Patent Publication Number: US-6210311-B1

Title: Turbine driven centrifugal filter

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a non-provisional patent application based upon provisional patent application serial No. 60/101,804, entitled “AUXILIARY POWERED CENTRIFUGAL FILTER”, filed Sep. 25, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to centrifugal filters for filtering particulates from a liquid using centrifugal force. 
     2. Description of the Related Art 
     Many types of fluids contain particulates which need to be filtered out for subsequent use of the fluid. Examples of such fluids include medical and biological fluids, machining and cutting fluids, and lubricating oils. With particular reference to an internal combustion engine, a lubricating oil such as engine oil may contain particulates which are filtered out to prevent mechanical or corrosive wear of the engine. 
     Diesel engine mechanical wear, especially that relating to boundary lubricated wear, is a direct function of the amount of particulates in the lubricating oil. A particulate which is extremely detrimental to engine wear is soot, formed during the combustion process, and deposited into the crankcase through combustion gas blow-by and piston rings scraping of the cylinder walls. Soot is a carbonaceous polycyclic hydrocarbon which has extremely high surface area whereby it interacts chemically with adsorptive association with other lubricant species. Particle sizes of most diesel engine lubricant soot is between 100 Angstroms and 3 microns. Ranges of concentration are between 0 and 10 percent by weight depending on many factors. Because engine wear will dramatically increase with the soot level in the lubricating oil, engine manufacturers specify a certain engine drain oil interval to protect the engine from this type of mechanical wear. Current sieve type filters do not remove sufficient amounts of soot to provide soot related wear protection to the engine. 
     Centrifugal filters for lubricant filtration are generally known. Current production centrifugal lubricant oil filters are powered by hero turbines, which are part of the oil filter canister, or through direct mechanical propulsion. Hero turbine powered filters are limited by the supplied oil pressure from the engine, and only can be operated up to maximum speeds around 4000 revolutions per minute (RPM) with oil pressures nominally at less than 40 psi. In addition, hero turbine powered filters pass oil through the filter canister as it migrates toward the attached hero turbine jets. Therefore, the lubricant mean residence time is less than a few minutes. None of the currently available centrifugal filters which operate on the basis of a hero turbine provide satisfactory soot removal rates. Soot removal from engine lubricating oil requires greater G forces and longer residence times than is demonstrated with currently commercially available hero turbine powered filters. 
     Is also known to drive a centrifugal filter using a mechanical linkage from a turbine. The turbine receives a flow of engine exhaust air and drives a mechanical output shaft which nozzle impinges upon the turbine and causes the filter to rotate about the axis of rotation. 
     An advantage of the present invention is that the turbine is directly driven by a pressurized fluid to rotate the filter at a speed which is sufficient to effect centrifugal separation. 
     Another advantage is that the turbine is impacted upon by the pressurized fluid substantially orthogonal to the axis of rotation of the filter, thereby improving efficiency by substantially eliminating force vectors on the turbine parallel to the axis of rotation. 
     Yet another advantage is that the turbine may be configured as rigidly attached to, removably attached to or integral with the filter. 
     Still another advantage is that the nozzle may be disposed either radially within or outside of the turbine. 
     A further advantage is that the nozzle may be adjustably positioned relative to a fixed or variable geometry turbine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective, sectional view of an embodiment of a centrifugal filter assembly of the present invention; in turn is coupled with a filter inside a centrifugal filter assembly. The rotational speed of the filter is sufficient to separate particulates within the engine oil. An example of such a filter is disclosed in U.S. Pat. No. 5,779,618 (Onodera, et al.). 
     All of the units described above and others commercially available fall generally in groups of hero turbine design or direct mechanical actuation. While direct mechanically driven systems are capable of reaching the necessary G forces to provide soot removal, this type of linkage is generally very expensive and requires extensive modification of engines to adapt. While hero turbines do not suffer from this problem, insufficient G forces limit these filters from removing soot. 
     SUMMARY OF THE INVENTION 
     The present invention provides a centrifugal filter for filtering particulates from a liquid, wherein a turbine attached to a rotatable filter is driven with a pressurized fluid at a speed which is sufficient to separate the particulates from the liquid via centrifugal force. 
