Support Poles

Description

TECHNICAL FIELD

The present invention relates to support poles and methods of manufacturing support poles.

BACKGROUND

Support poles such as utility poles, also known as telephone poles, power poles, hydro poles (e.g. in Canada), telegraph poles or telegraph posts, are conventionally made of solid timber. There have also been proposals for utility poles made of metal, concrete, or composites like fibreglass. Utility poles may typically be used for low and medium voltage power transmission, communications (e.g. carrying fibre-optic lines for internet connectivity), or overhead irrigation systems. As the poles are usually spaced relatively close together in a power transmission network, a huge number of poles is needed and they must allow for ease of installation and maintenance.

Conventional timber poles are vulnerable to attack by pests such as termites, rodents and woodpeckers. The lifetime of timber poles is usually extended by treating them with creosote or other chemicals as a pesticide. However, such treatment adds to maintenance costs. Moreover, the environmental impact of creosote-treated timber has been called into question, especially the potential pollution of ground water and top soil. Properly treated wooden poles can last for 15-20 years before requiring replacement, but in developing countries such as Africa timber poles are typically left untreated and then only last for less than 10 years. A further problem with using timber for utility poles is its contribution to global deforestation.

Alternative pole materials also have a range of drawbacks. Concrete poles require internal steel reinforcement for strength but the steel component is vulnerable to corrosion while the concrete often degrades quite rapidly, especially if poor quality cement is used. The poles are prone to cracking and brittle fracture. Concrete poles are also very heavy for handling and installation purposes. Cranes or other types of lifting equipment are required for installation. The costs involved in producing and installing concrete poles are higher than for timber poles. The lifetime of even a high-quality concrete utility pole is typically 15-20 years. In many cases, materials recycling after use is not easy.

The costs involved in materials and in manufacturing, transporting, installing and maintaining the poles in a power transmission network may be of particular concern in developing countries, for example in Africa and Asia due to poor infrastructure (e.g. roads) prohibiting the use of large and heavy vehicles. Furthermore the environmental impact (i.e. the carbon footprint) of building the infrastructure in such countries is now a serious factor to be taken into consideration.

NO 20072814 describes a pole made from whole bamboo canes arranged inside an outer tube of plastic with the gaps between bamboo canes partially filled with a rigid matrix material. It is disclosed that such poles have a long lifetime and can be recycled. However, an important consideration in the design of utility poles is the strength requirement. By way of comparison, concrete poles can withstand working loads of at least 2.5 kN. A potential problem with the poles seen in NO 20072814 is that the matrix material may not fill the gaps between bamboo canes very well and leave voids i.e. air pockets that affect strength properties.

WO 2014/001811 describes a method of manufacturing poles by cutting openings into the side walls of whole bamboo canes so as to enable the internodal cavities of the bamboo to be filled with a binder material. This was found to provide a strength improvement as compared to hollow bamboo canes encapsulated in a matrix material. However, the strength and reproducibility of such an “internodal locking” arrangement may depend on the ability of the manufacturing process to reliably fill in and around the bamboo canes with the binder material.

WO 2017/191473 describes a method of manufacturing poles using split lengths of bamboo encapsulated by a matrix material. WO 2021/186082 describes a fibre-reinforced support pole comprising split lengths of bamboo encapsulated by a matrix material.

SUMMARY

The Applicant has recognised that there may be a need for support poles that have improved strength and reliability whilst still providing environmental benefits.

According to a first aspect of the present invention there is provided a support pole extending along a longitudinal axis, the support pole comprising:

• • a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis;
  • a cable inlet;
  • a cable outlet; and
  • a hollow complete tube of bamboo or similar tubular plant material extending within the longitudinally parallel arrangement to provide a cable route from the cable inlet to the cable outlet; and
  • a matrix material that encapsulates the plurality of split lengths and the hollow complete tube.

Thus, it will be recognised by those skilled in the art that support poles according to the embodiments of the present invention may beneficially provide an internal cable route within the hollow complete tube. Providing a cable route with the hollow complete tube facilitates installation (e.g. as a cable can simply be pulled through the cable route rather than being manually attached to the outside of the pole) and also ensures that the cable is protected during use by the hollow tube, the surrounding split lengths and the matrix material. The cable route may be suitable for use with power cables or communication cables.

When bamboo or similar plant material is used with a matrix material as reinforcement it might ordinarily be desirable to avoid hollows or voids to which the matrix material cannot flow, as this could lead to weak points in the resulting structure. However, the inventors have recognised that the use of a complete hollow tube (i.e. a whole tube without any gaps, for instance a cane of bamboo with an unbroken outer wall) into which the matrix material cannot penetrate is useful in embodiments of the current invention, because it can mitigate the cable route being obstructed.

