Welding gun tip

#This invention relates to a welding gun tip of the kind through which a welding wire extends and more particularly to a welding gun tip having a guide through which the welding wire extends to avoid erosion of the tip.

#Welding guns of the type having a replaceable tip and an axial passage through which a welding wire extends are in wide usage, particularly in automatic or robotic welding machines. The welding wire typically is fed through the welding gun and the tip from a coil of such wire. Although that portion of the wire which extends through the tip is substantially straight during its passage through the tip, that portion of the wire which projects beyond the tip tends to retain some residual curvature as a result of its being withdrawn from a coil. The residual curvature of the wire causes it to bear against the edge of the tip defining the wire-accommodating passage. Since the welding wire usually is formed of metal which is harder than that forming the tip, movement of the wire through the tip soon causes the wearing of a groove in the tip adjacent its free end. Such groove causes that portion of the welding wire which extends from the free end of the tip to occupy a position to one side of the longitudinal axis of the tip. Consequently, movement of the tip toward an article to be welded causes the free end of the welding wire to engage the workpiece at a position to one side of the intended point of engagement. This results in inaccurate welding and, in some instances, improper welding of the workpiece.

#Another problem encountered with conventional welding tips of the kind referred to is that repeated welding operations using a welding wire that is not accurately located with respect to the workpiece can result in arcing between the welding wire and the tip and electrical discharge machining of the tip adjacent the passage through which the welding wire extends. Such machining is undesirable inasmuch as it further deforms the wire-accommodating passage in the welding tip, thereby introducing further errors in the positioning of the free end of the welding wire with respect to the workpiece that is to be welded.

#FIG. 1 is a fragmentary, sectional view illustrating a welding gun in which is accommodated a welding tip constructed in accordance with the invention;

#FIG. 2 is an enlarged, end elevational view of the tip shown in FIG. 1;

#FIG. 3 is a greatly enlarged, fragmentary view of a portion of the welding tip; and

#A welding tip constructed in accordance with the invention is designated generally by the reference character 1 and comprises a body 2 formed of a relatively soft material such as copper. One end 3 of the body is threaded for removable accommodation in a threaded bore 4 at one end of a welding gun 5, as is conventional. The body 2 has an axial passage 6 extending therethrough and is of such diameter as freely to accommodate a welding wire 7 which is unwound from a coil thereof (not shown) and has a free end 8 which projects beyond the free end 9 of the tip body 2 for engagement with a workpiece, as also is conventional.

#At the free end 9 of the body 2 is a counterbore 10 having a flat base 11. Accommodated in the counterbore 10 is a guide 12 comprising an annular body 13 having a central opening 14 therethrough. The inner side 15 of the guide 12, i.e., the side which confronts and seats on the recess base 11, is convexly arcuate or crowned, thereby providing a tapered welding wire inlet 16 to the opening 14. The opposite or outer surface 17 of the guide 12 may be flat.

#The guide 12 may be maintained in fixed position within the counterbore 10 in any suitable manner, such as by peening the outer end of the body 2 to provide a lip 18 which overlies and bears against the outer surface 17 of the guide.