US3218793A

US3218793A - Pulse timer

Info

Publication number: US3218793A
Application number: US246897A
Authority: US
Inventors: Richard S Walton
Original assignee: Hamilton Watch Co
Current assignee: Hamilton Watch Co
Priority date: 1962-12-26
Filing date: 1962-12-26
Publication date: 1965-11-23
Anticipated expiration: 1982-11-23
Also published as: CH1568863A4; GB1001176A; DE1523918B2; DE1523918A1; CH434426A; CH424648A

Description

Nov. 23, 1965 R. s. WALTON PULSE TIMER 2 Sheets-Sheet 1 Filed Dec. 26, 1962 Q24 (SW 2 4 G w 6 H 4 w 6 l [I T. U 0 4 WV 3 J m mm R H M im R E V W V3? 1 w a Q B 4 2 6 firz 2/:

FIGS

INVENTOR.

RICHARD S. WALTON ATTORNEYS N 1965 R. s. WALTON 3,218,793

PULSE TIMER Filed Dec. 26, 1962 2 Sheets-Sheet 2 V70 I F I65 INVENTOR.

70 RICHARD S. WALTON BY 76 L98 Jam M 44M A TTORNEYI-S' United States Patent 3,218,793 PULSE TIMER Richard S. Walton, Willow Street, Pa., assignor to Hamiltori Watch Company, Lancaster, Pa., a corporation of Pennsylvania Filed Dec. 26, 1962, Ser. No. 246,897 17 Claims. (Cl. 58-28) This invention relates to pulse timers and more particularly to a mechanically synchronized electronic oscillator of the self-starting electric watch or clock-type.

Various arrangements are known for mechanically controlling the output of an oscillator. As is well known the accuracy of an electronic oscillator, particularly at relatively low frequencies, varies substantially with both temperature and voltage changes. For this reason, it has been proposed in the past to control the output of such an oscillator through the use of a separate oscillatory system in the form of a watch or clock mechanism. The mechanical oscillator is not so susceptible to fluctuations in output and the overall accuracy of the oscillator being substantially that of the mechanical movement is significantly increased.

A serious disadvantage of prior constructions, particularly those involving horological mechanical movements, is the fact that, in general, no simple and eflective selfstarting arrangement has been provided.

The present invention avoids these difliculties by providing an electrical pulse timer having the accuracy of a mechanical movement which incorporates a simple and reliable self-starting feature. The device of the present invention, if provided with an electrical output, may be used as a pulse timer, providing accurately spaced low repetition rate pulses for use as a low frequency time base, particularly in the frequency range of about 1 to 20 cycles per second. Conversely, the device of the present invention if incorporated in an electric clock may be provided with a mechanical output (movement of the watch hands) and in this form is a highly accurate and reliable electric watch or clock that is automatically self-starting.

It is, therefore, one object of the present invention to provide a novel pulse timer.

Another object of the present invention is to provide a highly accurate pulse source usable as a time base.

Another object of the present invention is to provide a self-synchronized relaxation oscillator.

Another object of the present invention is to provide an automatic self-starting electric Watch or clock.

Another object of the present invention is to provide a mechanically synchronized electronic oscillator.

These and further objects and advantages of the invention will be more apparent upon reference to the following specification, claims and appended drawings wherein:

FIGURE 1 shows one embodiment of the present invention in the form of the self-synchronized relaxation oscillator.

FIGURE 2 shows a modified embodiment in the form of a mechanically synchronized oscillator usable either as a pulse source or as a watch or clock movement.

FIGURE 3 is a circuit diagram of a further modified embodiment of the present invention.

FIGURE 4 is an elevational view with parts in section showing a modified mechanical oscillatory system usable in the circuit of FIGURE 3.

FIGURE 5 is a plan view with parts broken away and parts in section of the mechanical oscillatory system of FIGURE 4; and

FIGURE 6 is a cross-section through the coils taken along line 6-6 of FIGURE 4.

Referring to the drawings, FIGURE 1 shows a selfsynchronized oscillator constructed in accordance with the 'ice present invention, generally indicated at 10 including a unijunction transistor 12 connected between a positive power supply terminal 14 and negative or grounded terminal 16. Unijunction transistors are well known and include an emitter 18 and two

base contacts

20 and 22. Connected between the emitter 18 and the positive supply 14 is a resistor 24. A capacitor 26 is connected between the emitter 18 and the negative power supply terminal 16. A second resistor 28 is connected between base contact 20 and the positive side of the power supply, while a load resistor 30 is connected between the other base contact 22 and the negative terminal 16 of the power supply.

