Extension brackets for retrofit of metric lamping to existing fluorescent lighting fixtures

Extension brackets capable of being rapidly attached to standard lampholder brackets of conventional fluorescent lighting fixtures for retrofit of such fixtures to accommodate lamping, including metric lamping such as T5 lamping, of generally shorter lengths than conventional tubular fluorescent lamping. The extension brackets of the invention attach by interference fit to standard cutouts in standard lampholder brackets, which cutouts normally attach conventional "tombstone" T12 lampholders, the extension brackets further acting to mount conventional lampholders capable of mounting the metric lamping at locations disposed inwardly of the fixtures to accommodate the several conventional lengths of metric lamping or the like while locating the metric lamping on a plane no higher than that of the conventional lamping for which the lighting fixtures are originally configured.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates generally to apparatus for converting conventional 
fluorescent lighting fixtures to use with metric lamping of differing 
lengths and particularly to extension brackets which facilitate the use of 
T5 lamping in lighting fixtures intended for use with conventional T12 
lamping. 
2. Description of the Prior Art 
Fluorescent lighting fixtures most commonly employ tubular fluorescent 
lamps which are of standard designation and which are commonly known as 
T12 lamps, these lamps typically having nominal lengths of 48 inches, 36 
inches and 24 inches. Recently introduced fluorescent lamps having metric 
dimensions with nominal lengths of 1149 mm, 849 mm, and 549 mm exhibit 
favorable energy efficiencies and other characteristics which would cause 
a lighting engineer to consider retrofit of this lamping, known by the 
standard designation T5, in conventional fluorescent fixtures originally 
and optimally designed for use with T12 imperial fluorescent lamps. The 
various lengths of the T5 lamp are considerably shorter than the lengths 
of the standard T12 lamp sizes. The existing lamp mounting hardware of 
conventional fluorescent fixtures are not therefore practical for mounting 
of T5 lamping when considering only the respective lengths of the lamping 
per se. Since fluorescent lighting fixtures designed for use with T12 
lamping are optimized in view of the characteristics of the T12 lamping, a 
retrofit must necessarily locate T5 or other lamping used in aretrofit 
situation in locations within the fixtures which provide the best possible 
photometric performance. Still further, the exigencies of a retrofit 
situation require accommodation of the differing lengths of T5 or such 
similar lamping with a minimum number of physical parts which are devoted 
to this purpose and which therefore must be inventoried in advance of 
actual assembly to conventional fixtures. The physical parts or articles 
of manufacture necessary to accomplish the retrofit function must also be 
inexpensive in addition to being few in number and must accommodate wiring 
which must pass into an existing lampholder bracket while adequately 
shielding the wiring from raw metal edges of bracket cutouts and the like. 
It has previously been contemplated in the prior art to provide adapter 
structure for fluorescent lamping which permits fluorescent tubes of 
differing wattage and shorter length to be installed in lighting fixtures 
originally configured for use with fluorescent tubes of greater wattage 
and longer length. Rowe, in U.S. Pat. No. 3,993,386, provides an adapter 
structure capable of extending the length of a tubular fluorescent lamp. 
In U.S. Pat. No. 4,758,173, Northrop provides an adapter for extending 
"tombstone" lamp sockets to permit the use of shorter lamps in fluorescent 
fixtures. Coldren, in U.S. Pat. No. 5,615,943, describes brackets intended 
to support fluorescent lamp terminal posts and having individual lamp 
reflectors extending therebetween and secured to opposing pairs of the 
brackets for retrofitting existing lamp fixtures with fluorescent lamps 
and reflectors of a design which differs from those lamps and reflectors 
for which the fixtures were originally designed. The devices of the prior 
art do not provide either singly or in combination simple and inexpensive 
apparatus capable of the retrofit of existing fluorescent lighting 
fixtures with metric lamping or the like configured as a standard series 
of differing lengths and which further mount such lamping at an 
appropriate location within the retrofitted lighting fixtures to provide 
desirable photometric characteristics. 
