EP2899453A1

EP2899453A1 - Lighting unit

Info

Publication number: EP2899453A1
Application number: EP14195516.1A
Authority: EP
Inventors: Justin Maeers
Original assignee: Collingwood Lighting Ltd
Current assignee: Collingwood Lighting Ltd
Priority date: 2014-01-22
Filing date: 2014-11-28
Publication date: 2015-07-29
Also published as: GB201401065D0; GB2522419B; GB2522419A

Abstract

A lighting unit including a first part (3) having a mounting structure (5); a second part (9) including at least one solid state lighting device (15) and a heat sink (17), said heat sink (17) being mounted in thermal contact with the solid state lighting device (15) such that at least some of the heat generated by the solid state lighting device (15) is transferred to the heat sink (17) by conduction, wherein the second part (9) is pivotable with respect to the first part (3); and a seal (21) arranged to seal the first part (3) to the second part (9), said seal (21) being arranged to deform to accommodate pivoting movement of the second part (9) with respect to the first part (3).

Description

The present invention relates to a lighting unit, for example a downlight that includes a solid state lighting device. In particular, to a lighting unit that is adjustable.
An adjustable downlight typically includes a static mounting structure, for example an outer casing that is mounted in an aperture in a ceiling and an internal structure that carries a light source that is pivotable with respect to the mounting structure. Pivoting the internal structure with respect to the mounting structure adjusts the angle at which light is emitted from the lighting unit. For example, the light source can be adjusted so that it is aligned with a vertical axis, or it can be adjusted such that the light source is inclined to the vertical axis.
The internal structure can be pivotally attached to the mounting structure by pivot members and can pivot about a single axis. Other lighting units have more than one degree of freedom.
With angularly adjustable lighting units there are several design challenges.
A first challenge is adapting adjustable lighting units for moist environments, such as bathrooms, kitchens, and outdoor applications. This is because there is a gap between the static mounting structure and the adjustable internal structure to enable the internal structure to pivot relative to the mounting structure. Moisture enters the lighting unit via the gap and can cause damage to electrical components, which overtime may cause the lighting unit to fail.
A known way to deal with this problem is to apply a steel can over the entire lighting unit, which is closed off at its upper end. The steel can acts as a moisture barrier and prevents moisture from entering the void above the ceiling. An example of this type of lighting unit is shown in Figure 1. The unit A includes a steel can B, heat sink C and solid state lighting unit having a lens unit D.
A second challenge is to meet the requirements of building regulations, where applicable. Some countries have regulations regarding fire resistance. Fire-rated lighting units of the type that fit into an aperture in a partition are designed to maintain the integrity of the partition in the event of a fire. Some countries' building regulations, such as United Kingdom building regulations, require ceilings to survive for a specified period of time when a fire occurs and the fire-rated lighting units play a very important role in achieving this rating. The holes that are cut through the partition to accommodate the lighting units provide pathways for the flames to access the floor above the ceiling. The lighting units close these pathways off and therefore in order for the ceiling to adequately defend the floor above, the lighting units must not fail within the specified rating period, such as 30 minutes, 60 minutes or 90 minutes.
Since adjustable lighting units have a gap between the internal structure and the mounting structure, this provides a potential weakness to fire resistance. In some arrangements, increasing the angle of inclination of the internal structure with respect to the mounting structure increases the size of the gap, and hence the vulnerability to fire. To mitigate this problem, many adjustable fire-rated lighting units include a large fire resistant can which is mounted over the entire lighting unit (see arrangement in Figure 1, where the steel can B acts as a moisture barrier and a fire resistant barrier). However the can is relatively large, which increases the weight and cost of the lighting unit. Alternatively, a fire resistant hood can be placed over the entire lighting unit. The hood is a separate component from the lighting unit and is applied during installation. The fire can/hood can significantly impede air flow around the light source, and in some instances, particularly with some solid state lighting units, can lead to overheating problems.
A third challenge for angularly adjustable lighting units arises when the light source comprises one or more solid state lighting devices. The performance and the useful life of solid state lighting devices, such as Light Emitting Diode (LEDs), is significantly affected by heat generated in use by the LEDs. In order to obtain good performance, and a long life, it is necessary to remove heat from the LEDs as efficiently as possible, therefore good thermal management is required. However, this can be difficult to achieve when the light source is movable, there is a need to seal the lighting unit against moisture ingress, and/or there is a need to make the lighting unit fire resistant.
One way to deal with the overheating problem is to include several openings in the can B, typically in the end wall E, to enable heat to dissipate to the environment by convection. However this compromises the ability of the can B to act as a moisture barrier. Therefore there is a desire to provide a solid state lighting unit that is arranged to have good thermal management, is fire resistant and prevents moisture from entering the void in the ceiling.
