US3377021A - Centrifuge rotors, buckets and combinations of such buckets and rotors - Google Patents

Description

A rl 9, 1968 G. D. FOX ETAL 3,377,02l CENTRIFUGE ROTORS, BUCKETS AND COMBINATIONS OF SUCH BUCKETS AND ROTORS 2 Sheets-Sheet L Filed May 17, 1965 G. D. FOX ETAL 3,377,02l CENTRIFUGE ROTO ETS AND COMBINATIONS 2 Sheets-Sheet Aprl 9, 1968 RS, BUCK I OF SUCH. BUCKETS AND ROTORS Filed May 17, 1965 United States Patent O 3,377,021 CENTRIFUGE ROTORS, BUCKETS AND COM- BINATIONS OF SUCH BUCKETS AND ROTORS Gerald D. Fox and John E. Joyce, Quincy, Mass., and

Robert C. Leif, Los Angeles, Calif., assigno's to International Equipment Company, Needham Heiglts,

Mass., a corporation of Massachusetts Filed May 17, 1965, Ser. No. 456, 310 6 Claims. (Ci. 233-26) ABSTRACT OF THE DISCLOSURE Centrifuge rotors and buckets and combinations of buckets and rotors, the buckets and rotors having, respectively, detachablytmating, ball and socket connecting por tions.

'The present invention relates to combinations of centrifuge buckets and rotors of the type where the buckets are detachably connected to 'a rotor to swin-g from a depending, 'vertical position into a position at right angles to the rotor aXis in response to centrifngal force. T-he in- Vention also relates to centrifuge rotors and to the buckets tor use in such combinations.

The Construction used to etiect the attachment of *buckets to centrifuge rotors has 'heretofore placed limits on rotor designs and, -accordingly, on such important factors as the number of buckets that a head may carry and the speed at which it may be safely rotated without the r-isk of breakage. Existing constructions employ pivotal connections between the buckets and the rotors. In one such commonly used construction, the rotors have their peripheries formed with an outwardly disposed fl-ange i provided with a circumferentially spaced series of vertical slots, one for each bucket. Each bucket is provided with trunn-ions adjacent its end that has a removable closure and at the upper end of each bucket-receiving slot there are undercut shoulders receiving the trunnions and pivotally confining them during centrifugation. Any proposal to increase the strength of pivot connections leads,'=for any size of head, to -a reduction in the number of buckets that it can carry, to increased rotor weight, or both. The avoidance of rotor breakage is, accordingly, troublesome and has been considered largely a metallurgcal problem.

The general objective of the present invention is to provide centrifuge rotor and bucket combin-at-ions in which the connection between each bucket and its rotor is of a ball andsocket type.

In accordance with the invention, the objective is attained 'by providing .a centrifuge rotor and bucket for use therewith. Each bucket is of the type including a tubul ar portion closed at one end and provided with fiange structure ad-jacent the other end, the flange structure providing diametrically opposed portions whose faces that are disposed towards the closed end are sphen'cal. The rotor has top and bottom faces, a plurality of spherical sdckets spaced inwardly of but adjacent its periphe-y and a slot opening upwardly into each socket, and bucket entrances through one of its faces, one entrance for each socket and associated slot. Each socket receives the flanged end of a bucket and the slot in communication with that socket receives the tubular portion thereof and is of a length 3,377,021 Patented Apr. 9, 1968 ice is 'intersected by the associated slot.

In one embodiment of the invention, the rotor has a plurality of radial slots opening through the lower part of its :periphery and its undersurface, each slot being dimensioned to slidably receive the tubular portion of a bucket as -it swings from its position of rest into its position of use. -Each slot has an entrance through a rotor face adjacent the rotor axis dimensioned to receive the flanged end of a bucket and is undercut to accommodate that end, each undercut terminating in a socket adjacent the periphery of the rotor for supporting a bucket both when the rotor is at rest and when it is brought up to speed with the bucket then at right angles to the rotor axis, the socket and ilange being dimensoned so that together they provide a bucket-to-rotor connection of the ball and socket type.

'Each centrifuge rotor in -accondance with the invention is possessed of adequate strength to ensure against 'break- 'age at rotor speeds that are relatively high for its size and weight while providing support for a number of buckets that is relatively large for its size. This result is due not only to the relatively 'large areas of mutual contact between the rotor and its buckets -but also because the invention makes it possible to support the buckets within 'open slots extending from points adjacent 'the `rotor aXs outwardly and upwardly through the lower part of its periphery, leaving the upper part thereof as an annular reinforcement for the upper parts of the sockets.

