US3456875A

US3456875A - Air driven centrifuge

Info

Publication number: US3456875A
Application number: US573412A
Authority: US
Inventors: George N Hein
Original assignee: GEORGE N HEIN
Current assignee: GEORGE N HEIN
Priority date: 1966-08-18
Filing date: 1966-08-18
Publication date: 1969-07-22
Anticipated expiration: 1986-07-22
Also published as: GB1159868A; GB1159869A

Description

July 22, 1969 G. N. HEIN 3,456,875

AIR DRIVEN CENTRIFUGE Filed u 18, 1966 s Sheets-Sheet a 7/ 55 fir 2/ K 4G 4 a" K 623 y I 40 4 I g 33 f J0 FIG. 4

' INVENTOR BY. (A!

ATTORN Y5 July 22, 1969 G. N. HEIN 3,456,875

AIR DRIVEN CENTRIFUGE Filed Aug. 18. 1966 5 Sheets-Sheet I5 INVENTOR 6501966 M fi/f/A/ KM, QM,

ATTORNEY;

United States Patent 3,456,875 AIR DRIVEN CENTRIFUGE George N. Hein, 331 Chesham Ave., San Carlos, Calif. 94070 File-d Aug. 18, 1966, Ser. No. 573,412 Int. Cl. BlMb 1/02, 9/06; F16c 7/04 US. Cl. 233-24 22 Claims ABSTRACT OF THE DISCLOSURE An air driven centrifuge which includes a rotor having a chamber therein to contain a liquid specimen to be fractionated. The rotor also has a first opening means which communicates with the chamber and through which the liquid specimen may be introduced and removed from the chamber. The rotor also has a second opening means which communicates with the chamber through which a displacement liquid may be introduced therein. Collecting means are provided in association with the rotor to collect the expelled fractions of the liquid specimen. A stator is provided to support the rotor when it is not rotating. Additionally, there are means to supply air under pressure to the surface of the rotor so that the rotor is rotated and, while rotating at high speeds, is supported only by air under pressure, and otherwise is contacted only by the liquid specimen and the displacement liquid. The fractions of the liquid specimen are being expelled and collected by the collecting means while the rotor is still rotating. Furthermore, stabilizing means are provided to stabilize the rotor when necessary at low speeds of rotation.

This invention relates to an air driven centrifuge which is used to separate a liquid into various fractions and then accurately collect the desired fraction while the rotor of the centrifuge is still rotating. In this disclosure, blood has been chosen by way of example, as the liquid for separation into fractions and plasma, the constituent for removal and accurate collection.

In order to separate certain fluid mixtures, very high speeds of rotation are often required. In addition, a small portable centrifuge which can fractionate small amounts of these liquids is often desirable. Blood separation can be accomplished at various speeds including very high speeds of rotation, however, the separation of materials such as protein can only be accomplished at extremely high speeds. Some other processes which require speeds beyond normal centrifuging speeds are the separation of minute virouses such as rubella, the concentration of viruses from clinical specimens, the concentration of immunoglobulins from urine salva and bronchial washings, and quantitatives electron microscopy such as particle coating. I have found, an air driven centrifuge can attain sufficieut speeds to be used for such applications and in addition can be made small enough to be portable and to handle minute samples. Other advantages of an air driven centrifuge which exist because the rotor rotates and is supported on a cushion of air are: no lubrication is needed; there is a negligible amount of noise at high speeds; there is no wearing of parts; there is extreme stability at high speeds, and the extreme speeds can be attained without accompanying excessive heat. If very delicate heat control is required, the compressed air source can be refreigerated or a coil can be placed around the air supply to keep the temperature at a precise level. The above mentioned factors plus others combine to reduce the maintenance required for the centrifuge and to increase its efficiency in operation.

Consideration must be given to certain rotor disturbing factors which occur while the rotor is rotating such as: rotor imbalance caused by imperfections or threads on the rotor; possible imperfection that might exist in the air jets; the effect of external air currents and air friction; and possible sonic vibrations that may exist. These fac tors could cause a critical rotating speed where all of these factors harmonize together to act in a deleterious manner on the rotor to cause excessive vibration or fluttering or even dislodgment of the rotor. Means are therefore required to stabilize the rotor during the critical speeds of ortation. One way to solve this problem is to resiliently mount the stator assembly. This, however, increases the number of parts, therefore the cost and results in a delicate structure which may be readily disturbed during shipping and use. Under these circumstances, a substantially rigid stator mounting would be more practical and desirable.

