AU2015255325A1 - Illumination system - Google Patents

Abstract

An illumination system for use in hazardous environments. The illumination system includes a flameproof enclosure housing a light source; and a light transmitting conduit having a light emitting distal end and being releasably connectable to the enclosure at or near its proximal end. The proximal end of the light transmitting conduit is positioned for light transmitting alignment with the light source when the conduit is connected to the enclosure. 'C It C A> 'Kr 0-' if iF c4 ii H I +14 ~Ir&>t> +7- * ~A i/ -~ A LY~ t\ TKiK~

Description

ILLUMINATION SYSTEM Related Applications [0001 ] This application claims priority from (country) Application No. 2008904301 filed on 21 August 2008, the contents of which are to be taken as incorporated herein by this reference. Field of the Invention [0002 ]The present invention relates to an illumination system for use in hazardous or awkward environments. The invention is particularly concerned with an illumination system including a flameproof light source which has particular application to such environments as in an underground coal mine or a potentially explosive industrial location. Background of the Invention [0003] Hazardous areas, in which potentially explosive atmospheres exist, are encountered in a wide variety of industries. In coal mines, where combustible gases such as methane occur naturally, and in oil refineries, chemical plants, gas works, or any other places where a flammable gas or vapour may be present, it is a requirement that safeguards be applied to electrical equipment to prevent ignition of the gas or vapour and consequent explosion or fire. [0004 ] Flameproof protection essentially refers to the placement of all electrical apparatus within a special enclosure that is capable of containing an explosion that initiates inside. Flameproof enclosures provide for a type of protection for electrical equipment, such as lighting and power installations, in which the enclosure will withstand, without injury, any explosion of a flammable gas that may occur within it. Typically, flameproof enclosures are manufactured from metal, such as steel and have a removable flameproof cover enclosing a flameproof chamber. [0005 ] There are a number of National and International Standards which regulate the features and properties of flameproof enclosures. In Australia, the relevant standard is set out in the Ex(d) category of the International Electrotechnical Commission (IEC) and the Australian and New Zealand (ANZEx) standards. Importantly, flameproof enclosures must 1 prevent the transmission of flame such as will ignite the flammable gas which may be present in the atmosphere surrounding the flameproof enclosure. Accordingly, flameproof enclosures must ensure that any explosion within the enclosure does not create an external explosion. [0006 ] It is therefore essential that the mechanical design of the flameproof enclosure is such that, not only can it withstand the explosion, but further, that it prevents any explosion initiating inside the enclosure from igniting the external atmosphere. This latter requirement is achieved by ensuring that joints and other openings (such as bearings) provide a sufficiently long and restricted flame path to prevent external ignition. Some designs use special wide flanges that enable any flame escaping through a joint gap to be quenched before it reaches the potentially flammable atmosphere outside the enclosure. [0007 ] A flameproof joint corresponds to the position at which corresponding parts of a flameproof enclosure come together. It is here that the flame or products of combustion may be transmitted from the inside to the outside of the flameproof enclosure. The shortest path through a joint from the inside to the outside of a flameproof enclosure is known as the length of flame path. A strictly defined gap, being a distance between corresponding surfaces of a flameproof joint, is provided when the electrical equipment has been assembled. This gap assists in relieving the pressure inside the enclosure caused by an explosion. [0008 ] Current flameproof illumination systems typically employ a small metal flameproof enclosure, fitted with an incandescent light globe, which is used to illuminate the work area. The size and intensity of the light globe is governed by the heat it produces. Typically the light globes are limited to a maximum wattage of 50w for a normal sized lighting flameproof enclosure. The flameproof enclosure is fitted with a thick glass lens to allow for light transmission from within the enclosure to the work area. However, substantial light intensity is ordinarily lost during transmission through the thick lens. In order to provide sufficient illumination to a work area, either the light source containing enclosure must be positioned close to the work area or a higher wattage bulb with attendant larger flameproof enclosure needs to be provided. [0009 ]Either case results in greater likelihood of damage of the flameproof enclosure by flying rock. Moreover, a significant ignition source can be produced if the glass lens is 2 cracked or broken while in service thus exposing a potentially explosive atmosphere to a source of electric spark. [0010 ] If an electrically powered lighting device is located in a hazardous area, (for example, in the vicinity of the cutting drum of a coal mining machine), and the light is damaged during mining operations, such as by debris and fly-rock, many jurisdictions require that the incident be reported to the mine administration and to relevant coal mine regulatory authorities. A number of regulated activities are then typically initiated which may include relocation of the light from the original position to a safer location (even though the original position may have been optimal) and the establishment of a paper trail detailing the incident and measures taken to prevent its re-occurrence. The financial cost to the coalmine can be the equivalent of about one week of paper work for a senior employee and the loss of a minimum of four hours in coal production. This can accumulate to several tens of thousands of dollars. [0011 ] The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge at the priority date of any one of the claims of this specification. [0012 ] It would therefore clearly be desirable to provide a safe, effective illumination system for use in hazardous environments which provides a sufficient light intensity and could be repaired conveniently in situ without the need to follow any time consuming and costly 'incident' reporting or regulatory procedures. It is therefore an object of the present invention to provide an illumination system for use in hazardous environments which overcomes, or at least alleviates, one or more disadvantages of the prior art. Description of the Invention [0013 ] According to the present invention, there is provided an illumination system for use in hazardous environments, including: (a) a flameproof enclosure housing a light source; and (b) a light transmitting conduit having a light emitting distal end and being releasably connectable to the enclosure at or near its proximal end, 3 wherein the proximal end is positioned for light transmitting alignment with the light source when the conduit is connected to the enclosure. [0014 ] By providing the illumination system of the invention with a light transmitting conduit, it is possible to remotely position the flameproof enclosure containing the light source in a relatively less hazardous location and direct the light emitting distal end of the conduit to the work area. If the conduit is damaged during use, such as by flying debris which is always generated by a coal mining machine (eg a long wall shearer), the conduit can simply be repaired or replaced. Because the flameproof enclosure itself has not been damaged, there would be no need to report the incident, and accordingly no expensive loss of employee time or coal production. [0015 ] Typically, the light source in the illumination system of the invention is any nonincandescent light source. Preferably the light source includes one or more light emitting diodes (LEDs). Preferably, the LED's are high power LED's. More preferably, the light source includes more than one LED, preferably an array of LEDs. LEDs are mechanically robust which is advantageous in many hazardous environments where physical damage is possible. They also give a better intensity of light for a given power input as compared with incandescent light. This is particularly advantageous for relatively long conduits in which light intensity may be compromised over the length of the conduit. [0016 ] Typically, the light transmitting conduit includes one or more optical fibres. As used herein, the term "optical fibre" means a light guide of unspecified diameter ranging from the order of micrometres to centimetres. Preferably, the light transmitting conduit includes a plurality of optical fibres. More preferably, the light transmitting conduit is flexible. More preferably, the light transmitting conduit includes a bundle of optical fibres arranged such that, when the conduit is connected to the enclosure, the proximal end of each optical fibre is in light transmitting alignment with a respective light emitting diode in the array. More preferably, the optical fibres are arranged in a longitudinally helical manner in the bundle. Such an arrangement assists in preventing misalignment of optical fibres at the distal end of the bundle. [0017 ] Preferably, the, or each, LED has an associated lens positioned between it and a respective proximal end of an optical fibre. The lens focuses the light from its adjacent LED so that the emitted light is transmitted into the optical fibre more efficiently. 4 [0018 ] Advantageously, the optical fibre/s are polymeric. It has been found that polymeric optical fibres possess the desired amount of flexibility and robustness as compared with glass optical fibres. Typically, the light transmitting conduit includes a fire resistant sleeve, in accordance with safety regulations. Where the optical fibres comprise or are clad with a potential static electricity producing material (such as PVC cladding), the light transmitting conduit typically should be covered with a fire resistant anti-static ("FRAS") sleeve to minimise the risk of explosion caused by static discharge. [0019 ] The light transmitting conduit is releasably connectable to the enclosure at or near its proximal end. Preferably the proximal region of the conduit includes mounting means for releasably mounting the conduit to the flameproof enclosure. [0020 ] In one embodiment of the invention, the proximal region of the conduit includes a flameproof cover for the flameproof enclosure. Preferably the proximal region of the conduit and the flameproof cover are joined together so as to form a unitary component. This may be effected by adhesion using a flameproof glue. The cover and enclosure are preferably connectable in such manner as to provide a flameproof joint having a sufficiently long flame path to extinguish flames in the event of an explosion within the enclosure. [0021] The proximal region of the conduit may also include aligning means for aligning the ends of optical fibres with respective LEDs and lenses, if present, in the array. Preferably the aligning means comprises a sleeve or gland in which at least part of the proximal region of the conduit is received. When connected to the flameproof enclosure, the positioning sleeve or gland typically extends into and/or from the enclosure and assists in aligning respective proximal ends of the optical fibres with corresponding LEDs. [0022 ] In a first embodiment, the proximal region of the conduit additionally includes an adaptor for spacing the proximal ends of the optical fibres such that each end is adjacent and aligned with a respective light emitting diode (and associated lens, if present). An adaptor may be necessary in the situation where the dimensions of the optical fibres do not correspond to the dimensions of the LED array. For example, the cross sectional diameter of 5 the optical fibre bundle may be less than that of the LED array, meaning that optical fibres within the bundle cannot be centred on the LEDs of the array. This is problematic, because significant loss of light is likely to occur during operation. [0023 ] However, by spacing the fibres from each other a predetermined distance in order to centre each fibre with a respective LED, light loss can be minimised. The adaptor preferably comprises a perforated member having a number