Abstract:
A filter module is formed of wound filter material having openings wherein the boundary surfaces of the openings constitute flow-through surfaces. The openings of the wound layers of the filter material form channels angled relative to the winding axis, wherein one group thereof opens at the outer peripheral surface of the roll and the other group opens at the inner peripheral surface of the roll and wherein the channels on the other end, respectively, are closed and wherein the channels, angled relative to the winding axis, are separated from one another by filter material, and wherein the inner area of the roll has a central channel arranged around a winding axis.

Description:
[0001]    The present disclosure relates to the subject matter disclosed in international application No. PCT/EP02/12544 of Nov. 9, 2002, which is incorporated herein by reference in its entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a filter module of the kind defined in the preamble of claim  1  and a method for manufacturing a filter module of the kind defined in the preamble of claim  19 . 
         [0003]    WO 98/35740 discloses a filter module in which openings are formed in the filter material whose boundary surfaces constitute the filter surface. The filter module is produced by stacking a plurality of identical disc-shaped filter elements whose openings are substantially arranged atop one another so that channels are formed in the longitudinal direction of the filter module through which the unfiltered material flows into the filter module and from which filtrate flows out of the filter module. The filter elements are arranged in a frame which compresses the discs. For exchanging the filter material, the individual filter discs must be removed and new individual filter discs must be inserted into the frame. The expenditure for exchanging the individual filter discs is very great. When producing the circular discs from sheet-like filter material, a lot of waste is produced. 
         [0004]    The object of the invention is to provide a filter module of the aforementioned kind which can be easily exchanged. 
         [0005]    Moreover, the object resides in that a method for a simple manufacture of the filter module is to be provided. 
       SUMMARY OF THE INVENTION 
       [0006]    This object is solved by a filter module with the features of claim  1  and, with respect to the method, by a method having the features of claim  19 . 
         [0007]    By winding the filter material to a roll, a compact filter results which, in its entirety, can be inserted with minimal expenditure into a filter housing and can be removed therefrom. The effective filter thickness is independent of the thicknesses of the filter material because flow through the filter material is parallel to its surface. Flow through the filter material takes place from one channel that opens at an outer peripheral surface to a channel that opens at an inner peripheral surface. The opposite flow direction is also possible. By means of the arrangement of the openings, which form the channels, the effective filter thickness can be varied within a broad range without this requiring filter materials with different thicknesses. The diameter of the roll and thus the size of the effective filter surface is determined by the length of the wound web and can thus be varied within a broad range. The axial length of the roll is determined by means of the width of the wound material, wherein, by varying it, the filter surface can be varied also. The filter module can be adjusted in this way with minimal expenditure to very different filtration requirements. The filter material can be, for example, metal, plastic material, or cellulose. Mixtures of these materials can also be advantageous. 
         [0008]    As a result of the winding step, the filter material is shape-stable so that in the most favorable case no foreign materials are required; disposal is simplified in this way. The filter module comprises a large integrated filter surface because the filter size in the direction of the longitudinal axis is determined only by the required filter surface and filter thickness and not by additional holding elements. It is possible to produce filter modules having a very large filter surface and requiring only a small space. The filter module can be inserted into inexpensive compression-proof filter housings so that no complex frame constructions are required. The compact, robust configuration reduces the required expenditure for packaging a filter module and thus lowers the logistic expenses. 
         [0009]    Expediently, the filter material is a depth filter material. In particular, the central channel and the outer peripheral surface are cylindrical. In this way, the filter module can be advantageously employed in a cylindrical housing. However, it can also be advantageous when the central channel and the outer peripheral surface have an elliptical cross-section. 
