GB1603485A - Capping an artificial kidney casing - Google Patents

Description

PATENT SPECIFICATION

( 11) 1 603 485 ( 21) Application No 30590/80 ( 22) Filed 10 May 1978 ( 19) ( 62) Divided out of No l 603 483 ( 31) Convention Application No 799 582 ( 32) Filed 23 May 1977 in ( 33) United States of America (US) ( 44) Complete Specification published 25 Nov 1981 ( 51) INT CL ' A 61 M 1/03 B Ol D 13/00 ( 52) Index at acceptance Bl X 6 A 1 6 B 1 6 C 6 F 6 6 H 1 6 L 2 ( 54) CAPPING AN ARTIFICIAL KIDNEY CASING ( 71) We, EXTRACORPOREAL MEDICAL SPECIALITIES, I Nc, a corporation organized and existing under the laws ut 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 process of securing a cap on the end of a tubular artificial kidney casing, and to an artificial kidney produced using such a process.

Accordingly, the invention resides in one aspect in a process of securing a cap on the end of a tubular artificial kidney casing wherein the casing has an outwardly extending encircling flange of fusible plastic near said end, the cap is also of fusible plastic and has a body thickness of at least 2 millimetres, and the cap has a skirt that is welded to the flange by applying a high-frequency vibrating member, as herein defined, to the cap body while supporting the remote face of the flange By a "high-frequency" vibrating member, we mean herein one vibrating at a frequency high enough to permit welding of fusible plastics.

In a further aspect, the invention resides in an artificial kidney having a tubular casing and an end cap, the casing having an encircling flange to substantially the entire length of which the bottom edge of a skirt on the end cap is bonded by welding by the process of the present invention, a ringshaped gasket between the body of the end cap and an internal end wall near the end of the casing to enclose and seal in a chamber between the cap body and said end wall, and a passageway through the cap at a location outside the sealed-in chamber.

In the accompanying drawings, Figure 1 is a front elevation, partly in section, of an artificial kidney 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 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, 55 for example, of polystyrene with enlarged header end portions 14, 16 and with securing flanges 18 and 20 encircling each end portion Ultrasonically welded to each flange is a plastics end cap 22, 24 which covers the 60 casing ends and has a central nipple 26, 28 for introducing the liquid to be dialyzed at one end and removing it at the other The caps can be made of the same plastics material as the casing 65 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 partitioning 30 sub 70 divides the interior of the casing into three large-bore chambers 31, 33 and 35 as well as two small-bore passageways 32, 34 The chamber and passageways extend the length of the casing and are only interconnected 75 near the casing ends Near the upper end a port 41 in the partitioning 30 establishes communication between the upper portions of chamber 31 and passageway 32 A similar port (not shown) in the lower portion of the 80 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 85 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 90 A dialyzate inlet connector 51 is mounded 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 95 provided in the upper enlarged casing end portion 16 opens into the upper portion of chamber 35 to complete the dialyzate flow path.

A bundle of hollow dialysis fibres 48 is 100 inserted in each chamber 31, 33, 35, the fibres extending the length of the casing At L O I O mr 1,603,485 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, 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 fibres in that chamber, then down through passageway 32, after which it flows upwardly through chamber 33 around and between the individual fibres there, then descends through passageway 34 for a final pass upwardly through chamber 35 around and between the individual fibres 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 48, 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.

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 2 j centimeters so that each chamber can be packed with something over 3,000 hollow fibres to provide a total membrane dialysis surface of about 1 square meter per dialyzer or about i square meter per chamber The passageways 32, 34 in this embodiment are cylindrical with diameters of about 4 to about 41, 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 artificial kidney, a volume of gas such as air is deliberately introduced into the dialyzate contained in the artificial kidney 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 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.

