US1772555A - Electric clock and the like - Google Patents

Description

Au 12, 1930. A. FZPOOLE ELECTRIC CLOCK AND THE LIKE Filed Jan. 31. 1927 s Sheets-Sheet 1 INVENTOR flrZ/Zar F, 1 0026 ATTORNEY AugQlZ, 1930. ALF. POOLE ELECTRIC CLOCK AND THE LIKE Filo'd Jan; 31, 1927 3 Sheets-Sheet 3 INVENTOR JJT'WZTPOOZG %J 9 5 a 5 a T H i wvh l 2 1| L f 2 z I. a 4

V ISATTORNEY Patented Aug. 12, 1930 UNITED STATES PATENT OFFICE.

ARTHUB I. POOLE, OF ITEAGA NEW YORK, ASSIGNOB T POOLE MANUFACTURING CO. INC., A CORPORATION OF NEW YORK ELECTRIC CLOCK AND THE LIKE Application filed January 31, 1927.

This invention relates to electricclocks or the like, and is in the nature of an improvement upon the type of clock illustrated in my prior U. S. patent Number 1,531,026, is-

sued March 24, 1925.

An object of the invention is to provide an improved and simplified clock mechanism which will'operate without attention for a long period of time; which will consume a minimum amount of current; with which there will be no arcing of contacts when circuits are made and broken; and which will be relativel simple, durable, compact, dependable and inexpensive.

A further object of the invention isto provide an improved polarized electromagnet;

with which both limits of oscillation of the armature may be varied uniformly and simultaneously in a simple, novel and accurate manner.

Various other objects and advantages will be apparent from the following description.

of an embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings Fig. 1 is an elevation of a clock constructed in accordance with this invention;

Fig. 2 is a plan of the same;

Fig. 3 is a sectional elevation of a part of the same, the section being taken approximately along the line 3-3 of Fig. 2;

Fig. 4 is a sectional elevation through a part of the polarized electromagnet, with the section taken approximately along the line 4-4 of Fig. 2; V

--Fig. 5 is a side elevation of the clock;

Fig. 6 is a sectional elevation through a part of the contact mechanism;

Fig. 7 is a diagram of the circuits of the clock in the preferred form;

Fig. 8 is a sectionalelevation of the clock, with the section taken approximately along the line 8-8 of Fig. 2;

Fig. 9 is an elevation of the polarized electromagnet;

Fig. 10 is a sectional elevation through the balance wheel shaft and illustrating the mov connects the pawl 13 and a suitable Serial No. 164,874.

able anchorage for one end of the hair spring in one of its positions;

Fig. 11 isa similar elevation but with the anchorage in anotherof its positions; and

Fig. 12 is a diagram of a modified circuit arrangement adapted for storage battery operation, which may be used instead of that shown in Fig. 7. g

In the illustrated embodiment of the invention, the time train mechanism 1, Fig. 1, is mounted in any usual or suitable manner in a clock frame 2 formed of spaced plates, as usual in horological mechanism. The time train is driven through. a ratchet wheel 3 carrying a driving pinion 4.

A balance wheel 5 is mounted upon a balance wheel shaft 6, which extends between and is mounted for oscillation in suitable bearing screws 7 and 8 (Figs. 2 and 5) as usual in clock mechanisms. The balance wheel carries the usual or any suitable roller pin 9 which cooperates with and oscillates the forked end of a lever 10 somewhat resembling in action the usual pallet lever. The lever 10 is secured upon a shaft 11 which extends between and is rotatably mounted in spaced plates of the frame 2, as shown clearly; in Fig. 2. The shaft 11 extends forwardly t rough one of the plates of the frame-2, and carries an arm 12 (Figs. 1 and 5). The arm 12, at a distance from its pivot, pivotally mounts a driving pawl 13, and a spring 14 art of l the arm 12, so as to urge the nose of t e pawl 13 yieldingly and resiliently into contact with the teeth of the ratchet wheel 3. Thus whenwhen the balance wheel oscillates, it will oscillate the lever 10 and the arm '12, and the pawl 13 of the latter will drive the time train through the ratchet wheel 3. l

Regular oscillations of the balance wheel and its shaft may be obtained byahair-spring 15, one end of which is connected to the balance wheel shaft, and the other end of'which is adjustably anchored by a wedge pin 16 to an arm 17 extending from an armature 18 of a polarized electromagnetic device 19. The movements of the armature are thereforeim parted to the spring 15 to vary the tension of the same and this variation in tension of the hair spring is utilized to maintain the balance Wheel and its shaft in oscillation.

