Device for ultrasonic welding of at least two plastic foil layers

A device (1) for ultrasonic welding of at least two plastic foil layers (7, 9) for manufacturing a package, which device comprises at least one sonotrode (3) and at least one anvil (5) positioned opposite each other and which are each provided with a pressure surface (11, 13), which pressure surfaces can be moved away from each other and towards each other from a position of rest to a welding position and vice versa, the pressure surfaces in the welding position forming at least one welding section (L′) as well as at least one first and a second flow-out section (U′, U″) between which the welding section is located, at least one of the pressure surfaces in the welding section being of a convex shape for directing the ultrasonic energy, the pressure surfaces in the flow-out sections being provided with at least two pressure surface areas (30, 31) in essence extending parallel to each other for supporting the foil layers, characterised in that both the anvil and the sonotrode have inclined face areas between the welding section and the flow-out section by means of which inclined face areas the welding section passes into the flow-out section.