     The invention comprises, in one form thereof, a centrifugal filter assembly for filtering particulates from a fluid. A rotating filter is disposed within a housing and rotatable relative to the housing about an axis of rotation. A turbine is connected to the filter and includes a plurality of turbine blades extending generally radially relative to the axis of rotation. A nozzle having an outlet is aligned relative to the turbine, whereby a pressurized fluid which is jetted from the 
     FIG. 2 is a side, sectional view of another embodiment of a centrifugal filter assembly of the present invention; 
     FIG. 3 is a sectional view taken along line  3 — 3  in FIG. 2; 
     FIG. 4 is a fragmentary, side view of still another embodiment of a centrifugal filter assembly of the present invention; 
     FIG. 5 is a fragmentary, side view of another embodiment of a centrifugal filter assembly of the present invention; 
     FIG. 6 is a perspective view of an embodiment of a filter of the present invention; 
     FIG. 7 is a simplified, side view of still another embodiment of a centrifugal filter assembly of the present invention; 
     FIG. 8 is a perspective view of an embodiment of a turbine for use with the centrifugal filter assembly of the present invention; 
     FIG. 9 is a perspective view of another embodiment of a turbine for use with the centrifugal filter assembly of the present invention; 
     FIG. 10 is a perspective view of yet another embodiment of a turbine for use with the centrifugal filter assembly of the present invention; 
     FIG. 11 is a perspective view of still another embodiment of a turbine for use with the centrifugal filter assembly of the present invention; 
     FIG. 12 is a perspective view of a further embodiment of a variable geometry turbine for use with the centrifugal filter assembly of the present invention; and 
     FIG. 13 is a perspective view of yet another embodiment of a turbine for use with the centrifugal filter assembly of the present invention. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to FIG. 1, there is shown an embodiment of a centrifugal filter assembly  10  of the present invention for filtering particulates from a fluid. For example, centrifugal filter assembly  10  may be used to filter soot from engine oil in a diesel engine, and will be described accordingly. Centrifugal filter assembly  10  may be used for other applications, such as medical applications for separating particulates from a bodily or medical fluid, or machining and cutting applications for separating metallic particles from a hydraulic fluid or lubricating oil. 
     Centrifugal filter assembly  10  generally includes a housing  12 , rotating filter  14  and turbine  16 . Housing  12  contains filter  14  and defines a generally fluid-tight vessel. For example, housing  12  may be used as part of a bypass filter assembly for use with an internal combustion engine. When configured as such, a central supply tube  18  disposed in communication with a sump  28  extends outwardly from the engine. Housing  12  includes a hub  20  which is rigidly attached therewith. Hub  20  includes an internal threaded portion  22  which threadingly engages external threads on supply tube  18 . Screwing hub  20  onto supply tube  18  causes housing  12  to axially seal against the engine. An annular seal  24  on an axial end face of housing  12  effects a fluid tight seal with the engine. Hub  20  includes external threads  26  allowing attachment with suitable fluid conduits (not shown) for recirculating oil transported through filter assembly  10  back to sump  28 . 
     Filter  14  is disposed within and rotatable relative to housing  12  about an axis of rotation  30  defined by supply tube  18 . Filter  14  may be rotatably carried using a pair of reduced friction bearings  32  and  34  disposed at each axial end thereof. Bearings  32  and  34  may be, e.g., roller bearings, ball bearings or another type of reduced friction bearing supports such as a bushing. Filter  14  may include a suitable medium therein (not shown) allowing filtration of the fluid which is transported through filter  14 . For example, the medium disposed within filter  14  may be in the form of a spiral wrapped and embossed sheet of metal or plastic material, as will be described in greater detail hereinafter. 
     Turbine  16  is connected to filter  14  at an axial end thereof. In the embodiment shown, turbine  16  is attached to a bottom wall  36  of filter  14  via welding, a suitable adhesive or the like. The interconnection between turbine  16  and filter  14  causes rotation of turbine  16  to in turn rotate filter  14  about axis of rotation  30 . 
     Turbine  16  includes a plurality of blades  38  which extend generally radially relative to axis of rotation  30 . Blades  38  may extend substantially through axis of rotation  30 , or may be positioned at an angle offset from axis of rotation  30 . Moreover, blades  38  may be configured with a particular shape which is curved, straight, segmented, a combination of the same, etc., to provide a desired rotational speed of filter  14  during operation. 
