US2441269A - Electron discharge compass system - Google Patents

Description

May 11, 1948. H. E. HARTIG ELECTRON DISCHARGE COMPASS SYSTEM Filed May 31, 1943/ Patented May 11, 1948 2,441,269 ELECTRON DISCHARGE COMPASS SYSTEM Henry E. Hartig, Robbinsdale, Minm, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application my 31, 1943, Serial No. 489,117

8 Claims. (Cl. 318-31) This invention relates generally to the art of control devices and more particularly to such devices in which it is desired to operate an indicator or a control mechanism according to the position of a continuously rotatable member. Still more particularly, my invention relates to control apparatus in which the position of a pickup or controlling member with respect to a magnetic field is continuously made evident or effective at a distance by the operation of an indicator or by the actuation of some controlled device.

I am aware that use has already been made of the deflection of the beam of a cathode ray tube in response to the earth's magnetic field in an attempt to provide remotely or locally indicating compasses, but the known devices are defective in numerous ways. 'A particular disability common to all prior devices having in mind the consummation of the objects of my invention lies in the fact that they are able to deliver only an insignificant amount of power, and for that reason they are in a commercial sense inoperative except for instruments for viewing said deflection of the cathode ray beam. With my invention, the limit on the power available, controlled in accordance with the position of the controlling element, is set only by the desire of the user.

An object of this invention is to provide an improved remotely indicating'or operating compass.

Another object of this invention is to provide an improved electronic system for continuously transmitting the angular position of a continuously rotatable member.

Still another object of this invention is to provide a remotely indicating or operating device which is continuously responsive to the angular position of a controlling or pick-up member.

Yet another object of this invention is to provide a cathode ray tube having a plurality of target plates upon which the beam is adapted to impinge or between which it is adapted to pass, combined with means for modulating the intensity of the beam.

Other objects and advantages of the present invention will become apparent upon a study of the specification and claims, and of the figures of the drawing which is attached hereto and which I make a part hereof, and wherein the single figure is a diagrammatic showing of the electrical circuit and of the cathode ray tube arranged in what I consider a preferred embodiment of my invention, the cathode ray tube being shown in side elevation.

In the figure. element in refers generally to a cathode ray tube. Reference numeral l'l refers generally to the amplifier which I use in association with my cathode ray tube. Reference numeral l2 refers to a split phase motor which is used in accordance with the practice of my invention as is set forth below. Element 13 refers to a power supply and numeral l4 refers to a potential divider arrangement, all of which will be discussed in detail in the specification which follows. I

In cathode ray tube It comprising a portion of my invention, reference numeral l5 refers to an evacuated and'sealed envelope enclosing the electrodes of the tube. A cathode i6 is connected by a conductor IE to a point on potential divider I4 and thence to ground through a portion of the divider and conductor 29. The cathode is indi- 'rectly heated by a filament ll. Coaxial electrodes 20, 2|, and 22 are arranged to provide a concentrated beam of electrons moving through the tube in the direction of the arrow. Electrode 20 is a control grid whose purpose is to vary the intensity of the beam current. Electrode 2i is a focusing anode for concentrating the electrons into a beam, and electrode 22 is an accelerating anode for increasing the velocity of the electrons comprising the beam. Physical elements l1, i6, 20, 2| and 22 comprise what has come to be referred to in the art as an electron gun. Spaced on either side of the intended normal position of the electron beam and located at a distance from the accelerating anode are a pair of deflecting plates 23 and 24 whose function, as is well known, is to cause a deflection of the beam away from its normal axis.

I now come to more novel features of my invention. In my cathode ray tube I provide an additional pair of electrodes 25 and 26 spaced along the normal axis of the beam from the deflecting plates, and having the same oppositely disposed relation about theaxis of the beam as do the deflecting plates. With respect to one another, however, the pair of deflecting plates is in 90 degree rotated relationship about the axis of the beam with respect to the pair of target lates. I refer to these electrodes as target plates, and these target plates are spaced mutually a suificient distance so that the properly focused electron beam may pass between them without impinging upon either plate, although deflection of the beam in either direction may cause it to impinge upon one or the other of the target plates.

