Electric heating – Metal heating – By arc
Reexamination Certificate
2002-04-25
2003-09-16
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C015S093100
Reexamination Certificate
active
06621051
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to gas-shielded welding tip reconditioning apparatus, and particularly to improvements therein useful in robotic MIG welding operations.
“Welding” in the context of the present invention relates to the co-joining of two or more metal parts. The quality of the weld is affected by a number of factors, including the selection of any given welding technology, the competency of the operator, and of particular importance in the present context, the condition of the welding equipment. With regard to the condition of the equipment, the condition of the welding tip is often important. In the case of resistance welding equipment, for example, there are a variety of devices useful in connection with welding electrode maintenance—including surface reconditioning apparatus those disclosed in the following patents: U.S. Pat. No. 4,682,487; U.S. Pat. No. 4,856,949; U.S. Pat. No. 4,916,931; and U.S. Pat. No. 4,921,377.
Another well known welding technique is ARC welding—which differs from resistance welding in that ARC welding electrodes are deliberately consumed during the welding process so that the electrode material becomes an integral component of the finished weld. As a result, the problem of electrode reconditioning that is associated with resistance welding equipment, is not a problem in ARC welding.
MIG (and acronym for “metal-inert-gas”) arc welding is an arc welding technique in which a relatively fine wire electrode is fed continuously from a large spool mounted on by a variable speed drive whose speed is controlled to optimize arc length and burnoff rate. During the welding process, the electrical arc that extends between the electrode and the metal surfaces that are being welded, is shielded within a gas flow. Typically argon or other gases having suitable characteristics, or mixtures thereof are used—with carbon dioxide often being the gas of commercial choice.
In gas shielded welding the wire electrode and the gas are generally channeled through a so-called “torch”, which includes a central, electrically charged “tip”. The tip directs the wire electrode toward the weld site, and a concentrically arranged metal gas shield (that is electrically insulated from the tip), acts as a hood to direct and maintain a coaxial flow of the inert gas in surrounding relation about the wire. The quality of the weld is contingent on both consistent and continuous gas flow and arc patterning. Anything that interferes with the gas flow or redirects or otherwise militates against the desired electrical arc pattern, will diminish the quality of the weld.
MIG welding, when properly executed, permits high welding speeds, and necessitates less operator training than is required in the case of other welding techniques. In applications where one or the other or both of these benefits are sought, the weld quality is especially sensitive to those variations that are attributable to adverse gas flow or anything which could negatively influence the desired arc pattern.
Gas flow in MIG welding can be adversely effected as a consequence of molten metal deposition. This arises as a result of backsplash splatter on the respective mutually opposed surfaces of the tip and the hood, within the interior of the torch.
Similarly, (since the dielectric strength of the gas flow is otherwise a constant), the accumulation of such backsplash splatter decreases the physical and hence “electrical” distance between the charged tip and the electrically insulated hood. If the distance decreases sufficiently, the voltage differential will exceed the dielectric strength of the intervening gas flow, and the arc will jump between the tip and the hood. This results in a diminished amount of electrical energy being delivered to the weld site and a concomitant compromise in weld quality.
In view of the foregoing, it is important that MIG welding torches be cleaned regularly, in order to avoid these two latter mentioned problems. A variety of devices are available for this purpose, and many if not most involve mechanical devices such as torch clamps and reaming tool drives, that can be exposed to and damaged by the debris that is dislodged from the torch. The present invention is intended to help remedy or at least reduce the incidence/severity of such damage.
SUMMARY OF THE INVENTION
In one aspect, a MIG welding torch reconditioning apparatus of the present invention generally comprises a pneumatic supply line; vent means; and a mechanical transmission shaft. The pneumatic supply line supplies air to the vent means for venting a directed debris-scattering air-flow against the mechanical transmission shaft proximal to exposed seals thereon.
In another aspect, the MIG welding torch reconditioning apparatus generally comprises a pneumatic supply line for supplying pneumatic rotary drive means and drive vent means for venting a directed debris-scattering air-flow towards a mechanical transmission shaft proximal to seals thereon. In yet another aspect, the MIG welding torch reconditioning apparatus generally comprises a pneumatic supply line for supplying pneumatic lift means and lift vent means for venting a directed debris-scattering air-flow towards a mechanical transmission shaft proximal to seals thereon.
In another aspect of the present invention, a MIG welding torch reconditioning apparatus generally comprises a pneumatic supply line; pneumatic lift means powered from said supply line and pneumatic rotary drive means powered from said supply line. A mechanical transmission shaft is connected in rotary driven relation to the drive means and is retractably extensible on operation of the lift means. An exhaust vent is supplied by at least one of air from the supply line, air exhausted from the lift means and air exhausted from the rotary drive means to vent a directed debris-scattering air-flow towards said transmission shaft proximal to seals thereon.
In still another aspect of the present invention, a MIG torch reconditioning apparatus generally comprises an in-line, direct-drive arrangement of a motor, a mechanical transmission shaft, and chuck means for receiving a reaming tool. Pneumatic lift means is provided to lift the direct drive arrangement into reaming tool engagement with a gas shield of a torch wherein the tool is operable to remove at least some of any back-splash deposits laid down on interior surfaces of the gas shield.
In another embodiment of the present invention, a clamp is provided for engaging a cylindrical body between a pair of generally orthogonally-offset faces of a “V”-block and respective gripping surfaces on gripping surface members of a pair of opposed jaws. The jaws are arranged on respective jaw pivots and also include respective lever arms which extend beyond the pivots. Each such lever arm supports respective cam followers in spaced apart relation from their respective jaw pivots. The clamp also includes movable cam surfaces which are adapted to act on the cam followers in such a way as to rotate the lever arms and associated jaws about their pivots. This translates in turn, into movement of the gripping surfaces in and out of a three-way engagement of the cylindrical body between said surfaces and the “V”-block (or more specifically, the above mentioned “faces” thereof.
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Senniger Powers Leavitt & Roedel
Shaw Clifford C.
Tweco Products, Inc.
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