Patent Document

TECHNICAL FIELD  
         [0001]    The present invention relates to an improved, spin-on high-pressure fluid filter of the type having a bead-lock arrangement in lieu of a rolled lock seam to secure the cover to the housing, wherein the improvement comprises the use of a low-cost cover assembly formed from stamped metal plates, as well as a method of assembly thereof.  
         BACKGROUND OF THE INVENTION  
         [0002]    Spin-on filters have been employed in a variety of applications including hydraulic systems and engine lubrication systems. Such filters generally include a filter element within a housing with a cover or nut plate secured at one end of the housing by which the filter can be screwed onto or off of a filter head. A central opening surrounded by a plurality of smaller openings is provided in the cover to direct flow through the filter element contained within the housing of the filter. In an inside/out flow arrangement, pressurized, unfiltered fluid (such as the lubricating oil used in a diesel engine) enters the central opening and exits through the surrounding openings after passing through the filter element within the housing. In an outside/in flow pattern, the pressurized, unfiltered fluid enters the surrounding-openings and-exits through the central opening after passing through the filter element. A circular gasket is provided on a top surface of the cover to serve as a seal between the filter and the filter head. A spring is provided at the lower end of the housing to push the filter element in sealing engagement with the underside of the nut plate that forms the cover.  
           [0003]    Although satisfactory in low and medium applications, generally spin-on filters of the prior art have not been satisfactory for use in high-pressure applications such as in hydraulic transmission pumps, where surges of 1,000 psi or more can occur. Most spin-on filters currently available include covers constructed of a stamped steel disk, and a relatively thinner secondary disk spot welded thereto. The base disk includes an extruded, relatively shallow, internally threaded neck portion by which the filter can be connected to a filter head. Flow openings are punched into the base disk around the neck portion. The lip at the open end of the housing is connected, by means of a rolled lock seam, to the periphery of the secondary disk which is also formed to serve as a seat for the external gasket. In this design, fatigue failure is most likely to occur at the rolled lock seam or at the spot welds. A burst failure is most likely to occur either upon bending of the cover (which allows leakage to pass the external gasket) or upon unfolding of the rolled seam. Thus, prior art spin-on filters have been susceptible to failure at the cover and/or at the connection between the cover and housing. Welding of the housing and cover is often unacceptable due to the incompatibility of housing and cover materials such that a satisfactory weld cannot be formed.  
           [0004]    To solve these problems, the applicants developed a novel high-strength, spin-on filter in which a reliable and durable seal between the cover and the open end of the housing was achieved without the use of either a rolled lock seam, or a weld by means of a bead-lock arrangement. This filter is described and claimed in U.S. Pat. No. 5,080,787, assigned to the Fleetguard, Inc., the entire specification of which is incorporated herein by reference. In this particular filter, a round cover formed from die-cast metal is provided which is circumscribed around its outer edge by both an upper, C-shaped groove and a lower groove having a rectangular cross section which seats an O-ring. The die-cast cover further includes a centrally located, threaded aperture which can be screwed onto the nipple of a filter head, and a plurality of oil outlet openings surrounding the threaded, centrally-located aperture. On the top surface of the die-cast cover, a circular groove is provided which circumscribes the outlet openings that surround the threaded aperture. This groove receives a gasket which creates a seal between the top surface of the cover of the filter and the filter head when the threaded aperture of the filter cover is screwed onto the threaded nipple of the filter head. In the method of assembling this prior art filter, the filter element is first placed into the interior of the housing. An O-ring is then seated around the second groove which circumscribes the lower part of the die-cast cover, and the cover is then inserted into the open end of the housing until the C-shaped groove which circumscribes the upper portion of the housing is positioned adjacent to the upper periphery of the housing. A roller is then used to inwardly deform the metal around the periphery of the housing in conformance with the C-shaped groove in the cover in what is known in the art as a “spin beading” operation. The spin-beading secures-the cover to the housing without the need for rolled lock seams which, as previously pointed out, are proven to rupture when exposed to high pressures. The use of a spin-beading operation to secure the cover to the housing, instead of a lock seam, allows this filter to be assembled rapidly and inexpensively.  