The operation of this portion of my invention is as follows. It is well known that a cathode ray traversing a magnetic field is deflected out of its normal path in one direction or the opposite, depending on the relation of the polarity of the field to the direction of electron flow. terms of my invention, it the horizontal component of the earths magnetic field, or any other artificially created field which it is designed to use in the practice of my invention, has a direction H1 perpendicular to and into the plane or the paper, the beam is deflected trom-the normal path suggested by the solid arrow into a path suggested by the upper broken arrow, and the beam impinges upon plate 26.

, If the influencing field is directed out of the paper, the beam is deflected in the opposite direction, to impinge on plate 25. If on the other hand, the influencing field has a direction parallel to the axis of the ray, the field has no deflecting effect on the path or the beam, causing it to impinge upon neither plate 25 nor plate 26, but rather allowing it to pass through the space between them. Accordingly, it will be seen that if the cathode ray tube comprising a portion of my invention be rotated about an axis other than that of the beam in its normal state, for instance an axis normal to that of the beam and in the horizontal plane of the paper, there is a position oi! the tube in which the beam is not deflected either upwardly or' downwardly; This position I will refer to as the normal or zero position of the tube.

Now suppose my cathode ray tube to be mounted in a vehicle, for example, an aircraft with its axis in fixed relation parallel to the longitudinal axis of the craft, and in such rotated position that the horizontal component of the earths magnetic field acts in a direction normal to the plane of the paper in the drawing. Then it will be clear that when the axis oi. the craft is in a magnetically northand south direction, the beam of the tube is undeviated and no potential appears upon either plate 25 or plate 26. As long as the craft continues to travel along the course indicated, this situation continues. However, if the'craft deviates from the course indicated, the beam of the cathode ray tube is deflected to fall upon plate 25 or plate 26, depending upon the direction of deviation of the craft from .its course, and a potential appears upon the plate receiving the beam. It is clear that by properly focusing the beam and by properly proportioning the space between the plates 25 and 26, the sensitivity of my tube can be substantially adjusted.

It now a modulating potential be impressed upon the control grid 20, and the beam be deflected so that it impinges, for example, on plate 25, a potential modulated in intensity appears upon plate 25 with respect to cathode I5, and the frequency of this modulated potential is the frequency of the modulating potential impressed upon grid 20. I conceive it to be a part of my invention to so modulate the beam, and to make use of the modulated potentials in a manner I am about to describe, and in other suitable applications.

Conductors 21 and 28 lead respectively from plates 25 and 26 to the ends or a resistor 3|. Center tap 32 of resistor.3I is adjustably maintained at a high positive potential with respect to thecathode by being connected by conductor 33 to the movable arm 34 of a potentiometer 35, which draws its energy from potential divider I4. Plates 25 and 26 are further connected by conductors 36 and 31, coupling condensers 48 and 41, conductors 58 and 5|, and conductors 52 and 53 to the grids 54 and 55 or vacuum tubes 56 and 51, all respectively. Cathodes 68 and BI of vacuum tubes 56 and 51 are grounded as by conductors 63, 64 and 86. A pair of resistors 66 and 81 are provided having a common connection grounded as by conductor 68. The other end of one resistor 68 is connected as by conductors 50 and 52 to condenser 46 and grid 54 of tube 56, respectively. The other end 01 the other resistor 61 is connected as by conductors 5I and 53 to condenser 41 (electrically equivalent to condenser 46) and grid 55 of tube 51, respectively.

Thus it will be seen that there is a continuous direct current path, when the beam is deflected, from the negative terminal of potential divider I4 through a portion or the divider, thence by conductor I8 to the cathode I5 of the cathode ray tube, to plate 25 or plate 26 of the cathode ray tube, to center tap 32 of resistance 3| byway of conductor 21 or conductor 28, to the positive pole of potential divider I4 by way of conductor 33 and potentiometer 35, and back-through the potentiometer. tinuous paths for modulated currents from the negative terminal of potential divider I4, through a portion of the divider, thence by conductor I8 to the cathode of the cathode ray tube, to plate 25 or plate 26 of the cathode ray tube, then either to grid 54 or tube 56 by way or conductor 21, conductor 36, condenser 46, conductor 50 and conductor 52 or to grid 55 of tube by way of conductor 28, conductor 31 condenser 41, conductor 5|, and conductor 53. Thepotentials are thus impressed upon the grids of the tubes: the circuits are completed through the resistor 66 or resistor 61 to ground by conductor 68 and thence back to the negative terminal of potential divider I4. The values of resistors 66 and 61 are so 'chosen that the IR. drops across them, which are the potentials impressed on the grids of the tubes respectively, due to impingement of the beam on the target plates are within the range desired.

