US3539096A

US3539096A - Hy-g centrifuge

Info

Publication number: US3539096A
Application number: US634197A
Authority: US
Inventors: Kenneth D Lewis; Robert W Honeychurch; James C Elsken
Original assignee: Dow Oliver Inc
Current assignee: Dow Oliver Inc
Priority date: 1967-04-27
Filing date: 1967-04-27
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10

Description

United States Patent Kenneth D. Lewis Wilton, and

Robert W. Honeychurch, Stamford, Conn., and James C. Elsken, Elmhurst,

[72] lnventors Illinois [21] Appl. No. 634,197 [22] Filed April 27, 1967 [45] Patented Nov. 10, 1970 [73] Assignee Dow-Oliver Incorporated Stamford, Connecticut a corporation of Delaware [54] l-lY-G CENTRIFUGE 54 Claims, 14 Drawing Figs.

2,872,104 2/1959 Cizinsky 233/23 2,905,380 9/1959 Matthews 233/27 3,216,655 11/1965 Wind 233/27 3,219,265 11/1965 Los 233/27 Primary Examiner-Robert W. Jenkins Attorney-Arnold Grant, William .1. Fox and Dominic M.

Mezzapelle ABSTRACT: A high-speed ultracentrifuge for the separation of millimicron size particles having either a flexible suspension system or a hydrostatic bearing interconnecting the motor and the rotor to allow the rotor to shift its position due to an imbalance effect. The rotor is mounted in an explosion resistant refrigerated housing, has floating bearings and uses molecular pump-type seals to maintain the pressure differential between the rotor and the housing. A damping system is provided at the lower end of the rotor to reduce the amplitude of vibrations to a tolerable level as the speed of rotation approaches and surpasses critical speed. The rotor has peripheral dead pockets in the separating chamber to gather the separated sludge prior to its discharge; and the hub is connected to the drive shift by grip springs. The centrifuge is continuously being operated and feed is being continuously added during alternating steps of washing and sludge discharge.

Patented Nov. 10, 1970 v 3,539,096

Sheet 2 of6 FIG. 2

FIG. 3 I34 |22 25 28 I30 I28 l |54Zv E g |6 8 FIG. FIG. 4 2 la; 9 fig-WEN I28 INVENTORS.

KENNETH 0. LEWIS ROBERT w. HONEYCHURCH JAMES C.ELSKEN BY: 2 y\ A TORNEY.

Patented Nov. 10, 1970 Sheet FIG.13

S R O T N E V N KENNETH D. LEWIS ROBERT W. HONEYCHURCH C. ELS KEN JAMES ATTORNEY.

Patented Nov. 10, 1970 3,539,096

Sheet 1 016 lNVENTORS.

KENN H D. LEWIS ROBE W. H EYCHURCH JAM ES C. E KEN ATTORNEY.

Patented Nov. 10, 1970 5 3,539,096

Sheet 5' of 6 INVENTORS.

KENNETH o. LEWIS ROBERT w. HONEYCHURCH JAMES c. ELSKEN A TORNEY.

Patented N0). 10, 1970 3,539,096

Sheet 6 of 6 INVENTORS.

KENNETH D. LEWIS ROBERT w. HONEYCHURCH JAMES C. ELSKEN ATTORNEY.

HY-G CENTRIFUGE The present invention relates to a high-speed ultracentrifuge for the separation of millimicron size particles from a carrying liquid. More particularly, the present invention relates to a high-speed ultracentrifuge for the continuous separation of a-sludge having a milklike consistency wherein the particle size of the solids in the carrying liquid precludes centrifugation at normal operating speeds and gravities.

Centrifuge rotors, unless assembled and maintained in a perfectly balanced state, are inherently subject to the eccentric rotation and vibrations which result from an imbalance condition. Whether the imbalance is caused by an uneven distribution of solids in the rotor, the plugging of a discharge tube, or imperfections arising in machining or assembly, the resulting shift in the center of gravity of the rotor causes a gyratory effect which becomes more intolerable as the speed of the rotor increases. If the rotor were free of restraining forces, i.e., the rigid drive shaft connection between it and the motor, then the rotor would compensate for this movement of the center of gravity by shifting its position so as to realign its new principal axis of inertia with the spin axis. In normal operating speed centrifuges the problem of imbalance and shifting of the center of gravity does not require much consideration because the bearings can absorb the almost negligible movement within standard engineering tolerances. However, at the extremely high operating speeds prevalent in the ultracentrifuges the gyratory effect of the imbalance condition is more pronounced and any attempt to maintain a rigid restrained connection between the drive motor and the rotor would fracture the bearings. An allowance must therefore be made to enable the rotor to shift its position according to the demands of the center of gravity so that the principal axis of inertia is again coincident or proximately coincident with the spin axis.

Applicants herein present two solutions to this critical problem. The first incorporates a flexible suspension as the drive connection between the motor and rotor. The drive shaft has a deformable portion which is relatively massless when compared to the mass of the rotor. In this manner, the rotor is essentially free swinging, i.e., instead of the rotor having to conform to the axis of the drive shaft, the drive shaft will deform so as to conform to the principal axis of the rotor.

Thus, if an imbalance condition does occur the rotor will be.

free to move and realign its principal axis of inertia with the spin axis.

The second embodiment pendulously floats the rotor on the relatively frictionless film of oil of a hydrostatic bearing. The rotor is suspended from a convex spherical runner which is in turn connected to the drive motor and supported in a matching concave spherical ring. Pressurized oil is continu ously pumped into the space between the runner and the ring, and the runner and the rotor are thus suspended off of the ring to float on the film of oil. Any imbalance conditions which causes a shift in the center of gravity of the rotor can thus be compensated for by the runner shifting its position in the ring to realign the center of gravity with the spin axis. The angle between the geometric axis and the principal axis of inertia is small enough that the shift and realignment of the center of gravity with the spin axis is sufficient to reduce imbalance caused vibrations to a tolerable level. An additional advantage of the hydrostatic bearing, beyond the potentially indefinite life afforded by the film of oil separating moving parts, is that the film of oil acts as a seal to maintain the differential pressure between the housing and the rotor.

