Note: Descriptions are shown in the official language in which they were submitted.
FILTER
_
Th~ pres~nt invention relates to a filter housing
~or holding linear tangential membrane filters.
There are many instances where separation of a desired
5 microorganism or dxug from impurities is required to be
effected, especially in the production o IV fluids, insulin,
viral and bacterial vaccines and other drugs in pure form. The
prior art has made several approaches to this purification
problem and none has been entirely satisfactory.
One prior art approach is the use of chemical absorp-
tion and adsorption but such procedures are expensive and
occasionally introduce toxicity to the product, thereby causing
advèrse reaction when administered. Centrifugation has been
used with excellent results but the cost of equipment and
15 operation is very highO
Straight through filtration is another approach but
suffers from the drawback that there is a low throughput and
a low recovery. Stralght through filtration is suitable only
for final filtration when, for example, microorganisms must be
removed from a liquid with moderate levels of suspended solids.
Tangential filter membrane holders are known and have
shown promising results. However, the circular design of such
holders limlts the utility to laboratory testing and research
applications where only small volumes are filtered.
A yet further prior art approach is the utilization
o ultrafiltration in the form of casettes, spiral wound
cartridges, hollow tube cartridges, hollow fiber cartridges and
plate and frame types. A11 but the hollow tube cartridge clog
up when particulate concentration is high and/or when particu-
late sizes exceed 5 microns. However, the hollow tube
cartridge has not been developed for pharmaceutical applica-
tions, where a high level of residue-free sanitation and/or
sterilization are required. In addition, ultrafiltration
cartridges are limited in pore size, membrane material and flow
pattern-
The prior art, therefore, suffers the major disadvan-
~f~36
tages of cost and toxic side effects, along with other problems,such as, space requirement, inflexibility, high energy use,
sophis~icated equlpment operation and product loss.
In accordance with the present invention, there is
provided a novel filter which enables the defects of the
prior art to be overcome and enables purification of biological
fluids to be attained in a simple, inexpensive and low energy
requirement manner.
The filter of the present invention comprlses upper
and lower generally planar and rectangulax housing portions
-~hich are releasably joined together and define a cavity therein.
A planar filter medium spans the cavity and is supported therein
to separate the cavity into two fluid flow zones. Each of the
fluid flow zones is separated into a plurality of parallel fluid
flow paths extending from one end to the other, with each flow
path being of essentially uniform cross-sectional flow area.
An lnlet communicates in parallel with the fluid flow paths in
one only of the fluid flow zones at one end thereof and a first
outlet communicates in parallel with the same fluid flow paths
at the other end thereof. A second outlet communicates in
parallel with the fluid flow paths only in the other of the fluid
flow path zones.
Liquid to be concentrated or filtered is flowed from
the inlet along the fluid flow paths in the one fluid flow zone
25 across the face of the filter medium~ Some liquid, dissolved
material and particulates pass through the filter medium int-.
the fluid flow p~ths in the other of the fluid flow zones and
flo~ out of the second outlet r while the remainder of the
liquid, dissolved material and particulates flow out of the
30 first outlet. Depending on the pore size of the filter membrane
and the relative particle sizes of the desired or undesired
materials~ desired materials may be filtered and collected as
the permeate or may be concentrated.
The invention is described further, by way of illustration,
3~ with reference to the accompanying drawings, in which:
Figure 1 is a perspective view, with parts cut-away
for clarity, of a filter in accordance with one preferred
embodiment of the invention;
Figure 2 is a sectional view of the ~ilter housing
40 taken on line 2-2 of Figure l; and
Figure 3 is a schematic xepresenta-tion oE a filtra-
tion apparatus embodying the filter housing of Figures 1 and
Referring first to Figures 1 and 2 of the drawings,
5 which illustrate the current best mode of the invention known
to the applican~, a filter 10 is provided. The filter 10 is
generally planar and of rectangular shape and includes an
upper housing portion 12 and a lower housing portion 14 joined
together by any suitable means, such as bolts 16.
The lower housing portion 14 has an integral upstand-
ing wall member 18 extending perimetrically adjacent the outer
perimeter of the lower housing portion 14. The upper surface
20 of -the w?ll 18 has a groove 22 therein in which is seated
a sealing O-ring 24.
The wall 18 acts as a spacing element and receives a
perimeter surface 26 of the upper housing portion 12 in engage-
ment with the upper surface 20 of the wall 18 when the housing
10 is assembled, the O-ring 24 providing a fluid tight seal in
the area of engagement.
The upper housing portion 12 has an integral upstand-
ing wall member 28 extending perimetrically immediately
adjacent to and defining the inner extremity of the perimeter
surface 26 and-having a lower surface 30. When the upper
housing portion 12 is assembled with the lower portion 14 the
25 wall member 28 extends downwardly in engagement with the wall
member 18 towards an annular surface 32 of the lower lousing
portion 14, which has a sealing O-ring 34 seated in a groove
36 formed therein.
Mounted between lower surface 30 of the wall 28 and
30 the annular surface 32 is a filter medium 37 consisting of a
porous filter support plate 38 and a filter membrane 40. The
filter support plate 38 may be of any convenient construction
to permit fluid flow therethrough while supporting the filter
membrane 40. The filter membrane 40 may be of any convenient
35 type having pore sizes sufficient to achieve the desired fil-
trationO For example, Millipore Corporation manufacture and
sell a line of filter membranes of differing pore size from
10,000 NMWL to 8 microns, which are suitable for use in the
filter lO.
