US2275974A - Sweep circuit for cathode ray tube distributors - Google Patents

Description

March 10, 1942. R. E. MATHEs SWEEP CIRCUIT FOR CATHODE RAY TUBE DISTRIBUTOR Filed Feb. 28, 1939 -2 Sheets-Sheet l NN n @md L INVENTOR. I R/CHA D E. MATHES BY )7&6

' ATTORNEY.

March 1.0, 1942. R E MATHES 2,275,974

SWEEP CIRCUIT FOR CATHODE RAY TUBE DISTRIBUTOR` v Filed Feb. 28, 1939 2 Sheets-Sheet 2 I Il".

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Patented Mar. 110, 1942 ySVVEEP CIRCUIT FOR CATHOIDE )RAY TUBE DESTRIBUTRS Richard E. Mathes, Westfield, J., assigner to Radio Corporation of America, a corporation of Delaware Application February Z8, 1939, Serial No. 258,870

1-3 Claims.

This vinvention relates to sweep circuits for cathode ray tube distributors. Electronic distributors are well known in the art. Some types of these distributors comprise a cathode ray tube having an array of targets against which an electron bea-m is projected by an electron gun. The beam itself is deflected so as to impinge successively on different targets. A preferred system is one in whichthe targets are arranged in'a circle and the beam is deected in a rotary path over the segmentary targets thereby to control different external circuits. A primary use for such a system of distribution is in the communications field where multiplex telegraph channels are involved. When the apparatus of my invention is so used, the cathode ray tube distributor constitutes a substitute for any of the well known types of distributors, which include face plates and brushes rotating thereover,' or which comprise cam operated contact springs.

It is an object of my invention to provide a novel sweep circuit for controlling the deflection of an electron beam in a cathode ray tube.

It is a further object of my invention to provide a cathode ray tube and associated circuits suitably adapted for use as a multiplex distributor in a telegraph system.

Further objects and advantages of my invention will be set forth in the following detailed description. The description itself will be made clear by reference to the accompanying drawings, in which:

Figure 1 shows schematically a preferred circuit arrangement including various elements in combination for carrying out the objects. of the invention; and I Fig. 2 shows an alternative embodiment of the s-ystem.

One ofthe problems encountered in designing a suitable sweep circuit for the control of a cathode ray tube which is to be employed in a-mu1ti pleX telegraph system is to produce beam deflection in a rotary path at a relatively slow speed. In practice it may be necessary to provide a twophase current of 'sine wave characteristic the frequency of which must be maintained constant at as low a value as one or even one-half cycle per second. It is apparent that ordinary methods of oscillation generation and coupling of circuits for the transfer of energy at such a low frequency would involve special considerations. A pure sine Wave of such low frequency would lack the necessary power to energize the deflecting' coils of the cathode ray tube if developed by ordinary transformation methods. I have; therefore, resorted to a high audio frequency `monotone generator as a source of sweep circuit power, and the output 'from such a generator is suitably 'modulated at the desired low frequency, so that, when the high frequency component is filtered out, this low frequency becomes available for actuating the deflecting coils or electrostatic plates of the cathode ray tube.

Referring first to Fig. 1, I show therein a high frequency oscillator 5 which may be of any well known type. Part of the output from this oscillator is fed to a set of polarizing coils 62 whose cores are here shown as the four stator 4poles of a rotary machine. The windings 62 are so directed as to render the physically opposedl pole faces opposite in instantaneous polarity. Another part of the output from the oscillator 5 is fed to an armature coil 6. 'I'he armature lpole faces are presented alternately to the horizontal and vertical poles of the stator field. A potentiometer 6I is in circuit with the field coils, and another poentiometer 63'is similarly disposed in the armature circuit. These potentiometers can be so adjusted as to neutralize the magnetism inthe vertical stator poles in one position of the armature and to produce maximum magnetization thereof when the armature is turned through 180. The same is true of the horizontal stator poles. Currents are, therefore, induced in the coils I2 and I3.

Coils I2 are series-connected to4 a rectifier It, while coils I3 are likewise series-connected to another rectier I5. The amplitude variations in" the two circuits have ,a phase difference of 90. The output from the rectiflers is fed to different low pass filters IB and I'l where the high frequency component is filtered out, leaving only the .low frequency component which represents the modulation envelope, or frequency of rotation of 'Ihe low frequency components of the outputl -from the filtersl I5 and Il are in 90 phase relation to one another so that the beam in the cathode ray tube is deflected rotatively.

