US2322861A - Constant speed body - Google Patents

Description

June 29, 1943.

G. LUCKEY CONSTANT SPEED BODY Filed Nov. '24, 1937 3 Sheets-Sheet 1 FIG.

650. P. Lycxzr FIG.8

IIIIIIII'IIIIIIIIIII VIII'III'IIIIIIIII INVENTGR.

ATTORNEYS June 29, 1943. P, LU Y 2,322,861

CONSTANT SPEED BODY 2 Filed Nov. 24, 1937 3 Sheets-Sheet 2 E 45 4| 4s as 1 as f 1 I h 1 a 5 77/ W 3 7 I 54 35 I as '7 12 lzlr 23 I J J as I' 6'50. 1? Lac/ Er 2 m II 2: [IT Q uvwzzvmk I Y g7 nc x FIG. 3 RESPOMSWE ATTORNEYS. owner 4 June 19434 G. P. LucKEY CONSTANT SPEED BODY Filed Nov. 24, 1937 3 Sheets-Sheet 3 650. P. LUC/(EY INVENmR. BYWZ;%

Ammvsys.

Patented June 29, 1943 I 2,322,861 CONSTANT SPEED BODY Y George P. Lackey, Lancaster, Hamilton Watch Company,

Pa., assignor to Lancaster, Pa.

Application November 24,1937, Serial No. 176,297

27 Claims.

The object of this invention is to obtain an exactly constant speed rotating body. This is preferably done by mounting upon an approximately constant speed body, a second body which is periodically controlled to exactly constant speed.

A further object of thisinvention is to provide mechanical means and instrumentalities by which approximately constant rotation can be controlled by exactly constant impulses to effect exactly constant rotation.

A further object of this invention is to provide improved means for testing a moving body under observation by means of an exactly constant speed rotating shaft. A still further object is to provide improved means for supporting and operating a testing device.

Further and more specific objects, features, and advantages will more clearly appear from a consideration of the specification hereinafter taken in connection with the accompanying drawings which form part of the specification, and which illustrate several forms the invention may take.

In the drawings:

Fig. 1 is a diagrammatic view illustrating the apparatus embodying my invention, and as used for watch timing.

Fig. 2 is a diagram showing the cumulative effect of error.

Fig. 3 is an enlarged sectional view of the rotat ing system illustrated in Fig. 1.

Fig. 4 is a, plan view of the correcting portionof the rotating system'.

Fig. 5 is a modification of Fig. 4 showing a different type rotor or correction arm. I

Fig.6 is a top view of the particular type motor taken on the line 6-6 of Fig. 3.

Fig. 7 is a modified form of rotating system.

Fig. 8 is another modification of the upper end of the rotating system.

Fig. 9 is a further modification of the upper end of the rotatingsystem.

Fig. 10 is still a further modification of the upper end of the rotating system.

Although it is expensive and diificult to obtain a rotating body which will-rotate at an exactly constant speed, it is fairly cheap and inexpensive to obtain an oscillating body whose period is exactly constant. For many purposes it is desirable to have a constant speed rotating body, as such a body has many advantages over an oscillating body. An oscillating body can only be used for timing objectswhere the period of the period of the oscillating body. On the other hand, a body rotating with an exactly uniform velocity can be used by stroboscopic or other means to obtain accurate timing of devices which timing may be any small fraction of the rotational period of the said body. In the following invention a method is described whereby the accuracy easily obtainable with an oscillating system can be transformed to obtain a body rotating at exactly constant speed.

