US3418503A - Oscillating motor for electric clock - Google Patents

Description

Dec. 24, 1968 R. SIEFERT ET AL 3,418,503

OSCILLATING MOTOR FOR ELECTRIC CLOCK Filed Sept. '7, 1965 2 Sheets-Sheet 1 A "Q b I Q La. u.

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OSCILLATING MOTOR FOR ELECTRIC CLOCK Filed Sept. 7, 1965 v 2 Sheets-Sheet 2 QIIF FIG. 5

United States Patent OSCILLATING MOTOR FQR ELECTRIC CLOCK Roland Siefert and Eberhard Schafer, Bad Durrheim,

Germany, assignors to Kienzle Uhrenfabriken G.m.b.H.,

Schwenningen am Neckar, Germany, a limited-liability company of Germany Filed Sept. 7, 1965, Ser. No. 485,474 2 Claims. (Cl. 310-39) ABSTRACT OF THE DISCLOSURE An electrically driven oscillator for a timepiece wherein a driven oscillatory magnet actuates a control leaf switch for a coil cooperating with the magnet. The switch is biased to open position but has detaining means to keep the contacts close together.

This invention relates to an electric timepiece having a directly driven oscillatory member whose drive is controlled by a contact-type switch.

Timepieces are known in which a contact switch is actuated by a magnetic field of a permanent magnet on the oscillatory system. By means of this switch the electrical circuit for the adjacent timepieces is closed as in German Patents 888,829 and 881,327.

Other magnetically sensitive contact switch systems are shown in French Patent No. 70,016 and German published application 1,163,254.

All the known arrangements have drawbacks that are avoided in the features of combinations and elements of the present invention.

In the first mentioned forms of the prior art the control is not for a clocks own oscillatory system but for the nonpertinent use of controlling adjacent clocks. In the French patent, wherein a transistor is used with a switch between the base and emitter, the number of parts is excessive and the timepiece is greatly susceptible to variations in temperature and applied voltage.

In the mentioned German published application a magnetically actuated contact switch in the circuit of an impulse coil in series with a voltage source is controlled by a permanent magnet. That arrangement is not functionally satisfactory because the switch and coil are mounted near one another on the same wheel in the same orbit about the balance wheel axis. In this arrangement, a half swing results from a current flow through the impulse coil, if the coil has already at least partially swung past the magnet. If both magnetic fields repel each other in this system there is a mere impulse instead of a half swing. For the other half swing the switch becomes closed, if the coil is still situated ahead of the magnet. In the case of the above mentioned repulsion of the magnetic fields, there follows a pronounced suppression of the oscillation, or at least no driving force for the half swing.

In contrast, the present invention assures an objectionfree drive, normally in both directions of swing. The invention includes a directly driven oscillatory system, suitably composed of a balance wheel and hair spring. A permanent magnet on the balance cooperates with a periodically excited coil and, also actuates a magnetically sensitive contact switch. The switch itself contains no magnet and is so constructed that only as small as possible an amount of flux flows for contact closure. Therefore the stray field of the permanent magnet of the oscillatory system suffices for operating the contact switch. The

switch is not so located that it lies in the air gap of the permanent magnetic circuit, but is alfected only by the field in the edge portion of the latter.

The influence on the balance system having a permanent magnet by the magnetically operated contact switch is therefore reduced to a minimum. The isochronic characteristics of a timepiece having this balance system is substantially unaffected by the switch.

The arrangement of the permanent magnet, the coil and magnetically sensitive contact switch is so chosen that an impulse is produced in both swinging directions by the control. This is accomplished owing to the fact that the moving part of the oscillator in nullage is perpendicular to a common plane of the oscillatory axis, the impulse or drive coil and the magnetically sensitive contact switch.

Furthermore the switch is so formed that its instants of closure and opening are fixed relative to the duration of oscillator swing, and according to the geometry of the coil and magnet, the resulting field strength values show a definite relationship to each other during build-up and decay.

Therefore, by means of adjusting the distance between the switch and path of the magnet, it is possible to attain a distance of the switch from the path so as to affect the instants of switch closure and opening, and hence duration of driving impulse, so as to make the influence of variation the driving voltage or current on the amplitude of swing a negligible amount.