A fourth challenge is to provide an adjustable lighting unit that is low weight, and easy to manufacture and assemble.
Accordingly the invention seeks to provide a lighting unit that mitigates at least one of the above-mentioned problems or provides an alternative solution thereto.
According to one aspect of the invention, there is provided a mounting structure, such as a ceiling or wall; and a second part including at least one solid state lighting device and a heat sink, said heat sink being mounted in thermal contact with the solid state lighting device such that at least some of the heat generated by the solid state lighting device is transferred to the heat sink by conduction, wherein the second part is pivotable with respect to the first part. A seal is provided to seal the first part to the second part, said seal being arranged to deform to accommodate pivoting movement of the second part with respect to the first part. The mounting structure is arranged for insertion into an aperture in the partition and the seal prevents moisture travelling through the lighting unit into the void above the ceiling, even when the orientation of the second part is adjusted with respect to the first part. The invention provides a very simple, light weight, sealed adjustable LED lighting unit.
Advantageous features of preferred embodiments are recited in the dependent claims and are further described below.
Advantageously the seal is annular. This enables the seal to be mounted around the inner part. The seal is substantially circular in plan view.
Advantageously the seal includes a membrane having an outer peripheral portion that sealably engages to the first part. The seal includes an inner peripheral portion that sealably engages to the second part. The seal includes a central connector portion connecting the outer peripheral portion to the inner peripheral portion. In preferred embodiments, at least the central portion of the membrane is flexible. Preferably the entire seal is flexible. The membrane provides a thin walled structure that enables the seal to deform when the second part is pivoted with respect to the first part without compromising the seal between the first and second parts.
Advantageously the outer peripheral portion is annular. Advantageously the inner peripheral portion is annular.
Advantageously the connector portion of the membrane is shaped to include at least one hollow substantially ∩-shaped cross-section having an annular inner side wall and an annular outer side wall; and/or at least one hollow substantially U-shaped cross-section having an annular inner side wall and an annular outer side wall. The connector portion extends into the gap between the first and second parts, for example between a heat sink and casing (see below). The connector portion of the seal is not clamped and therefore is able to freely deform when the orientation of the second part is adjusted with respect to the first part. The or each ∩-shaped, and/or U-shaped, cross-section provides sufficient membrane material to enable the seal to deform easily, which reduces the load required in order to deform the membrane. This helps to increase the useful life of the seal.
Advantageously at least a part of the seal is resilient. In preferred embodiments the or each ∩-shaped, and/or U-shaped, portion is resilient. Preferably the entire seal is made from a resilient material. This enables the seal to deform resiliently. The seal may include a resilient material such as silicone, rubber or a silicone rubber.
Advantageously the inner peripheral portion includes an inner lip and/or the outer peripheral portion includes an outer lip. The inner lip is annular and extends substantially perpendicularly inwardly from the inner side wall. The outer lip is annular and extends substantially perpendicularly outwardly from the outer side wall.
The seal has a central axis, and advantageously the inner lip is offset from the outer lip in the axial direction.
In preferred embodiments, the seal is a moulded component.
Advantageously the second part includes a support member. Advantageously, in some embodiments, the support member is fire resistant. This arrangement is particularly useful for buildings where materials located behind the lighting unit are flammable, such as a wooden upper floor.
Advantageously the support member includes material that melts at a temperature greater than or equal to 900C, preferably greater than or equal to 950C, more preferably still greater than or equal to 1000C, and more preferably still greater than or equal to 1050C. The support member can be made from a single material or can include a plurality of materials. The support member can comprise a single piece construction or can include a plurality of components. In preferred embodiments the support member includes steel. Of course, if the lighting unit is to be used in applications where fire resistance is not required, the support member can be made from non-fire resistant material(s), for example, may include aluminium.
Advantageously the support member includes sheet material. In preferred embodiments the support member substantially consists of sheet material. The support member preferably has a thickness of at least 0.3mm. The thickness is typically less than 4 mm, and preferably less than 3mm. It has been found that providing a steel fire resistant member of a sufficient thickness provides the fire resistant quality, that is, it does not melt at temperatures below 900C. Of course, other materials having a high melting point can be used, for example brass, ceramic and/or copper.
Advantageously the support member has a front side and a rear side, and the heat sink is located on the rear side of the support member.
Advantageously the inner peripheral portion of the seal is clamped between the heat sink and the support member. For example, the inner lip can be clamped between the rear side of the support member and an end face of the heat sink. The heat sink is attached to the support member by at least one screw member, which applies the clamping load to the seal. In some embodiments, a central screw member secures the support member-solid state lighting device-heat sink-driver unit assembly together.
