Patent Publication Number: US-2019176060-A1

Title: Filter element and filter unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/515,157, filed on Mar. 29, 2017, which is a U.S. national stage application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/072135, filed on Sep. 25, 2015, and claims benefit to Indian Patent Application No. 3110/MUM/2014 and British Patent Application No. 1421171.8, respectively filed on Sep. 30, 2014, and November 28, 2014. The International Application was published in English on Apr. 7, 2016, as WO 2016/050649 A1 under PCT Article 21(2). All of the above applications are hereby incorporated by reference herein. 
    
    
     FIELD 
     The invention relates to a filter element. 
     BACKGROUND 
     Filtration is widely used throughout industry, commerce and domestic life. Filtration involves the physical separation of one or more components from a carrying fluid by passage of that fluid through or across a barrier that is permeable only to some of these components. Filtration can be distinguished in depth filtration and cake filtration. Using the depth filtration a particle can be trapped in the depth of the filter medium. Using the cake filtration a thick layer or cake of particles accumulates on the surface of the filter medium. 
     Depth filters separate coarse and fine haze substances and offer colloid retention rates while simultaneously preserving beneficial ingredients with low color retention. Gentle treatment of flavor and color plays a particularly important role in the filtration of spirits. In addition to reliable separation of fine colloidal and coarsely dispersed haze substances, the aim of filtration includes selective separation of haze-producing long-chain fatty acid esters. Depth filters with a low calcium and magnesium ion content as well as high fusel and essential oil absorbing capacity are used in particular for this purpose. 
     The production of mineral water, table water, and product water as well as industrial water places particularly high demands on filtration technology. Particular emphasis is placed on reliable particle separation by depth filtering. Depth filters assure safe and reliable filtration. There are multitudes of possible filtration applications in the food industry in which depth filters play a major role. Filtration processes are typically used in the production of gelatin, liquid sugar and invert sugar syrup, glucose, dextrose, extracts, essences, enzyme solutions, and rennin. Filtration is especially important, for example, in the production of edible oils where top priority is placed on retaining taste, vitamins, and the fatty acid composition while removing haze and mucilaginous substances. 
     U.S. Pat. No. 4,032,457 A discloses a filter cartridge wherein the filter has two or more distinctly different fibers layers with at least one of the fibers layers containing active particles. The different layers are formed in place on the filter by a wet accretion process. The filter has an inner annular core in the form of a perforated tube. The tube might be made of a plastic material such as polypropylene and is perforated with holes. The size of the holes may vary depending on the physical characteristics of the fibers to be accreted onto the tube. The tube functions to provide compressive strength to the filter element and defines a central flow passage through which the filter material is discharged after having passed through the filtering faces which have been accreted onto the tube. 
     DE 90 16 243 U1 discloses a filter module for filtering fluid media comprising a plurality of annular filter cells which are stacked. The filter cells have a circular ring-shaped form having an outer filter sheet and an intermediate mounted spacing element for keeping open an inner flow passage. The filter cells are stacked along a central filtrate passage element. By this arrangement with stacked filter cells the surface area of the filter medium is increased compared to a filter tube according to U.S. Pat. No. 4,032,457 A. 
     The filter sheets according to DE 90 16 243 U1 are manufactured in a papermaking process. The manufacturing of the filter sheets is a wet-laid papermaking process with all ingredients of the filter medium being suspended in water with a special mixer. The consistency of the suspension may range from 0.5 to 5.0%. The suspension (pulp) is dewatered on a Fourdrinier wire mesh. After dewatering, the flat paper is dried. The filter sheets are cut out from the dried paper and arranged onto the spacing elements in order to obtain filter elements which can be stacked. The dried paper can also be used for rolled filter modules and single use filter units. 
