Abstract: Device (10) for ultrasonic welding of a flexible, notably tubular, structure (F), to be conformed into sachets, this device including at least two airgaps each defined between a sonotrode (20) and an anvil (30,40) carried by respective support structures (28,54) the distance between which varies between a close together welding position and a spaced apart flexible structure movement position, in which airgaps the flexible structure to be welded is intended to be received to produce at least two weld lines, wherein for each airgap an anvil and/or a sonotrode both associated with this airgap is at least partially mobile relative to a support structure (54) of this anvil or sonotrode.

Abstract: The present invention relates to a device for ultrasound welding of at least two overlapping sheets, comprising: at least one sonotrode for emitting ultrasound, at least one reaction part disposed at least partially facing the sonotrode, at least one intermediate wall other than a roller, movable relative to the at least one sonotrode and the reaction part, said intermediate wall at least partially defining a gap in which the sheets to be welded are inserted so as to execute at least one seal weld extending parallel in the direction of movement of the intermediate wall at the gap. At least one of the intermediate wall and the sonotrode has a transverse section comprising at least one relief projecting toward the gap.