EP1914604A1 - Clock movement with constant torque energy transmission between the energy source and the mechanical oscillator - Google Patents

Abstract

The movement has a barrel with an output torque variable based on its charging state. A compensation device transmits a constant torque to a mechanical oscillator irrespective of the state of the barrel, and has a cam (12) with a radius variable based on the variations of the output torque. The device has an intermediate connection mechanism to assure sliding-less kinematic connection between a periphery of the cam and the gear-train. The mechanism has a lever (13) to carry a mobile wheel (10) with a permanent kinematic connection with a wheel (9).

Description

Technical area

The present invention relates to a movement for a timepiece comprising a power source mounted on a frame and having a variable output torque depending on its state of charge.

The energy source is intended to maintain the oscillatory movement of a mechanical oscillator through a finishing gear comprising a compensation device. The latter has an input kinematically connected to the power source, directly or via at least one mobile, and an output kinematically connected to the mechanical oscillator and is arranged to transmit a substantially constant torque to the mechanical oscillator regardless of the state of charge of the energy source.

State of the art

Such movements have been known for a long time, especially in the field of clocks, to allow the use of a spring with a large power reserve, as a source of energy, while smoothing the inevitable variations in the torque applied by this spring to the work train, these arising from the change in the state of charge of the spring during the operation of the clock. More specifically, it can be generally considered that the more a spring is loaded, the higher the torque that it transmits to the finishing gear train.

Many mechanisms have already been proposed, commonly called constant force escapements or equal windings and, involving a secondary spring which is loaded from the energy of the main spring, periodically. The corresponding period must be short enough so that the force that the secondary spring applies to the movement can be considered as being constant between its states of minimum load and maximum load.

Other types of mechanisms have also been proposed, including some called chain rocket, arranged to act further upstream, more precisely in contact with a barrel, compared to the secondary spring mechanisms.

These movements comprise a rocket, which is a conically shaped member provided with a helical groove on which a chain connected to the barrel is wound. When the corresponding timepiece is reassembled, the chain wraps around the rocket and the barrel spring stretches. A constant radius wheel is mounted coaxially to the rocket and is provided to transmit the energy of the mainspring from the rocket to the workings of the movement. The energy of the mainspring is thus transmitted with a constant torque to the workings of the movement.

Indeed, when the mainspring is in its maximum state of load and exerts its full force, the chain pulls on the smallest circumference of the rocket, whereas, when the state of charge of the mainspring drops, the chain draws on a circumference of the rocket with increasing radius.

Although such mechanisms are known since the ^16th century, their implementation remains complex and costly, especially for the realization of the chain that has a number of important components. This manufacturing complexity becomes critical when it comes to implementing this mechanism in a wristwatch, and reserves these timepieces to very rare privileged.

Disclosure of the invention

The main purpose of the present invention is to propose an alternative to the known mechanisms of the prior art, by proposing a movement for a timepiece comprising a device for compensating the variations of the torque released by a power source whose construction makes it possible to ensure high operating reliability, while providing limited space, reasonable complexity and reasonable manufacturing costs.

For this purpose, the present invention more particularly relates to a movement for a timepiece of the type mentioned above, characterized in that the compensation device comprises a cam having a periphery of variable radius extending substantially in a general plane, the variations of the radius of the cam being a function of those of the output torque of the energy source. The compensation device further comprises an intermediate linking mechanism arranged so as to provide a kinematic connection substantially without sliding between the periphery of the cam and the finishing train.

Advantageously, the compensation mechanism comprises exclusively constituents having respective rigid general forms.

By these characteristics, the movement according to the invention has a less bulky structure than the mechanisms of the prior art and less complex and therefore less expensive to manufacture. In addition, the compensation device provides great flexibility in its construction, in particular to define the implantation of the cam in the movement.

According to a first preferred embodiment of the invention, the intermediate link mechanism comprises a rocker pivoting about a fixed shaft on the frame and carrying a pinion having a permanent kinematic connection with a wheel, mounted freely in rotation around the wheel. fixed shaft and arranged in permanent engagement with at least one mobile of the work train, the gear also being arranged in engagement, substantially without sliding, with the periphery of the cam.

Thanks to these particular characteristics, the shape of the periphery of the cam can be adjusted precisely, with great flexibility, depending on the behavior of the energy source, in terms of the torque transmitted as a function of its state of charge, while ensuring a reliable transmission of energy from the power source to the mechanical oscillator.

