US20020098084A1

US20020098084A1 - Blower housing with inlet guide

Info

Publication number: US20020098084A1
Application number: US09/769,720
Authority: US
Inventors: William Gatley
Original assignee: Jakel Inc
Current assignee: Jakel Inc
Priority date: 2001-01-25
Filing date: 2001-01-25
Publication date: 2002-07-25

Abstract

A blower for a furnace is provided with an inlet guide to increase efficiency and pressure output of the blower. The blower includes a blower housing with an inlet opening and an outlet discharge opening. A cylindrical wall is provided around the inlet opening and projects into a hollow interior of the blower housing. A radial wall extends outward form the cylindrical wall toward the discharge outlet opening to prevent recirculation of gases from the outlet to the inlet during operation of the blower.

Description

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a draft blower for a furnace. More specifically, the invention pertains to an improved construction of the blower housing for the blower where the housing has a simplified, inexpensive construction that includes an inlet guide that improves the efficiency and pressure output of the blower.

(2) Description of the Related Art

Household furnaces utilize a draft blower or inducer to draw combustion air into a combustion chamber of the furnace where the combustion air is mixed with fuel and ignited to produce heat for the furnace. By the flow created by the draft blower, the combustion exhaust gases are drawn through a heat exchanger of the furnace where heat from the combustion exhaust gases is transferred to temperature controlled circulating air that is circulated through the house by a main furnace blower. The draft blower or inducer then draws the combustion exhaust gases from the heat exchanger and expels the combustion exhaust gases into exhaust piping that leads to the outside environment.

Generally speaking, these draft blowers or inducers are designed to provide a constant high pressure flow through the combustion chamber and heat exchanger into the exhaust piping to ensure a proper combination of combustion air with fuel to optimize burning and to ensure proper heat transfer in the heat exchanger. The pressure and flow rates developed by the draft blower are a function of the blower size, blower configuration, and the speed of rotation of the blower impeller. Typically, the size of the blower is specified by the furnace manufacturer so that the blower may fit dimensionally on the furnace within a predetermined envelope. Thus, the size of the impeller that fits within an interior of the blower housing is also constrained by these requirements. As a consequence, in order to increase the pressure output of a blower having a set dimensional size, the speed of rotation of the impeller must be increased. This requires outfitting the blower with a larger motor with increased power and design requirements. The larger motor often results in additional noise and increases the overall cost of the blower. Additionally, the larger blower motor also generally decreases overall system efficiency as it requires increased power input.

In order to increase the pressure output of a blower without increasing the rotational speed of the impeller or without utilizing a larger motor, conventional blowers use a system of baffles in the blower housing to direct the combustion gases drawn into the blower housing and to prevent inefficiencies from fluid recirculation or leakage within the blower housing. Conventional blowers that do not use baffles often experience fluid recirculation or leakage from the exhaust outlet side of the blower housing to the vacuum inlet side of the blower housing. This causes inefficiency in the blower that reduces the flow rate and pressure output of the blower. Baffles have been used in the prior art to prevent this recirculation and leakage. However, the baffles of the prior art generally have complex geometries that include additional structures such as elaborate directional vanes and surfaces added to the interior of the blower housing that substantially alter the housing from the conventional volute shape of the blower housing. Thus, these baffles must be formed in the blower housing by additional manufacturing steps or the baffles are added as separate parts and installed separately into the blower housing. These added manufacturing and/or assembly steps increase the cost of manufacturing the blower housing.

Thus, what is needed is a blower having a blower housing with an improved construction that generates increased vacuum drawing input, increased interior flow rates and increased pressure output using a conventionally sized impeller and blower motor. Such a blower would have baffles integrally formed in the blower housing so as to eliminate secondary assembly operations. The baffles would be formed in a simple geometry to allow the baffles to be formed integrally with the blower housing and to reduce material and eliminate costly tooling for forming the blower housing and baffles. Additionally, such a blower housing would have baffles that do not appreciably contribute to turbulence or noise generated in the blower housing during operation of the blower.

