WO2013175154A1

WO2013175154A1 - Helmet mounted bicyclist's lamp, adjustable fixture and method

Info

Publication number: WO2013175154A1
Application number: PCT/GB2012/000471
Authority: WO
Inventors: Paul David Sherring; Karel KAIVANTO
Original assignee: Neonight Lighting Solutions Limited
Priority date: 2012-05-25
Filing date: 2012-05-25
Publication date: 2013-11-28

Abstract

A fixture comprises an anchor element (10) which engages a body element (30), the anchor element being rotatable relative to the body element to define a plurality of alternative positions. A flexible tie (22) is used to attach the anchor element to a support such as a bicyclist's helmet, and draws the anchor element and locking element together so as to mount the assembly in the desired orientation in fixed relation to the support.

Description

Helmet mounted bicyclist's lamp, adjustable fixture and method

This invention relates particularly but not exclusively to lamps for mounting on a bicyclist's helmet and to fixtures, i.e. elements that are adapted to be mounted on a support, particularly but not exclusively for mounting a lamp in a desired orientation on a helmet.

A modern bicyclist's helmet typically comprises a padded shell that presents a complex array of irregularly shaped apertures and curved surfaces oriented in different directions. The outer surface of the helmet is usually smoothly curved so as to allow the cylist to roll out of a fall. Whereas it is often desirable to mount a battery operated safety light or the like on such a helmet, in order that the cyclist should be more visible to other road users, the shape of the helmet makes it difficult to find a suitable attachment point, and still more difficult to ensure that the light remains securely fastened in the correct (e.g. horizontal) orientation in use.

Adhesive pads may provide an unreliable fixing due to the curvature and limited surface area between adjacent apertures. The light can be mounted directly on the helmet using a flexible strap, but it is then difficult to fasten the strap securely in the correct position and orientation. It is undesirable to use a threaded fastener such as a bolt or screw that penetrates the shell, since this may weaken the helmet and also present a hazard to the user in the event of impact. US 2007/0256528 and EP 2192032 disclose brackets which are attachable to a bicycle using a band or strap and on which a lamp or the like may be releasably mounted. Other mounting assemblies are disclosed for example by US 6283620, EP 2065747, US 2007/01 14252, and DE 20017853 U. Such fixtures are often bulky and do not provide for automatic detachment of the lamp in the event of an accident. They are therefore unsuitable for use on a bicyclist's helmet since the protruding part of the fixture as well as the lamp attached to it could prevent the helmet from rolling on the ground, increasing the risk of neck injury. Rotationally adjustable joints can also work loose, causing the attached lamp to wobble. WO 2004/062410 teaches a safety light comprising an electroluminescent light source powered by a battery and inverter and housed within a protuberant diffuser. The safety light is releasably mounted on a bracket by means of a breakaway connection comprising cooperating magnetic elements (respectively, magnets and steel plates) which release the safety light on impact. The bracket is permanently attached to the helmet by adhesive or the like and advantageously does not protrude beyond the footprint of the safety light, and is relatively much thinner than the safety light. This allows the base of the safety light to be fixed close to the surface of the helmet, optimising the rider's balance and minimising wind resistance, and provides minimum resistance to rolling after the safety light is detached.

The safety light is elongate and is mounted horizontally so as to indicate the orientation and direction of travel of the bicyclist. However, the configuration of many bicyclists' helmets makes it difficult to find a suitable surface on the side of the helmet on which to mount the bracket in the desired orientation.

In a first aspect, the present invention sets out to provide a more suitable and convenient way of mounting a safety light in a desired orientation on a helmet. It is often preferable for a bicyclist's safety light to be mounted on the helmet, where it is most visible, and to be detachable on impact so as to avoid

compromising the protection afforded by the helmet. However, this configuration gives rise to the problem that the user will often not be aware if the light has been inadvertently switched off. A further problem is that the transparent or translucent diffuser may be more rapidly degraded by ultraviolet radiation if it is left on the helmet during the day.

In a further aspect, the invention sets out to address these problems.

