US3577874A

US3577874A - Electric clocks with magnetic drives

Info

Publication number: US3577874A
Application number: US738977A
Authority: US
Inventors: August Mutter
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-06-27
Filing date: 1968-06-21
Publication date: 1971-05-11
Anticipated expiration: 1988-05-11
Also published as: DE1673670A1; FR1571040A; CH911368A4; DE1673670B2; CH505417A

Abstract

An electric clock employs a mechanical oscillator which is driven at its natural frequency and which contains a magnetic drive for driving the clock. The magnetic drive contains a nonmagnetized ferromagnetic pole spider, which on its circumference has disposed a single ring of magnetic poles. The poles of the magnetic drive which interact with the spider poles are assymmetrically positioned with respect to poles on opposite sides of the circumference of the pole spider.

Description

United States Patent Inventor August Mutter Schwenningen (Neckar), Germany Appl. No. 738,977 Filed June 21, 1968 Patented May 11, 1971 Assignee Muller-Schlenker Schwenningen (Neckar), Germany Priority June 27, 1967 Germany ELECTRIC CLOCKS WITH MAGNETIC DRIVES 13 Claims, 10 Drawing Figs.

US. Cl 58/23, 310/36 Int. Cl G04c 3/00 Field of Search 58/23, 23 (D), 1 16,23 (V), 116 (M); 310/36, 46, 152, 156; 74/25, 1.5, 126

[56] References Cited UNITED STATES PATENTS 3,208,287 9/ I965 lshikawa et al.

Primary Examiner-Richard B. Wilkinson Assistant ExaminerEdith C. Simmons Attorney-Craig, Antonelli, Stewart & Hill ABSTRACT: An electric clock employs a mechanical oscilla= tor which is driven at its natural frequency and which contains a magnetic drive for driving the clock. The magnetic drive contains a nonmagnetized ferromagnetic pole spider, which on its circumference has disposed a single ring of magnetic poles. The poles of the magnetic drive which interact with the spider poles are assymmetrically positioned with respect to poles on opposite sides of the circumference of the pole spider.

Patented May 11, 1971 3,577,874

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406437 Mun-{R aw/W ELECTRIC CLOCKS WITH MAGNETIC DRIVES The present invention relates to an electric clock with a time-determining mechanical oscillator excited at its natural frequency and carrying a magnet system which drives the clock and the poles of which are disposed opposite two substantially diagonally opposed points of a nonmagnetized ferromagnetic pole spider, said mechanical oscillator moving said poles in substantially radial relation to said pole spider, to which a rotary motion in synchronism with the movements of said oscillator is imparted by the movements of said magnet system.

An example of a clock of this kind is shown in US. Pat. No. 3,212,252. ln these known clock-s, the pole spider consists of a disc punched out of a sheet of iron and provided with circumferentially disposed radially projecting teeth and, additionally, a ring of radial webs disposed in a staggered arrangement with respect to said teeth and separated by recesses between the individual webs. The known pole spiders are thus provided with two concentric rings of staggered poles. The manufacture of such discs is comparatively difficult since the punching tools call for a plurality of pins and corresponding openings in the die plate, which are rather'diffrcult to make, especially in view of the required trapezoidal shape. Furthermore, the pins of such tools tend to break, as their cross sections are very slim.

Another clock provided with two rings of staggered poles formed by raised portions of a disc made of a magnetic material of high permeability is known. A disc of this kind is also very difficult to make.

In yet another clock, the pole of a magnet is disposed opposite the sinusoidal rim of a ferromagnetic disc and moved by a plate-type oscillator in a direction perpendicular to the plane of the disc. Owing to the absence of salient poles the synchronizing forces are very weak so that the disc tends to fall out of step and additional means are required for stabilization. In the known clock, stabilization is achieved by'means of a flywheel 52. It is, however, a particular disadvantage that the magnet exerts a continually changing radial pull on the disc which tends to set up lateral vibrations in the shaft supporting said disc and subjects the shaft bearings to substantial unidirectional radial loads so that a special design is required for said bearings. Nevertheless, this alternating unidirectional friction in the bearings adversely affects the rate of the known clock and leads to rapid wear.

