Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
It is know well-recognized that intravenous solutions
which are to be infused must be filtered just before such
infusion. It is well-known that such solution-containers and
solution-administration sets contain quantities of particulate
material in the um (micro meter) and sub um ranges, and air for
a number of reasons, one being the fact that the solutions may
contain solubilized air which may form bubbles. It is for this
purpose that devices have been constructed to act as final
filters prior to the infusion of such solutions. A well-known,
highly-rated filter of this type is described in U. S. patent
3,471,019. This filter functions satisfactorily except when
in certain positions an air bubble can spread over the surface
of the hydrophilic filter thereby effectively cutting off
further fluid flow. The present filter assembly is designated
to obviate such and other difficulties by being position-
insensitive.
SUMMARY OF THE INVENTION
The present invention is concerned with an air-
blocking filter assembly for filtering intravenous solutions.
The device includes an open-ended, rectangularly-shaped housing.
The open end is closed by a plate which carries normally thereto
a hollow filter structure which itself is open at the far end.
The plate has an egress tube communicating with the internal
portion of the internal filter. The housing possesses an ingress
tube at the opposite side to the opening. The hollow filter
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`\~ 3~ructure is sufficiently long whereby it extends to the end
wall carrying the ingress tube but displaced therefrom. The
filter structure is secured to the said wall and the mentioned
plate is secured into the opening to enclose the housing. ~he
filter assembly is essentially constructed of two plastic, in-
tegrally-molded pieces. The actual filter material is secured
over a rib cage to produce the stated hollow filter structure.
Thereafter, the two pieces are easily and inexpensively assembled
and adhered under the aegis of ultrasonic welding, or thermal
sealing, or solvent sealing to thereby result in the filter assem-
bly of the present invention. The herein-disclosed filter will
permit, under practically all conditions at least some solution
to continue to flow since at least a portion of the filter surface
will remain in contact with the solution regardless of position.
In one particular aspect the present invention provides
an air-blocking filter comprising a cylindrical housing having
spaced end walls, a filter element defining a hollow chamber ex-
tending across the housing and into the housing, said filter ele-
ment being hydrophilic and adapted to pass liquid and block air
when wetted with liquid and being positioned in the housing so as
to be wetted by any liquid in the housing, ingress means communi-
cating with the housing and egress means communicating with the
chamber whereby liquid is passed through the housing and the fil-
ter for discharge through the egress means while air is blocked
from passing through the wetted filter.
In another particular aspect the present invention
provides an air-blocking filter comprising a housing, said housing
having a top, a bottom, side walls and an end wall, and an opening
opposite the side of the housing having-the end wall, said end
wall having an ingress port, a filter-support means, said filter-
support means having a plate arranged and constructed to mate with
said opening in said housing to thereby enclose said housing, a
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- hydrophilic filter mounted on the filter-support means, said
plate having an egress port on the outside thereof; and said plate
having projecting from the other side a hollow filter open-ended
structure extendlng into said housing and terminating in abutment
with the inside of said end wall of the housing and displaced from
said ingress port, with the filter positioned in the housing so as
to be wetted by any liquid contained in the housing whereby the
wetted filter passes liquid therethrough while blocking air.
BRIEF DESCRIPTION OF THE DR~WINGS
Figure 1 is a side elevation of the filter assembly of
the present invention.
Figure 2 is a perspective exploded view of the fi~ter
assembly.
Figure 3 is a top-plan view of the filter per se.
Figure 4 is a cross-sectional view taken along line
4-4 of Figure 2 with the elements in an assembled condition.
Figure 5 is a top-plan view of the housing for the '
filter.
Figure 6 is an end view of the filter.
Figure 7 is an enlargement of a portion of Figure 4.
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DETAILED DESC~IPTION OF THE INVENTION
Now, turning to the figures illustrating the preferred
embodiment of the invention, attention is directed to reference
numeral 10 which depicts the filter assembly of the present
invention generally. The filter assembly is shown in Figure 1
to be connected to a conduit which carries the filtered liquid,
that is, intravenous solution, away from the filter in the direc-
tion of utilization which, of course, will be in a patient. The
conduit 11 is connected to an egress tube 12 (shown by dotted
lines in Figure 1). The filter assembly also has an ingress
tube 13.
