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[0001]    This application claims priority from European Patent Application No. 09179271.3 filed Dec. 15, 2009. The entire disclosure of the above patent application is hereby incorporated by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a conveyor belt filter device for mechanically cleaning a fluid that is polluted with solids and flows in a channel or the like, with 
         [0003]    an endless filter belt of flat, interconnected filter elements that can be respectively pivoted relative to one another about a horizontal link axis and 
         [0004]    flexible driving means that are respectively provided to both sides of the filter belt and consist, for example, of a chain drive with deflection elements and two endless drive chains, on which the filter elements are laterally mounted, as well as 
         [0005]    a framework that carries the deflection elements and the filter belt, wherein each filter element is rigidly mounted on a chain link and front surfaces of the filter element respectively feature an abutment edge that extends parallel to the link axes of the chain links, namely such that the opposite abutment edges define a filter gap formed between two filter elements. 
       BACKGROUND OF THE INVENTION 
       [0006]    Conveyor belt filter devices of the initially cited type are also referred to as so-called “paternoster filter rakes” and primarily serve for mechanically cleaning waste water flowing in channels designed for this purpose. The waste water flows through the filter elements that remove the filtered matter unable to pass through the filter screens from the channel. Due to the design of the filter belt in the form of interconnected filter elements that are connected by means of flexible driving means mounted on both sides of the filter elements, the required relative movements between the filter elements in the deflection regions, in particular, make it necessary to provide a gap between the individual filter elements in order to realize these relative movements. 
         [0007]    Successful developments known from the state of the art already make it possible to realize such a filter gap constant regardless of the actual relative positioning of the filter elements such that the filter gap can be maintained constant in the region of the straight transport sections of a revolving filter belt, as well as in the deflection segments that are provided with a curvature radius. A conveyor belt filter device of this type is known, for example, from EP 0 676 227 A1. 
         [0008]    Although this already makes it possible to maintain a filter gap formed between two filter elements constant over the entire transport distance, it is possible, for example, that filter gaps between different filter elements are formed differently due to manufacturing tolerances of the chain and the filter bodies. Due to the inevitable elongation of the drive chain over the service life thereof, the filter gaps furthermore are regularly enlarged in a more or less continuous fashion such that the filter effect or the effectiveness of the conveyor belt filter device can deteriorate accordingly due to the increasing gap width, particularly toward the end of the service life of the driving means. 
         [0009]    In addition, the advantageous development known from aforementioned EP 0 676 227 A1 already makes it possible to maintain an adjusted filter gap constant over the distance of the conveyor belt. As explained above, the realization of a filter gap is required for constructive reasons such that the filter gap in any case represents a discontinuity in the filter surface that otherwise has the uniform hole pattern arranged in the filter elements and an exact definition of the active filter surface is only possible to a limited degree. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention therefore is based on the objective of additionally developing a conveyor belt filter device in such a way that the above-described disadvantages resulting from the realization of a filter gap in a conveyor belt filter device are eliminated. 
         [0011]    This objective is attained according to the invention with the characteristics of a conveyor belt filter device, characterized in that the conveyor belt filter device for mechanically cleaning a fluid ( 16 ) that is polluted with solids and flows in a channel ( 14 ) or the like, with an endless filter belt ( 11 ) of flat, interconnected filter elements ( 31 ) that can be respectively pivoted relative to one another about a horizontal link axis ( 52 ) and flexible driving means that are respectively provided to both sides of the filter belt and consist, for example, of a chain drive ( 12 ) with deflection elements and two endless drive chains ( 28 ), on which the filter elements are laterally mounted, as well as a framework ( 10 ) that carries the deflection elements and the filter belt, wherein each filter element is rigidly mounted on a chain link ( 30 ) and front surfaces ( 34 ,  35 ) of the filter element respectively feature an abutment edge ( 36 ) that extends parallel to the link axes of the chain links, namely such that the opposite abutment edges define a filter gap ( 41 ) formed between two filter elements, characterized in that the filter gap is provided with a gap seal ( 43 ,  60 ) that on one side of the filter belt features a sealing strip ( 43 ) that covers the filter gap and is supported on the filter elements with the sealing force and on the other side of the filter belt features a prestressing device ( 55 ,  65 ) that is connected to the sealing strip and serves for generating the sealing force. Additional, particular beneficial, embodiments of the invention are provided in accordance with the following subsidiary conveyor belt filter devices. 
