Gear reserve indicator

Description

Technical field of the invention

[0001] The present invention relates to the field of watchmaking, and in particular to a display device for the power reserve of a wristwatch. State of the art

[0002] In the prior art, devices are known that allow the user to be informed at any time about the amount of energy stored in the mainspring barrel of a movement, in order to determine whether the movement is close to stopping or to its maximum winding level, and thus anticipate the watch stopping. Such a device is described, for example, in patent EP0568499B1.

[0003] In most of these devices, safety mechanisms are also provided to allow the display mechanism to disengage from the driving force exerted by the movement's mainspring barrel, particularly at the end of its travel. This prevents the display hand from continuing to rotate after it has already reached its stop against a pin. Such solutions often use friction mechanisms to achieve this disengagement.

[0004] Alternatively, as described in patent CH711236, disengagement can be achieved using elastic elements rather than friction; however, the solution disclosed in this patent only allows disengagement in the disarming direction, not the arming direction. Patent application EP3699694 similarly uses coupling between a display element and a drive element by means of an elastic element, one end of which can move within a loop. However, this solution again only allows coupling between the display element and the drive element within a predefined angular range, dependent on the dimensions of the available angular sector within the loop.

[0005] Furthermore, we know of display solutions that use differential systems which allow us to recover information on the winding of the barrel spring, and information on its unwinding, in order to average them and thus improve the display accuracy by indicating a more reliable stored energy level at the output.

[0006] This type of mechanism has been known since the 1950s, and is described in particular in B. Humbert's reference work "The Swiss Self-Winding Watch by B. Humbert, 1955") .

[0007] More recent solutions, such as the one described in patent EP1139182B1, use such a differential mechanism for powering the movement and also propose a safety system based on a coupling between a drive wheel and a display wheel. This coupling uses an elastic element, one end of which is attached to a pin inserted in a loop arranged radially in the drive wheel. The movement of this element is controlled by a cam that rotates with a drive pinion coaxial with the drive wheel. However, this disengagement system still appears to be effective only during disengagement, and not necessarily during winding. Indeed, it is sufficient to calibrate the length of the loop relative to the shape of the cam so that it is long enough to prevent jamming at the end of its travel. This is relatively easy since the remaining torque exerted by the mainspring barrel at the end of its travel is low.However, during the winding, there may be a risk of the pin jamming at the distal end of the loop, the radial play being generally sized to prevent the pin from passing over the other side of the cam on which no stable resting position is possible.

[0008] The improvement proposed by the solution described in international application WO2005 / 085963 from the same applicant aims precisely to solve this problem at the arming stage by reintroducing a friction mechanism in parallel with the elastic device provided for disarming.

[0009] There is therefore a need for a solution free from these known limitations regarding disengagement, particularly at the arming stage. Summary of the invention

[0010] One aim of the present invention is to provide a new safety mechanism for a power reserve display device that is free of friction means and more robust than the usual mechanisms using elastic means.

[0011] These goals are achieved, according to the invention, through the features of the attached claim 1.

[0012] One advantage of the proposed solution is that it provides a more robust safety mechanism than those relying entirely on elastic means, i.e., those completely devoid of friction, by allowing the clutch to be disengaged indefinitely regardless of the direction of the display hand's movement. In this way, any risk of breakage to one or more components of the transmission chain is avoided in a particularly effective and durable manner, without risk during both the winding and unwinding of the mainspring barrel that powers the movement.

[0013] Another advantage of the proposed solution is to gain in compactness for the proposed safety mechanism, and in particular in height, since such a mechanism is now made on a single floor, in the plane of the display mobile, without requiring a dedicated linking element interposed for example between an indicator mobile and a drive wheel.

[0014] Another advantage of the proposed solution is that it simplifies the provision of a safety mechanism for the power reserve indicator thanks to a reduced number of components. The safety mechanism is fully integrated into the indicator unit in the form of a "spring wheel," which facilitates assembly and thus optimizes production costs by reducing assembly time.

[0015] According to a preferred embodiment for the power reserve display mechanism according to the invention, the hub is further provided with a loop extending over a first angular sector corresponding to the first predefined angular range, and a fixed limiting pin is housed in the loop and can come to rest on either side of it for the respective display of the minimum display value and the maximum display value.

[0016] In this way, the safety mechanism is made particularly simple in the plane of the display wheel, the location of the pin defining a fixed reference point to determine the positioning of the mechanism, allowing not only a simplified structure compared to those using friction means, but also further simplifying the manufacture and assembly operations.

