VEHICLE WHEEL RIM

A rim for a vehicle wheel, including: an axial axis; a radial axis; a spoke bed wall having an outboard surface, an inboard surface, and a radial thickness; a spoke hole to receive a spoke having an outboard opening and a spoke hole axis. At least one of the inboard surface and outboard surface is radially variable to provide a first radial thickness region laterally surrounding said spoke hole and a second radial thickness region of reduced radial thickness relative to the first radial thickness region. The outboard surface includes a radially inwardly recessed surface within the first radial thickness region. At least a portion of the recessed surface is configured to provide a bearing surface for engagement with the spoke and to support of spoke tension forces.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to spoked vehicle wheels and bicycle wheels in particular. More specifically, this invention relates to the spoke bed of a vehicle wheel rim where the spoke bed is contoured to optimize its strength and to optimize the connection with a spoke connected thereto.

(2) Description of the Related Art

In the development of a tension-spoked wheel, the geometry of interaction between the spoke and the rim is of particular importance as it relates to the strength, stiffness, and longevity of the completed wheel structure. The overlie engagement between the under-head surface of the spoke nipple and the spoke bed of the rim serves to provide the requisite bracing to resist the spoke tension forces of the wheel.

The spoke commonly has a bracing angle with the rim. In wheels with “crossed” or tangential lacing, the spoke commonly has a circumferential angle with the rim. This is particularly understood and is evident on the conventional spoked bicycle wheel. Firstly, it is shown that, due to the bracing and/or circumferential angles of the spoke, the under-head surface of a conventional spoke nipple commonly contacts and braces against the rim's spoke bed at only a single contact point. This is explained in greater detail in U.S. Pat. No. 7,427,112 discussions of prior art. This singular contact point results in a very small area of contact such that the high spoke tension of modern wheels, creates very high contact stress at this contact point. The result is excessive galling between the spoke nipple and the rim as the nipple is rotatably adjusted to bring the spoke up to the desired tension. This creates resistance to rotation of the nipple and thereby makes the nipple more difficult to adjust. In addition, this also causes the nipple and rim to abrade against each other, removing nipple and/or rim material and potentially weakening the structural integrity of one or both of these components.

Further, it is well understood that the spoke hole of the rim constitutes a structural stress riser in the rim. Accordingly, it may be viewed that the spoke hole effectively causes a localized weakness to the rim. With conventional spoke nipples, the bearing interface between the nipple and the rim occurs directly at the edge of the spoke hole, commonly the weakest point of the rim's spoke bed. It is also understood that, in use, the wheel is subject to both static loads (due to spoke pre-tension) and cyclic loads (due to rolling of the wheel under load). The combination of rim weakness and high contact stresses at this interface results in cracks in the spoke bed due to fatigue loading. These cracks commonly radiate outwardly from the spoke hole. This requires that rims be heavily reinforced and thickened in the spoke bed region of the rim, which adds weight to the rim and to the assembled wheel. Since rims are commonly produced in an extrusion process, selective thickening is not feasible and this thickened spoke bed extends around the full circumference of the rim, not just in the regions surrounding the spoke holes. As such, this further increases additional weight of prior-art rims.

Secondly, this single contact point is laterally offset from the centerline of the spoke. Since the spoke tension acts along the spoke's centerline, and the resisting force acts at the singular contact point, this offset creates a bending moment at the spoke nipple. Since the spoke tension increases and decreases cyclically as the wheel is rotated, this bending moment introduces a cyclic bending stress to the spoke, which reduces the fatigue life of the spoke, the nipple, and/or rim. In fact, it is not at all uncommon for a spoke to fail due to cyclic fatigue under normal use.

Further, this bending moment tends to deflect the spoke and add a bent region in the spoke adjacent the nipple. The bent region will tend to flex somewhat due to the variations in spoke tension experienced during normal use of the wheel. This flex has the effect of reducing the effective tensile stiffness of the spoke and thus tends to reduce the lateral stiffness of the wheel. The result is a wheel that is “flexier” and more easily deflected, lending a less responsive feel on the part of the rider. This bending also serves to increase fatigue stresses and exacerbate spoke failure due to fatigue.

SUMMARY OF THE INVENTION

The present invention includes a rim having a thickened spoke bed region surrounding the spoke hole and the connection with the spoke. The thickened region provides additional strength and stiffness in this most highly stressed region of the rim.

The present invention further includes a bearing surface that is longitudinally inwardly recessed from the outboard surface of the spoke bed. This recessed bearing surface preferably provides an optimized bearing interface with the spoke to increase the contact area of interface and thereby reduce stress in both the spoke and the rim. Since the spoke bed is thickened in this region, any reduction in spoke bed thickness associated with the recessed bearing surface is compensated by this additional thickness of the thickened region.

In comparison with conventional spoke/rim connections, this optimized bearing surface serves to provide (i) a greater area of bearing interface, thus reducing the corresponding bearing stresses; and/or (ii) alignment of this bearing interface with the spoke to minimized any bending moment to further reduce stresses and bending or flex of the spoke.

In accordance with the present invention, it has now been found that the forgoing objects and advantages may be readily obtained.

Since the rim may be thinned in the low-stress regions between the adjacent spoke connections, the overall weight of the rim may be reduced. Lighter weight serves to increase the performance of the rim and minimize raw material used for potential manufacturing cost savings.

Since the area of bearing interface is increased, the associated stresses in the spoke and/or rim are reduced. This serves to reduce any galling or resistance to threadable adjustment of the spoke nipple. This also serves to reduce the aforementioned lateral offset and associated bending moment to further reduce stresses and bending or flex of the spoke.

The thickened regions surrounding the spoke holes may provide additional strength and stiffness to support spoke tension forces.

The advantages of the present invention provide several benefits over existing wheel designs, including: an increase in the fatigue life of the wheel; a reduction in the weight of the wheel; an increase in the lateral stiffness of the wheel; reduction or elimination of the galling and abrasion between the spoke and the nipple; the ability to produce the wheel economically at low cost; and an increase in strength of the rim.

