US3693343A

US3693343A - Wrist watch with a piezoelectric crystal as time-keeping oscillator

Info

Publication number: US3693343A
Application number: US876880A
Authority: US
Inventors: Friedrich Assmus; Wolfgang Ganter; Hans Flaig
Original assignee: Gebrueder Junghans GmbH
Current assignee: Gebrueder Junghans GmbH
Priority date: 1968-11-15
Filing date: 1969-11-14
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: CH1618369A4; AT300670B; FR2023409B1; CH541177A; DE1809223C3; DE1809223A1; DE1809223B2; FR2023409A1

Abstract

A wrist watch using a piezoelectric crystal as the time-keeping oscillator. The time-keeping oscillator has its output fed to a number of frequency divider stages so as to reduce the ultimate frequency to some low value, e.g., below 5 cps. By reducing the frequency to this low value, the moving device can directly engage the second-wheel thereby minimizing the size and friction losses in the wheel mechanism. Two exemplary moving devices are disclosed, one of which utilizes a rotating coil assembly which has a shift finger to engage the toothing on the second-wheel. The other disclosed example utilizes a driving fork fastened to the shaft of an oscillating magnetic system with the arms of the driving force engaging the toothing on the second wheel. The basic frequency divider also includes a number of various electronic circuits for reducing the width of the driving pulses so as to minimize power losses and maximize the effective battery life.

Description

United States Patent Assmus et al.

[451 Sept. 26, 1972 [72] Inventors: Friedrich Assmus; Wolfgang Gunter; l-Ians Flaig, all of Schramberg-Sulgen, Germany [73] Assignee: Gebruder Junghans GmbH,Schramberg, Germany [22] Filed: Nov. 14, 1969 [21] Appl. No.: 876,880

[30] Foreign Application Priority Data Nov. 15, 1968 Germany ..P 18 09223.4

[52] US. Cl. ..58/23 TF, 318/129 [51 Int. Cl. ..G04c 3/02 [58] Field of Search ..58/23 AC, 23, 23 A, 23 TF, 58/23 V, 28, 28 A, 28 B; 310/95; 3l8/l29 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Edith C. Simmons Jackmon AnomeyBurns, Doane, Benedict, Swecker & Mathis [5 7 ABSTRACT A wrist watch using a piezoelectric crystal as the timekeeping oscillator. The time-keeping oscillator has its output fed to a number of frequency divider stages so as to reduce the ultimate frequency to some low value, e.g., below 5 cps. By reducing the frequency to this low value, the moving device can directly engage the second-wheel thereby minimizing the size and friction losses in the wheel mechanism. Two exemplary moving devices are disclosed, one of which utilizes a rotating coil assembly which has a shift finger to engage the toothing on the second-wheel. The other disclosed example utilizes a driving fork fastened to the shaft of an oscillating magnetic system with the arms of the driving force engaging the toothing on the second wheel. The basic frequency divider also includes a number of various electronic circuits for reducing the width of the driving pulses so as to minimize power losses and maximize the effective battery life.

22 Claims, 14 Drawing Figures PATENTEBsErzs Ian SHEET 1 [IF 5 wnlfganlg Gamer BY Hans Fang INVENTORS Friedrich Assmus Afforne r PATENTEUserzs m2 3,693,343

sum 5 or 5 IN V EN TORS Friedrich Assmm Wolf an (unlrr Hans Fh lig WRIST WATCH WITH A PIEZOELECTRIC CRYSTAL AS TIME-KEEPING OSCILLATOR The invention relates to a wrist watch with a piezoelectric crystal as time-keeping oscillator; an oscillator circuit for the excitation of the oscillations in the piezoelectric crystal; several electronic frequency divider stages; and a hand-moving device to which the output pulses of the frequency dividers are fed.

A quartz wrist watch is known (Retail Jeweller" of Feb. 28, 1968) in which a quartz crystal is employed for stabilizing a high-frequency oscillator. The frequency of the output pulses of this oscillator is reduced by means of several electronic frequency divider stages to such an extent that the pulses can be utilized to feed a motor which drives the hand mechanism. The electronic circuits are constructed as integrated circuits.

