Disposable, self-driven centrifuge rotor

Abstract

 A disposable, cone-stack, self-driven centrifuge rotor assembly (20) for separating particulate matter out of a circulating flow of oil includes first and second rotor shell portions (22 and 23) which are injection molded out of plastic and joined together by ultrasonically welding engaging edges (26 and 27) so as to create an enclosing shell with a hollow interior. An injection molded, plastic support hub (25) is assembled into a central opening in the lower half (23) of the rotor shell and extends upwardly into the hollow interior. An injection molded, plastic bearing/alignment spool (24) is assembled into a central opening in the upper portion (22) of the rotor shell and extends downwardly into the hollow interior. A cone-stack subassembly (21), including a plurality of individual separation cones which are injection molded out of plastic, are arranged into an aligned stack and positioned within the hollow interior and cooperatively assembled between the support hub (25) and the bearing/alignment spool (24). The all plastic construction for the centrifuge rotor assembly (20) allows the entire assembly (20) to be disposed of without any disassembly required.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates in general to the design and construction of self-driven centrifugal separators with disposable component parts. More specifically, a first embodiment of the present invention relates to the design and construction of a self-driven, cone-stack centrifuge wherein the entire cone-stack assembly and rotor shell combination is designed to be disposable, including the structural configuration as well as the selected materials. In a related embodiment, all of the disposable-design features are retained, but the cone-stack subassembly is removed.

[0002] The evolution of centrifugal separators, self-driven centrifuges, and cone-stack centrifuge configurations is described in the Background discussion of U.S. Patent No. 5,637,217 which issued June 10, 1997 to Herman, et al. The invention disclosed in the '217 Herman patent includes a bypass circuit centrifuge for separating particulate matter out of a circulating liquid which includes a hollow and generally cylindrical centrifuge bowl which is arranged in combination with a base plate so as to define a liquid flow chamber. A hollow centertube axially extends up through the base plate into the hollow interior of the centrifuge bowl. The bypass circuit centrifuge is designed so as to be assembled within a cover assembly. A pair of oppositely disposed tangential flow nozzles in the base plate are used to spin the centrifuge within the cover so as to cause particulate matter to separate out from the liquid. The interior of the centrifuge bowl includes a plurality of truncated cones which are arranged into a stacked array and are closely spaced so as to enhance the separation efficiency. The incoming liquid flow exits the centertube through a pair of fluid (typically oil) inlets and from there is directed into the stacked array of cones. In one embodiment, a top plate in conjunction with ribs on the inside surface of the centrifuge bowl accelerate and direct this flow into the upper portion of the stacked array. In another embodiment of the '217 invention the stacked array is arranged as part of a disposable subassembly. In each embodiment, as the flow passes through the channels created between adjacent cones, particle separation occurs as the liquid continues to flow downwardly to the tangential flow nozzles.

[0003] While this prior patent discloses a disposable subassembly, this subassembly does not include the rotor top shell or what is called the permanent centrifuge bowl 197 in the '217 patent, nor the rotor bottom shell or what is called the base 198 in the '217 patent. Accordingly, in order to actually dispose of subassembly 186 (referring to the '217 patent ), the subassembly must be disassembled from within the rotor shell. In contrast, in the present invention, the entire cone-stack subassembly, as well as the top bearing, hub, and rotor shell, are all combined into a single, disposable unit.

[0004] Earlier products based on the '217 patent utilize a non-disposable metallic rotor assembly and an internal disposable cone-stack capsule. While these products provide high performance and low life-cycle cost to the end user, there are areas for improvement which are addressed by the present invention. These areas for improvement which are addressed by the present invention include:

1. High initial cost of the centrifuge rotor assembly which consists of an aluminum die-cast rotor, machined steel hub, pressed in journal bearings, two machined nozzle jets, the cone-stack subassembly or capsule, deep-drawn steel rotor shell, O-ring seal, and a large machined "nut" to hold everything together. This design approach is best suited for large engines with a displacement of something greater than 19 liters where the initial cost of the centrifuge (and engine) is less important that life-cycle cost. Also, the larger rotor size, coupled with low production volume of these engines leads towards the use of metallic components and the corresponding manufacturing processes.

