U.S. patent application number 10/996911 was filed with the patent office on 2005-04-28 for shaped diaphragm for a centrifuge system rotor.
Invention is credited to Headley, Thomas D., Lamphere, David G..
Application Number | 20050090375 10/996911 |
Document ID | / |
Family ID | 24948428 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050090375 |
Kind Code |
A1 |
Lamphere, David G. ; et
al. |
April 28, 2005 |
Shaped diaphragm for a centrifuge system rotor
Abstract
A shaped diaphragm as a part of a fluid processing disposable
set acting as a centrifuge system rotor. The fluid processing
disposable set has a variable-volume chamber and a fluid port. The
shaped diaphragm defines a wall of the variable-volume chamber. The
chamber is in fluid communication with the fluid port and is
defined by a fixed wall and an elastic wall. The elastic wall is
formed by the shaped diaphragm. The disposable set may also have a
rotary seal coupled to the fluid port and fluidly coupled to the
variable-volume chamber. The shaped diaphragm may be convoluted.
The convolution may be a single fold and may have a plurality of
folds located symmetrically about an axis. The shaped diaphragm
may, alternatively, be essentially planar in an unstretched
position while varying in thickness along a diaphragm dimension.
Centrifuge rotors, systems, and methods for selective harvest of
fluid constituents from a whole fluid are detailed.
Inventors: |
Lamphere, David G.;
(Framingham, MA) ; Headley, Thomas D.; (Wellesley,
MA) |
Correspondence
Address: |
HAEMONETICS CORPORATION
400 WOOD ROAD
BRAINTREE
MA
02184-9114
US
|
Family ID: |
24948428 |
Appl. No.: |
10/996911 |
Filed: |
November 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10996911 |
Nov 24, 2004 |
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09733624 |
Dec 8, 2000 |
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6824506 |
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Current U.S.
Class: |
494/41 ;
494/45 |
Current CPC
Class: |
B04B 5/0428 20130101;
A61M 1/3696 20140204; A61M 1/3693 20130101; A61M 1/3698
20140204 |
Class at
Publication: |
494/041 ;
494/045 |
International
Class: |
B04B 011/00 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. A rotor for use in a centrifuge system, the system having means
for spinning the rotor about an axis, the rotor comprising: a fixed
portion including a conduit assembly; a rigid mounting member,
rotatably mounted around the fixed portion and the axis of rotation
of the rotor, the mounting member capable of being held and spun by
the spinning means; and a shaped diaphragm mounted to the rigid
mounting member, the diaphragm adapted to rotate with the rigid
mounting member, the diaphragm defining a variable-volume
chamber.
9. A rotor according to claim 8 further comprising: a rotary seal
located around the axis, the rotary seal providing a seal between
the rigid mounting member and the fixed portion.
10. A rotor according to claim 8, wherein the rigid mounting member
includes a boundary wall which, together with the shaped diaphragm,
defines the variable-volume chamber.
11. A rotor according to claim 8, wherein the shaped diaphragm is
convoluted.
12. A rotor for use in a centrifuge system, the system having means
for spinning the rotor, the rotor comprising: a rigid mounting
member for being held and spun by the spinning means; a shaped,
elastic diaphragm mounted on the rigid mounting member so as to
spin with the rigid mounting member, the diaphragm defining a
chamber of varying volume; and a conduit in fluid communication
with the chamber, the conduit defined by the rigid mounting
member.
13. A centrifuge system comprising: a rotor comprising: a fixed
portion including a conduit assembly; a rigid mounting member,
rotatably mounted around the fixed portion and an axis of rotation
of the rotor, the mounting member capable of being held and spun by
a chuck; and a shaped, convoluted diaphragm mounted to the rigid
mounting member, the diaphragm adapted to rotate with the rigid
mounting member, the diaphragm defining a chamber of varying
volume; and a chuck having a surface, the surface having chuck
features disposed upon it; wherein the surface and the diaphragm
define a plurality of chamber segments.
14. A method for selective harvest of fluid constituents from a
whole fluid comprising: providing a centrifuge system according to
claim 13; introducing whole fluid to the rotor of the centrifuge
system; spinning the chuck and the rotor about the axis; collecting
fluid constituents within chamber segments defined by the rotor;
and harvesting a constituent from within a chamber segment.