Although lamps comprising an electroluminescent light source driven by a high frequency inverter are both efficient and particularly effective as safety lights for use on a bicyclist's helmet in night-time urban conditions, it is found that the inverter can produce audible noise which is undesirable when the lamp is worn on a helmet. In yet further aspects, the invention sets out to reduce this problem.

According to the present invention in its various aspects there are provided an apparatus, a lamp and a method as defined in the claims. Further features and advantages will be apparent from the following illustrative embodiments which will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which: Figs. 1A - 1C are respectively a front, rear and side view of the body element of a first fixture configured as a bracket for attachment to a bicylist's helmet;

Figs. 2A and 2B are respectively a front and a side view of the anchor element of the first fixture;

Figs. 3 A and 3B are front views showing the anchor element engaged with the body element in two alternative locking positions, with Fig. 3B showing a variant having indicia;

Fig. 3C is a side view corresponding to Figs. 3 A and 3B; Figs. 4 A and 4B are respectively a front view and a side view of a compressible pad of the first fixture; Figs. 5 A - 5F are respectively side, bottom, oblique, and left and right end views of a safety light;

Fig. 5F shows the safety light being charged via a USB charger; Fig. 6 shows the first fixture during assembly and prior to mounting on a support; Fig. 7 A shows a bicyclist's helmet; Figs. 7B shows the first fixture mounted on the helmet;

Fig. 7C shows the helmet with the safety light releasably attached to the first fixture;

Figs. 8A and 8B are respectively a top view and a side view of one of the first magnetic elements of the first fixture;

Figs. 9 A - 9D illustrate the consecutive steps in the attachment to a bicyclist's helmet of a second fixture substantially corresponding to the first fixture; Figs. 10A and 1 OB show the safety light respectively before and after mounting on the second fixture;

Figs. 1 1 A - 1 1C illustrate the consecutive steps in the attachment of the second fixture to another bicyclist's helmet having a solid shell; Figs. 12A - 12D show a third fixture configured as a bracket to be worn on the user's arm, wherein Figs. 12A and 12B show the third fixture without magnetic elements, Fig. 12C shows the central portion of the third fixture with magnetic elements, and Fig. 12D is a longitudinal section at D-D of Fig. 12C; and

Figs. 13A and 13B show the safety light respectively before and after attachment to the third fixture in use.

Corresponding parts are indicated by the same reference numerals in each of the figures.

Referring to the figures, a first fixture comprises a generally flat, thin anchor element 10 and a generally flat, thin body element 30, both of which parts may be moulded from polycarbonate or other plastics material. The body element 30 comprises a central, circular recess 31 having a raised rim 32 surrounding a serrated inner circumferential wall 33 and an annular seat 34, the seat having a flat front surface 35, an opposite, flat rear surface 36, and a central, circular aperture 37. A pair of flexible wings 38 with first magnetic elements 39 at their distal ends extend outwardly from the central region.

The anchor element 10 comprises a disc 1 1 with a serrated outer rim 12, a flat front wall 13, an opposite, flat, annular rear wall 14, and a raised, circular central portion 15 having a flat rear wall 16. The central portion comprises a bar 17 between two apertures 18. The anchor element is rotatable with respect to the body element to define a plurality of alternative locking positions as illustrated by Figs. 3A and 3B.

The body element 30 has mutually orthogonal maximum length (L), width (W) and thickness (T) dimensions extending in alignment with its respective length, width and thickness axes as shown in Figs. 3A - 3C. Advantageously, the width dimension is at least three times the thickness dimension, and the body element is rotatable relative to the anchor element about an axis X₄ (Fig. 3C) extending in alignment with the thickness dimension. This provides a relatively thin, generally planar fixture which can be clamped to the helmet with the rotation axis X₄ extending orthogonally to a plane P| (Fig. 10A) tangent to the outer surface of the helmet so as to present minimal resistance to rolling in the event of a fall.