It is relatively easy to obtain a body rotat-' ing at approximate speeds. This can be done with an electric motor either by the induction, series, or synchronous type or by a spring motor with a centrifugal governor. Such a motor can be made to carry on its rotating element another rotating body free to rotate thereon but bound to the rotating body with a light frictional contact. Such frictional means can either be the pivot bearings carrying th second rotor, a lightly pressed frictional spring, or frictional means such as air or liquids If the motor is thenset in rotation, the second rotor will eventually assume the velocity of the first rotor for by so doing the frictional drag between the two moving objects will then be a minimum The second rotor being lightly coupled to the first rotor will, over a period of time, assume the average speed of the first rotor. Changes in speed in the first rotor will require considerable time to efiect the second rotor, due to the light frictional coupling, so that the second rotor will be little influenced by any rapid accelerations or decelerations of the first rotor.

It is desirable, however, in inany cases to obtain a more constant rotational velocity of the second rotor than can be obtained by its assuming the average rotational speed of the first rotor. To this end use is made of impulses of whatever kind, obtained from an exactly constant period oscillating body. Such a constant period oscillating body may be a pendulum of a clock, a tuning fork, element of a chronograph, fine watch, or other time piece, or any other exactly constant period body. An impulse canibe picked up at one portion of the path of the oscillating body either by an electrical contact in the path of the oscilof various types.

the periodic oscillating time pieces 2 ruption of the light beam which is picked up by a photo-electric cell and amplified to give a uniform recurring impulse, or by many other arrangements. This impulse can then be transferred to the first rotating body through brushes and by means of electro-magnets properly placed, was jets, or other mechanical means which ght affect the rotation of the second rotor.

One general way of accomplishing this is as follows: assume that there are stationary electromagnets through which a periodic electrical impulse is sent from a clock. On the second rotating bodyis an arm which may be in the shape of a bar, a rectangular-like shape, or a composite element having more than two poles or projections. The speed of the first rotating body is so adjusted that it is approximately in step with the periodic impulses. When these impulses occur, the arm on the second body, and rigidly fastened to it, may be either ahead or behind the position of the energized magnets. The electrical impulses will then cause the magnets to receive a deceleration if the arm is ahead of, and an acceleration if the arm is behind, the central position in which it lines up with the magnets. In this way each time the magnet receives an electrical impulse the arm receives a correction or a check on its speed so that it is held in step with the period of the oscillating body at one or more points in its path. It has been found that, at times, the action of the arm would tend to be unsteady to a very small degree. Pole faces were attached to the electro-magnets, but that did not solve the problem. After much research and experimentation the damping cup or friction cup was invented, which always'gives smooth and steady operation. The cup or ring is mounted .on the first rotating body, and movement of the cup creates either air or liquid currents which resultin a frictional pull against the second, rotating body causing the second body to follow the first body although always, of course, lagging behind in time in accelerating and decelerating.

By adjusting the strength of the impulses, the frictional coupling between the first and second rotors, and the approximate speed of the first rotor, it is possible to obtain a rotating arm whose rotational period will be veryclose to if not equal to that of the controlling electrical impulses; and because of the inertia of the second rotating body, its rotational velocity between, the moments at which it is affected by the electrical impulses will be very constant.

The above general principles of means to obtain an exactly constant period of rotation will be now specifically applied to testing a watch and the devices invented therefor. However, it is to be understood that this method and apparatus is not limited to its use to this particular field,

nor limited to the very accurate timing of any oscillating, reciprocating, or vibrating unit, but is claimed in its broadest aspect as described hereinbefore in the general description of the invention.

In the'checking of watches or other esca'pement itis customary to allow these to operate over a long period of time, for example twenty-four hours, to determine whether are correctly timed. In case the timing can be checked to one second in twenty-four hours an error of plus or minus one second in 86,400 seconds is possible, which means that the error of a watch can, by timing it over a twenty-four hour period, be checked within one part in 86,400. To

they.

I obtain accurate timing by this method it is necessary that the watch be placed under for long periods of time, and it is not possible to observation wheel, when illuminated byv flashes of light occurring with extreme accuracy at constant intervals. In the following description the method is described in its application and in connecton with the timing of a conventional watch escapement, consisting of a balance wheel and hairspring forming the oscillating system which are driven by a pallet and fork from an escape wheel.

