GB2507185A

GB2507185A - Lamp unit with cooling body

Info

Publication number: GB2507185A
Application number: GB1317532.8A
Authority: GB
Inventors: Murray Ward
Original assignee: WILA GROUP Ltd
Current assignee: WILA GROUP Ltd
Priority date: 2012-10-17
Filing date: 2013-10-03
Publication date: 2014-04-23
Also published as: GB201317532D0; DE202012103988U1

Abstract

A lamp unit for a ceiling light fitting has a lamp holder and a cooling body 4 serving to cool LEDs held by the lamp holder. The cooling body 4 comprises several cooling channels 9 framed by walls 6, 10, 11, that are open at both ends and are arranged around the lamp holder. The cooling channels 9 vary in cross sectional area from the lamp holder end to their opposite end. A motor driven fan may be provided (Fig. 7).

Description

LAMP UNIT FOR A LIGHT FITTING

Field of the Invention

The invention relates to a lamp unit for a light fitting, in particular a ceiling light fitting with a lamp holder and a cooling body used to cool the one or more illuminants, in particular LEDs, mounted in the lamp holder, wherein the cooling body is connected with the lamp holder via a heat-conducting connection.

Background of the Invention

Lamp units for light fittings, in particular for light fittings in the form of ceiling-recessed spotlights, comprise a lamp holder. The lamp holder is provided to hold the one or more illuminants. For reasons of energy efficiency the illuminants used nowadays are predominantly in the form of is LEDs. These develop heat when in use. As they heat up, their light output reduces. For this reason the cooling of such illuminants is effected using cooling bodies which are connected with the lamp holder via a heat-conducting connection. The cooling bodies are intended to enlarge the heat-dissipating surface of the lamp unit. A light fitting of this kind uses LEDs, and these are typically arranged in a recess of the lamp holder. The lamp holder in many cases consists of a solid piece of metal serving as a heat sink. The cooling body is connected via a heat-conducting connection with the heat sink. The heat sink, apart from being provided for the purpose of dissipating heat emitted by the illuminants, also serves, in the case of several LEDs, to even out the temperature across the lamp holder, so that the typically several LEDs used as illuminants operate at the same or at least approximately the same temperature, in other words so that there are no variations in their light emission. This is particularly desirable with focussing spotlights because with such spotlights an uneven light distribution is particularly noticeable.

The cooling bodies used for cooling such lamp holders are extruded cooling profiles. These encompass a cooling body core and, in radial direction, cooling ribs protruding therefrom. In axial direction such a cooling body is connected to the rear side with respect to the lamp holder.

Cooling using cooling bodies of this kind, may be effected passively or actively depending on the design of the light fitting and the required cooling output. With an active cooling body conception the cooling body has a fan connected with it. This fan serves to provide an air current s flowing past the cooling ribs.

Due to the use of increasingly powerful LEDs and the generation of heat associated with it when using such illuminants in a light fitting, in particular if this is provided as a ceiling light fitting, special attention must be paid to ensure that sufficient cooling is provided.

Summary of the Invention

In view of the foregoing the invention is based on the requirement to is propose a lamp unit which ensures an improved cooling output, even without the use of fans or the like.

According to the invention this requirement is met by a generic lamp unit mentioned in the beginning, where the cooling body comprises several cooling channels which are framed by walls, open at both ends and arranged in radial direction around the lamp holder or a heat sink body forming the lamp holder or supporting it, wherein the cooling channels, in their end portion open towards the lamp holder, at least in sections, comprise a smaller cross-sectional area than on the output side.

With this lamp body provision is made for the cooling body to comprise several cooling channels arranged around the lamp holder. These cooling channels are framed by walls, but are open at both their mouth ends. The cooling channels are aligned in a certain way so that an air current including a passive air current is able to form therein. Therefore the cooling channels are typically provided so as to extend vertically or so as to be inclined at a pointed angle towards the longitudinal axis. Due to the provision of circumferentially closed cooling channels a directional air flow is created as the walls framing the cooling channels heat up, thereby causing a chimney effect to be created. The air current carrying the heat away flows away from the lamp holder causing relatively cooler ambient air to be sucked in on the input side with respect to the cooling channels.

