US1852739A - Incandescent cathode - Google Patents

Description

Patented Apr. 5, 1932 STATS er Fries.

POPKO REINDER DIJKSTERHUIS, F EINIDIIOVEN, NETHERLANDS, ASSIGNOR, BY MESN E ASSIGNMENTS, TO RADIO CORPORA'EXON OF AMERICA, OFINEW YORK, N. Y.,

A CORPORATION INCANDEEZCENT CATHODE Application filed March 30, 1925, Serial No.

This invention relates to incandescent cathodes for. electric discharge tubes, more particularly to incandescent cathodes adapted to emit a comparatively great flux of electrons.

Such incandescent cathodes are used, for ex ample, in transmission tubes for large outputs provided with three or more electrodes and destined for wireless telegraphy and the like or in rectifiers for large outputs.

The invention has in particular for its object to improve the manner in which the incandescent cathodes in discharge tubes are supported.

It is known to compose an electric incandescent body of two or more parallel connected filament portions and to connect points of them with substantially the same potential by conductive members.

Where hereinafter the term filament is used, it has to be understood to mean the whole filament pertaining to the incandescent cathode. This filament may consist of two or more portions which are separated from each other. The term incandescent cathode has to be understood to mean the complex of the filament with the members that support it.

The invention has reference to an incandescent cathode comprising parallel connected filament portions, which are supported by two or more metal carriers serving at the same time to supply the current and it con sists in that between the carriers serving to supply the current are arranged one or more other metal carriers which are connected to interjacent equipotential points of the parallel filament portions.

According to the invention the filament may be wound on a number of metal supports, at lease two of which serve to supply the current.

Further characteristics of the invention will appear from which follows:

The accompanying drawings illustrate some constructions of incandescent cathodes according to the invention, as well as a discharge tube provided with an incandescent cathode constructed in accordance with the invention. In the said drawings:

Figure 1 shows an incandescent cathode Gil 19,351, and in the Netherlands April 8, 1924.

with three parallel carriers, two of which serve to supply the current, the if-shaped filament portions being stretched at acute angles relatively to the carriers.

Figure 2 represents an incandescent cathode in which the filament is helically wound on a number of metal supports.

Figure 8 is a cross-section taken on the line HIIII of Fig. 2.

Figure l shows an incandescent cathode in which the filament consists of two loops, the tops of which are directly connected to each other and have wire wound around them.

Fig. 5 represents a discharge tube with three electrodes provided with an incandescent cathode of the same construction as shown in Figure 4.

In the incandescent cathode according to Figure 1 of the drawings metal carriers and 62 serve at the same time as leading-in wires for V-shaped filament portions 63. The tops of the wires (53 are connected to each other by a carrier 61 which is secured by means of a wire to an insulating tube 64 of quartz or similar material, which keeps the carriers 60 and 62 spaced apart at the required mutual distance. The wires 63 form acute angles with the'carriers so that the length of the wire between two, carriers is materially greator than the distance between the carriers, which offers the advantage that the resistance of the filament portions located between two carriers is greater than in the case of a perpendicular arrangement.

The incandescent cathode according to Figures 2 and 3 of the drawings comprises a filament 5, which is helically wound on four metal supports 6, 7, 8 and 9. The filament may be secured to the supports for example by welding; the supports may also be pro vided with grooves, in which case the filament is inserted in these grooves and the teeth lying between the said grooves, are preferably so bent as to lock up the filament in the grooves.

The supports 8 and 9 are electrically connected to each other by transverse pieces 10 and ll. and are arranged on a metal hood 12 which is hermetically sealed to the. end of a glass tube 13.

The supports 6 and 7 serve for the'supply (leading-in wires 19 and 20 being secured to the other side of the metal hoods. The glass tubes 13, 17 and 18, are sealed to a glass tube 21. At the other end the supports 6 and 7 are kept spaced apart at the required mutual distancev by a rod 14 of insulating material,

for example, of quartz which rests on the transverse piece 10.

In this construction the helically wound filament consists in efiect of a number of parallel connected filament portions, the supports 8 and 9 which serve to support these portions, being connected to points having the same potential.

The incandescent cathode according to Figure 4 of the drawings comprises two loop shaped filament portions 32 and 33 arranged on U-shaped metal members 35 and 37 which are secured to supporting wires 36 and 38 which also serve as lead-in conductors. The tops of the loops 32 and 33 are directly connected to each other by a wire 34, for example, of tungsten which is. wound around said tops. This construction offers the advantage that during the operation the tops of the filament have a lower temperature than the other filament portions.

In the construction according to Figure 4 the two halves of each loop are connected in parallel to each other.

The discharge tube illustrated in Figure 5, may be used for example, as a transmission tube forwireless telegraphy. The envelope of the dischargetube consists of an insulating part 40'made, for example, of glass and a metal part 41 sealed atits edge to the insulating part. The metal vessel 41 acts at the same time as anode..

A re-entrant glass tube 59 is provided with glass tubes 42, 43 and 44 the ends of which are hermetically closed by metal hoods 45, 46 and 47. A grid supporting structure is secured to the hood 46 and comprises a support 48 and a metalplate 49 carried thereby.

0 this plate are secured four metal supports 50 on which the grid wire 51 is helically wound. This wire may be connected to the supports'50, for example, in the same way as described with reference to the incandescent cathode'according to Figure 2.

Within the grid thus formed is arranged the incandescent cathode formed by two loops 57' and58, the tops of which are electrically connected to each other and-which are secured to bent metal supports and 56. The

latter are carried by leading-in wires 53 and 54 which are secured to the metal hoods 45 and 47. The discharge tube may be exhausted'in any known manner or may be provided with a suitable gaseous filling of low pressure. The metal vessel 41 and the hoods 45, 46 and 47, may advantageously consist of chrome-iron of suitable composition.

What I claim is:

1. An incandescent cathode comprising a single coiled filament portion wound about a plurality of current conducting support members whereby a plurality of parallel current carrying paths are provided.

2. An incandescent cathode comprising a pair of conducting support members insulatingly separated from each other and adapted to receive current, a second pair of support members insulated from said first named support members, and a single coiled filament wound about said support members whereby current from one to the other of the first mentioned pair of support members is caused to flow through the coiled filament in a plurality of parallel paths.

3. An incandescent cathode structure comprising a pair of conducting support men1- bers insulatingly supported from each other and adapted to be supplied with heating current, a second pair of support members insulated from said first named members, and a filament helically wound about said first and second support members, whereby current from one to the other of the first named pair of support members is caused to How through the filament in a plurality of parallel paths, the second pair of support members being arranged to support the filament at equipotential points along its length.

In testimony whereof I afiix my signature, at the city of Eindhoven, this 19th day of February, A. D. 1925.

POPKO REINDER DIJKSTERHUIS.

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