Fluorescent reflector lamp assembly

A ballast transformer for fluorescent reflector lamp assemblies used in screw-type sockets for conventional incandescent bulbs.

TECHNICAL FIELD 
The present invention generally relates to fluorescent lamps and, more 
particularly, to fluorescent lamp assemblies that may be conveniently 
mounted in conventional sockets in substitution for incandescent reflector 
bulbs. 
BACKGROUND OF THE INVENTION 
It is well known that fluorescent lamps consume substantially less 
electrical power than conventional incandescent lighting while producing 
equivalent illumination levels. For example, some conventional fluorescent 
lamps may produce illumination equivalent to a 60-watt incandescent bulb 
on just 15 watts of power. Further, it is known that fluorescent lamps can 
often provide substantially longer service lives, sometimes in excess of 
nine thousand hours, than incandescent bulbs. Because of such advantages 
of fluorescent lighting, substantial efforts have been made to provide 
fluorescent lamp assemblies that can be substituted for incandescent bulbs 
in standard lighting fixtures. 
Pursuant to such efforts, fluorescent lamps have been formed in various 
shapes and have been fitted with base connectors that are compatible with 
sockets for standard incandescent bulbs. Examples of such fluorescent 
lamps include ones that are sold under the trademarks "Refluor" and 
"Reflect-A-Star PL" by Lumatech Corporation of Oakland, California; those 
fixtures employ so-called PL fluorescent lamps that have U-shaped tubes 
with starters built into their bases. In some models of such lamps, 
replaceable starters are also provided. Further it is known in such lamps 
to provide external plug-in ballasts. Although these lamps usually produce 
satisfactory lighting levels, the arrangement of their components and 
their length prevents them from being completely satisfactory for lighting 
applications such as recessed lighting. 
It is also known to fit fluorescent tubes and built-in starters into 
bulb-shaped housings. Such lamps are available from Mitsubishi Corporation 
under part number BFT 17 LE. In such lamps, the ballast components (i.e., 
reactance ballasts) are located in ballast compartments located at the 
base of the bulb compartments. 
Adapters that permit fluorescent lamps to be used in sockets in 
substitution for incandescent bulbs are available from several sources and 
are described, for example, in U.S. Pat. Nos. 4,570,105 and 4,623,823. The 
adapters disclosed in those patents include hollow cylindrical housings, 
Edison-type bases, and covers enclosing the ends of the housings opposite 
the bases. Further according to the patents, toroidal ballasts are located 
within the housings to receive the stems of fluorescent lamps to enhance 
spacial efficiency. Other adapters and components for fluorescent lamps 
are available from Eastrock Technology, Inc. of Staten Island, New York. 
Various other configurations of fluorescent lamps compatible with sockets 
with incandescent bulbs are suggested by the following U.S. Pat. Nos: 
2,505,993; 3,551,736; 3,611,009; 3,815,080; 3,953,761; 4,093,893; 
4,173,730; 4,270,071; 4,347,460; 4,375,607; 4,405,877 and 4,414,489. 
One serious disadvantage of known designs of such fluorescent lamps, 
however, is that their ballast components often preclude the lamps from 
being completely satisfactorily employed in recessed lighting 
applications. (A recessed lighting application can be defined, for present 
purposes, as one in which an illuminating lamp, with or without a 
reflector, is mounted within a canister-like container having an open end 
through which the lamp shines.) Moreover, although some known fluorescent 
lamps may have appropriately compact dimensions for use in recessed 
lighting applications, actual usage of compact fluorescent lamps is 
problematical because the service lives of the lamps fall far short of 
expectations. In other words, fluorescent lamps in recessed lighting 
applications have demonstrated a tendency to fail over periods far shorter 
than their rated lives. 
In recessed lighting applications, failures of fluorescent lamps are 
believed to be caused by high temperatures, sometimes exceeding 
225.degree. F, which may be generated at the base of the stem of the lamp. 
Such temperatures can substantially exceed the maximum temperatures 
recommended by manufacturers, usually about 185.degree. F, and may cause 
early deterioration and failure of lamp starter and ballast components. 
For example, the adapter assemblies disclosed in U.S. Pat. Nos. 4,570,105 
and 4,623,823 are not well adapted for use in recessed lighting 
applications because the stems of fluorescent lamps encompassed by the 
toroidal ballasts would often reach temperatures that would severely limit 
their service lives.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIGS. 1 and 2, a fluorescent reflector lamp assembly generally includes 
a screw-type base connector 11, a generally annular ballast housing 15 
mounted outboard of base connector 11, a heat conductive reflector member 
19 having a base 19A that seats within a recessed area encompassed by 
ballast housing 15, and a fluorescent illuminator tube assembly 23 that 
mounts within the recessed area while engaging base 19A of reflector 
member 19. In the following, each of the components of fluorescent 
reflector lamp assembly 9 will be described in detail. 