The cooling channels are typically arranged in such a way that the ambient air sucked in by the described chimney effect flows past the lamp holder and is thus able to absorb heat therefrom as it passes by, even if the majority of the heat is not transferred to the air current until this flows s through a cooling channel.

In contrast to known cooling bodies where the aim was to make the surface of the cooling body as large as possible, the concept described above uses cooling channels enabling the cooling body to have a closed surface also on the outside. The cooling output of such a cooling body, as tests have shown, is surprisingly improved due to directional air currents being formed compared to previously known cooling bodies which are traditionally used for cooling the illuminants of light fittings. This could not be anticipated.

The possibility of providing cooling channels which are circumferentially closed but open at their ends means that the cooling air current therein can be accelerated. This can be effected by forming a bottle neck, which acts as a nozzle. For example, a cooling channel of this kind, in the mouth area facing the lamp holder, may comprise a lesser cross-sectional area than on the output side. Due to such a measure the velocity of the suction current created by the chimney effect and thus the direct cooling output of the cooling body is improved.

The above-described concept also offers the possibility of connecting one or several further cooling body parts to one or several of such channels.

This may be effected circumferentially or asymmetrically. In case of an asymmetric arrangement of an additional cooling body part on the external walls of one or several such cooling channels the walls framing the cooling channels are simultaneously used for heat distribution and the introduction of heat into the additional cooling body part. Whilst with known cooling bodies, due to the radial arrangement of the cooling ribs and in view of a desired uniform cooling across the lamp holder one had to take care to achieve a cooling output which circumferentially is as uniform as possible, the described concept enables a heat distribution also in circumferential direction to be achieved by using rings or ring parts representing cooling-channel-framing walls or wall parts, which in turn also make it possible to asymmetrically attach one or several cooling bodies. This is particularly convenient in the case of ceiling light fittings, since it allows a cooling body to be inserted through an opening in the ceiling or through the bottom opening of a mounting frame, the cross-sectional area of which is larger s than the opening width of the opening. The mounting frame can be pushed, detached from the other components of the light fitting, through a ceiling opening, to be connected again behind the suspended ceiling with the other light fitting components. Due to such a measure the cooling capacity of such a cooling body can be further improved, above all without the use of additional active cooling means such as a fan.

A cooling body of this kind is typically manufactured from a material with good heat-conducting properties such as an aluminium or magnesium alloy by way of a casting process.

The efficiency of such a cooling body can be further improved by arranging, in such a cooling channel, one or more inward-pointing cooling ribs following the longitudinal extension.

According to one embodiment of the invention provision is made for the several cooling channels to be formed by a cooling ring body framing the lamp holder in circumferential direction and arranged at a radial distance therefrom. This cooling ring body is connected by webs with a central cooling body part. The central cooling body part in turn is in heat-conducting connection with the lamp holder. With this embodiment the heat is carried from the lamp holder into the central cooling body part and via the webs into the cooling ring body. These components of the cooling body are heated by the illuminants when in operation, whereby the desired convection and the directional and preferably accelerated cooling air flow forms in the cooling channels between the connecting webs. The outside of such a cooling ring body can be utilised to attach an additional cooling body to it. This may be comprised of traditional cooling ribs or a cooling body designed as a honeycomb. In the latter case individual honeycombs form the cooling channels in which directional cooling air currents are or may be generated.

In a preferred exemplary embodiment the lamp holder is manufactured in one piece together with the cooling body by way of a casting process. The heat conduction between the lamp holder and the cooling body then is particularly good.

s Even although with the above-described concept the passive cooling output of such a lamp unit is improved, it can be even further improved by connecting a fan, which can be used to further increase the velocity of the cooling air current flowing through the cooling channels. This can be achieved utilising the closed outside structure of such a cooling body also for the purpose of using such a fan. With conventional fans this comprises, apart from the fanwheel mounted on the engine shaft, an air-conducting ring radially surrounding the fanwheel. This is not required with a fan which uses for example the cooling ring body of the described cooling body, because this function can be performed by the cooling ring body. With is such a design the cooling body comprises a suitable recess for attaching a fan.

