HK1192334B - Wheel with a flexible toothing - Google Patents

Description

Gear with flexible gear ring

Technical Field

The invention relates to a timepiece gear comprising a plurality of teeth with play compensation, each tooth comprising a catch (catch) projecting from a catch foot, and an elastic strip projecting from a strip foot opposite the catch, the strip being separated from the catch by a ventral notch, the intrados profile (intrados profile) of the strip defining a dorsal notch on the side opposite the catch, the strip foot being defined by the inner end of the ventral notch and the inner end of the dorsal notch towards the pivot axis of the gear.

The invention also relates to a timepiece train including at least one gear of this type.

The invention also relates to a timepiece movement including at least one wheel train of this type.

The invention also relates to a timepiece comprising at least one timepiece movement of this type and/or at least one wheel train of this type.

The present invention relates to the field of timepiece mechanisms or scientific measuring devices including wheel trains.

Background

The manufacture of timepiece wheel trains comprising gear means without backlash is complicated, since it involves finding compatibility between optimum torque transmission with the best possible output (yield) and good impact resistance.

The solution of a flexible toothing, in which each tooth comprises a rigid portion and an elastic portion, satisfactorily solves the problem of energy transmission, but is less satisfactory in terms of the problem of impact resistance. The above problem is even more pronounced if these flexible ring gears are typically designed to be made of micro-machinable material, silicon or similar by a "LIGA" or similar method. EP patent application No.2112567A1 in the name of Rolex discloses a gear arrangement with backlash compensation comprising a gear wheel with a flexible elastic part manufactured in this way.

Disclosure of Invention

The present invention proposes to define a compliant gear geometry that can be made of micromachinable material, silicon or similar by "LIGA" or similar methods and satisfactorily solves both problems posed by output and impact resistance.

The invention therefore relates to a timepiece gear comprising a plurality of teeth with play compensation, each tooth comprising a clip projecting from a clip foot, and an elastic strip extending from the strip foot opposite the catch, the elastic strip being separated from the catch by a ventral notch, the intrados profile of the elastic strip defines a dorsal notch (dorsal notch) on the side opposite the clip, the strap foot is bounded by an inner end of the belly cutout and an inner end of the dorsal cutout towards the pivot axis of the gear, wherein the inner end of the dorsal notch is located closer to the axis than the inner end of the ventral notch, and extends on one side of the axis below the clip foot or below the internal geometry extension of the ventral notch towards the pivot axis.

The invention also relates to a timepiece gear train including at least one toothed wheel of this type, characterized in that said toothed wheel is geared with an opposite toothed shaft, the teeth of said toothed shaft including an area of maximum cross section arranged to cooperate in driving abutment with an outer portion of said clip or said bar, substantially radially with respect to said pivot axis of said toothed wheel.

The invention also relates to a timepiece movement including at least one wheel train of this type.

The invention also relates to a timepiece comprising at least one timepiece movement of this type and/or at least one wheel train of this type.

Drawings

Other features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

figure 1 shows a schematic plan view of a gear with a flexible ring gear according to a first embodiment of the invention.

Fig. 2 shows a schematic plan view of a detail of the gearing region of a gear train comprising a gear according to fig. 1 and a rigid, opposed toothed shaft, wherein on the first tooth the catch and the bar are in mutual contact, while on the second tooth the corresponding catch and bar are still far from each other. Due to the particular configuration of the flexible strip surrounded by the cut-outs specifically defined according to the invention, the arrows represent the stress exerted by the teeth of the rigid toothed shaft on the flexible strip of the second teeth, the double line representing the lever arm on which the thrust is exerted.

Fig. 3 is a schematic view similar to fig. 2, showing another variant of the invention and another relative position between the rigid toothed shaft and the flexible gear, in which no (flexible) strip is pressed against one of the catches.

Fig. 4 shows a schematic plan view of an end detail of an integral section of the gear according to the variant of fig. 3, comprising a clip of this type and a strip of this type.

Fig. 5 shows a schematic plan view of the different operating radii of the components of the invention.

Fig. 6 shows a schematic plan view of a rigid toothed shaft designed to cooperate with the flexible gear of fig. 1.

Fig. 7 shows a schematic plan view of a detail of the periphery of a flexible gear according to the invention, in a variant different from that shown in the previous figures, with the inner end of the dorsal notch located between the pivot axis of the gear and the foot of the nearby clip.

Fig. 8 shows a schematic plan view of a detail of the inner ends of the dorsal and ventral incisions of the gear of fig. 1, while fig. 9 shows a different configuration which is less advantageous compared to fig. 8.

Figure 10 shows a block diagram of a timepiece comprising a movement, which in turn comprises a gear train comprising a flexible gear according to the invention.

