WO2007064615A1

WO2007064615A1 - Light guide and illuminating fixture comprising it

Info

Publication number: WO2007064615A1
Application number: PCT/US2006/045482
Authority: WO
Inventors: Marcella L. Pesenti; Luigi Tassoni
Original assignee: 3M Innovative Properties Company
Priority date: 2005-11-30
Filing date: 2006-11-27
Publication date: 2007-06-07
Also published as: EP1955099A4; EP1955099A1

Abstract

A light guide (1) comprising an outer carrier pipe (3) and an inner light-guiding optical film (2) is disclosed, wherein the outer carrier pipe (3) comprises a first sector (4) made of a transparent material and a second sector (5) made of an opaque material, the two sectors (4, 5) being co-extruded. (Fig. 1)

Description

LIGHT GUIDE AND ILLUMINATING FIXTURE COMPRISING IT

Field

The present invention relates to a light guide and to an illuminating fixture comprising it, in particular a road or cycle path illuminating fixture. The term "illuminating fixture" encompasses merely luminous fixtures, for example road or cycle path marking fixtures.

Background

Light guides are well known that are formed by a hollow conduit the walls of which include a transparent material having a smooth side and a side with an array of microprisms, commonly referred to as light-guiding optical film. According to the angle formed with the walls of the light guide, light is either emitted from the light guide or conveyed within the light guide through total internal reflection (TIR). To protect and support the light-guiding optical film, a transparent, outer carrier pipe having a suitable strength is typically included in the walls of the light guide.

A light projector is provided at one or both ends of the light guide to project light into the light guide at a suitable angle.

Light guides of the above kind are disclosed e.g. in U.S. 6,621,973 Bl; U.S. 5,745,632; U.S. 5,692,822 that disclose light guides having a circular cross-section; in U.S. 6,621,978 Bl and U.S. 5,715,347 that disclose light guides having a non-circular cross-section; and in U.S. 5,483,119 that discloses a light guide in which a transparent carrier tubing is provided around the light-guiding optical film.

It is known to control the amount of light that is emitted from the light guide by providing for so-called light extracting means, such as light diffusing patterns that change the angle of some of the light rays travelling within the light guide so that they will be emitted therefrom. A light extractor of the above kind is disclosed e.g. in WO 02/23084, the whole content of which is incorporated herein by reference.

It is further known to control the dihedron of light emission from the light guide by providing for only a sector of the light guide to be transparent, the remaining sector being opaque. This can be achieved by providing for an opaque cover to be applied to the selected sector of the light guide as described in U.S. 5,339,382. Summary

The present invention is directed at providing for a light guide having a controlled dihedron of light emission, still being of a simplified construction.

The objective is solved by a light guide comprising an outer carrier pipe and an inner light- guiding optical film, characterised in that the outer carrier pipe comprises a first sector made of a transparent material and a second sector made of an opaque material, the two sectors being co-extruded.

The light guide is thus simply manufactured by co-extruding the outer carrier pipe and internally lining it with the light-guiding optical film. The angular position of the opaque sector is furthermore prefixed.

Preferably, the opaque material is a polymeric material, more preferably a fibre-reinforced polymeric material, and even more preferably a polyester resin reinforced with fibre glass. Other suitable polymeric materials include epoxy resins and urethane resins, and other suitable reinforcing materials include carbon fibres and aramid fibres.

Typically, the transparent material is polycarbonate. Other suitable transparent materials include polyester and acrylic.

The angular extent of the first and second sectors will be selected according to the needs of having a properly sized emission window, and of having a proper mechanical strength of the light-guide, that is mainly provided by the second, opaque sector.

In an embodiment, the first sector extends over about 90°. Such an embodiment is particularly useful when the light guide of the invention is used in a road or cycle path illuminating fixture, in that light can be emitted towards the road or path without glaring the riders or drivers.

In another embodiment, the first sector extends over about 180°. Such an embodiment is useful for example for ceiling or wall illuminating fixtures.

Preferably, at the interfaces between the first and the second sector, ribs are formed in the walls of the first sector and corresponding grooves are formed in the walls of the second sector, or vice versa, to increase the hold between the two materials.

Fastening means such as adhesive, screws, nails or similar may also be used to assist in holding the two sectors together. The opaque material of the second sector preferably also forms at least one channel outside the light guide, to house electric cables, control devices etcetera.

