EP1437633B1 - Chronograph gear train - Google Patents

Description

The present invention relates to a chronograph wheel.

• une roue menante, généralement dénommée « roue sur champ », solidaire de la roue des secondes,
• une roue intermédiaire engrenant continuellement avec la roue menante, et
• une troisième roue appelée généralement « roue de chronographe » ou « roue de centre », portant l'aiguille de chronographe.

In traditional chronographs, such as that described in document US 143,619, the movement of the seconds wheel is transmitted to the chronograph second hand by means of three wheels with fine teeth:

• a driving wheel, generally called "wheel on field", secured to the wheel of seconds,
• an intermediate wheel meshing continuously with the driving wheel, and
• a third wheel generally called "chronograph wheel" or "center wheel", bearing the chronograph hand.

The intermediate wheel can take an engaged position in which it meshes with the chronograph wheel to transmit to the latter the movement of the driving wheel, and a disengaged position in which its meshing with the chronograph wheel is broken, which is then immobilized by a brake. The clutch / clutch is effected by means of a rocker connected to the intermediate wheel and controlled by the pushbutton of the chronograph. In order to reduce the meshing play between the different wheels, the chronograph wheel is constantly slightly braked by a friction spring.

Figures 1 and 2 show, respectively in an engaged state and a disengaged state, a chronograph wheel constituted by the three aforementioned wheels. In these figures, the driving wheel is designated by the reference R1, the intermediate wheel by the R2 mark and the chronograph wheel by the reference R3. It can be seen that the teeth of the intermediate wheel and the chronograph wheel have a triangular shape. The angle at the top of these teeth is large enough to minimize the play of meshing and small enough to avoid too much friction. The teeth of the driving wheel are generally of triangular shape or, as shown, of epicycloidal shape.

A major problem encountered with this type of gear is that, when the clutch, that is to say when the intermediate wheel meshes with the chronograph wheel, the penetration of the teeth of the intermediate wheel in that of the chronograph wheel may cause an unwanted jump of the chronograph wheel and therefore the chronograph hand, either in the direction of advance or in the direction of the recoil of the needle. This second case which occurs when, as illustrated in FIG. 3, the tip of the first tooth D1 of the intermediate wheel penetrating into the toothing of the chronograph wheel does not appear in front of the space between two consecutive teeth of the chronograph wheel but near the tip of a tooth D2 and the side of the front flank of this tooth, is particularly detrimental to the quality of the display. It is indeed surprising for the user to see, after pressing the push button, the chronograph hand first jump back.

In order to reduce the risk of inadvertent jumping of the chronograph hand during clutching, the chronograph wheel generally carries a number of teeth twice that of the intermediate wheel. A tooth tip of the intermediate wheel is thus more likely to meet an empty space between two consecutive teeth of the chronograph wheel when it enters the teeth of the chronograph wheel. This solution certainly provides an improvement but only reduces the risk of accidental jump in a limited way.

Another disadvantage of conventional chronograph wheels is that the meshing between the intermediate wheel and the chronograph wheel is uneven. Because of the triangular shape of the teeth of these wheels, the right flanks of the teeth can indeed cooperate between them only instantaneously, the driving of a tooth of the chronograph wheel by a tooth of the intermediate wheel being made by intermediate the tip of the tooth of the intermediate wheel pushing a right flank of the tooth of the chronograph wheel and then by the right side of the tooth of the intermediate wheel pushing the tip of the tooth of the chronograph wheel. These contacts point on the side between the teeth of the intermediate wheel and the teeth of the chronograph wheel also cause wear of the teeth, which is even more important than the loads exerted on the chronograph wheel (in particular by the spring of friction) are high. These contacts also create torque transmission variations that can increase the friction and load disturbances applied to the wheels.

The present invention aims in the first place to eliminate or at least reduce the risk of unwanted recoil of the chronograph hand during clutch.

To this end, it is proposed a chronograph wheel comprising a first wheel, an intermediate wheel permanently engaged with the first wheel and comprising an intermediate wheel, and a third wheel located substantially in the same plane as the intermediate wheel, one first and third wheels being a driving wheel and the other a chronograph wheel intended to be connected to a chronograph hand, the gear train being able to assume an engaged position in which the intermediate wheel meshes with the third wheel and a disengaged position in which the meshing between the intermediate wheel and the third wheel is broken, each tooth of the intermediate wheel, respectively of the third wheel, having a so-called "active" side intended to cooperate with the toothing of the third wheel, respectively of the intermediate wheel , when the gear train is in the engaged position and an opposite side called "inactive", characterized in that that the teeth of the intermediate wheel and the third wheel are shaped so that, at a given moment during the clutch, the radial axis of any of the teeth of the intermediate wheel and the radial axis of any of the teeth of the third wheel are merged with the axis passing through the respective centers of the intermediate wheel and the third wheel and the vertices respective of these teeth are in contact with each other, the profile of the inactive flank of the tooth of the intermediate wheel, respectively of the tooth of the third wheel, is oriented, at least in the portion of the tooth intended to cooperate with the toothing of the third wheel, respectively of the intermediate wheel, substantially along the epicyclic path of penetration of the top of the tooth of the intermediate wheel in the toothing of the third wheel.

The present invention aims secondly to improve the quality of the meshing between the intermediate wheel and the third wheel.

To this end, the chronograph wheel according to the invention is characterized in that the profile of the active side of the teeth of the intermediate wheel is convex at least in the portion of these teeth intended to cooperate with the toothing of the third wheel and / or in that the profile of the active side of the teeth of the third wheel is convex at least in the portion of these teeth intended to cooperate with the toothing of the intermediate wheel.

Particular embodiments of the gear train according to the invention are defined in the appended claims 4 to 13.

