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July?, 1937. ’ ' H.' |_. VAN DER HORST GRID CONTROLLED DISCHARGE TUBE Filed June V15, 1936 By /% 2,086,057" Patented July 6’, 1937 2,086,057 UNITED STATES PATENT OFFICE 2,086,057 .. GRID CONTROLLED DISCHARGE TUBE Hajo Lorens van der Horst, Eindhoven, Nether lands, assigno-r to N. V. Philips’ Glceilampen fabrieken, Eindhoven, Netherlands Application June 15, 1936, Serial No. 85,413 . ' ' In Germany July 19, 1935 _ > 5 Claims. (Cl. 250-275) My invention relates to grid-controlled dis-_ tube having a plurality of control grid members charge tubes and more particularly to incan whose corresponding ignition characteristic descible-cathode ionic relay tubes having a plu curves are identical. 5 rality of control grids. By the term “ionic relay tubes” as used herein is meant grid-controlled recti?er tubes having a gaseous ?lling comprising one or more gases, vapors, or a mixture thereof. Such tubes, which are used in relay circuits and also as current con 10 verters of different kinds, for instance, recti?ers, frequency-changers, and inverters, do not as a rule operate continuously, and the anode current is not established until after the anode'igniting voltage-which is governed by the grid poten 15 tial-has been reached. Furthermore, as the grid does not recover its blocking e?ect until after the anode current has become zero and the discharge path has become deionized, the origi— 2 o. 2 nally-established anode current cannot be con tinuously biased as is done with a high-vacuum triode. When an ionic relay tube is provided with a plurality of control grids there is considerable di?iculty in securing for all the grids the same ignition characteristic curves, i. e. anode ignition voltage-grid potential curve. This is because in both types of grid constructions now used, one grid is arranged nearer the anode than are the remaining grids, i. e. the grids are arranged either ’ successively in the discharge path or concentri cally with the larger grids surrounding the smaller ones. Although it has been proposed to overcome this di?iculty by symmetrically arranging a plurality of equally-dimensioned grid members in an equi potential surface of the electrostatic ?eld set up between the anode and the cathode, such con In accordance with my invention, I provide be-' tween the anode and cathode a grid structure comprising a plurality of equally-dimensioned grid members arranged symmetrically to the axis of the electrostatic ?eld set up between the anode and cathode and comprising portions traversing Y the discharge space between cathode and anode 1d . in an equipotential surface of said ?eld so as to form a single aperture arranged symmetrically with said axis and serving as the only passage for the discharge. ‘ . . In one embcdimentof my invention, the grid . structure has the form of a cylindrical box sur rounding the cathode and comprising a plurality of sector-shaped mutually-insulated grid mem bers spaced apart to form radial slots serving as ,- y the arrange onlythe passage box-like for grid the structure discharge.symmetrically I prefer to N). to the cathode and axially of the tube, and to locate the anode centrally with and immediately above this structure. To prevent starting of the tube at the normal anode voltages,‘ I make the radial slots of su?iciently small width, whereas I 5 provide in the structure opposite the anode a cen tral aperture symmetrically circumscribed by the grid members and controlling by its area the ig nition characteristic curves of the tube. In order that my invention may be clearly un 30 derstood and readily carried into effect I shall describe same more fully by way of example, with reference to the accompanying drawing, in which: ‘ Figure 1 is a partly sectionized side view of an 35 structions provide very irregular ignition. This ionic relay tube according to the invention, and is due to the fact that the grid members, sim 2-4 of Fig. 1. 40 ilarly to a tubular grid, delimit a plurality of con trol apertures and thus do not insure a uniform control. In both types of grid constructions, the igni iion characteristic curves for the various grids, clue to discrepancies in the electrostatic condi tions, will not be exactly the same. Such con structions are unsuited for those applications in which it is essential that the ignition character istic curve of all the grids be exactly the same, for example, in circuit arrangements in which two grids must alternately perform the same function, or in which a relay tube must be biased in an identical manner from two di?erent sides. The object of my invention is to overcome the above draw-backs and to provide an ionic relay 5 Figure 2 is a sectionized View taken along line ' The ionic relay tube shown in the drawing comprises an envelope I having at its bottom a reentrant portion forming a press 2 and contain ing a gaseous ?lling, for instance argon at a r ' pressure of 0.5 mm. Supported from press 2 by lead-supports 3 and 4 is an incandescible cathode. gs 5. Centrally disposed above the cathode 5 and 5 supported from press 2 by means of a lead-sup