CH709755B1 - Clock mechanism with a tuning fork resonator. - Google Patents

Abstract

The invention relates to a mechanical clockwork mechanism comprising a frame on which is mounted: a tuning fork (1) composed of a base (2) and two branches (3, 4), the base being fixed with reference to the frame and the two branches (3, 4) being able to oscillate in phase opposition, a tuning fork wheel (10) provided with a set of teeth (11) and driven in rotation by a motor unit to which it is connected by a gear train, a stop tooth (8, 9) integral with a branch (3, 4) of the tuning fork (1) and capable of cooperating with the toothing (11) of the tuning fork wheel (10) so as to block the rotation of the tuning fork wheel (10) periodically related to the oscillating frequency of the tuning fork (1), a pulse member (12) for sustaining oscillations of the tuning fork (1), the impulse member (12) being separate from the tuning fork wheel (10) and mounted on a frame member. The clockwork mechanism further comprises a device for arming and relaxing (17) the pulse member (12), synchronized with the tuning fork wheel (10) and arranged so that the period of the body of pulse is at least twice the oscillation period of the tuning fork.

Description

Description

Technical Field [0001] The present invention relates to the field of watchmaking. More particularly, it relates to an exclusively mechanical clockwork mechanism fitted with a tuning fork resonator.

It is known that a tuning fork constitutes an oscillator which has a quality factor much higher than that of a balance-spring oscillator conventionally used in watchmaking, partly due to the friction forces present at the pivot of the balance. In addition, the higher frequency of oscillation of the tuning forks compared to balance-spring oscillators, improves the precision of a clockwork mechanism incorporating such an oscillator. It is therefore advantageous in terms of precision and power reserve, to use a tuning fork oscillator to count the time.

STATE OF THE ART Despite these advantageous properties, little example is known of integrating a tuning fork in an exclusively mechanical clockwork mechanism.

We know, in particular, the patent FR 73 414 issued to Louis-François-Clément Breguet on the basis of a request of October 26, 1866, which offers a clockwork mechanism comprising a cog completed by an escape wheel cooperating with an anchor secured to the end of a branch of a tuning fork. This device has been implemented in a clock with a large tuning fork, having a low resonant frequency. Such a system is difficult to adapt to a small clockwork mechanism like that of a wristwatch. Furthermore, this escapement is not of the free type since one of the two pallets of the anchor is still engaged with the escapement wheel. The energy transmitted by the escapement wheel to the anchor to maintain the oscillations of the tuning fork, requires significant engine torque and induces high friction forces between the anchor and the escapement wheel. This results in significant wear of the parts in contact and a high energy consumption.

WO 2013/045 573 discloses another mechanical tuning fork resonator involving an anchor pivoted on the frame and provided with arms cooperating with pins fixed to a support integral with a branch of the tuning fork. This arrangement is similar to that of a conventional balance-spring type resonator in which the anchor fork and the platform pin have been replaced by the arms and the support.

In the two above mechanisms, an impulse is transmitted by the escapement wheel to the tuning fork at each half-cycle, ie twice per period of oscillation. This results in a number of shocks and accelerations of the moving parts which are greater the higher the oscillation frequency, which causes significant energy consumption and disturbances of the oscillation period. The interactions of the escapement wheel with the anchor several times during a period of oscillation do not fully benefit from the high quality factor of a tuning fork.

It should be noted that other technical solutions have been proposed using a tuning fork having magnetic interactions with a mechanical device or an electrical circuit. These solutions are not purely mechanical, they do not fall within the scope of the invention.

The present invention aims to provide a clockwork mechanism provided with a tuning fork resonator whose energy consumption and operation are optimized and which can be integrated into a wristwatch.

