Patent GB-1414788-A (GB)
Title: Process and apparatus for making plastics mesh structures
IPC: B29C48/08
Filed: 1972-11-09
Abstract: 1414788 Forming nets by extrusion GENERAL ALIMENTAIRE SA 9 Nov 1972 [10 Nov 1971 15 Dec 1971] 51822/72 Heading B5A [Also in Division D1] In the formation of a tubular or flat plastics net, longitudinally extending filaments are continuously extruded from orifices arranged in an annular or linear path, and are connected by transversely extending strands extruded from further orifices, arranged along an adjacent coextensive path, upon intermittent opening and closing of the further orifices by a reciprocating knife blade which, in its closing stroke, also thrusts the transverse strands into fusing contact each across, or between, a different adjacent pair of longitudinal strands. With the transverse strands being of greater strength, the net has a stretch which is greater transversely than in the direction of the longitudinal filaments. Different extrusion passages may extrude plastics of different colour or mechanical properties. In the Fig. 2 embodiment, the longitudinal filaments, e.g. 48-52, are continuously extruded from orifices 14-17 &c. arranged on an annular path, and transverse strands 57, 58 and 59, 60, are alternately extruded, respectively to be fused across different alternate pairs of adjacent longitudinal filaments and respectively on different sides thereof, from upper and lower orifices 44, 45 ... &c., and 46, 47 ... &c., which are opened and closed by blades 29, 32 connected, Fig. 1 (not shown), for simultaneous reciprocation in the same directions. The net is two dimensionally stretched and cooled during passage over a sizing mandrel attached to the die, Fig. 1 (not shown). In a modification, Figs. 3-7 (not shown), the longitudinal strands are extruded from circular orifices, and the transverse strands from rectangular orifices each extending over a smaller distance between the circular orifices than in the Fig. 2 embodiment, so that a similar net is produced but with the transverse strands either extending only between, or to a lesser extent across adjacent longitudinal filaments. In the Figs. 8-9 embodiment (not shown) the orifices of the Figs. 3-7 embodiment are employed but with upper and lower blades simultaneously reciprocating in opposite directions to produce the net of Fig. 10 with the transverse strands 68 and 69 extending between the longitudinal filaments 63. In the Figs. 11 and 12 embodiment, producing the Figs. 13 or 14 net, the longitudinal filaments 63 are continuously extruded from circular orifices spaced apart by the diameter of an orifice, the transverse strands 68 and 69 being alternately intermittently extruded each on a different side of the filaments 63 and from orifices of the same cross-section, respectively aligned intermediate different alternate adjacent pairs of filament extrusion orifices. In the Fig. 16 embodiment, producing the staggered mesh of Fig. 17 (not shown), the continuous filaments are extruded from orifices 63, and the transverse strands alternately extruded from lower orifices 65, and upper extensions 64 of the orifices 63. The net of Fig. 20, comprises longitudinal filaments 75 continuously extruded from circular orifices spaced apart by the diameter of an orifice, and the transverse strands 76 are intermittently extruded from orifices of the same diameter located above the intermediate adjacent filament orifices. Staggered mesh of the Fig. 20 nature may be produced by alternately extruding the transverse strands from adjacent ones of the upper orifices.