The present invention also relates to a chronograph incorporating the wheel as defined above.

• la trajectoire épicycloïdale de pénétration dans la denture de la troisième roue décrite par le sommet de l'une quelconque des dents de la roue intermédiaire dont l'axe radial se trouve, à un moment donné lors de l'embrayage, confondu avec l'axe passant par les centres respectifs de la roue intermédiaire et de la troisième roue et dont le sommet se trouve à ce même moment sur le cercle de diamètre extérieur de la troisième roue,
• la tangente à cette trajectoire au point d'intersection entre cette trajectoire et le cercle de diamètre extérieur de la troisième roue,
• la trajectoire de pénétration relative dans la denture de la roue intermédiaire décrite par le sommet de l'une quelconque des dents de la troisième roue dont l'axe radial se trouve, à un moment donné lors de l'embrayage, confondu avec l'axe passant par les centres respectifs de la roue intermédiaire et de la troisième roue et dont le sommet se trouve à ce même moment sur le cercle de diamètre extérieur de la roue intermédiaire, et
• la tangente à cette trajectoire de pénétration relative au point d'intersection entre cette trajectoire de pénétration relative et le cercle de diamètre extérieur de la roue intermédiaire.

The present invention also proposes a method of producing a chronograph wheel including a first wheel, an intermediate wheel permanently engaged with the first wheel and comprising an intermediate wheel, and a third wheel located substantially in the same plane as the wheel. intermediate, one of the first and third wheels being a driving wheel and the other a chronograph wheel intended to be connected to a chronograph hand, the gear train being able to assume an engaged position in which the intermediate wheel meshes with the third wheel and a disengaged position in which the meshing between the intermediate wheel and the third wheel is broken, each tooth of the intermediate wheel, respectively of the third wheel, having a so-called "active" side intended to cooperate with the toothing of the third wheel, respectively of the intermediate wheel, when the gear train is in the engaged position and an opposite side said "inactive", characterized in that, during the design of the chronograph wheel, to reduce the risk of unwanted recoil of the chronograph wheel during clutching, the shape of the inactive flank of the teeth of the intermediate wheel and the teeth of the third wheel is determined as a function of at least one of the following curves:

• the epicyclic path of penetration into the toothing of the third wheel described by the apex of any one of the teeth of the intermediate wheel whose radial axis is, at a given moment during the clutch, coincident with the axis passing through the respective centers of the intermediate wheel and the third wheel and whose top is at the same time on the outer diameter circle of the third wheel,
• the tangent to this trajectory at the point of intersection between this trajectory and the outer diameter circle of the third wheel,
• the path of relative penetration in the toothing of the intermediate wheel described by the apex of any one of the teeth of the third wheel whose radial axis is, at a given moment during the clutch, coincident with the axis passing through the respective centers of the intermediate wheel and the third wheel and whose apex is at the same time on the circle of outside diameter of the intermediate wheel, and
• the tangent to this relative penetration trajectory at the point of intersection between this relative penetration trajectory and the outer diameter circle of the intermediate wheel.

• les figures 1 et 2, déjà commentées, sont des vues planes de dessous (c'est-à-dire depuis le fond du chronographe) d'un rouage de chronographe selon la technique antérieure, respectivement dans un état embrayé et débrayé ;
• la figure 3, déjà commentée, montre schématiquement une partie de la denture d'une roue intermédiaire incluse dans le rouage des figures 1 et 2 pénétrant dans la denture d'une roue de chronographe lors d'une phase d'embrayage ;
• les figures 4 et 5 sont des vues planes de dessous d'un rouage de chronographe selon un premier mode de réalisation de l'invention, respectivement dans un état embrayé et débrayé ;
• la figure 6 montre une partie de la denture d'une roue intermédiaire incluse dans le rouage illustré aux figures 4 et 5 et une partie correspondante de la denture d'une roue de chronographe, dans une position débrayée ;
• la figure 7 montre les parties de denture illustrées à la figure 6 dans une position embrayée ;
• la figure 8 montre une partie de la denture d'une roue menante incluse dans le rouage selon l'invention engrenant avec la denture de la roue intermédiaire ;
• les figures 9 à 13 sont des vues schématiques montrant comment est déterminée la forme des flancs inactifs des dents de la roue de chronographe et de la roue intermédiaire dans le rouage selon l'invention ;
• la figure 14 est une vue plane de dessous d'un rouage de chronographe selon un second mode de réalisation de l'invention, avec une roue intermédiaire de ce rouage partiellement coupée pour montrer une partie d'une autre roue intermédiaire située au-dessus de ladite roue intermédiaire ;
• la figure 15 est une vue en coupe du rouage de chronographe selon le second mode de réalisation de l'invention, prise suivant la ligne XV-XV de la figure 14 ; et
• la figure 16 est une vue plane de dessous d'un rouage de chronographe selon un troisième mode de réalisation de l'invention.

