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.
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.
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.
The use of a composite construction for the shaft, in which reinforcement fabrics or fibers are captured within a resin matrix, provides a greater ability to create a pole with both stiffness (or flexibility) and weight characteristics that are unachievable with an alloy shaft. Indeed, materials such as carbon fibers can have many-times the stiffness and/or strength by weight of aluminum alloy.
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 synthetic fibers of the reinforcement fabrics used in composites, such as carbon fibers, fiberglass, Kevlar, boron, etc., with renewable fibers. The difficulty in making this transition lies in the inherent difference of mechanical characteristics exhibited by these natural fibers and their synthetic counterparts.
Embodiment of the present disclosure address all or some of the drawbacks of known shafts for athletic activities.
One embodiment provides a shaft for athletic activities comprising, along at least a part of the length of the shaft:
According to an embodiment, there are at least three cavities between the internal wall and the external wall.
According to an embodiment, at least one portion of the fibers of the first and/or second fiber-reinforced composite are natural fibers.
According to an embodiment, the fibers of the first and/or second fiber-reinforced composite are vegetal-based fibers including those of bamboo, flax, ramie, pineapple leaf and/or extracted cellulose or nanocellulose.
According to an embodiment, the first and second composites each have a weight percentage of resin of between 20% and 60%, for example of between 35% and 45%.
According to an embodiment, the first and/or second composite is a fabric-reinforced composite.
According to an embodiment, the internal wall and/or the external wall are filament wound plies.
According to an embodiment, at least one of the first and/or second composites comprises a fabric, a filament-wound ply, or braid having fibers at an orientation angle of between 30° and 60°, and/or of between −30° and −60°, with respect to an axis of the shaft.
According to an embodiment, at least one of the first and second composites comprises a fabric, tape or filament-wound ply, having fibers at an orientation angle of between −15° and 15° with respect to an axis of the shaft.
According to an embodiment, the external wall is round, or substantially round, in cross-section.
According to an embodiment, the internal wall is tubular.
According to an embodiment, the internal wall comprises a plurality of planar wall portions, linked for example by curved corners.
According to an embodiment, fibers of the external wall are orientated in one or more first directions with respect to an axis of the shaft, and fibers of the internal wall are orientated in one or more second directions, different to the first directions, with respect to the axis of the shaft.
One embodiment provides a method of manufacturing a shaft, the method comprising:
According to an embodiment, the outer surface of the structure is round, or substantially round, in cross-section, and covering the structure with at least one second ply involves the use of roll-wrapping.
The solution presented herein involves making natural fiber reinforcement competitive with synthetic fiber reinforcement by utilizing a unique geometry for the construction of the natural fiber shaft, where each fiber reinforcement is used more-efficiently than is standard practice for current synthetic fibers poles.
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, for example, a maximum outer dimension of 30 mm and a minimum outer dimension of 8 mm. The structure of the shaft 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.
One embodiment provides the utilization of spacer elements in the process of fabrication of the shaft in the form of solid, removeable elements, which may be variably affixed to the mandrel/mold. The purpose of the spacer elements is to create a final structure which is more complex and more rigid than a standard solid-wall shaft at a given weight utilizing the same materials. As such, it is also possible to use a material with lesser mechanical characteristics to achieve a similar rigidity at a similar weight, depending on the ratios of weight to mechanical characteristic of the two materials.
One embodiment provides the fabrication of the shaft by various combinations of fabric reinforcement plies impregnated with resin and spacer elements around a rigid or flexible mandrel, or an expanding bladder. Plies may be added by roll-wrapping, hand-layup, filament winding, or any other method typical to composite layup assembly.
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.
The significantly tubular shape of the shaft may incorporate shaping such as a rounded-triangular, rounded-square, or other shape or shapes around the vertical axis of the shaft.
The shaft may include tapers, bends, and other features along its vertical axis.
Plies of reinforcement fabric may be composed of carbon fiber, fiberglass, Aramid/Kevlar, Twaron, boron, Zyex, Spectra/Dyneema; 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); 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.
The reinforcing fabric may be constructed of fibers in a braided, woven, knit, stitched, or uni-directional arrangement.
The resin may be a thermoset or thermoform resin, and may be added to the fabric through: pre-pegging, i.e. impregnating the fabric with a combination of wet and/or dry resins at or around the time the fabric is produced; wet layup, i.e. introducing a wet resin to the fabrics in close proximity to when the fabrics are utilized for construction of the shaft; or an infusion process, i.e. where resin is introduced to the fabric once the layup is placed in a contained mold or compression system.
