Furnaces – Draft regulators – Fan exhaust
Reexamination Certificate
2000-08-30
2002-05-14
Lazarus, Ira S. (Department: 3749)
Furnaces
Draft regulators
Fan exhaust
C415S206000, C415S214100, C425SDIG004
Reexamination Certificate
active
06386123
ABSTRACT:
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's requirements for air moving capacity with a lower speed motor. Such a blower would meet furnace manufacturers' 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 inter
Jakel Incorporated
Lazarus Ira S.
Rinehart K. B.
Thompson & Coburn LLP
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