US2465769A - Discharge device with connector of low thermal and high electrical conductivity - Google Patents

Description

March 29, 1949. HA. VAN MEURS 2,

DISCHARGE DEVICE WITH CONNECTOR OF LOW THERMAL AND HIGH ELECTRICAL CONDUCTIVITY Filed July 20, 1946 AGE/VT Patented Mar. 29, 1949 DISCHARGE DEVICE WITH CONNECTOR F LOW THERMAL AND HIGH ELECTRICAL CONDUCTIVITY Hubertus Anthonius van Meurs, Eindhoven, Netherlands, assi'gnor to Hartford National Bank and Trust Cpmpany, Hartford, Conn.,

as trustee Application .Iuly 20, 1946, Serial No. 685,177 In the Netherlands June 15, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires June 15, 1965 4 Claims. 1

This invention relates to an electric discharge tube, the electrode system of which is su ported substantially by one or more supporting rods which are sealed into the wall of the tube and outside the tube have the shape of contact pins. It more particularly relates to the structure of such supporting rods.

There is a general aim to give discharge tubes as small a height as possible. This means that the length of the supporting rods which is located between the electrode system and the place of sealing must be as small as possible. If the supporting rods are sealed into the Wall of the tube and outside the tube have the shape of contact plus, there are soon dimculties, however, since such supporting rods must have a fairly large thickness, due to which heat is transmitted from the electrodes to the contact pins. Especially in tubes that are highly loaded the pins may thus become so hot as to oxydise resulting in 'poor contact in the tube holder and consequently in further production of heat and disturbances, in the course of which even burning of the contact springs and deterioration of the seal may arise.

Several means were already suggested for preventing the transmission of heat by cathodes. Thus it was known to provide indirectly heated cathodes with sleeves of poorly conductive material, due to which the transmission of heat "to the points of support is reduced.

Furthermore it is known to avoid undue transmission of heat from a directly-heated cathode to the supply-wires by forming a certain number of circumferential roovesin the supporting rods. In order to obviate as much as possible the attenuation of the rods resulting from these grooves, little tubes of insulating material are slipped over the grooves. Furthermore it was known to provide for the same purpose thinwalled little tubes of resistance material between the current supply wires and the extremities of the filament of an indirectly heated cathode. In order to reduce the heat emission losses of these little tubes, they could be gilt, copper-plated or silver-plated. In these tubes, however, a Joule production of heat must occur which is equal to the thermal losses resulting from the transmission. Consequently, the tubes must have a fairly high electric resistance. In all these constructions, however, the drawback arises, that, owing to these means, either the electric resistance is also increased, or besides the mechanical strength is greatly reduced. These constructions need not, however, withstand any great forces, since they serve only to support a filament. The requiremen'ts which a supporting rod has to satisfy are entirely different if it has to serve for the heavier electrodes or for the whole of the electrodes system and, in addition, fulfills the function of a supply conductor. In this case it is not possible without any further expedients to utilise one of the above mentioned known means without involving great drawbacks in connection with either the mechanical strength, or the electrical resistance.

Now, according to the invention, in an electric discharge tube comprising an electrode system carried substantially by at least one supporting rod which is sealed into the wall of the tube and V which outside the tube has the shape of a contact pin, that portion of the supporting rod which is located between the system and the place of sealing has such a shape that the transmission of heat alon the rod is reduced at least so strongly as to avoid any oxydation of the portion of the supporting rod protruding from the tube, whilst the electrical resistance for the operating currents of the tube and the mechanical strength of the rod are substantially unvaried.

It is thus possible for the distance between the electrode system and the place of sealing to be given a comparatively short length without difilculties being involved during the deprivation of gases of the electrodes or in operation, even in tubes with electrodes that are loaded very highly and which may therefore acquire a high temperature in operation.

The invention is particularly advantageous for tubes having a plane base into which the supply wires which outside the bulb have the shape of contact pins are sealed. In this case the invention is only applied to those supply conductors which serve at the same time as supporting rods for the electrode system. The other supply wires are connected in known manner to the electrode supports by means of a flexible connecting piece of fairly great length. Consequently these conductors cannot really contribute to a rigid support of the electrode system.

In order that the invention may be clearly understood and readily carried into effect, it will be described more fully with reference to the accompanying drawing.