A composite of an internal wall of the pole can be constituted of tubular braid, or any construction of reinforcement fabric.
The length of the pole may be segmented into multiple sections to create a telescopic or folding pole.
The process of situating the reinforcement fabric for the shaft fabrication can be hand-lay-up, roll wrapping, filament winding, or any other process typical to the fabrication of fiber-reinforced composite items.
A rigid mandrel may have any form that is advantageous to the construction of the correct internal geometry of the shaft.
The spacer elements may be affixed to the mandrel, or held in position by a combination of the mandrel geometry and the layup, or in such a manner that they are not rigidly held in place and are captured only by the layup.
The spacer elements may extend the full length of the shaft, or be limited to a portion of the length of the shaft, or any segment of the shaft when utilized to form multi-segment shafts.
One or more spacer elements may be used to create a cross-section that is significantly round or which is more-lobular in shape.
One or more spacer elements may be added between multiple plies to strengthen the structure as needed.
The spacer elements may be constructed of steel, aluminum, or other metals or materials that, for example, possess appropriate stiffness and/or dimensional stability to function in the layup and curing processes.
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:
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.
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.
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 shaft.
Unless specified otherwise, the expressions “around”, “approximately”, “substantially” and “in the order of” signify within 10%, and preferably within 5%.
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.
The ski pole 11 of
In the embodiment of
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.
The pole 13 illustrated in
In the embodiment of
The pole 13 illustrated in
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.
The golf club 12 of
The oar 14 of
It is known to fabricate poles such as the ones of
In the case that the shaft 151 is a shaft of the ski pole 11 or 13 of
The shaft 151 shown in
Each of the internal and external walls 31, 30, for example comprises one or more plies formed of a fabric or of fibers held within a resin matrix.
In the example of
In some embodiments, the cavities 32A, 32B and 32C do not extend the full length of the shaft 15. For example, a portion of the shaft 15 of the pole 11 closest to the tip end, or at least a portion of the bottom part 15B, or the upper part 15A of the shaft 15 of the pole 13, has a cross-section view similar to the cross-view illustrated in
In one embodiment, the internal wall 31 is tubular, implying that, in cross-section, it forms a continuous wall. Furthermore, the internal wall 31 for example comprises a plurality of planar wall portions linked, for example, by curved corners that make contact with the inner surface of the external wall 30. For example, the internal wall 31 of the shaft 151 consists of three planar wall portions 31A, 31B and 31C linked by three curved corners. Furthermore, in one example, the three planar wall portions are orientated at between 40° and 100° with respect to each other, in order to form a tube that in cross-section has substantially the shape of a triangle with rounded corners. Each of the rounded corners for example has a curvature that matches the curvature of the inner surface of the external wall 30. An angled θ occupied by each curved corner is for example between 5° and 60° in the example of
In one embodiment, the internal wall 31 has, in cross-section, one of a rounded equilateral triangle shape, a rounded isosceles triangle shape, a rounded-square shape, a rounded-pentagonal shape, a rounded-hexagonal shape, a rounded-heptagonal shape, or a rounded-octagonal shape. The shape of the internal wall 31 is not limited to the cited shapes and the internal wall 31 can have any other shape. For example, the internal wall 31 could alternatively have an octagonal shape, a circular shape, a triangular shape, a decagonal shape, a dodecagonal shape or any shape that can be inscribed within a circle, and which is advantageous to the desired mechanical characteristics, dimensions, and flex pattern desired for the shaft.
In the cross-section view of
The fibers of the fiber- or fabric-reinforced composites of the internal and external walls 31, 30 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 (ie. 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 including extracted cellulose or nanocellulose. In some embodiments, the internal or external wall 31, 30 may further comprise a metal mesh, such as a Titanal mesh, titanium mesh or steel mesh.
In some embodiments, the fibers of the internal wall 31, and the fibers of each of the plies 35, 37 and 39 of the external wall 30, are all different from each other, whereas in other embodiments, there are at least two different types of fibers among the plies of the internal and external walls 31, 30. In one embodiment all the plies and reinforcements comprising the shaft 151 are produced from the same types of fibers, and the plies are then only different in terms of fabric construction or orientation.
In one embodiment, the fibers of the internal wall 31, and/or of at least one of the plies 35, 37 and 39, are natural fibers, such as organic fibers, or vegetal or vegetal-derived fibers. For example, the fibers of the internal wall 31 and of each of the plies 35 and 37 are bamboo fibers, while the fibers of the ply 39 are, for example, ramie fibers.
