Arrangement for the diffusion of substances between two fluids via semipermeable membranes

An arrangement is disclosed for the diffusion of substances between two fluids via semipermeable membranes. The membranes are arranged in a stack of at least two pairs of such membranes, a first fluid being conducted between the membranes in these pairs, while another fluid is conducted outside the same membranes, the membranes in the pairs being interconnected so that they form a grating of channels between themselves for the first fluid by being joined to one another at a plurality of points.

BACKGROUND OF THE INVENTION 
This invention relates to the diffusion of substances between two fluids 
via semi-permeable membranes and, more particularly, to an improved 
arrangement for interconnection of the membranes. 
In such an arrangement, the membranes are arranged in a stack of at least 
two pairs of membranes, with a first fluid being conducted between the 
membranes in these pairs and a second fluid being conducted outside the 
same membranes. In prior art arrangements for the diffusion of substances 
between two fluids via semi-permeable membranes, providing channels 
between membranes arranged in pairs was brought about by clamping the 
membranes together at points or along certain lines within carefully 
defined areas. Most frequently relatively complicated spacing plates were 
used with a plurality of projections and channels arranged between them. 
Examples of such constructions are described for example in U.S. Pat. Nos. 
3,411,630 and 3,516,548. 
In a later construction which forms the subject of the U.S. Pat. No. 
4,016,082, a similar grating of channels is produced instead by glueing, 
hot-sealing, etc. within a pattern of points, lines and/or small areas. 
This made it possible to simplify the spacing plates and to design them as 
simple frames, which required less precision in manufacture than the 
aforementioned complicated spacing plates. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to produce a further 
simplification as a result of which the need for spacing plates and/or 
frames can be eliminated. This is achieved by an arrangement which is 
characterized in that adjacent membranes from different membrane pairs 
lying next to one another are joined together along their peripheries for 
the purpose of forming between themselves a closed space for the second 
fluid, this closed space being connected to an inlet and outlet for this 
fluid. The inlet and outlet for the second fluid each comprises suitable 
holes in adjacent membranes, the holes being in stacked relationship 
relative to each other along an axis substantially perpendicular to the 
membranes. The membranes in each membrane pair are also joined to one 
another along a closed connection around the periphery of these holes. 
This ensures that the second fluid cannot penetrate in between membranes 
in the respective membrane pair and be mixed with the first fluid present 
there. 
For the first fluid the inlet and outlet can be arranged in the form of 
holes in adjacent membranes, the holes being in stacked relationship 
relative to each other along an axis substantially perpendicular to the 
membranes. The adjacent membranes of the separate membrane pairs lying 
next to one another are joined to one another also along a closed 
connection around the periphery of these holes. In this manner the first 
fluid is prevented from penetrating out into the closed spaces outside the 
respective membrane pair which is intended for the second fluid. 
The closed connections around the respective holes are produced 
appropriately by glueing or hot-sealing, but they can of course also be 
produced in a different manner, e.g. by some kind of clamping 
arrangements. 
In a preferred arrangement a number of membranes are joined to one another 
in the form of a bellows-like construction. The uppermost and the 
lowermost membrane in this bellows-like construction can then be fixed in 
an outer enclosure so that the construction can be maintained spread out 
even if anyone of the said fluids is subjected to a vacuum. 
The space between the bellows-like construction and the outer enclosure may 
also be filled by a packing which further facilitates the maintaining of 
the construction in spread out condition whilst it can at the same time 
seal up possible leakages. 
For the feed and discharge of the different fluids the outer enclosure may 
be provided with connecting nozzles for the inlet and outlet respectively 
of these fluids. The outermost membranes in the bellows-like construction 
are appropriately arranged so that they can be connected to the enclosure 
to form a seal along a closed line around the periphery of the mouth 
facing inwards of the nozzle concerned. These outer membranes may be 
connected over the whole of their surface to a top or bottom plate of this 
outer enclosure. 
In practice it has been found appropriate in two adjacent membrane pairs to 
join the membranes belonging to the respective membrane pairs to one 
another along an outer contour which is situated completely inside the 
outer contour along which adjacent membranes from different membrane pairs 
are joined to each other. 
