Abstract: In a grid welding machine with a horizontal longitudinal wire guide path (4) and transverse wire feeders (27, 28) arranged above and below the latter and transverse rows of active welding electrodes (7, 8), the two rows of electrodes (7, 8) are moved up or down away from the longitudinal wire path (B--B) in synchronization with the welding cycle before transverse wires (Q1, Q2) are placed simultaneously on each side of the longitudinal wire assemblage (L). The transverse wires (Q1, Q2) are then brought into the welding position between the two rows of electrodes (7, 8) and the electrodes are applied to these transverse wires (Q1, Q2). Finally, a row of electrodes (7) are stopped as an abutment against which the welding pressure is applied through the other row of electrodes (8) so that a welding current flows between each electrode pair (7, 8) in series over the point of intersection of each longitudinal wire (L) with two contacting transverse wires (Q1, Q2).

Abstract: A convertible single or double spot welding machine operating by the electrical resistance method for producing grids or bar grates by single spot welding or double spot welding, has a transverse row of electrodes and at least one welding transformer on one side of the welding plane. Electrically conductive connections, which pass through the welding plane, connect the welding transformer to the electrodes located on the other side of the welding plane and close the welding current circuit for single spot welding. In order to convert from single spot welding to double spot welding, the connections which pass through the welding plane are removed, selected electrodes on the side of the welding plane remote from the welding transformer are connected in pairs by current bridges, and the supply lines from the welding transformer are respectively connected to the two electrodes opposite the electrodes connected by the current bridges.