[0017] According to an even more preferred embodiment, the power reserve display mechanism according to the invention, the partial toothing of the rim extends over a second angular sector strictly included in the first angular sector.

[0018] In this way, the second angular sector on which the partial teeth of the display mechanism are arranged extends over only a second angular range strictly smaller than that of the first display angular range, and additional clearance formed by the differential angular sector at each end minimizes the tensile stresses on the arms each time a disengagement occurs. Thus, the efficiency and durability of the system are further optimized.

[0019] According to another preferred embodiment for the power reserve display mechanism according to the invention, the partial toothing of the serge is formed by an external peripheral toothing of the display mobile.

[0020] Such a configuration makes it possible to minimize the overall thickness of the safety mechanism by making the gear plane opposite the drive pinion, or more generally any drive element of the display mechanism, directly in the plane of the display unit.

[0021] According to an even more preferred embodiment for the power reserve display mechanism according to the invention, the serge is further provided with an external peripheral bead extending over a third angular sector corresponding to a third angular range, the third angular sector being located strictly outside the second angular sector.

[0022] This configuration allows for improved balancing of the display unit by compensating for the absence of teeth with a counterweight, thus preventing any tendency to tilt relative to the gear plane. Furthermore, the addition of the bead creates a shock-absorbing device by limiting the movement of the display unit, which is designed as a spring wheel within a slightly larger diameter housing. Indeed, the bead compensates not only in terms of weight but also in terms of volume in the radial direction, thereby simulating a wheel that would have retained all of its peripheral teeth. This limits its displacement relative to an adjacent surface should an impact cause it to collide at that point.

[0023] According to a particularly preferred embodiment for the power reserve display mechanism according to the invention, the number of elastic arms is between 2 and 5.

[0024] Such a configuration is advantageous for maximizing the stability of the mobile display in the plane.

[0025] According to a particularly preferred embodiment for the power reserve display mechanism according to the invention, the total number of coils is between 4 and 8.

[0026] This configuration optimizes the flexibility and suppleness of the arm. By facilitating each disengagement operation, thanks to the use of a force required to deform the elastic wheel that is negligible compared to the characteristics of the materials used, wear on the gear teeth is minimized, thus further improving the durability of the proposed mechanism.

[0027] According to a particularly preferred embodiment for the power reserve display mechanism according to the invention, the arms are also made of a non-magnetic material.

[0028] Thanks to this choice of material, which offers advantageous characteristics in addition to the desired elastic properties, the power reserve indicator mechanism can be easily integrated as a module of a non-magnetic movement designed to also exhibit non-magnetic properties. It should be noted that, within the framework of this invention, the elastic wheel forming the display mechanism will preferably be made entirely of a non-magnetic material.

[0029] According to a particularly preferred embodiment for the power reserve display mechanism according to the invention, the display unit is formed in one piece by said hub, said rim provided with partial teeth and said at least one elastic arm connecting said rim to said hub.

[0030] Such a one-piece arrangement makes it possible to considerably simplify the assembly and mounting operations of the proposed safety mechanism for the display mechanism compared to prior art solutions using separate elastic coupling elements and having to be fixed respectively to each of the parts they are supposed to mechanically couple.

[0031] According to the invention as claimed, the power reserve display mechanism according to the invention is characterized in that the energy source is formed by a first barrel and a second barrel arranged in series, and that said input mobile is formed by a differential in contact on one side with a first shaft of the first barrel and on the other side with a second shaft of the second barrel.

[0032] This arrangement optimizes the accuracy of the stored energy readings by deducing them from both a winding indicator on the first barrel and a winding indicator on the second barrel, while simultaneously doubling the available power reserve thanks to this series-connected configuration. In this way, the overall power reserve is maximized while simultaneously improving the accuracy of the power reserve values ​​displayed to the watch's wearer.

[0033] Advantageously, the differential has a lower plate in contact with the first shaft of the first barrel, and a planet carrier in contact with the second shaft of the second barrel, the lower plate and the planet carrier being coaxial and superimposed.

[0034] Such an arrangement for the differential is proposed in order to improve the acquisition of power reserve information and to considerably simplify its structure compared to conventional differentials using friction wheels; moreover, it provides an additional gain in compactness of the overall display system.

[0035] According to an even more preferred embodiment of the power reserve display mechanism according to the invention, the input moving element is formed by a differential drive pinion, the drive pinion being coaxial and superimposed on the lower board and the planet carrier.