Other features and advantages of the present invention will appear on reading the following detailed description given with reference to the accompanying drawings in which:

• Figures 1 and 2, already commented, are plane views from below (that is to say from the bottom of the chronograph) of a cogwheel chronograph according to the prior art, respectively in an engaged and disengaged state;
• Figure 3, already commented, schematically shows a portion of the teeth of an intermediate wheel included in the gear train of Figures 1 and 2 entering the teeth of a chronograph wheel during a clutch phase;
• Figures 4 and 5 are plan views from below of a chronograph train according to a first embodiment of the invention, respectively in an engaged and disengaged state;
• Figure 6 shows a portion of the toothing of an intermediate wheel included in the train illustrated in Figures 4 and 5 and a corresponding portion of the toothing of a chronograph wheel, in a disengaged position;
• Figure 7 shows the toothing portions illustrated in Figure 6 in an engaged position;
• Figure 8 shows a portion of the teeth of a driving wheel included in the train according to the invention meshing with the toothing of the intermediate wheel;
• Figures 9 to 13 are schematic views showing how is determined the shape of the inactive flanks of the teeth of the chronograph wheel and the intermediate wheel in the train according to the invention;
• FIG. 14 is a plan view from below of a chronograph train according to a second embodiment of the invention, with an intermediate wheel of this wheel partially cut to show a part of another intermediate wheel situated above said intermediate wheel;
• Figure 15 is a sectional view of the chronograph wheel according to the second embodiment of the invention taken along the line XV-XV of Figure 14; and
• Figure 16 is a bottom plan view of a chronograph train according to a third embodiment of the invention.

With reference to FIGS. 4 and 5, a chronograph wheel according to a first embodiment of the invention comprises, in a same plane, a first wheel RM called "driving wheel" or "wheel on field", an intermediate wheel RI, and a third RC wheel called "chronograph wheel" or "center wheel". The driving wheel RM is integral with the work train (not shown), more particularly the seconds wheel, and thus rotates continuously in the direction indicated by the arrow F1 by traveling one revolution per minute. The RC chronograph wheel carries the chronograph hand (not shown). The intermediate wheel RI, meanwhile, is in permanent engagement with the driving wheel RM and can take an engaged position (Figure 4) in which it also meshes with the chronograph wheel RC to transmit to it the movement of the wheel driving RM and a disengaged position (Figure 5) in which its meshing with the RC chronograph wheel is broken. The clutch / clutch, that is to say the passage from the disengaged position to the engaged position and vice versa, is performed by means of a rocker B, under the control of the push button (not shown) of the chronograph operated. manually by the user.

The chronograph wheel RC is constantly under the action of a friction spring (not shown), which exerts on this wheel a slight braking to catch the gear sets between the wheels RM and Rl on the one hand and the Rl and RC wheels on the other hand and thus reduce the fidelity of the chronograph hand. A brake (not shown) is also provided to immobilize the RC chronograph wheel at the time of disengagement.

All the characteristics mentioned above are well known to those skilled in the art and will therefore not be described in more detail.

In accordance with the invention, the teeth of the intermediate wheel RI and those of the chronograph wheel RC do not have the conventional triangular shape, but an asymmetric shape designed to improve the quality of the clutch and the meshing between them. wheels.

It will be observed, with reference to FIGS. 6 and 7, that the teeth of the intermediate wheel RI have a distal portion 1 of asymmetrical shape intended to cooperate with the toothing of the chronograph wheel RC, and a proximal portion 2 intended to cooperate with the teeth of the driving wheel RM.

The rear flank 3 of the teeth of the intermediate wheel RI, in the distal portion, and the leading edge 4 of the teeth of the chronograph wheel RC are designed to prevent the chronograph wheel from reversing substantially when the intermediate wheel meshes with the wheel. Chronograph (clutch).

The rear flank 3 of the teeth of the intermediate wheel RI, partly proximal, and the leading edge 5 (FIG. 8) of the teeth of the driving wheel RM are designed to improve the regularity of the meshing between the intermediate and driving wheels.

Finally, the leading edge 6 of the teeth of the intermediate wheel RI, in the distal portion, and the rear flank 7 of the teeth of the chronograph wheel RC are designed to improve the regularity of the meshing and to reduce the phenomena of wear between the intermediate wheel and the chronograph wheel.

In the context of this patent application, the rear flank 3 of the teeth of the intermediate wheel R1 and the leading edge 4 of the teeth of the chronograph wheel RC will be described as "inactive" because they do not cooperate with, respectively, the gearing of the chronograph wheel RC and the toothing of the intermediate wheel R1 when the gear train is in the engaged position, as opposed to the front flank 6 and the rear flank 7 ("active" flanks) which serve as a contact surface with the toothing of the RC chronograph wheel and the intermediate wheel R1, respectively.

Figures 9 and 10 show schematically how is determined the shape of the rear flanks, inactive, 3 teeth of the intermediate wheel RI and front flanks, inactive, 4 of the chronograph wheel RC. In FIG. 9, the wheels RM, RI and RC are represented by the circles corresponding to their respective outside diameters δM, δ1 and δC, that is to say the circles defined by the tops of the teeth.

During clutching, the intermediate wheel RI rotates in a satellite around the driving wheel RM. Thus, the center OI of the intermediate wheel RI describes a trajectory in an arc (see Figure 9, reference 8) while, if we neglect the rotation performed by the drive wheel RM during the duration of the clutch, each point of the periphery of the intermediate wheel R1 describes an epicycloid portion.

FIG. 9 illustrates the epicycloid (reference 9) on which the vertex or tip 10I of a tooth DIn of the intermediate wheel moves whose radial axis is at a given moment of this clutch phase coinciding with the AC axis passing through respective centers OI, OC of the intermediate wheel and the chronograph wheel and whose top 10I is, at the same time, on the circle of outer diameter δC of the chronograph wheel. By "radial axis" means, for a given tooth, the axis passing through the top of the tooth and the center of the corresponding wheel. In Figure 9, the tooth Dln has been represented by a portion of its radial axis, drawn in strong line. The initial positions of the wheel RI (dashed circle), the center OI of the wheel RI (reference Ol ') and the tooth Dln (reference Dln') have also been represented.

When clutching, the tooth Dln only describes a portion of the epicycloid 9 constituting the path 9 'of penetration of the tooth Dln into the toothing of the chronograph wheel RC. Locally, in the vicinity of the point of contact between the circles of outside diameters δ1 and δC, this penetration trajectory 9 'is substantially an arc of a circle.

