US3343015A

US3343015A - Drive means for a timepiece

Info

Publication number: US3343015A
Application number: US455443A
Authority: US
Inventors: Dome Peter
Original assignee: SSIH Management Services SA
Current assignee: SSIH Management Services SA
Priority date: 1964-05-15
Filing date: 1965-05-13
Publication date: 1967-09-19
Anticipated expiration: 1984-09-19
Also published as: CH637464A4; NL6506222A; CH429601A

Description

Sept. 19, 1967 P. DOME 3,343,015

I I DRIVE MEANS FOR A TIMEPIECE Filed May 13, 1965 2 Sheets-Sheet 1 Sept. 19, 1967 P. DOME 3,343,015

DRIVE MEANS FOR A TIMEPIECE Filed May 15, 1965 2 Sheets-Sheet 2 \JL/ \JU" United States Patent 3,343,015 DRIVE MEANS FOR A TIMEPIECE Peter Dome, Onex, Geneva, Switzerland, assignor to Societe Suisse pour llndustrie Horlogere S.A., Geneva, Switzerland Filed May 13, 1965, Ser. No. 455,443

Claims priority, application Switzerland, May 15, 1964,

6,374/ 64 10 Claims. (Cl. 310-84) This invention relates to a device for driving the mechanism of a timepiece in dependence on electrical voltage impulses supplied at contsant frequency.

The device according to the invention comprises a prime-mover-forming toothed wheel, means for constantly subjecting said wheel to a torque of given direction, and an electrodynamic relay energizable by said impulses, said relay including a rocking part having two stable positions, one for each impulse of two successive said impulses and having a pair of abutment fingers alternately engaging the teeth of said wheel upon said part rocking from one of said stable positions to the other, each change of engaging fingers allowing escapement of said wheel by one halfpitch under the action of said torque.

For a better understanding of the invention and to show how it may be carried into effect, the same will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a plan view of an embodiment of the device according to the invention;

FIGURE 2'is a section along II--II of FIGURE 1;

FIGURES 3 and 5 are two explanatory diagrams; and

FIGURES 4 and 6 show two variants of a portion of the device shown in FIGURES l and 2.

The device illustrated in FIGURES 1 and 2 comprises an electrodynamic rocker relay of which the rocking par-t is formed-by a plate 1 rigid with a pin 2 pivotally mounted in a support not shown. On plate 1 are secured four permanent magnets 3 to 6 arranged so as to' form two pairs of poles 3-4 and 5-6, with one on each side of pin 2, oriented parallel to the latter. The stationary part of the relay is formed by a coil 7, in the form of a flattened annulus disposed coaxially with, and parallel to, plate 1 so as to be able to cooperate with magnets 3 to 6. An abutment 8, of magnetic material of low coercive force, limits, in both directions, the angular displacement of the movable part of the relay and maintains this part, by magnetic attraction, in one or other of these two extreme positions when brought there by electrodynamic action.

On the side opposite that cooperating with abutment 8, plate 1 carries two

fingers

9 and 10 arranged on opposite sides of pin 2 and intended to cooperate alternately with a toothed wheel 11 rigid with a pin 12 and forming the prime mover of the mechanism, not shown, of a watch. This wheel 11 is made of electrically conductive material.

The device further comprises a disc 13 rotating about a pin 14 parallel to the pin 12 of toothed wheel 11 and arranged at a distance such from pin 12 that a portion of wheel 11 and a portion of disc 13 come to lie in spaced overlapping relationship. Disc 13 carries, set in at its periphery, four permanent magnets 15 to 18 oriented parallel to pin 14 and arranged so as to form two pairs of poles 1516 and 17-18, which pairs are positioned in facing relationship on opposite sides of pin 14, the north pole of one pair lying opposite the south pole of the other pair and vice versa. The distance separating the two magnets of one pair and the polar area of these magnets are such that the latter simultaneously overlie each one limb of a flattened annulus-shaped coil 19 arranged coaxially with, and parallel to, disc 13 so as to be able to cooperate with magnets 15 to 18. The end 19a of coil 19 is con- Patented Sept. 19, 1967 nected to the collector of a pnp type transistor T of which the emitter is connected to the positive side of a direct voltage source S, the other end 19b of the coil being connected to the negative side of source S through the intermediary of a make and break switch 20. The base of transistor T is connected to the collector of a npn type transistor T which is thus complementary to transistor T the emitter of transistor T being connected to the negative pole of source S. The base of transistor T is connected, on the one hand, to the collector of transistor T through the intermediary of a resistor R and of a capacitor C, and, on the other hand, to the positive side of source S, through the intermediary of the resistor R and of a second resistor R The illustrated device operates as follows:

The closure of contact 20 causes a voltage to be supplied to capacitor C, through the intermediary of coil 19 and of resistor R which is charged with a relatively weak current, thereby causing an increase of the potential difference between the base and emitter of transistor T and consequently an increase of its collector current, and hence of the base current in transistor T and of its collector current. The increase of the voltage drop in the coil 19, due to the increase of this latter current, causes a fresh increase of the base and collector currents of transistors T and T and so forth until the astable multivibrator circuit formed by coil 19 and of the complementary transistors T and T changes over through this postive feedback to the conductive state. Coil 19 being then energized by current from source S, the interaction between this current and the magnets carried by disc 13, gives rise to a Laplace force that causes disc 13 to rotate, i.e. causes the rotor of the DC. motor, formed by coil 19 and disc 13 with its magnets 15 to 18, to start.

The current impulse in coil 19 is interrupted by the change-over of the astable circuit to its blocked state. This is due to the positive feedback brought about by the reduction in potential difference between the base and emitter oftransistor T due to the discharge of capacitor C through transistor T resistor R and the emitter-base diode of transistor T However, once rotation of the rotor has been initiated, the changeover of the astable multivibrator circuit from one to the other of its two states is carried out by means of the voltage induced in coil 19, thus enabling repetition of the current impulses in the coil and consequently rotation of the rotor. In this connection, when the voltage induced in the coil is such that it gives rise to an increase of the potential differ Foucault currents are induced therein by the variations of the magnetic flux clue to the passage of magnets 15 to 18. The interaction between these Foucault currents and of the magnets further gives rise to a Laplace force tending to drive wheel 11. Supposing the direction of rotation of disc 13 to be that indicated by arrow 21, wheel 11 is then subjected to a torque constantly tending it to 1 rotate in the direction indicated by arrow 22. The wheel will not rotate because it is locked through its tooth 11a bearing against the stop finger 10 of the bistable electrodynamic relay.

Supposing now that coil 7 of the relay is connected to a source supplying electric voltage impulses of constant frequency, e.g. a source supplying bidirectional rectangular voltage impulses 27 at a frequency proportional to that of the regulating member of the timepiece of which the described device is to drive the mechanism. One of the first two impulses will thus be that which will cause the relay to change-over to its stable position other than that illustrated in the drawing by virtue of the Laplace force resulting from the interaction between the magnets 3 to 6 carried by plate 1 and the current flowing through coil 7. The change-over of the relay will in effect amount to displacement of its rocking part from one position to the other, and, in this particular instance to anti-clockwise pivotal movement of plate 1 about pin 2 until it comes to rest against abutment 8. This will, by way of consequence, cause the release of finger from the toothing of wheel 11 and the engagement therewith of finger 9. This will enable wheel 11 to advance by half a pitch in the direction of arrow 22, under the action of the abovementioned torque, since, as soon as finger 10 releases tooth 11a nothing will oppose movement of the wheel until tooth 11b will abut against finger 9 which has in the meantime moved into engagement with the toothing (shown partially in phantom lines in FIGURE 1). The pitch of wheel 11, the distance between

fingers

9 and 10 and the oscillatory movement of plate 1 are so arranged that the advance of wheel 11 at each change-over of the relay will amount to half a pitch. At the next change-over of the relay which will be due to the next impulse of opposite sign and after which the relay will resume the position shown in phantom lines, the wheel will again advance to the extent of a half-pitch and so on: at each impulse sent to coil 7 there will be a change-over of the relay and an advance of wheel 11 by one half-pitch. The wheel 11, which forms the prime mover of a time piece mechanism, will thus be given with an intermittent movement at a frequency which is constant and equal to the impulse frequency which is itself proportional to that of the regulating means (timing-device) As will be appreciated from the above, the device only requires very little power. This is due to the design of the driving and locking means and to their separation. The electrodynamic rocking relay, which acts as the locking means and which can be of very reduced size, only requires enough power to cause it to rock from one to the other of its stable states, i.e. the power that is necessary to overcome the magnetic attraction of abutment 8 and friction. This power can be very slight while ensuring an amply sufficient torque by virtue of the Laplace forces that are brought into action and that remain practically constant over the entire path travelled by he movable part of the relay, which path can also be very short. The very small size of the relay further renders the latter sensitive only to a very slight extent to the external disturbances to which a worn watch may be subjected.