Brief Description of the Drawings

Further advantages and designs of the invention are revealed in the description of an embodiment below with reference to the attached figures in which Fig. I shows a perspective rear view of a ceiling light fitting designed as a spot light, with a cooling body, Fig. 2 shows a perspective view from above onto the cooling body of the light fitting of figure 1, Fig. 3 shows a longitudinal section through the cooling body of figure Fig. 4 shows a top view of the cooling body, Fig. 5 shows a view of the cooling body from the bottom up, Fig. 6 shows a perspective view of a further cooling body in the manner of an explosive view with a fanwheel, Fig. 7 shows the active cooling body of figure 6, and s Fig. 8 shows a perspective representation of a fan holder for holding the fan of the cooling body of figures 6 and 7.

Detailed Description of the Preferred Embodiment

In the exemplary embodiment shown the ceiling light fitting 1 is designed as a spot light. The mounting frame is connected to a lamp unit 3 comprising a lamp holder and a cooling body 4. The lamp holder and the cooling body 4 are manufactured in one piece, i.e. in the embodiment shown they are produced by a casting process from a light metal alloy. In is the embodiment shown in the figures an aluminium alloy was used. The cooling body 4 with the lamp holder moulded thereto is connected with the mounting frame 2 via a support arm 5.

The lamp unit 3 with its cooling body 4 will now be described with regard to its geometric design and the idea of the cooling principle. The cooling body 4 is a passive cooling body. It comprises a central cooling body part 6, which in the embodiment shown is moulded onto a heat sink body 7.

The arrangement of the central cooling body part 6 in relation to the heat sink body 7 can be viewed in cross-section in figure 6. In this representation the lamp holder 8 is also visible, which in the example shown forms the lower termination of the heat sink body 7. Therefore the surface 8 has the circuit board including the LEDs provided in the shown embodiment as illuminants arranged on it. The heat being created during operation of the LEDs is absorbed by the heat sink body 7 and, due to the good heat conducting properties of the material of which the lamp unit 3 consists, dissipated and directed into the cooling body 4.

With the cooling body 4, the speciality consists in that several cooling channels 9 are provided, some of which are recognisable in figure 2, which surround and thereby partly frame the heat sink body 7 and thus the lamp 8. These cooling channels 9 are formed by providing a cooling ring body forming the radially external termination of the cooling body 4, which cooling ring body 10 is moulded onto the central cooling body part 6 via webs 11. The cooling ring body 10 is arranged at a radial distance from the central cooling body part 6, resulting in an annular gap between these two elements. In circumferential direction this gap is divided by the webs 11 into individual cooling channels 9. Due to the cooling ring body 10 the cooling body 4 in this area comprises a smooth external surface. Starting from the central cooling body part 6 and protruding outwardly therefrom in radial direction into a cooling channel 9, are cooling ribs 12 which respectively follow the longitudinal direction of a cooling channel 9.

In the embodiment shown two circular-segment-shaped cooling ribs 13 moulded onto the rear side of the heat sink body 7 are framed by the central cooling body part 6.

is The cooling channels 9 are framed circumferentially and thus in parallel with their longitudinal extension by a portion each of the central cooling body part 6, by the webs 11 and the cooling ring body 10. At both their ends, however, the cooling channels 9 are open. The perspective view of the lamp unit 3 with its cooling body 4 of figure 2 shows the mouths or the cooling channels 9 on the outflow side. In the top view of the cooling body 4 in figure 4 the geometry of the cooling channels can be very clearly seen. The cross-sectional geometry of two cooling channels 9 is highlighted by shading the same. In the top view of the cooling body 4 shown in figure 4 where the surface of the heat sink body 7 is recognisable when looking into the cooling channels 9 it becomes readily clear that the cross-sectional geometry above the heat sink body 7 and thus on the output side relative to the cooling channels 9, is larger than on the input side. In order to make this clear, the view of the lamp unit 3 in figure 5 is a view from the bottom up. The surface provided for the lamp holder 8 is shown to comprise attachment openings for connecting the circuit board supporting the illuminants. The essential fact is that this representation reveals the cross-sectional geometry of the cooling channels 9 in the area of their mouth region on the inflow side. For comparison the cooling channels 9 which were marked in figure 4 relative to their cross-sectional geometry on the outflow side, have been marked with the same shading in the bottom view of figure 5. A comparison of the cross-sectional geometries marked by shading reveals that the cross-section area of the cooling channels 9 is distinctly smaller on the input side than on the output side.

