Abstract:
A fluorescent lighting system having a low-cost nonconductive plastic housing and a plurality of fluorescent lighting tubes carried in sockets in the housing and a square-wave alternating current source connected to drive the fluorescent lighting tubes.

Description:
REFERENCE TO RELATED APPLICATION 
     The present application is based on Provisional Application No. 60/137,508 filed Jun. 2, 1999 entitled PLASTIC “TROFER” FOR FLUORESCENT LIGHTING. 
     Reference is made to application Ser. No. 08/942,670 filed Oct. 2, 1997 entitled LOW VOLTAGE NON-THERMIONIC BALLAST-FREE FLUORESCENT LIGHT SYSTEM AND METHOD and U.S. Pat. No. 6,034,485 which are incorporated herein by reference. 
    
    
     BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION 
     A fluorescent lighting fixture housing includes a space for housing a ballast transformer, a metal reflector, tube socket members and wiring between the ballast transformer and the tube sockets. Conventionally, these housings (commonly called “trofers” because they hold 2-4 fluorescent tubes) have been made out of sheet metal to convey heat generated by conventional heating of the filaments, ballast transformers and the heating from the plasma in the gas. This heating requires that the fixture be spaced from wood and other flammable structures using, in many cases, chains, hooks, etc., which suspend the fluorescent fixture from a ceiling, for example, which also allows cooling air to circulate and cool the fixture. In addition, these prior art fixtures require the use of heat resistant wire. Moreover, in most cases a metal housing is required to be conductive so as to provide an electrical ground to avoid shock hazards due to high voltage. 
     For the following reasons a standard fluorescent fixture should have ground: 
     1. A grounded metal housing of a predetermined size and gauge acts as a “heat sink” for the ballast. 
     2. A grounded metal reflector with the lamps installed within about ½″ of the reflector. 
     3. The ballast must be an integral part of the fixture. 
     4. The wiring in the fixture must be of at least #12 gauge and covered with high temperature insulation (over 95° C.). 
     5. The inner space between the “drop ceiling” and the structural ceiling must be ample enough to dissipate the heat from the fixture (from 2′ to 3′ average). 
     6. Power to the fixture must be supplied by a 3-wire system, 12 gauge or better, with a ground (bonded). 
     7. The metal fixture should have enough area of contact with the air to dissipate the heat. 
     8. Standard systems are “ground plane systems.” 
     An object of the present invention is to provide a fluorescent lighting fixture and system which has a housing made of plastic. 
     Another object of the invention is to provide a fluorescent lighting fixture of the “trofer” type which is significantly cooler and as a result may be safely mounted directly on a ceiling. 
     Still another object of the invention is to provide a fluorescent lighting fixture and system which is ballast-free, significantly cooler in operation than prior art fixtures, and a fluorescent lighting fixture which is significantly less hazardous and thus safer from fire and high-voltage hazards. 
     Another object of the invention is to provide a lighting fixture of the trofer type which is shallow and of less volume than prior art trofers. 
     DESCRIPTION OF THE INVENTION 
     A fluorescent lighting fixture includes a plastic or non-conductive housing, preferably made of a thermoplastic resin, sockets for fluorescent tubes and an alternating current square-wave alternating voltage source (sometimes hereinafter called “square-wave driver” or “driver”) for driving the fluorescent tubes. In one embodiment, the square-wave driver is thin (not requiring a large heavy ballast transformer) and can be mounted by screws or an adhesive on the housing or carried in a slot molded or formed in the non-conductive housing. In another embodiment, since the driver is small and does not require a ballast transformer, it can be mounted in a light switch housing. In this case, since the current and voltage levels are low due to the improved efficiency of driving the fluorescent lamps or tubes with the high frequency alternating square waves supplied by the driver as described in my above-identified application, smaller gauge wires and less insulation can, if desired, be used. A conventional light diffuser may be mounted in the housing to diffuse the light from the lamps. 
     Features of a Plastic Fixture (Trofer), Driver and Lamp Array According to the Invention 
     1. Lamps can be driven by individual drivers, i.e. integral to the sockets or integral to the lamp. Or the lamps can be connected in series to the appropriate capacity driver in any numbers, odd or even. 
     2. The driver could be integral to the fixture or can be non-integral, mounted on a remote location, i.e. the switch assembly. 
     3. No grounded metal reflector is needed. 
     4. No clearance from combustible materials needed. 
     5. No heat release area between the finish ceiling and the structural ceiling needed. 
     6. No bonded ground is needed, no “ground wire.” 
     7. No reinforcing of the finish ceiling is needed, due to low weight. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The above and other objects, advantages and features of the invention will become more apparent when considered with the following specification and accompanying drawings wherein: 
     FIG. 1 is a diagrammatic illustration of a fluorescent lighting fixture (trofer) incorporating the invention, and 
     FIGS. 2A-2C are block diagrams illustrating different embodiments of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a fluorescent lighting fixture LF includes a plastic or non-conductive housing  10 , preferably made of a thermoplastic resin, bi-pin sockets  16 - 17  for fluorescent tubes and an alternating current square-wave alternating voltage source  21  (sometimes hereinafter called “square-wave driver” or “driver” for driving the fluorescent tubes FE. The basic circuit block diagram is shown in FIG.  2 A and includes a DC supply or source DCS and an AC square-wave driver SWD for driving one or more lamps. The square-wave driver circuit may incorporate a rectifier, or a common rectifier CR connected to an AC source may supply a plurality of drivers  21  (FIG.  2 B). In one embodiment, the square-wave driver is thin (not requiring a large heavy ballast transformer) and can be mounted by screws or an adhesive on the housing or carried in a slot molded in the non-conductive housing. In another embodiment, since the driver is small and does not require a ballast transformer, it can be mounted in a light switch LS housing (FIG.  2 C). In this case, since the current and voltage levels are low due to the improved efficiency of driving the fluorescent lamps or tubes with the high frequency alternating square waves supplied by the driver as described in my above-identified application, smaller gauge wires SGW and less insulation can, if desired, be used. A conventional light diffuser LD may be mounted in the housing to diffuse the light from the lamps. 
     While the invention has been described in relation to preferred embodiments of the invention, it will be appreciated that other embodiments, adaptations and modifications of the invention will be apparent to those skilled in the art.