System and method for balancing a centrifuge rotor

Abstract

To provide an improved system and method for balancing a rotor.SOLUTION: A rotor (102) for use in a centrifuge, comprising: a rotor body (210) including an axis of rotation; and a plurality of balancing apertures (432) arranged circumferentially about the axis of rotation, the balancing apertures (432) being configured to selectively receive weights (433), wherein the balancing apertures (432) are comprised in a lid (212). 432.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] (Reference to Related Application) This application claims the benefit of co-pending U.S. Provisional Patent Application No. 62 / 969,932, filed February 4, 2020, and co-pending U.S. Provisional Patent Application No. 63 / 112,018, filed November 10, 2020, the disclosures of which are incorporated herein by reference in their entireties.

[0002] (Technical field) The present invention relates generally to centrifuge rotors, and more particularly to balancing rotors for use with centrifuges. [Background technology]

[0003] Rotors are commonly used in laboratory centrifuges to hold samples during centrifugation. While rotors can vary significantly in configuration and size, one common rotor structure is a fixed-angle rotor with a solid rotor body containing multiple cavities radially distributed within the rotor body and symmetrically arranged about the axis of rotation. In this type of rotor, samples are placed within the cavities, allowing multiple samples to be centrifuged.

[0004] Conventional fixed-angle rotors can be made from metal or a variety of other materials. However, rotors can also be constructed using compression molding and filament winding processes, where the rotor is manufactured from a suitable material, such as composite carbon fiber. For example, fixed-angle rotors can be compression molded from layers of resin-coated carbon fiber laminate material. Examples of composite rotors are described in U.S. Patent Nos. 8,147,392, 8,273,202, 8,323,169, and 10,086,387.

[0005] Centrifuges may feature a rigid rotor shaft or spindle that provides rotational torque to a rotor mounted on a spindle within the centrifuge. However, for high-speed centrifuges, such as ultracentrifuges, which can spin rotors at speeds of 50,000 revolutions per minute (RPM) or more, flexible shafts are typically used instead of rigid shafts. The flexible shaft limits the transmission of vibrations to the centrifuge framework, which may be generated by any imbalance in the rotor or poor distribution of the sample load within the centrifuge.

[0006] For example, rotors used in high-speed applications, at speeds exceeding tens of thousands of revolutions per minute, must be carefully balanced to reduce the rotor's tendency to vibrate during high-speed rotation. Variations in the mass of the rotor load can create undesirable force imbalances when the rotor operates at high speeds. This force imbalance can distort the spindle, causing damage to the centrifuge, reduced efficiency, excessive wear, and unwanted noise. Traditional balancing techniques for rotors operated by rigid spindles use a combination of samples and balance tubes, all of which have the same weight, or various other balancing patterns without the addition of balance tubes.

[0007] A diagnostic device or balancing machine, such as those commercially sold by American Hofmann Corporation of Lynchburg, Virginia, or Schenck Corporation of Deer Park, New York, can be used to detect rotor imbalance, typically for rotors mounted on rigid spindles, and to identify specific locations on the rotor body where additional weights are needed to balance the rotor. Holes are then manually drilled in the rotor body at the identified locations, and weights are press-fit into these holes according to information provided by the diagnostic device. The weights can be, for example, metal cylinders, each having a specific mass that compensates for the imbalance detected by the diagnostic device.

[0008] A rotor may need to be rebalanced multiple times over its lifespan. For example, as the rotor ages and wears, the rotor's mass distribution may change, thereby requiring rotor rebalancing. When this occurs, previously installed weights typically need to be removed from previously drilled holes. New holes are then drilled in the rotor body, and the weights are press-fit into the new holes. The previously drilled holes are therefore rendered unused. It is often desirable to seal the previously drilled holes for structural and / or aesthetic purposes, which requires repair of the rotor body. The cycle of drilling new holes in the rotor body and repairing the rotor body to seal the previously drilled holes is repeated each time the rotor is rebalanced.

[0009] It would therefore be desirable to provide an improved system and method for balancing a rotor that addresses these and other problems associated with conventional rotors. Summary of the Invention

[0010] In one embodiment of the present invention, a rotor is provided that includes a rotor body having an axis of rotation and a plurality of balancing apertures circumferentially arranged about the axis of rotation, each balancing aperture configured to selectively receive a weight.

[0011] In one aspect of the invention, the rotor body may further include a lid having a plurality of circumferentially spaced tubular cavities and a balancing aperture formed therein. Each tubular cavity may have an open end configured to receive a sample vessel. The lid is configured to be supported by the rotor body and overlie the open ends of the tubular cavities when the lid is positioned on the rotor body.

[0012] In another aspect of the invention, the lid may further include a top surface and a bottom surface opposite the top surface, and the balancing aperture may be formed in one of the top surface or the bottom surface.

[0013] In another aspect of the invention, at least one weight may be received by at least one of the balancing apertures.

[0014] In another aspect of the invention, at least one weight may be a screw including a threaded outer surface, and each of the balancing apertures may include a threaded inner surface configured to threadably mate with the weight.

[0015] In another aspect of the invention, each balancing aperture may be the same radial distance from the axis of rotation as the other balancing apertures.

[0016] In another aspect of the invention, each balancing aperture may be angularly spaced the same angular distance from each adjacent balancing aperture.

[0017] In another aspect of the invention, the balancing apertures may be coplanar.

[0018] In another aspect of the invention, the rotor body may further include an upper surface and a lower surface opposite the upper surface, the upper surface including a first annular groove. The rotor may further include a balance ring positioned in the first annular groove, the balance ring including a balance ring upper surface, and a balancing aperture formed in the balance ring upper surface.

[0019] In another aspect of the present invention, the rotor body may include an elongated bore extending along the axis of rotation between the upper surface of the rotor body and the lower surface of the rotor body, and the rotor may further include a drive hub, a cap screw, a cap, and an elastic member. The drive hub may include a cylindrical shaft mounted within and projecting upward through the elongated bore, and an upper portion having a threaded outer surface. The cap screw may include a lower bore having a threaded inner surface configured to threadably mate with the threaded outer surface of the drive hub, and a cap screw flange extending radially outward from a lower end of the cap screw. The lid may include a wall portion extending radially outward and having a lower surface with a third annular groove. The elastic member may be positioned within the third annular groove and compressed against the upper surface of the balance ring in response to threading of the cap screw with the drive hub.

[0020] In another aspect of the invention, the first annular groove may include a shoulder, and the balance ring may include a balance ring flange that projects radially inwardly to engage the shoulder.

[0021] In another aspect of the invention, the rotor body may include a circumferential sidewall, and the rotor may further include a stiffener extending around the circumferential sidewall.

[0022] In another aspect of the invention, the stiffener may extend around and above the circumferential sidewall of the rotor body to define a channel with a first annular groove, and the balance ring may be positioned within the channel.

[0023] In another aspect of the invention, the circumferential sidewall may include a circumferential recess and the reinforcement may fit into the circumferential recess.

[0024] In another aspect of the invention, the balance ring may be operably coupled to the first annular groove by an adhesive, a shrink fit, or both an adhesive and a shrink fit.

[0025] In another aspect of the invention, the rotor body may be constructed of a polymer composite material, a carbon fiber material, or both a polymer composite material and a carbon fiber material.

[0026] In another embodiment of the present invention, a method for balancing a rotor including a plurality of apertures, each configured to selectively receive a weight, is provided, the method including detecting an imbalance in the rotor while rotating the rotor in a centrifuge, and selectively placing balancing weights in selected balancing apertures in response to the detection of the imbalance.

[0027] In one aspect of the invention, detecting the imbalance may include identifying a critical speed of the rotor and determining the rotor imbalance at a test speed that is less than the critical speed.

[0028] In another aspect of the invention, the critical speed may be one of a plurality of critical speeds, and rotor unbalance may be determined for each of the plurality of test speeds, each test speed being a fraction of the critical speed of a respective one of the plurality of critical speeds.

[0029] In another aspect of the invention, identifying the critical speeds may include, for each of a plurality of rotational speeds, spinning the rotor at the rotational speed, applying an external force to the rotor while the rotor is spinning at the rotational speed, measuring and recording a vibratory response of the rotor to the external force, and determining a natural frequency of the rotor based on the vibratory response. The method may then identify one or more critical speeds of the rotor based on the natural frequency.

[0030] In another aspect of the present invention, selectively installing balancing weights within selected balancing apertures may include measuring rotor unbalance at a first test speed, installing trial weights within the balancing apertures at a reference position, and measuring rotor unbalance at the first test speed with the trial weight installed at the reference position. The method may then include repeatedly moving the trial weight from the current balancing aperture to a next balancing aperture a predetermined angular distance away and measuring rotor unbalance at the first test speed until the next balancing aperture is at or beyond the reference position. Based on the measured unbalance, the method may then determine a first target location and a first target mass to be added to the first target location to balance the rotor.

[0031] In another aspect of the invention, the method may further include determining a first balance vector provided by a first target mass at a first target location; selecting a first balancing aperture on one side of the first target location and a second balancing aperture on the other side of the first target location; and determining the first balancing mass and the second balancing mass, which when positioned within the first balancing aperture and the second balancing aperture, respectively, provide a second balance vector equivalent to the first balance vector.

[0032] In another aspect of the invention, the method may further include installing a first weight having a first balancing mass in the first balancing aperture, installing a second weight having a second balancing mass in the second balancing aperture, and measuring the imbalance at a first test speed with the first weight installed in the first balancing aperture and the second weight installed in the second balancing aperture.

[0033] In another aspect of the present invention, the method may further include measuring the unbalance of the rotor at a second test speed faster than the first test speed, installing a trial weight in the balancing aperture at a reference position, and measuring the unbalance of the rotor at the second test speed with the trial weight installed at the reference position. The method may further include repeatedly moving the trial weight from the current balancing aperture to the next balancing aperture a predetermined angular distance away and measuring the unbalance of the rotor at the second test speed until the next balancing aperture is at or beyond the reference position. Then, based on the measured unbalance, the method may determine a second target location and a second target mass to be added to the second target location to balance the rotor.

[0034] In another aspect of the invention, the method may further include determining a second balance vector for a combination of the first target mass at the first target location and the second target mass at the second target location, and determining a third target mass and a third target location that provides a third balance vector equivalent to the second balance vector.

