Packaging machine

A packaging machine (1) moves its heater unit (50) for longitudinal sealing of a tubularly formed film between a sealing position at which the heater unit contacts the film and a retracted position at which it is separated from the film. In addition to the mechanism for this motion, an air cylinder (66) is provided for controlling the compressive force with which the heater unit (50) at its sealing position compresses the film. A pressure controlling system regulates the air pressure supplied to the air cylinder. If the mechanism for moving the heater unit (50) also employs another air cylinder (71), a higher pressure for moving the heater unit and a lower pressure for controlling its compressive force may be generated from a single air source and supplied to the two air cylinders by a switching mechanism. A single air cylinder (71) with two air chambers (71c,71d) may be used for the both functions. A motor (73) is additionally provided for removing the heater unit and its support unit much farther away from the film to provide a large enough space for exchanging the former and/or the chute of the packaging machine.