Patent Description:
In the entire present description and in the claims, the spatial indications, such as in particular those of radial, axial or circumferential direction, will be given with reference to the rotation axis of the wheel of the bicycle, unless indicated otherwise.

It is well known that in spoked bicycle wheels each single spoke is fixed to the rim of the wheel through a respective nipple, which is a component with a stem provided with a threading (normally internal) and a head projecting from the stem. The rim is provided with a plurality of holes in the bridge thereof (or in the lower bridge thereof, in the case of a rim with two or more bridges). The stem of a nipple is inserted in each hole from a radially outer direction, while the projecting head remains outside, hooked to the bridge. The stem of the nipple is thus screwed to the end of a spoke. In this way, the nipple provides the hooking of the spoke to the rim and allows the tensioning thereof: by rotating the nipple, indeed, it is possible to screw in or unscrew the spoke with respect to the stem. Often an abutment washer is arranged between the nipple and the bridge to improve the contact, particularly when the material of the rim is delicate (for example aluminium or composite materials) and it could be damaged by an excessively high pressure exerted by the nipple on a limited area.

During tensioning, the nipple should ideally be arranged aligned with the spoke, as a substantial extension thereof. This is normally true, because normally the spoke is arranged in the wheel in a substantially radial direction.

The Applicant has, however, observed that if the spoke is not arranged in the radial direction, for example because it is fastened tangentially to a flange of the hub of the wheel, the tensioning of the spoke-nipple set results in a misalignment between the two, due to the unbalanced abutment of the nipple on the bridge. Indeed, the natural abutment of the nipple (with or without washer) is with the stem in the radial direction, perpendicular to the bridge (or rather to the tangent thereof); if, however, the spoke is not in the radial direction, the nipple fastened to it is also not in the radial direction, before tensioning begins; in this position, the stem of the nipple forms two different angles with the direction tangential to the bridge (observing in the axial direction), one less than <NUM>° and one greater than <NUM>°. Proceeding with tensioning, the head of the nipple will tend to press on the bridge more on one side than on the other, in particular more on the side of the angle greater than <NUM>°, thereby tending to take the tensioned nipple back towards a radial position.

This deviation of the nipple with respect to the direction of the spoke increases as the tensioning proceeds and results in an anomalous distribution of stresses on the spoke, on the nipple and on the bridge of the rim. In particular, the nipple is subjected to stresses not only in the radial direction but also in the tangential direction; the spoke is also subject not only to traction forces, but also to flexing forces. The consequence of this anomalous distribution of stresses is that the designer is forced to somehow oversize these components, in order to avoid yielding. Thus, however, there is an increase in weight, particularly undesirable in high-performance bicycles, in particular racing bicycles.

It has been proposed to address this drawback by shaping both the head of the nipple and the face of the washer on which it abuts according to spherical surfaces. However, even with this provision the misalignment between spoke and nipple is not avoided.

The problem at the basis of the present invention is to allow a coupling between spoke, nipple and bridge in which the alignment between spoke and nipple is maintained during tensioning and thus in the finished wheel, even when the spoke is not arranged in the radial direction.

Document <CIT> describes a support system for nipples that addresses a very different problem: the possibility of access from only the radial inner face of the rim, so that these nipples can be used on double-bridge rims provided with holes in only the lower bridge, i.e. without having to drill the upper bridge as well; in this way, the rim is suitable for tubeless tyres. A complex support is provided, by means of a first annular washer with a smaller diameter contacting the nipple and a second washer contacting the rim, this second washer being split in two parts and having a larger diameter when reassembled.

Another document disclosing a support system for nipples is known from <CIT>.

Consequently, in a first aspect thereof, the present invention relates to an abutment interface according to claim <NUM>; in a second aspect thereof, the invention relates to a bicycle wheel according to claim <NUM>.

Preferred features of the abutment interface and of the wheel are given in the dependent claims.

More specifically, with reference to the first aspect of the invention, the abutment interface between a head of a nipple for fixing a spoke and a bridge of a rim of a bicycle wheel, comprises:.

The faces of the washers are shaped so as to allow the washers to make adjustment movements both with respect to each other and with respect to the nipple, during an initial step of the fixing operation of the spoke to the rim, and vice-versa so as to prevent the washers from making any adjustment movement both with respect to one another and with respect to the nipple, during a subsequent fixing step of the spoke to the rim in which the nipple has a tension applied to it through the spoke.