In such watches numerous problems occur with relation to the maintenance of high time-keeping accuracy over a longer period and under varying environmental conditions. Thus it is difficult to construct the electronic circuit, including the hand-moving mechanism, in such a way that sufficiently low energy consumption is achieved so as to burden the battery lodged in the small available space only to such an extent that the watch runs for a sufficiently long period of time. Besides, the operation of the hand-moving mechanism meets with difficulties as a result of the desired low energy consumption. That is, the operation becomes increasingly difficult and subject to losses with an increase in the drive pulse frequency, i.e., a decrease in the number of divider stages. On the other hand, energy consumption increases with the number of divider stages. The moving mechanism also poses a problem with respect to the bearings. When a motor of relatively high rotational speed is employed, lubricated bearings are required. Furthermore, the energy necessary for the motor drive should be small. If then, in due course of time, the oil thickens, the friction may increase to such an extent that the motive power no longer suffices to assure the synchronous movement of the motor.

The invention aims at providing a piezoelectric wrist watch of very high accuracy which, with a battery customary in trade, runs at least for a year. Furthermore, variations in position or temperature, shocks and the like, resulting from the various customs of the watch-wearers, should not substantially impair the movement accuracy. With all this and urider any prevailing conditions, a faultless drive should be assured. According to the invention this is accomplished by a combination of the following characteristics;

a. Use of a piezoelectrically excited tuning fork;

b. Frequency division down to a frequency of below 5 cps;

0. Use of an electric circuit arrangement for narrowing the output pulses of the frequency divider circuit;

d. Use of an electromagnetic step-by-step switch arrangement, to which the output pulses are fed, as the moving device;

e. The moving device engages the second-hand.

A piezoelectric crystal in the shape of a tuning fork and of specific dimensions has a relatively low natural frequency, so that an oscillator of relatively low frequency can be used and the number of the subsequent frequency divider stages can be kept small. The frequency division down to below 5 cps. requires, to be sure, a large number of frequency divider stages.

This fact however, permits the employment of a moving device which for instance engages the second-wheel directly, so that the wheel mechanism can be so constructed that it occupies little space and its friction losses are relatively small.

By the use of frequency divider stages in the form of flip-flop circuits, pulses are produced at the output of the divider circuit whose width equals that of the pulse interval. Since for the drive of the moving device only relatively brief pulses are necessary, energy consumption is diminished by the narrowing of the pulses. Utilization of an electromagnetic step-by-step switch mechanism as the moving device results in a very reliable movement at low frequency. In this process, effects from a possible thickening of the lubricant are avoided, due to the low speed of rotation. It is also possible to use entirely oil-free bearings.

An electromagnetic step-by-step switch arrangement, preferably a moving-coil arrangement is provided which consists for instance of a centrally located stationary permanent magnet core and a self-supporting coil rotatable about the core, which coil bears a shift finger engaging the second-wheel. In this structure the moment of inertia of the rotatable part can be kept small, e.g., by using a moving coil of aluminum wire, whereby energy consumption is kept small and a rapid movement is assured.

The crystal tuning fork and the moving coil arrangement should be positioned so that they are parallel to each other and their longitudinal axes are perpendicular to the hand shaft. The plane of oscillation of the tuning fork should be perpendicular to the dial, whereby the effect of strong shocks is reduced.

Furthermore, as the electromagnetic step-by-step switch mechanism a rotary magnet arrangement may be provided which may consist of a four-pole magnet arrangement with radially outward pointing magnet poles, a stationary magnetic return which encloses the magnet arrangement while leaving the airgap, and a coil arrangement positioned in the airgap and acting upon the magnetic poles. The rotary magnet device supports preferably a driving fork engaging the secondwheel. As the switching arrangement for narrowing the output pulses of the frequency divider circuit a flip-flop circuit may be provided which is switched on by the last frequency divider stage and switched off by a preceding frequency divider stage. However, it is also feasible to provide as switching arrangement for narrowing the output pulses of the frequency divider circuit a NAND gate to which the pulses are fed from the last frequency divider stage and from several preceding frequency divider stages. A reversing stage may be connected on the output side of the NAND gate.

