Abstract:
A filter device includes a housing ( 2 ) having at least two rotation bodies ( 4 ,) which are arranged therein and are driven by a shaft ( 3 ). The rotation bodies ( 4 ) are designed and arranged for producing a centrifugal pumping effect. A guidance device ( 7 ) is provided between the rotation bodies ( 4 ), which connects the pressure side ( 6 ) of a first rotation body ( 4 ) to the suction side ( 5 ) of a rotation body ( 4, 18 ) arranged therebehind in the flow direction ( 8 ). The intermediate spaces between the rotation bodies are provided with a filter arrangement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Section 371 of International Application No. PCT/EP2007/003889, filed May 3, 2007, which was published in the German language on Nov. 15, 2007, under International Publication No. WO 2007/128484 A1 and the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a filter device having a housing and at least two rotation bodies arranged in the housing and driven by a shaft. Such filter devices consist typically of stacks of hollow filter plates, which are arranged in an essentially cylindrical filter housing, also in a rotating manner as the case may be. The fluid to be filtered is introduced into the housing and goes through the filter formed in the region of the surface of the filter plates into the inside of the plates, and from there into a central channel, via which the filtered fluid is drawn off. Such filter plates are known, for example, from German published patent application DE 196 24 176 A1 or European patent application publication no. EP 0 723 799 A1, and corresponding filter arrangements are known from DE 196 24 176 A1 as well as U.S. Pat. No. 5,326,512. 
         [0003]    Since the filter housing is mostly subjected to the fluid to be filtered from an end-side, the material held back by the filter typically connects at the end of the filter device which is distant to the feed opening. If a tough scum forms here, it may be a problem to remove this from the filter device. Flushing procedures and back-flushing procedures are unfavorable, since they interrupt the continuous filter operation. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    Against this background, it is the object of the invention to design a filter device of the known type, such that a removal of the filter mass remaining in the device is improved. 
         [0005]    The filter device according to an embodiment of the invention comprises a housing in which at least two, typically a stack, of rotation bodies are arranged driven by a shaft. According to an embodiment of the invention, the rotation bodies are thereby designed and arranged for producing a centrifugal pumping effect, wherein at least one guidance device is provided between the rotation bodies, which connects the pressure side of a first rotation body to the suction side of the rotation body which is arranged behind the first rotation body in the flow direction, and wherein either the rotation bodies themselves or even additionally the intermediate spaces between the rotation bodies, are provided with a filter arrangement in this filter device. 
         [0006]    The basic concept of the present invention is to improve the transport of the filter mass which is held back by the filter arrangement, within the filter housing, by designing and arranging at least two, preferably several, of the rotation bodies, for producing a centrifugal pump effect, wherein a guidance device is provided within the filter housing between the rotation bodies producing the centrifugal pump effect, which ensures that the pressure side of a first rotation body is connected to the suction side of a rotation body which is arranged therebehind in the flow direction. According to an embodiment of the invention, the filter arrangements may thereby be provided either on the rotation body side or in the region of the intermediate spaces between the rotation bodies. The rotation bodies and the guidance device are thereby arranged such that a type of multi-stage pump arises within the filter housing, so that the pressure level in the flow direction of the filter mass increases from the entry to the exit. This is particularly advantageous, since specifically on account of the greater pressure in the region of the outlet of the filter mass, this filter mass may yet reliably be led away from the filter device there, even if it is a tough mass in the form of mush. The rotation bodies, which are arranged and designed such that they have a centrifugal pumping effect, take up the fluid close to the shaft, and transport this outwardly in accordance with the active principle of a centrifugal pump. Then, with the help of a suitable guidance device, the higher speed of the fluid at the outer periphery of the rotation body is converted into pressure, which is then led through the guidance device in a targeted manner to the suction side of the rotation body which is arranged therebehind in the flow direction, this rotation body again ensuring a pressure increase. 
         [0007]    In order to form such a guidance device in a manner as effective as possible and with little constructional effort, according to a further embodiment of the invention, one envisages providing at least two plates arranged in a stationary manner in the housing. These plates form part of the guidance device and, seen in the flow direction, the first plate comprises or forms a flow channel distant to the shaft, and the second plate, seen in the flow direction, comprises or forms a flow channel which is close to the shaft. With the help of two such plates, the flow feedback from the outer periphery of a rotation body to the region of the subsequent rotation body, this region being close to the shaft, may be effected in a very efficient manner, and the pressure gain which may be achieved on account of the centrifugal pumping effect may be led to the next rotation body in the manner of a multi-stage pump. 
