U.S. patent number 3,864,265 [Application Number 05/373,160] was granted by the patent office on 1975-02-04 for edge sealed folded membrane.
This patent grant is currently assigned to Galen Laboratories, Inc.. Invention is credited to Finley W. Markley.
United States Patent |
3,864,265 |
Markley |
February 4, 1975 |
Edge sealed folded membrane
Abstract
A semipermeable membrane is folded to form a stack of accordian
pleats of which the edges are sealed to and within a housing that
provides ports for flow of blood through channels formed on one
side of the membrane and provides ports for flow of a dialysate
through channels formed on the other side of the membrane. End
edges of the folded membrane are sealed by a unique end fold sealer
plate that positions the end edges of the membrane for
encapsulation within a solidifiable liquid and also blocks passage
of the sealing material into the liquid flow ports formed in the
sides of the case. The case is formed with enlarged end portions
that facilitate the flow of the solidifiable liquid sealer material
for improved encapsulation of side edges of the stack of membrane
pleats. The case is made in two mating sections in a configuration
readily adapted to vacuum forming. The parts are arranged so that
they may be assembled in a substantially dry form and substantially
all of the solidifiable liquid sealant may be injected into the
case after all parts are assembled. Thus, the edge sealing
encapsulation of side and end edges is performed upon the
positioned and assembled parts.
Inventors: |
Markley; Finley W. (Tustin,
CA) |
Assignee: |
Galen Laboratories, Inc. (Santa
Ana, CA)
|
Family
ID: |
23471242 |
Appl.
No.: |
05/373,160 |
Filed: |
June 25, 1973 |
Current U.S.
Class: |
210/321.77;
264/257 |
Current CPC
Class: |
B01D
63/14 (20130101); B01D 61/28 (20130101); B01D
2313/04 (20130101) |
Current International
Class: |
B01d 031/00 () |
Field of
Search: |
;210/321,493
;264/257,286 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Spear, Jr.; Frank A.
Attorney, Agent or Firm: Gausewitz, Carr &
Rothenberg
Claims
What is claimed is:
1. Fluid flow transfer apparatus comprising
a membrane having
first and second surfaces,
first and second end edges,
first and second side edges,
said membrane being folded to form a stack of folds having a first
end fold terminating at said first end edge intermediate the sides
of a first end of the stack and having a second end fold
terminating at said second end edge intermediate the sides of the
other end of the stack, said stack including a plurality of fold
edges collectively forming opposite sides of the stack,
a case encompassing said stack and including
first and second case sides extending along respective sides of
said stack adjacent said end folds,
first and second case ends extending along the respective side
edges of te folded membrane,
said case including a plurality of flow ports in said case sides in
communication with said first and second membrane surfaces at said
fold edges,
a plurality of spacer members positioned between selected folds of
said stack in contact with one of said membrane surfaces,
means for positioning a portion of at least one of said end folds
including the end edge thereof at a distance from the adjoining
case top and at a distance from an adjacent membrane fold to
provide first and second end edge sealing spaces on oppostie
surfaces of said end fold,
a solidified fluid material within said first and second sealing
spaces encapsulating said one end edge, and means for blocking flow
of said fluid material from said first and second sealing spaces to
said flow ports of said case sides.
2. The apparatus of claim 1 wherein said means for positioning said
one end fold comprises an end fold plate positioned on one end of
the stack between said end fold and an adjacent inner fold of said
membrane, a first sealer spacer positioned between one surface of
said end fold and said plate, a second sealer spacer positioned at
the other surface of said end fold, and wherein said means for
blocking flow from said first and second sealing spaces comprises
first and second mutually spaced shoulders positioned adjacent
first and second sides of said stack and said case top.
3. The apparatus of claim 2 wherein said shoulders comprise first
and second blocking strips mounted along mutually opposed sides of
said plate to define a channel running along said plate between the
sides of the stack, said one end edge and said first and second
sealer spacers being positioned within said channel, said
solidified fluid material substantially filling said channel
between said plate, said blocking strips and said case top.
4. The apparatus of claim 2 wherein said plate and shoulders are
formed integrally of a substantially rigid bar, said channel being
formed as a dove-tailed groove cut in one surface of the bar and
extending longitudinally thereof intermediate its sides, said one
end edge terminating intermediate the walls of said dove-tailed
groove, and said first and second sealer spacers extending on
opposite sides of said end fold for substantially the full length
and width of said dove-tailed groove.
5. The apparatus of claim 2 wherein the side edges of said folded
membrane extend beyond the ends of said end fold plate and further
including solidified material encapsulating the side edges of said
membrane and extending between said side edges and said case top
and bottom, and extending over both surfaces of said membrane at
said side edges including the outermost surface of the end folds of
said stack, the end folds of said stack extending over said
shoulders between the shoulders and the case top and bottom.
6. The apparatus of claim 1 wherein said case top is formed with an
outwardly projecting portion intermediate the case sides, at least
one of said first and second sealer spacers being positioned within
said outwardly projecting case top, and wherein said means for
blocking flow from said sealing spaces to said flow ports comprises
an inwardly rebated portion of said case top at the outer side
edges of said case top in contiguous juxtaposition to outer side
portions of said plate, the space between said sealer strip and
said outwardly projecting case top portion being substantially
filled with said solidified material.
7. The apparatus of claim 6 wherein said end fold terminates in a
portion that is angulated with respect to the plane of the membrane
folds.
8. The apparatus of claim 6 wherein the outermost portion of said
end fold extends in a direction substantially parallel to the folds
of said stack and is spaced from said plate and said casing top by
sealer spacers positioned upon respectively opposite surfaces of
said end fold.
