Abstract:
A filter element ( 10 ) comprises a pleated filter media ( 34 ) having spaced apart pleats ( 40 ) and an external filter media surface ( 38 ) comprising the external peaks of the pleats ( 40 ) and a flexible foam filter media sleeve ( 42 ) in contact with the external filter media surface ( 38 ). The filter media sleeve ( 42 ) maintains the spacing between the external peaks of the pleats ( 40 ) of the pleated filter media ( 34 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to filter elements and, more particularly, to standard and coreless filter elements having pleated filters.  
           [0003]    2. Brief Description of the Prior Art  
           [0004]    Fluid systems often include an in-line filtration system for filtering out particles or other impurities in the fluid. The in-line filtration systems generally include a housing forming a hollow center chamber, a fluid inlet port, and a fluid outlet port. A replaceable filter element, usually forming a plurality of pleats, is positioned inside the hollow center chamber of the housing. An example of such a pleated element is disclosed in U.S. Pat. No. 3,552,553 to Redding. The fluid enters the inlet port of the filter, which is generally positioned at an outer edge of the housing, flows through the replaceable filter element, and exits the outlet port which is usually positioned adjacent a center portion of the housing.  
           [0005]    One drawback of filters having pleated filtering elements is that the spacing of each individual pleat can vary as the differential pressure of the fluid passing through the pleats is increased. Upon filtration of high viscosity oil, for example at cold start-up, the pleats may move toward one another causing bunching which restricts the flow of fluid flowing through the filter and also decreases the effectiveness of the filter.  
           [0006]    One approach to overcoming this problem is disclosed in PCT application WO 97/31695. That application discloses using a spun-bonded support disposed within a cylindrical, internal cavity formed by a pleated filter element. Internal peaks of the filter element, formed by the pleats, are glued to the support wrap to increase the stability of the filter element and maintain separation of the pleats. One drawback of that approach is the manufacturing and material costs associated with accurately fixing the internal peaks of the pleats to the support wrap such that the pleats are evenly spaced.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a filter element generally including a pleated filter media forming an external media surface comprised of the external pleat peaks with each filter pleat being fixed spaced apart from a neighboring pleat. A filter media sleeve is positioned adjacent the external media surface of the filter media, wherein the filter media sleeve is in contact with the external filter media surface to maintain the separation between each pleat.  
           [0008]    The filter element according to the present invention may be manufactured by positioning the filter media sleeve adjacent to the external filter media surface and then compressing the filter media sleeve partially into indentations formed between each pleat of the filter media. Alternatively, the filter media sleeves can be preformed with ridges and valleys that correspond to opposing ridges and valleys in the external filter media surface of the filter media.  
           [0009]    These and other advantages of the present invention will be clarified in the description of the preferred embodiment taken together with the attached drawing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0010]    [0010]FIG. 1 is an exploded view of one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    The preferred embodiment of the present invention is generally shown in FIG. 1 showing a filter  10  having a first end  12  and a second end  14 . A first end cap  16  is positioned adjacent the first end  12  of the filter  10 . The first end cap  16  is provided with a groove  18  in the interior surface of hollow cylindrical cavity  20 . An O-ring  22  is received in the groove  18  of the first end cap  16 .  
         [0012]    A filter assembly  24  is positioned adjacent the first end cap  16 . The filter assembly  24  generally includes a hollow perforated tube  26  with perforations  28  formed therethrough, an internal tubing surface, an external tubing surface  32 , and a pleated filter media  34 . The tube  26  is preferably formed from polypropylene, nylon, or other suitable material. The pleated filter media  34 , having an internal filter media surface  36  comprising internal pleat peaks and an external filter media surface  38  comprising external pleat peaks, is positioned with the internal media surface  36  adjacent the external tube surface  32  of the tube  26 . The internal filter media surface  36  and the external filter media surface  38  bound a plurality of individual pleats  40 . The peaks of each pleat  40  are preferably spaced from peaks of a neighboring pleat  40  by a uniform distance. The pleated filter media  34  is preferably formed from cellulose, glass, or other suitable material.  
         [0013]    A filter media sleeve  42 , having an internal sleeve surface  44  and an external sleeve surface  46 , is positioned adjacent the external filter media surface  38  of the pleated filter media  34 . The filter media sleeve  42  is preferably formed from reticulated flexible ether foam, approximately 0.16 cm to 2.5 cm thick T. However, the thickness can be increased or decreased depending on the size or application of the filter  10 . One such foam is sold under the SIF trademark and is available commercially from Foamex International Inc., 1000 Columbia Avenue, Linwood, Pa. 19061. It is a reticulated flexible polyurethane foam, characterized by a three-dimensional skeletal structure of strands which provide void space. With controlled pore sizes ranging from 1 pore per linear cm to 50 pores per linear cm, it offers uniformity.  
         [0014]    The internal sleeve surface  44  of the filter media sleeve  42  is in direct physical contact with the external filter media surface  38  of the pleated filter media  34 . A support sleeve  48 , preferably formed from polypropylene, nylon, or other suitable material, may be used to hold the filter media sleeve  42  in constant contact with the external filter media surface  38  of pleated filter media  34 . The support sleeve  48  is provided with a plurality of orifices  50  and an internal support sleeve surface  52 .  
         [0015]    A second end cap  54  is positioned adjacent the second end  14  of the filter  10  with the second end cap  54  provided with a groove  56  in the interior cylindrical surface in the hollow cylindrical cavity  58 , wherein an O-ring  60  is received in the groove  56 . The O-rings  22 ,  60  are preferably formed from rubber, synthetic rubber, nylon, or other suitable material. A handle  62  is attached to the second end cap  54  by pins  66 .  
         [0016]    The filter media sleeve  42  can be preformed with ridges and indentations that correspond to the external peaks of the pleats  40  of the pleated filter media  34 . Alternatively, the filter media sleeve  42  can be wrapped around or positioned adjacent pleated filter media  34  and compressed by the support sleeve  48  partially into the spaces formed between the pleats  40 .  
         [0017]    It has been found that positioning the filter media sleeve  42  in direct contact with the external surface of the pleated filter media  34 , without adhesive, keeps the pleats  40  from bunching together during flow of a fluid through the pleated filter media  34 . This antibunching effect helps prevent flow resistance exerted on the fluid during movement through the pleated filter media  34 .  
         [0018]    Having thus described our invention with the detail and particularity required by the Patent Laws, what is desired protected by Letters Patent is set forth in the following claims.