The novel features, which are believed to be characteristic of the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description of the accompanying drawings of the embodiments of the present invention. It is expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

Further features of the present invention will become apparent from considering the drawings and ensuing description.

DETAILED DESCRIPTION OF THE INVENTION

FIG.1describes the basic schematic configuration of an exemplary prior art vehicle wheel, in particular, a bicycle wheel1, as well as a description of the direction conventions used throughout this disclosure. For clarity, the bicycle frame and the quick release skewer assembly are not shown in this figure. The hub shell14is rotatable about the axle9and includes at least two axially spaced hub flanges16aand16b, each of which include a means for connecting with a multiplicity of spokes2connected thereto. Axle9includes end faces11aand11bthat define the spacing of its mounting with the frame (not shown). The axial axis28is the axial centerline of rotation of the bicycle wheel1. The hub flanges16aand16bmay be contiguous with the hub shell14or may be separately formed and assembled to the hub body12portion of the hub shell14. Each spoke2is affixed to its respective hub flange16aor16bat its first end4and extend to attach the rim8at its second ends6. The tire10is fitted to the outer periphery of the rim8. The wheel ofFIG.1is generic and may be of tension-spoke or compression-spoke design.

The axial direction92is any direction parallel with the axial axis28. The radial direction93is a direction generally perpendicular to the axial direction92and extending generally from the axial axis28radially outwardly toward the rim8. The tangential direction94is a direction generally tangent to the rim at a given radius. The circumferential direction95is a cylindrical vector that wraps around the axial axis28at a given radius. A radial plane96is a plane perpendicular to the axial axis28that extends in a generally radial direction at a given axial intercept. An axial plane97is a plane that extends along the axial axis28. An orientation that is radially inboard (or inward) is nearer to the axial axis28of rotation and a radially outboard (or outward) is further from the axial axis28. An axially inboard (or inward) orientation is an orientation that is axially proximal to the axial midpoint between the two end faces11aand11b. Conversely, an axially outboard (or outward) orientation is an orientation that is axially distal to the axial midpoint between the two end faces11aand11b. A radially inboard orientation is an orientation that is radially proximal to the axial axis28and a radially outboard orientation is an orientation that is radially distal to the axial axis28. An axially inwardly facing surface is a surface that faces toward the axial midpoint between the two end faces11aand11b. Conversely, an axially outwardly facing surface is a surface that faces away from the axial midpoint between the two end faces11aand11b.

The axial axis28is the central axis of rotation of the wheel. A radial axis29is an axis extending perpendicular to and intersecting with the axial axis28. A tangential axis31is an axis in the radial plane96that is perpendicular to the radial axis29and radially offset from the axial axis28.

While it is most common for the hub shell14to rotate about a fixed axle9, there are some cases where it is desirable to permit the axle9to be fixed with the wheel1such as the case where the wheel1is driven by the axle9.

For the purposes of using conventional terminology, the term “hub flange” is used herein to describe a region of the hub shell14to which the spokes2are joined. While the surface of the hub flange may be raised and flange-like in comparison to other surfaces of the hub shell14, this is not a requirement for the present invention and the hub flange16may alternatively be flush or recessed relative to other hub shell surfaces.

As is well known in the art, a wheel1may be of tension-spoke construction, where the central hub hangs in tension by the spokes from the rim portion directly above, or it may be of compression-spoke construction, where the hub is supported by compressing the spoke directly beneath it. Since the present invention may be directed toward bicycle wheels and since the tension-spoke wheel is generally a more efficient structure than compression-spoke wheel, most of the discussion herein is focused with an eye toward tension-spoke wheel construction. However, it is anticipated that most, if not all, of the embodiments of the present invention may be adapted or otherwise applied to compression-spoke wheel construction as well. For a tension-spoke wheel, it is preferable that the wheel includes at least two hub flanges that are axially spaced on either side of the rim or, more specifically, the spoke attachment points at the rim. Thus, the spokes fixed to opposite hub flanges will converge as they extend to the rim as illustrated inFIG.2b. Additionally, a tension-spoke wheel will usually be pre-tensioned during assembly to create a pre-tensioned structure of balanced spoke tension that allows the axle supporting loads to be distributed among several, if not all, of the spokes of the wheel. It is this ability to share the stresses among its spokes that helps to make the tension-spoke wheel the highly efficient structure that it is. For a compression-spoke wheel, it is often preferable to employ at least two axially spaced hub flanges, however, in the case where the spokes have sufficient bending stiffness to support the requisite lateral or side-to-side loads, only a single hub flange may be employed.

The spoke2is a generally long slender tensile element with a longitudinal axis62along its length and generally parallel to its sidewalls. The spoke2also has a tensile axis61of applied tensile load58that extends along the span portion of the spoke2between its anchor points at the rim8and hub flange16. The tensile axis61is generally collinear to the longitudinal axis62, except where the spoke2is bent to deviate from the tensile axis61. For the purposes of definition, as relating to spokes2and connections thereto, the term “longitudinal” herein refers to alignment along the longitudinal axis62. A longitudinally inboard (or inward) orientation refers to an orientation proximal the midpoint of the span portion. Conversely, a longitudinally outboard (or outward) orientation refers to an orientation distal the midpoint of the span portion. The term “lateral” herein refers to an orientation in a direction generally perpendicular to the longitudinal axis62. A laterally inboard (or inward) orientation refers to an orientation proximal the longitudinal axis. Conversely, a laterally outboard (or outward) orientation refers to an orientation distal the longitudinal axis62.