Disclosure of the invention The invention relates to a mechanical clockwork mechanism comprising a frame on which is mounted:

- a tuning fork composed of a base and two branches, the base being fixed with reference to the frame and the two branches being liable to oscillate in phase opposition,

- a tuning fork wheel with teeth and rotated by a drive member to which it is connected by a gear train,

a stop tooth secured to a branch of the tuning fork and capable of cooperating with the toothing of the tuning fork wheel so as to block the rotation of the tuning fork wheel periodically in relation to the oscillation frequency of the tuning fork,

- an impulse member intended to maintain the oscillations of the tuning fork, the impulse member being separate from the tuning fork wheel and being mounted on an element of the frame.

The clockwork mechanism further includes a device for winding and expanding the impulse member, synchronized with the tuning fork wheel and arranged so that the period of the impulse member is at least twice. the period of oscillation of the tuning fork.

Thus, the objective of the invention is achieved by separating the oscillation counting function from that of the impulse. It is thus possible to minimize the torque applied to the tuning fork wheel and to use small tuning forks with high resonance frequency.

CH 709 755 B1

Brief description of the drawings [0012] Other details of the invention will appear more clearly on reading the description which follows, made with reference to the appended drawing in which:

fig. 1 shows a view of a tuning fork resonator of a timepiece mechanism according to the invention;

fig. 2 shows a view of detail A of FIG. 1.

Embodiment of the invention [0013] There is shown in FIGS. 1 and 2, an embodiment of a clockwork mechanism according to the invention. Only the components essential to understanding the invention have been shown.

The timepiece mechanism according to the invention comprises a tuning fork 1 composed of a base 2 fixed to an element of the frame of the timepiece mechanism and of two branches 3 and 4 capable of oscillating in phase opposition so known. Each of the free ends of the two branches is provided with an inertial mass 5. Advantageously, the position of the center of gravity of the inertial masses 5 can be finely adjusted along the longitudinal direction defined by the branches 3 and 4, in order to vary the frequency of oscillation of the tuning fork. Limitation stops 6, fixed to an element of the frame, make it possible to limit the amplitude of the pendulum's oscillations. Each branch has a dowel 7, which can be attached to the branches 3, 4. Stop teeth 8 and 9 are arranged respectively on the branches 3 and 4. These stop teeth can be attached or come in one piece with branches 3, 4. The usefulness of the pegs 7 and the stop teeth 8 and 9 will become apparent later. The tuning fork 1 can, for example, be made of or based on materials of the silicon or sapphire type.

A tuning fork wheel 10, pivoted on the frame, is rotated by a drive member, of the barrel type, to which it is connected by a gear train, not shown. The tuning fork wheel 10 is provided with a toothing 11 capable of cooperating with the stop teeth 8 and 9 as will be explained in more detail below.

An impulse member 12 is arranged to maintain the oscillations of the tuning fork 1. It comprises a hammer 14 disposed at one end of a flexible arm 13, the other end of the flexible arm being fixed to an element of the frame. A lifting pallet 15 is mounted at the end of the impulse member 12, on the side of the hammer 14, or directly on the hammer 14. A impulse stop 16 is arranged so as to adjust the stroke of the 'impulse member 15. The stopper is advantageously mounted eccentrically to a frame element. The role of these different elements will appear later.

A winding and detent device 17 is further provided for elastically deforming the flexible arm 13 and releasing it so that it suddenly returns to its rest position while restoring the accumulated energy. This winding and detent device 17 comprises a toothed wheel 18 pivoted on the frame and driven in rotation by the gear train. Its rotation is thus synchronized with that of the tuning fork wheel. A cam 19, typically a spiral spiral, is mounted for rotation with the toothed wheel 18. The cam includes a rapid change of radius, in an essentially radial direction, to allow the flexible arm to return suddenly to its rest position.

We will now describe the operation of the mechanism, to illustrate the interactions between the different parts which have just been described. When the drive unit is unloaded and the clockwork mechanism is stopped, no engine torque is transmitted to the train and the tuning fork is at rest in the neutral position shown in figs. 1 and 2. In the neutral position of the tuning fork, a clearance is provided between the stop teeth 8 and 9 and the teeth 11 so that the stop teeth 8 and 9 do not cooperate with the teeth 11 of the tuning fork wheel 10.

