AU601634B2 - A window panel for improved daylighting of room interiors - Google Patents

Description

signature of applicant or Australian attornley TO REEIE THE COISIsONgR This form must be accompanied by either a provisional specificatio In (Form 9 and true cop Y) or by a complete specification (Form 10 and true copy).

'a AM., a i-I' -XIAXJTRALIA k PATENTS ACT 1952 P/00/01 1 Form COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: 601634 Application Number: Lodged: 11

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C;omplete Specification-Lodged: Accepted: Lapsed: Published: Priority: This document co ata ills [hain end~ made Lid~ Section 49 and L- Correct fo, printing.

Related Art: Name of Applicant: Address of Applicant: TO BE COMPLETED BY APPLICANT IZ -E NTA~ S K TzM 0?%,FI GRIZANS)h 0. LD 4009.

Actual Inventor: I R N R0oSF Z'T Address for Service: Complete Specification for the inventi I nvioveav 1 on entitled: P\ WINtD6\\/ PfA EL QD.406q1 Fox~ OF RooM IN-T iZs The following statement is a full description of this invention, including the best method of performing it known to me- Note: The description is to be typed in double spacing, pica type face, in an area not exceeding 250 mm in depth and 160 mm in width, on tough white paper of good quality and it is to be inserted inside this form.

14599/78-L 1459978- LPrinted by C. I. THOMPSON, Commonwealth Government Printer, Canberra This invention relates to a method for making a thin sheet of material which bends and transmits incident light. While there are many uses for a material which both bends and transmits light the embodiments of the invention described here are directed principally to its application as a window which bends incoming daylight upwards so that the ceiling of a room is illuminated, thereby improving the natural lighting deep within the interior of a room.

There are several advantages in redirecting daylight towards the ceiling of a room. As shown in Figure 1. the ceiling can be illuminated o1, over the greater part of the room if most of the incoming daylight is bent through the appropriate angle. As the ceiling is usually white, 0 daylight reflected from the ceiling is distributed as a diffuse downcoming illumination deep inside the room. This provides higher illuminance levels on work surfaces deep within the room and may 1 5 substantially reduce both the requirement for artificial lighting and o the energy costs associated with artificial lighting. Personnel, work *o surfaces and furniture below windows are not subjected to intense S direct sunlight and the variation of natural lighting with distance from S a window is more gradual.

The conventional means of bending light is by deviation in a prism of transparent material or by reflection in a metallic mirror.

Transparent material with a prismatic surface may be formed in a thin sheet suitable for windows by moulding the surface of glass or plastic or by extruding glass or plastic through a die. Prismatic sheets so formed have been used for diffusing or redirecting daylight into rooms and buildings however prismatic sheets are suitable for bending incident light through angles up to about 45 degrees only. If the prisms are formed on the surface with very acute angles as described in AU 88953/82 more control is obtained over the direction in which the light is bent however it is difficult with this method also to achieve bending through angles greater than about 45 degrees. It seems that generally the efficiency with which light is bent through the larger angles by prismatic panels is low. Other disadvantages of prismatic panels are that the light is not bent uniformly so that focusing of the bent light occurs (for example as in AU 88953/82 Figure causing bright and dark bands on the surfaces on which it falls. Also surface moulding or extrusion to produce prisms on a thin sheet is expensive for small runs, the sheet material so formed is not suitable for viewing through due to the severe distortion caused by the prisms, and the 1P exposed prismatic surface is so difficult to clean that prismatic Swindow panels are usually produced as double glazings with the prismatic surface on the internal faces.

Metallic reflectors have been used to form light bending window panels by incorporating a number of plane metal reflectors at intervals between two panes of glass, as in the German patent OS 1497348. A development of this arrangement incorporates metallic reflectors of alternating parabolic and planar form between panes of glass as in AU 56802/86. Both systems are suited to thick rather than thin window panels and both are expensive due to the cost of producing highly reflecting metal surfaces.

The objective of the present invention is to produce a thin sheet of material, suitable for use as a window, which is able to bend light through large angles (greater than 90 degrees), which has relatively undisturbed flat external surfaces so that it is suitable for viewing through and which is relatively inexpensive to manufacture in a wide range of shapes and sizes.

