NZ207424A

NZ207424A - Windbreak material

Info

Publication number: NZ207424A
Application number: NZ207424A
Authority: NZ
Inventors: A C Wood
Original assignee: A C Wood; Wood J E
Priority date: 1983-07-22
Filing date: 1983-07-22
Publication date: 1987-06-30

Description

<div class="application article clearfix" id="description"> 2074 Attorney's ref. P514/83L Patents Form No. 5 Fee $80 Patents Act 19 53 _N.Z. t'ATENT OFFICE v 12 APR 1984 'M RECEIVED Number; 207 424 Date: 22 July 1983 (antedated from 8 March 1984 under Reg. 23) COMPLETE SPECIFICATION BARRIER NETTING We, ALEXANDER CHRISTOPHER WOOD and JEWEL EDNA WOOD, both of 94 East Tamaki Road, Auckland, New Zealand, and both citizens of New Zealand hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- 207424" This invention relates to screening material and has special, but not exclusive, application to materials which are intended to be used to protect plants from the effects of wind while allowing sunlight to reach the plants. In our co-pending patent application Mo. 204993, we have described a wind barrier for growing plants such as kiwifruit which comprises a screening material arranged non-vertically above the plants. We have found that growing plants, such as kiwifruit, are particularly susceptible to a downward component of wind, and that the above-mentioned arrangement of a screening material is particularly valuable to protect plants from such component. Because such a screening material is likely to be interposed between the plants and the sun, it is desirable to combine adequate wind protection with a relatively high transmission of light. In this specification, and in the claims, reference is made to the "shade factor" of a screen. This is a known term in the art of measuring the light transmission of screens, and means the loss of luminous intensity of the light passing through a screen expressed as a percentage of the luminous intensity of the light impinging on the screen. It is measured with-a light meter in unshaded conditions and with the light impinging on the screen in the most favourable manner for transmission, usually perpendicularly to the screen. Thus, for example, where the luminous intensity on the sunny side of a screen is 100 207424 candelas and on the shady side of the screen is 20 candelas, the shade factor is 80%. We have found that, if a screen is to be used as an overhead screen for common horticultural plants requiring sun for growing and ripening, the shade factor should be less than 30%, preferably less than 25% and, if possible, less than 20%. At the same time, if the overhead screen is to be useful to provide a wind barrier as required by our co-pending application No. 204933, the area of the apertures in the screen should 2 not be greater than 300mm . Thus, this invention provides a screen having apertures therethrough, wherein the area of each aperture is not 2 more than 300mm and the shade factor as hereinbefore defined of the screen is less than 30%. Preferably, the shade factor is less than 25% and, yet preferably, it is less than 20%. In current screen-making technology, the area of each aperture should be 2 2 in the range of 10mm to 300mm . Where a screening material is to be mounted horizontally over plants, it is desirable to provide also for effective transmission of light through as much as possible of the daylight hours, preferably through 120° of movement of the sun. To this end, preferably the ratio of the width of each said aperture (measured in at least one direction) to the thickness of the material of the screen immediately adjacent to such aperture is not less than 1.73:1. A screen observing the criteria which have been set forth may be formed "3 ~ 0 0 A "7 n ^ 1 u / 42 m- of spaced-apart ribs formed by knitting filaments together, interlinked by spaced-apart filaments. Preferably, the width of an aperture between two adjacent filaments is in the range 2.5mm to lOrran. A screen of this kind may be made from ultraviolet-stablised polyethylene monofilament, 5 and the thickness of the monofilament is preferably in the range 200 to 900 denier. In order that the invention may be more clearly understood, one embodiment thereof is hereunder described by way of example only with (^) 10 reference to the accompanying illustration which is a direct photocopy in 1:1 scale of a piece of screening material made according to the invention. The screen herein particularly described and shown in the drawing is the 15 same as the screen particularly referred to as a knitted flexible plastics material in the provisional specification. The screen is knitted from 500 denier polyethylene monofilament which includes a carbon black ultraviolet inhibitor. 20 The screen is knitted in the form of a plurality of spaced-apart ribs, for example 1, which are interlinked by a plurality of single-thread filaments, for example 2. The space between adjacent ribs is at least five times greater than the space between adjacent threads, so that when the material is placed under even edge tension so as to straighten the O 25 ribs and the threads, substantially rectangular, oblong apertures are - 4 - 207424 formed by adjacent pairs of ribs and adjacent pairs of threads. As can be seen in the drawing, the spacing is very much greater than the ratio of 3.73:1 which has been mentioned so that the screening material provides a negligible barrier to the passage of sunlight. 5 . The screening material thus made allows sufficient sunlight to reach the plants which are growing under an overhead screen formed of this material, while at the same time providing a useful wind barrier above the plants for the purposes of the barrier of our co-pending application 10 No. 204993. Because of the fineness of the materials used, and the consequent sroallness of the apertures within the stated ratios, the screen also provides collateral benefits including a substantial protection from hail damage, a substantial barrier to flying insects, and the ability to create a zone of substantially still air around the 15 plants. The advantages depend, of course, to some extent on the way in which the screen is mounted and used. It has been found, for example, that a substantially horizontal overhead screen can stop sufficient hail to collapse the screen onto the plants 20 underneath under the weight of the hail, thus giving very substantial protection against hail damage to the plants. It has been found also that pollinating insects such as bees do not readily pass through the screen and may, therefore, be liberated inside a space bounded by the screening material for pollination. It has also been found that sprays 25 and powders may be used inside a space bounded by the screen material - 5 - 207424 and the wind-barrier properties of the screen help to prevent the material from being dispersed. It has also been found in practice that surrounding growing plants with the screen material can cause a temperature increase within the screen space, which may be more than 2°C and may provide valuable frost protection. </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 207424 WHAT WE CLAIM IS:

1. An outdoor crop protection net made of flexible filament comprising a plurality of substantially parallel ribs, each consisting of filaments knitted together, adjacent ribs being interlinked by filament to create cell apertures wherein the average area of the cell apertures when the net is under edgewise tension is 10-3 OOmm^ and the shade factor as herein before defined is less than 30%.

2. A net according to claim 1, wherein the said shade factor is less than 25%.

3. A net according to claim 2, wherein the shade factor is less than 20%.

4. A net according to claim 1, wherein the cells are elongated.

5. A net according to any preceding claim wherein the ends of the cells are constituted by adjacent ribs and the sides are constituted by one or more linking filaments.

6. A net according to claim 5, wherein the width of each cell aperture between those sides thereof which are formed by the filament or filaments is in the range 2mm to 10mm.

7. A net according to any preceding claim, made from ultraviolet-stablized polyethylene monofilament.

8. A net according to claim 7, wherein the thickness of the monofilament is in the range 200 to 900 denier.

9. A net substantially as hereinbefore described with reference to the accompanying drawing. ALEXANDER CHRISTOPHER WOOD and JEWEL EDNA WOOD by their Attorneys </div>