The impulse system is composed in known manner of an impulse coil which is periodically excited by an impulse current and one or two permanent magnets which form, with a soft iron part, a magnetic circuit. In the air gap of this magnetic circuit, at nullage of the system, is a fixed impulse coil. The contact switch is situated radially outer from the air gap directly near the coil, whereby the magnetic field, during the flow of current through the coil can, in cooperation with the field of the permanent magnet, assist in action upon the switch.

The flux of the coil must naturally be as small as possible at the switch, so that with decaying flux the switch can open again.

The switch consists of a glass, plastic or similar envelope in which are mounted fixed and springy switch members respectively having little plates or leaves of nickeliron alloy. The desired predetermined contact-closing delay is obtained by the addition of oil of suitable viscosi- -ty into the envelope. The two contact leaves are mounted on a common base so that a simple adjustment of the switch is possible before the envelope is put on. The contact points or surfaces are provided with bonded gold plate. One of the contacts may be provided with a contact disc or point while the other is fashioned with a smooth surface contact area. The leaves or members are bent at right angles at their ends so that the bent free ends serve as armatures operable under magnetization by an external field. One of the members or leaves is springy and though, biased to opening position, is pre-stressed toward closing position to produce increased delay in the closing and for an objection-free opening of the switch. The springy member is mechanically pre-stressed a distance toward closing by about two thirds of its normal springy movement. The distance or air space between the contact members is several tenths of a millimeter and is considerably greater than that present in commercial reed switches.

In the invention the switch is so designed and the permanent magnet so dimensioned that for amplitudes too large, the time for closure of the switch is greater than the period necessary for the magnet to effect closure of the switch as the magnets swing past it. This is because large amplitudes mean fast motion at nullage. When the amplitude diminishes to normal, that is, when the speed of the magnet past the switch is' not excessive, closure of the switch can be accomplished.

This condition is enabled by a proper relationship among the variables: Strength of permanent magnet, the degree to which the leaf of the switch is prestressed, the viscosity of the oil in the switch, the working proximity of the drive coil to the magnet, and the magnetic sensi tivity or permeability of the nickel-iron switch members.

While there are pendulum drives known that give an impulse to both swings, they are not really dependent on the amount of swing amplitude. Others which are responsive to amplitude require energy consuming engagement of teeth and a prong and are complicated by the requirement of unusual magnet shape.

The present invention provides a clock oscillator that utilizes energy in a most efficient manner, without disturbance of accuracy, through making the period of impulse dependent on the amplitude of swing, or rather the speed at nullage. Excessive speeds can cause a skipping of an impulse. Furthermore the clock is self starting due to a very long acting impulse when the usual source of current is first connected. It is desirable that all of the above mentioned variables be so chosen that at amplitudes of more than 280 the switch does not close.

In the drawing:

FIG. 1 shows a curve indicating the dependence of amplitude on time as the oscillatory system is started from rest.

FIGS. 2a, 2b, 2c and 2d show the varying impulse phases of the driving impulses at different amplitudes of swing.

FIGS. 3 and 4 show, schematically, the arrangement of an oscillatory body, drive coil, permanent magnet and a magnetically actuated switch.

FIGS. 5 and 6 show details of construction of the switch of FIGS. 3 and 4.

If at time T= a battery B is connected into a system as shown in FIGS. 3 and 4, the impulses from the coil 3, acting on magnets 1a, set the system in mechanical oscillation of increasing amplitude. The amplitude gradually increases to a value phi shown at T3 in FIG. 1 Where even then the closing of switch 2 results as the magnets 1a swing past the switch. This amplitude is exceeded for a short time and then falls, due to the damping of the system, again to the predetermined limiting amplitude because at excessive amplitude the system swings too fast to operate the switch, as explained later. The system then fluctuates about this limiting amplitude of swing, which may be 280 as a suitable example.

FIGS. 2a, 2b, 2c and 2d show impulse characteristics with respect to the different amplitudes with the sine wave curve depicting the induced voltage in the drive or impulse coil due to the permanent magnet, and the rectangular curve of the voltage in the coil at contact closure.

In FIG. 2a there is shown the position of the impulses at time T When the permanent magnet assumes a definite position before nullage with respect to the impulse coil, the magnetically sensitive switch is operated by the permanent magnet. The switch has a closing contact time t which is so chosen that the imparted impulse due to the coil occurs shortly after nullage. When the flux from the permanent magnet aflecting the switch falls below the limiting operative value for the switch the switch opens. The position of the induced voltage, when the flux build up and flux decay are attained, are shown at 11 and 12 respectively.