port l4 provided with one insulating sleeve [6 is a disc-shaped anode 9. . Between the anode 9 and cathode 5 is a box like grid structure 20' comprising two-sector shaped grid members 6 and ‘I supported from press 2 by means of support-leads l2 and I3 re spectively, and forming a single aperture in the shape of a radial slot I0 (see Fig. 2) lying in an 55 2,086,057 2 equipotential surface of the electrostatic ?eld set up between the cathode 5 and anode 9. The slot II] is given a sufficiently small width to prevent the discharge from passing therethrough at the nor mal anode voltage. The bottom of structure 20 is closed by a screen i5 of insulating material supported from lead supports 3 and 4, whereas the lower edges of the grid members 6 and 1, and the screen 8 are protected from the discharge by 10 a cup-shaped member 15 of mica supported from support 3. ' Arranged centrally with respect to the anode 9 and formed half by grid member 6 and half by grid member ‘I is an aperture H which permits the discharge to pass to the anode and whose cross-sectional area governs the ignition char acteristic curves of the tube. Due to the symmetrical arrangement and identical shape of the grid members 6 and ‘I, the 20 ignition characteristic curves of the tubes com prising two grids agree to a marked extent. I have found, that when the slot H! was given a width of about 0.25 mm. it was impossible to initiate starting of the tube at a normal anode 25 alternating voltage of about 170 volts and that it was necessary to give the central aperture H a diameter of about 5 mm. to enable normal oper ation of the tube at this anode alternating volt age and with a gas ?lling of argon at a pressure 30 of 0.5 mm. of mercury. ‘ While I have described my invention in connec anode and cathode and comprising a plurality of mutually-insulated identical grid members de limiting said discharge path along a curve lying substantially within an equipotential surface of the electrostatic ?eld set up between said anode and cathode, and comprising portions forming a single aperture arranged symmetrically to the axis of said ?eld and allowing the passage of a discharge, said members blocking the remainder 10 of the discharge path. 3. An ionic relay tube comprising an envelope, an anode and an incandescible cathode within said envelope and spaced apart to form a dis charge path, and a circular box-like grid struc ture comprising a plurality of mutually insulated sector-shaped grid members forming for the only pasage of the discharge a single radially-ex tending aperture arranged symmetrical to the axis of the electrostatic ?eld set up between the anode and cathode, the edges of said members bounding said aperture and delimiting said dis charge path lying substantially in an equipoten tial surface of said ?eld. 4. An ionic relay tube comprising an envelope, an incandescible cathode, a box-like grid struc ture arranged symmetrically to said cathode and axially of the tube and comprising a plurality of sector-shaped grid members, and an anode ar ranged above said grid structure and centrally therewith, said grid members having between 30 them, as the only passage for the discharge, a tion with speci?c application and examples, I single aperture constituted by radially-extending do not wish to be limited thereto but desire the appended claims to be construed as broadly as slots of small width to prevent initiation of the discharge therethrough at the normal anode volt ages and a central portion whose size controls 35 the ignition characteristic curve of the tube. 5. An ionic relay tube comprising an envelope, 35 permissible in view of the prior art. ’ What I claim is: . 1. An ionic relay tube comprising an envelope, an anode and an incandescible cathode within said envelope and spaced apart to form a dis 40 charge path, and a grid structure between said anode and cathode and comprising a plurality of similar grid members insulated from each other and symmetrically cooperating to form a single aperture for the passage of the discharge and 45 interrupting the remainder of the discharge path, the edges of said members bounding said aper ture lying substantially in an equipotential sur face of the electrostatic ?eld set up between said anode and cathode. 2. An ionic relay tube comprising an envelope, 50 an anode and an incandescible cathode within said envelope and spaced apart to form a dis charge path, and a grid structure between said an incandescible cathode, an anode, and a multi ple grid structure between said anode and cath ode and comprising a plurality of sector-shaped 40 members forming a single aperture as the only passage for the discharge between said anode and cathode, said aperture having a central por tion whose area controls the ignition character istics of the tube, and radially-extending slots of 45 small width to prevent initiation of the dis charge therethrough at the normal anode volt ages, the edges of said members bounding said central portion lying substantially in an equi potential surface of the electrostatic ?eld set up 50 between said anode and cathode. HAJO LORENS VAN DER HORST.