         [0012]    In accordance with a second conveyor belt filter device embodiment of the invention, the first embodiment is modified so that the sealing strip ( 43 ) is arranged on the inflow side of the filter belt ( 11 ) and the prestressing device ( 55 ,  65 ) is arranged on the outflow side of the filter belt. In accordance with a third conveyor belt filter device embodiment of the invention, the first embodiment and the second embodiment are further modified so that the front surfaces ( 34 ,  35 ) of the filter elements ( 31 ) form on the inflow side of the filter belt ( 11 ) a wedge-shaped filter gap ( 41 ) with gap flanks that are arranged relative to one another in an essentially V-shaped fashion and formed by the front surfaces, and in that the sealing strip adjoins the front surfaces in a sealing fashion with its longitudinal edges. In accordance with a fourth conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment and the third embodiment are further modified so that the longitudinal edges of the sealing strip ( 43 ) are formed by a convexly designed peripheral contour of the sealing strip. In accordance with a fifth conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment, the third embodiment and fourth embodiment are modified so that the sealing strip ( 43 ) has a circular cross section. 
         [0013]    In accordance with a sixth conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment, the third embodiment, fourth embodiment and the fifth embodiment are modified so that the sealing strip has a hollow cross section. In accordance with a seventh conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment, the third embodiment, fourth embodiment, the fifth embodiment and the sixth embodiment are modified so that the sealing strip is provided with flow-through openings for the passage of the flowing fluid. In accordance with an eighth conveyor belt filter device embodiment of the invention, the seventh embodiment is modified so that the sealing strip is provided with a hole pattern such that the sealing strip acts as a filter element. In accordance with a ninth conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment, the third embodiment, fourth embodiment, the fifth embodiment, the sixth embodiment and the seventh embodiment are modified so that the sealing strip is composed of individual sealing elements that are arranged in a row. 
         [0014]    In accordance with a tenth conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment, the third embodiment, fourth embodiment, the fifth embodiment, the sixth embodiment and the seventh embodiment, the eighth embodiment and the ninth embodiment are modified so that the prestressing device ( 55 ,  65 ) features a tension element ( 45 ,  61 ) that is connected to the sealing strip ( 43 ) with one end and extends through the filter gap ( 41 ) in the flow direction, wherein the other end of said tension element is connected to a pressure spring element ( 46 ) that is supported on a base that bridges the filter gap on the side of the filter belt that faces away from the sealing strip. In accordance with a eleventh conveyor belt filter device embodiment of the invention, the tenth embodiment is modified so that the pressure spring consists of a dimensionally elastic plastic element. In accordance with a twelfth conveyor belt filter device embodiment of the invention, the eleventh embodiment is modified so that the plastic element is realized in a tubular or sleeve-shaped fashion. In accordance with a thirteenth conveyor belt filter device embodiment of the invention, the first embodiment, the second embodiment, the third embodiment, fourth embodiment, the fifth embodiment, the sixth embodiment and the seventh embodiment, the eighth embodiment, the ninth embodiment, the tenth embodiment, the eleventh embodiment and the twelfth embodiment are modified so that the prestressing device ( 55 ,  65 ) is arranged centrally referred to the width of the filter gap ( 41 ). 
