Ultrasonic sealing apparatus

Abstract

Plastic film in sheet form is supplied to a forming unit which forms it into tubular form with overlapping or fin-type edges. The edges are then caused to pass along an anvil and the horn of an ultrasonic sealing unit is positioned adjacent the edges for effecting ultrasonic sealing of the edges, the edges of the film passing through a gap between the horn and the anvil. An adjustable guide wheel is provided for ensuring that the edges are guided into proper relationship for ultrasonic sealing. The apparatus includes an adjustable rigid connection between the forming unit and the ultrasonic sealing apparatus for establishing a proper relationship between the forming unit and the ultrasonic unit and for providing the necessary rigidity. In order to ensure that the ultrasonic unit is effectively energized only when the film is moving therethrough, a tachometer or other speed-sensitive device responsive to movement of the sheet film is provided. A signal developed by this tachometer is transmitted to the ultrasonic sealing unit to ensure that the unit is effectively energized only when the film is moving through the sealing area and to control the level of energization of the ultrasonic unit in accordance with the speed of movement of the film. The horn is mounted on a support for adjustable movement toward and away from the anvil to vary the pressure exerted against the film edges. A transducer is mounted for movement into engagement with the support, the transducer being suitable for generating a signal indicative of the pressure exerted by the horn against the film edges.