Patent ID: 12248279

DETAILED DESCRIPTION OF THE INVENTION

As explained hereinabove, the invention relates to an impact striking mechanism1. The striking mechanism1is intended for a timepiece10, such as a watch shown inFIG.1. The timepiece10comprises a middle2and a horological movement3, preferably a mechanical movement, which is for example provided with a plate4and a barrel spring to supply the operating energy. The embodiment described hereinbelow is based on the combination of the “Gaussian magnetic cannon” principle and the principle of conservation of momentum during a collision.

InFIGS.1to5, the striking mechanism1comprises a resonant element5, for example a gong conventionally used in horological striking mechanisms. The resonant element5allows a sound to be emitted when struck. In the figures, the resonant element5is a rod comprising a rectilinear portion6. The resonant element5is preferably fixed to the plate4, so as to extend above and beside the plate4, for example in a plane parallel to that of the plate.

Other configurations of the resonant element5are possible. The resonant element5can further comprise a circular portion7, shown inFIG.1, in particular running along the inner face of the middle2.

To emit a sound, the mechanism1comprises a hammer8that is capable of moving relative to the plate4. The hammer8is capable of moving between two positions, a rest position9away from the resonant element5, and a strike position11in which it strikes the resonant element to cause it to vibrate. Thus, the resonant element5produces a vibration that propagates through the watch. The outer part of the watch radiates these vibrations such that a sound is emitted. Other embodiments are possible with various forms for the hammer8and the resonant element5.

The mechanism1in this case comprises a flexible guide12on which the hammer8is mounted to allow it to move between the rest position9thereof and the strike position11thereof. The flexible guide12preferably comprises a first flexible strip13assembled with the plate4on the one hand, and with the hammer8on the other hand. The first flexible strip13is preferably arranged substantially parallel to the resonant element5when the hammer8is in the rest position9. Through the elastic deformation of the first flexible strip13, the hammer8moves from the rest position9into the strike position11and vice versa.

The mechanism1further includes a magnet15that is fixed relative to the plate4. The magnet15is preferably assembled on the plate4. The magnet15is, for example, disposed on a promontory14facing the resonant element5.

Preferably, the magnet15is configured to retain the hammer8in the rest position9thereof. For this purpose, the hammer8includes a magnetically conductive material, which induces an attractive force on the hammer8against the magnet15.

Alternatively, a hammer8can be chosen that does not comprise any magnetically conductive material. In such a case, the flexible guide12is configured to apply a prestressing to the hammer8, so as to press it against the magnet8.

Thus, in the rest position9, the hammer8is in contact with a front face29of the magnet15. The hammer8remains in this position at all times, except in the moments when it strikes the resonant element5. The flexible guide12is assembled to the plate4between the promontory14and the resonant element5. Thus, the hammer8can move between the magnet15and the resonant element5thanks to the flexible guide12.

The front face29preferably has a substantially planar surface. The hammer8has, for example, a cylindrical or spherical shape. These rounded shapes make it easier to separate the hammer8from the front face29of the magnet15.

According to the invention, the mechanism1comprises a system for actuating the hammer8. This mechanism is configured to cause the hammer8to move from the rest position9thereof to the strike position11thereof. In particular, it serves to separate the hammer8from the magnet15and allow it to reach the resonant element5.

To this end, the actuation system20includes at least one movable impactor16,17,18configured to transmit to the hammer8a sufficient momentum to move it from the rest position9thereof to the strike position11thereof and to cause the resonant element5to vibrate.

The impactor16,17,18is configured to move from a release position19into an impact position21wherein it transmits a momentum to the hammer8.

In the embodiment shown inFIGS.1to5, the actuation system comprises a rotary device20provided with three movable impactors16,17,18.

The rotary device20comprises a hub22and three arms23,24,25, which are angularly distributed around the hub22and are connected to the hub22by one end. Each arm23,24,25bears a movable impactor16,17,18disposed at the opposite end of the arm23,24,25relative to the hub22. The arms23,24,25are preferably arranged in the same plane substantially perpendicular to the axis of the hub22. This plane preferably further passes through the magnet15, the hammer8and the resonant element5.

Each movable impactor16,17,18is mounted on an arm23,24,25so as to form an angle with the arm23,24,25. The angle is comprised between 30 and 60°, when the movable impactor16,17,18is in the release position19, and the angle is comprised between 60 and 90°, when the movable impactor16,17,18is in the impact position21. An arm can, for example, be an oblong body, a tooth of a gear train or a small plate.

Preferably, each movable impactor16,17,18is mounted on the arm23,24,25by a flexible guide to enable it to move relative to the arm23,24,25, and to switch from the release position19into the impact position21. The flexible guide here includes a second flexible strip26assembled to the movable impactor16,17,18on the one hand and to the end of the arm23,24,25on the other hand.

