GB2489980A

GB2489980A - Waterproof lighting arrangements

Info

Publication number: GB2489980A
Application number: GB1106343.5A
Authority: GB
Inventors: James Theobald
Original assignee: Greengage Lighting Ltd
Current assignee: Greengage Lighting Ltd
Priority date: 2011-04-14
Filing date: 2011-04-14
Publication date: 2012-10-17
Anticipated expiration: 2031-04-14
Also published as: GB2489980B; GB201106343D0

Abstract

A waterproof light bulb holder 12 comprises: a socket for receiving and engaging a cap 26 of a light bulb 14 and for powering the light bulb 14; and a resilient member 50 for forming an annular seal with and around a neck 28 of the light bulb 14 when the light bulb 14 is engaged with the socket. The seal prevents entry of liquid into the socket. The holder 12 may include an attachment (e.g. a cylindrical flange 60 with gasket 52 and external thread 62) for attaching the holder 12 to a body portion 10 of a waterproof light bulb housing and for forming a waterproof seal with the body portion of the housing. In a separate embodiment, an LED light unit comprises an LED, circuitry for illuminating the LED when powered by an electricity supply, and an attachment for attaching the light unit to a body portion of a waterproof light bulb housing and for forming a seal with the body portion of the housing to resist or prevent passage of liquid between the light unit and the body portion of the housing.

Description

LIGHTING ARRANGEMENTS

In many applications, it is desirable to provide waterproof electric lighting. One such application is in chicken houses, where it is desirable to be able to wash down the chicken house periodically using aqueous cleaning solutions.

A known manner to provide waterproof electric lighting is to use an incandescent light bulb in a waterproof light bulb housing. The waterproof light bulb housing comprises a body portion, a socket portion and a transparent dome portion. The socket portion provides a light bulb socket which lies generally within the body portion. The body portion has at least one cable gland which allows an electrical cable to pass into the body portion in a waterproof manner. More commonly, the body portion of the waterproof housing will have two cable glands which allows a plurality of waterproof housings to be connected together in a "daisy chain" arrangement being powered by a single electrical cable. Within the body portion, the light bulb socket is connected to the electrical cable to power a light bulb engaged with the socket. The body portion, the socket portion and the transparent dome portion of a waterproof housing are connected together in a waterproof manner with a light bulb engaged with the socket within the housing. The transparent dome portion allows light from the light bulb to pass out of the waterproof housing.

The body portion, the socket portion and the transparent dome portion of the waterproof housing may be connected together in different ways. For example, the body portion may have a cylindrical formation with an internal helical thread. The transparent dome portion may have a corresponding cylindrical formation with a corresponding helical thread so that the body portion and the transparent dome portion can be connected together by screwing the dome portion cylindrical formation into the body portion cylindrical formation. In this case, a gasket or seal may be provided between the two portions to ensure water tightness.

Another possible mode of connection is to provide a cylindrical formation on the body portion and a corresponding cylindrical formation on the transparent dome portion with one of the cylindrical formations fitting within the other and with the body portion being connected to the transparent dome portion by a catch.

Another possibility is for the socket portion to connect to the body portion and for the transparent dome portion to connect to the socket portion.

However, the use of such known waterproof light bulb housings is not always appropriate. An example of a situation where the use of a known waterproof light bulb housing is not appropriate is when it is desired to use an LED light bulb. Use of an LED light bulb in a waterproof light bulb housing often leads to overheating of the LED light bulb.

According to a first aspect of the invention there is provided a light bulb holder, comprising a socket for receiving and engaging a cap of a light bulb and for powering a light bulb so engaged, and a resilient member for forming an annular seal with and around a neck of a light bulb engaged with the socket to resist or prevent entry of liquid into the socket.

