Bicycle rim and process for manufacturing a bicycle rim

Abstract

The present invention relates to a bicycle rim and a process for manufacturing a bicycle rim, the bicycle rim comprising a wall made of a composite material, the wall having a plurality of perforated spoke attachment seats (58), each of the perforated seats (58) being defined by at least one first region (62) and at least one second region (64), the first region including a stacking of continuous structural fibres (60), and the second region being circumferentially spaced from the first region (62) and including cut structural fibres (60).

Description

Technical Field

[0001] The invention relates to a bicycle rim.

[0002] The invention also relates to a process for manufacturing such a rim.

[0003] The rim of the invention comprises a composite material at least on its wall in which the perforated spoke attachment seats are made. Hereinafter, such a rim will also be identified with the expression "rim made of a composite material".

[0004] In this specification and claims, the term "perforated spoke attachment seat" is used in a broad sense to include: seats into which spokes are directly inserted (spokes such as spokes with enlarged heads or threaded spokes); and seats into which nipples or other elements associated with the spokes are inserted.

[0005] In the present description and claims, the term "composite material" is used to indicate a material comprising a plurality of structural fibers incorporated in a polymeric material. Typically, the above-mentioned structural fibers are unidirectional or bidirectional fibers. In the first case, a single layer of unidirectional fibers or at least two parallel layers of unidirectional fibers inclined relative to each other can be provided. In the area of ​​the rim remote from the perforated spoke attachment seat, the structural fibers of each layer extend substantially parallel to each other along a respective longitudinal direction. In the second case, the composite material defines a fabric comprising a first plurality of substantially parallel structural fibers (weft fibers) extending along the above-mentioned first longitudinal direction and a second plurality of substantially parallel structural fibers (warp fibers) extending along a second direction substantially perpendicular to the aforementioned first direction.

[0006] Hereinafter, when unidirectional fibers are mentioned, it refers to the structural fibers of the unidirectional fiber layer, and when bidirectional fibers are mentioned, it refers to the structural fibers of the fabric of the bidirectional fibers. Background Art

[0007] Rims made of composite materials are known and are typically manufactured by molding the composite material according to various cross-sectional shapes.

[0008] Typically, in the case of a composite material including a thermosetting polymer material, compression molding is performed, whereas in the case of a composite material including a thermoplastic polymer material, injection molding is performed.

[0009] Before the rim is associated with the hub to form a bicycle wheel, a plurality of perforated spoke attachment seats must be made in the rim.

[0010] The above-mentioned perforated seats must be made in the positions required by the spoke pattern of the specific wheel, i.e. depending on the number of spokes, their distribution along the circumference of the rim, their position in the cross-section of the rim and the orientation adopted by each spoke, for example by means of radial or tangential attachment of the spoke to the hub and / or the camber angle.

[0011] The patent applications EP2422959 and US10315461 of the applicant disclose a process for manufacturing a bicycle rim made of composite material, in which a plurality of perforated spoke attachment seats are made before molding the composite material, so that after molding, a bicycle rim equipped with the above-mentioned perforated seats is obtained. In particular, before molding the composite material, the perforated spoke attachment seats are formed in the desired positions by the displacement of the structural fibers.

[0012] In EP2422959, this displacement is carried out by using a non-cutting pointed tool such as an awl. Once this tool is inserted into the composite material, it causes local displacement of the structural fibers without cutting or shearing or removing the structural fibers (except for a very limited number of structural fibers ultimately, especially those exactly located at the tip of the tool).

[0013] In US10315461, all the structural fibers located at each perforated seat to be made are displaced (except for the ultimately provided cutting structural fibers, the percentage of which is at most equal to 10% of the total structural fibers arranged at each perforated seat).

[0014] In the solutions described in EP2422959 and US10315461, in the case of unidirectional fibers, the displacement of the structural fibers results in the presence of two regions including accumulations of continuous (i.e., uncut) structural fibers, which are arranged in regions diametrically opposite with respect to the perforated seat and along a generally transverse direction with respect to the longitudinal direction of the structural fibers. On the other hand, in the case of bidirectional fibers, the displacement of the weft structural fibers and the warp structural fibers results in the presence of four regions including accumulations of continuous structural fibers, which are at four regions spaced apart by about 90° around the perforated seat.

[0015] The applicant has observed that the disadvantage of the solutions described in EP2422959 and US10315461 is that, especially in the case of unidirectional fibers and also in the case of bidirectional fibers, due to the displacement of such fiber regions, only polymeric material is formed at the opposite part with respect to each perforated seat and spaced apart from the region including the fiber accumulation. Such regions define structurally weak parts in the rim. In such regions, there may also be small parts without polymeric material, i.e., parts with air bubbles, thus further weakening the rim.

[0016] Another disadvantage of the solutions described in EP2422959 and US10315461 is related to the fact that the structural fibers are not sufficiently stretched around the perforated seats and, in order to function correctly, the structural fibers must first be stretched out and loaded. This results in a structural weakening of the rim or, at least, a delay in the response of the rim to the mechanical stresses to which it is subjected during spoke tensioning and pedaling.