[0036] Thanks to this particularly advantageous configuration, not only does the differential have a particularly simple structure, whose inputs and outputs are all coaxial and mutually superimposed, but it can be easily and directly connected to the display unit equipped with the integrated safety mechanism.

[0037] According to an even more preferred embodiment of the power reserve display mechanism according to the invention, the lower plate of the differential is rotationally fixed to a central wheel in contact with the input wheel of a satellite, the satellite also comprising an output pinion in contact with the drive pinion.

[0038] Thanks to this particularly advantageous differential configuration, the transmission of information for cocking or uncocking the cylinder is achieved using a moving part with a reduced number of components and in a particularly compact form.

[0039] Finally, according to a particularly preferred embodiment for the power reserve display mechanism according to the invention, the display element is a needle moving on a first angular sector corresponding to a first angular range of 240 degrees.

[0040] Such an arrangement is particularly advantageous for displaying a potentially high power reserve level, especially when several barrels are used in series, the angular sector available for the display then being chosen accordingly as being deliberately large; the choice of a range greater than 180° degrees but significantly less than 360° aims to provide the most intuitive display possible by always clearly separating the highest level from the lowest. Brief description of the drawings

[0041] Other advantageous features will become clearer from the following description of a particular embodiment of the invention given by way of non-limiting example and represented by the accompanying drawings, in which: there figure 1 is a top view of a power reserve display mechanism according to a preferred embodiment within the scope of the present invention, using two barrels mounted in series and a differential; the figure 2 is a profile view of the display mechanism of the figure 1 ; there figure 3 is an enlarged view of the mobile display of the figure 1 highlighting the total number of turns, the thickness of the arms, and the number of turns per arm according to the preferred embodiment illustrated; The figure 4is a schematic view illustrating the details of the angular sectors and angular ranges used in the preferred embodiment for implementing the present invention; the figure 5A is a view of the power reserve display mechanism of the figure 1 in a disarmed position of the movement; the figure 5B is a view of the power reserve display mechanism of the figure 1 in armed position of the movement Detailed description

[0042] There figure 1is a top view of the power reserve display mechanism 1 of a mechanical watch movement according to the invention, equipped with a safety device for both winding and unwinding using only elastic coupling elements. The movement has the particularity of having two barrels mounted in series, i.e. a first barrel 21 and a second barrel 22, whose respective drum teeth, i.e. the teeth 211A of the first drum 211 and the teeth 221A of the second drum 221, are in mutual gear mesh.The first barrel 21 is wound by the first shaft 210, whose teeth 210A mesh with those 51A of an input wheel of a differential gear 5, formed by a lower plate 51 of this differential gear 5. The torque accumulated by these two barrels (first barrel 21 and second barrel 22), forming the mechanical energy source 2 for the movement, is transmitted via the second shaft 220 of the second barrel 22, whose teeth 220A mesh with the main finishing gear. The teeth 220A of the second shaft 220 of the second barrel also mesh, via a gear train formed by a reduction gear 3 and an intermediate gearbox 4, with a second input wheel of the differential, formed by a planet carrier 52, whose external teeth 52A can be seen meshing with those 4A of the intermediate gearbox 4.

[0043] With such a construction, it is possible to simultaneously retrieve information on the winding level of the first barrel 21, and the unwinding level of the second barrel 22, and to average them via the differential mobile 5. Thus, the accuracy of the information on the amount of energy stored by the energy source of the movement is improved compared to that of usual solutions using only information relating alternately to a winding level or a unwinding level.

[0044] In what follows, we will describe in a little more detail the transmission of the movement via the second shaft 220 of the second barrel and the reduction mobile 3, as well as the differential mobile.

[0045] On the figure 1The teeth of all the wheels or pinions are shown in solid lines, except for those of the reduction pinion 32 (teeth referenced 32A) and the central wheel 55 (whose teeth are referenced 55A), which are shown in dashed lines. Indeed, these gear elements are hidden and only visible on the figure 2 aiming to show the different gear planes of all the transmission elements. For the sake of readability, however, these elements have also been represented on the figure 1 so that the understanding of how the movement works can be based solely on reading this figure.

