US2474960A - Electronic device and circuit arrangement therefor - Google Patents

Description

July 5, 1949. A. M. sKELLETT ELECTRONIC DEVICE AND 'CIRCUIT ABRANGEMENT THEREFOR 2 sneetsh-sheet 1 Filed April 28, 1945 Fig. 3

INVENTOR.

T l E u. E y M W E E L IJuly 5, 1949. A. M. sKELLE'rT ELECTRONIC DEVICEAAND CIRCUIT ARRANGEMENT THEREFOR Filed'April 2B, 1945 2 Sheets-Sheet 2 MASTER OSCILLATOR RADIAL BEAM TUBE INVENTOR. ALBERT M. SKE'LLETT Patented July 5, 1949 ELECTRONIC DEVICEAND CIRCUIT ARRAN GEMEN T THEREEQB Albert M. Skellett, Madison, N. il., ass'ignorv to National Union Radio N. J., a corporation of D Corporation, Newark, elaware Application April 28, 1945, .Serial No. 590,912,

(Cl. SI- 91) 4 Claims.

The present invention relates to a method lof generating the tones for an electronic organ, more particularly to a tone generator system employing Va plurality of radial beam vacuum tubes-as the tone source. In my prior Patent No. 2,217,774, granted October 15, 1940, there is described an electronic switching tube wherein an electron beam is deflected to impinge in succession upon a plurality of targets or anodes. Means are provided for shifting or rotating a magnetic eld between the cathode and the targets, the lines of force of the field being normalto the longitudinal axis of the cathode. A tube of this character may be employed in a variety of signal translating systems, as, for example, a multiplex telephone system.

In my Patent No. 2,320,756, issued June 1, 1943, I disclose the application of a type of radial beam tube as a frequency multiplier capable of producing an alternating current having a frequency within the limits of the Vordinary musical scale which may be used as a static generator employed as a source of stone for various purposes.

A general description as to structure and characteristics of my magnetically focused radial beam vacuum tube involving the foregoing construction is described in the Journal of Applied Physics, vol. 15, No. 1'0, pp. 704-709, October 1944.

An object of the present invention is the adaptation of my prior radial beam vacuum tube construction and circuit arrangements, as set forth in `the foregoing references, to the problem of generating tones for electronic organs, such as described in the Hammond Patent No. 1,956,350, granted April 24, 1934.

The instrument disclosed in the aforesaid Hammond Patent No. 1,956,350 operates upon the principle of synthetically producing electrical waves of the desired frequency, and including various proportions of harmonics necessary to produce a tone of the desired quality or tone color. The means for generating the electric currents of diiferent frequencies comprise a plurality of alternators, one for each frequency necessary to produce the fundamental of the tempered musical scale. The rotors of the alternators are driven from a constant speed motor.

In the embodiment of the Hammond organ described in the aforesaid patent there are eighty-nine alternators, there being seven different shapes of rotors employed, the rotors hav ing respectively 2, 4, 8, 1'6, .32, 64 and 128 high points Whichrepresent the harmonic tones of the fundamental." A selector'mechanism is provided for selectingthe several frequencies constituting a fundamental land its harmonics.

From the foregoing lit will be seen that in the Hammond 'organ alternators produce electrically the vtones Ibythe mechanicalcontrol and/or operation of the vmechanisms constituting the system. These mecha-nical parts have substantial inertia which, in turn, indirectly produce a source of distortion from the theoretrical frequency of notes in the musicalscale with a consequent distortion `of tone qualityl It is therefore an object of the present invention to substitute a modiiied Iform of my prior radial Abeam vacuum tube as the tone generator in place `of the alternators employed by Hammond. More generally I propose the application of a radial beam vacuum tube for the generation of tones for electronic organs.

Another object of -the invention is the provision of tone generating means 'free of inertia and without mechanical ymoving parts, said means preferably `taking the lform of one or more specially designed radial beam vacuum tubes electricallyassociated with a master oscillator which may be individual .to a given fundamental and its harmonics.

