US1952428A

US1952428A - Electrode for gaseous electrical discharge tubes

Info

Publication number: US1952428A
Application number: US629045A
Authority: US
Inventors: Albert C Forst
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-08-16
Filing date: 1932-08-16
Publication date: 1934-03-27
Anticipated expiration: 1951-03-27

Description

27, 1934. c FQRST 1,952,428

ELECTRODE FOR GASEOUS ELECTRICAL DISCHARGE TUBES Filed Aug. 16, 1932 WINV wfiw v "fliuiiicd Mar. 27,

UNITED STATES ELECTRODE FOR GASEOUS ELECTRICAL DISCHARGE TUBES Albert C. Forst, Alameda, Calif.

Application August 16, 1932, Serial No. 629,045

3 Claims.

The invention relates to means for effecting a connection between an .electrode and lead in" wire therefor as utilized in combination with a gaseous electrical-discharge tube, and more particularly to the construction and disposition of the connecting portions of such electrodes and lead in wires.

An object of the invention is to provide a connection between an electrode and "lead in wire for an electrical-discharge tube that will retain the members in contacting relation when subjected to severe heats even when the members are comprised of metals having widely different co-eflicients of expansion.

Another object of the invention is to form the cooperating connecting portions of the electrode and lead in wire in such manner, and of such materials, that without the use of extra parts and by simply pressing the portions together a most effective and permanent interlocking connection will be afforded both electrically and mechanically under all operating conditions.

The invention possesses other objects and features of advantage, some of which, with the fore-, going, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Referring to the drawing:

Figure 1 is a sectional view of an electrode and lead in wire connected in accordance with my invention and operatively disposed within an end of a gaseous discharge tube.

Figures 2 and 3 are side elevations partially in section of the electrode and lead in wire respectively before and after the electrode has been pressed about the wire.

Figures 4 and 5 are plan views of Figures 2 and 3 respectively.

Figure 6 is a side elevation partially in section of a modified form of my connection.

Figure 7 is a plan view of Figure 6.

Each of the views represents the members considerably oversize in order to better illustrate the invention.

As illustrated in the drawing, my invention concerns a connection means for joining and retaining in contacting relation an electrode 11 and a conductor 12 therefor commonly termed the "lead in wire. The member 11 is mounted with part of the wire 12 within a glass tube 13, the wire 12 passing through and sealed within an end 14 of the tube. The members 11 and 12 are usually connected before insertion in the tube, and when sealed within the tube form with the latter a unit convenient for distribution to the trade for use with electrical-discharge tubes such as employed for illuminated signs and the like. Connection of the unit aforesaid to a tubular glass sign is ordinarily readily effected by merely joining the glass surrounding the electrode to the end of the sign in a manner sealing theelectrode in the end of the sign tube. The disposition of an electrode on each end of the sign tube completes the entire sign assembly.

In rendering a sign tube operable, however, the air between the electrodes must be substantially entirely withdrawn and replaced with a small amount of a rarified gas such as argon, neon, helium or the like. After the electrodes have been sealed in the ends of the tube, a pump is connected to a tubulation provided on the tube for such a connection and the air drained from between the electrodes; In the electrodes themselves however are small amounts of entrapped gases which if not withdrawn during the pumping operation are subsequently liberated incident to heating of the electrodes such as during operation of the sign, and in mixing with the other gases in the tube deleteriously affects the character of the light emitted. These entrapped gases therefore must be removed during the pumping operation and their removal is generally effected by energizing the electrodes with a high electrical potential which in causing a bombardment of electrons thereon sufficiently heats the electrodes to effect a liberation of the gases. In order to insure a substantially complete release of the gases contained in the electrodes, the latter are heated during the pumping of the tube well above their normal operating temperature. In instances where the lead in" wire and the electrode are comprised of different metals with unlike coefficients of expansion, this severe heating is likely to affect the strength of the jointure between these members. The lead in wire being necessarily sealed in the end of the glass tube, is selected of a metal having a coeflicient of expansion most nearly approaching that of the glass and is therefore usually formed of tungsten when the tube is comprised of pyrex or other hard glass, and of a copper clad wire where German lead glass is employed.

