Abstract:
A filter element with a replaceable filtration panel held in place in a frame by elastic straps. A course support screen may be included atone side of the filtration panel.

Description:
REFERENCE TO EARLIER FIELD APPLICATION 
   The inventor claims the benefit of U.S. provisional patent application No. 60/383,669 entitled Filter Devices filed May 28, 2002. 

   TECHNICAL FIELD 
   This invention relates to a filter element for a heating, ventilating and cooling. system generally referred to as a HVAC system. 
   BACKGROUND OF THE INVENTION 
   HVAC systems typically have a plurality of return air ducts, each of which is provided with an air inlet covered by a hinged or removable louver or screen. The inlet also includes a frame for supporting a replaceable quadrilateral filter element. The typical replaceable filter element includes a cardboard frame and a fibrous mesh panel or similar filtration material which may be held in place by grids or large mesh screens. Also pleated filter panels have been used in replaceable filter elements. 
   The filter elements in HVAC systems are replaced periodically in order to insure effective filtration of air. Replacement of the filter elements several times a year results in a considerable expense to occupants and owners of buildings. 
   Heretofore a variety of fluid filters have been heretofore been proposed. Pleated air filters are disclosed in a U.S. Pat. No. 4,199,387 issued Apr. 22, 1980 to S. M. Hladik for an Air Filter Fabrication Method, in U.S. Pat. No. 4,042,358 issued Aug. 16, 1977 to S. H. Frohmader for a Filter Media and in U.S. Pat. No. 5,167,740 issued Dec. 1, 1992 to U. Michaelis et al. for a Method of Making a Filter Element Insert of Nonwoven Material in the Form of a Pleated Pack. Filter elements for liquids are disclosed in U.S. Pat. No. 4,629,474 issued to D. I. Thornton for a Thermally Formed Filter and in U.S. Pat. No. 5,456,836 issued Oct. 10, 1995 to A. B. Jeffery et al. for a High Efficiency, Self-Supporting Filter Element Make From Fibers. 
   SUMMARY OF THE INVENTION 
   It is an object of this invention to reduce the cost of replacing filter elements in a HVAC system. It is a further object of this invention to permit easy replacement of the filtration material of a filter element. The filter element includes a quadrilateral frame, a filtration panel in the frame, a course grid in the frame at one side of the filtration panel and an elastic strap across each of the four corners of the frame at the other side of the filtration panel. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the invention is illustrated in the accompanying drawings, in which: 
       FIG. 1  is an exploded view of a filter element 
       FIG. 2  is a perspective view of the filter element and 
       FIG. 3  is a section view taken along line  3 — 3  in FIG.  2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1-3 , a filter element  11  includes a quadrilateral frame  12  formed of four L section sides which produces a flat rim  13  with a quadrilateral window  14  and four side walls  16 ,  17 ,  18   19  secured to the four outer edges of the rim  13 . The four side walls  16 ,  17 ,  18 ,  19  extend perpendicular to the outer edges of the flat rim  13  and form four box-like comers therewith. The window  14  is covered by a course grid  21  with large openings and rests on the rim  13  at the inner side of the walls  16 ,  17   18   19 . The course grid  21  serves as a support for one side of a flat removable filtration panel  26  made of pliant fibrous material. The filtration panel  26  is held in place in the frame  12  by four elastic retention straps  31 ,  32 ,  33 ,  34  extending diagonally across the four comers of the frame  12  with ends secured, as by fasteners  36 , to the side walls  16 ,  17 ,  18 ,  19  of the frame  12 . The frame  12  may be made of a aluminum cardboard, stiff fibrous material or plastic and the grid  21  is preferable made of a relatively stiff plastic. 
     FIG. 2  shows the filtration panel  26  held in place in the frame  12  against the grid  21  by the straps  31 ,  32 ,  33 ,  34 . The grid  21  may also be held in place in the frame  12  by the straps or it may be fastened to the rim  13  by a suitable adhesive. The frame  12  and the grid  21  may be made of a plastic and the grid  21  may be secured to the frame  12  by fusion. When positioned the filter element  11  is installed in the inlet of the air return duct, not shown, of a HVAC system, the filtration panel  26  is on the air intake side of the grid  21  and the return air tends to hold the filtration panel  26  against the grid  21 . Thus the upstream side of the filtration panel  26  requires no additional support other than the corner straps  31 ,  32 ,  33 ,  34  which releasably hold the filtration panel  26  within the frame  12 . When installed, the four edges of the filtration panel  26  are in juxtaposed relation to the walls  16 ,  17 ,  18 ,  19 . 
   The useful like of filter element  11  of this invention is renewed by merely replacing the filtration panel  26  rather than the entire filter element  11 . This results in a substantial saving. For instance, by purchasing a roll of 20 inch wide filtration panel material a homeowner can cut the common size 20 inch by 20 inch panels and the common size 20 by 30 inch panels and easily replace panels that periodically need replacing. 
   When renewing a filter element the homeowner removes the usual air return cover, not shown, from the return air opening of the return air duct and removes the filter element  11 . Next the filtration panel  26  is removed and a replacement filtration panel, cut to proper size, is installed. Then the filter element  11  is installed in the return air opening and the cover is replaced. Only the filtration panel is discarded. Heretofore the entire filter element, that is the frame and filtration panel, was discarded. Thus by using this invention the homeowner saves money and considerably less refuse is placed in landfill depositories for waste.