`
`
`
`US 20020122309Al
`
`(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0122309 A1
`Ahdelhafez et al.
`(43) Pub. Date:
`Sep. 5, 2002
`
`(54) LED BEACON LAMP
`
`Publication Classification
`
`(76)
`
`Inventors: Mohamed M. Abdelhafez, Old Bridge,
`NJ (US); Robert L. Martin, Little
`Silver, NJ (US); Robert Eric Johnson,
`Howell, NJ (US); John T. Adinolfi,
`Milltown, NJ (US); Chenhua You,
`Manasquan, NJ (US)
`
`Correspondence Address:
`OBLON SPIVAK MCCLELLAND MAIER &
`NEUS'I‘AIYI‘ PC
`FOURTH FLOOR
`1755 JEFFERSON DAVIS HIGHWAY
`ARLINGTON, VA 22202 (US)
`
`(21) Appl. No.2
`
`09/784, 160
`
`(22)
`
`Filed:
`
`Feb. 16, 2001
`
`Int. Cl.7 .............................. F21V 29/00; F21V 5x04
`(51)
`(52) US. Cl.
`........................... 362/294; 362-373; 362.5335
`
`(57)
`
`ABSTRACT
`
`A beacon lamp which may find use in and around airports,
`communication towers, etc. The beacon lamp includes a
`plurality of light emitting diodes (LEDs) its as light source.
`The plurality of LEDs can be mounted on an LED module
`which is in turn secured to a base. A transparent outer cover
`is provided to cover the plurality of LEDs. The LED module
`can include heat fins to enhance heat sinking properties. The
`outer cover and base can also include portions to improve
`free air convection to also improve heat sinking properties.
`The LEDS may be connected in parallel to provide redun-
`dancy in the event that certain LEDs burn out. The beacon
`lamp is also structured to allow the outer cover to be easily
`removed from the base to access the LED modules, to allow
`easy relamping of the beacon lamp.
`
`
`
`

`

`Patent Application Publication
`
`Scp. 5, 2002 Sheet 1 0f 7
`
`US 2002/0122309 A1
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`Patent Application Publication
`
`Sep. 5, 2002 Sheet 2 0f 7
`
`US 2002/0122309 A1
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`Sep. 5, 2002 Sheet 3 of 7
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`US 2002/0122309A1
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`Patent Application Publication
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`Sep. 5, 2002 Sheet 4 of 7
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`US 2002/0122309 A1
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`Patent Application Publication
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`Sep. 5, 2002 Sheet 5 0f 7
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`US 2002/0122309 A1
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`Patent Application Publication
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`Scp. S, 2002 Sheet 6 0f 7
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`US 2002/0122309 A1
`
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`US 2002/0122309 A1
`
`Sep. 5, 2002
`
`LED BEACON LAMP
`
`BACKGROUND OF TIIE INVENTION
`
`[0001]
`
`1. Field of the Invention
`
`[0002] The present invention is directed to a beacon lamp
`which, for example,
`|nay be used in and around airports,
`communication towers, etc.
`
`[0003]
`
`2. Discussion of the Background
`
`[0004] Beacon lamps are in a widespread use in and
`around airports and on communication towers. Such beacon
`lamps provide warnings and indications for approaching
`aircraft.
`
`[0005] Currently known beacon lamps in and around
`airports and on communication towers utilize incandescent
`or xenon lamps and typically flash their incandescent or
`xenon light bulbs. However, the use of such incandescent or
`Xenon lamps results in certain drawbacks, as recognized by
`the inventors of the present invention.
`
`[0006] Afirst drawback is that incandescent light bulbs are
`relatively energy inefficient, and thus use a large amount of
`power. A second drawback with both incandescent and
`xenon beacon lamps is that such lamps typically burnout
`within 18 to 24 months as that is the typical lifetime of an
`incandescent
`light bulb or a xenon light bulb. That is a
`particular drawback in beacon lamps because beacon lamps
`are often placed in locations which are 20 difficult and
`dangerous
`to reach. As a result,
`the maintenance and
`replacement of background incandescent and xenon beacon
`lamps can be both diflicult and costly. A third drawback is
`that xenon light bulbs require a large amplitude, short
`duration driving pulse. That pulsing of a Xenon light bulb
`can cause noise or electrical
`interference which can be
`extensive and detrimental to radio and cell tower transmis­
`SIOHS.