The second fixture (Figs. 9 - 1 1) comprises substantially the same parts as the first fixture, but the body element 30' is slightly radiused to correspond to an average radius of the outer side of a typical bicyclist's helmet, and is made from nylon which is sufficiently flexible to allow the wings 38 to flex so that the first magnetic elements 39 make flat abutting contact with the second magnetic elements 21 of the safety light. In the example shown, the body element of the fixture is a bracket to which a battery powered lamp 20 configured as a safety light is releasably attachable by engaging second magnetic elements 21 on the safety light with the corresponding first magnetic elements 39 on the body element. The second magnetic elements 21 are slightly recessed into the safety light so that they hold the safety light securely to the bracket, but allow it to break away instantly in the event of an impact leaving only the relatively much thinner body element 30 attached to the bicyclist's helmet 40; this allows the helmet to roll on the ground as it is designed to do, which helps to avoid injury to the user's neck. The lamp 20 comprises a protuberant, transparent or translucent casing 201 containing a light source 202, a power supply 203 comprising rechargeable batteries, and a switch 204 for selectively energising the light source from the power supply, as further described below. The bracket is intended to be mounted on a support comprising the portion 41 of the helmet, which extends generally along the axis Xj, so that the safety light is correctly positioned on the side of the helmet with its longitudinal axis X3 in a generally horizontal orientation.

In use, a flexible tie 22, such as an ordinary nylon cable tie, is passed through the apertures 18 in the anchor element and around the bar 17. The ends of the tie are then led through the central aperture 37 in the body element. A self-adhesive compressible foam pad 23 is then arranged between the rear surface 36 of the body element and the helmet 40, with the ends of the tie 22 passing through holes 24 in the pad.

With the anchor element 10 separated from the body element 30 as shown in Fig. 6, the body element is arranged in the desired orientation with respect to the support, so that its length axis X₃ is generally horizontal in the use position of the helmet. The anchor element 10 is then rotated as indicated by the arrows relative to the body element 30 to approximately the position shown in Fig. 3A, so that the bar 17 is aligned with the axis Xj of the portion 41 of the helmet on which the fixture is to be mounted, with the flexible tie 22 extending along an axis X₂ transverse to the bar 17 and axis X 1.

The tie 22 is then passed through the apertures 42 and around the support portion 41 of the helmet, and its ends engaged together and tightened in the conventional way so as to attach the anchor element in fixed relation to the support. The disc 1 1 of the anchor element is received in the recess 31 in the selected locking position (Fig. 3 A), so that the seat is arranged between the anchor element and the support. The raised portion 15 of the anchor element is received in the aperture 37 with its rear wall 16 recessed behind the rear surface 36 of the body element, as shown in Fig. 3C, so that the anchor element is spaced apart from the support in the mounted position (Fig. 7B), with a part of the body element being arranged between the anchor element and the support so that when the tie 22 is tensioned, the body element is clamped between the anchor element and the support.

As the tie 22 is tightened, the rear wall 14 of the anchor element 10 is engaged pressingly against the front surface 35 of the seat 34 of the body element 30 so that the body element is engaged pressingly against the support 41 , and the serrated surfaces 12 and 33 mutually abut one another and are locked together in opposed relation in the selected locking position, preventing the anchor element from rotating. The serrated surfaces 12, 33 thus form locking means comprising a locking structure which locks the anchor element in fixed relation to the body element so that the anchor element in turn secures the body element in fixed relation to the support portion 41 of the helmet in the mounted position as shown in Fig. 7B. The pad 23 is compressed between the surface of the support portion 41 of the helmet and the rear surface 36 of the body element, which prevents the body element from rocking on the curved surface of the helmet. The rear surface 36 of the body element forms an abutment surface which engages the support (via the interposed pad 23) in use.

In the example illustrated, the seat 34 of the body element is interposed between the directly opposed surfaces of the anchor element and the side wall of the helmet, so that it acts in compression to react the tension force of the strap between those surfaces. If the fixture were arranged differently on the helmet, a wider region of the body element could be arranged between respective opposed surfaces of the anchor element and support which are spaced apart laterally with respect to the direction of the tension force applied by the strap, the tension force applying a bending moment or shear force to the respective region which acts between the respective surfaces in the manner of a cantilever.

In each case, the lamp is advantageously mounted on the body portion which is clamped directly to the helmet. This provides a simple and compact fixture which avoids looseness by minimising the number of frictional interfaces and

permanently clamping the rotational interface in the selected position.

