Seal for cartridge-type filter assemblies
BACKGROUND OF THE INVENTION 
     The engine employed on a construction vehicle, such as a tractor, has a filter assembly mounted thereon to continuously filter oil during operation of the engine. As shown in FIG. 4 of applicant&#39;s drawing, the filter assembly may comprise a base B attached on the engine and a case C, enclosing a cartridge-type filter, mounted on the base. The open end of the case is disposed within an annular recess R formed on the base and a seal S is disposed within the recess and is compressed therein by the case. 
     Since the wall thickness of the case is less than the width of the recess, the case is oftentimes mounted on the base in an off-center relationship indicated at C&#39; whereby a portion S&#39; of the seal is extruded on one side of the case. Such extrusion gives rise to obvious sealing problems and the seal is usually sufficiently deformed and damaged so that it cannot be reused. In addition, upon replacement of the filter, a tool must be used to scrape the remnants of seal S out of recess R which not only increases service time but also damages the sealing surfaces defined by the recess. 
     SUMMARY OF THIS INVENTION 
     An object of this invention is to overcome the above, briefly described problems by providing an economical and reusable sealing means for filter assemblies which exhibits sealing and self-centering desiderata hereinafter more fully explained. 
     The seal is particularly adapted for use in a filter assembly comprising a base defining an annular recess therein and a filter and enclosing case mounted on the base. The annular sealing means is disposed within the recess for automatically centering an open end of the case therein and for also applying substantially equal sealing pressures against bottom and sidewalls defining the recess. 
     The sealing means preferably comprises an annular metallic insert, having a generally U-shaped cross section, defining a top wall and a pair of sidewalls connected thereto. An annular elastomeric member is molded as an integral part of the insert and comprises an outer sealing portion disposed exteriorly on the top and sidewalls of the insert to define three contiguous sealing surfaces adapted to intimately contact the wall portions defining the recess. The sealing means also preferably has a plurality of slots formed through the sidewalls thereof which are adapted to be engaged by a tool for removal purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Other objects of this invention will become apparent from the following description and accompanying drawing wherein: 
     FIG. 1 is a longitudinal sectional view of a filter assembly employing the sealing means of this invention therein; 
     FIG. 2 is an enlarged and partial perspective view of the sealing means; 
     FIG. 3 is an enlarged sectional view of the sealing means, generally taken within circle III--III in FIG. 1; and 
     FIG. 4 is a view similar to FIG. 3, but illustrating a prior art seal mounted in a filter assembly of the type generally illustrated in FIG. 1. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a filter assembly 10 comprising a base 11 adapted to be mounted on an internal combustion engine, for example. The filter is adapted to function in a conventional manner whereby crankcase oil is circulated therethrough to remove wear products and the like from the oil. The filter assembly further comprises an impervious case 12 and a cartridge-type filter 13 disposed within the case and releasably mounted on the base therewith by a bolt 14 in a cnventional manner. 
     Referring to FIGS. 2 and 3, this invention relates to an annular sealing means 15 disposed within an annular recess 16 defined on an underside of base 11. As will be hereinafter more fully understood, the annular sealing means functions to automatically center the open end of case 12 therein and also applies substantially equal sealing pressures against the bottom and sidewalls defining recess 16 in the base. The sealing means comprises an annular metallic insert 17 having an annular elastomeric member 18 molded as an integral part thereof. 
     Insert 17 has a U-shaped cross section defining a generally flat top wall 19 and a pair of sidewalls connected to the top wall to normally extend therefrom in diverging relationship. The sidewalls will thus provide a wedging action upon insertion of the sealing means in recess 16 to aid in providing the above-mentioned equalized sealing pressures within the recess and to also clamp case 12 therebetween. Elastomeric member 18, composed of a standard rubber or plastic based material employed for sealing applications, comprise an outer sealing portion disposed exteriorly on the top 19 and sidewalls 20 and 21 of insert 17 to define three contiguous sealing surfaces thereon. 
     The elastomeric member further comprises an inner portion 23 disposed within the cavity defined by the top and sidewalls of the insert. A plurality circumferentially spaced apertures 24 are formed through top wall 19 of the insert whereby the inner and outer portions of the elastomeric member are integrally connected to each other during the molding process whereby the composite sealing means is formed. A pair of radial flanges 25 and 26 are integrally formed on the bottom of sidewalls 20 and 21 of the insert, respectively, whereas a plurality of circumferentially disposed and equally spaced slots 27 and 28 are formed through such sidewalls. As shown in FIG. 3, the slots are disposed below inner portion 23 of the elastomeric member and are exposed below base 11. 
     Upon installation of case 12 and filter 13 on base 11, sealing means 15 is initially disposed in recess 16 with the top portion of the seal being maintained out of contact with the bottom wall of the recess, as indicated at 22&#39;. Upon tightening of bolt 14, case 12 will be drawn further into the recess to compress the three contiguous and outer sealing surfaces of elastomeric member 18 into sealing contact within the recess. Simultaneously therewith, normally diverging sidewalls 20 and 21 of the insert will tend to provide a wedging function in the recess whereby the case is clamped therebetween, i.e., the wall thickness of the case substantially equals the distance between inner surface portions of the sidewalls. 
     Upon servicing of the filter assembly for filter replacement purposes, bolt 14 is removed to thus permit removal of the case and filter from base 11. Although sealing means 15 could remain within recess 16 prior to the reinstallation of the case and a new filter thereon, the sealing means may be removed from the base for cleaning purpose. In particular, the workman need only insert a screw driver through apertures 27 and 28, also formed through outer sealing portion 22 of elastomeric member 18, to release the sealing means from the recess. 
     As briefly discussed above, FIG. 4 disclosed a prior art seal S which gives rise to sealing and filter replacement problems. Regarding the sealing problem, it should be noted that even the slightest off-center relationship of case C within recess R, as indicated at C&#39;, would tend to extrude a portion S&#39; of the seal to effect a non-uniform sealing pressure in the recess. In addition, oil pressures within the filter may tend to effect further extrusion of the seal to increase the sealing problem. 
     Thus, upon replacement of the filter the seal must be discarded and a new one reset in recess R. The workmen must also spend some time in scraping remnants of the old seal from the recess. Such scraping could cause indentations on the wall portions of the base defining recess R which would further increase the sealing problem thereat.