1. Field of the Invention
This invention is directed to light fixtures, in general, and, more particularly, to a light fixture which is readily converted from a fixture which uses conventional incandescent light bulbs to a fixture which uses fluorescent tubes.
2. Prior Art
There are many types of light fixtures which are known in the art. These include recessed fixtures, surface mounted fixtures, track-light fixtures and the like. Most of the known light fixtures use incandescent light sources therein. However, incandescent light sources have a short life and are inefficient. The number of lumens generated per electrical watt consumed is, generally, in the uneconomical range of about 14 to 17 lumens per watt.
In addition, these types of light sources generally use a thin filament which glows when heated by electrical power and tends to burn out or break rather easily.
Also, incandescent light sources tend to generate a large amount of heat which is given off into the surrounding area. This has the secondary shortcoming of producing heat in many places where excessive heat is not desired. Consequently, it becomes necessary to use air conditioning equipment or the like to counteract this unwanted heat.
Clearly, incandescent light sources tend to consume and waste energy. Power companies, as well as government agencies, and the like are becoming aware of the energy that can be conserved by changing out inefficient incandescent light bulbs in favor of fluorescent or other types of energy efficient light sources.
Several types of alternative light sources are known in the art. For example, fluorescent, high pressure sodium and metal halide lamps, and the like, are typical. These light sources generally tend to operate quite efficently and to provide 50 to 120 lumens per watt. The lower wattages do not, as a rule, produce excess heat during operation.
Many power companies have addressed the increasing demand for energy efficient lighting by employing fluorescent adapters that screw into existing incandescent lighting sockets. This facilitates the conversion of light sources with a resulting energy savings of 60% or more. Thus, many utilities have actually embarked upon programs to offer cash rebates to the customers who convert light sources. Alternatively, such companies have even given away energy-saving light bulbs in an effort to shed electrical load demands.
However, these alternative light sources are normally not interchangeable with conventional incandescent lamps or bulbs. For one thing, the different light sources may have different couplings or bases, as is the case with a fluorescent tube. The "Edison-base" coupling which is common on the ordinary incandescent lamp and light fixture will not accept standard fluorescent fittings.
Conversely, certain light sources such as electric-discharge lamps require a ballast in order to operate. For example, high pressure sodium and metal halide lamps with screw bases can be screwed into an Edison-base socket, but they cannot operate without a ballast which is used to deliver the appropriate circuit (i.e. voltage, current and waveform) for starting and operating. Also, the term "ballast" refers to a step down transformer. Typically, a ballast which steps down the line voltage of 120 volts to operate 12 volt lamps is contemplated.
In essence, the ballast is used to deliver the proper voltage to a particular light source. The wattage of the lamp, the lamp type and the line voltage will dictate the specific ballast design to match the lamp. For example, line voltage is normally 120 volts or 277 volts. However, other voltages may be encountered. Therefore, a specific ballast must be used to drive a specific lamp.
In order to convert an existing inefficient incandescent lighting system to a more efficient light source, it has been necessary to replace the existing lighting fixture with a totally new lighting fixture that incorporates the proper socket configuration and a ballast assembly.
Certain retrofit light fixtures were developed which included ballasts built into the fixture itself or an attached housing. These light fixtures, however, required an ample amount of space within the existing fixture to include the ballast and socket assemblies.
Consequently, it is highly desirable to develop light fixtures which permit these alternative light sources to be retrofitted into existing electrical system hardware efficiently and economically.