Electric heating – Metal heating – By arc
Patent
1980-10-28
1982-12-21
Goldberg, Elliot A.
Electric heating
Metal heating
By arc
219 7614, 2191251, B23K 904
Patent
active
043651372
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to welding processes and equipment, and particularly to an apparatus for electric-arc gas-shielded surfacing by droplets with consumable electrode.
The best use of the invention can be made in building up electric contacts onto contact holders used in manufacturing switching equipment in electrical engineering and instrument making.
In addition, the invention may be used for welding and soldering various articles by separate droplets with consumable electrodes made of such materials as high-temperature solders, low-temperature solders and steels.
BACKGROUND ART
The efficiency and quality of droplet surfacing depends to a great extent on the rate of electrode melting and on a method used for controlling the detachment of droplets from the electrode and transferring said droplets onto the surface of an article being surfaced.
The problem of controlling the process of droplet detachment and the droplet transfer onto the surface of the article is of a special importance in forming the contacts on contact holders.
Known in the art methods of forming contacts on the contact holders have a number of disadvantages. Thus, a widely spread method of forming the contacts by rivetting contact plates onto the contact holders does not provide for a high stability of contact resistance since in the course of operation the riveted contacts may get loose which results in that the area of contact between the contact plate and the contact holder changes.
Furthermore, the above method is a highly labour-consuming one and causes an elevated consumption of precious metals such as platinum, gold and silver used for manufacturing contact plates. In some cases the loss in weight of a precious metal in the process of cutting-out the contact plate and securing the latter to a contact holder by rivetting exceeds by 25-40% the weight of the contact plate proper.
Soldering the contact plates onto contact holders provides for a higher reliability of the contact connection, however said reliability being ensured only at normal temperatures. At elevated temperatures soldered contacts are not reliable in operation. This method is also a labour-consuming one. In addition, soldering contacts does not practically lend itself to be readily automated, and has therefore a relatively low efficiency.
For fabricating electric contacts use is also made of a method incorporating fixing the contact plates onto contact holders by means of resistance welding, and in particular spot welding. This method feature a higher efficiency and readily lend itself to automation, but does not provide for a high strength and reliability of the joint weld between the contact plate and the contact holder, since the area of the weld spot is much smaller than that of the contact plate. Moreover, quality control of the joint weld produced by this method is difficult to effect.
At present the most efficient technique of forming the electric contacts on contact holders is a process including electric-arc surfacing which in comparison with the above-mentioned methods makes it possible to considerably enhance the strength and reliability of the contact joint, and the stability of the contact resistance, to reduce the consumption of precious materials, and to fully automatize the process.
There is known a method of electric-arc consumable-electrode droplet surfacing /USSR Author's Certificate No. 260,768, 1970/ which comprises feeding a consumable electrode through a current contact tip with a constant rate towards the surface of an article being surfaced, igniting arc between the electrode and the surface of the article so as to form a droplet on the electrode end, moving the tip relative the electrode in the direction opposite to the direction of feeding of the electrode in order to cause detachment of the molten droplet onto said surface of the article. The magnitude of the arc ignition current, the electrode feed rate, and the distance between the end of the current contact tip and the surface of the article are selected so
REFERENCES:
patent: 2504761 (1946-08-01), Simmie
patent: 2916601 (1959-12-01), Lesnevich
Brontman Rostislav L.
Gurnov Nikolai I.
Mizik Valery V.
Rogachev Evgeny P.
Slesarev Boris A.
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