Patent GB-1230458-A (GB)
IPC: B29C48/05
Filed: 1968-05-23
Abstract: 1,230,458. Extruding woven netting. FMC CORP. 23 May, 1968 [24 Oct., 1967], No. 24700/68. Heading B5A. [Also in Divisions B3, Cl and D1] An extruded woven net comprises strands 79, 81, 83, Fig. 3, which cross, but are not connected to strands 85, 87, 89, and wherein any individual strand passes successively over and under crossing strands. In one embodiment of extrusion apparatus, material is delivered either side of a bar 21, Fig. 1, to grooved rollers 27, 29 which are separated by a comb-like plate 25 having slots 75 defining partitions 77. Roller 27 has equal-length grooves 39, 41, 43, Fig. 2, formed on a helix 45 and similar grooves 47, 49 formed on a helix 51 of opposite hand. Roller 29, which is rotated in the opposite sense to roller 27, has a similar array of grooves 53, 55, 57 and 61, 63. In operation, material extrudes from the grooves at the underside of the rollers, see Fig. 3, the strands from each roller crossing but remaining separate due to partitions 77 situated therebetween. However, the groove arrangement and slot 75 spacing is such that, e.g. one end of both groove 39 and groove 61 simultaneously arrive at a slot 75, see Fig. 2. As a result the strand just extruded from groove 61 is continued by extrusion from groove 39. Previously the strand was extruded from groove 41, i.e. a continuous strand is extruded first from one roller then the other. The rollers have grooves 67, 69, 71, 73 at their ends to provide terminal strands 91, 95. In modifications, helices 51 and 65 may be grooved for a half pitch length at both ends of the rollers to produce an edging as shown in Fig. 5 (not reproduced). With this arrangement of helical grooves, grooves 67, 69, 71, 73 may be omitted, Fig. 4 (not shown). In a second embodiment, Figs. 6-9 (not shown), rollers 27, 29 are replaced by horizontally reciprocable grooved blocks (117, 119) separated by a comb-like plate (133) and horizontally reciprocable plates (147, 149) having recesses (163) and mounted on blocks (117, 119). In operation, blocks (117, 119) are moved in the direction of arrows (167, 169), Fig. 9A (not shown), and material extrudes from grooves (S, t, U, v, W, x and Y). The resulting strands cross as grooves (U, t), (W, v), (Y, x) come into coincidence, Fig. 9B (not shown), but remain separate due to the interposition of partitions (141) of plate (133). At groove coincidence (U, s), (V, t) &c., Fig. 9C (not shown), the grooves are in communication via slots (139) in plate (133). At this juncture the direction of movement of blocks (117, 119) is reversed and simultaneously plates (147, 149) are moved to the positions shown in Fig. 9D (not reproduced). As a result a strand initially delivered, e.g. from groove (t) is now delivered from groove (V), i.e. a continuous strand is formed by extrusion first from one block then the other. The material delivered to the rollers or blocks may differ in colour and/or in composition. The extruded net is set by cooling, solvent removal or chemical action. It is stated that the blocks may be annular rather than linear. Materials specifically mentioned are polyamides and superpolyamides, polyesters, PVC, cellulose aceate, natural or synthetic rubber, viscose, cupro-ammonium cellulose, carboxymethyl cellulose and metal or glass. An additive mentioned is a blowing agent.