Liquid purification or separation – Structural installation – Flume stream type
Patent
1996-11-21
1998-09-01
Lithgow, Thomas M.
Liquid purification or separation
Structural installation
Flume stream type
210160, 210159, 210400, 210791, 210783, 210107, B01D 33056, B01D 33333, E02B 508
Patent
active
058007016
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to an endless filter chain for removing solids from a liquid.
2. Description of the Prior Art.
Filtering liquid in order to separate solid material from a liquid is a well known basic operation which is used in many different fields of application. The core component of a filter may be described as a mechanical fixed component provided with openings which allow liquid to pass through while solid objects will be withheld if they are too large to pass the openings. Basic specification parameters for a filter comprise the mesh size which substantially determines which particle sizes are withheld or, alternatively, allowed through, as well as the pressure differential required to force the liquid through the filter. Depending on the operating conditions, such as the characteristics of the materials to be filtered out and the desired capacity, requirements to maintenance, longevity, etc., a wide variety of different specific technical filter embodiments are available.
For the purification of sewage water it is common to use a filter at an early stage of the purification process, i.e. before the sedimentation and digesting tanks. Experience has shown that sewage water conveys solid components which hamper or hinder the processes desired to take place in order to realise the purification of the sewage water and therefore, it is advantageous to remove them at an early stage. Due to the large quantities of water in question, it is desired that the filtration be carried out with a very low pressure loss, as in practice every pressure difference across the filter represents a loss of energy. Conveniently flow filters are used which are dimensioned to allow suitably large quantities of water to pass at a low pressure differential.
It is usually desired that the solid materials withheld in the filter be drained of water and removed with a minimum of manual interference. This may conveniently be realised with a filter apparatus featuring an endless chain which carries strainer elements along a path comprising a section where they are conveyed below the liquid surface level where liquid is forced therethrough and another section extending above the liquid surface level where the withheld material, usually designated the filter cake, is further drained and may be removed from the individual strainer elements.
EP-B-0,291,574 discloses a filter apparatus of this type where a number of strainer elements are suspended between two carrier chains which are trained about an upper and a lower end roller in a path which extends substantially rectilinearly between the turning rollers. The ascending strainer elements move in a direction slantingly backwards relative to the flow direction of the water and the apparatus comprises at a point located shortly after the elements have been driven around the upper turning roller, rotatable cleaning brushes which may be operated to brush the filter cake off the strainer elements and from where it may drop into a receptacle. The individual strainer elements have rectangular profiles and comprise perforated plates or grates which are arched or angled outwards in order to increase the free flow area of the filter and to strengthen the strainer elements. To seal the sides of the filter chain, the individual strainer elements are provided with laterally delimiting staggered sliding planes which constitute a safeguard against lateral displacement and serve as a protective screen. The sliding planes slide along a row of stationary brushes at each side contacting the outer faces of the sliding planes and serving the purpose of preventing water from bypassing the filter.
With the known filter apparatus the lateral sealing is a critical point. The laterally delimiting planes of the strainer elements which are fastened to the chains slide onto each other when the chain moves and are thus exposed to wear and may give rise to interruptions of service in case hard objects enter between the planes, e.g. when the chain is
REFERENCES:
patent: 1190920 (1916-07-01), Leoni
patent: 1190921 (1916-07-01), Leoni
patent: 3608727 (1971-09-01), Grutsch
patent: 4188294 (1980-02-01), Higihara
patent: 4892652 (1990-01-01), Rudy
I. Kruger Systems A/S
Lithgow Thomas M.
Vigil Thomas R.
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