GB2458345A

GB2458345A - Sealed lighting unit having array of LEDs

Info

Publication number: GB2458345A
Application number: GB0804540A
Authority: GB
Inventors: Gordon Routledge; Carl George
Original assignee: Dialight Lumidrives Ltd
Current assignee: Dialight Lumidrives Ltd
Priority date: 2008-03-12
Filing date: 2008-03-12
Publication date: 2009-09-23
Anticipated expiration: 2028-03-12
Also published as: GB0804540D0; GB2458345B

Abstract

A sealed lighting unit 105 comprises an array of Light Emitting Diodes (LEDs). The LEDs 200 are mounted on a printed circuit board (PCB) 300. Each LED is covered by a lens 201 which is secured to the PCB to surround the LED. The surface of the PCB between the lens elements may be covered by an encapsulant. The sealed lighting unit is particularly suitable for use in a zone having a potentially explosive atmosphere.

Description

METHOD AND APPARATUS FOR PROVIDING ILLUMINATION

The present invention relates to an apparatus and method for providing illumination at a desired location. In particular, but not exclusively, the present invention relates to a sealed lighting unit including an array of light emitting diodes (LEDs), covered by an array of lens elements, which can be utilised to provide illumination in a hazardous environment.

From time to time it is known that ft is desirable to provide illumination at a fixed or movable position. In such instances luminaires have been designed which include one or more light emitting elements. A luminaire Is a lighting unit including one or more lamps, parts to distribute illumination, to protect the lamp/s and to provide power to the lamp/s. When supplied with power illumination from the light emitting elements can be used to illuminate a location where the luminaire is located.

In some instances luminaires must be designed so that they do not provide a source of ignition (by spark or heat). This is particularly true where luminaires are located or are usable in potentially explosive atmospheres. By way of example such hazardous atmospheres are typically found at petrol filling stations or in gas and oil installations. In the past there have been two main ways proposed for preventing explosion caused by luminaires in such environments. One way has been to contain any explosion within the body of the luminaire. The other way is to prevent any source of ignition from the iuminaire from reaching any potentially flammable gas and thus eliminating art initial "** 25 reaction. S...

* . In order to achieve this, some conventional luminaires have reinforced compartments ** with labarynthine baffles to maxirnise a distance to the outside atmosphere. Other luminaires which have been proposed in the past have complicated latches and safety .... 30 shut-off devices to ensure all electric circuits are isolated before a body can be opened to the potentially explosive atmosphere. It will be appreciated, however, by those skilled in the art that known luminaires have been prone to failure and require complex manufacturing processes to make and repair.

Some luminaires have been proposed using incandescent bulbs, fluorescent tubes, sodium lamps or other such forms of illumination emitters. Such light sources are, however, prone to failure and can require complex circuitry for power supply and control.

It is an aim of the present invention to at least partly mitigate the above-mentioned problems.

It is an aim of embodiments of the present invention to provide a source of light which does not present a source of ignition to a potentially hazardous environment where the light source is located.

It is an aim of embodiments of the present invention to provide a lumirisire and a method of manufacturing a luminaire which has a long illumination life.

According to a first aspect of the present invention there is provided apparatus for providing illumination at a desired location, comprising: a sealed lighting unit comprising a plurality of light emitting diodes (LEDs) mounted on a first surface of a printed circuit board (PCB), and a plurality of lens elements each covering an emission surface of a respective one or more LED and secured to the first surface of the PCB to surround said LED.

According to a second aspect of the present invention there is provided a method of manufacturing apparatus for providing illumination at a desired location, comprising the steps of: * ** mounting a plurality of light emitting diodes (LEDs) on a first surface of a printed circuit board (PCB); ** ** * s locating a lens element over an emission surface of a respective one or more ** LED for all of the plurality of LEDs; arid securing each lens element to the first surface of the PCB to thereby surround each LED by a respective lens element.

According to a third aspect of the present invention there is provided a method of providing illumination at a desired location, comprising the steps of: emitting illumination from a sealed lighting unit comprising a plurality of light emitting diodes (LEDs) mounted on a first surface of a printed circuit board (PCB), illumination being emitted from an illumination surface of a plurality of lens elements each covering an emission surface of a respective one or more LED and secured to the first surface of the PCB to surround said LED.

Embodiments of the present invention provide a luminaire including an array of LEDs.

Such a luminaire has an illumination life of over 50,000 hours compared to the typical lifetime of 15,000 hours for a typical fluorescent tube. This means that the fufly sealed LED unit can operate for almost 6 years continuous use rendering regular servicing and bulb filament/tube replacement unnecessary.