In order to provide self-synchronization, the output terminal 32 of the oscillator is connected through a time delay circuit 34 and an inverter 36 to the base contact 20. In this way, a portion of the output pulse waveform is fed back to the unijunction transistor 12. The delay inserted by delay element 34 is preferably slightly less than the natural pulse spacing of the oscillator. The positive output pulses appearing at output terminal 32 are inverted in invertor 36 and applied as negative pulses to the base contact 20.

In operation, when DC. power is applied across

terminals

14 and 16, capacitor 26 charges up and the potential of emitter 18 rises in accordance with the RC time constant of the oscillator. When the potential of emitter 18 reaches a predetermined value, transistor 12 conducts and draws heavy current through resistor 30 both from emitter 18 and from

base contacts

20 and 22. The conduction of transistor 12 causes capacitor 26 to discharge until the potential of the emitter 18 drops below cutoff and the transistor 12 is cut off. This surge of heavy current through load resistor 30 appears as a positive pulse at output terminal 32. After the transistor has turned off capacitor 26 begins to recharge in accordance with the natural time constant of the oscillator.

However, a portion of the output in the form of a positive pulse is fed to the time delay circuit 34 and invertor 36 to appear as a delayed negative pulse at base contact 20. The time delay of circuit 34 is preferably chosen so that the negative pulse appears at contact 20 before the transistor 12 is again turned on by the recharging capacitor 26. The negative pulse applied to base contact 20 momentarily lowers the voltage gradient along the base between

contacts

20 and 22 so that the potential of emitter 18 due to the potential across recharging capacitor 26 is suflicient to again turn the transistor on. With the transistor turned on heavy current is again drawn through load resistor 30, capacitor 26 is again discharged and the entire cycle repeated. The resultant output at terminal 32 is a series of positive pulses having a repetition rate governed by the time delay circuit 34.

It is apparent that the time delay inserted by circuit 34 is independent of the supply voltage across

terminals

14 and 16 and if this circuit is carefully selected to be substantially independent of temperature a very accurate pulse output spacing can be obtained suitable for use as a low frequency time base. The time delay device 34 may be any of the well known electrical or mechanical delay devices.

FIGURE 2 shows a modified embodiment wherein the time delay element 34 takes the form of a mechanical balance of the type conventionally employed in an electric watch or clock. In FIGURE 2 like parts bear like reference numerals and the electronic oscillator portion of the device generally indicated at 10 again includes the unijunction transistor 12 in combination with the previously described relaxation oscillator circuit parameters. The load resistor takes the form of a semiconductor diode 38 connected to the output terminal 32 and the entire oscillator circuit is connected between a positive nine volt D.C. source and ground.

Base contact is connected to the emitter 40 of a PNP junction transistor 42, having a base 44 and collector 46. Collector 46 is connected to the negative side of the power supply or ground while base 44 is connected to one side of a resistor 48; the other side of which is likewise connected to the negative side of the power supply. Transistor 42 acts as an amplifier and pulse inverter.

The mechanical timing device 34 includes a generally U-shaped frame 50 rotatably supporting a balance staff 52 upon which is mounted a conventional balance wheel 54. Balance staff 52 is connected to the usual hairspring 56 and the balance wheel receives through a suitable aperture in its rim a small permanent magnet 58.

Magnet 58 is provided at each end with poles to create a vertical flux extending from the top and bottom edges of the balance wheel rim which flux is periodically intercepted by the adjacent windings of a drive coil 60 and pick up or trigger coil 62 positioned below and above the balance wheel rim respectively. Drive coil 60 is connected by way of

leads

64 and 66 across output diode 38 while pickup coil 62 is connected by way of leads 68 and '70 to the emitter and base respectively of amplifier transistor 42.

