Patent Application
20240260561
The present disclosure concerns net insect strips obtained by cutting a wide insect net by means of a one-step ultrasonic cutting and welding process, and the method of producing said insect net strips.
In greenhouses it is sometimes necessary to use insect nets in ventilation openings to prevent unwanted insects to enter the greenhouse and in some instances to keep wanted insects from leaving the greenhouse. When installing insect nets in an existing greenhouse, problems with elevated temperatures or humidity or low carbon dioxide levels may arise since insect nets will always to some extent impair the ventilated air flow. This must be considered when designing greenhouses.
Roofs of conventional glass greenhouses are provided with ventilation windows that can be opened and closed. When installing insect nets in such windows, the net installation must be flexible to fill the opening of the window when it is opened, but also be able to fold out of the way of the closing window. One conventional way of doing this is to confection an accordion-type of net construction as seen in
To be able to produce such a construction it is conventional to first produce insect net lamellas, which thereafter are confectioned together into the accordion shape. The lamellas are easily produced using conventional band weaving technique resulting in lamellas with closed longitudinal edges, which can be confectioned with sewing machines.
However, there is also a substantial disadvantage of this way of making insect nets, since band weaving produces double weft inserts, and double yarns next to each other decrease the air flow through the net. Without double weft inserts, the airflow increases typically 30-50%.
To avoid this problem, a conventional full width weaving loom can be used, producing a net typically 2-4 m wide. This insect net can be chosen to have any weaving pattern, thereby optimizing ventilation and insect exclusion. The net is later cut into lamellas using a one-step ultrasonic cutting and welding process, leaving a closed edge on the net lamella, suitable to confection with a sewing machine.
The above objects may be achieved with an insect net strip in accordance with claims 10 and 11, obtained by using the one-step ultrasonic cutting and welding method of claim 1. The insect net strips are used according to claim 26 in accordion-style insect net constructions of claim 24. Further embodiments are set out in the dependent claims, the description and in the drawings.
As set out herein there is provided a one-step ultrasonic cutting and welding method of manufacturing an insect net strip suitable for confectioning by a sewing machine. The method comprises the steps of
As set out herein there is also provided an insect net strip produced by cutting the insect net described below along its warp direction (xnet) using the one-step ultrasonic cutting-and-welding method disclosed herein. The insect net strip comprises:
At least 90% of the warp and weft yarns of the insect net strip are monofilament yarns made of a thermoplastic material, and
In a further aspect of the invention there is also provided accordion-type assemblies wherein two or more of the inventive insect net strips as described herein which have been produced according to the method also described herein have been sewn together to form accordion-style insect net constructions for use in ventilation openings.
In yet a further aspect of the invention, there is provided a use of the insect net strip as described herein and produced as described herein, in a confectioned accordion-type assembly wherein two or more insect net strips are sewn together.
In the following detailed description, reference is made to the accompanying set of drawings that form a part of the description hereof and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are contemplated and may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense.
The insect net strip 20 described herein is made from a wide (1-5.5 m) woven insect net cut in the warp direction.
At least 90% of the warp and weft yarns in the insect net are monofilament yarns, made of a thermoplastic material. The insect net can be manufactured from monofilament yarns of any conventional thermoplastic fiber material but advantageously >80 wt. % of the thermoplastic monofilament yarn is a polyester or co-polyester conventional for fiber production, the wt. % being calculated based on the total weight of the yarn. Preferably the polyester is polyethylene terephthalate (PET), wherein at least 80 wt. % of the polyester originates from ethylene terephthalate monomers. Additives and other polymers make up the rest. The thermoplastic monofilament yarn material typically has a melting point of 240-260° C. and a density of 1.3-1.5 g/cm3.
Since high air permeability is vital to be able to cool and dehumidify the greenhouse, air permeability is a very important factor in the performance of the insect nets when placed in ventilation openings. However, the main purpose for applying an insect net in openings of a greenhouse is to prevent harmful insects from entering the greenhouse, as well as in some instances, preventing useful insects from escaping the greenhouse. This will only be successful if the size of each one of the open areas in the insect net is small enough to prevent insect passage. Thus, when manufacturing an insect net there is an important balance between optimizing the important air permeability, while at the same time preventing insects from passing through the net.