The present invention provides extension brackets capable of being rapidly 
attached to standard lampholder brackets of conventional fluorescent 
lighting fixtures for retrofit of such fixtures, these extension brackets 
accommodating metric lamping or other lamping which is of generally 
shorter lengths than conventional tubular T12 fluorescent lamping. The 
present extension brackets can be configured in two sizes which allow 
accommodation of the three common sizes of T5 lamping or similar lamping, 
the extension brackets of the invention attaching by interference fit to 
standard cutouts of differing configurations such as are variously formed 
in standard lampholder brackets. The extension brackets of the invention 
further act to mount conventional lampholders capable of mounting the 
metric lamping or the like at locations disposed inwardly of the fixtures 
to not only accommodate the several conventional lengths of such metric 
lamping but which also locate the metric lamping on a plane no higher than 
that of the conventional lamping for which the lighting fixtures are 
originally configured. The extension brackets of the invention can further 
be installed without effective alteration of existing hardware, thereby 
allowing rapid removal of the extension brackets and re-equippage of 
original hardware into the lighting fixtures to allow conversion back to 
the use of original lamping. The extension brackets of the invention are 
inexpensive to manufacture and inventory and extraordinarily easy to 
install in conventional fluorescent lighting fixtures and particularly 
commercial lighting fixtures utilizing conventional tubular fluorescent 
lamping. 
SUMMARY OF THE INVENTION 
The invention provides extension brackets which are easily and rapidly 
mountable to standard cutouts of standard lampholder brackets, said 
cutouts conventionally mounting lamp holders intended to mount 
conventional tubular fluorescent lamps such as T12 lamps. The extension 
brackets of the invention can be configured to retrofit lamping which can 
be shorter or even longer than the original lamping, the extension 
brackets of the invention particularly intending to retrofit existing 
fluorescent lighting fixtures with metric lamping such as T5 lamping which 
is shorter than corresponding T12 lamp sizes. 
The extension brackets herein described can be rapidly assembled to 
conventional fluorescent lighting fixtures and can rapidly mount 
lampholder capable of receiving and operating metric or other lamping such 
as T5 lamping. The extension brackets of the invention can then be just as 
easily and quickly removed from fluorescent lighting fixtures with 
remounting of original lampholder to reconvert the fixture to use with 
original lamping as desired. Retrofitting of existing fluorescent lighting 
fixtures with the present extension brackets does not destroy any original 
portion of the lighting fixture or prevent in any way its renewed use with 
original lamping and original lampholder equipment. 
The extension brackets of the invention can be formed in certain 
configurations for accommodation of a T5 lamp, for example, having a 
nominal length of 1149 mm and a T5 lamp, for example, having a nominal 
length of 549 mm, these two T5 lengths essentially replacing T12 lamping 
of nominal 48 inch and 24 inch lengths. In these situations, two each of 
the respective extension bracket forms are necessary to accommodate the 
respective lamping. With T5 lamping of a nominal length of 849 mm, one 
each of the two different forms of extension bracket according to the 
invention is necessary to accommodate this metric length which essentially 
replaces T12 lamping of a length of 36 inches. The extension brackets of 
the invention further act to mount the T5 lamping or other lamping on a 
plane no higher than that plane on which the original T12 lamping was 
located in the retrofitted fluorescent lighting fixture. Wiring to the 
lampholder mounted by the present extension bracket is accommodated with 
adequate shielding of the wiring from raw metal edges such as can exist in 
a standard cutout of a standard lampholder bracket. 
An extension bracket configured according to the invention essentially 
comprises a U-shaped bracket element having a cutout portion in the bight 
portion of the bracket at an inward end, this cutout portion being 
configured to facilitate mounting of a replacement lampholder capable of 
mounting the retrofit lamping such as a T5 metric lamp. According to the 
invention, the retrofit lampholder is mounted to the extension bracket 
rather than to the standard lampholder bracket which is typically mounted 
to a standard cutout of the conventional lampholder bracket. The extension 
bracket includes structure at its outward end which cooperates with 
standard cutouts in conventional lampholder brackets of conventional 
fluorescent lighting fixtures to attach the extension bracket to the 
standard lampholder bracket by means of an interference fit, the extension 
bracket being quickly and easily attached to the standard lampholder 
bracket or removed therefrom. 
The present extension brackets can be manufactured at low cost with 
conventional stamping and bending equipment and need only be inventoried 
in two different forms for accommodation of a series of differing lengths 
of retrofit lamping such as T5 metric lamping. The extension brackets of 
the invention thus provide inexpensive articles of manufacture which 
permit the retrofit of conventional fluorescent lighting fixtures with 
lamping of differing lengths from the lengths of lamping for which the 
fixtures were originally designed, the brackets of the invention further 
providing favorable photometric characteristics for the retrofitted 
lighting fixtures by virtue of favorable location of the retrofitted 
lamping within the lighting fixtures. 