A portion of the light-guiding optical film is preferably provided with extractor means to control the light emitted by the light guide.

The extractor means preferably comprises a pattern of light diffusing dots, that are preferably arranged according to the teachings of the above-cited WO 02/23084.

Moreover, preferably a locating ridge is longitudinally formed in the internal wall of the second sector to hold the light-guiding optical film in position. The cross-section of the locating ridge is preferably mushroom shaped.

The internal cross-section of the light guide is typically circular or semicircular, the latter cross-section being particularly suited for ceiling or wall illumination.

The second sector can include two flanges extending outwards along a common diameter for fixing the light guide partly recessed to a ceiling or wall.

In another aspect thereof, the invention relates to an illuminating fixture comprising the above light guide.

The illuminating fixture typically comprises a plurality of lengths of light guide.

To make shipment and insertion of the light-guiding optical film easy, each length of the ■ light guide is preferably up to about 6 meters long.

Preferably, moreover, a joint of two adjacent lengths of the light guide is external thereto.

The joint is preferably made of an elastic material such as silicone, fluoropolymer, nitrile, neoprene or butyl rubber and more preferably comprises a middle portion sized to forcedly receive the ends of the two adjacent lengths of the light guide. The joining of the lengths of the light guide is accordingly tight.

Typically, the illuminating fixture further comprises at least one light projector at a first end of the light guide.

Alternatively or in addition to the end light projector(s), the illuminating fixture can comprise at least one intermediate bi-directional light projector.

Preferably, up to five lengths of the light guide are arranged in sequence between a pair of light projectors.

Preferably each light projector includes a casing that replaces the first sector of transparent material of the light guide, to be coupled with the second sector of the light guide.

The projector casing is preferably made of painted iron but it could, alternatively, be made of painted mild steel or other painted or unpainted metals such as stainless steel, aluminium and brass.

At the edges of the casing, tangs are preferably provided that co-operate with the edges of casing to form a seat for housing the edges of the second sector of the light guide.

A seal may be provided between the projector casing and the second sector of the light guide, to prevent entry of dirt and moisture into the projector.

The light projector includes at least one transverse bracket for fixing at least one light source.

In the case of an intermediate light projector, two transverse brackets are included, for fixing back-to-back light sources to project light into the two adjacent lengths of light guide.

Preferably, a plurality of LEDs each coupled with a parabolic reflector are fixed to the transverse brackets, to form a light projector as disclosed in European patent application No. 04076541.4, Published as EP 1600559.

The at least one light source could, alternatively, be a discharge lamp, an halogen lamp or a metal halide lamp, preferably in combination with a suitable back reflector to direct a restricted cone of light into the light guide.

Preferably, the illuminating fixture further comprises vertical supports spaced along the illuminating fixture.

More preferably, each vertical support is hollow and provided with an aperture closed with a cover, to house electric cables, control devices etcetera.

To better support the illuminating fixture, each vertical support preferably comprises a top transverse bracket shaped as a bottom portion of the light guide, or of the light projector as the case may be.

Each vertical support is also preferably extruded from a fibre-reinforced polymeric material, and more preferably from a polyester resin reinforced with fibre glass as the second sector of the light guide.

When a light projector is provided at only one (or at neither) end of the light guide, an end cap is preferably provided at the other end (or at both ends) of the light guide.

The end cap is preferably internally reflective or diffusing, such as white.

Brief Description of the Drawings

Features and advantages of the invention shall now be further illustrated with reference to embodiments represented by way of non-limitative examples in the attached drawings, wherein:

- fig. 1 shows a perspective partial view of a light guide according to the invention, further showing cables not part thereof,

- fig. 2 shows a cross-sectional view of an outer carrier pipe of the light guide of Fig. 1,

- fig. 3 shows a detail of the outer carrier pipe shown in fig. 2,

- fig. 4 shows a diagrammatic perspective view of an example of illuminating fixture according to the present invention,

- fig. 5 shows a partially broken away view of components of an illuminating fixture according to the present invention,

- fig. 6 shows a perspective view of a casing of a light projector of the illuminating fixture of fig. 5,

- fig. 7 shows a longitudinal cross-section of a joint of the illuminating fixture of fig. 5,

- fig. 8 shows a perspective view of an end cap of the illuminating fixture of fig. 5,

- figs. 9 to 12 diagrammatically show alternative cross-sections of an outer carrier pipe of the light guide according to the invention.