[0017] The technical problem on which the present invention is based is to manufacture a rim made of a composite material that is able to optimally and most easily withstand the above-mentioned mechanical stresses. Summary of the Invention

[0018] In a first aspect of the present invention, the present invention relates to a bicycle rim comprising a wall made of a composite material, the wall having a plurality of perforated spoke attachment seats, each of which is defined by at least one first region and at least one second region, the at least one first region including a stack of continuous structural fibers, the at least one second region being circumferentially spaced apart from the first region, and the at least one second region including cut structural fibers.

[0019] In the present specification and claims, the term "region including a stack of continuous structural fibers" is used to indicate a region in which the local density of the continuous structural fibers is greater than the average nominal density of the continuous structural fibers in the composite material. Thus, if the composite material has a certain average nominal density of continuous structural fibers, in each region of the wall of the rim remote from the perforated seats, there will be a density of continuous structural fibers within the tolerance range around the average nominal density, and in the regions including a stack of continuous structural fibers, there will be a density of continuous structural fibers greater than the upper limit of such a tolerance range. The regions including a stack of continuous structural fibers are obtained during the manufacture of the perforated spoke attachment seats, before the composite material is molded, i.e., before the composite material is crosslinked. In fact, in such a case, due to the thrust exerted by the tool used to manufacture the perforated spoke attachment seats on the continuous structural fibers, the continuous structural fibers are able to move relative to the polymeric material.

[0020] Advantageously, since there are structural fibers in all regions around each perforated seat and thus also in those regions of the rim described in EP2422959 and US10315461 where only the polymeric material remains after the fibers have been displaced, the rim of the present invention is able to respond more quickly and effectively to the mechanical stresses to which it is subjected during use, as compared to the rims described in EP2422959 and US10315461. In addition, once the composite material is crosslinked after molding, at least some of the cut structural fibers incorporated in the polymeric material are properly stretched and are thus suitable for withstanding and effectively transmitting the stresses to which the rim is subjected at the spoke attachment seats.

[0021] Preferably, each perforated seat is delimited by at least two first regions and at least two second regions, the at least two first regions comprising a packing of continuous structural fibers, the at least two second regions being circumferentially spaced apart from the at least two first regions, and the at least two second regions comprising cut structural fibers.

[0022] More preferably, in the case of unidirectional fibers, two first regions comprising a packing of continuous structural fibers and two second regions comprising cut structural fibers are provided, while in the case of bidirectional fibers, four first regions comprising a packing of continuous structural fibers and four second regions comprising cut structural fibers are provided.

[0023] Preferably, the at least two first regions are arranged on two opposite sides with respect to the perforated seat in a first direction, and the at least two second regions are arranged on two opposite sides with respect to the perforated seat in a second direction inclined with respect to the first direction.

[0024] More preferably, the second direction is substantially perpendicular to the first direction.

[0025] Thus, preferably, in the case of unidirectional fibers, the two first regions comprising a packing of continuous structural fibers are diametrically opposite and are spaced apart by approximately 90° from the two second regions comprising cut structural fibers, while in the case of bidirectional fibers, four first regions comprising a packing of continuous structural fibers are provided, the four first regions being spaced apart from each other by approximately 90°, and four second regions comprising cut structural fibers are provided, the four second regions being spaced apart from each other by approximately 90° and being spaced apart from the four first regions comprising a packing of continuous structural fibers by approximately 45°.

[0026] Preferably, in a region remote from the perforated seat, the second direction is substantially parallel to the longitudinal direction of the continuous structural fibers and the cut structural fibers.

[0027] The aforementioned longitudinal direction may be parallel to the circumferential direction of the rim or may be inclined with respect to the circumferential direction of the rim by a predetermined angle, the predetermined angle being, for example, equal to approximately 45° or 60°. In both cases, the presence of structural fibers around the perforated seat results in a favorable local reinforcement in such regions of the rim, which is particularly critical for the stresses they undergo.

[0028] In a particularly preferred embodiment, at least two juxtaposed layers of unidirectional structural fibers are provided, and the structural fibers of each layer are oriented at approximately 45° with respect to the circumferential direction of the rim and are perpendicular to the structural fibers of the adjacent layer.

[0029] Preferably, at least some of the cut structural fibers in at least some of the second regions have a curved progression near the respective perforation seats and a substantially linear progression in regions remote from the perforation seats.

[0030] More preferably, in a region remote from the perforation seat, the cut structural fibers occupy a space having a dimension greater than 10% of the diameter of the perforation seat in a direction perpendicular to the longitudinal direction of the cut structural fibers.

[0031] Even more preferably, the aforementioned dimension is included between 20% and 70% of the diameter of the perforation seat, including the extreme values.