Furthermore, a clock in which a bar magnet oscillates in a direction perpendicular to the rim of a disc which is itself magnetized in such a manner that unlike poles alternate along its circumference is known. The manufacture of such polarized discs is expensive and necessitates the use of discs of a considerable thickness in order to achieve magnetization transversely to the disc. Again, the oscillating magnet exerts unidirectional radial forces on the disc entailing the same disadvantages with respect to the bearings as detailed above.

Pole spiders of the kind first above described, i.e., spiders with two rings of staggered poles, have been employed not only in the movements of clocks, in which a driving torque is applied to the pole spider by the oscillating magnets, but also for magnetic escapements, in which the pole spiders are driven while the oscillators are not self-excited. Such arrangements are known, and furthermore the use of a disc with a sinusoidal rim for a magnetic escapement is known. It is noted that a wave-shaped rim of this kind also forms two rings .of staggered poles disposed at the peaks of the sinusoidal rim so that this arrangement, too, features two concentric rings of staggered poles. Magnetic escapements with only one ring of poles are disclosed in U.S. Pat. No. 3,132,522. In these arrangements, the poles of a horseshoe magnet simultaneously approach, or move away from, one or two diagonally opposed poles of the disc, so that the alternating effect of the known drives, which consists in that the magnetic pole as it moves away from one pole of the disc approaches the disc pole staggered with respect to said first pole of the disc and thus produces a driving torque, is missing in this case. These known arrangements are, therefore, unfit for applying a driving torque .to the pole spider and can thus be used for magnetic escapements only, but not in clocks with a magnetic drive of the kind first above described.

It is thus apparent that the known electric clocks with magnetic drive which use a pole spider with two concentric rings of staggered poles are the least complicated and that they offer an additional advantage in that the spider and the bearings are not subjected to any axial or radial forces. It is the object of the present invention to further simplify these known arrangements.

According to the invention, this is accomplished by providing the pole spider with only one ring of poles along its circumference, in a manner known per se from magnetic escapements, and by disposing the poles of the magnet system so that they will be located between two poles at one side of the spider when they are opposite a pole on the other side of the spider.

The invention thus enables pole spiders to be used which have only one ring of poles and are, therefore, very much easier to manufacture than the pole spiders previously used in electric clocks. The necessary driving torque is nevertheless achieved, since the'arrangement of the magnet system according to the invention is such that as the distance between the magnet system and the .one pole is increased the distance from the following pole is again decreased so that the next pole is attracted. The present invention thus provides a substantial simplification without affecting the timing accuracy of the clock.

The desired arrangement of the poles of the magnet system with respect to the poles of the spider may be achieved, for example, by appropriately staggering the poles of the magnet system with respect to each other or by slightly displacing the magnet system with respect to the plane extending through the arbor of the pole spider. However, in a preferred embodiment of the invention the poles of the magnet system are disposed, in a manner known per se, in a plane extending through the arbor of the pole spider and the pole spider is provided with an odd number of poles.

A further embodiment of the invention provides for a pole spider with radially projecting teeth the ends of which are .bent off in the direction in which the pole spider rotates. Preference is given to an embodiment in which the ends of the teeth of the pole spider are provided with lugs projecting at a right angle in the direction of rotation. This ensures a particularly smooth transition from one pole to another so that the spider runs very quietly, thus obviating the need for the lowfriction flywheel arrangements on the pole spider shafts of the known clocks. By properly dimensioning the bent off ends of the poles it is even possible to provide for a self-starting feature, which constitutes an additional advantage of the present invention.

The oscillator and the magnet arrangements may take a great number of different forms. For example, a horseshoe magnet extending in a plane parallel to the pole spider and having its poles disposed opposite diagonally opposed points of the pole spider may be attached to the oscillator. Alternatively, the oscillator may be provided with two horseshoe magnets, each extending in a plane perpendicular to the pole spider with the poles of each magnet enveloping the pole spider from two sides at one of two diagonally opposed points of the spider. The last-mentioned arrangement affords the particular advantage that apart from the driving torque no forces are applied to the pole spider by the magnet system. The magnets may be attached to the ends of a vibrating reed, which may be formed by one leg of a tuning fork while the other leg of the fork carries a suitable balance weight. Alternatively, magnets may be attached to both legs of a tuning fork.

