Liquid purification or separation – With repair or assembling means
Patent
1995-09-12
1997-06-17
Walker, W. L.
Liquid purification or separation
With repair or assembling means
21032167, 21032174, 21032183, 210356, 210359, 210387, B01D 3352
Patent
active
056393652
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a filter, to a method of making a filter, and to separation systems which include filters.
U.S. Pat. No. 2,864,506 discloses a device for ultrafiltration, which comprises a tubular membrane and a porous sleeve which surrounds the membrane along its entire length. A fluid which is to be filtered can be passed through the membrane from the supply end to the collection end under pressure. Filtrate passes through the membrane and the sleeve. Material in the fluid which is unable to pass through the membrane remains in the fluid, so that the concentration of that material in fluid leaving the membrane at the collection end thereof is increased. This filtration technique is sometimes referred to as cross-flow filtration.
Examples of materials said to suitable for use for the tubular membrane include cellulose, parchment, rubbers and plastic materials, selected according to the nature of the filtration to be accomplished. Examples of materials said to be suitable for the porous sleeving include cotton, nylon, muslin, copper, stainless steel and glass.
A problem which is encountered in connection with cross-flow filtration systems is that of cleaning any residue which collects on the internal surfaces of the membrane filter. This problem is significant: if collected material cannot be displaced from the filter surface, the entire filtration device must be replaced. This is undesirable because of the costs involved.
The problem is solved in the device disclosed in U.S. Pat. No. 4,765,906 by use of a double ply of a filter support material in which is disposed a layer of particulate filter material, such as floc, cellulose, kieselguhr, possibly with a second coating such as of a metal hydroxide. Residue is removed from the device by washing, which removes the residue together with the particulate filter material. The filter material must be replaced before the device can be used again.
It has been found that the problem of cleaning a filter, such as might be used in a cross-flow filtration system, can be solved by use of a filter whose configuration tends to change, towards a flattened configuration, when fluid pressure within it is relaxed.
Accordingly, in one aspect, the invention provides a filter which comprises: has a tendency to collapse towards a pre-determined flattened configuration, and against internal fluid pressure while providing no more resistance to flow of fluid than the filter tube.
In another aspect, the invention provides a method of making a filter, which comprises: that it has a tendency to collapse towards a pre-determined flattened configuration, and tube against internal fluid pressure while providing no more resistance to flow of fluid than the filter tube.
The filter of the present invention has the advantage that material which collects on the internal surface of the filter tube during a filtration process, for example during cross-flow filtration, is dislodged when the tube collapses towards its pre-determined flattened configuration. The collapse takes place when pressure in the filter tube is relaxed.
Preferably, the support sleeve is set so that it too has a tendency to collapse towards a pre-determined flattened configuration. This has the significant advantage of enhancing the collapse of the filter tube, and therefore the release of collected material from the internal surface of the filter tube, especially when the filter tube and the support sleeve are oriented relative to one another such that they align with one another when they collapse.
The flattened configuration of the filter tube, and of the support sleeve when applicable, is a flattened configuration which is pre-determined, in the sense that the tube or sleeve reverts always to that configuration when internal fluid pressure is released. The flattened configuration will generally involve the tube or sleeve being folded along at least two fold lines, and the tube or sleeve will tend to fold along the same lines when it collapses. Especially when the tube or sleeve has two fold lines, they will b
REFERENCES:
patent: 2864506 (1958-12-01), Hiskey
patent: 3521753 (1970-07-01), Schoening
patent: 3989626 (1976-11-01), Bentley et al.
patent: 4765906 (1988-08-01), Downing et al.
patent: 4787982 (1988-11-01), Caro et al.
patent: 5256288 (1993-10-01), Lee
Cook John Anthony
McLoughlin Robert Hamilton
Scimat Limited
Walker W. L.
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