US1432989A - Electromagnetic clock - Google Patents

Description

M. P. FAVRE-BULLE AND M. A. MOULIN. B-MJILMDULIN,NEECHENARD,GUARD\IAN 0fM-0.AND M.A.A.MOUL|N.SOLE MINOR HEIRSOFSAID M.A.MOULIN,DEC'D ELECTROMAGNETIC CLOCK.

APPLICATION FILED AUG.23, I920.

1,432,989. Patented Oct. 24, 1922.

2 SHEETSSHEE1 1.

1 3 men/tom mm ubaln, Becki, 11181 g annual,

and M, P. Fayre -.B wLLe.,

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Awozzugy M. P. FAVRE-BULLE AND M. A. MOULIN.

mm. M.MOULIN, NEE'CHENAREGUARDIAN OF M. 0.AND M.A.A. MOULIN,SOLE MINOR HEIRS OF SAID M.4A. MOUL|N,DEC'D ELECTROMAGNETIC CLOCK.

APPLICATION FILED AUG.23, I920. 1,432,989, Patented Oct. 24, 1922.

2 SHEETS-SHEET 2.

Patented Oct. 24, 1922.

UNITED STATES PATENT OFFICE.

MAURICE PHILIPPE FAVRE-BULLE, OF BOULOGNE, AND MARCEL ANDRE MOULIN,

DECEASED, LATE OF BFSANCON, FRANCE, BY BERTHA MARIE MARG-UERITE MOULIN, NEE CHENARD, OF PARIS, FRANCE, GUARDIAN OF MADELINE ODETTE MOULIN AND MARIE ANNE ANDREE MOULIN, SOLE MINOR ANDRE MoULm.

HEIRS OF SAID MARCEL ELECTROMAGNETIC CLOCK.

Application and August as, 1920. Serial No. 405,434.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

To all whom it may concern:

Be it known that MAURICE PHILIPPE FAvnn-BULLn, acitizen of the French Republic, and residing at Boulogne, Seine, France, and MARCEL ANDRn MOULIN, deceased, late a citizen of the French Republic, and residing at Besancon, France (Mme. MARCEL ANDRI MoULIN, of Paris, France, guardian of MADELINE Onn'r'rn MOULIN and MARIE ANNE ANDREE MOULIN, minor heirs of said MARCEL ANDRE MOULIN, legal representative), invented certain new and useful Electromagnetic Clocks (for which they filed application in France Dec. 23, 1918, No. 510,234, and in Great Britain Jan. 9, 1920), of which the following is a specifica tion.

This invention relates to electromagnetic clocks.

In electric clocks as constructed hitherto, in order to assure the connection between the motion of the pendulum and the motion of the hands, the greater part of the devices employed in ordinar mechanical clocks have been retained, w erein the regulating pendulum is actuated by the actual toothed wheels driving the hands, and designers have always sought to realize the conditions produced in this case by clockwork escapements that allow of imparting to the pendulum very short impulses close to the dead point.

In the case of a pendulum actuating the hands this condition is difficult to execute, and it entails various drawbacks hereinafter referred to. ()n the other hand it is insufficient to assure the isochronism of the oscillations of the pendulum, on account of the disturbances caused by the retarding force due to driving the whole constituted by the devices for effecting the actuation of the hands.

The improvements forming the present invention relate to the combination of a mechanical device for actuating the hands with an electromagnetic device for maintaining the oscillations of the pendulum having a very good efficiency, for allowing of compensating at each instant the passive rc istanccs by an equivalent motive force in such a manner that the pendulum will behave just as if it were free.

The present improvements relate also to the mechanism which is distinguished by a great simplicity of manufacture and which further allows of reducing the value of the retarding forces, and consequently the electric energy necessary for operating the clock.

Means are provided for assuring a good conservation of the electric battery and of the automatic circuit breaker by making prolonged contacts that allow of reducing the necessary current to a very low value, and cutting off this current the moment when the counter electro-motive induction force generated by the variations in the magnetic flux passing through the coil is a maximum.

