Patent Publication Number: US-6901766-B1

Title: Coil drain pan apparatus

Description:
BACKGROUND OF THE INVENTION 
   The present invention generally relates to air conditioning apparatus and, in representatively illustrated embodiments thereof, more particularly relates to condensate drain pan structures used in conjunction with air conditioning cooling coils. 
   A coil used in air conditioning apparatus such as furnaces, air handling units, and heat pumps extracts moisture from the air which is being flowed externally across the coil (by a blower portion of the apparatus) and cooled by the coil for delivery to a conditioned space served by the apparatus. This moisture extraction creates condensation (water) on the exterior of the coil which drips from the coil into an associated drain pan structure within the air conditioning apparatus. Coil condensation dripping into the pan flows away therefrom by gravity via a condensate drain line suitably connected to the pan. While this general approach to coil condensate removal has long been utilized and is generally suitable for its intended purpose, it typically presents several well known problems, limitations and disadvantages. 
   For example, an air conditioning apparatus (such as a furnace, air handling unit or heat pump) incorporating a cooling coil therein may customarily be fabricated in either (1) a vertical configuration in which air is to be operationally flowed upwardly or downwardly through the cooling coil, or (2) a horizontal configuration in which air is to be operationally flowed horizontally in one of two opposite directions through the coil. To permit a given vertical air flow coil/drain pan subassembly to be utilized in a horizontal air flow application (in which the associated drain pan is vertically oriented) it is typically necessary to attach to the re-oriented drain pan a horizontal drip shield structure to catch the condensate falling from the coil. Attachment of the auxiliary drip shield structure to the drain pan tends to be a fairly tedious procedure requiring the use of separate fasteners, and the application of a suitable sealing material at the joint between the pan and the shield. Such fabricational complexity undesirably adds to the overall cost of the air conditioning apparatus. 
   Additionally, condensate drain pans of conventional constructions often present problems associated with the coil condensate which they receive. Such problems arise from the often unavoidable presence of standing water within the pans for long periods of time, and include sweating of the pans, fungus growth, and reduction in the quality of air delivered to the conditioned space. 
   As can readily be seen from the foregoing, a need exists for a coil drain pan structure which eliminates or at least substantially eliminates the above-mentioned problems, limitations and disadvantages of conventionally constructed coil drain pans. It is to this need that the present invention is directed. 
   SUMMARY OF THE INVENTION 
   In carrying out principles of the present invention, in accordance with representatively illustrated embodiments thereof, air conditioning apparatus is provided which is representatively in the form of an air conditioning unit having has operatively incorporated therein a cooling coil for lowering the temperature of supply air internally traversing the apparatus. The air conditioning apparatus may be utilized in either a vertical air flow or horizontal air flow orientation, and is provided with a specially designed condensate drain pan structure for receiving and draining away condensation dripping off the cooling coil during its operation. While the coil is representatively a cooling coil, the present invention is not limited to cooling coils, with the term “air conditioning” as used herein encompassing both heating and cooling applications. 
   According to one aspect of the invention, the coil drain pan is selectively positionable in horizontal and vertical air flow orientations and includes a drain structure having an outlet opening therein, and a plurality of interconnected troughs, in drainage flow communication with the outlet opening. The drain structure includes a wall area which projects downwardly beyond the interconnected troughs and is in fluid flow communication herewith, the outlet opening extending through a wall portion of the well area. The interconnected troughs representatively border a generally rectangular air flow opening and, when the drain pan is in its vertical air flow orientation, lie generally in a horizontal plane, are positioned above the outlet opening, and are sloped relative to one another in a manner such that essentially all condensation entering any of the troughs flows by gravity to and outwardly through the outlet opening, thereby substantially eliminating standing water in the drain pan structure. 