In some embodiments, the support member comprises a housing. In preferred embodiments, the housing is fire resistant. The housing includes an end wall and at least one side wall. The housing is open at the front end. For substantially cylindrical housings, the housing has one side wall. For other shapes of housing, the housing includes a plurality of side walls, for example a substantially cuboid housing includes four side walls. Advantageously the housing includes a flange at the open end. The flange extends outwardly from the or each side wall.
Advantageously the support member includes at least one first hole formed there through from the front side to the rear side; and the solid state lighting device is at least partly located on the rear side of the support member. For embodiments where the support member comprises the housing, the or each hole is preferably formed through the end wall of the housing.
The solid state lighting device is mounted in relation to the or each first hole such that light emitted from the solid state lighting device exits a front side of the lighting unit. The lighting device is positioned adjacent to, or at least partly within, the hole. For example, the lighting device can be arranged in relation to the hole in one of the following ways: the lighting device is located fully on the rear side of the support member and light emitted from the lighting device passes through the hole; the lighting device is partly located in the hole but does not protrude therefrom; and the lighting device is partly located in the hole and protrudes therefrom on the front side of the support member.
Advantageously the support member includes a plurality of holes formed there through, and the solid state lighting device includes a plurality of LEDs, typically each LED having an associated hole. Each LED is arranged in relation to its associated hole similarly to that described above. Any practicable number of holes can be included in the support member that does not compromise its fire resistant ability. The support member can have n holes for receiving LEDs, wherein n is typically in the range 1 to 20, and preferably n is in the range 1 to 10 holes. Advantageously the or each hole in the support member has a diameter N, wherein N is less than or equal to around 10mm. Each hole is relatively small to maintain the fire resistant qualities of the member. The larger the or each hole the greater the propensity of flames to pass through the hole and damage things on the other side of the partition. Preferably each hole has a diameter N in the range 1mm to 8mm, and more preferably still within the range 1mm to 5mm.
Advantageously the sold state lighting device includes at least one LED and a PCB, wherein the PCB is mounted on the rear side of the support member, and the heat sink is mounted on the rear side of the PCB. In embodiments including the housing, the PCB is mounted on the rear side of the end wall of the housing and the heat sink is mounted onto the rear of the PCB (a thermal paste and/or thermal pad can be located between the heat sink and PCB in order to assist heat transfer by way of conduction). Thus there is a substantially direct connection between the heat sink and the solid state lighting unit, which promotes good heat transfer by conduction.
In an alternative advantageous arrangement, the solid state lighting device is mounted on the front side of the support member wherein the lighting element is mounted in thermal contact with the support member so that heat generated in use by the lighting device is transferred by conduction into the support member. The heat sink is mounted in thermal contact with the rear side of the support member to dissipate heat from the support member, the arrangement being such that heat generated in use by the lighting device is transferred by conduction to the heat sink via the support member. Preferably the solid state lighting device includes at least one LED and a PCB. For embodiments including a housing, the PCB is mounted on the front side of the end wall of the housing, and the heat sink is mounted on the rear side of the end wall. Thus the solid state lighting device and the heat sink are separated by the thickness of the end wall, however at least that part of the housing is thermally conductive, and therefore heat generated by the solid state lighting device is conducted into the heat sink via the housing. A thermal paste and/or thermal pad can be located between the heat sink and the support member / housing in order to assist heat transfer by way of conduction.
Advantageously the support member, preferably in the form of the housing, is pivotally attached to the first part. Since the solid state lighting device and heat sink are mounted on the support member, they pivot with the support member as a unit. The support member-solid state lighting assembly-heat sink assembly is pivotally attached to the first part towards one end thereof, and preferably towards a lower end thereof, that is, towards the front of the lighting unit.
Advantageously the first part of the lighting unit includes a casing. The casing at least partly houses the second part of the lighting unit. The casing includes at least one side wall. For a cylindrical casing having a single side wall, the side wall circumferentially surrounds the second part. The casing may of course take other shapes, for example may have a substantially rectangular cross-section, and include a plurality of side walls that together surround part of the periphery of the second part.
Advantageously the casing includes first and second ends, and the casing is open at the first and second ends. This provides a substantially tubular structure. The opening at the second end provides good ventilation for the heat sink.
Advantageously the first part includes a bezel. The bezel is attached to the first end of the casing, preferably via the first opening.
Advantageously the bezel is fire resistant. The bezel includes material that melts at a temperature that is greater than or equal to 900C. For example, the bezel can include steel. It preferably has a thickness of at least 0.3mm. The thickness is typically less than 4 mm, and preferably less than 3mm.
