US2071382A

US2071382A - Electron discharge device

Info

Publication number: US2071382A
Authority: US
Publication date: 1937-02-23
Anticipated expiration: 1954-02-23

Description

1937- J. R. BALSLEY ELECTRON DISCHARGE DEVICE Filed July 11, 1934 3 Sheets-Sheet 1 QMAX/mum INVENTOR JAMES E. BALsLEY ATTORNEY Feb. 23-, 1937. r ABALSLEY I 2,071,382

ELECTRON DISCHARGE DEVICE Filed July 11, 1934 3 Sheets-Sheet 2 W4 l? L+ INVENTOR JAMES A? -5AL5LEY ATTORNEY b I J. R. BALSLEY 2,071,382

ELECTRON DISCHARGE DEVICE .Filed July 11, 1934 3 Sheets-Sheet 3 52 FIG. 8.

PIE. 5.

INVENTOR JAMES P. BALSLEY A'ITORNEY Patented, Feb. 23, 1937 ELECTRON DISCHARGE DEVICE James LBalaley, La Canada, CaliL, o!

one-hallto FrankLAGraham,-S

Marlno,

Application July 11, 1934, Serial No. 734,607

-4 Claims. (01. 250-27) This invention has to do in a general way with the construction and operation of electron discharge devices, and more particularly with that class of tubes ordinarily employed in communication circuits, such as radio and telephone circuits for the purpose of amplifying, rectifying and modulating electric currents.

As is well known to those-familiar with the art, the conventional vacuum tube, such as is used in amplifying, modulating and demodulating or detecting electrical impulsm, consists essentially of at least three elements, namely, the

cathode or'fllament, the plate and the grid. The cathode and the plate are connected across an electric potential and, since they are enclosed in a tube or envelope which isevacuated, the application of potential across the plate and the ills.- ment is followed by the flow of a stream of electrons from the cathode'to the plate, the intensity of such stream being dependent upon the applied potential. This is attended by a ilpw of current in a direction opposite to the flow of electrons in the circuit containing the filament and the plate.

Another well known fact is that the grid which is in the nature of a wire mesh screen interposed between the plate and the cathode can be made to function as a valve controlling the intensity of the electron stream and the characteristics of i the consequent flow of current by the application of a varying or oscillating potential to the grid. This varying or oscillating potential, which is applied to the grid is, in radio or telephone circuits, generally referred to as the input or the "signal voltage and the resultant action as is well known is the variation of the current flowing between the plate and the cathode by the input or signal voltage.

It is obviously necessary in obtaining an accurate reproduction of signal oscillations in the plate-filament circuit that a linear relation must exist between the input voltage and the plate current. It will also be readily observed from the study of any grid voltage-plate current curve for any grid controlled tube, that such a linear relationship exists only for a relatively small'r'ange, of grid voltage. In any case if the grid is permitted to have a positive potential with respect to the cathode, the grid will draw current.

cycle and distortion results. 'l'o increase the efflciency of the tube, this practice is employed in class B and class C amplifiers. Both of these types require elaborate means to remove harmonics and eliminate distortion generated by the tubes so operated. It is conventional practice in class A amplifiers to apply a negative bias voltage to the grid of the tube for the purpose of holding the signal voltages within that particular range where the linear relationship exists. If for any reason the grid voltage falls below or rises above the particular range for which the tube has a linear relationship between the grid voltage and the plate current, considerable distortion results giving most unsatisfactory results. Innumerable attempts have been and are constantly being made to eliminate or reduce this very undesirable factor in a conventional vacuum voltage or the signal, have not been successful I in satisfactorily solving the problem.

It therefore becomes a primary object of this invention to produce a new and improved type of vacuum tube or electron discharge device wherein the. output or plate current is exactly proportional to the input voltage over the entire range of current in the load circuit from zero to saturation.