Detailed Description

With reference to figs. 1 and 2, a light guide 1 according to the invention comprises an internal light-guiding optical film 2 and an outer carrier pipe 3. The light-guiding optical film 2 is typically a film of a transparent material having a smooth side (the inner side in fig. 1) and a side with an array of microprisms (the outer side in fig. 1). A suitable light-guiding optical film 2 is that commercially available as Scotch™ Optical Lighting Film 2301 from 3M Company, St. Paul, Minnesota, U.S.A.

As is well known in the field, the tilted sides of the microprisms and the index of refraction of the film material co-operate to refract, out of the light guide 1, those light rays for which the incidence angle falls outside a given range. Such light is thus emitted from the light guide 1, possibly according to preferential directions. The tilted sides of the microprisms and the index of refraction of the film material further co-operate to reflect, back towards the inner of light guide 1 through total internal reflection (TIR), those light rays for which the incidence angle falls within a given range. Such light is thus conveyed further within the light guide 1.

The outer carrier pipe 3 comprises a first sector 4 made of a transparent material and a second sector 5 made of an opaque material. The two materials are co-extruded to form a one-piece outer carrier pipe 3.

More in particular, the first sector 4 extends over 90°, and is preferably made of polycarbonate.

The second sector 5 accordingly extends over 270°, and is preferably made of a fibre- reinforced polymeric material, such as a polyester resin reinforced with fibre glass. Second sector 5 provides proper mechanical strength to the light-guide 1.

By co-extruding the first and second sectors 4, 5, the need for a separate opaque shield in addition to the outer carrier pipe and light-guiding optical film is avoided, light still being emitted from light guide 1 within a dihedron that is only dictated by the angular extent and position of the transparent first sector 4.

As can be seen in figs. 1 and 2, and in the detail of fig. 3, at the interfaces between first sector 4 and second sector 5, ribs 6 are formed in the walls of first sector 4 and corresponding grooves 7 are formed in the walls of second sector 5. Such matching ribs 6 and grooves 7 improve the hold between the two materials. It will however be understood that the interface between first sector 4 and second sector 5 may also be smooth, and/or that separate fastening means such as an adhesive (preferably a polyurethane adhesive), screws, nails or similar may be used to assist in holding the two sectors 4, 5 together.

The cross-section of the second sector 5 comprises, outside an arcuate wall 8 that co- operates with first sector 4 to form the inner cylindrical cavity of the light guide 1, an outermost wall 9 spaced therefrom through one or more partition walls 10. Channels 11 are thus formed outside the light guide l,that can be used for electric cables, control devices etcetera to pass. Cables C are shown by way of an example in fig. 1.

The inner surface of the arcuate wall 8 of second sector 5 is also provided with a ridge 12 that extends inwards longitudinally along light guide 1. Said ridge 12 serves as a locating feature to hold the light-guiding optical film 2 in the correct angular position inside the outer carrier pipe 3, in other words to prevent the light-guiding optical film 2 from rotating inside the outer carrier pipe 3. As can be seen in fig. 2, the cross-section of locating ridge 12 is preferably mushroom shaped, so that the two edges of the light-guiding optical film 2 will be retained below the mushroom's cap.

The above provision is particularly useful when, as shown, the light-guiding optical film 2 is provided with a pattern 13 of light diffusing dots, that are preferably arranged according to the teachings of the above-cited WO 02/23084.

Said pattern 13 of light diffusing dots acts to control the light emitted by the light guide by changing the angle of some of the light rays travelling within the light guide 1 so that they will be emitted from the light guide 1.

It will be understood that different extractor means may substitute for pattern 13 of light diffusing dots, such as diffusing stripes, diffusing solid bodies held in axial position along the light guide, and other known mechanisms.

Fig. 4 diagrammatically shows a light guide 1 used in an exemplary illuminating fixture 20, in particular a road or cycle path illuminating fixture 20.