This objective is achieved in accordance with the invention by arrarg'ng a number of parallelepipeds, formed of transparent material, one above the other so as to produce a thin vertical sheet of parallelepipeds, the general crossection of each parallelepiped being a 2.

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srrl' parallelogram with vertical sides. Each parallelepiped extends horizontally across the width of the sheet so formed and the array of parallelepipeds extends from the top to the bottom of the sheet. Each individual parallelepiped bends incident light by a combination of refraction at the vertical external surfaces and total internal reflection at the surfaces between neighbouring parallelepipeds. The array of parallelepipeds so formed provides a transparent sheet which bends light.

The invention is now described in detail with reference to the ,.1R accompanying drawings.

Figure 1. is a sectional view of a room in which a light bending panel redirects incoming light onto the ceiling of the room.

Figure 2. is a crossectional view of the light bending panel showing the arrangement of the parallelepipeds one above the other to form a thin sheet.

Figure 3. is a crossectional view of an individual parallelepiped showing the bending of light by reflection and total internal reflection within the parallelepiped.

Figure 4. shows a crossectional view of light bending panels protected by lamination between two sheets of glass or films of plastic. j Figure 5. shows the sectional view of light bending panels incorporated in a window in the form of louvres for the purpose of admitting or rejecting incident sunlight depending on the angle at which the louvres are set.

The parallelepipeds used to form the light bending sheet may be produced by extrusion of transparent material through a die in the shape of a parallelogram or by cutting parallelepipeds from a flat sheet of transparent material and polishing the faces. The parallelepipeds so formed may then be placed one above the other as shown in Figure 2. to 3.

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form a light bending panel. These methods, while straightforward, are labour intensive and a simpler method of obtaining the required arrangement will now be described.

A particular and best method of producing an array of parallelepipeds in the form of a thin sheet is by making cuts through a flat sheet of transparent plastic with a laser cutting tool. The laser cutting tool is directed across a sheet of thickness, T, to make a series of parallel cuts of spacing, D, at a small angle, e, to the normal to the sheet so that the sheet is cut into an array of parallelepipeds the general crossection of each being a parallelogram with two sides o 0 parallel to the sheet surface as shown in Figure 2. Narrow regions of S the sheet are left uncut at the edges of the sheet and at intervals across the sheet to provide a continuum of material supporting the 00 array of parallelepipeds. The laser cuts produce smooth internal surfaces within the sheet at which light being transmitted through the sheet undergoes total internal reflection and is thereby bent through some required angle. The cuts may be spaced so that a high proportion of light incident from some particular direction is transmitted and bent through some required angle.. Provided the laser cuts are '2d' sufficiently narrow the external surfaces of the sheet are essentially undisturbed so that the sheet remains suitable for viewing through provided the viewing angle is near normal to the sheet.

The method of fabricating the panel with a laser cutting tool as outlined above is relatively inexpensive as compared with moulding or extrusion and is much more readily adapted to different shape, thickness and size of panel.

Referring to Figure 3. the total angle through which light is bent is given by i iT where i is the angle of incidence on the input face and iT is the angle at which light leaves the output face after undergoing total internal reflection at the internal interface. If the 4.

r1 i :i--L1 -p-Pie-; internal surfaces of the parallelepipeds lie at an angle, e, to the normal to the panel and if n is the refractive index of the material then iT arcsin(n sin(r 29) where r arcsin(sin(i)/n).

In the simplest case when e 0, iT i so that for example when i 60 degrees the incident light is bent through a total angle iT i 120 degrees. The proportion of incident light which is bent depends on the angle of incidence and on the ratio of the vertical depth of each parallelepiped, D, to the thickness of the sheet, T.

When used as a window the laser cut sheet would usually need to be protected by enclosure or lamination between two planes of glass or plastic with sealant applied to the perifery. Alternatively the laser cut sheet could be protected by the lamination of two films of clear plastic bonded to each face of the laser cut sheet.

When the laser cut sheet is used as a window for improved daylighting it may be advantageous to make the laser cuts in the sheet at varying angles, such that light incident from a given direction is bent by different parts of the sheet at different directions into the room. This allows the designer of light bending windows considerable scope to move the incoming daylight to various parts of the room.

