Abstract:
A blower for a high efficiency furnace is provided with an increased interior space for accommodating an impeller of maximum practicable diameter. The blower includes a blower motor and a blower housing having a bottom piece and a top piece assembling with the bottom piece to define an interior of the blower housing. The top piece includes an annular lower support portion for supporting the blower motor and an annular upper portion extending above and around the lower portion. The upper portion has an outer peripheral edge and lugs extending outward beyond the outer peripheral edge. The lugs have lug holes to receive mechanical fasteners to secure the blower housing to an external device. The head of the mechanical fasteners are positioned above the lugs on the upper portion of the top piece. In this arrangement the diameter of the bottom piece is not limited by a need to accommodate spacing for the head of the mechanical fastener. Additionally, the top piece and bottom piece have interlocking internal seals that provide positive engagement when the blower housing is assembled.

Description:
This application is a continuation of patent application Ser. No. 09/651,650, filed Aug. 30, 2000, now U.S. Pat. No. 6,386,123 and presently pending. 
    
    
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to blowers used on high efficiency (e.g. 90% or higher efficiency) furnaces for drawing air from outside the home into the furnace to support combustion and for expelling the combustion exhaust products outside the home. More particularly, the invention relates to a construction of a blower housing that maximizes the interior space available for the blower impeller. 
     (2) Description of the Related Art 
     Combustion blowers for high efficiency furnaces are common in the art. These blowers are used to draw air for combustion from outside the home. Generally, these blowers are located downstream of a combustion chamber or combustion tubes in the furnace, depending upon the style of furnace, into which the combustion air is drawn, mixed with fuel, and ignited to generate heat for the furnace. The exhaust gases are drawn into the suction side of the blower and discharged from the blower through an exhaust pipe that vents to outside atmosphere. 
     Although the mounting arrangement and available space inside the blower is similar between one furnace model and the next, each model of furnace typically is designed to use a specific type and size blower. Among other general specifications set by the furnace manufacturer, the blower must meet requirements for dimensional size, mounting arrangements, and air moving capacity. In particular, the size of the blower housing must fit within a given space which then in turn determines the location of mounting holes in the furnace bonnet. Thus, these dimensional size requirements limit the air moving capacity of a blower because the impeller size must be chosen to fit and operate efficiently within the given size housing. 
     In order to increase the air moving capacity of the blower given the fixed size for the blower housing and the impeller, the designer may choose to increase the speed of the impeller. This in turn requires that the blower be operated with a higher speed motor. This option has significant drawbacks, including increased cost to buy, to operate, and increased noise. The speed of the motor and the speed of the impeller must be closely matched to maximize efficiency of the impeller. This requires additional engineering considerations in designing the impeller to operate efficiently at increased speeds. Efficient high speed motors are generally more expensive and tends to increase the cost of the blower. A blower with a higher speed motor also tends to produce more noise and vibration. The higher speed motor also has greater electrical demands. High speed blower motors tend to operate at higher temperatures and generate more heat than lower speed motors. Since the motor is in close proximity to hot exhaust gases in the blower, higher speed motors may require auxiliary cooling systems such as a shaft mounted fan, or a larger bonnet interior to avoid heat buildup. Auxiliary cooling systems lower motor efficiency, and the higher operating temperatures tend to decrease the life cycle of the blower motor. 
     FIG. 1 shows a blower  20  of the prior art arranged on a blower mounting surface  21  of a furnace  22 . The blower  20  includes a blower motor (not shown) and a blower housing  24 . In FIG. 1, the blower motor has been removed from its center mount  26  on top of the blower housing  24  to show greater detail of the blower housing  24 . The blower housing  24  has a side wall  28  extending between a top piece  30  and a bottom piece  32 . The top piece  30  is molded with the center mount recess  26  to receive the blower motor (not shown). The side wall  28 , top piece  30 , and bottom piece  32  form a volute  34  for the blower housing  24 . When the blower  20  is energized, an impeller (not shown), operably connected to a shaft of the blower motor (not shown), rotates in the volute  34  to draw exhaust gases through an inlet hole  35  in the center of the bottom piece  32  and to compress gases in the volute  34 . The pressurized exhaust gases are directed into a discharge pipe  36  that extends outward and away from the blower  20  and the furnace  22 . 