Moreover, the inventors have recognised that providing a complete tube of bamboo or similar plant material within the support pole can actually improve the stiffness of the pole, limiting any structural drawbacks associated with having a hollow volume within the pole.

Bamboo-based poles provide many benefits over conventional timber or concrete utility poles. Bamboo is a very fast growing material and its production does not contribute to deforestation. Bamboo has a unique strength to weight ratio compared to soft wood. Using a matrix material to encapsulate (i.e. fill in and around) the split lengths protects the bamboo from pest damage or environmental degradation. Toxic treatment e.g. with creosote is not required. The poles are expected to have a lifetime of at least 50 years, i.e. much longer than standard utility poles. The manufacturing process does not generate CO₂ emissions, as does the production of cement; rather bamboo collects CO₂ while growing and the opportunity for local bamboo farming can reduce the carbon footprint involved in production. Furthermore the poles are recyclable after use.

The hollow complete tube may consist of a single cane of bamboo or similar tubular plant material. Bamboo (and other similar plants) can grow canes of up to 10 m or more and so a hollow complete tube made from a single cane can be used to form support poles of a reasonable length relatively straightforwardly.

However, in some cases a longer complete tube may be needed than can be practically provided by a single cane. Using a single cane for the complete tube can also be complicated by any defects or deviations in the cane. Therefore, in a set of embodiments the hollow complete tube comprises a plurality of canes of bamboo or similar tubular plant material that are joined together. The canes are preferably joined in a way that maintains resistance to matrix material penetrating into the tube. In a set of embodiments the plurality of canes are joined by organic tape and/or polyester fibre.

The cane(s) of bamboo or similar tubular plant material used to form the hollow complete tube may be processed to connect internodal cavities within the cane(s), to ensure that the cable can pass through the tube.

The hollow complete tube may be sized to accommodate various standard dimensions of cables. The hollow complete tube may have an inner diameter of 1 cm or more, 2 cm or more or 5 cm or more. The hollow complete tube may have an inner diameter of no more than 10 cm, no more than 5 cm or no more than 2 cm.

In a set of embodiments, the hollow complete tube extends along a substantial length of the support pole, e.g. at least 20%, 30%, 40%, 50%, 60% or 70% of the support pole. In some embodiments the hollow complete tube extends along substantially an entire length of the support pole (e.g. more than 80%, 90% or 95% of the length of the support pole). In such embodiments the hollow complete tube may provide a stiff core along the whole pole.

The cable inlet may be formed at an end of the support pole (e.g. within an end 10% of the support pole).

The cable inlet may comprise an aperture in an end face of the support pole that leads to the hollow complete tube. In some examples, the cable inlet may be formed by the hollow complete tube extending to the outside of the support pole (e.g. through the matrix material), e.g. with no significant change in direction from the rest of the hollow complete tube.

However, in a set of embodiments the cable inlet is formed in the side of the support pole. This may be at an end of the support pole or away from an end of the support pole. The cable inlet may comprise an inlet tube that leads from an aperture in the side of the support pole to the hollow complete tube. The inlet tube may also comprise a hollow complete tube of bamboo or similar tubular plant material. The inlet tube may extend at an angle to the main hollow complete tube (e.g. roughly perpendicular). Because the inlet tube leads to the hollow complete tube, it will be appreciated that the inlet tube will also extend at least partially within the longitudinally parallel arrangement.

The cable outlet may be formed at an end of the support pole (e.g. within an end 10% of the support pole). The cable outlet may be formed at an opposite end of the support pole to the cable inlet.

The cable outlet may comprise an aperture in an end face of the support pole that leads to the hollow complete tube. In some examples, the cable outlet may be formed by the hollow complete tube extending to the outside of the support pole (e.g. through the matrix material), e.g. with no significant change in direction from the rest of the hollow complete tube.

However, in a set of embodiments the cable outlet is formed in the side of the support pole. This may be at an end of the support pole (e.g. an opposite end to the cable inlet) or away from an end of the support pole. The cable outlet may comprise an outlet tube that leads from an aperture in the side of the support pole to the hollow complete tube. The outlet tube may also comprise a hollow complete tube of bamboo or similar tubular plant material. The outlet tube may extend at an angle to the main hollow complete tube (e.g. roughly perpendicular). Because the outlet tube leads to the hollow complete tube, it will be appreciated that the outlet tube will also extend at least partially within the longitudinally parallel arrangement.

