U.S. patent number 3,827,563 [Application Number 05/161,645] was granted by the patent office on 1974-08-06 for supporting plates for the membranes of a dialyzer, particularly for hemodialysis.
This patent grant is currently assigned to Aktieselskabet De Danske Sukkerfabrikker. Invention is credited to Christian Thorkild Boe, Steen Gamwell Dawids.
United States Patent |
3,827,563 |
Boe , et al. |
August 6, 1974 |
SUPPORTING PLATES FOR THE MEMBRANES OF A DIALYZER, PARTICULARLY FOR
HEMODIALYSIS
Abstract
For use in a dialyzer consisting of a stack of alternate pairs
of membranes and supporting plates for these, a supporting plate is
provided which has supporting projections arranged in a pattern
such as to subdivide the path of flow from one end of the dialyzer
to the other into a multitude of short longitudinal sections each
connected at both ends through transverse flow paths with adjacent
longitudinal sections at both sides thereof.
Inventors: |
Boe; Christian Thorkild (Farum,
DK), Dawids; Steen Gamwell (Klampenborg,
DK) |
Assignee: |
Aktieselskabet De Danske
Sukkerfabrikker (Copenhagen, DK)
|
Family
ID: |
8125171 |
Appl.
No.: |
05/161,645 |
Filed: |
July 12, 1971 |
Foreign Application Priority Data
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|
|
|
|
Jul 13, 1970 [DK] |
|
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3641/70 |
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Current U.S.
Class: |
210/321.75;
210/321.77; 210/541 |
Current CPC
Class: |
B01D
63/082 (20130101); B01D 61/28 (20130101); B01D
2313/00 (20130101) |
Current International
Class: |
A61M
1/00 (20060101); B01d 031/00 () |
Field of
Search: |
;210/22,321,541
;23/258.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Spear, Jr.; Frank A.
Attorney, Agent or Firm: Watson, Cole, Grindle &
Watson
Claims
We claim:
1. A supporting plate for the membranes of a dialyzer, particularly
for hemodialysis, said plate being provided within the active part
of the plate, and on both sides thereof with projections adapted to
support a membrane and in conjunction with such membrane to form
flow paths for the dialysis liquid from one end of the plate to the
other, the blood flowing on the opposite side of the membrane in
the same direction as the dialysis liquid or in the opposite
direction, characterized in that the projections are divided into
first and second groups of projections, the projections of said
first group being substantially perpendicularly arranged with
respect to the projections of said second group, said groups of
projection are constructed and arranged in a pattern subdividing
each of the paths through which the dialysis liquid flows from one
end of the dialyzer to the other into a multitude of short
longitudinally extending path sections, said path section being
arranged for enabling the dialysis liquid to flow along both
lateral sides of each of the projections, each of said path
sections being obstructed at each end thereof by a projection and
communicating with a laterally offset longitudinal path section
through a transverse path section.
2. A supporting plate as in claim 1, characterized in that the
projections of said first group are constructed in the form of
transverse rows of ribs separated by gaps defining the longitudinal
path sections, the gaps of two consecutive rows of ribs being
laterally offset from one another.
3. A supporting plate as in claim 2, characterized in that the
distance at which the gaps of two consecutive rows of ribs are
laterally offset from one another is equal to one half of the
spacing of two consecutive gaps of each row.
4. A supporting plate as in claim 3, in which the spacing of two
consecutive gaps of each row is approximately five times the width
of each gap.
5. A supporting plate as in claim 2, in which the spacing of two
consecutive gaps of each row is approximately five times the width
of each gap.
6. A supporting plate as in claim 1, characterized in that each
longitudinal path section communicates at each end thereof with
longitudinal path sections laterally offset therefrom in both
transverse directions.
7. A supporting plate as in claim 6, characterized in that the
projections of said first group are constructed in the form of
transverse rows of ribs separated by gaps defining the longitudinal
path sections, the gaps of two consecutive rows or ribs being
laterally offset from one another.
8. A supporting plate as in claim 7, in which the spacing of two
consecutive gaps of each row is approximately five times the width
of each gap.
9. A supporting plate as in claim 7, characterized in that the
distance at which the gaps of two consecutive rows of ribs are
laterally offset from one another is equal to one half of the
spacing of two consecutive gaps of each row.