According to a preferred embodiment, in which the periphery of the cam is associated with the input of the compensation device, it is advantageously provided that the pinion is arranged in engagement with a wheel of a reduction gear for tuning the characteristics. of the energy source, especially in the case of a spring, the amplitude of its deformations, with the dimensioning and the number of teeth of the cam.

In a second preferred embodiment of the invention, provision is made for the linking mechanism to comprise an additional cam, of variable radius, kinematically connected, by its periphery, at the periphery of the first cam and dimensioned and in such a way that the sum of their respective radii, taken on a segment connecting their respective centers, is constant, the additional cam being integral in rotation with a drive wheel kinematically connected to the energy source.

Thanks to these characteristics, each of the two cams partially compensates for the output torque variations of the energy source, so that the torque delivered at the output of the compensation device is constant regardless of the state of charge of the source. energy, the kinematic connection between the two cams being very safe.

In general, it can be advantageously provided that the compensation device comprises a differential gear whose cam defines an input and whose output is kinematically connected to the mechanical oscillator. In this case, it is advisable to provide that the differential has an additional input through which the load of the energy source can be realized.

Brief description of the drawings

Other features and advantages of the present invention will appear more clearly on reading the detailed description of preferred embodiments which follows, made with reference to the accompanying drawings given as non-limiting examples and in which:

- Figure 1a shows a simplified top view of a part of a movement for a timepiece having a compensation device according to a first embodiment of the present invention;

- Figure 1b shows a simplified top view of a first detail of the movement of Figure 1a;

Figure 2a shows a simplified cross-sectional view of the movement of Figure 1a;

- Figure 2b shows a simplified top view of a second detail of the movement, visible in Figure 2a;

FIG. 2c represents a simplified top view of a third detail of the movement, visible in FIG. 2a, and

- Figure 3 shows a simplified top view of a part of a movement for a timepiece having a compensation device according to a second embodiment of the present invention.

Mode (s) of realization of the invention

In all the figures, only the elements useful for understanding the invention have been shown, for the sake of clarity.

Figure 1a shows a simplified top view of a part of a timepiece movement having a compensation device according to a first embodiment of the present invention. More precisely, only the elements of the movement involved in the kinematic chain relating to the transmission of energy, from the energy source to the mechanical oscillator whose oscillations are maintained by this energy, have been illustrated.

As an indication, the energy source takes the form of a barrel 1 housing a barrel spring (visible in Figure 2a), the latter being intended to maintain the oscillations of a pendulum 2, in particular via of a finishing train and an exhaust of which only the wheel 3 and the pinion 4 have been schematized.

Since the mainspring is of conventional type, the torque that it transmits at the output, to the work train, varies according to its state of charge, in known manner, which can affect the accuracy of the operation of the balance. Also, the present invention provides that the finishing gear comprises a compensation device 5 to allow to maintain oscillations of the balance with a constant force and thus improve its accuracy of operation.

A toothed output wheel 6 is mounted on the barrel, being integral with it in rotation and, being arranged in engagement with a first mobile 7 of a reduction gear of the compensation device, carried by the frame of the movement. (visible in Figure 2a). A pinion 8 of the first mobile meshes with a first wheel 9 of the wheel, which itself is engaged with a second wheel 10 of the wheel.

The second wheel 10 is arranged in engagement with the periphery of a cam 12, toothed, advantageously having a shape substantially following an archimedean curve.

To ensure the maintenance of the kinematic connection between the second wheel 10 and the periphery of the cam 12, the first is mounted on a rocker 13 pivoting relative to the frame of the movement, about the axis 14 of rotation of the first wheel 9 Thus, the second wheel 10 continuously transmits the movements of the first wheel 9 to the cam 12, whatever the value of the radius of the cam in contact with the second wheel 10.

This mechanical connection appears more clearly in Figure 1b, in which it is shown isolated from the rest of the movement, while the mainspring is in a state of significant load. Indeed, when the movement operates, from a high load state of the barrel, the radius of the cam which is in contact with the second wheel 10 is low to minimize the value of the output torque of the barrel which is high. While the barrel spring discharges, it rotates the kinematic chain just described, which also rotates the cam 12 in the clockwise direction in the figures. The more the cylinder spring discharges, the more its output torque decreases and the more the radius of the cam in contact with the second wheel 12 increases, in order to compensate for the decrease in the output torque of the barrel.

Returning to FIG. 1a, it appears that an output wheel 15 of the compensation device, the board of which here has five arms in a non-limiting manner, is mounted coaxially with the cam 12, in order to provide a constant torque to the finishing gear located downstream, that is to say in the direction of the mechanical oscillator. The structure of the planned mechanical connection between the cam 12 and the output wheel 15 will be discussed in detail below, in connection with Figure 2a.