The modulating potential for grid 28 of my cathode ray tube is taken from one secondary winding 10 of a transformer II having a plurality of such secondary windings. A potentiometer I is connected across winding 10, and one terminal of the potentiometer is grounded as at I3I. The movable arm I32 of the potentiometer is connected to the grid 28 by conductor I33, condensers I34, and conductor I35. Another secondary winding 12 of transformer II has its terminals connected to the plates 13 and I4 0! a pair of tubes 15 and I6, respectively, while its center tap I1 is grounded through a winding 82 of split phase motor I2 and a conductor 83. A condenser I8 is connected in parallel with motor winding 82. A third secondary winding 80 or transformer II provides potential to the other winding 8| of motor I2 through a condenser 19, and one terminal of this winding 8| is connected to the grounded terminal of motor winding 82.

Plate 84 of tube 56 is connected to one terminal of a primary winding 85 of a coupling transformer 86, and the other terminal thereof is connected to plate 88 of tube 51. A center tap of this winding is connected with the positive terminal of potential divider I4 as by conductor 87. Thus, a signal impressed upon grid 55 will cause current to flow through primary winding 85 in one direction, while a signal upon grid 54 will cause current to flow through primary winding There are also a pair of conductor I06.

85 in the opposite direction. one terminal of a secondary winding 90 of transformer 86 is connected to the grids SI and 92 of tubes 15 and 16 as by conductors 93, 98, and 95. The other terminal of secondary 90 is grounded as by conductor 96, while the cathodes 91 and 98 of tubes 15 and 16 are grounded as by conductors IIlI, I62, I03, condenser I04, resistor I05, and con- Condenser IN is in parallel with resistor I05.

In my drawing I have also shown a conventional power supply for providing the potentials necessary in the operation of my invention. This power supply, as will be seen, comprises a pair of diodes H and III, the plates of which are provided with potentials from still another secondary winding II2 of transformer H. A filter comprising chokes II 3 and I I 4 and condensers H5 and H6 is provided to smooth out the ripple in the rectified output current, and this filter current is applied to resistor I9 of potential divider It by conductors H1 and H8.

It will be seen that numerous potentiometers have been connected in parallel with the resistor I9 at various points for the purpose of adjustably taking ofi potentials which may be suitably varied. The purpose of potentiometer 35 has already been set forth. Potentiometer I20 is to provide proper bias potential to the grid of the cathode ray tube as by conductor I40, resistor I4! and conductor I35. Potentiometer I22 is to provide a suitable accelerating voltage upon the accelerating anode 22 and is connected thereto by conductor I42, and potentiometer I23 is to provide a suitable voltage on the focusing electrode 2i and is connected thereto by conductor M3. Potentiometer I2I is to provide a proper potential difference between deflecting plates 23 and 26 for a purpose about to be set forth.

Thus far I have discussed only the horizontal component of the earths magnetic field. However, it must be remembered that there is also a vertical component to this field, and that this component is directed downwardly in the Northern hemisphere and upwardly in the Southern hemisphere. If the cathode ray tube is mounted as I have shown and described, with its axis horizontal and the opposed edges of the target plates also horizontal, the effect of this vertical component alone is simply to deflect the beam longitudinally in the space between the target plates. For moderate vertical components this may not be serious, but for large vertical components, especially in combination with large horizontal components, the force may be sufiicient to deflect the beam entirely oif the target plates, thus rendering the device wholly inoperative.

Application of proper potentials between plate 23 and 24 brings electrical force to bear, retuming the cathode ray to a central position longitudinally of the space between the target plates, but the polarity of this recentering potential must be opposite in the two hemispheres. Thus for a craft which is to be operable in any desired locality means must be provided both for varying this potential in magnitude and for reversing it in polarity. I follow the customary practice and maintain one of the target plates at cathode potential, while impressing the recentering potential upon the otherplate. For this purpose I use a reversing switch of the conventional double pole double throw type, as indicated at I54. To the input or center terminals of the switch" I connect the cathode I6 and the movable arm of potentiometer I2I as by conductors I55 and I49,

respectively. The "output terminals of the reversing switch are connected to plates 23 and 24 as by conductors I56 and I51, respectively. Thus, when switch I54 is thrown in the left position plate 23 is positive with respect to plate 24 which is at cathode potential, while when switch I54 is thrown in the right position plate 23 is at cathode potential and plate 24 is positive with respect thereto: the magnitude of the potential difference in either case is regulable by adjustment of potentiometer I2I.