The resins of the fiber- or fabric-reinforced composites of the internal and external walls 31, 30 are, for example, thermosets resins or/and thermoforms resins. In some embodiments the same resin is used in each of the walls 31, 30, whereas in alternative embodiments, there are at least two different types of resin.
In one embodiment, the fiber-reinforced composite of the internal and external walls 31, 30 is composed of between 20% w (weight percent) to 60% w of resin, for example, between 35% w to 45% w of resin.
In some embodiments, the fibers of the internal wall 31 and of each of the plies 35, 37, 39 of the external wall 30 are in the form of a fabric, such as a braid, or a woven, knitted, meshed or stitched fabric. The fibers in the fabric are for example orientated in a multi-directional, bi-directional or uni-directional arrangement. For example, the fibers are prepared in the form of a thread, or in the form of uni-directional strips, and the threads and/or strips are woven, stitched or otherwise assembled in a multi-directional, bi-directional or uni-directional arrangement in order to form a multidirectional, bi-directional or uni-directional fabric respectively.
In one embodiment, in order to provide a relatively high bending strength of the shaft 151, the fabric of at least one of the plies of the walls 30, 31 comprises a uni-directional fabric oriented substantially in line with the Z axis of the shaft, and for example at around an angle of between −5° and +5° with respect to that axis, and the fabric of at least one other ply of the walls 30, 31 comprises a multi-directional fabric, and/or a bi-directional fabric having fibers in a first direction oriented with an angle of between 30° and 60°, and in some cases between 40° and 50°, with respect the axis Z, and having fibers in a second direction oriented with an angle of between −30° to −60°, and in some cases between −40° and −50°, with respect the axis Z.
In one example, a ply of the internal wall 31 is a tubular braid, the ply 35 is a woven bi-directional fabric, the ply 37 is a uni-directional fabric, and/or the ply 39 is a stitched bi-directional fabric.
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.
A method of manufacturing the shaft 151 of
The outer surface of the mandrel 29 is, for example, shaped in accordance with the shape of the internal wall 31 of the shaft that is to be formed.
In the example of
For example, the mandrel 29 has, in the cross-section view of
In the embodiment of
In the embodiment of
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 styrene (ABS), or polyamide.
In the present description, a central axis of the mandrel 29 running along its length will be called axis Z, like the axis of the shaft.
In the embodiment of
In the embodiment illustrated in
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 401 being formed at a first orientation, and certain tows 403 being formed at another different orientations, one example of each of these tows being labelled in
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 401 and the axis Z, and the angle between the tows 403 and the axis Z, are not the same at the upper end and at the lower end. At the upper end, the tows 401, and thus also the fibers within the tows 401, are for example oriented with an angle of between 30° and 60°, and for example of between 40° and 50°, with respect to the axis Z, and the tows 403, and thus also the fibers within the tows 403, are for example oriented with an angle of between −30° and −60°, and for example of between −40° and −50°, 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 401 for example being orientated at an angle of between 10° and 40° with respect to the axis Z, and the tows 403 for example being orientated at an angle of between −10° and −40° with respect to the axis Z.
The spacer elements 33 are used to form the cavities 32A, 32B and 32C between the internal wall 31 and the external wall 39 of finished shaft. In some embodiments, an inner surface of the external wall 39 of the finished shaft is to be round, and the spacer elements 33 are formed around the outer surface of the structure so that the cross-section view of the structure shown in
In the embodiment of
The spacer elements 33 are for example positioned so as to leave regions of the exterior surface of the ply 31′ exposed between spacer elements 33. In the example of
In some embodiments, the spacer elements 33 do not extend the whole length of the mandrel 29, but have dimensions that are progressively reduced towards the thin end of the mandrel, the spacer elements 33 for example stopping between 10 and 40 cm from the end of the ply 31′.
The spacer elements 33 are, for example, made of steel, aluminum or other rigid metals or materials. In some embodiments, the spacer elements 33 are made of the same material as the mandrel 29.
In the example of
In one embodiment, the ply 35 is wrapped at least two times around the outer surface of the structure shown in
The ply 35 is, for example, formed around the structure shown in
The ply 35 has, for example, the same length as the ply 31′.
For example, in one embodiment the plies 31′ and 35 are both filament windings, and the ply 35 is formed during the same process step as ply 31′ within a filament-winding process. In such a case, the plies 31′ and 35 can be formed of a single continuous filament. For example, the ply 31′ is formed around the mandrel 29 without cutting the filament at the end of the formation of the ply 31′, the spacer elements 33 are then placed around the structure, and the ply 35 is then formed around the structure using the same filament as the ply 31′.
