Pipe resistance butt welding apparatus

A pipe resistance butt welding apparatus comprising:

• (a) a body having an elongated carrying member;
• (b) an internal expanding clamp including current-feeding shoes and rigidly attached to said body;
• (c) an internal expanding clamp including current-feeding shoes and movably mounted on said elongated carrying member for axial motion;
• (d) a drive intended to enable reciprocating motion of said internal expanding clamp mounted on the elongated carrying member;
• (e) a trimming mechanism for removing flash, mounted on at least one of said internal expanding clamps;
• (f) centering supporting rollers mounted on the body by means of spring-loaded levers;
• (g) three-arm rockers rotatably mounted on said body, spring-loaded, and having three arms;
• (h) driving wheels mounted on the first arms of said three-arm rockers so as to be movable between first positions engaged with the internal surface of pipe being welded and second positions disengaged from the internal surface;
• (i) a rotation drive enabling rotation of said wheels and mounted on said body;
• (j) additional supporting rollers mounted on the second arms of said three-arm rockers so as to movable between positions disengaged from the internal surface and positions engaged with the internal surface, said additional supporting rollers being in the disengaged positions thereof when said driving wheels are in engaged positions and said additional supporting rollers being in the engaged positions thereof when said driving wheels are in disengaged positions;
• and
• (k) a power cylinder mounted on said body and having a rod connected with the third arms of said three-arm rockers for controlling movement of said three-arm rockers.