The safety light can then be releasably attached to the body element as shown in Fig. 7C.

Indicia 43, 44 (Fig. 3B) may be provided on the front surfaces respectively of the body element and the anchor element. By rotating the anchor elements of two identical fixtures to the same locking positions, as indicated by the indicia, and then mounting the two fixtures in mirror-identical positions on the opposite sides of a helmet, the user can ensure that both body elements, and so both safety lights attached to them, are identically and symmetrically positioned.

Advantageously, the safety light is elongate and a pair of safety lights may be arranged horizontally, one on the side of the helmet. This minimises wind resistance and provides an elongate band of light which indicates the orientation and direction of travel of the bicyclist.

Referring particularly to Figs. 5A - 5F, in the illustrated embodiment the light source 202 is a flexible strip of electroluminescent sheet material (comprising e.g. powder phosphor or thin film phosphor on a substrate of plastics sheet material) extending along the length of the casing 201 whose light is reflected from a reflector 205 which encloses the other components. Of course, LEDs or other light sources may equally be used. The power supply 203 is recharged (Fig. 5F) via a USB connection to a USB port 206 via an integral charging circuit 207, and powers the light source via a booster circuit 208 which provides a constant voltage output to a high frequency inverter 209 including a coil 210 as the battery voltage declines, the inverter maintaining a constant output (typically at 100V or more) to energise the electroluminescent strip until the batteries are exhausted. In order to reduce audible noise from the inverter, the inverter coil 210 or the whole inverter circuit may be mounted (for example, using adhesive) on the flexible electroluminescent strip 202 as shown, which decouples the high frequency vibration from the casing. The strip is made from flat, thin

electroluminescent sheet material, and is conveniently longer than it is wide, although of course it could have equal length and width dimensions. Optionally, the inverter coil could be mounted on a portion of the electroluminescent sheet material which is modified, e.g. to comprise only a substrate of the sheet material. The novel inverter coil mounting may be applied to lamps other than safety lights for bicyclists.

Referring to Figs. 8A - 8B, each of the first magnetic elements 39 comprises a magnet 391, and each of the second magnetic elements 21 comprises a

ferromagnetic element such as a mild steel plate. The first and second magnetic elements are attracted together in use to releasably attach the lamp to the fixture.

It is desirable to maximise the irequency of the inverter so as to reduce its size and maximise its power output; however, it has been found in practice that this can cause undesirable high frequency audible noise if the inverter is exposed to the field from the magnets used to attach the lamp to the fixture.

In order to avoid this problem and allow the efficiency of the inverter to be optimised, the magnet 391 is partially enclosed within a magnetic shield 392 so that the magnet and shield together form a cup magnet assembly, and an annular end face 393 of the magnetic shield is arranged to abut the respective other one of the first and second magnetic elements (in the illustrated embodiment, the ferromagnetic element 21) when the lamp is releasably attached to the fixture. The shield contains the magnetic field from the magnet except at the annular end surface of the shield which abuts the ferromagnetic plate in use and surrounds the exposed end surface 394 of the magnet. The shield comprises a magnetically permeable material, preferably having a magnetic permeability not less than that of steel or iron, e.g. iron, mild steel, nickel alloy or another ferromagnetic material. It is found that by arranging the end face 393 to abut the plate 21, the magnetic shield may be contained to a sufficient extent to avoid interference with the inverter. In order to achieve the required abutment, it is desirable to mount at least one of the first and second magnetic elements on a flexible arm so that it can move slightly relative to the lamp and the fixture, accommodating manufacturing tolerances to provide a close abutting fit. In the illustrated embodiment, the flexible wings 38 provide this slight movement to ensure a perfect fit between the respective magnetic elements 21 and 39.

It is also desirable that one of the first and second magnetic elements 21 is arranged in a shallow recess 211 in the respective lamp or the fixture, and the respective other one 39 of the first and second magnetic elements is received in the recess when the lamp is releasably attached to the fixture. The recess locates the magnetic elements in position and prevents displacement of the lamp in a direction transverse to the abutting faces in which the holding power of the magnets is weaker, so that relatively less powerful magnets may be used, again reducing interference.

