Abstract:
A hollow fiber filter device for dialysis having a housing and an end cap is described. The end cap is attached to an axial end of the housing, and has a curved channel in fluid communication with a fluid port, a fluid chamber having a flow path defined by a plurality of curved members connected to an upper interior surface. The distance between circumferentially adjacent curved members may decrease in a radially outward flow direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of prior application U.S. Ser. No. 10/675,310, filed Sep. 29, 2003, now abandoned, which is a continuation application of prior application U.S. Ser. No. 09/464,605, filed Dec. 15, 1999, now U.S. Pat. No. 6,641,731, each of which is expressly incorporated herein in its entirety by reference thereto. 

   FIELD OF THE INVENTION 
   The present invention concerns a filter device for mass exchange between two media separated by a membrane and an end cap for such a filter device. 
   BACKGROUND OF THE INVENTION 
   such filter devices are generally used as dialyzers, hemofilters or ultrafilters. The filter devices generally consist of a casing in the form of a tubular section with end caps in its end areas. A tubular fiber bundle which functions as a membrane is usually arranged in the casing so that a reliable seal is provided between the first flow space formed by the fiber cavities and a second flow space surrounding the membrane on the outside. 
   One problem with the design of the inflow and/or outflow chambers connected to the first flow space, i.e., to the hollow fiber bundle, is how to distribute the liquid so that it is apportioned evenly to the individual fibers of the hollow fiber bundle, and so that dead zones in the distribution of liquid are avoided. 
   There are known dialyzers where the inlet of the chambers connected to the hollow fiber bundle is arranged axially, with the axis of the flow channel running approximately through the mid point of the hollow fiber bundle. This generally yields the disadvantage that use of the fibers varies greatly, and at the same time there are areas where the flow velocity is approximately zero (dead zones). After finishing a dialysis treatment, such dead zones are the areas where the patient&#39;s blood remains behind. In addition, there is a great difference between the flow velocity in the inlet and that in the fibers. The blood is exposed to a stress situation due to the resulting velocity gradient. 
   Unexamined German Patent DE-OS 26 46 358 describes a filter device where the end caps have a tangential inlet and the blood is carried in a channel in circulation through the ends of the hollow fibers. Blood flows tangentially through the hollow fiber ends. To achieve the most uniform possible distribution of liquid, only the areas of the casting compound in overflow circulation are provided with hollow fibers, while the rest of the core area does not have any fibers. This achieves uniform loading of the fibers but also results in a relatively low capacity or suboptimal utilization of the filter device on the whole due to the lack of hollow fibers at the center of the casing. To achieve a uniform rate of circulation of blood in the channel, the cross-sectional area of the channel in one embodiment decreases in the direction of flow. 
   It has also been proposed that the inlet be located parallel to the plane of the fiber ends and that the medium should change directions by 90 degrees in the end area of the inlet. Due to the small amount of available space and the manufacturing restrictions due to the injection molding process, only an abrupt change of directions is possible in general, but that would constitute a considerable burden on the blood. 
   The object of the present invention is to improve upon a generic filter device so that the transfer of blood from the inlet into the fibers is accomplished at a low load and the fibers are loaded uniformly. 
   SUMMARY OF THE INVENTION 
   This object is achieved according to the present invention by a filter device whose membrane is designed in the form of a hollow fiber bundle, its fiber cavities forming a first flow space, with at least one inflow or outflow chamber which communicates with the first flow space being provided for supplying a medium to the hollow fiber bundle or removing a medium from it, said chamber being adjacent to an essentially circular or semicircular channel which communicates with an inlet or outlet of the filter device and is designed to be open in the direction of the ends of the hollow fibers, said channel being arranged approximately centrally with the hollow fiber bundle, having a cross-sectional area that decreases in the direction of flow and having an outside diameter smaller than the diameter of the hollow fiber bundle. This yields, first, the advantage that the blood flow undergoes only relatively gentle and low-stress changes in direction and velocity of flow. With the device according to the present invention, the flow velocity in the path through the essentially circular or semicircular channel gradually approaches the value of the velocity inside the fibers with the device according to the present invention. 
