Mechanical wristwatch bracelet with which an electronic function is associated

Abstract

Wristwatch comprising a mechanical device for executing a first mechanical function arranged to produce a first acoustic alarm signal, and an electronic device housed in a bracelet and arranged to produce a second acoustic alarm signal and/or a mechanical vibration, wherein the electronic device is arranged to produce the second acoustic alarm signal at the moment when the mechanical device for executing the first mechanical function produces the first acoustic alarm signal.

Claims

1. A wristwatch comprising a watch case in which is housed a mechanical timepiece movement including a mechanical device for executing at least a first mechanical function, wherein the watch case is associated with a bracelet or strap in which is housed an electronic device arranged to execute at least a second electronic function, wherein the execution of the second electronic function is dependent on the execution of the first mechanical function.

2. The wristwatch according to claim 1, wherein the mechanical device for executing the first mechanical function is a mechanical striking device arranged to produce a first acoustic alarm signal, and wherein the electronic device housed in the bracelet is arranged to produce a second acoustic alarm signal and/or a mechanical vibration, wherein the electronic device is arranged to produce the second acoustic alarm signal at the moment when the mechanical striking device produces the first acoustic alarm signal or after a predefined or user-selectable duration following the start of operation of the mechanical striking device.

3. The wristwatch according to claim 2, comprising a transparent case back, wherein the electronic device for executing the second electronic function includes an image sensor arranged in the bracelet so as to be located beneath the transparent case back and capable of detecting the start of motion of a movable element of the mechanical striking device.

4. The wristwatch according to claim 3, wherein the image sensor is arranged to be capable of detecting a change in the levels of grey in an image scanned by the sensor.

5. The wristwatch according to claim 4, wherein the image sensor is of the CMOS type.

6. The wristwatch according to claim 3, wherein the electronic device for executing the second electronic function includes a light source arranged in the bracelet in order to improve the conditions in which the image sensor takes shots.

7. The wristwatch according to claim 3, wherein the image sensor is arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the image sensor detects that the mechanical striking device starts to operate and emits the first acoustic alarm signal.

8. The wristwatch according to claim 7, wherein the image sensor is arranged to send an electrical signal to the electronic control unit that is arranged to stop the electronic sound or vibration generator when the movable element scanned by the image sensor stops and when the first acoustic alarm signal stops.

9. The wristwatch according to claim 3, wherein the image sensor is covered by a collimator lens.

10. The wristwatch according to claim 1 comprising an opaque non-electrically conductive case back, wherein the electronic device for executing the second electronic function includes a capacitive sensor, a magnetic sensor or an inductive sensor arranged in the bracelet so as to be located beneath the opaque non-electrically conductive case back and capable of detecting the start of motion of a movable element of the mechanical device.

11. The wristwatch according to claim 2 comprising an opaque non-electrically conductive case back, wherein the electronic device for executing the second electronic function includes a capacitive sensor, a magnetic sensor or an inductive sensor arranged in the bracelet so as to be located beneath the opaque non-electrically conductive case back and capable of detecting the start of motion of a movable element of the mechanical device.

12. The wristwatch according to claim 10, wherein the capacitive sensor includes an RC oscillator, a demodulator and an output stage that are arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the capacitive sensor detects a capacitance change caused by the start of operation of the mechanical device for executing the first mechanical function and the emission of a first acoustic alarm signal.

13. The wristwatch according to claim 11, wherein the capacitive sensor includes an RC oscillator, a demodulator and an output stage that are arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the capacitive sensor detects a capacitance change caused by the start of operation of the mechanical device for executing the first mechanical function and the emission of a first acoustic alarm signal.

14. The wristwatch according to claim 10, wherein the magnetic sensor is a reed switch with flexible reeds that is arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the flexible reeds attract each other and come into contact with each other as a result of the displacement of a magnet which starts to move when the mechanical device for executing the first mechanical function starts to operate.

