US3221487A

US3221487A - Electric pocket or wrist-watch

Info

Publication number: US3221487A
Application number: US338421A
Authority: US
Inventors: Greuter Andre; Korom Arpad
Original assignee: Gesellschaft zur Foerderung der Forschung an der Eidgenoessischen Technischen Hochschule
Current assignee: Gesellschaft zur Foerderung der Forschung an der Eidgenoessischen Technischen Hochschule
Priority date: 1963-01-22
Filing date: 1964-01-17
Publication date: 1965-12-07
Anticipated expiration: 1982-12-07
Also published as: CH81663A4; CH393198A; DE1302049B

Description

1965 A. GREUTER ETAL 3,221,487

ELECTRIC POCKET OR WRIST-WATCH Filed Jan. 1'7, 1964 5 Sheets-Sheet 1 mar. Energy Energy flnaw% Wall/mm, Wy 6M D .7 1965 A. GRE UTER Em 3,221 487 ELECTRIC POCKET OR WRIST-WATCH Filed Jan. 17, 1964 5 Sheets-Sheet 2 C D1 C:

11 a i Al -19 U, 1: D; I D 55R U2 Fig.3

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1965 A. GREUTER ETAL 3,221,487

ELECTRIC POCKET OR WRIST-WATCH Filed Jan. 17, 1964 5 Sheets-Sheet 5 Fig.6

mm, W

United States Patent Ofiice 3,221,487 Patented Dec. 7, 1965 3,221,487 ELECTRIC POCKET OR WRIST-WATCH Andr Greuter and Arpad Korom, both of Zurich, Switzerland, assignors t Gesellschaft zur Forderung der Forschung an der Eidg. Techn. Hochschule, Zurich, Switzerland Filed Jan. 17, 1964, Ser. No. 338,421 Claims priority, application Switzerland, Jan. 22, 1963,

2 Claims. (Cl. 5823) This invention relates to improvements in electrically powered watches and in particular pocket and wristwatches.

In electrical pocket and wrist-watches, the problem arises of providing in a small space a standard frequency transmitter having an extremely small power requirement. Known electrical watches use as frequency-stabilizing elements either an electromechanical resonance element, such for example as an electrically driven balance wheel, or an electro-acoustic resonance element, such for example as an electrodynamically driven tuning fork. In principle, however, other resonance elements could be used, for example, piezoelectric, electrostrictive or magnetostrictive elements. All these resonance elements have in common the property that their resonance frequency increases as their dimensions become smaller.

In hitherto known proposals, the transmission of energy from the standard frequency transmitter is effected to an electromechanical transducer so as to drive a mechanical time-indicating device directly at the frequency of the resonance element which, for constructional reasons, implies relatively low values, for example, below about 1 kc./s., of the natural frequency of the resonance element, and thereby sets narrow limits to the choice of a suitable material for the resonance element, and to its constructional form and mechanical dimensions.

If a watch which is to be worn is to have high accuracy, the following conditions, inter alia, should be satisfied:

(1) The resonance element of the standard frequency transmitter must have a high quality factor, and

(2) Its natural resonant frequency must lie far above the frequency spectrum produced by vibrations in normal use.

A characteristic feature of electro-acoustic resonance elements is that the quality factors tend to attain their optimum values at substantially higher frequencies than those required by the time-indicating device. Thus, the advantages attainable by means of a high standard frequency are:

(1)High quality factor, i.e. high accuracy of movement,

(2) Lower disturbance sensitivity to vibrations, and

(3) Reduction in the disturbing influence of the gravitational field in the case of 'forms of oscillators which are not gravitational invariant, for example as tuning forks, the reduction being proportional to the square of the natural frequency.

The principal object of the present invention is the provision of an electrical pocket or wrist-watch which is free from the drawbacks due to a low standard frequency of the resonance element.

A further object of the invention is to provide an elec trical pocket or wrist-watch with a resonance element having a substantially higher standard frequency as was the case hitherto.

According to the present invention there is provided an electrical pocket or wrist-watch which comprises an electrical standard frequency transmitter having a resonance element as frequency stabilizer, an electromechanical transducer, a mechanical time-indicating device, and an electronic frequency reducer provided between the standard frequency transmitter and the electromechanical transducer, wherein the electronic frequency reducer preferably includes a backward diode.

