US2291810A - Time system - Google Patents

Description

Aug. 4, 1942.

E. B. JACKSON TIME SYSTEM INVENTOR.

Edward 3. Jackson Original Filed Oct. 24, 1936 ATTORNEY.

Patented Aug. 4, 19,42

UNETED STAT S OFFICE TIME SYSTEM Edward B. Jackson, Downers Grove, 111., assignor,

by mesne assignments, to General Time Instruments Corporation 4 Claims.

The present invention relates in general to an electrical control system and particularly to a method of remote control of electromagnetic apparatus. The object of the invention is to provide a remote control system in which the operation or non-operation of electromagnetic apparatus may be selectively controlled by means of half-wave and full-Wave rectified alternating current.

This application is a division of my co-pending application Serial No. 107,389, filed October 24, 1936, in which I claim a time system employing the method of control claimed broadly here- According to a feature of the invention, a resistance or a one-way valve is connected in shunt of a magnet winding in series with a contact. The presence or absence of this device in the eucuit and the kind of impulses being received determine Whether or not the magnet will be operated by such impulses.

According to a further feature of the invention, the operation of an electromagnet by rect fied alternating current is greatly improved by bridging an asymetric cell or so-called one-way electric valve across the terminals of the magnet winding. I

Another feature of the invention lies in the elimination of sparking or arcing at the contacts of an electric circuit which control the flow of current to an inductively wound electri- K This is accomplished to a much cal device.

heretofore possible by coneater degree than meeting a one-way valve in shunt of the inductive winding.

The above and other objects and features of my invention will best be understood from a perusal of the following specification when read in connection with the accompanying drawing comprising Figures 1 to 3, inclusive, in which:

Figure 1 is a schematic circuit diagram of a corrective time system embodying the present invention,

Figure 2 is a schematic circuit diagram showing a modification of the secondary apparatuses, and

Figure 3 is a schematic circuit diagram illustrating the use of a one-way electric valve to eliminate sparking or arcing at the circuit controlling contacts.

Referring to the drawing in general, Fig. l discloses a two-wire corrective circuit in which M diagrammatically represents the master clock having a frame indicated at l, the usual minute contacts l2, closed momentarily once each min- Cir ute, the fast contacts M which may be closed momentarily every two seconds, and the cut-in contacts 9 which connect the fast contacts into the circuit for the accelerating operation of slow secondary apparatus. These contacts may preferably be closed from 59 minutes 10 seconds after the hour to 59 minutes 40 seconds after the hour. In addition the master clock is equipped with contacts 5 to 8, inclusive, which control the connections of rectifier R in the circuit as will fully appear in the detailed description of the operation of the system. Cams 3 and 4 are hour cams mounted on the minute hand shaft 2 and cam mounted on the second shaft I0 of the master clock. The fast contacts I4 are controlled by the Verge [3 of the clock in well-known manner.

SI and S2 diagrammatically represent the secondary apparatuses, each comprising an operating magnet (23, 43) adapted to drive the secondary time mechanism by means of the usual ratchet and pawl construction including an armature (26, 45) for the magnet, an armature stop (28, 41) an operating spring (27, 45), apawl (29, 49) mounted on the armature, and a ratchet wheel (30, 48) engaged by the pawl. The ratchet wheel is mounted on the minute shaft (3|, 5!!) of the secondary apparatus as is also the cam (32, BI) which controls the contacts (33, 52), connecting or disconnecting the resistance (34, 44) from in shunt of the magnet winding.

Figure 2 of the drawing discloses a modification of the secondary apparatus circuit in which a one-way electric valve (62, 12) is substituted in the shunt circuit for the resistance of Figure 1.

Figure 3 discloses a spark reducing or eliminating circuit in which an inductively wound agnet or other device T5 is connected in series with a battery H and the circuit 18. A one-way electric valve 16 is connected in shunt of the inductive Winding.

Having briefly described the apparatus shown on the drawing, a detailed explanation of the operation of the several circuits will now be lVell.

Referring first to Fig. 1, contacts [2 are closed momentarily once each minute by cam l I, thereby transmitting an operating impulse to the secondary apparatuses over the following circuit: from line ll of the A. C. supply source, contacts l2, conductor 18, section 40 of the sectifier R, conductor 20, through conductors 36 and 54, magnets 23 and 43 and conductors 35 and 53 in multiple, conductor 2|, contacts 8 and B, to the other side of the supply source over conductor Referring to the secondary apparatuses SI and S2 it will be seen that the secondary apparatus Sl' is fast and has reached its 59th minute position, in which position the cam 32 operates contacts 33 to open the shunt circuit through resistance 34. Secondary apparatus S2 is on time or slow since it has not yet reached its 59th minute position.