[0032] In particular, if the structural fibers are unidirectional, the aforementioned dimension is preferably included between 20% and 50% (including the extreme values) of the above diameter, while if the structural fibers are bidirectional, the aforementioned dimension is included between 50% and 70% (including the extreme values) of the above diameter.

[0033] In a first preferred embodiment of the rim according to the invention, the continuous structural fibers and the cut structural fibers are unidirectional fibers arranged in at least two juxtaposed layers. In this case, preferably, the at least one first region and the at least one second region are defined in each of the at least two juxtaposed layers.

[0034] In a second preferred embodiment of the rim according to the invention, the continuous structural fibers and the cut structural fibers are bidirectional fibers and include weft fibers and warp fibers. In this case, preferably, the at least one first region and the at least one second region are defined by both the weft fibers and the warp fibers.

[0035] In a second aspect of the invention, the invention relates to a process for manufacturing a bicycle rim, comprising:

[0036] - arranging a composite material in a mold, the mold comprising a radial inner wall provided with a plurality of first through-holes;

[0037] - perforating the composite material at the plurality of first through-holes by a cutting tool, thereby making a plurality of second through-holes in the composite material;

[0038] - after having made the plurality of second through-holes, molding the composite material in the mold, thereby forming a corresponding perforated spoke attachment seat at each of the second through-holes;

[0039] Wherein the perforation seat is defined by at least one first region and at least one second region, the at least one first region comprising a stack of continuous structural fibers, the at least one second region being circumferentially spaced apart from the first region, and the at least one second region comprising structural fibers cut by the cutting tool.

[0040] In this specification and the claims:

[0041] - "Cutting tool" is used to indicate a rotary tool having at least one cutting edge, such as a drill bit;

[0042] - "Perforation" is used to indicate a mechanical operation that causes the cutting of continuous structural fibers.

[0043] The foregoing process can be carried out to manufacture a bicycle rim according to the first aspect of the present invention. Thus, such a process has all the advantages described above with reference to the rim of the present invention and preferably has all its preferred features.

[0044] Preferably, perforating the composite material comprises: at each of the first through-holes, inserting the cutting tool into the first through-hole from the radially inner side of the mold in a first direction, and then pushing the cutting tool in the first direction until a corresponding second through-hole is made in the composite material.

[0045] Advantageously, a second through-hole is made at the first through-hole of the mold, and the movement of the cutting tool is guided by the foregoing first through-hole. The first through-hole of the mold uniquely defines the position and direction of the perforation seat, so that the perforation operation is extremely fast and precise.

[0046] Preferably, the mold has a generally annular shape, and the mold includes a circumferential groove on the radially inner surface of the mold, and the circumferential groove is connected to the first through-hole.

[0047] More preferably, the process according to the present invention comprises: after the composite material has been arranged in the mold and before perforating the composite material to make each second through-hole, inserting the cutting tool into the circumferential groove and moving the cutting tool along the circumferential groove until it reaches the corresponding first through-hole.

[0048] Advantageously, the cutting tool is easily guided between the first through-holes by the circumferential groove. Such an arrangement helps to make the perforation operation fast and precise.

[0049] Preferably, perforating the composite material comprises: after the cutting tool has been pushed in the first direction, removing the cutting tool from the second through-hole by moving the cutting tool in a second direction opposite to the first direction.

[0050] More preferably, perforating the composite material includes: after the cutting tool has been removed from the second through-hole, sizing the second through-hole by inserting a non-cutting pointed tool into the mold from the opposite side of the first through-hole relative to the composite material.

[0051] In this specification and the claims, the term "sizing" is used to indicate a mechanical operation that causes the severed structural fibers and continuous structural fibers to shift until a desired hole size is achieved in the composite material. After molding the composite material, such holes define the nominal design dimensions of the perforation spoke attachment seats. In the case of pre-impregnated structural fibers, the polymeric material is also shifted by the non-cutting pointed tool.

[0052] Preferably, sizing the second through-hole includes: pushing the non-cutting pointed tool into the second through-hole until the non-cutting pointed tool is inserted into the corresponding first through-hole.

[0053] Advantageously, the first through-hole of the mold uniquely defines the position and orientation of the perforation seat, and thus the above-mentioned sizing is extremely fast and precise.

[0054] Preferably, the non-cutting pointed tool is heated.

[0055] Advantageously, such an arrangement enables the ability and speed of the structural fibers encountered by the pointed tool to be shifted while the pointed tool advances in the second hole to be increased.

[0056] Preferably, the cutting tool includes a cylindrical cutting portion and a conical cutting tip.

[0057] Advantageously, the conical cutting tip enables the perforation to be precisely started, while the cylindrical cutting portion defines the diameter of the second hole, thereby calibrating the diameter of the second hole to the desired size.