When the user goes up the clockwork mechanism, a driving torque is transmitted by the gear train to the tuning fork wheel 10 which can turn without being hindered by the stop teeth 8 and 9. Concomitantly, the train also causes the toothed wheel 18 rotating clockwise with reference to FIG. 1. The lifting pallet 15 is gradually raised by the cam 19, by arming the flexible arm 13. Arriving at the level of the rapid change of radius of the cam, the lifting pallet 15 and the hammer 14 suddenly fall under the action of the return force of the flexible arm 13 and the hammer 14 strikes the pins 7 disposed on the branches 3 and 4 of the tuning fork. The impulse stop 16 has the effect of raising the hammer 14 after striking and of preventing the hammer from rebounding on the pegs 7. The impulse stop 16 also has the function of preventing the hammer from accidentally striking the ankles in the event of an impact on the watch. This particular arrangement allows the described mechanism to be self-starting.

The impact of the hammer on the pins 7 moves the branches 3 and 4 from their equilibrium position and starts the vibration of the tuning fork according to its natural frequency of resonance. During the first half-period of oscillation, the branches pass from the neutral position to a distal position where their spacing is maximum and return to the neutral position. During the second half-oscillation period, the branches move from the neutral position to a proximal position and then return to the neutral position.

From the first oscillation following the striking of the hammer 15, the stop tooth 9, carried by the branch 4, moves in an almost rectilinear trajectory and enters between two teeth of the toothing 11. During the first half-period , a tooth of the teeth 11 comes to bear against the stop tooth 9 which has the effect of stopping the rotation of the tuning fork wheel

CH 709 755 B1

10. At the end of the first half-period of oscillation, the stop tooth 9 emerges from the toothing 11 and the tuning fork wheel resumes its rotation anti-clockwise with reference to FIG. 2.

A speed regulator system, of known type, for example an inertia regulator used in striking mechanisms, can be added to the mechanism, in order to limit the speed of the tuning fork wheel in the start-up phase, and therefore to control the speed and the position of the first impact of the teeth 11 with the stop tooth 9, regardless of the starting position of the wheel 18.

Just after the tooth 9 is released from the teeth 11, the stop tooth 8, which moves in the opposite direction to the tooth 9, in turn enters between two teeth of the teeth 11. During the second half-period of oscillation, a tooth of the toothing 11 comes to rest against the stop tooth 8, which again stops the rotation of the tuning fork wheel 10 until the tuning fork goes back into the neutral position and the stop tooth 8 disengages from the toothing 11 and again releases the tuning fork wheel 10.

To guarantee the isochronism of the two phases of advance of the tuning fork wheel 10, the spacing between the stop planes of the stop teeth 8 and 9 will preferably be (n + 1/2) times the pitch of the pitch of the tuning fork wheel, where n is an integer greater than or equal to zero. In fig. 2, n = 1 which means that the distance between the stop teeth is 1.5 times the pitch of the toothing 11.

Twice per oscillation period, the tuning fork wheel is stopped, successively by one and the other of the stop teeth 8 and 9, which makes it possible to clock the speed of rotation of the tuning fork wheel and of the entire train as a function of the frequency of oscillation of the tuning fork so that the tuning fork wheel 10 advances by one step of the teeth

11, at each period of oscillation of the tuning fork 1. In other words, in the interval after a tooth of the teeth 11 has left one of the stop teeth 8 or 9, until the tooth next stop on the same stop tooth, the tuning fork wheel is stopped once by the other stop tooth.

Advantageously, the profiles of the stop teeth 8 and 9 and the teeth of the teeth 11 intended to be in contact, are cut so that the sliding of a stop tooth 8 or 9 on the teeth 11 cause the least possible, or even no, rotation, particularly of recoil, of the tuning fork wheel 10.

The amplitude of the oscillations of the tuning fork 1 gradually decreases so that it is necessary to maintain them by giving a boost to the tuning fork periodically to keep the movement running. It is the cocking and detent device 17 which performs this maintenance.

