Патент USA US2108589код для вставки
F@; n, 1%. H. LEMS 2,308,589} OXIDE CATHODE MORE PARTICULARLY FOR A GAS-FILLED DISCHARGE TUBE Filed Sept. 7, 1934. f/. .. .. ‘2,108,589 Patented Feb. 15, 193s‘ PATENT OFFICE ' UNITED‘ ’ STATES _/.:_’o_xID'E cs'rnoni‘ MORE PARTICULARLY ' FOR A GAS-FILLED’ DISCHARGE TUBE Hendrik Items, Eindhoven, ‘Netherlands, assignor ' to N. V. Philips’ Gloeilampenfabrieken, Eind hoven, Netherlands Application September 7, 1934, Serial No. 743,139 ‘ ‘ _ In. Germany September 14, ‘1933 4 Claims. a (Cl. 250-275) The present invention relates to a novel cathode construction for ‘discharge tubes, and more par ticularly to ‘a cathode construction having a large electron-emissive area. The cathode structure of preferably of a core wire of a refractory metal, for instance of tungsten, which is covered with a coiled nickel wire whose adjacent turns are in contact with each other. ~ During operation, the heating current passes 5 the invention is especially useful in gas-?lled dis > charge'tubes, for instance, recti?er tubes, adapted to handle large currents. - ' . To obtain a high efficiency cathode, its surface is activated by providing it with a highly electron emitting layer, usually with an oxide layer. In such cathodes, when adapted to handle large cur rents, a large amount of oxide is to be distributed over a large surface area and the oxide must ?rmly adhere to the surface of thebody carrying the oxide layer. If such cathodes are notproperly degasi?ed, the occluded gases liberated during the operation of the tubesdeleteriously influence the through one, more or all of the coiled wires, so that the cathode structure is heated both directly and indirectly. The coils of the assembly can be degasi?ed individually, or simultaneously e. g. by sending 10 a series current through all of them if the con struction permits. After degasifying this results in a compact large-surface area ‘cathode struc— ture which gives excellent performance and long life. 'When used in a gas-?lled discharge device, for instance in a recti?er tube, the gaseous ?lling proper operation of the tube and also reduce the may be either an inert gas, or a vapor or a mix life of the cathode. ture of the two. My invention will be more clearly understood ‘ 'Various constructions have been already sug gested to obtain in a comparatively compact form such cathodes of large electron-emitting surface area. . ' For example, it has been proposed for such by reference to the accompanying drawing. 20' Figure 1 is a view of a coiled wire cathode of a construction very commonly used in present day practice‘. ' posed heating element, whereby the surface of Fig. 2 is a schematic view showing one embodi 25 ment of the invention. Fig. 3 is a top view of a discharge tube having a cathode structure according to the invention; the cylinders and of the radial walls was coated with an oxide layer.‘ However, such and similar discharge tube shown in Fig. 3. “ purpose to form a cathode'of a system of con centric cylinders which are interconnected by radial‘ walls and provided with a centrally dis structures have the drawback that it is difficult to readily and completely degasify same. Forvgas-?lled recti?er tubes adapted to handle comparatively small currents, a construction has been suggested in the patent to Dobben et al. No. 1,718,123, which provides for a cathode structure comprising a core of refractory metal, for in stance of tungsten, around which is wound a coiled nickel wire, the adjoining turns of the-nickel wire 40 being in intimate contact with each other. The whole cathode body is provided with a coating of highly electron-emissive‘substance, for instance, a coating of alkaline earth metal, which ?rmly ‘adheres to the nickel. Such a cathode can be readily deprived of all occluded gases by passing a Fig. 4 is a partly secticnized side view of the . 30 In Fig. 1 the core l consists of a refractory metal, for instance tungsten, a coiled wire 2, preferably of nickel, covering the core with closely wound turns and ensuring a ?rm adherence of the electron emitting layer to the cathode surface. In Figure 2 the cathode coil l consists of a coiled tungsten wire surrounded by a nickel wire, the entire coil being provided with a surface coat ing of a high electron-emitting substance, for instance with barium oxide. The cathode coil is provided with supply leads 2 and 3. Within the coil I is disposed a second coil ll of a construction similar to that of coil l and having a smaller di ameter, the two coils being preferably concentric. highly electron-emitting surface, which at the One end of the coil 4 is connected at 5 with the lead 2 of cathode coil l, whereas the other end of coil t is provided with a separate lead 6. The leads 2, 3 and 5 are sealed to the envelope of the a discharge tube in known manner. same time has the advantage of easy degasifying obtainable with the construction of said prior bulb l containing a cathode constituted by two ’ high-intensity heating current through same. The present invention provides for a compact cathode construction having a large area and patent. . According to the invention, a plurality of coile Wires are disposed within each other, preferably concentrically; the individual wires consisting In Figs. 3 and It a recti?er tube comprises a ' ' concentrical coiled tungsten wires 2 and 3, which are covered with a layer of emitting material ad hering to an intermediary layer of nickel wire wound with adjacent turns upon a tungsten core. 55 2 ‘A 2,108,589 The coiled wires 2 and 3 are supported by a common metal rod 4, and two separate rods 4', 4" welded to sector shaped plates of special alloy 5, 5’, 5" respectively, to which the lead wires 6, 6', 6"are welded in their turn. The plates 5, 5’, 5" are hermetically sealed to the glass bulb of the recti?er tube and through glass to each other, for instance in the manner described in the U. S. Patent #1334509. The rods 4, 4’,'4i’~arlLsurrounded by porcelain 10 tubes 1, ‘l’, 1”, respectively, which tu ' similar‘ni‘anner. Thereby each coil is preferably connected‘with one of its ends to a common lead— through which the discharge current passes dur ing operation—and with its other end to individu al leads and for degasifying, each coil is individu ally heated during’ the, evacuation of the tube, whereas in operation the heating current is sent through an optional number of coils. While I have described my inventionrorrhanwg‘” of speci?c embodiments and specl?