GB2479758A

GB2479758A - Light source

Info

Publication number: GB2479758A
Application number: GB1006655A
Authority: GB
Inventors: Paul Littlefair; Andrew Williams
Original assignee: Building Research Establishment Ltd
Current assignee: Building Research Establishment Ltd
Priority date: 2010-04-21
Filing date: 2010-04-21
Publication date: 2011-10-26
Anticipated expiration: 2030-04-21
Also published as: GB2479758B; GB201006655D0

Abstract

A light source has a base 1, which may be an Edison screw or bayonet fitting, an open framework 3 of interconnected limbs 7 and a number of LEDs 5 supported by the framework 3. The open frame 3 allows cooling of the LEDs 5. The frame 3 may take a polygonal, spherical or other shape. The limbs 7 may be moveable to alter the shape of the frame 3, for example, between a collapsed and expanded position. The limbs 7 may be formed from a single piece of flexible sheet material (fig 4). A sensor may be provided.

Description

Light Source The present disclosure relates to a light source and more particularly to a light source that utilizes light emitting diodes (LED5).

Traditionally incandescent bulbs have been used to light homes, offices and other spaces. In recent years, however, there has been a move away from incandescent bulbs towards more energy efficient lighting solutions.

A particularly efficient source of electrical light is LEDs. A number of light sources that feature a plurality of LEDs have emerged as, among other things, replacements to traditional incandescent bulbs. These generally comprise a solid, or at least closed, body or substrate to which are mounted one or more LEDs or clusters of LEDs. However, these existing LED light sources suffer from a number of drawbacks that serve to reduce their efficiency. In particular, the light distribution is restricted and thermal control of the LEDs is hindered, reducing efficacy.

The present invention arose in a bid to provide a more efficient light source.

According to the present invention in a first aspect, there is provided a light source comprising a base and a frame, which is connected to the base and supports a plurality of light emitting diodes (LED5), wherein the frame is an open structure comprising a plurality of interconnected limbs.

By virtue of the open frame arrangement, cooling air can circulate within and around the frame, which allows the LEDs to run more efficiently. Moreover, the open frame arrangement allows for the omission of an envelope around the light source.

The frame preferably comprises a three-dimensional structure.

The frame preferably comprises two or more limbs that are connected to the base at their first ends and are connected to each other and/or to further limbs at their second ends.

The limbs may be arranged such that the distance between their first and second ends may be varied.

The limbs may combine to form a substantially polyhedral or spherical frame. In particular, the limbs may combine to form a tetrahedron, a hexahedron, an octahedron, a dodecahedron, an icosahedron, a pyramid, a bipyramid, any other polyhedron, or a sphere.

The limbs may comprise elongate wire-like elements.

The limbs may comprise strips of sheet material. The limbs may extend radially outwardly from a central region. The limbs and central region may be unitarily formed from a single sheet of material.

Opposite ends of the limbs to the ends connected to the central region may be attached to the base. The central region may be maintained in spaced relation to the base bythe limbs.

The central region may be attached to the base, and the opposite ends of the limbs to the ends connected to the central region may be arranged to be movably connected to the base, such that the distance between the first and second ends of the limbs may be varied. The base may comprise a substantially tubular element, wherein the central region may be fixed to an end of the base and the opposite ends of the limbs to the ends connected to the central region may be connected to a collar that is slidably received on the tubular base. Means may be provided for maintaining the spacing between the first and second ends of the limbs at a desired and/or predetermined distance. The means may comprise one or more stops that resist movement of the collar relative to the base.

By providing means for varying the distance between the first and second ends of the limbs, the light source be collapsed for storage and transportation. Moreover, a single light source may be provided that may be user configured to suit various situations, simply by varying the distance. By varying the distance, the curvature of the limbs will vary and so will the light distribution. Different degrees of limb curvature will provide different light distributions that suit different situations.