Preferably, the light bulb holder includes an attachment for attaching the holder to a body portion of a known type of waterproof light bulb housing (in the absence of the transparent dome portion and the socket portion of the waterproof housing). In this way, the socket of the holder may be electrically connected to an electrical cable in the body portion. The attachment serves both to attach the holder to the body portion and also for forming a waterproof seal with the body portion. It is important to resist entry of water into the interior of the body portion to prevent contact between water and the electrics. The attachment may comprise a screw thread for threaded engagement with a corresponding thread on the body portion. The attachment may comprise a cylindrical flange. Preferably, the attachment comprises a cylindrical flange which fits closely within or outside of a corresponding cylindrical formation of the body portion, the cylindrical flange of the attachment having a screw thread which engages with a corresponding screw thread on the cylindrical formation. While this is the preferred attachment, other arrangements are possible. For example, the attachment and the body portion may fit together by a bayonet mechanism. A cylindrical geometry is preferred for the attachment and for the engaging formation of the body portion but other geometries may be used.

The attachment may include a gasket or seal ring for forming the seal with the body portion.

Preferably, the light bulb holder has a body which includes the socket and the resilient member of the holder is mountable on and separable from the body. This is desirable because it allows the resilient member to be replaced if it becomes damaged without the need to replace the whole of the holder. When the resilient member is mounted on the body, the resilient member forms an annular waterproof seal with the body. When the resilient member is replaccable in this way, the resilient member may include an annular groove and the body of the holder may include an annular flange which is received closely within the annular groove when the resilient annular member is mounted on the body. This interaction serves to fix and locate the resilient member relative to the body and to form the waterproof seal between the resilient member and the body. In one specific example of this arrangement, the resilient member is generally annular and has a radially outer annular wall and a radially inner annular wall, the annular groove being formed between the outer and inner walls. In such a resilient member, there may be an annular lip extending radially inwardly from the inner wall for sealing with and around a neck of a light bulb. Where the resilient member has such an annular lip, the resilient member may have an end which is positioned outwardly from the body when the resilient member is mounted on the body and a radially-inwardly-facing frustro-conical surface which extends from the outer end of the resilient member to the annular lip and which tapers inwardly as it extends towards the sealing lip.

In a preferred example of the light bulb holder, the holder has a body and a resilient member which is mountable on and separable from the body. The body includes a plate with a circular hole through the plate. An annular flange extends from a first side of the plate and around the circular hole. The resilient member has an annular groove which receives the annular flange to mount the resilient member on the body and to form a waterproof seal between the resilient member and the body. A cylindrical flange extends from a second side of the plate and serves for attachment to a body portion of a waterproof light bulb housing. The socket is located at the second side of the plate so that a cap of a light bulb is introduced through the resilient member and the circular hole for engagement with the socket. This brings the neck of the light bulb into sealing engagement with the resilient member to prevent entry of water into the socket.

In a preferred embodiment, the light bulb holder is adapted for use with a light bulb that has an annular flange extending around its neck. The resilient member of the holder has a surface that bears against the annular flange of the light bulb so as to form a seal. As discussed above, the resilient member may be mountable on a body of the holder by an annular groove in the resilient member and an annular flange on the body. In this case, engagement between the annular flange of the light bulb and the resilient member urges the resilient member against the body to improve the seal between the resilient member and the body.

In many cases, it will be desirable to use the light bulb holder with an LED light bulb but other types of light bulb may also be used.

The light bulb holder may also be used with a plug. The plug has a formation for engagement with the socket of the holder in the absence of a light bulb and a part which, when the formation is so engaged, forms a seal with the resilient member to resist or prevent entry of liquid into the socket.

In accordance with a second aspect of the invention, there is provided an LED light unit, comprising an LED, circuitry for illuminating the LED when powered by an electricity supply, and an attachment for attaching the light unit to a body portion of a waterproof light bulb housing and for forming a seal with the body portion of the housing to resist or prevent passage of liquid between the light unit and the body portion of the housing.

The attachment may comprise a screw thread for threaded engagement with a corresponding thread on the body portion. The attachment may comprise a cylindrical flange. Preferably, the attachment comprises a cylindrical flange which fits closely within or outside of a corresponding cylindrical formation of the body portion, the cylindrical flange of the attachment having a screw thread which engages with a corresponding screw thread on the cylindrical formation. While this is the preferred attachment, other arrangements arc possible. For example, the attachment and the body portion may fit together by a bayonet mechanism. A cylindrical geometry is preferred for the attachment and for the engaging formation of the body portion but other geometries may be used.

