Patent Application
20080116288
The invention relates to dampers for controlling the air flow in a duct, and more particularly, to dampers configured to be retrofitted to an existing duct.
Many buildings, particularly relatively small buildings such as single-family houses, have a single heating, ventilation, and air conditioning (HVAC) unit that is controlled by a single thermostat. The HVAC unit typically comprises some type of fluid temperature modifying device, such as a furnace for heating air, a boiler for heating a liquid or steam, or an air conditioner having an evaporating coil for cooling air. If the fluid is air, it is typically ducted to various locations within the building, or if it is liquid or steam, it is typically piped to heat exchangers at various locations in the building. The thermostat in this type of space conditioning system is typically positioned at a location where the heating and cooling loads are representative of the entire structure. For example, the thermostat may be installed in an interior room away from windows and doors that would tend to influence the sensed temperature. The HVAC equipment then controls the heating and cooling of the entire structure according to the thermostat signal received from the single location.
However, a single thermostat location may not accurately represent the heating or cooling needs throughout the structure. Other locations of the building may have significantly greater or lower heating and cooling loads than exist at the location of the thermostat. For example, rooms having a larger surface area of windows, or rooms having exterior walls, may require greater heat inputs to maintain the desired temperature. Similarly, rooms facing south or west, or rooms that are on an upper story, may require greater cooling inputs to maintain the desired temperature. Where the HVAC equipment is controlled only by a single thermostat, the heating or cooling supplied to each individual area of the building will be based on the heating or cooling needs at the thermostat location and not on the actual heating and cooling needs of each individual area. As a consequence, the heating and cooling loads of individual areas of the structure may not be satisfied and the temperature of these areas will tend to deviate from the desired temperature.
In some situations, it may be desired to control different locations within a building at different temperatures. For example, rooms that are seldom occupied may not need to be maintained at the same temperature as rooms that are frequently occupied. Energy that is used to heat or cool these unoccupied rooms is not used effectively or economically. Also, rooms may be occupied by people having special temperature needs, such as an elderly person or an infant, that are preferably maintained at a different temperature than the rest of the building. However, a system that has only a single thermostat is generally unable to accurately control different locations in the building at different temperatures.
One solution to this problem is to utilize HVAC zone control. Rather than having a single thermostat controlling the HVAC equipment, multiple thermostats are positioned at locations within the building that are expected to have different heating and cooling loads. Although it is possible that each of these thermostats could control a separate fluid temperature modifying device such as a separate furnace or air conditioner for each zone, that is generally neither efficient nor economical. Rather, most commonly the ductwork or piping that is used to transmit the conditioned fluid to the building spaces is configured with controls to adjust fluid flow. For example, an air duct may be configured with a controllable damper that is capable of opening and closing to control the flow of air to a space within the building.
A system having HVAC zone control generally requires the use of a zone controller to receive the signals from the various thermostats, control the operation of the heating or cooling device, and control the distribution of the conditioned fluid through the ductwork. The zone controller typically comprises electronic circuitry for evaluating the heating or cooling needs of the various zones of the building and for determining an appropriate control of the heating or cooling device and the dampers or valves that control distribution. The distribution control where the conditioned fluid is air is typically accomplished with a duct damper. A duct damper typically comprises a variable obstruction within the duct that can be actuated to one position where there is relatively little resistance to air flow within the duct, and can be actuated to another position where there is relatively great, or complete, resistance to air flow. Duct dampers can be controlled by any of a number of actuation means, including electronic, pneumatic, or mechanical. The HVAC zone controller generally is configured to open or close a duct damper in order to effectuate control over a zone in response to thermostat signals.
There is a need, however, for improved duct dampers.
The invention relates to duct dampers for controlling air flow in air ducts of HVAC systems. A first embodiment of the invention relates to a plurality of HVAC duct dampers that are configured for controlling air flow in ducts having a plurality of different sizes. The plurality of duct dampers includes a first duct damper and a second duct damper. The first duct damper includes a first damper blade that has a first major dimension and that is configured to be installed within a duct that has an interior dimension that is selected to correspond to the first major dimension. The first duct damper also includes a first blade shaft having a first length and having a first end and a second end. The first blade shaft is attached to the first damper blade and forms an axis of rotation of the first damper blade. The first end of the first blade shaft extends beyond a first edge of the damper blade and the second end of the first blade shaft extends to a point between the first edge of the first damper blade and a second edge of the first damper blade, where the second edge is opposite to the first edge. The point to which the first blade shaft extends defines a first shaft mounting distance from the second edge of the first damper blade to the second end of the first blade shaft. The first duct damper also includes a first actuator that is configured to rotate the first blade shaft and first damper blade within the duct to control a flow of air within a duct.