To determine the shape of the rear flank 3 of the teeth of the intermediate wheel and that of the front flank 4 of the teeth of the chronograph wheel, one places oneself in the critical situation where the radial axis of any one, Dln, of the teeth of the intermediate wheel and the radial axis of any one, DCk, teeth of the chronograph wheel are coincident with the axis AC passing through the respective centers OI, OC of the intermediate wheel and the wheel chronograph and where the respective vertices 10I, 10C of these teeth are in contact with each other. As is apparent from FIG. 10, the teeth Dln and DCk are shaped so that, in this critical situation, the profile of the leading edge 4 of the tooth DCk and of the distal portion of the trailing edge 3 of the tooth Dln is oriented substantially following the trajectory 9 'of penetration of the tooth Dln into the toothing of the chronograph wheel.

In this way, if the tooth Dln enters the gearing of the chronograph wheel on the side of the leading edge 4 of the tooth DCk, the tooth DIn will not be hindered by this sidewall before it will marry. On the other hand, the penetration depth of the tooth Dln will be improved.

The leading edge 4 of the tooth DCk and the distal portion of the rear flank 3 of the tooth Dln can precisely follow the path 9 'of penetration of the tooth Dln into the toothing of the chronograph wheel and thus have a curved, convex profile for the tooth Dln and concave tooth DCk, as shown in Figure 10. Alternatively, the profile of the sidewalls 3, 4 can be straight and oriented along the tangent to the trajectory 9 'taken at the point of contact between the vertices 10I, 10C teeth Dln, DCk (or in other words at the point of intersection between the trajectory 9 'and the circle of outer diameter δC of the RC wheel), as shown in Figure 11 where the tangent is designated by the reference In practice, the difference between these two variants is very small, so that we can prefer the right profile, easier to implement.

The tops of the teeth of the intermediate wheel RI and the chronograph wheel RC as shown in Figures 10, 11 are pointed. These vertices may however be slightly rounded, as shown in Figures 4 to 7. In the latter case, when the top of a tooth DIn is in contact with the top of a tooth DCk, the distal portion of the sidewall 3 and the flank 4 of these two teeth are slightly offset relative to each other.

$$\mathrm{y}=(\mathrm{Rpm}+\mathrm{Rpi})\times \sin \left(\mathrm{\alpha }\right)+\mathrm{Rei}\times \sin [\mathrm{\beta }0+(\mathrm{\alpha }-\mathrm{\alpha }0)\times (\mathrm{Rpm}+\mathrm{Rpi})/\mathrm{Rpi}]$$

où :

• Rpm est le rayon primitif de la roue menante RM,
• Rpi est le rayon primitif de la roue intermédiaire RI,
• Rei est le rayon extérieur de la roue intermédiaire RI (Rei = δI / 2),
• α est l'angle de rotation (paramètre variable) du centre Ol de la roue intermédiaire RI par rapport au centre OM de la roue menante RM (la valeur initiale, α', de cet angle α est représentée sur la figure 9),
• α0 est la valeur de l'angle α de rotation du centre OI de la roue intermédiaire RI par rapport au centre OM de la roue menante RM, à l'instant où les sommets 10I, 10C entrent en contact l'un avec l'autre,
• β0 est la valeur de l'angle de rotation de la roue intermédiaire RI par rapport à son centre OI, à l'instant où les sommets 10I, 10C entrent en contact l'un avec l'autre (la valeur initiale, β', de cet angle de rotation est également représentée sur la figure 9).

Le vecteur tangent à la trajectoire 9' au point de contact entre les sommets 10I, 10C est donné par les équations suivantes : $$\mathrm{dx}=(\mathrm{Rpm}+\mathrm{Rpi})\times \sin \left(\mathrm{\alpha }0\right)-\mathrm{Rei}\times \sin \left(\mathrm{\beta }0\right)\times (\mathrm{Rpm}+\mathrm{Rpi})/\mathrm{Rpi}$$

$$\mathrm{dy}=(\mathrm{Rpm}+\mathrm{Rpi})\times \cos \left(\mathrm{\alpha }0\right)+\mathrm{Rei}\times \cos \left(\mathrm{\beta }0\right)\times (\mathrm{Rpm}+\mathrm{Rpi})/\mathrm{Rpi}$$

We give below the equation of the epicycloid 9 in an orthogonal coordinate system (OM, x, y) originating from the center OM of the driving wheel and whose axis (OM, x) passes through the centers OM and OC: $$\mathrm{x}=(\mathrm{rpm}+\mathrm{Rpi})\times \cos \left(\mathrm{\alpha }\right)+\mathrm{Rei}\times \cos [\mathrm{\beta }0+(\mathrm{\alpha }-\mathrm{\alpha }0)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{Rpi}]$$

$$\mathrm{there}=(\mathrm{rpm}+\mathrm{Rpi})\times \sin \left(\mathrm{\alpha }\right)+\mathrm{Rei}\times \sin [\mathrm{\beta }0+(\mathrm{\alpha }-\mathrm{\alpha }0)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{Rpi}]$$

or :

• Rpm is the pitch radius of the RM drive wheel,
• Rpi is the pitch radius of the intermediate wheel RI,
• Rei is the outer radius of the intermediate wheel RI (Rei = δI / 2),
• α is the angle of rotation (variable parameter) of the center Ol of the intermediate wheel RI with respect to the center OM of the driving wheel RM (the initial value, α ', of this angle α is represented in FIG. 9),
• α0 is the value of the angle α of rotation of the center OI of the intermediate wheel RI with respect to the center OM of the driving wheel RM, at the moment when the vertices 10I, 10C come into contact with each other ,
• β0 is the value of the angle of rotation of the intermediate wheel RI with respect to its center OI, at the moment when the vertices 10I, 10C come into contact with each other (the initial value, β ', this angle of rotation is also shown in Figure 9).

