WO2021099836A1

WO2021099836A1 - Shaft for athletic activities and method of forming the same

Info

Publication number: WO2021099836A1
Application number: PCT/IB2020/000966
Authority: WO
Inventors: Lance Johnson
Original assignee: Pda Ecolab
Current assignee: Pda Ecolab
Priority date: 2019-11-19
Filing date: 2020-11-19
Publication date: 2021-05-27
Anticipated expiration: 2022-05-19

Abstract

The present disclosure relates to a pole or shaft for athletic activities having a tubular structure and comprising, along at least a part of its length: an inner layer (39) formed of a first fiber-reinforced composite comprising a tubular braid of fibers; and an outer layer (43) comprising a second fiber-reinforced composite.

Description

DESCRIPTION

Shaft for athletic activities and method of forming the same

[0001] The present patent application claims priority from the US patent application filed on 19 November 2019 and assigned application no. US 62/937270, the contents of which is hereby incorporated by reference.

Technical field

[0002] The present disclosure relates generally to a shaft or pole and more particularly to a shaft for athletic activities, such as a ski pole, hiking pole, trekking pole, shaft for a kayak paddle or a rowing paddle, etc.

Background art

[0003] Millions of athletes utilize one or more stabilization poles, often referred to as trekking, hiking or ski poles, in outdoors and sporting activities. Typical construction utilizes an aluminum alloy, fiberglass, carbon fiber or a combination of these materials, to create the main body or shaft of the pole.

[0004] Other athletic equipment designed to provide propulsion either to a user or an object (e.g. a ball or puck) including, but not limited to, the shaft separating the two paddling blades of a kayak paddle, the boom of a wind surfing sail, the shaft of a hockey, a floorball or lacrosse stick, or the shaft of a golf club, also use similar materials and construction techniques in order to resist similar stresses which the shaft is subjected to during use.

[0005] Aluminum and steel are unique among these materials in that they are isotropic, having similar strengths in all directions or planes based on dimension and geometry. By comparison, carbon and glass-fiber composites are anisotropic, providing significantly greater strength along the orientation of the reinforcing fibers and a significantly higher resistance to tension than to compression.

[0006] With increasing global demand for reducing consumption of non-renewable resources and extracted raw materials (such as petroleum-based carbon fiber), there is a demand to replace the synthetic fibers of reinforcement fabrics, such as carbon fibers, fiberglass, Kevlar, boron, etc., with renewable fibers .

[0007] Like their synthetic counterparts, natural reinforcement fibers, when used in a fiber-reinforced composite construction, have anisotropic properties. However, importantly, natural fibers can have an advantage over synthetic fibers related to resistance to compression that may be more similar to the tensile strength of the fiber.

[0008] There are, however, technical difficulties in providing a natural-fiber-reinforced composite shaft for support or propulsion during athletic activities, which is light-weight, durable and has suitable resistance to forces that will be imparted on the shaft during use.

Summary of Invention

[0009] There is a need of improve the drawbacks of known shafts for athletic activities.

[0010] One embodiment of the present disclosure address all or some of the drawbacks of known shafts for athletic activities .

[0011] One embodiment provides a pole or shaft for athletic activities having a tubular structure and comprising, along at least a part of its length: an inner layer formed of a first fiber-reinforced composite comprising a tubular braid of fibers; and an outer layer comprising a second fiber-reinforced composite.

[0012] According to an embodiment, at least a portion of the fibers of the first and/or second fiber-reinforced composite are natural fibers.

[0013] According to an embodiment, the fibers of the first and/or second fiber-reinforced composite are vegetal-based fibers, such as fibers of bamboo, flax, ramie, pineapple leaf and/or extracted cellulose or nanocellulose.

[0014] According to an embodiment, the shaft has a weight percentage of resin of between 20 % and 60 %, for example of between 35 % and 45 %.

[0015] According to an embodiment, the first composite comprises an epoxy resin.

[0016] One embodiment provides a ski pole or a trekking pole, comprising the pole or shaft.

[0017] One embodiment provides a golf club comprising the pole or shaft.

[0018] One embodiment provides a floorball, hockey, or broomball stick comprising the pole or shaft.

[0019] One embodiment provides an oar or paddle comprising the pole or shaft.

[0020] One embodiment provides a method of manufacturing a pole or shaft for athletic activities, the method comprising: positioning a tubular braid around a mandrel; positioning at least one further ply around the tubular braid, the at least one further ply being impregnated with resin; wrapping a compressive layer around the at least one further ply, or otherwise positioning a compressive element or apparatus around the at least one further ply; and curing by heating.

[0021] According to an embodiment, the mandrel is covered by a polymeric sleeve.

[0022] According to an embodiment, a resin film is wrapped around the mandrel, or placed on the internal surface of the tubular braid, before the step of positioning the tubular braid around the mandrel.

[0023] According to an embodiment, a resin film is placed on the external surface of the tubular braid before the step of positioning the tubular braid around the mandrel.

[0024] According to an embodiment, the resin film is a film of epoxy resin.

[0025] According to an embodiment, the at least one further ply is lined with a further resin film.

[0026] One embodiment provides a molded, fiber-reinforced composite shaft having a significantly-tubular shape which may incorporate one or more tapers over its length, with a maximum outer dimension of 30mm and a minimum outer dimension of 8mm. The composite structure incorporates plies of reinforcing fiber fabric which are oriented variously to resist the forces exerted during use of the shaft, and which are captured within a resin matrix.

