Appurtenance for building vents
An improved cover for an outlet intended to exhaust gases from a building to the atmosphere and particularly for chimneys intended to exhaust the products of combustion and for vents intended to exhaust ventilating air from within a building. The cover prevents precipitation as rain, sleet and snow from entering into the outlet while allowing the exhaust gases to rise away from the building in a vertical column essentially unimpeded.
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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable
REFERENCE TO MICROFILCHE APPENDIXNot applicable
BRIEF DESCRIPTION OF THE DRAWINGS
There is a variety of vents that serve as conduits for exhausting gases from within a building. In a residential building, one of the more common vents is a chimney that is used to exhaust the heated products of combustion. In commercial and industrial buildings, vents are used to exhaust a wide variety of gases from within the confines of the building; one of the more common vents found in commercial buildings are the vents intended to exhaust ventilating air from the building. Chimneys are often fitted with a cap to prevent the entrance of precipitation as rain, snow or sleet which, should the precipitation be allowed to enter within the vent, could cause a number of problems. A common problem with currently available chimney caps is that these caps cause the exhaust gases to abruptly change direction thereby severely impeding the upward flow.
Building vents intended to exhaust gases from within a building are often fitted with a curved section of ducting at the end of the ducting that faces downward so as to preclude the entrance of precipitation. The function of the curved section is much the same as that of a chimney cap which is, namely, to exclude atmospheric precipitation from entering into the interior of the vent. Building exhaust ducts that are fitted with a curved section at the end of the ducting have two inherent problems. First, the exhausted gases are directed back toward the building rather than upward and away from the building. If the exhausted gases are merely building ventilating air, there is generally no resulting problem. However, if the exhausted gases are of a toxic nature, directing the gases back toward the building may cause a serious hazard. It is possible that the gases may be returned to interior spaces of the building by fans that are intended to draw into the building fresh outside air. A second problem with the use of curved ducting on the end section of a vent is that it necessarily rises above the roof of the building thereby presenting an unsightly profile that distracts from the more pleasing lines of the building.
Consider, first, the problems with conventional chimney caps. Many residential buildings have a chimney for exhausting the products of combustion from heating implements used within the residence. In temperate climates, various type of heating appliances are often used to heat the air within the internal spaces of the dwelling. Typical types of heating implements include furnaces and boilers. A furnace is used to heat air that is circulated throughout the spaces of a residence. A boiler is used to heat either water or steam that, in turn, is circulated to heat exchangers that are located in the internal spaces of the residence. In either a furnace or a boiler, some type of fuel is burned to generate heat. Some of the typical types of fuels include fossil fuels as natural gas, propane gas, oil and coal. Various other types of organic fuels as wood and straw are likewise used to heat buildings. In a residence, a fireplace is often used to burn fuels as wood or coal. Aside from the need to heat the air within residences, some type of heater is also commonly used to heat domestic water. Frequently, a fossil fuel is likewise used to heat domestic water within buildings.
Whenever a fuel is used to heat either the dwelling spaces within a residence or the domestic hot water, there is the need to safely exhaust the products of combustion from within the building to atmosphere. In past years, the common method was to use a chimney. The hot gases from the combustion process are directed through ducts or similar conduits to the internal spaces of the chimney where these gases pass up through the chimney and are then exhausted to atmosphere at the top of the chimney. There are various designs of chimneys. Until recent years, chimneys have traditionally been of masonry construction. The exterior of a masonry chimney would typically be constructed of stone, block of brick. Masonry chimneys would generally contain a liner, or ‘flue’, that would be fabricated of a material that is relatively resistant to deterioration caused by the hot exhaust gases. Typically, flues are fabricated of a clay tile or ceramic.
Traditional masonry chimneys are relatively expensive to construct. Accordingly, the use of either electric heat or a heat pump can avoid the cost of the chimney. There are, of course, alternatives to the traditional masonry chimney. In more recent years, stainless steel ducts have been used in lieu of masonry chimneys. In recent years, highly efficient gas-burning implements have been developed which have relatively low exhaust temperatures and relatively small volumes of exhaust gases. These high efficiency gas burners require merely a relatively short exhaust duct that often extends out the side of a building. Accordingly, a building that uses these types of high efficiency heating implements would not require a chimney.
