GB2325266A - Prismatic light redirecting blind or curtain - Google Patents

Abstract

A blind or curtain, preferably a roller blind, is placed over a window so as to redirect light into a room rather than immediately towards the floor. The inner surface of the blind or curtain is formed with a plurality of elongate prisms, which may have a width of up to approximately 100 micrometers. The angle of the operative surface of each prism can be chosen in dependence upon in particular effect sought, although it is preferably 45‹ or more relative to the plane of the blind or curtain when in use. The prisms may be formed on both sides of the curtain and be of different characteristics (figure 5).

Description

BLIND OR CURTAIN The present invention relates to a blind or curtain.

It often happens that it is desirable to redirect light entering from a window. For example, if the window faces an adjacent building, light will only come from above and project onto the floor just inside the room. It has been realised in the past that if such window panes were provided with a series of prisms, the prisms would direct light further into the room where it could be better used and where it could reduce the need for electric lighting and air conditioning, as is apparent from the schematic diagram in Figure 1.

Windows of the above-mentioned type have been produced but have normally been too expensive to justify their costs on the grounds of energy savings and their use has therefore generally been restricted to prestige buildings. Moreover, it is understood that building regulations often specify that rooms for certain purposes must have a view of the outside world, even if such a view is not particularly attractive. In such circumstances, it is not possible to provide windows of a prismatic surface of the above-mentioned type.

The present invention seeks to provide a roller blind or curtain able to redirect light into a room.

According to an aspect of the present invention, there is provided a blind or curtain comprising at least one prismatic surface able to redirect light impinging on the blind or curtain. The term "prismatic surface" is intended to refer to a surface upon which there are provided a plurality of prismatic structures. These may be formed on the surface or attached to the surface, as preferred.

The prismatic surface is preferably provided on an interior surface of the blind or curtain.

Preferably, the or each prismatic surface is formed of a plurality of prisms having a width up to about 50 micrometers. In the most preferred embodiment, the width of each prism is preferably up to 30 micrometers and most preferably between 25 and 30 micrometers.

The angle or angles of the or each prism of the prismatic surface is preferably 25 or more relative to the plane of the roller blind or curtain when unrolled.

As will be apparent, the invention can provide a series of prismatic structures across the surface of a window by means of a roller blind or other temporary device for holding the material in place over the window. The use of a roller blind or curtain can provide a relatively cheap system for redirecting light passing through a window and can also provide the user with a choice of either having redirected light or light straight from the window. Thus, any building regulations of the type mentioned above can be met.

It will be apparent that in some embodiments the prismatic surface can be provided by means of a curtain which could, for example, be drawn laterally across a window.

An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a prior art prismatic window system; Figure 2 is a schematic diagram of a preferred embodiment of roller blind; Figure 3 is an electron micrograph of the preferred prism structure for the roller blind of Figure 2; Figure 4 is a photograph of a window onto which are located two small squares of prismatic structure used for the roller blind of Figure 2; and Figure 5 is a schematic diagram in side elevation of another embodiment of prismatic structure.

The preferred embodiment described below is in the form of a roller blind of flexible translucent or semi-translucent material. As will be apparent from Figure 2, the roller blind has an outer surface which, when deployed, is substantially flat and an inner surface formed of a plurality of elongate prisms extending across the width of the roller blind.

The roller blind is intended to be placed over an existing window so as to redirect light impinging thereon from the window. The orientation of the prisms is such that light from the sky above the window is reflected into the room as shown by the upper arrow in the Figure, rather than immediately towards the floor as shown in the lower arrow in Figure 2. In one tested embodiment, each prism had a width of approximately 27 micrometers. Other embodiments have included prism widths of up to and greater than 100 micrometers. It is preferable that the width of each prism is limited to no more than a width which maintains sufficient flexibility of the structure so as to be useable in a roller blind.

The angle of the operative surface of each prism can be chosen in dependence upon in particular effect sought, although it is preferably 45" or more relative to the plane of the roller blind or curtain when in use. For example, angles of 60 and 70" have produced advantageous results.

The use of a very fine prism structure enables the device to be replicated using ultraviolet curing techniques at a cost which enables it to be used in common applications such as houses and offices. Not only does this make the device cheap enough to be commercially viable, but it also enables it to be cast on a flexible material. This makes it possible for it to be produced in the form of a roller blind, curtain or other temporary window cover.

It is envisaged in many applications that light will be directed upwardly towards the ceiling of a room to reduce or eliminate glare.

The advantages of such a temporary cover include: 1. giving the user a choice of either extra daylight (saving on lighting and air conditioning bills and providing a more natural form of lighting) or a non reflected view from the window; 2. avoidance of possible restrictions of use because of building regulations; 3. diffusion of light caused by the fine prismatic structure, which can provide a more uniform illumination of the room. This can also "scramble" any direct image viewed through the window, as will be apparent from Figure 4.

In the preferred embodiment, the material is formed by ultraviolet embossing from a master preferably a blazed infrared diffraction grating.

In another embodiment, the roller blind or other flexible window covering may be formed of a plurality of panes of flexible prismatic material. This can allow different light effects to be produced both at the junctions of the individual panes and by their use of panes of different light transniissive or reflective properties.

Figure 5 shows an embodiment in which both sides of the roller blind are provided with prismatic structures. The structure closest to the window serves to direct light into a room, while the second side serves to spread light throughout the room.

It is envisaged in some applications that the prismatic surface used to spread the light may have prism structures which vary along the height of the blind to produce a varying light scatter. For example, it may be desirable not to direct light to a particular area of the room and to direct the light away from this area.

Claims (8)

1. A blind or curtain comprising at least one prismatic surface able to redirect light impinging on the blind or curtain.

2. A blind or curtain according to claim 1, including a prismatic surface provided on an interior surface of the blind or curtain.

3. A blind or curtain according to claim 1 or 2, wherein the or each prismatic surface is formed of a plurality of prisms having a width up to about 100 micrometers.

4. A blind or curtain according to claim 1, 2 or 3, wherein the angle or angles of the or each prism of the prismatic surface is 25 or more relative to the plane of the blind or curtain when deployed.

5. A blind or curtain according to claim 4, wherein said angle is around 60 to 700.

6. A blind or curtain according to any preceding claim, including first and second prismatic surfaces on opposite sides of the blind or curtain.

7. A blind or curtain according to claim 6, wherein the first and second prismatic surfaces have different prism characteristics.

8. A blind or curtain substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.