US2620460A - Gas tube - Google Patents

Description

Dec. 2, 1952 I w. J. O'BRIEN 2,620,450

GAS TUBE Original Filed April 10, 1941 5 Sheets- Sheet 1 Dec. 2, 1952 w, O'BRIEN 2,620,460

GAS TUBE Cliginal Filed April 10, 1941 3 Sheets-Sheet 2 Dec. 2, 1952 vy J. OBRIEN GAS TUBE 3 Sheets-Sheet 3 Original Filed April 10, 1941 xOm 50 Patented Dec. 2, 1952 GAS TUBE William J. OBrien, London, England, assignor, by mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application April 10, 1941, Serial No. 387,908. Divided and this application June 12, 1947, Serial No. 754,194

11 Claims.

The present invention relates to improvements in stop-on-signal radio receivers and control circuits therefor including fast-operating, low impedance relays, and more particularly to circuits wherein said relays are controlled by means of gas tubes.

The present invention relates also to the provision of new and improved stop-on-signal radio receiver circuit arrangements for preventing deleterious effects resulting from oscillations in circuits including gas tubes, fast-operating, low impedance relays, and condensers utilized to provide the relays with current impulses to increase the rapidity of operation thereof.

This invention relates also to the provision of new and improved gas tubes,- and more specifically to the provision of gas tubes having an auxiliary anode by means of which the gas in the tube is maintained ionized and the tube conductive in spite of fluctuations in anode potential to values below that at which the gas would be deionized and the tube rendered nonconductive.

The present invention further relates to the provision of a new and improved stop-on-signal or stop-on-carrier control for radio receivers, certain forms of which are disclosed and claimed in the Patents of Edward F. Andrews, Nos. 2,262,218, issued November 11, 1941, and 2,326,737, issued August 17, 1943. My Patents Nos. 2,426,580, issued August 26, 1947, and 2,489,721, issued November 29, 1949, and my copending application Serial No. 681,183, filed July 3, 1946, which is now Patent No. 2,526,266.

The present invention relates especially to the use of the special type of gas tube with an auxiliary anode in a stop-on-carrier control system of the type shown in my above-mentioned patents, whereby the number of tubes required i reduced by one. This application is a division of my copending application Serial No. 387,908, filed April 10, 1941, which is now Patent No. 2,442,430, issued June 1, 1948.

Other aspects and advantages of the present invention will become apparent from the ensuing description, in the course of which reference is had to the accompanying drawings, in which:

Fig. .1 is a diagrammatic representation of a control circuit for a fast operating relay embody-.

Fig. 4 is a view similar to Fig. 3 of another 1 embodiment of the tube;

Fig. 5 is a fragmentary perspective view of a further embodiment of a tube constructed in accordance with the invention;

Fig. 6 is a diagrammatic representation of a standard automobile superheterodyne receiver, in connection with which the present invention has been utilized; and

Fig. 7 is a diagram showing the details of a portion of the circuit of Fi 6.

The circuit arrangement illustrated in Fig. 1

comprises a'relay l0 whose energization is controlled by a gas tube II. In order to effect fast operation of the relay, it is constructed to have a low impedance and low inductance winding so that with a given voltage a large current flow through it will be established in a short length of time. The low impedance and inductance are obtained by utilizing low resistance wire and winding having relatively few turns. Reduction of the number of turns reduces the actuating force exerted by the relay as the number of ampere turns is reduced (assuming the voltage supplied to the relay to remain the same), and to compensate for this reduction and to obtain fast operation the relay winding, indicated by reference character [2, is supplied with a considerable current impulse upon energization by means of a condenser 13 discharging through the winding when tube H is rendered conductive, the discharge fiowing through the tube. This discharge of a large current by the condenser occurs rapidly because of the low impedance of the relay winding and of the gas tube, thereby to effect fast operation of the relay. However, the circuit including the relay winding, tube and condenser has a tendency to oscillate because of its'low resistance, and the oscillations reduce the anode potential of the tube and are likely to cause deionization of the gas in the tube and to render the tube nonconductive. These fluctuations are prevented from deionizing the gas in accordance with the present invention, as illustrated in Fig. 1, by providing the tube with an auxiliary anode supplied with a potential sufficient to maintain ionization of the gas in spite of fluctuations in anode potential. r

