Abstract:
A dual bag filter is provided where a replaceable filter element resides in and is sealed to a filter housing. The filter element has a mounting ring, an inner bag, and an outer bag. The inner bag is sized such that it has more surface area than the outer bag and is constrained by the outer bag. The inner bag is formed from a filter medium of different densities such that when the inner bag is crumpled, fluid flow is not restricted.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/842,258, filed Jul. 2, 2013, the disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Large filtering vessels are commonly used for filtering industrial chemicals, such as solvents, cleaning fluids, etc. Such filtering devices are of two different types. One type uses a filtering bag that is suspended within a liner within the filtering vessel. The fluid to be filtered is communicated into the bag, and then communicates through the wall of the bag and the liner to the fluid outlet. Another type of filtering device uses a filtering cartridge mounted within the vessel. The filter cartridge defines an outer circumferential surface which cooperates with the wall of the filtering vessel to define an inlet chamber. In either case, the bag or filter cartridge must be changed periodically, as the contaminants removed from the fluid being filtered are captured within the bag or within the filtering media of the filter cartridge. Accordingly, it is necessary for the filter cartridge to be easily removable and for a new filtering cartridge to be easily installable in the filtering vessel. It is also necessary to maintain a fluid tight seal between the inlet chamber and the outlet from the filtering vessel, so that all of the fluid communicated into the inlet chamber must communicate through the filtering media; it is undesirable that an with entrained contaminants bypasses the filter cartridge and passes directly to the outlet. It is further necessary to have a filter with a large surface area; a large surface area helps to lengthen the time a filter is usable before replacement and increases the filter&#39;s allowable flow rate. It is further necessary to produce a low-cost filter. 
       SUMMARY OF THE INVENTION 
       [0003]    The present disclosure describes a filter which is suitable for use in a filter housing. The filter described herein is formed from a felt material. The filter described herein is suitable for use in a variety of filters, such as bag filters, pleated filters, cartridge filters or other filters as are known. The felt material is formed from fibers of varying diameters. The felt material includes three layers which are woven together, a first layer, a second layer, and a third layer. There is a fourth material that constrains the felt material to a maximum size and it is smaller than the felt material. The first layer is formed from fibers having a relatively large diameter. The second layer is formed from fibers having a relatively small diameter. The third layer is formed from fibers having a relatively large diameter. With this configuration, fluid enters the filter through the first layer and exits the filter through the third layer. The first layer serves to filter out large particles and the second layer serves to filter out small particles. The first and third layers serve to provide structure and support to the filter to allow fluid passage and to prevent the second layer from folding over on itself. The fourth material prevents the felt material from expanding beyond the allowable size for use in a filter housing. The felt material is in the shape of a bag and includes an interior. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a cross-sectional side view of a filter canister and filter bag; 
           [0005]      FIG. 2  is a perspective view of the filter bag of  FIG. 1  cut away to show the inner bag; 
           [0006]      FIG. 3  is a close-up view of the portion of the filter bag and housing marked  3  in  FIG. 1 ; 
           [0007]      FIG. 4  is a perspective view of the filter bag of  FIG. 2 ; 
           [0008]      FIG. 5  is a close up view of the fiber structure marked  5  in  FIG. 4 ; and 
           [0009]      FIG. 6  is a close up view of the inner bag as crumpled marked  6  in  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]    In reference to the several FIGS, elements which are common among the FIGS are referenced by the same ordinal. Any directional references herein, such as above, below, up, down, or similar terminology, are in reference to the spatial relationship of the elements as shown in a given FIG. It is appreciated that the elements described herein could be used in any number of spatial orientations, and as such any directional references herein are merely to aid in the description provided herein and do not limit use. 
         [0011]    The present disclosure describes an improved filter element  10 . The filter element  10  is suitable for being used in combination with a housing  12 . In one instance, the filter element  10  is a bag-type filter, in other instances the filter element  10  is a cartridge filter or a pleated filter. The filter element  10  is suitable for filtering fluids. Generally speaking, the filter functions by filtering solids from a fluid. 
         [0012]    Referring to  FIGS. 1-4 , the filter is formed haying a mounting ring  14 , an outer bag  16  and an inner bag  18 , the specific details of which are described in greater detail below. The housing  12  includes a lid (not shown) which is removable to allow the filter element  10  to be inserted or removed from the housing  12 . The housing  12  also includes an inlet  22  and an outlet  24 , whereby the fluid to be filtered enters the housing  12  through the inlet  22 , subsequently passes through the filter element  10 , and then exits the housing  12  through the outlet  24 . 
