GB1603486A - Hollow fibre assembly - Google Patents

Description

PATENT SPECIFICATION

( 11) 1 603486 ( 21) Application No 30591180 ( 62) Divided out of No 1 603 483 ( 31) Convention Application No 79 ( 33) United States of America (US ( 44) Complete Specification publist ( 51) INT CL ' A 61 M 1/03 B Ol D ( 52) Index at acceptance Bl X 6 A 1 6 B 1 6 C 6 F 6 6 L ( 22) Filed 10 M 9 582 ( 32) Filec ied 25 Nov 1981 13/00 ay 1978 ( 19) d 23 May 1977 in ( 54) HOLLOW FIBRE ASSEMBLY ( 71) We, EXTRACORPOREAL MEDICAL SPECIALITIES, INC, a corporation organized and existing under the laws of the State of Pennsylvania, United States of America, located at Royal and Ross Roads, King of Prussia, State of Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly des-

cribed in and by the following statement:-

This invention relates to a method of assembling a hollow fibre mass transfer device.

The invention resides in a method of assembling a hollow fibre mass transfer device by centrifugally potting both ends of a bundle of open-ended hollow fibres in a casing, wherein the casing is fitted with at least one such bundle of open-ended fibres, each fibre of which has each end projecting at least millimetres beyond the desired outer face of the potted assembly in the device, and wherein the method includes the steps of mounting the casing with the projecting fibres in a centrifugal potting apparatus for simultaneous centrifugation of both ends of the fibre-carrying casing, centrifuging the mounted fibre-carrying casing and delivering a liquid settable potting composition substantially simultaneously to both ends of the centrifuging casing to cause that composition to enter the casing ends and the fibre ends, but to move into the fibre ends a distance less than the length of said projecting end, and, after the potting composition is set, cutting off the projecting masses of fibre ends to provide the desired outer faces having cut fibre potted in the casing ends with the cut ends of the fibres open.

In the accompanying drawings:

Figure 1 is a front elevation partly in section, of a dialyzer including a hollow fibre mass transfer device assembled by a method according to one example of the invention, Figure 2 is a sectional view along the line 2-2 in Figure 1, and Figure 3 is a sectional view along the line 3-3 in Figure 2.

Referring to the drawings, the dialyzer is shown generally at 10 and includes a plastics casing 12 formed, for example, of polystyrene with enlarged header end portions 14, 16 and securing flanges 18 and 20 55 encircling each end portion Ultrasonically welded to each flange is a plastic cap 22, 24 that covers the casing ends and has a central nipple 26, 28 for introducing the liquid to be dialyzed at one end end remov 60 ing it at the other The caps can be made of the same plastic as the casing.

The interior of the casing contains partitioning that subdivides it into a plurality of chambers and passageways extending 65 longitudinally through it, as more clearly seen in Figure 3 Thus partitioning 30 subdivides the interior of the casing into three large-bore chambers 31, 33 and 35 as well as two small-bore passageways 32, 34 The 70 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 partitioing 30 establishes communication between the upper portions of 75 chamber 31 and passageway 32 A similar port (not shown) in the lower portion of the partitioning establishes communication between the lower portions of passageway 32 and chamber 33, a third port 43 in the upper 80 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 communica 85 tion between the lower portions of passageway 32 and chamber 35.

A dialyzate inlet connector 51 is molded integrally with the enlarged lower end portion 14 of the casing and opens into the 90 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 95 path.

A bundle of hollow dialysis fibres 48 is inserted in each chamber 31, 33, 35, the fibres extending the length of the casing At or near each casing end, the fibers are potted in an 100 end wall 54 of a sealing resin that can project somewhat from the casing end as illus1,603,486 trated 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 body 60 of each end cap.

Potting resin 54, which can be a polyurethane, leaves the hollow inferiors of the fibers 48 open so that the liquid to be dialyzed flows through these fibers, preferably countercurrent to the flow of the dialyzate in chambers 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 introduced into connector 51 and withdrawn through connector 52 The dialyzate flows upwardly through chamber 31 around and between the individual fibers in that chamber, then down through passageway 32, after which it flows upwardly through chamber 33 around and between the individual fibers there, then descends through passageway 34 for a final pass upwardly through chamber 35 around and between the individual fibers there Fromn 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 fibers 48 and when a dark liquid like blood is being dialyzed isn't much detail that can be made out visually other than the presence or absence of gas bubbles in front of the fibers.

