Abstract:
A fluid filter assembly incorporates a filter element and valve assembly within a filter housing and base plate. The filter element and valve assembly is a single pre-assembled unit which includes an anti-drainback valve seat and diaphragm, a by-pass valve assembly, a pleated paper filter element, and a spring endcap. The filter housing and base plate separably clamp together to enclose the filter element/valve cartridge which is replaceable, as a single assembly, once its filtering ability is degraded. The anti-drainback valve seat engages complementary features on the base plate to correctly align and position the filter/valve cartridge during assembly. Further, a recess within the top of the filter housing receives a protrusion on the filter element endcap to provide additional alignment and to provide pressure to seal the filter/valve cartridge to the base plate in a fluid-tight manner.

Description:
This application claims the benefit of U.S. provisional application 60/084,967, filed on May 11, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates generally to the field of fluid filters. More specifically, the present invention is related to a fluid filter with a replaceable filter element assembly. The device of this invention has particular application in providing a self-aligning, quick-and-easy assembling fluid filter element assembly. 
     2. Discussion of Prior Art 
     Until recently, the design of standard spin-on oil filters had not undergone major changes since introduction in the early 1960s. Recently, however, concerns regarding the environmental impact of millions of disposable oil filters have led to the development of reusable filter housings which incorporate replaceable filter elements. Replaceable filter elements contain less residual oil and break down far easier than typical disposable spin-on filters. The current inventor&#39;s earlier patent (5,411,659) introduced an exemplary replaceable filter element design. These replaceable filter elements, which are assembled infrequently and usually by do-it-yourself mechanics, must be correctly assembled and aligned within a filter housing to ensure proper operation of the filter and to prevent serious damage to a vehicle&#39;s engine. However, the related prior art often includes multi-piece filter and valve assemblies which can be mis-assembled or, at the least, mis-aligned during assembly. 
     The patent to Baldwin (3,557,958) teaches a standard, disposable oil filter anti-drainback valve positioned near the filter&#39;s base plate and constructed of a rubber-like material. While ease of assembly is discussed by this reference, the discussion is limited simply to improved placement of a separate valve seat. 
     The patent to Thornton (3,567,022) provides for a combination valve assembly, for a standard, disposable oil filter, which includes a relief valve and anti-drainback valve in an integral assembly. 
     The patent to Stack (3,957,640) provides for a cone-shaped elastomeric anti-drainback valve, for a standard, disposable oil filter, which positions the filter assembly into a correct position for assembly. 
     The patent to Bumb (3,984,318) provides for a simple to assemble anti-drainback valve which combines the bypass valve and anti-drainback valve on the same support. The example oil filter is of disposable, not reusable, construction. 
     The patent to Anderly et al. (5,256,280) provides for an anti-drainback valve which rests a valve diaphragm against a slanting valve seat. 
     The patent to Jones et al. (5,711,872) provides for a reusable filter which incorporates the relief valve as a permanent part of the replaceable filter cartridge. 
     The patent to Roll et al. (5,817,232) provides for a replaceable filter assembly which has the by-pass valve and anti-drainback valve in a “rebuild” kit separate from the filter element. 
     The patent to Smith et al. (5,830,371) provides for an alternative arrangement of by-pass valve and anti-drainback valve for a reusable oil filter. 
     The patent to Matsubara et al. (5,876,600) provides for a two-piece filter housing for a reusable oil filter which uses rotating grooves and channels within each half of the filter housing to keep the housing bodies aligned during assembly. 
     Whatever the precise merits, features and advantages of the above cited references, none of them achieve or fulfill the purposes of the present invention. Accordingly, it is an object of the present invention to provide for a replaceable fluid filter element assembly which is pre-assembled as a single unit. 
     It is another object of the present invention to provide for a replaceable fluid filter element assembly which assembles quickly, easily and correctly in a filter housing. 
     It is an additional object of the present invention to provide for a replaceable fluid filter element assembly which engages self-aligning features of a filter housing. 
     It is an additional object of the present invention to provide for a self-aligning, replaceable fluid filter element assembly which creates a fluid-tight seal within a filter housing without the need for an endcap spring element. 
