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Apparatus for producing a machine-direction heat seal in a moving web of plastic film including a block adapted to be supported on one side of the hem and having a plurality of rollers mounted thereon at spaced locations in tandem for engaging the film along the path of the heat seal to be formed in

Apparatus for producing a machine-direction heat seal in a moving web of plastic film including a block adapted to be supported on one side of the hem and having a plurality of rollers mounted thereon at spaced locations in tandem for engaging the film along the path of the heat seal to be formed in the hem. The block has a corresponding plurality of surfaces each of which is adapted to be engaged by a side of one of the rollers. A heater is provided for heating the block and its plurality of surfaces and the rollers are maintained in contact with the plurality of surfaces whereby movement of the hem though the heat sealing apparatus causes the plurality of rollers to rotate and maintain contact with the plurality of surfaces whereby the rollers are in turn heated by conduction from the block and produce the heat seal in the hem.

대표청구항 ▼

Apparatus for producing a machine-direction heat seal in opposing layers of thermoplastic film in a hem in a moving web of thermoplastic film comprising: a blok supported on one side of the hem, a plurality of rollers mounted on said block at spaced locations in tandem in the direction of web moveme

Apparatus for producing a machine-direction heat seal in opposing layers of thermoplastic film in a hem in a moving web of thermoplastic film comprising: a blok supported on one side of the hem, a plurality of rollers mounted on said block at spaced locations in tandem in the direction of web movement for engaging one of the opposing layers of film along the path of the hem in the direction of web movement, said block having a corresponding plurality of surfces each of which is engaged by a side of one of said rollers, means for heating said block and its plurality of surfaces, means for maintaining said rollers in contact with said plurality of surfaces on said block for heating said rollers by conduction from said block, and means supported on the opposite side of the web comprising a plurality of back-up rollers for engaging the other opposing layer of film in the hem and cooperating with said plurality of heated rollers to press together the opposing layers of films in the hem, said plurality of heated rollers and said plurality of back-up rollers being freely rotatable whereby movement of the web through the heat sealing apparatus causes the pluralities of rollers to rotate and heat seal the opposing layers of film in the hem in the direction of web movement. In a machine for making bags having front and back panels from thermoplastic film, apparatus for heat sealing a pair of hems in a moving web of the thermopalstic film, each of the hems comprising folded oppposing layers of the web in the front and back panels, comprising: a first support means supported on one side of one of the hems, a plurality of rollers mounted on said first support means at spaced locations in tandem in the direction of web movement for engaging one of the layers of film in the one hem along a first path in the direction of web movement, a second support means supported on one side of the second hem, a plurality of second rollers mounted on said second support means at spaced locations in tandem in the direction of web movement for engaging one of the layers of film in the second hem along a second path in the direction of web movement, means for heating each of said plurality of rollers, and means supported between the pair of hems comprising a plurality of back-up rollers for engaging the other layers of film in the hems and cooperating with the pluralities of heated rollers to press together the opposing layers of film in each of the hems, said back-up rollers being alternated so that every other back-up roller is used as the back-up for the heated rollers sealing the hem on the front of the bag and alternate back-up rollers are used for the back-up of the heated rollers sealing the hem on the back of the bag to minimize separation distance between the hems during the heat sealing operation, said pluralities of heated rollers and said plurality of back-up rollers being freely rotatably whereby movement of the web through the heat sealing apparatus causes the pluralities of rollers to rotate and heat seal the opposing layers of the web in the pair of hems along the respective paths in the direction of web movement.