9. The apparatus of claim 1 wherein said case top is formed with an
outwardly projecting portion intermediate the casing sides, and
wherein said means for positioning a portion of at least one of
said end folds comprises an end fold plate between said end fold
and an adjacent inner fold, a plurality of protuberances on
mutually facing surfaces of said plate and said case top projecting
portion, and wherein said means for blocking flow comprises an
inwardly rebated portion of said case top at outer edges thereof in
contiguous juxtaposition to outer side portions of said plate.
10. The apparatus of claim 1 wherein the interior of the case is
enlarged at the ends of said top and bottom walls to provide a
space to receive encapsulating material between outermost surfaces
of said end folds and said enlarged case ends.
11. The apparatus of claim 1 wherein the interior of the case is
enlarged at end portions of said case sides and wherein
encapsulating material is positioned between said enlarged case
sides and the stack fold edges at ends of said case thereby to
effect edge encapsulation around said side edges.
12. The apparatus of claim 1 wherein at least one of said ports is
formed as a port enlargement of a portion of the case side at a
point spaced from the case end, said case side having a portion in
close juxtaposition to the fold edges of said stack between said
one port and said enlarged case side wall.
13. The apparatus of claim 12 wherein said port enlargement has a
cross section that decreases along the height of said stack and
includes a port connection in communication with the port at a
portion thereof having a relatively large cross section.
14. The apparatus of claim 1 wherein said case includes a plurality
of encapsulating liquid injection channels extending through the
walls thereof and communicating with the interior of the case.
15. The apparatus of claim 14 wherein said case is formed of first
and second mating integral case sections having conjoining securing
flanges, said encapsulating liquid injection channels being jointly
defined by mating grooves formed in adjoining portions of the
flanges of said first and second sections.
16. The method of making a fluid flow apparatus comprising the
steps of
folding a membrane having first and second surfaces, first and
second end edges, and first and second side edges into a stack of
accordian pleated folds having fold edges defining sides of the
stack and having first and second end folds on the top and bottom
of the stack, and terminating at said end edges intermediate said
stack sides,
positioning flow enabling spacers between adjacent folds of said
stack in contact with at least one surface of said membrane,
positioning an end fold plate at each end fold,
positioning portions of said end folds including said end edges at
a distance from an intermediate portion of said end fold plate,
inserting said stack together with said end fold plates into a
case,
injecting a solidifiable encapsulating material through said case
to encapsulate both said end edges and both said side edges of said
membrane along both said surfaces thereof, allowing said injected
material to solidify, and
blocking flow of said material toward the fold edges of said stack
and toward outer sides of said case during solidification of said
injected material.
17. The method of claim 16 wherein said step of inserting the stack
includes the step of positioning surfaces of said membrane at outer
sides of said end fold plates in close contiguity with inner
surfaces of said case, wherein said step of blocking flow of
material toward the fold edges comprises the step of maintaining
said end fold plate in closely contiguous relation to said case
during solidification of the injected material, and wherein said
step of positioning the end fold plate comprises positioning the
plate between each end fold and in adjacent inner fold.
18. Fluid flow transfer apparatus comprising
a membrane having
first and second surfaces,
first and second end edges,
first and second side edges,
said membrane being folded to form a stack of folds having a first
end fold terminating at said first end edge intermediate the sides
of a first end of the stack and having a second end fold
terminating at said second end edge intermediate the sides of the
other end of the stack, said stack including a plurality of fold
edges collectively forming opposite sides of the stack,
a case encompassing said stack and including
first and second case sides extending along respective sides of
said stack adjacent said end folds,
first and second case ends extending along the respective side
edges of the folded membrane,
said case including a plurality of flow ports in said case sides in
communication with said first and second membrane surfaces at said
fold edges,
a plurality of spacer members positioned between selected folds of
said stack in contact with one of said membrane surfaces,
means for positioning a portion of at least one of said end folds
including the end edge thereof at a distance from the adjoining
case top to provide an end edge sealing space for said end fold, a
solidified fluid material within said sealing space encapsulating
said one end edge,
said case being enlarged at the ends thereof to provide spaces for
receiving said fluid material between the case and the stack
whereby said fluid encapsulating material may readily flow to and
be received about side edges of the stack.
19. The apparatus of claim 18 wherein said enlargement of the case
end includes an enlargement of the interior of the case at the ends
of the top and bottom of the case to receive said fluid material
between the top of the case and the outer surface of the side edge
of the membrane end fold.
20. The apparatus of claim 18 wherein a substantially rigid end
fold plate is positioned between each end fold and an adjacent
inner fold of the membrane, said plate extending for a major
portion of the width of said case and stack to thereby facilitate
handling of the subassembly of folded membrane and spacer
members.
21. The apparatus of claim 20 wherein said case enlargement
includes enlargements of the case sides at the ends thereof, said
case sides including rebated portions in abutting relation with the
sides of the stack between the flow ports and the enlarged portions
of the ends of the case sides.
22. The apparatus of claim 20 wherein said case includes a
plurality of encapsulation material injection channels, and wherein
said end fold plate includes first and second plate sections having
elongated face-to-face grooves formed therein, one of said
elongated plate sections having a plurality of apertures formed
therethrough in communication with the grooves of the plate
sections and in communication with said injection channels, said
end folds each being sandwiched between said first and second plate
sections and having an end edge terminating within said grooves,
and first and second spacer sealer members positioned between said
end fold end edges and opposite sides of the mating grooves of said
plate sections.