   To permit the drain pan to be utilized in its horizontal air flow orientation, with the trough portion lying generally in a vertical plane, a drip shield structure is removably connected to the trough portion of the drain pan to lie generally in a horizontal plane and receive condensate from the cooling coil and drain the received condensate into one of the drain pan troughs for discharge therefrom through the outlet opening. According to another feature of the invention, the drip shield structure is connectable to the drain pan trough portion without the use of separate fasteners, tools, or sealant material. 
   Illustratively, the drip shield structure is press-fittable onto a support wall extending outwardly from one of the drain pan troughs using resilient tabs formed on the support wall, and lanced-out locking barbs formed on an edge portion of the drip shield structure. The drip shield edge portion is pressed into spaces between the resilient tabs and the support wall to outwardly deflect the tabs and bring the barbs into locking engagement with inner side surface portions of the tabs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1 and 1A , respectively, are schematic side elevational views of vertical flow and horizontal flow furnaces incorporating therein air conditioning coil sections embodying principles of the present invention; 
       FIGS. 2 and 2A , respectively, are schematic side elevational views of vertical flow and horizontal flow air handling units incorporating therein similar air conditioning coil sections embodying principles of the present invention; 
       FIG. 3  is an enlarged scale cut away side elevational view of one of the vertically oriented air conditioning coil sections; 
       FIG. 3A  is an enlarged scale cut away side elevational view of one of the horizontally oriented air conditioning coil sections; 
       FIG. 4  is a front and right side perspective view of a specially designed drain pan/drip shield subassembly used in the air conditioning coil sections; 
       FIG. 4A  is a simplified cross-sectional view through a corner portion of the drain pan/drip shield subassembly taken along line  4 A— 4 A of  FIG. 4 ; 
       FIG. 5  is an enlarged scale cross-sectional view through a portion of the drain pan/drip shield assembly taken along line  5 — 5  of  FIG. 4 ; 
       FIG. 6  is a front and left side perspective view of the trough portion of the  FIG. 4  drain pan/drip shield subassembly; 
       FIG. 7  is an exploded perspective view of the drain pan/drip shield interface area of the drain pan/drip shield subassembly shown in  FIG. 4 ; 
       FIG. 8  is an enlarged scale detail view of the dashed circle area “ 8 ” in  FIG. 7 ; and 
       FIG. 9  is a perspective view of a corner portion of an alternate embodiment of the trough part of the drain pan/drip shield subassembly. 
   

   DETAILED DESCRIPTION 
   Schematically depicted in  FIGS. 1–2A  are four representative types of air conditioning apparatus embodying principles of the present invention—(1) a vertical air flow furnace  10  shown in  FIG. 1 ; (2) a horizontal air flow furnace  12  shown in  FIG. 1A ; (3) a vertical air flow air handling unit  14  shown in  FIG. 2 ; and (4) a horizontal air flow air handling unit  16  shown in  FIG. 2A . Each of these four illustrative units incorporates therein a specially designed air conditioning coil section  18 , and is operative to flow air  20  from a conditioned space therethrough, with the air exiting the unit as cooled air  20   a , for return to the conditioned space, during operation of the coil section  18 . 
   As used herein, the term “air conditioning” is intended to encompass both cooling and heating applications. Thus, while the air conditioning coil section  18  is illustratively a cooling coil section, it could alternatively be a heating coil section without departing from principles of the present invention. Also, the air flow in the units  10  and  14  could alternatively be downwardly directed, and the air flow in the units  12  and  16  could alternatively be rightwardly directed. Further, the coil section  18  could be mounted in other types of air conditioning units such as in a heat pump, or simply mounted in a duct, without departing from principles of the present invention. 
   The coil section  18 , shown in a vertical air flow orientation in  FIG. 3  and in a horizontal air flow orientation in  FIG. 3A , includes a rectangular outer housing  22 , having opposite inlet and outlet openings  24  and  26 , in which an air conditioning cooling coil  28  is disposed and operatively associated with a specially designed drain pan structure  30  adapted to receive and drain away condensate (i.e., water) dripping from the coil  28  during it operation. Representatively, the coil  28  is a direct expansion type refrigerant coil having three alternatingly sloped sections  32 , but could be another type of cooling coil, such as a chilled water cooling coil or a heat pump coil, and have a different configuration, without departing from principles of the present invention. 
