US2209723A - Centrifugal machine - Google Patents

Description

,July 30,- 1940.

Filed April 2, 1938 2 sheets-sheet' 1 49 9 0- Pmi ATTORNEY.

July 30,. 1940.

A. U. A'YRES GNTRIFUGAL MACHINE Filed April l2, 1 938 59 w si 2 Sheets-Sheet 2 .56 8o 60 52 Ases JUG 28 102 INVENTOR. 116 QRTHURUQYQES.

ATTORNEY.

Patented July 3o, 1940 e "UNITED .STATE-s 2,209,723- cEN'rRirUGAL MACHINE Arthur Underwood Ayres, Chestnut Hill, Pa., as-

signor to The Sharples Corporation, a corporation of `Delaware Application April z, 193s, seria1N0.'199,730

5 Claims. (Cl. 233-23) This invention relates to improvements in high speed analytical centrifuges adapted to effect the rapid sedimentation of extremely small dispersed particles for the performance of analyses gener- 55A ally of the kind described in Svedberg and' Nichols United States Patent No.'1,648,369.

The invention has been developed in connection with a machine for revolving'a 'small sample of the substance to be studied transversely through a narrow beam of light at such high speed that a, continual image of the illuminated sample is formed at the point of observation. Photographs of the rotating sample may be taken at intervals of time and at the termination' of the treating period the photographs may be checked with a microphotometery for density against a known standard. In-this way the amount of subsidence in each photograph can be determined and therate of subsidence can be calculated.

In thecentrifugalanalysis of colloids, filterable viruses, and the like, it is necessary to rotate the substance under treatment at a sufficiently high rate of speed to generate the very high centrifugal forces necessary'to cause sedimentation. It is also desirable to maintain a uniform- These objects areobtained through the use of improved bearing and drive mechanism and by adapting .the machine for the maintenance of an unusually high vacuum during the operation thereof.

More specifically the invention contemplates the reduction ofl friction in the rotating parts by guiding the drive spindle in radial bearings of a special design and by supporting the entire weight of the rotating members on a thin iilm of air without any further thrust bearings, and to provide for the rotation of the substance under treatment under sub-atmospheric conditions.

It is a further object of the invention to provide a centrifugal machine which is capable of high speed operation without generating vibrational forces which would otherwise interfere with successful operation of the machine. To the end that vibration at high rotational speeds may be minimized, the invention utilizes al flexible rotor shaft which is rotated in resiliently mounted bearings. Further objects and advantages of the invenn tion will become apparent as the description thereof proceeds in light of the drawings forming a part of this application. In the drawings, like reference numerals indicate like parts throughout the several figures, and

Figure 1 is a vertical sectional view taken 10 through a high speedcentrifugal machine embodying the features of the invention; and

Figure 2 is an enlarged vertical sectional view more particularly illustrating the bearing and drive structure with associated parts.

'I'he centrifugal machine illustrated in the drawings comprises a body member A providing a. rotor casing and an oil collecting chamber, and a head member B providing rotor drive mechanism and an oil reservoir'. -1

The body member A is of relatively heavy nickel steel construction and has formed centrally therein a chamber I adapted to house a centrifugal rotor during operation of the machine. The chamber I0 is formed by the side 25 wall, the bottom, and by overhanging lip portion VIl at the top thereof. In the base of the body member is an cnil collecting chamber I2 having an oil drain outlet I4 normally closedI by a closure plug I6. Near the top ofthe body is a l.drip cup I8 which communicates with -the oil collecting chamber I2 through a vertical passage 20 in the side .wall. The body member A is provided in its bottom with a through passage 22, the in ner end of which is closed by a. glass or quartz plate 24. Through vthe side of the body is a port 26 adapted for connection with a vacuum pump. The body member A may be supported on a suitable base 28 having therein a transverse pas- 40 sage 30 which is in communication with the through passage 22 of thebody. In the transverse base passage 30 and located immediately under the ,through body passage 22is a mirror 32, the angular position of which may be adjusted through a rod34 and a thumb wheel 5 6. The adjusted position of the mirror 32 may be maintained by a set screw 38 which engages'the l rod 34. l