`
`SUMMARY OF THE INVENTION
`
`[0007] Accordingly, one object of the present invention is
`to provide a novel beacon lamp which can overcome the
`drawbacks in the background art.
`[0008] Afurther more specific object of the present inven­
`tion is to provide a novel beacon lamp which has improved
`energy elficiency.
`[0009] A further more specific object of the present inven­
`tion is to provide a novel beacon lamp which has a long life,
`to thereby reduce maintenance costs.
`[0010] A further more specific object of the present inven­
`tion is to provide a novel beacon lamp which does not emit
`any detrimental electrical interference.
`
`[0011] To achieve the above and other objects, the present
`invention sets forth a novel beacon lamp which utilizes light
`emitting diodes (LEDs) as the illumination source. The
`LEDs may be interconnected and mounted on a bracket to
`form an I.ED subassembly module. The I.ED subassembly
`module may provide heat sinking for the LEDs. Further, the
`novel beacon lamp of the present invention is structured to
`allow easy relamping of the I.ED components. The drive
`circuitry for the LED components can also include various
`features such as providing a regulated DC current, power
`factor correction, harmonic distortion correction, etc.
`
`[0012] The use of LEDs as a light source in the novel
`beacon lamp of the present invention provides the benefits
`that LEDs are significantly more energy efiicient than both
`incandescent and Xenon lamps, and thus the novel beacon
`lamp of the present
`invention has improved energy effi­
`ciency. LEDs also have a lifetime typically four to five times
`greater than that of incandescent and Xenon light bulbs, and
`thus the novel beacon lamp of the present invention will
`have to be relamped less frequently than the background
`beacon lamps, to thereby reduce maintenance costs. Further,
`LEDs do not require short duration, large amplitude driving
`pulses, and thus do not emit interference which may inter­
`fere with the radio or cell towers.
`
`BRIEF DESCRIPTION OF TIIE DRAVVINGS
`
`[0013] Amore complete appreciation of the present inven­
`tion and many of the attendant advantages thereof will be
`readily obtained as the same becomes better understood by
`reference to the following detailed description when con­
`sidered in connection with the accompanying drawings,
`wherein:
`
`[0014] FIG. 1 shows the novel beacon lamp of the present
`invention from a top perspective view;
`
`FIG. 2 shows a novel beacon lamp of the present
`[0015]
`invention from a bottom perspective view;
`
`[0016] FIG. 3 shows a novel beacon lamp of the present
`invention in an exploded view;
`
`FIGS. 4A-4D show a specific module and lens
`[0017]
`arrangement of the novel beacon lamp of the present inven­
`tion; and
`
`[0018] FIG. 5 shows a circuit overview of drive and light
`emission elements of the novel beacon lamp of the present
`invention;
`
`FIG. 6 shows a schematic in control circuitry of the
`[0019]
`present invention; and
`
`FIG. 7 shows in further detail control circuitry in
`[0020]
`the present invention.
`
`DESCRll"l‘lON OF Tl-IE PREFERRED
`EMBODIMENTS
`
`[0021] Referring now to the drawings, wherein like ref­
`erence numerals designate identical or corresponding parts
`throughout
`the several views, and more particularly to
`FIGS. 1 and 2 thereof, the novel beacon lamp 19 of the
`present invention is shown.
`
`[0022] As shown in FIGS. 1 and 2 the beacon lamp 19 of
`the present invention includes a base 6. The base 6 typically
`is a structural assembly and may be formed from a metal
`such as aluminum which has good heat dissipation proper­
`ties, or from fiberglass or other materials. Mounted on the
`metal base 6 is a terminal housing 5 which provides a site for
`wire termination. The terminal housing 5 is a junction for
`wiring to connect
`the wiring of the beacon lamp 19 to
`existing wiring, such as existing tower wiring. Formed
`above the base 6 is an outer housing 3. The outer housing 3
`is mounted onto the base 6 by a clamp latch 4. The clamp
`latch 4 can be clamped and unclamped to allow the outer
`cover 3 to be lifted off of the metal base 6. Thereby, easy
`
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`
`US 2002/0122309 A1
`
`Sep. 5, 2002
`
`access to the lamp wmponents housed inside the outer cover
`3 is provided with the structure in the present invention.
`
`[0023] The outer cover 3 also includes a screen portion 2.