With the light fitting 1 in operation the heat given off by the illuminants held by the lamp holder 8 -here several LEDs -is drawn off via the heat sink body 7 onto the further components of the cooling body 4 through heat conduction. Due to the good heat-conducting properties of the material employed in the manufacture of the cooling body 4 this will heat up the wall sections of the cooling body 4, which frame the cooling channels 9. As a result a directional convection is created within the cooling channels 9.

The air heated up in the cooling channels 9 by the said wall sections endeavours to rise, with the consequence that cooler ambient air is sucked in on the input side. In this way a so-called chimney current is created within the circumferentially closed cooling channels 9, which chimney is current undergoes acceleration due to the cross-sectional narrowing in the input region of the cooling channels. Since the mouths of the cooling channels on the input side are arranged adjacently to the lamp holder 8 or the heat sink body 7, the sucked-in cooler ambient air flows directly past the lamp holder 8 so that cooling of the illuminants employed is effected not only by heat conduction into the inside of the cooling body 4 but also by the cooling air current flowing past it. Insofar, despite the passive cooling body concept in this embodiment a directional air current is generated based on the above-described effect, which causes active cooling of the one or more illuminants held by the lamp holder 8 due to the creation of the cooling air current. It is understood that the cooling created by the cooling air current, in particular also due to the acceleration thereof, which is comparable to active cooling. At this point it should be emphasized that in the embodiment shown this cooling is effected without actuators (fans). 3(1

It is understood that the cooling process is additionally supported also by heat given off via the cooling ring body 10 in a radial outward direction.

The concept of providing circumferentially closed cooling channels 9 within the cooling body 4 which extend longitudinally in parallel or at least approximately in parallel with the longitudinal axis of the heat sink body 7 or the lamp holder 8, makes it possible to attach further additional cooling elements to the outside of the cooling ring body 10. In the embodiment shown in the figures an additional cooling structure 14 is moulded onto one side of, and thus asymmetrically, of the cooling ring body 10, this being an additional cooling body part. The cooling structure 14 is designed S as a passive element and is implemented in the embodiment shown in the form of a honeycomb structure. The cross-sectional surface of individual honeycombs of the cooling structure 14 increases in radial direction from inside to outside. The honeycombs of the cooling structure 14 are also open at their ends and form themselves cooling channels. Due to the concept of the lamp holder 3 with its cooling body 4 with the cooling structure 14 attached thereto, there is no reason to fear that cooling could be uneven across the area of the lamp holder 8.

The possibility of connecting one or even more additional cooling is structures, as shown by way of the examplary cooling structure 14 in the figures, enables the surface of the lamp unit 3, which can be used for cooling, to be enlarged, wherein the surface occupied by the lamp unit 3 can be larger than the width of an opening in the ceiling, for example. The lamp unit 3 of the embodiment shown may, for example, be pushed, holding it upright, through the ceiling opening and then manoeuvred into its intended position behind the suspended ceiling and connected to the mounting frame 2, for example by pushing the lamp unit 3 onto the support arm 5. This kind of enlargement of the cooling surface is not possible for rotation-symmetric coaling bodies. Another special feature of the described concept consists in that such a cooling body, for the same cooling output, can be distinctly flatter in height compared with traditional cooling bodies. One factor here making this possible is the fact that one or several additional cooling structures can be employed.

