DESCRIPTION

The invention relates to a method for the manufacture of self-locking nipples and a nipple manufactured according to that method.

It is known from US2778690 that it is possible to manufacture nipples for spoked wheels provided with a threaded hole which receives the threaded end of a spoke and also provided with an insert affecting a length of the threaded hole acting to prevent the nipple from accidentally working loose from the spoke as a result of vibration occurring during use of the wheel. In this case the insert is made of fibrous material and is inserted into an axial hole in the nipple, coaxially with the threaded hole. This embodiment is suitable for the production of inserts extending within the shank of the nipple, and is suitable for screwing in spokes of various lengths, but nevertheless requires nipples and inserts of relatively large diameter because it is very difficult if not impossible to insert relatively small inserts into holes of small diameter such as those made in small nipples.

This disadvantage has partly been overcome by the method described in US6205664 by the same applicant. This patent suggests the use of substantially spherical inserts which are applied to the nipple by bevelling the head. However in this way only nipples of limited length which are not suitable for use with relatively short spokes can be manufactured, because the thread at the end of the spokes may not engage a self-locking insert sufficiently or at all.

The problem underlying this invention is that of providing a method for manufacturing self-locking nipples which are structurally and functionally designed to overcome all the disadvantages mentioned with reference to the cited known art.

This problem has been resolved by the invention through a method for the manufacture of self-locking nipples and a nipple manufactured according to that method in accordance with the specifications in the following claims. Characteristics and advantages of the invention will be more apparent from the following detailed description of a method and corresponding nipple according to the invention illustrated by way of indication without limitation with reference to the appended drawings in which :

- Figure 1 is a lateral view in partial cross-section of a nipple according to the invention fitted to a spoke of a wheel;

- Figure 2 is a perspective view of the nipple in Figure 1 according to a first embodiment;

Figures 2A to 2E are diagrammatical lateral views in cross-section of the stages of manufacturing the nipple in Figure 2;

Figure 3 is a perspective view of the nipple according to this invention according to a second embodiment;

Figures 3A to 3E are diagrammatical lateral views in cross-section of the stages of manufacture according to the variant embodiment of the nipple in Figure 3;

Figures 4 and 5 are perspective views of further variants of construction of the nipple in Figure 2 and Figure 3;

Figures 4A to 4E and 5A to 5E are diagrammatical lateral views in cross-section of stages in manufacture of the nipples in Figure 4 and Figure 5, respectively; Figures 6, 7 and 8 are views in transverse cross-section respectively of the semi-finished product which forms the nipple according to this invention during the stages of processing in Figures 4C, 5C and 5D, respectively; and

- Figure 9 is a view in transverse cross-section of the semi-finished product forming the nipple according to this invention during the processing stage in Figure 3B.

In the figures 1 indicates as a whole a nipple which is intended to connected a threaded extremity 2 of a spoke 3 to a rim, not shown, of a spoked wheel . In nipple 1 there is an enlarged head 5 which is coaxial with respect to a shank 6 of axis X.

Head 5 and shank 6 have an axial threaded hole 7 and one or other or both have externally an adjustment member such as a polygonal portion 8, 8' and/or a slot for screwdrivers 8" used to rotate nipple 1 with respect to the spoke when the wheel is assembled and/or tensioned.

An insert 9 formed from a resin injected in the fluid state is provided over a length 11 of axial hole 7 extending from head 5.

In a variant of this invention, in order to produce nipples according to the teaching of patent application No. PD2010A000004 by the same applicant, the contents of which are to be considered to be incorporated herein for the purposes of description, nipple 1A is manufactured with two or more inserts 9a of plastics material arranged in a ring about the X axis of the nipple and at a distance therefrom which is less than a diameter of second hole 7, as illustrated in Figure 3, and of a diameter such that the lateral surface of hole 7 is wholly in contact with the plastics material of inserts 9a. The stages in the method of manufacturing nipple 1, 1A are illustrated in Figures 2A to 2F and 3A to 3F respectively. Nipple 1, 1A is obtained from a round metal bar which is shaped by pressing to obtain a semi-finished product 10 in which the shank 6 and head 5 may be seen . This semi- finished product may be provided with adjustment members 8, 8', 8" .