The LED light unit preferably includes a mounting plate on which the LED is mounted and a cover sealingly connected to the mounting plate to prevent entry of water to the LED. The LED light unit preferably includes a heat sink for absorbing and dissipating heat produced by the LCD.

In accordance with a third aspect of the invention, there is provided an LED light bulb having a cap and a neck, an annular flange extending around the neck.

Preferably, the cap and the neck have a common axis and the annular flange has a surface facing towards the cap and lying generally normal to the axis.

The following is a more detailed description of embodiments of the invention, by way of example, reference being made to the appended schematic drawings in which: Figure 1 is a perspective assembly view of a known body portion of a waterproof light bulb housing, together with a light bulb holder and an LED light bulb; Figure 2 is an elevational assembly view of the components of Figure 1; Figure 3 is a perspective view of the components of Figures 1 and 2 with the components connected together; Figure 4 is an enlarged elevational view of the LED light bulb of Figures 1 to 3; Figure 4a is a still greater enlargement of a portion of the LED light bulb of Figure 4; Figure 5 is a perspective view of a rigid body of the light bulb holder of Figures 1 to 3; Figure 6 is an elevational view of the rigid body of Figure 5; Figure 7 is a cross-sectional view of the rigid body of Figures 5 and 6; Figure 8 is a perspective view of a resilient annular member which forms part of the light bulb holder of Figures ito 3; Figure 9 is an elevational view of the resilient annular member of Figure 8; Figure 110 is a cross-sectional view of the resilient annular member of Figures 8 and 9; Figure ii is a perspective assembly view showing the known body portion and the light bulb holder of Figures 1 to 3, together with a plug; Figure i2 shows the components of Figure ii with the plug engaged with the light bulb holder; Figure 13 shows the body portion of the waterproof housing and the light bulb holder of Figures i to 3, together with an alternative LED light bulb; Figure 14 shows a known body portion of a waterproof light bulb housing together with an LED light unit; Figure 15 is a cross-sectional view of the body portion of the waterproof housing and the LED light unit of Figure 14; and Figure 16 is an enlarged view showing part of the LED light unit of Figure 15.

Referring first to Figures i to 3, the body portion iO is a body portion of known design of a prior art waterproof light bulb housing. However, in Figures 1 to 3, the body portion 10 is not used in combination with the other components of the prior art waterproof tight butb housing -namely the transparent dome portion and the socket portion. Instead, the body portion 10 of the waterproof housing is used in combination with the light bulb holder 12 and the LED light bulb 14. As will be described in more detail below, the light bulb holder 12 is adapted for connection to the body portion 10 so as to allow the use, in a waterproof manner, of the LED light bulb 14, without overheating of the LED light bulb 14.

The body portion 10 has a lower cylindrical formation 16 provided with an internal helical thread 18. The body portion 10 has a closed upper end 20 which is provided with two cable glands, one of which is shown at 22. The closed upper end 20 is also provided with support means 24 which can be used to attach the body portion 10 to a ceiling or to hang the body portion 10 from a catenary wire.

It should be noted that the body portion 10 does not itself contain a light bulb socket, as the socket portion of the waterproof light bulb housing has been removed.

The LED light bulb 14 is shown in more detail in Figures 4 and 4a. The LED light bulb 14 has a cap 26, a neck generally indicated at 28, a heat sink 30, and an illuminating portion 32. As seen best in Figure 4a, the neck 28 of the tight bulb 14 has a cylindrical portion 34 and an annular flange 36. The annular flange extends around the neck 28. The annular flange 36 has a planar surface 38 which faces generally in the direction of the cap 26 and which lies in a plane normal to an axis that is common to the cap 26 and the neck 28.

The LED light bulb 14 is very similar to a prior art LED light bulb 40 shown in Figure 13. The only difference between the LED light bulb 14 of Figures 4 and 4a and the prior art LED light bulb 40 of Figure 13 is the annular flange 36 provided on the LED light bulb 14. In the prior art LED light bulb 40, a cylindrical neck 42 is provided between a heat sink 44 and a cap 46.

The prior art light bulb 40 of Figure 13 is commercial available and is marketed by Greengage Lighting Ltd under the trade name Agrilamp (trade mark).

