Title:
Furnace distribution blower without a blower housing
Kind Code:
A1


Abstract:
A furnace distribution blower for use in a conventional furnace that is configured without a blower housing. The furnace distribution blower includes a backward curved impeller mounted around a drive motor having a central drive shaft. The drive motor rotates the backward curved impeller to draw air into the inlet of the impeller. Preferably, the inlet of the impeller is closely mounted to an inlet bell of the furnace. The furnace distribution blower can be mounted to a support tray such that the furnace distribution blower can be moved from an operating position in which the impeller is positioned beneath the heat exchanger and a service position in which the impeller is removed from within the furnace housing. The elimination of the blower housing decreases the cost of the furnace distribution blower as compared to a blower having a housing.



Inventors:
Paulsen, Frederick D. (Holiday Island, AR, US)
Post, Steven W. (Cassville, MO, US)
Platz, John A. (Springfield, MO, US)
Application Number:
11/005541
Publication Date:
09/08/2005
Filing Date:
12/06/2004
Assignee:
PAULSEN FREDERICK D.
POST STEVEN W.
PLATZ JOHN A.
Primary Class:
International Classes:
F24H3/02; (IPC1-7): F24H3/02
View Patent Images:
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Primary Examiner:
BASICHAS, ALFRED
Attorney, Agent or Firm:
Joseph D. Kuborn (Milwaukee, WI, US)
Claims:
1. A furnace distribution blower comprising: a drive motor having a drive shaft; and an impeller having an inlet surrounding the drive motor, the drive motor being operable to rotate the impeller around the drive motor to draw a flow of air into the inlet of the impeller such that the impeller radially discharges the inlet air, wherein the impeller is not surrounded by a housing.

2. The furnace distribution blower of claim 1 wherein the drive motor is mounted above an inlet opening of a furnace by a plurality of mounting arms.

3. The furnace distribution blower of claim 2 wherein the inlet of the impeller is closely spaced from an inlet bell of the furnace that defines the inlet opening of the furnace.

4. The furnace distribution blower of claim 1 wherein the impeller is a backward curved impeller having a plurality of backward curved impeller blades.

5. The furnace distribution blower of claim 4 wherein the inner blade tips of each impeller blade are spaced from the drive motor such that the impeller is rotatable about the drive motor.

6. The furnace distribution blower of claim 1 wherein the impeller is mounted to a sidewall of the furnace.

7. The furnace distribution blower of claim 1 wherein the impeller is mounted to a support wall spaced from the bottom wall of the furnace.

8. A furnace distribution blower for use in a furnace having a furnace enclosure including a pair of spaced sidewalls and a bottom wall, the distribution blower comprising: a drive motor having a drive shaft; an impeller having an inlet surrounding the drive motor, the drive motor being operable to rotate the impeller around the drive motor to draw a flow of air into the inlet of the impeller such that the impeller radially discharges the inlet air, wherein the impeller is not surrounded by a housing; and a scroll-shaped outer wall surrounding the impeller, wherein the scroll-shaped outer wall has an open upper end and directs the flow of air from the impeller into the furnace enclosure

9. The furnace distribution blower of claim 8 further comprising a support wall spaced above the bottom wall of the furnace enclosure, the support wall including an inlet bell aligned with the inlet of the impeller.

10. A furnace distribution blower for use in a furnace having a heat exchanger and a support frame, the blower comprising: a drive motor having a drive shaft; an impeller having an inlet surrounding the drive motor, the drive motor being operable to rotate the impeller around the drive motor to draw a flow of air into the inlet of the impeller such that the impeller radially discharges the inlet air; and a support tray positioned below the heat exchanger of the furnace and surrounding the impeller, the support tray including an inlet bell and a scroll-shaped outer wall to direct the flow of air from the impeller toward the heat exchanger.

11. The furnace distribution blower of claim 10 wherein the drive motor is mounted above the inlet bell formed in the support tray by a plurality of mounting arms.

12. The furnace distribution blower of claim 11 wherein the inlet of the impeller is closely spaced from the inlet bell of the support tray.

13. The furnace distribution blower of claim 10 wherein the impeller is a backward curved impeller having a plurality of backward curved impeller blades.

14. The furnace distribution blower of claim 13 wherein the inner blade tips of each impeller blade are spaced from the drive motor such that the impeller is rotatable about the drive motor.