     As shown in FIG. 1, mounting feet  38  for attaching the blower  20  to the blower mounting surface  21  of the furnace  22  are provided on the side wall  28  of the blower housing  24 . In order to secure the blower housing  24  to the furnace, mechanical fasteners  40  are used. The typical mechanical fastener  40  used to secure the blower  20  to the furnace  22  has a screw head driving end  42  and an opposite driven end  43  spaced from the driving end  42  by a shaft  44 . The driving end  42  is larger than the shaft  44  such that it engages a seating surface  46  on the mounting foot  38  and holds the blower  20  to the furnace. The seating surface  46  of the mounting foot  38  is sized to allow clearance between the driving end  42  of the fastener  40  and the side wall  28  of the blower housing  24 . 
     In the construction of older blower housings, a cut-out in the side wall of the blower housing is sometimes provided adjacent the mounting feet for clearance of the driving end of the mechanical fastener. A sponge foam rubber or rubber type sealing insert is then used once the fastener is installed to completely seal the housing along the narrow spacing adjacent the driving end of the fastener. These inserts and gaskets are problematic in that they tend to leak over time and represent the weak link in exhaust system integrity. Additionally, some blower housing constructions require the use of gasket material to build up the axial height of the bottom piece in the area of the mounting foot when the blower is installed on the furnace. This gasket material seals the blower housing in the area of the mechanical fastener and prevents the mounting foot from heeling over when the mechanical fastener is tightened and the blower housing is attached to the furnace. 
     What is needed to overcome the disadvantages of the prior art is a blower housing which has a maximized interior space to permit the use of the largest capacity impeller practicable while meeting the size restrictions set by the mounting holes located in the furnace by the manufacturer. The blower housing having the largest practicable capacity impeller would meet the manufacturer&#39;s requirements for air moving capacity with a lower speed motor. Such a blower would meet furnace manufacturers&#39; specifications for air moving capacity with decreased noise and vibration, and cost for the blower. Additionally, such a blower would eliminate the need for sealing inserts or gasket materials at the mounting locations for the blower housing. 
     SUMMARY OF THE INVENTION 
     In order to overcome the disadvantages of the prior art, the blower of the present invention provides an increased interior spacing while maintaining fixed exterior dimensions including especially the mounting hole locations. By having a larger interior for containing a larger impeller than in the prior art design, the blower of the present invention is capable of generating a higher air moving capacity with a decreased operating speed, cost, and lower noise and vibration levels. The blower of present invention also improves the containment of exhaust gases in the blower housing by improving the integrity of the seal around the housing against the furnace bonnet. 
     The blower of the present invention includes a blower housing and a blower motor. The blower housing has a top piece, a side wall, and a bottom piece that detachably engages the top piece to enclose the blower housing. The top piece includes an annular lower support portion for supporting the blower motor and an annular upper portion extending above and around the lower portion. The upper portion of the top piece of the blower housing has an outer peripheral edge and at least one lug extending outwardly beyond its outer peripheral edge. The bottom piece of the blower housing has a flange extending beyond its periphery that aligns with the lug of the top piece when the blower housing is assembled. The flange interlocks with the lug to detachably engage the top piece to the bottom piece. The top piece, side wall and bottom piece thus form a volute for the blower housing when assembled. 
     The lug on the top piece has a lug hole to receive a mechanical fastener such as a threaded bolt or screw. The flange on the bottom piece preferably has a flange hole that receives the mechanical fastener therethrough when the mechanical fastener joins the top piece to the blower mounting surface of the furnace. The mechanical fastener preferably attaches the blower housing to the furnace such that the blower housing is positioned between a blower motor and exterior mounting surface of the furnace. Thus, by locating the mechanical fastener with its head above the top piece, it may be driven tightly against the lug at the top of the blower and space need not be provided for the head of the mechanical fastener to be driven tightly against a blower housing surface which itself is located within the envelope of the impeller space. 