Figure 6 shows a lamp unit 3.1 which in principle is constructed in the same way as the lamp unit 3 in figures 1 to 5. The cooling body 4.1 of the lamp unit 3.1 is designed for active cooling in contrast to the cooling body 4 of lamp unit 3. The cooling body 4.1 also comprises cooling channels such as already described for the cooling body 4 of the lamp unit 3. The cooling body 4.1 has an electro-motoric fan 15 associated with it, which is inserted into a central recess 16 in the rear side of cooling body 4.1. The fan 15 is held by a holder 17 comprising several holding arms shown again separately in figure 8. The fan 15 merely comprises an electrornotor with a fanwheel. With this fan 15 there is no need for an air-conducting ring surrounding the fanwheel. This air-conducting function is performed by the cooling ring body 10.1 of the cooling body 4.1 because, as can be seen in figure 7, the fan 15 is framed by a portion of the cooling ring body 10.1.

The housing of the fan 15 is glued to a mounting plate 18 of the holder 17.

The mounting plate 18 is, if at all, only marginally larger than the diameter of the housing of the fan 15. The mounting plate 18 has several holding arms 19 moulded onto it, which at their respective ends form a holding fork 20. The holding forks 20 serve to frame a cooling rib portion respectively, as can be seen in figure 7. The holding forks 20 also comprise a holding strap folded downwardly and supported against the side of a cooling rib segment which is pointing inwards in radial direction. The straps 21 are is slightly angled enabling the holder 17 to be held free of play and typically at a certain fixing tension between the three cooling rib segments received in the holding forks 20.

In other respects the details given in respect of the lamp unit 3 also apply to the lamp unit 3.1.

List of reference symbols 1 ceiling light fitting 3 mounting frame 3, 3.1 lamp unit 4, 4.1 cooling body support arm 6 central cooling body part 7 heat sink body 8 lamp holder 9 cooling channel cooling ring body 11 web 12 cooling rib 13 cooling rib 14 cooling structure fan 16 recess 17 holder 18 mounting plate 19 holding arm holding fork 21 strap

Claims

--Claims 1. A lamp unit for a light fitting, in particular a ceiling light fitting with a lamp holder (8) and a cooling body (4) serving to cool the one or more illuminants, in particular LEDs, held by the lamp holder (8), wherein the cooling body (4) Es connected with the lamp holder (8) via a heat-conducting connection, characterised in that the cooling body (4) comprises several cooling channels (9) which are framed ic by walls (6, 10, 11), open at both ends and arranged in radial direction around the lamp holder (8) or a heat sink body (7) forming the lamp holder or supporting it, wherein the cooling channels (9), in their end portion open towards the lamp holder (8), at least in sections, comprise a smaller cross-sectional area than on the output side.
2. The lamp unit according to claim 1, characterised in that one or more cooling ribs (12) are arranged protruding into some of the several cooling channels (9) and following the longitudinal direction thereof.
3. The lamp unit according to one of claims 1 to 2, characterised in that the several cooling channeFs (9) are provided by a cooling ring body (10, 10.1) framing the amp holder or a heat sink body (7) forming or supporting the same in circumferential direction and arranged at a distance from the heat sink body (7), as well as by several webs (4) connecting the cooling ring body (10, 10.1) with a central cooling body part (6).
4. The lamp unit according to claim 3, characterised in that the central cooling body part (6) is connected with the lamp holder or a heat sink body (7) forming or supporting the same via a heat-conducting connection.
5. The lamp unit according to claim 3 or 4. characterised in that the central cooling body part (6) supports radially protruding cooling ribs extending in longitudinal direction away from the lamp holder.
6. The lamp unit according to claim 5, characterised in that a recess (16) for attaching an electro-motorically driven fan (15) is provided in the termination of the cooling body (4.1) opposite the lamp holder (8).
7. The lamp unit according to one of claims
S to 5, characterised in that the lamp holder (8) or the heat sink body (7) forming or supporting the same and the cooling body (4, 4.1) are io manufactured as a joint assembly in one piece, in particular by way of a casting process.

6. The lamp unit according to one of claims 6 to 7: characterised in that an additional passively functioning cooling structure (14) is ES moulded onto one side of the cooling ring body (10, 10.1) in radial direction towards the outside.
9. The lamp unit according to claim 8, characterised in that the additional cooling structure (14) is implemented as a honeycomb structure.
10. The lamp unit according to claim 9. characterised in that the cross-sectional area of individual honeycombs of the additional honeycomb cooling structure (14) increases in radial direction from the inside to the outside.