         [0008]    According to a further embodiment of the invention, one or preferably both plates comprise filter arrangements, wherein these plates, since they are arranged within the housing in a stationary manner, are usefully connected on the outer side via a discharge channel arranged there, in order to withdraw the filtered fluid in this region. 
         [0009]    Basically, according to the invention, any suitable filter arrangement may be applied. However, it is particularly advantageous if the filter arrangement is formed by a hollow filter plate, as known in the prior art and whose preferred design is described further below. An ideal pump effect is achieved, if, according to a further embodiment of the invention, the rotation body is formed by a centrifugal pump impeller. In particular, if several such centrifugal pump impellers are arranged one after the other within the device, an intensive removal of the filter mass is effected, so that even tough filter masses and ones largely freed of fluid, may be pumped out of the device. 
         [0010]    A less intensive pump effect, but instead a more compact filter device, may be achieved, according to another embodiment of the invention, by the rotation bodies also being formed by filter plates themselves, which are conductively connected via at least one channel to the discharge channel in the shaft for the removal of the filtered fluid. Thereby, either the filter plate itself is designed encouraging the centrifugal pumping effect or, as the case may be, even additionally may be driven with an increased speed, in order to achieve a suitable pump effect. 
         [0011]    According to one embodiment of the invention, the filter plate forming the rotation body, is designed with a suction-port-like opening near the outer periphery of the shaft, so that the fluid to be delivered within the filter housing penetrates the filter plate close to the shaft, then flows along the filter plate surface from the inner periphery to the outer periphery, whereupon the conversion of the kinetic energy into potential energy, i.e. into a pressure again, is effected within the guidance device. In order, on the one hand, to permit the discharge of the filtered fluid which has reached within the filter plate, through the central shaft, but on the other hand, to create a suction port structure as efficient as possible in the region close to the shaft, according to an embodiment of the invention, one envisages the filter plate forming the rotation body comprising a central recess, which is mechanically as well as conductively connected to the shaft merely via spokes which form channels. The spokes are usefully arranged distributed symmetrically to the rotation axis and are to be dimensioned such that, on the one hand, an adequate cross section for the removal of the filtered fluid is formed, and on the other hand, the torque required for the drive of the rotation body may be transmitted. 
         [0012]    According to a preferred embodiment of the invention, the rotation bodies are designed in the form of rotating filter plates, which are driven via the central shaft, and discharge the filtered fluid through the central shaft. The guidance device is preferably also formed by filter plates, which however, since they are connected to the housing in a rotationally fixed manner, are connected via a discharge channel within the housing for leading away the filtered fluid. The housing, which advantageously has an essentially cylindrical design, advantageously comprises an annular channel as a discharge channel on the outer side. Such an annular channel may be formed in a simple manner by the housing being formed in a double-walled manner in this region. In this manner, on the one hand, an adequate cross section for the discharge channel is formed, and on the other hand, a very compact constructional shape is formed. 
         [0013]    In order to keep the flow losses within the filter device due to backflow in the region of the rotation body as low as possible, particularly with the use of a centrifugal pump impeller within the device, a centrifugal pump impeller is usefully arranged such that the suction port of the centrifugal pump impeller projects up into the recess of the stationary filter plate arranged in front, the recess surrounding the shaft at with a spacing. 
         [0014]    In particular, if filter plates are applied as rotation bodies, it is advantageous if the rotation bodies are arranged in groups of two or more rotation bodies, wherein then in each case a guidance device is arranged between the groups of rotation bodies. The arrangement of rotatably driven filter plates in groups effects an improved centrifugal pumping effect, in particular if the filter plates are only adapted to a small extent with regard to the centrifugal pumping effect, and merely comprise a suction-port-like recess in the region around the shaft, and otherwise correspond to the designs according to the prior art. 
         [0015]    The filter mass, which is delivered by the device with the help of the previously described pumping effect, may be led completely or partly in the circuit, wherein then a suitably large quantity of fluid yet to be filtered is to be added, in order to reduce the concentration of the filter mass in relation to the fluid. The filter fluid, which is withdrawn through the shaft and the annular channel on the outer periphery of the housing, is then available for further use. 