2. Awkward and time-consuming service. The centrifuge rotor must be disassembled to remove the cone-stack capsule which is a rather messy job to perform, despite the encapsulation of the cone-stack subassembly and the accumulated sludge. With a disposable rotor design, the complete rotor is simply lifted off of the shaft, discarded, and replaced with a new centrifuge rotor assembly.

[0005] The disposable centrifuge rotor design of the present invention provides the needed improvements to the problem areas listed above by reducing the initial cost of the rotor subassembly by approximately 75% ($6.00 versus $25.00 for comparably sized rotor of prior design) and by allowing quick and mess-free service. While a majority of the invention disclosure, as set forth herein, is directed to the embodiment that uses a cone-stack subassembly for enhanced separation efficiency, a lower-cost embodiment is also disclosed.

[0006] The molded plastic and plastic welded design of the rotor shell of the present invention in combination with the cone-stack subassembly provides improved separation performance compared to all-metal designs. The present invention also provides an incinerable product which is important for European markets. The rotor shell of the present invention also provides a design improvement due to a reduced number of parts which results from the integration offered by molding as compared to metal-stamping designs. The present invention is intended primarily for lube system applications in diesel engines with displacement less than 19 liters. It is also believed that the present invention will have applications in hydraulic systems, in industrial applications such as machining fluid clean up, and in any pressurized liquid system where a high capacity and high efficiency bypass separator is desired.

SUMMARY OF THE INVENTION

[0007] A disposable, self-driven centrifuge rotor assembly for separating an undesired constituent out of a circulating fluid according to one embodiment of the present invention comprises a first rotor shell portion, a second rotor shell portion joined to the first rotor shell portion so as to define a hollow interior, a support hub positioned within the hollow interior adjacent the second rotor shell portion, a bearing/alignment spool positioned within the hollow interior adjacent the first rotor shell portion, and a cone-stack subassembly including a plurality of individual separation cones arranged into an aligned stack with flow spacing between adjacent separation cones, the cone-stack subassembly being positioned within the hollow interior between the support hub and the bearing/alignment spool.

[0008] One object of the present invention is to provide an improved self-driven, centrifuge rotor assembly.

[0009] Related objects and advantages of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 

FIG. 1 is a perspective view of a disposable, self-driven centrifuge assembly according to a typical embodiment of the present invention.

FIG. 2 is a front elevational view in full section of the FIG. 1 centrifuge assembly based on a first cutting plane.

FIG. 2A is a front elevational view in full section of an alternative centrifuge assembly embodiment according to the present invention.

FIG. 3 is a front elevational view in full section of the FIG. 1 centrifuge assembly based on a second cutting plane.

FIG. 4 is a perspective view of a rotor top shell which comprises one component of the FIG. 1 centrifuge assembly.

FIG. 5 is a bottom plan view of the FIG. 4 rotor top shell.

FIG. 6 is a front elevational view in full section of the FIG. 4 rotor top shell as viewed along cutting plane 6-6 in FIG. 5.

FIG. 7 is a perspective view of a rotor bottom shell which comprises one component of the FIG. 1 centrifuge assembly.

FIG. 8 is a front elevational view of the FIG. 7 rotor bottom shell.

FIG. 9 is a bottom plan view of the FIG. 7 rotor bottom shell.

FIG. 10A is a front elevational view in full section of the FIG. 7 rotor bottom shell as viewed along cutting plane 10-10 in FIG. 9 and rotated 180 degrees.

FIG. 10B is a front elevational view in full section of the FIG. 7 rotor bottom shell.

FIG. 11 is a perspective view of a hub which comprises one component of the FIG. 1 centrifuge assembly.

FIG. 12 is a front elevational view of the FIG. 11 hub.

