EP0244453A1

EP0244453A1 - Microwave shielding means

Info

Publication number: EP0244453A1
Application number: EP86906379A
Authority: EP
Inventors: William Nevil Heaton Johnson; Noel Robertson Mckenzie
Original assignee: APPLIED AGRICULTURAL RESEARCH Ltd
Current assignee: APPLIED AGRICULTURAL RESEARCH Ltd
Priority date: 1985-10-23
Filing date: 1986-10-21
Publication date: 1987-11-11
Also published as: GB8526157D0; AU6520386A; WO1987002578A1

Abstract

Dans une serre, cloche, ou similaire, afin de garder le maximum d'énergie fournie par les ondes ionosphériques, notamment sous la forme d'énergie de micro-ondes, et également pour garder l'énergie des micro-ondes produites artificiellement si celle-ci est utilisée pour chauffer les végétaux à l'intérieur de la serre ou de la cloche, le verre ou le matériau en plastique transparent ou translucide recouvrant la serre ou la cloche est rendu partiellement réfléchissant par pulvérisation d'un mince revêtement métallique d'étain, d'or ou d'argent par exemple.In a greenhouse, bell, or similar, in order to keep the maximum energy supplied by the ionospheric waves, in particular in the form of microwave energy, and also to keep the energy of microwaves produced artificially if that -this is used to heat the plants inside the greenhouse or the bell, the glass or the transparent or translucent plastic material covering the greenhouse or the bell is made partially reflective by spraying a thin metallic coating of pewter, gold or silver for example.

Description

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Title: "Microwave shielding means"

THIS INVENTION relates to agricultural and horticultural greenhouses, hot¬ houses, plastic tunnels, frames, cloches and all similar purpose structures and devices..

Such protective units are normally clad with clear materials such as glass, rigid plastics or flexible plastic films to allow full light transmission to the interior. A variety of structural shapes exist which normally conform to either barn, tent or tunnel configurations.

However, growing units of whatever size normally require some form of heating during cold periods due to the poor U value of cladding materials. Heating costs can be high as a result. A recent development in heating equipment utilises microwave energy to directly heat plants and crops and heating costs can be greatly reduced by this method. Whilst the microwave emissions are of a fairly low level, it is nevertheless desirable to contain within the growing unit as much of the sky wave energy as possible both for reasons of running costs of efficiency. Standard clear cladding material is almost totally transparent to microwave energy allowing emissions to pass directly to the outer atmosphere.

The present invention provides for a microwave attenuating deposit to be coated over the entire surface of the cladding material. Such coatings can be accomplished by the sputtering process whereby very thin atomic layers of a suitable metal can be deposited on a flexible substrate such as polyester or polyethylene film.

Specific embodiments of the invention will be described by way of example in the accompanying drawings in which:-

FIGURE 1 illustrates a sectional view of sputtered material laminated to rigid plastic sheeting or glass. FIGURE 2 shows a sectional view of a typical rigid structure,

FIGURE 3 shows a sectional view of a typical flexible plastic tunnel.

The layers illustrated are separated only to indicate laminate sequence and there, is normally full surface to surface bonding of materials.

Referring to the illustrations, Figure 1 comprises at 4 a rigid cladding material such as glass or thick plastic. A thin flexible plastic film 6 has been sputter-coated with a metal deposit 5 such as tin, gold, silver or bronze all giving high attenuation values. The flexible film 6 is bonded directly onto the rigid base 4.

Figure 2 shows a rigid framed barn structure where the treated film 6 is laminated to the inside surface of the cladding material 4 which can be either glass or thick plastic.

Figure 3 shows a typical plastic tunnel shape. In this case the cladding and attenuating layers serve to stretch across a frame system to provide surface tension and rigidity. The attenuating deposit 5 is situated on the inside surface of the flexible plastic film 6.

SUBSTITUTE SHEET

Claims

1. An agricultural or horticultural growing enclosure, such as a greenhouse, 5 hothouse, cloche or the like, which comprises or is clad with a material which is partially light transmitting and at least partially reflective to microwave electromagnetic radiation.

2 An enclosure according to claim 1 wherein said material comprises a 0 layer of transparent material having at least one surface thereof provided with a thin metallic coating by the sputtering technique.

3. An enclosure according to claim 1 which is clad with transparent rigid sheets having bonded thereto a thin layer of plastics film which has been 5 rendered part-reflective by metallic sputtering.

4. An enclosure according to claim 1 which comprises a frame covered by an envelope of flexible plastics film to which a reflective metallic coating has been applied by sputtering. 0

5. An enclosure substantially as hereinbefore described with reference to, and as shown in, Figure 2 or Figure 3 of the accompanying drawings.

6. A partially light transmissive material which is at least partially 5 reflective to microwave radiation, and comprising a sheet of transparent material metallised by metallic sputtering.

7. A material according to claim 6 which comprises a rigid transparent sheet and a thin film of transparent plastics which has been rendered reflective

30 to microwave energy by metallic sputtering bonded to one surface of said rigid sheet.