Patent Publication Number: US-6341949-B1

Title: Inducer fan motor assembly

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a high efficiency furnace and, in particular to an inducer fan unit for use in a high efficiency multi-poised gas furnace. 
     In general, gas furnaces that are used to heat homes or small buildings draw air from the comfort region being serviced, heat the air within a heat exchanger, and return the heated air back to the comfort air region. The heat exchanger typically contains a series of passages, each of which is heated by an ignited air/gas mixture and the products of combustion are vented by a flue pipe to the surrounding ambient. Air drawn from the comfort region is arranged to pass over the exterior surfaces of the heat exchanger where it is heated prior to being returned to the comfort region. 
     The flue gas leaving the heat exchanger is delivered into a collector box from which it is discharged to ambient via a chimney or flue pipe. An inducer fan is typically located in the collector box which induces sufficient draft in the flue gas flow to optimize combustion within the furnace. 
     Many later model gas furnaces are arranged so that they can be mounted and operate efficiently in a number of different positions. These furnaces are referred to as multi-poised units. Generally, the furnace is in an up-flow position wherein the unit is in a normal upright position and room air moves from a bottom entrance upward through the heat exchanger into return air duct located in the top of the unit. The unit can also operate in an inverted position wherein room air flows in the downward direction. In addition, the furnace may be positioned on its side whereupon room air can flow through the furnace generally in horizontal direction to either the right or left side of the furnace. 
     The multi-pose furnace allows for installation in many different positions that are generally not available to more conventional units. Special care, however, must be given to various components of the furnace to insure that they operate effectively in each of the positions. One of these components is the inducer fan assembly. The motor is typically mounted in assembly upon isolators that effectively dampen motor vibration when the furnace is in an upright or upflow position. However, the isolators have been found to be sensitive to the furnace&#39;s orientation and do not provide the same level of damping in all positions which can result in excessive noise and, in some extreme cases, may lead to early inducer fan failure. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to improve the ability of a multi-poised furnace to operate efficiently in a variety of different positions. 
     It is a still further object of the subject invention to render the inducer fan assembly of a multi-poised furnace relatively insensitive to the furnace&#39;s orientation. 
     Another object of the present invention is to provide a vibration isolation mount for an inducer fan motor that will reduce the unwanted effects of motor vibrations regardless of the motor&#39;s orientation. 
     These and other objects of the present invention are attained by an inducer fan unit for use in a gas fired multi-poised furnace that includes an inducer housing. The housing has an opening in one of the housing walls and a cover is placed over the opening and is secured to the walls. The cover contains three brackets that are circumferentially spaced about its periphery at equal intervals. A support plate having the inducer motor attached to its front face is connected to the brackets by means of mounting tabs. Each mounting tab extends from the periphery of the support plate and has a mounting surface turned at about a 45° angle with respect to the plane described by the front face of the plate with the plane of each support surface passing through the central axis of the plate. Each support face complements a mounting surface on one of the brackets and is secured thereto by a threaded fastener or the like. A vibration isolator is mounted between the two support surfaces. The reaction of the isolators is such that uniform damping is provided regardless of the furnace&#39;s orientation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of these and other objects of the present invention, reference will be made to the following detailed description of the invention, read in connection with the accompanying drawings, wherein: 
     FIG. 1 is a front view of a multi-poise gas furnace in an upright position with the front cover removed to show the inducer and burner sections of the furnace; 
     FIG. 2 is an exploded perspective view illustrating the inducer fan unit employed in the present furnace; 
     FIG. 3 is an enlarged perspective view of the motor and fan assembly used in the inducer fan unit; 
     FIG. 4 is an exploded perspective view showing the component parts of the motor and fan assembly; 
     FIG. 5 is a front view of the support plate employed in the fan motor assembly; 
     FIG. 6 is a view taken along lines  6 — 6  in FIG. 5; 
     FIG. 7 is a front view of the motor support plate employed in fan motor assembly; and 
     FIG. 8 is a sectional view taken along lines  8 — 8  in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning initially to FIG. 1, there is illustrated a gas fired multi-poise furnace, generally referenced  10 , that contains an inducer fan unit  12  that embodies the present invention. The furnace is shown in an upright position wherein the return air from the comfort region enters the lower part of the furnace and passes vertically in an upward direction through a bank of heat exchangers in the upper part of the furnace prior to being sent back to the comfort region. The burner assembly  13  seen in the front opening  16  in the furnace contains four burners  15 , although the furnace may contain more or less burners. Mounted directly over the burner assembly is the inducer unit  12 . The inducer fan motor assembly  20  is secured to the front wall of the inducer housing  21  along with a vent elbow  22  that connects the housing with a flue pipe  23 . 
