TREE SHELTER

Abstract

A tree shelter comprising an elongate tubular body having a wall formed from a biodegradable material comprising a natural fibre substrate and a matrix of a natural binder in which the fibres are held.

Claims

1. A tree shelter comprising an elongate tubular body having a wall formed from a biodegradable material comprising a natural fibre substrate and a matrix of a natural binder in which the fibres are held; wherein the natural fibre is wool.

2. A tree shelter according to claim 1, wherein the natural binder is a plant or insect derived natural binder.

3. A tree shelter according to claim 2, wherein the binder is derived from a natural plant based polyol.

4. A tree shelter according to claim 3, wherein the binder is derived from a cashew nut shell liquid (CNSL) based polyol, a castor nut oil based polyol or a combination of a cashew nut shell liquid (CNSL) and castor nut oil based polyol.

5. A tree shelter comprising an elongate tubular body having a wall formed from a biodegradable material comprising a natural fibre substrate and a matrix of a natural binder in which the fibres are held, wherein the natural fibre is selected from the group consisting of: wool, recycled wool, goat hair, alpaca and angora, or a combination of any two or more of these fibres; and the natural binder is derived from a cashew nut shell liquid (CNSL) and castor nut oil based polyol.

6. A tree shelter according to claim 5, wherein the natural fibre is wool.

7. A tree shelter according to claim 1, wherein the biodegradable material from which the tree shelter wall is formed is translucent or transparent.

8. A tree shelter according to claim 1, wherein the wall of the elongate tubular body is formed from a sheet of the biodegradable material formed into a tube with opposite edge portions of the sheet overlapping one another to form a double thickness wall region in the formed tube.

9. A tree shelter according to claim 8, wherein the width of the double thickness wall region is at least 20 mm.

10. A tree shelter according to claim 8, wherein the wall region comprises attachment formations for use in attaching the tree shelter to a stake.

11. A tree shelter according to claim 10, wherein the attachment formations comprise at least one pair of holes extending through the sheet, whereby the tree shelter can be secured to a stake by passing opposite ends of a strap from within the tube through a respective hole to the outside of the tube around opposite sides of the stake and securing the ends of the strap together.

12. A tree shelter according to claim 11, wherein the tree shelter is intended for use with a stake having a predetermined width, inner edges of the at least one pair of holes being spaced from one another by a distance that is greater than the width of the stake, whereby when the strap is tightened around the stake, the strap cuts into the sheet adjacent the inner edges of the holes.

13. A tree shelter according to claim 11, further comprising the strap, wherein the strap is a metal tie.

14. A tree shelter according to claim 1, wherein a top end portion of the wall of the elongate tubular body is flared outwardly or rounded.

15. A tree shelter according to claim 1, comprising a plurality of ventilation holes extending through the wall of the elongate tubular body, wherein there are no ventilation holes in at least the bottom 0.45 m of the wall.

16. A tree shelter according to claim 1, comprising at least one longitudinal line of weakness in the wall of the tubular body extending the full height of the wall.

17. (canceled)

18. (canceled)

19. A biodegradable sheet material comprising a natural fibre substrate and a matrix of a natural binder in which the fibres are held, wherein: the natural fibre is wool; and the binder is derived from a natural plant based polyol.

20. A biodegradable sheet material according to claim 19, wherein comprising a natural fibre substrate and a matrix of a natural binder in which the fibres are held, wherein: the natural fibre is selected from the group consisting of: wool, recycled wool, goat hair, alpaca and angora, or a combination of any two or more of these fibres; and the binder is derived from a cashew nut shell liquid (CNSL) and castor nut oilbased polyol.

21. A tree shelter according to claim 1, wherein the natural fibre substrate and binder are selected such that when they degrade they break down to form nitrogen, CO.sup.2 and H.sup.2O.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 shows an elevation of a tree shelter according to an embodiment of the invention;

[0044] FIG. 2 is a top plan view of the tree shelter of FIG. 1;

[0045] FIG. 3 illustrates a process for constructing the tree shelter of FIG. 1;

[0046] FIGS. 4a, 4b and 4c illustrate the steps of attaching a tree shelter to a stake with a tie (e.g. a metal tie);

[0047] FIG. 5 illustrates a preferred light transmission spectrum for the walls of a tree shelter; and

[0048] FIG. 6 shows light transmission spectrum results from a test of a material made in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

[0049] An embodiment is described below by way of example with reference to the accompanying drawings.

[0050] The tree shelter 10 illustrated in FIGS. 1 and 2 addresses problems identified with known tree shelters by providing a sustainable, biodegradable, non-plastic alternative, whilst retaining desired characteristics including a translucent, hydrophobic and UV resistant wall, along with the required strength to provide the desired physical protection for a sapling tree.