FIGS.2a,2band2cdescribe the current technology in conventional bicycle wheels that most cyclists are familiar with. This prior art design includes a rim8, a hub shell14and a plurality of spokes3. The hub shell14is rotatable about the axle9and includes a pair of axially spaced hub flanges16aand16b. The wheel is assembled by first threading each individual spoke3through an axial hole17in the hub flange16until the j-bend19of the first end4is hooked within the hole17. The spoke3is then pivoted to extend in a generally radial direction toward the rim8. The enlarged portion34or “head” of the spoke3prevents the spoke3from pulling through the hole17in the hub flange16a. The second end6of each spoke3is then fixed to the rim8via spoke nipples21. The span of the spoke3is defined herein as the portion of the spoke3that spans between its connection to the hub flange (16aor16b) at its first end4and its connection to the rim8at its second end6and the span length refers to the longitudinal length of the span. Tightening the threaded engagement between the spoke nipple21and the spoke3serves to effectively shorten the span length of the spoke3. Thus, as the nipples21are threadably tightened, the spokes3are drawn up tight and a degree of pre-tension is induced in each spoke3. By selectively adjusting this threaded engagement, the spoke pre-tension may be adjusted and balanced relative to the other spokes3and to also align the trueness and roundness of the rim8. The spoke pre-tension is resisted by circumferential compression of the rim8and it is this balance of forces that imparts efficient structural integrity to the bicycle wheel1. Also shown inFIG.2b, there is lateral bracing angle38between the radial centerline plane of the rim8and the centerline62of the spoke3. As this bracing angle38is increased, the lateral or side-to-side stiffness (i.e. stiffness in the axial direction92) of the wheel1is also increased. As shown inFIG.2a, the spokes are shown with common “crossed” lacing where the spokes2span to be tangent to their corresponding hub flanges16aand16b. As such, there is a circumferential angle35between the longitudinal axis62and the radial axis29.

It is noted that the threadable connection between the nipple21and its mating spoke3serves both as a pre-tensioning means and as a means to lock the second end6of the spoke3to the rim8during use of the bicycle wheel. This pre-tensioning means occurs within the spoke itself since the engagement interface (i.e. the threadable engagement) serves to both induce the pre-tension in the spoke and to maintain this pre-tension during operation of the wheel1. This requires that this threadable connection be robust enough to perform both of these functions and that the threadable engagement must operate smoothly and consistently. As such, both the spoke3and the nipple21are preferably metallic materials with sufficient strength and hardness to achieve a smooth and consistent threadable adjustment as well as having a high degree of structural strength of the threadable engagement. However, these metallic materials are generally heavy in comparison with fiber reinforced spoke materials. Further, if one attempts to incorporate such metallic threads with a fiber reinforced spoke, this is difficult to achieve and adds complexity and cost to the fiber reinforced spoke while also increasing weight.

It is further noted that in a tension spoke wheel1, the pre-tension of the spokes3induce a longitudinal tensile strain and stretch in the corresponding spokes, as well as a circumferential hoop compression strain of the rim8. There may also be a strain of the hub assembly14, however such strains are commonly quite small in comparison to strain of the spoke3and/or rim8. In order for the wheel1to effectively support cycling loads, it is important to carefully balance this spoke pre-tension so that the cycling loads are evenly distributed throughout the wheel1and so that the wheel rim8rotates round and true. It is usually preferable that these strains be within the elastic limit of the corresponding spoke3and/or rim8. This is commonly achieved by adjusting the length of the spoke span to induce strain in the wheel and then locking the spoke connections at its first end4and second end6to fix the length of the spoke span therebetween and maintain the pre-tension in the spokes3while the wheel1is in its free-state (i.e. prior to loading the wheel in use).

FIGS.3a-fdescribe an exemplary rim20of generally conventional geometry. As detailed inFIGS.3aand3b, rim20is of a generally hollow construction, commonly termed “double-wall” construction, and includes a radially inboard spoke bed22wall of thickness23and a radially outboard tire bed24wall and generally radially extending sidewalls26aand26bto define a generally hollow circumferential cavity27. Spoke bed22is defined by a radially inboard surface32and a radially outboard surface33. Hooked flanges30aand30bare adapted to engage the beads of a conventional tire (not shown).

The spoke bed22is pierced with a plurality of spoke holes36adapted for connection with their respective spokes2via spoke nipples48. It may be seen that the spoke hole36has a radially inboard edge39at its intersection with the inboard surface32and a radially outboard edge40at its intersection with the radially outboard surface34. Further, outboard edge40may be seen to have axially spaced quadrant points42aand42bas well as circumferentially spaced quadrant points44aand44b. The tire bed24is pierced by access hole37that is aligned with spoke hole36, to permit the nipple48to be assembled as shown inFIGS.3aand3c. Note that access hole37is merely one common means to permit the nipple48to be assembled to the rim; a wide range of alternative means may be substituted, including means that do not require an access hole.

It is useful to understand that it is common to manufacture the rim20by extruding the straight profile shown here and rolling the extrusion into a circumferential hoop with its ends joined by either a welded, sleeved or pinned connection. Spoke holes36and access holes37are then drilled in their proper locations.

FIG.3ashows an exploded view that describes the conventional arrangement by which the second end6of the spoke2is connected to the rim20. The second end6of spoke2includes external threads46to mate with internal threads47of spoke nipple48. Spoke nipple48includes an enlarged head50and a shank52, with a generally conical tapered transition portion54extending between the underside of the head50and the shank52. Spoke nipple48also includes flats56for engagement with a mating wrench (not shown) for manual manipulation to adjust the spoke pre-tension by adjusting the threaded engagement between external threads46and internal threads47. Nipple48is considered an “external” spoke nipple, since it has a shank52that extends through the spoke hole36so that its flats56are exposed and may be manipulated externally to the rim20. A “nipple” or “spoke nipple” is defined herein as an element that is connected to the spoke and that includes a bearing surface for overlie engagement with the rim. Most commonly, the nipple is connected to the spoke by a threadable engagement. An “external nipple”, such as spoke nipple48, is defined herein as a spoke nipple that extends to a point longitudinally inwardly of the inboard surface of the spoke bed.FIGS.3c-fshows the spoke nipple48threadably assembled to the spoke2such that the transition portion54overlies and contacts the outboard edge40. The transition portion54serves as a bearing surface or engagement surface of the spoke2for bearing interface with the rim20to support spoke tension58forces. The spoke nipple48is thereby braced against the spoke bed22to resist the spoke tension58of the spoke2.