15. The wristwatch according to claim 11, wherein the magnetic sensor is a reed switch with flexible reeds that is arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the flexible reeds attract each other and come into contact with each other as a result of the displacement of a magnet which starts to move when the mechanical device for executing the first mechanical function starts to operate.

16. The wristwatch according to claim 10, wherein the magnetic sensor is a giant magnetoresistive sensor that is arranged to send an electrical signal to an electronic control unit which is arranged to actuate an electronic sound or vibration generator as soon as the electrical resistance of the sensor varies as a result of the displacement of a magnet which starts to move when the mechanical device for executing the first mechanical function starts to operate.

17. The wristwatch according to claim 11, wherein the magnetic sensor is a giant magnetoresistive sensor that is arranged to send an electrical signal to an electronic control unit which is arranged to actuate an electronic sound or vibration generator as soon as the electrical resistance of the sensor varies as a result of the displacement of a magnet which starts to move when the mechanical device for executing the first mechanical function starts to operate.

18. The wristwatch according to claim 10, wherein the inductive sensor includes a winding made around a magnetic circuit and is arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator soon as an electrical current is induced in the winding as a result of the displacement of a magnet which starts to move when the mechanical device for executing the first mechanical function starts to operate.

19. The wristwatch according to claim 11, wherein the inductive sensor includes a winding made around a magnetic circuit and is arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator soon as an electrical current is induced in the winding as a result of the displacement of a magnet which starts to move when the mechanical device for executing the first mechanical function starts to operate.

20. The wristwatch according to claim 10, wherein the inductive sensor includes an LC oscillator circuit arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the inductance varies as a result of the displacement of a movable metal element of the mechanical device for executing the first mechanical function.

21. The wristwatch according to claim 11, wherein the inductive sensor includes an LC oscillator circuit arranged to send an electrical signal to an electronic control unit that is arranged to actuate an electronic sound or vibration generator as soon as the inductance varies as a result of the displacement of a movable metal element of the mechanical device for executing the first mechanical function.

22. The wristwatch according to claim 1, wherein the electronic device for executing the second electronic function includes a microphone arranged to detect an acoustic wave produced by the start of operation of the mechanical device for executing the first mechanical function and to send an electrical signal to an electronic control unit which actuates an electronic sound or vibration generator.

23. The wristwatch according to claim 2, wherein the electronic device for executing the second electronic function includes a microphone arranged to detect an acoustic wave produced by the start of operation of the mechanical device for executing the first mechanical function and to send an electrical signal to an electronic control unit which actuates an electronic sound or vibration generator.

24. The wristwatch according to claim 1, wherein the electronic device for executing the second electronic function includes an accelerometer arranged to detect the mechanical vibrations generated by the start of operation of the mechanical device for executing a first mechanical function and to send an electrical signal to an electronic control unit which actuates an electronic sound or vibration generator.

25. The wristwatch according to claim 2, wherein the electronic device for executing the second electronic function includes an accelerometer arranged to detect the mechanical vibrations generated by the start of operation of the mechanical device for executing a first mechanical function and to send an electrical signal to an electronic control unit which actuates an electronic sound or vibration generator.

26. The wristwatch according to claim 1, wherein the mechanical device for executing the first mechanical function includes a mechanical indicator member that provides an indication as to whether the mechanical device for executing the first mechanical function is in a set or non-set state, and wherein the electronic device includes means arranged to scan the indication provided by the mechanical indicator member and means which are arranged to detect the moment at which the first mechanical function will start.

27. The wristwatch according to claim 2, wherein the mechanical device for executing the first mechanical function includes a mechanical indicator member that provides an indication as to whether the mechanical device for executing the first mechanical function is in a set or non-set state, and wherein the electronic device includes means arranged to scan the indication provided by the mechanical indicator member and means which are arranged to detect the moment at which the first mechanical function will start.

