Liquid purification or separation – Filter – With movable means to compress medium
Patent
1993-04-28
1994-06-07
Dawson, Robert A.
Liquid purification or separation
Filter
With movable means to compress medium
210359, 210385, 21049701, 55475, 55510, 55527, B01D 2446
Patent
active
053187040
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to apparatus for filtering solids from liquids or for coalescing droplets of one liquid dispersed in another liquid.
EP 0 004 724 discloses an apparatus for removing contaminants from a liquid which comprises bundles of fibres aligned parallel to one another between two end plates. The end plates may be moved axially to stretch or compress the fibres. Liquid flows through the apparatus parallel to the fibre bundles.
EP 0 207 797 discloses another apparatus for removing contaminants from a liquid. This apparatus also comprises fibres connected at each end to end supports, which end supports can be moved away from or towards each other to place the fibres under tension or to relax any applied tension. The end supports can also be rotated relative to each other. The fibres are attached to the end supports so as to form a tube of fibres surrounding a central tubular core provided with perforations. The fibres are in turn surrounded by a perforated tube which restrains the fibres from radial movement (in relation to the axis of the tubular core). The liquid to be treated passes across the fibres between the central core and an outer compartment surrounding the fibres. In use the end supports are moved towards one another and rotated relative to one another to twist the fibres and to compress them against the perforated tube.
An arrangement of perforated inner and outer tubes with fibres arranged parallel to the axis of the tubes is disclosed in U.S. Pat. No. 4 299 699.
The disadvantage of using perforated inner tubes is that they impose a restriction on the flow through the apparatus so giving increased pressure drop if the rate of flow is to be sustained. Because liquid can only pass through relatively narrow openings the local liquid velocity near these openings will be relatively high which may disturb particles of contaminants already deposited on the fibres. The techniques required to produce perforated tubes will also increase the cost of the apparatus. In the case of apparatus which requires both axial as well as rotary movement of the end supports it will be necessary to provide lengths of perforated tube in excess of the length required to give support to the fibre bundle in the shortened operational position in order to be able to support the fibres in the elongated position required for back-washing. This will increase the mechanical complexity of the apparatus. The production of perforated tube is a relatively expensive process. It would be desirable to provide an apparatus which did not require a perforated inner tube but which replaced it by a cheap and easily available component which gave reduced pressure drop.
According to the present invention an apparatus for removing contaminants from a liquid, which apparatus comprises a casing, divided into two compartments by a tubular fibrous filter, said fibrous filter being formed of fibres attached at each end to an end support, said end supports being moveable axially relative to one another, and rotable relative to one another about the longitudinal axis of the tubular fibrous filter, is characterised in that a helical spring is disposed within the tubular fibrous filter and is so dimensioned that it does not close when the end supports are in their closest operational position and resists inward movement of the fibres tending to close the compartment surrounded by the tubular filter when the end supports are moved axially towards each other and rotated to twist the fibre.
By using a helical spring in place of the perforated tube of the present invention adequate support can be given to the tubular fibrous filter both during use and during backwashing to remove impurities. Helical springs are relatively easy to manufacture and were therefore cheaper than using perforated tubes which will require more expensive fabrication techniques for their manufacture. The helical spring can be used to replace only the inner perforated tube disclosed in EP0 027 797. However it is preferred to eliminate the outer perforated tube also.
REFERENCES:
patent: 4411791 (1983-10-01), Ward
Dawson Robert A.
Kalsep Limited
Mehosky B. L.
Untener D. J.
Walker W. L.
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