Method and apparatus for extruding plastic netting

摘要

Apparatus for the continuous extrusio of a netting or meshed structure of resinous plastic material or metal includes a plurality of extrusion nozzles, at least some of which are swingably mounted on a hollow die head and, power means for swinging the nozzles in a known time sequence, pairs of which nozzles are arranged to contact each other at their discharge ends at the ends of the arcs of swing so that adjacent strands are periodically welded together as they are being extruded. In a preferred embodiment (Figs. 1, 2, 10) a die head 15 is provided with heating means (not shown) and an inlet 16 via which plastic material under pressure enters axial ducts 17 formed in a plurality of oscillating pins 18 and fixed pins 18a, said pins being provided with screw-in discharge nozzles 19, 19a. The pins 18 are rotatable in the head 15 by arms 30a, 30b transversely fixed thereto, said arms being pivotally connected to reciprocating rods 31, 32 driven by a power actuated shaft 39 by means, for example, of cranks 37, 38. The nozzles 19 are provided with tapered extrusion passages terminating in openings 27 in knife edges 26 formed by the bevelled ends of said nozzles. In operation, reciprocation of the rods 31, 32 causes the nozzles 19 to swing such that at the ends of the arcs of swing the bevelled ends of adjacent nozzles make contact so that the extruded strands C are periodically welded in pairs as at W. The flat netting N formed thereby is cooled in a water tank (not shown) beneath the head 15. In another embodiment (Figs. 5 and 6, not shown), the die head comprises two clamped parts to facilitate cleaning &c. In a further embodiment (Figs. 7, 8), to produce netting as a continuous tube, a die head 70 has an inlet passage 71 to a chamber 72 therein, which chamber receives the open ends of radially disposed, oscillating pins 73, 74. The pins carry nozzles 75 of the type previously described and links 81, 82 with ball-shaped heads 83, 84 which are received by sockets in rings 85, 86 surrounding the die head. The rings 85, 86 are contra-oscillated by a mechanism comprising cranks 87, 90, a crank disc 88 and a power actuated shaft 89, to cause a rocking of the nozzles 75. The process for forming single and welded strands, C and W, is then similar to that previously described. In further embodiments described, the extruded strands may be of tubular section, in which case, means are provided to supply air under pressure to the interior of the tubes as they are formed.