28. The wristwatch according to claim 26, wherein the mechanical indicator member includes a disc having a first surface portion that is absorbent and a second surface portion that is reflective, wherein the disc is arranged to move between a first and a second position depending on whether the mechanical device is non-set or set, and wherein the means arranged to scan the indication provided by the mechanical indicator member comprise a light source and a light sensor housed in the bracelet, beneath the disc, wherein the light emitted by the light source is absorbed or reflected depending on whether the light falls on the first absorbent surface portion or on the second reflective surface portion of the disc, wherein the means arranged to detect the moment at which the first mechanical function is going to start, includes an image sensor capable of detecting the start of motion of a movable element of the mechanical device, and starts to scan for the moment when the mechanical device will start to operate when the light sensor senses the light reflected by the second reflective surface portion of the disc.

29. The wristwatch according to claim 26, wherein the means arranged to scan the indication provided by the mechanical indicator member include a light source and a light sensor housed in the bracelet, beneath a disc having a first surface portion that reflects light in the direction in which the light sensor cannot sense light and a second surface portion that reflects light in the direction of the light sensor), wherein the disc is arranged to move between a first and a second position depending on whether the mechanical device is non-set or set, wherein the light emitted by the light source is thus deviated or reflected depending on whether the light falls on the first surface portion or on the second surface portion of the disc, wherein the means arranged to detect the moment at which the first mechanical function will start include an image sensor capable of detecting the start of motion of a movable element of the mechanical device and starts to scan for the moment when the mechanical device will start to operate when the light sensor senses the light reflected by the disc.

30. The wristwatch according to claim 26, wherein the electronic device comprises an image sensor having, respectively, a first surface portion that is used to scan the indication provided by the mechanical indicator member, and a second surface portion used to detect the start of operation of the mechanical device.

31. A method for generating an acoustic alarm signal in a wristwatch that includes a watch case in which is housed a mechanical timepiece movement that includes a mechanical striking device arranged to produce a first acoustic alarm signal, wherein the watch case is associated with a bracelet in which is housed an electronic device for producing a second acoustic alarm signal and/or a mechanical vibration, wherein the method has the step of producing the second acoustic alarm signal at the moment when the first acoustic alarm signal is produced or after a predefined or user-selectable duration following the start of operation of the mechanical device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will appear more clearly from the following detailed description of an embodiment example of a mechanical wristwatch according to the invention with which an electronic function is associated, this example being given solely by way of non-limiting illustration with reference to the annexed drawing, in which:

(2) FIG. 1 is a bottom view of an embodiment example of a wristwatch according to the invention comprising a watch case equipped with a bracelet having an electronic function.

(3) FIG. 2 is a perspective bottom view of the wristwatch of FIG. 1.

(4) FIG. 3 is a perspective view of an embodiment example of the mechanical striking device.

(5) FIG. 4a is a perspective view of the bracelet in which is housed the electronic device arranged to execute the second electronic function.

(6) FIG. 4b is a larger scale view of the electronic device surrounded by a circle in FIG. 4a.

(7) FIGS. 5, 6 and 7 schematically illustrate the assembly formed by the mechanical device arranged to produce the first acoustic alarm signal and the electronic device arranged to produce the second acoustic alarm signal according to whether the mechanical striking device is at rest, in operation, and then stopped again.

(8) FIGS. 8 and 9 are cross-sectional views respectively along the lines VIII-VIII and IX-IX of FIGS. 5 and 6.

(9) FIG. 10 is a partial schematic view of the watch case according to the invention in the case where the back cover of the watch is opaque and non-electrically conductive and where the electronic device arranged to execute the second electronic function comprises a capacitive sensor.

(10) FIG. 11 is a partial schematic view of the wristwatch in the case where the back cover of the watch is opaque and non-electrically conductive and where the electronic device arranged to execute the second electronic function comprises a magnetic sensor.

(11) FIG. 12 is a partial schematic view of the wristwatch in the case where the back cover of the watch is opaque and non-electrically conductive and where the electronic device arranged to execute the second electronic function comprises an inductive sensor.