         [0016]    The filter device according to the invention may not only be applied as a filter, but preferably also as a part of a biological reactor, wherein the device then simultaneously serves for the circulation of the fluid/masses located in the reactor, or at least supports this. It is to be understood that then, as the case may be, no closed filter housing is required, but merely a tubular housing which creates the hydraulic environment required for the pumping effect. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0017]    The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
           [0018]      FIG. 1  is a schematic, simplified representation of a longitudinal section through a part of a filter device according to one embodiment of the invention, 
           [0019]      FIG. 2  is a schematic representation of a filter device according to  FIG. 1  within the reactor, 
           [0020]      FIG. 3  is a schematic representation of alternative embodiment of the invention, shown in a representation similar to  FIG. 2 , 
           [0021]      FIG. 4  is a schematic representation of another embodiment of a filter device according to the invention, in which filter plates are applied as rotation bodies, shown in a representation similar to  FIG. 2 , and 
           [0022]      FIG. 5  is a schematic representation of a still another embodiment of a filter device according to the invention, in which filter plates are applied in a grouped manner, shown in a representation similar to  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The filter device  1  represented by  FIG. 1 , in a middle section, comprises a cylindrical housing  2 , close to whose end on the left in  FIG. 1  an inlet for the fluid to be filtered is provided. In an analogous manner, an outlet for the filter mass remaining in the housing  6  after the filter procedure, is provided on the right end of the filter device, seen in the representation according to  FIG. 1 . 
         [0024]    A shaft  3  runs centrally through the housing  2  and is mounted in the end-side covers of the housing  2 , which are not represented, and is driven in a rotatable manner by a motor arranged outside the housing  2 . A multitude of rotation bodies in the form of centrifugal pump impellers  4  are seated on the shaft  3  in a rotationally fixed manner. The centrifugal pump impellers  4 , which are shown only schematically in  FIG. 1 , in each case comprise a suction port  5  and a pressure side  6  arranged radially to the outside. The impellers are in each case hydraulically separated from the adjacent impeller  4  by guidance devices  7  within the housing  2 , in a manner such that the pressure side  6  of one impeller is hydraulically connected via the guidance device  7 , to the suction port  5  of the impeller  4  which is subsequent in the throughflow direction of the housing  2 . Each guidance device  7  consists of a first filter plate  9 , which is arranged in a stationary manner in the housing and which is seen in the flow direction  8 , as well as a second filter plate  10 , which is arranged with a spacing thereto. With regard to the filter plates, these are hollow plates which form a mechanical filter over their entire surface, through which fluid located in the filter device  1  may pass, but not the matter suspended therein. The filter plates  9  and  10  are firmly connected to the housing  2 , wherein their inner space, via radial channels  11  and  12 , runs out in a discharge channel  13  on the housing side, which is formed by an annular channel of the housing  2  formed in a double-walled manner in this region. The fluid, which has penetrated through the filter plates  9  and  10  into the inside of the plates and then been filtered, is led via the channels  11  and  12  into the discharge channel  13  and from there out of the filter device  1 . 
         [0025]    The respective first filter plate  9  of a guidance device  7  reaches up to the shaft  3  and is sealed with respect to this. Each first filter plate  9  ends radially outwardly at a significant distance to the inner side of the housing  2  and is connected in the region of its radial outer side, via spokes  14 , to the housing  2 , the insides of which spokes form the radial channels  9 . These spokes  14  ensure that an adequate free space remains between the filter plate  9  and the inner wall of the housing  2 , so that the fluid which is sucked by the centrifugal pump impeller  4  via the suction port  5  and which exits radially at the pressure side  6  of the impeller  4 , is deflected by about 180°, in order then to pass between the first filter plate  9  and the second filter plate  10 , back in the direction of the shaft  3  and thus to the suction port  5  of the impeller  4  which follows next in the throughflow direction  8 . For this, the second filter plate  10  comprises a central recess  15 , into which the suction port  5  of the centrifugal pump impeller  4  engages. The outer side of the second filter plate  10  connects to the inner side of the housing  2  in a flush and tight manner, wherein radial channels  12  are formed, which connect the inside of the second filter plate  10  to the discharge channel  13 . 
