U.S. patent number 3,913,828 [Application Number 05/177,379] was granted by the patent office on 1975-10-21 for reinforcing ultra-centrifuge rotors.
This patent grant is currently assigned to Avco Corporation. Invention is credited to Paul A. Roy.
United States Patent |
3,913,828 |
Roy |
October 21, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Reinforcing ultra-centrifuge rotors
Abstract
The disclosure illustrates a method and apparatus for
reinforcing ultra-centrifuge rotors to enable operation at
significantly increased rates. The rotor is selectively reinforced
around its periphery by a sleeve comprising a plurality of turns of
a boron filament impregnated with a curable epoxy resin. The boron
filament may be wound on a spindle to preform a sleeve which then
is telescoped over the periphery of the rotor, or it may be wound
directly on the rotor itself. An additional variation shows the
boron filament wound on various spindles to preform a series of
coaxial interfitting sleeves telescoped over the periphery of the
rotor.
Inventors: |
Roy; Paul A. (Andover, MA) |
Assignee: |
Avco Corporation (Cincinnati,
OH)
|
Family
ID: |
22648371 |
Appl.
No.: |
05/177,379 |
Filed: |
September 2, 1971 |
Current U.S.
Class: |
494/81;
57/76 |
Current CPC
Class: |
B04B
7/085 (20130101); B29C 63/0021 (20130101); B29C
53/845 (20130101); B29C 63/42 (20130101); B29K
2707/02 (20130101); B29L 2031/7498 (20130101); B29K
2707/04 (20130101); B29K 2063/00 (20130101) |
Current International
Class: |
B29C
53/00 (20060101); B29C 53/84 (20060101); B29C
63/42 (20060101); B29C 63/38 (20060101); B29C
63/00 (20060101); B04B 7/08 (20060101); B04B
7/00 (20060101); B04b 007/06 () |
Field of
Search: |
;233/27,1R,1E,26,7
;57/76,14R ;106/55 ;117/46 ;264/DIG.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Krizmanich; George H.
Attorney, Agent or Firm: Hogan, Esq.; Charles M. Ogman,
Esq.; Abraham
Claims
Having thus described the invention, what is claimed as novel and
desired to be secured by Letters Patent of the United States
is:
1. A reinforced ultra-centrifuge rotor comprising:
a. a titanium bowl element; and
b. a plurality of turns of a filamentary material having a lower
density, higher modulus of elasticity and higher tensile strength
than titanium, secured around the periphery of said rotor element,
whereby the maximum rate of rotation of said rotor is substantially
increased.
2. A reinforced centrifuge rotor as in claim 1 wherein said
filamentary material comprises a boron filament.
3. A reinforced centrifuge rotor as in claim 1 wherein said
filamentary material comprises graphite in an epoxy matrix.
4. A reinforced centrifuge rotor as in claim 1 wherein said
filamentary material is preformed in the shape of a sleeve and
telescoped over the periphery of said annular rotor element.
5. A reinforced centrifuge rotor as in claim 1 wherein said
filamentary material is formed from a plurality of preformed
sleeves of multi-layers of filamentary material, each being formed
from a single run of material and telescoped over one another and
over the outer periphery of said rotor element.
6. A reinforced centrifuge rotor as in claim 1 wherein:
said annular rotor element has an annular groove formed in the
outer periphery thereof;
said filamentary material is positioned around the periphery of
said rotor element in said annular groove.
Description
The present invention relates to ultra-centrifuges and more
particularly to rotors incorporated in an ultracentrifuge
assembly.
In recent years there has been a need by medical research for more
effective centrification from batch-type centrifuges. This has been
done by increasing the R.P.M.'s of the centrifuge rotors to as high
as 48,000.
This is known as an ultra-centrifuge that subjects its contents to
an extremely high centrifugal force field. However, this same force
field causes the stresses in the rotor to approach such enormous
proportions that the material cannot resist the force produced by
the centrifugal multiplication of its own weight. Attempts have
been made to form the rotors from a low density, high strength
material, such as titanium. However, this material has a strength
to weight ratio that still limits the upper R.P.M.'s that can be
achieved.