While the usual regulating mechanism commonly found in clocks for regulating the oscillations of the balance Wheel through the hair spring, may be applied to the hair spring 15, l have found it advantageous to provide a second or regulating hair spring connected at one end to the balance Wheel shaft and at its other end by a Wedge pin 21 to a bracket pin 22 extending from the clock name. A regulating arm 23 having regulating pins 24 straddling the outer convolution of the hair spring 20 may be pivotally mounted upon the adjustable bearing screw 8' and confined thereon between the head of the screw and frictional spider 25 which Erictionally holds the arm 23 in angulnrly adjusted positions. One end of the arm 23 may have an angular ear 26 extending forwardly through an arcuate slot 27 in one of the plates of the frame 2 for manipulation in regulating the period of oscillation of said balance wheel, as usual in clock mechanisms of the balance wheel type.

The rearward plate of the clock may have a tongue 28 (Figs. 2, 5 and 9) s ruc outwardly therefrom, which tongue is connected at its free end to a bar 29 connecting the two projecting core ends 30 of two electromagnets 31 of the electromagnetic device 19. The two electromagnets 31, at their opposite ends, are secured to a bar 32 which is secured to rearwardly extending cars 33 of the clock frame, so that the twoelectromagnets will be mounted upon the clock frame. A lei-shaped permanent magnet 3% extends along one side of the pair of electromagnets 31, with its arms extending into and terminating in proximity to and between the ends of the cores of the two electromagnets. The upper arm of the permanent magnet terminates in K) above. the armature 18 but in proximity thereto. The lower end is secured by a screw 35 to the bar 32 which bar may be of good magnetic flux conducting material, so that the permanent magnet acts as a thin conducting part between the ends of the pair of electromagnets and including in the path the armature 18.

The armature 18 is pivotally mounted intermediate of its ends by a pointed hearing pin 36 riveted at its blunt end to an upstanding ear 37 of a plate 38, and by a pointed hearing screw 39, which is adjustable through onother and opposite ear l0 of the plate 3'. The plate 38 is oi resilient flexible non-magnetic material, such as spring brass, and is normally arcuate in shape between its ends and disposed between the armature end the scent ends of the electromagnet cores 30. The nlate 38 may be forked at its ends, so as to sci eddle the core ends 30 and extend between them, and be disposed with the concave face of the plate toward the connecting her 29.

rt /ares The plate 38 is clamped against the bar 29 by a screw 41 which passes through a clearance aperture 4-2 in the upper arm of the permanent magnet 34 and through a clearance aperture 4:3 in the armature (see Figs. 4- and 5). This screw has a reduced threaded end passing through an aperture 44 in the plate 323 and threaded into the bar 29, as shown in Fig. 'lhe shoulder at the innor end of the threaded portion of this screw bears against the upper face oi the plate 38, so that the screw clamps the plate 38 against the bar 29 and confines the plate in straddled relation over the core ends 30. By adjusting the screw ll, the plate 38 may be sprung intermediate of its ends toward or from the bar 29 to various extents, and thereby the pivots 36 and 39 o no armature may be shifted or from the electromagnets. This movement of the pivots of the armature car- 1 'es the armature bodily toward and from the nds 30, of the electromagncts, so as to on .lv limit the throw of the armature in magnetic conditions in the electromagnets 81. The armature, which is of magnetic material, moi have a plate 18 of non-magnetic material (Fig. 9) secured to its face abutting the core ends 30 so as to prevent the armature from sticking to the core when stri ing the same.