The invention is subsequently explained in greater detail with the aid of the drawing by means of several embodiments. The drawing shows in FIG. 1, a rear view of a preferred embodiment of the invention with a moving-coil moving device partially in section along line I---[ of FIG. 2;

in FIG. 2, an individual representation of the embodiment of FIG. I, in section, along line II-Il in FIG. I, on an enlarged scale;

in FIG. 3, an individual representation of the switch finger cooperating with the second-wheel, in perspective view and on an enlarged scale;

in FIG. 4, a modified embodiment with a rotary magnet moving device partially in section along line IV-IV of FIG. 5;

in FIG. 5, a partial illustration of the rotary magnet of FIG. 1 in a section along line V--V of FIG. 4',

in FIG. 6a a block diagram of an electronic circuit arrangement for narrowing the output pulses of the frequency divider circuit with employment of a flipflop circuit;

in FIG. 7, a graphic representation of the pulses produced by the circuit of FIG. 6, namely a. control pulses ofa frequency of 8 cpss,

d. control pulses of a frequency of l cps and e. the output pulses of the flip-flop circuit;

in FIG. 8, a diagram of another circuit arrangement for narrowing the output pulses of the frequency divider circuit, with utilization of a NAND gate and of dividers;

in FIG. 9 and 10, further electronic circuit arrangements for narrowing the output pulses of the frequency divider circuit, with employment of NAND gates with transistors;

in FIG. 11, a circuit similar to that of FIG. 8 in which however, only three inputs are provided,

in FIG. 12, a circuit arrangement as in FIG. 11, however, in connection with a circuit for the self-starting of the moving device;

in FIG. 13, a modified switch arrangement for narrowing the output pulses of the frequency divider circuit, with employment of a TTL NAND-gate, and

in FIG. 14, a graphic representation of the pulses produced, e.g., by means for the circuit of FIG. 11.

In FIG. 1, numeral 10 indicates the plate for the mechanism ofa wrist watch. 11 is the wheel mechanism bridge in which, among other things, the second-wheel 12 is supported. 13 indicates a support plate, fastened to the case, for a piezoelectric tuning fork, preferably a quartz tuning fork 14 which is fastened to support plate 13.

Tuning fork 14 is excited into oscillation in any known manner by an electric oscillator circuit. The pulses produced by the oscillator circuit are further fed to a frequency divider circuit which reduces the pulse frequency. A series connection of different flip-flop circuits is preferably used as frequency divider circuit. A frequency of, e.g., 8,l92 cps., reduced by 13 divider stages to a frequency of preferably 1 cps. may be used as pulse frequency for moving tuning fork 14. The output pulses of the frequency divider circuit are suitably fed to a circuit for narrowing the output pulses. All electronic circuits are preferably constructed in the form of integrated circuits. In the watch shown in FIG. 1 they are contained in bridge 15. Numeral 16 indicates a space for lodging the battery which feeds the electronic circuit.

A moving coil arrangement, generally marked 17 is provided as the moving device. This moving coil arrangement contains a cylindrical permanent magnet polarized in the direction of the diameter, as shown in FIG. 2. The magnetization is chosen in such a way that the moving coil is positioned in the strongest magnetic field so as to reach highest effectiveness. Core 30 is fastened by means of

supports

26 and 27 to plate 10. A self-supporting coil 28 is arranged so as to enclose magnet core 30 and is mounted rotatably in bearings 19 and 18 by means to axle journals 20 and 2I. Return springs 22 and 23 are mounted on

axle journals

20 and 21. These return springs serve also for feeding the current to coil 28 as well as or holding the coil or the shift finger 29 in abutment against a setscrew 34 by means of which the position of rest of coil 28 can be adjusted. Suitable supply lines are welded on at 24 and 25. Furthermore, return

metal sheets

31 and 32 are provided which surround coil 28 and keep the straying of the magnet system small.

