carton sealing apparatus for sealing a rectangular end closure of a thermoplastic coated paperboard carton by ultrasonic vibrations . the apparatus includes an anvil , or backup member , and an ultrasonic vibrating tool . the mandrel is received in the carton with the end closure to be sealed folded against the smooth end surface thereof . the ultrasonic vibrating tool engages the end closure on the opposite side thereof from the mandrel , and , when energized , generates heat sufficient to cause the thermoplastic coating of the paperboard to flow and weld the layers of the end closure together . ribs project from the end surface of the vibrating tool to provide a sealing pattern of &# 34 ; bow - tie &# 34 ; configuration , the ribs having various heights with respect to the end surface of the vibrating tool to accommodate changes in the number of layers of paperboard at the different areas on the end closure .