US2894164A - Gas-filled electric discharge tube - Google Patents

Description

July 7, 1959 F. KLEPP GAS-FILLED ELECTRIC DISCHARGE TUBE Filed Aug. 10, 1954 Inuentdr o. F. KLEPP Atforhey ted S a es Patent George Francis .Klepp, London,

ternational Standard Ele en-it: (39m ti sc im?! Application August 10, "19.5 4,

w-ta s Claims priority, application 25, 19.53

2 Claims. (Cl, 313-188) The present invention relates to cold cathode gasfilled electric glow discharge tubes and is particularly concerned with the problem of stabilising the position of the anode end of the discharge path in such tubes.

For some time it has been recognised that in a glow discharge there is a tendency for the cathode glow. to wander over the face of a cathode of a discharge gap, which wandering tends to a certain instability of operation, which may be apparent merely as noise, or, with the discharge at one gap priming another gap, undesired wandering of the cathode glow may result in incorrect Operation. Comparatively little attention, however, has been paid to effects at the anode end of the discharge path, particularly in the case of multicathode tubes sharing a common anode. I have found it desirable to localize the elfective area of the anode which is to cooperate With each cathode when a gap is discharging, so as to prevent the anode end of the discharge path from wandering in position and consequently upsetting the stability of operation of the tube. I have also found that the localisation of the anode end of the discharge path may be effected by providing a depressed irregularity on the anode surface opposite the cathode so that the anode end of the discharge path sits in a hollowed-out portion of the anode.

According to the present invention there is provided a cold cathode gas-filled electric glow discharge tube comprising a cathode and an anode electrode defining a discharge gap, the said anode having a depressed irregularity in the surface thereof facing the cathode to stabilize the position of the discharge path at the anode.

The nature of the depressed irregularity does not appear to be critical and in preferred embodiments of the invention I provide, for convenience of manufacture, an irregularity formed by a small hole. In a multicathode tube according to the invention the common anode is provided with a plurality of depressed irregularities, one opposite each cathode.

The invention will be described with reference to the accompanying drawings, in which:

Fig. 1 shows diagrammatically an array of discharge gaps formed by a plurality of cathodes and a common anode, embodying the invention;

Fig. 2 shows a discharge tube, of otherwise known type, to which the present invention is applied, and

Fig. 3 shows an enlarged view of the anode of the tube of Fig. 2 with indications of the positions of the several cathode electrodes.

In Fig. 1 each cathode 1, 2, 3 and 4 co-operates with a common anode 5 to form an array of discharge gaps. The cathodes are so formed and arranged with respect to one another, that, if say, a discharge is maintained at cathode 2 the cathode glow will cover the larger plateshaped area 6 but not the ribbonshaped area 7; owing to its shape, the latter requires a higher maintaining voltage to sustain discharge to the common anode than does the plate portion 6. If a negative pulse is applied to cathodes 1 and 3 simultaneously it may be arranged 2,894,164 ,l'iets ted duly ,7, ..1.9,

. 2 th t, d e t s isa i n c u lin f om e at ases sprea on to1th"ribbon-shapedpoition I and thenceon" to the plate parliament I ode, circuit'connec'tions being such thafat'the dtini itheglb w at cathode-2 is extinguished. In this ,liifay successive "pulses may cause glow 'dischargeto' be transferred to successive cathodes from. left .toright along the array. Thistype of construction and operation .is described and claimed in detail in United States .application Serial No. 118,055, .filed September 27, 1949,1 23! H. -.Hough tor tEleeti D sc arg Tube mow-Unit States Patent No. 2,553,585, granted May 22, 1951. For satisfactory operation, allowing wide limits on the values of circuit components and the potentials applied to the tube, it is necessary to insure that the glow maintained at any cathode is stable and that the anode end of the discharge path does not vary in position. The structure of the tube shown in said patent may be improved in accordance with the present invention, by providing a depressed irregularity in the surface of the anode facing each cathode above the plate-shaped portion, as indicated at 8, 9, 10 and 11 respectively.

As mentioned above, I have found that the actual shape and size of these depressions is not critical, and, in fact, they are most simply provided by drilling a hole or punching a slot through the material of the anode in the appropriate position, in which case the discharge is localised to the inner Wall surface formed by the hole.

A typical practical application of the invention is shown in Figs. 2 and 3. Fig. 2 shows a view of a tube such as is disclosed in the aforesaid patent. The tube is housed in a glass envelope 12, having a multi-pin base 13. An exhaust and gas-filling tubulation is taken out of the bottom of the glass envelope 12, being protected by a locating spigot 14. The cathode array is mounted by means of suitable insulators within the cup-shaped anode 15, an enlarged view of which is shown in Fig. 3. The assembly is supported in the base of the tube envelope by means of support rods 16 secured to the anode 15. The cathode assembly, with the details of which we are not here concerned, comprises storage cathodes 17, indicated in dotted lines in Fig. 3, which are shaped to provide directional characteristics in similar manner to the cathodes of Fig. 1. Intermediate these storage cathodes are transfer cathodes, 18, which in the embodiment illustrated have non-directional or only partially directional characteristics. The discharge surfaces of the cathodes 17 and 18 are opposite the cylindrical wall 19 of the anode. A series of small holes 20 at the base of the cylindrical wall permits observation of the cathode glow at the storage cathodes. In applying the present invention to this construction a series of circular holes 21, having a .060 inch diameter is provided opposite each storage and transfer cathode. Any tendency for the anode end of the various discharge paths to wander over the cathode surface is thus prevented, and improved stability of operation of the tube results. It will be seen from Fig. 3 that the holes opposite the storage electrodes are symmetrically positioned with respect thereto, but those over the transfer cathodes 18 are not so placed; although it might be desirable to position the apertures facing the transfer cathodes opposite the centroids of the triangular discharge surfaces of these transfer cathodes, in practice it is found sufficient to provide apertures equally spaced along the anode Wall.

While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What I claim is:

1. A cold cathode gas-filled electric glow discharge a common anode spaced therefrom anddefining'an array of discharge gaps therewith, said anode having a plurality of spaced apertures, each aperture cooperating with a difiere nt one of said cathodes, each cathode being plosi tioned closer to the edgeof its associated aperture than any other part of said anode, the wall of each aperture constituting the anode terminus of a discharge in thegap constituted by said anode and its cooperating cathode when a firing potential is applied across said anode and cooperating cathode, each aperture serving to localize the anode end'of such discharge thereby preventing same from migrating across the surface of said anode.

-2. A cold cathode gas-filled tube as claimed in claim 1,

wherein said anode 1s a cup-s electrode and said "cathodes cohapriseelectrodes-mountedin a circular array within said anode electrodegeach cathode electrode having its facing surface spaced from and opposed to the cylindrical wall of the cup.

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