It is therefore an object of this invention to provide an air driven centrifuge that will alleviate the above mentioned problems and that will operate smoothly without noise at any desired speed to facilitate the accurate fractionization and collection of a desired fluid mixture While the rotor is still rotating.

Another object of this invention is to provide an air driven centrifuge with means to stabilize the rotor while it is vibrating and fluttering during the critical speeds of rotation, thereby preventing damage to the rotor and as a result the centrifuge can be rigidly mounted, be made in a portable size, and various size rotors can be used with any size base.

Still another object of this invention is to provide an air driven centrifuge for accurately fractionating and collecting a fluid mixture while the rotor is still rotating that requires a minimum amount of maintenance, is economic to manufacture, and is efficient to use.

I have provided an air driven centrifuge with a rotor having a cavity in which to place a flexible receptacle with a fluid mixture to be fractionated. The rotor rests on a stator which contains means to provide air pressure to rotate and at higher speeds support entirely the rotor. The stator also containing means to stabilize the rotor during the critical speeds of rotation. Means are incorporated for introducing a hydraulic displacement liquid into the rotor cavity to accurately displace the desired fractions of the mixture into an attached collection means while the rotor is still rotating.

With these and other objects in mind, reference is had to the attached drawings illustrating the invention in which:

FIG. 1 is a sectional elevational view of a centrifuge embodying this invention with arrows showing the direction and path of flow of the fluids used in conjunction with the invention;

FIG. 2 is fragmentary sectional elevational view of the centrifuge while the rotor is rotating with arrows depicting the displacement of the pumping and fractionated fluid;

FIG. 3 is bottom plan view of the centrifuge rotor;

FIG. 4 is a fragmentary top plan view of the centrifuge stator;

FIG. 5 is a fragmentary sectional elevation view of an alternative embodiment of a centrifuge embodying the invention in which the source of pumping liquid is removed from the stator; and

FIG. 6 is a partial sectional view of an alternate embodiment of the centrifuge rotor.

Referring pimarily to FIG. 1, the illustrated centrifuge embodying my invention is comprised of the rotor 20 and the stator 40. In addition, a flexible receptacle 80 is provided to be placed into cavity 21 in the rotor 20 to contain the liquid to be fractionated, and a fraction collection cup is provided to receive the liquid after it has been fractionated and expelled from the rotor. The, remaining accessory parts of the centrifuge include a reservoir 60,

means 61 for connection to a compressed air source, and means 62 and 63 for connection to a source of displacement fluid.

Referring now to motor 20, its underside 21 is essentially conically shaped and formed with flutes 23. The flutes 23 serve to facilitate the driving of rotor 20 by compressed air. There are passages to cavity 21 from the lower and upper parts of the rotor. Centrally located in the bottom portion 22 of rotor 20, is a vertical bore 24. Bore 24 communicates with a plurality of oblique passages 25 which communicate with cavity 21. This network of passages allows fluid entering the bottom of rotor 20 to subsequently enter cavity 21 where it can be used to expel the fractionated liquid. A further passage 26 may extend upwardly through the rotor 20 in line with the center line thereof and communicate with bore 24 to serve as an air vent. A cap 27 combines with rotor 20 by means of an inter-engagement of threads 28 to define cavity 21.

A moveable base washer 29 rests on the lower surface of cavity 21 thereby covering the openings to oblique passageways 25 and preventing the receptacle 80 from entering the opening during rotation of the rotor 20. Being moveable, base washer 29 may be displaced by fluid entering cavity 21 from passageways 25.

A receptacle 80 is used to contain the liquid to be fractionated and is constructed so that it may be placed within cavity 21. Receptacle 80 includes a flexible base portion 81 and a rigid transparent upper portion 82. Both parts have

flanges

83 and 84, respectively, which engage with one another when receptacle 80 is within cavity 21. When cap 27 is threaded on rotor 20,

flanges

83 and 84 are immovably fixed in position thereby fixing the position of receptacle 80 in position within cavity 21. The rigid upper portion 82 of receptacle 80 is provided with a centrally located opening 85 around which an upstanding flange or wall 86 is provided. This wall 86 flares in an outward direction to a slight degree. These parts when disposed in proper positions as illustrated, turn with the rotor of the centrifuge.