(12) FIG. 13 is a partial schematic view of the wristwatch in the case where the watch case comprises an opaque electrically conductive back cover and wherein the electronic device for detecting the indication provided by the mechanical striking device comprises a simplified device comprising a microphone, which detects the acoustic wave produced by the start of operation of the mechanical striking device and sends an electrical signal to the electronic control unit that controls the start of operation of the electronic sound generator.

(13) FIG. 14a is a partial schematic view of the wristwatch in the case where the mechanical striking device comprises a mechanical indicator member which indicates the non-set state of the mechanical striking device and wherein the electronic device comprises a light source and a light detector.

(14) FIG. 14b is a similar view to that of FIG. 14a in the case where the mechanical indicator member indicates the set state of the mechanical striking device and where the light emitted by the light source is reflected by the reflective surface portion of the mechanical indicator member towards the light detector.

(15) FIG. 15a is a partial schematic diagram of the wristwatch in the case where the mechanical striking device comprises a mechanical indicator member that indicates the non-set state of the mechanical striking device and wherein the electronic device comprises an image sensor having a first surface portion which is used to scan the indication provided by the mechanical indicator member, and a second surface portion used to scan the start of operation of the mechanical striking device.

(16) FIG. 15b is a similar view to that of FIG. 15a in the case where the mechanical indicator member moves aside, out of the field of vision of the image sensor when the mechanical striking device is set by the user.

(17) FIG. 16a is a partial schematic view of the wristwatch of the invention in the case where the mechanical striking device comprises a mechanical indicator member which conceals the mechanical striking device when the latter is not set.

(18) FIG. 16b is a similar view to that of FIG. 16a in the case where the mechanical indicator member has moved aside.

DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

(19) The present invention proceeds from the general inventive idea that consists in associating a mechanical wristwatch, devised to execute a first mechanical function in addition to the current time display, with a bracelet, in the thickness of which is housed an electronic device devised to execute a second electronic function, the execution of the second electronic function being dependent on by the execution of the first mechanical function. In a preferred but non-limiting embodiment of the present invention, the mechanical wristwatch is arranged to emit a first acoustic alarm at a predetermined moment programmed by the user, and the electronic device housed in the bracelet is arranged to emit a second acoustic alarm and/or a mechanical vibration at the moment when the watch emits the first acoustic alarm. It is therefore possible to increase the acoustic power of the alarm signal produced by the wristwatch according to the invention without requiring any modification to be made to the mechanical movement housed in the watch. It is also possible to increase the duration of the alarm signal and to emit sounds other than those produced by the mechanical movement, in harmony with such sounds.

(20) Designated as a whole by the general reference numeral 1, the wristwatch according to the invention comprises (see FIGS. 1 and 2) a watch case 2 devised to be worn on a user's wrist by means of a bracelet 4. In the preferred but non-limiting embodiment of the invention, the base of watch case 2 is closed by a back cover 6 and the top is closed by a crystal 8 which covers a dial 10 above which move the hour hand 12, minute hand 14 and seconds hand 16 for the current time display. In the example represented in FIG. 1, dial 10 is illustrated transparently. It is evident, however, that for the purposes of the present invention, dial 10 is not required to be transparent and will preferably be opaque.

(21) A mechanical timepiece movement 18, devised to drive the current time display hands 12, 14, 16, is housed in watch case 2. This mechanical timepiece movement 18 further includes a mechanical device 20 arranged to produce at least a first mechanical function, for example to emit a first acoustic alarm signal.

