| 摘要 |
<p>A co-extrusion head (20) having no moving parts and a system including the head, each designed for the fabrication of, e.g., differential stiffness tubing. In the transition section of the tubing, the tube wall gradually changes from a first resin to a second resin to form a continuous unbroken tube without abrupt joints. The co-extrusion head includes a body defining a first flow channel (38), a second flow channel (44), and a joint flow channel (51), each having an upstream end and a downstream end. The downstream ends of the first and second channels open into the upstream end of the joint flow channel. The body further defines a first inlet (32) for the introduction of the first resin into the upstream end of the first channel, a second inlet (34) for the introduction of the second resin into the upstream end of the second channel, and an exit (52) for the discharge of the resins from the co-extrusion head (20). The co-extrusion head (20) further includes a die (40) closely fitting within the exit, and a tip (42). The contact volume within the joint flow channel is selected to determine the length of the tubing transition section. The co-extrusion system includes the above-described co-extrusion head and modulating means for controlling the flow of the second resin into the second inlet.</p> |
