GB2356921A

GB2356921A - A lamp with a fibre optic cable to provide a light output externally of the lamp housing

Info

Publication number: GB2356921A
Application number: GB9928406A
Authority: GB
Inventors: John Clayton Ruddick
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-12-02
Filing date: 1999-12-02
Publication date: 2001-06-06
Also published as: GB9928406D0

Abstract

A lamp comprising a light source 3 and a power source (69, Fig. 4) within a housing 2 and at least one fibre optic cable (5, Fig. 1) arranged to receive light from the light source 3 and provide a light output externally of the housing 2. The housing 2 may provide a sealed enclosure for the light source 3 and there may be a temperature sensor for monitoring the temperature within the housing and switching off the light source to prevent overheating. The fibre optic cable may comprise a bundle of optical fibres 6 within an outer plastic sheath 7. There may be a lens 40 and a reflecting surface 41 to direct light onto the inner end of the fibre optic cable. The lamp may be an inspection lamp suitable for use in the interior of gas cylinders or containers for flammable materials.

Description

2356921 LAMP This invention relates to lamps and in particular, though not

exclusively, to portable lamps, especially inspection lamps.

Currently, it is usually a requirement for gas cylinders to be visually inspected internally for signs of corrosion every five years, although there are some circumstances where the inspection period may be every ten years.

At present, such visual inspection is commonly carried out by illuminating the interior of the cylinder with an electric light bulb attached to a power source by a length of cable by means of which the bulb is suspended within the cylinder.

The use of an unshrouded bulb introduces a source of glare into the cylinder, thereby reducing the contrast in visible detail. Furthermore, the bulb can sometimes shatter, exposing the hot filament as it is inserted in or removed from the cylinder or by contact with the walls of the cylinder as the bulb is moved within the cylinder.

1 The hot filament provides a safety hazard and may ignite any flammable gas in the cylinder.

Also, it is sometimes necessary to carry out inspections in hazardous environments such as in mines where exposure of the hot filament may ignite any flammable gas in the atmosphere.

The present invention has been made from a consideration of the problems and disadvantages of existing lamps.

2 It is an object of this invention to provide a lamp which is of simple construction which can be used for inspection purposes in hazardous environments without risk of igniting any flammable material.

According to the present invention there is provided a lamp comprising a housing, a light source and a power source for the light source within the housing, and at least one fibre optic cable arranged to receive light from the light source and provide a light output externally of the housing.

By this invention, the fibre optic cable can be inserted inside a cylinder to illuminate the interior of the cylinder for inspection purposes with the light source such as a filament bulb located outside the cylinder and protected by the housing. The light output from the fibre optic cable provides a simple and safe way of illuminating the interior of the cylinder without glare or risk of igniting any flammable material inside the cylinder.

Furthermore, the fibre optic cable can be made to any suitable length and be flexible so as to facilitate positioning the cable in the cylinder and moving the cable within the cylinder to provide direct illumination of selected regions of the cylinder when carrying out an inspection for signs of corrosion or other faults which may require the cylinder to be scrapped.

Preferably, the housing provides a sealed enclosure for the light source enabling the lamp to be used in hazardous environments, such as mines, without risk of the light source igniting any flammable material in the surrounding atmosphere.

3 Advantageously, the light source is arranged to illuminate an inner end of the fibre optic cable whereby light is transmitted to an outer end of the cable to provide the light output externally of the housing. For example, the housing may have a socket in which the inner end of the fibre optic cable is received and sealed so as to expose the inner end to the light source.

In one arrangement, the socket is open to the interior of the housing and the inner end of the fibre optic cable extends through the socket and is secured within the housing. For example, a connector such as a ferrule may be attached to the inner end of the fibre optic cable and secured within the housing by a circlip. The ferrule and socket may have opposed abutment shoulders for locating the ferrule with a seal therebetween, for example an 0-ring. In this way, accidental removal of the cable is prevented but a damaged cable may be replaced by opening the housing to release the ferrule. The housing may be assembled with tamper proof fasteners to prevent unauthorised opening of the housing.

In an alternative arrangement, the socket is closed to the interior of the housing by a transparent window for transmitting light from the light source to the inner end of th fibre optic cable received in the socket. In this arrangement, cables of different length may be selected and fitted enabling the lamp to be adapted for a particular application.

Preferably, the fibre optic cable comprises a bundle of optical fibres comprising filaments or strands of light transmitting material such as glass enclosed within an outer sheath of plastics or other suitable protective material.

