Abstract:
A cone-stack centrifuge for separating particulate material out of a circulating fluid includes a rotor assembly configured with a hollow rotor hub and is constructed to rotate about an axis by the ejection of the fluid from nozzles in the rotor assembly. The rotor assembly is mounted on a shaft that is attached to the hub of a base. The base further includes a fluid inlet, a passageway connected to the inlet and in fluid communication with the rotor assembly, and fluid outlet. A bearing arrangement is positioned between the rotor hub and the shaft for rotary motion of the rotor assembly about the shaft. The base further includes a baffle for re-directing a swirling flow of fluid out of the base in a radial direction and into the fluid outlet.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the continuous separation of solid particles, such as soot, from a fluid, such as oil, by the use of a centrifugal field. More particularly the present invention relates to the use of a cone (disk) stack centrifuge configuration within a centrifuge assembly with a base that redirects the residual velocity of fluid discharge from the rotor jet nozzles to assist drainage rate and reduce pooling of oil in the centrifuge base. 
     Diesel engines are designed with relatively sophisticated air and fuel filters (cleaners) in an effort to keep dirt and debris out of the engine. Even with these air and fuel cleaners, dirt and debris, including engine-generated wear debris, will find a way into the lubricating oil of the engine. The result is wear on critical engine components and if this condition is left unsolved or not remedied, engine failure. For this reason, many engines are designed with full flow oil filters that continually clean the oil as it circulates between the lubricant sump and engine parts. 
     There are a number of design constraints and considerations for such full flow filters, and typically these constraints mean that such filters can only remove those dirt particles that are in the range of 10 microns or larger. While removal of particles of this size may prevent a catastrophic failure, harmful wear will still be caused by smaller particles of dirt that get into and remain in the oil. In order to try and address the concern over small particles, designers have gone to bypass filtering systems which filter a predetermined percentage of the total oil flow. The combination of a full flow filter in conjunction with a bypass filter reduces engine wear to an acceptable level, but not to the desired level. Since bypass filters may be able to trap particles less then approximately 10 microns, the combination of a full flow filter and bypass filter offers a substantial improvement over the use of only a full flow filter. 
     While centrifuge cleaners can be configured in a variety of ways as represented by the earlier designs of others, one product which is representative of part of the early design evolution is the Spinner II® oil cleaning centrifuge made by Glacier Metal Company Ltd., of Somerset, Ilminister, United Kingdom, and offered by T.F. Hudgins, Incorporated, of Houston, Tex. Various advances and improvements to the Spinner II® product are represented by U.S. Pat. Nos. 5,575,912; 5,637,217; 6,017,300; and 6,019,717 issued to Herman Nov. 19, 1996; Jun. 10, 1997; Jan. 25, 2000; and Feb. 1, 2000, respectively. These four patents are expressly incorporated by reference herein for their entire disclosures. 
     Hero-turbine centrifuges, as commonly used as bypass separators on diesel engine lube systems, operate by ejecting a high velocity fluid jet from a nozzle, which drives the centrifuge rotor via reaction force. After ejection from the centrifuge rotor, the fluid must be quickly evacuated from the centrifuge base and drained back to the sump. If the fluid begins to pool in the base, a condition known as flooding can occur, whereby the fluid contacts the turbine ends of the centrifuge rotor and dramatically slows down the speed of rotation. In this flooded condition, the centrifuge is rendered useless since it is no longer spinning at the desired speed and separating particulate from the oil. This condition is usually avoided by designing a very large outlet drain and providing enough head space beneath the rotor to allow some pooling to occur without the oil contacting the rotor. 
     The need therefore exists for a design that reduces the necessary size of outlet drain or reduces the required head space beneath the rotor, thereby allowing more room for rotor sludge capacity. The present invention meets this need in a novel and non-obvious way. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention described herein is providing a centrifuge base with means for redirecting the residual velocity of fluid discharge from the rotor jet nozzles from a tangential direction to a radial direction in order to assist drainage rate and reduce pooling of oil in the centrifuge base. 
     One form of the present invention contemplates a centrifuge base with a radially directed gravity drain outlet configured with an outlet baffle oriented to redirect the residual fluid velocity in the radially outward direction of the drain outlet. 