Advantageously the support member, preferably in the form of the housing, is pivotally attached to at least one of the casing and the bezel. In preferred embodiments the housing is pivotally attached to the bezel, since this aids assembly of the lighting unit.
Advantageously the bezel includes a flange and a collar. The collar connects the bezel to the casing. The collar is arranged to fit into the first end of the casing. The support member is pivotally attached to the collar. For embodiments including the housing, at least one side wall of the housing is pivotally attached to the collar.
Advantageously the outer peripheral portion seals against one of the casing and the bezel. In preferred embodiment the outer peripheral portion seals against the bezel collar. For example, the collar can include an annular groove that is arranged to receive the outer lip.
Advantageously the lighting device includes a lens module. The lens module is located on a front side of the support member, and preferably inside the housing.
Advantageously the lens device is coupled to at least one of the heat sink and the support member by way of a push-fit coupling. This obviates the requirement for screws and speeds up the assembly process. For example, the support member can include a plurality of holes formed there through from the font side to the rear side.
The lens module includes a plurality of male coupling members. The heat sink includes a plurality of female coupling members. The lens module is attached to the heat sink in a push-fit manner with the male and female coupling members connecting via respective second holes. The PCB may also include through holes to enable the male connector members to engage the female connector members.
Advantageously at least some of the male coupling members are arranged to deform, and preferably plastically deform.
Advantageously the lighting unit is a downlight.
According to another aspect of the invention there is provided a method for preventing moisture from penetrating a hole formed in a partition, including inserting into the hole a lighting device according to any configuration described herein, and optionally sealing the lighting device to the partition.
A method for preventing fire from penetrating a hole in a partition, including inserting into the hole a lighting device according to any configuration described herein that includes a fire resistant support member and/or a fire resistant bezel.
According to another aspect of the invention, there is provided a mounting structure which is arranged for insertion into an aperture in a partition, such as a ceiling or wall; and a second part including at least one solid state lighting device and a heat sink, said heat sink being mounted in thermal contact with the solid state lighting device such that at least some of the heat generated by the solid state lighting device is transferred to the heat sink by conduction, wherein the second part is pivotable with respect to the first part.
An embodiment of the invention will now be described by way of example only with reference to the drawings, wherein:

Figure 1 is a cross-sectional view diagrammatic view of a prior art device;
Figure 2 is a cross-sectional view of a lighting unit according to an embodiment of the invention;
Figure 3 is a cross-sectional view of an enlarged section of Figure 1;
Figure 4 is a cross-sectional view of a seal used in the first embodiment of the invention;
Figure 5 is a side view of a lens module used in the embodiment of Figure 1;
Figures 6 and 7 are cross-sectional views of the lighting unit of Figure 2 with a pivotable interior part shown in different orientations (in Figure 6, a lens module is omitted for clarity);

Figures 2 to 6 show a lighting unit 1 in accordance with an embodiment of the invention. The lighting unit 1 is in the form of a downlight, which is typically mounted in an aperture in a ceiling, though of course can be mounted in other partitions such as a wall.
The lighting unit 1 includes a first part 3, having: a casing 5; and bezel 7.
The lighting unit 1 includes a second part 9, having: a support member in the form of a fire resistant housing 11; a lens module 13; a solid state lighting device 15; a heat sink 17, and a driver unit 19 for the solid state lighting device. The second part 9 is pivotally attached to the first part 3 in the manner described below. This enables the angular orientation of the solid state lighting device 15 to be adjusted with respect to the first part 3, thereby adjusting the angle at which light is emitted from the lighting unit 1.
The lighting unit 1 also includes a seal 21 that seals the first part 3 to the second part 9. The seal 21 prevents moisture passing through the lighting unit via the gap between the first and second parts.
The casing 5 provides a mounting structure. It comprises a substantially cylindrical shell that includes a first opening 23 at a first end 25 and a second opening 27 at a second end 29. The first opening 23 is arranged to receive and engage the bezel 7. The second opening 27 is a vent and is provided to promote good air circulation around the heat sink to assist heat transfer to the environment by convection. The casing 5 also includes several apertures 31 formed through a side wall 33 of the casing for similar reasons to the second opening 27.
The bezel 7 includes a flange 35 and a collar 37, and is preferably made from steel. The flange 35 provides an initial barrier against fire leaking through the hole formed in the ceiling, for example in the situation where the installer has not cut a neat hole into the ceiling. The bezel 7 also provides an aesthetically pleasing finish to the front side of the lighting unit.
