US3562613A

US3562613A - Timepiece driven by nuclear energy

Info

Publication number: US3562613A
Application number: US815356A
Authority: US
Inventors: Karl Adler; Georges Ducommun
Original assignee: Baumgartner Freres SA
Current assignee: Baumgartner Freres SA
Priority date: 1968-04-17
Filing date: 1969-04-11
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09
Also published as: DE1966834A1; SE351933B; GB1267399A; CH521625A; ES366013A1; DE1918308A1; CH566368A4; NL6905976A; DE1918308B2; FR2007470A1; DE1918308C3; BE731610A

Abstract

A timepiece driven by nuclear energy, wherein the radiation of a radioactive source serves at the same time for producing the electric power for energizing a counting circuit and for control of a counting frequency or recombination frequency determining the advance of the timepiece.

Description

O United States Patent 1111 3,562,613

[ 7 2] lnventors Karl Adler [56] References Cited grenchenn; F [db UNITED STATES PATENTS j z i e 2,520,603 8/1950 Linder 310/3 2,720,582 10/1955 Linder et al, 310/3X [21] Appl. No. 815,356

. 2,835,105 5/1958 Favey 58/28 [22] Filed Apr. 11, 1969 2,837,666 6/1958 Lmder 310/3 [45] Patented Feb. 9, 1971 [73] Assi nee Baum arm" FreressA 2,858,459 10/1958 Schwarz 310/3 g g 2,926,268 2/1960 Reymond 310/3 2 952 817 9/1960 K 1 310 3x Priority Apr. 17 1968 enne y [33] swmerland 3,204,133 8/1965 Tschudln 310/22 [31] 5,663 3,370,414 2/1968 Lazrus et al. 58/23 Primary ExaminerD. F. Duggan 2 2 Att0rneylmirie, Smiley, SnyderEButrum [54] TIMEPIECE DRIVEN BY NUCLEAR ENERGY 22 Claims, 6 Drawing Figs.

[52] U.S. Cl 318/130,

310/3, 310/21;58/2 3 331/185 ABSTRACT: A timepiece driven by nuclear energy, wherein [51] Int. Cl ..H02k 33/00 the radiation of a radioactive source serves at the same time [50] Field of Search 310/3, 3A, for producing the electric power for energizing a counting cir- 3B, 3C, 3D, 119-134, 21, 22, 37, 15; 250/106, 83.3;33l/185;58/23,23C, 23AV, 123FS, 23D, 28

cuit and for control ofa counting frequency or recombination frequency determining the advance of the timepiece.

PATENTEUFEB 9197'. 3,562,613

INVENTORS KARL ADLER GEORGES bucermuu g M ATTORNEYS TIMEPIECE DRIVEN BY NUCLEAR ENERGY This invention relates to a timepiece driven by nuclear energy, wherein the radiation of a radioactive source acts onto an electronic element or counter for control of the advance of the timepiece. A prior timepiece of this type is based on the fact that a radioactive source having a high half-life period releases an equal number of pulses in a radiation meter during each time unit, such that counting of these pulses would result in a very accurate time measurement, particularly over long periods. The difficulty is that for obtaining suiiicient accuracy within shorter time intervals a very high pulse frequency would be required in order to keep down the statistic error. This requires a radioactive source of relatively high intensity, that it is of high Curie-value necessitating a screening which cannot possibly be accommodated in a wrist watch. Further a pulse counter with extremely highdivision ratio would be required, of which accommodation in a wrist watch would also be difficult. With weak sources, for instance B-sources, it would be possible to provide sufficient screening, but the required Curie-value would be too high for usual safety standards. In any case, a separate energy source producing the electric power is also required.

It is generally known, that electric energy may be produced by thermoelectric, radiophotovoltaic or radiovoltaic transformation. However, all prior energy sources of this type are not proper for use in a watch, particularly a wrist watch for some reason. Either, such energy sources required too strong radioactive sources, or have too low life time because some constituents are chemically changed, or their voltage and/or current is not suitable for energizing the circuits of a timepiece.

