Abstract:
The present invention also includes a method for installing filters, particularly HEPA filters, into an air handling unit. The method includes providing a filter and a positioning frame, the positioning frame having a geometry that positions the filter adjacent to the frame. The positioning frame also has a latching mechanism for attaching the positioning frame and filter to the filter cabinet. The method further includes positioning the filter and the positioning frame into an opening in a filter cabinet. The frame is then secured to the cabinet by the latching mechanism where the latching mechanism provides a force to the positioning frame and filter, sealing the filter against the filter cabinet to help prevent the flow of air around the filter.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention is directed to a method and apparatus for installing filters for air handling unit in HVAC systems.  
       BACKGROUND OF THE INVENTION  
       [0002]     Air handling unit for HVAC systems typically employ a filter arrangement for removing particles from the air. Some known filter applications include specialized filters that remove contaminants from the air, such as biological and/or chemical pollutants. To remove chemical pollutants, activated carbon or activated alumina adsorbing filters, may be used to adsorb chemical pollutants present in the air in order to neutralize the chemical pollutant. The adsorbing filters must be replaced periodically to maintain their effectiveness. To remove biological pollutants from the air, a high efficiency particulate air (HEPA) filter is used. HEPA filters remove at least 99.97% of contaminants that have a size of 0.3 microns or larger. These HEPA filters have been utilized to remove biological agents from the air. Like the adsorbing filters, the HEPA filters must be replaced periodically to maintain their effectiveness.  
         [0003]     Installation of the activated carbon or activated alumina and HEPA filters have typically taken place through the side of the unit. Large sections of filters are hoisted through an opening in the side of the air handling unit. The filters are then positioned and sealed using mechanical positioning devices. The known method of installing filters suffers from several drawbacks. One drawback of the known method includes the requirement of the mechanical positioning devices for each bank of the adsorbing filters and HEPA filters. These mechanical positioning devices require additional structural material, such as metal, adding weight, bulk and cost to the filter system. In addition, the filter housing, including a stainless steel casing, and a filter access door, previously required for HEPA filters, are required for installation of the filters. An additional drawback is that the filter banks are heavy and typically require the assistance of a forklift or other lifting device. Still another drawback of the known system is that the banks of HEPA filters are replaced through a single opening. The HEPA filters are typically installed in banks of three, where one filter is placed into the unit and subsequent filters are placed adjacent to the first. A force is placed on the side of the filters in order to seal each the filters and substantially prevent leakage of airflow around the filters. If a single HEPA filter is damaged or is not functioning correctly, the entire bank of HEPA filters must be replaced because the seal between the filters must be released in order to replace the filter. Once a seal on a HEPA filter is released, the filter generally must be replaced in order to ensure that the seal is the original factory seal between the filters and is adequate to prevent leakage. Still another drawback of the known system is that the airway length is extended, requiring additional space, weight, material at a greater cost.  
         [0004]     What is needed is a method for installing filters for air handling unit and an apparatus for installing filters for air handling unit that does not suffer from the drawbacks of the prior art.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention includes a positioning frame for positioning and sealing a filter into a filter cabinet in an air handling unit for an HVAC system. The positioning frame includes a filter frame for retaining a first filter, preferably a prefilter. The positioning frame further including a first and second frame stiffening locator attached to a first and second end of the filter frame. The first and second frame stiffening locators have a geometry that positions a second filter adjacent to the positioning frame. One or both of the first and second frame stiffening locators have one or more flanges extending from a surface of the first and second frame stiffening locators. Each of the flanges including an attachment device for attaching the positioning frame to a filter cabinet. The attachment device is configured to attach the positioning frame to the cabinet and seal the second filter into the filter cabinet to prevent airflow from traveling around the second filter.  
         [0006]     The present invention also includes a filter cabinet for retaining filters in an air handling unit for an HVAC system. The cabinet according to the present invention positions and seals filters, preferably HEPA filters, into a filter cabinet in an air handling unit. The filter cabinet includes a flange portion that extends in a first plane outward from one or more openings configured to receive filters. The flange portion has a geometry that substantially prevents the flow of air around filters positioned in the cabinet. The cabinet further includes one or more attachment devices arranged and disposed on the first plane of the filter cabinet capable of attaching to a positioning frame for positioning a filter. The opening or openings along the flange portion include a duct extending perpendicularly from the first plane having a geometry that retains and seals the filter to substantially prevent air from flowing around the filter.  
