Illumination – Light fiber – rod – or pipe – Light emitting diode
Reexamination Certificate
2002-04-01
2004-09-28
Sember, Thomas M. (Department: 2875)
Illumination
Light fiber, rod, or pipe
Light emitting diode
C362S303000, C362S800000, C362S247000, C340S815450
Reexamination Certificate
active
06796698
ABSTRACT:
BACKGROUND OF INVENTION
The invention relates to the lighting arts. It is especially applicable to the retro-fitting of incandescent light source-based traffic signals with higher efficiency and a more durable light emitting diode (LED)-based light source, and will be described with particular reference thereto. However, the invention will also find application in numerous types of lamps, flashlights, and other illuminators which presently employ inefficient incandescent or fluorescent light bulbs that have high failure rates principally due to filament fragility or fluorescent tube failure. The invention provides LED-based light sources which are safer and have improved versatility and greater compatibility with existing lighting standards.
With reference to
FIG. 1
, a conventional traffic signal ball
10
such as is used in the ubiquitous three-color (red, yellow, green) traffic control signal is schematically shown. The traffic signal ball
10
is suitable for providing the red, yellow, or green light of a three-color traffic signal, and includes an incandescent light bulb
12
which emits light via a filament
14
which glows when driven by an electrical current. The light bulb
12
includes a threaded electrical connector
16
adapted for connection to a threaded socket
18
. The threaded socket
18
and the threaded electrical connector
16
cooperate to transmit electrical power from electrical conductors
20
to the filament
14
. Light produced by the light bulb
12
is collected by traffic signal optics including a reflector
22
, which is typically a parabolic reflector, and a lens
24
to produce a light beam outwardly directed from the traffic signal ball
10
with a suitable beam spread. The beam spread should be narrow enough to direct the light toward roadway users with a high degree of efficiency, but wide enough so that roadway users including pedestrians at the periphery of the road and drivers a substantial distance from the intersection can readily see the signal.
The aforementioned components are arranged within a traffic signal ball housing
26
having a cover
28
which typically includes the lens
24
. The cover
28
is selectively opened, typically in a hinged manner, to provide access to the light bulb
12
for bulb replacement. The cover
28
optionally includes additional elements such as a visor or a tinted filter (elements not shown) for spectrally filtering the light to produce a red, green, or yellow output. The tinted filter is optionally incorporated into the lens
24
by tinting the lens material. The light bulb
12
typically produces a white light which is colored by passing through the tinted filter or tinted lens
24
to produce one of the red, yellow, and green lights of a known three-ball traffic light. For traffic signal balls providing a shaped light such as a left turn arrow, an “X” lane marker indicating “wrong way”, a pedestrian “walk” or “don't walk” signal, or the like, a masking filter (not shown) is typically included with the cover
28
to define the selected shape.
The conventional incandescent traffic signal ball
10
suffers from some disadvantages. The light bulb
12
frequently fails, usually due to a failure of the filament
14
. Light bulb replacement is inconvenient, and the intersection is uncontrolled or improperly controlled and unsafe until the failed light bulb
12
is replaced. Furthermore, those skilled in the art will appreciate that the optical components such as the reflector
22
and the lens
24
which direct the white light produced by the light bulb
12
toward roadway traffic can also operate to reflect sunlight or other external light sources outward toward traffic, with the reflected light tinted according to the tinted filter or lens
24
. Re-directed external light, known as “phantom” light, can confuse roadway users into believing the traffic signal ball
10
is lit when it is not. In some incandescent traffic signal balls, an anti-phantom optical component is included to reduce phantom light. In spite of these disadvantages, however, incandescent traffic light signals are the predominant technology in use today.
The frequency of light source replacement in a traffic light can be reduced by replacing the light bulb
12
with a light source employing light emitting diodes (LEDs), which are more durable and longer-lasting than incandescent sources. However, retro-fitting the traffic signal ball
10
with an LED-based light source is complicated by the very different electrical and optical characteristics of the LED versus the incandescent source. The light bulb filament
14
acts as an approximate point or line light source, and the optics of the traffic signal ball
10
are designed around such a source. An LED, in contrast, produces generally forwardly directed light. Furthermore, a single LED typically exhibits low optical power output, and so LED-based light sources usually employ a plurality of LEDs, further complicating attempts to shape the light distribution using conventional traffic signal ball optics.
A number of LED-based light sources have been developed for retro-fitting a conventional incandescent traffic signal ball
10
. Examples can be found in U.S. Pat. Nos. Des. 388,726 and 6,268,801 both issued to Wu, U.S. Pat. No. 6,283,613 issued to Schaffer, U.S. Pat. No. 6,054,932 issued to Gartner et al., U.S. Pat. No. 5,898,381 issued to Gartner et al., and U.S. Pat. No. 5,782,555 issued to Hochstein. These LED-based light sources employ arrays of LEDs distributed to substantially conform to the desired light shape (a round circle or a left-turn arrow, for example) mounted onto a cover that replaces the cover
28
of the traffic signal ball
10
. These sources retro-fit the cover
28
, and therefore are configured to match the size, shape, and attachment mechanism of the cover
28
. As a result, these sources are highly specific to the signal ball being retro-fitted, and have limited interchangeability. Since the replacement of an incandescent source by an LED source is typically performed in the field under tight time constraints, the maintenance crew must ascertain beforehand exactly which LED light source is needed, and obtain that source.
Another disadvantage of past methods for LED-based retro-fitting of the incandescent signal ball
10
is that it fails to make use of the existing components of the incandescent signal ball
10
. Schaffer (U.S. Pat. No. 6,283,613), for example, points out that typical LEDs without associated optics produce a light beam with spatial characteristics that do not comply with Institute of Transportation Engineers (ITE) requirements and other regulations, and teaches incorporating individual optics associated with each LED in the retro-fit array. This introduces additional cost to the LED-based source and does not make use of the existing signal ball optics. Similarly, some past retro-fit methods have required extensive re-wiring of the electrical connections within the traffic light, negating the convenience, simplicity, and speed of conventional light bulb replacement.
Yet another disadvantage associated with some past LED retro-fitting methods is that, because at least the cover
28
is replaced, the signal ball
10
is no longer suitable for operation with an incandescent source. In some retro-fits, the reflector and other optical components are additionally removed. In view of the present predominance of incandescent light sources in traffic signaling, the practical and commercial viability of LED retro-fitting is hindered by retro-fitting which renders the traffic light unsuitable for use with incandescent light bulbs.
The present invention contemplates an improved LED-based light source apparatus and method for retro-fitting an incandescent signal light therewith that overcomes the above-mentioned limitations and others.
SUMMARY OF INVENTION
In accordance with one embodiment of the present invention, a traffic signal ball is disclosed, including a lamp having a plurality of LEDs, an optical element arranged to disperse forwardly directed light
Martineau Patrick
Sommers Mathew
Fay Sharpe Fagan Minnich & McKee LLP
GELcore LLC
Sawhney Hargobind S.
Sember Thomas M.
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