A fraction collecting cup 70 is disposed around upstanding wall 86 of receptace 8t) and may be held in a fixed position by a stationary deck 71. Cup 70 is positioned so as to receive the fractionated liquid as it is expelled from the rotating rotor 20. Cup 70 may be removed and replaced as desired during operation of the centrifuge. Receptacle 20 is constructed of a disposable type of material which may select from any one of a number of well known natural or synthetic resins. Cup 70 and upper portion 82 of receptacle 80 are generally constructed of a transparent material in order that the liquid being fractionated may be observed during the fractionization process.

Referring to the stator 40 of the centrifuge, a bore in the side wall of stator 40 may be connected to a compressed air source by means of interposed fitting 61 and tube 42. An ring 43 may be employed to help maintain an air tight connection. Compressed air from the air source may then pass through bore 44 in connecting means 61 into stator 40.

Stator 40 includes a body portion 30 and a stator pad base 31 connected by means of threads 32. A gasket 33 maintains an air tight relationship between these members. A lateral flange 34 extending from the inner circumference of stator pad base 31 which rests on a lateral flange 35 extending from the outer circumference of the inner portion of body 30 of stator 40. The engagement of

flanges

34 and 35 is made tight when stator pad base 31 is interengaged with body 30.

The inner portion of the upper surface of stator pad base 31 is recessed thereby forming annular shoulder 36 on which rests a floating stator pad 37. Stator pad 37 includes two buttons or extended portions 38 which stand on shoulder 36. The ring-like stator pad 37 has a lesser outer diameter than annular shoulder 36 thereby providing a clearance 39 between the outer surface of stator pad 37 and longitudinal surface of stator pad base 31. Clearance 39 together with the inner clearance of the pad and the fact that stator pad 37 is raised and pivotal by buttons 38 allows the stator pad 37 to move in both a nutational and precessional manner. When rotor 20 is not in motion or during slow speeds of rotation, rotor 20 rests on stator pad 37 thereby creating the only point of contact between stator 40 and rotor 20. Stator pad 37 acts as a buffer for vibrations resulting from rotation of rotor 20 at slow speeds either during starting or stopping of rotor 20. This allows stator 40 to be rigidly mounted and for many different sized rotors and stator pads to be used with the same stator because the vibrations of the rotor are not transmitted to the stator but are completely absorbed by stator pad 37. At high speeds rotor 20 rests only on a cushion of air and does not touch stator 40 at any point. This is depicted in FIG. 2 which shows rotor 20 at a high speed of rotation. It is seen that air space 46 is created because rotor 20 rests only on a cushion of air. Air space 46 acts as an exit passage for the compressed air after it has contacted, rotated, and supported 20. As shown, stator pad 37 has an oblique inner face thereby increasing the efliciency of the centrifuge by providing a uniform flow path for the compressed air between rotor 20 and stator 40.

Reservoir 60 used to contain the displacement fluid and stator 40 may be coupled by means of a clamp 47 which interengages with the threaded surface 48 of the stator 40.

A large cylindrical air chamber 49 is located between the core 50 and the outer portion 51 of body portion 30 of stator 40. Air may enter chamber 49 through bore 44 in connecting means 61. The exit from chamber 49 for the compressed air is through a plurality of air jet holes 52 which are in the inverted cone shape uper face 53 of core 50. Air jet holes 52 and the inverted cone shape face 53 are best shown in FIG. 4. These jets have been disposed at an angle of 45 in accordance with a successful application of the invention. Centrally located about the point where inverted cone face 53 should reach its apex is a bore 54 which extends the length of stator 40. A plug 55 extends within bore 54 and has a threaded outer surface which interengages with threaded surface 56 of bore 54. The narrower body portion 57 of plug 55 extends almost the entire length of bore 54 and is of a lesser diameter than the diameter of bore 54 thereby forming passageway 58 through which displacement liquids may drain after the fractionating and collecting processes have been completed. Passage 58 communicates with lateral drainage opening 59 near the lower end of bore 54 which in turn communicates with reservoir 60. This system of drainage passages together with the aforementioned system of passages in rotor 20 provide a path of drainage for the displacement liquid from cavity 21 to reservoir 60 where it may be stored.