         [0007]     The present invention also includes a method for installing filters, particularly HEPA filters, into an air handling unit. The method includes providing a filter and a positioning frame. The positioning frame has a geometry that positions the filter adjacent to the frame. The positioning frame also has a latching mechanism for attaching the positioning frame and filter to the filter cabinet. The method further includes positioning the filter and the positioning frame into an opening in the filter cabinet. The frame is then secured to the cabinet by the latching mechanism where the latching mechanism provides a force to the positioning frame and filter, sealing the filter against the filter cabinet to help prevent the flow of air around the filter.  
         [0008]     In another embodiment of the present invention, the positioning frame further includes a hinge that is capable of attachment to the filter cabinet that permits pivotal rotation of the positioning frame sufficient to permit installation and removal of the HEPA filter.  
         [0009]     An advantage of the installation method and apparatus of the present invention is that the mechanical positioning devices required for the bank of HEPA filters is not required for the individual filter installations of the present invention. In addition, the apparatus to maintain the seal in the HEPA filter bank is not required. Therefore, filter cabinet of the present invention is smaller, requiring less cabinet material, achieving reduced weight and cost.  
         [0010]     An additional advantage of the installation method and apparatus of the present invention is that the HEPA filters can be installed individually. The individual installation of the HEPA filters allows replacement of an individual filter, while retaining an original seal, instead of the whole bank of filters, if one filter is damaged or is not functioning correctly. The ability to replace single filters also allows the maximizing of the useful life of the individual HEPA filters.  
         [0011]     An additional advantage of the installation method and apparatus of the present invention is that the airway length of the filter is reduced, achieving reduced weight, space, and manufacturing material.  
         [0012]     Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  schematically illustrates an elevational side cross-sectional view of an air handling unit according to the present invention.  
         [0014]      FIG. 2  schematically illustrates a top cross-sectional view of an air handling unit according to the present invention.  
         [0015]      FIG. 3  is a perspective view of a positioning frame according to the present invention.  
         [0016]      FIG. 4  is a elevational front view of a positioning frame according to the present invention.  
         [0017]      FIG. 5  is an elevational side view of a positioning frame according to the present invention.  
         [0018]      FIG. 6  is an elevational side view of a filter cabinet according to the present invention.  
         [0019]      FIG. 7  is a elevational front view of a filter cabinet according to the present invention.  
         [0020]      FIG. 8  is a perspective view of the alternate embodiment according to an alternate embodiment of the present invention.  
         [0021]      FIG. 9  is an elevational front view of a positioning frame according to the alternate embodiment of the present invention.  
         [0022]      FIG. 10  is an elevational side view of a positioning frame according to the alternate embodiment of the present invention.  
         [0023]      FIG. 11  is a elevational side view of a filter cabinet according to an alternate embodiment of the present invention.  
         [0024]      FIG. 12  is a elevational front view of a filter cabinet according to the alternate embodiment of the present invention. 