If a residence is to have a fireplace, a chimney of some sort will certainly be required. For this reason, it may be expected that many homes built in the future will continue to have a fireplace. Many homeowners will continue to enjoy the comfort imparted by a wood-burning fireplace. Also, a fireplace serves to act as an emergency source of heat in the event of the failure of the building's electrical service at an inconvenient time. Buildings that have oil heat will certainly require a chimney. And, many homeowners who have heating equipment that requires a chimney will decide upon a masonry chimney. A masonry chimney gives a residence a stately and traditional appearance. In other words, the presence of a chimney adds to the appearance of the building as seen from the street. Accordingly, it may be expected that many homes built in the future will continue to have masonry chimneys of the type that have been popular for many years in the past.
Aside from the chimneys to be used in new construction of the future, it is pertinent to note that there are currently existing a large number of existing homes that are fitted with chimneys.
Details of the flue liners as they extend above the masonry construction of the chimney are shown in
Details of the construction of a typical masonry chimney are shown in Section A-B of
When the flue is in use and exhausting the products of combustion, the path of the gases through the upper section of the chimney would be similar to that represented in
Commonly, problems occur with flues in masonry chimneys that are not covered to protect them from rainwater. The products of combustion result in the formation of residues that, when combined with rainwater, will form an acid that in turn will slowly dissolve the internal surface of the liner. In time, deterioration of the internal walls may cause cracks or openings in the liner. In consequence, dangerous gases may enter into the residence. These gases may under some conditions cause affixation of the residences or smoke damage. Under other circumstances, escaping gases may cause a fire within the building where the chimney is located. Rainwater can also become the source of odors that the occupants of the building may find highly disagreeable. When a chimney is not exhausting products of combustion, the interior of the chimney will cool and air will flow downward through the flue liners and into the interior spaces of the residence. That downward flowing air often will carry with it the objectionable odors that may develop within the chimney. Rainwater can also leak from the interior of the chimney and cause damage to structural members of the residence.
Should damage occur to a liner it may be replaced with a new liner, but replacement costs can be very expensive. An alternative and less expensive procedure involves the installation of stainless steel liners. The stainless steel liners can often be installed within the old and damaged masonry liner. The use of replacement stainless steel liners is a less expensive alternative to the installation of ceramic liners. However, the stainless steel liners detract from the stately appearance rendered by an all-masonry chimney.
Aside from allowing the entrance of precipitation, an uncovered chimney flue can also be a point of entrance for foreign objects as dead birds or leaves for adjacent trees. In cold weather, birds are often attracted to the areas of a flue liner because of the warmer gases found there. In consequence, birds often are overcome with the carbon monoxide in the gases and then they fall into the flue liner. An accumulation of dead birds or leaves may result in an interference to the path of the products of combustion. This obstruction in turn can result in toxic gases being forced into the building thereby present a life-threatening hazard to the occupants of the building.
To avoid the damage to the flues of a chimney caused by the entrance of rainwater, homeowners often will install a rain cap over the flue liners. A chimney with a typical rain cap installed is shown in
When a chimney cap is placed on the top of a chimney, the flow of the products of combustion from within the chimney to atmosphere would be similar to that represented in
While the presence of a properly designed, conventional chimney cap will prevent the ingestion of rainwater into the chimney liner, in some ways it hampers the proper functioning of the chimney. Because conventional chimney caps are placed directly over the opening of the flue liner, its position blocks the upward flow of hot gases from within the chimney. The chimney cap prevents the mixture of hot gases and particulates from exiting the flue liner on a continuous straight path to atmosphere. As represented in
Essentially the mixture of hot gases and particulates would flow straight up through the chimney flue until the mixture comes into proximity of the chimney cap. The turns in the flow path are undesirable for several reasons. First, the required turns introduce a restriction to the flowing gases. These restrictions and required turns in the flow path are counter to the function of a chimney which is to expel gases away from a building and to atmosphere. Any objects in the path of those gases would normally tend to interfere with that function. In addition, the required turns cause the upward flowing gases and particulates to be mixed with colder outside air at the height of the flue cap. This mixing of the gases reduces the impetus of the gases to rise up and away from the building which action is also counter to the purpose of the chimney. The net effect of the addition of a chimney cap to a chimney flue is to decrease the effective height of the chimney from that which it would have if there were no chimney cap.
A masonry chimney design of a typical residential fireplace is represented in
While a chimney cap minimizes the ingestion of precipitation, as rainfall, and foreign objects, as dead birds, into the interior of a chimney flue, common designs of chimney caps present distinct problems. According to Page 30.8 of the Handbook of HVAC Design by Grimian and Rosaler, (McGraw-Hill), “ . . . most chimney caps defeat the proper functioning of a chimney even though designed to be above the eddy area . . . . The cap forces the pollutants below the eddy area and close to the roof, where they can be recirculated into the building by intake ducts or infiltration . . . ”.