It will now be evident that when the beam is deflected to impinge on one of the target plates an alternating potential is impressed on the grid of one of the tubes 55 and 51. This potential has the same frequency of alternation as does the alternating potential in secondary winding 10, and the phase relationship between the two alternating potentials depends primarily on the characteristics of condenser I 34 and of condenser 45 or condenser 41 as the case may be. Since condensers 46 and 41 are electrically equivalent, the grid potential is in the same phase relationship to the potential in secondary winding 16 whether it is impressed upon grid 53 or grid 55.

Moreover, the change in phase due to tube 56 is the same as that due to tube 51.

However, the potential across the primary of the transformer 86 due to impressed potential on rid 54 is 180 out of phase with the potential across the primary due to impressed potential on grid 55. The change in phase due to the transformer is the same regardless of which grid supplies the signal potential. Therefore the potentials impressed upon grids 9| 'and 92 due to beam impingement on target plates 25 and 26 respectively are 180 out of phase and have otherwise a relationship with the potential across secondary winding 10 influenced by the effect of elements I35, A6 (or 41), 56 (or 51), and 86. Since-the electrical characteristics of these elements have been selected so that in the present circuit their overall phase shifting effect is n68- ligible; this means that the grid potentials on tubes 15 and 16 are either in phase or 180 out of phase with the potentials in secondary winding 10, and therefore with the potential in secondary winding 12 which has the same primary.

The plate of tube 15 is negative when the plate of tube 16 is positive and at the same instant the grids of both tubes are either positive or negative, depending on the direction of deviation of the beam. Current can flow in tubes 15 and 16 only when the plates are positive, and when tube 15 is conducting current flows through field winding 82 of motor I2 in a. direction onposite to that in which it flows when tube 16 is conducting. This corresponds to a reversal of phase in field winding 82, with respect to the current in secondary winding 12 or secondary winding which again has the same primary. The other winding 8| of the motor is always in a fixed phase relationship with the secondary winding '80 and, as is well known, reversal of the phase of current in field winding 82 cause. reversal of the motor.

It will therefore now be clear that I have found a means for operating motor I2 in a forward or reverse direction, depending on which target plate of the cathode .ray tube is impinged upon by the deviated beam.

I will now point out the utility of my invention. Suppose the cathode ray tube of my invention to be mounted in a craft in such a direction that the earths magnetic field is that of H2 when the torn. The axis of craft is on its proper course. It now the craft departs from thatcourse in one direction or the other, the beam will be deflected to impinge on: plate 25 or plate 26, and as set forth above, current will be induced in one winding of motor l2 in phase with or 180 degreesiout of phase with the current in the other winding which will cause motor l2 to rotate in one direction'or the other, depending uponthe direction in which the craft veered from its course. This motor may be mechanically connected to operate a control device having to do with returning g the craft to its course.

1 Another modification of myinvention may be conceived to operate in the following fashion.

8 form shown and described, but. rather by the scope of the appended claims.

I claim as my invention:

1. In a device of the class described, in comblnation, means normally directing a beam of electrons along an axis to comprise a beam current, said beam beingadapted for deflection from said normal axis in response to change in a condition from a normal value, means for modulating the intensity 01" said beam, target means comprising anodes located about said axis for impingement by said beam upon deflection from said axis, an envelope hermetically enclosing said I foregoing means, a source of, alternating cur- My cathode ray tube may be mounted to rotate about an axis which may be. forexample, substantiallyverticalfand normalto the axis of the beam. For this purpose I have shown my tube as supported on a large disc I50 arranged for rotation as at I53 and havinggear teeth in its periphery for engaging with a gear I5l carried by a shaft 552 operatively associated with 1110- to be approximately horizontal so thatthe angular position of the beam with respect to the field may be varied. The tube may therefore be sorset at any time with respect to the earths magnetic field that. the craft keeping on encappointed course, the beam of the tube will be the beam may be considered horizontal'component of the earths magnetic rent of a desired frequency, means energizing saidmodulating means from said source whereg by to modulate the intensity of said beam at the frequency of. and in phase with the current from said source, anode circuits including said target anodes, impingement of said beam upon the combined current due to impingement of a 1 second of said anodes being of opposite phase undeviated. Should the, craft now depart from its course, operation of the motorwill take place:

as set forth above, and this moti'onmay beused tooperate an indicator at a distant point show ing the'departure of the craft from its course, andat the same time to cause'rotation of my cathode ray tube about the axis to which I re- "ferredtso that simultaneously the beam will be brought back into its undiverted position, and

the indicator will come to rest at a point showing the extent to which the craft has varied from its course.