Indeed, it has been observed that in order to obtain the desired result of the alignment between spoke and nipple in the finished wheel, even when the spoke is in a non-radial direction in the wheel, it is important for the coupling between nipple and rim to have two features, apparently contrasting: firstly, to be such as to allow the nipple to be arranged in the direction of the spoke at the start of the tensioning operation; and then, to be such as to prevent movements of the nipple with respect to the rim during tensioning, so that in the finished wheel the nipple is aligned with the spoke.

The two aforementioned features are obtained by providing that the abutment between the second face of the first washer and the first face of the second washer takes place along a first abutment track and the abutment between the second face of the second washer and the head of the nipple takes place along a second abutment track, wherein the first and/or the second abutment track have an extension of less than <NUM>%, and preferably less than <NUM>%, of the area of the first face and of the area of the second face of the second washer, respectively. The measurement of the extension of the abutment tracks is meant to be carried out before the tensioning of the spoke, since tensioning naturally implies an increase in the extension of the abutment tracks, due to the deformability of the materials. With the aforementioned values, at least one among the contact between the two washers and the contact between the second washer and the nipple takes place over a limited area, much less than the area of the faces of the second washer; this allows both great initial freedom of movement, when tension is not yet applied, and subsequent substantial locking, when the tension applied on these small areas results in high contact pressures and thus high friction.

Both the first and the second abutment tracks have limited extension, so that the two aforementioned features (initial freedom of movement and prevention of movement under tension) occur singularly both between the two washers themselves, and between the second washer and the nipple.

Thanks to this abutment, in the initial step of mounting when the tensioning is zero or minimal, the nipple and the two washers are free to take a position also in a non-radial direction of the wheel, guided by the coupling of the nipple with the spoke. However, as soon as the tension becomes substantial, the abutment tracks having limited extension ensure that the high pressure that is immediately established both between the washers and between the second washer and the nipple prevents any further mutual movement, despite the natural tendency to be oriented in the radial direction due to the tension applied. As the tension progressively increases (and therefore the tendency of the nipple to move towards the radial direction increases), the pressure at the abutment tracks becomes so high as to prevent any movement.

The first and/or the second abutment tracks are lines, i.e. they have substantially zero width, which maximizes the contact pressure. Of course, this geometric condition refers to the initial conditions, before tensioning, and is lost as the tension applied increases, due to the deformation of the materials.

The first face of the second washer is delimited by a first inner circumference and a first outer circumference and the second face of the second washer is delimited by a second inner circumference and a second outer circumference, whereby the first abutment track coincides with the first outer circumference and the second abutment track coincides with the second inner circumference. In this way, the feature of the abutment tracks of minimal width is obtained in a constructively simple manner.

Preferably, the first and the second face of the second washer are conical or spherical. These surfaces are relatively simple to obtain and ensure the desired results in terms of abutment.

Preferably, the first face of the second washer is conical. Preferably, the second face of the second washer is conical. Preferably, the second face of the first washer is spherical. These features of shape, singularly or preferably all together, facilitate the onset of the conditions of initial freedom of movement and prevention of movement under tension.

Preferably, the second washer is conical, with vertex facing towards the first washer and angle at the vertex comprised between <NUM>° and <NUM>°, preferably between <NUM>° and <NUM>°, more preferably equal to about <NUM>°. This shape promotes the aforementioned abutment conditions.

With reference to the second aspect, the invention relates to a bicycle wheel comprising a rim connected to a hub by a plurality of spokes, wherein at least one of the spokes is anchored to the rim through a nipple having a stem inserted in a hole in a bridge of the rim and facing towards the hub and an enlarged head hooked to the bridge, comprising an abutment interface between the head of the nipple and the bridge of the rim, wherein the abutment interface has one or more of the features mentioned above.

The first washer has an opening of a width that would allow the head of the nipple to pass, in the absence of the second washer. This large width of the opening of the first washer facilitates the freedom of movement between the two washers and thus facilitates the alignment, at the start of tensioning of the spoke with the nipple.

Preferably, the head of the nipple has a spherical surface facing towards the second face of the second washer. The spherical surface of the head of the nipple promotes the abutment conditions described above, making it easier to limit the extension of the second abutment track. Preferably, the spherical surface of the head of the nipple has a radius comprised between <NUM> and <NUM>, more preferably equal to about <NUM>.

