CROSS REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO MICROFILCHE APPENDIX
Not applicable
BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1
Typical Temperate Zone Residence with Chimney
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FIG. 2
Typical Construction of Top Area of Chimney
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FIG. 3
Cross-sectional View of Top Area of Chimney
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FIG. 4
Typical Chimney Less Chimney Cap with Rising Smoke
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FIG. 5
Typical Chimney with Common Type of Chimney Cap
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FIG. 6
Flow Paths of Rising Smoke around Typical Chimney Cap
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FIG. 7
Appearance of Rising Smoke around Typical Chimney Cap
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FIG. 8
Construction Details of Typical Chimney
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FIG. 9
Typical Commercial Building with Roof Exhaust Vent
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FIG. 10
Typical Form of Exhaust Section of Roof Vent
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FIG. 11
View of Typical Embodiment of Invention
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FIG. 12
Sectional Views of Embodiment of Invention
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FIG. 13
Details of Construction of Typical Baffle
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FIG. 14
Typical Course of Rainfall along Baffle
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FIG. 15
Details of Construction of Typical Collector
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FIG. 16
Typical Course of Rainfall along Collector
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FIG. 17
Typical Paths of Rainfall into Chimney Cap
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FIG. 18
Smoke rising through Chimney Cap
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FIG. 19
Details of Smoke Flow through a Set of Baffles and Collectors
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FIG. 20
Flow Lines through a Set of Baffles and Collectors
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FIG. 21
Critical Dimensions within Collectors
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FIG. 22
Comparison of Features of Typical Embodiment of Invention
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to Conventional Vent Exhaust
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BACKGROUND OF THE INVENTION
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.
FIG. 1 shows a typical residence with a masonry chimney. Chimney 1 in the illustration contains two liners. The liners are typically allowed to extend above the masonry construction of the chimney. In the illustration of FIG. 1, small liner 2 would commonly be connected to a heating implement as a water heater or a furnace, or both, while larger liner 3 would typically be provided for a fireplace.
Details of the flue liners as they extend above the masonry construction of the chimney are shown in FIG. 2. In the illustration of FIG. 2, two flues are shown, much as is represented in FIG. 1. The small flue 4 would typically be used for a fossil-fired furnace or a boiler or for a fossil-fired water heater. In fact, both a water heater and a furnace could be connected to small flue 4. Typically, small flue 4 may measure approximately 8 inches×8 inches inside, and the wall of the flue might be in the area of ¾ inches thick. Large flue 5 would typically be required for a fireplace, and typically would have outside dimensions of 12 inches×12 inches.
Details of the construction of a typical masonry chimney are shown in Section A-B of FIG. 2. Typically, both flues of the chimney would be constructed of ceramic or clay liners. In Section A-B, the small flue is shown as being constructed of sections of ‘liners’ 6. Each section of the small flue liner 6 typically would be two feet in length and stacked one upon the other. In a similar fashion, large flue 7 would be constructed of ceramic material or clay material. Within the chimney, the flue liners are supported horizontally by members attached to the masonry components of the flues. The exterior of the chimney shown in FIG. 2 is constructed of brick 8. Within the chimney, air spaces 9 serve to insulate the masonry construction from the high temperatures that may be found within the flue liner. A concrete top 10 serves to prevent rainwater from falling into the cavities that surround the ceramic liners.
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 FIG. 3. FIG. 3 is a representation of a vertical section through the upper part of a typical chimney similar to that shown in Section A-B of FIG. 2. Essentially, the gases flow straight up through the flue and exhaust into the atmosphere. The path of the gases would be similar to that represented in FIG. 3 by arrows 11. If the products of combustion were accompanied with particulates, the flow of the mixture through the upper portion of the chimney would be similar to that shown in FIG. 4. The mixture of hot gases and particulates 12 flow through the interior of the flue and essentially exhaust vertically from the opening of the flue to atmosphere. The flow paths as represented in FIG. 3 and FIG. 4 are the most unrestricted paths that can be expected for gases exhausting from a chimney.
