US3060340A - Device comprising a gaseous glowdischarge tube - Google Patents

Description

Oct. 23, 1962 s. M. FRouws 3,069,340

' DEVICE COMPRISING A GASEOUS GLOW-DISCHARGE- TUBE Filed July 15, 1960 2 Sheets-Sheet 2 INVENTOR BY amkmfdz' AGENT Unite This invention relates to devices comprising a gaseous glow-discharge tube having, in addition to a main cathode and a main anode, at least one auxiliary anode and in which a primer discharge shielded relative to the main discharge path is maintained in order to prevent delays in ignition, an atomised metallic layer being present on the wall of the tube. The invention also relates to gaseous glow-discharge tubes intended for such devices.

In tubes of the above-mentioned kind having on their wall an atomised metallic layer originating from the electrodes, wall charges may give rise to spontaneous initiation of the main discharge, more particularly if the potential of the wall charge is increased due to external causes. The conductive metallic layer on the wall permits of initiating a discharge more readily than in the absence of such an atomised metallic layer, since due to the conductive layer the charge of the whole surface of the wall can be carried away.

Due to the presence of a primer discharge, wall charges may readily occur due to diffusion of charge carriers to the wall which thus can assume a potential which is only little less, namely not more than several tens of volts, than the potential of the anode of the primer dis charge.

An object of the invention is to provide steps which permit of preventing interference due to the presence of wall charges.

According to the invention, in a device comprising a gaseous glow-discharge tube having, in addition to a main anode and a main cathode, at least one auxiliary anode and wherein a primer discharge shielded relative to the main discharge path is maintained in order to prevent delays in ignition, whilst an atomised metallic layer is present on the wall of the tube, the auxiliary anode has a shape such that part thereof co-acts with the cathode for bringing about an auxiliary discharge, the auxiliary anode having a peak extending up to so short a distance from the Wall of the tube that, upon increasing potential of the coating on the wall and at a low potential of the auxiliary anode, the wall charge flows off towards the peak of the auxiliary anode without resulting in a decreaseof the igniting voltage in the main discharge path.

With the invention it is ensured that wall charges cannot bring about a discharge, for example, towards the cathode or towards a portion of the auxiliary anode such that the main discharge is initiated, since in circuits having glow discharge tubes, when in the rest condition, the auxiliary anodes usually have cathode potential or a potential which is several tens of volts lower.

The step according to the invention is important more particularly if the tube contains two auxiliary anodes which consist, like the cathode, of molybdenum. In the case of two auxiliary anodes, it is substantially unavoidable to make then from similar material to that of the cathode for which molybdenum is chosen on account of its favourable discharge technical properties. In fact, when the main discharge has been ignited by one auxiliary anode, the other auxiliary anode which, owing to its connection, is at cathode potential or a lower potential also draws part of the current, resulting in this auxiliary anode being somewhat atomised. If

Bfihhfiifi Patented Oct. 23, 1962 the auxiliary anode consists of a different material from that of the cathode, then in the vicinity of this auxiliary anode the cathode will be somewhat covered with auxiliary anode material which is not atomised immediately by the main discharge burning on another portion of the cathode. The covering of the cathode with material of the auxiliary anode results in a modification of the properties of the cathode and more particularly of the igniting voltage. It is therefore necessary for the auxiliary anode to be manufactured of similar material to that of the cathode. Since molybdenum has a low work function and hence, as a cathode in a discharge path, a low igniting voltage, sparks readily pass over from the charged coating on the wall towards an arbitrarily shaped auxiliary anode of molybdenum, thus resulting in ignition of the main discharge. It will be evident that the use of the particular shape of the auxiliary anode according to the invention is of special importance if the tube has a molybdenum cathode and two auxiliary anodes likewise of molybdenum.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 is a perspective elevational View of a gaseous glow-discharge tube, partly broken up, according to the invention.

FIGURE 2 shows a circuit comprising a plurality of such tubes.