     
    
       [0025]     Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0026]      FIG. 1  shows a side view of an air handling unit  100  having a filter arrangement according to one embodiment of the present invention. Airstreams  103  flow through dampers  105  into mixing box  101 . Airstreams  103  can be a mixture of return air from an interior space, outdoor air or a mixture thereof. Airstreams  103  are mixed in the mixing box  101  prior to entering prefilters  107 . Prefilters  107  remove larger particles from the air prior to entering HEPA filters  109 . Air from the mixing box  101  is prevented from flowing around the prefilters  107  and HEPA filters  109  by a flange  111 . Flange  111  extends from the outer walls at the air handling unit  100  and forces the air to flow into prefilters  107  and HEPA filters  109  and substantially prevents air from flowing around prefilters  107  and HEPA filters  109 . Prefilters  107  are held in place by a positioning frame  113 . Positioning frame  113  is releasably attached to filter cabinet  115  and provides a force against HEPA filter  109 , such that the HEPA filter  109  is secured within an opening in filter cabinet  115  and seals against filter cabinet  115 . Sealing against the filter cabinet  115  provides a substantially airtight seal that forces air through the HEPA filter  109  and substantially prevents air from bypassing or flowing around the HEPA filter  109 . Flange  111  is attached to filter cabinet  115 . Filter cabinet  115  includes a duct (not shown) that extends substantially perpendicularly from flange  111  in a direction opposite of mixing box  101 . In one embodiment, the duct of filter cabinet  115  is arranged to secure HEPA filters  109  and adsorbing filters  117 , while substantially preventing the bypassing of around the HEPA filters  109  and the adsorbing filters  117 . The geometry of the duct preferably includes a geometry that is capable of receiving at least a portion of the HEPA filter. The geometry of the duct may be any suitable geometry including, but not limited to geometries having a rectangular cross-section, an oval cross-section or circular cross-section. In addition to prefilter  107 , the HEPA filter  109 , the adsorbing filter  117 , additional filters, such as postfilters  119 , may be secured to filter cabinet  115 . Postfilters  119  are filters that are temporarily installed in order to remove excess carbon that may be present in the air during the startup of the air handling unit  100 . Filtered air leaves the postfilters  119  and returns to the conditioned space through the HVAC system. The air treated by the HEPA filters  109  and adsorbing filters  117  is substantially free of chemical and biological pollutants.  
         [0027]      FIG. 2  shows a top view of an air handling unit  100  having a filter arrangement according to one embodiment of the present invention,  FIG. 2  shows the mixing box  101 , the prefilters  107 , the HEPA filters  109 , the flange  111 , the positioning frame  113 , the filter cabinet  115 , the adsorbing filter  117  and the postfilters  119 , as described above with respect to  FIG. 1 . In addition,  FIG. 2  shows the access doors  201  and  203  through which the adsorbing filters  117  and the HEPA filters  109  are replaced. Adsorbing filter access door  203  provides access to the adsorbing filters  117 . To access the adsorbing filters  117 , adsorbing filter access door  203  is opened to expose one side of the adsorbing filters  117 . A mechanical arm  205  is rotated to release the adsorbing filters  117 . As the mechanical arm  205  rotates, a mechanical positioning device  207  disengages the adsorbing filters  117 , which releases the seal for the adsorbing filters  117  and allows the filters to be removed through the adsorbing filter access door  203 . With respect to HEPA filters  109 , access door  201  provides access to the mixing box  101  to replace the HEPA filters  109 . Inside the mixing box  101 , the HEPA filters  109  are installed individually into the filter cabinet  115  from inside the mixing box  101 . Individual filters have a weight that is sufficiently low for manual installation by a human installer. The positioning frame  113  is fastened to the filter cabinet  115  and provides a force on the HEPA filters  109  sufficient to seal the HEPA filters  109  against the filter cabinet  115 . The mechanical arm  205  and mechanical positioning device  207  are not required to position the HEPA filters  109 , permitting the filter cabinet  115  to be smaller, less weight and requiring less filter cabinet material than in frames previously used to hold filter assemblies.  
         [0028]      FIG. 3  shows a positioning frame  113  according to an embodiment of the present invention. When installed, the positioning frame  113  is adjacent to HEPA filter  109  and includes a filter frame  301 , which secures prefilters  107 . The positioning frame  113  also includes a first frame stiffening locator  303  and a second frame stiffening locator  305 . The first frame stiffening locator  303  and second frame stiffening locator  305  are preferably attached to opposite ends of the filter frame  301 . The first and second frame stiffening locators  303  and  305  attach and cover a portion of the surface of the filter frame  301 . The first and second frame stiffening locators  303  and  305  each include a substantially planar attachment surface  311  and a substantially planar side surface  313 . The attachment surface  311  includes a portion that extends along the plane of the surface  311  in the direction of the HEPA filters  109  for a length sufficient to align the HEPA filters  109  adjacent to the positioning frame  113 . Likewise, the side surfaces  313  extend in the direction of HEPA filters  109  in order to align the HEPA filters  109  adjacent to the positioning frame  113 . While  FIG. 3  shows attachment surfaces  311  and side surfaces  313 , the present invention may include a single attachment surface  311  on each of the first and second frame stiffening locators  303  and  305  in order to align the HEPA filters  109  adjacent to the positioning frame  113 .  