In the figure reference numeral l denotes the electrode system of a transmitting tube housed in a bulb 2 and fixed to a base 3. Contact pins are sealed into the base 3, pin 4 inside the tube changing into a supporting rod 4, 4", which substantially carries the system I. The distance between the system and the bottom of the tube is comparatively small so that there would be a risk of contact pin 4 being overheated if the supporting rod 4' would extend in a straight line, Especially in degassing the tube, during which treatment the electrodes acquire a high temperature, this risk would be great, as well as the danger of cracking of the bottom of the tube whilst furthermore, due to the prolonged heating during the operation of the tube, there is in this case the risk of oxidation with all consequences involved. Now, according to the invention, the supporting rod 4' is interrupted at 5, the two parts 4', 4" being electrically connected by means of a metal strip 6. In order to keep down the electrical and more particularly the high-frequency resistance of the strip, it is made either from copper or silver, or from resistance material which is copperplated or silver-plated, due to which especially the high-frequency resistance as a result of the skin effect need not be higher in practice than it would be if the rod 4' 4" would extend in a straight line. Consequently in tubes in which the supporting rod concerned must convey great high-frequency currents, use will preferably be made of a strip of nickel-iron which is copperplated or silver-plated, since the heat conduction is in this case smaller than it is with a strip of the same size which is made from copper or silver. In tubes for low-frequency amplification, however, use is preferably made of a strip of copper or silver. A low electrical resistance of the strip is also of importance in view of the Joule heat produced in the strip, by which the efiect of the decrease of the heat transmission would for the greater part be neutralised. With high-frequency operating currents the essential point therefore is a good conductivity of the surface of the strip. The strip 6 can withstand only a certain stress, but the support proper of system I is effected by means of U-shaped clasp I, the two limbs of which are secured in an insulating centreing body of the electrode system and the middle of which is welded to the part 4' of the supporting rod 4', 4". Owing to the fact that the clasp is only connected to the electrode system by means of insulating material, the heat transmission through this clasp is small. If desired, the system maybe supported by further supporting pins to which the invention is applied. The other pins II] are connected to the electrode supports by means of long thin conductors 9 and cannot therefore contribute to an appreciable extent to the support proper of the system.

The clasp I may be secured in the insulating body by means of little rings welded on it, so that any shift along this clasp is avoided. If desired, the strip 6 may be of copper, in which event it is advantageous to place it in a curvature so that its heat emission is increased and its heat transmission is decreased and, even if the whole of the strip consists of copper, no overheating of the lead-through of the contact pins can occur. If the strip has to withstand a certain stress or must convey strong high-frequency currents, it will preferably be made from resistance material 4 such material is stronger than copper or silver.

It is evident that still further embodiments according to the invention are possible.

What I claim is:

1. An electric discharge device comprising an envelope, electrodes within said envelope, an insulating body secured to and supportin one of said electrodes, a member secured to and supporting said insulating body, an electrically conductive pin extending through and sealed to said envelope and being secured to and supporting said member, and a connector of high electrical conductivity and low thermal conductivity electrically interconnecting said pin and said one electrode.

2. An electric discharge device comprising an envelope, electrodes within said envelope, an insulating body secured to and supportin one of said electrodes, a member secured to and supporting said insulating body, an electrically conductive pin extending through and sealed to said envelope and being secured to and supporting said member, and a connector of low thermal conductivity plated with a metal of high electrical conductivity electrically interconnecting said pin and said one electrode.

3. An electric discharge device comprising an envelope, electrodes within said envelope, an insulating body secured to and supporting One of said electrodes, a U-shaped member supporting said insulating member and secured thereto at the ends of the legs of the U-shaped member, an electrically conductive pin extending through and sealed to said envelope and supporting said U- shaped member and secured thereto at the curved portion thereof by a weld, and a connector of low thermal conductivity plated with a metal of high electrical conductivity electrically interconnecting said pin and said one electrode.

4. An electric discharge device comprising an envelope, electrodes within said envelope, an insaid insulating member and secured thereto at which is silver-plated or copper-plated, since the ends of the legs of the U-shaped member, an

electrically conductive pin extending through and sealed to said envelope and supporting said u shaped member and secured thereto at the curved portion thereof by a weld, and a connector of low thermal conductivity plated with a metal of high electrical conductivity electrically connected to said pin at said weld and electrically connected to said one electrode.

HUBERTUS ANTHONIUSvAN MEURS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,197,615 Eldred Sept. 12, 1916 2,244,358 Ewald June 3, 1941 2,355,083 Krim Aug. 8, 1944 2,380,496 Beard July 31, 1945

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