초록 ▼

An extrusion die and flow control method incorporates a flow control in the form of 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 enlargement which may be moved along the window across the

An extrusion die and flow control method incorporates a flow control in the form of 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 enlargement which may be moved along the window across the flow path from one side to the other or preferably, from the center symmetrically outwardly, or vice versa, to divert flow from the center proportionally to the edges without changing the total cross sectional 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 preferred 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 end of the middle of each bar. Where the enlargement simply moves from one transverse end 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 the enlargement across the flow path is obtained by axial rotation of the bar. Tandem pairs of bars may be used separately or in conjunction with each other, and may have axially inclined flats.

대표청구항 ▼

An extrusion die having die lips comprising in combination a flow control upstream of the die lips and having an opening extending transversely across the flow path within the die and forming a restricted narrow rectangular window having an enlargement therein along the long side of the window, and

An extrusion die having die lips comprising in combination a flow control upstream of the die lips and having an opening extending transversely across the flow path within the die and forming a restricted narrow rectangular window having an enlargement therein along the long side of the window, and adjustment means uniformly to move such enlargement along the long side of the window across the flow path. A method of controlling the profile of an extrudate comprising the steps of forming a plastic melt, extruding the melt through a die having die lips, providing upstream of the die lips a restricted narrow elongated flow path window symmetrical with the transverse extent of the die lips, providing an enlargement in the long side of the window, and adjusting the position of the enlargement uniformly across the flow path to control the flow through the die lips.