Removable fiber winding mandrel assembly having axially slidable inner and outer mandrel parts provided with axially directed opposing guiding surfaces and complementary coupling portions

Abstract

A removable fiber winding mandrel assembly (1) for winding fibers around during production of hollow fiber-wound composite material components (7), comprising at least two elongate outer mandrel parts (2) that together define an elongate central insertion space (3) and an elongate inner mandrel part (11) that has a central axis (X) extending in an axial direction; the outer mandrel parts (2) are displaceable in the sideways direction between an expanded winding state and a compacted removing state; the mandrel parts comprise complementary coupling portions (8) which are configured to delimit the outer mandrel parts (2) in the sideways outward direction in the expanded winding state; inner guiding surfaces (4) of the outer mandrel parts (2), as well as outer guiding surfaces (12) of the inner mandrel part (11) that lie opposing to said inner guiding surfaces (4) as well as the complementary coupling portions (8), all extend parallel to the central axis (X), and the inner mandrel part (11) has a constant cross section.

Description

[0001] REMOVABLE FIBER WINDING MANDREL ASSEMBLY HAVING AXIALLY SLIDABLE INNER AND OUTER MANDREL PARTS PROVIDED WITH AXIALLY DIRECTED OPPOSING GUIDING SURFACES AND COMPLEMENTARY COUPLING PORTIONS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a removable fiber winding mandrel assembly for winding fibers around during producing hollow fiber-wound composite material components, in particular for hollow fiber-wound composite materials bicycle components. The invention furthermore relates to a method for producing hollow fiber-wound composite material components around such a removable fiber winding mandrel assembly.

[0004] BACKGROUND TO THE INVENTION

[0005] Fiber winding is a fabrication technique that involves winding fibers under tension over a rotating fiber winding mandrel. The mandrel rotates around a spindle while a delivery eye on a carriage traverses horizontally in line with the axis of the rotating mandrel, laying down fibers in a desired pattern or angle over the mandrel. The angle at which the fiber is wound has an effect on the properties of the final product. A high angle will provide circumferential strength, while lower angle patterns will provide greater longitudinal / axial tensile strength. The most commonly used fibers are glass or carbon fibers that preceding, during or after winding around the mandrel get impregnated with a resin. For example the fiber may be passed through a resin bath just before it is wound around the mandrel. Instead of the fibers being impregnated with the resin before winding (wet winding) it is also known to make use of pre-impregnated fibers (dry winding) or postimpregnation. Wet winding has the advantage of being able to use low cost materials with long storage life and low viscosity. The pre-impregnated systems are able to produce components with more consistent resin content that can be wound faster.

[0006] Once the mandrel is completely covered to a desired thickness, the resin is cured. Depending on the resin and its curing characteristics, often the hollow fiber-wound composite material component still lying around the mandrel gets autoclaved or heated in an oven or rotated under radiant heaters until the component has cured sufficiently. After that, the mandrel can be removed for example by extracting it out of the hollow fiber-wound composite material component. It is also possible to remove the mandrel before the curing starts.

[0007] Hollow fiber-wound composite material components currently being produced using this fiber winding process technique include hollow bicycle components like forks and rims made of fiber- wound composite material. In particular carbon fiber cured with resin is then used. These hollow fiberwound composite material bicycle components are lightweight, strong, and durable, making them ideal for high-performance bicycles.

[0008] A challenge during this producing is removal of the mandrel out of the hollow shape of tightly wound fibers, particularly if this is foreseen to be done before curing. The mandrel might be tightly wrapped with the fibers, making it difficult to access and extract the mandrel without damaging the hollow shape of tightly wound fibers. If not removed carefully, the mandrel's extraction can lead to cracks, chips, or deformations in the hollow fiberwound composite material component.

[0009] EP0206268 A2 discloses a multi-part fiber winding mandrel for winding resin saturated fibers around. The fiber winding mandrel consists of an elongate central core with four elongate outer mandrel parts positioned around it that together define a winding surface. The four outer mandrel parts are formed by two pairs of diametrically opposing outer mandrel parts. The central core can be moved back and forth in axial direction inside a central space that is left free inside the pairs of outer mandrel parts. Two sets of diametrically opposed and spaced apart T-shaped sliding blocks are provided on opposing faces of the central core as male coupling portions. Those T-shaped sliding blocks fit slidable inside respective sets of diametrically opposed and spaced apart T-shaped grooves that are provided in opposing faces of the outer mandrel parts as female coupling portions. The sets of T-shaped grooves extend in opposing inwards directions under oblique angles relative to the axial direction.

[0010] Due to wedge action of the inwardly tapering pairs of diametrically opposed and spaced apart coupling portions, an axial movement of the central core shall simultaneously firstly start to gradually pull the first pair of diametrically opposing outer mandrel parts radially inwards towards each other, to then secondly start to gradually pull the second pair of diametrically opposing outer mandrel parts radially inwards towards each other. This reduces the outer dimensions at which the outer mandrel parts lie. This reduction makes it possible to demould a hollow fiber-wound composite material component even after the resin has set, and without the entire fiber winding mandrel needing to be disassembled for this. A special pulling device for forcedly pulling a produced hollow fiber-wound composite material component of the mandrel is not necessary.

