Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S8/00—Lighting devices intended for fixed installation
  • F21S8/02—Lighting devices intended for fixed installation of recess-mounted type, e.g. downlighters
  • F21S8/026—Lighting devices intended for fixed installation of recess-mounted type, e.g. downlighters intended to be recessed in a ceiling or like overhead structure, e.g. suspended ceiling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
  • F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
  • F21K9/20—Light sources comprising attachment means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V25/00—Safety devices structurally associated with lighting devices
  • F21V25/12—Flameproof or explosion-proof arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
  • F21V29/50—Cooling arrangements
  • F21V29/70—Cooling arrangements characterised by passive heat-dissipating elements, e.g. heat-sinks
  • F21V29/71—Cooling arrangements characterised by passive heat-dissipating elements, e.g. heat-sinks using a combination of separate elements interconnected by heat-conducting means, e.g. with heat pipes or thermally conductive bars between separate heat-sink elements
  • F21V29/713—Cooling arrangements characterised by passive heat-dissipating elements, e.g. heat-sinks using a combination of separate elements interconnected by heat-conducting means, e.g. with heat pipes or thermally conductive bars between separate heat-sink elements in direct thermal and mechanical contact of each other to form a single system
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
  • F21V29/85—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems characterised by the material
  • F21V29/89—Metals
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V29/00—Protecting lighting devices from thermal damage; Cooling or heating arrangements specially adapted for lighting devices or systems
  • F21V29/15—Thermal insulation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
  • F21Y2101/00—Point-like light sources
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
  • F21Y2115/00—Light-generating elements of semiconductor light sources
  • F21Y2115/10—Light-emitting diodes [LED]

