NZ224627A - Overhead protective netting for crops - Google Patents

Description

224627 Patform.#5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION NET I, John Harry Hall, a New Zealand citizen of Main Road South, Katikati, New Zealand do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: 2743comp/jw 224627 This invention relates to a net.

In the past nets have been provided in a very wide variety of patterns. The pattern of a net is devised for various reasons including the function which it is to perform and in some cases it is governed by fashion. In the past nets have been made by various methods including weaving, knitting and extruding.

Netting is gaining increasing acceptance for use as shelter over horticultural crops; that is to say the netting is erected so as to partially , or wholly overlie an entire crop as opposed to being erected upright along the boundary of the crop. Netting is erected over crops in this manner for various purposes including providing shade, wind shelter, bird shelter and protection against hail.

There are at least two problems associated with such use of netting. In the first place, while considerably cheaper nowadays than, for example, chicken wire which has been in use as bird shelter for many, years, it is nevertheless still relatively expensive especially when the area to be covered in this way is taken into account. The expense arises due to the amount of material which is used to make up most nets; and also due to the cost of the materials and labour required for the structure which is necessary to support the net. Second, it is self evident that any net will block off a certain amount of sunlight from the area over which it is erected. The concept of the "shade factor" of a net is well known. The shade factor is taken as the percentage reduction in the amount of light (or sunshine) which falls on a given area with a net present compared to the amount of light which falls on the same area when the net is removed. Certain crops require a lot of sunshine in order to thrive so the shade factor of any net which is to erected over the crop should be minimised. One way of reducing the shade factor is to provide a net with an open mesh. Another way is to provide a net constructed of fine gauge yarn with a reduced number of filaments making up the wales and courses. However a balance has to be struck between on the one hand reducing^fter-shade factor and on the other hand providing a net which has sufficient strength withstand the stresses and strains applied to it by such pi / t 1 224627 3 wind and hail. Further, the mesh cannot be too open if the net is intended as wind or hail shelter since such a net will not offer a sufficient barrier to the wind or hail.

According to the invention there is provided a net including: (a) ribs made up each of at least one yarn which is knitted to form stitches, at least some of the ribs being disposed in a pattern comprising closed figures each having at least four sides, each of the four sides being disposed obliquely to the direction in which the net is knitted; and (b) at least one single yarn crossing each said closed figure and disposed in a direction other than perpendicular to the direction in which the net is knitted.

The pattern may, for example, comprise four- or six sided figures.

In the case of a pattern comprising six sided figures two sides of each may, according to the invention, be disposed parallel to the direction in which the net is knitted.

In one aspect (applicable to either a four- or six sided figure), of the four said sides two are parallel to a first line and the other two are parallel to a second line, the first and second lines being inclined at equal and opposite angles to the direction in which the net is knitted.

In another aspect a first said single yarn crosses the figure between the two sides which are parallel to the first line and and a second said single yarn crosses the figure between the two sides which are parallel to the second line. At least two of the four said sides may be of equal length.

In one form of the invention at least one said single yarn is laid into the ribs so as to be movable therethrough.

Further according to the invention there is provided a net comprising two portions, the first portion comprisinq a structure conforming to that of the net as defined above and the second portion including ribs made up each of 224G2 at least one yarn which is knitted to form stitches, the ribs of the second portion being disposed in a pattern comprising figures which are crossed by no said single yarns or at least fewer said single yarns than the figures in the first portion.

In one aspect the figures in the second portion are geometrically similar to the figures in the first portion.

The invention is further discussed with reference to the accompanying drawings in which various embodiments are illustrated by way of example and in which: Figure 1 is a schematic illustration of three nets each with a hexagonal mesh pattern; Figure 2 is a schematic illustration of two nets each with a tetragonal mesh pattern; Figures 3 to 6 are schematic illustrations each of another net; Figure 7 is a photocopy of an actual net knitted with a first mesh pattern; and Figure 8 is a schematic illustration of a net with two mesh patterns.

All of the nets are illustrated in their working disposition; i.e. they do not necessarily have this appearance as they emerge from the knitting machine which in the present case is a Raschel warp knitting machine. It is an important advantage of the invention that the nets are able to undergo sideways stretch when being erected.

Figures 1 and 2 are provided to indicate more clearly what are meant herein by hexagonal and tetragonal mesh patterns.

In Figure 1 the first net 10 has a mesh made up of ribs 12 and cross filaments 14. The ribs 12 are composed of a number of yarns knitted together while the cross filaments 14 are composed of single (i.e. monofilament) yarns. The ribs are disposed in a clearly visible hexagonal patteiiTT the six 224627 sides of the hexagon in the present case being of equal length. Two of the ribs, 12a, making up each hexagon are disposed in the direction in which the net is knitted, this direction being indicated by the arrow 16. It is convenient to consider these two ribs 12a as a first pair. The remaining four ribs making up the hexagon are disposed at 120° to each other and 60° to the ribs 12a and are thus each at an oblique angle to the direction in which the net is knitted. It is convenient to consider these four ribs also as being paired, the ribs 12b making up a second pair and the ribs 12c making up a third pair. The two ribs in each of the three pairs are disposed opposite each other across the hexagon. One cross filament 14 is disposed between the pair of ribs 12b and a second cross filament 14 is disposed between the pair of ribs 12c. The yarns making up the cross filaments are not necessarily formed into stitches incorporated in the ribs. The yarns are furthermore not necessarily joined to each other where they cross in the centre of the hexagon.

