US1917739A - Electric discharge device - Google Patents

Description

Patented July 11, 1933 UNITED STATES D'PATENT OFFICE mrz OI BERLIN, 63m, ASS 161103 TO GESELLSOHAI'I. FUR DIR-Am LOSE TELEGRAPH! I. B. 3., OF BERLIN, GED-IA, A CORPORATION 01' GM ELECTRIC DISCHARGE DEVICE Application fled Iarch 18, 1881, Serial li'o. 522,869, and in Germany Iamh 7, 1980.

This invention relates to electric discharge devices, and more particularly to devices which are capable of operating as relays, amplifiers, and for anala ous purposes, and in which the discharge ta es place in a rarified gaseous atmosphere.

The principal object of this invetnion is to provide an improved discharge tube of the type having a control electrode and in which the source of electrons is a permanentl maintained unassisted glow-discharge iusi e a rarified gas atmosphere consisting chiefly of a rare gas, such as helium, neon, or argon but primarily the former. The principle underlyin these discharge tubes is well known.

Anot er object of the invention is to provide such tubes, which, although of limited dimensions, furnish a comparatively copious supply of electrons with a low drop of potential in the glow discharge, and which furthermore are of simple construction. The control electrode of the tube is preferably the external type well known in the prior art and may be in the form of a conductive coating on the glass wall of the tube.

According to the invention, the cathode which constitutes the primary source of the electrons is tubular or hollow and the glow discharge occurs in the interior of this hollow and more or less closed electrode, the electrons coming off from the inside walls of the electrode. As such a cathode furnishes high current densities with a relatively low dro of potential, high electron currents are ava' able for the amplifier function of the tube, while at the same time the maximum velocities of the electrons to be controlled electrostatically are low compared with those in a high vacuum tube, with the further incidental results that the harmful grid current is also low. If the cathode drop within the interior of the cathode is to be made especiall low, markedly electro-positive metals, suc as alkali or alkaline earth metals, may be introduced into the hollow cathode.

For a better understanding of the invention, reference may be made to the accompanying drawing, which shows examples of embodiments of the invention, and in which Fig. 1 and Fig. 2 are Views, partly in longitudinal section, of two examples of tubes constructed in accordance with thelinvention.

The devices shown in both Fi 1 and Fig. 2 comprise a sealed bulb, enve ope, or discharge vessel 1 of cylindrical shape having a circular or sli htly elliptic cross-sectional shape, an ampli er or main anode 5, a hollow cathode 8 also cylindrical and concentric with the bulb to leave an annular space between it and the bulb walls and an auxiliary anode 9 adapted and connected to maintain between it and the cathode 8 an unassisted glow discharge which constitutes the primary source of electrons. 10 denotes the control electrode upon the outside of the tube. to

p which the voltage variations to be amplified are fed. 11 is the tip left on the bulb when it is sealed oil from the pump. 7

In the particular embodiment shown in Fig. 1 all of the internal electrodes are supported upon a stem having one press 2. The hollow cathode 8 comprises an upwardly extending cylinder or cup which is 0 en at the upper end, and is supplied wit current through the central lead in wire sealed into the press 2. This cathode 8 is preferably surrounded by an insulatin sleeve or sheath 6 which may for example, ie made of glass, porcelain, quartz, steatite, magnesia, or the like. The insulatin sheath 6 may have a tubular bottom end which is smaller than the body of the sheath, or is tapered, and which may be set over an insulating or glass tube which is fused or welded to the press 2 to project from the press and position the cathode and thru which the central lead wire extends to the cathode. The auxiliary anode 9 for the low discharge is preferably perforated or as openings to allow the electrons in the glow discharge in the cathode to pass out into the vessel. In the example shown in Fig. 1 the auxiliary anode 9 has the shape of a sort of cap over the open end of the oathode and fitted upon the insulating sleeve 6; and it is held in place by the aid of the current-suppl wire 3. The amplifier anode 5 is on the s eeve 6 below and remote from the open end of the cathode as compared with the auxiliary anode and ma be in the form of a sheet metal ring or o a drawn metal cap fitted over the sleeve 6 near the bottom pndl and is connected with the current supply The preparation of the tube so far as exhaustion and the selection of the electrode materials is concerned, is in accordance with modern principles known in the tube, building art. After exhaustion and degassing of the internal parts, the discharge vessel or bulb is filled with a rare gas or a mixture thereof at a pressure suitable for a glow discharge in the cathode and is then disconnected from the pump. l or practical operation and use a glow discharge is maintained between the primary electron source or hollow cathode 8 and the anode 9, thru which the electrons emerge from the cathode 8 and which constitutes a sort of secondary cathode in reference to the amplifier portion of the tube. Because the cathode 8 is hollow it maintains a low discharge of high current density and hence in a relatively reduced space or volume there is a copious supply of electrons of not unduly high velocity. The electrons are retarded to some extent when passin thru the auxiliary anode 9, and further y impacting with the gas molecules in the space above the auxiliary anode 9, hence they produce a cloud of comparatively slow moving electrons (space charge). These electrons are the source of supply for the amplifier circuit, and by the application of a potential to the main or amplifier anode 5, which is positive with reference to the auxiliary electrode 9, the electrons can be attracted towards the main anode 5. Now, as these electrons flow down beneath the internal structural parts and the wall of the tube, thru the annuar space or shell between those parts and the bulb wall, they are subjected to the controlling action of the external control electrodes 10. The plate reaction (reciprocal of the amplification factor) is adjusted by the suitable selection and dimensioning of the control electrode 10 with reference to the internal proportions of the tube.