The two electromagnets may be connected in series With one another and be so Wound that when a current passes through them, the core ends 30 will always have opposite polarities. Since the magnet 34 serving to complete the flux path between the ends of the electromagnets is a permanent magnet, the upper end above the armature will always have n polarity similar to one of the core ends and also opposite to that of the other core end, even though the polarities 01": the core ends 30 may fluctuate With changes in the direction o'l' current through the electromagnets. Since the armature 18 is disposed in proximity to t 1e up r end of the permanent magnet, it Will also d: magnetized and have the same polarity as that end of thepermanent magnet. Hence, one end of the armature will always be attracted and the other end repelled by the core ends, in one direction or the other depending upon the direction of current through the electromagnets.

A pair of lea spring contact lingers or elements d5 and .6 (Figs. 2, 8) are secured to an insulating blocl: or support A, so

extend on op; osite sides of the lever 11, in position for contact with con- Lips or terminals 4'? of a contact ed upon and osites with the shaft ll. Jhe contact arm or member 49 includes arms extending in opposite directions from the and bent anerly thereto opposite directions their i at the contact tips or terminals A. haw, member or arm as which 47 and 48 will be spaced apart, considered len thwise of the axis of the shaft 11, and the lea springs and 46 are also spaced apart from one another along the shaft 11 in a similar manner. As the shaft 11 oscillates with the balance wheel, the contact tips or terminals 47 and 48 will contact alternately with the leaf contact- springs 45 and 46.

An abutment strip may be disposed adjacent to each strip 45 and 46 in spaced relation to the free ends of the same, and also secured to the block or support A. A screw 51 is threaded through the free end of each strip 50, so as to abut endwise against its corresponding contact spring 45 or 46 and limit movement of the latter toward the shaft 11. By adjusting the screws 51, the extent to which the contact springs 45 and 46 may flex of their own accord or bias toward the shaft 11 may be selectively varied, and thus the instants at which contact is made between the arm 49 and the sprin s 45 and 46 may be varied to some extent. bince the springs 45 and 46 and their abutment strips 50 are spaced apart from one another, considered lengthwise or endwise of the shaft 11, neither spring 45 or 46 and its abutment strip will interfere with free access to the head of the screw forming the adjustable abutment for the other spring. A short leaf spring 52 may be secured to each abutment strip 50 with its free end spaced from the strip 50 where the screw is threaded therethrough, and may be provided at its free end with an aperture through which the screw 51 may pass. Thus the springs 52 by yieldingly bearing against the heads of the screws will frictionally hold the screws against turning, and thus against changes in adjustment which are not intended or man ually given.

Referring nowto Fig. 7, a diagram of the preferred circuit arrangement is illustrated. The electromagnets 31 which are connected in series are connected at one end by a wire 53 to a suitable source of electric energy 54, such as a battery. The electromagnets 31 are also connected at theirother end by wire 55 to one side of a suitable condenser 56, the other side of the condenser being connected by a wire 57 to the frame of the clock, and thus to the lever shaft 11 and the arm 49. One of magnets 31 back to the battery. At the closing of such a circuit, there will be a surge of current through the condenser and electromaghets, and this surge of current will set up a magnetic field in the electromagnets acting u n the armature 18, and cause a movement 0 the armature in one direction. This movement, through the arm 17 of the armature causes a tightening or loosening of the hair spring 15. This current will be only for an instant, that is, momentary, while the coner 56 directly across the electromagnets 31.

This circuit will include the condenser 56,

wire 57, the clock frame 2, arm 49, contact spring 45, wire 59, wire 53, the electromagnets and. wire 55 back to the condenser. The condenser, which was charged by the previous surge of current, will now be discharged through the electromagnets and will. send a surge of current in the opposite direction therethrough which will cause a reversal of polarity of the core ends 30, and consequently a rocking of the armature 18 in the opposite direction to cause a different tension in the hair-spring 15.

