US2122499A - Switching device - Google Patents

Description

July 5, 1938. A C` STQCKER 2,122,499

- SWITCHING DEVICE Filed sept. .27, 1954 Fig. i.

Patented July 5, 1938 PATENT OFFICE SWITCHING DEVICE Arthur C, Stocker, Haddon Heights, N. J., as-

signor, by mesne assignments, to Radio Corporation of America, New York, N.

ration of Delaware Y., a corpo- Application September 27,'1934, Serial No. '145,765

1o claims.

My inventionv relates to switching devices, and

it has particular relation to switching devices adapted for use in connection with cathode-ray Oscilloscopes and the like.

In utilizing cathode-ray Oscilloscopes for the investigation of electrical current and/or potential wave forms it is oftentimes desirable to s imultaneously view the traces of waves emanatingv from a plurality of sources. In other words, assuming, for example, that the output potentials from the horizontal and vertical ray deilection oscillation generators, in a television receiving system or the like, are to be investigated, it is convenient to so arrange the circuits of the oscilloscope that both potentials are represented as luminous traces simultaneously upon the fluorescent screen thereof. In order that this may be accomplished,it has been found desirable to supply the vhorizontal deflection plates of the oscilloscope with alternating potential at the sweep-frequency, which potential controls the horizontal travel of the cathode ray, and to supply to the vertical deflection plates the several frequencies, rapidly commutating between the frequencies applied at a rate such that the phenomenonof persistence of vision causes the two traces to appear simultaneously upon the screen.

My invention, as will hereinafter be apparent, is also applicable to cathode ray tubes equipped with electromagnetic deection coils instead of plates.

Various devices such as buzzers vibrating relays and motor driven commutators, and the like have been unsuccessfully tried for commutating potentials from the several oscillation generators at a rate of approximately twenty cycles per second, it being a requirement that no high frequency potentials must exist in the vicinity of the contacts, since they would militate against Operation of the system if the commutated frequencies appear at low potentials.

The use of a commutator driven by a remotely located motor was rejected on the basis of cost and vibration. Numerous vibrating relays were also tried, but it was found that inductive surge voltages were developed which, when picked up by the wiring adjacent the contacts, marred the appearance of the wave-traces on the fluorcscent screen.

It is, accordingly, an object of my invention t provide switching means substantially devoid of inductive surge-potentials.

Another object of my invention is to provide switching means adapted to commutate potentials or currents from a plurality of alternating potential or alternating current sources without the introduction of spurious electrical surges or the like.

Another object of my invention is to provide switching means, adapted to commutate electric currents or potentials wherein the rate of commutation may be controlled electrically without mechanical adjustment of the relay device per' se. A still further and more specific object of my invention is to provide switching means,adapted to commutate electric currents or potentials from two sources, which may at will be rendered operative or kept in a static condition, with either of the said sources semi-permanently connected to an output circuit, upon the simple manipulation of a switching element.

Yet another and still more speciiic object of my invention is to provide switching means especially adapted for use in connection with an oscilloscope of the cathode ray type that is potential-responsive' In a preferred embodiment of my inventionI attain the foregoing objects and other objects ancillary thereto through the use of a thermionlc device for the purpose of causing the current in the winding of a plural-armature relay to automatically rise to a value at which the armatures are picked up and to fall automatically to a value 3o at which the said armatures are released. Also, when the armatures are picked up the conditions are such that one of the sources is operatively connected to the vertical deflection plates of an oscilloscope or cathode-ray tube, and when the armatures are released the other source is connected thereto thus effecting commutation of the said sources. As will be apparent hereinafter, a single movingelement may be utilized, associated with a plurality of contact devices. 40 instead of the plural armature relay shown.

The novel features that I consider characteristic of my invention :are set forth with particularity in the apended claims. The invention itself, however, both as to its organization and its method of operation together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment, when read in connection with the accompanying drawing, in which Figure 1 is a diagrammatic view of a cathoderay oscilloscope system including a preferred embodiment of my invention;

Fig. 2 is a view in elevation of the fluorescent screen of the cathode-ray tube exemplifying the 55 ing to my invention includes a cathode-ray tube I wherein are disposed an electron gun 3, a plurality of vertical deflection plates 5, a plurality v of horizontal deflection plates 1, a ray-focusing anode 9, and a fluorescent screen I. The horizontal deflection plates are connected to a horizontal sweep-frequency generator |3, the frequency of which is adjustable.