     In other words, in the prior art construction as seen in FIG. 1, a seating surface  46  is provided against which the driving end must be snugged to adequately secure the blower to the furnace. This requires a shoulder of a minimum width between the lug hole and the blower housing sidewall, which shoulder width (along with any clearance between the mounting hole sidewall and the shoulder) represents wasted space as the location of the blower housing sidewall is what limits the diameter of the impeller. With the present invention, the blower housing sidewall may be immediately adjacent the shaft  44  as the driving end is snugged against a surface located above the blower housing sidewall. Thus, little clearance need be provided between the shaft as the screwdriver or other tool used to secure the mechanical fastener has complete and unimpeded access to the driving end as it remains above the blower housing. 
     In another aspect of the present invention, the blower housing is provided with an improved seal between the top and bottom pieces. Preferably, the blower housing comprises a bottom piece having a disk shaped bottom portion with an outer perimeter border and an upstanding annular wall extending outward from the bottom disk around the outer perimeter border. The upstanding annular wall has an interior surface that forms a portion of the volute for the blower housing. The upstanding wall has an annular end axially opposite the bottom disk portion that extends between the exterior and interior surfaces of the upstanding wall. The annular end has an annular lip axially spaced from the annular end. 
     The top piece fits over the bottom piece to enclose the volute and form a casing for the blower. The top piece has a lower portion recessed into the top piece and extending into the casing. This lower portion receives the blower motor. The top piece also has an upper portion which extends around and above the lower portion. The upper portion has a primary groove and an outer peripheral edge surrounding the primary groove. The primary groove has an annular outer side wall and an annular inner side wall spaced apart by an annular groove wall. The groove wall has a secondary groove intermediate the coterminous edges of the groove wall and inner and outer side walls. The inner side wall of the primary groove abuts the interior surface of the upstanding wall of the bottom piece and the annular lip of the bottom piece is received in the secondary groove when the casing is assembled. 
     The inner side wall of the primary groove preferably has an annular rib extending outwardly from the side wall into the primary groove. The interior surface of the upstanding annular wall preferably has an annular notch on its interior surface. In this arrangement, as the annular notch receives the annular rib in the primary groove, the pieces tend to “snap” together as the bottom piece is fully assembly with the top piece. This construction thus provides a positive indicator of sealing between the top and bottom pieces when the blower housing is assembled. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     Further objects and features of the invention are revealed in the following detailed description of the preferred embodiment of the invention and in the drawings wherein: 
     FIG. 1 is an exploded, perspective view of a blower of the prior art; 
     FIG. 2 is a side view of a blower of the present invention installed on a mounting structure of the furnace; 
     FIG. 3 is a perspective view of a blower housing of the blower of FIG. 2; 
     FIG. 4 is a top, perspective view of a top piece of the blower housing of FIG. 3; 
     FIG. 5 is a bottom, perspective view of the top piece of FIG. 4; 
     FIG. 6 is a top, perspective view of a bottom piece of the blower housing of FIG. 3; 
     FIG. 7 is a bottom, perspective view of the bottom piece of FIG. 6; 
     FIG. 8 is a cross-sectional view of the top piece installed with the bottom piece to form the blower housing of FIG. 3; and 
     FIG. 9 is a cross-sectional view of the top piece installed with the bottom piece to form the blower housing of FIG.  3 . 
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2 shows the blower of the present invention installed in a furnace. The blower  50  includes a blower motor  52  and a blower housing  54 . The blower housing  54  has an annular upstanding wall  56  extending between a top piece  58  and bottom piece  60 . The bottom piece  60  is mounted on a blower mounting surface  21  in the furnace  22 , or the furnace bonnet, using mechanical fasteners  40 . The driving end  42  of each of the fasteners  40  seats against the top most portion of top piece  58  and the driven end  43  is installed in the blower mounting surface  21  on the furnace  22 . In the arrangement shown in FIG. 2, the bottom piece  60  is preferably held in position between the top piece  58  and the blower mounting surface  21  by compression from the mechanical fasteners  40 . 
     As shown in FIG. 2, the blower  50  is mounted on a blower mounting surface  21  on the furnace  22  where the blower housing  54  is positioned to allow the impeller (not shown) to draw exhaust gases directly from the combustion chamber or combustion tubes (not shown) into the blower housing  54 . A discharge pipe  61  is coupled to an exhaust pipe  62  using a gasket  64  to vent the exhaust gases to atmosphere. 