In obtaining this objective I take advantage of the fact that a vacuum tube of the trlode type has at least three factors which may be varied to effect variations or oscillations in the plate current. These variable factors are, first, the voltage applied to the grid, second the space relationship between the filament, the plate and the grid, and, third, the mesh of the grid. As was pointed out above, it has always been the practice heretofore to apply the input voltage or the signal to the grid to obtain oscillations in the output current corresponding to the signal and in conventional practice the mesh oi the grid and the'spaced relationship between the filament, the plate and the grid are therefore always fixed for all input voltages. Inasmuch as the plate current varies substantially as the three halves power of the grid voltage (E8 it will be seen that it is obviously impossible to obtain a straight line relationship between the grid voltage and the plate current over a wide range of plate current.

In the tube contemplated by this invention I propose to apply a constant voltage to the grid (if one is used) and introduce the signal into the tube in an entirely new and different manner.

More specifically, I propose to use the input sigan intensified beam and swingin such beam angularly from side to side by means of the signal voltage, the angular motion of the beam being proportional to the applied signal voltage. The grid and the plate are then formed or shaped so that the eflective space relation between the cathode and the other two elements varies with the angular displacement of the electron beam thereby establishing a different space relationship between the elements of the tube for each variation in signal voltage, the shape of the plate and' grid being such that these changes in the effective space relationship between the elements are eifective to vary the output current in direct proportion to theinput voltage overthe entire range of input voltage for which the tube is designed.

In this connection I have devised a method whereby the grid and plates can be shaped so that .the output or plate current in an amplifier for example is an exact reproduction of the input voltage except in amplitude over the entire range a flat grid and a flat plate, the grid having a variable mesh therein. variations in the mesh being such as to give the same effect as the curve on a curved plate and grid. For this reason when the term changing the effective space relationship" between the plate andthe cathode is used herein, I have reference to a structure employing the swinging beam referred to above in con- Junction with either the curved plates, the curved plate and grid, or a flat plate and a flat grid, the mesh of the grid being varied to produce what is in eflect a change in the space relationship between the elements of s the tube.

It will be apparent to those familiar with the art. especially when the detailed description of my invention, is taken into consideration, that it is notnecessary to employ a grid. In other words. the invention is equally adapted to use in connection with a diode as it is with atriode type of tube. However, in a device where ampli-; iication is a factor it will be seen that, by using a grid having the proper bias, the amplification factor of thetubewillbe greatly increased. It will alsobe-apparent that, where the effective spaced relationship" between the elements is electrically varied through changing the mesh of the grid at diiferent points to obtain the straight line relationship between the applied volthieand theplate current, a grid is essential. The device. can be used with varlcu'scircuits and various shapes in the grid and plate element For the purpose of amplification, rectification, and modulation.

As was pointed out hereinabove, the tube con-.- templated by this invention can be broadly considered as one in which an intensifled beam is formed between .the plate and the grid and is swung back and forth over a predetermined angle by the input voltage, and the construction of the elements in the tube is such that the efiective space relationship" between the filament and the plate varies for each angular increment of motion. This so-called change in effective space relationship can be obtained either by shaping the plate so that it does not lie on a radius from the point of emission or by varying the mesh of the grid. Looking at it in another way, the socalled change in eifective spaced relationship produces a change in the intensity of the beam at the point where it strikes the plate. In other words the intensity of the beam at the point it strikes the plate can be varied either by changing the distance between the plate and point of emission successively for each increment of angular motion or by changing the mesh of the grid at the successive points where the beam passes therethrough during its swing. In this latter case it will be seen that I may employ a plate and a grid all points of which are on a radius from the cathode or the point of emission and with proper changes in the mesh of the grid can obtain a result similar to that obtained with a shaped plate or a shaped plate and grid.