(22) Purely by way of example (see FIG. 3), mechanical striking device 20 comprises a winding stem 22 which via first, second and third intermediate wheels 24a, 24b and 24c, rotates a release wheel 26. The tube of release wheel 26 carries or is kinematically connected to an index 28 seen in FIG. 1, which can be placed facing the desired alarm time. The plate of release wheel 26 is pierced with three openings 30 placed on three different radii (see FIG. 9). An hour wheel 32 pivots above release wheel 26 and is pressed against release wheel 26 by a release lever 34 wound by a spring 36. The plate of hour wheel 32 has three catches 38, each provided with an inclined plane 40. Hour wheel 32, driven by the movement, rotates and, at the set alarm time, the three catches 38 are positioned facing openings 30 and fall therein, such that hour wheel 32 is pressed against release wheel 26. As a result of this movement, release lever 34 tilts upwards and releases a strike pallets 42 which, driven by a strike wheel 44, starts to oscillate in a horizontal plane about its pivot point 46 (see FIG. 9). Strike wheel 44, which is directly driven by a strike barrel (not shown), acts like an escape wheel that drives strike pallets 42. Strike pallets 42 carries a hammer 48 which strikes a pin fixed at the back of the case to sound the alarm. The end of a rocking lever 50 for winding the striking mechanism is in contact with a slide lever 52 which acts on a strike lock 54. Strike lock 54 immobilises strike pallets 42 when winding stem 22 is in the time-setting position.

(23) As shown in FIGS. 4a and 4b, an electronic device 56 housed in bracelet 4 is arranged to execute at least a second electronic function, for example to emit a second acoustic alarm signal and/or to produce a mechanical vibration, the execution of the second electronic function being dependent on the execution of the first mechanical function. In other words, electronic device 56 will emit the second acoustic alarm signal and/or produce a mechanical vibration at the moment when mechanical striking device 20 produces the first acoustic alarm signal. Mechanical striking device 20 housed in watch case 2 is thus the master of electronic device 56 which acts as the slave. It will be noted that the master function is not dependent on slave function and can operate normally even if the slave function is not in operation. It will also be noted that, according to a variant, it is possible to envisage offsetting, by a fixed duration, for example 5 or 10 seconds, or a duration selected by the user, the moment when electronic device 56 will start and produce the second acoustic signal.

(24) Electronic device 56 housed in bracelet 4 of wristwatch 1 comprises an image sensor 58 which scans, at close regular intervals, for the moment when mechanical striking device 20 starts to operate. Mechanical striking device 20 is initially at rest (FIGS. 5 and 8). At the moment when mechanical striking device 20 starts to operate (FIGS. 6 and 9), hour wheel 32 presses against release wheel 26 and release lever 34, pressed against hour wheel 32 by spring 36, pivots upwards, releasing strike pallets 42, which starts to oscillate in the horizontal plane about its pivot point 46. Hammer 48, carried by strike pallets 42, follows the motion of the latter and strikes for example a pin. Image sensor 58 detects the start of motion of a movable element of the mechanical striking device, such as strike pallets 42, and sends an electrical signal to a control unit 60 which will actuate an electronic sound generator 62 of the electromechanical or piezoelectric type. Advantageously, image sensor 58 is covered by a collimator lens 64, and a light source 66, such as a light emitting diode, illuminates the inside of watch case 2 through transparent case back 6. All these electronic components are mounted on a printed circuit sheet 68 housed in the thickness of bracelet 4 and are powered by an electrical current source 70. Naturally, openings 72 and 74 are provided above image sensor 58 and light source 66 in the material forming bracelet 4, so as to allow image sensor 58 to scan mechanical striking device 20, and to allow light source 66 to illuminate the scene.

(25) Image sensor 58 is, for example, an image sensor marketed by ST Microelectronics under the reference VD5376. It has a thickness comprised between 180 m and 725 m, sides respectively measuring 1900 m and 1932 m and an active surface of 608608 m.sup.2 formed of a 2020 pixel matrix. Such an image sensor 58 is capable of detecting a change in the levels of grey in an image that it scans and thus of detecting, for example, the displacement of an object such as strike pallets 42. It will be understood that image sensor 58 can detect the start of motion of another movable element, such as strike wheel 44, or hammer 48. Another change is observed by image sensor 58 when the first acoustic alarm signal stops and the movable element scanned by image sensor 58 stops (FIG. 7). The image that image sensor 58 sees in fact becomes immobile again. Image sensor 58 then sends an electrical signal to control unit 60 which will stop electronic sound generator 62.