‘cma'ppli'c’ation, 10 glass sleeves 8, 8', 8", fused to the glass covering ' '. ‘sh to be limjtedfthereto, but desire the appended c - ~ t'p‘lle construed as broadly the plates 6, 6’, 6", so as to form an absolutely as permissible in view of the prior art. tight protective layer, insulating the metal parts 15 of the leading in construction from each other and from the discharge space. . 7.» Supported fromgaorcelain tube ‘I is a wire 9 >_,,d-/~‘/C9l1‘ryll1g a piece of a suitable getter material I0. The wire is bent to a shape permitting the getter 20 to be retained in the position shown throughout the pumping process, thus at a suflicient distance from the incandescent cathode 2—3. After the pumping process the piece of getter material I0 is slipped over the upwardly bent 25 part of wire 9 and caused to drop to the coiled part II in close proximity to the incandescent cathode 2--3. Then the getter material I0 is evaporated by the heat generated by the cathode in order to 30 clean up'the tube. At the bottom of the cathode bulb a mercury container 23, ?lled with a small quantity of mer cury, protrudes downwards from the cathode bulb proper and serves to maintain the mercury vapor 35 pressure constant and at a value corresponding to a temperature slightly above that of the sur roundings. To the cathode bulb I are fused two arms I2, each of which contains an anode I3 which is 40 screwed onto a rod I4, this rod being led through the wall of the anode-arm by the intermediary of a disc I5 in the manner set out above with rela tion to the cathode construction of this tube. The anodes I3 are closely surrounded by metal 45 gauze caps I 6, which con?ne the negative glow to the front surface of the anodes I3. > The grids I‘! are provided closely to the anodes l3 and consist of concentrical cylinders I8, I9 interconnected by radial partitions 20. This grid 50 construction is provided with an outside con nection at 2| . At 22 an auxiliary anode is provided in order to improve the ignition conditions of the tube. Referring to Fig. 2, the cathode coils I and 4 are degasi?ed during the exhaust of the tube by their being heated individually to the proper tem perature, whereby current is individually passed through coils I and 4. In the operation of the tube either pair of sup 60 ply wires 2-3 of 2-6 or both pairs may be used for the passage of the heating current through the respective coils. As a rule it su?ices to di rectly heat either the outer coil I or the inner coil 4, whereby the other coil is indirectly heated. Normally the oxide layer provided on the coils is su?icient to properly insulate them from each other. However, if desired, insulating rods, indi cated in the drawing by 'I and 8, for instance of procelain, can be interposed between the coils. 70 It should be well understood that instead of using only two coils so placed within each other, the cathode structure can be formed of a larger number of coils disposed within each other in a What I claim is: V H.” -l m 1. A/"dischargee tube'coriiprising an envelope, electrodes within said envelope including a cath ode structure comprising a plurality of cylindri cally-shaped coils concentrically-disposed in a heat~retaining relationship, said coils being elec trically interconnected and spaced apart to per 20 mit the discharge to readily reach both the in ternal and'external surfaces of each coil, a layer of a highly electron-emitting substance on the surface of said coils, and leads for supplying dis charge current to all of said coils and for supply 25 ing heating current to only a portion of said coils, the remaining portion of said coils being indi rectly heated from the directly-heated coils. 2. A discharge tube comprising an envelope, electrodes within said envelope including a cath ode structure comprising a plurality of cylindri cally-shaped coils disposed one within the other in heat-retaining relationship, said coils being spaced apart and having spaced turns to permit the discharge to readily reach all portions of the surfaces of all the coils, a layer of a highly electron-emitting substance on the surface of each coil, a lead for supplying cathode-heating current and discharge current to said cathode structure, said lead being connected to one end 40 of each coil, and heating current leads connected to the free ends of a portion of said coils, the remaining portion of the coils being indirectly heated. 3. A discharge tube comprising an envelope, 45 electrodes within said envelope including a cath ode structure comprising a plurality of cylindri cally-shaped electrically-interconnected coils dis posed one within the other in heat-retaining re lationship, said coils being spaced apart and hav 50 ing spaced turns to permit the discharge to readily reach all portions of the surface of each coil, a layer of a highly electron-emitting sub stance on the surface of said coils, and means including leads within said envelope to supply discharge current to all the coils and to directly heat only a portion of said coils during the oper ation of the tube, the remaining coils being indi rectly heated. 4. A discharge tube comprising an envelope, an anode, and a cathode structure comprising two cylindrically-shaped coils disposed one within the other in heat-retaining relationship, said coils be ing spaced apart and having spaced turns to allow the discharge to readily reach the entire surface of both coils, a layer of a highly electron~ emitting substance upon said coils, a lead con nected to one end of each of said coils, a heating current lead connected to the free end of one coil, and a degasifying-current lead connected to 70 the free end of the second coil. HENDRIK LEMS.