It is an object of this invention to match together the element controlling the advance of the timepiece, the nuclear energy source serving for irradiating this element and an electric battery energized by the same nuclear energy source that all conditions are fulfilled for use of these constituents in a watch, particularly in a wrist watch. The timepiece according to this invention broadly comprises a radioactive energy source with firadiation, a nuclear battery for direct conversion of this fi-radiation into electrical energy, a window in said battery allowing passage of a beam of B-radiation, an electric pulse detector in said beam of radiation, and a timekeeping electric circuit controlled and energized by said radioactive energy source through said detector and battery respectively. A battery such as a secondary-emission battery or a directemission battery as well as an electronic element irradiated for producing a counting frequency or counting frequency suitable for control of the timepiece may properly be energized by a source of B-radiation of relatively low energy level. The pos sibility of using a nuclear source of relatively low energy level of say .2 to l MeV. is advantageous in that neither in the battery nor in the irradiated electronic element which may be a semiconductor element, modifications of the material will occur. For this reason the system according to this invention has a very high life time.

This invention will now be explained in detail with reference to the accompanying drawing wherein:

FIG. 1 is a schematic view of a first embodiment;

FIG. 2 illustrates a modified circuit for use in an embodiment as shown in FIG. 1;

FIG. 3 is a diagram of another embodiment; and

FIGS. 4 to 6 show modified forms of electromechanical transducers.

The timepiece illustrated in FIG. 1 has a battery with a source 1 of radioactive radiation, for instance a suitable preparation of Ni 63 or Sr 40. This source has the form of a thin disc or layer between two plates 2 and 2' of magnesium oxide or any other suitable emission medium. The plates 2 and 2' of magnesium oxide have a thickness of .4 mm. as an example. A

collector electrode

3, 3 is provided outside each of the emission plates 2 and 2 respectively. The space between plates 2 and 3 or 2 and 3' may be in the order of .03 mm. The space between plates 2 and 3 and between plates 2' and 3' is evacuated. To this end the battery made of parts I to 3 may be accommodated in a sealed evacuated casing. The plates 2 and 2' are connected to a common conductor 4 while

plates

3 and 3 are connected to a conductor 5.

Plates 2 and 3 have

windows

6 and 7 respectively covering each other. These windows form a duct through which the [3- radiation is emitted from the source I to a semiconductor element 8. A semiconductor element having a marked recombination frequency under the action of a B-radiation is used. Preferably a PN-counting element is used. It is connected in series with a coupling coil 9 between the conductors 4 and 5 of the battery. Coil 9 is coupled with the coil of an oscillating circuit l0 tuned to the recombination frequency of element 8. The resonance oscillation of recombination frequency or counting frequency in circuit 10 is amplified by a transistor I l and is applied to the input of a frequency divider or pulse divider 12 of which the output is connected'to the actuating coil 13 ofa stepping pawl 14 by which a ratchet wheel 15 is driven. The hands of the timepiece or a counter is driven from the ratchet wheel through a gear in a manner well known in the art.

An adjustable diaphragm 16 is disposed between element 8 and window 7 for regulating the beam of radiation reaching element 8.

Operation of the timepiece is as follows:

The B-radiation from source 1 entering into the emission plates 2 and 2' releases high numbers of secondary electrons of which the energy has such a level that the

collector electrodes

3 and 3 are charged to a suitable voltage. As men tioned above, a radioactive source with relatively low energy level of say .2 to 1 MeV., for instance Ni 63 may be used. A source of about 20 me. is sufficient. The electrical energy of the battery is suitable and sufficient for energizing the semiconductor element 8, transistor 11 and the divider 12.