[0046] The reduction unit 3 has a reduction wheel 31 whose teeth 31A mesh directly with the teeth 220A of the second shaft 220 of the second barrel 22. As previously indicated, under this reduction wheel 31 and arranged coaxially with it, is the reduction pinion 32 which has teeth 32A meshing with the external teeth 4A of an intermediate gearbox 4 which is also in gear mesh with the second input wheel of the differential formed by the planet carrier 52, and whose external teeth are materialized by the reference 52A.The satellite 53, mounted on the periphery of the satellite carrier 52, has a first gear stage formed by the input wheel 531, whose teeth 531A mesh with those 55A of the central wheel 55, arranged coaxially under the drive pinion 54 at the output of the differential wheel 5, and an output pinion 532, whose teeth 532A mesh precisely with those 54A of the drive pinion of the differential wheel 5. The satellite 53 is thus driven in rotation relative to the lower plate 51 of the differential wheel, i.e., its first input wheel, only if the winding signal for the first barrel 21, supplied to it via the teeth 210A of the first shaft 210, differs from the winding signal for the second barrel 22, transmitted by the teeth 220A of the second shaft 220 via the gear formed by the reduction gear 3 and the intermediate link 4 to the second input wheel of the differential 5, i.e. the planet carrier 52.

[0047] In any case, the average of these two pieces of information is transmitted, at the output of the differential gear, by the drive pinion 54 to the power reserve display 6, the complete structure of which, according to this preferred embodiment of the invention, will be described in more detail on the figure 3 which follows. For this reason, a rectangle (A) surrounds the display mobile 6 and the content of the elements contained within this rectangle (A), including the integrated safety mechanism and the advantageous properties of coupling and selective disengagement conferred.

[0048] On the figure 1However, the partial toothing 61A of the rim 61 of this display mechanism 6 can be visualized. At its center, this mechanism has a hub 60 that is rotationally fixed to a display element, here represented by a hand 8, but which could, for example, take the form of a colored angular sector sliding under a display window. The hand points to a current power reserve value (V) when the watch is in use. The hub 60 is also connected to the rim 61 via a plurality of elastic arms 62. These arms allow, at the end of the travel of the sector corresponding to the partial toothing 61A, a release and thus an indefinite disengagement at the end of the winding or unwinding of the movement's power source. To complement the additional untoothed sector of the rim, a peripheral bead 610 is also provided, the technical functions of which will be specified later.

[0049] There figure 2The illustration shows a profile view of the transmission gear for the display mechanism according to the invention, that is to say, the same elements as those of the figure 1 , simply without the two barrels or the hand as a display element 3. In other words, this figure focuses the transmission to the display mobile 6 via the reduction mobile 3, the intermediate link 4, and the differential mobile 5 to show the compactness obtained, both in terms of thickness and space occupied on the movement plate thanks to at least a partial superposition of the display mobile 6 with respect to the other elements.

[0050] Each of the elements—the reduction gear 3, the intermediate gear 4, the differential gear 5, and the display gear 6—is shown around its respective axis of rotation (O3, O4, O5, O6). The power take-offs relative to this transmission gear are no longer illustrated in this figure, but it should be noted that the transmission to the lower plate 51 of the differential gear 5 is achieved by direct gearing to the first shaft 210 of the first drum 21, while the transmission of the drive torque to the planet carrier 52 of the differential gear 5 results from the indirect gearing of the latter to the second shaft 220 of the second drum 22 via the reduction gear 3 and then the intermediate gear 4. The reduction gear 3 includes a reduction wheel 31 whose teeth 31A mesh with those of the second shaft of the second drum 220 (not shown in this figure, but referenced as 220A on the figure 1), as well as a coaxial reduction pinion 32, fixed in rotation with the reduction wheel 31, and whose teeth referenced 32A mesh with those, referenced 4A, of the intermediate gearbox 4, and which meshes on the opposite side, with the satellite carrier 52 whose teeth are referenced 52A, which is mounted coaxially, but not fixed in rotation just above the lower plate 51 of the differential mobile 5. This lower plate 51 is mounted coaxially and fixed in rotation, on the other hand, with a central wheel 55, whose teeth referenced 55A mesh with the teeth referenced 531A of the input wheel of the satellite 53, whose output pinion of the satellite 532, coaxial and fixed in rotation with the input wheel of the satellite 531, meshes with the drive pinion 54 of the differential mobile 5.This drive pinion 54 has teeth referenced 54A in direct mesh with the partial teeth 61A for transmitting motion to the display unit, not shown in this figure. The drive pinion 54 constitutes the output in the kinematic transmission chain with respect to the lower plate 51 and the planet carrier 52, which together form a first and second input wheel for this differential; the four gear planes of the differential unit 5 can be distinguished in this figure, consisting of those of its two input wheels (i.e., the lower plate 51 and the planet carrier 52), and those of the two coaxial elements fixed in rotation to the planet 53, i.e., its input wheel 531 and its output pinion 532.The drive pinion 54 is thick enough so that it can finally mesh with the display mobile 6 on a fifth gear plane slightly raised relative to that of the output pinion 532 of the satellite 53, so that the satellite 53 can rotate under it in case of movement of the satellite carrier 52; a slight vertical gap is provided to allow for manufacturing and assembly tolerances.