of apertures there through each dimensioned to receive a proximal end of a fibre and spaced from each other a distance corresponding to that between LED centres in the array. Preferably the perforated member is a perforated disc. [0024 ] In a second embodiment of the invention, the conduit is mountable at a window provided in the flameproof enclosure. The window is positioned so as to be in light communication with the light source. Light from the light source can be transmitted through the window and into the conduit. The light source should preferably be in light transmitting alignment across the window in order to minimise light loss. While this embodiment may experience some loss of light intensity because of transmission losses through the window, it still provides improved light intensity as compared with prior art incandescent illumination systems. [0025 ] In one variation of the second embodiment, the conduit is separated into two portions, with one portion extending inside the enclosure from the window to the light source and a second portion extending distally outside the enclosure away from the window. The optical fibres within the first and second portions should preferably be in light transmitting alignment across the window in order to minimise light loss. [0026 ] In another variation of the second embodiment, the proximal end of the conduit is mountable at the window provided on the external surface of the flameproof enclosure. Preferably, the proximal end of the conduit is mountable in a sleeve or mechanical gland which is provided about the window on the external surface of the flameproof. In this form of the invention, the LED array is advantageously positioned as close as possible to the inner side of the window, again to minimise light transmission loss. However, care needs to be taken that the window does not become too hot and thereby present an ignition risk. Accordingly, cooling means may need to be provided in order to cool the window during 6 operation. Light from the light source is transmitted through the window and into the proximal end of the conduit. [0027 ] It is an advantageous feature of the invention that the distal end of the light transmitting conduit remains at a low temperature, such as less than 1500C, preferably less than 85CC during operation. This is by virtue of the distance between the light source and light emitting end, meaning a low rate of heat transmission. Further, the nature of the invention lends itself to application in other hazardous or awkward places in industrial sites, such as under staircases, up ladders, at pinch points and in cramped operating conditions. [0028 ] Further, due to the preferred flexibility of the light transmitting conduit, it could conveniently be located in hazardous areas on a reel (similar to a fire hose reel) and deployed when a safe light source is required. Detailed Description of Preferred Embodiments [0029 ] The invention will now be described in greater detail with reference to the accompanying drawings in which: Figure 1 is a schematic view of a first embodiment of an illumination system of the invention. Figure 2 is perspective view of the LED array of the first embodiment. Figure 3 is a schematic cross sectional view of the optical fibre bundle along line 11 -Ill. Figure 4 is a schematic view of a second embodiment of an illumination system of the invention. Figures 5a and 5b are perspective views of a guide plate and an adaptor, respectively, for use in the illumination system of the invention. Figure 6a is a schematic view of a third embodiment of an illumination system of the invention. Figure 6b is a schematic view of a fourth embodiment of an illumination system of the invention. 7 Figure 7 is a perspective view of an end cap for use in the illumination system of the invention. [0030] In the following description of the drawings like elements are given the same or analogous reference numerals. Referring now to the first embodiment of the invention in Figures 1, 2 and 3, there is shown an illumination system 10 for use in an underground coal mine. [0031] The illumination system 10 includes a flameproof enclosure 20, comprising a housing 21 formed from steel or other suitable material, in which is housed a light source 30 comprising an array 31 of LEDs 31a. A flexible light transmitting conduit 40 generally includes a first proximal region 41 extending inside the housing 21 and a second region 43 extending outside the housing 21. The conduit 40 is connectable to the housing 21 at its proximal region 41 and has a light emitting distal end 44. The length of the light transmitting conduit 40 is shown shortened for ease of illustration, however it is to be appreciated that the conduit may be of any suitable length, depending on the desired application. The light transmitting conduit 40 includes a plurality of polymeric optical fibres 46 arranged longitudinally in a bundle 51. The proximal region 41 of the light transmitting conduit 40 includes a mounting means 45 for releasably mounting the conduit 40 to the housing 21. [0032 ] The mounting means 45 incorporates a flameproof gland 48 sealingly attached to the conduit by flameproof glue 49. The flameproof gland 48 is mountable to the housing 20 via bolts 50. A flameproof joint 52 is established between the gland 48 and housing 20 when connected, such that if an explosion occurs within the flameproof enclosure, a sufficiently long flame path is provided to extinguish any flames before they reach the external atmosphere. The flameproof cover 48 additionally includes an aligning means 47 comprising a sleeve in which part of the proximal region 41 of the conduit is received. [0033 ] The light source 30 is shown in greater detail in Figure 2. The light source 30 includes an array 31 of seven LEDs 31a which are spaced from each other by a predetermined distance, largely dictated by dimensions of each LED 3 1a. Arranged in front of each LED 3 1a is a respective lens 54 for focusing the emitted light. The light source 30 also includes necessary electrical circuitry 56 including a series of power resistors 56a for 8 limiting the current to the LEDs below a predetermined value, and a temperature switch 58 for switching off the array should the temperature exceed a set value. Also included is a cooling means