US1925300A - Electron discharge device - Google Patents

Description

Sept. 5, 1933. V. BUSH ELECTRON DISCHARGE DEVICE Filied NOV. 24. 1922 2 Sheets-Sheet 1 fivenzor:

I UarznvarBas/z Sept. 5, 1933.

v. BUSH 1,925,300

ELECTRON DISCHARGE DEVICE Filed Nov. 24. 1922 2 Sheets-Sheet 2 F 9&1 7 55 L/Hl I x: J H L ULQOMO lhven Z0 r: D0 2172 6220 r 23 as]:

Patented Sept. 5, 1933 PATENT; OFFICE ELECTRON DISCHARGE navrca Vannevar Bush, Medford, Mass., assignor to Raytheon, Inc., Cambridge, Mass., a corporation of Massachusetts Application November 24, 1922 Serial No. 602,97!

7 Claims.

Owing to the high internal drop of the usual type of thermionic tube a relatively high potential between the cathode and anode is equired to .produce a substantial current flow, even though '5 the cathode is heated to incandescence, and the electrons therefore impinge upon the anode with high velocity. Consequently the efliciency of the tube is very low and the anode heats excessively. For'example, to produce a current ofone-tenth 10 ampere a voltage of the order of 200 volts is usually required; and such a voltage causes the electrons to strike the anode with enormous speed. Inasmuch as the energy loss is the productof current and potential drop in the tube it is evident that the loss is high for such small current flow. A thermionic tube requiring a high voltage to drive current through it is relatively inefiicient when employed in a circuit of moderate voltage.

The principal object of the present invention is to produce a copious flow of electrons between electrodes at a low or even zero internal drop and to control such flow for purposes of amplifying or rectifying currents, generating high frequency oscillations, receiving radio messages, converting heat into electrical energy, etc. Other objects are to increase the efiiciency of thermionic tubes and to decrease the heating of the anode.

In one aspect the invention consists in directing the electronic discharge from the cathode to the region of the anode with an electric field substantially independently of the potential difference betweenthe cathode and anode so that little if any potential drop is required between the cathode and anode. The invention also consists in decelerating the electrons as they approach the anode, this preferably being effected with the same electric field employed in impelling the electrons from the cathode. Thus the electric field acts first to accelerate and then to decelerate the electrons, and also to control the course of the electrons.

Apparatus for producing an electronic discharge according to the present invention is characterized by means other than the anode for pro- 45 ducing an electric field adapted both to impel the electrons from the cathode and also to direct the electrons to the region of the anode with little or no potential difference between the cathode and anode. The field producing means prefer- 50 ably comprises at least one primary charged surface for impelling the electrons from the cathode and at least one secondary charged surface for assisting in controlling the course of the electrons, the charged surfaces producing component fields 55 which together form a resultant field adapted to impel and direct the electrons as aforesaid. The arrangement of the charged surfaces is such that the electrons are decelerated as they approach the anode so that the electrons lodge upon the anode with negligible velocity.

In an elementary form my improved tube comprises a cathode, ananode, a charged primary electrode and a charged secondary surface, all in a gas free space. The anode may take any suitable form, as for example that of a block or plate. The primary electrode may be in the form of a wire or plate located between the cathode and anode. Thesecondary electrode preferably comprises a plate located between the primary electrode and the cathode. The tube may also be provided with additional auxiliary electrodes as will appear hereinafter.

For the purpose of illustration typical concrete embodiments of the invention are shown in the accompanying drawings, in which,--

Fig. 1 is a longitudinal section of a thermionic tube according to the present invention, the cathode and anode and other interior electrodes being shown in elevation;

Fig. 2 is a central longitudinal section taken at right angles to that of Fig. 1;

Fig. 3 is a transverse section on line 33 of Fig. 2;

Fig. 4 is a longitudinal central section of a modified tube;

Fig. 5 is a transverse section on line 5-5 of Fig. 4; and

Figs. 6 to 11 are diagrams illustrating typical applications of the invention.

The particular embodiment of the invention shown in Figs. 1, 2 and 3 comprises a glass tube T evacuated to a substantially perfect vacuum, the tube containing a cathode K in the form of an incandescent filament, an anode A in the form of a rectangular plate, a primary electrode P in the form of a wire located between the cathode and anode, a secondary electrode S in the form of a narrow plate or strip located between the cathode and primary electrode, and auxiliary electrodes X in the form of narrow plates or strips located at opposite sides of the cathode K.

As shown in Fig. 2 the cathode and primary electrode are parallel to each other and the anode and secondary electrode are disposed in planes parallel to each other and parallel to the cathode and primary electrode. The various electrodes may be supported in the glass tube in any suitable manner, the leading-in conductors serving as supports in the illustrated embodiment. The cathode may be heated by battery H and the primary electrode P is given a relatively high positive charge through the leading-in conductor 12. The auxiliary electrodes X may be charged through leading-in conductor :0. The leading-in wire s is connected to the secondary electrode S for the purpose of impressing a' charge on this electrode if desired.