Even though the flexible suspension system permits the rotor to shift its position to realign the principal axis of inertia with the spin axis, and the hydrostatic bearing shifts the rotor to realign the center of gravity with the spin axis, a vibrational problem still exists. This is because the relationship between the amplitude of the vibrations of the rotor caused by the imbalance and the revolutions per minute of the rotor is hyperbolic with the amplitude going to infinity as the speed of rotation approaches bending critical speed. The tendency of the rotor to align the inertia axis withthe spin axis occurs only at speeds above the natural frequency of the shaft and the rotor system. Below this speed the opposite is true and the rotor would tend to move in a direction which would aggravate the unbalance condition; the amplitude of vibration gradually increasing with an increase in speed and then sharply increasing as it nears the bending critical speed to approach infinity at the critical speed. The criticality of an imbalance on the rotor is brought sharply into focus when it is realized that a gyration of .1 inch off the spin axis will result in a failure and destruction of the rotor. The gyratory effect-critical speed relationship is also de minimus in normal operating speed centrifuges because while they may approach either of the rigid body critical speeds, causing an almost imperceptible, readily absorbable, deflection, they do not operate in the rotor shifting and realignment region of bending critical speed. Furthermore, the added, almost negligible amount of thrust added by an imbalance condition at relatively low speed can be tolerated within the bearings clearance by standard engineering allowances.

High-speed ultracentrifuges, however, operate in the range of, and often exceed, bending critical speeds so that the maximum destructive amplitudes prevalent at these speeds must be reduced to a tolerable level. Applicant herein incorporates a damping system to countercurrently restrain the amplitude of vibrations to permissible and workable levels as the speed of the rotor approaches and passes through bending critical speed.

Since, as explained above. the relative position of the rotor vis-a-vis the housing is liable to shift due to an imbalance condition means must be provided to retain the positions of the various feed and effluent conduits relative to the shifting rotor and housing. These conduits must be free to move with the rotor so as to retain contact with the rotor, but they must not rotate with the rotor so as to lose contact with the housing. For this purpose the present invention incorporates a floating bearing for the rotor and sliding block couplings between these bearings and the housing. The couplings which are comprised of two parts which will slide relative to each other are free to move in any radial direction by the interaction and cooperation of the parts; but they are constrained against rotation by a square sliding block between them. The bearings, which provide the actual support for the influent and effluent conduits are in turn supported at one end by one of the relatively slideable parts of the coupling. The other end of the bearing is accepted in a pocket in the rotor without any connection between the two so that the rotor can rotate relative to the bearing; thus the bearing floats in the rotor. The other relatively slideable coupling member is rigidly connected to the housing. The result is a bearing which can be articulated in any radial direction to shift with the rotor but which will not rotate with the rotor.

The vacuum conditions in the rotor often required in many of the industrial applications of high-speed ultracentrifuges presents a difficult sealing problem between the rotor and the housing. The present invention utilizes a molecular pump-type seal between the nonrotating floating bearing housings and the rotor to prevent the escape of vapor from the rotor to the housing. The seal, which is a series of annular grooves cut into one of the mating interface surfaces, acts as a pump to return any vapor which may have leaked between the bearing housings and the rotor from the low pressure in the housing to the high pressure in the rotor.

An additional source of vibration in any centrifuge is the slight eccentricity between shaft and hub. This may be caused by among other things, the machining tolerances and allowances required for economic manufacture and assembly. The problem becomes more acute as the operating speed increases until over a period of time this added vibration will cause the shaft to work within the hub bore to enlarge it in an uneven manner. Applicants have solved this problem by the use of grip springs between the shaft and the hub. Grip springs are two solid interfitting metallic rings which when positioned between the hub and the shaft and compressed together will expand to fill the area between the hub and shaft to transmit the rotative force of the shaft to the hub. This type of connection between the shaft and the hub transmits the maximum torque without being subject to the eccentricities and stress concentrations of keyway-type connections.

Two of the principal features of the present invention are the continuous and automatic operation of the high-speed ultracentrifuge and the dual function of the wash inlet system. With the present invention, once operating speed is reached it may be maintained as long as there is feed material to be separated. Thus the attendant starting and braking difficulties inherent in prior art high-speed centrifuge is obviated. As will be explained in detail below a typical operating cycle of the present invention consists of constant introduction of feed and repetitive, alternating stages of washing and sludge discharge. With the repetitive cycling in mind, Applicants have made the wash system serve a double function. Not only does it feed wash liquid to the separating chamber during the washing stage of the separating cycle but instead of being idle during the sludge discharge stage the same tubes and conduits serve to remove the sludge from the separating chamber.

It is, therefore, an object of the present invention to provide a continuously operating high-speed ultracentrifuge.

It is another object of the present invention to provide means to introduce a wash liquid to, and discharge separated sludge from, the separating chamber of a high-speed ultracentrifuge.

It is still another object of the present invention to support the rotor of a high-speed ultracentrifuge by a flexible suspension system.

It is yet another object of the present invention to allow for shifting of the principal axis of inertia of the rotor of a highspeed ultracentrifuge by supporting the rotor from a hydrostatic bearing.

A further object of the present invention is to support the influent and effluent ducts of a high-speed ultracentrifuge in "floating" bearings.

A still further object of the present invention is to provide means to dampen the amplitude of vibration of the rotor of a high-speed ultraccntrifuge as it approaches the critical speeds.

Yet a further object of the present invention is to provide means to retain the differential pressure between the rotor and the housing ofa high-speed ultracentrifuge and to prevent the escape of vapor from the rotor to the housing.

Still another object of the present invention is to provide an explosion resistant housing for the rotor of a high-speed ultracentrifugc.

Another object of the present invention is to provide peripheral dead pockets at the discharge tubes of the rotor of a high-speed ultracentrifuge.

Yet another object of the present invention is to connect and transmit force from the shaft to the hub ofa high'speed ultracentrifuge by means of grip springs.

