JPS63296856A - Rotor of centrifugal separator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD This invention relates to ultrahigh speed centrifuge rotors, and more particularly to composite rotors made of low density and high strength materials.

BACKGROUND OF THE INVENTION Ultracentrifuge rotors are subjected to forces of 6 o'o, ooog or more that create stresses that ultimately lead to wear and disintegration of the rotor body.

All centrifuge rotors have a limited lifespan before failure and fatigue of the materials that make up the rotor surface renders the centrifuge unusable.

Stresses generated in the rotor due to the high rotational speeds and centrifugal forces produced during centrifugation are one cause of rotor failure. Metal fatigue occurs in conventional rotors following numerous repeated stress cycles. As the rotor repeatedly reaches working speed, runs and decelerates, the expansion and contraction cycles of the metal change its microstructure. The small changes result in microscopic cracks after a large number of cycles. As usage increases, fatigue cracks grow larger and eventually lead to rotor failure. In addition, the stress in the conventional metal rotor body causes the rotor to elongate,
Change dimensions. When the metal rotor body reaches its elastic limit, the rotor will not return to its original shape, subsequently causing damage to the rotor.

Conventional titanium and aluminum alloy rotors have relatively high strength for their weight. Aluminum rotors are lighter than titanium ones and experience less physical stress and lower kinetic energy when operated at ultracentrifugal speeds. However, titanium rotors have better corrosion resistance than aluminum rotors.

As the performance and speed of ultracentrifugation increases, the safe operating limit for centrifuges lies in traditional density yet high weight metal rotors.

One attempt to overcome the imposed design limitations is shown in US Pat. No. 3,997,106 to Balam, where the centrifuge rotor consists of two layers of different materials stacked together. The wire is wrapped around a metal cover surrounding a central filler of chemical resistant plastic. Patent No. 3,997,106 to Balam contemplates a rotor with increased chemical resistance and low specific gravity that achieves optimal strength through the use of a laminate manufacturing process. U.S. Patent No. 2,974 to Ginaben. No. 684 is directed to a woven wire cloth mesh reinforcing a liner of plastic material for use in centrifugal cleaners.

Green (No. 1,827,648), Ziezel (
No. 3,993,243) and Lindogen (No. 4,1
No. 60,521) are all directed to rotor bodies comprised of resin and fibrous reinforcement. In particular, U.S. Patent No. 1,827,648 to Green
The vertical axis of inertia is greater than the horizontal axis passing through the center of gravity of the packet, so that the rotor packet is stable at rotational speeds of 7,500 to 10.00 ORPM (relatively slow centrifugation speeds by current standards). It is directed at the fibers that are wound to create a moment of inertia about the axis.

U.S. Pat. No. 4,468,269 discloses an ultracentrifugation rotor that includes a plurality of pre-rings of filament-wound cages surrounding the cylindrical wall of the rotor's metal body. The pre-insert links reinforce the metal rotor body and provide strength and rigidity to the rotor. These rings are nested together by applying a thin embossed coating between the layers. U.S. Patent No. 3.913,82 to Roy
No. 8 discloses a structure substantially equivalent to that disclosed in U.S. Pat. No. 4,468,269.

None of the conventional constructions yields great strength at ultracentrifugal speeds through the use of specially designed materials that accommodate local stresses and also resist fatigue in the rotor body! It's not something to get excited about. Conventional metal bodies, ie reinforced rotor metal bodies, undergo metal stress and fatigue failure during centrifugation.

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

The rotor body must be specially designed to withstand stress and corrosion and to counter localized stresses.

DESCRIPTION OF THE INVENTION Described herein is a centrifugal rotor body constructed of multiple layers of anisotropic material.

(As used in this specification, the term "anisotropic"
Refers to a material that has properties such as bulk modulus, strength and stiffness in a particular direction. ) Each layer has a different modulus or tensile strength that is fine-tuned based on the rotor geometry, design speed loading, or dimensions to accommodate the particular stresses to which the layer is subjected.