It is another object of the invention to provide a pocket or wrist-watch of the kind described, having an electronic frequency reducer with a frequency dividing ratio of at least 10, preferably 15. This can best be achieved with a frequency reducer comprising a relaxation oscillator having a backward diode as active member.

A still further object of the invention is the provision of an electronic frequency reducer and an electronic standard frequency transmitter with an extremely low consumption of DC. For this purpose backward diodes are particularly well suited as the active members in the frequency reducer and in the stand-ard frequency transmitter.

The above and other objects and advantages of the invention will best be understood from the following detailed description of a preferred embodiment thereof, given by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 shows diagrammatically the basic construction of the electrical wrist-watch according to the invention;

FIGURE 2 shows the current-voltage characteristic of a backward diode, which is used as active member in the electronic frequency reducer and in the electronic standard frequency transmitter of the watch;

FIGURE 3 is a circuit diagram of the electronic frequency reducer;

FIGURE 4 shows a portion of the characteristic according to FIGURE 2 situated in the blocking region of the backward diode on a larger scale, together with a resistance characteristic;

FIGURE 5 is a graph showing the output voltage of the frequency reducer as a function of the time;

FIGURE 6 represents a vacuum-tight housing containing a resonance element in the form of a fiexural resonator, serving to stabilize the standard frequency transmitter of the watch, partly in section along line VIVI in FIGURE 7;

FIGURE 7 is a section along line VIIVII in FIG- URE 6; and

FIGURE 8 shows a circuit diagram of the electronic standard frequency transmitter of the watch.

The electrical pocket watch or wrist-watch shown in FIGURE 1 has an electrical standard frequency transmitter comprising an oscillator 10 and a resonance element 11 as frequency stabiliser. The resonance element may be, for example, an electrically driven torsion resonator or fiexural resonator. It is, however, equally well possible to use an electrostrictive, piezoelectric or magnetostrictive resonator as resonance elements. Advantageously, the resonance element 11 is accommodated in a vacuum-tight housing, so as to protect it as far as possible from the effects of changes in the surrounding atmosphere. A detailed example of such a resonance element is given later on with reference to FIGS. 6 and 7.

The oscillator 10 for maintaining the oscillation of the resonance element 11 is preferably a relaxation oscillator, an example of which is illustrated in FIG. 8 and described with reference thereto. The oscillator 10 and resonance element 11, together, form a standard frequency transmitter which is fed from an electrical energy source 12, for example, a small battery. The oscillation frequency f generated and transmitted by the

standard frequency transmitter

10, 11 generally lies between 2 kc./s. and 20 kc./s.

The output of the standard frequency transmitter 10,

11 is connected to an electronic frequency reducer 13 which converts the electrical oscillatory energy signal having the frequency f into a signal of much lower frequency The frequency reducer 13 is followed by an electromechanical transducer 14, which converts the electrical oscilliatory energy signal into mechanical energy for driving a mechanical time-indicating device 15. The transducer 14 may consist, for example, of a small synchronous motor, or of a step-by-step mechanism, operable by electrical pulses.

Considerable demands are made on the reducer 13 since it has to deal with frequencies of 20 kc./s. or more and must not have a power requirement of more than two microwatts for it to be suitable for use in a pocket watch or wrist-watch. Prior proposed reducer circuits have an excessively high power consumption at the given working frequency. Thus, for example, a flip-flop which absorbs 1 microwatt has an upper limit frequency of, at the best, 200 c./s. and its frequency reduction is only a half. A transistorized blocking oscillator is somewhat better, but like the tunnel diode relaxation oscillator reducer, is far from satisfying the requirements. The watch according to the invention uses, as frequency reducer, a synchronised relaxation oscillator with a backward diode as the active member.

Backward diodes have been designed as switches for very rapid computers and in this application they show as an unwanted secondary effect in the blocking region, a small region of negative resistance. This is illustrated in the characteristic shown in FIGURE 2. This secondary effect is utilised in the frequency reducer 13. One difference between a backward diode and a tunnel diode which is important for the present application, resides in the fact that the peak current I of the backward diode is only about 1 to microamperes compared with a few milliamperes in the tunnel diode.

