US2377164A - Electrical assembly - Google Patents

Description

y 1945- R. LOWIT ELECTRICAL ASSEMBLY Filed Feb. 6, 1942 INVENTOR. 51/001; 1 0W/7 A TTORNEY Patented May 29, 1945 ELECTRICAL ASSEMBLY Rudolf Lowit, Union City, N. J assig'nor to Callite Tungsten Corporation, Union City, N. J a corporation of Delaware Application February 6, 1942, Serial No. 429,769

2 Claims.

The present invention relates to metallic assemblies suitable for leading in current to the electrodes of incandescent lamps, radio tubes, and other electron discharge devices. More particularly, it relates to such an assemblage in which the support element is constructed of iron, and to the support itself apart from the assembly as a whole.

At the present time the assemblages generally used for this purpose are the so-called triple welds consisting of a. nickel support welded to a short length of a copper clad nickel iron wire which in turn is welded to a length of pure copper wire which makes the connection with'the contact in the base of the device. The copper clad nickel iron wire is sealed into the press of the stem. The nickel support projects into the interior of the envelope of the device and holds the electrodes.

The assembly of the present invention does not employ a nickel support. It consists of an iron support welded to a copper clad nickel iron wire which, in turn, is welded to a pure copper wire. In the past it has always been considered that iron was wholly unsuitable for use as a support in devices of the kind here contemplated. The well known tendency of iron to oxidize and to take up gases seemed to'render it unusable.

I have found, however, that if an iron wire is coated with a thin film of finely divided copper or other diflicultly oxidizable material, such as carbon or silver, the coating will seal the surface of the iron so as to prevent the emission of gases that may be occluded in the iron. Furthermore, the copper coating when heated in the open air, as is the case in constructing the assembly and in sealing it into the stem, forms a somewhat porous coating of a black copper oxide about the point of sealing.

In the preparation of the support I prefer to coat the iron wire with copper by the displacement method. The iron wire is cleaned and anhealed and is placed in a copper sulphate solution. The action of the solution is to take up a small amount of the surface iron and to deposit in its place a like amount of copper until a finely divided copper coating is produced. This thin film or coating prevents the formation of detrimental oxides and absorbs and sufiiciently binds or seals in the gases occluded within the iron so as to inhibit the emission of gases therefrom. Furthermore, if the iron wire were left bare it would soon oxidize in the open air while lying on the shelf in the factory, and would thus not be suitable for the purpose desired. However, when coated with a thin film of copper as above described, it may be allowed to stand in the open air indefinitely and is still suitable for use when desired.

Having prepared the iron wire with its copper coating, 9. suitablelength is now welded into the described assembly, and it then is sealed through the glass of the stem press of the device. At the temperatures employed for these operations which are conducted in the open air, the copper coating becomes converted into a somewhat porous black oxide about the point of sealing. This oxide is not detrimental and even seems to be of advantage as a getter.

Referring now to the drawing, Fig. 1 represents the assembly of this invention mounted in the stem of an incandescent lamp; Fig. 2 is a crosssection of the support shown at I of Fig. 1; Fig. 3 is a cross-section of the copper clad nickel iron wire shown at 2 of Fig. 1.

Referring now to Fig. 1, the assembly consists of the support I, the copper clad nickel iron sealing-in section 2, and the external conducting element of pure copper 3. It will be seen that the support wire I protrudes into the chamber within the envelope of the lamp. The scalingin element 2 is very short and is placed in the assembly at the point where the glass of the stem press encloses it. The external conductor 3 of copper extends outside the envelope of the lamp and connects with the contacts in the base thereof. As will be seen in Fig. 2, the support I is of iron and has a thin film of copper as a coating. On the other hand, Fig. 3 shows the sealing-in element 2 of Fig. 1 with a core of nickel iron and a somewhat substantial sheath of copper surrounding the core. The nickel iron core of the sealingin element 2 is so proportioned as between the nickel and iron that it will have a coeiilcient of expansion approximating that of the glass through which it is to be sealed.

In coating the support wire with copper I have found it advantageous to coat it at a size slightly larger than the size at which it is to be used and then to pass the coated wire through a smooth die for a smoothing and drying draft. For example, wire .025" is coated with a thin film of copper and then, while still wet from the bath, is drawn through a die to .0245" diameter.

piece weld assembly by means well known in the art, or it may be used as a support without external connections.

Instead of coating with copper, a thin coating of finely divided silver or carbon, or other material diflicultly oxidizable at ordinary temperatures, may be employed with like effect.

This wire is then used to form the support in a two or three The support wire of the invention so coated with finely divided copper, silver or carbon seems to have a getter action in that it seems to take up and hold gases that may be occluded in the iron or that may be freed from other surfaces within the envelope. I have been found that by this getter action, the useful life of the electronic device is materially increased.

It will be obvious, furthermore, that the coated iron support wire of the invention will be useful also for those electrode supports that have no connections external to the device.

Having thus described my invention, what I claim is:

1. An assembly of electrical elements for conducting electrical current through the envelope of sealed electrical devices which comprises a conducting wire of pure copper, at length of copper clad nickel iron wire welded thereto, and a supporting wire of iron coated with a thin film of a material diflicultly oxidizable at ordinary temperatures welded to said copper clad nickel iron wire thereby forming a single lead-in conductor of three difierent sections in the order mentioned.

2. An assembly of electrical elements for conducting electric current through the envelope of sealed electrical devices which comprises a conducting wire of purecopper, a length of copper clad nickel iron wire welded thereto; and a supporting wire of iron coated with a thin coating of finely divided copper welded to said copper clad nickel iron wire thereby forming a. single lead-in conductor of three different sections in the order mentioned.

RUDOLF LOWIT.

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