The output wheel meshes with a first mobile 16 of a multiplicative gear train having, after the first mobile 16, a second mobile 17, a large average 18, a third mobile 19 and a second mobile 20 meshing with the pinion. exhaust 4.

Of course, the number of mobile gear that has just been described is not limiting. It should be noted that the mechanical characteristics of the mainspring as well as the dimensions and the number of teeth of the cam affect the composition of the gear train which connects them to one another. Likewise, the dimensions of the cam and of the output wheel of the compensation device, the nature and the characteristics of the mechanical oscillator supplied with energy influence the composition of the multiplicative gear train.

The skilled person will not encounter any particular difficulty in adapting the gear of the movement described above to his own needs, without departing from the scope of the present invention.

FIG. 2a represents a simplified cross-sectional view of the movement of FIG. 1a, on which the mainspring 22 is apparent, as well as the fact that the drum of the barrel 1 does not have toothing as far as the transmission of the couple of its spring is made from the output wheel 6.

It also emerges from FIG. 2a that the compensation device comprises a differential gear 23 whose cam 12 defines a first input, while the wheel 15 defines its output, at constant torque.

The differential gear 23 is mounted on the frame 24 of the movement by a central shaft. The output wheel 15 is screwed onto a core 26, free to rotate on the shaft 25 and having a radial toothing 27.

A differential bridge 30 is screwed onto the cam 12, two satellites 31 being rotatably mounted by their respective ends, on the one hand, in the cam 12 and, on the other hand, in the differential bridge 30. satellites 31 comprises a pinion 32 and a wheel 33, the pinion 32 being arranged in engagement with the toothing 27 of the core 26.

The differential gear 23 has a second input in the form of a wheel 35 mounted rotatably on the central shaft. The wheel 35 carries a radial toothing 36 directed towards the shaft 25 and arranged in engagement with the wheel 33 of each of the satellites 31.

The wheel 35 fulfills the input function of the differential to allow the winding of the mainspring as shown better in FIG. 2b, on which has been schematized the kinematic chain connecting an external control member 40 to this wheel 35.

The external control member is arranged so as to drive in rotation a winding pinion 41 meshing with a crown wheel 42, itself engaged with a winding crown 43. This is arranged in engagement with the wheel input 35 of the differential gear 23, the latter ensuring the establishment of a kinematic connection between the external control member 40 and the barrel 1, as will be explained in detail below. A ratchet (not shown) of conventional type is also provided in the winding train to prevent unwanted rotation of the wheels when no winding operation is in progress.

When the external control member 40 is actuated in rotation to carry out the winding of the mainspring 22, the input wheel 35 is rotated by means of the winding train which has just been described. Considering that the output wheel 15 of the differential is locked most of the time, namely during the rest phases of the escape wheel 3, the rotation of the input wheel 35 is reflected on the satellites 31, via the tooth 36, causing rotation of the cam 12, in the counter-clockwise direction in FIGS. 1a and 1b, because the core 26 of the differential can be regarded as immobile during this operation, as a first approximation, to illustrate the operating principle of the differential.

The rotation of the cam 12 is transmitted to the wheel 10, then to the wheel 9, to the mobile 7 and finally to the output wheel 6 of the barrel. Barrel 1 is by consequently driven in rotation, in the counter-clockwise direction in FIG. 1a, reloading its spring 22 whose inner end is integral with the barrel shaft 50, fixed with respect to the frame.

When the winding train is not biased from the external control member, it can be considered that the input wheel 35 of the differential is locked.

As mentioned above, the barrel spring 22 transmits its force to the cam 12 tending to rotate it clockwise, in Figures 1a and 1b. This rotation of the cam is however possible only outside the rest phases of the escape wheel 3, namely when the output wheel 15 of the differential is not locked. The satellites 31 being integral with the cam by their respective axes, they are driven in the same rotational movement, which rolls their wheels 33 on the toothing 36 of the input wheel 35. The satellites then turn on their own by transmitting a torque to the core 26, by its toothing 27, thus to the output wheel 15.

Insofar as the differential input torque is kept constant by the variation of radius of the cam 12, the torque transmitted at the differential output by the wheel 15 is also constant, regardless of the state of charge of the spring. barrel 22 and thus the output torque that it transmits to the gear train.

Consequently, the torque finally transmitted to the escape wheel 3 is constant, which makes it possible to supply the same amount of energy to the balance 2 at each pulse and to guarantee excellent running accuracy.