(26) According to a simplified variant of the invention, it may be envisaged to set the duration of the second alarm in advance. Once started after the activation of the first alarm, the second alarm will stop independently once this time has elapsed

(27) It is noted that a comparison of FIGS. 5 and 6 reveals that, in FIG. 6, hour wheel 32 is pressed against release wheel 26 and that in FIG. 7, hour wheel 32 has moved away from release wheel 26 again.

(28) In the case where watch case 2 comprises an opaque, non-electrically conductive back 6, electronic device 56 for detecting the indication provided by mechanical striking device 20 comprises a capacitive, magnetic or inductive sensor.

(29) In the case of a capacitive sensor 76 (FIG. 10), this typically comprises an RC oscillator 78, a demodulator 80 and an output stage 82. The operation of such a capacitive sensor 76 occurs without any physical contact with mechanical striking device 20 and relies on an electric field change in its active area. Capacitive sensor 76, disposed under the watch case back, detects a certain capacitance value which remains fixed as long as mechanical striking device 20 is at rest. At the moment when mechanical striking device 20 starts to operate and emits the first acoustic alarm signal, capacitive sensor 76 detects a capacitance change caused by the start of operation of the mechanical striking device 20, which causes a change in the oscillation frequency of RC circuit 78. Following detection of this frequency variation, an electrical output signal is generated and sent to electronic control unit 60 which actuates the electronic sound generator. By way of example, the capacitive sensor may be the sensor marketed by the Swiss company EM-Microelectronic under the reference EM6420. This is a very low-power capacitive sensor able to operate with both transparent case backs (sapphire, Plexiglass, glass) and opaque non-metal case backs (plastic, ceramic). The EM6420 circuit must be connected to an electrode which will be placed inside the bracelet facing the metal part that will be set in motion when the alarm is activated.

(30) Likewise, (FIG. 11), the magnetic sensor, such as a GMR sensor marketed by NVE or a reed switch 84 with flexible reeds 86, detects a change in the magnetic field caused by the start of operation of mechanical striking mechanism 20. To this end, at least one of the components of mechanical striking device 20, for example strike pallets 42, which starts to move when mechanical striking device 20 starts to operate, is provided with a magnet 88. Thus, when the component moves, magnet 88 is moved concomitantly which magnetizes the flexible contacts 86 which attract each other and come into contact with each other. Reed switch 84 is then closed and can send an electrical output signal to electronic control unit 60 which actuates electronic sound generator 62.

(31) Finally, (FIG. 12), inductive sensor 90 conventionally comprises a winding 92 made around a magnetic circuit 94 whose role is to channel the magnetic field. At least one component of mechanical striking device 20, for example strike pallets 42, which starts to move when mechanical striking device 20 starts to operate, is provided with a magnet 88. Thus, when mechanical striking device 20 starts to operate, magnet 88 moves and induces an electrical current in winding 92 of inductive sensor 90. Inductive sensor 90 sends an electrical output signal to electronic control unit 60 which actuates electronic sound generator 62.

(32) By way of variant, the inductive sensor may comprise an LC oscillator circuit whose inductance will vary under the effect of the displacement of a metal component of the mechanical device.

(33) Whether the back 6 of watch case 2 is transparent or opaque, conductive or non-conductive of electricity (FIG. 13), electronic device 56 for detecting the indication provided by mechanical striking device 20 may comprise a simplified device comprising a microphone 96, which simply detects the acoustic wave produced by the start of operation of mechanical striking device 20 and sends an electrical signal to electronic control unit 60 which actuates electronic sound generator 62.

(34) Likewise, regardless of the properties of back 6 of watch case 2, it may be envisaged to use as a sensor an accelerometer which will measure the activity of the mechanical striking device and detect the vibrations generated by hammer 48 at the moment when the mechanical striking device starts to operate. One accelerometer that is well suited to the requirements of the present invention is marketed under the reference ADXL362. This is a very low power circuit which constitutes an advantageous alternative to the microphone, particularly from the point of view of sealing and incorporation costs.

