Patent Description:
Nipples of the self-locking type are widely used in the construction of spoked wheels in order to prevent the loosening of the nipple which is screwed to the spoke without using thread-locking liquids and the like.

A self-locking nipple which is known and particularly appreciated in the field of cycling and motorcycling is described in <CIT> from the same Applicant.

Other nipples of the same type are described in <CIT>, <CIT> and <CIT>.

All the above-mentioned nipples have a threaded axial seat, at one end of which, generally in the region of the head of the nipple, there is applied an insert made of deformable resin, generally a polyamide resin. The insert is bored so as to define a passage, the internal diameter of which is less than the crest diameter of the thread of the spoke. In this manner, when the spoke is screwed in the nipple, it deforms the walls of the passage of the insert while being inserted therein with an interference fit.

This interference produces the desired locking between the thread of the spoke and the nipple, preventing the accidental unscrewing thereof.

In all the above-mentioned cases, the insert is applied to an axial end of the nipple, generally the end furthest away from the rod of the nipple itself. This involves the spoke having to be long enough to reach the insert and to be introduced into the passage thereof because otherwise the self-locking effect of the nipple would inevitably not be provided.

In order to ensure that this is brought about, it is necessary to construct spokes which are needlessly long and in particular to process the threaded end over a significant portion so that the thread of the spoke can engage with the entire length of the thread of the nipple and become completely inserted in the passage of the insert made of resin.

Therefore, this technique requires a certain waste of material of the spoke, a greater overall weight of the wheel and in particular a weight which is distributed at the distal ends of the spokes with respect to the hub, which in turn causes undesirable inertia effects, and a great expenditure of energy and wear of the tools for processing spoke portions which in reality do not contribute to the mechanical resistance of the wheel.

A self-locking nipple for the spokes of a bicycle wheel, wherein the insert is applied in an intermediate axial position of the nipple, is known from <CIT>. However, it is evident that, as a result of the over-dimensioning of the insert with respect to the diameter of the threaded hole of the nipple, the axial insertion process of the insert into the nipple presents substantial difficulties, particularly when considering the fact that the material of the insert has to provide a given resistance to deformation in order then to also ensure adequate engagement with the thread of the spoke following repeated screwing and unscrewing operations thereof.

On the contrary, it would be desirable to provide a self-locking nipple, in which the insert can be applied rapidly and precisely by means of a repeatable process.

Furthermore, it must be observed that the nipple described in <CIT> can be manoeuvred only by means of a tool which extends axially from the head of the nipple itself. Therefore, this nipple cannot be manoeuvred without at least partially disassembling the wheel.

On the contrary, it would be desirable to provide a self-locking nipple which allows adjustment of the tension of the respective spoke without having to disassemble the wheel.

The technical problem addressed by the present invention is to provide a self-locking nipple for spokes of spoked wheels which is structurally and functionally configured to at least partially overcome one or more of the disadvantages set out with reference to the cited prior art.

This problem is solved by the invention by means of a nipple for spokes of spoked wheels including one or more of the features mentioned in the appended claims.

In one embodiment, the nipple includes a rod with an axial development, a threaded hole which is formed axially in the rod, the thread of the hole defining a root diameter and a crest diameter, a head which is widened with respect to the rod and a deformable insert which is inserted in a seat which is axially aligned with the hole, the insert, at least when it is inserted in the seat, having a passage for a threaded spoke end, the internal diameter of which is less than the root diameter of the thread of the hole so as to interfere with the thread of the spoke when it is screwed into the threaded hole. The seat is formed in an intermediate position of the hole and, preferably, in a position with spacing from the head, that is to say, between the head and an axially opposite opening of the threaded hole.

It may be noted that, in this context, the term "intermediate position" of the hole is intended to be understood to be an axial intermediate position of the hole.

In one embodiment of the invention, the passage of the insert, when it is inserted in the seat, has an internal diameter which is approximately identical to the crest diameter of the thread of the hole and so as to generate an interference fit with the thread of the spoke.

Preferably, the seat for receiving the insert has such a radial depth that the insert is retained axially in the seat.

It is also provided for the insert to be radially contractile, in particular in a resilient manner, in order to allow it to be inserted in the respective seat from the exterior, through the axial hole of the nipple.