FIG. 2 illustrates a modification of the timepiece of FIG. 1 with a simplified electronic circuit. An RC-member I9 is a series-connected with coil 9. It may serve for regulating the frequency because by changing the capacity of the RC- member connected in series with the capacity of the element 8 a change and adjustment of the frequency is possible. An armature l7 projecting into the coil 9 is suspended by means of parallelogram arms 18. The stepping pawl 14 is mounted on the armature 17. Elements 10-13 of FIG. 1 are omitted in this simplified modification.

Other modifications of the embodiment of FIG. I are feasible. Parts 2 and 3 may be of cylindrical form instead of being plates as described above. In this case a radiation source in the form of a rod is accommodated in a hollow cylinder of emission material. Other materials may be used as well for the radiation source as for the emission medium.

Instead of the secondary-electron battery as shown a semiconductor-battery with PN-junction may be used, whereby the radiation source, for instance Sr is located between two suitable doped mixed crystals of PN-type or NP- type, and wherein up to 10 pairs of electrons and holes may be produced by each B-particle having an energy in the order of .2 MeV. For an intensity of the source in the order of 20 mc. a voltage of .2 v. and a current of 4. l()- A may be obtained. By series connection of two sources of this type and of a suitable semiconductor counter a circuit operating in the manner described above in relation with FIG. 1 may be obtained.

Of course the battery shown in FIG. 1 may be used in any other field of application.

In the embodiment schematically shown in FIG. 3 a battery 20 is used wherein no secondary emission effect occurs but the collector electrode is directly charged by the B-radiation of the radioactive source in a manner well known per se. Any suitable source of radiation, preferably H3, may be used. With proper design of the battery, a voltage in the order of 300 v. is obtained. As indicated in FIG. 1, the collector electrode (not shown) of battery 20 has a window through which a beam of B-radiation is directed towards a counting tube 21. The

tapping 22 of a potentiometer 23 is connected through a diode 24 to a condenser 25. This condenser 25 may be discharged through a suitable trigger element 26, for instance a gas discharge tube or a Zener diode and a coil 27 wound onto a core 28 acting onto an armature 29 carrying a stepping pawl 30. A ratchet wheel 31 may be advanced by pawl 30 in a manner explained in connection with FIG. 1 for driving the hands or a counter of the timepiece.

By means of a diaphragm 32 disposed between the window of the battery 20 and the counting tube 21, the beam of B- radiation is so adjusted that the counting tube 21 operates within a suitable frequency range. It is known that counting tubes have an upper limit frequency or saturation frequency above which counting is no longer possible due to continuous ionization of the gas in the tube, this resulting in continuous short-circuiting of the tube. Practically, the counting frequency will be adjusted for instance to 100 pulses/second. With a current through diode 24 of Ill- A a condenser 25 of IO- F is charged within 1 second to about 60 volts, the charge being in the order of IO" As. The ignition voltage of element 26 is adjusted to about 60 volts so that the condenser 25 is discharged at the end of each second through element 26 and coil 27. A current pulse in the order of I A will produce a force on armature 29 in the order of 4 mg. at 15 Gauss and a core surface of 40 mm This force is sufficient for actuating the stepping pawl 30 and advancing the ratchet wheel 31 with the gearing of the timepiece. The mechanism of the timepiece is thus advanced by one step per second. The extremely low power rating of the battery is accumulated in condenser 25 during the time interval of 1 second and the accumulated energy is sufficient for advancing the mechanism of the timepiece by 1 step per second.

Adjustment of proper timekeeping is possible in two ways. Basically the interval between succeeding stepping pulses may be adjusted by the number of counter pulses occurring per second, that is by adjustment of the intensity of the beam of B- radiation by means of diaphragm 32. Another adjustment is possible by changing the pulse voltage transmitted to condenser 25 by adjustment of the ratio of potentiometer 23.

FIG. 4 illustrates a somewhat modified electromechanical transducer, similar parts having the same reference numerals as in FIG. 3. The armature 29 is a leaf spring having high elasticity fixed to the one leg of the core 28 and carrying a calibrated weight 33 at its other end. The resonance frequency of this spring armature is adjusted to double the pulse frequency in coil 27 or to any other multiple of this pulse frequency. When a mechanical oscillating system of relatively high Q-factor is used, its oscillation may properly be sustained by a pulse frequency which is substantially lower than the frequency of the mechanical oscillating system. This frequency may be in the order of 50 c/s.