With the cathodeK heated to incandescence by battery H and a high positive potential impressed upon primary electrode P current may be caused to flow in the output circuit with little or no potential drop between the cathode and anode, the positive charge on electrode P drawing electrons away from the cathode K and with the assistance of secondary electrode S causing the electrons to travel along paths approximately indicated by broken lines 0 in Fig. 3. If a negative charge is impressed upon secondary electrode S through the leading-in wire s the electrons leaving the cathode are thereby restrained from moxing directly toward the primary electrode P; and if no charge is impressed upon the secondary electrode through the leading-in wire s electrons from the cathode will quickly establish a negative charge on the secondary electrode suflicient to cause the electrons to travel in the curved paths indicated in Fig. 3. After the electrons have progressed far enough to be traveling away from the primary electrode their momentum is relied upon to carry them the rest of the way to the anode. Thus the primary electrode P first accelerates the electrons and subsequently decelerates them as they approach the anode. If the parts are properly co-ordinated and the strength of the field is properly adjusted the electrons may be caused to lodge upon the anode with negligible velocity, the electrons thus being transmitted from the cathode to the anode with little or no potential drop between the cathode and anode and producing little or no heating of the anode by virtue of their deceleration before contact with the anode. The primary electrode P may be assisted in drawing electrons from the cathode by impressing a positive charge upon the auxiliary electrode X, although it is to be understood that this is not necessary. With a tube substantially of the size and shape shown in Figs. 1, 2 and 3 a suitable potential for the primary electrode P is 500 volts, although it will be understood that this will depend upon the purpose for which the tube is being used, etc.

Inasmuch as the electrons travel in curved paths and approach the anode region more or less tangentially to the anode it is sometimes desirable (although not essential especially if the electrostatic field, potentials and electrode spacings are properly co-ordinated) to provide one or more surfaces transverse of the paths of the electrons to intercept the electrons, thereby to prevent the electrons from passing tangentially past the anode. Such a surface is shown in Figs. 2 and 3 in the form of a fin a fast to the anode in its central longitudinal plane.

The embodiment sh in Figs. 4 and 5 comprises an evacuated tube T', a coil filament cathode K, an anode A in the form of a cylinder having an electron receiving surface in the form of a flange at the upper end of the cylinder, a primary electrode P in the form of a small disk above the mouth of the cylindrical anode, and a secondary electrode S in the form of a larger disk between the primary electrode and the cathode. In Fig. 4 the battery for heating the cathode is indicated at H and the battery for impressing high positive potential upon the primary electrode is indicated at B, the output circuit being designated O'-O.

Theoperation of the tube shown in Figs. 4 and 5 is similar to that of the tube shown in Figs. 1, 2 and 3, the cathode K being heated to incandescence and the primary electrode P' being charged with a positive potential suflicient to impel electrons from the cathode to the anode along paths which are approximately indicated by the roken ines 0'. In this tube no auxiliary electrodes corresponding to X in Figs. 1, 2 and 3 are provided and the secondary electrode S is charged negatively by the battery B which charges the primary electrode P positively.

In Fig. 6, which illustrates the application of the invention to a high potential switch, D represents the high potential circuit which may be one of the three phases of a high voltage threephase transmission line, and E two branches in each of which is connected a thermionic tube comprising a cathode K, an anode A, a primary electrode P, and a secondary electrode S, all according to the present invention, the tubes being inserted in the respective branches in reverse sense so that electrons flow from left to right in the upper tube and from right to left 'in the lower tube. The cathodes are heated by batteries H, the heating I circuits being controlled by switches F. With the heating circuits closed and the positive potential impressed upon the primary electrodes P alternate cycles of current flow through the respective tubes. However, when the switches F are opened current is interrupted by the cooling of the cathodes. Inasmuch as the power flowing in the heating circuits is low no arcing results when the switches F are opened to interrupt the flow in the high potential circuit.

By regulating the tubes so that the maximum current flowing therein is less than the satura-' tion current the electrons arrive at the anodes with low speed so that the anodes are heated very little. Since the speed of the electrons depends merely on the net diiference of electrostatic potential between the cathode and anode and since the electrons are impelled from the cathode to the anode with substantially no potential difference therebetween, the tube losses are small and the presence of the tubes in the power circuit is ordinarily without substantial eifect upon the operation of the circuit. For example, if the working potential of the circuit is 110,000 volts the voltage drop across each tube may be of the order of five volts or less.