     Hub  20  of housing  12  includes at least one fluid port  40  defining a nozzle through which a pressurized fluid is jetted to impact upon turbine blades  38 . In the embodiment shown, hub  20  includes a single fluid port  40  defining a nozzle, although a greater number of fluid ports may also be provided. A wall  42  disposed within hub  20  defines a pressure chamber  44  in communication with each of an internal bore of supply tube  18  and fluid port  40 . The pressurized fluid is transported through supply tube  18  into pressure chamber  44  and is jetted from fluid port  40 . The pressurized fluid which is jetted from fluid port  40  sequentially impinges upon blades  38  of turbine  16 . The pressurized fluid is jetted from fluid port  40  in a direction which is substantially perpendicular to axis of rotation  30 , thereby eliminating force vectors in a direction parallel to axis of rotation  30  and maximizing the force imparted on each blade  38 . The curvature and/or positioning of each blade  38  causes a rotational moment to be exerted on turbine  16 , which in turn causes turbine  16  and filter  14  to rotate about axis of rotation  30 . 
     A splash shield  46  is attached to housing  12  and is disposed radially around turbine  16  above blades  38 . Pressurized fluid which is jetted radially outwardly from fluid port  40  against turbine blades  38  falls to a bottom of housing  12  and exits through drain holes  48  in hub  20 . Splash shield  46  prevents an appreciable amount of pressurized fluid from spraying against a side wall of housing  12  and impacting against filter  14 . Impact of the pressurized fluid would provide aerodynamic drag on filter  14  and slow the rotational speed thereof. A relatively small radial clearance is provided between turbine  16  and splash shield  46  to minimize the amount of pressurized fluid which flows past splash shield  46  to an area adjacent filter  14 . 
     Filter  14  fills with oil to be filtered during operation. One or more exit holes  50  are provided in the bottom side of filter  14 . The size and number of holes  50 , as well as the fluid input rate into filter  14  is a function of the desired throughput rate through filter  14  and residence time of the fluid within filter  14 . Engine oil which drains through holes  50  in the bottom of filter  14  flows down the top of splash shield  46 , through one or more holes  52  in splash shield  46 , and out through drain holes  48  in hub  20 . 
     During use, a pressurized fluid is transported from sump  28  to supply tube  18 . When used with an internal combustion engine, the pressurized fluid may be in the form of engine oil which is pressurized using an oil pump to a pressure of between 30 and 70 pound per square inch (psi), and more particularly approximately 45 psi. Approximately 90 percent (which actual percentage may vary) of the circulated engine oil is transported through supply tube  18  to pressure chamber  44  for discharging in a generally radially outward direction relative to axis of rotation  30  against turbine blades  38  of turbine  16 . The pressurized engine oil causes turbine  16  to rotate at a speed of between approximately 5,000 and 20,000 revolutions per minute (RPM), more preferably between approximately 10,000 and 20,000 RPM. The remaining 10 percent of the engine oil is transported into filter  14  for centrifugal filtration. The high rotational speed of filter  14  creates a G force which is high enough to cause centrifugal separation of particulates carried within the engine oil. The particulates migrate radially outwardly within filter  14  and are contained within filter  14 . Periodic changing of filter  14  allows the trapped particulates within filter  14  to be merely discarded along with filter  14 . 
     Referring now to FIGS. 2 and 3, there is shown another embodiment of a centrifugal filter assembly  60  of the present invention. For purposes of illustration, centrifugal filter assembly  60  will be described for use with an internal combustion engine, but it is to be understood that filter assembly  60  may be utilized for other applications. 
     Housing  62  is attached to an engine (not shown) utilizing flanges  64  and bolts  66 . A bottom cover  68  is threadingly engaged with housing  62  and is sealed with housing  62  using an annular O-ring  70 . Bottom cover  68  may be removed from housing  62  to allow replacement of filter  72 , as will be described in greater detail hereinafter. 
     Turbine  74  is rotatably carried by housing  62  using one or more reduced friction bearings, such as ball bearing assemblies  76  and  78 . Turbine  74  includes a plurality of blades  80  disposed around the periphery thereof. Blades  80  extend generally radially relative to an axis of rotation  82 , and have a selected shape to provide a desired rotational speed of turbine  74 . The shape of blades  80  and the distance from axis of rotation  82  both have an effect on the rotational speed and are determined for a particular application (e.g., empirically). 
     A top cover  84  is fastened to housing  62  using, e.g., bolts  86 . Seals such as O-rings  88  provide a fluid tight seal between top cover  84  and housing  62 . Top cover  84  includes suitable porting  90  and  92  to be fluidly connected with a source of pressurized fluid and the fluid to be filtered, respectively. In the embodiment shown, porting  90  and  92  are each connected with a source of pressurized engine oil which provides both the source of pressurized fluid for rotating turbine  74  and the fluid to be filtered. 
