Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a process of secur;ng a
cap on the end of a t~bular artificial kidney casing, and to an
artificial kidney produced using such a process.
Accordingly, the invention resi`des in one aspect in
a process of securing a cap on the end of a tubular artificial
kidney casing wherein the casing has an outwaLdly encircling
flange of fusible plastic near said end, the cap is also of
fusible plastic and has a body thickness of at least about 2
millimeters, and the cap has a skirt at the bottom edge of which
is welded to the flange by applying a high frequency vibrating
member to the cap body while supporting a face of the flange
remote from the cap and holding it against the skirt body.
In the accompany;ng drawings,
Figure 1 is a front elevation, partly in section, of
an artificial k;dney produced using a process according to one
example of the present invention,
- Figure 2 is a view generally along the line 2-2 of
Figure 1, illustrating the internal operation of the artificial
kidney; and
2Q Figure 3 is a sectional view along the line 3-3 of
Figure 2.
Referring to the drawings, an artificial kidney 10
has a plastics casing 12 formed, for example, of polystyrene with
enlarged header end portions 14, 16 and with securing flanges
18 and 20 encircling each end portion.
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Ultrasonically welded to each flange is a plastics
end cap 22, 24 which covers the casing ends and has a
central nipple 26, 28 for introducing the liquid to be
dialy~ed at one end and removing it at the other. The
caps can be made of the same plastics material as the
casingO
The interior of the casing contains partitioning that
subdivides it into a plurality of chambers and passageways
extending longitudinally through it, as more clearly seen
in Figure 3. Thus parti-tioning 30 subdivides the interior
of the casing into three large-bore chambers 31, 33 and 35
as well as two smallbore passageways 32, 34. The chamber
and passageways extend the length of the casing and are
only interconnected near the casing ends. Near the upper
end a port 41 in the partitioning 30 establishes communi-
cation between the upper portions of chamber 31 and pas-
sageway 32. ~ similar port ~not shown) in the lower por-
-tion of the partitioning establishes communication between
the lower portions of passageway 32 and chamber 33, a
third port 43 in the upper portion of the partitioning
establishes communication between the upper portions of
chamber 33 and passageway 34, and a fourth port (also not
shown) at the lower portion of the partitioning
establishes communication between the lower portions of
passageway 32 and chamber 35.
A dialyzate inlet connector 51 is moulded integrally
with the enlarged lower end portion 14 of the casing and
opens into the lower portion of chamber 31, while a
dialyzer outlet connector 52 correspondingly provided in
the upper enlarged casing end portion 16 opens into the
upper portion of chamber 35 to complete the dialyzate flow
path.
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A bundle of hollow dialysis fibres 48 i5 inserted in
each chamber 31, 33, 35, the fibres extending the length
of the casing. At or near each casing end the fibres are
potted in an end wall 54 of a sealing resin that can
project somewhat from the casing end as illustrated in
Figures 1 and 2. End caps can be sealed against these end
walls by gaskets such as 0-rings 56 shown in Figure 1 as
fitted between short flanges 58 projecting from the end
wall 60 of each end cap.
Potting resin 54 which can be a polyurethane, leaves
the hollow interiors of the fibres 48 open so that the
liquid to be dialyzed flows through these fibres, prefer-
ably countercurrent to the flow of the dialyzate in cham-
bers 31, 33 and 35. Thus blood or other liquid to be
dialyzed can be introduced through upper nipple 28 and
withdrawn from lower nipple 26, while dialyzate is intro-
duced into connector 51 and withdrawn throuyh connector
52. The dialyzate flows upwardly through chamber 31
around and between the individual fibres in that chamber,
then down through passageway 32, after which it flows
upwardly through chamber 33 around and between the indi-
vidual fibres there, then descends through passageway 34
for a final pass upwardly through chamber 35 around and
between the individual ibres there. From the upper
portion of chamber 35 the dialyzate flows out of the
dialyzer 10 through the outlet connector 52.
The casing 12 is made of transparent plastic like
polystyrene so that the contents of passageways 32, 34 as
well as their side walls are clearly seen from outside the
casing. Chambers 31, 33 and 35 are also seen from outside
the casing, but these chambers are essentially filled with
the hollow dialysis fibres ~8, and when a dark liquid like
blood is being dialyzed very little detail can be made out
visually other than the presence or absence of gas bubbles
in front of the fibres.
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In one embodiment of the present invention the
lengths of chambers 31l 33 and 35 between the enlarged
casing ends :L4l 16 are cylindrical with diameters of about
2 1/3 centimeters so that each chamber can be packed with
something over 3,000 hollow fibres to provide a total
membrane dialysis surface oE about 1 s~uare meter per
dialyzer or about 1/3 square meter per chamber. The pas-
sageways 32, 34 in this embodiment are cylindrical with
diameters of about 3/4 to about 4/5 centimeter. So dimen-
sioned the standard dialyzate flow rates of 300 or 500
millimeters per minute will be rapid enough to flush out
of the dialyzer essentially all gas bubbles that may
appear in the dialyzate as the dialyzate passes through
it.
