Abstract: A method of constructing a filter screen is described. This involves forming a polymer support frame including therein a plurality of substantially similarly sized rectilinear apertures, defined by an integral rectilinear matrix of wire reinforced struts of polymer material. An upper edge of each strut is ridged and an upper surface of each boundary of the support frame provided with a plurality of ridges. One or more woven wirecloths are fitted over the ridges and tensioned. The wirecloths are secured in place by heating at least the ridges so as to soften the polymer material sufficiently to allow the wirecloths to penetrate crests of the ridges and upon cooling to remain embedded therein. This maintains tension in the wirecloths after cooling. The wires in one of the wirecloths are preferably tensioned differently from those in the other, so that different tensions exist in the wires of the two cloths after bonding to the frame.

Abstract: A method of constructing a frame (10) for a filtering screen from a polymer material is described in which a wire frame reinforcement is wholly encapsulated during the frame moulding process so that two parallel spaced apart wires extend through each of the intersecting orthogonal ribs (14, 16) which define the open area of the frame (10) across which the wirecloths (158, 159) are stretched. The surfaces of the frame (10) in which the wirecloths (158, 159) are embedded are formed with ridges (22, 30, 32) and the crests of the latter extend to different heights. The crests are softened by heating during the manufacturing process and the wirecloths (158, 159) stretched over the frame (10) are forced into the softened crests after which the assembly is allowed to cool and cure. The frame (10) is re-usable by stripping wirecloths (158, 159) from the top of the frame (10) and fitting fresh wirecloths over the plastics material and heating the regions which are to encapsulate the fresh wirecloth.

Abstract: A method is described for making a reinforcing wire frame for embedding in a moulded polymer support frame over which woven wire cloth is to be stretched and secured to form a sifting screen. The method involves locating lengths of cut wire substantially equally spaced apart in a jig to form a first array. A second array of lengths of cut wire is located over the first array with the lengths of wire in the second array being substantially at right angles to those of the first array. The lengths of wire in the first and second arrays are resistance welded at points of mutual intersection so as to form a first substantially rectilinear matrix.

Abstract: A method of repairing or refurbishing a filter screen is described. The type of screen is defined in the specification. The repair or refurbishment is effected by stripping worn or damaged wirecloth from the surface of the frame and placing fresh cloth over the frame and tensioning it as appropriate. Heat is then applied so as to soften surfaces of the frame over which wirecloth is stretched, so that the latter can penetrate softened plastics material in the surfaces and become embedded therein. The frame and its associated fresh cloth is allowed to cool, after which the applied tensioning is removed. Exposed edges of the wirecloth can be trimmed back to the surrounding flange. Plastics material may be applied to the surface of the frame which is to receive the new wirecloth, before the latter is fitted, to provide additional plastics material for bonding the wirecloth to the frame.

Abstract: A filter screen having support frame including an outer peripheral flange surrounding a central region. Faces of the outer peripheral flange of the support frame to which the wirecloth is bonded by heating are formed with a plurality of closely spaced apart parallel ridges including outer ridges and inner ridges, each having a crest, so that when heated, the crests of the ridges soften, and the woven wirecloth laid thereover and tensioned can, under an appropriate downward loading, penetrate and become embedded in the softened ridge crests. The outer ridges extend to a greater height above the frame than said inner ridges, whereby there is a greater volume of polymer to be melted and spread by the application of heat and pressure to the wire cloth near outer regions of the outer peripheral flange than near inner regions of the outer peripheral flange.

Abstract: A method is described for making a reinforcing wire frame for embedding in a moulded polymer support frame over which woven wire cloth is to be stretched and secured to form a sifting screen. The method involves locating lengths of cut wire substantially equally spaced apart in a jig to form a first array. A second array of lengths of cut wire is located over the first array with the lengths of wire in the second array being substantially at right angles to those of the first array. The lengths of wire in the first and second arrays are resistance welded at points of mutual intersection so as to form a first substantially rectilinear matrix.

Abstract: A method of repairing or refurbishing a filter screen is described. The type of screen is defined in the specification. The repair or refurbishment is effected by stripping worn or damaged wirecloth from the surface of the frame and placing fresh cloth over the frame and tensioning it as appropriate. Heat is then applied so as to soften surfaces of the frame over which wirecloth is stretched, so that the latter can penetrate softened plastics material in the surfaces and become embedded therein. The frame and its associated fresh cloth is allowed to cool, after which the applied tensioning is removed. Exposed edges of the wirecloth can be trimmed back to the surrounding flange. Plastics material may be applied to the surface of the frame which is to receive the new wirecloth, before the latter is fitted, to provide additional plastics material for bonding the wirecloth to the frame.

Abstract: apparatus for repairing or refurbishing a filter screen (of the type defined in the specification) is described. The apparatus comprises a tray for accommodating a filter screen frame from which worn wirecloth has been stripped. Wirecloth stretching means surrounds the tray which includes attachment means for securing to edges of a sheet of wirecloth laid over an upper surface of the frame in the tray. Tensioning means is provided for exerting tension on the wirecloth in at least two mutually different directions so as to stretch it over the frame, and heating means is provided for heating the frame to soften the uppermost edges of a matrix of struts and periphery of the frame. Forcing means serves to force the wirecloth into the softened edges such that after cooling, the wirecloth remains bonded to the frame. Thereafter the wirecloth can be trimmed back to the edges of the frame.

Abstract: A method of constructing a frame (10) for a filtering screen from a polymer material is described in which a wire frame reinforcement is wholly encapsulated during the frame moulding process so that two parallel spaced apart wires extend through each of the intersecting orthogonal ribs (14, 16) which define the open area of the frame (10) across which the wire-cloths (158, 159) are stretched. The surfaces of the frame (10) in which the wirecloths (158, 159) are embedded are formed with ridges (22, 30, 32) and the crests of the latter extend to different heights. The crest are softened by heating during the manufacturing process and the wirecloths (158, 159) stretched over the frame (10) are forced into the softened crests after which the assembly is allowed to cool and cure. The frame (10) is re-usable by stripping wirecloths (158, 159) from the top of the frame (10) and fitting fresh wirecloths over the plastics material and heating the regions which are to encapsulate the fresh wirecloth.

Abstract: A method of constructing a filter screen is described. This involves forming a polymer support frame including therein a plurality of substantially similarly sized rectilinear apertures, defined by an integral rectilinear matrix of wire reinforced struts of polymer material. An upper edge of each strut is ridged and an upper surface of each boundary of the support frame provided with a plurality of ridges. One or more woven wirecloths are fitted over the ridges and tensioned. The wirecloths are secured in place by heating at least the ridges so as to soften the polymer material sufficiently to allow the wirecloths to penetrate crests of the ridges and upon cooling to remain embedded therein. This maintains tension in the wirecloths after cooling. The wires in one of the wirecloths are preferably tensioned differently from those in the other, so that different tensions exist in the wires of the two cloths after bonding to the frame.

Abstract: A vibratory screening machine such as used for separating solid particulate material from drilling mud to allow the latter to be re-used, is described. The general form of the construction is similar to that of the VSM100 shaker machine as supplied by the applicant company, but significant differences in the design and construction of the new unit allow a higher throughput of mud to be accommodated. An upper filtering screen (88) extends generally horizontally and serves to separate out the larger particles from the rest. The slurry which passes down to the lower screen (90) (of finer mesh than the upper screen) is further filtered and a mud-like residue of particulate material slowly accumulates on the lower screen (90) and migrates up the screen--to be discharged at the upper outlet end thereof, while liquid material filters through the screen to be recovered in a sump below.