The circuit of the frequency reducer 13 is shown in FIGURE 3. Two

input terminals

16 and 17 are connected to the oscillator 10, and an A.C. voltage U With the standard frequency f passes from these terminals to an input circuit which comprises a capacitor C and two diodes D and D Connected to this input circuit is a relaxation oscillator comprising a backward diode D, an induction coil having an inductance L and an ohmic loss resistance R, and a DC. source B with a terminal voltage E The backward diode D is poled in the backward direction, and an AC. voltage U produced across it with the frequency f is passed to

output terminals

18 and 19 via a separating capacitor C The

terminals

18 and 19 are connected to the electromechanical transducer 14.

The operation of the frequency reducer shown in FIG- URE 3 is now explained with reference to the characteristics shown in FIGURE 4. The backward diode D, operated exclusively in its blocking region, has a characteristic K while the rectilinear characteristic of the loss resistance R is denoted by K The voltage E of the DC. source B and the loss resistance R of the inductance coil are selected so that the two characteristics K and K intersect at a point P inside the negative resistance region of the backward diode characteristic K When the source B is connected into circuit, the current passing through the induction coil and the backward diode D increases from the origin 0 through point 1 to point 2 of the characteristic K approximately in accordance with an exponential curve. The negative characteristic region begins at the point 2, and on further increase in voltage, the current ought to decrease, but this is prevented by the inductance L. The variation in the current through the induction coil in fact produces across the inductance L an inductance voltage, which is added to the terminal voltage E of the DC. source, so that backward diode D very quickly assumes the condition according to point 3 of its characteristic K Because the voltage drop across the backward diode D is now greater than the DC. voltage E the current begins to decrease approximately exponentially according to the portion of the characteristic between the points 3 and 4. When the point 4 of the characterstic K is reached, the current begins to increase again, which reverses the sign of the induced voltage and causes the backward diode D to return rapidly to the condition according to point 1 of its characteristic. This completes a cycle, which is immediately followed by a fresh cycle, corresponding to that just described, except that it does not begin at the origin 6 but at the point 1 of the characteristic K all the subsequent cycles being substantially identical with the second cycle.

The time-variation of the voltage U across the backwardard diode D is shown graphically in FIGURE 5, the frequency f of the relaxation oscillator depending upon the time constant An advantageous property of the relaxation oscillator described enables it to be operated as a synchronised oscillator, or if the synchronising signal is a whole multiple of the frequency of the relaxation oscillator, as frequency reducer. If, in fact, an AC. voltage U is applied to the

input terminals

16 and 17, this voltage influences the transition from the condition according to point 2 to the condition according to point 3 of the characteristic K The voltage U has no other influence. The controlling voltage U is fed with positive polarity to the backward diode D through the combination of diodes D and D The frequency 1 of the voltage U may be up to about 15 times higher than the frequency f of the relaxation oscillator. Only those voltage peaks which, in regard to time, come to be situated immediately in the vicinity of point 2 in FIGURE 5, produce in each case the change in the backward diode condition according to point 2 of the characteristic K to that according to point 3. By suitable choice of the time constant it is ossible to arrange that this will always be true for the x voltage peak, where x may be any whole number from 1 to 15. The AC. voltage U occurring at the

output terminals

18 and 19, consequently has a frequency f, amounting exactly to the x part of the standard frequency f and consequently the synchronised relaxation oscillator described operates as frequency reducer or frequency divider.

In order to be able to respect as well as possible the hereinbefore mentioned favourable conditions of an electrical watch with standard frequency transmitter, the ratio of f to 1 should be made as large as possible. Good results are obtained with a standard frequency f of 4500 c./s. and a frequency f of 300 c./s. for feeding the electromechanical transducer 14.

If desired, two similar frequency reducers may be connected in series, so that with a standard frequency i of 11,250 c./s., a feed frequency f of 50 c./s. is obtained, if the frequency dividing ratio of each reducer is 15.

Since, at the above-mentioned standard frequency f the resonance element 11 of the oscillator 10 is of relatively small dimensions, and has not to serve directly for the mechanical drive of the time-indicating device by means of its oscillations, the resonance element may be accommodated in a vacuum-tight housing without trouble. Damping of the resonance element can thereby be reduced, and any dependence of the natural frequency on air-pressure fluctuations is eliminated or at least reduced at the same time.