           [0005]    While the filter disclosed and claimed in U.S. Pat. No. 5,080,787 represents a substantial advance in the art, the applicants have observed two areas where improvement would be desirable. First, while the die-cast cover used in this filter works well for its intended purpose, it is unfortunately expensive as compared to covers formed from one or more stamped metal plates. Secondly, because the seal between the cover and the housing is dependent upon the proper compression of the O-ring between the cover and the housing, the dimensional tolerances of the O-ring, and the depth of the groove in the cover that seals it are narrow. These narrow tolerances prevent the substitution of a less precisely dimensioned, but lower cost lathe-cut gasket for the O-ring. Thirdly, when the cover is inserted into the open end of the housing incident to the assembly operation, sheer forces are applied to the O-ring that has been previously seated around the lower circumferential groove of the cover which are capable of either damaging the O-ring, or rolling it out of the lower circumferential groove of the cover, thereby destroying the cover seal. While the application of a lubricant to the seated O-ring prior to the insertion of the cover into the housing solves much of this problem, it also adds an unwanted step in the assembly operation.  
           [0006]    Clearly, it would be desirable if an improved filter could be developed which maintained all of the structural and assembly advantages associated with the filter disclosed and claimed in the &#39;787 patent, but whose cover could be replaced with a lower cost cover assembly formed from stamped metal plates and lathe-cut gaskets. It would further be desirable if the assembly of such an improved filter did not apply unwanted sheer forces onto any of the sealing O-rings or gaskets during the assembly of the filter, and did not require the application of any O-ring or gasket lubricants.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the present invention to provide an improved filter which maintains all of the advantages associated with the filter disclosed and claimed in U.S. Pat. No. 5,080,787, but which is less expensive and easier to manufacture.  
           [0008]    It is a further object of the invention to provide such an improved filter which utilizes a relatively inexpensive cover assembly formed from stamped metal plates and lathe-cut gaskets, and which does not require the application of any lubrication to the sealing gaskets.  
           [0009]    Finally, it is an object of the invention to provide an improved filter in which none of the O-rings or sealing gaskets is subjected to sheer forces; during the assembly of the filter which could either damage or misalign the sealing gaskets.  
           [0010]    To this end, the filter of the invention comprises a housing having a periphery that includes an inwardly deformed portion, and a cover assembly including a cover plate means and a retainer plate means having mutually spaced apart outer edges for forming a recess that receives the inwardly deformed portion of the housing. A gasket means is disposed in the recess defined by the mutually spaced apart outer edges for effecting a seal between the outer edge of the cover assembly and the inwardly deformed portion of the housing when said portion is inwardly deformed incident to a spin-beading operation.  
           [0011]    In the preferred embodiment, both the cover plate means and the retainer plate means are formed from a stamped metal, such as steel. Additionally, the retainer plate means further includes a deformed portion located inside of its outer edge that defines a groove for receiving a second gasket means for effecting a seal between the cover assembly, and a filter head. One of the walls of the deformed portion of the retainer plate means may function to compress the first gasket means when this gasket means is engaged by the spin-beaded portion of the housing. Finally, the deformed portion of the retainer plate means may have an exterior portion that acts as a spacer to uniformly space apart the outer edges of the cover plate means and retainer plate means.  
           [0012]    The outer edges of the retainer plate means may be dimensioned to extend over the periphery of the housing to limit the extent to which the cover assembly may be inserted into the housing during the assembly thereof. These outer edges may be deformed into frictional engagement with the inwardly deformed portion of the housing to prevent relative rotation between the cover assembly and the filter housing when the filter is screwed into a nipple of a filter head.  
           [0013]    The invention also encompasses a method of forming such a fluid filter which comprises the steps of providing a filter housing as previously described, placing a filter element within the housing, forming a cover assembly with first and second plate means by interconnecting the two plate means together so that they have mutually spaced apart outer edges that define a recess, seating a gasket means in the recess, inserting the cover assembly into the open end of the housing such that the periphery of the filter housing is adjacent to the recess, and deforming at least some of the housing periphery inwardly into the recess to both secure and seal the cover assembly to the housing.  