     SUMMARY 
     In an embodiment, the present invention provides a method of manufacturing a filter element, comprising: providing a carrier element, which is permeable to fluid, including a support surface having a surface area increasing contour; immersing the carrier element into a suspension of water and ingredients for a filter medium; depositing the filter medium onto the support surface so as to form a uniform layer of suspended filter medium onto the support surface; stopping the depositing of the filter medium onto the support surface when a thickness of the layer reaches a desired thickness so as to form the filter element; and removing the filter element from the suspension. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  a top view of a first embodiment of a filter element having a lenticular shape; 
         FIG. 2  a sectional view of the filter element according to  FIG. 1 ; 
         FIG. 3  an enlarged perspective view of a surface area of the filter element according to  FIGS. 1 and 2 ; 
         FIG. 4  an enlarged sectional view of a surface area of the filter element according to  FIGS. 1 and 2 ; 
         FIG. 5  a sectional view of a filter unit having a plurality of filter elements according to  FIGS. 1 to 3 ; 
         FIG. 6  an enlarged view of a pair of adjacent filter element of the filter unit according to  FIG. 4 ; 
         FIG. 7  a sketch of the manufacturing process of a filter element according to  FIGS. 1 to 3 ; 
         FIG. 8  a cross-sectional view of a second embodiment of a filter element having a coral-like structure as a surface increasing structure; 
         FIG. 9  a cross-sectional view of a third embodiment of a filter element having a palm-tree-like structure as a surface increasing structure; 
         FIG. 10  a sectional view of a fourth embodiment of a filter element having sticks or fingers as a surface increasing structure; and 
         FIG. 11  a perspective view of the filter element according to  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention particularly refers to, but is not limited to, a filter element for depth filtration. Depth filtration is applicable in a large variety of applications. Depth filtration removes impurities and undesired particles from foods and beverages to enhance the natural flavor. The clear trend worldwide continues to be towards cold-sterile filtered draft and bottled beer. Gentle beer production without heat treatment thus requires a fully developed and reliable filtration technology. Beer-contaminating microorganisms are removed while simultaneously retaining the brightness of the beer and improving the chemical-physical stability. Great importance is attached to microbiological safety when depth filtration is used in the area of wine production. 
     An aspect of the present invention provides a filter element that has an improved filter performance and to provide an easy process of manufacturing such a filter element. 
     An aspect of the invention relates to a filter element comprising a carrier element being permeable to fluid and having a support surface wherein a filter layer is deposited to the support surface 
     An aspect of the invention provides a filter element comprising a carrier element being permeable to fluid and having a support surface, said support surface having a surface area increasing contour. The filter element further comprises a filter medium deposited onto the support surface of the carrier element forming a filter layer adopted to the surface area increasing contour of the carrier element. The filter layer will have an increased filter area which will result in an improved filter performance of the filter element. 
     The filter element itself already provides for an increased surface area of the filter layer. Of course, in order to further increase the surface area of the filter layer a plurality of filter elements according to the invention may be provided in a filter unit, similarly as described in the prior art DE 87 17 200 U1. 
     A filter element according to an aspect of the invention also provides for an easy manufacturing of the filter element because the carrier element is a more or less rigid element comprising the surface area increasing contour and the filter medium is disposed onto the support surface of the carrier element so that by depositing the filter medium onto the support surface the filter medium forms a filter layer following the surface area increasing contour. In addition, after the filter layer has been produced it does not have to be removed from the carrier element to be used. It stays on the carrier element which is part of the filter element. 
     For manufacturing a filter element according to an aspect of the invention a wet-laid papermaking process is performed directly onto the support surface of the carrier element having the three dimensional surface area increasing contour. The carrier element is immersed into a suspension of water and the ingredients for the filter medium. The filter medium is deposited onto the support surface by vacuum suction through the carrier element. During the vacuum suction a uniform layer of the suspended filter medium is built onto the support surface of the carrier element. Due to the flow resistance of the built layer, a homogenous growth of the layer on the support surface occurs. The process is stopped when the thickness of the filter medium is grown up to a sufficient thickness, preferably between 2 and 10 mm. Eventually, the carrier element is pulled out of the suspension, dewatered and dried. After drying the filter element it can be assembled to a filter unit. It is not necessary to remove the filter layer from the carrier element. The carrier element is part of the filter element. 
     Preferably, the surface area increasing contour comprises convex and/or concave surface portions. The convex and/or concave surface portions may have a polyhedral shape such as a tetrahedral shape. Compared to other 3D-shapes, the tetrahedral shape has the advantage of the best surface area to volume ratio. This means that the surface area compared to the volume, which is enveloped by the filter layer, is as big as possible. 
     The carrier element may comprise a screen, a mesh or an open porous body so that it is permeable to fluid. The carrier element may comprise open porous plastic material, such as polyolefin porous material or porous glass. 
     In particular the filter medium comprises a wet-laid nonwoven fibrous material. It is also possible to have a multiple layer structure obtained by wet-laid process with several different formulations, e.g. small pore and then a second layer with bigger pores. 