[0011] A drawback however is that the functioning of this known multi-part fiber winding mandrel leaves to be improved. High precision is required for aligning the outer mandrel parts with their spaced apart angled T-shaped grooves and the central core with its spaced apart T-shaped sliding blocks, and keeping them aligned during axial inward or outward movements of the central core. This is critical to ensure the foreseen stepwise inwards and outwards movements of outer mandrel parts. Any misalignment or dimensional deviations could lead to damaging of the vulnerable tight-fitting coupling portions.

[0012] Furthermore, the central core as well as the outer mandrel parts all need special machined cross-sectional shapes for this, making the central core and outer mandrel parts complex and costly to manufacture.

[0013] Yet another drawback is that the outwardly projecting spaced apart T- shaped sliding blocks are vulnerable and may well get damaged during handling.

[0014] Also it may occur that the T-shaped sliding blocks get jammed inside the T-shaped grooves during axial movement of the central core. If such jamming occurs then this not only leads to delays on the work floor, but also shall make the demoulding after winding harder and possibly lead to a damaging of the produced hollow fiber-wound composite material component, because then it may not be possible to reduce the outer mandrel parts to their aimed smaller cross-sectional dimensional positions.

[0015] Yet another drawback is that the sliding of the blocks within the grooves makes them prone to mechanical wear during frequent use. Consequently, these components might necessitate frequent maintenance or even replacement, leading to production downtime and increased operational costs.

[0016] BRIEF DESCRIPTION OF THE INVENTION

[0017] The aim of the present invention is to overcome those drawbacks at least partly or to provide a usable alternative. In particular the present invention aims to provide a user-friendly and reliable removable fiber winding mandrel assembly that is fool-proof during use and capable of delivering constant quality hollow fiber-wound composite material components, in particular for the bicycle industry.

[0018] According to the present invention this aim is achieved by a removable fiber winding mandrel assembly for winding fibers around during production of hollow fiber-wound composite material components, in particular for carbon fiber reinforced bicycle components, according to claim 1. The removable fiber winding mandrel assembly comprises:

[0019] • at least two elongate outer mandrel parts that together define an elongate central insertion space; and

[0020] • an elongate inner mandrel part having a central axis extending in an axial direction and having a sideways direction perpendicular to this axial direction, wherein the outer mandrel parts are displaceable in the sideways direction between an expanded winding state and a compacted removing state, wherein the outer and / or inner mandrel parts are provided with complementary coupling portions which are configured to delimit the outer mandrel parts in the sideways outward direction in the expanded winding state, wherein the outer mandrel parts in the expanded winding state define an outer winding surface for winding the fibers around during production of a hollow fiber-wound composite material component, and wherein the outer mandrel parts in the compacted removal state define a reduced outer winding surface for removal of the mandrel parts in the axial direction out of the hollow fiber-wound composite material component.

[0021] According to the inventive concept inner guiding surfaces of the outer mandrel parts that together define the central insertion space, as well as outer guiding surfaces of the inner mandrel part that lie opposing to said inner guiding surfaces, as well as the complementary coupling portions, all extend parallel to the central axis, wherein the inner mandrel part has a constant cross section that is configured to fit with a sliding form fit of its outer guiding surfaces along the inner guiding surfaces that together define the central insertion space when the outer mandrel parts are in their expanded winding state, and wherein the inner mandrel part is removable out of the central insertion space while its outer guiding surfaces slide in the axial direction along the inner guiding surfaces of the outer mandrel parts, such that, after the inner mandrel part has been removed out of the central insertion space, the outer mandrel parts are displaceable in the sideways inward direction towards the compacted removing state while reducing the central insertion space. In the expanded winding state, the inner mandrel part lies within the central insertion space as defined by the outer mandrel parts. The outer mandrel parts together form a form closure around the inner mandrel part, while the coupling portions delimit the outer mandrel parts to move further sideways outwards. Form closure in this context implies that the arrangement of the outer mandrel parts and the shape of the inner guiding surfaces of the outer mandrel part is such that any relative movement between the inner mandrel part and outer mandrel parts is prevented, without relying on additional forces like pulling, pushing, or friction.

[0022] After the winding process around the fiber winding mandrel has been completed, the invented multi-part mandrel construction makes it possible to remove the mandrel parts in a specific order and manner out of the hollow fiber- wound composite material component. During this demoulding, the inner mandrel part can first be removed out of the central insertion space with its outer guiding surfaces sliding smoothly along the elongate parallel axially directed outer guiding surfaces.

[0023] After the inner mandrel part has thus been entirely pulled out of the central insertion space, the free central insertion space gives way to the outer mandrel parts to easily and quickly move sideways inwards. Due to the initial tight winding of the fibers around the outer winding surface, this inward moving of the outer mandrel parts from their expanded winding state towards their compacted removing state may well start automatically, but can be aided manually or mechanically.

[0024] The sideways inwards movement of the outer mandrel parts towards the central insertion space immediately takes the initial tight winding tension of them and diminishes contact between the outer mandrel parts and the inner wall of the hollow fiber-wound composite material component.

