Abstract: A heat sealing device in a packaging apparatus utilizing a plastic film for continuously seal both ends of a plurality of cylindrical bags made from the plastic film. The device comprises a pair of heat sealing members provided separatably and oppositely against each end portion of each cylindrical bag which is to be sealed transversely across the film. Each heat sealing member has a heat sealing surface which is to be pressed against the film and at least a pair of sealed chambers inside the heat sealing surface containing working liquid as a heat medium. A heat source is provided to heat at least a portion of the sealed chamber so that the working liquid generates vaporized gas by the heat. The sealed chamber is controlled to be kept at a pressure and a temperature so that the vaporized gas is condensed substantially at a temperature under which the film is sealed.

Abstract: A heat sealing device in a packaging apparatus utilizing a plastic film for continuously seal an overlapped axial portion of the plastic film. The device comprises a pair of heating rollers which are rotatably and oppositely placed to hold the overlapped portion of the film between them. Each of the heating rollers has a heating surface in its outer periphery which is pressed against the film and a coaxial and annular sealed chamber which is formed inside the heating surface and contains working liquid as a heat medium. A heat source is provided to be opposite at least to a portion of the sealed chamber to heat the working liquid. The working liquid generates vaporized gas upon heating by the heat source, and the pressure and the temperature in the sealed chamber are maintained at a predetermined degree so that the vaporized gas is condensed substantially at the temperature for fusing the film.