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 FIG. 5. The flue cap would normally consist of a thin sheetmetal component 13 that blocks the downward flow of rainwater into the liner of the chimney. Component 13 would typically consist of a piece of flat sheetmetal and it would be free of holes or similar openings. Rainwater that would fall on the top of the chimney cap would flow to the outer edges of the chimney cap where it would fall downward to a location on the outside of the chimney liner. Typically flue cap assemblies have as a component a flame arrestor 14 that would typically consist of wire mesh. The purpose of the flame arrestor is to prevent large flaming objects as cardboard, paper or wood from exiting the flue. Flue gases rising up the chimney would be forced to exit through the flame arrestor. All of the products of combustion as well as smaller particulates would exhaust through the flame arrestor while any larger pieces of burning material would be stopped by the arrestor. Generally the smaller pieces of burning material are not considered a potential source of a fire as smaller burning objects would cool adequately before landing on combustible objects and combustion of foreign objects would thereby be avoided.
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 FIG. 6. The mixture of the hot gases and particulates 15 flows up to the interior of the chimney cap and out the sides. (Note: for the purposes of illustration, the flow path of the gases and particulates through and out the back portion of the chimney cap is not shown. Only the flow paths through and out the left and right sides are represented.) If a viewer could see the flowing gases through the sectional view, it would appear much as that represented in FIG. 7. As represented in FIG. 7, the mixture of hot gases and particulates 16 pass through the chimney cap and out the openings provided at the sides of the chimney cap. The hot gases would not be highly visible but the particulates carried along with the hot gases would be visible.
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 FIG. 6 and FIG. 7, the upward flowing mixture of hot gases and particulates must change its course and turn to pass through a chimney cap in order to exit from the interior of the chimney cap to atmosphere. Once outside the chimney cap, the gases must change course again to rise upward from the building.
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 FIG. 8. The liner serves to guide the hot gases and particulate mixture from the area where the combustion process takes place up through the chimney to atmosphere. The liner typically may have a square, round or rectangular cross-section and would be characterized by a height A as shown in FIG. 8. A properly designed chimney would have cross section dimensions matched to the expected volume of gases. Various guidelines prescribe the proper dimensions for both components of a fireplace and the associated chimney. An efficient chimney would have a liner with internal dimensions that are neither too small yet not too large. The height of the chimney determines to a large extent how effective a chimney will be in exhausting hot gases. If the height A of the liner within the chimney is too short, the chimney will not be able to provide an adequate draft and hot gases will not flow up through the chimney at a sufficient rate. Of course, there are practical limits to the height of a chimney. The higher the chimney, the greater the cost. In addition, an excessively high chimney will detract from the profile of a residence. So, the owner of the chimney will not wish to have a chimney that is higher than what is necessary. Furthermore, in some instances an excessively high chimney may detract from the appearance of a building.
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)]
Where,
- 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]
Further in the way of illustration, consider the details of construction of a typical chimney. A typical chimney 17 is shown in FIG. 8. The chimney 17 in FIG. 8 is located above a typical fireplace. The fireplace has as components a fire box 18 and a smoke shelf 19 that connects the firebox 18 to the flue 20 of the chimney 17. A hearth 21 facilitates loading combustible material into the firebox 18. The products of combustion are totally enclosed within flue 20 and the smoke shelf 19 of the chimney 17. So, that vertical portion of the chimney 17 that induces the draft is at least from the bottom of the smoke shelf 19 to the top of the flue 20. (The construction of a typical fireplace is explained in the textbook, “Book of Successful Fireplaces”, by R. J Lyhtle and Marie-Jeanne Lytle, Copyrighted 1972 and registered in the Library of Congress as #79-166418.) The vertical dimension of that portion of the chimney 17 that provides the draft is represented by the dimension ‘A’ of FIG. 8. Draft is also provided by a vertical portion of the fire box 18 in that area where the products of combustion mix with air in the front of the fire box 18. It is expected that a chimney without a chimney cap would in fact have an effective height in excess of dimension ‘A’ illustrated in FIG. 8. As the column of smoke rises above the top of the chimney, cooler gases from atmosphere will gradually mix with the smoke on the periphery of the column. Nevertheless, there will be a central core of hot gases and particles that will continue to rise for a considerable distance above the top of the chimney. Accordingly, it would be fair to state that a chimney without a chimney cap in fact has an effective height that is somewhat in excess of the height of the chimney.