The support pole may have only a single hollow complete tube, i.e. to provide a single cable route. However, in a set of embodiments the support pole comprises one or more additional hollow complete tubes of bamboo or similar tubular plant material extending within the longitudinally parallel arrangement. The additional tubes may simply provide additional stiffness to the pole. However, in a set of embodiments the additional hollow complete tube(s) provide one or more additional cable route(s). The additional cable route(s) may between from the same cable inputs and outputs as the (first) cable route. However, in some embodiments the support pole comprises at least one additional cable input from which at last one additional cable route runs. Similarly, the support pole may comprise at least one additional cable outlet to which at least one additional cable route runs. In other words, any additional hollow complete tubes may connect the same or different cable inputs or outputs.

In a set of embodiments, the hollow complete tube is located centrally within the longitudinally parallel arrangement (e.g. roughly equidistant from opposite sides of the longitudinally parallel arrangement, or at the centre of a circular or elliptical longitudinally parallel arrangement). Accordingly the hollow complete tube may be located centrally within the finished support pole. This may provide symmetrical improvement in stiffness and provide flexibility on where fixings can be attached to the support pole without potentially impinging on the hollow complete tube.

Alternatively, the hollow complete tube may be located off-centre within the longitudinally parallel arrangement and/or support pole (e.g. nearer to one side of the longitudinally parallel arrangement than an opposite side, or away from the centre of a circular or elliptical longitudinally parallel arrangement). This may be useful for resisting asymmetrical loading conditions and/or for enabling the attachment of longer fixings into the pole. In embodiments featuring multiple hollow complete tubes (i.e. comprising one or more additional hollow complete tubes), some or all of the hollow complete tubes may be located off-centre.

Split lengths of bamboo or similar tubular plant material are formed by splitting whole canes of bamboo or similar tubular plants parallel to their length e.g. to expose the internal internodal cavities. This allows the matrix material to enter the internodal cavities, helping to ensure good distribution of matrix material throughout the support pole. This increases the material density of the longitudinally parallel arrangement and contributes to the strength of the resultant pole. Each cane may be split into several split lengths, e.g. 4-16 split lengths.

In at least some embodiments, preferably some or all of the plurality of split lengths extend along a substantial portion of the length of the longitudinally parallel arrangement, e.g. at least 20%, 30% or 40% of the length of the longitudinally parallel arrangement. Further preferably at least some of the plurality of split lengths extend at least halfway along the longitudinally parallel arrangement, e.g. at least 50%, 60%, 70%, 80% or 90% of the length of the longitudinally parallel arrangement. In a particularly preferable set of embodiments, some or all of the plurality of split lengths extend along substantially the entire length of the longitudinally parallel arrangement (e.g. at least 95% of the length of the longitudinally parallel arrangement). This may result in a particular strong and/or resilient support pole.

Bamboo is a tubular plant material (naturally hollow inside) that belongs to the grass family Poaceae. There are more than 1,000 different bamboo species and nearly a hundred different kinds. However it is an advantage of the present invention that support poles can be made from locally available materials, with a reduced carbon footprint as compared to conventional poles, and so the choice of bamboo or other tubular plant material species may be based on local availability.

In at least some embodiments, in addition or alternatively, the support pole may comprise an outer tube that contains the plurality of split lengths (of bamboo or similar plant material), the hollow complete tube (of bamboo or similar plant material) and the matrix material. One or both ends of the outer tube may be closed (and preferably sealed closed), to help contain the split lengths, complete tube and the matrix material. One or both ends of the outer tube may be closed with end caps or plates.

The outer tube is preferably formed of a polymeric material, e.g. polyethylene. The outer tube can protect against the ingress of water and humidity, ensure that the pole can withstand rough handling, and protect from UV damage. The outer tube determines the final outer diameter of the support pole and therefore using different tubes easily enables manufacture of a range of different diameter poles. This is an advantage over conventional timber poles, where the diameter may be limited by the size of trees used. In a set of embodiments the outer tube has a substantially constant outer diameter along its length, i.e. such that the pole has an outer diameter that is uniform along its length.

In at least some embodiments, the matrix material protects the split lengths (e.g. from moisture, salt or pests such as termites) and prevent degradation of the bamboo. The matrix material may also contribute to the lightweight properties of poles made according to the present invention. The matrix material may be any rigid or semi-rigid material that can be injected (e.g. in molten or liquid form). Examples may include plastics or rubber. A polymeric or elastomeric matrix material may be preferred for its low density. However at least some plastics may not bind very well to the bamboo stems.

In a set of embodiments the matrix material comprises a polyurethane resin, such as a polyurethane (PUR) foam.

In a set of embodiments, the matrix material comprises a bio-based polyurethane (PU) or a recycled polyurethane. The PU may be in the form of a foam, coating or a dispersion. The bio-based PU employed in the matrix material is a product of a reaction of a bio-based polyol with a polyisocyanate (bio-based or otherwise). A recycled PU is a product of a reaction of a recycled polyol with a polyisocyanate (recycled or otherwise).

