US2512193A - Milliamperage stabilizer - Google Patents

Milliamperage stabilizer Download PDF

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US2512193A
US2512193A US617625A US61762545A US2512193A US 2512193 A US2512193 A US 2512193A US 617625 A US617625 A US 617625A US 61762545 A US61762545 A US 61762545A US 2512193 A US2512193 A US 2512193A
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current
discharge device
electron discharge
cathode
voltage
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US617625A
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Charles T Zavales
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CBS Corp
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Westinghouse Electric Corp
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/12—Regulating voltage or current wherein the variable actually regulated by the final control device is ac
    • G05F1/40—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices
    • G05F1/42—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices discharge tubes only
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/26—Measuring, controlling or protecting
    • H05G1/30—Controlling
    • H05G1/34—Anode current, heater current or heater voltage of X-ray tube

Definitions

  • the present invention relates to X-ray systems and more particularly to a milliamperage stabilizer system :for maintaining the current through the X-ray tube constant under all conditions.
  • Another Object of the presentiinvention is the provision of .a milliamperage stabilizer for an X-ray tube wherein compensation is made for the .decreasecharacteristic in tube filament heat, required to ,maintain constant tube current, as the,kilovoltage.across the tube. is raised.
  • Anotherobjectofthe present invention is the provision of a ,milliamperage stabilizer foran X-ray tube whereinthe effects of heating in.
  • X-rayfilamentcircuit are'overcome so that the filamentarycathodeis maintained at a truevconstanttemperature.
  • vA further object .of the present invention is the provision ,of a Qmilliamperage stabilizer for an X-ray tube wherein compensationis made for substantially all variables which would otherwise tend to alter the current flowing through the X-ray tube duringits operation.
  • an X-l y tube 5 having .its anode (i connected through a rectifying valve 1 to one end of thesplit secondary winding 8 ofahigh tension transformerfl, with the remaining end of this secondary winding ,Bgrounded at Hi.
  • the filamentarycathode 12.0 the X-ray tube 5 is connected through a rectifying valve l3 to one end of the ,remaining portion of a sec,- ondary winding I14 of ,the high tension transformer ,9.
  • Theotheriendofthis secondary winding connects l-through various instrumentalities constituting thestabilizeras will be hereinafter explained.
  • Thefilamentary cathode .12 of the X-ray tube 5 receives heating current ,from the secondary winding [5 Ma low tension transformer 16. a
  • auto-transformer H is provided with its primary being adjustably connected to a source of supply of the customary commercial potential of 200 to 250 volts so that once adjusted for the available voltage, upon closure of a magnetically operated switch l8, this voltage will be supplied to the auto-transformer II.
  • the auto-transformer is provided with large steps throughout most of its length comprising several turns of its winding between taps, for the purpose of giving a voltage differential therebetween of ten volts, while the remainder of its winding is tapped at substantially each individual coil, for giving a voltage variation between taps in units.
  • An additional winding 19 is carried by the core of the auto-transformer I1 which is also tapped to give a voltage variation in units therebetween.
  • An adjustable contact 2!] is operable to engage the various taps of the unit sectionofthe autotransforiner for selecting the desired units of kilovoltage for the X-ray tube 5 whicharm is connected to one end of the additional winding l9.
  • One'en'd of the primary winding 22 of the,hig h tension transformer 9 is adjustably connected to theadditional winding i9, so that the adjustment maybe altered to compensate for voltage drops in the interconnecting cable, drops due to leakage reactance, and auto-transformer drop at each value of milliamperage andchange inline voltage conditions.
  • this primary winding 22 i connected, upon closure of a magnetically operated switch 23, to an adjustable arm.2 4 engageablewith the large ten .volt taps of the auto-transformer l! with the arms 20 and 2 1, thuspreselecting the desiredkilovoltage forthe X-ray tube accurately in units and tens or 20 kv. and 2 kv. steps.
  • the magnetic winding of switch 23 receives electrical energy from taps of the auto transformer l1 upon closure ofa pair of contacts 25 with the circuit to winding of switch zfiremaining closed for a period of time determined by a timing device 26. Contacts 25 are closed by a relay 21, as hereinafter described.
  • the primary winding 28 of low, tension heatingtransformer H3 receives energy ofthe proper voltage from auto-transformer I! by having one end of its winding connected directly to a. tap
  • the saturable reactor 35 is provided in order to vary thefilament heat ofthe cathode ii to compensate for any inverse variations thereof due to decrease in line voltage, change in kilovoltage jor changeof resistance in the filament circuit by heating of its components. In addition to its A. C.
  • an electronic control tube 31 which has a relatively high value of transconductance rather than a high voltage gain.
  • high value of transconductance is meant a tube, such as identified in the trade as SAGl, which will vary the effective plate current in the greatest possible manner with the least possible change in grid voltage, since this tube type has the characteristics desired in a control circuit which is dependent on current rather than voltage as a means of operation. Accordingly, the plate of tube 31 is connected to one end of D. C.
  • a milliampere meter 38 and shunted by a capacitor 39 to a milliamperage preselector shown generally within the dotted frame 46.
  • the latter constitutes a resistance type of control which increases or decreases the X-ray tube filament current, thus raising or lowering the milliamperage flowing through the high voltage circuit of the X-ray tube.
  • this milliamperage preselector adjusts the current at which the stabilizer operates.
  • This milliamperage preselector comprises resistors R1, R2, R3, R4, together with previously mentioned resistance 30 connected across the taps of auto-transformer i1.
  • Resistors R1 to R4 select the magnitude of the voltage which is ap-, plied to the milliamperage stabilizer across the terminals G1 and MAi.
  • Resistance 39 controls the filament heat of the X-ray tube in such mannor as to increase the available filament voltage as the milliamperage is raised, with its adjustable arm 29 being operable in tandem (as shown by the legend) with the adjustable arm 42 of resistor R1.
  • adjustable arms 29 and 42 are operable from the front of the control panel and are employed in conjunction with a precalibrated milliamperage scale.
  • the high and low ends of the milliamperage selec tor scale is made to track with the selector pointer, which is assured by the resistors R2, R3 and R4.
  • Adjustable resistor R2 is provided to set the upper or high milliamperage to which the selector is adjusted while adjustable resistor R3 and fixed resistor R4 adjust the lower milliampere value on the precalibrated scale. Once these are set for a given installation, they need rarely be further adjusted with the simultaneously operable resistor R1 and the variable resistance 30 preselecting the milliamperage desired.
  • This milliamperage preselector 40 operates by being supplied with current from the milliampere admirs master the high tension itransformer winding -I-'4- through-milliammeterMa and resistorsEz-arid R1 '--to ground through ad-justable' arm-l2, and since the apper en'd or adjustable resistor' Rr is connected to stabilizer terminal- Ge andthe" lower end of resistor Rz is conneeted to stabilizer terminal 'Mnn a definite controkvoltage is impressed across the mill-iampere stabilizer.
  • a 'safety' circuit is 'included 'in the milliamperage preseiector.
  • This safety circuit includes two voltageregulator tubes- 43'and with said tubes being connected in series with 'each other across the "stabilizer terminal "ll/1A1 and ground.
  • Resistors R -arid" l'tq 'shuntthe respective-tubes "43 and 64" to equally *dividethe voltage thereacross. 'These tubes'accordinglyare so arranged as tobreakfiownshoul'd the voltage across capacitor-C1 exceed abodt300 volts.
  • the output of the neon discriminator 1 circuit "connects to the control grid of electronic control'tube 3'! through a battery 55 and aressistancelelement 55.
  • 'Thiszbattery 55. is provided to select the operating point Withregard to the characteristic curves of the tube .31, and :isnot subjectto normal deterioration effects since no .currenti'istaken' from the battery 55 itself during-operation, with the battery merely adding to the output voltageoof the neon discriminator .circuit,.thereby varying the plate'current in'the control tube 31.
  • a power transformer 1151 In order to supply the 350 volts D. C.1tothe D. --'C. V winding 35 :of .the saturablereactor 135, a power transformer 1151 is provided which has" its primary winding :58 connected toappropriate voltage-taps of auto transformerl1.
  • The-high voltagesecondary windingfiii delivering approximately350volts' has its center tap connected-to the cathode-eithe control tube 13'! (and thusf'to oneside MA1:of the stabilizer input i'potential) while the ends of 1' this secondary Windingi'59 .-;conmeet to the respectiveanodes of 'a full vvave rectifier itube $60.
  • the thermionic cathode oi. rectifier 60 connects to one side of the D. C. winding 36 of the saturable reactor 35, as previously mentioned, which, upon closure of a pair of contacts 64 as hereinafter described, thus places the supply of D. C. to'the winding 36 completely under the control of the control tube 31.
  • This D. C. supply for reactor winding36 is provided with a choke input filter comprising an inductance 65 and capacitor 66. Accordingly, the capacitor 66 is charged each half wave of the alternating current cycle in well known manner since by virtue of the center tapped secondary winding 59, its respective halves are 180 out of phase, and the resulting D. C. output voltage appears across one end of the D. C.