A radius of the balance wheel, as for example the balance arm in oscillating moves from the position in which it would be at rest in case it were not oscillating (hereinafter called the zero position) to a position where the hairspring is stressed to its maximum. When this position is reached the balance wheel comes to a stop, and reversing its motion starts to move in the oppoe site direction. Up to the time the balance wheel reaches zero position the energy stored in the hairspring is supplied to the balance wheel, in-

creasing its speed, until at the zero position there is no longer any tension in the hairspring and the balance wheel has attained its maximum speed. From this point on, the balance wheel stores its kinetic energy as potential energy in the hairspring, and the hairspring is stressed in the opposite direction. The balance wheel continues its motion until all its energy of motion has been transferred into a stress in the hairspring; at which point the balance wheel stops, and again starts to move in the reverse direction:

As long as sufllcient'energy is supplied to overcome energy lost through friction, the balance wheel will oscillate back and forth, and if properly designed the oscillations of the balance wheel will be very constant. The time for a complete oscillation of the balance wheel, that is, the time required to move from zero position to the point where the hairspring has received its maximum stress in one direction then through zero position to the point where the hairspring has received its maximum stress in the opposite direction and again back to its zero position is the period of oscillation of the balance wheel.

In watches the period of the balance wheel is usually two-fifths second. In case a watch has a two-fifths second period and is accurately timed the balance wheel will pass zero position every one-fifth second, and as it passes through this zero position it will have its maximum velocity. Thus, every one-fifth second the balance arm of the watch will be seen passing its zero position, first going in one direction and then in the oposite direction, and will'be traveling with its maximum velocity.. I

Now, if a light were made to illuminate the balance wheel for a very short period of time, say one-three thousandth second, each time the balance arm is in its zero position the balance arm will be illuminated for such a short time that it will "appear to remain stationary. This stationary image of the balance arm will be seen in one case when the balance arm is passing in one direction, the next time when the balance arm is passing in the opposite direction. From this it can been seen if the flashes of light are occurring exactly one-fifth second apart and if the position in the v make the balance'arm appear asaaser flashing light.

wheel is a trifle shorter than two-fifth second,

and to start with the light is made to flash at the time the balance arm is in its zero position, the next time the light flashes the balance arm will have passed through its zero position and gone a trifle beyond. On its next return the balance arm will go twice as far beyond the zero opposite direction, on the next passage three times as far, etc. Thus, for each succeeding flash of light the balance arm will be seen farther from its zero position, the images alternating right and left. If such a balance wheel is observed by means of a flashing light and thetime of the light'flash is adjusted to stationary at its zero position, first a single image of the balance arm will be observed. Then as time passes the images of the balance arm moving in opposite directions will no longer be at the zero position and the observed effect will be a slight flicker in the image of th balance arm. This flicker will increase as the images of th balance arm move farther and farther from their zero position until flnally two distinct images of the balance arm are observed on either side of the zero position. These two images during further observation will appear to move farther apart. From this it can be seen that if the period of the balance wheel is not the same as the period of the flashing light,

this fact can be quickly noticed.

This method of observing the difference in rates between the balance wheel and the flashing light is extremely sensitive. Assume, for example, that the balance wheel has an amplitude of turn, that is, that the balance arm moves turn to the right and turn to the left from the zero position. The velocity of 'the balance at its zero position will be such that it would make a turn, if th velocity would remain constant, in approximately /24 second. Assuming that by the above method a difference of /100 of one turn between the two images of a balance arm would be noticeable by the flicker produced, then this /100 of a turn difference would be produced when one image was /200 of a turn to the image /200 of a turn to the left of the zero position. The time necessary for.

right and the other move /200 of a turn past the be about View of a second. From this it can be seen that as soon as the difference in time between the balance wheel ,and the flashing light amounts to /4800 second, a noticeable flicker of the balance arm will be observable. In other words, if the two images of the balance arm traveling in opposite directions are superimposed, then a change in the rate of the balance wheel with respect to the flashing of the light of /4800 of a second will be observable. If, after the superposition of the balance arm images, a minute is required for the flicker to become observable then the balance wheel is gainthe balance arm to zero position would ing at the rate of /4800 second a minute or seconds in twenty-four hours. Thus, in on minute greater accuracy can be obtained by this method of timing than can be obtained in twenty-four hours by the conventional method.