   Turning now to  FIGS. 4 and 6 , the drain pan structure  30  includes a rectangular, generally frame-shaped trough portion  34  which borders an air flow opening  35  and is representatively of a molded plastic construction, and a generally rectangular drip shield structure  36  (which has been removed from the drain pan structure  30  in  FIG. 6  for illustrative purposes) which is formed from a suitable material such as, for example, plastic or sheet metal. With the drain pan  30  in its vertical air flow orientation shown in  FIGS. 4 and 6 , the trough portion  34  is generally horizontally oriented and includes spaced apart, parallel and facing front and rear trough portions  38  and  40 , and spaced apart parallel and facing left and right trough portions  42  and  44  which are transverse to the troughs  38  and  40 . For purposes later described herein, the left side of the trough  42  has an upstanding support wall  46  formed thereon and having four mutually spaced apart, upwardly projecting resilient tabs  48  formed on its inner side surface. While the representatively illustrated trough portion  34  has four interconnected troughs, it will be readily appreciated by those of ordinary skill in this particular art that it could alternatively have a greater or lesser number of interconnected troughs, if desired, without departing from principles of the present invention. 
   With the drain pan  30  in its vertical air flow orientation shown in  FIGS. 4 and 6 , all of the troughs  38 , 40 , 42 , 44  are sloped in a manner such that condensation from the cooling coil  28  (see  FIG. 3 ) entering any of the troughs flows downwardly by gravity to the junction of the troughs  38  and  42  (i.e., to the left corner of the overall troughs portion  34  as viewed in  FIG. 4 ). Specifically, as viewed in  FIG. 4 , the left and right troughs  42 , 44  slope downwardly toward trough  38  as indicated by the arrows  50  and  52 , trough  38  slopes downwardly toward the trough  42  as indicated by the arrow  54 , and an outer or right end portion of the trough  40  slopes downwardly toward the trough  44  as indicated by the arrow  56 . The portion  40   a  of the trough  40  between the troughs  42  and  44  is sloped in opposite directions from a longitudinally intermediate point  58 , with a left section of the trough portion  40   a  sloping downwardly toward the trough  42 , and a right section of the trough portion  40   a  a sloping downwardly toward the trough  44 . 
   Accordingly, with the drain pan  30  in its vertical air flow orientation cooling coil condensation received by any of the troughs  38 , 40 , 42 , 44  flows by gravity to the juncture of the troughs  38  and  42  which forms the low point of the interconnected troughs  38 , 40 , 42  and  44 . Disposed at this low point of the interconnected troughs is a drain structure  60  comprising a well area  61  (see  FIG. 4A ) which projects downwardly beyond the juncture of the troughs  38  and  42  and serves as a condensate disposal area which is positioned below the troughs and their associated coil. Well  61  has an inner wall  63  (see  FIG. 4A ), a main condensate outlet opening  62  (see  FIGS. 3 and 6 ), a vertical orientation condensate overflow opening  64 , and a horizontal orientation condensate overflow opening  66 . Conventional condensate drain tubing (not shown) may be appropriately connected to these openings during field installation of the air conditioning apparatus in which the drain pan  30  is incorporated, and the overflow openings  64 , 66  are adapted to receive removable plugs  68  as shown in  FIGS. 3 and 3A . 