Accordingly, it is a primary object of the invention to provide extension 
brackets capable of being rapidly attached to standard lampholder brackets 
of conventional fluorescent lighting fixtures for retrofit of such 
fixtures to accommodate lamping of differing lengths from that lamping for 
which the lighting fixtures were originally designed. 
It is another object of the invention to provide extension brackets of 
appropriate sizing which allows accommodation of a series of retrofit 
lamps having different lengths which can be accommodated within 
conventional lighting fixtures originally designed for lamping of lengths 
which differ from those lengths of the retrofit lamping. 
It is a further object of the invention to provide extension brackets 
capable of retrofitting conventional fluorescent lighting fixtures with 
lamping of lengths differing from the lamping for which the fixtures were 
originally designed, the extension brackets being readily and easily 
removable from the fixtures to allow reconversion of the fixtures to use 
with original lamping. 
Further objects and advantages of the invention will become more readily 
apparent in light of the following detailed description of the preferred 
embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings and particularly to FIGS. 1 and 2 inclusive, 
an extension bracket configured according to the invention is shown 
generally at 10 to comprise a U-shaped frame 12 having a top wall 14 and 
essentially identical side walls 16. The bracket 10 is preferably stamped 
from a suitable metal having a suitable thickness which imparts rigidity 
to the bracket 10. Flat metal stock of a thickness of 18 gauge or the like 
is considered to be suitable. Each of the side walls 16 are substantially 
rectangular in shape and have an arcuate notch 18 formed along a lower 
edge thereof essentially medially of the length thereof. Upper edges of 
the side wall 16 round to join with the top wall 14. The top wall 14 is 
formed with a cruciform cutout 20 at a first end 22 of the bracket 10. A 
substantially rectangular cutout 24 is formed in the top wall 14 at a 
second end 26 of the bracket 10. Corners of the cutout 24 can be radiused 
so that the corners of the cutout 24 will not bind insulated wiring which 
extends into the cutout 24 as will be described hereinafter. 
Side tab elements 28 which are essentially identical in shape and structure 
partially define the cruciform cutout 20 formed in the top wall 14. 
Inwardly disposed edges 30 of the elements 28 in cooperation with lateral 
edges 32 of the top wall 14 and facing edges 34 of the wall 14 define a 
lateral, substantially rectangular notch 36 on each side of the bracket 
10, the notches 36 essentially defining arm-like portions of the cruciform 
cutout 20. Edges 38 which extend inwardly of the notches 36 are joined by 
an edge 40 of the top wall 14 to complete definition of the cruciform 
cutout 20 and particularly to form a substantially rectangular notch 42 
which can have radiused corners for the same reason as the corners of the 
cutout 24 can be radiused, that is, to prevent binding of insulated wiring 
which extends into the notch 42. Lateral walls 44 form a portion of the 
top wall 14 between each of the notches 36 and the rounded junctures 
between the side walls 16 and the top wall 14. 
As will be described in more detail hereinafter, the substantially 
rectangular opening provided by the two notches 36 and that portion of the 
cruciform cutout 20 lying therebetween, is dimensioned to receive from 
underneath the bracket 10 a lampholder (as is shown in FIGS. 3 through 5) 
for snap attachment to the bracket 10. 
Referring again particularly to FIG. 2A and to FIG. 6, each of the side 
walls 16 are seen to be provided with leg elements 46 which connect by 
means of a shoulder element 48 to the main body of each of the side walls 
16. Distal end 50 of each leg element 46 is essentially squared off, outer 
portions of the leg elements 46 substantially having rectangular 
conformations. Inward edge 52 of each leg element 46 is substantially 
parallel with lower edge 54 of the side wall 16, an arcuate boss element 
53 extending from the edge 52 of each leg element 46 and toward rear 
portions of the arcuate notches 18 formed in the side walls 16. The inward 
edge 52 of each of the leg elements 46 extends obliquely at 56 to form a 
reduced-in-thickness portion 58 of each of the leg elements 48. The 
portions 58 of said leg elements 46 connect to the respective shoulder 
elements 48, an inner edge 60 of each portion 58 defining with respective 
oppositely facing edges 62 of the side wall 16 and perpendicular edge 64 a 
substantially rectangular cutout portion of a complex cutout seen 
generally at 66 which is defined between the body of each of the side 
walls 16 and each of the respective leg elements 46 and shoulder elements 
48. Definition of the contours of the complex cutout 66 is also provided 
by a rounded edge 68 located at the rear extent of the notch 18, lower 
edges 70 disposed rearwardly of the rounded edges 68 essentially being 
straight edges which are substantially parallel to opposing inward edges 
52 of the leg elements 46. A squared off shoulder is formed in each of the 
lower edges 70 at 72 to serve as a detent as will be described 
hereinafter. 
