Illumination – Plural light sources – With modifier
Patent
1986-09-15
1988-03-01
Davis, Jr., Albert W.
Illumination
Plural light sources
With modifier
362294, 362373, 362800, 340 84, 16510433, F21V 2900
Patent
active
047290765
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a signal light unit which has a signal light that uses as the light source a number of light-emitting diodes (LEDs) arrayed in the form of a plane and which has a function to effectively dissipate heat of large calorie generated inside the lignt unit.
BACKGROUND OF THE INVENTION
Conventionally, signal lights have been proposed that use as the light source a number of LEDs arrayed in a plane on a board for the purpose of energy saving. LEDs, however, have a low electricity-to-light conversion efficiency and change most of the electricity to heat despite of their high illumination efficiency and energy saving effectiveness. When used collectively in a large number at a time, therefore, LEDs generate a substantially large calorific power. In addition, LEDs have a negative temperature coefficient of light emission, so that their illumination decreases as the ambient temperature rises; for example, the light intensity is halved at an ambient temperature of 80.degree. C. as compared with that at 25.degree. C. To keep a high illumination efficiency of LEDs, therefore, their own temperature must be kept low. The abovementioned conventional signal light which uses many LEDs has such a fault that the LEDs arrayed as many as meet a prescribed illumination standard as the light source generate a substantially large calorific power when they are energized at the same time. As a result, not only the illumination efficiency of the LEDs will lower but also their service life will shorten, thus resulting in a failure as a signal light unit.
This invention solves the problem of such fault with a purpose of providing a signal light unit that has a heat dissipating function that can dissipate effectively the heat generated inside the LEDs to open air through a heat sink located on the back face of the board on the right face of which many LEDs are arrayed in a plane, thus preventing lowering of the light emission efficiency of the LEDs by heat and reverse effects of heat on the signal light.
DISCLOSURE OF THE INVENTION
The signal light unit of this invention comprises heat sink fitted on the back face of a board on the right face of which many LEDs are arrayed as the light source of the signal light. The heat sink efficiently induces and dissipates the heat of LEDs generated in the signal light unit to open air. This type of heat sink is generally formed as an aggregate of many fins. However, it need not always be fitted directly on the back face of the abovementioned board as one piece but can be indirectly connected to the back face with a heat absorber placed between them.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings, there is shown a signal light unit embodying this invention which has a heat dissipating function of this invention.
FIG. 1 is a top view,
FIG. 2 a side view,
FIG. 3 a sectional view along lines III--III of FIG. 1,
FIG. 4 a fragmentary enlarged vertical section and a fragmentary enlarged traverse cross section of FIG. 1, and
FIGS. 5A, 5B, 5C, 5D, 5E (1-3), and 5F are different schematic structural representations embodying this invention for use of a signal light unit having a heat dissipating function of this invention as a traffic signal light equipment.
THE MOST PREFERABLE EMBODIMENT OF THE INVENTION
This invention will be better understood from the following description taken in connection with the accompanying drawings.
As shown in FIGS. 1 to 4, part 1 is an LED used as the signal light source, part 2 a printed circuit board (PCB) on which many LEDs 1 are arrayed in a plane and connected electrically, and part 3 a board constructed in one piece with a finned heat sink 4 on its back face. On the right side of board 3, an insulation sheet 5 is fitted, and on the sheet the PCB 2 to which many LEDs 1 are fitted in array is fixed with resin filler 6. Then, on the right face of board 3, a lens 7 is mounted.
The heat generated by LEDs 1 on the right face of board 3 is led to heat sink 4, provided on the whole back face of board 3 s
REFERENCES:
patent: 2477957 (1949-08-01), Briskin
patent: 3502858 (1970-03-01), Habro et al.
patent: 4325146 (1982-04-01), Lennington
patent: 4419716 (1983-12-01), Koo
patent: 4471415 (1984-09-01), Larson et al.
patent: 4598347 (1986-07-01), Peppers
Hiroshi Kato
Masami Tsuzawa
Muneharu Tominaga
Osamu Waki
Tadahiro Morikawa
Cole Richard R.
Davis Jr. Albert W.
Semmes John G.
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