US3279689A - Centrifuges - Google Patents

Description

Oct. 18, 1966 R. w. HONEYCHURCH 3,

CENTRIFUGES Original Filed March 14, 1962 4 Sheets-Sheet 1 FIG. 1

INVENTOR ROBERT W. HONEYC RCH ATTOR N EY.

Oct. 18, 1966 R. w. HONEYCHURCH GENTRIFUGES Original Filed March 14, 1962 4 Sheets-Sheet 2 INVENTOR.

ROBERT W. HONEYCHU 5H ATTORNEY.

Oct. 18, 1966 R. w. HONEYCHURC H 3,

7 CENTRIFUGES Original Filed March 14, 1962 4 Sheets-Sheet 5 FIG. 3

35 I 7 RM FIG. 4

INVENTOR.

ROBERT W. HONEYCH CH ATTORNEY.

Oct. 18, 1966 R. WHONEYCHURCl-j 3,279,689

GENTRIFUGES Originl Filed March 14, 1962 4 Sheets-Sheet 4 FIG.

R m V m ROBERT w. HONEYC,

H v C ATTORNEY.

United States Patent 3,279,689 CENTRIFUGES Robert W. Honeychurch, Stamford, Conn., assignor to Don-Oliver Incorporated, Stamford, Conn., a corporation of Delaware Continuation of application Ser. No. 179,610, Mar. 14, 1962. This application July 27, 1964, Ser. No. 386,114 12 Claims. (Cl. 233-14) This application is a continuation of application Serial No. 179,610 filed March 14, 1962 and now abandoned.

This invention relates to improvements in centrifugal machines for separating a feed mixture or emulsion into at least two distinct overflow fractions. In one specific embodiment, the invention relates to a three-product centrifuge of the type having two liquid overflow fractions and a solids-carrying underflow fraction.

It is a primary object of the invention to improve the quality of the separation accomplished in such machines to an extent not attainable in the prior art.

The invention may be exemplarily incorporated in a three-product machine of the type disclosed in the copending patent application of Honeychurch, Serial No. 34,303 filed June 6, 1960, now Patent No. 3,204,868. In that particular machine, the two liquid overflow fractions (respectively denominated primary and secondary or intermediate) discharge over annular dams at respective opposite axial ends of the machines rotor, and provision is made for returning to the rotor a portion of the underflow fraction discharged from the rotors peripherally located nozzles and/or for introducing .wash water or control liquid into the rotor. More particularly, this type of machine features a combination of two sets of conduits arranged within the rotor, namely a set of overflow conduits for the intermediate or secondary fraction and a set of return conduits forunderflow return and/or wash liquid introduction. Both sets of conduits are disposed generally radially to connect respective chambers adjacent the rotor axis to respective fraction zones near the rotor periphery. The inlets of the intermediate fraction overflow conduits are, of course, located at an intermediate radial position within the rotor so as to withdraw a fraction having a specific gravity between that of the primary overflow and that of the underflow.

During operation of such a machine, underflow material or solids from the feed necessarily pass through the intermediate fraction zone on the way to the peripheral nozzles. Therefore, under some operating conditions and with certain kinds of feed suspension, there is the tendency for some of the solids, especially the fines, to be carried into the intermediate fraction overflow conduits along with the intermediate liquid fraction. In particular, this condition of solids carry-over is aggravated where there is only a minor specific gravity differential between the intermediate overflow fraction and the solids in the underflow or where the rate of intermediate overflow is relatively large as compared with the rate of the primary overflow. Further, in this type of machine the localized nature of the intermediate overflow inlets in relation to the total periphery of the rotor bowl may cause unevenness in the interface between the primary and intermediate fraction with a resultant adverse effect on the quality of the separation of the two overflows.

Accordingly, an object of the invention is the elimination of carry-over solids in the intermediate liquid fraction by providing for special flow conditions and structural improvements in the rotor. Further, an object of the invention is the improvement of the separation of the primary and intermediate overflow fractions.

