| 摘要 |
1525439 Nozzles; mixing in conduits N LUNDBERGS FABRIKS AB 18 Nov 1976 [18 Nov 1975] 48205/76 Headings B1C and B2F [Also in Division B5] A nozzle suitable for the production of an expanded plastics layer in a cavity comprises an outer casing 24 closed at both ends, a central tube 26 coaxially disposed in said casing and open at one end to form the nozzle outlet, and two supply tubes 27, 28 arranged at diametrically opposed sides of the central tube and forming therewith a partition extending axially through the casing, said supply tubes being closed at their downstream ends and communicating with the bore of the central tube 26 through cross bores 29. In use, the two components forming the expanded plastics are supplied to tubes 27 and 28 respectively and pass into tube 26 where they are mixed prior to discharge, a liquid cooling or heating medium being supplied to the spaces (31, 32), Fig 3 (not shown), in the casing on either side of the partition formed by the tubes. An axially displaceable rod 30 in the tube 26 acts as both a cleaning rod and a valve. In Fig. 4 (not shown) the cleaning rod is omitted and the central tube 26 has a Venturi constriction (34); compressed air supplied to the tube 26 carries with it the components of the expanded plastics and has a cleaning effect. Extrusion Process. In Fig. 1 (not shown) a cylindrical sheath (15) of a thermoplastic material such as polyethylene is extruded from a circular die (14) in a cross-head (13), said cross-head also having a central passage (16) through which a tube (17) is advanced axially at the speed of extrusion of the sheath, a vent (19) and a further passage through which is inserted a nozzle (18) of the invention to fill the extruded sheath with expanded plastics material. The sheath (14) is surrounded by a cylindrical cooling jacket (20).
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