Liquid purification or separation – Filter – Movable medium
Patent
1995-12-12
1997-11-11
Lithgow, Thomas M.
Liquid purification or separation
Filter
Movable medium
210394, 210403, B01D 3311, B01D 3313, B01D 3376
Patent
active
056859830
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an apparatus for filtering liquids containing particles including a hollow body having walls of filter material, and drive means arranged to rotate the hollow body such that the walls of filter material are rotated about a substantially horizontal axis. Inlet means is adapted to supply the liquid to be filtered to the interior of the hollow body. Means is provided for maintaining a pool of the liquid in the hollow body, such that the pool has a free surface situated below a top portion of the filter material. A basin is arranged at the descending side of the hollow body. Guide means is arranged to guide cloudy filtrate penetrating the descending side of the rotating hollow body to the basin. There is an outlet from the basin for discharging cloudy filtrate. Means is provided for removing particles from said top portion of the filter material and for discharging the removed particles out of the hollow body.
BACKGROUND OF THE INVENTION
An apparatus of this type is known from the British Patent No. 1008617 and the Swedish Patent No. 224131, and has the advantage that cloudy filtrate, which develops initially when clean filter material descends below the free surface of the liquid pool in the hollow body, is prevented from mixing with the more clear filtrate, which develops when particles have accumulated on the filter material to form a filter layer. The cloudy filtrate can be fed back to the interior of the hollow body to be refiltered.
The prior art apparatus according to said British patent comprises a hollow body in the form of a circular drum having its mantle covered with filter material. The guide means comprises a stationary shielding device extending along the mantle.
The prior art apparatus according to said Swedish patent comprises a hollow body in the form of a number of connected hollow discs having annular side walls of filter material. The guide means comprises a stationary comb-shaped device, the teeth of which extend in between the discs. These teeth may be provided with sealing lips of rubber abutting against the side walls of filter material, such that the lips are dragged along the discs as the latter rotate.
A problem of the British and the Swedish apparatus is that some cloudy filtrate inevitably escapes through the gap formed between the moving filter material and the stationary device, and mixes with clear filtrate. The sealing lips of the Swedish apparatus would not be a good solution to this problem, because they would give rise to another problem, namely that the filter material, which often comprises cloth material, would be damaged or worn by said lips. Also, the energy consumption for rotating the discs would increase, because of the frictional resistance occurring between the filter material and the lips.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the above described prior art apparatus so that a more clear filtrate is obtainable without the use of any sealing means dragging along the filter material.
This object is fulfilled by means of a filtering device of the type discussed above, which is characterized in that the guide means comprises a plurality of guide members attached to the hollow body and distributed about said axis.
It is preferred to distribute the guide members evenly about said axis and to select the number of the guide members in the range of 10 to 36.
Each guide member is adapted to receive cloudy filtrate from a descending portion of the filter material defined by the guide member and an upper adjacent member, and is positioned on the hollow body such that cloudy filtrate received by the guide member as the latter descends flows by gravity along the guide member in a direction outwardly from the hollow body.
The basin is suitably positioned relative to the hollow body such that it receives cloudy filtrate which is poured from a descending guide member.
Each guide member has at least a portion extending radially outwardly from the hollow body, whereby the cloudy filtr
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Lithgow Thomas M.
Nordic Water Products AB
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