To accomplish the foregoing objects, the invention provides peripherally extensive inlet structures to avoid high velocity or turbulent flow at the inlets to the inter- "ice mediate fraction overflow conduits and structure to mini mize the quantity of solids passing in close proximity to these inlets. That is, the intermediate overflow inlets are specially configured as peripherally elongated apertures of greater cross-sectional area than the corresponding conduits. In this way, the flow of intermediate fraction liquid will have a velocity low enough to promote laminar flow conditions at the conduit inlet. Further, these elongated inlets are spaced away from the internal rotor surface so that solids moving along the rotor surface will not pass closely adjacent to the inlets and therefore will not be carried over into the intermediate overflow. With this improved arrangement, solids from the feed mixture will tend to move rapidly outwardly seeking to settle against the surface of the rotor bowl. These heavy solids will then slide radially outwardly upon this surface through the spaces under the conduit inlets directly into the region of the nozzles for discharge therethrough in the underflow.

In the preferred embodiment of the invention, the intermediate overflow fraction conduits terminate within the rotor in shallow, flat, fan-shaped or sector-shaped tubes having inlet openings across the fan periphery. These fan-shaped tubes are disposed obliquely within the rotor. in such a manner that the several tubes define a cone-like configuration. As a result of this structural'arrangement, a clarified layer of intermediate fraction liquid will form under the outer external surface of the fan-shaped tubes and will pass across the associated inlet edge or lip for discharge through the overflow conduit. Furthermore, the laminar flow and the resultant quasi-separating-disc effect induced in the shallow fan-shaped tubes are effective to encourage any carry-over solids that may have succeeded in entering the inlet to settle out and build up on the outer internal tube surface to the returned from the conduit back to the region of the nozzles for discharge with the underflow.

According to one feature of the invention, the foregoing improved centrifugal separating effects induced within the rotor are enhanced by a extension of the inner lip of the elongated inlet to form a substantial overhang ex tending beyond the opposite or outer lip. By this arrangement, lighter solids from the mixture that settle against the inwardly facing external surface'of these fan-shaped tubes will tend to slide outwardly thereon to fall toward the nozzles from the respective inner lip extensions at a point beyond the actual inlet opening, thus avoiding carryover into the intermediate fraction.

Other features and objects of the present invention will more fully appear from the following description and appended claims when read in conjunction with the accompanying drawings wherein:

FIGURE 1 is a vertical section of a rotor of a threeproduct centrifugal machine featuring the novel inter mediate fraction overflow conduits of the present invention.

FIGURE 2 is a fragmentary horizontal section taken substantially on line 22 of FIGURE 1.

FIGURE 3 is a fragmentary vertical section of the rotor of FIGURE 1 showing one of the specially constructed overflow conduits.

FIGURE 4 is similar to FIGURE 3 lbut shows flow lines indicative of the improved separating operation of the invention.

FIGURE 5 is a detail section of the inlet end of the conduit of FIGURE 4.

FIGURE 6 is a vertical section of the conduit of FIG- URE 3 illustrating the conduit mounting arrangements.

The rotor structure embodying this invention is mounted for rotation in a stationary housing which may be in the form shown in the aforementioned Honeychurch copending application. Such a housing provides'threeam nular receiving sections spaced axially from one another for receiving the underflow fraction from the rotor nozzles and the two overflow fractions respectively. However, for purposes of this invention, the housing itself need not be shown or described.

An example of a rotor structure embodying the invention is shown in FIGURE 1. The rotor includes a rotor bowl which defines an annular centrifugal separating chamber 11 and has a double cone-shaped body 12, preferably in the form of an integral member, having conical internal walls or surfaces 12!). Rotor body 12 contains in its outer periphery the well known nozzles 12a for discharging the solids carrying mixture that constitutes the underflow. Rotor bowl 10 includes a conical extension 13 locked to rotor body 12 as by a securing ring 14 having a threaded engagement with the rotor body. The conical extension constitutes one constricted end and one overflow dam of the rotor bowl and defines an annular overflow-lip 15 for centrifugally discharging the primary liquid overflow fraction from the bowl.

