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

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.

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; at least one reinforcing polymer fibre running substantially parallel to the longitudinal axis; and a matrix material that encapsulates the plurality of split lengths and the at least one reinforcing polymer fibre.

Thus it will be appreciated by those skilled in the art that the reinforcing longitudinal 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), compared to a support pole without a reinforcing longitudinal polymer fibre. The use of a reinforcing longitudinal polymer fibre may reduce the number of split lengths required to provide a certain level of performance (e.g. bending load resistance and/or flexural strength). Reducing the number of split lengths may reduce the weight of the support pole and/or reduce manufacturing costs by reducing the number of split lengths that need to be grown and prepared for use (which can be a time-consuming and labour-intensive process). Conversely, a stronger pole can be produced for the same weight.

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.

The at least one reinforcing polymer fibre is arranged to run substantially parallel to the longitudinal axis, in other words, it is not a fibre amongst a random distribution that happens to be oriented longitudinally but a fibre that has been purposefully arranged to run substantially parallel to the longitudinal axis. As explained above, the reinforcing polymer fibre running substantially parallel to the longitudinal axis serves to increase the bending resistance and/or flexural strength of the pole by resisting elongation. In view of this intended function, the polymer fibre therefore has a length (i.e. extending in a direction parallel to the longitudinal axis) that is sufficient to increase bending resistance and/or flexural strength of a given pole. In some embodiments, the reinforcing polymer fibre has a length of at least 10 cm, 20 cm, 30 cm, 40 cm, or at least 50 cm. In some embodiments, the reinforcing polymer fibre has a length of at least 1 m, 2 m, 3 m, 4 m, or at least 5 m or more. Of course a minimum length for the reinforcing polymer fibre may be chosen having regard to the overall length of the pole or at least the length of the pole requiring a bend- resisting function. For instance, the reinforcing polymer fibre may not comprise or be provided by short chopped fibres in the matrix material (e.g. dispersed throughout the matrix material with random orientations). Whilst the matrix material may be additionally “fibre-reinforced” using short fibres (e.g. fibres that are less than 10 cm long), this kind of reinforcement would not function to increase the bending resistance and/or flexural strength of the pole by resisting elongation in the same way as the at least one reinforcing polymer fibre running substantially parallel to the longitudinal axis according to the present invention. In at least some embodiments, in addition or alternatively, preferably the reinforcing polymer 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 (i.e. part of the way along the support pole).

Further preferably the reinforcing polymer fibre runs along at least 50%, 60%, 70%, 80% or 90% of the length of the longitudinally parallel arrangement. In some particularly preferable embodiments, the reinforcing polymer 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). This means that pole has increased bending resistance along its whole length. The at least one reinforcing polymer fibre may run adjacent the longitudinally parallel arrangement or within the longitudinally parallel arrangement.

In some embodiments, in addition or alternatively, the reinforcing polymer fibre may be preloaded in tension. This may mitigate elastic extension of the fibre when the support pole experiences a bending load, reducing the amount of deflection experienced. Preferably, the reinforcing polymer fibre is preloaded with sufficient tension to restrict elastic elongation of the preloaded fibre to less than 20%, and preferably to less than 15%, e.g. 10% or less.

In some sets of embodiments, the reinforcing polymer fibre is secured at a first and/or a second end of the longitudinally parallel arrangement (e.g. secured at opposite ends of the longitudinally parallel arrangement). The fibre may be secured directly to the longitudinally parallel arrangement (e.g. by a mechanical connection with one or more of the split lengths), but in some preferred embodiments the support pole comprises one or more securing members positioned at the first and/or second end of the longitudinally parallel arrangement and arranged to secure the reinforcing polymer fibre at the first and/or second end. The one or more securing members may be independent of the plurality of split lengths of bamboo.

At least before the matrix material is added during manufacture, to encapsulate the plurality of split lengths and the at least one reinforcing polymer fibre, the one or more securing members may be moveable relative to the plurality of split lengths of bamboo. This movement can be used to tension the reinforcing polymer fibre, as described further below. A securing member such as an end plate or cap (e.g. a substantially planar end plate or cap) may serve to spread an axial load generated by the longitudinal fibre (e.g. due to tension in the reinforcing polymer fibre) over the plurality of split lengths, and may also facilitate assembly of the support pole. Preferably, the securing member extends over at least 25% of the cross-sectional area of the first and/or second end.

