GB2454028A

GB2454028A - Fire rated electric light fitting

Info

Publication number: GB2454028A
Application number: GB0800423A
Authority: GB
Inventors: Peter Staniforth
Original assignee: NVC
Current assignee: NVC
Priority date: 2007-10-18
Filing date: 2008-01-11
Publication date: 2009-04-29
Also published as: GB0720402D0; GB0800425D0; GB0800423D0; GB2457871A

Abstract

A fire rated electric light fitting which comprises a solid housing, 1, formed from an inner, 2, and outer, 3, generally cylindrical casings each open at one end and closed at its other end apart form an aperture, 6, 7, through which electric cables or wires can pass, wherein the side wall of each casing includes a plurality of ventilation openings, slots 22, 23, with openings of one casing side wall lying opposite to openings of the other casing side wall to define passageways for the flow of air from the housing interior to the housing exterior, and wherein the space between the casing side walls is at least partially filled with an intumescent material. 11.

Description

Electrical Fittings This invention relates to fire rated electric light fittings. More especially, but not exclusively, the invention relates to a fire rated electric light fitting intended to be recessed in an aperture formed in a ceiling or wall.

Light fittings recessed into ceilings or walls are well known. Such light fittings are known as downlighters. The heat generated by such light fittings can be considerable and represents a fire risk. Also, in the event of a fire the aperture in which the recessed light fitting is located can provide a path for fire and smoke to neighbouring areas.

Fire resistant downlighter light fittings are well known. Such fittings are described inter alia in European patents 1459008 and 0805903, and in GB2422191, GB24 15245 and GB2426321. The first two of these documents relate to flexible covers for light fittings which are coated with an intumescent material and, in use, are positioned above and around a light fitting. The other three documents describe light fittings housed within solid heat resistant casings which include pieces of intumescent material. In GB2422191 pieces of intumescent are located in an outwardly extending flange of the casing and in GB24 15245 a collar of intumescent is located around the outer surface of the casing. In GB2422191 and GB2415245, intumescent is also secured to or positioned below the top surface of the fitting. In one embodiment of GB2426321 intumescent material is provided within an annulor air gap between inner and outer tubular bodies of a downlightcr casing. The intumescent material is adapted to fill the void within the cavity of the casing in the event of a fire. An intumescent material is one which exfoliates, i.e. rapidly expands, in the presence of excessive heat.

Each of the fittings described in these documents exhibits disadvantages and it is an object of this invention to provide an improved fire rated light fitting having fire resistance properties which at least match those of earlier light fittings and which is easier to install. It is a further objective of this invention to provide an air cooled fire rated light fitting in which intumescent material used to provide enhanced fire protection is positioned to ensure maximum effectiveness in the event of a fire without imposing excessive pressure on the internal structure of' the downhighter casing and/or the ceiling or wall panel in which it is mounted,.

In one aspect the invention provides a fire rated electric light fitting which comprises a solid housing formed from inner and outer generally cylindrical casings each open at one end and closed at its other end except for an aperture through which electric cables or wires can pass, wherein the side wall of each casing includes a plurality of ventilation openings with openings of one casing side wall lying opposite openings of the other side wall to define passageways for the flow of air from the housing interior to the housing exterior, and wherein the space between the casing side walls is at least partially filled with intumescent material without obstructing the flow of air through the opposed pairs of ventilation openings of the two casings, the arrangement being such that in the event of a fire the material intumesces completely to close the ventilation openings.

In a preferred arrangement the space between the casing side walls is entirely filled with intumescent material apart from the spaces between opposed side wall openings. The openings preferably comprise elongate slots formed in the opposed walls of the inner and outer casings. In a preferred arrangement the slots extend lengthwise of the casings and are spaced around the circumference of each casing and are separated from one another by lands. The slots may be evenly spaced around the casing circumferences. Typically eight slots are formed in each casing, four slots positioned to each side of sprung clips connected to the outer wall of the outer casing and operable to locate the light fitting securely within a ceiling or wall aperture. The elongate slots are preferably positioned so that they extend over the casing length remote from the open end of each casing. Thus, the slots typically extend from positions generally mid-height of the casings, or close to mid-height, to positions close to the closed ends of the casings.

Each casing may also be provided with a plurality of complementary slots positioned close to its open end. In one arrangement these slots extend generally radially and are separated one from another by lands. Typically two rows of radial slots are provided in the outer casing and one row in the inner casing.

The intumescent material may comprise a plurality of individual solid strips positioned lengthwise of the downiighter casing. In one arrangement the intumescent material comprises one or more strips or sheets of intumescent material formed with openings whose positions correspond to the positions of the slots formed in the inner and outer casings.

Inrumescent material is preferably also positioned between the closed ends of the inner and outer casings to close the apertures through which wires or cables pass in the event of fire.