Coil 28 may consist, e.g., of aluminum wire so that its moment of inertia is as small as possible. The winding suitably takes place in such a manner that oblong holes 33 are formed in the inactive coil sides which are located outside the magnetic field.

Axle journals

20 and 21 are inserted in these oblong holes 33 and can be fastened by glueing or also by coating of the entire coil with a synthetic resin layer. This makes it possible to displace the axle journals laterally and thus to effect a center of gravity compensation, particularly with respect to unilaterally mounted shift finger 29. The end of a spiral spring 23 can be connected with the watch mechanism, whereas the end of the other spiral spring is connected to the circuit contained in bridge 15. At least one of the bearings (in this case 19) must be insulated. In this embodiment axle journal 20 runs on jewels of bearing 19.

A shift finger, generally marked 29, fastened to selfsupporting coil 28, engages the toothing of secondwheel 12 and effects the movement. This shift finger 29 is preferably fastened to coil 28 by glueing. It consists suitably of two parts 29a and 29b which may be glued to each other. Each part 290 and 29b is provided with a driving

surface

29c and 29d which, when finger 29 moves, effect at each instance an advance of the second-wheel by half a tooth pitch. Second-wheel 12 is provided with a further toothing (locking tooth system) 36 whose pitch is half of that of toothing 35. A retaining spring 37 engages locking tooth system 36 by means of a jewel 38 fastened to its free end. Retaining spring 37 is adjustable in its length by means of a rotatable post 39 and its prestressing by means of a rotatable eccentric 40.

Movable coil arrangement 17 is elongated and of relatively small diameter. As a result of this and of the use of a self-supporting coil of aluminum wire the moments of inertia are very small so that the drive power can be kept small. The moving coil arrangement, l.e., self-supporting coil 28 performs only relatively short back and forth movements so that employment of oilfree bearings becomes possible.

The moving coil is kept, when no current passes through it, by means of

helical springs

22, 23 and shift finger 29 in such a position as to rest against setscrew 34. When a current pulse passes through the coil it is moved, in the embodiment of FIG. 2, in counterclockwise direction. In this process driving surface 29c moves second-hand 12 by half a tooth pitch of moving toothing 35. After termination of the current pulse, coil 28 is returned by

helical springs

22 and 23 to its position of rest in which shaft finger 29 abuts against setscrew 34. In this process driving surface 29d again advances second-wheel 12 by half a tooth pitch of toothing 35. The switching process takes place, e.g., with a frequency of l cps., whereas the switching itself takes only a fraction of a second.

Shift finger 29 and also second-wheel 12 may consist of plastic, beryllium or chromium-plated aluminum or aluminum provided with a hard eloxal coating. It is essential that the material has a sufficient abrasive resistance and is also relatively light. When plastic is used it is of course not necessary that shift finger 29 consist of two parts.

In the embodiment of FIG. 4 and 5, numeral 50 indicates the clock-mechanism supporting plate. 51 is the watch mechanism bridge with second-wheel 52 whose toothing is marked 52a. 55 is the bridge which contains the electronic circuits and 56 the space for lodging the electric battery. 53 is the support plate for quartz tuning fork 54 mounted in support plate 53.

In the embodiment of FIG. 4, the electronic circuit may be the same as in the embodiment of FIG. 1. In the embodiment of FIG. 4, however, rotary magnet system 57 is provided as moving device. This magnet system consists of a stationary magnetic return 58 and a rotatable permanent magnet arrangement 63-66 which is rotatable on a shaft 61. The permanent magnet arrangement contains four permanent magnet poles 63-66. In the airgaps between magnet poles 63 to 66 and the magnetic return 58, two

coils

59 and 60 are arranged to which the output pulses of the electronic divider circuit and the subsequent circuit for the narrowing of the drive pulses are fed. In this case a movable supply to the coils is not required.

A driving fork 68 is fastened to shaft 61 of the magnet system. The arms 68a and 68b of this driving fork support pins 69a and 69b which engage toothing 52a of second-hand 52 and effect the movement thereof.

