| 摘要 |
A method and apparatus are described for coextruding two materials A and B, in which B is extruded on A through a port (3), in which the separating wall between the flows of A and B is formed as a flap closure (4) adapted to act as a non-return valve for the flow of B into A, and further means are provided for extruding B through the port in pulses. The pulses may be effected by opening and closing the closure, by mechanical transmission means or by the effect of imposing pressure difference on the flap (4) by the flows of A and/or B. The pulsing means preferably involves rams (1). The invention is particularly suitable for extruding a low viscosity material B onto a higher viscosity material A, or for making sheets or pipes with alternating segments of differential flexibility, or for coextruding a flow of solid particles with a flow of liquid. |
