GB2301692A - Illuminated signs - Google Patents

Abstract

An illuminated sign (10, Fig.1), includes a fabricated aluminium housing (12) which supports a fluorescent tube holder 14 and a transparent panel (16). A transparent sheet of Plexiglass GS 1001 material 18 is gripped by the tube holder 14 and between the transparent panel (16) and the Plexiglass material 18 is sandwiched a poster (20) or other sign to be illuminated. First 22 and second 24 aluminium extrusions cooperate together as shown to grip the fluorescent tube 25 between substantially cylindrical portions 26, 28 of the extrusions. Each of the two extrusions has a second substantially cylindrical portion 30; 32, larger in radius than and adjacent to the first substantially cylindrical portions 26, 28 and a gripping flange 34; 36. The second substantially cylindrical portions 30, 32 define an air space 38 between the holder 14 and the tube 25; the gripping flanges 34, 36 grip between them the edge of the sheet material 18 and, to assist, are coated with a black rubber strip 35; 37. The rubber strips act as an absorptive coating to prevent light banding at the edge of the sign. Cylindrical portions 26, 28 are provided with reflective coatings.

Description

ILLUMINATED SIGNS This invention relates to illuminated signs of the kind including a sheet of transparent material which is lit from the sides and to which a poster or other sign is affixed.

To ensure that the poster or sign is properly illuminated, the transparent material is chosen to have light-scattering properties and various such materials have in the past been tried. Existing signs, however, suffer from disadvantages.

Unless the range of angles at which light enters the edge of the material is small, light which enters at relatively large angles from the plane of the sheet material is not totally internally reflected within the material and gives rise to bright stripes at the edge of the sign.

This problem has been addressed in two ways. To ensure a relatively narrow angular range of light entering the edge of the transparent material, fluorescent tubes which are narrower than the width of the sheet material have been proposed, spaced from the edge of the material, to provide the side lighting. The tubes are surrounded by a reflective box, the side of which are spaced from the tube to prevent the tube getting too hot. Because of the small size of the tube and the amount of light it must produce, it runs hotter than, say, a domestic fluorescent light. It has also been proposed to coat the faces of the sheet, adjacent its edges, with an absorptive coating, to narrow further the range of angles of light passing through the material.This precaution affects substantially the proportion of the light generated by the tube which passes into the sheet material and, taken together with the small size of the tube, tends to make the signs rather dim.

The present invention addresses these problems and seeks to provide a side-lit illuminated sign which is able to use much larger dimension fluorescent tubes, yet does not produce banding at the sides of the sign. Accordingly, the present invention provides an illuminated sign comprising a sheet of transparent material having means for scattering light distributed across it, a fluorescent tube and an elongate holder for the tube, the holder having a first substantially cylindrical part adapted to grip the outer circumference of the tube and coated with a reflective coating, a second part adapted to be spaced away from the outer circumference of the tube when the tube is gripped in the first part and a third part adapted to grip the faces of an edge of the sheet and coated with an absorptive coating.

The three parts of the fluorescent tube holder have distinct yet complementary functions. The first substantially cylindrical part, coated with a reflective coating, not only grips the tube but effectively defines with it a crown silvered source, ensuring that the intensity of light escaping from it is heavily biased in terms of direction and it is of course arranged that this direction be the direction straight into the edge of the sheet of transparent material. The second part defines a space with the fluorescent tube for the circulation of air.

It has been found that with standard fluorescent tube sizes, sufficient cooling by convection can be achieved, despite the enclosure of the tube by the holder. The third part grips the side of the sheet material and also provides an absorbing band to absorb the small amounts of light which escape the holder at angles deviating substantially from the direction of maximum intensity.

The third part of the holder may be adjacent the second part. For example, it may be bounded on both sides by the second part and lie substantially centrally within it.

This ensures that the air cooling space is adjacent to the point at which most of the light from the tube is emitted and absorbed by the absorptive coating, i.e. the hottest part.

Preferably, the second part of the holder is substantially cylindrical and coated with a reflective coating. This ensure that the arrangement as a whole is effectively as close as possible to a crown silvered source with a single direction of emission.

A fourth part remote from the second part may be provided, adapted to be spaced away from the outer circumference of the tube when the tube is gripped in the first part, thus defining a second cooling space. To distribute the cooling uniformly, it is preferred that the fourth part of the holder lie opposite the third part. The fourth part may be substantially flat and face the third part.

For ease of assembly, it is preferred that the holder comprises two elongate pieces which fit together to grip the fluorescent tube and the sheet of transparent material.

For example, one piece of the holder may include an elongate projection which cooperates with a recess on the other when the two are so fitted together.

For reasons which will be apparent, it is preferred that the sign further comprises a second fluorescent tube and a second such holder adapted to grip the second tube and the faces of the opposite edge of the sheet.

To ensure uniform light scattering, it is preferred that a light-scattering additive is distributed throughout the transparent material. For example, the transparent sheet may be Plexiglass GS 1001.

It has been found that the invention works best if the reflective coating is white, rather than silvered, and the absorptive coating is black.

The present invention will now be described with reference to the accompanying drawings in which: figure 1 is a horizontal cross-section through one edge of an illuminated sign; and figure 2 is a similar cross-section through the sheet material, tube and holder.

