US2130191A - Electron discharge device and circuit - Google Patents

Description

Sept. 13, 1938. w. 1.. MEIER 2,130,191

ELECTRON DISCHARGE DEVICE AND CIRCUIT Filed Jan. 25, 1958 INVENTOR. W/LBER L. MEIER ATTORNEY.

Patented Sept. 13, 1938 UNITED S 'l'ATES PATENT OFFICE,

ELECTRON DISCHARGE DEVICE AND CIRCUIT Wilber L. Meier, North Arlington, N. 1., a-ignor,

assignmen bymesne ts,iolladlo0orporation oi America, a corporation of Delaware Application January :5, 1938, Serial No. 186,789

5 Claims.

My invention relates to devices for amplifying direct currents and using electron discharge tubes having a gaseous atmosphere and capable of being continuously controlled.

The present application is a continuation in part oi my copending application, Serial No. 133,300, filed March 2'1, 1937 and assigned to the same assignee as the present invention.

In the conventional grid controlled vacuum.

tubes provided with a thermionic cathode, control grid and anode, the space charge which builds up around the cathode makes necessary the use of comparatively high voltages, such as volts or more, for obtaining current sumciently large for practical purposes. It is also Qnecessaryto use comparatively large grid voltage swings to produce usable variations in the output of the tube. Thus, in the. conventional high vacuum tubes comparatively large transconductances are not easily obtainable nor can large anode currents be'obtained with small anode voltages. It has been recognized that by introducing a gas in a tube and ionizing the gas the space charge around the cathode could be neutralized and thus large anode currents obtained with the usual anode voltages. However, in the conventional grid controlled tube containing gas, ionization of the gas causes the control grid to lose its control of the electron stream so that while initiation of ionization can be controlled the current cannot be controlled by the control electrode after ionization takes place. Furthermore, in these types of tubes comparatively high voltages, much above ionization voltages, are applied between the anode and cathode to cause a gas discharge between the anode and the cathode. Thus while comparatively high currents can be obtained the loss of grid control and the necessity for high anode-cathode voltages limits the application of this type of tube and prevents its use in conventional radio circuits.

It is the principal object of my invention to provide a device particularly suitable as a direct current amplifier and utilizing an improved electron discharge device of the continuously controlled gas type depending upon gas ionization for operation and described and claimed in my copending application identified above.

The tube described in my copending application above identified has an envelope containing the electrodes immersed in a gas at a low pressure. The space between the cathode and the anode is ionized to neutralize the space charge and thus make available a large number of electrons. Only a very small voltage of the order of 6 volts, for example, which is considerably below ionizing voltage may be applied between the anode and cathode to obtain a comparatively large anode current. The flow of electrons from the cathode to the anode can then be continuously controlled by an electrode to which may be applied comparatively small voltage swings inasmuch as there is no gas discharge between the main cathode and the anode. To produce the ionization of the gas between the cathode and anode an auxiliary cathode may be employed. A discharge is established between this auxiliary cathode and anode electrode, the electrode being so positioned that the space between the main cathode and the anode is in the path of the auxiliary discharge initiated between the auxiliary cathode and its cooperating electrode.

In the tube described in the above identified ccpending application there'is mounted within an envelope containing gas at low pressure, a straight indirectly heatedcathode surrounded by a cylindrical anode closed at both ends. An aperture, preferably covered by a mesh material, is provided at one end of the anode. Registering with this aperture are a control grid and an aux iliary cathode for supplying the electrons within the anode to ionize the gas between the main cathode and the anode. The auxiliary cathode, grid and the aperture covered by mesh material are all spaced less than the mean free path of electrons in the gas so that no ionization takes place between these electrodes. This arrangement permits continuous grid control oi! the ionization within the main anode. A voltage less than that required to produce ionization is applied between the main cathode and the main anode. A voltage sumciently high to cause the electrons to have a great enough velocity in entering the space between the main cathode and the main anode is applied between the auxiliary cathode and the main anode, the control voltage being applied through an input circuit to the control grid.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a vertical section in perspective of an electron discharge device of the type described above, Figure 2 is a section along 22 of Figure 1 showing details of construction, and Figure 3 is a diagrammatic showing of a direct current amplifier arrangement made according to my invention and using a tube of the kind shown in Figure 1.

