| 摘要 |
A method for heat sealing a film with a smooth seam which extends the transverse width of a wrapped package utilizes a mechanism having a cool clamping portion and a hot sealing portion which are sequentially actuated. The clamping portion, with segments upstream and downstream of a sealing position, is activated to firmly hold the film. The sealing portion is located between the upstream and downstream segments of the clamping portion. The heated sealing portion is brought into very brief, instantaneous contact with the film and retracted, leaving the clamping portion in contact with the film for a comparatively long time to allow longitudinal film shrinkage and prevent transverse film shrinkage of the film. Lastly, the clamping portion separates and the next package in a succession of film-enclosed packages is moved downstream of the sealing position.
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