Abstract:
This invention provides a duct cover system for ducts installed in exposed locations. For use primarily with ducts having generally rectangular cross sections, the duct cover system provides a roof over the duct that may be integral with the duct or retrofitted to the duct. The roof includes at least one cover panel extending along the duct length. The cover panel is inclined laterally relative to the duct bottom wall thereby to shed water and prevent snow accumulation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of priority to U.S. Provisional Application No. 60/473,903, filed on May 28, 2003, the content of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to an exterior duct work design and more particularly to a ductwork design having an integral peaked roof for the protection of the plenum from the elements.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional central air conditioning and heating equipment comprises a blower which forces air through a heat exchanger and thereafter distributes the air through a system of air distribution ducts or plenums to various parts of a building. Similarly such systems include a return path also comprising ducts for returning air from within the building to the heat exchanger. Optionally the system of ducts may include ducts for introducing fresh air from outside the building into the system.  
         [0004]     As such heating and air conditioning system have become larger to accommodate larger volumes in larger buildings, cross sections of the air circulating ducts have become progressively larger, and it has often become necessary to direct some of the larger ducts outside the building. With most industrial air conditioning and heating systems currently being located on the roof of buildings a substantial effort has been expended to reduce the heat transfer characteristics particularly of exposed duct work, as illustrated by numerous patents on duct insulation schemes, including U.S. Pat. Nos. 4,735,235 issued to Anderson et al. and number 6,360,783 issued to Faviero, IV et al.  
         [0005]     While insulating the ducts as taught by these patents provides substantial improvement in reducing the heat losses in such duct systems, particularly when such ducts are located within a building structure and therefore protected from the elements, ducts located on building roofs or other exposed areas present a host of additional problems due to their exposed nature, such as water or snow accumulation on their top surface. This problem is particularly vexing since the large ducts used on roof tops often have a square or rectangular cross section, such cross sections offering other unrelated advantages over circular cross section ducts. Such accumulation adversely effects the heat exchange characteristics, water being a better heat conductor than air, promotes oxidation, results in material degradation, and places excess weight on the duct system requiring extra supports. Providing a separate cover or placing the ducts in a protected area on the roof is most often not practical.  
         [0006]     There is, therefore, still need for a duct design that alleviates some of the problems associated with exposed duct work, without requiring changes or additions to the installation area.  
       SUMMARY OF THE INVENTION  
       [0007]     It is, therefore, an object of this invention to provide a duct cover system comprising at least one inclined panel extending longitudinally along a length of said duct and laterally inclined relative to a bottom wall of said duct.  
         [0008]     In one embodiment of the invention there is provided an air circulation duct for external installation on a building. It is, therefore, an object of this invention to provide a duct cover system comprising at least one inclined panel extending longitudinally along a length of said duct and laterally inclined relative to a bottom wall of said duct.  
         [0009]     In another embodiment of the invention there is provided an air circulation duct design for external installation on a building.  
         [0010]     Such duct has an axis and comprises two side walls, a bottom wall extending between the side walls and a duct cover panel opposite the bottom wall also between the side walls. All walls and panels extend longitudinally substantially parallel to the axis and the cover panel is inclined laterally to form an acute angle relative to the bottom wall in a plane substantially perpendicular to the axis.  
         [0011]     Such duct has an axis and comprises two side walls, a bottom wall extending between the side walls and a duct cover panel opposite the bottom wall also between the side walls. All walls and panels extend longitudinally substantially parallel to the axis and the cover panel is inclined laterally to form an acute angle relative to the bottom wall in a plane substantially perpendicular to the axis.  
         [0012]     Still within the scope of this invention the above described duct further comprises a top wall located under the cover panel extending between the side walls also along the duct axis and being substantially parallel to the bottom wall, to provide a plenum having a rectangular cross section.  
         [0013]     The cover panel may be inclined along a single direction or may form a substantially peaked roof having a first side forming a first acute angle relative to the bottom panel and a second side forming a second acute angle relative to the bottom panel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows a perspective view of a duct constructed in accordance with this invention.  
         [0015]      FIG. 2  shows an elevation cross section taken in the plane A as shown in  FIG. 1 .  
         [0016]      FIG. 3 . shows an elevation cross section of an alternate embodiment of a duct constructed in accordance with this invention.  
         [0017]      FIG. 4  shows yet another elevation cross section of an alternate embodiment of a duct constructed in accordance with this invention.  
         [0018]      FIG. 5  shows yet another embodiment of this invention wherein the roof panels are inclined at more than one angle relative to the bottom wall of the duct.  
         [0019]      FIG. 6  shows in schematic representation a support for use in supporting the roof panels on the duct structure.  
         [0020]      FIG. 7  shows an elevation cross section of a duct having a roof panel installed thereon supported by the support shown in  FIG. 6 .  
         [0021]      FIG. 8  shows a laminated structure for use in this invention.  
         [0022]      FIG. 9  shows a laminated peaked roof made using the laminated material shown in  FIG. 8 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention. Furthermore the figures are intended to illustrate this invention and do not represent actual engineering drawings of the duct construction nor are the dimensions to scale.  
