US3196603A - Magnetic movement system for electronic or electric clocks - Google Patents

Description

July 27, 1965 w, cH 3,196,603

MAGNETIC MOVEMENT SYSTEM FOR ELECTRONIC OR ELECTRIC CLOCKS Filed Jan. 15, 1964 FIG. 1

FIG. 2

9 FIG. 3

1 (W WV 4 4 7/6 United States Patent 3,196,693 MAGNETTC MOVEMENT SYSTEM FUR ELEC- TRONTC UR ELECTRTQ CHECKS Robert Walter Reich, Merzhauserstr. 143, Freiburg im Breisgau, Germany Filed Jan. 15, 1964, Ser. No. 337,842 1 Claim. (Cl. 58-28) Great numbers of electrical or electronic clock driving systems are already known. Some of them have been reduced to practice, and some have merely been proposed. For example, a number of models have been made of clocks with a coil system on the balance wheel, which oscillates through a magnetic field. The disadvantage of this driving system is, however, that the supplying of current to the coil on the balance wheel presents great dificulties. These driving systems have the additional disadvantage that they operate with resilient contacts and the balance wheel itself does not undergo free oscillation. The resultant inaccuracies of motion and the contact wear make it appear that this system is not one that is to be preferred. However, driving systems have also been reduced to practice which have iron in the balance wheel, so that the balance wheel is driven by the iron spoke by attraction to the poles of electromagnets. This system has the very great disadvantage that it is sensitive to magnetic fields, so that no final solution can be seen in this method, either. The best prospect for practical usability over a relatively long period of time is offered by magnetic driving systems which are constructed with permanent magnets as spokes, or with small permanent magnets disposed the direction of the axis of the balance wheel. Unfortunately, however, this arrangement has disadvantages which are very hard to remedy. L1 small movements, for example, such as those in pocket watches and wrist watches, the works can be made only of steel. Even steel screws must be used. The magnets stick to these steel parts and interfere with the harmonic oscillation. in many cases breakdowns and disturbances may even occur. The arrangement of the coils which, by cooperating with permanent magnets, produce and transmit the driving impulse offers considerable difficulties. The magnets may have only small dimensions, and accordingy the coils must be made large so as to be able to produce a sut'iiciently great driving force. In the case of miniature movements, such as those of wrist watches, etc., such coils cannot be housed in them without changing the size of the watch. Quite a few attempts have therefore been made to create systems using shaped coils, toroidal rings, and coils with premagnetized iron cores. But since, precisely in the case of miniature movements, the current consumption is the most important factor, on account of the space required by the necessary batteries, most systems cannot be reduced to practice, from the very outset. The current consumption becomes so great that it is impossible to achieve an adequate operating time for a watch movement.

The invention aims at a design of the magnetic driving system which operates with a higher efiiciency and yet requires naught but coil arrangements and sizes which can be housed even in wrist watches of the sizes customary up to now.

The invention is more specifically described in the drawing in which:

FIGURE 1 is a top sectional view of a magnetic drive system in accordance with this invention;

FIGURE 2 is a side sectional View of the magnetic drive system of FIGURE 1; and

FIGURE 3 is a top view of a modification of the magnetic drive system of FlGURE 1.

Referring to the drawing, FIGURES l and 2 show a design of a magnetic driving system for electrical or electronic timepieces in accordance with this invention which is characterized in that the balance wheel 1 itself is arranged, with a permanent magnet serving as a spoke 2, within a solenoid coil 3. The interior chamber of the solenoid coil is of such a size as is necessary to enable the balance wheel to oscillate just freely within the cavity. The coil is designed as a solenoid and has a hole in the middle to accommodate the shaft of the balance wheel. The windings are accordingly laid on around a boss /8 in the molded plastic body of the coil, the shaft being brought out through the said boss. To simplify assembly, it is also possible to produce two coil halves with the same dimensions and to push them on from the side after the balance wheel is assembled, and then fasten them together either to the watch block or through the coil body. In other words, a quadrangular coi body is thus produced, having an interior chamber corresponding to the diameter and the thickness of the balance wheel disc. The hairspring 6 is best arranged outside of the coil and fastened in a known manner with adjuster, etc. The advantage of such an arrangement lies in the fact that, as it is known, the magnetic field within a coil is several times stronger than outside it. Furthermore, the lines of force within the coil run strictly parallel. The maximum torque is exerted on the permanent magnet when the latter is at an angle of to the coil axis. It is expedient, therefore, to locate the reversal point or" the balance wheel at this an le of 90. The efficiency of such an arrangement is several times greater than that of any other possible coil arrangement. The overall height needs to be only very slight, since a complete utilization of to magnetic field takes place. Such systems can, therefore, be housed even in very small ladies wrist watches. Due to the extraordinarily high elliciency, the battery loading is very slight and the result is a substantially longer running time than in all previously known arrangements. To increase the etficiency it is furthermore possible additionally to place around the coil a fiat iron ring 9 having the same height as the balance wheel disc and being a few tenths of a millimeter larger than the balance wheel disc. This does not result in a toroid coil; instead, it is an iron core, which, as usual, can be placed around a solenoid coil. The lines of force emerge as usual from the iron core and join outside of the coil. Since the bal ance wheel oscillates quite freely inside the coil, disturbances of motion by magnetic fields or by steel parts outside the interior chamber of the coil cannot occur. The same arrangement can be selected for the design of an electrically or electronically controlled timepiece winding mechanism by making the coil and the permanent ma net correspondingly larger and using a spiral spring equivalent to the hairspring as the mainspring for the clockwork. Comparative tests have shown that, for the same current consumption, the running time of the mechanism is several times greater. Using the same amount of space hitherto occupied for the magnetic system used for electrical clock winding systems, coils and a permanent magnet can be installed which permit the running time to be ten times longer.