         [0026]    Since a multitude of such centrifugal pump impellers  4 , each with a subsequently arranged guidance device  7 , are arranged one after the other within the filter device  1 , and the pressure gain of an impeller  4  lying in front in the flow direction  8  is led via the guidance device  7  to the suction port of the impeller  4  lying therebehind, the filter device  1  operates according to the principle of a multi-stage pump, i.e. the pressure within the housing  2  increases in  FIG. 1  from the left to the right after each impeller  4 . This has the effect that, on account of the pressure increase, in the throughflow direction  8 , on the one hand a fluid discharge through the filter plates  9  and  10 , which becomes more and more intensive is effected, and on the other hand the mass remaining within the filter device  1  is delivered with an increased pressure in the direction  8  and thus to the exit of the filter device  1 . Thus, an intensive filtering occurs with a simultaneously constant discharge of the residual masses, which occur in the device and which may have a mush-like consistency at the exit side. 
         [0027]    With the representation according to  FIG. 2 , it is schematically indicated how the filter device previously described by  FIG. 1  may be arranged within a reactor. Such reactors are applied, for example, for treating waste water. The reactor housing is characterized at  16  and typically, apart from the actual filter device, comprises further assembly parts, but since the remaining assembly parts are not essential with regard to the realization of the invention, these are represented here only with regard to the filter device. It is to be understood that the assembly housing typically has a multiple of the longitudinal extension of the filter device  1 . The central discharge channel  13 , as  FIG. 2  shows, is led out of the reactor housing  16 , whereas the conveyor flow is led through the filter device  1  in the circuit. However, suitable measures for the discharge of the remaining mass are provided. As this embodiment example is to make particularly clear, in this case the filter device  1  has no closed housing, but one which is open at the end sides, since here the housing merely has the task of ensuring the required hydraulic closure to the outside in the region of the centrifugal pump impellers  4  and the guidance devices  7 , whereas the actual housing function is ensured by the reactor housing  16 . The represented filter device  1  may typically serve for circulating the fluid located in the reactor, since the filter device  1  has the effect of a multi-stage pump. 
         [0028]    The alternative embodiment represented in  FIG. 3  differs from that according to  FIG. 2 , in that with the filter device  1   a , the shaft  3  with the centrifugal pump impellers  4  seated thereon, is firmly connected to the reactor housing  16 , whereas the housing  2  with the filter plates  9  and  10  attached thereto, is rotatably driven within the reactor housing. For this, the discharge channel  13  is led into a central channel  13   a , which is led out of the reactor housing  16 , concentrically to the rotation axis of the housing and in a central manner. The throughflow direction  17  through the filter device  1   a  is accordingly exactly opposite to the throughflow direction  8  of the filter device  1 . 
         [0029]    The filter device  1   b , which is arranged in the reactor housing  16  according to  FIG. 4 , differs from the filter device  1  represented by  FIGS. 1 and 2  by the fact that filter plates  18  are inserted instead of the centrifugal pump impellers  4 , and these filter plates in the same manner are hollow as the filter plates  9  and  10 , but are arranged with a spacing from the housing  2 , as with the filter plates  9 , as well as with a spacing from the shaft  3   b , as with the filter plates  10 . The mechanical connection of the filter plates  18  to the shaft  3   b  is effected via spokes  19  which are directed from the inner periphery of the filter plates  18  radially to the shaft  3   b  and are fastened there. The spokes  19  are hollow, just as the shaft  3   b , so that a radial channel  20  is formed via the inside of the spokes, which runs out into a central discharge channel  21  within the shaft  3   b . Additional filter surface is created within the filter device  1   b  by the filter plates  18 . The pump effect is achieved by a suction-port-like central recess being formed between the shaft and the inner periphery of the filter plate  8 , through which recess only the spokes  19  pass, so that the fluid located in the filter device  1   b , at both sides of the filter plate  18 , may flow around this and be carried away radially to the outside, when the filter plate stack arranged on the shaft  3   b  is driven at an adequate speed. A sufficient speed is typically given when this is more than 3 m/s, thus the filter plates  18  to the housing have a minimum speed of more than 3 m/s. The throughflow direction  8  corresponds therefore roughly to that of the filter devices  1  and  1   a , wherein the filter plates are subjected to peripheral flow on both sides. 
         [0030]    One further embodiment of this device represented by  FIG. 4  is represented in  FIG. 5 . There, instead of individual filter plates  18 , these are arranged in groups, here in pairs, so that in each case a guidance device  7  connects in the flow direction  8  between a pair of filter plates  18 . On the one hand, the filter surface is thereby further increased, and on the other hand, the pump effect, which is reduced compared to the centrifugal pump impeller arrangement, is improved, since the fluid is entrained radially to the outside in a particularly intensive manner, particularly in the region between a filter plate pair  18 , when the shaft  3   b  is rotated. 
         [0031]    It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.