The details in the construction of certain forms of my invention together with the method contemplated thereby will be best understood from the following description of the accompanying drawings, which are chosen for illustrative purposes only, and in which Fig. 1 is a diagram illustrating the procedure followed in obtaining the factors which determine the shape of the plate and grid in a triode tube of the type contemplated by this invention;

Fig. 2 is a diagram in polar co-ordinates illustrating the manner in which the procedure of Fig. 1 is used to actually design the shape of the plate and the grid;

Fig. 3 is a wiring diagram illustrating a preferred form of triode tube contemplated by this invention;

Fig. 4 is a diagram similar to Fig. 1 illustrating the first step in the procedure followed in designing a full wave rectifying tube;

Fig. 5 illustrates the second step of the procedure followed in designing a rectifying tube;

Fig. 6 illustrates a preferred form of full wave rectifying tube contemplated by this invention;

Fig. 7 is a wiring diagram of a modulating circuit equipped with one form of modulator contemplated by this invention;

Fig. 8 is an elevation, more or less diagrammatic in character. illustrating the manner in which the mesh of the grid may be varied to produce corresponding variations in the intensity of the electron beam as it passes through diflerent sections of the grid; and

Fig. 9 is a wiring diagram illustrating the manner in which a grid of the type shown in Fig. 8 maybeused in avacuumtube.

Before entering into a detailed description of the drawings, it is again em that the plate current in a vacuum tube can be varied by changing the space relationship which exists between the plate and the cathode or if the tube employs a grid by changing the spaced relationship which exists between the Plate, the cathode and the grid. The extent of this variation or the ratio between the variation in plate current and the variation in space relationship may change somewhat with other fixed factors in the tube design such as the area of the grid, the area of the plate, the mesh of the grid, the diameter of the wires making up the grid and the materials forming the grid and the plate, etc.

For any fixed set of conditions, however, there is a constant relation which exists between the Zran IOQQE; wheren=number of wires percm.

r=radius of grid wires. This equation is for a structure consisting of plane parallel elements with a grid placed symmetrically between cathode'and anode, the grid being maintained at a negative potential with respect to the cathode. It does not contemplate additional electron acceleration by means external to the three elements mentioned.

Assuming all of the factors to be constant except-the distances, (at and p) thisequation may be expressed roughly by stating that the plate current (Ip) varies-inversely -as (=+K) or (fi l-K) For the purpose of clarity in illustrating and describing the invention, it may be assumed that a and p are equal or that the grid is placed midway between the plate and the cathode. With these points in mind I now refer to Fig. 1 ofthe drawings which is a graphic representation of a preferred procedure followed in determining the shape of the plate and the grid in a modulating or amplifying tube designed so as to establish a straight line relationship between the signal or input voltage and the plate current. In "Fig. 1, 5 that portion of the ordinate above the abscissa indicated at 1, represents the plate current. The portion of the abscissa to the right of the ordinate indicated by fe or p representsthe distancefrom the cathode to the grid or'from the grid to] the.

plate. The left hand portion of the ordinate, indicated at "Ed" represents the deflecting voltage or the voltage of the input signal. The bottom of the ordinate, indicated by 0, indicates the angle produced in an electron beam by the deflect- 65 ing voltage.

The curve in which may be obtained by experiment or from an equationsuch as equation (1) above, therefore, represents the relation which exists between.

70 the plate, current and the distance from the plate the upper right hand quadrant,

in a diode is substantially the same as in a triode, this curve may also be considered as representing such relationship and the distances from the abscissa to the curve in such case represent the distance from the cathode to the plate. It will be understood, of course, that the shape of this curve may vary with diiferent conditions in the tube, as was pointed out above, but the fact always remains that there is in any tube a deflnite relation which exists between the distance from the plate to the other element or elements in the tube and theplate current which can be graphically expressed in this manner.

The first step in designing a tube of this character is therefore to determine the shape of the plate current-electrode distance curve in the upper right hand quadrant, which I have indicated by reference numeral Ill. The next step in designing the shape of the plate or the plate and the grid is to plot in the upper left hand quadrant a curve showing the desired relationship between the input slgnal'and the plate current which will be hereinafter referred to as the plate current-input voltage curve. As has hereinabove been pointed out,'it is with very few exceptions desirable to produce a vacuum tube in which the plate current always bears a straight line relationship to the input signal, since this gives amplification or modulation without distortiori at any point. This relationship is indicated by the straight line H in Fig. l, the slope 'of this curve,

L 7 as, I being a measure of mutual conductance.

