JPH0761455B2 - Centrifuge rotor - Google Patents

Description

TECHNICAL FIELD The present invention relates to ultra high speed centrifuge rotors, and more particularly to synthetic material rotors made of low density and high strength materials.

(Prior Art) Ultracentrifuge rotors are subjected to forces of 600,000 g or more which result in stresses that eventually result in wear and disassembly on the rotor body. All centrifuge rotors have a limited lifespan before breakage and fatigue of the materials that make up the rotor preclude further use of the centrifuge.

The high rotational speeds that occur during centrifugation and the stresses that occur in the rotor due to centrifugal forces are one cause of rotor failure. Metallic fatigue occurs in conventional rotors following a number of repeated stress cycles. The metal stretching cycle changes its microstructure as the rotor repeatedly, reaches working speed, is operated and decelerated. The small change causes microscopic cracking after many cycles. With increasing use, fatigue cracks grow and eventually lead to rotor damage. Also, the stress of the conventional metal rotor body causes the rotor to expand and change its dimensions. When the metal rotor body reaches its elastic limit, the rotor does not return to its original shape, then
Causes rotor damage.

Conventional rotors made of alloys of titanium and aluminum have considerably high strength for their weight. Aluminum rotors are lighter than titanium ones and experience less physical stress and less kinetic energy when operated at ultracentrifugation speeds. However, titanium rotors have better corrosion resistance than aluminum rotors.
As the performance and speed of ultracentrifugation increases, the safe operating limits of centrifuges reside in traditional density yet heavy metal rotors.

One attempt to overcome the design limitations imposed is shown in U.S. Pat. No. 3,997,106 to Balaam, where a centrifuge rotor consists of two layers of different materials laminated together.
A wire is wrapped around a metal cover surrounding a chemical resistant plastic center filler. U.S. Pat. No. 3,997,106 to Balam contemplates a rotor with high chemical resistance and low specific gravity that achieves optimum strength through the use of a laminate manufacturing method. U.S. Pat. No. 2,974,684 to Ginaven is directed to a woven wire cloth mesh that reinforces a liner of plastic material for use in a centrifugal cleaner.

Green (No. 1,827,648), The Itzel (No. 3,993,2)
U.S. Pat. No. 43) and Lindgen (4,160,521) are all directed to rotor bodies consisting of resin and fibrous reinforcement. In particular, US Patent No.
No. 1,827,648 has 7,500 to 10,000 RPM rotor buckets
To create a moment of inertia about a vertical axis greater than a moment of inertia about a horizontal axis through the center of gravity of the bucket so that it stabilizes at its rotational speed (relatively slow centrifugation speed according to current standards). Directed to the struck fiber.

U.S. Pat. No. 4,468,269 discloses an ultracentrifugal rotor that encloses the tubular wall of the metal body of the rotor and includes a plurality of nested rings of filament windings. The telescopic ring reinforces the metal rotor body,
Provides strength and rigidity to the rotor. The rings are nested together by applying a thin epoxy coating between the layers. U.S. Pat.No. 3,913,828 to Roy
It discloses a structure substantially equivalent to that disclosed in 4,468,269.

None of the conventional constructions provide maximum strength during ultracentrifugation speeds through the use of materials specifically designed to accommodate local stresses and resist rotor body fatigue. Conventional metal bodies, ie the metal bodies of reinforced rotors, are subject to metal stress and fatigue failure during centrifugation.

What is needed is a rotor body of substantial strength, yet lightweight, capable of withstanding increasing high loads and high speeds.

The rotor body must withstand special stresses and corrosion and be specially designed to resist local stresses.

Structure of the Invention Described herein is a centrifuge rotor body made of multiple layers of anisotropic materials. (As used herein, the term "anisotropic" means a material that has properties such as bulk modulus, strength and stiffness in a particular direction.) Each layer is a particular It has different modulus or tensile strengths, fine tuned based on rotor geometry, load at design speed or size to accommodate stress.

In each particular layer, a selected portion of the material is oriented in a different direction than the main body of the layer to reinforce the test tube receiving cavity of the rotor and to accommodate the excessive stresses that occur in it. To be

In the preferred embodiment, the anisotropic material layer is made of fibrous filaments wrapped in synthetic material, where the fibers are graphite and the resin is epoxy. Each of the layers forms a disk of synthetic material, each disk extending radially from the central axis of the rotor and secured to the other disk by an epoxy adhesive.

