| 摘要 |
An extrusion die and flow control method incorporates a flow control in the formof a flow diverter which extends transversely across the flow path. The diverter forms part of a window upstream of the die lips and provides a slight tapering enl argement which may be moved along the window across the flow path from one side to th e other or preferably, from the center symmetrically outwardly, or vice versa, to di vert flow from the center proportionally to the edges without changing the total cross sect ional area of the window. The window is formed by a pair of axially rotatable cylindrical bars recessed in the die body which each have a flat forming the enlargement. In the prefe rred form the flat is helical. The helical flats are opposed or matched so that as the bars contra- rotate synchronously the enlargement will move across the window. Where the movement is symmetrical from the center or axis to each transverse edge and vice versa, the helical matching flats on each bar turn in opposite directions on each e nd of the middle of each bar. Where the enlargement simply moves from one transverse e nd of the window to the other the turn of the helix of each flat is the same from end to end of the bar, although for each of the pair, in the opposite direction. Movement of t he enlargement across the flow path isobtained by axial rotation of the bar. Ta ndem pairs of bars may be used separately or in conjunction with each other, and may ha ve axially inclined flats.
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