The pole spider itself may, for example, consist of a toothed disc of ferromagnetic material, especially sheet iron. Such a disc may be manufactured in a very simple manner by punching it out of a sheet of metal without any pins being required to provide openings, except one to make the central hole for the hub. Alternatively, the pole spider may be made from a nonmagnetic material and provided with ferromagnetic inserts such as radially or axially disposed pins.

Further details and embodiments of the invention will become apparent from the following specification, in which the invention will be described and explained more fully with reference to the embodiments shown by way of example in the accompanying drawing. In other embodiments of the invention, the features apparent from the specification and the drawing may be applied'individually or in any desired combination.

Reference will now be made to the schematic representations of the accompanying drawing, in which:

1 FIG. 1 is a top view of a first embodiment of the invention with a flat magnet yoke the ends of which are disposed opposite diagonally opposed points of the pole spider,

FIG. 2 is a side elevation of an embodiment according to FIG. 1 in the direction indicated by the arrow II,

FIG. 3 is a top view of a further embodiment of the invention with two horseshoe magnets at the ends of a U-shaped support,

FIG. 4 is a side elevation of the arrangement according to FIG. 3 in the direction indicated by the arrow IV,

FIG. 5 shows the arrangement of a magnet system on a vibrating reed,

FIG. 6 shows the arrangement of a magnet at the end of one leg of a tuning fork,

FIG. 7 is a top view of a further embodiment of the invention with horseshoe magnets at the ends of both legs of a tuning fork,

FIG. 8 is a side elevation of the embodiment according to FIG. 7 in the direction indicated by the arrow VIII,

FIG. 9 is a top view of a further embodiment of the invention with a pole spider provided with teeth bent off at a right angle, and

FIG. 10 shows an embodiment similar to that of FIG. 9 with teeth bent off at an oblique angle.

In the embodiment shown by way of example in FIGS. 1 and 2, the ends of a mechanical oscillator I, which is free to oscillate in the direction indicated by the double arrow 2, are provided with a magnet arrangement consisting of a short bar magnet 3 and an essentially U-shaped magnet yoke 4, the

ends

5 and 6 of which are bent off towards the inside so that they are disposed in spaced relation to each other on a straight line 7 parallel to the direction 2 in which the oscillations occur. Between the

ends

5 and 6 of the magnet yoke 4 there is disposed a pole spider 8 provided with an even number of radially projecting teeth 9 which constitute the poles of the spider. The pole spider 8, like the magnet yoke 4, may be punched out of a sheet of ferromagnetic material of high permeability. The arrangement is such that the yoke 4 and the pole spider 8 are disposed in closely spaced parallel planes and that 'the outside diameter 10 of the pole spider is slightly greater than the distance between

theends

5 and 6 of the yoke. Furthermore, the arbor 11 of the pole spider is displaced with respect to the centerline 7 of the yoke ends 5 and 6 by an amount sufficient to ensure that the one end, for example end 6, will be located between two teeth 9 of the pole spider when the other end 5 is opposite a pole 9, and vice versa.

If the pole spider 8 rotates counterclockwise, i.e., in the direction indicated by the arrow 12, and if at the moment represented in the drawing the oscillator I is deflected from its central position towards the left, that tooth of the pole spider which is then within reach of the left-hand end 5 of the magnet yoke' is released while the tooth approaching the right-hand end 6 of the yoke is attracted and accelerated by that end. If the oscillator is then deflected from its central position towards the right, the tooth which has just been attracted by the right-hand end of the pole shoe is released again, while the following tooth is drawn into the range of the left-hand end of the magnet yoke. The pole spider 8 is thus rotated in synchronism with the oscillations of the oscillator 1 and, may be used to drive a time indicator, connected to the shaft 13 of the pole spider.