A helical spring 64 surrounds head 65 of plug 55 and biases plug 55 away from body 30. This tightens the threaded interengagement between plug 55 and bore 54 thereby minimizing the danger of plug 55 turning due to vibration. As a result, the extension of plug 55 into stator 40 and the clearance between the rotor and the upper end of plug 55 may be closely controlled. A bore 66 extends the entire vertical length of plug 55. A tubular extension 67 fits into bore 66 and extends vertically upward into opening 24 in rotor 20. Tube 67 is held in a fixed position within plug 55 in a conventional manner such as by a weld 68, as shown in FIG. 1 or a friction fit. The combination of threaded plug 55 and tube 67 serve as the inlet passage control for the displacement fluid. As mentioned above, by threading plug 55, the clearance at the top of tube 67 and rotor 20 can be regulated thereby accurately controlling the fluid flow of the displacement liquid from tube 67 into rotor 20. The lower end of tube 67 may be connected to a hose 63 which would extend through bore 69 in stator 40. It may then be connected to a conventional type of pumping means to pump displacement fluid from reservoir 60 into the centrifuge for reuse. The hose 62 through which the displacement liquid would be removed from the reservoir could extend through bore 72 in stator 40.

-In explaining the actual operation of the centrifuge embodying this invention blood will be used as the exemplary liquid to be fractionated. It should be understood that the centrifuge may be used for fractionating other fluids as well. In actual operation, the blood is placed within receptacle 80 which is retained in cavity 21 in rotor 20. Compressed air is then allowed to enter the centrifuge through bore 44 in connector piece 61. The compressed air flows out of bore 44 into chamber 49 of stator 40. The air exists from stator 40 thorugh air jet holes 52 in the inverted cone shaped face 53. The compressed air upon leaving air jet holes 52, enters air space 73 between rotor 20 and stator 40. The air contacts the cone shaped under surface 74 of rotor 20 particularly flutes 23. Sufficient air pressure is provided to rotate rotor 20 at the desired speed. While the rotor is spinning and when subjected to the influence of centrifugal force, the heavy constituents of the blood, namely, the red blood cells, white blood cells and platelets, are forced to the outer extremeties of cavity 21 in rotor 20 and the lighter plasma congregates towards the central portion of cavity 21. Rotor 20 rests only on a cushion of air and does not touch stator 40 at any point. The compressed air after driving and supporting rotor 20 then exists through now present opening 46.

While rotor 20 is still spinning on the cushion of air, a displacement liquid is introduced. The displacement liquid is preferably heavier than the liquid being fractionated. When the blood is the liquid being fractionated, a liquid such as sucrose would be adequate for such purposes. The sucrose may be stored in reservoir 60 and may be pumped by a common type of two-way pumping device typified by my earlier patents and aplications. In such a case, the sucrose would be pumped out of reservoir 60 through hose 62 and 'would then be pumped into the centrifuge system through hose 63. The sucrose will flow from hose 63 through tube 67 into rotor 20. By regulating the clearance at the top of tube 67, the amount of sucrose which flows from the rotor and subsequently displaces the fractionated blood from cavity 211 can be closely regulated to fractions of a drop thereby accurately controlling the amount of fractionated blood collected.

As the sucrose leaves the top of tube 67 and enters rotor 20, centrifugal force causes it to flow through oblique passageway 25 until it displaces removable base washer 29 and enters the lower outer part of caviy 21. As shown in FIG. 2, by reason of the flexible bottom portion 81 of receptacle 80, the sucrose does not mix with the blood in receptacle 80. The sucrose, being heavier than blood, enters the outer extremity of cavity 21 where the heavier portions of the fractionated blood are located due to centrifugal force. The sucrose displaces the flexible portion 81 of receptacle 80 thereby forcing the heavier portion of the blood towards the center of cavity 21. This in turn forces the lighter plasma which is generally the desired portion of the blood to be collected, out of opening 85 in receptacle 80 and consequently out of the upstanding flanges 86 of receptacle 80 into the fraction collection cup 70. The directional flow of the fluids during the above operation of the centrifuge is depicted by arrows in FIG. 2.

After all of the desired plasma has been collected from cavity 21, the centrifuge may be stopped. Rotor 20 returns to rest on stator pad 37 and gravitational forces then cause the sucrose to drain from the rotor through the stator 40 into reservoir 60.