[0035] In another aspect of the invention, the method may further include selecting a third balancing aperture on one side of the third target location and a fourth balancing aperture on the other side of the third target location, and determining a third balancing mass and a fourth balancing mass that, when positioned within the third balancing aperture and the fourth balancing aperture, respectively, provide a fourth balance vector that is equivalent to the third balance vector.

[0036] In another aspect of the invention, the method may further include installing a third weight having a third balancing mass in the third balancing aperture, installing a fourth weight having a fourth balancing mass in the fourth balancing aperture, measuring an unbalance at a second test speed with the third weight installed in the third balancing aperture and the fourth weight installed in the fourth balancing aperture, and comparing the unbalance measured at the second test speed to the unbalance measured at the first test speed.

[0037] The above summary presents a simplified overview of some embodiments of the invention to provide a basic understanding of certain aspects thereof discussed herein. The summary is not intended to provide an extensive overview of the invention, nor is it intended to identify key or critical elements or delineate the scope of the invention. The summary's sole purpose is merely to present some concepts in a simplified form as a prelude to the detailed description presented below. [Brief explanation of the drawings]

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description of the invention given above and the detailed description given below, serve to explain the invention.

[0039] [Figure 1] 1 is a perspective view of a centrifuge including a rotor having a lid in accordance with an exemplary embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of the rotor of FIG. 1. [Figure 3] FIG. 3 is an exploded perspective view of the rotor of FIG. 2. [Figure 4] FIG. 4 is a bottom perspective view of the lid of FIGS. 1-3, showing various weights installed in various balancing apertures of the lid. [Figure 4A]FIG. 4 is a bottom perspective view of the lid of FIGS. 1-3, showing various weights installed in various balancing apertures of the lid. [Figure 4B] FIG. 4 is a bottom perspective view of the lid of FIGS. 1-3, showing various weights installed in various balancing apertures of the lid. [Figure 4C] FIG. 4 is a bottom perspective view of the lid of FIGS. 1-3, showing various weights installed in various balancing apertures of the lid. [Figure 4D] FIG. 4 is a bottom perspective view of the lid of FIGS. 1-3, showing various weights installed in various balancing apertures of the lid. [Figure 5] FIG. 3 is a cross-sectional view of the rotor of FIG. 2. [Figure 6] FIG. 6 is a detailed view of a portion of the rotor of FIG. 5, showing the balancing weights installed on the bottom surface of the lid. [Figure 7] 5 is a perspective view of an alternative embodiment of the lid of FIG. 4, showing multiple balancing apertures in the top surface of the lid. [Figure 8] FIG. 8 is a detailed view of a portion of the rotor of FIG. 7, showing the balancing weights installed on the top surface of the lid. [Figure 9] 4 is a flowchart illustrating an exemplary process that may be performed to balance a rotor, in accordance with one embodiment of the present invention. [Figure 9A] 10 is a flowchart illustrating an example sub-process that may be performed by the process of FIG. 9. [Figure 9B] 10 is a flowchart illustrating an example sub-process that may be performed by the process of FIG. 9. [Figure 9C] 10 is a flowchart illustrating an example sub-process that may be performed by the process of FIG. 9. [Figure 10] FIG. 2 is a perspective view of a rotor according to another exemplary embodiment of the present invention. [Figure 11] 11 is an exploded perspective view of the rotor of FIG. 10 showing the rotor body, balance ring, drive hub, and lid of the rotor. [Figure 12]FIG. 12 is a perspective view showing additional details of the lid of FIG. 11. [Figure 13] FIG. 12 is a top perspective view showing additional details of the rotor body of FIG. 11. [Figure 14] FIG. 12 is a bottom perspective view showing additional details of the rotor body and drive hub of FIG. 11. [Figure 15] FIG. 11 is a cross-sectional view of the rotor of FIG. 10. [Figure 16] FIG. 16 is an exploded cross-sectional view of a portion of the rotor of FIG. 15 showing additional details of the lid, balance ring, and rotor body. [Figure 17] FIG. 11 is a top view of the rotor of FIG. 10 with the lid removed. [Figure 18] FIG. 11 is a top view of the rotor of FIG. 10 with the lid removed. [Figure 19] 1 is a graph illustrating vibration data for a modally balanced rotor in accordance with one embodiment of the present invention. [Figure 20] FIG. 20 is a perspective view of the rotor used to generate the data of FIG. 19. [Figure 21] 1 is a graph showing vibration data for an unbalanced rotor, a conventionally balanced rotor, and a modally balanced rotor. [Figure 22] 1 is a graph showing vibration data for an unbalanced rotor, a conventionally balanced rotor, and a modally balanced rotor. [Figure 23] 1 is a graph showing vibration data for an unbalanced rotor, a conventionally balanced rotor, and a modally balanced rotor. [Figure 24] 1 is a graph showing vibration data for an unbalanced rotor, a conventionally balanced rotor, and a modally balanced rotor. [Figure 25] FIG. 1 is a diagram of a computer that may be used to implement one or more processes according to embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] 1-6 illustrate an exemplary lid 212 for a rotor 102 (e.g., an 8×100 mL capacity, fixed-angle rotor) according to one embodiment of the present invention. The lid 212 includes a plurality of balancing apertures 432, each configured to selectively receive a trial weight 433 or a balancing weight 436 that can be removably engaged with the lid 212. As described in more detail below, the balancing weights 436 can be selectively positioned at various predetermined locations on the lid 212 to balance the rotor 102 via a modal balancing method.

[0041] 1 shows an exemplary centrifuge 100 according to one embodiment of the present invention. Centrifuge 100 includes a housing 101, a drive motor 106, a rotor drive shaft or spindle 104, and a rotor 102 mounted on spindle 104. During operation, drive motor 106 imparts rotation to spindle 104, which in turn provides rotational torque to rotor 102 to rotate rotor 102 at a desired speed.

[0042] Depending on the type of centrifuge 100 used, such as a centrifuge operating at a maximum speed of up to 15,000 RPM, greater than 15,000 RPM up to 40,000 RPM, greater than 40,000 RPM up to 90,000 RPM, or greater than 90,000 RPM, the spindle 104 can be either rigid or flexible. A rigid spindle 104 can be used for low-speed centrifuges 100. However, for centrifuges 100 operating at high speeds, e.g., 50,000 RPM or greater, a flexible spindle 104 can be used to reduce the transmission of vibrations during centrifugation. A sensor 108, such as an accelerometer, can be operably coupled to the centrifuge 100 or a component thereof and configured to measure vibrations. The sensor 108 can be attached to the motor 106, for example, at a bearing supporting the rotating spindle 104. The sensor 108 may be placed as close as possible to the bearing, preferably positioned in the same plane as the bearing, to obtain an accurate measurement of the vibration signal at the bearing while the rotor 102 is rotating.

[0043] 2, 3, and 5 illustrate an exemplary rotor 102 according to one embodiment of the present invention. The rotor 102 includes a rotor body 210 and a rotor hub 322. The rotor hub 322 is configured to transmit torque from the spindle 104 to the rotor body 210. The rotor hub 322 may be constructed of a metallic material, such as titanium, and includes a head portion 548 and an elongated shaft portion 546 extending axially upward from the head portion 548. The shaft portion 546 includes a threaded outer surface 550, a threaded inner surface 552, and an inwardly facing circumferential surface 544. The inwardly facing circumferential surface 544 may taper radially inward and downward along a portion of the length of the rotor hub 322. The rotor hub 322 may be secured to the rotor body 210 by a hub retainer 320 operably coupled with the threaded outer surface 550 of the shaft portion 546 of the rotor hub 322. Hub retainer 320 may be threaded onto the threaded end of shaft portion 546 after rotor hub 322 is inserted through rotor body 210 .

[0044] The rotor 102 also includes an exemplary lid 212 removably coupled to the rotor hub 322 so as to overlie the rotor body 210. The lid 212 is generally disk-shaped and includes a central bore 551 and an annular peripheral groove 429 for receiving an O-ring 430. The O-ring 430 may provide a fluid-tight seal between the lid 212 and the rotor body 210 when the lid 212 is removably coupled to the rotor body 210. The lid 212 may be constructed of a carbon fiber material, a metal material, or any other suitable material. For example, the lid 212 may be compression molded from layers of resin-coated carbon fiber laminate material. The rotor body 210 and the lid 212 may also include respective indicators (e.g., arrows 438, 440) that indicate a designated reference location 213. The reference location 213 may designate a particular location on the rotor body 210 and the lid 212 so that the lid 212 can be aligned to the same reference location 213 relative to the rotor body 210. The reference location 213 may be identified by markings or indicators on both the rotor body 210 and the lid 212. Although a reference arrow is shown in Figure 2, it should be understood that the reference location 213 may be identified on the rotor body 210 and the lid 212 by any suitable means that indicates to a user where to align the rotor body 210 and the lid 212.

[0045] As shown in FIGS. 3 , 5 , 6 , and 8 , the lid 212 may be removably coupled to the rotor body 210 by a lid screw 214. The exemplary lid screw 214 includes an upper flange 554, a threaded lower outer surface 556, and a multi-step bore 558 extending axially through the lid screw 214. The lid screw 214 may include an outwardly facing circumferential surface 542 that tapers radially inward and downward along a portion of the length of the lid screw 214. This may configure the circumferential surface 542 to face the inwardly facing circumferential surface 544 of the rotor hub 322 when the lid screw 214 is engaged with the rotor body 210. As shown, the threaded lower outer surface 556 may be received by and threadably mate with the threaded inner surface 552 of the hub 322, causing the upper flange 554 to press the washer 316 against the lid 212. The retaining clip 318 may hold the lid screw 214, the washer 316, and the lid 212 together by sandwiching the lid 212 between the two washers 316. When coupled to the rotor body 210 via the engagement of the lid screw 214 with the hub 322 and the engagement of the retaining clip 318 with the lid 212, the lid 212 may overlie the plurality of tubular cavities 540 and the sample vessels contained within the plurality of tubular cavities 540. The lid 212 may thereby block access to the sample vessels held within the cavities 540, such as during high speed rotation. Each of the above rotor mounting components may be made of any suitable metallic or non-metallic material.