SUMMARY OF THE INVENTION

The present invention overcomes the shortcomings of the prior art by providing a blower housing with an inlet guide that increases the vacuum drawing input and the pressure output of the blower housing. Preferably, the inlet guide is integrally formed with the blower housing so as to reduce assembly operations. Alternatively, the inlet guide can be added to an existing housing by adding one or more additional parts. The inlet guide has a simple geometry that does not require complex or intricate tooling. The simple, two dimensional geometry of the inlet guide reduces the material and weight of the blower housing. By forming the inlet guide integrally with the blower housing, the cost to manufacture the blower housing is lowered. Even when assembling the inlet guide as a separate part with the blower housing, the assembly is simplified and does not appreciably increase manufacturing costs. The inlet guide also does not significantly contribute to the internal turbulence and noise of the blower housing during its operation.

The blower of the present invention includes a housing with a discharge outlet opening and an inlet opening with an inlet guide formed at the inlet opening. The inlet guide includes a cylindrical wall that projects from a peripheral edge of the inlet opening into the interior of the blower housing. The inlet guide also includes a radial wall that projects axially into the blower housing interior from an end wall of the housing and extends radially from the cylindrical wall to the side wall of the housing adjacent the discharge outlet opening.

The cylindrical wall and radial wall of the inlet guide direct combustion gases from the inlet opening into the blower housing interior where the gases can be compressed by the impeller and expelled through the discharge outlet opening to exhaust piping that is vented to the atmosphere. The cylindrical wall and radial wall isolate the vacuum inlet pressure drawing a flow of air into the housing, from the increased outlet pressure forcing the flow of combustion exhaust gases from the housing. The radial wall and cylindrical wall thereby prevent leakage and recirculation of combustion exhaust gases from the outlet side of the blower housing to the inlet side of the blower housing. Thus, the blower housing of the present invention eliminates inefficiencies of conventional volute blower housings with a simplified, inexpensive baffle construction.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objectives and features of the present invention are set forth in the following detailed description of the preferred embodiment of the invention and in the drawing figures, wherein: [0011]
FIG. 1 is a top plan view of a blower housing of the present invention; [0012]
FIG. 2 is a cross-sectional view of the blower housing of FIG. 1 taken along line [0013] 2-2 of FIG. 1;
FIG. 3 is a top cross-sectional view of the blower housing of FIG. 1 taken along line [0014] 3-3 of FIG. 2; and
FIG. 4 is a top plan view of an interior of the blower housing of FIG. 1 with the impeller removed therefrom.[0015]
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. [0016]