FIG. 13 is a top plan view of the FIG. 11 hub.

FIG. 14 is a bottom plan view of the FIG. 11 hub.

FIG. 15 is a front elevational view of a cone which comprises part of a cone-stack subassembly which comprises one component of the FIG. 1 centrifuge assembly.

FIG. 16 is a top plan view of the FIG. 15 cone.

FIG. 17 is a front elevational view in full section of the FIG. 15 cone as viewed along cutting plane 17-17 in FIG. 15.

FIG. 18 is a perspective view of a bearing/alignment spool which comprises one component of the FIG. 1 centrifuge assembly.

FIG. 19 is a front elevational view of the FIG. 18 bearing/alignment spool.

FIG. 20 is a bottom plan view of the FIG. 18 bearing/alignment spool.

FIG. 21 is a front elevational view in full section of the FIG. 18 bearing/alignment spool.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment 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.

[0012] Referring to FIGS. 1, 2, and 3, there is illustrated a disposable, self-driven cone-stack centrifuge assembly 20 which includes five injection molded plastic components, counting the cone-stack subassembly 21 as one component. The remaining components include the rotor top shell 22, the rotor bottom shell 23, a top bearing/alignment spool 24, and hub 25. The rotor top shell 22 and rotor bottom shell 23 are joined together into an integral shell by means of an "EMA Bond" weld at the lower annular edge 26 of shell 22 and the upper annular edge 27 of shell 23. The material and technique for the EMA Bond weld are offered by EMA Bond Systems, Ashland Chemicals, 49 Walnut Street, Norwood, New Jersey.

[0013] The FIG. 2A illustration shows the present invention without the cone-stack subassembly 21. While keeping all other components virtually identical, but simply removing the individual cones 71, a lower-cost version of the present invention is created. The FIG. 2A embodiment still functions in the matter described for the FIGS. 1, 2, and 3 embodiment as far as the remaining components. The only difference is the elimination of the cone-stack subassembly 21. By keeping the rotor top shell 22, the rotor bottom shell 23, the top bearing/alignment spool 24, and the hub 25 of FIG. 2A virtually identical to the corresponding components of FIGS. 1, 2, and 3, the cone-stack subassembly can be added or deleted as an option at the time of final assembly before the two rotor shells are welded together.

[0014] The rotor top shell 22 is illustrated in FIGS. 4, 5, and 6 and is constructed and arranged to provide a sludge containment vessel, suitable to handle the range of internal pressures which will be present, when welded together with the rotor bottom shell 23. Top shell 22 includes six equally-spaced integral acceleration vanes 31 which provide radial flow channels that direct liquid to inlet holes positioned in each cone. The vanes are integrally molded to the inner surface of outer wall 32.

[0015] The six vanes 31 are used to impart acceleration to the liquid and thus prevent "slip" of the liquid with respect to the spinning centrifugal rotor assembly 20. Each of the vanes 31 includes an axial edge 33 which extends into an approximate 45 degree outwardly radiating edge 34. The set of six 45 degree vane edges are constructed and arranged for establishing proper engagement with the top surface of the cone-stack subassembly 21. The outer wall 32 defines cylindrical sleeve 35 which defines cylindrical opening 35a which is concentric with lower circular edge 26. Lower edge 26 and upper edge 27 are cooperatively configured with a tongue and groove relationship for induction welding together the corresponding two shell portions. Top shell 22 provides the tongue portion and bottom shell 23 provides the groove portion. While the preferred welding technique employs the technology known as EMA Bond™, alternative welding and joining techniques are envisioned. For example, the two shell portions can be joined together into the integral shell which encloses the cone-stack subassembly 21 by means of spin-welding or ultrasonic welding.