The illuminating fixture 20 comprises a plurality of lengths 21 of light guide 1 , joined to each other through joints 22 and intermediate bi-directional light projectors 23 A (one being shown in fig. 4). At the ends of the illuminating fixture 20, a unidirectional light projector 23B can be provided as shown at the left end in fig. 4, or an end cap 24 can be provided as shown at the right end in fig. 4. A plurality of vertical supports 25 spaced along the illuminating fixture 20 is also shown in fig. 4.

More in particular, each length 21 of light guide 1, namely each single-piece extrusion, is preferably up to about 6 meters long, so that the light guide 1 can be easily shipped, and the light-guiding optical film 2 can be easily inserted within the outer carrier pipe 3. Since the light guide of the invention is able to convey light from a suitable projector up to 30 meters, up to five such lengths 21 of light guide 1 can be arranged in sequence, joined to each other by joints 22, before a further projector is necessary, although in fig. 4 only up to four adjacent lengths 21 of light guide 1 are shown for reasons of space in the drawing.

With further reference to fig. 5, a preferred embodiment of the above mentioned elements of the illuminating fixture 20 are shown in further detail.

The lengths 21 of light guide 1 are similar to that shown in fig. 1, apart from the angular extent of the transparent first sector 4 and of the opaque second sector 5 being shown as of 180° each. When the illuminating fixture 20 is used along a road or cycle path to mark or illuminate it, the 180° transparent first sector 4 is of course oriented towards the road or path.

It will be however understood that the same angular extents as shown in fig. 1 may be used, the 90° transparent first sector 4 being then oriented downwards, so that light can be emitted from the light guide 1 towards the road or path without glaring the riders or drivers.

The length 21 of light guide 1 shown to the right in fig. 5 merges with a bi-directional projector 23 A at an end portion thereof (to the left in fig. 5). In said end portion, only the opaque second sector 5 of the light guide 1 is extruded, the first sector 4 of transparent material of the light guide 1 being replaced by a casing 26 of projector 23A, having a similar shape to first sector 4.

The projector casing 26, better shown in fig. 6, is preferably made of painted iron, and includes two transverse brackets 27 for fixing two ballasts 28 and two sets of LED light sources each coupled with a parabolic reflector 29, forming a light projector as disclosed in the above-cited European patent application No. 04076541.4 (publication EP 1600559). The sets of light sources are arranged back-to-back, so that each set will project light into one of the two adjacent lengths 21 of light guide 1, thus effectively forming a bidirectional light projector 23 A.

It will be understood that in the case of a light projector coupled at an end of the illuminating fixture 20, only one set of LED light sources 29, and one ballast 28, will be provided to form a unidirectional light projector 23B. The casing 26 can therefore have a single bracket 27, or to eliminate the need of manufacturing separate casings 26, two brackets 27 may still be provided, one not being used. It will further be understood that in the case of a light projector coupled at an end of the illuminating fixture 20, casing 26 will include an end wall (not shown) at the side opposite the light guide 1. Alternatively, a cap such as cap 24 can be used in such a case also.

Moreover, it will be understood that different light sources can also be used, especially a single light source in the form of a discharge lamp, an halogen lamp or a metal halide lamp, typically in combination with a suitable back reflector to direct a restricted cone of light into the light guide.

Finally, it will be understood that the cross-section of casing 26 will extend over 90° only in the case in which it is used with a light guide where the transparent first sector 4 extends over 90° only, as shown in fig. 1.

At the edges of casing 26 of light projector 23, tangs 30 are provided that co-operate with the edges of casing 26 to form a seat 31 for housing the edges of the second sector 5 of the light guide. Coaxial holes 32 are provided in the edges of casing 26 and in tangs 30, to house removable fixing means such as screws.

In such a way, casing of light projector 23 may be easily removed to access the projector e.g. to replace a light source.

A seal (not shown) may be provided between casing 26 and the second sector 5 of the light guide, to prevent entry of dirt and moisture into projector 23.

The joint 22 of illuminating fixture 20 shown in fig. 5, and a longitudinal cross-section of which is shown in fig. 7, is in the form of a sleeve made of silicone rubber or similar elastic material.

Joint 22 comprises two end portions 33 of a shape and size matching the outer contour of the light guide 1, and of the light projector 23 as the case may be.

Joint 22 further comprises a recessed middle portion 34, thus sized to forcedly receive the ends of the two adjacent lengths 21 of the light guide 1. The joining of the lengths of the light guide is accordingly tight.

