Tip cleaning system for welding nozzle

Metal working – Scale remover or preventor – Mechanically powered operator

Reexamination Certificate

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Details

C029S081020, C029S081021

Reexamination Certificate

active

06295708

ABSTRACT:

THE FIELD OF THE INVENTION
This invention relates to the field of welding. More specifically, the invention relates to the removal of the slag from the tip of a MIG welding torch nozzle.
BACKGROUND OF THE INVENTION
Welding is used for many purposes, the most common being to join two pieces of metal together. In such a process, the abutting edges of the two pieces of metal are heated to an elevated temperature until they become molten, and a bead of molten metal is flowed from a welding rod or electrode along the molten edges to fuse the edges together. When the metal cools, it solidifies to form a unitary bond.
Many types of welding systems have been developed over the years. The most common are electric arc welding and gas welding. The present invention deals with gas metal arc welding (referred to as MIG). The MIG welding process is described in numerous articles, such as Gas Metal-Arc Welding (MIG Welding) by the ASM Committee on Gas Metal-Arc Welding and Flux-Cored Arc Welding of Steel, published in Metals Handbook, Vol. 6, Welding & Brazing, 8
th
Edition (1971). This article describes MIG welding as a process in which the heat for welding is generated by an arc between a consumable electrode and the work metal. The electrode is a bare solid wire that is continuously fed to the weld area and becomes a filler metal as it is consumed. The electrode, weld puddle, arc and adjacent areas of the base metal are protected from atmospheric contamination by a gaseous shield provided by a gas stream comprising a mixture of inert gases, typically a mixture of 90% argon and 10% carbon dioxide. During the process, the heat and the electric current causes the molten metal to splatter. Some of the splatter gets into the interior of the welding nozzle where it solidifies as slag on the interior wall. The slag, if allowed to continue to build up, reduces the size of the inner bore and smoothness of the nozzle, resulting in a reduction of gas flow and an alteration in the flow dynamics of the weld nozzle tip.
In the past, attempts have been made to prevent the build-up of slag in the nozzle tip by dipping the tip of the nozzle in a liquid such as a solution called Anti-Spat. Various means have also been tried to remove the slag, such as a rotating ream inserted into the nozzle tip to mechanically scrape the slag from the interior of the nozzle. Another technique has been to vibrate the nozzle tip in an effort to remove slag and other debris. In each case, the procedure requires a shutdown of the entire welding line so that the slag can be removed. Thus, the procedure has tended to be costly and time-consuming, particularly in automated production lines utilizing welding robotics.
BRIEF DESCRIPTION OF THE INVENTION
It is an objective of the present invention to provide a controlled method and apparatus for overcoming the drawbacks in the prior art procedures.
It is another objective to provide a controlled method and apparatus for rapidly and efficiently removing slag build-up in welding nozzles.
These and other objectives and advantages which will become evident upon a full understanding of the invention are achieved in the manner to be hereinafter described in detail.
This invention relates to an apparatus and the process for cleaning welding nozzles, and in particular welding nozzles used with gas metal arc welding (MIG) processes. The apparatus comprises holder means, such as a cradle, for positioning the tip of a nozzle at a fixed location away from the welding site and for preventing the nozzle from falling off. It also includes a hammer having a first end, and an impact face at the second end, and means to controllably, rapidly and repeatedly strike the hammer against the welding nozzle tip to dislodge slag from the nozzle and permit the slag to drop into a basket located beneath the cradle. Preferably, a double lobe, fast fall cam is mounted on the output shaft of a reciprocating air motor. A cam follower is connected to the first end of the hammer opposite the impact face. As each cam lobe rises, the cam follower withdraws the impact face of the hammer from the impact area. A compressed coil spring serves to rapidly drive the hammer into contact with the nozzle tip each time the cam falls and the cam profile is at a minimum.
The invention is useful with programmable robotic welders, and includes a simplified means of training the robotic welder to precisely position the nozzle tip in the holder during each cleaning cycle. This ‘training’ involves the use of a toggle including a lever and a pusher to displace the impact face of the hammer a small distance (about {fraction (1/18)}″) from the impact area, placing the tip of the nozzle against the displaced impact face, whereupon the robotics thereafter remember the precise location for placement of the tip at the start of each cycle.


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patent: 5465483 (1995-11-01), Fink et al.
patent: 5816986 (1998-10-01), Luecke et al.
patent: 5983430 (1999-11-01), Clark

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