EP2600055A1

EP2600055A1 - Street lighting

Info

Publication number: EP2600055A1
Application number: EP12195352.5A
Authority: EP
Inventors: Guy Harding
Original assignee: Marshalls Mono Ltd
Current assignee: Marshalls Mono Ltd
Priority date: 2011-12-02
Filing date: 2012-12-03
Publication date: 2013-06-05
Also published as: GB201120749D0; GB2497282A

Abstract

An extruded heat-sink (20) is provided to act as a lantern housing. Here, an external lantern (10) includes an LED element (30) as the light source. In order to achieve good light output and long service life, it is necessary to dissipate the heat generated from the LED element (30). Consequently, the LED element (30) is coupled directly to the extruded heat-sink (20). Because the extruded heat-sink (20) acts as the lantern housing, it is not covered with a further housing and is instead exposed directly to the environment. The cooling of the heat-sink (20) and therefore the ability to dissipate heat away from the LED element (30) is improved, because the cooling of the heat-sink (20) by the external environment is not affected by trapped debris such as leaves etc. Avoiding a secondary housing, which may form an enclosure, also reduces the chance of hot air becoming trapped inside the lantern, which increases the heat of the LED unit (30), and provides an enclosure to act as a possible insect nest.

Description

The invention relates to exterior illumination devices, and in particular, although not exclusively, to LED based street lanterns and luminaries.
Street lanterns typically use discharge lamps. In such cases, a discharge lamp element is housed within a lantern housing which is supported atop a lamp post. The lamp post supplies the electrical supply and control signal to the lantern where required. The lanterns are typically arranged above a highway or a pedestrian area. The lamp posts are therefore typically several or more meters high in order to situate the lantern out of the way of passing traffic and potential vandalism threats and also to direct the light output downwards to help reduce light pollution.
There would be an advantage in providing an external lantern having reduced energy consumption whilst still maintaining a light output suitable to meet lighting standards. There would also be an advantage in reducing the service costs of the lantern by increasing the working life of the lamp element and reducing generally any maintenance or repair services to the lamp element during its operational life.
According to the present invention there is provided an external lantern and method of manufacturing an external lantern as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.
According to the exemplary embodiments, an extruded heat-sink is provided to act as the lantern body or lantern housing. Here, an external lantern includes an LED element as the light source. An optical element such as a lens or reflector is coupled to the LED element to modify the LED output for use as a lantern. In order to achieve good light output and long service life, it is necessary to dissipate the heat generated from the LED element. Poor or insufficient heat dissipation can lead to any of overheating, loss of efficiency and reduced product life. Consequently, the LED element is coupled directly to the extruded heat-sink. Because the extruded heat-sink acts as the lantern housing, it is not covered with a further housing and is instead exposed directly to the environment. If a secondary housing were used, vents may be provided to allow air to circulate around the heat-sink within the secondary housing. Because no secondary housing is used, the production and material costs can be reduced. The cooling of the heat-sink and therefore the ability to dissipate heat away from the LED element is also improved, because, for instance, the cooling of the heat-sink by the external environment is not affected by blockages caused by falling debris such as leaves etc. Avoiding a secondary housing, which may form an enclosure, also reduces the chance of hot air becoming trapped inside the lantern, which increases the heat of the LED unit, and provides an enclosure to act as a possible insect nest.