This invention relates also to the improvements in the construction of the automatic circuit breaker of the pendulum and of the various mechanical parts which have been designed for the purpose of a very cheap manufacture and very simple assembla e. It comprises also means for avoiding all risk of damage during transport of the clock, such transport being capable of being done without previously taking the clock to pieces and withoutany special precaution.

To enable the invention to be properly understood a practical embodiment thereof is described hereinafter by way of example with reference to the accompanying drawings wherein:

Figure 1 is a front elevation partly in section of the general arrangement of the clock. a

Figure 2 is a corresponding side elevation partly in section.

Figures 3 and 3 are detail views of the automatic interrupter for effecting the successive closings of the circuit of the coil.

Figure 4 is a diagram of the'circuit and the electrical connections of the clock.

Figure 5 is a fragmentary perspective view of the magnetized bar and pendulum coil.

As shown in Figures 1 and 2, the clock comprises a pendulum of constant length whose mass is constituted by the coil 1 attached by means of two wires 2 and 3, preferably of invar metal, to a rigid cross member 4 of brass.

The wires 2 and 3 form the sides of an isosceles tra ezoid so that the whole shall be indeformab e by the weight of the coil 1 which assures the tension of the wires. The pendulum thus constructed is suspended to a support 5'by a silk thread 6 fixed by means of screws 7 and 8 which are carried by the support 5 and afford a convenient means of regulating the length of the pendulum. The support 5 is fixed on a slab 9 of wood. or marble.

The coil 1 is traversed by a fixed magnetized bar 10 which has the same S polarity at its ends and an intermediate N pole on its middle portion. This bar has the form of an arc of a circle and is fixed to the slab 9 b means of pillars 11 and 12.

o the cross member 4 of the pendulum there is fixed a stem 13 carrying a spring 14 serving as a pawl. At each oscillation of the pendulum in the direction of the arrow F, Fig. 1, the pawl 14 causes the ratchet wheel 15 mounted on the arbor 16 to turn through the width of one tooth. This arbor is journalled in two plates 17 and 18, stayed together by the pillars 19 and 20 which are held by the bracket 21 fixed to the slab 9 of the clock. The mechanism for transmitting the rotational motion of the ratchet wheel 15 to that of the hands is character ized by a double speed-reducing gear consisting of a worm and worm wheel.

The arbor 16 of the ratchet wheel carries a worm 22 meshing with a worm wheel 23 carried by the intermediate arbor 24 (Figure 1).

This arbor 2-1 is journalled in angles 25 and 26 fixed to the plate 18. It carries a worm 27 meshing with a worm wheel 28 carried by the arbor 29 of the minute hand.

At each return of the pendulum the pawl is raised, and the ratchet wheel 15 is pre-' vented from moving back by the arresting spring 30 fixed on a pillar carried by the.

. plate 18.

The maintenance of the oscillations of the pendulum is effected by means of an automatic interrupter operated by the pendulum itself, thusallowing of closing an electric circuit comprising the coil 1 and a battery P during a portion of the strokes of the E endulum in the direction of the arrow F.

he passage of this current has the effect of generating an electromagnetic force acting in the direction of the arrow F owing to the presence of the magnetized bar 10 with consequent poles.

The automatic interrupter consists of parts which assure the driving of the mechanism for actuating the hands.

The electric circuit comprising the coil 1 and the battery P terminates on the one hand at the pawll4 and on the other hand at the ratchet wheel-1 5.

When the pendulum oscillates in the direction of the arrow F, contact is made at the instant when the pawl. 14 touches the ratchet wheel 15 and causes it to rotate. This pawl has the shape shown in the detail Figures 3 and 3, and it is provided at its end with a' fibre block 31.:

As will be seen from Figure 3, contact when made remains only during a portion of the course of the pendulum in the direction of the arrow F. The said contact is then broken during the end of the said course and during the return of the pendulum, because the insulating, fibre block 31 is then rubbing over the tooth of the ratchet wheel.