     Nozzles  94  are attached to and carried by top cover  84 , and direct a source of pressurized fluid at selected locations against blades  80  of turbine  74 . As viewed in FIG. 2, the left hand nozzle  94  is disposed behind central supply tube  96  and the right hand nozzle  94  is disposed in front of supply tube  96 . Nozzles  94  thus both jet a pressurized fluid which impinges upon blades  80  of turbine  74  on opposite sides of turbine  74 . Because nozzles  94  are carried by top cover  84  and directed generally inwardly relative to axis of rotation  82 , the specific impingement angle of the pressurized fluid on blades  80  can easily be adjusted for a specific application. The angle of impingement, flow velocity of the pressurized fluid, shape of blades  80  and impingement location relative to axis of rotation  82  may be configured to provide a desired rotational speed of turbine  74 . 
     Drive nut  98  includes internal threads which are threadingly engaged with external threads of turbine  74 . Drive nut  98  includes an upper, angled surface  100  defining a fluid port for providing lubricating oil to bearings  76  and  78 . Drive nut  98  includes a lower drive portion  102  with a cross sectional shape which is other than circular (e.g., hexagonal). The shape of lower drive portion  102  allows turbine  74  to interconnect with filter  72  and rotatably drive filter  72  during use. A flange  104  extends from drive portion  102  and seals with filter  72  around the outer periphery thereof with a slight compression fit. 
     Splash shield  106  is attached with housing  62  and directs oil away from filter  72  which is used to drive turbine  74 . Splash shield  106  is press fit into housing  62  in the embodiment shown. Pressurized fluid in the form of oil which is used to drive turbine  74  falls via gravitational force and flows through holes  108  and into a trough  110  defined by splash shield  106 . The trough  110  is connected with an exit port (not shown) in housing  62  for recirculating the fluid to the sump of the engine. 
     Filter  72  generally includes a body  112 , end cap  114  and impingement media  116 . Body  112  includes a top opening  118  which surrounds and frictionally engages flange  104  of drive nut  98 . The press fit between flange  104  and top opening  118  is sufficient to prevent fluid leakage therebetween. Body  112  also includes a plurality of exit holes, such as the two exit holes  120  in the top thereof. Exit holes  120  allow filtered oil to flow therethrough and into trough  110  during operation after filter  72  is full of the oil to be filtered. 
     End cap  114  is attached with body  112  in a suitable manner. In the embodiment shown, end cap  114  and body  112  are each formed from plastic and are ultrasonically welded together. However, it is also possible to attach end cap  114  with body  112  in a different manner, such as through a threaded or snap lock engagement. End cap  114  includes an upwardly projecting stud  122  with an angled distal face which acts to radially distribute oil to be filtered which is ejected from central supply tube  96 . 
     Impingement media  116 , shown in more detail in FIG. 3, is in the form of a long, continuous sheet  124  of material which is wrapped in a spiral manner about supply tube  96  and stud  122 . Sheet  124  is formed with a plurality of randomly located dimples  126  which are approximately {fraction (3/16)} inch diameter and 0.070 inch deep. Each dimple  126  defines a generally concave surface facing toward axis of rotation  82 . Sheet  124  is approximately 0.020 inch thick and includes a plurality of holes  128  between dimples  126  which have a diameter of approximately 0.060 inch. Holes  128  are also substantially randomly placed on sheet  124  at locations between dimples  126  at a ratio of approximately one hole pre every three dimples. In the embodiment shown, dimples  126  have a center-to-center distance which varies, but with a mean center-to-center distance of approximately ⅝ inch. Of course, it will be appreciated that the specific geometry and number of dimples  126  and/or holes  128  within sheet  124  may vary depending upon the specific application. 
     Impingement media  116  in the form of a spiral wrapped sheet with dimples  126  and holes  128  provides effective centrifugal separation of particulates within the oil, and also regulates the residence time of the oil within filter  72 . As filter  72  rotates at a desired rotational speed during use, the oil to be filtered is biased radially outwardly against an adjacent portion of sheet  124 . Particulates within the oil settle into the concave surfaces defined by dimples  126  and the filtered oil migrates toward a hole  128  to pass therethrough in a radial direction and impinge upon the next radially outward portion of sheet  124 . The radially outward flow of the oil through holes  128  in sheet  124  and trapping of particulates within dimples  126  continues until the filtered oil lies against the inside diameter of body  112 . An annular cap  130  at the end of spiral wrapped sheet  124  prevents the oil from prematurely exiting in an axial direction toward the end of filter  72 . The filtered oil flows in an upward direction along the inside diameter of body  112  and through exit holes  120  into trough  110  to be transported back to the sump of the engine. 