It is a well known fact, from the operation of the oscillograph, that an alternating or oscillating electric current can be made to deflect or swing a beam of electrons back and forth, the amplitude of the swing being dependent upon the voltage. when alternating current is used the beam is swung from side to side relative to its zero or normal axis, and the line l2 in. the lower left hand quadrant of Fig. 1 indicates the relationship which exists between the deflecting voltage and the angle of deflection, its shape will be a function of the method of deflection employed, and can be determined as in the case of the curve or line It explained above.

Since it is the object of this form of my invention to change the distance from the cathode to the plate, or from the cathode to the grid, for each angular increment in the swinging movement of the beam, so that the space relationship at the diflerent angular increments will produce a straight line relation between the plate current and the deflecting voltage, it will now be seenthat I can obtain this distance for each angular increment by plotting the distance from the plateto the grid or from the grid to the filament in the lower right hand quadrant against corresponding angles produced in the beam by the signal voltage. The curve is indicated by reference numeral l3 and the procedure followed in locating points on this curve is to choose a number of points on the curve ll, carrying these points over to the curve l0 locating the distance necessary to obtain a straight line relationship on the upper right hand quadrant and then carrying the same points down to the straight line l2 and back over to the lower right hand quadrant to determine the. angleswhich will give suchdission and referencanumeral N indicates the normal axis of the beam. In other words, reference numeral l4 indicates the neutral position of the electron beam when no deflecting voltage is applied to the tube. Since'the distance d of Fig. 1 corresponds to the linear distance along a radius of the beam from the virtual cathode or the point at which the beam is'defiected, it is.

necessary, in determining the final shape of the plate, to plot these distances in polar co-ordinates. This is the step illustrated in Fig. 2 where numeral l5 indicates the position of the beam at various angles and the procedure followed is to locate points 'on these angles from the distances d of Fig. 1. Since the grid is placed midway between the virtual cathode and the plate it will be seen that the location of points on the grid can be determined by measuring the distance d corresponding to a given angle on the radius of that angle and then taking the same distance d from'the grid to locate a corresponding point on the plate. Following this procedure through for a plurality of chosen angles, the points will be located for determining the shape of the plate and the grid indicated by curves P and G respectively. It will thus be seen that the plate and grid obtained in this way are shaped in accordance with a curve of which the abscissa-(considering the axis of ordinates as normal to the neutral position of the beam) is a function of the curve Ill in the upper right hand quadrant, and the ordinate is a function of the preselected curve I l in the upper left han quadrant. v Referring now to Fig. 3 which-illustrates a preferred form oftriode typet'tube contemplated by this invention, and shows the same as being connected in an electrical circuit foramplification purposes, reference numeral It indicates an envelope which contains a cathode I], a grid l8 and a plate IS, the plate I! and the grid l8 having the shape of the curve P and G which were designed in the manner above described.

As will be understood by those familiar with the art various types of cathodes or filaments may be used in a tube of the typecontemplated by this invention. It is important. however, for the purposes of the invention, that the-beam formed by or emitted from the cathode .be of a confined or intensified nature. The intensification of this beam may be obtained through the-design of the cathode itself, but for the purpose of this description and to clarify the illustration I show the tube provided with means to concentrate the beam into a thinsheet. This may be done in many ways known to the art and classified as electron optics. In the method shown, shield 2 l' is made with a narrow slit. A positive potential 23 is applied to this electrode for the purpose of increasing the electron velocity. Shield 20 is also built with an aperture and a negative potential 22 applied thereto so as to force the greatest plate current I is flowing from the plate to the cathode along the electron beam.

