Abstract:
A lenticular style of filtration in a first stage and a final filtration in a second stage incorporated into a single filtration housing to provide filtration of liquid suitable for pharmaceutical use where the lenticular style filter is formed by a plurality of cellulose filters stacked on a polypropylene cylindrical mesh support tube having a membrane filter cartridge removably mounted inside the mesh support tube.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to sanitary filtering of liquid for the pharmaceutical industry, chemical plants, hospitals and house hold product packagers, for example, and others requiring completely sterile conditions for production of a sanitary product.  
         BACKGROUND OF THE INVENTION  
         [0002]    Traditionally, filtration of liquids used in the pharmaceutical industry, for example, where sterility of the fluid must be assured, requires the repeated filtration of the liquid through several interconnected filter housings. Each filter housing includes a filter and produces a predetermined amount of filtration depending upon the particular filter media used. After successive filtration steps requiring several interconnected filter housings, the filtered liquid may be used in a pharmaceutical process. This process is very expensive and requires sterilization and the maintenance of sterile conditions in multiple filter housings.  
           [0003]    Usually, liquid is initially filtered by a cellulose filter in a sealed filter housing. The filtered liquid is then passed downstream through a piping system to at least a second filter housing having a membrane filter for filtration of liquid to a pharmaceutical grade.  
           [0004]    Accordingly, there is a long felt need in the industry to reduce the number of steps and equipment required to achieve multiple levels of filtration of a liquid under sterile conditions.  
         SUMMARY OF THE INVENTION  
         [0005]    By the present invention, liquid is pumped into a filter housing and passed through a cellulose filter which filters materials greater than one micron in size. The filtered liquid passes through a polypropylene cylindrical mesh support tube and into a centrally located membrane filter cartridge. The membrane filter cartridge removes particulate matter greater than 0.5 microns in size. Other combinations of filtration efficiency may be made by the customer, according to their particular filtration needs.  
           [0006]    The filtered liquid passes through the membrane filter cartridge towards its hollow center. The filtered liquid flows by gravity, outside of the filter housing for further processing and/or use. Optionally, the liquid to be filtered may be moved in an opposite direction, passing initially through the membrane filter cartridge and radially outward to be filtered by a cellulose filter or other filter cartridge.  
           [0007]    The polypropylene cylindrical mesh support tube accommodates the easy insertion and removal of a premade membrane filter cartridge or other filter cartridge in a reverse direction filtration. After the useful life of the filter cartridge is over, the filter cartridge can easily be removed and replaced.  
           [0008]    This assembly facilitates the use by a customer of two different filter suppliers. One supplier may provide the cellulose filters mounted on the polypropylene cylindrical mesh support tube. A second supplier may be used to provide pre-formed membrane filter cartridges which are easily removed and replaced by the slidable mounting of the filter cartridge in the support tube.  
           [0009]    The cylindrical mesh support tube is dimensioned to accommodate a particular diameter of membrane filter cartridge so that the exterior of the filter cartridge engages the interior of the cylindrical mesh tube. Thereby, liquid is communicated directly from the cellulose filters to the filter cartridge for complete and thorough filtration.  
           [0010]    Accordingly, it is an object of the present invention to provide a lenticular style of filtration in a first stage and a final filtration in a second stage incorporated into a single filtration housing to provide filtration of liquid suitable for pharmaceutical use.  
           [0011]    It is another object of the present invention to provide a lenticular style of filtration in a first stage and a final filtration in a second stage incorporated into a single filtration housing to provide filtration of liquid suitable for pharmaceutical use where the lenticular style filter is formed by a plurality of cellulose filters stacked on a polypropylene cylindrical mesh support tube having a membrane filter cartridge slidably and removably mounted inside the mesh support tube.  
           [0012]    It is still yet another object of the present invention to provide a lenticular style of filtration in a first stage and a final filtration in a second stage incorporated into a single filtration housing to provide filtration of liquid suitable for pharmaceutical use where the lenticular style filter is formed by a plurality of cellulose filters stacked on a polypropylene cylindrical mesh support tube having a membrane filter cartridge slidably and removably mounted inside the mesh support tube with the liquid to be filtered passing through the cellulose filters and radially inwardly through the mesh openings of the support tube and into a hollow interior of the filter cartridge after passing through the filter media of the cartridge.  
           [0013]    It is still yet another object of the present invention to provide a lenticular style of filtration in a first stage and a final filtration in a second stage incorporated into a single filtration housing to provide filtration of liquid suitable for pharmaceutical use where the lenticular style filter is formed by a plurality of cellulose filters stacked on a polypropylene cylindrical mesh support tube having a membrane filter cartridge slidably and removably mounted inside the mesh support tube with the liquid to be filtered passing through the cellulose filters and radially inwardly through the mesh openings of the support tube and into a hollow interior of the filter cartridge after passing through the filter media of the cartridge or optionally passing from the interior of the filter cartridge radially outwardly through the filter cartridge, the support tube and the plurality of cellulose filters.  