[0051] Thus, thanks to the power reserve display mechanism 1 proposed within the framework of the present invention, it is possible not only to improve the display accuracy while maximizing the power reserve, but also to minimize the space required on the plate and its height.

[0052] There figure 3 shows the detail of the display unit 6 with integrated safety mechanism, as previously indicated, illustrating more precisely the elements contained within rectangle (A) of the figure 1 .

[0053] There figure 3 Thus, the display wheel 6, along with its partial teeth 61A on its rim 61, and the hub 60 at its center, all of which are movable about the axis of rotation referenced O6, that is, corresponding to that of the display wheel 6 as a whole. The hand, fixed in rotation to the hub 60 and positioned above it, constitutes a preferred display element 8 for implementing the invention; this hand can move, for example, along a scale extending over a predefined angular sector according to the total power reserve of the movement. The hand points to a current power reserve value (V) of the movement, indicating the time remaining before any manual winding is required.

[0054] The safety device here consists of a coupling between the hub 60 and the rim 61 of the display unit 6, that is, very simply in the plane of the latter, so as to save as much vertical space as possible. This coupling is achieved using a plurality of elastic arms 62, wound with a total number of turns N, here equal to 6, but which is preferably between 4 and 10 in order to guarantee stability of the rim 61 around its hub 60, that is, in the gear plane of the partial toothing 61A with the drive pinion 54 of the differential unit (not shown in this figure). The total number of turns N corresponds to the number of turns per arm Ns multiplied by the number of arms Nb: N = Ns * Nb

[0055] The number of turns per arm Ns allows adjustment of the disengagement flexibility and, in this preferred embodiment, has been chosen to be two to ensure sufficient flexibility according to the chosen dimensions. The number of arms Nb, on the other hand, contributes more significantly to the rigidity of the display unit 6 in its gear plane; the number of attachment points relative to the serge 61 must be greater than one to avoid any imbalance in terms of inclination, and preferably strictly greater than two to guarantee the best possible balance relative to the hub 60. Thus, according to the illustrated embodiment, the number of arms Nb is 3, while the number of turns per arm Ns is 2, which aims to provide an excellent compromise in terms of flexibility and stability. However, in order to avoid making the display unit 6 too rigid, a number of arms Nb less than or equal to 5 is preferably chosen.

[0056] The final adjustment parameter for coupling the serge 61 to the hub 60 is the thickness E of each elastic arm 62. This is preferably chosen to be between 0.05 and 0.25 millimeters in the proposed configuration, again with the aim of ensuring the best compromise between flexibility and rigidity; in the example chosen, it is preferably equal to 0.15 millimeters. Increasing the thickness E of the arms increases their rigidity, but simultaneously prevents a greater total number of turns N from being arranged for a given footprint, which is limited by the internal space of the serge 61.

[0057] The proposed configuration ensures both sufficient rigidity and flexibility to avoid excessive frictional forces on the meshing teeth during disengagement at the end of the engagement and disengagement strokes, i.e., on either side of the angular sector formed by the partial tooth 61A. As can be seen on the figure 3Clearances of amplitude D are formed on either side of the ends of the partial teeth 61A of the rim 61, in order to allow optimal interpenetration of the teeth of the gears in mutual meshing, namely that of the rim 61 and that (referenced 54A in the other figures) of the drive pinion 54. The first clearance 611 is located at one end of the partial teeth 61A of the rim 61, while the second clearance 612 is located at the other end of this partial teeth 61A. As can be seen, the partial teeth 61A and the peripheral rim 610 extend over "complementary" angular sectors, the peripheral rim 610 aiming to virtually replace the missing teeth on the periphery of the rim outside the two clearances.This peripheral bead 610 thus has a balancing purpose for the display mobile 6 in order to avoid any tendency for it to tilt; it also fulfills a shock-absorbing function by minimizing the potential movement of the display mobile relative to the wall of a housing where it would be placed, thus avoiding both damage to the axes and the impact of the shock.