The conditionv of the hair spring 15 when the armature is at one limit of its movement is shown in Fig. 10, and another condition of the hair spring when the armature is in the other position is shown in Fig. 11. The armature during its movements therefore tends to wind the hair spring in one direction or the other depending u on its direction of oscillationat any time. T is movement. however, which is caused by the alternate closure of the two circuits described, must be such that the hair spring will be wound or moved in a direction opposite to that in which the balance wheel is traveling at the time the movement is made, in order that the balance wheel will be maintained in oscillation by these variations in the tension of the hair spring. r

In order that there may be no danger of a poor circuit connection between the shaft 11 carrying the contact arm 49 and the clock frame 2, I ma provide a coil of non-resilient wire 60 loosel y around the shaft 11, firmly "attach one end of the coil to the shaft, and firmly secure the other end of the coil to the clock frame, as shown clearly in Fig. 2. This loose coil 60 will thus furnish a good electrical circuit between the shaft 11 and the clock frame, without exerting any material influenced upon the oscillations of the shaft 11 and inde endently of any lubricating oil on the hearings of the shaft 11. It will also be understood that the arm 49 should break contact with one spring 45 or 46 before it makes contact with the other.

In the operation of a clock constructed in this manner, let it be assumed that the balance wheel 5 and its shaft 6 are oscillating in a clockwise direction (Fig. 8). During such oscillation, the lever 10 will be rocked in a counterclockwise direction, (also in Fig. 8) and the contact 49 will carry its contact tip 48 into engagement or contact with the leaf spring or contact element 46 before the balance wheel reaches the limit of its oscillation in a clockwise direction (Fig. 8). WVhenthe arm 49 does contact with spring 46, a circuit will be established from the battery through the series-connected condenser 56 and the electromagnets 31, which will cause a momentary surge of current through the electromagnets in a direction to shift the arm 17 from the position shown in Fig. 11 to the position shown in Fig. 10, which will be in effect a movement in a direction to wind the spring 15 in a direction op osite to that in which the balance wheel at t iat moment is traveling.

The balance wheel will continue its move ment in the same direction in the usual manner and when returning, it will 0 en the battery circuit previously establishe and shortly after passing the position of the parts shown in Fig. 8, the arm 49 will contact with the spring 45 and shunt the condenser across the electromagnets 31. Since the condenser was charged by the previous surge of current from the battery, it will now discharge through the electromagnets and cause a momentary surge of current in the opposite direction through the electromagnets, and cause a rocking of the armature in a reverse direction to carry the arm 17, to which the hair spring 15 is connected, from the position shown in Fig. 10 to the position shown in Fig. 11, which will be in a direction opposite from that in which the balance wheel is moving at that particular instant. These changes in the tension of the hair spring thus produced will give the necessary impulses or bias to the balance wheel to maintain it in oscillation, and the balance wheel'will in turn drive the time train so long as its oscillations are maintained.

it will he noted that the current from the battery is utilized only during alternate oscillations or movements of the armature, and that even when the battery circuit is closed, there will only be a momentary surge of ourrcnt rerardless of how long the circuit remains c osed. Thus the current consumption required for the operation of such a clock or the like will be a minimum. However, in view" of the fact that only a momentary surge of current is utilized, the voltage of the source energy or battery should preferably be quite considerable, such as twenty volts or more order th the electromagnets wilt have energy suiiicient to real: the armature.

The natural period of oscillation of the balance wheel may be varied by adjustment of the regulator arm 23, as usual in clock mechanisms.

In some instances it may be desirable to operate such a clock mechanism from a battery having a relatively low voltage, such as the ordinary storage battery used in automobiles and having a voltage of only six volts. The circuit for such a battery is illustrated diagrammatically in Fig. 12. The mechanism of the clock is the same as explained hereinbefore, except that two condensers 56' and 56 are utilized in place of a single'condenser 56. Referring particularly to Fig. 12, a battery or source of current 61 is connected at one end to the wire 62 which connects the electromagents 31 in series. The other end or terminal of the battery is connected b a wire 63 to the contact arm 49 and also by ranch wires 64 and 65 to one side of each of the condensers 56 and 56 The other side of one electromagnet is connected by a wire 66 to one of the contact s rings 45, and the other terminal of the other of the electromagnets 31 is connected by a wire 67 to the other of the contact springs, such as 46. The wire 67 is also connected to the other side of the condenser 56", and the wire 66 is also connected to the other side of the condenser 56 The operation of this modified circuit arrangement would be as follows: When during the oscillation of the balance wheel the contact arm' 49 engages with the contact spring 45, a circuit will be established from the battery 61 through wire 63, contact arm 49, contact spring 45, wire 66 and one of the electromagnets 31, back to the battery through wire 62. This causes a rocking the armature 18 in one direction, there being no current flow at that time in the other of the electromagnets. This rocking of the armature 18 causes a change in the tension of the hair spring 15 as before, and when the balance wheel travels in the opposite direction, the contact arm 4; will be shifted in a manner to open this CiiCilllJ previously established and be moved into engagement with the contact spring 46. At the opening of the previously closed circuit, the condenser 56 which is connected in shunt across the arm 49 and contact 45, will prevent any sparking between the spring 45 and the arm 49 as they separate.