In addition to the auxiliary anode, indicated by reference character it, the tube is provided with an anode l5, a grid l6, an indirectly heated cathode l1, and a cathode heater I8. The physical construction of the tube may take various forms, three forms being shown in Figs. 2 and 3, 4, and 5. In the embodiment of Figs. 2 and 3'the tube is shown with the usual glass envelope l9 and base 20. The envelope surrounds the previously enumerated elements of the tube and contains an ionizable gas. The anode I5 is cylindrical in shape and is supported in conventional manner by a pair of spaced posts 2! between insulating plates 22. The cathode I! is cylindrical in shape and supported concentrically with respect to the anode by a refractory post 23 in which the cathode heater I8 is embedded. The grid it is a helical wire located in proximity to the cathode and concentrically arranged with respect to both the cathode and anode. The auxiliary anode M is also a helical wire, it being located in this embodiment in proximity to the anode and concentric with respect to the other tube elements. Suitable leads are brought from the tube elements to prongs on the tube base 20. 'All the tube elements are of substantially the same-length in order that the tube may operate in its intended manner, as will be described shortly in connection with Fig. 1.

The tube illustrated in Fig. 4 is similar to that just' described except thatthe grid and auxiliary electrode are constituted by metallic cylindrical members 25 and 25 provided with two or more aligned apertures 26 and 21, respectively.

The tube illustrated in'Fig. 5differs from those previously described mainly in that the grid and auxiliary anode are constituted by apertured flat structural elements 230 and 23!, respectively, and the anode by a cylindrical wire 232'. These elements-and the cathode 233 and cathode heater 234 are surrounded by a grounded metallic shield 235, the open ends of which are closed by insulating plates 236. The shield comprises an apertured partition 23! located between the grid and-auxiliary anode, thus defining two compartments, one for the cathode, cathode heater and grid and a second for the auxiliary anode and anode. The apertures in the grid, partition and auxiliary anode are in alignment with each other and the cathode and anode. A tube of this construction may be constructed simply and economically and possesses a high control factor.

Returning now to a further detailed description of the circuit of Fig. 1, it may be seen that the relay winding 12 is composed of two series connected coils. One terminal of the winding is connected directly to anode 15 by conductor 23 and the other to the positive terminals of a source of potential, such as battery 36, through a current limiting resistor 3| and conductors 32 and 33. The battery thus'serves as a source of anode potential for the tube and as a source of energizing current for the relay. The other terminal of the battery is grounded through conductor 34.

The power consumption of the relay is reduced by the resistor 3! which is chosen to have a value such that once the relay is energized, the current flow therethrough is only sufiicient to maintain the relay in its operated position.

The current impulse supplying condenser I3 is connected to the cathode by conductor 35 and to a point intermediate the relay and resistor 3| by a conductor 36. It is thus connected so as to be charged by battery 30 when the tube is nonconductive and to discharge through the tube and relay when the tube is conductive.

The auxiliary anode is supplied with a potential sufiicient to maintain the gas ionized and the tube conductive in spite of fluctuations in anode potential from a suitable source, preferably the battery 30, through a current limiting resistor 31 and conductors 38, 39 and 33.

Grid-bias voltage is obtained through the use of an adjustable resistor 40 connected between the cathode and ground. This resistor is connected to the cathode by. conductor 4| and to ground '4 through switch 42 and ground connection 43. The grid is connected to ground through conductor it, resistor 45 and conductor 46. A gridbias voltage sufhcient normally to maintain the conductors 48.

The relay'may be utilized to control circuits or mechanisms and the like. In stop-on-carrier controls it is utilized to control circuits and a clutch, asindicatedin Fig. l. The relay may also take various forms,that shown in Fig. 1 being of a novel construction requiring but little space. It comprises a metallic base 49 having an upturned flange 50 at its front end- The coils l2 together with their cores 51 are secured to the flange. The cores have upturned ends above which is supported an armature 52 mounted at the ends of contact carrying switch blades 53 and 5 1. The switch bladesare 'biased-upwardlyinormally to complete circuits through fixed switch blades 55 and 56 and are movable downwardly upon energization of the relay to completecircuits through switch blades 51 andy58prespectively. The switch blades as well as theterminals to which conductors 28 and 32 are attached are mounted at the rear of base 49, by spacer blocks 59 and suitable bolts. The spacer blocks-are made of insulating material toinsulate the'terminals and switch blades from one another.

Switch blades 53 and 54 are'biased upwardly by a spring 63 that serves also to maintain the clutch engaged whenever the relay is deenergized. The biasing is effected through a combined clutch operating and power transmitting rod 6| slidably and rotatably mounted in a supporting bearing 62 forming part of the base member. The spring is held between the bracket and a washer 63 secured to the rod above the bracket.

The clutch comprises a pair of selectively engageable-elements 5'4 and 65, the former of which is secured to rod 6 l and the latter of which is driven from a suitable source of motive power, such as an electric motor, by gear'fia. When the clutch is engaged, rod 6| rotated to impart movement to a driven gear 67 used to drive tuning condensers in stop-on-carrier controls, as will be explained more fully in connection with Figs. 6 and 7.