Using a plant-derived matrix material such as bio-based polyurethane may dramatically reduce the carbon footprint of the support pole, whilst facilitating manufacture and eventual disposal at the end of its life. Some or all components of the bio-based polyurethane more easily be produced near to manufacturing facilities compared to petrochemical-based alternatives, e.g. by growing the necessary plants nearby. Moreover, bio-based polyurethane matrix materials have been found to be stronger and lighter than petrochemical-based alternatives, e.g. enabling the production of longer support poles.

Biopolyols are typically synthesized from the triglycerides contained in vegetable oils, which are esters formed by a molecule of glycerol coupled with three fatty acid molecules. Hence, they are more commonly known as nature oil polyols (NOPs). The three fatty acids can have the same structure, i.e., homotriglyceride (for example, stearin is composed of three stearic acids; palmitin is composed of three palmitic acids), or may differ, depending on the vegetable oil source. Most fatty acids, except for ricinoleic and lesquerolic acids, do not bear any hydroxyl group in their structure, and therefore they have to be functionalized to introduce hydroxyl moieties.

The biopolyols used in the present invention are typically derived from plant-based oils (e.g. vegetable oils), but may also be based on other biomass-derived components such as lignin. Possible sources of plant-based oils include, but are not limited to, caster oil, palm oil, palm kernel oil, peanut oil, linseed oil, olive oil, rapeseed oil, sunflower oil, corn oil and soya bean oil. Some vegetable oils, such as castor oil, are high in ricinoleic acid and thus may be preferred. Vegetable oils such as castor oil, linseed oil and soya bean oil are particularly preferred. Bio-based polyols are typically synthesised by epoxidation followed by nucleophilic ring opening by water, mono-or di-alcohols, alcoholamines or amine. However, they may be synthesised by any known conventional method, such as hydroxylation, ozonolysis, esterification, hydroformylation followed by reduction, or alkoxylation, of the natural oils or fats.

The bio-based carbon content in the polyol, which is a measure of the amount of biomass-derived carbon in a product compared to its total carbon content may be at least 70%, such as 74%, but may be as high as 80% or 90%. 100% of the carbon in the biopolyol may be bio-based carbon.

The bio-based polyols may be a bio-based polyester polyol, bio-based polyester-ether polyol, or mixture thereof. By “polyester polyol” we mean any polymer which contains more than one ester functional group. By “polyester-ether polyol” we refer to polymers comprising both polyether units and polyester units in their molecular chain. The “polyester polyol” or “polyester-ether polyol” contains at least two hydroxyl functional groups.

The polyol preferably comprises no aromatic segments in the backbone of the polymer structure. In other words, the polyol is preferably aliphatic. The polyols are preferably hydrophobic.

The functionality of the biopolyol polymer (i.e. the number of hydroxyl groups present per molecule) may range from 2.0 to 10. Preferably, the functionality is from 2.0 to 4.5, more preferably 2.0 to 3.5. The polyols of the invention preferably have a hydroxyl number of 150-450 mg KOH/g, such as 220-450 mg KOH/g, more preferably 350-450 mg KOH/g. The hydroxyl content may range from 5.0-20.0%, preferably from 8.0-15.0%, more preferably from 10.0-13.0% based on the average OH equivalent [g]=1700/hydroxyl content [%]. The viscosity at 25° C. of the polyols of the invention may range from 10 mPa·s to 10,000 mPa·s, such as 500 mPa·s to 7,000 mPa·s, especially 900 mPa·s to 4,500 mPa·s. The moisture content may be low so that it does not exceed 0.5%. Preferably, the moisture content does not exceed 0.2%, more preferably the moisture content does not exceed 0.1%. The average acid value may range from 1.0-1.6 mg KOH/g, such as 1.2-1.5 mg KOH/g, more preferably 1.3-1.4 mg KOH/g.

Examples of suitable commercially available biopolyols are Merginol 901, Merginol 903 and Merginol 910 from HOBUM. An example of a suitable commercially available recycled polyol is Recypol from RAMPF.

The polyisocyanate may be, but is not limited to, an aliphatic diisocyanate, an aromatic diisocyanate, an alicyclic diisocyanate or a plant-derived isocyanate. For example, the isocyanate may be one selected from the group consisting of toluene-2,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy 1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4′-methylene bis (phenylene isocyanate) (MDI), juriylene diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate, Benzidine diisocyanate and o-nitrobenzidine diisocyanate.

The bio-based polyurethane may be prepared by reaction of the bio-based polyol with the polyisocyanate using routine methods as well known in the art. Similarly, recycled polyurethane may be prepared by reaction of the recycled polyol with the polyisocyanate using routine methods as well known in the art.