The frame may be rigid or, alternatively, may be flexible to allow re-configuration of its three-dimensional shape, and means may be provided to maintain the frame in its reconfigured shape.

The limbs may be formed from a flexible material and the means for maintaining the frame in its reconfigured shape may comprise a plurality of bendable elements, which are arranged to hold their shape when bent to a desired position. The bendable elements may comprise conductors connected to the limbs, which form part of a circuit to which the LEDs are connected. The bendable elements may be formed from metal.

A plurality of spaced apart LED connection points may be provided at predetermined points on the frame. One or more of the connection points may be arranged to receive a single LED. One or more of the connection points may be arranged to receive a cluster of LEDs. The connection points may be provided at vertices between interconnected limbs and/or may be provided at intermediate points on the frame. The connection points may comprise sockets arranged to removably receive the LEDs.

A plurality of LEDs may be arranged to emit light in the same direction.

A range of light sources may be available with different frame configurations and/or different LED configurations, wherein the configurations are arranged to suit different lighting situations, such as use in different shaped shades or different styles of lamp. In one or more of these light sources, there may be provided a number of LEDs that emit light in the same direction as each other with the remaining LEDs emitting light in different directions to each other.

The base preferably comprises a lamp base, arranged for connection to a conventional light fitting. The lamp base may comprise an Edison screw fitting, a bayonet fitting, a bi-pin fitting or a bi-pin turn and lock fitting.

The lamp base preferably houses a power supply and/or control circuitry arranged to power/control the LEDs.

At least one sensor may be provided on the frame, which is arranged to control the LEDs. The sensor may comprise an occupancy sensor, a daylight sensor or an IR controller.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of a light source according to the invention in a first embodiment; Figure 2 shows a perspective view of a light source according to the invention in a second embodiment; Figure 3 shows a schematic view of a frame (in developed state) of a light source according to the invention in a third embodiment; Figure 4 shows a perspective view of a light source (in a collapsed state) according to the present invention in a fourth embodiment; and FigureS shows a perspective view of the light source of the fourth embodiment in an expanded state.

Referring to Figure 1, there is shown a light source according to a first embodiment.

The light source comprises a base 1, a frame 3 and a plurality of LEDs 5. The LEDs may be organic or inorganic. The frame, as clearly shown, comprises an open structure/framework.

The frame supports the plurality of LEDs in spaced relation to one another. The LEDs, by virtue of the open frame, lie substantially in free space. There is no envelope, such as a diffuser or cover element, around (or inside) the frame. The frame is connected to the base.

The frame is formed by a plurality of interconnected limbs 7, which combine to form a polygonal frame. The faces of the polygonal frame are open. The limbs are thin elongate elements. The frame is a three dimensional structure in the form of a dodecahedron. It should be noted, however, that the number and configuration of limbs is not particularly limited and the frame may therefore take a range of geometrical shapes. Alternative suitable shapes include, for example, a tetrahedron, a hexahedron, an octahedron, a pyramid, a bipyramid and an icosahedron.

Furthermore, the limbs need not be linear but may be curved to provide for spherical or curved frame shapes.

Special frame geometries may be used to tailor the optical distribution of the light source and to optimise the light output ratio of the fitting. For example, for use in a cylindrical lampshade the light source could be based on a substantially cylindrical frame with the LEDs pointing predominantly upwards and downwards, whereas, for use in an uplighter or wall washer, the LEDs could be mounted on a substantially flat or spoon shaped open frame, pointing upwards.

The frame may be formed from plastic. Any suitable plastic may be used, as will be readily appreciated by those skilled in the art. The frame may be formed as a unitary structure from a one piece moulding, or may be built up from two or more component parts. The wiring (not shown) to provide power to the LEDs from the base may be routed through the limbs of the frame. This is preferred since it limits any obstruction to the passage of light or cooling air. Alternatively, however, the wiring may be run along the respective limbs, or between the limbs.