In the description of the operation it is assumed that the tube is nonconductive by reason of the bias applied to grid 16 and that, as a result, relay It! is deenergized. At this time the grid is biased negatively by reason of current flow through resistors 46 and 41, which are connected across the battery 36 through conductors 33' and 39, switch 42 and ground connections 34 and43. The condenser I3 is fully charged by reason of its connection to the battery and battery potentials are applied to auxiliary anode l4 and anode [5.

The tube is rendered conductive and the gas therein ionized when a positive signal of sufficient strength is applied across resistor 45, after which the grid l6 becomes inefiective to exert further control. Immediately the tube is rendered .conductive, current flows through the'relay windings I2 and fast operation of the relay is. insuredby reason of its low resistance and impedance and the discharge of condenser 13 therethrough; The

low'resistance' series circuit including the condenser, tube and relay winding-has a tendency to oscillate'with the result that thepotential applied to anode I may be periodically reduced to a value 'below thepotential required to maintain ionization. In the ordinary three element gas tube the result would be the deionization of the tube',"but in the described apparatus, the gas' in the'tube is maintained ionized by the auxiliary anode I4, which is connected to the battery through resistor 31 and which is not effected by the oscillatory circuit.

The'relay is supplied with current sufficient to maintain it energized through a circuit including the battery, ground connections 34 and 43,-the tube and resistor 3|. Resistor Si is so propor tionedthat it limits the relay current to the desired value. Resistor 31 is so proportioned that only a very limited amount of current flows through it, thereby reducing power consumption by "preventing any substantial flow of current through it and the auxiliary anode in excess of that required to maintain ionization.

When it is desired to deenergize the relay and to render the tube nonconductive, it is necessary only'momentarily to open switch 42. Opening of this switch results in the opening of both the anode'v and auxiliary anode circuits as the switch is in series with the tube and battery.

' The present invention is particularly adapte for stop-on-carrier radio receiver control. The use of a gas tube provided with an auxiliary anode results in a reduction of the number of tubes required. For instance, when used in a control of the type disclosed in my copending application, one tube is eliminated. An application of the tube to this type of control is illustrated in Figs. 6 and'7. Referring now more particularly to Fig. 6, it may be noted that this figure illustrates in block diagram form a standard automobile superheterodyne receiver to which the elements of the present invention have been added. For the most part the receiver and control circuits are those disclosed and claimed in my Patents 1 Nos. 2,426,580, 2,489,721, 2,442,430, and my copending application Serial No. 681,183, previously mentioned, and consequently only the portion of the circuit associated with the operation of the novel gas tube of the present invention will be described in detail hereinafter. r

The receiver comprises an aerial II3, a radio frequency stage I I I, a first detector and oscillator section I I2, an intermediate frequency stage I I3, a second detector section II4, a balanced bridge circuit section II5 forming part of the stop-oncarrier-control and illustrated in greater detail in Fig. '7, gas tube II6 also forming part of the stop-on-carrier control, a volume control potentiometer II I, an audio frequency amplifier section H8, and a loudspeaker H9.

Energy is supplied by a battery I20 adapted to be connected by a switch I2I to a tuning means operating motor I22 of the reversible type, a cathodeheater circuit I23, and through an interrupter, step up transformer and B supply unit I24 to a B supply line I25. The B supply line leads to the various receiver portions and the stop-on-carrier control in a manner to be considered in great detail hereinafter. The switch I2I is illustrated as a manually operable switch, but it may be operated by the motor I22, as set forth in my copending application.

The receiveris provided with the usual tuning condensers I26 which are actuated by motor I22. The tuning and receiver volume are controlled from 'a remote point, such as the dashboard of an automobile, by means of a tuning control switch I21, which is normally closed, and a volume control switch I28, which is selectively operable from a normal circuit breaking position (into which it is biased as by springs) to the left to increase the volume and to the right to decrease the volume. Before describing in detail the various control means and control circuits, it may be well to review briefiy the mode of operation of stop-oncarrier radio receiver control. In so far as tuning is concerned, the tuning is initiated manually at the remote point by momentary opening of switch I21. This sets the motor in operation to rotate the tuning condensers through a clutch until the receiver is tuned to the carrier frequency of a station received with a certain intensity. The motor operates first in one direction over the entire range of movement of the condensers and then in the other, the direction of rotation of the motor being controlled by limit switches cooperatively associated with the condenser shaft. The same motor is used to control the volume but, when so used, it is selectively operable in either direction upon operation of switch I28 to. either of its two positions. volume control also includes a clutch through which the motor is selectively connected to the movable portion of the potentiometer II'I heretofore referred to.

