| 摘要 |
A method of manufacturing a filtering screen in which a frame of plastics coated metal or reinforced plastics material is located in a jig and at least one sheet of wire cloth is placed over the frame and its edges are gripped by pneumatically operated clamps carried by the jig. The clamps are pneumatically driven outwardly of the frame to tension the cloth in orthogonal directions. The tensioned cloth is pressed against the frame and heated in order to bond the cloth to the frame. The heated material is allowed to cool, and after completion of the bonding step the clamps are released, allowing the frame to be removed from the jig. Where necessary the cloth is trimmed back to the edges of the frame. Two or more layers of wire cloth are bonded to the frame, one above the other, and typically the cloth in contact with the frame is of coarser mesh then the cloth or cloths above it. Apparatus is described comprising a jig adapted to receive and locate the frame, pneumatically operated clamps carried by the jig are adapted in use to grip the edges of a layer of wire cloth placed over the frame and pneumatically driven tensioning means, on the jig, drives the clamps outwardly from the frame to tension the cloth in orthogonal directions. A heated platen is employed to press the cloth against the frame in order to heat and locally melt the plastics material and cause the wires of the cloth to become embedded in ridges in the upper surface of the frame. Drive means effects relative movement between platen and jig to bring the platen into contact with the wirecloth and after heating and bonding has occurred to retract the platen and/or jig so as to remove the source of heat to allow the frame and cloth to cool, to complete the bonding of the cloth to the frame. A separate set of pneumatically operated clamps is provided for gripping all four edges of each wire cloth layer to allow each layer to be individually tensioned. Typically the jig is adapted to receive two frames side by side and the wirecloths are large enough to cover both frames, and after bonding the covered frames are separated by cutting the wirecloth spanning the junction between the two frames. |
