US2002664A - Relay for synchronizing systems - Google Patents

Description

May 28, 1935. g JENKINS 2,002,664-

RELAY FOR SYNCHRONIZING SYSTEMS Original Filed July 21, 1927 3 Sheets-Sheet l anwntoz c. F. JENKINS 2,002,664

RELAY FOR SYNCHRONIZING SYSTEMS Original Filed July 21, 1927 May 28, 1935.

3 Sheets-Sheet 2 anbentoz May 28, 1935. F, JENKINS 2,002,664

- RELAY FOR SYNCHRONIZING SYSTEMS Original Filed July 2l, 1927 3 Sheets-Sheet 3 0, 5 ,va is Jan Mb;

anvzntoz 83 fitted Leaf Patented May 28, 1935 UNITED STATES RELAY FOB SYNGHBONIZING srs'rsnrs Charles Francis Jenkins, Washington, D. 0., assignor, by mesne assignmentyto Radio Corporation of-America, a corporation of Delaware Original application July 21, 1927, Serial No. 207,515, now Patent No. 1,766,644, dated June 24, 1930. Divided and this application May 22, 1930, Serial No. 454,590

3 Claims. (Cl. 200-413) This invention relates to picture transmission systems, and in particular to arrangements for maintaining synchronous operation between the transmitting apparatus at the transmitting sta-- 5 tion and the receiving apparatus at the receiving station, and is a division of application Serial No. 207,515,,filed July 21, 1927 which has matured into Patent- #1,766,644, granted June-24, 19301 An ob'ject 'of myinvention is to provide means for automatically-maintaining a definite speed relationshipbetween the transmitting and receiving apparatus.

Another object of my invention is to devise novel relay apparatus capable of responding to electric current variations .of relatively high frequency.

My invention is illustrated in the accompanying drawings in which like reference characters represent like parts.

Figure 1 is a diagrammatic showing of one form of my invention employed at the receiving station.

Fig. 2 is a diagrammatic representation of a second form of apparatusemployed at the receiving station.

Fig. 3 is a third modification of the invention.

In Figure 1, a motor M is arranged to drive a cylindrical" drum C upon which is mounted the surface or filrnxwhich is to receive the picture being transmitted. The motor M comprises an armature A- and a field winding F, each of which is supplied .with current from the battery B. The armature circuit of the motor is completed from battery 13 through the output circuit of amplifier A3, armature A, and back to battery B. The armature also has a shunt circuit from battery B through resistance RI.

The receiving station is provided with a radio receiving set comprising a detector DI and an amplifier Al. Connected to the output circuit of amplifier Al is a second amplifier A2, the output circuit of which contains an incandescent lamp L. The picture recording apparatus is also connected to the output circuit of amplifier Al and comprises, for example, a solenoid S arranged to operate an inking pen P. A lens Ll is arranged to gather the divergent rays proceeding from lamp L and focus themupon a light-sensitive cell LS connected in the input circuit of amplifier A3. A disc D, provided with a series of holes arranged around its periphery, is mounted upon the shaft of motor A and is arranged to rotate in the path of the rays of light projected upon light-sensitive cell S by the lens Ll. The width of the openings in disc D is preferably equal to half the distance between the openings, although this ratio may be varied considerably if desired.

The operation of Figure 1 is as follows:

It is to be understood that a radio wave is being transmitted from the transmitting station and that the wave is modulated in accordance with the light variations of successive elementary areas of the picture being transmitted and also in accordance with-the speed. of'rotation of the transmitting apparatus. The synchronizing modulations bear. a definite relation to the 7 speed of the transmitting apparatus and may be produced in any desired manner, but I. prefer to employ a light-chopper for this purpose, as disclosed in my Patent No. 1,694,065 granted De cember 4, 1928. The modulated wave is received at the receiving station and detected by detector DI to derive therefrom low frequency currents.

