Abstract:
The present invention relates generally to 90% Annual Fuel Utilization Efficiency gas or oil burning devices that depend on external air for combustion. More particularly it discloses an alternate intake apparatus for air for combustion that opens automatically when the inlet air conduit from outside is blocked or severely restricted.

Description:
BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates generally to 90% Annual Fuel Utilization Efficiency (AFUE) gas furnaces and water heaters. 90% AFUE devices bring combustible air into the device from outside the structure being heated through an outside air conduit with a screen cap on the outside end. When outside temperatures drop below 10 degrees Fahrenheit, the inlet air screens tend to freeze or get covered in snow. More particularly it discloses an alternate intake apparatus that is installed on the outside air conduit that opens automatically to a second source of combustible air inside the heated structure when the inlet air screen from outside is blocked or frozen. 
         [0003]    2. Prior Art 
         [0004]    90% AFUE gas furnaces have a combustible air inlet conduit that runs from outside the building to the combustion chamber of the furnace or water heater. Typically they have a screen cap over the inlet end to prevent entrance of pests into the conduit. The inlet screen of this conduit tends to freeze-up or become blocked with snow and ice when the outside temperature falls below 10 degrees Fahrenheit. Prior art attempts to resolve this problem include numerous expensive service calls to knock the ice off the conduit screen or even worse, calls to repair extensive damage from frozen water lines in an unattended home. To date the prior art attempts to resolve this problem have been ineffective and costly. 
       SUMMARY OF THE INVENTION 
       [0005]    The present Invention is an apparatus that mounts on the outside air conduit that provides an alternative source of air for combustion when the outside air conduit is blocked and the gas or oil burning device is trying to draw combustible air. It opens a normally closed unbalanced pivot plate to inside air when outside air conduit head pressure decreases because of the failed attempt to draw outside air. The unbalanced pivot plate automatically closes, returning the system to maximum efficiency, when the outside conduit opening thaws or the blockage is removed and the outside air again is flowing freely. The cost and time of a service call or the costs of repairing frozen pipes in an unattended house damaged when the furnace shuts down in very cold weather are thus saved. 
     
    
     
       DRAWINGS 
         [0006]    In order that the invention is fully understood it will now be described with reference to the following drawings in which: 
           [0007]      FIG. 1A  is a top view of alternate intake apparatus in its normally closed position. 
           [0008]      FIG. 1B  is a front view. 
           [0009]      FIG. 1C  is a bottom view. 
           [0010]      FIG. 1D  is a right side view where the left side is a mirror image of right side. 
           [0011]      FIG. 2  is a section view taken on cutting plane  2 - 2  in  FIG. 1C  in its closed position. 
           [0012]      FIG. 2A  is a section view taken on cutting plane  2 - 2  in  FIG. 1C  in its open position. 
           [0013]      FIG. 3  is a bottom view of cylindrical tube base. 
           [0014]      FIG. 4  is a partial section view taken along cutting plane  4 - 4  in  FIG. 3 . 
           [0015]      FIG. 5  is a partial section view taken along cutting plane  5 - 5  in  FIG. 4 . 
           [0016]      FIG. 6  is a block diagram of a 90% AFUE furnace or water heater installation in the basement of a building with an alternate intake apparatus mounted on a T fitting spliced into a horizontal inlet air conduit inside the basement. 
           [0017]      FIG. 7  is an enlarged partial view of an alternate intake apparatus mounted on a T fitting. 
           [0018]      FIG. 8  is a block diagram of a 90% AFUE furnace or water heater installation in the basement of a building with an alternate intake device mounted on a downward angled T fitting spliced into a vertical inlet air conduit inside the basement. 
           [0019]      FIG. 9  is an enlarged partial view of an alternate intake apparatus mounted on a downward angled T fitting. 
           [0020]      FIG. 9A  is an enlarged partial view of an alternate intake apparatus mounted on a downward mounted elbow attached to a T fitting installed in a vertical air conduit. 
       
    
    