It may be seen that the outboard surface34of the spoke bed22is of generally concave geometry as viewed in the cross-sectional views ofFIGS.3d-f. Thus, the intersection between the cylindrical spoke hole36and the concave outboard surface34creates a saddle-shaped outboard edge40, such that quadrant points42aand42bare spaced by radial distance60to be radially outboard of quadrant points44aand44b. With spoke nipple48aligned with angle of inclination18bas shown, it may be seen that the transition portion54contacts the outboard surface34of the spoke bed22only at the quadrant point42a, which is offset from the longitudinal axis62by distance64. Shank52also contacts inboard edge38, which restrains axial movement of the nipple48and forces the transition portion54against quadrant point42a. With the transition portion54supported only by quadrant portion42a, it may be seen that the transition portion54does not contact, and is spaced from, the outboard edge40at quadrant points42b,44aand44b.

Since the spoke tension58acts along the longitudinal axis62, the offset distance64(between the longitudinal axis62and contacting quadrant point42a) tends to induce a bending moment to rotate the spoke nipple48in the direction66toward a reduced angle of inclination18bthat is no longer in alignment with the spoke centerline62or longitudinal axis62. Further, the spoke tension58tends to induce the conical transition portion54to ramp against its contact point at quadrant point42a. This, in combination with the contact between the inboard edge39and shank52at contact point45further induces the nipple48to pivot in the direction66. The result is that the spoke2tends to bend in response to the aforementioned moment, thus creating a bent region68(FIG.3f) just inboard of the spoke nipple48and thereby inducing a bending stress in the spoke2. As with all tension-spoke wheels, as the loaded wheel1is rotated along the ground, each successive spoke undergoes a cycle of reduced and increased spoke tension58. This causes the bent region68to flex with each revolution of the wheel, creating a much higher potential for fatigue failure of the spoke2as compared to a spoke without a bent region68and its associated bending stress. Further, the bending and associated flex described here tends to reduce the effective tensile stiffness of the spoke2between its attachment points, thereby reducing the overall structural stiffness of the wheel1.

Additionally, since the majority of the spoke tension58is braced and resisted by the overlie engagement between the nipple48and only the single contact point at quadrant point42a, the contact load due to spoke tension58induces a very highly concentrated contact stress at this singular contact point. This high contact stress may result in localized galling as the nipple48is rotatably manipulated with in its spoke hole36. Furthermore, this high contact stress may cause excessive stress and deformation of the nipple48and/or spoke hole36. This very high localized stress also commonly causes cracking and failure of the rim due to fatigue. To resist the stress and minimize such failure, the spoke bed22needs to be very thick, which adds weight to the rim, detracting from the performance of the wheel.

It is noted that the concentrated single contact point at quadrant point42ais also coincident with the edge of the spoke hole36. Thus, not only does the existence of spoke hole36create a stress riser in the spoke bed22, but the region of highest contact stress occurs right on the edge of this spoke hole to amplify this stress riser. As a result, due to high usage and fatigue loading, it is very common for cracks to form in the spoke bed22that radiate out from the spoke hole.

It is noted that some have attempted to mitigate this elevated stress by drilling the spoke holes36at an angle from the radial axis29that is intended to correspond to the longitudinal axis62in a procedure known as “angled spoke drilling”. However, this angled spoke drilling does not appreciably increase the contact area of engagement between the transition surface54and the outboard edge40. Correspondingly, the contact stress at this interface remains very high. It would therefore be beneficial to mitigate these fatigue cracks is to modify the conventional design to distribute the spoke contact loads over a larger area of the rim to reduce the contact stress.

FIGS.4a-cdescribe another exemplary rim70of conventional geometry. Rim70is generally identical to rim20, however the outboard surface72of spoke bed74instead has a generally flat contour defining a generally flat cylindrical surface. This means that outboard edge78of spoke hole76is a flat circular edge. However, due to the angle of inclination18bof the spoke2and spoke nipple48, the transition portion54contacts the outboard edge78at only a single contact point80, which is offset from the longitudinal axis62by offset distance82. The angle of inclination18bmay also be considered to be an axial skew angle of the longitudinal axis62relative to the radial axis29. Like the prior art embodiment ofFIGS.3a-f, this offset distance82induces a bending moment in the spoke2, including the associated bending and flex previously described herein.

Thus, it may be seen that it is advantageous to reduce or eliminate the offset distance64or82to minimize the bending or flex associated with the prior-art arrangements described inFIGS.3a-fandFIGS.4a-b. The following embodiments of the present invention describe a variety of methods to reduce or eliminate this offset distance.

As illustrated inFIG.2a, spokes are commonly laced such that their longitudinal axis36is radially offset from the axial axis28such that the spokes cross past each other. This well understood in industry and where the term “cross” is commonly used to describe how many spokes an individual spoke crosses within its span. This radial offset means that the spoke is commonly circumferentially skewed from a radial axis29at its intersection with the rim. This is particularly illustrated inFIG.4c, where longitudinal axis62(also considered the “longitudinal axis”) of spoke2is skewed from the radial axis29by a circumferential clockwise skew angle73and longitudinal axis62′ (also considered the “longitudinal axis”) of spoke2′ is skewed from the radial axis29by a circumferential counterclockwise skew angle73′.

In contrast toFIGS.4a-c, which show the nipple48as extending through the spoke hole76to extend inboard of the spoke bed74,FIGS.5a-cdescribe an arrangement that utilizes a nipple84that is entirely radially outboard of the spoke bed89. Rim86is similar to rim70, with the exception that its spoke hole90is sized to provide clearance for only the spoke83. The rim86includes a spoke bed88with a radially outwardly facing outboard surface89. Spoke83is similar to spoke2and is of conventional configuration, including longitudinal axis85and external threads. The nipple84includes an engagement face91to bear against the outboard surface89of spoke bed88and internal threads (obscured). Such a nipple84is conventional and known in industry as a “hidden” or “internal” nipple.

