GB2472627A

GB2472627A - Light filtering and transmission apparatus

Info

Publication number: GB2472627A
Application number: GB0914146A
Authority: GB
Inventors: Fabian Redpath
Original assignee: SUBZERO LIGHTING Ltd
Current assignee: SUBZERO LIGHTING LIMITED
Priority date: 2009-08-12
Filing date: 2009-08-12
Publication date: 2011-02-16
Also published as: GB0914146D0; WO2011018628A1

Abstract

Light filtering and transmission apparatus 1 for use in a lighting system lighting the interior (34, fig 3) of a cold store (30, fig 3), has a hollow body 3 with an evacuated cavity 4, the body 3 having windows 5,7 so that light passes through the body 3. A heat filter at the first window 5, filters light that passes through the hollow body 3 so as to allow transmission of visible wavelengths and suppress transmission of infra-red wavelengths of light through the body 3. The apparatus 1 prevents the interior of a cold store from the heating effects of a light.

Description

LIGHT FILTERING AND TRANSMISSION APPARATUS

TECHNICAL FIELD

The invention relates to a light filtering and transmission apparatus. The apparatus finds particular, though not exclusive, utility in a lighting system lighting the interior of a cold store. The invention also relates to a lighting system including light filtering and transmission apparatus, the lighting system finding particular utility in providing light to the interior of a cold storage unit. The invention also relates to use of the lighting system to light the interior of a cold store.

BACKGROUND OF THE INVENTION

Large cold storage units are cooled below the environmental ambient temperature to near or below freezing by refrigeration units and are maintained in this cooled state by thick thermal insulation surrounding the unit. These cold stores may be used to chill foodstuffs for warehousing purposes or keep frozen foods, or may provide a cooled area for food preparation.

The lighting systems that are required to light the interiors of these large cold storage units are themselves large, extensive and consume a large amount of power.

A significant amount of heat is generated by the lighting systems, particularly by the light sources thereof, and as the lighting systems are usually built into the walls (i.e. walls andlor ceilings) of the cold storage units, at least some or all of this heat is typically transmitted into the cold store itself, raising the temperature thereof. The input of this heat from the lighting system must be removed from the cold store by the refrigeration unit, which may significantly increase the power consumption and running costs thereof and may also lead to a general or localised elevation in the temperature of the cold store, which may spoil foodstuffs and breach requirements.

To reduce the amount of heat input to a cold store by a lighting system it is known in the art to replace the light sources in the lighting system with more suitable ones which may themselves be expensive and may not lead to a significant reduction in the input heat, or to employ complicated and expensive fibre optics to provide light to the cold store. Further, these solutions may lead to a reduced amount of light entering the cold store.

SUMMARY OF THE INVENTION

The inventors have recognised that there is a need for an alternative solution the above problem. It is therefore an object of the invention to provide an apparatus for use in a lighting system of a cold store that has the effect of limiting the amount of input heat.

Viewed from one aspect, the invention provides light filtering and transmission apparatus for use in a lighting system lighting the interior of a cold store, comprising: a hollow body defining an evacuated cavity, the body having first and second windows and the light filtering and transmission apparatus being configured such that light can pass through the body between the first and second windows; and heat filtering means arranged to filter light that passes through the hollow body between the first and second windows, the heat filtering means being configured so as to allow transmission of visible wavelengths and suppress transmission of infra-red wavelengths of light through the body.

In accordance with this aspect of the invention, the light filtering and transmission apparatus can be used in a lighting system of a cold store, and when positioned such that light from the light source used to light the interior of the cold store passes between the first and second windows, the apparatus acts to transmit visible light into the interior of the cold store, but not transmit the heat. In particular, the heat filter removes (e.g. by absorption and/or reflection) the thermal infra-red wavelengths from the light spectrum output by the light source, which is otherwise a significant source of heating, thereby suppressing transmission of the thermal infra-red into the cold store. The heat filter allows the visible wavelengths of the spectrum to be transmitted to light the cold store. By suppression, it is meant that the energy of the light transmitted through the apparatus into the cold store at thermal infra-red wavelengths is significantly reduced, preferably with the thermal infra-red being completely or almost completely removed or eliminated.