4 Advantageously, light from the light source is directed onto the inner end of the fibre optic cable by a lens such as a Fresnel lens which magnifies the light source, for example the filament of a bulb such as a tungsten halogen bulb, to cover the inner end of the cable. The lens may be made of clear and colourless plastics such as polycarbonate to transmit and focus the light from the light source.

Preferably, a reflecting surface such as a concave mirror is provided behind the light source to redirect light from this side of the light source so that it also illuminates the inner end of the cable. In this way, the inner end of the cable collects both direct and reflected light from the light source thereby increasing the light output.

Advantageously, the light source and/or mirror is/are adjustable for aligning the real and reflected images of the light source to cover the inner end of the fibre optic cable. In a preferred arrangement, the light source and/or reflecting surface are mounted through one or more adjusting screws for altering the position(s) of one or both of the light source and/or reflecting surface to obtain the optimum light output.

The power source preferabl comprises a battery which may consist of one or more cells connected in series with manually operable switch means for switching the light source on and off. In this way, the lamp is completely self-contained and no separate power source is required.

Advantageously, the or each cell is re-chargeable, for example nickel cadmium cells, and the housing is preferably adapted for connection to a charger for re-charging the battery in situ. This enables the battery to be re-charged without opening the housing which may be assembled with tamper proof fasteners as mentioned previously to restrict or prevent unauthorised access to the interior of the housing. The lamp may include means providing a visual and/or audible warning when re-charging is required and/or is completed.

In a preferred construction, the housing comprises a main body and a cover or lid secured to one end, for example by the afore-mentioned tamper proof fasteners. The cover and body define the enclosure for the light source and power source which is preferably sealed by any suitable means such as one or more O-rings between the cover and body and between the cover and fasteners.

Advantageously, the or each cell is located in the main body and is retained by the lens for magnifying the real and reflected images of the light source, and the light source is supported from the cover with the mirror positioned behind the light source on the underside of the cover.

This provides a particularly convenient arrangement for assembly and dis assembly of the lamp.

Preferably, the cover and body are provided with mating plug and socket connectors which engage automatically when the cover is fitted to the body to provide an electrical connection between the power source and light source. The cover and body may be adapted to ensure assembly in the correct orientation with the plug and socket connectors aligned for such engagement. For example, the cover and body may have co operating alignment formations.

Advantageously, the cover mounts a wiring board such as a printed circuit board in which one of the mating connectors is provided to make the electrical connections between the power source and the light source in 6 response to actuation of the switch, and between the power source and the charger to re-charge the power source.

A temperature sensor may be provided for monitoring the temperature within the housing and switching the light source off at a pre-determined upper temperature limit to prevent the lamp over-heating. The temperature sensor interrupts the power supply to the light source to enable the lamp to cool down. The power supply may be re-connected automatically when the temperature has fallen to a pre-determined lower temperature limit but more preferably the power supply is switched off at the upper temperature limit and has to be positively switched on again by actuating the switch when the lamp has cooled down. The lamp may include means providing a visual and/or audible warning to the user when the temperature sensor causes the lamp to be switched off and/or when the lamp can be switched on again e.g. a light may be illuminated when the lamp is switched off or the light goes out when the lamp can be switched on.

Advantageously, the housing includes a handle by means of which the lamp can be carried and held or mounted in a desired position for carrying out an inspection. The handie may be formed integrally with one of the cover and main body.

In a preferred construction, the housing is made of plastics, preferably impact resistant plastics such as filled nylon but other materials may be used.

The invention will now be described in more detail by way of example only, with reference to the accompanying drawings, wherein:

7 Figure 1 is a side view of a lamp embodying the invention; Figure 2 is a view from the cable end of the lamp shown in Figure 1; Figure 3 is a sectional view of the lamp shown in Figure 1; Figure 4 is an end view of the inside of the main body with the cover removed; Figure 5 is an end view of the inside of the cover; and Figure 6 is a sectional view, similar to Figure 3, showing a modification of the lamp depicted in Figures 1 to 5.

Referring to Figures 1 to 5 of the drawings, there is depicted a self contained, portable, battery operated inspection lamp 1 for use in hazardous environments such as when inspecting the interior of gas cylinders or other containers for flammable materials such as a petrol tank for corrosion.