The head member B is provided with a pasl sage 40 in which are housedbearing and drive mechanism for a relatively flexible rotor spindle 42 which is connected to a'rotor 44. At one side of the passage 40-is an oil reservoir I6 from y which communication for oil under pressure is I in driving relation to the spindle 42.

provided to the rotating parts of the drive and 1 bearing mechanism and from which oil may be drained by removing a. drain plug 41. A bracket 48 extends upwardly from they top of the head B and a transversely extending arm 49 thereof is adapted to support a bearing housing. In the transversely extending arm 46 is a bearing hous- 1 ing 50 which is threaded at its upper end into the arm 49. Intermediate the ends of the bearing housing 50 is a radial fln 52.which maintains the housing in proper location, and serves the more importanty functionof av pivot which permits oscillation of the lower endof the housing 50.

The space between the housing50 and the depending portion 54` of the transversely extending -arm 49 is sealed by means of a flexible member 56 which is held in place by a capnut 58. 'Ihe upper end of the bearing supporting bracket is suitably closed by means of va closure screw 59. The rotor spindle 42 passes through a bearing sleeve 60 which is fixed in the lower open end of the bearing housing 50 by tight engagement with the wall thereof.

A second bearing housing 62 is located in the passage for positioning two vspaced bearing sleeves providing support to the rotor spindle at A spaced points towards its lower end. Aspindle bearing sleeve 68 is xed snugly in the upper end of the bearing housing 62 While a second spindle bearing sleeve 10 is xed in snug engagement 4with'the lower end of the bearing l1ousing62.

The bearing housing 62 is located in spaced relation to the walls ofthe passage 40, and the space between it and the walls of -the passage 40'is sealed by means of mounting and packing rings 64 and 66. These mounting and packing rings, aswell as the ring 56, are constructed of relatively resilient andoil resisting composition.

'I'he sealing function of the resilient rings 56,

64 and 66, is however, no more important than y their .function as resilient mountings for the toA bearing housings 50, 62. A relatively rigid motor shaft mounted in unyielding` bearings would -set up severe vibrational disturbances at very high rotational speeds. The present invention permits simple construction through the use of a flexible .rotor shaft. and by mounting the rotor shaft in its bearings on the yielding rings 56, 64, 66. This construction reduces vibration to a minimum.

Intermediate the lower end of the bearing housing 50 and the upper end of the bearing housing 62 is located the drive mechanism for the rotor spindle. This mechanism consists of an air motor or turbine 12 which issuitably fastened through suitable ducts formed in the head B (not shown) to an annular passage 60 surrounding a turbine housing k84 from which the same is discharged through tangential passages or jets 82 in the turbine housing against the face of the turbine wheel 12` Air under pressure from the oil chamber 46 passes through an air passage |60 to the space'E quence of the pressure on the oil around the bearing means which embodies a maximum below metbine wheel 12 with sumcient fore wheel 12 and the underlying wheel support 86.`

The turbine wheel support 66 may be molded of suitable yielding plastic compositionl and the same rests on a yielding annulus I81 Vwith which it forms an eiective cushion into which the part 86 will be pressed'by the air pressure.

During the operation of the machine oil under pressure inthe chamber 46 is forced through the oil conduit 88 and passes around the bearing housing 50 and into the bearing housing through apertures 90 in the wall thereof. As a conser`to the turbine and directs it into a drip pan 92 -o which surrounds the same. Excessive'I amounts of oil pass through an overow pipe 96 lwhich dischargesinto a suitable container.

The oil under pressure which surrounds the bearing housing 62 deforms the resilient rings 64 and 66 into contact with` adjacent'surfaces to seal the rotor chamber against leakage. -It will be noted that the turbine wheel housing 84 isv provided with a downwardly projecting lip 68 which lies against the upper packing ring 64, while at the lower end of tlie bearing housing 62 an oil catch |00 has an inwardly extending iiange |02 which the lower ring abuts.

