WO2010035007A1

WO2010035007A1 - Light fitting

Info

Publication number: WO2010035007A1
Application number: PCT/GB2009/002303
Authority: WO
Inventors: Robert Cole
Original assignee: Robert Cole
Priority date: 2008-09-29
Filing date: 2009-09-28
Publication date: 2010-04-01
Also published as: GB0817817D0; GB2463796A; GB2463796B; GB0916999D0

Abstract

A light fitting (1) is provided in which a lamp can be housed in a housing (2). The housing (2) comprises a wall (4) in which one or more ventilation holes (7) are formed. A plate (25) overlies the ventilation holes (7) and is biased towards the wall (4). During normal use the plate (25) is separated from the wall by a sacrificial member (24), allowing air flow through the ventilation holes (7). However, in case of a fire the sacrificial member (24) melts and the plate (25) moves towards the wall (4) covering the ventilation holes (7). This can prevent ventilation through the ventilation holes (7) acting to spread the fire throughout a building.

Description

LIGHT FITTING

Field of the invention

This invention relates to a light fitting. The invention has particular, but not exclusive, application to a recessed downlighter.

Background to the invention

A recessed downlighter is a type of light fitting that is usually mounted in a hole in a ceiling board and recessed behind the hole so that it appears flush with the board. A recessed downlighter usually has a housing for accommodating a lamp in the recess behind the hole in the board. The housing is usually open through the board to allow fitting of a light bulb in the lamp. The housing may have ventilation holes for allowing the passage of air out of the housing to cool the lamp.

In the event of a fire, ventilation through a light fitting mounted in a hole in the ceiling of a room can allow fire to spread through a building more quickly. Accordingly, it is desirable to limit ventilation through such light fittings in the event of a fire. Indeed, regulations often dictate that such light fittings must limit ventilation for a specified period in the event of a fire.

For this purpose, it is known to provide recessed downlighters with intumescent material at locations of potential ventilation. Intumescent materials expand on heating and can therefore be positioned to block ventilation holes or other locations of potential ventilation in the event of a fire. However, intumescent materials are expensive. Also, the extent of their expansion can be difficult to predict, which means in practice that an excess of intumescent material is usually provided to ensure blocking occurs, further increasing expense.

The present invention seeks to overcome these problems.

Summary of the invention

According to the present invention, there is provided a light fitting comprising: a housing for housing a lamp, the housing having a wall with a ventilation hole therein; a plate that overlies the ventilation hole and is biased towards the wall; and a sacrificial member for holding the plate apart from the wall such that the ventilation hole is open, wherein melting of sacrificial member allows the plate to move towards the wall to close the ventilation hole. It will be understood that when the sacrificial member melts, the plate can move to close the ventilation hole under influence of the biasing force, so preventing ventilation through the housing.

Advantageously, the plate can be made from an easily manufactured material, e.g. pressed steel. Whilst the sacrificial member may be required to have particular melting properties and may therefore need to be made of a more specific material, its function of holding the plate away from the wall allows it to be relatively small in comparison to the amount of intumescent material required to block a ventilation hole in the prior art. The sacrificial member may also be less precisely positioned than the intumescent material of the prior art, as its behaviour in the presence of a fire can be simply to melt and release the plate, rather than to expand in a particular way to block a ventilation hole. Overall, this allows the light fitting of the invention to be manufactured much more cheaply than the light fittings of the prior art that use intumescent materials.

Furthermore, the plate can provide improved sealing in comparison to light fittings of the prior art that use intumescent materials, as its position when the ventilation hole is closed can be reliably defined by mechanical movement, whereas an intumescent material expands unpredictably.

Preferably, the sacrificial member has a melting point above a normal operating temperature of the light fitting but below that of a typical house fire. Preferably, the sacrificial member has a melting point between around 150⁰C and 400⁰C. More preferably, the sacrificial member has a melting point between around 15O⁰C and 300⁰C. the sacrificial member may be formed of a variety of materials. In preferred embodiments the sacrificial member is a eutectic alloy.

Preferably, the wall has a plurality of ventilation holes therein and the plate overlies the plurality of ventilation holes. This ensures good ventilation during normal operation of the light fitting.

The sacrificial member is preferably a spacer.

In preferred embodiments, the light fitting comprises a spring for biasing the plate towards the wall. This provides a reliable means for biasing the plate towards the wall.