Another advantage of the ball and socket conne'ctio-n's between the rotor and its buckets 'is that the slots receiving the tubular bucket portions may be shaped to permit the buckets to Swing in trailing directions to a desred augu- Iar extent as the rotor speed increases or decreases.

'In the -accompanying drawings, there are shown illustratve embodiments of the invention from which these :and other of its objectives, novel features, and advantages will be apparent.

In the drawings:

F-IGURE 1 is a partly sectioned, top pl=an view of a rotor tin -accordance with the invention showing the flange d end of one bucket in its socket,

FIGURE 2 is a section taken approxmately along the indicated lines 2-2 of FIGURE 1 and showing buckets in side elevation,

FIGUR'E 3 is a fragnentary section of the rotor taken vertical ly through a 'bucket-supporting socket and slot,

FIGURE 4 is a fragmentary side elevat'ion of -a rotor,

FIGURE 5 is a longitudinal section of .a bucket drawn on an increased scale, and

FIGURE 6 is a view similar to FIGURE 4 but illustrating another embodiment of the invention.

The centrifuge 'bucket-s shown in the drawings are generally indicated at 10. Each bucket 10 includes a tubular portion 1 1 that is closed at one end and has its other end counte' bore-d to provide a seat 12 for' a seal -13 and th-readed to receive a cap 14. Adjacent the capped end of ea'ch bu cke t, there is a circul'ar flange '15 whose face that is dspdscd towards the closed end there'of is spherical. As will be apparent from FIGURE 5, each tubular portion 1'1 is externally tapercd inwardly towards its closed end in order to achieve the best weight distribution of the tube and its contents during centrfug'ation, the taper being necessarily slight because the bucket walls 'are relatively thin and because the inside diameter of the tubular portion 1*1 is constant.

A rotor in accordance with the invention is generally indicated at 16 and is shown -as having an aXial bore 17 to receive the centrifuge spindle, not shown, the bore 17 having -diametrically disposed channels 18 to receive the driving pins thereof as one example of a conventional way of securing a rotor to its drive. The ohamber in which this type of rotor is spun may or may not be a va'cuum chamber, vacuum chambers being commonly used when high speeds are desired that would otherwise place undue loads on the motors.

'The rotor 16 has a plurality of circumferentially spaced, open slots 19 extending vertically from the bottom of the rotor through the lower part of its periphery. The width of the slots 19 is such that each may accommodate the tubular portion 1 1 of 'a bucket 10.

Each slot 19 is undercut to accommodate the flanged end of a bucket 10, the undercut being shown as starting in the un'dersurface adjacent the rotor axis and terminating short of the periphery of the rotor to provide =a se'at that is suficiently spherical to provide a socket 20 for the sp'herical .face of a flange of the bucket both when the rotor is at rest and when its speed is such as to cause the buckets 10 to swing outwardly into positions in which their axes are at right angles to the axis of the rotor 16. Each socket 20 is -also shown as slightly elongated and downwardly inclined, say relative to a plane at right angles to the rotor axis, so that each socket 20 may serve to securely retain a bucket when the rotor 16 is at rest.

Reference is now made to FIGURE 2, Wherein the right hand bucket -10 has had its stoppered and flanged end entered upwardly through the open, undercut end of a slot 19 and moved radially outwardly toward it's socket 20. The left hand bucket 10 is shown as ful-ly supported by its socket so that, when the rotor is turnng rapidly enough, it will swing smoothly outwardly into its dotted line position.

The production of rotors may be effected as with an appropriately dimensioned spherical cutter utilizing the slots 19 as a guide for the shank of the tool, introducing the cutting head of the tool at the undersu'rface endof a slot 19 and advancing it first upwardly and then radially outwardly and preferably downwardly at -a small angle relative to the horizontal, say 5, to ensure bucket retention when the rotor 16 is 'at rest.

A rotor in accordance with the invention is of adequate strength for high speed Operations since the area o'f its contact with the bucket flanges is large due to the balland-socket type of connection between the buckets and their rotor.