To optimize air flow, i.e., to increase the air flow, the insect net disclosed herein has a weaving pattern wherein at least 40%, preferably at least 60%, more preferably at least 80%, of the weft inserts are single yarn inserts. Weaving with single weft inserts is advantageous since it enables many different weaving patterns that can optimize insect control. Single weft inserts are advantageous compared to double weft inserts which often diminish air permeability, as will be explained below.
Another factor influencing the air permeability of an insect net is its relative hole area (Ah). The larger the hole area the insect net has, the better air permeability becomes. The insect net used for manufacturing insect net strips herein has a relative hole area in a two-dimensional projection (Ah) of 15-50%. However, the relative hole area for the insect net is normally 20-48% to avoid passage of some common insects (see below). The relative hole area in a two-dimensional projection is defined by the ratio of the area of holes to the area covered by yarns in a given area of insect net, and is calculated as follows:
For example, in an insect net wherein
This means that 48% of the total area of the net is covered with holes, the rest (i.e., 52%) is covered by yarn.
This should be compared to an insect net with double weft inserts wherein the dimension of the hole is the same, i.e., 0.70 mm×0.40 mm, the warp yarn diameter (øwa) is 0.23 mm, and the weft yarn diameter (øwe) is 0.20 mm.
Such an insect net has a relative hole area (Ah) of
With double weft inserts which is often used in conventional band weaving, the air permeability is less, 40% as compared to 48% with single weft inserts. With wide weaving the weave can be optimized for insect control and high air flow, meaning better possibility to cool and dehumidify the greenhouse, while still preventing passage of unwanted insects.
The insect net disclosed herein has a hole size of 0.10-0.70 mm in a two-dimensional projection, i.e., in warp and weft directions of the insect net 10. Preferably the hole size in a two-dimensional projection of the insect net 10 is 0.10-0.60 mm, more preferably 0.10-0.50 mm, most preferably 0.15-0.40 mm. This means that the holes of the insect net should have an extension in the warp and/or weft direction of 0.10-0.70 mm, i.e., the extension a in the weft direction is 0.10-0.70 mm and the extension b in the warp direction is between 0.10 to 0.70 mm. The hole size of the insect net limits the possibility for insects to enter/exit the greenhouse and should be adjusted depending on the type of insect the net is intended to stop. Whiteflies (of the family Aleyrodidea) are stopped by holes having a size of about 0.28×0.38 mm, and Thrips require holes having the size 0.15×0.15 mm, or less to prevent passage.
The insect net disclosed herein has a cross-sectional weft yarn area per net length (A′we/x) of 20-80 mm2/m in a warp yarn direction. Advantageously, the cross-sectional weft yarn area per net length (A′we/x) is 25-70 mm2/m in a warp yarn direction. The cross-sectional weft yarn area per net length indicates the area of material the weft yarns accumulate per unit length in the warp direction and is influenced both by the weft yarn diameter (øwe) and weaving picks per cm.
The cross-sectional weft yarn area per net length in the warp yarn direction (A′we/x) of the insect net is determined by the cross-sectional area (A′we) of the weft yarn 12 used for weaving the insect net 10, and the number of weaving picks per meter in the warp yarn direction (xnet). Each weft yarn 12 has a cross sectional area A′we=π·r2 measured in mm2. The weaving picks indicates the number of weft yarns 12 inserted between the warp yarns 11 per meter in the warp yarn direction (xnet) and depends on the distance between two adjacent weft threads, i.e., the length (b) of a hole 13, as well as the diameter of the weft yarn (øwe), both measured in mm (see
A method of manufacturing an insect net strip 20 from the insect net 10 as disclosed above will now be described. The insect net strips 20 are advantageously used for confectioning accordion-type insect net assemblies 63 (see
A one-step ultrasonic cut and seal process is used to manufacture the insect net strip 20, wherein the method comprises the steps of
The ultrasound cutting and welding tools 42 are advantageously cutting wheels (see detail of
Advantageously an ultrasonic device 40 wherein the cutting and welding tool 42 is a rotating blunt U-, V- or a mixed U/V-shaped cutting edge is used. The advantage of a rotating wheel is the slower blunting of the edge. The machine also runs smoother with less friction.
