Liquid purification or separation – Comminuting – Cylindrical strainer
Reexamination Certificate
1999-12-08
2001-07-10
Kim, John (Department: 1723)
Liquid purification or separation
Comminuting
Cylindrical strainer
C210S350000, C210S383000, C210S402000, C100S116000
Reexamination Certificate
active
06258262
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a screw press type filter for filtering raw water containing sludge and other suspensions to separate it into filtrate and dehydrated cake.
BACKGROUND ART
As for conventional screw press type filters, there is, for example, a through-screw type filter cylinder system, as disclosed in Japanese Patent Publication No. SHO 63-65364 (U.S. Pat. No. 1,520,106). A filter of this system comprises a drum, a filter cylinder installed in a substantial length excluding the opposite ends of the drum for filtering raw water to separately migrate the water content thereof radially from inside to outside of the drum, a number of through-holes formed in the peripheral surface of the drum in said substantial length, a screw installed throughout the length of the drum to extend through said filter cylinder, the spaces within said drum at the opposite ends thereof being used as an inlet chamber for raw water and an outlet chamber for dehydrated cake. The filtration passage in the filter cylinder is defined by small clearances between alternating annular fixed and movable plates that constitute said cylinder.
In the above arrangement, normally as the water content is pressed out from the clearances between the plates toward the outer periphery of the filter cylinder, the volume of an object material to be processed (the residue remaining after the pressing of the raw water) that is pressed against the screw vanes corresponding to one pitch is progressively reduced according to the amount of water pressed out. In contrast thereto, in the usual construction wherein the volume ratio (processing volume/unit length) and the screw pitch are constant throughout the length of the filter cylinder, the screw load becomes lighter as the rear end of the filter cylinder is approached, resulting in the rear end of the screw feeding no substantial load.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a screw press wherein the processing capacity per screw pitch of the filter cylinder (volume/screw pitch) is progressively reduced over a region ranging from the inlet to the outlet, according to the amount of an object material processed per pitch of the screw normally decreasing, as the object material is pushed to move in a filter cylinder to press out its water content.
To achieve the above object, the invention provides a screw press type filter comprising:
a) a filter cylinder including an alternately superposed arrangement of a number of annular fixed plates each having an inner diameter, and a number of annular movable plates each having an inner diameter slightly larger than the inner diameter of said fixed plates and capable of shaking in the same plane with an amplitude corresponding to a difference between the respective inner diameters of said fixed and movable plates, with small filtration clearances defined therebetween, said filter cylinder having a fixed cylindrical space defined by the series of openings in said fixed plates; and
b) a screw installed in the cylindrical space of said filter cylinder to extend therethrough, with a mechanism provided for shaking said movable plates by rotation of the screw, whereby raw water fed in through an inlet port in an inlet end of said filter cylinder is pushed or propelled toward an outlet port in an outlet end thereof while said filtration clearances between the plates are always reproduced by the shaking movement of the movable plates;
c) said screw press type filter being characterized in that processing volume per screw pitch of said filter cylinder is progressively reduced over a region ranging from the inlet end to the outlet end.
In the above arrangement, there are three systems of means for progressively reducing the processing volume per screw pitch over a region ranging from the inlet end to the outlet end: {circle around (1)} means for progressively reducing the pitch of the screw over a region ranging from the inlet end to the outlet end of said filter cylinder, {circle around (2)} means for progressively increasing the shaft diameter of the screw over a region ranging from the inlet end to the outlet end of said filter cylinder, and {circle around (2)} means for progressively reducing the inner diameter of the filter cylinder and the projected area of the cross section of the screw corresponding thereto over a region ranging from the inlet end to the outlet end of said filter cylinder.
In a screw press filter according to the invention in which the processing volume per screw pitch of the filter cylinder is progressively reduced over a region ranging from the inlet end to the outlet end according to one of said three systems, the processing amount per screw pitch of an object material which is subjected to gradual water press-out to become harder is gradually accordingly reduced, whereby the distribution of the load on the screw is made uniform to ensure efficient water press-out throughout the length of the filter cylinder.
REFERENCES:
patent: 3585924 (1971-06-01), Nolan
patent: 3780645 (1973-12-01), Farmer
patent: 3802566 (1974-04-01), Hata
patent: 4041854 (1977-08-01), Cox
patent: 4266473 (1981-05-01), Hunt et al.
patent: 4271754 (1981-06-01), Homann
patent: 4838995 (1989-06-01), Kalusen
patent: 5160428 (1992-11-01), Kuri
patent: 48-95657 (1973-12-01), None
patent: 54-112570 (1979-09-01), None
patent: 63-65364 (1988-12-01), None
patent: 4-4997 (1992-01-01), None
Armstrong Westerman Hattori McLeland & Naughton LLP
Kim John
Terra Separator Co., Ltd.
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