         [0029]     As shown in  FIG. 3 , the first frame stiffening locator  303  includes an attachment flange  307 . The attachment flange  307  includes latching mechanism  309 . Although  FIG. 3  depicts a latching mechanism  309  attached to attachment flange  307 , any suitable attachment device may be used with the present invention, so long as the attachment device is capable of attaching to filter cabinet  115  and providing a force against HEPA filters  109  sufficient to seal the HEPA filters  109  against the filter cabinet  115 . Although  FIG. 3  shows a pull-latch, any suitable latching device may be utilized. The second frame stiffening locator  305  includes substantially the same arrangement of attachment flange  307  and latching mechanism  309 , as described with respect to the first frame stiffening locator  303 . While  FIG. 3  shows two attachment flanges  307  for each of the first and second frame stiffening locators  303  and  305 , any number of attachment flanges  307  may be used, so long as the attachment flanges  307  and latching mechanisms  309  secure the HEPA filters  109  to the filter cabinet  115  and provide a force on the HEPA filters  109  sufficient to seal the HEPA filters  109  against the filter cabinet  115 . Attachment flanges and attachment devices as herein defined include any structure extending from the first and/or second frame stiffening locator  303  and  305  capable of attaching or pivoting alone or in combination with a latching mechanism  309  to the filter cabinet  115 .  
         [0030]      FIG. 4  shows a front elevational view of the embodiment shown in  FIG. 3 . As shown in  FIG. 4 , the first and second frame stiffening locators  303  and  305  each include attachment flanges  307  and latching mechanisms  309 . Each of the first and second frame stiffening locators  303  and  305  include attachment surface  311  and side surface  313 .  
         [0031]      FIG. 5  shows a side elevational view of the embodiment shown in  FIG. 3 . As shown in  FIG. 5 , the first and second frame stiffening locators  303  and  305  include surfaces extending from the filter frame  301 . The surface extending from the filter frame  301  is configured to provide positioning support for HEPA filters  109  (not shown in  FIG. 5 ).  
         [0032]      FIG. 6  shows a side elevational view of a filter cabinet  115  according to one embodiment of the present invention.  FIG. 6  shows a filter frame  301  having first and second frame stiffening locators  303  and  305  installed on the filter cabinet  115 . The first and second frame stiffening locators  303  and  305  include attachment flanges  307  and the latching mechanisms  309 , as described above in the discussion of  FIG. 3 .  FIG. 6  also shows filter cabinet  115  including flange  111 , a HEPA filter section  401 , which includes HEPA filters  109  (not shown in  FIG. 6 ) and an adsorbing filter section  403 , which includes adsorbing filters  117 . Flange  111  includes attachment devices  405  attached to the flange  111  and extending away from the surface of flange  111  in a direction opposite the direction of the HEPA filter section  401 . The attachment devices  405  may include any device that is suitable for receiving latching mechanisms  309 .  
         [0033]      FIG. 7  shows a front elevational view of filter cabinet  115 , as viewed from a mixing box  101  of air handling unit  100 , according to one embodiment of the invention.  FIG. 7  shows nine positioning frames  113 , which secure nine HEPA filters  109 . Although  FIG. 7  shows nine HEPA filters  109 , any number of filters may be used, depending on the application and space restrictions of the air handling unit  100 . The attachment flanges  307  on the positioning frame  113  includes latching mechanisms  309 , which attach to corresponding attachment devices  405 . Although  FIG. 7  shows placement of the four sets of attachment flanges  307 , latching mechanisms  309  and attachment devices  405  for each positioning frame  113  as one set substantially in each corner of the positioning frame  113 , any arrangement of attachment flanges  307 , latching mechanisms  309  and attachment devices  405  may be used so long as the positioning frame  113  attaches to the filter cabinet  115  and provides a force against the HEPA filter  109  sufficient to seal the HEPA filter  109  against the filter cabinet.  