`The screen portion 2 is provided to allow free convection of
`air within the beacon lamp 19. The outer cover 3 also
`includes a top cover portion 1 mounted on the top of the
`outer cover 3. The top cover 1 may typically be formed of
`aluminum sheet metal, and the outer cover may typically be
`formed of acrylic, a clear glass, plastic material, etc., and
`could also be tinted to match a desired emission color. The
`outer cover 3 is attached to the screen portion 2, and the
`screen portion 2 is attached to the top cover 1.
`
`[0024] As shown more specifically in FIG. 2, the metal
`base 6 also includes a screening portion 9 which is also
`provided to allow the free convection of air to occur within
`the beacon lamp 19. The screening portion 9 can also
`prevent infestation from bugs or birds. As also shown in
`FIG. 2 the clamp latch 4 is mounted to a base block 7.
`Module knobs 8 are also provided to secure a lamp module
`(shown later) to the metal base 6. The module knobs S also
`allow for the easy removal of the lamp module for relamp­
`ing, as discussed further below.
`
`[0023] FIG. 3 shows the beacon lamp 19 of the present
`invention in an expanded view. As shown in FIG. 3 the outer
`cover 3 is mounted on a telescoping tube 24 which is
`securely mounted to the metal base 6 by a flange 26.
`
`[0026] As also shown in FIG. 3, an electrical housing 21
`is connected by cable 22 to the terminal housing 5. The
`electrical housing 21 includes at least two power-input wires
`23 to connect to an existing controller (discussed further
`below). With such a structure in the present
`invention,
`providing power to LEDs and LED driving circuitry in the
`beacon lamp 19 is simply performed by connecting the
`beacon lamp 19 to an existing light controller, as discussed
`further below.
`
`[0027] As also shown in FIG. 3 two LED modules 20 are
`provided on which LED elements as the illumination source
`for the beacon lamp 19 are provided. The LED modules 20
`each include a connector 25.
`
`[0028] A specific structure of each LED module 20 is
`shown in FIG. 4A.
`
`[0029] As shown in FIG. 4A each LED module 20
`includes an LED assembly 13 mounted on an inner heat sink
`bracket 10. The LED assembly 13 is mounted to the inner
`heat sink bracket 10 via a thermally conductive electrical
`insulator 15, which can be formed of a material such as a
`pressure sensitive adhesive loaded with oxide particles and
`coated in Kapton thermally cool polymide film, as one
`example. A lens 18 is provided to mount over each LED
`assembly 13. The lens 18 may be formed of acrylic.
`
`[0030] The LED assembly 13 includes a plurality of
`individual LED elements 13a. The LEDs 13a are specifi­
`cally chosen to be high power LEDs capable of withstanding
`at or above 55° C. Acceptable LEDs for this purpose are
`SnapLED LEDS manufactured by Lumileds, such as model
`No. HPWS-FH00. A specific construction of the lens 18 is
`shown in FIGS. 4E-4D, which also specifically illustrate the
`shape of the lens 18. As shown in FIGS. 4B-4D, the lens 18,
`in the embodiment disclosed, includes six one-directionally
`powered plano/convex Fresnel lenses 41. Each Fresnel lens
`
`41 is aligned with one row of LEDs of the LED assembly 13.
`Each Fresnel
`lens 41 converges light emitted from the
`respective row of LEDs aligned therewith in a vertical
`direction to keep the light unchanged in a horizontal direc­
`tion, so as to better comply with applicable lighting regu­
`lations. Each Fresnel lens 41 has a convex surface as an
`outer surface to better rollimate the light beam and reduce
`light loss. The lens 18 is thus one directionally powered to
`converge light emitted from the LEDs. Utilizing 36 for each
`of two modules of such high powered LED assemblies 13
`and one directionally powered converging lens 18 provides
`an effective luminous intensity output of minimum 1500
`candela to maximum 2500 candela in an omnidirectional
`360°, which meets FAA requirements set forth in circular
`150/5345/43 for beacon lighting equipment.
`
`[0031] One factor the inventors considered by utilizing
`LEDs as light sources is that LEDs generate heat and LEDs
`are sensitive to heat in the sense that light output of an LED
`decreases with increasing temperature. That is, the intensity
`of the light output by an LED typically diminishes at a rate
`of about 1% per ° C. Further, exposure of LEDs to increased
`temperatures can also reduce the lifetime of the LEDs.