DETAILED DESCRIPTION OF THE INVENTION

In the foregoing discussion, the terms “top”, “bottom”, and “side” will be used for illustrative purposes to describe the parts of the blower and blower housing of the present invention as those parts appear and are oriented in the drawing figures. It is not intended to limit the invention in any way through use of these terms. [0017]
FIGS. 1 and 2 show the blower of the present invention, generally indicated at [0018] reference character 20. The blower 20 includes a housing 22 with a top end wall 24 and an opposite facing bottom end wall 26. The top end wall 24 has opposite interior and exterior surfaces 28,30 and the bottom end wall 26 has opposite interior and exterior surfaces 32,34 where each of the top and bottom end walls 24,26 are bounded by respective spiral shaped peripheral edges 36,38. The interior surfaces of the top and bottom walls 28,32 face each other and a volute shaped side wall 40 extends between the top and bottom end walls 24,26 at the top and bottom end wall peripheral edges 36,38. Together the top and bottom end walls 24,26 and the side wall 40 define a hollow interior 42 for the blower housing 22. Preferably, the blower housing 22 is constructed of a high-temperature resistant plastic material capable of being manufactured in high speed injection molding processes, although other materials, such as sheet metal, may also be used.
The blower housing [0019] hollow interior 42 is adapted to receive an impeller 44 for rotation within the blower housing interior 42. Preferably, the impeller 44 has a back plate 46 with an outer diameter D₁and vertical impeller blades or vanes 50 arranged in a ring around the impeller outer diameter D₁. The impeller vanes 50 depend from the impeller back plate 46 and are supported by a support ring 52 opposite the back plate 46. The support ring 52 also has an outer diameter dimension of D₁and has a radial width dimension that corresponds to the radial width dimensions of the impeller vanes 50. This leaves a large opening 53 through the support ring 52 that provides access to the impeller interior, as is conventional in impeller construction.
The blower housing [0020] bottom end wall 26 is provided with a vacuum inlet opening 54 therethrough that is spaced from the peripheral edge 38 of the bottom end wall. The vacuum inlet opening 54 is concentric with the impeller 44 and is adjacent the impeller opening 53. Rotation of the impeller 44 draws gases into the blower housing interior 42 through the inlet opening 54. Preferably, the inlet opening 54 is circular with a center axis A-A and the impeller 44 is aligned coaxially with the inlet opening center axis A-A and rotates about the inlet opening center axis A-A. Although, the drawing figures show the inlet opening 54 with a generally circular cross section, the inlet opening 54 may have another shape so as to be compatible with the furnace on which the blower is installed.
The [0021] blower housing 22 includes an outlet channel 60 formed by a semicylindrical outer wall 62 and a semicylindrical inner wall 64. The outer wall 62 projects tangentially from both of the top and bottom end wall peripheral edges 36,38 and is an extension of the side wall 40. The inner wall 64 is positioned opposite the outer wall 62 and merges with the side wall 40 and the top and bottom wall peripheral edges 36,38 between respective top and bottom “U”-shaped transitions 66,68. The spiral wound side wall 40 expands radially outwardly as it extends from the “U”-shaped transitions 66,68 at an inlet region 70 of the blower housing 22 to the outlet channel outer wall 62. The outlet channel outer wall 62 merges with the side wall 40 at the outermost expansion of the side wall 40, and the outlet channel inner wall 64 connects to the side wall 40 at the “U”-shaped transitions 66,68. Rotation of the impeller 44 in a counterclockwise direction as viewed in FIG. 3 creates a vacuum that draws exhaust gases through the inlet opening 54 and into the housing interior 42 and compresses the gases in the housing interior 42 before forcing the pressurized gases from the blower housing through the outlet channel 60 and its outlet discharge opening 72.
Preferably, the [0022] blower housing 22 is formed as two pieces which are interlocked together to enclose and seal the blower housing hollow interior 42. As shown in the Figures, the blower housing 22 of the present invention is formed with a top piece 80 and matching bottom piece 82 that assemble together to form an integral unit of the blower housing 22. In this arrangement, the top piece 80 preferably includes the top end wall 24, a portion of the side wall 40, and a portion of the outlet channel 60. Similarly, the bottom piece 82 includes the bottom end wall 26, a portion of the side wall 40, and a portion of the outlet channel 60. As shown in the Figures, the bottom piece 82 is formed with a sealing lip 84 and the top piece 80 is formed with a matching sealing groove 86 where the lip 84 is received in the groove 86 to lock the top and bottom pieces 80,82 together. To maintain the sealed blower housing interior 42 at the interface of the top and bottom pieces 80,82, matching engagement pads 88 are provided. The engagement pads 88 are circumferentialy spaced about the side wall and extend outward from the side wall 40. Each of the engagement pads 88 has a fastener hole 90 therethrough and a mechanical fastener (not shown) is directed through the hole 90 to secure the top and bottom pieces 80,82 together. Other means may be employed to secure the top and bottom pieces together, for example adhesives.
