Abstract:
A filter device having two flow paths. The first flow path having at least one cap and fluid port. The second flow path surrounding the first fluid flow path and having at least one cap that overlaps the cap of the first fluid flow path. The second flow path also having at least one fluid port. The filter device providing a simple arrangement that is easily disinfected or sterilized.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to a filter device having two flow spaces, of which a first space, preferably a permeate space, is formed by the tubular or capillary tube passages of a hollow-fiber bundle poured at its ends into a molding compound, and a second space, preferably a filtrate space, is formed by a housing enclosing the fiber bundle, the first space being sealed off by caps, placed on the molding compounds, with sealing devices running over the peripheral areas of said molding compounds, and the molding compounds being braced against the housing.  
         BACKGROUND OF THE INVENTION  
         [0002]    The German laid open print 26 46 358 discloses a filter device in which the hollow-fiber bundle encloses a central conduit in a ring-like manner, and the ends of the ring-shaped hollow-fiber bundle are sealed off by a molding compound both with respect to the central conduit and with respect to the housing casing concentrically enclosing it.  
           [0003]    Another known filter device likewise comprises a tubular housing which encloses the hollow-fiber bundle, the ends of the hollow-fiber bundle being joined to the ends of the tubular housing by a molding compound. In this filter device, the housing is provided in each case with radial connection pieces, adjacent to the molding compounds, which form the inlets and outlets to the second flow space. The capillary tubes of the hollow-fiber bundle enclosed by the molding compounds are cut at their end faces to open them. Caps provided with connection pieces which form the inlets and outlets of the first flow space are then placed sealingly on the ends of the tubular casing.  
           [0004]    These known filter devices are used, for example, as capillary dialyzers, the flow spaces formed by the capillary-tube passages forming the blood chamber, and the housing enclosing the hollow-fiber bundle forming the dialysate chamber in which the dialysate flows around the hollow fibers.  
           [0005]    The problem existing in the known filter devices is that the molding compound, usually made of PU [polyurethane fiber], which hardens in a disk shape and forms a sealing between the two flow spaces, shrinks when hardening, so that stresses develop in the disk-shaped sealings formed by the molding compounds which can lead to cracks and even detachments of the molding compounds from the housing casing enclosing them. As a result, the two flow spaces are no longer completely sealed off from one another, and the adhesion of the sealing compounds to the housing enclosing the fiber bundle, said adhesion producing the seal, is no longer reliably assured.  
           [0006]    In a filter device of the type indicated at the outset disclosed by EP 0 305 687 B1, the disk-shaped molding compounds are enclosed by interposed rings to which the molding compounds do not adhere, so that they can shrink free of stress. This stress-free shrinking prevents cracks in the disk-shaped molding compounds, and makes it possible to dispense with a direct sealing between the peripheral edge of the sealing compounds and the housing enclosing them. To nevertheless maintain a sealing between the two flow spaces, the first space is sealed off by caps placed on the molding compound, and specifically by sealing devices which run over the edge area of the molding compound and against which the caps are pressed.  
           [0007]    In this known filter device, the problem now exists of producing a connection to the second space formed by the housing enclosing the fiber bundle. This connection is produced in the known filter device, in that the diameter of the tubular housing is widened at its end areas more or less in the manner of a sleeve, these widened areas being provided with radial connection pieces. These connection pieces open through into the second space formed by the housing, the widened sections of the housing being sealed off from the first space because the caps are sealingly joined to the widened sections, so that a sealing is produced to the outside by the cap edge, and a sealing is produced with respect to the first space by the circumferential sealing ring. This type of arrangement of the connection pieces at the second space formed by the housing is relatively costly. Furthermore, dead spaces which are poorly rinsed develop above or below the connection pieces, at which gas bubbles can collect. This can have a disadvantageous effect during disinfecting or sterilization, as well as generally when handling.  
         OBJECTS AND SUMMARY OF THE INVENTION  
         [0008]    Therefore, the object of the invention is to produce a filter device of the type specified at the outset in which, on one hand, it is reliably assured that the two flow spaces are sealed off from one another by the hardened molding compounds, and on the other hand, a simple arrangement of the connection pieces for the second flow space is produced and poorly rinsed dead spaces are moreover avoided.  