The insert has a discontinuous mantle and is made radially contractile by the discontinuous mantle. This radial contractility is improved if the insert has the discontinuous mantle and is preferably cylindrical and even more preferably has a mantle which is interrupted circumferentially by a notch in order to promote the radial contraction thereof. It may be noted that, in this context, the term "mantle" is preferably intended to be understood to be the wall of the insert and more particularly the cylindrical wall thereof.

As a result of the discontinuity of the mantle, the insert has a generous radial contractility which allows an easy and precise axial insertion of the insert itself in depth through the threaded hole of the nipple, without however that the aforementioned radial contractility presupposes that the insert is constructed from a particularly yielding material.

As a result of the radially contractile nature provided by the discontinuity of the mantle, therefore, it is also possible to construct the insert from a rather tough material, such as, for example, Nylon, which has the advantage of also withstanding repeated screwing and unscrewing actions of the spoke.

In one embodiment, the insert has a metal core which can improve the elastic return thereof once it has been inserted in the respective seat. Therefore, the metal core has the value of increasing the precision and repeatability of the process of inserting the insert in the respective seat.

The core is preferably arranged circumferentially and is also interrupted at the notch of the mantle.

A preferred material for constructing the metal core of the insert is harmonic wire or spring steel.

Advantageously, the insert is constructed from plastics material, preferably from Nylon.

A preferred method for manufacturing a nipple according to the invention comprises the steps of:.

The features and advantages of the invention will be better appreciated from the following detailed description of a preferred though non-exclusive embodiment which is illustrated by way of non-limiting example with reference to the appended drawings, in which:.

In the Figures, there is generally designated <NUM> a nipple which is manufactured according to the present invention. The nipple <NUM> is intended to be applied to the threaded end <NUM> of a spoke <NUM> in order to construct a spoked wheel which is not illustrated.

The nipple <NUM> comprises a rod <NUM> and a head <NUM> which is widened with respect to the rod <NUM>. There are preferably formed in the head and in the rod respective manoeuvring keys 6a, 6b in order to rotate the nipple <NUM> with respect to the spoke for screwing purposes. The first manoeuvring key 6a is preferably built in an axial recess of the head <NUM> (but may also be constructed, for example, by conferring a polygonal shape to the head itself) and may have different forms which are known per se, for example, with a hexagon socket, a torqx profile, Philips profile, notched profile, and the like. In this manner, the nipple can be manoeuvred by means of a tool which extends from the first manoeuvring key 6a along the axis of the nipple.

The second manoeuvring key 6b is preferably constructed in the form of a polygonal impression (for example, a square impression, as shown in <FIG> or a hexagonal impression) in the portion of the rod axially opposite and distal with respect to the head <NUM>. In this manner, the nipple is also accessible and manoeuvrable when it is mounted on the wheel so as to allow adjustment of the tension of the spoke without having to disassemble the wheel, by means of a tool which extends from the second manoeuvring key 6b in a direction transverse to the axis of the nipple.

The nipple further has a tapped axial hole <NUM>, preferably a through-hole (or, alternatively, a blind hole) which extends from an opening <NUM> to the distal end with respect to the head <NUM> as far as the seat of the first manoeuvring key 6a. The thread of the hole <NUM> defines a root diameter D and a crest diameter d.

The nipple <NUM> is further provided with an insert <NUM> made from deformable resin, for example, a polyamide resin.

The insert <NUM> is preferably formed with a cylindrical tubular (annular) shape which is radially contractile so as to be able to be installed from outside in a seat <NUM> which is formed in the hole <NUM> in an intermediate position thereof between the head <NUM> and the opening <NUM>. The seat <NUM> preferably has a shape with a cylindrical mantle and has a diameter <NUM> which is preferably greater than the crest diameter d and even more preferably greater than or equal to the root diameter D of the thread. In this manner, the radial depth of the seat <NUM> is such that the insert <NUM> is axially retained in the seat <NUM>. The seat <NUM> further has an axial extent which is sufficient to receive and retain the insert <NUM>.

In order to make the insert <NUM> radially contractile, there is provision for it to be constructed with a discontinuous mantle, for example, by providing a notch <NUM>. Alternatively, there is provision for using the resilience of the insert <NUM> itself or a multiplicity of partial discontinuities in the mantle thereof.

There is defined in the insert <NUM> a passage <NUM>, the internal diameter of which, at least when it is inserted in the seat <NUM>, is less than the root diameter of the thread of the hole <NUM> so as to interfere with the thread <NUM> of the spoke <NUM> when it is screwed in the threaded hole <NUM>. This generates the self-locking connection between the spoke and nipple.