         [0015]    According to the invention, generally, a filter gap is respectively realized in the conveyor belt filter device between two adjacent filter elements, wherein said filter gap is provided with a gap seal featuring a sealing strip that covers the filter gap and is supported on the filter elements with the sealing force on one side of the filter belt. A prestressing device connected to the sealing strip is provided on the other side of the filter belt in order to generate the sealing force. 
         [0016]    Due to the inventive design of the conveyor belt filter device with a gap seal, the filter gap is effectively sealed without impairing the function of the conveyor belt filter device that requires an unobstructed movement of the filter elements over the transport distance. Since the sealing strip is prestressed against the filter element in a sealing fashion, relative movements are not only possible between the individual filter elements, but also between the sealing strip and the adjacent filter elements. In this case, the prestressing device neither impairs these relative movements nor the sealing effect of the sealing strip because it is situated on the opposite side of the filter belt referred to the sealing strip. 
         [0017]    The sealing strip arranged in accordance with the invention therefore makes it possible to seal a filter gap regardless of its actual width, as well as regardless of the fact whether this filter gap changes during a revolution of the conveyor belt or over the service life of the conveyor belt filter device and its driving means, respectively. A filter gap consequently can be regularly inhibited or sealed such that the effective filter surface actually is defined by the hole pattern of the individual filter elements only. 
         [0018]    In one preferred embodiment, the sealing strip is arranged on the inflow side of the filter belt and the prestressing device is arranged on the outflow side of the filter belt in order to ensure that the fluid flowing against the sealing strip contributes to an increase in the sealing force. 
         [0019]    It is particularly advantageous if the front surfaces of the filter elements form a wedge-shaped filter gap on the inflow side of the filter belt, wherein the gap flanks formed by the front surfaces are essentially arranged relative to one another in a V-shaped fashion, and wherein the sealing strip adjoins the front surfaces in a sealing fashion with its longitudinal edges. Due to the V-shaped arrangement of the gap flanks, it is ensured that the normal force component that acts upon the gap flanks and is decisive for the generation of a sealing force is not only realized in the deflection regions of the conveyor belt, but also in the straight transport sections. 
         [0020]    An additional increase of the sealing effect regardless of the position of the sealing strip relative to the front surfaces can be achieved, particularly with gap flanks that are formed by the front surfaces, if the longitudinal edges of the sealing strip are formed by a convexly designed peripheral contour of the sealing strip. If the sealing strip consists of a flat bar, this can already be realized by simply rounding off the longitudinal edges of the flat bar. 
         [0021]    In this context, it is particularly advantageous if the sealing strip has a circular cross section. It would naturally also be possible to consider different cross-sectional shapes or such as, for example, a triangular cross section. 
         [0022]    If the sealing strip has a hollow cross section, it is possible to limit the mass of the sealing strip to a required degree because only the type and design of the peripheral contour of the sealing strip are important for the sealing effect. 
         [0023]    In order to prevent the filter gap from being completely sealed, if so required, the sealing strip may be provided with flow-through openings for the passage of the flowing fluid, wherein the sealing strip itself may also act as a supplementary filter element, particularly if the sealing strip is provided with a hole pattern. For example, the hole pattern can be realized in accordance with the hole pattern of the filter elements such that an undesirable filter gap is inhibited by the sealing strip on one side and the sealing strip contributes to an increase of an exactly defined filter surface on the other side. 
         [0024]    In one preferred embodiment, the prestressing device features a tension element that is connected to the sealing strip with one end and extends through the filter gap in the flow direction, wherein the other end of said tension element is connected to a pressure spring element that is supported on a base that bridges the filter gap on the side of the filter belt that faces away from the sealing strip. In this way, a particularly advantageous prestressing device is realized that does not even impair gap changes occurring over the distance of the conveyor belt such that the risk of the prestressing device impairing the required relative movements between the filter elements can be largely precluded, namely even if the filter gaps change. 
         [0025]    It is also particularly advantageous if the pressure spring element consists of a dimensionally elastic plastic element such that no components that are sensitive to corrosion need to be used for realizing the pressure spring. 