           [0009]    This objective is achieved according to the invention, given a filter device having two flow spaces, the first space formed by tubular or capillary tube passages of a hollow-fiber bundle, said fiber bundle being poured at its ends into a molding compound, and a second space formed by the housing surrounding the fiber bundle. The invention further entails the first space being sealed off by caps, placed on the molding compounds, with sealing devices being placed over the peripheral areas of the molding compounds, and the molding compounds being braced against the housing. The molding compounds are hardened in molds enclosing them at their end faces and peripheral sides to form disks. Caps are provided for the ends of the first space that seal to the molding compound and have a connection piece providing inflow/outflow access to the first space. A second set of caps, overlapping the first caps, is provided, said caps having a connection piece providing inflow/outflow access to the second space. The edges of the second caps being joined to the housing in a fluid tight manner, so that between the first and second set of caps, interspaces are formed, said interspaces being connected to the second space.  
           [0010]    In the filter device according to the invention, the molding compounds are hardened in molds enclosing them on the face and at their sides, so that the molding compounds are able to shrink free of stress. As in the known filter device, the sealing between the disk-shaped molding compounds thus formed and the first caps is effected by inserted sealing means. However, to produce a simple access to the second flow space, the corresponding connection pieces are no longer arranged on the housing itself, but on the second cap overlapping the first cap. This simplifies the filter device.  
           [0011]    The inner edges of the second caps overlapping the molding compounds advantageously extend beyond the molding compounds to the inside, so that a flow space is produced between the circumferential wall of the second caps and the molding compounds or the fiber bundles enclosed by them.  
           [0012]    According to a preferred specific embodiment, the pipe-section-shaped housing, into which the hollow-fiber bundle is drawn, is provided at the ends of its casing with tooth-like or scalloped projections formed by axial notches or indentations running out freely, the outer areas of the projections being integrated into the molding compounds, so that the free inner areas of the notches or indentations form flow passages for the fluid. Since the housing, which is pipe-section-shaped or preferably provided with a circular cross-section, is made of a material having elastic properties such as PC (polycarbonate), wreath-shaped edges made of flexible tongues are formed by the notches or indentations, said edges being at least partially enclosed by the molding compound. When the molding compound then hardens to form the disks, they can shrink essentially free of stress, because the flexible tongues offer no significant resistance to this shrinking. According to this refinement of the present invention, the disks formed by the molding compounds are firmly joined to the ends of the tubular housing, so that the two flow chambers can then be reliably separated from one another by the two caps overlapping one another, with the appropriate sealing means.  
           [0013]    It may be that the filter device known from EP 0 305 387 B1 has a tubular housing, in which wreath-shaped edges formed by notches or indentations are produced in the widened end sections and are partially enclosed by the molding compounds hardened to form disks. However, these wreath-shaped edges made of rectangular projections demand a complicated design of the housing, because in addition, they are still enclosed by the widened end sections of the housing which are provided with the connection pieces.  
           [0014]    The housing is expediently provided in the area of the inner ends of the projections with radial flanges, on which the edges of the second caps are sealingly supported, or to which they are secured.  
           [0015]    Advantageously, the distance of the projections from one another in the circumferential direction is greater than their width.  
           [0016]    According to one inventive embodiment, for which independent protection is claimed, the cross-sectional area of the regions of the notches or indentations free of the molding compounds is so dimensioned that, starting from a radial connection piece, they increase in their cross-section, so that essentially equal partial quantities of the fluid can enter and exit through the cross-sections. This embodiment takes into account the circumstance that, in the annular space surrounding the fiber bundle and into which the liquid is fed through a radial connection piece, a pressure drop occurs in the circumferential direction starting from the mouth of the connection piece. Adjusting the cross-sections of the intake ports to this pressure drop assures that essentially equal quantities of fluid enter the openings distributed over the circumference.  