10. A supporting plate as in claim 9, in which the spacing of two
consecutive gaps of each row is approximately five times the width
of each gap.
Description
BACKGROUND OF THE INVENTION
The invention relates to a supporting plate for the membranes of a
dialyzer, particularly for hemodialysis, said plate being provided
on both sides with projections adapted to support a membrane and in
conjunction with such membrane to form flow paths for the dialysis
liquid from one end of the sheet to the other, the blood flowing on
the opposite side of the membrane in the same direction as the
dialysis liquid or in the opposite direction.
Dialyzers of this kind usually comprise a plurality of membranes
which are arranged in pairs between the said supporting plates so
that the blood flows in a relatively thin layer between the two
membranes of each pair. The dialysis liquid flows on the opposite
side of the membranes in passages formed by the projections which
at the same time support the membrane, the latter being slightly
deformed between the projections and thereby forming corresponding
passages for the flow of blood. The membranes may either be
separate sheets or may be formed by a continuous length of suitable
semipermeable material folded in zigzag between and around the
edges of the supporting plates. The assembly of the stacked
membranes and plates may be clamped together by means of bolts
placed outside the periphery of the plates and the membranes.
In the known dialyzers, the projections of the plate are so
constructed as to form continuous flow passages from one end of the
plate to the other for both the dialysis liquid and the blood, the
latter flowing in the passages formed by the bulging of the
membranes between the projections. In the known dialyzers some of
the passages may be sinuous, and parallel passages may be mutually
connected.
SUMMARY OF THE INVENTION
According to the invention, in a dialyzer of the kind described,
the projections of the supporting plates are constructed and
arranged in a pattern subdividing each of the flow paths of the
dialysis liquid into a multitude of short longitudinal path
sections, each being obstructed at either end by a projection and
communicating with a laterally offset longitudinal path section
through a transverse path section.
It has been found that by arranging the projections in the pattern
described a substantial improvement of the efficiency of the
dialyzer is obtained, the efficiency being measured e.g., as the
reciprocal value of the time required at a predetermined flow of
blood and dialysis liquid and with a certain membrane area for
obtaining a predetermined change of the concentration in the blood
of a chemical compound or ion to which the membrane is permeable.
Consequently the total membrane area of the dialyzer and thereby
the size of the dialyzer may be reduced which again means that the
volume of blood in the extracorporal circulatory system and the
time of stay of the blood in the dialyzer are reduced so that the
treatment is gentle to the patient. The reduction of the size of
the dialyzer also results in a reduction of the manufacturing
expenses which is of particular importance in the case of a
disposable dialyzer.
One probable reason for the increased efficiency of the dialyzer
according to the invention is that the projections arranged in the
pattern described will prevent the membranes from bulging in such a
manner as to form dead pockets extending continuously in the
direction of flow. Besides the dialysis liquid and the blood are
forced continually to change direction of flow from longitudinal to
transverse. Owing to these circumstances the danger of formation of
deposits is reduced and both flows of liquids will become very
homogenous and uniform. A further factor contributing towards
homogeneity and uniformity is the continual mixing of the
individual parallel flows of blood resulting from the transverse
flow between offset longitudinal path sections. It has also been
found that obstruction of the flow passages owing to the formation
of bubbles of air is practically eliminated because any such
bubbles will be caught and taken along by the flowing liquids
instead of being trapped by the walls of the flow passages, thereby
to obstruct the flow so that the corresponding portions of the
membrane area are put out of action.
Advantageously, each longitudinal path section communicates at each
end thereof with longitudinal path sections laterally offset
therefrom in both transverse directions. By this arrangement the
tendency towards intermixing of the individual flows of blood is
increased.
In a preferred embodiment of the invention the projections are
constructed in the form of transverse rows of ribs separated by
gaps defining the longitudinal path sections, the gaps of two
consecutive rows of ribs being laterally offset from one another.