A polymeric matrix material, in particular an elastomeric material (such as biobased PUR foam) may provide the poles with a improved flexural strength compared to more rigid matrix materials, allowing the pole to withstand high winds and external vibrations. Using a polymeric or elastomeric matrix material, the poles are capable of absorbing significantly more elastic energy than conventional materials such as steel or concrete. The poles will flex back to their original configuration after loading or offloading. Some elastomeric materials, such as natural or synthetic rubber, may make the support poles too flexible. Polyurethane resin has been found to provide a good balance between resilience and stiffness, i.e. between rigid and flexible properties. Such poles can bend under loads without the PUR matrix material breaking.

Advantageously, support poles according to embodiments of the present invention have been found to have a low weight per unit length, preferably a weight per unit length less than 60 kg/m, e.g. less than 52 kg/m. By way of comparison, a standard concrete pole typically has a weight per unit length of around 100 kg/m, i.e. five times heavier. Support poles according to embodiments of the present invention may therefore provide the same load capacity as standard concrete poles, but they can be more than 80% lighter in weight. Support poles made from stems of bamboo can also be more than 50% lighter than standard timber poles. This makes them easier to handle, reduces transport and installation costs, and reduces the associated carbon footprint.

Support poles according to embodiments of the present invention may find use not only as utility poles (e.g. power or telegraph poles), but also as fence poles, poles used in growing fruit and berries, or as naval poles for docks, marinas, quays, etc. The precise dimensions of the support pole may be selected based on its intended use (e.g. an intended ultimate load capacity). In a set of embodiments, the support pole has a length of at least 2 m. As explained above, the provision of the complete hollow tube and potentially the use of biobased polyurethane for the matrix material can facilitate aid strength, enabling the manufacture of longer poles. In a set of embodiments, the support pole has a length of 10 m or more, 15 m or more, 20 m or more, 25 m or more or 30 m or more. The support pole may have a diameter of between 15 cm and 30 cm (e.g. a diameter of about 18 cm, 20 cm or 22.5 cm).

In a set of embodiments, the support pole comprises at least one reinforcing fibre wound helically around the longitudinally parallel arrangement. The reinforcing fibre resists elongation, providing the support pole with increased resistance to bending loads (i.e. reducing the degree of deflection for a given bending load) and/or an improved flexural strength (i.e. a higher failure point for bending loads). The reinforcing fibre may extend at a helix angle (i.e. relative to the longitudinal axis of the longitudinal arrangement) of between 10° and 45°, e.g. approximately 30°. A helix angle in this range is expected to produce sufficient flexural strength in many scenarios without sacrificing deflection resistance.

The matrix material may encapsulate the at least one reinforcing fibre. In relevant embodiments, the outer tube may contain the helical reinforcing fibre.

The reinforcing fibre may be preloaded in tension. In a set of embodiments the reinforcing fibre is preloaded with sufficient tension to restrict elastic elongation of the preloaded fibre to less than 20% or to less than 15%, e.g. 10% or less.

In some embodiments, the at least one reinforcing fibre is anchored at one or both ends of the longitudinally parallel arrangement. The at least one reinforcing fibre may be anchored at one or both ends of the longitudinally parallel arrangement using one or more securing members. Preferably, a securing member extends over at least 25% of the cross-sectional area of the first and/or second end.

The support pole may comprise a single reinforcing fibre (e.g. a single strand or yarn wound helically around the longitudinally parallel arrangement). However, in some embodiments the support pole comprises a plurality of reinforcing fibres (e.g. a bundle of reinforcing fibres). The plurality of reinforcing fibres may comprise several separate strands each wound helically around the longitudinally parallel arrangement and/or one or more continuous fibres wound helically around the longitudinally parallel arrangement and passing two or more times along the longitudinally parallel arrangement.

The support pole may comprise several layers of helical reinforcing fibre wound around the longitudinally parallel arrangement. The number reinforcing fibre layers may be selected based on the size of the longitudinally parallel arrangement (e.g. outer diameter and/or length) and/or on an expected operational load of the support pole. For example, more layers may be used in support poles designed for high operational loads.

The reinforcing fibre may comprise a polymer (i.e. the fibre may be a polymer fibre), e.g. made from any polymeric material with suitable properties for reinforcing the support pole (e.g. high tensile strength). In some embodiments the fibre comprises a synthetic fibre, such as polyester or Kevlar.

In a set of embodiments, the helical reinforcing fibre runs along a substantial portion of the length of the longitudinally parallel arrangement, e.g. at least 20%, 30% or 40% of the length of the longitudinally parallel arrangement (e.g. part of the way along the support pole), or at least 50%, 60%, 70%, 80% or 90% of the length of the longitudinally parallel arrangement (e.g. most of the way along the support pole). In some embodiments, the reinforcing fibre runs along substantially the entire length of the longitudinally parallel arrangement (e.g. from one end of the longitudinally parallel arrangement to the other end of the longitudinally parallel arrangement).

