Automatic Welder

The invention provides an automatic welder (1). The automatic welder comprises a support frame (2) and a tensioning device (17) for reversibly engaging at least two oppositing cantilever arms (3,3') and applying a tensioning force between cantilever arms (3,3'); an opening position in which the oppositing cantilever arms (3,3') are relatively spaced apart and a closed position in which the oppositing cantilever arms (3,3') are mutually engaged and supported. A cantilever arm (3) is installed on the tensioning device (17) in a anti-reverse mode and is pivotable relative to the other cantilever (3'). One cantilever arm is moved from the opening position to a closed position by means of pivoting the tensioning device (17). The tensioning force is generated by a spring-loaded element (9) on the tensioning device (17). One end of the spring-loaded element (9) is rigidly connected to a support element (2') of the tensioning device, and the other end is pivotally installed on the support frame (2) by means of a doub