[0046] FIG. 4 illustrates an exemplary lid 212 with a trial weight 433 installed in accordance with one embodiment of the present invention. The lid 212 may be configured to be supported by and overlie the rotor body 210, as best shown in FIG. 5. The lid 212 includes a top surface 426, a bottom surface 424 opposite the top surface 426, and an outwardly extending circumferential sidewall 428 extending between the top surface 426 and the bottom surface 424. The circumferential sidewall 428 tapers radially inward and downward from near the top surface 426 of the lid 212. The circumferential sidewall 428 may taper at a taper angle ranging from approximately 10° to 30° relative to the top surface 426 of the lid 212. Preferably, the circumferential sidewall 428 may taper at a taper angle of approximately 10° relative to the top surface 426 of the lid 212. The lid 212 may also include an O-ring 430 supported by a circumferential sidewall 428 of the lid 212. The lid 212 may also include an annular ridge 434 extending from the top and bottom surfaces 426, 424 of the lid 212 to define a cavity configured to receive the washer 316.

[0047] The lid 212 may further include a plurality of balancing apertures 432 circumferentially spaced apart from one another on the lid 212. Each balancing aperture 432 may include a threaded inner surface and may be of uniform configuration. That is, each of the balancing apertures 432 may have, for example, the same depth, cross-sectional dimension, or thread pitch. Thus, each of the balancing apertures 432 may be configured to threadably receive the same type of balancing weight 436 or trial weight 433. The balancing apertures 432 may be positioned on the bottom surface 424, the top surface 426, or both surfaces 424, 426 of the lid 212.

[0048] The exemplary embodiment best shown in FIG. 4 includes 24 balancing apertures 432 on the bottom surface 424 of the lid 212. The balancing apertures 432 are equally spaced circumferentially about the central bore 551. The balancing apertures 432 thus define predetermined locations on the lid 212 for receiving balancing weights 436 or trial weights 433. However, any suitable number of balancing apertures 432 may be used at any suitable spacing. Accordingly, the cross-sectional dimensions of the lid 212 may affect the surface area available for the balancing apertures 432 and may be increased to provide additional surface area for accommodating more balancing apertures 432. It should be understood that the number of balancing apertures 432 may correlate to the number of options for installing balancing weights 436 or trial weights 433. Thus, the number of balancing apertures 432 may correlate to the degree of control of the center of gravity of the lid 212, which may affect the stability of the rotor 102. Figure 4 shows a single trial weight 433 installed in the balancing aperture 432, referred to as the reference location 213. Furthermore, it should be understood that the number of balancing weights 436 installed in the lid 212 may vary depending on the amount of imbalance in the rotor 102 to be corrected.

[0049] Imbalance can occur whenever the center of gravity of the rotor 102 is not aligned with the axis of rotation. The forces generated by imbalance can be characterized as follows: F imb =M×ε×ω 2 where M is the mass of the rotor, ε is the radial offset of the center of gravity from the rotor's axis of rotation (or "eccentricity"), (M × ε) is the unbalance, and F imb is the force caused by the imbalance, and ω is the rotational speed (rad / sec). The rotational speed ω is given by:

number

number

number

[0050] In the embodiment shown in Figures 4-4D, the reference location 213 may correspond to the reference location 213 described in Figures 1-3, but it should be understood that it is located on the exact opposite side (bottom surface 424) of the lid 212. Figures 4A and 4B show bottom perspective views of the lid 212 of Figure 3. Figure 4A shows the trial weight 433 installed in the balancing aperture 432 located 120 degrees (θ) from the reference location 213 of the trial weight 433 installed in Figure 4. Figure 4B shows the trial weight 433 installed in the balancing aperture 432 located 240 degrees (2θ) clockwise from the location of the trial weight 433 installed in Figure 4, i.e., 120 degrees (θ) clockwise from the reference location 213 of the trial weight 433 installed in Figure 4A.

[0051] 4C and 4D each show a bottom perspective view of the lid 212 of FIG. 3. FIG. 4C shows one balancing weight 436 installed in a balancing aperture 432, and FIG. 4D shows two balancing weights 436 installed in adjacent balancing apertures 432. The number of balancing weights 436 installed in the balancing apertures 432 of the lid 212 can depend on the amount of imbalance in the rotor 102. The number of installed balancing weights 436 can vary from as few as none to as many as the number of balancing apertures 432 present in the lid 212.

[0052] Each balancing or trial weight may include a set screw including a threaded outer surface, a proximal end, and a distal end. The distance between the proximal and distal ends of the set screw may define the length of the weight. A hex socket or other suitably keyed bore may be provided at the proximal end to receive a tool, such as an Allen wrench, to aid in advancing or removing the weight from one of the balancing apertures 432. The threaded outer surface of the weight may allow the weight to be inserted into or removed from one of the balancing apertures 432 without damaging the lid 212. Although the weights 433, 436 and the balancing aperture 432 are shown herein as threaded so that the weights may be removably engaged with one or more balancing apertures 432, embodiments of the present invention are not so limited. Accordingly, the weights 433, 436 may be removably engaged with the lid 212 by any suitable means. In some embodiments, multiple balancing weights 436 having a variety of different lengths or masses may be provided so that balancing weights 436 having different balancing characteristics can be selectively positioned in particular balancing apertures 432 to achieve customized balancing. It should be understood that other suitable devices, such as press-fit dowel pins, may also be employed. Accordingly, embodiments of the present invention are not limited to the exemplary trials and balancing weights shown.

[0053] Although the balancing weights 436, trial weights 433, and corresponding balancing apertures 432 have been described with respect to the illustrated lid 212 and rotor 102, the balancing weights 436, trial weights 433, and balancing apertures 432 may be incorporated into any suitable lid. In alternative embodiments, the balancing apertures 432 may be included within the rotor body 210, such as within the upper annular surface 437 of the annular rim 439 of the rotor body 210. The balancing weights 436, trial weights 433, and balancing apertures 432 may also be incorporated into other carbon fiber rotors of various designs or rotors constructed of different materials.

[0054] 5 shows a side cross-sectional view of rotor 102 according to one embodiment of the present invention. Rotor 102 includes rotor body 210 that is symmetrical about an axis of rotation defined by rotor hub 322. A sample contained in a sample container (not shown) can be positioned within rotor body 210 and centrifugally spun about the axis of rotation. The illustrated rotor body 210 includes a central bore 560 for receiving a rotor insert 562 that can be co-molded with rotor body 210. Rotor insert 562 includes a threaded central bore 564 configured to operably engage at least a threaded shaft portion 550 of hub 322 to securely seat rotor body 210 in hub 322.

[0055] The rotor body 210 may include a plurality of cavities 540. In one embodiment of the present invention, the plurality of cavities 540 may comprise a plurality of circumferentially spaced tubular cavities, each having an open end configured to receive a sample vessel. Each of the plurality of cavities 540 may extend into the rotor body 210 from the upper cavity and may be of a size and shape suitable to receive at least one of the sample vessels for centrifugal rotation about the rotation axis. The exemplary rotor 102 shown in FIGS. 1-3, 5, 6, and 8 has eight cavities 540, each sized to receive a 100 mL sample vessel, although it should be understood that any suitable number of cavities 540 may be used, and the cavities 540 may be configured to fit sample vessels of various sizes. As used herein, the term "tubular" refers to any suitable cross-sectional shape, including, but not limited to, shapes with rounded corners (e.g., oval, circular, or conical), quadrilaterals, regular or irregular polygons, or any other suitable shape. Thus, the term "tubular" is not intended to be limited to the generally circular cross-sectional profile of the exemplary cavity 540 shown in the figures.

[0056] In one embodiment, rotor body 210 may be constructed of a polymer composite material. For example, rotor body 210 may be compression molded from layers of resin-coated carbon fiber laminate material. It should be understood that rotor body 210 may also be formed using a variety of other materials and by a variety of other methods. For example, rotor body 210 may be compression molded from discontinuous resin-coated carbon fiber strips or a combination of discontinuous carbon fiber strips and stacked layers of carbon laminate.

[0057] With rotor body 210 operably engaged with rotor hub 322, hub retainer 320 may be removably fastened to hub 322 to further facilitate holding rotor body 210, rotor hub 322, and insert 562 in place relative to one another. In this regard, hub retainer 320 may include an internally threaded bore 326 for receiving and threadably engaging at least a threaded outer surface 550 of shaft portion 546 of hub 322.

[0058] FIG. 6 shows a detailed view of a portion of the rotor 102 of FIG. 5 , illustrating the interface between the lid 212 and the rotor body 210. The lid 212 may include an O-ring 430 seated in an annular peripheral groove 429 in a circumferential sidewall 428 of the lid 212. The lid 212 may be configured to fit within an inwardly facing circumferential sidewall 538 of the rotor body 210 such that the lid 212 rests against the circumferential sidewall 538. Preferably, the lid 212 may be formed such that when the lid 212 rests against the circumferential sidewall 538 of the rotor body 210, there is a sliding contact between the lid 212 and the circumferential sidewall 538 that does not prevent removal of the lid 212. To create a tight seal, the lid 212 may be pressed downward against the circumferential sidewall 538 by the lid screws 214, as described above. In response to compression, O-ring 430 may expand radially such that it bears against circumferential sidewall 428 of lid 212 and circumferential sidewall 538 of rotor body 210, thereby creating a seal. This may allow lid 212 to be tightly sealed adjacent to the top end of rotor body 210, but easily removable by loosening lid screws 214 to release the downward force applied to lid 212. Once the force applied by lid screws 214 is released, O-ring 430 may retract away from circumferential sidewall 538 of rotor body 210 such that only sliding contact exists between lid 212 and circumferential sidewall 538 of rotor body 210. Lid 212 may then be easily removed.

[0059] FIG. 6 also shows the orientation of the balancing weights 436 within the balancing apertures 432 of the lid 212. In the illustrated embodiment, the balancing apertures 432 are located on the bottom surface 424 of the lid 212. Therefore, the balancing weights 436 must be installed within the balancing apertures 432 of the lid 212 before securing the lid 212 to the rotor body 210. To add, remove, or move the balancing weights 436 or trial weights 433 to the lid 212, the lid 212 must be removed. FIG. 7 shows an alternative embodiment of the lid 212 in which the balancing apertures 432 are located on the top surface 426 of the lid 212. In this embodiment, it may not be necessary to remove and replace the lid 212 during the modal balancing process.

[0060] 8 shows a detailed view of one embodiment of rotor 102, focusing on lid 212 of FIG. 7, with balancing aperture 432 positioned on top surface 426 of lid 212. The detailed view shows the interface between lid 212 and rotor body 210, and the orientation of balancing weight 436 within balancing aperture 432 of lid 212.