  • the rectifier tube 60 being of the thermionic cathode type requires a normal delay period of approximately 20 seconds before the tube reaches its normal operating temperature. Advantage is taken of this delay characteristic, as hereinafter described, in order to provide a desired time delay prior to operation of the control by giving the tube 60 an opportunity to arrive at its proper operating temperature.
  • a preset circuit Forthe purpose of presetting the filament heat in the X-ray tube circuit, to approximately the normal operating range as will be required for the particular milliamperage selected and to also make the milliamperage stabilizer independent of line voltage variations, a preset circuit includin a voltage regulator tube 61 is provided for controlling the voltage supplied to the screen grid of control tube 31.
  • This preset circuit includes the voltage regulator tube 61 having its cathode connected to one side of capacitor 66 and thus to the negative side of the D. C. output of the previously described filter circuit which includes the capacitor 66.
  • the anode of voltage regulator tube 61 is connected through a' resistance 68 to the opposite or positive side of the choke filter circuit and hence to one side of the D. C.
  • the control tube 31 has such characteristics that if the screen-grid voltage is held constant the plate current through the control tube 31 is relatively independent of line voltage and. hence variations in the latter have substantially no eiiect on the plate current.
  • a relay 10 is provided for the purpose of controlling the screen grid voltage of control tube 31 to enable the filament of the X-ray tube to be properly preset at the termination of a given exposure.
  • This relay 10 is provided with a pair of contacts12 which upon closure short-circuit the adjustable resistance 69 and also provided with a set of contacts13 connected to the motor of timer 26 so that the latter operates as soon as the X-ray tube is energized.
  • the milliamperage stabilizer is de- 8 pendent on;the.magnitude of the voltage EP'. plied to the control grid of the control tube 31. Accordingly, when the voltage is removed from the control grid of tube 31, the grid bias will then drop to the valueof the bias battery iii. This will increase the; plate current in tube 31 and decreases the effective impedanceof the saturable reactor 35 and the filament heat of the X-ray tube will be increased, which produces an undesirable condition in that current through the X-ray tube reaches relatively high values upon resumption of another exposure. It is to prevent such undesirable result that provisions are made to control the voltage on the screen grid of control tube 31.
  • the relay 1B Prior to initiation of an X-ray exposure, the relay 1B is inoperative and the screen grid is supplied with a voltagethrough resistances 68 and 69. Since the voltage drop across these resistances are additive; a voltage somewhat lower than that required for normal operation is supplied to the screen grid of control tube 31, and with this reduced screen-grid voltage the plate current in the control tube is reduced. Under conditions of reduced plate current, the impedance of the saturable reactor 35 will be raised thereby lowering the filament heat of the X-ray tube cathode as 1011;! as X-rays are not being produced.
  • relay 1B When the X-ray On push button is operated, relay 1B is energized and closes its contacts 12, which thus short-circuits the resistance 69-, as previously mentioned, and raises the voltage supplied to the screen grid of control tube 31 to its normal operating voltage of about volts. This irnmediatelyraises the plate current of control tube 31 and reduces the reactance of the saturable reactor 35, which in turn increases the filament heat of'the X-ray tube cathode during the exposure and until the latter is terminated b the timing dev ce 25 or by depression of the X-rav Off" push button.
  • the voltage regulator tube. to ether with its circuit as above described.
  • control tube 31 is preferably one having a high value of transconductance so as to give optimum performance in a milliarnperage type stabilizer.
  • Such high value of transconductance enables the milliamoerage stabilizer in general to have sufiicient ga n to overcome eifects of increased filament voltage, increased temperature in the filament circuit which affects filament resistance and incre s d kiiovolta we. Howe er. because of the act th t a hi h ain is obtained. a feedback condition arises between the milliamperage stabilizer and the X-ray tube.
  • a feedback circuit comprising afee'd back transformer 14-, the primary winding: 15' of which is connected across the resistance 3i included in series with the primary winding 28" of the heating transformer l6 for the'cathode l2'of X-ray tube and the A. C. windings 33' and 34 of reactor 35.
  • the primary winding Hi-of the feedback transformer is thus subjected to the voltage drop across the resistance 3
  • the output from the-'step-up windinglfi is accordingly impressed across resistor 19 with the filter capacitor 18- sl'iunt'ed across the resistor 19 toadd sufficient time duration to the voltagepulsesappearing acrossthe resistor 19-- which averages out over a half cycle since the constants of this capacitor 18 and resistor 155 are so chosen that the voltage durationis /120 of a second.
  • the voltage which appears across resistor 19 is in turn cap'acitativ'ely coupled to the previously mentioned resistance element 56 through a capacitor 80.
  • the voltage drop across resistor'lfl remains" constant and is blocked'b'y' capacitor 80 from in any way affecting the control grid of control tube 31.
  • contacts-83 complete aholding circuit .for the winding-P of relay 10- so that the contacts I2. and 13+: of the latter. maintain theshort-circuit condition of;resistance'69-'and' the timer 26 in operation hntil the exposure .is completed by, opening oisthehormallyclosed contacts ofthe. timer-2t, oropening *of the control circuit by depressionaof. the ,fX-ray Off, push :button. .It. can thus-'beseen that the X-ray On pushibut-v ton v,is, therefore.
  • circuit receives energyiromtaps on-theautotransformer IT.
  • a conductor extends from a tap of, autotrah'sformer'. l.'l to. one side, of winding ,of magnetically, operated-switch 23, and this same conductor also extends to'onerside of the Wind ng; of relay;.18,mas well: as to one contact thereof. The other. side of.
  • this-control circuit extends; fromranother tap -of the autotransformer l'l and by: a conductor-85: through the pi s of the v lta e regulator tubes-Hand 44; in series; and through the icontacts 250i the relay; 2], and then through normally closed" X ray: Off? push, button, the, normally closed'contacts of the timer 26, and to, one-side of the, ,X-iray-On push button as Well; aszi'one of thecontacts -83 of ma n al y 0 erated switch:23. l ,i
  • This control circuit is: thus" initi 126. the'vcontactsza: and the normally open ii-ray ;v
  • milliamperage stabilizer has beenshown and described with what is termed half-wave equipment, which means that the rectified alternating current is supplied to the X-ray tube during half-waves of the alternating current cycle.
  • half-wave equipment which means that the rectified alternating current is supplied to the X-ray tube during half-waves of the alternating current cycle.
  • - suchstabilizer can be just as readily employed with a full wave bridge circuit by inserting the milliamperage stabilizer in the D. C. circuit of the milliammeter and utilizing a rectifier bridge arrangement. wave arrangement has not been shown for the sake of simplicity.
  • a milliamperage stabilizer is herein provided which maintains the current through the X-ray tube substantially constant during an exposure. Moreover, such stabilizernot only compensates for fluctuations of voltage in the source of supply but also compensates for increased filament voltage, increased temperature in the filament' circuit which affects filament resistance, and increased 'kilovoltage.
  • a source of alternating current electrical energy subject to changes in resistance with an attendant variable current component for heating the cathode of said electron discharge device a saturable reactoroperatively connected with said source of heating energy and operable upon the imposition .of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge dewce, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in voltage across and current through said electron discharge device, as well as line voltage fluctuations and change in resistance in the source of heating energy for saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a unidirectional current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the voltageacross and current through said electron discharge device as well
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operably connected with said source of heating energy and operable upon the imposition of a, unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to varia-.
  • said adjustable preselector means including a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector with both said aforementioned means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor differing from that of said heating source accompanied by a variation in the heating current supplied 'to-the' cathode of: said'electrofi discharge device inversely to variations in-the discharge current flowing through the latter.
  • an excitation circuit for said device including a high tension transformer having its secondary wind ing'connected through arectifying arrangement to said electron discharge device for supplying unidirectional current thereto, source of alternating current electrical energy 'for' heating the cathode of said-electron discharge device normally subject to'a variable current component, a saturablereactor operatively connected with said source of heating energy andoperable'upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the'flow ofheating current to the cathode of said electron discharge device, adjustable preselector' meansconnected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and said adjustable preselector means including a filter arrangement comprising two inductanceelements in series relation together with a capacitor shunting one of said inductance elements and a capacitor in shunt with said adjustable preselector means and
  • an excitation circuit for said device including a high tension'transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a, source of alternating current electrical energy for heating the cathode of saidelectron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device and including a voltage divider discriminator arrangement for amplifying the voltage across said adjustable preselector means, and electrical cir-i "cuit means operatively connected with said-saturable reactor and said adjustable preselector means and operable upon a variation in the potential across
  • an excitation circuit for said device includinge; high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device nor.- mally subject to a variable current component, a
  • adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in dis-charge current through-said electronvdischarge device and including a voltage divider discriminator arrangementcomprising a discharge device having a constant: voltage drop thereacross in series with said adjustable preselector means and a resistor in parallel with thelater foramplifying the voltage across said adjustable: preselector means, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the im position of a current component upon said saturable reactor differing from the current com ponent of said heating source accompanied by a variation in the heating current supplied to-the cathode of said electron discharge device
  • adjustable preselector means connected to said excitation circuit and subject to variations. in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the.