At the closing of the new circuit with the spring 46, the current will flow from the battery 61 through wire 63, contact arm 49, con tact spring 46, wire 6?, the other of the electromagnets 31, and wire 62 back to the battery. This causes a rocking of the armature 18 in the other direction, and thereby a change in the tension of the hair spring 15. The condenser 56* being in shunt across arm 49 and spring 46 prevents arcing therehetween when the circuit is opened by their separation. These changes in the tension of the hair spring 15 maintain the balance wheel in oscillation as before. While the current consumption in such a modified circuit arrangement is considerably higher than for the circuit described in Fig. 7 such a modified battery circuit isusually used in connection with a storage battery, where the relative amount of current utilized is not important or objectionable.

It will be obvious that various changes in the details, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the inventionas expressed in the appended claims.

I claim 1. In an electric clock or the like, an oscillating control element, aspring connected to said element for securing regular oscillations thereof, polarized electromagnetic means for varying the influence of the spring upon said element, a source of electrical energy,

a condenser, and circuit means including said electromagnetic means, said source of energy, and said condenser, and rendered effective automatically through the oscillations of said element for causing surges of current through said electromagnetic means in opposite directions, alternately, in a manner to vary the influence of said spring upon said element and thereby maintain said element in oscillation.

2. In an electric clock or the like, an oscillating control element, a spring connected to said element for securing regular oscillations thereof, polarized electromagnetic means operable upon said spring to vary the force of the latter upon said element, a source of electrical energy, a condenser, and circuit means including said electromagnetic means, said source of energy and said condenser and rendered effective automatically through the oscillations of said element for causing surges of current through said electromagnetic means in opposite directions, alternately, in a manner to nary thexaction of said spring upon said element and thereby maintain said element in oscillation.

3. In an electric clock or the like, an oscillating control element, a springconnected to said element for securing regular oscillations thereof, polarized electromagnetic means for varying the influence of the spring upon said element, a source of electric energy, a condenser in series with said electromagnetic means, contact means operable through the oscillations of said element, and circuits connecting said source of energy, said contact means and said condenser and electromag netic means in such a manner that surges of current from said source of energy will be sentthrough said electromagnetic means alternately and in opposite directions by the operation of said contact means, whereby said element will be maintained in oscillation by the Varying influence of said spring thereon.

4. In an electrical clock or the like, an oscillating control element, a spring connected to said element for securing regular oscillations thereof, polarized electromagnetic means for varying the influence of said spring upon said element, a condenser connected in series with said electromagnetic means, a source of energy, contacteleme'nts, a contactmember oscillatable through the oscillations of said element and making and breaking contact with said contact elements alternately, a circuit including said contact member, said series connected condenser and electromagnetic means, and one of said contact elements, a second circuit including said source of energy, the other of said contact elements, said contact member and said series connected condenser and electromagnetic means, whereby when said circuit is completed by contact of said contact member and said other of said contact elements, a surge of current Will pass from said source of energy through said condenser and electromagnetic means in one direction and cause a change in the in fluence of the spring upon said element by said electromagnetic means, and when the first circuit is completed by contact of said one of the contact elements and said contact member, said condenser will be shunted across said electromagnetic means and will discharge a surge of current through said electromagnetic means in the opposite directions to again vary the influence of the spring upon said element by a reverse operation of said electromagnetic means.