Figures 11-14 show a particular solution in which the outer part of the clip is fork-shaped and comprises a first tooth and a second tooth bounded by a hollow. Both teeth are much stiffer than the resilient strip.

Fig. 11 shows an exemplary application of this type of gear, which meshes with two gear shafts: a central gear shaft providing torque to be transmitted. The pinion drives a gear, which in turn drives a small seconds pinion on which a small seconds hand (not shown) is pinned;

figures 12 and 13 show specific solutions that will be described hereafter;

the configuration of figure 14 is designed for driving a date mechanism with hands via a flexible plate forming a gear.

Detailed Description

The present invention relates to the field of timepiece mechanisms or scientific measuring devices including drive trains.

The present invention proposes to define a compliant gear geometry that can be made with micromachinable materials, silicon or similar by "LIGA" or similar methods, and that guarantees both good output and good impact resistance.

The present invention relates to the improvement of the performance of this type of flexible ring gear, taking into account the constraints imposed by the manufacturing method. In fact, in order to guarantee a sufficient resistance of the flexible strips or just the teeth of the toothed wheel made of micromachinable material and placed on the plate, a minimum aspect ratio (aspect ratio), i.e. the ratio of the minimum width of the solid or hollow portion with respect to the thickness of the plate, must be considered, in addition to other constraints not detailed here. The aspect ratio is typically between 5 and 10, and the closer it is to 5 the easier it is to produce. The aspect ratio is equally effective for solid portions, such as elastic strips, as well as hollow portions, slots or cuts. Square recessed corners are prohibitive, particularly at the bottom of the slot or cut-out. In general, a minimum radius of curvature must be observed for each portion of the geometry of the part.

The invention thus relates to a timepiece gear 10, the timepiece gear 10 comprising several teeth 2 with play compensation. Each tooth 2 comprises a catch 3 and an elastic strip 4, said catch 3 projecting from a catch foot 31 and the elastic strip 4 projecting from a strip foot 41 opposite said catch 3, said catch being separated from said elastic strip by a ventral cut 5. The strip 4 has an intrados profile 43 on the side opposite to the above-mentioned clip 3. The intrados profile 43 defines a back/ridge cut 6. Strip foot 41 is delimited towards pivot axis D of gear 10 by inner end 51 of ventral notch 5 and by inner end 61 of dorsal notch 6.

According to the invention, the inner end 61 of the dorsal notch 6 is located closer to the axis D than the inner end 51 and extends on the side of said axis D below the catch foot 31 or below the inner extension 52 of said ventral notch 5 towards the pivot axis D. "extension 52" here refers only to the geometrically curvilinear extension of the median profile of the ventral incision, represented in the figures by the double dashed line, and not to a specific part or profile of the gear 10.

More specifically, for the timepiece mechanism, the gear 10 includes a plurality of play compensation teeth 2 having a variable geometry at the periphery of a gear body 11.

Each of these teeth 2 comprises at least one clip 3 and at least one elastic strip 4, said clip 3 being attached to the gear body 11 in a cantilevered arrangement via a clip foot 31, and said elastic strip 4 being attached to the gear body 11 in a cantilevered arrangement via a strip foot 41; the strip 4 is positioned opposite a clip 3 of this type, the strip 4 being separated from the clip 3 by a ventral cut 5. The elastic strip 4 extends between an additional back profile 42 on one side of said clip 3 and an intrados profile 43 on the opposite side of said clip 3. The intrados profile 43 defines a back cut 6 separating the strip 4 from the rest of the gear wheel 10. Strip foot 41 is delimited on the one hand by the inner end 51 of ventral notch 5 on the side of pivot axis D of gear 10 and on the other hand by the inner end 61 of dorsal notch 6.

According to the invention, in order to allow clip 3 to bend when gear train 100, in which gear 10 is included, is impacted, inner end 61 of dorsal notch 6 is located closer to pivot axis D than inner end 51 of ventral notch 5. The inner end 61 of dorsal notch 6 extends on the side of pivot axis D below catch foot 31 or below the inner extension 52 of ventral notch 5 towards pivot axis D.

In fact, the constraint of making this type of gear 10 of micromachinable material requires that the ventral and dorsal incisions 5, 6 be curved at their inner ends 51, 61, respectively, with a certain radius. Minimum value R of the end radius_min1Defined by the nature of the material and the thickness of the panel. Likewise, any value of radius of curvature R_min2But also by the nature of the material and the thickness of the panel.