Connector 51 is latched in sealing engage 80 ment 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 unlatched by sliding the slide ring toward 85 the body 72 against the resistance of spring 79, far enough to bring a relieved internal taper of the slide around the walls thus permitting the balls to be moved outwardly in a radial direction into the wall of socket 71 90 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 95 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 100 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 91, 92 in tubes 81 and 90 control the air 105 injection action, and a filter such as a plug 94 of foamed plastic or rubber can be used to make sure solid particles arc kept out of the entering air.

Valves 91, 92 can be of any desired type, 110 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 conventional laboratory pipette filling adap 115 tors, 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 themn are manually pinched toward each other, and in such de 120 formation 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 ballgripping engagement over its entire peri 125 phery 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 130 1,603,485 of blood or other l Equid to be dialyzed at 28 as well as to a return for such liquid at 26.

For measurin ultrafiltration, the dialyzer preferably has its dialysis chamber and passageways first filled with dialyzate, following which a volume of air is in'roduced into chamber 31 by operation of the air injector 70 Such operation is easily effected by pinching tube 84 at valve 91 and squceezing bulb 88 The bulb can be drmans oned 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 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.

If the volume of air injected 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 it 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 Figure 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 70 fibres As a result there will be a gradual increase in volume of thc 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 passage 75 way 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 be used but is not necessary inasmuch as 80 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 85 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 outside of the dialyzer casing Inasmuch as 90 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 presence of a scale also enables the making 95 of two or more successive measurements during a single traverse of the gas bubble through passageway 32.

Inasmuch as the ultrafiltration rate essentially depends on the difference between 100 the pressures on the inside and outside of the hollow fibres, those pressures should be adjusted to the values at which the ultrafiltration rate is to be measured, and should not be changed during the measurement 105 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 superatmo 110 spheric pressure of a hundred om 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 115 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 subatmospheric pressure, the use of sub 120 asmospheric 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 entering the blood stream in the 125 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 1,603,485 the dialyzate supply system that develops such negative pressure.

As previously stated, the plastics end caps 22, 24 are ultrasonically welded to the flanges 18, 20 respectively, this method producing a very sturdy structure which is inexpensive to manufacture To effect the welding operation, the casing 12 is placed in a holder which supports it by engaging the lower face of flange 20 The cap 24 is then placed in position over the flange 20 and a cylindrical 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 nippie 28 and the immediately surrounding portions of wall 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 thicknesses are susceptible to damage during the ultrasonic welding Preferred thicknesses are from about 3 to about 4 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 only about 1 to 2 millimeters wide and about 2 millimeters deep, extending across the lip of the cap's side wall This simplifies 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 28 to a source of pressurized air, closmng 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 that both end cap seals are satisfactory and also that there is no significant leakage through or around the dialysis fibres.

We draw attention to our Application No.

18632/78 (Serial No 1603483) which relates 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 30589 (Serial No.

1603484) 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.

Claims (4)

WHAT WE CLAIM IS: -

1 A process of securing a cap on the end of a tubular artificial kidney casing wherein the casing has an outwardly extending encircling flange of fusible plastic near 70 said end, the cap is also of fusible plastic and has a body thickness of at least 2 millimeters, and the cap has a skirt that is welded to the flange by applying a highfrequency vibrating member, as herein de 75 fined, to the cap body while supporting the remote face of the flange.

2 A process as claimed in Claim 1, wherein the casing end has an internal end wall and a resilient gasket is interposed be 80 tween the wall and the inner face of the cap body before the welding.

3 A process as claimed in Claim 1 or Claim 2, wherein the cap skirt has a transverse passageway that is not sealed by the 85 welding and communicates with the periphery of the gasket.

4 A process of securing a cap on the end of a tubular artificial kidney casing substantially as hereinbefore described 90 An artificial kidney having a tubular casing and an end cap, the casing having an encircling flange to substantially the entire length of which the bottom edge of a skirt on the end cap is bonded by welding by a 95 process as claimed in claim 1, 2, 3 or 4, a ring-shaped gasket between the body of the end cap and an internal end wall near the end of the casing to enclose and seal in a chamber between the cap body and said 100 end wall, and a passageway through the cap at a location outside the sealed-in chamber.

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.