| 摘要 |
A filter element is made by coating a metal frame with a thermoplastic material, heating the frame and the thermoplastic material to, or slightly above, the fusion temperature of the latter, pressing the coated frame and one or more layers of filter material together and allowing the thermoplastic material to cool thus bonding the filter material to the frame. Heating may be effected in an oven or by electromagnetic induction. The filter material may comprise natural or synthetic fibres and/or woven or random metal filaments, or it may comprise one or more layers of synthetic fibre fabrics either of woven fibres or random felted fibres bonded together, or it may comprise expanded materials or combinations of any of the above materials. The frame may be of wire or of metal strip, channel or angle, or of metal tubing and it may have a plain or knurled or serrated surface to improve the bond. It may consist of a closed figure and may have one or more lateral members. The layer or layers of filter material are assembled with the frame in a press. The frame may be between layers of filter material which may be of larger size than the frame or the material may be only on one side of the frame, or one or more layers of the material may be disposed between two frames. The frame or frames may be heated before assembly with the filter material. When the element is cool a binding tape may be applied to its periphery. The tape may be of the self-adhesive type and may be secured in place by sewing or it may have a thermoplastic or thermosetting adhesive and may be applied by passing the edges of the element between heated rollers. Alternatively, the edges of the element may be provided with plastic coatings. This may be applied by casting on polyester or other setting or polymerizing compounds either in a gravity mould or by injection moulding with the element so gripped in the mould that the moulding material will not leak past its edges. Alternatively, the frame may be reheated and the edges dipped in P.V.C. paste. |