Definitions

• the present invention relates to improved heat sinks. It is particularly applicable, but in no way limited, to fire proof or fire rated heat sinks incorporating a thermal insulating barrier and downlights incorporating such heat sinks.
• Downlights or downlighters are becoming more and more widely used as light sources in domestic and commercial environments. They are particularly neat and unobtrusive in their appearance, since almost the entire downlight fitting is concealed behind a ceiling or other suitable panel or surface, whilst giving out a pleasing light.
• these downlights When initially introduced, these downlights were designed to accommodate a bulb or lamp secured in a lamp holder inside the downlight.
• This arrangement provided a number of advantages. For example, a lamp could be easily replaced in the event of failure.
• a variety of different types of lamps, particularly lamps offering different light temperatures or different efficiencies, could be used in the same downlight fitting to suit a customer's requirement. If these requirements changed or more efficient lamps became available, then a new lamp could be installed to better meet these new requirements.
• LED light emitting diodes
• the downlight casing was considerably more expensive to produce than the lamp, and because conventional lamps often failed, there was a need for easy lamp replacement.
• LED's in contrast have a very long working life, provided any heat generated is dissipated efficiently.
• LED light engines, or solid state lighting elements do not have to be contained within a traditional lamp but can be mounted directly inside a downlight can or housing. As a result, many LED downlights have the LED light engine mounted directly within the downlight can or casing, without the use of a lamp in the conventional sense.
• heat sinks are used to dissipate heat generated by a light engine.
• Heat sinks for this application are generally made from aluminium, usually aluminium extrusions. When such heat sinks are in contact with or attached to the downlight housing, heat is dissipated throughout the whole of the housing by conduction.
• This arrangement is particularly disadvantageous when the surface in which the downlight is mounted is a decorative surface, or any surface for that matter, which can discolour or otherwise deteriorate over time when exposed to heat. In such prior art downlights the whole fitting tends to get hot when the light is switched on, leading to damage to the surface over time.
• a fire resistance rating means the duration for which an item can withstand a standard fire resistance test and is generally expressed as a time, such as 60 minutes fire rating.
• a fire resistant downlight would typically have a fire rating of 30 minutes, 60 minutes or 90 minutes, when exposed to test conditions of around 900 to 1000°C. Aluminium melts at around 660° and therefore an aluminium heat sink will inevitably melt during a standard fire resistance test such as BS 476 Part 21.
• a heat sink according to Claim 1 there is provided a heat sink assembly for dissipating heat from an object, said assembly comprising:-
• a first heat sink portion comprising a first body of heat conductive material having a high thermal conductivity and having a melting point or decomposition point at or below 900°C, said first body having a first end, a second end and at lease one sidewall;
• a second heat sink portion comprising a second body of heat conductive material having a high thermal conductivity and having a melting point at or above 900°C, said conductive material having a first side and a second side; wherein the first side of the second body is adapted to form a thermally conducting fit with the object from which heat is to be dissipated, and wherein the second side of the second body is adapted to form a thermally conducting fit with the first end of the first body.
• the first heat sink body incorporates fins and preferably the first heat sink body is substantially cylindrical in cross-section and preferably substantially circular cylindrical in cross-section. In this way a conventional finned aluminium extrusion can be used for the first heat sink body.
• the cross-section of the first heat sink body varies between the first end and the second end.
• the second heat sink portion comprises a sheet of heat conductive material, which preferably extends over substantially the whole of the first end of the first heat sink portion.
• a sheet of the higher melting material is a particularly cost effective way of introducing fire resistance.
• the second heat sink portion may be made from a wide variety of materials, as selected by the materials specialist.
• the second heat sink portion comprises brass or copper and more preferably the second heat sink portion comprises a brass or copper disc.
• the sheet of heat conductive material extends beyond the outer circumference of the first end of the first heat sink portion, forming a flange or shoulder around the circumference of the first end of the first heat sink portion adapted to enable the flange to be mounted on another object such as a downlight housing component.
• the heat sink assembly further comprises a third heat sink portion consisting of an annular ring of a thermal insulating material adapted to sit on or co- operate with the flange of the second heat sink portion.
• This thermal insulating layer prevents heat being transferred from the heat sink into the object that the heat sink is mounted on.
• a downlight assembly adapted to fit into an aperture in a surface such as a ceiling, said downlight assembly comprising:-
• a mounting ring comprising a tubular body having a front end and a rear end and at least once side wall, said front end of the tubular body incorporating a first, outwardly extending flange adapted to engage with the surface around the aperture, said rear end of the tubular body incorporating a second, inwardly extending flange;
• the layer of thermal insulating material takes the form of an annular ring.
• the thermal insulating material may consist of a wide variety of materials as selected by the materials specialist, including temperature resistant silicone rubber or an intumescent material.
• Figure 1 shows a bezel 01 , the front face of which is retained on the room side of an aperture in a ceiling (not shown).
• the bezel can be formed from any suitable decorative material such as aluminium, stainless steel or a chrome plated material.
• the bezel is attached by screws or other fixing means to a first flange 31 on the front of a mounting ring 10 described in more detail below.
• This mounting ring is formed from a material that melts at or above about 900°C and preferably at or above 1000°C. Mild steel is a particularly suitable material for this purpose as it both withstands the temperature of typical fire rating tests such as BS 476 Part 21 , and can be pressed into the desired shape shown in Figure 1.
• This shape provides a front end, a rear end and a tubular side wall and includes a first, outwardly directed flange 31 at the front end of the mounting ring or casing 10 and a second, inwardly directed flange 32 at the rear end of the mounting ring 10.
• the flange 32 provides a convenient fixing point for both the bezel 01 and the heat sink assembly 09, 24 and 14 described below.
• the heat sink assembly comprises a first portion made up of a finned aluminium substantially cylindrical extrusion 14, of a type typically found in downlights of this type.
• the cross-section of this first heat sink body 14 reduces towards the end that fits into the rear end of the mounting ring 10 to allow that end of the first heat sink body to pass through the aperture in the rear end of the mounting ring, without making heat conducting contact with the rear end of the mounting ring.
• a second portion of the heat sink assembly consists of a disc 9, made in this example of brass. Any material having high conductivity and that melts or decomposes at or above about 900°C is suitable for use in the second portion of the heat sink assembly.
• high thermal conductivity any material with a k value of 70 or above (W/m.K), and preferably above 90 (W/m.K).
• This second portion of the heat sink assembly protects the first portion in the event of a fire, such that fire will not penetrate beyond the second portion.
• the second portion 09 of the heat sink assembly is attached to the flange 32 on the inside of the mounting ring 10.
• An important feature of this invention is the presence of a thermal insulating barrier 24, located between the brass disc 09 and the flange 32. This prevents any significant conduction of heat between the light engine/heat sink assembly and the mounting ring 10.
• the thermal insulating barrier consists of a material having a k value of 5 or less, preferably less than 1 , and more preferably less than 0.5 W/m.K.
• An LED light engine or light engines 07 mounted on a metal core PCB as a primary heat sink is mounted to a first side of the brass disc. Heat generated by the LED light engine(s) is drawn away by conduction through the PCB and the brass disc 09 and into the heat sink portion 14 to be lost by convection.
• Various lenses and diffusers 02, 03, 04 are located between the bezel 01 and the light engine(s) 07 as required.
• thermal insulating barrier or layer of thermal insulating material including high temperature resistant silicone rubber, intumescent compounds or glass fabrics.
• a materials specialist will determine the optimum material for use in this application.
• the downlight assembly is completed by an LED high efficiency driver 21 and its associated mounting components 16, 17, 18, 19, 20 and a connector 23 to connect the downlight to mains electricity.

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Cited By (7)

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• 2012
  • 2012-07-20 GB GB1212923.5A patent/GB2504133B/en not_active Expired - Fee Related
• 2013
  • 2013-07-19 WO PCT/GB2013/051933 patent/WO2014013265A1/en active Application Filing
  • 2013-07-19 CN CN201380049260.1A patent/CN104641176B/zh active Active

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