[0061] FIG. 9 shows a flowchart illustrating an exemplary modal balancing process 945 for balancing the rotor 102 in a centrifuge 100. Centrifuges may have natural harmonic resonant frequencies that can result in standing wave patterns at certain critical speeds. These standing wave patterns are often referred to as “critical modes.” Advantageously, by minimizing rotor imbalance, it may be possible to move through these critical modes without interruption and achieve smooth operation of the centrifuge at high speeds. Process 945 may detect rotor 102 imbalances that occur in the identified critical modes and identify at least one target location on the lid 212 and at least one corresponding target weight amount whose addition at the target location will aid in proper balancing of the rotor 102. The illustrated process 945 may be used to balance a rotor 102 including any of the various embodiments of the lid 212 shown in FIGS. 4-8 , although for clarity, reference may be limited to the specific embodiment of the lid 212.

[0062] In block 946, process 945 determines one or more critical modes in which the rotor 102 may become unbalanced. Next, process 945 may proceed to block 956, where the rotor 102 within the centrifuge 100 may be spun at a test speed that is a fraction (e.g., ¾ or 75%) of the critical speed of one of the critical modes determined in block 946, e.g., a fraction of the lowest critical speed. Spinning the rotor 102 at the critical speed may damage the centrifuge 100 due to the unbalanced forces experienced while in the critical mode, so the test speed may be slower than the critical speed. There may be a range of acceptable values ​​for the test speed at which the rotor 102 is spun. For example, the rotor 102 may be spun at 70% to 95% of the critical speed. By way of example, the rotor 102 may be spun at 70% or 85% of the critical speed.

[0063] In block 958, process 945 may correct the imbalance of rotor 102 at the test speed at which rotor 102 was spun in block 956. By correcting the imbalance determined at the test speed, it may be possible to spin rotor 102 at a higher speed than before the imbalance was corrected.

[0064] In block 982, process 945 may spin rotor 102 in centrifuge 100 at another test speed that is a fraction of another (e.g., higher) critical speed determined in block 946. As previously described, rotor 102 may be spun at this other test speed that is slower than the other critical speed to avoid damage to centrifuge 100. In block 984, process 945 may correct for imbalance of rotor 102 at the other test speed at which rotor 102 was spun in block 982.

[0065] At block 986, process 945 may spin rotor 102 at yet another test speed that is a fraction of the yet another critical speed determined at block 946 (i.e., a speed faster than the previous critical speed), if another critical speed is available. At block 988, process 945 may again correct the unbalance of rotor 102 at the test speed at which rotor 102 was spun at block 986. Thus, process 945 may iteratively spin the rotor up to a fraction of the critical speed, correct the unbalance that occurs at that speed, and then select another critical speed at which to balance the rotor. This process may continue until the desired level of balance is achieved. It should be understood that the number of balancing runs can vary (e.g., may be less than or more than three runs). For example, in some cases, process 945 may need to perform only one balancing run to achieve the desired level of balance.

[0066] In block 990, the process 945 may evaluate balancing of the rotor 102 at a target speed in the centrifuge 100. The target speed may preferably be the rotational speed at which a user would typically operate the centrifuge 100. In an alternative embodiment, the target speed may be the maximum operating speed of the centrifuge 100, which may depend on the type of centrifuge 100 being used.

[0067] 9A shows a flowchart illustrating an example subprocess 947 that may be used to determine the critical modes of the rotor system in block 946. In block 948, subprocess 947 may apply an external force to a component of the centrifuge 100, such as the motor 106. The external force may include a vibration frequency in a predetermined frequency band. One method of applying the external force may be to operably couple a chirp signal or a sine sweep signal generated by a modal shaker to the motor 106. In an alternative embodiment, the external force may be provided by an impulsive load delivered to the motor 106 by an instrumented hammer. Other methods of applying an external force to the motor 106 or other components of the centrifuge 100 that have a vibration component in a predetermined frequency band may also be used.

[0068] In block 950, subprocess 947 may measure the vibration response of rotor 102 to the applied external force. The vibration response may be measured at a motor bearing supporting rotating spindle 104 while rotor 102 is spinning within centrifuge 100. The vibration response measurements may be taken at selected rotational speeds of rotor 102. For example, vibration response measurements may be taken at intervals of 1,000 RPM up to a typical or maximum operating speed of centrifuge 100. The vibration response of the bearing to the external force may be measured at each of the selected rotational speeds by sensor 108. The output of sensor 108 may be operably coupled to a suitable device for analyzing the output signal, such as a dynamic signal analyzer or a computer running digital data recording software.

[0069] In block 952, subprocess 947 may plot or otherwise analyze the measured vibration response data obtained in block 950 as a function of both the rotational speed of the rotor 102 and the frequency of the applied force at which the vibration response was recorded. The data used to generate the plot may be obtained, for example, by using a modal shaker to generate an external force via a chirp or sine wave swept over a predetermined frequency band. The plot may be a waterfall plot, commonly referred to as a Campbell diagram, of the experimentally measured rotor vibration response as a function of rotational speed and excitation frequency. A Campbell diagram typically includes multiple slices, each corresponding to the rotational speed of the rotor 102 and showing the power spectrum of the vibration frequencies detected at that rotational speed. Each slice may include peaks corresponding to the rotor's natural frequencies at that rotational speed. As the rotational speed approaches a critical mode, the intensity of vibration at the natural frequencies may increase.

[0070] In block 954, sub-process 947 may identify one or more critical rotational frequencies (i.e., critical speeds) of rotor 102 based on the Campbell diagram. In an exemplary embodiment of the invention, the critical speeds may occur at 5,000, 37,000, and 55,000 RPM. From the natural frequencies of rotor 102, critical modes of rotor 102 may be identified by computer analysis. The critical modes of rotor 102 may occur at rotational speeds where vibrations in the bearings are most severe. It is at these rotational speeds that unbalance of rotor 102 may be greatest. Therefore, these rotational speeds are the rotational speeds at which rotor 102 will need to be further balanced. With knowledge of the speeds at which rotor 102 needs to be unbalanced, process 945 may proceed to determine where to place balancing weights 436.

[0071] 9B shows a flowchart illustrating an exemplary unbalance correction sub-process 963 that may be used to correct rotor unbalance at blocks 958, 984, and 988 of process 945 at fractions of a critical speed, e.g., 5,000, 37,000, or 55,000 RPM. Each time sub-process 963 is used to correct rotor unbalance at a subsequent critical speed (e.g., 37,000, 55,000), the corrective action may differ in at least one detail from the result determined for the initial or previous critical speed (e.g., 5,000 RPM), as described in more detail below.

[0072] In block 960, subprocess 963 may spin rotor 102 at an initial test speed that is a fraction of the initial critical speed. Advantageously, by using a test speed that is a fraction of the initial critical speed, subprocess 963 may avoid damaging centrifuge 100 due to the magnitude of the level of imbalance that may be experienced operating in critical mode.

[0073] In block 962, subprocess 963 may measure and record the imbalance of rotor 102 experienced while rotor 102 is spinning at the initial test speed. The imbalance of rotor 102 may be measured, for example, by sensor 108. To this end, subprocess 963 may determine the root mean square ("RMS") value of a power spectrum diagram of the measured vibration response. The RMS value of the power spectrum diagram may be recorded and may be a preferred measurement parameter for determining rotor imbalance.

[0074] In block 964 of sub-process 963, a trial weight 433 having a known mass may be placed in the balancing aperture 432 at the reference location 213 on the lid 212. Preferably, the trial weight 433 may be similar in mass to the balancing weight 436 used to balance the rotor 102. The reference location 213 may be any of the balancing apertures 432 located circumferentially around the rim of the lid 212. Once the reference location 213 is selected, the same reference location 213 should be used, and the lid 212 should be maintained in a consistent circumferential position relative to the rotor body 210 during the remainder of the balancing process.

[0075] In block 966, sub-process 963 again spins rotor 102 at a fraction of the initial critical speed with trial weight 433 in place. Once rotor 102 reaches speed, sub-process 963 proceeds to block 968 to again measure and record the unbalance of rotor 102 while spinning at this speed. Sub-process 963 can then determine and record the RMS value of the power spectrum of the measured vibration response.

[0076] In block 970 of sub-process 963, the trial weight 433 may be moved from the reference location 213 to another balancing aperture 432. In one embodiment, the trial weight may be moved to a balancing aperture that is offset 120 degrees clockwise from its previous location on the lid 212. Moving the trial weight 120 degrees may allow sub-process 963 to correct the rotor imbalance in three runs. In an alternative embodiment, the trial weight 433 may be moved 60 degrees clockwise each time, in which case sub-process 963 may need to perform six runs. In yet another embodiment, the trial weight 433 may be moved 90 degrees clockwise each time, in which case sub-process 963 may include four runs. Embodiments of sub-process 963 that move the trial weight 433 in smaller increments and perform more runs may have more data to determine where to place the selected balancing weight 436. However, three measurements involving 120 degrees of radial displacement have generally been determined to be sufficient to determine the positioning and mass of a selected balancing weight 436.

[0077] In response to the trial weight 433 being moved, sub-process 963 may proceed to block 972 to spin the rotor 102 at a fraction of the critical speed. Once the rotor 102 reaches speed, sub-process 963 may proceed to block 974 to measure and record the imbalance of the rotor 102, determine the RMS value of the power spectral components of the vibration, and record the RMS value.

[0078] Sub-process 963 may return to block 970 and iteratively repeat the process of moving the trial weight 433, spinning the rotor 102, and measuring and recording imbalance data until the trial weight has been placed at each of multiple positions within the lid 212. For a 120-degree incremental offset angle, one additional run may be performed to move the trial weight 433 an additional 120 degrees from the previous trial weight 433 location on the lid 212, i.e., 240 degrees from the original reference location 213. Each run provides an additional imbalance data point. The initial imbalance information for the lid 212 without the trial weight 433, along with the imbalance data from the trial weight 433 placed at three locations on the lid 212, may provide the user with the information necessary to determine where the balancing weight 436 should be placed on the lid 212 and how much mass the balancing weight 436 should have to counteract the inherent imbalance of the rotor 102. The incremental offset angle θ may be selected so that 360 degrees is an integer multiple of the offset angle θ. That is, the incremental offset angle θ=360 / n, where n is an integer greater than 1.