[0058] The one-piece design of the display unit 6 with integrated disengagement mechanism formed by the elastic arms 62 is particularly advantageous in terms of productivity gains, since the proposed power reserve display mechanism 1 has an integrated safety device formed as a single unit with a display wheel. The materials chosen for the arms preferably possess hardness, flexibility, and abrasion resistance properties configured such that each disengagement operation generates virtually negligible wear.As an example, Durnico can be used, which has interesting properties in terms of both elasticity and friction; however, according to a particularly preferable variant, Phynox will be used instead, which also has very good properties in terms of elasticity and ductility for easy realization of the elastic arms 62, but which also has the advantage of providing magnetic shielding to the movement, and thus contributing not only to the robustness of the proposed display mechanism against magnetic disturbances, but more generally to the stability of the overall operation of the watch movement.

[0059] At the center of the hub is a loop 601, into which a fixed limiting pin 7 is inserted. This limiting pin 7 can move within the loop 601 until it reaches a stop against a first stop 6011 in one direction when the movement is in the fully unwound position (and the power reserve therefore displays "0") and against a second stop 6012 in the other direction when the movement is in the fully wound position. The angular sector over which the loop 601 extends allows the amplitude of the display sector to be defined in a particularly simple and efficient manner, in the plane of the display arm 6, and without requiring any other dedicated limiting mechanism.In the configuration of the limiting pin 7 relative to the loop, the hand can move a greater clockwise than counterclockwise, meaning that, according to the illustrated preferred embodiment, the current power reserve value (V) is more than half the maximum possible level. It may also be noted that the angular range over which the loop extends corresponds approximately to that of the partial teeth 61A of the serge 61; the following will explain the slight differences observed in the described preferred embodiment and the technical advantages conferred by such an optimized configuration.

[0060] On the figure 4This diagram, which represents a schematic representation of the operation of the display unit 6 between each extreme, i.e., the maximum and minimum winding levels, emphasizes the comparison of the different angular display ranges and angular display sectors of various elements, and in particular the loop 601 of the hub 60, the partial toothing 61A, and the peripheral bead 610 of the rim. Inside the loop 601 of the hub 60, the limiting pin 7 is shown in its two extreme display positions, i.e., during the complete disassembly of the movement where it is abutted against the first stop 6011 of the loop 601, and during the complete winding of the movement where it is abutted against the second stop 6012 of the loop 601.The first angular sector S1, over which the bezel 601 extends, corresponds to a first angular display range P1 of 240°. This has the advantage of being large enough to precisely indicate variations in a significant power reserve, preferably 120 to 130 hours of operation within the framework of the invention, thanks to the use of two barrels in series. It also allows for the intuitive differentiation of the maximum and minimum power reserve values, which would no longer be the case if the angular range approached 360° too closely. On either side of the partial toothing 61A, at the level of the first clearance 611 and the second clearance 612, the angular play of amplitude D allows the first toothed angular sector S1 to be separated from a third, untoothed angular sector S3, corresponding to the one over which the peripheral rim 610 of the bezel extends.The benefit of such a play is clearly visible in this figure; it is indeed to allow optimal penetration of the teeth of the gear pinion 54 (whose external teeth are designated 54A) into those of the external partial teeth 61A of the serge. It can be noted, however, that this partial toothing 61A extends over a second angular sector S2, slightly smaller than the first angular sector S1 of the display; the second angular range P2 of this second sector being preferably approximately 224°. The technical explanation for this slight difference is due to the fact that at the end of the cocking or disarming stroke, only one tooth, i.e. the last of the partial teeth 61A of the serge, is to be engaged with the teeth 54A of the drive pinion 54, so as to generate the minimum possible tension on the elastic arms 62 in order to perform the disengagement.If the partial toothing 61A extended over exactly the same angular range of 240°, then there would be a mutual meshing of at least two more teeth on each of the respective teeth of the gear pinion 54 and the sergeant 61, such that disengagement could only occur after a significantly greater rotational movement, thus generating much more tension on the elastic arms before the disengagement could take place. Furthermore, the time required to disengage the clutch is reduced (between one and two hours for the preferred variant shown, compared to five to six hours when the first angular sector S1 used for the display and the second angular sector S2, on which the partial toothing 61A of the sergeant 61 is intended, coincide).

