Note: Descriptions are shown in the official language in which they were submitted.
Q~
BACKGROUND OF THE INVENTION
This invention relates to a machine used in
the manufacture of hollow fiber dialyzers of the type
used in artificial kidney systems, and to the fiber
bundles and dialyzers produced thereby.
Artificial kidney systems include dialyzers or
membrane diffusion devices through which blood from a
patient flows for treatment. One type of dialyzer is
known as a hollow-fiber dialyzer.
A hollow-fiber dialyzer includes an elongated,
and generally-cylindrically-shaped casing within which
' many very-fine, hollow and semipermeable fibers are
! positioned and secured adjacent their terminal ends to
the casing. Blood from the patient flows through the
dialyzer inside the fibers. Dialysis solution flows
through the dialyzer and surrounds and-contacts the fibers
~, ,
so as to receive bodily waste products from the blood and
remove them from the dialyzer.
The fibers are made from a long hollow filament
of Cellophane* or of a cellulose derivative, such as sold
under the trade name Cuprophan*. The filament is continuous
' and is supplied on a spool.
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*denotes trade mark
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In manufacturing the dialyzer it is impractical
to individually cut the filament into individual fibers,
group or bunch the fibers, and then assemble the dialyzer.
One suggested process for bunching the fibers is to form
the filament into a hank or bundle by winding the filament
on a wheel, grasping the wound filaments at two points and
removing the hand from the wheel. The hank or bundle is
then pulled into a cylindrical casing. In this form the
filament is still continuous, and after further preparation
the looped ends of the hank are cut so as to form the open-
ended fibers. As can be appreciated, only one device can be
made from each hank.
In other winding systems the filament is wound on
a support, which support ultimately becomes a part of the
device. Unfortunately, in the dialyzer the support is an
inactive element which occupies space and thereby reduces the
efficiency of the device.
Hollow fiber dialyzers of other diffusion devices
are made from bundles of fibers which are positioned in gen-
erally parallel relation to the longitudinal axis of thefiber bundle. The result of this is to create, during use,
relatively inhomogeneous flow spaces about the exterior of the
fibers, where shunting of the dialysis or other solution passing
around the exterior of the fibers takes place, providing
uneven and poor dialysis results. Also, stagnant areas are
formed in the dialyzer which can enhance blood clotting.
Some commercial hollow fiber dialyzers of the
prior art use fibers made from cellulose acetate, which is
then regenerated into cellulose. Those fibers, when wet,
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are very soft and do not provide a good, generally self-
supporting, fiber matrix for providing generally homogenous
flow channels through the bundle of fibers.
- As a result, the longitudinally arrayed parallel
5 fiber bundles, particularly when made of cellulose
regenerated from a cellulose ester, have exhibited dialysis
clearance rates and blood clotting characteristics which-
are below optimum.
Furthermore, the soft cellulose filaments gen-
10 erally are packed together to provide an undesirably low
"void fraction" (which is the fraction of the fiber bundle
which is not occupied by fibers, and which constitutes in
` a dialyzer the flow path for dialysis fluid). Since the
wet, soft filaments are not very self-supporting, if a void
15 fraction of as much as 0.4 is utilized, the tendency of the
soft filaments to permit the formation of fluid shunt paths
through the space between the filaments becomes very pro-
, nounced.
? Stiffer hollow cellulose filaments can be obtained
through the cuprammonium-regenerated cellulose process, which
is an old and well-known process. Such filaments are commer-
cially available, for example, from Enka Glanzstoff A.G. in
Wuppertal, West Germany. However, these fibers have been
difficult to assemble on a commercial basis into an effective
dialyzer.