         [0026]    If the plastic element is furthermore realized in a tubular or sleeve-shaped fashion, the desired effects with respect to the dimensional elasticity can be realized with particularly simple means. 
         [0027]    It is also particularly advantageous if the prestressing device is arranged centrally referred to the width of the filter gap because a reliable function of the gap seal can be achieved in this fashion with only one prestressing device and the prestressing device furthermore does not impair the flow, particularly if the gap seal or the sealing strip is realized in the form of a supplementary filter element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Preferred embodiments of the invention are described in greater detail below with reference to the drawings. 
           [0029]    In these drawings: 
           [0030]      FIG. 1  shows a side view of a conveyor belt filter device during its operation; 
           [0031]      FIG. 2  shows two filter elements that are connected to one another on both sides by means of a drive chain, as well as their relative arrangement on a longitudinal transport section and a first embodiment of a gap seal; 
           [0032]      FIG. 3  shows the filter elements illustrated in  FIG. 2  viewed in the transport direction; 
           [0033]      FIG. 4  shows a sectional representation of the filter elements illustrated in  FIG. 3  along the line of section IV-IV; 
           [0034]      FIG. 5  shows an enlarged detail of a filter gap formed between the filter elements illustrated in  FIG. 4 ; 
           [0035]      FIG. 6  shows the filter elements illustrated in  FIG. 2  in a deflection region of the transport section; 
           [0036]      FIG. 7  shows the filter elements illustrated in  FIG. 6  viewed in the transport direction; 
           [0037]      FIG. 8  shows a sectional representation of the filter elements illustrated in  FIG. 7  along the line of section VIII-VIII; 
           [0038]      FIG. 9  shows an enlarged detail of the filter gap formed between the filter elements in the deflection region; 
           [0039]      FIG. 10  shows two filter elements that are connected to one another on both sides by means of a drive chain, as well as their relative arrangement on a longitudinal transport section and a second embodiment of a gap seal; 
           [0040]      FIG. 11  shows the filter elements illustrated in  FIG. 10  in a deflection region of the transport section, and 
           [0041]      FIG. 12  shows a sectional representation of the gap seal illustrated in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    The conveyor belt filter device illustrated in  FIG. 1  features a framework  10 , a filter belt  11  that is guided on the framework  10 , a chain drive  12  that is connected to the framework  10  and the filter belt  11  and an arrangement  13  for transporting away filtered matter that is designed for cleaning a channel  14  extending below ground level  15 . 
         [0043]    A fluid  16  polluted with solids flows through the channel  14  in a flow direction  17  that is indicated by a directional arrow, wherein the channel  14  may extend perpendicular to the plane of projection with a significant width. The conveyor belt filter device extends up to a channel bottom  18  such that the entire flow cross section of the channel  14  is blocked transverse to the flow direction  17  and the fluid  16  needs to pass through the part of the conveyor belt filter device situated in the channel  14 . 
         [0044]    Due to its arrangement in the channel  14  such that the filter belt  11  is directed transverse to the flow direction  17 , the conveyor belt filter device illustrated in  FIG. 1  is also referred to as a “flow-through filter belt rake.” However, the invention that is described below and defined in claim  1  may also be used in conveyor belt filter devices, in which the filter belt is directed parallel to the flow direction, wherein experts also refer to these conveyor belt filter devices as “central-flow” or “dual-flow” filter band rakes, in which the fluid flows through the filter belt transverse to the flow direction in the channel. 
         [0045]    In the present embodiment, the framework  10  consists of a lower frame part  19  that forms the part to be passed by the fluid  16  and an upper frame part  20  that is situated outside the channel  14  and serves for mounting an electromotive drive that drives a shaft  21 . A connecting frame  22  is provided between the frame parts  19  and  20  and makes it possible to stationarily lock the framework  10  to both sides of the channel  14 , for example by means of screw-type anchors  24  embedded in the concrete sidewalls  23  of the channel  14 . 