[0079] Once sufficient imbalance data has been collected, sub-process 963 may proceed to block 976 and solve a system of equations to determine where balancing weight 436 should be placed on lid 212 and how much mass it should have. The system of equations solved, in one embodiment, may include the following three equations:

number

number

number

number

number

number

number

number

[0080] As an example, assume that the following measurements were made by sub-process 963 while measuring and recording the unbalance of rotor 102: A0=0.225 A1=0.357 A2=0.184 A3=0.395 T W = 1.01 grams Inserting these measurements into the equations provided above gives: |R|=0.178

number

[0081] 9B , in block 978 of sub-process 963, the identified balancing weight 436 may be installed in a designated location determined by the modal balancing process. A suitable balancing aperture 432 corresponding to the target location and a balancing weight 436 having a weight relatively close to the target weight amount determined by the modal balancing method may then be selected. Generally, a user may obtain a balancing weight 436 of an appropriate mass and install it in the balancing aperture 432 corresponding to the designated location. Returning to the example above, if the lid 212 being used has a balancing aperture 432 located 109.57° from the reference location 213, the user may simply install a balancing weight 436 of an appropriate mass in that particular balancing aperture 432.

[0082] If the lid 212 does not have balancing apertures 432 specifically located at the locations determined by the modal balancing method, vector calculations can be used to determine approximate locations for placing balancing weights 436. The resulting balance vector of multiple balancing weights 436 can be equivalent to the balance vector of a single balancing weight 436 at the specified location. Referring back to the example above, if the lid 212 does not have balancing apertures 432 that are 109.57 degrees from the reference location 213, vector calculations can be used to determine the mass of balancing weights 436 required for locations near the 109.57 degree mark, e.g., the two balancing apertures 432 closest to the target location. For a lid 212 having 24 balancing apertures 432 spaced 15 degrees from each other circumferentially around the rim of the lid 212 (as shown in FIG. 4), the selected balancing apertures 432 may be located at 105 degrees and 120 degrees, which are the balancing apertures 432 on either side of the 109.57 degree mark. The vector resulting from placing balancing weights 436 at the 105 degree balancing apertures 432 and the 120 degree balancing apertures 432 can be calculated. In this example, the resulting vectors from one balancing weight 436 weighing 1.01 grams and located in a balancing aperture 432 105 degrees clockwise from the reference location 213, and one balancing weight 436 weighing 0.44 grams and located in a balancing aperture 432 120 degrees clockwise from the reference location 213, respectively, provide a vector equivalent to the vector of the 1.44 gram balancing weight 436 located 109.57 degrees from the reference location 213. In certain embodiments of the present invention, balancing weights 436 having predetermined masses close to the calculated masses may be selected to provide the optimal balance vector. For example, in the above case, weights having masses of 1.00 grams and 0.50 grams may be selected from a set of balancing weights having predetermined masses in 0.25 gram increments. In either case, the determined correction weight W c, and the resulting vector equal to phase Φ can be generalized and used to determine the appropriate number, mass, and location of balancing weights 436.

[0083] In block 980, subprocess 963 may test the rotor 102 with balancing weights 436 installed in the appropriate balancing apertures 432 to determine whether balancing is sufficient. To this end, the rotor 102 may be spun to a fraction of the previously determined critical speed, the vibration response measured, and the RMS value of the power spectral components of the vibration response determined and recorded. This RMS value may be compared to the RMS value of the rotor 102's imbalance before initiating subprocess 963. If balancing was performed correctly, the RMS value of the imbalance after balancing should be less than the RMS value of the imbalance before modal balancing. Furthermore, the imbalance after balancing should fall within the allowable tolerances for operation of the centrifuge 100.

[0084] 9, if the target speed for using rotor 102 is greater than the initial critical speed, process 945 may proceed to block 982 and spin rotor 102 to a fraction of another critical speed (e.g., next incrementally higher). In block 984, process 945 may correct the imbalance as described above with respect to sub-process 963, except that the balancing weight 436 (as shown in FIG. 4C) or multiple balancing weights 436 (as shown in FIG. 4D) previously added to the lid 112 of rotor 102 remains within the balancing aperture 432 shown during the modal balancing process.

[0085] Thus, in block 964 of sub-process 963, the trial weight 433 may be installed in the reference location 213 of the lid 212, with the lid 212 having the balancing weight 433 installed substantially as shown in FIG. 4C or 4D. In block 966, sub-process 963 may spin the rotor 102 at a fraction of the next (e.g., higher) critical speed. In block 970, the trial weight 433 may be moved clockwise by an incremental offset angle θ, e.g., 120 degrees relative to the position shown in FIG. 4A. During this iteration of the imbalance correction sub-process 963, the balancing weight 436 or weights 436 from the previous modal balancing process remain in place. Sub-process 963 then proceeds to block 972, where the rotor 102 may again be spinned at a fraction of the currently selected critical speed. This may cause sub-process 963 to repeat the balancing process as described above for the initial critical speed, but with the balancing weight 436 or weights 436 from the previous balancing run still in place at the currently selected critical speed. The analysis of positions and weights needed to correct the measured imbalance, described above with respect to FIG. 4C for the initial modal balancing, may then be repeated for the current modal balancing.

[0086] If the primary focus is on modal balancing at or near the second critical speed, sub-process 963 proceeds to block 978, where the entire mass of the identified balancing weight 436 may be installed at the identified location (or locations). Sub-process 963 then proceeds to block 980, where the amount of imbalance that may occur at or near the initial critical speed may be estimated and tested. The testing may include performing test balancing at defined fractions of both the initial critical speed and subsequent critical speeds. If the amount of imbalance becomes excessive at or near the initial critical speed, the mass of the balancing weight 436 may be reduced and the balance retested at both critical speeds to determine whether the imbalance is at an acceptable level for each rotational speed.

[0087] 9, if there is one or more higher critical speeds within the desired operating range of the rotor 102, the modal balancing process 945 may proceed to block 988 and repeat the unbalance correction sub-process 963 as described above, but with the balancing weights 436 in place from each previous iteration of the unbalance correction sub-process 963. Thus, the process of correcting the unbalance may be performed for one or more critical modes until the rotor 102 is balanced in a manner that optimizes operation of the centrifuge over the desired operating range of rotational speeds.

[0088] There is reference in the preceding discussion to additional balancing weights 436 being added during the modal balancing process 945 while leaving in place the balancing weights 436 from the previous iteration of the unbalance correction subprocess 963. However, it should be understood that the same result can be achieved by calculating and subsequently running an equivalent balance vector using a fewer number of balancing weights 436 after removing the previously installed balancing weights 436.

[0089] 9C shows a flowchart of a balance assessment subprocess 991 that may be performed by the modal balancing process 945 in block 990. The balance assessment subprocess 991 may be used to assess the balancing of the rotor 102 at a target speed. In block 992, the subprocess 991 may cause the centrifuge 100 to spin the rotor 102 at a target speed. The target speed may be the rotational speed at which a user wishes to operate the centrifuge 100. Alternatively, the target speed may be the maximum operating speed of the centrifuge 100. The maximum speed of the centrifuge 100 may depend on the type of centrifuge 100 being used and how well the rotor 102 is balanced.

[0090] In block 994, sub-process 991 may measure and record the imbalance of rotor 102 experienced when rotor 102 is spun at the target speed in centrifuge 100 as described above. Sub-process 991 may then proceed to block 996 and compare the imbalance recorded at the target speed with the imbalance recorded for the initial critical speed after balancing. To this end, the RMS value of the imbalance at the target speed may be compared to the RMS value of the imbalance at a fraction of the initial critical speed after balancing rotor 102 at that speed.

[0091] In block 998, subprocess 991 may determine whether the level of balancing is appropriate. For example, balancing may be considered properly performed if the RMS value of the unbalance at the target speed is approximately equal to the RMS value of the unbalance at a fraction of the initial critical speed immediately after balancing the rotor 102 at that speed. This is before further iterations of the unbalance correction subprocess 963. The approximately equal RMS values ​​may demonstrate that balancing the rotor 102 at the subsequent critical speed did not interfere with balancing the rotor 102 at the previous critical speed. In other words, balancing the rotor 102 at the subsequent critical speed did not upset the balancing previously performed at the initial critical speed. Furthermore, the imbalance after balancing the rotor 102 must fall within the acceptable tolerances for operation of the centrifuge 100.

[0092] The rotor 102 may then be rebalanced, for example, by detecting a new imbalance in the rotor 102 and unthreading one or more balancing weights 436 from their respective balancing apertures 432, repositioning the removed balancing weights 436 in different balancing apertures 432, threading one or more different balancing weights 436 into one or more different balancing apertures 432, or replacing the removed balancing weights 436 with one or more balancing weights 436 having different lengths or masses. The use of balancing weights 436 and balancing apertures 432 may eliminate the need to repeatedly drill holes in the rotor body 210 or to plug such drilled holes when they are no longer in use during rebalancing.

[0093] 10-18 illustrate an exemplary rotor 1010 (e.g., a 12×1.5 mL fixed-angle rotor) according to another exemplary embodiment of the present invention. The rotor 1010 includes a rotor body 1012, a stiffener 1014, a balance ring 1016, a lid 1018, a drive hub 1020, and a lid screw 1022. The rotor 1010 has an axis of rotation 1024 about which the rotor 1010 is configured to rotate when used in a centrifuge, and about which the components of the rotor 1010 are arranged concentrically.

[0094] The rotor body 1012 may be made from carbon fiber composite or other suitable lightweight and rigid material and includes an upper surface 1026, a lower surface 1028, a circumferential sidewall 1030, and an elongated bore 1032 passing through the upper and lower surfaces 1026, 1028. The elongated bore 1032 may be axially aligned with the axis of rotation 1024 and intersects an upper recess 1034 in the upper surface 1026 and a lower bore opening 1036 in the lower surface 1028 of the rotor body 1012. As described in more detail below, the lower bore opening 1036 may have a horizontal cross-sectional shape that is keyed to the drive hub 1020 to prevent rotation of the rotor body 1012 relative to the drive hub 1020.

