Abstract:
A fluorescent lamp assembly that has a planar configuration with an open area defined within the lamp tube. A low profile, integral common housing encloses a ballast and a portion of the lamp structure within the open area of the lamp tube. The housing mechanically secures the lamp tube and contains an electrical connector allow the lamp electronics to plug into an electrical main. The electronics and the lamp are contained in a common structure so they can be used, handled, and discarded as a single unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electronically self-ballasted fluorescent lamp system. More particularly, the fluorescent lamp is substantially planar, i.e., flat, and encloses a low profile housing within an open area inside the fluorescent lamp in which an integral, common housing encloses the ballast and the lamp ends to securely hold the assembly together. 
     2. Discussion of the Art 
     Fluorescent lamps are generally economical to operate and thus the energy savings makes them a desirable lamp. One particular type of fluorescent lamp that has found commercial acceptance is referred to as a “2D” lamp in which the lamp is generally shaped like a pair of capital letter Ds disposed in back-to-back, or mirror, relationship. The lamp is an elongated tube bent into the desired 2D shape. Typically, a first housing receives first and second ends of the lamp tube, and a second housing carrying the electronic ballast components is adapted for selective connection to and extends outwardly from one face of the generally planar lamp assembly. Thus, although the tube of the lamp assembly is configured in a substantially planar configuration, and the first housing receiving the lamp ends has a generally planar, low profile, the second or ballast housing extending outwardly from the lamp assembly defeats the advantages offered by the low profile lamp arrangement. 
     Fixture manufacturers are always searching for an extremely flat or planar lamp product that provides good light output. The system must be low cost and have a high efficiency to optimize the benefits to the consumer. For example, it would be desirable to have a lamp assembly that plugs into an electrical main, while at the same time being held securely in place until such time that the consumer desires to remove the lamp from the fixture, for example, when it reaches the end of its useful life or burns out. 
     Typically, the ballast is designed to have a life expectancy significantly greater than the lamp tube. However, it then becomes necessary to design the lamp so that it is easily removed without special tools. The design must also assure that good mechanical and electrical connections are made in the original lamp assembly, as well as when a consumer replaces the lamp tube. Accordingly, it is deemed desirable to combine the electronics and the lamp into a common structure so that the entire lamp assembly can be used, handled, and even discarded as a single unit. 
     BRIEF SUMMARY OF THE INVENTION 
     A fluorescent lamp assembly includes an integral, common housing that mechanically receives opposite ends of the lamp tube and also encloses lamp electronics therein. The lamp tube has a curved configuration disposed in a single plane. The lamp housing has a low profile that provides good light output while being confined within an inner space of the lamp. 
     The lamp can be advantageously smaller and more economical since the ballast or electronics need not survive longer than the lamp. 
     Any wattage lamp can potentially work in an arbitrary fixture socket. 
     The high frequency electronics ballast allows the construction of a very light weight, economical, high efficiency lighting product with good light output. 
     The lamp assembly is optimally thin and exhibits a low profile essentially limited only by the lamp thickness because the electronics, lamp, and recess connector all share the same housing and are preferably confined within the planar profile of the lamp. 
     Moreover, the shape, size, and position of the ballast prevents interference with the lamp ends or tip-offs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a planar view of a fluorescent lamp assembly. 
     FIG. 2 is a top view of FIG.  1 . 
     FIG. 3 is an end view taken generally from the right-hand end of FIG.  1 . 
     FIG. 4 is an exploded view of the lamp assembly in perspective. 
     FIG. 5 is a plan view of the lamp assembly with a portion of the housing removed for ease of illustration. 
     FIG. 6 is a cross-sectional view taken generally along the lines  6 — 6  of FIG.  5 . 
     FIG. 7 is a plan view similar to FIG. 5, with the lamp electronics added thereto. 
     FIG. 8 is a sectional view taken generally along the lines  8 — 8  of FIG. 7 FIG. 9 is a plan view of one of the housing portions. 
     FIG. 10 is a sectional view taken generally along the lines  10 — 10  of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a fluorescent lamp assembly A that includes a fluorescent lamp envelope or glass tube  20  that is configured or bent to a substantially planar conformation. The lamp tube is bent into what is generally referred to as a 2D conformation. It includes a substantially linear portion  22  bent at opposite ends  24 ,  26 , into second, generally parallel segments  28 ,  30  and further into bent regions  32 ,  34  which proceed toward the lamp ends  36 ,  38 . The lamp tube substantially encloses an open central region  40 . The lamp ends are preferably disposed in generally parallel relation as they enter a housing  50  received in the central region. 
     The housing is an integral, common structure that receives and mechanically retains the ends of the limp tube and also encloses the lamp electronics that are operatively connected to lamp leads. FIGS. 2-4 illustrate that the integral housing is originally formed of two mating portions  52 ,  54  that interlock along a tongue-and-groove portion  56  (FIG.  2 ). First and second arms  58 ,  60  extend from the first portion  52  of the housing and mate with first and second arms  62 ,  64  (FIGS. 5-8) extending from the housing second portion. Each of the arms includes a curvilinear recess or C-shaped recess  66  dimensioned for mating conformation with the outer periphery of the lamp tube. In particular, the arms are dimensioned for receipt over the first linear region  22  of the lamp tube to provide support at a central region of the extended length of the lamp tube. When the housing portions  52 ,  54  are brought into engagement, the recesses  66  in the arms define through openings that engage the outer periphery of the lamp tube. In addition, each housing portion includes semicircular recesses  70 ,  72  at a location generally opposite the arms. The recesses  70 ,  72  are adapted to closely receive the first and second ends  36 ,  38  of the tube. Thus, the elongated tube is mechanically supported by the housing at four distinct regions; namely, at the first end  36 , by arm  58 , by arm  60 , and at the second end  38 . 
