| 摘要 |
<p>A finishing welt, comprised of a reinforcing polyethylene rod surrounded by a fabric scrim and an outer encasing layer of polyvinyl chloride, is formed in an extrusion-embossment method and apparatus. The method includes feeding a composite preform, consisting of the polyethylene rod and the scrim, first through an essentially key-hole shaped passageway in a core pin of an extruder crosshead and then into a chamber within the crosshead where plastic material under pressure flows onto the preform. Immediately thereafter, the preform is conveyed through an essentially keyhole shaped orifice, where the welt is formed by extrusion. Next, the opposed sides of the welt are sequentially embossed as the welt is conveyed over external peripheral embossing surfaces of two spaced rollers. The resultant welt is essentially key-hole shaped in cross-section, with the scrim surrounding the rod within the enlarged head portion of the welt and extending into the smaller depending flange portion. As a result of the extrusion step, the outer encasing layer of polyvinyl chloride is bonded through the scrim in the welt flange; and as a result of the sequential embossment, the outer surface of the welt is free of any significant longitudinal rib.</p> |
