US2070239A - Electric clock - Google Patents

Description

FebiQ, 1937. LE 2,070,239

ELECTRIC CLOCK Filed Jan 11, 1952 IN V EN TOR.

Patented Feb. 9, 1937 UNITED STATES PATENT OFFICE Poole, administratrix of said Arthur F.

Poole, deceased, assignor to Maryline B. Poole,

Ithaca, N. Y.

Application January 11, 1932, Serial No. 585,903

3 Claims.

My invention is an electric clock and is particularly concerned with the synchronizing of a spring or weight driven clock with a source of alternating current of regulated frequency.

Regulated alternating current has now become quite common throughout the United States since the light and power companies regulate the frequency of their alternating current with a standard source of time. Secondary clocks, consisting of synchronous motors, suitably geared to clock hands, may be attached at any place reached by the line wires and will keep the time determined by the frequency of the current sent out. Regulating this frequency will, of course, simultaneously regulate all of the clocks attached to the line wires. In regulating the frequency no attempt is made to keep the frequency at the same value at all times, but merely to exert such control that the average frequency over substantial periods of time is constant. Hereinafter, I shall call a current of this kind a current of regulated frequency.

One of the objects of my herein described invention is to use a regulated alternating current 0 to bring an existing clock in synchronism therewith, particularly a large clock, such as an existing tower clock. It is well known that tower clocks are somewhat indifierent time pieces, due to the large excess force required to drive the clock hands and the extremes of temperature to which such clocks are exposed. It is one of the objects of my present invention to utilize the existing source of regulated alternating current to bring a tower clock in step therewith.

A further object of my invention is in the provision of novel mechanism and circuits to the above described end.

A further object of my invention is the provision of a phase determining device to prevent the current control from interfering with the running of the clock.

The above and other objects of my invention will hereinafter be described and claimed.

My invention will be best understood by re ferring to the accompanying figures which are all more or less diagrammatic. Fig. 1 shows a clock equipped with my invention. Fig. 2 shows a schematic circuit employed therewith, and Fig. 3 shows a modification of the pendulum synchronizing device. Similar numbers of reference refer to like parts in all of the figures.

Referring particularly to Fig. 1, l0 and II are light or power mains whichcarrya regulated alternating current. These are connected by conductors l2 and 13 to a synchronous motor M, which is preferably self-starting, such motors being well known in the art, do not require further description. The motor M carries on its armature shaft a pinion l5 geared to a wheel l6 rotating on a shaft ll which carries a pinion 18 into which meshes a gear is, mounted on a shaft 25 which carries a crank 21 rigid therewith. The pinions and gears just described serve as a speed reducing mechanism, the object of which is to reduce the speed of the motor i4 so that the crank 2! will make a certain number of revolutions per minute. For the purpose of the present description, I am going to assume that the tower clock which is to be regulated by my invention, has a pendulum which beats once every two seconds, or makes 15 com plete cycles per minute. Corresponding to this, the gear ratio between the motor i4 and the crank 21 is such that said crank makes 15 revolutions per minute also.

To this end, I have provided a contact arm 44 mounted on the crutch shaft 32 which contacts with a spring 45 insulated from the framework and which is connected to an arm :36 on the mounting for the tube 23 which contacts with a spring 41 also insulated from the framework. The spring 4'! is connected to a winding of the relay 40. tarting with the relay armature 39 in the position shown in Fig. 1, it will be observed that the circuit of the solenoid 38 is broken at the contact M by the armature 39. As long as said armature is in the position shown in Fig. 1, oscillations of the switch 23 will not effect the solenoid 38. However, a time arrives when the contact 14-65 is closed simultaneously with the contact 46-4l, in other words, as soon as the switch 23 and the pendulum (it are in phase, then a circuit will be closed through the winding 48 and the relay will pull up its armature, thus establishing an operating condition of the solenoid 33. To hold up the armature 39 in the position shown in Fig. 2, despite the interruption of the current made by the switch 23, I have provided the relay 4% with a locking winding 49 and armature 58 adapted to close a contact 5!, joined by the conductor 35 to the line wire ll, thus holding the relay it in its closed position which persists until an interruption of current of the line wires l8 and H. The adjustment of the arms i and is such that the former makes contact with its spring when it is in its extreme right hand position and the latter makes contact with the spring 47 when it is in the position of the upper dotted line (Fi 1).

On a shaft 22 is mounted an electric switch 23, which in its preferable form consists of a glass tube 24 into which are sealed two electrodes 25 and 26, adapted to be electrically connected by a mass of mercury 21. When the tube 23 is tilted by the action of a connecting rod 21' joining a crank arm 28 with the crank 2i the circuit is closed. The tube 23 is filled with an inert gas, such as hydrogen, which is put under pressure for the purpose of supressing the induction spark occurring when the circuit is opened. It is obvious that the mechanism thus far described will serve to close the electric circuit terminating in the electrodes 25 and 2S fifteen times a minute. By a circuit hereinafter to be described a solenoid is so placed to attract an armature which is mounted on the crutch shaft of the clock and the adjustment of the tube 23 is such that the circuit is closed approximately during half of the revolution of the crank 2|.