:
DESCRIPTION OF THE INVENTION
In accordance with the invention there is provided
an elongated, coreless bundle of homogeneously distributed
hollow, generally longitudinally-directed, semi-permeable
filaments, free of direct mechanical attachment to each
other, for use as a fluid separation element in a diffusion
device. The filaments are positioned in the bundle whereby
the majority of the lengthsthereof, and the overall direc-
tions thereof, define an angle to the longitudinal axes of
said filament bundle. The filaments are positioned in
crossing, overlying relation with adjoining filaments,
said filaments essentially occupying individual, parallel,
flat planes. The filaments define first sets of generally
parallel strands defining a first angular relation to said
~- 15 longitudinal axis and second sets of generally parallel
strands defining an opposite angular relation to said
longitudinal axis, a first filament of a first set being
overlaid by a first filament of a second set, which first
filament of said second set is, in turn, overlaid by a
second filament of said first set, which second filament
of said first set is, in turn, overlaid by a second fila-
ment of said second set. The said relationship continues
throughout the majority of the filaments of the first and
second sets to define interleaving relationships, in
which the filaments of each set overly the immediately-
preceding filaments of the other associated set, and are
overlaid by the immediately-following filaments of said
other set, the majority of individual filaments thereof
; extending across 15 to 50 percent of the width of said
filament bundle.
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B
Accordingly, the crossing angular relation of the
filaments provides a unique structure, from the viewpoint
of longitudinal, unattached filament bundles, providing a
substantial improvement in the dialysis solution flow char-
,,.~
5 acteristic in the space between the filaments in the bundle.
The filament bundle may be fabricated as described
herein and assembled into a dialyzer, or other diffusion de-
vice such as an oxygenator, a reverse osmosis device, an
ultrafiltrator, or the like. The filament bundle is prefer-
10 ably characterized by a void fraction of at least 0.4, and
preferably about 0.6 to 0.8, which provides a desirably
greater volume for dialysis solution to percolate through
,~ the bundle outside of the filaments, for improved diffusion
f characteristics-. Preferably, relatively stiff filaments are
15 used such as cuprammonium-regenerated cellulose filaments,
polycarbonate filaments, or other filaments of generally
similar stiffness, to provide for a self-supporting
characteristic in the filaments of the bundle when wet.
Furthermore, the filamtnt bundles of this invention
20 comprise filaments, the majority of which define an angle (of
preferably about one to five degrees) to the longitudinal axis
of the bundle, and are in nonwoven crossing relationship with
neighbor filaments with the filaments each preferably essen-
tially occupying individual, paralle, flat places. The result
25 of this is to create an improved and generally more uniform
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configuration in the flow space exterior of the filaments in
the bundle, resulting in a substantial improvement in diffusion
and dialysis characteristics.
As a further characteristic of the above structure,
30 the majority and preferably essentially all of the lengths
of the filament are disposed at preferably a generally uni-
form angle to the longitudinal axis of the bundle, and also
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at an angle to a plane passing through the longitudinal axis
of the bundle, which plane is perpendicular to the planes
which contain individual filaments. Preferably, such a
_ central plane perpendicular to the planes of the individual
filaments will intersect from fifteen to fifty percent of
the filaments in the bundle, and generally most preferably
from twenty to thirty-five percent, to provide a bundle
which exhibits an improved fluid flow path, particularly
for dialysis solution, through the bundle outside of the
filaments
A further characteristic of the preferred fila-
ment bundles of this invention is that they have the pro-
perty of exhibiting increased resistence to being pulled
apart, due to their unique structure, in a direction trans-
verse to the longitudinal axis and parallel to the planeswhich contain individual filaments, when compared with
the direction transverse the longitudinal axis and perpen-
dicular to the planes which contain individual filaments.
Thus, the filament bundles of this invention exhibit an
increased independent self-supporting characteristic des-
pite the fact that they are nonwoven and free of direct
- mechanical attachment to each other. Thus they tend to
remain together in a coherent, generally-ordered bundle
while it is being assembled into a dialyzer.
Preferably, the void fraction, as defined above,
in the bundles of this invention is in excess of 0.4, and
. . .
most preferably between about 0.6 and 0.8. As a result
of this, there is more room for dialysis solution or other
fluid passing through the bundle between the filaments,
to provide an improved dialysis solution flow path which,
in particular, provides good access of the dialysis solution
to the filaments in the central region of the bundle. In
the filament bundles of the prior art, the void fraction
can be as low as 0.1.