An “internal nipple”, such as spoke nipple84, is defined herein as a spoke nipple that is entirely longitudinally outboard of the inboard surface of the spoke bed. Most commonly, an internal nipple extends longitudinally outboard of the engagement surface or bearing surface of the nipple.FIG.5ashows the nipple84prior to its threadable assembly with the spoke83.

FIG.5bshows the nipple84as next threadably assembled to the spoke83in the conventional manner until its engagement face91first contacts the outboard surface89as shown inFIG.5b. Due to the bracing angle99of the spoke83, the engagement face91does not mate squarely with the outboard face89, but instead is tilted or canted by angle87. Further threadable tightening of the nipple84, and the resulting spoke tension, causes the nipple84to rotate in direction98so that engagement face91bears squarely against the outboard surface89as shown inFIG.5c. However, this rotation results in a kink or bend93in the spoke83, resulting in increased stress and misalignment of the spoke83, as also described inFIG.3f. These figures illustrate the particular problems associated with the use of internal nipples with conventional rims.

It is an object of the present invention to increase the contact area and improve the alignment between the transition portion54and the spoke hole76and/or between the engagement face91and the outboard surface89. This will serve to reduce the contact stress therebetween and result in increased fatigue resistance of the rim and spoke and also greater overall stiffness of the wheel1. This may be achieved by modifying the spoke bed74such that the outboard edge78and/or the portion of the outboard surface72surrounding the spoke hole76is more closely matched to the transition portion54. For the purposes of definition herein, the outboard edge78and/or the portion of the outboard surface72that provides blocking contact with a mating surface of the spoke, such as the transition surface54, is termed the “bearing surface”, since this is the surface and/or edge that bears against the spoke nipple48to provide connection between the spoke2and the rim70.

One method for such modification of the spoke bed74is to remove material of the spoke bed74such that the outboard edge78and/or the portion of the outboard surface72surrounding the spoke hole76is more closely matched to the transition portion54. An example of such a method is described inFIGS.6a-e. As shown inFIG.6a-e, the rim100is formed such that spoke bed111includes a generally smooth circumferential outboard surface132of constant radius and a radially variable inboard surface136to provide radially inwardly thickened regions140surrounding the locations associated with spoke holes107, and a radially outwardly thinned region141(shown inFIG.6e) circumferentially positioned between adjacent thickened regions140. This results in a spoke bed111of variable thickness where thickened regions140have a thickness142greater than the thickness143of thinned region141, including a step dimension144therebetween. The thickened regions140provide structural reinforcement of the spoke bed111in the highly stressed region for connection with the mating spokes and the thinned regions141served to minimize the material of the spoke bed111for weight savings and reduction of material cost where stresses may be lower. Rim100is of double-wall construction and includes a tire bed wall113, a spoke bed wall111, and a radial gap112therebetween. The rim100may be bladder-molded of reinforced composite material or other materials and processes known in industry.

The rim100is first shown inFIG.6awhere its spoke bed111wall is initially formed without any spoke holes or recesses. A step drill102is shown inFIG.6ato be aligned prior to drilling the spoke hole in the rim100. A step drill102is of a configuration known in industry and includes a cutting surface with a small-diameter portion104for piercing the spoke hole107through the spoke bed111, a large diameter portion105for piercing the spoke access hole109through the tire bed wall113, and a transition portion106therebetween. This step drill102is but one well-known and representative methods for adding a spoke hole107to a rim100. Other methods known in industry may be substituted. The step drill102may be aligned such that its drill axis103has an axial angle115and a circumferential angle (not shown) relative to the radial axis29such that the resulting spoke hole107will be angled to correspond to the bracing angle and/or the circumferential angle of the spoke. Such angled spoke hole drilling is well known in industry. The step drill102is positioned such that the resulting spoke holes107are aligned to axially and circumferentially overlap the thickened regions140. Alternatively, the spoke hole107may be drilled in alignment with the radial axis29or another angle deemed suitable.

As shown inFIG.6b, the rim100has next been drilled by the step drill102in direction114in the conventional manner as described hereinabove to pierce both the tire bed wall113and the spoke bed wall111, creating the spoke hole107and spoke access hole109respectively, with both holes aligned along a hole axis108. Spoke hole107includes a radially outward entrance or outboard edge110. As shown, a rotary facing tool121is aligned such that its rotation axis123is preferably collinear with drill axis103and has an axial skew angle125and a circumferential skew angle119relative to the radial axis29. It is further preferred that rotational axis123corresponds to the bracing angle and circumferential angle of a mating spoke (not shown) and is shown here to have a flat and square cutting face129and a cylindrical pilot tip130. Cutting face129face is shown to be flat and planar and perpendicular to rotational axis123.

When the facing tool121is rotated in direction122about its rotation axis123and presented to the outboard surface132of the spoke bed111in direction120, it will remove some material of the spoke bed111and create a radially inwardly recessed counterbore or spot face127of depth146therein. The pilot tip130may also be piloted within the spoke hole107to aid in alignment of the facing tool121. As shown inFIG.6c, the facing tool has next formed a recess or spot face127of radial recess depth138in the outboard surface132of the spoke bed111. The spot face127provides a bearing surface145that is flat and planar and generally perpendicular to the rotation axis123.

Since Spot face127may be considered to be a revolved surface that is revolved about a revolved axis, such as face axis128, which is collinear to rotational axis123of the cutting face129. The face axis128may be considered as an axis generally perpendicular to the bearing surface145. Since bearing surface129is created with a rotary cutting tool (i.e. facing tool121), it is considered to be a revolved surface that is revolved about face axis128, which is shown here to be collinear with rotation axis123. Additionally, the spot face127creates a new outboard edge135of the spoke hole107. This describes a spot-facing machining operation that is well-known in industry. A “revolved surface” herein may be used to describe a surface that is rotationally symmetrical about a revolved axis (i.e. face axis128) and does not necessarily require that it has been formed with a rotary tool. It may be considered that the outboard surface132has thus been modified (as shown inFIG.6c) to include spot face127.

