LIGHTING SYSTEM WITH EDGE EFFECT

This invention relates to a lighting system and in particular a Light Emitting Diode (LED) based lighting system that has an edge light effect. More specifically, although not exclusively, the present invention relates to a system that provides light from a modular system that utilises LED's and a particular light guide design to provide a unique light engine, which offers unique edge lit aesthetic appearance providing a light output distribution with very high lighting efficiency and thermal management.

The present invention has applications in lighting system in general and in particular to lighting systems that have a central lighting arrangement where the light is to be distributed to remote sites for usage. A typical example of one of these types of systems is a general purpose illuminated bollard. In this application the lighting arrangement will be described and exemplified with respect to a bollard based system.

Lighting bollards have been a part of common day life, within city and town or other urban or extra-urban environments, for a number of years, and are often used as pedestrian, traffic or feature bollards. One conventional bollard system comprises a louvred light unit, whereby light generated by a central lamp (obscured by a plurality of louvres) is reflected off louvre surfaces and generally directed into the area to be lit. Normally the bollard only has two conditions, namely on and off.

A problem associated with such conventional arrangements is that a significant proportion of the light generated by the bollard light source is wasted. It is estimated that, in a conventional bollard, in the region of only 30% of the light generated may be emitted into the area to be lit. The remaining 70% is wasted. This represents a significant wastage both in terms of energy and cost.

The aim of the current application is to provide a system in which the efficiency of energy usage and light provision in the bollard is significantly increased leading to a smaller carbon footprint.

In accordance with a first aspect of the present invention there is provided a lighting system including at least one LED (Light Emitting Diode) array which has at least one LED connected to a circuit board; at least one support provided and connected to LED array(s); and an optical transmission waveguide element composed of

transparent or translucent material to guide the light to the required components of a device including said lighting system for illumination wherein the waveguide element is arranged and configured so that the light entering the waveguide element enters at an angle that it impinges the boundaries of the waveguide element at an angle below the internal refractive angle of the waveguide element and is reflected back into the body of the waveguide element and transmitted along the length of the element.

The present invention is advantageous in that the resultant light control may enable a tailored light distribution into ^' the area to be lit, which could be used to prevent light pollution.

It will be well appreciated by those skilled in the art that the choice of material for the forming of the waveguide element depends significantly on the actual usage to which the lighting system is to put and well as the effect that is desired. In the instance where the waveguide element is being used to simply transmit light from one point to a second point for usage the choice of material will be of a clear or transparent material to achieve maximum efficiency in the transmission. However in the circumstances where a lighting effect, such as a glow, is desired in the waveguide element then a translucent material that glows will be selected.

It will be appreciated that the angle of incidence of the light with the edges of the waveguide are critical to whether the light will be reflected and thereby transmitted along the length of the element to its point of usage or alternatively is transmitted through the walls of the element and into the surrounding space. It is therefore important to the efficient working of the present invention that the waveguide design is correct.

It is well known that light introduced into a transparent material can be guided inside the body of the material between points if total internal reflection is achieved when light impinges the walls of the body of material, waveguide element in this case. These bodies of material are commonly referred to as Light Guides. In a preferred embodiment of the present invention the optical system works on the principles of the original light guide architecture and guides light from the LED's until it reaches the desired destination.

In one embodiment of the present invention the waveguide element comprises with the circuit board a means by which the light transmission system is controlled so as

to control the light transmitted through the lighting system to the destination. In one embodiment of the present invention the waveguide element includes means so that the light being transmitted along the waveguide is guided towards the edge for transmission to the desired point of usage, the desired output site in the desired direction. Different light output distributions and lighting patterns can be achieved and controlled by:

• changing the cross sectional profile of the and inclination of the waveguide element:

• selection of the material from which the waveguide guide element is manufactured:

• design of specific waveguide edge profiles, for example via incorporating single or multiple edge prisms, single edge curvatures or multiple edge curvatures: and

• adjusting the size and proportion of the material in the material shape.

• Changing the position of LED's with respect to the light guide to adjust focus in one or more directions (typically horizontal & vertical focus).

In one embodiment of the present invention the circuit board is a PCB (printed circuit board) and may be a rigid or flexible circuit board. Using high powered LED's as the primary light source and intermediate low powered LED's to create coloured effects.

The LED arrays of the system may be mounted onto the circuit board. Alternatively the system may include more than one circuit board each of which circuit boards has one or more LED arrays attached or connected thereto.

In. one arrangement of the present invention the support is a common support for all the circuit boards in the bollard. Further in a preferred arrangement of the invention the support for the circuit board or boards also acts as the heat sink for the system.