15. A method for selective harvest of fluid constituents from a
whole fluid comprising: providing a fluid processing disposable set
according to claim 1; introducing whole fluid to the
variable-volume chamber; spinning the chamber to separate fluid
constituents; and harvesting a constituent from the chamber.
Description
TECHNICAL FIELD
[0001] This invention relates to centrifuge systems for the general
processing of fluids and, more specifically, the separation of such
fluid into its constituents.
BACKGROUND ART
[0002] Centrifugal fluid-processing systems have been in existence
for some time. A particularly common use for such systems is for
the processing and separation of whole blood into red blood cell,
white blood cell, plasma, platelet and other constituents or
components. Such centrifuge systems are generally categorized as
either being continuous-flow devices or discontinuous-flow
devices.
[0003] In continuous-flow systems, whole fluid is input through a
conduit into a spinning rotor where the fluid is separated into its
components. A component of interest may be collected and any
unwanted components may be removed through a second conduit on a
continuous basis while more whole fluid is being input. These
systems typically employ a belt-type rotor which has a relatively
large diameter but a relatively small (typically 100 ml or less)
processing volume. Although continuous-flow systems have an
advantage that the total amount of fluid being processed may be
relatively small, they have the disadvantage that the diameter of
the rotor is large. Therefore, such systems are large and also tend
to be complicated to set up and use.
[0004] In discontinuous-flow systems, whole fluid is also input
through a conduit into a rotor where component separation takes
place. These systems usually employ a bowl-type rotor having a
relatively large (typically 200 ml or more) volume that must be
essentially filled with fluid before any of the desired components
can be harvested. When the bowl is full, the input of fresh fluid
is stopped and the unwanted components are removed through the same
conduit. When the rotor has been emptied, new whole fluid is
introduced and a second cycle begins. This process continues until
a required amount of component has been collected. Thus, removal
occurs intermittently in batches rather than on a continuous basis.
Discontinuous-flow systems have an advantage that their rotors are
relatively small in diameter but have the disadvantage that the
total volume of fluid being processed is large.
[0005] Centrifuge systems and methods for processing blood and
other fluids that are compact and easy to use and that do not have
the disadvantages of prior-art discontinuous-flow systems have been
previously disclosed in a number of U.S. patents assigned to
Transfusion Technologies Corporation. Such systems generally
include a disposable set that acts as a centrifuge rotor. In
particular, U.S. Pat. No. 6,074,335, entitled "Rotor with Elastic
Diaphragm Defining a Liquid Separating Chamber of Varying Volume,"
issued on Jun. 13, 2000, as well as its parent, U.S. Pat. No.
5,733,253, issued on Mar. 31, 1998, are hereby incorporated herein
by reference. Embodiments of this rotor include an elastic,
impermeable wall (elastic diaphragm) which defines at least a
portion of a variable-volume fluid processing chamber. Rotor
embodiments include a rigid mounting member to which the elastic
diaphragm is mounted and which is held onto and spun by a chuck.
This rigid mounting member may include a rigid wall which, together
with the elastic diaphragm, defines the variable-volume chamber.
Both the diaphragm and the rigid wall are referred to as chamber
boundaries since each of them define portions of the interior of
the variable-volume processing chamber with each having one side
which does not come into contact with the biological fluid. In some
embodiments, the diaphragm may be located inside other walls on the
exterior of the rotor, such as the rigid boundary wall or an
exterior shell.
[0006] Numerous rotor embodiments are disclosed in U.S. Pat. No.
6,074,335. By way of example, the rigid boundary wall may be large
enough to surround the maximum volume that may be taken up by the
chamber, or the rigid mounting member may be only large enough to
provide a place where the diaphragm may be mounted and where a
chuck can hold and spin the rotor. In another rotor embodiment, the
rigid boundary wall is a substantially imperforate circular wall
which extends to the periphery of the processing chamber, so as to
define the top of the processing chamber. The elastic diaphragm is
attached to the perimeter of the wall and defines the remainder of
the processing chamber. In yet another embodiment, the rigid
boundary wall is substantially imperforate but defines one opening
near the rotor's axis of rotation permitting a conduit to pass
therethrough so as to be in fluid communication with the processing
chamber. In alternative embodiments, the rigid boundary wall may
have a plurality of openings and, possibly, numerous conduits for
controlling the flow into and/or out of the rotor while the rotor
is being spun. Some rotors feature a fixed portion that does not
rotate during centrifugation. In particular, such a fixed rotor
portion may provide a fluid conduit or, perhaps, more than one such
conduit, affording fluid communication between an input source of
whole fluid, the rotating portion of the rotor, and an output.
