US2291973A - Ignitron construction - Google Patents

Description

1942- D. E. MARSHALL EE'AL 2,291,973

IGNITION cous'rnucnon Filed Oct. 9, 1940 INVEN TOR .51 E". MfiEV/WLZ BYZQZ/VOCf/EZ ATTO R N EY Patented Aug. 4; 1942 2,291,973 IGNITRON CONSTRUCTION Allwood, and William J.

Donald E. Marshall, Knochel, Irvington,

. 3., assixnors to Westinghouse Electric & 'Manll! act Company,

East Pittsburgh, Pa., a corporation oi Pennsyl- Application October 9, 1940, Serial No.

2 Claims. (01. 250-275) Our invention relates to discharge devices and more particularly to the type of discharge device known as sealed-off ignitrons.

An object of our invention is to simplify the arrangement and material of the metal casing of a sealed-off ignitron so that the device will occupy a very small space.

Another object of the invention is to modify the anode structure to eliminate breaking of the .anodes.

Other objects and advantages of the invention will be apparent from the following description and drawing in which:

Fig. 1 is a view in cross section of a device embodying our invention.

Fig. 2 is a top elevational view of Fig. 1.

Fig. 3 is a cross section on lines III-III of Fig. 1.

Sealed-off ignitrons such as disclosed in Patent 2,140,369, issued December 13, 1938, in the name of D. E. Marshall, have occupied considerable space and the structure has also utilized considerable material.

It is an object of our invention, as mentioned above,-to simplify the casing so that the device will occupy a very small space. In simplifying the casing and reducing the dimensions of the electrodes, we have discovered that the effect on the prior art structure is a tendency to crack the carbon anode usually employed in these devices. Our invention also includes modifying the anode structure to eliminate this cracking of the carbon anode.

In Fig. 1 we have disclosed the cylindrical casing l0, preferably of stainless or cold-rolled steel, having an inverted cap-shaped bottom header ii welded therein. The cap-shaped header, in combination with the adjacent casing, supports the mercury pool l2. A tubulation 33 extends through the bottom portion of the casing and this tubulation is preferably of a non-corrosive metal such as nickel.

This'tubulation has a flange M with an eyelet l5 welded thereto. The flange M is welded to the top of the header ll after the tubulation 63 has been inserted through the opening it in. this header. After the assembled tube has been heattreated and exhausted, the tubulation is closed off at the tip 51. If desired, a solder 18 may enclose this tubulation and be surrounded by a protecting non-corrosive cap i9 such as brass. The casing i0 may be flanged out at the upper por tion thereof at for the purpose of support or for suitable attachment to a water-cooling jacket, or to an air-cooling arrangement, as desired.

We preferably weld a cylinder 2| to the upper interior wall of the casing Hi. This cylinder 2! is of an iron-nickel-cobalt alloy sold under the trade name of Kovar. To the other edge of this cylinder is sealed a cylinder of insulating material 22 preferably of borosilicate glass. At the other end of this cylinder is sealed a cap 23 likewise of the iron-nickel-cobalt alloy sold under the trade name of Kovar.

The cap 23 in place of having a closed end has an integral upwardly extending cylindrical stem portion 24. This stem portion 24 is in turn sealed to a cylindrical borosilicate glass portion 25 that in turn is sealed to a perforated cylindrical cap 26, also of the alloy metal sold under the trade name of Kovar. Through the central perforation of this cap 26 extends a long ignitor stand ard 21 which may be of steel. This standard at 28 has an enlarged portion that is welded to the bent-in flange 29 of the cap 26. At the lower end of the standard 21 is a tapered tip 30 of a high resistance material, such as boron carbide, dipping into the mercury pool l2. The upper end of the standard has an enlarged portion 3| to which may be connected a flexible connector to a source of electricity for igniting the device.

To the underside of the cap 23 is welded a cylinder 32, preferably of steel, extending down- Wardly to the location of the anode 33 which is of carbon. In the prior art such a tubular metal connection was screwed to the carbon anode. It will be noted that the heat applied to the sealing operation of the borosilicate glass 25 and the cap 23, as Well as the heat applied to the sealing of the glass 22 to the cap 23, has a good conductive path through this cylindrical member 32 to the carbon anode 33 in these devices of the prior art.