Preferably, the stem of the nipple is joined to the head of the nipple according to a joining angle comprised between <NUM>° and <NUM>°, more preferably between <NUM>° and <NUM>°. This angle is intended as the angle formed by the axis of the stem of the nipple with a plane tangent to the head of the nipple in the point in which the head of the nipple is joined to the stem of the nipple. The aforementioned values make it possible to obtain the desired abutment conditions, particularly in the case in which the second washer has the features of conicity indicated above.

Preferably, at least one of the spokes has orientation according to a non-radial direction with respect to the rotation axis of the wheel. It is, indeed, precisely the spokes with such a non-radial inclination that get the maximum benefit from the invention.

Preferably, the bridge of the rim is flat in the axial direction of the wheel. In this way, the construction of the rim is particularly simple; in particular, it does not require special processing to form shaped seats for the heads of the nipples. Moreover, thanks to the invention, a precise and balanced hooking of the head of the nipple is equally ensured, without there being misalignments between spoke and stem of the nipple during tensioning.

Further features and advantages of the invention will become clearer from the following description of some preferred embodiments thereof, made with reference to the attached drawings. In such drawings:.

The figures show a bicycle wheel <NUM>, comprising a rim <NUM> connected to a hub <NUM> by means of spokes <NUM> under tension; X is used to indicate the rotation axis of the wheel <NUM>. The spokes <NUM> have a head <NUM> with which they are fastened to the hub <NUM> and a threaded end <NUM> opposite to the head <NUM>, with which they are hooked to a bridge <NUM> of the rim <NUM> through a nipple <NUM>. The bridge <NUM> is flat in the axial direction, i.e. it extends on a cylindrical surface coaxial to the axis X.

Each nipple <NUM> comprises a stem <NUM> extending along an axis Y and a head <NUM> projecting with respect to the stem <NUM>. The stem <NUM> of the nipple <NUM> is inserted in a hole <NUM> formed in the bridge <NUM> and projects from it in the radial direction towards the axis X of the wheel <NUM>, whereas the head <NUM> remains in radially outer position with respect to the bridge <NUM>. A threaded axial hole <NUM>, engaged with the threaded end <NUM> of one of the spokes <NUM>, is formed in the stem <NUM>; the spoke <NUM> coupled with the nipple <NUM> is thus aligned along the axis Y. The nipple <NUM> also comprises a first handling portion <NUM> with non-round section (for example, hexagonal), formed externally on the stem <NUM>, and a second handling portion <NUM> with non-round section (for example, square), formed externally on the head <NUM>; the two handling portions <NUM> and <NUM> make it possible to rotate the nipple <NUM> with suitable keys (not shown) so as to screw in or unscrew the nipple <NUM> with respect to the spoke <NUM>, thus obtaining a change in the length of the spoke <NUM> - nipple <NUM> set and thus a change in the tension of such a set in the rim <NUM>. The handling portion <NUM> or the handling portion <NUM> is used depending on the accessibility, i.e. depending on the shape of the rim <NUM>. The head <NUM> of the nipple <NUM> has a convex spherical shape towards the stem <NUM>.

In the illustrated wheel <NUM>, some of the spokes <NUM> have substantially radial orientation, others have markedly non-radial orientation; when seen from the axial direction of the wheel <NUM>, the spokes <NUM> with substantially radial orientation form substantially right angles with the bridge <NUM> (i.e. with the tangent T to the bridge <NUM>), whereas the spokes <NUM> with markedly non-radial orientation form an acute angle α and an obtuse angle β with the bridge <NUM> (see <FIG>).

Between the head <NUM> of the nipple <NUM> and the bridge <NUM> an abutment interface <NUM> is arranged, which comprises a first annular washer <NUM> and a second annular washer <NUM>. The first washer <NUM> is in contact with the bridge <NUM>, whereas the second washer <NUM> is in contact with the nipple <NUM>.

The first washer <NUM> has a radially inner first face <NUM>, which rests on the bridge <NUM>, and a radially outer second face <NUM>, which rests against the second washer <NUM>. The first face <NUM> is substantially flat, whereas the second face <NUM> is concave, with spherical shape. Centrally, the first washer <NUM> has a very wide opening <NUM>: the head <NUM> of the nipple <NUM> could easily pass through it, if not held by the second washer <NUM>, as will be seen hereinafter.