The collar 37 is connected to the casing 5. This can be achieved, for example by way of at least one of: an external screw thread formed on the collar 37 and an internal screw thread formed on the casing; screws; rivets; and a push-fit coupling for example that has interference fit. The collar 37 includes a circumferential groove 39 formed in its inner surface 41, which engages with the seal 21. First and second holes 43,45, or recesses, are formed in the collar 37. The first and second holes 43,45, or recesses, are formed diametrically opposite to one another, and enable the second part 9 to be pivotally connected to the first part 3.
The lighting unit 1 can optionally include spring loaded clips (not shown) that are pivotally mounted to, for example the casing 5, and are arranged to be manually pinched closed when inserting the lighting unit into the partition and to spring outwards when released by the installer to load the partition. The biasing force generated by the spring loaded clips is sufficient to retain the lighting unit within the partition.
The second part 9 comprises an assembly that is pivotable with respect to the first part 3 as a unit. The arrangement of the assembly is described below.
The fire resistant housing 11 resembles an open ended cylindrical box having a side wall 47 and an end wall 49. The housing 11 may of course take any convenient shape. The housing 11 has a front side 'A' that faces outwards from the casing 5 and a rear side 'B' that faces towards the casing 5. The housing 11 is made from material having a melting point that is greater than or equal to 900°C, for example at least part of the housing, and preferably the entire housing, is made from a metal such as steel. The housing 11 is preferably made from sheet material, such as sheet steel, and is formed by a pressing process. Typically the thickness of the sheet material, and hence the walls of the housing 47,49, is in the range 0.3 to 4mm, and preferably 0.3 to 3mm. Thus the housing 11 is arranged such that it does not melt at temperatures below 900°C. The housing 11 preferably comprises a single pressed component, however the housing can comprise a plurality of parts connected together. Each component part can be made from a different material.
The housing 11 includes two pivot members 47a,47b formed in the side wall 47. The pivot members 47a,47b are arranged to engage with the holes 43,45, or recesses, formed in the collar 37. The pivot members 47a,47b enable the second part 9 to pivot with respect to the first part. The pivot members 47a,47b can be formed integrally with the housing 11, for example can be pressed from the housing material. For a substantially cylindrical housing 11 having one side wall 47, the pivot members 47a,47b are arranged diametrically opposite to one another. Each pivot member 47a,47b extends radially outwardly from the side wall 47.
The housing 11 includes first and second sets of holes 51,53 formed through the end wall 49.
The solid state lighting device 15 includes at least one LED 55, and typically 1 to 10 LEDs 55 (three are provided in the embodiment shown in the Figures) mounted on a printed circuit board (PCB) 57. The solid state lighting device 15 is at least partly mounted on the rear side 'B' of the end wall 49 of the housing 11 and is arranged such that light emitted by the LEDs 55 passes through the first set of holes 51. The PCB 57 lies on the rear side of the end wall 49 and each LED 55 is positioned in and/or adjacent a respective hole 51. For example, each LED 55 can be located fully outside of its respective hole 51 on the rear side 'B' of the housing, partially within its respective hole 51, or such that it at least partly protrudes out of its respective hole 51 into the front side 'A' of the housing. However at least a part of the solid state lighting device 15, typically a part including the PCB 57, is located on the rear side 'B' of the housing so that it can be thermally connected with the heat sink 17 (see below) to enable heat to be conducted from the LEDs 55 to the heat sink 17.
Each hole 51 is sized such that it is just large enough to accommodate the light emitting part of the LED 55, and therefore typically has a diameter in the range 1 to 10mm depending on the size of the LED 55. Since the holes 51 are relatively small, and few in number, the ability of the housing to resist fire is not compromised.
The heat sink 17 is at least partly made from a thermally conductive material, for example can comprise an aluminium extrusion. The heat sink 17 is mounted on the rear side 59 of the PCB and is arranged such that there is good thermal contact between an end face 61 of the heat sink and the rear side 59 of the PCB. This may be assisted by using a thermal paste and/or a thermal pad to displace air pockets between them. Thus, during use, heat generated by the solid state lighting device 15 is transferred from the device 15 to the heat sink 17 by thermal conduction. Since the heat sink 17 is mounted on the rear side 59 of the PCB the thermally conductive pathway is very short, with minimal thermal interfaces, and thus heat can be removed from the solid state lighting device 15 very efficiently. This helps to ensure good performance for the LEDs 55 and a long service life.
The heat sink 17 includes a third set of holes 63. The holes 63 in the third set are formed in the end face 61 of the heat sink and extend axially into the heat sink 17. Each hole 63 is aligned with a respective hole 53 in the second set of holes formed through the end wall 49 of the housing (and where required, a corresponding set of holes formed through the PCB).
