US1852896A - Time keeping mechanism - Google Patents

Description

April 5, 1932. A. FVPOOLE 3,852,396

TIME KEEPING MECHANISM Original Filed March 25. 1927 3 Sheets-Sheet 1 INVENTOR flrZ/aati'loak April. 5, 1932. A, F, OOLE 1,852,896

TIME KEEPING MECHANISM Original Filed March 25. 1927 3 Sheets-Sheet 2 2192 v Q i lNVNTOR flZ/zarif ooze zfsATTORNEY April 5', 1932, F Lfi fiiifi TIME KEEPING MECHANISM Original Filed March 25. 1927 I5 Sheeis-Sheet 3 Z'SATTORNEY Patented Apr. 5, 1932 UNITED STATES,

PATENT OFFICE ASSIGNOB TO POOLE MANUFACTURING 60.,

CORPORATION OF NEW YORK TIME KEEPING MECHANISM Application filed March 25, 1927, Serial No. 178,382. Renewed March 27, 1930.

This invention relates to electric time keeping devices, and has for its object the provision of a simple and accurate mechanism for driving clockwork, recording apparatus, or

55 other devices in which a uniform rate of motion is desired. In such devices, as well as in clockwork, the frictional load on the time keeping mechanism tends to vary somewhat and accordingly affects the accuracy of the 1 time keeping.

vention is to provide a driving mechanism whose power will increase or decrease according to the demands upon it, leaving a substantially constant residuum of drive the pendulum or other time determining element, so that a variation in the external load will not react on the time keeping. Another object of my invention is to provide a vibratory motor, an electromagnetic means for actuating it, the vibratory motor being adapted both ,to deliver power to an external gear train and to maintain a time keeping element such as a pendulum or balance wheel in vibration.- A' furtherobject of my invention is to provide a vibratory motor and timekeeping element as described above and means for synchronizing the vibratory motor with the time keeping element. These and other objects of my invention will be apparent to those skilled in the art from the accompanying drawings and specifications.

In the accompanying drawings forming part of this specification and illustrating the principles of the mechanism, Fig. 1 is a side elevation of the mechanism showing the general arrangement ofparts.

Fig. 2 is a rear elevation partly in section taken substantially along the line 2-2 of Fig. 1.

Fig. 3 is a detail view illustrating the escapement and contact mechanism.

Fig. 4 is a perspective view of the pallets.

Fig. 5 is a plan view of the mechanism as viewed from above with the pendulum omitted. 7

Fig. 6 is a detail view of one form of pallet drive element. a y

The same reference numerals refer to the 50 same parts throughout the various views.

One object of the present in-' power to the shaft 5 engages Referring now to Fig. 1, the load or driven device which it is desired to operate at a regular rate of movement is represented by the clock 1, though it will be understood that the invention is equally applicable to various forms of meters, recording instruments, and other devices where an element must be moved according to time. The time determining element is represented by the pendulum 2, though it will be understood that any equivalent element such as a balance wheel may be employed.

lnmany instances the load of the clock or driven device becomes rather heavy for the ordinary clock mechanism, due to dust, paper friction, or other causes, and the power applied to the pendulum 2 may become so weakened as to afiect its time keeping qualities. To overcome this diiiiculty, I provide a second periodic device to carry the load, this device consisting of a vibratory electro-magnetic motor 3, having an armature 4: mounted on the shaft 5, which also carries the balance wheel 6, and is controlled in its oscillation by the spiral spring 7. This balance wheel is driven thru the attraction of the armature 4; by the pole pieces 8, 8, or the electro-magnet 9, which is periodically energized by the action of an electric contact operated by the pendulum 2, as will be described.

The electric current for the electro-magnetic motor 3 may be obtained from any suitable source. For example, in the mechanism illustrated dry cells such as the ordinary flashlight battery are contained in the post 30 and the current is conducted out thru the clip 31 and wire'32 to the electro-magnetic motor 3 and thence to the wire 83 toan electric contact device which will be described, after which it is grounded back thru the frame to the battery. The source of supply of electricity may vary of course to suit the conditions of various installations.