The magnets 23 and 43 are so wound that they will not operate on receipt of half-wave rectified alternating current impulses with the shunt circuit through the associated resistances open. However, when the resistance is connected in multiple with the magnet winding, the magnet will respond to such impulses. The probable explanation for this operation is that with the shunt circuit open, the magnetism built up in the bore of the magnet by one half-wave of current will die away during the following interval of no current before the succeeding half-wave occurs to continue the building up of the magnetic field. Thus during a half-wave rectified A. C. impulse the magnetic field does not build up to the point where the magnet will operate.

With the resistance connected in shunt of the magnet winding, a closed path is provided for the current which is induced in the inductive winding due to the dying down of the magnetic field during the interval between successive halfwaves of current. This induced current fiows in such a direction as to tend to main the magnetic field and as a result the field ha died down very little before the next half -wave occurs to continue to increase the magnetism. As a result the magnetic field will be built up to a point where the magnet will operate.

The shunt circuits of the secondary magnets are normally closed and the system operates on half-wave rectified alternating current impulses transmitted over the circuit previously traced. Magnet 43 will operate in this circuit and advance the secondary apparatus S2 one step. Apparatus SI, however, is assumed to be fast and cam 32 has already opened contacts 33 as previously explained. Magnet 23 therefore cannot operate and SI remains in its 59th minute position.

The normal operation described above continues until shortly after the master clock has transmitted the 59th impulse. At about 59 minutes seconds after the hour, cam 4 allows contacts 9 to close thereby connecting the fast contacts l4 in the impulsing circuit. These contacts send out a momentary impulse about every two seconds and all secondary apparatuses, such as S2 which is assumed to be slow, are rapidly advanced until each reaches its 59th minute position, in which position the contacts such as 52 open the shunt circuit through resistance 44 and render the associated magnet 43 unresponsive to the half-wave rectified A. C. impulses.

At about 59 minutes seconds after the hour, cam 4 again opens contacts 9 thereby removing the fast contacts I4 from the circuit and stopping the transmission of the rapid accelerating impulses. All of the secondary apparatuses have now been operated to position 59 and have been stopped in that position.

Shortly before the master clock reaches position 60 or the hour position, at about 53 minutes seconds after the hour, cam 3 opens contacts 6 and 8 and closes contacts 5 and 1. When minute contacts I? are then closed in position 0f the master clock, the circuit for the secondary operating magnets extends from one side of the power source over the conductor I1, contacts I2, conductor l8, section 40 of rectifier R, conductor 20, conductor 36 of secondary apparatus S I, winding of magnet 23, conductor 35, conductor 2|, contact I, conductor 22, section 42 of rectifier R, conductor I9, contacts 5, and over conductor I6 to the other side of the power source. Alternate half-Waves will of course pass through sections 4| and 43 of rectifier R instead of sections 40 and 42. Parallel circuits extend from lines 20 and 2| through each of the other secondary apparatuses connected to the circuit.

The above impulsing circuit now includes the full-wave bridge rectifier and the secondary magnets will all respond to the impulse of the fullwave rectified alternating current to advance the secondary apparatuses into position 60 and into synchronism with the master clock. In position 60, the cam in each secondary, such as cam 32 of SI, again permits the contacts such as 33 to close, thereby again closing the shunt circuit through the associated resistance. All the secondary apparatuses are now again in condition to be operated by half-wave rectified alternating current impulses. Several full-wave rectified current impulses may be sent out by the master clock before cam 3 again open contacts 5 and l and closes contacts 6 and 8 to disconnect the full-wave bridge rectifier and reconnect the halfwave rectifier unit 40 in the circuit. This will insure that all of the secondary apparatuses have been advanced from position 59 and are again in condition to be advanced by half-wave rectified alternating current impulses. Therefore, the switch-over from full-wave to half-Wave operation may preferably occur several minutes after the hour.

The secondary apparatuses S3 and S4, shown in Fig. 2 of the drawing, operate with the master clock shown in Fig. 1. The principle of operation is the same as in the system of Fig. 1. However, a one-way electric valve has been provided in each secondary apparatus to take the place of the resistance used in the embodiment shown in Fig. 1.