Suitably, in order to achieve the required light output, a plurality of LED elements may be used, for instance an array of LED elements. In one exemplary embodiment, an array of LED elements is used having a plurality of LED elements arranged in a matrix. Here, a plurality of LED elements are arranged in at least one direction, e.g. a width or length. Because different situations require different light levels, it is advantageous to be able to provide external lanterns having a different number of LED elements. Suitably, the LED elements are packaged within an LED bezel unit. In the exemplary embodiments, because the heat sink is extruded, the length of the heat sink and therefore lantern housing can be easily varied simply by cutting or extruding the extrusion to different lengths in order to mount a different number of bezel units. In contrast, if the lantern housing were, for instance, cast or formed from other moulding techniques, different moulds would be required for each lantern size and therefore the associated tooling costs would be dramatically increased. Consequently, according to the exemplary embodiments, there is provided a method of manufacturing an external lantern, the method comprising extruding a heat-sink and attaching at least one LED to the extruded heat-sink, wherein the extruded heat-sink forms the housing of the external lantern. Advantageously, the manufacturing method provides an adaptable process where different sized external lanterns can be formed by extruding or cutting the extruded heat sink to different lengths. Alternatively, the different lengths can be achieved by joining together multiple heat-sinks. Here, the heat sink is formed from a plurality of heat-sink modules. Advantageously, the extruded heat-sink is able to be anodised to provide protection from the environment, for instance corrosive protection. Furthermore, the heat-sink can be black anodised or anodised in a dark colour, which improves thermal transfer and heat emission.
In the exemplary embodiments, the extruded heat-sink has a constant cross-section. In one exemplary embodiment, a recess is formed along the length of the extrusion to receive the LED element. Preferably, the LED element is combined with the optical element in a sealed bezel unit. The bezel unit is suitably secured within the recess and sealed in place to provide hermetic protection to the electrical connections to the LED elements. Here, the LED elements are in direct thermal contact with the heat-sink. Whilst the LED elements can be in direct thermal contact with the heat-sink without being secured within a recess, for instance if the extruded heat-sink has a substantially flat attaching point so that the bezel unit stands proud of the heat-sink, the recess is preferable as it provides better protection to the bezel unit and also provides better thermal transfer properties as it substantially covers three-sides of the bezel unit. End cover plates may suitably be attached to the end of the extruded heat-sink. Importantly, because the cross-section of the extrusion does not change, the cover plates can be a common part independent to the number of LED elements present. The extruded heat sink preferably has a flat surface for interfacing with the LED bezel unit. This flat surface provides good thermal contact to the bezel unit, which improves thermal transfer. As a result of the extrusion process, no post-processing of the recess is required to achieve the flat surface.
In the exemplary embodiments, the heat-sink includes a side extension that extends to at least one side of the recess. A second side extension may also extend to the other side of the recess. The side extensions may include a plurality of fins that run the length of the extension. The fins may be arranged to cover substantially at least one or at least both of a top and bottom surface of the side extension relative to the recess. Here, the fins are formed during the extrusion process and form a plurality of ridges on the surface of the heat-sink to increase the surface area thereof. In one exemplary embodiment the heat-sink or each heat-sink module, when the heat-sink is formed from a plurality of heat-sink modules, is formed from a single extrusion. However, in an additional exemplary embodiment, the heat-sink or each heat-sink module is formed from one or more extrusions joined together in thermal contact. For instance, the side extensions may be extruded separately to the central or main body extrusion and attached thereto.
In the exemplary embodiments, a bracket head is attached to a portion of the heat-sink. The bracket head provides a connection to a bracket arm of a lamp post. For instance, the bracket head serves as a spigot entry for mounting the lantern. The bracket head may provide a housing for any of the power supply to the LED element, control gear, and a photocell where required. The bracket head is suitably attached to the heat-sink co-axially with the axis of the extruded heat-sink.
