Abstract:
A filter element for filtering fluids and gasses flowing through a filter housing is provided. The filter element includes a permeable filter media for filtration of contaminants and a rigid frame for supporting and retaining the filter media. To ensure that gasses and fluids flow through the filter media rather than around the filter element, a resilient seal element is attached along an outer peripheral surface of the frame. The seal element can be resiliently compressed between the inner surface of the filter housing and the outer peripheral surface to create a sealing effect therebetween. To prevent the filter media from interfering with the seal element, the filter media is substantially constrained within the outer peripheral surface of the frame.

Description:
FIELD OF THE INVENTION 
   This invention pertains generally to fluid and gas filtration and more particularly to filter elements for filtering such fluids and gasses that can be received within filter housings through which those fluids and gasses flow. 
   BACKGROUND OF THE INVENTION 
   Filtration devices and systems are employed in a wide range of applications for filtering contaminants from various process fluids. For example, it is known to pass air or similar gasses through filter assemblies that enclose filtration media such as filter paper to remove dust and other contaminants. The filtration media is typically enclosed within a housing that is permanently fixated within a larger overall process system that utilizes the filtered air or gas. The filter media is often configured into a filter element or filter cartridge that can be removably received within the housing to remove the containments from the fluids or gasses flowing therein. Because of the potential for a single or primary filter element to be displaced or fail, and to prevent dislodged debris during installation or removal of the primary filter from entering the engine, it is known to provide a second or safety filter element typically downstream of the primary filter element. 
   One method of constructing such safety filter elements, as taught in U.S. Pat. No. 6,221,122 to Gieseke et al., herein incorporated by reference, involves a rigid support frame for supporting and retaining a planar sheet of flexible filter media. The planar sheet includes a skirt that is folded between the peripheral edge of the frame and an inner surface of the filter housing for creating a sealing effect therebetween and ensuring that process fluids and gasses flow through the safety filter element. The skirt when folded during slidable insertion of the filter element into the filter housing provides the potential for leak paths past the safety filter element. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention provides a filter element intended for use as a secondary or safety filter element that includes a rigid frame for supporting and retaining a filter media. The filter media is permeable and capable of filtering contaminants from process gasses flowing therethrough while the rigid frame is substantially non-permeable. To ensure that the process gasses and fluids flow through the filter media, the filter element includes a resilient seal element attached to an outer peripheral surface of the frame. When the filter element is received in a filter housing, the seal element resiliently engages the inner surface of the housing to provide a sealing effect therebetween. In an aspect of the invention, to prevent the filter media from interfering with the engagement between the seal element and the inner surface, the filter media is constrained or confined within the outer peripheral surface of the frame. 
   An advantage of the invention is that it provides for a seal between a filter element and a filter housing. Another advantage is that the invention prevents filter media from interfering with a seal created between the filter element and the filter housing. These and other advantages and features of the invention will become apparent from the following drawings and detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the invention, and together with the description serve to explain the principles of the invention. In the drawings: 
       FIG. 1  is a top perspective view of a filter element designed in accordance with the teachings of the invention to include a filter media, a frame, and a seal element. 
       FIG. 2  is cross-sectional view taken along line  2 - 2  of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of a filter assembly including the filter element of  FIG. 1  arranged as a secondary filter element with respect to a primary filter element. 
       FIG. 4  is a bottom perspective view of the outer ring component of the frame. 
       FIG. 5  is a top perspective view of the inner ring component of the frame. 
       FIG. 6  is an exploded view taken of the area indicated in  FIG. 2  illustrating the assembly of the outer and inner rings with the filter media. 
       FIG. 7  is a detailed view of the area indicated in  FIG. 2  illustrating the interlocking engagement of the outer and inner rings. 
   

   While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Now referring to the drawings, wherein like reference numbers refer to like elements, there is illustrated in  FIGS. 1 and 2  a filter element  100  through which process fluids and particularly gasses such as air may flow. The filter element  100  includes a filter media  102  for removing containments from the process gasses and a rigid frame  104  for supporting and retaining the filter media. The gas-permeable filter media  102  can be made from any suitable material including, for example, a fibrous non-woven filter material or, more preferably, polyester fiber. Likewise, the non-permeable rigid frame can be made from any suitable material including, for example, thermoplastic. As illustrated in  FIG. 3 , the filter element  100  is designed to be accommodated within a tubular filter housing  106  fixed within a larger overall system and preferably is to be used as a secondary or safety filter element located upstream or downstream of a primary filter element  108 . The primary filter element can be constructed from a corrugated, multilayered sheet having a plurality of fluted channels. 
   Referring back to  FIGS. 1 and 2 , the filter element  100  includes a first face  110  and a spaced-apart second face  112  that define the overall height, designated as  114 , of the filter element. In operation, process gasses impinge upon either the first or second faces  110 ,  112 , flow through the filter media  102  and out the opposite face. In the illustrated embodiment, the filter element  100  including the rigid frame  104  are circular in shape and define an axis line  116  but in other embodiments could have other shapes such as oval, rectangular, etc. Accordingly, geometric references such as “annular,” “ring-shaped,” and the like are intended to encompass these and other shape alternatives. 