[0095] The upper surface 1026 of the rotor body 1012 may include an annular surface 1038, a central surface 1040 recessed axially downward relative to the annular surface 1038, and an annular groove 1042. The annular groove 1042 may define an outer periphery 1044 of the annular surface 1038 and an upper edge 1046 of the circumferential sidewall 1030. The annular groove 1042 may be defined by an upper rabbet 1048 and a lower rabbet 1050 that overlap to define a shoulder 1052. The central surface 1040 may be connected to the annular surface 1038 by a connecting surface 1054. The connecting surface 1054 may extend axially upward and radially outward from the outer periphery of the central surface 1040 to the inner periphery of the annular surface 1038. The connecting surface 1054 may be oriented such that it faces axially upward and radially inward and may include a lower portion 1056 and an upper portion 1058. An upper portion 1058 of the coupling surface 1054 may be elevated above the lower portion 1056 in a direction perpendicular to the coupling surface 1054 .

[0096] The rotor body 1012 may further include a plurality of cavities 1060 (e.g., 12 cavities) each extending axially downward and radially outward into the rotor body 1012 from a lower portion 1056 of the coupling surface 1054. In one embodiment of the present invention, the plurality of cavities 1060 may comprise a plurality of circumferentially spaced tubular cavities, each having an open end configured to receive a sample vessel. Each cavity 1060 may have a central axis perpendicular to the coupling surface 1054 and may be of a size and shape suitable for receiving a sample vessel 1062. Each cavity 1060 may be configured to hold its respective sample vessel 1062 in a position and orientation suitable for centrifugation, e.g., at a 45-degree angle relative to the axis of rotation 1024.

[0097] Each sample vessel 1062 may be configured to hold a volume of sample suspension (e.g., 1.5 ml) and includes a cap 1064 that seals the sample vessel 1062 when pressed into a closed position. The cap 1064 may include a tab 1066 configured to facilitate opening of the sample vessel 1062. The cavity 1060, sample vessel 1062, and cap 1064 may be configured such that the tab 1066 is supported by the upper portion 1058 of the coupling surface 1054 when the sample vessel 1062 is fully inserted into its respective cavity 1060. The upper portion of the cavity 1060 may also include a counterbore 1067 configured to receive a cylindrical skirt of the cap 1064. Advantageously, pressure on the upper surface of the cap 1064 from the counterbore 1067 and the bottom surface of the lid 1018 may provide sufficient support to prevent deformation of the cap 1064 under the high g-forces generated by centrifugation. These features may thereby prevent the seal between the cap 1064 and the body of the sample vessel 1062 from being compromised or damage to the sample vessel 1062 itself.

[0098] The stiffener 1014 may include one or more helical windings extending around and above the circumferential sidewall 1030 of the rotor body 1012. The inner surface 1068 of the stiffener 1014 may cooperate with the annular groove 1042 of the rotor body 1012 to define a channel 1070 in which the balance ring 1016 is positioned. The stiffener 1014 may be formed by a filament winding process followed by a compression molding process using a suitable material, such as epoxy-coated carbon fiber. For example, the stiffener 1014 may be compression molded onto the rotor body 1012 and balance ring 1016 after laying down a layer of resin-coated carbon fiber laminate material or wrapping one or more strands of carbon fiber around the outward surface of the circumferential sidewall 1030.

[0099] To prevent axial movement of the stiffener 1014, the circumferential sidewall 1030 may include an inward taper that defines a circumferential recess 1072 in the circumferential sidewall 1030. The inner surface 1068 of the stiffener 1014 may conform to the circumferential recess 1072 such that the stiffener 1014 resists axial movement relative to the rotor body 1012. The stiffener 1014 may be configured to withstand a majority of the centrifugal forces exerted on the rotor 1010. Methods of forming centrifugal rotor stiffeners using a filament winding process are described in detail by U.S. Patent No. 8,323,169, issued December 4, 2012, the disclosure of which is incorporated herein by reference in its entirety.

[0100] The balance ring 1016 may include a body 1074 having a rectangular cross-section and a flange 1076. As best shown by FIG. 15 , the flange 1076 may protrude radially inward from a top of the body 1074 of the balance ring 1016 and may be configured to engage a shoulder 1052 of the rotor body 1012. In one embodiment of the present invention, the balance ring 1016 may have an outer diameter equal to or slightly larger than the diameter of the inner surface 1068 of the stiffener 1014. In this embodiment, the balance ring 1016 may be operably coupled to the rotor 1010 by cooling the balance ring 1016 to a temperature below ambient temperature such that the balance ring 1016 shrinks sufficiently such that its outer diameter is below the diameter of the inner surface 1068 of the stiffener 1014. The balance ring 1016 may then be placed in the channel 1070 and allowed to warm back up to ambient temperature. As it warms, the balance ring 1016 may expand until it compresses the inner surface 1068 of the stiffener 1014 so that it is held firmly in place. In an alternative embodiment of the invention, the balance ring 1016 may be heated to expand before placing it on the annular groove 1042, and cooled in place so that it is held in the rotor body 1012 by a shrink fit. In this case, the balance ring 1016 may be placed in the annular groove 1042 of the rotor body 1012 before forming the stiffener 1014. In either case, the stiffener 1014 may hold the balance ring 1016 in place. An adhesive may also be used to operably couple the balance ring 1016 to the annular groove 1042 of the rotor body 1012.

[0101] The balance ring 1016 may include a plurality of balancing apertures 1078, each configured to receive a balancing weight 1080. One or more balancing weights 1080 may be selectively positioned within one or more of the balancing apertures 1078 of the balance ring 1016 to balance the rotor 1010. In one embodiment of the present invention, each balancing weight 1080 may include a threaded shank 1082 and a head 1084. Each balancing aperture 1078 may include a threaded bore 1086 configured to receive the threaded shank 1082 of the balancing weight 1080, and a receptacle 1088 (e.g., a countersink, a counterbore, etc.) configured to receive the head 1084 of the balancing weight 1080. This allows the receptacle 1088 to allow the top of the balancing weight 1080 to be flush with or recessed below the top surface 1090 of the balance ring 1016 when the balancing weight 1080 is fully inserted into the balancing aperture 1078.

[0102] The balance ring 1016 may be angularly positioned about the axis of rotation 1024 relative to the rotor body 1012 such that the balancing apertures 1078 of the balance ring 1016 are symmetrically positioned relative to the cavities. This symmetry ensures that each of the two balancing apertures 1078 closest to a respective cavity 1060 in the rotor body 1012 is equidistant from and on either side of a line extending radially outward from the axis of rotation 1024 and passing through the central axis of the cavity 1060. This angular positioning of the balance ring 1016 may provide a ring with an orientation such that each cavity 1060 in the rotor body 1012 is angularly centered between the two balancing apertures 1078 of the balance ring 1016 closest to the cavity 1060, ensuring positional symmetry between the cavities 1060 in the rotor body 1012 and the balancing apertures 1078 of the balance ring 1016.

[0103] The balance ring 1016 may be made of aluminum or any other suitable lightweight, rigid material. One or more balancing weights 1080 may be selectively placed in each balancing aperture 1078 to offset imbalances in the rotor 1010. For example, balancing weights 1080 may be added to align the center of gravity of the rotor 1010 with the axis of rotation 1024 (i.e., to achieve static balance), to align the principal axes of the rotor's moments of inertia with the axis of rotation 1024 (i.e., dynamic balance), or to ensure that the rotor 1010 is both statically and dynamically balanced. As described above with respect to FIGS. 9-9C , balancing weights 1080 may be added to the balance ring 1016 during the modal balancing process.

[0104] The lid 1018 of the rotor 1010 may include an annular wall 1092, a central wall 1093, and a conical wall 1094 and may be made from carbon fiber composite, aluminum, or any other suitable rigid, low-mass material. The conical wall 1094 of the lid 1018 may connect an inner edge 1095 of the annular wall 1092 to an outer edge 1096 of the central wall 1093. The conical wall 1094 may be joined to each of the central and annular walls 1092, 1093 of the lid 1018 at an obtuse angle such that the annular wall 1092 is axially offset from and parallel to the central wall 1093. The resulting shape of the lid 1018 may generally conform to the shape of the top surface 1026 of the rotor body 1012.

[0105] The annular wall 1092 of the lid 1018 may include a lower surface 1098 having an annular groove 1100 configured to receive a resilient member 1102, such as an O-ring. The resilient member 1102 may be made of any suitable material (e.g., silicone) and may be configured to engage the upper surface 1090 of the balance ring 1016 when the lid 1018 is operably coupled to the rotor 1010.

[0106] The central wall 1093 of the lid 1018 may include an upper surface 1104, a central bore 1106, and a lid lifting handle 1108 projecting axially upward from the upper surface 1104. The central bore 1106 may have the same diameter as the elongated bore 1032 of the rotor body 1012 such that the bore is axially aligned by the drive hub 1020. The lid lifting handle 1108 may include a cylindrical wall 1109 joined to the lid 1018 at its lower end and having an inner surface 1110, and a flange 1112 projecting radially outward from the top of the lid lifting handle 1108 at a free end of the cylindrical wall 1109 remote from the central wall 1093 of the lid 1018. The flange 1112 of the lid lifting handle 1108 may provide a grip for gripping the rotor 1010. This gripping portion may improve ease of installation and removal of the rotor 1010 into and from a centrifuge compared to rotors lacking this feature. The inner surface 1110 of the cylindrical wall 1109 may include a neck 1114 proximate or adjacent to the top surface 1104. The neck 1114 may have a diameter d1 that is smaller than a diameter d2 of a major portion of the inner surface 1110. The major portion of the inner surface 1110 may be joined to the neck 1114 by a bevel 1116.

[0107] The drive hub 1020 may include a shaft 1120, a flange 1122 projecting radially outward from the bottom of the shaft 1120, and a central bore 1124 extending axially within the bottom end of the shaft 1120. The central bore 1124 of the drive hub 1020 is axially aligned with the rotational axis 1024 of the rotor 1010, includes a bottom surface 1130, and may be configured to receive a centrifuge spindle (not shown). An upper portion 1126 of the shaft 1120 may be configured to receive the cap screw 1022. To this end, the upper portion 1126 of the shaft 1120 may include a threaded outer surface 1128 configured to threadably mate with the cap screw 1022.

[0108] The portion of the shaft 1120 adjacent to and below the threaded outer surface 1128 may have a small radius (e.g., an undercut) to provide thread relief. This thread relief may ensure that the lower surface 1148 of the flange 1146 engages the upper surface 1104 of the central wall 1093 of the cap screw 1018 without interference from the shaft 1120 when the cap screw 1022 is threaded with the drive hub 1020. The upper portion 1126 of the shaft 1120 may include a protruding end 1129 thereon. The protruding end 1129 may have a diameter approximately the same as the minor diameter of the threaded outer surface 1128 and may extend a distance of 1.5 to 2.5 thread widths beyond the threads of the threaded outer surface 1128. The drive hub 1020 may be manufactured from a solid billet of metal using computer numerically controlled (CNC) machining or any other suitable process.