For the purpose of swinging the beam with the oscillations of the input voltage, I may employ various devices, either inside or outside the tube, but for purpose of illustration I show a pair of deflecting plates 26 and 26' positioned within the envelope between the grid l8 and the cathode l1 and on opposite sides of the path of the beam. These deflecting plates 26 and 26' are connected across a signal or input source of potential generally indicated by reference number 21.

For the purpose of amplification I provide a suitable bias to the grid from a source of potential generally indicated at 28.

pose of effecting fullwave rectification of an alternating current. Fig. 4 shows a graphic illustration similar to Fig. 1 in which the ordihate and abscissa are indicated by the same reference characters. The curve l0 of Fig. 4 is also the same as the curve ,lil in Fig. 1. Assuming that the fixed factors of the tube produce a relationship between I and a or p, the same as the tube from which the curve III was drawn. In the case of full wave rectification each pulsation of the alternating voltage whether positive or negative must produce a positive pulsation of the plate current, the amplitude of the plate current to be directly proportional to the amplitude of the alternating voltage. The minimum plate current or that value produced by zero voltage on the deflecting plates is represented by point 0 on line 3| and may be chosen near zero plate current to eflect the maximum output of the tube. Such a curve is graphically represented by reference numeral 3| in the upper left hand corner of Fig. 4. The relationship between the deflecting voltage and the angle of deflection is represented by reference numeral 32.

Following through the same procedure described in Fig. 1, the distances from the cathode to the plate or the plate to the grid can be established by plotting points in the lower right hand quadrant of Fig. 4. These points give a curve 33 which determines the distances from the various elements enumerated above for various angles of deflection. Plotting points on the curve 33 in polar co-ordinates as indicated in Fig. 5, in which 0' indicates the point of emission or the cathode and reference numeral 34 indicates the normal or neutral axis of the electron beam and in which reference numeral 35 represents radii for various angular deflections of the beam, I obtain curves P and G which give the exact shape of the plate and the grid.

It will be observed that both the plate and the grid are substantially symmetrical with respect to the normal adds 34 and that as they continue away from the axis the radius from the point 0' to the plate or the grid, as the case may be, becomes shorter. It will be understood, of course, that this type of design may also be incorporated to give amplification.

I is

A triode type of tube. embodying a plate and grid of the shapes indicated at P and G in Fig. 5 is shown in Fig. 6, such tube comprising an envelope 36 provided with a cathode 31 adapted to project an intensified beam of electrons through the grid onto the plate 39. Defiecting plates 40 and 40' are connected across an input or sig-' nal voltage generally indicated by reference nu: The grid 38 is provided with a biasing plate 39 being connected across a potential 43 and a load 44. g

It will be seen from the description above that this tube gives full wave rectification. If it is desired to obtain half-wave rectification, a biasing potential may be applied to one or the other of the deflecting plates 40 and 40', suchpotential being regulated so that the normal position or the beam is at the extreme edge of the plate,

(angle 0' maximum) so that only one half cycle of the alternating voltage is efiective in producing a change in plate current. It is obvious that a tube type shown in Fig. 6 is better adapted for half wave rectification by the method described.

As has been previously pointed out, my invention consists broadlyin forming an intensified electron beam in a discharge device of the class described, swinging such beam from side to side with an input or signal voltage and varying the beam in intensity where it strikes the plate for each successive increment in its angular movement. In the forms described above, this variation or change in intensity is obtained by ac tually changing the distance from the point of emission to the point'ot reception for the successive angular increments. As has been previously pointed out, I may also obtain this result by using a grid in whichthe mesh 01. the grid varies progressively along its width, the variations in meshbeing worked out along the same lines as the distances described above so as togive the desired characteristics between the deflecting voltage and the plate current. In Fig. 8 I illustrate diagrammatically one form in which the grid may be formed to vary the intensity of the beam as it swings back and forth across the grid. It will be observed that the grid is formed so that the openings or mesh decrease in area from left to right. In this form of my invention this is accomplished-by tapering the horizontal wires 5! and gradually decreasing the distance between the vertical wires 5|. It will be obvious, however, that numerous grid structures may be made to accomplish this same result. I i