The electric circuit connecting the interrupter thus constituted to the coil land the battery P, is established by means of the wires 2 and 3 suspending the said coil. This coil is constructed of a brass tube 32 to the ends of which cheeks 33 and 34 are soldered or provided.

A cross member 35 fixed to these cheeks carries the parts 36 and 37 for attaching the wires 2 and 3. The part 37 is made of brass so that the wire 3 is connected to the mass. One of the ends of the solenoid of insulated thin wire wound around the tube 32 constituting the movable coil 1. is likewise connected to the mass.

The tube 32 and likewise the cheeks 33 and 34 are split along a generatrix of the cylinder so as to avoid the generation of oucault currents due to the movement of the coil relatively to the magnet, which currents would oppose the said movement.

The other end of the solenoid is insulated from the mass and is connected to the end of the second suspension wire 2 attached to the cross member 35 and insulated from the latter by means of the part 36 composed of bone or any other insulating material.

The upper end of the wire 2 is bent back so as to form a small loop clamped between the screw threaded stem 38 and the part 39 sliding in a square hole in the insulating fibre sleeve 40 fixed to the cros member 4. The attachment of the wire 2 to this cross member is effected by means of the nut 41 screwed upon the screwthreaded stem 38. The wire 2 is kept stretched by the weight of the coil, and as is seen, it is insulated from the cross member 4. The wire 3 isattached to this cross member in a similar manner, but the sleeve 42 is of brass instead of fibre, so that the wire 3 and the cross member are short-circuited. The length of the pendulum can be easily adjusted by screwing or unscrewing the nuts 41 and 43.

The stem 13 upon which the pawl is fixed. is insulated from the cross member 4 by matter of fact su'ilicient to approximate this condition, because the pendulum has a to assume a normal velocity for which the mean value of the g force balances the mean value of the retarding force.

As a matter of fact it this first value were greater than the second value, the oscillations of the pendulum would have a tendency to increase.

In these circumstances the velocity of the pendulum. at the instant when it passes through the vertical would be greater, and c nsequently the counter-electro-motivc inductive force would be higher.

The energy absorbed by the coil would diminish and consequently the electromagnetic force would be weaker. n the other hand the value of the retarding force would be greater owing to the increase in velocity. A normal velocity (regime) would not be long in being established for an amplitude very slightly greater than the initial amplitude, before a disturbance would be pro duced; The swing would be likewise very small it the retarding force were to increase relatively to the driving force.

It will thus be seen that the arrangement employed for maintaining the motion of the pendulum allows of attaining a very great accuracy notwithstanding the slight varia tions that may occur in the value of the friction or of the electro-motive force of the battery, whereas in clocks o1 the same type as constructed hitherto the theo retical conditions of isochro-nism are not satisfied owing to the infl .ence of the resisting effort which designers have not sought to make equal at each instant to the driving force.

Thespecial magnet which is employed allows also of attaining a very good utilination of the material whilst at the same time it can be manufactured very cheaply. This magnet consists simply of a round bar of steel formed into the shape of an arc of 1: circle of a very large radius of curvature. Permanent magnetization can be very easily pi'oduced by means of two solenoids arranged in series around the bar and traversed in the reverse direction by a strong current in such a manner that the bar will have the same polarity at its ends and a difi'erent polarity in its middle. By this means the magnetic flux emanating from the intermediate pole has a perfectly regular radial field which is very intense in the region occupied by the coil at the moment of closing; the circuit.

Further, the position of the intermediate N pole made exactly such that the coil will embrace the said pole when the automatic interrupter is-closed, and when the latter is traversed by the maximum current intensity. In these circumstances it will be perceived that each element of current in the coil situated opposite the N pole is at right angles to the lines of force, and'on the other hand the elements of currents and the lines of force are contained in planes at right angles to the axis of the magnet.

