| 摘要 |
<p>In an extrusion head for use in producing multi-layered plastics products, the head comprises a central mandrel 15 and an outer structure 4, 5, 6, 7, 8, encircling the mandrel and defining, with the mandrel, a passage extending to an extrusion outlet 16. A plenum chamber 40 is provided at the end of said passage remote from the extrusion outlet, and ducts 43, 43a are provided for supplying plastics material to said plenum chamber 40 to pass therefrom along said passage. The said passage includes, at a position therealong which is downstream of the plenum chamber, a portion of limited axial extent defined between the outer structure and an equalisation ring 102 accommodated within a complementary groove 104 formed around the mandrel and projecting radially @therefrom@. The equalisation ring is adjustable transversely of the longitudinal axis of the head by adjustment screws extending, for access, to the exterior of the head, without passing through said passage. The head includes further supply passages 48, 52 extending from respective further plenum chambers 46 and 50 which communicate with the extrusion passage defined between the mandrel 15 and the outer head structure at respective positions downstream of the ring 102.</p> |