Base connector 11 is a conventional component, often referred to as a 
screw-type or "Edison" base, preferably adapted to screw into so-called 
"medium base receptacle" sockets for incandescent bulbs. As such, base 
connector 11 includes a metallic threaded member 29 that engages the 
interior sidewall of a conventional socket to provide mechanical and 
electrical connection. Further, base connector 11 includes a cylindrical 
core member 31 formed of an electrically insulating material to support 
threaded member 29. Also, base connector 11 includes a metallic contact 
member 33 mounted to the lower end of core member 31 for electrically 
engaging the base of a socket for an incandescent bulb. Contact member 33 
is electrically isolated from threaded member 29 by the insulating core 
member 31. Thus, threaded member 29 and contact member 33 each provide 
separate conduction paths for carrying electrical current to illuminator 
tube assembly 23. In FIG. 1, the electrical leads that comprise those 
conduction paths are designated 29A and 33A respectively. 
Ballast housing 15 includes a generally cylindrical sidewall 37 mounted in 
upright condition to a generally frusto-conical member 39 whose smaller 
end engages the outer periphery of cylindrical core member 31. Further, 
ballast housing 15 includes a receiver member 41 whose outer periphery 
engages cylindrical sidewall 37. In the preferred embodiment, receiver 
member 41 includes an interior wall 37A (FIG. 2) that defines a generally 
rectangular central recess 42 (FIG. 1) to receive the base and stem of a 
standard conventional fluorescent lamp, referred to herein as fluorescent 
illuminator tube assembly 23, of the so-called double twin tube type. As 
so constructed, ballast housing 15 can be assembled, as shown in FIG. 2, 
to provide a generally annular enclosure that extends generally 
symmetrically about the axial centerline of fixture 9. 
In the preferred embodiment, ballast housing 15 is formed of a generally 
heat insulating material, such as plastic or thermoplastic, that is 
electrically non-conductive. In the illustrated embodiment, it may be 
noted that ballast housing 15 also includes an interior wall 44 that abuts 
interior wall 37A to complete the enclosure of the ballast housing 15. 
Mounted within ballast housing 15 is a reactance ballast 45. As best shown 
in FIG. 1, reactance ballast 45 comprises a pair of generally U-shaped 
core members 47A and 47B mounted so that the ends of their legs are 
secured together opposite one another with a spacer between the ends. 
Conducting wire 46 is wound about the opposing legs of core members 47A 
and 47B in series in a configuration as is customary in auto transformers. 
In the illustrated embodiment, a first winding comprises a first plurality 
of turns of wire 46A formed about one of the junctures of the legs of 
U-shaped core members 47A and 47B. A second winding comprises a plurality 
of turns of wire 46B formed about the other juncture of the legs of 
U-shaped core members. Thus, there may be said to be a pair of windings 
formed about the U-shaped core members 47A and 47B. It may be noted that a 
substantial area, preferably exceeding about seventy percent of the total 
area of the core members, is exposed between the windings to convect heat. 
The end 46A of coil wire 46 extends for connection to conductor 29A and 
the end 46B extends for connection to the fluorescent illumination tubes 
23. Preferably, U-shaped core members 47A and 47B are formed of laminated 
material, stacked in horizontal layers, to reduce eddy-current effects 
while providing suitable reactance. In the preferred embodiment, as best 
shown in FIG. 2, a gap space 48 is provided between the reactance ballast 
45 and the interior sidewall of ballast housing 15. 
Reflector member 19 has a generally tubular base 19 and a shell 19B that is 
generally concave as viewed from the central axis of lamp assembly 9. 
Preferably, reflector shell 19B has substantially parabolic curvature to 
reflect light originating from illuminator tube lamp assembly 23 as a 
generally collimated beam directed to the area being lighted. Reflector 
shell 19B and base 19A are integral and are formed of a substantially 
heat-conducting material such as aluminum or other suitable metal. In 
practice, the interior surface of reflector shell 19B is formed of, or 
coated with, highly reflective (i.e., specular) material. Further in 
practice, a transparent protective cap or lens 51 is sealingly mounted 
across the enlarged open end, or mouth, of reflector shell 19B. 
For reasons that will be explained in detail in the following, reflector 
base 19A is dimensioned to seat within central recess 40 in receiver 
member 41 and to surround the base 23B of fluorescent illuminator tube 
assembly 23 in heat conducting contact therewith. In the illustrated 
embodiment, reflector member 19 is secured to ballast housing 37 by screws 
55 that extend through apertures 57 formed in the sidewall of reflector 
shell 19B. It should be in the sidewall of reflector shell 19B. It should 
be appreciated, however, that other means can be utilized to secure the 
reflector 19 to other portions of lamp assembly 9. As best shown in FIG. 
2, an annular air gap 49 separates tubular base 19A from the surrounding 
sidewall 37A of ballast housing 15. 