In one arrangement of the present invention the lighting system includes a number of circuit boards each of which circuit boards has a number of LED arrays deployed thereon. In one arrangement it is envisaged that the lighting system will include a

number of waveguide elements deployed vertical spaced apart along the length of a post which includes the circuit board support or heat sink member, and circumferentially spaced apart around said post are a number of vertically hanging flexible circuit boards each of which includes a number of vertically spaced apart LED arrays wherein the LED arrays are spaced on the circuit boards to coincide with the vertical disposition of the waveguide elements.

The heat sink may be formed from any suitable material such as aluminium or other good heat conductor. The heat sink may be formed by casting or extruding.

In one arrangement of the present invention the heat sink also provides the support for the circuit boards. The heat sink may be formed with a central flow channel so that fluid cooling medium, for example air, can be circulated to assist and any cooling.

The waveguide element may be formed from any suitable material. This is a material that is transparent or if desired translucent and which is capable of being worked to a define shape which retains the defined form. Typical examples of suitable materials are polymeric materials such as for example acrylic polymers, or polycarbonates.

In a preferred embodiment of the invention the waveguide element is formed by thermoforming, for example injection moulding.

The waveguide element is shaped to assist the transmission of the light within the body of material and to assist this and also attain the correct angle of incidence for the light against the boundaries of the waveguide element.

When the waveguide element is deployed for use, for example in an illuminated bollard, the waveguide element may be deployed so that it circumferentially surrounds the heat sink and support for the LED array(s) and in particular the LED's. In one particular arrangement it is envisaged that the waveguide element is formed with a central orifice into which the support/heat sink may be located. Preferably, the heat sink and the orifice are both shaped and sized so that when deployed with respect to each other they are a close fit. In one example of the present invention the waveguide element may be push fitted onto and about the LED's mounted on the heat sink.

The waveguide element may be formed so that its thickness tapers from an inner portion towards the outer edge. Further the major surfaces of the waveguide element are formed with flat surfaces the shape of which changes in a continuous manor so that there are no discontinuities in the major surfaces.

The light directed into the waveguide element from the LED's is directed in via a dedicated surface which surface may be shaped to enhance the catchments of the light emitted as well direct the light at the correct angle into the body of material. In one example the surface is shaped to curve about the LED's to maximise the catchments of light.

Waveguide element may also include means at the point of usage for the light that directs the emitted light towards the point of usage in a focused manner. The means that directs the emitted light may comprise a series of prisms or other optical changing means that modifies the angle and/or focus of the emitted light.

In one embodiment of the present invention it is envisaged that the waveguide element may be divided into more than one discrete light transmission path.

The lighting system of the present invention has been developed for use with the visible spectrum to provide a bollard with a controlled and efficient lighting arrangement. In one arrangement of the system it is envisaged that the bollard will include a lighting arrangement in which the LED arrays are directed or mounted such that light is directed into the element at the correct angle to allow transmission of the light through and along the length of the element,

The present invention may be used with any wavelength of light or a mixture of wavelengths.

In one arrangement of the present invention it is envisaged that a combination of low powered and high powered LED arrays will be used wherein the high powered LED are used to transmit light into the waveguide elements and the low powered LED provide a general lighting effect.

The circuit board of the present invention may include means which controls the power supply to the LED's connected the circuit and the circuit board carries means which enables the individual or groups of the LED's connected to the board to be switched on and off as desired. The LED's of an array or of the arrays of the system may emit light of different wavelengths and therefore different colours. In

this manner the system can be controlled so that the bollard emits light of a different wavelength or colour in response to a control signal received by the circuit board.

Further the ability to switch the LED's of an array on and off can be used to control the actual light distribution pattern that is emitted by the bollard or a group of bollards. This function may additionally or alternatively be used to control the colour of the light emitted by the Bollard, resulting in the creation of light flashing patterns and/or signalling. The bollard may be operated in a number of modes including a stable on mode in which the light emitted by the bollard is substantially constant and a number of time-dependent or flashing modes as required. Such different modes may be used for day and night time operation respectively.

Further with regard to the light bollard design the optics of the bollard can be modified to have different external shapes to create different edge lit profiles, thus enabling different light distributions per light guide louvre. A collection of vertical louvres, each using a different lit edge effect, could be collated into a single luminaire with a pre-determined overall light distribution.

In brief, the present invention can be said to comprise a LED lighting system that has an architecture adapted to produce optimum light control and a unique edge lit external aesthetic. The system allows lot of embodiments by changes the shape of the edge lit or mixing different LED colours or LED's switching configurations.