[0027] One embodiment provides the utilization of a natural fiber such as Bast Fiber (ie. flax, ramie, hemp), Leaf Fiber (i.e. Pineapple, Banana, Sisal), Stalk Fiber (i.e. rice, corn, wheat), Seed Fiber (ie. kapok, cotton), or Grass Fiber (i.e. bamboo); or other natural fibers having compressive strength which is between 80% and 120% of the tensile strength of the fibers. In some embodiments, the fibers are arranged in a tubular-braided configuration having a final orientation angle which is between 20 and 80 degrees to the vertical axis of the shaft.

[0028] One embodiment provides an external compression to a rigid mandrel or situating the completed layup and expanding bladder or flexible mandrel inside a rigid outer form and a step to cure the resin component of the composite with time and heat exchange in order to create the rigid form of the shaft .

[0029] The significantly tubular shape of the pole may incorporate shaping such as a rounded-triangular, rounded- square, stadium shape or other shape which is radially- symmetrical around the vertical axis of the pole.

[0030] Plies of the reinforcement fabric may be composed of carbon fiber, fiberglass, Aramid/Kevlar, Twaron, boron, Zyex, Spectra/Dyneema; mineral fibers, such as flax, cellulose or other natural fibers; Titanal, titanium, or steel mesh; other natural or synthetic vibration-damping materials such as elastomer or cork; or other such fibers or materials that provide advantageous characteristics to the structure. Reinforcing fabric may be constructed of fibers in a braided, woven, stitched, or unidirectional arrangement.

[0031] The resin may be a thermoset or thermoform resin, and may be introduced to the fiber reinforcement before, during or after layup of the composite shaft.

[0032] The length of the pole may be segmented into multiple sections to create a telescopic or folding pole.

[0033] The process of situating the reinforcement fabric for the pole fabrication can be hand-lay-up, roll wrapping, filament winding, or any other process typical to the fabrication of fiber-reinforced composite items.

[0034] Another embodiment provides rigid, solid mandrel, typically formed from steel, aluminum or other metal, which adds a tubular sleeve of silicone rubber composition containing entrained air voids which expands at a prescribed rate when heated. The layup of the shaft is performed when the mandrel and the sleeve combination is at such temperature where the combination of the elements is at its minimum diameter. The mandrel is wrapped with any combination of plies of resin matrix and reinforcing materials. A viscose compression wrapper is applied to the outside of the assembly. Under cure temperature the silicone portion of the sleeve expands, placing an outward force on the layup and infusing the resin into the fabrics or other reinforcements situated adjacent to the location of the resin component. As the silicone portion of the mold expands, it is resisted by the compression forces applied by the viscose compression wrapper and the layup receives the necessary compaction to infuse the resin well through the matrix without creating voids or crimps in the reinforcements.

[0035] The significantly tubular shape of the pole may incorporate shaping such as a rounded-triangular, rounded- square, or other shape which is radially-symmetrical around the vertical axis of the pole.

[0036] One embodiment provides any additional plies of the reinforcement fabric composed of any synthetic or natural reinforcement fiber including mineral fibers, cellulose fibers, or any other natural fiber that is or may become typically used in the construction of fabric-reinforced composite structures; other natural vibration-damping materials such as natural-rubber based elastomer or cork; or other such fibers or materials that provide advantageous characteristics to the structure. Reinforcing fabric may be constructed of fibers in a braided, woven, stitched, or unidirectional arrangement. [0037] The resin may be a thermoset or thermoform resin. Layup may contain other fibers to create the reinforcement such as meltable polylactic acid (PLA), polyamide(PA) or other polymeric fibers.

[0038] The length of the pole may be segmented into multiple sections to create a telescopic or folding pole.

[0039] The process of situating the reinforcement fabric for the pole fabrication can include any combination of hand-lay- up, roll wrapping, filament winding, or any other process typical to the fabrication of fiber-reinforced composite.

Brief description of drawings

[0040] The foregoing features and advantages, as well as others, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0041] Figure 1A is a side view of a ski pole according to an example embodiment;

[0042] Figure IB is a side view of a ski pole according to a further example embodiment;

[0043] Figure 2A is a side view of a golf club according to an example embodiment;

[0044] Figure 2B is a side view of an oar for athletic water activities according to an example embodiment;

[0045] Figure 3 is a cross-section view of a shaft according to an example embodiment of the present disclosure;

[0046] Figure 4 shows a cross-section view and a side view of a mandrel for using in a method of manufacturing the shaft of Figure 3;

[0047] Figure 5 is a cross-section view illustrating a step in the method of manufacturing the shaft of Figure 3; [0048] Figure 6 illustrates an example of a tubular braid;

[0049] Figures 7 and 8 are cross-section views of further steps of a method of manufacturing the shaft illustrated in Figure 3;

[0050] Figure 9 is a cross-section view of a shaft according to another example embodiment of the present disclosure;

[0051] Figure 10 shows a cross-section view and a side view of part of mandrel for using in a method of manufacturing the shaft of Figure 9; and

[0052] Figures 11 to 15 are side views illustrating steps of a method of manufacturing the shaft illustrated in Figure 9.