The second duct damper includes a second damper blade having a second major dimension, where the second major dimension is different from the first major dimension. The second damper blade is configured to be installed within a duct that has an interior dimension that is selected to correspond to the second major dimension. The second duct damper also includes a second blade shaft that has the same length as the first blade shaft and also has a first end and a second end. The second blade shaft is attached to the second damper blade and forms an axis of rotation of the second damper blade. The first end of the second blade shaft extends beyond a first edge of the second damper blade and the second end of the blade shaft extends to a point that is between the first edge of the second damper blade and a second edge of the second damper blade, where the second edge is opposite to the first edge. The point that the second blade shaft extends to defines a second shaft mounting distance from the second edge of the second damper blade to the second end of the second blade shaft. The second shaft mounting distance is different from the first shaft mounting distance. The second duct damper also includes a second actuator that is configured to rotate the second blade shaft and second damper blade within the duct to control a flow of air within the duct.
A second embodiment of the invention relates to a method of manufacturing a plurality of duct dampers for use in a plurality of ducts of different sizes. The method includes the step of providing a plurality of damper blades having a range of sizes that are configured to control airflow in a corresponding range of duct sizes, where the range of damper blade sizes includes a maximum blade size and a minimum blade size. The method further includes the step of providing a plurality of damper blade shafts, where each shaft has the same shaft length, the shaft length being at least more than one-half of a major dimension of the maximum blade size, the shaft having a first end and a second end. The method also includes the step of attaching one of the plurality of damper blade shafts to each damper blade to form a plurality of blade shaft and damper blade assemblies and to define an axis of rotation through the center of each damper blade. The attaching step also involves, for each blade shaft and damper blade assembly, configuring the first end of the blade shaft to extend beyond a first edge of the damper blade, and configuring the second end of the blade shaft to extend to a point between the first edge of the damper blade and a second edge of the damper blade that is opposite to the first edge that the first end extends beyond. Furthermore, if the damper blade selected from the plurality of damper blades has the maximum blade size, then the second end of the shaft defines a first distance to the second edge of the damper blade. If the damper blade selected from the plurality of damper blades has the minimum blade size then the second end of the shaft defines a second distance to the second edge of the damper blade. The first distance is greater than the second distance.
Yet another embodiment of the invention relates to a plurality of round HVAC duct dampers configured for controlling air flow in ducts having a plurality of different diameters. The plurality of round duct dampers includes a first duct damper and a second duct damper. The first duct damper includes a first damper blade that has a first diameter. The first damper blade is configured to be installed within a first duct having an interior diameter that is greater than the first diameter. The first duct damper also includes a first blade shaft having a first length and having a first end and a second end. The first blade shaft is attached to the first damper blade and forms an axis of rotation of the first damper blade. The first end of the first blade shaft extends beyond a first edge of the first damper blade, and the second end of the first blade shaft extends to a point between the first edge of the first damper blade and a second edge of the first damper blade that is opposite to the first edge. The point that the first blade shaft extends to defines a first shaft mounting distance from the second edge of the first damper blade to the second end of the first blade shaft. The first duct damper also includes a first actuator that is configured to rotate the first blade shaft and first damper blade within the duct to control a flow of air within a duct.
The second duct damper includes a second damper blade that has a second diameter, where the second diameter is different from the first diameter. The second damper blade is configured to be installed within a second duct that has an interior diameter that is greater than the second diameter. The second duct damper also includes a second blade shaft having the same length as the first blade shaft and having a first end and a second end. The second blade shaft attaches to the second damper blade and forms an axis of rotation of the second damper blade. The first end of the second blade shaft extends beyond a first edge of the second damper blade and the second end of the blade shaft extends to a point between the first edge of the second damper blade and a second edge of the second damper blade that is opposite to the first edge. The point that the second blade shaft extends beyond defines a second shaft mounting distance from the second edge of the second damper blade to the second end of the second blade shaft. The second shaft mounting distance is different from the first shaft mounting distance. The second duct damper also includes a second actuator that is configured to rotate the second blade shaft and second damper blade within the duct to control a flow of air within the duct.
The invention may be more completely understood by considering the detailed description of various embodiments of the invention that follows in connection with the accompanying drawings.
While the invention may be modified in many ways, specifics have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives following within the scope and spirit of the invention as defined by the claims.
A zone control system requires that certain components be installed in an HVAC system in order to function properly. In some cases, zone control system components are installed when the building and/or HVAC system is originally constructed. However, in other cases the building or HVAC system is constructed first and only later does the building owner or occupant decide to install a zone control system. In this case, it is necessary to retrofit the existing HVAC system with zone control components.