The same effect in the changing of the position of the balance arm image would be observable if the watch were running slower than the Thi is made more apparent in Fig. 2, which shows a balance wheel and arm and also a chart showing the different positions of the balance arm at different times. Point A on this chart shows the position of the balance arm each time it is illuminated by a flashing light if the flashing light has half the period of the balance. Point 13 shows the position of the balance arm image in successive stages if the period of the balance arm is shorterthan the flashing light, and the points designated C show the position of the balance arm if the balance is greater than the period of the flashing light. I Y

To obtain the illumination of the balance arm it is desirable to have a flashing light in which the time at which the light flashes can be readily changed to make the light flash sooner or later without changing the time between the light flashes. In this way the light can be'made to illuminate the balance arm in any position and can be adjusted'so that the balance arm is illuminated when at its zero position. Then, if the half period of the balance arm and the period of the light are not the same, the time at which the light flashes can at a later time be slightly changed until the balance arm is again in its zero position. If the balance arm is faster than the flashing light the light can be made to flash at an earlier time, and if it is slower than the flashing light, the light can be made to flash later. Then the amount it has been necessary to change the time of the light flashes I ance arm to its zero position after a certain elapsed time will give an exact measurement of the time change between the two and the period of the balance wheel. Whether it is necessary to speed up or slow down the time at which the light flash occurs will show whether the watch is running fast or slow. a

A mirror, 49, is mounted upon a shaft 46, rotating at exactly 300 R. P. M., thus making a revolution every one-fifth second. A light source, II, and lens, H, are placed above the rotating shaft directed toward the mirror so that the light is reflected and the image of the light, as the mirror thrown around a circle centered in In case a slit, II, is placed on the circumference of this circle and the light is allowed to shine through it into the watch, the light will be thrown through this slit once during each revolution of the rotating shaft. If the slit is ,6 inch wide and the circumference of the circle on which the image of the light source is cast is 60 inches, then the light will traverse the circumference every one-fifth second for a period of 0 second. If the balance wheel is placed behind this slit it will be illuminated during this period of time. Now, if the housing or mounting "5, for rotating shaft, 46, is rotated, or if the slit is moved around the rotating shaft, the light can be made to flash at a time ing upon the amount the mounting or the slit is moved. Howevenas soon as this movement has stopped, the time between the flashes will be exactly one-fifth second apart. In case the mounting, l6, of the rotating shaft or the slit, I5, is moved one complete turn, the time at which the light flashed will second. If the housing or slit is moved /60 turn. the flashes occur will have sooner or later dependand the phase of half period of the to again bring the bal have been changed one-fifth the flashing light is adjusted by moving the rotor mounting or the slit until the balance arm appears in i s zero position without flicker, then if after observing the balance arm I for one minute it is found that the rotor mounting has to be moved in the direction of'rotation it turn to bring the images of the balance arm together again, this will show that in onggninute the watch has gained 5 of a second or it is gaining at the rate of less than $5 second, i. e., second, a day. A reverse rotation of the rotor mounting of the same amount to superimpose the images would show a loss in the rate of the" watch of the-same amount.

There are two ways to obtain correctly timed light flashes, or what amounts to the same thing,

a, shaft which will rotate at exactly a constant speed. One of these ways is to drive a motor at approximately constant speed, and to mount on the rotor shaft of the motor a second rotor or correction arm which is in very light frictional engagement therewith. This correction arm is thus free to turn on the rotor shaft of the motor when it is attracted at accurately timed periodic intervals by another force, and the arm can therefore be rotated at exactly constant speed. This apparatus is shown in Figs. 1-6, and 8-10.

asoaaoi The other method is to drive a motor by an alterhating current which has an extremely constant frequency such as can be obtained from a quartz crystal oscillator or a vibrating tuning fork, controlled by a master clock, or by any other means which may furnish extremely constant frequency. This apparatus is illustrated in Figs. 1, 2, and 'l.

