LED traffic light with individual LED reflectors

Details LED traffic light with individual LED reflectors LED traffic light with individual LED reflectors

1999-07-29

2001-09-04

O'Shea, Sandra (Department: 2875)

Illumination

Plural light sources

With modifier

C362S247000, C362S800000, C362S545000, C362S328000, C116S06300T

Reexamination Certificate

active

06283613

ABSTRACT:

TECHNICAL FIELD
The invention relates to an LED illuminated traffic signal.
BACKGROUND
Traffic signal lamps or illuminated overhead road signs have conventionally used incandescent lamps for lighting. More recently, efforts have been made to replace the incandescent lamps with light emitting diodes (LEDs). LEDs offer the considerable advantage of consuming significantly less power than incandescent lamps. LEDs also generally require less frequent replacement due to burn out than incandescent lamps. LEDs, in short, offer a desirable reduction in power and maintenance costs as compared to incandescent lamps.
There are, however, several issues to consider when using LEDs in lieu of incandescent lamps for traffic signals and other applications. First, the light emitted from a given LED is of low intensity compared to that of a comparably sized incandescent lamp. Second, conventional LEDs emit light in a relatively tight pattern that requires the redistribution of that light in order to attain spatial distributions in compliance with, for example, Institute of Transportation Engineers (ITE) requirements or other regulations. Also, due to their thermal-sensitivity, heat generated during operation of the LEDs and associated components must be low enough (or adequately dissipated) to assure reliable operation over extreme temperature ranges.
Known implementations of LED signal modules make use of hundreds of individual LEDs to generate light that is sufficient and of satisfactory spatial distribution. The large number of LEDs leads to a more expensive module and one with greater power consumption. The increased power usage leads to greater thermal output, which, if not adequately addressed at additional expense, impacts device reliability.
SUMMARY
An overhead signal module may provide improved illumination qualities through use of LEDs with associated individual reflectors. The individual reflectors provide a substantial increase in the useful luminous output of the signal module relative to a signal module without the reflectors.
The increased efficiency of LEDs coupled with reflectors allows for the use of fewer LEDs in a signal module. This, in turn, leads to lower component cost and reduced power consumption. The reliability of the signal module is also improved due to a reduced part count and a decrease in self-generated thermal energy, which can reduce component life.
A further advantage of this signal module is that it is considerably less prone to the “blink out” effect associated with other LED signals. When viewed from their periphery and off of their optical axis these signals appear to “blink out” due to the tight emission pattern of their LEDs. Multiple individual reflectors increase this signal module's output of anecdotal light, thereby providing a signal more readily visible from the module's periphery.
In one general aspect, an overhead signal module includes a module casing defining a cavity. Positioned within this cavity is a mounting board which carries an array of LEDs. Each LED is equipped with an individual reflector shaped to capture and direct side lobe light of the LED. Mounted parallel to the LED array and covering the cavity is a lens. The lens is shaped to efficiently focus the luminous output of the LEDs below the horizontal plane and to provide the appearance, when viewed from below the horizontal plane, of full uniform illumination.
Embodiments may include one or more of the following features. For example, the reflectors used to gather the side lobe light may be conical. Alternatively, parabolic reflectors may be used. In either case, the reflectors may be formed into an insert assembly which will fit over the LED mounting board and integrate each LED with its corresponding reflector.
The signal module lens may be manufactured of clear polycarbonate and may be either flat or domed. When the lens is clear, the color of the output light will be generated by use of appropriate color LEDs.
The lens may be compound, and may include fresnel lenses positioned to provide each LED with a fresnel lens aligned with the optical axis of the LED. The outer surface of the lens may be smooth, with all of the optical details of the component fresnel lenses on the inner surface of the lens. An advantage of this configuration is that it helps prevent the accumulation of dirt on the lens.
Each fresnel lens may include a two facet upper portion which refracts upward directed light downward below the horizontal axis. The lower portion of the lens may act as a simple window and may be configured to have a neutral effect upon the direction of light propagating through it.
Implementations of the signal module may include an eight-inch diameter and a twelve-inch diameter module. In the case of an eight-inch diameter module, illumination may be provided by 72 LEDs and associated reflectors. A twelve-inch module may include 144 LEDs. In either case, the LEDs are symmetrically distributed in a generally uniform manner.
An individual overhead signal may include a clear lens designed to efficiently redirect light to conform with ITE specifications or other regulations. This lens may be, in turn, a composite of individual fresnel lenses, including one for each LED. Furthermore, each of the LEDs may be provided with its own individual reflector to redirect the LEDs' side lobe light which would otherwise be lost.
Other features and advantages will be apparent from the following description, including the drawings, and from the claims.


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DuraLED—Lean, mean and eighteen.
Dialight—Beat the heat.
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Dialight—Have Your Head Examined.
Dialight—New DuraLED from Dialight.

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