Patent Publication Number: US-6658904-B2

Title: Panel retention mechanism for air handler cabinet

Description:
FIELD OF THE INVENTION 
     This invention relates generally to the field of air handling, and more particularly to a mechanism for retaining panels in an air handler cabinet. 
     BACKGROUND OF THE INVENTION 
     Many air handling units in the prior art are simply fabricated from sheet metal ducts that are brought together in the field to establish an enclosed flow path through which air is conducted. The sheet metal walls of the ducts readily conducts heat and provide little in the way of a thermal barrier so that energy flows into or out of the duct work. When the air handling unit is conducting conditioned air, this flow of energy into or out of the duct work is costly and places an unwanted load on the air conditioning equipment. 
     In addition, when the air handling unit is installed in an unconditioned space and is carrying cooled air, the outer casing of the unit “sweats.” The moisture so developed runs off the unit onto the floor or equipment contained in the unconditioned space. This in turn leads to a safety hazard for people working in the area and causes damage to the equipment. 
     The traditional method for attaching AHU panels to each other is to use mechanical fasteners such as screws that are time consuming to remove and install, prone to getting lost and can strip out. Removal of the panels for equipment installation and maintenance is time consuming and does not allow complete access to the unit&#39;s interior. Other similar panel retention designs place the retainer within the panel. If the retainer fails and requires replacement, the entire panel must then be replaced. Placing the retainer within the panel also places the retainer in the inner conditioned air stream, leading to external sweating or the use of expensive composite retainers to avoid sweating. 
     SUMMARY OF THE INVENTION 
     Briefly stated, an air handling unit (AHU) includes a frame structure and panels that are assembled to provide ducting for handling air. Each panel is rectangular with two sides and four edges. Each edge is integrally formed with the panel by extruding a perimeter of the panel. The extrusion has one flat edge that serves as a receiver for a cammed leg of a latch that is mounted in the same frame structure that retains the panel. While the latches are unengaged, the panel is inserted into the rectangular opening in the structure. The latches are then individually rotated 90 degrees such that the cammed leg pushes the panel further into the pocket, thus compressing a perimeter seal and eliminating air leakage. 
     By placing the panels in a freestanding frame and attaching them with quick release latches, the “ease of maintenance” requirement is achieved. The inherent stiffness of foam filled panels also allows for the use of fewer retainers, further shortening the assembly/disassembly process. By placing the retainers in the frame and not the panel, the retainers do not cause a thermal path which leads to exterior sweating. Replacing defective or worn retainers is facilitated in that they are mounted in the easily accessible frame and not in the panel. In addition, the retainer preferably incorporates a cam shape that pushes the panel inward, compressing the perimeter seal as the latch is engaged. 
     According to an embodiment of the invention, an air handling unit includes a frame structure; at least one panel which fits into a corresponding opening in the frame structure formed by first, second, third, and fourth sides of the frame structure, wherein the first and third sides are substantially parallel and the second and fourth sides are substantially parallel; the panel having first, second, third, and fourth edges, wherein the first and third edges are substantially parallel and the second and fourth edges are substantially parallel; at least the first edge including a pocket formed therein; at least the first side including a latching mechanism therein; the latching mechanism including a rotatable cammed leg, such that when the leg is in a first position, the leg is within the first side, and when the leg is in a second position, the leg extends outside of the first side, such that when the panel is fitted into the frame structure such that the first edge of the panel is adjacent the first side of the frame structure, and the leg is in the second position, the first edge of the panel is latched to the first side of the frame structure. 
     According to an embodiment of the invention, an air handling unit includes a frame structure; at least one panel which fits into a corresponding opening in the frame structure formed by a plurality of sides of the frame structure; the panel having a plurality of edges corresponding to an equal number of the plurality of sides of the frame structure; at least one of the plurality of edges including a pocket formed therein; and means for latching the at least one of the plurality of sides to the at least one edge containing the pocket, the means for latching being contained within at least one of the plurality of sides of the frame structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of a section of duct work for conducting air along a desired flow path with a panel shown removed from the support frame of the duct work. 
     FIG. 2 shows a perspective view of a panel employed to enclose the support frame of the duct work illustrated in FIG.  1 . 
     FIG. 3 shows an exploded view illustrating the panel frame and covers. 
     FIG. 4 shows a sectional view of the panel frame taken along line  4 — 4  in FIG.  3 . 
     FIG. 5 shows a sectional view of the panel assembly taken along lines  5 — 5  in FIG.  2 . 
     FIG. 6 shows a partial sectional view of a section of the duct work skeleton with one panel removed from the duct work. 
     FIG. 7 shows a view similar to FIG. 6 showing the panel locked to the duct work skeleton. 
     FIG. 8 shows a perspective view showing a latching mechanism for locking a panel to the duct work skeleton with the mechanism in a retracted position. 
     FIG. 9 shows a view similar to FIG. 8 showing the latching mechanism in a raised locking position. 
