Support Poles

Abstract

A method of forming a support pole, comprising splitting one or more canes of bamboo, or similar tubular plant material, into a plurality of split lengths; inserting a bundle of the split lengths from one or more canes into an outer tube (4); tilting the outer tube (4) at an angle from horizontal and injecting a matrix material into the outer tube (4) so as to fill in between the split lengths and encapsulate the split lengths to form a substantially solid core. The method may comprise injecting the matrix material at multiple injection points (25a, 25b, 25c, 25d) along the length of the tube (4).

Claims

1. A method of forming a support pole, comprising: splitting one or more canes of bamboo, or similar tubular plant material, into a plurality of split lengths; inserting a bundle of the split lengths from one or more canes into an outer tube; and tilting the outer tube at an angle from horizontal and injecting a matrix material into the outer tube so as to fill in between the split lengths and encapsulate the split lengths to form a substantially solid core.

2. The method according to claim 1, further comprising applying a vacuum at a high point along the tilted tube.

3. The method according to claim 1, comprising injecting the matrix material at multiple injections points along the length of the tube, wherein the multiple injections points comprise a first injection point that is lower than subsequent injection points along the tilted outer tube.

4. The method according to claim 3, wherein the multiple injections points comprise a final injection point that is higher than all the other injection points, the method further comprising applying a vacuum at another point that is even higher than the final injection point.

5. The method according to claim 1, further comprising closing at least an upper end of the outer tube with a convex end cap before injecting the matrix material into the tilted outer tube.

6. A method of forming a support pole, comprising: splitting one or more canes of bamboo, or similar tubular plant material, into a plurality of split lengths; arranging a bundle of the split lengths from one or more canes inside an outer tube; and closing at least one end of the outer tube with a convex end cap and injecting a matrix material into the outer tube so as to fill in between the split lengths and encapsulate the split lengths to form a substantially solid core.

7. The method according to claim 6, comprising butt welding each convex end cap onto an end of the outer tube.

8. The method according to claim 1, comprising injecting a polyurethane foam as the matrix material.

9. The method according to claim 1, comprising injecting the matrix material into the outer tube so as to fill in between the split lengths and encapsulate the split lengths to form a solid core containing substantially no voids.

10. The method according to claim 1, further comprising inspecting how the matrix material fills in between the split lengths in the outer tube using infrared radiation emitted from the core.

11-15. (canceled)

16. The method according to claim 1, further comprising arranging a plurality of split lengths having different lengths in a longitudinally parallel arrangement to form a bundle having a greater number of split lengths at one end than the other end.

17. The method according to claim 1, wherein splitting one or more canes of bamboo further comprises separating the split lengths and supporting them while air drying.

18. The method according to claim 1, wherein splitting one or more canes of bamboo further comprises removing any internal nodes from the split lengths.

19. A support pole made according to the method of claim 1.

20. A support pole comprising an outer tube and a substantially solid core that comprises a plurality of split lengths of one or more canes of bamboo, or similar tubular plant material, encapsulated by a matrix material inside the outer tube, Wherein one or both ends of the outer tube is closed by a convex end cap.

21-24. (canceled)

25. The support pole according to claim 20, comprising a greater density of bamboo, or similar tubular plant material, at one end than the other end.

26. The support pole according to claim 20, wherein the substantially solid core comprises at least 20% by volume of split lengths.

27. (canceled)

28. The support pole according to claim 20, wherein the pole has a weight per unit length less than 25 kg/m.

29. The support pole according to claim 20, wherein the pole has a density between 300 kg/m.sup.3 and 600 kg/m.sup.3.

30. The support pole according to claim 20, consisting of a utility pole.

Description

[0057] Some preferred embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0058] FIG. 1 shows a support pole made from whole canes of bamboo encapsulated in a matrix material as described in WO 2014/001811;

[0059] FIGS. 2a-2e show the steps involved in forming a bundle of bamboo split lengths according to embodiments of the present invention;

[0060] FIGS. 3a-3b show the steps involved in inserting a bundle of split lengths into an outer tube according to embodiments of the present invention;

[0061] FIG. 4 shows the attachment of end caps to the outer tube according to embodiments of the present invention;

[0062] FIG. 5 shows filling of a tilted outer tube according to embodiments of the present invention;

[0063] FIGS. 6a-6c show the structure of a support pole made according to embodiments of the present invention;

[0064] FIGS. 7a-7b show a support pole closed by end caps according to embodiments of the present invention; and

[0065] FIG. 8 shows some cantilever test results for support poles made according to different manufacturing techniques.

[0066] There is seen in FIG. 1 a cross-sectional view of a support pole made according to the methods described in WO 2014/001811. The support pole 2 comprises an outer tube 4, for example a polyethylene (e.g. HDPE) tube, that contains a core volume comprising substantially whole canes or stems of bamboo 6 encapsulated in a matrix material 8 such as PUR foam. Prior to filling the outer tube, the bamboo canes 6 have longitudinal slots cut into their side walls so that the matrix material 8 is able to access the internodal cavities of each cane. However, the Applicant has found that the ability of the matrix material 8 to fill the internodal cavities is in practice very sensitive to multiple factors and it can be difficult to ensure that support poles made in this way have a uniform density, both along the length of a given pole and when comparing multiple poles in a manufacturing batch. Accordingly it is now proposed to make support poles using split lengths of bamboo material instead, as will be described with reference to FIGS. 2-7.