`
`In view of those problems the beacon lamp 19 of
`[0032]
`the present invention takes approaches to ensure adequate
`heat sinking for heat generated by the LEDs 13a. More
`specifically, the inner heat sink bracket 10 includes convec­
`tion fins 1011and is designed to provide heat sinking for the
`LED assemblies 13 by providing a conductive heat path to
`the convection fins 10a. The convection fins 1011 are
`designed to allow for maximized heat transfer to air and free
`convection.
`
`[0033] Also, and as noted above with respect to FIGS. 1
`and 2, the outer cover 3 includes the screen portion 2 and the
`base 6 includes the screen portion 9, which allow airflow to
`enhance the free convection.
`
`It is also noted that the embodiment disclosed in
`[0034]
`FIGS. 3 and 4 of the present specification utilizes LED
`panels which each include six series-connected clusters of
`three parallel-connected LEDs. The parallel interconnection
`of the LEDs 13a ensures that if a single LED extinguishes
`only that single LED is effected. The remaining two LEDs
`in parallel with the extinguished LED would then share the
`current from the failed LED, to thereby increase the LED
`current and intensity in each of those two remaining LEDs
`by one-third, to compensate for the extinguished LED. VVith
`such a structure, three parallel LEDs 13a must fail before the
`entire LED panel 13 fails.
`
`[0035] Further, in the structure shown in FIGS. 3 and 4
`two LED modules 20 are provided for each beacon lamp 19.
`Each LED module 20 can include 18 LED panels 13. With
`such a structure there are 324 LEDs 13a for each LED
`module 20, with two parallel-connected strings of nine
`series-connected LED panels 13 for each module. Of course
`other possible embodiments could provide for LEDs 13a in
`series/parallel paths to provide continued, albeit partial,
`illumination.
`
`[0036] Further, in the structure shown in FIG. 3 module
`brackets 12 are provided to secure the two LED modules 20
`to each other. These brackets 12 can be replaced by clamps
`or other devices to fasten the two LED modules 20 to each
`other.
`
`

`

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`
`US 2002/0122309 A1
`
`Sep. 5, 2002
`
`3
`
`[0037] The beacon lamp 19 of the present invention is also
`structured to ensure easy relamping. That is, when the LEDs
`13a fail or another maintenance problem arises, the system
`of the present invention can be easily relamped. To achieve
`a structure which allows for easy relamping, and as dis­
`cussed above with respect to FIGS. 1 and 2, the outer cover
`3 is secured to the base 6 by clamp latches 4, and the LED
`modules 20 are secured to the base 6 by modules knobs 8.
`[0038] With such a structure, to relamp the beacon light 19
`of the present invention first the outer cover 3 is unclamped
`from the base 6 by releasing the clamp latches 4. The outer
`cover 3 is then lifted from the base 6 by the operation of the
`telescoping tube 24. The telescoping tube 24 can then lock
`in an extended position to enable access to the LED modules
`20. The LED modules 20 can be removed by disconnecting
`the connectors 25, loosening the module knobs 8, loosening
`the module brackets 12, and then lifting the LED modules 20
`from the base 6. Then, the LED modules 20 can be replaced
`by new modules.
`[0039] As discussed above, and as shown in FIG. 5, the
`beacon lamp 19 can be connected to an existing controller 51
`for a beacon lamp, so that the beacon lamp 19 can be easily
`retrofit onto existing lamp sites. As also shown in FIG. 5, the
`beacon lamp 19 is connected to an LED beacon controller
`50. That LED beacon controller 50 may be housed in the
`electrical housing 21, and directly connects to the existing
`controller 51. FIGS. 6 and 7 detail driving and control
`circuitry for the beacon lamp 19 as housed in the electrical
`housing 21. The driving circuitry to the beacon lamp 19 can
`provide an adjustable electronically controlled current
`source.
`[0040] The existing controller 51 provides to the beacon
`lamp 19 properly timed flashing signals and provides moni­
`tor and alarm interfaces. The LED beacon controller 50
`provides a constant current source to the beacon lamp 19. By
`providing a constant current from the LED beacon controller
`50, the LED beacon controller 50 can operate if the beacon
`lamp 19 is provided on a tower of any length with negligible
`affects. That results because the LED beacon controller 50
`can adjust
`its output voltage to accommodate different
`conductor lengths, by maintaining an output of a constant
`current. The LED beacon controller 50 can also be adjust­
`able in order to accommodate variations in the output of the
`LEDs of the beacon lamp 19.