Preferably, the light fitting further comprises an alignment member on which the plate is slidably mounted. In preferred embodiments, the alignment member is a tube through which wires can electrically connect the lamp to a power supply outside the housing. Preferably, the sacrificial member is mounted on the alignment member. Moreover, the spring for biasing the plate towards the wall is preferably mounted on the alignment member.

Preferred embodiments of the light fitting are for recessed mounting in a board. In some preferred embodiments, the light fitting further comprisies a fixing frame for mounting the light fitting to the board. This can improve the structural integrity of the board at the point at which the light fitting is mounted, further improving the fire resistance of the light fitting. Preferably, the fixing frame comprises a top plate and a bottom plate, the bottom plate comprising an axially extending portion which, in use, extends through a hole in the board and around the housing. More preferably, the top plate is substantially C-shaped. Preferably, the light fitting is arranged to be rotatably mounted to the fixing frame. In preferred embodiments, the light fitting comprises a flange extending from the housing, wherein rotatable mounting of the light fitting to the fixing frame is effected by engagement of the flange with a radially extending portion of the bottom plate of the fixing frame.

Preferred embodiments of the invention are described below, by way of example only, with reference to the accompanying drawings.

Brief description of drawings

Figure 1 is a cut-away perspective view of a light fitting;

Figure 2 is an exploded perspective view of the light fitting shown in Figure 1 ;

Figure 3 is a cross-sectional view of the light fitting shown in Figures 1 and 2;

Figure 4 is a cut-away perspective view of an alternative light fitting having a fixing frame;

Figure 5 is a cut-away exploded perspective view of the light fitting shown in Figure 4; and

Figure 6 is a cut-away perspective view of the light fitting shown in figures 4 and 5 when in use.

Detailed description of preferred embodiments

Referring to Figures 1 , 2 and 3, a light fitting 1 according to a preferred embodiment of the invention comprises a recessed downlighter for mounting in a hole in a board 30 (see Figures 4, 5 and 6), such as a ceiling board. In other examples, the light fitting 1 may not be recessed downlighter. For example, it might be a light fitting that is - A -

mounted so as to cover the hole in the ceiling board and/or may be adapted to be mounted in a hole in a wall, beam or other building fixture.

The light fitting 1 comprises a housing 2, which in this example is a tube with an open bottom end 3 and a closed top end 4. The housing 2 may be pressed steel and constructed to provide a barrier to fire and noise. The open bottom end 3 has a flange 5 extending outwardly from the housing 2 around the rim 6 of the open bottom end 3 of the housing 2. The closed top end 4 of the housing 2 is provided with ventilation holes 7 and a fitting hole 8. In this example, there are four ventilation holes 7 evenly circumferentially spaced around the fitting hole 8. In other examples, a smaller or larger number of ventilation holes 7 may be provided and these may be located elsewhere on the housing 2. However, it is preferred that the ventilation hole or holes 7 is/are located above a position at which a lamp may be located in the housing 2 in use. This helps to ensure effective ventilation of air heated by the lamp inside the housing 2.

Two retaining arms 9 are mounted on the side wall 10 of the housing 2. The retaining arms 9 are arranged to extend downwardly and outwardly from the side wall 10 such that the ends 11 of the retaining arms 9 distal to the side wall 10 extend to a location spaced vertically above the flange 5 by approximately the thickness of the board 30 in which the light fitting 1 is to be mounted. The retaining arms 9 are hinged about a substantially horizontal axis. During insertion of the light fitting 1 through the hole in the board 30, the arms 9 deflect resiliently toward side wall 10 of the housing 2. Once the light fitting 1 is properly inserted and the retaining arms 9 have passed through the board 30, the resilience of the retaining arms 9 causes them move outwardly from the side wall 10 of the housing 2. The distal ends 11 of the retaining arms 9 are then located on the top surface of the board 30, whilst the flange 5 is located on the bottom surface of the board 30. In these positions, the distal ends 11 of the retaining arms 9 and the flange 5 together hold the light fitting 1 in position.

A first seal 12 is provided on a top surface 13 of the flange 5. When the light fitting 1 is mounted in the board 30, the first seal 12 is positioned between the flange 5 and the bottom surface of the board 30. The first seal 12 extends around the entire periphery of the housing 2. The first seal 12 is therefore annular in this example. The first seal 12 can be made of any suitable sealing material, such as silicone. The first seal 12 eliminates flow of air between the board 30 and the light fitting 1. This can help to reduce the passage of moisture that may be carried in the air. It can also limit ventilation between the light fitting 1 and the board 30 in the event of a fire. A bezel 14 is mounted on a bottom surface 15 of the flange 5. The bezel 14 improves the appearance of the light fitting 1 from below the board 30. lnside the housing 2 is a lamp. In more detail, a lamp holder 16 is provided inside the housing 2 below the fitting hole 8. Inside the lamp holder 16 is a bulb fitting 17, such as a bayonet socket. A bulb 18 can be fitted in the bulb fitting 17.

