Electric lamp and discharge devices: systems – Plural series connected load devices – Christmas lights
Reexamination Certificate
2000-07-07
2001-07-31
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural series connected load devices
Christmas lights
C315S192000, C315S193000, C362S231000, C362S545000
Reexamination Certificate
active
06268702
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a lamp for an external warning light, particularly for use in an aircraft navigation light.
BACKGROUND OF THE INVENTION
It is known to fit infra-red light emitting diode (IR LED) lamps adapted with bayonet fittings in place of filament bulbs in the navigation lights of an aircraft to suit it for convert night flying. The IR LED lamps enable the aircraft to be seen by the pilot of a companion aircraft using night vision goggles.
Night vision goggles intensify images, whereby a small number of IR LED chips can be used. An equivalent number of visible light, light emitting diodes (VL LEDs) would be scarcely visible to the human eye at more than a few tens of meters.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a VL LED filament lamp replacement.
According to the invention, there is provided a lamp for an external warning light comprising a body providing a drive terminal and a return terminal, a series/parallel array of a plurality of visible light, light emitting diodes (VL LEDs) arranged on a carrier mounted on the body and a current limiting device mounted within the body for limiting current drawn by the VL LEDs, the current limiting device being connected in series with the array of VL LEDs, with the array and the limiting current being connected between the drive terminal and the return terminal.
Preferably, the body is a bayonet fitting body adapted to co-operate with a bayonet fitting socket, with the drive terminal being a central terminal and the return terminal being bayonet fitting lugs.
Whilst the current limiting device mounted within the body can be simply a resistor; the preferred device is an integrated circuit device in series with the VL LEDs, which is adapted to limit forward current through them when their resistance falls on heating in use. Additionally, a forward voltage regulation resistor can be connected in series with the VL LED array and the integrated circuit, forward current limiting device.
Normally, the carrier will comprise a ceramic substrate on which the VL LED array is mounted and covered in transparent material, with the ceramic substrate being mounted on a metal heat sink. The material can be a rigid potting material or a flexible encapsulant.
In accordance with an important preferred feature of the invention, the lamp can include at least one infra-red light emitting diode (IR LED) arranged on the carrier in like manner to the VL LEDs, the IR LED(s) and the VL LED array being respectively oppositely connected between the drive terminal and the return terminal; whereby application of voltage of one polarity will illuminate either the IR LED(s) or the VL LEDs and voltage of the opposite polarity will illuminate the other(s) of the VL LEDs and the IR LED(s).
Whilst a plurality of the IR LEDs can be arranged in another series/parallel array or a parallel array; there will normally be an order of magnitude more VL LEDs than IR LEDs.
In one embodiment, there is provided an optical screen, the IR LED(s) being placed adjacent the optical screen, whereby the lamp can be arranged in use for the infra red light to be emitted upwards only with the screen intercepting downward infra red light.
Preferably, an electrical protection device, typically a forward voltage regulation resistor and/or a reverse voltage limiting diode, will be connected in series with the IR LED(s).
Normally, the values of the LEDs and the electrical protection devices will be such that the lamp is adapted to be powered at one voltage (with one polarity) for illumination of the VL LEDs and another voltage (with the opposite polarity) for illumination of the IR LED(s).
In accordance with another aspect of the invention there is provided an aircraft lighting circuit for operating one or more lamps of the invention, the circuit including an opposite voltage generation circuit and a switch arranged to switch the polarity of voltage applicable to lamps fitted in the circuit for illuminating the VL LEDs with one polarity and the IR LED(s) with the other polarity.
Preferably, the aircraft lighting circuit includes a differential amplifier circuit to which the switch is connected for switching on alternative inputs of the amplifier and a power output circuit for powering the VL LEDs or the IR LED(s).
REFERENCES:
patent: 4211955 (1980-07-01), Ray
patent: 4580196 (1986-04-01), Task
patent: 4870325 (1989-09-01), Kazar
patent: 4912334 (1990-03-01), Anderson
patent: 4963798 (1990-10-01), McDermott
patent: 5463280 (1995-10-01), Johnson
patent: 6011493 (2000-01-01), Bushell et al.
patent: 3622025 C1 (1987-10-01), None
patent: 3832109 A1 (1990-03-01), None
patent: 3932213 A1 (1991-04-01), None
patent: 2426381 (1978-05-01), None
patent: 2586844 A1 (1987-03-01), None
patent: 2307977 A (1996-09-01), None
patent: 1264276 (1989-10-01), None
L.F.D. Limited
Vu David
Ware, Fressola, Van Der Der Sluys & Adolphson LLP
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