The subject matter which Applicants regard as their invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however. as to its organization and method of operation together with further objects and advantages thereof will best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. I is an elevational view in section showing the highspeed ultracentrifuge embodying the present invention;

FIG. 2 is an enlarged elevational view in section with parts removed for clarity of showing of the upper portion of the flexible" drive shaft of-the high speed ultracentrifuge embodying the present invention;

FIG. 3 is an enlarged elevational view in section with parts removed for clarity of showing of the lower portion of the flexible drive shaft ofthe high-speed ultracentrifuge embodying the present invention;

FIG. 4 depicts the relationship between FIGS. 2 and 3;

FIG. Sis an enlarged plan view with parts removed for clarity ofshowing taken along the line 5-5 of FIG. 1;

FIG. 6 is an enlarged, exploded, perspective view of the floating block" connection incorporated in the high-speed ultracentrifuge of the present invention;

FIG. 7 is an enlarged elevational view in section depicting the placement of one of the floating block" connections as incorporated into the high-speed ultracentrifuge of the present invention and its interrelationship with the surround ing parts;

FIG. 8 is an enlarged broken away elevational view in section depicting the positioning and function of the thrust rings as used in the present invention;

FIG. 9 is an enlarged, exploded, perspective view of the thrust rings incorporated into the high-speed untracentrifuge ofthe present invention;

FIG. I0 is an enlarged perspective view of the "hopper blocks" and wash and discharge tubes of the high-speed ultracentrifugc ofthe present invention;

FIG. 11 is an elevational view in section with parts broken away for clarity ofshowing ofa modification ofthe high-speed ultracentrifuge ofthe present invention;

FIG. I2 is an enlarged elevation view taken along the lines 12-12 of FIG. II; and

FIGS. 13 and 1311 are a diagrammatic representation of the effect of an imbalance condition on a high-speed ultracentrifuge.

Referring now to FIG. I a high-speed ultracentrifuge i0 is shown to have a rotor 12, a protective housing 14, a motor coupling 16 connected to a motor (not shown) and a main bearing assembly 18.

The rotor 12 comprises a double frustoconically shaped bowl 20, a matching rotor cover 22, held in place by an interengaging threaded lock ring 24, and a threadedly attached hub member 26. The hub member 26 has a generally cylindrical shell portion 28 and a depending flared rim portion 30, which together with the inner walls of the rotor bowl and the rotor cover defines an annular separating chamber 32. A generally cylindrical disc spider 34, concentric with shell portion 28, is supported on the rim portion of the hub and is held in position between a pair of grip springs 36. to be described in greater detail below, and the rotor cover 22 by a hold down nut 38 (FIG. 2). The disc spider supports a stack of nested separating discs 39 and provides a set of annularly spaced axially extending llow channels (not shown) for the separated ef fluent.

The feed material for which the high-speed ultraccntrifuge embodying the present invention was designed to separate, contains a solution of milliniicron size particles which precludes centrifugation at normal operating speeds and gravities. The feed material enters the housing through inlet 40 and proceeds into the rotor through conduit 42. The feed material is received in annular chamber Ml and, in a manner well known in the art, is then pumped by acceleration disc 46 and vanes 48 into vertical feed tubes 50 for distribution into the disc stack 39 in separating chamber 32.

The intense centrifugal forces. in the order of 43,700 gravities, created by rotating the rotor at 12,000 rpm. strips the solid particles from the carrying liquid and moves them toward the outer periphery of the separating chamber. The carrying liquid proceeds inwardly along the separating discs and as more feed material is introduced into the rotor, filling the separating chamber, the clarified mother liquor begins to rise along the flow channels cut into the disc spider until it reaches overflow lip 52. The liquid then proceeds into annular chamber 54 and effluent pickup 56. Conduit 58 connects effluent discharge 60 and pickup 56 to discharge the separated effluent from the rotor.

A wash liquid, preferably having a specific gravity similar to that of the-carrying liquid, is continuously introduced to the separating chamber during the washing stage of the separating cycle to block the solubles present in the separated sludge and to insure the purity of the discharged product. A unique feature of the present invention is the dual function of the wash liquid inlet system. It not only introduces wash liquid to the separating chamber but, as will be presently described,

discharges the separated sludge from the rotor when the discharge stage of the separating cycle is reached. The wash liquid is introduced into the housing through inlet 62 and to the rotor through inlet 64. The wash liquid enters the separating chamber through conduit 66, discharge pickup/inlet 68, conduit 70 and tubes 72. The solids, after being separated from the carrying liquid in the separating discs, proceed radially outward toward the periphery of the bowl for concentration and subsequent discharge. Concurrently the wash liquid after discharge from tubes 72, proceeds radially inward to join the separated effluent in the disc spider flow channels. The result is a countercurrent scrubbing of the solids by the wash liquid to block and remove any solubles from the solids slurry.

A series of circumferentially spaced hopper blocks 74 (FIG. intermittently spaced between tubes 72 and extending radially into separating chamber 32 is provided at the periphery of the separating chamber to gather the separated solids and to prevent effluent from short circuiting" into the tubes 72 during the discharge stage of the separating cycle. Without hopper blocks the separated solids would be spread evenly around the inner wall of the rotor bowl with the denser solids immediately adjacent the wall and the less dense solids and finally effluent spaced radially inward therefrom, in the same annular plane as the mouth 76 of tubes 72. Since the separated solids have a very small radial component of velocity the less dense solids and effluent in the same annular plane as the mouth of the tubes 72 would be the only product discharged from the separating chamber, thus short circuiting the separation cycle. With hopper blocks the separated solids are gathered in the dead pockets 78 between adjacent blocks, with the desired denser solids extending radially inward beyond the mouth of tubes 72. In addition the inclined sides of the hopper blocks takes advantage of the large transverse component of velocity of the retained solids to assist-their discharge into tubes 72 because the solids are now moving transversely as well as radially.

When sufficient solids have been separated from the carrying liquid to warrant their removal from the separating chamber the effluent discharge 60 is closed by valve 80, the flow of wash liquid is discontinued and valve 82 (FIG. 3) is shunted to switch the separating cycle from the wash stage to the solids discharge stage. The flow of feed material continues to fill the separating chamber, displacing the solids. The solids with no place else to go, are forced to discharge through tubes 72, conduit 70, discharge pickup/inlet 68, conduit 66, inlet 64 and valve 82, i.e., in the reverse order that the wash liquid is introduced into the separating cycle.

During the shutdown cycle, if any solids transferred to annular chamber 84 through conduit 70 should not be picked up by discharge pickup/inlet 68, or any wash liquid from discharge pickup/inlet 68 should remain in chamber 84, it will drain through conduit 86 and be discharged from the rotor through outlet 88. lnlet 64, feed conduit 40, and outlet 88 are all supported and retained in position by a yoke 89, to be described in greater detail hereinafter.

