It is known to supply and control heating and ventilation from a centralized source. Buildings are often built with dampers and temperature sensors within air ducts. These dampers can be controlled from a centralized location. Examples of this technology may be found in U.S Pat. No. 4,585,163 (the '163 patent), U.S. Pat. No. 4,732,318 (the '318 patent), U.S. Pat No. 4,406,397 (the '397 patent), and U.S. Pat. No. 4,646,964 (the '964 patent). A common problem of the devices cited in these patents is the difficulty and expense involved in fitting an already constructed building with a heating and air conditioning system. This problem of retrofittability is solved with the present invention.
One of the reasons the devices cited in prior art are difficult to fit into existing buildings is that their dampers are located within the air ducts. Most of the these dampers are single blade devices. Single blade dampers need significant amounts of space (about equal to the width or height of a damper, depending on the pivot direction) to reach a fully opened state. The space requirement, therefore, dictates that these single blade dampers be positioned within the actual duct, rather than at the duct outlet or opening. This single blade design can be seen in the '318 patent, the '964 patent, the '397 patent, and the '163 patent.
U.S. Pat. No. 4,258,877 (the '877 patent), issued Mar. 31, 1981, to White, discloses an electric, motor driven damper, with thermostatic switch control, for opening and closing air ducts. The actuator also shows the damper position from outside the duct, by the use of an indicator arm on the damper pivot. Like those devices mentioned above, the White damper blade must be located within the actual air conditioning duct. This is because the damper blade is comprised of an L-shaped member having a relatively long leg and a relatively short, slightly curved leg. The relatively long leg is rotatably mounted to a shaft which is mounted perpendicular to the flow of air. Therefore, the relatively long leg of the damper blade would be parallel or at an angle to the sides of the air conditioning duct. This would prevent this damper blade from being used directly behind the duct opening. Since the damper must be located within the air conditioning duct, retrofitting is impractical.
U.S. Pat. No. 2,790,372, issued Mar. 30, 1963, to Cooper, discloses an electric, motor driven damper, controlled by a thermostat, to increase the flow of cool/heated air into the individual rooms. There is no provision for controlling the temperature of the incoming air or for controlling the overall system temperature. The damper in this patent only functions in conjunction with an air supply duct which extends horizontally above the ceiling of a room and has a duct opening on its lower side. This single blade damper requires significant amounts of room to swing open. Therefore, like those dampers discussed above, this damper would not be easily retrofittable and, additionally, would be limited to a specific type of duct.
There are many methods of regulating individual room air temperature. The invention disclosed in the '318 patent issued Mar. 22, 1988, to Osheroff, regulates individual room air temperature by increasing the velocity of the heated or cold air through the ducts. The invention disclosed in the '397 patent, issued Sep. 27, 1983, to Kamata, regulates air temperature in an individual room by using an air quantity control device in each branched duct of a central heating and air conditioning system. The air quantity delivered to each room is monitored by velocity sensors in each branch duct, and the command sent to the central blower unit for either increased or decreased air volume. The invention disclosed in the '163 patent, issued Apr. 29, 1986, to Cooley, regulates air temperature by monitoring air volume.
It also should be noted that most of the prior art systems have sensing devices which are located within the air ducts. This is true in the '318 patent, the '397 patent, the '163 patent, and the '964 patent. This requirement makes retrofitting difficult.
The '964 patent, issued Mar. 3, 1987, to Parker, addresses the opening and closing of a duct, and the air temperature in the duct. The room temperature is set by a thermostat in the individual room, and commands the duct to open and close, based on the difference between room temperature and air duct temperature, measured by a sensor in the duct. This system cannot control individual room temperature by commanding the heater/air conditioner to add cooler air or heat, and relies on the main thermostat, for the overall temperature condition.
Accordingly, a principal object of the present invention is to provide an improved heating and air conditioning system which is easily retrofittable to a single family dwelling with a single duct system.