  • the combination 01 an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its'secondary wind:- ing connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected associated with said source of heating energy and operable upon the imposition of a unidirectional component thereupon difiering from the current component of the heating source to control the flowof heating current to the cathode of said electron discharge device, a source of unidirectional electrical energy for supplying the unidirectional component to said saturabie reactor, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselect
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying current to the cathode of said electron discharge; device, a source of unidirectional electrical energy for supplying the unidirectional component to said saturable reactor, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in.
  • said electron discharge device including an electronic control tube having a high value of transconductance to cause a variation of relative- ,ly great magnitude in plate current through said.
  • control tube in response to relativelysli ghtvarizji tions in grid voltage supplied thereto and oper-' able to control the supply of unidirectional en ergy from said source to said saturable reactor; electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause operation of said control tube with the imposition of a current component from said unidirectional source upon said saturable re actor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to varia tions in the discharge current flowing through the latter, and a relay operatively connected to said source of unidirectional electrical energy and energizable by the latter to cause a time-delay before said excitation circuit becomes effective to energize said electron discharge device.
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon diifering from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube provided with a control grid and a screen grid and having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, and electrical circuit means operatively connected with said
  • an electron discharge device provided with a cathode to be heated
  • an excitation circuit for said device including a high thereupon difierin from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device
  • adjustable preselector means con.- nected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device
  • an'electronic control tube provided with a control grid and a screen grid and having a high value of transconductance to cause a variation of rela tively great magnitude in plate current through said control tube'in response to relativel slight variations in grid voltage supplied thereto
  • electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of direct current power for said control tube and a voltage regulator tube for controlling the power supplied 'by said direct current source to the screen grid of said control tube to causeoperation of the later with attendant imposition of a current component upon said saturable reactor differing
  • excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the currentcompon'ent of the heating source to control the flow of heating current to, the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube provided with acontrol grid and a screen grid and having a high value of transconductance to cause a variation of relatively Jgreat magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of
  • a voltage regulator tube for controlling the power sup-- plied by said direct current source to the screen grid of said control tube to cause operation of the latter with attendant imposition of a current component upon said saturable reactor differin from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to line voltage fluctuations eifecting the discharge current flowing through said electron discharge device, a resistance in series with said voltage regulator tube, and a relay operable simultaneously with energiz'ation of said electron discharge device by said excitation circuit to short-circuit said resistance and cause an increase in the potential supplied to the grid of said electronic control 1 tube with an attendant automatic increase in the current supplied to the cathode of said electron discharge device, and operable to connect said resistance in series with said voltage re ulator tube and cause an automatic decrease in the cur rent supplied to the cathode of said electron discharge device upon deenergization of said electron discharge device.
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device norma1- 1y subject to a variable current component, a
  • saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including anelectronic'control tube provided with a control grid anda screen grid and having a high value of transconductan'ce to cause a variation of relatively great magnitude in plate current through said'cont'rol tube in re sponse to relatively slight variations in grid Voltage supplied thereto, and electrical circuit means operatively connected with saidsaturable reactor and said adjustable preselector means and including a "source of direct current power for said control tube and a voltage regulator tube for controlling the power supplied by said direct current source to the screen grid of saidcont'rol tube to cause operation of the latter with attendant imposition of a current component upon said saturable reactor differing from
  • excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube provided with a control grid and a screen grid and having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of direct current power for
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectiiying'arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, and electrical circuit means operatively connected with said saturable reactor and said adjustable
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reaction differing from the current component of said heating source accompanied by
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable currentcomponent, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor differing from the current component of said heating source accompanied by
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device and including a resistor in series with said adjustable preselector means, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device, normally subject to a variable voltage component, a saturable reactor operatively connected with said 22 sourceof heating energy and operable upon the imposition of a unidirectional component thereupon difiering from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device and including a voltage divider discriminator arrangement for amplifying the voltage thereacross and a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said
  • an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and said adjustable preselector means including an electronic control tube having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, a filter arrangement to remove the current component due to distributed capacitance in said excitation
  • gal-gm '23 20 The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy subject to changes in resistance and a variable current component for heating the cathode of said electron discharge device, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the oathode cf said electron discharge device, adjustable preselector means connected to said excitation circuit and including a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, a voltage divider discriminator arrangement for amplifying the voltage across said means, an electronic control tube havin

Description

June 20, 1950 c, ZAVALES I 2,512,193
MILLIAMPERAGE STABILIZER Filed Sept. 20-, 1945 ATTORN EY Patented June 20, 1950 UNITED STATES IHILLIAMPERAGE 'STABIIJIZER Charles T. Zavales, Baltimore, Add ,agssignorgto Westinghouse ElectricrCorporation,East'Pittse burgh, Pa., a corporation of Pennsylvania Application September 20, 19,45,- Serial Nip--61 16,25
20 Claims. (Cl. 31 5-10Z) The present invention relates to X-ray systems and more particularly to a milliamperage stabilizer system :for maintaining the current through the X-ray tube constant under all conditions.
It has long been recognized in the art that an X-ray tube is generally subject to variations of several kinds during its operation which affect the quality of the resulting radiographic exposure. In order toeliminate the effect of some of these variables, numerous circuit arrangements have been long utilized :in the art in an effort to stabilize the operation of the X-ray tube. Practically all of such systems are directed to merely maintaining the temperature of the thermionic cathode of the X-ray tube constant by causing an inverse variation in the cathode heating current in response to line voltage fluctuations or variations in the high voltage supplied to the X-ray tube.
Thereiare, however, other factors which cause a variation in the voltage supplied to the cathode of the X-ray tube, or filament voltage as it will be hereinafter referred to. Such variation in filament voltage which necessarily controls the temperature of the filament are heating of the entirefilament circuit, changes in the characteristics of the X-ray tube and the change in kilovoltage across the X-ray tube. In all present type X-ray tubes employing filamentary. cathodes, the emission current is dependent on a definite.relationship which shows the emission current is dependent upon thetemperature of the filamentary cathode, but a rise in emission current is not proportionate to the actual filament voltage. Accordingly, as the voltage of the filament is raised, the quantity of emitted electrons rises greatly, thus necessitating some means of voltage stabilization ior the filament of the X-ray tube in order to insure consistent tube milliamperages. 1 Such voltage stabilization of the filament does not compensate, however, for the characteristic of filamentary cathode X-ray tubes requiring that .fora particular milliamperage setting, a decrease in actual filament heat is required in order to maintain the emission current constant as the kilovoltage across the X-ray tube is increased. Therefore, to meet this requirement it is essential toinsure proper decrements in X-ray filament ,heat as the kilovoltage across the X-ray tube is increased.
As above mentioned, a further variable affect- .ingstabilization arises from the fact that components-of theX-ray-filament circuit are inhera 2 ently heated to some extent. Consequently, as the temperature of the X-ray filament circuit increases, due to :heating of its components, the filament heat of the X-ray tube decreases .and continuedv operation of the X-ray tube withtconstant filament voltage across the primary of the X-ray filament transformer will result in continued diminution of the-tube milliamperage. It is accordingly the object of the present in.- vention to provide a milliamperage stabilizer for an X-ray tube wherein compensation is made for the rapid change ofemission characteristics of thefilament as the kilovoltageacross the tube is increased.
Another Object of the presentiinvention is the provision of .a milliamperage stabilizer for an X-ray tube wherein compensation is made for the .decreasecharacteristic in tube filament heat, required to ,maintain constant tube current, as the,kilovoltage.across the tube. is raised.
Anotherobjectofthe present invention is the provision of a ,milliamperage stabilizer foran X-ray tube whereinthe effects of heating in. the
, X-rayfilamentcircuit are'overcome so that the filamentarycathodeis maintained at a truevconstanttemperature.
vA further object .of the present invention is the provision ,of a Qmilliamperage stabilizer for an X-ray tube wherein compensationis made for substantially all variables which would otherwise tend to alter the current flowing through the X-ray tube duringits operation.
Still further objects of the ,present invention .will ,become obvious to, those skilled in the art by reference to the accompanying drawing wherein the single figure is a diagrammatic illustration of .a milliamperage stabilizer constructed in accordance withthe present invention.