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 FIG. 9. Vent 23 of FIG. 9 is typical of the exterior portion of a vent used to exhaust ventilating air from a commercial building. Vent 23 would typically be the end section of a ducting system which ducting system includes a fan powered by an electric motor and which ducting system is arranged to draw interior air from all corners of the building. That portion of the vent that extends above the roof is also represented in FIG. 10 in greater detail. The end portion of the ducting typically has a curved section 24. The open end of the curved section faces downward thereby preventing precipitation from entering into the duct. Since the open end of the duct faces downward, exhaust gases 25 naturally are forced downward toward the roof of the building. While the curved section adequately prevents precipitation from entering into the duct, it presents two difficulties. First, it directs the exhaust gases back toward the building rather than upward and away from the building thereby increasing the potential that the exhausted gases may be drawn within the building. Since the curved section by necessity must extend above the roofline, the profile of the curved section is often considered unsightly.
BRIEF SUMMARY OF THE INVENTION
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 INVENTION
This 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 INVENTION
A typical embodiment of the invention in the form of a chimney cap is represented in FIG. 11. While a chimney cap is a special type of vent cap, the principles of the invention as disclosed for a chimney cap are generally applicable to a any type of vent cap intended for the exhaust of a conduit that expels gases from a building. It will also be demonstrated by means of a typical embodiment that the invention is also well suited for use on the exhaust of building vents.
FIG. 11 shows a front view, a side view and a top view of a chimney cap that incorporates the features of the invention. The chimney cap of FIG. 11 consists of sheetmetal enclosure 26 that surrounds the top of the chimney liner. An opening 27 on the top of chimney cap provides the normal escape path for the flue gases. Gas rising up through the chimney liner will normally rise on an upward path and pass through opening 27 and thence continue upward essentially unimpeded on a direct vertical path. Opening 27 is fitted with a flame arrestor screen 28 that is intended to block the escape of large flaming objects. Openings 29 are provided on two sides of the chimney cap to serve as emergency paths in the event that opening 27 would become blocked for some reason. Since top opening 27 is essentially flat it could become blocked or partially blocked with falling debris as leaves from trees located higher than the top of the chimney cap. Snow could also accumulate on the flat surface. As with top opening 27, the side ports 29 are fitted with flame arrestor screens 30. The chimney cap would be fastened to the chimney flue by means of screws or a metal band (not shown).
The design of the interior of the chimney cap is illustrated in greater detail in Section A-B of FIG. 11, Section C-D of FIG. 11 and Section E-F of FIG. 11. The details of these sections are shown in FIG. 12. The typical embodiment illustrated in FIG. 12 includes baffles 31 and collectors 32 and collectors 33. Baffles 31 serve to intercept the downward flow of precipitation and to direct that flow to collectors 32 that are located immediately below the baffles at a lower elevation. Collectors 33 are provided to collect precipitation that might enter through the side ports 27. Baffles 31, collectors 32 and collectors 33 are fastened to end plates 34 that secure the baffles in-place. Baffles 31 guide rainfall onto collectors 32 that in turn direct the rain horizontally to a location outside the chimney flue where it falls downward. Baffles 33 trap rain that might enter through one of the side ports 27 and guide that rainfall to a location outside the chimney. Collectors 32 and collectors 33 are of a configuration that not only trap falling rain but also provides essentially little interference to the vertical flow of gas that rises within the chimney flue and, subsequently, through the chimney cap.
The manner in which the typical embodiment of FIG. 12 performs its function can be explained by an examination of the details of the cited typical embodiment. In the way of illustration, one of the baffles 31 of FIG. 12 is shown in FIG. 13. The single baffle represented in FIG. 13 would typically be fabricated of sheetmetal as aluminum, galvanized steel or stainless steel. Material thickness for stainless steel or galvanized steel would commonly be in the proximity of 0.040 inches whereas aluminum would be in the proximity of 0.060 inch. For a chimney cap, materials used for the baffles and collectors must of necessity be able to withstand temperatures in excess of 500 degrees Fahrenheit without undergoing any bending, warping or significant deterioration. The representation of FIG. 13 is an isometric view of the baffle, and it is not shown to-scale for the purposes of illustration. The baffle is shown in a horizontal orientation whereas in a chimney cap it would be positioned at an angle inclined from the vertical. Surface 36 of the baffle comprises the largest area of the element and would act to intercept falling precipitation as rain. Lower flange 35 and upper flange 37 also serve to gather falling precipitation and because they are bent away from surface 36 would add strength to the baffle. End tabs 38 located at both ends of the baffle serve to facilitate mounting of the baffle to a supporting structural member. Holes 39 in the baffle allow fastening by some type of fastening device as a rivet or screw.