[0058] Preferably, the diameter of the aforementioned cylindrical cutting portion is included between 20% and 100% of the diameter of the second through-hole, more preferably between 20% and 70% of the diameter of the second through-hole. The applicant has observed that even when the diameter of the cylindrical cutting portion is equal to the diameter of the second through-hole, a certain percentage of the structural fibers are not severed (uncut) but shifted. Since the cutting tool is machining on the non-crosslinked polymeric material, this shift can be initially caused by the conical cutting tip and then by the cylindrical cutting portion, thus allowing the structural fibers contained therein to be shifted.

[0059] According to a preferred embodiment of the process of the present invention, the conical cutting tip is diamond-tipped.

[0060] Advantageously, the diamond tip has significant performance in terms of cutting reliability and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Further features and advantages of the present invention will become more apparent from the following description of preferred embodiments of the invention made with reference to the accompanying drawings, in which:

[0062] - Figure 1 A perspective view schematically shows a bicycle rim according to the present invention;

[0063] - Figure 2 A plan view schematically shows a part of a composite material provided in a bicycle rim of the prior art ("prior art");

[0064] - Figure 3 A plan view schematically shows a part of a composite material provided in a rim according to the present invention;

[0065] - Figure 4 A perspective view schematically shows the manufacturing steps of a bicycle rim according to the process of the present invention;

[0066] - Figure 5 A schematic shows Figure 4 A top view side view of a partial section of the manufacturing step;

[0067] - Figure 6 A schematic shows Figure 4 A perspective view of a cutting tool used in the manufacturing step;

[0068] - Figure 7 A perspective view schematically shows another manufacturing step of a bicycle rim according to the process of the present invention. DETAILED DESCRIPTION

[0069] First, referring to Figure 1 , the bicycle rim according to the present invention is generally indicated by 50.

[0070] The rim 50 is at least partially made of a composite material 6, as shown in Figure 3 .

[0071] In the composite material 6, the structural fibers are generally selected from the group consisting of carbon fibers, glass fibers, boron fibers, aramid fibers, ceramic fibers, and combinations thereof, preferably carbon fibers.

[0072] The polymer of the composite material 6 can be thermoplastic or thermosetting. Preferably, the polymer of the composite material 6 is a thermosetting resin.

[0073] The mechanical properties of the composite material 6 vary according to the type of structural fiber, the type of its weaving / pattern, the type of polymer material, and the percentage ratio between the structural fiber and the polymer material.

[0074] In Figure 3 the non-limiting case shown, the structural fiber of the composite material 6 is a unidirectional fiber. Figure 3 Particularly shown is a layer of unidirectional structural fibers 60. The structural fibers of the composite material 6 can also be arranged in a number of juxtaposed layers.

[0075] In Figure 3 it, the unidirectional structural fibers 60 extend substantially parallel to each other along a longitudinal direction L that is parallel or inclined with respect to the circumferential direction of the rim 50. Preferably, different juxtaposed unidirectional fiber layers are provided, and the different juxtaposed unidirectional fiber layers are arranged such that the unidirectional fiber directions of two adjacent layers form angles in opposite directions with respect to the circumferential direction of the rim 50, preferably angles of +45° and -45°.

[0076] The rim 50 has a predetermined rotational angle X and is mounted on a bicycle hub 54 by a plurality of spokes 52.

[0077] The rim 50 has a radially inner annular wall 56 made of a composite material. A plurality of perforated spoke attachment seats 58 are made on such an annular wall 56. The plurality of perforated spoke attachment seats 58 are preferably of a substantially circular shape, and the spokes 52 are mounted at the plurality of perforated spoke attachment seats 58.

[0078] In Figure 1 the non-limiting example, the annular wall 56 has a symmetric shape with respect to the rotational axis X and a diameter intermediate plane perpendicular to the rotational axis X, and the spokes 52 extend along a substantially radial direction. However, alternative embodiments are provided, in which the annular wall 56 has an asymmetric shape and / or in which the spokes 52 extend along a direction inclined with respect to the radial direction.

[0079] In this specification and the claims, the terms "inner" and "outer" refer to the radial direction of the rim 50, or in some cases, may refer to the direction occupied by the spokes 52. In any case, the foregoing terms are used to indicate positions that are proximal and distal, respectively, with respect to the rotational axis X of the rim 50.

[0080] Figure 2 Schematically and by way of example, the progression of unidirectional fibers similar to the foregoing documents EP 2422959 and US 10315461 according to the prior art near the perforated spoke attachment seat 58a of the bicycle rim is shown. Before molding the composite material, the perforated seat 58a is formed by the displacement of the unidirectional structural fibers 40.

[0081] In particular, it should be noted that there are two regions 42 including a stack of continuous unidirectional structural fibers 40. The two regions 42 are arranged at diametrically opposite portions with respect to the perforated seat 58a and along a transverse direction T that is substantially perpendicular to the longitudinal direction L of the unidirectional structural fibers 40 in the region away from the perforated seat 58a.

[0082] It should also be noted that there are two regions 44 at opposite regions that are spaced apart from the regions 42 including the stack of fibers 40 by approximately 90° with respect to each perforated seat 58a. Only the polymeric material is provided in the two regions 44, and there are small regions 46 without the polymeric material.