FIGURE 1 shows the glass wall 1 of the tube, which is partly broken up, and a base 2. A ceramic tube 3 surrounds a lead-through pin 4 to which a cathode 5 is soldered with the aid of a bent tongue. The cathode has a rounded edge 6 to prevent ignitions from a coating 12 on the wall towards the cathode. An anode 8 of the tube is positioned somewhat eccentrically. Below the anode 8 a metal strip 9 is provided on a lead-through pin. During the operation of the tube, the strip 9 is connected to the cathode lead through so high-ohmic a series-resistor that a current of about Srnicroamps flows between the anode 8 and the strip 9. The charge carriers diffusing from this weak discharge towards the main discharge path prevent therein the occurrence of delays in ignition, but without giving rise to decreases in the igniting voltage. The cathode 5 has pointed projections 7, one on each side and opposite each projection is a plate-shaped auxiliary anode 10. The auxiliary anodes Ill are likewise mounted on lead-through pins surrounded by ceramic tubes. Each auxiliary anode has a sharp peak 11 as a projection which extends up to a distance of about 0.4 mm. from the metal layer 12 present on the wall 1. The metal layer is produced in forming the electrodes by means of intense discharges for cleaning more particularly the cathode surface, resulting in material at'omisation.

If wall charges occur as a result of diiiusion of charge carriers from the primer discharge, the coating 12 on the wall may acquire a potential which can easily be 200 volts for an anode voltage of 250 volts. In the rest condition of the circuit, the auxiliary anodes 10 are at cathode potential or at a lower potential. With the small distance between the peaks 1]. and the Wall coating 12, this may give a rise to a weak discharge between one of the peaks l1 and the coating 12. Since the area of discharge are comparatively far remote from the main discharge path between the electrodes 5 and 8, these weak discharges do not bring about a decrease in igniting voltage and certainly do not bring about ignition in the main discharge path. The discharges between ll and 12 may occur more or less continuously or, for example, only if the potentialof the coating 12 rises due to external electrostatic influences.

u The envelope has an outer diameter of 9.5 mms. Due to this small size, it is substantially impossible to provide a contact with the coating on the wall, which contact would still be doubtful without particular steps. A strong contact pressure would otherwise impede mechanical sealing of the base into the bulb. Due to the small diameter of the tube, the use of large numbers of tubes in printed circuits is possible.

FIGURE 2 shows a portion of a counting circuit comprising gaseous gloW-discharge tubes according to the invention. The first glow discharge tube shown, indicated by 21, has a cathode 22 an anode 23, auxiliary anodes 24 and 25, a primer discharge cathode 26 and a coating 27, shown in a broken line, on the wall. Reference numerals 31 to 37 are used for the second tube. The tube 21 is preceded by a tube 11 and the tube 31 is followed by tubes 41, 51 etc., which tubes are not shown. Each tube has associated with it a cathode resistor 102, bridged by a capacitor 103. Each of the primer cathodes 26, 36 etc., is connected through a high-ohmic resistor 105 to the cathode lead. A common cathode resistor is indicated by 101. Each of the auxiliary anodes 24, 34, etc. is connected through a resistor 104 to the cathode of the preceding tube and through a capacitor 107 to an input lead 106. Each of the auxiliary anodes 25, 35, etc. is connected through a resistor 108 to the cathode of the next-following tube and also through a capacitor 109 to an input lead 110.

When it is assumed that a discharge takes place in the tube 21, tube 31 is ignited if a positive pulse of sufficient strength occurs across the lead 106, since the auxiliary anode 34 already takes a positive biassing potential from the cathode resistor 102 of tube 21. Tube 41 is ignited upon a subsequent pulse across the lead 106.

If, however, it is assumed that the discharge takes place in tube 31, tube 21 is ignited if a positive pulse of suflicient strength occurs at the lead 110 and tube 11 is ignited upon a subsequent pulse. The circuit is thus suitable for moving the discharge in two directions or, since it is used as a counting circuit, for adding and for subtracting. Due to the presence of the coatings 2 7, 37, etc. on the walls of the tubes, interference might occur which is prevented, however, by the auxiliary anodes of particular shape and configuration as shown in FIG- URE 1.