In such a pattern where all the projections are rectilinear and
parallel there will be a smooth and rounded transition between the
longitudinal and the transverse path sections and there will be no
sharp edges or dead corners with stagnant blood which would
according to experience result in a risk of clotting with
precipitation of fibrin. The distance at which the gaps of two
consecutive rows of ribs are laterally offset from one another is
equal to one half of the spacing of two consecutive gaps of each
row, whereby all liquid particles will be caused to travel from one
end of the dialyzer to the other along paths of practically the
same length which contributes towards uniform and thereby optimum
utilization of the membrane area.
It has been found that a spacing of two consecutive gaps of each
row amounting to approximately five times the width of each gap
will be suitable for obtaining a favourable mutual proportion of
the lengths of the transverse and longitudinal flow path sections
and also of the supported and the non-supported membrane areas with
a view to obtaining the advantages mentioned above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a plane view of a supporting plate according to one
embodiment of the invention before the plate is stacked in a
dialyzer,
FIG. 2 a section along the line II--II in FIG. 1 showing four
plates and a continuous membrane sheet folded therebetween, such as
these parts will be located in the finished dialyzer, the plates
and the membrane sections being, however, drawn apart to improve
the illustration,
FIG. 3 a plane view on a larger scale showing a fraction of the
supporting ribs of the plate shown in FIG. 1,
FIG. 4 a section on a larger scale along the line IV--IV in FIG. 1,
and
FIG. 5-8 views corresponding to FIG. 3 of four examples of
alternative patterns of projections.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The figures of the drawings are in part diagrammatical.
FIG. 1 shows a substantially rectangular supporting plate 1 which
is provided on both faces with a multitude of supporting ribs 2 for
a semipermeable dialyzer membrane 3, see FIG. 2. At the ends of the
supporting area formed by the ribs 2 the plate is constructed at
both ends with chambers 4 and 5 serving to distribute the dialysis
liquid supplied to the dialyzer, and to collect the individual
flows of dialysis liquid to be discharged from the dialyzer,
respectively. In both chambers 4 and 5 ribs 6 are provided which
are similarly constructed as the ribs 2, but have greater
dimensions and a correspondingly greater spacing. To simplify the
illustration, only some of the ribs 2 and 6 are shown, but it is to
be understood that these cover the whole of the relevant areas of
the surface of the plate in the patterns illustrated. At each of
the chambers 4 and 5 one side edge of the plate is cranked
outwards, and between the edge and the ribs 6 openings 7 and 8 are
provided extending through the whole thickness of the plate. When a
number of plates are stacked in the finished dialyzer, as
diagrammatically illustrated in FIG. 2, with membranes 3
therebetween, and are clamped tightly together, the openings 7 and
8 of the individual plates from vertical passages extending through
the whole stack of plates and being connected through openings in
bottom and top plates, not shown, to an inlet conduit and an outlet
conduit for the dialysis liquid, respectively. As is apparent from
FIGS. 2 and 4, the ribs 2 and 6 are produced integrally with a
plane body 9, e.g., by injection moulding, said body extending to
the edge of the plate 1, with the exception of the openings 7 and
8.
At the longitudinal edge of the plate 1 remote from the openings 7
and 8 a connector element 10 for the supply and discharge of blood,
respectively, is provided at each corner. By means of a hinged
connection 11 each element 10 can be folded from the position shown
in FIG. 1 to a position on top of the plate 1, where the element
will overlap an incision 12 of the edge of the plate. Details of
the connector element 10 and the components belonging thereto for
controlling the supply and discharge of blood to and from the
dialyzer are described in further detail in a copending application
filed simultaneously with the present application. The
specification of the said co-pending application should be regarded
as part of the specification of the present invention.