Referring .n,ow .,to the drawing in detail an X-l y tube 5 is shown having .its anode (i connected through a rectifying valve 1 to one end of thesplit secondary winding 8 ofahigh tension transformerfl, with the remaining end of this secondary winding ,Bgrounded at Hi. In a similar manner the filamentarycathode 12.0: the X-ray tube 5 is connected through a rectifying valve l3 to one end of the ,remaining portion of a sec,- ondary winding I14 of ,the high tension transformer ,9. Theotheriendofthis secondary winding connects l-through various instrumentalities constituting thestabilizeras will be hereinafter explained. Thefilamentary cathode .12 of the X-ray tube 5 receives heating current ,from the secondary winding [5 Ma low tension transformer 16. a
auto-transformer H is provided with its primary being adjustably connected to a source of supply of the customary commercial potential of 200 to 250 volts so that once adjusted for the available voltage, upon closure of a magnetically operated switch l8, this voltage will be supplied to the auto-transformer II. It will be noted that the auto-transformer is provided with large steps throughout most of its length comprising several turns of its winding between taps, for the purpose of giving a voltage differential therebetween of ten volts, while the remainder of its winding is tapped at substantially each individual coil, for giving a voltage variation between taps in units. An additional winding 19 is carried by the core of the auto-transformer I1 which is also tapped to give a voltage variation in units therebetween.
An adjustable contact 2!] is operable to engage the various taps of the unit sectionofthe autotransforiner for selecting the desired units of kilovoltage for the X-ray tube 5 whicharm is connected to one end of the additional winding l9. One'en'd of the primary winding 22 of the,hig h tension transformer 9 is adjustably connected to theadditional winding i9, so that the adjustment maybe altered to compensate for voltage drops in the interconnecting cable, drops due to leakage reactance, and auto-transformer drop at each value of milliamperage andchange inline voltage conditions. The other end of this primary winding 22 i connected, upon closure of a magnetically operated switch 23, to an adjustable arm.2 4 engageablewith the large ten .volt taps of the auto-transformer l! with the arms 20 and 2 1, thuspreselecting the desiredkilovoltage forthe X-ray tube accurately in units and tens or 20 kv. and 2 kv. steps. The magnetic winding of switch 23 receives electrical energy from taps of the auto transformer l1 upon closure ofa pair of contacts 25 with the circuit to winding of switch zfiremaining closed for a period of time determined by a timing device 26. Contacts 25 are closed by a relay 21, as hereinafter described.
The primary winding 28 of low, tension heatingtransformer H3 receives energy ofthe proper voltage from auto-transformer I! by having one end of its winding connected directly to a. tap
of the auto-transformer'winding, while the remaining end of primar winding. 28 is adjustably connected by an arm .29 to a resistance 30 bridged across several windings of the auto-transformer 111, with a resistance 3! and the A. C. windings 33 and 3 of a saturable reactor being in series with the primary winding 2B..of filament heating transformer l6. e j H The saturable reactor 35 is provided in order to vary thefilament heat ofthe cathode ii to compensate for any inverse variations thereof due to decrease in line voltage, change in kilovoltage jor changeof resistance in the filament circuit by heating of its components. In addition to its A. C. windings 33 and 34 disposed about the outermost legsof the core, such reactor is provided with a, D. C. winding 35 wound about its centerleg. As is well known in the art, a change in magnitude of the current flowing in thecentral D. C. winding 35 will vary the impedance 'of the two A. C. windings 33 and 34, i. e., an increase in cure rent through the D. C. winding will decrease the effective impedance of the two A. C. windings 33 and 34 allowingmore current to flowto the pri mary of transformer it with an attendant increase in filament heat and a decreasein current through the D. C. winding 35 will increase the impedance of the two A. C. windings with a decrease in filament heat of cathode [6.
If, therefore, the magnitude of the current flowing through the D. C. winding 36 is suitably controlled, the filament heat of the filamentary cathode i2 is conveniently varied to maintain substantially uniform heat. Accordingly, an electronic control tube 31 is provided which has a relatively high value of transconductance rather than a high voltage gain. By high value of transconductance is meant a tube, such as identified in the trade as SAGl, which will vary the effective plate current in the greatest possible manner with the least possible change in grid voltage, since this tube type has the characteristics desired in a control circuit which is dependent on current rather than voltage as a means of operation. Accordingly, the plate of tube 31 is connected to one end of D. C. winding 36 while its indirectlyheated cathodeis connected to one side MAI of the input circuit of the stabilizer and to the ne'gative side of a D. C. source of supply of about 350 volts, as hereinafter described, and the opposite end of the D. C. winding 36 is connected to the positive side of this D. C. source of supply. The supply of a D. C. current at a voltage of about 350 volts to theD. C. winding 36 of the saturable reactor 35 is thus under the control of tube'3'l. A capacitorv M is shunted across the D. C. winding 36 to reduce the effects of self-induction which occurs due to rapid changes in plate cur rent through the tube 31. v
Referring now to high tension secondary winding M of transformer 9, it will be noted that an end thereof is connected, through, a milliampere meter 38 and shunted by a capacitor 39, to a milliamperage preselector shown generally within the dotted frame 46. The latter constitutes a resistance type of control which increases or decreases the X-ray tube filament current, thus raising or lowering the milliamperage flowing through the high voltage circuit of the X-ray tube. At the same time this milliamperage preselector adjusts the current at which the stabilizer operates.
This milliamperage preselector comprises resistors R1, R2, R3, R4, together with previously mentioned resistance 30 connected across the taps of auto-transformer i1. Resistors R1 to R4 select the magnitude of the voltage which is ap-, plied to the milliamperage stabilizer across the terminals G1 and MAi. Resistance 39 controls the filament heat of the X-ray tube in such mannor as to increase the available filament voltage as the milliamperage is raised, with its adjustable arm 29 being operable in tandem (as shown by the legend) with the adjustable arm 42 of resistor R1.
These two adjustable arms 29 and 42 are operable from the front of the control panel and are employed in conjunction with a precalibrated milliamperage scale. For the sake of accuracy, the high and low ends of the milliamperage selec tor scale is made to track with the selector pointer, which is assured by the resistors R2, R3 and R4. Adjustable resistor R2 is provided to set the upper or high milliamperage to which the selector is adjusted while adjustable resistor R3 and fixed resistor R4 adjust the lower milliampere value on the precalibrated scale. Once these are set for a given installation, they need rarely be further adjusted with the simultaneously operable resistor R1 and the variable resistance 30 preselecting the milliamperage desired. I
This milliamperage preselector 40 operates by being supplied with current from the milliampere amazes master the high tension itransformer winding -I-'4- through-milliammeterMa and resistorsEz-arid R1 '--to ground through ad-justable' arm-l2, and since the apper en'd or adjustable resistor' Rr is connected to stabilizer terminal- Ge andthe" lower end of resistor Rz is conneeted to stabilizer terminal 'Mnn a definite controkvoltage is impressed across the mill-iampere stabilizer. A capacitor 01 is shunted across *the resistors Br and i to insure' proper tracking of the*calibrated milliam penage scale use to =waveform'=changes which occur in the milliampere-=circu-it at higher-values of *X raytzibe-current. *Aspreviously-mentioned,
resistors R3 and liware =prima1' ily employed to trim the low milliampere scale of the *precalimated-selector, =hutthey also play a second role. Should *resistor ER-z become open-circuit'ec l',- due to any particular surge,=resistors *R3 and R4 insure the application er the control voltage to the G1 andMAr terminals or the stabilizer.
Also in order to protect'capacitorCl "from deleterious surges or open circuiting 0f resistors R1 =or 'Rz, a 'safety' circuit is 'included 'in the milliamperage preseiector. This safety circuit includes two voltageregulator tubes- 43'and with said tubes being connected in series with 'each other across the "stabilizer terminal "ll/1A1 and ground. Resistors R -arid"=l'tq 'shuntthe respective-tubes "43 and 64" to equally *dividethe voltage thereacross. 'These tubes'accordinglyare so arranged as tobreakfiownshoul'd the voltage across capacitor-C1 exceed abodt300 volts. "These voltage regulator tubes 43'and M' are connected or interlocked into -the'"X-rayn push-button circuit, asindica'tedby the legendfbyvirtue of the safety contacts contained within the tube base. In-other-wor'ds'two pins in the voltage regulator tube"base are connected together and the "two tubes connected 'in series with each other and connected to the 'X-ray On circuit at terminals 4'5*and"43 extendingfrom' the tubes "Aland M. In additionto protecting capacitorfli from overvoltage. "the tubes 43 and M. protect'the "entire equipment in the sense *that theymust be "insorted in their respective "sockets to render the fiiter in the *form of a capacitor 49 is Fshunte'd" acrosstlre inductancedfito remove'anypossibility of-thdGOcycle component getting-through inductanc'e fil'dueto any i-distrihuted capacitance existing in' this inductance "kl. Air-additional *capa'citor .E'Gismonnected *across tlie stahiiizer'supply' conductors G1 and MArtofurther filter 'theen'- cu it and across which the output vo'ltage ofthe filter circuit appears. This filter circuit thus removes the current componentj due to cable capacitance of the conductors and "current due to She -'distributed capacitance in the high +tensien windings:and'accordingly applies "to the stabilizer a --volta-ge= whicheis only dependent-oaths actual tube current.