Referring again to Fig. 6, it may be noted the condensers I26 are mounted for rotation with a shaft I30 connected by gears Him a shaft I32. The latter is adapted to be connected to a shaft I33 driven by motor I22 whenever a relay I34, associated with the stop-on-carrier control, is deenergized or released, at which time the clutch I35 is engaged. The relay and clutch may be constructed in accordance with those illustrated in Fig. 1, i. e., the relay is of the fast acting type and the clutch is operable by the relay armature. The energization of the relay is controlled by gas tube I I6 and when it is energized,

shafts I32 and I33 are disconnected to prevent further driving of the condensers whenever a station received with a certain intensity is tuned in. As already indicated, the tuning condensers are rotated first in one direction and then the other, the direction of rotation being reversed at .the limits of their movement by a limit switch I36 operated by two arms or the like I31 suitably secured to condenser shaft I30.

The volume control includes a clutch I38 operable by a relay I39 and adapted whenever the relay is energized to interconnect shafts I33 and I40. The latter isoperatively connected to the movable member of potentiometer I II.

The motor I22 has a pair of windings MI and I42 selectively energizable to rotate the motor in opposite directions. Winding MI is connected by conductors I43 to the right contact of volume control switch I28 and by branch conductor I44 to one of the two contacts associated with limit switch I36. Winding I42 is connected by conductor I45 to the left contact of the volume control switch and by a branch conductor I46 to the other contact of the limit switch. The movable blade of volume control switch I28 is connected by conductor M1 to one terminal of clutch operating relay I39, the other terminal of which is grounded. Thus, when switch I28 is operated to either of its two positions, the motor is energized simultaneously with energization of V the relay and, as a result, the movable member of the potentiometer is operated in one direction The.

orathe other 'tOfiHCITBflSBLOI. decrease-the volume.

of :reception. The, energizing, circuit is completed inboth cases through the-armatureof motor I22,

switch ;I2I,, battery I.20J and ground.

Theiremotetuning control switch .121, which is opened. to. initiate the tuning of another 5132-.

tion, :has one of its fixed contacts connected to.

conductor IA], this conductor serving, as will appear more-fully hereinafter, :as a ground-conned.

tion, and its other fixed. contact connected to adjustable resistor LI 4B. Aiconductorilfl connects the latter to the cathode of .gas tube I;I.fi:whereby the switch and resistor .areincluded .in. the plate circuit 'ofthe stop-on-carrier gas tube ISIS.

The .energization of motor I22. during tuning is controlled by .relay I34 which .actuates .switch blades I50 and I51. Switch blade 15!]: has associated with it a .pairof relatively fixed switch blades I52 and I53, while blade .I 5.! has associated with it .a, relatively fixed blade .154. Blades 15% and "I5I, areconnected to. groundby conductor I55. Blade I52 is connected Itolimit switch I35. Blade .153 .is connected zbyconductor lfificand an AVG delay condenser I51 :to .an AVC' conductor.

I58. .Blade I54 is connected .by conductor I59to- I41 or 142 depending .uptontlreiposition of limit switch .I-.36,;switch .blaides. I52 .and I51 ,and. ground connection I55 b'ack'to the battery. .At thesame time conductor-I56 and condenser I5! are disconnected :from ground to :provide fast acting AVCiasdescribed inzmy copending application), while conductor, I59 is connected to ground through switch blades I51 and I54 andconductor 155. Connection .of conductor I59 to ground serves to connect the gridsiof the. amplifier tubes of the lastamplifier (audio-frequency) .to ground to mute the loudspeaker during tuning. When the relay is energizedby tube I Iiibecoming conductive, as .now about to be described, the condensers are declutched from the motor and :the latter deenergized. The motor is .deenergized by reason of the opening of its energizing circuit by disengagement :of blades .ISELand I52. The A-VC delay condenser I5! is simultaneously rendered efieotive 1160 increasethe time :delay applied to the .AVCyoltage toa value "necessary for proper .treception during normal reception. Furthermore, thetground is removed from the audiofrequency amplifier tubes. to condition these for normal operation.

The primary function of gas tube 11.6 is to control the energization of relay I34 so that it is substantially instantaneously operated when the receiver is tuned to the carrier frequency of a broadcast station. A further function of this gas tube, which is provided with .an auxiliary anode H1, is to employthe high positive control voltage impressed on theauxiliaryanode 130.}3167 vent premature deionization of thetuhe as a result of oscillations .in the plate. circuit after, it has been ionized. To fulfill this function,'the

gas tube I.I6 operates ;in a .manner somewhat similar to that described in connection with Fig. 1. The relay is energized when the tube is renderedconductivexand the latter is rendered con-- ductive whenever thecondensers. I26 :aremotated age to be referred to later.

to tune. the. receiver to. carrierireqnencymf a broadcast station, To insure the 'tubebeing rendered conductive :wheny'the station inexact.- ly tunedin, the tube is controlled .in response to the. tuning. In brief,;the tube 1 I6 is controlled by two potentials, oneacting upon the auxiliary anode I11! and the other upon :a :grid 2 -12.. These potentials. vary with the tuning of the receiver and render the tube conductive :when the station is substantially exactlytuned: to ogcarrierwfrequency.