Further, the provision of the body as a hollow body having an evacuated cavity suppresses heat transfer from the light source into the interior of the cold store by conduction or convection. The portion of the body nearest the light source and first illuminated thereby may be heated by the light source, either by absorption of

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thermal radiation (i.e. infra-red light) produced thereby, or by conduction and convection. However, the evacuated cavity of the hollow body removes the mechanism for heat transfer into the cold store by convection that would otherwise occur in a non-evacuated cavity, and the cavity also provides thermal insulation to relatively reduce heat transfer into the cold store by conduction.

Therefore the light filtering and transmission apparatus enables lighting of the interior of a cold store but limits heat transfer into the cold store by suppressing thermal radiation, conduction and convection.

Further still, the light filtering and transmission apparatus of the invention allows transmission of light produced by a light source located outside a cold store (which may be an artificial or natural light source -e.g. daylight) into the interior of a cold store. This further reduces heat transfer from the light source to the cold store.

The hollow body may be a tubular member having said first and second windows at its ends. The tube may have a substantially circular cross-section. The tube may be a straight tube having first and second windows at its opposite ends.

The tube preferably has an axial length of at least 200mm, more preferably at least 250mm. Further, the tube preferably has an axial length of between 300mm and 600mm, more preferably between 400mm and 550mm, and more preferably still between 450mm and 500mm. These preferred arrangements are particularly advantageous in that tubular constructions are easily manufactured and provide end windows for light entry and exit. Tubes having circular cross sections are particularly advantageous and easy to produce, though tubes having other, non-circular cross sections, are possible. A straight tube provides line-of-sight illumination. Tubular arrangements, particularly those having the aforementioned axial lengths, are particularly suitable for installation in the wall (i.e. wall andlor ceiling) of a cold storage unit extending through the thermal insulation thereof, which is typically between 250mm and 300mm thick. The light source may then be provided outside (i.e. external to), or at least near the outer surface of the thermal insulation surrounding the cold store, which further reduces heat transfer into the cold store, particularly by limiting heat conduction. Further, such tubular and straight-tubular forms are particularly advantageous for easy installation.

The apparatus may be configured such that light is guided between the first and second windows by reflection. The apparatus may further comprise a reflective material arranged to guide light between the first and second windows. The reflective material may be a reflective film or coating arranged on the internal surface of the cavity. Alternatively, the reflective material may be a reflective film arranged on the external surface of the hollow body. These preferred arrangements provide particularly efficient transfer of light into the interior of the cold store to provide light therein, significantly reducing light losses and thereby keeping down the number of required light sources and improving the light levels therein.

The hollow body may have a non-return valve usable to create the vacuum.

The hollow body is sealed to maintain the evacuated state therein. To create the evacuated state initially, the hollow body may be formed and sealed (for example by applied windows in a tubular construction) in, for example, an evacuated chamber.

Alternatively the body may provided with a non-return valve and be formed and sealed in, for example, atmospheric pressure conditions, and the non-return valve be used to out-gas or pump down the cavity to evacuate it.

The heat filtering means may be further configured to suppress transmission of ultraviolet wavelengths of light through the body. Suppression of ultraviolet wavelengths further reduces heat transmission into the interior of the cold store.

The apparatus may further comprise a lens or a diffuser arranged to direct or diffuse light passing through a window of the body. The lens or diffuser may be provided as or arranged adjacent a said window of the body. The use of lenses or diffusers, separately, in combination, or together as a single unit enables the light transmitted into the interior of the cold store to be directed or diffused as desired.

The heat filtering means may be provided as or arranged adjacent a said window of the body. The light filtering and transmission apparatus may be arranged such that the heat filtering means is provided as or arranged adjacent the said window of the hollow body on which light from an associated light source is, in normal use, first incident. Providing the heat filter at or as the light input window is advantageous in the suppression of heat transfer into the interior of a cold store.

When the hollow body is provided as a tubular member, the heat filter and the lens(es) and/or diffuser(s) are preferably provided as or at opposite end windows.

