CENTRIFUGE/ROTOR ATTACHMENT ASSEMBLY

Abstract: A rotor attachment assembly to provide efficient and secure connection between a rotor (10) and a centrifuge drive mechanism (18). The assembly is designed in such a manner that not only attachment, but also disconnection is accomplished in a convenient one-step operation. The utilization of a single connecting shaft (24) with flexible fingers (30) contributes to the ease of operation as well as the ease of manufacture of the assembly.

Description: 1 CENTRIFUGE/ROTOR ATTACHMENT ASSEMBLY Background of the Invention '* The present invention is directed to high speed centrifuges and, more particularly, is directed to the 5 connection between a centrifuge rotor and the drive mech¬ anism in a centrifuge. Centrifuges are designed to create a high force field that is utilized in clinical as well as laboratory 10 analysis of various fluid samples. The centrifuge rotors rotate at very high speeds to create the tremendous G forces necessary to cause the separation of the constitu¬ ents of the fluid sample for analysis. 15 In certain centrifuges, it is necessary to provide positive engagement between the rotor and the drive mechanism to prevent relative motion between the drive hub on which the rotor rests and the rotor. The torque drive in some centrifuges is low enough in con- 20 junction with the relatively high weight of the rotor that no relative motion will occur between the rotor and the drive hub. In this situation, no positive connection or engagement is necessary between the rotor and the drive hub. 25 But where the rotor tends to be lighter and where the drive system does operate with a high torque, need exists for positive connection or attachment between ■ » the rotor and the centrifuge drive hub. Otherwise, some " . 30 relative motion would occur between the rotor and the drive hub which is not acceptable for longevity of the system. Further, the existence of relative motion be¬ tween the rotor and the drive hub affects the ability to control and determine the speed of the rotor. This un- 35 desirable relative motion also adversely affects rotor dynamics. In certain high speed operation, the hub may vibrate within the rotor, causing metal- o-metal fretting which is not acceptable for the proper operation of the centrifuge. One typical approach for providing the connec¬ tion between the rotor and the drive hub is the utiliza¬ tion of a threaded stud. The stud extends up through the rotor and a handle is used to properly secure the rotor into the drive hub. In other configurations, the drive hub has vertical flats on it to mate with flat areas within the rotor to provide the necessary positive con¬ nection to prevent relative motion between the rotor and the drive mechanism. Typically, rotors have to be removed from the centrifuge subsequent to the centrifugation run. Threaded types of connection mechanisms become very time consuming in laboratory practice where the rotor may be removed and reinserted in the centrifuge several times during a relatively short period of time. Summary of the Invention The present invention is directed to an attach¬ ment assembly for securing a centrifuge rotor to the drive mechanism in a centrifuge in such a manner that no relative motion " will occur between the rotor and the drive mechanism. In particular, the attachment assembly utilizes a connecting shaft which is designed to operate in a convenient one-step operation to not only provide the connection between the rotor and the drive hub, but also provide disengagement of the rotor from the drive hub. The elongated connecting shaft has a plurlity of flexible fingers which, when moved to a first position in a longitudinal direction, will provide for the locking of the rotor on the drive hub. The movement of the con- necting shaft in the same longitudinal direction to a second position will provide for the unlocking of the rotor from the drive hub. Brief Description of the Drawings Figure 1 is a partial sectional view of the present invention's attachment assembly with the connect¬ ing shaft in the unlocked position; Figure 2 is a partial sectional view similar to Figure 1 with the connecting shaft moved in a direction toward its locked position; Figure 3 is a sectional view similar to Figure 1 with the connecting shaft in its locked position; Figure 4 is a sectional view similar to Figure 1 with the connecting shaft in its disengaging position; and Figure 5 is a sectional view similar to Figure 1 with the connecting shaft moved toward its unlocked position. Brief Description of the Invention In Figure 1, a rotor 10 is shown having a body portion 12 and a lid 14. Fluid samples are placed in the body portion 12 of the rotor 10 for centrifugation. The rotor is mounted on a drive hub 16 that is connected to a drive shaft 18. The drive hub 16 is located within a rotor chamber (not shown) while the drive shaft 18 is connected below