A tooth or pin 10 mounted on an arm of the teeth of a. fork 11 as the shaft 5 oscillates, the pin 10 generally swinging free of the fork for the end portions of its swing (see Fig. 2) and picking it up again on the return. The fork 11 is pivoted at 12 and carries at its other end the pallets 13 and 13', which are .thus rocked to and fro with a definite motion regardless of variations in the amplitude of vibration of the armature 4--due to the fact that the pin 10 is' only in driving engagement during the middle portion of its swing.

The pallets 13, 13', alternately engage the sides of the teeth of an escapement wheel 14, and the faces of the pallets are properly inclined-to feed the wheel 14 around one tooth at a time. The wheel 14 turns the pinion 15, by which motion is transmitted thru any suitable reduction gearing 16 to the clock 1 or'other apparatus which it is desired to drive.

The regularity with which this clock or other driven apparatus 1 is operated depends of course on the rate of vibration of the armature 4 of the vibrating motor 3. It is desired to maintain this rate of vibration constant, regardless of ordinary variations in the amount of the load 1, which necessitates that the power input to the motor 3 must increase as the load increases, and vice versa. A vibrating type of motor 3 is used because it has itself a certain natural period of vibration, and because it avoids brush friction and other ditficulties of a rotary motor. To

regulate the speed and power output of the' vibratory motor 3 there is provided a pendulum 2 or other time determining device and a flexible, leaf spring 17.

The spring 17 at one end is anchored to the frame, adjacent but at one side of the axis of oscillation of the pendulum, so that the free end of the spring may flex in the directions of oscillations of the pendulum 2. An impulse element 18 in the nature of a lever is pivoted between its ends by a pivot 19. One end of the element or lever 18 has a nose 20 which rides over the teeth of wheel 14, so that as the wheel 14 is rotated step by step, its teeth will rock the lever 18 in one direction, gravity holding the nose 20 against the teeth of the escapement wheel. The other end of the lever 18 extends laterally of its length and into the flexing path of the free end of the spring 17 so that the lateral arm of leverl8 may engage the free end of the spring 17 and flex it away from the position into which it is urged by its own resiliency. I

The free end of the spring 17 carries a contact button 21 which engages with a contact screw 22 carried by and insulated from the frame of the clock and extending endwise in a direction to oppose the movementof the button 21. The button 21 is urged against the end of the contact screw 22, by the resil- '22. The spring 17 is tensloned by. the leftiency of the spring 17, .and the screw 22 acts as a limit stop for the spring 17. When the lever 18 is rocked by an operation of the escapement wheel; its lateral arm will engage with the free end of spring 17 and flex it in a direction to carr the button 21 away from the screw 22, as s own in Fig. 2.

the .rig t.

The spring 17 extends somewhat beyond the button 21.and into the path of travel of the head of a screw 23 which is threaded through the pendulum 2, intermediate of its ends, and moves with the pendulum duril ig its oscillations The spring 17 is disconnected from the pendulum except for the bearing contact of its free end upon the screw 23. 1V hen the lever-18 is rocked positively by the teeth of the escapement wheel, the lat eral arm which engages and flexes the spring 17 will swing upwardly through an are which terminates substantially tangent to the spring 17 and hence the spring'will hold the lever 18 frictionally in this position until the pendulum flexes the spring and releases the lever in a manner to be explained presently.

As the pendulum swings to the right beyond its midposition, as observed in igs. 2 and 3, the head of the screw 23 will travel away from the spring 17 as shown in full lines in Fig. 3. As the pendulum swings in the reverse direction or toward the left in Figs. 2 and 3, it will-move, unaffected by spring 17 until it closely approaches its midposition of swing, as shown in Fig. 2, at which time the head of the screw'23 engages with the free end of the spring 17 that has been flexed bylever 18, whereupon the pendulum carries with it and further flexes the free end of the spring during the remainder of its swing to the left. The movement of the spring 17 with the pendulum releases the lever 18, which is then free to action of gravity and insert its nose 20 between the teeth of the escapement wheel. Since the escapement wheel is being operated rotate by the step by step from the vibratory electric motor while the ifl'rdulum is oscillating, the escapement wheel will have moved a half step position ,from that shown in Fig. 2 into the position shown in- Fig. 3, while the pendulum swings from mid-position to the left and back again to mid-position, which allows the nose 20 to enter the space between the escapeas the pendulum moves toward the right, the

button 21 may engage the screw 22 and close the electric circuit.