The body of the light filtering and transmission apparatus may comprise an acrylic or polycarbonate material. These preferred materials are particularly advantageous in that they are able to withstand the heat produced by a light source at one portion of the body (where temperatures of up to around 90 degrees Centigrade may be sustained), and the cold of the cold store at another section of the body (where temperatures of minus 30 degrees Centigrade or lower may be sustained), without being prone to frosting or vitrification.

The apparatus may further comprise mounting means arranged to be usable to mount a light source adjacent a said window. Providing mounting means is advantageous in that the light source can be rigidly mounted to the apparatus, creating a robust and easy-to-install configuration.

The apparatus may further comprise fixing means configured to be usable to hold the hollow body in place when the apparatus is arranged to extend through the insulated wall of a cold store.

Viewed from another aspect, the invention provides a lighting system for providing light to the interior of a cold storage unit, the lighting comprising: a light filtering and transmission apparatus according to any of the aforementioned arrangements; a light source arranged to, in normal use, provide light to a said window of the light filtering and transmission apparatus; the lighting system being arranged such that the light source is provided outside the cold storage unit and such that the light filtering and transmission apparatus provides light from the light source to the interior of the cold storage unit.

The heat filtering means of the light filtering and transmission apparatus may be provided as or arranged adjacent the window of the hollow body on which the light source is, in normal use, first incident.

Viewed from yet another aspect, the invention provides use of a lighting system according to any of the aforementioned arrangements to light the interior of a cold store.

The above-described advantages of the first described of the invention are also provided by the subsequently described aspects of the invention.

DESCRIPTION OF THE EMBODIMENTS

Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic side view of a cross-section of a first embodiment of a light filtering and transmission apparatus; Figure 2 shows a schematic side view of a cross-section of a second embodiment of a light filtering and transmission apparatus; and Figure 3 shows a schematic side view of a cross-section of a cold storage unit incorporating a lighting system according to an embodiment of the invention.

A light filtering and transmission apparatus 1 of a first embodiment of the invention 1 shown in Figure 1 includes a hollow tubular body 3, integrally formed and having a circular cross section. The tubular body 3 may be provided by an acrylic or polycarbonate material and may be formed by, for example, moulding, machining or extrusion. The tubular body has an axial length of between 450mm to 500mm and an external diameter of 60mm. Alternatively, both the diameter and length of the tube may be larger or smaller.

The ends of the tubular body 3 are closed by first and second windows 5, 7 which hermetically seal the interior of the tubular body 3, with the internal surface of the tubular body 3 thereby defining a cavity 4. The cavity 4 is sealed in normal atmospheric conditions and thereafter evacuated using a non-return valve 11 to pump down or out-gas the cavity as much as is desired. The greater the degree of evacuation of the cavity 4, the more pronounced the advantageous effects of the invention. Alternatively the cavity may be sealed in an evacuated chamber.

The first window 5 and the second window 7 provide a direct line of sight for light to pass through the body. In normal use in a lighting system for a cold store, light from a light source (not shown) passes first through the first window 5, located distant from the interior of the cold store, and secondly through the second window 7, located proximal to (e.g. in the wall andlor ceiling of) the interior of the cold store.

Thus the first window 5 is provided as a light input window which, in normal use, is where light from an adjacent external light source (not shown) is first incident. The first window 5 is also provided as a heat filtering means. The first window 5 has a transmission function that varies across different wavelengths of light and is configured as desired so as to allow transmission of visible wavelengths of light from an adjacent light source into the cavity 4 and suppress transmission of infra-red and ultra-violet wavelengths of light into the cavity 4. The first window 5 preferably provides substantially zero transmission of thermal mid-infra-red wavelengths of light. The heat filtering means of the first window 5 may be configured such that the non-transmitted wavelengths of light are absorbed thereat and/or reflected away. The first window 5 is made of 6mm thick toughened glass.

The heat filtering means may be deposited on the surface of the first window 5 in one or more layers. Alternatively the window material itself may provide the filtering effect. Alternatively the heat filtering means may be provided separate from but adjacent to the first window 5.