The dotted line labeled 50 in the drawing of the net 10 illustrates the typical pattern in which a single cross filament is laid into the net. An important advantage results from laying the cross filaments into the ribs rather than forming them into stitches. They are then able to move or slide longitudinally in and through the ribs. As the net is stretched sideways (i.e. perpendicular to the arrow 16) during erection the width of each hexagon which a cross filament must span changes and the cross filament is able to accommodate this change by moving or sliding through the ribs. Thus the cross filaments are not caused to sag when the net is stretched neither do they inhibit the stretching.

The second net 10' shown in Figure 1 is constructed from the same number of yarns as the net 10, also knitted into a hexagonal mesh pattern. However, in the net 10', the sides of the hexagon are not of equal length. Rather the ribs 12a' which lie in the direction of knitting are relatively long compared to the ribs 12b' and 12c'. The ribs remain at 120° to each other but the construction has the effect that the cross filaments 14' intersect at a different angle to that at which the cross filaments 14 in the net 10 intersect.

The third net 10" shown in Figure 1 is again constrjic,tgd^ from the same 2246 number of yarns as the nets 10 and 10' which again are knitted into a hexagonal mesh pattern. However, in the net 10",. the ribs 12a" which lie in the direction of knitting are relatively short compared to the ribs 12b" and 12c". Cross filaments are shown at 14".

The nets 20 and 20' shown in Figure 2 are yet again constructed from the same number of yarns as the nets shown in Figure 1. However the nets 20 and 20' have been knitted in a pattern in which there are in effect no ribs disposed in the direction in which the nets are knitted, indicated by the arrow 16'. The nets 20 and 20' thus have meshes which clearly appear as tetragons, being made up of two pairs of opposed ribs. These ribs are indicated by the numerals 22b, 22c in the net 20; and 22b', 22c' in the net 20'. Cross filaments 24 are disposed between each pair of ribs 22b, 22c; and also between each pair of ribs 22b', 22c'. As may clearly be seen in the illustrations, in the net 20 each tetragon has four sides of equal length with each pair of adjoining sides intersecting at right angles. The sides are thus disposed at 45° to the arrow 16' and the diagonals of each tetragon are of equal length. In the net 20' however each tetragon, while having four sides of equal length, has a major axis which is perpendicular to the arrow 16' and a minor axis which is parallel to the arrow 16'. It would equally be possible to provide a net similar to the nets 20 and 20' in which each tetragon has four sides of equal length but having a major axis parallel to the arrow 16' and a minor axis perpendicular to the arrow 16'. Indeed a net in which the ribs are disposed in a pattern comprising tetragons made up of four equal sides would emerge from the knitting machine with the major axes of the tetragons parallel to the arrow 16' and much longer than the minor axes which would be perpendicular to the arrow 16'. As this net is stretched in a sideways direction it could assume the shape of the net 20 and, if stretched further, the shape of the net 20'.

Another important advantage of the nets illustrated is that they combine inherent strength (due to the interconnected ribs) and a high degree of protection from birds, wind and hail while having a low shade factor. The high degree of protection and low shade factor arise from the provision of the cross filaments which offer little obstruction to light but at the same time reduce the effective size of the apertures througK^whi^h birds, wind and hail might otherwise penetrate. In fact in the net illustrated 224627 7 schematically in Figure 3 the ribs are of considerable length and four cross filaments extend between each pair of opposed ribs. The net of Figure 3 will have a very low shade factor, probably of the order of 8%.

In Figure 4 a net is shown comprising ribs arranged in a hexagonal pattern. One pair of opposed sides of each hexagon is spanned by a single cross filament and another pair of opposed sides of the hexagon is spanned by two spaced cross filaments. In Figure 5 the single cross filament shown in Figure 4 is replaced by two spaced cross filaments.

Where there are two or more parallel cross filaments in a net it may be desirable in certain circumstances to locate them very close together. If they are of fine gauge they might then appear to the eye to be a single filament.

In Figure 6 there is shown a net with ribs arranged again in a hexagonal/tetragonal pattern. However in this case each hexagon/tetragon is spanned by but a single cross filament 24" which is disposed parallel to the direction in which the net is knitted (indicated by the arrow 16"). In fact the cross filament 24" spans the hexagon from the point of intersection of one pair of the obliquely ribs to the point of intersection of the second pair. In this construction the cross filaments again do not stabilise the net in the sideways direction, i.e. they do not inhibit the stretch in that direction.

Figure 7 is a photocopy of an actual sample of a net. It was knitted on a Raschel knitting machine from 800 denier yarns of black monofilament polyethylene provided with an ultraviolet inhibitor. The ribs are comprised of a single yarn knitted to form stitches. The net was 4 meters wide as it emerged from the machine and can be stretched to 13.5 meters width upon erection. It has a shade factor of about 14%.

