Abstract:
A heat exchanger system and a method of assembly is provided for a gas appliance such as a furnace. The heat exchanger system includes an attachment plate having at least one recess sized to receive an inlet of a heat exchanger. The heat exchanger has a first flange disposed at the inlet that is positioned in the recess. A second flange in the attachment plate recess is crimped onto the inlet flange to couple the heat exchanger to the attachment plate. The attachment plate may also include a pair of slots that extend from the recess that are sized to receive a pair of third flanges on the heat exchanger.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to gas furnaces and in particular to gas furnaces having a sealed connection between a combustion chamber and a primary heat exchanger. 
         [0002]    Gas fired appliances, such as residential and light commercial heating furnaces for example, often arrange a combustion chamber in series with one or more heat exchangers. The heated gas from the combustion chamber flows through the heat exchanger that transfers thermal energy from the combustion gas to air passing over the heat exchanger. In general, the pressure within the heat exchanger is less than atmospheric pressure. As a result, atmospheric air may be drawn into the system resulting in a disruption of the combustion process that decreases efficiency. 
         [0003]    The connection between the combustion chamber and the heat exchanger is one area where a seal to prevent infiltration of air is desired. This connection is typically adjacent the combustion chamber. As a result, the infiltration of air may impinge upon the flame, which disrupts the combustion process resulting in an incomplete combustion of the fuel. The heat exchanger typically has an inlet with a flange that extends from one end. A flat plate that includes sponge rubber gaskets is crimped to the flange. While this seal arrangement is suitable, the process of crimping requires additional backup tooling to prevent separation of the heat exchanger during assembly. Further, the circular/parallel inlet flange causes aggressive wear on the fabrication tooling. 
         [0004]    Accordingly, while existing gas furnaces are suitable for their intended purposes improvements may be made in improving the coupling and sealing of the heat exchanger to a combustion chamber to minimize the impingement of air on the combustion process. 
         [0005]    This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    According to one aspect of the invention, a heat exchanger system is provided. The heat exchanger system includes an attachment plate having at least one recess and a pair of slots extending from the at least one recess. A heat exchanger member having an inlet, the inlet having a first flange coupled within the at least one recess and a pair second flanges disposed within the pair of slots. 
         [0007]    According to another aspect of the invention, a heat exchanger system for a gas appliance having a combustion chamber is provided. The heat exchanger system includes an attachment plate coupled to the combustion chamber, the attachment plate having at least one recess, a first slot extending from one side of the at least one recess and a second slot extending from the at least one recess opposite the first slot. A heat exchanger member having an inlet fluidly is coupled to receive a combustion gas from the combustion chamber. The inlet has a first flange arranged about an opening and fixedly disposed in the at least one recess, and a pair of second flanges arranged adjacent and substantially perpendicular to the first flange. The pair of second flanges is disposed in the first slot and the second slot. 
         [0008]    According to yet another aspect of the invention, a method of assembling a heat exchanger system to a combustion chamber is provided. The method includes the step of providing an attachment plate having at least one recess and a pair of slots extending from the at least one recess. A heat exchanger member is provided having an inlet with a first flange disposed about an opening and a pair of second flanges adjacent the first flange. The first flange is disposed in the at least one recess. The pair of second flanges is disposed in the pair of slots. The heat exchanger member is coupled to the attachment plate in the at least one recess. The inlet is supported with the at least one recess when the heat exchanger member is coupled to the attachment plate. 
         [0009]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0010]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0011]      FIG. 1  is a perspective cut away illustration of a gas furnace in accordance with an embodiment of the invention; 
           [0012]      FIG. 2  is a schematic illustration of a combustion chamber and heat exchanger arrangement in accordance with an embodiment of the invention; 
           [0013]      FIG. 3  is a perspective illustration of an attachment plate for use with the gas furnace of  FIG. 1 ; 
           [0014]      FIG. 4  is a perspective illustration of another embodiment attachment plate for use with the gas furnace of  FIG. 1 ; 
           [0015]      FIG. 5  is a perspective view illustration of a primary heat exchanger for use with the gas furnace of  FIG. 1 ; 
           [0016]      FIGS. 6-7  are perspective view illustrations of the primary heat exchanger of  FIG. 5  being assembled to the attachment plate of  FIG. 3 ; 
           [0017]      FIG. 8  is a perspective view illustration of the attachment plate of  FIG. 3  crimped onto the primary heat exchanger of  FIG. 5 ; and, 
           [0018]      FIG. 9  is a partial cross sectional view of the attachment plate of  FIG. 4  crimped onto the primary heat exchanger of  FIG. 5 . 
