A spoke-nipple and a method for its manufacture

Abstract: A spoke nipple comprises a body (2) of substantially undeformable material with a head (5) and a shank (4) which have an at least partially threaded axial hole (3) for housing the thread (18) of a spoke (19), and with a perforated insert (16; 22) of substantially deformable material fixed to the body (2) with the holes (3; 17) in the body and in the insert (16; 22) arranged coaxially, the insert having an inside diameter such as to house the thread (18) of the spoke (19) with interference when it is screwed into the axial hole (3) in the nipple body (2).

Description: The subject of the present invention is a spoke nipple according to the preamble of the main claim 1. The invention also relates to a method of manufacturing the nipple. Nipples having the characteristics indicated above, an example of which is known from DE 825657 and US 2778690, are used widely in the construction of spoked wheels, for restraining the threaded end of the spoke on the rim of the wheel. This US prior art comprises the features mentioned in the preamble of claim 1 of the present application. In this field, it has been noticed in the past in wheels with conventional spokes and, more recently, with some types of spokes, particularly so-called straight spokes which do not have a bend at the axially opposite end to the thread for the attachment of the nipple, that the nipple may slowly unscrew under load, in use. This leads to inadequate functioning of the wheel owing to the gradual loosening of the nipples, and consequently to a dangerous weakening of the wheel as a whole. To prevent this problem, some wheel assemblers use special adhesives or glues which are spread on the threaded portions of the spoke and/or of the nipple before it is tightened. However, the effect of these glues is difficult to control - in some cases they may completely block the nipple, preventing its subsequent removal - and, in any case, the effect is cancelled out if the wheel is subjected to successive adjustments of the tension in the spokes involving the release of one or more nipples. The technical problem upon which the invention is based is that of providing a spoke nipple which overcomes the problems complained of with reference to the prior art mentioned. This problem is solved by the invention by means of a nipple having the aforementioned features and characterized in that it comprises a perforated insert of substantially deformable material which is fixed to the body with the holes in the insert and in the body arranged coaxially, the hole in the insert having an inside diameter such as to house the thread of the spoke with interference when it is screwed into the hole in the body. The characteristics and advantages of the invention will become clearer from the following detailed description of a preferred embodiment thereof, shown by way of nonlimiting example in the appended drawings, in which: Figure 1 shows a nipple formed according to the present invention, half as a front elevational view and half in longitudinal section, Figures 2 and 3 are longitudinal sections of two successive stages of the manufacture of the nipple of Figure 1, Figures 4 and 5 are a section of the nipple of the preceding drawings taken on the line IV-IV of Figure 3, and a corresponding section of a variant thereof, respectively, Figure 6 is a longitudinal section of a variant of the nipple of the invention, Figures 7 to 11 are longitudinal sections of the nipple of Figure 6 in the various stages of manufacture. With reference to Figure 1, a nipple 1 formed in accordance with the invention comprises a metal body 2 which has an axis X and an axial hole 3, and in which a shank 4 and a head 5 with a polygonal key portion 7, possibly with a notch 8 for a screwdriver, are identified. A further key portion 6 formed on the outside of the shank 4 on an end portion thereof is also polygonal, generally square, in plan (figure 4) but, in a possible variant of the invention, may have the configuration of Figure 5, that is a grooved profile 6a. At the opposite end to the head 5, the axial hole 3 has an enlarged mouth 10 followed by a threaded portion 11, the hole 3 terminating, at the free end of the head 5, in a greatly enlarged seat 12. In this seat, a wall 13 with a cylindrical surface of axis X, a shoulder 14 close to the threaded portion 11, and a lip 15 at the axially opposite end can be seen. An insert 16 of plastics material or another material which is relatively deformable, at least relative to the low deformability of the metal body 2, is force-fitted in the seat 12. The insert 16 has an axial hole 17 in which a threaded portion 18 of a spoke 19 screwed into the nipple 1 can engage by screwing, forming its own thread but maintaining an interference fit with the insert 16. In the embodiment of Figures 1 to 3, the seat 12 has a cylindrical surface and the insert 16 is in the shape of a tubular sleeve which has a chamfered end and is fitted in the seat 12 after the threading of the hole 3, being held therein by the upsetting of the lip 15 from the position of Figure 2 to that of Figure 3. In a variant of the invention, generally indicated 20 in Figure 6, the seat 21 is generally spherical and the external shape of the insert 22 is also spherical. The insert is fitted in the seat 21 before the hole 3 is machined so that the hole is formed simultaneously in the body 2 and in the insert 22, thus achieving a better guarantee that the holes are coaxial. This aspect is particularly important on account of the very small dimensions of the nipple of the invention, owing to which serious problems may arise in the coaxial arrangement of the holes during separate machining of the body 2, particularly the seat 21, and of the insert 22. With reference specifically to Figures 7 to 11, however, it is envisaged that the metal body 2 of the nipple 20 will be produced from a blank 25 (Figure 7) produced, for example, by upsetting or moulding, and that the hole 3, complete with the thread 11 (Figure 8) as well as the seat 21, will then be formed therein, although without the upsetting of the lip 15 (Figure 9). The insert 22 will then be fitted, without a hole (Figure 10), and the lip 15 will be upset so as to lock it in the seat 21. It will be noted that the spherical shape of the insert facilitates its positioning in the seat 21 and prevents it from being damaged during the upsetting of the lip 15 by virtue of the optimal distribution of the forces achieved precisely by virtue of the spherical shape. The insert will then be perforated with a tool from the head end 5 and machined to the final shape of Figure 11. It will also be noted that the axial extent (SI) of the insert is quite large relative to the axial extent (SF) of the threaded portion of the nipple. Preferred values ofthis ratio (SI/SF) are between 0.2 and 0.4. The invention thus conceived achieves the results set as well as many advantages in comparison with conventional nipples. In particular, it achieves effective clamping which is not dependent upon actions of the assembler of the wheel. The clamping is repeatable, even if the nipple is subsequently rotated relative to the spoke during the adjustment of the wheel and the result offers a lasting guarantee of safety of the wheel. Moreover, the use of approximately spherical inserts facilitates the location and clamping of the nipple in the body, particularly with small nipples. Finally, the solution of the second embodiment, that is, the simultaneous machining of the hole in the body of the nipple and in the insert solves any problems with the coaxial arrangement of the holes resulting from the small dimensions of the respective details. Another advantage unespectedly obtained with this invention is that the normal life of spoke-wheels assembled using the nipples of this invention is consistently extended, probably because the insert made of plastic material provide a damping effect on the vibrations induced in the spokes and these are therefore less subjected to wear.