One of the major advantages of the present system relates to the power usage and therefore the carbon footprint of the system. It will be well appreciated by those skilled in the art that the use of LED's in system when considering the level of light generate to power consumption are more efficient that standard lighting elements. However in addition to this with the present invention the efficiency of the light generated by the system to the light used and emitted by the bollard is also significantly increased because of the controlled way in which light is transmitted to the point of usage.

It will be well appreciated by those skilled in the art that the lighting system and the control that it provides is suitable for use with any lighting system in which light is transmitted from a source point to a point of usage that is separated from the source, and particularly where there may be separate and disparate points of usage.

In accordance with a second aspect of the present invention there is provided apparatus including a lighting system made in accordance with the first aspect of the present invention.

There may be provided apparatus including at least one lighting system made in accordance with the first aspect of the present invention.

The invention will now be illustrated by way of description of an example made in accordance with the present invention and with reference to the accompanying drawings:

Figure 1 is schematic representation of a general lighting bollard made in accordance with the present invention;

Figure 2 is a schematic side view representation of a light box and waveguide arrangement of the current invention;

Figure 3 is a schematic representation of the edge structure of a waveguide element made in accordance with the present invention;

Figure 4 is schematic plan view of the light box and waveguide element as shown in Figure 2 of the drawings;

Figure 5 is detailed view of the system of Figures 2 to 4;

Figure 6 is a detailed view of a lighting device including the lighting system of the current invention;

Figure 7 shows a part cut away side view of a second lighting device incorporating a lighting system made in accordance with the present invention; and,

Figure 8 shows an exploded three dimensional view of the embodiment of figure 7.

The invention will now be described with regard to a lighting bollard 1. A bollard according to the present invention finds one particular use in relation to pedestrian management. More specifically, the bollard may be used in an amenity application in order to provide illumination of pedestrian thoroughfares. However it will be appreciated that the present invention is not limited to any such use and may be applicable to any situation in which a visual indication and/or physical obstruction is required.

The illuminated bollard 1 takes the form of a generally upright post or housing and includes a an outer shell member 2 which includes a number of discrete sections adapted to be illuminated to either display a message or sign or simply provide an indication that the bollard is in fact there; a central post 3 including at least one light box; and a number of waveguide elements 4 deployed about said central post and extending outwardly thereform to the outer shell of the bollard 1.

Now referring to Figures 2 to 5 of the drawings there is shown a lighting arrangement 10 for use with the present invention. The lighting arrangement includes:

a support member 11 of circular cross section which has an upper end 12 of greater diameter than the lower end 13 and which has a longitudinally extending passage 14 through the centre thereof:

a number of circuit boards (PCB) 14 deployed about the upper lip of the support member; and

a waveguide element 15 having an inner orifice 16 so that when deployed, the waveguide element circumferential extends around the upper section of the support member 11 spaced therefrom.

The circuit boards are rigid circuit boards having an elongate nature. The circuit boards are suspended to hang substantially vertical along the surface of the post 2. A number of LED arrays are spaced along the length of the circuit board at discrete positions.

The circuit boards may be used to control the light pattern of the bollard including circuitry that enables the power supply to the individual arrays on the circuit board to be varied and even switch on and off so that the appearance of the bollard can be suitably controlled as desired.

The waveguide element 15 is in a preferred embodiment a substantially continuous or uniform solid body and may be formed by injection moulding. The waveguide element 15 is formed so that the orifice 16 substantially conforms to the shape and sizing of the post 2. The waveguide element is fitted to the post by push fitting the waveguide element over the post and sliding it into position. In position the waveguide elements 15 overlays the appropriate LED array of each of the circuit boards so that the arrays are trapped between the waveguide element 15 and the

post 2. Therefore the waveguide element 15 is deployed about the central post so that the LED's are adjacent the edge of the waveguide element 15 formed about the orifice 16.

Further the waveguide element 15 of the present example is shaped so that it extends outwardly and downwardly from its centre. Thus the waveguide element is angled obliquely to the post in a generally downward direction. The non linear, curved shape of the waveguide element results in a non-uniform angle between the waveguide element and post. However the approximate angle of inclination of the waveguide is approximately between 5 and 45° from horizontal when the post is substantially vertical.

Further the overall cross sectional shape of the waveguide element 15 slightly tapers from the innermost portion towards its outer peripheral edge. Thus the waveguide element 15 is thinnest towards its outer periphery.

In addition the edge of the waveguide element 15 surrounding the orifice 16 is curved so that it extends slightly around the LED's to maximise the take up of light from the LED into the waveguide element 15. In this regard, the wave guide element has an inner rim or flange adjacent its inner edge which may be shaped to define a curved or otherwise shaped inner periphery of the waveguide element to receive the LEDs.