It is noted that, corresponding to axial skew angle125, the bearing surface129is inclined, tilted, or canted by axial tilt angle137relative to a plane tangent to the outboard surface132. Correspondingly, the outboard edge135of spoke hole107is now also tilted by axial tilt angle137. Thus, whether a mating spoke nipple will bear against the bearing surface129or against the outboard edge135, the both geometries are skewed from the radial axis29and aligned to be square or otherwise be more closely matched to the mating bearing surface (i.e. transition surface54, for example) of the spoke nipple for greater surface contact and reduced misalignment therebetween. For this example, it is preferable that the outboard edge135be aligned to be generally matched with the transition surface54around the perimeter of the outboard edge135to maximize the mating contact therebetween, with a maximum gap therebetween of 0.1 millimeters. This is in contrast to the higher contact stresses and greater misalignment of a conventional outboard surface72and outboard edge78as illustrated inFIGS.4a-cand5a-c. For bicycle wheel applications, it is preferred that the axial skew angle125and corresponding axial tilt angle137be between 4 degrees and 12 degrees, or more preferably greater than 4 degrees. Also, for bicycle wheel applications with crossed spoke lacing (i.e. not radially laced), it is preferred that the circumferential skew angle119and corresponding circumferential tilt angle139be between 2 degrees and 10 degrees, or more preferably greater than 3 degrees.

As shown inFIG.6c, the bearing surface145surrounds and circumscribes the spoke hole107about the hole axis108as is most preferred. However, it is also envisioned that less material is removed during spot facing such that the spot-faced bearing surface only partially circumscribes the spoke hole107about hole axis108, such that some original outboard surface132remains adjacent the spoke hole107. It is preferred that the spot-faced bearing surface circumscribes the spoke hole107by at least 180 degrees. The facing tool121may also be aligned such that its rotation axis123has a circumferential skew angle relative to the radial axis29such that the resulting bearing surface129will correspondingly be a revolved surface that is perpendicular to the circumferential skew angle119. As shown here inFIGS.6a-e, the longitudinal axis62, the hole axis108, and the face axis128are all collinear as is preferred.

As shown inFIG.2b, the spoke2connected to hub flange16ahas an axial bracing angle38. It is also understood that the spoke2connected to hub flange16balso has an axial bracing angle in an axially opposed direction. Similarly, it is understood that the rim100may include some bearing surfaces129that have the axial tilt angle137optimized for connection with a spoke2that is connected to a first hub flange (such as hub flange16aofFIG.2b), and also include other bearing surfaces (not shown) that have a tilt angle axially opposed to tilt angle137that are optimized for connection with a spoke2that is connected to a second hub flange (such as hub flange16bofFIG.2b).

The process described inFIGS.6a-cis a 2-step process, including a drilling process using step drill102and a spot-face process using facing tool121. Alternatively, the drilled spoke hole107and the spot-faced bearing surface129may be achieved in a single operation or process. For example, the transition portion106of step drill102may be configured to provide a square cutting surface like the cutting face129of the facing tool. By carefully controlling its depth-of-cut in the drilling process, this transition surface may be utilized to cut into the outboard surface132to create the bearing surface129. As a further alternative, the transition surface106and/or the cutting face129may be shaped to any desired profile to create a correspondingly profiled bearing surface. Examples of such alternatively profiled bearing surfaces are described inFIGS.6gand6h. As a still further alternative, the bearing surface129may be formed prior to the forming of the spoke hole107, where the spoke hole107may be formed by piercing through the bearing surface129.

It is noted that some material is removed from the spoke bed111by spot face127reducing the spoke bed thickness142in this region to thickness148. For this reason, it is very advantageous to position the spot face127within the thickened region140to provide sufficient structural thickness and support to compensate for this removal of material. This thickened region140serves to provide additional thickness142(as compared to the thinned region141) to ensure that the material removal associated with spot face127leaves sufficient thickness148and does not adversely weaken the spoke bed111in this highly stressed region surrounding the spoke2. The step dimension144may be less than or equal to depth146or it may be greater than depth146as may be preferred to provide additional structural reinforcement at this highly stresses region surrounding the spoke hole107. Further, it is preferable to provide a lateral margin147between the thickened region140and the spot face127to ensure that sufficient structural thickness of spoke bed111material surrounds the contour of the spot face127. It may be preferable that lateral margin147be equal to or greater than 1 millimeter or more preferably equal or greater than thickness148. It is noted that the spot face127extends laterally outwardly of the spoke hole107and the thickened region140extends laterally outwardly of the spot face127.

FIG.6dshows the spoke2and nipple48as next assembled to the rim100in the conventional manner. Spoke2and nipple48are identical to those described inFIGS.4a-c. The transition surface54is shown to squarely contact the outboard edge135for a full circular perimeter of contact therebetween. Thus, the outboard edge135provides a bearing surface or edge to create a blocking engagement with the nipple48and to support spoke tension58forces. As such, the outboard edge135(in addition to bearing face145) may also be considered a bearing surface, especially since outboard edge135provides blocking engagement with the nipple48to support spoke tension forces58. This is a significant improvement over the single point of contact described inFIGS.4a-cand serves to reduce bearing stress between the nipple48and the rim100. It is noted that bearing surface145and/or outboard edge135provide for an abutting and blocking overlie engagement with the mating spoke2(and nipple48).