A relay winding 2I is disposed in a telegraph receiving circuit. The armature of this relay plays between a positive contact 22 and a negative contact 23 so as to impress positive marking impulses across a condenser 24 and to apply the same to a control grid 25 within the cathode ray tube in response to the reception of marking and spacing impulses. The positive and negative potentials which are impressed upon the relay the cathode ray tube by means of a biasing source 29 and a resistor 30. l

Lockingcircuits for` channels A, B, C and D respectively are shown in block diagram and each in circuit with one of the anode `targets 20 of the cathode ray tube. The details of the locking circuits are well known in the artand are, therefore, not shown in detail herein. An example of a locking circuit which I have used advantageously in this connection is one that was constructed in accordance with the disclosure of James J. Finch in his United States Patent 1,844,950, granted February 16,1932. It will be understood, however, that these locking circuitsl may be cpnnected to any suitable recorders such as R1 Rz R3 and R4, as shown in Fig. 1.

In order that synchronism may be maintained between the incoming signals and the rotation of the rotor .6, a striking impulse generator 50, a commutator I, a synchronous correction circuit 3| and correction motor 32` are provided. The striking impulse generator 50 is under control of the incoming signals as derived from the receiving relay 2|. Short impulses are generatediwith each shift of the armature of relay 2l. Ihese impulses are fed to Ia commutator brush 5I mounted on the shaft 1. When truesynchroin succession and with a 90 phase difference between the moments of maximum energy transfer. In Fig. 2 the same arrangement of rectiflers I4 and 1I5 and low pass lters I8 and I1 may beA employed as previously described in connection with Fig. 1. As a modification of the circuit arrangement, however," electrostatic deecting plates 43 and 44 are shown in place of the deflecting coils I8 and I9'. As a further modification, the cathode ray tube distributor comprises only three target electrodes 45 each occupying approximately a 120 segment as would be required nism and phase are maintained, the striking impulses are applied to the brush 5I at the moment of its passage over an insulation gap between twocommutator segments 52 and 53. When the phase of the shaft 1 leads or-,Lags, however, then segment 52 or segment53 receives the striking impulse, which is then fed to a correction circuit 3I for actuating a polarized relay therein.

Such correction circuits are wellLknown in the art. They usually .include thermionic devices, as illustrated in my United States Patent 2,038,375, granted April 21, 1936.v The polarized relay, though not shown herein, will be understood to control two circuits 54 and 55 leading to the field windings of the correction motor 32,. for reversibly actuating the same.

'I'he correction motor 32 has a pinion 33 -mounted on its shaft. This pinion engages with a gear 34 attached to the field frame of the motor I0. By rotating this field framesuitable phase correction is applied for maintaining the necessary synchronism between the equipment at the transmitter and that at the receiver.

Accurate phase adjustment of the modulator rotor on which the coil 6 is mounted is obtained by means of a gear reduction whichv includes the worm 9 on the shaft of themotor I0, and a worm wheel 8 on the armature shaft 1. The motor III is preferably driven by current from a constant frequency source I I.

Referring now to Fig. 2, I show a modified sweep circuit arrangement for a telegraph' dis-A tributor. Certain of the units therein employed have the same functions as those of corresponding units shown in Fig. 1. The substitution of these alternative units may be made individually and independently of one another. A

In place ofv the four-pole modulator system as shown in Fig. 1, I have shown'an arrangement of doughnut coils in Fig. 2. These coils include four pairs of stator coils and one pair of rotor nected to the high frequency oscillator 5. These rotor coils 4I are driven by the motor III so as to induce currents in the stator coils 40 and 42 for three-channel multiplex distribution. Each of the segments is connected to a different keyer circuit for channels A, B and C respectively. Anode potential is supplied to the targets 45 of the cathode ray tube from a source 46.

The keyers of Fig. l2 are shown in block diagram since the details of such devices are well known in the .art and do not constitute any part'of the instant invention.- 'I'he output circuits for these keyers may, however, be connected in common. to any suitable transmitter such as that shown diagrammatically at 41 and having an output circuit feeding to a radio antenna 48.

Any of the alternatively used pieces of equipment such as'shown in Fig. 2 may be employed in connection with receiving devices as well as 'in the art in view of the foregoing description.

The scope of the invention itself is, therefore,

' limited only in accordance with the claims.

I claim:

1. In a telegraph system a source of alternating current of 4,a relatively high frequency, rotary converter` means for applying variable attenuation to said currentI at a relatively low frequency cyclic rate, a pair of output circuits connected to said converter means, means for maintaining a quadrature phasedisplacement between the at. Ytenuation envelopes of the currents in said output circuits, means for deriving sine wave currents corresponding in frequency to that of said attenuation envelopes, meansfor deiiecting an electron stream rotatively under control of said sine wave currents, and means responsive to telegraph signals for -keying said electron stream.