the rotor chamber to drive means (not shown) for spinning the shaft at very high speeds. The rotational speed of the drive shaft 18 is imparted to the rotor when placed on the rotor hub 16. The rotor will spin at a high speed of rotation to create the necessary centrifugal forces to provide the separation of the con¬ stituent parts of the fluid samples. Located within the body portion 12 of the rotor is a drive hub recess 20 for receipt of the drive hub 16. in certain arrangements of centrifuge drive systems and rotors, the only connection necessary between the rotor and the drive hub is the physical contact be¬ tween the two items. If the weight of the rotor is suf¬ ficient and the drive has a relatively low torque, the drive hub will provide the proper transfer of rotation to the rotor 10 without any relative motion between the drive hub and the rotor. However, in some instances when the rotor is not of sufficient weight and when the drive mechanism does not have low torque, it is necessary to provide a connection mechanism*between the rotor and the drive hub so that no relative motion will occur between the two. In the present invention an attachment assembly 22 is utilized for providing connection between the rotor and the drive hub 16. The attachment assembly includes an elongate connecting shaft 24 that is slidably posi¬ tioned within an opening 26 in the lid 14. The connect¬ ing shaft 24 has at its lower end with respect to Figure i at least two flexible fingers 30 which in their relaxed position have an exterior diameter the same as the diam¬ eter of the connecting shaft 24 above the area of the fingers 30. Located on the locking end 32 of each of the flexible fingers 30 is an anchoring collar section 34 which together form a collar with an exterior diameter greater than the diameter formed by the fingers 30 or the main portion of the connecting shaft 24. This difference in diameter forms an anchoring ledge 36 on each finger. This anchoring ledge 36 will be utilized for providing the locking function of this connecting shaft as will be explained below. The rotor lid 14 has a spring recess 38 which receives a biasing spring 40. The biasing spring 40 is positioned between a shoulder 42 in the spring recess 38 and a shoulder 44 formed at the upper end of the connect¬ ing shaft 24 with respect to Figure 1 where the connect¬ ing shaft contacts an activating knob 46. Consequently, the connecting shaft 24 is always biased in a direction upward toward the rotor lid 14. Formed within the drive hub 16 is a locking cavity 48 having an enlarged upper recess 50 forming a shoulder 52. Positioned on the shoulder 52 is a retain¬ ing ring 54 having an internal opening 56 with a diameter approximately the same as the exterior diameter of. the connecting shaft 24. .The retaining ring 54 is held in place by a clip 58. In Figure 2, the connecting shaft 24 is moved in a downward direction to move the flexible fingers 30 toward the recess 48 in the drive hub 16. Because the exterior diameter of the total of the anchoring collar sections 34 on the locking ends 32 of the flexible fing¬ ers 30 is greater than the interior diameter of the open- ing 56 of the retaining ring 54, the flexible fingers 30 will be compressed toward each other as shown in Figure 2. The tapered surfaces 60 on the locking ends 32 of the fingers 30 provide guidance through the opening 56. Once the anchoring ledges 36 of the anchoring collar sections 34 pass through the opening 56, they will move into en¬ gagement with the locking surface 62 of the retaining ring 54. The size of the drive hub recess 48 allows for the flexible fingers 30 to flex away from each other to their original relaxed position and secure the anchoring collar in a locked position with respect to the retaining 5 ring 54. As the rotor assembly is accelerated to high speed, the centrifugal loading on the fingers 30 tends to positively seat them out against the interior diameter 56 of the retaining ring 54. The biasing spring 40 in the rotor lid will provide an upward force on the connecting 0 shaft 24 to provide tight engagement between anchoring collars and the retaining ring. In this position, as shown in Figure 3, the connecting shaft 24 is in its locked position so that the rotor is secured to the drive hub 16. During the operation of the centrifuge, this 5 positive connection between the rotor and the drive hub will prevent any relative motion occurring between the drive hub and the rotor. Once the centrifugation operation has been 0 completed and it is desired to remove the rotor from the centrifuge, it is necessary to unlock the connecting shaft 24 from the drive hub 16. In order to accomplish this process, the connecting shaft 24 is moved to a sec¬ ond downward position as shown in Figure 4 wherein the 5 tapered surfaces 60 on the locking ends 32 of the flexi¬ ble fingers 30 move into a stripping collar or sleeve 64 which is slidably positioned in the drive hub recess 48. The stripping sleeve 64 has an exterior diameter less than the interior diameter of the hub recess 48 so ° that the sleeve will freely slide within the recess 48 and, unless otherwise moved, will maintain a position at the bottom 66 of the recess 48. The stripping sleeve 64 has an interior opening 68 having a diameter which is approximately the same as the diameter of the connecting shaft 24 and the diameter of the opening 56 in the re¬ taining ring 54. Once the anchoring collar sections. 