Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO9Z/18390 2107 8 01 I'Cr/US92/0213Z
TiTL~
CAPPING ASSEMBLY ENABLING Tt 1~ USE OF SEAL~D TUB~S IN A
SWINGING ~l)CKET CENTRIFUGE
BACKGROUND OF TH~ INVENTION
Field of the Invention The present invention relates to a
tube capping assembly having a plug and an associated
10 crimpabie sleeve that, when deformed, forms a seal with the
neck of a centrifuge tube, and in particular, to a tube capping
assembly especially adapted to permit the use of a centrifuge
tube of this type in a swinging bucket rotor.
Desçription of the Prior Art A swinging bucket
centrifuge rotor is a rotor of the type in which the sample
carrying container (either a centrifuge tube or a bottle) is
received within a pivotally movable bucket. At rest the bucket
occupies a first, generally vertical, position in which the axis
20 of the container lies generally parallel to an axis of rotation
VCL. As the rotor spins the bucket swings from the first
position toward a second, senerally horizontal, position. In the
second position (Figure 3) the axis of the container is almost
aligned with a horizontal reference datum HR extending
25 perpendicular to the axis of rotation.
Sample receiving bottles typically include a
corresponding capping arrangement. On the other hand,
centrifuge tubes of the open-mouth variety are most commonly
30 used in a swinging bucket rotor. Since the mouth of the tube is
not subject to hydrostatic pressure during operation of the
rotor no capping arrangement is used to retain the sample in
the tube.
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Recently, however, due primarily to tho hazardous nature
of many of the materials being processed, the demand to seal
the sample receiving tube.within the swinging bucket rotor has
increased.
Tube capping arrangements for open mouth tubes
adapting the same for use in a vertical rotor or a fixed angle
rotor are known. Representative of such capping arran~ements
are thoss disclosed in United States Patent 3,938,735 (Wright)
10 and in United States Patent 3,635,370 (Romanauskas), United
States Patent 4,166,573 (Webster), United States Patent
4,190,196 (Larsen) and United States Patent 4,222,513
(Webster et al.), all of the latter being assigned to the
assignee of the present invention. Since such capping
15 assemblies are relatively massive and difficult to use, their
applicability to seal open mouth tubes in a swinging bucket
would appear to be somewhat limited. The substantial mass of
a capping arrangement for an open mouth tube is undesirable
since the walls of the tube, the bucket and the rotor body are
20 subject to additional load during centrifugation from the body
forces of such a capping assembly. As a result, possible
premature failure of any one of the above components may
occur or reduced performance may be derived from the rotor
system.
Z5
Sealed centrifuge tubes having a reduced diameter neck
portion have been commonly used in rotors having vertical or
fixcd angle cavities. Exemplary of such soaled tubes are those
disclosed in United States Patent 4,301,963 (Nielsen), heat
30 sealable in the manner disclosed in United States Patent
4,291,g64 (Ishimaru), and those manufactured and sold by
Nalgene Inc. as the "UltraLol~" tube.
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Att~mpts hav~ been mad~ to use such sealed tubes in a
swinging bucket rotor. The us~ of tubes as exemplified by the
last-m~ntioned patents is described in the Beckman
Instruments Inc. Rotor and Tubes User Manual, April 1990. To
5 facilitate such use a floating spacer, similar t~ that described
in United States Patent 4,304,356 (Chulay et al.), is required.
This arrangement is believed disadvantageous inasmuch as
sealing of the tube requires exposure of the sample under test
to the potentially harmful effects of heat.
1 0
Use of the "UltraLok" tube in a swinging bucket rotor
requires the use of a spacer sold by Nalgene Inc. as the
UltraLok Swinging Bucket Spacer. This spacer completely
surrounds the small diameter neck portion and an intermediate
15 diameter capping portion at the top of the tube. The spacer is
split in two semi-cylindrical parts to enable installation and
removal of the spacer from the tube. This system carries the
disadvantage of adding undesirable load to the tube due to the
mass of the spacer. Moreover, multiple pieces must be handled
20 and stored.
