Abstract: A protective ground connector for establishing a direct ground connection in response to a fault voltage in a welding circuit. A pair of smooth-faced metal blocks are clamped in face-to-face relationship with each other with a relatively thin shim of electric insulating material clamped between the opposed faces of the blocks. One of the blocks is electrically connected to a circuit to be monitored, the other block is electrically connected to ground. The electrical characteristics of the shim are such as to electrically insulate the two blocks from each other in the face of normal circuit voltages and to break down in response to a fault voltage in the monitored circuit to thereby establish a direct ground connection.

Abstract: A high speed seam welding system wherein single phase alternating current welding pulses are applied to electrode mechanism during only a less than maximum amplitude fractional portion of the wave form representing each successive current half cycle, and the current is substantially cut off between current applications to permit cooling. The relative seam welding movement of the electrode mechanism and the material to be seam welded is coordinated with the duration of the welding and cooling periods to more rapidly form a line of uniform weld nuggets. The system may also be operated at more conventional welding speeds to weld relatively heavy gauge materials.

Abstract: Resistance welding apparatus for simultaneously welding spaced generally parallel seams in sheet metal workpieces, as for example joining a pair of side panels to the back panel of a refrigerator cabinet. The panels are clamped upon a support table with their edges to be welded disposed in overlapping relationship. Support members of high electrical conductivity engage the underside of the clamped panels along and adjacent to the overlapped edge portions of the panels. A movable overhead carriage supports a pair of rotatable disc electrodes which are positioned to roll along the overlapped edge portions of the panels in opposed relationship to the underlying support members. Also mounted on the carriage are a pair of highly conductive shoes which roll along the central panel closely adjacent the respective electrodes.

Abstract: An electrode system for spot welding difficult-to-weld materials, such as aluminum, wherein a pair of spaced apart electrodes, one of which is a roller, clamp the overlapped strips of material to be spot welded. Mechanism moves the roller electrode toward and away from the other electrode, and other means is operated responsively to this movement for indexing the roller electrode incrementally circumferentially to successively present a new surface to the work held between the electrodes. A control circuit applies DC power to the electrodes such that the roller mentioned has the positive polarity and the other electrode the negative polarity.