For the present purposes, "welding" can fairly be said to embrace the fusing together of, in particular, two or more metal parts. Welded joints often exhibit greater rigidity than bolted or riveted constructions, and good quality welds are nonporous and leak-proof. In point of fact, good quality welds approximate the level of strength of the parent materials. Weld strengths are only slightly reduced below those levels as a consequence of unfavourable heat stresses that are set up in the immediate vicinity of the weld during the welding process. The potential advantages of welding in manufacturing processes include reduced capital investment requirements, greater flexibility of design, quicker change over to new or alternate designs, reduced machining and cleaning of parts, and improved strength to weight ratios in the assemble product.
The realization of any one or more of these associated advantages is, of course, contingent on the quality of the weld in question. There are a number of factors which impact on the character and quality of the weld, 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.
A commonly used welding technique involves resistance welding. At least two welding electrodes are arranged in mutually opposed relation along a common axis, along which they are relatively movable. The two or more work pieces that are sought to be welded ar interposed between the two electrodes while they are arranged in axially spaced relation from one another. When the workpieces are properly mutually aligned there between, the electrodes are moved towards one another, and embrace the workpieces in forcibly clamped relation, whereupon an electric current is passed between the electrodes and the heat generated by the electrical resistance of the interposed workpieces results in localized melting of the workpieces proximal to the contacting electrode surfaces. The melted materials from the two or more clamped workpieces fuses together and the intermingled materials harden into a unified piece once the electrical current is discontinued. This welding technology utilizes large, physically robust electrodes in order to provide the prerequisite clamping strength. Typical electrodes used in industrial applications may be one half inch in diameter, or more.
The quality of the weld is to some degree, contingent on the condition of the mating surfaces of the electrodes. It was with this in mind that a variety of devices were produced, which were intended to recondition the electrodes. Such a treatment is necessary since the surfaces of the electrodes degrade quite quickly over the course of normal use. Examples of surface reconditioning apparatus for use in treating resistance welding electrodes are disclosed in the following patents: U.S. Pat. Nos. 4,682,487; 4,856,949; 4,916,931; and 4,921,377.
ARC welding is another well known welding technique. This differs fundamentally from resistance welding in that ARC welding electrodes are deliberately consumed during the welding process, and thereby come to form an integral component of the welded product. Accordingly, the problem of electrode reconditioning that arises in association with resistance welding, does not arise in ARC welding practices.
MIG (metal-inert-gas arc) welding is such an ARC welding process. More particularly, it is a process in which the electrode, in the form of a relatively fine wire, is continuously fed from a large spool driven by a variable speed welding drive. The speed at which the wire electrode is delivered to the weld is controlled in order to optimize arc length and burnoff rate during the welding process.
The electrical arc is enveloped in a moving gas flow, usually argon or other inert gas, or mixtures thereof. In an especially preferred form, MIG welding utilizes carbon dioxide as a shielding gas.
In MIG welding generally, both the wire electrode and the gas are 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 which 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 allows for 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 which are attributable to adverse gas flow or arc patterning influences.
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. This realization has led to the development of a number of devices that are intended to perform the necessary operations.
By way of example, one such device, which is intended for use in robotic MIG welding operations, there is provided a heavy gauge wire that is clamped at one end thereof, in upstanding relation, with its uppermost free end available to be received internally of the torch, between the hood (or gas shield) and the tip. The robotic arm is preprogrammed to essay the torch along a predetermined circular path during the cleaning cycle, so that the upstanding wire dislodges splatter material from the two opposed surfaces of the hood and the tip. This approach to the problem can result in the tip being bent out of concentric alignment within the hood, which will in turn result in the very problems that the cleaning cycle is intended to help avert.
Two other such devices each employ a two-part clamping chuck, having a fixed jaw and a movable jaw. Such arrangements do not compensate for differences or vacations in torch nozzle sizes, or off-centred torch insertion, and can result in significant torch nozzle damage.
These clamps are intended to secure the torch in a rigidly-held and centred position, relative to an axially aligned rotating platform. This platform supports one end of each of a number of rotatable, longitudinally extending, substantially elongated blades which are aligned in such a way as to extend in free standing relation within the space between the hood and the tip, and upon rotation to dislodge the splatter from the two surfaces. In both such devices the design of the clamping chuck with its stationary jaw and the use of the substantially elongated blades, can still result in the tip being bent out of alignment relative to the hood, with the seriously adverse consequences already alluded to herein before.
As a consequence of the forgoing, there remains a need in the art for devices that are adapted to minimize the risk of misaligning the tip, while at the same time effectively removing the splatter from within the MIG torch.