Population biology of social insect conservation

The present invention relates to an apparatus suitable for use in the automatic welding of pipes. The apparatus according to the invention comprises a fixed part or rail band which is clamped around the pipe at a prefixed position and a moving part which is driven with an orbital motion along the rail band and supports a swinging welding torch, a welding rod feeding mechanism and a torch position adjusting mechanism. The swinging motion of the welding torch is produced by a pneumatic system which permits both the amplitude and the frequency of said swinging motion to be adjusted. It is also possible to produce high swing frequencies and various times of stoppage for the torch at the ends of the swinging motion.