GB836555A - Improvements relating to the production of net or netlike fabrics by extrusion methods - Google Patents

Abstract

<PICT:0836555/IV (a)/1> <PICT:0836555/IV (a)/2> An extruded net-like fabric of plastic material has net intersections a and strands b which are divisions from the intersections a, the whole fabric being an extruded entity. The net may have various patterns (Figs. 20 to 25, not shown) and the strands may have various cross-sections (Figs. 9 to 11, not shown). Lists of suitable plastic material and uses for the fabric are given, e.g. polyesters, polyamides, polyethylene, polyvinyl chloride, copolymers of vinyl chloride with vinylacetate or vinylidene chloride. A method of making the integral net-like fabric comprises extruding a plastic material through a number of dies located in a pair of members mutually displaceable transversely to the direction of extrusion, through positions in which the dies of each member are out of register and extrude separate strands, to a position in which the dies of each member register and extrude confluent strands forming integral intersections of the net. The die members may be annular to extrude a tube-like net, arcuate, or rectilinear to extrude a sheet-like net. Plastic material is fed by a screw 2 through a gauze screen and breaker plate 3a into a feed chamber 3 coupled to an extrusion chamber 5 having a movable inner member 12 and a movable die member 6. The members 12, 6 have die apertures 14, 10 in slideways 13, 9 respectively which operate in mating adjustable engagement and are actuated by variable-speed motors 18b, 11c and chain drives 18a, 11a. Differential rotation of the members 6, 12 causes the plastic extruded through the die apertures 10, 14 to form separate strands when the dies are out of register and confluent integral strands when the dies are in register. The extruded fabric may be tensioned, before setting in a cooling bath 25, to alter the shape of the mesh and may be slit by a knife blade 22 to form a flat sheet. Various methods of rotation or oscillation of the die members are described to produce various shaped meshes and one die member may be stationary whilst the other rotates or oscillates. The rotations or oscillations may be "stepwise." The die apertures may be of various sections to produce different sectioned strands and may be convergent (Fig. 12, not shown). A series of separate fabrics may be extruded by forming portions of the slideways without die apertures. The die apertures may be formed in endless steel bands or reciprocal steel plates. The extruded fabrics may be laminated one upon another or applied as a coating or armouring to one or both sides of plastic or other cloths. Specification 836,556 is referred to.