Filtering panel and method of making the same
The present invention relates to a filtering panel ( 100 ) for a disk filter and a disk filter for water purification, comprising a metal filter cloth ( 16, 116 ) such as a stainless steel filter cloth, pre-tensioned in both warp and weft directions and fastened to a frame ( 10, 110 ) comprising a peripheral portion ( 11, 111 ), which is integral with an inner grillwork ( 12 ) and which divides the inner area of the peripheral portion ( 11, 111 ) into fields ( 15, 115 ). The frame ( 10, 110 ) comprises a plastic material reinforced with glass fibers or carbon fibres such as polypropylene loaded with fibreglass in an amount of at least 20 weight percent. Each field of the grillwork ( 12, 112 ) has an area not exceeding 10% of the inner area of the peripheral portion ( 11, 111 ). The pre-tensioning of the filter cloth ( 16, 116 ) in both directions is from at least 20% of the yield stress of the cloth ( 16, 116 ). Further the present invention relates to a disk filter comprising said filtering panels ( 100 ) and method of making said filtering panel ( 100 ).
1. A method for making a filtering panel, the method comprising:
injecting plastic material loaded with fibers of glass or carbon into a mold tool to integrally form a frame with a peripheral portion and a grillwork;
locating the frame into a tensioning tool;
placing a metal filter cloth on top of the frame;
fixing a peripheral edge region of the metal filter cloth by the tensioning tool;
pre-tensioning the metal filter cloth to at least 20% of a yield stress limit of the metal filter cloth to form a pre-tensioned filter cloth; and
applying pressure and heat on the pre-tensioned filter cloth to fasten the pre-tensioned filter cloth on at least a portion of the peripheral portion by embedding the pre-tensioned filter cloth in the plastic material of the frame.
2. The method according to claim 1 , further comprising cooling the plastic material of the frame, wherein the plastic material is selected from the group consisting of polypropylene (PP), polyethylene (PE), polyphenylene oxide (PPO), a blend of PPO and styrene, polyphenylene sulfide (PPS), polyvinyl chloride (PVC) and a mixture thereof.
3. The method according to claim 2 , wherein the plastic material of the peripheral portion comprises a ridge along at least at a portion of the inner edge region of the peripheral portion for bonding the metal filter cloth.
4. The method according to claim 1 , wherein the metal filter cloth is a metal selected from the group consisting of stainless steel, bronze, copper, brass, titanium, nickel and alloys.
5. The method according to claim 2 , wherein the metal filter cloth is a metal selected from the group consisting of stainless steel, bronze, copper, brass, titanium, nickel and alloys.
6. The method according to claim 3 , wherein the metal filter cloth is a metal selected from the group consisting of stainless steel, bronze, copper, brass, titanium, nickel and alloys.