Patent Grant
6869203
1. Field of the Invention
The present invention relates to light emitting diode (LED) signals, specifically to an LED symbol signal with a uniform display aspect despite having a reduced number of LEDs.
2. Description of Related Art
Symbol signals, for example turn signals, pedestrian signals, and walk/don't walk signals previously have been designed with incandescent point light sources in a housing with a mask covering. The mask defining the symbol desired. Incandescent bulbs suffer from drawbacks of high power consumption and the requirement for frequent maintenance as the bulbs burn out.
LED symbol signals have reduced maintenance and operating costs due to the extreme life span of LEDs and their low power consumption in comparison to incandescent bulbs. Previously, LEDs were used to form the symbol desired by filling the symbol space with a full matrix of LEDs. As new, improved generations of LEDs become available, they emit more light from each individual LED. Therefore, the full matrix of LEDs is not required to create a suitably bright signal. The LEDs may then be spaced further apart from each other, omitting LEDs thereby saving material costs and lowering the signals operating power consumption. However, as the LEDs spacing increases, an undesirable “pixel effect” appears in which the individual LEDs become increasingly discernable to the viewer.
An object of the present invention is to provide a high efficiency and cost effective LED symbol with a reduced or eliminated “pixel effect”. A further object of this invention is to provide a LED symbol signal with a design that may be easily modified as new generations of LEDs with increased light output become available, reducing the number of LEDs required to achieve a similar light output level.
A LED symbol signal with LEDs arrayed to correspond to a desired symbol. Light from the LEDs is directed onto corresponding optical segments of a multiple collimating zone element and directed into a forward direction/distribution. A mask defines the desired symbol. The optical segments and or a diffusion surface on the cover or multiple collimating zone element(s) diffuses the display aspect, obscuring the individual LEDs. A diameter of the optical features of the diffusion surface is smaller than a diameter of the optical segments. The LED symbol signal may be configured for retrofitting into an incandescent lamp signal housing.
d is an isometric cut-away side view of a thin mask embodiment with a diffusion surface on an outer side of the cover.
Key to Figure Elements
LED signals are disclosed in detail in U.S. patent application Ser. No. 09/756,670, filed Jan. 9, 2001 and further in U.S. patent application Ser. No. 09/827,429, filed Apr. 6, 2001, both applications assigned to Applicant, GELcore LLC, and hereby incorporated by reference in their entirety.
One embodiment of the present invention is shown in
MCZE 3 has optical segments 18 (collimating zones) matching the distribution of the LED 8 and/or LED 8 clusters on the PCB 5. As shown in
A diffusion pattern 19 on the inner or outer surface of the MCZE 3 or on an inner or outer surface of the cover 1 may be used to further obscure discernability of individual LEDs 8 in the display aspect. The diffusion pattern may be composed of circular, rectilinear or other geometric forms. Also, the diffusion pattern 19 may be formed on the desired surface via abrasion, impact and/or sandblasting. The diffusion pattern 19 preferably has individual diffusion element diameters D in a less than 1 to 1 ratio to the diameter O of the associated optical segments 18.
Cover 1 provides an environmental seal for the signal. A flat or a large radius outer surface on cover 1 prevents dirt build-up on the MCZE 3. Sealing means, for example an o-ring 21, between the cover 1 and housing 4 seals the signal from the environment.
Mask 2 may be integrated with the MCZE 3 and/or with the cover 1. The mask 2 may be in the form of a dark or opaque material, created via insert film molding, tape, paint coating or other means for blocking the LED 8 light not passing through the optical segments 18.
To increase the symbol definition and minimize spurious light emissions, the mask 2 may be designed with a depth M that substantially fills the space between the MCZE 3 and the cover 1 (
MCZE 3 may be a full disk or other shape dimensioned to cover the open end of the housing, with optical segments formed thereon or there may be discrete elements snap-fitting for example, into openings in the mask 2. For highest economy of materials, the cover 1, mask 2 and MCZE 3 may be integrated into a single component.
To combat sun phantom effect, the cover 1 may include an angled outer surface. Also, the diffusion pattern may be limited to only those areas in alignment within apertures in the mask 2 which define the desired symbol.
To allow directional signals to be used in any orientation, without requiring changes to the internal components, the cover 1 may be optically neutral allowing the assembled housing to be turned in any direction to orient, for example, a signal arrow as desired. A symmetrical optical design focusing the light output along the axis beam of the housing with minimal spreading allows the housing to be turned in any direction without losing the correct display aspect. An asymmetrical optical design may be used to minimize sun phantom effect and or meet Institute of Transport Engineers (ITE) specifications for the display aspect of traffic signals.
The distance H between the MCZE 3 and the PCB 5 is approximately 1 inches in a standard twelve-inch signal (FIG. 1). For designs where the symbol may be fully illuminated by a shorter distance between the LEDs 8 and MCZE 3, standoffs or shallower housings may be used. The proper distance allows the LEDs 8 to fully illuminate each optical segment 18 without creating overlap, noticeable shadows or dark areas. The resulting light beam from the signal may be changed by moving the PCB 5 with respect to existing optical components (changing H) thereby changing the light output distribution. This spacing also allows use of light degradation sensor circuitry as described in applicant Ser. No. 09/827,429 application incorporated herein.
As shown in
The size of the PCB 5 may be determined by the smallest circle, rectangle or other shape that will encompass the desired LED pattern, thus saving material costs by minimizing the size of the PCB 5. Where arrow symbols are being displayed, the arrow form may be cut from a bulk PCB panel 22 cut out as shown in
Other embodiments of the present invention include but are not limited to pedestrian signals, pedestrian signals with countdown displays, informational signals including emergency exit signs, and any other form of LED symbol signal which would otherwise suffer from the “pixel effect”. In the case of pedestrian signals or other large graphical symbols the cover may be omitted and or integrated with the mask, the diffusion surface located, for example on an inner surface of the optical elements 18 or on the signal's external surface.
This invention is entitled to a range of different embodiments and their equivalents, and is to be limited only by the scope of the following claims.
This application claims the benefit of U.S. Provisional Application No. 60/283,882, filed Apr. 13, 2001 and U.S. Provisional Application No. 60/361,140, filed Mar. 1, 2002, both applications hereby incorporated by reference in their entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3678458 | Ljungkull et al. | Jul 1972 | A |
| 5687500 | Lamparter | Nov 1997 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20020149494 A1 | Oct 2002 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60361140 | Mar 2002 | US | |
| 60283882 | Apr 2001 | US |
