초록

A filter assembly for ultra-filtration of fluids such as waste water comprises a porous tube which is incrementally advanced into the fluid so as to expose a fresh portion periodically and maintain a flow rate over a period of time.

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What is claimed is: 1. A filter assembly for obtaining a sample of filtrate from a contaminated fluid, the assembly comprising a filter element comprising an elongate porous tube having an exterior surface wherein a portion of the exterior surface is arranged to be immersed in a fluid to be filtere

What is claimed is: 1. A filter assembly for obtaining a sample of filtrate from a contaminated fluid, the assembly comprising a filter element comprising an elongate porous tube having an exterior surface wherein a portion of the exterior surface is arranged to be immersed in a fluid to be filtered and wherein the tube is substantially rigid so that, in use, the interior bore is maintained as a passage for the filtered fluid; and a pump, having an inlet and coupled to the interior bore of the filter element and an outlet, for drawing filtrate through the filter element from the exterior surface of the filter element to the interior bore and through the interior bore to the inlet of the pump; means for incrementally extending a further portion of the exterior surface of the filter element to immerse the further portion in the contaminated fluid as the filter element becomes clogged. 2. Apparatus according to claim 1 wherein a single drive means is arranged to operate the pump to draw fluid through the filter element and to advance the filter element to expose further portions of the surface. 3. Apparatus according to claim 1 wherein the assembly includes coupling means arranged to couple a rotary drive to the pump to draw fluid through the filter element when rotation is applied in a first direction and to advance the filter element when rotation is applied in the opposite direction. 4. Apparatus according to claim 1 wherein the pump is arranged to pump fluid back through the filter element from the interior surface of the filter element to the exterior surface of the filter element to effect back-flushing of the filter element. 5. Apparatus according to claim 1 wherein the filter assembly is removably coupled to a drive means so that the filter assembly may be renewed without having to renew the drive means. 6. Apparatus according to claim 1 wherein the filter element comprises a substantially cylindrical tube. 7. Apparatus according to claim 1 wherein the further portion of the exterior surface of the filter element is incrementally exposed by means of a relatively rotatable threaded shaft or screw and nut member, one of the screw or shaft being arranged to be rotated by drive means. 8. A filter assembly for obtaining a sample of filtrate from a contaminated fluid, the assembly comprising: a filter element comprising an elongate porous tube having an exterior surface wherein a portion of the exterior surface is arranged to be exposed to a fluid to be filter; and means for incrementally exposing a further portion of the exterior surface of the filter element to the contaminated fluid as the filter element becomes clogged; the interior bore of the tube being arranged to couple to an inlet of a pump for drawing filtrate through the filter element from the exterior surface of the filter element to the interior bore of the filter element; a single drive means being arranged to operate the pump to draw fluid through the filter element and to advance the filter element to expose further portions of the surface; and the filter assembly further including coupling means arranged to couple a rotary drive to the pump to draw fluid through the filter element when rotation is applied in a first direction and to advance the filter element when rotation is applied in the opposite direction.