Rotors having a fixed portion may include a rotary seal.
Embodiments of rotary seals are disclosed in both U.S. Pat. Nos.
6,074,335 and 5,904,355, the latter reference hereby incorporated
herein by reference.
[0007] FIG. 1 is a top plan view of a prior art rotor embodiment,
while FIG. 2 shows a cross-section of the rotor embodiment
illustrated in FIG. 1. Rotor 2a has an elastic boundary (i.e., an
impermeable diaphragm 31) sealed to a rigid, imperforate boundary
wall 10 by an O-ring 35 or other means. Diaphragm 31 is preferably
made of an elastic, stretchable and resilient material, such as
latex or silicone rubber. Diaphragm 31 is a simple diaphragm as
shown because, as is hereby defined, in its unstretched condition,
it exhibits an essentially constant thickness and is essentially
planar. It is to be understood that a simple diaphragm 31 may
include a non-planar region in the immediate vicinity of its
attachment to (or its seal with) wall 10 (i.e. a rim for mounting
or other such equivalently functional mounting feature). A
perforate interior wall 40--also referred to as a plate--having
holes 39, is attached under the rigid boundary wall 10. Preferably,
the boundary wall 10 and the interior wall 40 are made out of a
rigid thermoplastic. The perforate interior plate 40 is held a
short distance away from the imperforate boundary wall 10 by
standoffs (not shown), thereby forming a passage 44.
[0008] FIG. 3 is a bottom view of another prior art rotor
embodiment illustrated without a diaphragm 31 in place. FIG. 4 is a
cross-section of the rotor of FIG. 3. The embodiment of FIGS. 3 and
4 illustrate a different type of fluid outlet control from the
previous configuration. This rotor embodiment features grooves 244,
that are preferably radially aligned, formed on the bottom of
boundary wall 10 as the outlet control means, instead of tubes or
an interior perforate wall/plate 40. The grooves 244 are defined by
vertical channel walls 240 provided by boundary wall 10; if the
vertical channel walls 240 are placed close enough to each other so
that diaphragm 31 will not block off grooves 244 under pressurized
or static conditions, they can keep channels (the grooves 244) open
from the holes 239, which connect the processing chamber 30 and the
collector assembly 46, to, if desired, the periphery of the rotor,
or to whatever radius (the radius is illustrated generically in
FIGS. 3 and 4 as reference item 245) it is desired to maintain a
channel. The FIG. 4 rotor has a fixed portion (including the
collector assembly 46) which interfaces with the rotating portion
of the rotor at a rotary seal 48. An internal wall 237, shown in
FIGS. 3 and 4 as a portion of boundary wall 10, is necessary to
keep the spinning diaphragm 31 from coming into contact with the
fixed portion and possibly being abraded leading to premature
failure.
[0009] Referring now to FIGS. 5 and 6 (showing a system
incorporating, by example only, the rotor embodiment of FIG. 1),
rotor 2a may be spun in a centrifuge system that includes a chuck
4a, for holding (with clamp 8 and sealing O-ring 35) and spinning
the rotor 2a, and a pressurized fluid supply for supplying a
pressurized control fluid (preferably, a gas) adjacent the rotor's
diaphragm 31 (in this embodiment, out of hole 65 in chuck 4a, gas
pumped through channel 53 by pump 61), while the rotor 2a is being
spun by motor 50 and shaft 51. The pressurized gas may be used to
force fluid out of the rotor's processing chamber 30. The system
may also include means for applying a vacuum to the exterior side
of the diaphragm 31 (i.e., the side that does not come into contact
with the fluid being processed), so as to draw fluid into the
processing chamber 30. The chuck, generally, has an outer
peripheral wall extending from a rotatable base so as to define a
cylindrical cavity into which the rotor's diaphragm may expand.