In operation, when the voltage across capacitor 26 reaches a certain value as determined by the circuit parameters, the unijunction transistor 12 conducts, discharging the capacitor through the drive coil 60. When the drive coil 60 is energized it creates a magnetic field which reacts with the field of permanent magnet 58 in the rim of the balance wheel. This impulses the balance wheel and starts oscillation of the balance system. After capacitor 26 has discharged to a certain level, the unijunction transistor no longer conducts. When the unijunction transistor is not conducting capacitor 26 again begins to charge at a rate determined primarily by resistor 24. As the balance wheel swings under the influence of hairspring 56 the magnet 58 passes the trigger or pickup coil 62 and induces a voltage on that coil. This voltage is fed to the base of transistor 42 which causes this transistor to conduct. When transistor 42 draws current between emitter 40 and collector 46 it lowers the voltage gradient across

contacts

20 and 22 of the unijunction transistor 12. This causes the unijunction transistor to conduct and when this transistor conducts it discharges capacitor 26 through the drive coil 60 and again impulses the balance wheel. In this manner, the frequency of the electronic network is determined by the frequency of the balance wheel rather than by the combination of resistor 24- and capacitor 26. A highly accurate pulse generator is obtained which is not dependent upon the characteristics of the electrical circuit. The electronic oscillator circuit is used for starting and as a fairly accurate secondary pulse source in the event of failure in the mechanical system.

It is apparent that the arrangement of FIGURE 2 can be used as a power source for an electric watch where, instead of taking an output from terminal 32, the output may be that of the watch or clock hands driven in the conventional manner of an electric clock or watch from the balance staff 52. In such a case, the electronic oscillator functions as a simplified and reliable self-starting power circuit for the electric watch.

FIGURE 3 shows a circuit diagram for a modified device constructed in accordance with the present invention with like parts again bearing like reference numerals. The mechanical portions of this embodiment are shown in FIGURES 4-6. The circuit of FIGURE 3 is similar to the electronic circuit portion of the embodiment of FIGURE 2 with the exception of the elimination of output diode 38 and the incorporation of modified drive and trigger coils. In FIGURE 3 the trigger coil indicated by the dash box at 70 is shown as having an inductance 72 and an internal resistance '74. Similarly, the drive coil in- 4 inductance 78 and an internal resistance 30. In some dicated by the dash line box 76 is illustrated as having an instances it may be desirable to provide the output through a coupling capacitor 33 and to provide a bias resistor 35 for the collector of transistor 42.

FIGURES 4 through 6 show a mechanical timer usable with the electronic circuit of FIGURE 3. The mechanical timer, again generally indicated by the reference numeral 34 comprises a balance staff 82 rotatably journalled in suitable supports (not shown). Carried by the balance staff is a conventional hairspring collet 84 coupled in a conventional manner to the hairspring 85 of a conventional electric watch movement. The balance staff may drive the hands of the watch through an index and gear train in a well known manner. Mounted on and rotatable with the balance staff 82 is a generally U-shaped keeper 86 made of soft iron or other suitable material. Balance staff 82 also carries a balance wheel 87 of non-magnetic material such as aluminum formed of two

semi-circular sections

88 and 89. Joined to the ends of semi-circular sections 83 and 39 is an elongated rectangular permanent magnet 91) having a central aperture received over the balance staff 82. Keeper 86, balance wheel 8'7 and permanent magnet are all rotatable with the balance staff 82. The adjacent ends of the balance wheel sections are spaced to receive the opposite ends of the permanent magnet 99 which extend to the outer edges of the balance wheel.

Coils

70 and 76 are of bifilar wire and are simultaneously wound on a common coil form in the shape of a closed generally rectangular loop having short

vertical sides

92 and 94 and longer

horizontal sides

96 and 98. As best seen in FIGURE 5, the longer sides 96 and 93 are both curved in a gentle arc to provide clearance for the balance staff 82. The direction of the windings, i.e., current flow through these coils, in indicated by the arrows 100 in FIGURE 4.

Coils

70 and 76 are provided with

terminals

102 and 104 for connection into the electrical circuit of FIGURE 3.

With reference to the embodiment of FIGURES 3 through 6, the coils are fixed by a suitable support so that the balance wheel is placed such that the coil windings surround the balance wheel but not the shunt 86. This provides shielding for the hairspring connected to collet 84. The

vertical portions

92 and 94 of the coils lie in the air gaps labelled A and B in FIGURE 4.