Accordingly, it is an object of the present invention to
substantially increase the maximum capable operating R.P.M. of an
ultra-centrifuge rotor in a simplified and economical fashion.
This end is achieved by winding a plurality of turns of a low
density, high strength, high modulus filamentary material so that
it forms a sleeve around the periphery of a rotor. The filamentary
material then is impregnated with a curable resin. The sleeve
selectively reinforces the periphery of the rotor.
In a more specific aspect of the invention the filamentary material
comprises a boron filament.
The above and other related objects and features of the present
invention will be apparent from a reading of the description of the
disclosure shown in the accompanying drawing and the novelty
thereof pointed out in the appended claims.
In the drawing:
FIG. 1 illustrates a step in a method embodying the present
invention for reinforcing the periphery of an ultra-centrifuge
rotor;
FIG. 2 shows an ultra-centrifuge rotor whose periphery is
reinforced using the method shown in FIG. 1;
FIG. 3 shows an enlarged view of an alternate embodiment of the
present invention; and
FIG. 4 shows still another embodiment of the present invention.
Turning first to FIG. 2 there is shown an ultra-centrifuge 10
comprising a rotor element 12 rotatably driven by a low torque,
high R.P.M. motor 14. The rotor 12 as herein illustrated is for a
batch-type centrifuge. The liquid to be separated into its
constituents is placed in a central bowl 16 containing various
baffles and bleed passages (not shown to simplify the description
of the invention). The rotor is rotated to separate the
constituents according to their specific gravity, as is the usual
practice for centrifuges. The rotor 12 has an annular peripheral
wall 18 which is positioned at a rather substantial distance from
the axis of rotation of the rotor. When the rotor is rotated at
R.P.M.'s approaching 48,000, the internal hoop stresses limit the
maximum R.P.M. that can be obtained. Therefore, in accordance with
the present invention the peripheral wall 18 of the rotor 12 is
selectively reinforced as follows:
A spindle 20 is mounted on a shaft 22 rotatably driven by a
suitable motor 24. A plurality of turns of a low density, high
strength, high modulus filamentary material 26 is wound around the
periphery of spindle 20 by the rotation of motor 24. The
filamentary material 26 is wrapped in a predetermined pattern by
feeding it through a guide 28 displaceable in a slot 30 in arm 32.
An articulated link 34 extends from guide 28 to a crank arm 36
driven by motor 38. Motor 38 is snychronized with motor 24 so that
a predetermined pattern results from winding the filamentary
material 26 onto spindle 20. The filamentary material 26 passes
around guide rollers 40 and through receptacle 42 containing a
curable resin material 44. Filamentary material 26 is fed from a
supply reel 46 which is appropriately braked to produce a given
pretension in the filamentary material 26 for relatively tight
winding onto spindle 20.
Preferably the filamentary material 26 is comprised of a boron
filament having an average diameter of approximately 0.0056 inch.
This boron filament, for example, may be manufactured by vapor
depositing a mixture of boron trichloride and hydrogen onto thin
tungsten substrates. This type of boron filament is available from
the Avco Systems Division of Avco Corporation, Lowell Industrial
Park, Lowell, Mass. 01851. The curable resin material may be a
mixture of 89% resin with 11% hardener by weight. The resin and
hardener may be selected from a wide variety of brands well known
to those skilled in the art. Brands that have given acceptable
results are: ERL-2256 Epoxy Resin, available from Union Carbide,
and Curing Agent Z, available from Shell.
The boron filamentary material 26 is wound onto spindle 20 and
saturated with the resin material. It should be pointed out that
the boron filament 26 may be applied wet, as shown in FIG. 1, or
applied dry and then impregnated with the resin. The spindle 20 is
wound with a large number of turns to produce a number of layers of
boron filament. It has been found that 48 layers, for example,
produce a sleeve 48 with a predetermined thickness (FIG. 2). After
the boron filament is wound and the resin cured, the sleeve 48 is
slipped off of the spindle 20. The sleeve 48 is then telescoped
over the peripheral wall 18 of the rotor 12 to selectively
reinforce its periphery.