Embodiments of the present invention provide a luminaire whereby at the end of usable life the unit can be sent for environmentally sound recycling.

Over a given period of time the luminaire according to embodiments of the present invention requires less access than a typical fluorescent luminaire thus requiring less man time spent in potentially dangerous environments. Additionally, embodiments of the present invention offer an extra level of protection than that of prior known luminaires in that in addition to the main unit being environmentally sealed, an electrical drive unit seated within the body of the luminaire is itself a sealed unit which helps prevent any sparks from the internal circuitry reaching the environmentally hazardous atmosphere.

According to still further embodiments of the present invention, a further level of safety is offered by the fact that the unit is supplied through-wired between two end units. This allows for easy wiring connection to either or both ends of the unit without having to access main seaid body pail. * a.

a... 25

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Embodiments of the present invention also provide an additional safety factor in that the p. *l. . . . . * *. LED unit reaches full illumination on switch on in a much shorter time frame than known fluorescent/sodium illumination luminaires where several minutes can be required. For workmen installing the device or carrying out a repair, this can be highly advantageous. 0*I. I $ ***

Embodiments of the present invention wilt now be described hereinafter, by way of example only, with reference to the accompanying drawings in which: Figure 1 illustrates a hazardous location; Figure 2 illustrates a luminaire; Figure 3 illustrates an exploded view of the luminaire; Figure 4 illustrates encapsulation; and Figure 5 illustrates another view of encapsulation.

In the drawings like reference numerals refer to like parts.

Embodiments of the present invention can be used to provide illumination at any desired location. Aptly where that location is a potentially hazardous area. A hazardous area is a region or zone in which precautions must be taken due to the presence of explosive atmospheres. In such circumstances explosions and fires can occur regardless of size of installation. Hazardous areas are often found where vapour gases and dust are mixed with oxygen and then provided with an ignition source. With increasing pressure from legislation, it will be appreciated that there is today a great need for electrical equipment able to comply with industrial standards set for such environments.

Whilst an embodiment of the present invention is described herein below by way of example only with respect to a petrol station environment, it is to be appreciated that embodiments of the present invention are widely applicable to one or more illumination sources which can be mobile or fixed and located in a desired location within a hazardous environment. For example, but not exclusively, in flour mills, glue manulacturers, paper mills, garages, petro stations, textile/spinning factories, * ** petrochemical plants and offshore oil exploration standings. *t.

In a hazardous area there are three well-known types of zone which are generally recognised and these are identified in sequence as zone 0, zone I and zone 2. Zone 0 refers to an area in which an explosive atmosphere in the form of gas, vapour or mist is a..

., 30 continuously present or present for a long period or frequently. Zone I is an area in which an explosive atmosphere in the form of gas, vapour or mist is likely to occur in normal operation and zone 2 is an area in which an explosive atmosphere in the form of gas, vapour or mist is not likely to occur in normal operation but if it does occur will persist for a short period only. Aptly, embodiments of the present invention can be used in any of these zoned regions.

Figure 1 illustrates a zone 2 type environment 100 identified as a petrol filling station. In such areas vehicles 101 can be refuelled from a filling pump 102 as will be appreciated by those skilled in the art. Illumination 103 should be provided at such areas particularly, though not exclusively at night. As illustrated in Figure 1 this can be achieved by providing one or more lighting units 105 each supplied with power through a respective electrical connector 106. Whilst illustrated in Figure 1 as a lighting unit suspended from a ceiling 107, it will be appreciated that embodiments of the present invention can be utilised to provide a lighting unit which can be wall mounted, floor mounted and/or mobile.

Hereinafter the lighting units 105 will be referred to as tuminaires. It is understood that a luminaire is a lighting unit including one or more lamps, that is to say lighting elements able to provide illumination, parts to distribute illumination such as lensing and focusing elements, parts to protect the lamps such as covers and also parts which are utilised to provide power and control signalling to the lamp elements.

Figure 2 illustrates a luminaire 105 in more detail. The luminaire includes 45 light emitting diodes (LEDs) arranged in a 3 x 15 array. It will be appreciated that other shapes, numbers and sizes of LEDs may be utilised. Each LED 200 is covered by a lens 201 designed and manufactured from optical grade polycarbonate and fitted over each lens. Each lens is designed to suit the exact light output of the LED and the polycarbonate material provides a very high temperature resistance. Each optical lens may be provided in a wide variety of forms to produce a desired beam angle including spot (60 ha ange), medkam (15° f ane) and wide (25° half angla). It wili bc appreciated that other types of optical lenses could be utilised such as oval and directional lenses and that other types of material may be utilised to manufacture the * * * lenses. Also whilst the embodiment illustrated in Figure 2 shows a single lens covering a * respective single LED it will be appreciated that single lenses could be utilised to cover more than I LED. S... * .