Yet more preferably, the exposed end face 394 of the magnet is recessed below a plane P₂ containing the annular end face 393 of the magnetic shield by a distance of 0 - 40 microns, most preferably 0 - 20 microns. This is found to couple the magnetic flux most effectively between the magnet and the plate 21. By using a combination of these measures, it is found that magnetic interference is substantially eliminated.

The cup magnet assemblies may advantageously be used in any releasably mounted lamp comprising a light source powered by an inverter.

The switch 204 is preferably a reed switch which is operable by proximity to the magnetic field of the first magnetic element 39, so that the switch is operated simply by attaching or detaching the lamp to or from the fixture. When the lamp is attached to the fixture it is automatically illuminated as illustrated by the highlighted electroluminescent element in Figs. 7C, 10B and 13B. When it is removed from the fixture the light is extinguished as illustrated in Figs. 10A and 13 A.

The reed switch 204 comprises two conductors 2043, 2044 extending respectively from two contacts 2041, 2042 encapsulated in a glass housing 2045. Each second magnetic element 21 comprises a ferromagnetic plate, one of which is positioned between the encapsulated contacts 2041, 2042 and the magnet when the lamp is attached to the fixture. At least one of the conductors 2043 extends laterally beyond an edge 21 Of the plate as shown, which is found to cause the field to effectively operate the reed switch even where the magnetic field is shielded as described. Since the lamp must be removed from the fixture on the helmet in order to switch it off, this effectively ensures that the lamp will generally be protected from damaging UV light (for example, carried in a pocket or a case) during the day. At the same time, since the switch is operable by proximity to the magnet when the light is correctly mounted on the fixture, the light is reliably switched on at all times in use. The novel switching arrangement may be applied to other types of lamps which are releasably attachable to fixtures. In alternative embodiments, each of the first and second magnetic elements might comprise a magnet, and the lamp and the fixture may each comprise only one, or more than two, cooperating magnetic elements.

In yet further alternative embodiments, rather than cooperating magnetic elements, the lamp may be attachable to the fixture using any other releasable attachment means, for example, a resilient clip made from metal or plastics material, which is preferably configured to release the lamp on impact. Instead of a reed switch, the switch might be a Hall effect or other type of sensor. Rather than being operable by proximity to a magnetic field, the switch might be mechanically operable (for example, comprising a spring loaded abutment which contacts the fixture), or might be a Hall effect or other sensor arrangement operable by non-contact means other than an extraneous magnetic field as known in the art.

In yet further alternative embodiments, instead of the novel rotationally adjustable fixing, the fixture may be mounted on a support comprising a helmet (such as a bicyclist's or motorcyclist's helmet) or any other convenient support by adhesive, rivets or other suitable mechanical fasteners, hook and loop fabric fastening material, or any other attachment means. Referring to Figs. 1 1 A - 11C, the second fixture is provided with a blanking plug 400 which is inserted in place of the anchor element 10 when the second fixture is attached to a bicyclist's helmet having a substantially solid shell. The adhesive foam pad 23 forms a central part of a larger pad 23'; rather than removing the central part as shown in the preceding figures, the entire pad is used to stick the second fixture to the helmet as shown. Referring to Figs. 12A - 13B, a third fixture comprises a bracket with an armband 401 which is worn on the user's arm. The central portion 402 of the bracket has hinges 403 and slightly flexible wings 404 carrying first magnetic elements 39 which extend outwardly beyond the hinges 403. A respective buckle 405 is hingedly attached to the central portion at each of the hinges 403. In use, the buckles can be pivoted to adapt to the circumference of the user's arm, while the lamp 20 is releasably attached to the first magnetic elements 39 as described above in a horizontal orientation in the standing position of the user (Figs. 13 A, 13B). Abutments 406 retain the lamp in position.