The tube shown in Figure 1 includes an envelope I containing a gas at low pressure for example between 150-600 microns pressure. Helium at pressures between 250 and 300 microns is very satisfactory. A stem II supports the electrode mount assembly within the envelope. The electrode mount assembly comprises an indirectly heated cathode I2 enclosed within a cylindrical anode I3 provided with a screen covered aperture I4 and closed ends I5 and I6. Aperture I4 is to provide a gas communication between the interior of the anode and the inside of the envelope. The cathode I2 is insulatingly supported from the upper closed end I6 of the anode by means of the insulating bushing II. The lower end I5 is provided with an aperture I! covered with foraminous or mesh material I8, the shape of this aperture being best shown in Figure 2. The cathode I2 and anode I3 are the main discharge electrodes between which the output current passes.

In order to neutralize the space charge around the cathode I2 during operation of the tube I provide an auxiliary electrode system comprising an indirectly heated cathode and grid in registry with the aperture I8 to project electrons from the auxiliary cathode into the space surrounding the cathode I2.

This electrode system comprises an indirectly heated auxiliary cathode I9 supported and electrically connected to the metal disc 20. Insulatingly separated from the disc by means of an insulating disc member 2| having an aperture 22, in which the cathode I9 is positioned, is a grid comprising a metallic disc member 23 having an aperture 24 covered with a mesh material 24', this aperture being in registry with the aperture I8 in the lower end of the anode. This grid is insulatingly separated from the anode by means of the insulating disc 25 having an aperture 26 in registry with the aperture I8. This whole mount assembly is supported from the stem II by means of the supports and leads 21, 28 and 29 connected respectively to the cathode disc, grid disc and anode. The main cathode I2 is provided with a lead 30.

In operation a low voltage less than that required for maintaining ionization is applied between the main cathode I2 and anode I3 so that a gas discharge cannot take place between these electrodes. Voltages are applied between the auxiliary cathode I9 and the anode I 3, which are high enough to cause electrons from the cathode to be projected through the aligned apertures into' the space around the cathode I2 with sufiicient velocity to ionize the gas and thus neutralize the space charge. The grid 23 may have applied to it a control voltage which will control the flow of electrons from the auxiliary cathode I5 into thespace surrounding the main cathode I2 to thereby control the ionization and hence the current from cathode I2 to anode I3.

According to my invention I provide a D. C. amplifier comprising a self-excited oscillating circuit which can be used to provide a high voltage D. C. output source from a low voltage D. C. source. In Figure 3 the cathode I2 is connected through the low voltage D. C. source or battery 40 to one side of the inductance 4|, the other side of which is connected through an output resistor 42 to the auxiliary cathode IS. The

voltage obtained from battery 40 is less than that required to maintain ionization between cathode I2 and anode I3. An intermediate point of the inductance 4| is connected by means of conductor 43 to the anode I3. The grid 23 may be connected to the cathode. A condenser 44 connected across a part of the inductance 4I furnishes with the inductance 4| an oscillating circuit. The output resistor 42 is shunted by av filter condenser 45. In order to start oscillations a resistance 46 and switch '41 is provided.