When the ultrasonic cutting and welding tools has a V-profile it advantageously has an edge angle α of 80°-175°, preferably an edge angle α of 100°-175°, or more preferably an edge angle α of 120°-170° (see
When the ultrasonic cutting and welding tools has a U-shape it advantageously has an edge radius r of 0.25-3.00 mm, preferably an edge radius r of 0.50-2.00 mm (see
When the ultrasonic cutting and welding tools has a U/V-mix profile it advantageously has an edge angle α of 80°-175°, preferably an edge angle α of 100°-175°, or more preferably an edge angle α of 120°-170°, and an edge radius r of 0.25-3.00 mm, preferably an edge radius r of 0.50-2.00 mm (see
The ultrasonic cutting and welding tool may also have a V-profile with more than one angle, wherein the first angle α1 is 80°-130° and the second angle α2 is 120°-175° (see
The ultrasonic energy is applied through a sonotrode 41 (see detail of
The ultrasonic cutting and sealing device must apply enough energy in relation to the speed feeding the insect net 10 through the ultrasonic cutting device 40 to be able to properly melt together the weft yarns resulting in a sealed edge. The cutting edge of the cutting and welding tool 42 must have an angle large enough to not just cut, but also to melt the adjacent material. Merely cutting can be performed with a sharper tool and is an easier task than the combined sealing/melting process described herein.
The shape of the cutting tool 42 and the power applied will result in a deformed (melted) zone 26 some distance away from the edge as seen in
In a further embodiment, the ultrasonic cutting and welding tool 42 may be provided with a flat anvil block 46 which is placed in front of the cutting wheel (see
The flat anvil block 46 ensures that at least one warp yarn 22 is included in the deformation zone 26, resulting in reliable edges for the insect net strip 20 without risk of warp yarns 22 unraveling from the edges 24, 25.
The resulting edges 24, 25 are suitable for further confectioning of insect net systems if the weft yarns are connected (melted together) in most cases. The edge is considered suitable if 90% or more of the gaps between adjacent weft yarns in the deformation zone 26 have a mechanical connection by weft yarns being melted together. The deformation zone 26 along the insect net strip is visible under a microscope and can be measured on the end product.
At least 90% of the warp and weft yarns 21, 22 of the insect net strip 20 are monofilament yarns, made of a thermoplastic material. The insect net strip 20 can be manufactured from monofilament yarns of any conventional thermoplastic fiber material but advantageously >80 wt. % of the thermoplastic monofilament yarn is a polyester or co-polyester conventional for fiber production, the wt. % is calculated based on the total weight of the yarn. Preferably the polyester is polyethylene terephthalate (PET), wherein at least 80 wt. % of the material originates from ethylene terephthalate monomers, with the remaining 20 wt. % being additives and/or other polymers. Such a material typically has a melting point of 240-260° C. and a density of 1.3-1.5 g/cm3.
The insect net strip 20 has a weaving pattern wherein at least 40%, preferably at least 60%, more preferably at least 80%, of the weft inserts 22 are single yarn inserts. As explained above for the insect net, weaving with single weft inserts provides the insect net strip with advantageous air-permeabilities.
Advantageously, the insect net strip 20 has a relative hole area (Ah) in a two-dimensional projection of 15-50%, but in order to better prevent insect passage, the relative hole area (Ah) for the insect net strip is advantageously 20-48%. The relative hole area (Ah) in a two-dimensional projection is defined by the ratio of the area of holes to the area of yarns in a given area of insect net strip and is calculated as shown for the insect net in Formula I above.
