GB2226654A

GB2226654A - Screen

Info

Publication number: GB2226654A
Application number: GB8827086A
Authority: GB
Inventors: Archibald William Ke Macgregor
Original assignee: NAPIER CONSULTANCY SERVICES LI
Current assignee: NAPIER CONSULTANCY SERVICES LI
Priority date: 1988-11-19
Filing date: 1988-11-19
Publication date: 1990-07-04
Anticipated expiration: 2008-11-19
Also published as: GB2226654B; GB8827086D0

Abstract

A screen 1 whose light transmission properties may be varied by controlling the concentration of light absorbing particles 15 held in suspension in a fluid. The fluid circulates in the chamber between two parallel translucent sheets which form the outer boundary of the screen. The concentration of said particles may be controlled by means of varying the mass flow rate of said fluid through the screen, or otherwise. The heat generated by absorption of light in said particles is transferred by means of the circulating fluid to a heat store or heat exchanger which is connected to the screen by a pipework circuit. A pump 12 provides circulation of the fluid. <IMAGE>

Description

SCREEN The present invention relates to screens and in particular to a variable light transmission screen.

With the increasingly extensive use of glazing in modern building construction as well as in greenhouses and conservatories, there is a need for screens which can and heat control the amount of light#entering the glazed space.

Conventionally there have been used various mechanically operated screen such as, for example, venetian blinds in which individual screen elements are moved between screening and non-screening positions. The large number of moving parts involved in such screens however introduces significant limitations in relation to reliability and the life of the system as well as the problems of complexity of maintenance and cost thereof.

More recently there have been introduced screens in which the screening element is in the form of a solution of a dye or pigment whose light absorption can be modulated in one way or another. Whilst such screens involve fewer moving parts, they do have the significant disadvantage of relatively high cost.

It is an object of the present invention to avoid or minimise one or more of the above disadvantages.

The present invention provides a variable light transmission screen comprising a double glazed translucent panel defining a chamber between opposed panes of translucent sheet material; fluid circulation means formed and arranged for circulation of a fluid containing a plurality of particles of reduced translucence material in said chamber so as to maintain said particles in suspension in said fluid in said chamber in use of the screen in a screening condition thereof; and control means formed and arranged for reducing suspension of the particles in the chamber in a light transmission condition of the screen, whereby the light transmission of the screen may be readily varied by changing the degree of suspension of the particles in the fluid in said chamber.

With a screen of the present invention, the degree of light transmission can be readily varied in a relatively simple manner, for example, by adjusting the flow rate of the fluid through the chamber, e.g. by varying the speed of a fluid circulation pump.

Advantageously, the particles are formed of a material so as to have a density closely similar to but slightly greater than that of fluid in which they are suspended, for example a density of from 1 to 50%, most preferably from 5 to 30%, greater than that of the fluid. The particles may be made of any suitable generally inert material, for example a plastics material and may contain one or more closed cell cavities so as to reduce the overall density of the particles.

The reduced translucence of the particles may be achieved by the use of materials of greater or lesser opacity, and/or the use of reflective or absorbent surfaces. In the latter case, for example, by the use of dark coloured particles, the absorbance of radiant energy by the particles may be used to heat the fluid which may then be passed through a suitable heat exchanger in order to provide a useful heat supply.

Whilst the degree of suspension of the particles is conveniently controllable by adjustment of the flow rate of the fluid through the chamber, other means of controlling the degree of suspension may be used. Thus for example, by using particles containing magnetic or magnetisable material, externally applied magnetic or electromagnetic fields may be used to control the degree of suspension of the particles in the fluid.

Desirably the distribution of the suspended particles in the fluid is made to be generally uniform and accordingly, the fluid circulation means and chamber are formed and arranged, e.g. with the aid of suitable baffle means, so as to minimise "dead" spaces within the chamber of substantially reduced flow rate.

Further preferred features and advantages of the present invention will appear from the following detailed description given by way of example of a preferred embodiment illustrated with reference to the accompanying drawings in which: Fig. 1 is a schematic front elevation of a variable light transmission screen of the invention; Fig. 2 is a cro-r#-.#ection#cf the screen c; Fig.1; .nd Fig. 3 is a schematic perspective view of a typical screen installation.