(35) As seen in detail hereinbefore, electronic device 56 housed in bracelet 4 is arranged to execute at least a second electronic function, for example to emit a second acoustic alarm signal and/or to produce a mechanical vibration, the execution of the second electronic function being determined by the execution of the first mechanical function. In other words, electronic device 56 will emit the second acoustic alarm signal and/or produce a mechanical vibration at the moment when mechanical striking device 20 produces the first acoustic alarm signal. Mechanical timepiece mechanism 18 housed in watch case 2 is thus the master of electronic device 56 which acts as the slave.

(36) According to a complementary feature of the invention, mechanical device 20 for executing the first mechanical function, housed in watch case 2, further comprises a mechanical indicator member 98 which provides an indication as to whether mechanical device 20 for executing the first mechanical function is in a set or non-set state. Thus, if mechanical device 20 is set by the user to produce an acoustic alarm signal at a predetermined time selected by the user, mechanical indicator member 98 will indicate that mechanical device 20 is set.

(37) According to a first embodiment illustrated in FIG. 14a, mechanical indicator member 98 comprises a disc 100 having a first surface portion 100a which is absorbent and a second surface portion 100b which is reflective. This disc 100 is arranged to move between a first and a second position depending on whether mechanical device 20 is set or non-set. Electronic device 56 comprises a light source 102 such as a light emitting diode, and a light sensor 104 such as a photodiode, housed in bracelet 4 beneath disc 100. The light emitted by light source 102 will thus be absorbed or reflected depending on whether it falls on absorbent surface portion 100a or reflective surface portion 100b of disc 100. Finally, an image sensor 106, which may be of the same type as that described hereinbefore or simpler, scans for the moment when mechanical striking device 20 starts to operate.

(38) The operation of this device is as follows. Light source 102 will, at regular intervals, send a light beam across disc 100. If, due to the absence of signal provided by light sensor 104, electronic device 56 observes that the light emitted by light source 102 falls on absorbent surface portion 100a of disc 100 and is therefore absorbed, it concludes that mechanical striking device 20 is not set. Consequently, it is not necessary for image sensor 106 to scan for the moment when mechanical striking mechanism 20 starts to operate, which saves energy. Indeed, light source 102 illuminates disc 100 less often than image sensor 106 scans for the moment when striking device 20 starts to operate. When the user sets mechanical striking device 20, for example by pressing a push-button, disc 100 will move such that the light emitted by light source 102 falls on the reflective surface portion 100b of disc 100. Thus, due to the signal provided by light sensor 104, electronic device 56 will note that the light emitted by light source 102 falls on the reflective surface portion 100b of disc 100 and is therefore reflected, and concludes that mechanical striking device 20 is set. At that moment, electronic device 56 cuts the electrical power to light source 102 and actuates image sensor 106. Image sensor 106 will then scan, at close regular intervals, for the moment when mechanical striking mechanism starts to operate. When mechanical striking device 20 starts to operate, the operation of mechanical striking device 20 and of electronic device 56 is the same as that described hereinbefore with reference to the first embodiment of the invention.

(39) According to a second embodiment which is not shown, instead of having a reflective surface portion and an absorbent surface portion, disc 100 could be provided with a surface portion that reflects light towards light sensor 104 and a surface portion that reflects light in a direction in which light sensor 104 cannot sense light.

(40) According to a third embodiment (see FIG. 15a), the mechanical striking device comprises a mechanical indicator member 98, of the type of a disc 108 that indicates the non-set state of the mechanical striking device, and electronic device 56 comprises an image sensor 110 of the type described hereinbefore having a first surface portion 110a, which is used to scan the indication provided by mechanical indicator member 98, and a second surface portion 110b used to scan for the start of operation of mechanical striking device 20. It can, for example, be envisaged that disc 108 is visible to the first surface portion 110a of image sensor 110 when mechanical striking device 20 is in the non-set state, and then that disc 108 moves aside out of the field of vision of image sensor 110 when mechanical striking device 20 is set by the user (FIG. 15b). At that moment, electronic device 56 observes a change in the signal produced by image sensor 110 and will instruct image sensor 110 to scan mechanical striking device 20 by means of surface portion 110b.

