BACKGROUND OF THE INVENTION 
       [0001]    The invention relates generally to filter elements and, more specifically, to a novel, non-obvious filter element having a magnetic array for assisting in the removal of ferrous particles from a fluid flow. 
         [0002]    In the process of making hydraulic components, such as gears, pumps, motors, valves and cylinders, ferrous metal particles are produced that contaminate the fluids used in the manufacturing process. These ferrous particles can result in decreased life of the fluid system. Current ISO standards require the removal of particles down to the level of 4 microns. Filters capable of removing particulate contaminants down to 4 microns are expensive and often must be combined into a bank of filter elements in parallel or series to handle the amount of fluid flow that must be processed. When filtering oil used in manufacturing processes, magnetic are known for use in removing ferrous contaminants, including even sub-micron sized contaminants, from the fluid flow. Typically, these magnetic filters are a one-time expense and can be placed upstream of traditional filter media to help extend the life of the standard filter, thus reducing overall costs of operation. 
         [0003]    In operational systems, such as engines, transmissions, and mobile construction equipment hydraulic systems, iron based contaminates will be generated in the normal wear and tear of operation, Typically, these metal contamination particles are relatively hard and can induce wear in a system. Many times these systems are operated outside in cold environments and putting in a fine filter medium to trap effectively these fine particles can have a negative impact on performance due to the increased pressures from the high viscosity of low temperature oil. Therefore, the filters used tend to be higher in absolute micron rating which allows larger contaminants to flow through the system and ultimately leads to lower component life. Magnetic filters can dramatically improve the filtration of the oil to much finer filtering without the cold weather bypass restrictions of a standard filter. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is a filter element having a magnetic array and which is designed to trap the most abrasive contaminates, which are ferrous based, from a fluid system with a low service cost. The filter element has an outer cylindrical can and a coaxial inner liner with a plurality of axial magnets extending substantially the length of the liner interposed in a cylindrical array either between the liner and the outer can or around the outer can. In contrast to known filters, the magnets are thus placed inside the metal can and so are more effective at trapping ferrous contaminants. The ferrous based contaminates are attracted to the liner by the magnets and held. When it is time to service the magnetic filter, the liner is removed to either be washed and reused, or simply thrown away if the liner can be made cheaply enough. The design should be modular in nature such that multiple filters can be stacked in parallel circuits to slow the flow down to maximize the contaminant removal. In some installations, the parallel system is placed in front of the standard filter to act as both an absolute filter as well as an indicator when to service the system. Other versions could be made to target specific markets such as diesel engines used in transportation and logistics, as well as other markets. 
         [0005]    In a preferred embodiment, a spiral baffle is placed inside the filter to increase the flow path of fluid through the filter, thereby also increasing residence time in the filter, and to direct the higher density contaminants toward the liner at outer wall of the filter where the magnetic filed is the strongest and where trapping of the ferrous contaminants is most effective. An advantage of the spiral flow path is that it has a constant cross-sectional area which eliminates restrictions in the fluid flow path. Alternatively, an insert which induces a vortical flow of the fluid along the axis of the filter can be used. 
         [0006]    In another preferred embodiment, the magnets are arranged in pairs of alternating polarity. Alternatively, they may be arranged in a spaced relationship with adjacent magnets having alternating polarity. 
         [0007]    In another preferred embodiment, multiple filter elements of the present invention are arranged in series to increase the holding capacity of trapped contaminants. Alternatively, multiple magnetic filter elements of the present invention may be arranged in parallel arrays that will slow down the fluid flow through each element, thereby increasing the residence time in each element to allow more time for trapping of the ferrous contaminants. The stacked and parallel arrays can be combined with a filter having standard filtering medium to catch non-ferrous contaminants for absolute filtration capability. The standard filter can then use a pressure differential detection across the filer medium to indicate when to check the magnetic array filter elements for cleaning. 
         [0008]    In another embodiment, an air purge can be used to push fluid out of the array to facilitate changing of the filter elements. 
         [0009]    In an alternative embodiment, the stacked arrays of the standard filter element and the magnetic array filter elements of the present invention may be assembled in two parallel circuits such that one side of the two parallel circuits can be serviced while the other side remains operational. 
         [0010]    There is, accordingly, an interest in developing a magnetic arrays filter element with more effective trapping characteristics and which can be more easily serviced. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0011]      FIG. 1  is a cross-sectional view of a filter element of the present invention wherein an insert which induces a vortex in the fluid flow is used. 
           [0012]      FIG. 2  is an exploded view of the embodiment of  FIG. 1 . 
           [0013]      FIG. 3  is a perspective view of a filter element of the present invention wherein a spiral-shaped insert is used to direct the fluid in a spiral flow pattern inside the filter element. 
           [0014]      FIG. 4  is an exploded view of the embodiment of  FIG. 3 . 
           [0015]      FIG. 5  is a cross-sectional view of the embodiment of  FIG. 3 . 
           [0016]      FIGS. 6 a  and 6 b    are alternative arrangements of magnets of the filter elements of the present invention. 
           [0017]      FIG. 7 a    is a side view of an alternative embodiment of the filter of a filter of the present invention;  FIG. 7 b    is a cross-sectional view of the filter of  FIG. 7 a   ;  FIG. 7 c    is a partially exploded view of the filter of  FIG. 7 a    wherein the outer pressure wall has been removed to show the interior of the filter. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0018]    Illustrated in  FIGS. 1 and 2 , generally at  10 , is a preferred embodiment of a filter element of the present invention. The filter element  10  includes a cylindrical filter housing  12  to which is affixed a top plate  14  and a bottom plate  16 . A non-ferrous liner  18  is received in a close fit inside the housing  12 . An insert  20  extends from the top plate  14  axially down the housing  12 , terminating above the bottom plate  16 . The insert  20  includes a central return tube  22 . Fluid is directed into the filter element  10  through a port  24  in the top plate  14  and is returned to the exterior of the filter element  10  via the return tube  22 . The insert  20  preferably has a plurality of radially extended plates  26  that act to introduce a flow pattern to fluid inside the filter element  10 . Encircling the exterior of the filter housing  12  are a plurality of annular rings of magnets  28  which will act to attract ferrous contaminants present in the fluid where they will be held against the liner  18 . 