It will also be clearly understood that it is within the spirit of my invention to provide a second set of plates similar to plates and 26 but at right angles thereto, so that the beam of the tube will be responsive not only to deviation in a single plane, but deviation in a plane at right angles to that plane. By this means, it will be seen that the cathode ray tube may be maintained in a given position with respect to the earth's magnetic field regardless of the levelness of the axis of the craft in which it is mounted; for instance, in an aircraft which can descend or ascend at a steep angle.

I further wish it clearly understood that I do not intend my invention to be limited to the use of this device in connection only with the magnetic field of the earth, since I conceive it to be a part of my invention to provide this type of indicating or controlling. device wherever a controlling and indicating instrument responsive to rotation may be desired. This can be done, as I have pointed out before, by providing an artificially created magnetic field having the desired angular relationship with the beam, the two being mounted for relativerotation as I have set forth above.

While I have shown a preferred embodiment of my invention, it is obvious that many other modifications and adaptations of the present invention will occur to those skilled in the art. Therefore, is should be clearl understood that the invention is not to be limited only to that to that from said source, an electric motor op erable at said frequency upon energization by two currentsof said frequency and of displaced phase, discriminator means energizing said motor with a first current which is in phase with or ofopposite phase to the current from said,

source depending on whether said first or said second anode is impinged by said beam, and means energizing said motor. with a second cur rent displaced in phase by ninety degrees from the current from said source.

2. Ina device of the class described, in com-- bination, means normally directing a beam of electrons along anaxis tocomprise a beam current, said beam being adapted for deflection from said normal axis in. response to change in a condition from a normal value, means for modulating the intensity of said beam, target means comprising anodes located about said axis for impingement by said beam upon deflection from said axis, an envelope hermetically enclosing said foregoing means, a source of alternating current of a desired frequency, means energizing said modulating means from said source whereby to modulate the intensity of said beam at the frequency of and in phase with the current from said source, anode circuits including said target anodes, impingement of said beam upon a target anode causing the flow in the related anode circuit of modulated anode current having a component of said desired frequency, means combining said anode currents, the combined current due to impingement of a first of said anodes being in phase with that from said source, the combined current due to impingement of a second of said anodes being of opposite phase to that from said source, an electric motor operable at said frequency upon energizetion by two currents of said frequency and of displacedv phase, discriminator means energizing said motor with a first current which is in phase with or of opposite phase to the current from said source dependingon whether said first or said second anode is impinged by said beam, means energizing said motor with a second current displaced in phase by ninety degrees from the current from said source, means mounting said 9 envelope for rotation about an axis other than said normal axis of said beam, and means associating said motor in driving relation with said last named means.

3. In a device of the class described, in combination,- means normally directing a beam of electrons along an axis to comprise a beam current, said beam being, adapted for deflection from said normal axis in response to change in a condition from a normal value, means for modulating the intensity of said beam, target means comprising opposed anodes spaced about said axis for impingement by said beam upon deflection from said axis in a first direction, means for electrostatically deflecting said beam in asecond direction perpendicular to said first direction, an envelope hermetically enclosing said foregoing means, a source of alternating current of a desired frequency, means energizing said modulating means from said source whereby to modulate the intensity of said beam at the frequency of and in phase with the current from said source, anode circuits including said target anodes, impingement of said beam upon a target anode causing the flow in the related anode circuit of modulated anode current having a component of said desired frequency, means combining said anode currents, the combined current due to impingement of a first of said anodes being in phase with that from said source, the combined current due to impingement of a second of said anodes being of opposite phase to that from said source, means mounting said envelope in a normal orientation with respect to the ambient magnetic field, in which orientation said beam passes along said axis, movement of said envelope from said normal orientation causing impingement of said beam upon one of said anodes, and means responsive to said combined current for correlating said combined current with the change in orientation of said envelope.