It will be noted that the button 21 is spaced from the screw 22 when the spring 17 is picked up by the screw 23 of the pendulum during its leftward swing (F i 2), and the spring ceases its action on t e pendulum during the swing of the pendulum to the right when the button 21 engages the screw ward swin of the pendulum, and exerts a retarding orce thereon which is converted into a ropelling force during the swing to Inasmuch as the action of the spring on the pendulum in a proplelling direction is somewhat longer than t -ment wheel teeth, at which time the lateral e retard- 1 I after the contact 21 meets '18 represents sufiicient power ing action, the net result is a propelling impulse on the pendulum which maintains itin oscillation. The adjustment of the screws 22 and 23 provides for a regulation of the amount of the impulse given the pendulum.

The spring 17 is mounted in the pendulum 2 under a certain amount of initial tension, as determined by the adjustable screw 20: mounted'in the pendulum rod, so that the fiexure given the spring 17 by the element to drive the pendulum. Since the throw of the element 18 is fixed, the amount of power transmitted to the pendulum spring 17 and pendulum 2 depends principally on the strength and initial tension of the spring 17l In operation, the contact 22 as shown in Fig. 3, the screw 2a swings on with the pendulum free of the spring 17, and picks it up again on the return strokeas shown in Fig. 2.

The method by which the pendulum 2 regulates the vibratory motor 3-so that the two stay in synchronism is as follows:

When the pendulum 2 swings to the right, the electric contact 21 carried on the spring 17 meets the contact screw 22 and closes an electric circuit thru the magnet 9, which tends to accelerate the armature 4. The circuit remains closed until the armature 4:, in passing thru the middle of its swing, actuates the pallets which drive the wheel 14 and thus swings the element 18 against and flexes the spring 17 away from the contact screw 22 and breaks the circuit.

To start the clock, the pendulum is first started swinging in the as the contact 21, 22, is closed, the armature 1 which has been held somewhat retracted by hand is released, so as tobreak the contact 21, 22, immediately after it is madeit being necessary to start the armature 4 and pendulum 2 initially in substantially the proper phase-of synchronism, as the clock will not start by the pendulum alone.

The length of time that the electric power is applied is measured from the instant the pendulum action closes the circuit until the instant the action of the vibratory armature opens it. Therefore, if the period of the vibratory armature tends to lag behind, the

- length of time that the electric power is apthe pendulum within a plied will increase. The increased power then tends to accelerate the armature action; and as the armature action catches up with the period quicker and the power impulses of the vibratory motor correspondingly diminishso that the armature keeps in synchronism with fraction of a vibration. The power input, with constant potential, is of course proportional to the length of time that the circuit is closed; that length of time is proportional to the'lag of the armature, and that lag is in general proportional usual way, and then. i

of the pendulum, the cut-oil comes to the load; so that the power input is substantially proportional to the load of the driven apparatuswithin the limits of synchronism. This permits the desired functioning of the device.

- The natural period of the vibrating armature 1, considered as a balance wheel, is so proportioned that it would be slightly slower than synchronism were it not for the impetus of the magnetic impulses. The magnetic impulses tend to accelerate the armature and make its period faster. The reason for making the natural or unassisted period of the armature slightly slower than that of the pendulum 2 is that this permits the armature tohave an increasing lag with the increasing load, this lag being utilized to bring in the compensating increase in power input as described.