In the exemplary embodiments, the heat-sink is extruded to include a recess suitable to act as a cable conduit. The conduit-recess is connected to the LED elements in order to provide a cable routing from the bracket head to the LED elements. For instance, in the exemplary embodiments, the conduit recess is connected to the LED recess via through holes. The conduit recess is sealed by a cover plate.
It will therefore be appreciated that the exemplary embodiments provide an external lantern or luminaire that provides improved efficiency savings by allowing LED elements to be used at the optimum operating temperatures, whilst also reducing the complexity and cost of the manufacturing process. For instance, because an extrusion process is used for the heat-sink, the external lantern is easily adaptable to different lighting requirements by changing the length of the extruded heat-sink to accommodate a different number of LED elements with reduced tooling costs and part changes.
In an alternative exemplary embodiment of an external lantern, an external heat-sink is directly coupled to an LED bezel unit. The heat-sink includes a first side extension, wherein the heat-sink extends a distance from the LED bezel unit that is at least 50% of the width of the bezel unit. The heat sink has a substantially smooth upper surface, where, in use, the upper surface is arranged to be facing upwardly. Here, substantially smooth does not preclude the surface having ridges or cavities, however, in such instances, an opening of the ridge or cavity must be at least twice as wide as a depth of the ridge or cavity, but preferably at least three times as wide as a depth of the cavity. Advantageously, the heat-sink having a substantially smooth upper surface and a side extension provides a large surface area, without providing high profile ridges or cavities that may become blocked by leaves and other debris thereby negating the thermal transfer ability of the heat-sink. In the exemplary embodiments, the lower surface of the side extension is also substantially smooth. Preferably, a second side extension is provided. As with the foregoing exemplary embodiments, it is advantageous for the heat-sink to be extruded, though in this alternative exemplary embodiment, the heat-sink is not necessarily limited to being extruded.
In a further alternative exemplary embodiment of an external lantern, an external heat-sink is formed from a first heat-sink module and a second heat-sink module. The first heat sink module is connected to the second heat sink module. Each heat-sink module includes a receiving area for an LED bezel unit. Joining the heat-sink modules allows the heat-sink to accommodate more or larger LED bezel units to increase the illumination capacity of the lantern. In one particular exemplary embodiment, the first and second heat-sink modules are identical. Here, a base heat-sink module may also be used. The heat-sink modules may be coupled using mechanical fixings such as bolts. In one embodiment, each heat-sink module includes a through hole through which a mechanical fixing or part thereof may extend to fix the heat-sink modules together. As with the foregoing exemplary embodiments, it is advantageous for the heat-sink to be extruded, though in this alternative exemplary embodiment, the heat-sink is not necessarily limited to being extruded. Furthermore, it is advantageous for the heat-sink to comprise a first side extension, though in this alternative exemplary embodiment, the heat-sink is not necessarily limited to include a side extension.
For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figures 1 and 2 are top and bottom perspective views respectively of an external lantern according to a first embodiment;
Figure 3 is a bottom perspective view of a sealed LED unit;
Figure 4 is a bottom perspective view of a heat-sink according to a further embodiment;
Figures 5 to 7 show views of a further embodiment, where Figure 5 is a bottom perspective view of an external lantern including a heat-sink of Figure 4, Figure 6 is a bottom view and Figure 7 is a cross-sectional view along sectional line B-B of Figure 6;
Figure 8 is a bottom perspective view of an external lantern according to a further embodiment;
Figures 9 to 11 are views of a bezel unit for use with the exemplary embodiments where Figure 9 is an exploded perspective view, Figure 10 is a bottom view, and Figure 11 is a side view; and
Figure 12 is a cross-sectional view along a central length of a lantern according to a further embodiment.