[0083] Figure 3 Schematically and by way of example, the progression of the structural fibers according to the invention towards the perforated seat 58 of the annular wall 56 of the rim 50 is shown.

[0084] In Figure 3 a non-limiting example, the composite material includes unidirectional structural fibers 60 that extend along the longitudinal direction L in the region away from the perforated seat 58. The longitudinal direction L may be parallel to the circumferential direction of the rim 50 or may be inclined, for example, by approximately 45° or approximately 60° with respect to the circumferential direction of the rim 50.

[0085] Each perforated seat 58 has a substantially circumferential shape and is bounded along its entire perimeter circumference 59 by two first regions 62 and two second regions 64. The two first regions 62 include a stack of unidirectional continuous structural fibers 60, and the two second regions 64 include cut unidirectional structural fibers 60. The first region 62 and the second region 64 are spaced apart from each other circumferentially.

[0086] The two first regions 62 are arranged on two opposite sides with respect to the perforated seat 58 along a transverse direction T that is substantially perpendicular to the longitudinal direction L.

[0087] The two second regions 64 are arranged on two opposite sides with respect to the perforated seat 58 along the longitudinal direction L.

[0088] Thus, in this non-limiting case of the unidirectional structural fibers, the two first regions 62 are diametrically opposite and are spaced apart from the two second regions 64 by approximately 90°.

[0089] As shown in the figure, although schematically shown, but in Figure 3In [the above], some unidirectionally cut structural fibers 60 of the second region 64 have a curvilinear progression near the perforation seat 58 and a substantially linear progression parallel to the longitudinal axis L in a region remote from the perforation seat 58. Near the peripheral circumference 59 of the perforation seat 58, the unidirectionally cut structural fibers 60 tend to open with respect to a diametrical plane A parallel to the longitudinal direction L of the perforation seat 58, i.e., as approaching the first region and thus the perforation seat 58, the unidirectionally cut structural fibers 60 assume an increasingly greater inclination with respect to the longitudinal axis L.

[0090] In a region remote from the perforation seat 58, the unidirectionally cut structural fibers 60 occupy a space, the dimension of which along the transverse direction T is preferably included between 20% and 70% of the nominal diameter D of the perforation seat 58, more preferably between 20% and 50% of the nominal diameter D.

[0091] The applicant has foreseen an alternative embodiment of the rim of the present invention, which differs from the embodiment described above Figure 3 only in that the structural fibers of the composite material are bidirectional fibers and are arranged in at least two juxtaposed layers to form a fabric comprising weft fibers and warp fibers. In this case, the first region 62 including the continuous structural fiber stack and the second region 64 including the cut structural fibers are defined by the weft fibers and the warp fibers.

[0092] In particular, each perforation seat 58 is defined by four first regions 62 and four second regions 64, the four first regions 62 including a stack of continuous structural fibers and being spaced apart from each other by approximately 90°, the four second regions 64 including cut structural fibers and being spaced apart from each other by approximately 90°, and the four second regions 64 being spaced apart from the four first regions 62 including the stack of continuous structural fibers by approximately 45°.

[0093] Furthermore, in a region remote from the above-mentioned perforation seat 58, in this case, the bidirectionally cut structural fibers occupy a space, the dimension of which along the transverse direction T is preferably included between 50% and 70% of the nominal diameter D of the aforementioned perforation seat 58.

[0094] Reference Figures 4 to 7 describes a preferred embodiment of a process for manufacturing a bicycle rim (e.g., the above-mentioned rim 50) according to the present invention.

[0095] The process includes molding a composite material in a mold 70.

[0096] The mold 70 has a generally annular shape and includes two annular elements 1, 2 coupled to each other to define a mold cavity 3.

[0097] In the embodiment shown in the figures, the die cavity 3 is shaped to produce a symmetrical rim 50, in particular for a tubeless tyre.

[0098] Figure 5 A semi - cross - sectional view of the die 70 taken at the through - hole 5 is shown.

[0099] The annular elements 1, 2 define a plurality of through - holes 5 when joined, and perforation seats 58 will be made at the through - holes 5.

[0100] The die 70 includes a circumferential groove 72 on its radially inner surface 71, and the circumferential groove 72 is connected to the through - hole 5.

[0101] In the embodiment shown in the figures, the through - hole 5 is made to be partly in the annular element 1 and partly in the annular element 2, and the through - hole 5 includes a substantially cylindrical radial outer part 5a and an inwardly diverging radial inner part 5b having a substantially frustoconical shape.

[0102] The diameter of the radial outer part 5a is approximately equal to the nominal diameter D of the perforated spoke attachment seat 58, or slightly larger than the nominal diameter D.

[0103] The radial outer part 5a extends in a direction corresponding to the direction in which the spoke 52 to be received in the perforation seat 58 of the rim 50 will extend.