All of the above shaping is determined based on the characteristics of a particular system, and is worked on the basis of ensuring the angle of impingement of light being transmitted through the waveguide element 15 on the boundaries of the waveguide element 15 is below the internal refractive angle of the material.

The waveguide element 15 is shaped so that the light entering the waveguide element 15 from the LED's enters at angle which means when the light impinges the boundary of the waveguide element 15 at an angle that is below the internal refractive angle of the material and is therefore reflected back into the body of the waveguide element 15. In this way the light is transmitted from one edge, the edge surrounding the orifice, to the other edge, the outer edge of the waveguide element 16 and thereby to its point of usage.

Further to improve the efficiency of the transmission to the point of usage of the light the outer edge of the of the waveguide element 15 may be adapted to direct

and/or focus the light appropriately. The edge may be formed with prisms, see figure 3 of the drawings.

The waveguide element 15 is formed from a polymeric material, for example Poly Methyl Methacrylate (PMMA) that is a very good light transmitter and is freely available. Thus the waveguide is a substantially solid and may be formed of a material which is substantially uniform throughout.

Figure 5 of the drawings shows the assembled lighting arrangement for use in a system and shows the light paths through the system.

Now turning to Figure 6 of the drawings there is shown lighting assembly using the lighting arrangement of the present invention. In this example of the invention there is shown a central post 2 about which is disposed four waveguide elements 15 spaced apart along its length. The components of the system are identical to those described above and like numerals have been used to describe like components.

It can be seen that each waveguide takes the form of an angled brim-like or annular body depending outwardly from the central post 2. The form of the waveguides is generally frusto-conical save that the inner and outer peripheral edges are not circular in plan in the embodiment shown. However such edge profiles are not excluded. Thus the waveguides are arranged about and at least partially surround the post 2.

Now turning to Figures 7 and 8 of the drawings there is shown a second device incorporating a lighting system made in accordance with the present invention. This lighting system is an attachment 100 for use on a bollard.

The attachment includes a top aluminium plate 102, a bottom aluminium plate 103 including a fitting 101 for attachment to a bollard; and a circumferentially extending body member 106 which spaces the top plate 102 from the bottom plate 103: and a central post 105 extending centrally of the plates 102 and 103 between the two plates.

It will be appreciated that the device 100 is shown part in section, such that the right hand side of figure 7 shows the internal formation of the device, whilst the left hand side shows the outer surface of the circumferentially extending body member.

The body member 106 is formed from PMMA and is cast moulded. The body member includes an outer wall section 107 and includes four internal formations

108 extending inwardly from the wall section 107 to define free space in the centre of the body member 106 between adjacent formations 108. The formations are plate like and may be generally annular in form. The body member 106 and the internal plates 108 thereof comprise the waveguide elements of the present invention.

Each of the internal plates 108 extends at an angle downwardly from the centre to the wall 107 and tapers from the centre to the wall 106. The plates 108 are formed integrally with a section of the wall 107. Thus the body 106 is divided into a series of levels or tiers, each of which- are connectable to an adjacent tier to form the body member. Accordingly each tier is provided with a connection formation on its upper and lower edge for engagement with a corresponding connection formation on the adjacent tier. Each of the tiers may be substantially the same shape as the remaining tiers.

The centre post 105 includes an upper section and a lower section and is octagonal in shape. Disposed about the outer surface of the post are a number of rigid circuit boards that may hang down the post so that they are in contact with one of the octagonal sides of the post. The circuit boards may be located at the upper edge of the post. Each circuit board has disposed thereon a series of equally spaced high powered LED arrays 109 and a series of equally spaced low powered LED arrays 110. The high 109 and low powered 110 LED series are interspersed such that the high and low power LED arrays alternate along the length of the post.

In this embodiment four high powered LED arrays 109 three low powered LED arrays 110 are provided.

The LED arrays are connected to the circuit board that includes a control circuit to control the operation of the LED's. The circuit board is configured to be able to switch the LED arrays on and off independently as desired. Further the high powered arrays may emit white light and the low powered arrays may emit coloured light. With this arrangement the white light is directed along the length of the waveguide elements and emitted through the sides of the body member. The coloured light from the low powered light passes into the waveguide element and acts to colour the appearance of the bollard.

The device may be constructed by positioning the tiers of the body member 106 over the central post 105 as shown in figure 8. The post may be conductive as in

the earlier embodiment and may be at least in part hollow so as to permit airflow therethrough.

It is intended that the features of the embodiments of figures 7 and 8 are interchangeable as far as practicably possible with the features of the embodiments of figures 1 to 6.