29 is the escape wheel of a tower clock and mounted on a shaft 30. Actuating pallets 3! are mounted on a shaft 32 on which is a crutch 33 transmitting impulse to a pendulum 3d. The escape wheel 29 is actuated by a gear 35 which serves to transmit the power of the clock which is preferably electrically wound but may be Wound by hand if desired. Rigid on the shaft 32 is an iron armature 36 having a pole piece 3'? which is attracted in a solenoid 38 when current flows through said solenoid. Referring now to Fig. 2 when the switch 23 is closed a circuit may be traced from the line wire it through switch 23 to armature 39 of relay lfl contact 4|, wire 42 through solenoid 38 wire 43 to line wire H. The closing of the switch 23 fifteen times a minute results in the solenoid 38 attracting the pole piece 31 at the same frequency. Since this is approximately the frequency of the pendulum 34, said pendulum will be brought into, and kept in synchronism with the impulses given to the pole piece 31.

As before noted, the clock is provided with an independent source of power and in the event that the current on the line wires Ii) and H, is interrupted, the clock will go on as usual turning its hands (not shown) until the current is resumed. During a period of no current the clock rate, of course, will not be regulated. However, since current interruptions on systems of this kind are of comparatively short duration, the accumulated error of the clock during a period of no current, will not be material, and when curent is again resumed, the pendulum 32 will be brought into step therewith and continue to run in synchronism with the regulated current.

In the above arrangement, it will be observed that the solenoid 38 may be excited so that it will act in opposition to the motion of the pendulum 3 3 and that such opposition will tend to slow up the pendulum and possibly might stop it. However, this stopping tendency will occur only when the pendulum is widely out of phase with the current and since the pendulum by hypothesis is regulated with the current, such abnormal phase cannot occur during the clocks running. However, if the current is cut off, it may be resumed at any part of the pendulums swing and it therefore becomes desirable to provide some means which will prevent or hold up the synchronizing action following an interruption until the motor and pendulum are in phase.

From the above it will be evident to those skilled in the art that when an interruption of current occurs, the relay 49 will be de-energized and its armatures 39 and 50 will fall against their backstops 53 and 5 thus opening, the one, the solenoid 38, and the other the locking coil 19. This condition will persist as long as the current is off, during which time the clock will run without synchronization. When current is resumed, the solenoid 38 will be inoperative until the crank 21 andthe pendulum 34 reach the same phase at which time the relay 49 will be energized and the synchronizing solenoid 88 will start to function.

In Fig. 3, I have shown a modification of the synchronizer which consists in providing an arm 55 attached to the crutch shaft 32 and connected by a spiral spring 56 to a bell crank lever 51 rotating on a shaft 58 and provided with armatures 59 and B0. Said armatures are attracted by magnets 6! and 62 respectively which are connected to the contact 4! and wire 43 by the conductors 64 and 65. A condenser 53 is placed in the circuit of the magnet 62 to split the phase of the current and thus prevent chattering of the bell crank 51. t will be recognized that the magnets 51 and 52 have the same function as the solenoid 38 and are placed in the circuit in the same manner, that is, the magnets El and 62 are controlled by the joint action of the switch 23 and the relay armature 39. It is, of course to be understood that the armatures 39 and 50 are to be made with large inertia and sluggish, so that they will not chatter against their coopcrating contacts when held up by an alternating current.

While I have described my invention as applied to tower clocks it is obvious that it may be applied to a clock of any description, since what is necessary is to gear down from a synchronous motor to a crank which revolves at the same period as the oscillating member of the clock and have this crank periodically close an electric circuit which applies a periodic force to the vibrating member of the clock. From the fact that my herein described apparatus may be attached to existing clocks without materially changing their structure, it is quite useful for the synchronization of existing tower clocks.

While I have described the device for preventing the synchronizing action until the crank 2! and the pendulum 34 come into phase with each other, there will be installations where this phase device will not be required since the departure from frequency by the current supply in the mains ID and I! will be so slight that the correcting influence on the clock will be small.

In some cases it will be desirable to experiment with different intensities of the synchronizing action of the solenoid 33 and to this end it may be desirable to insert an adjustable resistance 66 in the circuit of the solenoid 38. By this means the magnitude of the correcting impulse may be altered to suit the particular case. The same consideration will also apply to the strength of the spring 56 in Fig. 3. Many changes and variations from the precise apparatus herein shown may be made by those skilled in the art, without departing from the spirit of my inven tion, since I claim:-

1. In an electric clock the combination of a source of commercial alternating current of regulated frequency, a contact making device moving in step therewith, a clock movement, a penddulum oscillated by said clock movement, means controlled by said contact device to synchronize said pendulum with said contact device and means to prevent the operation of said synchronizing means on said pendulum until said contact device is in a certain phase relation to said pendulum.

2. In an electric clock the combination of a source of commercial alternating current of regulated frequency, a contact device in step therewith, a clock movement, a pendulum oscillated by said movement, means controlled by said contact device to keep said pendulum in synchronism with said current and means to prevent the operation of said synchronizing means on said pendulum until said contact device has a certain phase relation to said pendulum.

3. In an electric clock the combination of a source of commercial alternating current of regulated frequency, a contact making device moving in step therewith, a clock movement, a pendulum regulating the motion of said movement, synchronizing means controlled by said contact making device to keep said pendulum in step with said contact device and means operated on the interruption of said current to prevent the operation of said synchronizing means when said current is resumed until said contact device is in a certain phase relation with said pendulum.

ARTHUR F. POOLE.

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