Referring now more particularly to Fig. 17;, this figure illustrates .in greater -;detail:.certa1 portions of the apparatus illustrated diagram.- maticallyin Fig. 6. These portions are: those from which the control potentials for the gas. tube are obtained. Corresponding :elementsnoi- Figs. 6 and 7 are indicated by like. reference characters.

The radio .frequencysection- I-Irl. of :6yi5 shown to comprise .atubeqfl l. Its :controhg d is coupled in conventional manner 170517118 lantenna by conductor-I12 and connected :to, the

AVG conductor I58: through resistor II3., Its anodeis-connected to the primary winding 1-14 of a, coupling. transformer which has. not :been,

illustrated in full but which is utilized to :con-

necttubeg'lll to the first detector. and oscillatorsection I I2, which likewise .has tnot. been; illustrated in Fig. 6. Elle -terminaloi? '-.windingyfI1;-I4

remote .from the anode is connected to .the; .B" supply conductor I through conductor. .1 151311121] resistor :I'iSand-to the-.auxiliaryaanodeIFI-TI of ithe gas tube through conductor H5 iandqa resistor 17:8. The same terminal is also :by-passedto ground through condenser. 111A.

The automatic, volume .controlmcludes {a sistor I119 connected between ,aconductor. I 53 :andv

asconductor I leading to" a source -:of AVC'wolte.

very small radio frequency by-IDaSS, condenser I81 connected between conductor ;I5 8:and,zground and the previously mentioned AVG time delay condenser 15! that is controlledfby switch blades;

I59 and I53 operated .byrelay 134.

The outputv .from the 'IadiOvfIBQJlBIICX "section I I I .is, as already, described, supplied-to :the first detector and oscillator section 1| I2,:and thence to the intermediate frequency section [13,, A. portion of the output from the latter :is supplied to the second detector stage I14 and :a portion to the balanced bridge circuit ;and-stop,-;on-. carrier control section 11.5.

The intermediate frequency section comprises a tube I32, the anode of which-ls connected to one terminal of the-primary *windingIB3 of..:a

closely coupled transformer, the other terminal,"

of which is connectedto B-supp ly-conductor I25. A portion-of'the output of'tube I82 45 sunplied to the detector stage through the secondary winding I84 of the :transformer. Oneterminal of winding. 1 84 is connectedi-to the detectorganode.

I85 of a multi-fiunction tube. IB6 .through-;:con-

ductor I81, and the otherterminal by rconductor I88- to volume control resistor I-I 'I, whichisv frequency amplification. Its control grid- 92 is.

connected to the movable .member of the volume control potentiometer through a suitable .source of grid biasing potential,,:such;as battery 193 It .also, :includes .a.

further connected to ground by a grid leak resistor I96. The amplifiedaudio-frequency output is supplied to the succeeding stage of amplification through the anode connection I91.' From the foregoing description it may be noted that the circuit of Fig. 7 does not correspond exactly to the block diagram of Fig. 6, in that in the, latter the second detector and audio- !requencyamplifier sections have been entirely separated. However, in a practical installation the tube I86 may well perform the dual function of a detector and amplifier, and it has been illustrated as doing this in Fig. '7. As a matter of fact, and as will appear shortly, tube I86 is utilized also as a rectifier to provide a second conand 2,489,721, previously mentioned. This circuit comprises a first tank circuit including primary winding I83, condenser 20I, condenser 202,

" resistor 203, and an adjustable condenser 204,

whereby this circuit may be tuned to resonance at the intermediate frequency; The circuit also comprises a second tank circuit including condenser 202, inductance coil 205'and an adjust able condenser 206 for tuning this tank circuit to resonance at the intermediate frequency.

The commonxc'onnection of condensers 20I, 202 and 206 is grounded. The common side of winding I83 and condenser 204 is connected to the common, side of inductance 205 and condenser 206 through condenser 201.