The disadvantages of each of the above-referenced
sealed centrifuge tubes are believed overcome using the
centrifuge tube having a reduced diameter neck portion as sold
25 by E. I. du Pont de Nemours and Company as the
~ULTRACRIMP"TM tube and the sealing assembly therefor
disclosed in United States Patent 4,552,278 (Romanauskas),
assigned to the assignee of the present invention.
As noted earlier, during operation of a swinging bucket
rotor the bucket pivots from a first, generally vertical,
position to a second, generally horizontal, position. As may be
seen with reference to Figure 3, when rotating at operational
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speed the bucket B assumes a position wherein the axis 10A of
the tube 10 lies an predetermined angular distance e below the
horizontal reference HR. This orientation is due to the weight
of the pivoting bucket assembly B, the tube 10 and the sample
5 acting in conjunction with centrifugal force. Rotation of the
rotor R generates a horizontal, radially outwardly directed
total forc~ F on the tube 10. The total force F, acting through
the center of gravity (CG) of the capping assembly, is
resolvable into an axial component Fc and a transverse
10 component FB The axial component Fc, having a magnitude
equal to F (COS ~), acts along the axis 10A of the tube and
would tend to axially compress the tube. The transverse
component FB, having a magnitude equal to F (sin ~), acts in a
direction perpendicular to the axis 10A of the tube and would
15 tend the bend the neck of the tube toward the side of the
bucket. If unchecked, either force component would cause
damage to the sealed tube.
Heretofore, no arrangement exists for accommodating
20 such compressing and bending forces to permit the use of a
sealed "ULTRACRIMP"TM tube in a swinging bucket centrifuge
rotor. Accordingly it is believed advantageous to provide a
capping assembly that would accommodate both the
compressing and the bending components imposed by the
25 capping assembly on the tube when it is received in a swinging
bucket, thereby maintaining, in a swinging bucket rotor
environment, the advantages attendant with the
"ULT~ACRtMP"TM tube and its associated sealing assembly.
3 0 ~ MARy QF THE INVENTIQN
Disclosed is a capping assembly for a centrifuge tube
made of a deformable material. The tube has a neck which
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defines a fluid port. The neck communicates with a transition
portion having a predetermined exterior configuration. The
capping assembly comprises a stopper having a plug sized and
configured for close fitting receipt on the interior of the neck
5 of the tube and a sleeve sized and configured for close fittin~
receipt over the exterior of the neck in concentric telescopic
relationship with respect to the plug. The sleeve is responsive
to a crimping force to deform and to compress the rnaterial of
the neck intermediate the plug and the sleeve to form an
10 annular seal between the neck and the plug. The seal resists
fluid leakage out of the fluid port from the interior of the tube.
When the sealed tube is rotated in a swinging bucket rotor the
capping assembly generates a body force that is resolvable
into a compressing component acting generally along the axis
15 of the tube and a bending component acting generally
perpendicular to the axis of the tube.
In accordance with a first embodiment of the present
invention the capping assembly includes a force transmitting
20 member that is integrally formed with and flares from the
sleeve. The force transmitting member has an undersurface
thereon that corresponds to the configuration of the transition
portion of the tube. The force transmitting member
distributes both the bending and the compressing components
25 of the body force into the transition portion of the tube where
they are opposed by hydrostatic pressure of the sample within
the tube. This embodiment of the invention may be modified by
the provision of a generally cylindrical band having a
peripheral bearing surface thereon The band may ~xtsnd
30 toward or away from the sleeve. In these modifications to the
first embodiment of the invention the peripheral bearing
surface on the band engages the bucket to transmit thereto a
portion of the bending force imposed on the tube.
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In accordance with a second embodiment of the present
invention the force transmitting member takes the form of an
annular collar having a central opening therethrough. The
5 collar has an undersurface corresponding in shape to that of
the transition region of the tubo and a second, generally
cylindrical, peripheral bearing surface th~reon. A engagement
surfac0 is disposed about tho opening in the collar that
engages the end of the sleeve. The collar may be either formed
10 as an integral member or formed of at least two conjoinable
segments. In the former instance the collar must be inserted
over the neck of the tube prior to the crimping of the sleeve to
the neck of the tube.