From the first impulse given to the tuning fork, the toothed wheel 18, like the rest of the gear train, is rotated in clockwise fashion. At each revolution of the toothed wheel 18, a new impulse is given to the tuning fork 1 according to the same principle as the starting impulse, that is to say by winding and releasing the flexible arm 13. Thanks to the fact that the toothed wheel 18 and the tuning fork wheel are synchronized, due to their common drive by the gear train, the pulse is also synchronized with the oscillations of the tuning fork. Preferably, the synchronization is established so that the hammer strikes the ankles when they deviate from each other at their maximum speed, that is to say when the tuning fork is in the neutral position at when the stop tooth is released 8.

It should be noted that the impulse force given to the tuning fork by the return force of the flexible blade 13, is constant and does not depend on the engine torque delivered by the engine member.

The limit stops 6 limit the travel of the tuning fork branches and therefore the travel of the stop teeth 8 and 9, in order to prevent the tip of the stop teeth from striking the bottom of the teeth in the case where the clock mechanism is subjected to a shock.

Unlike the devices of the prior art, the tuning fork wheel 10 which counts the oscillations of the tuning fork 1, is not an escapement wheel because it does not transmit any impulse to maintain the oscillations of the tuning fork. As a result, the engine torque of the tuning fork wheel 10 can be greatly reduced compared to that of an escapement wheel, which also has the advantage of reducing the friction between the stop teeth 8 and 9 and the toothing 11.

The tuning fork resonator according to the embodiment described, unlike those of the prior art, biases the two branches of the tuning fork symmetrically.

Furthermore, the pulse member 12 and the winding and detent device 17 are arranged so that the period of the pulse member is at least twice the period of oscillation of the tuning fork 1 and preferably at least 50 times the period of oscillation of tuning fork 1. Thus the device according to the invention makes it possible to take full advantage of the high quality factor of tuning fork 1 by greatly reducing the number of pulses to maintain the oscillations.

To minimize friction, the toothing 11, the stop teeth 8 and 9, the hammer 14, the pins 7, the lifting pallet 15 and the spiral 19 are made of materials with reduced coefficient of friction, or covered such materials as rubies, diamonds, silicon ...

By reducing the energy losses due to the number of shocks and friction, by making it possible to integrate a tuning fork resonator of high frequency in a watch, the device according to the invention makes it possible to meet the objectives set in terms of gains in precision and power reserve.

Other embodiments not shown and their combinations are also covered by the invention.

CH 709 755 B1 In a first variant, the stop teeth cooperate with the teeth 11 when the tuning fork is in the neutral position. In this case, automatic starting is no longer possible since the cog is immobilized by the tuning fork wheel which is itself blocked by one or the other of the stop teeth. It is then advisable to provide an additional starting device which makes it possible to give the first impulse to the tuning fork to start the movement. This starting device can be produced on the model of the winding device described above, in which the wheel carrying the cam is no longer driven by the gear train but by a control member actuated by the user, for example the control of reassembly. This configuration makes it possible to ensure that there is never a jump of a tooth of the toothing since there is always at least one of the two stop teeth in the field of the toothing 11.

In another variant, the tuning fork resonator has only one stop tooth on one of the branches of the tuning fork. The single stop tooth jumps from one tooth to the other of the toothing 11, so that, as in the two stop tooth variants, the tuning fork wheel advances one step at each period of oscillation of the tuning fork.

In another variant, two stop teeth are mounted on the same arm of the tuning fork and cooperate with two teeth carried by the same tuning fork wheel or by two tuning fork wheels engaged with the train.

From the above description, a person skilled in the art will be able to produce an oscillation maintenance device intended to periodically excite any resonator of a timepiece. The maintenance device comprises an impulse member and an arming and detent device.

The impeller has an elastic return means capable of accumulating energy and returning it in kinetic form. The winding and detent device is kinematically connected to the gear train and is arranged so as to arm the elastic means and to release it suddenly, at a precise instant synchronized with the oscillations of the resonator. The winding and detent device can then supply a portion of energy to the resonator to maintain its oscillations. Those skilled in the art can directly take up the teaching given in connection with the particularly illustrated embodiment. If necessary, it can adapt on the oscillator, for example on a pendulum, an area intended to receive the excitation transmitted by the winding and detent device.