The lamp 1 comprises a housing 2 for a light source which in this embodiment is a tungsten halogen bulb 3 having a filament 4 powered by a battery which in this embodiment consists of six cells 69 connected in series, and a light output which in this embodiment is a fibre optic cable 5 comprising a plurality of optical fibres 6 within an outer protective plastic sheath 7.

The cable 5 is flexible and can be of any suitable length enabling the position of the light output to be easily adjusted to any desired position 8 when carrying out an inspection. The maximum length of the cable 5 to provide an acceptable light output depends on transmission losses but, in general, a length of 75cm may be sufficient for most applications although longer or shorter cables 5 may be employed.

A rod (not shown) may be attached to the cable 5 to facilitate remote manual adjustment of the position of the light output, for example when carrying out an inspection in a confined or relatively inaccessible position such as the interior of gas cylinders or petrol tanks. The rod may also be provided with a mirror to facilitate inspection in such locations.

The housing 2 comprises a main body 8 of hexagonal cross-section and a cover 9 also of hexagonal section releasably secured at one end of the body 8 by six screws 10. The main body 8 and cover 9 are both mouldings of plastics material, preferably impact resistant plastics, such as filled nylon, although other materials may be used.

Each screw 10 has a threaded shank 11 which extends through a countersunk hole 12 in the cover 9 and engages a blind tapped hole 13 in side wall 14 of the body 8. An enlarged head 15 at one end of the shank 11 is received in the countersink 16 and is sealed on the underside by an 0-ring 17. The head 15 has a tamperproof drive formation 18 for engagement by a suitable tool to secure the cover 9 and prevent unauthorised removal.

An 0-ring 19 is located in a groove 20 in the end face of the main body 8 inboard of an upstanding rib 21 extending around the marginal edge of the end face and outboard of the screws 10. The rib 21 locates a flange 22 on the underside of the cover 9 which engages the 0-ring 19 to seal the 9 cover 9 to the body 8 when the screws 10 are tightened to secure the cover 9.

The O-rings 17,19 are made of elastomer such as neoprene but this is not essential and other materials may be used to suit any given application.

Also, the O-rings 17,19 may be replaced by sealing rings of any suitable cross-section.

Formed integrally with the cover 9 is a handle 23 for carrying and holding the lamp 1. The handle 23 is spaced from and extends generally parallel to the main body 8 in the manner of a hook by means of which the lamp I may be detachably mounted on a support such as a rail. In this way, the lamp 1 does not have to be held leaving the user's hands free for positioning the fibre optic cable 5 when carrying out an inspection.

The main body 8 has a base wall 24 at the other end remote from the cover 9 with a central frusto-conical boss 25 projecting outwards from the base wall 24. The boss 25 has a through bore 26 forming a socket for mounting the fibre optic cable 5. The bore 26 is stepped to form an internal annular shoulder 27.

A connector sleeve or ferrule 28 is attached to one end of the fibre optic cable 5 and is a sliding fit in the socket. The ferrule 28 has an external annular shoulder 29 and is sealed within the socket by an O-ring 30 seated between the shoulder 29 and the shoulder 27 of the socket. The O-ring 30 is made of elastomer such a neoprene but other materials may be used.

Also the O-ring 30 may be replaced by a sealing ring of any suitable cross-section.

The ferrule 28 is secured within the main body 8 by a spring clip 31 such as a circlip to connect the fibre optic cable 5 to the housing 2 and prevent accidental removal of the cable 5 while permitting a damaged cable 5 to be replaced by opening the housing 2 to release the clip 31.

Upstanding from the base wall 24 within the main body 8 are six pillars 32 spaced from and parallel to the side wall 14 of the body 8. The pillars 32 terminate below the open end of the body 8 and are arranged to locate the cells 69 of the rechargeable battery in corresponding semi circular recesses 33 formed in the inner surface 34 of the side wall 14.

The cells 69 may be of any suitable rechargeable type such as nickel/cadmium.

A retainer plate 35 of clear plastics material such as polycarbonate is secured to the upper ends of the pillars 32 by screws 36 inserted through openings 37 in the plate 35 to engage blind tapped holes 38 in the pillars 32 and retain the batteries in the recesses 33.

The plate 35 has an annular raised centre portion 39 which is formed as a Fresnel or aspheric condenser lens 40 spaced above and aligned with the inner end of the fibre optic cable 5 secured in the base wall 24. The bulb 4 is spaced above and aligned with the lens 40 and a part-spherical concave mirror 41 is mounted on the underside of the cover 9 behind the bulb 4 and aligned with the lens 40.

