), said first wheel (21) being integral in rotation with a tube (23) housing a number N of elastic disengagement elements (25) each comprising an inner part (25a) cooperating with a rod (27) integral in rotation with said second wheel (29), as well as at least one elastic arm (25b) the end of which cooperates with the inner wall of said tube (23), in which said tube (23) is arranged to house a maximum number Nmax of elastic disengagement elements (25), Nmax being at least three and the number N of elastic disengagement elements (25) housed in said tube (23) is between 1 and Nmax, preferably between 2 and Nmax, preferably between 3 and Nmax. 2. Torque limiting mobile (19) according to the preceding claim, wherein said inner wall of said tube (23) has at least one notch (23a) arranged to cooperate with said at least one end of each elastic disengagement element (25). 3. Winding gear (3) for a watch movement (1), comprising a winding stem (5) connected to a member (9) arranged for winding a barrel (7), said winding gear (3) comprising a torque limiting wheel set (19) according to one of the preceding claims kinematically arranged between said winding stem (5) and said member (9) arranged for winding a barrel (7). 4. Gear (3) according to the preceding claim, wherein the axis of rotation of said torque limiting mobile (19) is perpendicular to the axis of rotation of said rod (5). 5. Gear (3) according to one of claims 3 and 4, in which said torque limiting mobile (19) is arranged laterally with respect to said barrel (7). 6. Clock movement (1) comprising a gear (3) according to one of claims 3 to 5. 7. A watch movement (1) comprising: – a barrel (7) housing a mainspring; – an oscillator (41) arranged to be driven by said barrel (7); – a power reserve device (31) arranged to control the position of a rack (35) as a function of the power reserve of said mainspring; – a brake (43) arranged to stop said oscillator (41) at a predetermined minimum power reserve level as a function of said position of said rack (35), in which: – said brake (43) is carried by a first elastic arm (51a) of an elastic fork (51) pivotally mounted on a lever (52) arranged to move between a first position, in which said brake (43) is distant from said oscillator (41), and a second position, in which said brake (43) is in contact with said oscillator (41); – said rack (35) comprises an actuating member (55) cooperating with a tab (53) carried by the end of a second elastic arm (51b) which said elastic fork (51) comprises, so as to allow said rocker (52) to move towards said second position when said actuating member (55) cooperates with said tab (53). 8. Movement (1) according to the preceding claim, wherein said tab (53) has an oblique flank (53a) arranged so as to cooperate with said actuating member (55) to retain said second elastic arm (51b) against the effect of an elastic actuating element (57) acting on said rocker (52) and arranged to be flexed by a stop (53c) integral with said rack (53, as well as a flat end face (53b), the transition of said actuating member between said oblique flank (53a) and said flat end face (53b) being arranged so as to release said second elastic arm (51b) so that said rocker (52) can adopt its second position under the effect of said elastic actuating element (57). 9. Movement (1) according to one of claims 7 or 8, in which an elastic return element (54) is provided and is arranged to push said rocker (52) towards its first position. 10. Movement (1) according to the preceding claim, in which said elastic return element (54) is arranged to act on a lever (63) pivotally mounted and articulated to said rocker (52). 11. Movement (1) according to the preceding claim, wherein said lever (63) is arranged to be actuated by a winding stem (59), preferably via a pull tab (61). 12. Movement (1) according to one of claims 7 to 11, wherein said brake (43) is arranged at a free end of a shaft (47) fixed to the free end of said first elastic arm (51a). 13. Clock movement (1) according to one of claims 7 to 12 further comprising a gear (3) according to one of claims 3 to 5.