34 are received within the opening 68 in the stripping sleeve 64, the fingers 30 will be flexed toward each other. The stripping sleeve will contain the anchoring collars 34 in a position where their exterior dimension is approximately the same as the diameter of the connect¬ ing shaft 24. Movement of the anchoring collars into the stripping sleeve is accomplished by the operator exerting a downward force on the connecting shaft 24 against the force of the biasing spring 40. When the collar sections 34 are in the strip¬ ping sleeve 64 and the operator's downward pressure on the connecting shaft 24 is released, the force of the biasing spring will move the locking ends of the flexible fingers 30 upward with the stripping sleeve 64. The outward pressure exerted by the anchoring collars 34 against the interior of the opening 68 in the stripping sleeve provides a gripping force on the sleeve to carry the sleeve with the connecting shaft in its upward trav¬ el. Attention is directed to Figure 5 where the stripping s.leeve 64 has been moved up to a position in contact with the retaining ring 54. At this point, con¬ tinued upward movement of the connecting shaft 24 will allow the anchoring flanges to move into the opening 56 of the retaining ring 54. Because the stripping sleeve 64 has retained the flexed orientation of the flexible fingers 30 toward each other sufficiently enough so that the outside dimension of the total collar formed by the anchoring collar sections 34 is no larger than the open- ing 56 in the retaining ring 54, the anchoring collar sections will continue up through the retaining ring 54 under the upward biasing force of the spring 40. Once the anchoring collar sections 34 have cleared the in- terior opening 56 of the retaining ring 54, the connect- ing shaft and the flexible fingers 30 will assume the orientation as shown in Figure 1 wherein the rotor is in the unlocked position with respect to the drive hub 16. In this position the operator may then remove the rotor from the centrifuge. The present invention is designed for ease of operation in both the locking and unlocking functions. Because the connecting shaft 24 is prebiased in an upward direction by the biasing spring 40, the only motion re¬ quired by the operator is a downward or pushing motion on the knob 46 of the connecting shaft. Indicator areas 70 and 72 in the form of indicia or colors adjacent the push knob 46 in Figure 1 will provide a visual indiction of the locked or unlocked position of the rotor on the drive hub. In other words, if both the indicator areas 70 and 72 are shown above the top 74 of the lid 14, the operator would know that the rotor is unlocked from the drive hub 16. However, as shown in Figure 3, when only the indica- tor area 70 is shown above the top 74 of the rotor lid, the operator would know that the rotor is locked onto the drive hub 16. The operator will know that when it is desirable to unlock the connector shaft from the drive hub 16, the connecting shaft 24 will be pushed downward to its lowest extreme wherein the lower ends of the flex¬ ible fingers will contact the bottom of the recess 66 and the drive hub 16. As shown in Figure 4, both .indicator areas 70 and 72 will be oriented generally below the top surface of the rotor lid. At this point, the operator simply releases his pressure on the connecting shaft 24 and the upward movement caused by the biasing spring 40 will unlock the connecting shaft from the drive hub. In summary, downward movement of the connecting shaft 24 from the position in Figure 1 to a first posi¬ tion in Figure 3 will provide automatic locking of the rotor to the drive hub 16. Further, the downward move¬ ment of the connecting shaft to a second position, as shown in Figure 4, will provide for the automatic unlock¬ ing of the connecting shaft from the drive hub. The utilization of a simple one-finger vertical manipulation to control the locking and unlocking of the rotor from the centrifuge drive hub assembly utilizes few components to promote ease of manufacture. Although the present invention is shown in the accompanying figures and described above as having a particular configuration, this configuration is for exem¬ plary purposes and it is envisioned that the present invention is applicable with respect to other configura- tions utilizing the principles shown in the present in¬ vention.