For measuring the rate of ultrafiltration taking
place in the artificial kidney a volume o:E gas such as air
is deliberately introduced into -the dialyzate contained in
the artificial kidney. To this end Figure 1 shows a gas-
injecting attachment 70 that has a body 72 carrying a
standard dialyzate connector 74, which connector is fitted
to the dialyzer's dialyzate intake connector 51. Body 72
also carries another standard dialyzate connector 76 for
connection to the dialyzate supply output of a source of
dialyzate, and a bore 78 that establishes communication
between the two connectors 74, 76~
Connector 74 is shown as of the female type having a
socket 71 that receives connector 51 and an O-ring seal 73
against which a tapered tip 53 on connector 51 seats.
Connector 51 is latched in sealing engagement with the 0-
ring by a set of balls 75 held in apertures around the
wall of socket 71 and forced into a grocve 55 in connector
51 by a slide ring 77. The engagement is unlatched by
sliding the slide ring toward the body 72 against the
resistance of spring 791 far enough to bring a relieved
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internal taper 57 of the slide around the walls thus per-
mitting ~he balls to be moved outwardly in a radial direc-
tion into the wall of socket 71 when the connectors are
pulled apart. A locking snap ring 59 can be snapped into
a groove on the outer face of the socket 71 to keep the
slide ring 77 from coming off the connector when in use,
but permitting disassembly when desired.
Also communicating with bore 78 is a branch 80 that
leads to a nipple 82 projecting from the surface of body
74 and onto which is frictionally mounted a plastic or
rubber outlet tube ~4 of a gas injector 86. This injector
has a squeezable bulb 88 secured as by cementing or weld-
ing to tube 84, and carrying an air inlet tube 90. Valves
91, 92 in tubes 81 and 90 control the air injection
action, and a filter such as a plug 94 of foamed plastic
or rubber can be used to make sure solid particles are
kept out of the entering air.
Valves 91, 92 can be of any desired type, but are shown
as balls of relatively inert material such as stainless
steel very snugly held in encirclinq seats moulded into
thick-walled portions of tubes 84 and 90. As in conven-
tional laboratory pipette Eilling adaptors, by making the
tube walls at least about 3 millimeters thick but still
yieldable, the valve seats will deform when opposed portions
of the tube around them are manually pinched toward each
other, and in such deformation at least one section of the
seat will be forced away from the valve ball~ This opens
the valve. Releasing the pinch permits the valve seat to
return to ball-gripping engagement over its entire periphery
and this keeps the valve closed.
The apparatus of Figures 1 through 3 is placed in
operation by connecting it to a source of dialyzate at 76
as well as to dialyzate removal means at 52, and to a
source of blood or other liquid to be dialyzed at 28 as
well as to return for such liquid at 26.
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For measuring ultrafiltration, the dialyzer
preferably has its dialysis chambers and passageways first
filled with dialyzate, following which a volume of air is
introduced into chamber 31 by operation of the air
injector 70. Such operation is easily effected by
pinching tube 84 at valve 91 and squeezing bulb 88. The
bulb can be dimensioned so that one squeeze will inject a
suitable quantity of air into bore 78 and from there by
way of connector 51 into chamber 31. Valve 91 can then be
released to cause it to close, and it is sometimes helpful
to tilt the apparatus to help move the large air bubble
into chamber 31. After valve 91 is closed, valve 92 can
be opened momentarily to permit the bulb to expand and
suck in a fresh supply of air through filter 94. This
places the apparatus in condition for the next injection
of air.
The connection between connector 76 and the dialyzate
source is preferably closed as by a shut-off valve r when
the air injection is taking place. This will assure that
the injected air is not carried by incoming dialyzate too
far through dialyzer 10 to permit the desired measurement
of ultrafiltration rate. The introduction of dialyzate
into the dialyzer is also shut off when that measurement
is being made.
Immediately after the injected air reaches chamber 31
it rises to the top of that chamber. If the dialyzer is
maintained generally upright the air will not only reach
the top of chamber 31 but it will also move into the upper
portion of passageway 32 and part way down that passageway
until the height occupied by the air is about the same in
that passageway as in that chamber. This leaves the
liquid level in passageway 32 relatively low so that the
volume of ultrafiltration that can be measured by downward
movement of that water level is limited.
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If the volume of air lnjected is kept small 50 as to
provide a high liquid level in passageway 32r then the
liquid level in chamber 31 is also relatively high and
liquid from that chamber will spill over into the
passageway after a very limited amount oE ultrafiltration.