23. Fluid flow transfer apparatus comprising
a membrane having
first and second surfaces,
first and second end edges,
first and second side edges,
said membrane being folded to form a stack of folds having a first
end fold terminating at said first end edge intermediate the sides
of a first end of the stack and having a second end fold
terminating at said second end edge intermediate the sides of the
other end of the stack,
said stack including a plurality of fold edges collectively forming
opposite sides of the stack,
a case encompassing said stack and including
first and second case sides extending along respective sides of
said stack adjacent said end folds,
first and second case ends extending along the respective side
edges of the folded membrane,
said case including a plurality of flow ports in said case sides in
communication with said first and second membrane surfaces at said
fold edges,
a plurality of spacer members positioned between selected folds of
said stack in contact with one of said membrane surfaces,
means for positioning a portion of at least one of said end folds
including the end edge thereof at a distance from the adjoining
case top to provide an end edge sealing space for said end
fold,
a solidified fluid material within said sealing space encapsulating
said one end edge, and
first and second rigid end fold plates extending substantially the
full width of said positioned respectively between each end fold
and an adjacent inner fold of the membrane, each said plate
terminating at a point short of the side edge of the folded
membrane whereby the subassembly of folded membrane, spacer members
and rigid plates may be readily handled and inserted into the case
and whereby the side edges of the end folds which extend beyond the
rigid plates are free to be encapsulated by said fluid
material.
24. The apparatus of claim 23 wherein said case includes top,
bottom and first and second sides at least some of which are
outwardly enlarged to provide a space between the stack and the
case for receiving encapsulating fluid material to enhance
encapsulation of the side edges thereof.
25. The apparatus of claim 23 wherein the interior of the case is
enlarged at the ends of said top and bottom walls to provide a
space to receive encapsulating material between outermost surfaces
of said end folds and said enlarged case ends.
26. The apparatus of claim 23 wherein the interior of the case is
enlarged at end portions of said case sides and wherein
encapsulating material is positioned between said enlarged case
sides and the stack fold edges at ends of said case thereby to
effect edge encapsulation around said side edges.
27. The apparatus of claim 23 wherein at least one of said ports is
formed as a port enlargement of a portion of the case side at a
point spaced from the case end, said case side having a portion in
close juxtaposition to the fold edges of said stack between said
one port and said enlarged case side wall.
28. The apparatus of claim 23 wherein said case includes a
plurality of encapsulation material injection channels, and wherein
said end fold plates each includes first and second plate sections
having elongated face-to-face grooves formed therein, one of said
elongated plate sections having a plurality of apertures formed
therethrough in communication with the grooves of the plate
sections and in communication with said injection channels, said
end folds each being sandwiched between said first and second plate
sections and having an end edge terminating within said grooves,
and first and second spacer sealer members positioned between said
end fold end edges and opposite sides of the mating grooves of said
plate sections.
Description
The present invention is an improvement on the invention disclosed
in my copending patent application for A Folded Membrane Dialyzer,
Ser. No. 233,528 now U.S. Pat. No. 3,788,482.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods and apparatus for flow of fluids
through common wall conduits and more particularly concerns methods
and apparatus for juxtaposed flow of fluids separated by a folded
membrane.
2. Description of Prior Art
Although experimental drug and diet treatments for persons having
damaged or failed kidneys have recently been suggested, the many
thousands of persons suffering from chronic kidney failure still
require either artifical blood purification or the drastic
procedure of kidney transplant. One method of artificial blood
purification, hemodialysis, involves counterflow of juxtaposed
blood and a dialysate, separated by a semi-permeable membrane.
Hemodialysis is, at present, most commonly performed in a hospital
under supervision of trained personel and present systems require
complex, expensive equipment and facilities and, at least in part
because of the great expense, are not readily available or
accessible. These systems are employed for periodic treatment of
any one patient. Thus, during periods between treatments, blood
impurities increase in concentration and the resulting ill feeling
builds up until the next treatment. Further, the treatment itself
is time consuming and painful, at least in part, because of the
necessity of connection and disconnection of the patients's blood
supply to the external apparatus.
In attempts to overcome disadvantages, complexities and expense of
prior hemodialysis treatment systems, various types of simplified
portable and small-size dialysis systems have been suggested.
Among these efforts have been those described in my prior U.S. Pat.
Nos. 3,522,885 and 3,565,258. These parallel-flow hemodialyzers are
designed to operate without use of an external blood pump and to
employ inexpensive, readily available materials so that the unit
may be discarded after each use. A major drawback of the
hemodialyzer of these prior patents resides in the use of a
relative expensive, in the preferred thickness, flattened
cellophane tube stacked in a case for separating blood from the
juxtaposed dialysate. The assemblies employing such tubes are
expensive, complex and difficult to fabricate.
Among the many dialyzers employing sheet membrane rather than
tubes, are those described in U.S. Pat. Nos. 3,396,849 and
3,442,388. However, these require complex and costly support
arrangements for the membrane as in U.S. Pat. Nos. 3,396,849 or a
corrugated support member to hold a membrane that is made in a
corrugated form as in U.S. Pat. No. 3,442,388. Adhesive bonding of
the membrane edges to a case is a significant problem in the latter
arrangement since materials used internally of the dialyzer that
may be in contact with the blood must be chosen with regard to
reaction with the blood.
In my copending application, Ser. No. 233,528, U.S. Pat. No.
3,788,482 the disclosure of which is fully incorporated herein by
this reference, I have disclosed a dialyzer designed to be used
frequently for short periods of time and which may be discarded
after use. The design eliminates the need for a blood pump and also
avoids the requirement of complex associated equipment and safety
circuits In particular, the apparatus of the invention of my U.S.
Pat. No. 3,788,482 is adapted for use under a program of daily
dialysis at home so as to provide a more nearly continuous removal
of poisons from the blood and thus avoid the increased build-up of
blood contaminates that occur with less frequent treatment.
However, the folded membrane dialyzer of my U.S. Pat. No. 3,788,482
requires a multi-element or form in place case that is relatively
expensive to fabricate. In the invention of my U.S. Pat. No.