The second washer <NUM> has a radially inner first face <NUM>, which rests on the first washer <NUM>, and a radially outer second face <NUM>, which rests against the spherical head <NUM> of the nipple <NUM>. The faces <NUM> and <NUM> are both conical, with vertex facing towards the first washer <NUM>, i.e. towards the axis X of the wheel <NUM>. The angle at the vertex of the cone of the two faces <NUM> and <NUM> is comprised between <NUM>° and <NUM>°, preferably between <NUM>° and <NUM>°; in particular and more preferably, such an angle is about <NUM>°. It should be noted that this angle at the vertex is not represented graphically in the figures, so as not to complicate the figures with further lines.

The first face <NUM> of the second washer <NUM> is delimited by a first inner circumference <NUM> and by a first outer circumference <NUM>; the second face <NUM> of the second washer <NUM> is delimited by a second inner circumference <NUM> and by a second outer circumference <NUM>. The inner circumferences <NUM> and <NUM> are wide enough to allow the stem <NUM> of the nipple <NUM> to pass, but not the head <NUM> of the nipple <NUM>.

Between the second face <NUM> of the first washer <NUM> and the first face <NUM> of the second washer <NUM> a first abutment track is defined, which ideally coincides with the first outer circumference <NUM> of the first face <NUM> of the second washer <NUM>. Between the second face <NUM> of the second washer <NUM> and the head <NUM> of the nipple <NUM> a second abutment track is defined, which ideally coincides with the second inner circumference <NUM> of the second face <NUM> of the second washer <NUM>. In reality, the aforementioned abutment tracks can comprise a narrow band around the respective circumferences <NUM> and <NUM>, provided that they are indeed narrow, in particular so that the area of the abutment tracks does not exceed <NUM>% (and preferably <NUM>%) of the area of the respective faces <NUM> and <NUM> of the second washer <NUM>. Of course, what has just been stated refers to the initial mounting conditions of the wheel <NUM>, i.e. before a substantial tension is applied between the spoke <NUM> and the nipple <NUM>; under the traction stress due to tensioning, the abutment tracks tend clearly to widen due to the deformability of the materials.

In the construction of the wheel <NUM>, the mounting of every spoke <NUM> (whatever the inclination thereof with respect to the radial direction) takes place by firstly fastening the spoke <NUM> with its head <NUM> to the hub <NUM>. Thereafter, a nipple <NUM> is inserted with its stem <NUM> in the hole <NUM> of the bridge <NUM>, interposing the abutment interface <NUM>, i.e. the two washers <NUM> and <NUM>; the first washer <NUM> is placed with its first face <NUM> against the bridge <NUM>, the second washer <NUM> with its first face <NUM> against the second face <NUM> of the first washer <NUM>. It should be noted that the width of the opening <NUM> of the first washer <NUM> would not be such as to hold the head <NUM> of the nipple <NUM>, which would easily pass through it if the second washer <NUM> was not present.

By rotating the nipple <NUM>, it is thus possible to screw it to the threaded end <NUM> of the spoke <NUM>, until the contact is established at the abutment tracks <NUM> and <NUM>. In this condition, the freedom of movement ensured by the washers <NUM> and <NUM> allows the nipple <NUM> to be arranged easily as an extension of the spoke <NUM>, so that the assembly of spoke <NUM> and nipple <NUM> is perfectly aligned according to the axis Y, even if it does not coincide with a radial direction of the wheel <NUM>.

By further rotating the nipple <NUM>, there is thus progressive tensioning of the nipple <NUM> at the spoke <NUM>, so that they exert a traction between the rim <NUM> and the hub <NUM>. This tensioning, thanks to the very limited extension of the abutment tracks <NUM> and <NUM>, quickly causes a high contact pressure between the parts, in particular between the nipple <NUM> and the second washer <NUM> and between the latter and the first washer <NUM>. The friction that is produced due to this high pressure prevents any mutual movement of the washers <NUM>, <NUM> and of the nipple <NUM>, ensuring that the alignment of the nipple <NUM> and of the spoke <NUM> along the axis Y is maintained, even if such an axis Y is not oriented radially in the wheel <NUM>. Consequently, the spoke <NUM> is not subjected to bending stress and the nipple <NUM> is not subjected to stresses in the tangential direction.

<FIG> shows a wheel <NUM> according to a second embodiment of the invention; elements of the wheel <NUM> the same as those of the wheel <NUM> are indicated by the same reference numerals and are not described, whereas elements corresponding but in some way different are indicated with reference numerals increased by <NUM> and are described by comparison with the elements of the wheel <NUM>.