The insect net strip 20 disclosed herein has a hole size of 0.10-0.70 mm in a two-dimensional projection, i.e., in both the longitudinal and transverse direction of the insect net strip 20. Preferably the hole size in a two-dimensional projection of the insect net strip 20 is 0.10-0.60 mm, more preferably 0.10-0.50 mm, most preferably 0.15-0.40 mm.
The insect net strip 20 disclosed herein has a cross-sectional weft yarn area per net length (A′we/x) of 20-80 mm2/m in a longitudinal direction (xstrip). Advantageously, the cross-sectional weft yarn area per net length (A′we/x) is 25-70 mm2/m in a longitudinal direction (xstrip). The cross-sectional weft yarn area per net length (A′we/x) indicates the material area the weft yarns 22 add per unit length in the longitudinal direction (see
The insect net strip 20 is obtained by cutting the insect net 10 described above in the warp direction (xnet) into strips 20 having a width (wstrip) in the transverse direction (ystrip) of 0.030-0.110 m, preferably a width of 0.050-0.090 m.
After cutting the insect net 10 using the method described herein, the obtained insect net strip 20 will have a first edge 24 and a second edge 25 extending in a longitudinal direction of the insect net strip 20 (i.e., in a warp direction (xstrip)) and parallel to the warp yarns 21. The first and second edges 24, 25 each comprise a deformation zone 26 being constituted by consolidated thermoplastic material deriving from at least the weft yarns 22 which have melted together to form a deformation zone 26.
The deformation zone 26 is defined as the average distance between the outer edge 24, 25 and the visual deformations that has affected the roundness of the outer-most tips of the weft yarns and can be measured under a calibrated microscope.
The deformation zone 26 will have a length along the first and second edge 24, 25, and a width (wdz) in the transverse direction (ystrip), wherein the width (wdz) of the deformation zone 26 is 0.5-35 times the weft yarn diameter (øwe) as seen in
This means that with a weft yarn diameter of 0.15 mm, the width (wdz) of the deformation zone 26 is between 0.075 mm to 5.25 mm, and with a weft yarn diameter of 0.23 mm, the deformation zone 26 is between 0.115 mm and 8.05 mm wide. Preferably the deformation zone 26 has a width (wdz) which is 0.6-25 times the weft yarn diameter (øwe), 0.7-20 times the weft yarn diameter (øwe), or more preferably the deformation zone 26 has a width (wdz) which is 0.8-15 times the weft yarn diameter (øwe).
To form strong first and second edges 24, 25 which will enable good confectioning and prevent unraveling, at least 90% of gaps 23 between adjacent weft yarns 22 in the deformation zone 26 must be closed by consolidated thermoplastic material deriving from at least the weft yarns 22 which have melted together. This means that no more than one gap 23 out of ten gaps 23 between two adjacent weft yarns 22 in the deformation zone 26 is left unclosed along the cut edge 24, 25. Preferably at least 92%, such as at least 94%, such as at least 96% of the gaps 23 between adjacent weft yarns 22 are advantageously closed by consolidated thermoplastic material from the weft yarns 22 having been melted together in the deformation zone 26.
When used herein, the expression “closed by consolidated thermoplastic material” is intended to mean that adjacent weft yarns 22 together with preferably no more than two warp yarns 21a, 21b are melted together with each individual weft yarn 22 in the deformation zone 26 and form a continuous, or substantially continuous reinforced band-shaped edge portion 24, 25 of the insect net strip 20. Ideally, at most one warp yarn 21a is melted together with each individual weft yarn 22 in the deformation zone 26 to form a continuous, or substantially continuous reinforced band-shaped edge portion 24, 25 of the insect net strip 20.
As described above, the width (wdz) of the deformation zone depends on weft yarn thickness. A thinner yarn may give a narrower deformation zone but can still result in a well-sealed edge if the weft material area per net length (A′we/x) is high enough. Wider deformation zones require more power to produce, and consequently there is a practical/economical upper limit of how wide the deformation zone should be.