Figures 2 and 8 show the inner ends 51 and 61 of the ventral notch 5 and dorsal notch 6, the inner ends 51 and 61 being curved with respective values of radius R1 and R2, both of which are necessarily greater than the value R_min1And R_min2。

The stiffness of each portion of the tooth 2 depends mainly on the length and width of the portion concerned, under the simplified assumption that the thickness of the plate is constant. In the particular embodiment of fig. 1 and 2, the length of clip 3 from its clip foot 31 and the length of bar 4 from its bar foot 41 are similar. This can be simplified by explaining that the cube of the width determines the force required to obtain a specified deflection at the ends of the strip or clip. For example, if the ratio of clip width LE to bar width LL is 4, the force ratio is 64.

In normal operation, the torque to be overcome is practically zero, the rigid portion formed by the clip 3 not undergoing any significant deformation. In order to obtain zero play, the flexible portion formed by the strip 4 must bend, and this bending is related to the torque take-off, which is related to the gear transmission. On impact, the situation is very different, since the rigid part formed by the clip bends significantly and its effective rigidity is crucial for the impact resistance; the strip 4 has a negligible effect on impact resistance. However, if these strips 4 are sandwiched between the teeth 71 of the opposite toothed shaft (pinion) 7 and the rigid clip 3, their deformation must be limited to prevent them from breaking. Advantageously, therefore, the clip 3 has an intrados profile 36 similar to the additional back profile 42 of the strip 4 and an additional back profile 37 similar to the intrados profile 43 of the strip 4, as seen in fig. 2. The relative parallelism under stress between the clip and the outer profile of the bar provides the gear 10 with greater stability in the event of an impact than prior art compliant gears.

The width LL of the bars 4 is determined by an aspect factor. In the preferred case where all the teeth 2 of the same gear 10 are engaged, as shown in fig. 1, the width of the back cut 6 is limited by the circumferential distribution of the teeth 2 on the gear. Fig. 1 and 2 show a particular variant in which the width LL of the strip 4 extends from the strip foot41 to its distal end 47, where the strip 4 is simply curved with a radius greater than or equal to R_min2. In the free state without stress, the width of the back incision 6 is close to or equal to the width of the strip 4.

One problem that arises is therefore the relative position of these ends 51 and 61, which must give the strip 4 sufficient flexibility to distribute the stresses exerted by the gear train 100 to which the gear 10 concerned belongs appropriately on the above-mentioned strip 4 (or vice versa) and therefore not to weaken the clip 3 more than necessary. According to the invention, the positions of the inner ends 51 and 61 of the ventral and dorsal incisions 5 and 6 are dimensioned and positioned in such a way that the clip 3 has a minimum deformation during normal use and can only be bent when much higher stresses than usual are applied, in particular when subjected to an impact.

In the plane of the gear wheel 10, the width LE of the clip 3 at its clip foot 31 is more than 3 times, preferably more than 6 times, the corresponding width LL at the bar foot 41. In the variant of fig. 1 and 2, the width of clip 3, which is also more than 5 times the corresponding width of the inflection point (inflection) zone 48 included in strip 4, does not vary much over its length and in the contact zone in the outer portion 34 of clip 3 with the opposite toothed shaft 7 in the gear train 100 in which gear 10 is included, this inflection zone 48 forming a preferred contact zone with toothed shaft 7.

Of course, other variations of clip 3 (e.g., clip 3 of fig. 3) may taper in width from foot 31 to distal end 35 thereof. It is important that clip 3 have the greatest width at its base at clip foot 31 because this area is subjected to the greatest stress upon impact.

The ends 51 and 61 should not be located at the same radius value with respect to the pivot axis D, since this would provide too much flexibility for both the clip 3 and the strip 4: the section of strip 4 will no longer match the aspect ratio and strip 4 can no longer be manufactured and clip 3 will be too flexible, i.e. it will be flexible in normal operation, which is not desirable to maintain a good output. Thus, the distance between end 51 of ventral notch 5 and pivot axis D is preferably different from the distance between end 61 of dorsal notch 6 and the same axis D as described above.

Similarly, forming the end radius R1 or R2 in the axis of symmetry at the foot 51 or 61 of the ventral notch 5 or dorsal notch 6 is disadvantageous for the remaining section of the strip 4. Preferably, therefore, the end radius is offset laterally at the inner end of the cut-out with respect to the axis of the cut-out, in particular when the end radius is greater than the half-width of the cut-out in question at its inner end.

The end radius R1 of the abdominal incision 5 cannot move away on the strip 4 side due to the extreme stress imparted by the aspect ratio. It can only be moved away on one side of the clip 3 as seen in the preferred embodiment of fig. 2.

The end radius R2 of the back cut 6 cannot move away on the side of the strip 4 either because of the ultimate stress imparted by the aspect ratio. It can only be moved away on one side of the clip 3 as seen in the preferred embodiment of fig. 2. However, the rigidity of the clip 3 must be maintained during normal gearing operations, and it is therefore undesirable to produce too much local weakness in the clip foot 31. This is why, according to the invention, the radius R2 is located "below" the radius R1, i.e. closer to the pivot axis D than the radius R1. Thus reducing the weakening of the clip 3. Moreover, any impact reaching the bottom of the back cut 6 now has an effect in a substantially radial direction and thus just into the solid material.

