| 摘要 |
The present invention provides a portion of a die assembly (20) for use in the extrusion of foamed polystyrene. The die assembly includes a first plate (21), a second plate (22), and an insert (23). The first plate has an upstream face (24), a downstream face (25), and a first opening (26) extending between the two first plate faces. The walls (28) of this opening are divergent in a downstream direction. The second plate has an upstream face (29) arranged to abut the first plate downstream face, a downstream face (30), and a second opening (31) extending between the second plate faces and communicating with the first opening. The second opening is bounded by non-divergent walls (32). The insert has a forward marginal end portion mounted on the first plate in the first opening, and has a rearward marginal end portion arranged in the second opening. The insert has a leading edge (33) that is spaced substantially equidistantly from the first opening walls in the vicinity of the first plate upstream face by a distance (D), and has a rear edge (34). The rear edge has a transverse cross-section configured and arranged such that a distance between adjacent portions of the rear edge and between the rear edge and the second plate opening walls in the vicinity of the second plate downstream face is no more than a predetermined distance (d). The velocity profile of foamed polystyrene passing sequentially through the first and second plate openings is increased in length or amplitude and distributed substantially uniformly across the transverse cross-sectional area of the second plate opening in the vicinity of the insert rear edge.
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