The alternate embodiment depicted in FIG. 5 employs a reservoir 60' which is not in vertical alignment with stator 40 and rotor 20' while in all other respects is similar to the previous embodiment. Slots 77 and

additional drainage passages

75 and 76 are provided and communicate to define the continuous drainage passage for the displacement fluid through stator 40' and into reservoir 60'. In this embodiment, plug 55 'which combines with tube 67' to form the inlet control passage for the displacement fluid is positioned without reservoir 60 and therefore may be manipulated to control the flow of the displacement fluid while the centrifuge is operating.

In FIG. 6, a further embodiment of rotor construction is illustrated. This rotor is essentially all plastic and accordingly can be disposable after a single use. It Would be constructed with a rigid top portion 82 and a rigid bottom portion 81". A flexible membrane 78 would be positioned within rotor 20" to define the bottom of chamber 21" and would function the same as flexible bottom portion 81 of receptacle 80 in the previous embodiment. Molded flutes 23" are provided on the exterior of rigid bottom portion 81" to facilitate the rotation of the rotor as in the previous embodiment. The peripheral edge 79 of flexible membrane 78 and flanges 83" and 84" of portion 81" and 82', respectively, are fastened together by any common means such as a heat seal to maintain those parts in a fixed relationship and to prevent any leakage of fluid to or from the bottom of chamber 21". There is a centrally located hold 88 in bottom portion 81" to permit entrance of the displacement fluid and an opening 87 in top portion 82 through which the liquid to be fractionated may be placed into cavity 21" and through which fractions thereof may be removed. This economic rotor may be used once and then disposed of and an entire new rotor may be positioned for the next sample.

Thus, this invention provides a small portable air driven centrifuge for fractionating and accurately collecting fractions of a liquid such as blood, both economically and efficiently. Only a relatively few parts are required and a minimum amount of maintenance needed. Virtually any desired speed is attainable and speeds up to and beyond 200,000 r.p.m. have been actually employed. For all practical purposes, vibration and noise are eliminated at any speed. Minute amounts of fractionated liquid may be accurately collected in an easy and efficient manner while the rotor is still turning. Extremely small aliquots of liquid to be separated need only be employed and optimum fractionation is now possible with the virtual elimination of vibration. In certain applications rotor and liquid receptacle capacities have been such that aliquots of 0.5 ml. and less to and beyond 35 ml. have been used.

Thus, the above mentioned objects of this invention, among others, are achieved. The range and scope of the invention are defined in the following claims.

I claim:

1. An air driven centrifuge comprising a rotor having a plurality of flutes on its outer surface and means for supporting a liquid mixture to be centrifuged and having a lower surface with a supporting portion on which the rotor rests when it is stationary, a stator having supporting means for engaging the supporting portion of the rotor when it is in a state of rest, means for introducing the air between the lower surface of the rotor and the supporting means including air jet means directed angularly upward to cause the rotor to rotate and be supported on an air cushion above the stator while so rotating, stabilizing means associated with said supporting means and said rotor and located therebetween for stabilizing said rotor during low speeds of rotation and said air cushion only supporting and stabilizing said rotor during high speeds of rotation with said stabilizing means being free for substantial unrestricted movement with respect to said stator in response to movements of said rotor, said rotor rotating about an axis of rotation at a speed sufficient to cause the mixture to separate into fractions of different densities, receptacle means having an opening on said rotor for receiving the liquid mixture to be separated and having parts thereof flexible, centrifugally induced pressure means in the rotor for acting on said receptacle means by flexing the flexible parts thereof to reduce the capacity of the receptacle means by moving at least one liquid fraction centripetally inwardly and out through the opening for controlled expulsion of the liquid fraction, and collecting means operatively associated with the receptacle means for receiving the expelled fraction while the rotor is still rotating.

2. This invention in accordance with claim 1 wherein said means for introducing air between the lower surface of the rotor and the stator includes a series of interconnected passages within the stator which connects said jet means with a source of air under pressure.

3. This invention in accordance with claim 1 wherein said stabilizing means comprises at least one floating stator pad having a portion on which to rest the rotor when it is at rest, said stator pad being on said stator so as to allow the pad to move in a precessional and nutational manner thereby facilitating the stabilization of said rotor during rotation.