By way of review, a typical operating cycle of the highspeed ultracentrifuge of the present invention would consist of feed being introduced constantly throughout the operating period while alternate cycling of wash, sludge discharge and effluent discharge is taking place. An equilibrium condition for the liquid levels is maintained in the rotor throughout the repetitive cycling. During the washing stage the wash liquid in passage 66 and feed level in feed impeller 44 will establish themselves according to their rates of flow so as to pump the sum of these rates over the overflow lip 52. During this period solids will be constantly settling toward the periphery of the rotor bowl. Wash water enters the separating chamber through tubes 72 moving inwardly toward the axis of rotation to block soluble solids and exiting through the effluent discharge 60. At the end of the specified period the effluent discharge port is closed by valve 80 and valve 82 is actuated to close the wash liquid port and open the sludge discharge port. Since feed continues the liquid level in the feed impeller 44 will move inboard. This in turn moves the liquid level of the residual wash liquid in the wash passage inboard where it is picked up by discharge pickup/inlet 68 and discharged. The sludge concentrated at the periphery of the bowl in pockets '78 follows the wash liquid being displaced inwardly by the addition of the constant feed rate. Liquid level in the feed impeller moves inboard until equilibrium conditions are again reached and the sludge is being removed at the same rate as the feed material is introduced. Once all the solids are discharged, valve 82 is again switched to the wash liquid stage and valve is opened to permit discharge of separated effluent through outlet 60. The original equilibrium condition is quickly reached and the cycle is then repeated.

A centrifuge rotor assembly intended to accomplish a liquid-solid separation on a continuous basis is inherently subject to relatively high imbalance. This may be due to an uneven distribution of solids in the rotor, the plugging of a discharge tube, or to eccentricities resulting from assembly procedures. But, no matter the cause, the eccentric rotation of the rotor and vibration resulting from such imbalance is the same and becomes more intolerable as the speed of rotation of the rotor is increased. Theoretically, a body spinning freely in space tends to spinabout its principal axis of inertia. If an imbalance condition on the body shifts the center of gravity the body will adapt to the changed conditions by shifting its principal axis of inertia to coincide with the spin axis. To illustrate the consequence of an imbalance condition assume a freely suspended rotor whose center of gravity has been shifted away from the spin axis. As the speed of rotation increases the radial runout of the center of gravity and the eccentricity of rotation will correspondingly increase until the rotor has realigned its position in space with its principal axis of inertia once again coincident with the spin axis. As the principal axis of inertia approaches the spin axis imbalance forces which contribute to vibration will approach zero. I

The rigid connection between the drive motor, drive shaft and rotor found in normal-operating speed centrifuges makes no allowance for such movement of the rotor because at those speeds the problem is relatively de minimus. At normal operating speeds any imbalance effect and subsequent shifting of the center of gravity of the rotor can be accommodated by the bearings within the usual engineering tolerances. However, at the high operating speeds encountered in ultracentrifuges the problem takes on critical dimensions and allowance must be made for the shifting and realignment of the principal axis of inertia of the rotor. Applicant herein presents two solutions to thisproblem. The first, shown in FIGS. 13, utilizes a flexible suspension system to allow the rotor to move freely in any direction so as to realign the principal axis of inertia with the spin axis. The second solution, shown in FIGS. 11 and 12, makes allowance for this shifting by pendulously supporting the rotor on a hydrostatic bearing.

Referring again to FIGS. 1 and 2 the flexible suspension system interconnecting the rotor 12 and the motor coupling 16 will be described in detail. The drive shaft connection between the motor and the rotor is divided into a relatively rigid upper portion and a flexible lower portion 92. The upper portion 90 comprises a shaft 94 connected to the motor coupling 16 by a central bolt 96 and supported for rotation in a housing 98 by two sets of

ball bearings

100 and 102. The bearings are mounted in tandem to support the thrust and give the maximum sidewise stiffness. Lubricating oil for the bearings is fed into the housing 98 through inlet 104 and discharged from outlet 106. A double mechanical face type seal 108, having lubricating oil inlet and outlet 112, maintains the pressure differential between the inside and outside of the protective housing 14.

The guiding principle behind a flexible suspension system is to design the flexible lower portion of the shaft 92 so that it is relatively massless when compared to the mass of the rotor. In this manner the rotor is essentially free of the restraining forces inherent in a rigid shaft connection. Thus, as the center of gravity shifts due to an imbalance effect the rotor will be free to move and realign its principal axis of inertia with the spin axis. A comparison of FIGS. 13 and 130 shows in a much exaggerated form, the effect ofa shift in the center of gravity of a high-speed rotor. Note how the flexible shaft deforms to allow the rotor to shift clockwise to realign itself so that its principal axis of inertia is again coincident with the spin axis. The eccentric portion of the shaft has negligible inertia and is so flexible that the rotor is essentially spinning free in space.

The flexible lower portion 92 of the drive shaft comprises an enlarged head 114 which is received in socket 116 of upper shaft 94 and is threadedly connected thereto by the lower end of central bolt 96; a depending relatively thin body portion 118 concentric with the shell portion 28 of the hub; and a toe portion 120 which provides the direct connection between the shaft and the rotor. A hollow shaft 122 concentric with the shell portion of the hub and the flexible shaft is connected at its lower end to the toe portion of the shaft by two sets of grip springs 124, 126 and a thrust sleeve 128. The hollow shaft is in turn connected to the shell portion of the hub by another group of grip springs 130, 132 and a thrust sleeve 134.

' A common contributing source of vibration in a centrifuge is the slight eccentricity between shaft and hub. This normally exists due to the combination of machining tolerances and allowances on shaft and hub bore required for economic manufacture and ease of assembly and disassembly. The problem is compounded at the acute high speeds of ultracentrifuges and over a period of time the vibration will cause the shaft to work within the hub bore enlarging it in a nonuniform fashion. A press fit between the shaft and hub is one solution to the problem, but such tolerances are impractical from the standpoint of assembly and disassembly. A precision taper of the shaft and hub bore would also be a solution, but the increased cost involved in such accurate machining and inspection could not be economically justified.