In Fig. 9 I show a vacuum tube 53 which is equippedwith the grid 50 contained in an envelope 53 and positioned between a plate 54 and a cathode 55. Defiecting plates 56 and 58' are connected across an input or signal potential indicated'at' 51. In this form of my invention the grid 60 and the plate 54 are shown as being formed on a radius from the point of emission orthe cathode 65. It will be understood, however, that by properly varying the mesh of, the grid the same might be made fiat or curved or both the grid and the plate may be set at angles similar to the angles of Fig. 3, the grid and the.

plate in this instance being fiat.

Fig.7isawiringdiagramsimilarinall essentials to Fig. 3 and showing a modification oi the Ila is of any preferred type which will give a concentrated or intensified beam type of emission and is shown as being assoclated with a slit system comprising concentrating and accelerating shields 20a. and 2la.

v In this system I employ two sets of deflector plates indicated by

reference numerals

50, 60 and 6|, 6|, respectively. Thecarrier wave potential is shown as being applied to the deflector plates 60, 50' from a suitable source indicated by reierence numeral 62, and the modulating or audio wave potential is applied from the source 63 across the plates GI and ii. In this particular arrangement the cathode and the plate are connected across a potential 85 and the circuit connecting the plate and the cathode is associated with a transmitting antenna 10 through a trans-' former generally indicated at II.

It will be apparent from the foregoing description that my invention contemplates a new departure in the design of vacuum tubes or electrical discharge devices in which the amplification, modulation or rectification may be effected by utilizing an oscillating input signal voltage to swing or deflect an intensified beam of electrons projected from a cathode to a plate, and it is to be understood that while I have herein de scribed and illustrated certain preferred forms or my invention, the invention isnot limited to the precise structures disclosed nor the precise methods described herein, but includes within its scope whatever changes fairly come within the spirit of the appended claims. a

I claim as my invention:

1. In an electron discharge device: a cathode: aplate; means for confining the electron stream emitted from said cathode to form a beam projected on said plate; a pair of deflecting plates positioned on opposite sides of the path oi said beam between said cathode and said plate; and means for applying an oscillating potential across the gap between said deflecting plates whereby said beam is swung with the oscillations, said plate being shaped and positioned to conform with a curve the axis of ordinates 01 which is perpendicular to the neutral position of said beam, the abscissa of said plate curve being a function of a plate current-electrode distance curve obtainw able with constant input voltage and the ordinate of said plate curve being the iunction oi a preselected plate current-input voltage curve which is based on a swinging electron beam and constant electrode distance.

2. In an electron discharge device: a cathode; a plate; a' grid between said cathode and said plate; means for confining the electron stream emitted from said cathode to form a beam proiected on said plate; a pair oi deflecting plates positioned on opposite sides of the path of said beam between said cathode and said plate; and means for applying an oscillating potential across the gap-between said deflecting plates whereby said beam is swung with the oscillations, said plate being shaped and positioned to coniorm with a curve the axis of ordinates of which is perpendicular to the neutral position of said beam, the abscissa of said plate curve being a function 01' a. plate current-electrode distance curve obtainable with constant input voltage and the ordinate of said plate curve being the function of a preselected plate current-input voltage curve which is based on a swinging electron beam and constant electrode distance.

3. In an electron discharge device: a cathode a P te; a grid between said cathode and said plate;

means for confining the electron stream emitted from said cathode toform a beam projected on said plate; a pair of deflecting plates positioned on o osit -side's of the path of said beam between grid curve being the function of a preselected plate current-input voltage curve which is based on a swinging electron beam and constant spacing between the cathode grid and plate.

4. In an electrondischarge device; a cathode; a plate; means for forming an intensified beam of .the electrons emitted from said cathode to said plate; means operated by signal potential for swinging said beam; and means comprising a variable mesh grid interposed between said cathode and said plate for varying the intensity 0! the beam with various angular increments thereof.

JAMES R. BAISLEY.