The second window 7 is provided as a light output window and is a 6mm thick appropriately-shaped acrylic disc. Other window thicknesses and materials are of course possible and within the scope of the invention. The second window 7 is lightly frosted to diffuse light incident thereon and give a diffuse illumination of the interior of the cold store. The second window 7 may also be provided as a light-directing lens or may be provided merely as a transparent window. Alternatively, a separate diffuser or lens member may be provided adjacent to or on the second window 7 to diffuse and/or direct the light. Such separate lens/diffuser members are advantageous when provided with an apparatus having a second window 7 that is merely a transparent window. Any separate diffuser/lens may be mounted directly to the second window 7 or may be mounted to be spatially separated from the window. A separate lens/diffuser member mounting means (not shown) may be provided as part of the apparatus 1 for this purpose. Alternatively a fixative may be used to mount any diffuser/lens member.

Of course, for the windows 5, 7 other, non-circular, window shapes are within the scope of the invention. Such non-circular window shapes are particularly advantageous to seal the ends of the tubular body 3 where the tubular body 3 has a non-circular cross section.

The interior surface of the hollow tubular body 3 is coated with a highly reflective material 9 (for example by silvering) to guide light input at the first window 5 to be output at the second window 7 and to substantially prevent light losses along the length of the hollow body 3. Alternatively, the highly reflective material may be provided around the outer surface of the hollow body 3. The highly reflective material 9 may be deposited on the relevant surface of the body or may be separate from the body 3 and be merely located adjacent to the body 3 or be affixed thereto.

The light filtering and transmission apparatus 1 of the first embodiment may be located adjacent to the light output aperture of a light source. The light source may be provided in a separate fitting with the light filtering and transmission apparatus 1 being registered to it.

A light filtering and transmission apparatus 20 of a second embodiment of the invention shown in Figure 2 is identical to the first embodiment described above with the addition of a mounting means 21 (for example a light fixing) to receive a light source 23 in use. The mounting means 21 is rigidly connected to the first window 5 (andlor the hollow body 3) to locate the light source in the optimal position. Alternatively, the mounting means 21 may be formed integrally with the hollow body 3. Power input means for the light source 23 may also be provided with the mounting means 21, or may be separately provided.

Figure 3 shows a large cold store 30 having a lighting system 31 including a plurality of light filtering and transmission apparatus 20 according to the second embodiment of the invention. The cold store 30 has an internal wall 33 that defines an interior 34 of the cold store from which a refrigeration unit 32 extracts heat to cool the interior 34 to below the ambient temperature. A 250mm thick layer of thermal insulation 35 is provided surrounding the wall (i.e. wall or ceiling) 33 to limit the conduction of ambient heat into the interior 34.

The lighting system 31 is configured such that each light filtering and transmission apparatus 20 extends through the thermal insulation 35 to transmit visible light but little or no heat from a number of external light sources 23 to the interior 34 of the cold store 30. Each light filtering and transmission apparatus 20 is arranged such that the diffuse output second window 7 of each light filtering and transmission apparatus 20 is located in the internal wall (i.e. wall or ceiling) 33 of the cold storage unit 30. Each light filtering and transmission apparatus 20 then extends through the insulating material 35 such that its input first window 5 is located outside the insulating material 35 and the cold store 30. The light sources 23 are located externally to the cold store 30, away from the insulating layer 35 such that the heat transmission from the light sources 23 to the cold store, for example by conduction through the insulation, is substantially prevented.

In use, power is provided to the light sources 23 and the light filtering and transmission apparatus 20 acts to filter out infra-red and ultra-violet light produced by the light source and efficiently transmit substantially all of the remaining (visible) light entering the cavity 4 through the first window 5 of each light filtering and transmission apparatus 20 to the interior 34 of the cold storage unit, the second window 7 being such that the lighting system 30 efficiently provides a diffuse light to the interior 34. The lighting system 31 is such that heat produced by the external light sources 23 is substantially not transmitted to the interior 34 of the cold store and the refrigeration unit 32 therefore does not have to operate to remove that heat.