One or more first blind holes 11, 11a, corresponding in position, depth, diameter and relative orientation to inserts 9, 9a which it is intended to provide, and which consequently define lengths 11 extending from head 5 in which they are located, are initially made in the sem i-finished product. In the first embodiment of nipple 1 a first hole 11 having axis X of a diameter greater than that of hole 7 is initially made, while several holes are made in the other embodiment of nipple 1A. In this latter embodiment, in positions such that part of the cross-section of blind holes 11a subsequently intersects hole 7 when this is subsequently made in the nipple.

Semi-finished product 10 so obtained is then taken up again, injecting a plastics material (nylon or other thermoplastic resin) into holes 11 in the fused state. After subsequent cooling semi-finished product 10 will therefore have holes 11 filled with inserts 9, 9a, of resin of generally cylindrical shape.

Subsequently hole 7, which may be provided with an entry portion 7b of larger diameter intended to receive the free end of spoke 3, is then made in the semi-finished product.

Once hole 7 has been made, this is threaded over the length of metal necessary to perform the conventional function of the nipple, that is from entry portion 7b, if present, to inserts 9 and 9a, without involving the surfaces of the latter.

In this way it is possible to make nipples with inserts of small diameter provided directly in the place of their corresponding seats, overcoming the difficulty of the separate insertion of the latter into corresponding receiving seats. It is thus possible to manufacture nipples with relatively long inserts in relation to their diameter, or multiple inserts according to the teachings of patent application PD2010A000004 by the same applicant.

When the nipple is threaded to the end of a spoke, as the latter engages the length of hole 7 in contact with insert 9, 9a there is a friction coupling between the thread on the spoke and that in the insert producing the desired self-locking effect between the spoke and nipple.

Figures 4 and 5 illustrate two further embodiments of the nipple according to this invention .

In particular the nipple in Figure 4 differs from the embodiment in Figure 2 through the presence in insert 9 of at least one stop member 9b which engages corresponding seats made in hole 11. These stop members 9b extend along an axis X along the length of insert 9. In this way members 9b can prevent rotation of insert 9 with respect to the X axis, in particular during the machining of through hole 7.

The seats for stop members 9b may be made jointly with blind hole 11, in particular through pressing, and in such a way that the stage of filling the same with plastics material in a fused state makes it possible to manufacture the aforesaid members 9b together with the insert, as illustrated in Figures 4B and 4C. Figure 5 describes a further variant embodiment of the nipple according to this invention .

The method for the manufacture of this embodiment provides for the making of a blind hole 11 with a diameter greater than the diameter of second hole 7 and at least two holes l ib located in the rim around the X axis at a distance from the latter which is less than the diameter of second hole 7, as illustrated in Figure 5B.

Holes l ib may advantageously be of shallower depth than hole 11, in such a way that the former extend only along head 5 of the nipple while the latter may also extend along shank 6, thus favouring the possibility of using shorter spokes, with a corresponding saving of weight and cost.

Holes 11 and l ib provided in this way are filled with plastics material in the fused state in such a way as to form an insert 9 comprising a single body and provided with extensions 9b which engage holes l ib.

Again in this case therefore rotation of insert 9 will be prevented by extensions 9b, and hole 7 and the corresponding partial thread may be made more easily. In addition to this it will be possible to use an insert 9 which also extends along shank 6 without the risk of excessively weakening the structure of the nipple, the stability of the insert being ensured by extensions 9b and a minimum thickness of plastics material in hole 7 to achieve the self-locking effect.

The invention thus resolves the problem set in a simple, effective and inexpensive manner.