The mirror 41 is secured by three triangularly disposed adjusting screws 42 which engage the marginal edge of the mirror 41. The mirror 41 is provided with deformable supports 43 for allowing adjustment of the position of the mirror 41 through the screws 42.

The bulb 3 is mounted on a holder 44 attached to a flange 45 extending from the inside of the cover 9. The holder 44 is resiliently secured by two holding screws 46 with spring washers 47 interposed between the holder 44 and the screw heads 48 allowing the position of the holder 44 to be adjusted by three triangularly disposed adjusting screws 49 for adjusting the position of the bulb 3.

The cover 9 also mounts a printed circuit board (PCB) 50 spaced from the underside of the cover 9. The PCB 50 has a plug 51 for releasable engagement with a socket 52 at the upper end of a protrusion 53 on the upper surface of retainer plate 35 to provide an electrical connection to the power source provided by the cells 69 of the battery. The PCB 50 also has a pair of connectors 54 extending to the outside and sealed to the cover by 0-ring or other seals (not shown) for receiving the plug of a battery charger (not shown) when it is desired to re-charge the battery.

The connectors 54 are isolated by a diode network so that no discharge from the battery can take place if the connectors 54 are shorted.

Mounted in the cover 9 is a switch 55 operable by a push button 56 for switching the lamp on and off. The switch 55 is of the non-latching type and the ON/OFF state of the lamp is reversed by the PCB each time the button 56 is depressed. In this embodiment, the PCB 50 provides solid state switching of the lamp current and the only physical switching is of an extremely small current inside the separately sealed switch 55 so there is no risk of any arcing within the housing 2.

The PCB 50 includes a temperature sensor (not shown) to switch the lamp off if the temperature within the housing 2 exceeds a pre-determined upper temperature limit such as may occur if the lamp 1 is operated for a prolonged period of time with the bulb 3 illuminated. After the lamp 1 is 12 switched off in response to the temperature sensor, it can be switched on again when the temperature in the housing has fallen below a lower pre determined temperature limit by actuating the push button 56.

In use, the lens 40 magnifies the direct and reflected images of the filament 4 of the bulb 3 and focuses these images to cover the bundle of optical fibres 6 at the inner end of the fibre optic cable 5. The adjustable mounting of the bulb 3 and the mirror 41 enables the position of the direct and reflected images of the filament 4 to be aligned so as to maximise the light collected by the bundle of optical fibres 6 at the inner end of the fibre optic cable 5 for transmission along the fibres 6 to form the light output at the outer end of the fibre optic cable 5.

As will be appreciated from the foregoing description, the invention provides a completely self-contained portable lamp in which main body 8 and cover 9 form a sealed enclosure for the light source and power supply and the fibre optic cable 5 provides a light output which can be easily manoeuvred for inspection purposes but does not become hot even if the cable 5 is damaged. Accordingly, the light output does not provide an ignition source for flammable material and the lamp 1 can be used in hazardous environments withbut igniting any flammable material that may be present. More specifically, the bulb 3 which becomes hot when illuminated is contained in an enclosure that is sealed from the surrounding environment avoiding any risk of ignition of flammable material even if the bulb 3 shatters exposing the hot filament within the housing 2.

Referring now to Figure 6, there is shown a modification of the lamp 1 abovedescribed. For convenience, like reference numerals are used to indicate parts of the lamp corresponding to Figures 1 to 5.

13 In this embodiment, the socket for mounting the fibre optic cable 5 is formed by an insert 60 slidably received in a central opening 61 in the boss 25 in the base wall 24 of the main body 8. The insert 60 has an external screw thread at the inner end for mounting a retainer nut 62 and an external flange 63 at the outer end that locates against the outer surface of the boss 25 and is sealed by an 0-ring 64 on tightening the nut 62 to secure the insert 60 in the opening 61.

The insert 60 is provided with a window at the inner end in the form of a glass disc 65 located and retained by a lock ring 66 and sealed by an 0 ring 67. The fibre optic cable 5 has a connector sleeve or ferrule 28 attached to the inner end releasably secured within the insert 60 by a connector assembly 68 which is a slidable and latchable fit in the insert 60 and enables the fibre optic cable 5 to be detached and replaced by a different fibre optic cable while maintaining the integrity of the scaled enclosure containing the bulb 3 within the housing 2. In this way, the lamp 1 can be adapted for a given application by selection and fitment of the appropriate fibre optic cable 5 without opening the housing 2. In other respects the construction and operation of the lamp is the same as the first embodiment. 1 Other modifications and improvements will be apparent to those skilled in the art and are deemed within the scope of the invention.