The one-way valve must of course be properly connected across the secondary magnet winding so that it will block the rectified current pulsations. Thus during normal operation on halfwave rectified alternating current impulses with the valve connected in the circuit as shown for S4, the impulses are received from the master clock over line 20', which corresponds to line 20 of Fig. 1, conductor 14, winding 65, conductor 13, and to the master clock over line 2|. The pulsations of these impulses are in such a direction that even though contacts II are closed, the valve 12 blocks the current so that the entire current must pass through the magnet winding. During the intervals between the pulsations which make up the impulse, the induced current in winding 65 is in such a direction as to keep up the magnetic field. This induced current therefore has a low resistance path through valve 12 and contacts H From the foregoin it will be realized that the one-way valve has characteristics which make it much more efiicient for the purpose than the resistance used in Fig. 1. The valve offers practically an absolute block for the current pulsa tions, thereby forcing all of the current through the magnet winding, and is practically a short circuit of the winding during the intervals between pulsations, thereby presenting very little opposition to the flow of the induced current. With the resistance of Fig. 1 some of the current of each pulsation flows through the resistance in multiple with the magnet winding and is therefore ineffective on the magnetic field f the magnet. Also during the intervals between pulsations, the induced current is lower due to the high resistance of the shunt.

The operation of the system of Fig. 2 being the sam as that of Fig. 1, it is not thought necessary to repeat the explanation of a complete cycle of operation. The circuits of secondary apparatuses S3 and S4 correspond in all respects to those of SI and S2 except that the one-way valves 62 and 12 are substituted for resistances 34 and 44. As pointed out above, the function of the valve is the same as that of the resistance but its operation is much more efficicnt as its characteristics make it ideal for the purpose.

Figure 3 of the drawing discloses a schematic circuit diagram of the use of a one-way valve to reduce or eliminate arcing at the contact controlling current through an inductive device. Since it is this arcing at the contacts which rapidly deteriorates the metal, pits the surfaces and causes contact trouble, it is highly important that arcing be reduced to a minimum or eliminated entirely in electric circuits. This is especially true where the contacts are frequently operated as in electric time systems.

The circuit of Fig, 3 includes an inductively wound device such as a magnet 15, a source of current 11, and the circuit making and breaking contacts 18. In order to eliminate the spark which would occur at contacts 18, when opened, due to the induced voltage in the winding of magnet 15, a one-way valve is bridged across the terminals of the magnet winding. This valve is connected so that it blocks the flow of current when contacts 18 are closed, forcing all of the current through th magnet winding. When contacts 18 are opened a voltage is induced in the windings of magnet 15 due to the collapse of the magnetic field, As is well known, this voltage produces a current in a direction so as to oppose the change in the magnetic field. The one-way valve is practically a short circuit for current in this direction and the induced current therefore has a low resistance path through the valve and dissipates itself in the magnet winding. There is no tendency for the current to seek the high resistance path through th separating contacts 18 and accordingly the sparking or arcing at these contacts is eliminated.

From the foregoing it will be seen that the use of a one-way valve in shunt of the inductive winding provides the ideal conditions for the elimination of contact arcing. With the contacts closed it offers practically an open circuit to th flow of any current through the shunt. As soon as the contacts are opened and the magnetic field begins to die down, the valv offers ractically a zero resistance path for the current induced in the magnet winding.

Having described the invention, what is claimed as new and is desired to have protected by Letters Patent is:

1. The combination in an electric circuit of an electromagnet having a winding, said electromagnet being operative by full-wave rectified alternating current and inoperative by half-wave rectified alternating current, a shunt circuit for said winding including a one way electric valve, and contacts for closing said shunt circuit to render said electromagnet operative by half-wave rectified alternating current,

2. lhe combination in an electric circuit of an electromagnet having a winding, said electromagnet being operative by full-wave rectified alternating current and inoperative by half-wave rectified alternating current, a shunt circuit for said winding including polarity trap means, and contacts for closing said shunt circuit to render said electromagnet operative by half-wave rectified alternating current.

3. In combination, an electric circuit, means for transmitting half-wave rectified alternating current and full-wave rectified alternating current over said circuit, electromagnetic means normally operative by said full-wave current and inoperative by said half-wave current, a normally open shunt circuit for said electromagnetic means including a resistance device, and means for closing said shunt circuit to render said electromagnetic means operative by said half-wave current.

4. In combination, an electric circuit, means for selectively transmitting half-wave and fullwave rectified alternating current over said circuit, electromagnetic means responsive to said full-wave current but unresponsive to said haliwave current, a non-inductive resistance device, and a switch for connecting said non-inductive resistance device in parallel with said electromagnetic means to render the latter responsive to said half-wave rectified alternating current.

EDWARD B. JACKSON.

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