The driving system can be controlled in a prior-art manner by contacts or by electronic circuits using transistors, zener diodes, magnetic field-sensitive resistance, tunnel diodes, etc. Since, when the reversal point of the balance wheel is at 90 to the coil axis, only one impulse may be transmitted each time a full swing is made (because a repulsion would take place in the other direction of swing, or an attraction ii repulsion is used for the drive), the current consumption, in comparison with other driving systems, is again reduced by one half. Contact arrangements can be very easily made such that a contact takes place only when contacts are closed on the one side. Precise adjustment is unnecessary in this case,

3 since a precise angle of 98 is not important. Contact rub of 15 to 29 has no effect on the motion or" the balance wheel. For example, the contacts can be arranged so that only one catch is provided on the balance wheel itself, which applies a contact spring, which is fastened on the block, to two contact pins, one of which consists of insulating material. it is also possible, however, to design the same magnetic driving system for operation with two alternating driving impulses for each full cycle. For a design such as this, one catch and one or two contact springs are in like manner provided, along with cooperating contacts as in the familiar polarityreversing switch. The electronic control can also be designed for either one contact for each full cycle or two alternating contacts for each full cycle. The contact itself in this case serves only to trigger a blocked oscillater, for example, which emits an opposite current impulse on each operation. Multivibrators or trigger circuits are also suitable for driving impulses of this kind. For completely contactless electronic control, a free-swinging oscillator is used as a blocked oscillator consisting of an errciter coil 5 and a driving coil 4, using square-wave impulses which are controlled as to duration in such a manner that the alternate impulse approximately coincides with the reversal point of the balance wheel. Since, as already explained, the point of operation of the circuit is not critical and since the angular position of the permanent magnet at which the driving impulse occurs is of no importance to the transmission of the driving impulse, changes in temperature, which otherwise would modify the oscillation parameters of the electronic circuit, can not affect the precision of movement. The permanent magnet used as a spoke in the balance wheel is drawn each time into the parallel interior field of the coil. To prevent sensitivity to voltage variations it is eX- pedient to use a zener diode in the circuit of the driving coil. One the basis of my own data and suggestions, a zener diode was made with a zener voltage of 0.7 volt, making use of the swell voltage. The zener diode circuit is so designed that, even at the lowest battery voltage, the driving voltage of 0.7 volt remains effective beyond the knee voltage of the transistor circuit. On self-winding clock systems using this magnetic driving system it was found, for example, that normal moving-armature winders were still able to operate on batteries having a short-circuit output of only 1.8 amperes. Nevertheless, in addition to the improved eihciency, self-winding clock systems using permanent magnets in the solenoid according to the invention were still able to operate on batteries with a short-circuit output of only 0.5 ampere. By this fact alone, the running time of the clock is more than two to three times the running time of a moving armature winder.

A number of further advantages in design are offered for balance-wheel driven timepieces. For example, steelspring stepping mechanisms and magnetic detents can be used, since these parts are placed outside of the actual driving system. in this manner, very elegant designs for clock drives are possible, which are furthermore simple, reliable in operation and inexpensive.

If encapsulated, careless coils are used, a thickness of 1 mm. on each side of the balance wheel disk can be achieved, so that the total overall height of the system need not exceed 4 millimeters. This overall height corresponds approximately to that rendered necessary, in any case, by the use of batteries.

The driving system of the invention is outstandingly suited for magnetic shielding so as to eliminate completely the effect of iron or magnetic fields. To shield it, a seamless iron ring 9 made of soft iron is Wrapped around the coil. If this ring is precisely centered, a circuit is created for the lines of force, i.e., all the lines of force from the permanent magnet are joined through this iron ring. It is expedient, therefore, to make this iron ring at least as high as the magnet is thick. In this manner, magnetic lines of force cannot emerge from the driving system.

in cases in which it is more advantageous to locate the permanent magnet on the outside and have a coil rotate inside of it, the driving system of the invention is easy to reverse. A special magnet is used, Which has the shape of a rectangular solenoid coil, and inside of it a shaped coil matching the cavity of the magnet is made to rotate. For many kinds of timepiece, this sort of arrangement may offer still other special advantages.

1 claim:

In an electric clock comprising a magnetic drive system and an electric circuit associated with a source of energy for energizing said system, an improved magnetic drive system which comprises: a solenoid coil comprising a generally cubically shaped coil body provided with an interior chamber enclosed by top and bottom Walls and two opposite side walls; a rotatable shaft extending through said top and bottom walls and said chamber; a balance wheel provided with a magnetized spoke mounted on said shaft within said chamber, the relative dimensions of said balance wheel and said chamber being such as to permit said balanced Wheel to oscillate freely and uninhibited in said chamber; windings in said coil body surrounding said shaft, and an iron ring of substantially the same thickness as said balance wheel provided around the sidewalls of said coil body.

References Cited by the Examiner UNITED STATES PATENTS LEO SMILOW, Primary Examiner.

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