Fig. 1 shows a variable light transmission screen 1, comprising a double glazed translucent panel 2 comprising a double glazed panel defining a chamber 3 between opposed panes 4 of a transparent plastics sheet material such as a polyacrylate (see Fig.2). The chamber 3 includes a plurality of baffles 5 formed and arranged so as to define a convoluted fluid passage 6 extending from an inlet 7 at a lower end 8 of the panel 2 up to an outlet 9 at the upper end 10. A conduit 11 extends from the outlet 9 to a fluid circulation means in the form of a pump 12 which is provided with a control means 13. A suitable fluid such as water 14, preferably containing some antifreeze to provide protection against freezing at low temperatures, is circulated through the screen by the pump 12.A large number of small particles 15 which are conveniently in the form of small spheres of a plastics material such as polyamide are maintained in suspension in the circulating fluid 14.

As the speed of the pump 12 is reduced by the control means 13, the degree of suspension of the particles in the water 14 will be reduced thereby increasing the transmission of light 16 through the screen 1.

Conveniently the particles may be made with a range of densities and/or a range of particle sizes in order to allow increased control over the particular degree of screening provided between the maximum and minimum levels of screening available (corresponding to complete suspension of the particles and complete settling out, respectively).

It will be appreciated that various modifications may be made to the above described embodiment without departing from the scope of the present invention. Thus for example there could be connected to the conduit 11 a heat exchange unit 17 (shown in dashed outline) whereby heat absorbed by the particles into the fluid 14 may be extracted and exploited via a suitable heating circuit 18.

Fig. 3 shows a typical screen installation in which a glazed space l9e#.aconservatory, is provided with a plu reality of screen panels at the underside 20 of the roof panel 21. The screen panels 1 are connected in series and the final outlet 9 is connected to a reservoir 22 which contains a substantial body of the fluid 14 containing the particles 15. When the fluid circulation slows down and is stopped the particles settle out 23 at the bottom 24 of the reservoir 22. The return pipe 25 from the screen panel outlet 9 is directed at its outlet end 26 towards the base 24 so as to stir up the body 23 of settled particles in the reservoir 22 as the flow rate through the system is increased thereby increasing the amount of particles in suspension in the fluid and thus in turn increasing the screening effect of the screen panels 1.

The circulating pump 12 at the downstream side 27 of the reservoir 22 has a speed control 13 connected to a thermostat 28 mounted inside the glazed space 19 so as to increase the pump speed with increasing temperature inside the glazed space. In this way the screening of the glazed space 19 is automatically increased with increasing radiation in a simple and economic manner. In contrast attempts to automate mechanical screening systems such as venetian blinds tend to be relatively complex and expensive and may further be relatively noisy in operation.

Claims

1. A screen comprising two parallel sheets of translucent materiai with a chamber between them in which a fluid carrying solid particles in suspension is caused to circulate. The concentration of said suspended particles can be controlled such that the light transmissivity of the screen may be varied so that the screen functions as a variable shading device.

2. A screen as claimed in Claim 1 wherein the concentration of suspended particles in the circulating fluid is controlled by means of varying the flow rate of the fluid through the screen.

3. A screen as claimed in Claim 1 wherein the concentration of suspended particles in the circulating fluid is controlled by means of an externally applied magnetic or electromagnetic field, the said particles containing magnetic or magnetisable material.

4. A screen as claimed in Claim 2 or Claim 3 wherein the said particles may be made with a range of densities and/or a range of particle sizes in order to allow increased control over the degree of light transmission.

5. A screen as claimed in any preceding claim wherein the reduced light transmissivity of the screen may be achieved by using particles of greater or lesser opacity and/or the use of reflective or absorbent surfaces.

6. S screen as claimed in any preceding claim wherein the heat resulting from the absorption of light by the suspended particles is tranferred to the fluid in which the particles are suspended and thence by circulation of the fluid through pipes to a thermal store or heat exchanger.