The lens module 13 is mounted in the housing 11 on the front side 'A'. The lens module 13 includes three lenses 65 (one for each LED 55) and three connector members 67. Each lens 65 includes four crush pins 69 protruding substantially perpendicularly therefrom. Each crush pin 69 has a substantially conical form.
When the lighting unit 1 is assembled, the crush pins 69 impinge on the housing 11 and collapse under load. The purpose of the crush pins 69 is to account for manufacturing tolerances between the housing 11 and the bezel 7.
The connector members 67 are arranged to connect the lens module 13 to the heat sink by way of a push-fit interference fit with the third set of holes 63, and passing through the second set of holes 53 formed in the end wall 49 of the housing. Each connector member 67 tapers along its length from a broader proximal end 71 to a narrower distal end 73. Each connector member 67 includes four crush ribs 75 that run longitudinally along the connector member 67 and protrude radially outwards therefrom. Each rib 67 tapers towards the distal end 73. The crush ribs 75 plastically deform when inserted into their respective holes 63 in the third set, thereby tightly holding the lens module 13 to the heat sink. The connector members 67 effectively replace screws and therefore simplify the assembly process.
The lens module 13 comprises a moulded component and therefore the lenses 65, connector members 67, and crush pins 69 are integrally formed. Preferably the lens module 13 is made from a plastics material such as acrylic and is formed by injection moulding.
The lens module 13 closes the open side of the housing 11. The lens module 13 is sealed to the housing 11 thereby preventing moisture from entering the fire resistant housing 11.
The seal 21 provides a moisture barrier between the first and second parts 3,9, and therefore prevents moisture from entering the void above the ceiling via the gap between the first and second parts 3,9. The seal 21 is flexible. It is made from a resilient material such as silicone or natural rubber, and is able to deform elastically.
The seal 21 comprises a flexible membrane having the shape shown in Figure 3, said shape being formed by a moulding process. The flexible membrane provides the seal 21 with a thin walled structure that enables the seal to deform, for example flex and/or stretch, when the second part 9 is pivoted with respect to the first part 3, without compromising the seal between the first and second parts 3,9.
The seal 21 is annular, and is substantially circular in plan view. The seal 21 includes a central portion 78 having a hollow substantially ∩-shaped, or U-shaped, cross-section. It includes an annular inner side wall 79 and an annular outer side wall 81. At least a portion of the inner side wall 79 is substantially parallel with at least a portion of the outer side wall 81. The ∩-shaped, or U-shaped, cross-section provides a flexible folded membrane structure, which reduces the load required in order to deform the membrane. The seal 21 is closed at a first side 83 and open at a second side 85. The closed side 83, inner side wall 79 and outer side wall 81 define an annular channel 87.
The seal 21 is located within the unit such that the closed side 83 is oriented upwards (∩-shaped), however it will be appreciated by the skilled person that the seal 21 can be inverted with respect to the first and second parts 3,9, thereby providing a substantially U-shaped arrangement.
The seal 21 includes an annular inner lip 89. The inner lip 89 extends substantially radially inward from the end portion of the inner side wall 79, towards the end thereof. The inner lip 89 surrounds the solid state lighting unit 15, in one plane. The seal includes an annular outer lip 91. The outer lip extends substantially radially outwards from the outer side wall 81, towards the end thereof. The central portion 78 connects the inner lip 89 to the outer lip 91.
The seal 21 has a central axis 93, and the inner lip 89 is offset from the outer lip 91 in the axial direction.
The outer lip 91 is seated in the annular groove 39 formed in the bezel collar 37. The outer lip 91 is sized and shaped to form a seal with the groove 39 and hence the first part 3. The outer lip 91 is firmly attached to the groove 39 by an adhesive 92, and preferably a quick drying adhesive 92 to aid assembly. The function of the groove 39, and adhesive, is to ensure that the seal 21 does not disassociate from the bezel 7 when the second part 9 is tilted with respect to the first part 3. The inner lip 89 is sized and shaped to be clamped between the heat sink 17 and the rear side 'B' of the end wall 49 of the fire resistant housing 11, thereby forming a seal with the second part 9. Since the inner lip 89 surrounds the solid state lighting unit 15, in one plane, clamping the inner lip 89 between the heat sink 17 and housing 11, helps to protect at least parts of the device 15 from moisture ingress.