Heretofore the connection between the electrode and the lead in wire has commonly been effected through the use of a stem-like projection extended from an end of the electrode and provided with a bore in which an end of the wire is inserted, the retention of the wire in the bore being brought about by contracting the stem portion sufficient to cause a frictional or resilient gripping of the wire between the side walls of the bore. This type of connection has been suitable in instances where the electrode is formed of copper or iron or other comparatively hard metal of approximately the same coeflicient of expansion as the lead in wire. These harder metals however are difficult to obtain in a pure state and in a form not containing a relatively large amount of foreign matter and occluded gases which are likely to be discharged into the tube after the latter has been in operation for sometime. One of the best metals for use as an electrode appears to be aluminum. This metal not only may be obtained in a very pure state and free from an excess of occluded gases, but also appears to withstand disintegration when used as an electrode for a longer period of time than the harder metals aforementioned. Considerable trouble, however, has been experienced in the use of aluminum electrodes due to the latters relatively high coefficient of expansion. When joined to a tungsten or a copper-clad lead in wire in the manner effecting merely a frictional or resilient grip as aforesaid, the aluminum electrode rapidly expands away from a gripping position on the end of the wire during the bombarding of the electrode, with the result that the electrode drops off the end of the wire and renders the apparatus inoperative. In accordance with my invention however, and as hereinbefore stated, the connection between the electrode and the lead in' wire is so made that the differences in expansion between the parts will not effect a disconnection of the jointure.

It will be noted that the electrode 11 as here shown comprises a cylindrical metal body and is arranged with its current emitting portion confined to a bore 16 extending longitudinally and inwardly from an end 17 of the electrode. The other end 18 of the electrode is reduced in diameter and is provided with an inwardly extending bore 19 preferably terminating short of the bore 16 and arranged for receiving an end 21 of the lead in wire. Adjacent the end 21, the lead in wire is provided with an offset or shoulder portion 22 which is arranged for disposition within the bore 19. When the wire has been inserted in the bore 19, the reduced end of the electrode is compressed around the wire, but since the lead in wire is of a harder metal than the aluminum comprising the electrode, the latter will not merely frictionally engage the wire but the portion thereof defining the bore 19 will fill in and around the offset 22 whereby a stop surface will be formed in opposing relation to the offset 22 to prevent any longitudinally outward displacement of the wire relative to the electrode. The compression is effected in a direction at right angles to the plane in which the portion 22 is offset, and for this reason this latter portion will be pressed substantially in its original, form into the walls of the bore and thereby more effectively prevent a withdrawal movement of the wire from the electrode. It will now be clear that instead of the wire and electrode being held together merely by a frictional or resilient grip, an actual interlocking of the members is provided, and before the wire can become loosened and pull out of the electrode on expansion of the compressed walls during the bombarding operation, these side walls would need retreat the full width of the offset, or in other words the length of the component of the wire disposed at right angles to the axis of the bore, which would necessitate an expansion far greater than would be present even in cases of extreme difference in coefllcients of expansion of the wire and electrode.

A modified form of the lead in" wire is illustrated in Figures 6 and '7 of the drawing. As here disclosed, the wire 12 is folded at its end to provide a loop 23 for insertion into the bore 19. As with the previously described embodiment, the connection is effected by compressing the electrode about the wire and thereby impressing the latter into the side walls of the bore 19. The material of the electrode, it will be clear, engages over the inner side of the bend or the .connected end 24 of the loop and thus provides for the interlock. which positively prevents a withdrawal movement of the wire even, as with the first connection, under extreme conditions of expansion differences between the wire and electrode.

While'the connection of my invention has been particularly-designed to join an aluminum electrode to a lead in wire of the character described, it will be clear that the same may be advantageously employed with an electrode of any metal of less hardness than the lead in wire used.

I claim:

1. In a connection of the character described, a cylindrical electrode provided with a bore longitudinally and inwardly extending from one end thereof arranged to provide the current emitting portion of said electrode, the other end of said electrode being reduced and having a bore inwardly extending from said end and terminating in spaced relation to said first named bore, a connector wire for said electrode having a crooked portion disposed within said second named more, said wire being of a harder metal than that comprising said electrode whereby upon compressing said reduced end in a direction'transverse to its length said wire Will be impressed into the'walls of said second bore to define a surface opposing and engaging said crooked portion to resist withdrawal of the wire from the bore.

2. In a connection of the character described, a cylindrical electrode provided with a bore longitudinally and inwardly extending from one end thereof arranged to provide the current emitting portion of said electrode, the other end of said electrode being reduced and having a bore inwardly extending from said end and terminating in spaced relation to said first named bore, a connector wire for said electrode being folded at its end to form a loop and disposed with the connected end of said loop inserted in said second bore, said wire being of a harder metal than that comprising the electrode whereby upon compressing said reduced end in a direction substantially at right angles to the plane of said loop said wire will be impressed into the walls of said second bore with portions of said walls disposed between the opposed folds of said loop to thereby engage and stop movement of said connected end of the loop incident to a withdrawal movement of the wire from the bore.

3. An electrode for neon type tubes, comprising a solid aluminum member having a bore adjacent one end providing electrical contact with the neon or equivalent gas in the tube, the other end of the electrode being solid and provided with a relatively small bore, a conductor in said bore and having an offset portion, the mass of material adjacent said last named end being crushed inwardly substantially closing said second bore about said conductor and offset.

ALBERT C. FORS'I'.