In the preferred embodiment of the invention, the [0023] top end wall 24 is provided with a plurality of screw connections 92 that allow a blower motor (not shown) to be secured to the blower housing 22. The top end wall 24 is also formed with a blower motor shaft hole 94. A blower motor shaft 96 extends from the blower motor (not shown) through the blower motor shaft hole 94 into the blower housing hollow interior 42 where it is coupled to the impeller back plate 46. Preferably, the shaft hole 94 and the inlet opening 54 are coaxially aligned along the inlet opening center axis A-A. In this configuration, the bottom end wall 26 is formed with the inlet opening 54 axially opposite the blower motor shaft hole 94.
In order to minimize piping connections in the furnace, the blower housing inlet opening [0024] 54 is preferably directly aligned with an outlet of the furnace, or furnace bonnet (not shown), where the combustion gases exit the heat exchanger (not shown) of the furnace. In order to secure the blower housing 22 to the furnace bonnet (not shown), mounting pads 98 are preferably provided on the coterminous edge of the side wall 40 and the bottom end wall 26 and are circumferentialy spaced about the spiral wound side wall 40 extending outward from the side wall 40.
As shown in the Figures, the [0025] inlet opening 54 has a peripheral edge 100 and a cylindrical wall 102 extends around the inlet opening center axis A-A and projects axially into the blower housing interior 42 at the inlet opening peripheral edge 100. Although the drawing figures show the cylindrical wall 102 as having a generally circular cross-section that is consistent with the geometry of the inlet opening 54, the cylindrical wall 102 may have a shape other than a cylinder so as to match the general shape of the inlet opening 54 and form a smooth transition therewith. The cylindrical wall 102 has a smooth interior bore 104 with an inner diameter dimension D₂. In the preferred embodiment, the inner diameter dimension D₂is less than half of an interior dimension of the housing measured across the housing from the “U”-shaped transition 68, across the inlet open center axis A-A to the opposite side of the housing 22. The bore 104 is preferably aligned concentric with the impeller 44. The cylindrical wall 102 has an outer surface 108 with an outer diameter dimension D₃. To provide radial support for the cylindrical wall 102, a support wall 112 is formed around the outer surface 108 of the cylindrical wall 102 and the bottom end wall interior surface 32. The support wall 112 has a smaller axial height dimension than the cylindrical wall 102 so that the support wall 112 does not interfere with the flow of exhaust gases drawn into the blower housing interior 42 through the bore 104 of the cylindrical wall 102.
The [0026] bottom end wall 26 of the blower housing 22 is provided with a radial wall 114 that projects axially from the bottom end wall interior surface 32 and extends radially from the cylindrical wall outer surface 108 to the “U”-shaped transition 68. Preferably, the radial wall 114 is a planar member that projects perpendicularly from the bottom wall interior surface 32 so as to simplify the shape of the housing bottom piece 82 and to allow simplified molding of the bottom end wall 26 and the radial wall 114. Preferably, the radial wall 114 defines a plane that also includes the inlet opening center axis A-A. In this arrangement, the radial wall 114 connects to the side wall 40 at the position in the blower housing interior where the radial clearance between the impeller 44 and the side wall 40 is the smallest. At this position, the potential for fluid flow crossing from the outlet channel 60 of the blower housing to the inlet region 70 of the blower housing 22 is the highest. By aligning the radial wall in a plane that includes the inlet opening center axis, the flow of exhaust gases exiting the blower housing is directed by the radial wall 114 toward the discharge outlet opening 72. In addition, the angles between the radial wall 114 and the outer surface 108 of the cylindrical wall 102 are both equal and are maximized, which simplifies the removal of the mold (not shown) from the molded radial wall 114 and cylindrical wall 102 of the housing. Preferably, the axial height of the cylindrical wall 102 and the radial wall 114 are the same so as to minimize turbulence within the blower housing interior 42 and also to simplify molding and the removal of the mold from the walls. For example, if the cylindrical wall were higher than the radial wall it may have a tendency to stick in the mold making removal of the blower housing difficult. The axial height of the radial wall 114 is such that when the impeller 44 is installed in the blower housing interior 42, the impeller support ring 52 has an axial clearance above the radial wall 114 that permits free rotation of the impeller 44 in the blower housing hollow interior 42. This also axially spaces the impeller 44 from the cylindrical wall 102. Preferably, the housing bottom piece 82, cylindrical wall 102, support wall 112, and radial wall 114 are integrally formed. More preferably, the bottom piece 82, cylindrical wall 102, support wall 112, and radial wall 114 are formed monolithically by molding them as one piece.