     FIG. 10 shows a partial view of a section of the duct work skeleton with two sides of a panel latched to the duct work. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a section of an air handling unit (AHU)  10  employs a plurality of wall panels  12 . AHU  10  includes a series of rectangular shaped modules, each of which has its own structure formed by a pair of end frames  13 ,  14 . Each end frame  13 ,  14  includes two opposed side rails  17 ,  18  and an upper rail  20  and a lower rail  21 . End frames  13 ,  14  are connected at the corners by horizontally disposed upper beams  15  and lower beams  16 . In assembly, the rails and the beams are slidably retained in corner pieces  23 . The rails and the beams in assembly thus establish an open skeleton. 
     Wall panels  12  are placed in the skeleton openings to close the AHU sections. Each panel is constructed so that it has low thermal conductance, thus greatly impeding the flow of heat into or out of the unit which in turn prevents the unit from sweating. 
     Referring to FIGS. 2-3, each panel  12  includes a frame  25 , preferably rectangular, having a pair of opposed side walls  27  and  28  and a pair of opposed end walls  29  and  30 . Each wall preferably contains mitered ends so that the walls can be brought together to form right angle corners. Panel  12  includes a top cover  40  and bottom cover  41  connected by a wall partition  31  having a recess  32  formed centrally therein that preferably extends along the length of the partition. Recess  32  is inwardly disposed with reference to the outer surface of partition  31 . Partition  31  is preferably of a plastic having low thermal conductance. 
     Referring to FIG. 4, an upper tab  33  and a lower tab  34  are integrally molded on the inside of partition  31  on either side of recess  32 . Tabs  33 ,  34 , like recess  32 , preferably extend along the length of the wall. Tabs  33 ,  34  run parallel to the partition and coact therewith to form channels  35  and  36 . Upper channel  35  opens towards the top of the wall while lower channel  36  opens toward the bottom of the wall. A flange  38 , which is integral with wall partition  31 , runs along the top edge of partition  31 . Flange  38  extends outwardly from wall partition  31  to form an angle that is slightly less than 90 degrees with partition  31  so that flange  38  extends downwardly at a slight angle from the top edge of partition  31 . 
     Referring to FIG. 5, top cover  40  and bottom cover  41  are used to close the frame and create a cavity  43  inside the panel. Each cover  40 ,  41  is preferably of sheet metal or optionally of a plastic or nylon-reinforced plastic material with a thermal conductivity less than conventional metal ductwork. Each cover  40 ,  41  contains an inwardly directed skirt  45  that depends downwardly from the cover and extends around the entire periphery of the cover. In assembly, skirts  45  are inserted into upper and lower channels  35 ,  36  that encircle the panel frame. A curable foam is injected into the cavity to entirely fill the cavity with the foam. When the foam cures, it bonds the frame walls together in abating contact and bonds covers  40 ,  41  to the frame. The curable foam is preferably a polyurethane foam filler with low thermal conductivity. 
     Each panel is sized so that the panel frame can be slipped into an opening in one of the unit sections. A close sliding fit is provided between panel frame walls and the side rails and upper and lower beams that form the receiving opening. When the panel is fully received within the opening, flange  38  that surrounds the panel frame is compressed against the outer surfaces of the rails and beams that form the opening. 
     Referring to FIGS. 6-7, a plurality of seals  50 , which are preferably compressible and hollow, are mounted around the panel receiving opening. At panel closure, lower cover  41  of panel  12  compresses seal  50  as shown in FIG. 7 to prevent the air being conducted inside the unit from escaping around panel  12 . Panels  12  are held in a closed position by a series of latching mechanisms, generally referenced  60 , that are mounted inside the rails and the beams surrounding each opening. The rails and the beams are preferably square metal tubes that are slidably retained in corner pieces  23 . 
     Referring also to FIGS. 8-9, each latching mechanism  60  includes a cylindrical tumbler  62  that is contained within the tube. The tumbler contains an outer flange  64  that has a six sided slot  65  that passes inwardly through the flange. An Allen wrench  67  is insertable into the slot and is used to turn the tumbler between an open position and a locking position. An elongated arm  70  is secured to the tumbler that is arranged to pass upwardly through a slotted hole  69  in the containing tube as the tumbler is turned from an open position as illustrated in FIG. 8 to a locking position as illustrated in FIG.  9 . Arm  70  is arranged to pass into recess  32  surrounding the panel frame and force the panel into sealing contact against the seals  50  surrounding the panel receiving opening. 
     Referring to FIG. 10, at least one latching mechanism is preferably employed to engage each of the walls making up the panel frame  25 . If one latching mechanism per side is used, it is preferably located midway along the frame section. If two latching mechanisms per side are used, each mechanism is preferably located closer to a frame corner than to the midpoint of the frame section. Latching mechanism is optionally located within corner piece  23 . 
     While the present invention has been described with reference to a particular preferred embodiment and the accompanying drawings, it will be understood by those skilled in the art that the invention is not limited to the preferred embodiment and that various modifications and the like could be made thereto without departing from the scope of the invention as defined in the following claims.