Electric heating – Metal heating – By arc
Reexamination Certificate
2000-02-07
2002-04-09
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
C219S137200, C219S137430
Reexamination Certificate
active
06369357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates to systems and/or methods of use for significantly increasing the amount of time between maintenance shutdowns in an automatic continuous welding application for an automated welding machine. Also disclosed are products which can be used to accomplish some of the steps of the processes or systems disclosed.
2. Description of the Prior Art
In the industry, various welding systems and processes are employed to weld two pieces of metallic material. Typically, a diffuision nozzle (or nozzles in the case of twin electrodes) of a continuous electrode is moved near an article or articles to be welded, and an arc is established between the continuous electrode and the article or articles to be welded, so as to raise the temperature of the article or articles to be welded to the point at which the parts locally melt. Throughout the welding process an inert gas is dispensed through a gas diffuser disposed adjacent the nozzle to keep the molten metal at the weld engulfed in a controlled atmosphere. The controlled atmosphere controls the characteristics of the weld deposit as well as excluding air. The three gases that cause the most difficulty in welding are oxygen, nitrogen, and hydrogen. When any welding process is used, the molten puddle creating the weld should be shrouded or shielded from the air in order to obtain a high quality weld deposit.
A problem typically arises with this type of welding whereby spatter builds up on the welding nozzle tip and gas diffuser. Spatter is developed as molten metal droplets from the molten metal being welded are expelled and strike against the nozzle tip and gas diffuser. The droplets of molten metal solidify and adhere to the surface of the nozzle tip and gas diffuser as deposits of spatter. When a significant amount of spatter accumulates on the surface of the nozzle tip and gas diffuser adjacent the nozzle, the flow of inert gas to the weld is disturbed and becomes uneven. This disturbance in the flow of the inert gas allows areas of the weld to be exposed to atmospheric air while in the molten stage, which will result in the deterioration of the strength and quality of the weld.
Conventionally, spatter is removed by using a brush as disclosed in Japanese Patent Application Laying Open Publication Ser. No. 59-73186 (1984), or by using a device with rotary blades to scrape the spatter from the nozzle as disclosed in Japanese Utility Model Application Laying Open Publication Ser. No. 5847381 (1983). However, the usefulness of these methods is limited as direct contact with the welding nozzle is likely to cause damage to the welding nozzle, and the brushing or scraping of the welding nozzle is extremely time and labor intensive. Another approach involves the use of ceramic welding nozzles, instead of metal welding nozzles, as disclosed in Japanese Utility Model Application Laying Open Publication Ser. No. 48-12323 (1973). However, even though the use of ceramic material reduces the amount of spatter accumulation, spatter removal must still be performed, and a ceramic welding nozzle is even more susceptible to damage when the spatter is removed by scraping or brushing. In all of these cases it is necessary for the operator to be in close proximity to the welding nozzle in order to remove the spatter, which may lead to injuries, such as when an operator is burned by the extremely hot welding nozzle while trying to clean it by hand.
In order to make the process more streamlined, and to reduce the danger to the operator, spatter may be removed from the welding nozzle by inserting the welding nozzle within an electromagnetic field that magnetically pulls the spatter accumulation from the welding nozzle. A product performing this function is disclosed in U.S. Pat. No. 4,838,287. This product allows the spatter accumulation to be removed with no physical contact to the welding nozzle and with no requirement for the operator to get close enough to the welding nozzle to be burned. This product also can be utilized with an automated welding system application such that the electromagnetic cleaner is placed within reach of an automated welding system, where periodically the automated welding system would automatically move the welding nozzle over to the cleaning station to have the spatter accumulation removed. The product allows the automated welding system to clean the nozzle and continue operation without being shut down. Since the welding nozzle is cleaned often, the life of the welding nozzle is also increased so that it need not be replaced as often as it would without the cleaning procedure.
However, this product does not work well with a metal welding nozzle because the spatter bonds very strongly to the metal welding nozzle. Typically this product will only be used effectively with a welding nozzle made from either a ceramic or a carbon composite material Characteristics of carbon composite or ceramic materials make welding nozzles made therefrom resistant to adhesion and to pitting. The resistance to adhesion allows the use of the electromagnetic cleaner to efficiently remove spatter from the various elements of the ceramic or carbon composite welding nozzles.
In process, the ceramic or carbon composite welding nozzle may be dipped in water prior to cleaning in order to solidify the spatter. The electromagnetic field will not be effective if the spatter is in a liquid or molten state, so the water dip is necessary to insure that the spatter is completely hardened. After dipping the welding nozzle in water, the welding nozzle is moved to the electromagnetic station and the hardened spatter droplets are pulled off magnetically.
Another measure utilized to prevent spatter accumulation or to at least make spatter removal easier are anti-spatter compounds. These compounds can be liquid, gel, or an aerosol spray. When placed on the part to be welded prior to welding, the anti-spatter agent will act as a barrier between the molten droplets of metal and the welding nozzle to either prevent or weaken the bond to the welding nozzle after the molten metal droplets cool. Use of an anti-spatter compound generally slows the accumulation of spatter on the welding nozzle and makes for the easier removal of any spatter that accumulates on the welding nozzle. However, the usefulness of the anti-spatter compounds is limited in that unless applied before each weld, the anti-spatter compound will be consumed with successive welds, thereby requiring frequent shutdowns of the welding operation to manually apply fresh anti-spatter compound to the welding nozzle. Each stop makes the cycle time longer, and also requires an operator to manually apply the anti-spatter compound. Generally, the use of anti-spatter compounds in this manner has had minimal beneficial effects due to the labor-intensive nature of the application in any manufacturing setting.
Welding nozzle replacement is another significant cause of downtime on a welding operation. As a welding nozzle is used, it wears out due to arcing and abrasion. Friction and/or conductivity between the continuous electrode and the passage for the electrode in the welding nozzle causes the passage in the welding nozzle to become out of round and enlarged, which, in turn, permits the continuous electrode to move around in an uncontrolled manner within the passage. Such action eventually causes inaccuracy in the weld and eventually requires that the welding nozzle be replaced. To prevent or postpone this wear on the welding nozzle, feeders have been developed to feed the continuous electrode to the welding nozzle in a defined manner, because some contact between the electrode and the welding nozzle has been found to bear on the repeatable accuracy of the weld. Lubricants can also be applied to the continuous electrode to reduce the friction and the conductivity between the continuous electrode and the welding nozzle.
SUMMARY OF THE INVENTION AND ADVANTAGES
Various methods and/or systems are disclosed for providing an improved welding system and/o
Baum Gary Lee
Zaccagni Anthony John
Dunn Tom
Edmondson L.
Howard & Howard
Weld Aid Products Inc.
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