Claims: CLAIMS 1. A centrifuge comprising a rotor chamber; a drive hub (16) projecting into the chamber; means (18) for driving the hub; a rotor (10) positioned on the hub; a connecting shaft (24) within the rotor and movable in 5 one direction to a first position and a second position; and an engaging member (54) within the hub to contact with one end of the connecting shaft, movement of the shaft to the first position locking the rotor on the hub, movement of the shaft to the second position unlocking 10 the rotor from the hub, the second position being farther from the rotor than .the first position. 2. A centrifuge as defined in claim 1, character¬ ized in that flexible fingers (30) are on the one end of the shaft. 3. A centrifuge as defined in claim 2 , character¬ ized in that anchoring collar sections (34) are on the flexible fingers. 4. A centrifuge as defined in claim 3, character¬ ized in that the engaging means has a holding surface (62) on which the anchoring collar sections contact when the shaft is in the first position to lock the rotor on 5 the hub. 5. A centrifuge as defined in claim 4, character¬ ized in that the hub has unlocking means (64) to discon¬ nect the connecting shaft when in the second position. 6. A centrifuge as defined in claim 5, character¬ ized in that the unlocking means comprises a sleeve, the flexible fingers being inserted in the sleeve when the shaft is in the second position, the flexible fingers 5 being biased toward each other when in the sleeve to allow movement of the anchoring collar sections in a * direction opposite the one direction past the holding surface. 7. A centrifuge as defined in claim 5, character¬ ized in that the unlocking means comprises a stripping sleeve (64) slidably mounted in the hub cavity, movement of the one end of the shaft away from the hub causing the anchoring collar with the stripping sleeve to move to a position adjacent the engaging means, the interior perim¬ eter of the sleeve being approximately the same perimeter as the interior perimeter of the engaging means so that the one end of the shaft can move above the engaging means and permit disengagement of the rotor from the hub. 8. A centrifuge as defined in claim 1, character¬ ized in that the connecting shaft comprises an elongate shaft, a portion (46) of the shaft extending above the top of the rotor, the shaft movable longitudinally toward and away from the drive hub in response to controlled movement of the portion of the shaft above the rotor. 9. A centrifuge as defined in claim 8, character¬ ized in that the shaft is biased in a first direction, movement of the shaft in a second direction opposite the first direction into contact with the engaging means preventing the shaft from moving in the first direction. 10. A centrifuge as defined in claim 1, character¬ ized in that the connecting shaft is movable in a path coincident with the spin axis of the rotor toward and away from the hub. 11. A centrifuge as defined in claim 3, character¬ ized in that the engaging means comprises a generally annular retaining ring (54) in the hub cavity for receipt of the anchoring collars of the fingers, the ring forming an interior perimeter smaller than the exterior perimeter defined by all of the anchoring collars of the fingers, the fingers flexing toward each other as the shaft moves between the first and second positions, the ring having a retaining shoulder for receipt of the anchoring collar to lock the connecting shaft and the rotor on the hub. -

Inventors: WRIGHT HERSCHEL E, WRIGHT, HERSCHEL, E.
Applicants: BECKMAN INSTRUMENTS INC, BECKMAN INSTRUMENTS, INC.
Application year: 1983
Main classification: B04B5
IPC codes: B04B5, B04B9, F16B21, F16D1