1. Field of the Invention
The present invention relates to lighting systems, such as architectural and environmental lighting systems. The invention especially relates to cove lighting systems for residential applications.
2. Description of the Related Art
In a typical cove lighting system, lighting elements are located in an architectural recess and gently illuminate the wall and/or ceiling space adjacent the recess. Light coves are most frequently located near junctions between walls and ceilings. However, light coves may be placed in other locations, and may be provided in many orientations, including horizontal and vertical.
Cove lighting systems have many applications. For example, cove lighting systems may be used to illuminate book cases, wine and glass racks, furniture, and display cases. Cove lighting systems may be employed anywhere that the introduction of a soft halo of light is desired.
Examples of lighting elements that have been used for cove lighting systems include incandescent bulbs, PL lamps, and standard fluorescent hot cathode lamps. As explained below, all such lighting elements have significant drawbacks.
Incandescent bulbs are energy inefficient. Incandescent bulbs also have a short lifetime. The lifetime of a standard incandescent bulb may be only two thousand hours. Therefore, incandescent bulbs must be replaced frequently. Moreover, incandescent bulbs do not produce uniform illumination. A row of incandescent bulbs produces uneven bright and dark areas of illumination.
A PL lamp is a small diameter U-shaped gas discharge fluorescent lamp. PL lamps, like incandescent bulbs, produce uneven bright and dark areas of illumination. Moreover, PL lamps cannot be dimmed without specialized auxiliary power supplies. Another disadvantage associated with PL lamps is that they are not commercially available in colors other than white. The lifetime of a standard PL lamp is approximately ten thousand hours.
Standard fluorescent (hot cathode gas discharge) lamps are not commercially available in curved configurations suitable for cove lighting applications. Moreover, fluorescent lamps are not commercially available in colors other than white, and are not dimmable without special equipment. The rated lives of commercially available fluorescent lamps are from ten thousand to fifteen thousand hours.
Low voltage cold cathode lamps, in contrast to the lamps discussed above, are especially well suited for cove lighting applications. Cold cathode lamps are dimmable and can be relatively easily fabricated to follow a curved architectural recess without loss of light. Moreover, cold cathode lamps can be ordered in almost any color imaginable, from whites to hot pinks, vibrant blues, purples, and aquas.
A cold cathode lamp is a gas discharge lamp whose electrodes are not heated to the point of thermionic emission. A hot cathode lamp is a gas discharge lamp whose electrodes are heated to the point of thermionic emission. Because of this difference, cold cathode lamps may last much longer than hot cathode lamps. A well manufactured cold cathode lamp may last fifty thousand hours. Unlike regular hot cathode fluorescent lamps, a cold cathode lamp does not lose three hours of its rated lifetime each time it is turned on.
Examples of cold cathode gas discharge lamps are disclosed in U.S. Pat. Nos. 5,155,668 (Tanner) and 4,004,185 (Edmondson et al.), the entire disclosures of which are incorporated herein by reference.
High voltage cold cathode lamps (including conventional neon lamps) have been used for some cove lighting applications with some success. However, high voltage lamps cannot be used in residences. According to the National Electric Code, NEC 410-75A, voltages over one thousand volts are not suitable for residential applications. Standard high voltage cold cathode lamps are particularly hazardous for residential applications. The high voltage operation of such lamps can also cause humming and buzzing noises which are unacceptable for many applications, particularly residential applications.
Another disadvantage with high voltage lamps is that the ends of such lamps electrostatically attract and incinerate dust. The resulting soot accumulates on the ceiling. The higher the voltage, the worse the problem. Eventually, the ceiling has to be repainted to cover the accumulated soot. It may be necessary to repaint the ceiling every year. To avoid the problem of soot accumulation, coves with high voltage lamps may be spaced farther away from the ceiling. However, for architectural and aesthetic reasons, it is generally advantageous to locate a cove as close to the ceiling as possible.