The accuracy of operation can then be seen in a time display, illustrated here conventionally, which will have a very small deviation in time. A carriageway 60, intended to carry a minute hand (not shown) is carried by the shaft of the large average 18 and itself carries a wheel of hours 61, intended to carry an hour hand (not shown), a timer 62 ensuring the necessary multiplication between these two bodies.

There is shown a pavement 60 lantern type, to be able to time the corresponding timepiece in a conventional manner, without disturbing the operation of the mechanical oscillator. A time setting train, not shown, is thus advantageously provided for connecting the external control member to the timer 62.

Preferably, a mechanism for indexing the angular position of the barrel shaft 50 is provided and shown isolated in FIG. 2c, by way of nonlimiting illustration.

This mechanism has the shape of a wheel 70 with sawtooth toothing, integral in rotation with the barrel shaft 50 and cooperating with a pawl 71. This indexing mechanism makes it possible to adjust the angular position of the barrel. barrel shaft for controlling the minimum value of the output torque provided by the mainspring 22 which will be associated with the greatest useful radius of the cam 12. This minimum value is predefined during the manufacture of the movement, depending on the mechanical properties the barrel spring 22 used. This value generally defines the beginning of a range in which the torque delivered by the mainspring has regular variations as a function of its state of charge, typically characterized by the number of turns of the barrel.

Furthermore, there is also shown a stop 72, carried by the cam 12 and intended to cooperate with a fixed bearing surface 73 (shown schematically in Figure 1b) of the frame for stopping the rotation of the cam when the minimum value selected in manufacturing for the output torque of the barrel is reached.

A similar stop may be provided to limit the reassembly when the minimum radius of the cam is reached, the latter being advantageously associated with a maximum value of the output torque supplied by the mainspring 22. This value then marks the end of the range of use of the mainspring as mentioned above. Those skilled in the art may also provide a torque limiting mechanism of conventional type in the winding train, to avoid damaging the gears, without departing from the scope of the present invention.

Optimally, when the choice of a particular mainspring is stopped, the gear train, namely the wheels 6, 9 and 10 and the mobile 7, can be chosen so that the total number of revolutions of the barrel 1, corresponding to its range of use, is associated with substantially one revolution of the cam 12.

FIG. 3 represents a simplified top view of a part of a timepiece movement comprising a compensation device according to a second embodiment of the present invention.

This second embodiment illustrates an alternative linking mechanism to that of the first embodiment.

The output wheel 6 of the barrel 1 meshes with a first mobile 80 of a gear train, itself engaged with a second mobile 81. The latter drives a mobile link via a wheel 82, mounted integral in rotation with a first cam 83, being coaxial therewith.

The first cam 83 is arranged in engagement, by its periphery, with a second cam 84 which, for example, can advantageously fulfill the input function of a differential gear, similar to the differential 23 described in connection with the first embodiment.

The two cams 83 and 84 are dimensioned such that their respective peripheries are engaged continuously. For this purpose, their respective rays are such that, when considering the rays located on the segment 85 connecting the centers of the cams, at each moment, their sum is constant. In addition, the respective values of their radii are adjusted in such a way that the torque supplied by the second cam 84 is constant regardless of the state of charge of the spring of the barrel 1, therefore whatever the output torque transmitted by the barrel at the exit wheel 6.

Thus, when the mainspring discharges, its output torque decreases and the radius of the first cam increases to compensate for substantially more than the decrease in the torque that it receives, that is to say to transmit to the second cam 84 a couple whose value tends to increase very slightly. At the same time, the radius of the second cam 84 decreases progressively so as to compensate exactly for the increase in the torque that the first cam 83 transmits to it, in order to globally provide a constant torque to the mechanical oscillator (not shown) disposed downstream.

The combination of these two cams makes it possible to control with great accuracy the compensation of the output torque variations of the barrel while greatly limiting the manufacturing and construction efforts compared to the mechanisms of the prior art. In addition, the reliability of the kinematic connection thus formed between the two cams is excellent, especially when it is performed, preferably by gearing.

The above description corresponds to preferred embodiments of the invention described in a non-limiting manner. In particular, the shapes shown and described for the various constituent elements of the movement for a timepiece are only shown by way of example. It may be mentioned here, in a nonlimiting manner, the fact that the present invention can advantageously be implemented in a timepiece of the wristwatch type due to its small size.