Preferably, the angle of intersection between
the filaments and a second plurality of parallel planes
which are perpendicular to the plurality of planes which
contain individual filaments, is about one to five degrees,
and preferably two to three degrees.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a perspective view of one side of
the winding machine used to manufacture the filament bun-
! dle of this invention showing the take-up reel, two fila-
ment supply spools and the filament guide;
FIGURE 2 is a diagrammatic and perspective view
of a drive system for driving-the take-up reel and for
moving the filament guide;
FIGURE 3 is a perspective view, partially in
section, showing a two-cam system for controlling the
:~ movement of the filament guides on each side of the
machine;
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FIGURE 3A shows an alternative single cam system
for controlling the guides;
FIGURE 4 is an enlarged perspective view showing
a filament guide assembly;
FIGURE 5 is a side elevational view showing the
take-up reel;
FIGURE 6 is a sectional view taken substantially
along line 6-6 of FIGURE 5 and showing a hub-and-locking
mechanism for the take-up reel;
FIGURE 7 is a greatly enlarged elevational view
showing a portion of the take-up reel;
FIGURE 8 is a view taken substantially along line
8-8 of FIGURE 7 and showing the filament crossover;
FIGURE 9 is a perspective view showing a split
sleeve for use in bundling the filament for cutting into
the fibers; and
FIGURE 10 is an end view of the split sleeve with
one side opened;
FIGURE 11 is a schematic view of a filament
bundle of this invention showing the typical arrangement
of a few of the filaments in the bundle for illustrative
purposes;
FIGURE 12 is a sectional view taken along line
: 12-12 of FIGURE 11;
FIGURE 13 is a perspective view of a dialyzer
utilizing the filament bundle in accordance with this
invention.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
. ~
General
Referring now to FIGURE 1, winding machine 10
for making the filament bundle of this invention includes
a body 12 on each side of which is provided a winding
mechanism. The body includes a boxlike main section 14,
which is supported by a pair of legs 16 and 18. A control
console and supply spool mounting section 20 is supported
in a cantilever fashion from the back end of the main body
section 14.
Two substantially identical winding mechanisms
are provided, one on each side of the body. Thus, two
winding operations can be performed simultaneously, if
desired.
Each winding mechanism includes upper and lower
spool support shafts 22 and 24, which extend laterally
from the mounting section 20. Two filament supply spools
26 and 28, each having wound thereon a continuous hollow
filament, are mounted on the shafts 22 and 24. The filaments
30 and 32 extend from ~he spools through the filament
guide assembly 34 and to the driven take-up reel assembly
36. A protective and transparent case, such as 38, having
two access doors 38a and 38_ is carried by the main body
section so as to enclose the guide assembly and take-up
reel.
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Drive System
The rotation of the take-up reel assembly 36
_ and movement of the filament guide assembly 34 are con-
trolled by a drive system, which is enclosed with the
main body section 14. The system includes an electric
motor 40, which drives both the reel assembly and the
guide assembly. The motor speed can be caried between
0-2000 rpm.
The Reel Drive. The motor 40 is connected to
the take-up reel through a gear and timing belt system
as described hereinafter. The motor 40 is connected to
a 5:1, worm-gear-type speed reducer 42 having an output
gear 44. A geared output drive timing belt 46 is trained
; about the gear 44, as well as the driven gear 48, which
is mounted on the cross-shaft 50. A counter, take-off
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gear 52 is mounted on the cross-shaft 50 and is connected
to a rpm counter 54 by a counter timing belt 56. The gearing
system is arranged such that the counter is synchronized
with the take-up reel rpm.
A reel drive gear 58 is also mounted to the
shaft 50 and is connected to a reel drive shaft 60 by
a gear 62 on the shaft 60 and a timing belt 64. The
take-up reel assembly 36 is mounted to an end of the
shaft 60. Thus the take-up reel is driven: by the motor
40; through the gear reducer 42; through the gear 44, belt
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46 and gear 48; through shaft 50; through gear 58, belt
64 and gear 62; and through shaft 60. Through this system
the take-up reel can be driven at between 0-400 rpm.
he Guide Drive. The guide assembly 34 is mounted
so as to cause the filament to reciprocate or move
laterally with respect to the take-up reel assembly
36 at a rate related to the rotation of the take-up reel.