     Another form of the present invention contemplates a centrifuge housing base having a central bottom drain where the base is equipped with spiral vanes to redirect the residual fluid velocity radially inward toward the drain outlet. 
     One object of the present invention is to provide a unique centrifuge base that assists the oil drainage rate and reduces pooling of oil in the base. 
    
    
     Further objects, features, and advantages of the present invention will be apparent from the description and drawings contained herein. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view in full section of a cone-stack centrifuge according to one embodiment of the present invention. 
     FIG. 2 is a top plan view in full section of the FIG. 1 centrifuge as view along line  2 — 2  in FIG.  1 . 
     FIG. 3 is a perspective view of the base of a cone-stack centrifuge according to an alternative embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring to FIG. 1, there is illustrated a cone-stack centrifuge  20  according to a preferred embodiment of the present invention. Centrifuge  20  includes as some of its primary components base  21 , bell housing  22 , shaft  23 , and rotor assembly  24  including rotor hub  25 , cone-stack  26 , tangential flow jet nozzles  27  and  28 , bottom plate  29 , and centrifuge bowl  30  securely sealed to bottom plate  29 . Axially extending through the center of bottom plate  29  and through the interior of centrifuge bowl  30  is hollow rotor hub  25 . Rotor hub  25  is bearingly mounted to and supported by shaft  23  by means of upper and lower bearings  34  and  35 , respectively. 
     At the lower region of bottom plate  29  are two tangential flow nozzles  27  and  28 . These tangential flow nozzles are symmetrically positioned on opposite sides of the axis of rotor hub  25 , and their corresponding flow jet directions  99 , as seen in FIG. 2, are opposite one another. As a result, these flow nozzles are able to create the driving force for rotating rotor assembly  24  about shaft  23  within bell housing  22 , as is believed to be well known in the art. Spinning of centrifuge  20  can also be accomplished with a single flow nozzle, or with the use of more than two flow nozzles. 
     The assembly between centrifuge bowl  30  and bottom plate  29  in combination with O-ring  70  creates a sealed enclosure defining an interior volume  73  which contains cone-stack  26 . Each cone  74  of cone-stack  26  has a center opening  75  and a plurality of inlet holes disposed around the circumference of the cone adjacent the outer annular edge  77 . Typical cones for this application are illustrated and disclosed in U.S. Pat. Nos. 5,575,912 and 5,637,217. The typical flow path for rotor assembly  24  begins with the flow of liquid upwardly through the hollow center  78  of rotor hub  25 . The flow through the interior of rotor hub  25  exits out through apertures  79 . A flow distribution plate  80  is configured with vanes and used to distribute the existing flow out of hub  25  across the surface of top cone  74   a . The manner in which the liquid (lubricating oil) flows across and through the individual cones  74  of cone-stack  26  is a flow path and flow phenomenon which is well known in the art. This flow path and the high RPM spinning rate of the cone-stack assembly enables the small particles of soot which are carried by the oil to be centrifugally separated out of the oil and held in the centrifuge. 
     The focus of the present invention is on the design of base  21  which is configured with and defines fluid inlet  82 , passageway  83  connected to the inlet, and a fluid outlet that permits the fluid entering base  21  from flow nozzles  27  and  28  to exit base  21 . Base  21  further includes base hub  87  and base sidewall  96  defining interior space  95  of base  21 . In one embodiment of the present invention, the fluid outlet is radial outlet drain  97  defined by sidewall  96 . Shaft  23  which extends through rotor hub  25  is attached to base hub  87  and includes passageway  91  which is in fluid communication with base passageway  83  at one end and with hollow center  78  of rotor hub  25  at the other end. 
     In operation of centrifuge  20 , pressurized fluid enters base  21  through fluid inlet  82  and flows through passageway  83  of base  21 . The fluid continues up through base hub  87  and into passageway  91  of shaft  23 . The fluid is then delivered to rotor assembly  24  via throttle passageway  93  in shaft  23 . The fluid flows through rotor assembly  24  as described above and then exits rotor assembly  24  through tangential flow nozzles  27  and  28  into interior space  95  of base  21 . 
