Rooftop Exhaust System for Exhausting Air from a Building

The present invention entails a rooftop exhaust system for a building. The exhaust system includes a motor that is configured to directly drive a fan. The fan during the course of operation generates a negative pressure on the upstream side of the fan. This negative pressure is utilized to induce outside cooling air into a shroud that partially encloses the motor. Cooling air passing through the shroud contacts the motor and heat associated with the motor is transferred to the cooling air after which the cooling air exits the shroud.

FIELD OF THE INVENTION

The present invention relates to rooftop exhaust systems that exhaust air from buildings.

BACKGROUND OF THE INVENTION

Many buildings employ rooftop exhaust systems for exhausting air from the building. Typically, rooftop exhaust systems include a motor that drives a fan. In some applications, the air being exhausted by the exhaust fan can be relatively hot and this can have adverse effects on the motor. In these cases, the motor is asked to perform in a hot environment. This hot environment impacts the performance and life of the motor which in turn results in the motor requiring replacement too often and also contributes to increased maintenance cost.

Hence, there is a need for a rooftop exhaust system designed to minimize heat buildup in and around the motor. Further, there is a need to incorporate into the exhaust system features that positively cool the motor when the exhaust fan is operating.

SUMMARY OF THE INVENTION

The present invention relates to a rooftop exhaust system for exhausting hot or warm air from a building. The exhaust system includes a motor which drives a fan. To protect the motor from hot or warm air passing through the exhaust system, a partially open shroud extends around the motor. As the fan is driven, a region of negative pressure forms between the fan and the motor. The shroud is open to this negative pressure. Due to the negative pressure, ambient cooling air from outside of the building is directed into and through the shroud. As the cooling air moves through the shroud, it contacts the motor and in the process cools the motor.

In one particular embodiment, the motor and fan are supported inside a housing having a wall. The shroud is also mounted in the housing and extends around the sides and bottom of the motor but is open at the top. The shroud generally isolates and protects the motor from hot air that is being exhausted from the building. However, the shroud is open at the top. Hence, the opening in the top of the shroud lies below the fan. The wall of the housing is provided with one or more cooling air inlets. The cooling air inlets formed in the housing are connected to one or more air cooling conduits. The air cooling conduits are in turn connected to cooling air inlets formed in the shroud. As noted above, when the fan is operating, a region of negative pressure lies between the fan and the motor. Since the shroud is open at the top, it is open and exposed to this negative pressure. This negative pressure that lies about the top opening in the shroud causes ambient cooling air to be induced into the cooling air inlets in the housing. From there, the cooling air enters the cooling air conduits that directs the cooling air into and through the shroud and out the open top thereof where the cooling air joins with the exhaust air from the building. The continuous flow of cooling air through the shroud results in the cooling air continuously contacting the motor and in the process cooling the motor.

DESCRIPTION OF PREFERRED EMBODIMENT

With further reference to the drawings, an exhaust system is shown therein and indicated generally by the numeral10. SeeFIG. 1. In the embodiment illustrated, the exhaust system is what is generally referred to as an upblast-type. Conceptionally, the present invention can be employed with other types of exhaust systems. Exhaust system10is used for general ventilation. As shown inFIG. 1, the exhaust system10is installed on the roof of a building. Exhaust system10is mounted on a curb13which in turn is supported on the roof of the building. In operation, the exhaust system10exhausts air from the building, resulting in exhaust air being drawn towards the roof of the building and into and through the curb and out the exhaust system.

Exhaust system10includes a housing indicated generally by the numeral12. It is appreciated that the specific design and construction of the housing can vary from one application to another. In any event, in the embodiment illustrated herein, housing12includes a lower housing12A that can assume a generally rectangular, square, or round configuration. In the particular embodiment illustrated, the lower housing12A includes a plurality of side walls12C. Housing12further includes an upper housing12B that extends upwardly from the lower housing12A and functions as an air duct for directing exhaust air upwardly through a portion of the exhaust system. Upper housing12B is sometimes referred to as an air shaft. In the embodiment illustrated, the upper housing12B assumes a generally circular form.

Exhaust system10is provided with means for inducing exhaust air to move upwardly through the exhaust system where the air is exhausted to the atmosphere. In the application illustrated, the housing12A is mounted on a curb13. SeeFIG. 1. Hence, when the curb13is used, exhaust air from the building moves from the building through the curb13and then through the exhaust system10. Various fan and motor arrangements can be incorporated into the exhaust system. In an exemplary embodiment, the exhaust system includes a propeller16which is directly driven by an axially aligned motor18. Motor18is supported by a frame structure in the housing12. Note that the propeller16and motor18are axially aligned with the upper circular housing or air shaft12B. It is appreciated by those skilled in the art that a fan wheel may be used in lieu of the propeller16. It is understood and appreciated by those skilled in the art that other types of fans can be incorporated into the exhaust system10. As used herein, the term “fan” includes propeller-type fans and wheel-type fans. As noted above, in the arrangement shown in the drawings, propeller16is directly driven by the motor18. Generally when a direct drive is employed, the propeller is mounted to the drive shaft of the motor18or to an extension therefrom. In other cases, the propeller or fan wheel can be driven from a side mounted motor through a belt drive.