[0109] To prevent the drive hub 1020 from rotating relative to the spindle, one or more drive pins 1132 may extend axially downward from a bottom surface 1130 of the central bore 1124. Each drive pin 1132 may be configured to engage a respective receptacle on the centrifuge spindle. Each drive pin 1132 may include a rod 1134 inserted into a respective bore 1136 extending axially into the bottom surface 1130 of the central bore 1124. Each bore 1136 may be radially offset from the central axis of the central bore 1124, such that the drive pins 1132 may be subjected to shear forces in response to the spindle applying sufficient torque to the rotor 1010 to cause slippage between the spindle and the drive hub 1020 in the absence of the drive pins 1132.

[0110] The drive portion 1138 of the hub 1020 may extend axially upward from the flange 1122 and radially outward from the shaft 1120. The drive portion 1138 of the hub 1020 may have a horizontal cross-sectional shape that is keyed to or otherwise complements the horizontal cross-sectional shape of the lower bore opening 1036 of the rotor body 1012. Keying the drive portion 1138 to the lower bore opening 1036 may prevent the angular position of the rotor body 1012 from shifting relative to the drive hub 1020 under angular acceleration. To this end, the cross-sectional shape of the drive portion 1138 may be the same as the cross-sectional shape of the lower bore opening 1036, have one or more surfaces 1139 that fit within and engage corresponding surfaces 1141 in the sidewall of the lower bore opening 1036, or may be a different shape that is differently keyed to the cross-sectional shape of the lower bore opening 1036.

[0111] For example, the cross-sectional shape of the drive portion 1138 may be a polygon (e.g., a square) with the same number of faces 1139 as the shape of the lower bore opening 1036, or more faces 1139. By way of example, in the case of a lower bore opening 1036 having a square horizontal cross-section, the drive portion 1138 may have a square, octagonal, or other cross-sectional shape in which one or more faces 1139 complement faces 1141 of the lower bore opening 1036. The lower bore opening 1036 may also include one or more axially aligned channels 1143 that are otherwise positioned such that the apexes of the faces 1141 facilitate insertion of the drive portion 1138 of the drive hub 1020 into the lower bore opening 1036.

[0112] The lid screw 1022 may be made from any suitable material (e.g., aluminum) and comprises a cylindrical body having an outer surface 1140, an upper bore 1142, a lower bore 1144, and a flange 1146 protruding radially outward from the lower end of the cylindrical body. The flange 1146 may have an outer diameter that is the same as or slightly smaller than the diameter d1 of the neck 1114. The bevel 1116 may guide the flange 1146 into the neck 1114 when the flange 1146 is inserted into the lid lifting handle 1108 and the lid screw 1022 is threaded onto the drive hub 1020. The neck 1114 and bevel 1116 thereby work in concert with the flange 1146 to position the lid screw 1022 concentrically with the lid 1018 and drive hub 1020, thereby aligning the lid 1018 with the axis of rotation 1024 of the rotor 1010 during engagement of the lid screw 1022 with the drive hub 1020. The final alignment between the lid 1018 and the axis of rotation 1024 of the rotor 1010 may be defined by engagement of the shaft 1120 of the drive hub 1020 with the central bore 1106 of the lid 1018.

[0113] The flange 1146 may include a lower surface 1148 having an annular groove 1150 configured to receive a resilient member 1152. The resilient member 1152 may be an O-ring or other type of gasket made of a suitable material, such as silicone. The resilient member 1152 may be compressed against the upper surface 1104 of the central wall 1093 of the lid 1018 in response to tightening of the lid screws 1022 onto the drive hub 1020. The resilient member 1152 may thereby urge the lid 1018 into operative engagement with the rotor 1010.

[0114] The lid screw 1022 may further include one or more pairs of radially aligned holes 1156 on opposite sides of the upper bore 1142. The radially aligned holes 1156 may be configured to receive a rod or other tool for applying torque to the lid screw 1022. The radially aligned holes 1156 may thereby facilitate tightening and loosening the lid screw 1022 to the drive hub 1020.

[0115] The lower bore 1144 of the lid screw 1022 may include a threaded inner surface 1158 configured to threadably mate with the threaded outer surface 1128 of the drive hub 1020. The protruding end 1129 of the shaft 1120 may facilitate this threading between the drive hub 1020 and the lid screw 1022 by providing a tactile start for engagement between the threaded outer surface 1128 of the shaft 1120 and the threaded inner surface 1158 of the lower bore 1144. Threading of the lid screw 1022 with the drive hub 1020 may urge the lid 1018 against at least a portion of the upper surface 1026 of the rotor body 1012. The lid screw 1022 also urges the lid 1018 against the cap 1064 of the sample vessel 1062, thereby keeping the cap 1064 fully seated on the sample vessel 1062. In this manner, the lid 1018 may also hold the sample vessels 1062 in a fully seated position within their respective cavities 1060 by applying a nominal force to the face of each cap 1064 .

[0116] Embodiments of the present invention that include balancing rings may be balanced using a modal balancing process 945 in a manner similar to that described above with respect to FIGS. 9-9D. That is, process 945 may determine one or more critical modes of rotor 1010 by applying external forces to rotor 1010 while rotor 1010 is rotated at each of a plurality of rotational speeds. Process 945 may measure and record the vibration response at each rotational speed. Based on this data, process 945 may determine the severity of vibration at each rotational speed. Process 945 may then identify the rotational speed with the most severe vibration as the critical speed.

[0117] Once the critical speeds are identified, process 945 may spin rotor 1010 in centrifuge 100 at an initial test speed that is a fraction of the critical speed, e.g., the lowest critical speed. Process 945 may measure and record the imbalance of rotor 1010 experienced while rotor 1010 is spinning at the initial test speed, e.g., as an RMS value of the power spectral density of vibrations detected in components of centrifuge 100, e.g., motor bearings.

[0118] A trial weight of known mass may then be placed within the balancing aperture 1078 at a reference location on the balance ring 1016, which may be at any balancing aperture 1078 on the balance ring 1016, as long as the same balancing aperture 1078 is used as the reference aperture for the remainder of the balancing process. To facilitate consistent placement of the weight within the balance ring 1016, one or both of the rotor body 1014 and the balance ring 1016 may include a reference mark proximate one of the balancing apertures 1078. One or more reference marks may also be included on the lid 1018 and rotor body 1014 to facilitate placing the lid 1018 in the same position relative to the rotor body 1014 during use of the rotor 1010.

[0119] The balancing process 945 may then spin the rotor 1010 at an initial test speed and measure and record the imbalance of the rotor 1010 with the trial weight in place, for example, by determining and recording the RMS value of the power spectrum of the measured vibration response. The trial weight may then be moved to another balancing aperture 1078, and the resulting imbalance may be measured and recorded as described above. The process of moving the trial weight and measuring the rotor imbalance may be repeated until sufficient imbalance measurements have been recorded to determine where correction masses need to be placed on the balance ring 1016 and how large the correction masses must be to counteract the inherent imbalance of the rotor 1010. One or more balancing weights 1080 may then be placed in each balancing aperture 1078 of the balance ring 1016, for example, providing balancing masses close to or equivalent to the correction masses, using the simultaneous equations described above with respect to adding balancing weights 436 to the lid 212.

[0120] The above process of placing trial weights in balancing apertures 1078 of balance ring 1016, spinning rotor 1010 at a test speed, measuring and recording the unbalance, and placing balancing weights 1080 in balance ring 1016 to balance the rotor may be repeated 1010 for one or more additional critical speeds to achieve an appropriate level of balance. The rotor 1010 may then be spun at a target speed, the unbalance measured and recorded, and the unbalance compared to the unbalance recorded at some other rotational speed (e.g., the initial test speed) to determine if the rotor 1010 is properly balanced.

[0121] Experimental results FIG. 19 shows a graph including a three-dimensional plot 1160 (sometimes referred to as a waterfall plot) of experimentally measured rotor vibration response as a function of rotational speed and excitation frequency. The vibration data was generated using a SORVAL MX Plus micro-ultracentrifuge to spin the rotor, including the balance ring, in accordance with one embodiment of the present invention. The SORVAL MX Plus micro-ultracentrifuge is available from Thermo Fisher Scientific of Waltham, Massachusetts, United States. Prior to measuring the vibration data shown in plot 1160, the rotor was modally balanced for critical speeds of 5,000, 37,000, and 55,000 RPM by selectively adding balancing weights to the balancing apertures of the balance ring.

[0122] Plot 1160, commonly referred to as a Campbell diagram, includes one horizontal axis 1162 corresponding to the rotational speed of the rotor, another horizontal axis 1164 corresponding to the frequency of vibration detected by the vibration sensor, and a vertical axis 1166 corresponding to the amplitude of the detected vibration in decibels (dB) relative to a reference level. Plot 1160 includes multiple slices 1168, each corresponding to the rotational speed of the rotor. Each slice 1168 includes a peak 1170 corresponding to the rotor's natural frequency at that rotational speed. For example, slice 1168a corresponds to a rotational speed of 5,000 RPM and has peak 1170a occurring at 83 Hz. Other peaks 1170 include peak 1170b on slice 1168b, which corresponds to a natural frequency of 617 Hz for a rotational speed of 37,000 RPM, and peak 1170c on slice 1168c, which corresponds to a natural frequency of 917 Hz for a rotational speed of 55,000 RPM. As can be seen, the vibration response of the modally balanced rotor performed well over the entire test range of 5,000 to 55,000 RPM.

[0123] Figure 20 shows the 12 x 1.5 mL fixed-angle rotor 1172 used to generate the test data described above. The rotor 1172 includes a balance ring 1174 with 24 balancing apertures 1176 and contains 12 sample containers 1178. During the modal balancing process, one balance weight 1180a was installed to compensate for the imbalance at 5,000 RPM, another balance weight 1180b was installed to compensate for the imbalance at 37,000 RPM, and a final balance weight 1180c was installed to compensate for the imbalance at 55,000 RPM.

