WO2004020897A1

WO2004020897A1 - Luminaire

Info

Publication number: WO2004020897A1
Application number: PCT/GB2003/003768
Authority: WO
Inventors: Peter Byrne
Original assignee: Full Vision Productions Limited
Priority date: 2002-08-28
Filing date: 2003-08-28
Publication date: 2004-03-11
Also published as: AU2003260764A1; GB0220027D0

Abstract

A luminaire for use in illuminating a picture or other work of art comprising an illumination head (10) including at least one fluorescent tube (42), a reflector (40) for directing light to a light outlet (38) of the illumination head (10), and a high frequency ballast unit for driving the at least one fluorescent tube (42). The luminaire may further comprise a diffuser (50), a polarising means (60) and/or an ultra-violet filter.

Description

Luminaire

This invention relates to luminaires. In particular, it relates to a luminaire that can be used to provide high-quality illumination of a picture or other work of art on display, for example, on a wall of a gallery or other room.

It is widely recognised that providing illumination for a picture is challenging. Both the pictures themselves and the environment in which they are displayed are subject to a great deal of variation, yet the requirement is for the luminaire to provide even light of a consistent colour temperature in all cases. This is particularly problematic where if is desired that the luminaires themselves have a consistent appearance, since this limits the choice of luminaires available to a lighting engineer for any particular picture.

Conventional picture luminaires have suffered from many problems, including (but not limited to) uneven illumination, uncontrolled reflection, and light quality that changes over time, either individually or in combination.

An aim of this invention is to provide a luminaire that is versatile in its ability to provide illumination that is as near as possible optimal for a wide range of applications.

A first aspect of the invention provides a luminaire for use in illuminating a picture or other work of art comprising an illumination head including at least one fluorescent tube, a reflector for directing light to a iight outlet of the illumination head, and a high frequency ballast unit for driving the at least one fluorescent tube. A second aspect of the invention provides a luminaire for use in illuminating a picture or other work of art comprising an illumination head that includes a plurality of fluorescent tubes, a reflector for directing light to a light outlet of the illumination head, and a diffuser within the light outlet; and a high-frequency ballast unit for driving the fluorescent tubes.

The invention may further comprise means for modifying the light emitted via the light outlet.

The means for modifying the light emitted via the light outlet may be a diffuser. The diffuser may be a cross-blade diffuser. The blades may typically be in a square arrangement with a pitch of between 5 mm and 20 mm, 10 mm being preferred. It has been found that a high-frequency fluorescent system in combination with a diffuser can give a surprisingly effective and controllable light output that is particular effective in lighting works in an art gallery.

Additionally or alternatively, the means for modifying the light emitted via the light outlet can be an ultra-violet filter. This is particularly desirable in embodiments that are intended to illuminate pictures, since these can be damaged by ultra-violet radiation.

Additionally or alternatively, the means for modifying the light emitted via the light outlet can also be a polarising sheet through which the light passes before being emitted from the luminaire. It has been found that this is very effective in controlling reflection, and has particular (but not exclusive) application to a luminaire that is too small to contain a diffuser.

The high frequency ballast may operate at a frequency of several kHz. For example, it may operate at a frequency of approximately 20 - 50 kHz. For example, in a preferred embodiment, the operating frequency is 41 kHz. Any flickering in light output at these frequencies are virtually imperceptible to a human observer, giving an impression of a constant, natural light source. The quality of light produced by such lights is more suited to illumination of pictures than an incandescent light source, the latter being subject to variation in light output and colour temperature with age.

Certain embodiments of the invention may have two fluorescent tubes. However, only providing a single fluorescent tube may be preferable in certain situations.

Where two tubes are provided, they may be arranged generally parallel to one another or end-to-end. The tubes may be narrow-diameter tubes, for example, with a diameter of approximately 16 mm. Two narrow-diameter tubes have been found to produce more controllable and even illumination than a single larger tube.

In order that the light source can be adapted for a specific installation, the ballast may be provided with an intensity control. This is typically embodied in an inductive or resistive dimming control. By adjustment of such a control, the optimum level of illumination for a particular work, often a compromise between providing optimum visual appearance and preserving the work against deterioration.

In embodiments in which space permits, the ballast may be located within the head. Alternatively, it may be located within or adjacent to a mounting body of the luminaire. In this latter case, when the luminaire is mounted for use in illuminating a picture, the ballast will typically be concealed behind the picture. The tubes can be selected to produce light produced of a colour temperature suitable for a specific application. For example, the tubes may produce light at a colour temperature within the range of 2000 K to 0500 K.

The tubes may be contained within a head assembly of the luminaire, the head assembly being carried on a mounting assembly. The head assembly is preferably adjustable in position and/or direction with respect to the mounting assembly, in order that the direction of light emitted from the luminaire can be controlled to achieve optimum illumination of an object.

A luminaire embodying the invention may be provided with a bracket upon which its other components are carried. Advantageously, the bracket may include an electrical connector, from which components of the luminaire may be provided with electrical power. The bracket may be suitable for mounting on a wall, on a picture frame or on another suitably strong foundation.