The mounting or housing It containing the motor assembly and the upper rotor or correction arm assembly, is securely fastened to shaft 29 which in turn is journaled in base 21. To the neck of the base auxiliary dial is is fastened, while to the movable shaft 29 auxiliary pointer 20 and worm gear 18 are fastened.

The bearing and stationary pointer 22 are movably supported with respect to the base 2'! by stud 24. Shaftlb having a worm H at one end, and an adjusting knob and main dial at the other end is rotatably supported in bearing 25. If the worm i1 is out of engagement with the worm gear it! the housing It may be quickly movedto get'a magnets M3, is operative.

and the other end of which is fastened to the slip ring directly above. The two lowermost brushes connect the two bottom rings to the source of approximately constant current such as is commercially available and which is indicated at A. By fastening the line wires A to the support 28 instead of connecting the wires directly to the coil or rings 33 prevents the wires from becoming entangled and torn during the moving of mounting It. When the coil it slip ring,

is-energized it induces a field of one polarity in one set of pole pieces, and a difierent polarity in the other set of pole pieces thereby causing the rotor 38 of the motor to operate at approximately constant speed.

Rotor 3b is fastened on a shaft 39 which rotat'es on insulation 51 positioned on the upper end. of shaft 25. Said shaft 39 has a semi-circular knob it on the upper end, and a circular damping cup M intermediate. its ends. The shaft 39 passes through a guide 52 having upwardly extending arms 43 which support electromagnets M having pole faces 52 thereon. The upper rotor or correction arm 65 rests upon the semi-circular head 40, and although thearm is in light frictional engagement therewith it is free to rotate faster or slower when another force, such as supplied by the energised electro- The arm as may be of any width, and may be very narrow as shown in Fig. 5 at 65. The arm is preferably of soft iron or other highly permeable metal, but may be formed instead of a permanent magnet. In

- the latter case, however, a complete revolution quick adjustment of the phase of the light flashes to bring the balance arm to its zero position. The worm ll may then be engaged and a fine adjustment secured for observing changes in the time 01 the watch which is being tested. The stationary pointer 22 then indicates on the movable main dial 2 I, and the movable pointer 20 indicates on the stationary auxiliary dial IS, .the degree of. rotation of the mounting required by the error of the balance wheel, and data necessary to correct the error. The reason for the two dials is for the purpose of reading the instrument either from a standing or sitting position, and providing also an accuracy check on any reading.

The insulated rod 28 is fastened to base 21 and, extending through the slot 3| in the mounting 16, carries the brushes 32 which slide on the slip rings 33. These slip rings are carried by insulated rods which are supported either on the plate 34 or the bottom of the mounting l5. The slot 3| may be of any length short of 360 must be made between energizing periods instead of a half revolution as in the case of a soft iron bar. If desired, the number of electromagnets maybe increased for greater sensitivity. A shaft 65, made in one or two pieces, extends upwardly through the guide ti and has a mirror or other deflecting surface 63 adjustably mounted thereon by means of thumb screw 48. In moving the mounting it, the rotor 38 follows the pole pieces, and the arm 65, by means of the light frictional engagement with the head 40, also tends to follow the mounting. When current is supplied to the coil, the rotor almost instantly attains approximately constant speed.