         [0046]    The frame parts  19 ,  20  are connected to the connecting frame  22  in such a way that the framework  10  is inclined relative to the vertical line by an acute transport angle  25  when the ground level  15  extends about horizontally. In the exemplary embodiment shown, the transport angle amounts to approximately 15°, but may, in particular, also be larger. In contrast to the embodiment shown, the transport angle  25  does not have to be a fixed angle, but may also be variable, in which case the framework  10  is connected to the connecting frame  24  in a pivoted fashion. 
         [0047]    The shaft  21  drives chain wheels  26  that are arranged to both sides of the filter belt  11  and respectively serve for driving a drive chain  28 . The drive chains  28  are composed of chain links  30 , wherein a synopsis of the illustrations in  FIGS. 2 and 3  elucidates, in particular, that two respective chain links  30  of the drive chains  28  accommodate a filter element  31  between one another, namely such that the drive chains  28  form the filter belt  11  together with the filter elements  31 . 
         [0048]    The filter elements respectively feature a filter basket  40  that consists of a perforated sheet metal material in the present embodiment and features an inflow bottom  33  that is designed convexly toward the flow direction  17  and features front surfaces  34 ,  35  that are angled toward its edges in the transport direction and form an abutment edge  36 . The filter baskets  40  feature sidewalls  37 ,  38  with a disk-shaped design in order to form a lateral boundary of the inflow bottom  33  and to connect the chain links  30 . 
         [0049]      FIGS. 2 and 3  furthermore show that a filter gap  41  is formed between the abutment edges  36  of two adjacent filter elements  31 , wherein a gap seal  42  is arranged in said filter gap. The adjacent abutment edges  36  are arranged parallel and to both sides of the link axis  52 , on which the chain links  30  and therefore the filter elements  31  are pivotally connected to one another by means of chain bolts. 
         [0050]    According to  FIG. 4  and, in particular, the enlarged illustration of the gap seal  42  in  FIG. 5 , the gap seal features a sealing strip  43  that is manufactured of a round material in the exemplary embodiment shown and non-positively connected to a prestressing device  55 . The prestressing device  55  features a tension element  45  that is realized in the form of a tie rod in this case and connected to the sealing strip by means of a connecting end  44 . A pressure spring element  46  that is realized in the form of a dimensionally elastic plastic sleeve in this case is arranged on the tension element  45  and penetrated by the tension element  45  in such a way that the pressure spring element  46  is accommodated between a spring stop  47  that is formed by a nut screwed onto the free end of the tension element  45  in the present embodiment and a supporting stop that is arranged on the tension element  45  in a longitudinally displaceable fashion. The supporting stop  48  is realized in the form of a supporting sheet metal in the present embodiment and supported on supporting edges  54  formed by free ends of the respective front surfaces  35  and  34 . 
         [0051]    Due to the tensile force exerted upon the sealing strip  48  by the pressure spring element  46 , the sealing strip  43  is pressed against the front surfaces  34 ,  35  of the adjacent filter elements  31  with its peripheral contour  49 , wherein the front surfaces  34 ,  35  form a wedge-shaped receptacle for the sealing strip  43  due to their V-shaped arrangement relative to one another and define the narrowest point of the filter gap  41  in the flow direction  17 . 
         [0052]    In contrast to  FIGS. 2 to 5  that shows two adjacent filter elements  31  in a relative arrangement during the movement along a longitudinal transport section  50  (see  FIG. 1 ) of the conveyor belt filter device,  FIGS. 6 to 9  show the relative arrangement of two filter elements  31  in the deflection region  51  (see  FIG. 1 ) of the conveyor belt filter device. In other respects,  FIGS. 6 to 9  show the same elements and components of the conveyor belt filter device, wherein these elements and components in  FIGS. 6 to 9  are identified by the same reference symbols as in  FIGS. 2 to 5 . 