- stabilizer :is:-.a1so :Prcv-ided irrith what" is terme'dwa fneon idiscriminator :wlfichrccmpris'es a neonitubeifil in: seriesxwi th onetofz'ithezstabilizer conductors together with :a fixed: resistancer 53 and variable; resistance? .14 connected across, the stab'ilizersupply :conductorsw G1 and F'MA1. x The pun-pose of 'rthis neonediscriminator is to provide fiurtheramplification for proper control of z'the stabilizer-system. .Sin cetheneon tube 52 115 a colds'cathode'tube and so constructed thati th'e voltage :rdr'opacrossthe tube is constant, regardless :of :current passing through the tube, :athe addition of resistance "53and variablecresistance 54' -wi'llregulatei thei divisionof voltage.
' :1'Ilhisemay-fbe' betterappreciated by assuming certain fvalues of'voltage s-uch,x'fors-example, as L00.woltsabeingfiimpressed across the neon lamp andrithe 'erid :ofrvariablexresistance 54. "Due-t0 thevoonstant voltage :drop characteristic 10f the neon lamp :52, the voltage- -drop thereacrossrrwill approximate volts, leaving'a-voltage drop .of approximately .30-volts across the resistances-53 amid-i4. Ifnowthevoltage-across the terminals is increased from volts to volts, the voltagea rdrop .across'the neon lamp still remains at '70 volts but increasing thevoltage dropacross the resistancestfiuand r54 to-40 'volts. Thus, only a ten percent "increase in input voltage hasfioccurred, but thevoltage drop across resistances 53 and 54 has increased thirty-three percent, therebyygiving an approximate gain in the amplifications-factor;- of three which facilitates the :need for voltage gain in: the Xg-ray :tube circuit The magnitude of the current flowing in the neon discriminatorcircuit is controlled by the'resistan'ces2-53rand54 with the adjustabi-lityqof the latter enabling closer tuning oflthe filter circuituconsisting of the inductanees'tl-and '48' together- rwithithe capacitors 49 and 50 byefiectively. clipping the peak of the voltage wave present atzlngher kilovoltage-wvhile maintainingthe milliamperage constant for all practical purposes at:a11-kilovo1tage settings.
The output of the neon discriminator 1 circuit "connects to the control grid of electronic control'tube 3'! through a battery 55 and aressistancelelement 55. 'Thiszbattery 55. is provided to select the operating point Withregard to the characteristic curves of the tube .31, and :isnot subjectto normal deterioration effects since no .currenti'istaken' from the battery 55 itself during-operation, with the battery merely adding to the output voltageoof the neon discriminator .circuit,.thereby varying the plate'current in'the control tube 31.
In order to supply the 350 volts D. C.1tothe D. --'C. V winding 35 :of .the saturablereactor 135, a power transformer 1151 is provided which has" its primary winding :58 connected toappropriate voltage-taps of auto transformerl1. The-high voltagesecondary windingfiii delivering approximately350volts' has its center tap connected-to the cathode-eithe control tube 13'! (and thusf'to oneside MA1:of the stabilizer input i'potential) while the ends of 1' this secondary Windingi'59 .-;conmeet to the respectiveanodes of 'a full vvave rectifier itube $60. The athermionic cathode of "this rectifiertFl-receives heating currentfrorn a low voltage secondary winding .'6:2-provided on the transformer-'51. which delivers about '5' volts; and a second low voltage winding 63 delivers about 6.3 volts to the thermionic cathode of control tube 131 with the 1 center tap "of this latter sec ondary winding 63 being connected to ztheicenter tap#dffitha'liigherrvoltagersecorrdarycfifi and thus tonne sidc ofahe stabilizerizinput suppiyrMal;
The thermionic cathode oi. rectifier 60 connects to one side of the D. C. winding 36 of the saturable reactor 35, as previously mentioned, which, upon closure of a pair of contacts 64 as hereinafter described, thus places the supply of D. C. to'the winding 36 completely under the control of the control tube 31. This D. C. supply for reactor winding36 is provided with a choke input filter comprising an inductance 65 and capacitor 66. Accordingly, the capacitor 66 is charged each half wave of the alternating current cycle in well known manner since by virtue of the center tapped secondary winding 59, its respective halves are 180 out of phase, and the resulting D. C. output voltage appears across one end of the D. C. winding 36 and the cathode of control tube 31 as above noted. The rectifier tube 60 being of the thermionic cathode type requires a normal delay period of approximately 20 seconds before the tube reaches its normal operating temperature. Advantage is taken of this delay characteristic, as hereinafter described, in order to provide a desired time delay prior to operation of the control by giving the tube 60 an opportunity to arrive at its proper operating temperature.
Forthe purpose of presetting the filament heat in the X-ray tube circuit, to approximately the normal operating range as will be required for the particular milliamperage selected and to also make the milliamperage stabilizer independent of line voltage variations, a preset circuit includin a voltage regulator tube 61 is provided for controlling the voltage supplied to the screen grid of control tube 31. This preset circuit includes the voltage regulator tube 61 having its cathode connected to one side of capacitor 66 and thus to the negative side of the D. C. output of the previously described filter circuit which includes the capacitor 66. The anode of voltage regulator tube 61 is connected through a' resistance 68 to the opposite or positive side of the choke filter circuit and hence to one side of the D. C. winding 36, and such anode is also connected through an adjustable resistance 69 to the screen grid of control tube 31. The previously mentioned contacts 64 are connected to two pins on the base of the voltage regulator tube 61 which provides a safety feature by requiring this tube to be inserted in its socket before the D. C. power supply becomes operative. This safety feature precludes the possibility of too high a screen grid voltage being applied to control tube 31, which might otherwise be above the safe continuous screen grid voltage recommended by the tube manufacturer.
As hereinbefore mentioned, the control tube 31 has such characteristics that if the screen-grid voltage is held constant the plate current through the control tube 31 is relatively independent of line voltage and. hence variations in the latter have substantially no eiiect on the plate current. However, for the purpose of controlling the screen grid voltage of control tube 31 to enable the filament of the X-ray tube to be properly preset at the termination of a given exposure, a relay 10 is provided. The winding of this relay is controlled by the X-ray On control circuit. This relay 10 is provided with a pair of contacts12 which upon closure short-circuit the adjustable resistance 69 and also provided with a set of contacts13 connected to the motor of timer 26 so that the latter operates as soon as the X-ray tube is energized.
In the absence of provision to the contrary operation oithe milliamperage stabilizer is de- 8 pendent on;the.magnitude of the voltage EP'. plied to the control grid of the control tube 31. Accordingly, when the voltage is removed from the control grid of tube 31, the grid bias will then drop to the valueof the bias battery iii. This will increase the; plate current in tube 31 and decreases the effective impedanceof the saturable reactor 35 and the filament heat of the X-ray tube will be increased, which produces an undesirable condition in that current through the X-ray tube reaches relatively high values upon resumption of another exposure. It is to prevent such undesirable result that provisions are made to control the voltage on the screen grid of control tube 31.
Prior to initiation of an X-ray exposure, the relay 1B is inoperative and the screen grid is supplied with a voltagethrough resistances 68 and 69. Since the voltage drop across these resistances are additive; a voltage somewhat lower than that required for normal operation is supplied to the screen grid of control tube 31, and with this reduced screen-grid voltage the plate current in the control tube is reduced. Under conditions of reduced plate current, the impedance of the saturable reactor 35 will be raised thereby lowering the filament heat of the X-ray tube cathode as 1011;! as X-rays are not being produced.
When the X-ray On push button is operated, relay 1B is energized and closes its contacts 12, which thus short-circuits the resistance 69-, as previously mentioned, and raises the voltage supplied to the screen grid of control tube 31 to its normal operating voltage of about volts. This irnmediatelyraises the plate current of control tube 31 and reduces the reactance of the saturable reactor 35, which in turn increases the filament heat of'the X-ray tube cathode during the exposure and until the latter is terminated b the timing dev ce 25 or by depression of the X-rav Off" push button. Thus the voltage regulator tube. to ether with its circuit as above described. performs the desired function of maintain ng relativelv stable operation of the milliamnerage stabilizer regardless of line voltage fluctuations and provides a desirable preset characteristic for t e X-ray filament circuit by autom ticallv reducin the filament heat of the X-rav tube cathode at the termination of an X-ray exposure andraising the filament heat upon initiation of a given exposure.