*..: Figure 3 shows an exploded view of the luminaire 105 shown in Figure 2 in more detail.

The LEDs 200 are mounted on a thermally conductive aluminium backed printed circuit board (PCB) 300. This PCB 300 is thermally bonded to an aluminium extruded heat sink. The transfer of heat away from the LEDs helps improve efficiency of the light output. As the temperature rises then the light output will be adversely affected and will be greatly reduced. The PCB is fitted with a thermal transducer to reduce current supply and prevent heat exceeding a threshold which might destroy the LED.

A metal casing 301 provides a rigid housing for the LED array and also holds a separate power supply and control circuitry 302 which is itself a sealed unit. The power supply 302 provides a current output and operating power able to drive the multiple LEDs. End plates 303 with cable grommets 304 are used to seal the open ends 305 of the aluminium housing 301 and a clear polycarbonate cover 306 are sealed together to form a sealed unit.

Independently sealed junction boxes 307 which include a terminal block 308 are fitted to each end which include knock-out holes and IP (Atex) approved cable glands for input wiring. This enables the luminaire to be connected to a local power source in a very convenient fashion. The end boxes each include a respective cover which can be sealed once the lurninaire is connected.

The luminaire 105 is through connected and includes a through cable 309 connected between terminal blocks 308 in each end. Also a connection is made with an end terminal block to the driver 302 via a cable 310. A further cable 311 is terminated at an end region 312 for connection to the PCB 300. The outer insulation is stripped back with secondary insulation remaining.

Figure 4 illustrates a partial cross section through the metal casing 301 and LED array 2 in more detai. Figure 4 is taken through the cross section A-A in . 25 Figure 2. As may be seen in Figure 4 LEDs 200 are connected to an upper surface 400 of the PCB 300. A lens 201 is located over the LED 200. The lens 201 has an outer substantially frusto conical upper surface 401 extending into a circular foot region 402.

A space 403 is formed at an underside of the lens 201 between the circular foot and a lower lens surface 404. The lens 201 includes an upper lens surface 405 which S...

*" 30 together with the lower surface 404 and the material of the lens body, determines the illumination pattern generated by the lens when the LED 200 is illuminated. An adhesive ring 406 extends around the lower surface of the circular foot 402 of the lens. During manufacture of the sealed unit, the lens may be adhered to the upper surface 400 of the PCB 300 by the adhesive ring 406 thus effectively sealing the LED 200 within the space of the chamber 403 defined at the undersurface of the lens. In this way should a source of ignition occur by virtue of the LED malfunctioning the spark or the light is prevented from accessing the outside of the sealed unit by virtue of the LED being located in the chamber area.

As a further means of preventing an ignition source caused by the LED functioning areas of the PCB are partitioned by walls 407 extending upwardly away from the upper surface 400 of the PCB. The walls can be circular or rectangular or any desired shape to encapsulate one or more of the LED and lens combinations. During manufacture encapsulant is introduced in liquid form within the walled area. As shown in Figure 4 encapsulant 450 can be added to a depth d so as to secure the foot region 402 of the lens in place. In this way each lens is secured and encapsulated within its own chamber thus ensuring that no source of ignition can be offered.

As illustrated in Figure 4 the partitioning wall may be utilised to partition further elements of the luminaires which themselves otherwise provide ignition sources. For those electrical elements 460 which stand a higher height above the upper surface 400 of the PCB encapsulant 470 can be introduced into those partitioned areas to a greater height than the height d in other areas.

Figure 5 illustrates a view of a part of the luminaire 105 shown in Figure 4. As illustrated in Figure 5 the partitioning wall 407 defines therein a chamber. The cable 311 extends upwardly through a passageway through the partitioning wall and is then bent downwards before the wires of the cable are bared for connection to a male connector 460 which is connected to a mating female connector 480 connected to the PCB 300.

A?1:... :...44.......4..4.. 41.-..L....,...l...... 1... H,, *. +.. - 6 LII,alJUIIl( á U I IlIUVUU..vu lilly lll..llaliIM, UIlll%8 S.DJ liii... .llIfldlIaal VVlSI p.i b% predetermined level over an upper surface of the electrical connector 460 and covering *...

the wiring. Encapsulant 450 such as resin or the like covers the upper surface of the PCB together with the foot regions 402 of each lensing element 201. By utilising one or more compartments different levels of encapsulant can be utilised so as to cover all required components but making an efficient use of encapsulant.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example ucomprisingn and "comprises" means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. * ** *1 * ** * S S... S. * . . * . *5S