In one embodiment of the present invention the lengths of chambers 31, 33 and between the enlarged casing ends 14, 16 are cylindrical with diameters of about 21 centimeters so that each chamber can be packed with something over 3,000 hollow fibers to provide a total membrane dialysis surface of about 1 spuare meter per dialyzer or about -i square meter per chamber The passageways 32, 34 in this embodiment are cylindrical with diameters of about 3 to about 4/,_, centimeter So dimensioned 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 diazylate passes through it.

For measuring the rate of ultrafiltration taking place in the dialyzer a volume of gas such as air is deliberately introduced into the dialyzate contained in the dialyzer To this end Fig 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 70 connectors 74, 76.

Connector 74 is shown as of the female type having a socket 71 that receives connector 51 and an 0-ring seal 73 against which a tapered tip 53 on connector 51 seats 75 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 groove 55 in connector 51 by a slide ring 77 The engagement is 80 unlatched by sliding the slide ring toward the body 72 against the resistance of spring 79, far enough to bring a relived internal taper of the slide around the balls thus permitting the balls to be moved outwardly in 85 a radial direction 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 90 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 95 which is frictionally mounted a plastic or rubber outlet tube 84 of a gas injector 86.

This injector has a squeezable bulb 88 secured as by cementing or welding to tube 84, and carrying an air inlet tube 90 Valves 100 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 105 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 encircling seats moulded into thickwalled portions of tubes 84 and 90 As in 110 conventional laboratory pipette filling adaptors, by making the tube walls at least about 3 millimetres thick but still yieldable, the valve seats will deform when opposed portions of the tube around them are manually 115 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 120 gripping engagement over its entire periphery and this keeps the valve closed.

The apparatus of Figs 1 through 3 is placed in operation by connecting it to a source of dialyzate at 76 as well as to dia 125 lyzate removal means at 52, and to a source of blood or other liquid to be dialyzed at 28 as well as to a return for such liquid at 26.

For measuring ultrafiltration, the dialyzer 130 1,603,486 preferably has its dialysis chamber 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, when the air injection is taking place This will assure that the injected air is not carried by incoming dialyzate too far through diaiyzer 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.

If the volume of air iniected is kept small so as to provide a high liquid level in passageway 32, 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 of 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 t causes liquid 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 Fig 2.

So long as the blood or other liquid being dialyzed flows through the hollow fibers, ultrafiltration takes place causing water to move from the liquid being dialyzed through the walls of the fibers 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 70 Fig 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 stopwatch can 75 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 80 from the time it leaves the level of the floor 41 of header 16, to the time it reaches the top 43 of header 14 It is preferred however to apply a scale alongside passageway 32, as, by means of a label 69 cemented onto the 85 outside of the dialyzer casing Inasmuch as a label is generally used to carry instructions as to the connections made to the dialyzer, the ultrafiltration-measuring scale can be conveniently added to such a label The 90 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 ultrafiltration rate es 95 sentially depends on the difference between the pressures on the inside and outside of the hollow fibers, those pressures should be adjusted to the values at which the ultrafiltration rate is to be measured, and should 100 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 105 Blood is generally under a superatmospheric pressure of a hundred or so tor when it is being dialyzed, althoug that pressure can range from a low of about 30 tor to a high of about 160 tor or even higher The 110 dialyzate is generally under a subatmospheric pressure of about minus 50 to about minus 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 115 subatmospheric pressure, the use of subasmospheric 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 dia 120 lyzate from entering the blood stream in the event there is a leak in the dialyzer To maintain subatmospheric pressure in the dialyzate the dialyzer's dialyzate outlet 52 is preferably maintained in connection with 125 the dialyzate supply system that develops such negative pressure.

As previously stated, the dialysis fibres 48 are potted adjacent each end of the casing 12 in resin 54 This operation is effected 130 4 1,603,486 4 in a single centrifugal pressurizing operation and does not require closure of the fibres ends before applying the potting composition By arranging for the potting composition to be fed in a liquid condition substantially simultaneously to both ends of the centrifuging casing 12 filled with hollow fibres open at both ends, the potting composition is kept from excessive penetration into the fibre ends, and the internal plugging of the open fibre ends by the potting composition is then quite shallow, generally not more than about 3 to 4 millimetres Accordingly, the potting can be arranged so that at least about 5 or 6 millimeters of each potted end is cut off to expose the hollow fibres at each pot end wall 54.

Thus the casing can be fitted with openended fibres each of which projects more than about 5 millimeters beyond the desired location of each end wall 54 A seven millimeter projection has been found very effective The casing so fitted is mounted in a centrifugal potting assembly as described in U S Patent 3,442,002 so that both casing ends are potted during one centrifugation.

