Electric heating – Metal heating – By arc
Reexamination Certificate
2000-04-25
2002-06-04
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C015S093100
Reexamination Certificate
active
06399917
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 optimise 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 channelled 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
The present invention relates generally to a MIG welding torch reconditioning apparatus including a pneumatic supply line; vent; and a mechanical transmission shaft. The pneumatic supply line supplies air to the vent which in turn then vents a directed debris-scattering air-flow against the mechanical transmission shaft proximal to exposed seals thereon. This arrangement is particularly advantageous as part of a combination in which the MIG welding torch reconditioning apparatus has a pneumatic supply line that is connected to supply a pneumatically driven mechanical means, and to vent “spent-drive” air that exits from the mechanical means, through vent means as described above.
In a more specific embodiment, a MIG welding torch reconditioning apparatus according to the present invention includes a pneumatic supply line for supplying pneumatic rotary drive means, as well as a drive vent means for venting the directed debris-scattering air-flow towards a mechanical transmission shaft proximal to seals thereon. Preferably, this transmission shaft is a rotary drive shaft that is arranged in driven relation to the pneumatic drive means. The transmission shaft is also connected, in turn, in driving relation to a reaming tool that is adapted to be aligned and inserted within a torches gas-shield and to be operable therein to remove at least some of any back-splash deposits laid down on interior surfaces of the gas-shield. In an especially preferred embodiment of this aspect of the invention, the transmission shaft is an extensible rotary drive shaft, adapted to be retractably extended past a seal to position the reaming tool within said gas shield.
In an alternative aspect of the present invention there is provided a MIG welding torch reconditioning apparatus which includes a pneumatic supply line for supplying pneumatic lift means and wherein lift vent means is included, for venting a directed debris-scattering air-flow towards a mechanical transmission shaft proximal to seals thereon. In a preferred form of this particular embodiment, the transmission shaft is an extensible shaft, adapted to be retractably extended past said seals to position a reaming tool within a gas shield. An especially advantageous embodiment of this aspect of the invention involves the transmission shaft being a rotary drive shaft arranged in driving relation with a reaming tool to be aligned and inserted within a torches gas-shield and to be operable therein to remove at least some of any back-splash deposits laid down on interior surfaces of said gas-shield.
In a general sense, the present invention relates to MIG welding torch reconditioning apparatus comprising: a pneumatic supply line; pneumatic lift means powered from said supply line, pneumatic rotary drive means powered from said supply line; a mechanical transmission shaft that is connected in rotary driven relation to paid drive means and is retractably extensible on operation of said lift means. In this type of embodiment, an exhaust vent supplied by one of: air directly from said supply line; exhausted air flow from said lift means; exhausted air from said rotary drive means; or a combination of any of the forgoing. This exhaust vent is operable to vent a directed debris-scattering air-flow from these various sources, towards a said transmission shaft proximal to seals thereon. In an especially preferred form this exhaust vent is supplied at least in part by exhausted air from the rotary drive means.
In another embodiment, there is generally provided a MIG torch reconditioning apparatus which comprises an in-line, direct-drive arrangement of a motor, a mechanical transmission shaft, and chuck for receiving a reaming tool. A pneumatic lift means is provided to lift
Shaw Clifford C.
Tweco Products, Inc.
LandOfFree
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