           [0014]    The method of the invention may further comprise the step of stamping a deformed portion in the first plate means that is offset with respect to the outer edge of the first plate means, and using this offset portion to uniformly space apart the outer edges of the first and second plate means to form the recess. In the preferred method of the invention, the deformed portion of the first plate means defines a groove, and the method further includes the step of seating a second gasket means in the groove which forms a seal between the filter and a filter head when the filter is secured onto the head.  
           [0015]    The improved filter allows the cover assembly to be made of inexpensive stamped steel plates, and further allows the substitution of a less expensive lathe-cut gasket for the O-ring used in the prior art. The improved filter also obviates the need for applying potentially damaging sheer forces to the gasket that seals the cover assembly to the housing, or lubricants to minimize the damaging effects of such forces, as the gasket does not engage the housing until the bead rolling step. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a cross-sectional side view of the improved filter of the invention as it would appear mounted on a filter head;  
         [0017]    [0017]FIG. 2 is a plan view of the improved filter of the invention with the filter head gasket removed;  
         [0018]    [0018]FIG. 3 is an enlarged view of the portion of FIG. 1 enclosed by a dashed square, and  
         [0019]    [0019]FIG. 4 is a cross-sectional side view of both the improved filter of the invention and the roller mechanism which inwardly deforms the upper peripheral portion of the filter housing to both secure and seal the cover assembly of the filter to the housing. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    With reference now to FIGS. 1 and 2, the improved filter  1  of the invention is particularly adapted to be mounted in sealing engagement against a filter head  3  of the type typically used in the lubrication systems of diesel engines. Such a filter head  3  includes a centrally disposed threaded nipple  4  onto which the filter  1  is spun-on in sealing engagement.  
         [0021]    The filter  1  itself generally comprises a cylindrical housing  5  formed from drawn steel, and a cover assembly  6 . The housing  5  includes an integrally formed, closed bottom end  7 , and a open top end  9  circumscribed by an upper peripheral portion  10 . An annular filter element  11  is disposed in the interior of the housing  5 . The filter element  11  is sealingly captured between top and bottom filter element retainers  13  and  15 , respectively. The top filter element retainer  13  includes a centrally disposed aperture  17  for admitting the distal end of the threaded nipple  4  of the filter head, as well as an annular recess  18  which receives the upper end of the filter element  11 . The bottom filter element retainer  15  includes a centrally disposed, circular wall  19  which is circumscribed by an annular recess  20  which in turn sealingly receives the bottom portion of the annular filter element  11 . A spring  21  applies a compressive force between the closed bottom end  7  of the housing  5  and the circular wall  19  of the bottom filter element retainer  15  in order to bias the top filter element retainer  13  in sealing engagement against an annular seal  23 . This seal  23  includes upper and lower flanges  24   a ,  24   b  for simultaneously sealing both the inner edge, and the inner top portion of the top filter element retainer  13  with respect to the outer diameter of the threaded nipple  4 , and the cover assembly  6 , respectively.  
         [0022]    With reference now to FIGS. 2 and 3, the cover assembly  6  of the improved filter  1  generally comprises a relatively thick cover plate  25  (typically referred to as a “nut plate” in the art), in combination with an annular retainer plate  27 . Both the cover plate  25  and retainer plate  27  are preferably formed from stamped steel. The cover plate  25  has a central opening  29  for the admission of pressurized, unfiltered fluid (such as unfiltered lubricating oil) from the threaded nipple  4  of the filter head  3 . The central opening  29  is circumscribed by an annular bent portion  30  which terminates in a threaded flange  31  as shown. The screw threads on the flange  31  are, of course, compatible with the screw threads on the exterior of the threaded nipple  4 . Circumscribing the threaded flange  31  are a plurality of peripheral openings  33  which act as flow outlets for admitting a flow of filtered fluid back up into an annularly-shaped flow inlet  35  of the filter head  3  that is concentrically disposed around the exterior of the nipple  4 . The cover plate  25  terminates in an outer edge  37  whose diameter is slightly less than the inner diameter of the housing periphery  10 .  
