GB2041187A

GB2041187A - Lamp change-over system

Info

Publication number: GB2041187A
Application number: GB7903766A
Authority: GB
Original assignee: Stone Platt Crawley Ltd
Current assignee: Stone Platt Crawley Ltd
Priority date: 1979-02-02
Filing date: 1979-02-02
Publication date: 1980-09-03

Abstract

A lamp-changer for use in visual signalling on navigational beacons comprises a number of lamps 1a-1d and a number of light guides 3a-3d each of which receives light emitted from a respective one of the lamps, the light guides being brought together to form a common exit point 4 for light emitted from the lamps. Thus to effect a lamp change it is only necessary to electrically switch from one lamp to another. <IMAGE>

Description

SPECIFICATION Improvements relating to lamp-changers This invention relates to lamp-changers for use in visual signalling and navigational beacons.

In signalling and navigation beacons the life of a lamp (i.e. a light source) may be less than the required interval of servicing, so that some form of changeoever to a standby lamp is usually necessary. Such a changeoever system may comprise several lamps and means for automatically effecting interchange of the lamps in sequence when failure of an active lamp is detected.

Many mechanical and electro-mechanical devices for effecting the lamp interchange by moving the lamps into the operative position are known but they tend to be unreliable in the necessarily intermittent operating conditions. It is the object of this invention to provide a changeover system without recourse to the use of such devices.

According to the present invention a lamp changer comprises a plurality of lamps and a plurality of light guides each of each is arranged to receive at one end light emitted from a respective one of said lamps, the light guides being brought together to form a substantially common light exit point from all said lamps, and electrical switching means for selectively energising one or more of said lamps at a time. Thus the interchange between lamps is effected by a simple electrical switching operation.

Advantageously said light guides each comprise a bundle of optical fibres.

The invention will now be further described by way of example with reference to the accompanying diagrammatic drawings, in which Figure 1 illustrates one form of lampchanger in accordance with the invention, and Figures 2 and 3 show alternative ways of arranging the optical fibres to form light guides.

Referring more particularly to Fig. 1 of the drawings, lamps 1 a, 1 b, 1 C, 1 d, are equipped with condensing means of known kind such as converging mirrors 2a, 2b, 2c, 2d, to focus a sufficient portion of their light output onto the first ends of optically transmissive light guides 3a, 3 b, 3c, 3d. The second ends of these light guides are brought together in a manner to be described to form a single exit 4 from which rays originating at any of the lamps 1 a, 1 b, 1 C and 1 d emerge. Thus lamp 1 a may be first in service and when it fails lamp 1 b is energised followed sequentially by 1 C and 1 d.If required more than one lamp can be in action at one time and the lamps can be switched to vary the intensity of the signal for instance between night and day, by switching means not shown but which may be of conventional form. Alternatively or additionally the colour of the light emerging from the second ends may be varied by using lamps of different colours or interposed colour filters Z he combined second ends of the guides omit light within an angle which depends on the design of the guide and the form of the condensing means illuminating the first ends.

Although in some applications it may be satisfactory for the second ends to be used directly as the viewed signal it will usually be necessary to pass the light emerging from the second end through a further optical system and it is then desirable for the optical character of the combination of second ends to be as nearly as possible independent of which lamp or lamps are active. To achieve this the light guides are each formed of a bundle of typically some hundreds of fibres of known optically transmissive form for instance having an outer layer of refractive index sufficiently lower than the refractive index of the optically transmissive core. At the said second ends of these guides the fibres of the several guides are dispersed so fibres of each guide are substantially uniformly distributed within the combined exit area.The distribution may be random or organised irito regular axially symmetrical arrangements such as concentric circles or spirals. One means of achieving this is illustrated in Fig. 2. The optical fibres 5 are arranged as a thin layer of substantially parallel fibres by adhesion to a tape 6. The layer is then subdivided along the length of the tape into groups 7a, 7b etc. to allocate fibres to bundles and then rolled up to form a combined exit bundle with spirally arranged filaments giving nearly axial symmetry to filaments originating from each of the different bundles. An alternative assembly method is to weave the filaments with an inactive weft which may be of any suitable textile for instance polyester as illustrated in Fig. 3 subsequent grouping and rolling being performed as previously described.

1. A lamp-changer comprising a plurality of lamps and a plurality of light guides each of which is arranged to receive at one end light emitted from a respective one of said lamps, the light guides being brought together to form a substantially common light exit point from all said lamps, and electrical switching means for selectively energisine cne or more of said lamps at a time.