         [0053]    A comparison of  FIGS. 4 and 5  that show the relative arrangement of the gap seal  42  in the filter gap  41  during a movement of the filter elements  31  along the longitudinal transport section  50  with  FIGS. 8 and 9  that show the relative arrangement of the gap seal  42  in the filter gap  41  in the deflection region  51  elucidates, in particular, that the relative pivoting movement of the filter elements  31  about the link axis  52  (see  FIG. 6 ) causes a shift in the position of the sealing strip  43  on the front surfaces  34 ,  35  of the adjacent filter elements  31 . However, this comparison also elucidates that the contact of the peripheral contour  49  of the sealing strip  43  with the front surfaces  34 ,  35  is still ensured despite the changed relative positioning. The changed arrangement of the front surfaces  34 ,  35  relative to one another caused by the deflection merely leads to an increase in the tensile stress acting upon the sealing strip, namely as the result of a compression of the pressure spring element  46  that takes place between the spring stop  47  of the tension element  45  and the supporting stop  48 . 
         [0054]    In order to ensure that the tension element  45  is not clamped in the filter gap  41  in the relative arrangement of the front surfaces  34 ,  35  illustrated in  FIG. 9 , the front surfaces  34 ,  35  may be provided with corresponding recesses in the region of the abutment edges  36 . 
         [0055]      FIGS. 10 to 12  show another optional embodiment of a gap seal  60  that serves for sealing a filter gap  41  formed between the front surfaces  34 ,  35  of adjacent filter elements  31 . In the present embodiment, the gap seal  60  features a sealing strip  43  that corresponds to the sealing strip  43  of the gap seal  42 . In contrast to the gap seal  42 , the gap seal  60  features a prestressing device  65  with a tension element  61  that, according to a synopsis of  FIGS. 10 and 12 , consists of a sheet metal strip with a rectangularly designed recess  62  for accommodating the sleeve-shaped pressure spring element  46 . In order to non-positively position the pressure spring element  46  in the recess  62  of the tension element  61 , a supporting stop  63  is provided that consists of a sheet metal strip in the present embodiment and features a correspondingly designed through-slot  64 , through which the tension element  61  extends. 
         [0056]    According to  FIGS. 10 and 11  that show the relative positioning of the sealing strip  42  of the gap seal  60  between the front surfaces  34  and  35  of the adjacent filter elements  31  during the movement along a longitudinal transport section  50  ( FIG. 10 ) and the aforementioned relative positioning during a movement in the deflection region  51  ( FIG. 11 ), the pressure spring element  46  is supported during a compression on a supporting edge  65  of the recess  62  arranged in the tension element  61 , as well as on the supporting stop  63  that can be longitudinally displaced relative to tension element  61 . 
         [0057]    The preceding explanation of the design of the gap seal  60  makes it clear that an installation of the gap seal  60  in a filter gap  41  formed between adjacent filter elements  31  can be realized in a particularly simple fashion because no tool is required and the gap seal  60  can be securely positioned in the filter gap  41  by locking the supporting stop  63  relative to the tension element  61  under prestress by means of a pressure spring element  46 . 
         [0058]    In contrast to the exemplary embodiments shown, it is naturally also possible, if so required, to assign several prestressing devices to the sealing strips of the gap seals rather than only one prestressing device.

Summary:
The invention pertains to a conveyor belt filter device comprising: (a) an endless filter belt of flat, interconnected filter elements that can be respectively pivoted relative to one another about a horizontal link axis; (b) flexible driving means that are respectively provided to both sides of the filter belt and consist of a chain drive with deflection elements and two endless drive chains, on which the filter elements are laterally mounted; and (c) a framework that carries the deflection elements and the filter belt, wherein each filter element is rigidly mounted on a chain link and front surfaces of the filter element respectively feature an abutment edge that extends parallel to the link axes of the chain links, such that the opposite abutment edges define a filter gap formed between two filter elements, and wherein the filter gap is provided with a gap seal.