Furnaces – Process
Reexamination Certificate
2000-12-05
2002-12-17
Look, Edward K. (Department: 3745)
Furnaces
Process
C110S162000, C415S204000, C415S206000, C415S207000, C415S212100
Reexamination Certificate
active
06494152
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a blower for a furnace that is used to remove combustion products and exhaust gases from the furnace. Specifically, the invention pertains to the construction of a housing for the blower where the housing has a 4″ diameter discharge that couples directly to industry standard 4″ exhaust piping.
(ii) Description of the Related Art
Furnaces utilize a blower to induce a draft through the furnace 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. The combustion products are drawn through a heat exchanger where the heat from the combustion products is transferred to temperature controlled circulating air which is directed through the house. The combustion products exit the heat exchanger and enter the furnace blower where they are propelled from the furnace blower into exhaust piping that leads to the outside atmosphere.
The blower housings that have been used to construct these furnace blowers have been conventionally made of sheet metal. The sheet metal is stamped to form the housing with a generally flat top wall and depended side wall that extends around a peripheral edge of the top wall. The top wall and side wall generally define a hollow interior for the blower housing. Typically, a motor is mounted on the top wall and a motor shaft is directed through a shaft hole in the top wall into the hollow interior of the blower housing. The motor shaft is coupled to an impeller, and the rotation of the impeller moves the combustion products and exhaust gases through the furnace. Generally, the impeller compresses the gases against the side wall of the blower housing where the exhaust gases are pressurized and directed toward a discharge formed in the blower housing. The discharge is then coupled to the exhaust pipe so that the exhaust gases and combustion products may be propelled into the exhaust pipe to be vented to the atmosphere.
In the prior art, the discharge generally has a rectangular cross-section and the exhaust piping has a generally circular cross-section. Moreover, exhaust piping in residential housing has an industry standard 4″ diameter. Thus, in order to couple the discharge to the exhaust, conventional blowers utilize a transition piece. The transition piece is attached to the blower housing and converts the rectangular discharge into a circular exhaust port that can be connected to the circular exhaust pipe. Moreover, this transition piece expands the discharge of the exhaust port into the industry standard 4″ exhaust piping connection.
These transition pieces are typically made of cast aluminum and are expensive to manufacture. The transition piece increases the cost of the blower and the associate furnace with which the blower is assembled. In the prior art, the exhaust transition pieces are often attached to the rectangular blower housing exhaust port by screws. Usually, 3 or 4 sheet metal screws are used to attach the exhaust transition piece to the discharge of the blower housing. A manual operation is required to attach the transition pieces to the blower housing. This increases manufacturing costs associated with production of the blower. Additionally, the screws sometimes loosen, causing the exhaust transition piece to become loosely connected to the discharge. This sometimes causes leaks and may product undesirable noise as the exhaust transition piece rattles and vibrates when the blower is operated.
In order to overcome the shortcomings of the prior art cast aluminum pieces, the inventor has succeeded in developing an exhaust transition that is considerably less expensive to manufacture and eliminates the problems with leakage and undesirable vibration. In a pending application Ser. No. 09/651,645 filed on Aug. 30, 2000, entitled “Furnace Blower Housing With Integrally Formed Exhaust Transition,” (incorporated herein by reference) a two-piece exhaust transition is described. In this arrangement, the exhaust transition has a first section which is integrally formed with the blower housing body and a second section which attaches to the first section to form the exhaust port of the discharge in a circular configuration that can be easily coupled to the exhaust pipe. The first and second sections may be joined together by crimping or other mechanical fastening methods so as to produce a seamless exhaust transition from the blower housing to the exhaust pipe.
Generally speaking, furnace manufactures specify the size and configuration of the blower and require that the blower fit in a predetermined envelope on a furnace. Thus, the blower manufacturer must design the blower to meet the size requirements while assuring the blower has sufficient air moving capacity to remove combustion products and other gases from the furnace. Typically, in most residential housing furnace constructions, the blower housing must have an axial height of no more than 2¼″. This poses a problem for the blower manufacturer when forming an exhaust transition at the discharge that directly meets the industry standard 4″ exhaust piping requirement. In order to reduce costs of blower housing, the housings are generally stamped from metallic stock blanks. As described previously, the blank is formed with a top wall and a depending side wall. The side wall is generally sized with an axial height of 1½″ to 2″. With an overall diameter constraint and the side wall dimension constraints, the maximum size exhaust transition that may be formed is approximately 3″. Thus, in order to couple the exhaust transition portion of the discharge to the exhaust piping, a 3″ to 4″ expander piece is required. Use of the 3″ to 4″ expanded case is problematic as described previously in that it increases the parts associated with the furnace, increases assembly labor of attaching the blower to the exhaust piping, and increases the possibility of leakage.
In order to avoid use of the transition piece, several attempts have been made to form the blower housing discharge with an exhaust port at 4″ that may be directly coupled to the exhaust pipe. However, in attempting to stamp the discharge exhaust port at 4″, several manufacturing problems occur. The extreme rapid change of the axial dimension at the discharge causes failure of the blower housing by separation of the top wall from the side wall. This is also coupled with extreme distortion and insufficient thickness of the top wall in the area around the discharge. Due to size constraints, the overall discharge exhaust port cannot be extended outward from the blower housing. Thus, in order to create a more gradual increase in the axial height of the blower housing to the discharge, the transition point has been formed within the interior of the blower housing. However, as the transition point is moved into the interior of the blower housing, overall blower performance is degraded. The rapid increase in area at the discharge of the blower leads to a decrease in the overall pressure that can be developed by the impeller in the blower housing.
Thus, what is needed is a blower housing having an integrally formed 4″ transition piece which may be easily manufactured without causing failure of the blower housing and without degrading overall performance of the blower. Such a blower housing would eliminate parts and reduce assembly labor. The blower housing would directly couple to the exhaust pipe and provide a seamless transition to the exhaust pipe to reduce the possibility of leakage.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings of the prior art by providing a blower housing with a discharge that couples directly to the 4″ industry standard exhaust pipe. The blower of the present invention reduces the number of parts associated with the blower, reduces assembly labor, and increases reliability by reducing the possibility of leakage. The
Edgar Richard A.
Jakel Incorporated
Look Edward K.
Thompson & Coburn LLP
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