LIGHTING SYSTEMS

Abstract: A system, for example for defining or controlling vehicle pathways, in which light is transferred from remotely situated visible light producing units (19) to roadway or runway surface mounted display units by optical fibre cables (20) includes means for transferring heat from the light units (19) to the display units. Heat may be generated by infra-red light generators (31) and be conducted to the display unit by the same optical fibre cable (20) which transfers the visible light thereto, or by a separate optical fibre cable. Alternatively heat produced by the visible light generating means (24) may be piped, in the form of heated air, to the display unit, where said air may be vented or be returned to the light unit (19).

Description: LIGHTING SYSTEMS The present invention relates to lighting systems, and in particular to such systems as used for the definition of vehicle pathways such as aircraft runways and roads. 5 One of the methods currently in use by traffic planners in their efforts to overcome traffic congestion is a "tidal flow system". In this system multi-lane roads have the direction of traffic flow in one or more lanes changed according to the direction of main traffic flow. A major problem with this method is defini¬ te" tion of direction of flow in the particular lane. One means for defining the flow is the use of signals on gantries, but these tend to distract a driver's attention from the road ahead, and can be missed. It has been suggested that lanes be designated by a series of 15 lights in the road surface, the lights being illuminated either red or green. Light installations suitable for this purpose are already in use in airfield runway and perimeter track layouts. These light installations have to be extremely robust to withstand vehicle impact, and also have to be constructed to allow access for the 20 change of light bulbs. A major drawback with this type of system for road use rises from the life of the light bulbs, which is typically of the order of 500 hrs. This means that sections of road will have to be periodically closed to allow bulbs to be replaced, and this will inevitably result in local traffic congestion of the 25 type which the planners are aiming to avoid. One method of over¬ coming this problem, as taught in GB 2076042A, is to provide the illumination by means of optical fibres leading from light sources situated at the side of a road. Use of the system according to GB 2076042A can, in certain 30 circumstances, lead to more problems. Conventional use of light bulbs involves the production of heat. Whilst this heat is often regarded as a nuisance it is, in fact, of benefit in wet or cold conditions when used for vehicle pathway definition systems. In such use the heat is usually sufficient to prevent misting and 35 icing. However, optical fibres do not conduct heat from con¬ ventional light bulbs, and in consequence vehicle pathway definition systems using optical fibre conducted light can lose their effec- tiveness in wet or cold conditions. In such conditions they can become in practice dangerous. According to the present invention an illuminated device includes at least one optical display unit and at least one light unit situated remotely from the optical display unit, the or each light unit being connected to at least one display unit by means of a fibre optic cable whereby light is conveyed from each light unit to at least one optical display unit, and means for conveying heat from each light unit to at least one optical display unit. Heat may be generated in the light unit by an infra red light generator, and this heat can be conducted through the same fibre optic cable as the visible light. However the materials from which fibre optic cables are made differ in the efficiency with which they transmit light in different wavelengths. It will therefore usually be preferable to use a separate fibre optic cable for the conduction of heat in the form of infra-read light. A material such as "Red Vycor", as manufactured by Corning, might be suitable for the conduction of heat. An alternative source of heat is the visible light generator itself. The light unit is advantageously small and sealed and the heat generated therein is likely to result in a requirement for cooling of the unit. In view of the siting of the units (typically, embedded in a pavement) and of a necessity for keeping the units free of dust and moisture, cooling is a problem. Another form of the invention, therefore, includes means for transferring warm air from the light unit to the display unit. In a preferred form of this embodiment of the invention air is then transferred back from the display unit to the light unit, forming a closed system with minimal requirement for drying of the air. Alternatively air can be allowed to exhaust from the display unit, but in such a case fresh air must be supplied to the light unit and this air must be filtered and dried. Air can be transferred by pipes of, for example, plastics material and the light unit may include means, such as a fan, to provide a pressure differential. There might also be provision in a closed air system for air to be exhausted from the display, unit and fresh air admitted to the light unit in very warm conditions. A typical fibre optic cable as used in the invention may be single stranded at the light unit end and multi-b anched at the display unit end. Each visible light unit may be equipped with a series of filters, preferably remotely controlled, by which the colour of the light displayed by any associated display unit can be adjusted as required. The infra-red light generators or air delivery systems are preferably controlled independently from the visible light unit by, for example, moisture