In some sets of embodiments, the one or more securing members are constrained between an end of the longitudinally parallel arrangement (i.e. the ends of the split lengths) and the reinforcing fibre. For instance, the reinforcing polymer fibre may be arranged to pass over a securing member to constrain it between the end of the longitudinally parallel arrangement and the reinforcing fibre. In some embodiments, the securing member may comprise one or more grooves or channels in which the reinforcing fibre is located when passing over the securing member. This may help to prevent the fibre slipping off the securing member (e.g. when under high tension), and may also help to position the fibre centrally over the securing member (e.g. to ensure symmetrical application of axial force generated by the reinforcing fibre to the longitudinally parallel arrangement).

As mentioned above, it may be beneficial in some embodiments for the reinforcing polymer fibre to be preloaded in tension. The reinforcing fibre may be preloaded in tension as it is added to the longitudinally parallel arrangement during manufacture, although it may be more convenient to generate tension or to increase the tension in the reinforcing polymer fibre after it has been added (i.e. after the fibre has been positioned within or adjacent the longitudinally parallel arrangement). In some embodiments, the support pole comprises one or more components for adding tension to the reinforcing polymer fibre. As explained in more detail below, tension may be added to the reinforcing fibre during manufacture before the matrix material is added or fully set. The support pole may comprise one or more components for adding tension to the reinforcing polymer fibre before matrix material is added or fully set. Tension may be added via any suitable mechanism such as mechanical, chemical, thermal, or electromagnetic.

In some sets of embodiments, the securing member(s) or a part thereof may be adapted for adding tension to the reinforcing polymer fibre. The securing member(s) or a part thereof may be moveable to add tension to the reinforcing polymer fibre.

As mentioned above, the securing member(s) or a part thereof may be moveable relative to the plurality of split lengths of bamboo. For instance, the securing member(s) or a part thereof may be moveable longitudinally and/or laterally to add tension to the reinforcing polymer fibre, e.g. by pulling the fibre more taut. In at least some embodiments, the securing member(s) or a part thereof is rotatable to twist and thus add tension to the reinforcing polymer fibre. The securing member(s) or a part thereof may comprise one or more surfaces or structures to which torque may be applied to rotate the securing member(s) or the part thereof to twist and add tension to the reinforcing polymer fibre. For example, the securing member(s) may comprise one or more raised or indented surfaces or structures, or through-holes, with which a tool (e.g. a forked tool) can be engaged to rotate the securing member(s) or the part thereof to twist the reinforcing polymer fibre and thus add tension thereto. The securing member(s) or a part thereof may therefore be arranged and/or adapted for adding tension to the reinforcing polymer fibre before matrix material is added or fully set. In the final pole, the matrix material may optionally encapsulate or otherwise fix the securing member(s).

In at least some embodiments, the one or more securing members are locked in position after being moved to add tension to the at least one reinforcing polymer fibre. For example, the one or more securing members may comprise a locking feature (such as a through hole) to enable them to be locked in position e.g. with the at least one reinforcing polymer fibre pulled taut.

In at least some embodiments, in addition or alternatively, the one or more securing members may be made from any suitable rigid material, for example made of polymer, metal or organic material.

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 reinforcing polymer fibre 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 and the matrix material. The securing member(s) may be arranged to close (or at least partially close) one or both ends of the outer tube, or additional closing members (such as end caps) may be arranged to close one or both ends of the outer tube.

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. Preferably the outer tube has a substantially constant outer diameter along its length. This means that the pole advantageously has an outer diameter that is uniform along its length. The use of an outer tube may also facilitate manufacture as a separate bulky mould may not be required. Instead, the outer tube may act as the mould for the matrix material, as well as outer protection for the finished pole.