           [0017]    A special problem in filter devices of the type indicated at the outset is assuring that in the second space, the surfaces of the fibers in the hollow-fiber bundle are circumflowed as completely and uniformly as possible by the introduced fluid, in order to increase the effectiveness of the filter device. Therefore, according to one particularly preferred specific embodiment of the invention, inserted into the housing are saucer-shaped rings whose legs are joined to the inside wall of the housing and which are provided with bore holes, and that the inside wall is provided with bore holes opening through into the annular spaces formed by the rings. An annular space is formed by the saucer-shaped ring, in which the introduced fluid can spread out well. The bore holes can be distributed uniformly over the periphery, in doing which the cross-sections of the bore holes can be adapted to the pressure drop occurring in the introduced fluid if it is fed into the annular space only through one bore hole or one radial connection piece.  
           [0018]    To maintain an essentially uniform fluid pressure given a one-sided introduction of the fluid into the annular space, the bore holes and openings respectively having identical flow-through cross-sections can be distributed with appropriately variable clearances over the periphery of the inside wall of the annular space.  
           [0019]    Advantageously, the rings have a U-shaped cross-section, the bore holes being arranged in the radial legs of the rings.  
           [0020]    In the known filter device, the annular spaces formed by the annular grooves have an axial clearance with respect to the end disks formed by the molding compounds. Because of this, in the case of a vertically standing filter device, for example, air bubbles can collect at the upper disk formed by the molding compound. Furthermore, air bubbles can also collect in the lower annular groove between the mouth of the radial connection piece and the groove bottom. A result of this undesired collecting of air or air bubbles is that, for example, during sterilization or disinfection of the filter, the air-filled areas do not come in contact, or come only insufficiently in contact with the sterilizing or disinfecting means.  
           [0021]    To achieve a complete deaeration of the hollow-fiber space, a further inventive development provides that the annular spaces or the passages connecting the annular spaces to the second space are joined directly to the molding compounds, or extend in the axial direction to their area.  
           [0022]    This refinement of the present invention prevents dead spaces between the connection pieces and the annular spaces respectively into which they discharge, so that no air can accumulate in unwanted manner in dead spaces, and a complete circumcirculation of the hollow-fiber bundle by the fluid between the molding compounds is assured.  
           [0023]    Expediently, both sides of the filter are identically shaped, so that the effects provided according to the invention are attainable in any position of the filter.  
           [0024]    The embodiment of the filter according to the invention also has a favorable effect on the discharge side of the second space, since the fluid is withdrawn from the second space essentially uniformly distributed over the annular space.  
           [0025]    A further advantage of the present device is that its housing can be made of a material such as propylene which does not form a tight adhesive bond with the molding compound. Therefore, it is possible to produce the filter device according to the invention from less costly plastic materials, which increases its economic efficiency.  
           [0026]    A further inventive refinement relates to a filter device having two flow spaces, of which a first space, preferably a permeate space, is formed by the tubular or capillary tube passages of a hollow-fiber bundle poured at its ends into a molding compound, and a second space, preferably a filtrate space, is formed by a housing enclosing the hollow-fiber bundle. The filtrate space is sealed off from the inlets and outlets of the tubes of the hollow-fiber bundle by the molding compound. Furthermore, at least two connection pieces are provided for the feeding and removal of fluids into or out of each of the two spaces, of which at least one connection piece of the second space opens through into an annular space formed between the housing and the area of one end of the hollow-fiber bundle. To assure that there is no dead space in the annular space in which air bubbles can collect, the present invention provides that in the position of normal use, at least one annular space is located at the top, and that the annular space extends to the supply line and discharge line respectively. Preferably dialysate can be fed or removed through the upper annular space.  
