Crimping sonotrode

An ultrasonic welding apparatus for crimping and welding an edge of a container by means of a counter-tool and a sonotrode for crimping an edge of a container, the sonotrode having an end face, the sonotrode being adapted to contact the edge of the container during a relative movement along a longitudinal axis, wherein the end face comprises a crimping portion, at least portions of the crimping portion forming an angle with the longitudinal axis that is greater than 0° and is smaller than 90° and the crimping portion being adapted to contact a crimping edge,

• wherein the sonotrode is characterized in that the end face comprises a groove, the crimping portion being arranged within the groove, the end face comprising an inner end face portion and an outer end face portion, wherein the inner end face portion is separated from the outer end face portion via the groove, wherein in an axial direction perpendicular to the end face, either the inner end face portion protrudes over the outer end face portion, or the outer end face portion protrudes over the inner end face portion, and wherein the sonotrode is intended to be adapted to be moved between two positions, an initial position and a welding position, wherein the counter-tool comprises a sealing surface which, when in the welding position of the groove wall adjoining the end face portion, which protrudes opposite the other end face portion, said sealing surface is arranged opposite such that, when in the welding position, when the inner end face portion protrudes opposite the outer end face portion, the inner end face portion is arranged at least partially within a cavity of the counter-tool and, when the outer end face portion protrudes opposite the inner end face portion, the counter-tool is arranged at least partially within a cavity of the sonotrode.