         [0034]      FIG. 8  shows a positioning frame  113  according to an alternate embodiment of the present invention. When installed, the positioning frame  113  is adjacent to HEPA filter  109  and includes a filter frame  301 , which secures prefilter  107 . The positioning frame  113  also includes a first frame stiffening locator  303  and a second frame stiffening locator  305 . The first frame stiffening locator  303  and a second frame stiffening locator  305  are preferably attached to opposite ends of the filter frame  301 . The first and second frame stiffening locators  303  and  305  attach and cover a portion of the surface of the filter frame  301 . Unlike the embodiment shown in  FIG. 3 , this embodiment includes a second frame stiffening locator  305  having an attachment surface  311  and no side surface  313 . The first frame stiffening locator  303  in the embodiment shown in  FIG. 8  includes an attachment surface  311  and a side surface  313 . The attachment surface  311  includes a portion that extends along the plane of the attachment surface  311  in the direction of the HEPA filter  109  for a length sufficient to align HEPA filter  109  adjacent to the positioning frame  113 .  
         [0035]      FIG. 8  also shows an alternate arrangement of attachment flanges  307  and latching mechanisms  309 . The first frame stiffening locator  303  includes hinges  310  which pivotably attach to filter cabinet  115 . The second frame stiffening locator  305  includes attachment flanges  307  and latching mechanism  309 . Attachment flanges  307  and latching mechanisms  309  form a unitary component capable of releasably engaging the filter cabinet  115 .  
         [0036]      FIG. 9  shows a front elevational view of the embodiment shown in  FIG. 8 . As shown in  FIG. 9 , the second frame stiffening locator  305  includes a unitary attachment flange  307  and latching mechanism  309 . The latching mechanism is preferably a spring latch capable of manual release. Although the mechanism shown in  FIGS. 8-12  is a spring latch, any suitable latching mechanism may be utilized to provide a detachable engagement that permits removal of the HEPA filter  109 . The first frame stiffening locator  303  includes attachment surface  311  and side surface  313 , while the second frame stiffening locators  305  includes only the attachment surface. As discussed above with respect to the embodiment shown in  FIGS. 3-7 , the arrangement of attachment surface  311  and side surfaces  313  may be any arrangement that permits positioning of the HEPA filter  109  and supports the filter frame  301 .  
         [0037]      FIG. 10  shows a side elevational view of the embodiment shown in  FIG. 8 . As shown in  FIG. 10 , the first and second frame stiffening locators  303  and  305  include surfaces extending from the filter frame  301 . The surface extending from the filter frame  301  provides positioning support for HEPA filters  109  (not shown in  FIG. 10 ).  
         [0038]      FIG. 11  shows a side elevational view of a filter cabinet  115  according to an alternate embodiment of the present invention.  FIG. 11  shows a filter frame  301  having first and second frame stiffening locators  303  and  305  installed on the filter cabinet  115 , as shown and described above with respect to  FIG. 3 .  FIG. 11  also shows filter cabinet  115  including flange  111 , a HEPA filter section  401 , which includes HEPA filters  109  (not shown in  FIG. 11 ) and an adsorbing filter section  403 , which includes adsorbing filters  117 , also shown and described above with respect to  FIG. 3 . However, the embodiment shown in  FIG. 11  includes hinge  310  attached to filter cabinet  115  at one end of the filter frame  301  by the first frame stiffening locator  303 . The second frame stiffening locator  305  includes a latching mechanism that detachably engages the filter cabinet  115 .  
         [0039]      FIG. 12  shows a front elevational view of filter cabinet  115 , as viewed from a mixing box  101  of air handling unit  100 , according to one embodiment of the invention.  FIG. 12  shows four positioning frames  113 , which secure four HEPA filters  109 . Although  FIG. 12  shows four HEPA filters  109 , any number of filters may be used, depending on the application and space restrictions of the air handling unit  100 . The attachment flanges  307  and latching mechanisms  309  on the positioning frame  113 , which attach to corresponding attachment devices  405 . Hinge  310  pivotably attaches to filter cabinet  115  and permits sufficient pivotal rotation to facilitate installation and removal of the HEPA filter  109 . Although  FIG. 12  shows placement of the one set of attachment flanges  307 , latching mechanisms  309  and attachment devices  405  and two hinges  310  for each positioning frame  113 , any arrangement of attachment flanges  307 , latching mechanisms  309  and attachment devices  405  and hinges  310  may be used so long as the positioning frame  113  attaches to the filter cabinet  115  and provides a force against the HEPA filter  109  sufficient to seal the HEPA filter  109  against the filter cabinet.  
         [0040]     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.