4. In a device of the class described, in combination, an electron gun directing a beam of electrons of modulated intensity along an axis to comprise a modulated beam current, said beam being subject to the efiect of a magnetic field, spaced target anodes displaced along said axis in the direction of said beam, means for electrostatically deflecting said beam in a second direction perpendicular to said first direction, an anode circuit for each of said target anodes, said beam impinging a predetermined one of said target anodes for each orientation of said axis with respect to said field, impingement of said beam on each said anode resulting in modulating anode current in the related anode circuit, said anode circuits including means combining currents flowin therein, said combined current changing in phase with respect to a standard with change in the anode impinged by said beam,

5. In a device of the class described, in combination, means normally directing a beam of electrons along an axis to comprise a beam current,

said beam being adapted for deflection from said normal axis in response to change in a condition from a normal value, means for modulating the intensity of said beam, means for deflecting said beam with respect to said axis in a selected plane, target means comprising anodes located about said axis for impingement by said beam upon de- ,flection from said axis in a direction having a component normal to said plane, an envelope hermetically enclosing said foregoing means, a source of alternating current of a desired frequency, means energizing said modulating means from said source whereby to modulate the intensity o1' said beam at the frequency or and in phase with the current from said source, anode circuits including said target anodes, impingement of said beam upon a target anode causing the flow in the related anode circuit of modulated anode current having a component of said desired frequency, means combining said anode currents, the combined current due to impingement of a first of said anodes being in phase with that from said source, the combined current due to impingement of a second of said anodes being of opposite phase to that from said source, an electric motor operable at said frequency upon energization by two currents. of said frequency and of displaced phase, discriminator means energizing said motor with a first current which is in phase with or of opopsite phase to the current from said source, depending on whether said first or said second anode is impinged by said beam, means energizingsaid motor with a second current displaced in'phase by ninety degrees from the current from said source, and means energizing said deflecting means to maintain said beam centered with respect to said plane, said energizing means being of reversible polarity. 6. In a device of the class described, in combination, an envelope, an electron gun and a pair of spaced opposed target anodes enclosed by said envelope, sai-d gun emitting a beam of electrons along an axis in the direction of said anodes to comprise a beam current, said envelope having an orientation in which said beam is deflected from said axis by the ambient magnetic field, change in said orientation of said envelope resulting in deviation of said beam from said axis to increase its effective impingement upon a target anode, said deflection of said beam having components in two mutually perpendicular planes, means for neutralizing the component of said deflection in the first of said planes, said first plane passing between said target anodes, means modulating the intensity of said beam at a desired frequency, an anode circuit for each of said anodes, impingement of said beam on each said anode resulting in modulated anode current in the related anode circuit, said anode circuits including means combining current flowing therein, said combined current changing in phase with respect to a standard with movement of designed for energization with alternating voltage of a selected frequency; a source of alternating voltage of said frequency; means enere gizlng said modulating means from said source to give to said target currents alternating components having fixed phase relationships to said source; means energizing one winding of said motor fromsaid source; means, including means combining said target currents, for energizing the other phase of said motor in accordance with the relationship between said components of said target currents, so that as said relationship reverses the direction or operation or said motor also reverses: and controlled means actuated by. said motor. 1 v

8. In a compass: a cathode ray tube including an electron gun directing 'a beam 01"electrons along a'normal axis from which it is subject to deflection in response to the earths magnetic field, means energizable to modulate the intensity of said beam, and a plurality of target plates mounted for variable impingement, according as said beam is deflected, to transmit variable target currents; a source of alternating voltage or a selected frequency; means energizing said modulating means from said source to give to said target currents alternating components having fixed phase relationships to said source; a controlled device; and means. including means combining said target currents, for energizing said controlled device with alternating voltage which reverses in phase with reversal in the relationship between said components of said target currents.

HENRY E. HARTIG.

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

Number UNITED STATES PATENTS Name Date Soller Sept. 14, 1937 Englehart Dec. 24, 1935 McCreary Jan. 14, 1936 LaPierre Sept. 1, 1936 Seller Oct. 19, 1937 Zworykin Dec. 28, 1937 Skellett July 11, 1939 Skellett July 11, 1939 Vingerhoets et a1. Oct. 17, 1939 Hollm-ann Apr. 2, 1940 Hansell May 28, 1940 Gray Sept. 10. 1940 Preisach et al. Dec. 9, 1941 Bath Jan. 13, 1942 Dallos June 3, 1942 Hansell Dec. 22, 1942 Noxon Jan. 19, 1943 Ziebolz June 22, 1943 1945 Nagy Feb. 20,

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