RESISTANCE BUTT WELDER

A welder arranged inside pipes to be welded comprises a housing with the longitudinal axis thereof matched with the axis of the pipes. On the housing are a welding transformer and two mechanisms clamping the pipes, each having a drive moving the mechanism along the axis of the housing, and each being electrically connected to the transformer. The housing has mounted thereon a pipe flashing and upsetting mechanism with its own hydraulic drive, kinematically coupled to one of the pipe clamping mechanisms, a hydraulic pump supplying fluid to said drives, and a mechanism driving the welder along the pipes' axis. The housing carries two bearing discs secured at opposite ends and three clips mounted on roller supports and movable along the housing's axis. Two clips are incorporated in the first and second clamping mechanisms, respectively, and the third is part of the flashing and upsetting mechanism. The clip incorporated in the first pipe clamping mechanism is interposed between the bearing disc and the clip of the second clamping mechanism and is coupled to the bearing disc by means of its hydraulic drive. Another kinematic coupling is between this clip and the bearing disc. The clip of the flashing and upsetting mechanism is close to the second bearing disc and coupled thereto by means of its own hydraulic drive. The clip of the second clamping mechanism is interposed between the clip of the first clamping mechanism and that of the flashing and upsetting mechanism and is coupled to the clip of the flashing and upsetting mechanism by its hydraulic drive; and an additional kinematic coupling is between the clip of the second clamping mechanism and said clip of the flashing and upsetting mechanism.