     FIG. 3 shows a perspective view of the blower housing  54  with top piece assembled on the bottom piece  60 . The top piece  58  covers over the bottom piece  60  to tightly enclose the blower housing  54  and prevent exhaust gases from leaking from the blower housing  54  during operation. The top piece  58  has a lower portion  66  that is recessed into the top piece  58  and extends into the blower housing casing  54 . The diameter of the recessed lower portion  66  is sized to accommodate the blower motor  52 . The lower portion  66  has mounting fittings  68  for securing the blower motor to the top piece  58 . The lower portion  66  may also have screw fittings  70  for securing the motor to the top piece  58 . At the center of the lower portion  66 , a through hole  72  is provided to allow a shaft (not shown) from the blower motor to pass into the interior of the blower housing  54  to be coupled with the impeller (not shown). The top piece  58  has an upper portion  74  which extends around and above the lower portion  66  and includes a seating surface  76  for the mechanical fasteners  40 . 
     FIGS. 4 and 5 provide greater detail of the top piece  58 . The upper portion  74  of the top piece  58  has an outer peripheral edge  78  and lugs  80  extending radially outward beyond the outer peripheral edge  78 . The lugs  80  preferably have arcuate lug holes  82  formed therein to allow adjustable positioning of the blower housing  54  on the blower mounting surface  21  of the furnace  22  when the blower  50  is installed on the furnace  22 . Preferably, each of the lugs  80  has a depending leg  84  extending downward and away from the outer peripheral edge  78  of the top piece  58 . Each leg  84  preferably has an exterior surface  86  and an arcuate interior surface  88  which gives each leg  84  a generally concave aspect when it is installed on the blower housing  54 . The arcuate interior surface  88  of the depending leg  84  preferably has a circumferential guide portion  90  that conforms to the upstanding annular wall  56  on the bottom piece  60 . The circumferential guide portion  90  on the depending leg  84  supports and aligns the top piece  58  with the bottom piece  60  during operation. The depending leg  84  bears some of the weight of the blower motor when the blower  50  is installed on the blower mounting surface  21  of the furnace  22 . 
     As shown in FIG. 5, an annular locating groove  92  is provided around the upper portion  74  radially inward of the outer peripheral edge  78 . The annular locating groove  92  is positioned a sufficient distance away from the outer peripheral edge  78 , lug hole  82 , and depending leg  84  so as not to interfere with the seal between the top piece  58  and bottom piece  60  when the blower housing  54  is assembled. Greater detail of the annular locating groove  92  and seal between the top and bottom pieces  58 , 60  will be discussed later with reference to FIG.  8 . 
     FIGS. 6 and 7 provide detail of the bottom piece  60  of the blower housing  54 . The bottom piece  60  has a bottom disk portion  94  with a center inlet hole  95  that allows the blower  50  to draw exhaust gases into the housing  54  during blower operation. The bottom disk portion  94  has an outer perimeter border  96  and the upstanding annular wall  56  extends outward and away from the outer perimeter border  96 . The underside of the bottom disk portion  94  of the blower housing  54  is generally flat so that it may be mounted flush against the blower mounting surface  21  of the furnace  22 . The upstanding annular wall  56  has an interior surface  98  which defines a portion of a volute  100  of the blower housing  54  and an exterior surface  102  that surrounds the interior surface  98 . The discharge pipe  61  extends outward and away from the annular wall  56  and communicates with the volute  100  to direct pressurized exhaust gases from the blower housing  54 . The discharge pipe  61  may have a boss end  105  to allow connection to the exhaust pipe  62 , as required. Preferably, the bottom disk portion  94 , the upstanding wall  56 , and the discharge pipe  61  are formed monolithically. 