In short, the foot 31 of the clip 3 is weakened at the radius R1 of the inner end 51 of the ventral notch 5 on the one hand, and at the radius R2 of the inner end 61 of the dorsal notch 6 on the other hand, said inner end 61 being located closer to the axis D than the inner end 51. This gradual weakening maintains the resistance of the catch 3 during normal operation and therefore ensures a good output of the gear train, while providing just enough flexibility at impact. More specifically, in the usual case, the gear train drives a large second hand, with a large unbalance: weakening clip foot 31 according to the present invention provides resistance to typical impacts (e.g., a clock hand being dropped) according to typical experimental values that will not be described in detail herein.

All other things being equal, the passage of the dorsal incision 6 under the ventral incision 5 extends the effective length of the strip 4 without weakening the clip 3 too much.

This relative positioning of the radii R1 and R2 also provides for fitting the strip 4 obliquely at its strip foot 41 at an angle β relative to a radial line starting from the pivot axis D and passing through the strip foot 41.

Thus, when the flexible strip 4 is bent, its inner portion 44 tends to pivot about the strip foot 41 and the distal end 47 undergoes almost one rotation about a point which is approximately one third of the length of the strip 4 and between the inner portion 44 and the intermediate region 45, the intrados profile 36 of the clip 3 and the profile 42 of the strip 4 being preferably substantially parallel to one another once such rotation is applied.

In a particular embodiment, as shown in the figures, each tooth 2 is separated from the next by a back cut 6.

In a particular embodiment, as seen in the figures, each tooth 2 comprises a clip 3 of this type and a strip 4 of this type. Embodiments with more components are theoretically possible, but the width of each component is limited by the implementation method and to comply with the aspect ratio, whereas designing the teeth 2 with only two components (i.e. the clip 3 and the strip 4) allows an optimal manufacture and provides sufficient resistance for these components.

In a particular embodiment, as shown in the figures, the cut 6 extends between the catch 3 of a tooth 2 and the strip 4 of the tooth 2 adjacent to the previous tooth.

In a particular embodiment, as shown in particular in fig. 1, the ventral notch 5 has substantially parallel edges, and the clip 3 comprises, between the clip foot 31 and the intermediate region 33, an inner substantially rectilinear portion 32, which rectilinear portion 32 forms an angle α E with a radial line from the pivot axis D, which angle α E is between 10 ° and 30 °, preferably between 15 ° and 20 °. Between the intermediate region 33 and its distal end 35 furthest from the pivot axis D, the clip 3 further comprises an outer portion 34, which outer portion 34 extends substantially radially with respect to the pivot axis D.

Similarly, between strip foot 41 and intermediate region 45, strip 4 comprises a substantially rectilinear inner portion 44, which inner portion 44 forms an angle al with a radial line from pivot axis D, which angle al is between 10 ° and 30 °, preferably between 15 ° and 20 °, and between intermediate region 45 and its distal end 47 furthest from pivot axis D, an outer portion 46 extending substantially radially with respect to pivot axis D.

This angle al enables the lever arm to increase relative to the foot 41 of the bar 4 when the toothed shaft 7 or the opposite gear of the gear 10 exerts a bearing stress on the distal end 47 of the bar 4. In fig. 2, the arrows represent the forces exerted by the teeth of the rigid toothed shaft 7 on the flexible arm 4t, while the double lines show the lever arm on which this thrust is exerted.

Preferably, the angles α E and α L are close to or equal in value; especially a value of 15 deg. gives good results.

In the particular embodiment of fig. 2 and 8, the inner end 51 of the abdominal incision 5 is curved at a first radius R1. The inner end 61 of the dorsal notch 6 is curved with a second radius R2, which second radius R2 has a greater value than the first radius R1. Preferably, dorsal notch 6 has a profile followed near its inner end 61 by a third radius R3, the third radius R3 having a higher value than the second radius R2, so that dorsal notch 6 passes between pivot axis D and inner end 51 of ventral notch 5.

In the variant shown in fig. 1, between strip foot 41 and intermediate region 45, strip 4 has a substantially rectilinear inner portion 44, which inner portion 44 forms an angle al with a radial line from pivot axis D, which angle al is between 10 ° and 30 °. Between the intermediate region 45 and its distal end 47, which is furthest from the pivot axis D, the strip 4 further comprises an outer portion 46, which outer portion 46 extends substantially radially with respect to the pivot axis D up to an inflection region 48, which inflection region 48 is between a concave portion defined by the inner portion 44 and the outer portion 46 and a convex portion 49 as far as the distal end 47. This male portion 49 is arranged to fit in an abutting manner on the distal end 35 of the clip 3.