As hereinbefore mentioned, the control tube 31 is preferably one having a high value of transconductance so as to give optimum performance in a milliarnperage type stabilizer. Such high value of transconductance enables the milliamoerage stabilizer in general to have sufiicient ga n to overcome eifects of increased filament voltage, increased temperature in the filament circuit which affects filament resistance and incre s d kiiovolta we. Howe er. because of the act th t a hi h ain is obtained. a feedback condition arises between the milliamperage stabilizer and the X-ray tube. This condition causes a ra id osc llatio in the mi liammeter circuit and undesirable characteristics are obtained. In ns'inc a contrnltub'e ha ing a high value of transc nductance to obtain its high volta e again. as above-noted, it would be im ossible to successfullv compensate For the efiects o increased filament voltage. increased tem erature n the filament circuit which affects filament resistance and increased kilovoltage without overcoming this fe dback condition. 7
To accomplish the latter, a feedback circuit is provided comprising afee'd back transformer 14-, the primary winding: 15' of which is connected across the resistance 3i included in series with the primary winding 28" of the heating transformer l6 for the'cathode l2'of X-ray tube and the A. C. windings 33' and 34 of reactor 35. The primary winding Hi-of the feedback transformer is thus subjected to the voltage drop across the resistance 3| which is thus proportional to the current flowing in-the primary winding of the low tension cathode heating transformer Hi. This voltage across primary winding boosted by acenter tapped step-up secondary winding It whichis connected to a fullwaverectifier circuit comprisinga rectifier- Ti; capacitor l8 and resistor 19; The output from the-'step-up windinglfi is accordingly impressed across resistor 19 with the filter capacitor 18- sl'iunt'ed across the resistor 19 toadd sufficient time duration to the voltagepulsesappearing acrossthe resistor 19-- which averages out over a half cycle since the constants of this capacitor 18 and resistor 155 are so chosen that the voltage durationis /120 of a second.
The voltage which appears across resistor 19 is in turn cap'acitativ'ely coupled to the previously mentioned resistance element 56 through a capacitor 80. Under normal conditions, that is a condition in which oscillations do not occur in the X-ray tubemilliampera'geand hence inthe' filament heating circuit for the X'-ray tube oath; ode, the voltage drop across resistor'lfl remains" constant and is blocked'b'y' capacitor 80 from in any way affecting the control grid of control tube 31. On theother hand, should oscillations occur in the filament circuit and in turn the milliamperage of the" X-ray tube, a pulsating of' the control tube 3 lwheneveroscillationsde velopin the filament circuit," since the applica tion of such negative'pulse to the grid'iminedt This" is accomplished by selecting the polarity of the voltage across the'capa-citor 80 so -that a negative" pulse is supplied to the'grid ately result in dampening of the oscillations in th'fllanient circuit. I
As" previously referred to, advantage is'take'n of the time delay characteristic ofthe (rathode of rectifier 6G in reaching an electron emitting temperature to provide-arr additional safety featurewhich enablesthe-entire system to be properly conditioned before an atte'mptismtde to operate the apparatus-to produce -X-rays3 To this end, the previously mentioned relay 2'! "hasits winding connected across the' capacitor '66: and isthus subjected to the voltage across thelatter. I Accordingly, since the voltage across capacitor 66*does' not appear until-the expiration of the time-delay required b'y 'the cathode ofrectifier ously mentioned contacts 25; Closure of these latter contacts 25 accordingly "conditions the" X-ray On control'circuit 'for 'operation upon depression'of the -X-ray O-n push button, since the control is' theri -=completed except at 10 thc poirit-oiiacltisure hy creamer. Upon dpres..-; si'o 1 of the-X-ray ow'push buttomthe winding-r. ofrelay 1'0="lcecom"e'senergized by completion of the -K ra Qh control circuit and closes its pair of-= contacts 12* and 13. Whencontacts -12 are thus close theieslstance 69 is-short-cir-- cuit'ed to raise thevoltage supply to the screen grid of 5 control 31-, previously described, and-simultaneously therewith'closure of contacts 13* com 1etesa'circuit-to the timer 26 starting the 'latter inoperation:
At the same-"tiine -depression of the X-ray On p=ush-buttoncompletesa circuit to the winding; ofmagnetic'ally operated switch 23 energizing-the latter with attefidant closure' of its contacts 82 and- 33. r@ontacts':82--'accordingly causeenergization of :the primary winding 22-of high tensiontrans'former Qahd the'generatiQnof the X-rays' forthe period of time for-iwhich: the timer .26 has been preset,-'-or until=' the X-ray Off push abutton-- isdepressed while closurewofcontacts 83, completes-aholding: circuit for the Windingsof'. magnetically operated' switch 23, thus enablingthe-X-ray On? push'button to be immediately released following initial depression thereof Also contacts-83: complete aholding circuit .for the winding-P of relay 10- so that the contacts I2. and 13+: of the latter. maintain theshort-circuit condition of;resistance'69-'and' the timer 26 in operation hntil the exposure .is completed by, opening oisthehormallyclosed contacts ofthe. timer-2t, oropening *of the control circuit by depressionaof. the ,fX-ray Off, push :button. .It. can thus-'beseen that the X-ray On pushibut-v ton v,is, therefore. inoperativev to complete the, fX1ray.,ncontrol circuit; to energize relays 23 and H1, which thus precludes the generation of X-rayauntil relay 21is energized after expiration of -.=the,above noted time-delay and closure of its contacts 25:
By-reference .tothe drawing, it will be noted; thatv thefX-ray On control, circuit receives energyiromtaps on-theautotransformer IT. For; example; a conductor, extends from a tap of, autotrah'sformer'. l.'l to. one side, of winding ,of magnetically, operated-switch 23, and this same conductor also extends to'onerside of the Wind ng; of relay;.18,mas well: as to one contact thereof. The other. side of. this-control circuit extends; fromranother tap -of the autotransformer l'l and by: a conductor-85: through the pi s of the v lta e regulator tubes-Hand 44; in series; and through the icontacts 250i the relay; 2], and then through normally closed" X ray: Off? push, button, the, normally closed'contacts of the timer 26, and to, one-side of the, ,X-iray-On push button as Well; aszi'one of thecontacts -83 of ma n al y 0 erated switch:23. l ,i
This control circuit is: thus" initi 126. the'vcontactsza: and the normally open ii-ray ;v
Orr-'1? push-'button Upon initial energization oj On pu h -b o fs orth u o me ta y pression of the latter, the X-ray Onfl contrgl circuit"'is' i completed in themanner abovedescribed-"1? .-It: w il1: :also 'rbe acted that the magnetieaiii,
operated switch l8, which to all intents and-pure poses may be considered as the main line switch, is energized by depression of push button 86, which thus completes a circuit to the winding thereof directly from the commercial source of supply'of 200-250 volts or such winding may be energized from taps of autotransformer H as desired. Upon energization of the winding of magnetically operated switch l8, three sets of contacts are closed, two of such sets completing the commercial source of supply to the autotransformer ,l'l, while the other set of contacts completes a holding circuit to the winding of magnetically operated switch l8. When this main line switch is closed, the thermionic cathodes of the various tubes are heated, including the thermionic cathode OI rectifying valves '1 and Hi, although the specific heating source therefore is not'shown for simplicity. Once the main line switch l8 has been closed, the entire apparatus is then in condition for operation in the manner above described and after completion of an exposure, the main line switch is de-energized when desired by depression of a normally closed push button Bl.
The foregoing milliamperage stabilizer has beenshown and described with what is termed half-wave equipment, which means that the rectified alternating current is supplied to the X-ray tube during half-waves of the alternating current cycle. However,- suchstabilizer can be just as readily employed with a full wave bridge circuit by inserting the milliamperage stabilizer in the D. C. circuit of the milliammeter and utilizing a rectifier bridge arrangement. wave arrangement has not been shown for the sake of simplicity.
It thus becomes obvious to those skilled in the art that a milliamperage stabilizer is herein provided which maintains the current through the X-ray tube substantially constant during an exposure. Moreover, such stabilizernot only compensates for fluctuations of voltage in the source of supply but also compensates for increased filament voltage, increased temperature in the filament' circuit which affects filament resistance, and increased 'kilovoltage.
' By the utilization of a filter choke net-work, oscillations within the high voltage circuit are precluded from affecting the stabilization and a discriminator arrangement advantageously amplifies the current so as to better control the latter through a control tube having a high value of conductance. Also to prevent a feedback, a
circuit is provided, thereby eliminating any tendency of the tube current to fluctuate. Moreover, safety features are provided so that the apparatus is precluded from operating to produce X-rays until certain voltage regulator tubes have been inserted in their appropriate sockets, and in addition the stabilizer prevents exposures from being initiated until the thermionic cathodes of the various tubes have reached their electron emitting temperature, thus eliminating any possibility of an over voltage being impressed across any part of the system.
Although one specific embodiment of the present invention has been shown and described, it is to be understood that other modifications thereof may be made without departing from the spirit and scope of the appended claims.
I claim:
'1. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high Such full I 12 tension transformer'provided with a primary winding connected toa commercial source of supply subject to line voltage fluctuations and having its secondary winding connected through. a rectifying arrangement to said electron discharge device for supplying unidirectional. cur
rent thereto, a source of alternating current electrical energy subject to changes in resistance with an attendant variable current component for heating the cathode of said electron discharge device, a saturable reactoroperatively connected with said source of heating energy and operable upon the imposition .of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge dewce, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in voltage across and current through said electron discharge device, as well as line voltage fluctuations and change in resistance in the source of heating energy for saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a unidirectional current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the voltageacross and current through said electron discharge device as well as line voltage fluctuations and change in resistance in the source of heating energy for the cathode of said electron discharge device.
2. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operably connected with said source of heating energy and operable upon the imposition of a, unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to varia-.
tions in potential thereacross in response to variations in discharge current through said electron discharge device, and said adjustable preselector means including a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector with both said aforementioned means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor differing from that of said heating source accompanied by a variation in the heating current supplied 'to-the' cathode of: said'electrofi discharge device inversely to variations in-the discharge current flowing through the latter.
3; The combination of an electron discharge device provided with'a cathodeto be heated, an excitation circuit for said device including a high tension transformer having its secondary wind ing'connected through arectifying arrangement to said electron discharge device for supplying unidirectional current thereto, source of alternating current electrical energy 'for' heating the cathode of said-electron discharge device normally subject to'a variable current component, a saturablereactor operatively connected with said source of heating energy andoperable'upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the'flow ofheating current to the cathode of said electron discharge device, adjustable preselector' meansconnected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and said adjustable preselector means including a filter arrangement comprising two inductanceelements in series relation together with a capacitor shunting one of said inductance elements and a capacitor in shunt with said adjustable preselector means and operable to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor difiering from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the discharge current flowing through the latter.
4. The combination of an'electron discharge device provided witha cathode to be heated, an excitation circuit for said device including a high tension'transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a, source of alternating current electrical energy for heating the cathode of saidelectron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device and including a voltage divider discriminator arrangement for amplifying the voltage across said adjustable preselector means, and electrical cir-i "cuit means operatively connected with said-saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means std-cause the imposition of a current component upon said saturablei reactor differing? from'ithe current component of said heating source ac;- companied by a variation in the heatingcurrent supplied to the cathode of said electron dis.- charge device inversely to variations in the discharge current flowing through the latter.
5. The combination of an electron discharge device provided with a cathode to be heated,,an excitation circuit for said device includinge; high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device nor.- mally subject to a variable current component, a
saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in dis-charge current through-said electronvdischarge device and including a voltage divider discriminator arrangementcomprising a discharge device having a constant: voltage drop thereacross in series with said adjustable preselector means and a resistor in parallel with thelater foramplifying the voltage across said adjustable: preselector means, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the im position of a current component upon said saturable reactor differing from the current com ponent of said heating source accompanied by a variation in the heating current supplied to-the cathode of said electron discharge device inversely, to variations in the discharge current flowing through the latter.
6. The. combination of an electron discharge deviceprovided with a cathode to be heated, an excitation circuit for said deviceincluding ahigh tension transformer having its secondary winding connected'through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a sourceof alternating current electrical energy for heating the cathode of said electron discharge device normal ly subject to a variable current component, a saturable reactor operatively connected withsaid source of heating energy and operable .upon the imposition of a unidirectional component thereupon differing from the current component ofthe heating source to control the flow of heating cur-- rent to the cathode ofsaid electron discharge device,. a source of unidirectional electrical energy for supplying the unidirectional component to said saturable' reactor, adjustable preselector means connected to said excitation circuit and subject to variations. in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the. potential across said adjustable pres elector means to cause said source of unidirectional electrical energy ,to' impose" the aforementioned; current component upon said saturable reactordiffering 75.:from1 the: current component.- of said heating tource acor'ripa'iiid by a variation in the heating current supplied to the cathode of said electron discharge device inversely torvariations in the discharge current flowing through the latter, and means connected to said source of unidirectional electrical energy and operable by the latter to cause a time-delay before said excitation circuit becomes effective to energizesaidelectron discharge device.
7. The combination 01 an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its'secondary wind:- ing connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected associated with said source of heating energy and operable upon the imposition of a unidirectional component thereupon difiering from the current component of the heating source to control the flowof heating current to the cathode of said electron discharge device, a source of unidirectional electrical energy for supplying the unidirectional component to said saturabie reactor, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause said source of unidirectional electrical energy to impose the aforementioned current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the discharge currentflowing through the lat- ;ter, and a relay operatively connected to said source of unidirectional electrical energy and en- .ergizable by the latter to cause a time-delay be- ;fore said excitation circuit becomes eifective to energize said electron discharge device.
8. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying current to the cathode of said electron discharge; device, a source of unidirectional electrical energy for supplying the unidirectional component to said saturable reactor, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in.-
response to variations in discharge current through said electron discharge device including an electronic control tube having a high value of transconductance to cause a variation of relative- ,ly great magnitude in plate current through said.
control tube in response to relativelysli ghtvarizji tions in grid voltage supplied thereto and oper-' able to control the supply of unidirectional en ergy from said source to said saturable reactor; electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause operation of said control tube with the imposition of a current component from said unidirectional source upon said saturable re actor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to varia tions in the discharge current flowing through the latter, and a relay operatively connected to said source of unidirectional electrical energy and energizable by the latter to cause a time-delay before said excitation circuit becomes effective to energize said electron discharge device.
9. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon diifering from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube provided with a control grid and a screen grid and having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of direct current power for said control tube to cause operation of the latter with attendant imposition of a current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to line voltage fluctuations effecting the discharge current flowing through said electron discharge device, and means connected to said electronic control tube and operable to cause the latter to-become operable and cause an attendant automatic increase in the current supplied to the cathode of said electron discharge device simultaneously with energization of said electron discharge device by said excitation circuit and to automatically cause a decrease in the current supplied to the cathode of said electron discharge device simultaneously with deenergization of said electron discharge device from said excitation circuit.
10. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high thereupon difierin from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means con.- nected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an'electronic control tube provided with a control grid and a screen grid and having a high value of transconductance to cause a variation of rela tively great magnitude in plate current through said control tube'in response to relativel slight variations in grid voltage supplied thereto,electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of direct current power for said control tube and a voltage regulator tube for controlling the power supplied 'by said direct current source to the screen grid of said control tube to causeoperation of the later with attendant imposition of a current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to line voltage fluctuations affecting the discharge current flowin through said electron discharge device, and means connected to said electroniccontrol tube and operable simultaneously withenergization of said electron discharge device by said excitation circuit to cause an increase in the potential supplied to the grid of said electronic control tube with an attendant automatic in crease in the current supplied to the cathode of said electron discharge device and operable to automatically cause a decrease in the potential supplied to the grid of said electronic control tube with an attendant decrease in the current supplied to the cathode of said electron discharge device upon deenergization of said electron discharge device.
11. The combination of an electron discharge device provided with a cathode to be heated, an
excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the currentcompon'ent of the heating source to control the flow of heating current to, the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube provided with acontrol grid and a screen grid and having a high value of transconductance to cause a variation of relatively Jgreat magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of direct current power for said control tube and. a voltage regulator tube for controlling the power sup-- plied by said direct current source to the screen grid of said control tube to cause operation of the latter with attendant imposition of a current component upon said saturable reactor differin from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to line voltage fluctuations eifecting the discharge current flowing through said electron discharge device, a resistance in series with said voltage regulator tube, and a relay operable simultaneously with energiz'ation of said electron discharge device by said excitation circuit to short-circuit said resistance and cause an increase in the potential supplied to the grid of said electronic control 1 tube with an attendant automatic increase in the current supplied to the cathode of said electron discharge device, and operable to connect said resistance in series with said voltage re ulator tube and cause an automatic decrease in the cur rent supplied to the cathode of said electron discharge device upon deenergization of said electron discharge device.
12. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device norma1- 1y subject to a variable current component, a
saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including anelectronic'control tube provided with a control grid anda screen grid and having a high value of transconductan'ce to cause a variation of relatively great magnitude in plate current through said'cont'rol tube in re sponse to relatively slight variations in grid Voltage supplied thereto, and electrical circuit means operatively connected with saidsaturable reactor and said adjustable preselector means and including a "source of direct current power for said control tube and a voltage regulator tube for controlling the power supplied by said direct current source to the screen grid of saidcont'rol tube to cause operation of the latter with attendant imposition of a current component upon said saturable reactor differing fromthe current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge deviceinversely to line voltage fluctuations effecting the dis- 19 charge current flowing through said electron discharge device.
13. The combination of an electron discharge device provided with a cathode to be heated, an
excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube provided with a control grid and a screen grid and having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and including a source of direct current power for said control tube and a voltage regulator tube for controlling the power supplied by said direct current source to the screen grid of said control tube to cause operation of the latter with attendant imposition of a current component upon said saturable reactor difierlng from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to line voltage fluctuations effecting the discharge current flowing through said electron discharge device, and voltage limiting means connected to said voltage regulator tube and short-circuited simultaneously with energization of said electron discharge device by said excitation circuit to cause said voltage regulator tube to vary the potential supplied to the screen grid of said electronic control tube with an attendant'automatic increase in the current supplied to the cathode of said lectron discharge device and the short-circuit condition of said Voltage limiting means being removed to automatically decrease the current supplied to said cathode upon deenergization of said electron discharge device.
14. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectiiying'arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and including an electronic control tube having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the discharge current flowing through the latter.
15. The combination or an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reaction differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the discharge current flowing through the latter, and feedback means connected to the source of heating energy for the cathode of said electron discharge device and to said adjustable preselector means and operable to apply a pulsating voltage to said adjustable preselector means upon the occurrence of oscillations in said excitation circuit.
16. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable currentcomponent, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the discharge current flowing through the latter, and feedback means comprising a transformer having its primary winding associated with the source of heating energy for the cathode of said electron discharge device and the secondary winding thereof connected to said adjustable preselector means and operable to apply a pulsating voltage to said adjustable preselector means upon the occurrence of oscillations in said excitation circuit.
17. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device and including a resistor in series with said adjustable preselector means, electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor difiering from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the discharge current flowing through the latter, and feedback means comprising a transformer having its primary winding associated with the source of heatin energy for the cathode of said electron discharge device and the secondary winding thereof connected through a rectifier arrangement across said resistor and operable to apply a pulsating voltage to said adjustable preselector means upon the occurrence of oscillations in said excitation cincuit.
18. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device, normally subject to a variable voltage component, a saturable reactor operatively connected with said 22 sourceof heating energy and operable upon the imposition of a unidirectional component thereupon difiering from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device and including a voltage divider discriminator arrangement for amplifying the voltage thereacross and a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, and electrical circuit means operatively connected with said saturable reactorand said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor differing from the current component of said heating source accompanied by a variation in the heating current supplied to. the cathode of said electron discharge device inversely to variations in the discharge current flowing through the latter.
19. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy for heating the cathode of said electron discharge device normally subject to a variable current component, a saturable reactor operatively connected with said source of heating energy and operable upon imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the cathode of said electron discharge device, adjustable preselector means connected to said excitation circuit and subject to variations in potential thereacross in response to variations in discharge current through said electron discharge device, and said adjustable preselector means including an electronic control tube having a high value of transconductance to cause a variation of relatively great magnitude in plate current through said control tube in response to relatively slight variations in grid voltage supplied thereto, a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, and a voltage divider discriminator arrangement for amplifying the voltage across said adjustable preselector means; and electrical circuit means operatively connected with said saturable reactor and said adjustable preselector means and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor diifering from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the dischargecurrent flowing through the latter.
gal-gm '23 20. The combination of an electron discharge device provided with a cathode to be heated, an excitation circuit for said device including a high tension transformer having its secondary winding connected through a rectifying arrangement to said electron discharge device for supplying unidirectional current thereto, a source of alternating current electrical energy subject to changes in resistance and a variable current component for heating the cathode of said electron discharge device, a saturable reactor operatively connected with said source of heating energy and operable upon the imposition of a unidirectional component thereupon differing from the current component of the heating source to control the flow of heating current to the oathode cf said electron discharge device, adjustable preselector means connected to said excitation circuit and including a filter arrangement to remove the current component due to distributed capacitance in said excitation circuit and to make the voltage across said adjustable preselector means dependent only on the actual current supplied by said excitation circuit to said electron discharge device, a voltage divider discriminator arrangement for amplifying the voltage across said means, an electronic control tube havin a screen grid and operable to control the imposition of the unidirectional component on said inductive means, feedback means connected to the source of heating energy for the cathode of said electron discharge device and to said adjustable preselector means and operable to apply a pulsating voltage to said adjustable preselector means upon the occurrence of oscillations in said excitation circuit; and electrical circuit means 24 operatively connected with said saturable reactor and said adjustable preselector means including a voltage regulator tube for controlling the voltage applied to the screen grid of said electronic control tube to cause operation of the latter and operable upon a variation in the potential across said adjustable preselector means to cause the imposition of a current component upon said saturable reactor difiering from the current component of said heating source accompanied by a variation in the heating current supplied to the cathode of said electron discharge device inversely to variations in the voltage across and current through said electron discharge device as well as line voltage fluctuations and change in resistance in the source of heating energy for the cathode of said electron discharge device.
CHARLES T. ZAVALES.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,893,299 Morrison Jan. 3, 1933 1,953,889 Mutscheller Apr. 3, 1934 1,961,703 Morrison June 5, 1934 1,999,736 Morrison Apr. 30, 1935 2,001,567 Case May 14, 1935 2,048,203 Spencer July 21, 1936 2,236,195 McKesson Mar. 25, 1941 2,262,044 Philpott Nov. 11, 1941 2,319,378 Weisglass May 18, 1943
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US2608662A (en) * 1949-09-09 1952-08-26 Massiot Jean Arrangement for checking the temperature of the anode of x-ray tubes
US2617045A (en) * 1949-01-08 1952-11-04 Philips Lab Inc Tube current stabilizer
US2617047A (en) * 1948-09-30 1952-11-04 Hartford Nat Bank & Trust Co X-ray apparatus
US2626360A (en) * 1950-07-12 1953-01-20 Westinghouse Electric Corp Compensator for x-ray systems
US2667587A (en) * 1950-12-15 1954-01-26 Hartford Nat Bank & Trust Co Protecting device for x-ray apparatus
US2752509A (en) * 1950-09-02 1956-06-26 F R Machine Works X-ray apparatus and controls
US2792503A (en) * 1953-09-04 1957-05-14 Westinghouse Electric Corp X-ray protective circuits
US3061729A (en) * 1959-10-12 1962-10-30 Profexray Inc X-ray tube current metering circuit
US4297638A (en) * 1978-09-15 1981-10-27 Lafrance Robert R X-ray system signal derivation circuits for heat unit indicators and/or calibration meters
US4377748A (en) * 1979-05-07 1983-03-22 Siemens Aktiengesellschaft X-Ray diagnostic system comprising means for the fixed specification of exposure time, x-ray tube voltage, and mAs-product
US20140140474A1 (en) * 2012-11-21 2014-05-22 David J. Caruso Dynamically Adjustable Filament Control through Firmware for Miniature X-Ray Source
US10342107B2 (en) 2015-11-12 2019-07-02 Kimtron, Inc. Cascaded filament transformer within a resistive shroud
US10398011B2 (en) 2015-11-12 2019-08-27 Kimtron, Inc. Method and apparatus for active filament management

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US1893299A (en) * 1930-12-31 1933-01-03 Westinghouse X Ray Co Inc Discharge tube stabilizer system
US1961703A (en) * 1931-06-30 1934-06-05 Westinghouse X Ray Co Inc Stabilizer system
US1999736A (en) * 1931-07-10 1935-04-30 Westinghouse X Ray Co Inc Discharge device stabilizer system
US2048203A (en) * 1931-08-04 1936-07-21 Raytheon Mfg Co Thermionic gaseous discharge device
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US2001567A (en) * 1933-12-22 1935-05-14 Gen Electric Electric valve translating circuit
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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2617047A (en) * 1948-09-30 1952-11-04 Hartford Nat Bank & Trust Co X-ray apparatus
US2617045A (en) * 1949-01-08 1952-11-04 Philips Lab Inc Tube current stabilizer
US2608662A (en) * 1949-09-09 1952-08-26 Massiot Jean Arrangement for checking the temperature of the anode of x-ray tubes
US2626360A (en) * 1950-07-12 1953-01-20 Westinghouse Electric Corp Compensator for x-ray systems
US2752509A (en) * 1950-09-02 1956-06-26 F R Machine Works X-ray apparatus and controls
US2667587A (en) * 1950-12-15 1954-01-26 Hartford Nat Bank & Trust Co Protecting device for x-ray apparatus
US2792503A (en) * 1953-09-04 1957-05-14 Westinghouse Electric Corp X-ray protective circuits
US3061729A (en) * 1959-10-12 1962-10-30 Profexray Inc X-ray tube current metering circuit
US4297638A (en) * 1978-09-15 1981-10-27 Lafrance Robert R X-ray system signal derivation circuits for heat unit indicators and/or calibration meters
US4377748A (en) * 1979-05-07 1983-03-22 Siemens Aktiengesellschaft X-Ray diagnostic system comprising means for the fixed specification of exposure time, x-ray tube voltage, and mAs-product
US20140140474A1 (en) * 2012-11-21 2014-05-22 David J. Caruso Dynamically Adjustable Filament Control through Firmware for Miniature X-Ray Source
US8964940B2 (en) * 2012-11-21 2015-02-24 Thermo Scientific Portable Analytical Instruments Inc. Dynamically adjustable filament control through firmware for miniature x-ray source
US10342107B2 (en) 2015-11-12 2019-07-02 Kimtron, Inc. Cascaded filament transformer within a resistive shroud
US10398011B2 (en) 2015-11-12 2019-08-27 Kimtron, Inc. Method and apparatus for active filament management

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