A cavity 42 is deined in the interior of the filter
lO by a recessed inner surface 44 in the lower housing
portion 14 whi.ch is spaced from the inner surface 46 of the
5 upper housing portion 12. The filter medium 37 spans the
cavity 42 and separates the same into a lower fluid flow zone
48 and an upper fluid flow zone 50.
Upstanding from and integral with the recessed
surface 44 are spaced ribs 52 which extend in parallelism from
10 one end of the recessed surface 44 to the other. The ribs 52
extend upwardly into engagement with the underside of the
filter medium ~7to separate the lower fluid flow zone 48
into three parallel flow paths 54.
Similarly, upstanding from and integral with the inn~r
15 surface 46 of the upper housing portion 12 are spaced ribs 56
which extend in parallelism from one end of the surface 46 to
the other. The ribs 56 extend downwardly coplanarly with the
corresponding ribs 52 and into engagement with the topside of
the ~ilter medium 37to sand~ich t~e filter medium 37 between
20 the ribs 52 and 56 and to separate the upper fluid flow zone
48 into three parallel flow paths 58.
~ n inlet bore 60 extends from one side of the lower
housing portion 14 towards the other and communicates in
parallel with the flow paths 54 through depressions 62 in the
25 recessed surf~ce 44 which intersect the inlet bore 60.
An outlet bore 64 extends from the sa~e side of the
lower housing portion 14 towards the other and communicates in
parallel with the flow paths 54 through depressions 66 in the
recessed surface 44 which intersect the outlet bore 64. If
30 desired, the outlet bore 64 may extend from the other side of
the lower housing portion 14 from the inlet bore 62.
A second outlet bore 68 extends from one side of the
upper housing portion 12 towards the other at approximately
the midpoint of the length thereof so as to avoid inter-
35 ference of the flow line therefrom with those communicatingwith bores 60 and 64~ The outlet bore 68 communicates in
parallel with the flow paths 58 through grooves 70 cut into
the inner surface 46 of the upper housing portion 12 and
intersec~ng the bore 68.
Turning now to Figure 3, there is shown therein a
filtering and concen~ration apparatus utilizing the filteL 10.
An inlet line 72 is connected between the inlet bore 60 and
a reservoir 74 of liquld to be purified through a peristaltic
pump 76. A first outlet line 78 is connected between the
outlet bore 64 and the reservoir 74 while a second outllne
line 80 is connected between the outlet bore 68 and a con-
tainer 82.
In the operation of the filter 10 in the apparatus
of Figure 3, two different modes are possible, namely a fil-
tering mode and a concentxation mode, depending on the rela-
tive dimension of the desired and undesired materials~ In the
filtering mode, the liquid to be filtered containing the
desired product and undesirable particulate matter of different
dimensions from the desired product, which may have a wide
size range, fr~m 20 M~ to 1 mm., is pumped by the pump 76 from
the reservoir 74 containing ~he liquid to be filtered to the
inlet bore 60 of the filter 10.
The liquid enters the parallel fluid flow paths 54
and flow across the filter medium 37 towards the outlet bore
64 at the opposite end of the fl-~id flow paths54. The pore
size of the filter membrane 40 is chosen to reject the un-
desirable particulates but to permit passage of the desired
dissolved and particulate material therethrough.
As the liquid flows across the filter medium 37 along
the fluid flow paths 54, a portion of the liquid phase passes
through the filter membrane 40 into the corresponding fluid
flow path 58 on the opposite side of the filter medium 40. The
ou~let bore 68 collects the permeate in parallel from the flow
paths 58 and the permeate flows by outline line 80 to the per-
meate reservoir 82.
The remaining liquid of higher concentration of par-
ticulate waste is collected from the flow paths 54 by outlet
bore 64 and is passed by line 78 to the reservoir 74. The
procedure is repeated until the permeate contains all the
material desired to be passed through the filter membrane 50.
Additional aqueous solvent may be added to the reservoir 74
if permeate recovery becomes difficult at high solids con-
centrations.
In the concentration mode, the filter membrane 40 is
chosen to reject the desirable particulates while permitting
undesirable particulates and dissolved materials to pass
therethrough. In this case, the liquid from the reservoir 74
5 is pumped from the inlet 60 to the outlet 64 and back to the
reservoir 74 and is purified in its flow through the filter 10
by passage of part of the liquid, particulates and dissolved
solids through the filter membrane 40. The latter material
passes out of the filter 10 through outlet bore 68 by line 80
10 to a drain 82.
The concentration may be continued until the pump runs
dry, so that the volume remaining is that contained in the flow
paths 54 and the tubing. This volume is readily recovered and
fed back to the reservoir 74 by the use of inert gas. The
15 final concentration may be controlled from this mimimum to any
desired level by the addition of pure solvent or by stopping
the concentration at any desired point.
The concentrated liquid may be purified further by
adding pure solvent to the reservoir 7~ and continuing con-
20 centration until the desired purity is achieved.
The filter 10 provided in accordance with this inven-
tion is of relatively simple construction and is relatively in-
expensive to manufacture and operate. The filter 10 is able
to accept very high concentrations of particulates and
25 particulates up to 1 mm in size do not clog the filter operation.
The filter 10 may use filter membr~ne, of varying
pore size to achieve filtration or concentration of desired
fluid, as needed. Little turbulenc~ is involved in -the fluid
flow, so that delicate microorganisms or particulates are
30 readil~ handled. A wide range of material of construction may
be used and a wide range of filter dimensions is possible.
In summary of this disclosure, the present invention
provides a filter unit in which fluid flow occurs across the
face of the filter element housed in a flat rectangular
35 housing to achieve efficient fi:Ltration in a simple and inex-
pensive manner. Modifications are possible within the scope
of this invention.