The output from the bridge circuit is led to the anode 208 of the second diode rectifier section of tube I86 through a condenser 209 and conductor 2I 0, and the rectified output appearing as avoltage drop across resistor 2 is supplied to the control grid 2I2 of gas tube I I6 through a time delay circuit including 'the resistor 2I2 and condenser 2l3. The resistor 2I2 is in series with the grid lead 2 l4 connecting the grid to the anode end of resistor 2 I I. A radio frequency bypass condenser 2I5 is connected across ground conductor I 9| and the previously referred to conductor I49 leading to the cathode 21s of gas tube '6. v 1

The relay I34 is connected to anode 2 I8 of tube II S by conductor 2I9 and the B supply is connected tothe anode through the relay winding and current limiting resistor 220. A current impulse-is supplied to therelay winding when the tube is rendered conductive by a condenser 22I having one terminal connected to the cathode 2l6 through conductor I49 and its other terminal connected to a point intermediate relay winding I34 and resistor 220. A bleeder resistance 222, connected at one end to the B supply and at the other end to the cathode lead I49, provides proper bias of the grid 2I2 when the tube is nonconductive, current flowing therethrough and the previously mentioned bias adjusting resistor I48. I

The operation of the system of- Figs. Sand '7 is swi q Ibl des. MB" aedb ek t ii tery through ground connection I 55; Since clutch I35 is engaged when relay I34 is deenergized, as it is at this time, the motor rotates the condensers I26 first in one direction and then the other as the windings MI and I42 are alternately energized by operation of limit switch I36 from one position to another by the arms I31 mounted on condenser shaft I30. This rotation of the condensers in alternate directions continues until the various tubes are heated and a broadcast station received. When a station is received, the gas tube H6 is rendered conductive and relay I34 immediately operated to' declutch the condensers from the motor shaft and to deenergize the motor.

The gas tube is rendered conductive by the application of an increased positive potential on the auxiliary anode I11 and by a reduction of the negative voltage impressed on the grid'2l2 from the diode 208. The auxiliary anode is made more positive as a result of the application of automatic volume control voltage to the grid of radio frequency tube I1I. This control voltage is obtained from the second detector section of tube I86 and is applied to the grid of tube '-I1I through a circuit including conductor I80, resistor I19, conductor I53, resistor I13, and conductor I12. As a result of the'application-of this control voltage on thegrid of tube I1I, the plate current of this tube is decreased, with the-further result that the voltage drop across resistor I16 is decreased and an increased positive potential is applied to the auxiliary anode I11, which is connected to the anode side or resistor I 16. This connection is through resistor I18 which serves to limit current flow through the auxiliary anode. The voltage applied to the auxiliary anode rises rapidly as a s-tationis being tuned in and is at a maximum'when a station is exactly tuned in, as described at considerable length in my Patents 2,426,580 and 2,489,721, previously mentioned.

The voltage thus applied to the auxiliary anode I11 when ionization'occurs is considerably in excess of the ionizing potentialpand remains so until the next station is tuned in by. manually operating push button switch I 21, to 'deionize tube H6. Thus, even though oscillationf'in the circuit, including tube H6, relay I34, and con denser 22I, may reduce the voltageof the plate 2I9 below ionizing potential, ionization is-mainpotential until the switch I21 isagain opened.

The balanced bridge circuit 200 supplies asignal to the diode 208 which increases as resonance with the station is approached until it :is within about one kilocycle of resonance. 0 From this point the amplitude of this signal falls .rapidly,

substantially to zero. -Thus, a negative direct current voltage from the diode 208 is applied to the grid 2I2 of the gas tube 6, which-increases as resonance is approached to a maximum negative value around one kilocycle from resonance,

and then falls steeply substantially to zero at resonance. The reduction of this negative signal on the grid 2I2 when the station is correctly sition correctly to tune in the station.

The primary winding I83 of thetrans'iormer .associated with theintermediate frequency tube enser:;206. is.substantially zerojwhen a signal of xactlyi-intermediateffrequency is placed: across H the. primary .windirxgtitl. In otherwords; the reflect of? the coupling occurring-..through-.,con- 1 denser? 201 produces avoltage drop-across the in-: ductance-205 whichis equal and opposite .t0,ithe .voltagei-drop across :condenser202 at; resonance. z;-'. :The valuerofre'sistanc'e 20-3 isselected so* as to bring: thevoltage across .the condenser 2 02, 180 utxof phase-with thexyoltagez across inductance 05.". Undertheseconditions-there is substantially eroiyoltagaacross condenser=2fl6 atresonance. In;-:onertaspectwthe; arrangement of the coupled ircuitszmay'be considered as a-balanced bridge 1 50n1;the."otherahand, ifvthevsignal" across the primary winding- |83 slightly-out of resonance, hereis n'oilonger a balance'betweenthe opposing reater;:.than:that otthe-other, and a potential arying with-:the ideparture fromresonantfreuency :exists ;:acrosscondenser- 205. When the ondensers l 26" are: 2approaching.iexact :tuning, that. is;yne Or'ItWO-kiIOCyCIGS :away from: exact tuning, a. very :large; alternating i currentj voltage is applied to the anode 208*ofthe: rectifier section. The'routput'of;the rectifier-appears as a; 'voltage dropracrosst resistorflIl :anduthistvoltage is appliedrthroughrresistor '2l2fl to the grid.;2l2 of. ubeZlGJi The greater theiyoltageapplied to'the armament therectifier, themore negative. the grid ZIZ.