As regards the DC. motor formed by disc 13 and coil 19, it suffices that its rotor, formed by disc 13, rotates continuously without stopping, the rotor being able to rotate at any speed, this speed being variable. This greatly simplifies its design and makes it possible to select a high efliciency rate of operation and consequently to store sufficient energy while preserving a small overall size.

In the device described by way of example, the torque to which is submitted wheel 11 forming the prime mover of the mechanism, is provided by the interaction between the Foucault currents induced in the wheel by the two pair of magnetic poles carried by a disc forming the rotor of a DC. motor. By virtue of the arrangement of magnets 15 to 18, rotor 13 will always rotate in the direction indicated by arrow 21, i.e. in a direction such as to ensure that the resulting torque will cause rotation of wheel 11 in the direction indicated by arrow 22. Even if the rotor were to start in a direction opposite to that of arrow 21, the starting direction being dependent on the position of magnets 15 to 18 in relation to coil 19, it could not continue so to rotate because of the shape of the voltage induced in coil 19 each time the magnets 15 to 18 come to pass opposite the latter.

The induced voltage will only have the shape that is necessary to synchronize the oscillations of the astable multivibrator circuit with its own frequency if rotor 13 rotates in the direction of arrow 21. It is only in this instance that the positive half-cycles of the induced voltage, which is here capable of causing the circuit to changeover to its conductive state, will have a sufficient amplitude as shown by FIGURE 3 (twice as large as the negative half-cycles) The device could by way of modification comprise only one of the two pairs of poles, i.e. either 15 and 16 or 17 and 18. The shape of the induced voltage would then be the same as that shown in FIGURE 3 but its amplitude would be halved.

Safety as regards driving the rotor 13 in the desired direction can yet be increased by differently sizing the two magnets forming one pair of poles. When one of the two magnets is dimensioned so that its polar surface will simultaneously overlie both limbs of coil 19, the amplitude of one of the half-cycles of the voltage induced in the coil 19 will be four times larger than that of the other halfcycle. Thus, by dimensioning the

magnets

16 and 17 as shown in FIGURE 4, there is obtained, when rotor 13 rotates in the direction of arrow 21, an induced voltage having the waveform shown in FIGURE 5.

The torque acting on wheel 11 could be obtained in a manner different from that described above. It could, for example, be obtained by using a rotating field (Ferraris). FIGURE 6 shows such a variant. Wheel 11 successively passes through the air gap of each of two electro-

magnets

23 and 24 whose

windings

25 and 26 are supplied by outof-phase, e.g. alternating voltages having the same frequency. The two out-of-phase magnetic fields induce in wheel 11 out-of-phase Foucault currents which give rise to a rotating field, of desired direction, which transmits the necessary torque to the wheel 11. The energy consumption may be reduced by only energising the electromagnets while the relay is rocking. In this case the feeding of voltage impulses to

windings

25 and 26 must take place at least while feeding impulses to coil 7.

The torque acting on wheel 11 could also be obtained by pneumatic means. Thus, a rotatably driven disc could be bladed in order constantly to subject wheel 11 to an air blowing action.

The bidirectional voltage impulse source to which coil 7 of the electrodynamic relay has to be connected could also be a source of unidirectional impulses. In this case, coil 7 would have to be replaced by two oppositely mounted coils each connected to an impulse source and cooperating with one of the two pairs of poles 3-4 and 5-6. Further, the stationary part of the relay :could be formed by magnets and the rocking part by the coil or coils which would be secured to plate 1.

I claim:

1. A device for driving the mechanism of a timepiece in dependence on electric voltage impulses supplied at constant frequency, which comprises a prime-mover-forming toothed wheel, means for constantly subjecting said wheel to a torque of given direction, and an electrodynamic relay energizable by said impulses, said relay including a rocking part having two stable positions, one for each impulse of two successive said impulses and having a pair of abutment fingers alternately engaging the teeth of said wheel upon said part rocking from one of said stable positions to the other, each change of engaging fingers allowing escapement of said wheel by one half-pitch under the action of said torque.