In summary, a preferred fixture comprises an anchor element which engages a body element, the body element being rotatable relative to the anchor element to define a plurality of alternative rotational positions. The novel fixture may be attached to any convenient portion of a bicyclist's helmet and the body portion rotated to the desired orientation before tightening the tie to clamp the body portion directly to the helmet. Cooperating surfaces of the anchor element and body element form locking structure that prevents rotation of the anchor element in the selected position. A flexible tie is used in tension to attach the anchor element to a support, and draws the anchor element and locking element together so as to engage the locking structure and mount the assembly in the desired orientation in fixed relation to the support, irrespective of the orientation of the support. A lamp is releasably attachable to the body element. The fixture may comprise a bracket for a detachable safety light comprising an electroluminescent strip energised by an inverter controlled by a reed switch which is operated by cup magnet assemblies on the bracket, the cup magnet assemblies minimising magnetic interference with the inverter.

Instead of cooperating serrations, the locking structure may comprise frictional surfaces of the anchor element and the body element; for example, the anchor element may be tapered to fit tightly into a corresponding tapered aperture in the body element. In alternative embodiments, the anchor element need not be received in a recess in the body element. The locking structure may comprise a separate locking element that engages both the anchor element and the body element; for example, a pin or locking ring that is inserted between the two parts. In less preferred embodiments, instead of a locking structure, the fixture may comprise locking means such as, for example, adhesive arranged between the anchor element and the body element. Rather than being a separate part that is engageable with the anchor element as shown, the flexible tie might be permanently engaged with the anchor element, for example, moulded integrally with it from flexible plastics material. Rather than a conventional, flat cable tie with a serrated end that is engaged by a locking tab in an aperture in the opposite end, as shown in the illustrated embodiment, the tie could be round, flat, or any other shape, could be made from metal or plastics material, and could be wrapped around the support or attached at one end directly to the support.

In alternative embodiments, the novel method can be used to provide an attachment to any of a wide variety of supports, including without limitation pipes, cables, metal struts, tree limbs, and the like. Instead of a lamp, a sign or any other element may be releasably attachable to the fixture. Instead of providing a bracket to which another item may be attached, the body element of the fixture may incorporate a sign, a clip or support for pipes, cables or wires, or any other useful element which is to be mounted on the support in a predetermined orientation. The parts may be made from metal rather than plastics material, and the flexible tie may be a heavy duty steel strap or the like.

Many further adaptations are possible within the scope of the claims.

Claims

1. An apparatus comprising a lamp and a fixture for mounting the lamp on a support;

the lamp including:

a light source;

a power supply; and

a switch for selectively energising the light source from the power supply; the fixture including:

an anchor element;

a flexible tie engaged or engageable with the anchor element, the flexible tie being attachable to a support so as to mount the fixture on the support in a mounted position in fixed relation to the support; and

a body element, the body element being rotatable with respect to the anchor element to define a plurality of alternative rotational positions;

wherein the lamp is releasably attachable to the body element,

and the body element includes an abutment surface for engaging the support in the mounted position,

and a part of the body element is arranged in use between the anchor element and the support, so that the anchor element may be engaged in fixed relation with the body element in a selected one of the alternative rotational positions by tightening the tie so as to clamp the body element between the anchor element and the support.

2. An apparatus according to claim 1, wherein the body element has mutually orthogonal maximum length, width and thickness dimensions, and the width dimension is at least three times the thickness dimension, and the body element is rotatable relative to the anchor element about an axis extending in alignment with the thickness dimension.

3. An apparatus according to claim 1 or claim 2, wherein the body element has a circular recess, and the anchor element is arranged in the recess.

4. An apparatus according to any preceding claim, wherein the fixture includes a compressible pad which is arranged in use between the abutment surface and the support.

5. An apparatus according to any preceding claim, wherein the lamp is releasably attachable to the body element by means of cooperating magnetic elements arranged respectively on the body element and the lamp.

6. An apparatus according to claim 5, wherein at least one of the magnetic elements is arranged on a flexible portion of the body element.

7. An apparatus according to claim 5 or claim 6, wherein the body element includes a magnet, and the switch is operable by proximity to the magnet.

8. A method of attaching a fixture in a mounted position in fixed relation to a support, the support extending along a first axis, the fixture including a body element, an anchor element, and a flexible tie engaged or engageabie with the anchor element; comprising:

arranging the body element in a desired orientation with respect to the support;

rotating the anchor element with respect to the body element to a position in which the flexible tie extends transversely to the first axis;

passing the tie around the support so as to attach the anchor element in fixed relation to the support; and

securing the body element to the support in the desired orientation by tightening the tie so as to clamp the body element between the anchor element and the support and engage the anchor element in fixed relation with the body element in a selected one of the alternative rotational positions.