15. The furnace distribution blower of claim 10 wherein the support tray is movable along the support frame of the furnace.

16. The furnace distribution blower of claim 15 wherein the support tray is movable between an operating position in which the impeller is positioned beneath the heat exchanger and a service position in which the impeller is removed from beneath the heat exchanger.

17. The furnace distribution blower of claim 15 wherein the support tray is formed from stamped metal.

18. The furnace distribution blower of claim 10 wherein the support tray includes an angled bottom wall, wherein the drive motor and impeller are mounted to the angled bottom wall such that the impeller is positioned at an angle relative to horizontal when the impeller is positioned beneath the heat exchanger.

19. The furnace distribution blower of claim 10 wherein the support tray includes a pair of spaced side edges that are slidably movable along the support frame of the furnace such that the support tray can be moved from an operating position in which the impeller is positioned beneath the heat exchanger and a service position in which the impeller is removed from the beneath the heat exchanger.

20. The furnace distribution blower of claim 10 wherein the support tray includes a scroll-shaped side wall that directs the flow of air from the impeller upward toward an outlet of the support tray.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is based on and claims priority to U.S. Provisional Patent Application Ser. No. 60/528,124, filed on Dec. 9, 2003 and U.S. Provisional Patent Application Ser. No. 60/545,183, filed on Feb. 17, 2004.

BACKGROUND OF THE INVENTION

The present invention generally relates to a furnace, and particularly to a furnace distribution blower used within the furnace. More specifically, the present invention relates to a unique configuration and mounting for a furnace distribution blower that does not include a blower housing surrounding a rotating impeller that creates a flow of air over the furnace heat exchanger.

Typically, a household furnace includes a furnace distribution blower that draws a supply of fresh air into the furnace housing and directs the flow of fresh air over a heat exchanger. The heated air, after passing over the heat exchanger, is directed to the environment to be heated.

In typical prior art furnaces, the furnace distribution blower includes a blower housing that surrounds a forward curved impeller wheel. The blower housing includes an inlet opening that receives the flow of fresh air. The rotating forward curved impeller directs the fresh air radially outward against a scroll shaped housing, which ultimately directs the flow of air out of an outlet formed in the housing and over the heat exchanger of the furnace. In this type of system, the impeller for the furnace distribution blower is positioned in the center of the housing such that the flow of fresh air is directed by the housing.

One disadvantage of the prior art furnace distribution blower is the cost and materials required for the housing. Typically, the housing is formed from either a metallic or plastic material that must be separately formed and assembled.

Therefore, it is an object of the present invention to provide a furnace distribution blower that does not include a housing yet provides the required airflow characteristics for proper operation of the furnace.

SUMMARY OF THE INVENTION

The present invention utilizes a backward curved impeller mounted on a vertical motor shaft of a drive motor. The backward curved impeller surrounds the drive motor including the vertical motor shaft. The drive motor preferably includes a plurality of brackets that mount the motor to a bell-shaped inlet plate of the furnace housing to draw air into the impeller from the bottom portion of the furnace. The bell-shaped portion of the inlet plate is generally the same size as the inlet of the impeller and is designed to be close vertically to the inlet of the impeller so that pressurized air in the furnace will not escape back through the inlet bell.

The impeller of distribution blower draws air through the cool air inlet of the furnace, over the drive motor and moves the cool air across the heat exchanger. The inlet air flow, now warmed by the heat exchanger, is exhausted from the top of the furnace.

In one embodiment of the invention, the inlet of the backward curved impeller is mounted slightly above the bottom wall of the furnace housing such that cool air can be received from the bottom of the furnace. Alternatively, the impeller can be rotated 90° and mounted to one of the sidewalls of the furnace housing such that inlet air is received from next to the furnace housing. In yet another alternate embodiment of the invention, the impeller can be suspended above the bottom wall of the furnace housing such that the flow of cool air can be received from both the bottom and the sides of the furnace housing.

In yet another alternate embodiment of the invention, the rotating backward curved impeller can be spaced from the bottom wall of the furnace housing and surrounded by a scroll-shaped outer wall. The scroll-shaped outer wall increases the efficiency of the rotating backward curved impeller by directing the air flow upward toward the heat exchanger without the use of a housing. The outer wall allows the inlet air to be drawn from both the side and the bottom wall of the furnace housing.