Simple diaphragm 31 is mounted along the bottom of interior wall
40. In the chuck embodiment of FIG. 5, chuck 4a also has, extending
from its base, a core 64, so that chuck 4a defines an annular
cavity into which simple diaphragm 31 may expand and from which it
may contract, thereby accepting and releasing fluid. FIG. 6 shows
the rotor 2a (FIG. 1 embodiment shown, although use of FIG. 4
embodiment would be functionally equivalent) while it is spinning
and while whole fluid flows into the rotor 2a from the rest of a
disposable set. The disposable set includes, but is not limited to,
tube 13, boundary wall 10, and collector assembly 46. While rotor
2a is spun by chuck 4a, the collector assembly 46, including the
conduit connected to tube 13, is held in place by a brace (not
shown). When fluid touches either boundary wall 10 or interior
plate 40, it is propelled by centrifugal force towards the
periphery of rotor 2a. As more fluid enters, it continues to be
propelled to the perimeter eventually flowing through the holes in
the interior plate 40. Alternatively, in the case of the rotor of
FIGS. 3 and 4, fluid would flow toward the periphery via holes 239
and channels 244. As the volume of the fluid and the processing
chamber 30 increases, simple diaphragm 31 stretches to allow the
fluid to reach the furthest diameter and, at some point in the
process, takes on a shape shown by line 31a. As fluid enters the
rotor, displaced air in the chuck 4a escapes through hole 65, down
the shaft hole 53 and out of exhaust valve 63. If necessary, the
fluid flow rate may be increased by a vacuum in the chuck 4a
generated by the pump 61 or a separate vacuum supply (such as a
separate vacuum pump or a centralized, institutional vacuum
provided through a vacuum line). As more and more fluid enters
rotor 2a, the diaphragm 31 changes shape to accommodate it. As it
is filled further, simple diaphragm 31 sequentially takes on the
shapes shown by line 31b and line 31c and finally, when the rotor
2a is full, takes on the shape of the annular cavity of chuck 4a,
as shown by line 31d. As diaphragm 31 stretches to accommodate the
expanding size of the processing chamber 30, it comes into contact
with the annular chuck cavity in a sequential manner. As successive
portions of diaphragm 31 come into contact with the cavity, those
portions may become immobilized and cease to stretch, while other
portions of diaphragm 31 that have not yet come into contact with
the chuck continue to stretch. This sequence of events clearly
demonstrates that processing chamber 30 is truly a variable-volume
chamber.
[0010] Chuck 4a may be shaped so as to minimize variations in the
amount of stretching between different portions of the diaphragm.
The inherently non-uniform loading/stretching of simple diaphragm
31 could, potentially, reduce its useful life.
[0011] Further, the prior art embodiments of chuck 4a have
centrosymmetric features. In other words, the annular cavity
(cavities) which the elastic diaphragm 31 is capable of expanding
into, upon the filling of the resultant fluid processing chamber
30, and contracting out from, upon the emptying of chamber 30, are
symmetrically provided about the axis of rotation of the centrifuge
system. Thus, filling with whole fluid and harvesting of fluid
constituents take place essentially evenly as measured from a given
radial distance away from the axis at any point around the rotor
circumference. The axis is generally viewed to be collinear with
shaft 51.
[0012] These prior art rotor and centrifuge systems may be used in
many different processes involving biological fluid. A method for
using the rotor generally includes the steps of introducing an
unseparated fluid into the rotor's processing chamber, spinning the
rotor so as to separate the fluid into denser and lighter
constituents, and applying pressure to the diaphragm's exterior
side so as to force fluid components--usually the lighter fluid
components--through a conduit out of the chamber.
SUMMARY OF THE INVENTION
[0013] In a first embodiment of the invention, there is provided a
fluid processing disposable set having a variable-volume chamber
and a fluid port, wherein a shaped diaphragm defines a wall of the
chamber. The chamber is in fluid communication with the fluid port
and is defined by a fixed wall and an elastic wall. The elastic
wall is formed by the shaped diaphragm. The disposable set may also
have a rotary seal coupled to the fluid port and fluidly coupled to
the variable-volume chamber. The shaped diaphragm may be
convoluted. The convolution may be a single fold and may have a
plurality of folds located symmetrically about an axis. The shaped
diaphragm may, alternatively, be essentially planar in an
unstretched position while varying in thickness.