[0025] The hollow fiber-wound composite material component may come to lie spaced around the compacted winding surface. This helps to reduce friction between the inner wall of the hollow fiber-wound composite material component and the compacted winding surface as then defined by outer mandrel parts in their compacted removing state during demoulding. The outer mandrel parts then can easily, quickly and carefully be pulled out of the hollow fiber-wound composite material component in the axial direction. This helps to guarantee the integrity of the freshly produced hollow fiber-wound composite material component.

[0026] The demoulding / disassembly process can thus be truly systematic and controlled. During removal of the inner mandrel part out of the central insertion space, the parallel inner and outer guiding surfaces sliding along each other, allow for a precise and well- controllable movement of the inner mandrel part from out of the outer mandrel parts. As a result, any potential jamming between the inner and / or outer mandrel parts is fully prevented.

[0027] Advantageously, the foreseen first sideways inwards movement of the outer mandrel parts, before pulling them in the axial direction, results in minimal disturbances to the hollow fiber-wound composite material component. The outer mandrel parts can be removed not by sliding them with high friction along the vulnerable inner wall of fragile winded fibers, but by firstly moving them perpendicular inwards away from the vulnerable inner wall of fragile winded fibers for some distance and then pulling them out in the axial direction without any or hardly any contact with the vulnerable inner wall of fragile winded fibers. This minimizes a risk of damaging or compromising the final product at the end of the fiber winding process, resulting in a higher level of product quality and consistency.

[0028] Thus owing to the present multi-part mandrel construction, the outer cross-sectional dimensions of the outer mandrel parts can be smoothly reduced stepwise after the winding process has been completed without having to use some kind of slope system.

[0029] Owing to the invention a user-friendly and reliable winding mandrelassembly is thus provided with which a constant and superb quality of hollow fiber-wound composite material components can be produced. The various mandrel parts of the mandrel-assembly advantageously can easily and quickly be assembled together. No high precision alignment is required for this. The inner mandrel part can simply easily and quickly be pulled out of the central insertion space defined by the outer mandrel parts in one go. There is no risk for jamming or damaging because all critical guiding surfaces and coupling portions are axially directed and do not have to incur simultaneous movements of the outer mandrel parts in sideways inwards directions.

[0030] Furthermore, the inner mandrel part advantageously now is foreseen to have a constant cross-sectional shape, making it easy and economic to manufacture, for example by means of extrusion. Another important advantage hereof is that one and the same central core, for example a strong and rigid massive metal bar, can be used as inner mandrel part. This one and the same inner mandrel part can then be used in combination with all kinds of different mandrel parts getting assembled around it. Those outer mandrel parts may have all kinds of different lengths and differently shaped outer winding surfaces.

[0031] Likewise, the outer mandrel parts together may define a constant cross-section for the elongate central insertion space in the expanded winding state. This makes their inner guiding surfaces economic and easy to manufacture, for example by moulding or 3D-printing.

[0032] The coupling portions main function now is to block the outer mandrel parts in the sideways outward direction when lying in their expanded winding state as soon as the inner mandrel part has been inserted into the central insertion space. They do not have to incur some kind of combined axial and sideways inwar d / outward movement.

[0033] Another advantage of the parallel guiding surfaces is that, by preventing any potential jamming or interference, this helps to reduce wear and tear on the mandrel parts, thereby prolonging their lifespan. The sliding of the opposing inner and outer guiding surfaces along each other during insertion and pulling out of the inner mandrel part prevents mechanical wear during use. Consequently, the mandrel parts hardly need maintenance or replacement, leading to optimized production and decreased operational costs.

[0034] In a preferred embodiment, neighboring ones of the outer mandrel parts may comprise elongate facing abutment surfaces between them, which facing abutment surfaces also extend parallel to the central axis, wherein the facing abutment surfaces are configured to lie spaced apart from each other in the expanded winding state, and wherein the facing abutment surfaces are configured to abut against each other in the compacted removing state. After the inner mandrel part has been fully removed out of the central insertion space, the outer mandrel parts can be moved sideways inwards while the spacing between the facing abutment surfaces decreases. During the sideways inwards movement of the outer mandrel parts, the facing abutment surfaces of the outer mandrel parts do not simultaneously have to slide along each other. As such, there is no friction between the facing abutment surfaces, which allows for a smooth sideways inwards movement of the outer mandrel parts towards each other, and thus minimal distortion of freshly wound fibers together forming the hollow fiber-wound composite material component.

[0035] It is noted that the spacings between the facing abutment surfaces also are present as spacings at the location of the winding surface as long as the outer mandrel parts are still in their expanded winding state. Owing to this, those spacings can be used for making local cuts in the axial direction through the wound fibers at the outer ends of the freshly produced hollow fiber-wound composite material components. Those axially cut through outer ends of the hollow fiber-wound composite material components then can be used to connect them with each other, for example when they are to placed at an angle to each other, like in a bicycle frame with its triangular orientated seat, drop and down tubes. For this it is then possible to produce distinctive seating, down and top hollow fiber-wound composite material tube components, cut through their outer ends before removing of the inner mandrel part, to then after demoulding be able to connect the axially cut through outer ends with each other.

