Patent Publication Number: US-6334439-B1

Title: Tubular heat exchanger for infrared heater

Description:
This application claims the benefit of U.S. Provisional Application No. 60/138,908, filed Jun. 11, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a radiant heater and, more particularly, to an infrared radiant heater including a heat exchanger which facilitates the packaging and transportation of the heater. 
     Low-intensity infrared heaters utilizing tubular heat exchangers are well known in the art. These heaters typically incorporate a burner unit at one end, which burns an air/fuel mixture to provide hot combustion product gases. These gases are then passed through a plurality of heat transfer pipes, referred to collectively as the heat exchanger, and are then exhausted via a fan or other flow-inducing device. The surrounding space is heated via radiant heat transfer from the heated pipes. 
     Prior art low-intensity infrared heaters utilize heat transfer pipes which typically range in length from 12′ to 20′, but may also utilize pipes having even greater lengths. Accordingly, these units require oversized packaging crates, i.e., 12 to 20′ crates or larger. These oversized crates make shipping and handling of the heaters quite difficult, leading to increased shipping costs and greater likelihood of damage to the packaged units. Alternatively, prior art heaters utilize individual sections of pipe which must be coupled together using clamping collars and the like. 
     There is therefore a need in the art for a heater (utilizing a tubular heat exchanger) which readily “breaks down” for shipping (thus allowing the use of significantly smaller packaging crates which saves shipping costs and reduces the likelihood of damages), but which is readily unpackaged and installed without requiring any significant assembly at the installation site. 
     SUMMARY OF THE INVENTION 
     The present invention, which addresses the needs of the prior art, relates to a heater. The heater includes a burner for burning a combustible gas to provide hot combustion product gases. The heater further includes first and second heat transfer pipes each having first and second ends. The first end of the first pipe communicates with the burner for receipt of the gases. The heater further includes first and second header plates configured for securement to one another. Each of the header plates includes an aperture. The second end of the first pipe is coupled to the first header plate such that the first pipe communicates with the aperture extending therethrough. The first end of the second pipe is coupled to the second header plate such that the second pipe communicates with the aperture extending therethrough whereby the pipes fluidly communicate with each other when the header plates are secured together thus allowing the gases to flow from the first pipe to the second pipe. Finally, the first and second header plates of the heater are rotatably connected to one another. 
     In another embodiment of the present invention, the heater includes a burner box having a burner for burning a combustable gas to provide hot combustion product gases. The heater further includes a first outflow pipe and a first return pipe. Each of the first pipes has first and second ends. The first end of the first outflow pipe communicates with the burner box for receipt of the product gases and the first end of the first return pipe communicates with the burner box for return of the product gases. The first pipes extend from the burner box in a substantially common direction. The heater further includes a first header plate. The first header plate includes a first outflow pipe aperture and a first return pipe aperture. The first aperture is sized and positioned to communicate with the second ends of the first pipes. The second end of the first outflow pipe is coupled to the first header plate such that the first outflow pipe communicates with the first outflow pipe aperture. The second end of the first return pipe is coupled to the first header plate such that the first return pipe communicates with the first return pipe aperture. The heater further includes a second outflow pipe and a second return pipe. Each of the second pipes has first and second ends. The heater further includes a second header plate. The second header plate includes a second outflow pipe aperture and a second return pipe aperture. The second apertures are sized and positioned to communicate with the first ends of the second pipes. The first end of the second outflow pipe is coupled to the second header plate such that the second outflow pipe communicates with the second outflow pipe aperture. The first end of the second return pipe is coupled to the second header plate such that the second return pipe communicates with the second return pipe aperture whereby the second pipes extend from the second header plate in a substantially common direction. The heater further includes a fluid passage connecting the second end of the second outflow pipe to the second end of the second return pipe. Finally, the first header plate is configured to be coupled to the second header plate whereupon the first outflow pipe is brought into fluid communication with the second outflow pipe and the first return pipe is brought into fluid communication with the second return pipe. 