Referring now also to FIGS. 3 through 5, a standard lampholder bracket is 
seen at 74, the bracket 74 being one example of literally hundreds of 
extremely similar lampholder brackets such as are used in conventional 
fluorescent lighting fixtures (not shown). In a conventional lighting 
fixture, two of the brackets 74 are utilized, one each of the brackets 74 
being located at each end of the fixture with each of the brackets 74 
mounting standard polymeric "tombstone" lampholders such as is seen at 76. 
The lampholders 76 fit into standard cutouts 78 formed in the lampholder 
brackets 74, the bracket 74 of FIGS. 3 through 5 being seen to be formed 
with three of the cutouts 78. In a usual situation, each of the three 
standard cutouts 78 would be provided with one of the standard lampholders 
76 with the lampholders 76 facing inwardly toward a second, similarly 
configured lampholder bracket such as the bracket 74 so that standard, 
tubular lamping (not shown) could be mounted between the spaced sets of 
the standard lampholders 76. As is common in the lighting arts, the 
arrangement just described intends the mounting of T12 fluorescent tubular 
lamps, the brackets 74 being part of a lighting fixture arrangement 
capable of mounting three such T12 lamps. 
As seen best in FIGS. 3 and 5, the standard cutouts 78 are seen to be 
T-shaped with an arcuate tab 80 extending below the plane of that portion 
of the bracket 74 in which the cutout 78 is formed, the arcuate tab 80 
extending from an inward edge of the leg of the T-shaped cutout 78 with 
arcuate portions of the tab 80 effectively lying beneath the said plane. 
The nature and conformation of the arcuate tab 80 can vary depending upon 
individual structures of the bracket 74. However, the contours of the 
cutouts 78 are typically very similar particularly as having spaced 
shoulders 82 on either side of the tab 80, the shoulders 82 effectively 
defining a reduced portion of the cutout 78 inwardly of the "arms" of the 
cutout 78. 
The standard lampholder 76 is seen to snap-fit into the standard cutout 78, 
lower arcuate portions of the tab 80 as can be seen in FIG. 5 typically 
biasing against an upper surface of a base of the lampholder 76 and 
snapping thereonto in a known manner. The standard lampholder 76 can be 
quickly and easily attached to the standard lampholder bracket 74 and can 
just as easily be removed therefrom. Conversion of a conventional 
fluorescent lighting fixture (not shown) such as utilizes T12 lamping 
mounted by the bracket 74 and lampholder 76 to use with lamping of 
different types such as is shorter in length is accomplished by first 
removing the lampholder 76 from the bracket 74, it being understood that 
two of the brackets 74 are mounted in oppositely facing relation to each 
other within the lighting fixture (not shown). A lampholder 84 capable of 
mounting the lamping, such as T5 lamping, which is to be retrofitted into 
the lighting fixture (not shown) has side tabs 86 which extend from each 
side of the tombstone-shaped lampholder 84, lower portions of the side 
tabs 86 being serrated (not shown) in a conventional manner. The 
lampholder 84 is understood to be a conventional lampholder intended for 
mounting of the lamping, such as T5 metric lamping, which is being 
retrofit into a lighting fixture of which the standard lampholder bracket 
74 is a part. The lampholder 84 is typically formed of a polycarbonate 
material as opposed to use of a polymeric, thermosetting material as with 
the lampholder 76. 
The retrofit lampholder 84 is attached to the extension bracket 68 by 
pushing the lampholder 84, top side up, into and through the underside of 
the bracket 10 immediately below the rectangular notches 36, the notches 
36 being sized and spaced apart across the cruciform cutout 20 as 
indicated above and dimensioned to receive the lampholder 84 therethrough, 
the side tabs 86 acting in a ramp-like fashion to engage the lateral edges 
32 of the wall 14 and to snap-fit onto the bracket 10 on passage of lower 
portions of the tabs 86 through the respective notches 36, serrations (not 
shown) formed in lowermost edges of the tabs 86 facilitating the mounting 
of the retrofit lampholder 84 to the extension bracket 10. 