Referring to Figures 1 and 2, an external lantern 10 is described. The external lantern 10 comprises an extruded heat-sink 20. The heat-sink 20 remains substantially directly exposed to the environment when the external lantern is installed. That is, the extruded heat-sink is not housed within its own housing or cover. Consequently, the heat-sink forms the lantern body. Whilst end plates 22 and covers 24 may be used to provide hermetic protection to electrical connections within the lantern, the heat-sink remains substantially uncovered.
The heat-sink 20 is extruded so that it has a constant cross-section. The heat-sink is extruded from a thermal conductive material such as a metal, for instance aluminium. The heat-sink 20 is preferably protected from the environment in any suitable manner. Whilst paints or the like can be applied, these are prone to flaking or other degradation and require maintenance. Any maintenance to the lantern often involves closing a highway in order for access to be obtained. It is therefore preferable, for instance, to protect against corrosion from salts and hydrocarbons by anodising the heat-sink. Here, the extrusion process is important because it allows for a grade and metallurgy of the heat-sink to be suitable for anodising. Also, it has been found that dark anodising improves the heat transfer characteristics of the heat-sink. To improve thermal transfer to the environment, the exposed portions of the heat-sink suitably include fins to increase the surface area of the heat-sink. The fins are formed during the extrusion process and are a plurality of ridges that run the length of the extrusion. The ridges are extruded on one or both of two opposed surfaces of the heat-sink, for instance the top and bottom of the heat-sink with respect to the direction of light emission.
In the exemplary embodiments, the heat-sink 20 provides a connection to high power light sources such as LED elements. Dependant on the lighting requirements, one or more LED elements are connected. However, typically a plurality of LED elements will be required to provide the required illumination. Here, the LED elements are provided in a sealed bezel unit having a plurality of LED elements aligned to optical elements such as a lens 32. The sealed bezel unit also provides electrical connection to the LED elements. It will be appreciated that the bezel unit therefore has a light emitting surface and opposed, base surface. The base surface of the bezel unit is in direct thermal connection with the LED elements for connection to a heat-sink in order to dissipate heat away from the LED elements, which have preferred operating temperatures for optimum energy efficiency and service life. The sealed bezel units include a standard number of LED elements and can be standard parts. The illumination capacity of the external lantern can therefore be selected by mounting one or more bezel units directly to the heat-sink.
Suitably therefore, the heat-sink 20 includes a connection area 26 for the bezel units. The connection area extends the length of the heat-sink. Consequently, the heat-sink can be extruded, cut or machined to have a length corresponding to a multiple of the length or width of the bezel units. Here, the bezel units can be attached to the heat-sink in a length along the extrusion axis of the heat-sink. In the exemplary embodiments, the bezel units are secured within a recess of the heat-sink. Again, because the recess is formed as part of the extrusion process, the recess extends the length of the heat-sink. Suitably, the depth of the recess may substantially correspond to the depth of the bezel unit. Here, the depth of the bezel unit is taken as the depth of a housing portion of the bezel unit and the lenses or other portions may protrude therefrom. Due to the extrusion process, the connection area is formed with a flat, smooth surface that requires no post-processing to achieve the flatness and smoothness required for good thermal connection between the surface and bezel unit. End plates 22 may be secured to the heat-sink to cover the ends of the extrusion, and in-particular to provide a hermetic cover to the recess.
In the exemplary embodiments shown in the figures, the heat-sink includes two side extensions that extend from the connection area of the bezel units. However, although this is preferable as the side extensions can act as a shield to the light emission, one or no side extensions are envisaged and the side extensions may extend upwardly or downwardly relative to the light emission. The side extensions remain substantially uncovered and may include fins on the top and bottom surfaces thereof relative to the light emission. The side extensions are suitably shown as being substantially wider than they are thick. For instance, in the exemplary embodiments, the side extensions are more than twice or more than three times wider than they are thick, where the thickness is taken as distance between two ridges on opposed surfaces, or if one or both of the opposed surfaces does not have ridges, between the thickest point of the surface. To provide good thermal dissipation, the side extension may extend a distance from the bezel unit at least half as wide as the distance of the bezel unit taken across the width of the extrusion, but in the exemplary embodiments is shown as suitably extending two-thirds the distance of the bezel unit, but may be more.
Referring to Figure 4, an exemplary heat-sink 20 is shown. The heat-sink comprises a central section 20c and left and right side extensions (20l, 20r). As mentioned, the sections of the heat-sink may be separately formed and connected together, or, as shown may be a single body. The central section includes a connection area 26 for an LED bezel unit. The connection area is substantially smooth to aid good thermal connection between the heat-sink and LED bezel unit. The side extension sections extend away from the central section as herein described. Furthermore, as shown in Figure 6, the side extension also extends downwards from the central section relative to the direction of light output from the bezel unit, so as to provide a recess for covering at least three sides of the LED bezel unit. The sections of the heat-sink may be solid, but preferably include cavities 28 that reduce the weight of the heat-sink without affecting the outer surface area. Connection fixings 29 can be machined or formed post extrusion of the heat-sink to allow connection of the LED bezel unit.