In these circumstances the electromagnetic forces due to the action of the elements of the current upon the magnet reach a maximum value. Moreover, since these forces are at right angles to the planes containing the elementsof the current and the lines of force, they are all'di'rected along the axis of the coil, and their resultant reaches a maximum value in the sense that is favourable to the maintenance of the motion of the pendulum (Figure 4).

Consequently the theoretical conditions for the best utilization of the magnet and the coil are thereby realized.

In order to utilize the energy of the but tery under the best conditions and to increasethe efficiency of the conversion of electric energy into mechanical energy, a contactis employed which is prolonged during a considerable portion of the course of the pendulum. Under these conditions the electro-magnetic force that is required is very small, because it acts upon a considerable length of movement. Therefore the coil can be madeof very strong wire, and the energy lost in the form of heat can be reduced to a very small amount.

This arrangement is much more advantageous thanthe one employed in electric clocks of the same type constructed hitherto wherein designers have attempted'to obtain very short current impulses because in that case itis necessary to have a considerable electromagnetic force as the displacement of this force is very small. Therefore, the intensity must reach a'relatively high value and the result is that the heat developed. as a Joule effect which is proportional to the square of this intensity, is considerable and thus reduces the efliciency.

For the same reason it is diflicult to assure the maintenance of the interrupter in proper working condition in the case of short current impulses, because it is necessary to break the circuitwhilst carrying relatively high intensities with the result of producing considerable sparking. This drawback is remedied in our improved clock by employing a lower intensity and in breaking the circuit carryingthis intensity, close to the dead point, that is to say, at the instant when the counter-clectro-inotive inductive force is greatest, and consequently the. intensity has a minimum value. It will be perceived that this circuit-lnreaking takes place atthe mo ment when the conducting portion of the pawlv it ceases to drive the ratchet wheel (Figure 9,). percehed that the circuit-breaking takes ()n the other hand it will be place at a part of the tooth of the ratchet wheel which is different from the part at which contact has been made.

By this-means the contact surfaces are thoroughly cleaned and contact remains in a good condition indefinitely. This last feature allows of obtaining perfect results even without having recourse to the use, for the purpose of contact, of cappings of precious metals, such as are employed in the majority of electric clocks.

The mechanical apparatus for actuating the hands has been designed to reduce to a minimum the mechanical energy required for maintainin the motion of the pendulum. This resu t is achieved by the use of a mechanism of very small size for reducing the motion, which in similar clocks is usually done by means of a series of wheels and pinions similar to the wheel-work employed in clocks driven by weights or springs. The ratchet wheel 15 has very few teeth andit has a very small diameter as have also the worm wheels and worm in order to reduce the moments of inertia to a minimum. Under these conditions the retarding force due to the inertia of these parts when they are started is very small. This resistance is also utilized to effect the pressure of the electric contact assured by the pawl 14 and the ratchet wheel 15, which contact does not add any supplementary effort, or consume any additional power.

On the return of the pendulum the friction of the nose of the pawl takes place on the fibre block 31, thereby reducing the coeflicient otf friction.

The diminution of the necessary force and the use of a coil of high resistant wire allows also of reducing considerably the wear of the battery. Consequently batteries may be employed made like the standards of electromotive force, thereby allowing of obtaining a constancy of the voltage which is very diflicultly attained in the case of a high rate r of discharge as in electric clocks hitherto constructed. This propert is very important in the case of pen ulums of small length when it is desired to get amplitudes for which isochronism is no longer strictly required.

The diminution of the intensity of the current passing through the coil is likewise very favourable to a good preservation of the magnet.

The costs of manufacture of the improved pendulum are incomparably lower than the cost of manufacture of electric clocks of the same type hitherto constructed owing to the very small number of arts that are employed, the majorit of whic serve to perform a number of different functions. For instance the wei ht or mass of the pendulum is constituted by the actual coil 1.

