Capstan drive assembly for filler wire in electric arc welding

A wire feeder for providing filler wire in electric arc welding, comprising:

• a capstan having an annular groove in the periphery thereof for receiving said filler wire,
• a motor for driving said capstan,
• an inlet wire guide for receiving said filler wire and supplying said filler wire tangentially to said capstan at said groove,
• a floating pressure shoe having a leading roller and a trailing roller, said leading and trailing rollers driven by said shoe against the periphery of said capstan for holding said filler wire in said groove, said pressure shoe having a contoured first scraper plate between said leading and trailing rollers for driving a leading tip of said filler wire between said trailing roller and said capstan,
• a first wire straightening roller offset from the periphery of said capstan,
• a stripper plate having a leading edge positioned at the periphery of said capstan, said stripper plate for lifting the leading tip of said filler wire to the surface of said first wire straightening roller,
• a second wire straightening roller offset from the periphery of said capstan, and positioned parallel to said first wire straightening roller,
• the first wire straightening roller directs the leading tip of said filler wire from the surface of said first wire straightening roller to the surface of said second wire straightening roller, and
• said first and second wire straightening rollers positioned for passing said filler wire on opposite sides thereof, wherein said filler wire receives a first cast as it passes between the leading and trailing rollers of said pressure shoe and said capstan, and recesses a second cast when said filler wire passes over said first and second wire straightening rollers.

A method for straightening filler wire which is drawn from a spool which supplies wire to a an arc for electric arc welding, comprising the steps of:

• advancing said filler wire by rotating a capstan having said filler wire pressed against a predetermined arcuate length of the periphery of said capstan by first and second rollers spaced about the periphery of the capstan,
• deforming said filler wire to have a predetermined cast as said filler wire is drawn over a portion of the periphery of said capstan, wherein said predetermined cast substantially overcomes previous casts impressed to said filler wire,
• removing said filler wire from contact with said capstan after deforming said filler wire to have said predetermined cast, and
• after removal from said capstan, deforming said filler wire in an opposite direction to said predetermined cast with apporximately an equal magnitude to that of said predetermined cast for making said filler wire substantially straight.

A method for self-feeding filler wire through a wire feeder for supplying the filler wire to an arc for electric welding, comprising the steps of:

• directing a leading tip of said filler wire tangentially to a peripheral surface of a capstan, said surface having an annular groove for receiving said filler wire,
• capturing the leading tip of said filler wire in said groove between a first pressure roller and said capstan,
• rotating said capstan to advance said filler wire,
• deflecting the leading tip of said filler wire by a first scraper plate which directs the leading tip of said filler wire between a second pressure roller and said capstan, said filler wire being deformed to have a first cast as the filler wire passes between first said and second pressure rollers,
• deflecting the leading tip of said filler wire from out of said groove by a stripper plate toward the surface of a first wire straightening roller which is offset from the periphery of said capstan,
• directing said leading tip of said filler wire to the surface of a second wire straightening roller aftter the leading tip of said filler wire has passed said first wire straightening roller, and
• said filler wire passing on opposite sides of said wire straightening rollers to an outlet whereby said filler wire rides on said rollers and said capstan without contact to said scraper plate and stripper plate when said leading tip has passed to said outlet.

A method for feeding and straightening filler wire for electric arc welding wherein the filler wire has been stored on a spool and has been impressed with undesirable casts, comprising the steps of:

• directing said filler wire between a first pressure roller and the periphery of a capstan which has a groove in the periphery thereof for receiving said filler wire,
• rotating said capstan to advance said filler wire wherein said filler wire is captured in said groove, said filler wire being maintained in said groove by a scraper plate as said capstan is advanced,
• passing said filler wire in said groove between a second pressure roller and said capstan, said second pressure roller fixed in position relative to said first pressure roller, whereby said filler wire is defomred to have a predetermined cast during the travel of said filler wire between said first and second pressure rollers,
• removing said filler wire from said groove after said filler wire has passed said second pressure roller, and
• passing said filler wire on opposite sides of straightening rollers, after removal of said filler wire from said groove, for deforming said filler wire between said straightening rollers in a direction opposite to that of said predetermined cast with a magnitude substantially equal to said predetermined cast, whereby said filler wire is rendered to be substantially straight following passage between said straightening rollers.