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

In at least some embodiments, in addition or alternatively, the reinforcing polymer fibre preferably runs substantially centrally within the longitudinally parallel arrangement (i.e. along the longitudinal axis of the support pole). This may provide symmetrical resistance to bending forces on the support pole from any direction. Of course, in some embodiments the reinforcing polymer fibre may run parallel to but away from the longitudinal axis (i.e. off-centre) within the longitudinally parallel arrangement, e.g. to provide resistance to bending forces on the support pole from a particular direction. In some embodiments, the support pole comprises a plurality of separate reinforcing polymer fibres or bundles of reinforcing polymer fibres located at different radial positions within the longitudinally parallel arrangement.

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

In some sets of embodiments, in addition or alternatively, the support pole may further comprise at least one further reinforcing polymer fibre wound around the longitudinally parallel arrangement (e.g. around the entire length or a portion of the longitudinally parallel arrangement). For example, the support pole may comprise at least one further reinforcing polymer fibre wound helically and/or circumferentially around the longitudinally parallel arrangement (i.e. helical and/or circumferential reinforcing polymer fibre). Circumferential reinforcing polymer fibre may, for instance, help to pull the split lengths together to straighten out any kinks or bends in the split lengths and increase the density of the split lengths in the longitudinally parallel arrangement. However, the Applicant has appreciated that helical reinforcing polymer fibre may be particularly beneficial because, in addition to pulling the split lengths together, it may also resist elongation in a similar manner to the longitudinal reinforcing polymer fibre(s) to increase the bending resistance and flexural strength of the support pole.

Preferably, the support pole comprises at least one further reinforcing polymer fibre wound helically around the longitudinally parallel arrangement with a helix angle (i.e. relative to the longitudinal axis of the longitudinal arrangement) between approximately 10° and 45° and preferably approximately 30°. A helix angle in this range is expected to produce sufficient flexural strength in many scenarios without sacrificing deflection resistance.

In at least some embodiments, in addition or alternatively, the at least one further reinforcing polymer fibre may be anchored at one or both ends of the longitudinally parallel arrangement. The at least one further reinforcing polymer fibre may be anchored at one or both ends of the longitudinally parallel arrangement using one or more securing members (e.g. the same securing members used to secure the longitudinal fibre).

The support pole may comprise several layers of further (e.g. helical and/or circumferential) reinforcing polymer fibre wound around the longitudinally parallel arrangement. The number of further reinforcing polymer 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.

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 softwood. 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.

In at least some embodiments, the matrix material can act to protect 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, rubber, cement, ceramic, metal foam, etc. 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. A synthetic polymer foam, such as polyurethane (PUR) foam, has been found to bind well to the split lengths of bamboo. In preferred embodiments the matrix material therefore consists of a polyurethane resin, in particular a polyurethane foam. PUR foam has demonstrated good mechanical properties as well as being lightweight, non-toxic and non-flammable. An advantage of using PUR foam (or similar) is that it may be formed by mixing liquid precursors (e.g. isocynate and polyol) that react in situ to create a foam that expands to fill the outer tube. The injecting step may therefore comprise injecting at least two precursor materials that react to form the matrix material in situ. For polyurethane, this step may comprise injecting polyol and polyisocyanate in liquid form, in the presence of water, to produce an exothermic reaction forming the polyurethane foam.

A polymeric matrix material, in particular an elastomeric material (such as PUR foam) may further be beneficial as it can provide the poles with a unique flexural strength as compared to more rigid matrix materials. As mentioned above, flexural strength allows a 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 very low weight per unit length, preferably a weight per unit length less than 50 kg/m, e.g. less than 45 kg/m or less than 40 kg/m. In some embodiments, the support pole may have a weight per unit length of less than 35 kg/m and further preferably even less than 10 kg/m, for example only 7-8 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), but preferably the support pole has a length of between 2 m and 12 m (e.g. a length of about 8 m, 9 m or 10 m) and/or a diameter of between 15 cm and 30 cm (e.g. a diameter of about 18 cm, 20 cm or 22.5 cm).

From a second 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; adding at least one reinforcing polymer fibre running substantially parallel to the longitudinal axis; and applying matrix material to encapsulate the split lengths and the at least one reinforcing polymer fibre.