           [0027]    In the following, an exemplary embodiment of the invention is explained in more detail with the aid of the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 shows a longitudinal cross-section through one side of a filter device according to the invention,  
         [0029]    [0029]FIG. 2 to  4  show top views onto one end face of a disk formed by the molding compound,  
         [0030]    [0030]FIG. 5 shows a longitudinal cross-section through the housing of a known filter device,  
         [0031]    [0031]FIG. 6 shows a section through the upper area of the housing of a filter device according to the invention with closed annular space  
         [0032]    [0032]FIG. 7 shows a side view of a filter device according to the invention and  
         [0033]    [0033]FIG. 8 shows a section through the filter device according to FIG. 7. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    Filter device  1  is made of a pipe-section-shaped housing  2  of plastic such as PC, whose edges merge into a radial, annular flange  3 . Joined to the housing, to the inner edge area of this flange  3  or to the transition region between the cylindrical pipe section and the flange, is a cylindrical ring which is provided with indentations  5  that form rectangular notches which run out freely. Formed between these notches  5  are scallop-like or tongue-like projections  4  which are likewise essentially rectangular and extend in the axial direction. At their upper, outer, end areas, these projections  4  have projections  6  pointing radially outwardly.  
         [0035]    A hollow-fiber bundle  55  is introduced into pipe-shaped housing  2 . The ends of this hollow-fiber bundle are embedded in a molding compound  7  made, for example, of PU, which is disk-shaped after hardening. Since during its hardening, the molding compound is centrifuged about an axis of rotation at right angles to housing axis  8 , disk  7  in the top view evident from FIG. 1 has a cylindrical saucer-shaped inner side  9 . The hardening is carried out in a cap which rotates along and which delimits the end face and the peripheral side. The tolerance range within which cylindrical, saucer-shaped, inner side  9  can move is indicated by broken lines  9 ′ and  9 ″.  
         [0036]    After hardening the molding compound, disk  7  is cut at its end face  10 , thus opening the small capillary tubes of the hollow-fiber bundle embedded in the molding compound.  
         [0037]    A first cap  11  having a central connection piece  12  is then placed on end face  10  of disk  7 , said cap being sealed off at its edge-area, by means of an O-ring  13 , from the edge area of disk  7  free of hollow fibers.  
         [0038]    First cap  11  is enclosed by a second cap  14  having a cylindrical wall  15  whose edge area is joined in a fluid-tight manner to the outer edge of annular flange  3 . Second cap  14  possesses a central, cylindrical extension prolongation  16  which forms a connection piece and concentrically encloses the double-walled connection piece  12  of first cap  11 . Second cap  14  is provided on its inner side with ray-shaped webs  17  which assure the necessary clearance to first cap  11 , and thus define flow channels. Cylindrical extension prolongation  16  is also provided on its inner side with radial webs  19  which are supported on the outer casing of connection piece  12  and define flow channels.  
         [0039]    Radial webs  20 , arranged in a star shape and used as stiffening, are provided on the lower side of first cap  11 .  
         [0040]    With its cylindrical edge  15 , second cap  14  encloses, with radial clearance, disk  7  and scalloped or tooth-shaped extension prolongations  4 , thus forming an annular space  21  through which the fluid, introduced through connection piece  16 , can enter through the inner areas of ports  5  into the flow space enclosing the hollow-fiber bundle.  
         [0041]    As FIGS.  2  to  4  show, the tooth-like or scallop-like projections  4  and gaps  5  formed between them can have different lengths and form different angles at circumference. The nose-shaped, radial projections  6  can also vary in length and width.  
         [0042]    [0042]FIG. 5 shows a longitudinal cross-section through the housing of a known dialyzer. In this known dialyzer, the ends of hollow-fiber bundle  25  are enclosed by the molding compounds which have hardened to form disks  26  and which form secure bonds to outer edges  27 ,  28  of housing  29 . At a distance from disks  26 , the housing is provided with radial connections  30 ,  31  that open into channel-shaped annular spaces  32 ,  33  which, in the manner shown, are formed by inner, ring-shaped wall sections  34 ,  35  which run out freely and whose edges terminate with axial clearance before the disks. If, for example, given a vertically standing housing, a fluid such as dialysate is introduced through lower radial connection piece  31  into the space accommodating hollow-fiber bundle  25 , the fluid tends to overflow the edge of wall  35  bordering annular groove  33 , mainly in the areas near connection piece  31 , so that an unsymmetrical fluid flow, that is to say dialysate flow, develops in housing  29 .  