[0124] Figures 21-23 show graphs 1182-1184 of the experimentally measured vibration response of a rotor before any balancing was performed on the rotor (graph 1182), after the rotor was balanced on hard bearings (graph 1183), and after modal balancing of the rotor according to an embodiment of the present invention (graph 1184). The vibration data was generated by spinning the rotor at 37,000 RPM using a SORVAL WX+ Series micro-ultracentrifuge. This centrifuge is also available from Thermo Fisher Scientific Inc. The rotor used was an 8 x 100 mL rotor with a lid having 24 balancing apertures.

[0125] Each graph 1182-1184 includes a horizontal axis 1186 corresponding to time in seconds and a vertical axis 1188 corresponding to acceleration due to vibration in units of g, which corresponds to gravity. Each graph 1182-1184 includes a respective plot 1190-1192 of the rotor's vibration response. The RMS value of the vibration acceleration shown in plot 1190, without balancing (i.e., the vibration of the unbalanced rotor), is approximately 0.43 g, with a peak value of slightly more than 0.60 g. The RMS value of the vibration acceleration shown in plot 1191 is approximately 0.20 g, i.e., slightly less than half the RMS vibration magnitude of the unbalanced rotor. In contrast, the RMS value of the vibration acceleration shown in plot 1192 is approximately 0.06 g. Therefore, the vibration acceleration of the modally balanced rotor is only approximately 28% of that of the conventionally balanced rotor and only approximately 13% of that of the unbalanced rotor.

[0126] FIG. 24 shows a graph 1193 illustrating vibration RMS level versus rotational speed. Graph 1193 includes a horizontal axis 1194 corresponding to rotor rotational speed (RPM x 1,000) and a vertical axis 1195 corresponding to the RMS value of the sensed vibration (g). Plot 1196 shows the vibration level of the conventionally balanced rotor that generated the data shown in FIG. 22, and plot 1197 shows the vibration level of the modularly balanced rotor that generated the data shown in FIG. 23. Lower threshold 1198 indicates an exemplary 0.3 g threshold for the centrifuge's acceptable vibration tolerance limit, while upper threshold 1199 indicates an exemplary 0.7 g imbalance switch trigger limit at which the centrifuge may be shut down. As can be seen, the RMS vibration of the conventionally balanced rotor increases with increasing rotational speed. In contrast, the RMS vibration of the modally balanced rotor is lower than that of the conventionally balanced rotor at all speeds. In the particular example shown, the RMS vibration reaches a maximum value between 15,000 and 20,000 RPM and then decreases with increasing rotational speed. However, there may be slight variations at various speeds for different serial numbers of the same rotor model. Thus, graph 1193 in FIG. 24 provides an overview of the effectiveness of modal balancing on centrifuge rotors, particularly those driven by flexible spindles. In any event, it should be clear that modally balanced rotors can be operated at higher rotational speeds and with less vibration than conventionally balanced rotors.

[0127] 25 , the above-described embodiments of the present invention, or portions thereof, may be implemented using one or more computing devices or systems, such as an exemplary computer 1200. The computer 1200 may include a processor 1202, a memory 1204, an input / output (I / O) interface 1206, and a human-machine interface (HMI) 1208. The computer 1200 may also be operatively coupled to one or more external resources 1210 via the I / O interface 1206 or a network 1212. The external resources may include, but are not limited to, servers, databases, mass storage devices, peripheral devices, cloud-based network services, or any other resources that may be used by the computer 1200.

[0128] Processor 1202 may include one or more devices selected from a microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuit, analog circuit, digital circuit, or any other device that manipulates signals (analog or digital) based on operational instructions stored in memory 1204. Memory 1204 may include a single memory device or multiple memory devices, including, but not limited to, read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, cache memory, or a data storage device such as a hard drive, optical drive, tape drive, volatile or non-volatile solid state device, or any other device capable of storing data.

[0129] Processor 1202 may operate under the control of operating system 1214 on memory 1204. Operating system 1214 may manage computer resources such that computer program code embodied as one or more computer software applications, such as applications 1216, resident in memory 1204 may have instructions executed by processor 1202. In alternative embodiments, processor 1202 may execute applications 1216 directly, in which case operating system 1214 may be omitted. One or more data structures 1218 may also reside in memory 1204 and may be used by processor 1202, operating system 1214, or applications 1216 to store or manipulate data.

[0130] I / O interface 1206 may provide a machine interface that operatively couples processor 1202 to other devices and systems, such as external resources 1210 or network 1212. Applications 1216 may thereby cooperate with external resources 1210 or network 1212 by communicating via I / O interface 1206 to provide various features, functions, applications, processes, or modules that comprise embodiments of the present invention. Applications 1216 may also have program code that is executed by one or more external resources 1210 or that relies on functions or signals provided by other systems or network components external to computer 1200. Indeed, given the nearly infinite number of possible hardware and software configurations, those skilled in the art will understand that embodiments of the present invention may include applications provided by computing resources (hardware and software) that are located outside computer 1200, distributed across multiple computers or other external resources 1210, or offered as a service over network 1212, such as a cloud computing service.

[0131] The HMI 1208 may be operatively coupled to the processor 1202 of the computer 1200 and may allow a user to interact directly with the computer 1200. The HMI 1208 may include a video or alphanumeric display, a touch screen, a speaker, and any other suitable audio and visual indicators capable of providing data to a user. The HMI 1208 may also include input devices and controls, such as an alphanumeric keyboard, a pointing device, a keypad, push buttons, control knobs, a microphone, etc., capable of accepting commands or input from a user and transmitting the entered input to the processor 1202.

[0132] Database 1220 may reside in memory 1204 and may be used to collect and organize data used by the various systems and modules described herein. Database 1220 may include data and supporting data structures that store and organize the data. In particular, database 1220 may be arranged in any database organization or structure, including, but not limited to, a relational database, a hierarchical database, a network database, or combinations thereof. A database management system in the form of a computer software application executing as instructions on processor 1202 may be used to access information or data stored in records of database 1220 in response to queries, which may be dynamically determined and executed by operating system 1214, other applications 1216, or one or more modules.

[0133] In general, the routines executed to implement embodiments of the present invention may be referred to herein as "computer program code," or simply "program code," whether executed as part of an operating system or a specific application, component, program, object, module, or sequence of instructions, or any subset thereof. Program code typically resides at various times in various memory and storage devices within a computer, and comprises computer-readable instructions that, when read and executed by one or more processors within the computer, cause the computer to perform the operations necessary to carry out the operations or elements embodying various aspects of embodiments of the present invention. Computer-readable program instructions for carrying out operations of embodiments of the present invention may be, for example, assembly language, source code, or object code written in any combination of one or more programming languages.

[0134] Various program code described herein may be identified based on the application in which it is executed within a particular embodiment of the invention. However, it should be understood that the specific program nomenclature below is used merely for convenience, and thus the present invention should not be limited to use with only the specific application identified or implied by such nomenclature. Furthermore, given the generally limitless number of ways in which computer programs may be organized into routines, procedures, methods, modules, objects, etc., as well as the various ways in which program functionality may be allocated among the various software layers (e.g., operating system, libraries, APIs, applications, applets, etc.) resident in a typical computer, it should be understood that embodiments of the present invention are not limited to the specific organization and allocation of program functionality described herein.

[0135] The program code embodied in any of the applications / modules described herein may be distributed individually or collectively as a computer program product in a variety of different forms. In particular, the program code may be distributed using a computer-readable storage medium having computer-readable program instructions thereon to cause a processor to perform aspects of embodiments of the present invention.

[0136] Computer-readable storage media that are non-transitory in nature may include volatile or non-volatile, removable and non-removable tangible media implemented in any method or technology for storing data, such as computer-readable instructions, data structures, program modules, or other data. Computer-readable storage media may also include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other solid-state memory technology, portable compact disc read-only memory (CD-ROM), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to store data and that can be read by a computer. Computer-readable storage media should not be interpreted as transient signals themselves (e.g., radio waves or other propagating electromagnetic waves, electromagnetic waves propagating through a transmission medium such as a waveguide, or electrical signals transmitted through wires). The computer-readable program instructions may be downloaded into a computer, another type of programmable data processing apparatus, or another device from a computer-readable storage medium, or over a network to an external computer or external storage device.

[0137] Computer-readable program instructions stored on a computer-readable medium can be used to instruct a computer, other type of programmable data processing apparatus, or other device to function in a particular manner, such that the instructions stored on the computer-readable medium produce an article of manufacture that includes instructions that perform the functions, acts, or operations specified in the flowchart, sequence diagram, or block diagram. The computer program instructions are provided to one or more processors of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus to produce a machine such that the instructions, executed by the one or more processors, cause the machine to perform a series of calculations to perform the functions, acts, or operations specified in the text of the specification, flowchart, sequence diagram, or block diagram.

[0138] The flowcharts and block diagrams depicted in the figures illustrate the architecture, functionality, or operation of possible implementations of systems, methods, or computer program products according to various embodiments of the present invention. In this regard, each block in the flowcharts or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing a specified logical function(s).

[0139] In certain alternative embodiments, the functions, acts, or operations specified in a flowchart, sequence diagram, or block diagram may be reordered, processed sequentially, or processed simultaneously, consistent with embodiments of the present invention. Moreover, any flowchart, sequence diagram, or block diagram may include more or fewer blocks than shown, consistent with embodiments of the present invention. It should also be understood that each block of a block diagram or flowchart, or any combination of blocks in a block diagram or flowchart, may be implemented by a dedicated hardware-based system configured to perform the specified functions or acts, or may be performed by a combination of dedicated hardware and computer instructions.

[0140] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include both the singular and the plural, and the terms "and" and "or" are each intended to include both alternatives and conjunctions unless the context clearly dictates otherwise. Furthermore, as used herein, it should be understood that the terms "comprises" or "comprising" specify the presence of stated features, integers, acts, steps, operations, elements, or components, but do not exclude the presence or addition of one or more other features, integers, acts, steps, operations, elements, components, or groups thereof. Furthermore, to the extent the terms "including," "having," "having," "comprising," or variations thereof are used in either the detailed description or the claims, such terms are intended to be inclusive as synonyms of the term "comprising."

[0141] While the present invention has been illustrated in its entirety by description of exemplary embodiments and those embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will be readily apparent to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicants' general inventive concept.

Claims

[Claim 1] 1. A rotor for use in a centrifuge, comprising: a rotor body including a rotating shaft; a plurality of balancing apertures arranged circumferentially about the axis of rotation, each balancing aperture configured to selectively receive a weight; Rotor.

Images