comprising a fan 60. The circuitry 31, 56, 58 and fan 60 are in electrical connection with an external power supply (not shown) via electrical wire 62. The light source 30 is additionally cooled during operation by a water jacket 64. [0034 ] The proximal end 42 of the conduit is positioned for light transmitting alignment with the light source 30. In the arrangement shown in Figure 1, the proximal end 46a of each optical fibre 46 is aligned with a respective LED 31a and associated lens 54 in the array 31. Accordingly, geometrical arrangement of the optical fibres in the bundle 51 is similar to that of the LEDs 31 a in the array. [0035 ] Figure 3 illustrates schematically the arrangement of optical fibres in the conduit 40 as seen in cross section along line Ill-Ill in Figure 2. The conduit 40 contains seven optical fibres 46 which are arranged in a geometry corresponding to that of the LEDs 31a in the array 31. [00 35] As seen in Figure 1, the diameter of the bundle 51 of optical fibres in the second region 43 of the conduit is less than the dimensions of the LED array 31. Accordingly, in order to ensure that the proximal ends 46a of the optical fibres 46 are centred on respective LEDs 3 1a, an adaptor 66 is provided near the proximal end 42 of the conduit 40 in order to space the proximal ends 46a of the optical fibres from each other a distance corresponding to the spacing between LEDs 31a .A detailed perspective view of the adaptor 66 is provided in Figure 5a. It comprises a disc 68 having a number of apertures 70 therethrough for receiving and supporting the proximal ends 46a of the optical fibres 46. In this manner, each proximal end 46a is centred on a respective LED 31a and associated lens 54. Light from each LED 31a is focused by a respective lens 54 directly into the adjacent proximal optical fibre end 46a, thereby minimizing light transmission losses. [0036 ] As shown in Figure 1, the conduit 40 further includes a fire resistant anti-static ("FRAS") sleeve 72 which is provided about the aligning means 47 and extends about the conduit 40 to the distal end 44 thereof. [0037 ] Figure 7 illustrates an end cap 96 for use on the light emitting distal end 44 of 25 the conduit 40. The end cap 96 includes an elongate ribbed connector 97 which can be 9 inserted into the distal end of the FRAS sleeve 72 such that the optical fibres (not shown) are received longitudinally therein. The end cap 96 also includes a lens 98 for focussing light emitted therethrough. A second embodiment 110 of the invention is illustrated in Figure 4. [0038 ] Discussion of the second embodiment will focus on those features which differ from those of the first embodiment. The light transmitting conduit 140 comprises two separate portions: a first proximal portion 141 located within the housing 120 and a second portion 143 extending away from the housing 120. [0039 ] The two portions are separated by a light transmitting, flameproof window 180 which is provided in a wall of the housing 120 and joined thereto, such as by gluing, to provide a flameproof seal. The second portion 143 of the conduit 140 is mounted within a mechanical gland 147a and the first portion 141 is mounted within a guide plate 147b. The mechanical gland 147a and the guide plate 147b together provide aligning means to ensure that the first and second portions 141, 143 are in light transmitting alignment across the window 180. [0040 ] Figure 5b shows a detailed perspective view of the guide plate 147b. It comprises a disk 184 having a lobed aperture 186 centrally extending therethrough. Each lobe 186a is shaped to receive therein a corresponding conduit 141 of the optical fibre bundle 151. Third and fourth embodiments of the invention 210, 310 are illustrated in Figures 6a and 6b respectively. Discussion of the third and fourth embodiments will focus on the features which differ from those of the first and second embodiments, respectively. The major difference in the third and fourth embodiments is in the configuration of the respective flameproof covers 248, 388. [0041] Figure 6a shows the third embodiment 210 of the invention, which is a modification of the first embodiment 10. The mounting means 245 incorporates a flameproof gland 248, comprising a spigot gland which is mountable to the housing 220 via bolts 250 so as to provide a flameproof joint 252. Depending from the flameproof gland 248 is an aligning means 247 which extends into the housing 220 and in which the 30 proximal region 241 of the conduit 240 is received. Also positioned within the aligning means 247 are guide plate 247b and adaptor 266. A compression gland 290 is in threaded engagement with the inner axial surface of the flameproof gland 248. The compression gland 290 includes two components 290a and b, which are also in threaded engagement, having opposed respective angled surfaces 291a and b. A resilient sealing ring 292 is provided between the angled 10 surfaces 291a and b and can be compressed for sealing engagement with the optical fibre bundle 251 when component 290b is screwed into component 290a. [0042 ] The compression gland component 290b includes an annular extension 293 comprising a collar for receiving a FRAS sleeve 272 therearound. [0043 ] The mounting means 245 further includes potting material 294 which fills and seals the spaces surrounding the optical fibres 246 between the resilient sealing ring 292 and the adaptor 266. The third embodiment 210 further includes a flameproof cover 288 which is mountable to the housing 220 via bolts 250. A further flameproof joint, 295, is established between the cover 288 and housing 220 when connected. The cover 288 enables an operator to inspect the interior of the housing 220 without needing to remove the flameproof gland 248. [0044] Figure 6b shows a fourth embodiment of the invention which is a modification of the second embodiment shown in Figure 4. The principal difference in the fourth embodiment is the inclusion of a flameproof cover 388, which is mountable to the housing 320 by bolts 350. In a similar manner to the third embodiment 210, the flameproof cover 388 establishes a flameproof joint 395 25 between the cover 388 and housing 320, and facilitates inspection of the housing interior. [0045 ]The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the above description. 11