(41) Finally, according to a last embodiment (FIG. 16a), the mechanical striking device includes a mechanical indicator member 112 which conceals mechanical striking device 20 from the view of image sensor 58 when said device is not set. When the user sets mechanical striking device 20 (FIG. 16b), mechanical indicator member 112 moves aside and control unit 60 detects a change in the signal provided by image sensor 58. In response to this change, control unit 60 instructs image sensor 58 to scan mechanical striking device 20 to detect the start of operation thereof.

(42) It goes without saying that the present invention is not limited to the embodiments that have just been described and that various simple modifications and variants can be envisaged by those skilled in the art without departing from the scope of the invention as defined by the annexed claims. It will be noted, in particular, that it is possible to envisage offsetting in time, by a fixed duration or user-selectable duration, the activation of the second acoustic alarm signal. In other words, the production of the second acoustic signal generated by the electronic device will be offset in time with respect to the emission of the first acoustic signal produced by the mechanical device. It will also be understood that the electronic device emits a second acoustic alarm signal or, equally, a mechanical vibration through the use of a vibrating mechanism housed in the thickness of the bracelet. At the moment when the mechanical device starts to produce the first acoustic alarm signal, the electronic device will activate the vibrating mechanism which will generate vibrations that the user will feel on his wrist. The vibrating mechanism is typically an eccentric mechanism which activates an inertia block. Likewise, it will be noted that, in a simplified variant of the invention, it may be envisaged to set the duration of the second alarm in advance. Once started after the activation of the first alarm, the second alarm will stop independently once this time has elapsed. In other words, the second alarm will be activated at the moment when the first alarm starts to operate and will stop at the end of a predefined time, independent of the duration of activation of the first alarm. It will also be noted that, in the case where the sensor is a microphone or an accelerometer, it is not essential for such a sensor to be disposed beneath the watch case back. Consequently, it is possible to envisage a bracelet formed of two separate strands, each fixed via one end thereof to the watch case, and in which are incorporated the components necessary for implementation of the invention. Finally, it will be noted that the present invention also covers a method for generating an acoustic alarm signal in a wristwatch comprising a watch case 2 in which is housed a mechanical timepiece movement 18 comprising a mechanical striking device 20 arranged to produce a first acoustic alarm signal, watch case 2 being associated with a bracelet 4 in which is housed an electronic device 56 for producing a second acoustic alarm signal and/or a mechanical vibration, electronic device 56 being arranged to produce the second acoustic alarm signal at the moment when mechanical device 20 for executing the first mechanical function produces the first acoustic alarm signal or after a predefined duration or user-selectable duration following the start of operation of mechanical device 20.

LIST OF PARTS

(43) Wristwatch 1 Watch case 2 Bracelet 4 Case back 6 Crystal 8 Dial 10 Hour hand 12, minute hand 14 and seconds hand 16 Mechanical timepiece movement 18 Mechanical striking device 20 Winding stem 22 First, second and third intermediate wheels 24a, 24b and 24c Release wheel 26 Index 28 Three openings 30 Hour wheel 32 Release lever 34 Spring 36 Three catches 38 Inclined plane 40 Strike pallets 42 Strike wheel 44 Pivot point 46 Hammer 48 Rocking lever 50 Slide lever 52 Strike lock 54 Electronic device 56 Image sensor 58 Control unit 60 Electronic sound generator 62 Collimator lens 64 Light source 66 Printed circuit sheet 68 Electrical current source 70 Openings 72, 74 Capacitive sensor 76 RC oscillator 78 Demodulator 80 Output stage 82 Reed switch 84 Flexible reeds 86 Magnet 88 Inductive sensor 90 Winding 92 Magnetic circuit 94 Microphone 96 Mechanical indicator member 98 Disc 100 First absorbent surface portion 100a Second reflective surface portion 100b Light source 102 Light sensor 104 Image sensor 106 Disc 108 Image sensor 110 First surface portion 110a Second surface portion 110b Mechanical indicator member 112