| 摘要 |
<p>An apparatus for welding webs of synthetic thermoplastic material as they move around a deflecting roller comprises an elongate housing, which is movable toward the deflecting roller to assume a position in which said housing is approximately concentric to said roller and closely surrounds said roller around a part of its periphery, and said housing is provided with at least one longitudinally extending hot-air duct, which is curved in the same sense as the housing and is provided with an inlet for receiving flowing hot air and is formed with a plurality of outlet bores or gaps in that wall of the housing which faces the deflecting roller. In order to minimize heat losses, the housing contains a second passage, which approximately concentrically surrounds the hot-air passage and contains an elongate heating element, and the second passage adjacent to one end thereof is provided with an inlet opening for receiving flowing air and adjacent to its opposite end is provided with an opening or line through which the second passage communicates with the hot-air passage.</p> |