   Second, this yields the advantage that the blood is distributed in a pattern having approximate radial symmetry due to the changing cross-sectional area along the path through the channel. This means that approximately the same amount of blood flow leaves the channel and flows outward radially in each angular area. This yields a uniform utilization of the individual fibers of the hollow fiber bundle and thus yields optimum utilization of fiber capacity. 
   In contrast with the previously known solutions to this problem, there is no marked turbulence with the arrangement according to the present invention, but instead the distribution of the fluid or the blood has a mainly uniform radial symmetry. 
   It is especially advantageous if the end areas of the hollow fibers are held in a casting compound which extends parallel to the channel. The casting compound is usually designed in the form of disks, with the ends of the hollow fibers being arranged in a uniform distribution in the casting compound. 
   According to a preferred embodiment of the present invention, the height and/or width of the channel decreases in the direction of flow. It is especially advantageous if the cross-sectional area of the channel decreases linearly with the flow path. Such a design yields the result that identical quantities of liquid or blood are discharged from the channel per angle area, thus resulting in a distribution that has approximate radial symmetry. 
   It is especially advantageous if there is an inlet or outlet extending radially, developing into the channel according to the present invention in its one end area and forming the mouth of a connection of the filter device in its other end area. 
   The diameter of the circular or semicircular channel may advantageously be 2 to 4 times, preferably 2.5 to 3.5 times, the diameter of the inlet or outlet. 
   In another embodiment of the present invention, the diameter of the circular or semicircular channel may be less than 9/16, preferably less than ⅜, of the diameter of the hollow fiber bundle. 
   It is especially advantageous if the channel is circular, i.e., circumferential. Thus, not only a semicircular design of the channel is conceivable, but also a complete circulation. 
   In another embodiment of the present invention, guide elements are provided in the areas adjacent to the essentially circular or semicircular channel, so that the direction of flow of the fluid leaving the channel can be influenced by these guide elements. 
   The guide elements may be designed as curved ribs. This makes it possible to distribute the fluid, in particular the blood, uniformly and in a defined manner. This may lead to the development of a small central vortex, but it always has radial symmetry. 
   It is especially advantageous if the ribs are equidistant in the circumferential direction of the channel. In addition, any other desired arrangement of ribs and guide elements is also conceivable. 
   The hollow fiber bundle may be held in a tubular casing, with a second flow space being formed through the interior of the casing surrounding the hollow fiber bundle, and with the inflow or outflow chamber being arranged in an end cap connected to the casing at the end. End caps may be provided in both end areas of the casing. 
   According to a preferred embodiment of the present invention, the hollow fiber bundle extends over the entire cross-sectional area of the casing. It is also conceivable for only partial areas of the cross-sectional area of the casing or the casting compound to be provided with hollow fibers. 
   It is especially advantageous if each of the end caps has two connections, one of which is connected to the first flow space and the other to the second flow space. Thus, an inlet and an outlet are created for each of the flow spaces, which permits continuous flow through both flow spaces accordingly. The assignment as an inlet or outlet is not fixed, because the connections can be exchanged as needed. 
   In another embodiment of the present invention, the connections are arranged radially. This applies accordingly for the blood side as well as for the connection for the dialysis solution, which is usually carried through the second flow space. The radial arrangement of the connections may have hydrodynamic advantages. In addition, the arrangement of the connections may also be predetermined by the tube system to be used or by the mounting of the filter device. 
   According to a preferred embodiment of the present invention, the center lines of the connections run parallel to one another. It is also possible for the center lines of the connections not to pass through the mid point of the end cap. 
   The mouths of the connections may lie in one plane or in parallel planes. The corresponding design depends essentially on the mount holding the filter device, which should permit rapid and reliable replacement of the filter devices. In another embodiment of the present invention, the connections point in opposite directions. 
   It is especially advantageous if the casing and the end caps are designed as injection molded parts. This guarantees a reliably simple manufacture, with numerous different embodiments being conceivable. 