3,788,482, end edges and side edges of the folded membrane are
sealed by encapsulation in a plastic material that forms a portion
of the housing. Access ports for blood and dialysate are formed by
removal of studs that are positioned during curing or
solidification of the sealing plastic. In the invention of my U.S.
Pat. No. 3,788,482, the end edges of the folded membrane are
positioned between support strips and encapsulated as a
sub-assembly step before the stack is mounted to the remaining
portions of the case. Alternatively, the case and edge
encapsulation are formed in place about the folded membrane
stack.
Accordingly, it is an object of the present invention to provide
dialysis that eliminates or minimizes problems of the prior art and
further eliminates or minimizes problems remaining with my prior
invention.
SUMMARY OF THE INVENTION
In carrying out principles of the present invention in accordance
with a preferred embodiment thereof, a membrane having a pair of
surfaces, end edges and side edges is folded into a stack of
accordian pleated folds. Liquid flow enabling spacers are
positioned between adjacent folds of the stack in contact with one
of the membrane surfaces. An end fold plate is positioned upon each
end edge of the membrane and the folded stack assembly is
positioned within a preformed case having appropriate liquid flow
ports and encapsulation injection channels. The case configuration
cooperates with the end fold plate to facilitate encapsulation of
the end and side edges of the folded membrane and, further, to
block flow of liquid encapsulation material into the liquid flow
ports. The end folds of the stack of folds are positioned relative
to the end fold plates so that upon injection of the encapsulation
material through the encapsulation channels, the end edges of the
folded membrane, for their entire length and including the side
edges thereof, are completely embedded in the encapsulation
material.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a dialyzer embodying principles of
the present invention;
FIG. 2 is an exploded view of FIG. 1 with one part of the case
removed;
FIG. 3 is a cross section of the dialyzer of FIG. 1;
FIG. 4 is an enlarged fragmentary view of the section of FIG.
3;
FIG. 5 is a cross section showing ports of the dialyzer;
FIG. 6 is a cross section showing an end portion of the dialyzer of
FIG. 1;
FIG. 7 is a horizontal section showing various elements of the
dialyzer of FIG. 1 with parts broken away;
FIG. 8 is a vertical section of the dialyzer of FIG. 1;
FIG. 9 is a schematic perspective of the dialyzer, with parts
broken away, and elements simplified to illustrate the flow
paths;
FIG. 10 illustrates a dove-tailed form of modification of the end
fold plates;
FIGS. 11 through 13 show still another modification of end fold
sealing;
FIG. 14 illustrates a further modification of an end fold sealing
arrangement;
FIG. 15 shows a further modification of an end fold sealing
arrangement;
FIG. 16 illustrates a modified form of split housing;
FIG. 17 illustrates still another form of split housing for the
dialyzer of the present invention; and
FIG. 18 shows still another form of end fold plates.
DETAILED DESCRIPTION
Referring to FIGS. 1 through 8, a dialyzer embodying the principles
of the present invention includes a case 10 having first and second
case sides 11a, 11b, a top 13a, a bottom 13b and first and second
case ends 16a, 16b. Although the terms top and bottom are employed
to designate specified portions of the case, these terms do not
imply or identify any preferred or required orientation of the
dialyzer in use. It will be readily understood that the described
apparatus may be used with any one of the sides, top and bottom, in
upper position or with either of the ends in upper position.
The case is conveniently made of two substantially identical vacuum
formed half sections, each having a continuous peripheral flange 15
having semicircular depressions 17a through 17h, mating with
corresponding depressions in the other case half section to form
encapsulation material injection channels 18a through 18h, that are
used as described below. Integrally formed in the case sections are
flow ports 20, 21, 22 and 23, each having a diminishing cross
section (see FIG. 5) as the ports approach the case bottom 13b and
respectively having flow connecting fittings 24, 25, 26, 27
extending through the casing top 13a and bonded to the ports at the
points thereof of maximum cross section. When the case is formed by
injection molding, the fittings may be integral with the ports.
Both casing sides are formed with enlargements 28, 29, 30, 31 (as
best seen in FIG. 7) at points adjacent the case ends and include
rebated portions 32, 33, 34, 35 (relative to enlargements 28, 29,
30, 31) formed between the enlarged side portions 28, 29, and the
flow ports.
The top and bottom of the case are also formed with enlarged
portions (FIGS. 2, 5, 8) identified at 37, 38, 39, 40. For reasons
that will appear from the ensuing description, the enlargements of
the case sections at the ends thereof are required only as
enlargements of the interior of the case at the identified areas.
Exterior enlargement is not required. Nevertheless, because of the
mode of the forming of the case sections, vacuum forming in a
preferred embodiment, it is most convenient to form the ends of the
case sections with outwardly projecting walls that inherently form
the described enlargements of the case interior. Therefore, when
enlargements of the case are referred to herein, the primary
reference is to the functional enlargement of the case
interior.
Although vacuum forming of the case is described as a method of
manufacture that is preferred because of lower initial costs of
tooling, it will be readily appreciated that the case sections may
be made by other means such as for example, injection molding.
Where other methods of manufacture are used, the various elements
of the case, the ports, the injection channels, connection flanges
and enlargements, may be formed by those related methods that are
more readily adaptable to the specific manufacturing processes.
Nevertheless, regardless of the method of manufacture chosen, the
interior dimensions and configurations of the case will be as
described herein with regard to the exemplary vacuum formed
embodiment, and these will achieve the improvements deriving from
the present invention.