     The bottom piece  58  is provided with a plurality of mounting flanges  106  circumferentially spaced around the outer perimeter border  96  of the bottom disk portion  94 . Each of the mounting flanges  106  extends radially outward from the outer perimeter border  96  and has a flange hole  108  therethrough. Each of the mounting flanges  106  preferably aligns with a corresponding lug  80  on the top piece  58 . The alignment of the lugs  80  and flanges  106  may be such that the top piece  58  and bottom piece  60  are assembled in only one orientation. Similar to the lug hole  82 , the flange hole  108  is also preferably arcuate to allow minor adjustment of the blower  50  when the blower  50  is mounted on the blower mounting surface  21  of the furnace  22 . To maximize the diameter of the upstanding annular wall  56 , an inner edge  110  of the flange hole  108  may be formed flush with the exterior surface  102  of the upstanding annular wall  56 . 
     Preferably, the flange hole  108  is also formed to receive the depending leg  84  of the top piece  58  when the blower  50  is assembled. As shown in FIG. 9, the flange hole  108  preferably has a step recess  112  which is shaped to receive the depending leg  84  from the lug  80  of the top piece  58  and a through hole  113 . The through hole  113  allows the mechanical fastener to be directed from the lug  80  and lug hole  82  on the top piece  58  to the blower mounting surface  21  on the furnace  22  when the blower  50  is secured to the blower mounting surface  21  on the furnace  22 . The step recess  112  positively aligns the depending leg  84  and captures a bottom portion of the circumferential guide portion  90  of the depending leg  84  so that the top piece  58  and bottom piece  60  are positively engaged both during assembly and operation of the blower  50 . It is preferred that the bottom piece  60  be held in position by the compressive forces exerted by the mechanical fastener  40  on the top piece  58 . The step recess  112  bears some of this compressive force and stabilizes the position of the bottom piece  60  adjacent the blower mounting surface  21  of the furnace  22 . 
     Details of the attachment between the top and bottom pieces are best shown in FIG.  8 . The upstanding annular wall  56  of the bottom piece  60  has an upper section  114  that cooperates with the annular groove  92  in the upper portion  74  of the top piece  58 . The upper section  114  includes an annular end  116  that extends between the interior and exterior surfaces  98 , 102  of the upstanding wall  56 . The annular end  116  has a lip  118  extending axially outward from the bottom disk portion  94  intermediate the coterminous edges of the annular end  116  and the interior and exterior surfaces  98 , 102  of the upstanding annular wall  56 . Preferably, the annular lip  118  has a generally triangular shaped cross section to act as a guide during assembly as well as an overlapping fit between the top and bottom pieces  58 , 60 . The upper section  114  also importantly includes an annular notch  120  extending around the interior surface  98  of the upstanding wall  56 . 
     The annular groove  92  formed in the upper portion  74  of the top piece  58  includes a primary groove  122  and a secondary groove  124 . The primary groove  122  includes an annular inner side wall  126  and an annular outer side wall  128  spaced apart from the annular inner side wall  126  by an annular groove wall  130 . When the top piece  58  is installed on the bottom piece  60 , the annular inner side wall  126  abuts the interior surface  98  of the upstanding annular wall  56 , and the annular outer side wall  128  faces the exterior surface  102  of the upstanding annular wall  56 . The annular outer side wall  128  may be formed with a lead-in taper  132  to allow the top and bottom pieces  58 , 60  to more easily fit together. 
     The primary groove  122  also includes an annular rib  134  axially spaced below the annular groove wall  130 . The annular rib  134  cooperates with the annular notch  120  in the upstanding annular wall  56  of the bottom piece  58  to form a first sealing area  136  for the blower housing  54 . When the top piece  58  is fully installed on the bottom piece  60 , the top piece  58  will snap fit onto the bottom piece  60  as the annular rib  134  slides across the interior surface  98  of the upstanding annular wall  56  and into the annular notch  120 . The rib  134  and notch  120  provide a positive lock indication for a blower assembly operator when assembling the blower housing  54 . 
     The secondary groove  124  in the annular groove  92  on the upper portion  74  of the top piece  58  is formed internal to primary groove  122 . The secondary groove  124  is formed intermediate the coterminous edges of the annular groove wall  130  and inner and outer side walls  126 , 128 . The secondary groove  124  has a generally triangular shaped cross section that matches the geometry of the annular lip  118  on the upstanding wall  56  of the bottom piece  60 . The secondary groove  124  provides a secondary sealing area  138  for the blower housing. 