The method may comprise putting the at least one reinforcing polymer fibre under tension, preferably before applying the matrix material. The method may comprise adding tension to the at least one reinforcing polymer fibre after it is added.

The method may comprise securing the at least one reinforcing polymer fibre at a first end of the longitudinally parallel arrangement and preferably at a second end of the longitudinally parallel arrangement (e.g. using one or more securing members as described above). The securing member(s) or a part thereof may be used (e.g. moved) to add tension to the at least one reinforcing polymer fibre. In at least some embodiments, the method may comprise applying torque and/or force to the securing member(s) or a part thereof so as to twist and/or pull the at least one reinforcing polymer fibre and add tension to the at least one reinforcing polymer fibre. In other embodiments, the method may comprise directly applying torque and/or force to the at least one reinforcing polymer fibre so as to add tension (e.g. by pulling taut). In at least some embodiments, in addition or alternatively, the method comprises placing the split lengths and the at least one reinforcing polymer fibre into an outer tube and introducing the matrix material into the outer tube to encapsulate the split lengths and the at least one reinforcing polymer fibre. The method may comprise sealing one or both ends of the outer tube (e.g. using the securing member(s) or other means such as end caps or plates). As explained above, in such embodiments a separate mould (which may be heavy, bulky and expensive) may not be required because the outer tube acts as a mould for the matrix material.

In at least some embodiments, in addition or alternatively, the method may further comprise winding at least one further reinforcing polymer fibre around the longitudinally parallel arrangement (e.g. around the entire length or a portion of the longitudinally parallel arrangement). For example, the method may comprise winding at least one further reinforcing polymer fibre helically and/or circumferentially around the longitudinally parallel arrangement. Preferably, the method comprises winding at least one further reinforcing polymer fibre helically around the longitudinally parallel arrangement with a helix angle (i.e. relative to the longitudinal axis of the longitudinally parallel arrangement) between approximately 10° and 45° (e.g. approximately 30°).

In at least some embodiments, in addition or alternatively, the method may comprise anchoring the at least one further reinforcing polymer fibre at one or both ends of the longitudinally parallel arrangement, e.g. by winding the at least one further reinforcing polymer fibre over one or more securing members (e.g. the same securing members used to secure the longitudinal fibre). The method may comprise winding several layers of the further reinforcing polymer fibre helically and/or circumferentially around the longitudinally parallel arrangement.

As explained above, at least some embodiments may comprise putting the at least one reinforcing polymer fibre under tension before the matrix material is applied. Thus an intermediary pole may be manufactured and the reinforcing polymer fibre adjusted in this intermediary pole before finally adding the matrix material to make the finished pole. Such embodiments may comprise forming an intermediate support pole structure comprising the longitudinally parallel arrangement and the at least one reinforcing polymer fibre running substantially parallel to the longitudinal axis. This intermediate support pole structure may comprise all of the features of a complete support pole aside from the matrix material (or at least a portion of the matrix material) and/or the outer tube (in relevant embodiments).

The Applicant believes the manufacture of this intermediate support pole structure to be independently inventive and thus from a third aspect of the invention there is provided a method of manufacturing an intermediate support pole structure comprising: arranging a plurality of split lengths of bamboo into a longitudinally parallel arrangement extending along the longitudinal axis; adding at least one reinforcing polymer fibre running substantially parallel to the longitudinal axis; and optionally, putting the at least one reinforcing polymer fibre under tension, e.g. by adding tension to the at least one reinforcing polymer fibre in the support pole structure.

Correspondingly, from a fourth aspect of the invention there is provided an intermediate support pole structure comprising: a plurality of split lengths of bamboo or similar tubular plant material in a longitudinally parallel arrangement extending along the longitudinal axis; and at least one reinforcing polymer fibre running substantially parallel to the longitudinal axis, wherein optionally the at least one reinforcing polymer fibre is held under tension.