Embodiments of the invention will now be described in detail, by way of example, and with reference to the accompanying drawings, in which:

Figure 1 is a side view of a luminaire being a first embodiment of the invention;

Figure 2 is a larger cross-sectional view of a head of the luminaire of Figure 1 ; Figure 3 is a front view of a luminaire of being a second embodiment of the invention;

Figure 4 shows an orthographic projection of an alternative embodiment of the head assembly of the luminaire; Figure 5 shows α perspective view of an alternate embodiment of the head of the invention;

Figure 6 shows a perspective view of a further alternate embodiment of the head of the invention;

Figure 7 is a cross-section through figures 5 and 6 on X-X; and '

Figure 8 shows a perspective view of an optional aperture shield.

With reference first to Figure 1 , a luminaire embodying the invention includes a head assembly 10, a mounting body 12, and an arm 14 interconnecting the head assembly 10 and the mounting body 12. The mounting body can be secured to a support, most typically, a wall. The mounting body 12 is positioned above or behind a picture or other item that is to be illuminated. Alternatively, the mounting body can be secured to a picture or other object that is to be illuminated.

The arm 14 is formed as from hollow tubing. When the luminaire is mounted for normal use, a first part 20 of the arm extends approximately vertically upwards. The arm 14 then is curved to an adjoining horizontal part 22. From the horizontal part, the arm 14 extends upwardly at an angle of approximately ό0° from the horizontal and then curves in an arc 24 through an angle of 180° to its end. The various curves of the arm are formed in a single plane.

The head assembly 10 is carried at the end of the arm 14 upon a joint 26 that allows the head to be pivoted about an. axis that is normal to the plane of the arm 14 and that is substantially horizontal. Either a knuckle joint, which allows pivoting movement in one plane, or a ball joint, which allows pivoting movement in any plane, can be provided to carry the . head. The head assembly 10 has a case 30 of fabricated metal. The case 30 has a substantially uniform cross-section having a domed rear wall 32, a parallel sidewall section 34, and a front wall 36 within which an elongate rectangular aperture 38 is formed.

As can be seen from Figure 2, the head assembly includes two fluorescent tubes 42 that extend along its length. The tubes 42 are carried by clips 44 mounted on a support member 40 within the head assembly 10. The support member 40 is of angular, concave cross- section, the tubes 42 being located within the concavity. A flat base section of the support member 40 provides a locating surface for the clips 44, flat sidewall sections extending from the base section. The support member 40 is formed of reflective material, in this case, polished metal, to reflect light from the tubes 42 towards the aperture 38.

Within the parallel sidewall section 34 there is a diffuser. The diffuser in this embodiment is a cross blade diffuser (also known as an "egg crate" diffuser), 12 mm deep, with diffusing elements 50 arranged in a square grid of 10 mm pitch. The outer surface of the diffuser is covered by an optically transparent ultra-violet filter 52.

In this embodiment, the tubes 42 used are Philips TL5 39W units driven by a Philips HF-Regulator electronic ballast that operates at a frequency of approximately 42 kHz. Such tubes are available in colour temperatures of 2700 , 3000 K, 3500 K, 4000 K, 5000 K and 6500 , this allowing an installer to select illumination at a colour temperature most appropriate to a particular application.

These lamps, for example, are 849 mm in length, excluding connecting pins, and approximately 16 mm in diameter. Light output can be controlled by a control potentiometer, such as the Philips LPS100S range. A variety of other lengths is available within this range to suit a specific application. ■

In this embodiment, the ballast for the tubes 42 is contained within the head, thereby minimising the length of conductor that is required -to carry the high frequency high voltage required to drive the tubes. Mains power is provided to the ballast by way of conductors that pass within the arm 14.

Where it is required to provide a luminaire of length that exceeds the maximum ' available length of tube (which is 1449 mm in the range referred to above) two or mote tubes may be provided, aligned end-to- end.

An alternative embodiment of the invention is shown in Figure 3. The construction of this embodiment is particularly suited to small luminaires.

In this embodiment, the diffuser is omitted from the head. Light control is achieved by providing a polarising filter 60 at the output aperture 38 of the head assembly 10.

The ballast is contained within the mounting body 12, conductors interconnecting the ballast and the lamps being located within the arm 14. A dimming control 62 is provided on the mounting body 12.

For use, the mounting body 12 is received within a bracket 64 that can be secured to a foundation, such as a wall. A plug 66 on the mounting body 12 is received by a socket (not shown) of the bracket to connect the luminaire to an electrical supply. Thus, to install the luminaire, an electrical connection is first made to the bracket 64, and the bracket is secured to the wall (or other foundation) in the desired position. The mounting body 12 is then lowered into the bracket to complete installation the luminaire. Once the luminaire is installed, the subject of the illumination can be positioned. In the case of a picture, this will typically be positioned on the wall to cover the bracket 64 and the mounting body 12. Alternatively, the bracket can be secured to a frame ^" of a picture that is to be illuminated.

The head assembly 10 has a case 30, which is generally tubular. An elongate rectangular aperture 38 is formed in the case 30 to allow light out of the head assembly 10. A portion of the infernal surface of the casing 30 is preferably reflective to serve as a reflector for reflecting light out of the head assembly 10 through the aperture 38.