The clamping load is partly provided by the lens module 21 being push-fit coupled to the heat sink 17 and partly by a headed screw 95 and nut 97. The screw 95 passes through a central hole 99 formed in the end wall 49 of the housing, a hole 100 formed through the PCB 57, and a bore 101 that extends axially through the heat sink and engages the nut 97, which is located at the opposite end of the heat sink to end face 61. The nut 97 is formed in the casing for the driver unit 19, and therefore the screw 95 attaches the driver unit 19 to the heat sink 17. The bore 101, or an additional bore, can be used to enable electrical cables to pass through the heat sink 17 from the driver unit 19 to the solid state lighting device 15.
In use, the lighting unit is arranged such that a user is enable to adjust the angle of the second part 9 of the lighting unit by a limited amount, typically ± 20 degrees, without breaking the seal between the first and second parts 3,9. Figures 6 and 7 illustrate diagrammatically how the seal 21 deforms, for example by stretching and/or flexing in the fully tilted positive orientation and fully tilted negative orientation respectively. Thus the seal 21 provides an effective moisture barrier regardless of the operational orientation of the second part 9 with the respect to the first part 3. Since the seal 21 is resilient it returns to its original shape when the lighting unit is adjusted so that the central axis of the second part 9 is substantially co-axial (or at least substantially parallel) with the central axis of the first part 3.
In the event of a fire, the fire barrier formed by the partition and the fire resistant housing 11 is not compromised for the period of its fire rating. For example, a ceiling may be rated in accordance with the test outlined in BS 476: Part 21: 1987, or BS EN 1363-1:2012. The material and thickness of the material for the fire resistant housing 11 is selected according to the rating of the ceiling. Typically the fire resistant housing 11 is designed to withstand temperatures of around 900°C and will not fail in fires having temperatures below its design threshold. For a lighting unit rated at 90 minutes, the fire resistant barrier must not melt in temperatures of around 1000C, according to the test. Thus the lighting unit according to the invention has the advantage that it meets current standards, while at the same time providing a simple structure that is relatively cheap to manufacture and relatively easy to install when compared with known fire resistant lighting units.
It will be appreciated by the skilled person that modifications can be made to the above-mentioned embodiment that fall within the scope of the invention, for example the solid state lighting device 15 does not strictly require a printed circuit board, for example the or each LED can be mounted directly onto the heat sink. The lighting device can include any practicable number of LEDs and an equivalent number of holes.
The seal 21 can be arranged to sealingly engage with the casing 5 in addition to, or as an alternative to, the bezel 7.
The seal 21 can include a plurality of folds formed in the membrane, for example a plurality of ∩-shaped and/or U-shaped cross-sectioned formations, to increase the flexibility of the seal and/or to account for larger lighting units.
The housing 11 can be replaced by a fire resistant plate having at least one hole 51 formed through it for each LED 55.
The housing 11 can have a different shape from a cylindrical housing, for example the open box like structure can be substantially cuboid having four side walls. The shape of the seal 21 moulding is adjusted accordingly, for example may have a substantially rectangular form when viewed in plan. For a substantially cuboid housing 11 having four side walls 47, the first pivot member 47a is mounted on a first side wall, and the second pivot member 47b is mounted on a second side wall 47, which is opposite to the first side wall. The pivot members 47a,47b are arranged co-axially. The 47a,47b members are preferably integrally formed in their respective side walls.
The solid state lighting device 15 can be located within the fire resistant housing 11 on the front side 'A' thereof. In this arrangement the first set of holes 51 are not required. The solid state lighting device is mounted on the front side 'A' of the end wall 49 of the housing and the heat sink 17 is mounted on the rear side 'B' of the end wall 49. Heat is conducted from the solid state lighting device 15 to the heat sink 17 via the end wall 49.
Materials other than steel can be used in the construction of the fire resistant housing 11 that have a high melting point, for example brass, ceramic and/or copper. Although the housing 11 is preferably made from a single material in the form of a single component, a housing including a plurality of components and/or materials can be used.
Thermal pastes and/or pads can be used at the thermal interfaces of components to promote thermal conduction. For example, a thermal pad and/or paste can be used between the heat sink and the PCB in the embodiment described above. A thermal pad and/or paste can be used between the heat sink and the fire resistant housing/member in the adaptions described above.
The housing can be made from materials that are not fire resistant. For example, the housing can be made from at least one non-fire resistant metal, such as aluminium, or from at least one plastics material.
The support member can be in the form of a plate rather than a housing. The plate has a front side and a rear side. In one arrangement, the plate includes a plurality of holes formed through it from the front side to the rear side and the LEDs, PCB and heat sink are mounted on the rear side of the plate such that light from the LED shines through the holes formed in the plate. In another arrangement, the LEDs and PCB are located on the front side of the plate and the heat sink is mounted on the rear of the plate. Heat is transferred from the solid state lighting device through the support plate.