The invention will now be described by way of example only with reference to the accompanying drawings in which:- 1 5 Figure 1 is a side view of a fire rated downlighter in accordance with the invention; Figure 2 is a plan view from above of the downlighter shown in Figure 1; Figure 3 is a section taken along lines 3-3 of Figure 2; Figure 4 is a view to an enlarged scale of a detail marked "A" on the downlighter shown in Figure 3; Figure 5 is a section taken along lines 5-5 of Figure 2; Figure 6 is a view to an enlarged scale of a detail marked "B" on the downlighter shown in Figure 5; Figure 7 is a perspective view of the outer casing of the illustrated downlighter; Figure 8 is a sectional view of the casing shown in Figure 7; Figure 9 is a perspective view of the inner casing of the illustrated downlighter; Figure 10 is a sectional view of the casing shown in Figure 9; and Figures 11, 12 and 13 are respectively plan, end and side views of a hinged bracket for a terminal bracket of the illustrated downlighter.

The illustrated down]ighter comprises a solid housing 1 having inner and outer generally cylindrical casings 2,3 each of which is open at one end and formed at its other end with a top 4,5 respectively. Each top includes an opening 6,7 through which electric wiring or cabling for an electric light positioned within the housing can pass. As will be seen from the drawings, the diameter of the inner casing 2 is slightly less than that of the outer casing 3 to provide an annular space when the inner casing is located within the outer casing. This annular space extends over the full height of the housing I and is filled with intumescent material 8. The material 8 may comprise discrete strips of intumescent material or one or more sheets of such material.

The top 4 of the inner casing 2 is formed with an indent 9 which defines with the under surface of the top 5 a chamber in which is positioned a piece of intumescent material 11. The intumescent piece 11 has an opening which corresponds with the openings 6,7 to enable wiring or cabling to pass through.

The outer casing has a lip 12 which borders its open end and which locates against the adjoining edge of a wall or ceiling panel when the downlighter is in use. As will be seem particularly from Figure 5, immediately above this lip is an annular channel 14 for receiving a supporting clip 15 for an electric light 16. An outwardly extending flange 17 of the light 16 is retained below an outwardly extending lip 18 of the inner casing 2 and is trapped between this lip and the clip 15. The open end of the downlighter can be closed, in use by a suitably dimensioned transparent cover.

Formed in the upstanding walls of the casings 2,3 are a series of longitudinally extending ventilation slots 19,21. The slots 19 formed in the inner casing 2 are complementary to those formed in the outer casing 3 in the sense that the former are positioned immediately opposite the latter. The margins of the slots 19 may have outwardly protruding returns. The intumescent material 8 is positioned to fill the space between the two casings I,3. In this way, air to ventilate the downlighter interior passes freely through the slots to cool the downlighter interior and the light.

In the event of a fire, however, the inturnescent material 8 quickly exfoliates to close the slots and prevent the passage of fire and smoke from the downlighter interior to the surrounding structure. The outwardly protruding returns at the margins of the slots (if provided) assist in directing the exfoliating intumescent into and through the slots to close the same. At the same time the intumescent piece expands to close the openings 6,7.

Additional slots 22,23 are formed in the upstanding walls of the inner and outer casings. These slots extend radially of the casings and, as for the slots 19,21 the slots 22 are positioned immediately behind the slots 23; in other words, the slots are complementary. As will be seen from the drawings, the slots 22,23 extend radially about the circumference of the casings with each slot being separated from its neighbouring slots by lands 24. Two rows of slots are provided in the outer casing with the lowermost row positioned close to the open end of the respective casing and indexed relative to the uppermost row. Only one row of slots 22 is formed in the inner casing 2. Unlike the slots 19,21 intumescent material is sited between the slot openings. In the event of a fire it is important to ensure that flames and smoke are prevented from passing through the ceiling or wall aperture in which the downlighter is located. In the event of a fire, the intumescent positioned between the slots 22,23 intumesces to pass through the slots 23 and completely fill any spaces between the downlighter housing I and the adjoining edge surfaces of the ceiling or wall surface in which it is mounted.

The amount of intumescent employed is sufficient to close the ventilation slots and any space between the downlighter housing completely and the adjoining ceiling or wall structure but not to fill the housing interior. This ensures rapid closure of the housing and the area between the housing and the ceiling or wall panel in which it is mounted thereby preventing the spread of fire and smoke to adjoining areas.

The downlighter is secured in place within a ceiling or wall space with spring mounted clips 25. Each clip includes downwardly extending arms 26 joined to a spring piece 27. Each piece 27 locates on inwardly extending pieces of a bracket 29 located one on each opposed side of the outer casing 3 and operates to urge the arms 26 downwardly. The ends of the arms 26, in use, bear against the upper surface of the ceiling or wall panel in which the downlighter is mounted to hold it firmly in place. Two pairs of brackets 29 are provided, one above the other. The lower pair are for use with ceilings or walls formed from two or three plasterboard sheets providing 60 minute fire rating and the upper pair for ceilings or walls comprising three or more plasterboard sheets providing upwards of 90 minutes fire rating.

