| 摘要 |
1,138,938. Extrusion dies. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 22 March, 1967, No. 13485/67. Heading B5A. An extrusion die for use with foamed thermoplastic material comprises a batch of die plates 15, 16, Fig. 2, secured together, which define a plurality of extrusion slits 18. Pairs of plates 15 situated in the same vertical plane define the height of the slits and plates 16 which sandwich the plates 15 define the width of the slits. In operation, sufficient back-pressure is created to prevent premature foaming, foaming only occurring after the material leaves the die in the form of separate streams which are thereby coalesced to form an integral extrudate. Various forms of plate are described, those of Fig. 8 viz. 20, 21, forming a continuous square-wave slit and those of Figs. 3 and 5 (not shown) being of one shape only, but combining to form a series of rectangular slits, Fig. 7 (not shown). Some or all of the plates may be tapered, Figs. 4, 11 and 14 (not shown), the plates being situated in the die with the taper in the downstream or upstream direction as required. Typical dimensions are:- slit width 0À3-0À5 mm., spacing between slits:- not more than 2 mm., height of slit:-5-50 mm. and land length parallel to extrusion direction:- 10-15 mm. |