During operation of the [0027] blower 20, exhaust and combustion gases are drawn through the inlet opening 54 and through the cylindrical wall bore 104 into the blower housing hollow interior 42 by a vacuum created in the impeller interior by rotation of the impeller 44. As the inlet opening and cylindrical wall inner diameter D₂is smaller than the impeller outer diameter D₁, the combustion gases are expanded radially outward in the blower housing interior 42 as they flow from the cylindrical wall 102 through the vanes 50 to the outer diameter D₁of the impeller. By sizing the inlet opening 54 and cylindrical wall inner diameter D₂with a smaller dimension than the impeller outer diameter D₁, a stronger vacuum drawing pressure is formed in the blower housing 22. This enables a blower 20 with a standard impeller to develop higher flow rates and increased outlet pressures. Preferably, the impeller 44 used in the blower 20 has an outer diameter dimension D₁that is at least twice as large as the inner diameter D₂of the cylindrical wall 102 and preferably is between 4¾ inches and 5 inches and has an axial height between 1.700 inches and 1.900 inches, and, preferably, the cylindrical wall outer diameter dimension D₃is between 1⅞ inches and 2⅛ inches, and with a tube wall dimension of between {fraction (7/32)} inches and {fraction (9/32)} inches, the bore inner diameter D₂is roughly 1⅝ inches to 2 inches. The inventor has found that the sizes and dimensions stated herein provide the most effective combination for maximizing the flow characteristics of the blower. As will be apparent to those skilled in the art, other sizes and dimensions of components of the blower may also be used in accordance with the general principles of the invention.
The rotation of the [0028] impeller 44 compresses the combustion exhaust gases as it forces a flow of the gases counterclockwise around the blower housing interior 42 as viewed in FIG. 3 and expels the combustion exhaust gases through the outlet channel 60 and the outlet discharge opening 72. The radial wall 114 provided in the bottom end wall 26 prevents combustion exhaust gases from recirculating from the outlet channel 60 across the area adjacent the “U”-shaped transitions 66,68 to the inlet region 70 of the blower housing 22. This creates a more efficient flow within the blower housing interior 42 and enables a blower 20 with a set impeller diameter and a set impeller rotational speed to develop increased output pressure and flow rates. In order to minimize recirculation of exhaust gases from the outlet channel 60 back toward the blower housing inlet region 70 along the top wall end 24, the top end wall 24 is preferably formed flat in a plane perpendicular to the inlet opening center axis A-A and the impeller back plate 46 is positioned with minimal axial clearance between it and the top end wall 24.
As will be apparent to those skilled in the art, the inlet guide, including the [0029] cylindrical wall 102 and the radial wall 104 described herein, is of a simple geometry that facilitates the manufacturing of the blower housing 22. Thus, the blower housing 22 may be formed from simple molding processes that do not require sophisticated tooling with intricate surfaces or tooling that requires die inserts. Moreover, the inlet guide described herein may also be retrofitted into existing blower housings by securing the cylindrical wall 102 and radial wall 114 to the housing interior at the inlet opening 54. For example, a blower housing may be retrofit with the inlet guide described herein by securing a section of tubing, such as a PVC pipe, within the existing inlet opening of the blower housing so that it extends a short distance into the blower housing interior. The pipe section may also be attached to the interior surface of the bottom end wall such that the bore of the pipe section matches the inlet opening. A section of flat stock may then be used to form the radial wall in the manner described previously. In addition to forming the blower housing from a plastic material, the blower housing may also be constructed from sheet metal in which case the inlet guide may be similarly constructed and joined to the blower housing using metal joining techniques common in the art, i.e. welding, brazing, clinch joints, mechanical fasteners, adhesives.
While the present invention has been described by reference to specific embodiments, it should be understood that modifications and variations of the invention may be constructed without departing from the scope of the invention as defined by the following claims. [0030]

