Ultrasonic welding apparatus

An ultrasonic welding apparatus (100) for welding together at least two superposed sheets (1, 2) made of plastics material and travelling continuously along a determined path (F), the apparatus (100) comprising a sonotrode (101) and an anvil (102) disposed facing each other so that their facing surfaces (101′, 102′) define a through gap (103) through which two superposed sheets (1, 2) to be welded together pass, the gap having an inlet section (104) and an outlet section (105), the sonotrode (101) vibrating at high frequencies to emit ultrasound waves, wherein the anvil (102) is fixed and said facing surfaces (101′, 102′) of the sonotrode (101) and of the anvil (102) are generally plane and converge towards each other such that the section of said through gap (103) decreases continuously between its inlet section (104) and its outlet section (105), and the surface (102′) of the anvil (102) facing the sonotrode (101), presents a pointed profile formed by two sloping flats (102a, 102b) that between them form an obtuse angle.