Abstract:
A replacement filter for conventional throw-away spin-on oil filter cartridge on an internal combustion engine. The replacement filter uses a porous metallic filter element, preferably a woven stainless steel, pleated filter element, within a housing physically simulating the conventional throw-away spin-on oil filter cartridge. The housing is disassembleable, typically by unscrewing the top cap of the housing, for removal, cleaning and reuse of the filter element. This avoids the problems of cost and availability of replacement filters and of disposal of used filters. Various embodiments are disclosed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of oil filters, and more particularly to oil filters as are frequently used on internal combustion engines. 
   2. Prior Art 
   Internal combustion engines, including gasoline and diesel engines as are commonly used in cars, trucks, boats and stationary power plants, frequently use a canister type oil filter for filtering the crankcase oil as it circulates through the pressure lubrication system. A typical filter of this type may be seen in  FIG. 1 . Such filters are characterized by a can-like housing  20  with a top cap  22  permanently attached thereto having an internally threaded center region or hub  24 , openings  26  and a flat rubber seal  28 . Within the can-like housing  20  and separating the center region in communication with the opening through hub  24  and the outer region in communication with the openings  26  is a pleated paper filter material through which oil may pass. In use, the threaded center hub  24  threads onto a short threaded pipe on the oil filter mount on the engine until rubber member  28  seals against a flat surface on the oil filter mount. Porting adjacent the short threaded pipe-like protrusion on the oil filter mount provides oil communication with the openings  26 . Normally oil flow is through the openings  26 , through the paper filter and then out through the threaded pipe-like structure threaded into hub  24 . 
   Filters of the type shown in  FIG. 1  have the primary advantage of being easily replaced by simply unscrewing the used filter and screwing a replacement filter back on. However, they also have certain disadvantages, since not only is the filter element (the paper filter) effectively replaced on each oil change, but the pressure container in which the filter element is mounted is also replaced on each oil change. Consequently, the cost of these filters substantially increases the cost of the oil change itself. Further, because of the wide variety of filter sizes, a substantial number of filters must be inventoried to have an adequate supply of the various sizes that may be required. Also, the filtering of the paper is less than ideal, the paper catching only a percentage of particles of a given size, with the paper clogging over time so that increasing percentages of the recirculating oil bypasses the filter entirely. 
   While filters of the foregoing type are easily removed from an engine and replaced with a new filter, the used filter is not easily disposed of. Being toxic, the used filter cannot simply be thrown out, so to speak, as before, but rather must be disposed of using prescribed and relatively expensive procedures. Consequently, there is room for improvement in both the performance and the economics of internal combustion engine oil filters. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a representative prior art conventional throw-away spin-on oil filter cartridge as used on many internal combustion engines. 
       FIG. 2  is a perspective view of one embodiment of replacement filter cartridge as may be used for replacement of the filter cartridge of  FIG. 1 . 
       FIG. 3  is an exploded perspective view of the filter cartridge of  FIG. 2 . 
       FIG. 4  is an exploded cross section of the filter cartridge of  FIGS. 2 and 3 . 
       FIG. 5  is a cross section of the filter cartridge of  FIGS. 2 ,  3  and  4 . 
       FIG. 6  is an exploded cross section of an alternate embodiment filter cartridge in accordance with the present invention. 
       FIG. 7  is an exploded cross section of an alternate embodiment filter cartridge incorporating a bypass valve. 
       FIG. 8  is a plan view showing the feet on the bypass valve housing. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First referring to  FIG. 2 , a perspective view of one embodiment of the present invention may be seen. The filters and methods of the present invention are intended to provide a direct replacement for the prior art filters of the type shown in  FIG. 1 , and accordingly may be substituted for such prior art filters with absolutely no change to the internal combustion engine itself, and more particularly, with no change to the oil filter mount. Thus, the filter shown in  FIG. 2  has a physical appearance very similar to that of the prior art filter of  FIG. 1 , being characterized in appearance by a can-like housing  30  and a top cap  32 , having an internally threaded central hub  34  and openings  36  through the top cap  32  within the periphery of a rubber or elastomeric seal ring  40 . However, internally the oil filters of the present invention are very different from the prior art, as may be seen in  FIGS. 3 and 4 . 
     FIG. 3  presents an exploded perspective view of the embodiment of  FIG. 2 , with  FIG. 4  presenting an exploded cross-sectional view of the filter of  FIGS. 2 and 3 . The can-like housing  30  in this embodiment has an internally threaded region  42  adjacent its open top, with a top land  44  which, as shall subsequently be seen, provides a cylindrical sealing surface for an o-ring seal on the top cap, generally indicated by the numeral  46 . The can-like housing  30  in this embodiment also has a raised center region  46  at the bottom thereof that receives and holds concentric a seal plate  48 . Alternatively, the seal plate  48  could locate on its outer diameter  50  on the inner periphery  51  of the can-like housing  30 . 
   The filter cartridge itself, generally indicated by the numeral  52 , is a stainless steel woven mesh which is pleated, formed into the cylindrical shape, the mating edges welded, and then cemented in upper and lower stainless steel cup-like members  54  with epoxy to form an integral and durable filter assembly. In that regard, woven stainless meshes are commercially available in the desired porosity ranges. They capture a larger percentage of particles larger than their rated porosity and do not clog as readily as paper filter materials do. 