2. A lamp-changer according to claim 1, wherein said light guides each comprise a bundle of optical fibres.

3. A lamp-changer according to claim 2, wherein the optical fibres of each said bundle are dispersed at said exit point so that they are distributed over the light emitting area of said exit point.

4. A lamp-changer according to claim 3,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements relating to lamp-changers This invention relates to lamp-changers for use in visual signalling and navigational beacons. In signalling and navigation beacons the life of a lamp (i.e. a light source) may be less than the required interval of servicing, so that some form of changeoever to a standby lamp is usually necessary. Such a changeoever system may comprise several lamps and means for automatically effecting interchange of the lamps in sequence when failure of an active lamp is detected. Many mechanical and electro-mechanical devices for effecting the lamp interchange by moving the lamps into the operative position are known but they tend to be unreliable in the necessarily intermittent operating conditions. It is the object of this invention to provide a changeover system without recourse to the use of such devices. According to the present invention a lamp changer comprises a plurality of lamps and a plurality of light guides each of each is arranged to receive at one end light emitted from a respective one of said lamps, the light guides being brought together to form a substantially common light exit point from all said lamps, and electrical switching means for selectively energising one or more of said lamps at a time. Thus the interchange between lamps is effected by a simple electrical switching operation. Advantageously said light guides each comprise a bundle of optical fibres. The invention will now be further described by way of example with reference to the accompanying diagrammatic drawings, in which Figure 1 illustrates one form of lampchanger in accordance with the invention, and Figures 2 and 3 show alternative ways of arranging the optical fibres to form light guides. Referring more particularly to Fig. 1 of the drawings, lamps 1 a, 1 b, 1 C, 1 d, are equipped with condensing means of known kind such as converging mirrors 2a, 2b, 2c, 2d, to focus a sufficient portion of their light output onto the first ends of optically transmissive light guides 3a, 3 b, 3c, 3d. The second ends of these light guides are brought together in a manner to be described to form a single exit 4 from which rays originating at any of the lamps 1 a, 1 b, 1 C and 1 d emerge. Thus lamp 1 a may be first in service and when it fails lamp 1 b is energised followed sequentially by 1 C and 1 d.If required more than one lamp can be in action at one time and the lamps can be switched to vary the intensity of the signal for instance between night and day, by switching means not shown but which may be of conventional form. Alternatively or additionally the colour of the light emerging from the second ends may be varied by using lamps of different colours or interposed colour filters Z he combined second ends of the guides omit light within an angle which depends on the design of the guide and the form of the condensing means illuminating the first ends. Although in some applications it may be satisfactory for the second ends to be used directly as the viewed signal it will usually be necessary to pass the light emerging from the second end through a further optical system and it is then desirable for the optical character of the combination of second ends to be as nearly as possible independent of which lamp or lamps are active. To achieve this the light guides are each formed of a bundle of typically some hundreds of fibres of known optically transmissive form for instance having an outer layer of refractive index sufficiently lower than the refractive index of the optically transmissive core. At the said second ends of these guides the fibres of the several guides are dispersed so fibres of each guide are substantially uniformly distributed within the combined exit area.The distribution may be random or organised irito regular axially symmetrical arrangements such as concentric circles or spirals. One means of achieving this is illustrated in Fig. 2. The optical fibres 5 are arranged as a thin layer of substantially parallel fibres by adhesion to a tape 6. The layer is then subdivided along the length of the tape into groups 7a, 7b etc. to allocate fibres to bundles and then rolled up to form a combined exit bundle with spirally arranged filaments giving nearly axial symmetry to filaments originating from each of the different bundles. An alternative assembly method is to weave the filaments with an inactive weft which may be of any suitable textile for instance polyester as illustrated in Fig. 3 subsequent grouping and rolling being performed as previously described. CLAIMS

4. A lamp-changer according to claim 3, wherein said optical fibres at their said other ends are secured to a spirally wound tape, which in the laid-flat condition reveals said fibres as a layer of substantially parallel fibres.

5. A lamp-changer according to claim 3 wherein said other ends of said fibres form the warp threads of a weave with optically inactive weft threads to interconnect them together, the thus woven ends being wound into spiral form.

6. A lamp-changer according to claims 4 or 5, wherein each of said bundles is formed from a group of fibres whose said other ends lie adjacent each other, so that each said bundle is distributed in spiral form over the light emitting area of said exit point.

7. A lamp-changer substantially as hereinbefore described with reference to the accompanying drawings.