The vector tangent to the trajectory 9 'at the point of contact between the vertices 10I, 10C is given by the following equations: $$\mathrm{dx}=(\mathrm{rpm}+\mathrm{Rpi})\times \sin \left(\mathrm{\alpha }0\right)-\mathrm{Rei}\times \sin \left(\mathrm{\beta }0\right)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{Rpi}$$

$$\mathrm{dy}=(\mathrm{rpm}+\mathrm{Rpi})\times \cos \left(\mathrm{\alpha }0\right)+\mathrm{Rei}\times \cos \left(\mathrm{\beta }0\right)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{Rpi}$$

One could also, according to another variant, draw more precisely the path of penetration of the tooth Dln in the toothing of the chronograph wheel RC, taking into account the rotation performed by the drive wheel RM during the clutch. However, this complication would only slightly alter the design of the trajectory and the resulting improvement in terms of the risk of accidental recoil of the chronograph wheel would be minimal.

Note that the solution proposed above of giving to the distal portion of the rear flank of the teeth of the intermediate wheel and the front flank of the teeth of the chronograph wheel a profile corresponding to the path of penetration of the teeth of the intermediate wheel in the gearing of the chronograph wheel, makes it possible to avoid unwanted reversals of the chronograph wheel not only during the clutch but also during the disengagement. This solution is indeed between the conventional configuration where the angle that makes the rear flank (respectively the leading edge) of the teeth of the intermediate wheel (respectively the chronograph wheel) with the radial axis of the teeth is greater than that what is the tangent to the path of penetration with this radial axis (Figure 12, item 11), causing a risk of recoil of the chronograph wheel when the clutch, and a configuration where the aforementioned angle would be lower than that makes the tangent to the path of penetration with the radial axis (Figure 12, mark 12), which would increase the operating clearances between the wheels and would cause a risk of recoil of the chronograph wheel during the disengagement.

In the foregoing, in order to determine the shape of the flanks 3 and 4, the trajectory described by the vertex 101 of the tooth DIn in a fixed reference relative to the chronograph has been used. Alternatively, it is possible to place in a fixed reference relative to the intermediate wheel R1 and therefore mobile with respect to the chronograph. In the latter reference, the intermediate wheel R1 remains fixed during the clutch while, if we neglect the rotation of the driving wheel RM on itself (corresponding to the rotation of the second wheel), the driving wheel RM rolls on the intermediate wheel Rl and the chronograph wheel RC moves such that, for each point of the periphery of the RC wheel, the distance between this point and the center OM of the driving wheel RM remains constant.

FIG. 13 shows the curve (reference 13) on which, in a reference frame linked to the intermediate wheel RI, the vertex 10C of any tooth DCk of the chronograph wheel RC, the radial axis of which is at a given moment, moves given during the clutch coincides with the axis AC passing through the respective centers OI, OC of the intermediate wheel and the chronograph wheel and whose vertex 10C is, at the same time, on the circle of outside diameter δl of the intermediate wheel. Also shown in FIG. 13 are the positions of the wheels RM and RC at the aforementioned moment (solid circles) and the initial positions of these wheels RM and RC (dashed circles), centers OM and OC (OM 'marks, OC ') and tooth DCk (DCk' mark).

During clutching, the apex 10C only describes a portion of the curve 13 constituting the trajectory 13 'of relative penetration of the apex 10C in the toothing of the intermediate wheel R1. Locally, in the vicinity of the point of contact between the outer circles of diameters δ1 and δC, that is to say at the level of the teeth of the wheels R1 and RC, this relative penetration trajectory 13 'is substantially coincident with the trajectory 9' illustrated in Figures 9 and 10, and its tangent to said point of contact is the same as that of the trajectory 9 '. By determining the shape of the flanks 3, 4 as a function of the trajectory 13 'or of the tangent to this trajectory 13' at said point of contact, the same results are obtained as with the trajectory 9 '.

$$\mathrm{y}=\mathrm{yOl}+(\mathrm{Rpm}+\mathrm{Rpi})\times \mathrm{sin\hspace{1em}}\left(\mathrm{\delta }\right)+\mathrm{\Delta }\times \mathrm{sin\hspace{1em}}[\mathrm{\Gamma }0+(\mathrm{\delta }-\mathrm{\delta }0)\times (\mathrm{Rpm}+\mathrm{Rpi})/\mathrm{Rpm}]$$

où:

• xOl et yOl sont les coordonnées du centre Ol dans sa position illustrée à la figure 13,
• Rpm et Rpi sont les rayons primitifs respectifs des roues RM et RI,
• δ est l'angle de rotation (paramètre variable) du centre OM de la roue menante RM par rapport au centre OI de la roue intermédiaire Rl (la valeur initiale, δ', de cet angle de rotation δ est représentée sur la figure 13),
• δ0 est la valeur de l'angle δ de rotation du centre OM de la roue menante RM par rapport au centre OI de la roue intermédiaire Rl, à l'instant où les cercles de diamètres extérieurs δI et δC entrent en contact l'un avec l'autre (le point de contact entre ces cercles est désigné par les repères 10I, 10C correspondant à des sommets de dents Dln, DCk en regard),
• Δ est la distance entre le centre OM dans sa position illustrée à la figure 13 et le point de contact entre les cercles de diamètres extérieurs δl et δC, et
• Γ0 est la position angulaire du point de contact entre les cercles de diamètres extérieurs δI, et δC.