Mounted within the case 10 is an edge sealed folded membrane stack
assembly 41 (FIG. 2) that is arranged to provide a number of
fluid-flow channels. The arrangement is such that all flow channels
in contact with one surface of the membrane are in communication
with each other. The two sets of channels are sealed and isolated
each from the other. As illustrated in FIGS. 3, 4 and 9, the folded
membrane stack assembly comprises a sheet of a semipermeable
membrane, initially in an exemplary rectangular configuration,
having end edges, side edges, and opposite surfaces. The membrane
is preferably formed of cellophane having a thickness of 0.0006
inches, a widely available, inexpensive and effective dialysis
material. Nevertheless, other semi-permeable membranes known in the
art may be employed without departing from principles of this
invention. The membrane is folded into the configuration
illustrated in FIGS. 2, 4 and 9 in a stack of accordian pleats,
providing a plurality of folds such as folds 42a, 42b, 42c and 42d.
The stack includes a first or top end fold 44 that terminates in a
first end edge 45 of the membrane, and a second or bottom end fold
46 terminating in a second end edge 47 of the membrane. The folds
of the stack reverse their direction at fold edges such as 48a,
48b, on one side of the stack, and fold edges 49a, 49b, etc., on
the other side, which collectively form sides of the stack.
In the exemplary arrangement illustrated in the drawings, each end
fold 44, 46 extends in the same direction, from the right side of
the stack as viewed in FIG. 4 to an intermediate portion of the
stack. The stack includes pleats or channels that comprise first
and second groups of channels for the juxtaposed flow of the two
fluids. FIG. 9 shows the arrangement of the invention with
simplified parts and illustrates the relative positioning of major
components that allow the desired flow patterns. In this drawing,
flow of contaminated fluid(blood) is indicated by the dashed lines
(arrows B) and flow of contaminated absorbing fluid (dialysate) is
indicated by solid flow lines (arrows D). All of the channels of
the first group of channels open to the left as viewed in FIG. 4
and are formed between adjacent folds defined by a single surface
of the folded membrane. All channels of the second group open to
the right as viewed in FIG. 7, and all are formed by the other
surface, between adjacent folds, of the membrane. Solely for
convenience of exposition, and not by way of limitation, the first
group of channels, those opening to the left, may be termed
"dialysate" channels since these will direct flow of a cleansing
fluid such as a dialysate, while the second group of channels,
those opening to the right, may be termed the "blood" channels
since a fluid containing contaminates or other elements to be
removed, such as blood, flows through these. Within each of the
dialysate channels is a liquid flow enabling spacer or support
member preferably formed of a plastic, non-woven mesh that will
maintain a suitable spacing between adjacent folds and yet provide
a minimum impediment to flow of dialysate through the channels.
Such non-woven mesh has two layers of threads, each layer being in
a different plane. These spacer members (not shown in FIG. 9) are
identified in the drawings by reference numerals 50a, 50b, etc.
Preferably, no spacer members are inserted between adjacent folds
of the blood channels wherefor such adjacent folds are
substantially in contact each with the other until a pressurized
liquid is caused to flow therethrough. In some cases, spacer
members may be used between all folds of both groups of channels,
particularly if the higher pressure fluid does not act to open the
higher pressure channels.
Inserted between end fold 44 at one end of the stack and the next
adjacent inner fold 42a, is an end fold plate 52. Similarly, at the
other end of the stack an end fold plate 54 is inserted between the
end fold 46 and the next adjacent inner fold 42n. The end fold
plates are identical to each other, each comprising a substantially
rigid plastic support and positioning strip 55 and a pair of
mutually spaced shoulders or liquid flow blocking strips 56, 57
that are bonded to support strip 55 to define a channel 58
therebetween. End fold 44 extends around the end fold plate over
and around the blocking strip 56 and terminates at a point
intermediate the sides, top and bottom of channel 58. The end
portion of the end fold including end edge 45 is positioned within
the channel by means of first and second end fold spacers or sealer
spacers 59, 60 that extend across the full width and length of the
channel 58 on opposite sides of the end portion of end fold 44. The
end fold spacers are conveniently formed of the same non-woven mesh
material as are spacers 50a, 50b, etc. End fold spacers 59, 60
position the end edge and an outer portion of the end fold relative
to the end fold plate so as to provide sealing spaces between the
end fold and the surface of positioning strip 55 and also between
the outer portion of the end fold and the adjoining inner surface
of the case, as best seen in FIG. 4. Preferably, the mutually
facing edges of blocking strips or shoulders 56, 57 are slightly
inclined as indicated at 64, 65 to enhance retention of of end fold
spacers 59, 60.
Each plate or support and positioning strip 55 may be a rigid
plastic bar of a width equal to the width of the stack and a length
slightly less than the length of the stack for reasons to be
described below. Shoulders 56, 57 are conveniently formed as
polycarbonate, polyurethane, polyvinyl or the like or foam strips
bonded to the flat plastic bar 55 so as to cooperate therwith to
define the channel or groove 58 for reception of encapsulating
solidifiable fluid as will be described below.
For assembly of the dialyzer, the folded assembly of accordian
pleated membrane, spacer strips and end fold plates is slightly
compressed in a vertical dimension as viewed in FIG. 4, and
inserted into the two case halves after the inner surfaces of the
sides 11a, 11b thereof have been coated with a suitable thixotropic
encapsulating material for substantially the entire length of the
casing sides between the flow ports 20, 21 and between the flow
ports 22, 23. The rigidity of the nearly full length end fold
plates 52, 54 completes a sub-assembly of membrane folds and mesh
spacers that is readily handled. The encapsulating material coating
that is placed on the interior of the case sides prior to
positioning of the folded stack assembly in the casing section is
indicated at 66 and 68 in FIG. 3. The confronting or contiguous
surfaces of flanges 15 are coated with a solvent or other bonding
agent prior to mounting of the stack assembly within the casing
sections so that when the two case sections are pressed against one
another, the flanges are bonded to each other to fix the two case
sections together. Other arrangements may be used to bond the
flanges, including clamping devices, ultrasonic welding and thermal
welding.