A special feature .of 'the invention is the provision of a radial beam vacuum tube having a screen element provided with one or more bands, each comprised of `a series lof apertures coaxially arranged with .respect to the cathode. The apertures of each Aseries are ldesigned to produce sinewave currents when the electron beam, which is substantially rectangular in cross section, sweeps across them. By varying the number of apertures in the several 'ba-nds., the frequency of the sine waves may-.be altered to produce the musical notes and their harmonics..

'Other objects of :the invention will manifest themselves as the description proceeds.

Referring to the accompanying drawings:

Fig. 1 is a perspective View of the screen element of a radial bea-m vacuum tube embodying a feature of the .present invention;

Fig. 2 isa perspective view -of an electron discharge Idevice illustrating one embodiment of the invention, :a portion of the enclosing envelope being broken away fand, also portions of the electrode assembly, to, lshow the internal structure more clearly;

Figure 3 is a diagrammatic view showing the screen element., as illustrated in Fig. 1, unrolled;

4is a top view, partly insection, of a magnetic :field producing structure utilizing two phase current;

Fig. is a diagrammatic View of the circuit arrangement for operating a pair of my electron beam tubes in connection with a master oscillator; and

Fig. 6 is a side view of the magnetic system shown more particularly in Fig. 4.

Referring to the drawings, more particularly Figs. 1 to 3, it will be noted that I have illustrated the invention embodied in a simplified form of my prior radial beam vacuum tube, and only so much of the circuit organization is diagrammatically and/or schematically represented in Figs. 4 and 5 for one to comprehend the features and/or operation of my tone generating system as applied to a common form of an electronic organ.

The tube comprises an envelope i, having mounted therein an electrode assembly, which may be referred to generally by the reference character 2. The electrode elements are supported between a pair of spaced insulating members such as mica discs 3, and comprise respectively a cylindrical indirectly heated cathode d, surrounded by a coaxial cylindrical screen element E. Encompassing the screen 5, are a plurality of spaced, ring-like targets or anodes 6, l', 8 and 9. The electrode assembly 2 may be conventionally supported from a stem l l terminating in a press l2. Extending through the press I2 are conductors i3 for electrically connecting the electrodes forming the assembly 2 in the operating circuits comprising the circuit organization of the tone generator system.

The screen element 5 is provided with series of apertures, each series constituting an individual pattern and forming bands l5, I6, I7 and I8 coariially arranged with respect to the cathode and oppositely disposed with respect to a given one of the anodes 6 to e. When the screen e is unrolled the several series of apertures have a sine-wave shape varying in the number of the peaks as determined by the frequency of the note or harmonic desired. Stating somewhat differently what has just been described, there are two apertures it in the series constituting the band l5, which is opposite the fundamental frequency anode 6, and when the screen element 5 is unrolled the form of the apertures is a sine wave and they extend the full length of the screen. 1n a similar manner the apertures i4 comprising the band le represent the second harmonic of the fundamental, and there are four apertures in the series which produce a sine-wave form of the same amplitude and of twice the frequency as that of band I5. The apertures comprising bands il and I8 are likewise multiplied by two, resulting in eight and sixteen peaks respectively, which are also of the sine-wave form, and represent the fourth and eighth harmonic of the fundamental tone. The production of the harmonics of the several fundamentals comprising the musical scale will hereinafter be more fully explained, but it is significant to note at this point the relation between the shape of the apertures lll and the wave form. The present adaptation of my tube contemplates the focusing of the electrons in a double beam in of a substantial rectangular cross section so that as the beam sweeps across the apertures, the amplitude of the current to the anode has the form of a sine-wave modulation of a selected frequency.

The focusing of the electron beam lil is 0btained by the magnetic field. The type of electrostatic eld I prefer to employ in the present application has cylindrical symmetry and is secured by putting a positive potential on the screen and also on all of the anode elements 6 to Si, their potential likewise being positive with respect to the cathode 4. The magnetic field may be obtained from a suitable structure comprising a set of four coils 2B having four equally spaced poles 2 l. A magnetic core 22, for example of iron, surrounds the tube l and preferably has a depth substantially equal to the electrode assembly 2. Diametrically opposite coils 2e are connected, the arrangement being that opposite poles 2i are opposite in polarity.