(Embodiment) Referring to FIGS. 1 and 2, a synthetic rotor 10 (FIG. 2) is shown in its entirety. The rotor 10 is composed of a plurality of layered discs as shown at 26 and 28 (FIG. 2).

The synthetic materials selected for construction of the rotor of the preferred embodiment include (but are not limited to) graphite fiber filaments wound in an epoxy resin or a thermoplastic or thermosetting matrix. Fiber amount is 60%
That is all. This configuration has a density of about 0.065 lb / in ³ and is made of aluminum (0.11 lb / in ³ ) and titanium (0.16 lb / in ³ ).
Advantageous compared to conventional rotor designs including / in ³ ). Alternative fiber filaments include glass, boron and graphite. The fibrous material Kevlar (trade name), which is an organic fiber manufactured by DuPont, is also useful in place of graphite.

Due to the high stresses caused by ultracentrifugation, material selection is affected by the need for "anisotropic" materials such as graphite synthetic filament wraps.

In the preferred embodiment, a vertical tube rotor 10 represents the design principle of the present invention.

Referring to the plan view of rotor 10 shown in FIG.
The varying densities of the rotor 10 filament design are separated by circular boundaries 24 and 18. The inner area from the circumference of the circle 18 to the rotor shaft cavity 14 is wound to have the same density as the portion of the circle 24 beyond the outer boundary. The area 12 between the circular boundaries 18 and 24 is characterized by a denser wound filament, as shown in area 30 of FIG. When the center of the rotor 10 is adapted for insertion of the drive shaft 32 (FIG. 2) into the drive shaft cavity 14 from below the rotor, the upper surface of the rotor 10 is inserted into the machined cavity 20 into a metal test tube insert 16. Suitable for insertion. The test tube 22 is then inserted into the test tube insert 16 so that it fits snugly within the body of the rotor 10.

In a vertical test tube rotor 10, as shown in FIGS. 1 and 2, the stress is greatest in the upper layer, particularly in area 30 of FIG. 2 where the maximum stress is shown as the hoop stress. One test tube cap (aluminum, synthetic or rubber) is placed on top of the rotor for each test tube. Screwing these caps onto the rotor body causes additional stress on the rotor body at the point of cap insertion.

A significant advantage of using a composite construction is that the elastic modulus
Signs to be adjusted to accommodate the specific stresses experienced at each of the 10 interiors and several locations around it
Each layer as shown at 26 and 28 is to form a uniquely tuned disc.

Each of the disks, such as disks 26 and 28, is a filament wrap around a central core. 1,000, 3,000, 6,00 fiber filaments per bundle
At least four types of sizes of 0 and 12,000 fibers are available. The preferred embodiment is 12 per bundle
It uses a bundle of 000 filament fibers. The filament bundles are wound to provide a tension range of 2 to 10 pounds per bundle, and this tension results in multiple disks. Average density of synthetic disc is 0.065l
b / in ³ . These discs, like disc 28, are subject to greater stresses during the operation of the rotor and are therefore created with greater tension than discs such as disc 40 which are subject to less stress.

Each disk is individually machined to form a cavity, such as machined cavity 20. Once formed, cured and machined, the disks are stacked along the longitudinal central axis of the axial cavity 14 and sandwiched between the layered disks 42, 40, 26 and 28.
41, 34, 36 and 38 are fixed to each other by the layered application of epoxy resin. After the epoxy resins 41, 34, 36 and 38 have been applied between the disc layers, the entire assembly is then cured in a furnace, which produces the composite rotor 10.

Each disk is uniquely wound to accommodate the local stresses the assembled rotor will experience during centrifugation. For example, the disk 26 is shaped and manufactured to accommodate different local stresses along its radius. Each disk may be manufactured from different grades or tensile strength fiber filament materials. The fiber wrapping angle may be changed from wrapping parallel to the horizontal plane. Around the core cavity 14, outside the circular boundary 18, the fibers are wound at 0 ° with respect to the horizontal plane of the rotor 10. When the filament is wound in the area between the boundaries 18 and 24, the wrapping of the filament in the vicinity of the machined cavity 20 provides for additional support to surround the cavity 20 relative to the horizontal plane. Carefully wound so that they intersect at an angle of approximately ± 45 °. The intersecting stitches of filament fibers in the area 12 (FIG. 1) between the boundaries 18 and 24 ensure that the material strength of the rotor is not reduced by the presence of the machined cavity as shown at 20. To provide the cavity 20 with additional support. Optimal strength is obtained when the fibers are wound at an angle of approximately ± 45 ° where they intersect. However, the use of angular ranges achieves high strength over horizontal winding if it is changed from the optimum value of ± 45 ° by 10 ° in each direction (from ± 35 ° to ± 55 ° from horizontal).