1 5 BRIEF DESCRIPTION C)F THE DRA~3S
This invention may be more fully understood from the
following detailed description thereof taken in connection
with the accompanying drawings which form a part of this
2 0 application and in which:
Figure 1 is an exploded view of a centrifuge tube and a
separate capping assembly in accordance with a first
embodiment of the present invention;
Figure 2 is an elevation view partially in section
illustrating the tube capping assembly of Figure 1 in its
assembled and sealed relationship with respect to the
centrifuge tube, prior to centrifugation of the tube;
Figure 3 is a side elevational view, in section, of a tube
sealed with a capping assembly of Figure 1 with the tube being
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received in a bucket of a swinging bucket rotor, the view bein~
taken during operation of the centrifuge;
Figures 4 and 5 are views similar te Figures 2 and 3,
5 respectively, illustrating a first modification of the
embodiment of the invention shown in Figure 1;
Figures 6 and 7 are views similar to Figures 2 and 3,
respectively, illustrating a second modification of the
10 embodiment of the invention shown in Figure 1;
Figure 8 is an exploded view of a centrifuge tube and a
separate capping assembly in accordance with a second
embodiment of the present invention;
1 5
Figure 9 is an exploded view illustrating a modification
of the capping assembly shown in Figure 8;
Figure 10 is a side elevational view, in section, of a tube
20 sealed with a capping assembly of Figure 8 or Figure 9
received in a bucket of a swinging bucket rotor during
opsra~ion of the centrifuge;
Figure 11 is an exploded view illustrating another
25 modification of the capping assembly shown in Figure 8; and
Figure 12 is a side elevational view, in section, of a tube
sealed with a capping assembly of Figure 11 recelved in a
bucket of a swinging bucket rotor during operation of the
3 0 centrifuge.
'`
W~ 92/18390 '' ) PCT/US92/~ 2
~ETAILED DESCF~IPTION OF THE INvENllOy
Throughout the following detailed description similar
reference numerals refer to similar elements in all figures of
5 the drawings.
Shown in Figure 1 is an ultracentrifuge tube generally
indicated by the reference character 10 with which a separate
capping assembly generally indicated by the reference
10 character 12 in accordancs with the present invention may be
utilized to seal the tube 10 and provide the necessary support
to permit the use of the tube 10 in a swinging bucket rotor.
The tube 10 includes a body portion 14 having a bottom
15 (not shown), a neck portion 16, and a transition region 18
extending between the neck 16 and the body 14. The body 14
has a predetermined dimension 14D measured transversely to
the axis 10A of the tube 10. The dimension 14D is greater than
the reduced transverse dimension 16D of the neck 16. The
20 main body portion 14 defines a fluid capacity of any
predetermined volume dependent upon the volumetric size of
the samples which are to be carried therewithin for
centrifugation. The neck 16 has an opening 16A therein that
defines a fluid port through which a liquid sample under test
25 may be introduced into the tube 10.
The transition region 18 has a frustoconical exterior
configuration that defines a predetermined angle a with
respec~ to the axis 10A. It should be understood that the
30 exterior configuration of the transition region 18 may take any
other convenient shape. For example, it may be domed.
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2107~
WO 92/18390 PCI/VS92/02132
The tube 10 is preferably an extrusion blow molded
member formed of a polyallomer plastic material. Of course,
the tube 10 can be formed of other deformable materials, such
as a co-polyester material such as a polyethylene
5 terephthalate (PET). It should also be understood that the tube
10 can be formed by other molding techniques, such as
injection blow molding.
The separate capping assembly 12 is simiiar to that
10 disclosed and claimed in United States Patent 4,552,278
(Romanauskas) assigned to the assignee of the present
invention. This patent is hereby incorporated by reference
herein. The separate capping assembly 12 comprises a stopper
22 and a complementary sleeve 24. In the preferred case, the
15 stopper 22 includes an elongated cylindrical plug portion 28
that has a taper 30 at one end thereof and a flange 32 disposed
at the opposite end thereof. The cylindrical plug portion 28 is
surrounded by an elastomeric skin 34. The external
configuration of the plug portion 2~, with the elastomeric skin
20 34 thereon, is configured and sized for close fitting receipt
within the opening 16A of the neck 16 of the tube 10.