       
    
    
       [0019]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0020]      FIG. 1  is a perspective cutaway view of furnace  10 . Furnace  10  includes burner assembly  12 , combustion chamber  14 , combustion air pipe  16 , gas valve  18 , primary heat exchanger  20 , condensing heat exchanger  24 , condensate collector box  26 , exhaust vent pipe  28 , induced draft blower  30 , inducer motor  32 , thermostat  34 , low pressure switch  42 , high pressure switch  44 , and furnace control  50 . 
         [0021]    Burner assembly  12  is located within combustion chamber  14  and is supplied with air via combustion air pipe  16 . Fuel gas is supplied to burner assembly  12  through gas valve  18 , which may be a solenoid-operated gas valve, and is ignited by an igniter assembly (not shown). The gases produced by combustion within combustion chamber  14  flow through a heat exchanger assembly, which includes primary or non-condensing heat exchanger  20 , secondary or condensing heat exchanger  24 , and condensate collector box  26 . It should be appreciated that while only a single heat exchanger  20  is illustrated, the furnace  10  may have multiple heat exchangers  20  coupled in parallel to the combustion chamber  14 . The gases are then vented to the atmosphere by inducer motor  32  through exhaust vent pipe  28 . The flow of these gases, herein called combustion gases, is maintained by induced draft blower  30 , which is driven by inducer motor  32 . Inducer motor  32  is driven in response to speed control signals that are generated by a furnace control circuit located within furnace control  50 , in response to the states of low pressure switch  42  and high pressure switch  44 , and in response to call-for-heat signals received from thermostat  34  in the space to be heated. 
         [0022]    Air from the space to be heated is drawn into furnace  10  by blower  52 , which is driven by blower motor  54  in response to speed control signals that are generated by furnace control  50 . The discharge air from the blower  52 , herein called circulating air, passes over condensing heat exchanger  24  and primary heat exchanger  20  in a counter-flow relationship to the flow of combustion air, before being directed to the space to be heated through a duct system (not shown). 
         [0023]    It should be appreciated that it is desirable to provide an adequate seal between the combustion chamber  14  and the primary heat exchanger  20 . Since the pressure within the primary heat exchanger  20  is lower than atmospheric pressure (ΔP˜0.2-0.3 inches of water, 49.8-74.7 Pascal) air will tend to be drawn into the heat exchanger  20  and combustion chamber  14  disrupting the combustion process. Referring to  FIGS. 2-3 , in one embodiment the primary heat exchanger  20  is coupled to the combustion chamber  14  by an attachment plate  36 . In the exemplary embodiment, attachment plate  36  is formed from a metal sheet material, such as steel or aluminum for example. The sheet is formed with one or more embossed portions or recesses  38  having an opening  40  substantially centered therein as shown in  FIG. 3 . A flange  48  extends from the opening  40  within the recess  38  to form a groove  56 . Extending from each recess are a pair of slots  46  that are arranged substantially 180 degrees apart. The slots  46  intersect and extend between the groove  56  and the edge of the attachment plate  36 . As will be discussed in more detail herein, the recess  38 , flange  48 , groove  56  and slots  46  are sized to receive and cooperate with an inlet opening flange on the primary heat exchanger  20 . Further, the attachment plate  36  may include multiple recesses  38  to allow multiple primary heat exchangers  20  to be coupled in parallel to the combustion chamber  14 . 
         [0024]    The attachment plate  36  may also include a second plurality of recesses  58  disposed about the periphery. The recesses  58  include a hole  60  that is formed in the bottom of the recess  58 . The holes  60  may be sized to receive a fastener (not shown) that couples the attachment plate  36  to the combustion chamber  14 . In some embodiments, a gasket (not shown) is disposed between the attachment plate  36  and the combustion chamber  14 . The recesses  38 ,  58  provide additional advantages in compressing or pinching the gasket material as the attachment plate is coupled to the combustion chamber  14 . It should be appreciated that while the embodiments described herein refer to a separate attachment plate  36 , in other embodiment the recesses  38 , opening  40 , flange  48  and slots  46  may be integrated into the housing of the combustion chamber  14 . It should be appreciated that the recesses  58  allow the fasteners to be tightened to the combustion chamber  14  when the primary heat exchanger  20  is installed. 