5. In an electric clock or the like, an oscillating control element, a sprin connected to said element for securing regu ar oscillations thereof, polarized electromagnetic means for varying the influence of the spring upon said element, a source of energy, a condenser, and means including circuits controlled by the oscillations of said elements for conducting a surge of current from said source through said electromagnetic means in one direction to vary the influence of the spring upon said element and charge said condenser at one instant in the oscillations of said element, and for causing. a discharge of the condenser through said electromagnetic means in the reverse direction to cause a restoration of the influence of said spring upon the element to initial condition at another instant in the oscillations of said element, whereby said element will be maintained in oscillation by the variatiens in influence oi" the spring thereon produced by the operation of said electromagnetic means. n

6. In an electric clock or the like, an osc1llatxng control element, a spring connected to said element for securing regular oscillations thereof, polarized electromagnetic means for varying the influence of the spring upon said element, a source of electric energy, a condenser, means including a circuit connecting said source of energy, said electromagnetic means and said condenser rendered effective at one instant in the oscillation of said element for causing an operation of said elec tromagnetic means to vary the influence of the spring upon said element and for charging said condenser, and means operable automatically at another instant in the oscillations of said element tor shunting said coir denser across the electromagnetic means to cause a surge of current through said electro magnetic nieansin a reverse direction and another operation of said electromagnetic means to restore the original influence of the spring upon said element, whereby said element will be maintained in oscillation by the variations in the influence of the spring thereon.

l. in an electric cloclr or the like, an oscillatin g balance Wheel, a hair spring connected one end to said balance Wheel for causing regular oscillations thereof, electromagnetic means having a movable armature connected to said hair spring for changing its influence upon said balance Wheel, a contact member oscillatable concomitantly with said balance wheel, contact elements With which said memcooperates alternately at different instants in the oscillations of said balance Wheel, a source of electric energy, and circuits including said contact member, said contact elements and said electromagnetic means for causing movements of said armature synchronously with the oscillations of said balance Wheel, whereby said balance Wheel will be maintained in oscillation by the varying influence of said armature upon said hair sprin 8. in an electric clock or the like, an oscillating balance wheel, a hair spring connected to said balance Wheel to secure regular oscillations thereof, polarized electromagnetic means having an armature oscillating with changes in direction of current passing through said electromagnetic means, said armature being connected to said spring for varying the tension of said hair spring at each oscillation of said armature, a condenser connected in series with said electromagnetic means, a source of electric energy, and means including circuits connected to said source energy, said condenser and said electromagnetic means, and in turn controlled by the oscillations of balance Wheel for senda surge oil current through said electromagnetic means and condenser at one instant in the oscillation of said balance Wheel to a change in the tension or said spring,

for shunting said condenser across said Elma electromagnetic means at another in the oscillation of said balance Wheel to send a surge of current through said electromagnetic means in the opposite direction and thereby cause a restoration of the tension of said spring to initial cgndition.

9. in an electric clock or the like, an oscillating balance wheel, a hair spring connected to said balance wheel for securing regular oscillations thereof, polarized electromagnetic means having an armature oscillating in accordance with reversals of current through said electromagnetic means, said an mature being connected to said hair spring for varying the tension thereof by the oscillation of said armature, a contact member connected to and oscillatable by said balance wheel, pair of contact elements With Which said member contacts alternately at different instants in the oscillation of said balance Wheel, a source of electric energy, a condenser, a primary circuit including said source of ener y, said electromagnetic means, said condenser, said contact member, and one of said contact elements, whereby a closing of said circuit by said member and one of said contact elements will cause a surge of current through said electromagnetic element in one direction to cause a movement of said armature and through it a change in the tension of said hair spring, and a shunting circuit including said electromagnetic means, said condenser, said contact member'and the other of said contact elements for shunting said condenser across said electromagnetic means at a different instant in the oscillation of said elements, when said primary circuit is open, to cause a surge of current through said electromagnetic means by the discharge of said condenser, and thereby cause another movement of said armature in a manner to cause a return of the hair spring to its initial ten sion, whereby said balance wheel Will be maintained in oscillation by the variations in tension of said hair spring.