[0036] In a further preferred embodiment, the complementary coupling portions can be provided between the facing abutment surfaces of the neighboring ones of the outer mandrel parts. This allows the absence of coupling portions between the outer and inner mandrel parts. An additional advantage hereof is that blockages between the complementary coupling portions themselves during the step removal of the inner mandrel part are fully prevented. This results in an almost effortless removal of the inner mandrel part from between the outer mandrel parts.

[0037] An additional advantage of the absence of coupling portions between the inner and outer guiding surfaces of the outer and inner mandrel parts is that conventional elongate shapes can be used for the inner mandrel part. For example massive rods or bars.

[0038] The inner mandrel part preferably may have flat outer guiding surfaces, in particular together forming a square constant cross- section for the inner mandrel part. Such bars with angular cross- sections are preferred, as these automatically provided a form fit to force the outer mandrel parts to co-rotate along around the central axis with the inner mandrel part in the assembled expanded winding state.

[0039] The outer mandrel parts then preferably may also have flat inner guiding surfaces, in particular together forming a square constant crosssection for the central insertion space.

[0040] The coupling portions may for example comprise complementary male and female parts configured to grip into each other.

[0041] In a further preferred embodiment, the complementary coupling portions may comprise a male keying portion and a female chambered portion, wherein the female chambered portion is oversized relative to the male keying portion for allowing the male keying portion to shift with a sliding form fit in the sideways direction inside the female chambered portion between the expanded winding state and the compacted removing state. Having the male keying portions be able to move in sideways direction within the female chambered portion with the sliding form fit allows for precise control of the inwards movement of the outer mandrel parts. Moreover, when the male keying portions lie against sideways outermost walls of the female chambered portions, this automatically defines and delimits the expanded winding state, whereas when the male keying portions lie against sideways innermost walls of the female chambered portions, this automatically defines and delimits the compacted removing state. The sideways outwards delimitation of the outer mandrel parts positions by the coupling portions in combination with the sideways inwards delimitation of the outer mandrel parts by the form-fitting inserted inner mandrel part, provides stability and secure positioning of the outer mandrel parts, thereby providing a stable surface for winding and thus preventing distortion of the fibers during winding.

[0042] Preferably, the male and female coupling portions are slidable relative to each other in the axial direction. This makes it possible to easily and quickly disassemble all outer mandrel parts from each other whenever desired.

[0043] In addition thereto, the male keying portion and the female chambered portion can be L-shaped, of which the female chambered portion has a larger dimension in the sideways direction for allowing the male keying portion to shift in the sideways direction inside the female chambered portion between the expanded winding state and the compacted removing state. This hook-like shape for the male and female coupling parts prevents the outer mandrel parts from falling apart when the inner mandrel part is removed.

[0044] In a further embodiment, the at least two outer mandrel parts may have merely one pair of opposing elongate outer mandrel parts that between the two of them together define the entire elongate central insertion space while lying with their facing abutment surfaces opposite and spaced apart from each other in the expanded winding state. This reduces the number of components.

[0045] In an alternative further embodiment, the at least two outer mandrel parts may have two pairs of opposing elongate outer mandrel parts that between the four of them together define the entire elongate central insertion space while lying with their facing abutment surfaces opposite and spaced apart from each other. This makes it possible to have the outer dimensions of the winding surface reduced in all directions when moved towards their compacted removing state.

[0046] In a further embodiment, the abutment surfaces may lie in different sideways directed planes than the guiding surfaces. For example, in the case of the inner mandrel part having a square cross-section with perpendicular orientated outer guiding surfaces, the abutment surfaces may extend in line with comers of the square cross-section, that is to say at 45 degrees relative to the orientations of the outer guiding surfaces.

[0047] In a preferred embodiment, the inner mandrel part in the axial direction can be configured to project out of the opposing outer ends of the outer mandrel parts to form a drive shaft for rotating the mandrel assembly in the expanded winding state during fiber winding.

[0048] The drive shaft as inner mandrel part provides a stable and rigid supporting structure for the outer mandrel parts. This strengthens the overall rigidity of the mandrel assembly in the expanded winding state and offers good support for tight winding of the fibers during the winding process and thus aid to the quality of the end products without deformations or misalignments. The stably supporting drive shaft also allows for good control over tension of the fibers during winding, and makes it more convenient to handle and manipulate the mandrel assembly during the entire production process.

[0049] In a preferred embodiment, the inner mandrel part can be made out of metal, for example extruded metal bar of square cross-section, whereas the outer mandrel parts can be made out of plastic, for example manufactured by means of moulding or 3D-printing.

[0050] In a preferred embodiment, the outer winding surface can be profiled to vary along the axial direction and / or circumferential direction. In particular it may be bilateral symmetrical. This may be advantageous in producing hollow fiber-wound composite material components which have specific profiled shapes, such as aerodynamically designed frame portions of bicycles, handlebars, wheel rims and other structural elements.

[0051] Optionally, the inner and / or outer mandrel parts in the axial direction may comprise multiple sections that are connected with each other, for example by means of metal pins. For example, the sections can be 3D printed separately and then connecting them together. The multiple sections facilitate creation of relative long mandrel parts. In particular each section can be up to 50 cm or longer. This allows to use a winding process over truly long lengths, e.g. over a length of 2,5 m (5 sections) which gives high winding efficiency, and much flexibility for the outer shape of the winding surface.