Whilst a rigid frame is shown, it should be appreciated that the frame may alternatively be flexible. The frame may be made flexible by forming it from flexible limbs.

The use of a flexible frame allows for reconfiguration of the three dimensional shape of the frame to thereby alter the directionality of light emitted from the LEDs. It also allows for the frame to be flattened for packaging/transporting. In the event the frame is flexible, means will be provided to maintain the frame in its reconfigured shape. This means may, for example, take the form of a bendable metal wire attached to or embedded within each or some of the limbs. It should be appreciated that such bendable wires may form part of the wiring that provides power and/or control signals to the LEDs. In addition to maintaining the frame in the reconfigured shape, the wire (or other means) will aid to ensure sufficient rigidity in the frame to allow the light fitting to be inserted into a light fitting by the user.

In the case of either a rigid or flexible frame, the frame may be made up of coaxial limb elements that contain the conductive elements for providing power to the LEDs. In the event of a flexible frame, a bendable metallic sheath may be provided that maintains its shape when bent, which may or may not comprise one of the conductive elements.

An alternative means for allowing for reconfiguration of the frame is by the provision of a frame that is formed from rigid limbs but which is provided with flexible joints at the interconnections of the limbs/vertices of the frames. These flexible joints may be in the form of ball joints or bendable joining elements.

The LEDs are attached to the frame at connection points, which are located only at vertices between the limbs of the frame. The connection points may alternatively, however, be located at points on the limbs other than the vertices (as shown in Figure 2), or may be located both at the vertices and at other points on the limbs.

The LEDs are outwardly directed, so as to emit their light outwardly from the frame.

The LEDs are each individually mounted to a substrate that is attached to the frame at an appropriate connection point, wherein any suitable fixing means may be used to connect the substrates to the frame connection points. Alternatively, however, a fixing/socket may be provided at each connection point that is arranged to removably receive the pins of an LED. By such arrangement it is possible to provide fixed frame configurable light sources or to increase the configurability of flexible frames or frames provided with flexible joints. The frame may be adapted to suit several different applications by plugging LEDs into appropriate points on the frame to optimise the distribution of light for a particular application, increasing the efficacy of the light source. Such configuration could be performed by a user or alternatively during manufacture.

Rather than providing isolated LEDs at the connection points, or providing fixings that receive a single LED only, there may be clusters of LEDs provided at each of these points, formed either by mounting plural LEDs on each of the substrates or by forming fixings that may receive clusters of LEDs. The clusters may each comprise a plurality of LEDs, for example 2 to 5 LEDs, in close proximity to one another. There may also be arrangements provided that include both clusters and single LEDs at different connection points. The LED configurations may be tailored to meet specific lighting requirements.

The LEDs may all be of the same colour, may comprise a plurality of different coloured LEDs (arranged to balance the colour rendering of the light source), or may be colour changing LEDs.

The base comprises a lamp base for connection to a conventional light fitting. In the present embodiment the lamp base comprises an Edison screw fitting. It will be appreciated, however, that the base may take numerous other forms, including but not limited to, a bayonet fitting, a bi-pin fitting or a bi-pin turn and lock fitting. The light source is provided as a replacement to conventional light bulbs (including, but not limited to, incandescent, fluorescent, halogen, or existing LED based bulbs) and may therefore be adapted to fit any conventional light fitting/lamp holder.

The light source may be arranged to be powered from a mains supply or from a low voltage (e.g. 12v) power supply. In the event it is arranged to be powered from a mains supply, there will be provided a power supply unit (not shown), the power supply unit in the present embodiment is mounted in the lamp base. In alternative arrangements, however, the power supply circuit may be located within the frame, i.e. within the dodecahedron of the Figure 1 arrangement, rather than in the lamp base. The power supply unit may include a rectifying circuit and may include a voltage reducing network. Any suitable power supply unit may be used, as will be readily appreciated by those skilled in the art.

A suitable power supply unit may also be provided when the light source is arranged for use with a low voltage power supply.

