Note: Descriptions are shown in the official language in which they were submitted.
76~
It is frequently desirable in medical practice to cause
blood to flow through an extracorporeal circuit, e.g~ during
surgery, dialysis, etc. When this is done, the blood may come
to contain undesirable foreign matter, e.g., tissue or bone
debris resulting from surgery or injury, gas bubbles, clots, or
other matter which it is desirable to remove from the blood be-
fore it returns to the body.
There are several blood filter assembly structures known
to and/or used by the art. Among these are Esmond Patent No.
3,795~088, Luceyk et al. Patent No. 4,038,194 and Mouwen Patent
No. 4,056,476. Other known blood filters are disclosed in United
States Patents 3,457,338; 3,696,932 and 3,701,433.
Unlike the typical blood filter assembly in use today,
the present invention does no~ have the blood inlet at or near
one end of the assembly and the blood outlet at or near the other
end. Rather, the assembly of the present invention provides a
blood inlet in tlle region of the bottom end of the assembly and
the blood outlet at the bottom end of the assemb]y as well. The
blood inlet is located such that the incoming blood is directed
ZO against the inner wall of the tubular shell of the assembly such
that the blood follows a spirally upward path within the shell.
The blood then passes through a filter medium which is spaced rad-
ially inwardly from the shell and is of a generally tubular
configuration. After
passing inwardly through the filter medium, the blood
Elows downwardly and out of the assembly through an
outlet in the bottom wall thereof. The location of the
blood inlet at ~he bottom end of the filter assembly
facilitates the removal of gas bubbles because they can
rise upwardly and out of the blood rather than being
carried downwardly in an entrained condition as is the
case with blood assemblies having a top-end inlet. The
design of the present blood filter assembly also makes it
possible to provide a relatively large volume on the
10 outside of the filter whlch in turn provides space for
gas contained in the blood to escape into wherl the vent
is closed or clogged~
In addition, the spiral flow of the incoming blood
reduces the risk of blood damage because the blood is not
required to fall through a space between the inlet and
the filter medium as is the case with some top-end
assemblies and because the smooth flow path does not
require the blood to encounter sharp edges or abrupt
changes in direction.
The blood filter medium which may be used in the
assembly of the present invention may be of any of a
variety of constructions, e.g.l foam, fabric or other.
However, the preferred medium is nylon monofilaments
woven in a regular, even-sided two up and two down twill
weave having an average pore si~e in the range of 23 to
27 rnicrons and a nominal pore si~e of 25 microns. The
nylon yarn preferably has a nominal diameter of 32
mlcrons and the diameter is preferably in the range of 30
30 to 36 microns~
--2--
In the preEerred embodiment of the present inven-
tion, the filter medium is generally in the shape of a
cylindrical tube, the con.ically shaped shell tapers from
a wider diameter bottom end to a narrower diameter top
end and a cylindrical core member is positioned inside of
the filter medium and spaced therefrom.
Figr 1 shows an axial cross-sectional view of the
blood filter assembly.
Fig. 2 shows an exterior view oE the assembly.
Figs. 3 and 4 show the details of the filter med.ium
construction.
ReEerring now to the drawings in more detail, it can
be seen from Fig. 1 that the assembly comprises a shell
1, a bottom wall 2 and is provided with blood inlet 3,
blood outlet 4 and gas vent S. Positioned between the
blood inlet and the blood outlet is filter medicum 6 and
positioned within the filter medium is core 7. Bottom
wall 2 is provided with recess 8 to accommodate the
filter medium ~ and cap member 3 rests upon flange 10 of
20 core 7. Flange 10 is provided with lip 11 which also
functions to hold and position filter medium 6. Filter
medium 6 is secured in flange 10 and bottom wall 2 by a
suitable potting compound or adhesive 12. Lip 11 is
provided with spaced tabs 13 which function to center the
upper end of the filter medium in shell 1. In the
preferred embodiment shown in FigO 1, the filter medium
has a generally cylindrically tubular shape and the
radially outwardly positioned shell wall tapers from the
larqer diameter bottom end toward the smaller diameter
30 top end~ The location o~ blood inlet 3 i.5 such that ~he
~3--
incoming blood is directed along a spirally upward path
by the inner wall of the shell. As shown in Fig. 2, the
blood inlet 3 is positioned such that the incoming blood
enters in a generally tangential direction.
The blood then passes through the filter medium 6
where foreign materials are removed. The iltered blood
then passes downwardly through the space between the
filter medium 6 and the core 7 and finally out of the
filter assembly through outlet 4.
Core 7 also functions to reduce the amount of
priming fluid required during start-up.
Gas which has been removed from the blood rises
upwardly through the assembly and exits through vent
5.
The detailed construction of the filter medium 6 is
shown in Figs. 3 and 4. As indicated in Fig. 3, the
filter medium is pleated and the cylindrical filter
medium constitutes, in the preferred embodiment of the
invntion, a series of parallel pleats. In addition, in
20 the preferred embodiment of the invention, ~he woven
filter is supported between an inner and an outer poly-
propylene netO Referring to Figs. 3 and 4~ the poly-
propylene nets are indicated by numerals 14 and 15,
respec~ively, and sandwiched between them is the woven
filter 16. The polypropylene nets 14 and lS serve to
rigidify the filter structure.
It will of course, be understood by those skilled in
the art that other Eilter materials, e.gO, woven polyester
monofilament yarns or other yarns which will not degrade
or have a deleterious effect on the blood or foam mater-
ials such as polyurethane foams or other known filter
media which have proved suitable for blood filtration,
may be used. Similarly, when woven yarns are ~sed,
various weave constructions other than those specifically
set forth herein may be used without departing from the
present invention~
Having fully described the present invention, it is
to be understood that it is not limited to the specific
10 embodiments set forth above, but rather is of the full
scope of the appended claims.
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