It may be noted that the ribs of the net illustrated in Figure 6 are of lighter construction than those of the net illustrated in, say. Figure 7. A net of lighter construction might be useful in conditions in which the strength of the net was less important than a lower shade factor.^ 224627 Figure 8 shows a net 40 which is a development of the net according to the invention. It is knitted with two outer zones 42, 44 having meshes constructed according to the net shown in Figure 2; i.e. the meshes being provided with cross filaments as shown in Figure 2. Between the outer zones an inner zone 46 has ribs defining meshes of the same size as those in the outer zones. However the meshes of the inner zone have no cross filaments. This net is erected over a crop sewn in rows with the outer zones directly over the rows of the crop and the inner zone over the area between the rows. The inner zone has a greater degree of stretchability and furthermore the structure supporting the net may be such as to allow more stretch in the inner zone than in the outer zones. As a consequence if hail falls on the net the inner zone of the net will sag much more under the weight of the hail than the outer zones and the hail will gravitate to the centre zone and be dumped through the meshes which are unobstructed by the cross filaments.

Yet another important characteristic of the net of the invention is that it can behave somewhat in the manner of an elastic membrane such as a trampoline when hailstones fall onto the net, i.e. in some circumstances during a hailstorm hailstones may rebound and migrate towards the centre of. a net supported at its edges in a horizontal position. A crop under the net can thus be positioned so that when the net sags under the weight of an excessive amount of hail there is a reduced danger of damage to the crop.

Moreover the net has a pronounced ability to return to its original shape after distension as for example by the wind or by hail or even, in extreme circumstances, by large objects which may fall onto the net in exceptionally stormy conditions. This characteristic is also useful during erection and maintenance as personnel are able to walk over the top of the net after erection without fear of damage thereto.

It should be explained that when the nets are being knitted on a Raschel warp knitting machine the meshes are very much elongated in the direction of knitting and correspondingly narrowed in the direction transverse thereto. This characteristic is made use of in the nets according to the present invention as it enables a net to be made which can in use be stretched sideways to a considerable extent. In an extreme case an Article of the pattern shown in Figure 8 and which is 4.3 meters wide as it emerges fro'nr---a.. 224627 Raschel knitting machine of that nominal width can be stretched to a width of up to 38 meters. Because of the reduced amount of material which goes into it and the reduced machine time per unit working width required to make it, such a net is very economical to make. It is also very economical to erect on account of the reduced amount of material required for the supporting structure and also the reduced time required to erect the supporting structure and the net itself.

Nets according to the invention may be constructed in sizes ranging from a very fine mesh for use, for example, as shade cloth to a very open mesh, for example of the order of 5 or 6 cm across or even larger. Also the colour of the nets may vary as desired. Furthermore they may if desired be knitted from translucent yarn. This might be an advantage, for example, in order to minimise the shade factor.

It is not intended that the scope of a patent granted in pursuance of the application of which this specification forms a part should exclude modifications and/or improvements to the embodiments described and/or illustrated which are within the spirit of the invention as defined in the claims or be limited by details of such embodiments further than is necessary to distinguish the invention from the prior art.

Claims (10)

10 224«27 WHAT I/WE CLAIM IS:

1. A net including: (a) ribs made up each of at least one yarn which is knitted to form stitches, at least some of the ribs being disposed in a pattern comprising closed figures each having at least four sides, each of the four sides being disposed obliquely to the direction in which the net is knitted; and (b) at least one single yarn crossing each said closed figure and disposed in a direction other than perpendicular to the direction in which the net is knitted.

2. A net according to claim 1 in which the pattern comprises four sided figures.

3. A net according to claim 1 in which the pattern comprises six sided figures.

4. A net according to claim 3 in which two sides of each six sided figure are disposed parallel to the direction in which the net is knitted. A net according to any one of claims 1 to 4, in which of the four said sides two are parallel to a first line and the other two are parallel to a second line, the first and second lines being inclined at equal and opposite angles to the direction in which the net is knitted. A net according to claim 5, in which a first said single yarn crosses the figure between the two sides which are parallel tQ^^&>first line and a second said single yarn crosses the figure between the two; sides which are

5.

6. 224627 n parallel to the second line.

7. A net according to any one of claims 1 to 6, in which at least two of the four said sides are of equal length.

8. A net according to any one of claims 1 to 7, in which at least one said single yarn is laid into the ribs so as to be movable therethrough. A net comprising two portions, the first portion comprising a structure conforming to that of the net claimed in any one of claims 1 to 8, and the second portion including ribs made up each of at least one yarn which is knitted to form stitches, the ribs of the second portion being disposed in a pattern comprising figures which are crossed by no said single yarns or at least fewer said single yarns than the figures in the first portion. A net according to claim 9, in which the figures in the second portion are geometrically similar to the figures in the first portion. 11. A net substantially as herein described with reference to any of the examples illustrated in the accompanying drawings.

9.

10. J t CO A :he Applicant John Harry Hall