The return elements 58 consist of ferromagnetic material whereas the support element 62 need not be ferromagnetic and consists therefore suitably of as light a material as possible, e.g., of aluminum or plastic. The driving fork 68 may consist of such material. Secondwheel 52 is suitably made of one of the materials mentioned in connection with FIG. 1.

FIG. 4 shows driving fork 68 in the position of rest. When a current pulse passes through

coils

59 and 60,

magnet system

61 and 66 is moved in counterclockwise direction. In this process fork pin 69a advances secondwheel 52 by half a tooth pitch. After the termination of the current pulse, driving fork 68 is returned by the restoring force of the magnet system in cooperation with return element 58 to the position of rest shown in FIG. 4, in which process the fork pin 69b moves the second-wheel by another half tooth pitch. The restoring force is produced by the fact that return element 58 is not a closed ring but open on one side.

Return element 58 is suitably rotatable. By means of an eccentric 70, return element 58 can be turned and thereby the position of rest of driving fork 68 can be adjusted.

In the embodiments of FIGS. 1 and 4, the oscillation plane of

tuning fork

14, 54 is perpendicular to the dial of the watch. By this device, an inadmissibly strong stress of the tuning fork by shock due to an arm movement in the direction of maximum acceleration is largely avoided.

FIGS. 6 to 14 show circuits for narrowing the output pulses of the frequency divider circuit. In the circuit of FIG. 6, AB, C, D, indicate, for example, some frequency divider stages. The pulses supplied from the frequency divider circuit are symmetrical pulses of equal polarity which may control, e.g., an amplifier for the drive of a moving device. This amplifier supplies then at the output side pulses of a polarity in which the ratio between pulse duration and pulse interval equals 1. This however, means that during half a period of movement of the moved driving system a drive current flows, although the coil of the moving device is located only during a part of this period in the magnetic field of the magnet system. Temporarily, therefore, there flows a driving current of no, or only small, effect upon the moved system, so that an unfavorable effect results.

In FIG. 6, E indicates a pulse former which, like the frequency divider stages A to D, may be, e.g., a flip-flop circuit, connected at the input side to the last frequency divider stage D and a further frequency divider stage. In this process the pulse-forming stage E is switched on by the last frequency divider stage and switched off by the other connected frequency divider stage. When in the embodiment shown, the last frequency divider stage D furnishes a pulse frequency of l cps. (d in FIG. 7), frequency divider stage A supplies a pulse frequency of 8 cps. (a in FIG. 7). This setup produces at the output of pulse-forming stage E pulses of a frequency of 1 cps. and a pulse duration of 62.5 milliseconds (e in FIG. 7). When pulse-forming stage E is connected to stage A, e.g., to the 64 cps. stage, output pulses of a pulse duration of, e.g., only 7.8 milliseconds are obtained, which is readily achieved by means of the circuit shown. This pulse period of 7.8 milliseconds, proved favorable with a pulse frequency of l cps.

In place of the pulse-forming stage according to FIG. 6, a NAND gateof known type (of, e. g., periodical Elektronik,"No. 10/1968, Arbeitsblatt (Work Gazette) No. 20 Integrated digital circuits) can be used which is fed from the last frequency stage and from several preceding divider stages. In this process the last frequency divider stage determines the pulse frequency whereas the frequency divider stage of highest frequency determines the width of the pulse. The frequency dividers may be, e.g., a chain of bistable elements.

FIG. 8 shows a circuit with a four input NAND gate with diodes D1 to D4, transistor Tr l with working resistance RI and reversing stage with transistor Tr 2 and coil L which may be, e.g., coil 28 of FIG. 1 or coil 59, of FIG. 4.

FIG. 9 shows another embodiment of a NAND gate with a transistor Tr 3 in whose exciting circuit transistors Tr 4 to Tr 7 are series-connected. R2 to R 6 are series resistors. In this circuit a current flows in coil L when all transistors Tr 4 to Tr 7 are conducting.

In the circuit of FIG. 10, on the other hand, transistors Tr 9 to Tr 12 are connected in parallel in the input circuit of a transistor Tr 8. In this set-up a current flows in coil L only when none of the transistors Tr 9 to Tr 12 is conducting.