   The present invention also concerns an end cap for a filter device according to the present invention having an inflow or outflow chamber adjacent to an essentially circular or semicircular channel, which is designed to be open in the direction of the ends of the hollow fibers of a hollow fiber bundle arranged in a filter device casing that can be connected to the end cap, and being connected to an inlet or outlet of the end cap, arranged approximately centrically to the hollow fiber bundle and having a cross-sectional area that decreases in the direction of flow, and which has an outside diameter which is less than the inside diameter of the area of the end cap accommodating the hollow fiber bundle. 
   Advantageous embodiments of the end cap are presented by the embodiments according to the claims. 
   Additional details and advantages of the present invention are explained in greater detail below on the basis of one embodiment illustrated in the figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a longitudinal sectional view of an end cap with inflow or outflow chambers having a semicircular channel. 
       FIG. 2  shows a partial side view of the end cap according to line A-A in  FIG. 1 . 
       FIG. 3  shows a partial side view of the end cap according to line B-B in  FIG. 1 . 
       FIG. 4  shows a top view of the end cap according to  FIG. 1 . 
       FIG. 5  shows a detailed view of a sectional diagram according to line C-C in  FIG. 4 . 
       FIG. 6  shows a view of the end cap according to  FIG. 1  from beneath. 
       FIG. 7  shows a schematic diagram of the size relationships of the inlet or outlet, the channel and the hollow fiber bundle. 
       FIG. 8  shows a longitudinal sectional view of an end cap with an inflow or outflow chamber having a circular, i.e., circumferential channel. 
       FIG. 9  shows a top view of the end cap according to  FIG. 8 . 
       FIG. 10  shows a detailed view of a sectional diagram according to line D-D in  FIG. 9 . 
       FIG. 11  shows a view of the end cap according to  FIG. 8  from beneath. 
       FIG. 12  shows a detailed view of the circular channel and the adjacent guide elements designed as ribs according to  FIG. 11 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a longitudinal sectional diagram of the end cap  30 , which is in fluid-tight connection with the casing  40 . End cap  30  has inflow or outflow chamber  10  adjacent to the semicircular channel  12 . Liquid leaving semicircular channel  12  is carried into the inflow or outflow chamber  10  and is distributed in an essentially radially symmetrical pattern over the ends of the hollow fibers of a hollow fiber bundle. 
   Channel  12  is connected to the inlet or outlet  20  which in its end area forms the mouth  320  of connection  32  of the filter device according to the present invention. 
   End cap  30  is provided with bead  36  which extends radially, with connection  32  being formed in its end area. 
   In the area of end cap  30  shown at the right in  FIG. 1 , connection  34  is provided, having mouth  340  which is connected to the second flow space formed by the interior  42  of the casing surrounding the fibers. 
     FIGS. 2 and 3  show the side views of the end cap  30  according to  FIG. 1  in the perspectives defined by lines A-A and B-B respectively. Both connection  32  and connection  34  are arranged radially. This is also true of bead  36  in whose end area is arranged connection  32 . 
   Mouths  320  and  340  of connections  32  and  34  lie in parallel planes, but they point in opposite directions, as shown in  FIG. 1  in particular. This may be necessary for reasons of compatibility with tubing systems already present or corresponding mounts holding the filters or because of advantages in handling. However, it is essentially also possible to provide the connections on the same side and to arrange the mouths in one plane. 
     FIG. 4  shows a top view of the end cap  30  and illustrates the arrangement and embodiment of channel  12  and inlet and outlet line  20  with a dotted line. 
     FIG. 4  shows that the inlet or outlet line  20  running through the connection  32  is arranged radially. Inlet line  20  develops into channel  12 , which is semicircular in shape according to this invention and extends approximately centrally through the hollow fiber bundle and/or the casting compound. 
   The height of channel  12  decreases in the direction of flow, which has the advantage that liquid carried through channel  12  leaves channel  12  in equal distribution over the angular sections, i.e., with radial symmetry, and is carried into the inflow or outflow chamber  10  and is thus distributed uniformly among the fibers of the hollow fiber bundle. 
   According to the present embodiment, channel  12  is designed so that its height is zero in its end area, i.e., it develops into the bottom of end cap  30 . 
