Liquid purification or separation – Flow – fluid pressure or material level – responsive – Discharge of treated material
Reexamination Certificate
1999-03-30
2001-02-13
Simmons, David A (Department: 1724)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Discharge of treated material
C210S147000, C210S408000, C210S409000, C210S414000, C210S415000, C100S117000
Reexamination Certificate
active
06187180
ABSTRACT:
The present invention relates to an apparatus for screening substantially solid bodies and/or particles from a liquid, according to the preamble to the independent claim.
In, for example, treatment plants such as municipal waste water treatment plants, in process industries such as papermills and food industries, there is a need for separating solid and semi-solid bodies and impurities from water and other liquids. There is also a need to reduce the liquid content in the separated bodies in order to facilitate their continued handling. Depending upon what continued handling the bodies are to be subjected to, different requirements are placed on the dryness of the bodies before the continued handling is commenced. As a rule, total solids exceeding 20%, in certain practical applications total solids exceeding 30% are required, and in addition ti must be possible simply to control the dryness of the accumulated bodies depending upon the composition of bodies relevant at any given time.
According to prior art techniques, it is not possible to satisfy the above-outlined requirements in one single apparatus.
There is also a need, for example, in solid matter (grid screenings) separated in the mechanical cleaning stages in treatment plants for waste-water, for such material to be freed of adhering or accompanying biological material to the greatest possible extent prior to landfill deposition. In order to satisfy this need, new types of apparatuses have been developed in recent years to satisfy these needs.
PCT-application No. WO 95/19212 describes such an apparatus comprising a treatment container
12
and an inclining conveyor
42
with a casing which is provided with a screening aperture and which surrounds a conveyor screw. In its upper region, the conveyor is provided with a discharge aperture. This is preceded by a conveyor section where the cross-section of the casing is reduced as compared with the cross-section in that section where the screenings are fed into the conveyor.
Prior art equipment of the above-described type suffers from any shortcomings. In static screens and rotating drum screens, only screening of the liquid takes place, for which reason dewatering and possible washing must be carried out in separate machines. The drum screens use only a slight part of their screen surface for effective screening. The newly-developed combination machines for washing/screening/dewatering have a small screening surface, operate unreliably, for example suffer from problems in upward conveyance of screenings, in addition to which it is not possible to regulate the total solids of the material discharged at the machines. The machines are unwieldly, bulky and have high energy consumption. Moreover, the grid screenings which leave these machines have an undesirably high liquid content.
The demands placed on efficient screening combined with dewatering of entrapped screenings and regulation of the total solids in material fed from the apparatus cannot be satisfied in one and the same apparatus according to the prior art technique. In the characterizing clause of the appended independent claim, a technique is defined which satisfies these established wishes and requirements.
Expedient embodiments of the present invention also for satisfying the desired washing function are disclosed in the appended subclaims.
REFERENCES:
patent: 3938434 (1976-02-01), Cox
patent: 4155299 (1979-05-01), Tuttle
patent: 4528098 (1985-07-01), Treyssac et al.
patent: 4915830 (1990-04-01), Mackay et al.
patent: 5034128 (1991-07-01), Hillstrom et al.
patent: 5122263 (1992-06-01), Huber
patent: 5205930 (1993-04-01), Obrestad
patent: 5372713 (1994-12-01), Huber
patent: 3122131 (1982-12-01), None
patent: 4143376 (1993-04-01), None
patent: 0565898 (1993-10-01), None
patent: 9519212 (1995-07-01), None
English Abstract of EP 0565898.
English Abstract of DE 3122131.
Ladas and Parry
Prince Fred
Simmons David A
Spirac Engineering AB
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