The motor 40 drives the guide assembly. A variable speed
control 64 is mounted to the motor 40. The speed control
includes a manual spee-' adjuster 65 and an output gear 66.
The speed of the output gear 66 is controllable between
0-400 rpm. A drive timing b~lt 68 is trained about the
r ,~ output gear 66 and a smaller drive gear 70. For each
revolution of the output gear 66, the driven gear 70
revolves 2.25 times, so as to provide a 2.25:1 gear ratio.
The driven gear 70 is secured to one end of a shaft 72,
which enters a gear box 74. A second aligned shaft 76
;- exits the gear box and a gear 78 is secured to the outer
end of the shaft 76~ A rotatable cam drive shaft 80
extends upwardly from the gear box and is driven by the
shaft 72. A bevel gear arrangement (not shown) is pro-
vided within the gear box for driving the shafts 76 and 80.
Another timing belt 82 is trained about the gear
, 78 and a gear 84 for driving a second rotatable cam drive
' ~ 25 shaft 86 and a counter 88, through a gear box arrangement
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89, which is similar to that previously described in
connection with the gear box 74. The counter 88 is syn-
chronized with the rotation of the shafts 80 and 86, which
in turn, is related to the rate of reciprocation of the
guide arm, so that the counter indicates the rate of
guide arm reciprocation or oscillation.
Referring now to FIGURE 3, each of the shafts
80 and 86 carry at their upper end a cam, such as 90 and
92, which controls the reciprocation of the guide assem-
bly 34 and the filaments. A reciprocating control rod 94
extends from within the body 14 through a sidewall 14a
and connects at its outer end to the guide assembly 34.
At the inner end, the rod 94 includes a cam follower 96,
which is biased against the cam 90 by a coiled compression
15 spring 98 that bears against a bearing plate 100
and the cam follower 96. Rotation of the cam 90 causes
the rod 94 to reciprocate. It will be appreciated that
the guide arm on the other side of the machine (not shown)
is controlled in a similar manner.
With this arrangement the rate of reciprocation
of the guide arm can be controlled between 0-900 oscilla-
ions per minute.
In the alternative cam construction shown in
FIGURE 3_, there is a single grooved cam 102. Here there
is only one drive shaft 80a which drives the single cam,
'
which, in turn, controls the two control rods 93a and 94a.
It will be appreciated that the speed of the
cam drive shaft 80 relative to the take-up reel drive
shaft 60 can be controlled and adjusted with the speed
control adjuster 65. If no adjustment is made, the ratio
of guide arm reciprocation to take-up reel rotation remains
constant regardless of the speed of the take-up
reel. However, use of the adjuster 65 permits adjustment
and control of the ratio of guide arm reciprocation to
take-up reel rotation.
Guide Arm Assembly
The guide arm assembly 34 is mounted to the
outside of sidewall 14a by a vertically adjustable mounting
plate 101, a pivotally adjustable side plate 102 and a
forwardly and rearwardly adjustable lateral support plate
104. An upper filament sensing switch 106 is mounted to the
top side of the plate 104 and a lower filament sensing
switch 108 is supported by and is positioned below the plate
104. Each switch includes leaf-life member, such as 110,
which is biased toward the filament and which engages and
senses the presence of the filament, such as 30. In the
event the filament breaks during wlnding, the member 110
moves upwardly and actuates means (not shown) for disabling
the drive system and for applying a controlled braking action
to the supply spool shafts and the take-up reel to minimize
breakage of filaments on other reels.
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An elongated and swingable guide arm 112 is
pivotally mounted at its back end to the support plate
104, forwardly of the switch 106, by a pin 114. The con-
trol rod 94 is connected to the arm at a point intermediate
the ends of the arm by a universal-type joint 116. The
head 112a at the forward end of the guide arm carries
upper and lower spring-like filament guides such as 118,
which cooperates with the spring-like filament guides, such
- as 119, associated with the switches. As the control rod
reciprocates, the head 112a swings back and forth in a
manner controlled by the cam 90.