It is often useful or necessary to attach other items and accessories to the support pole, e.g. crossarms, cable support and/or insulator devices, or other hardware for supporting the cable's function such as transformers or fuses. The inventors have however recognised that using reinforcing fibres within the support pole can complicate this attachment. Typically, items are attached to support poles by driving a fastener such as a screw into the pole, which engages with the underlying structure of the pole to firmly hold any desired items in place. However, the application of such fasteners to support poles featuring helical fibre reinforcement can damage or sever helical fibres within the pole, compromising the strength benefits that the fibre can provide (e.g. by reducing tension in the fibre). Conversely, the fibre itself can interfere with the application of fasteners and potentially compromise the strength of the fixing.

Therefore, in a set of embodiments, the helical reinforcing fibre extends only within a first section of the support pole and the support pole comprises a second section that is free of helical reinforcing fibre. In other words, at least one section of the pole may be free of helical reinforcing fibre. The second section can then be used for fixings without encountering any issues with the reinforcing fibre. Having a second section that is free of reinforcing fibre may also facilitate the creation of the cable inlet and/or outlet. In some embodiments, the support pole comprises a item that is secured to the second section of the support pole by a fastener (e.g. a screw or bolt).

The first section may be a lower section of the support pole and the second section may be an upper section of the support pole (i.e. the first section may be at or towards the bottom of the pole and the second section at or towards the top of the pole when the pole is made vertical in use).

The first section may make up more than half of the length of the support pole, e.g. at least 50%, 60%, 70% or 80% of the length of the support pole. Conversely, the second section may make up less than half of the length of the support pole, e.g. less than 50%, 40%, 30% or 20% of the length of the support pole. In a set of embodiments, the first section is between 3 m and 30 m long. In a set of embodiments, the second section is between 0.5 m and 10 m long (e.g. approximately 3-4 m).

In some sets of embodiments, the hollow complete tube may extend from the first section of the pole into the second section of the pole. This may advantageously provide a strong structural link between the first and second sections. As mentioned above, the hollow complete tube may extend over substantially an entire length of the pole.

Additionally or alternatively, one or more of the split lengths of bamboo in the longitudinal parallel arrangement may extend from the first section of the pole into the second section of the pole. In some embodiments, the whole longitudinal parallel arrangement extends from the first section into the second section.

However, in a set of embodiments, the longitudinal parallel arrangement extends only in the first section. This may simplify manufacture, e.g. allowing a manufacturer to simply reinforce the entirety of the longitudinal parallel arrangement with helical fibre without needing to avoid certain parts.

In such embodiments, the support pole may comprise additional split lengths of bamboo or similar tubular plant material (e.g. shorter than the split lengths of the longitudinal parallel arrangement) in the second section. These may add useful reinforcement in the absence of the longitudinal parallel arrangement. As explained below the second section may be shorter than the first section and so the second section may be reinforced with offcut split lengths from those cut for the longitudinal parallel arrangement, which may be an efficient use of material that reduces wastage.

The use of a bio-based polyurethane matrix material, or a recycled polyurethane matrix material as explained above is believed to be independently inventive and so from a second aspect of the present invention there is provided a support pole extending along a longitudinal axis, the support pole comprising:

• • a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis; and
  • a matrix material comprising a bio-based polyurethane and/or a recycled polyurethane that encapsulates the plurality of split lengths.

From a third aspect of the present invention there is provided a method of manufacturing a support pole extending along a longitudinal axis, the method comprising:

• • arranging a plurality of split lengths of bamboo into a longitudinally parallel arrangement extending along the longitudinal axis; and
  • applying matrix material comprising a bio-based polyurethane and/or a recycled polyurethane to encapsulate the split lengths and fix the longitudinally parallel arrangement.

The provision of a fibre-reinforced support pole with a fibre-free section for facilitating attachments is also believed to be independently inventive and so from a fourth aspect of the present invention there is provided a support pole extending along a longitudinal axis, the support pole comprising:

• • a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis;
  • at least one reinforcing polymer fibre wound helically around the longitudinally parallel arrangement; and
  • a matrix material that encapsulates the plurality of split lengths and the at least one reinforcing polymer fibre;
  • wherein the helical reinforcing fibre extends only within a first section of the support pole and the support pole comprises a second section that is free of helical reinforcing fibre.