The vibratory armature t and the pendulum 2 are of course in synchronism so far as vibration per minute are concerned, so that power drawn from the armature 4 can drive the pendulum 2the lag referred to being no more than a fraction of a vibration.

Tn the foregoing l have described one embodiment of my invention for purposes of. illustration, and it will be understood that it is not limited to the particular form shown, but is susceptible to various modifications and changes oi arrangement, form, and details to adapt it to various installations, as will be apparent to those skilled in the art, without departing from the scope of the invention as specified in the following claims.

ll claim:

1. In a time keeping apparatus, the combination of a time determining element having a periodic motion, a vibratory motor having a natural period somewhat slower than the time determining element, and electrical means for increasing the speed of the motor so that it is maintained in synchronism with the time determining element.

p 2. In a time keeping apparatus, the combination of a time determining element having a periodic motion,'a vibratory motor of the electro-magnetic type, means operated by said time determining element for energiz-.

ing a periodic motion, a vibratoy motor, means for keeping the time determining element and the vibratory motor in -synchronism, including means by which the motor may supply power to drive mining element.-

4. In a time keeping apparatus, the combination ofa time determining element have the time detertime keeping apparatus, the com- 1 -bination of a time determining element havportion of the power ing a periodic motion, a vibratory motor, an external load, means for keeping the time determining element'and the vibratory motor in synchronism, including means by which a portion of the power of the motor is diverted to drive the time determining element, while the balance of the power of the motor is applied to the external load.

5. In a time keeping apparatus, the combination of a time determining element having a periodic motion, a vibratory motor, an external load, means for keeping the time determining element and the vibratory motor in synchronism, includ ng means by which a of the motor is diverted to drive the time determining element, while the balance of the power of the motor is applied to the external loads, and means for varying the power of the motor in proportion to the external load.

6. In a time keeping apparatus, the combination of a t me determining element having a periodic motion, a vibratory motor, means for driving the time determining element by mechanical energy derived from the motor, and means for regulating the motor by electrical energy controlled in synchronism with the period of the t me determining element, whereby the time ment and the vibratory motor may be maintained' in synchronism.

7. In a time keeping apparatus, the combination of a time determining element having a periodic motion, a vibratory motor of the electro-magnetic type, means for drivin the time determining element by mechanical energy derived from the motor, and means for regulating the motor by electrical energy controlled in synchronism with the period of the time determining element, whereby the time determining element and the vibratory motor may be maintained in synchronlsm.

8. In a time keeping apparatus, the combination of a time determining element having aperiodic motion, a vibratory motor of the electro-magnetic type, means operated by said time determ ning element for energizing said motor, means operated by said motor for de-energizing said motor, said de-energizing means being operated in the middle portion motor so as tobc independent of the amplitude of vibrat on,

the amount of power applied to said motor depending on the lag of the motor, whereby the motor and the time determining element are kept in synchronism.

9. In a time keeping apparatus, the combin ation of a vibratory motor, an escapement wheel driven by said motor, a rocker arm driven by said escapement wheel, a t me determining element having a periodic o.scilla-. 'tory motion. a driving spring urging said time determining element in one direction, said driving spring being stressed from the determining ele-' 1 somewhat in said opposite operation of the rocker arm by saidvibratory motor, and an electric circuit controlling said motor and periodically rendered effective by said spring.

10. In a time keeping apparatus, the combination of a vibratory motor of the electromagnetic type, -an escapement wheel driven by said motor, a rocker arm driven by said escapement wheel, a time determining element having a periodic oscillatory motion, a driving spring urging said time determining element in one direction, an" electric circuit periodically rendered effective by said spring and controlling said vibratory motor, said rocker arm being arranged to operate in conjunction with said spring to cut off the flow of power and at the same time to store in said spring mechanical energy by which the time determining element is maintained in its periodic oscillation.