4. The invention in accordance with claim 3 wherein said stator pad is mounted on two approximately diametrically opposed buttons extending downwardly from the pad and the pad has suflicient axial clearance between surfaces thereof and adjacent surfaces of the stator to thereby allow said pad to move in a precessional and nutational manner.

5. This invention in accordance with claim '1 wherein said centrifugally induced pressure means includes hydraulic liquid heavier than said liquid mixture.

6. The invention in accordance with claim 5 wherein said centrifugally induced pressure means includes a series of interconnected passages in said centrifuge which provides a passageway from the source of said hydraulic fluid to a position where it may act upon said receptacle, and a displaceable base washer resting on the end of said passageway which is adjacent to said receptacle thereby preventing said flexible receptacle from entering said passageway during rotation of the rotor, said base washer being displaceable by said hydraulic liquid to allow said hydraulic liquid to reduce the capacity of said receptacle.

7. This invention in accordance with claim 5 wherein a centrally located tube within said stator extends upwardly out of said stator into the central portion of the rotor, means to regulate said clearance at the upper extremity of said tube thereby controlling the flow of said hydraulic fluid to within a fraction of a drop thereof and consequently the amount of the mixture expelled and collected.

8. An air driven centrifuge having a stator and a rotor rotatably associated therewith, said rotor having a lower surface with a supporting portion on which the rotor rests when it is stationary, said stator having supporting means for engaging the supporting portion of the rotor when it is a state of rest, means for introducing air between the lower surface of the rotor and the supporting means including an air jet means to cause the rotor to rotate and be supported on an air cushion above the stator while also rotating, said supporting means including a floating stator pad associated with said rotor and said stator and located therebetween for use in stabilizing the rotor during critical speeds of rotation, with said stator pad being free for substantial unrestricted movement with respect to said stator in response to movement of said rotor, and with said rotor being contacted and supported by air only at high speeds of rotation.

9. The invention in accordance with claim 8 wherein said floating stator pad is shaped like a cylindrical ring and supports said rotor when it is at rest, said pad having means for association with said stator, said pad and said stator having means for permitting mutational movement of the pad relative to the stator and means for permitting precessional movement of the pad relative to the stator whereby said pad is connected in a manner which allows it to move in a mutational and precessional manner thereby enabling it to stabilize the rotor during critical speeds of rotation.

10. This invention in accordance with claim 8 wherein means are provided for substantially rigidly mounting the stator.

11. The invention in accordance with claim 8 wherein a centrally located tube within said stator extends upwardly out of said stator into the central portion of the rotor, means to regulate said clearance at the upper extremity of said tube thereby controlling the flow of fluid therethrough to within a fraction of a drop.

12. An air driven centrifuge having a stator and a rod rotatably associated therewith, said rotor comprising an essentially rigid plastic top and bottom and an intermediate flexible membrane, the membrane together with the top defining a liquid receiving chamber for receiving liquid, and cooperating means on said stator and rotor bottom to supply a flow of air from said stator to impinge on said rotor bottom to induce rotation of said rotor.

13. The invention in accordance with claim 12 wherein the top includes a centrally located opening to facilitate the introduction and removal of liquid, the bottom includes a centrally located opening through which a hydraulic liquid can be introduced for purposes of flexing said membrane to reduce the capacity of said liquid receiving chamber, and the bottom has circumferentially extending molded flutes.

14. This invention in accordance with claim 12 wherein the bottom includes a centrally located opening through which a hydraulic liquid can be introduced for purposes of flexing said membrane to reduce the capacity of said liquid receiving chamber.

15. This invention in accordance with claim 12 wherein the bottom has circumferentially extending molded flutes.

16. An essentially all-plastic disposable rotor for use in an air driven centrifuge comprising an essentially rigid top and bottom and an intermediate flexible membrane, the membrane together with the top defining a liquid receiving chamber for receiving liquid.

17. The invention in accordance with claim 16 wherein the top includes a centrally located opening to facilitate the introduction and removal of liquid, the bottom including a centrally located opening through which a hydraulic liquid can be introduced for purposes of flexing said membrane to reduce the capacity of said liquid receiving chamber, and the bottom has circumferentially extending molded flutes.

18. This invention in accordance with claim 16 wherein the bottom includes a centrally located opening through which a hydraulic liquid can be introduced for purposes of flexing said membrane to reduce the capacity of said liquid receiving chamber.