From a fifth aspect of the present invention there is provided a method of manufacturing a support pole extending along a longitudinal axis, the method comprising:

• • arranging a plurality of split lengths of bamboo into a longitudinally parallel arrangement extending along the longitudinal axis;
  • winding at least one reinforcing polymer fibre helically around the longitudinally parallel arrangement; and
  • applying matrix material to encapsulate the split lengths and the reinforcing polymer fibre;
  • wherein the helical reinforcing fibre extends only within a first section of the support pole and the support pole comprises a second section that is free of helical reinforcing fibre.

Features of any aspect or embodiment described herein may, wherever appropriate, be applied to any other aspect or embodiment described herein. Where reference is made to different embodiments, it should be understood that these are not necessarily distinct but may overlap. It will be appreciated that all relevant features of the support pole according to the first aspect described above may also apply to the other aspects of the invention.

The following clauses outline various options for the present invention.

Clause 1. A support pole extending along a longitudinal axis, the support pole comprising:

• • a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis;
  • a cable inlet;
  • a cable outlet; and
  • a hollow complete tube of bamboo or similar tubular plant material extending within the longitudinally parallel arrangement to provide a cable route from the cable inlet to the cable outlet; and
  • a matrix material that encapsulates the plurality of split lengths and the hollow complete tube.

Clause 2. The support pole of clause 1, wherein the hollow complete tube consists of a single cane of bamboo or similar tubular plant material.

Clause 3. The support pole of clause 1, wherein the hollow complete tube comprises a plurality of canes of bamboo or similar tubular plant material that are joined together.

Clause 4. The support pole of any preceding clause, wherein the hollow complete tube extends along at least 20% of the length of the support pole.

Clause 5. The support pole of any preceding clause, wherein the cable inlet is formed at an end of the support pole.

Clause 6. The support pole of clause 5, wherein the cable outlet is formed at an opposite end of the support pole to the cable inlet.

Clause 7. The support pole of any preceding clause, wherein the cable inlet comprises an inlet tube that leads from an aperture in the side of the support pole to the hollow complete tube.

Clause 8. The support pole of any preceding clause, wherein the cable outlet comprises an outlet tube that leads from an aperture in the side of the support pole to the hollow complete tube.

Clause 9. The support pole of any preceding clause, wherein the support pole comprises one or more additional hollow complete tubes of bamboo or similar tubular plant material extending within the longitudinally parallel arrangement.

Clause 10. The support pole of clause 9, wherein the additional hollow complete tube(s) provide one or more additional cable route(s).

Clause 11. The support pole of any preceding clause, wherein the hollow complete tube is located centrally within the longitudinally parallel arrangement.

Clause 12. The support pole of any of clauses 1-10, wherein the hollow complete tube is located off-centre within the longitudinally parallel arrangement.

Clause 13. The support pole of any preceding clause, comprising an outer tube that contains the plurality of split lengths, the hollow complete tube and the matrix material.

Clause 14. The support pole of any preceding clause, wherein the matrix material comprises a bio-based polyurethane and/or a recycled polyurethane.

Clause 15. The support pole of any preceding clause, comprising at least one reinforcing fibre wound helically around the longitudinally parallel arrangement

Clause 16. The support pole of clause 15, wherein the helical reinforcing fibre extends only within a first section of the support pole and the support pole comprises a second section that is free of helical reinforcing fibre.

Clause 17. The support pole of clause 16, wherein the hollow complete tube extends from the first section of the pole into the second section of the pole.

Clause 18. The support pole of clause 16 or 17, wherein the longitudinal parallel arrangement extends only in the first section.

Clause 19. The support pole of clause 18, comprising additional split lengths of bamboo or similar tubular plant material in the second section.

Clause 20. The support pole of any of clauses 16-19, wherein the second section makes up less than half of the length of the support pole.

Clause 21 a Support Pole Extending Along a Longitudinal Axis, the Support Pole comprising:

• • a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis; and
  • a matrix material comprising a bio-based polyurethane and/or a recycled polyurethane that encapsulates the plurality of split lengths.

Clause 22. a Support Pole Extending Along a Longitudinal Axis, the Support Pole comprising:

• • a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis; at least one reinforcing polymer fibre wound helically around the longitudinally parallel arrangement; and
    a matrix material that encapsulates the plurality of split lengths and the at least one reinforcing polymer fibre;
    wherein the helical reinforcing fibre extends only within a first section of the support pole and the support pole comprises a second section that is free of helical reinforcing fibre.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:

FIG. 1 is a schematic cross section drawing of a support pole according to an embodiment of the present invention;

FIG. 2 is another schematic cross section drawing of the support pole, taken along the plane labelled F2 in FIG. 1;

FIG. 3 is a schematic cutaway drawing of the support pole; and

FIG. 4 is a schematic drawing of the longitudinally parallel arrangement of the support pole.