There is also a disadvantage with a deformation zone which is too wide or solid since it will be harder for a needle to penetrate when confectioning. Very wide deformation zones also tend to smear the melted plastic, resulting in an uneven edge, which also is negative in confectioning.
There are several advantages in manufacturing the insect net strips 20 using the method disclosed herein as compared to conventional band weaving to produce the lamellas. The most important advantage being the possibility to use many different weaving patterns and the avoidance of any double weft inserts. With conventional band weaving double weft inserts are often used which will diminish air permeability of the insect net. With wide weaving, the weave can be optimized for insect control and high air flow, resulting in an improved possibility to cool and dehumidify the greenhouse.
Careful selection of weft yarns and the number of picks per centimeter will give the insect net strip 10 a high stiffness in the weft direction, making the finished
accordion construction robust and more self-supporting, thereby reducing the need of other mechanical support to hold the construction in place in the greenhouse. The shape of the holes in the net may be turned such that they have their longest extension in the weft direction. In this way more material is available for the one-step ultrasonic cut and seal process which will also improve the stiffness in the weft direction, making a subsequent accordion construction stiffer, thereby further reducing the need for extra support in the final product.
Since the selection of warp yarns is of less importance in the present process, it is instead possible to use the warp yarns to optimize the net for insect control and high air flow.
Another advantage is that narrow edges are produced on each side of the insect net strip by the method disclosed herein. Conventional band weaving produces lamellas with bulky selvage edges. This can be seen in
The ultrasonic cutting and sealing technique used in the present method provides an insect net strip with a smooth edge having a deformation zone with a limited width. Weft yarns and the number of picks per centimeter can be selected to give a cross-sectional weft yarn area per net length which is high enough for the edges along the insect net strip to be sealed without including any warp yarn, or at the most one warp yarn. However, one, or at most two warp threads may be included in the deformation zone with consolidated weft and warp yarns. As long as at least 90% of the gaps between adjacent weft yarns are closed, the edges are suitable for confectioning.
The narrow deformation zones are advantageous since wide areas with melted plastic are more difficult for the needle on the sewing machine to penetrate. When lamellas are sewn together to an accordion-type assembly later in the process, the total thickness of the construction becomes substantially lower (>25%) using insect net strips produced with the method disclosed herein. In a greenhouse, everything that is smaller in the ceiling means less shading and more light reaching the plants.
Weaving wider nets and thereafter cutting them into narrow strips using the one-step cutting and sealing method described herein provides a great advantage for the end product.
The insect net strips 20 produced by the disclosed method are advantageously used for producing accordion-type insect net assemblies 63 (see
During production of an insect net accordion-style assembly 63, two insect net strips 20a, 20b are put flat on top of each other and sewn together along one edge 24, 25 at the most 10 mm from the outer edge 24, 25. An additional insect net strip 20c is put on top of the first two and sewn together with the upper most insect net strip 20b along the opposite longitudinal edge 24, 25 in the same way. This can be repeated with the desired number of insect net strips 20 to form an accordion-style assembly 63 as seen in
Since the insect net strips 20 are made from a material which is stiff enough, no undesired creases or folds will form and when the accordion-style assemblies 63 are folded shut, the individual insect net strips 20 will lie flat against each other.
For the side screens 61, a triangular recess 64 is cut from the accordion-style assembly 63 as can be seen in
The accordion-type screen construction 60 can be used in all greenhouse ventilation openings to stop unwanted insects entering the greenhouse. The accordion style confectioning gives a larger total net area than a flat net, with typically 20-40% higher air flow through the ventilation opening. It is also a flexible construction and easily fixed in a greenhouse ventilation window that can be opened and closed. An example of an accordion style construction is described in NL1007720(C2).
The following examples disclose net insect strips having been cut using the one-step cutting and sealing method described herein.
The same applies to the insect net strip shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2150652.2 | May 2021 | SE | national |
| 2151184.5 | Sep 2021 | SE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/063621 | 5/19/2022 | WO |