Referring now to Figure 2, there is shown a second embodiment. The frame is of an octagonal shape in profile and the LEDs are located on the limbs at positions between the vertices. In addition to LEDs there is provided a sensor 9. Whilst a single sensor is shown, there may be a number of sensors provided. The sensor is attached to a control circuit. The control circuit may be combined or integrated into the power supply unit.

The sensor may be a presence detector, such as a passive IR (infrared radiation) sensor, configured to switch off the light source when a room is unoccupied; a photocell, configured to switch or dim the light source when ambient light reaches a predetermined level; or an IR detector linked to a remote control, or similar, arranged to allow a user to dim or switch the light source or change the colour of the LEDs. The open frame allows the sensor to be integrated into the light source itself. Moreover, since there is no diffusing envelope, there is nothing to obstruct the operation of the sensor.

It should be appreciated that any of the light sources according to the present invention may include one or more sensors as described above.

Referring now to Figure 3, there is shown, in developed state, the frame of a light source according to a third embodiment. The inner face of the developed frame is shown schematically.

The frame is arranged to provide a substantially spherical frame. The frame comprises six interconnected limbs, which are all formed from a single piece of flexible plastic. More or less limbs may, however, be provided. The limbs are interconnected in a central region 11 and are arranged to extend radially outwardly therefrom. The free ends of the limbs are arranged to be connected to the lamp base, which is in accordance with the lamp base described above. With the free ends connected to the lamp base the limbs will bow outwardly between the central region and the lamp base to produce a substantially spherical light source.

The inner face of the frame is provided with a wiring pattern that comprises two circuits. The circuits may be printed. The circuits may alternatively be provided on the outer face or lie within the frame. The first circuit is arranged to provide power to the LEDs, from the power supply unit, and comprises a pair of power rails extending along each of the limbs, which are connected to respective rings in the central region. The second circuit is arranged for connection to a control circuit (not shown), which includes one or more sensors of any of the types discussed above for controlling the LEDs. The second circuit comprises a pair of secondary power rails extending along one of the limbs and connected to respective secondary rings in the central region. Alternative circuit arrangements will be readily appreciated by those skilled in the art.

The limbs may be provided with means for configuring the shape of the limbs, such means may comprise bendable metal elements, as discussed above. Such elements may comprise one or more of the power rails that extend along the limbs.

The LEDs are connected to the outer face of the limbs (the opposed face to that shown in Figure 3) at predetermined connection points. The LEDs are directed outwardly of the sphere. The LEDs may be connected by any of the previously discussed means. The sensor is mounted to the outer face of the central region.

It should be appreciated that the sensor may be omitted, in which case the second circuit may also be omitted.

-10 -Referring now to Figures 4 and 5, there is shown a fourth embodiment. The light source of this embodiment is shown in a collapsed state in Figure 4 and in an expanded state in Figure 5.

The lamp base 1 is extended, as compared to the previously described embodiments. The lamp base is substantially tubular and comprises a fitting at its end for connection to a conventional light fitting. Whilst it is shown to be an Edison screw fitting, any of the abovementioned fittings may be adopted.

The frame 3 is connected to the base. The frame is similar in construction to the frame of the third embodiment. In contrast to the frame of the third embodiment, however, it comprises eight interconnected limbs 7. More or less limbs may be provided.

The limbs are all formed from a single piece of flexible plastic. The limbs represent strips that are interconnected in a central region (not shown) in the same manner as in the third embodiment and are arranged to extend radially outwardly therefrom. The central region is positioned at the opposite end of the tubular base to the light fitting and is fixed thereto.

The outwardly extending limbs are arranged to extend along the outer surface of the tubular base and are connected at their outer ends to an annular collar 13. The annular collar comprises a ring that is slidably received on the outer surface of the tubular base.