[0051] The tree shelter 10 in the illustrated example has an elongate, tubular body 12 formed from a sheet of material that is rolled into a tube, with opposite edge portions 12a, 12b of the sheet overlapping to form a double-walled portion 14 (as best seen in FIG. 2). In this example the tube 12 has a generally circular cross-section but other cross-sectional shapes can be used.

[0052] The overlapping wall portions include wire tie attachment holes 16 towards the top and towards the bottom of the tube, via which the tube can be secured to a stake 18 (typically a wooden stake) by metal ties 20. The overlapping portions have pairs of holes 16 that are brought into alignment when the ends 12a, 12b of the sheet are overlapped, allowing opposite ends of a metal tie 20 to be pushed from the inside of the wall portion through respective aligned holes 16 so as to protrude outwardly from the tree shelter wall. The ties 20 can then subsequently be used to secure the shelter to the stake 18, as described further below. In the illustrated example, the ties pass from the inside of the tube through both overlapping ends 12a, 12b of the sheet. In other examples, the ties 20 may pass through holes only in the outer of the two overlapping ends of the sheet, so that the inner part of the tie is between the two overlapping ends 12a, 12b.

[0053] The tree shelters 10 can be formed in any number of different sizes. Typically, they will have diameters (inside and/or outside) in the range of about 7 cm to about 20 cm. The dimensions need not be precise and manufacturing tolerances need not be tight, so diameters may vary by a few millimeters from tube to tube. Typically, tree shelters for tree saplings will have diameters between 7 cm and 12 cm, tree shelters for shrubs will typically have larger diameters up to 20 cm, and tree shelters for vines (“vine shelters”) will have diameters similar to those of a shelter for tree saplings. The heights of the tubes typically range from 0.6 m to 1.2 m. Whilst taller tubes could easily be manufactured, they become cumbersome to handle and if a taller shelter is required it is more usual to stack two shelters on top of one another (e.g. to put a 0.6 m tube or a 0.75 m tube on top of a 1.2 m tube). The tube wall thickness will generally be in the order of a few millimeters, for example 2 to 3 mm. The wall overlap 14 will generally be 20 cm to 40 cm, with 30 cm being a typical overlap.

[0054] The sheet material from which the tree shelter body 12 is formed is a natural fibre, wool in this example, in a matrix of a natural binder, in this example a TPU binder derived from a cashew nut shell liquid (CNSL) and castor nut oil based polyol.

[0055] These materials are naturally hydrophobic, UV resistant and resistant to microbes. They can be formed into a sheet material that has the desired semitransparent (i.e. translucent) characteristic to ensure sufficient light can penetrate the tube wall, as well as being smooth surfaced (to avoid damage to the sapling tree growing inside), lightweight and sufficiently strong to protect the tree from wind and animal damage. The material also provides an effective barrier to herbicide spray.

[0056] The wall of the shelter includes a line of spaced apart slits 22 through the wall, the line extending from the top of the tube 12 to the bottom. There is a corresponding line of slits diametrically opposed on the other side of the shelter (although in some embodiments only a single line of slits is used). The slits 22 provide lines of weakness, as discussed above, so that the tree can push apart the tubular shelter wall as the tree grows.

[0057] In embodiments where the overlapping portions 12, 12b of the tube are held together by the ties, in addition to the slit lines, or as an alternative, the metal ties 20 can be designed (in terms of materials, shape and size) to erode at a rate that means they rust away within a desired time frame (4 to 5 years), thus releasing the tree shelter 10 from the stake 18 and releasing the overlapping wall portions 12a, 12b of the shelter from one another. This allows the tree shelter wall to expand as the growing tree pushes against it.

[0058] The wall of the shelter also includes an array of ventilation holes 24. These extend in several rows, one above the other, around the full circumference of the wall. The lowest row of ventilation holes 24a is at least 0.45 m from the bottom of the tube, to provide a herbicide resistant base portion 26 of the tube, as discussed above.

[0059] FIG. 3 broadly outlines the process by which the tree shelter is constructed.

[0060] First, the wool/CNSL and castor nut oil polyol TPU sheet material is formed. In one exemplary process, the wool is provided as a web (typically in a roll form). The wool web is drawn off the roll into a generally flat web, where it can be sprayed on one or both sides with a polyol composition to coat the wool fibres. The coated wool web is then semi-cured to form a natural, semi-cured TPU matrix in which the wool fibres are bound.

[0061] Next, the sheet material is pressed to reduce its thickness to the order or a few millimeters before it is cut to size, for example die cut, and the features, including the ventilation holes, the holes for the ties, the slits to form the lines of weakening and the flared or rounded top edge are formed. In some cases, some or all of these features can be formed prior to or at the same time as the sheet is cut to size.

