Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
1998-07-31
2001-06-26
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C257S079000, C362S229000
Reexamination Certificate
active
06252350
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of lamp indicators, and more particularly, to light emitting diode (“LED”) lamps employing surface mount technology.
BACKGROUND OF THE INVENTION
Incandescent lamps are commonly used for a wide variety of indicator lights. Although these incandescent lamps generally provide good optical performance, they have several significant drawbacks. Namely, incandescent lamps have low reliability and a short life cycle so that replacement is frequently required. These shortcomings can be particularly troublesome when the lamp is mounted in a difficult to access location. The cost of the labor to replace the lamp is often several orders of magnitude greater than the cost of the lamp itself.
Due to the high demand for increased reliability, there have been recent efforts to utilize LEDs as replacements in existing incandescent lamps. The LED is an attractive alternative because of its high reliability and longer life expectancy. Moreover, the LED can also be easily retrofitted into incandescent bulb applications. This approach, however, suffers from poor optical performance when compared to conventional incandescent lamps. The single LED simply does not produce the same amount of light as a single incandescent bulb, and therefore, it is generally necessary to employ a number of LEDs in a cluster to produce the same amount of light. Moreover, the light emitted from most LEDs is highly directional resulting in a narrow effective viewing angle often requiring the viewer to be positioned directly in front of the lamp. Accordingly, there is a current need for a visual indicator lamp with the high reliability of an LED and the optical performance of an incandescent lamp.
SUMMARY OF THE INVENTION
The present invention is directed to an LED lamp which satisfies the need for combined high reliability and good optical performance. There is, therefore provided, in accordance with a preferred embodiment of the present invention, a surface mounted LED installed in a lamp housing. This surface mount lamp construction produces diffused light having improved optical performance and wider viewing angles than conventional LEDs. Specifically, a printed circuit board is used to support the surface mount LED. The printed circuit board has a first conductive path having one end connected to a first terminal and a second conductive path having one end connected to a second terminal. The surface mount LED is installed on the printed circuit board with the anode mounted on the first conductive path and the cathode mounted on the second conductive path. A lamp housing with electrical contacts is used to deliver power to the surface mount LED through the terminals on the printed circuit board.
Further variations in optical performance can be achieved by combining surface mount LEDs with non-surface mount LEDs. In one embodiment, a printed circuit board is disposed in a lamp housing with a surface mount and a non-surface mount LED installed thereon. Other LED arrangements include a number of surface mount LEDs positioned along the periphery of the printed circuit board with one non-surface mount LED positioned in the center of the printed circuit board. Alternatively, a number of surface mount LEDs can be positioned along the periphery of the printed circuit board with a non-surface mount LED positioned between each surface mount LED.
In small space applications, vertical stacking of the LEDs is an attractive approach. Namely, a first printed circuit board with a non-surface mount LED is disposed in the lamp housing. A second printed circuit board with a surface mount LED is disposed in the lamp housing longitudinally displaced from the first printed circuit board. The second printed circuit board also has an aperture aligned with the non-surface mount LED to allow light to pass through.
Multi-directional light emissions can be achieved with a lamp having a base supported by a lamp housing, a cap, and a number of printed circuit boards extending between the base and the cap. Each printed circuit board has at least one surface mount LED positioned on an outward surface. Preferably, the cap is formed with conductive paths for delivering power applied to the electrical contacts of the lamp housing to the surface mount LEDs. Improved thermal dissipation over conventional devices can be achieved by physically installing a voltage dropping resistor or diode between the base and cap.
It is understood that other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only embodiments of the invention by way of illustration of the best modes contemplated for carrying out the invention. As it will be realized, the invention is capable of other and different embodiments and the details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be illustrative in nature and not restrictive.
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Christie Parker & Hale LLP
Gerike Matthew J.
Patel Ashok
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