     It is an additional object of the present invention to provide for a self-aligning, replaceable fluid filter assembly for use as an oil filter in an internal combustion engine. 
     These and other objects are achieved by the detailed description that follows. 
     SUMMARY OF THE INVENTION 
     A fluid filter assembly incorporates a filter element and valve assembly within a filter housing and base plate. The filter element and valve assembly is a single pre-assembled unit which includes an anti-drainback valve seat and diaphragm, a by-pass valve assembly, a pleated paper filter element, and an endcap spring. The filter housing and base plate separably clamp together to enclose the filter element/valve unit which is replaceable, as a single assembly, once its filtering ability is degraded. The anti-drainback valve seat engages complementary features on the base plate to correctly align and position the filter/valve unit during assembly. Further, a recess within the top of the filter housing receives a protrusion on the filter element endcap to provide additional alignment and to provide pressure to seal the filter/valve unit to the base plate in a fluid-tight manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a cut-away side view of an assembled fluid filter of the present invention. 
     FIG. 2 illustrates an exploded view of the filter element and valve unit assembly of the present invention. 
     FIG. 3 illustrates a cut-away view of the assembled filter element and valve unit assembly of FIG.  2 . 
     FIG.  4   a  illustrates a detailed view of the base plate of the present invention. 
     FIG.  4   b  illustrates a detailed view of the base plate and anti-drainback valve seat surface engagement. 
     FIG. 5 illustrates a cut-away view of the filter housing and base plate of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is illustrated and described in a preferred embodiment, the device may be produced in many different configurations, forms and materials. There is depicted in the drawings, and will herein be described in detail, a preferred embodiment of the invention, with the understanding that the present disclosure is to be considered as a exemplification of the principles of the invention and the associated functional specifications of the materials for its construction and is not intended to limit the invention to the embodiment illustrated. Those skilled in the art will envision many other possible variations within the scope of the present invention. 
     An assembled fluid filter  100  is illustrated in FIG.  1  and is comprised of three major sub-assemblies: base plate  110 , filter housing  102 , and a filter and valve cartridge (including elements  116 - 134 ). 
     In a preferred embodiment, fluid filter  100  is attached to an engine block nipple (not shown) by threads inside center exit hole  112 . Gasket  106 , which is preferably constructed of silicone based rubber, forms a seal against the machine mounting area (not shown). 
     Filter housing  102 , a hollow tube shaped canister, is sealed in a fluid-tight arrangement with base plate  110  by locking band  104 . Preferably, filter housing  102  is constructed from automotive nylon; however, injection molded poly, 20 gage cold rolled steel, or other functionally equivalent materials can also be used. Also, the dimensions of filter housing  102  are not an integral part of the current invention; all standard-size filter housings are contemplated. 
     Locking band  104  is preferably an over-center latch clamp, which is known in the art, and constructed of 20 gage cold rolled steel. The purpose of locking band  104  is to secure base plate  110  to filter housing  102 . Furthermore, o-ring  108  ensures the seal is fluid-tight. Other types of functionally equivalent clamping means are also contemplated which provide a secure seal between filter housing  102  and base plate  110  but can be removed without the need for special tools. 
     Base plate  110  is a contoured, annular disk, preferably constructed of 8 gage cold rolled steel, and has circular center exit hole  112  and a plurality of evenly spaced entry holes  114 . Automotive nylon is an alternative, functionally equivalent, construction material which provides the strength and wear-resistance necessary for re-usable base plate  110 . 
     The operation of filter  100  is not considered a novel feature of the present invention but its description is included to show the interaction of all elements of the present invention. In operation, a pump (not shown) provides pressurized fluid to entry holes  114 . With references to FIGS.  1  and  2 , the fluid enters filter  100  and fills cavity  138  beneath anti-drainback valve seat  126 . Once the cavity is filled, the fluid pressure causes the fluid to pass through perforations  202 , displace anti-drainback valve diaphragm  128 , and enter filter housing  102 . Washer  124 , constructed of sturdy plastic or steel, prevents diaphragm  128  from overflexing. 
