Tube joining

The patent deals with the pressure-tight joining of two aluminium tubes in a solder bath, e.g. of a capillary tube, outer diameter 6 mm, as is common in cooling systems, with a stronger standard tube with inner diameter of about 8 mm. In the proposed soldered joint using ultrasonics, trapped air within the ring gap between the tubes to be filled with solder (in the mentioned example 1 mm all round) is avoided. The tubes pushed into one another to a distance of several cm are fixed for a uniform air gap prior to placing in the solder bath. This is done by several beads of the same diameter pressed in from outside. To weld the two tubes, which can no longer move relative to one another, these are vertically immersed in the solder bath until the inner tube, with its tube end pointing upwards, remains above the solder bath level. Hence no solder rising in the gap can get into the inner tube. The outer tube is free from solder in its flow section. The beads do not prevent the penetration of the solder into the gap. (HP)