[0052] The multiple sections of the mandrel parts preferably may start and stop at different points as seen in the axial direction. This helps to make the assembly of outer mandrel parts strong and less likely to kink.

[0053] Further preferred embodiments of the invention are stated in the dependent subclaims. The invention also relates to a method according to claim 14.

[0054] DETAILED DESCRIPTION OF THE DRAWINGS

[0055] The invention shall now be explained in more detail below by means of describing some exemplary embodiments in a non-limiting way with reference to the accompanying drawings, in which:

[0056] Figgs, la-f show multiple states of a removable fiber winding mandrel assembly having an inner and two outer mandrel parts according to an embodiment of the invention;

[0057] Fig. 2a schematically shows a cross-sectional view of a removable fiber winding mandrel assembly having an inner and two outer mandrel parts according to an embodiment of the invention;

[0058] Fig. 2b shows a perspective view of the removable fiber winding mandrel assembly according to Fig. 2a;

[0059] Fig. 3a shows a perspective view of a removable fiber winding mandrel assembly having an inner and four outer mandrel parts according to an embodiment of the invention;

[0060] Fig. 3b schematically depicts a cross-sectional view of the removable fiber winding mandrel assembly according to Fig. 3a;

[0061] Fig. 4a-c show perspective views of another embodiment of the removable fiber winding mandrel assembly according to the invention;

[0062] Fig. 5a-d schematically depict cross-sectional views of multiple states of the removable fiber winding mandrel assembly of Fig. 4a-c;

[0063] Fig. 5c' shows a perspective view of Fig. 5c;

[0064] Fig. 6 shows the view of Fig. 4a indicating that two sets of outer mandrel parts are connected to each other in the axial direction behind each other;

[0065] Fig. 7 shows a perspective view of another embodiment of the removable fiber winding mandrel assembly having an inner and two outer mandrel parts according to the invention; and

[0066] Fig. 8 shows the outer mandrel parts of the assembly of Fig. 7 with the inner mandrel part removed.

[0067] In Figures la-f the removable fiber winding mandrel assembly is shown having reference numeral 1. The mandrel assembly 1 in this embodiment comprises a single pair of elongate outer mandrel parts 2 that define a square elongate central insertion space 3 between them. The outer mandrel parts 2 have flat inner guiding surfaces 4. Said inner guiding surfaces 4 of the outer mandrel parts 2 form a square constant cross-section for the central insertion space 3. The outer mandrel parts 2 in Fig. la and lb are shown in an expanded winding state. In this expanded winding state, the outer mandrel parts 2 define an outer winding surface 6 for winding fibers around during production of a hollow fiber-wound composite material component 7. Neighboring outer mandrel parts 2 are shown to have elongate facing abutment surfaces 5 between them. In the expanded winding state, the facing abutment surfaces 5 of neighboring outer mandrel parts 2 lie opposite and spaced apart from each other. The spacing between the facing abutment surfaces 5 of the outer mandrel parts 2 may advantageously be used for making local cuts in the axial direction through the wound fibers at the outer ends of the freshly produced hollow fiber-wound composite material component 7. The spacing between the facing abutment surfaces 5 furthermore allows the outer mandrel parts 2 to be displaced in the sideways direction between the expanded winding state and a compacted removing state in which the facing abutment surfaces 5 abut against each other, as shown in Figures Ic-ld. In this compacted removal state, the outer mandrel parts 2 define a reduced outer winding surface 6 for removal of the outer mandrel parts 2 in the axial direction out of the hollow fiber-wound composite material component 7.

[0068] Complementary coupling portions 8 are provided between the facing abutment surfaces 5 of the neighboring ones of the outer mandrel parts 2. The coupling portions 8 couple the neighboring outer mandrel parts 2 and delimit them from moving in the sideways outward direction when in the expanded winding state. The coupling portions 8, as shown in Fig. 1c, comprise a male keying portion 9 and a female chambered portion 10. The female chambered portion 10 is oversized relative to the male keying portion 9. As a result, the male keying portion 9 may shift in the sideways direction inside the female chambered portion 10, thereby displacing the outer mandrel parts 2 between the expanded winding state and the compacted removing state. The male keying portion 9 and the female chambered portion 10 are L-shaped, and the female chambered portion 10 has a larger dimension in the sideways direction for allowing the male keying portion 9 to shift in the sideways direction inside the female chambered portion 7, thereby displacing the outer mandrel parts 2 between the expanded winding state and the compacted removing state.

[0069] As seen in Fig. la-d, the outer winding surface 6 of the outer mandrel parts 2 is profiled. This advantageously allows the production of hollow fiber-wound composite material components 7 which have specific profiled shapes, such as aerodynamically designed frame portions of bicycles, handlebars, wheel rims and other structural elements.