The Applicant also believes the use of helically wound, further reinforcing polymer fibre to be independently inventive, as it may lead to many of the benefits of the invention even in embodiments without the longitudinal reinforcing polymer fibre. Thus, from a fifth aspect of the 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 reinforcing polymer fibre.

There will now be described some general features that may be applied to any aspect of the methods described above.

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).

In at least some embodiments, in addition or alternatively, preferably the reinforcing polymer 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 (i.e. part of the way along the support pole). Further preferably the reinforcing polymer fibre runs along at least 50%, 60%, 70%, 80% or 90% of the length of the longitudinally parallel arrangement. In some particularly preferable embodiments, the reinforcing polymer 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).

In some embodiments, in addition or alternatively, the reinforcing polymer fibre may be preloaded in tension. Preferably, the reinforcing polymer fibre is preloaded with sufficient tension to restrict elastic elongation of the preloaded fibre to less than 20%, and preferably to less than 15%, e.g. 10% or less. Thus, embodiments of any of the methods may comprise a step of preloading the reinforcing polymer fibre in tension. In at least some embodiments, in addition or alternatively, the at least one reinforcing polymer fibre may be anchored at one or both ends of the longitudinally parallel arrangement. The at least one reinforcing polymer 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.

In some sets of embodiments, the one or more securing members are constrained between an end of the longitudinally parallel arrangement (i.e. the ends of the split lengths) and the reinforcing fibre. For instance, the reinforcing polymer fibre may be arranged to pass over a securing member to constrain it between the end of the longitudinally parallel arrangement and the reinforcing fibre. In some embodiments, the securing member may comprise one or more grooves or channels in which the reinforcing fibre is located when passing over the securing member.

In at least some embodiments, in addition or alternatively, the one or more securing members may be made from any suitable rigid material, for example made of polymer, metal or organic material.

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 reinforcing polymer fibre and the matrix material. Thus, embodiments of any of the methods may comprise a step of adding an outer tube to contain the plurality of split lengths of bamboo (or similar plant material), the reinforcing polymer fibre 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 and the matrix material. The securing member(s) may be arranged to close one or both ends of the outer tube, or additional closing members (such as end caps) may be arranged to close one or both ends of the outer tube.

The outer tube is preferably formed of a polymeric material, e.g. polyethylene. Preferably the outer tube has a substantially constant outer diameter along its length. The support pole may comprise a single reinforcing polymer 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 polymer fibres (e.g. a bundle of reinforcing polymer fibres). The plurality of reinforcing polymer 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 polymer fibre wound around the longitudinally parallel arrangement. The number reinforcing polymer 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 polymer fibre may comprise any polymeric material with suitable properties for reinforcing the support pole (e.g. high tensile strength). However, in some preferred embodiments the fibre comprises a synthetic fibre, such as polyester or Kevlar.

In some sets of embodiments, in addition or alternatively, the support pole may further comprise at least one further reinforcing polymer fibre wound circumferentially around the longitudinally parallel arrangement (e.g. around the entire length or a portion of the longitudinally parallel arrangement).

Support poles according to embodiments of the fifth aspect of the invention may also 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), but preferably the support pole has a length of between 2 m and 12 m (e.g. a length of about 8 m, 9 m or 10 m) and/or a diameter of between 15 cm and 30 cm (e.g. a diameter of about 18 cm, 20 cm or 22.5 cm). Correspondingly, from a sixth aspect of the 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.

Preferably, the method comprises winding at least one reinforcing polymer fibre helically around the longitudinally parallel arrangement with a helix angle (i.e. relative to the longitudinal axis of the longitudinally parallel arrangement) between approximately 10° and 45° (e.g. approximately 30°).

In at least some embodiments, in addition or alternatively, the method may comprise anchoring the at least one reinforcing polymer fibre at one or both ends of the longitudinally parallel arrangement, e.g. by winding the at least one reinforcing polymer fibre over one or more securing members (e.g. the same securing members used to secure the longitudinal fibre). The method may comprise winding several layers of the reinforcing polymer fibre helically around the longitudinally parallel arrangement.

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 or sets of embodiments, it should be understood that these are not necessarily distinct but may overlap.