     Since the discharge velocity of exit flow jets  99  from nozzles  27  and  28  is always higher than the counter-rotational velocity of nozzles  27  and  28 , a residual velocity component exists in the fluid discharge that is substantially oriented in a tangential direction opposite to the rotor assembly rotation. Illustrated in FIG. 2, this residual velocity causes the liquid in base  21  of the centrifuge to swirl around in a cyclonic fashion. Energy from this residual velocity can be harnessed to assist fluid drainage from base  21  by attaching upstream-directed baffle  98  that scoops the swirling flow off of base sidewall  96  and re-directs the fluid in a radially outward direction into radial outlet drain  97 . Baffle  98  is positioned over at least a portion of radial outlet drain  97  and projects in an upstream direction relative to the swirling flow in base  21 . Baffle  98  preferably has a first end  98   a  attached to bottom surface  94  of base  21  and a second end  98   b  attached to sidewall  96  above radial outlet drain  97 . In a preferred embodiment, baffle  98  further includes, as best seen in FIG. 2, a first side  98   c  projecting into the swirling flow of fluid and a second side  98   d  attached to sidewall  96  at a radial location downstream from radial outlet drain  97 . As shown in FIG. 2, baffle  98  is oriented for the clockwise rotation of rotor assembly  24  produced by exit flow jets  99  from nozzles  27  and  28 . The use of baffle  98  in base  21  of centrifuge  20  is similar in concept to the use of upstream-oriented air-ram inlets on highway trucks to increase the pressure at the air inlet location, thereby improving air flow to the truck engine. 
     In some cone-stack centrifuges, such as that illustrated in FIG. 3, the fluid outlet in base  121  is preferably central bottom drain  197 . In order to assist the drainage of fluid from base  121 , vanes  198  are connected to bottom surface  194  of base  121 . Vanes  198  are oriented in a direction such that they re-direct the swirling flow near sidewall  196  radially inward toward central bottom drain  197 . Additionally or alternatively, vanes  198  may be connected to sidewall  196  of base  121 . In a preferred embodiment, vanes  198  are spiral-shaped and cast or molded into base  121 . Further, vanes  198  preferably project vertically away from bottom surface  194 . 
     Base  121  preferably includes between 1 and 10 vanes, with 2-6 vanes being more preferred. Provided that vanes  198  redirect the tangential velocity of the fluid at base sidewall  196  radially inward, vanes  198  can take on a variety of shapes, including but without limitation to, logarithmic spiral, planar, circular arc section, or hyperbolic spiral. 
     To achieve the desired radial redirection of the fluid flow, the included intercept angle between vane  198  and base sidewall  196  should be less than 90° which corresponds to a straight radial vane. Useful intercept angles range between 10°-80° and preferably range between 0°-45° in order to minimize fluid shock, and the concomitant loss in energy upon impact with the vane at the vane-sidewall interface. A 0° intercept angle can be achieved by employing a generous fillet radius between the vane and sidewall  196  at the point of intersection. Of course, the direction of the spiral, and the associated included intercept angle, must be oriented with respect to the direction of exit flow jets  99 . FIG. 3 illustrates the proper orientation of vanes  198  for the counterclockwise rotation of a rotor assembly that creates a swirling flow in the direction of arrow  199 . 
     From the above description, a person of skill in the art will readily appreciate that bases  21  and  121  can be incorporated into any number of designs of self-driven centrifuges. The present invention is therefore, not limited to the design of rotor assembly  24  of cone stack centrifuge  20 . In this regard, the rotor assembly could take on various designs provided that it is constructed and arranged to rotate about an axis and that it is adapted to receive a fluid and to discharge at least a portion of that fluid through a tangential flow nozzle, such as nozzles  27  and  28 . This discharge of fluid causes the rotor assembly to rotate and simultaneously causes the swirling of fluid in the base. Thus, the incorporation of either base  21  or  121  with such a rotor assembly assists the drainage rate and reduces the pooling of fluid in the base. Alternative rotor assemblies include, for example but without limitation, a take-apart hero turbine without a cone stack, as well as centrifuges in which the vertical cone stack is replaced by a unitary, molded spiral vane module. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.