[0061] Therefore, the arrangement of differential angular sectors of amplitude Δ, preferably symmetrically along the edge of the first angular sector S1, allows, on the one hand, minimizing the tension on the elastic arms 62 during the release and disengagement operations; on the other hand, these differential angular sectors, whose sum corresponds to an angular range equal to the difference between the first angular range P1 of the first angular sector S1 and the second angular range P2 of the second angular sector S2 [in other words: 2*Δ = P1 - P2], are intended to minimize the latency of the display pointer during a subsequent re-engagement, particularly after disengagement at the end of the winding cycle, without risk of losing the mesh. In the specific case illustrated on the figure 4, the amplitude of each differential sector is on the order of 8° which means that the second angular range of the partial toothing is 224°, allowing this optimal compromise to be obtained between minimizing the tension on the elastic arms 62 during disengagement, and at the same time reducing the latency time during re-engagement.

[0062] It can also be observed that the differential angular sectors of amplitude Δ are completely included respectively in the first clearance 611 and the second clearance, which thus possess an even greater angular play D, on the order of twenty degrees. Since the annular peripheral bead 610 is intended to "simulate" an almost complete tooth profile of the rim 61 outside the clearances designed to improve the mutual meshing with the drive pinion 54 of the differential, the third angular amplitude P3 of the third angular sector S3 over which the annular peripheral bead 610 of the rim extends is determined by the following formula: P 3 = 360 ° − P 2 − 2 * D .

[0063] This third angular range P3 thus corresponds, according to the preferred embodiment illustrated, to an angular sector of about one hundred degrees (~100°).

[0064] In the preceding embodiment, the amplitude of the throw of each of the releases D and the differential angular sectors Δ, as well as the number of arms Nb and the total number of turns N, are configured such that the stresses experienced by the elastic arms 62 are as low as possible during each disengagement operation. In this way, the risks of breakage and fatigue are limited over time. Furthermore, the materials used in connection with this configuration are chosen such that the forces required to tension the arms are negligible compared to the characteristics of the materials used; in this way, the durability of the system is improved by minimizing, in particular, the wear generated on the gear teeth and pivots.

[0065] Finally, the Figures 5A And 5Brespectively show the display mechanism in its two extreme positions, that is, when the power reserve is exhausted (case of the movement totally unwound) and respectively at its maximum (case of the movement totally wound).

[0066] These two figures illustrate elements already introduced in the previous figures; they will not be repeated in detail, particularly concerning the transmission gear (reduction gear 3 - intermediate gearbox 4 - differential gear 5). It should be noted that the elements shown in these figures are, moreover, identical in every respect to those shown in the... figure 1 , except for the drums of each cylinder (i.e. the first drum 211 of the first cylinder 21 and the second drum 221 of the second cylinder 22).

[0067] On the figure 5AThe movement is completely unwound, and consequently the limiting pin 7 is against the first stop 6011 of the loop 601 of the hub 60; the hand is then in a position where it can only move in the winding direction Sa, which here corresponds to the counter-clockwise direction. The displayed power reserve value thus corresponds to the minimum value (Vmin), typically "0".

[0068] Conversely, on the figure 5B The movement is fully wound, and consequently, the limiting pin 7 is against the second stop 6012 of the loop 601 of the hub 60; the hand is then in a position where it can only move in the unwinding direction Sd, which here corresponds to a clockwise direction. The displayed power reserve value thus corresponds to the maximum value (VMax).

[0069] The choice of reduction ratios allows for the indication of a full power reserve of approximately five days (120 hours), corresponding to the difference between the maximum (Vmax) and minimum (Vmin) values ​​over a 240-degree display area. This corresponds to the amplitude of the first angular range P1, over which the first angular sector of the hub's 601 band extends. The display is thus extremely precise, as one hour of power reserve corresponds to approximately two degrees.

[0070] Outside this 240-degree display range, the safety device provided by the elastic arms 62 connecting the central hub 60 to the serge 61 of a partially toothed display wheel 6 driven by the drive pinion 54 at the output of the differential mobile prevents any breakage of one or more components, despite the fact that the limiting pin 7 then blocks any additional movement of the indication system.

[0071] In the foregoing, apart from the introduction of a new solution with a more reliable safety system using elastic coupling means between the indicator and drive parts of the power reserve mechanism, an embodiment for implementing the present invention has been described, which uses two mainspring barrels in series as the power source. The type of barrel, i.e., fixed-flange or sliding-flange, has not been specified. However, those skilled in the art will understand that the invention can be implemented with any type of barrel and regardless of their number as the mechanical power source. The core of the invention lies in decoupling the power reserve indicator, such as a hand, potentially to infinity both during winding and at the end of its travel when the movement continues beyond the minimum level of the intended display range.