Description of embodiments

[0053] Like features have been designated by like references in the various figures. In particular, the structural and/or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties.

[0054] For the sake of clarity, only the operations and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail.

[0055] In the following disclosure, unless indicated otherwise, when reference is made to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or to relative positional qualifiers, such as the terms "above", "below", "higher", "lower", etc., or to qualifiers of orientation, such as "horizontal", "vertical", etc., reference is made to the vertical orientation of a pole. [0056] Unless specified otherwise, the expressions "around", "approximately", "substantially" and "in the order of" signify within 10 %, and preferably within 5 %.

[0057] Figure 1A is a side view illustrating an example of a ski pole 11.

[0058] It will be apparent to those skilled in the art that the principles described herein can be applied to other types of shaft for athletic activity, for example, hiking or trekking poles, the shaft of a kayak paddle or of a rowing oar, the mast of a windsurfing rig, etc. For example, depending on the application, the pole is used for stabilizing and/or propelling a user of the pole.

[0059] The ski pole 11 of Figure 1A comprises a shaft 15 having, at its upper end, a grip formed of a body 19 and a head 21, and a hand strap 23. At the lower end of the shaft, there is a basket 25 and a tip 27 of the pole.

[0060] In the embodiment of Figure 1A, the shaft 15 of the ski pole 11 is in one part, and the grip is, for example, positioned around and on the shaft 15. The grip is, for example, made of rubber, plastic, or a composite material. The body 19 of the grip has, for example, a shape adapted to sitting comfortably between the palm and fingers of the left or right hand of a user. Indeed, the pole 11 is for example interchangeable between the left and right hands of a user.

[0061] In one embodiment, the basket 25 is located a few centimeters from the lower end of the pole. The basket 25 is, for example, located around the shaft 15 and shaped like a disc. The basket 25 is made of plastic or a composite material and has, for example, some apertures. The tip 27 is the portion of the pole 11 positioned below the basket 25. In some embodiments, the tip 27 is formed from the same piece as the basket 25, while in other embodiments, it is formed by a separate piece to which the basket 25 is fixed to the tip 27, for example by a threaded joint. The bottom end of the pole may exhibit a variety of constructions and attachment methods for the basket 25 and the tip 27, listed examples being illustrative but not exhaustive.

[0062] Figure IB is a side view illustrating a ski pole 13 according to an alternative example to that of Figure 1A.

[0063] The pole 13 illustrated in Figure IB is similar to the pole 11 illustrated in Figure 1A, except that the pole 13 illustrated in Figure IB is a telescopic ski pole having its shaft 15 formed of two parts 15A and 15B.

[0064] In the embodiment of Figure IB, one of the parts of the shaft 15 is arranged to slide into the other. For example, the lower part 15B of the shaft 15 closest to the tip 27 is arranged to slide into the part 15A of the shaft 15 closest to the grip.

[0065] The pole 13 illustrated in Figure IB comprises a locking adjuster 17, which is used to block the position of one part of the shaft 15 with respect to the other. The locking adjuster 17 thus enables the length of the pole 13 to be adjusted .

[0066] In alternative embodiments, the shaft 15 of the ski pole 13 could have more than two parts. The ski pole 13 can then have more than one locking adjuster 17. Furthermore, rather than being telescopic, the portions of the shaft 15 could be joined by other means, for example by hinges and locking mechanisms, thereby allowing the pole to be foldable.

[0067] Figure 2A is a side view of a golf club 12 according to an example embodiment.

[0068] The golf club 12 of Figure 2A comprises a shaft 15 having, at its upper end, a grip 20. At the lower end of the shaft 15, there is a club head 16. [0069] Figure 2B is a side view of an oar 14 for athletic water activities according to an example embodiment.

[0070] The oar 14 of Figure 2B comprises a shaft 15 having, at its lower end a blade 18.

[0071] It is known to fabricate poles such as the ones of

Figure 1A to Figure 2B using fiber-reinforced composites to form the shaft 15. However, the present inventor has noted that, due to the anisotropic nature of composites and the geometry of fibers within the matrix, inherent to the construction of a shaft, this results in susceptibility to "crush" damage to the shaft. With increasing global demand for reduced consumption of natural resources, the present inventor has also noted an inherent inefficiency of utilizing excess carbon or glass fiber reinforcement in a composite shaft to prevent "crush" failure. Instead, improving the load- transfer characteristics of the inner-most, or "core" ply of the layup to naturally resist "crush" forces will provide a more-efficient use of all other fiber reinforcements in the remaining portion of the composite construction. Such a solution will now be described with reference to Figures 3 to 15.

[0072] Figure 3 is a cross-section view of a shaft 151, and corresponds for example to: a cross-section of at least a portion of the shaft 15 of the pole 11 of Figure 1A; or of at least a portion of the lower part 15B of the shaft 15 of the pole 13 of Figure IB, between the locking adjuster 17 and the tip 27; or at least a portion of the upper part 15A of the shaft 15 of Figure IB, between the locking adjuster 17 and the grip. Moreover, Figure 3 can correspond to a cross-section of the shaft 15 of the golf club 12 of Figure 2A or the shaft 15 of the oar 14 of Figure 2B. In the case that the shaft 151 is a shaft of the ski pole 11 or 13 of Figure 1A or IB, it for example has an outer dimension of between 8 mm and 30 mm, depending on where the cross-section is taken. More generally, the diameter of the shaft 151 is for example of between 5 mm and 100 mm, depending on the application.