The manner is which the baffle of FIG. 13 would be oriented in the chimney cap assembly is represented in FIG. 14. As shown in FIG. 14, the baffle would be tilted slightly from the vertical. FIG. 14 shows raindrop 40 and raindrop 41 that represent raindrops that are falling vertically downward onto the surface of baffle 29. As shown in the representation of FIG. 14, the raindrops fall until they come in contact with the inclined surface of the baffle at which point they travel by gravity along the surface of the baffle to the lower flange 33 at which point they fall vertically downward and away from the baffle.
The above-described baffles of FIG. 13 serve to direct falling precipitation to the collectors that would be located at an elevation below the baffles. A typical collector is shown in FIG. 15. The collector has a surface 42 that, when positioned in the chimney cap assembly would serve to gather falling precipitation. Surface 42 would collect falling precipitation and channel it to a trough 43. End tabs 44 are provided to facilitate mounting of the collector to a supporting structural member of the chimney cap. Holes 45 in the end tabs are to permit fastening by means of rivets, screw or the like. The collector of FIG. 15 would typically be oriented in a chimney cap assembly as represented in FIG. 16.
As shown in the illustration of FIG. 16, the collector would be tilted from the vertical. That portion of the collector that is both within the boundary of a tubesheet as well within that area that is directly above the interior of the chimney is represented by section 46 of FIG. 16. Should falling rain somehow bypass the collector in section 46, it would fall within the chimney. Sections 47 and 48 are outside the tubesheet. The paths of raindrops that fall vertically downward are represented by raindrop 49 and raindrop 50. As shown, raindrop 49 and raindrop 50 fall onto the inclined surface of the collector and are directed by gravity to trough 43 located at the bottom of the inclined surface. After arriving in trough 43 the raindrops flow by gravity to the open ends of trough 43 which are located outside the tubesheet and fall by gravity outside the chimney.
Raindrop 40 and raindrop 41 of FIG. 14 and raindrop 49 and raindrop 50 of FIG. 16 represent raindrops that are falling directly downward along a vertical axis. Of course, due to the horizontal forces caused by wind it is apparent that rain often falls at an inclined angle from the vertical. For this reason, any configuration of the mentioned baffles and collectors must be arranged so as to intercept rain that may be falling at severe angles from the vertical. Intercepted rain must then be directed to an area outside the vertical boundary of the chimney flue. A typical arrangement that would serve to direct falling rain outside the vertical boundary of the chimney flue is represented in FIG. 17.
FIG. 17 shows baffles 51 positioned above collectors 52 in an arrangement that might typically be used in a chimney cap. The representation of FIG. 17 shows a number of raindrops 53 that might fall from the shy into the confines of the chimney cap. Some of the depicted raindrops are shown at an inclined angle to the vertical. The representation of FIG. 17 depicts a variety of paths along which the raindrops might fall. Of course, there would be almost innumerable paths along which raindrops could fall. Nevertheless, it will be apparent that by means of the combination of baffles and collectors there are no paths along which raindrops might follow in order to enter within the interior of the chimney flue. In other words, the combination of baffles and collectors as represented in the configuration of FIG. 17 would act to direct falling rain to the channels of the collectors whence it would flow through openings in the attached tubesheets and to locations outside the perimeter of the chimney flue.
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 FIG. 18 shows the representation of FIG. 17 with the rising products of combustion from a fireplace. The representation is typical of the appearance of the products of combustion that would occur if wood were burned in a fireplace. As shown, particles of burnt wood are mixed with the rising gases. The depiction shows the mixture of hot gases and particles 54 rising through the chimney cap 55 and exhausting in essentially a continuous column above the chimney cap as is claimed to be one of the features offered by the invention. In the representation of FIG. 18 certain details of construction as the baffle and collector mounting means are not shown for the purposes of illustration. While the representation of FIG. 18 shows what would be a typical cross section through a chimney cap with the products of combustion flowing through it, the representation does not show the change in flow pattern that would occur as the rising mixture of hot gases and particles pass through the collectors and baffles of the chimney cap.