After centrifuging is under way the settable liquid potting composition which can be a polyurethane such as described in U S.

Patent 3,962,094, is delivered to both ends of the centrifuging assembly substantially simultaneously Sufficient potting composition is delivered to bring the level of that composition into each end of the casing the desired distance, generally at least about one centimetre at the lowest point It will be found that the potting composition penetrates into the open fibre end, only about 4 millimeters, so that after composition is set the ends can be cut off at location 54 to leave each cut fibre end open.

The liquid potting composition can be loaded into the assembly to be centrifuged, before centrifuging is started Thus a feed cup that forms part of the assembly is arranged to hold the liquid potting composition and is connected by separate tubes to the interiors of hollow potting moulds clamped to each end of the dialyzer casing.

By making those tube connections to outlet openings in the side wall of the cup well above its floor, the cup when stationary (not centrifuging) is enabled to hold liquid up to the level of the side wall openings without delivery any of the liquid through the outlet openings The feed cup can thus be conveniently loaded with the settable potting liquid before centrifuging is begun.

When the assembly so loaded is centrifuged, the centrifuged force foices the liquid in the cup to climb higher onto its side wall, and thus enter the discharge outlets and be delivered to the hollow potting moulds Substantially simultaneous delivery of the potting liquid to both casing ends is thus 65 assured.

The foregoing centrifugally started feed of potting liquid takes place whether the centrifuging assembly is centrifuged around a vertical axis or around a horizontal axis 70 or around an axis having any other orientation Centrifuging around a horizontal axis is desirable in that it can be effected with apparatus that occupies less floor space.

When using potting liquids having suf 75 ficient viscosity it is not necessary to rely on having a feed cup with outlets above its floor The delivery tubes can with such liquids be made sufficiently small in internal cross-section to make sure the viscous pot 80 ting liquid takes at least a number of seconds to flow from the feed cup to the hollow moulds The feed cup can then be loaded and the centrifuging promptly thereafter started before that number of seconds has 85 elapsed Centrifugal force will then be developed before the potting liquid can penetrate into the open ends of the fibres, and once developed will greatly speed the flow of the viscous liquid so as to assure that 90 there will not be excessive penetration into those ends.

The desired simultaneous delivery to both hollow moulds can also be effected by not pouring the potting liquid into the feed cup 95 until after the centrifuging has started, but it is a somewhat more awkward chore to pour into a rapidly spinning cup.

We draw attention to our Application No.

18632/78 (Serial No 1603483) which relates 100 to a dialyzer having a transparent dialyzate passageway and a method of measuring the rate of ultrafiltration through a dialysis unit containing a dialysis chamber, and also to our Application No 80 30590 (Serial No 105 1603485) which relates to a process of securing a cap on the end of a tubular artificial kidney casing, by welding with a vibrating welding member, and in addition to our Application No 80 30589 (Serial No 1603484) 110 which relates to a gas-injecting attachment for a dialyzer.

Having regard to the provisions of Section 9 of the Patents Act, 1949, attention is directed to the claims of Patent No 1569182 115

Claims (4)

WHAT WE CLAIM IS: -

1 A method of assembling a hollow fibre mass transfer device by centrifugally potting both ends of a bundle of open-ended 120 hollow fibres in a casing, wherein the casing is fitted with at least one such bundle of open-ended fibres, each fibre of which has each end projecting at least millimetres beyond the desihed outer face 125 of the potted assembly in the device, and wherein the method comprises the steps of mounting the casing with the projecting fibres in a centrifugal potting apparatus for 1,603,486 1,603,486 sirnult eous centrifugation of both ends of the fibre-carrying casing, centrifuging the mounted fibre-carrying casing and delivering a liquid settable potting composition substantially simultaneously to both ends of the centrifuging casing to cause that composition to enter the casing ends and the fibre ends, but to move into the fibre ends a distance less than the length of said projecting end, and, after the potting composition is set, cutting off the projecting masses of fibre ends to provide the desired outer faces having cut fibre potted in the casing ends with the cut ends of the fibres onn.

2 A method of assembling a hollow fibre mass transfer device by centrifugally potting both ends of a bundle of openended hollow fibres in a casing, substantially as hereinbefore described.

3 A hollow fibre mass transfer device assembled by a method as claimed in Claim 1 or Claim 2.

4 A dialyzer including a hollow fibre mass transfer device as claimed in Claim 3.

For the Applicants, CARPMAELS & RANSFORD, Chartered Patent Agents, 43 Bloomsbury Square, London WC 1 A 2 RA.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd -1981.

Published at The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.