     Fluid within housing  102  is forced through filter paper element  122 , enters column  136  through perforated filter element center column  134 , and exits column  136  through hollow by-pass valve receiving area  132  and ultimately center exit hole  112 . 
     If filter paper element  122  becomes clogged, and can no longer pass unfiltered fluid, the resulting fluid pressure forces by-pass valve diaphragm  130 , with retainer  120 , to compress spring  108  which, in turn, allows fluid to pass through perforated by-pass valve housing  116  at entry holes  145 . This mechanism allows fluid, although unfiltered, to return to center exit hole  112  and maintain lubrication in the attached machine (not shown) even if filter paper element  122  no longer works. 
     When the pump (not shown) stops pumping liquid through the system, the fluid will no longer push against anti-drainback valve diaphragm  128 . Anti-drainback valve diaphragm  128  will then rest against perforated anti-drainback valve seat  126  forming a liquid-tight seal. The pressure of the fluid within housing  102  trying to exit filter  100  holds anti-drainback valve diaphragm  128  against anti-drainback valve seat  126 . 
     The construction, materials and size of paper filter element  122  and by-pass valve assembly  116 ,  118 ,  120 ,  130 , and  132  are well known industry standards with a number of functionally equivalent alternatives which are contemplated within the scope of this invention. 
     FIG. 2 illustrates an exploded view of the by-pass valve system and the anti-drainback valve system and more clearly shows the number of items that previously had to be individually assembled when replacing a filter cartridge in a reusable filter system. By-pass valve receiving area  132  holds spring  118 , by-pass valve retainer  120 , by-pass valve diaphragm  130  and perforated by-pass valve body  116 . As previously indicated, the operation and construction of a filter by-pass valve is well known. 
     However, by-pass valve body  116 , which is press-fitted into by-pass valve receiving area  132 , has a novel tapered region at its bottom which allows washer  124 , anti-drainback valve diaphragm  128 , and perforated anti-drainback valve seat  126  to be easily attached by press-fitting. Alternative attachment means include spot welding or the use of appropriate adhesive materials; however, press-fitting is a simple manufacturing step and provides sufficient securing forces for all the elements. 
     Washer  124 , constructed of sturdy plastic or steel, prevents diaphragm  128  from overflexing while fluid is flowing through filter  100 . Also included in washer  124 , is channel  204  which provides even more security for attaching anti-drainback valve diaphragm  128 . Diaphragm  128  is preferably constructed of silicon based rubber and conforms in shape to perforated anti-drainback valve seat  126 . Neoprene and other resilient materials are also possible construction materials for diaphragm  128 ; however silicon based rubber, the preferred material, does not become brittle as easily as most of these materials do within this environment. Again, the shape and size of diaphragm  128 , depend on the shape and size of anti-drainback valve seat  126 ; but in relation to one another, diaphragm  128  is slightly larger than seat  126  so that its peripheral edges adequately seal against seat  126  thus preventing fluid from draining back out of baseplate  100  and returning to the machine (not shown) via entry holes  114 . 
     Anti-drainback valve seat  126  is a rigid, perforated support structure the serves a number of purposes. In a preferred embodiment, seat  126  is shaped like a cone; however dome shaped or trapezoidal shaped seats are functionally equivalent. Also, while the preferred construction material for seat  126  is sheet metal, automotive nylon or other sturdy plastic are also contemplated materials. The precise radius of seat  126  is not critical to its function. The two design criteria which must be met is that seat  126  extend past entry holes  114  so that fluid can enter filter  100  and that seat  126  not extend so far that it interferes with the clamping of housing  102  with base plate  110 . Our preferred embodiment sizes seat  126  so that it reaches approximately half-way between entry holes  114  and the bottom inside edge of housing  102 . The number and size of perforations  202  in anti-drainback valve seat  126  are also not critical. Too few holes or too small of holes cause a back pressure towards the pump (not shown) and too many holes or too large of holes damage the sturdiness and integrity of seat  126 . Any arrangement, size and number of perforations which avoid these critical conditions are contemplated by this invention. A working example would be 48 holes evenly spaced in two concentric rings of 24 holes. With this number of holes, the appropriate diameter of each hole is approximately 0.125 inches. These design values provide a structurally sound valve seat that does not impede fluid flow for a typical-sized automobile engine. 