However, retrofitting an existing HVAC system with zone control components can be challenging. One particular difficulty is associated with installing the dampers required for the operation of a zone control system within the existing ductwork. In many cases, the air supply ductwork forms an integral part of the building structure, such that the building structure surrounds the ductwork or there is very little clearance between the ductwork and other building components. Also, the ductwork is not readily disassembled to introduce a new piece part into the ductwork. Therefore, it is preferred that a damper for retrofitting an existing HVAC system be configured to be readily installed into a duct where limited access space is available and to be installed in a manner that does not require the disassembly or rework of the existing duct work. In addition, many different sizes and configurations of ductwork are typically used in HVAC systems, often in common sizes such as round duct that is 5 inches, 6 inches, 7 inches, and 8 inches in diameter. It is thus desired that a damper be available to retrofit into any size or configuration of duct that may be commonly found in the existing HVAC system. Furthermore, the decision by a building owner or occupant to install a zone control system is typically cost-sensitive. Therefore, it is also desired that a damper for retrofit use be cost-effective.
A variety of control strategies for zone controller 46 are usable. In general, however, zone controller 46 is configured to open and close dampers 40, 42, 44, in response to signals from thermostats 26, 28, 30, respectively, and to operate conditioning unit 32. For example, if zone controller 46 senses that thermostat 26 is calling for heat because the temperature in zone 20 has fallen below a preset level, then zone controller 46 sends a signal to conditioning unit 32 to turn on and signals damper 40 to be in an open position. Heated air from conditioning unit 32 will then travel through duct 34, through damper 40, and into zone 20, thereby tending to increase the temperature within zone 20. If at the same time thermostats 28, 30 in zones 22, 24 do not call for heat, dampers 42, 44 will be closed and heated air will not travel through ducts 36, 38 into zones 22, 24. The operation of HVAC system 10 in response to other thermostat signals from other zones and other combinations of zones is similar. HVAC system 10 may include other sensing devices and other sources of input to zone controller 46, as well as other actuating devices and other devices that are controlled by zone controller 46.
An embodiment of a damper configured for installation in a duct is shown in perspective view in
Damper blade 126 is configured to control air flow in a duct having a certain cross-sectional profile. For example, where a duct is generally round, damper blade 126 will be generally round, or where a duct is generally rectangular, damper blade 126 will be generally rectangular. Damper blade 126 is generally planar in shape, so that its thickness is significantly less than its height and width or diameter. The height and width or diameter of damper blade 126 are examples of major dimensions of the damper blade 126. Damper blade 126 generally has a major dimension that is sized to correspond to the duct sizing, such that the major dimension of the damper blade 126 is slightly smaller than an interior dimension of the duct. For example, in one embodiment the major dimension of damper blade 126 is about 1.625 inches smaller than an interior dimension of the duct. In another embodiment, the major dimension of damper blade 126 is 1.5 inches to 1.75 inches less than an interior dimension of the duct. The major dimension of damper blade 126 corresponds to a dimension that is useful for controlling the air flow in a duct.
For example, in cases where round ducts are provided having standard inner diameters of 5 inches, 6 inches, 7 inches, and 8 inches, corresponding damper blades 126 are provided that each have a major dimension that is a diameter that corresponds to the duct diameter by being slightly less than the duct diameters. For the standard inner duct diameters of 5 inches, 6 inches, 7 inches, and 8 inches, exemplary corresponding damper blade diameters are 3.375 inches, 4.375 inches, 5.375 inches and 6.375 inches, respectively.
Alternatively, damper blade 126 may also be configured for use in a range of standard rectangular duct sizes, such as 6 inches tall×8 inches wide, 6 inches tall×10 inches wide, 10 inches tall×12 inches wide, 12 inches tall×20 inches wide, and 16 inches tall×30 inches wide. In this case, damper blade 126 has major dimensions of width and height that are sized to correspond to the duct sizing, such as the height or width of the duct. For example, for the standard inner duct dimensions of 6×8 inches and 6×10 inches, exemplary corresponding damper blade dimensions are 4.375×6.375 inches, and 4.375×8.375 inches, respectively.
In one embodiment, damper blade 126 further includes a gasket 142 around the outer edge of damper blade 126 that is configured to create a seal with an interior duct wall when damper assembly 120 is installed in a duct and damper blade 126 is in a closed position. Damper blade 126 is generally configured to correspond to the duct sizing by being slightly smaller than the nominal dimensions of the duct, so that the inherent variability in duct dimensions as well as the potential for ducts to flex or bow under pressure or gravity will not cause the damper blade to bind or not turn within the duct. One example of an appropriate material for the damper blade is two layers of 20 gauge sheet metal. Gasket 142 is constructed from a flexible material that extends beyond the edges of damper blade 126 and is configured to seal a gap formed between the damper blade 126 and duct 130. In one embodiment, gasket 142 is attached to damper blade 126 by having at least a portion that is sandwiched between two layers used to form damper blade 126.
