Imperforate bowl: centrifugal separators – Including sealing means – For sealing between stationary and moving elements
Patent
1991-06-28
1993-02-16
Hornsby, Harvey C.
Imperforate bowl: centrifugal separators
Including sealing means
For sealing between stationary and moving elements
494 48, 494 64, 494 70, B04B 108, B04B 708
Patent
active
051867087
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal separator comprising a rotor body which forms a separation chamber and comprises two axially separated end walls and a surrounding wall situated axially between the end walls, a stack of conical separation discs arranged between the end walls in the separation chamber coaxially with the rotor, and a fastening means separate from the surrounding wall and arranged to keep the end walls and the stack of separation discs therebetween axially together. A centrifugal separator of this kind is described e.g. in U.S. Pat. No. 1,343,325.
As can be seen from U.S. Pat. No. 1,343,325 the two end walls of the known centrifugal separator are kept axially together by means of a central locking joint. This comprises a vertical column permanently connected with the lower end wall and extending centrally through the centrifuge rotor, and a looking ring threaded on to the column and retaining the upper end wall relative thereto. The surrounding wall of the rotor is formed in one piece with the upper end wall and is kept axially in sealing engagement with the lower end wall by means of the central locking joint. Centrifugal separators of this kind were common around the turn of the century when the centrifuge rotors were still relatively small.
When larger centrifuge rotors were developed and higher rotational speeds were used the demands on strength of the central locking joint were increased. As a consequence thereof another type of locking joint was developed. One example of such a locking joint is shown in U.S. Pat. No. 1,571,943. This locking joint comprises a locking ring dimensioned and arranged to keep the rotor end walls axially together in the area of the largest peripheries thereof instead of, as previously, centrally in the rotor. Thus, the locking ring has been given a substantially larger diameter than before, whereby its threads may take up correspondingly larger shearing forces.
A locking joint of the last mentioned type is more difficult to deal with than a central locking joint and, therefore, is not desirable in connection with relatively small centrifuge rotors.
SUMMARY OF THE INVENTION
The object of the present invention is, partly, to enable use of a central locking joint in a centrifuge rotor of the kind here in question and, partly, to make it possible to give such a centrifuge rotor a relatively large diameter and/or a relatively high rotational speed without overloading the central locking joint.
This object may be obtained according to the invention in a centrifugal separator of the initially defined kind in a way such that the surrounding wall is formed separate from both the end walls and arranged to seal against them, that the surrounding wall has a smaller diameter in both the areas, in which it seals against the end walls, than it has in an area axially between these areas, and that the surrounding wall is free to move axially during rotor operation relative to at least one of the end walls in the area of its sealing thereagainst.
By this invention the rotor body may be given a relatively large diameter and/or be given a relatively high rotational speed without the axial forces, by which the rotor body is loaded during rotor operation as a consequence of the overpressure of liquid rotating within the rotor, loading to their full extent the end walls and the central fastening means keeping these together. In other words, the surrounding wall of the rotor body may be shaped in a way such that it takes up, to a desired degree, oppositely directed axially forces from the liquid within the rotor, axial deformation of the rotor body being allowed during operation thanks to the axial movability between the surrounding wall and at least one of the end walls.
In a preferred embodiment of the invention the surrounding wall has substantially the same inner diameter in both the areas in which it seals against the end walls, so that the whole axial pressure exerted by liquid within the rotor against the rotor body radially outsid
REFERENCES:
patent: 1343325 (1920-06-01), Leitch
patent: 1519629 (1924-12-01), Rohl
patent: 1571943 (1926-02-01), Hall et al.
patent: 2898037 (1959-08-01), Dega
patent: 3012710 (1961-12-01), Steinacker
patent: 4015773 (1977-04-01), Thylefors
patent: 4067494 (1978-01-01), Willus et al.
patent: 4164317 (1979-08-01), Nelson
patent: 4285462 (1981-08-01), Buffet
patent: 4871458 (1989-10-01), Purvey
Ridderstrale Rolf
Stroucken Klaus
Alfa-Lavel Separation AB
Cooley Charles
Hornsby Harvey C.
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