For a short while the speed of the arm lags far behind the speed of the rotor because of the slippage between the head and the arm, but gradually the arm rotates at the same speed as the rotor. By supplying exactly constant periodic excitation such as might be controlled by a slave pendulum, a master clock, or by some other means, through the leads B to the electromagnets M, the speed of the arm can be advanced or retarded slightly, and thus the arm and deflecting surface kept rotating at exactly constant speed. The damping or friction cup 41, sometimes also called a stabilizing cup or ring as previously mentioned tends to accelerate or decelerate the speed of the arm to its own speed by reason of its movement setting up air currents and air friction which operate onthe arm thus providing extremely smooth operation.

In Figures '7 and 10, as well as in Figure 3, the deflecting surface is shown mounted on a shaft extending from a rotating element, while in Riga. 8 and 9, the reflecting surface 69' is mounted on the rotating element. The configuration of the rotating element might be such as to provide a reflecting surface itself.

Fig. 8 shows a modified point support forthe asaaacr to keep said arm in correction arm. Rotor l8 and damping cup 4| are secured to shaft 39-11. A narrow strip 58 extends inwardly from the cup to provide a support for the pin 53. By adjusting the screw 53 the friction between the rotor shaft 13-12 and the arm shaft 46' may be either increased or decreased.

Figs. 9 and 10 illustrate damping rings 4|", fastened to the rotor shafts 39' and 3!" respectivelyand filled with water, oil, or some other liquid. In addition to the light frictional engagement between the moving element, the liquid also provides friction for stabilizing purposes- In the device illustrated in Fig. 9 the force of the electro-magnets is lessened slightly by being positioned at a distance from the arm, while in Fig. 10, which shows the correction arm and electro-magnets elevated above the liquid damping bath, the full force of the correctly timed impulses is exerted directly on the am. In Figs. 9 and 10 the cup 54 and hollow receptacle 54' respectively provide a certain amount of buoyancy to counteract the weight of the arm.

Fig. 7 illustrates a testing device which may be used where exactly constant frequency current is available. In this modification only two slip rings and two brushes are necessary. 0,

indicates leads to a source of exact constant frequency power.

The testing devices are illustrated with reflecting surfaces which turn at the same speed as the arm. However, the arm might as easily be used to operate any sort of indicating device or scale, in which an approximate constant speed of rotation is checked or corrected, if necessary,

to an exact constant speed of rotation.

What I claim is:

1. An apparatus for producing an exactly constant speed rotating shaft comprising a constant frequency source of electrical energy, a mounting, a shaft, a rotor fixed to said shaft, a stator electromagnetically connected to said rotor'and fixedly positioned within said mounting, slide rings within the mounting connecting said stator to said constant frequency source of electrical energy, said slide rings permitting appreciable travel of the mounting so that the constant speed shaft will take more or less time to make a complete revolution if the mounting is being moved and indicating means mounted on said shaft.

2. An apparatus comprising an element rotatable at approximately constant speed, a second element in light frictional engagement with the first element and driven thereby, electromagnetic means for controlling the second element to exactly constant speed by timed impulses at short intervals by periodically accelerating or decelerating the speed of the second element.

3. An apparatus comprising an element driven at approximately constant speed, a second element carried by said first element, said second element being in light frictional engagement with the first element, electro-magnetic means energized at periodic intervals to bring said second element to exactly constant speed, and an indicating device supported y and rotated byv the second element.

4. An apparatus for producing an exactly constant speed rotating body comprising a motor, a shaft, a rotor on said shaft which revolves at approximately constant speed, an arm in light frictional engagement with theshaft, and means causing rotation or for exactly constant speed by electromagnetic lmlmlses.

5. An apparatus comprising a stator, a rotor, and a stabilizing. damping cup, a shaft for fixedly supporting both said rotor and said stabilizing, dam-ping cup, means to rotate said shaft, a correction arm frictionally supported by and movable on'said shaft. said stabilizing cup surrounding said correction arm so as to produce a damping effect upon said correction arm thereby tending to prevent rapid acceleration and deceleration, an indicator supported by said arm, and means for supplying a periodic force to said correction am so that said correction arm will rotate at a constant speed.