which represent both the picture light variations and the synchronizing impulses. This complete current is supplied to amplifier Al where it is amplified and supplied to the output circuit. The amplified current is supplied to the recording apparatus which responds to the picture variations and causes the pen P to record upon the picture receiving surface, mounted upon drum C, ink marks corresponding to the dark portions of the picture being transmitted. The recording apparatus need not necessarily respond to the synchronizing interruptions or variations. A portion of the current in the output circuit of amplifier Al is supplied to the input circuit of amplfier A2, and lamp Ll is caused to vary in intensity inaccordance with the current variations. Accordingly, the beam of light falling upon the light-sensitive cell S will vary in intensity in accordance with the synchronizing variations. The beam of light is also subject to control by disc D in the following manner: In case the motor M is rotating at such speed that the holes in disc D rotate past the beam at a frequency equal to the frequency of the synchronizing variations, and the phase relation of the disc with respect to the synchronizing impulses is such that each pulse reaches a maximum as a hole in disc D is centered with respect to the beam of light, the effect of the beam of light upon the light-sensitive cell LS will be a maximum. It will thus be seen that light-sensitive cell LS will be intermittently illuminated at a frequency equal to that of the synchronizing variations. The light-sensitive cell will cause amplifier A3 to produce corresponding current variations in the armature cirmaximuni when a solid portion of disc D is passing in front of the light ray, the eifect of the ray upon light-sensitive cell LS will be a minimum, and the current variations produced in the armature circuit of motor M will be very small.

' For intermediate phase relations of the holes in chronizing pulses.

disc D with respect to the synchronizing pulses. the efiect of the light rays upon the light-sensitive cell will be to produce intermediate values of current variation in the armature circuit. The speed of motor M is adjusted by resistance RI to such value that it is slightly below the desired synchronous speed. The efiect of the current pulses produced by the light-sensitive cell 15 in the armature circuit is to increase the motor speed. Accordingly, disc D will assume such phase relation with respect to the synchronizing pulses or variations of lamp L that the amplitude of the'current pulses produced by LS is just suiiicient to maintain the motor in synchronous operation with the incoming syn- In case the load upon the motor is increased for any reason, disc D will lag behind the synchronizing pulses by an amount suflicient to increase the amplitude of the current pulses produced by light-sensitive cell LS and to thereby supply to the armature A, increased current sufilcient to accommodate the increased load. Conversely, if the load is dewill be correspondingly reduced, and the motor will be prevented from getting out of synchronism.

The arrangement shown in Fig. 2 is the same as that shown in Figure 1, except for the details of the motor control arrangement. In this figure, as in Figure I, both the armature and the field of the motor are supplied with current from battery B. The armature circuit of the motor also includes an adjustable resistance RI. In a shunt path around resistance Ri, a rotating commutator CM mounted upon the shaft of the motor is connected in series with contacts GT-CP of a special electric relay. Therelay comprises a glass tube MF provid with an electrode E mounted in each end thereof. The tube is filled with an acidulated solution and also contains a globule of mercury GM immersed within the solution. The insulated contacts GT-CP are mounted upon the tube and extend into the solution and normally contact with the globule of mercury as shown in the figure. Electrodes E--E are connected to the output circuit of amplifier AI, and contact points GT-CP are connected in series with commutator CM in a shunt circuit around resistance RI in the armature circuit. r

The operation of Fig. 2 is as follows:

The speed of motor M is adjusted byresistance RI until it is slightly lower than the desired synchronous speed. With contacts GT-CP bridged by mercury GM, resistance RI will be periodically short-circuited by commutator CM, twice for each revolution, and e time of shortcircuit will depend upon the extent of the contact surface of the commutator and upon the speed electrodes E-E, the globule of mercury elongates and breaks the connection between contact points GT-CP. The connection between contacts GTCP will, therefore, be broken synchronously with the synchronizing impulses. 5