Encapsulating material 70 is then injected into the interior of the
casing through the encapsulation channels 18a through 18h (FIG. 1).
Because of the configuration and positioning of the end folds, end
edges and side edges in relation to the interior of the case, all
edges of the folded membrane are fully and completely encapsulated
by the injected material, and the laterally outwardly directed
openings of the blood and dialysate channels at the fold edges of
the stack are also embedded in the encapsulating material at the
inner surface of the case sides. Therefore, one surface of te
folded membrane is fully and completely sealed from and isolated
from the other surface.
The one surface as folded forms a number (such as 60 for example)
of blood channels each communicating at one end with a first flow
port, such as port 20, and each communicating in common at a second
end to a second flow port, such as flow port 21. The dialysate
channels formed by the opposite surface of the membrane all
communicate in common with a flow port, such as 22, at one end of
each channel and with another flow port such as 23 at the other end
of each channel. Note that the encapsulating material 66, 68 on the
inner surfaces of case sides 11a, 11b, does not extend to the flow
ports and thus, each of the channels that opens to a respective
flow port remains open at the area of the flow port.
The encapsulating material is liquid when injected and has a
relatively high viscosity to enable it to flow through the channel
injection ports and over and around edges of the membrane. Because
of its thixotropic properties, the material does not penetrate any
significant distance into the channels between adjacent pleats. The
liquid material solidifies in place and accordingly provides a full
and complete encapsulation of all end edges and side edges of the
membrane. A wide variety of encapsulating materials may be employed
without departing from principles of the invention but the material
chosen must be inert to blood since it will be in contact with the
blood in the blood channels. The encapsulating material readily
flows when liquid and is capable of rapid solidification, remaining
solid at room temperature. Examples of substances that can be used
for encapsulation include polyethelene, polypropylene,
polycarbonate, epoxy resins, polyester resins, polystyrene and the
like.
A particular example of a plastic material formulation which has
been successfully used in 100 parts of EPON 828, a diglycidyl ether
of bisphenyl A epoxy resin produced by Shell Chemical Company, 10
parts of triethelenetetramine which acts as a curing agent, and
10-12 parts of a thickening agent Cab-O-Sil which is a silica
aerogel produced by Cabot Corporation. Still other materials are
mentioned in my copending application, Ser. No. 233,528.
Illustrated in FIG. 4 is a significant feature of the end edge
sealing arrangement that permits use of preformed flow ports which
remain unaffected by flow of the encapsulating material during its
injection. As particularly illustrated in this figure, the blocking
strip 56 in conjunction with blocking strip 57 forms an
encapsulating material channel 58, which receives and confines the
encapsulating material as it is injected in its liquid state.
Because of the close and contiguous juxtaposition of the facing
surfaces of the blocking strips 56, 57 and the adjacent inner
surface of the top of the case top 13a, the liquid encapsulating
material cannot flow to the case sides 11a, 11b, and thus will not
flow down over the fold edges at the portions thereof that must be
open to the flow ports 20, 21, 22, 23. The same is true for the
blocking strips at the case bottom 13b.
In order to insure and facilitate encapsulation of the side edges
of the membrane, each end fold plate is made of a length less than
the width of the membrane so that the edges 43 of the latter will
extend beyond the edge 51 of the end fold plates 52, 54 as
illustrated in FIGS. 7, 8 and 9. Further, the length of the case
(FIG. 7) is somewhat greater than the total width of the membrane
so that the side edges 43 of the folded membrane will be spaced
from the inner surface of the case ends 16a, 16b.
In order to insure flow of the liquid encapsulating material over
the outermost surfaces of the side edges 43 of the end folds 44, 46
of the membrane, the interior of the case top and bottom at the
case ends is enlarged as at 37, 38 in FIG. 8. Thus, the
encapsulating material 70 can flow over and around both surfaces of
the side edges of the folded membrane.
As illustrated in FIGS. 6 and 7, case sides 11a, 11b are enlarged
at 28, 29, at the end portions thereof to provide additional space
for flow of encapsulating material around the ends of the membrane
fold edges, thus insuring a complete sealing of the membrane side
edges. Portions such as 32, 33 (in FIG. 7) of the case between the
enlarged case side ends 28, 29 and ports 20, 22 are a snug fit
against the membrane fold edges. This further assists in blocking
the flow of liquid encapsulating material from the end portion of
the case to the flow ports. The viscosity of the injected
encapsulating material is such that it will flow only a short
distance into the stack folds between adjacent side edges,
extending from the end of the case inwardly of the end of the end
fold plate by a short distance toward the outermost wall of the
flow ports. Thus, it will be seen that the end fold plates provide
encapsulation and sealing of the end edges of the folded membrane
while preventing blockage of the communication path between the
several channels and flow ports. The configuration and relative
spacing and positioning of case end enlargements, membrane side
edges and ends of the end fold plate insure sealing of side edges
of the membrane to thereby seal the ends of the several flow
channels.
In operation of the dialyzer described herein, and as best shown in
FIG. 1, 5 and 9, one of te two liquids employed in the dialysis is
introduced into a first port 21 and flows along the side of the
stack for the length of the port. The decreasing cross section of
the port insures proper distribution of the liquid, blood for
example, into all of the blood channels. Improved distribution into
all of the channels is accomplished since resistance to flow
increases as the cross section of the port narrows and,
concomitantly, resistance to flow is minimum at the portion of the
port near the blood entrance that is of greater cross section.
