Imperforate bowl: centrifugal separators – Rotatable bowl – Driven by energy of material supplied
Reexamination Certificate
1999-05-28
2001-02-06
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Rotatable bowl
Driven by energy of material supplied
C494S075000
Reexamination Certificate
active
06183407
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to centrifugal separators intended for freeing a liquid from particles suspended therein and having a larger density than the liquid. More precisely the invention concerns a rotor for a centrifugal separator of this kind, which is rotatable around its center axis and includes a casing having two axially separated end walls and a surrounding wall situated therebetween and surrounding the center axis; an inlet member delimiting an inlet channel centrally in the casing; a separation means mounted in the casing; and at least one outlet member situated in the area of one of the end walls, spaced from the center axis and delimiting an outlet channel, which is directed in a way such that liquid flowing out therethrough accomplishes a reaction force on the rotor in its circumferential direction.
BACKGROUND OF THE INVENTION
Rotors of this kind, formed for reaction drive by means of an overpressure of the liquid to be cleaned, are previously known. As a rule they have been used for cleaning of relatively small liquid flows and have been relatively small and light.
In connections where rotors of this kind have been used the demands on separation efficiency have not been extremely large, but still certain means in the form of rotor inserts of different kinds have been suggested for improvement thereof.
Thus, inserts have been suggested in the form of filters of different kinds. GB 1 089 355 and GB 1 595 816 show examples of such filter inserts. Furthermore, different kinds of separation inserts have been suggested which are formed such that they shorten the sedimentation distance for particles, which are to be separated within the rotor from liquid supplied thereto. For instance, GB 729 169 shows a separation insert in the form of a helical wall, which delimits a helical flow path within the rotor for the liquid to be cleaned. U.S. Pat. No. 5,637,217 shows a separation insert having conical separation discs.
U.S. Pat. No. 2,067,273 shows a further construction of a centrifugal rotor of the initially defined kind. In this centrifugal rotor there is mounted a separation means including a lot of separation discs, which are arranged within the casing between the center axis and the surrounding wall of the casing and distributed around the center axis, so that they form a lot of axially extending separation channels. Each separation disc extends both axially and in a direction from the center axis towards the surrounding wall of the casing from a radially inner edge to a radially outer edge, forming an angle with imaginary radii extending from the center axis to the surrounding wall.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a rotor of the initially defined kind, intended for reaction drive and provided with a particular separation means in the separation space of the rotor, which rotor can be given a better separation efficiency than previously known rotors of this kind.
This object can be achieved according to the invention if a rotor of the initially defined kind is provided with a separation means of the kind included in a centrifugal rotor according to U.S. Pat. No. 2,067,273 and, further, is provided with an inlet member delimiting an inlet channel centrally in the casing, which inlet channel communicates with the separation channels through a distribution chamber situated between a first one of the casing end walls and said separation means, said separation channels extending from the distribution chamber to an area close to the other end wall of the casing. A rotor of this kind is further characterized in
that the separation discs leave a sludge space for accumulation of separated particles between their radially outer edges and the surrounding wall of the casing,
that a partition is arranged between the separation discs and said other end wall of the casing in a way such that it delimits on its one side a collection chamber, in which the separation channels open, and on its other side delimits an outlet chamber,
that the collection chamber communicates with the outlet chamber at a radial level in the rotor substantially corresponding to the radial level of the radially inner edges of the separation discs, and
that the afore-mentioned outlet channel communicates with the outlet chamber and extends to the outside of the rotor, where it opens in a liquid free space at a radial level outside said level, at which the collection chamber and the outlet chamber communicate with each other.
In a rotor according to the invention it is possible to accomplish a relatively small through-flow resistance for the liquid to be cleaned, when this liquid passes through the rotor separation means, i.e. through said separation channels delimited between the separation discs. Compared with an ordinary filter or a set of conical separation discs a separation means of the kind suggested according to the invention and, per se, previously known in other kinds of centrifugal separators creates a surprisingly small through-flow resistance for the liquid to be cleaned, particularly if the liquid has a low viscosity. Despite a small through-flow resistance there can be achieved in the afore-mentioned separation channels a separation efficiency, which is as good as the one obtained in the spaces between conical separation discs. In connection with centrifugal separators of the kind here in question it is important that a part as large as possible of the overpressure of the liquid supplied to the rotor for being cleaned is utilized for the driving of the centrifugal rotor. By use of a separation means in the rotor of the kind suggested according to the invention a larger part of the overpressure of the liquid to be cleaned can be used for the driving of the centrifugal separator than by use of a technique according to, for instance, the afore-mentioned U.S. Pat. No. 5,637,217. This means that the centrifugal rotor according to the invention may be given a higher rotational speed and, thereby, a better separation efficiency than said previously known centrifugal rotor according to U.S. Pat. No. 5,637,217.
Also in comparison with a centrifugal rotor according to the afore-mentioned U.S. Pat. No. 2,067,273, which contains a separation means similar to that of the centrifugal rotor according to the invention, the centrifugal rotor according to the invention may be given a better separation efficiency. This depends on the circumstance that the known centrifugal rotor has a less effective driving means than the centrifugal rotor according to the invention. Thus, the outlet nozzles for the reaction drive of the known centrifugal rotor are situated at a very small radius. Furthermore, the outlet channels of these nozzles open into liquid which is subjected to a certain overpressure.
That the overpressure, by which a liquid to be cleaned is supplied to a reaction driven centrifugal rotor, may be critical for the drive of the centrifugal rotor has been noticed for instance WO 96/23589. In this case the liquid in question is constituted by liquid flashed back from an automatically cleanable filter. In this connection it may be difficult sometimes to obtain a sufficiently high pressure of the returned liquid for achievement of a good operation of the reaction driven centrifugal rotor. In WO 96/23589 the problem has been resolved in a way such that the centrifugal rotor is continuously supplied not only with the returned liquid but also with a separate driving liquid. An arrangement of this kind is complicated and expensive and can often be avoided by use of the present invention, a good separation efficiency of the rotor being simultaneously maintained.
REFERENCES:
patent: 648664 (1900-05-01), Hoyt
patent: 660360 (1900-10-01), Burrell
patent: 661943 (1900-11-01), Arend
patent: 663111 (1900-12-01), Berrigan
patent: 715493 (1902-12-01), Lundstrom
patent: 787179 (1905-04-01), Hult et al.
patent: 855189 (1907-05-01), Ljungstrom
patent: 869808 (1907-10-01), Shee
patent: 929697 (1909-08-01), Ohlsson
patent: 950331 (1910-02-01), Hoyt
patent: 96939
Davidsson Thomas
Hallgren Ingvar
Larsson Leif Gunnar
Moberg Hans
Alfa Laval AB
Cooley Charles E.
Fish & Richardson P.C.
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