Preferably the diameter of the flange 32 is coextensive with
the exterior dimension 16D of the neck 16. The flange 32
serves to iimit the extent of entry of the plug portion 28 of
25 the stopper 22 into the neck 16 of the tube 10.
Th~ plug portion 28 of th~ stopper 22 is formed of a
stiff, relatively llghtwelght material. The materlal must be of
sufficient stiffness to insure that the flange 32, which rests
30 on the edge of the neck 16 of the tube 10, is able to resist any
force tending to urge the stopper 22 towards the bottom of the
tube -i 0 durlng centrifuge operatlon. A relatively lightweight
material reduces the loading that the tube 10 mùst withstand
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9~ 1 o
from the capping assembly during centrifugation. In the
preferred case the plug portion 28 is injection molded of
polypropylene having a durometer of about 75 on the Shore D
scale.
The elastomeric skin 34 is, in the preferred case, insert
injection mold~d onto the plug portion 28. Functionally, the
skin 34 provides a resilient sealing layer between ths plug
portion 28 of the stopper 22 and the neck 16 of the tube 10. A
10 suitable material for the elastomeric skin 34 is a low
durometer (about 85 on the Shore A scale) polyethylene. A skin
thickness on the order of about .010 inches is suitable.
Similar to the capping assembly disclosed in the
15 incorporated United States Patent 4,5~2,278 (Romanauskas)
the sleeve 24 of the capping assembly 12 includes a tubular
portion 35. The tubular portion 35 of the sleeve 24, in the
preferred case, is open at one end, as at 36. The opposite end
37 may be closed, as is preferred, or may be left open, if
20 desired. The tubular portion 35 of the skirt 24 has an axial
length approximately equal to the axial length of the neck 16
of the tube 10. The interior of the tubular portion 35 of the
sleeve 24 is sized and configured for close fitting receipt over
the exterior of the neck 16 of the tube 10.
As noted earlier, in a swinging bucket rotor the axis
10A of the tube 10 does not coincide with a hori~ontal
reference datum HR extending transversely to the axls of
rotation VCL of the rotor. Accordingly, the mass of the
30 capping assembly imposes both a compressing force acting
along tho axis 10A and a ben~ing component acting
transversety thereto. In accordance with the present invention
the capping assembly further includes a force transmitting
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- 11
member generally indicated by the reference character 38
adapted to transmit both the compressing component and the
bending component into the tube 10.
In accordance with a first embodiment of the present
invention the force transmitting member 38 is formed
integrally at the open end 36 of the tubular portion 35 of the
sleeve 24. The undersurface 40 of the force transmitting
member 38 matches the frustoconical configuration of the
transition portion 18 of the tube 10. Thus, the undersurface
40 forms an angle a with respect to the axis 10A of the tube
10. The largest diameter dimension 38D of the force
transmitting member 38 is substantially equal to the diameter
14D of the body 14 of the tube 10. The sleeve 24 with the
integral force transmitting member 38 thereon is formed,
preferably by progressive die stamping, from aluminum or any.
crimpably deformable material having sufficient strength to
minimize deformation during centrifugation.
In use, the tube 10 is filled and the bi-material stopper
22 inserted into the neck 16 of the tube 10 until the entry
thereof is limited by the abutment of the flange 32 against the
upper end of the tube neck 16. The sleeve 24 having the
integral force transmitting member 38 is telescopically
inserted over the neck 16 so that the tubular portion 35 of the
sleeve 34 concentrically overlaps a portion of the length of the
plug portion 28 of the stopper 22. A radially inwardly directed
crimping force is circumferentially applied about the e~terior
of the tubular portion 35 of the sleeve 24 using a tool
3 0 described in above-incorporated United States Patent
4,552,278 (Romanauskas).
WO 92~18390 - I PCr/lJS92/~ 2
~ 1 2
Figure 2 is a partially cut-away view of a tube 10 with
~n assembled and crimped capping assembly in accardance
with the first embodiment of the present invsntion. The
tubular portion 35 of the sleeve 24 responds to the radially
5 directed crimping force by crimping to compress the material
in ths neck 16 of the tube 10 between the outer elastomeric
skin 34 of the plug 28 and the tubular portion 35 of Ihe sleeve
24. The radially inwardly directed crimping force is imposed
at at least one but preferably at a plurality of spaced axial
10 locations along the neck 16. As a result of the imposition of
the radially directed crimping force at least one or a plurality
of circumferentially extending sea~ed interfaces 42A, 42B are
defined between the nec~ 16 and the stopper 22 at each
location at which the crimping force is applied due to the
15 compression of the material of the neck 16 between the
stopper 22 and the tubular portion 35 of the skirt 24. The
seals 42A and 42B developed in the manner described are each
able to prevent the leakage of liquid from within the tube 10
during centrifugation.