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:

Figure 1 shows a support pole according to an embodiment of the present invention;

Figure 2 is a cutaway view of the support pole of Figure 1 ;

Figures 3-8 illustrate various stages in the manufacture of the support pole shown in Figures 1 and 2; Figures 9 and 10 show a support pole with additional radial reinforcement; and

Figure 11 is a graph showing the performance of an exemplary support pole of the present invention compared to previous support poles.

Figures 1 and 2 show a complete support pole 2 according to an embodiment of the present invention. The support pole 2 comprises a plurality of split lengths of bamboo 4 in a longitudinally parallel arrangement 5 (i.e. a bundle), extending along a longitudinal axis L. A reinforcing polymer fibre 6 runs longitudinally within the longitudinally parallel arrangement 5 and is secured at each end of the support pole 2 by passing over securing members 8. The longitudinally parallel arrangement 5 and the reinforcing polymer fibre 6 are enclosed in a cylindrical outer tube 10, for example a polyethylene (e.g. HDPE) tube. The longitudinally parallel arrangement 5 and the reinforcing polymer fibre 6 are encapsulated within a matrix material 12 (e.g. PUR foam) retained by the outer tube 10.

The reinforcing polymer fibre 6 runs roughly centrally within the longitudinally parallel arrangement 5 (i.e. coincident with the longitudinal axis L). The reinforcing polymer fibre 6 extends between the securing members 8 under tension, reducing the amount of elastic extension it exhibits to less than 15%. Thus, when the support pole 2 is subject to bending loads (i.e. radial force that is non-uniform across the length of the pole 2), the amount of bending (i.e. how much an end of the pole deflects away from the longitudinal axis L) is limited because the fibre 6 resists elongation. The reinforcing polymer fibre 6 thus provides the support pole 2 with increased resistance to bending forces. Because the fibre 6 runs roughly centrally within the longitudinally parallel arrangement 5, the pole 2 has an increased resistance to bending forces from all directions.

An exemplary method of manufacturing the support pole 2 will now be described with reference to Figures 3-8.

The initial steps of manufacture (not illustrated) include growing, harvesting, limbing, cleaning, splitting and drying bamboo canes. 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.

As shown in Figures 3 and 4, the split lengths of bamboo 4 and the reinforcing polymer fibre 6 are arranged, with the reinforcing polymer fibre 6 positioned roughly centrally within the longitudinally parallel arrangement 5 (i.e. along the longitudinal axis L) (e.g. forming an intermediate support pole structure). A securing member 8 (shown in Figure 5) is positioned at each end of the longitudinally parallel arrangement 5, and the reinforcing polymer fibre 6 passes over and between the securing members 8 at least once and preferably several times (see Figure 6). In other words, the reinforcing polymer fibre 6 may run within the longitudinally parallel arrangement 5 between the securing members 8 at each end of the support pole 2 several times. The number of turns of reinforcing polymer fibre 6 along the axis L of the longitudinally parallel arrangement 5 and over the securing members 8 may determine the stiffness of the support pole 2. Each securing member comprises a plurality of through holes 14 and a pair of slots 16. The reinforcing polymer fibre 6 is guided into the slots 16 as it passes over the securing member 8. The longitudinally parallel arrangement 5 and the reinforcing polymer fibre 6 (e.g. an intermediate support pole structure) are then inserted into the outer tube 10.

As shown in Figure 7, a forked tool 20 is inserted into two of the through holes 14 of one securing member 8. The other securing member 8 is held stationary and the tool 20 is rotated (e.g. clockwise) to turn the securing member 8 so as to twist the reinforcing polymer fibre 6. This tightens the reinforcing polymer fibre 6 (i.e. puts it under additional tension), which therefore exerts an axial force on the securing members 8, pulling them towards each other. The securing members 8 distribute the axial force created by the tensioned fibre 6 over the underlying split lengths of bamboo 4. This limits the movement of the split lengths of bamboo 4 in both the axial and radial directions. Once a sufficient tension is achieved (e.g. after a predetermined number of rotations), the tool 20 is removed and rods 22 (e.g. made of metal, polymer or organic material) are inserted through the through holes 14 and into the longitudinally parallel arrangement 5 (i.e. between the split lengths of bamboo 4). This locks the securing members 8 in position (i.e. stops them from rotating), preventing the reinforcing polymer fibre 6 from untwisting and releasing the axial force. A matrix material 12 (e.g. PUR foam) is then injected into the outer tube 10 to encapsulate the split lengths of bamboo 4 and the reinforcing polymer fibre 6 in the longitudinally parallel arrangement 5. The through holes 14 in the securing members 8 may be used to inject the matrix material 12. The ends of the outer tube 10 are then sealed to contain the matrix material 12, which is allowed to cure.