Thus, flow into all of the blood channels is provided and flow
continues between and along each of the flat blood channels to the
end of the channels which are in communication with flow port 20.
Similarly, and concomitantly, a counterflowing dialysate is
introduced into port 22 of which the tapering cross section
optimumly distributes the dialysate to all of the dialysate
channels. The counterflow is preferred, but not required. These
channels, like the blood channels, also extend across the full
width of the stack between case sides 11a and 11b, but are formed
by the opposite surface of the membrane. The dialysate flows
through the membrane channels, substantially the full length of the
case to port 23 from which it is collected for regeneration or
disposal.
The operation and pressures are as described in my copending
application Ser. No. 233,528. Blood is introduced into the blood
inlet port, with or without pumping, at approximately arterial
pressure or higher, and thus separates the closely adjacent sides
of the blood channels. Dialysate is introduced into the dialysate
inlet port at a slightly lower pressure. In a well-known operation,
the unwanted accumulations in a higher concentration in the blood
pass through the membrane to the dialysate which has a lower
concentration of such contaminates. Water also passes through the
membrane because of the pressure difference across the
membrane.
Illustrated in FIG. 10 is a modified form of end fold plates. In
the arrangement of FIG. 10, the end fold plate (the plates at top
and bottom of the stack are mutually identical) is made of a single
integral strip 80 having a longitudinally extending dovetailed
groove 82 formed therein. End fold 44 and end fold sealer spacers
59, 60 are mounted to the end fold plate within the dovetailed
groove or channel 82 just as in the arrangement heretofore
described. The assembly and encapsulation operation of the
arrangement of FIG. 10 is also exactly like that previously
described.
Still another form of end fold plate is illustrated in FIGS. 11, 12
and 13 wherein the plate 84 is formed with a plurality of
protruberances 85 on one surface thereof as by forming a network of
corrugations or grooves. These protruberances on plate 84 cooperate
with similar protruberances or linear corrugations 86, 87 formed on
the inner surface of outwardly projecting portions 88, 90 of the
tops of the casing sections. The tops include rebated portions 92,
94 that are in close abutting fit against outer portions of the end
fold plate on opposite sides of the case. A portion of end 44 is
interposed between the end fold plate 84 and the rebated portion 92
of the case top. In this arrangement, the cooperating
protruberances on the case top and end fold plate perform the
function of the sealer spacers of the previously described
embodiment to position the end fold together with its end edge and
form sealing spaces on opposite surfaces thereof for reception of a
free-flowing solidifiable encapsulation material. This provides
edge sealing as is described in connection with the previously
mentioned embodiments. The arrangement of plate, end fold, spacers
and case is the same at the bottom of the case. In the embodiments
of FIGS. 11 through 13, and also in the embodiment of FIG. 10, the
end fold plates are made somewhat shorter than the full width of
the folded membrane just as descirbed in connection with the first
embodiment.
Illustrated in FIG. 14 is still another modification of the end
fold edge sealing employing a case having outwardly projecting
portions 98, 100 formed on the top of the case sections and having
rebated portions 101, 102 that cooperate with an end fold plate
104, to block flow of liquid encapsulating material toward the case
sides 111a, 111b. The end fold plate 104 is formed as a flat bar of
plastic inserted between the end fold and the next adjacent inner
fold. The end fold plate is positioned in close contiguity with the
inner surface of the case section top at portions 101, 102 thereof
and the end fold 44c has an end portion 44d that is angulated with
respect to the rest of the end fold and extends into the projecting
case section top portions 98, 100. Mesh sealer spacer strips 105,
106 are positioned on opposite sides of the end portion 44d of the
end fold so that liquid encapsulation material injected through the
case top will flow over, through and around the mesh sealer spacers
to fully encapsulate both surfaces of the end fold. Again, as in
previously described embodiments, the end fold plate 104 has a
length less than the width of the folded stack to allow the side
edges of the latter to protrude beyond the ends of the plate 104
thus improving side edge encapsulation.
As shown in FIG. 15, the arrangement of FIG. 14 may be modified to
provide a slightly extended outwardly projecting portion 108, 110
of the top of the case sections and rebated portions 112, 113 in
close contiguity with outer portions of an end fold plate 115
having the end fold 44e interposed between portions 112, 113, and
strip 115. The end fold 44e has an end portion 44f that is spaced
from the case section top 110 and from the end fold plate 115 by
mesh spacer strips 116, 117 that are in contact with opposite
surfaces of end fold end portion 44f. The end fold plate 115, like
the end fold plate 104, FIG. 14, is made as a thin, flat, rigid
plastic bar having an extent less than the width of the folded
membrane to allow the side edges of the membrane to extend beyond
the end fold plate for improved side edge encapsulation.
Encapsulating material, as in previously described embodiments,
fills the sealer spaces between the case section top 108, 110 and
the end fold plate 115, flowing through the spacers 116, 117 upon
both surfaces of the end fold.
Other arrangements for encapsulating the end edge of the end fold
may be employed without departing from principles of the present
invention, bearing in mind that each arrangement should provide a
configuration, in addition to facilitating handling, that will
block flow of the liquid encapsulating material to the ports and to
those portions of the blood and dialysate channels that are in
communication with the flow ports. End fold sealing is the same at
top and bottom of the case in the arrangements of each FIGS. 14, 15
and 16.
The end fold plates 52, 54 perform two separate functions. The
first of these, which is of importance in handling and assembly of
the apparatus, derives from the fact that the two rigid end fold
plates are positioned on either side of a stack of membrane folds
and thus stiffen and support the stack together with the
interleaved mesh spacers before the stack is inserted in the case.