The head assembly 10 is adapted to receive a fluorescent tube (not shown), which is retained using combined retainers/electrical connectors (not shown) at either end of the tube.

The casing 30 also has. an aperture 70 therein to receive an end of the arm 14. The head assembly 10 can be affixed to the arm 14 using a clip connection or screw-threaded connection, where appropriate.

Figures 5 and 6 show perspective views of the alternate embodiment of the invention adapted to receive long and short fluorescent tubes respectively. Figure 5 has two apertures 70 for connection to a corresponding pair of arms 14, whereas Figure 6 has only one aperture 7 for connection to a single arm 14. The number of apertures 70 required will depend on the size and/or weight of the head assembly 10.

Figure 7 shows a cross-section through the casing 30 of the head assembly 10. The aperture 38 can be made wider or narrower to control the angle 72 of light emitted from the head assembly 10.

Figure 8 shows a perspective view of an aperture shield 74, which, is formed from a curved sheet material; The aperture shield 74 has a tongue 76, which sits inside the casing 30 of the head assembly and a shield portion 78, which protrudes through the aperture 38 of the casing 30. A step 77 is provided on the aperture shield 74 to engage with the edges 37 of the aperture 38.

Claims

Claims:

1. A Luminaire for use in illuminating a picture or other work of art comprising an illumination head including at least one fluorescent tube, a reflector for directing light to a light outlet of the illumination head, and a high frequency ballast unit for driving the at least one fluorescent tube.

2. A Luminaire as claimed in claim 1 , wherein the high frequency ballast operates at a frequency of several kHz.

3. A Luminaire as claimed in claim 1 or claim 2, wherein the high frequency ballast operates at a frequency of approximately 20 to 50 kHz.

4. A Luminaire as claimed in claim 3, wherein the high frequency ballast operates at a frequency of approximately 41 kHz.

5. A Luminaire as claimed in any one of claims 1 to 4, wherein the ballast comprises an intensity control.

6. A Luminaire as claimed in claim 5, wherein the intensity control is an inductive dimming control.

7. A Luminaire as claimed in claim 5, wherein the intensify control is a resistive dimming control.

8. A Luminaire as claimed in any one of claims 1 to 7, further comprising a diffuser.

9. A Luminaire as claimed in- claim 8, wherein the diffuser is a cross- blade diffuser.

10. A Luminaire as claimed in claim 9, wherein the blades are arranged in a substantially square arrangement.

- 1 1 . A Luminaire as claimed in any one of claims 1 to 10, further comprising an ultra-violet filter arranged to filter ultra-violet light from the light emitted by the Luminaire.

12. A Luminaire as claimed in any one of claims 1 to 1 1 , further comprising a polarising means arranged to polarise the light emitted by the Luminaire.

13. A Luminaire as claimed in any one of claims 1 to 12, wherein the at least one tube is adapted to produce light at a colour temperature within the range of 2000 K to 6500 K.

14. A Luminaire as claimed in any one of claims 1 to 13, wherein the illumination head is adjustable in position and/or direction.

15. A Luminaire for use in illuminating a picture or other work of art comprising an illumination head that includes a plurality of fluorescent tubes, a reflector for directing light to a light outlet of the illumination head, and a diffuser within the light outlet; and a high-frequency ballast unit for driving the fluorescent tubes.

16. A Luminaire as claimed in claim 15, wherein the high frequency ballast operates at a frequency of several kHz.

17. A Luminaire as claimed in claim 15 or 16, wherein the high frequency ballast operates at a frequency of approximately 20 to 50 kHz.

18. A Luminaire as claimed in claim 17, wherein the high frequency ballast operates at a frequency of approximately 41 kHz.

19. A Luminaire as claimed in any one of claims 15 to 18, wherein the ballast comprises an intensity control.

20. A Luminaire as claimed in claim 19, wherein the intensity control is an inductive dimming control.

21. A Luminaire as claimed in claim 19, wherein the intensity control is an resistive dimming control.

22. A Luminaire as claimed in any one of claims 15 to 21 , wherein the diffuser is a cross-blade diffuser.

23. A Luminaire as claimed in claim 22, wherein the blades are arranged in a substantially square arrangement.

24. A Luminaire as claimed in any one of claims 15 to 23, further comprising an ultra-violet filter arranged to filter ultra-violet light from the light emitted by the Luminaire.

25. A Luminaire as claimed in any one of claims 15 to 24, further comprising a polarising means arranged to polarise the light emitted by the Luminaire.

26. A Luminaire as claimed in any one of claims 15 to 25, wherein the ballast is located within the head.

27. A Luminaire as claimed in any one of claims 15 to 25, wherein the ballast is located within or adjacent to a mounting body of the

Luminaire.

28. A Luminaire as claimed in any one of claims 15 to 27, wherein the tube or tubes are adapted to produce light at a colour temperature within the range of 2000 K to 6500 K.

29. A Luminaire as claimed in any one of claims 15 to 28, wherein the illumination head is adjustable in position and/or direction.

30. A Luminaire substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.