   With the drain pan  30  in its vertical air flow orientation, the main outlet opening  62 , which communicates with the interior of the well  61 , and the vertical overflow opening  64  is slightly higher than the main outlet opening  62 . Thus, when the drain pan  30  is in its vertical air flow orientation, substantially all of the coil condensation entering the trough portion  34  flows by gravity into the downwardly projecting well  61  and is discharged by gravity through the main outlet opening  62 , thereby substantially eliminating standing drain pan water and its attendant problems such as sweating, fungus growth and reduced indoor air quality. Should the main outlet opening  62  be restricted or blocked, the pan-received condensation is simply discharged through the back-up overflow opening  64 . The downwardly projecting well  61  acts as a condensate collection area to hold only a small amount of condensate before it is discharged through opening  62 , thus preventing or minimizing the growth of mold and mildew that can be exposed to the indoor airstream. 
   Referring now to  FIG. 3A , with the drain pan  30  and its associated cooling coil  28  in their horizontal air flow orientations, the trough portion  34  lies generally in a vertical plane, and the generally flat pan-shaped drip plate structure  36  underlies the coil  28  to receive condensation dripping therefrom, lies generally in a horizontal plane, and is sloped slightly downwardly toward the trough  42  (see  FIG. 4 ) which now forms a lower edge section of the vertically disposed trough portion  34 . Coil condensation received by the drip plate structure  36  flows therethrough by gravity into the trough  42  for discharge through main outlet opening  62  in the drain structure  60  via the downwardly projecting well  61 . In the event that the main outlet opening  62  becomes restricted or clogged, this condensation simply flows outwardly through the horizontal overflow opening  66  which is now positioned somewhat above the main outlet opening  62 . 
   In accordance with a feature of the present invention, the drip plate structure  36  may be removably and operatively connected to the support wall  46  of the trough portion  34 , without the use of separate fasteners or joint sealant material, by simply press-fitting the drip plate structure  36  onto the support wall  46  as will now be described with reference to  FIGS. 4 ,  5 ,  7  and  8 . 
   As best illustrated in  FIGS. 7 and 8 , a horizontally spaced plurality of lanced-out triangular locking barbs  70  are formed in a lower edge portion  36   a  of the drip plate structure  36  and are alignable with the tabs  48  on the support wall  46 . To quickly attach the drip plate structure  36  to the support wall  46 , the barbs  70  are aligned with the tabs  48 , and the lower drip plate edge portion  36   a  is pushed downwardly toward the support wall  46 , as indicated by the arrow  72  in  FIG. 7 , until the lower drip plate edge portion  36   a  and its associated locking barbs  70  are forced downwardly between the support wall  46  and the resilient tabs  48 , as cross-sectionally depicted in  FIG. 5 , to bring the drip plate structure  36  to its installed orientation as shown in  FIG. 4 . 
   This laterally outwardly deflects the resilient tabs  48  and causes upper end points  70   a  on the barbs  70  (see  FIG. 8 ) to engage the inner sides of the outwardly deflected tabs  48  in a manner releasably locking the drip plate structure  36  on the trough structure  34  without the use of any separate fasteners or tools of any sort. Since, with the drain pan  30  in its horizontal air flow orientation, the inner edge portion  36   a  of the drip plate  36  overlies the top side of the horizontally oriented support wall  46 , no sealant material need be utilized at the juncture between the support wall  46  and the drip plate structure  36 . This feature of the present invention advantageously simplifies the assembly of the coil/drain pan subassembly and thus reduces the fabrication cost for the overall air conditioning apparatus in which it is operatively incorporated. 
   A drain corner area of an alternate embodiment  34   a  of the previously described drain pan trough portion  34  is perspectively illustrated in  FIG. 9 . In order to facilitate a comparison of the drain portion embodiments  34  and  34   a , components in the embodiment  34   a  similar to those in the embodiment  34  have been given identical reference numerals with the subscripts “a”. The trough structure  34   a  is substantially identical to the previously described trough structure  34  with the exception that in the trough structure  34   a  the drain structure  60   a  extends outwardly from the trough structure  34   a  in a direction substantially parallel to the length of the trough  42   a , whereas in the previously described trough structure  34  the drain structure  60  is leftwardly angled as viewed in  FIG. 4 . 
   The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.