The application of each of the plies 37 and 39 is for example the same or similar to the application of the ply 35, and will not be described in detail.
The plies 37, 39 have, for example, the same length as the ply 35.
For example, the resin is add to fibers to form the fabric of each ply 31′, 35, 37, 39 through either: pre-impregnating, meaning that the fibers are impregnated with a combination of wet and/or dry resins at or near 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 layup and the plies.
After the step of formation of the ply 39, the structure shown in
After the curing step, the cellulose layer is for example removed by sanding or by unwinding, and the mandrel 29 is removed from the structure. The spacer elements 33 are also removed to form the cavities 32A, 32B and 32C of
In the case that the shaft 153 is a shaft of the ski pole 11 or 13 of
The shaft 153 for example has the same internal wall 31 as the shaft 151 shown in
The shaft 153 for example comprises an intermediate wall 41, which is for example round in cross-section, contacting and fixed to the curved corners of the internal wall 31. Stacks 43 of tape are for example positioned at certain points around the outer surface of the intermediate wall 41, with spaces in between these stacks 43 defining further cavities 50 within the structure. The external wall 30 is for example round in cross-section, and has an inner surface that contacts each of the stacks 43, thereby rigidly fixing the external wall 30 to the internal wall 31. The external wall 30 for example comprises an inner ply 47 and an outer ply 49.
In alternative embodiments, the internal wall 31, the intermediate wall 41, and the external wall 30, could have any combination of different shapes when situated in the manner prescribed by the design of the mold and spacing system result in a shape of the external wall 30, which is substantially circular, such as an ellipse, a stadium shape or a rounded-multi-faceted shape.
In
In
The tape forming the stacks 43 is for example a uni-directional fiber tape held in a resin matrix, such that each stack 43 forms a fiber-reinforced composite stack.
Fibers of the plies forming the internal, intermediate, and external walls 31, 41, 30, and of the tapes of the stacks 43 are, for example, chosen from the same list as the fibers of the plies of the shaft 151. In some embodiments, the fibers of the plies forming the internal, intermediate, and external walls 31, 41, 30, are all different from each other, whereas in other embodiments, there are at least two different types of fibers among the plies. In one embodiment, the fibers of at least one of the plies forming the internal, intermediate, and external walls 31, 41, 30 are natural fibers, such as organic fibers, or vegetal or vegetal-derived fibers.
Resins of fiber- or fabric-reinforced composites of the internal, intermediate and external walls 31, 41, 30, and in some cases of the stacks 43, are, for example, thermoset resins or/and thermoform resins. In some embodiments, the same resin is used for each of these composites, whereas in alternative embodiments, there are at least two different types of resin. In one embodiment, each of these composites is composed of between 20% w to 60% w of resin, for example, between 35% w to 45% w of resin.
In one embodiment, in order to provide a relatively high strength of the shaft 153, the fabric of at least one ply of the internal wall 31, the intermediate wall 41 and the external wall 30 comprises a uni-directional fabric oriented 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, and the fabric of at least one other ply of the internal wall 31, intermediate wall 41 and external wall 30 comprises a multi-directional fabric, and/or a bi-directional fabric having fibers in a first direction oriented with an angle of between 30° and 60°, and in some cases between 40° and 50°, with respect the axis Z, and having fibers in a second direction oriented with an angle of between −30° to −60°, and in some cases between −40° and −50°, with respect the axis Z.
In one example, a ply of the internal wall 31 is a tubular braid of bamboo fibers, a ply of the intermediate wall 41 is a tubular braid of ramie fibers, the ply 47 of the external wall 30 is a uni-directional tape of ramie fibers, and/or the ply 49 of the external wall 30 is a stitched ply of +45°/−45° bamboo fiber fabric.
In one embodiment, at least two plies of the shaft 153 have fibers oriented in different directions to each other with respect to the axis of the shaft.
In an alternative embodiment (not illustrated) to that of
In an alternative embodiment (not illustrated) to that of
The method for example starts with the same steps as described above with reference to
In
For example, in one embodiment the plies 31′ and 41′ are both filament windings, and the ply 41′ is formed during the same process step as ply 31′ within a filament-winding process. In such a case, the plies 31′ and 41′ can be formed of a single continuous filament. For example, the ply 31′ is formed around the mandrel 29 without cutting the filament at the end of the formation of the ply 31′, the spacer elements 33 are then placed around the structure, and the ply 41′ is then formed around the structure using the same filament as the ply 31′.