The rigid strips enable the fragile membrane and mesh spacer stack
to be maintained in a somewhat compressed (as when grasped by a
hand, for example) rectilinear configuration so that it may be
readily moved about, handled and inserted into the one case half,
and further, so that the second case half may be inserted over and
about the stack.
The second major function of the end fold plates in some of the
described configurations is to prevent flow of the liquid
encapsulating material into the ports 20 through 24. For this
function, the plate need not extend the full length of the
assembly, but need extend only for a short distance from its ends,
adjacent to the casing end, to a point somewhat inwardly (in the
longitudinal direction of the case) of the inward side of the
ports. Nevertheless, in order to obtain the advantages of improved
handling of the stack, the end fold plates are made as unitary
rigid strips extending nearly the full length of the stack.
Still another arrangement for blocking flow of liquid encapsulating
material into the ports may be achieved by direct contact of an
inwardly rebated portion of each corner of the top and bottom of
the case which presses directly upon the respective corner of the
end fold and next adjacent inner fold of the folded stack. To allow
such direct contact between the case top and bottom at the corners
thereof with the membrane folds at portions of the case adjacent
the ports and the corresponding corners of the outermost mesh
spacers are removed. Thus, the blocking function is achieved by
direct contact of the case with the membrane while the handling
function of the end fold plates, which now perform little or no
sealing function, is still available.
In the arrangement described above, the end fold 44 on either side
of the stack is the outermost element of at least one part of the
stack on both the top and bottom. Since the material of which the
membrane is made is fragil and may be accidently torn or otherwise
disturbed during handling or insertion into the case, it may be
desirable to afford some protection for even this end fold on both
sides of the stack. To this end, the arrangement shown in FIG. 18
may be employed wherein each end fold plate is made of two nearly
identical and facing sections 54a, 54b, each having a channel, but
with the two channels facing each other as illustrated. The outer
of the two sections, 54b, is formed with a series of apertures such
as that indicated at 54c, in alignment with the liquid
encapsulation material injecting channels, such as that designated
118b, of which a series are formed in the top and bottom of the
case as previously described. In this arrangement, the end fold 44a
extends around the inner section 54a of the split end fold plate
and terminates in the space formed by the mating grooves of the
upper and lower sections 54a and 54b. Thus, the end fold 44a is
fully and completely protected by the outer end fold plate section
54b during assembly and during handling before insertion into the
case. Liquified encapsulation material is injected through the
channel 118b, and through other similar channels, and through the
plurality of the registering apertures 54c in the upper end fold
plate section to flow into the space formed by the mating grooves
and through and along the mesh spacers that are also positioned as
previously described within the groove on either side of the end
fold 44a. The arrangement on the other end of the stack may be
identical to that shown in FIG. 18.
Although the preferred arrangement of the case employs two
substantially identical sections for economy of manufacture, it
will be readily appreciated that the case may be made in shapes
other than rectangular in section for example, and in two or more
than two non-symmetrical sections. Illustrated in FIG. 16 is an
arrangement wherein the case is formed by a first section 120 that
includes both top and bottom and one side of the case and a second
section 122 forming but a single side of the case and including the
two flow ports formed in such sides. Suitable flanges 123a, b, c
and d, are formed in the two case sections for bonding of the
sections together so as to confine and position a folded membrane
stack, exactly as previously described.
An alternate configuration of a case employing identical
symmetrical sections is illustrated in FIG. 17 as comprising
triangular cross section case halves 125, 127, each having mating
flanges 128a, b, c and d to fix the two case sections to each other
with the previously described folded membrane stack assembly
confined therein. Tapered cross-section blood ports and
encapsulating material injecting channels (not shown) are formed in
the case sections of FIGS. 16 and 17 in a manner similar to those
in previously described embodiments.
In the arrangements described herein, the use of barrier sheets and
studs or other devices to maintain communication between the
several channels and the flow ports is not required. Further, the
entire folded assembly can be pre-assembled in a totally dry
condition including folded membrane, end fold plates and the
several sealer spacer strips, requiring no adhesive, encapsulation
material nor curing time. The assembly may be positioned dry within
the casing sections of which the sides have been previously coated
with encapsulation material or with a closed cell sponge, a soft
rubber sheet, or a gel sheet, these materials not requiring cure
and which may not require liquid application. However, these
arrangements result in loss of the case stiffening effect of
bonding membrane fold edges to the case sides. The encapsulation
material is then injected into the case as needed and only one
period of cure or solidification time is necessary, greatly
minimizing the cost, effort and complexity of manufacture and
assembly.
In a preferred configuration employing a membrane with 60 folds,
the case dimensions are approximately 1-3/4 inches wide by 1-3/4
inches high by 11 inches long and the width of the ports (in the
longitudinal direction of the case) is between 1/8 and 1/2 inch.
The relatively small ratio of channel width to length and the input
flow velocities provided by the preferred port width, achieve
improved flow distribution over the surface area of the
membrane.
Although the invention has been described in a form particularly
adapted for use as a hemodialyzer, it will be readily appreciated
that it may be employed for filtering other fluids or liquids,
flowing other types of contaminated fluid through the "blood"
channels and flowing other types of cleansing solution through the
"dialysate" channels or effecting different types of transfer
between particular fluids. Of course, other encapsulation materials
compatible with the particular membrane and case material will be
chosen from those materials that exhibit proper flow
characteristics and which may be conveniently solidified.
Accordingly, the terms "blood" and "dialysate" as employed herein
to identify liquids, channels and ports, are used merely for
convenience of exposition and are to be construed as including
other fluids. Also other types of membranes or folded sheets may be
employed as dictated by the particular fluids and by the nature of
the desired transfer between the fluids.
The foregoing detailed description is to be clearly understood as
given by way of illustration and example only, the spirit and scope
of this invention being limited solely by the appended claims.
* * * * *