     An assembled filter element and valve cartridge  300  is illustrated in FIG.  3 . This cartridge, completely assembled, fits within filter housing  102  and base plate  110 . Instead of disposing of an entire spin-on filter with residual oil, locking band  104  is removed to separate housing  102  and base plate  110 , and a used cartridge is removed and replaced by new cartridge  300 . Thus only the used cartridge is disposed of. Two elements introduced in FIG. 3 are end cap  306  and element holder  304 . These two sheet metal pieces securely hold filter paper element  122  and add some rigidity to cartridge  300 . 
     A key inventive feature of the present invention pertains to insuring that replaceable cartridge  300  can easily be correctly inserted into housing  102  and properly aligned. Misalignment of cartridge  300  causes damage to anti-drainback valve seat  126  and by-pass valve body  116  when base plate  110  is forcibly clamped onto housing  102 . Also, even if no damage occurs, both the by-pass valve and anti-drainback valve will not work unless their surfaces are properly sealed and positioned within housing  112 . 
     FIGS.  4   a  and  4   b  illustrate a first self-alignment feature to assist with the inserting of cartridge  300 . Base plate  110  has ridges  402  for engaging the bottom of perforated anti-drainback valve seat  126 . By seat  126  properly sitting on ridges  402 , replaceable cartridge  300  is properly centered and aligned within housing  102 . To further assist with this self-aligning step in the preferred embodiment, ridges  402  have sloped region  404  which is slightly smaller than the inner diameter of anti-drainback valve seat  126 . When seat  126  is somewhat close to being aligned, sloped region  404  guides seat  126  into precise alignment on base plate  110 . In the preferred embodiment, ridges  402  are a continuous circle around base plate  110  which engage the peripheral underside of anti-drainback valve seat  126 . However, other arrangements are just as effective at providing the self-aligning function; segments of spaced ridges or recesses is an alternative embodiment that also aids in properly positioning cartridge  300  within housing  102 . 
     FIG. 5 illustrates the second self-aligning feature of the present invention. Recessed region  502 , on the inside of housing  102 , receives complementary convex region  302  located on end cap  306 . In a preferred embodiment, the complementary surfaces are spherical in nature and centered in relation to fluid filter  100 . Other functionally equivalent alternative shapes and arrangements are also contemplated; however, the spherical shapes of the preferred embodiment provide the benefit of ease of manufacturing. The sloped nature of both concave region  502  and convex region  302  further assist in guiding cartridge  300  into proper position and alignment within housing  102 . 
     A second function of recess  502  and endcap convex region  302  is the elimination of a separate endcap spring (not shown) that is present in current fluid filter designs. By eliminating this spring element, cartridge  300  truly becomes the only element that needs to be replaced when reusing fluid filter  100  and thereby prevents improper insertion and positioning of the spring during assembly. In the preferred embodiment, spherical housing recess  502  has a radius approximately 0.01 inches smaller than spherical endcap convex region  302 . This slight size difference is not enough to effect the self-aligning function and provides downward pressure on cartridge  300  that was previously provided by a separate endcap spring. The downward pressure assists in ensuring all appropriate sealing surfaces within housing  102  are fluid-tight. 
     An alternative embodiment contemplated is to continue to use a separate endcap spring (not shown) in the design of fluid filter  100 . In this embodiment, endcap  306  would simply be manufactured as a straight piece (as illustrated in FIG.  1 ). However, when assembling this embodiment, an operator would have to ensure proper insertion and positioning of the endcap spring and rely solely on base plate  110  self-aligning ridges  402  to properly position cartridge  300 . 
     CONCLUSION 
     A system and method has been shown in the above embodiments for the effective implementation of replaceable filter element cartridge that is pre-assembled and engages self-aligning features within a reusable filter housing. While various preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims. For example, the present invention should not be limited by size, materials, connection methods, composition, or sealing elements.