The opposite constricted end 16 of rotor bowl 10 is closed by a hub 17 having a hub rim 17a preferably thread connected as at 18a to the rotor bowl. Hub 17 is securely fastened to a rotor shaft 18 as by a key 19, a pair of opposedly arranged conical wedge devices 20 and 21, a locking washer 22, and a lock nut 23. A recess 24 provided in the bottom of the hub to accommodate which. closely fits against the upper surface of the hub and extends across channel 27 to sealingly abut the internal surface of rotor body 12 as by an O-ring (FIGURE 3). Adaptor ring 29 is fastened to hub 17 by means of screws 30a.

Ring 29 has a set of return flow passages. 31 spaced aroundthe rotor axis to communicate with the annular distributing channel 27. A set of return conduits 32 is connected to the respective passages 31 to return underflow material and/or control liquid into the region of the nozzles. The conduits are disposed adjacent and substantially parallel to the surrounding conical internal surface 12b of the rotor bowl. More particularly, each of these conduits 32 comprises a short connector 32a threaded into a respective passage 31 and a much longer free-ended tube 32b removably connected to the connector as by suitable coupling means or a union 32c. Return tubes 32b terminate at a circumferential position intermediate underflow nozzles 12a.

Ring 29 also has a set of overflow passages 33 spaced around the rotor axis in alternation with the return passages 31. Passages 33 register with overflow ducts 34 provided to extend in a generally axial direction through pumping vane 28 of the hub. A set of specially constructed and particularly shaped conduits 35 are connected to respective overflow passages 33 and thus to the associated overflow ducts 34.

More particularly, each overflow conduit 35 of the present invention comprises a short tubular male connector 36 extending in sealed relation (FIGURE 3) through a respective passage 33 in ring 29 and across annular distributing channel 27. Connectors 36 are thread-connected as at 37 (FIGURE 6) in the associated overflow ducts 34 of the hub. Conduit 35 further comprises a sector-shaped or fan-shaped overflow tube 38 formed with a significantly widened although shallow.

inlet end. As shown in FIGURE 2, the inlet edges or lips of the widened tube 38 occupy a significant portion of the circumference of the separating chamber between respective return tubes 32.

purposes fully described below, plate 42 is spaced a relatively small distance from .plate 40 (in the order of one to two times the spacing between the conventional separating discs of the rotor). An elongated inlet or mouth 44 is thus formed between lip41 and the opposite portion of plate 42 in the intermediate liquid fraction zone of the separating chamber 11.

45 (FIGURE 2) to form the tube structure.

The two sector-shaped plates 1 40 and 42 are suitably interconnected along their sides;

Conduit 35 further includes a tubular stub 46 secured to the apex end of sector-shaped tube 38. A coupling means or union 39 detachably interconnects stub tube 46 with male connector 36.

Sallow centrifugal separating spaces 360 having a depth in the range of a% or more are formed between the conduits 35 and the surrounding conical surface 12b of the rotor bowl for-purposes fully described below. The

sector-shaped tubes 38 of these conduits have lugs 36b to brace the tubes with respect to the surrounding rotor wall. Spacer pins 360 (FIGURES 2 and 6), unitary with the aforementioned spacer lugs 36b, may be provided within the sector-shaped or fan-shaped tube to stiffen the walls thereof against each other.

The rotor structure further comprises an axially extending feedwell 48 (FIGURE 1) surrounding rotor shaft 18. The feedwell includes a flaring foot 49 having enclosed, radially extending feed ducts 51 leading into the sur.-

rounding separating chamber 11. The feed ducts are separated by internal pumping vanes formed integrally in the feedwell. The flaring-foot is fastened to hub 17 by the aforementioned screws 30:: extending through the feedwell pumping vanes. Feedwell 48 has external, longitudinally extending impeller vanes 52 around which are seated a stack of the familiar separating discs 53 confined between a conical face 54 at the bottom of the stack presented by the feedwell flaring foot and a conical face 55 at the top presented by conical extension 13 of the rotor bowl. Feedwell 48 extends axially outwardly through the primary overflow end of the bowl for receiving the feed mixture.