As is seen in Figure 2, when in the above-described
assembled relationship a gap 43 is defined between the
undersurface 40 of the force transmitting member 38 of the
sleeve 24 and the frustoconical transition region 18 of the
25 tube 10. The gap 43 is due to the crimping action forming the
seals 42A, 42B.
Figure 3 illustrates a tube 10 with an assembled capping
assembly 12 of Figure 1 disposed in a bucket B having a cover
~0 C operating in a swinging bucket rotor R. The cover C is sealed
to the bucket B by an O-ring or other appropriate seal S. The
cover C is pivotally mounted to the rotor body R at the pivot
location P. For simplicity and clarity of illustration the
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details of the pivot mechanism have been omitted from Figure
3.
The bucket B and the cover C shown are most commonly
5 used to process samples in open mouthed test-tube like
containers. Accordingly, no support means are inherent to the
bucket B or cover C to accommodate a tube 10 having a reduced
diameter neck 16 and a capping arrangement 12. For use with
any of the various embodiments or modifications of the
10 invention discussed herein the diameter D of the bucket B
should be within a few thousandths of an inch of the dimension
14D of the tube 10. Also, for proper functioning of the
invention the tube 10 should be almost entirely filled with
sample liquid.
1 5
During operation of the rotor R the bucket B pivots about
the pivot point P from a first, generally vertical, position to a
second, generally horizontal, position. As discussed the bucket
B assumes a position a predetermined angular distance e just
20 below the horizontal reference datum HR.
The force transmitting member 38 of the slesve 24
distribùtes both the compressive component Fc and the bending
component FB Of the total force F imposed by the capping
25 assembly 12 into the tube 10. The liquid sample within the
tube 10 generates a reaction force that counters the
compressive component Fc and the bending component Fa Of the
total force F imposed thereon. As a result, the neck 16 of the
tubc 10 is relatively unstressed and the integrity of the tube
3 0 10 is preserved during centrifugation.
Figures 4 and 5 illustrate a modification of the first
embodiment of the present invention. In Figures 4 and 5 the
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force transmitting member 38 has a band 44 with a cylindrical
bearing surface 46 defined thereon. The band 44 projects
toward the end 37 of the sleeve 24. The diameter 44D of the
band 44 is substantially equal to the dimension 14D of the
5 body 14 of ths tube 10. The band 44 provides additional
bearing area against the bucket B to withstand a higher
bending component FB of the force F of the capping assembly
12. This embodiment of ths sle~ve 24 with the inte~ral forcs
transmitting member 38 thereon is atso preferably formed by
10 progressive die stamping from aluminum or any crimpably
deformable material having sufficient strength to minimize
deformation ~uring centrifugation.
Figures 6 and 7 illustrate another modification of the
15 embodiment of the invention shown in Figures 1 to 3. In this
modification the band 44 projects away from the end 37 of the
sleeve 24. The body portion 14 of the tube 10 has an annular
step 14S formed therein to accept the end 44E of the band 44.
In this arrangement the band 44 also provides additional
20 bearing area against the bucket B to withstand a higher
bending component FB Of the force F Of the capping assembly
12. This embodiment of the sleeve 24 is also preferably
formed by progressive die stamping from aluminum or any
crimpably deformable material having sufficient strength to
2 5 minimize deformation during centrifugation.