     The filter medium preferably comprises at least one material of the group of materials comprising cellulose fibers, diatomaceous earth, perlite, active carbon, wet strength resin, bicomponent fibers, polymer powder, absorbers, glass fibers, acrylic resin and epoxy resin. 
     The carrier element may have a lenticular or disc shape. The carrier element can have two outer surface portions facing away from each other on a non-filtrate side of the filter element and constituting the support surface. 
     Preferably, the carrier element comprises two screen-like carrier members each of which forms one of said outer surface portions of the carrier elements and wherein the outer surface portions are facing away from each other. Between the carrier elements the filtrate side of the filter element is realized wherein the filtrate fluid can be led to a central passage way. Alternatively, the carrier element can be made of a porous material having a lenticular or disc shape having two outer surface portions facing away from each other. Between these surfaces the body of the carrier element being made of the porous material can conduct the filtrate fluid to a central passage way. 
     Preferably, the screen-like carrier members are sealingly connected to each other at an outer circumference in order to obtain an inner space on the filtrate side within the carrier element. 
     A filter unit can be obtained by providing a plurality of filter elements as described above which are consecutively arranged along a longitudinal axis. Any adjacent pair of filter elements face each other with one of their outer surface portions. 
     The surface area increasing contour of each carrier element comprises convex and/or concave surface portions wherein the convex and/or concaves surface portions of an adjacent pair of filter elements mesh with each other. This means that adjacent filter elements are positioned as near to each other as possible without contacting each other in the area of the filter layers. 
     In order to enhance the possibility to arrange two adjacent filter elements as near as possible to each other, a first filter element of any pair of adjacent filter elements has convex surface portions on its outer surface facing a second filter element of the pair of adjacent filter elements and wherein said second filter element of said pair of adjacent filter elements has concave surface portions on its outer surface which faces said first filter element. The convex surface supportions of the first filter element can be arranged within the concave surface portions of the second filter element without being in contact with the second filter element. Therefore, between the convex surface portions of the first filter element and the concave surface portions of the second filter element a fluid can flow. The space between the convex surface portions of the first filter element and the concave surface portions of the second filter element constitute a passageway for the unfiltered fluid. 
       FIGS. 1 to 4  disclose a first embodiment of a filter element  1  and are described in the following together. The filter element  1  comprises a carrier element  2  having a filter layer  3  which is deposited onto a support face  4  of the carrier element  2 . The carrier element  2  is permeable to fluid. In the present case the carrier element  2  is preferably made of a mesh or a screen having an outer surface constituting the support surface  4  and an inner space constituting a peripheral passageway  10 . The carrier element  2  and, hence, the filter element  1  has a lenticular shape with a central passageway  9  which penetrates the filter element  1  along a longitudinal axis L. The filter element  1  has an annular ring-shape forming the central passageway  9 . The filter element  1  has an upper outer surface portion  5  and a lower outer surface portion  6  which are facing away from each other. The upper outer surface portion  5  is formed by a filter layer onto an upper carrier member  7  and the lower outer surface portion  6  is formed by a filter layer on a lower carrier member  8 . The upper carrier member  7  and the lower carrier member  8  are connected to each other along a circumference  12  around the longitudinal axis L and are spaced from each other in an axial direction so that between the upper carrier member  7  and the lower carrier member  8  the peripheral passageway  10  is provided. The upper carrier member  7  and the lower carrier member  8  are formed substantially as an annular ring. 
     The upper outer surface portion  5  and the lower outer surface portion  6  together form the support surface  4  of the carrier element  2 . The support surface  4  has a plurality of convex surface portions  11  having a tetrahedral shape, which will result in an increase of the filter area. The filter medium constituting the filter layer  3  is deposited onto the support surface  4 , i.e. the upper outer surface portion  5  and the lower outer surface portion  6 , so that the filter layer  3  follows the contour of the support surface  4 . The convex surface portions  11  constitute a surface area increasing contour of the support surface  4 . 
     In use the central passageway  9  can be fluidly connected to a discharge passageway so that unfiltered fluid can pass from the outside of the filter element  1  the filter layer  3  and afterwards the carrier element  2  into the peripheral passageway  10 . From the peripheral passageway  10  the now filtered fluid will be led radially inwardly to the central passageway  9  in order to be transferred to the discharge passageway of a filter unit. 