[0070] Within the central insertion space 3, an elongate inner mandrel part 11 is provided, said inner mandrel part 11 having a central axis X and extending in an axial direction. The inner mandrel part 11 has flat outer guiding surfaces 12 that together form a square cross-section for the inner mandrel part 11. The inner mandrel part 11 has a constant cross section that is configured to fit with a sliding form fit of its outer guiding surfaces 12 along the inner guiding surfaces 4 of the outer mandrel parts 2 when the outer mandrel parts 2 are in their expanded winding state. The inner mandrel part 11 in this embodiment projects in the axial direction out of the opposing outer ends of the outer mandrel parts 2 to form a drive shaft. During winding of the fibers for forming the hollow fiber-wound composite material component 7, the inner mandrel part 11 is rotated around its central axis X, thereby rotating the outer mandrel parts 2 simultaneously.

[0071] According to the invention, the inner guiding surfaces 4 of the outer mandrel parts 2, the outer guiding surfaces 12 of the inner mandrel part 11 that lie opposing to said inner guiding surfaces 4 as well as the complementary coupling portions 8, all extend parallel to the central axis X. This allows the inner mandrel part 11 to be entirely removed out of the central insertion space 3 during demoulding while its outer guiding surfaces 12 slide in the axial direction along the inner guiding surfaces 4 of the outer mandrel parts 2. After the inner mandrel part 11 has been entirely pulled out of the central insertion space 3, the free central insertion space 3 gives way to the outer mandrel parts 2 to easily and quickly move sideways inwards, thus eliminating contact with the hollow fiber-wound composite material component 7. The outer mandrel parts 2 may then be easily, quickly and carefully pulled out of the hollow fiber-wound composite material component 7 in the axial direction. This helps to reduce friction between the inner wall of the hollow fiber-wound composite material component 7 and the compacted winding surface 6 as then defined by outer mandrel parts 2 in their compacted removing state, and therefore helps to guarantee the integrity of the freshly produced hollow fiber-wound composite material component 7.

[0072] In Figures 2a and 2b, an embodiment of the removable fiber winding mandrel assembly 1 is shown having one pair of the elongate outer mandrel parts 2’, and having two pairs of coupling portions 8 that are provided at respective facing abutment surfaces 5 of the pair of outer mandrel parts 2’.

[0073] In Figures 3a and 3b, an embodiment of the removable fiber winding mandrel assembly 1 is shown having two pairs of the elongate outer mandrel parts 2’, 2”. The two pairs of outer mandrel parts 2’, 2” also have inner guiding surfaces 4 that together define the elongate central insertion space 3 while lying with the facing abutment surfaces 5 opposite each other. Having two pairs of outer mandrel parts 2’, 2” makes it possible to have the outer dimensions of the winding surface 6 reduced in all directions when moved towards their compacted removing state. The two pairs of outer mandrel parts 2’, 2” lay with the abutment surfaces 5 of neighboring outer mandrel parts 2’, 2” spaced apart when in the expanded winding state, shown in both Figures 3a and 3b. The abutment surfaces 5 in this embodiment extend in line with corners of the square cross-section of the inner mandrel part 11, that is to say at 45 degrees relative to the orientations of the inner guiding surfaces 4.

[0074] Fig. 3b shows a cross-section of the outer mandrel parts 2', 2" of the removable fiber winding mandrel assembly 1, with the inner mandrel part 11 still to be inserted, but with the outer mandrel parts 2', 2" already lying in their expanded winding state. Coupling portions 8 are provided on the abutment surfaces in the form of an L-shaped male keying portion 9 and an L-shaped female chambered portion 10. Such coupling portions 8 are provided on each of the neighboring abutment surfaces. All the male keying portions 9 extend in same sideways directions. As such, after the removal of the inner mandrel part 11, the first pair of opposite outer mandrel parts 2’ may be displaced in the sideways direction inwardly to eliminate contact of this first pair of outer mandrel parts 2’ with a freshly made hollow fiberwound composite material component (not shown here). This pair of opposite outer mandrel parts 2’ may then be removed from the hollow fiberwound composite material component by sliding the male keying portion 9 from the female chambered portion 10 in the axial direction. After removal of the first pair of outer mandrel parts 2’, the remaining second pair of outer mandrel parts 2” may then be displaced in the sideways direction inwardly to also eliminate contact with the fiber-wound composite material component, and then remove the second pair of outer mandrel parts 2” in the axial direction from said material component.

[0075] Figures 4a-c, 5a-d, 5c' and 6 show an alternative embodiment of the removable fiber winding mandrel assembly 1, comprising a first pair of outer mandrel parts 2’ (highlighted in Fig. 4b) and a second pair of outer mandrel parts 2” (highlighted in Fig. 4c). The facing abutment surfaces 5 of neighboring outer mandrel parts 2 in this embodiment lie against each other in the expanded winding state. The coupling portions 8 are provided at the respective guiding surfaces 4, 12 of the inner 11 and outer mandrel parts 2. The coupling portions 8 allow the outer mandrel parts 2 to be directly connected to the inner mandrel part 11, thus delimiting the outer mandrel parts 2 in the sideways outward direction when in the expanded winding state. The coupling portions 8 comprise rounded mushroom-shaped male portions 9, that project into the insertion space 3 from their respective guiding surfaces 4, and complementary mushroom- shaped female portions 10 that are saved into the inner mandrel part 11 at the respective guiding surfaces 12 (see also Fig. 5a-d).

[0076] The inner guiding surfaces 4 of the outer mandrel parts 2, the outer guiding surfaces 12 of the inner mandrel part 11 that lie opposing to said inner guiding surfaces 4, as well as the complementary coupling portions 8, all extend parallel to the central axis X.