[0062] The sheet material is then formed into a tube. To do this, the cut sheet is rolled around a mandrel with the ends of the sheet overlapping and the overlapping ends are pressed. As part of this process, the flared top rim is also formed in the tube. The formed tubes then go through a final curing process to fix the shape of the tube and bond the overlapping portions to one another.

[0063] Conventional isocyanate-based polymerization methods can be employed to form the TPU, as will be understood by the skilled person. In other examples, non-isocyanate polymerization methods may be used to form the TPU from the CNSL/castor nut oil polyol.

[0064] This tube formation step is completed, in this example, as part of the original manufacturing process.

[0065] Alternatively, the tree shelters can be packed and transported in a flat format and subsequently rolled into tubes at another site. This may be desirable, for example, where the tubes are being shipped long distances and transport costs can be significantly reduced by shipping the flat sheets.

[0066] Once the tubes are formed, the ends of the metal ties can be pushed through the attachment holes from the inside of the tube, ready for installation. Preferably, once inserted through the tube wall, the ends of the ties are twisted together and the tie is shaped so that it can easily be dropped over a stake. This makes installation quick and easy because all that is required is to drop the tree shelter into place (e.g. over a sapling tree), with the ties around the stake, and then for the installer to add a few more twists to the metal tie to tighten it against the stake.

[0067] To install the shelter, the wooden stake is driven into the ground adjacent a newly planted sapling tree. The shelter is then placed over the tree with the stake arranged against the double-walled portion of the tube and with the wire ties around the stake. Additional turns are then applied to the wire tie to secure the ties around the stake, pulling the wall of the tree shelter against the stake and securing it in place.

[0068] As shown in FIG. 4a, the attachment holes are spaced either side of the stake, so that inner edges of the holes are offset to opposite sides of the stake. This means that as the metal tie is initially brought around the stake, the tie is held away from the stake where is passes through the holes (as seen in FIG. 4b). However, as the metal tie is tightened, as seen in FIG. 4c, the metal tie cuts into the tree shelter wall adjacent the inner edges of the attachment holes, until it is pulled tightly against the stake. This attaches the tree shelter very securely to the stake.

[0069] Tree shelter stakes typically have a 25 mm square cross-section. Consequently, the inside edges of the attachment holes are preferably spaced apart by a minimum of about 30 mm, more preferably by a minimum of about 35 mm, 40 mm or more. Generally, it will not be desirable for the holes to be spaced apart by more than 50 mm, as the slits cut by the wire tie as it is tightened could be great long enough to start to affect the integrity of the tube wall.

[0070] The attachment holes may be formed in single-layer portions of the wall, either side of the overlapping, double wall portion that is to be placed adjacent the back of the stake. The metal tie can cut more easily into the single thickness wall.

[0071] For larger tree shelters, 32 mm stakes may be used and the spacing of the attachment holes for tree shelters to be used with these stakes can be set accordingly.

[0072] In addition to providing protection for saplings and small trees, it is important that the tree shelter provides an appropriate environment for plant growth. In particular, as well as providing adequate ventilation, it is important to ensure that sufficient light reaches the plant within the shelter.

[0073] In addition, it is recognized that the spectrum of the transmitted light is important, as different wavelengths of light are more or less important to plant growth. For example, the red light wavelengths (600-700 nm) are among the most effective for stimulating photosynthesis and promoting biomass growth. With this in mind, FIG. 5 shows a preferred light transmission spectrum for the walls of a tree shelter.

[0074] By appropriate design of the tree shelter wall material, the walls can be engineered to transmit an adequate level of light. Typically, it is adequate if the walls transmit 70% to 80% of incident light.

[0075] FIG. 6 shows light transmission spectrum results from a test of a material made in accordance with an embodiment of the invention, using wool and a natural CNSL and castor nut oil polyol TPU binder. It can be seen that this combination of materials can effectively transmit light in the important 600-700 nm spectrum.

[0076] As the tree grows, the tree shelter tube and the metal ties will slowly degrade over a period of, typically, 5 to 7 years (depending on environmental conditions) and will eventually fall away or be forced apart by the tree from the now established tree and harmlessly continue to degrade on the ground, along with the metal ties.

[0077] Advantageously, as discussed above, the wool and CNSL/castor nut oil polyol TPU binder break down to release nitrogen, CO.sup.2 and H.sup.2O as they degrade, helping to support plant growth.

[0078] If the tree grows sufficiently to press against the walls of the shelter before it has broken away through degradation of the tube and ties, the shelter expands and breaks apart along the split lines, thus avoiding any constraint on tree growth.

[0079] The skilled person will understand that various modifications and additions can be made to the examples described above without departing from the spirit and scope of the present invention.