Fluorescent illuminator tube lamp assembly 23 preferably is of the type 
known as a double twin tube lamp. As best shown in FIG. 2, the lamp 
assembly includes two U-shaped tubular illuminating tubes 23A, base 
portion 23B, a stem portion 23C, and a pair of electrical connector prongs 
23D. It should be understood that a starter and RF condenser (not shown) 
are located in base portion 23B. Such lamps are sold under part number 
F9DTT/27K 02 by the Sylvania Company of Danvers, Massachusetts as well as 
other companies. 
In assembled condition, as can best be seen in FIG. 2, illuminator tube 
assembly 23 is mounted in recess 40 in receiver member 41 such that 
electrical connector prongs 23D extend into sockets 40D formed in receiver 
member 40 and such that lamp base 23B abuttingly engages a substantial 
area of the interior sidewall of reflector base 19A. Thus, reflector base 
19A is sandwiched between the lamp base 23B and the surrounding adjacent 
sidewall 40 of ballast housing 15. It should also be noted that stem 23C 
of fluorescent illuminator tube assembly 23 extends substantially inward 
of, and is encompassed by, base connector 11; as a result, stem 23C is 
substantially thermally isolated from reactance ballast 45. 
OPERATION 
Operation of the fluorescent reflector lamp assembly of FIGS. 1 and 2 will 
now be described. Initially, it should be assumed that screw-type base 
connector 11 has been mounted in a standard socket for an incandescent 
bulb and that a source of electrical power is available at the socket. In 
such circumstances, source electrical current (ac) can flow through 
threaded member 29 and conductor 29A to coil 46 of reactance ballast 45. 
Likewise, electrical current can flow through contact member 33 and 
conductor 33A. With the source current and voltage appropriately modified 
by reactance ballast 45, the electrical current flows through connector 
prongs 23D of fluorescent illuminator tube assembly 23 to energize and 
illuminate lamp assembly 9. 
Upon illumination, a minor fraction of the heat generated by fluorescent 
illuminator tube assembly 23 is radiant upon the specular surface of 
reflector shell 19B and is reflected through lens 51. The majority of the 
heat generated by fluorescent illuminator tube assembly 23, however, is 
conducted to lamp base 23B. From lamp base 23B, the heat is conducted to 
the surrounding base 19A of reflector member 19, and then such heat is 
conducted to reflector shell 19B and dissipated into the surrounding air. 
At this juncture, it can be appreciated that fluorescent reflector lamp 
assembly 9 effectively minimizes the amount of heat from illuminator tube 
assembly 23 that reaches the interior of ballast housing 15. In part, such 
thermal isolation of ballast housing 15 is due to the fact that it is 
mounted radially outboard of illuminator tubes assembly 23. Further, 
thermal isolation of ballast housing 15 is achieved by the mechanical 
intervention, or heat barrier shielding, provided by reflector base 19A; 
in effect, reflector base 19A conducts heat to reflector shell 19B where 
it is dissipated from lamp assembly 9 prior to reaching ballast housing 
15. Still further, heat transfer to and from reactance ballast 45 is 
minimized by the insulating material that forms housing 15 and by annular 
spacing gap 48 that separates reactance ballast 45 from the interior 
sidewall of the housing. The design of ballast member 45 also contributes 
to heat dissipation because of the extended large surface area of the 
U-shaped laminated core members 47A and 47B. Also, the design of ballast 
housing 15 is such that the stem 23C of fluorescent tube assembly 23 
extends substantially inward of base connector 11 and is thermally 
isolated from reactance ballast. 
It can thus be understood that fluorescent reflector lamp assembly 9 
permits satisfactory use in recessed lighting applications of 
high-illumination fluorescent lamps having compact profiles (i.e., 
profiles approximating those of standard R-30 and R-40 incandescent 
bulbs). More particularly, fluorescent reflector lamp assembly 9 operates 
to dissipate heat effectively enough to substantially reduce the risk of 
premature thermal deterioration of its ballast core and starter 
components. In tests conducted according to standards prescribed by 
Underwriters Laboratories (U.L.) for recessed lighting fixtures, the 
temperatures at the bottom 23E of stem 23C of illuminator tubes 23 were 
found to be about 165.degree. F when ambient temperatures were maintained 
at about 77.degree. F. Such temperatures are well within ranges 
recommended by U.L. and fluorescent lamp manufacturers and, consequently, 
cause minimal deterioration of the ballast, starter, and other components 
of the fluorescent reflector lamp assembly. 
Although the present invention has been described with particular reference 
to the preferred embodiment, such disclosure should not be interpreted as 
limiting. Various alterations and modifications, in addition to those 
mentioned above, will no doubt become apparent to those skilled in the art 
after having read the preceding disclosure. Thus, it should be apparent to 
those of skill in the art that numerous changes may be made without 
departing from the spirit and scope of the invention as defined by the 
claims which follow.