The seat <NUM> is preferably formed in a position of the hole <NUM> which is axially intermediate between the head <NUM> and the opening <NUM>. This positioning allows the use of shorter spokes with respect to what is required by the known self-locking nipples, in any case ensuring both an optimum self-locking function and correct sealing of the spoke/nipple connection. In order to allow this connection, the seat <NUM> is spaced apart from the opening <NUM> of the nipple by at least three or more threads.

In some embodiments, in order to promote the widening of the insert <NUM> once it is inserted in the seat <NUM>, there is provision for a metal core (not illustrated) to be present in the mass of resin, for example, made of harmonic steel wire which is preferably arranged circumferentially and embedded in the insert <NUM> at an approximately median diameter thereof. In this manner, the insert <NUM> is radially contracted for the insertion thereof in the seat <NUM> but is urged both by the elastic return thereof and by the elastic return of the metal core to expand radially once it is released in the seat <NUM>.

The metal core is also interrupted at the notch <NUM> of the insert <NUM>.

In order to construct the nipple, a semi-finished product S which is obtained by moulding from a metal rod which is straightened and cut beforehand is taken as a basis; the semi-finished product S is formed so as to define the external geometries of the nipple, including the head <NUM>, the rod <NUM> and the respective manoeuvring keys 6a, 6b.

The semi-finished product S is therefore axially drilled so as to obtain the hole <NUM> and the opening <NUM>, as shown in <FIG>.

The processing of the seat <NUM> is then carried out, as shown in <FIG>, and the tapping of the hole <NUM>, as shown in <FIG>.

Meanwhile, the insert is provided in a radially contracted condition in a loader C, the external diameter of which is less than the crest diameter d of the thread of the hole <NUM> so as to be able to be introduced, preferably from the head <NUM> side, inside the hole <NUM> up to a location near the seat <NUM>, as shown in <FIG>.

In order to increase the precision and the repeatability of the application process of the insert <NUM> in the nipple, it is preferable for the insert to have a discontinuous mantle (so as to improve the radial contraction of the insert when it is inserted in the loader C) and a metal core (so as to improve the elastic return of the insert once it is inserted in the respective seat <NUM>).

The radially contracted insert is therefore placed in the seat <NUM>, where it expands radially, regaining an external diameter identical to that of the seat <NUM> itself so as to remain embedded in the seat between the shoulders formed by the end threads of the hole <NUM> close to the seat <NUM> itself.

<FIG> shows the nipple <NUM> ready to receive the threaded end <NUM> of a spoke <NUM>. When the nipple is screwed onto the threaded end <NUM> of the spoke <NUM>, the thread of the spoke is screwed into the thread of the nipple until reaching the insert <NUM>.

The screwing action then continues in the passage <NUM> of the insert, deforming the plastics material of the insert as a result of the interference effect between the internal diameter of the insert and the thread of the spoke. At the limit, it is sufficient for the length of the spoke to be such as to be at least partially screwed in the insert <NUM> of the nipple in order to obtain a self-locking connection. However, it is preferable for the length of the spoke to be selected so that the nipple is screwed on the spoke, with the wheel mounted, with engagement of both the threaded portions of the hole <NUM> separate from the seat <NUM>.

It is preferable for the loader C to be constructed so as to contain a plurality of inserts <NUM> which can therefore be placed one at a time in the respective seats <NUM> of nipples being processed following the sliding thereof into the loader C via the force being applied thereto by means of a piston P.

Claim 1:
A nipple (<NUM>) for spokes of spoked wheels including a rod (<NUM>) with an axial development, a threaded hole (<NUM>) which is formed axially in the rod (<NUM>), the thread of the hole (<NUM>) defining a root diameter (D) and a crest diameter (d), a head (<NUM>) which is widened with respect to the rod (<NUM>) and a deformable insert (<NUM>) which is inserted in a seat (<NUM>) which is axially aligned with the hole (<NUM>), the insert (<NUM>), at least when it is inserted in the seat (<NUM>), having a passage (<NUM>) for a threaded spoke end, the internal diameter of which is less than the root diameter (D) of the thread of the hole (<NUM>) so as to interfere with the thread of the spoke when it is screwed into the threaded hole (<NUM>), wherein the seat (<NUM>) is formed in an intermediate axial position of the hole (<NUM>), characterized in that the insert (<NUM>) is radially contractile and has a discontinuous mantle, wherein the insert (<NUM>) is made radially contractile by the discontinuous mantle.