An alignment member 20 comprises a tube that has a threaded outer surface 21. The fitting hole 8 is threaded on its inner surface 22 and, by means of the threaded surfaces 21 , 22, the alignment member 20 can be inserted in the fitting hole 8 and secured to the housing 2. A bottom end 23 of the alignment member 20 abuts against the lamp holder 16 when the alignment member 20 is inserted to the required extent, such that there is no gap between the lamp holder 16 and the bottom end 23 of the alignment member 20. This means that there can be no ventilation from the inside of the housing 2 into the alignment member 20.

Electrical wires 19 connect the lamp to a power supply (not shown) outside the housing 2. The electrical wires 19 pass from the lamp holder 16, into the bottom end 23 of the alignment member 20 and through the alignment member 20 to the outside of the housing 2. The electrical wires 19 are connected to contacts (not shown) inside the lamp holder 16 and the contacts are closed inside the lamp holder 16. This means that there can be no ventilation through the lamp holder 16 into the bottom end 23 of the alignment member 20. The lamp holder 16 is made of porcelain or mica, which are both highly temperature resistant. So, in the event of a fire, the lamp holder 16 resists melting and any risk of ventilation through the lamp holder 16 into the alignment member 20 is reduced.

A plate 25 overlies the ventilation holes 7. The plate 25 is located outside the housing 2. In this example, the plate 25 is annular and the plate 25 is slidably mounted on the alignment member 20. A sacrificial member 24 is provided for holding the plate 25 apart from the housing

2, or more specifically away from the closed end 4 of the housing 2 in which the ventilation holes 7 are provided. In this example, the sacrificial member 24 is annular. It is mounted around the alignment member 20 between the plate 25 and the closed end 4 of the housing 2. In other words, the sacrificial member 24 may comprise a spacer. Although the plate 25 overlies the ventilation holes 7, as the plate 25 is spaced apart from the closed end 4 of the housing 2 by the sacrificial member 24, air may flow from the inside of the housing 2, through the ventilation holes 7 and between the periphery of the plate 25 and the closed end 4 of the housing 2 to ventilate the housing 2.

The plate 25 is biased towards the closed end 4 of the housing 2. A spring 26 is provided for biasing the plate 25 towards the closed end 4 of the housing 2. In this example, the spring 26 is a coil spring located around the alignment member 20. The spring 26 is held in place by a nut 27 that engages with an upper end 28 of the alignment member 20. The nut 27 is tightened on the alignment member 20 to compress the spring 26 against the plate 25, which is held in position away from the closed end 4 of the housing 2 by the sacrificial member 24. The sacrificial member 24 has a melting point above a normal operating temperature of the light fitting 1 but below that of a typical house fire. Typically, the melting point of the sacrificial member 24 is between around 150⁰C and 400⁰C. In the event of a fire, the sacrificial member 24 melts and the plate 25 is no longer held apart from the closed end 4 of the housing 2. Under the biasing force of the spring 26, the plate 25 moves towards the closed end 4 of the housing 2. As the plate 25 comes to rest against the closed end 4 of the housing 2, it closes the ventilation holes 7. This prevents ventilation of air from inside the housing 2 through ventilation holes 7 in the event of a fire.

Although the melting point of the sacrificial member is typically between around 15O⁰C and 400°C, this range may be altered according to circumstances. For example, should the lamp to be held by the light fitting 1 operate at a high temperature, the melting point of the sacrificial member may be between around 200°C and 400⁰C, between around 300°C and 400°C, or even between around 350°C and 400°C. This ensures that the sacrificial member 24 does not melt except in the event of fire. On the other hand, in other circumstances the melting point of the sacrificial member 24 may be chosen to be between around 15O⁰C and 300⁰C or between around 150°C and 250⁰C.

The sacrificial member 24 may be tin, which has a melting point of 232 ⁰C. Preferably, the sacrificial member 24 is a eutectic alloy. Eutectic alloys change from a solid to liquid state very quickly at their melting point. This is useful to ensure swift movement of the plate 25 in the event of a fire and at the same time reduce degradation of the sacrificial member 24 during normal operation of the light fitting (below the melting point of the sacrificial member 24).