In this embodiment of the invention, which is of a particularly simple design, the pole spider is loaded in the axial direction. Such axial loading may be prevented by the use of two magnet yokes 4 disposed on either side of the magnet 3 and, simultaneously, on either side of the pole spider 8.

The embodiment of the invention according to FIGS. 3 and 4 differs from the embodiment according to FIGS. 1 and 2 in that a U-shaped yoke 22 provided with a horseshoe magnet at each of its

ends

23 and 24 is attached to the free end of the oscillator 21. These horseshoe magnets are located in a plane perpendicular to the pole spider 25 and are disposed so that the teeth 26 of the pole spider pass between the

poles

27 and 28 of the magnets. Furthermore, the poles of the magnets are, in this case, disposed in a plane 29, which intersects the arbor 30 of the pole spider. To ensure that nevertheless the poles of the one magnet, in the drawing identified as magnet 24, will be located betweentwo teeth of the pole spider when the poles of the other magnet are opposite the teeth of the pole spider, the pole spider is provided with an odd number of teeth.

The operating principle of this drive is the same as that of the embodiment according to-FIGS. I and 2, except that the lines of magnetic force run through the teeth of the pole spider between the poles of each of the two magnets only rather than extending diagonally across the pole spider. Thus, it would also be possible to use a pole spider of nonmagnetic material in which suitable poles of magnetic material areinserted instead of a pole spider made of magnetic material. With this magnet arrangement no radial or axial forces of any kind act on the pole spider. The

magnets

23 and 24 may be attached to the U-shaped yoke 22 or may be formed directly by the magnetized ends of said yoke.

As shown schematically in FIG. 5, the oscillator 32, which supports the U-shaped magnet arrangement 31, may be formed by a baror plate-type oscillator, e.g., a leaf spring, which is restrained at its other end. Alternatively, the U- shaped magnetarrangement 31 may be attached to one leg 33 of a tuning fork, the other leg 34 of which is provided with a balance weight 35, as shown in FIG. 6. In either case, the oscillator is excited, in a manner known per se and not shown in detail, with the aid of electromagnetic arrangements which are part of electronic oscillation generators.

Similar to the embodiment of the invention shown by way of example in FIGS. 3 and 4, the embodiment according to FIGS. 7 and 8 again uses two

horseshoe magnets

41 and 42, which are disposed in planes perpendicular to the pole spider 43 and the

poles

44 and 45 of which envelope the pole spider from two sides. However, unlike the magnets of the embodiment according to FIGS. 3 and 4 the

magnets

41 and 42 are disposed at the ends of the

legs

46 and 47 of a tuning fork. This arrangement offers the advantage that the rotation of the pole spider '43 is effected by both legs of the tuning fork so that the tuning fork is damped to a lesser degree, which results in a higher efficiency.

Again the pole spider 43 has an odd number of teeth and the

poles

44 and 45 of the

magnets

41 and 42 move in a plane which intersects the arbor of the pole spider. In this case, the pole spider takes the form of a nonmagnetic disc, in which radial pins 48 serving as poles are inserted. Furthermore, the pole spider 43 is laterally displaced with respect to the centerline 49 of the tuning fork by an amount sufficient to ensure that the poles of the magnet 41 will be located at the outer ends and the poles of the magnet 42 at the inner ends of the pins 48 when the tuning fork is not oscillating. This arrangement is necessary to ensure that when the magnets oscillate towards each other the magnet poles will alternately move in and out between the poles of pole spider 43. The use of a nonmagnetic disc with inserted poles is, in this case, particularly advantageous inasmuch as the right-hand magnet 42 will then not enclose any magnetic material between its poles during its inward deflection, which otherwise might produce a damping effect on the motion of the pole spider 43. In all other respects, this arrangement operates on the same principles as described with reference to FIGS. 1 and 2.