Both the LED light bulb 14 shown in Figures 4 and 4a, and also the LED light bulb 40 in Figure 13, are waterproof This is to say that water cannot penetrate into the interior of the light bulb.

Although not shown in Figures 4 and 4a, the LED light bulb 14 contains in its interior an LED and also suitable circuitry for illuminating the LED when the light bulb 14 is powered using electrical contacts provided on the cap 26. In the LED light bulb 14 of Figures 4 and 4a, the illuminating portion 32 comprises a translucent cover that covers the LED and which is sealed, in a waterproof fashion, to the heat sink 30.

For the purposes of the current invention, the "neck" of a light bulb is any part of a light bulb which is located between a cap and an illuminating portion and which is suitable for sealing against the light bulb holder as will be described in more detail below. Generally, the neck of a light bulb will have a smooth surface so as to facilitate sealing.

The light bulb 14 shown in Figures 4 and 4a and the light bulb shown in Figure 13 are generally pear shaped with the illuminating portion 32 being generally spherical.

However, this need not be the case and a light bulb may have an illuminating portion of any practical shape.

Referring now to Figures 1 to 3, the light bulb holder 12 comprises the rigid moulded body 48, the resilient annular member 50, a gasket 52 and a socket (not shown) for receiving the cap 26 of the LED light bulb 14.

The rigid body 48 may be moulded from a suitable rigid plastic material. As best seen in Figures 5 to 7, the rigid body 48 includes a flat wall 54 with a circular hole 56 extending through the wall 54. On a first side of the wall 54, an annular flange 58 extends outwardly from the wall 54 and around the circular hole 56. On a second side of the wall 54, a cylindrical flange 60 extends outwardly from the wall 54 near the perimeter of the wall 54. The cylindrical flange 60 is provided with an extemal helical thread 62. A cup formation 64 extends from the second side of the wall 54 so that an internal opening 66 of the cup formation 64 opens generally at the circular hole 56.

The internal opening 66 of the cup formation 64 receives a metal socket of known type for engaging the cap 26 of the LED light bulb 14. As shown in Figure 4, the cap 26 of the LED light bulb 14 is a traditional Edison scrcw. Accordingly, the socket, in this particular example, is a fcmale Edison socket. However, the cap 26 of thc LED light bulb 14 may be of any suitable type and the socket may be any corresponding type for receiving, engaging and applying electrical power to the cap 26. For example, the cap 26 and the socket may be of bayonet type. Although not shown in the drawings, electrical wires pass through the cup formation 64 for applying electrical power to the socket.

The socket may be attached in any suitable manner within the internal opening 66 of the cup formation 64, such as by adhesive.

The resilient annular member 50 of the light bulb holder 12 is best seen in Figures 8 to 10. The resilient annular member 50 is formed of a resilient, heatresistant material, such as silicone rubber. The rcsilient annular member 50 has a radially inner wall 68 and a radially outer wall 70 which are connected at an outer end 72 of the annular member 50. The outer end 72 is provided with a planar outer surface 74 which lies generally normal to the axis of the resilient annular member 50.

An annular groove 76 is formed between the inner wall 68 and the outer wall 70 and opens at an inner end 78 of the resilient annular member 50.

As best seen in Figure 10, an annular lip 80 extends radially inwardly from the inner wall 68. A frustro-conical surface extends from the planar outer surface 74 to the annular lip 80 and tapers radially inwardly as the frustro-conical surface 82 extends towards the annular lip 80.

The annular groove 76 is sized so that the annular flange 58 of the rigid body 48 fits tightly within the annular groove 76 and this engagement serves to hold the resilient annular member 50 on the rigid body 48 with the inner end 78 of the resilient annular member 50 lying against the wall 54 of the rigid body 48.

The gasket 52 is best seen in Figure 1. The gasket 52 is generally annular in shape and is formed of a resilient material, such as silicone rubber. The gasket 52 is sized so as to fit radially outside of the cylindrical flange 60 lying against the second side of the wall 54.