2. Apparatus according tn claim 1 in combination with an adjustable phase correction device operatively associated with said converter' means, and means responsive to said telegraph signals for adiusting said phase correction device.

3. In a telegraph system including a device for producing a very 4low frequency rotative deflecting torce to be .applied to the deflecting elements of a cathode ray tube, a source of high audio frequency current, cyclically operable means for varying lthe amplitude of said current, and for producing two envelopes thereof, one of said en'- velopes being in quadrature phase relation to the vothe` of said envelopes, rectifying and filtering ducting said telegraph signals through y'the discharge path of said cathode ray tube.

4. In a telegraph system` including a sweep circuit for a cathode ray tube distributor, an oscillation generator, means for modulating the output energy from said generator thereby to produce two relatively low constant frequency envelopes having a 90 phase diierence between their respective moments of maximum amplitude, means for rectifying themodulated 'ener-l gies, means including a pair of low pass filters for deriving 90 phase-displaced sine waves of said low constant frequency envelopes free from the frequency component of said oscillation generator, a cathode ray tube having horizontal and vertical deflecting elements combined therewith,

rotor coils in inductive relation to said stator coils and for causing currents of cyclically variable attenuation to be induced in said stator coils, means .for maintaining a quadrature phase relation between the instants of like attenuation of the currents induced in the two sets of stator coils, means for converting said currents into sine wave currents of a frequency corresponding to the cycles of variable attenuation, a utilization device comprising a cathode ray tube having horizontal and vertical beam deflect'ing means operable by one and the other of saidsine wave currents respectively to produce rotary beam deiiection, and distributor means in said cathode ray tube for assigning multiplex telegraph signals to their respective channels according to said rotary beam deection.

6. In a telegraph system including apparatus for applying relatively slow alternations of elec: tromotive force to the horizontal and vertical de# fleeting means of a cathode ray tube, the method of distributing telegraph signals to diierent channels which method comprises causing the telegraph signals to control the emission in said cathode ray tube and totraverse the space path therein, producing a relatively high frequency current, inducing currents of said high frequency in two separate circuits. causing said induced currents to be cyclically attenuated at a frequency corresponding to relatively slow alternations, causing the cycles of attenuation in-one of said circuits to lag 90 behind corresponding cycles in the other of said circuits, rectifying and filtering said induced currents to producesine waves having the frequency of said slow alternations, and utilizing said sine Waves separately to control said horizontal and vertical deecting means thereby to produce a rotary scanning actionin said tube. Y

7. In a telegraph system, a source ofrelatlvely high frequency waves, means for modulating same relatively low frequency, means for main Cal taining a quadrature phase relation between'the low frequency components of the energies thus separately modulated, two rec'tiers each fed respectively with energy from an appropriate one of said modulating means, a cathode ray tube distributor having a horizontal deflectirig device controlled by output energy from one of said rectiers and a vertical deecting device controlled by output energy from the other of said rectiers, said distributor having anodal targets arranged to be scanned by an electron beam under` control of said deflecting devices and means for keying the emission in said distributor of telegraph signals.

8. Apparatus comprising the combination set by a train forth in claim 7 and including twolow-'pass lters, one in circuit with the horizontal deilectng device and one in circuit with the vertical deflecting device.

9. The method of distributing telegraph signals `to different multiplex channels by rotative` deflection of an electron beam in a cathode vray tube which comprises generating a relatively high frequency, producing two 90 phase-displaced components of a relatively low frequency, separately modulating different portions of said relatively high frequency' each by one of said lowfrequency components respectively, separately rectifying said modulated portions to derive two 'substantially 90 phase-displaced wave trains of said l low frequency, filtering out the residuahhigh frequency components in saidwave trains, applying one of said wave trains for deilction of said beam in a horizontal direction, and applying the other of said wave trains for deflection of saidbeam in a vertical direction, and keying the emission in said cathode ray tube by means of said `two quadrature phase related currents of said low frequency, an electron discharge device having an electron gun, beam deilecting means, and

circularly disposed` target electrodes, means including a source of telegraph signals for impulsively controlling the action of said electron gun, and circuits for so feeding said low frequency currents to said beam deflecting means as to produce rotative beam deection, thereby to cause successive impulses of electronic emission corresponding to said telegraph signals to be distributed/to v appropriate ones of'said target electrodes.

11 An electronic distributor in accordance with claim 10,- in combination with means responsive to saidy telegraph signals for regulating the speed of said modulator.

12. An electronic distributor according to claim 10 and having magnetic deiiecting coils in saidbeam deiiecting means.

13. A51 electronic distributor according to claim 10, and having electrostatic deiiecting plates in said beam deflecting means.

, y RICHARD EMATHES.

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