Liquid purification or separation – Filter – Medium – cleaner or agitator moved by fluid
Reexamination Certificate
1999-08-04
2001-11-20
Walker, W. L. (Department: 1723)
Liquid purification or separation
Filter
Medium, cleaner or agitator moved by fluid
C210S370000, C210S391000
Reexamination Certificate
active
06318562
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a filtering centrifuge. More specifically, this invention relates to a filtering centrifuge with a mechanism for removing cake from filter media disposed along the inner surface of a rotatable filter basket. This invention also relates to an associated method for cleaning a filtering type centrifuge of cake deposited along filter media in the centrifuge.
A filtering centrifuge generally comprises a rotating perforated drum commonly referred to as a basket. This basket is lined with pervious filter media. During operation of the centrifuge, the basket is rotated while a slurry of solids suspended in a liquid is introduced into the basket. The rotation of the basket generates a multiplied centrifugal force which flings the slurry outwardly onto the filter media. The solids portion of the slurry is captured by the filter media and is deposited as a cake layer thereon, while the liquid portion of the slurry drains through the filter media and out of the basket through the perforations therein.
Once the processing of the captured solids is complete, in many cases the solids are automatically discharged by introducing a deflector blade or plow into the captured solids (filter cake) as the basket slowly rotates. The cake is thereby deflected out through an opening in the bottom of the basket. In executing this operation, the plow is stopped short of contacting the filter media to prevent damage thereto. This procedure results in a thin layer of undischarged cake being left in the basket. This undischarged layer of cake is referred to as “heel.”
SUMMARY OF THE INVENTION
The present invention is directed to providing a structure and a process for removing heel from the basket of a filtering centrifuge without damaging the filter media. The present invention is intended to provide a simple and inexpensive structure for achieving this end. A process or method for cleaning a filtering centrifuge in accordance with the present invention has an aim of being quick and reliable, as well as preservative of the filter media.
A centrifuge in accordance with the present invention comprises a case, a perforated filter basket disposed for rotation in the case, filter media disposed along an inner surface of the filter basket and a cake removal mechanism at least partially disposed in the case outside of the filter basket and engageable with the filter media to distort the filter media and induce separation of deposited cake from the filter media. The cake removal mechanism specifically includes an ejector element movably mounted to the case for shifting between a use position adjacent to the filter basket and a neutral position spaced from the filter basket.
More specifically, the cake removal mechanism includes a nozzle assembly having a base element fixed to said case and a sleeve movably mounted about a core portion of said base element for shifting between a use position adjacent to the filter basket and a neutral position spaced from the filter basket.
In accordance with another feature of the present invention, the core portion of the nozzle assembly base is provided with a bore or channel for directing a pressurized fluid through the filter basket and against the filter media. The base element is provided with an additional bore, surrounding and generally coaxial with the core bore, the sleeve being slidably disposed in that additional bore. The sleeve is thus sandwiched, in a telescoping fashion between the core portion of the base and an outer portion of the base.
In accordance with further features of the present invention, the sleeve is provided with a flange disposed in the additional bore and defines an enlarged recess at a free end of the core portion. The flange provides an increased surface area for exerting pressure against the sleeve to shift the sleeve radially inwardly towards the filter basket, while the enlarged recess increases the time interval that the filter media experiences an inward pressure owing to fluid (e.g., air) ejected from a radially inner end of the nozzle assembly through perforations in the filter basket.
A method for use in automatic cleaning of a filtering centrifuge comprises, in accordance with the invention, providing a centrifuge having a perforated filter basket in a case, a filter media being disposed along an inner surface of the filter basket. The method further comprises providing a nozzle assembly having a base element and an ejector element movably mounted to the base element for shifting between a use position adjacent to the filter basket and a neutral position spaced from the filter basket. Pursuant to the method, the base element is fixed to the case so that the ejector element extends in a radial direction relative to the filter basket and so that the ejector element is spaced from the filter basket.
The method further comprises shifting the ejector element radially inwardly towards the filter basket during a rotating of the filter basket. The base element is connected to a source of pressurized fluid, so that the shifting of the ejector element is achieved by directing pressurized fluid from the source against the ejector element to force the ejector element in a radially inward direction. Fluid is directed through the ejector element and perforations in the filter basket upon the shifting of the ejector element radially inwardly. By virtue of the directing of fluid through the ejector element and the filter basket, a radial force is exerted against the filter media through the perforations during the rotation of the basket in the case. By virtue of the force exerted on the filter media through the perforations, the filter media is distorted to induce separation of deposited cake from the filter media.
The method further includes holding the ejector element in sliding contact with an outer surface of the filter basket while the filter basket rotates.
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Kleyn James F.
Wilkie William John
Baker Hughes Incorporated
Coleman Henry D.
Sapone William J.
Sorkin David
Sudol R. Neil
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