Supported at the outlet end of the upper housing12B are one or more dampers30. In the embodiment illustrated, there is provided two dampers30with the dampers being pivotally mounted about a transverse axis about the top of the upper housing12B. Thus, the dampers30are supported, at least indirectly, by the upper housing or air shaft12B. As seen the drawings, the dampers30are disposed over the propeller16and motor18. Since the dampers30are pivotally mounted, they are moveable from a generally horizontally closed position to a raised or inclined open position. SeeFIG. 2. In a normal operation, the force of the air being exhausted upwardly through the exhaust system is sufficient to open the dampers30so as to permit the exhaust air to escape.

A shroud32is mounted in the housing12. Shroud32can assume various shapes and configurations. In the embodiment illustrated in the drawings, the shroud32includes multiple sides, a bottom and an open top. Note that the shroud32is disposed around the motor18. SeeFIGS. 3 and 4. Shroud32generally isolates the motor18from the grease laden exhaust air passing through the housing12. As seen in the drawings, shroud32extends approximately the full length of the motor18. That is, the walls of the shroud32can terminate below the top of the motor, even with the top of the motor or above the top of the motor. As noted above, the specific design of the shroud32and its orientation in and around the motor18can vary. Also, as people of ordinary skill in the art appreciate, the material used to construct the shroud32can vary but it is preferable to use a material that provides a good thermal insulation.

The exhaust system10of the present invention is designed to induce ambient cooling air from outside of the building into the shroud for the purpose of cooling the motor18. This is achieved by the provision of one or more air cooling inlets34formed in the side walls of the housing12A. In the case of the embodiment illustrated, there are two air cooling inlets34but it is understood that there could be one or a multiplicity of air cooling inlets. There is also provided air cooling inlets36formed in the shroud32. Here again in this particular embodiment, there are two air cooling inlets36formed in the walls of the shroud32. Air cooling inlets34and36are connected by air cooling conduits38. As will be appreciated from the discussion below, the function of the air cooling conduits is to channel cooling air from the air cooling inlets34and the housing12A to the shroud32.

During the operation of the exhaust system10, the propeller16will generate a negative pressure zone40on the upstream side of the fan16. This negative pressure zone40is illustrated particularly inFIG. 4. Note that the propeller16is fixed to the output shaft of the motor18and that the top of the motor is spaced relatively close to the propeller16and the open top of the shroud32. The negative pressure zone40stretches across the open top of the shroud32. Because the top of the shroud is open, the shroud and the interior thereof includes the negative pressure generated by the propeller16during the operation of the exhaust system. More particularly, the negative pressure in and about the shroud causes outside or ambient cooling air to be induced into the air cooling conduits34formed in the side wall12C of the housing12A. From the air cooling conduits34, the cooling air is induced to enter the air cooling conduits38after which the cooling air flows into and through the internal areas of the shroud32. This cooling air contacts the motor18and heat is transferred from the motor to the cooling air as it flows through the shroud32. Because the top of the shroud32is open, the cooling air that exits the shroud32is mixed with the exhaust air and together they are exhausted from the exhaust system via the upper housing12B. InFIG. 4, the cooling air and the exhaust air are referred to by arrows. Arrows with dotted line tails represent the exhaust air and arrows with full line tails represent the cooling air.

The exhaust system of the present invention is useful for more than cooling the motor18during normal operations. In addition, the exhaust system is designed to keep the motor18running in case of a building fire. With the addition of the cooling conduits and the shroud, the motor18can run continuously when exposed to a temperature of up to 572° F. and can run up to four hours when exposed to a temperature of 1000° F. In the case of a building fire, the exhaust system pulls smoke out of the building and this improves visibility inside of the building for occupants and firefighters.

In the specification and claims, the term “configured to” is used. The term “configured to” is defined to mean “designed to”. The term “configured to” is more narrow than terms such as “for” and “capable of”.

From the foregoing specification and discussion, it is appreciated that the present invention is a relatively simple, efficient and cost effective way of cooling the motor18that forms a part of a rooftop exhaust system. It is particularly efficient and cost effective since the negative pressure generated by the propeller in the course of exhausting air is employed to induce the cooling air into and through the shroud32.

The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and the essential characteristics of the invention. The present embodiments are therefore to be construed in all aspects as illustrative and not restrictive and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.