Suitable eutectic alloys include tin/lead, tin/lead/silver, tin/antimony, tin/copper, tin/silver, tin/indium, tin/silver/copper, tin/silver/copper/bismuth, indium/lead, indium/silver or tin/bismuth. Examples of specific eutectic alloys and their melting points are given in Table 1 below. Eutectic Alloy Melting Point (⁰C)

5Sn-95Pb 307

0.5Sn-92.5Pb-2.5Ag 280

Sn-5Sb 243

99.3Sn-0.7Cu 227

96.5Sn-3.5Ag 221

52ln-48Sn 118

Sn-3.0Ag-0.5Cu 219

Sn-3.8Ag-1.0Cu 217

Sn-3.5Ag-1.0Cu-3Bi 213

50ln-50Pb 209

45Sn-55Pb 204

55Sn-45Pb 193

60Sn-40Pb 186

63Sn-37Pb 183

62Sn-36Pb-2Ag 179

97ln-3Ag 143

Sn-57Bi 139

Table 1

A second seal 29 is provided on the closed end 4 of the housing outward of the ventilation holes 7 and underlying the plate 25. In this example, the second seal 29 is annular and extends around the outside of all of the ventilation holes 7. The second seal 29 is made of a heat resistant fibre. In other examples, the second seal may comprise a plurality of seals provided around each ventilation hole 7. When the plate 25 rests against the closed end 4 of the housing 2, it sandwiches the second seal 29. This improves sealing between the plate 25 and the closed end 4 of the housing 2 and hence further limits ventilation of air from the inside of the housing 2 through the ventilation holes 7 in the event of a fire.

Referring to Figures 4, 5 and 6, in an alternative embodiment, the light fitting 1 has a fixing frame for mounting the light fitting 1 to the board 30. The fixing frame acts to strengthen the hole in the board 30 in which the light fitting is mounted, thereby increasing fire resistance. Except where otherwise stated, the features of the light fitting 1 of this embodiment are the same as those of the embodiment described above with reference to Figures 1 to 3. The fixing frame comprises a top plate 31 and a bottom plate. When in position, the top plate 31 is disposed on the upper surface of, and around the hole in, the board 30. The top plate 31 is substantially annular with a gap at one sector. In other words, the top plate 31 is substantially C-shaped. This allows the top plate 31 to be passed through the hole in the board 30 from below in order to rest in place upon the upper surface of the board 30. This is best illustrated in Figure 4. The bottom plate has a radially extending portion 32 and an axially extending portion 33. The radially extending portion 32 is substantially annular with gaps extending circumferentially in the form of sectors. The axially extending portion 33 extends perpendicularly from the inner edge of the radially extending portion 32. When the bottom plate is in position the radially extending portion 32 contacts the bottom surface of the board 30, while the axially extending portion 33 passes through the hole in the board 30 to a level equal with or above the upper surface of the board 30.

In use, the top plate 31 and the radially extending portion 32 of the bottom plate are coupled together by screws 34 which extend through the board 30. The exploded view of Figure 5 illustrates how the screws 34 are used to couple the top plate 31 to the radially extending portion 32 of the bottom plate. Once secured in this manner, the fixing frame can form a seal around the hole in the board 30, which increases the structural integrity of the board 30. For example, the board 30 is often formed of a layered material, and the fixing frame can be used to compress the board 30 in order to ensure that the layers do not delaminate. The fixing frame is typically made of a metal, such as steel, but alternative materials may be used. Preferably, the fixing frame is formed of a material with a sufficiently high melting point to retain its integrity in case of a fire. Preferably, the fixing frame is formed of a material having a higher melting point than the sacrificial member 24. The light fitting 1 can be rotatably mounted to the fixing frame. In this embodiment, the flange 5 of the light fitting 1 has gaps extending circumferentially in the form of sectors. The gaps in the flange 5 are angularly spaced around the flange 5 in substantially the same way as the gaps in the radially extending portion 32 of the bottom plate. This allows the gaps in the flange 5 to coincide with the gaps in the radially extending portion 32 of the bottom plate when the two are brought together. A plurality of first tabs 35 project from an upper surface of the flange 5 and extend in a first circumferential direction (e.g. clockwise) offset from, and substantially parallel with, the upper surface of the flange 5. The first tabs 35 are each associated with, and extend partially or completely across, one of the gaps in the flange 5. In the present embodiment, the first tabs 35 are formed integrally with the flange 5 and each extend from a radial edge of the associated gap in the flange 5. A plurality of second tabs 36 project from a lower surface of the radially extending portion 32 and extend in a second circumferential direction (e.g. anticlockwise) offset from, and substantially parallel with, the lower surface of the radially extending portion 32. The second tabs 36 are each associated with, and extend partially or completely across, one of the gaps in the radially extending portion 32. In the present embodiment, the second tabs 36 are formed integrally with the radially extending portion 32 and each extend from a radial edge of the associated gap in the radially extending portion 32. Preferably, the positions of the second tabs 36 of the radially extending portion 32 correspond with those of the first tabs 35 of the flange 5. In order to couple the light fitting 1 to the fixing frame, the first tabs 35 are passed through the gaps in the radially extending portion 32 of the bottom plate. The light fitting 1 is then rotated in the first circumferential direction (e.g. clockwise) relative to the fixing frame. Consequently, the flange 5 is rotated in the first circumferential direction relative to the bottom plate. This causes the first tabs 35 to move into a position between the second tabs 36 of the radially extending portion 32 and the lower surface of the board 30, thereby rotatably mounting the light fitting 1 to the fixing frame. As shown in Figure 6, the first and second tabs 35, 36 can then interlock with each other to secure the light fitting 1 in the fixing frame.