FIG. illustrates another modification wherein the oscillation of a tuning fork 34 is sustained by the pulses flowing in coil 27 wound on a special core 35. The tuning fork 34 has a pawl 30 for advancing the ratchet wheel 31.

Instead of an electrodynamic or electromagnetic transducer as shown in FIGS. 1 to 5, an electrostatic transducer as schematically shown in FIG. 6 may be used. This transducer has two

plane electrodes

36 and 37 fixed to a frame 38. At least the lower electrode 37 is a membrane of elastic material. A stepping pawl 30 engaging the ratchet wheel 31 isfixed on the lower electrode 37. The

electrodes

36 and 37 are equipped with

contacts

39 and 40 respectively.

The electrostatic transducer shown in FIG. 6 may be connected into the circuit shown in FIG. 3 instead of the coil 27. When a pulse of 60 v. and -A is applied from condenser 25 through trigger element 26, the transducer shown in FIG. 6 will also produce a force in the order of 4 mg., provided it has a capacity in the order of 2 X l0- F or a surface of 16 mm. and a distance between

electrodes

36 and 37 of 1 mm. By this force, the lower elastic electrode 37 is bent inwardly until the discharging

contacts

39 and 40 touch each other whereby the condenser 25 is discharged. Electrode 37 now returns into its initial position whereby the ratchet wheel 37 is advanced by one step by pawl 30. When the transducer of FIG. 6 is used instead of coil 27 in FIG. 3, the trigger element 26 may be omitted. It is obvious that with increasing charge of condenser 25 the electrode 37 would be bent more and more towards electrode 36 until

contacts

39 and 40 touch each other and discharge condenser 25. Since

contacts

39 and 40 would always touch each other at the same voltage, it is obvious that the transducer of FIG. 6 may replace the trigger element 26.

However, the electrostatic transducer of FIG. 6 may also be connected directly between tapping 22 of potentiometer 23 and terminal 41 of the circuit shown in FIG. 3, whereby elements 25 to 27 of that circuit would be omitted.

Contacts

39 and 40 of the transducer may also be omitted. The electrode 37 carrying the stepping pawl 30 now oscillates at the frequency of pulses produced by the counting tube. In this

case electrodes

36 and 37 may have a surface in the order of 20 mm. and may be spaced from each other by .1 mm. With a voltage per pulse of v. a force in the order of 5 mg. at a speed of .02 cm./s would be produced. The power is in the order of 5.l0 Ws or 5 X 5cmgs. This is sufficient for driving a stepping pawl and a ratchet wheel with the gearing of the timepiece.

We claim:

1. A timepiece driven by nuclear energy. comprising a radioactive energy source with B-radiation, a nuclear battery for direct conversion of this B-radiation into electrical energy, a window in said battery allowing passage of a beam of B- radiation, an electric pulse detector in said beam of radiation, and a timekeeping electric circuit controlled and energized by said radioactive energy source through said detector and battery respectively.

2. A timepiece according to claim 1, comprising a semiconductor detector and an electric circuit adapted for selection of the recombination frequency of said semiconductor detector.

3. A timepiece according to claim 1, comprising a radioactive energy source having an energy level of at least approxi mately .2 to l MeV.,for instance Ni 63.

4. A timepiece according to claim 1, comprising a radioactive source of at least approximately 20 me.

5. A timepiece according to claim 1, comprising a secondary-emission battery.

6. A timepiece according to claim 5, comprising MgO having a thickness of at least approximately .4 mm. as a secondary-emission medium.

7. A timepiece according to claim 1, comprising a diaphragm disposed between said window and said detector for regulating the intensity of said beam of radiation.