         [0013]    The housing  12  includes a shoulder  26  as shown in  FIG. 3  at which the mounting ring  14  is mounted. The mounting ring  14  includes a flange portion  20  and an attachment portion  44 . The flange portion  20  forms a fluid-tight seal with the shoulder  26  such that any fluid entering the housing  12  must pass through the filter element  10 . The flange portion  20  is formed from a flexible material which flexes when inserted against the shoulder  26  such that a tight seal is formed between the mounting ring  14  and the housing  12 . The attachment portion  44  is on the outside of the mounting ring  14  as is shown in  FIG. 4 , but can be located anywhere on the mounting ring  14 . The mounting ring  14  has sufficient structure and rigidity to maintain its shape during use. The mounting ring  14  serves as an opening through which fluid enters the filter element  10 . Filter housings typically have a round cross-section, and the housing illustrated herein is shown having as such. The mounting ring  14  is shaped to mate with the shoulder  26 , and as such the mounting ring  14  is shown as circular, as viewed from the top of the filter. It is appreciated that the filter element  10  and the associated mounting ring  14  described herein could be of any cross-sectional shape that is suitable for mating with the corresponding housing  12 . 
         [0014]    The opening of the outer bag is joined to the mounting ring  14  at the attachment portion  44  and extends downwardly therefrom to a closed end  28 . The closed end  28  is positioned at the bottom end of the housing in proximity of the outlet  24  as shown in  FIG. 1 . The outer bag  16  is preferably formed from a mesh-like or screen-like material, such as nylon, Wherein the outer bag  16  is formed from fibers which define openings through which the fluid may pass. The size of the openings is chosen depending on the type of fluid being filtered. The outer bag  16  is structured to allow fluid to pass and resist stretching from any pressure generated by an inner bag  18  as fluid flows from the inlet  22  to the outlet  24  in the filter housing  12 . The primary purpose of the outer bag  16  is to constrain the larger inner bag  18  in a particular shape, as described below. 
         [0015]    The opening of the inner bag is joined to the mounting ring  14 . The inner bag  18  is carried within the outer bag  16 . The inner bag  18  is sized larger than the outer bag  16 , such that when the inner bag  18  is in the outer bag  16 , the inner bag  18  is folded, creased, and otherwise randomly situated within the outer bag  16  such that the inner bag  18  has a crumpled appearance. The inner bag shape is such that it is longer than the outer bag  16 . The outer bag  16  has a diameter that is sized to fit inside of filter housing  12  without making excessive contact with an inside wail of the housing  12 . The fitment of the outer bag  16  to the housing  12  is demonstrated in  FIG. 1 . The inner bag  18  is of a similar diameter or smaller than the outer bag  16 . The inner bag is significantly longer than the inner bag, but is constrained by the outer bag  16 . Gravity and the nature of fluid flow through the filter element  10  naturally situate the crumples and folds of the inner bag  18  towards the closed end  28  of the outer bag  16 . The distance between the mounting ring  14  and the closed end  28  as shown in  FIG. 1  defines the length of the outer bag. If the inner bag  18  was not constrained by the outer bag  16 , the distance between the mounting ring  14  and a closed end of the inner bag would extend significantly past the lower portion of the filter housing  12 . For simplicity, the extent of the folds and crumples in the inner bag are only shown in  FIG. 6 . The various folds and creases of the inner bag  18  form a much larger surface area than the outer bag  16  provides. The larger surface area of the inner bag  18  allows the filter element  10  to filter a greater amount of fluid before needing replacement, as compared to the use of an inner bag  18  that is of roughly the same size as the outer bag  16 . 
         [0016]    It may be necessary to include a reinforcing strip  42  where the inner bag  18  and outer bag  16  are joined to the attachment portion  44 . The reinforcing strip  42  is folded over the openings of both inner and outer bags. The reinforcing strip  42 , inner bag  18 , and outer bag  16  are all joined together to the attachment portion  44 . The attachment method can be with ultrasonic welding, heat sealing, crimping, epoxy, or other methods that securely attach and seal the inner and outer bag to the attachment portion. Proper attachment and sealing are necessary in order to direct all fluid through the inner bag  18 . 
         [0017]    The inner bag  18  is preferably formed from a filter material  36  as shown in  FIG. 5 , commonly felt, or a felt-like material, as is commonly known in the art. More specifically, the inner bag  18  is farmed from a non-glazed felt. Non-glazed felts have previously been used only in dry filtering applications since non-glazed felt tends to allow the particulates in the filtered media to cake or buildup on the felt material. When felt is used in liquid filters, the felt is glazed to prevent the filtered media from caking or building up on the surface of the felt. However, it has also been found that glazed felt collapses on itself When folded or creased, which prevents proper filtering. The present disclosure finds that the use of non-glazed felt prevents the inner bag  18  from collapsing on itself, and also allows the inner bag  18  to efficiently drain. As such, the use of a non-glazed felt inner bag  18  provides a filter having improved filtering characteristics at lower costs as compared to previous filters. 