         [0019]    In certain embodiments, it may be desirable to induce a predetermined flow pattern of the fluid inside the filter element  10  so as to improve the filtering efficiency of the filter element  10 . For example, inducing a vortex in the fluid around the longitudinal axis will increase the residence time of the fluid inside the filter element  10  and will also cause a centripetal force that will urge the higher density ferrous contaminants toward the liner  18  and arrays of magnets  28 . The vortex can be induced by angling of the port  24  and by selecting a shape and placement of the plates  26  that will help maintain the vortical flow. 
         [0020]    Illustrated in  FIGS. 3 and 4 , generally at  110  is an alternative embodiment of the present invention filter element. The filter element  110  includes a cylindrical filter housing  112  to which is affixed a top plate  114  and a bottom plate  116 . A non-ferrous liner  118  is received in a close fit inside the housing  112 . An insert  120  extends from the top plate  114  axially down the housing  112 , terminating above the bottom plate  116 . The insert  120  includes a central return tube  122 . Fluid is directed into the filter element  110  through a port  124  in the top plate  114  and is returned to the exterior of the filter element  110  via the return tube  122 . The insert  120  has helical fighting  126  to induce a spiral flow pattern to fluid inside the filter element  110 . Encircling the exterior of the filter housing  112  are a plurality of annular rings of magnets  128  which will act to attract ferrous contaminants present in the fluid where they will be held against the liner  118 . The helical fighting  126  acts to increase the residence time of fluid inside the filter element  110  and creates a centripetal force that will urge higher density ferrous contaminants into proximity of the liner  118  and magnet arrays  128 . 
         [0021]    A further preferred embodiment is illustrated generally at  210  in  FIG. 5 . It is similar to filter element  110  except that the magnet arrays  228 , including individual magnets  130 , have been placed inside the filter housing  112  but outside the non-ferrous liner  118 . By placing the magnet arrays  228  inside the filter housing  112 , any shielding effect of the filter housing  112  will be eliminated and the capture of ferrous contaminants improved. If desired, a plurality of openings can be created in the liner  118 , preferably not in the areas of the magnets  130 , to allow the pressure to equalize on either side of the liner  118 . 
         [0022]    The individual magnets  130  may be arranged in at least two different ways. The magnets may be arranged in adjacent pairs of alternating polarity, as illustrated in  FIG. 6 a    and similar to that described in U.S. Pat. No. 7,662,282 (which is incorporated herein in its entirety by this reference), or as individual magnets spaced apart from each other with alternate magnets having opposite polarity, as illustrated in  FIG. 6   b.    
         [0023]    In certain applications, it may be preferable to provide a port in the bottom plate  16 ,  116  through which compressed gas can be directed into the filter housing  12 ,  112 , to assist in purging fluid from the filter  10 ,  110 . 
         [0024]    An alternative embodiment is illustrated in  FIGS. 7 a   - 7   c,  wherein the filter is illustrated generally at  210 . The filter  210  includes a filter housing or pressure vessel wall  212  to which is affixed a top plate  214  and a bottom plate  216 . A non-ferrous liner  218  is received in a close fit inside the housing  212 . An insert  220  is comprised of a central, closed spacer tube  222  about which are arranged in a vertically spaced, stacked relationship a plurality of spacer plates  224 . Each spacer plate  224  has a partial annular shape wherein a portion of an otherwise annular piece of material has been removed, as at  226  in  FIG. 7 c   . The arrangement of the removed sections  226  alternate from one side of the filter  210  for odd-numbered spacer plates  224  to the opposite side of the filter  210  for even-numbered spacer plates  224 . 
         [0025]    Oil to be filtered is introduced into the filter  210  at inlet  230  and is removed from the filter  210  at outlet  232 . The path of the oil inside the filter  210  is determined by the arrangement of the removed sections  226  of the stacked spacer plates  224 . Since the removed sections  226  alternate sides of the filter  210  as described, the oil is forced to go from one side of the filter  210  to the other side as it encounters each spacer plate  224 . The path of the oil through the filter  210  is thus increased as is the residence time it spends near the circumferential periphery of the filter  210 . The oil thus has a stepped flow path in contrast to the spiral flow path of the filter  10 . A series of magnet arrays  228 , similar to those described in the other embodiments are arranged outside the filter housing  212  and will serve to trap ferrous contaminants against the non-ferrous liner  218 . An advantage of the embodiment filter  210  is that the stacked spacer plates can be easily and inexpensively manufactured, for example, by laser cutting. 
         [0026]    The foregoing description and drawings comprise illustrative embodiments of the present inventions. The foregoing embodiments and the methods described herein may vary based on the ability, experience, and preference of those skilled in the art. Merely listing the steps of the method in a certain order does not constitute any limitation on the order of the steps of the method. The foregoing description and drawings merely explain and illustrate the invention, and the invention is not limited thereto, except insofar as the claims are so limited. Those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.
A filter for removing ferrous particles from a fluid. The filter has an outer filter housing and a non-ferrous liner inside the housing. A plurality of magnets are longitudinally extended at intervals outside the liner. An insert inside the liner imparting a directional flow to the fluid inside the filter whereby ferrous particles in the fluid are trapped by the magnets and held against the non-ferrous line.