The arrangements according to FIGS. 9 and 10 are substantially the same as those of the embodiment according to FIGS. 3 and 4, except that the pole spiders are provided with teeth of a different shape. In the embodiment shown by way of example in F IG. 9, the ends of the teeth 51 of the pole spider 52 are provided with lugs 53 projecting from the teeth 51 at a right angle and extending in the direction 54 in which the pole spider rotates. This arrangement ensures that when the pole spider 52 rotates in synchronism with the oscillations of the magnet system 55 the front edge 56 of the lug 53 will always be opposite the pole shoes 57 of the magnet system as these pole 'shoes move into the range of the poles so that a driving torque is applied to the teeth 51 of the pole spider 52 while the rotary motion of the pole spider is stabilized. This obviates the need for additional measures to prevent the rotor from falling out of step or stalling as a result of shocks and torsional vibration.

As an alternative to the embodiment according to FIG. 9,

FIG. shows an embodiment in which the teeth 61 of the.

pole disc 62, at their ends 63, are bent off at an oblique angle in the direction of rotation 64. This design, too, ensures a stabilization of the rotary motion.

it shall be understood that the present invention is not restricted to the embodiments shown by way of example, but that deviations therefrom are possible without leaving the scope of the invention. This applies both to the design of the pole spider and the design of the magnet system and the mechanical oscillator moving the magnet system.

lclaim:

1. An electric clock with a time-determining mechanical oscillator excited at its natural frequency and carrying a magnet system which drives the clock and the poles of which are disposed opposite two substantially diagonally opposed points of a nonmagnetized ferromagnetic pole spider, said mechanical oscillator moving said poles in substantially radial relation to said pole spider, to which a rotary motion in synchronism with the movements of said oscillator is imparted by the movements of said magnet system, characterized in that said pole spider is provided with only one ring of poles along its circumference, and in that the poles of the magnet system are disposed so that they will be located between two poles at one side of the pole spider when they are opposite one pole at the other side of that spider.

2. A clock according to claim 1, characterized in that said pole spider is provided with an even number of teeth, and in that said poles of said magnet system are displaced with respect to the plane extending through the arbor of said pole spider.

3. A clock according to claim 1, characterized in that the poles of the magnet system are disposed, in a plane extending through the arbor of the pole spider and in that said pole spider is provided with an odd number of poles.

4. A clock according to claim 1 characterized in that the pole spider is provided with radially projecting teeth the ends of which are bent off in the direction of rotation of said pole spider.

5. A clock according to claim 4, characterized in that the ends of the teeth of the pole spider are provided with lugs projecting at a right angle in the direction of rotation.

6. A clock according to claim 1, characterized in that the oscillator has secured to it a horseshoe magnet which extends in a plane parallel to the pole spider and the poles of which are disposed opposite substantially diagonally opposed points of said pole spider.

7. A clock according to claim 1, characterized in that the oscillator is provided with two horseshoe magnets, which each extend in a plane perpendicular to the pole spider and the poles of which envelope said pole spider from two sides at one point each of two substantially diagonally opposed points of said pole spider.

8. A clock according to claim 7, characterized in that said magnets are disposed at the ends of a U-shaped support.

9. A clock according to claim 6 characterized in that said magnet is secured to the end of a vibrating reed.

10. A clock according to claim 9, characterized in that said vibrating reed is formed by one leg of a tuning fork, the other leglof which carries an appropriate balance weight.

1. A clock according to claim 7, characterized in that the oscillator is formed by a tuning fork and in that the magnets are each secured to one leg of said tuning fork.

12. A clock according to claim 1, characterized in that the v pole spider is formed by a toothed disc of ferromagnetic material, in particular sheet iron.

13. A clock according to claim 1, characterized in that the pole spider consists of a nonmagnetic material provided with ferromagnetic inserts, in particular radially or axially disposed pms.

Claims

10. A clock according to claim 9, characterized in that said vibrating reed is formed by one leg of a tuning fork, the other leg of which carries an appropriate balance weight.

11. A clock according to claim 7, characterized in that the oscillator is formed by a tuning fork and in that the magnets are each secured to one leg of said tuning fork.

12. A clock according to claim 1, characterized in that the pole spider is formed by a toothed disc of ferromagnetic material, in particular sheet iron.

13. A clock according to claim 1, characterized in that the pole spider consists of a nonmagnetic material provided with ferromagnetic inserts, in particular radially or axially disposed pins.