In each particular layer, selected portions of material are oriented in a direction different from the main body of said layer in order to stiffen the test tube-receiving cavity of said rotor and to accommodate the excessive stresses occurring therein. directed towards.

In a preferred embodiment, the anisotropic lunar 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 composite material, each disk extending radially from the central axis of the rotor and secured to the other disks by epoxy adhesive.

EXAMPLE Referring to FIGS. 1 and 2, there is shown a rotor 10 (FIG. 2) made entirely of synthetic material. Rotor 10 is code 2
The composite material chosen for the construction of the preferred embodiment rotor, which is comprised of multiple layered disks as shown at 6 and 28 (FIG. 2), is an epoxy or thermoplastic or thermoset material. 7
Including, but not limited to, graphite fiber filaments wound into a trix. The amount of fiber is 60
% or more. This configuration is approximately 0.0651 b/in
Aluminum (0,11lb/1n3
) and titanium (0,161 b/in"). Alternative fiber filaments include glass, boron, and graphite. Fibrous materials that are organic fines manufactured by DuPont Kevlar (trade name) is also a useful substitute for graphite.

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

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

Referring to the top view of rotor 10 shown in FIG. 1, the varying density of the filament design of rotor 10 is separated by circular boundaries 24 and 18. The interior region from the circumference of circle 18 to rotor shaft cavity 14 is wound to have a similar density as beyond the outer boundary of circle 24. Area 12 between circular boundaries 18 and 24 is shown as area 30 in FIG.
Characterized by more densely wound filaments. The center of the rotor 10 or the drive shaft 32 (Fig. 2)
The −F plane of the rotor 1o accommodates the insertion of the metal test tube insert 16 into the machined cavity 20. The test tube 22 is then inserted into the test tube insert 16 so that it fits snugly into the body of the rotor 10.

In the vertical test tube gauge 10, as shown in FIGS. 1 and 2, the stress is greatest in the upper layer, particularly in the area 30 of FIG. 2 where the maximum stress is shown as hoop stress. One test tube cap (made of 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 modulus of elasticity is adjusted to suit the particular stresses experienced at each of several locations within and around the rotor 10, indicated at 26 and 28. The idea is to form a disc in which each layer is uniquely fine-tuned such that the

Each of the disks, such as disks 26 and 28, is a body of filament wrapping around a central core. The number of fiber filaments is 1,000 per bundle, 3,
At least four different sizes are available: 000, 6,000 and 12,000 fibers. The preferred embodiment utilizes 12,000 filament fiber bundles per bundle. The filament bundles are wound to provide a tension range of 2 to 10 bonds per bundle, depending on which tension a plurality of disks are constructed. The average density of the composite disc is 0.0651 b/in3. These disks, like disk 28, are subjected to greater stress during rotor operation and are therefore built with greater tension than disks, such as disk 40, which are subject to less stress.

Each disk is individually machined to form a cavity, such as machined cavity 20. molding,
Once cured and machined, the discs are stacked along the longitudinal solid axis of the shaft cavity 14 and are sandwiched between layered discs 42, 40, 26 and 28, 41, 34. They are secured together by the application of layers of epoxy resin shown at 36 and 38.

After the epoxy resins 41, 34, 36 and 38 are applied between the disk layers, the entire assembly is then cured in a furnace, thereby creating the composite rotor 10.

Each disk is uniquely wound to specifically accommodate the local stresses that the assembled rotor will experience during centrifugation. For example, disk 26 is shaped and manufactured to accommodate different local stresses along the radius of the disk. Each disc may be manufactured from different grades or tensile strengths of fibrous filament materials. Furthermore, the fiber wrapping at the corners may be changed from wrapping parallel to the horizontal plane. Around the core cavity 14, outwardly of the circular boundary 18, the fibers are wound at 0° to the horizontal plane of the rotor 10. When the filament is wound in the area between boundaries 18 and 24, the winding of the filament in the vicinity of the machining cavity 20 is directed to the horizontal plane in order to provide additional support surrounding the cavity 20. It is carefully wound so that it intersects at an angle of approximately ±45°. The intersecting stitching of filament fibers in the area 12 (FIG. 1) between boundaries 18 and 24 ensures that the material strength of the rotor is not reduced by the presence of machined cavities, as indicated at 20. To provide additional support to the cavity 20. Optimal strength is obtained when the fibers are wrapped at approximately ±45° angles of intersection.

