Patent ID: 6759000
Filing Date: 2004-07-06
Classification: B01D,B07B,B29C,B29L,Y10T

Abstract:
A method of constructing a polymer support frame over which woven wire cloth is to be stretched and secured to form a sifting screen, the method comprising the steps of:locating in a mould tool a reinforcing wire frame assembly comprising two parallel stated apart arrays or reinforcing wires:(a) closing the mould tool; (b) injecting liquid polymer into the mould tool by injection moulding so as to wholly encapsulate the wire frame and to form an article having an open central region criss-crossed by intersecting orthogonal ribs bounded on all sides by a rigid flange, the article being such that each of said ribs includes two parallel spaced apart wires of said frame assembly; (c) exerting an inward force an opposite faces of the wire frame assembly within the mould tool by fingers protruding inwardly from inside faces of the tool, said fingers being operable to engage the arrays when the tool closes, the fingers comprising inwardly projecting pegs which align with crossing points of wires in the upper and lower reinforcing matrices, to space the arrays from the corresponding upper and lower internal surfaces of the mould tool and ensure that the arrays are buried within the plastics material which is injected into the mould tool during the manufacturing process, and the ends of the pegs taper to an edge, or a point and wherein after the mould tool is opened the protruding pegs disengage from the struts leaving openings in the polymer, and the method further comprises the step of plugging the openings with plastics material or filler, (d) permitting the polymer to cure; and (e) opening the tool; and removing the article.