   With the seal plate  48  positioned in the can-like housing  30  with filter element  52  also in position in the can-like housing  30 , the bottom cup  54  will seal on its bottom against an o-ring seal  56  and a second o-ring seal  58  to prevent unfiltered oil from passing around the inner end of the filter. The entire assembly is held together by top cap  46 , having external threads  60  thereon for threading into threaded region  42  at the top of the can-like housing  30 . Top cap  46  in this embodiment includes O-ring seals  62  for sealing against the inner periphery of the filter element  52 , face o-ring seal  64  for sealing against the top surface of member  54  on filter  52 , O-ring  66  for sealing against the cylindrical lip  44  of can-like structure  30 , and finally, an O-ring  40  (see also  FIG. 2 ) for sealing against the oil filter mount on the internal combustion engine like the rubber or elastomeric ring  28  of the prior art ( FIG. 1 ). 
   A cross-section of the final assembly may be seen in  FIG. 5 . As shown therein, the filter element  52  is sealed at the top and bottom so that oil flow between openings  36  and the central region  68  must necessarily pass through the metal filter. In any specific filter configuration, the proportions will change to simulate the prior art filter it replaces and various design details may change as desired, though an essential feature of the present invention is the ability to remove the metal filter for cleaning and reuse. In that regard, being able to disassemble the filter cartridge allows the rapid removal of oil therefrom, with the metal filter element itself not retaining much oil. The entire filter assembly is preferably removed from the oil filter mount  70  for disassembly by unscrewing the entire assembly from the threaded member  76 , cleaning and reassembly and remounting, though if desired, the cap  32  could be left mounted, and only the can-like housing and filter element  52  removed from the engine for cleaning and replacement. The filter element, being metal, may readily be cleaned with an appropriate solvent or even cleaned with soap and water and reused indefinitely. This, of course, eliminates the new filter stocking requirements, the old filter disposal problems and the costs associated with both, providing highly reliable, high quality oil filtration. In that regard, while sintered metal filter elements could be used, the woven wire mesh is preferred as not being so easily clogged, as being more easily cleaned, and in general presenting a substantially larger filter area for a given size filter cartridge by pleating. 
   Now referring to  FIG. 7 , an exploded cross section of an alternate embodiment filter in accordance with the present invention incorporating a bypass valve may be seen. In this embodiment, various parts may be identical or substantially identical in form and function to the parts of the embodiment of  FIGS. 3  of  4 , and accordingly, are given the same reference numerals. The difference in the embodiment of  FIGS. 7 and 8 , however, is the inclusion of a bypass valve body  78  having a ball  80  normally held against a valve seat by spring  82  acting between the ball and top closure member  84 . The bypass valve body  78  has a lower flange thereon with O-rings  86  and  88  for sealing against the inner periphery and the face of the bottom end of filter element  52 , with the flange having feet  90  adjacent the lower periphery thereof. The diameter of the flange is intentionally made less than the diameter of the can-like housing  30  so that when the various parts of the filter are assembled, there will be a good flow path for unfiltered oil through openings  36  around the outer periphery of the filter element  52 , around the lower end of bypass valve housing  78  and between feet  90  to the lower side of the ball valve  80 . Thus if filter element  52  becomes sufficiently dirty to unreasonably restrict the flow through the filter element, pressure will build up under ball  80  to above some predetermined pressure, causing ball  80  to rise against the force of spring  82 , allowing flow through the valve seat, around ball  80  and through openings  92  in the bypass valve housing  78  and out through the center of top cap  32 . 
   Another other feature of the embodiment of  FIG. 7  is illustrated in that Figure. In particular, the threaded members, such as threaded member  76  (see  FIG. 5 ), on various oil filter mounts are of different diameters and threads, but otherwise the filters are or may be the same, including the top seal  40 . Accordingly, in accordance with this embodiment, the threaded opening  94  in top cap  32  is preferably made to fit the larger threaded members  76  on filter mounts, with one or more internally and externally threaded inserts  96  being provided to adapt the same filter cartridge assembly to other, smaller threaded members on filter mounts. Alternatively, the threaded opening  94  may be made even larger than on any suitable filter mounts so that inserts  96  may be provided for even the larger filter mounts. This would ensure a minimum wall thickness for all inserts  96 , if any required insert otherwise would have too thin a wall. 
   The inserts  96  preferably have a short top region  98  of a somewhat larger diameter  100  than the internal threaded area  94  so that the insert  96  may be threaded into top cap  32 , yet will not inadvertently thread through the top cap when the filter assembly is screwed onto the threaded member of a filter mount. In one embodiment, the external threads on insert  96  are made continuous, though are later upset so as to interfere with the threads on the threaded region  94 . 
   As previously mentioned, various design details of the filter assembly of the present invention will vary, depending upon such factors as designer preferences, manufacturing ease, requirements of the filter to be replaced, etc. One such variation may be seen in  FIG. 6 , wherein the bottom cup-like member  54  of the embodiment of  FIGS. 2 ,  3  and  4  is fabricated as a closed cup  72 , providing a permanent seal at the bottom of the filter element and negating the need or desirability of a separate seal as shown in the embodiments of  FIGS. 2 ,  3  and  4 . This, of course, is but one variation in design, as many others will be apparent to those skilled in the art. By way of example, while the parts illustrated for the preferred embodiment, the housing may be a drawn can, the cap may be of an alternate fabrication, and/or the housing and cap may be an assembly of more than two parts. The seals may also be of alternate configurations. These and other modifications will be apparent to one skilled in the art, all within the full scope of the following claims.