An ultrasound unit

摘要

The disclosure relates to an ultrasound unit comprising an annular tool (4) or sonotrode intended for welding packaging containers with circular cross section. The tool (4) has a mass plane (10) located at a right angle to the centre axis (8) of the tool, and with a mean circumference (6) whose length is adapted to the wavelength of the ultrasound source. With a view to making possible the welding of packaging containers with a circumference which is larger than the mean circumference of the sonotrode, a circular working surface (7) is employed which is located in a working plane (9) a distance from the mass plane (10).