       FIGS. 5 and 6  depict a filter unit with a plurality of filter elements. The filter elements  100 ,  101 , are stacked along their longitudinal axis L onto a tube  102 . The filter elements  100 ,  101  are substantially comparable to the embodiment according to  FIGS. 1 to 3 , which means the filter elements  100 ,  101  according to  FIGS. 5, 6  have also a lenticular shape with a central passageway. The central passageway serves to stack the filter elements  100 ,  101  onto the tube  102 . The filter elements  100 ,  101  also have a peripheral passageway  107 ,  108  as described in regard to the embodiment according to  FIGS. 1 to 3 . The peripheral passageways  107 ,  108  of each of the filter elements  100 ,  101  is fluidly in communication with holes  103  within the tube  102  so that fluid can pass from the peripheral passageways  107 ,  108  through the holes  103  into the inner of the tube  102  which forms a discharge passageway  109 . Between the outer surfaces of adjacent filter elements  100 ,  101  the holes  103  are sealed to the outside, i.e. the unfiltered side, by sealing rings  104 . For the sake of clarity only the upper and the lower sealing ring  104  is shown in  FIG. 5 . However, between each of the filter elements  100 ,  101  a sealing ring  104  is provided. 
     The filter unit comprises two different types of filter elements  100 ,  101 , first filter elements  100  and second filter elements  101  which are alternately arranged along the longitudinal axis L. The filter elements  100 ,  101  of each pair of adjacent filter elements  100 ,  101  do have a different shape of their support surfaces. The first filter elements  100  do have convex surface portions  105  according to the embodiment of  FIGS. 1 to 3  and do have a shape according to the sectional view of  FIG. 4 . 
     The second filter elements  101  do have concave surface portions  106 . The convex surface portions  105  are of tetrahedral shape. The concave surface portions  106  also have a tetrahedral shape but in a negative form compared to the convex surface portions  105 . 
     The filter elements  100 ,  102  are formed such that each convex surface portion  105  faces, in a longitudinal direction along the longitudinal axis L, a concave surface portion  106 . As best can be seen from  FIG. 6  the convex surface portions  105  and the concave surface portions  106  are meshing with each other. This means that the convex surface portions  5  are arranged partly within the concave surface portions  106  in an axial direction. 
     The filter elements  100 ,  101  are not in contact to each other, at least over the major part of the outer surfaces. Between the convex surface portions  105  of the first filter elements  100  and the concave surface portions  106  of adjacent second filter elements  101  a passageway for unfiltered fluid is established. 
       FIG. 7  shows a filter element  1  according to  FIGS. 1 to 3  wherein for simplification reasons the surface area increasing contour is not shown. For manufacturing the filter element  1  the central passageway  9  of the carrier element  2  is sealed by a sealing plate  13  on a lower side. On an upper side the central passageway  9  is provided with an adapter  14  which is connected to a tube  15  or a hose producing a vacuum within the central passageway  9  and, hence, within the peripheral passageway  10 . The carrier element  2  is submerged into a tank  16  which is filled with a suspension of fluid, preferably water, and ingredients for filter medium. The filter medium is deposited onto the support surface  4  of the carrier element  2  by vacuum suction through the tube  15 , the central passageway  9  and the peripheral passageway  10  so that water flows from the tank  17  through the carrier element  2  into the peripheral passageway  10  and the central passageway  9  and is discharged through the tube  15 . Thereby, the filter medium is deposited onto the support surface  4  building a uniform layer of the suspended filter medium. Due to the flow resistance of the built filter layer  3  a homogeneous growth of the filter layer  3  on the support surface  4  occurs. The process is stopped when the thickness of the filter layer  3  is grown up to a sufficient thickness and the carrier element  2  is pulled out of the suspension  17 . After drying the filter element  1  it can be assembled to a filter unit. 
     The carrier element  2  can be made of a mesh or screens. Alternatively, the carrier element  2  can be made of a porous material body which constitutes a peripheral passageway  10 . Hereby the carrier element  2  needs not to be hollow because of the permeability to fluid. 