Finally, at the bottom of the rotor a chamber ring 56 is coaxially fastened to the outer annular face 57 of rim 17a as by upwardly extending screws 58. Chamber ring 56 together with hub 17 constitute a centrally disposed return chamber 59 adjacent to but separate from separating chamber 11 of the bowl. Inwardly extending radial pumping vanes 60 are provided internally on the chamber ring to cause, together with pumping vanes 28 on the hub,

return material or the like to be impelled into return conduits 32 for delivery in the region of the nozzles.

Chamber ring 56 also has an annular intermediate overflow chamber 61 surrounding the central return chamber 59. Overflow ducts 62a in ring 56 register with over flow ducts 34 in hub rim 17a. This composite duct arrangement enables the secondary or intermediate liquid fraction from overflow conduits 35 to finally discharge over a ring dam 62 secured to chamber ring 56 by the above-mentioned screws 58.

Located in the central return chamber 59 is an auxiliary arrangement of vertically. extending but horizontally curved blades 64 carried by a terminal ring65 removably fastened as by screws to the outer end of a chamber? separating portion 66 of ring 56. These auxiliary blades 64 in turn carry above them a bathe plate 67 spaced axially from terminal ring 65 whereby the incoming return material or the like is deflected in radial directions for delivery into the divergent tube members 32 by the conjoint action of the pumping vanes 28 and 60.

Operation The operation of the invention in the above described three-product machine can best be described by referring to a type of feed material or slurry consisting of a mixture of three substances of different specific gravities, for instance, oil as the light fraction, water as the intermediate fraction, and solids (ranging from relatively coarse particles to fines) as the heavy fraction. When this mixture is subjected to centrifugal separation in a three-product machine, an aqueous slurry of the solids discharges from the nozzles while the water and oil discharge from the respective intermediate and primary overflows. The present invention produces these three fractions cleanly separated from one another, and in particular, produces an intermediate fraction of high purity with respect to solids, the potential carry-over of which into the intermediate overflow is averted by the improved separating flow conditions induced in the separating chamber by this invention.

When the rotor is rotated, the feed mixture or emulsion entering the feedwell member 48, as indicated by flowlines A, is propelled by the impeller vanes 50 and is forced outwardly through the downwardly inclined feed inlet passages 51 into the annular separating chamber 11. There, centripetal force will cause the separation of the separation of the mixture into an extreme outer zone of a Water-solids slurry, an intermediate zone of the clean Water fraction, and an inner zone of the light oil fraction. With proper hydraulic balance established in the centrifugal system of the rotor bowl, there will be a continuous discharge of these three fractions. That is, the under.- flow will discharge through nozzles 12a, the water will discharge as indicated by flowlines C from the ring dam 62 at the rotor bottom, and the oil will discharge as indicated byflowlines D from extension 13 at the top of the rotor structure.

In the exemplary embodiment disclosed, underflow recirculation and/or introduction of a control liquid into the bowl may be effected for well-known control purposes such as control of the underflow concentration and/or control of the location of the above described fraction zones. As indicated by flowlines B, this underfiow material and/or control liquid are introduced into the central return chamber 59 and are propelled 'by the cooperating pumping vanes 64, 60, and 28 through the return conduits 32 for delivery into the extreme outer peripheral zone in the region of the nozzles.

Referring to FIGURES 4 and 5, as the feed mixture enters the separating chamber 11 there occurs an immediate separation of the coarse or heavier solids due to the tendency thereof to settle outwardly against the conical bowl surfaces 12b. As indicated by flowlines R-1, these solids then slide along the bowl surfaces to the region of the discharge nozzles. It should be noted that at the transverse rotor plane passing through the outlets of feed ducts 51, where solid-particle flowlines R-l intersect overflow conduits 35 (FIGURE 4), the conduits occupy only a small portion of the circumference of the rotor bowl as clearly shown in FIGURE 2. In this way, almost all of the coarse solids will pass outwardly and upwardly through the shallow separating spaces 36a (FIGURE 3) underneath the sector-shaped tubes rather than impinging on the overflow conduits.