The oil under pressure from chamber 46 communicates with the passage 40 through the aper. tures 14 and 15, and with the interior ofthe bearing housing through apertures |04 formed therein. Any oil escaping from the bearing housy ing 62 must do so by passing between the bearing sleeves 10 and 68 and the spindle 42, thus insuring constant lubrication of the bearing surface and at the same time forming an effective seal for the rotor chamber. A deflector |06 attached to the spindle 42 prevents oil which escapes from the lower end ofthe lower bearing assembly from passing along the spindle into the rotor chamber. The deilecting plate |06 discharges oil into the oil collector |00 from which it ows to the oil cup I8 and to the oil collecting chamber I2 in the base of the machine. The oil which escapes through the bearing sleeve 66 passes through a passage 94 in the turbine housing 64 and is discharged through the -overflow pipe 96.

The above describedconstruction provides a the means for adjusting the height o i the bearingv '5 ||0 formed inthe upper end of the bearing bracket 48. The vertical height of the bearing 60 can be altered merely by turning the housing 50 to adjust its positionin the bracket 48.

The rotor 44 is provided with a-cel] carryingl passage ||0 which is adapted to receive'a cell composed of an outer casing ||2 and an inner casing ||4 both of which are held against rotation by a pin IIB which extends therethrough and into a socket in the rotor. The cell I2 is also provided with two glass or quartz discs I I8 spaced from each other by a spacing member |20 to prof vide therebetween a space for a small sample of substance to be treated. An annulus |22 having a pin |24 resting in a slot formed in the cell I2 to prevent relative rotation is fixed by a locking ring |26 threaded into the rotor. The rotor 44 'is cut away'at points opposite the cell passage ||0 as at |28 and |30 to povideproper balance,

' The rotor, which is preferably constructed of aluminum or an aluminum alloy, is ixed `to its drive shaft 42 by means of a split collet |32. The lower end of the collet engages a shoulder |34 formed' on the lower end of the shaft 42 tolock the two parts securely. A set screw |36 is provided in the upper end of the collet to engage the shaft 42 in order to prevent shaft whip. 'Ihe rotor is interchangeable with others lof the -same or of different design. t

When the head B is properly located on the body A, the space therebetween is sealed by means of a gasket |38.1 The optical system for observing the sedimentation in a sample of substance under treatment is completed by an adjustablemirr'or |40 which is carried'on a mirror shaft |42, journaled for rotation in the head member. The mirror |40 may b e adjusted to any desired angular position -by manipulation of a thumb wheel |44 and the adjusted position of the mirror may be secured through a set screw |46 which engages the mirror shaft |42. The base plate of the head B has formed therein an aperture |48 which is closed by a glass or quartz plate |50. The passage 22 in the body and the passage |48 in the head are in alignment and include the vertical planes through' which the rotor cell must pass'during its rotation. As -a consequence, light reflected by the mirror 32 is caused to pass through the rotating cell and the constant image of the substance under treatment in the cell is reflected by the mirror |40 for observation by an attendant or for photographic purposes'as hereinbefore suggested. The chamber |52 which houses the mirror |40 is normally closed by a removable plate |54.

In a typical operation of the machine a sample to be studied is placed in the cell of the rotor and the rotor is rst operated at a speed of approximately l10,000 R. P. M. as the vacuum within the rotor chamber is being brought to approximately .2 micron, after which the rotational speed is increased to 80,000 R. P. M. to develop a maximum centrifugal force of 1250,000 times gravity. Under these conditions the temperature rise in the sample under treatment .does not exceed .2

C. during the course of a four-hour treatment. 'I'he use of vacuum enables the rotor to turn five times as fast without increasing the driving power, and more'important, the vacuum avoids local heating from air friction. During high speed operation, a shaft of light is directed aaoavas 3 through the rotating cell and photographs are of the treating period the photographs are. compared as hereinabove suggested.

eration, a blurred image would be recorded and d precise results in the analysis'of the photograph would be precluded. The machine'is self-conand attention for its successful operation.

vtaken at intervals of time and at the termination Should vibration Itained and requires a minimum amount of skill'v While hereinabove a single embodiment of the I invention has been illustrated itis obvious that extensive modifications in the con/struction may be made without departing from the spirit vof the invention as defined in `the subjoined claims.