We give below the equation of the curve 13 in an orthogonal coordinate system (OM, x, y) originating from the center OM of the driving wheel RM and whose axis (OM, x) passes through the center OC of the chronograph wheel RC, centers OM and OC being considered in their position illustrated in Figure 13: $$\mathrm{x}=\mathrm{XoL}+(\mathrm{rpm}+\mathrm{Rpi})\times \cos \left(\mathrm{\delta }\right)+\mathrm{\Delta }\times \cos [\mathrm{\Gamma }0+(\mathrm{\delta }-\mathrm{\delta }0)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{rpm}]$$

$$\mathrm{there}=\mathrm{Yol}+(\mathrm{rpm}+\mathrm{Rpi})\times \sin \left(\mathrm{\delta }\right)+\mathrm{\Delta }\times \sin [\mathrm{\Gamma }0+(\mathrm{\delta }-\mathrm{\delta }0)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{rpm}]$$

or:

• xOl and yOl are the coordinates of the center Ol in its position illustrated in FIG. 13,
• Rpm and Rpi are the respective prime rays of the wheels RM and RI,
• δ is the angle of rotation (variable parameter) of the center OM of the driving wheel RM with respect to the center OI of the intermediate wheel R1 (the initial value, δ ', of this rotation angle δ is represented in FIG. 13) ,
• δ0 is the value of the angle δ of rotation of the center OM of the driving wheel RM with respect to the center OI of the intermediate wheel R1, at the moment when the circles of outside diameters δI and δC come into contact with each other. the other (the point of contact between these circles is designated by the marks 10I, 10C corresponding to tooth vertices Dln, DCk opposite),
• Δ is the distance between the center OM in its position illustrated in FIG. 13 and the point of contact between the circles of outside diameters δ1 and δC, and
• Γ0 is the angular position of the point of contact between the circles of outside diameters δI, and δC.

$$\mathrm{dy}=(\mathrm{Rpm}+\mathrm{Rpi})\times \mathrm{cos\hspace{1em}}\left(\mathrm{\delta }0\right)+\mathrm{\Delta }\times \mathrm{cos\hspace{1em}}\left(\mathrm{\Gamma }0\right)\times (\mathrm{Rpm}+\mathrm{Rpi})/\mathrm{Rpm}$$

The vector tangent to the path 13 'at the point of contact between the circles of outside diameters δI and δC is given by the following equations: $$\mathrm{dx}=(\mathrm{rpm}+\mathrm{Rpi})\times \sin \left(\mathrm{\delta }0\right)-\mathrm{\Delta }\times \sin \left(\mathrm{\Gamma }0\right)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{rpm}$$

$$\mathrm{dy}=(\mathrm{rpm}+\mathrm{Rpi})\times \cos \left(\mathrm{\delta }0\right)+\mathrm{\Delta }\times \cos \left(\mathrm{\Gamma }0\right)\times (\mathrm{rpm}+\mathrm{Rpi})/\mathrm{rpm}$$

According to another characteristic of the invention, in order to reduce the operating clearances between the wheels RM, RI and RC, the wheels R1 and RC preferably carry a number of teeth such that each free space between two consecutive teeth of the wheel RI embraces two teeth of the RC wheel, as shown in Figures 6 and 7.

Referring again to FIGS. 6 and 7, it will be noted that the "active" rear flank 7 of the teeth of the chronograph wheel RC and the distal portion of the "active" front flank 6 of the teeth of the intermediate wheel RI have a profile. convex, preferably in an arc. These two flanks 6, 7 cooperate with each other to allow a smooth meshing between the wheels RI, RC and to avoid the edge-to-flank contacts that are encountered in conventional chronograph wheels and which lead to wear of the teeth.

As indicated above, when the gear train is in the engaged position, the proximal portion 2 of the teeth of the intermediate wheel R1 cooperates exclusively with the toothing of the driving wheel RM while the distal portion 1 cooperates exclusively with the toothing of the chronograph wheel RC . In other words, the engagement diameter of the intermediate wheel RI with the chronograph wheel RC is greater than the engagement diameter of the intermediate wheel RI with the drive wheel RM. Thus, the shape of the distal portion 1 of the teeth of the intermediate wheel RI is optimized for its function of clutch / declutching without recoil of the chronograph wheel RC and regular meshing with the chronograph wheel RC and the shape of the Proximal portion 2 is optimized for its regular meshing function with the RM drive wheel. It will be observed that the profile of the rear flank 3 of the teeth of the intermediate wheel RI at their proximal portion 2 is concave. This profile is complementary to the convex profile of the leading edge 5 of the teeth of the driving wheel RM (FIG. 8).

Figures 14 and 15 illustrate a chronograph wheel according to a second embodiment of the invention. This wheel differs from that previously described in that the intermediate wheel comprises not a single wheel but two wheels RI1, RI2 located in two different planes. These two wheels are integral with each other and linked by the same axis AL. One of these wheels, RI1, is located in the same plane as the drive wheel RM 'and meshes continuously with it. The second of these wheels, RI2, is located in the same plane as the wheel Chronograph RC '. The intermediate mobile, such as the intermediate wheel RI of the first embodiment, can take an engaged position and a disengaged position. In the engaged position (configuration illustrated in Figures 14, 15), the wheel R12 meshes with the chronograph wheel RC 'to communicate to the latter the movement of the driving wheel RM'. In the disengaged position, the meshing between the wheels RI2 and RC 'is broken.

In this second embodiment, the teeth of the wheel RC 'and at least the distal portion of the teeth of the intermediate wheel RI2 are shaped in the same manner as, respectively, the teeth of the wheel RC and the wheel RI of the first embodiment. The shape of the proximal part of the teeth of the wheel R12 is of little importance because, unlike that of the wheel RI of the first embodiment, it has no meshing function. The shape of the teeth of the driving wheel RM 'and the intermediate wheel RI1 may be conventional, for example epicyclic as shown in FIG. 14.