The LED5 5 are connected to the outer face of the limbs at predetermined connection points. The LEDs are directed outwardly. The LEDs may be connected by any of the previously discussed means. A sensor 9 is mounted to the outer face of the central region. One or more of the previously mentioned sensors may be used. In alternative arrangements, the sensor may be omitted.

-11 -The power supply unit, and the control circuit for the sensor, is located within the tubular base. The power supply circuit and the control circuit may be integrated. To limit heat gain to the LEDs the power supply unit may be located in the top of the tubular base, adjacent to the light fitting.

The frame is provided with a wiring pattern that comprises a circuit for providing power to the LEDs. The circuit may be printed. The circuit may alternatively be provided on the outer face or lie within the frame. A pair of power rails for providing power to the LEDs may extend along each of the limbs in a similar manner to the arrangement of Figure 3.

Suitable wiring will be provided for connection of the sensor. Any suitable circuit arrangements may be adopted, as will be readily appreciated by those skilled in the art.

The frame may be expanded from the state shown in Figure 4 to the state shown in Figure 5 by sliding the collar down the outer surface of the tubular base towards the end of the tubular base, i.e. by bringing the ends of the limbs (connected to the collar) towards the opposite ends of the limbs (connected to the central region). Such movement causes the limbs to bow outwardly between the collar and the central region, which is fixed to the end of the tubular base.

The plastic from which the limbs are formed preferably has an inherent resilience such that when the limbs are bowed by pushing down the collar, a return force is applied to the collar in the opposite direction. As shown in Figure 5 a series of stops are provided on the tubular base, these are arranged to allow the downward travel of the collar but to prevent the return of the collar back up the tubular base, and allow for varied degrees of curvature of the limbs and to thereby provide different light distributions. These stops may take any suitable form. In the depicted arrangement they comprise flexible plastic tabs 15.

Preferably, a user may manipulate the tabs to allow for upward travel of the ring should they want to return the light source to the collapsed configuration. Alternative means may be provided for maintaining the light source in the expanded state of Figure 5, as will be -12 -readily appreciated. For example, the collar may be arranged such that friction between the collar and the outer surface of the tubular base is sufficient to maintain the collar in a desired position along the tubular base.

The expanding design, in addition to offering the benefit of different light distributions, offers particular benefits for packaging and shipping the light source. For packaging/shipping the sliding collar may be positioned at the top of the lamp base, reducing the size of the light source (see Figure 4). The user may then slide the collar down to one or more predetermined positions to form the light source into a sphere (see Figure 5).

As will be appreciated, whilst the light source is shown in Figures 4 and 5 in collapsed and expanded states, respectively, a number of other states are possible by varying the spacing between the opposed ends of the limbs, as discussed above. The collar may be retained at a number of appropriate positions, which positions may be pre-determined in the event that tabs are provided or may be any desired position in the case of a frictional engagement. The collar may, for example, be arranged to be retained at positions ranging from that in Figure 4 to beyond that shown in Figure 5 (to create frames that are wider than they are high, i.e. over-spheres) and including positions inbetween.

By virtue of the present invention, as defined by the claims, a light source is provided in which: air can circulate around the LEDs ensuring that they are kept cool and run more efficiently; there is no envelope around the light source, eliminating optical losses and allowing uninhibited air flow and the provision of one or more sensors to control the LED5; an arrangement of LEDs may be provided that allows an even distribution of light in all directions or a specially configured arrangement of LEDs may be provided to achieve a desired distribution of light; and the number and distribution of LEDs that may be provided limits their intensity, reducing glare.