A terminal block 3 1 for the light is carried on a bracket 32 secured to the outer surface of the top 4 of the outer casing 3. The bracket can be seen most clearly in Figures 11 to 13. When locating a downlighter into, for example, a ceiling space, an aperture is cut in an appropriate ceiling panel and the downlighter pushed up into the ceiling space with the arms 26 of the sprung clips 25 pulled inwards towards the housing 1. If, as is conventional, the terminal block bracket is a solid one piece structure, installation of the downlighter will either prove to be extremely cumbersome or a larger aperture will be required. In the present invention, the bracket 32 is formed in two sections 33,34 joined together by a hinge 35. Thus, as will be seen from Figures 11 to 13, the terminal block 31 is secured to the bracket section 33 with the section 34 being secured to the top of the outer casing. This arrangement allows the terminal block to lie generally in line with the housing during installation of the downlighter and then to move or be moved to the conventional position shown in full line in Figure 1.

In use, the illustrated fire rated downlighter is installed in a ceiling or wall panel as described. In the event of a fire, the intumescent material 8,11 expands rapidly to close the ventilation slots and the openings through which wires or cables pass to the light 16 to seal the housing and prevent the passage of flames and smoke. At the same time exfoliating intumescent passes through the slots 22,23 to fill the space between the housing I and the sides of the ceiling or wall panel in which it is located. Positioning the intumescent as described ensures that the expanding material quickly and controllably seals the ventilation slots and the open end of the housing to prevent the passage of flames and smoke to surrounding areas. As mentioned previously, the amount of intumescent is insufficient to fill the housing interior completely thereby avoiding undue pressure being imposed on the internal structure of the downlighter housing and the ceiling or wall panel in which it is mounted. Also, the presence of intumecent sandwiched between and in contact with the opposed walls of the inner and outer casings provides a degree of heat insulation supplemented by the flow of ventilating air via the opposed slots of the two casings.

It will be appreciated that the foregoing provides a description of embodiments of the invention and that modifications can readily be made without departing from the true scope of the invention as set out in the appended claims.

Claims

Claims A fire rated electric light fitting which comprises a solid housing formed from inner and outer generally cylindrical c&sings each open at one end and closed at its other end apart from an aperture through which electric cables or wires can pass, wherein the side wall of each casing includes a plurality of ventilation openings with openings of one casing side wall lying opposite to openings of the other casing side wall to define passageways for the flow of air from the housing interior to the housing exterior, and wherein the space between the casing side walls is at least partially filled with intumescent material without obstructing the flow of air through the opposed pairs of ventilation openings of the two casings, the arrangement being such that in the event of a fire the material intumesces completely to close the ventilation openings.
2. An electric light fitting as claimed in claim 1 wherein the space between the casing side walls is entirely filled with intumescent material apart from the airflow passageways between the opposed ventilation openings of the inner and outer casing side walls.
3. An electric light fitting as claimed in claim I or claim 2 wherein the ventilation openings comprise elongate slots formed in the opposed walls of the inner and outer casings.
4. An electric light fitting as claimed in claim 3 wherein the slots extend lengthwise of the casings and are spaced around the circumfcrcnce of each casing.
5. An electric light fitting as claimed in claim 4 wherein the slots are evenly spaced around the casing circumferences and are spaced apart by lands.
6. An electric light fitting as claimed in any one of the claims 3 to 5 wherein eight slots are formed in each casing side wail, four slots positioned to each side of sprung clips connected to the outer wall of the outer casing and operable to locate the light fitting securely within a ceiling or wall aperture. c-i
7. An electric light fitting as claimed in any one of claims 3 to 6 wherein the elongate slots extend over at least one half of each casing length.
8. An electric light fitting as claimed in any one of claims 3 to 7 wherein the slots extend from positions generally mid-height of the casings, or close to mid-height, to positions close to the closed ends of the casings.
9. An electric light fitting wherein the edges of slots formed in the side wall of the inner casing are turned outwardly towards the side wall of the outer side wall.
10. An electric light fitting as claimed in any one of claims 4 to 10 wherein each casing also has a plurality of opposed clots positioned towards it open end.
11. An electric light fitting as claimed in claim 10 wherein the opposed slots extend generally radially of each casing and are separated one from another by lands.
12. An electric light fitting as claimed in claim 11 wherein two rows of radial slots are provided in the side wall of the inner casing and one row in the side wall of the outer casing.
13. An electric light fitting as claimed in any one of the preceding claims wherein intumescent material is positioned between the closed ends of the inner and outer casings to close the apertures through which wires or cables pass in the event of fire.
14. A fire rated electric light fitting comprising a solid housing including an inner and an outer generally cylindrical casing each of which is open at one end and closed at its other end apart from apertures through which electrical wires or cables can pass, and opposed ventilation openings formed in the side wall of each casing to provide air flow pathways between the housing interior and exterior, the casings being spaced one from the other with intumescent filling this space apart from the air flow pathways between the ventilation openings. (C
15. A fire rated electric light fitting substantial as herein described and as described with reference to the accompanying drawings.