10. in an electric clock or the like, an oscillating balance wheel, a hair spring connected to said balance Wheel for securing regular oscillations thereof, "aolarizcd electromagnetic means having an armature oscillating in accordance With reversals of current through s id electromagnetic means, said armature being connected to said hair spring for varying the tension thereof by the oscillation of said armature, a contact member connected to and oscillatable by said b ance Wheel, a pair of contact elements wwhich said member contacts alternately ditlerent instants in the oscillation of said balance Wheel, a source of electric energy, a condenser, a primary circuit including said source of energy, said electromagnetic means, said condenser, said contact member, and one or" said contact elements, whereby a closing of said circuit by said member and one of said contact elements will cause a surge of current through said electromagnetic element in one direction to cause a movement of said armature and through it a change in the tension of said hair spring, a shunting circuit including said electromagnetic means, said condenser, said contact member and the other of said contact elements for shunting said-condenser across said electromagnetic means at a different instant in the oscillation of said elements. when said primary circuit is open. to cause a surge of current through said electromagnetic means by the discharge of said condenser. and thereby cause another movcment of said armature in a manner to cause a return of the hair spring to its initial tension, whereby said balance wheel will be maintained in oscillation by the variations in tension of said hair spring, and means for varying the natural period of oscillation of said balance wheel.

11. In an electric clock or the like, an oscillating balance wheel. ahair spring connected to said balance wheel for securing regular oscillations thereof, a lever oscillated by said balance wheel, a pair of contact arms on said lever and having contact ends spaced apart at different points along the length of the axis of oscillation of said lever, a pair of contact springs extending into position for contact by said contact portions alternately during the oscillations of said lever, adjustable abutments for limiting the movements of said contact springs toward the paths of said contact, ends, and means including circuits controlled by said contact spring and said arms for varying the influence of said spring upon said wheel to thereby maintain said balance wheel in oscillation.

12. In an electric clock or the like, an oscillating balance element, a hair spring connected at one end to said balance element, electromagnetic means having an armature movable between two positions and connected to the free end of said spring to tension the same varying amounts upon the oscillation of said armature, a contact device having a controlling member operated directly by said balance element in synchronism therewith, and means including said contact device and said electromagnetic means fon rocking said armature in synchronism with said element to vary the stress of said spring at each oscillation of the element and thereby maintain said element in oscillation. Y

13. In an electric clock or the like, an oscillating balance wheel. a hair spring connected to the balance Wheel for securing regular oscillations thereof, electromagnetic means for varying the tension of said spring, and means controlled by said balance wheel and including said electromagnetic means and a pair of circuit rendered efiective by the balance wheel alternately for varying the tension of said spring in synchronism with the oscillations of said wheel to thereby maintain said wheel in oscillation.

14. In an electric clock or the like, a balance wheel, a spring for imparting oscillatory movements to said wheel, a member connected to and oscillated by said balance wheel in synchronism therewith, pawl means carried by said member, a time train including a ratchet wheel driven by said pawl means, and means includin an electric circuit made and broken in sync ronism with the oscillations of said balance wheel to vary the torque of said spring on said wheel and thereby maintain said balance wheel in oscillation.

15. In an electric clock or the like, a balance wheel, a member connected to and oscillated by said balance wheel in synchronism therewith, pawl means carried by said member. a time train including a ratchet wheel driven by saidpawl means, a hair spring connected to said balance wheel for securing regular oscillations thereof, and means including circuits made and broken in synchronism with the oscillations of said balance wheel for varying'the tension of said spring to maintain said balance wheel in oscillation.

16. In an electric clock, an electromag netic device includin a pair of electromagnets having paralFel spaced apart cores, a concave plate of non-magnetic resilient material extending between said cores and bearing against the ends of the electromagnet's with the concave face toward the electromagnets, an armature rockably mounted intermediate of its ends on said plate at a point between said cores, means for clamping said plate against said electromagnets and adjustable to compress said plate toward the electromagnets variable amounts at a point intermediate the ends of said plate, whereby said armature will be carried toward or from said cores by the flattenin of said plate and the limits of oscillation 0% the armature variedequally, and a flux conducting bar having an end adjacent said armature and its opposite end adjacent the opposite end of said electromagnets.

17 In an electric clock, an oscillatory time member, a spring connected to and synchronizing the oscillations of said member, an electromagnet. an oscillating pivoted armature for said electromagnet connected t o said spring for varying the stress therein as the armature oscillates to maintain said member in oscillation, and means for varying equally the limits of movement of said armature on both sides of its pivot.

. ARTHUR- F. POOLE.

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