Claims

-13 -Claims 1. A light source comprising a base and a frame, which is connected to the base and supports a plurality of light emitting diodes (LED5), wherein the frame is an open structure comprising a plurality of interconnected limbs.
2. A light source as claimed in Claim 1, wherein the frame comprises a three-dimensional structure.
3. A light source as claimed in Claim 1 or 2, wherein the frame comprises two or more limbs that are connected to the base at their first ends and are connected to each other and/or to further limbs at their second ends.
4. A light source as claimed in Claim 3, wherein the limbs are arranged such that the distance between their first and second ends may be varied.
5. A light source as claimed in any preceding claim, wherein the limbs combine to form a substantially polyhedral or spherical frame.
6. A light source as claimed in Claim 5, wherein the limbs combine to form a tetrahedron, a hexahedron, an octahedron, a dodecahedron, an icosahedron, a pyramid, a bipyramid, or a sphere.
7. A light source as claimed in any preceding claim, wherein the limbs comprise elongate wire-like elements.
8. A light source as claimed in any preceding claim, wherein the limbs comprise strips of sheet material.
9. A light source as claimed in Claim 8, wherein the limbs extend radially outwardly from a central region. -14-
10. A light source as claimed in Claim 9, wherein the limbs and central region are unitarily formed from a single sheet of material.
11. A light source as claimed in Claim 9 or 10, wherein the opposite ends of the limbs to the ends connected to the central region are attached to the base.
12. A light source as claimed in Claim 11, wherein the central region is maintained in spaced relation to the base by the limbs.
13. A light source as claimed in Claim 9 or 10, wherein the central region is attached to the base, and the opposite ends of the limbs to the ends connected to the central region are arranged to be movably connected to the base, such that the distance between the first and second ends of the limbs may be varied.
14. A light source as claimed in Claim 13, wherein the base comprises a substantially tubular element, wherein the central region is fixed to an end of the base and the opposite ends of the limbs to the ends connected to the central region are connected to a collar that is slidably received on the tubular base.
15. A light source as claimed in Claim 13 or 14, wherein means are provided for maintaining the spacing between the first and second ends of the limbs.
16. A light source as claimed in Claim 15, wherein the means comprises one or more stops that resist movement of the collar relative to the base.
17. A light source as claimed in any preceding claim, wherein the frame is flexible so as to allow re-configuration of its three-dimensional shape, and wherein means are provided to maintain the frame in its reconfigured shape.
18. A light source as claimed in Claim 17, wherein the limbs are formed from a flexible material and the means for maintaining the frame in its reconfigured shape comprises a -15 -plurality of bendable elements, which are arranged to hold their shape when bent to a desired position.
19. A light source as claimed in Claim 18, wherein the bendable elements comprise conductors, which form part of a circuit to which the LEDs are connected, and which are connected to the limbs.
20. A light source as claimed in any preceding claim, wherein a plurality of spaced apart LED connection points are provided at predetermined points on the frame.
21. A light source as claimed in Claim 20, wherein one or more of the connection points is arranged to receive a single LED.
22. A light source as claimed in Claim 20 or 21, wherein one or more of the connection points is arranged to receive a cluster of LEDs.
23. A light source as claimed in any of Claims 20 to 22, wherein the connection points are provided at vertices between interconnected limbs.
24. A light source as claimed in any of Claims 20 to 23, wherein the connection points are provided at intermediate points on the limbs.
25. A light source as claimed in any of Claims 20 to 24, wherein the connection points comprise sockets arranged to removably receive the LEDs.
26. A light source as claimed in any preceding claim, wherein a plurality of the LEDs are arranged to emit light in the same direction.
27. A light source as claimed in any preceding claim, wherein the base comprises a lamp base, arranged for connection to a conventional light fitting.

-16 -
28. A light source as claimed in claim in Claim 27, wherein the lamp base comprises an Edison screw fitting, a bayonet fitting, a bi-pin fitting or a bi-pin turn and lock fitting.
29. A light source as claimed in any preceding claim, wherein the lamp base houses a power supply unit and/or control circuitry arranged to power/control the LED5.
30. A light source as claimed in any preceding claim, wherein at least one sensor is provided on the frame, which is arranged to control the LEDs.
31. A light source as claimed in Claim 30, wherein the sensor comprises an occupancy sensor, a daylight sensor or an IR controller.
32. A light source substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.