Preferably the diameter D of the spindle 20 is selected to be as
near to the outside diameter D.sub.R of the rotor 12 as
manufacturing tolerances will allow to produce an ultimate zero
clearance fit between the sleeve 48 and the peripheral wall 18 of
rotor 12. It has been found that manufacturing variations in size
can be compensated for by selecting the diameter D of spindle 20 to
be approximately 0.003 under the diameter D.sub.R of rotor 12. This
results in an interference fit between sleeve 48 and the periphery
of rotor 12. To telescope the sleeve 48 over the periphery of rotor
12 the sleeve 48 is heated to expand it and the rotor 12 cooled to
contract so that the two fit together. When they have reached
equilibrium temperatures the sleeve 48 is tightly held on the
periphery of rotor 12.
The sleeve 48 of the boron filament substantially reinforces the
periphery of the rotor 12 and enables a significant increase in the
maximum R.P.M.'s attainable. It has been found the the maximum
R.P.M.'s can be increased from 48,000 to 56,000 R.P.M. The reason
for the substantial increase in performance is that the boron
filament is an extremely low density, high strength, high modulus
material. Typical properties of the boron filament are: a density
of 0.094 lbs./in..sup.3, a modulus of 58 .times. 10.sup.6 PSI, and
a tensile strength of 500,000 lbs. per square inch. The modulus of
elasticity of the boron is substantially greater than that for the
titanium in the wall 18. Therefore the sleeve of boron filament
resists deformation due to the hoop stresses far greater than the
titanium in the peripheral wall 18 of the rotor 12 thereby
preventing deformation of the titanium.
Referring to FIG. 3 there is shown an alternate embodiment of the
present invention. In this embodiment the peripheral wall 18' of
the rotor 12 is reinforced by three sleeves 50, 52 and 54. The
total thickness of these sleeves is the same as the thickness of
the sleeve 48 shown in FIG. 2. It has been found that the windings
are compacted and quite uniform in their spacing in the initial
turns making up the sleeve 48. The turns thereafter tend to be less
uniform and have a lower degree of compaction. Therefore each
sleeve 50, 52 and 54 is preformed from a smaller number of turns
than that for sleeve 48 and then telescoped into one another to
form the resultant reinforcing sleeve for the periphery of wall
18'.
The sleeves 50, 52 and 54, respectively, are formed by winding on
three separate spindles using the procedure shown in FIG. 1 and
described above. The diameter of the spindle for sleeve 50 is
approximately the outer diameter of wall 18'. The diameters for the
spindles used to form sleeves 52 and 54 are progressively larger.
The boron filament is wound on the various spindles to a
predetermined thickness so that the sleeves interfit with one
another with a zero clearance.
For manufacturing convenience the sleeves may be formed with an
interference fit relative to each other and to the wall 18' of
rotor 12'. These are assembled by the heating and cooling method
illustrated for the method of FIGS. 1 and 2. For example, sleeve 50
is cooled, sleeve 52 heated and telescoped over sleeve 50. Then
both sleeves 50 and 52 are cooled. Sleeve 54 is heated and
telescoped over sleeve 52. The coaxial interfitting sleeves 50, 52
and 54 are heated and telescoped over rotor 18' which has been
cooled.
The methods described above are directed to an embodiment where the
boron filament is wound on a spindle, cured, and then placed over
the rotor 12. In the embodiment shown in FIG. 4 the boron filament
is wound directly on the periphery of wall 18" of rotor 12". The
boron filament windings form a sleeve 56 which is received in an
annular recess 58 around the periphery of wall 18'. However, the
sleeve may be wound directly on the smooth exterior surface of the
rotor with generally equal results.
Each of the methods described above enable a high degree of
reinforcement of the periphery of ultra-centrifuge rotors which
greatly increases the maximum operating R.P.M.'s.
While a preferred embodiment of the filamentary material has been
shown, it should be apparent to those skilled in the art that other
materials with similar properties may be used with equal results.
For example, graphite in an epoxy matrix could be used.
* * * * *