[0073] The shaft 151 shown in Figure 3 comprise a tubular wall formed of: an inner ply 31, formed of a fiber-reinforced composite, and comprising a tubular braid of fibers; and one or more further plies 33, 35, each formed of a fiber- reinforced composite, wherein the ply 35 for example forms an outer layer of the shaft.

[0074] Each of the plies 31, 33, 35 is, for example, formed of a fabric or of fibers, held within a resin matrix.

[0075] In some embodiments, each of the plies 33 and 35 is wrapped more than once around the shaft. In the example of Figure 3, each of the plies 33, 35 is double-wrapped, although in alternative embodiments, a different number of wraps would be possible.

[0076] In some embodiments, the ply 33 and/or the ply 35 comprises a unidirectional fabric, which is a fabric having an arrangement of fibers that are generally oriented in a same direction. For example, the fabric is formed of tows, or of strips of fibers that are stitched together. The unidirectional fabric of the ply 33 and/or ply 35 is for example oriented such that the fibers are substantially in line with the Z axis of the shaft, and for example at an angle of between -5° and +5° with respect to that axis.

[0077] Additionally or alternatively, the ply 33 and/or the ply 35 may comprises a bidirectional, or biaxial, fabric, which is a fabric having an arrangement of fibers that are generally orientated in two directions, these directions for example being perpendicular. For example, such a fabric is formed by weaving tows or strips of fibers together. For example, the bidirectional fabric of the ply 33 and/or 35 is oriented such that some of its fibers are substantially in a first direction at an angle of between 30° and 60°, and in some cases between 40° and 50°, with respect the axis Z, and other fibers are substantially in a second direction at an angle of between -30° to -60°, and in some cases between -40° and -50°, with respect the axis Z.

[0078] In the cross-section view of Figure 3, the plies 31, 33 and 35 form a tubular wall having a circular shape in cross-section, although in alternative embodiments, different shapes would be possible, including shapes that are substantially circular, such as an ellipse or stadium shape.

[0079] The fibers of the fiber- or fabric- reinforcement composites of the layers 31, 33 and 35 are, for example, carbon fibers, glass fibers, aramid fibers, such as fibers known under the brand names Kevlar and Twaron, boron fibers, fibers known under the brand names of Zyex, Spectra or Dyneema, basalt fibers, bast fibers, such as flax fibers, ramie fibers or hemp fibers, or other natural fibers such as Leaf Fiber (i.e. Pineapple, Banana, Sisal), Stalk Fiber (i.e. rice, corn, wheat), Seed Fiber (i.e. kapok, cotton), or Grass Fiber (i.e. bamboo), or other natural or synthetic vibration-damping material fibers such as elastomers fibers or cork fibers. In some embodiments, the natural fibers are vegetal or vegetal- derived fibers. In some embodiments, the plies 31, 33 and 35 may further comprise a metal mesh, such as a Titanal mesh, titanium mesh or steel mesh.

[0080] In some embodiments, the fibers of the layers 31, 33 and 35 are all different from each other, whereas in other embodiments, the fiber composition may be shared by multiple plies among the plies 31, 33 and 35. In still further embodiments, all of the reinforcements comprising the shaft are produced from the same fiber, and are for example differentiated in terms of fabric construction and/or orientation .

[0081] In one embodiment, the fibers of at least one of the layers 31, 33 and 35 are natural fibers, such as vegetal fibers .

[0082] In one embodiment, the fibers of the ply 31 are ramie and pineapple leaf fibers, while the fibers of the ply 33 are extracted cellulose fibers, and the fibers of the ply 35 are basalt fibers.

[0083] The resins of the fiber- or fabric-reinforced composites of the plies 31, 33 and 35 are, for example, thermosets resins or/and thermoforms resins. In some embodiments the same resin is used in each of the plies 31, 33 and 35, whereas in alternative embodiments, there are at least two different types of resin.

[0084] In one embodiment, the fiber-reinforced composite of the plies 31, 33 and 35 is composed of between 20 %w (weight percent) to 60 %w of resin, for example, between 35 %w to 45 %w of resin.

[0085] In one embodiment, at least two plies of the shaft 151 have fibers oriented in different directions to each other with respect to the axis of the shaft.

[0086] An example of a method of manufacturing the shaft 151 of Figure 3 will now be described with reference to Figures 4 to 8.

[0087] Figure 4 illustrates, with a cross-section view A and a side view B, an example of a mandrel 29 used in the method. The view A is a cross-section view taken along a cutting line AA shown in the view B.

[0088] For example, the mandrel 29 has, in the cross-section view of Figure 4 (view A), a round shape. In other embodiments, the mandrel 29 has an octagonal shape, an oval shape, a decagonal shape, a dodecagonal shape, although in alternative embodiments different shapes that are substantially circular, such as an ellipse or stadium shape, would also be possible.

[0089] In the embodiment of Figure 4, the mandrel 29 has a length 11 in the range from 60 cm to 200 cm, although this length will depend on the length of the shaft that is to be formed .