`[0041] FIG. 6 provides a more detailed disclosure of the
`LED beacon controller 50 of FIG. 5.
`[0042] The LED beacon controller 50 has a function of
`providing an electrical interface between the existing amn­
`troller 51 and the beacon lamp 19. The LED beacon eon­
`troller 50 receives a flashing signal from the existing con­
`troller 51, processes the signal, and sends the proper amount
`of electrical energy to the beacon lamp 19. The LED beacon
`controller 50 also provides a monitoring function which can
`signal to the existing controller 51 that the beacon lamp 19
`is functional.
`[0043] As shown in FIG. 6 an AC line filter 51 receives an
`input AC voltage. The AC line filter filters the high fre­
`quency components of the input current, and provides a
`filtered output of the input AC voltage to a doubler and filter
`52, i.e. a rectifier filter, and to a bias supply 56. The bias
`supply 56 provides the unit with the required voltages to
`operate the power control circuits and the interfaces to the
`existing controller 51.
`
`[0044] The dor|bler and filter 42 multiplies the input
`voltage to twice the peak on the AC input. The doubler and
`filter circuit 52 can also increase the input voltage above a
`maximum voltage required by the beacon lamp 19 based on
`and the height of the tower, and can filter out
`the low
`frequency AC line ripple. The filtered AC line voltage
`provided to the doubler and filter 52 is multiplied by two, to
`provide a voltage to the main control 54. As one typical
`operating embodiment, the AC input to the doubler and filter
`52 can be multiplied by two to provide a voltage input to the
`main control 54 of 300 Vdc filtered. The main control 54
`processes the input voltage,
`i.e.
`the 300 Vdc, by PWM
`techniques to supply the beacon lamp 19 with an adjustable
`current source.
`
`[0045] The main control 54 provides its output voltage to
`the over voltage protection circuit 55 and the control inter­
`face 53. The over voltage protection circuit 55 monitors the
`voltage output of the main control 54 and can short out the
`output to protect the beacon lamp 19 when an over voltage
`is output. That is, the over voltage protection circuit 55 can,
`when activated, generate a short circuit across the beacon
`lamp 19 and cause a series fuse to open,
`to protect
`the
`beacon lamp 19 from an over voltage. The control interface
`53 receives signals from the existing controller 51, processes
`the signal, and sends an on/ofi‘signal to the main control 54.
`The control interfanx:53 can also receive a status of the lamp
`from the main control 54 and can provide the status to the
`existing controller 51 via, e.g., a 10 amp ac signal for
`incandescent monitor circuits or other formats in the existing
`controller 51.
`
`[0046] The main control 54 thus provides several func­
`tions of power control, alarm control, lamp protection, on/off
`control, and other miscellaneous functions. The main control
`54 thus controls the current supply to the beacon lamp 19 on
`the tower to thereby control the intensity of light output by
`the beacon lamp 19.
`
`Further details of the main control 54 of FIG. 6 are
`[0047]
`provided in FIG. 7.
`
`[0048] First, FIG. 7 includes a block power converter 70,
`shown in the dotted lines, which itself is made up of a power
`converter 71, an I sense circuit 73, an isolation circuit 75, a
`driver control circuit 76, and a PWM circuit 77.
`
`[0049] The current [lows from the main control 54 through
`the beacon lamp 19 and back into the main control 54 via the
`lamp return input. The lamp current
`is regulated by the
`power converter circuit 71. Such a function may be achieved
`by utilizing a standard buck converter topology with feed­
`back.
`
`[0050] The lamp current is sensed by the I sense circuit 73
`and is compared against a reference current to produce an
`error signal through the isolation circuit 75 provided to the
`PWM circuit 77. That error signal is representative of the
`difference between the sensed lamp current and the refer­
`ence lamp current. The PWM circuit 77 converts the error
`voltage to a pulse width modulated signal, proportional to
`the error voltage. The pulse width modulation signal is then
`fed to the driver control 76, which controls the current
`provided to the beacon lamp 19.
`
`[0051] The LED beacon controller 50 also provides cir­
`cuitry to protect from over voltage and over current situa­
`tions. A voltage failure mode can occur when resistance in
`
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