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Claims

1 A lamp comprising a housing, a light source and a power source for the light source within the housing, and at least one fibre optic cable arranged to receive light from the light source and provide a light output externally of the housing.

2. A lamp according to Claim 1 wherein the housing provides a sealed enclosure for the light source.

3. A lamp according to Claim 1 or Claim 2 wherein the light source is arranged to illuminate an inner end of the fibre optic cable whereby light is transmitted to an outer end of the cable to provide the light output externally of the housing.

4. A lamp according to Claim 3 wherein the housing has a socket in which the inner end of the fibre optic cable is received so as to expose the inner end of the light source.

5. A lamp according to Claim 4 wherein the socket is open to the interior of the housing and the inner end of the fibre optic cable extends through the socket and is secured within the housing.

6. A lamp according to Claim 5 wherein a connector such as a ferrule is attached to the inner end of the fibre optic cable and secured within the housing by spring clip.

7. A lamp according to Claim 6 wherein the ferrule and socket have opposed abutment shoulders for locating the ferrule with a seal therebetween.

8. A lamp according to Claim 4 wherein the socket is closed to the interior of the housing by a transparent window for transmitting light from the light source to the inner end of the fibre optic cable received in the socket.

9. A lamp according to Claim 8 wherein the fibre optic cable is detachably mounted in the socket.

10. A lamp according to any preceding claim wherein the fibre optic cable comprises a bundle of optical fibres comprising filaments or strands of light transmitting material enclosed within an outer sheath.

11. A lamp according to Claim 3 wherein light from the light source is directed onto the inner end of the fibre optic cable by a lens which magnifies and focuses the light source to cover the inner end of the cable.

12. A lamp according to 1blaim 11 wherein the lens is made of clear plastics to transmit the light from the light source.

13. A lamp according to Claim 11 or Claim 12 wherein the lens is a fresnel lens.

14. A lamp according to Claim 3 wherein reflecting surface is provided behind the light source to provide a reflected image of the light source.

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15. A lamp according to Claim 14 wherein the light source and/or reflecting surface is/are adjustable for aligning the real and reflected images of the light source to cover the inner end of the fibre optic cable.

16. A lamp according to any one of the preceding claims wherein the light source and/or reflecting surface is/are adjustable through one or more adjustable screws.

17. A lamp according to any one of the preceding claims wherein the power source comprises a battery with manually operable switch means for switching the light source on and off.

18. A lamp according to Claim 17 wherein solid state switching responsive to the manually operable switch means is employed to eliminate arcing in the housing.

19. A lamp according to Claim 17 or Claim 18 wherein the battery is re-chargeable and the housing is adapted for connection to a charger for re-charging the battery in situ.

20. A lamp according to daim 19 including means providing a visual and/or audible warning when re-charging is required and/or completed.

21. A lamp according to any one of the preceding claims wherein the housing comprises a main body and a cover or lid secured to one end.

22. A lamp according to Claim 21 wherein the cover is secured by tamper proof fasteners.

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23. A lamp according to Claim 21 or Claim 22 wherein the cover and the body define an enclosure for the light source and power source.

24. A lamp according to Claim 23 wherein the enclosure is sealed.

25. A lamp according to Claim 21 as dependent on Claim 17 wherein the battery is located in the main body, and the light source is supported from the cover.

26. A lamp according to Claim 25 wherein the cover and body are provided with mating plug and socket connectors to connect the power source to the light source.

27. A lamp according to any preceding Claim including a temperature sensor for monitoring the temperature within the housing and switching the light source off at a pre-determined upper temperature limit to prevent the lamp over-heating.

28. A lamp according to Claim 27 including means providing a visual and/or audible warning when the temperature sensor causes the lamp to be switched off and/or when the lamp can be switched on again.

29. A lamp according to any preceding claim wherein the housing includes a handle by means of which the lamp can be carried and held or mounted in a desired position for carrying out an inspection.

30. A lamp according to any preceding claim wherein the housing is made of plastics.

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31. A lamp substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

32. A lamp substantially as hereinbefore described with reference to Figures 1 to 5 as modified by Figure 6 of the accompanying drawings.