         [0018]    Referring to  FIG. 5 , the felt-like material  36  used to construct the inner bag  18  is a three-layer structure: a first layer  30 , a second layer  32 , and a third layer  34 . Each of the three layers  30 ,  32 , and  34  are formed from fibers of a particular diameter. The first layer  30  is formed from fibers having a relatively large diameter, therefore creating a larger pore size filter medium. The second layer  32  is formed from fibers having a relatively small diameter, therefore creating a smaller pore size filter medium. The third layer  34  is formed from fibers having a relatively large diameter, therefore having a larger pore size filter medium. The three materials are bonded together as is shown in  FIG. 5 . The inner bag  18  has more surface area than the outer bag  16 , and therefore has folds and creases as shown in  FIG. 6 . The primary purpose of the third layer  34  is to maintain a gap between adjacent second layers  40  when the material is folded on itself as shown in  FIG. 6 . Without the third layer  34 , the second layer would fold over on itself, requiring fluid to flow lengthwise through the layer instead of through the thickness. A folded second layer without a gap would render the surface area of the folded over portion useless. Fluid flow through the inner and outer bag is demonstrated in  FIG. 6 . 
         [0019]    In one instance the first layer  30  is wovenly joined to the second layer  32 , and the second layer  32  is wovenly joined to the third layer  34 . The inner bag material  36  is produced by the following method: 
         [0020]    (a) providing a quantity of relatively large diameter fibers; 
         [0021]    (b) weaving the large diameter fibers on a needle loom into a first layer of material; 
         [0022]    (c) providing a quantity of relatively small diameter fibers distributed over the top surface of the first layer of material; 
         [0023]    (d) weaving the small diameter fibers and the first layer of material on a needle loom into a combined first layer and second layer of material; 
         [0024]    (e) providing a quantity of relatively large diameter fibers distributed over the top surface of the second layer of material; and 
         [0025]    (f) weaving the large diameter fibers and the first and second layers of material on a needle loom into a combined first layer, second layer and third layer of material. 
         [0026]    The process of forming the felt-like material  36  results in a material having three layers, where the individual layers are joined to one another by the weaving process, whereby the material  36  forms a single piece of material. 
         [0027]    In another instance, each individual layer  30 ,  32 ,  34  is manufactured separately, and held in position by the mounting ring  14  as follows: 
         [0028]    (a) providing a quantity of relatively large diameter fibers; 
         [0029]    (b) weaving the large diameter fibers a needle loom into a first layer of material; 
         [0030]    (c) providing a quantify of relatively small diameter fibers; 
         [0031]    (d) weaving the small diameter fibers on a needle loom into a second layer of material; 
         [0032]    (e) providing a quantity of relatively large diameter fibers; 
         [0033]    (f) weaving the large diameter fibers on a needle loom into a third layer of material; and 
         [0034]    (g) joining the first, second, and third layers of material to a support structure. 
         [0035]    This process forms three distinct layers, the first layer, the second layer, and the third layer. The layers are held together in the filter by mechanical joining, such as by crimping the layers together and then to the attachment portion  44  of the mounting ring  14 , or by other mechanical joining that would be suitable for forming other filter types. If increased strength is necessary where the bags  16 ,  18  are secured to the attachment portion  44 , a reinforcing strip  42  can be folded over the opening of the bags  16 ,  18  before they are secured to the attachment portion  44 . 
         [0036]    The material  36  is suitable for forming a variety of filter types.  FIGS. 1-4  illustrate a bag filter which includes an inner bag  18  formed from the material  36 . Alternatively, the material  36  is suitable for forming a pleated filter (such as the type of filter used in oil filters). 
         [0037]    One benefit of the filter structure shown in  FIG. 5  is that when used to filter fluids, the fluid may pass through the material  36  from either direction, either starting with the first layer  30  or the third layer  36 . In the first instance, the fluid passes through material  36  by first passing through the first layer  30 , which first layer filters out the relatively large particles. Next, the fluid passes through the second layer  32 , which second layer filters out the relatively small particles. Last, the fluid passes through the third layer  34 . In the filter shown in  FIG. 2 , after leaving the third layer  34 , the fluid passes through the outer bag  16 . In the second instance, the fluid passes through material  36  by first passing through the third layer  34 , which third layer filters out the relatively large particles. Next, the fluid passes through the second layer  32 , which second layer filters out the relatively small particles. Last, the fluid passed through the first layer  30 . The ability to use the same material  36  to construct filters that either filter fluid from the outside in or from the inside out is a significant improvement over previous filter materials. Typically, bag-type filters filter fluid from the inside of the filter to the outside of the filter, while cartridge-type filters filter fluid from the outside of the filter to the inside of the filter. Here, the same material  36  may be produced and then formed into a shape that is suitable for use with either a bag-type filter or a cartridge-type filter without modifying the structure of the material  36 . This flexibility of use with varying types of filters represents a significant improvement over the prior art. 
         [0038]    It is understood that while certain aspects of the disclosed subject matter have been shown and described, the disclosed subject matter is not limited thereto and encompasses various other embodiments and aspects. No specific limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. Modifications may be made to the disclosed subject matter as set forth in the following claims.