Figure 16 shows a chronograph wheel according to a third embodiment of the invention. In this third embodiment, the intermediate wheel, designated Rla, is in permanent engagement with the chronograph wheel, designated RCa, and not with the driving wheel as in the first and second embodiments. Under the action of a rocker Ba connecting the wheels RCa and Rla, the train can take an engaged position in which the intermediate wheel Rla meshes with the driving wheel, designated RMa, and a disengaged position in which the meshing between the Rla and RMa wheels is broken. When the train is in the engaged position, the intermediate wheel Rla is driven by the driving wheel RMa and in turn drives the chronograph wheel RCa. In the disengaged position, the driving wheel RMa rotates without driving any of the wheels Rla and RCa, which therefore remain stationary.

This third embodiment makes it possible to obtain an energy saving with respect to the first two embodiments described above since at the rest state of the chronograph (disengaged position), the driving wheel RMa does not have to rotate the intermediate wheel Rla.

Similarly to the first and second embodiments, the distal portion of the inactive flank of the teeth of the intermediate wheel Rla (that is to say the sidewall which does not rest on the toothing of the driving wheel RMa during the normal operation of the gear train in the engaged position) and the inactive side of the teeth of the driving wheel RMa (that is to say the sidewall which does not rest on the teeth of the intermediate wheel Rla during normal operation of the gear wheel engaged position) have a profile to eliminate or at least reduce the risk of unwanted recoil of the chronograph wheel RCa during clutch. This profile is shaped so that when the radial axis of any one of the teeth of the intermediate wheel Rla coincides with the radial axis of any one of the teeth of the driving wheel RMa and the respective apices of these teeth are in contact with each other, it is oriented substantially along the path of penetration into the teeth of the driving wheel RMa from the top of said tooth of any intermediate wheel Rla or, which amounts to the same , substantially along the path of relative penetration into the teeth of the wheel Rla of any tooth of the wheel RMa. In this third embodiment, the inactive flank of the teeth of the intermediate wheel Rla is the leading edge, 6a, and that of the teeth of the driving wheel RMa is the rear flank, 5a. This profile of the flanks 6a, 5a prevents the flank 6a from striking the flank 5a during clutching, which would cause a recoil reaction of the intermediate wheel Rla and therefore the chronograph wheel RCa.

Preferably, similarly to the sidewalls 6 and 7 of the first embodiment, the distal portion of the active side of the teeth of the wheel Rla, that is to say the rear flank 3a intended to be pushed by the teeth of the wheel RMa, and the active flank of the teeth of the wheel RMa, that is to say the leading edge 5a 'intended to push the flank 3a of the teeth of the wheel Rla, are convex to avoid edge-to-edge contacts between the Rla and RMa wheel teeth.

Also preferably, similarly to the sidewalls 3 and 5 of the first embodiment, the proximal portion of the flank 6a is concave and complementary to the profile, convex, of the rear flank 7a of the teeth of the chronograph wheel RCa, in order to obtain a smooth and regular meshing between the wheels Rla and RCa.

It will also be noted that, according to the same principle as the second embodiment (FIGS. 14, 15), the gear train according to this third embodiment can be modified so that the intermediate wheel comprises two intermediate wheels superposed and secured to one of the other, one of these wheels being in permanent engagement with the chronograph wheel RCa and the other being intended to mesh with the driving wheel RMa.

Claims (15)