The coils 2u may be connected to be excited by two-phase alternating current source, such an alternator, which effects the rotations of the magnetic field and the consequent shifting of the electron beams I around the periphery. If the neld is rotated continuously, the beams will be rotated continuously and will move around the anodes producing currents of sine-wave form in the circuits connected to the anodes. This arrangement of magnetic eld serves both to focus the beams and to direct them to successive or various points on the anode periphery.

The geometry of my radial beam tube disclosed herein is not very critical, and one may get suilicient data for designing the tube from the references mentioned above. The devices included as part of the tube circuit organization may be of conventional design, since the invention relates primarily to the generation of tones for an electronic organ by the application of a radial beam vacuum tube as the tone generator.

In my tone generator system, which is especially applicable to an electronic organ such as disclosed in the aforesaid Hammond Patent No. 1,956,356, I propose to use twelve master oscillators 25, which may be of the resistance-capactance type or inductance-capacitance type. The function of the oscillators 25 is to generate the `first submultiples of the twelve fundamentals of the musical scale. Figs. 28 and 28a of the Hammond Patent No. 1,956,350 constitute a chart usable in conjunction with his wiring diagram to indicate the connections not shown in said diagram and includes data utilized to drive the tone generators of his system, an explanation of this chart being given in lines 118 to 156, page 3, and lines 1 to 15, page 9 of the patent. A feature of the chart is the comparison of the frequency of the current generated (column 8) for a given key with the theoretical frequency of note or key in an equally tempered musical scale (column 9). It will be noted that there is close fidelity of these two frequencies for the same note, and that for the lower notes C, Ct', D, Dali, E, F, Ft, G, Gi?, A, A# and B, the theoretical frequencies are 32.7, 34.6, 36.7, 38.9, 41.2, 43.6, 46.2, 48.9, 51.9, 55.0, 58.3, 61.7 cycles.

In each of the master oscillators 25 the phase is split so that two phase currents of the proposed submultiple frequency are available for each of two stators to be used in conjunction with two radial beam tubes to generate the fundamental and the 2nd, 4th, 8th, 16th, 32nd, 64th and 128th harmonic tones of the fundamental. See Fig. 5.

The construction of the two radial beam tubes to be used with the two stators has been clescribed above. The rotating magnetic field reivolves at a cyclic frequency of only one-half the fundamental, i. e., the rst submultiple. For ex" ample, the frequency of the first master oscillator 25 will be 16.35 cycles per second.

For the higher harmonics it may be inconvenient to accommodate so many peaks in the apertures in the screens and it may be more practical to take the 8th harmonic 'from the first tube of each set and to split its phase and feed this frequency to the stator ofthe second tube. By these means all of the radial |beam tubes would be identical in design and construction. The magnetic field in the stator for the second tube would revolve sixteen times as fast vas that in the first stator.

The stators used with the radial beam tubes mayV be 4of conventional design such as those mentioned in my prior Patents Nos.. 2,217,774 and 2,320,756 referred to above. From the foregoing it will be understood that there will be twelve master oscillators, each connected up as shown in Fig. 5. This will require a total of twentyfour stators and twenty-four radial beam vacuum tubes for the tone generating system contemplated herein.

The following brief explanation of the general operation of my tone system contemplated herein will probably be helpful to a full understanding of the invention. The complete system consisting of the twenty-four radial beam tubes may be connected to the keys and stops of the organ in a similar fashion to the connections of the electromechanical generators of the Hammond organ. All twenty-four tubes will be in continuous operation generating the ninety-six separate tones (of the sine-wave form) These ninety-six tones consist of the twelve lowest notes on the organ, plus the first seven harmonics of each. These tones are approximately equal to the eighty-nine frequencies listed in column 9 of Figs. 28 and 28a of the Hammond patent above referred to, plus seven additional higher harmonics. The function of the stops of the organ is to add higher harmonics to the note that is sounded when a key is struck. By varying the selection of the harmonics added, the timbre or quality of the tone is varied, this selection being accomplished by pulling out the different stops. As is well known in the art, any organ tone may be synthesized by adding harmonics of the fundamental tone in varying proportions.