FIG. 19 shows a depiction of a mixture of hot gases and particles 56 as the mixture rises through a set of collectors and baffles of the chimney cap. The mixture would first rise between collector 57 and collector 58. As shown, most of the mixture would be expected to exit the collectors and flow between baffle 59 and baffle 60. Nevertheless, some of the mixture would also rise through baffles 60 and baffle 61. A common means of representing flow through conduits, ducts and the like uses a series of lines as shown in FIG. 20 to represent the flow paths that would occur in the circumstances represented by FIG. 19.
In FIG. 20 flow line 62 through flow line 70 represent the flow profile of the gases as they flow up and through the collectors and baffles of the chimney cap. As the gases rise, they first enter between collector 71 and collector 72 before continuing on an upward path and subsequently pass through the baffles that are situated above the collectors. Flow line 73 through flow line 76 represent the flow profile that would enter between collector 71 and the collector that would be next to collector 71. As shown in FIG. 20, and in accordance with industry practice for the representation of a flow profile, the flow lines come close together as they pass around an obstruction in the flow path. In FIG. 20, the necessary presence of gutter 77 presents one type of obstruction, as will be explained in greater detail. The more narrow flow path that is presented by the arrangement of the collectors presents another, although minor, obstruction. The full nature of the mentioned obstructions is treated in greater detail in FIG. 21.
In FIG. 21, dimension K represents the width of the original flow path that is occupied by flow line 62 through flow line 70 of FIG. 20. As the gases enter between the collectors, they must pass through the more narrow channel caused by the presence of gutter 77 of FIG. 20. The width of the narrower channel in FIG. 21 is of dimension L. After the gases pass gutter 77, they continue to rise and pass between the collectors. Because the collectors are inclined at an angle to the vertical, the sides of the collectors present a reduced width. In FIG. 21, the reduced width is shown as dimension M. The collectors are shown inclined at angle N to the vertical which in FIG. 19 is 35°. In FIG. 18, FIG. 19, FIG. 20 and FIG. 21, the ratio of dimension L to dimension K is 0.60 and the ration of dimension M to dimension K is 0.82. Obviously a wider gutter would increase the ratio L/K and a greater inclination to the vertical would decrease the ratio M/K. Since the baffles are inclined to the vertical much as the collectors are, they would also present a passage that is of a reduced width much as is found between the collectors.
In the specific embodiment that is disclosed above, it is apparent that gutter 77 of FIG. 20 is an essential component and, further, it must be of a finite width. Likewise, it is apparent that the collectors and the baffles must be inclined at some angle to the vertical. Without these mentioned characteristics falling precipitation would not be adequately trapped as it entered the chimney cap. Nevertheless, the combination of the inclined baffles and collectors and the width of the gutter can be of configurations that these devices perform their function and yet essentially offer little impedance to the upward flow of gases. The net result is that flow of the column of rising gases is not materially interrupted and the column is allowed to pass through the chimney cap and continue on a path that is essentially on a vertical path. Yet, precipitation is presented from falling within the chimney.
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 INVENTION
Above 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 FIG. 22 shows the invention as applied to the end section of a ducting system that exhausts ventilating air from within a building. Vent cap 78 would typically be constructed of components of the types used in the typical embodiment for a chimney cap as treated above in FIG. 11 through FIG. 17. Essentially the embodiment of FIG. 22 would be constructed in a manner similar to chimney cap 26 of FIG. 11. One significant difference, of course, is that in the case of a vent cap for a building exhaust the material of construction need not be selected to withstand the high temperatures characteristic of the gases emanating from a chimney.
The typical embodiment of FIG. 22 has many features in common with the typical embodiment for a chimney cap that is treated in detail above. By necessity, the typical embodiment of FIG. 22 would have an overhand 79 so as to provide an escape path for rainfall that is trapped in vent cap 78. Vent cap 78 would have side ports 80 much as the discussed chimney cap would. Side ports 80 would offer an escape path for ventilated air should the top of vent cap 78 become blocked for some reason.
As suggested by the representation of FIG. 22, the invention affords a lower and more attractive profile than what would be afforded by a conventional curved section. In addition, it would direct the ventilated air to rise directly upward and away from the building thereby minimizing the potential for the exhausted air to be drawn again into the building.
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.
Patent Application
20080256883