The invention also has the advantage of being insensitive to variations in the centre distance between the pivot axis D of the gear wheel 10 and the pivot axis Ω PR of the opposite toothed shaft 7.

For example, in NiP embodiments implemented with the "LIGA" (ultraviolet) method, wherein the modulus of elasticity is about 90Gpa, as shown in figures 1, 2 and 5, the thickness of the plate is between 0.10mm and 0.18 mm.

The variants shown in fig. 3 and 4 are designed along the same lines as in fig. 1 and are designed to reach the aspect ratio value 5 as close as possible. The torque release and impact resistance of these two variants are similar. To meet these criteria, the variant of fig. 3 comprises 90 teeth when the variant of fig. 1 has 99 teeth, and the variant of fig. 3 has a thickness of 0.12mm when the variant of fig. 1 has a thickness of 0.15 mm. The depth and slope of the ventral and dorsal incisions are optimized to obtain good performance both during normal gearing and when impacted. In this variant of fig. 3, the inner portion 44 of the strip 4 and the inner portion 32 of the clip 3 are both substantially linear from their respective feet 41 and 31, whereas the strip 4 and the clip 3 of the variant of fig. 1 have a profile in their inner portions 44 and 32 which is more nearly circular or parabolic and continues to their intermediate portions 45 and 33. An aspect ratio of 5.5 for the fig. 3 variant is chosen for mass production and is used in this example with a machine plate having a thickness of 0.12 mm.

As a non-limiting example of experimental confirmation, to clarify the geometry of the variant of FIGS. 1 and 2, the distance E of the centers is 2.78mm and allows a variation of +/-0.03 mm. The module of the rigid gear shaft 7 comprising 11 teeth is 0.052, its maximum tooth width LD at a radius of 0.286mm is 0.073mm and the maximum radius RH of the gear shaft is 0.35 mm. The maximum radius RA of the bar 4 of the gearwheel 10 with 99 teeth is 2.64mm, the maximum radius RB of the clip 3 is 2.63mm, the gearwheel radius (gear radius) RC is 2.574mm, the end radius RE of the abdominal incision is 2.23mm and the end radius RF of the dorsal incision is 2.19 mm. The width LE of the clip 3 is 0.070mm and the width LL of the strip 4 is 0.022 mm. The radius of the strip 4 at the inflection zone 48 is 0.062mm, said strip 4 also having a concave radius of 0.020mm at its distal end 47, which distal end 47 is arranged to bear against the distal end 35 of the clip 3.

The expected results are achieved by this geometry:

in the case of an increase or a decrease of the center distance by 0.03mm or 0.03mm from the nominal value, the gear arrangement still has no backlash (backlash). The toothed shaft 7 is therefore always in contact with the plate of the toothed wheel 10, regardless of their respective pivoting direction: the flexible strip 4 is wound or the plate is rotated and then contact occurs on the clip 3;

even in the case where the distance of the centers is at its lowest value, the average torque release does not exceed 5% of the barrel torque relative to the plate. The strip 4 bends and rubs and uses up the torque on the teeth 71 of the toothed shaft 7;

the most rigid part of each tooth formed by the clip 3 does not break when the unbalance of the hand carried by the toothed shaft (in particular the small second hand) applies a torque to the plate in the event of an impact. The traction stress never exceeds the elastic limit of Nip, i.e. about 17000 Mpa.

Due to the slope of the legs 31 and 41 of the clip 3 and the strip 4, a large length of the flexible part of the strip 4 is obtained, which is advantageous for reducing the torque release. At the smallest center distance, this inclination also prevents the teeth 71 of the toothed shaft 7 from coming into contact with the distal end 35 of the clip 3 in an almost arched state, which is disadvantageous.

The invention also relates to a timepiece gear train 100, this gear train 100 comprising at least one toothed wheel 10 of the type forming a gear transmission with an opposite toothed shaft 7, the teeth 71 of the aforementioned toothed shaft 7 comprising an area 72 of maximum section, this area 72 being arranged to cooperate in driving abutment substantially radially with respect to the pivot axis D of the toothed wheel 10 with an outer portion of the clip 3 or bar 4 of the aforementioned toothed wheel 10, as can be seen in fig. 2.

A preferred application is to obtain a timepiece gear arrangement without backlash. One particular application is small counters, such as small seconds counters (seconds), which are untensioned in the train and can move freely in the set of gear arrangements. The invention thus avoids the need to be held steady by friction, springs or magnets to stabilize the floating pointer.

In a preferred embodiment, the zone 72 with the largest cross section cooperates with the gear wheel 10 on a radius corresponding to the radius of the inflection zone 48 of the strip 4.