The Take-Up Reel Assembly
' The take-up reel assembly 36, as shown in FIGURES
5 and 6, includes a filament winding plate 120 and a
hub-and-locking system 122 for removably securing the
plate to the machine.
` The Winding Plate. The plate 120 has a large,
.. j.
circular and centrally positioned opening which defines
the inner edge 124, and has six support edge carrying
sections 126, 128, 130, 132, 134 and 135. Each of the
- sections are positioned radially outwardly from the center
of the plate and equally about the periphery.
A V-shaped filament support assembly, such as
136, is mounted on the plate at each of the support sec-
tions, such as 126. Each of the support assemblies, such
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as 136, includes a pair of outwardly extending U-shaped
filament supports 138 and 140, each of which terminates
in a lower beveled edge, such as 138a and 140a. Each of
the supports, such as 138 and 140, is bolted to the plate
through bolt-receiving apertures in the plate 120. As
can be seen in FIGURE 5, the filament support assemblies
can be movably positioned in one of three different radial
; positions. Thus the supports 138 and 140 can be moved from
the inner position as shown to an intermediate position
at 142 and 144, or to an outer position at 146 and 148.
It will be appreciated that such changes in
position can increase or decrease the length of the fila-
.:
ments bundles between the sets of supports. For example,by moving the supports radially outwardly, the length of
the bundles between the adjacent supports is lengthened.
This permits the manufacture of hollow fiber dialyzers of
different lengths.
The Hub-and-Locking System. The system 122
for securing the plate 120 to the machine is shown in
both FIGURES 5 and 6. That system includes a hub as-
sembly 150, which is secured to an end of the winding
shaft 60 by a set screw 151. The hub assembly includes
a flanged, boss-like member 152 to which~a wheel-like
support plate 154 is secured. The support plate includes
~-~ 25 three radial spokes 156, 158 and 160, each of which has
; j -16-
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an elongated guide slot, such as 162. The outer periphery
of the plate is L-shaped in section and defines an axial
or laterally-extending shoulder 164 and a circumferential
- shoulder 166.
The take-up reel winding plate 120 is constructed
such that the inner edge 124 can be fitted onto the shoulder
164 with the plate against the circumferential shoulder
166. This fit prevents radial movement of the reel plate
120 relative to the hub 150. The plate 120 is removably
secured in driving relation to the hub assembly by six
studs, such as 167a, which extend outwardly from the
shoulder 166 and which engage six stud-receiving apertures,
such as 167_, in the winding plate.
- Three generally radially-extending locking arms
168, 170 and 172 are provided to secure the winding plate
,~,,
120 to the support plate 154 by preventing axial movement
of the winding plate with respect to the support plate
' shoulder 166. The arms are secured at their inner ends
to the hub 150 by a pin, such as 174, and a pivotable
collar-like member 176. Each arm carries a guide block,
~- such as 178, which moves radially within the slot 162 in
the arm. The guide block 178 is secured to the arm and
in the slot by a pin 180. Each of the locking arms is of
a length such that when the arms are in the extended, radial
and locking position, the outer end of the arm is positioned
radially outwardly over the shoulder 164 and in overlying
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relationship to the plate 120 With this construction
the arm can lock and hold the take-up plate on the winding
machine in fixed relation to the shaft 60.
The collar 176 is pivotable with respect to the
shaft 60 and to the support arms, such as 160. As can be
seen in FIGURE 5, a stop pin 182 defines the limits of
movement for the collar 176~ The collar is held in the
`~ locked position by a spring-loaded detent assembly (not
shown). In the position shown in FIGURE 5, in full line,
the arms are positioned to lock the plate in position,
Pivoting of the collar 176 causes the arms to retract and
the guide members, such as 178, slide within the slots
162, until the outer ends of the arms move within the
inner edge of the shoulder 164. With the locking arms
retracted, the take-up plate 120 can be removed from the
: machine by pulling it axially outwardly.