The invention is principally intended to be used in connection with the 
dialysis of blood. The first fluid in such a case consists of blood whilst 
the other fluid consists of a salt solution with the help of which toxic 
and other undesirable substances are removed from the blood. To those 
versed in the art it will be clear, however, that the construction can 
also be used for other purposes, e.g. the oxygenation of blood when the 
first fluid consists of blood whilst the other fluid consists of air or 
oxygen. The term fluid is intended to cover liquids as well as gases. 
In the following a preferred embodiment of the arrangement in accordance 
with the invention is shown as an example with reference to the enclosed 
drawings. This embodiment is intended for the purification of blood, that 
is to say for blood dialysis, and is described therefore in connection 
with such an application, but the invention is only intended to be limited 
by the scope of the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The dialysis arrangement shown as an example consists of an outer enclosure 
which as a whole is designated 1 and which comprises an upper part 2 and a 
lower part 3. The upper part 2 is provided with an inlet nozzle 4 for the 
blood and an outlet nozzle 5 for the purifying liquid. In the same manner 
the lower part 3 is provided with an outlet nozzle 6 for the blood and an 
inlet nozzle 7 for the purifying liquid. 
The construction of these nozzles can best be seen in FIG. 3 which shows 
that the nozzles are provided with inserts 8 and 9 respectively which are 
meant on the one hand to facilitate the connecting up of flexible tubes 
for blood and purifying fluid respectively and on the other hand are 
connected to the outer membrane in a bellows-like construction of 
membranes arranged in pairs. This construction is shown on a larger scale 
in FIG. 5 where the outermost membrane is designated a.sub.1 and the 
following a.sub.2, a.sub.3, a.sub.4, a.sub.5, etc. The outermost membrane 
a.sub.1 is intended to be fixed to the insert 8 within an annular area 
marked b.sub.1. In the same manner the insert 9 is intended to be fixed 
within an annular area marked c.sub.1. The membrane a.sub.1 and a.sub.2 
are joined to one another in a point pattern which will be appreciated 
best by a comparison between FIGS. 4 and 5. The points are designated by 
the letter d. Furthermore, the membranes within each such membrane pair 
a.sub.1, a.sub.2, a.sub.3, a.sub.4, a.sub.5, a.sub.6, etc. are joined to 
one another along a closed line designated e and marked in FIG. 4 as well 
as in FIG. 5. Adjacent membranes in membrane pairs lying next to one 
another, e.g. membranes a.sub.2 a.sub.3 or membranes a.sub.4 a.sub.5 are 
joined to each other instead along annular zones b corresponding to the 
zone b.sub.1 where the outer membrane a.sub.1 is fixed to the insert 8. 
Furthermore, the lastmentioned membranes are joined to one other along a 
closed line around the periphery, this line being designated f in FIGS. 4 
and 5. By the abovementioned design an inlet 10 for the blood and 11 for 
the purifying liquid is formed. The blood is then discharged through the 
channels 12 between the membranes arranged in pairs whilst the purifying 
liquid is discharged into the closed space 13 between the different 
membrane pairs. By the attachment of the outermost membrane a.sub.1 and 
the corresponding membrane in the bottom of the membrane packet to the top 
and bottom respectively of the enclosure 1, the bellows-like design is 
maintained in spread out condition and prevented from collapsing even if 
anyone of the liquids is subjected to a vaccum. This spreading out can be 
further assisted if the spaces 14 between the enclosure 1 and the 
membranes are filled up with the help of a suitable packing. This packing 
may be utilized in such a case to achieve extra sealing of the total 
construction. The letter c finally designates annular zones along which 
membranes in the respective membrane pairs are joined together to form the 
closed channels 11 for purifying liquid. 
Naturally the invention is not limited exclusively to the embodiment of the 
subject of the invention described above, but may be varied within the 
scope of the following claims. For example, the point pattern shown may be 
substituted by a wide range of other patterns, some of which are shown as 
examples in the aforementioned U.S. Pat. No. 4,016,082. 
The term point pattern includes different types of line patterns, e.g. of 
the type as shown in the said patent application. This is justifiable 
since a line can also be regarded as being composed of a number of points.