           [0014]    These and other objects of the invention, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is an exploded view of the two stage filtration of the present invention illustrating a membrane filter cartridge to be slidably and frictionally mounted within a polypropylene cylindrical mesh support tube.  
         [0016]    [0016]FIG. 2 is a partial cross-sectional view illustrating the mounting of a cylindrical mesh support tube inside of a stainless steel filter housing with a membrane filter cartridge slidably mounted inside the support tube and a plurality of cellulose filters mounted exteriorly of the cylindrical mesh support tube so as to provide a flow path from the cellulose filters through-the support openings of the support tube and into the membrane filter cartridge to pass filtered liquid through an outlet pipe of the filter housing.  
         [0017]    [0017]FIG. 3 is an enlarged partial cross-sectional view illustrating the mounting of the support tube in the filter housing.  
         [0018]    [0018]FIG. 4 illustrates an exploded view of an alternate embodiment of a cylindrical mesh support tube.  
         [0019]    [0019]FIG. 5 is an enlarged cross-sectional view of the bottom end of the mesh support tube shown in FIG. 4.  
         [0020]    [0020]FIG. 6 is a cross sectional view taken along line  6 - 6  of FIG. 1 to illustrate the construction of the filter cartridge. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.  
         [0022]    With reference to the drawings, in general, and to FIGS. 1 and 2, in particular, a unitary two stage filtration system embodying the teachings of the subject invention is generally designated as  10 . With reference to its orientation in FIG. 2, the filtration system  10  is mounted within a stainless steel filter housing  12  illustrated by dotted lines. A base plate  14  of the housing includes an outlet pipe  16  passing therethrough having a hollow interior channel  18 .  
         [0023]    Mounted in the housing  12  is a polypropylene cylindrical mesh support tube  20  as shown in FIG. 1. Spaced along the length of the tube are a plurality of openings,  22   a ,  22   b ,  22   c , . . . , for example. At opposite ends  24   a ,  24   b  are mounted end caps  26   a ,  26   b . End caps  26   a ,  26   b  are shown removed from the tube  20  in FIG. 1. It is understood as being within the scope of the present invention that one end cap may be integral at one end of the tube  20  as shown in FIG. 4.  
         [0024]    Slidably and frictionally mounted in the interior of the tube  20  is a membrane filter cartridge  30 . The filter cartridge  30  as shown in FIG. 6, includes an exterior wall  32  having a plurality of openings  34 . The openings  34  expose interior paper or other filter material  36  which is repeatedly folded upon itself between exterior wall  32  and interior wall  38 . Interior wall openings  39  lead to a hollow passageway  40  extending along the length of the cartridge  30 .  
         [0025]    When the tube  20  and the filter cartridge  30  are mounted inside a filter housing as shown in FIGS. 2 and 3, one end cap  26   b  fits over and around an upper end  18   a  of outlet tube  18 . O-rings  42 ,  44  assist in sealing the connection between the end cap  26   b  and the end  18   a  of the outlet tube  18 . Alternative arrangements for securing the tube  20  to the outlet tube  18  may be made and are considered to be within the scope of the present invention. An example of a filter housing is shown in U.S. Pat. No. 5,443,720, hereby incorporated in its entirety by reference.  
         [0026]    As shown in FIG. 2, the filter cartridge  30  is located inside the support tube  20 . Mounted on the exterior of the tube  20  are a plurality of cellulose filter cells  50 . An example of one such filter cell is shown in U.S. Pat. No. 5,316,678, hereby incorporated in its entirety by reference. The filter cells  50  extend along the length of the support tube between its end caps. A cover cap  52  closes off the end of the support tube  20  opposite to the end mounted on the outlet tube  18 .  
         [0027]    End  30   a  of the filter cartridge may, by a bayonet extension  30   b , be locked in the end  18 a of the outlet tube. O-rings  30   c ,  30   d  assist in sealing the filter cartridge  30  to the outlet tube  18  to provide a path for filtered liquid passing from the hollow passageway  40  of the filter cartridge to the filter outlet tube  18 . Alternatively, the filter cartridge may be inverted with both O-rings at the top or one O-ring at the bottom and one O-ring at the top.  
         [0028]    Accordingly, liquid to be filtered is passed into the interior of the filter housing and after passing through the filter cells  50  the first stage filtered liquid passes through the openings in the support tube and then into the filter cartridge. The second stage filtered liquid is passed through the outlet tube  18  for further processing.  
         [0029]    Optionally, the flow of liquid may be in a reverse direction by entering the filter housing through tube  18  and passing radially outwardly through the filter cartridge or other filter media and through the filter cells into the interior of the filter housing for subsequent processing. Under either scenario, the filter cartridge may be slidably removed and easily replaced, as necessary. The plurality of filter cells are also slidably mounted on the support tube for removal and replacement. The assembly of the present invention provides two stage filtration in a single filter housing while including the use of a slidably mounted, frictionally held, pre-assembled filter cartridge having interior and exterior walls with filter media therebetween.  
         [0030]    The foregoing description should be considered as illustrative only of the principles of the invention. Since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.