Attention is now directed to Figure 2 for greater
elucidation of the filter assembly. Note that the filter assem-
bly comprises essentially two parts. The filter assembly 10
has a generally rectangularly-shaped housing 14, having a top
15, a bottom 16, front wall 17, and back wall 18. It also
has an end wall 19, seen better in Figure 4. The top and
bottom have longitudinally-disposed, elongated concavities,
thereby making it easier to tape the filter assembly to the
lower portion of a patient's arm. It will be appreciated
that from Figure 2, the housing 14 is open at 20 at one end.
The opening is opposite the end wall 19 which also carries the
ingress tube 13 which is normal to the end wall. The opening
20 is defined by the top, bottom, front and back walls,
respectively. The just-mentioned elements, together, also
produce shoulder 21 having a raised portion facing outwardly
to form an energy ring 31 to facilitate ultrasonic welding.
When ultrasonic energy is applied to the energy ring it tends
to flatten and seal against the material in abutment therewith.
Figure 7 illustrates the energy ring. Turning to Figure 4, it
will also be discerned that internally of end wall 19 is a well
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22, arranged and constructed to accept one end of the filter 23,
more about which will be imparted below~
The ingress tube 13 is formed integral with respect
to the housing. The tube possesses an internal bore 24 which
convgrges inwardly. The tube 13 is connected to a conduit (not
shown) which is the source of fluid, that is, intravenous solution
which is to be subjected to the filtering action or the present
invention. The mentioned conduit also has a taper and an outer
diameter matching the taper and diameter of the bore 24. The
conduit, in other words, is secured internally with respect to
the bore by friction fit. The conduit may be a friction fit
or may be more permanently implanted in the tube 13 as by
heat-sealing, or by solvent adhesion, all well-known and useful
methods.
Figure 5 illustrates the housing 14 by means of a
top-plan view. Of interest to the instant matter is the fact
that the housing may be constructed by means of injection-
moulding techniques. Propitiously, it has been found favorable
to employ a plastic material such as polystyrene, ABS plastic,
or an acrylic resin. Furthermore, the preferred synthetic
plastic material is a transparent material whereby the filter
assembly of the present invention finds utility as a means for
determining the presence of solution or air in the assembly,
Now, attention is directed to the filter 23, in order
to complete the understanding of the invention. First, Figures
2 and 3 should be considered. T~e filter 23 is arranged and
constructed to present an in-line filter surface. The filter
23 has a plate 25 which has a configuration and suitable
dimensions to constitute an end wall for heretofore mentioned
opening 20. On one side of the plate 25, normal thereto, is
the egress tube 12. On the other side of the plate and also
normal thereto, is a hexagonal structure 26 which has six ribs 27
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shown by dotted lines in Figure 3~ The preferred embodiment
herein described relates to a hexagonal configuration. However,
it is contemplated that many other shapes, for example, square,
circular or the like, structures are within the purview of the
inventive concept and the number of ribs may be adjusted
accordingly. A microporous filter membrane 28 extends over and
between the ribs 27 to enclose the hexagonal structure 26. The
hexagonal structure terminates in a hollow hexagonal ring 28
which is integrally attached to a rectangular plate 29. The
hexagonal structure also terminates in a hexagonal ring 30 ~
which is integrally secured to the backside of plate 25. The
filter memhrane is hydrophilic and is reinforced with a screen
material, such as, nylon, polyester or other suitable organic
or inorganic materials. It has a nominal pore size of 0.45 um
(micro meters), but other sizes, larger or smaller, may be used.
For example, it should be possible to use a pore size from
between .1 um to 14 um. The filter membrane can be a sleeve
or in strip form and attached to the ribs 27 and the hexagonal
rings 28 and 30 by thermal means, during the molding cycle of
the support structure, for instance. It has been expeditious
to apply the membrane during the molding step as the support
structure will be soft and the membrane will adhere when it is
cooled. The rectangular plate 29 is adapted to fit into the
well 22 of end wall 19 of the housing when the filter assembly
is assembled.