In use, the resilient annular member 50 is held on the rigid body 48 as discussed above, and the gasket 52 is positioned on the second side of the wall 54 as discussed above. In this assembled configuration, the light bulb holder 12 is attached to thc body portion 10 by screwing the external helical thread 62 of the light bulb holder 12 into the intemal helical thread 18 of the body portion 10. During this process, the cylindrical flange 60 of the light bulb holder 12 moves into the cylindrical formation 16 of the body portion 10. This is continued until the gasket 52 is compressed between the body portion 10 and the flat wall 54 of the light bulb holder 12. The gasket 52 provides a water tight seal between the body portion 10 and the light bulb holder 12.

Before screwing the light bulb holder 12 into the body portion 10, the electrical wires (not shown) leading from the socket (not shown) are connected to an electrical cable which passes through the body portion 10 via the cable glands 22.

The LED light bulb 14 can then be inserted into the light bulb holder 12. In order to do this, the cap 26 of the LED light bulb 14 is passed through the resilient annular member 50 and through the circular hole 56 and the cap 26 is then engaged with the socket in the conventional manner (whether by way of screw attachment or by way of bayonet attachment, for example).

The light bulb holder 12 is configured so that when the cap 26 of the LED light bulb 14 is fully engaged with the socket, the annular lip 80 of the resilient annular member bears against and forms a water tight seal with the cylindrical portion 34 of the neck 28 of the LED light bulb 14. In addition, the planar outer surface 74 of the resilient annular member 50 bears against and forms a waterproof seal with the planar surface 38 of the annular flange 36 of the LED light bulb 14.

The frustro-conical surface 82 of the resilient annular member 50 may provide additional sealing against the neck 28 of the LED light bulb 14 or may simply serve to guide the cap 26 of the LED light bulb 14 through the annular lip 80 of the resilient annular member 50. The seals formed between the resilient annular member 50 and the neck 28 of the LED light bulb 14 serve to prevent entry of water into the socket.

As discussed above, the tight engagement of the annular flange 58 of the rigid body 48 within the annular groove 76 of the resilient annular member 50 also prevents passage of water between the resilient annular member 50 and the rigid body 48. In addition, as the annular flange 36 of the LED light bulb 14 bears against the planar outer surface 74, this urges the resilient annular member 50 against the wall 54 of the rigid body 48 which further serves to improve the water tight seal between the resilient annular member 50 and the rigid body 48.

Hence, the light bulb holder 12 connects to the prior art body portion 10 in a water tight manner and the LED light bulb 14 can be engaged with the light bulb holder 12 in a water tight manner. Water cannot penetrate into the socket or into the interior of the body portion 10. Hence, the light bulb holder 12 allows the use of an LED light bulb with the prior art body portion 10, in a water tight manner, without requiring the prior art transparent dome portion that would normally be used in conjunction with the body portion 10. In turn, because the LED light bulb 14 is not enclosed within a transparent dome, overheating of the LED light bulb 14 does not incur.

In chicken houses, it is common practice to use a very large number of conventional water proof light bulb housings, each housing containing an incandescent light bulb.

However, this is undesirable because incandescent light bulbs are not energy efficient.

The light bulb holders 12 can be retro-fitted to the body portions 10 of the conventional waterproof light bulb housings and this allows the existing wiring to be retained and to be used with more energy efficient LED light bulbs.

It will be appreciated that there may be occasions on which it is desirable to be able to remove a light bulb 14 from the light bulb holder 12 while still preventing entry of water into the light bulb socket of the light bulb holder 12. This can be achieved by using the plug 84 shown in Figures 11 and 12. The plug 84 has a formation 86 which engages the socket of the light bulb holder 12 in a similar manner to a cap of a light bulb. In this particular example, the formation 86 takes the form of an externally threaded cylinder resembling a standard light bulb Edison screw for screwing into a female Edison socket. The plug 84 also includes a sealing part 88 which, when the formation 86 is engaged with the socket seals against the resilient annular member 50 of the light bulb holder 12. In addition, the sealing part 88 is provided with a slot 90 which facilitates screwing of the plug 84 into and out of the socket of the light bulb holder 12.