1. Chronograph gear train, comprising a first wheel (RM), an intermediate rotating part in permanent engagement with the first wheel (RM) and comprising an intermediate wheel (RI), as well as a third wheel (RC) situated substantially in the same plane as the intermediate wheel (RI), one of the first and third wheels being a driving wheel, and the other being a chronograph wheel intended to be linked with a chronograph hand, the gear train being able to assume a coupled position in which the intermediate wheel (RI) is engaged with the third wheel (RC), and an uncoupled position in which the engagement between the intermediate wheel (RI) and the third wheel (RC) is interrupted, each tooth of the intermediate wheel (RI) and third wheel (RC), respectively, having a flank said to be "active" (6, 7) and intended to cooperate with the toothing of the third wheel (RC) and intermediate wheel (RI), respectively, when the gear train is in its coupled position, as well as an opposite flank said to be "passive" (3, 4), characterised in that the teeth of the intermediate wheel (RI) and those of the third wheel (RC) are shaped so that, when at a given moment during coupling the radial axis of any (DIn) of the teeth of the intermediate wheel (RI) and the radial axis of any (DCk) of the teeth of the third wheel (RC) coincide with the axis (AC) passing through the respective centres (OI, OC) of the intermediate wheel (RI) and third wheel (RC), and the tips (10I, 10C) of these teeth (DIn, DCk) are in contact with each other, the profile of the passive flank (3) of the tooth (DIn) of the intermediate wheel (RI) and that of the tooth (DCk) of the third wheel (RC), respectively, be oriented, at least within the segment of the tooth intended to cooperate with the toothing of the third wheel (RC) and intermediate wheel (RI), respectively, substantially along the epicycloidal path (9') of penetration of the tip (10I) of the tooth (DIn) of the intermediate wheel (RI) into the toothing of the third wheel (RC).
2. Chronograph gear train of claim 1, characterised in that the profile of the active flank (6) of the teeth of the intermediate wheel (RI) is convex, at least within the segment (1) of these teeth intended to cooperate with the toothing of the third wheel (RC).
3. Chronograph gear train of claim 1 or 2, characterised in that the profile of the active flank (7) of the teeth of the third wheel (RC) is convex, at least within the segment of these teeth intended to cooperate with the toothing of the intermediate wheel (RI).
4. Chronograph gear train of any of claims 1 to 3, characterised in that said profile of the passive flank (3, 4) of the tooth (DIn) of the intermediate wheel (RI) and tooth (DCk) of the third wheel (RC), respectively, is curved, at least within the segment of the tooth intended to cooperate with the toothing of the third wheel (RC) and intermediate wheel (RI), respectively.
5. Chronograph gear train of any of claims 1 to 3, characterised in that said profile of the passive flank (3, 4) of the tooth (DIn) of the intermediate wheel (RI) and tooth (DCk) of the third wheel (RC), respectively, is straight and substantially oriented along the tangent to said path (9') in the point of contact between said tips (10I, 10C), at least within said segment of the tooth intended to cooperate with the toothing of the third wheel (RC) and intermediate wheel (RI), respectively.
6. Chronograph gear train of any of claims 1 to 5, characterised in that the first wheel (RM), the intermediate wheel (RI), and the third wheel (RC) are substantially in the same plane, and in that the intermediate wheel (RI) is permanently engaged with the first wheel (RM).
7. Chronograph gear train of any of claims 1 to 5, characterised in that the intermediate rotating part in addition to said intermediate wheel (RI2) comprises a second intermediate wheel (RI1) situated in another plane than said intermediate wheel (RI2) but in substantially the same plane as the first wheel (RM'), and in that this second intermediate wheel (RI1) is secured to said intermediate wheel (RI2), and permanently engaged with the first wheel (RM').
8. Chronograph gear train of claim 6, characterised in that a distal segment (1) of the teeth of the intermediate wheel (RI) cooperates exclusively with the toothing of the third wheel (RC), and a proximal segment (2) of the teeth of the intermediate wheel (RI) cooperates exclusively with the toothing of the first wheel (RM), when the gear train is in its coupled position.
9. Chronograph gear train of claim 8, characterised in that the passive flank (3) of the teeth of the intermediate wheel (RI) has a concave profile in the proximal segment (2) of these teeth.
10. Chronograph gear train of claim 9, characterised in that the flank (5) of the teeth of the first wheel (RM) cooperating with the toothing of the intermediate wheel (RI) has a convex profile complementary to the concave profile of the proximal segment (2) of the passive flank (3) of the teeth of the intermediate wheel (RI).
11. Chronograph gear train of one of claims 1 to 10, characterised in that the number of teeth of the intermediate wheel (RI) and that of the third wheel (RC) are such that every free space between two successive teeth of the intermediate wheel (RI) embraces two teeth of the third wheel (RC).
12. Chronograph gear train of one of claims 1 to 11, characterised in that the first wheel (RM) is the driving wheel and the third wheel (RC) is the chronograph wheel, and in that the passive flank (3) of the teeth of the intermediate wheel (RI) is a trailing flank while the passive flank (4) of the teeth of the chronograph wheel (RC) is a leading flank.
13. Chronograph gear train of one of claims 1 to 11, characterised in that the first wheel (RCa) is the chronograph wheel and the third wheel (RMa) is the driving wheel, and in that the passive flank of the teeth of the intermediate wheel (RIa) is a leading flank (6a) while the passive flank of the teeth of the driving wheel (RMa) is a trailing flank (5a).
14. Chronograph, comprising a gear train as defined in any of claims 1 to 13.
15. Method of realising a chronograph gear train comprising a first wheel (RM), an intermediate rotating part in permanent engagement with the first wheel (RM) and comprising an intermediate wheel (RI), as well as a third wheel (RC) situated substantially in the same plane as the intermediate wheel (RI), one of the first and third wheels being a driving wheel, and the other being a chronograph wheel intended to be linked with a chronograph hand, the gear train being able to assume a coupled position in which the intermediate wheel (RI) is engaged with the third wheel (RC), and an uncoupled position in which the engagement between the intermediate wheel (RI) and the third wheel (RC) is interrupted, each tooth of the intermediate wheel (RI) and third wheel (RC), respectively, having a flank said to be "active" (6, 7) and intended to cooperate with the toothing of the third wheel (RC) and intermediate wheel (RI), respectively, when the gear train is in its coupled position, as well as an opposite flank said to be "passive" (3, 4), the method characterised in that during the designing of the chronograph gear train, in order to reduce the risk of an untimely recoil of the chronograph wheel during coupling, the shape of the passive flank (3, 4) of the teeth of the intermediate wheel (RI) and of the teeth of the third wheel (RC) is determined as a function of at least one of the following curves:

    - the epicycloidal path (9') of penetration into the toothing of the third wheel (RC) described by the tip (10I) of any (DIn) of the teeth of the intermediate wheel (RI) which, at a given moment during coupling, has its radial axis coincident with the axis (AC) passing through the respective centres (OI, OC) of the intermediate wheel (RI) and third wheel (RC), and its tip (10I) situated on the circumscribed circle (δC) of the third wheel (RC),

    - the tangent (9") to this path (9') in the point of intersection between this path (9') and the circumscribed circle (δC) of the third wheel (RC),

    - the path (13') of relative penetration into the toothing of the intermediate wheel (RI) described by the tip (10C) of any (DCk) of the teeth of the third wheel (RC) which, at a given moment during coupling, has its radial axis coincident with the axis (AC) passing through the respective centres (OI, OC) of the intermediate wheel (RI) and third wheel (RC), and its tip (10C) situated on the circumscribed circle (δI) of the intermediate wheel (RI), and

    - the tangent to this path (13') of relative penetration in the point of intersection between this path (13') of relative penetration and the circumscribed circle (δI) of the intermediate wheel (RI).

Images