     Finally, the present invention relates to a multiple pipe assembly. The assembly includes a first set of pipes. Each of the pipes in the first set has a first end and a second end. The assembly further includes a first header plate. The first header plate includes a plurality of apertures. The second end of each of the pipes in the first set is coupled to the first header plate such that each of the pipes in the first set communicates with one of the apertures in the first header plate. The assembly further includes a second set of pipes. Each of the pipes in the second set has a first end and a second end. The assembly further includes a second header plate. The second header plate includes a plurality of apertures. The first end of each of the pipes in the second set is coupled to the second header plate such that each of the pipes in the second set communicates with one of the apertures in the second header plate. Finally, the header plates are configured to be coupled to one another whereby the pipes of the first set are brought into fluid communication with the pipes of the second set. 
     As a result, the present invention provides a heater utilizing a tubular heat exchanger which readily “breaks down” for shipping thus allowing use of significantly smaller packaging crates which saves shipping costs and reduces the likelihood of damages, but which is readily unpackaged and installed without requiring any significant assembly at the installation site. The present invention also provides a multiple pipe assembly for use in applications wherein it is desired to combine separate tubular subsections to provide a set of pipes having an overall longer length. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the hinged tubular heat exchanger of the present invention in its open installation position; 
     FIG. 2 is an elevational view showing the tubular heat exchanger of FIG. 1 in its closed packaging/shipping position; 
     FIG. 3 is a perspective view of the partially assembled burner box of the present invention; 
     FIG. 4 is an elevational view of the fully assembled burner box of the present invention; 
     FIGS. 5-7 are enlarged details showing the hinged header plates and heat transfer pipes of the present invention; 
     FIG. 8-9 are views of the header plate shown in FIGS. 5-7; 
     FIG. 10 is an enlarged detail showing a lip formed on the header plate sealing against an attached heat transfer pipe; 
     FIG. 11 is an enlarged detail showing the swaged flange at the end of a heat transfer pipe; 
     FIG. 12 is a cross-sectional view of the expansion joint of the present invention; and 
     FIG. 13 is a perspective view of an alternative embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Low-intensity infrared heater  10 , including a hinged tubular heat exchanger  12 , is shown in FIG.  1 . Heater  10  is shown in its open installation position, and spans a length of approximately 14½ feet. It has been discovered herein that the hinged tubular heat exchanger allows the overall length of the heater to be reduced for shipping/handling purposes without substantially increasing the installation time and/or complexity. Heater  10  is shown in its closed packaging/shipping position in FIG.  2 . In this closed position, heater  10  has a length of approximately 7½ feet. Accordingly, the packaging/shipping length is approximately one-half the open installation length. Of course, the dimensions described with respect to heater  10  are merely exemplary, and the heat exchanger associated therewith could be produced having any desirable length. 
     It is contemplated herein that, if necessary, heat exchanger  12  may include more than one hinged joint, which would allow further reduction in the packaging/shipping length. It is also contemplated that heat exchanger  12  can simply include a plurality of discreet subsections which are secured together without the use of a hinge. It is further contemplated that the disclosed heat exchanger may be incorporated into heater units (other than low-intensity infrared heaters) utilizing relatively long sections of piping. Finally, it is contemplated that the multiple pipe assemblies disclosed herein may be used in applications unrelated to infrared heaters, i.e., applications which require long lengths of multiple pipes, but which would benefit from a design wherein separate tubular subsections are connected together to provide a set of pipes having an overall longer length. 
     Heater  10  includes a burner box  14 . As shown in more detail in FIGS. 3-4, burner box  14  houses a pair of burners  16  for burning a combustible gas to provide hot combustion product gases. The combustible gas is supplied to burners  16  through a gas valve  18  and a manifold  20 . In this regard, burner box  14  further includes an ignition control board  22 , a transformer  24 , a spark electrode  26 , a carryover burner  28  and a flame sensor  30 . The forward wall of the burner box, i.e., wall  32 , includes apertures  34  and  36  through which the hot combustion product gases are directed. Burner box  14  also houses a venting unit  38  which includes a fan assembly  40  and a housing assembly  42 . The venting unit is designed to draw gas through apertures  44  and  46  formed in wall  32  and discharge such gas through exhaust port  48 . 