Figures 9 and 10 shows a support pole 102 according to another embodiment of the invention. The support pole 102 comprises a plurality of split lengths of bamboo 104 in a longitudinally parallel arrangement 105 (i.e. a bundle), extending along a longitudinal axis L. At least one reinforcing polymer fibre (not shown) optionally runs within the longitudinally parallel arrangement 105 and is secured at each end of the support pole 102 by passing over securing members 108. This longitudinal reinforcing polymer fibre may be put under tension as described above. In this embodiment, at least one further helical reinforcing polymer fibre 109 is wound around the longitudinally parallel arrangement 105 to provide additional flexural strength (i.e. resistance to bending). The angle of the helical reinforcing polymer fibre 109 relative to the longitudinal axis is between 10° and 45° (e.g. 30°). The securing members 108 also serve as an anchor for the additional helical reinforcing polymer fibre 109. Several layers of helical reinforcing polymer fibre 109 may be used, depending on the size (e.g. the radius) of the longitudinally parallel arrangement 105 and the final operational load of the support pole 102.

Although not shown in Figures 9-10, in addition to the helical reinforcing polymer fibre 109, or as an alternative, at least one further reinforcing polymer fibre may be wound circumferentially around the longitudinally parallel arrangement 105.

The longitudinally parallel arrangement 105, the (optional) longitudinal reinforcing fibre and the helical reinforcing polymer fibre 109 are enclosed in a cylindrical outer tube 110, for example a polyethylene (e.g. HDPE) tube. A matrix material 112 is injected into the tube to encapsulate the longitudinally parallel arrangement 105, the (optional) longitudinal reinforcing polymer fibre and the helical reinforcing polymer fibre 109. Whilst the support pole 102 described above with reference to Figures 9 and 10 comprises helical reinforcing polymer fibre in addition to longitudinal reinforcing polymer fibre, this is not essential. In some embodiments the support pole 102 may comprise only helical reinforcing polymer fibre (i.e. without any longitudinal reinforcing polymer fibre).

Example

A support pole according to an embodiment of the invention was manufactured and tested. The support pole comprised a longitudinally parallel arrangement of 80 split lengths of bamboo encapsulated in a PUR foam matrix material within a polyethylene outer tube. Longitudinal polymer reinforcing fibres ran longitudinally within the longitudinally parallel arrangement, secured under tension at each end of the longitudinal arrangement. The support pole was 12 m long, and had a diameter of 0.225 m.

The bending load performance of the support pole is illustrated in Figure 11, which for comparison also shows the performance of two standard poles with the same dimensions and general composition, but without any reinforcing fibre.

Figure 11 is a graph 200 showing the deflection of the tips of two standard (i.e. non fibre reinforced) support poles 202, 204 and the tip of the exemplary fibre-reinforced support pole 206 for different levels of a bending load applied at a point 0.3 m from the tip. It can be seen that the standard support poles 202, 204 demonstrated lower resistance to bending loads than the fibre-reinforced support pole 206, e.g., deflecting roughly 200-300 mm (roughly 20-30%) more than the fibre reinforced support pole 206 when subject to a bending load of 2 kN.

Furthermore, the two standard support poles 202, 204 had a much lower flexural strength than the fibre-reinforced support pole 206. The standard poles 202, 204 both failed before reaching a bending load of 2.5 kN, whilst the fibre-reinforced pole 206 withstood a bending load of over 3.5 kN (-40% greater).

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.