It will be noted that the diameter of the easing iii and the diameter of the carbon anode 33 are greatly reduced over the diameter of the casing and anode in Patent 2,140,369. The result of the transfer of heat from a metal cylinder to the anode to which it was directly screwthreaded caused an uneven expansion of the two connected devices and cracks resulted in the anode. In order to prevent this, we utilize an intermediate sleeve 34 which is directly connected by screw threads to the cylindrical member 32 and then in turn is attached to the anode 33 by screw threads. Ihere is a slight space 35 between the bottom portion of the cylindrical member 32 and the top of the anode 33. The conduction of heat is accordingly cut down before it reaches the anode by the boundary between the "nickel-cobalt and cylindrical member 32 and the sleeve 84, as well as the intervening space 8| between the anode and the cylindrical member 82.

The cap member I! may be made of very thin material and we preferably copper solder a steel member iitothetop ofthiscap ll. Onthis additional member 38 we preferably silversolder athick ring 81 of copper which is preferably, screw-threaded on its inner side 38, and a cylinder member 30 preferably of copper is attached bysimilarscrewthreadstothisringll. This cylinder member 3! preferably rises to a height to protect the small glass cylinder 25 and the thin cap 20 sealed thereto, and also acts as an electrical connection for the anode 88.

The reason for these various solders is that the iron-nlckel-cobalt alloy cannot be used with silver, and the copper solder cannot be used with copper. We desire the cap to be made of irontheringll tobeof copper. It will be noted that we have simplified the lllmaybeassmallaslyfi inches.

small diameter can effectively carry current having i000 amperes peak and 25 amperes average. It will also be noted that in spite of the reduction of the diameter of the casing and the diameter of the anode, we have greatly strengthened the anode structure over that disclosed in the prior art. We have also made the tubuiation and its protection of non-corrosive material so that there will be no danger of leakage therethrough by an accumulation of corrosion.

It is apparent, however, that many modifications may be made in the preferred embodiment disclosed, and accordingly we desire only such limitations to be imposed upon our invention as are necessitated by the spirit and scope of the following claims.

We claim: I

i. In a discharge device, a plurality of cylindrical members the body portions whereof are substantially of equal diameter and sealed successively to each other one above another thereby providing an elongated cylindrical chamber of substantially the same size throughout the length intermediate one of said members comprising insulating material and the others being of metal. a bottom header for the lower end of said chamber sealed with respect to the lowermost one of said members. the uppermost of said members comprising a cap having a rethat the diameter of g and having a duced hollow neck portion projecting upwardly therefrom, a cylinder axially of said chamber depending from said same entirely through the member next below said cap, an anode immediately below said depending cylinder. said anode and cylinder having adjacent portions of equal diameter and screw threaded, a sleeve having interior threads throughout its length engaging the threads of both the depending cylinder and anode, said sleeve being of relatively thin metal and tending to stop heat conduction between said depending cylinder and anode. an ignition standard depending from above said neck to the proximlty of, said header and having a tip on the lower end thereof, and a pool cathode in said chamber into which said till 619 2. In "a discharge device, a plurality of cylindrical members the bo y portions whereof are substantially of equal diameter and sealed successively to each other one above another thereby providing an elongated cylindrical chamber of substantially the same size throughout the length thereof, an intermediate one of said members comprising insulating material and the others being of metal, a bottom header for the lower end of said chamber sealed with respect to the lowermost one of said members, the uppermost of said members comprising a cap having a reduced hollow neck portion projecting upwardly therefrom, an upper cylindrical insulating member sealed to the upper end of said neck diameter throughout its length substantially that of the said neck, a cylinder axially of said chamber depending from said cap within the body of the same entirely through the member next below said cap, an anode immediately below said depending cylinder, said anode and cylinder having adjacent portions oi equal diameter and screw threaded, a sleeve having interior threads throughout its length engaging the threads of both the depending cylinder and anode, said sleeve being of relatively thin metal and tending to stop heat conduction between said depending cylinder and anode, an ignition standard depending from above said upper insulating member to the proximity of said header and having a tip on the lower end thereof, and a pool cathode in said chamber into which said tip dips.

DONALD E. MARSHALL- WILLIAM J. KNOCHEL.

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