         [0023]    The retainer plate  27  of the cover assembly  6  includes a centrally disposed, circular opening  40  which is slightly smaller than the diameter of the flow inlet  35  of the filter head  3 . In its inner portion, the retainer plate  27  includes an annular deformed portion  42  having a U-shaped cross section as is most clearly seen in FIG. 3. This U-shaped deformed portion  42  includes inner and outer side walls  43   a, b , respectively, as well as a bottom wall  44 . The retainer plate  27  is affixed over the top surface of the cover plate  25  by a plurality of spot welds  45  between the bottom wall  44  of the U-shaped deformed portion  42 , and the top surface of the cover plate  25 . A filter head gasket  46  is seated within the U-shaped deformed portion  42 . This gasket  46  has an upper, tapered sealing surface  46 . 5  which is complimentary in shape to a frustro-conical shoulder  47  which extends down from and circumscribes the-flow inlet  35  of the filter head  3 . When the cover plate  25  of the cover assembly  6  is screwed onto the nipple  4  of the filter head  3  in the position illustrated in FIG. 1, the annular bent portion  30  of the cover plate  25  applies a compressive spring force against the bottom wall  44  of the U-shaped deformed portion  42  of the retainer plate  27  to squeeze the complimentary top surface  46 . 5  of the gasket  46  into seating engagement with the frustro-conical shoulder  47  of the filter head  3 . To prevent the inner and outer side walls  43   a, b  from spreading in response to the compressive force applied to them by the filter head gasket  46 , the retainer plate  27  is further provided with inner and outer bead-like shoulders  49  and  51  at the top of the inner and outer side walls  43   a, b , respectively. These shoulders  49 ,  51  are preferably formed by stamping in order to work harden the upper portions of the side walls  43   a, b , thereby rendering them stronger.  
         [0024]    In its outer portion, the retainer plate  27  terminates in an outer edge  53  which overhangs the outer edge  37  of the retainer plate  27 . This outer edge  53  is formed by inwardly bending a circular flange  55  that forms the outer edge of the retainer plate  27  prior to the assembly of the filter  1 , as may be best understood with reference to FIG. 4. It is important to note that the outer diameter of the circular flange  55  of the retainer plate  27  is larger than the inner diameter of the upper peripheral portion  10  of the housing  5  such that the flange  55  limits the extent to which the cover assembly  6  may be inserted into the open top end  9  of the housing  5  during the assembly method.  
         [0025]    The outer edges  37  and  53  of the cover plate and retainer plate, along with the outer side walls  43   b  of the U-shaped deformed portion  42 , form a generally square recess  57  into which a gasket  59  having a generally rectangular cross section is seated. While virtually any gasket may be used in this application, gasket  59  is preferably of the inexpensive, lathe-cut variety in order to minimize the production expenses associated with the improved filter  1 . As may best be seen with respect to FIG. 3, the gasket  59  is compressed against the outer side wall  43   b  of the U-shaped deformed portion  42  of the retainer plate  27  by a C-shaped, inwardly deformed portion of the housing periphery  10  in order to form an effective seal between the outer edge of the cover assembly  6 , and the upper peripheral portion  10  of the housing  5 .  
         [0026]    In operation, the improved filter  1  is first mounted on the filter head  3  by screwing the threaded flange  31  over the threaded nipple  4  into the position shown in FIG. 1. Pressurized, unfiltered fluid flows through the threaded nipple  4  and into the center portion of the interior of the housing  5 , where it is forced through the inner diameter of the annular filter element  11 . The sealing engagement between the top and bottom portions of the filter element  11 , and the bottom filter element retainer  15 , top filter element retainer  13 , and annular seal  23 , does not allow the pressurized fluid flowing in from the nipple  4  to flow anywhere but through the filter element  11 . Once the pressurized fluid has passed completely through the filter element  11 , it flows through the annular space defined between the outer diameter of the filter element  11 , and the inner diameter of the housing  5 , where it collects and eventually flows through the flow outlets  33  defined in the cover plate  25 . From the flow outlets  33 , the filter fluid then flows into the annular flow inlet  35  of the filter head  3 . The compressed, lathe-cut gasket  59  disposed between the cover assembly  6  and the upper peripheral portion  10  of the housing  5  prevents pressurized fluid from escaping through this inner face, while the filter head gasket  461  prevents filtered, pressurized fluid from flowing out between the inner face between the filter  1 , and filter head  3 .  