[0072] The invention also enables the creation of a differential with a simplified construction compared to the relatively complex ones using a friction wheel for disengagement. This simplifies manufacturing and assembly by eliminating the time spent searching for the optimal friction torque through specific sizing and lubrication, as well as the need to inspect each batch of components produced. In this way, the risk of excessive friction, which would cause excessive wear on the parts, or insufficient friction, which would cause transmission problems by failing to engage the clutch when necessary, is also eliminated. Precision and durability are thus improved.

[0073] Eliminating lubrication is an additional argument in favor of durability, as there is no longer any wear related to oil aging, and after-sales service will also be facilitated.

Claims

1. A power reserve display mechanism (1) of a timepiece supplied by a mechanical power source (2), comprising an input wheel and pinion provided with a driving element driven in a first direction during the winding and in a second direction opposite to said first direction during the unwinding of said power source (2), said driving element being arranged to receive an information value (V) relating to said current power reserve, and to transmit it to a display member (8) which is movable in rotation and is likely to move over a first angular sector (S1) corresponding to a first predefined angular range (P1) between a minimum display value (Vmin) and a maximum display value (Vmax), said movable display member (8) being integral in rotation with the hub (60) of a display wheel and pinion (6), which display wheel and pinion (6) furthermore comprises a felloe (61) provided with partial teeth (61A) extending solely over a part of its circumference and which is arranged to mesh with said driving element, said felloe (61) and said hub (60) being connected to one another via at least one elastic arm (62), said power reserve display mechanism (1) being characterised in that said power source (2) is formed by a first barrel (21) and a second barrel (22) arranged in series, and in that said input wheel and pinion is formed by a driving pinion (54) at the exit of a differential (5) having two input wheels (51, 52) respectively engaged, on the one hand, with a first shaft (210) of said first barrel (21) and, on the other hand, with a second shaft (220) of said second barrel (22), said first input wheel being formed by a lower plate (51), and said second input wheel being formed by a planetary wheel (52), said lower plate (51) and said planetary wheel (52) being coaxial and superposed.

2. The power reserve display mechanism (1) according to Claim 1, said hub (60) furthermore being provided with a loop (601) extending over a first angular sector (S1) corresponding to said predefined first angular range (P1), and a fixed limiting pin (7) being housed in said loop (601) and being able to come into abutment on either side of the hub for the respective display of said minimum display value (Vmin) and said maximum display value (Vmax).

3. The power reserve display mechanism (1) according to Claim 2, the partial teeth (61A) of the felloe extending over a second angular sector (S2) strictly included in said first angular sector (S1).

4. The power reserve display mechanism (1) according to any one of the preceding claims, in which said partial teeth (61A) of said felloe (61) are formed by external peripheral teeth of said display wheel and pinion (6).

5. The power reserve display mechanism (1) according to any one of Claims 3 or 4, said felloe (61) being furthermore provided with an external peripheral bead (610) extending over a third angular sector (S3) corresponding to a third angular range (P3), said third angular sector (S3) being situated strictly outside of said second angular sector (S2).

6. The power reserve display mechanism (1) according to any one of the preceding claims, comprising a number of arms (Nb) of between 2 and 5.

7. The power reserve display mechanism (1) according to any one of the preceding claims, comprising a total number of coils (N) of between 4 and 10.

8. The power reserve display mechanism (1) according to any one of the preceding claims, characterised in that said at least one elastic arm (62) is furthermore produced in a non-magnetic material.

9. The power reserve display mechanism (1) according to any one of the preceding claims, characterised in that the display wheel and pinion (6) is formed in a monobloc fashion by said hub (60), said felloe (61) provided with partial teeth (61A) and said at least one elastic arm (62) connecting said felloe (61) to said hub (60).

10. The power reserve display mechanism (1) according to Claim 1, said driving pinion (54) being coaxial with, and superposed on, said lower plate (51) and said planetary wheel (52) .

11. The power reserve display mechanism (1) according to Claim 10, in which said lower plate (51) of the differential is integral in rotation with a central wheel (55) engaged with the input wheel (531) of a planetary (53), said planetary furthermore comprising an output pinion (532) engaged with said driving pinion (54).

12. The power reserve display mechanism (1) according to any one of the preceding claims, in which said display member (8) is a hand moving over a first angular sector (S1) corresponding to a first angular range (P1) of 240 degrees.