FIG. 2 shows how the dialyzer is assembled from a continuous
membrane sheet 3 and a number of plates 1 whereby, as likewise
described in more detail in the said co-pending application, a
number of pockets 13 are formed for the flow of blood between
consecutive membranes, as well as a number of pockets 14 for the
flow of the dialysis liquid along the opposite surface of each
membrane. In the chamber 4 the dialysis liquid supplied through the
opening 7 is distributed across the width of the plate 1, the
liquid flowing in paths between the individual ribs 6 on the upper
edge of which the membrane 3 is supported. To facilitate the
distribution in the transverse direction, the body 9 of the plate
1, which in the zone of the opening 7 is preferably located in the
middle of the thickness of the plate, may be located below the
middle of the thickness at the opposite edge of the plate, i.e., in
the zone of the incision 12, the ribs 6 being then constructed with
correspondingly decreasing height from the right to the left on
both sides of the body 9. The vertical height of the blood inlet
chamber which is delimited between two membranes supported on the
ribs 6 on the upper and lower face respectively of two adjacent
plates 1 will then decrease correspondingly from the left to the
right side of the plate. To avoid excessively sharp bends of the
membrane which at the ends of the plates 1 is clamped between the
sealing ribs 15, illustrated in FIG. 4, and the next plate above,
it is preferable, however, that at least the ribs 6 most adjacent
to the edge of the plate have a constant height, the height then
decreasing uniformly towards the middle of the chamber 4 or 5, and
thereafter increasing towards the transition to the primary
dialysis area where the ribs 2 support the membranes. This is
illustrated in FIG. 4.
As seen in FIGS. 1 and 4, the ribs 2 are arranged in transverse
rows, gaps 16 being provided between the individual ribs of each
row. Thus, a passage 17 extending transversely of the principal
direction of flow of the dialysis liquid and the blood is formed
between each two consecutive rows of ribs, the said passage 17
extending continuously from one edge of the effective membrane area
to the opposite edge. Moreover, the individual rows of ribs 2 are
preferably mutually offset at a distance such that the gaps 16 of
each row of ribs are located directly opposite the middle of the
ribs in the two adjacent rows such as illustrated in FIG. 3. A
great number of parallel flow paths for the dialysis liquid are
formed between the ribs 2, the body 9 and the membrane 3, each such
flow path being composed of alternate longitudinal and transverse
sections formed by the gaps 16 and parts of the passages 17,
respectively. Since the membrane 3 engages the rounded edge of the
ribs 2 under the influence of a pressure of the flow of blood above
that of the flow of dialysis liquid, flow paths of similar
configuration are on principle formed in the layers of blood
between the pairs of membranes 3 present between consecutive
supporting plates, though the ribs 2 will not necessarily form an
absolute barrier to the flow of blood, viz. if the ribs 2 of
consecutive supporting plates are kept at a slight distance from
one another by suitable spacing means. Both the blood and the
dialysis liquid will therefore during their flow through the
dialyzer be forced repeatedly to change direction and there will be
a continual mixing and exchange between the individual parallel
flows. As explained above these occurrences, which are caused by
the construction and placing of the ribs 2, have been found to
result in a very efficient utilization of the membrane area. The
membrane area required for a certain yield will thereby be
correspondingly reduced. Experiments indicate that it will be
possible to reduce the total area of the membrane of a hemodialyzer
cell by between 25 and 50 percent as compared with a dialyzer cell
used up to now. As an example of the dimensions of the supporting
pattern of the plates, very good results have been obtained with a
length of the ribs 2 to 4 mm and a minimum width of the gaps 16 of
1 mm, i.e., one-fifth of the rib spacing of the transverse row. The
width or thickness of the ribs in the principal direction of flow
was about 0.5 mm and the spacing in this direction about 1.5 mm,
the width of the passages 17 thus likewise being about 1 mm. The
height of the ribs 2 was about 0.8 mm while the thickness of the
body 9 of the plate was about 1.1 mm. The total thickness of the
plate 1 was 3.0 mm so that the ribs 2 on either side were retracted
about 0.15 mm whereby the height of the layer of blood between two
membranes supported by the ribs was about 0.3 mm.
In a dialyzer constructed as above described the blood in the
individual pockets may flow in the same direction as the dialysis
liquid or in the opposite direction. Theoretically, counter flow
dialysis is somewhat more efficient, but in practice flow of the
two liquids in the same direction will frequently be preferred
because it then becomes possible to have a practically constant
pressure difference across the membrane in the whole area
thereof.
FIGS. 5-8 illustrate other examples of patterns of supporting
projections according to the invention. In the patterns of FIGS. 5,
7 and 8 the projections 2 are in the form of ribs similar to those
of the embodiment illustrated in FIG. 3. In the embodiment of FIG.
6, the projections 2' are of rounded configuration with a generally
triangular cross section. In each of FIGS. 5-8 the direction of
flow is indicated by an arrow 18.
* * * * *