When the light fitting 1 is coupled to the fixing frame, the first tabs 35 are received in the gaps provided in the radially extending portion 32. Optionally, the second tabs 36 can partially or completely locate within the gaps formed in the flange 5 such that the flange 5 and the radially extending portion 32 abut each other when the light fitting 1 is installed.

In use, the housing 2 of the light fitting 1 extends through the fixing frame in such a way that the axially extending portion 33 of the bottom plate extends around the housing 2. In this embodiment, the bezel 14 is subsequently fitted to the lower side of the bottom plate 102.

The described embodiments of the invention are only examples of how the invention may be implemented. Modifications, variations and changes to the described embodiments will occur to those having appropriate skills and knowledge. These modifications, variations and changes may be made without departure from the scope of the invention defined in the claims and its equivalents.

Claims

1. A light fitting comprising: a housing for housing a lamp, the housing having a wall with a ventilation hole therein; a plate that overlies the ventilation hole and is biased towards the wall; and a sacrificial member for holding the plate apart from the wall such that the ventilation hole is open, wherein melting of sacrificial member allows the plate to move towards the wall to close the ventilation hole.

2. The light fitting of claim 1 , wherein the sacrificial member has a melting point

- above a normal operating temperature of the light fitting but below that of a typical house fire.

3. The light fitting of claim 1 or claim 2, wherein the sacrificial member has a melting point between around 150⁰C and 400⁰C.

4. The light fitting of claim 3, wherein the sacrificial member has a melting point between around 15O⁰C and 300⁰C.

5. The light fitting of any one of the preceding claims, wherein the sacrificial member is a eutectic alloy.

6. The light fitting of any one of the preceding claims, wherein the wall has a plurality of ventilation holes therein and the plate overlies the plurality of ventilation holes.

7. The light fitting of any one of the preceding claims, wherein the sacrificial member is a spacer.

8. The light fitting of any one of the preceding claims, comprising a spring for biasing the plate towards the wall.

9. The light fitting of any one of the preceding claims, comprising an alignment member on which the plate is slidably mounted.

10. The light fitting of claim 9, wherein the alignment member is a tube through which wires can electrically connect the lamp to a power supply outside the housing.

11. The light fitting of claim 9 or claim 10, wherein the sacrificial member is mounted on the alignment member.

12. The light fitting of any one of claims 9 to 11 , wherein a/the spring for biasing the plate towards the wall is mounted on the alignment member.

13. The light fitting of any one of the preceding claims, wherein the light fitting is for recessed mounting in a board.

14. The light fitting of claim 13, further comprising a fixing frame for mounting the light fitting to the board.

15. The light fitting of claim 14, wherein the fixing frame comprises a top plate and a bottom plate, the bottom plate comprising an axially extending portion which, in use, extends through a hole in the board and around the housing.

16. The light fitting of claim 15, wherein the top plate is substantially C-shaped.

17. The light fitting of any one of claims 14 to 16, wherein the light fitting is arranged to be rotatably mounted to the fixing frame.

18. The light fitting of claim 17, further comprising a flange extending from the housing, wherein rotatable mounting of the light fitting to the fixing frame is effected by engagement of the flange with a radially extending portion of a/the bottom plate of the fixing frame.

19. A light fitting substantially as described herein with reference to the accompanying drawings.