As the electronic circuitry energizes one of the coils, the current flowing through this coil creates a magnetic field such that it interacts with a magnetic field caused by the permanent magnet 90 in combination with magnetic shunt 86. This interaction causes the balance wheel and shunt to be pushed away from the coil. The interaction between the two fields impulses the balance wheel assembly and therefore starts it oscillating. The circuit of FIG- URE 3 allows only a short momentary pulse in the drive coil and therefore the balance wheel is allowed to pass the coils on its return swing without any impulse to the balance wheel. As the balance wheel completes one full oscillation, the coils are again in the air gaps A and B. This time the movement of the permanent magnet past one of the coils generates a voltage in this coil and therefore triggers the electrical circuit and allows current to flow in the drive coil. Again the interaction between the two magnetic fields imparts momentum to the balance and hairspring combination and thereby sustains the mechanical oscillations.

Referring specifically to FIGURE 3, when the mechanical oscillator is at rest and nine volts DC. is impressed across the power supply terminals, the capacitor 26 charges at a rate determined by resistor 24. The time required for capacitor 26 to attain a voltage of 0.707 9 volts is determined by the time constant of

elements

24 and 26. Also, when the nine volts is applied, this voltage is divided proportionally across resistor 28, unijunction transistor 12 and resistance 80. The ratio of these voltages is determined by the ratio of the resistances associated with each of these elements.

In a properly designed circuit of this type, the majority of the voltage is across the transistor 12. When the voltage across capacitor 26 reaches approximately 70% of the voltage across transistor 12 and resistance 80, transistor 12 exhibits a negative resistance characteristic between emitter 18 and base contact 22. This allows the capacitor to discharge through the emitter and base contact to resistor 80 and drive coil 78. The current passing through coil 78 generates a magnetic field which repels the field of the permanent magnet on the balance wheel, thus imparting momentum to the balance Wheel.

The charge continues to flow from capacitor 26 until the voltage across the capacitor reaches a certain level at which time the transistor cuts off and no longer exhibits a negative resistance characteristic. The time associated with the discharge of capacitor 26 is in the neighborhood of several milliseconds. When the transistor no longer exhibits negative resistance characteristics, capacitor 26 again begins to charge by virtue of the current passing through resistor 24.

As the permanent magnet on the balance wheel swings past the trigger coil 70 it generates a voltage in this coil. This generated voltage is impressed across

terminals

40 and 44 of transistor 42 which forces this transistor to exhibit negative resistance characteristics between its emitter and collector. The resistor turns on and current flows from the nine volt source through resistor 28 and through 42 to ground. The magnitude of the current flowing through these two elements is determined by the voltage generated in the trigger coil and thus the voltage impressed across the

terminals

40 and 44. The current flowing through resistor 28 due to the negative resistance characteristics of the amplifier transistor causes a higher than normal voltage drop across resistor 28 and thus lowers the voltage across unijunction transistor 12 and resistor 80. When this action occurs, the voltage associated with the charge on capacitor 26 becomes a higher percentage of the voltage across the unijunction transistor and the unijunction transistor again exhibits negative resistance characteristics.

It can be seen that with the natural frequency of the electronic oscillator slightly lower than the natural frequency of the balance and hairspring combination, the action of the balance wheel passing the trigger coil causes the electronic oscillator to oscillate at a higher frequency than its natural frequency. Therefore, the electronic oscillator is synchronized with the mechanical oscillator. In this Way, it is possible to make the electronic oscillator oscillate at a frequency determined by the mechanical oscillator with an accuracy which very closely approaches the accuracy of the mechanical oscillator. This is desir able since the accuracy of the electronic oscillator alone is dependent upon temperature variations and voltage variations whereas the mechanical oscillator is not nearly as susceptible to these fluctuations.

It is apparent from the above that the present invention provides a novel self-synchronized oscillator usable either as a time base or as a self-starting power source for an electric clock or watch. A novel feature of the present invention involves the synchronization of a relaxation oscillator by means of a more accurate time delay element, preferably in the form of a watch or a clock balance system. When used as a pulse standard or time base, the output has substantially the accuracy of the mechanical movement.

In every case the synchronization signal is applied to a separate electrode of a unijunction transistor and is completely isolated from the natural control circuit of the relaxation oscillator. This assures reliable self starting and permits operation of the electronic circuit as a secondary oscillator in the event of failure in the mechanical system.