In yet another alternate embodiment of the invention, the rotating backward curved impeller is spaced above the bottom wall of the furnace within a scroll-shaped support tray. The support tray is formed from stamped metal and is supported beneath the heat exchanger and is movable relative to the furnace housing. The support tray includes a scroll-shaped outer wall. The scroll-shaped outer wall directs the flow of air upward from the impeller toward the heat exchanger of the furnace and increases the efficiency of the rotating backward curved impeller without the use of a housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated of carrying out the invention.

In the drawings:

FIG. 1 is a schematic illustration of a traditional furnace employing a furnace distribution blower constructed in accordance with the present invention;

FIG. 2 is a magnified view of the furnace distribution blower of the present invention;

FIG. 3 is a schematic drawing of an alternate placement of the furnace distribution blower within a traditional furnace;

FIG. 4 is a schematic drawing of another alternate placement of the furnace distribution blower in a traditional furnace;

FIG. 5 is a schematic drawing of yet another alternate placement of the furnace distribution blower within a traditional furnace;

FIG. 6 is a top perspective view of a traditional furnace incorporating the furnace distribution blower of the present invention;

FIG. 7 is a view similar to FIG. 6 illustrating the movement of the furnace distribution blower and support tray into a service position;

FIG. 8 is a view similar to FIG. 7 illustrating the support tray in the service position;

FIG. 9 is a partial sectional view taken through the furnace distribution blower and support tray;

FIG. 10 is a top perspective view of the furnace distribution blower and support tray of the first embodiment of the invention;

FIG. 11 is a section view taken along line 11-11 of FIG. 10;

FIG. 12 is a top perspective view of the furnace distribution blower and a second embodiment of the support tray;

FIG. 13 is a section view taken along line 13-13 of FIG. 12;

FIG. 14 is a top perspective view of yet another alternate embodiment of the furnace distribution blower and support tray;

FIG. 15 is a section view taken along line 15-15 of FIG. 14;

FIG. 16 is a top perspective view of yet another alternate embodiment of the furnace distribution blower and support tray; and

FIG. 17 is a section view taken along line 17-17 of FIG. 16.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a conventional furnace 10 utilized to warm a supply of air and distribute the warmed air through a residence. The furnace 10 generally includes an outer housing wall 12 that surrounds a distribution blower 14, a heat exchanger 16, combustion chamber 18 and draft inducer 20. As is well known, a supply of fuel is provided to the combustion chamber 18 which creates a heated supply of air. The heated supply of air circulates through the heat exchanger 16, as illustrated by arrows 22. The flow of heated air from the combustion chamber is drawn through the tortuous path of the heat exchanger 16 by the draft inducer, including a blower housing 24 and a drive motor 26. The outlet 28 of the draft inducer 20 is connected to an exhaust pipe 30 such that the combustion gases can be expelled from the furnace 12.

The furnace distribution blower 14 creates a flow of air 31 that passes over the heat exchanger 16 and flows to the environment to be heated, as illustrated by arrow 32.

In prior art furnace configurations, the furnace distribution blower is typically a blower having a blower housing with an inlet and an outlet and a drive motor for rotating a forward curved (FWC) inlet wheel. The forward curved inlet wheel draws fresh air from outside of the furnace housing 12 and directs the flow of air over the heat exchanger 16. Typically, the distribution blower includes an external housing that is formed from either a molded plastic material or metal and encloses the rotating forward curved wheel to create the desired flow of air through the furnace.

Referring now to FIG. 1, thereshown is an improved furnace distribution blower 14 that is constructed without a blower housing in accordance with the present invention. As illustrated, the furnace distribution blower includes an impeller 34 having a plurality of impeller blades 36 extending between an inwardly recessed back plate 38 and a curved front wall 40. As illustrated, the impeller is a backward curved (BWC) or a radial (RAD) wheel made from either metal or molded plastic. The impeller 34 includes a central hub 42 that receives one end 43 of a drive shaft 44 of a central drive motor 46. As illustrated in FIG. 1, the drive motor 46 and the impeller 34 are concentric such that the impeller 34 rotates around the centrally mounted drive motor 46. As illustrated in FIG. 1, the inner blade tips 48 of the impeller 34 pass around the drive motor 46 such that the drive motor 46 can rotate the impeller.