[0104] In the case shown in the figures, such a direction extends in the Figure 5 plane (i.e., in the transverse plane of the rim 50) along a direction inclined with respect to the diametral median plane Y of the die 70. Thus, the corresponding spokes 52 are of the type radially attached to the hub 54 with a certain camber. Those skilled in the art will understand that other through - holes 5 are provided at appropriate positions along the circumferential direction of the annular elements 1, 2, and depending on the desired camber, the relevant radial outer parts 5a have an appropriate inclination.

[0105] Since in some spoke patterns, the perforation seats 58 in the rim 50 may not be aligned along a single median plane of the rim 50 and / or the spokes 52 may be tangential to the hub 54 or in any case not radially attached to the hub 54, the through - holes 5 in the annular elements 1, 2 will have suitable directions and positions, and some through - holes 5 may also extend only in one of the annular elements 1, 2.

[0106] The annular elements 1, 2 preferably have adjacent elements (not shown), such as pins and centering holes, reference marks, etc., to ensure that when the annular elements 1, 2 are joined to each other, the two parts of each through - hole 5 in the two annular elements 1, 2 are correctly aligned to generally define the through - hole 5 itself.

[0107] The process according to the invention first comprises arranging the composite material 6 in a mold 70, in particular on the radially outer wall 3a of the mold cavity 3.

[0108] More particularly, the mold cavity 3 is coated with one or more layers of sheet composite material 6, which sheet composite material 6 is preferably pre-impregnated. Such materials are commonly referred to in the art as sheet molding compounds (SMC) or "prepregs" and generally comprise structural fibers pre-impregnated with a polymeric material.

[0109] The arrangement of the composite material 6 in the mold cavity 3 can be carried out manually or automatically.

[0110] The composite material 6 is perforated at the through-hole 5 by a cutting tool 80, as Figure 6 shown.

[0111] The cutting tool 80 is a rotary tool and is mounted on a corner screwdriver 90 (shown in Figure 4 and Figure 5 ) or on a drill bit. The corner screwdriver 90 has the advantage of being easily manipulable in a narrow space (such as a narrow space inside the mold 70).

[0112] In the non-limiting example shown in Figure 6 , the cutting tool 80 comprises a cylindrical shank 81 which has a cylindrical cutting portion 84 and a conical cutting tip 86 at its free end. Both the cylindrical cutting portion 84 and the conical cutting tip 86 have at least one cutting edge 82.

[0113] In the specific example shown herein, there is more than one cutting edge 82 (for example, four), and these cutting edges extend seamlessly over the cylindrical cutting portion 84 and the conical cutting tip 86.

[0114] Preferably, the conical cutting tip 86 is diamond-tipped.

[0115] Perforating the composite material 6 by the cutting tool 80 produces through-holes 6a in the composite material 6 at each through-hole 5 of the mold 70.

[0116] The diameter of the cylindrical cutting portion 84 of the cutting tool 80 is selected according to the diameter of the through-hole 6a to be manufactured, according to the desired ratio of cut and continuous (uncut) structural fibers to be obtained at the through-hole 6a, and based on industrial evaluations (to avoid breakage of the cutting tool 80 and the need for working time).

[0117] Preferably, the diameter of the cylindrical cutting part 84 is included between 20% and 100% of the diameter of the through-hole 6a, more preferably between 20% and 70% of the diameter of the second through-hole 6a. During the perforation, a part of the structural fibers may shift because it has not been blocked by the cross-linked polymeric material.

[0118] For example, in order to make a through-hole 6a with a diameter equal to 5 mm, a cutting tool 80 with a cylindrical cutting part 84 having a diameter equal to 3.5 mm can be used.

[0119] Preferably, the cutting tool 80 is used at room temperature, that is, the cutting tool 80 is not heated before use, so as to avoid the part of the sheared structural fibers sticking to its surface, which will reduce the quality and dimensional accuracy of the through-hole 6a.

[0120] Perforating the composite material 6 to make the through-hole 6a first includes inserting the conical cutting tip 86 into the circumferential groove 72, and then moving the cutting tool 80 along the circumferential groove 72 until reaching each through-hole 5.

[0121] Once reaching the through-hole 5, the cutting tool 80 is inserted into the through-hole 5 along the first direction F starting from the radial inner part 5b of the through-hole 5. The generally frustoconical and inwardly flaring shape of the radial inner part 5b makes it easier to guide the insertion of the cutting tool 80.

[0122] After that, the cutting tool 80 reaches the generally cylindrical radial outer part 5a of the through-hole 5 and is pushed until it reaches the composite material 6 and perforates it, thus making the through-hole 6a in the composite material 6.

[0123] Then the cutting tool 80 is removed from the through-hole 5, so that the cutting tool 80 moves along the direction B opposite to the insertion direction F.

[0124] Thus, the conical tip 86 of the cutting tool 80 moves along and crosses the circumferential groove 72 until reaching the next through-hole 5, where the cutting tool 80 perforates the composite material 6 in the same manner as described above.