Claims: A spoke nipple comprising a body (2) of substantially undeformable material with a head (5) and a shank (4) which have an axial hole (3) for housing the thread of a spoke (19), and a perforated insert (16; 22) of substantially deformable material, said insert having an insert hole and being fixed to the body (2) such that said insert hole and said axial hole are arranged coaxially, said insert hole being thread-engaged with interference by the threads of the spoke (19) when said spoke is coupled to said nipple, characterised in that the axial hole (3) in the body is at least in part threaded to receive in thread-engagement the threads of said spoke (19) to retain axially said nipple to said spoke and in that the thread-engagement of the spoke and the insert is provided to prevent accidental rotation and loosening of the spoke relatively to the nipple body. A nipple according to Claim 1, in which the insert (16; 22) is housed in a seat (12; 21) formed at the free end of the head (5). A nipple according to Claim 2, in which the insert (16) is recessed in the head (5). A nipple according to one or more of the preceding claims, in which the seat (12) is defined between a shoulder (14) and a projecting lip (15) of the head (5), the insert (16) being restrained in the seat (12) between the shoulder (14) and the lip (15). A nipple according to one or more of the preceding claims, in which the material of the body (2) is metallic. A nipple according to one or more of the preceding claims, in which the insert (16; 22) is made of plastics material. A nipple according to one or more of the preceding claims, in which the insert (22) has an approximately spherical shape. A method of manufacturing a spoke nipple comprising a body (2) of substantially undeformable material with a head (5) and a shank (4) which have an axial hole (3) for housing the thread (18) of a spoke (19), and comprising the steps of: providing an insert (16; 22) of substantially deformable material, and providing a hole (17) in the insert (16; 22) and fixing it to the body (2) with the holes (17, 3) in the insert and in the body arranged coaxially, the hole (17) in the insert having an inside diameter such as to house the thread of the spoke (19) with interference when it is screwed into the hole (3) in the body (2), characterised in that it comprises the following steps: nesting said insert (16;22) in the axial hole (3) of the body (2) so that a portion of said axial hole in the body remains free from said insert, threading at least in part said free portion of the axial hole (3) in the body (2) to receive in thread-engagement the threads of said spoke (19) so as to retain axially said nipple to said spoke. A method according to Claim 8, in which the holes in the body and in the insert are formed simultaneously whilst the insert (16; 22) is restrained in a corresponding seat (12; 21) in the body (2).

Inventors: CAPPELLOTTO GUIDO, CAPPELLOTTO, GUIDO
Applicants: ALPINA RAGGI SPA, ALPINA RAGGI S.P.A.
Application year: 1997
Main classification: B60B1
IPC codes: B60B1