11. In a time keeping apparatus, the combination of a vibratory motor having a variable amplitude of vibration. oscillatory gearing arranged to be driven during the middle portion of the vibration, the vibratory motor swingine' free at the extremities of its vibrat on, pallets periodically oscillated by said gearing, an escapement wheel driven by said pallets, an impulse member driven by said escapement wheel, a time determining element having a periodic motion of oscillation. a driving spring urging said element in one direction and stressed by said element while said element is moving in the opposite direc- 85 tion, energv being periodically stored in sa d bv the action of the impulse member,

p g which stresses said spring somewhat in said opposite direction, said impulse member being mainta nedin position by friction with the spring until said spring is stressed by said element. and means controlled by said spring for controlling said motor.

12. In a. time keeping apparatus, the comb nation of avibratory motor having a variable amplitude of vibration. oscillatorygearing arranged to be driven during the middle portion of the vibration. the vibratory motor swinging free at the extremities of its vibration, pallets periodically oscillated bv said gearing, an escapement wheel driven by said pallets, an impulse member driven by said escapement wheel, a time determining element having a periodic motion of oscillation, a driving spring urging said element in one direction and'stressed by said element while said element is moving in the opposite direction, energy being periodically stored in pulse member, which stresses said spring pulse member having an arcuate motion terminating substantially tangent to said spring, whereby a definite amount of fiexure is given the driving spring irrespective of slight direction, said im termining el with each ing a periodic variations in the travel of the impulse mem- 13. In a time keepingppparatus having an electric circuit, the com ination of an escapement wheel having teeth, oscillatory pallets arranged to drive the escapement wheel thru lateral engagement with the teeth, and a rocker arm operated by engagement with the end of the teeth, the axis of oscillation of the rocker arm being at right angles to the axis of oscillation of the pallets, and means operated by the rocker arm for breaking the electric circuit.

14. In a time keeping apparatus having an electric circuit, the combination of an escapement wheel having teeth, oscillatory pallets arranged to drive the escapement wheel thru engagement with two sides of the teeth, a rocker arm'operated by engagement with a third side of the same teeth, and means operated by the rocker arm for breaking the electric circuit.

15; In a time keeping apparatus, the combination of a time determining eiement having a periodic moti'on, a driving spring stressed thereby and urging said element in one direction, a vibratory motor arranged to deliver energy to said driving spring with each vibration of the time determining element, and means for regulating the ampli tude of the vibratory motor, whereby it may be maintained in synchronism with the time determining element.

16. In a time keeping apparatus, the combination of a time determining element havmotion, a driving spring stressed thereby and urging said elements in one direction, a vibratory motor arranged to deliver energy to said driving spring with each vibration of the time determining element, and means for regulating the period of the vibratory motor, whereby it may be maintained in synchronism with the time deement.

17 In a time keeping apparatus, the combination of a vibratory motor, an-escapeinent wheel driven by said motor, a rocker arm driven by said escapement havmg a periodic oscilwheel, a time determining element 'latory motion, a drivin spring stressed by said time determinin e ement, said driving spring being arrange to receive mechanica energy from the operation of the rocker arm vibration of the time determining element, and an electric contact periodically operated b said time determining element for contro ing the application of power to the vibratory motor. a

18. In a time keep apparatus, the combination of a time determining element having eriodic motion of oscillation, a spring driving element stressed by said element and urgingsaid element in one direction, a vibratory motor of the electro-magnetic type having an electric circuit, said spring element serving also as conductor in said circuit, an electric contact operated by the movement of said spring for periodically closing the circuit of said vibratory motor, means operated by the vibratory motor for opening the circuit, the power input increasing with increasing lag of the motor, whereby the vibratory motor and the time determining element are maintained in synchronism.