Applicants have solved this problem by the use of grip springs 136 showing in cross section in FIG. 8 and in perspective in FIG. 9. Grip springs are two solid interfitting metallic rings which, when positioned between a hub and a shaft, and compressed together, will expand to fill the area between the hub and shaft to transmit the rotative force of the shaft to the hub. The outer or receiving member 138 has an annular exterior and an inclined interior and is designed to slide easily into the bore 144 of the hub member. The interior member 146 has an inclined exterior which corresponds to, and matches, the interior of the receiving member, and an annular interior which is designed to slide easily over the shaft 148. In use the outer member 138 is positioned in the bore and the interior member 146 is positioned on the shaft. The shaft is then placed in the hub until the interior member is seated in the receiving member. An axial, compressive force is then applied to the grip springs by a hold down nut 150 to radially deflect the outer receiving ring and contract the inner ring into a shrink fit between the shaft and the hub. The result is an exceedingly tight nonrotative connection between the hub and the shaft which will transmit the maximum torque between shaft and hub, permit economical tolerances in the machining of the shaft and hub bore, and not be subject to the eccentricities and stress concentrations of keyway-type connections.

A nonrotating upper auxiliary bearing housing 152 is provided at the upper end of the rotor to support the effluent pickup 56 and discharge 60. In a like manner a nonrotating lower auxiliary bearing housing 154 is provided at the lower end of the rotor to support the inlet-discharge tube yoke 89. The upper and lower auxiliary bearing housing are substantially identical so only the upper housing will be described. It is accepted into a pocket in the rotor between hollow shaft 122 and annular housing 160 and comprises two sets of bearings 162, 164 separated by a bearing spacer 166; conduit 58 which connects effluent pickup 56 and discharge 60; and, cooling tubes 168, to be described in greater detail below. Note that the bearing housings are not connected in any way to the rotor so that when they are supported, in a manner to be presently described, they will move with the rotor in relation to the vibrations and shifts caused by an imbalance condition, but they will not rotate with the rotor.

A molecular pump type seal 170 is used at the interface between the upper and lower auxiliary bearing housings and the

annular housings

160, 172. This type of sealing arrangement has provided optimum results for the high-speed ultracentrifuge of the present invention because of the near vacuum conditions required for most millimicron separations. The seal comprises a series of helical pumping grooves cut into the surface of the stationary bearing assemblies surrounded by a close fitting smooth cylindrical face, i.e., the

annular housings

160, 172, spinning concentrically about the bearing housings. The molecular seal prevents the escape of vapor from the rotor to the housing by maintaining the pressure differential between the rotor and the housing, i.e., actually pumping any vapor that may have escaped into the interface between the auxiliary bearing housing and the annular housing from the lower pressure in the housing to the higher pressure in the rotor.

Since, as explained above, the relative position of the rotor vis-a-vis the housing is liable to shift due to an imbalance condition and shifting of the principal axis of inertia, means must be provided to support the

auxiliary bearing housings

152, 154 so that they can "float with the rotor. The bearing housings must be free to move radially with the rotor to maintain the position of the inlets and discharges they support but they must also be restrained from rotation about their own axis so that these conduits can retain contact with the housing. For this purpose the present invention incorporates two sliding block type couplings 174, 176 (FIGS. 6 and 7) positioned at the extreme ends of the rotor and connecting the

auxiliary bearing housings

152, 154 to the centrifuge housing 14. Each connection comprises an upper sliding member 178, having a pair of opposed depending arms 180, a lower sliding member 182 having a pair of opposed extending arms 184, and a square-faced sliding block 186. Each arm covers approximately 90 so that when the upper and lower members are put together they completely enclose the square-faced sliding block. However, the upper member can, as illustratively depicted in FIG. 6, move forward and backward relative to the square-faced sliding block and the lower member. Likewise, as illustratively depicted in FIG. 6, the lower member can move left and right relative to the square-faced sliding block and the upper member. When this connection is incorporated between the

auxiliary bearing housings

152, 154 and the centrifuge housing 14, the bearing housings can be articulated in any radial direction, by a combination of moves by the upper and

lower members

178, 182. But the upper and

lower members

178, 182 and thus the upper and lower auxiliary bearing housings cannot rotate because of the square-faced sliding block between them. An added advantage of this type of restraint lies in the fact that the resultant of the sliding block friction always acts on the rotor in the direction opposite to its movement which tends to damp out gyratory motions.

Referring now to FIG. 11 and 12 Applicants second solution to the imbalance problem of high-speed ultracentrifuges will be described in detail. A floating universal coupling interconnects the drive motor (not shown) and a hydrostatic bearing rotor support 192. The hydrostatic bearing pendulously supports the rotor on a film of oil to provide inherent rotor stability under the influence of imbalance forces and to minimize transmission of forces onto the auxiliary bearing supports. Pressurized oil is continuously pumped into the bearing in a manner to be hereinafter described so as to frictionlessly float the rotor in the bearing. Thus any imbalance conditions which may cause a shift in the center of gravity and require a realignment of the principal axis of inertia can be compensated for by a relative and frictionless shifting of the parts of the bearing to be presently discussed. The rotor shifts its position until its center of gravity coincides with the spin axis and since the angle between the geometric axis and the principal inertia axis is very small the center of gravity shift is sufficient to produce a correction which will maintain vibration at a tolerable level.

The hydrostatic bearing comprises a convex runner 194 having a first annular socket 196 to engage the floating universal coupling 190 and a second annular socket 198 to accept the rotor drive shaft 200; and a matching concave ring 202 which supports the runner for rotation and allows for the deflective adjustments caused by rotor imbalance. Lubricating oil under pressure from manifold 204 is introduced to the ring 202 through annularly spaced inlets 206. The ring is divided into four shallow pocket recesses 208 each having an inlet 206 and each being separated by edge bands 210 and radial lands (not shown). The pockets 208 when filled with a film of pressurized oil pendulously supports the rotor, provides the desired radial stiffness by generating differential pressures when the shaft is displaced in any radial direction, and avoids oil circulation effects. The oil, after the runner is lifted off the ring, continues to flow from manifold 204 through inlets 206 to pockets 208 under the pressure difference between the pool pressure and external pressure, to lubricate the surfaces which are in relative motion, and to carry away the heat generated by the shearing effect between the clearance surfaces. The lubricating oil then flows out of the pockets and into upper and

lower collection chambers

212, 214 for subsequent discharge and recirculation back into the bearing pockets. The radial stiffness of the hydrostatic bearing, i.e., the amount of radial imbalance deflection that the bearing will permit, is directly related to the width of the radial lands which act as fiow restrictors to allow the buildup of differential pockets opposing the displacement of the shaft from the central position. A distinct advantage of this type of rotor support is that it is inherently self-centering, i.e., any radial movement shifts the relative positions of the runner and the ring which will in turn decrease the thickness of the oil film on one side increasing the pressure on that side (relative to the opposite side) which, as a result, tends to shift the rotor back to its central position. In addition, the bearing has a potentially infinite life and can operate at speeds which are prohibitive to conventional antifriction bearings because moving parts are separated by a definite fluid film.