In Fig. '7, which illustrates the application of the invention to a rectifier system, K designates the cathode, A the anode, P the primary electrode, S the secondary electrode, H the cathode heating battery, B the battery for impressing a high positive potential upon the primary electrode P, G the source of alternating current, J the transformer, L the load which may comprise an electro-plating device and M a condenser across the load L. From the foregoing it will be evident that the positive charge on the primary electrode causes electrons to flow from the cathode to the anode, thereby permitting current to fiow in one direction through the load circuit without permitting current to flow in the reverse direction. The principal advantage of my improved tube in such a circuit, or in any other rectifier circuit in which that the potential drop from the cathode to the anode is always small when the current is flowing, assuming that the load is adjusted so that the maximum, current drawn is less than the In Fig. 8, which illustrates the application of the unilateral conductivity may be made use of, is

the invention to an amplifying circuit, I represents the input circuit, 0 the output circuit, K the cathode, A the anode, P the primary electrode, S the secondary electrode, H the cathode heating battery, B the high potential battery for charging the primary electrode, and B a battery for negatively charging the secondary electrode S. Variation of the potential on the primary and secondary electrodes produced by variations in the current in the input circuit causes a variable current to flow between'the cathode and anode thereby producing a variable current in the output circuit having variations corresponding to those of the current in the input circuit. The secondary electrode S is always maintained negative by the batteries B and B so that it takes no current. A battery Q of low potential may be connected in the cathode-anode circuit to bring the tube to the proper operating point in its characteristic. The potential of battery B should be so adjusted that the current through the tube is somewhat less than saturation current, whereby the variations in the potential of the secondary electrode S will cause wide variations in the current flowing between the cathode and anode. Instead of varying the potential on the secondary electrode the input circuit may be connected to the primary electrode, although this arrangement is not usually desirable on account of the wider variations necessary in the input current in order to obtain the same output current.

Fig. 9 illustrates a circuit connection for utilizing my improved tube for producing high fre-' quency oscillations. In this figure K is the cathode, A the anode, P the primary electrode,

' S the secondary electrode, H the cathode heating battery, B the battery for impressing a high positive potential on the primary electrode, J a coupler, R a condenser and U and U batteries of low potential. Oscillations in the circuit comprising R.- and J produces variations in the potential on the secondary electrode S which varies the current flow between the cathode and anode, and this in turn augments the oscillations in the circuit R.J.

Fig. 10 shows a similar oscillator in which corresponding parts are correspondingly designated, the secondary electrode being connected directly to the oscillation circuit R-J and the coil J being directly connected to the cathode. The advantage of these oscillators resides in their high efiiciency as compared to the ordinary three electrode tube, this higher efiiciency resulting circuit.

One way oi. employing the invention in a radio receiving system is shown in Fig. 11 wherein the cathode K and anode A are connected to the anode.

example, current may be caused to flow -in the output circuit 0 merely by heating the cathode K. While a high positive potential is impressed upon the primary electrode P no energy is drawn from the charging battery inasmuch as no current flows in this electrode.

From the foregoing it will be evident that the present invention afiords a thermionic tube having a very low internal drop and having great versatility.

I claim:

1. An electron discharge device operating without substantial ionization comprising a cathode, an anode, an additional electrode for drawing electrons from the cathode, and electrostatic means for directing the. electrons away from said additional electrode to the region of the anode.

2. An electron discharge device operating without substantial ionization comprising an evacuated vessel containing a cathode, an anode, an electrostatic electrode for impelling electrons from the cathode to the anode, and a shield for restraining the electrons from impinging upon said electrode.

3. An electric discharge device operating without substantial ionization comprising an evacuated vessel containing a cathode, an anode, a primary electrode for impelling-electrons from the cathode and a secondary electrode for directing the electrons to the anode region, said primary and secondary electrodes being offset from the path of electron discharge.

4. An electron discharge device operating with-' out substantial ionization, comprising an evacuated envelope, a cathode and an anode spaced apart therein and means comprising a plurality of spaced additional electrodes for causing the current from the cathode to the anode to be a substantially pure function of the change in potential of one of the electrodes, said means preventing electrons from the cathode from going to any one of said additional electrodes.

5. An electron discharge device operating withan anode, electrostatic electrode means independent of the anode for impelling electrons from said cathode to the anode region along curved paths, said electrode means lying outside said paths, and separate electrostatic means for controlling the flow of electrons from the cathode to the anode. i

6. An electron discharge device operating without substantial ionization comprising a cathode, an anode, an electrostatically charged electrode independent of the anode for impelling electrons from said cathode to the anode region, said impelling electrode having a small surface transverse to the electron flow, so arranged that electrons attracted from the cathode travel beyond said impelling electrodeby virtue of their inertia, and impinge upon said anode, and means for distorting the electron paths so that substantially no electrons impinge upon said impelling electrode.

'7. An electron discharge device operating without substantial ionization comprising a cathode and anode, an electrostatically charged electrode independent of the anode for impelling electrons from said cathode to said anode, and electrostatic means for preventing electrons from impinging on said electrostatic electrode and for controlling the electron flow from said cathode to said VANNEVAR BUSH.

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