         [0025]    Another embodiment of the attachment plate  36  is illustrated in  FIG. 4 . In this embodiment, opening  40  has a scalloped flange  62  that includes a plurality of projections  64 . In one embodiment, the projections  64  are defined by a smooth curved profile that contiguously extends from a trough portion to a peak portion as the flange  62  extends about the opening  40 . In one embodiment, the plurality of projections  64  includes a first projection  66  and a second projection  68  are arranged on opposite sides of the flange  62  with each projection  66 ,  68  centered on one of the slots  46 . As will be discussed in more detail herein, the projections  66 ,  68  include additional material that provides advantages in reducing or eliminating the infiltration of atmospheric air into the combustion chamber  14 . 
         [0026]    The primary heat exchanger  20  is formed in two halves  70 ,  72  from a sheet metal material, such as steel or aluminum for example as shown in  FIG. 2  and  FIG. 5 . The two halves  70 ,  72  are joined together by a suitable process such as fasteners, crimping, welding, brazing or a combination thereof for example. The primary heat exchanger  20  includes an inlet  74  that is fluidly coupled to receive heated gases from the combustion chamber  14 . A serpentine path  76  extends through the heat exchanger  20  providing a surface area for the transfer of heat from the combustion chamber gases to air flowing over the primary heat exchanger  20 . The gases leave primary heat exchanger  20  via an outlet  78  that is fluidly coupled to the condensing heat exchanger  24 . 
         [0027]    In the exemplary embodiment, the inlet  74  has a first flange  80  arranged substantially perpendicular to the flow of combustion gases. The first flange  80  further defines the outer diameter of the inlet opening  82 . A pair of second flanges  84  extends away from the inlet  70  and provides an area for the crimping of the two heat exchanger halves  70 ,  72 . The outer surface of the inlet  70  and the first flange  80  are sized to fit within the groove  56  such that the flange  48  of the attachment plate  36  fits within and extends into the opening  82 . It should be appreciated that where the two halves  70 ,  72  meet, a small gap  86  may exist due to the curvature of the material in forming the second flanges  84 . 
         [0028]    Referring now to  FIG. 6-FIG .  8 , the assembly of the primary heat exchanger  20  with the attachment plate  36  will be described. The primary heat exchanger  20  is arranged such that the inlet  74  is inserted into the groove  56  with the second flanges  84  aligned with and disposed in the slots  46 . With the inlet  74  and attachment plate  36  so arranged, an operator inserts a crimping tool  88  or fixture into the opening  40 . When actuated, the tool  86  bends the attachment plate flange  48  over the inlet first flange  80  crimping the flanges  48 ,  80  and forming a seal without an intermediary gasket or seal member. The recess  38  provides support for the heat exchanger halves  70 ,  72  while the crimp is being formed. This support by the recess  38  provides advantages in preventing the heat exchanger halves  70 ,  72  from separating as a result of the radial crimping force applied to the flange  48 . It should be appreciated that by preventing separation of the heat exchanger halves  70 ,  72 , an increase in the gap  86  during the crimping process may be prevented or minimized. In one embodiment, the operator may place a sealant, such as a silicone material or a sponge rubber for example, into the groove  56  and slots  46  prior to inserting the primary heat exchanger  20  into the grooves  56  and slots  46 . It should be appreciated that the crimping of the attachment plate  36  to the primary heat exchanger  20  provides advantages in improving the seal and also assists in preventing the separation of the heat exchanger halves  70 ,  72  during the crimping operation. 
         [0029]    In embodiments where the attachment plate  36  includes the scalloped flange  62 , additional advantages are gained in increasing the amount of material that overlaps the gap  86 . As shown in  FIG. 9 , the projections  66 ,  68  extend up an inner wall  90  of the inlet  74 . In this arrangement, the projections  66 ,  68  over lap the gap  86  along a portion of the inner wall  90  in addition to the first flange  80 . In the event that air does infiltrate the gap  86 , the air will be directed with the flow of the combustion gases since the projections  66 ,  68  extend parallel to the wall  90 . By flowing the air in a direction parallel to the combustion gases there would be no or minimal impingement of infiltration air on the combustion flames, and thus not affecting combustion efficiency or reliability. 
         [0030]    As disclosed, some embodiments of the invention may include some of the following advantages: improving the seal between the combustion chamber and the heat exchanger inlet; not reducing the efficiency of the combustion process in the event of infiltration; improving the support of the heat exchanger during the assembly process; the directing infiltrating air away from the combustion chamber. 
         [0031]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.