[0090] In the embodiment of Figure 4, the mandrel 29 has cross-sectional dimensions that vary along its length, such that there is for example a difference in its diameter between one end and the other. The mandrel 29 has, for example, a gradual taper from one end to the other. For example, the mandrel has, at the upper end or handle end, which is the left-hand end in the view B of Figure 4, a width w at its widest point of between 10 mm and 20 mm, and for example of around 15 mm, and, at the lower end or tip end, which is the right-hand end in the view B of Figure 4, a width w at its widest point of between 8 mm and 3 mm, and for example of around 4 mm.

[0091] The mandrel 29 is for example solid, and is made of steel, aluminum or another rigid or flexible material such as silicone, elastomeric polymer, acrylonitrile butadiene (ABS), or polyamide (PA).

[0092] In the present embodiment, a central axis of the mandrel 29 running along its length will be called axis Z, like the axis of the shaft.

[0093] Figure 5 is a cross-section view of the mandrel 29 after application of the ply 31. In the embodiment of Figure 5, the ply 31 covers the mandrel 29 around its lateral circumference. For example, the ply 31 is a tubular braid that is formed separately and then pulled over the mandrel 29, or a tubular wrapping that is directly formed around the mandrel using a filament winding process to approximate the load-distribution characteristics of a tubular braid, such a process being known to those skilled in the art. The tubular braid 31 is for example formed of ramie and pineapple leaf fibers or other another natural or vegetal fiber.

[0094] The ply 31 for example has a length shorter than the length 11 of the mandrel 29, a portion of the mandrel of between 2 cm and 20 cm in length for example remaining exposed at each of its ends, thereby facilitating the manipulation of the mandrel 29 during subsequent processes.

[0095] In some embodiments, a wet resin is applied to the tubular braid 31 prior to, or after, positioning the braid on the mandrel 29.

[0096] Alternatively, a dry resin is used in the layup. For example, in one embodiment, a resin film is wrapped around the mandrel 29 before the application of the ply 31. In another embodiment, a resin film is formed on the internal surface of the ply 31 before the assembly of the ply 31 around the mandrel 29. In yet another embodiment, a resin film is placed on or fixed to the external surface of the ply 31 before the assembly of the ply 31 around the mandrel 29. According to this embodiment, resin, such as pieces of resin film, can be placed at several locations around the surface of the mandrel 29 before the assembly of the ply 31 around the mandrel, in order to hold the ply 31 in position during the subsequent steps prior to curing.

[0097] Figure 6 illustrates an example of a tubular braid 30. The braid 30 is for example formed of many fiber tows, for example between 20 and several hundred, that are braided to form a tubular shape by a tubular braiding loom. All of the tows used to form the braid may be of a same type of fiber, or two or more different fiber types can be mixed in order to obtain certain desired properties, such as shock damping and/or high tensile strength.

[0098] In some embodiments, the tows of the tubular braid are formed in two different orientations with respect to the axis of the braid, certain tows 301 being formed at a first orientation, and certain tows 303 being formed at another different orientations, one example of each of these tows being labelled in Figure 6.

[0099] Once the braid is situated and tightly drawn around the mandrel 29, in view of the variation in the diameter of the mandrel from one end to the other, the orientations of the tows of the braid with respect to the axis Z of the mandrel for example varies along the length of the mandrel. In particular, as the upper end of the mandrel 29 is wider than the lower end, the angle between the tows 301 and the axis Z, and the angle between the tows 303 and the axis Z, are not the same at the upper end and at the lower end. At the upper end, the tows 301, and thus also the fibers within the tows 301, are for example oriented with an angle of between 30° and 80°, and for example of between 40° and 60°, with respect to the axis Z, and the tows 303, and thus also the fibers within the tows 303, are for example oriented with an angle of between -30° and -80°, and for example of between -40° and -60°, with respect to the axis Z. At the lower end, the braid is tighter and thus narrower than at the upper end, such that the braid is in contact with the shaft 151. Thus, at the lower end, the fibers are for example oriented at a lower angle with respect to the axis Z, the tows 301 for example being orientated at an angle of between 10° and 40° with respect to the axis Z, and the tows 303 for example being orientated at an angle of between -10° and -40° with respect to the axis Z. [0100] Figure 7 is a cross-section view of the structure shown in Figure 5, after application of the ply 33. In the example of Figure 7, the ply 33 is wrapped at least two times around the outer surface of the structure, although a different number of wraps would be possible. The ply 33 is, for example, formed around the structure using a roll-wrapping process, or a hand-lay-up process. The ply 33 has, for example, the same length as the ply 31.

[0101] In some embodiments, the ply 33 is a non-woven stitched tri-axial ply, such as a 0/+45/-45 ply, formed for example of a combination of extracted cellulose, ramie, and pineapple leaf fibers. The ply 33 for example has a resin pre-impregnation of between 20 % and 60 %. In some embodiments, the amount of resin is chosen such that resin will not only bind with the ply 33, but also with the fibers of the tubular braid 31.

[0102] Figure 8 is a cross-section view of the structure shown in Figure 7 wrapped with the ply 35. The application of the ply 35 is for example the same or similar to the application of the ply 33, and will not be described in detail. The plies 35, 33 have, for example, the same length as the ply 31.