Fig. 11-14 show a particular solution in which the outer portion 34 of the clip 3 is fork-shaped and comprises a first tooth 81 and a second tooth 85 bounded by a hollow 87. Both teeth 81 and 85 are much stiffer than the resilient strip 4. Thus, as seen in the example of figure 11, for a small seconds display, the opposing gear wheel 7 engages with the flexible strip 4 once per second and with one of the teeth 81 or 85 of the clip 3.

The distal ends 47 of the elastic strip 4 and the distal ends of the teeth 81 and 85 are housed in the same cylinder centred on the pivot axis of the flexible gear 10, all of these distal ends preferably being tangential to the same cylinder and having the same maximum radial dimension.

The first tooth 81 is directly opposite the distal end 47 of the elastic strip 4 and adopts, on a first tooth side, a concave profile 84, which concave profile 84 is complementary to the above-mentioned convex profile 49 of the distal end 47, so as to be able to engage in abutment over a relatively wide surface when the elastic strip 4 is bent downwards towards the clip 3 concerned under the action of the tooth 71 of the opposite toothed wheel 7. The opposite flank of the aforementioned first tooth 81 has a profile 83, in particular an involute of a circle or the like, which profile 83 is arranged to cooperate with the tooth 71 of the gearwheel 7, as can be seen in fig. 11 or 14.

Such a gear solution, comprising several groups formed by flexible strips 4 and fork clamps 3 respectively, ensures the overall performance of the movement in terms of rate, amplitude and wear resistance, in particular a good shock resistance which is significantly improved. When integrated in the gear train, no "floating" of the small second hand was observed. Especially for the opposite gear and pivot, the wear and ageing resistance is even better than for the variants of fig. 1-9.

The improvement in wear resistance here is achieved by removing every other flexible arm, compared to the variant of fig. 1-9. The wear resistance can be further improved, the stress in the gear transmission reduced, or the winding of the flexible arm reduced by coating the gear ring with a gold layer.

For reducing the stresses in the gear transmission care must be taken to ensure that there is no play at the maximum centre distance. The geometry of the rigid teeth 81 and 84 and the flexible teeth 4 has been studied to ensure that there is no play in the gear transmission at the maximum centre distance (here chosen on the basis of the nominal centre distance, increased by 30 microns).

The configuration of fig. 14 is designed for driving a date mechanism with hands via a gear 1 formed of a flexible plate.

To facilitate assembly, and to avoid putting the teeth of the toothed shaft on the incorrect side of the flexible arm or even damaging it, the toothed wheel 10 advantageously has, at the end of the rigid teeth 81, a small hook 89 working together with the elastic strip 4. The aim is to obtain the correct side of the elastic strip 4, said elastic strip 4 having a first aperture 91, which first aperture 91 is substantially larger than a second aperture 92 on the other side, as can be seen in fig. 14. Therefore, during assembly, it is easy to position the teeth 71 of the counter gear 7 in the correct position.

The compliant gear 10 according to the present invention is designed to operate in both directions. Fig. 11 shows an exemplary application using a gear 10 of this type, the gear 10 being in mesh with two gear shafts: a central toothed shaft 701, which toothed shaft 701 provides the torque to be transmitted. The pinion 701 drives the gear 10, which gear 10 in turn drives the small seconds pinion 702, wherein the small seconds hand is pinned to the small seconds pinion 702. Therefore, the ring gear of the gear 10 operates differently from the central gear shaft 701 and from the small second gear shaft 702. In the first case, the elastic strips 4 are always deformed as much as possible until they touch the rigid portion formed by the closest tooth 81. Such contact must not cause retardation at this point, especially when the center distance is at a minimum tolerance; in the second case, however, the elastic strip 4 is in principle not in contact with the rigid portion 81 or 85, except in the event of an impact. Of course, there must never be any play in both gear transmissions.

The counter-gear 7 can have various types of teeth, in particular but not exclusively:

very wide teeth with almost square profile, thus contributing to the reduction of play. This profile is designed to reduce play, rather than to ensure improved transmission and torque/output efficiency;

or, have a standard involute profile that is more useful for torque transmission efficiency than for the lash problem. The end position of the elastic strip must therefore also be adjusted to eliminate play by means of such a profile.

The methodology of design is complex and requires long-term simulation and repetition (iteration). Starting from a standard rigid profile, an elastic strip is drawn at the minimum center distance, which eliminates play. The simulation test relates to all angular positions of the center distance. In each angular position, no play is checked and the profile of the strip is modified to achieve this first condition. The next test involves simulation in both pivoting directions. In particular, when the opposite gear 7 is driving, it is checked whether the elastic strip 4 is abutting against the teeth forming the rigid part and whether this contact is causing any retardation or undesired stress in the elastic strip. This simulation must be performed in all angular positions and at various center distances between the minimum center distance and the maximum center distance. The contour can be corrected as many times as necessary to obtain the desired result.