     FIG. 4 illustrates yet another embodiment of a centrifugal filter assembly  140  of the present invention. Filter assembly  140  includes a housing  142  with a filter  144  rotatably disposed therein. Housing  142  includes an integral fluid channel  146  which terminates at a nozzle  148 . Nozzle  148  directs pressurized fluid against turbine blades  150  of turbine  152 . 
     Filter  144  includes turbine  152  as an integral part thereof. That is, turbine  152  is monolithically formed with filter  144 . In the embodiment shown, filter  144  and turbine  152  are each formed at the same time using a plastic injection molding process. 
     Referring now to FIG. 5, another embodiment of a centrifugal filter assembly  160  is shown, including a housing  142  and filter  162 . Filter  162  includes a turbine  164  with a plurality of turbine blades  168 . Turbine  164  includes a deflector shield  170  attached to an axial end thereof which maximizes the efficiency of the pressurized fluid jetted from nozzle  148  by confining sideways deflection of the fluid impinging on blades  168 . 
     FIG. 6 illustrates another embodiment of a filter  174  which may be utilized with the centrifugal filter assembly of the present invention. Filter  174  includes a turbine  176  with a plurality of variable pitch turbine blades  180 . A nozzle  182  which is attached with and pivotable relative to a housing (not shown) about a pivot point  184  is adjustable during use to change the impingement angle on blades  180  and the distance from the axis of rotation. The composite curved shape of each blade  180  coacts with the variable impingement angle from nozzle  182  to vary the rotational speed of and/or torque applied to turbine  176 . 
     FIG. 7 illustrates yet another embodiment of a centrifugal filter assembly  190  of the present invention. Filter assembly  190  generally includes a housing  192 , filter  194  and turbine  196 . Filter  194  and turbine  196  are each disposed within housing  192  and are carried by suitable support structure (not shown) allowing rotation around respective axes of rotation  198  and  201 . A nozzle  200  defined by housing  192  jets a flow of pressurized fluid onto turbine  196  to cause rotation thereof about axis of rotation  201 . Rotation of turbine  196  in turn rotates pulley  202  which is connected via drive belt  204  with a pulley  206  rigidly attached to filter  194 . Thus, rotation of turbine  196  causes rotation of filter  194  about axis of rotation  198 . Using an elongate force transmission element, such as drive belt  204 , allows the rotational speed of filter  194  to not only be adjusted by changing the physical configuration of turbine  196 , but also by changing the diameters of the drive pulley  202  and driven pulley  206 . For example, providing drive pulley  202  with a diameter which is the same as turbine  196  but twice as large as driven pulley  206  provides filter  194  with a rotational speed which is twice that of turbine  196 . 
     FIGS. 8-12 illustrate perspective views of alternative embodiments of turbines which may be used in a centrifugal filter assembly of the present invention. The turbines shown in FIGS. 8-11 are fixed blade designs for use with a stationary nozzle, while the turbine shown in FIG. 12 is a variable geometry design for use with an adjustable nozzle. Turbine  218  (FIG. 8) includes a plurality of turbine blades  220  extending radially from a hub  222 . Turbine  224  (FIG. 9) includes a plurality of turbine blades  226  extending radially from a hub  228 . Turbine  230  (FIG. 10) includes a plurality of turbine blades  232  extending radially from a hub  234 . Turbine  224  (FIG. 11) includes a plurality of turbine blades  238  extending radially from a hub  240 . Lastly, Turbine  242  (FIG. 12) includes a plurality of turbine blades  224  extending radially from a hub  246 . 
     FIG. 13 is a perspective view of yet another embodiment of a turbine  210  which may be utilized with a centrifugal filter assembly of the present invention. Turbine  210  includes a plurality of turbine blades  212  extending radially from a hub  214 . A deflector shield  216  surrounds the periphery of turbine  210  and contacts blades  212 . For example, deflector shield  216  may be press fit onto turbine  210  around the periphery of blades  212 . Deflector shield  216  maximizes the efficiency of the pressurized fluid which is jetted from a nozzle  148  by confining radial deflections of the fluid impinging on blades  212 . 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.