[0016] The rotor bottom shell 23 is illustrated in FIGS. 7, 8, 9, 10A, and 10B and is constructed and arranged to provide a sludge containment vessel, suitable to handle the range of internal pressures which will be present, when welded together with the rotor top shell 22. The lower portion 37 of bottom shell 23 includes molded-in nozzle jet 38 and 39 with an oversized "relief" area 23a to maximize jet velocity (and rotor angular speed). Hollow cylindrical sleeve 42 is concentric with upper annular edge 27 and centered symmetrically between nozzle jets 38 and 39. Sleeve 42 includes a short extension 42a that extends beyond the defining surface of the relief area 23a. Sleeve 42 also includes a longer extension 42b that extends into the hollow interior of rotor bottom shell 23. Once the two rotor portions are welded together, sleeve 42 is concentric with opening 35a.

[0017] The internal annular ring-like wall 40 provides a mating engagement surface for the outside diameter of annular wall 41 of hub 25 (see FIGS. 11-14). Walls 40 and 41 are concentrically telescoped together into tight engagement in order to create a sealed interface and prevent any fluid flow from bypassing the cone stack. The sealed interface can be created by either an interference fit between or by welding together plastic walls 40 and 41. The upper edge 27 is configured with a receiving grove 27a which provides the cooperating portion of the tongue and groove connection with lower edge 26.

[0018] A further feature of rotor bottom shell 23 is the presence of a helical "V"-shaped ramp 44 which is molded as part of lower surface 45. Ramp 44 guides the liquid flow smoothly toward the two nozzle jets 38 and 39 and minimizes drag from air and splash (or spray) on the rotor exterior, and provides a strong structural configuration to withstand fluid pressure.

[0019] The hub 25 is illustrated in FIGS. 11, 12, 13, and 14 and is constructed with a conical base 48 and an integral tube 49 which extends through the conical base such that a first cylindrical tube portion 50 extends outwardly from one side of base 48 and a second cylindrical tube portion 51 extends from the opposite side of base 48. At the outermost edge 52 of base 48, the vertical annular wall 41 is located. Second tube portion 51 fits closely into sleeve 42 as illustrated in FIG. 1.

[0020] The first tube portion 50 has a substantially cylindrical shape and extends axially upwardly into the center of the cone-stack subassembly 21. The outside diameter surface 50a of first tube portion 50 includes two axially-extending radial projections 53 and 54 which act as alignment keys that interfit with inside diameter notches in each cone of the cone-stack subassembly.

[0021] The top surface or upper edge of each projection 53 and 54 includes a concave (recessed) notch 58 which is constructed and arranged to interfit with a cooperating projection on the tip of each finger of the bearing/alignment spool 24. The bearing/alignment spool 24 is illustrated in FIGS. 18-21 and described hereinafter. As will be explained, the spool 24 includes six equally-spaced, depending fingers, each of which have a distal edge which includes a convex projection. The size and shape of each convex projection is compatible with each notch 58 (two total, 180 degrees apart) such that any two projections which are 180 degrees apart interfit down into the two (recessed) notches 58. This interfit is designed to create a mating relationship between the bearing/alignment spool 24 and the hub 25. This in turn insures proper tangential alignment of the entire cone-stack subassembly 21, even if the cone-stack is "loose" which could be caused by a missing cone or a tolerance stack up problem.

[0022] The inside diameter surface 59 of the second tube portion 51 provides a journal bearing surface for rotation upon the shaft of the centrifuge. As would be understood, the second tube portion 51 is substantially cylindrical. One option for this portion of the design is to use this inside diameter surface for receipt of a metallic bushing. The diameter size can be reamed to the proper dimension if this option is selected. However, Consistent with attempting to make the entire assembly incinerable for the European market, an all-plastic construction is preferred.

[0023] The conical base (or skirt) 48 of hub 25 provides an axial support surface for the cone-stack subassembly and incorporates molded-in outlet holes 60 which provide for flow out of the cone-stack subassembly 21. Each cone includes an inside diameter edge with six equally-spaced recessed notches. While two of the six notches which are 180 degrees apart are used to align each cone onto the first two portions 50, the remaining four notches represent available flow passageways. The outlet holes 60 are arranged in an equally-spaced circular pattern (16 total) and are located beneath the cone notches.