The plate 29 does not cover the end portion of the
hollow hexagonal structure as can be seen from Figure 6. The
ends of the ribs 27 may be seen in the figure as well as the
bore of egress tube 12. The internal surface of the well 22
and the end wall 19 thereof serve to close the end of the hexa-
gonal structure 26. The entire structure of the filter 23,
except for the microporous membrane, may be constructed by
injection molding of synthetic resin or plastic material.
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Attention is now specifically directed to Figure 4 to
illustrate the assemblage. The plate 25 mates in the shoulder
21 of the housing against the energy ring 31 and is secured by
ultrasonic welding, for instance. As was mentioned before, the
plate 29 is designed to snugly fit into the well 22. The plate
29, as can be seen from Figure 6, also possesses a raised energy
ring 32. The plate 29 is also firmly secured as by ultrasonic
welding, for instance. Both plates can be joined to their
mating surfaces simultaneously, incorporating the technique of
near- and far-field ultrasonic welding. During the welding
step, the energy rings become molten causing those areas to
bond to their mating surfaces upon cooling The outer surface
of egress tube 12 is tapered to more easily accept the conduit
11 which is positioned outermost of egress tube 12.
Liqu~d flowing into the filter assembly of the present
invention is usefully cleared of small particulate material which
may be deposited on the surface of the microporous membrane
material on the outside of the hexagonal structure or trapped
in the membrane pores. The device is designed to provide
excellent filter surface area in the confines of a relatively
qmall filter assembly wherein the microporous membrane material
is adequately supported so that the mer,lbrane is not b~rst under
the normal pressures encountered during gravity infusion of
solutions of the liquid. Also, the ingress and egress tubes
are arranged and constructed so that the connections made to
the filter assembly are in a manner to avoid sharp corners.
As stated heretofore, even with a large quantity of air in the
filter aqsembly, there will be at leaqt a degree of useful
filter area through which some liquid may flow. The air will
not pass through the filter because the membrane is hydrophilic.
Also, the air will not be able to totally block the filter
because of access to the liquid along 360, so that the filter
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operates even when turned in any direction or position unless,
of course, the entire filter unit has been filled with air.
The fact that the housing 14 is preferably transparent makes
it possible to see whether or not there is any accumulated air.
The filter of the present invention may be easily purged of
excess air by momentarily disconnecting the conduit at ingress
port 13 to permit the air to be replaced therethrough while
liquid is still permitted to flow into the filter.
From a consideration of the present invention, it will
be appreciated that the filter assembly may be employed in a
reverse-flow manner. Of course, in such an instance, it would
be wise to change the structure of the ingress and egress ports.
One of the primary advantages of the present invention
is that the air-blocking filter of the invention is position-
insensitive, that is, it is capable of passing liquid through
the hydrophilic filter and blocking air no matter how the
filter is disposed provided that the filter has been wetted
with the liquid.
The position insensitivity of the filter of the
inv~tion is assured by the geometry of the housing 14 and
the geometry of the filter 23. As shown in Figure 2, the
housing is cylindrical in shape; as used herein, the term
ncylindrical" is intended to refer to and include a surface
traced by a straight line moving parallel to a fixed ~traight
line. The cross-section of the housing can thus be circular
or polygonal in shape.
The filter 23 has a relatively flat configuration
defining a hollow chamber; the filter extends substantially
across the cross-section and extends longitudinally into the
housing 14 to insure maximum surface area of the membrane 28.
The inlet or ingress means 13 is accordingly positioned to
discharge liquid onto the surface of the membrane 28 to wet
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the filter when the filter lO is disposed in the position shown
in Figures 2 and 4. If the filter is turned in any direction,
as by a change in position of a patient to which the filter is
fixed during intravenous administration, liquid contained in
the housing 14 continues to wet at least a portion of the
surface of the membrane 28. As long as the hydrophilic filter
or membrane 28 remains wetted by the liquid, it will pass
liquid through the pores thereof while blocking air or like
gases. The filter of the invention will thus continue to pass
liquid and block air if and untll the housing becomes completely
filled with air so as to no longer permit the filter to be
wetted with air. If such a point is reached, the air may be
bled from the system, as by removal of a tubing on the inlet
or ingress means, or by other such suitakle means.
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