The extension bracket 10, now mounting the retrofit lampholder 84, is then 
brought into engagement with one of the standard cutouts 78 formed in the 
standard lampholder bracket 74 with the leg elements 46 of the bracket 10 
fitting beneath body portion 88 of the bracket 74 and with major portions 
of the bracket 10 fitting above the body portion 88. The extension bracket 
10 is then caused to slide onto the bracket 74 with the uppermost edge 
portions of the arcuate tab element 53 contacting the underside of the 
body portion 88, lower edges of the side wallsl6, such as the lower edges 
54 and 70,biasing against upper surfaces of the body portion 88. An 
interference fit is thus formed which holds the extension bracket 10 in 
place at the location of each of the standard cutouts 78 formed in the 
standard lampholder bracket 74. 
One of the extension brackets 10 seen mounting one of the retrofit 
lampholders 84 on the standard lampholder bracket 74 is seen particularly 
in FIGS. 3 and 4. FIG. 5 further illustrates a portion of a retrofit lamp 
90, which can be a metric T5 lamp, connected to the retrofit lampholder 
84. Wiring 92 can be brought from a location rearwardly of the bracket 10 
and from underneath the lampholder bracket 74 to pass through the cutout 
24 and downwardly into the interior of the bracket 10 through the notch 
42. The notches 24 and 37 can be radiused as aforesaid in order to prevent 
binding of polymeric insulation covering the wiring 92. 
The complex cutouts 66 defined by lower edge portions of the side walls 16 
and facing edge portions of the leg elements 46 function to provide 
clearance during fitting of the bracket 10 to the bracket 74, the cutouts 
66 particularly being open in the vicinity of the edge 64 of the shoulder 
element 48 so that the leg elements 46 have an inherent "spring-like" 
action which facilitates the interference fit between the bracket 10 and 
the bracket 74. The shoulders 72 effectively serve as detents or locater 
elements which prevent the extension bracket 10 from being pushed too far 
onto the standard lampholder bracket 74. Once the shoulders 72 engage a 
desired portion of the bracket 74, such as the distal end of the tab 80, 
then the bracket 10 is known to be appropriately located on the bracket 74 
at a spacing from one of the brackets 74 at the opposite end of the 
fixture (not shown) for mounting of the retrofit lamping. 
The extension brackets 10 of the invention are intended to mount lamping 
which is shorter than the lamping originally intended for the lighting 
fixture (not shown) which is being retrofit or converted to use with 
shorter lamping such as metric T5 lamping. It is to be understood that, 
space permitting, bracket structure similar to the extension bracket 10 
can be utilized to mount lamping of a greater length than original lamping 
for which a given lighting fixture is desired. 
Metric lamping such as T5 lamping is provided to the market in differing 
sizes, these sizes conventionally being 1149 mm, 849 mm and 549 mm. The 
extension brackets 10 shown herein are intended to mount the 1149 mm lamps 
by virtue of having a length from the second end 26 to the edge 34 of 
0.972 inch. Extension brackets having identical features but of slightly 
different lengths from the second end 26 to the edge 34 are intended for 
mounting of the 549 mm lamps. A length of 0.783 inch is necessary for 
mounting of the 549 mm lamps. It is to be understood that a pair of the 
extension brackets 10 are required for mounting of one of the respective 
lamps. An 849 mm T5 metric lamp can be accommodated according to the 
invention with the use of one of the brackets used for mounting of an 1149 
mm lamp and one of the brackets intended for mounting of a 549 mm lamp. 
The brackets themselves may be of differing lengths to accommodate lamping 
of differing lengths. The brackets 10, regardless of the length of the 
lamps being mounted, are configured to place the top of a T5 lamp, in 
particular, on a plane no higher than that plane at which the top of a T12 
lamp is located, thereby providing desirable photometric performance of 
the retrofit T5 lamp in a lighting fixture originally designed for T12 
lamping. 
Accordingly, it is to be understood that the retrofit apparatus of the 
invention can be configured structurally to mount a retrofit lampholder 
capable of mounting lamping which is to be retrofitted to a conventional 
fluorescent lighting fixture, the invention further providing for mounting 
of the retrofit lampholder in a desirable location relative to and mounted 
by a standard lampholder bracket such as at the location of a standard 
cutout formed in standard lampholder brackets. The invention can further 
be used for retrofit of lighting fixtures which normally use T8 lamping in 
a manner essentially identical to the description herein provided relative 
to retrofit of T12 lamping. It is therefore to be realized that the 
invention can be configured other than as explicitly shown herein, the 
invention being effectively defined by the scope of the appended claims.