         [0010]    It is provided that the openings are formed as slots. For increasing the stability, it is expedient that the slots are interrupted in the peripheral direction by stays. The flow-through surfaces are arranged, in particular, perpendicularly to the winding axis in a disc shape about the winding axis. However, it may be advantageous to arrange the channels slantedly relative to the winding axis at an angle that is smaller than 90°. In this way, advantages are achieved, in particular, during backwashing. The angle between the winding axis and the channels is advantageously from 30° to 90°. It is provided that in the direction of the winding axis channels are arranged that open alternatingly at the inner peripheral surface and at the outer peripheral surface. In particular, in the radial direction of the filter module a border layer adjoins the openings and separates inner and outer area from one another. Expediently, the border layer is comprised of filter material and has a thickness in the radial direction which matches at least the effective filter thickness of a filter layer in the axial direction. No additional materials are required as a result of the embodiment of the border layer made from filter material. By means of a corresponding thickness of the border layer it is ensured that it does not constitute a bypass. 
         [0011]    For the fixation of the material wound to a filter module, the inner and/or outer layers of the roll are expediently glued and/or welded. It can also be advantageous to press the filter module. Alternatively, or in addition thereto, the filter module can be held together by clamping or supporting means. As a further embodiment it is provided that the filter module for increasing the stability is wound onto a support pipe. For increasing the stability it is advantageous to wind a support material into the filter module wherein, in particular, for depth filter materials, it is expedient, for the purpose of compressing the filter material in the direction of the filtrate side and for increasing the filtration resolution, to wind into the filter module straps with at least partially wedge-shaped cross-section which are arranged alongside the slots and which compress the filter material in a direction toward the slots. Preferably, the wedge-shaped straps are arranged along the slots open toward the inner area. 
         [0012]    The filter material can be a nonwoven, woven, screen, expanded metal, or mesh. Advantageously, sintered woven, sintered powder, foamed materials, filter layers, or depth filter layers can be employed. 
         [0013]    The method for manufacturing a filter module of filter material provides that openings, in particular, slots, are produced in the filter material in the longitudinal direction of the filter material and that the filter material is wound about a winding axis. In this way, the filter module can be produced simply and in an automated fashion. Winding of the filter material, in comparison to stacking individual filter material layers, constitutes a substantially faster process. The openings of wound layers positioned atop one another form channels which are sealed radially toward the inner area or outer area of the roll. It is provided that the filter material is in the form of a web and the slots are introduced by means of wedge-shaped knives which widen the slots and compress the adjacent filter material. Because of the widening of the slots, no waste is produced in the manufacture of the filter material. By means of the slot width the degree of compression and thus the filtration resolution can be adjusted in the case of depth filter material. 
         [0014]    Expediently, the knives are arranged on a roller. The filter module can be produced continuously when a station in which the slots are produced is arranged upstream of a winding station. In particular, the openings, particularly the slots, are realized by jet cutting. Expediently, the openings, particularly, slots, are cut out. When cutting out the openings, no compressed areas are produced in the border zones of the openings. This can be advantageous when a homogenous filter material is desired across the filter material thickness. 
         [0015]    Expediently, the filter module is glued together wherein the adhesive is, in particular, a resin which is also contained in the filter material. In this way, the introduction of an additional material is avoided so that the filter module is comprised exclusively of substances which are already contained in the filter material. As an alternative measure, the filter module can also be welded. However, it can also be taken into consideration to employ, instead of gluing or welding or in addition thereto, clamping means are arranged around the filter module. Also, winding of the filter module with compression may be advantageous. For increasing the stability, it can be provided that the filter module is wound onto a support pipe. For stabilization purposes, it is particularly provided that support material is wound into the filter module. By winding additional support material into the filter module, the stability of the filter module can be adjusted according to the requirements. Expediently, straps with at least partially wedge-shaped cross section are wound into the filter module and positioned alongside the slots, and thus compress the filter material in the direction toward to the slots. In particular, the wedge-shaped straps are arranged along slots open toward the inner area. 
