US2301980A - Metallic-vapor discharge device - Google Patents

Description

Patented Nov. 17, 1942 METALL IC-VAPOR DISCHARGE DEVICE Max Steenbeck, Berlin-Siemensstadt, Germany; vestcd in the Alien Property Custodian Application August 20, 1940, Serial No.`35 3,33 6 In Germany July 6, 1939 V 7 Claims. (Cl. 250-275) This invention relates to gaseous electrical discharge devices, particularly for operation at high voltages. It is known to provide the discharge vessel oi' such devices with inserts which are arranged in the discharge path and impressed with a voltage lying between the anode and cathode voltages. The inserts consist of annular members which create an electric field between every two adjacent inserts such as substantialiy occurs between concentric spherical shells.

The inserts in such a metallic-vapor discharge device reduce back fires to a `considerable extent, since the ions are deflected in the non-conducting period towards particular re-combnation surfaces by the electric field produced by the inserts,

so that a fresh formation of ions due to impact.

ionization is substantially avoided. However, the known arrangements often present the drawback that the inserts incur a considerable increase of the arc drop voltage. It is true that in discharge devices operated at high vcltages the losses caused by the increase of the are drop voltage are not appreciable as regards the emciency of the device. However, these losses cause a considerable development of heat which is dificult to dissipate in discharge devices for high current intensities.

The object of the present invention is to provide a discharge device with annular inserts between the anode and cathode, in which only a small arc drop voltage is required, while retaining the protection against back fires. This is accomplished, according to the invention by providing composite annular members whose inner portions have their surfaces inclined with respect to the discharge path to a greater degree than the outer portions. In this manner an increased number of ions impinge-upon the surfaces of the annular members during the non-conducting period. By the use of such inserts a considerable de-iom'zation of the ions is attained in the nonconducting period, in which the ions follow the radially directed field, whereas in the conductng period the ions may reach the electrodes Without hindrance, since the control efiect of the' inserts is rendered ineifective by the plasma of the discharge. The central member is designed preferably in the shape of a bowl so as to also prevent the ions from fiowing along the central axis.

Further details will be apparent from the description of an embodiment of the' invention illustrated in the accompanying drawing in which Fig. 1 shows diagrammatically a longitudinal section through a discharge tube, Fig. 2 part of another embodiment, and Fig. 3 a portion of the rectifier tube of Fig. 2 on a larger scale.

Referring to Fig. 1, l is the discharge vessel, for instance of ceramic material, [0 a mercury cathode from which an auxiliary arc passes to an auxiliary anode ll, |2 is the main' anode, l'l an alternating current source, and |8 a currentconsuming apparatus to be fed from sourcell through the rectifying discharge device. Two control grids l3 and !4 are arranged within a metallic shield !9 and connected with a direct current source IE supplyingta positive bias to grid a, and with a control set l5 supplying grid M with an alternating grid voltage. As iaras described above, the arrangement issimlar to the one more fully disclosed in my Patent No. 2,205,230, and merely incidental to the present invention proper. According to the 'present invention, the tube shown in Fig. 1 is provided with a set of composite inserts 2 which will be described in the following with reference to Fig. 3. Fig. 2 shows a similar arrangement except that the inserts 2 are arranged in an inverted position.

As apparent from Fig. 3, each of the inserts is composed of annular members 3, 4, 5 and 6 and of a bowl-shaped central member 1. The individual members forming an insert are secured together by means of insulatng bridgng members. During the non-conducting period an electric field is produced between two adjacent inserts substantially as occurring between two concentric spherical shells. The lines of force of each field run substantially as indicated by the dash lines 8. The surfaces of the individual members.

forming the inserts are somewhat inclined to the axis of the vessel so that in the non-conducting period the greatest possible number of ions followingthe electric field of the inserts are intercepted by the surfaces of the inserts, whereas in the conducting period this control action of the inserts is rendered ineffective by the predominant effect of the main discharge between the main anode and cathode.

The annular members 4, 5 and 6 have preferably 'such a height that the `lines of force 8 coming from the center of the spherical field cannot freely pass through an insert. The intercepting surfaces of the insert overlap one another to a slight extent as regards these radial lines of force. It is also possible to prevent an undue amount of heat from being developed in the central portions of the inserts. To this end, it is only necessary to make the passages between the inner members of each insert member longer than the passages'ofiered to the 'discharge between the' outer members of each composite insert. As a result, the discharge current, when passing through an insert, is throttled near the inner members as compared with the portion of the discharge current passing between the outer tral portions is not unduly prevented. Particular attention must further be directed to the design of the outer members 3 of the inserts, to prevent the formation of discharges between the parts 3 and the wall l of the vessel. To this end, the member 3 extends rather closely to the wall I and is considerably longer in the direction of the discharge path than the other insert members. In the discharge device shown in Fig. l, the sheld !9 forms part of the outer member 3 of one of the inserts 2.

