Manufacture of a filter screen
A method of manufacturing a filtering screen includes: attaching handle members ( 3 ) to edges of at least one wire cloth ( 1 ); providing a jig comprising tensioning means ( 23 ); placing the at least one wire cloth ( 1 ) in the jig and engaging the handle members ( 3 ) with handle member engagement portions ( 15 ) of the tensioning means ( 23 ). The tensioning means ( 23 ) are operated to drive the handle members ( 3 ) outwardly to tension the wire cloth ( 1 ) in orthogonal directions. The method also includes pressing the tensioned wire cloth ( 1 ) against a screen frame ( 6 ); bonding the wire cloth ( 1 ) to the screen frame ( 6 ); and trimming the wire cloth.
1. A method of manufacturing a filtering screen comprising:
attaching handle members to edges of at least one wire cloth;
providing a jig comprising tensioning means;
placing the at least one wire cloth in the jig and engaging the handle members with handle member engagement portions of the tensioning means;
operating the tensioning means to drive the handle members outwardly to tension the wire cloth in orthogonal directions;
pressing the tensioned wire cloth against a screen frame;
bonding the wire cloth to the screen frame; and
trimming the wire cloth;
wherein the handle members are attached to an edge of the wire cloth by an adhesive.
2. The method according to claim 1 wherein the wire cloth is tensioned before being pressed against the screen frame.
3. The method according to claim 1 wherein the screen frame is pressed into the wire mesh as it is tensioned.
4. The method according to claim 1 wherein wire cloth is bonded simultaneously to more than one screen frame.
5. The method according to claim 1 wherein the screen frame material is selected from the group consisting of plastics, reinforced plastics, plastics coated metal, metal and wood.
6. The method according to claim 1 wherein the at least one wire cloth is bonded to the screen frame by means of an adhesive.
7. The method according to claim 1 wherein the at least one wire cloth is bonded to the screen frame by heat softening a plastic surface of the screen frame.
8. The method according to claim 7 wherein the wire cloth is heated so that when pressed against the frame it acts to soften a plastic surface of the screen frame.
9. The method according to claim 8 wherein heat is applied selectively to the wire cloth, to those parts that form bonds to the screen frame.
10. The method according to claim 1 wherein more than one wire cloth layer is bonded to a screen frame and the layers of wire cloth are joined to each other by common handle members before tensioning and bonding to the screen frame.
11. The method according to claim 10 wherein the layers of wire cloth are pre-tensioned before fitting the handle members.
12. The method according to claim 1 wherein more than one wire cloth layer is bonded to the screen frame and each layer of wire cloth has separate handle members attached.
13. The method according to claim 1 wherein each edge of each wire cloth employed has at least one handle member attached.
14. The method according to claim 1 wherein a single handle member is provided, on each edge of the wire cloth; each handle member being sized to run along substantially the whole length of the edge of a screen frame to which the wire cloth will be attached.
15. The method according to claim 14 wherein the wire cloth is pre-tensioned before attachment of the handle members.
16. The method according to claim 1 wherein each wire cloth has four edges and a tensioning means is provided along at least two adjacent edges of each cloth layer for orthogonal tensioning.
17. The method according to claim 16 wherein a cloth tensioning means is provided for each cloth layer along each edge.
18. The method according to claim 1 wherein the handle members are provided with hooks or loops for interlocking with corresponding hooks or loops of engagement portions of the tensioning means or are wedge shaped.
19. The method according to claim 1 wherein the handle members are elongate bars of a plastics material.
20. The method according to claim 1 wherein the handle members are provided with slots for engagement with the handle member engagement portions of the tensioning means.
21. The method according to claim 20 wherein the handle member engagement portions of the tensioning means comprise pins that are sized to fit through the slots of the handle members.
22. The method according to claim 21 wherein the slots of the handle members are of larger dimension than the pins of the handle member engagement portions of the tensioning means.
23. The method according to claim 22 wherein the slots of the handle members fitted along an edge of a wire cloth are of larger dimension than the pins of the handle member engagement portions of the tensioning means in the direction parallel to the edge of the wire cloth to which they are fitted, thereby allowing some lateral movement of the handle members during tensioning, to remove creases.
24. The method according to claim 1 wherein the jig is supplied with breaker bars along its edges.
25. The method according to claim 1 wherein crease inhibiting members are fitted to the wire cloth, inward of the handle members.
26. The method according to claim 1 wherein the tensioning means comprises pneumatic or hydraulically driven pistons in cylinders, or a screw turned manually or by a motor drive, to which a handle engagement portion is attached.
27. The method according to claim 1 wherein wire cloth is provided in the form of a roll with handle members pre-fitted, for unrolling and bonding to a succession of screen frames.