Importance

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Abstract

An apparatus and method are disclosed for extruding a product which comprs a longitudinal component, e.g. a tubular sheet and/or longitudinal filaments in a circular array, and transverse filaments which follow a helical path relative to the longitudinal component, whereby the product may consist of a lattice or a reinforced sheet material. The transverse filaments are formed by cooperation between two die parts (101; 102) to which relative movement is imparted so that one part (102) performs a rocking motion progressing around a circular path to influence the extrusion orifice, without rotation of the die parts. The extrusion orifice may comprise an annular slot defined between two die members (106; 108) of the first die part (101) which is held stationary, while the second die part (102) extends around the first part and has an edge for alternatively opening and at least partially closing the slot at each point along its annular extent in response to the relative circular rocking movement imparted to the second part (FIG. 7). Alternatively, the extrusion orifice may be defined between cooperating frusto-spherical surfaces (4, 8) of the two die parts (3, 7) with the inner die part having a groove (9) which is alternately exposed and concealed due to circular rocking motion imparted to this die part (FIG. 1).

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First Claim