: The normal negative. loias ofith'e grid 2 I2 due istance '222 is such as to renderetheltube-conductive when thenegative bias applied to the grid' '2 [2 from: the balanced bridge; circuit and rectifier approaches a" minimum valve (which occurs 'at resonance'l Sothatwhen :a-station is exactlyrtuned in; the tube is rendered conductive by -the conjoint 'action's of the less negative grid and-" morepositive auxiliary anode 111. When the tube flfi-isionized', the plate to cathode resistance oi -the tube drops to a relatively low value? The condenser 221 which accumulates a 'high ch'arge through'its connection to the B -supplythrough resistor 22!) during the nonconductive period of I tube 2 [6-, now discharges rapidly through the low impedancewinding of relay 134, with the further resultthat-the relay 'is' instantly operated to '-declutch the condensers from the motor'shaft and to deenergi'ze the motor, "'--*thus*stopping the-condenserexactly on-the car: rier" frequency" as previously explained. The ""steady flow of current through the resistor22ll, relay winding'and tube, which" are connected in tank circuits, the potential appearingacrosscon-v 15 circuit or avcircuitaproviding-zeroacoupling at 30 'couplings-ethat is, the effectof-onecoupling is 35 v: to th'e:biasing -resistor lw and the bleeder re 50 series =across-theB"" potential, is sufficient to hold 7 I 5312 *As heretofore explained, ;-the operation. of'zrthe ...z-sw.itch ofsrelay, 134 results ;also intthee-disconl. nection oi conductor A a from :ground, thereby r removing ,thelground .connection. from the "last 5-- '-;;stage. oisaudio -f;requency amplification,i-andpthe (output oi the receiver can be heardthrougl-rloudspeakerl l 19,, llhe relayualso ;-efiects connection 10f ,switch-.;blades I 50 rand l 53, nwith the. result ;:that condensencl5l. is .connected. torground to 10-;renderit, :efiective. to increase; the. time; delay applied tcrthe automatic yolumeccontrol voltage necessary:- .for 1 proper, .quality receptionsd-unng l,.,..,taudible; reception xof-the signal.

-,=When ,it desired: to; tune inzaiidifferent; sta- 32,- ion, ;switch;r I21 iis. momentarilyppened; thereby l-lzefieotiyely gbreakm the plaitecircuit.v of the ;gas tube which results in ithesdeenergizaticn:cfaielay :l 34;:{I'l1emotonis thereby energized andz-the con- EdEIISBIS THEEQCOIIHBCBBQ to, the motor-shaft: :The tuning operation described above will be repeated ,and-s,thei motor-again;- deenergized; and: the icon- .3 drawers edeclutched upon reception": of: another gsignalexceeding-acertain rstrength. tiThe :signal M i---strength at which-.the..:tuning meanswil-l-roperate 25: may -bei adjusted at @Will by-means ofztheadjustai ble resistor, 1 48 which serves to control thenormal --negative.bias ofbthe grid 21 2 Of$th9f gaSjtub9.

f Thewolume may-becadjusted"at anyrtime by zr movingrtheivolume controlzswitch: l28-z'ieitherto lcthe-sright-or left, astindicated in Fig. (ii-#When '"move'd'into eitheri'ofrits :circuit makingzpositions, thecone orathenother of: motor windings I41 or I42: is g;energizedv simultaneously with: the enera ."1 :er ization of: clutch zoperating solenoid I39." The :.r:energization of the solenoid; results in the: clutchfixing of rthefvolumeicontrol-i shaft Into. the motor shaft I33, with theIresult .thati.the movable member ofzthewolumecontrolipotentiometerl I1 is eoperatediinthe.directionselected by-operation of hevolumecontrol switch "I 28.

When'it isdesired to turn the receiver'off, it s-l-necessary only to open' -the'power switch' I21 whicheliectively cuts offthe power to the radio receiver: proper and -to the various controls.

1 T Although the invention has been disclosed in connection" with specific details of preferred embodiment's thereof, itinust'v be'understoodthat suchg'details'aremot intended to be limitative of -the invention-exceptin so 'far as. set forth in the accompanying claims.