   To ensure that process gasses flow through the filter media  102  and not between the filter element  100  and the inner surface of the filter housing, the filter element includes a resilient seal element  120  attached to the outer peripheral surface  122  of the frame  104 . The outer peripheral surface  122  is oriented to oppose the inner surface of a correspondingly shaped filter housing. In the illustrated embodiment, the resilient seal element  120  is shaped as a uniform band that extends continuously about the frame  104 , though in other embodiments, the seal element can be configured in different shapes such as, for example, an O-ring. It will be appreciated that when the filter element  100  is axially inserted into the correspondingly shaped housing, the seal element  120  will be compressed between the inner surface of the housing and the outer peripheral surface  122  of the frame  104  to provide a sealing effect. Because of its uniform shape and resilient properties, the seal element  120  will compress and distort so as to avoid creating creases or folds, thereby eliminating potential leak paths. 
   The resilient seal element  120  can be made from any suitable resilient, compressive material, including for example urethane foam and foamed nitrile rubber. Preferably, the resilient seal element is made from foamed urethane tape having an adhesive backing. The adhesive backing on the urethane tape provides a convenient way of attaching the seal element  120  to the frame  104 . In other embodiments, the resilient seal element can be attached by dimensioning the seal element to provide a compressive fit about the outer peripheral surface of the frame. 
   To prevent the filter media  102  from interfering with the seal created between the seal element  120  and the inner surface of the filter housing, the filter media is preferably constrained or confined within the frame  104 . Referring to  FIG. 2 , to prevent displacement of the retained filter media  102  with respect to the frame  104  during operation, the frame includes various support ribs  124 ,  126  that extend across the first and second faces  110 ,  112  and thereby sandwich the filter media. Furthermore, the outermost portion or edge  128  of the filter media  102  is circumscribed and confined within the outer peripheral surface  122  of the frame  104 . Accordingly, even when a flexible filter media is utilized in the filter element, the frame restrains the filter media from shifting or repositioning itself between the seal element and filter housing. In addition to constraining the filter media  102 , the frame  104  also positions and supports the seal element  120  against the inner surface of the filter housing. 
   The rigid frame  104  to which the seal element  120  is attached is a two part structure including an outer ring  130  and an inner ring  132 , both having an annular shape. In the illustrated embodiment in  FIGS. 4 and 5 , both the outer and inner ring  130 ,  132  are circular and extend about the axis line  116  with the inner ring having a smaller diameter and situated inside of the outer ring. Referring to  FIG. 4 , the outer ring  130  has a generally thin, annular wall  134  that extends continuously about and is arranged parallel to the axis line  116 . The first plurality of support ribs  124  are joined to and extend across the annular wall  134  to provide a lattice structure that prevents displacement of the filter media. Referring to  FIG. 5 , the inner ring  132  also has a thin annular wall  136  that extends about the axis line  116  and a second plurality of support ribs  126  that extend across the annular wall. The outer and inner rings can be made from any suitable material including, for example, thermoplastic. 
   To engage the outer and inner rings  130 ,  132 , the first and second annular walls  134 ,  136  can be formed with an interlocking shoulder and groove feature. For example, referring to  FIG. 4 , a shoulder  140  can protrude from the inner surface  144  of the first annular wall  134 . The shoulder  140  can extend, as illustrated, intermittently along the inner surface  144  breaking to accommodate the support rib—annular wall joints  148  or, in other embodiments, can extend continuously along the inner surface. As illustrated in  FIG. 5 , a corresponding groove  142  is disposed into the outer surface  146  of the second annular wall  136 . 
   To assemble the filter element, referring to  FIGS. 6 and 7 , the inner ring  132  and filter media  102  are pressed axially into the outer ring  130  until the shoulder  140  and groove  142  align and interlock. As will be appreciated, making the outer and inner rings from thermoplastic material allows limited distortion of annular walls to facilitate assembly while still providing sufficient rigidity for the frame, especially when the outer and inner rings are interlocked. The seal element  120  can be attached to the outer peripheral surface  122  either prior to or after assembly of the outer and inner rings  130 ,  132 . 
   As illustrated in  FIG. 7 , when the outer and inner rings are interlocked, the outermost portion  128  of the filter media  102  becomes held between the first and second annular walls  134 ,  136  and is pinched by the shoulder and groove  140 ,  142 . Hence, the filter media  102  is securely retained to the frame  104 . Furthermore, this outermost portion  128  of the filter media  102  abuts against and is constrained by the inner surface  144  of the first annular wall  134 , thereby preventing the filter media from interfering with the seal element  120 . 
   Referring back to  FIG. 2 , in the illustrated embodiment it will be appreciated that to enable the inner and outer rings  130 ,  132 , including the support ribs  124 ,  126 , to properly engage, the heights of the annular walls  134 ,  136  differ. Specifically, the height of the first annular wall  134  dimensionally corresponds to the overall height  114  of the filter element  100  as measured between the first and second faces  110 ,  112 . The height of the second annular wall  136 , designated by reference number  118 , is dimensionally less than the height  114  of first annular wall  134 . When assembled, the second annular wall  136  is therefore spaced-apart from the second face  112  thereby providing a clearance for the first plurality of support ribs  124  to extend across the first annular wall  134  and adjacent to the second face. 
   Thus, the invention provides a filter element that can be removably inserted into a correspondingly shaped filter housing. The filter element includes a filter media for removing containments and a rigid frame for retaining and supporting the filter media. To create a seal between the filter element and the inner surface of the filter housing, a resilient seal element is attached to a peripheral outer wall of the frame. When the filter element is inserted into the housing, the resilient seal element is compressed between the inner surface and peripheral wall of the rigid frame. 
   All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
   The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
   Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.