2. A device according to claim 1, wherein said toothed wheel is made of electrically conductive material and said means for constantly subjecting said wheel to a torque of given direction includes a rotary disc axially spaced from and parallel to said toothed wheel, with said disc and wheel in partly overlapping relationship, and a pair of magnetic poles formed by two permanent magnets mounted on the periphery of said disc, thereby to induce Foucault currents in said Wheel and to produce said torque.

3. A device according to claim 1, wherein said disc carries two pairs of poles arranged facing one another on opposite sides of the axis of rotation of said disc with the north pole of one pair disposed facing the south pole of the other pair and vice versa.

4. A device according to claim 2, wherein said disc forms the rotor of a DC. motor having an armature formed by a flattened annulus-shaped coil having two limbs and disposed coaxially with, and parallel to, said disc, the distance between the two magnets forming said pair of poles and their polar surfaces being such as simultaneously to be able each to overlie one limb of said coil.

5. A device according to claim 4, wherein the polar surface of one of the two magnets forming said pair of poles is such as simultaneously to be able to overlie both limbs of said coil.

6. A device according to claim 4, wherein said means for constantly subjecting said wheel to a torque of given direction includes an astable multivibrator circuit incorporating said coil.

7. A device according to claim 6, wherein said astable multivibrator circuit includes a direct voltage source and two complementary transistors each having a base, an emitter and a collector, one of said transistors having the collector and emitter thereof connected in series with said coil and with said direct voltage source and the base thereof connected to the collector of the other of said transistors, said other transistor having the emitter thereof connected to one side of said direct voltage source and the base thereof connected to the collector of said one transistor through the intermediary of a first resist-or and of a capacitor in series and to the opposite side of said direct voltage source through the intermediary of said first resistor and a second resistor in series.

8. A device according to claim 1, wherein said toothed wheel is made of electrically conductive material and said means for constantly subjecting said wheel to a torque of given direction includes electromagnets each having an air gap through which extends the peripheral portion of said wheel, said magnets being successively energizable by out-of-phase alternating voltages to induce in said wheel out-of-phase Foucault currents for setting up a rotating field producing said field.

9. A device according to claim 1, wherein said relay includes, in addition to said rocking part, a stationary part, one of said parts having a coil and the other of said parts having a pair of magnetic poles, said coil and said poles being so arranged that, depending on the polarity of an electric impulse fed to the coil, the rocking part changes over to one or other of said stable positions.

10. A device according to claim 1, wherein said relay includes, in addition to said rocking part, a stationary part, one of said parts having two coils and the other of said parts having two pairs of magnetic poles, one for each coil, said coils and said poles being 30 arranged that, depending on whether an electrical impulse is fed to one or other of said coils, the rocking part changes over to one or other of said stable positions.

References Cited UNITED STATES PATENTS 2,864,018 12/1958 Aeschrnann 310-163 2,900,021 8/1959 Rechtmyer 74l.5 2,988,868 6/1961 Lovet 310- 2,994,023 7/1961 Devol 318254 3,168,690 2/1965 Lanet 318138 3,211,933 10/1965 Kohlhagen 310164 MILTON O. HIRSHFIELD, Primary Examiner.

I. D. MILLER, Assistant Examiner.

Claims

1. A DEVICE FOR DRIVING THE MECHANISM OF A TIMEPIECE IN DEPENDENCE ON ELECTRIC VOLTAGE IMPULSES SUPPLIED AT CONSTANT FREQUENCY, WHICH COMPRISES A PRIME-MOVER-FORMING TOOTHED WHEEL, MEANS FOR CONSTANTLY SUBJECTING SAID WHEEL TO A TORQUE OF GIVEN DIRECTION, AND AN ELECTRODYNAMIC RELAY ENERGIZABLE BY SAID IMPULSES, SAID RELAY INCLUDING A ROCKING PART HAVING TWO STABLE POSITIONS, ONE FOR EACH IMPULSE OF TWO SUCCESSIVE SAID IMPULSES AND HAVING A PAIR OF ABUTMENT FINGERS ALTERNATELY ENGAGING THE TEETH OF SAID WHEEL UPON SAID PART ROCKING FROM ONEOF SAID STABLE POSITIONS TO THE OTHER, EACH CHANGE OF ENGAGING FINGERS ALLOWING ESCAPEMENT OF SAID WHEEL BY ONE HALF-PITCH UNDER THE ACTION OF SAID TORQUE.