ROTARY ULTRASONIC SEALING

摘要

An apparatus comprising: a sonotrode (10) comprising an ultrasonic actuator (12) coupled to an elongate sealing end face (16) for delivering ultrasonic energy to webs in a sealing gap (17); and a rotating cylindrical anvil (24) having at least one raised portion (22) extending longitudinally along an outer surface thereof, said raised portion (22) having a radially outer surface, whereby said sealing gap (17) is defined intermittently between the end face (16) of the sonotrode (10) and the radially outer surface of the raised portion (22) of the anvil (24) as the raised portion (22) rotates past the end face (16) of the sonotrode (10), characterised in that the elongate sealing end face (16) of the sonotrode (10) has a substantially helical surface, whereby the sealing gap (17) travels helically along said surface as the raised portion (22) of the anvil (24) cylinder rotates past the end face (16) of the sonotrode (10). Also provided are methods of providing transverse seals in webs by means of the claimed apparatus.