Programmable resistance seam welding apparatus and method

An apparatus for resistance seam welding workpieces, the apparatus comprising:

• a support for holding a pair of workpieces in a temporary assembly with opposing surfaces in contact along a seam line;
• a first ball electrode and a second electrode simultaneously engagable with opposite surfaces of the assembly along the seam line for locally conducting welding current through the workpieces to weld the workpieces together along the seam line, each ball electrode being rotatable in any direction against its respective workpiece surface for conducting welding current therethrough;
• a first programmable positioner carrying the first ball electrode and operative to rotatably move the first ball electrode along the seam line in engagement with one side of the assembly;
• the second electrode operatively engaging an opposite side of the assembly and operative to conduct current passed through the assembly opposite the locations of the first ball electrode;
• and
• an electric current producing device connected with the electrodes for welding the assembly together along the seam line.

An electrode assembly for use in resistance seam welding of electrically conductive metal workpieces together, the assembly comprising:

• a ball electrode formed of low resistance electrically conductive heat resistant material of generally spherical configuration;
• and
• a coupler shank mountable to a welding tool holder and including an end defining a part-spherical socket receiving the ball electrode and a retainer secured to the shank and retaining the ball electrode for free omnidirectional rotation in the socket, the ball electrode protruding beyond the retainer for rotatable engagement with a workpiece;
• the socket being connectable with a source of welding current and formed of material capable of conducting resistance welding current to the ball electrode.