         [0016]    Examples of the invention will be explained in the following by means of the drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  a perspective view onto a depth filter module with depth filter material shown in section; 
           [0018]      FIG. 2  half a section of a depth filter module; 
           [0019]      FIG. 3  a plan view onto web-shaped depth filter material with slots arranged therein; 
           [0020]      FIG. 4  a sectional illustration of the depth filter module of  FIG. 1  in a filter housing; 
           [0021]      FIG. 5  a perspective view of a wedge-shaped strap material; 
           [0022]      FIG. 6  a sectional illustration of a portion of a depth filter module into which wedge-shaped strap material has been wound. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  shows an axially symmetrical depth filter module  1  which is comprised of depth filter material  2  wound about a winding axis  9 . The wound depth filter material  2  forms a roll  27 . In place of the depth filter material, other filter materials can be employed. The depth filter material  2  is wound about a support pipe  4  which is preferably made of a metal screen or plastic screen and serves for stabilizing the depth filter module  1  and which can assist in the winding step. The filter material  2  can be, for example, nonwoven, woven, screen, expanded metal, or mesh. It is also possible to employ sintered woven, sintered powder, foamed material, filter layers or depth filter layers. Within the support screen  4  a central channel  3  is formed. At the inner peripheral surface  29 , the depth filter material  2  rests against the support screen  4 . The depth filter material  2  has openings  25  which are embodied as slots  10 ,  11 . Other shapes of the openings  25  can be advantageous. 
         [0024]    In  FIG. 2 , half of a section view of the depth filter module  1  with the support pipe  4  and the depth filter material  2  wound about the support pipe  4  forming the roll  27  is illustrated. The central channel  3  arranged within the support pipe  4  forms together with the slots  10 , which form channels  26  opening at the inner peripheral surface  29 , the inner area of the depth filter module  1 . The outer area is separated from the inner area by depth filter material  2  and comprises the channels  26  opening at the outer peripheral surface  28  and formed by the slots  11 . A support screen  5  can be arranged on the outer peripheral surface  28  of the roll  27  which provides a clamping means that holds the roll  27  of depth filter material  2  together without closing off flow though the channels  26  opening at the outer peripheral surface  28 . The boundary surfaces of the slots  10  and  11  form the flow-through surfaces  6  which are arranged perpendicularly to the surface of the depth filter material  2  delimiting the channels  26 . The flow-through surfaces  6  extend disc-shaped about the central channel  3 . The channels  26  however can be slanted relative to the winding axis  9  at angles smaller than 90°. In particular, angles between the winding axis and the channels of 30° to 90° are advantageous. 
         [0025]    The thickness d of the depth filter material  2 , through which the fluid to be filtered flows, corresponds to the spacing between the two slots  10  and  11  in the axial direction. For separating the slots  11  from the inner area and the slots  10  from the outer area, the border layer  7  at the inner peripheral surface  29  and the border layer  8  at the outer peripheral surface  28  of the depth filter module  1  are arranged. The border layers  7 ,  8  are comprised of depth filter material  2 . The thickness a of the border layer  7  and the thickness b of the border layer  8  are at least as large as the thickness d of the depth material  2  through which flow is to be realized. It may be advantageous not to form the border layers  7 ,  8  of the depth filter material  2 , but of a material impermeable to fluid which then seals the slots  10  outwardly and the slots  11  inwardly. 
         [0026]    In  FIG. 3 , the depth filter material  2 , with openings  25  arranged therein that are embodied as slots  10  and  11 , is illustrated before winding the roll  27 . The depth filter material  2  has a rectangular shape and the slots  10  and  11  extend in the longitudinal direction of the depth filter material  2 . At the winding start  12 , which is positioned on the central channel  3  for the winding step, the slots  10  that are oriented toward the inner area are open. The area between the winding start  12  and the beginning of the slots  11  forms the border area  7  of the depth filter material  2  after completion of winding. The slots  10  end before the winding end  13  wherein the area between the end of the slots  10  and the winding end  13  forms the border area  8 . Three of the slots  10  are interrupted in the longitudinal direction by stays  30 . It may be advantageous that a preponderant number or all slots  10 ,  11  are interrupted by stays  30 . The transverse stays  30 , which are comprised of filter material, serve for increasing the stability of the wound depth filter module  1  and function as a winding aid. 