[0024] The underside of the conical base 48 is reinforced by sixteen radial webs 61 which are equally-spaced and located between each pair of adjacent outlet holes 60. Each web 61 is centered between the corresponding two outlet holes 60 as is illustrated in FIG. 14. The general curvature, geometry, and shape of each web and its integral construction as a unitary part of hub 25 and conical base is illustrated in FIG. 11. The radial web 61 on the underside of base 48 is provided to help reduce long-term creep of the base 48, due to any pressure gradient between the "cone side" and the rotor base side of the conical surface, which can occur in high temperature environments during sustained operation.

[0025] As is illustrated in FIG. 11, the second tube portion 51 includes an offset ledge or shoulder 62 which reduces the inside diameter size as well as the outside diameter size of the second tube portion. Effectively, this shoulder 62 means that the second tube portion has a first larger section 65 and a second smaller section 66. The webs are shaped so as to be integrally joined to both sections 65 and 66 and to the shoulder 62. The opposite end, outer portion of each web is integral with the inside surface 67 of conical base 48. Upper surface 68 of base 48 which is integral with the first tube portion 50 and with the second tube portion 51 actually defines the line of separation between the first tube portion 50 and the second tube portion 51.

[0026] With reference to FIGS. 15, 16, and 17, one of the individual cones 71 which comprise the cone-stack subassembly is illustrated. In the preferred embodiment, a total of twenty-eight cones 71 are aligned and stacked together in order to create cone-stack subassembly 21. However, virtually any number of cones can be used for the cone-stack subassembly depending on the size of the centrifuge, the type of fluid, and the desired separation efficiency. Each cone 71 is constructed and arranged in a manner virtually identical to the cone described and illustrated in U.S. Patent No. 5,637,217, which issued June 10, 1997 to Herman, et al.

[0027] Each cone 71 is a frustoconical, thin-walled plastic member including a frustoconical body 72, upper shelf 73, and six equally-spaced vanes 74 which are formed on the inner surfaces of body 72 and shelf 73. The outer surface 75 of each cone 71 is substantially smooth throughout, while the inner surface 76 includes, in addition to the six vanes 74, a plurality of projections 77 which help to maintain precise and uniform cone-to-cone spacing between adjacent cones 71. Disposed in body 72 are six equally-spaced openings 78 which provide the entrance path for the oil flow between adjacent cones 71 of the cone-stack subassembly 21. Each opening 78 is positioned adjacent to a different and corresponding one of the six vanes 74.

[0028] The upper shelf 73 of each cone 71 defines a centered and concentric aperture 82 and surrounding the aperture 82 in a radially-extending direction are six equally-spaced, V-shaped grooves 83 which are circumferentially aligned with the six vanes 74. The grooves 83 of one cone receive the upper portions of the vanes of the adjacent cone and this controls proper circumferential alignment for all of the cones 71 of the cone-stack subassembly 21. Aperture 82 has a generally circular edge 84 which is modified with six part-circular, enlarged openings 85. The openings 85 are equally-spaced and positioned midway (circumferentially) between adjacent vanes 74. The edge portions 86 which are disposed between adjacent openings 85 are part of the same part-circular edge with a diameter which is closely sized to the outside diameter of the first tube portion 50. The close fit of edge portions 86 to the first tube portion 50 and the enlarged nature of openings 85 means that the exiting flow of oil through aperture 82 is limited to flow through openings 85. As such, the exiting oil flow from cone-stack subassembly 21 is arranged in six equally-spaced flow paths along the outside diameter of the first tube portion 50.