An alternative arrangement is shown in Figure 13. In Figure 13, the body portion 10, the gasket 52, the rigid body 48 and the resilient annular member 50 are as described above. However, in Figure 13, the LED light bulb 40 is, as described above, a conventional waterproof LED light bulb which omits the annular flange 36. This arrangement demonstrates the fact that it is possible to use a conventional light bulb with the light bulb holder 12. In this case, prevention of entry of water between the light bulb 40 and the resilient annular member 50 relies primarily on the seal between the annular lip 80 of the resilient annular member 50 and the neck 42 of the LED light bulb 40.

A further arrangement is shown in Figures 14 to 16.

Figures 14 to 16 show a body portion 92 (of a known waterproof light bulb housing) which is very similar to the body portion 10 of Figures 1 to 3. The body portion 92 has a cylindrical formation 94 provided with an internal helical thread 96. The body portion 92 has two water tight cable glands 98, a closed upper end 100 and support means 102.

Instead of the light bulb holder 12 and the LED light bulb 14 described above, the arrangement shown in Figures 14 to 16 utilises a light unit 104 with an integral LED.

The LED light unit 104 includes a heat sink 106 which is generally cylindrical in shape and which has a plurality of angularly spaced fins extending radially outwardly.

At an outer end of the heat sink 106 an LED mounting plate 108 is fixed in a water tight manner so as to prevent entry of water into the internal space of the cylindrical heat sink 106. An LED 110 is mounted on the mounting plate 108. A generally hemispherical lens or cover 112 is mounted, again in a waterproof manner, to the LED mounting plate 108, to prevent entry of water to the LED 110.

Within the internal space of the cylindrical heat sink 106, appropriate circuitry in the form of the driver module 114 is housed. The driver module 114 serves to illuminate the LED 110 when the driver module 114 is provided with electrical power. At an inner end of the heat sink 106, an annular aluminium plate 116 lies against the heat sink 106 and an annular resilient seal 118 lies against the aluminium plate 116.

A mounting boss 120 is attached to the heat sink 106 so as to compress the resilient seal 118 against the aluminium plate 116. The arrangement prevents entry of water into the interior of the cylindrical heat sink 106. The mounting boss 120 includes a cylindrical formation 122 which has an external helical thread 124.

In operation, the LED light unit 104 is simply screwed into the body portion 92.

Hence, the external helical thread 124 of the mounting boss 120 engages with the internal helical thread 96 of the cylindrical formation 94 of the body portion 92 until the resilient seal 118 of the LED light unit 104 lies against and is compressed against the body portion 92. This forms a waterproof seal which prevents entry of water into the body portion 92.

Again, before screwing the LED light unit 104 into the body portion 92, electrical wires leading to the driver module 114 are connected to an electrical cable passing through the body portion 92 via the cable glands 98.

Hence, the LED light unit 104 can be attached, in a waterproof manner, to a body portion 92 connected to an existing wiring system. Because the components of the LED light unit 104 are themselves water tight, and because the LED light unit 104 forms a waterproof seal against the body portion 92, the arrangement is waterproof.

The structure of the LED light unit 104 prevents overheating of the LED 110.

Should the LED light unit 104 need replacing, it can simply be unscrewed from the body portion 92 and replaced by a new unit 104.