         [0024]     Referring next to  FIG. 1  there is shown in three dimensional representation a typical duct plenum  12  according to this invention installed on a building roof  10 . The duct  12  is supported on a support system  14  and  14 ′ as is known in the art. The duct has a generally rectangular cross section, and extends along an axis  16  substantially perpendicular to the rectangular cross section. The duct is formed with opposing top and bottom walls  22  and  24  respectively and opposing side walls  18  and  20 . Over top wall  22  there is shown a peaked roof structure providing two inclined cover panels  26  extending along the duct length and forming an acute angle α relative to the top wall  22  as better shown in  FIG. 2 .  
         [0025]      FIG. 2  shows in schematic representation a cut away view of the duct  12  taken in the plane “A” shown in  FIG. 1  along arrow “B”. Plane “A” is a plane perpendicular to axis  16 . As shown in  FIG. 2 , the peaked roof may include a rim  28  at one end of the cover panels which may be used for attaching the roof to an existing duct structure. In an alternate embodiment shown in  FIG. 5 , the cover panels may have side bands  29  extending partially along the duct side walls for attaching the peaked roof to the duct.  
         [0026]     The attachment of the peaked roof to the duct may be accomplished with any one of well known fasteners including screws, rivets, glue etc. The duct may be manufactured with the roof attached or the roof may be designed to be attached after installation to a new or existing duct system.  
         [0027]     In a alternate embodiment shown in  FIG. 3 , the duct has been constructed from the beginning with a cover panel forming a peaked roof and does not include the top wall  22 . The merging of the top wall with the cover panel has the advantage of increasing the size of the duct cross section for a similar size duct having separate top walls and roof cover panels, such as the duct shown in  FIG. 2 .  
         [0028]      FIG. 4  shows yet another embodiment of this invention, in which the peaked roof comprises a single inclined cover panel  30 , and wherein one of the side walls, side wall  20 ′ extends above the top wall  22  to connect with and form a support for the inclined cover panel. Insulation material  23  and  23 ′ may be incorporated in the inner surface of the cover panels or be added to uninsulated panels prior to installation. Not illustrated but still within the scope of this invention is filling the space between the cover panels and the top wall of the duct with insulating material.  
         [0029]      FIG. 5  is yet another embodiment of this invention in which the peaked roof is formed by panels having surfaces inclined at more than one acute angle relative to the bottom wall  24 . As shown in this figure cover panels  26  each comprises a first portion  25  forming an angle β with the bottom wall and a second portion  27  forming a different angle α with the bottom wall. Such structures have the advantage of providing extra stiffness in the cover panel.  
         [0030]     Preferably the cover panels are made of the same material as the duct. However this is not essential and the cover panels may be made of sheet metal or plastic or wood or any construction material that provides sufficient structural integrity to maintain its shape and resistance to exposure to the elements comparable to that of the duct itself.  
         [0031]     The cover panels are preferably made of laminated structures such as shown in  FIGS. 8 and 9 . Such panel structure provides additional rigidity as well as insulation to the cover panels requiring fewer or none supports along the length of the duct. As shown in  FIG. 8 , the panel may comprise a skin  43  such as aluminum, laminated onto an insulating substantially rigid material  44  such as a sheet of polyurethane. An alternative structure may comprise a sheet of melamine resin laminate panel, preferably high pressure laminates (HPL). The melamine sheets may be used by themselves or may in turn be laminated onto a protective exterior skin such as aluminum sheet. The aluminum skin may be incorporated during the melamine panel manufacturing or may be added to a melamine panel after the melamine panel formation. Melamine is desirable as it provides good structural strength coupled with lightness and good insulating properties in a single structure thus being a strong panel for use in a duct cover according to the present invention.  
         [0032]     As shown in  FIG. 8 , a generally “V” shaped notch  45  is cut along the length of the laminated panel extending through the insulating material  44  but not through the skin  43 . The skin may also be other than metal, such as Polyethylene Terephthalate sheeting, and need not necessarily be rigid when the laminated insulating material is sufficiently rigid by itself. The skin may be present on one of both sides of the laminated cover panel in which case the “V” notch is cut through one of the skins. An adhesive bead  46  is preferably placed on one or both sides of the groove  45  and the panel folded as shown in  FIG. 9  to form a peaked roof shaped self supporting cover panel which exhibits substantial rigidity requiring few if any additional supports in use. When the insulating material is polyurethane the adhesive is preferably also a polyurethane adhesive.  
         [0033]     In cases where the duct extends to a substantial length there is need for supporting structure to stiffen the inclined cover panels along the length of the duct. There is therefore contemplated in accordance with the present invention to provide structural support along the length of the duct such as shown in  FIGS. 6 and 7 .  FIG. 6  shows a shaped support  32  for a two panel peaked roof structure comprising a base  36  sized to fit on top wall  22  and to be attached thereon. The support also includes an upright body portion  34  rising from the base in a generally vertical direction. Upright body portion  34  is shaped to provide inclined panel supports  38  and  38 ′ angled a desired angle on which rest and are preferably fixedly attached roof panels  26 . While the support illustrated in  FIG. 5  is designed to support a peaked roof having two inclined panels  26  and  26 ′, it is still within the scope of this invention to provide similar supports designed to fit and support peaked roof having a single inclined panel of the type shown in  FIG. 4 .  
         [0034]     The support shown in  FIG. 6  is also preferably used at the end of a length of duct to provide an enclosed space if so desired to provide better insulating properties in cases where it is desired to enclose the roof volume. In the alternative, support  32  may include openings  40  (shown in dotted line) to permit air flow in the space under the roof.  
         [0035]     Although illustrated and described above with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.