[0029] Each of the vanes 74 are configured in two portions 89 and 90. Side portion 89 has a uniform thickness and extends from radiused corner 91 along the inside surface of body 72 down to annular edge 92. Each upper portion 90 of each vane 74 is recessed below and circumferentially centered on a corresponding V-shaped groove 83. Portions 90 function as ribs which notch into corresponding V-shaped grooves 83 on the adjacent cone 71. This groove and rib notching feature allows rapid indexing of the cone-stack subassembly 21. The assembly and alignment of the cones 71 into the cone-stack subassembly 21 is preferably achieved by first stacking the selected cones 71 together on a mandrel or similar tube-like object without any "key" feature. The alignment step of the cones 71 on this separate mandrel is performed by simply rotating the top or uppermost cone 71 until all of the cones notch into position by the interfit of the upper vane portions 90 into the V-shaped grooves 83. Once the entire cone-stack subassembly 21 is assembled and aligned in this fashion, it is then removed as a subassembly from the mandrel and placed over the hub 25. In this manner, the radial projections 53 and 54 which act as alignment keys will be in alignment with the inside diameter notches of each cone in the cone-stack subassembly 21.

[0030] The bearing/alignment spool 24 is illustrated in FIGS. 18, 19, 20, and 21 and is constructed and arranged to provide for rotation of the disposable centrifuge rotor assembly 20 on the centrifuge shaft. It is actually the inside diameter 95 of upper tube portion 96 which is cylindrical in form and concentric with body portion 97 which includes a substantially cylindrical outer wall 98. It is also envisioned that a metal bushing can be pressed into the inside diameter 95 of portion 96 in order to provide the journal bearing surface. Depending on the size of the selected metal bushing, the inside diameter 95 may need to be reamed to the proper dimension for the press fit. However, in order to have the entire assembly incinerable, a metal bushing would not be used and thus the preferred embodiment is an all-plastic construction. As illustrated in FIGS. 1-6, spool 24 is assembled into rotor top shell 22. In particular, the upper tube portion 96 fits within cylindrical opening 35.

[0031] The region of body portion 97 located between cylindrical outer wall 98 and inside diameter 95 includes eight equally-spaced and integrally molded radial ribs 99. Located between each pair of adjacent radial ribs 99 is a flow opening 100. In all, there are eight equally-spaced flow openings 100. The radial ribs 99 are in abutment with the lower annular edge of sleeve 35 and the flow openings 100 are in flow communication with the interior of hub 25, specifically the first and second tube portions 50 and 51. The abutting engagement between the spool 24 and rotor top shell 22 in cooperation with openings 100 creates radial flow passageways from the hub into the acceleration vane region of the centrifuge rotor assembly 20. The insertion of the upper tube portion 96 into opening 35a provides concentric alignment of the cone-stack subassembly 21.

[0032] Axially extending from the lower edge of the outer wall 98 in a direction away from tube portion 96 are six equally-spaced integrally molded fingers 101. The distal (lower) edge 102 of each finger 101 includes convex projection 103 which is constructed and arranged to fit within the concave (recessed) notch 58 in each projection 53 and 54.

[0033] Additionally, each finger 101 has a shape and geometry which corresponds to the flow openings 85 which are located in the circular edge 84 of aperture 82. The fit of the fingers into the flow opening 85 of the top or uppermost cone 71 of the cone-stack subassembly 21 is such that the flow openings 85 in the top cone are plugged closed. By plugging these flow openings closed, the design of the preferred embodiment prevents total flow bypass of the cone-stack subassembly. The inside surface of each finger 101 engages the outside diameter of the first tube portion 50, thereby holding the hub 25 in proper concentric alignment with the rotor top shell 22.

[0034] Since the molded fingers extend through more cones 71 than only the top cone, small recessed grooves 106 are formed into the radially-outer surface of each finger. These grooves 106 enable flow to occur through these other cones. Without the grooves 106, the "engaged" cones would represent a dead end to the flow and the affected cones would be of no value to the separation task.