The rigid pendulum that is ordinarily employed is replaced by a single mass suspended by two metal wires whose length may be adjusted in assembling the clock in a very easy manner by means of the nuts 41 and 43; said wires being also utilized for supplying current to the movable coil. The improved construction of the pendulum allows of approximating to the conditions of a simple pendulum and thus obtaining a maximum moment of inertia for a given mass of the pendulum. The apparatus for controlling the speed-reducing mechanism actuating the hands and the automatic interrupter are constituted by the same parts. The speed-reduction is effected by means of a mechanism which is much less extensive than those employed in ordinary mechanical clocks.

he very small bulk of this mechanism allows of reducing considerably the dimensions of the frame of the clock.

The improved general arrangement has further the great advantage of enabling the clock to be extremely easily transported without previous removal of the pendulum, and without any special precaution. As a matter of fact the weight mass of the pendulum constituted by the coil 1 is held perfectly by the fixed mangnet 10 which extends through it, and it is sufficient to fix it upon the latter in order to render the clock capable of being turned upside down or in anIyIway without risk of damaging any part.

aving now described our invention, what we claim as new and desire to secure by Letters Patent is 1. In electromagnetic clocks the combination with a mechanical apparatus for actuating the hands of an electromagnetic apparatus for keeping up the oscillations of the pendulum which allows of compensating at each instant the passive resistances by an equivalent driving force, in such a manner that the pendulum behaves as if it were free.

2. In electromagnetic clocks, a magnetized bar having consequent poles, and a movable coil adapted to traverse said magnetized bar.

3. In electromagnetic clocks a movable coil adapted to be traversed by an intermittent current, a magnetized bar having consequent oles which extend through the said coil, sai magnetized bar being curved and magnetized in such a manner that the coil surrounds the intermediate pole at the in stant when the intensity of the current passing through the same is a maximum.

4. In electromagnetic clocks an electromagnetically actuated pendulum, an electric circuit including the elebtro-magnetically actuated pendulum, and circuit-interrupting means operating to maintain the circuit closed for a long period starting before the pendulum reaches its vertical position, and lasting until the pendulum is close up to said osition, for the purpose of diminishing t e mean intensity of the requisite current and cuttin ofl said current at the moment when it is a minimum owing to the counter-electromotive inductive force, which latter is a maximum at the same time as the speed of movement of the coil.

5. In electromagnetic clocks effecting the control of the mechanism actuating the hands and the periodic closings and openings of the electric current circuit by means of the same parts comprising a pendulum, a pawl fixed to the pendulum, a ratchet wheel adapted to drive a hand-actuating mechanism; the ratchet wheel and pawl being made of electrical conducting material and adapted to be connected with an electric circuit, and an insulating member carried by the pawl movable over the ratchet wheel at the instant of the return of the pawl.

6. In electro-magnetic clocks, an electromagnetic coil constituting a pendulum, spaced suspending members on said coil having electrical connection therewith, and a clock hand actuating mechanism located between said suspending members.

7. In electromagnetic clocks, a pendulum whose mass is constituted solely by a movable coil attached by means of two metal wires, preferably of invar metal, to two transverse rigid parts one of which is carried by the coil and the other is fixed to a suitable suspension device.

8. In electromagnetic clocks a coil, wires for suspending the coil, in the form of independent electrical conductors for assuring the connections of the said coil and adjustable attaching means for the wires facilitating the regulation of their length.

9. In an electro-magnetic clock, a clock hand actuating mechanism, a pendulum, electro-magnetic actuating means for the pendulum, an electrical circuit including said electro-magnetic actuating means, a pawl actuated by the pendulum to intermittently engage and actuate the hand actuating mechanism incident to a swinging movement of the pendulum, and circuit interrupting means included in said circuit operating to close the latter at the precise instant at which resistance to the movement of the pendulum occurs due to the driving coaction of the pawl with the hand actuating mechanism.

In testimony whereof we have signed our names to this specification.

MAURICE PHILIPPE FAV'RE-BULLE.

v". MARCEL ANDRE mouuu.

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