Some medium sized particles as well as fines may travel further up into the separating chamber to the region where the separation of the two liquid fractions is taking place. These particles will be diverted either directly or after further separating act-ion in discs 53 toward the conical bowl surfaces. As indicated by respective flowlines R4 and R-3, a portion of these particles will settle against the inwardly facing surfaces 42a of the sectorshaped tubes and will slide outwardly to fall off the inner lip 43 directly toward nozzles 12a Well clear of the actual inlet 44 of the overflow tube. At the same time, as indicated by flowline R-5, intermediate fraction liquid is diverted around inner lip 43 into inlet 44 due to the established hydraulic balance in the system.

Additionally, a clarifying action takes place in space 36a under the sector-shaped tubes in the sense that a layer of the intermediate liquid forms at and moves out along the underside of the sector-shaped tubes to enter the elongated mouth 44 across the outer lip 41 thereof as indicated by the flowlines R-2 of FIGURE 4.

The sector shape of overflow tube 38 so increases the cross-sectional area of inlet 44 as compared to the crosssectional area of the circular portions of the overflow conduits that the resultant reduced velocity in conjunction with the shallowness of the inlet promotes laminar flow conditions in the inlet and between plates 40 and 42. This low velocity flow substantially reduces entertainment of solids in the overflow.

However, if any solids are entrained at inlet 44, a quasiseparating-disc effect Within overflow conduit 35 will tend to separate such solids within the fan-shaped tube and to return them to the nozzles. That is, sector-shaped plates 40 and 42 are so spaced from each other and are of such extended width that they separate the solids from the intermediate overflow liquid in a manner similar to the separation effected by discs 53. The rejected solids are separated and returned to the nozzles as indicated by flowlines R-6 (FIGURE 5).

From the foregoing it will be seen that the invention provides a novel arrangement and combination of parts preferrably in a three-product centrifugal machine although not necessarily of the type shown. The invention effects improved separating flow condition in the rotor bowl and a diversion of potential carry-over solids away from the intermediate liquid fraction inlets. That is, the invention largely eliminates those flow conditions involving the interference or intersection of intermediate liquid fraction stream with the stream of concentrated solids in the bowl and thereby avoids a condition encountered in other types of three-product centrifugal machines such at those which employ the well-known Schneider fractionation or divider disc. The invention provides for the peripheral overflow advantages of the Schneider disc without incurring any of the disadvantages thereof.

This invention is especially useful in centrifugal machines of a construction where the Schneider fractionation disc is structurally inapplicable as in an integral doublecone-shaped rotor bowl where the Schneider disc as a Whole is not insertable through the constricted end. In

contrast, the removable individual sector-shaped overflow conduits of this invention are capable of being introduced through the constricted end of an integral double-cone bowl for mounting substantially in the manner set forth above. This permits the use of the integral bowl in a double overflow machine with the attendant advantages thereof. I

The invention further provides a sharper liquid-liquid separation due to the peripheral extent of the intermediate overflow inlets and the laminar flow conditions induced therein. Accordingly, benefits and advantages will accrue from the invention in a liquid-liquid separation alone, that is, without a separation of a solids-carrying underflow.

It will be understood that each of the elementsof the invention described above, or two or more together, may find useful application in other types and constructions of centrifugal machines differing from the one herein described and exemplified. While the invention has been illustrated and described as embodied in a double-cone; shaped rotor structure with the primary and intermediate liquid fractions discharging from respective opposite constricted ends of the bowl and with the underflow discharging from the peripherally arranged nozzles, it is not intended to be limited to the details shown, since various modifications and structural as well as operational changes may be made without departing from the spirit of this invention.

Because this invention may thus be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is illustrative and not restrictive. The scope of the invention is defined by the appended claims rather than by the descript-ion preceding them, and all embodiments which fall within the metes and bounds of the claims or which are their functional or structional equivalents are therefore intended to be embraced by those claims.