To shock the system'into operation switch 41 is momentarily closed causing a flow of current through the right hand portion of inductance H, which in turn induces a voltage across the left hand portion of inductance 4| and condenser 44. The resistance 46 may have any suitable value for limiting the current to a desired amount. This voltage which is stepped up by proper ratio of turns of the two portions of inductances 4| acting as an auto transformer is applied between the cathode I9 and the anode I3 and causes electrons to discharge into the space surrounding the cathode I2 causing ionization which neutralizes the space charge thereby permitting a large flow of current between the cathode I2 and anode I3. This current flowing through the right hand portion of the inductance 4| again feeds back energy to the left hand portion producing a regenerative action so that the system is maintained in oscillation. Due to the rectifying action between the cathode I9 and anode I8, rectified voltages appear across the output resistance 42, the condenser acting as a filter so that substantially uniform D. C. voltage appears across this output circuit comprising resistor 42 and condenser 45. By proper circuit constants a step-up voltage can be provided across the D. C. output terminals.

While I have indicated the preferred embodiment of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device having an en velope containing a gas, a thermionic cathode within said envelope for emitting electrons, an anode for receiving electrons from said cathode and means for ionizing the space between the thermionic cathode and the anode and including an auxiliary cathode for providing an electron discharge in the space between the thermionic cathode and anode, an inductance, and a source of voltage less than that required for producing ionization between said thermionic cathode and anode and connected between the thermionic cathode and one side of said inductance, and a load connected between the other side of said inductance and the auxiliary cathode, and a. connection between the anode and an intermediate point on said inductance.

2. An electron discharge device having an envelope containing a gas, a thermionic cathode within said envelope and an anode spaced from said cathode, and an auxiliary cathode for providing an electron discharge between the thermionic cathode and anode to ionize the space between the thermionic cathode and anode, an inductance and a source of voltage less than that required to produce ionization between the thermionic cathode and anode connected between the thermionic cathode and anode, a second inductance and a resistor connected between the anode and the auxiliary cathode, said inductances being so positioned that current flowing in the inductance connected between the anode and the thermionic cathode will induce a voltage in the inductance connected between the anode and the auxiliary cathode.

3. An electron discharge device having an envelope containing a gas, a thermionic cathode within said envelope for emitting electrons, a hollow anode surrounding said thermionic cathode for enclosing the space between said thermionic cathode and the anode, and means for ionizing the space between the thermionic cathode and anode and including an auxiliary cathode, an inductance, a source of voltage connected between one end of said-inductance and said thermionic cathode, said source of voltage being less than that required to produce ionization between the thermionic cathode and anode, a resistor connected between the auxiliary cathode and the other end of said inductance, and a connection between the anode and an intermediate point on said inductance, and a condenser connected between the intermediate point on said inductance and the end of said inductance connected to said resistor.

4. An electron discharge device having an envelope containing a gas, a thermionic cathode within said envelope for emitting electrons, a hollow anode surrounding said thermionic cathode for enclosing the space between said thermionic cathode and the anode, and means for ionizing the space between the thermionic cathode and anode and including an auxiliary cathode and an inductance, a source 01' voltage connected between one end of said inductance and said thermionic cathode, said source of voltage being less than that required to produce ionization between the thermionic cathode and anode, a resistor connected between the auxiliary cathode and the other end of said inductance, and a connection between the anode and an intermediate point on said inductance, and a condenser connected between the intermediate point on said inductance and the end of said inductance connected to said resistor, and a resistor and a switch connected between the anode and the thermionic cathode.

5. An electron discharge device comprising an envelope containing a gas, a thermionic cathode within said envelope, a hollow anode surrounding said thermionic cathode to enclose the space between said thermionic cathode and said anode and having an aperture provided in said hollow anode, an auxiliary cathode positioned in registry with said aperture for supplying an electron discharge between the thermionic cathode and anode to ionize the gas between said thermionic cathode and anode, an inductance, a source of voltage vonnected between one end of said inductance and said thermionic cathode and said source of voltage being less than that required to produce ionization between the thermionic cathode and anode, a resistor connected between the other end of said inductance and said auxiliary cathode, and a condenser connected across said resistor, a connection between an intermediate point on said inductance and said anode, and a condenser connected between said intermediate point and between the resistor and the end of saidlnductance, and a switch and a resistor connected between the anode and the thermionic cathode.

W'ILBER L. MEIER.

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