     With particular reference to FIGS. 4-8, additional details of the mechanical and electrical connections will be described. Lamp tip-offs or exhaust tubes  80 ,  82  are formed in the end of the glass tube as is well know in the art. In addition, electrode leads  84 , associated with the first end, and electrode leads  86 , associated with the second end, extend outwardly from the glass tube for receipt in the housing. Support members  88 ,  90  receive and support the lamp tip-offs within the housing. The electrode leads  84 ,  86  are angled outwardly away from the second housing portion  54  as best illustrated in FIG.  6 . Upon introduction of lamp electronics board  100  (FIGS.  7  and  8 ), the electrode lead ins are of sufficient length so that the leads are fed through openings  102  in the board and electrical connections completed. As perhaps best illustrated in FIGS. 7 and 8, the electrode leads pass over the supports  88 ,  90 , respectively, on a first face of the board, and then are deflect to the other face of the board before protruding through the openings  102  toward the first face of the board again. Details of the lamp electronics incorporated into the electronics board  100  can be found in commonly-owned U.S. patent application Ser. No. 09/ 637,768, filed Aug. 11, 2000, now U.S. Pat. No. 6,459,215. By incorporating the electronics into the same housing as the lamp ends, and particularly using an electronics board as referenced in the co-pending application, a single, common housing having a low profile is achieved. The electronics is designed for substantially the same intended useful life as that of the fluorescent tube. Therefore, the electronics package can be smaller and more economical. 
     By incorporating the ballast, the lamp, and a recessed connector  10  to one housing, all confined within the planar space of the lamp, the overall lamp thickness is optimized to be as small as possible. As is particularly evident in FIGS. 1-3, the housing is substantially equi-spaced relative to the plane defined by the lamp tube. That is, the housing is centered in the same plane so that extensions of the housing from either side of the plane defined by the lamp tube are minimized. As will be noted, the overall thickness of the assembly is less than twice the diameter of the lamp tube. Just as importantly, minimizing the profile of the housing reduces any potential impact on the light output of the lamp assembly. 
     FIGS. 9 and 10 more particularly illustrate details of the first housing portion  52 . As previously noted, a housing portion  52  includes arms  58 ,  60  having recesses  66  that are received about the linear portion  22  of the lamp tube. In addition, flexible retaining tab portions  110 ,  112  are formed in the housing and adapted for mechanically engaging the outer diameter of the ends  36 ,  38  of the fluorescent tube. In this manner, when the tube ends are received in the housing, the retaining tabs  110 ,  112  are flexed outwardly from an at rest position and thus exert a holding force on the tube ends to secure them in place once the housing is assembled. The housing portions  50 ,  54  may be snap fit, adhesively secured, or joined together with fasteners  114 ,  116 . Enlarged cavity  118  is intended to accommodate the surface mount components of the lamp electronics mounted on board  100 . 
     In summary, the fluorescent tube has an elongated length that fits into a compact structure due to its curvilinear configuration, i.e., the 2D configuration. A central, open area defined by the lamp tube is usefully exploited in the low profile unitary housing  50 . The common housing does not extend appreciably outward from the plane of the lamp tube and advantageously mechanically secures the lamp ends, as well as providing mechanical support along the linear region  22  of the lamp tube. Moreover, the housing is dimensioned to receive the lamp electronics without adversely impacting on the operation of the lamp or overheating the electronics. The overall thickness of the lamp assembly is no greater than twice the thickness or diameter of the lamp tube. The housing is preferably centrally mounted relative to the plane of the lamp tube so that the overall profile of the lamp assembly is minimized. Particular details of the low pressure discharge tube, phosphor, gas fill, and details of the electrical circuit are generally known to those skilled in the art so that further discussion herein is deemed unnecessary to a full and complete understanding of the present invention. If necessary, the tube ends  36 ,  38  may be additionally adhesively secured in the housing. The fluorescent lamp and the lamp electronics have closely matched life expectancies. Moreover, by mating the lamp electronics with a specific individual lamp, the lamp electronics are more finely tuned to the operational range of the specific lamp with which it is integrated. This provides for improved operation for the lamp electronics and reliably controls operation of the lamp. 
     As is shown in the drawings, the electronics housing is supported by or hangs from the lamp tube. However, the relationship of the tube ends  36 ,  38  and the first and second arms supporting the electronics housing from the lamp tube may be altered from the particular arrangement shown and described herein without departing from the scope and intent of the invention. 
     While the invention has been described with respect to a specific embodiment, modifications and alterations will occur to others skilled in the art. For example, other configurations of a planar lamp, such as a circular lamp, can use various features of the invention. The appended claims are intended to cover all such modifications and alterations insofar as they fall within the scope of the present invention.