The vertical deflection plates 5 are connected to the output terminals of a voltage amplifier' |5 the input terminals I9 and I1 of which are connected, respectively to the grounded cathode 2| of a themiionic tube 23 and to an armature 25 of a relay device 21 such as Western Electric type 221-CB, the winding 29 of which is included between the anode 3| of the tube and a potential source exemplified in the drawing by a battery 33. A switch 35 may be included inthe anode circuit. The relay device is provided with an additional armature 31 which is connected to the cathode of the tube through a resistor 39 and a capacitor 4|. This capacitor may, if desired, be variable, as shown in the drawing.

In the absence of current in the winding 29 the armatures 31 and 35 of the relay device are biased by springs 43 and 45 against outer contacts 41 and 49, respectively. The' armatures are also `provided with inner iixed contacts 5| and 53, re-

spectively.

The outer contact 49, associated with the armature 25, is connected to the output terminal of an alternating potential source f1, and the inner contact 53 is connected to an output terminal of another alternating potential source, fz. 'I'he other output terminal of each source is connected to ground and, thence, to the cathode 2| of the thermionic tube. Vibration of the armature 25, therefore, between the inner and outer contacts results in alternate connection of the output terminals of the several sources to the input terminals of the voltage amplifier from which amplified potentials are applied to the vertical deflection plates 5 in the cathode ray tube.

In order that the armature 25 may be caused to vibrate, it is necessary that the space current in the thermionic tube, flowing in the relay winding, shall fluctuate. Furthermore, for the desired purpose, it is desirable that the armature shall dwell for av suiiicient length of time against each contact to permit a plurality of complete cycles of potential from each source to be impressed upon the vertical deflection plates during each half-cycle of potential from the sweepfrequency source.

To this end, a conductor 55 extends from the inner contact 5|, associated with the armature 31, to the negative end of a bias potential source, such as a battery 51, and another conductor 53 extends from the outer contact 41 to the movable element 6| of a potentiometer 63 connected across the said source, while the grid of the tube is connected to amovable switch-element which may be placed in engagement with a switch-point 61 connect/ed to the junction between the resistor 39 and the capacitor 4|. Naturally, the potentiometer may be omitted, if desired, and the conductor 59 may lead directly to an appropriate point on the source 51. Using the potentiometer enables finer adjustment, however. Movement of the armature 31, therefore, between the said inner and outer contacts, causes the application of bias potentials to the grid of the tube which alternate between the most negative potential supplied by the source v5| and a potential determined by the position of the potentiometer contact element. These potentials are so chosen that when the armature is against the inner contact 5| the space current is substantially cut ofi and when it is against the outer contact 41 suiiicient current ows to cause both armatures to be drawn up.

Assuming now that the thermionic tube hal been energized by the application of alternating potential to the cathode heater and that the several relay armatures are in the position shown. at which time the source of fluctuating potential f1 is connected across the input terminals of the voltage amplifier I5.

Referring to Fig. 3, if no plate potential has as yet been applied, the potential across the capacitor 4|, ec, equals the grid-biasing potential, e., applied to the grid of the tube from the source 51. This potential is so chosen that it permits the flow of space current in the tube. I! anode potential is now applied, for example by closing the switch 35 in the anode supply lead, the space current will rise immediately to the value at which the relay armatures are picked up,"indi cated by the symbols PU and t1 in 111g. 3. YAs

the grid bias, eg, does not change instantane-` ously but relatively slowly, as indicated by the curve a in Fig. 3. Y v

At a later time, indicated by tz in the drawing, the grid has received a charge suiiiciently negative to diminish the plate current, ip, to a value indicated by DO in the drawing, which permits the armatures to release or drop out, and the sequence of operation continues just so long as the tube is supplied with cathode heating and plate potential. The dwell in each position is represented by the successive time-intervals ti-tz, tz-ts, etc.