Claims

A lighting unit including a first part (3) having a mounting structure (5); a second part (9) including at least one solid state lighting device (15) and a heat sink (17), said heat sink (17) being mounted in thermal contact with the solid state lighting device (15) such that at least some of the heat generated by the solid state lighting device (15) is transferred to the heat sink (17) by conduction; wherein the second part (9) is pivotable with respect to the first part (3); characterised by a seal (21) arranged to seal the first part (3) to the second part (9), said seal (21) being arranged to deform to accommodate pivoting movement of the second part (9) with respect to the first part (3).
A lighting unit according to claim 1, wherein the seal (21) is annular.
A lighting unit according to claim 1 or 2, wherein the seal (21) includes a membrane having an outer peripheral portion (91) that sealably engages to the first part (3), an inner peripheral portion (89) that sealably engages to the second part (9), and a connector portion (78) connecting the outer peripheral portion (91) to the inner peripheral portion (89), wherein at least the connector portion (78) is flexible.
A lighting unit according to claim 3, wherein the connector portion (78) of the membrane includes at least one hollow substantially ∩-shaped, and/or U-shaped, cross-section portion having an annular inner side wall (79) and an annular outer side wall (81).
A lighting unit according to claim 3 or 4, wherein the inner peripheral portion includes an annular inner lip (89).
A lighting unit according to claim 5 when dependent on claim 4, wherein the inner lip (89) extends inwardly from the inner side wall (79).
A lighting unit according to any one of claims 3 to 6, wherein the outer peripheral portion (91) includes an annular outer lip.
A lighting unit according to claim 7 when dependent on claim 4, wherein the outer lip (91) is annular and extends outwardly from the outer side wall (81).
A lighting unit according to any one of the preceding claims, wherein the second part (9) includes a support member, and preferably the support member (11) includes sheet material.
A lighting unit according to claim 9, wherein the support member (11) is fire resistant, and preferably includes material that melts at a temperature greater than or equal to 900C.
A lighting unit according to claim 9 or 10, wherein the support member (11) has a front side (A) and a rear side (B), and the heat sink (17) is located on the rear side (B) of the support member.
A lighting unit according to any one of claims 9 to 11 when dependent on claim 3, wherein the inner peripheral portion (89) of the seal is clamped between the heat sink (17) and the support member (11).
A lighting unit according to any one of claims 9 to 12, wherein the support member (11) comprises a housing.
A lighting unit according to any one of claims 9 to 13, wherein the support member (11) includes at least one first hole (51) formed there through from the front side (A) to the rear side (B).
A lighting unit according to claim 14, wherein the solid state lighting device (15) includes at least one LED (55) and a PCB (57), wherein at least a part of the PCB (57) is mounted on the rear side (B) of the support member, and the heat sink (17) is mounted on the rear side (59) of the PCB.
A lighting unit according to any one of claims 9 to 15, wherein the solid state (15) lighting device includes at least one LED (55) and a PCB (57), and the solid state lighting device (15) is mounted on the front side (A) of the support member, the heat sink (17) is mounted on the rear side (B) of the support member, and heat generated by the solid state lighting device (15), in use, is conducted through the support member (11) to the heat sink (17).
A lighting unit according to any one of claims 9 to 16, wherein the support member (11) is pivotally attached to the first part (3).
A lighting unit according to any one of the preceding claims, wherein the first part (3) includes at least one of: a casing (5), which preferably includes first and second open ends (23,27); and a bezel (7) having a collar (37) and a flange (35), and preferably the bezel (7) is fire resistant and includes material that melts at a temperature greater than or equal to 900C.
A lighting unit according to claim 18, wherein the support member (11) is pivotally attached to at least one of the casing (5) and the bezel (7), and preferably the outer peripheral portion (91) seals against at least one of the casing (5) and the bezel (7).
A lighting unit according to any one of the preceding claims, including a lens module (13), preferably said lens module (13) is located on a front side (A) of the support member and is attached to at least one of the heat sink (17) and the support member (11) by way of a push-fit connection, and more preferably still the support member (11) includes a plurality of holes (53) formed there through from the front side to the rear side (B); the lens module (17) includes a plurality of deformable male coupling members (67); the heat sink (17) includes a plurality of female coupling members (63); and the lens module (13) is attached to the heat sink (17) in a push-fit manner with the male and female coupling members (67,63) connecting via respective holes.
A lighting unit according to any one of the preceding claims, wherein the lighting unit is a downlight.
A method for preventing moisture from penetrating a hole formed in a partition, including inserting a lighting device according to any one of the preceding claims into the hole.