Operation of the Winding Machine
As can be seen from the drawings, the two
-~ spools of hollow-fiber filaments are mounted on the
shafts 22 and 24 and each filament is guided through
the guide assembly 34 and started on the take-up reel
36. The machine is actuated so that the motor rotates
the take-up reel assembly 36. As this occurs, the take-
up reel draws filament from the supply reel through the
guide assembly. The action of the cams, such as 90,
causes the guide arm 112 to oscillate or move laterally,
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~ 7
inwardly and outwardly as the take-up reel rotates. The
cam is designed in a manner such as to provide an even
distribution of the filament on the guides. The shape of
the cam cooperates in preventing build-up of filament at
the edges of the guide by increasing the arm speed at.
each end of the oscillation. Also, the cam can be shaped
to lay down a filament which exhibits a generally constant
': angle to the axis of the bundle. Furthermore, the cam pre-
vents close-packing of the filament windings and causes
the filament which is being wound to crossover the pre-
vious winding of the filament. This crossover is dia-
grammatically shown in FIGURE 8 where it can be seen that
an upper filament winding 190 crosses over a lower fila-
ment winding 192.
15It has also been found that the use of the
two reels is beneficial from the point of view that a suf-
: ficient quantity of filament is supplied so as to contin-
- uously feed the take-up reel and thereby avoid the need
to stop the winding operation and start a second spool.
. 20 This stopping has been found to be detrimental to the ef-
ficiency of the dialyzer since undesirably large flow
channels may be formed where one spool ended and the other
began. It is believed that the channel may be formed as a
. result of differences in filament tension at the end of the
. 25 first spool and at the beginning of the second spool.
During winding it has been found to be often
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desirable to rotate the take-up reel at a speed greater
than the speed at which the guide arm oscillates. This,
at the maximum,can provide, after cutting of ten percent
of the length of the bundle during removal from the reel,
individual filaments which occupy about thirty percent of
the width of the bundle. In one particular operation the
take-up reel is driven at 200 rpm and the guide arm is
oscillated at 160 or 180 oscillations per minute. Overall,
it is generally preferred for there to be from about 0.45
to 1.7 back and forth oscillations per rotation of the take-
up reel, especially in a reel of the design shown where
six bundles are simultaneously manufactured. The above
ratio may correspondingly vary for take-up reels which
~, make different numbers of lengths of filament bundles.
Thus it will be appreciated that as the geo-
metry of the take-up reel, for example the size and dia-
meter of the take-up reel, changes, the oscillations of
the guide arm must also change in order to effectuate
~ .
; proper crossover.
Once the filaments are wound on the take-up
reel and the bundles are of a sufficient size for use in
hollow fiber dialyzers, the winding operation is stopped.
Preparation of Fiber Bundles
An elongated split case 200 as shown in FIGURE
7 25 9 is used in forming the fiber bundles from the filaments
~ and for removing the bundles from the take-up reel. The
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split case includes an upper semi-cylindrical member 202
and a lower semi-cylindrical member 204, which are joined by
a pair of flexible hinges 206 and 208. As can be seen
in FIGURE 10, the sections can be opened and positioned
and clamped about the wound bundles of the filament.
Referring now to FIGURE 7, once the members
are in position, they tightly grasp the bundles of fila-
ment therebetween and the filament may then be cut at either
end of the case so as to form open-ended fibers and permit
removal of the bundles from the reel. The cutting converts
the continuous filament to the individual hollow fibers used
in the dialyzer. After cutting and removal, the individual
-~ bundles are then treated and formed into the hollow fiber
dialyzers.
Referring to Figure 11, a schematic view of a
filament bundle 210 made in accordance with this invention
is shown, with the great majority of the filaments being
omitted for a clearer disclosure of the filament relation-
ships. Basically, most of the filaments shown in the bundle
210 fit the overall relationships of the filaments in the
bundle as schematically illustrated in Figure 8, resulting
from the winding techni~ue utilized as described in this
invention. The winding tension is preferably from about 0.5
to 5 gm. per filament being wound, preferably less than one
gram per filament.