     The inducer unit is shown in greater detail in FIG.  2 . The unit includes the previously noted housing  21  that is secured in assembly to a back wall  24  that closes against the heat exchanger discharge duct  25 . The back wall of the inducer housing contains a generous opening  27  that communicates with the heat exchanger outlets. The fan motor assembly includes a blower fan  28  which, in assembly, passes through an opening  29  formed in the front wall  30  of the housing. As will be explained in greater detail below, the fan motor assembly  20  is secured to the front wall of the housing over the blower opening to position the blower fan adjacent to and in axial alignment with the opening in the rear wall of the housing. 
     The vent elbow  22  is arranged to pass over a cylindrical discharge flange  32  that surrounds a flue gas discharge opening formed in the front wall of the inducer housing adjacent to the blower opening. The inducer housing is divided by a scroll cutoff  36  into two separate chambers that are the blower chamber  37  and the discharge chamber  38 . In operation, the blower fan creates a draft in the heat exchanger outlets, thereby inducing the flue gases to flow into the flue gases chamber via hole  27  formed in the inducer housing and then out of the furnace via the flue pipe. 
     The fan motor assembly  20  is shown in greater detail in FIGS. 3 and 4. The motor  40  contains a shaft that extends to both the front and the rear of the motor housing. The rearwardly extended section  43  of the shaft supports a small cooling fan  45  that is adapted to pass cooling air over the motor housing any time the motor is in operation. The forwardly extended section  46  of the shaft passes through axially aligned holes  47  and  48  formed in the motor support plate  50  and the housing cover  76  respectively. The fan blower  28  is secured to the extended section  46  of the shaft. The motor is secured to the front face  51  of the support plate by means of screws  52  that pass through holes  53  in the support plate and are threaded into the motor housing. When tightened down, the screws draw the support plate against the motor housing. 
     The support plate contains three equally spaced peripheral arms  60  (FIG. 5) each of which terminates in a distal end section that is separated. The distal end of each arm is bent back toward the motor so that it forms about a 45° angle with the front face  51  of the plate to create a mounting tab  65  so that the tabs are spaced at about 120° intervals about the plate. An elongated cutout  63  is also formed in each tab. The plane described by each tab passes through the central axis  67  of the motor fan unit. Stiffening ribs  66  are formed in the plate along the length of each arm to provide additional strength to the arms and tabs. 
     Resilient grommets  68 , preferably made of rubber, are mounted within each cutout. A cylindrical spacer  86  is passed through each grommet and a screw  70 , in turn, is passed through the center of each cylindrical spacer. As will be explained in further detail below, the distal end of each screw is threaded into a receiving hole  85  located in the cover  76  to draw the space against a mounting surface  82  located on one of the mounting brackets  80  located on the cover. 
     The cover  76  (FIGS. 7 and 8) of the inducer fan motor assembly contains a number of mounting holes  74  located about the rim of the cover. In assembly, the mounting holes are aligned with extruded holes  75  (FIG. 2) in the front wall  30  of the housing surrounding the fan opening in the inducer housing. Screws are passed through the holes in the cover and are threaded into the extruded holes to secure the cover to the front wall of the housing. Three mounting brackets are equally spaced at about 120° intervals around the periphery of the cover. The brackets are V-shaped structures that extend outwardly toward the motor support plate. Each bracket has a mounting surface  82  that forms an angle of about 45° with the front face  83  of the cover and the plane of the mounting surface complementing that of the tabs on the motor support plate. Each mounting surface further includes an extruded hole  85 . The screws  70  (FIG. 4) that pass through the resilient gaskets on the support plate tabs are threaded into the extruded holes. 
     As should be evident from the above disclosure, the inducer fan motor assembly is isolated from the furnace structure upon three circumferentially spaced resilient gaskets. Because the gaskets are additionally turned 45° with regard to a plane that is perpendicular to the axis of the motor shaft, the vibratory forces generated by the fan motor will be uniformly distributed to the three vibration isolators regardless of the orientation of the furnace. It should be further evident that the cover can be eliminated from the assembly and the mounting brackets formed as an integral part of the housing without departing from the teachings of the invention. 
     While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.