detectors, temperature sensing devices or both. Devices according to the invention are most advantageously used for illumination in situations to which there is difficulty of access, for example in vehicle pathway definition systems. In one use of the present invention a vehicle pathway defini¬ tion system includes a series of optical display units embedded in a surface of the pathway, and a series of light units situated re¬ motely from the optical display units, each light unit being con¬ nected to at least one display unit by means of a fibre optic cable, whereby light is conveyed from the light units to the optical display units, and means for conveying heat from the light units to the display units. It will be apparent that by suitably positioning the light units it becomes possible for lights to be changed without danger to personnel and without disrupting road traffic. There is still, however, provision for heating of the optical display units to prevent misting and icing, so enabling the optical display units to maintain their efficacity in adverse weather conditions. One embodiment of the invention will now be described, by way of example only, with reference j * _o the accompanying diagrammatic drawings, of which: Figure 1 is a plan view of part of a three lane road, Figure 2 is an elevation, in section, along line 2-2 of Figure 1, Figure 3 is an elevation, in section, of a- detail of Figure 2. Figure 4 is an elevation, in section, of an alternative form of light unit. A road 10 (Figure 1) has three lanes 11, 12, 13 defined between kerbs 14 and 15 and rows 16, 17 of display units such as those shown at 18. Each display unit 18 has an associated light unit 19 situ- 5 ated at some distance from the road 10. Each display unit 18 (see Figure 2) is joined to an associated light unit 19 by means of a fibre optic cable 20. Each light unit 19 lies in a hole 21 in a pavement 22 adjacent to the road and access thereto is by means of an access cover 23- Each light unit 1Q 19 (Figure 3) contains a visible light unit in the form of a bulb 24 from which light is passed via a prism 30 to the fibre optic cable 20, and an infra-red light generator in the form of a bulb 31 by means of which infra-red light passes via a prism 32 to the fibre optic cable 20. Each light unit also contains (not shown in Figure 15 3) for the visible light bulb 24 a filter unit 25 and a remotely operated filter selector 26. The light unit 19 also contains a remotely operated switching unit 33 for control of the infra-red bulb 3 • Operation of the remotely controlled switch 33 is prefer¬ ably by means of a moisture detector, a thermostat, or both. 20 In use, the display units 18 are illuminated to define vehicle flow paths using the visible light bulbs 24 only. In adverse weather conditions such as, for example, rain or frost sensors such as the moisture detector and thermostat operate to actuate the switch 33 to switch on the infra-red bulb 3 - As will be apparent 25 the infra-red bulbs 31 can be controlled independantly of the visible light bulbs 24. In this way when display systems are in non-continuous use the display units 18 can be cleared of misting or frost in adverse weather conditions prior to their being used for the display of visible light. A typical use of a display system -__- such as that described about is in a "tidal flow system". When the bulk of vehicle flow is in a particular direction, for example in the direction A of Figure . 1, two lanes 12, 13 are made available to traffic flowing in this direction. Light Units 19 are activated so that each visible light bulb 24 is illuminated and has a red filter 35 of the filter system 25 interposed between it and its associated fibre optic cable 20. The display units 18 or the row 16 are thereby illuminated red and drivers approaching will know that they are not allowed to cross this line. The other row 17 of display units 18 can be left un-illuminated, or alternatively can be ill¬ uminated green. When the volume of traffic changes the colour of illumination of rows 16, 17 can be adjusted accordingly. In good weather conditions, the infra-red light bulb 31 can be left switched off, to be switched on only when damp or icy conditions are present or expected. In another embodiment of the invention (Figure 4) each light unit 19 contains a visible light bulb 24 from which light is foσ- ussed by a mirror 50 and lens 51 onto a fibre optic cable 20. The unit 19 has connected thereto a pipe 52 for transferrence of warm air from the light unit to an optical display unit and a pipe 53 for transferrence of air back from the optical display unit to the light = unit 19. Air circulation is effected by a fan 54. It will be realised that there are many alternative embodiments within the scope of this invention. For example, it will usually be more efficient to use separate fibre optic cables such as 20 for each of the visible light bulb 24 and infra-red light bulbs 31. Likewise a single light unit 19 may be used for the illumination of a plurality of display units 18. Also there are many alternative versions of the embodiment of the invention as described with reference to Figure 4. Air might be allowed, for example, to vent from the optical display unit whilst fresh air, after filtering and drying, is admitted to the light unit 19. Whilst the invention has been described as used for vehicle pathways such as roads it could usefully be used in some instances for vertical display units such as road signs and advertisement ' s. However the latter are not so ' prone to misting and icing, due to their vertical disposition, and also are in general easier of access to allow conventional heating elements to be installed, and where necessary replaced, adjacent to display units 18.