It should also be added that when two or more fila-
ments are wound onto the reel at once, as specifically disclosed
herein, the pair of filaments lie side by side in a relationship
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in which each filament as shown in Figures 8 and 11 can
represent separate multiple, parallel filament members, located
adjacent to one another in the filament bundle. The term
"filament" as utilized herein is intended to include this
plural structure.
Filament bundle 210 may, in one embodiment, be
at least five thousand generally longitudinally directed,
semi-permeable individual filaments, free of mechanical attach-
; ment to each other, made of cellulose for dialysis, or any other
appropriate material for other diffusion functions. Preferably,the dialysis filaments are made of cuprammonium regenerated
cellulose, the individual filaments having a sufficient wet
tensile strength (e.g. at least about 100 grams) and are still
enough to retain, in the main, the crossing overlying structure
into which they are formed, as illustrated in Figures 8 and 11.
"Softer" fibers, such as cellulose acetate derived filaments,
when wet, may sag at random throughout the bundle, to form
uneven flow paths outside of the filaments.
Preferably, the individual cellulose filaments used
herein define an outer diameter of 100 to 400 microns, there being
preferably at least about nine thousand separate filaments
which exhibit an aggregate surface area of at least 0 5 square
meter and preferably one to two square meters. The wall thick-
ness of the individual filaments is preferably from 10 to 30
- 25 microns fon example, 16 microns.
As shown in Figure 8, the array of filaments 190,
192 are in angular relation to each other and to longitudinal
axis 212 of the filament bundle (Figure 11). In the manufacture
of the filament bundle of this invention, filaments 190 are laid
down as guide arm 112 is swinging transversely of the longitudinal
axis 212 in one direction. Filaments 192 are laid down while
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the guide arm 112 is swinging in the opposite transverse
direction.
As shown in the detail of FIGURE 8, filament l90a
is laid down by a first swing of the guide arm 112 in a
first transverse direction as the reel assembly 36 rotates.
- Filament 192_ is then laid down on top of filament 190_
by the further rotation of reel assembly 36, as arm 112
swings back in the opposite transverse direction, so that
filament 192a overlies filament l90a. Then, on the next
rotation of reel 36 as guide arm 112 swings back in the first
transverse direction again, filament 190_ is laid down, over-
lying filament 192a. Thereafter, as guide arm 112 is swung
back again in the opposite transverse direction, and reel
36 rotates, filament 192_ is laid down, to overlie filament
l90b, and so on through the entire assembly operation, to
form the resulting filament-bundled loop, which is cut into
six filament bundles 210 in the specific embodiment shown.
Filament bundle 210, in its completed form, may
be about 15 to 25 cm., specifically, 20.5 cm., in length prior
to assembly into a dialyzer housing, and may comprise about
11,500 individual filaments having an outer diameter of 247
microns and an inner diameter of 215 microns, to provide a
dialyzer unit having the useful surface area of about 1.5
s~uare meters. Each filament may traverse about 27 percent of
the width of the bundle, except for angled filaments 216.
It should be noted that the crossing points 214
of the respective filaments as shown in Figure 8 are in
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roughly linear arrangement with each other. This does not
necessarily have to be the case. The arrangement of the
various crossing points is dependent upon the revolutions
per minute of the reel, compared with the number of
oscillations per minute of arm 112. It is, in fact, generally
preferable for the crossing points to lie in different
positions with each rotation of the reel member, to avoid
uneven Fiber buildup or "resonance".
Filaments 216 should also be noted (Figure 11) as
a category of filament which is likely to be found in most
filament bundles 210. As can be seen, these filaments are
laid down on the reel during the time that guide arm 112
reaches a lateral limit of its swing, and begins to swing
back again in the opposite direction, causing the resulting
filament to first travel in one angular direction with respect
to axis 212, and then to turn and be oriented in the opposite,
similar angular direction to axis 212, defining a lateral apex
218 at the edge of the bundle. In fact, in the actual bundles
of this invention, it is noted that some of these and other
fibers can straighten out and form other wavy bends to some
degree, and thus do not assume the ideal configuration which
is as shown in Figure 11. Nevertheless, the bundle as a whole
exhibits the essential structure, characteristics, and advan-
tages described herein.