In FIG. 2b the position of impulse at time T is shown for a greater amplitude of swing. Since the duration between time points of attaining flux build-up and flux decay depends on speed when the system passes through nullage,

as the amplitude and speed increase, the duration of the drive impulse becomes shorter.

FIG. 2c shows the impulse phase position at times T T and T such as for an amplitude phi. This swing amplitude, phi, represents the limiting amplitude at which there is barely a making of contact; the duration between the attainment of build-up and decay of flux is here approximately equal to the closing time t for the switch.

In FIG. 2d is shown the induction impulse for the time T and T In this case no flow of current through the drive or impulse coil occurs. That is to say there is here no closure of the switch since the time period for closure of the switch is greater than the period of build-up and decay of flux. In other words the magnet, swinging through this excessively great amplitude, travels so fast past the switch that the latter cannot close.

FIG. 3 is a schematic side view of the oscillatory system at nullage. The balance with side pieces is indicated generally by the numeral 1, and upon the balance are mounted two permanent magnets Ia with an air gap therebetween the pivot portion or hub 101 serving to complete the magnetic circuit in a suitable manner.

At nullage the impulse or drive coil 3 lies in the air gap, and close by to the impulse coil 3 is a stationary magnetically sensitive contact switch 2. The whole combination is so arranged that at nullage the axis of the switch, the coil axis and the permanent magnet all lie in a radial plane from the balance axis, as is clearly shown in FIG. 3. The switch is at an adjustable distance a from the magnet. In FIG. 3 different positions of the balance, or rather the side pieces thereof, are shown for the instant of contact during various maximum amplitudes of swing. The position 5 in FIG. 3 for contact closure corresponds to that in FIG. 2a, i.e. shortly after nullage, whereby the contacts remain closed over the angular movement a. Corresponding to FIG. 3a the closure is somewhat more past nullage, as in position 4, and the closure endures over the angle The flux from the magnet diminishes as the latter swings sufficiently past the switch, and the switch opens about the time the balance reaches position 6.

In FIGS. 5 and 6, the construction of the contact switch is shown in detail, the two contact members being mounted on a common base or in a socket 7. One of the contact halves 8 is fixed on the socket and carries at its outer or free end a tiny plate 9 composed of a nickel-iron alloy, the other little plate 13 is mounted on a movable spring leaf, and as shown, is pretensioned. Both plates 9 and 13 are provided with an exterior coating of bonded gold. Both little plates are bent at right angles so their free ends run parallel to excited field shown by the arrow 14 for acting on them. For mechanically prestressing the movable contact lamina a stop 15 is used. An envelope 16 over the contact device is secured to the socket 7 and the envelope suitably filled with oil to effect a time-delay for switch closure.

.The invention claimed is:

1. For an electrically driven timepiece, an oscillatory drive device having an inertia member mounted for swinging about fixed axis and biased to assume a nullage position, a permanent magnet fast on the inertia member, a stationary drive coil for inductive cooperation with the magnet for applying a force to the member to swing the latter, a source of current for the coil, a stationary timedelayed magnetically actuated leaf switch interposed between the source and coil in the path of the stray field of the magnet, the axis, magnet, coil and switch being coplanar at nullage, said switch having a contact member and a contact leaf cooperating therewith and a stop member holding the leaf in a stressed condition toward the contact member, the switch being biased to open but closable under the influence of said field, said switch being located far enough from the path of the magnet to be in a sufficiently weak portion of the stray field when the magnet comes closest to the switch so that the switch will not close when the substantially predetermined speed of 6 the member through nullage for an attendant predeter- FOREIGN PATENTS mined swing amplitude is exceeded. 1 389 952 1/1965 France 2. In the combination as claimed in claim 1, said switch 1396:879 3/1965 France having a socket-like base, carrying the contact member and the contact leaf, the stop member being L-shaped and 5 J D MILLER Primal), Examineh mounted on the base and transversely bearing against the l f D. F. DUGGAN, Assistant Examiner.

References Cited UNITED STATES PATENTS 2,833,943 5/1958 Anthony 310-32 10 823;3 5 07

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