   In a cross-sectional diagram according to line C-C from  FIG. 4 ,  FIG. 5  shows the arrangement and the design of channel  12 .  FIG. 5  shows a cross section of the channel shown at the right in  FIG. 5  which is offset with respect to the inlet or outlet  20  because of its semicircular design, and the height of the channel  12  decreases in the direction of flow. 
     FIG. 6  shows a bottom view of the end cap  30  according to  FIG. 1 .  FIG. 6  shows a channel  12  having a semicircular shape, and in its outlet end area it develops into the bottom of end cap  30 .  FIG. 6  also shows that the mid point of the semicircle formed by channel  12  which corresponds to the mid point of the end cap  30  and thus also the mid point of the casting compound or that of the hollow fiber bundle. 
     FIG. 7  shows a schematic diagram of exemplary size relationships of the inlet or outlet  20 , channel  12 , and the hollow fiber bundle characterized by the circle. The diameter (d) of the circular or semicircular channel  12  preferably amounts to 2 to 4 times, more preferably 2.5 to 3.5 times the diameter (b) of the inlet or outlet  20 . The diameter (d) of the channel  12  preferably is less than 9/16, more preferably less than ⅜ of the diameter (D) of the hollow fiber bundle. 
     FIG. 8  shows a longitudinal sectional diagram of another embodiment of the filter device according to the present invention. The end cap  30  according to  FIG. 8  has a circular, i.e., circumferential channel  12 ′. The cross-sectional area of channel  12 ′ decreases in the direction of flow, which is implemented by the fact that its height decreases in the direction of flow, as shown in  FIG. 8 . 
   Curved ribs  14  arranged in the area extending around channel  12 ′ cause the fluid leaving channel  12 ′ to be distributed uniformly into the inflow or outflow chamber  10  or through the hollow fiber bundle in a defined manner. The distance between ribs  14  and the casting compound of the filter is advantageously designed so that almost complete flow control is achieved. This distance is, for example, approximately 0.2 mm. The distance between the casting compound and the connection of end cap  30  inside the circular channel  12 ′ is advantageously somewhat greater, e.g., 0.25 mm. 
     FIG. 9  shows a top view of end cap  30 , illustrating that channel  12 ′ in the embodiment according to  FIG. 8  is designed to be circular. 
     FIG. 10  shows a cross-sectional diagram according to line D-D in  FIG. 9 , illustrating an arrangement and design of the channel  12 ′. A comparison with  FIG. 5  shows that the section of the channel shown at the bottom of  FIG. 10  has a larger cross-sectional area than in the embodiment shown in  FIG. 5 , and in each instance the cross-sectional area does not drop back to zero in the remaining course in accordance with the circumferential design of channel  12 ′. 
     FIG. 11  shows a bottom view of the end cap in  FIG. 8 . In this embodiment, channel  12 ′ is designed to be circumferential. Furthermore, it can be seen in this embodiment that ribs  14  are arranged around the circumference of channel  12 ′ and do not run radially outward but instead are arranged with a curvature. Of course, in addition to the embodiment shown here, any other desired arrangement and embodiment of ribs  14  are also conceivable. Ribs  14  serve as guide elements for the liquid leaving the channel  12 ′. Ribs  14  are approximately one millimeter or a few tenths of a millimeter thick, for example. Due to the design and arrangement of such guide elements, it is possible to distribute the liquid leaving channel  12 ′ in a defined manner and in a defined direction in the inflow or outflow chamber  10  or through the hollow fiber bundle. 
   The arrangement of ribs  14  is shown in the detailed view according to  FIG. 12 . It can be seen in this embodiment that the ribs  14  are directly adjacent to the channel  12 ′. Ribs  14  are designed to be equidistant from one another. The distance between the individual ribs decreases in the direction of flow, leading to a corresponding acceleration of the fluid carried through ribs  14 . 
   The arrangement of the guide elements, in particular ribs  14 , is conceivable not only with the circumferential design of channel  12 ′ but of course also with a semicircular design according to  FIGS. 1 through 7 . 
   Advantageous dimensions of the circumferential channel  12 ′ according to  FIGS. 8 through 12  can also be derived from the discussion of  FIG. 7  above.