[0014] In another embodiment, a rotor for use in a centrifuge
system is provided. The rotor includes a fixed portion with a
conduit assembly and a rigid mounting member that is rotatably
mounted around the fixed portion and the axis of rotation of the
rotor. The mounting member is capable of being held and spun by a
spinning means. Further, the rotor has a shaped diaphragm mounted
to the rigid mounting member. The diaphragm is adapted to rotate
with the rigid mounting member thereby defining a variable-volume
chamber. The rotor may have a rotary seal providing a seal between
the rigid mounting member and the fixed portion. Its rigid mounting
member may have a boundary wall which, together with the shaped
diaphragm, defines the variable-volume chamber. The shaped
diaphragm may be convoluted.
[0015] Other rotors, systems, and methods for selective harvest of
fluid constituents from a whole fluid are provided in further
embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a top plan view of a prior art rotor
embodiment.
[0017] FIG. 2 shows a cross-section of the rotor embodiment
illustrated in FIG. 1.
[0018] FIG. 3 is a bottom view of another prior art rotor
embodiment shown without its simple diaphragm 31.
[0019] FIG. 4 is a cross-section of the rotor embodiment of FIG.
3
[0020] FIG. 5 illustrates, in cross-section, a prior art centrifuge
system incorporating, by example only, the rotor embodiment of FIG.
1
[0021] FIG. 6 depicts the prior art system of FIG. 5, further
indicating, by items 31a-d, sequential changes in the volume of
processing chamber 30.
[0022] FIGS. 7(a), 7(b), and 7(c) represent exploded views of a
simple diaphragm 71 (prior art, 7(a)) and of shaped, essentially
planar diaphragms (72, 7(b) and 75, 7(c)) as a part of a disposable
set to be used in conjunction with a centrosymmetric chuck, in
accordance with an embodiment.
[0023] FIGS. 8(a), 8(b), and 8(c) represent exploded views of
shaped, convoluted diaphragms 81 (8(a)), 82(8(b)), and 83 (8(c)) as
a part of a disposable set to be used in conjunction with a
centrosymmetric chuck, in accordance with embodiments.
[0024] FIGS. 9(a) and 9(b) schematically illustrate embodiments of
shaped, convoluted diaphragms with mated centrosymmetric chucks
(chucks shown in plan view) for selective fluid capture.
[0025] FIGS. 10(a) and 10(b) schematically illustrate embodiments
of shaped, convoluted diaphragms with mated asymmetric chucks
(chucks shown in plan view) for selective fluid capture.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0026] Referring first to FIGS. 7(b) and 7(c), selectively shaped
diaphragms such as are denoted therein as reference items 72 and 75
may be used in conjunction with prior art chucks and rotors for
fluid centrifugation. Such diaphragms become part of disposable
sets for fluid processing applications. Generically, within this
specification and the appended claims, the adjective "shaped" is
used as a modifier describing any diaphragm having a shape other
than that of an essentially planar body and other than having an
essentially constant thickness along a dimension when that body is
in its lowest energy state (namely, its unstretched position.) An
essentially planar diaphragm that has an essentially constant
thickness while in its essentially unstretched position (and, in
the case of the prior art rotor designs, thereby affording a
minimum volume fluid processing chamber) was earlier defined as a
"simple" diaphragm. Diaphragm 71 of FIG. 7(a) is such a simple
diaphragm. As described earlier, however, simple diaphragm 71 may
include a non-planar region in the immediate vicinity of its
attachment to/its seal with a wall or another mounting member (i.e.
a rim or other such equivalently functional mounting feature). The
above definition of "shaped" includes generally planar shapes
having intentionally variable thickness along an unstretched length
as are shown as items 72 and 75. The "variable thickness" shaped
diaphragms are described in the context of their use in providing
superior, versatile variable-volume fluid processing chambers in
conjunction with a prior art, centrosymmetric chuck 4a with core
64. Fabrication of such molded, shaped membranes is straightforward
and may, based upon application-specific stress calculations,
provide longer life diaphragms. Shaped diaphragm 72 is molded (or
otherwise formed) to be intentionally thicker within its first,
more central portion 74 than at outer portions 73. Alternatively,
shaped diaphragm 75 is formed intentionally thicker at outer
portions 76 than at more central portion 77. Factors which may
assist in determining optimal diaphragm shape include number of
centrifuge cycles required before breakage (diaphragm life), fluid
viscosity, quantity of fluid being processed, and the force
required/available to extend the diaphragm into its maximum chamber
volume position.