FIG. 11 shows a circuit with three-input NAND gate with transistor Tr l3, diodes D 5 to D 7 and working resistor R 8. A reversing stage with a transistor Tr 14, which feeds coil L, in series-connected to the gate via a resistor R 9.

FIG. 12 shows a corresponding circuit for an automatically controlled system with one transistor stage Tr 15, a control coil L and a drive coil LA. R 12 is an adjustable resistor. In this case the moving coil may consist of three partial windings L, L,,, LA. When the coil moves. voltage pulses are induced in control winding L which pulses after being amplified by transistor Tr l and flow through a drive winding LA and drive the moving coil. These windings L and LA in cooperation with the corresponding connection and transistor Tr l5 permit an automatic start of the moving device. Winding L through which the output pulses of the frequency divider stages flow, effects a synchronization of the moving coil to the desired frequency derived from the piezoelectric crystal.

FIG. 13 finally shows a circuit with a TTL'NAND gate with a transistor Tr 16 with several emitter electrodes and a reversing stage, connected as the output side, and with transistor Tr 17 which feeds coil L.

FIG. 14 shows a graphic representation of the pulses which occur. e.g., in connection with the circuit of H6. 11. Letter a indicates the output pulses of the frequency divider stage with 16 cps; b the output pulses of the frequency divider stage with 8 cps., and c the output pulses of the frequency divider stage with 4 cps; d are voltage pulses at the collector of transistor Tr 13, e are the voltage pulses at the collector of transistor Tr 14, and f the voltage pulses at the collector of transistor Tr 14 with superposed voltage pulses when the moving mechanism moves.

The circuits for narrowing the output pulses of the frequency divider circuit according to FIGS. 6 to 14 are usable not only for watches with moving coil arrangement engaging the second-wheel or rotary magnet arrangement, but also for watches in which the hand mechanism is driven by a moving device with a balance wheel oscillator or by a motor, and also for watches in which drive pulses with a frequency of more than 5 cps.

occur.

What is claimed is:

l. A wrist watch drive mechanism comprising:

a tuning fork piezoelectric crystal element operable to produce output electrical pulses;

frequency division means electrically connected to said tuning fork piezoelectric crystal element for dividing the frequency of the output electrical pul ses;

a second wheel; and,

electromagnetic drive means including a moving coil arrangement connected to said frequency division means and said second wheel for rotating said second wheel in response to electrical pulses from said frequency division means,

said moving coil arrangement comprising a centrally located, stationary permanent magnet core, a coil rotatable about the core, and a shift finger directly engaging the second wheel and supported by said coil.

2. A wrist watch drive mechanism as defined in claim 1, wherein the shift finger consists of two parts each of which is provided with a driving surface which advances the second-wheel by half a tooth pitch.

3. A wrist watch drive mechanism as defined in claim 1, wherein the shift finger is glued to a moving coil.

4. A wrist watch drive mechanism as defined in claim I, and further comprising; an adjustable stop positioned beneath said shift finger against which the coil is made to rest by return springs.

S. A wrist watch drive mechanism as defined in claim 1 wherein the moving coil consists of aluminum wire.

6. A wrist watch drive mechanism as defined in claim I, wherein the ends of the moving coil are conductively connected to insulated axle journals.

7. A wrist watch drive mechanism as defined in claim 6, wherein said coil has inactive sides and including oblong holes for receiving the axle journals parallel to the coil wires.

8. A wrist watch drive mechanism as defined in claim 7, wherein the axle journals are glued into the oblong holes.

9. A wrist watch drive mechanism as defined in claim 7, wherein the axle journals are fastened to the oblong holes by spraying synthetic resin around the coil.

10. A wrist watch drive mechanism as defined in claim 1, wherein a magnetic return element surrounding the coil is provided.

11. A wrist watch drive mechanism as defined in claim 1, wherein said shift finger is fashioned from a material of low specific weight and sufficient abrasive resistance.

12. A wrist watch drive mechanism as defined in claim 1, wherein said tuning fork and said moving coil arrangement are essentially parallel to each other and their longitudinal axes are parallel with said secondwheel.