However, the use of angular ranges is limited if the optimum value of ±45° is 10° in each direction (from ±35° to ±
(up to 55°), achieves higher strength than horizontal winding.

Additionally, disk 28 and its second disk are stiffer than the materials used to construct layer 28 and the layers below, in order to accommodate the maximum hoop stress area at the top of vertical tube rotor 10. Constructed from high tensile strength filament material. Therefore, the nominal dimensions of disks 26 and 28 may be fine-tuned and varied so that disks 26 and 28 are different from each other in order to respond with different tensile strengths to the different stresses to which disks 26 and 28 are subjected. , the winding direction is different to accommodate the high stresses around the cavity 20, as well as the material of which the fibers of the filament wound into the disk are made. By having separate disks, expensive, strong disks are used only where needed. Multiple discs allow the rotor to be specifically designed to resist large local stresses only where they occur.

If the fixed angle rotor body is designed or designed differently than the vertical tube rotor, the location of maximum stress in the fixed angle rotor will be different from that of the vertical tube rotor, so
The maximum stress on the disk is located approximately in the lower two-thirds of the rotor body.

It will be appreciated that the preferred embodiment contemplates the use of separate disks comprising the rotor body, rather than one continuous winding defining the entire rotor. Such a stamp construction is within the scope of the present invention in which the fibers are reoriented or oriented in a new direction to accommodate the large stresses shown in FIG. 2 that fall within the area between boundaries 24 and 18. It will be done.

However, the preferred embodiment does not allow for the obvious inability of a single rotor to overcome the axial residual stresses that occur when fibers wound around a disk exceed an empirically derived width. Multiple tethered discs are intended rather than a single fiber. Single filament wrapped synthetic rotors also do not allow for the selection of multiple fibrous filaments for different parts of the ronita body.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a synthetic rotor according to the present invention. FIG. 2 is a longitudinal sectional view of a composite lunar rotor according to the present invention. 10...Rotor, 26.28.40.42...Disk, 34.36.
38.41...Epoxy resin, 22...Test tube.

Claims (12)

[Claims] (1) A centrifuge rotor comprising a body comprising multiple layers of anisotropic material, each layer having a predetermined modulus to match the respective stress to which the layer is subjected. (2) Each of said layers is a radially extending disk of fiber filament-wrapped synthetic material, and each of said disks is secured to one another by a resin. Centrifuge rotor described in section ). (3) A centrifuge rotor according to claim 2, including a change in filament orientation in an anisotropic layer selected to accommodate the insertion and support of multiple test tubes. (4) The centrifuge rotor according to claim 2 or 3, wherein the fiber filaments are graphite and the resin is epoxy. (5) The resin is thermoplastic.
The centrifuge rotor according to item 2) or item (3). (6) The resin is thermosetting.
The centrifuge rotor according to item 2) or item (3). (7) A centrifuge rotor according to claim 2 or 3, wherein the fiber filaments are made of a material selected from the group consisting of glass, boron or graphite. 8. The centrifuge rotor of claim 3, wherein the filaments are reoriented at an angle ranging from 35° to 55° with respect to a horizontal plane of the rotor. (9) 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. Centrifuge rotor. (10) a body comprising at least one layer of anisotropic material, said layer being a disk consisting of filament-wound fibers bonded by a resin material, said disk comprising said fibers constituting the material of the disk; , wherein the fibers are reoriented so that successive wraps of the fibers intersect each other to provide additional strength to the disc material at selected locations where the greatest stress is expected. Separator rotor. (11) A centrifuge rotor according to claim (10), wherein the filament-wound fibers intersect with each other at a reorientation angle in the range of 35° to 55° with respect to the horizontal plane. . (12) The fiber around which the filament is wound is approximately 45
Claims Nos. (
The centrifuge rotor according to item 10).