..,Havingthus described my invention iwhat I claim as.newoand,desiretosecure by Letters .Pat- .;entioif=thellnitedfitates is:

5 A gags-tube,roilthetypapassing.asubstantial aspacecurrentwhenionized and-.a'hegligibleispace current .--.when deionized :andhaving av cathode, an .anode :surrounding- -said r-cathode', ;a, grid- 10- 1; cated-in proximity to? andsu-rrolmding said cath- 110618,? :and ran: auxiliary; anodersurroundingi. said grid. and: zlocatedzrbetween; the: latterxandisaid 1 anode, said auxiliary :anode being connected and arranged to control or maintain :the ionization ofs'aid tube. 6 2. A-gastube including-incombinatiomacath- 1 odehavinga substantially cylindrical exterior, an anode having a substantially cylindrical-interior spaced *from i and 1 located substantially: concentrically with respect to said cathode, agrid'comprising a wound wirehelix located in proximity to andsubstantially concentrically 'with'respect to "said. cathode-, an'd' anauxiliaryanode comprising a wound wire =heli-x:located betweenandspaced from-said anode and gridand-arranged substan- -tial-1y concentrically with respect thereto.

3. A'gas tube, including in combination, a, cathode having a substantially cylindrical exterior, an anode having a substantially cylindrical interior spaced from and located substantially concentrically with respect to said cathode, a grid comprising a metal cylinder located in proximity to and substantially concentrically with respect to said cathode, and an auxiliary anode comprising a metal cylinder located between and spaced from said anode and grid and arranged substantially concentrically with respect thereto, said grid and auxiliary anode being apertured for the passage of electrons and ions.

4. A gas tube, of the type passing a substantial space current when ionized and a negligible space current when deionized and having a cathode, an anode, a grid, and an auxiliary anode, said grid and auxiliary anode comprising plates having aligned apertures, said plates being spaced apart from each other and from the anode and cathode, said auxiliary anode being connected and arranged to control or maintain the ionization of said tube.

5. A gas tube, including in combination, a cathode, an anode, a grid, and an auxiliary anode,

said grid and auxiliary anode comprising plates having aligned apertures, said plates being spaced apart from each other and from the anode and cathode, and a grounded shield surrounding said tube elements, said shield having an apertured partition located between the grid and auxiliary anode.

6. A gas tube, including in combination, a cathode, an anode, a grid, and an auxiliary anode, a shield surrounding said cathode and grid and separating them from said auxiliary anode and said anode, said shield being apertured to provide a passage therethrough from the cathode to the anode side.

7. A gas tube as claimed in claim 6, wherein the grid and the auxiliary anode are located on opposite sides of the shield and. adjacent the aperture.

8. In a trigger type gas tube constructed and arranged to pass a uniformly high space current when ionized and negligible current when deionized, a cathode carrying said high space current, a grid located in proximity to said cathode, an anode spaced from the grid on the side opposite the cathode carrying said high space current,

and an auxiliary anode located between said grid and said anode carrying at least a part of the current carried by said cathode when ionized.

9. A gas tube having a cathode, anode, grid, and auxiliary anode, a conductive shield, partitioning means separating the space within the shield into two compartments including means defining an opening connecting the spaces in said two compartments, said cathode being located in one of said compartments, a grid in the shield compartment containing the cathode positioned between the cathode and the partitioning means, an anode in the other shield compartment. and an auxiliary anode in the compartment containing the anode positioned between said anode and said'partitioning means.

10. A gas tube as claimed in claim 9, wherein the grid and auxiliary anode are apertured so that a straight line connecting the cathode and anode will pass through both apertures and through the opening between the compartments.

11. A gas tube as claimed in claim 9, wherein means is provided in the tube to connect the shield and the cathode.

WILLIAM J. O'BRIEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,653,544 Brown Dec. 20, 1927 1,905,034 Marden et a1. Apr. 25, 1933 1,938,211 Biver Dec, 5, 1933 1,984,479 Heany Dec. 18, 1934 1,989,461 Ruven Jan. 29, 1935 2,032,137 Lubcke Feb. 25, 1936 2,044,619 Livingston June 16, 1936 2,080,235 Smith May 11, 1936 2,098,331 Bowman Nov. 9, 1937 2,106,847 Kniepkamp Feb. 1, 1938 2,185,852 Klopprogge Jan. 2, 1940 2,228,276 Le Van Jan. 14, 1941 2,398,772 Cone et al. Apr. 23, 1946 2,409,855 Hillyer, Jr., et a1. Oct. 22, 1946 2,426,580 OBrien Aug. 26, 1947 2,428,048 Stutsman Sept. 30, 1947 2,443,205 Stutsman June 15, 1948

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