Technical Field and Prior Art

Hollow fiber separation devices, for example for the processing of blood in dialysis or membrane plasmapheresis, are available comprising a bundle of appropriate hollow fibers for the intended purpose positioned in a tubular housing. Both of the above-mentioned types of hollow fiber separation devices are commercially available from Travenol Laboratories, Inc. of Deerfield, Illinois, and many patents, for example U.S. Patent No. 4,283,284, show various different designs of such hollow fiber devices.

Additionally, ultrafiltration devices and filters may also be made using the known hollow fiber technology for separation devices.

Typically the tubular housing has been rigid in the hollow fiber separation devices of the prior art, with screw-on end caps placed on the ends of the housings. In U.S. Patent Application of Lee et al. entitled "SEPARATION DEVICE MANUFACTURE" and filed simultaneously with this application, hollow fiber separation devices are disclosed in which the tubular housings are made by a blow molding or thermoforming process, and the end cap manifold members are applied to the ends of the tubular housing by preferably a heat sealing technique, for example ultrasonic sealing or spin welding, without the need for interlocking screw threads for retention as has been common in the prior art.

Since this represents a significant departure from the prior technology for hollow fiber separation devices, a new series of technological problems has arisen. Particularly, a problem arises in the fact that blow molding and thermoforming processes tend to be less

accurate than some other molding processes. Thus blow molded tubular housings exhibit less dimensional uniformity, and individual housings from a production line can have greater dimensional variance in particularly the diameter and shape of their ends. Nevertheless, it remains very important for the end cap manifold members to be applied in a tight seal, despite the reduced dimensional uniformity typically found in blow molded or thermoformed items. Also, blow molded and thermoformed tubular housings may have greater flexibility than the rigid, tubular housings typically used in the prior art for hollow fiber separation devices, which, of course, renders more complex the problem of providing a good end seal as an end cap manifold is applied.

In accordance with this invention, an improved end closure system is provided, being particularly contemplated for use with blow molded or thermoformed tubular housings for hollow fiber separation devices, but which can also be used for the end closure of conventional thermoplastic tubular housings which have been injection molded, or for sealing any tubular port made of thermoplastic material as may be desired. The invention of this application can make use of the fact that while one would normally not expect a good seal to be easily formable at the end of a semiflexible, blow molded or thermoformed tubular housing, a previously unforeseen advantage is obtained when one forms end-potted areas at the end of a housing containing a bundle of hollow fibers in accordance with previously known techniques. As such unexpected advantage, a rigidity is obtained which provides the unforeseen benefit of facilitating the sealing of an end cap to the end. Also, the particular structure of end cap used permits the creation of a good

seal even with a relatively wide dimensional variance from part to part.

Description of the Invention In accordance with this invention, an end cap closure for a tubular housing comprises an end cap fitting over the end of the tubular housing, said end cap defining an internal annular face which, in turn, defines an angle of essentially 5° to 70° to the axis of the tubular housing, the end of the tubular housing being carried in bonded relationship with the annular face.

The existence of the annular face imparts to the system a great tolerance of dimensional variance in both the end cap and the end of the tubular housing. Even if the tubular housing is of varied size or somewhat oval in shape, its entire periphery can come into firm contact with some point of the angled, internal, annular face, thus permitting the creation of a good annular seal between the end of the housing and the end cap. rThe tubular housing may be made of substantially flexible thermoplastic material, with the end of the tubular housing being filled with potted plastic compound in a manner well known to hollow fiber separation device technology, to provide relative rigidity to the end of the housing to facilitate a heat seal. Preferably, the angle of the internal annular face to the axis of the tubular housing is I5 ^β to 50°.

The tubular housing may define an outwardly extending flange at its end if desired, with the flange being in sealing engagement about its entire periphery with the internal annular face of the end cap.

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Description of the Drawings

Figure 1 is a fragmentary longitudinal sectional view showing a hollow fiber dialyzer and one of its end caps prior to the joining thereof. t- Figure 2 is a longitudinal sectional view of Figure 1 after joining of the hollow fiber dialyzer and end cap.

Figure 3 is a sectional view taken along line 3-3 of Figure 2.

Figure 4 is a perspective view of the hollow fiber dialyzer of the previous claims.

Description of Specific Embodiment

Referring to the drawings, hollow fiber dialyzer 10 is disclosed, which may be of generally conventional design except as otherwise disclosed. Alternatively, dialyzer 10 may be of the design disclosed in the previously cited patent application of Lee et al. in which the overall design of the dialyzer is conventional except that tubular housing 12 may be thermoformed or blow molded out of a relatively flexible, inexpensive material such as polypropylene, polyethylene, or glycol-modified polyethyleneterephthalate.

As is conventional, tubular housing 12 contains at each end an annular manifold portion 14 and a side port for dialyzate 16. At each end of the dialyzer, as also is conventional, a plug of potting compound 18 is provided through which the hollow fibers 20 pass, so that flowing blood or other fluid can pass through the bores of the hollow fibers 20 from end to end of housing 12. End cap manifolds 22 are provided to seal the housing ends. Manifolds 22 and tubular housing 12 may preferably both be made of thermoplastic materials, particularly when it is desired to use a heat sealing technique to join them rather than a gluing technique or the like.

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As shown in Figure 1, the initially separate housing 12 with its end plugs 18 of potting compound and end cap manifolds 22 may be provided, being placed in an ultrasonic sealing device, for example. For this purpose a Branson ultrasonic sealer may be used, or, if desired, commercially available spinwelding apparatus.

It may also be desired to provide annular depression 23 and outwardly extending annular flange 24 to each end of tubular housing 12, to help retain each end plug 18, among other reasons. As previously stated, the dimension of each end 26 of tubular housing may exhibit significant variability, deviating, for example, from the ideal dimension to which it is was intended to be molded by 20 to 30 thousandths of an inch or more.

Accordingly, in accordance with this invention, internal annular face 28 is provided to tubular housing 22, the specific angle of face 28 as shown being about 30" to the axis 29 of tubular housing 12 and manifold 22. Accordingly, internal annular face 28 receives annular en 26 (Fig. 1) of housing 12 with a snug fit at some point along face 28 irrespective of small dimensional deviations such as an out-of-round configuration or the like. Thus, as shown in Figure 2, a tight heat seal 30 can be formed between end 26 and internal annular face 28.

As a further advantage any "flash" 32 of molten plastic material which moves inwardly along face 28 is kept away from the ends 33 of hollow fibers 20 because of the acute angled relationship, i.e., no more than 70°, of face 28 to the axis of housing 12. Thus the flash material, which adheres to face 28, remains spaced from fiber ends 33 and does not block them. The "flash" material can also move outwardly along face 28 as at area 31.

Each end cap 22 typically carries at least one flow port 34 so that blood or other fluid may pass through port 34 into contact with the ends 33 of hollow fibers 20, passing through the bores of the hollow fibers to exit at their other ends, and out another port corresponding to port 34 of the end cap manifold on the other end of dialyzer 10, which may be of identical design to the one shown.

By this invention, a solid, firm, hermetic annular seal may be provided to a tubular housing or other tubular port, even when the tubular housing is fairly flexible in itself, by taking advantage of the presence of angled annular face 28, and typically also a plug 18 of potting - compound or other plastic material, to provide a relatively rigid end to the tubular housing. Accordingly, improvements in reliability and reduction of cost are achievable through the use of this invention.

The above has been offered for illustrative purposes only, and is not intended to limit the scope of the invention of this application, which as defined in the claims below.