Most preferably, the ideal angles of filaments 190,
192 and 216 to axis 212 are constant, at preferably 2 to 3
for example, 2.15 or 2.59.
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In the particular filament bundle which is
specifically described herein, the void fraction may be
about 0.64, resulting in a very substantial increase in
dialysis clearance when placed in a dialyzer housing. Also,
the dialyzer using the bundle structure of this invention,
made of cuprammonium regenerated cellulose filaments can
exhibit low blood clotting.
The filament bundle of this invention exhibits
the remarkable characteristic in that it resists being
laterally pulled apart in direction 218 (Figure 12) to a
degree which is perceptibly and significantly greater than
its resistance to being laterally pulled apart ln direction
220. The resistance of being pulled apart at direction 220
is essentially equal to the similar resistance of conventional
filament bundles, which is indeed very low. Accordingly,
while the filament bundle of this invention requires some
outside retention to hold together, it exhibits a better
tendency to retain its structure while being assembled into
a dialyzer than the conventional filament bundles.
Referring to FIGURE 13, a dialyzer for blood lS
shown incorporating filament bundle 210 of this invention.
; Basically, the dialyzer may, if desired, be of conventional
structure as currently used with filament bundles.
Bundle 210 is encased in a tubular housing 222,
.
~- 25 which encloses the squarish bundle 210 as wound (as in Figure 12),
and holds it in a cylindrical configuration for optimum flow
characteristics.~ The filament ends of bundle 210 pass through
.
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cured potting compound members 224, which are specifically
each in the shape of a disc, and sealingly positioned inside
enlarged chamber ends 226 of housing 222, so that the filaments
of bundle 210 pass through the disc-shaped structures
224 to permit flow through the Eilaments.
Caps 228 are placed on the ends of tubular
housing 222 in sealing manner, and each carry a port 230.
Potted discs 224 are slightly spaced from the inner ends
of caps 228, to provide a manifold chamber, for providing
a fluid flow path between the ports 230 through the hollow
filaments of bundle 210 in a sealed flow path.
A second flow path is provided to the dialyzer
by means of second ports 232, which may be laterally posi-
tioned adjacent the ends of housing 222 on opposite sides
thereof as shown. Enlarged portions 226 of the housing
serve as a second manifold means to uniformly distribute
fluid around the exterior of bundle 210 in the annular
chamber defined between the bundle and the inner wall of
the housing in that area. In the central, constricted
portion of housing 222, bundle 210 fits snugly within the
housing wall, without any outside space as there is in
enlarged chamber portions 226.
Accordingly, a second fluid flow path passes from
one port 232, about an enlarged chamber 226, and then in a
` 25 percolating flow path through the crossing filament of
-' .
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,.
.
-26-
'.
bundle 210 to the opposite enlarged chamber 226, and the
other port 232.
_ The flow path between ports 230 is typically used
for blood, while the flow path between ports 232 is for
dialysis solution.
The two flow paths are sealed from each other so
that there is no mixing of the fluids passing through them,
except by means of diffusion through the walls of the
filaments of bundle 210.
Preferably, a countercurrent flow pattern is
utilized, in which blood flows in one direction through
the dialyzer, and dialysis solution flows in the opposite
direction.
Dialyzers made as specifically described herein,
~; 15 having about 11,500 thin-walled capillaries of about 16
microns thickness, and defining an active surface area of
about 1.5 square meters, have been shown to provide supe-
rior clearance characteristics in the small and middle
molecule ranges, coupled with wide range, managable ultra-
filtration capabilites. The priming volume of such a
dialyser, made in accordance with this invention, may be
125 ml. in the blood compartment, with a volume change which
is relatively insensitive to pressure variations.
The dialyzer of this invention, utilizinq
,
; 25 Cupraammonium derived cellulose fibers, may be packed dry,
'.
-27-
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climinating the formaldahyde flushing procedure used insome prior art dialyzers.
It will be appreciated that numerous changes
and modifications can be made in the embodiments disclosed
herein without departing from the spirit and scope of
this invention.
:
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