The impeller 34 includes an inlet 50 having a diameter defined by a top lip 52. The top lip 52 of the impeller 34 is spaced slightly inward from an inlet bell 54 formed as a portion of the bottom wall 56 of the furnace housing 12. As illustrated, the close spacing between the top lip 52 of the impeller 34 and the inlet bell 54 prevents pressurized air within the furnace interior 58 from escaping back through the inlet.

As illustrated in FIGS. 1 and 2, the impeller 54 has its inlet 50 mounted facing downward with the motor 46 mounted vertically inside the impeller inlet 50. The motor 46 can have a wire-type bellyband mount with three or four radial mounting arms 60 resiliently mounted by connectors 62 to the bottom wall 56. The bottom wall 56 includes the inlet bell 54 that provides tight spacing between the bottom wall of the furnace and the inlet end of the impeller 34. This tight spacing is necessary so that the discharge side can be pressurized by the rotating impeller 34, thus forcing air over the furnace heat exchanger 16, and through the duct system.

Referring now to FIG. 2, thereshown is a more detailed view of the distribution blower, including the impeller 34, of the present invention. As illustrated, the impeller 34 includes multiple impeller blades 36 that each terminate at a radial blade tip 64. During rotation of the backward curved impeller 34, the impeller 34 develops most of its pressure on its blades and thus can operate efficiently without an external housing. As shown in FIG. 2, the inlet 50 has a diameter slightly less than the outermost diameter 66 defined by the impeller blades 64.

Referring back to FIG. 1, it can be understood that the flow of cool air, illustrated by arrows 68, is drawn through the inlet 50 and passes over the motor 46. Thus, the rotating impeller 34 not only provides the required airflow over the heat exchanger 16, but also supplies a flow of cooling air over the motor 46. The configuration of the rotating impeller 34 eliminates the need for an external housing, which dramatically decreases the cost of creating the furnace distribution blower 14 as compared to the prior art.

In the embodiment of the invention illustrated in FIG. 1, the motor 46 is a conventional and commercially available motor that is far less costly than a specialized “inside-out” motor utilized in a conventional motorized wheel application. This design enables maintenance to occur later in the furnace's life with just the motor being replaced instead of the entire blower and blower housing. The embodiment shown in FIG. 1 will reduce the overall price of the furnace distribution blower 14 as compared to a traditional forward curved (FWC) unit mounted in an expensive blower housing.

Referring now to FIG. 3, thereshown is an alternate embodiment of the present invention in which the furnace distribution blower 14 of the present invention is mounted at an alternate location along the furnace housing 12. Specifically, the furnace distribution blower 14, including the backward curved impeller 34, is mounted to a sidewall 70 of the furnace housing 12. The sidewall 70 includes the inlet bell 72 that is closely spaced to the inlet 50 of the impeller 34. Like the embodiment illustrated in FIG. 1, rotation of the impeller 34 creates a radial flow of air that passes over the heat exchanger 16 of the furnace 10. In the embodiment illustrated in FIG. 3, the bottom wall 56 of the furnace housing 12 does not include an inlet opening. The embodiment illustrated in FIG. 3 is particularly desirable where space restrictions prevent the inlet opening being formed in the bottom wall of the furnace housing.

Referring now to FIG. 4, thereshown is yet another embodiment of the furnace and furnace distribution blower 14 of the present invention. As illustrated, the furnace distribution blower 14, including the impeller 34, is suspended above the bottom wall 56 by an intermediate wall 74. The intermediate wall 74 includes the inlet bell 54 that is closely spaced from the inlet 50 for the impeller. The use of the intermediate wall 74 allows inlet air to flow into the furnace from either or both the bottom wall 56 and the sidewall 70. This type of mounting arrangement increases the flexibility of the furnace.