As described inFIG.4c, spokes2are commonly laced with a radial offset such that they are circumferentially skewed from a radial axis by angle73at its intersection with the rim100. This is particularly illustrated inFIG.6e, where spoke centerline133(also considered the “longitudinal axis”) of spoke2is circumferentially skewed from the radial axis29by a clockwise circumferential skew angle119, while spoke centerline133′ (also considered the “longitudinal axis”) of spoke2′ is circumferentially skewed from the radial axis by a counterclockwise circumferential skew angle119′. It is preferred that the spoke centerline133and133′ extend along the span portion of the respective spokes2and2′. During the drilling and spot facing operations described inFIGS.6b-c, the drill axis103and rotation axis123were skewed in a compound angle to also include circumferential skew angles119and119′ (in addition to axial skew angles125) such that bearing surface129is tilted by axial tilt angle137in the axial direction and by circumferential tilt angle139in the circumferential direction. Correspondingly, the outboard edge135of spoke hole107is now also tilted by both axial tilt angle137and circumferential tilt angle139. Bearing surface129and outboard edge135are preferably as close to being perpendicular to the spoke centerline133as possible, preferably within 3 degrees of each other. This perpendicularity results in the transition surface54squarely contacting the outboard edge135for a full circular perimeter of contact therebetween. This is a significant improvement over the single point of contact described inFIGS.4a-c. While this perfect perpendicularity may not always be feasible, it is understood that the skewed bearing surface129results in an improved interface with the spoke nipple48in comparison with the prior art designs shown that do not have a skewed bearing surface.

It is understood that, as the nipple48is threadably tightened during assembly, the transition surface54bears against the outboard edge135, causing the two surfaces to abrade each other and to deform each other slightly. As a result, the sharp edge of outboard edge135is softened somewhat to create a lapped and matched surface interface therebetween.

FIG.6fdescribes an arrangement similar to the embodiment ofFIGS.6a-e, where the rim150has been cut or machined to remove some material from its outboard surface152to create a recess159or spot face having a tilted bearing surface154that is perpendicular to face axis169. Rim150is similar to rim100ofFIGS.6c-e, with the exception that spoke hole156is smaller in diameter to provide clearance only for the spoke83. Like the rim100, rim150is initially formed such that spoke bed153includes a generally smooth circumferential outboard surface152of constant radius and a radially variable inboard surface151to provide localized thickened regions155surrounding the locations associated with spoke holes156and a thinned region157circumferentially positioned between adjacent thickened regions155. Spoke holes156and spot faces159are formed in the outboard surface152of the spoke bed153. Spoke83and nipple84are identical to those described inFIGS.5a-c, with nipple84being configured as an internal nipple as defined hereinabove.

FIG.6fshows the spoke83and nipple84as assembled to the rim150. The bearing surface154is tilted to compensate for the axial skew angle158of the longitudinal axis85of the spoke83. Also, in a manner similar to that described inFIG.6e, the bearing surface154is preferably circumferentially tilted to compensate for any circumferential skew angle(s) (not shown) of the longitudinal axis85. As such, the engagement face91is shown to squarely contact the bearing surface154for a full circular face contact (about longitudinal axis85) therebetween. In contrast toFIG.5c, this provides a generous surface-to-surface contact therebetween without inducing increased stress and misalignment of the spoke83. Spot face159may be considered a revolved surface about face axis169that is shown here to be collinear with longitudinal axis85.

FIG.6bshows a facing tool121with a flat planar cutting face129that is perpendicular to the rotation axis123. This produces the revolved flat planar bearing surface129shown inFIG.6cthat is recessed from the outboard face132. Alternatively, an alternate facing tool (not shown) or other means may be employed to provide a concave conical bearing surface164that is revolved and rotationally swept to be conical about a face axis169. The face axis169is skewed from the radial axis29by axial skew angle168, which may also include a circumferentially skewed orientation as described hereinabove. In contrast to the flat bearing surfaces145and154ofFIGS.6a-eand6frespectively, face axis169is not strictly perpendicular to the bearing surface, but may be considered a revolved axis about which the concave conical bearing surface164is generated. As shown in the rim160ofFIG.6g, the outboard surface162of the spoke bed161includes a localized concave conical bearing surface164(having a conical angle165) surrounding the spoke hole166. The conical angle165may be matched to the conical transition surface of a mating spoke nipple (not shown) such as the transition surface54of nipple48shown inFIG.4b. This provides a generous surface-to-surface contact between transition surface54and bearing surface164without inducing increased stress and misalignment of a spoke assembled thereto. In a manner similar to rim100, rim160is formed such that spoke bed161includes a generally smooth circumferential outboard surface162of constant radius and a radially variable inboard surface163to provide localized thickened regions167surrounding the locations associated with spoke holes166and a thinned region circumferentially spaced between adjacent thickened regions.

As a further alternative, an alternate facing tool (not shown) or other means may be employed to provide a semi-spherical concave bearing surface174that is rotationally swept and/or revolve about a face axis179to provide the semi-spherical concave bearing surface174as shown inFIG.6h. The face axis179is shown to be skewed from the radial axis29by axial skew angle178, which may additionally include a circumferentially skewed orientation as described hereinabove. As shown in the rim170ofFIG.6h, the outboard surface172of the spoke bed171includes a localized concave spherical bearing surface174surrounding the spoke hole176. The spherical radius175may be matched to a spherical transition surface of a mating spoke nipple (not shown). This provides a generous surface-to-surface contact between the spherical transition surface and bearing surface174without inducing increased stress and misalignment of a spoke (not shown) assembled thereto. The spherical ball-and-socket interface between the spherical transition surface and spherical bearing surface174may be utilized to provide a swivel therebetween such that the spoke nipple may be self-aligning to accommodate a range of bracing and/or circumferential angles of the spoke. In a manner similar to rim100, rim170is formed such that spoke bed171includes a generally smooth circumferential outboard surface172of constant radius and a radially variable inboard surface177to provide localized thickened regions180surrounding the locations associated with spoke holes176and a thinned region181between adjacent thickened regions180.

It is envisioned that the rim100may be bladder molded out of advanced composite material as is common. In bladder molding, it is generally easier to control the external surface of the part, since it is controlled by hard mold tooling, whereas the interior surface of the part is controlled by the bladder and the part contours are more difficult to control. Since the inboard surface136is an external surface and the outboard surface132is an interior surface, it is generally preferable to vary the thickness of the spoke bed by employing a radially variable inboard surface136, as described inFIGS.6a-h, because it is generally easier to mold and control the contour of the inboard surface. As such, it is preferable to provide a radially variable inboard surface136of the rim. Alternatively, it is also possible, but likely more difficult, to provide a radially variable outboard surface of the spoke bed to achieve a spoke bed of variable thickness. Such an alternative arrangement is described inFIGS.7a-b.