[0103] In one embodiment, the ply 35 is a double wrap of unidirectional fabric, for example of basalt fiber, having a 20% to 40% resin pre-impregnation, the unidirectional fabric for example being orientated at around 0°, for example at an angle of between +5° and -5°, with respect to the axis Z of the shaft.

[0104] For example, the resin is added to fibers to form the fabric of each ply 31, 33 and 35 through either: pre impregnating, meaning that the fibers are impregnated with a combination of wet and/or dry resins at or around the time the material is produced; wet layup, meaning that the material comprises wet resin at the time it is positioned around the mandrel 29; or an infusion process, meaning that the resin is introduced to the material after it has been positioned around the mandrel 29, for example by placing the layup in a contained mold or compression system with a vacuum-based pull or a pressure-based push system to force the resin into the part.

[0105] After the step of formation of the ply 35, the structure shown in Figure 8 is for example wrapped in a compression layer, such as a compressive cellulose layer (not illustrated), and cured by heating for a period of time depending on the nature and the formulation of the resin matrix .

[0106] After the curing step, the cellulose layer is for example removed by unwinding or sanding and the mandrel 29 is removed from the structure.

[0107] Figure 9 is a cross-section view of a shaft 153 according to another embodiment. Like the shaft 151, the shaft 153 for example corresponds to a cross-section of at least a portion of the shaft 15 of the pole 11 of Figure 1A; at least a portion of the lower part 15B of the shaft 15 of the pole 13 of Figure IB; or at least a portion of the upper part 15A of the shaft 15 of Figure IB. Moreover, Figure 3 can correspond to a cross-section of the shaft 15 of the golf club 12 of Figure 2A, or the shaft 15 of the oar 14 of Figure 2B.

[0108] The shaft 153 illustrated in Figure 9 is similar to the shaft 151 illustrated in Figure 3, but with different plies, as will now be described in more detail.

[0109] For example, the shaft 153 shown in Figure 9 comprises a tubular wall formed of: an inner ply 39, formed of a fiber-reinforced composite comprising a tubular braid of fibers, and for example similar to the ply 31 of Figure 3; and one or more further plies 41, 43, each formed of a fiber- reinforced composite, wherein the ply 43 for example forms an outer layer of the shaft.

[0110] In some embodiments, each of the plies 41 and 43 is wrapped more than once around the shaft. In the example of Figure 9, the ply 41 is triple wrapped, and the ply 43 is double-wrapped, although in alternative embodiments, a different number of wraps would be possible.

[0111] In some embodiments, one of the plies 41, 43 comprises a unidirectional fabric, and/or one of the plies 41, 43 comprises a multi-directional fabric.

[0112] In the cross-section view of Figure 9, the plies 39, 41 and 43 form a tubular wall having a circular shape in cross-section, although in alternative embodiments, different shapes would be possible, such as shapes that are substantially circular, such as an ellipse, a rounded triangle or other rounded geometric shape, or stadium shape.

[0113] The fibers of the fiber- or fabric- reinforcement composites of the plies 39, 41 and 43 are, for example, carbon fibers, glass fibers, aramid fibers, such as fibers known under the brand names Kevlar and Twaron, boron fibers, fibers known under the brand names of Zyex, Spectra or Dyneema; cellulose fibers, such as bast, leaf or grass fibers, or other natural fibers such as mineral fibers; or other natural or synthetic vibration-damping material fibers such as elastomeric fibers or cork fibers. In some embodiments, the plies 39, 41 and 43 may further comprise a metal mesh, such as a titanal mesh, titanium mesh or steel mesh. [0114] In some embodiments, the fibers of the plies 39, 41 and 43 are all different from each other, whereas in other embodiments, the fiber composition may be shared by multiple plies 39, 41 and 43. In still further embodiments, all of the reinforcements comprising the shaft are produced from the same fiber, and are for example differentiated in terms of fabric construction and/or orientation.

[0115] In one embodiment, the fibers of at least one of the layers 39, 41 and 43 are natural fibers, such as vegetal fibers .

[0116] In one embodiment, the fibers of the layer 43 are ramie fibers, while the fabric of the layer 39 is made of a bamboo and pineapple leaf fibers and the layer 41 is made of bamboo fibers.

[0117] Resins of the layers 43 can, for example, be thermosets resins or/and thermoforms resins. In some embodiments the same resin is used for each of these layers, whereas in alternative embodiments, there are at least two different types of resin.

[0118] In one embodiment, the resin of at least the ply 39, and for example also of the plies 41 and 43, is an epoxy resin.

[0119] In one embodiment, the fabric of the layer 43 is composed of between 20 %w (weight percent) to 60 %w of resin, for example, between 35 %w to 45 %w of resin.

[0120] An example of a method of manufacturing the shaft 153 of Figure 9 will now be described with reference to Figures 10 to 15.

[0121] Figure 10 illustrates, with a cross-section view A and a side view B, a mandrel 45 used in the method. The view A is a cross-section view taken along a cutting line AA shown in the view B. [0122] For example, the mandrel 45 has, in the cross-section view, a round shape. In another embodiment, the mandrel 45 can have a rounded triangular shape, a rounded square shape, an octagonal shape, an oval shape, a decagonal shape, a dodecagonal shape, although in alternative embodiments different shapes that are substantially circular, such as an ellipse or stadium shape, would also be possible.