Referring now to FIG. 5, thereshown is yet another alternate embodiment of the furnace and furnace distribution blower of the present invention. As illustrated in FIG. 5, the furnace distribution blower 14, including the impeller 34, is mounted to a support wall 76 suspended above the bottom wall 56 of the furnace housing. The support wall 76, in turn, is joined to upstanding sidewalls 78. The sidewalls 78 are preferably a continuous element that is scroll-shaped and has an open top 80. Thus, as the impeller 34 rotates, the flow of air 82 is directed radially against the sidewalls 78 and out of the open top 80 and into contact with the heat exchanger 16. The curved sidewall 78 has the advantages of increasing the efficiency of the backward curved impeller 34, while creating room around the sides and bottom to allow air to be drawn into the furnace from both the bottom wall 56 and the sidewall 70. Further, the open top 80 allows for the rails that furnace companies typically desire to use to slide in the blower. Further, the open top of the internal housing can be made from a single piece of sheet metal stamped on a large press.

The open topped scroll created by the sidewall 78 can also be created to increase the airflow upward toward the heat exchanger 16 of the furnace. As illustrated in FIG. 5, the bottom support wall 76 includes an inlet bell 84 to provide tight spacing between the inlet 50 of the impeller 34 to maintain the pressure within the open interior 58.

Referring now to FIGS. 6 and 7, thereshown is a preferred embodiment of the present invention in which the furnace distribution blower is mounted within a support tray 86. As shown, the support tray 86 is movable between an operating position (FIG. 6) and a service position (FIG. 7) in a manner to be described below. The support tray 86 includes a scroll-shaped outer wall 88 that is joined to a bottom wall 90. As shown in FIG. 8, the bottom wall 90 receives each of the mounting arms 60 such that the impeller and motor are mounted above an inlet opening 92 formed in the bottom wall 90. The inlet opening 92 is generally defined by the inlet bell 94, as best shown in FIG. 9.

As illustrated in FIGS. 6 and 8, the support tray 86 is mounted within an open, lower region 95 defined by a series of spaced support posts 96 that form part of the furnace frame. Inlet air can be drawn into the opening 92 from the area surrounding the support tray 86, as is clearly illustrated.

Referring back to FIG. 6, the draft inducer 20 is mounted within a recessed area 98 between the support posts 96, as is conventional.

Referring now to FIG. 7, the impeller 34 is positioned within a scroll-shaped well 100 defined by the outer wall 88 of the support tray 86. The outer wall 88 depends from a planar top surface 102 that is defined by a first side edge 104 and a second side edge 106. The first and second side edges 104, 106 are joined by a front edge 108. The well 100 includes an upwardly sloping front wall 110 that, in combination with the scroll shaped outer wall 88, directs the flow of air from the impeller 34 upward toward the heat exchanger of the furnace.

As can be understood in FIG. 8, the housing for the furnace includes a pair of spaced lower support rails 112 each mounted to the furnace housing and sized to support one of the side edges 104 or 106 of the support tray 86. As can be understood in FIGS. 7 and 8, the entire support tray 86 can be pulled out from beneath the metallic grate 114 positioned between the heat exchanger tubes 116 for servicing or initial installation. The flange 118 on the front edge 108 limits the travel of the support tray 57.

Referring now to FIG. 9, each of the support rails 112 includes an upstanding lip 119 that receives a U-shaped top edge 120 formed on the sidewall 88 of the support tray 86. The sidewall 88 is integrally formed with the bottom wall 90 to generally surround the impeller 34. As shown in FIG. 9, the mounting arms 60 support the drive motor 26 and impeller 34 across the inlet opening 92 defined by the inlet bell 94. As the drive motor 26 rotates the impeller 34, the cooling air is drawn into the impeller and is directed radially outward against the sloped front wall 110 of the support tray 86.

Referring now to FIGS. 10 and 11, the support tray 86 of the first embodiment of the invention is shown. The support tray 86 includes the generally flat bottom wall 90 that supports the impeller 34. The generally flat bottom wall 90 is joined to the upwardly sloping front wall 110 and the scroll shaped side wall 88. When the impeller 34 rotates, cooling air is drawn into the impeller through the inlet bell 94 and is expelled radially outward against the outer wall 88. The outer wall 88 is joined to the sloping front wall 100 to direct the flow of air upward toward the heat exchanger. Since the entire support tray 86 is configured to direct the flow of air upward toward the heat exchanger, the rotating impeller can be operated without the requirement of a housing. In the preferred embodiment of the invention, the support tray 86 is formed from a single sheet of stamped sheet metal in the configuration shown in FIGS. 10 and 11. As discussed previously, the support tray 86 includes the U-shaped side edges 104, 106 that rest upon the side support rails 112 to allow the support tray 86 to be moved between the operating and services positions relative to the furnace.