In the wheel <NUM>, the nipples <NUM> differ from the nipples <NUM> because their head <NUM> has a conical shape instead of spherical. The abutment interface <NUM> differs from the interface <NUM> for the shape of the second face of the first washer. More precisely, the first washer <NUM> has its first face <NUM> flat (like the face <NUM> of the washer <NUM>), whereas its second face <NUM> has a substantially toric shape. The second washer, on the other hand, is substantially the same as the washer <NUM>.

Consequently, as can be seen in <FIG>, the first abutment track is defined roughly in an intermediate annular area in the first face <NUM> of the second washer <NUM>, whereas the second abutment track is defined on an inner area of the second face <NUM> of the second washer <NUM>. The first abutment track - even if different from that of the interface <NUM> - still remains narrow (preferably with an area of less than <NUM>% of the area of the first face <NUM> of the second washer <NUM>, more preferably less than <NUM>% thereof); the second abutment track, on the other hand, has a wider extension, but still less than <NUM>%. For this reason, the abutment interface <NUM> is less suitable where the inclination of the spoke with respect to the radial direction is very high.

The construction of the wheel <NUM> takes place in the same way already described for the wheel <NUM>.

The conditions described above, whereby the first abutment track between the first washer and the second washer and/or the second abutment track between the second washer and the nipple have limited extension, can also be obtained with other combinations of shapes of the faces of the washers, as well as of the nipple.

An embodiment that is not illustrated could, for example, provide for a nipple with conical head, a conical second washer (with two conical faces) and a first washer with the second face also conical. In this case, the abutment tracks having limited extension are obtained by selecting conical shapes with different angles at the vertex: for example, an angle at the vertex of the conical second washer that is markedly greater than the angle at the vertex of the nipple and of the second face of the first washer.

Another embodiment that is not illustrated could, for example, be similar to the wheel <NUM>, with the sole difference that the second face of the first washer is not spherical but rather conical or toric.

Another embodiment could, for example, be similar to the wheel <NUM>, with the sole difference that the second face of the first washer is not toric, but rather spherical, with concavity facing towards the second washer.

Another embodiment could, for example, be similar to the wheel <NUM> or to the wheel <NUM>, with the nipple conical instead of spherical; in this case, the second washer (conical) has a different angle at the vertex, in particular greater, with respect to the nipple.

Other embodiments could, for example, provide that one or other of the faces of the second washer be spherical or toric.

Claim 1:
Abutment interface between a head (<NUM>) of a nipple (<NUM>) for fixing a spoke (<NUM>) and a bridge (<NUM>) of a rim (<NUM>) of a bicycle wheel (<NUM>), comprising:
- a first washer (<NUM>; <NUM>) with a radially inner first face (<NUM>; <NUM>) for abutting on the bridge (<NUM>) and a radially outer second face (<NUM>; <NUM>),
- a second washer (<NUM>), with a radially inner first face (<NUM>) abutting on the second face (<NUM>; <NUM>) of the first washer (<NUM>; <NUM>) and a radially outer second face (<NUM>) for abutting on the head (<NUM>) of the nipple (<NUM>),
wherein the abutment between the second face (<NUM>; <NUM>) of the first washer (<NUM>; <NUM>) and the first face (<NUM>) of the second washer (<NUM>) takes place along a first abutment track (<NUM>) and the abutment between the second face (<NUM>) of the second washer (<NUM>) and the head (<NUM>) of the nipple (<NUM>) takes place along a second abutment track (<NUM>),
wherein the first and/or the second abutment track (<NUM>, <NUM>) have substantially zero width before tensioning of the spoke (<NUM>) in the bicycle wheel (<NUM>),
wherein the first face (<NUM>) of the second washer (<NUM>) is delimited by a first inner circumference (<NUM>) and a first outer circumference (<NUM>) and wherein the second face (<NUM>) of the second washer (<NUM>) is delimited by a second inner circumference (<NUM>) and a second outer circumference (<NUM>),
wherein the first abutment track coincides with the first outer circumference (<NUM>) and the second abutment track coincides with the second inner circumference (<NUM>),
characterized in that the first washer (<NUM>; <NUM>) has an opening (<NUM>) of a width that would allow the head (<NUM>) of the nipple (<NUM>) to pass through, in the absence of the second washer (<NUM>).