Claims: CLAIMS What is claimed is: 1. ' An illuminated device including at least one optical display unit (18) and at least one visible light unit (19) situated remotely from the optical display unit, the or each light unit being connected to at least one display unit by means of a fibre optic cable (20), whereby light is conveyed from each light unit (19) to at least one optical display unit (18), and characterised in having means (20, 52) for conveying heat from each light unit (19) to at least one optical display unit (18). 2. An illuminated device as claimed in Claim 1 characterised in that heat is generated in the light unit (19) by an infra red light generator (31), and is conducted from a light unit (19) to a display unit (18) by the same fibre optic calbe (20) which connects the visible light unit to the display unit. 3. In illuminated device as claimed in Claim 1 characterised in that heat is generated in the light unit (19) by an infra red light generator (31) and is conducted from a light unit (19) to a display unit (18) by a separate fibre optic cable. 4. An illuminated device as claimed in Claim 1, 2 or 3 characterised in that the or each fibre optic cable (20) is single stranded at the light unit (19) end and multi-branched at the display unit (18) end. 5. An illuminated device as claimed in any one of Claims 1, to 4 characterised in having a series of filters (25) interposable between the visible light unit (19) and the fibre optic cable (20). 6. An illuminated device as claimed in any one of Claims 1 to 5 characterised in having at least one prism (30. 7. An illuminated device as claimed in Claim 1 characterised in that heat, in the form of air heated in the or each- light unit (19) is transferred by pipe (52) from the or each light unit to an optical display unit (18). 8. An illuminated device as claimed in Claim 7 characterised in that air is returned from the or each optical display (18) to a light unit (19). 9. An illuminated device as claimed in Claim 7 or in Claim 8 characterised in having means for venting air from the or each optical display unit (18) and for allowing fresh air into the or each light unit (19). 10. An illuminated device as claimed in any one of Claim ^ to 9 characterised in that each light unit (19) contains a fan (54). 11. A vehicle pathway definition system (16, 17) including a series of optical display units (18) embedded in a surface of the pathway (10), and a series of light units (19) situated remotely from the optical display units (18), each light unit (19) being connected to at least one display unit (18) by means of a fibre optic calbe (20), whereby light is conveyed from the light units (19) to the optical display units (18), characterised in having means (20, 52) for conveying heat from the light units (19) to the optical display units (18). 12. A vehicle pathway definition system (16, 17) characterised in having a series of illuminated devices such as those claimed in any one of Claims 1 to 40. 13. An illuminated device substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings. 14. A vehicle pathway definition system substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings. SUBSTITUTE SHEET

Inventors: ARMOUR JOHN SINCLAIR, WATSON PETER MICHAEL FREDERICK, ARMOUR, JOHN, SINCLAIR, WATSON, PETER, MICHAEL, FREDERICK
Applicants: SECRETARY TRANSPORT BRIT, THE SECRETARY OF STATE FOR TRANSPORT IN HER BRITAN
Application year: 1986
Main classification: F21V8
IPC codes: B64F1, E01F9, F21V8, G02B6, G09F9, G09F13