     Heater  10  includes a plurality of heat transfer pipes, namely outflow pipes  50 ,  52 ,  54  and  56  and return pipes  58 ,  60 ,  62  and  64 . As shown in FIG. 1, outflow pipes  50  and  54  are axially aligned and in fluid communication with outflow pipes  52  and  56 , respectively, and direct the hot combustion product gases away from burner box  14 . In this regard, the upstream ends of outflow pipes  50  and  54  communicate with apertures  34  and  36  respectively, whereby outflow pipes  50  and  54  receive the hot combustion product gases produced by burners  16 . Return pipes  58  and  62  are axially aligned and in fluid communication with return pipes  60  and  64 , respectively, and direct the hot combustion product gases back towards burner box  14 . In this regard, the downstream ends of return pipes  58  and  62  communicate with apertures  44  and  46 , respectively whereby the hot combustion product gases may be exhausted from the return pipes via venting unit  38  and discharged through exhaust port  48 . A turning box  66 , which functions as a manifold, fluidly couples the downstream ends of outflow pipes  52  and  56  to the upstream ends of return pipes  60  and  64 . Alternating, two separate closed loops could be formed with the heat transfer pipes, e.g., pipes  50 ,  52 ,  58  and  60  could form one closed loop and pipes  54 ,  56 ,  62  and  64  could form a second closed loop. 
     Tubular heat exchanger  12  includes header plates  68 ,  70 ,  72  and  74 . Outflow pipes  50  and  54  and return pipes  58  and  62  extend between header plates  68  and  70 , thus providing a first heat transfer subsection  76 , while outflow pipes  52  and  56  and return pipes  60  and  64  extend between header plates  72  and  74  thus providing a second heat transfer subsection  78 . The subsections, which are typically separately assembled, are then brought together to form heat exchanger  12 . Although heat exchanger  12  has been described herein as including two subsections, the heat exchanger could include any number of subsections. 
     It has been discovered herein that the overall length of the heater can be significantly reduced for packaging/shipping if heat exchanger  12  includes at least one heat transfer subsection which may be reoriented for packaging/shipping. In one preferred embodiment, heat exchanger  12  includes a hinge  80  which rotatably connects header plate  70  to header plate  72  (see FIGS.  2  and  5 ). Preferably, hinge  80  is a piano hinge sized to extend substantially across the width of the header plates. The hinge is preferably a separate component formed independently of the header plate, and thereafter secured thereto via a plurality of screws  82  (see FIG. 6) or by other suitable means such as riveting, welding, etc. Alternatively, the hinge may be intregally formed with one or both header plates. 
     Of course, it is contemplated herein that the subsections of the heat exchanger may be aligned and secured together without the use of a hinge, that is, the subsections may be secured together simply by the securing hardware discussed hereinbelow, or by other mechanical fastening means. Also, the hinge discussed above may be designed to allow removal of the pin whereby the subsections of the heat exchanger are detachable. In these embodiments, the separate subsections can be individually packaged, thus allowing the use of even smaller packaging crates. 
     At least one gasket is preferably installed adjacent each header plate interface to ensure sealing between the connected components. More particularly, at least one gasket is installed at the burner box  14 /header plate  68  interface, at the header plate  70 /header plate  72  interface, and at the header plate  74 /turning box  66  interface. Preferably, an individual gasket  84  is associated with each pair of co-axially arranged heat transfer pipes (see FIG.  5 ). 