End cap 24, that is better shown in fig. 8, comprises a peripheral wall 35 having a cross- section of a shape and size matching the outer contour of the light guide 1, and of the light projector when it is used as a unidirectional light projector 23B as discussed above. End cap 24 further comprises a transverse wall 36 extending at one end of the peripheral wall, that closes the illuminating fixture 20. Transverse wall 36 of end cap 24 is preferably an internally reflective or diffusing surface, such as a white surface, to reflect light back into the light guide 1.

Vertical support 25 of illuminating fixture 20 shown in fig. 5 is hollow and provided with an aperture 37 closed with a cover 38.

Vertical support 25 is also preferably extruded from a fibre-reinforced polymeric material, and more preferably from a polyester resin reinforced with fibre glass as the second sector 5 of light guide 1.

Electric cables, control devices etcetera can thus extend within the internal cavity of vertical support 25, for example to power and control light projectors 23. Aperture 37 provides an easy access to such cables and devices.

At the top, vertical support 25 comprises a transverse bracket 39 shaped as a bottom portion of light guide 1, and thus as bottom portion of the light projector 23. The transverse bracket 39 comprises a hole 40 to access the interior of the vertical support 25.

In figs. 9 to 12, only a few different cross-sections of the outer carrier pipe of the light guide according to the invention are diagrammatically shown by way of an example.

According to fig. 9, the opaque second sector 5 of the light guide includes two flanges 43 extending outwards along a common diameter for fixing the light guide partly recessed to a ceiling or wall.

According to fig. 10, that also shows an embodiment suitable for a light guide partly recessed to a ceiling or wall, again the opaque second sector 5 of the light guide includes two flanges 43 extending outwards along a common diameter for fixing the light guide partly recessed to a ceiling or wall. However, the opaque second sector 5 only comprises the arcuate wall 8 (fig. 1) that co-operates with first sector 4 to form the inner cylindrical cavity of the light guide 1, while it lacks the outermost wall 9 and the partition walls 10 forming channels 11 (fig. 1).

The cross-section shown in fig. 11 differs from the cross-section shown in fig. 10 in that also the flanges 43 are missing, the light guide then being simply circular, for any use.

The cross-section shown in fig. 12 shows an embodiment suitable for a light guide to be fixed to a ceiling or wall without being recessed. Such a cross-section is semi-circular, the opaque second sector 5 being flat and extending to the outside to form the flanges 43.

Claims

1. A light guide (1) comprising an outer carrier pipe (3) and an inner light-guiding optical film (2), characterised in that the outer carrier pipe (3) comprises a first sector (4) made of a transparent material and a second sector (5) made of an opaque material, the two sectors (4, 5) being co-extruded.

2. The light guide (1) of claim 1, characterised in that the opaque material of the second sector (5) is a fibre-reinforced polymeric material.

3. The light guide (1) of claim 1 or claim 2, characterised in that the transparent material of the first sector (4) is polycarbonate.

4. The light guide (1) of any one of the preceding claims, characterised in that at the interfaces between the first sector (4) and the second sector (5), ribs (6) are formed in the walls of the first sector (4) and corresponding grooves (7) are formed in the walls of the second sector (5) or vice versa.

5. The light guide (1) of any one of the preceding claims, characterised in that the opaque material of the second sector (5) also forms at least one channel (11) outside the light guide (1).

6. The light guide (1) of any one of the preceding claims, characterised in that a portion of the light-guiding optical film (2) is provided with extractor means (13) to control the light emitted by the light guide (1).

7. The light guide (1) of any one of the preceding claims, characterised in that a locating ridge (12) for the light-guiding optical film (2) is longitudinally formed in the internal wall of the second sector (5).

8. An illuminating fixture (20) comprising a plurality of lengths (21) of light guide (1) each according to any one of the preceding claims.

9. The illuminating fixture (20) of claim 8, characterised in that a joint (22) between two adjacent lengths (21) of light guide (1) is external thereto.

10. The illuminating fixture (20) of claim 8 or claim 9, characterised by further comprising at least one light projector (23) at a first end of a light guide.

11. The illuminating fixture (20) of claim 10, characterised in that the light projector (23) includes a casing (26) that replaces the first sector (4) of transparent material of the light guide (1), coupled with the second sector (5) of the light guide (1).