In order to fully understand the problems caused by a conventional chimney cap a person must understand the principles by which a chimney functions. As stated, the purpose of a chimney is to safely exhaust the products of combustion from within the building to atmosphere. Essentially this end is accomplished by means of the draft that is generated within the chimney. It is the function of the chimney to induce this draft which will, in turn, flush the products of combustion up the chimney and out of the interior of the building. It is the lower density of the gases within the chimney in comparison to the density of the gases outside the chimney that causes the necessary draft. Because of the lower density, atmospheric pressure pushes on the bottom of the column of heated gases within the chimney thereby forcing that column of gases up through the chimney and out the top of the chimney. If the chimney is not designed properly, there may not be sufficient draft and the products of combustion may not be adequately exhausted. The draft of a chimney is a function of several factors. The operation of a chimney is explained in a number of technical texts. One of these texts is Mechanical Engineers' Handbook, Marks, Fifth edition. The text presents the equation for the draft provided by a chimney on Page 1120. There it is stated that the draft may be calculated by the equation:
D=0.52 PH [(1T−(1/T1)]
- D=draft (inches water column)
- P=atmospheric pressure (psia)
- H=height of stack (feet)
- T=atmospheric temperature (° F. abs)
- T1=temperature of stack gases (° F. abs)
Consider, in the way of illustration, the magnitude of the draft that would be characteristic of a chimney at a typical residential installation. Use: - P=14.7 psia
- H=20 feet
- T=20° F.=(460+20)° F. abs=480° F. abs
- T1=550° F.=(460+550)° F. abs=1010° F. abs
D=(0.52)(14.7)(20)[(1/480)−(1/1010)]
D=(152.88)[(0.00208)−(0.00099)]
D=(152.88)[0.00109]
- D=0.166 in wtr
Further in the way of illustration, consider the details of construction of a typical chimney. A typical chimney 17 is shown in
As indicated above, the presence of a chimney cap will interfere with the proper functioning of a chimney. A chimney cap will disrupt the center core of hot gases and particles rising in the chimney. It will cause undesirable mixing of that column with gases of atmosphere. In consequence, the effective height of the column of rising gases is diminished. However, a chimney without a cap will permit the entrance of precipitation and foreign objects. Amongst other results, the precipitation may result in serious damage to the chimney liner. The entrance of foreign objects may interfere with the exhausting of the products of combustion, which in turn, can present life-threatening conditions to the occupants.
Vents, other than chimneys, used to exhaust gases from a building have problems in common with chimneys. A typical commercial building 22 with an exhaust vent 23 extending above the roofline is represented in
The invention generally pertains to the filed of mechanical devices intended for conduits to exhaust gases from within buildings. More specifically, the invention relates to an improved cover for an outlet intended to exhaust gases from a building to the atmosphere and particularly for chimneys intended to exhaust the products of combustion and for vents intended to exhaust ventilating air from within a building. The cover prevents potentially harmful precipitation as rain, sleet and snow from entering into the outlet while allowing the exhaust gases to rise away from the building in a vertical column essentially unimpeded.
DETAILED DESCRIPTION OF THE INVENTIONThis invention relates to a vent cap that avoids the interference that typical vent caps present to the flow of effluent gases exhausting from a conduit. As will be demonstrated, the invention is particularly suited to serve as a cap on a chimney. In the case of chimneys, the invention allows the effective height of a chimney to remain essentially equivalent to that of a chimney without a chimney cap. Yet, the vent cap that is the subject of this disclosure prevents the ingestion of precipitation into said conduit. The vent cap offers these features by means of components that are arranged to perform a dual function. The first function of the chimney cap is to trap rainfall that would otherwise enter the interior of the conduit and expel it to a location outside the chimney liner. The second function of the vent cap it to allow a column of rising gas to pass through the vent cap, with minimal restriction to flow, and to continue on a vertical upward path.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTIONA typical embodiment of the invention in the form of a chimney cap is represented in
The design of the interior of the chimney cap is illustrated in greater detail in Section A-B of
The manner in which the typical embodiment of
The manner is which the baffle of
The above-described baffles of
As shown in the illustration of
Raindrop 40 and raindrop 41 of
Precipitation in the form of snow could also enter into the chimney cap. Snow would not necessarily fall along straight line much as would be expected with rain or sleet. Accordingly, some snow, albeit a small amount could be expected to bypass the collectors of the chimney cap and fall within the chimney. It is expected that most of the initial falling snow would be caught in the troughs of the collectors. If there were no heated gases rising up the chimney, a heavy snowfall would result in a thick accumulation of snow on the top of the chimney cap. That accumulation could result in a compete, although temporary, blockage to the direct upward flow of rising gases should the rise of gases be initiated subsequent to the accumulation of snow. Under those conditions, the rising gases would escape through the side ports until the heated gases melt snow on the top of the chimney cap. Of course, after the snow is melted, the rising gases would then continue on a path directly through the chimney cap and in an upward direction.