19. In a time keeping apparatus, the combination of a vibratory motor of the electro magnetic type, a tooth rotated by said motor in alternate direction, a fork engaged by said tooth in a portion of its swing, the tooth swinging free of the fork at the exremes of its swing, pallets oscillated by said fork, an escapement wheel having teeth driven by said paliets, a pinion rotated by the escapement wheel, a gear train driven by said pinion, a rocker arm operated by engagement with the teeth of the escapement wheel, a time determining eiement having a periodic motion of oscillation, a spring driving element stressed by said element, the rocker arm being arranged to transmit methanical energy to said spring at each oscillation of the time determining element, the spring also being in the electric circuit of the motor, an electric contact in said circuit arranged to com plate the circuit when the spring swings into contact with it, the circuit being broken when the driving spring receives its mechanical ener whereby the vibratory motor and the time determining element are maintained in synchronism,

20. in a-time keeping apparatus, the com-- bination of a vibratory motor of the electromagnetic type, a tooth rotated by said motor in aitcrnate direction, a fork engaged by said tooth in a portion of its swing, the tooth swinging free of the fork at the extremes of its swing, pallets oscillated by said fork, an escapement wheel havin teeth driven by said pallets, a pinion rotat by the escapement wheel, a gear train driven by said pinion, a rocker arm operated by en agement with the teeth of the esca ement wheel, a time determining element aving a periodic motion of oscillation, a spring driving element stressed by said element, the rocker arm being arra d to transmit mechanical energy to said 1 spring at each oscillation of the time determining element, the spring also being in the electric circuit of the motor, an electric contact in said circuit arranged to complete the circuit when the spring swings into contact with it, the circuit being broken when the driving spring receives its mechanical energy,

and an adjustable screw carr'ed with the time determimng element, said screw engagmg said spring periodically to withdraw it out of contact with the rocker arm, whereby the vibratory motor and the time determining element are maintained in synchronism.

21. In a time keeping apparatus, the comtam it in operation, and means controlled b bination of'a time determining element having a periodic motion, a vibratory motor element, and an electro-magnetic means for maintaining the motor element in vibration, said electro-magnetic means being jointly controlled by the time determining element and the vibratory motor element, whereby the vibratory motor element and the time determining element may be maintained in synchronism.

22. In an electric clock, an electrically actuated vibratory motor having a control circuit effective at each beat of the motor, and means for varying the amount of energy delivered to the motor at each beat automatically whenever its vibratory rate deviates from a desired normal rate whereby the. period of the motor may be regulated and maintained normal.

23. In an electric clock, an oscillatory time keeping element, a vibratory motor, means including an electric circuit for delivering impulses to said motor at each beat to ma insaid element for varying the energy delivered to said motor at each beat in a manner to vary the period of said motor and synchronize the oscillations of the motor with those of said element.

24. In an electric clock, the method of synchronizing the oscillations of an electricall which comprises givi said motor a natural period of oscillation s ightcontrolled'by said driven by said pal determining tuated vib 1y different from that of said varying the energy delivered to the motor at each beat proportionally to the extent that the oscillations of the motor and element are out of step with one another, so as to temporarily change the period of said motor, and maintain it in oscillation synchronously with said element.

25. In a time keeping apparatus, the combination of a vibratory motor havin a va riable amplitude of vibration, osci atory gearing arranged to be driven during the middle portion free at the extremities of its vibration, pa ets periodically oscillated by said gearin an escapement wheel ets, an oscillating time element, and means coacting tween said element and said esca ement, wheel for controlling said motor an keeping it automatically in synchronism with said element and keeping said element in oscillation.

26. -In an electric clock, an electrically acratory motor havin a control circuit efiective at each beat 0 the motor, an oscillatory time element, means element for varying the amount of energy delivered to the motor at each beat in accordance with the degree of saidelement and motor,

synchronization of element, and

of the vibration, the vibrab tory-motor swingin whereby the period of said motor may be maintained in synchronism with said element, and means controlled by said motor for delivering an impulse to said element at intervals to maintain it in oscillation.

27. In an electric clock, an oscillating time measuring element means engaged and stressed by said element While said element is moving in one direction from an intermediate position, and imparting'an impulse to said element during its return movement towards said position, and means operable upon said first means while said element is continuin the remainder of a complete 0scillation ibr varying the point at which said first means is engaged by said element, whereby the propelling action of said first means will be reater than its retarding action and said e ement will be maintained in oscillation.