In the case of, for example, fig. 11, where severe stresses in terms of torque release and impact resistance must be dealt with, the shapes of the rigid and flexible portions must be further optimized, in particular the elastic strips 4 must be elongated to make them more flexible and bent in order to keep the rigid portions wide enough at the bottom of the ring gear to resist impacts.

According to these variants, the flexible strip 4 occupies a variable position in the gap between the two closest rigid teeth 81 and 85.

Fig. 12 shows a variant in which, in the non-operative, non-limiting configuration, the free spaces and the ends of the bars 4 and of the teeth 81 and 85 are distributed as follows:

the total sector starting from the centre Ω RF of the flexible gear 10 is defined between a radius R1 tangent to the salient point 82 of the first tooth 81 and a similar radius R10 of the subsequent set of teeth on one side of the bar 4. The gear 10 is shown here as a preferred but non-limiting embodiment, in which it is formed by a set of identical teeth grouped periodically arranged at the periphery of the gear. The sector is shared between 5 regions with substantially equal angular amplitude:

a first region between the radius R1 and the radius R2 of the foot 41 passing the next strip 4. This region encompasses the entire first tooth 81;

in a second region between the radius R2 and the radius R3, the radius R3 is tangent to the third tooth 85 at a point 870 on the side of the hollow 87 of the tooth. This region corresponds to the entire tooth hollow 87;

a third region between the radius R3 and the radius R4, the radius R4 being tangent to the other side of the second tooth 85 at the point 860. This region encompasses the entire second tooth 85;

a fourth region between the radius R4 and the radius R5, the radius R5 being tangent to the elastic strip 4 at a bulging point 491 on the side of the elastic strip 4 facing the second tooth 85. The area is empty;

a fifth region between the radius R5 and the radius R10. This region encompasses the entire distal end 47 of the strip 4.

Fig. 13 shows a variant in which, in the non-operative, non-limiting configuration, the free spaces and the ends of the bars 4 and of the teeth 81 and 85 are distributed as follows:

starting from the centre Ω RF of the flexible gear 10, the whole sector is defined between a radius R1 and a similar radius R10 of the next set of teeth, said radius R1 passing through the bar 4 of the set of teeth concerned and being tangent to the salient point 82 of the first tooth 81 on the side of the bar 4. The gear 10 is shown here as a preferred but non-limiting embodiment, in which it is formed by a set of identical teeth grouped periodically arranged at the periphery of the gear. The sector is shared between 5 regions with substantially equal angular amplitude:

a first region between the radius R1 and the radius R2 defining with the radius R1 a fifth total sector. This region encompasses the entire first tooth 81;

in a second region between the radius R2 and the radius R3, the radius R3 is tangent to the second tooth 85 at a point 870 on the side of the tooth hollow 87. This region corresponds to the entire tooth hollow 87;

a third region between the radius R3 and the radius R4, the radius R4 being tangent to the other side of the second tooth 85 at the point 860. This region encompasses the entire second tooth 85;

a fourth region between the radius R4 and the radius R5, the radius R5 originating from the inner end 51 of the ventral notch 5 of the next set of teeth. The area is empty;

a fifth region between the radius R5 and the radius R10. This region encompasses the entire distal end 47 of the strip 4.

The invention also relates to a timepiece movement 200 including at least one wheel train 100 of this type.

The invention also relates to a timepiece 300 comprising at least one timepiece movement 200 of this type and/or at least one wheel train 100 of this type.

Claims (14)

1. Timepiece gear (10) comprising a plurality of teeth (2) with play compensation, each tooth (2) comprising a catch (3) projecting from a catch foot (31) and an elastic strip (4) projecting from a strip foot (41) opposite the catch (3), the elastic strip (4) being separated from the catch (3) by a ventral notch (5), an intrados profile (43) of the elastic strip (4) delimiting a dorsal notch (6) on the side opposite the catch (3), the strip foot (41) being delimited towards a pivot axis (D) of the timepiece gear (10) by an inner end (51) of the ventral notch (5) and an inner end (61) of the dorsal notch (6), characterized in that the inner end (61) of the dorsal notch (6) is located closer to the pivot axis (D) than the inner end (51) of the ventral notch (5), and extends on the side of the pivot axis (D) below the clip foot (31) or below the inner curve geometry extension (52) of the belly cutout (5) towards the pivot axis (D).

2. The timepiece gear (10) of claim 1, wherein each tooth (2) is separated from the next tooth by the back cut (6).

3. The timepiece gear (10) according to claim 1, wherein each tooth (2) of the timepiece gear (10) comprises the snap piece (3) and the resilient strip (4).