     Installation of the hinged tubular heat exchanger simply requires the unpackaging of the heater from the packaging crate (not shown), and rotation of subsection  78  about hinge  80  until header plates  70  and  72  contact one another. In those embodiments without a hinge, the discreet subsections of the heat exchanger are brought together for securement. As shown, header plates  70  and  72  are configured for securement to one another. In this regard, header plates  70  and  72  include a plurality of holes  86  (see FIG. 5) sized to receive a plurality of bolts  88  (see FIG. 7) thus allowing the two header plates to be secured together once nuts  90  are installed on bolts  88 . Once the heater is secured in its open position, the heat transfer pipes of subsection  76  are co-axially aligned with the heat transfer pipes of subsection  78 . The installation of gaskets  84  ensures a sealing connection between the co-axially aligned pipes at the hinged joint. 
     Header plate  68  is shown in detail in FIGS. 8-9. In this regard, header plates  68 ,  70 ,  72  and  74  are identical to one another. As shown, a plurality of flanges are formed about the periphery of header plate  68  via bending of a portion of the sheet material which forms the header plate. Apertures  92  are formed via a punch and extrude method which creates a lip  94  (as seen in FIG. 8 a ). Lip  94  is also is shown in FIG.  10 . In this regard, the section of pipe which connects with the header plate passes through lip  94  (as shown in FIGS. 7,  10  and  12 ) and is thereafter subjected to a swaging operation which creates a flange  96  (see FIGS. 11 and 12) having a diameter greater than the diameter of aperture  92 , thereby preventing the withdrawal of the pipe from the header plate. The swaging operation also expands the portion of the pipe adjacent lip  94  thereby creating a sealing relationship therebetween. As shown, each of the header plates is provided with a pair of outflow pipe apertures and a pair of return pipe apertures. The number of outflow and return pipes can vary, and the pipes do not have to be equal in quantity or size. 
     As will be recognized by those skilled in the art, the outflow pipes operate at a significantly higher temperature than the return pipes. As a result, the thermal expansion of the outflow pipes is greater than the thermal expansion of the return pipes. Inasmuch as both pipes are connected to a common header plate, operation of the heater unit could potentially cause disconnection of the return pipes from the header plates. The present invention contemplates this dissimilar expansion of the heat transfer pipes and incorporates an expansion joint into each section of return pipe. As shown in FIG. 12, an expansion joint  98  is shown on one of the return pipes. Expansion joint  98  includes a short segment of pipe  100  which is connected to one of the header plates. Pipe  100  has an inner diameter D 1 . Return pipe  60  includes a terminating end  102  having a reduced outer diameter D 2 , wherein D 2  is less that D 1  allowing terminating end  102  to slide within pipe  100 . As a result, expansion joint  98  compensates for the greater thermal expansion experienced in the outflow pipes. Because the return pipes operate under a negative pressure, seals or gaskets are typically not required in the joint. 
     Inasmuch as heater  10  is typically suspended from an overhead structure, the heater preferably includes a plurality of hangers  104  fixed to an upper surface of the heater and configured for securement to conventional hanging hardware. The heat transfer pipes are preferably surrounded on three sides by reflectors  106  and  108 , which in the preferred overhead installation direct the heat downward towards the area to be heated. Of course, the reflectors can assume other configurations than that shown in FIGS. 1-2 and, may in some applications, not be used at all with the heater. It will be appreciated that the novel design of the present heat exchanger allows such reflectors to be integrated with the individual subsections of the heat exchanger even during shipping of the unit, thus facilitating unpackaging and installation of the heater at the installation site. 
     An alternative embodiment of the present invention, i.e., heater  10 ′, is shown in FIG.  13 . Heater  10 ′ is similar to heater  10 , but includes a total of only four heat transfer pipes. It will be appreciated that the heat output of heater  10 ′ will be less than the heat output of heater  10  (assuring other factors are constant). Heater  10 ′ is therefore suitable for application where less heat output is required. 
     It will be appreciated that the present invention has been described herein with reference to certain preferred or exemplary embodiments. The preferred or exemplary embodiments described herein may be modified, changed, added to or deviated from without departing from the intent, spirit and scope of the present invention, and it is intended that all such additions, modifications, amendment and/or deviations be included within the scope of the followings claims.