[0123] In the embodiment of Figure 10, the mandrel 45 has a length 11 similar to the length 11 of the mandrel 29 shown in Figure 4. The width w is, however, for example reduced to accommodate a flexible sleeve, as will be described in more detail below.

[0124] The mandrel 45 comprises, for example, a circumferential recess 451 on its lateral surface along the axis Z for receiving the sleeve. In the embodiment illustrated in Figure 10, the recess 451 has a length 12 shorter than the length 11 of the mandrel 45, a non-recessed portion of the mandrel 45 of between 2 cm and 20 cm in length for example remaining at each of its ends, thereby facilitating the manipulation of the mandrel 45 during subsequent processes. The mandrel 45 comprises, for example, on both sides of the recess 451, a lip 453 at the lower end, and a lip 455 at the upper end.

[0125] For example, the cross-section of the view B of Figure 10 corresponds to a cross-section of the mandrel 45 between the lips 453 and 455.

[0126] In the present embodiment, a central axis of the mandrel 45 running along its length will be called axis Z, like the axis of the shaft.

[0127] The mandrel 45 is for example solid, and is made of steel, aluminum or another rigid material. [0128] Figure 11 is a side view illustrating the mandrel 45 after application of the polymeric sleeve 47. The sleeve 47 has the property of expanding upon being heated.

[0129] In the embodiment of Figure 11, the polymeric sleeve 47 is fitted around the mandrel 45 and seated in the recess 451. The polymeric sleeve 47 has, for example, the same length as the recess 451 and extends between the lips 453 and 455.

[0130] For example, the sleeve 47 is made of a polymer such as an elastomeric rubber or silicone.

[0131] Figure 12 is a side view illustrating the structure shown in Figure 11, and a resin film 37, which is to be wrapped at least once around the sleeve 47 of the mandrel 45.

[0132] The film 37 is for example formed around the structure shown in Figure 11 using a roll-wrapping process, or a hand- lay-up process. The film 37 has, for example, the same length as the sleeve 47. The resin of the film 37 is for example any thermoformed or thermosets resin, for example, an epoxy resin.

[0133] Figure 13 is a side view illustrating the structure shown in Figure 12 after application of the ply 39. In the embodiment of Figure 13, the ply 39 covers the structure shown in Figure 12 around its lateral circumference. For example, the ply 39 is a tubular braid that is formed separately and then pulled over the structure of Figure 12, or a tubular braid that is directly formed around the mandrel using a filament winding process to approximate the load-distribution advantages of a tubular braid, such a process being known to those skilled in the art. The tubular braid 39 is for example formed of flax or other another natural or vegetal fiber.

[0134] In the embodiment illustrated in Figure 13, the ply 39 has, for example, the same length as the sleeve 47. [0135] Figure 14 is a side view of the structure shown in Figure 13, and of the ply 41 which is to be wrapped around the structure of Figure 13.

[0136] In one embodiment, the ply 41 is wrapped at least two times, for example three times, around the outer surface of the structure shown in Figure 13.

[0137] The ply 41 for example comprises a sub-layer 411 made of a fabric, which has a thickness of around 0.5 mm. This fabric is for example formed of natural fibers, such as of bamboo fibers. The ply 41 also for example comprises a further sub-layer 413 made of a resin film, such as an epoxy resin film. The sub-layer 413 is, for example, situated as a lining on the inner facer of the sub-layer 411.

[0138] For example, the two sub-layers 411 and 413 of the ply 41 are attached or placed together, and then wrapped around the structure shown in Figure 13 using a roll-wrapping process, or a hand-lay-up process. The layer 41 has, for example, the same length as the sleeve 47.

[0139] Figure 15 is a side view illustrating the structure shown in Figure 14 after application of the ply 41, and of the ply 43, which is to be wrapped around the structure of Figure 14.

[0140] The application of the ply 43 is for example the same or similar to the application of the ply 41, and will not be described in detail.

[0141] In one embodiment, the layer 43 is wrapped at least two times around the outer surface of the structure shown in Figure 15. The ply 43 has, for example, the same length as the sleeve 47. The ply is for example pre-impregnated with resin, such as an epoxy resin.

[0142] After the step of applying the ply 43, the structure shown in Figure 15 is for example wrapped in a compression layer, such as a compressive cellulose layer, and cured by heating. Under cure temperature the sleeve 47 expands, placing an outward force on the layup and infusing the resin of the film 37 at least into the ply 39. As the sleeve expands, it is resisted by the compression forces applied by the compression wrapper, and thus the layup receives the necessary compaction to infuse the resin well through the layup without creating voids or crimps in the reinforcements.

[0143] After the curing step, the cellulose layer is for example removed by sanding, and the mandrel 45 is removed from the structure.

[0144] An advantage of the use of natural fibers in the fabrics of the layer of the shaft is that it provides a pole having a lower ecological impact with respect to shafts made entirely of synthetic materials. Indeed, the production of 1 Kg of carbon fiber is estimated to result in around 30 Kg of greenhouse gasses, whereas the use of 1 Kg of natural fibers is estimated to result in only around 0.5 Kg of greenhouse gasses, and depending on the source of the natural fibers, can even be carbon neutral or carbon negative in some cases .

[0145] A further advantage of the use of natural fibers is that, since the density of natural fibers is lower than that of synthetic fibers, a relatively light-weight shaft can be produced .