         [0043]    The filter device according to the invention, explained with the aid of FIGS.  1  to  4 , prevents this unsymmetrical flow, because the fluid or dialysate spreads out in annular space  21  and then, essentially with uniform circumferential distribution, enters through the inner, free areas of inlet ports  5  into the space enclosing the hollow-fiber bundle. In the exemplary embodiment shown, annular space  21  is bounded outwardly by the cylindrical wall of cap  15 , the cap being provided with an axial, concentrically arranged intake nipple, so that the fluid spreads out with equal pressure in annular space  21 . Since an essentially equal fluid pressure occurs over the periphery of annular space  21 , the intake ports formed by the free areas of inlet notches  5  can also have equal cross-sections.  
         [0044]    In the exemplary embodiment according to FIG. 6, the fluid or the dialysate enters through radial bore holes  41  of pipe-section-shaped housing  36  into an annular space  37  which is formed by a U-shaped ring  38  whose outwardly-pointing legs are joined in a fluid-tight manner to the housing casing. Provided in the legs of U-shaped ring  38  are bore holes  39 , uniformly distributed over the circumference, through which the fluid introduced into annular space  37  can enter into the chamber containing the hollow-fiber bundle.  
         [0045]    The pipe-section-shaped housing is provided, in the area is of the lower side of the annular space, with an outer, radially circumferential flange  40  upon which the edge of a cap can be placed, in a corresponding manner as in the case of the device described with the aid of FIGS.  1  to  4 , so that between the cylindrical circumferential wall of the cap and the upper part of housing  6 , an annular space is formed through which fluid can be conducted, with equal pressure distribution, to radial bore holes  35  distributed over the periphery of the housing.  
         [0046]    [0046]FIG. 7 shows a side view of a filter device, in the case shown, a dialyzer. In this dialyzer, the connections or connection pieces used for connecting to the nozzles of a dialysis machine are located on one side and have center lines parallel to one another, so that they can be sealingly pressed, directly or through a suitable device, onto the nozzles of the dialysis machine.  
         [0047]    In the filter device evident from FIGS. 7 and 8, the upper and lower caps provided with the connections and connection pieces respectively are made of parts produced separately in the injection molding process whose edges are butt joined in a fluid-tight manner by suitable welded or adhesive joints to the edges of the housing which open out bell-shaped.  
         [0048]    As is clear from FIG. 8, the blood chamber and the dialysate chamber surrounding hollow fibers  55  are separated by a molding compound  50 . At its upper edge area, the molding compound has a circumferential groove into which an O-ring  51  is inserted to seal off the blood chamber from the dialysate chamber. As FIG. 8 clearly shows, opening  53  leading into connection piece  52  is joined directly to the lower side of O-ring  51 , the annular space  54  used for the supply and removal of the dialysate extending to the O-seal, so that there is no dead space in which air bubbles could collect.  
         [0049]    The function of the invention will be described using blood as an example of a fluid that requires the removal of impurities. According to the present invention, blood enters the first fluid flow space through a fluid port formed by connection piece  12 . The blood then travels through the first fluid path, which extends through the molding compounds  7 ,  50 , and exits through a second fluid port. During the course of traveling through the first fluid flow space the blood is cleaned of impurities, said impurities diffusing into and being carried away by the dialysate in the second fluid flow space.  
         [0050]    Clean dialysate fluid is introduced into the second fluid flow space through an extension  16  of the second cap  14  or through fluid port  52 . The dialysate spreads out in annular space  21 ,  54  and flows through notches  5  into the portion of the second flow path surrounding the first fluid flow path. Alternatively, the blood may flow through bore holes  41  into annular space  37  and then through second bore holes  39  into the portion of the second flow space surrounding the first flow space. The dialysate and the blood may flow in opposite directions (counter-current flow), or they may flow in the same direction. As the dialysate moves through the portion of the second flow space surrounding the first flow space, impurities diffuse from the blood into the dialysate and the impurity-laden dialysate exits the device through a second fluid port.