The spacer elements 45 are for example curved in cross-section so as to match the curvature of the outer surface of the intermediate wall 41 and the curvature of the inner surface of the external wall 30 to be formed. The spacer elements 45 are, for example, made of any type of material as the material described for the spacer elements 33 described in relation with
The stacks 43 of tape are, for example, formed using a hand-lay-up process. Each stack 43 for example extends the same length as the ply 41′.
The spacer elements 45 are for example of the same length as the spacer elements 33, or, for example, shorter than the spacer elements 33. The spacer elements 45 are, for example, situated in any portion of the length w2 as described in
In one embodiment, the ply 47 is formed of a fabric wrapped at least two times around the outer surface of the structure shown in
The application of the ply 49 is, for example, the same or similar to the application of the ply 47, and will not be described in detail. The ply 49 has, for example, the same length as the ply 41′.
After the step of formation of the ply 49, the structure shown in
After the curing step, the cellulose layer is for example removed by sanding or un-winding, and the mandrel 29 is removed from the structure. The spacer elements 33, 45 are also removed to form the cavities 32A, 32B and 32C, 50 of
In the case that the shaft 155 is a shaft of the ski pole 11 or 13 of
The shaft 155 is for example similar to the shaft 153 of
In
The tape forming the stacks 57 is for example the same as the tape of the stacks 43 of tape of
Fibers of the plies forming the internal and external walls 53, 30, and of the tapes of the stacks 57 are, for example, chosen from the same list as the fibers of the plies of the shaft 151. In some embodiments, the fibers of the plies forming the internal and external walls 53, 30, are all different from each other, whereas in other embodiments, there are at least two different types of fibers among the three plies. In one embodiment, the fibers of at least one of the plies forming the internal and external walls 53, 30 are natural fibers, such as organic fibers, or vegetal or vegetal-derived fibers.
Resins of fiber- or fabric-reinforced composites of the internal and external walls 31, 30, and in some cases of the stacks 57, are, for example, thermoset resins or/and thermoform resins. In some embodiments the same resin is used for each of these composites, whereas in alternative embodiments, there are at least two different types of resin. In one embodiment, each of these composites is composed of between 20% w to 60% w of resin, for example, between 35% w to 45% w of resin.
In one embodiment, in order to provide a relatively high strength of the shaft 155, the fabrics of the plies of the internal and external walls 53, 30 are for example chosen in a similar fashion to those of the shaft 151 described above.
In one example, a ply of the internal wall 31 is a tubular braid of bamboo fiber, the ply 59 of the external wall 30 is a tubular braid of ramie fibers, and/or the ply 61 of the external wall 30 is a bamboo fiber uni-directional tape.
In one embodiment, at least two plies of the shaft 155 have fibers oriented in different directions to each other with respect to the axis of the shaft.
The ply 53′, shown in
The stacks 57′ of tape are, for example, formed using a hand-lay-up process.
The ply 61 is, for example, formed around the structure shown in
After the step of formation of the ply 61, the structure shown in
After the curing step, the cellulose layer is for example removed by sanding, and the mandrel 51 is removed from the structure. The spacer elements 55 are also for example removed to form the cavities 52 of
According to one example embodiment, the shaft as described in the present disclosure is fabricated based on the following process:
An advantage of the shafts described herein is that it they a structure leading to increased strength-to-weight and/or stiffness-to-weight ratio with respect to a single-walled shaft. This for example permits natural fibers to be used in place at least some synthetic fibers.
An advantage of the use of natural fibers in the fabrics of the plies of the shaft is that it provides a shaft 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.
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.
An advantage of the overlap of fabrics having a uni-directional fiber arrangement and fabrics having a multi-directional fiber arrangement is that it improves mechanical resistance to forces imparted on the shaft during use.
An advantage of providing a shaft having both an internal wall 31, 53 and an external wall 30 that have different shapes is that it optimizes the fabrication of the shaft for different use dynamics.
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. For example, while embodiments have been described in which the curing of the shaft is performed under pressure exerted by an external compression cellulose layer, it will be apparent to those skilled in the art that alternative processes could be used, such as the use of a rigid external mold into which the layup is placed, and the use of an expandable bladder in place of the mandrel, the expandable bladder having a form significantly similar to that of the mandrel.
The present patent application claims priority from the US patent application filed on 19 Nov. 2019 and assigned application No. U.S. 62/937,274, the contents of which is hereby incorporated by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2020/000960 | 11/19/2020 | WO |
Number | Date | Country | |
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62937274 | Nov 2019 | US |