In the exemplary embodiments, the upper facing surface of the heat-sink and specifically the upper facing surface of the side extensions are substantially smooth. This is advantageous because it prevents debris from clogging and becoming snagged on recesses, which helps maintain a clean surface. However, to increase the surface area of the heat-sink, the substantially smooth upper surface may include fins such as ribs. Whilst, suitably, the ribs are shown as having an arcuate profile such as a sinusoidal profile, square or other profiles are also envisaged. However, the ribs maintain a low profile so that the surface can still be said to be substantially smooth. For instance, the channels or recesses formed by the ribs are substantially wider than they are deep. More specifically, the cavities are shown as being around two to three times wider than they are deep. Where the ribs are arcuate, the width is the pitch of the ribs. Otherwise, the width is the width at the top of the cavity formed by the ridges. It will be appreciated that the heat-sink may include further cavities, for instance, a cable conduit. In this case, the depth and width of the cavity is intended to be taken as the depth and width of a cavity when any covers or caps are installed. Because in the exemplary embodiments, the heat-sink is advantageously an extruded body, the ribs are formed the length of the heat-sink and are therefore constant in the length direction. However, in alternative possible embodiments where the heat-sink has been otherwise formed, the substantially smooth condition is preferably met in all directions.
Figures 5 to 7 shows an external lantern according to a further exemplary embodiment, wherein an LED bezel unit 30 is shown as being installed on the heat-sink 20. As will be appreciated, the number of LED elements within the attached bezel unit may be variable to vary the light output. However, in exemplary embodiments, the light output of the lantern is varied by varying the length of the heat-sink so as to enable multiple bezel units to be installed on the connection surface. As mentioned, this may be by forming or machining the heat-sink to different lengths. However, with reference to Figure 8, two or more heat- sink modules 20a, 20b may be connected together to extend the length of the heat-sink. Preferably, the heat- sink modules 20a, 20b are a single component so that different lanterns having a different illumination capacity can be formed from a common element.
An exemplary LED bezel unit 30 is shown in Figures 9 to 11. The LED bezel unit comprises an electrical substrate 32 having one or more LED elements 33 attached thereto. Typically the LED elements are packaged electrical modules and are affixed to a substrate such as a PCB. Typically, the bezel unit includes an overlaid cover 34. The cover 34 includes optical elements where necessary and is sealed to the electrical substrate to provide a sealed and hermetic enclosure for the LED elements. Suitably, the cover is formed using standard optical elements 37 such as lenses over moulded to produce a plate type cover. An electrical wire 38 is arranged to protrude from the sealed bezel unit 30. Suitably the wire would be provided as a tail with sufficient length to reach the electrical supply so that additional connections, which would require sealing, are not necessary. A backing plate 36 may be provided as part of the bezel unit. In this case the backing plate may be sealed to the overlaid cover. In any event, the bezel unit comprises a sealed enclosure housing the LED elements. In some instances, the backing plate may instead be a thermal conductive heat tape for connecting to the heat-sink. Alternatively or additionally, the bezel unit may be attached to the heat-sink directly by thermal adhesive.
In the exemplary embodiments and referring back to Figure 1 and 2, a bracket head 40 supports the heat-sink 20 for connection to a lamp bracket. The bracket head also provides a housing for any electrical drivers necessary for the LED units to operate. To avoid interference with the LED units 30 that in one embodiment substantially run the length of the heat-sink 20, the bracket head 40 is suitably shown as being connected to a surface opposed to the connection area of the LED units, for instance to a top of the heat-sink relative to the light direction, which is described as suitably being downwards. When connected to the heat-sink, the bracket head may cover an area having a width across the extrusion that is less than the width of the LED unit across the width of the extrusion. In an alternative embodiment, for instance, with reference to Figure 13, the bracket head 40 may be connected to the heat-sink 20 also on the side of the heat-sink that the LED bezel units are attached. Here, the bracket head 40 may cover the connection area to the bezel unit. The orientation and connection arrangements between the bracket head 40 and heat-sink 20 described herein are given as exemplary embodiments only and it will be appreciated that the bracket head and heat-sink may be attached in a number of various alternative configurations. For instance, the bracket head may extend at an angle to the extrusion's axis and may be connected to any surface or any combination of surfaces. In addition the bracket head or connection between the bracket heat and heat-sink may be adjustable.
Suitably, in the exemplary embodiments, the surface of the heat-sink opposed to the receiving surface for the LED bezel units may include a recess for running cable along. This conduit therefore is in connection with the attachment surface of the LED units, for instance by through holes. For instance and referring to Figure 12, a through hole 39 is formed through which the wire from the bezel unit may be threaded. Since the bezel unit is hermetically sealed, it is not essential, but it may be good practice to seal the hole, for instance with silicone. The cable can then be arranged to run along the cable conduit and be routed to the bracket head for electrical connection. Said conduit recess runs the length of the extrusion and may be covered and by a cover 24 to provide hermetic protection to the electrical components and connections. The cover 24 may clip or slide in place or be otherwise connected.
It will be appreciated from the foregoing that the illumination capacity of the external lantern can be changed by altering the length of the heat-sink to accommodate different numbers of the LED units. For instance in Figure 2, four LED units are shown whereas in Figure 4, only three LED units are shown. Other than the length of the heat-sink, the other parts of the external lantern, for instance the end covers, LED units and bracket head can remain unchanged. The manufacturing process is therefore more flexible and also capable of forming different lantern illumination capacity with reduced cost.
Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Claims