What is claimed is:

1. A glow-discharge tube comprising an envelope containing an ionizable gaseous medium therein at a pressure suflicient to initiate and maintain a glow-discharge, spaced apart main anode and cathode electrodes positioned in said envelope defining a main discharge path therebetween, a coating of a low work-function material on the inner wall of said envelope, a trigger electrode spaced from the main cathode electrode and having a projection positioned closer to the coating on the inner wall of said envelope than any other portion thereof for initiating a discharge between the wall coating and the trigger electrode when the wall coating assumes a given potential due to charge accumulations thereon, and a priming cathode located outside of and shielded from the main discharge path between the main anode and cathode for producing a priming discharge with the main anode which charges the coating on the inner wall of the envelope to a given potential relative to the main cathode.

2. A glow-discharge tube comprising an envelope containing an ionizable gaseous medium therein at a pressure sufficient to initiate and maintain a glow-discharge, spaced apart main anode and cathode electrodes positioned in said envelope defining a main discharge path therebetween, a coating of a low work-function material on the inner wall of said envelope, a pair of trigger elec trodes spaced from the main cathode electrode, each of said trigger electrodes having a projection positioned closer to the coating on the inner wall of said envelope than any other portion thereof for initiating a discharge between the wall coating and at least one of the trigger electrodes when the wall coating assumes a given potential due to charge accumulations thereon, and a priming cathode located outside of and shielded from the main discharge path between the main anode and cathode for producing a priming discharge with the main anode which charges the coating on the inner wall of the envelope to a given potential relative to the main cathode.

3. A glow-discharge tube comprising an envelope containing an ionizable gaseous medium therein at a pressure sufiicient to initiate and maintain a glow-discharge, spaced apart main anode and cathode electrodes positioned in said envelope defining a main discharge path therebetween, said cathode having at least a surface layer of a material of low work-function, a coating on the inner wall of said envelope of the same material as the surface layer of the cathode, a trigger electrode spaced from the main cathode electrode and having a projection positioned closer to the coating on the inner wall of said envelope than any other portion thereof for initiating a discharge between the wall coating and the trigger electrode when the wall coating assumes a given potential due to charge accumulations thereon, and a priming cathode located outside of and shielded from the main discharge path between the main anode and cathode for producing a priming discharge with the main anode which charges the coating on the inner wall of the envelope to a given potential relative to the main cathode.

4. A glow-discharge tube comprising an envelope containing an ionizable gaseous medium therein at a pressure sufficient to initiate and maintain a glow-discharge, spaced apart main anode and cathode electrodes positioned in said envelope defining a main discharge path therebetween, said cathode having at least a surface layer consisting of molybdenum, a coating of molybdenum on the inner wall of said envelope, a trigger electrode spaced from the main cathode electrode and having a projection positioned closer to the coating on the inner wall of said envelope than any other portion thereof for initiating a discharge between the wall coating and the trigger electrode when the wall coating assumes a given potential due to charge accumulations thereon, and a priming cathode located outside of and shielded from the main discharge path between the main anode and cathode for producing a priming discharge with the main anode which charges the coating on the inner wall of the envelope to a given potential relative to the main cathode.

5. A glow-discharge tube comprising an envelope containing an ionizable gaseous medium therein at a pressure sufficient to initiate and maintain a glow-discharge, spaced apart main anode and cathode electrodes positioned in said envelope defining a main discharge path therebetween, said cathode having at least a surface layer consisting of molybdenum, a coating of molybdenum on the inner wall of said envelope, a trigger electrode spaced from the main cathode electrode, said trigger electrode having at least a surface layer of molybdenum and having a projection positioned closer to the coating on the inner wall of said envelope than any other portion thereof for initiating a discharge between the wall coating and the trigger electrode when the wall coating assumes a given potential due to charge accumulations thereon, and a priming cathode located outside of and shielded from the main discharge path between the main anode and cathode for producing a priming discharge with the main anode which charges the coating on the inner wall of the envelope to a given potential relative to the main cathode.

Peck July 10, 1951 Thomas Feb. 26, 1957

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