[0027] Additional embodiments of selectively shaped diaphragms now
to be described exhibit some degree of convolution. By definition,
these shapes are not planar when in their essentially unstretched
position. These shaped, convoluted diaphragm embodiments may also
be formed with intentional thickness variations, although the
accompanying figures do not specifically show such embodiments. The
diaphragm embodiments of FIGS. 8(a), 8(b), and 8(c) have longer
"effective" length, so that when they are distended into core 64 of
chuck 4a, the provided slack will afford greater resistance to
catastrophic failure. These diaphragm embodiments are shown being
used in conjunction with prior art, centrosymmetric chucks. With
reference now to FIG. 8(a), shaped, convoluted diaphragm 81 is made
with a single fold 810 located in its more central portion. Shaped,
convoluted diaphragm 82 is made with a pair of dimples 820, located
essentially symmetrically about the axis of rotation (FIG. 8(b)),
while shaped diaphragm 83 features periodic undulations 830 which
thereby lead to a more substantial "effective" length increase.
Similar design factors to those previously described for
non-convoluted diaphragms would be useful to find optimal shapes
for specific fluid processing applications. It is to be understood
that the particular embodiments of shaped, convoluted diaphragms in
no way limits the concept and spirit of what is being disclosed
herein.
[0028] FIGS. 9(a) and 9(b), in accordance with further embodiments,
illustrate shaped, convoluted diaphragms and mated centrosymmetric
chucks (chucks are shown in plan view) for selective fluid capture.
What is different about these chucks is that their core features,
into which shaped diaphragms 91 and 92 would distend upon filling
and spinning, are discretely, symmetrically indexed around the
circumference of the chuck. Shaped diaphragm 91 is formed with a
pair of discrete convolutions 910; the first oriented at zero
degrees and the second at one-hundred and eighty degrees when
viewed along the axis of rotation. Features 600 of chuck 94 are
located at each of these two indexed positions to accept
convolutions 910 as they are filled with fluid. This arrangement
may provide superior harvesting, particularly when the volume of
whole fluid to be processed is small. The variation shown in FIG.
9(b) facilitates capture of constituents within the confines of
discrete convolutions 920 and, optionally, within discrete pockets
921 formed in shaped diaphragm 92. Other fluid constituents may
pass out of the rotor via a second outlet means, namely, groove
930. Features 710 of chuck 95 are, again, located at two discrete,
indexed positions to accept convolutions 920 and 921; outlet 700 is
mated to accept fluid from a one-dimensional port or a
two-dimensional channel 930.
[0029] Heretofore, shaped diaphragm embodiments have been described
in conjunction with centrosymmetric chucks (i.e. chucks having
centrosymmetric features disposed upon their mating surfaces.) In
yet other embodiments, illustrated by example in FIGS. 10(a) and
10(b), asymmetrically convoluted diaphragms 100 and 101, are formed
with asymmetrically-positioned convolutions 601-604. Diaphragm 100
is shown such that convolution 601 is located essentially on the
axis of rotation and is not mated with any core feature 610 of
chuck 600. In contrast, convolution 602 may be mated with any of
the three illustrated core features 610. Convolutions and core
features may be of any shape and dimension to achieve the desired
selective harvesting of fluid constituents. The embodiment of FIG.
10(b) first features small, shallow convolutions 603 formed in
shaped diaphragm 101 mated to core feature 621 located on a first
half of the surface of chuck 620. Second, it features a larger
convolution 604 formed in shaped diaphragm 101 mated to core
feature 622 located on a second half of the surface of chuck 620.
These more intricate embodiments reveal the numerous possible
design configurations possible when shaped diaphragms are used in
centrifuge rotors. The nature of the fluid constituents as well as
those particularly of interest for harvesting will impact
configuration selection.
[0030] Although the invention has been described with reference to
several preferred embodiments, it will be understood by one of
ordinary skill in the art that various modifications can be made
without departing from the spirit and the scope of the invention,
as set forth in the claims hereinbelow.
* * * * *