FIGS.7a-bdescribe an arrangement similar to that ofFIGS.6d-e, with the exception that rim280is formed such that spoke bed281includes a generally smooth circumferential inboard surface282of constant radius and a radially variable outboard surface283to provide thickened regions284surrounding the locations associated with spoke holes285and a thinned region286between adjacent thickened regions284. This results in a spoke bed281of variable thickness where thickened region284has a thickness287that is greater than the thickness288of thinned region286, including a step dimension289therebetween. The rim280may be bladder-molded of reinforced composite material or may be formed using other materials and processes known in industry.

The rim280includes spoke hole285and access hole290as described hereinabove. Outboard surface283includes a recess or spot face291positioned within thickened region284that provides a bearing surface292that is flat and planar identical to bearing surface145ofFIGS.6a-e. It is noted that, corresponding to axial skew angle293, the bearing surface292is inclined, tilted, or canted relative to the axial axis (not shown). Also, corresponding to circumferential skew angle279, the bearing surfaces292and292′ are inclined, tilted, or canted relative to a plane tangent to the outboard surface283. The outboard edge of spoke hole295is now correspondingly tilted and skewed as well. Thus, whether a spoke nipple will bear against the bearing surface292or the outboard edge295, the both geometries are aligned to be square or otherwise to be more closely matched to the mating bearing surface (for example, transition surface54) of the spoke nipple for greater surface contact and reduced misalignment therebetween.

As shown inFIGS.7a-b, the bearing surface292surrounds and circumscribes the spoke hole285about the hole axis296as is most preferred. It is preferred that the spot-faced bearing surface292surrounds the spoke hole285by at least 180 degrees. As shown here, the longitudinal axis62, the hole axis296, and the face axis297are all collinear as is preferred. Spoke2and nipple48are identical to those described inFIGS.3a-fand are shown inFIGS.7a-bto be assembled to rim280in the conventional manner and as described hereinabove.

Some material is removed from the spoke bed281by spot face291, creating a recess therein and reducing the spoke bed thickness in this region. For this reason, it is very advantageous to position the spot face291within the thickened region284to provide sufficient structural support to compensate for this removal of material. The step dimension289may equal depth289or it may be greater than depth289as is preferred to provide additional structural reinforcement at this highly stresses region surrounding the spoke hole285. Further, it is preferable to provide a lateral margin299between the thickened region284and the spot face291to ensure that sufficient structural thickness of spoke bed281material surrounds the contour of the spot face291. It is preferable that lateral margin299be equal to or greater than thickness300between spot face291and inboard surface282.

FIG.7ashows the spoke2and nipple48as assembled to the rim280. Spoke2and nipple48are identical to those described inFIGS.4a-c. The transition surface54is shown to squarely contact the outboard edge295for a full circular perimeter of contact therebetween. This is a significant improvement over the single point of contact described inFIGS.4a-c.

As described inFIG.7b, spokes2are commonly cross-laced with a radial offset at the hub such that they are circumferentially skewed from a radial axis at its intersection with the rim280. This is particularly illustrated inFIG.7b, where longitudinal axis62is skewed from the radial axis29by a circumferential clockwise circumferential skew angle279and longitudinal axis62′ is skewed from the radial axis29by a circumferential counterclockwise circumferential skew angle279′.

FIGS.8a-cdescribe an embodiment similar toFIGS.6a-e, however instead of utilizing a facing tool121that cuts, abrades, or otherwise removes material from the spoke bed111to create a skewed bearing surface145,FIGS.8a-cutilizes a punch260tool to locally coin, forge, or otherwise deform the spoke bed111to create a skewed bearing surface262. Rim100is identical to that shown inFIG.6b, including tire bed wall113with access hole109, and spoke bed wall111with outboard surface132and inboard surface136and with spoke hole107therethrough having a radially outboard edge110. As shown inFIG.8a, punch tool260includes: coining face266that is circular about tool axis264, and pilot pin268that is shown to be aligned along a tool axis264. Punch260is in alignment for subsequent coining operation. Tool axis264is skewed from the radial axis29by skew angle276. The radially inboard surface136of the rim100is shown to be temporarily supported in a rigid nest die272. As shown inFIG.8b, the coining tool260is pressed in direction270along tool axis264such that pilot pin268extends though spoke hole107and is piloted therein. Coining tool260is further pressed in direction270such that coining face266impacts and presses against the outboard surface132adjacent spoke hole107, causing the spoke bed111to become locally debossed, indented, and deformed to conform to the coining face266.

As shown inFIG.8c, with the coining tool260and nest die272removed, the resulting spoke bed111now includes an indent274that includes a bearing surface262that is aligned relative to the tool axis264and is tilted and skewed by skew angle276, which corresponds to tilt angle278. Indent274is radially inwardly recessed by dimension265from the adjacent outboard surface132. It is noted that outboard edge110also becomes distorted and/or displaced in this coining operation to create outboard edge110′ that is aligned with the bearing surface262. Bearing surface262and outboard edge110′ are similar in purpose and function to bearing surface129and outboard edge135respectively as described inFIGS.6c-e.

The deformation of the spoke bed111described inFIG.8bdescribes a coining operation known in industry. The nest die272is shown here to support the inboard surface136so that inboard surface does not become distorted during the coining operation. Alternatively, the nest die272may include a recess that will allow the inboard surface136to also deform during coining to create a locally bulged region (not shown) of the inboard surface adjacent the spoke hole107. The preferred material for the spoke bed111in such a coining operation is a lightweight metal such as aluminum. An advantage of such a coining operation is that it may serve to locally work-harden the spoke bed, thereby advantageously increasing the strength of the spoke bed111in this highly stressed region.