Such spill-over makes it impossible to subsequently
measure ultrafiltration by liquid level changes.
To avoid such limitation the dialyzer can be tilted
when the introduced air has risen. The degree of tilt is
such that it causes 1 iqu id to flow from near the tilted
upper end of chamber 31 into the -tilted upper end of
passageway 32. In this way the liquid levels can be
adjusted so that after restoring the dialyzer to its
upright position, they are generally in positions such as
shown at 37, 38 in Figure 2.
So long as the blood or other liquid being dialyzed
flows through the hollow fibers, ultraEiltration takes
place causing water to move from the liquid being dialyzed
through the walls of the fibres. As a result there will
be a gradual increase in volume of the dialyzate around
the fibres in chamber 31 and the air bubble will move down
into passageway 32. In Figure 2 the dialyzate level 37 in
passageway 32 is starting its slow traverse through that
passageway. That traverse is easily measured with an
ordinary watch or clock having a seconds hand. A stop-
watch can be used but is not necessary inasmuch as the
measurement times can be 30 seconds or longer and split-
second timing does not add much to the measurement
accuracy.
The traverse of level 37 can be measured from the
time it leaves the level of the floor 41 of header 16, to
the time it reaches the top 42 of header 14. It is
preferred however to apply a scale alongside passageway
32, as by means of a label 69 cemented onto the outside of
.,
the dialyzer casing. Inasmuch as a label is generally
used to carry instructions as to the connections made to
the dialyzer, the ultraEiltration-measuring scale can be
conveniently added to such a label. The presence of a
scale also enables the making of two or more successive
measurements during a single traverse of the gas bubble
through passageway 32.
Inasmuch as the ultra-filtration rate essentially
depends on the difference between the pressures on the
inside and outside of the hollow fibres, those pressures
should be adjusted to the valves at which the
ultrafiltration rate is to be measured, and should not be
changed during the measurement. The presence of a gas
bubble in chamber 31 and the traverse of part of the
bubble into passageway 32 will not significantly affect
either of the critical pressures.
Blood is generally under a superatmospheric pressure
of a hundred or so tor when it is being dialyzed, although
that pressure can range from a low of about 30 tor to a
high of about 160 tor or even higher. The dialyzate is
generally under a subatmospheric pressure of about minus
50 to about minus 100 tor but can range from almost zero
to an extreme of about minus 350 tor. While it is not
essential to have the dialyzate at subatmospheric
pressure, the use of subatmospheric pressure speeds up
ultrafiltration. As a matter of precaution the dialyzate
pressure is substantially below the pressure at which the
blood is supplied, to keep dialyzate from enterinq the
blood stream in the event there is a lealc in the dialyzer.
To maintain subatmospheric pressure in the dialyzate the
dialyzer's dialyzate outlet 52 is preferably maintained in
connection with the dialyzate supply system that develops
such negative pressure.
As previously stated, the plastics end caps 22, 24 are
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ultrasonically welded to the Elanges 18, 20 respectively t
this method producing a very sturdy structure which is
inexpenslve to manufacture. To effect the welding opera-
tionr the casiny 12 is placed in a holder which supports
it by engaging the lower face of Elange 20. The cap 24 is
then placed in position over the flange 20 and a cylindri-
cal vibrating piston is then lowered onto the cap 24 so
that the edge face of the cylinder engages the periphery
of the cap end wall 60. The piston is hollowed out at its
edge face to receive nipple 28 and the immediately sur-
rounding portions of wall 60 that extend up higher than
its periphery. The cylinder vibration is then actuated at
about 20 to 25 kilohertz for about one second or less to
complete the welding.
It has been found that the ultrasonic welding will
not produce a good product unless wall 60 of the end cap
is at least about 2 millimeters thick. Smaller thick-
nesses are susceptible to damage during the ultrasonic
welding. Preferred thicknesses are from about 3 to about
~ millimeters. The provision of a narrow ridge on the
welding face of flange 20, as shown at 39, also helps with
the ultrasonic welding process.
It is also very desirable to vent the portion of the
end cap outside the seal effected by the gasket 56. In
Figure 1 such venting is shown at a notch 40 on1y about 1
to 2 millimeters wide and about 2 millimeters deep, exten-
ding across the lip of the cap's side wall. This simpli-
fies testing of the seal between the end cap and the end
wall 54 of the dialyzer body. Such testing can be simply
accomplished by connecting nipple 2~3 to a source of pres-
surized air, closing off nipple 26, momentarily applying
pressure of about 300 tor through nipple 28 and permitting
the pressurized assembly to stand with a pressure gauge
attached to see whether there is a loss of pressure. No
loss of pressure after about 10 - 15 seconds demonstrates
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that both end cap seals are satisfactory and also that
there is no significant leakage through or around
the dialysis fibres.
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