As can be seen from figure 1, the illuminated sign 10 includes a fabricated aluminium housing 12 which supports a fluorescent tube holder 14 and a transparent panel 16.

A transparent sheet of Plexiglass GS 1001 material 18 is gripped by the tube holder 14 and between the transparent panel 16 and the Plexiglass material 18 is sandwiched a poster 20 or other sign to be illuminated. The holder consists of first 22 and second 24 aluminium extrusions which are coated with matt white reflective coatings and couple together to provide the desired shape and orientation. The second extrusion 24 can be removed to allow replacement of the tube (not shown).

Figure 2 is a section through the opposite end of the sign from that which is shown in figure 1. The first 22 and second 24 aluminium extrusions cooperate together as shown to grip the fluorescent tube 25 between substantially cylindrical portions 26, 28 of the extrusions. The first substantially cylindrical portion 26 is a part of the first aluminium extrusion 22; the second substantially cylindrical portion 28 is formed from boundary parts of the two extrusions.

Each of the two extrusions has a second substantially cylindrical portion 30; 32, larger in radius than and adjacent to the first substantially cylindrical portions 26, 28 and a gripping flange 34; 36. The second substantially cylindrical portions 30, 32 define an air space 38 between the holder 14 and the tube 25; the gripping flanges 34, 36 grip between them the edge of the sheet material 18 and, to assist, are coated with a black rubber strip 35; 37. The rubber strips act as an absorptive coating to prevent light banding at the edge of the sign as described above.

The first aluminium extrusion includes a box-shaped portion 40, defining a second air space 42. A tongue 43 along one edge of the first aluminium extrusion 22 mates with a groove 44 along one edge of the second aluminum extrusion 24.

As has been explained, the various portions of the fluorescent tube holder 14 have distinct yet complementary functions. The first substantially cylindrical portions 26, 28 define with the tube 25 a crown silvered source, ensuring that light escaping from it is arranged to emerge as far as possible straight into the edge of the sheet of transparent material 18. The second substantially cylindrical portions ensure that the arrangement as a whole is effectively as close as possible to a crown silvered source with a single direction of emission, even though the air space 38 is provided. Figure 2 includes a ray diagram showing the way in which the holder and tube cooperate in this respect.

Because the third part of the holder is bounded on both sides by the second part and lies substantially centrally within it, the air cooling space is adjacent to the point at which most of the light from the tube is emitted and absorbed by the absorptive coating.

The box-shaped portion 40 of the second aluminium extrusion defines a second cooling space 42, as described. The two spaces 38, 42 are on opposite side of the tube, allowing uniform cooling to the extent that that is consistent with the need for an effective crown silvered source.

As figure 2 illustrates, loss of light by scattering through the back surface of the Plexiglass sheet is prevented by a reflective matt white backing sheet 46. Of course, if a double-sided sign were required, this sheet 46 could be omitted and replaced with a second poster, so long as the Plexiglass sheet 18 were modified to include some form of diffuser to prevent direct sunlight from passing straight through it.

Claims (16)

1. An illuminated sign comprising a sheet of transparent material having means for scattering light distributed across it, a fluorescent tube and an elongate holder for the tube, the holder having a first substantially cylindrical part adapted to grip the outer circumference of the tube and coated with a reflective coating, a second part adapted to be spaced away from the outer circumference of the tube when the tube is gripped in the first part and a third part adapted to grip the faces of an edge of the sheet and coated with an absorptive coating.

2. An illuminated sign according to claim 1 in which the third part of the holder is adjacent the second part.

3. An illuminated sign according to claim 1 or claim 2 in which the third part of the holder is bounded on both sides by the second part and lies substantially centrally within it.

4. An illuminated sign according to any one of claims 1-3 in which the second part of the holder is substantially cylindrical.

5. An illuminated sign according to any preceding claim in which the second part of the holder is coated with a reflective coating.

6. An illuminated sign according to any preceding claim in which the holder comprises a fourth part remote from the second part and adapted to be spaced away from the outer circumference of the tube when the tube is gripped in the first part.

7. An illuminated sign according to claim 6 in which the fourth part of the holder lies opposite the third part.

8. An illuminated sign according to claim 6 or claim 7 in which the fourth part of the holder is substantially flat and faces the third part.

9. An illuminated sign according to any preceding claim in which the holder comprises two elongate pieces which fit together to grip the fluorescent tube and the sheet of transparent material.

10. An illuminated sign according to claim 9 in which one piece of the holder includes an elongate projection which cooperates with a recess on the other when the two are so fitted together.

11. An illuminated sign according to any preceding claim further comprising a second fluorescent tube and a second such holder adapted to grip the second tube and the faces of the opposite edge of the sheet.

12. An illuminated sign according to any preceding claim in which a light-scattering additive is distributed throughout the transparent material.

13. An illuminated sign according to claim 12 in which the transparent sheet is Plexiglass GS 1001.

14. An illuminated sign according to any preceding claim in which the reflective coating is white.

15. An illuminated sign according to any preceding claim in which the absorptive coating is black.

16. An illuminated sign substantially as described herein with reference to the accompanying drawings.