I claim: y n

l. In a head fora centrifugal machine having a iiexible spindle and a-rotor secured thereto 1 adapted for rotation at high speeds, the combination comprising a rotor spindle passage through said head, a bearing sleeve in said passage, resilient means for securing said sleeve.

in said passage for radially yieldable movement, axially spaced spindle-bearings mounted in said sleeve, a drive motor connected'to said spindle at a point opposite said bearings from the zone ofsecurement of the rotor spindle'to the rotor, a bearing for said spindle located alongsaid spindle at a point beyond said motor, .a bearing housing for said last-mentioned bearing, means for supporting said housing, a resilient mounting interposed between said housing and said supporting means to permit radially yieldable move.- lment of said housing, and fluid means for supporting the spindle and rotor during rotation thereof.

a exible spindle and .a rotor secured thereto adapted -for rotation at high speeds, the combination comprising a rotor spindle passage through said head, a bearing sleevel in said passage,.resilient means for securing said sleeve in said passage for radially yieldable movement,

spindle bearings mounted in said sleeve, a 'drive motor connected to said spindle at a point oppo-v site said bearings from the zone of securement of the rotor spindle to the rotor, a bearing for said spindle'located along said spindle at a point beyond said motor, abearing housing for said last' mentioned bearing, means for supporting said housing, a resilient mounting member interposed between said housing and saidsupporting means to permit radially yieldable movement of said housing, means for adjusting said housing 1ongitudinally of said spindle, and fluid means for supporting the spindle and rotor during rotation thereof. y

aliexible spindle and a rotor secured .thereto adapted for rotation athigh speeds, the combina- V f w 3. In ahead for a centrifugal 'machine having v operating means between the sleeve and the walls of the passage to form a seat for a resilient mounting member, a resilient and deformable mounting member interposed between said sleeve and the walls of said passage at the extremities thereof for securing said sleeve for radially yieldable movement and for sealing the space between said sleeveand said passage wallsLaxially spaced yspindle bearings mounted in said sleeve, a drive motor/connected to said spindle at va point 'opposite IsaidA bearings from the zone oi' securement ofthe rotor spindle to the rotor, an oil reservoir in-saidhead, means aiording communication from :said reservoir to said passage and -said sleeve, andinea'ns for placing said oil under pressure whereby a lubricant may be provided to said bearings and said ,resilient and. de`

formable member are urged into sealing contact` With adjacent surfaces.

4. `In a head for a centrifugal machine having an axially movable flexible spindle and a rotor securedv thereto adapted for rotation at high speeds, the combination comprisingl a rotor spindie passage through said head, a bearing sleeve in -said passage, resilient means interposed between said lsleeve and the' walls of said passage for securing said sleeve for radially yieldable movement, axia1ly spaced spindle bearings mounted in said sleeve, a drive motor connected to said -spindle at va point opposite said bearings from the -zione of -securement of the rotor spindle to the rotor, an oil reservoir in said head, means for admitting air under pressure to said reservoir,

sleeve in said passage, resilient means for securing said sleeve in said passage for radially yieldable movement, spindle bearings mounted in said sleeve, a drivemotor secured to said spindle at a -point opposite saidbearings from the zone of securement oi the rotor spindle tothe rotor, a bearing for said spindle v located along said spindle at a point beyond said motor, a bearing housing yfor said last-mentionedbearing, means for supporting said housing, a resilient mounting vinterposed between said housing'and' said.

supporting means to permit radially yieldable movement of said housing. an oil reservoir in lsaid head, means aiiording communication be.`

tween said reservoir and all' oi' they said bearings, means i'or admitting air under pressure to said reservoir, and means for admitting air from said reservoir to a space directly under said I motor. for axially moving said spindle.

ARTHUR. UNnEawooD A YREs.

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