         [0027]    The slots  10 ,  11  can be produced by a wedge-shaped knives which are arranged on a drum which extends in the transverse direction of the depth filter material  2 . The slots  10 ,  11  are cut by the knives and, because of the wedge shape, are widened to the required slot width without this producing waste. Advantageously, the knives for the slots  10  and for the slots  11  are arranged on separate rollers so that the slot length can be adjusted independently from one another. The slots  10 ,  11  can also be cut out or produced by means of a jet cutting. 
         [0028]    For producing a depth filter module  1 , the slotted depth filter material  2  is wound beginning at the winding start  12 . For increasing the stability, the depth filter material  2  can be wound onto a support pipe  4 . Winding with pressing of the filter material may be advantageous. However, for a satisfactory stability of the depth filter material  2  it is expedient to wind the depth filter material  2  onto an auxiliary mandrel which is removed after the winding process is complete. For fixation of the roll  27  of the depth filter module  1 , the depth filter material  2  can be glued together or welded. The fixation of the finish-wound depth filter material  2  by means of clamping means such a support screen  5  or clamping straps as well as a combination of these fixation possibilities can be advantageous. 
         [0029]    The depth filter module  1 , as illustrated in  FIG. 4 , can be arranged in a cylindrical filter housing  14 . Sealing between the inner area and outer area at the filter housing  14  is realized by means of a circular sealing ring  15  formed on the bottom  22  and the lid  23  of the filter housing  14 . The sealing ring  15  engages the depth filter material  2  and is pressed fixedly into it when the lid  23  is secured on the housing  14 . This configuration does not require separate seals. 
         [0030]    The unfiltered material flows in the direction of the arrows  16  into the filter housing  14  against the outer side of the depth filter module  1 . From the channels  26 , which open at the outer peripheral surface  28  and are formed by the slots  11 , the unfiltered material flows via the depth filter material  2  of the thickness d into the channels  26  opening at the inner peripheral surface  29  and formed by the slots  10 ; flow takes place parallel to the surface of the depth material  2 . The filtrate flows through the channels  26  formed by the slots  10  into the central channel  3  from where it exits the filter housing  14  in the direction indicated by arrow  17 . The filter, however, can also be used in the inverse direction, i.e., counter to the direction of the arrows  16  and  17 . A backwashing possibility is thus provided in principle. 
         [0031]    For improving the filtration results, filtering aids can be added to the unfiltered material, such as diatomaceous earth. For increasing the filtration surface, several filter modules can be inserted into a filter housing  14 , in particular, depth filter modules  1  which are stacked on top of one another and separated from another by plates; the plates are provided for sealing the filter modules relative to one another and for stabilization purposes. 
         [0032]    In  FIG. 5 , a wedge-shaped strap  18  is illustrated which serves for compressing the depth filter material  2  on the side of the filtrate. In this way, the filtration resolution is increased in the direction of filtration. The wedge-shaped strap  18  has two lateral wedges  24  which will come to rest between the wound layers of the depth filter material  2 . In this way, the edges  21  form together with the slots  10  the channels  26  opening at the inner peripheral surface  29 . The slot width corresponds to the width of a stay  19  which is arranged between the wedges  24  and the adjoining edges  21 . The openings  20  in the stay  19  serve as passages for the filtrate. 
         [0033]    In  FIG. 6 , a section of a depth filter module  1  is illustrated into which a wedge-shaped strap  18  has been wound. The edges  21  of the wedge-shaped strap  18  delimit a channel  26  formed by the slots  10  which in this case is arranged on the filtrate side. The wedge-shaped strap  18  has a stay  19  which is arranged perpendicularly to the flow direction in the slots  10 . The wedges  24  compress the depth filter material  2  in the direction toward the channel  26 . Because of the slant angle of the wedges  24 , the increase of filtration resolution can be adjusted in the direction of the channel  26 . 
         [0034]    For increasing the stability of the depth filter module, instead of the wedge-shaped strap  18 , or in addition thereto, straps of different materials can be wound into the roll which are positioned parallel to the flow direction between the individual layers of the depth filter material  2 . Instead of the wedge-shaped strap  18  with the stay  19  it is also possible to be employ a wedge-shaped strap which has two or several stays between the wedges  24 .