Patent ID: 8621827

Claim:
A sonotrode comprising: a head which defines a sealing surface elongated along a first direction; and at least one first and one second drive unit distinct from one another, each comprising at least one piezo-electric element; wherein said first and second drive units are electrically connectable to a unique generator so as to cause oscillation of said head along a second direction transversal to said sealing surface with a wave having a given wavelength during operation; the height of said head measured along said second direction being substantially equal to the half of said wavelength of said oscillation in the direction of said second direction; said sonotrode further comprising: at least one first slot which extends through said head transversally to said first and second directions; at least a finite number of nodal points where an amplitude of the oscillation of said head during operation is substantially equal to zero; and a plane on which at least some of said nodal points lie and which divides said head into a first portion and in a second portion; wherein said at least one first slot extends completely within one only of said first portion and said second portion, said at least one first slot being spaced apart from said plane.