9. A method according to claim 8, characterised by releasably attaching an item to the body element in the mounted position thereof.

10. A method according to claim 8 or claim 9, wherein the item is a lamp and the support is a helmet.

1 1. An apparatus comprising a lamp and a fixture for mounting the lamp on a support, the lamp being releasably attachable to the fixture;

the lamp including:

a light source;

a power supply; and

a switch for selectively energising the light source from the power supply; the fixture including attachment means for attaching the fixture to a support;

wherein the switch is operable by attaching or detaching the lamp to or from the fixture.

12. An apparatus according to claim 1 1 , wherein the switch is operable by proximity to a magnetic field.

13. An apparatus according to claim 1 1 , wherein the fixture includes at least one first magnetic element, and the lamp includes at least one second magnetic element, at least one of the first and second magnetic elements comprising a magnet, the first and second magnetic elements being attracted together in use to releasably attach the lamp to the fixture.

14. An apparatus according to claim 13, wherein the first magnetic element comprises a magnet, and the switch is operable by proximity to the first magnetic element.

15. An apparatus according to claim 14, wherein the switch is a reed switch.

16. An apparatus according to claim 15, wherein the reed switch comprises two conductors extending respectively from two encapsulated contacts, and the second magnetic element comprises a ferromagnetic plate which is positioned between the encapsulated contacts and the magnet when the lamp is attached to the fixture, and at least one of the conductors extends laterally beyond an edge of the plate.

17. An apparatus comprising a lamp and a fixture for mounting the lamp on a support;

the lamp including:

a light source;

a power supply, the power supply including an inverter;

a switch for selectively energising the light source from the power supply; and

at least one second magnetic element;

the fixture including:

attachment means for attaching the fixture to a support; and

at least one first magnetic element;

at least one of the first and second magnetic elements comprising a magnet, the first and second magnetic elements being attracted together in use to releasably attach the lamp to the fixture;

wherein the magnet is partially enclosed within a magnetic shield so that the magnet and shield together form a cup magnet assembly, and an annular end face of the magnetic shield is arranged to abut the respective other one of the first and second magnetic elements when the lamp is releasably attached to the fixture.

18. An apparatus according to claim 17, wherein an exposed end face of the magnet is recessed below a plane containing the annular end face of the magnetic shield by a distance of 0 - 40 microns.

19. An apparatus according to claim 17, wherein an exposed end face of the magnet is recessed below a plane containing the annular end face of the magnetic shield by a distance of 0 - 20 microns.

20. An apparatus according to any of claims 17 - 19, wherein at least one of the first and second magnetic elements is mounted on a flexible arm for movement relative to the lamp and the fixture.

21. An apparatus according to any of claims 17 - 20, wherein one of the first and second magnetic elements is arranged in a recess in the respective lamp or the fixture, and the respective other one of the first and second magnetic elements is received in the recess when the lamp is releasably attached to the fixture.

22. An apparatus according to any of claims 17 - 21, wherein the light source comprises an electroluminescent sheet material.

23. An apparatus according to any of claims 17 - 22, wherein the first magnetic element comprises the said magnet, and the switch is operable by proximity to the first magnetic element.

24. An apparatus according to claim 23, wherein the switch is a reed switch.

25. An apparatus according to claim 24, wherein the reed switch comprises two conductors extending respectively from two encapsulated contacts, and the second magnetic element comprises a ferromagnetic plate which is positioned between the encapsulated contacts and the magnet when the lamp is attached to the fixture, and at least one of the conductors extends laterally beyond an edge of the plate.

26. A lamp comprising:

a flexible electroluminescent sheet material;

a power supply; and

an inverter powered by the power supply, the inverter including a coil, the inverter being arranged to energise the electroluminescent sheet material;

wherein the coil is mounted on the electroluminescent sheet material.

27. An apparatus comprising a lamp and a fixture substantially as described and illustrated.