[0077] Figures 5a-d show the consecutive steps of removing the inner mandrel part 11 and sets of outer mandrel parts 2’, 2” out of a hollow fiberwound composite material component (not shown) according to the embodiment of Fig. 4, in which the coupling portions 8 are provided at the respective guiding surfaces 4, 12 of the inner 11 and outer mandrel parts 2. In Fig. 5a, the outer mandrel parts 2 are in their expanded winding state with the inner mandrel part 11 provided in the central insertion space 3 defined by the outer mandrel parts 2. The coupling portions 8 couple the outer mandrel parts 2 to the inner mandrel part 11.

[0078] The inner guiding surfaces 4 of the outer mandrel parts 2 that together define the central insertion space 3, as well as the outer guiding surfaces 12 of the inner mandrel part 11 that lie opposing to said inner guiding surfaces 4, as well as the complementary coupling portions 8, all extend parallel to the central axis. The inner mandrel part 11 may be removed from the central insertion space 3 by sliding of the inner mandrel part 11 in the axial direction along the inner guiding surfaces 4 of the outer mandrel parts 2.

[0079] The outer mandrel parts 2 after removal of the inner mandrel part 11 are shown in Fig. 5b. The facing abutment 5 surfaces of the outer mandrel parts 2 are slightly tapered seen in cross-section, such that the facing abutment surfaces 5 converge towards the outer winding surface 6 of the outer mandrel parts 2. This allows a smooth movement of the first pair of outer mandrel parts 2’ sideways inwardly, while at a same time the second pair of outer mandrel parts 2" sideways inwardly may take place, until the mushroom shaped male portions 9 of the four outer mandrel parts 2' and 2" are in contact with each other, and no further movement inwardly is possible (see Fig. 5c, 5c’). In this state, the first pair of outer mandrel parts 2’ may be slidingly removed along the facing abutment surfaces 5 in the axial direction from the hollow fiber- wound composite material (not shown). After removal of the first pair of outer mandrel parts 2’, the second pair of outer mandrel parts 2” may be displaced further sideways inward to thus further eliminate contact with the hollow fiber- wound composite material component (not shown) until the mushroom shaped male portions 9 of the second pair of outer mandrel parts 2" are in contact with each other, and no further movement inwardly is possible (see Fig. 5d), after which the second pair of outer mandrel parts 2” may also be removed in its entirety from the composite component (not shown).

[0080] Figures 4-6 show that the outer winding surface 6 in this embodiment is in particular bilateral symmetrical. This advantageously allows the production of hollow fiber-wound composite material components which have specific profiled shapes, such as aerodynamically designed frame portions of bicycles, handlebars, wheel rims and other structural elements. Moreover, the outer mandrel parts 2 have multiple removable sections as seen in the axial direction. In Fig. 6 a left and a right set of such outer mandrel sections 2 are indicated.

[0081] Figures 7 and 8 show a removable fiber winding mandrel assembly 1 having a single pair of outer mandrel parts 2, and wherein the coupling portions 8 are provided at merely one of the respective guiding surfaces 4, 12 of the inner mandrel part 11 and outer mandrel parts 2. The outer mandrel parts 2 are in the expanded winding state in both Fig. 7 and 8, such that the facing abutment surfaces 5 of the outer mandrel parts 2 then lie spaced apart.

[0082] Besides the shown and described embodiments, numerous variants are possible. For example the dimensions and shapes of the various parts can be altered. Also it is possible to make combinations between advantageous aspects of the shown embodiments. Instead of using L-shaped or mushroom shaped coupling portions, other kinds of slidable form fittings as coupling portions can be used, such as T- or J-shaped coupling portions. The number of outer mandrel parts may also be altered, such as having six outer mandrel parts, or having an odd number of outer mandrel parts, such as three or five outer mandrel parts. All kinds of other materials can be used for the inner and outer mandrel parts. Preferably however, the inner mandrel part is made out of metal and / or the outer mandrel parts are made out of plastic.

[0083] It should be understood that various changes and modifications to the presently preferred embodiments can be made without departing from the scope of the invention, and therefore will be apparent to those skilled in the art. It is therefore intended that such changes and modifications be covered by the appended claims.

[0084] The disclosures in Dutch Patent Application No. N2036634 from which this application claims priority are incorporated herein by reference.

