DE1244296B - Inert gas contact arrangement - Google Patents

Description

GERMAN 4m9w ^ PATENT OFFICE

German class: 21g-4/01

EDITORIAL

Number: 1244 296

File number: T 26941 VIII c / 21 g

1 244 296 filing date: September 2, 1964

Opened on: July 13, 1967

The present invention relates to a protective gas contact arrangement in which the contacts are in a protective tube that is hermetically sealed to the outside and filled with an inert gas. In known contact arrangements of this type, the protective tube is normally filled with an inert gas, z. B. nitrogen, often filled with the addition of hydrogen. The purpose of the gas is to prevent corrosion of the contact surfaces to be avoided, so that the contact resistance remains low. These contact arrangements usually have a sufficiently long service life for normal use in telephone technology. If the contacts are for a heavy load, e.g. B. used for digit impulses the contacts will only work satisfactorily for a limited time. The ones at the contacts Occurring errors consist in principle of sticking of the two contact parts. A such sticking occurs because of material transfer between the contact parts, through which smoothness occurs on the surfaces of the contact parts so that they can hook together. The sticking happens the easier and earlier, the greater the current that is switched through the contacts becomes, and in certain uses with a large number of contact operations, the life is these contacts are extremely unsatisfactory.

This disadvantage is eliminated by the invention. It makes the tendency to stick of contacts to such an extent that the life of the contact arrangement is multiplied. In the case of contact arrangements of the type mentioned at the outset, this is achieved in that according to the invention an addition of oxygen is added to the inert gas, the proportion of which depends on the Volume unit is less than normal air. For pipes with a small volume, a higher concentration of oxygen must be used, and vice versa with larger tube volumes the concentration of oxygen will be lower. The oxygen present in the pipe is to a certain extent Dimensions consumed by the oxidation of the iron and the nickel of the contacts, whereby the thereby chemically bound amount of oxygen is proportionally larger, the smaller the tube volume is, so that with a smaller tube volume the concentration of free oxygen faster than with one large pipe volume is reduced, in which the concentration is lower from the start.

When the contact surfaces of used protective contacts of conventional design with the help of a microscope considered and with inert gas contacts ver-inert gas contact arrangement

Applicant:

Telefonaktiebolaget LM Ericsson, Stockholm
Representative:

Dr.-Ing. H. Ruschke and Dipl.-Ing. H. Agular,
Patent Attorneys, Munich 27, Pienzenauer Str. 2

Named as inventor:
Hermann Theodor Theobald,
Bandhagen (Sweden)

Claimed priority:

Sweden September 24, 1963 (10 412)

that were needed in the presence of oxygen can then be considerable Detect differences. The former contacts have large bumps, while the latter Contacts are comparatively smooth. This depends on the influence of the oxygen and can result in the following Way to be explained. The inert gas contacts are made of an alloy of iron and nickel and wear a thin layer of a noble metal on the contact surfaces. At the break of the current, a material transfer occurs between the contact parts, wherein the material transfer Forms protrusions on one surface and voids on the other surface. With the known Contacts, these protrusions and cavities grow slowly and eventually become so large that that they cause sticking as the protrusions and depressions of the contacts hook together. Conversely, when oxygen is present, it is due to the transfer of materials and the wear oxidizes exposed iron and nickel particles. The oxide forms to a large extent an insulating protection at the point where the current was interrupted. If the The next time the circuit is closed, this is generally done at other points. This means that the contact points of contact are moved over the contact surfaces. When present

709 610/393

Claims (3)

When there is no oxygen, the number of projections on one of the contact parts or the cavities on the other contact part is very much greater and these are therefore very much smaller. It is important that the amount of oxygen is not too great. With a small amount of oxygen FeO and NiO are formed, with a higher concentration Fe2O3 and Ni2O3 are formed, whereby the latter oxides have a higher contact resistance. If the air had free access, a complete break in contact would occur very soon. Tests carried out have shown that the appropriate amount of oxygen is different for different contact materials. It has been found to be beneficial to use a higher proportion of oxygen in gold contacts than z. B. to be used with rhodium contacts. A percentage of 1 * / o seems to give a good increase in service life. The same also applies to an oxygen quantity of 20%, which, however, as already mentioned, results in a relatively high contact resistance. An oxygen content of up to 5% seems to produce the best result. Patent claims: 1. Inert gas contact arrangement in which the contacts are hermetically sealed to the outside sealed and filled with an inert gas protective tube, characterized in that that the inert gas is mixed with an addition of oxygen, its proportion per unit volume is less than normal air. 2. Inert gas contact arrangement according to claim 1, characterized in that the added The amount of oxygen is 1 to 5 percent by volume. 3. Inert gas contact arrangement according to claims 1 and 2, characterized in that the contacts have a contact-making surface layer made of a noble metal, for. B. gold or rhodium ₅ have. 709 610/393 7.67 © Bundesdruckerei Berlin