13. A wrist watch drive mechanism comprising:

a. a tuning fork piezoelectric crystal element operable to produce output electrical pulses;

b. frequency division means electrically connected to said tuning fork piezoelectric crystal element for dividing the frequency of the output electrical pulses',

c. a second wheel;

d. electromagnetic drive means connected to said frequency division means and said second wheel for rotating said second wheel in response to electrical pulses from said frequency division means; and,

e. means connected between said frequency division means and said electromagnetic drive means for narrowing the output pulses of said frequency division means.

14. A wrist watch drive mechanism as defined in claim 13, wherein the oscillating plane of the tuning fork is perpendicular to the said second-wheel.

15. A wrist watch drive mechanism as defined in claim 13 wherein said electromagnetic drive means includes:

a movable magnet arrangement.

16. A wrist watch drive mechanism as defined in claim 15, wherein said movable magnet arrangement comprises a four-pole magnet device with magnet poles pointing outward in radial direction, a stationary magnetic return surrounding the magnetic device while leaving an airgap, and a coil arrangement mounted in the airgap and energizing the magnet poles.

17. A wrist watch drive mechanism as defined in claim 16, wherein said magnet device supports a driving fork which directly engages said second-wheel.

18. A wrist watch drive mechanism as defined in claim 16, wherein said magnet return for producing a return force which acts upon the rotary magnet device comprises: a partly open ring.

19. A wrist watch drive mechanism as defined in claim 18, wherein said open ring which forms the return is rotatable for the purpose of adjustment of the position of rest of the rotary magnet arrangement.

20. A wrist watch drive mechanism as defined in claim 13, wherein said frequency division means comprises a plurality of stages and said means for narrowing the output pulses of said frequency divider means comprises: a flip-flop circuit turned on by a last frequency divider stage and turned off by a preceding frequency divider stage.

Claims

1. A wrist watch drive mechanism comprising: a tuning fork piezoelectric crystal element operable to produce output electrical pulses; frequency division means electrically connected to said tuning fork piezoelectric crystal element for dividing the frequency of the output electrical pulses; a second wheel; and, electromagnetic drive means including a moving coil arrangement connected to said frequency division means and said second wheel for rotating said second wheel in response to electrical pulses from said frequency division means, said moving coil arrangement comprising a centrally located, stationary permanent magnet core, a coil rotatable about the core, and a shift finger directly engaging the second wheel and supported by said coil.

4. A wrist watch drive mechanism as defined in claim 1, and further comprising; an adjustable stop positioned beneath said shift finger against which the coil is made to rest by return springs.

5. A wrist watch drive mechanism as defined in claim 1, wherein the moving coil consists of aluminum wire.

6. A wrist watch drive mechanism as defined in claim 1, wherein the ends of the moving coil are conductively connected to insulated axle journals.

12. A wrist watch drive mechanism as defined in claim 1, wherein said tuning fork and said moving coil arrangement are essentially parallel to each other and their longitudinal axes are parallel with said second-wheel.

13. A wrist watch drive mechanism comprising: a. a tuning fork piezoelectric crystal element operable to produce output electrical pulses; b. frequency division means electrically connected to said tuning fork piezoelectric crystal element for dividing the frequency of the output electrical pulses; c. a second wheel; d. electromagnetic drive means connected to said frequency division means and said second wheel for rotating said second wheel in response to electrical pulses from said frequency division means; and, e. means connected between said frequency division means and said electromagnetic drive means for narrowing the output pulses of said frequency division means.

15. A wrist watch drive mechanism as defined in claim 13 wherein said electromagnetic drive means includes: a movable magnet arrangement.

21. A wrist watch drive mechanism as defined in claim 13, wherein said frequency division means comprises a plurality of stages and said means for narrowing the output pulses of the frequency divider means comprises: a NAND gate to which current is fed from a last frequency divider stage as well as from several preceding frequency divider stages.

22. A wrist watch drive mechanism as defined in claim 21, and further comprising: a reversing stage connected to the output side of the NAND gate.