Further, the disk 28 and the disks above it are stiffer and taller than the material used to build the layers 28 and below to accommodate the maximum hoop stress zone at the top of the rotor 10 in a vertical tube. Made of tensile strength filament material. Therefore, in order to respond to the different stresses experienced by the disks 26 and 28 with different tensile strengths, the disks
In order to fine tune and change the reference dimensions of 26 and 28, the winding direction is not only different, as the disk 26 is different from 28, to accommodate the high stresses around the cavity 20, but also the filament wound on the disk. The materials made from the fibers are also different. By having separate discs, expensive, strong discs are used only where needed. The multiple disks allow the rotor to be specially designed to resist it only at the points of high local stress.

If a different design than a vertical tube rotor is contemplated, such as a fixed angle rotor body, then the position of maximum stress for a fixed angle rotor is different from the position of maximum stress for a vertical tube rotor.
The maximum stress on the disc is located about 2/3 of the downward direction of the rotor body.

It will be appreciated that the preferred embodiment allows for the use of separate discs that make up the rotor body, rather than one continuous wrap defining the entire rotor. Such a unitary structure is within the scope of the present invention and the fibers are reoriented or reoriented to accommodate the large stresses shown in FIG. 2 in the area between boundaries 24 and 18. However, the preferred embodiment is wound on the body because it is clearly not possible with a single rotor to overcome the axial residual stresses that occur when the fiber wound on the disk exceeds the empirically derived width. Intended for multiple tethered discs rather than single fibers. Also, single filament wound synthetic rotors cannot have multiple fibrous filaments selected for different parts of the rotor body.

[Brief description of drawings]

 FIG. 1 is a plan view of a synthetic material rotor according to the present invention. FIG. 2 is a vertical sectional view of a synthetic material rotor according to the present invention. 10 …… Rotor, 26,28,40,42 …… Disk, 34,36,38,41 …… Epoxy resin, 22 …… Test tube.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 61-153164 (JP, A) JP-A 58-219958 (JP, A)

Claims (12)

[Claims] 1. A centrifuge rotor comprising a body comprising a plurality of layers of anisotropic material, each layer having a predetermined modulus to accommodate the individual stresses experienced by the layers. 2. A method according to claim 1, wherein each of the layers is a disk in which a synthetic material of fiber filament winding extends in a radial direction, and each of the disks has the layers fixed to each other by a resin. The centrifuge rotor according to item (1). 3. A centrifuge according to claim (2), which comprises changing the orientation of the filaments in an anisotropic layer selected to accommodate insertion and support of multiple test tubes. Rotor. 4. The centrifuge rotor according to claim (2) or (3), wherein the fiber filament is graphite and the resin is epoxy. 5. The centrifuge rotor according to claim (2) or (3), wherein the resin is thermoplastic. 6. The centrifuge rotor according to claim (2) or (3), wherein the resin is thermosetting. 7. The fiber filament is made of a material selected from the group consisting of glass, boron or graphite.
Centrifuge rotor according to paragraph. 8. The centrifuge rotor according to claim 3, wherein the filaments are reoriented at an angle in the range of 35 ° to 55 ° with respect to the horizontal plane of the rotor. 9. The method of claim 3 wherein the filaments of the selected anisotropic layer of the rotor are reoriented at an angle of approximately 45 ° with respect to the horizontal plane of the rotor. The described centrifuge rotor. 10. A body comprising at least one layer of anisotropic material, said layer being a disk of filament wound fibers adhered by a resin material, said disk comprising the material of the disk. Of fibers, the fibers being reoriented such that successive windings of the fibers intersect one another to provide additional strength to the disc material at selected locations where the greatest stress is expected. , Centrifuge rotor. 11. The centrifuge of claim 10, wherein the filament-wound fibers intersect each other at a reorientation angle in the range of 35 ° to 55 ° with respect to the horizontal plane. Machine rotor. 12. The centrifuge rotor of claim 10 wherein the filament wound fibers intersect each other at a reorientation angle of approximately 45 °.