The smooth and potentially universal motion characteristc of ball-and-socket connections also permits additional advantages in centrifugation. To enable the closed ends of the buckets 10 to trail, as is sometimes recommend, at the start of a centrifuge cycle and also when the rotor slows down, each slot may have its lower end slightly widened and upwardly and inwardly tapered as 'at 19'A, see FIGURE, 6, to an extent permitting desired trailing of the buckets as the rotor is brought up to speed or slows down. As the rotor 1 6A shown in FIGURE 6 is otherwise identical to the rotor 16, it is not otherwise detailed.

We claim:

1. A centrifuge rotor for supporting buckets, each bucket of the ty pe including a tubular portion closed at one end and provided with flange structure adjacent its other end, the flange structure providing dametrically opposed portions whose faces that are dsposed towards said closed end are sphercal with respect to a common center, said rotor having a plurality of bucket entrance passages of circular sec't'on and of a diameter to accommodate the bucket flange structure and spaced uniformly from the center of the rotor and from each other, each entrance passage extending into said rotor in a vertical direction and outwardly and downwardly within the rotor in a radial direction and termin'ating in a retaining socket comple-mental to said fiange structure portions, and said rotor having means for each entrance passage to receive and guide the tubular :portion of a bucket as it is p0sitioned within the rotor with its fiange structure seate'd in the passage socket and as the bucket swings upwardly during centrifugation, each 'of said means being in the form of a radial slo't in vertical alignment with an appropriate one of said entrance passages and opening through the periphery and undersurface of said rotor and into the vertically aligned entrance passage and its socket, each slot, in at least a portion thereof, slidably receiving the tubular portion of a bucket and the extent of each slot being such that a bucket may be entered into a socket and swing vertically between positions of rest and use.

2. The rotor of claim 1 in which each slot, between the position therein of the tubular portion of a bucket in its position of rest and the position of the tubular portion in its position of use tapers outwardly from the retaining socket to enable the tubular portion to swing into a trailing position during acceleration and deceleration when the rotor speed is below a predetermined rate of rotation to a width such that the tubular portion is maintained radial with respect to the rotor axis when the predetermined rotor speed is a'ttained.

'3. The rotor of claim 1 in which the entrance passages open through the undersurface of the rotor.

4. In combination, a centrifuge rotor and buckets, each bucket of the type including a tubular portion closed at one en'd including fiange structure adjacent its other end, the flange structure providing diametrically opposed por tions whose faces that are disposed towards said closed end -are spherical with respect to a common center, and said rotor having a plurality of bucket entrance passages of circular section and of a diameter to accommoda'te the bucket fiange structure and spaced uniformly from the center of the rotor and from each other, each entr-ance 'passage extending into said rotor in a vertical direction and outwardly and downwardly within the rotor in a radial direction and terminating in a socket complemental to said flange structure portions, and said rotor having means for each entrance passage to receive and guide the .tubular portion of a bucket as it is positioned within the rotor with `its fiange structure seated in the passage socket and as the bucket swings upwardly during centrifiugation, each of said means being in the form of a radial slot in vertical alignment with an entrance and opening through the periphery and undersurface of said rotor and into the vertically aligned passage and its socket, each slot, in at least a portion thereof slidably receiving the tubular portion of a bucket and the extent of each slot being such that a bucket may be entered into a socket to have a depending position of rest and swing vertically between positions of rest and use, the tubular portion of each bucket extending through the appropriate one of said slotswith its fiange structure seated in a socket to provide a ball and socket type of bucket torotor connection. I

5. The combinaton of claim 4 in which each slot, between the position therein of the tubular portion of a bucket in its position of rest and the position of the tubular portion in its position of use, .tapers outwardly from the socket to enable that tubular portion to swing into a trailing position during acceleration and deceleration when the rotor speed is below a prede'termined rate of rotation to a width such that the tubular portion is maintained radal w'ith respect to the rotoaxs when the predeter- 1,839,944 1/ 1932 Barthels 233-26 X mined rotor speed iS attane'd- 1,997,919 4/1935 Strezyn'ski 233 z6 6. The combnaton of clam 4 n whch the entrance 2160411261 7/1952 slverstolpe 233 26 passages open through the undersurface of the rotor.

References cited 5 HENRY T. KLINKSIEK, Prmary Exam'er.

UNITED STATES PATENTS M. CARY NELSON, Exam'ner. 1,539,*102 5/1925 'Alexander 233-26

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