4. The timepiece gear (10) according to claim 3, wherein the back cut (6) extends between the clip (3) and the resilient strip (4).

5. The timepiece gear (10) of claim 1, wherein: the abdominal incision (5) has substantially parallel edges; between said clip foot (31) and an intermediate region (33), said clip (3) comprising a substantially rectilinear inner portion (32), which inner portion (32) forms a first angle (α E) of between 10 ° and 30 ° with a radial line from said pivot axis (D), and between said intermediate region (33) and a first distal end (35) of said clip (3) furthest from said pivot axis (D), said clip (3) comprising an outer portion (34) extending substantially radially with respect to said pivot axis (D); between the strip foot (41) and an intermediate region (45), the elastic strip (4) comprises a substantially rectilinear inner portion (44), the inner portion (44) forming a second angle (al) of between 10 ° and 30 ° with a radial line from the pivot axis (D), and between the intermediate region (45) and a second distal end (47) of the elastic strip (4) which is furthest from the pivot axis (D), the elastic strip (4) comprises an outer portion (46) extending substantially radially with respect to the pivot axis (D), when the opposing gear or gear shaft of the timepiece gear (10) exerts a compressive stress on the second distal end (47) of the elastic strip (4), the second angle (al) enables an increased lever arm with respect to the strip foot (41) of the elastic strip (4).

6. The timepiece gear (10) of claim 1, wherein: the inner end (51) of the abdominal incision (5) is curved with a first radius (R1); the inner end (61) of the dorsal notch (6) is curved with a second radius (R2), the second radius (R2) having a greater value than the first radius (R1); in the vicinity of the inner end (61) of the dorsal notch (6), the dorsal notch (6) has a profile following a third radius (R3), the third radius (R3) having a greater value than the second radius (R2) to pass the dorsal notch (6) between the pivot axis (D) and the inner end (51) of the ventral notch (5).

7. The timepiece gear (10) according to claim 5, wherein the clip member (3) is fork-shaped and comprises a first tooth (81) and a second tooth (85) delimiting a hollow (87), wherein the first tooth (81) and the second tooth (85) are each substantially more rigid than the elastic strip (4).

8. The timepiece gear (10) of claim 7, wherein the second distal end (47) of the elastic strip (4) and the distal ends of the first tooth (81) and the second tooth (85) all have the same maximum radial dimension.

9. The timepiece gear (10) according to claim 1, wherein between the bar foot (41) and a middle region (45), the elastic bar (4) comprises a substantially rectilinear inner portion (44), which inner portion (44) forms an angle (al) of between 10 ° and 30 ° with a radial line from the pivot axis (D), and between the middle region (45) and a second distal end (47) of the elastic bar (4) furthest from the pivot axis (D), the elastic bar (4) comprising an outer portion (46), which outer portion (46) extends substantially radially with respect to the pivot axis (D) up to an inflection region (48), which inflection region (48) is between a concave portion defined by the inner portion (44) and the outer portion (46) and a convex portion (49) as far as the second distal end (47), the male portion (49) is arranged to fit in an abutting manner on the first distal end (35) of the clip (3).

10. Timepiece gear train (100) comprising at least one timepiece gear wheel (10) according to claim 1, characterised in that the timepiece gear wheel (10) is geared with an opposite toothed shaft (7), the teeth (71) of the toothed shaft (7) comprising a zone (72) with maximum section, this zone (72) being arranged to cooperate in driving abutment with an outer portion of the clip (3) or of the elastic strip (4) substantially radially with respect to the pivot axis (D) of the timepiece gear wheel (10).

11. The timepiece gear train (100) according to claim 10, wherein between the bar foot (41) and a middle region (45), the elastic bar (4) comprises a substantially rectilinear inner portion (44), which inner portion (44) forms an angle (al) of between 10 ° and 30 ° with a radial line from the pivot axis (D), and between the middle region (45) and a second distal end (47) of the elastic bar (4) furthest from the pivot axis (D), the elastic bar (4) comprising an outer portion (46), which outer portion (46) extends substantially radially with respect to the pivot axis (D) up to an inflection region (48), which inflection region (48) is between a concave portion defined by the inner portion (44) and the outer portion (46) and a convex portion (49) as far as the second distal end (47), -said male portion (49) is arranged to fit in an abutting manner on a first distal end (35) of said clip (3); and the area (72) with the largest cross section is fitted with the timepiece gear (10) on a radius corresponding to that of the inflection point area (48).

12. Timepiece movement (200) comprising at least one timepiece train (100) according to claim 10.

13. Timepiece (300) comprising at least one timepiece movement (200) according to claim 12.

14. Timepiece (300) comprising at least one timepiece train (100) according to claim 10.