       FIG. 8  shows a second embodiment of a filter element  200  having a cross-section which is shaped coral-like with a tree structure. Several filter elements  200 ,  200 ′,  200 ″,  200 ′″ are arrange around a longitudinal axis and are line linked to a central tube  202  via holes  203 . The filter elements  200 ,  200 ′,  200 ″,  200 ′″ are ramify starting from the junction between the filter elements  200 ,  200 ′,  200 ″,  200 ′″ and the tube  202  into an increasing number of branches. The filter elements  200 ,  200 ′,  200 ″,  200 ′″ and the tube  202  constitute a filter unit. The filter elements  200 ,  200 ′,  200 ″,  200 ′″ form, on the filtrate side of the filter elements  200 ,  200 ′,  200 ″,  200 ′″ , peripheral passageways  207  which lead to the central tube  202  via holes  203  to discharge the filtrated fluid. On the opposite side of the peripheral passageways  207  the filter elements  200 ,  200 ′,  200 ″,  200 ′″ are provided with a filter layer on a support face of a carrier element. The filter elements  200 ,  200 ′,  200 ″,  200 ′″ are preferably in extruded form parallel to the longitudinal axis L. The filter elements  200 ,  200 ′,  200 ″,  200 ′″ together with the tube  202  can easily be inserted into a cylindrical housing  218 . 
       FIG. 9  shows a third embodiment of a filter element having a cross-section which is shaped Palm-tree-like. The third embodiment is comparable to the second embodiment. There are provided two different filter elements  300 ,  301  which are slightly different in their outer dimensions. The filter elements  300 ,  301  are also in extruded form parallel to the longitudinal axis L and are connected to slats  302 , so that the filter elements  300 ,  301  together with the slats  302  form a central passageway  309  to discharge filtrated fluid. The filter elements  300 ,  301  and the slats  302  constitute a filter unit. The entire filter unit can easily be inserted into a cylindrical housing  318 . 
       FIGS. 10 and 11  show a fourth embodiment of a filter element  401  having sticks or fingers  411  as surface increasing structure. The filter element  401  comprises a carrier element  402 . A filter layer  403  is deposited onto a support face  404  of the carrier element  402 . The carrier element  402  is permeable to fluid. In the present case the carrier element  402  is a body made of porous material. It can also be made of a mesh or screen having an outer surface constituting the support surface  404  and an inner space constituting a peripheral passageway. 
     The support surface  404  has a plurality of convex surface portions  411  in the form of sticks or fingers, which will result in an increase of the filter area. The filter medium constituting the filter layer  403  is deposited onto the support surface  404 , so that the filter layer  403  follows the contour of the support surface  404 . The convex surface portions  411  constitute a surface area increasing contour of the support surface  404 . 
     The carrier  402  has a flat lower surface  406  which is covered by a sealing plate  414  with a circumferential seal  413  for sealingly connecting the filter element  401  within a housing of a filter unit. In the centre of the sealing plate there is provided a central passageway  409 . In use the central passageway  409  can be fluidly connected to a discharge passageway so that unfiltered fluid can pass from the outside of the filter element  401  the filter layer  403  and afterwards the carrier element  402 . The filtered fluid will be led inwardly to the central passageway  409  in order to be transferred to the discharge passageway of a filter unit. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B, and C” should be interpreted as one or more of a group of elements consisting of A, B, and C, and should not be interpreted as requiring at least one of each of the listed elements A, B, and C, regardless of whether A, B, and C are related as categories or otherwise. Moreover, the recitation of “A, B, and/or C” or “at least one of A, B, or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B, and C. 
     REFERENCE NUMERALS LIST 
       1  filter element 
       2  carrier element 
       3  filter layer 
       4  support surface 
       5  upper outer surface portion 
       6  lower outer surface portion 
       7  upper carrier member 
       8  lower carrier member 
       9  central passageway 
       10  peripheral passageway 
       11  convex surface portion 
       12  circumference 
       13  sealing plate 
       14  adapter 
       15  tube 
       16  tank 
       17  suspension 
       100  first filter element 
       101  second filter element 
       102  tube 
       103  hole 
       104  sealing ring 
       105  convex surface portion 
       106  concave surface portion 
       107  peripheral passageway 
       108  peripheral passageway 
       109  discharge passageway 
       110  outer surface portion 
       111  outer surface portion 
       200  filter element 
       200 ′ filter element 
       200 ″ filter element 
       200 ′″ filter element 
       202  tube 
       203  hole 
       207  peripheral passageway 
       218  cylindrical housing 
       300  filter element 
       301  filter element 
       302  slat 
       303  hole 
       307  peripheral passageway 
       308  peripheral passageway 
       309  central passageway 
       318  housing 
       401  filter element 
       402  carrier element 
       403  filter layer 
       404  support face 
       406  lower surface 
       409  central passageway 
       411  convex surface portion 
       413  circumferential seal 
       414  sealing plate 
     L longitudinal axis