Claims

Claims 1. A light bulb holder, comprising a socket for receiving and engaging a cap of a light bulb and for powering a light bulb so engaged, and a resilient member for forming an annular seal with and around a neck of a light bulb engaged with the socket to resist or prevent entry of liquid into the socket.
2. A holder according to claim 1, including an attachment for attaching the holder to a body portion of a waterproof light bulb housing and for forming a seal with the body portion of the housing to resist or prevent passage of liquid between the holder and the body portion of the housing.
3. A holder according to claim 2, wherein the attachment comprises a screw thread for threaded engagement with a corresponding thread on the body portion of the waterproof light bulb housing.
4. A holder according to claim 2 or claim 3, wherein the attachment comprises a cylindrical flange.
5. A holder according to claim 4, when claim 4 is dependent on claim 3, wherein the holder screw thread is provided on a radially inner or a radially outer surface of the cylindrical flange
6. A holder according to any one of claims claims 2 to 5, wherein the attachment includes a gasket or seal ring for forming said seal with the body portion of the housing.
7. A holder according to any preceding claim, wherein the holder has a body which includes the socket, the resilient member being mountable on and separable from the body, and when the resilient member is mounted on the body the resilient member forms an annular seal with the body to resist or prevent passage of liquid between the body and the resilient annular member.
8. A holder according to claim 7, wherein the resilient member includes an annular groove and the holder body includes an annular flange which is received within the annular groove when the resilient annular member is mounted on the body.
9. A holder according to claim 8, wherein the resilient member has a radially outer annular wall and a radially inner annular wall, the annular groove being formed between the outer and inner walls, the resilient member having an annular lip extending radially inwardly from the inner wall for sealing with and around a neck of a light bulb.
10. A holder according to claim 9, wherein the resilient member has an end which is positioned outwardly from the body when the resilient member is mounted on the body and a radially-inwardly-facing frustro-eonieal surface which extends from the outer end of the resilient member to the annular lip and which tapers inwardly as it extends towards the sealing lip.
11. A holder according to any one of claims 8 to 10, when dependent on claim 4 or claim 5, wherein the holder body comprises a plate provided with a circular hole and having first and second opposed sides, the annular flange extending around the circular hole at the first side, the cylindrical flange extending from the second side of the plate, the socket being provided at the second side so that a cap of a light bulb is passed through the circular hole for engagement with the socket.
12. An assembly comprising a holder according to claim 2 or any claim dependent thereon and a body portion of a waterproof light bulb housing.
13. An assembly according to claim 12, wherein the body portion of the housing has first and second waterproof cable glands.
14. An assembly comprising a holder according to any one of claims 1 to 11 and a light bulb having a cap and a neck, the cap being engageable with the socket so that when the cap is so engaged the resilient member forms said annular seal with and around the neck of the tight butb to resist or prevent entry of liquid into the socket.
15. An assembly according to claim 14, wherein the resilient member has an annular surface and the light bulb has a flange extending around the neck of the tight bulb which bears against the annular surface when the cap is engaged with the socket.
16. An assembty according to claim 15, when dependent on claim 8, wherein engagement of the cap of the light bulb with the socket causes the bulb flange to press against the annular surface of the resilient member to form a seal between the bulb flange and the annular surface and to urge the resilient member against the holder body.
17. An assembly according to any one of claims 14 to 16, wherein the light bulb is an LED light bulb.
18. An assembly comprising a holder according to any one of claims 1 to 11 and a plug, the plug having a formation for engagement with the socket in the absence of a light bulb and a part which when the formation is so engaged forms a seal with the resilient member to resist or prevent entry of liquid into the socket.
19. An LED light unit, comprising an LED, circuitry for illuminating the LED when powered by an electricity supply, and an attachment for attaching the light unit to a body portion of a waterproof light bulb housing and for forming a seal with the body portion of the housing to resist or prevent passage of liquid between the light unit and the body portion of the housing.
20. An LED light unit according to claim 19, wherein the attachment comprises a screw thread for threaded engagement with a corresponding thread on the body portion of the waterproof light bulb housing.
21. An LED light unit according to claim 19 or claim 20, wherein the attachment includes a cylindrical flange.
22. An LED light unit according to claim 21, when claim 21 is dependent on claim 20, wherein the light unit screw thread is provided on a radially inner or a radially outer surface of the cylindrical flange.
23. An LED light unit according to any one of claims 19 to 22, wherein the attachment includes a gasket for forming said seal with the body portion of the housing.
24. An LED light unit according to any one of claims 19 to 23, including a mounting plate on which the LED is mounted and a cover sealingly connected to the mounting plate to prevent entry of water to the LED.
25. An LED light unit according to any one of claims 19 to 24, including a heat sink for absorbing and dissipating heat produced by the LCD.
26. An assembly comprising an LED light unit according to any one of claims 19 to and a body portion of a waterproof light bulb housing.
27. An LED light bulb having a cap and a neck, the neck including an annular flange extending around the neck.
28. An LED light bulb according to claim 27, wherein the cap and the neck have a common axis and the annular flange has a surface facing towards the cap and lying generally normal to the axis.