       [0021]    Building, gas or oil burning device, inlet air conduit, exhaust line and screen shown in broken lines as they are not part of this invention but shown for illustrative purposes only. 
       REFERENCE NUMBERS 
       [0022]    The same reference numbers will be used throughout this application for the same and like features. 
       DESCRIPTION 
       [0023]    In order that alternate intake apparatus  10  is fully understood it will now be described by way of the following example. This new invention is a convenient and easily adaptable apparatus for use as a part of an initial 90% AFUE gas furnace or water heater  30  installation. It also can be used as a simple addition to any gas or oil-burning system utilizing outside air conduit  26  to convey combustible air  32  to burner. Alternate intake apparatus  10  spliced into outside air conduit  26  inside the home, as shown in  FIGS. 6-9A , opens due to the drop in head pressure in outside air conduit  26  when inlet air screen  46  is blocked by ice, snow or any other reason. Alternate intake apparatus  10  allows furnace or heater  30  to continue to function as it opens and allows furnace or heater  30  to pull its combustible air  22  from basement  24  through an opened alternate intake apparatus  10  until the external blockage is removed. 
         [0024]      FIGS. 1-5  describe a preferred embodiment of alternate intake apparatus  10  in which cylindrical tubular base  12  is a 3 ¼ inch inside diameter cylindrical tube, approximately 2 ½ inches long and has approximately a ⅛ inch wall thickness. Pivot retaining means  36  are formed on the inside wall of cylindrical tubular base  12  at each end of a chord approximately ⅝ of an inch radially outward from cylindrical tube axis and approximately ½ inch axially above bottom face  48 . Upper rear stop  20  begins above and axially behind pivot retaining means  36  on the left side, extending radially inward from inside wall and arches over to the over to the top of and axially behind pivot retaining means  36  on the right side. The inside radius of upper rear stop  20  is a sufficient amount, approximately ⅛ of an inch, smaller than the outside radius of pivot plate  16  to act as a stop when pivot plate  16  is in its normally closed position. Lower front stop  14  begins below and axially in front of pivot retaining means  36  on the left side, extending radially inward from inside wall and arches under to the to the bottom of and axially in front of pivot retaining means  36  on the right side. The inside radius of lower front stop  14  is a sufficient amount, approximately ⅛ of an inch, smaller than the outside radius of pivot plate  16  to act as a stop when pivot plate  16  is in its normally closed position. Lower front stop  14 , pivot retaining means  36  and upper rear stop  20  lean axially toward bottom face  48  where the shorter section, approximately ⅝ inch above pivot pins  38  is rotated upward against upper rear stop  20  and the longer heavier section below pivot pins  38  is rotated downward against lower front stop  14 , supplementing the unbalanced forces caused by the different thicknesses of the upper and lower sections of pivot plate  16  and its off center pivot point. Pivot plate  16  is dimensioned such that the upper section can be slipped between upper and lower stops  14  and  20  while pivot pins  38  are slid along pivot pin guide ramp  52  from top face  50  between top and bottom guide rails  40  and  42  until it snaps over pivot pin back stop  54 . Pivot pin  38  is thus restrained axially by pivot pin front stop  56  and back stop  54  and radially by top and bottom guide rails  40  and  42 . 
         [0025]    Pivot plate  16  is pivotally mounted in the 3 ¼ inch diameter cylindrical tubular base  12  with a downward leaning upper rear stop  20  and lower front stop  14 . Pivot pins  38  are on the right and left sides of pivot plate  16  at matching points to pivot retaining means  36 . Pivot plate  16  has a larger mass of material below its pivot pins  38  than the mass above pivot pins  38 . This combined with the forward leaning stops  20  and  14  allows gravity to pull pivot plate  16  against stops  14  and  20  when alternate Intake apparatus  10  is positioned properly as shown in  FIG. 2  and inlet air screen  46  is clear and outside combustible air  32  is flowing. Relative masses of top and bottom sections of pivot plate  16  are chosen in such a manner as to eliminate pivot plate  16  flutter during normal operation. Relative masses are also balanced such that the decrease in line head pressure caused by blocking air inlet screen  46  while gas burning device  30  is trying unsuccessfully to draw outside air for combustion  32  causes pivot plate  16  to rotate about pivot pins  38 . Pivot plate  16  rotates until bottom guide rails  42  of pivot retaining means  36  block further rotation of back edge of pivot plate  16  as shown in  FIG. 2A . This rotated position of pivot plate  16  then allows ambient inside air  22  to be drawn through alternate intake apparatus  10 , preventing system shut down. 
         [0026]      FIG. 1C  shows UP indicia  18  for 45 degree to horizontal applications.  FIG. 1D  shows a side view of alternate intake apparatus  10  with installation guidance indicator arrows  44  on the sides pointing toward rear face  50  showing the direction of assembly required for a functioning installation. 
       OPERATION 
       [0027]    Furnaces and water heaters that draw air from the outside for combustion  32  typically draw the air through an inlet air screen  46  over the outside end of an outside air conduit  26  into a gas or oil burning device  30 . Exhaust gases are typically vented to the outside though an exhaust line  34 . Furnaces and water heaters  30  are often located in a basement, attic, crawl space or some other heated area  24  within building  28 . It is not uncommon for inlet air screens  46  to freeze or become blocked with blowing or drifting snow in areas where outside temperatures fall below  10  degrees Fahrenheit. When this blockage occurs and the heating unit attempts to draw air for combustion and it fails, an automatic triggering of a safety shutdown sequence occurs resulting in nuisance service calls to have the blockage removed and the heating device restarted or in the case of an unattended home, severe damage from broken pipes. 
         [0028]    Alternate intake apparatus  10  can be utilized either in a horizontal or in a vertical combustible air conduit  26  into a gas or oil burning device  30 .  FIGS. 6 and 7  show a horizontal installation where a standard plastic T is spliced into a horizontal air input line in an accessible location within the heated structure where sufficient quantities of combustible air are available to allow the device to continue operating with the depending member of the T fitting pointing downward. Alternate intake apparatus  10  is then installed over depending member of plastic T with installation indicia arrows  44  pointing up.  FIGS. 8 ,  9  show a vertical air feed line installation with an angled plastic T with the protruding member angling downward spliced into the vertical line and alternate intake apparatus  10  installed over depending member of plastic T with installation indicia arrows  44  pointing on an upward angle. On angled installations such as this, it is also important that UP indicia  18  on pivot plate  16  are also pointing in an upward angle. For elbow mounted installations as shown in  FIG. 9A  the direction of indicia  18  is not important as long as the elbow itself is opening in a downward attitude. 
         [0029]    The descriptions in the above specification are not intended to limit this invention to the 3 inch conduit application or the materials disclosed here. Rather, they are shown for illustration purposes only as one skilled in these arts could easily scale the invention&#39;s dimensions and materials to work with any size conduit feeding combustible air from outside to a furnace or water heater.