[0067] The initial steps for preparation of a bundle of split lengths of bamboo include harvesting, limbing, cleaning, splitting, drying and then bundling. Depending on the bamboo cane diameter, each cane or stem is split into 4-6 individual splits. Splitting can be performed manually (e.g. using a machete) or by a splitting machine. After the split lengths have been air dried they are ready to be bundled. FIG. 2a shows a stand 10 used to form a bundle 12 of split lengths 14. The stand 10 supports a number of jigs 16. In a first step, seen in FIG. 2b, the jigs 16 are open and the split lengths 14 are arranged into a bundle (i.e. longitudinal parallel arrangement). In a second step, seen in FIG. 2c, the jigs 16 are closed around the bundle 12. In a third step, seen in FIG. 2d, ropes 18 are fastened around the bundle 12 and tightened. In a fourth step, seen in FIG. 2e, the final bundle 12 is removed from the jigs 16.

[0068] The tight bundle 12 is then ready to be inserted into an outer tube 4, as is shown by FIGS. 3a and 3b. FIG. 3a shows the bundle 12 supported by a stand 10 while an outer tube 4 is slid around the bundle 12. FIG. 3b shows the outer tube 4 containing the bundle of split stems. FIG. 4 illustrates how a convex end cap 20 is attached to one or both ends of the outer tube 4. A butt welding machine 22 may be used for fusion of the end caps 20, for example a butt fusion machine version TM 250 or 315 available from Georg Fischer (GF) Piping Systems. The convex end caps 20 ensure that the bundle 12 of bamboo splits is contained in the outer tube 4 and, more importantly, after the outer tube 4 has been filled to form a solid core the resultant pole is resistant to deflections. The convex end caps 20 may be made of the same material as the outer tube 4, e.g. polyethylene.

[0069] FIG. 5 shows a tilted stand 24 used to support the outer tube 4 during the filling process. Multiple openings 25a-25d are spaced along the length of the outer tube 4 to act as injection points for the matrix material. Each injection point is designated by a downwards arrow. The stand 24 supports the outer tube 4 at an angle from horizontal, tilted at approximately 60.5. The matrix material is injected into the tube 4 starting at the lowermost injection point 25a, then moving upwards along the tube 4 to the injection points 25b, 25c, 25d. Throughout the injection process, a vacuum (designated by an upwards arrow) is applied at a final opening 26 which is positioned above the final injection point 25d close to one end of the tube 4.

[0070] Although not shown in FIG. 5, during and/or after the injection process an infrared camera may be moved along the outer tube 4 to provide an image of the solid core being formed inside the tube 4. The infrared images can be used to inspect how well the matrix material is filling between the bamboo splits.

[0071] FIG. 6 shows the internal structure of the resultant support pole 2. Inside the outer tube 4, there is formed a solid core containing bamboo splits 14 encapsulated in the matrix material 8. FIG. 6a provides an overview of the pole 2. FIG. 6b provides a cutaway view of the pole 2, showing how the bamboo splits 14 are in a longitudinal parallel arrangement with the matrix material 8 completely filling the gaps between the splits 14. FIG. 6c provides a cross-sectional view showing the uniform distribution of bamboo splits 14 and complete encapsulation by the matrix material 8 without any voids (e.g. air pockets) being present.

[0072] FIG. 7 shows the external structure of the resultant support pole 2. The outer tube 4 is closed at one or both ends by a convex end cap 20. FIG. 7a provides an overview of the pole 2. FIG. 7b provides a cutaway view of the pole 2, showing how the end cap 20 has a curved surface that is slightly convex away from the solid core 28 inside the tube 4. The solid core 28 is made up of the bamboo splits 14 and matrix material 8 as seen in FIGS. 6a-6c. It has been found that such convex end caps 20 advantageously help the pole 2 to resist deformation when subjected to bending forces.

EXAMPLE

[0073] Various support poles made of bamboo material in a polyurethane matrix with a surrounding outer tube were tested and compared. The materials used were the same, but the poles were formed using different techniques. Pole A (diameter 225 mm; length 9 m) was made from whole hollow stems of bamboo. Pole B (diameter 225 mm; length 9 m) was made from whole stems of bamboo that were slit open as seen in FIG. 1. Pole C (diameter 225 mm; length 10 m) was made from split lengths of bamboo as described above with reference to FIGS. 2-7. The cantilever test method described in Kenya Standard KS 2513:2014 was used to load the poles. The results of this test are seen in FIG. 8. It can be seen from the gradient of load vs. deflection that Pole C was similar to Poles A and B in terms of rigidity, but the maximum or ultimate load achieved with Pole C was much higher (referring to the load figures at the end of each line on the graph). Pole C achieved an ultimate load of 410 kg which was much greater than the ultimate load of 278 kg for Pole B and 228 kg for Pole A. In other words, Pole C was observed to bend elastically over a much greater range of deflection before reaching its ultimate load and hence Pole C is significantly improved in terms of bending strength. Pole C demonstrates the improved properties achieved using methods according to embodiments of the present invention.

[0074] It will be appreciated that various changes or modifications may be made to the embodiments described above. For example, the pole does not need to have a circular cross-section and could instead be made in a rectangular or other form. Other reinforcing material(s) might optionally be embedded in the matrix material inside the pole, in addition to the split lengths of bamboo, for example natural or synthetic fibres, metal rods, wires, grids, etc. and/or plastic or ceramic fibres, rods, particles, etc.

[0075] Poles made according to embodiments of the present invention may be used to support loads in a variety of applications, including utility poles (e.g. power or telegraph poles), and also finding use as fence poles, poles used in growing fruit and berries, and as naval poles for docks, marinas, quays, etc.