28. In an electric clock, an oscillating time measuring element, a spring device engaged by said element to retard yieldingly its movey ment while approaching one end of its arc of y ment of the action of said spring device duractuated vibratory motor with those of a tlme keeping element,

mg the remaining portion of a complete oscillation of said element, and means operable on said spring device to move it in the direction in which it is moved while retarding the oscillation of said element, whereby the retarding action of said spring device on said element will be less than the propelling action on said element, and said element will be maintained in oscillation.

29. In an electric clock, an time measuring element, a spring device engaged by said element to retard yieldingly its movement while approaching one end of its arc ofoscillation, and urging said element in the o posite direction during the ginning of the return swing of said element from said end, means engaged by said spring device at an intermediate position in t e oscillation of said element for relieving said element of Vice during the plete oscillation operable on said springdevice to move it in t c direction in which it is moved while retarding the oscillation of said element, whereby the retarding action of said spring device on said element will be less than the propelling action on said element, and said element will be maintained in oscillation,

oscillating the action of said spring deremaining portion of a comsaid first means being adjustable to vary of said element, and means tion of said pendulum, a stop engaged by erable the free end of said spring, with said spring flexed in one direction of oscillation of said pendulum, whereby said spring will be urged resiliently against said stop, said pendulum having means engageable with the free end of said spring to flex it away from said stop while said pendulum is swinging in one direction away from an intermediate position, whereby sa1d spring will retard such movement of the pendulum, and will propel said pendulum in a reverse direction after said pendulum reaches the limit of its flexing operation and starts a return swing, the pendulum releasing said spring and continuingits oscillation after the spring engages said stop until the pendulum completes a cycle of oscillation, and means opduring the movement of said pendulum while free from the action of said spring said stop to make the retarding action of said spring less than the propelling action, whereby the pendulum will be maintained in oscillation.

31. In an electric clock, an oscillating time measuring element, propelling means engaged and stressedby said element during movement oi said element in one direction away from an. intermediate position, and propelling said element in the reverse direction during the return movement to said intermediate position, said element being 'free to complete its cycle of oscillation uninfluenced by said propelling means, and

means rendered effective automatically by said propelling means when said element passes said propelling movement for stressing said propelling means in the direction in which it is stressed by said element.

32. In an electr1c clock, an oscillating time measuring element, a spring device engaged by said element and stressed during movement of said element in one direction from an intermediate position in its oscillation,

and propellingsaid element during the return movement to said intermediate position, a stop engageable 'by said spring at said intermediate position for relieving said element from'the action of said spring during completion of a cycle of oscillation of said element, means including an electric circuit closed by the engagement of said spring'device with said stop for stressing said spring device in the direction of its movement away from said intermediate position, whereby the retarding .action of-said-spring will be of shorter duration than the ropelling action, and said element will lie maintained in oscillation.

33. In an electric clock, an oscillating time measuring element, a spring device enfor flexing said spring away from,

gaged by said element andstressed during movement of said element in one direction from an intermediate position in its oscilla tion, and propelling said element during the return movement to said intermediate position, a stop engageable by said spring at said intermediate position for relieving said element from the action of said spring during' completion of a cycle of oscillation of said element, an electric circuit closed by engagement of said spring device with said stop at approximately said intermediate position of said element, an electrically actuated vibratory motor maintained in synchronism with said element by said circuit, and means controlled by said motor while said element is completing its cycle of oscillation free of the action of said spring device for stressing said spring device in the direction in which it is stressed by said element at the beginning of said cycle of oscillation from said intermediate position, whereby the retarding action of said spring device on said element will be less than its propelling action thereon, and said element will be maintained in oscillation.

34;. Ina horological device, an accurate time keeping unit, a power actuated time keeping unit, means-controlled jointly by said units for regulating the rate of operation of said power operated unit in a manner to cause it to operate in approximate synchronism with said first unit, and means operated by said power actuated unit for supplying driving energy to said first unit. In witness whereof I have hereunto set my hand this 22d day of March, 1927'.

, ARTHUR F. POOLE.

intermediate position during said k

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