8. A timepiece according to claim 2, wherein said radioactive source is a layer disposed between two plates of secondary-emission medium, and a collector electrode is associated with each of said plates of secondary-emission medium, said beam passing through windows covering each other of one of said plates of secondary-emission medium and one of said collector electrodes, a diaphragm being disposed between said windows and said semiconductor detector.

9. A timepiece according to claim 2, wherein said semiconductor detector is a PN-counter.

10. A timepiece according to claim 2, comprising an oscillating circuit for selection of the recombination frequency.

1 l. A timepiece according to claim 2, comprising a frequency divider for reduction of the recombination frequency.

12. A timepiece according to claim 2, comprising an RC- circuit series-connected with the semiconductor element.

13. A timepiece according to claim 12, wherein said RC-circuit comprises a variable condenser.

14. A timepiece according to claim 2, comprising a coil series-connected with said semiconductor detector, said coil being adapted for driving a stepping pawl.

15. A timepiece according to claim 1, comprising a secondary-electron battery having a PN-junction, the radioactive energy source being located between mixed crystals selected from the group consisting of PN-type and NP-type crystals.

16. A timepiece according to claim 1, comprising a highvoltage battery series connected with said pulse detector, a condenser adapted to be charged by each pulse released by said detector, said condenser being connected to the control input of a trigger, said trigger being released whenever the potential of said condenser has reached a predetermined value, whereby said condenser is discharged and a driving pulse is transmitted to an electromechanical driving system.

17. A timepiece according to claim 16, comprising a potentiometer series-connected with said detector, the tapping of said potentiometer being connected to said condenser.

18. A timepiece according to claim 17, comprising a diode connected between said tapping and said condenser.

19. A timepiece according to claim 16, comprising an electrostatic driving system having condenser plates of which at least one is displaceable and is coupled with a stepping pawl.

20. A timepiece according to claim 19. wherein said displaceable condenser plate is a part of a mechanical oscillator tuned to the frequency of the driving pulses.

21. A timepiece according to claim 19, wherein said pulse detector is a counting tube series connected with said highvoltage battery and with said electrostatic driving system including a condenser, this condenser being part of a RC-circuit series-connected with the counting tube.

22. A timepiece according to claim 19, wherein said electrostatic driving system has switch contacts short-circuiting and discharging said condenser plates whenever the condenser has been fully charged and contracted by its charge.

Claims

1. A timepiece driven by nuclear energy, comprising a radioactive energy source with Beta -radiation, a nuclear battery for direct conversion of this Beta -radiation into electrical energy, a window in said battery allowing passage of a beam of Beta -radiation, an electric pulse detector in said beam of radiation, and a timekeeping electric circuit controlled and eneRgized by said radioactive energy source through said detector and battery respectively.

3. A timepiece according to claim 1, comprising a radioactive energy source having an energy level of at least approximately .2 to 1 MeV., for instance Ni 63.

4. A timepiece according to claim 1, comprising a radioactive source of at least approximately 20 mc.

5. A timepiece according to claim 1, comprising a secondary-emission battery.

11. A timepiece according to claim 2, comprising a frequency divider for reduction of the recombination frequency.

12. A timepiece according to claim 2, comprising an RC-circuit series-connected with the semiconductor element.

16. A timepiece according to claim 1, comprising a high-voltage battery series connected with said pulse detector, a condenser adapted to be charged by each pulse released by said detector, said condenser being connected to the control input of a trigger, said trigger being released whenever the potential of said condenser has reached a predetermined value, whereby said condenser is discharged and a driving pulse is transmitted to an electromechanical driving system.

20. A timepiece according to claim 19, wherein said displaceable condenser plate is a part of a mechanical oscillator tuned to the frequency of the driving pulses.

21. A timepiece according to claim 19, wherein said pulse detector is a counting tube series connected with said high-voltage battery and with said electrostatic driving system including a condenser, this condenser being part of a RC-circuit series-connected with the counting tube.