Fig. 2 shows another and particularly simple embodiment of the invention. This embodiment is based u on the fact that, in the presence of a suitable gas pressure and suitable width or diameter of the bulb or discharge vessel, the cathodic glow-layer exhibits a tendency to spread out only upon the inside of the cylindrical hollow cathode 8 (effect of hollow Paschen cathode). Hence, electrode 8 need not specially be insulated upon its inside, though for the purpose of insuring enhanced safety, an insulating layer could be provided. The auxiliary anode 9 is a fiat imperforate disc and serves to shield the amplifier anode 5 from the electrons as they issue from the outlet end of cathode 9, so that the electrons are prevented from flying out of the open end of the cathode 8 ence only a low cathode drop,

directly into the space in which the amplifying effect is obtained. The amplifier or main anode 5 has likewise referably the form of a plate or disc or 0? an elongated sheet which, as shown, is welded onto the end of the current sup ly lead. Over the current suppl lead a tu ular insulator 12 is slipped in or er to prevent direct passage of the discharge between the main anode sup ly lead and the cathode 8. It is prefera 1e, particularly if the tube is of elliptical shape in cross section, to fix and maintain the supporting or anchor wires and the internal electrodes in the proper relative position to one another by means of a glass bridge piece or strut 13, the leads being hermetically sealed in a well known manner into a press 14.

Also in the embodiment shown in Fig. 2 there is obtained a copious supply of electrons which are not of unduly high velocity by virtue of the effect of such a hollow cathode. The required potential for the auxiliary discharge between the auxiliary anode 9 and the cathode 8 is diminished, and this is of practical advantage for tubes supplied from the usual supply circuits, especially when looked at from the viewpointof the means needed for smoothing the auxiliary current and thereby eliminating the alternating current hum. The proper control action of the external electrode 10 depends in turn upon its position and the dimensions of the electrodes in relation to one another.

I claim:

1. An electrical discharge device comprising a sealed cylindrical envelope containing a rarified gas, a hollow cylindrical cathode mounted in and concentric with said envelope, a tubular insulator on the outer walls of said cathode, an auxiliary anode mounted on said insulator adjacent the open end of said cathode, a main anode mounted on said insulator remote from the open end of said cathode, and a control electrode surrounding said insulator to produce in the annular space between said tubular insulator and the walls of said envelope an electro-static field to effect an electron stream flowing between said cathode and said main anode thru said annular space.

2. An electrical discharge device comprising a sealed cylindrical envelope containing a rarified gas, a hollow cylindrical cathode open at one end only and mounted in and concentric with said envelope, insulation on the outer walls of said cathode, an auxiliary anode mounted on said insulation to be adjacent the open end of said cathode, a main anode mounted on said insulation near the closed end of said cathode, and a control electrode mounted on the outside of said envelope to encircle said cathode and produce a field between the open end of said cathode and said main anode to affect an electron stream flowing between said cathode and said main anode thru the annular space between said tubular insulator and the walls of said envelope.

3. An electrical discharge device comprising a sealed cylindrical bulb containing a rarified gas, a cup shaped cathode mounted in and concentric with said bulb with its open end directed toward one end of said bulb, a perforated auxiliary anode mounted in front of and adjacent said open end of said cup shaped cathode, an annular main anode mounted to encircle said cathode between the other end of said bulb and the open end of said cathode in position to cause the electron stream from said cathode thru said auxiliary anode to fiow back along and outside of said cathode to said main anode thru the annular space between said cathode and the walls of said bulb, and a control electrode positioned to produce an electro-static field in said annular space.

4. An electrical discharge device comprising a sealed cylindrical bulb containing a rarified gas, a tubular cylindrical insulating sheath open at one end only and mounted in and concentric with said envelope, a cathode inside said insulating sheath, a n auxiliary anode mounted adjacentthe open end of said tubular sheath, an annular main anode mounted near and concentric with the closed end of said sheath, and a control electrode surrounding and coaxial with said sheath and between its ends to afiect a stream of electrons flowing between said cathode and said main anode thru the annular space between said tubular sheath and the walls of said envelope.

5. An electrical discharge device comprising a sealed cylindrical envelope containing a rarified gas and enclosing a hollow cylindrical cup cathode concentric with said envelope, an auxiliary anode positioned adjacent the open end of said cup cathode to maintain a glow discharge in said cathode, a main anode mounted outside of and near the bottom of said cup cathode to cause an electron stream flowing between said cathode and said main anode to flow thru the annular space between said cathode and the walls of said bulb, and an external control electrode positioned on the walls of said bulb to afiect said stream.

FRITZ scEaoTER.

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