     In assembling the blower housing  50  into the arrangement shown in FIG. 3, the top piece  58  may be installed with the bottom piece  60  to create the blower housing  54  of the present invention. The upper section  114  of the annular wall  56  of the bottom piece  60  may be inserted into the annular groove  92  on the underside of the top piece  58  and positively locked in place to seal the blower housing  54 . 
     The depending legs  84  of the lug  80  of the top piece  58  may be inserted into the step recess  112  formed in the flange hole  108  such that the circumferential guide portion  90  of the interior arcuate surface  88  of the depending lug  84  mounts flush against the exterior surface  102  of the upstanding annular wall  56  of the bottom piece  60  and a bottom portion of the leg  84  is nested within the recess  112  of the flange hole  108 . Preferably, the lengths of the depending legs  84  are sized such that when the upper section  114  of the annular wall  56  is fully inserted into the annular groove  92  in the top piece  58 , the leg  84  is captured by the flange hole  108 . The lugs  80  and matching flanges  106  may have irregular angular placement along each of the respective top and bottom pieces  58 , 60  to provide a keying assembly for the blower housing  54  such that the top and bottom pieces  58 , 60  may be assembled in only one orientation. 
     Each of the top and bottom pieces  58 , 60  may be formed from materials that are capable of withstanding relatively high temperatures from the exhaust gases being expelled from the blower housing  54 . The blower housing  54  may be made from a polypropylene or polyvinyl chloride (PVC) type plastic, although other materials capable of withstanding the heat from the exhaust gases may also be used. The material used must be sufficiently resilient to allow the top piece  58  and bottom piece  60  to flex during installation so that the top piece  58  and bottom piece  60  may properly form the primary and secondary seals  136 , 138  in the blower housing  54 . 
     By locating the lugs  80  on the upper portion  74  of the blower housing  54 , the diameter of the upstanding annular wall  56  can be increased. By moving the driving end  42  of the mechanical fastener  40  above the lug  80  on the top piece  58 , the clearance between the screw head driving end  42  and the upstanding annular wall  56  of the blower housing  50 , as well as any clearance between the shaft and the opening through which it extends can be eliminated. The mechanical fastener  40  used to secure the blower housing to the blower mounting surface of the furnace may run directly down the exterior surface  102  of the upstanding annular wall  56  because there is sufficient clearance on the upper portion  74  of the top piece  58  for the screw head driving end  42  of the mechanical fastener  40 . Furthermore, there may also be a savings in assembly time as the driving head is much more readily accessible with the fastening tool making it easier to apply the tool to the driving head. 
     As the top piece  58  snap fits with the bottom piece  60  to create a sealed unit, gasket materials and other sealing inserts commonly used in the prior art are no longer needed. By constructing the bottom piece  60  with a flat bottom disk and an upstanding annular wall  56  extending from the outer perimeter border  96  of the bottom disk portion  94 , and a top piece with the annular groove  92 , the locations for the seals  136 , 138  between the top piece  58  and bottom piece  60  are moved to a position on the blower housing  54  where use of mechanical fasteners  40  does not interfere with the integrity of the seals  136 , 138 . By locating the lugs  80  on the outer peripheral edge  78  of the upper portion  74  of the top piece  58 , the upper portion  74  of the top piece  58  may flex inward such that the normally tapered outer side wall  128  of the primary groove  122  contacts the exterior surface  102  of the upstanding wall  56 . Thus, the combination of the primary seal  136  and internal secondary seal  138  provides improved sealing characteristics for the blower housing  54  not found in the prior art. 
     Although the description of the blower housing presented herein refers to a primary and secondary seals formed on respective portions of the top and bottom pieces, it should be noted that the location and combination of the components comprising the primary and secondary seals may be reversed and positioned on the other of the top and bottom pieces of the blower housing. 
     Various other changes to the preferred embodiment of this invention described above may be envisioned by those of ordinary skill in the art. However, those changes and modifications should be considered as part of the invention which is limited only by the scope of the claims appended hereto and their legal equivalents.