Claims (12)

claims 1. Mechanical clockwork mechanism comprising a frame and, mounted on the frame: - a tuning fork (1) composed of a base (2) and two branches (3, 4), the base (2) being fixed with reference to the frame and the two branches (3, 4) being capable of oscillating in phase opposition, - a tuning fork wheel (10) provided with a toothing (11) and driven in rotation by a motor member to which it is connected by a gear train, - a stop tooth (8, 9) integral with a branch (3, 4) of the tuning fork (1) and capable of cooperating with the toothing (11) of the tuning fork wheel (10) so as to block rotation the tuning fork wheel (10) periodically in relation to the frequency of oscillation of the tuning fork (1), - an impulse member (12) intended to maintain the oscillations of the tuning fork (1), characterized in that the impulse member (12) is distinct from the tuning fork wheel (10), in that the member impulse (12) is mounted on an element of the frame, in that the clock mechanism further comprises a winding and detent device (17) of the impulse member (12), synchronized with the tuning fork wheel (10) and in that the period of the impulse member is at least twice the oscillation period of the tuning fork (1). 2. Mechanism according to claim 1, characterized in that the period of the impulse member is at least 50 times the period of oscillation of the tuning fork (1). 3. Mechanism according to one of the preceding claims, characterized in that the branches (3, 4) of the tuning fork (1) comprise an inertial mass (5) whose position is adjustable so as to be able to adjust the oscillation frequency of the tuning fork (1). 4. Mechanism according to one of the preceding claims, characterized in that the impulse member (12) comprises a hammer (14) fixed to one end of a flexible arm (13), the other end of the flexible arm being fixed to an element of the frame, and in that the winding and expansion device (17) is arranged to cause the elastic deformation of the flexible arm (13) and suddenly release the impulse member (12) so that the hammer (14) strikes an element integral with a branch (3, 4) of the tuning fork (1). 5. Mechanism according to the preceding claim, characterized in that the impulse member (12) comprises a lifting pallet (15) cooperating with a cam (19) that includes the winding and detent device (17) and in that the winding and detent device (17) is rotated by the train. 6. Mechanism according to the preceding claim, characterized in that it comprises an adjustable impulse stop (16) mounted on a frame element and arranged so that the hammer (14) strikes only once the tuning fork (1) on each pulse. 7. Mechanism according to one of claims 4 to 6, characterized in that each of the branches (3, 4) of the tuning fork carries an ankle (7), said pins (7) being arranged to be struck simultaneously by the hammer ( 14) and cause the excitation of the tuning fork (1). CH 709 755 B1 8. Mechanism according to one of the preceding claims, characterized in that each branch (3, 4) carries a stop tooth (8, 9) cooperating with the teeth (11) and arranged so as to lock the wheel twice of tuning fork (10) at each period of oscillation of the tuning fork (1). 9. Mechanism according to the preceding claim, characterized in that the stop teeth (8, 9) do not cooperate with the teeth (11) of the tuning fork wheel (10) when the tuning fork (1) is at rest. 10. Mechanism according to one of the preceding claims, characterized in that the profiles of the stop tooth (8, 9) and of the toothing (11) of the tuning fork wheel (10) are shaped so that the movement of the stop teeth (8, 9) engaged with the tuning fork wheel (10) does not cause rotation of the tuning fork wheel (10). 11. Mechanism according to one of the preceding claims, characterized in that it includes limiting stops (6) arranged to limit the amplitude of the oscillation of the branches (3, 4) of the tuning fork (1). 12. Mechanism according to claims 7 and 8, characterized in that the toothing (11), the stop teeth (8, 9), the hammer (14), the dowels (7), the lifting pallet (15) and the cam (19) are made of materials chosen from rubies, diamonds and silicon. CH 709 755 B1 Hg.1 CH 709 755 B1