It will thus be seen that the efiectiveness of resistance RI in the armature circuit is dependent upon the conjoint action of the commute. tor CM and the relay, and the time of shortcircuit of resistance RI is dependent upon the phase relationship existing between the commutator and the relay. If the commutator andthe relay operate simultaneously to close their respective contacts, resistance RI will be effectively cut out of the armature circuit for a maximum period. If the commutator and relay become displaced in phase in their operation the period of short-circuit will be reduced and resistance RI will have greater eflect in limiting the speed of motor -M. Accordingly, with a given load upon the motor and with a given adjustment of the circuits, the motor M will automatically adjust commutator CM to such phase relation with respect to the relay operation that the efi'ectiveness of resistance RI in the armature circuit is just sufiicient to maintain the motor' at synchronous speed. It the load upon the motor is increased for any reason, the commutator CM tends tolag behind the operation of the relay and thereby increases the period of shortcircuit of resistance RI which will tend to increase the speed of the motor. Commu ator CM will automatically assume such position that resistance RI is efiectively short-circuited for a period of time suflicient to increase the armature current by an amount necessary to compensate for the increased load. Conversely, if the load upon the motor is decreased, the commutator CM tends to advance in phase relation with respect to the operation of the relay and thereby decrease the period of short-circuit of resistance R! which will ofiset the tendency of the motor to increase in speed above synchronous speed.

The arrangement shown in Fig.3 is the same as that shown in Fig. 2, except for the details of the relay. The relay shown in Fig. 3 comprises a contact arm CA pivoted at a point (a). Cooperating with the contact arm is a stationary contact plate CP. The arm CA is normally held out of contact with plate CP by means of a wire W, one end of which is attached to the arm and the other end is anchored to a fixed terminal.

A spring SI is attached to the arm CA and tends I, to cause the arm to contact with plate CP. Wire W is connected to the output circuit of amplifier AI, and contact arm CA and plate CP are connected in series with commutator CM in a shunt path around resistance RI. Wire W is made of such material and such diameter that it is readily heated by current supplied from no amplifier At. The effect 0! the pulsating current flowing in wire W is to cause the wire to become elongated periodically and in syn- .chronism with the synchronizing impulses.

the amplified current. Thus, the .relay contacts will be closed periodically and in synchronism with the synchronizing signals. The action of the arrangement shown in Fig. 3 will be readily understood from the foregoing explanation of the operation of Fig. 2.-

It is apparent that the arrangements shown I in Figs. 2 and 3 will also operate with-only the relay connected in the shunt path around resistance RI, and the commutator CM connected in the armature circuit so as to periodically interrupt the total armature current.

While I have shown symbolically, and for the purpose of illustration only, a recording apparatus comprising an inking pen P operated by a magnet S, it will readily be understood that any other well known type of recording apparatus may be employed, such for example, as well known photographic recording apparatus.

The circuits of the relays have very little inductance and offer small impedance to high frequency currents.

It is to be noted that in Figure 1, I employ a form of electric relay having no moving mechanical parts, and the motor control system does not employ vibrating or sliding electric contact device.

What is claimed is:

1. An electric relay comprising a, pair of spaced input terminals and a pair of spaced contact points, said contact points being normally bridged by a body of mercury, said mercury being interposed between said input terminals wherebywhen current is applied thereto the mercury elongates in a certain direction and interrupts the connection between said contact points.

2. An electric'relay comprising a receptacle containing an acidulated solution, a pair of spaced input terminals having electrical contact with the solution, a body of mercury immersed in said solution and located between the input terminalsQand a pair of spaced contacts so positioned as to be normally bridged by said mercury but disconnected upon flow of current between the input terminals.

3. An electric relay comprising a receptacle containing an acidulated solution, a body of mercury immersed in saidsolution, a pair of contact points, and a pair of input terminals, whereby current supplied to said input terminals controls the electrical connection of said con- 20 tact points through said body of mercury.

FRANCIS JEN'HNS.

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