Referring now to FIGS. 12 and 13, thereshown is an alternate version of the support tray 122. In the alternate version of the support tray 122, the impeller 34 is mounted at an angle relative to horizontal, as best seen in FIG. 13. The impeller 34 is mounted to the generally sloping bottom wall 124 of the support tray 122. The sloping bottom wall 124 is joined to a generally vertical back wall 126 by a curved bottom end 128. Likewise, the bottom wall 124 is joined to a pair of spaced sidewalls 130 to define the well 132 that contains the rotating impeller 34. As the impeller 34 rotates, the flow of cooling air is directed radially outward against the pair of sidewalls 130. The sidewalls 130 direct the flow of air into contact with the sloping bottom wall 124. The bottom wall 124 includes an upwardly sloped front end 134 that directs the flow of cooling air upward into contact with the heat exchanger. It is anticipated that the sloping bottom wall 124 will aid in directly the flow of cooling air upward toward the heat exchanger for a more efficient operating system.

Referring now to FIGS. 14 and 15, thereshown is yet another embodiment of the support tray 136 and impeller 138 of the present invention. Like the support trays identified previously, the support tray 136 includes a pair of spaced side edges 140, 142 that allow the support tray 136 to be supported beneath the heat exchanger of a conventional furnace. As illustrated in FIG. 15, the furnace blower assembly includes the drive motor 144 connected to the impeller 138 by the drive shaft 146. However, in the embodiment of the invention illustrated in FIG. 15, the impeller 138 has an increased operating height as compared to the previous embodiments of the invention. The increased operating height of the impeller 136 will aid in the amount of air flow created during the rotational operation of the impeller 138.

As illustrated in FIG. 14, the support tray 136 includes a sidewall 148 that directs the flow of cooling air from the rotating impeller 138 toward the curved front end 150. As best seen in FIG. 15, the curved front end 115 includes a relatively smooth curve that directs the flow of cooling air upward toward the heat exchanger.

As illustrated in FIG. 15, the support tray 136 includes the inlet bell 152 that is closely spaced with the inlet 154 for the impeller 138. The drive motor 144 is mounted within the opening defined by the inlet bell 152 by the plurality of mounting arms 156. Once again, the mounting arms 156 support the drive motor 144 within the inlet of the impeller 138 such that the flow of cooling air passes over the drive motor 144.

Referring now to FIGS. 16 and 17, thereshown is yet another alternate embodiment of the support tray 158 and impeller 138. In the embodiment of the invention illustrated in FIG. 16, the support tray includes a sidewall 158 that is created to direct a flow of cooling air out of the support tray 158 at the outlet 160. Specifically, the sidewall 158 includes a scroll shaped bottom wall 162 that is upwardly curved to direct the flow of cooling air out of the support tray 158. The curved bottom wall 162 starts at its lowest point defined by the bottom shoulder 164 and curves upward to its highest position 166 generally aligned with the outlet 160. Once again, the sidewall 159 of the support tray 158 aids in directing the flow of air from the impeller 138 upward toward the heat exchanger of the furnace. As with all of the other embodiments previously discussed, the furnace blower assembly does not include a housing surrounding the impeller and the drive motor. Instead, the embodiment shown in FIGS. 16 and 17 includes a support tray that is used to create a scroll shape that directs the flow of cooling air toward the heat exchanger.

As can be understood in the drawings, the scroll-shape of the support tray has the advantage of increasing the efficiency of the backward curved impeller 34 while creating room along the sides and bottom to allow air to be drawn into the support tray. Further, the open top of the support tray allows the support tray to be slid into and out of the furnace housing, as clearly illustrated.

In the preferred embodiment of the invention, each of the support trays is formed from a single piece of stamped sheet metal formed on a large press. However, it is contemplated that the support trays could be formed from other materials while operating within the scope of the present invention.

Although not shown in the Figures, it is contemplated that the furnace distribution blower could be configured as two backward curved impellers mounted back-to-back and having a horizontal drive motor mounted in one of the wheel inlets. The motor would be mounted to a bracket to provide an inlet area and have a shaft passing through both of the impellers such that inlet air could be drawn in from both sides of furnace housing.

Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.