Many alternative embodiments can be provided without departing from the scope of the present invention. In particular, with reference to the first embodiment described, it is possible to provide that the periphery of the cam is associated with the output of the compensation device, rather than at its input. In this case, it is possible, for example, to have an input wheel, kinematically connected to the energy source, while the intermediate connection mechanism, connected to the periphery of the cam, is associated with the output of the compensation device, the cam being driven by the input wheel. In this case, one can even consider mounting the cam directly on the barrel, replacing the output wheel 6.

In general, the skilled person will not encounter any particular difficulty to modify the different gear trains, gearing or multiplicative, according to his own needs.

Of course, the present invention is not limited by the nature of the energy source described and shown here. However, it can be noted that thanks to its function, the invention allows the use of barrel springs so-called "slow" or low revolutions. This type of springs is not the most common because the output torque is high and has a significant variation between the two ends of its range of use in torque. However, they have the particular advantage of limiting the risk of sticking more common turns with springs "high speed" or high revolutions. Similarly, the present invention can be used to support the significant torque that is transmitted to the gear train by parallel drums.

Claims (13)

Movement for a timepiece comprising an energy source (1, 22) mounted on a frame (24), and having a variable output torque depending on its state of charge, the latter being intended to maintain the oscillating movement a mechanical oscillator (2, 3, 4) through a finishing gear comprising a compensation device (5), the latter having an input kinematically connected to said power source and an output kinematically connected to said oscillator mechanical and, being arranged to transmit a substantially constant torque to said mechanical oscillator regardless of the state of charge of said energy source,
characterized in that said compensation device comprises
a cam (12, 84) having a periphery of variable radius extending substantially in a general plane, the variations of the radius of said cam being a function of those of the output torque of said energy source, and,
an intermediate linking mechanism (9, 10, 13, 83) arranged to provide a kinematic connection substantially without sliding between said periphery of the cam and said finishing train. Movement according to claim 1, characterized in that said intermediate connecting mechanism (9, 10, 13, 83) exclusively comprises constituents having respective rigid general shapes. Movement according to claim 1 or 2, characterized in that said intermediate linking mechanism comprises
a rocker (13) pivoting about a fixed shaft (14) on said frame (24) and carrying a wheel (10) movable having a permanent kinematic link with a wheel (9) mounted free to rotate about said fixed shaft and arranged in permanent engagement with at least one mobile (7) of said work train, said movable wheel being also arranged in engagement, substantially without sliding, with said periphery of said cam (12). Movement according to any one of the preceding claims, characterized in that said periphery of said cam (12) is associated with said input of said compensation device (5) while being connected kinematically to said power source (1, 22) via said intermediate link mechanism (9, 10, 13). Movement according to claim 4, characterized in that said cam (12) is arranged in such a way that its radius, in the region of its periphery where said kinematic connection is implemented with said energy source, increases when the load of said energy source decreases. Movement according to claim 1 or 2, characterized in that said connecting mechanism comprises an additional cam (83), variable radius, kinematically connected by its periphery to said periphery of said cam (84) and dimensioned and such whereby the sum of the respective radii of said cam and of said additional cam, taken on a segment (85) connecting their respective centers, is constant, said additional cam (83) being integral in rotation with a drive wheel kinematically connected to said source of energy. Movement according to any one of the preceding claims, characterized in that said compensation device (5) comprises a differential gear (23) of which said cam (12) defines an input, said differential gear having an additional input (35), connected a winding mechanism (40, 41, 42, 43) of said energy source, and an output (15) kinematically connected to said mechanical oscillator. Movement according to claim 7, characterized in that said cam (12) carries at least one satellite (31), free to rotate, comprising a pinion (32) and a wheel (33) integral in rotation, one of which is connected to said additional inlet (35) while the other is connected to said outlet (15). Movement according to any one of the preceding claims, characterized in that said energy source comprises a spring (22) housed in a barrel (1), and in that it further comprises an indexing mechanism (70, 71), arranged to allow relative angular positions of said cam (12) and said barrel under predefined conditions. Movement according to any one of the preceding claims, characterized in that said compensation device (5) is arranged in such a way that said cam (12) makes one turn, at the most, when the state of charge of said energy source (1, 22) changes between its minimum and maximum values. Movement according to claim 10, characterized in that said compensation device comprises first and second stops (72) for defining respectively the minimum and maximum values of the state of charge of said energy source. Movement according to claim 10, characterized in that said cam (12) carries a stop (72) intended to cooperate with a bearing surface (73), fixed with reference to said frame, to define a minimum load state of said source energy. Timepiece comprising a movement according to any one of the preceding claims.

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