6. An apparatus comprising a mounting, a synchronous motor, a correction arm within the mounting, a shaft for said motor rotatable at approximately constant speed, said correction arm frictionally positioned on said motor shaft, magnetic means energized at periodic constant intervals to attract said arm, a shaft extending from said arm, and a reference member mounted on said shaft.

'7. An apparatus comprising a motorhaving a shaft rotatable at approximately constant speed, a second shaft impositively connected to said motor shaft, an arm mounted on said second shaft, electromagnetic means energized from an exactly constant source of supply and electromagnetically connected to said second shaft to control said second shaft, and reference means mounted on said am, and rotating with said arm.

8. .An apparatus for producing exactly constant speed rotation comprising a motor,'a shaft on said motor, a second shaft mounted on and normally turning with said first mentioned shaft,

a correction arm and a deflecting surfacemounted on said second shaft, and electro-magnetic means energized from an exactly constant source of energy so as to cause said correction arm and deflecting surface to turn at a rate, different than the rate of, the first mentioned shaft.

9. An apparatus for producing constant rotation comprising a synchronous motor, a shaft for said motor, a head forming the upper end of the shaft, a correction arm supported on said head and free to turn with respect thereto, indicating means mounted on said arm, means energized at periodic constant intervals to correct said am by electromagnetic impulses, and slide rings for said motor so that the apparatus may be turned through any angle.

10. An apparatus for measuring time intervals comprising a source of electrical energy, a motor comprising a stator and an approximately constant speed rotor, a body supported by and motivated impositively by said rotor, said body having an indicating surface, electromagnetic means to act on and cause said body to rotate at exactly constant speed, and slide rings connecting said stator with said source of electrical energy whereby said stator may be rotated throughout any angle without being disconnected from the source of energy.

11. An apparatus of the character described comprising a reference member, means to drive the reference member at substantially constant speed, a tick responsive device adapted to respond to ticks of a master watch, and actuating means controlled by the tick responsive device operatively connected to additionally control the movement of the reference member to synchro- 'nize the reference member with the master -watch.

12. An apparatus of the character described comprising a rotatable reference member, a shaft arranged to impositively drive said member. means to drive said shaft at a substantially constant speed, an armature rotatable with said member, an .electromagnet positioned to cooperate with said armature, a tick responsive device adapted to respond to ticks of a master watch, and an electrical circuit arranged to be closed by said tick responsive device and to energize said electromagnet.

13. An apparatus of the character described comprising a reference member, means to drive the reference member at substantially constant speed, a tick responsive device adapted to respond to ticks of a master watch, and actuating means controlled by the tick responsive device operative to give an adjusting movement to the reference member to synchronize the same with the master watch.

14. An apparatus of the character described comprising a rotatable reference member, means for rotating the reference member at a substantially constant speed, a tick responsive device adapted to respond to ticks of a master watch, and adjusting means controlled by the tick responsive device operative to retard the rotation of the reference member when the rtot'ation of the reference member leads with respect to the master watch.

15. An apparatus of the character described comprising a rotatable reference member, means for rotating the reference member at a substantially constant speed, a tick responsive device adapted to respond to ticks of a master watch. actuating means controlled by the tick responsive device operatively connected to give additional rotation to the reference member of an amount proportional to the extent to which the reference member lags relative to the watch, because of lack of perfect synchronism.

16. An apparatus of the character described comprising a rotatable reference member, means to drive the reference member at a substantially constant speed, a tick responsive device adapted to respond to ticks of a master watch, actuating means, and magnetic means controlled by said tick responsive device to rotate the reference member with respect to the substantially constant speed driving means to compensate for lack of synchronism between said constant speed driving mechanism and the master watch. 7

1'7. An apparatus of the character described comprising a ,shaft adapted to be rotated. at a substantially constant speed, a reference member rotatably mounted on said shaft,'a tick responsive device adapted to respond to the ticks of a master watch, means controlled in response to said tick responsive device for rotating the reference member on the shaft to compensate for lack of synchronism between the reference memiber and the master watch. 3

18 In an apparatus for timing a moving body, a synchronous motor comprising a rotor and a stator, a second rotor movably mounted on said first rotor and driven thereby, and indicating means mounted on said second rotor, said rotor being controlled to the proper speed at short intervals by electromagnetic impulses from a constant frequency source of current.