DETAILED DESCRIPTION

FIGS. 1, 2 and 3 illustrate a complete support pole 100 according to an embodiment of the present invention. The support pole 100 comprises a plurality of split lengths of bamboo 102 in a longitudinally parallel arrangement (i.e. a bundle) 104 extending along a longitudinal axis L. A hollow complete tube of bamboo 106 is located centrally within the bundle 104 (i.e. coaxial with the longitudinal axis L). The hollow complete tube of bamboo 106 is made from several shorter hollow compete canes of bamboo that are joined together by organic tape and/or polyester fibres.

The support pole 100 has two sections: a lower section 108 and an upper section 110. The bundle 104 of split lengths 102 extends in the lower section 108. In the upper section 110, the hollow complete tube 106 is surrounded by shorter split lengths 107 separate to the bundle 104 (e.g. offcuts from preparing the bundle 104). The upper section 110 may be around 3-4 m long. The lower section 108 may be around 5-25 m long.

The bundle 104 in the lower section 108 is shown in more detail in FIG. 4. Reinforcing fibre 112 is wound helically around the bundle 104. The reinforcing fibre 112 extends at a helix angle of approximately 30° to the longitudinal axis L. The fibre 112 resists elongation and thus provides the pole 100 with improved flexural strength. The fibre 112 does not extend into the upper section 110, to allow fixings to be attached to the pole 100 as described below.

The support pole 100 comprises a cable inlet 114 at the bottom of the pole 100 and a cable outlet 116 at the top of the pole 100. The hollow complete tube of bamboo 106 connects the cable inlet 114 to the cable outlet 116 to provides a cable route 118 therebetween.

The bundle 104, the hollow complete tube 106, the split lengths 107, the cable inlet and outlet 114, 116 and the helical fibre 112 are all contained within a cylindrical outer tube 120, for example a polyethylene (e.g. HDPE) tube, and encapsulated by a matrix material 122. The matrix material 122 is a bio-based polyurethane foam (e.g. comprising Merginol 910). Because the tube 106 is complete, the matrix material 122 does not infiltrate into the hollow interior of the tube 106. The tube 120 is closed with end caps 121.

The cable inlet and outlet 114, 116 extend through the outer tube 120, enabling a cable such as an electricity or communications cable to be routed into the pole 100 through the cable inlet 114 and along the cable route to the cable outlet 116. The portion of the cable inside the pole 100 is protected by the hollow complete tube 106, the split lengths 102, 107, the helical fibre 112, the matrix material 122 and the outer tube 120.

Finally, the support pole 100 comprises a cable support device 124 that is attached to the upper section 110 by a screw 126. The screw 126 penetrates into the split lengths 107 and the surrounding matrix material 122 but does not penetrate the hollow complete tube 106. Because there is no fibre reinforcement 112 in the upper section 110, this does not interfere with the application of the screw 126 and cannot be damaged by the screw 126.

A method of manufacturing the support pole 100 will now be outlined, although it will be recognised by one skilled in the art that other methods of manufacture (e.g. with one or more of the below steps omitted, modified or done in a different order) may also be used.

The initial steps of manufacture (not illustrated) include growing, harvesting, limbing, cleaning and drying bamboo canes. Some of the bamboo canes are split along their length (e.g. before or after drying). Depending on the bamboo cane diameter, each cane or stem may be split into 4-6 individual splits, for example. Splitting can be performed manually (e.g. using a machete) or by a splitting machine. Other canes are retained as complete tubes, but these may be cut perpendicular to their length into shorter sizes as required.

The whole canes of bamboo are used for the hollow complete tube 106 and the cable inlet and outlet 114, 116. These are arranged in the desired shape to form the cable route 118 and the split lengths of bamboo 102 are arranged around them and bound by the helical fibre 112 to form the bundle 104, with the hollow complete tube 106 and cable outlet 116 extending from the top end of the bundle 104. These components are then placed inside the outer tube 120. Holes for the cable inlet and outlet 114, 116 are made in the outer tube 120.

The shorter split lengths 107 are then added to the upper section 110 of the tube 120. The outer tube 120 is then sealed with the end caps 121.

A matrix material is then prepared by reacting a bio-based polyol (e.g. Merginol 910) with a polyisocyanate to form polyurethane. Alternatively a recycled polyurethane matrix material formed using recycled polyol may be used. Once mixed, the matrix material 122 is injected into the outer tube 120 through holes in the outer tube 120 and/or the end caps 121, to encapsulate the bundle 104, the hollow complete tube 106, the split lengths 107, the cable inlet and outlet 114, 116 and the helical fibre 112. The cable route 118 formed by the hollow complete tube 106 and the cable inlet and outlet 114, 116 is sealed to prevent any matrix material 112 penetrating thereinto. The injection holes are sealed and the matrix material 112 is allowed to cure.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.