Claims

What is claimed:

1. A housing for a furnace blower, the housing comprising:

a housing end wall having opposite interior and exterior surfaces and a peripheral edge with a volute shape, an inlet opening through the end wall spaced from the peripheral edge, and an outlet channel having opposite inner and outer walls with the outer wall projecting tangentially from the end wall peripheral edge and the inner wall merging with the peripheral edge through a “U”-shaped transition; and

a cylindrical wall extending around a center axis of the inlet opening and projecting axially from the end wall interior surface, the cylindrical wall having an interior diameter dimension that is less than half of an interior dimension of the housing measured across the end wall from the “U”-shaped transition, across the inlet opening center axis to the end wall peripheral edge opposite the center axis from the “U”-shaped transition.

2. The housing of claim 1, wherein:

the inlet opening is circular and the inlet opening and the cylindrical wall have interior diameter dimensions that are equivalent.

3. The housing of claim 1, wherein:

a radial wall projects axially from the end wall interior surface and extends between the cylindrical wall and the “U”-shaped transition.

4. The housing of claim 3, wherein:

the cylindrical wall and the radial wall have axial dimensions that are equivalent.

5. The housing of claim 3, wherein:

the radial wall is a straight wall.

6. The housing of claim 3, wherein:

the radial wall is positioned in a plane that also contains the inlet opening center axis.

7. The housing of claim 3, wherein:

the cylindrical wall and the radial wall are integrally connected to each other and are integrally connected to the end wall interior surface and the “U”-shaped transition.

8. The housing of claim 3, wherein:

the cylindrical wall, the radial wall, and the housing end wall are one monolithic piece.

9. The housing of claim 1, wherein:

an impeller is mounted for rotation in the housing and is axially spaced from the cylindrical wall.

10. A housing for a furnace blower, the housing comprising:

a housing end wall having opposite interior and exterior surfaces and a peripheral edge that spirals around the end wall, an inlet opening through the end wall spaced from the peripheral edge, and an outlet channel having opposite inner and outer walls with the outer wall projecting tangentially from the end wall peripheral edge and the inner wall merging with the peripheral edge through a “U”-shaped transition;

a cylindrical wall extending around a center axis of the inlet opening and projecting axially from the end wall interior surface, the cylindrical wall having a diameter dimension; and

an impeller mounted for rotation in the housing around the inlet opening center axis and the cylindrical wall, the impeller having a diameter dimension that is at least twice as large as the cylindrical wall diameter dimension.

11. The housing of claim 10, wherein:

the impeller outer diameter dimension ranges from 4¾″ and 5″ and the cylindrical wall outer diameter dimensions ranges from 1⅞″ and 2⅛″.

12. The housing of claim 11, wherein:

the impeller has an axial height of between 1.700″ and 1.900″.

13. The housing of claim 10, wherein:

14. The housing of claim 13, wherein:

15. The housing of claim 14, wherein:

the cylindrical wall, the radial wall, and the end wall are one monolithic piece.

16. The housing of claim 10, wherein:

the impeller is axially spaced from the cylindrical wall.

17. A housing for a furnace blower, the housing comprising:

a housing first end wall having opposite interior and exterior surfaces and a peripheral edge that spirals around the first end wall, an inlet opening having a center axis passing through the first end wall, and an outlet channel having opposite inner and outer walls with the outlet channel outer wall projecting tangentially from the peripheral edge and the outlet channel inner wall merging with the peripheral edge through a “U”-shaped transition;

a housing second end wall having opposite interior and exterior surfaces and a peripheral edge that spirals around the second end wall, a shaft opening coaxial with the inlet opening passing through the second end wall, and an outlet channel having opposite inner and outer walls with the outer wall projecting tangentially from the peripheral edge and the inner wall merging with the peripheral edge through a “U”-shaped transition;

a sidewall connecting the peripheral edge of the first end wall with the peripheral edge of the second end wall and together with the first and second end walls defining a hollow interior of the housing; and

an impeller mounted for rotation in the hollow interior of the housing, the impeller having first and second annular walls adjacent the respective first and second end walls, and portions of the first and second end walls that are adjacent the impeller first and second annular walls are entirely planar.

18. The housing of claim 17, wherein:

a radial wall projects axially from the first end wall interior surface and extends between the cylindrical wall and the “U”-shaped transition of the first end wall.

19. The housing of claim 18, wherein:

20. The housing of claim 17, wherein:

the cylindrical wall has an outside diameter dimension and the impeller has an outside diameter dimension that is at least twice as large as the cylindrical wall outside diameter dimension.