Claims (15)

1. An illumination system for use in hazardous environments, including: (a) a flameproof enclosure housing a light source; and (b) a light transmitting conduit having a light emitting distal end and being releasably connectable to the enclosure at or near its proximal end, wherein the proximal end is positioned for light transmitting alignment with the light source when the conduit is connected to the enclosure; wherein the light source is non incandescent and includes one or more light emitting diodes comprising high power LEDs and wherein, the light transmitting conduit includes one or more optical fibres; and wherein a proximal region of the conduit includes mounting means for releasably mounting the conduit to the flameproof enclosure.

2. The illumination system of claim 1, wherein the proximal region of the conduit includes a flameproof gland for the flameproof enclosure which provides a flameproof joint when connected to the enclosure.

3. The illumination system of claim 2, wherein the proximal ends of the optical fibres are received in a gland for connection to the flameproof enclosure.

4. The illumination system of claim 3, wherein the proximal region of the conduit is mountable at a window provided in a wall of the flameproof enclosure.

5. The illumination system of claim 4, wherein the light source includes an array of light emitting diodes.

6. The illumination system of claim 5, wherein the light source further includes respective lenses associated with the LEDs.

7. The illumination system of claim 6, wherein the optical fibre/s are polymeric. 1

8. The illumination system of any one of claims 1 to 7, wherein the light transmitting conduit is flexible

9. The illumination system of any preceding claim when dependent on claim 3, wherein the light transmitting conduit includes a bundle of optical fibres arranged such that, when the conduit is connected to the enclosure, the proximal end of each optical fibre is in light transmitting alignment with a respective light emitting diode and lens, if present, in the array.

10. The illumination system of claim 8, wherein the optical fibres are arranged in a longitudinally helical manner in the bundle.

11. The illumination system of any preceding claim, wherein the proximal end of the conduit includes an adaptor for spacing the proximal ends of the optical fibres such that each end is in alignment with a respective light emitting diode.

12. The illumination system of any preceding claim, wherein the distal end of the conduit remains at a low temperature preferably below 85*C during operation.

13. The illumination system of any preceding claim, further including an adjustable lens provided on the distal end of the conduit.

14. The illumination system of any preceding claim, wherein the light transmitting conduit includes a fire resistant antistatic sleeve.

15. An illumination system for use in hazardous environments, substantially as herein described with reference to either embodiment in the accompanying drawings. 2