Drive shaft 200 supports the rotor for rotation and is connected to the runner 194 of the hydrostatic bearing by threaded bolt 216 and to the hub and disc spider of the rotor by means of nut 218, washer 220, and grip springs 222. The upper end of the drive shaft has a conically shaped deflector 224 to channel the lubricating oil from the recessed pockets of ring 202 into the lower collection chamber 214. The diameter of the shaft receiving bore 226 in lower collection chamber 214 is about one-fourth of an inch larger than the diameter of the shaft 200 to allow for the radial deflection of the rotor caused by an imbalance effect. A set of bearings 228 in housing 230 allows for the rotation of the shaft relative to the housing to maintain the relatively fixed position of the effluent discharge system in the rotor in the manner discussed above. Corresponding parts of FIGS. 1 and 11 are connotated by primed numbers.

As discussed above, an imbalance condition in the rotor shifts the center of gravity and causes a corresponding shift in the relative position of the rotor. The result is a realignment of the rotor so that the principal axis of inertia is once again coincident, or proximately coincident, with the spin axis. However, the relationship between the amplitude of the vibrations of the rotor caused by the imbalance condition and the revolutions per minute of the rotor is hyperbolic with the amplitude going to infinity as the rpm. approaches the bending critical speed. Above the critical this runout decreases'as the principal inertia axis tends to align with the spin axis. Thus as the r.p.m. of the rotor approaches the bending critical speed the rapidly increasing amplitude of the vibrations can, unless checked, result in a failure of the rotor. The effect that this hyperbolic relationship has on the rotor is brought sharply into focus when it is realized that a gyration of .1 inch off the spin axis will result in a failure and destruction of the rotor. This problem is relatively de minimus in normal operating speed centrifuges because at those speeds any gyratory effect caused by a rotor imbalance can be readily absorbed by the bearings within standard engineering tolerances. Furthermore, while normal operating speed centrifuges may approach either of the rigid body critical speeds, causing an almost imperceptible, readily absorbable, deflection, they do not operate in, nor do they come close to, the region of bending critical speed wherein the actual shifting and realignment of the rotor prevalent in high-speed ultracentrifuges occurs. In order to reduce these maximum, destructive, amplitudes to a tolerable level, Applicants have provided a damping system which in effect restrains the amplitude of vibration to a permissible level while the rotation of the rotor approaches, is at, and exceeds bending critical speed.

The damping system (FIGS. 1, 5 and 11) is situated on the lower end of the rotor and comprises a set of three annularly spaced viscous dampers 232 interconnected between a fixed semicircular stanchion 234 and the lower auxiliary bearing housing 154. As can be seen from FIG. 1 the stanchion 234 which is merely an extension of the housing 14 has a radially extending arm 235 to provide the support for the lower auxiliary bearing housing 154 through feed yoke 89. Each damper consists of two concentrically mounted

cylinders

236, 238. The inner cylinders 236 are attached to the nonrotating inletdischarge tube yoke 89, and imbalance motions from the rotor are transmitted to the damper via the rotor lower auxiliary bearing assembly housing 154. The outer cylinder 238 is stationary and is rigidly attached to the stanchion 234 by means of bridge 240 and bolt 242. Between the cylinders there is a uniform annular gap of approximately .04 inches which is filled with oil of a specified viscosity. Unbalanced motions of the rotor are reduced to tolerable levels and dissipated by the action of the inner cylinder squeezing oil out of the narrow annular clearance. The viscous damping force of such a damper is directly proportional to the velocity of movement so that the greater the speed of rotation of the rotor the greater will be the force applied by the damping mechanism to reduce the amplitude of the vibrations.

Thus by the interaction of the damping system, either the hydrostatic bearing assembly or the flexible shaft suspension, and the friction generated in the sliding block coupling the rotor is free to realign itself with the principal axis of inertia on the spin axis, while the amplitude of the vibrations caused by the radial runout is maintained within safe, tolerable, parameters as bending critical speed is approached and surpassed.

In an operation of this proportion, rotor failure and destruction while not probable is possible so that safety becomes an overriding factor for consideration. To insure maximum safety, Applicants have incorporated an explosion resistant housing 14 to absorb and contain the extremely high energy, high velocity fragments from an exploded rotor. The housing comprises three

concentric layers

244, 246, 248 and an outer layer 250 each of armor quality stainless steel and each bolted to the other to give maximum dynamic energy absorption per unit volume.

Because of the extremely high operating speed of ultracentrifuges the removal of extraneous heat generated in the bearings by the friction of the relatively rotating parts, and in the housing, by the aerodynamic drag of the rotor, is an important design criteria. Applicants herein incorporate three cooling circuits, 254, 256 in the housing and 168 in the upper and lower

auxiliary bearing housings

152, 154 to remove the undesirable heat. As stated above the separating chamber 32 operates in a vacuum so that the effluent is near its boiling point when it is discharged. The cooling circuits 168 in the auxiliary bearing housings are located intermediate the bearings and the effluent ducts to prevent the heat of friction generated in the bearings from further heating the effluent above the boiling point and vaporizing it and to maintain the temperature of feed material within desired limits. The refrigerant for circuit 254, which consists of a series of annularly spaced axially extending refrigerating loops enters the housing through inlet 258 with a separate inlet and discharge for each loop.

Refrigerant for the circuits 168 in the auxiliary bearing housings enters the housing 14 through inlet 260 and is introduced into the circuit through flexible conduit 262. A similar flexible conduit (not shown) serves to discharge the refrigerant for recycling into the system.

We claim:

1. A high-speed ultracentrifuge for separating millimicron size particles comprising a housing, a rotor in said housing, a separating chamber in said rotor, means to introduce a feed material into said separating chamber, means to discharge the separated carrying liquid from said rotor, first means at the periphery of said separating chamber to collect the separated sludge, and secondmeans intermediate said first means for intermittently discharging the separated sludge from said separating chamber and for intermittently introducing a wash liquid into said separating chamber.

2. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 1, wherein said first means comprises a plurality of annularly spaced radially extending hopper blocks, the separated sludge being collected between said hopper blocks.

3. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 2, wherein said second means comprises a plurality of tubes annularly spaced around the periphery of said separating chamber, with at least one tube between each adjacent pair of said hopper blocks.

4. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 1, further including a motor, drive means interconnecting said motor and said rotor, said drive means having a first rigid portion and a second flexible portion, means connecting said first rigid portion to said motor, means connecting said second flexible portion to said rotor, said second flexible portion permitting the rotor to shift its relative position in the housing in response to imbalance caused shifts in its center of gravity so as to realign its principal axis of inertia with the spin axis.

5. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 4, wherein said means connecting said second flexible portion of said drive means to said rotor comprises at least one set of interfitting expandable annular grip springs.

6. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 4, further including first bearing means in said housing rigidly supporting the first portion of said drive shaft, and second bearing means in said rotor, said second bearing means having conduit means therein to discharge the separated carrying liquid from said separating chamber out of said rotor.

7. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 6, further including coupling means interconnecting said housing and said second bearing means, said coupling means being freely translatable in any radial direction to allow the second bearing means to maintain its position in said rotor as the rotor shifts its relative position in the housing in response to imbalance caused shifts in its center of gravity.

8. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 7, wherein said means interconnecting said housing and said second bearing means comprises a first member connected to said housing and having a pair of axially depending arms, a second member connected to said second bearing means and having a pair of axially extending arms perpendicular to the depending arms of said first member, and means interfittingly engaging the inner surfaces of said extending and depending arms to allow radial movement of said first and second members relative to each other and to restrain rotation of said first and second members relative to each other.

9. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 6, further including means at the outer interface between said second bearing means and said rotor to pump any vapor that may have leaked into said interface back into said rotor.

10. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 9, wherein said means at the outer interface between said bearing means and said rotor comprises a plurality of annularly spaced grooves cut into the outer face of said second bearing means. I

11. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 4, further including means connected to said rotor to depress the amplitude of the vibrations caused by an imbalance condition and a shift in the center of gravity of the rotor as the rotor approaches critical speed.

12. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 11, wherein said vibration depressing means comprises a plurality of damping mechanisms, each of said clamping mechanisms having one end fixedly attached to said housing and the other end fixedly attached to said rotor.

13. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 4, further including bearing means in said rotor adjacent the feed end of said rotor, said bearing means having conduit means therein to receive the separated sludge from said second means and transfer it out of said rotor and to receive wash liquid fed into said rotor and transfer it to said second means.

14. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 13, further including means at the interface between said bearing means and said rotor to pump vapor which may have leaked into the interface back into said rotor.

15. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 14, wherein said means comprises a series of annular grooves cut into the surface of said bearing means.

16. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 1, further including a motor, a drive shaft connected at one end to said rotor and at the other end to a hydrostatic bearing, and means interconnecting said motor and said hydrostatic bearing.

17. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 1, further including a motor, a bearing ring in said housing, a matching bearing runner, means to introduce a fluid between said ring and said runner to float said runner in said ring, means connecting said runner and said motor, and means connecting said runner and said rotor.

18. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 17, wherein said ring is concave and said runner is convex.

19. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 18, wherein said ring is open at both ends and has a plurality of annularly spaced recesses on the inner surface thereof the fluid being pumped into said recesses and discharging from said recesses through both open ends of said ring.

20. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 17, further including a bearing means in said rotor adjacent the bearing ring in said housing, said bearing means having conduit means therein to discharge the separated carrying liquid from said separating chamber out of said rotor.

21. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 20, further including means at the outer interface between said bearing means and said rotor to pump any vapor which may have leaked into said interface back into said rotor.

22. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 21, wherein said means comprises a series of annular grooves cut into said bearing means at the interface between said bearing means and said rotor.

23. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 17, further including a bearing means in said rotor adjacent the feed end of said rotor, said bearing means having conduit means therein to receive the discharged sludge from said second means and transfer it out of said rotor and to feed wash liquid introduced into said rotor to said second means.

24. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 23, further including means at the interface between said bearing means and said rotor to maintain the differential pressure between said separating chamber and said housing.

25. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 24, wherein said means comprises a plurality of annular grooves cut into said bearing means at the interface between said bearing means and said rotor.

26. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 17, further including at least one damping means interconnected between said rotor and said housing to depress the amplitude of the imbalance caused vibrations as the rotor approaches critical speed.

27. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 17, wherein said housing comprises a plurality of concentric spaced apart layers of high dynamic energy absorbing material and a relatively incompressible fluid between said layers.

28. A high-speed ultracentrifuge for separating millimicron size particles as defined in claim 1, wherein said housing comprises a plurality of concentric spaced apart layers of high dynamic energy absorbing material and a relatively incompressible fluid between said layers.

29. A continuous method for centrifugally separating millimicron size particles comprising the step of continuously feeding a material to be separated into the separating chamber; and the intermittent alternating step of feeding a wash liquid into the separating chamber, removing the separated carrying liquid from the separating chamber and collecting the separated sludge in the separating chamber; alternating with the intermittent step of discontinuing the flow of wash liquid into the separating chamber, discontinuing the flow of separated carrying liquid out of the separating chamber, and discharging the collected separated sludge from said separating chamber.

30. A continuous method for centrifugally separating millimicron size particles as defined in claim 29, wherein the wash liquid is introduced to the separating chamber and the separated sludge is discharged from the separating chamber through the same series of annularly spaced conduits.

31. A continuous method for centrifugally separating millimicron size particles as defined in claim 30, wherein the separated sludge is collected between annularly spaced radially extending hopper blocks located along the periphery of the separating chamber, and there is at least one of said series of conduits between each adjacent set of hopper blocks.

32. A high-speed ultracentrifuge comprising a housing, a rotor in said housing, a motor, a drive shaft interconnecting said motor and said rotor, said drive shaft having a first rigid portion connected to said motor and a second flexible portion connected to said rotor, said second portion being deformable so that the principal axis of inertia of the rotor can remain, coincident with the spin axis as the relative position of the rotor in the housing is shifted by imbalance conditions, a first bearing means in said housing adjacent the first rigid portion of said drive shaft, and a second bearing means in said rotor adjacent the second flexible portion of said drive shaft, said second bearing means having conduit means therein to transfer the separated effluent from said separating chamber out of said rotor.