As stated above the vent cap has a dual function, namely to trap and remove falling precipitation as well as to provide minimal interference to escaping gases. It was demonstrated above how a typical embodiment can remove falling precipitation. Next, it will be demonstrated how the typical embodiment provides negligible interference to rising gases that are being exhausted through the vent.
In
In
In
In the specific embodiment that is disclosed above, it is apparent that gutter 77 of
Above, it was demonstrated how falling precipitation would be trapped in the chimney cap and excluded from falling into the interior of the chimney. It was also demonstrated how, under normal circumstances, rising gases are allowed to pass through the chimney cap and continue on an upward path. It will be obvious that the chimney cap would perform its function either whenever there are heated, rising gases within the chimney or whenever there are no rising gases within the chimney cap. Falling precipitation would not interfere with the path of the column of rising gases. Likewise, rising gases within the chimney would not in any manner hamper the capability of the chimney cap to trap and remove falling precipitation.
DETAILED DESCRIPTION OF AN ALTERNATE EMBODIMENT OF THE INVENTIONAbove is a detailed description of a typical embodiment of the invention as it would apply to a chimney cap. A chimney, of course, is only one of a number of common vents found in buildings to exhaust gases from within the building. A chimney is generally provided to exhaust the products of combustion that result from the burning of fossil fuels. As explained above, another typical gas that is exhausted from buildings is the ventilating air that is drawn into buildings and circulated therein for the benefit of the human occupants. A portion of that air must be exhausted from the building and that exhaust duct must be arranged so that it does not allow precipitation to enter into the ducting system.
The representation of
The typical embodiment of
As suggested by the representation of
It will become obvious to one trained in the art that the above, two specific embodiment of a chimney cap disclosed in this invention are only two of the many possible specific embodiments of the invention.
Claims
1. Means intended for fitting on the outlet of a building venting conduit which building venting conduit is intended to exhaust gases from within a building and which means presents essentially insignificant resistance to the upward flow of said gases from said building vent conduit to atmosphere while simultaneously preventing the entrance of precipitation into said building conduit.
2. Means intended for fitting on the outlet of a building venting conduit which building venting conduit is intended to exhaust gases from within the building and which means both prevents the entrance of precipitation into said building venting conduit while simultaneously presenting essentially insignificant resistance to the flow of said gases thereby allowing said gases to rise upward and away from the building in an essentially undisturbed column.
3. A chimney cap intended for fitting on a chimney flue that prevents the undesirable entrance of precipitation into the interior of said chimney flue while simultaneously presenting little resistance to the upward flow of exhaust gases from said chimney thereby allowing said gases to continue flowing in an upward direction in the form of an undisturbed column.
4. A vent cap for a building exhaust vent which vent cap prevents precipitation from entering into the vent while simultaneously allowing upward flowing gases to exhaust essentially unimpeded and which vent cap allows a low profile to the end section of the exhaust vent.
5. A chimney cap intended for fitting on a chimney flue which chimney cap consists of a combination of members that are arranged so as to trap precipitation and direct said precipitation to a location outside the chimney flue while at the same time allowing rising gases to pass through the chimney cap with little resistance to the flow of the exhaust gases from the chimney flue to atmosphere thereby allowing the gases to continue on an upward path as an essentially undisturbed column.
6. A vent cap for a building exhaust vent which vent cap consists of a combination of members that are arranged so as to trap precipitation and direct said precipitation to a location outside the vent while at the same time allowing rising gases to rise vertically through the vent cap with little resistance to the flow of exhaust gases from said vent to atmosphere, said vent cap thereby allowing a low profile to the vent cap.
Type: Application
Filed: Apr 23, 2007
Publication Date: Oct 23, 2008
Inventor: Joseph Fleckenstein (Reading, PA)
Application Number: 11/788,853
International Classification: E04H 12/28 (20060101);