19. This invention in accordance with claim 16 wherein the bottom has circumferentially extending molded flutes.

20. A method of fractionating a fluid mixture and accurately collecting the desired portions of said liquid by means of an air driven centrifuge having a rotor, a stator, means for containing said fluid mixture in the rotor, means for rotating and supporting said rotor by air pressure, means for stabilizing the rotor during rotation With said stabilizing means being free for substantial unrestricted movement with respect to said rotor in response to movements of said rotor, means for introducing a hydraulic liquid to displace the fractionated mixture into a collecting means comprised of placing the fluid mixture to be fractionated into a receptacle placed in a cavity in the rotor, rotating said rotor by means of air under pressure until the contained liquid is fractionated by reason of centrifugal forces, accurately expelling the desired fractions by means of a hydraulic displacement liquid introduced into said cavity while the rotor is still rotating, collecting said expelled fractions while the rotor is'still rotating.

21. A receptacle assembly for use with an air driven centrifuge having a rotor with a lower surface including a supporting portion on which the rotor rests when it is stationary, a stator having supporting means for engaging the supporting portion of the rotor when it is in a state of rest, means for introducing air between the lower surface of the rotor and supporting means including an air jet means to cause the rotor to rotate and be supported on an air cushion above the stator while it is rotating, stabilizing means associated with said stator and said rotor and located therebetween for stabilizing said rotor during low speeds of rotation and said air cushion only supporting and stabilizing said rotorduring high speeds of rotation with said stabilizing means being free for sub stantial unrestricted movement with respect to said stator in response to movements of said rotor and said rotor having a receptacle receiving space therein comprising a base portion and an upper portion associated therewith, at least one of said portions being formed of substantially flexible material, the upper portion being substantially light, transparent and having a substantially centrally located opening, said lower portion having a centrally located upwardly extending conicalportion defining a substantially truncated cone the top of which includes substantially flat annular zones in closeproximity to surfaces of the upper portion defining the central opening whereby relatively small fractions of liquid to be separated by centrifugation are caused to enter the space of relatively reduced volume adjacent the central opening between the upper portion and the base of the cone upon flexing of the flexible material and the small fractions are adapted to assume relatively wide proportions in th espace of relatively reduced volume and be visibly observed through the upper portion to facilitate controlled expulsion of the fractions out through the central opening, and said upper portion being removably mounted on said lower portion to facilitate placing the liquid to be separated therein.

22. An air driven centrifuge comprising a rotor having a lower surface with a supporting portion on which the rotor rests when it is stationary, a stator having sup porting means for engaging the supporting portion of the rotor when it is in a state of rest, means for introducing air between the lower surface of the rotor and supporting means including an air jet means to cause the rotor to rotate and be supported on an air cushion above the stator while also rotating, means for stabilizing the rotor during rotation with said stabilizing means being free for substantial unrestricted movement with respect to said stator in response to movements of said rotor, said rotor having a receptacle receiving space therein, a receptacle assembly within said space and comprising a base portion and an upper portion associated therewith, at least one of said portions being formed of substantially flexible material, the upper portion being substantially light transparent and having a substantially centrally located opening, said lower portion having a centrally located upwardly extending conical portion defining a substantially truncated cone the top of which includes substantially flat annular zones in close proximity to surfaces of the upper portion defining the central opening whereby relatively small fractions of liquid to be separated by centrifugation are caused to enter the space of relatively reduced volume adjacent the central opening between the upper portion and the base of the cone upon flexing of the flexible material and the fractions are adapted to assume relatively wide proportions in the space of relatively reduced volume and visibly be observed through the upper portion to facilitate controlled expulsion of the fractions out through the central opening, and said upper portion being removably mounted on said lower portion to facilitate placing the liquid to be separated therein.

References Cited UNITED STATES PATENTS 2,213,107 8/1940 McBain 233-23 XR 2,872,104 2/ 1959 Cizinsky 233-23 3,297,244 1/1967 Hein 23327 1,679,790 8/1928 Sharples 23321 2,177,053 10/1939 Boyd 3089 XR FOREIGN PATENTS 783,685 9/1957 Great Britain.

HENRY T. KLINKSIEK, Primary Examiner US. Cl. X.R.