[0085] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1. A removable fiber winding mandrel assembly (1) for winding fibers around during production of hollow fiber-wound composite material components (7), in particular for carbon fiber reinforced bicycle components, comprising:• at least two elongate outer mandrel parts (2) that together define an elongate central insertion space (3); and• an elongate inner mandrel part (11) having a central axis (X) extending in an axial direction and having a sideways direction perpendicular to this axial direction, wherein the outer mandrel parts (2) are displaceable in the sideways direction between an expanded winding state and a compacted removing state, wherein the outer and / or inner mandrel parts (11) are provided with complementary coupling portions (8) which are configured to delimit the outer mandrel parts (2) in the sideways outward direction in the expanded winding state, wherein the outer mandrel parts (2) in the expanded winding state define an outer winding surface (6) for winding the fibers around during production of a hollow fiber-wound composite material component, and wherein the outer mandrel parts (2) in the compacted removal state define a reduced outer winding surface (6) for removal of the mandrel parts in the axial direction out of the hollow fiber-wound composite material component, characterized in that, inner guiding surfaces (4) of the outer mandrel parts (2) that together define the central insertion space (3), as well as outer guiding surfaces (12) of the inner mandrel part (11) that lie opposing to said inner guiding surfaces (4), as well as the complementary coupling portions (8), all extend parallel to the central axis (X),wherein the inner mandrel part (11) has a constant cross section that is configured to fit with a sliding form fit of its outer guiding surfaces (12) along the inner guiding surfaces (4) that together define the central insertion space (3) when the outer mandrel parts (2) are in their expanded winding state, and wherein the inner mandrel part (11) is removable out of the central insertion space (3) while its outer guiding surfaces (12) slide in the axial direction along the inner guiding surfaces (4) of the outer mandrel parts (2), such that, after the inner mandrel part (11) has been removed out of the central insertion space (3), the outer mandrel parts (2) are displaceable in the sideways inward direction towards the compacted removing state while reducing the central insertion space (3).

2. The removable fiber winding mandrel assembly (1) according to claim 1, wherein neighboring ones of the outer mandrel parts (2) comprise elongate facing abutment surfaces (5) between them, which facing abutment surfaces (5) also extend parallel to the central axis (X), wherein the facing abutment surfaces (5) are configured to lie spaced apart from each other in the expanded winding state, and wherein the facing abutment surfaces (5) are configured to abut against each in the compacted removing state.

3. The removable fiber winding mandrel assembly (1) according to claim 2, wherein the complementary coupling portions (8) are provided between the facing abutment surfaces (5) of the neighboring ones of the outer mandrel parts (2).

4. The removable fiber winding mandrel assembly (1) according to claim 3, wherein the complementary coupling portions (8) comprise a male keying portion (9) and a female chambered portion (10), wherein the female chambered portion (10) is oversized relative to the male keying portion (9) for allowing the male keying portion (9) to shift in the sideways direction inside the female chambered portion (10) between the expanded winding state and the compacted removing state.

5. The removable fiber winding mandrel assembly (1) according to claim 4, wherein the male keying portion (9) and the female chambered portion (10) are L-shaped, of which the female chambered portion (10) has a larger dimension in the sideways direction for allowing the male keying portion (9) to shift in the sideways direction inside the female chambered portion (10) between the expanded winding state and the compacted removing state.

6. The removable fiber winding mandrel assembly (1) according to anyone of claims 3-5, wherein the inner mandrel part (11) has flat outer guiding surfaces (12), in particular together forming a square constant crosssection for the inner mandrel part (11).

7. The removable fiber winding mandrel assembly (1) according to anyone of claims 3-6, wherein the outer mandrel parts (2) have flat inner guiding surfaces (4), in particular together forming a square constant crosssection for the central insertion space (3).

8. The removable fiber winding mandrel assembly (1) according to anyone of claims 2-7, wherein one pair of the elongate outer mandrel parts (2) is provided that together define the elongate central insertion space (3) while lying with the facing abutment surfaces (5) opposite each other.

9. The removable fiber winding mandrel assembly (1) according to anyone of claims 2-7, wherein two pairs of the elongate outer mandrel parts (2’, 2”) are provided that together define the elongate central insertion space (3) while lying with the facing abutment surfaces (5) opposite each other.

10. The removable fiber winding mandrel assembly (1) according to anyone of claims 2-9, wherein the abutment surfaces (5) lie in other sideways directed planes than the guiding surfaces, in particular at 45 degrees between them.

11. The removable fiber winding mandrel assembly (1) according to anyone of the preceding claims, wherein the inner mandrel part (11) in theaxial direction projects out of the opposing outer ends of the outer mandrel parts (2) to form a drive shaft for rotating the mandrel assembly (1) in the expanded winding state during fiber winding.

12. The removable fiber winding mandrel assembly (1) according to anyone of the preceding claims, wherein the inner mandrel part (11) is made out of metal, and wherein the outer mandrel parts (2) are made out of plastic.

13. The removable fiber winding mandrel assembly (1) according to anyone of the preceding claims, wherein the outer winding surface (6) is profiled.

14. A method for producing hollow fiber- wound composite material components (7) with a removable fiber winding mandrel assembly (1) according to anyone of the preceding claims, comprising the steps of:- sliding the inner mandrel part (11) with its outer guiding surfaces (12) along the inner guiding surfaces (4) in the axial direction into the central insertion space (3), while the form fit of the inner mandrel part (11) inside the central insertion space (3) together with the complementary coupling portions (8) lock the outer mandrel parts (2) to obtain the expanded winding state;- winding the fibers around the outer winding surface (6) of the outer mandrel parts (2);- sliding the inner mandrel part (11) with its outer guiding surfaces (12) along the inner guiding surfaces (4) out of the central insertion space (3);- displacing the outer mandrel parts (2) in the sideways inward direction towards each other while reducing the central insertion space (3) to obtain the compacted removing state; and- removing the hollow fiber-wound composite material component (7) from the outer mandrel parts (2) in their compacted removing state.

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