Since the inserts are non-symmetrically designed With respect to opposite discharge directions, they may, to a certain degree, effect a valve action. For this reason the inserts are positioned in rectifiers with respect to the cathode and anode preferably in a difierert manner than in inverted -converter, i. e. the inserts are preferably inverted as exemplied by Figs. 1 and 2.

What is claimed is:

1. A uniaterally-conducting gaseous electrical discharge device having a :cathode and an anode forming the electrodes of a discharge path, and conductive inserts arranged coaxial and transverse to said discharge path to assume voltages between the cathode and anode voltages, said inserts consisting each of a composite structure comprising a plurality of concentric annular members spaced radially from one another, each of said members having a surface inclined With respect to said discharge path, the inclination of the surfaces of the inner members of the insert structure being greater than the inclination of the surfaces of the outer members of the insert structure.

2. A unilaterally-conducting gaseous electrcal discharge device having a cathode and an anode forming the electrodes of a discharge path, and conductive inserts arranged coaxial and trans- Verse to said discharge path to assume voltages between the cathode and anode voltages, said inserts consisting each of a composite structure composed of a plurality of concentric annular members spaced radially from each other and arranged so that the insert structure has in general a curved shape following the general curvature of the adjacent insert structure so as to produce an electric field substantially such as occurrng between concentric spherical shells, each of said members having a surface inclined towards said discharge path, the inclination of the surfaces of the inner members of the insert structure being greater than the inclination of the surfaces of the outer members of the insert structure.

3. A unilaterally-conducting gaseous electrical discharge device having a cathode and an anode orming the electrodes of a discharge path, and

conductive inserts arranged coaxial and trans-' verse to said discharge path to assume voltages between the cathode and anode voltages, said inserts consisting of a composite structure composed of a central cup-shaped member and annular members concentrically surrounding said central member, said members having surfaces inclined towards the axis of the structure, the inclination of the surfaces of the inner members of the insert structure being greater than the inclination of the surfaces of the outer members of the insert structure.

4. A unilaterally-conducting gaseous electrical discharge device having a cathode and an anode forming the electrodes of a discharge path, and conductive inserts arranged coaxial and tranuverse to said discharge path to assume voltages between the cathode and anode voltages, said inserts consisting each of a composite structure comprising a plurality of concentric annular members spaced radially from one another and having inclined surfaces as regards the axis of the discharge path, the inclination of the surfaces of the inner members of the insert structure being greater than the inclination of the 'surfaces of the outer members of the insert structure, said members'of each insert structure being arranged in staggered relationship and overlapping one another so that the substantially radal lines of force of the electric field established between adjacent insert structures during the non-conductive period and extending from one insert structure towards the adjacent insert structure are preverted from extending through the anrular gaps between the members of said adjacent structure.

5. A unilaterally conducting gaseous electrical discharge device having a cathode and an anode forming the electrodes of a discharge path, and' conductive inserts arranged coaxial and transverse to said discharge path to assume voltages between the cathode and anode voltages, said in-- serts consisting each of a composite structure comprising a plurality of concentric annular members spaced radially from one another and having inclined surfaces as regards the axis of the discharge path, the inclination of the surfaces of the inner members of the insert structure being greater than the inclination of the surfaces of the outer members of the insert structure, said members of each insert structure being arranged in staggered relationship and overlapping one another in a degree increasing from the outer towards the inner members of the structure 'so that the interstitial annular passages for the discharge are longer between inner insert members than between outer insert members.

6. A unilaterally-conducting gaseous electrical discharge device having a cathode and an anode forming the electrodes of a discharge path, and conductive inserts arranged coaxial and transverse to said discharge path to assume voltages between the cathode and anode voltages, said inserts consisting each of a composite structure comprising a plurality of concentric annular members spaced radially from one another and having inclined surfaces as regards the axis of the discharge path, the inclination of the surfaces of the inner members of the insert structure being greater than the inclination of the surfaces of the outer members of the insert structure, said members of each insert structure being arranged in stepped relationship, each inner insert projecting from the adjacent outer insert to permit heat dissipation by radiation from the inner inserts.

7. A unilaterally-conducting gaseous electrical discharge device having a cathode and an anode forming the electrodes of a discharge path, and conductive inserts arranged coaxial and trans- Verse to said discharge path to assume voltages between the cathode and anode voltages, said inserts consisting each of a composite structure comprising a, plurality of concentric annuiar members spaced radally from one another and having surfaces inclined towards the axs of the discharge path, said members of each insert structure overlapping one another so that the lines of force of the electric field established between adjacent insert structures during the nonconductive period and extending from one insert structure toward-is the adjacent insert structure are prevented from extending through the annular gaps between the members of said adiacent structure, the extent of the overlapping of said members increasing from the cuter towards the inner members of the structure so that the interstitial annular passages for the discharge are longer between inner insert members than between outer insert members.

MAX STEENBECK.

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