[0125] After the cutting tool 80 is removed from the through-hole 6a, the through-hole 6a is finish-sized by a non-cutting pointed tool 8 (such as an awl), as Figure 7 shown.

[0126] The pointed tool 8 is inserted into the through-hole 6a from the radial outside of the mold cavity 3, and thus from the mold 70.

[0127] The pointed tool 8 crosses the composite material 6 and is partially inserted into the radial outer part 5a of the through-hole 5 of the annular elements 1, 2 of the mold 70.

[0128] The pointed tool 8 includes a cylindrical shank 8a having a predetermined diameter and a tip 8b or a tapered portion that ends substantially in a tip.

[0129] The predetermined diameter of the cylindrical shank 8a substantially corresponds to the nominal diameter D of the perforated spoke attachment seat 58 to be obtained in the rim 50, or is slightly larger than this nominal diameter D, and also substantially equals or is slightly smaller than the diameter of the substantially cylindrical radial outer portion 5a of the through hole 5.

[0130] The insertion depth of the tool 8 is selected such that, in addition to the tip 8b, a portion of the cylindrical shank 8a is also inserted into the radial outer portion 5a of the hole 5. Thus, the through hole 6a has a nominal diameter substantially equal to the predetermined diameter of the cylindrical shank 8a.

[0131] In practice, by inserting the pointed tool 8 into the through hole 6a of the composite material 6, the continuous structural fibers and the cut structural fibers caused by the previous perforation of the through hole 6a are displaced. The displacement of the aforementioned continuous structural fibers and cut structural fibers enables the desired size of the through hole 6a to be achieved, which, after subsequent molding of the composite material 6, defines the nominal design size of the perforated spoke attachment seat 58. Generally, the diameter of the through hole 6a after the sizing step by the pointed tool 8 is larger than the diameter of the through hole 6a after the perforation step by the cutting tool 80.

[0132] During the insertion step of the pointed tool 8, the pointed tool 8 follows the inclination of the radial outer portion 5a of the through hole 5 in the inner elements 1, 2 of the mold 70, and this inclination serves as a guide for the pointed tool 8.

[0133] The aforementioned sizing step can be performed after the pointed tool 8 has been heated. During the insertion of the composite material 6, the hot tip 8b reduces the viscosity of the polymeric material, thereby facilitating the displacement of the structural fibers therein. Of course, if the polymeric material of the composite material 6 is thermosetting, the temperature of the pointed tool 8 must be lower than its crosslinking temperature. The heating must also be carried out at a temperature that avoids dripping of the polymeric material into the through hole 5. By way of example only, the heating temperature can be 30 °C to 40 °C.

[0134] Then, the pointed tool 8 is withdrawn in the opposite direction.

[0135] Thus, the molding of the composite material 6 in the mold 70 continues, thereby forming a corresponding perforated spoke attachment seat 58 at each second through hole 6a.

[0136] During the molding step, crosslinking of the thermosetting or thermoplastic polymeric material occurs, thereby locking the structural fibers in place.

[0137] Of course, those skilled in the art can bring many changes and variations to the present invention to meet specific and accidental requirements, and all these changes and variations are within the scope of protection defined by the claims in any case. Therefore, the following content should only be taken as an example.

[0138] Instead of using pre-impregnated composite materials, materials in dry fibers can be used during the initial steps of the process, so that in particular the perforation step can be carried out only on the materials in dry fibers. After that, before applying the temperature and pressure curves necessary for the hardening of the composite material, the polymeric material is preferably injected at multiple points to bond the materials in the dry fibers.

[0139] The process may include the following steps: preferably before the aforementioned molding step, coupling the provided insert with the corresponding through-hole at the perforation seat. Thus, preferably, the insert is co-molded in the perforation seat. The insert increases the resistance of the rim to the traction stress exerted by the spokes of the wheel; in addition, the co-molding of the insert and the composite material prevents wear caused by friction due to the sliding of the insert on the composite material.

[0140] In addition, the process may include the step of temporarily sealing the perforation seat during the aforementioned molding step, for example, by means of an auxiliary element similar to that described in EP2422959. The temporary sealing of the perforation seat during the molding step can also be omitted in any case, which can be achieved by providing a cleaning step after molding.

[0141] The process of the present invention may include the step of co-molding an outer rim part made of metal or composite material with the aforementioned part of the rim made of composite material.

[0142] The above process can also be applied only to some of the perforated spoke attachment seats, so that other spoke attachment seats in the rim are made by traditional techniques.

[0143] The bicycle rim made according to the present invention is particularly suitable for tubeless wheels.

[0144] However, it should be understood that the present invention is also applied in its various aspects to: the rims of wheels having an air chamber; and the rims of wheels having tubular tires (clincher).