-o-O-o -
Figures 8 through 11 illustrate various modifications of
30 a second, alternate, embodiment of the present invention. In
each of these modifications of the alternate embodiment the
force transmitting member 88' is a generally annular washer-
like member separate from the sleeve 24 of the capping
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assembly 12. The member 38' has a central axial passage 47
extending therethrough. The force transmitting member 38'
has an undersurface 40' that corresponds in shape to the
configuration of the transition region 18 of the tube 10. A
peripheral bearing surface 44' is defined on the exterior of ths
member 38'. The peripheral bearing surface 44' extends
~enerally parallel to the axis 38'A of the member. The member
38' also includes an abutment surface 48 defined adjacent to
- the opening 47 that engages the end 36 of the sleeve 24 of the
10 capping assembly 12.
In the modification shown in Figure 8 the member 38' is
inte~rally formed, as by machining from a suitable metal (e. ~.,
aluminum) or by machining or molding from a suitable plastic
15 material (e. g., polypropylene, polyphenylene oxide, polyvinyl
chloride, polycarbonate or polyethylene). The transition
between the undersurface 40' and the peripheral bearing
surface 44' is preferably rounded, as shown.
The member 38' may be defined by cooperating
conjoinable segments 38'-1, 38'-2, as illustrated in Figure 9.
As suggested in Figures 8 and 9 the integral member 38' or
each of the conjoinable segments 38'-1, 38'-2, may be cored to
eliminate excess material in the region 50 between the
25 abutment surface 48 and the peripheral bearing surface 44'.
The cored region 50 is indicated in Fi~ures 8 and 9 by dot-dash
lines.
Figure 10 illustrates the relationship of the member 38'
30 and the capping assembly 12 when in use. In Figure 10 the
member 38' may be integrally formed or formed from the
conjoined segments 38'-1, 38'-2. If the integral form of the
member 38' is used, it is first inserted over the neck 16 of the
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1 6
tube 10 prior to orimping of the capping assembly 12. With the
sleeve 24 in place, the sleeve 24 is crimped, as described
earlier. The end 36 of the sleeve 24 engages the member 38'
along the abutment surfacs 48, the engagement being indicated
5 at reference character 49, effectively transmitting the body
forces of the capping assembly 12 during centrifugation to the
force transmitting member 38'. The undersurface 40' of the
force transmitting member 38' bears against the transition
region 18 of the tube 10, transmitting thereinto both the
10 compressing component Fc and the bending component FB Of the
total body force F of the capping assembly 12. Analogous to
the situation discussed earlier, the hydrostatic reaction
forces generated within the liquid within the tube 10
counteract the compressing component Fc and the bending
15 component FB of the total body force F of the capping
assembly, thereby preventing damage to the integrity of the
tube. In addition, some of the bending component FB jS
accommodated by the interaction of the peripheral bearing
surface 44' against the bucket B. If the member ~8' is formed
2 0 using the conjoined segments 38'-1, 38'-2, the segments 38'-
1, 38'-2 are inserted beneath the end 36 of the sleeve 24 after
the same has been crimped to the neck 16 of the tube 10.
Figure 11 illustrates a modification to the member 38'
25 when the same is formed of conjoinable segments In Figure 11
each of the segments 38'-1, 38'~2 is axially elongated by the
provision of an annular portion 52. Each portion 52 has a
central groove 54 defined therein, the groove being disposed
immediately adjacent to the abutment surface 48. The
30 exterior surface of each of the portions 52 define an axial
extension of the peripheral bearing surface 44'. As indicated
by the reference character 50 the segments may be cored or
uncQred.
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When assembled, as seen in Figure 12, the grooves 54
cooperate to define an interior cylindrical surface that
surrounds the exterior of the sleeve 24. The interior
5 cylindrical surface engages the sleeve 24 to transmit a portion
of the bending component FB to the wall of the bucket B.
Those skilled in the art may appreciate that a capping
assembly suitable for use with a tube having a reduced
10 diameter neck in a swinging bucket rotor has been provided. It
may also be appreciated that the subject capping assembly
provides the necessary seal and support for use in a swinging
bucket rotor with minimal additional load exerted on the tube,
bucket and rotor body. This capability is attained without
15 adding to the number of components that the user must
purchase and handle over what is required to seal identical
tubes for use in a fixed angle or vertical rotor.
Those skilled in the art having the benefit of the
20 teachings of the present invention as hereinabove set forth
may effect numerous modifications thereto. These
modifications are, however, to be construed as Iying within
the scope of the present invention as defined !n the appended
claims.
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