[0035] The fabrication and assembly of the disposable centrifuge assembly 20 which has been described and is illustrated herein begins with the injection molded of the individual cones 71. As described, the style of each cone 71 used in the present invention is virtually identical to the style of cone detailed in U.S. Patent No. 5,637,217. As described, this style of centrifuge cone includes its own self-alignment feature and is designed for automatically establishing the proper axial spacing between adjacent cones. The use of the V-groove and the V-rib interfit allows the cones to be stacked one on top of the other and then simply rotate the top cone until all of the cones "click in" to position.

[0036] The all plastic construction of the preferred embodiment of the present invention allows the assembly 20 to be disposed of in total or incinerated as a means of discarding without the need for any messy or complicated disassembly and without the need to exclude or salvage any metal parts.

[0037] 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.

Claims

1. A disposable, self-driven centrifuge rotor assembly for separating an undesired constituent out of a circulating fluid, said disposable, self-driven centrifuge comprising:

a first rotor shell portion;

a second rotor shell portion joined to said first rotor shell portion so as to define a hollow interior;

a support hub assembled into said second rotor shell portion and extending into said hollow interior;

a bearing/alignment spool assembled into said first rotor shell portion and extending into said hollow interior; and

a cone-stack subassembly including a plurality of individual separation cones arranged into an aligned stack with flow spacing between adjacent cones, said cone-stake subassembly being positioned within said hollow interior and cooperatively assembled between said support hub and said bearing/alignment spool.

2. A disposable, self-driven centrifuge rotor assembly according to claim 1 wherein said first and second rotor shell portions are injection molded from a plastic material.

3. A disposable, self-driven centrifuge rotor assembly according to claim 2 wherein said support hub, said bearing/alignment spool, and the individual separation cones of said cone-stack subassembly are each injection molded from a plastic material.

4. A disposable rotor assembly for a centrifugal separator for separating particulate matter from a fluid flowing through said disposable rotor assembly, said disposable rotor assembly comprising:

a rotor shell constructed and arranged with first and second shaft apertures and defining a hollow interior;

a support hub positioned within said hollow interior and assembled into said first shaft aperture;

a bearing/alignment spool positioned within said hollow interior and assembled into said second shaft aperture; and

a plurality of centrifuge cones arranged into an axial stack with substantially uniform axial spacing between adjacent centrifuge cones, said axial stack of centrifuge cones being positioned within the hollow interior of said rotor shell.

5. A disposable rotor assembly according to claim 4 wherein said rotor shell, said support hub, said bearing/alignment spool, and said plurality of centrifuge cones are each injection molded out of a plastic material.

6. A disposable, self-driven centrifuge rotor assembly for separating an undesired constituent out of a circulating fluid, said disposable, self-driven centrifuge comprising:

a first rotor shell portion;

a second rotor shell portion joined to said first rotor shell portion so as to define a hollow interior;

a support hub assembled into said second rotor shell portion and extending into said hollow interior; and

a bearing/alignment spool assembled into said first rotor shell portion and extending into said hollow interior.

7. A disposable, self-driven centrifuge rotor assembly according to claim 1 or claim 2 or claim 6 wherein said first and second rotor shell portions are welded together into an integral combination.

8. A disposable, self-driven centrifuge rotor assembly according to claim 1 or claim 7 wherein said first rotor shell portion defines a substantially cylindrical opening and said bearing/alignment spool includes an upper tube portion which fits into said substantially cylindrical opening.

9. A disposable, self-driven centrifuge rotor assembly according to claim 8 wherein said second rotor shell portion defines a substantially cylindrical sleeve and said support hub includes a substantially cylindrical tube portion which fits into said substantially cylindrical sleeve.

10. A disposable, self-driven centrifuge rotor assembly according to claim 9 wherein said substantially cylindrical opening is substantially concentric with said substantially cylindrical sleeve.

11. A disposable, self-driven centrifuge rotor assembly according to claim 1, claim 5 or claim 10 wherein each cone of said cone-stack subassembly defines a corresponding center aperture.

12. A disposable, self-driven centrifuge rotor assembly according to claim 11 wherein said support hub includes a cone tube portion which extends through the center aperture of each cone of said cone-stack subassembly.

Drawing