Claims

1. A bicycle rim (50), comprising a wall (56) made of a composite material, the wall (56) having a plurality of perforated spoke attachment seats (58), each of the perforated spoke attachment seats (58) having a substantially circumferential shape and being defined at the peripheral circumference (59) of each perforated spoke attachment seat (58) by at least two first regions (62) and at least two second regions (64): The at least two first regions (62) comprise a stacking of continuous structural fibers (60), and in the at least two first regions (62), the local density of the continuous structural fibers (60) is greater than the average nominal density of the continuous structural fibers (60), wherein the at least two first regions (62) are arranged on two opposite sides in a first direction (T) with respect to the perforated spoke attachment seat (58); The at least two second regions (64) are circumferentially spaced from the at least two first regions (62), and the at least two second regions (64) comprise cut structural fibers (60), wherein the at least two second regions (64) are arranged on two opposite sides in a second direction (L) inclined with respect to the first direction (T) with respect to the perforated spoke attachment seat (58), wherein the second direction (L) is substantially perpendicular to the first direction (T); Wherein some of the cut structural fibers (60) of the at least two second regions (64) have a curved progression at the peripheral circumference (59) of the perforated spoke attachment seat (58).

2. The bicycle rim (50) according to claim 1, wherein in a region remote from the perforated spoke attachment seat (58), the second direction (L) is substantially parallel to the longitudinal direction of the continuous structural fibers (60) and the cut structural fibers (60).

3. The bicycle rim (50) according to claim 1, wherein the cut structural fibers (60) have a substantially straight progression in a region remote from the perforated spoke attachment seat (58).

4. The bicycle rim (50) according to claim 1, wherein in a region remote from the perforated spoke attachment seat (58), the cut structural fibers (60) occupy a space having a dimension greater than 10% of the diameter (D) of the perforated spoke attachment seat (58) in a direction (T) perpendicular to the longitudinal direction (L) of the cut structural fibers (60).

5. The bicycle rim (50) according to claim 4, wherein the dimension is included between 20% and 70% of the diameter (D) of the perforated spoke attachment seat (58), including the extreme values.

6. The bicycle rim (50) according to claim 1, wherein: The continuous structural fibers (60) and the cut structural fibers (60) are unidirectional fibers arranged in at least two juxtaposed layers, and the at least two first regions (62) and the at least two second regions (64) are defined in each of the at least two juxtaposed layers; or The continuous structural fibers (60) and the cut structural fibers (60) are bidirectional fibers and include warp fibers and weft fibers, and the at least two first regions (62) and the at least two second regions (64) are defined by both the warp fibers and the weft fibers.

7. A method for manufacturing a bicycle rim (50), comprising: Disposing a composite material (6) in a mold (70), the mold (70) including a radial inner wall (3a) provided with a plurality of first through holes (5); Perforating the composite material (6) at the plurality of first through holes (5) by a cutting tool (80) to produce a plurality of second through holes (6a) in the composite material; After the plurality of second through holes (6a) have been produced, molding the composite material (6) in the mold (70) so as to form corresponding perforated spoke attachment seats (58) at each of the second through holes (6a); Wherein perforating the composite material (6) includes: after the cutting tool (80) has been pushed in a first direction (F), removing the cutting tool (80) from the second through hole (6a) by moving the cutting tool (80) in a second direction (B) opposite to the first direction (F), and subsequently sizing the second through hole (6a) by inserting a non-cutting pointed tool (8) into the mold (70) from the opposite side of the first through hole (5) relative to the composite material (6); Wherein the perforated spoke attachment seat (58) is defined by at least one first region (62) and at least one second region (64), the at least one first region (62) includes a stack of continuous structural fibers (60), the at least one second region (64) is circumferentially spaced apart from the first region (62), and the at least one second region (64) includes structural fibers (60) cut by the cutting tool (80).

8. The method for manufacturing a bicycle rim (50) according to claim 7, wherein perforating the composite material (6) comprises: At each of the first through holes (5), inserting the cutting tool (80) into the first through hole (5) from the radial inside of the mold (70) in a first direction (F), and then pushing the cutting tool (80) in the first direction (F) until a corresponding second through hole (6a) is produced in the composite material (6).

9. A method for manufacturing a bicycle rim (50) according to claim 7, wherein the mold (70) has a generally annular shape, and the mold (70) includes a circumferential groove (72) on a radially inner surface (71) of the mold (70), the circumferential groove (72) being connected to the first through hole (5), and wherein the method comprises: After the composite material (6) has been disposed in the mold (70) and before perforating the composite material (6) to produce each second through hole (6a), inserting the cutting tool (80) into the circumferential groove (72) and moving the cutting tool (80) along the circumferential groove (72) until reaching the corresponding first through hole (5).

10. The method for manufacturing a bicycle rim (50) according to claim 7, wherein the cutting tool (80) includes a cylindrical cutting portion (84) and a conical cutting tip (86).

11. A method for manufacturing a bicycle rim (50) according to claim 10, wherein the diameter of the cylindrical cutting portion (84) is included between 20% and 100% of the diameter of the second through hole (6a).

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