19. In an apparatus for comparing the differ- I ence between standard frequency impulses and unknown frequency impulses, a synchronous 1. 9-

aaeaaei tor, a rotor mounted on said motor in light frictional engagement therewith and frictionally driven by the rotating part of the motor, but

being free to move independently of the rotating part of the motor, said rotor being controlled to the proper speed by said standard frequency impulses, and indicating means including an element rigidly attached to the rotor, and means for angularly adjusting, as a unit, the m'o/tor and rotor a certain distance. r

20. Apparatus for determining the period of a body movable about a center of motion and which forms a member of the control system of a time piece, which comprises means for producin accurately timed light flashes at constant frequency, including a synchronous motor operated [by approximately constant frequency, a correcting rotor driven by said motor through a light frictional clutch, means to control said rotor to operate at constant frequency, a rotatable support for said motor shiftable to change the phase of the light flashes.

21. In a watch testing apparatus, a stroboscopic device including alight source and a rotatable member for comparing the rate of a watch'to be tested with the rate of a master watch, means for impositively rotating said member at substan-' tially constant speed, an armature rotatable with said member, an electromagnet positioned to cooperate with said armature, and means for periodically energizing said electromagnet in synchronism with the beats of said master watch.

22. In a watch testing apparatus, a rotatable member, a shaft arranged to impositively chive said member, means to rotate said shaft at a substantially constant speed, an armature rotatable with said member, an electromagnet periodically energized at a standard frequency to correct the speed of said memberthrough the medium of said armature, and means including said member and a light source co-operating with a part of the watch beingtested to indicate the rate of said watch.

23. In a timing mechanism, a motor, a rotor, a slippable friction clutch interconnecting the rotor and motor whereby to rotate the rotor normally in synchronism with the motor, means for intermittently modifying the speed of rotation of the rotor comprising an armature member affixed-to the rotor, an electro-magnet and timed means adapted to intermittently energize the magnet whereby to attract the armature and cause slippage in the clutch.

24. In a timing mechanism, a motor, a rotor, a slippable friction clutch interconnecting the rotor and motor whereby to rotate the rotor normally in synchronism with the motor, means for intermittently modifying the speed of rotation of the rotor comprising an armature member aifixed to the rotor, an electro-magnet and timed means adapted to intermittently energize the magnet whereby to attract the armature and cause slippage in the clutch, said timed means comprising a time piece, means to energize the magnet by the tick of said timepiece, the armature member having a plurality of armature points adapted, during rotation of the rotor, to pass successively through the area of the field of said magnet.

25. In a timing mechanism, a friction member rotated by a motor, a moving element having a frictional engagement with said member whereof rotation of the points of the armature and means for successively energizing the magnet at equal periods to attract one of the points to the core and thereby cause slippage in said frictional engagement, whereby to rotate the moving element by the motor but to intermittently synchronize the speed of rotation of the moving element with the intermittent energizing of the magnet.

26. An apparatus of the character described comprising a rotatable reference member. means for rotating the reference member at a substantially constant speed, a tick responsive device adapted to respond to ticks of a master watch,

and actuating means controlled by the tick re the reference member.

27. An apparatus of the character described comprising a rotatable reference member, a shaft driven at a substantially constant speed on which said reference member is yieldably mounted, an armature rotatable with said reference member, an electro magnet positioned to cooperate with said armature, a tick responsive device adapted to respond to ticks of a master watch, and an electrical circuit arranged to be closed by said tick responsive device and to energize said electro magnet.

GEORGE P. LUCKEY.

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