Duct 130 is shown in
In operation, damper assembly 120 is assembled to duct 130 and attached thereto by a plurality of fasteners 148 that engage duct 130. Many other types of attachment are usable, however, such as adhesives, welding, rivets, etc. In one embodiment, one or more wires are attached to actuator 124 that provide for the transmission of electrical signals from a controller, such as zone controller 46. Alternatively, other forms of control of actuator 124 may be utilized, such as pneumatic control through tubing or mechanical control through linkages, as well as wireless signals. Zone controller 46 (shown in
As discussed, damper assembly 120 is preferably provided in a number of different sizes or configurations to function with ducts having a number of different sizes or configurations. For example, round ducts may be provided having standard inner diameters such as 5 inches, 6 inches, 7 inches, and 8 inches, and it is desired to have a corresponding plurality of damper assemblies 120 having different damper blade diameters for each duct diameter. Such a plurality of damper assemblies may comprise a damper assembly product line 220, as shown in
Each damper assembly 222, 224, 226, 228 of damper assembly product line 220 preferably utilizes as many components as possible that are common with each of the other damper assemblies 222, 224, 226, 228. Having common components promotes ease of assembly of the damper assembly product line and reduces manufacturing piece part and inventory costs. For example, each damper assembly 222, 224, 226, 228 is configured to utilize the same frame 122 and actuator 124. By necessity, each damper assembly 222, 224, 226, 228 will utilize a different damper blade that corresponds to the intended duct size that it will be used with. For example, damper assembly 222 uses a damper blade 230 that is configured for a 5 inch duct, damper assembly 224 uses a damper blade 232 that is configured for a 6 inch duct, damper assembly 226 uses a damper blade 234 that is configured for a 7 inch duct, and damper assembly 228 uses a damper blade 236 that is configured for a 8 inch duct. Generally, the range of damper blade diameters of damper assembly product line 220 includes a maximum blade diameter and a minimum blade diameter corresponding to a maximum and minimum duct diameter that the product line 220 is configured for use with.
However, despite the fact that damper assembly product line 220 includes a variety of different damper blade sizes, in one embodiment, each damper assembly 222, 224, 226, 228 of damper assembly product line 220 uses a common damper blade shaft 128. As is seen more clearly in
In each damper assembly 222, 224, 226, 228, damper shaft 128 is attached to the respective damper blade 230, 232, 234, 236 through an approximate center of each damper blade to define an axis of rotation of the damper blade. As shown in
The blade part 164 of damper shaft 128 extends from the frame 122 to the second end 152. In the embodiment of
Furthermore, the range of possible blade 126 diameters for use with constant length shaft 128 is limited by the need to prevent the second end 152 of shaft 128 from extending past the far edge 168 of blade 126. Given the constraints that the length L1 of shaft 128 is constant and that the length L2 that shaft 128 extends beyond frame 122 is constant, there is only a limited range of blade 128 diameters within product line 220 that are usable. Alternatively, where conditions permit, the distance L2 can be allowed to vary, so that a longer shaft 128 can be used and a larger range of damper blade 126 diameters are usable.
A product line duct dampers may be configured, for example, for use with a plurality of round ducts having various sizes such as inner diameters of 5 inches, 6 inches, 7 inches, and 8 inches. In one embodiment of such a product line, the blade shaft length L1 is 5.5 to 9 inches. In another embodiment, the blade shaft length L1 is 7.0 to 7.5 inches.
It is preferred that blade 126 and blade shaft 128 be configured to have sufficient strength to resist excessive flexing when in the closed position in a pressurized duct. When blade 126 is in a closed position in a duct, there will be a relatively higher pressure on one side of blade 126 and a relatively lower pressure on the opposite side of blade 126. This pressure differential will create a force that acts on the blade 126, where the force is equal to the area of the blade multiplied by the pressure differential. Both damper blade 126 and damper shaft 128 contribute to resisting this force. However, a particular concern exists with respect to configurations where damper shaft 128 does not extend across the full width of damper blade 126, such as in dampers 224, 226, 228 having larger blade diameters. These dampers also have larger blade diameters, and therefore have larger forces to resist. Each of the damper blades, such as 230, 232, 234, 236, and damper shaft 128, should be configured with sufficient strength to resist these forces, such as through sufficient thickness of damper blade 230, 232, 234, 236 and sufficient cross-sectional area of shaft 128.
As discussed above, a damper assembly product line may also be configured for use with rectangular ducts. For example,
The present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
The above specification provides a complete description of the structure and use of the invention. Since many of the embodiments of the invention can be made without parting from the spirit and scope of the invention, the invention resides in the claims.