Referring again to the drawing, it will be noted that the source fi is connected across the horizontal deflection plates in the cathode-ray tube during the time the armatures are released and that the source fz is connected thereacrossduring the .time when the armatures are pulled up. If,-

therefore, it is desirable to separately examine the output from the frequency source fr, the switch 65 interposed in the grid circuit of the thermionic tube is moved to a switch point 53, connected' permanently to the negative terminal of the lbias source, thus cutting the plate current down to a value insuiilcient to hold in the armatures. On the other hand, if it is desired to individually examine the output of the second source f2, the switch 65 is moved into engagement with a switch point 1| connected to the movable element 6| of the potentiometer to therefore supply just suiiicient bias potential to the tube to pervand the capacitor 4| the rate at which the space current in the thermionic tube rises and falls may be quite easily adjusted, this rate obviously depending upon the time constant of the circuit so formed.

Since, in the operation of my improved relay circuit the space current in the thermionic device is never entirely broken, high potential surges do not appear across the winding of the relay and the possibility of such surges causing inductive disturbance in the remainder ofthe system is thus obviated. Furthermore, since the function of the movable armature is merely to commutate the several frequency sources with respect to the cathode-ray tube and since it plays no part in the operation of the system other than that, sparking does not occur and the inductive surges characteristic of a buzzer, in

which'the coil current is broken by an armature contact, are obviously missing. It should also be especially noted that, in my improved system, the current in the relay Winding changes in value at a relatively slow rate, as compared with analogous devices of the prior art. This is an especially valuable feature of my invention, since it permits the armature to dwell for appreciable time in both the open and the closed positions. p

Other advantages oi my improved system will at once be apparent to those familiar with the art to which it pertains. Also, many modifications will be obvious and my invention therefore is not to be limited except in so far as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, a thermionic tube having a relay winding in its output circuit, a grid circuit for said tube, a source of biasing potential and means whereby relatively slowly fluctuating negative potential, derived from said source, is introduced into said grid circuit to thereby cause the relay to be periodically actuated.

2. In combination, a, thermionic tube having a control-electrode, an output electrode ,and a cathode, a relaywinding connected between the output electrode and the cathode, a connection including a capacitor between the control-electrode and the cathode, a source of biasing potential the positive terminal of which is connected to the cathode, a resistor one end of which is connected to the control-electrode and means under control of said relay winding for connecting the other end of said resistor sequentially and repeatedly to points of differing potential on said source.

3. The invention set forth in claim 2, characterized in that the time-constant of the resistor and the capacitor is of the order of one twentieth of a second.

4. The invention set forth in claim 2, characterized in that the last mentioned means is constituted by a movable armature and a plurality of contact devices associated with the relay winding.

5. In combination with a cathode-ray tube, a relay device having a winding and a movable armature, and means whereby unidirectional current from any appropriate source may be caused to iiow in said winding and to fluctuate at'approximately the rate of persistence of vision between a magnitude at which the armature pulls in and a magnitude at which the armature drops out, whereby inductive surges are obviated during the operation of the device, and means for controlling the deflection of the cathode ray in accordance with the movement of said armature.

6. 'I'he invention set forth in claim 5, chai'- acterized in that the iirst named means includes a thermionic tube provided with a grid biasing circuit having a relatively low time-constant.

'7. In combination, a cathode ray tube having defiecting devices and a iluorescent screen, a relay having a winding, a thermionic tube having a grid and a plate circuit, said winding being connected in said plate circuit whereby plate current ows therethrough, means for applying a slowly uctuating bias to said grid, and means including said relay for connecting said deilecting devices to one or the other of two alternating voltage sources depending upon the value of said plate current, the frequency of said iiuctuations being high enough for causing two curves to be seen simultaneously on said iiuorescent screen.

8. In combination with. an indicating device for indicating characteristics of the output of alternating voltage sources, an electric discharge tube having a cathode, a control grid and a plate circuit, a relay having a winding included in said plate circuit, a condenser connected between said cathode and said control electrode, a resistor, means including said relay winding for sequentially and periodically connecting said grid through said resistor to points of differing potential whereby a fluctuating current is produced in said plate circuit, and means for sequentially and periodically connecting said sources to said indicating device in accordance with the iiuctuations of said plate current.

9. In combination, a cathode ray oscilloscope provided with both horizontal and vertical ray deilecting devices, a plurality of sources of alternating potential, connections for continuously applying potential from one of said sources to one of said ray deiiecting devices, commutating potential in said grid circuit and means for periodically connecting said resistor and capacitor in shunt to different portions of the biasing potential source whereby relatively slowly fluctuating negative potential is introduced into said grid circuit to thereby cause the relay to be periodically actuated.

ARTHUR C. STOCKER.

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