It may also be advantageous to place the cuts in part of the window only so that, for example, the part below eye level is not cut and acts as a conventional window transmitting light downward, while the part above eye level, being cut, acts as a light bending panel and bends incoming daylight towards the ceiling.

In another embodiment the light bending panel may be in the form of a hung window which may be tilted at some angle to the vertical thus varying the angle of incidence of daylight on the window and the direction in which light is bent into the room. In this way the penetration of light into the room may be varied daily or seasonally.

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In another embodiment the light bending panels as described herein may be incorporated into a window as louvres. This provides a new type of louvre window with the particular properties of admitting or rejecting sunlight depending on the angle at which the louvres are set. In particular if the louvre panels are in the closed position as shown in Figure 5A incident sunlight is admitted to the room and directed towards the ceiling. An adequate view through the closed louvres is available provided the viewing angle is near normal to the window. If the louvre panels are placed in the open position incident 1 C: direct sunlight is rejected as shown in Figure 5B. With the louvres in this position the window has the useful and possibly unique property of rejecting incident sunlight while the louvres are open allowing excellent viewing and maximum ventilation. This embodiment of the invention is well suited for environment control since in winter it is generally desirable to admit sunlight and keep the louvre windows closed, while in summer it is generally desirable to reject sunlight and keep the louvre windows open to maximise ventilation.

The present invention is not limited by the embodiments as described as variations and modifications of the invention will be apparent within the scope of this disclosure.

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Claims (5)

1. A transparent light deflecting panel adapted to be mounted in vertical orientation in an opening in the facade of a building so as to redirect incident daylight towards the ceiling of said building, said panel comprising a planar transparent plastic plate having over the major proportion of the surface of said plate parallel and horizontally aligned, equally spaced apart laser cuts made through said plate perpendicular to the surface of said plate, the depth of said laser cuts and the spacing of 1 0 said laser cuts being such that the ratio of the spacing of the cuts to the depth of the cuts is less than unity.

2. A transparent light deflecting panel adapted to be mounted in vertical orientation in an opening in the facade of a building so as to redirect incident daylight 7 towards the ceiling of said building, said panel comprising a planar transparent plastic plate having over the major proportion of the surface of said plate parallel equally spaced apart laser cuts made through said plate such that said plate is divided into a series of parallel, equally spaced apart and horizontally aligned parallelepipeds of rectangular crossection, said parallelepipeds being supported at each end by a narrow continuum of said transparent plate extending around the 1 0 perifery of said transparent plate and extending at intervals across said transparent plate in a direction perpendicular to the horizontal axis of said parallelepipeds.

3. A transparent light deflecting panel, as claimed in claims 1 or 2 to which is bonded or laminated one or |I more sheets of planar transparent solid material s whereby the entry of moisture or dust into the laser cuts is prevented. 8 f l js ul I 1 i o

4. A louvered light deflecting panel for controlling the direction and amount of light entering a building comprising a plurality of transparent light deflecting panels incorporated as louvered panels in an external opening in said building such that said louvered panels may be rotated to the substantially closed position whereby sunlight incident on said louvered panels is substantially transmitted into said building and deflected towards the ceiling; and such that said louvered panels may be rotated to the substantially open position whereby sunlight incident on said louvered panels is substantially deflected to the exterior of said building.

5. A louvered light deflecting panel for controlling the direction and amount of light entering a building comprising a plurality of transparent light deflecting panels incorporated as louvered panels in an external opening in said building such that said louvered panels 9I 'NT C' 1 whereby sunlight incident on said louvered panels is substantially transmitted into said building and deflected towards the ceiling; and such that said louvered panels rmay be rotated to the substantially open position whereby sunlight incident on said louvered panels is substantially deflected to the exterior of said building; and where said transparent light deflecting panels each comprise a planar transparent plastic plate having over the major proportion of the surface of said plate parallel and horizontally aligned, equally spaced apart laser cuts made through said plate perpendicular to the surface of said plate, the depth of said laser cuts and the spacing of said laser cuts being such that the ratio of the spacing of the cuts to the depth of the cuts is less than unity. t B I Dated this 18 th day of June 1990. Maria Anna Theresia Edmonds. j. 1 L 1 r 1 r