The light filtering and transmission apparatus of the invention may include multiple light sources, and may multiple input and output windows inputting and outputting light at different locations. The hollow body of the apparatus may be non-tubular. The hollow body may be configured such provide light transmission from an input to an output window by a non-direct line of sight. -10-

Claims

Claims: 1. Light filtering and transmission apparatus for use in a lighting system lighting the interior of a cold store, comprising: a hollow body defining an evacuated cavity, the body having first and second windows and the light filtering and transmission apparatus being configured such that light can pass through the body between the first and second windows; and heat filtering means arranged to filter light that passes through the hollow body between the first and second windows, the heat filtering means being configured so as to allow transmission of visible wavelengths and suppress transmission of infra-red wavelengths of light through the body.
2. Light filtering and transmission apparatus as claimed in claim I, wherein the hollow body is provided by a tube having said first and second windows at its ends.
3. Light filtering and transmission apparatus as claimed in claim 2, wherein the tube has a circular cross-section.
4. Light filtering and transmission apparatus as claimed in claim 2 or 3, wherein the tube is a straight tube having first and second windows at its opposite ends.
5. Light filtering and transmission apparatus as claimed in claim 4, wherein the tube has an axial length of at least 250mm.
6. Light filtering and transmission apparatus as claimed in any preceding claim, wherein the apparatus is configured such that light is guided between the first and second windows by reflection.
7. Light filtering and transmission apparatus as claimed in claim 5, further comprising a reflective material arranged to guide light between the first and second windows.
8. Light filtering and transmission apparntus as claimed in claim 7, wherein the reflective material is a reflective film or coating arranged on the internal surface of the cavity.
9. Light filtering and transmission apparatus as claimed in claim 7, wherein the reflective material is a reflective film arranged on the external surface of the hollow body.
10. Light filtering and transmission apparatus as claimed in any preceding claim, wherein the hollow body has a non-return valve usable to create the vacuum.
11. Light filtering and transmission apparatus as claimed in any preceding claim, wherein the heat filtering means is further configured to suppress transmission of ultraviolet wavelengths of light through the body.
12. Light filtering and transmission apparatus as claimed in any preceding claim, further comprising a lens or a diffuser arranged to direct or diffuse light passing through a window of the body.
13. Light filtering and transmission apparatus as claimed in claim 12, wherein the lens or diffuser is provided as or arranged adjacent a said window of the body.
14. Light filtering and transmission apparatus as claimed in any preceding claim, wherein the heat filtering means is provided as or arranged adjacent a said window of the body.
15. Light filtering and transmission apparatus as claimed in claim 14, wherein the light filtering and transmission apparatus is arranged such that the heat filtering means is provided as or arranged adjacent the said window of the hollow body on which light from an associated light source is, in normal use, first incident.
16. Light filtering and transmission apparatus as claimed in any preceding claim, wherein the body comprises an acrylic or polycarbonate material.
17. Light filtering and transmission apparatus as claimed in any preceding claim, further comprising mounting means arranged to be usable to mount a light source adjacent a said window.
18. Light filtering and transmission apparatus as claimed in any preceding claim, further comprising fixing means configured to be usable to hold the hollow body in place when the apparatus is arranged to extend through the insulated wall of a cold store.
19. A lighting system for providing light to the interior of a cold storage unit, the lighting comprising: light filtering and transmission apparatus as claimed in claims 1-18; a light source arranged to, in normal use, provide light to a said window of the light filtering and transmission apparatus; the lighting system being arranged such that the light source is provided outside the cold storage unit and such that the light filtering and transmission apparatus provides light from the light source to the interior of the cold storage unit.
20. A lighting system as claimed in claim 19, wherein the heat filtering means of the light filtering and transmission apparatus is provided as or arranged adjacent the window of the hollow body on which the light source is, in normal use, first incident.
21. Use of a lighting system as claimed in claim 19 or 20 to light the interior of a cold store.
22. Light filtering and transmission apparatus substantially as hereinbefore described with reference to the accompanying drawing.
23. A lighting system for providing light to the interior of a cold storage unit, substantially as hereinbefore described with reference to the accompanying drawing.
24. Use of a lighting system for providing light to the interior of a cold storage unit, substantially as hereinbefore described with reference to the accompanying drawing to light the interior of a cold store.