Abstract: In opposition to a lower electrode (31) fixed to a frame (3), an upper electrode (29) is carried by an upper pressing base (23), which is engaged with a vertical guide rail (25) and joined by a resilient slide mechanism to a piston rod (35L) of a hydraulic cylinder (35) connected to a hydraulic circuit operable for an increased distance (L3) between electrode shanks (15, 7) and fastened at a head end thereof to a lower pressing base (33), which is engaged with the guide rail and joined to a piston rod (37L) of an air cylinder (37) fastened at a head end thereof to the frame and connected to a pneumatic circuit operable for supplying a balancing pressure to have the piston rod (37L) thereof contracted to stand with a total load and for relieving the pressure when a mechanical valve (85) is operated with a pedal arm (49) stepped down for starting a welding, while the pneumatic circuit is changed over by a limit switch (57) to force down the lower pressing base.

Abstract: A spot welder apparatus includes: a single welding power source (5); a welding current distributor (7) connected to the single welding power source; and a plurality of spot welders (1A, 1B, 1C) connected to the welding current distributor. Each of a plurality of the spot welders is activated alternately by welding current distributed by the welding current distributor. When two start signals are generated almost simultaneously, a first spot welder which generates the start signal earlier is activated, and a second spot welder which generates the start signal later is kept under pressurized condition. Immediately after the first spot welder is deactivated, the second spot welder is then activated. The spot welder apparatus is low in cost and small in installation space, without increasing the user' current capacity.

Abstract: In a spot welding apparatus in which a column (7) is stood on a base (5) provided with a worktable (3) for supporting work (W); and a welding arm (15) having an electrode (13) at a free end portion thereof is pivotally supported up and down at a lower portion of a support cylinder (11) hung from a support beam (9) supported by the column (7) horizontally, the spot welding apparatus comprises an arm supporting section (47) for supporting support members (49, 55, 53, 57) for pivotally supporting the welding arm (15), so as to be movable up and down relative to the support cylinder (11) and further urged upward; and an arm pressing section (37) for pressing a free end portion of the welding arm (15) downward against an urging force of the arm supporting section.