An external lantern comprising:
an LED light source;

a lantern body for housing the LED light source; and

a heat-sink directly connected to the LED light source; wherein

the heat-sink is extruded and forms the lantern body; and the heat-sink includes a first side extension that extends outwardly from the LED light source.
The external lantern according to claim 1, wherein the heat-sink is formed from a plurality of extruded heat-sink modules connected together in end-to-end relationship.
The external lantern of any of claims 1 to 2, wherein the heat-sink is anodised.
The external lantern of claims 1 to 3, wherein the heat-sink includes a second side extension.
The external lantern of claim 4, wherein an upwardly facing surface is substantially smooth.
The external lantern of claim 5, wherein the upwardly facing surface includes a plurality of parallel fins, a channel formed between two adjacent fins being at least twice as wide as deep.
A method of manufacturing external lanterns having a lantern body for housing an LED light source, the method comprising:
extruding a heat-sink; and

directly connecting an LED light source to the heat-sink; wherein

the heat-sink forms the lantern body; and
the heat-sink includes a first side extension that extends outwardly from the LED light source.
The method of manufacturing external lanterns of claim 7, wherein the method comprises extruding a first heat-sink module and extruding a second heat-sink module and connecting the first and second heat-sink modules end-to-end to form the heat-sink.
The method of manufacturing external lanterns of claim 7, wherein a first external lantern is assembled by extruding a heat-sink having a first length and directly connecting an LED light source having a first output to the heat-sink, and a second external lantern is assembled by extruding a heat-sink having a second length and directly connecting an LED light source having a second output to the heat-sink.
The method of manufacturing external lanterns of claim 7, wherein a first external lantern is assembled by extruding a heat-sink having a first length and directly connecting an LED light source having a first output to the heat-sink, and a second external lantern is assembled by forming a heat-sink having a second length from two or more heat-sink modules connected together in end-to-end relationship and directly connecting an LED light source having a second output to the heat-sink.
The method of manufacturing external lanterns of claim 9 or 10, wherein the first LED light source comprises a first unit and the second light source comprises two or more of the first units.