Each movable impactor16,17,18comprises a contact face31,32,33, which is intended to come into contact with the magnet15, when it moves from the release position19into the impact position21. The contact faces31,32,33of the movable impactor16,17,18are preferably rounded, to allow for easier disengagement when the movable impactor16,17,18returns to the release position thereof.

When the rotary device20rotates, it positions one of the movable impactors16,17,18to face the magnet15. The movable impactor16,17,18then moves from the release position19into the impact position21in a radial movement. Once the impact has been made, the rotary device20continues to rotate in order to prevent the movable impactor16,17,18from remaining against the magnet15. The geometry of the movable impactors16,17,18is designed to require as little torque as possible on the rotary device20. For example, a contact face32is chosen that has a gradient tangential to the rotary motion.

The rotary device20is actuated by rotating the hub22about the axis thereof, such that the arms23,24,25rotate about the axis of the hub22. Thus, the movable impactors16,17,18also rotate about the axis of the hub22while remaining in the release position19. In other words, the movable impactors16,17,18remain in the same position relative to the arms23,24,25bearing them.

In order to rotate, the means22are mechanically connected to the barrel of the movement via meshing means, not shown in the figures. These meshing means comprise, for example, an actuation system configured to determine the strikes to be executed as a function of the time displayed by the movement3, in particular to act as minute repeaters or to signal a scheduled alarm time. Thus, when one or more strikes are to be sounded, the actuation system triggers the rotation of the hub22.

The rotary device20is configured to bring the impactor into the release position21in front of the magnet15.FIG.3shows one example wherein the impactor21is in the release position located the closest to the magnet15. The magnet15has an opposite face30oriented towards the rotary device20, such that the opposite face30of the magnet15and a contact face31,32,33of a movable impactor16,17,18are facing one another when the rotary device20is rotating. The opposite face30preferably has a substantially planar surface.

The attractive force of the magnet15and the distance between the contact face31,32,33of the movable impactor16,17,18in the release position and the opposite face30of the magnet15are chosen such that the magnet15attracts the impactor16against the opposite face30thereof, when it passes in front of the opposite face30thereof. Thus, the magnetic potential energy produced by the magnet15acting on the movable impactor16,17,18is transformed into kinetic energy by the movable impactor16,17,18. This kinetic energy is transmitted to the hammer8through the impact of the movable impactor16,17,18.

More specifically, when the movable impactor16,17,18is attracted by the magnet15, it is accelerated and strikes the magnet15. When the movable impactor16,17,18collides with the opposite face30of the magnet15, at least a part of the momentum thereof is transmitted to the hammer8through the magnet15, the hammer8being disposed against the front face29of the magnet in the rest position.

This principle of motion transmission combined with magnetic attraction is known as the “Gaussian cannon”. The attraction of the magnet15guarantees a minimum intensity for each strike of the hammer8. The resulting strike is more consistent over the entire duration of the strike, independently of the barrel torque.

As shown inFIG.4, each movable impactor16,17,18is configured to impact the magnet15in order to provide a pulse to the hammer.

Moreover, the movable impactors16,17,18and the rotary device20are configured such that the momentum transmitted to the hammer8by the impactor16,17,18is greater than the retaining force of the magnet acting on the hammer8, such that the hammer detaches from the magnet15and strikes the resonant element5with sufficient force, as shown inFIG.4.

As shown inFIG.5, the magnet15and the hammer8are further configured so that the front face29attracts the hammer8against it, after it has struck the resonant element5. Thus, the hammer8returns to the rest position9thereof, and can be actuated again by the next movable impactor16,17,18. It further prevents the hammer8from rebounding and striking the resonant element5again in an unwanted manner.

In the case of a hammer8that does not include magnetically conductive material, the flexible guide12brings the hammer back against the magnet15.

As it continues to rotate, the rotary device20pulls on the movable impactor16,17,18such that it detaches from the opposite face30of the magnet15. At the same time, as the hub22rotates, the next movable impactor16,17,18approaches the magnet15.

The rotation device20is actuated by the movement, when a stroke is required. Thus, the stroke sounds automatically thanks to the movable impactors16,17,18, the magnet15, the hammer8and the resonant element5.

During operation, each movable impactor16,17,18impacts the magnet15one after the other, to produce a sound each time. With each impact of a movable impactor16,17,18, the hammer8strikes the resonant element5, and returns to its rest position9against the magnet15between two successive impacts.

Depending on the number of strokes to be emitted, the rotation device is actuated over a predefined period of time.

Preferably, the rotation is carried out at a constant speed so that the strokes are periodically emitted at the same frequency.

The rotational speed can also be variable so as to emit a particular stroke.

It goes without saying that the present invention is not limited to the example shown but that various alternatives and modifications that may be apparent to a person skilled in the art can be made thereto. In particular, the device can comprise a greater or lesser number of arms and impactors than those illustrated in the embodiment described.