I claim:

1. In a centrifuge rotor having a cone-shaped rotor bowl, peripheral underflow discharge nozzles in said bowl, primary fraction overflow means at the end of said rotor, and an intermediate fraction overflow means, the improvement wherein said intermediate fraction overflow means comprises:

a. an intermediate fraction overflow outlet at one end of said rotor;

b. means for keeping primary overflow from said intermediate overflow outlet;

c. closed conduit means having an outlet communicating with said intermediate fraction overflow outlet and having an intermediate fraction overflow inlet within said bowl, said conduit means at said inlet being spaced away from the interval bowl surface whereby the entire cross-sectional area of said inlet is separated from said surface ,to permit underflow solids to pass along the bowl surface clear of said d. and means fixedly supporting said conduit within said bowl to maintain said spaced-away relationship between said inlet and said bowl surface under the centrifugal forces produced during rotor operation;

2. Apparatus as defined in claim 1: said intermediate overflow inlet being radially shallow and circumferentially elongated to prevent entrainment of solids in the overflow.

3. Apparatus as defined in claim 2: said conduit means including a fan-shaped tube terminating in said inlet and having opposed, closely spaced, sector-shaped walls lying substantially parallel to but spaced away from the conical internal bowl surface to permit quasi-disc-like separation within said fan-shaped tube of any solids entrained in the overflow.

4. Apparatus as defined in claim 3: the space between said sector-shaped walls being in the range of about .05 to 0.1 inch.

5. Apparatus as defined in claim 3: the space between said fan-shaped tube and the conical internal bowl surface being in the order of 0.25 inch.

6. Apparatus as defined in claim 3: the inner sectorshaped wall extending beyond the outer wall at said conduit inlet to define a lip to carry solids passing along the external surface of said inner wall clear of said inlet.

7. In the centrifuge rotor having a cone-shaped rotor bowl, feed means having an outlet'within said bowl, underflow discharge nozzles at the outer bowl periphery, a primary fraction overflow means at an end of said rotor bowl, and means defining an intermediate fraction overflow outlet closed off from the primary overflow fraction, the improvement comprising means defining a plurality of intermediate fraction overflow conduits having fanshaped inlet portions positioned within said bowl and connecting portions communicating between said inlet portions and said intermediate fraction overflow outlet means, said fan-shaped inlet portions being positioned substantially parallel to but spaced away from a respective portion of the internal surface of said conical bowl whereby the cross-sectional area of said inlet is separated from said bowl surface to permit solids to pass along the internal bowl surface under and clear of said conduit inlet portions and support means to secure said inlet portions in said spaced-away positional relation during rotor operation.

8. Apparatus as described in claim 7 said conduit connecting portions being positioned in said bowl to traverse the transverse rotor plane through said feed means outlet and being relatively narrow circumferentially of the rotor at said plane whereby underflow solids from said feed means pass directly outwardly to said rotor bowl with a minimum of impingement of the solids on said ends of said rotor and at a radial position outward of the truncated rotor bowl ends, said inlet portions being adapted to be separately inserted through a rotor bowl end for removable mounting in said rotor.

10. A centrifuge rotor comprising:

a. an integral, truncated-double-cone-shaped rotor bowl;

b. a primary fraction overflow means at an end of said rotor;

c. means defining a secondary fraction overflow outlet chamber at an axial rotor end;

(1. and a plurality of secondary overflow conduits connecting with said secondary overflow outlet chamber means and having fan-shaped inlet portions mounted within said bowl to terminate at radial positions outward of the truncated rotor bowl ends, said inlet portions having shallow elongated mouths oriented to occupy a substantial portion of the periphery of said bowl, said inlet portions at said elongated mouths being spaced away from the internal rotor bowl surface whereby the entire cross-sectional area of each said mouth is separated from said bowl surface, and means mounting said inlet portions in said rotor bowl to positively support said portions to maintain said spaced-away relationship under the centrifugal loads imposed by rotor operation, said inlet portions being adapted to be separately inserted through a rotor bowl end for removable mounting in said rotor. 11. In a centrifuge rotor having an integral, truncateddouble-cone-shaped rotor bowl, feed means having an outlet within said bowl, underflow discharge nozzles at:

the outer bowl periphery, means defining a primary fraction overflow darn at one axial end of said rotor, and means defining an intermediate fraction overflow chamber at the other rotor end, the improvement comprising: a. a plurality of intermediate fraction overflow conduits each having:

(1) a fan-shaped inlet portion with opposed,

spaced-apart, sector-shaped, parallel walls,

(2) and a relatively narrow connecting portion communicating between said inlet portion and intermediate fraction overflow chamber means;

b. said fan-shaped inlet portions being rigidly mounted in said bowl substantially parallel to but spaced from a a respective portion of an internal conical surface 7 of said bowl whereby the cross-sectional area of said inlet is separated from said bowl surface-during rotor operation, said inlet portions terminating in shallow, elongated mouths oriented to occupy a substantial portion of the periphery of said bowl at a radial position outward of the truncated rotor bowl ends;

c. said respective connecting portions being positioned.

outwardly from said feed means outlet to permit underflow solids from said feed means to pass directly outwardly to slide along the conical rotor bowl surface under said fan-shaped conduit inlet portions well clear of said conduit mouths with a minimum of the solids impinging on said over-flow conduits;

d. the inner sector-shaped wall of said inlet portion extending beyond the outer wall at said conduit mouth.

to define a lip to carry any impinging solids clear of the inlet mouth;

e. and said inlet portions being adapted to be separately inserted through a rotor bowl and for removable mounting in said rotor.

12. A centrifuge rotor comprising:

a. :a truncated-double-cone-shaped rotor bowl having underflow discharge nozzles at the outer periphery thereof;

b. means defining a primary fiaction overflow dam at one axial end of said bowl;

c. a rotor hub closing the other axial end of said rotor bowl;

d. a rotor shaft connected to said hub and extending through said one rotor 'bowl end;

e. a tubular feedwell extending into said one rotor bowl end in spaced relation to said primary overflow dam and around said rotor shaft;

f. means defining a centrally located open-ended return chamber adjacent to said hub on the side opposite from said rotor bowl;

g. means defining an annular intermediate fraction over flow chamber around said return chamber;

h. first closed conduit means connecting said return chamber to said rotor bowl for introducing fluid to the vicinity of said nozzles;

i. and second closed conduit means connecting said annular intermediate fraction overflow chamber to said rotor bowl for conducting intermediate fraction overflow out of said rotor bowl;

j. said second conduit means including fan-shaped inlet portions with opposed, spaced-apart, sector-shaped, parallel walls fixedly positioned in said bowl substantially parallel to but spaced from a respective portion of an internal conical surface of said bowl whereby the cross-sectional area of said inlet portion is separated from said bowl surface to permit underflow solids from said feedwell to slide along the conical rotor bowl surface under and clear of said fan-shaped inlet portions;

k. said inlet portions terminating in shallow, elongated mouths oriented to occupy a substantial portion of the periphery of said bowl.

References Cited by the Examiner UNITED STATES PATENTS 2,917,230 12/ 1959 Kaldewey 233-14 3,073,516 1/1963 Glasson 233-28 3,080,108 3/1963 Jacobson 233-14 3,111,490 11/ 1963 Halbach 23314 M. CARY NELSON, Primary Examiner.

H. KLINKSIEK, Assistant Examiner.

Claims (1)

1. IN A CENTRIFUGE ROTOR HAVING A CONE-SHAPED ROTOR BOWL, PERIPHERAL UNDERFLOW DISCHARGE NOZZLES IN SAID BOWL, PRIMARY FRACTION OVERFLOW MEANS AT THE END OF SAID ROTOR, AND AN INTERMEDIATE FRACTION OVERFLOW MEANS, THE IMPROVEMENT WHEREIN SAID INTERMEDIATE FRACTION OVERFLOW MEANS COMPRISES; A. AN INTERMEDIATE FRACTION OVERFLOW OUTLET AT ONE END OF SAID ROTOR; B. MEANS FOR KEEPING PRIMARY OVERFLOW FORM SAID INTERMEDIATE OVERFLOW OUTLET; C. CLOSED CONDUIT MEANS HAVING AN OUTLET COMMUNICATING WITH SAID INTERMEDIATE FRACTION OVERFLOW OUTLET AND HAVING AN INTERMEDIATE FRACTION OVERFLOW INLET WITHIN SAID BOWL, SAID CONDUIT MEANS AT SAID INLET BEING SPACED AWAY FROM THE INTERVAL BOWL SURFACE WHEREBY THE ENTIRE CROSS-SECTIONAL AREA OF SAID INLET

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