Referring now to FIGURES 6 and 7, the resonance element preferably is a flexural resonator constituted by an annular spring body 20 which is equivalent to a torus topologically. Two opposite points of the annular body 20 are connected by spokes 21 to fixing

pins

22 and 23 passing through the walls of a vacuum-tight housing 24 in which the resonance element is accommodated. Two other opposite points of the annular spring body are each provided with a

mass

25 and 26, respectively. Due to flexure of the spring body the two masses are able to oscillate, in opposite sense, on a common straight moving path, without producing external forces on the fixing pins 22 and 23. More details about the structure and the operation of the toroidal resonance element are described in the co-pending application Serial No. 224,901, filed on September 18, 1962, in the name of Theo Stutz.

The

masses

25 and 26 are three-legged permanent magnets cooperating with two identical field coils S and S which are firmly mounted to the inner side of the housing 24. The

terminals

31, 32 and 33, 34, respectively, of the coils S S pass through the walls of the housing 24 and are accessible from outside thereof.

The housing 24 is made of red brass or glass, and is evacuated.

A preferred example of the wiring diagram of the electronic standard frequency transmitter having an electronic oscillator suitable for use in connection with the resonance element described above, is shown in FIGURE 8. The two field coils S and S are connected in series and, together with a capacitor C form a tuned tank circuit which is a parallel resonant circuit. Said tank circuit, in series with a backward diode D is connected to a DC. feeding circuit comprising two resistors R and R which feeding circuit is in connection with the terminals of the DC. source 12. The tank circuit and the backward diode D constitute a relaxation oscillator wherein the backward diode is the active member. The backward diode is working as a negative resistance in the blocking region of its characteristic.

Output terminals

16 and 17 which are connected to the ends of the backward diode D are in connection with the

input terminals

16 and 17, respectively, of the frequency reducer as shown in FIG- URE 3.

The operation of the described standard frequency transmitters relaxation oscillator is substantially the same as described in view of the circuit shown in FIGURE 3. Relaxation oscillators are well known in the art, however, they have not yet been provided with a backward diode as the active member. Instead of the backward diode a tunnel diode has been used, the DC. consumption of which is several times higher than that of backward diode D By means of the field coils S S and the associated

permanent magnets

25, 26, the tank circuit of the oscillator is electrodynamically coupled with the flexural resonator 20. This coupling being a tight one, the

magnetic masses

25 and 26 of the resonator 20 are driven to oscillate in opposite sense to one another, while the movements of the permanent magnetic masses, in turn, cause a strong reaction on the tank circuit, by inducing a synchronizing signal in the field coils S and S Thus, the frequency of the oscillator is stabilized in synchronism with the vibration of the resonator 20.

What we claim is:

1. An electrical watch having the over-all size of a conventional watch, which comprises an electric power cell, an electrical standard frequency transmitter having a resonance element as frequency stabiliser, an electromechanical transducer, a mechanical time-indicating device, and an electronic frequency divider provided between the standard frequency transmitter and the electromechanical transducer, said frequency divider having a plurality of stages each of which is provided with a backward diode as active member, the standard frequency transmitter including a relaxation oscillator for maintaining oscillation of the resonance element, said relaxation oscillator being provided with at least one backward diode as active member.

2. An electrical watch having the over-all size of a conventional watch, which comprises an electric power cell, an electrical standard frequency transmitter having a resonance element as frequency stabiliser, an electromechanical transducer, a mechanical time-indicating device, and an electronic frequency divider provided between the standard frequency transmitter and the electromechanical transducer, said frequency divider having a plurality of stages each of which is provided with a backward diode as active member, each of said backward diodes having in the blocking region a small negative resistance, the standard frequency transmitter including a relaxation oscillator for maintaining oscillation of the resonance element, said resonance element being an electrically driven flexural resonator and said relaxation oscillator being provided with at least one backward diode as active member.

References Cited by the Examiner R. L. Watters: A Quartz Crystal Chronometer, Electronics, page 129, Sept. 29, 1961.

D. T. Howson: Backward-Diode Modulators, Industrial Electronics, vol. 1, March 1963, pages 334-337.

J. Przyeylski and G. N. Roberts: The Design and Construction of Tunnel Diodes, B.I.R.E. Journal, vol. 22, December 1961, pages 497-505; pages 503-505 relied upon.

LEO SMILOW, Primary Examiner.