[0146] According to one example embodiment, the shaft as described in the present disclosure is fabricated based on the following process: a tubular braid comprised of ramie and pineapple leaf fibers is situated upon the mandrel. A triaxial fabric comprised of ramie, extracted cellulose, and pineapple leaf fibers is situated with a sheet of bamboo fiber inset 2cm from its leading edge in the roll-wrapping layup which is the same length as the triaxial fabric but having a narrower width such that the triaxial fabric covers one complete revolution of the mold more than the bamboo fiber plus 2cm; a tubular braid comprised of ramie and pineapple leaf fibers is situated upon the mandrel. Mold is placed on a filament winding machine and a ply of extracted cellulose and pineapple leaf fibers is wound upon the mandrel in a +20/-20⁰ orientation. A unidirectional fabric comprised of ramie and extracted cellulose fibers in a 0° orientation is roll-wrapped to form the final ply; a tubular braid comprised of ramie and pineapple leaf fibers is situated upon the mandrel. Mold is placed on a filament winding machine and a ply of extracted cellulose and pineapple leaf fibers is wound upon the mandrel in a +20/-20⁰ orientation. A unidirectional fabric comprised of basalt fibers in a 0° orientation is roll-wrapped to form the final ply; a tubular braid comprised of ramie and basalt fibers is situated upon the mandrel. A triaxial fabric comprised of ramie, extracted cellulose, and pineapple leaf fibers is situated with a sheet of bamboo fiber inset 2cm from its leading edge in the roll-wrapping layup which is the same length as the triaxial fabric but having a narrower width such that the triaxial fabric covers one complete revolution of the mold more than the bamboo fiber plus 2cm; and additional permutations of the above layups may include changing the composition of the tubular braid such that the fiber content is comprised of ramie and basalt fibers, extracted cellulose and basalt fibers, extracted cellulose and pineapple leaf fibers, pineapple leaf and basalt fibers, or exclusively basalt fibers.

[0147] An advantage of the overlap of fabrics which have a unidirectional fibers arrangement and fabrics which have a multi-directional fibers arrangement is that it improves the mechanical resistance to the forces that will imparted on the shaft during use.

[0148] A further advantage of the overlap of fabrics which have an unidirectional fibers arrangement and fabrics which have a multi-directional fibers arrangement is that the nature of the fibers can easily be adapted in order to optimized the shaft for its intended use.

[0149] A further advantage of the overlap of fabrics which have an unidirectional fibers arrangement and fabrics which have a multi-directional fibers arrangement is that it reduces the quantity of raw materials that are required to reinforce the shaft.

[0150] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these embodiments can be combined and other variants will readily occur to those skilled in the art. In particular, the process of manufacturing the shaft 153 can be easily adapted to the shaft 151.

[0151] Finally, the practical implementation of the embodiments and variants described herein is within the capabilities of those skilled in the art based on the functional description provided hereinabove.

Claims

1.A pole or shaft for athletic activities having a tubular structure and comprising, along at least a part of its length: an inner layer (31, 39) formed of a first fiber- reinforced composite comprising a tubular braid of fibers; and an outer layer (35, 43) comprising a second fiber- reinforced composite.

2. The pole or shaft according to claim 1, wherein at least a portion of the fibers of the first and/or second fiber- reinforced composite are natural fibers.

3. The pole or shaft according to claim 2, wherein the fibers of the first and/or second fiber-reinforced composite are vegetal-based fibers, such as fibers of bamboo, flax, ramie, pineapple leaf and/or extracted cellulose or nanocellulose.

4. The pole or shaft according to any of claims 1 to 3, wherein the shaft has a weight percentage of resin of between 20 %w and 60 %w, for example of between 35 %w and 45 %w.

5. The pole or shaft of any of claims 1 to 4, wherein the first composite comprises an epoxy resin.

6.A ski or trekking pole comprising the pole or shaft according to any of claims 1 to 5, intended for a ski pole or a trekking pole.

7.A golf club comprising the pole or shaft according to any of claims 1 to 5.

8.A floorball, hockey, or broomball stick comprising the pole or shaft according to any of claims 1 to 5.

9.An oar or paddle comprising the pole or shaft according to any of claims 1 to 5.

10. A method of manufacturing a pole or shaft for athletic activities, the method comprising: positioning a tubular braid (31, 39) around a mandrel

(29, 45); positioning at least one further ply (33, 35, 41, 43) around the tubular braid, the at least one further ply being impregnated with resin; wrapping a compressive layer around the at least one further ply, or otherwise positioning a compressive element or apparatus around the at least one further ply; and curing by heating.

11. The method according to claim 10, wherein the mandrel (29, 45) is covered by a polymeric sleeve (47).

12. The method according to claim 10 or 11, wherein a resin film is wrapped around the mandrel, or placed on the internal surface of the tubular braid, before the step of positioning the tubular braid around the mandrel.

13. The method according any of claims 10 to 12, wherein a resin film is placed on the external surface of the tubular braid before the step of positioning the tubular braid around the mandrel.

14. The method of claim 12 or 13, wherein the resin film (37) is a film of epoxy resin.

15. The method of any of claims 10 to 14, wherein the at least one further ply (33, 35, 41, 43) is lined with a further resin film (412).