When a key is depressed, the stops having been previously set, the fundamental frequency corresponding to that note is taken from a radial beam tube by the contact under the key and passed on to the amplifiers and finally to the loud-speaker, and, at the same time, other contacts (energized by the stop) under the key add in the preselected group of harmonics so that the note that issues from the loud-speaker` consists of the fundamental frequency plus its selected harmonics.

Also in continuous :operation are the twelve master subharmonic generators furnishing the rotating magnetic fields for the twenty-four radial beam tubes. 'Ihe first submultiple (i. e., onehalf the fundamental frequency) is chosen for the master oscillators since there are two beams in each radial beam tube giving the effect of one beam rotating at twice the frequency.

From the foregoing description of the embodiment of the invention shown in the drawings, it will be seen there is provided a tone generator system utilizing a plurality of radial beam vacuum tubes as the tonev source. It will be obvious that various changes may be made by those skilled in the art in the design of the tube and the circuit organization in which it is incorporated, but it is desired to cover all such changes as come Within the scope of the appended claims.

. I c'laimz' 1. In an electronic circuit organizatiom in combination, a plurality of radial beam vacuum tubes each comprising a cathode and a pluralityof anodes mounted in the cylindrical boundaryiencompassing said cathode and coaxial therewith, means for concentrating electrons emanating from said cathode into a rotating Abeam including coils in quadrature for producing a rotating magnetic field, said field having its lines of force normal to the longitudinal axis of said cathode, a system of master oscillators designed to generate the submultiples of the fundamentals of a musical scale, the circuit arrangement/of each master oscillator being split to produce -two phase currents of the submultiple frequency available for each of the two stators of the several oscillators, two of said radial beam vacuum tubes being included in the two phase circuits of the oscillators, the several anodes being designed to give respective fundamentals and produce harmonics in conjunction with the associated pair of radial beam tubes, the unrolled screen elements of the several radial beam tubes being similar in design but adapted to produce the various frequencies and their harmonics of the musical scale.

2. In an electronic circuit organization, in combination, a pair of radial beam vacuum tubes each comprising a cylindrical indirectly heated cathode surrounded by a coaxial cylindrical screen element, a plurality of spaced ring-shaped anodes encompassing the screen, the screen element having a series of apertures forming bands coaxially arranged with respect to the cathode and oppositely disposed with respect to the several anodes, means for concentrating electrons emanating from said cathode into a rotating beam including coils in quadrature for producing a magnetic field, said magnetic field having its lines of force normal to the longitudinal axis of said cathode, a system of master oscillators designed to generate the submultiples of the fundamentals o-f a musical scale, the circuit arrangement of each master oscillator being split to produce two phase currents lof submultiple frequencies available for ea-ch of the two stators of the several oscillators, the pair of said radial beam vacuum tubes being included in the phase lcircuits of the oscillators, the rotation of the magnetic field of each radial beam tube being continuous, whereby the circuits connected between each anode and the cathode may be closed and opened in sequence, the magnetic field serving both to focus the bea-ms and to direct them to successive or various points on the periphery of the several anodes of each tube, the design of the screen element of each tube being adapted to produce sine-wave currents of the various frequencies of a musical scale by the rotation of the electron beams.

3. An electron discharge device having an evacuated enclosing envelope containing an electrode assembly, said assembly comprising a central elongated electron-emitting cathode, a plurality of individual anodes concentric with relation to the cathode and arranged in spaced tiers extending along the length of the cathode, an electron baille electrode concentric with respect to the cathode and located between the cathode and said anode, said baille having a series of windows arranged in tiers with each tier in radial alignment with one of said anodes, individual lead-ins for said anodes, and a common rotating field producing means for all said anodes for forming the electron from the cathode into a rotating REFERENCES CITED The following references are of record in the le of this patent:

Number UNITED STATES PATENTS Name Date Thompson Mar. 29, 1932 Hammond Apr. 24, 1934 Karolus June 12, 1934 Davis Sept. 8, 1936 Skellett Oct. 15, 1940 Gray Oct. 7, 1941 Stuart, Jr. Aug. 18, 1942 Skellett June 1, 1943 Hecht et al J-an. 1, 1946

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