33. A high-speed ultracentrifuge as defined in claim 32, further including coupling means interconnecting said bearing means and said housing, said coupling means being freely translatable in any radial direction to allow the second bearing means to maintain its position in said rotor as the rotor shifts its relative position in the housing in response to imbalance causes shifts in its center of gravity.

34. A high-speed ultracentrifuge as defined in claim 33, wherein said coupling means comprises a first member fixedly attached to said housing, a second member fixedly attached to said second bearing means, said first member being movable relative to said second member, said second member being movable relative to said first member and a third member interfitting between said first and second members to restrain relative rotation between said first and second members.

35. A high-speed ultracentrifuge as defined in claim 32, further including seal means at the outer interface between said second bearing means and said rotor, said seal means pumping any vapor which may leak into the interface back into said rotor.

36. A high-speed ultracentrifuge as defined in claim 35, wherein said seal means comprises a plurality of axially spaced annular grooves cut into the outer face of said second bearing means.

37. A high-speed ultracentrifuge comprising a housing, a rotor in said housing, a motor, a drive shaft interconnecting said motor and said rotor, said drive shaft having a first rigid portion connected to said motor and a second flexible portion connected to said rotor, said second portion being deformable so that the principal axis of inertia of the rotor can remain coincident with the spin axis as the relative position of the rotor in the housing is shifted by imbalance conditions, a bearing means in said rotor adjacent the feed end of said rotor, said bearing means having conduit means therein to discharge separated sludge from said separating chamber out of said rotor and to feed wash liquid into said separating chamber.

38. A high-speed ultracentrifuge as defined in claim 37, further including a coupling means interconnecting said bearing means and said housing, said coupling means being freely translatable in any radial direction so that the bearing means can maintain its position in the rotor as the rotor shifts its relative position in the housing in response to imbalance caused shifts in its center of gravity.

39. A high-speed ultracentrifuge as defined in claim 37, wherein said coupling means comprises a first member, a second member, said first member being translatable relative to said second member and said second member being translatable relative to said first member, and a third member intermediate said first and second members to restrain relative rotation between said first member and said second member.

40. A high-speed ultracentrifuge as defined in claim 37, further including means at the outer interface between said bearing means and said rotor to maintain the differential pressure between said housing and the separating chamber of said rotor. l

41. A high-speed ultracentrifuge as defined in claim 37, further including means at the outer interface between said bearing means and said rotor to return any vapor that may have leaked into theinterface back into said rotor.

42. A high-speed ultracentrifuge comprising a housing, a rotor in said housing, a motor, a drive shaft interconnecting said motor and said rotor, said drive shaft having a first rigid portion connected to said motor and a second flexible portion connected to said rotor, said second portion being deformable so that the principal axis of inertia of the rotor can remain coincident with the spin axis as the relative position of the rotor in the housing is shifted by imbalance conditions, means interconnected between said rotor and said housing to depress the amplitude of the imbalance caused vibrations in said rotor as the rotor approaches its critical speeds.

43. A high-speed ultracentrifuge comprising a housing, a rotor in said housing, a motor, a drive shaft interconnecting said motor and said rotor, said drive shaft having a first rigid portion connected to said motor and a second flexible portion connected to said rotor, said second portion being deformable so that the principal axis of inertia of the rotor can remain coincident with the spin axis as the relative position of the rotor in the housing is shifted by imbalance conditions, the flexible portion of said drive shaft being connected to said rotor by at least one set of grip springs.

44. A rotor for a centrifuge comprising a separating chamber, means to feed material to be separated to said separating chamber, means to discharge the separated carrying liquid from said separating chamber, a plurality of annularly spaced radially extending hopper blocks positioned about the periphery of said separating chamber to concentrate the separated solids, and a plurality of conduits, one between each pair of adjacent hopper blocks, to discharge the separated solids from said separating chamber.

45. A centrifuge comprising a housing, a rotor in said housing, said rotor having a separating chamber, means to introduce a feed material to be separated to said separating chamber, at least one bearing means in said rotor, each of said bearing means having conduit means therein to transfer one of the separated fractions of the feed material from said separating chamber out of said rotor.

46. A centrifuge as defined in claim 45, further including means at the outer face of said bearing means to pump any fluid which may have leaked into the outer interface between said bearing means and said rotor back into said rotor.

47. A centrifuge as defined in claim 46, wherein said means at the outer face of said bearing means comprises a plurality of axially spaced annular grooves cut into the outer face of said bearing means.

48. A centrifuge comprising a housing, a rotor in said housing, a motor, drive means interconnecting said motor and said rotor, at least one bearing means in said rotor, and means interconnecting said bearing means and said housing, said means being freely translatable in any radial direction.

49. A centrifuge as defined in claim 48, wherein said last mentioned means comprises a first member connected to said housing, a second member connected to said bearing means, said first and second member being movable relative to each other, and a third member intermediate said first and second members, said third member restraining relative rotation between said first and second members.

50. A high-speed centrifuge comprising a housing, a rotor in said housing, a motor, a bearing ring in said housing, a bearing runner on said bearing ring, means interconnecting said motor and said bearing runner, means interconnecting said rotor and said bearing runner, and at least one means to introduce a fluid between said bearing ring and said bearing runner to float said bearing runner on said bearing ring.

51. A high-speed centrifuge as defined in claim 50, wherein said bearing ring is open at both ends and the fluid is introduced intermediate the ends and discharges over both said ends.

52. A high-speed centrifuge as defined in claim 51, wherein said bearing ring has a plurality of annularly spaced recesses on the inner surface thereof, the fluid being introduced into said recesses.

53. A high-speed centrifuge as defined in claim 50, further including at least one damping means interconnected between said rotor and said housing to depress the amplitude of the imbalance caused vibrations as the rotor approaches its critical speed.

54. A rotor for a centrifuge comprising a hub, a drive shaft and at least one set of grip springs interconnecting said hub and said drive shaft and transmitting torque from said drive shaft to said hub, each set of said grip springs comprising a first member slideably received in said hub, a second member slideably received on said shaft and in said first member, and means to apply a compressive force to said first and second member when said second member is in said first member such that said first and second members expand to fill the space between said shaft and said hub.