Thus, in addition to providing self-starting, the electrical oscillator provides a secondary oscillatory source which is effective to continue to give fairly accurately spaced output pulses even if something should happen to cause breakdown of the mechanical system. Also provided is a novel arrangement for driving a balance system which substantially increases the overall efiiciency of the unit.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A timing device comprising a relaxation oscillator including a three terminal impedance, a second impedance coupled to a first terminal of said three terminal impedance for controlling the oscillations thereof, and time delay means for feeding a signal from a second terminal to a third terminal of said three terminal impedance.

2. A timing device comprising a. relaxation oscillator including a unijunction transistor having an emitter and a pair of base contacts, means for deriving a repetitive signal from said oscillator, and time delay means for feeding said signal to one of the base contacts of said transistor.

3. A device according to claim 2 wherein said time delay means is a mechanical timer.

4. A device according to claim 3 wherein said time delay means is the balance system of an electric watch.

5. A timing device comprising a unijunction transistor having two base electrodes and a third electrode, means for connecting a power supply across said base electrodes, a capacitor coupled to said third electrode of said transistor, a load impedance for said transistor, and time delay means for feeding a signal from said load impedance to one of said base electrodes of said transistor.

6. A timing device comprising a unijunction transistor having an emitter and two base contacts, means for coupling said transistor to a power supply, an R-C control circuit coupled to said emitter, means for deriving a repetitive signal from the base circuit of said transistor, and time delay means for feeding said signal to one of said base contacts.

7. A timing device comprising a unijunction transistor having an emitter and .a pair of base contacts, a pair of power supply terminals, a resistor coupling said emitter to one of said terminals, a capacitor coupling said emitter to the other of said terminals, a load impedance coupling one of said base contacts to one of said terminals, and time delay means coupling said load impedance to the other of said base contacts.

8. A device according to claim 7 including a pulse inverter in series with said time delay means.

9. A timing device comprising a unijunction transistor having an emitter and two base contacts, positive and negative power supply terminals, a first resistor connected between said emitter and said positive terminal, a capacitor connected between said emitter and said negative terminal, a second resistor connected between one of said base contacts and said positive terminal, a third resistor connected between the other of said base contacts and said negative terminal, and time delay means and a pulse inverter connected in series between said base contacts.

10. A device according to claim 9 including an electrical output terminal coupled to one of said base contacts.

11. A timing device comprising a unijunction transistor relaxation oscillator, a mechanical oscillatory system including impulse and trigger coils, means coupling said impulse coil to one base contact of said transistor, and means coupling said trigger coil to the other base contact of said transistor.

12. A device according to claim 11 including amplifier means coupling said trigger coil to said other base contact.

13. A device according to claim 12 wherein said amplifier means comprises a junction transistor.

14. A timing device comprising a unijunction transistor relaxation oscillator, a mechanical oscillatory system including a balance wheel, magnetic means rotatable with said balance wheel, impulse and trigger coils located adjacent the path of movement of said magnetic means, means coupling said impulse coil to one base contact of said transistor, and means coupling said trigger coil to the other base contact of said transistor.

15. A timing device comprising a unijunction transistor relaxation oscillator, a junction transistor having its output coupled to one base contact of said unijunction transistor, a mechanical oscillatory system including a balance staff and balance wheel, a permanent magnet carried by said balance staff, impulse and trigger coils positioned adjacent the path of movement of said permanent magnet for periodically reacting with the flux from said magnet, means coupling said impulse coil to the other base contact of said unijunction transistor, and

means coupling said trigger coil to the input of said junction transistor.

16. A device according to claim 15 wherein said permanent magnet is mounted transverse to said balance staff and a magnetic shunt is mounted on said balance staff having ends adjacent to but spaced from the ends of said permanent magnet.

17. A device according to claim 1 wherein said three terminal impedance has negative resistance characteristics.

References Cited by the Examiner UNITED STATES PATENTS 3,005,305 10/1961 Thoma 582l 3,026,485 3/1962 Suran 331-108 3,035,183 5/1962 Siebertz et a1 307-88.5 3,074,028 1/1963 Mammano 33l-11l 3,152,295 10/1964 Schebler 318118 20 MILTON O. HIRSHFIELD, Primary Examiner.

JOSEPH A. STRIZAK, Examiner.