         [0027]    The method of assembly of the filter  1  may best be understood with respect to FIG. 4. Prior to assembly, the housing  5  is circumscribed by an orthogonally disposed, peripheral flange  63  (indicated in phantom). Similarly, the retainer plate  27  of the cover assembly is circumscribed by a circular flange  55  (again indicated in phantom) whose outer diameter is greater than the inner diameter of the upper peripheral portion  10  of the housing  5 . As has been previously indicated, the outer diameter of the outer edge  37  of the cover plate  25  is slightly less than the inner diameter of the upper peripheral portion  10  of the housing  5 . Prior to the insertion of the cover assembly  6  into the housing  5 , the lathe-cut gasket  59  is seated in the recess  57  defined between the outer edges  37  and  53  of the cover plate  25  and retainer plate  27 , respectively, and the outer side wall  43   b  of the U-shaped deformed portion  42  of the retainer plate  27 . The outer diameter of the gasket  59  should be somewhat shorter than the outer diameter of the outer edge  37  of the cover plate  25 . Such dimensioning of the outer edges of the cover plate  25 , retainer plate  27 , and gasket  59  allows the cover assembly to be easily inserted over the open top end  9  of the housing  5  into position illustrated in FIG. 4 until the circular flange  55  of the retainer plate  27  abuts the peripheral flange  63  of the housing in the positions shown in phantom. Advantageously, during the cover insertion step of this method, no sheer forces of any kind are applied to the gasket  59 . As the cover assembly requires essentially no force to be inserted into the open top end  9  of the housing, the cover assembly is pushed down against the annular seal  23  with only enough force to overcome spring  21 .  
         [0028]    After the cover assembly  6  has been inserted into the upper peripheral portion  10  of the housing  5 , a swaging roller  65  having a rounded edge  67  which terminates in a stepped portion  69  forcefully engages the upper peripheral portion  10  of the housing  5  to deform the peripheral flange  63  into the C-shaped deformed portion  61 . The inner diameter of this deformed portion  61  compresses the gasket  59  such that a fluid tight seal is formed between the outer edge  37  of the cover plate  25 , the outer side wall  43   b  of the U-shaped deformed portion  42  on the retainer plate  27 , and the inner diameter of the C-shaped deformed portion  61  of the housing periphery  10 . This same C-shaped deformed portion  61  also further serves to mechanically interconnect the cover assembly  6  with the housing  5  by forming an interference type joint between the housing  5 , and the recess  57  defined between the outer edges of the cover plate  25  and retainer plate  27 , which in turn maintains the inner bent portion  30  of the cover plate  25  in sealing engagement against the annular seal  23 .  
         [0029]    In the final step of the method of assembly, the circular flange  55  of the retainer plate  27  is folded around the top edge of the C-shaped deformed portion  61  of the housing periphery  10  into the position illustrated. Such a folding of the flange  55  accomplishes three purposes. First, it creates a smooth, rounded edge that covers the relatively sharp edge of the C-shaped deformed portion  61 , thereby rendering the improved filter  1  safer to manually handle. Secondly, it increases the mechanical coupling between the cover assembly  6 , and the housing  5 . Thirdly, it provides a final sealing barrier between the cover assembly  6 , and the housing  5 , should the seal formed by the gasket  59  fail.  
         [0030]    Industrial Applicability  
         [0031]    The present invention provides a high strength filter capable of withstanding high pressures without failure occurring between the filter housing and a cover assembly formed from low cost, stamped steel plates. The structure of the cover assembly allows it to be inserted into the housing without the application of sheer forces to the sealing gasket. The filter housing is joined to the cover utilizing a simple spin beading operation which deforms the housing into a recess defined in the sidewall of the cover by the spaced apart outer edges of the stamped steel cover plate and retainer plate that forms the cover assembly, without substantially stretching or thinning of the housing sidewall. A single spin beading step both seals and couples the cover assembly to the housing. While the present invention is particularly suitable for filtering liquids in which high hydrostatic and hydrodynamic forces are incurred, it should be apparent to one of ordinary skill that inventive features are also applicable to other fluid filter applications.

Technology Category: b