| 摘要 |
<p>1,212,182. Film and net extrusion die. DU PONT OF CANADA Ltd. 7 Nov., 1967 [7 Nov., 1966], No. 49850/66. Headings B5A and B5B. A circular rotating die for extruding thermoplastic films or nets comprises an inner die member 35 and 54 with a lip 41 and an outer die member 43 with a lip 42, the lips defining the extrusion orifice 40, a reservoir 39 adjacent the orifice and a passage 53 through the inner die for conveying the thermoplastic material from the crosshead 52 to the orifice 40. As shown, the inner die member comprises an upper section 35 and a lower section 54 bolted to the upper leaving a gap 38. This section is rotated on bearings 37 in the mould framework 36 by sprocket 50 and is connected to the crosshead 52 by packing gland 34. The outer die member is rotated by sprocket 49 on bearings 44 attached to the mould framework 47 and is held in position by the overlap of member 48 and framework 47. Immediately upstream of the orifice 40, the space between the die increases to form a reservoir 39, which, in combination with the horizontal passage 38 balances nearly all the internal pressure in the die. When used for the production of netting each lip may contain a series of complementary orifices or a set of holes spaced annularly about the axis of rotation. The thermoplastic materials may be polyamides, polyesters, P.V.C. and copolymers with vinylacetate or vinylidene chloride, polyethylene and copolymers, cellulose acetate, natural or synthetic rubbers and foamable plastic material such as polystyrene and polyethylene.</p> |