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Claims

CLAIMS: 1. Apparatus for providing illumination at a desired location, comprising: a sealed lighting unit comprising a plurality of light emitting diodes (LEDs) mounted on a first surface of a printed circuit board (PCB), and a plurality of lens elements each covering an emission surface of a respective one or more LED and secured to the first surface of the PCB to surround said LED.
2. The apparatus as claimed in claim 1, further comprising: encapsulant covering a portion of the first surface of the PCB between the lens elements.
3. The apparatus as claimed in claim I or claim 2 wherein each lens element comprises a body portion including an inner chamber region in which an LED is locatable and a foot portion comprising an adhesive layer.
4. The apparatus as claimed in claim 3 wherein the foot portion and adhesive layer extends in a closed loop to provide a sealing surface of the lens element.
5. The apparatus as claimed in claim 3 or claim 4 wherein the body portion of each lens further comprises an illumination surface arranged to determine a pattern of illumination emitted from each lens element.
6. The apparatus as c!aimed in c!am 2 whercin tha ancapsuant has a thickness at *. 25 least as great as a predetermined minimum thickness. ***S I* SI*
7. The apparatus as claimed in any preceding claim, further comprising: ** a wall member extending upwardly away from the first surface and surrounding the plurality of LEDs. *I*I * Sa... 30 *..:
8. The apparatus as claimed in claim 7 wherein the wall member defines the portion of the first surface of the PCB covered by the encapsulant.
9. The apparatus as claimed in claim 8 wherein the wall member further surrounds at least one further electrical component.
10. The apparatus as claimed in claim 6 wherein the encapsulant covers all tracks on the PCB.
11. The apparatus as claimed in any preceding claim, further comprising: a plurality of wall members extending upwardly away from the first surface, each wall member surrounding a respective sub-region and at least one electrical component of the PCB.
12. The apparatus as claimed in claim I further comprising encapsulant covering each sub-region of the PCB.
13. The apparatus as claimed in any preceding claim wherein each lens element is made from a polycarbonate material.
14. The apparatus as claimed in any preceding claim wherein the PCB is thermally bonded to a heat sink.
15. The apparatus as claimed in any preceding claim wherein the sealed lighting unit further comprises a sealed electrical drive unit for supplying power and/or drive signals for the LEDs to the PCB.
16. The apparatus as claimed in any preceding claim wherein the desired location comprises a zone having a potentially explosive atmosphere and the apparatus presents no source of ignition to the atmosphere. * S S...
17. The apparatus as claimed in any preceding claim arranged to provide an illumination life of greater than 40,000 hours. S..
18. A method of manufacturing apparatus for providing illumination at a desired S...location, comprising the steps of: : mounting a plurality of light emitting diodes (LEDs) on a first surface of a printed circuit board (PCB); locating a lens element over an emission surface of a respective one or more LED for all of the plurality of LEDs; and securing each lens element to the first surface of the PCB to thereby surround each LED by a respective lens element.
19. The method as claimed in claim 18, further comprising the steps of: securing each lens element by urging a foot portion of each lens element against the first surface of the PCB, an adhesive layer carried by the foot portion sealing the lens element to the PCB.
20. The method as claimed in claim 19, further comprising the steps of: covering a portion of the first surface of the PCB between the lens elements with encapsulant.
21. The method as claimed in any one of claims 18 to 20, further comprising the steps of: mounting a wall member to the first surface to enclose said a portion of the surface prior to the step of covering with encapsulant.
22. The method as claimed in claim 21, further comprising the steps of: mounting at least a further wall member to the first surface to enclose a respective at least one further electrical component.
23. A method of providing illumination at a desired location, comprising the steps of: emitting illumination from a sealed lighting unit comprising a plurality of light emitting diodes (LEDs) mounted on a first surface of a printed circuit board (PCB), illumination being emitted from an illumination surface of a plurality of lens elements * ** * 55. ..t -r..........4. IS Sr ar5 I fl a.l a4 * .. wvca Ii Ij alt VU siaa,.i, Du. ji, V w ii s'#. .a..,., .u *.., 25 first surface of the PCB to surround said LED. S... 5.*: * *
24. The method as claimed in claim 23, further comprising the steps of: *. providing power and/or drive signals for the LEDs to the PCB via a sealed electrical drive unit in the sealed lighting unit. S... * * *.*25. The method as claimed in claim 23 or claim 24, further comprising the steps of: providing the illumination without presenting a source of ignition to a potentially explosive atmosphere at the desired location.26. Apparatus constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.27. A method substantially as hereinbefore described with reference to the accompanying drawings. * ** *0 * * S. S... p. ** p. * * S * S..S S... p * S. S* S. * b *S S *S