LIGHT ALLOY BICYCLE RIM

Abstract: The invention relates to a light alloy bicylde rim comprising a base portion (2), two lateral flanks (3) forming an outer braking surface (4), and a longitudinal hole (5) in particular a pinhole (5). In order to obtain a clear indication of the fact that the braking surface (4) is worn off, a first portion (H1) of the braking surface (4) is arranged to be worn off down to the longitudinal hole (5) so as to form a visible slit (8) whilst a second portion (H2), situated radially outwards with respect to the first portion (H1), has a thickness such that it maintains its strength when said first portion (H1) is worn off. In order to prevent the lateral flanks (3) from bending outwards when the braking surface (4) is worn off they are further reinforced, for example by a web (6) between the pinholes (5).

Description: "Light alloγ bicycle rim" The present invention relates to a light alloy bicycle rim comprising a base portion, two lateral flanks forming an outer braking surface, and a longi- tudinal hole provided along said lateral flanks and extending over a first portion of the height of the braking surface. Such a bicycle rim is generally known. This known rim is formed of an extruded profile showing pinholes along the lateral flanks to join both ends of the profile by means of pins which are pressed in the pinholes. These pinholes are located at the transition between the base portion and the lateral flanks. A drawback of the existing light alloy bicycle rims is that, due to the use of more abrasive rim brakes, the braking surfaces are subjected to consider¬ able wear which may result after prolonged use in a destruction of the rim. More particularly, the outer peripheral portion of the lateral flanks may break off, or may bend outwards under the pressure of the tyre, and may get stuck between the rim brakes. At the same time the tyre will come off the rim. It is clear that this is a dangerous situation which may lead to serious acci¬ dents. In order to avoid such accidents it has already been proposed to make an outer cut in the braking surface or to punch recesses therein. In this way, the user has an indication of the progress of the wear of the braking surfaces. However, even when the applied cut or recesses have completely disappeared, there is no real incentive to replace the rim or, in other words, there is no direct indication of the dangerous situation. An object of the present invention is there- fore to provide an original rim concept which clearly indicates when the braking surface has been worn off. To this end, the light alloy bicycle rim according to the invention is characterized in that the first portion of the braking surface is arranged to be worn off down to the longitudinal hole so as to form a visible slit whilst a second portion of the height of the braking surface, situated radially outwards with respect to the first portion, has a thickness such that it maintains its strength when said first portion is worn off, said lateral flanks being further reinforced to prevent them from bending outwards when the braking surface is worn off down to the longitudinal hole. In contrast to the known wear indicators set forth hereinabove, the wear of the bicycle rim according to the invention is indicated by the appearance of a visible slit in the braking surface. When such a slit is formed in the braking surface, it is immediately clear that the rim is worn off. The rim according to the present invention provides thus a clear indication that it should be replaced before any dangerous situa¬ tion arises. In practice there exists already bicycle rims having lateral flanks formed by an entirely hollow profile. When the outer wall of this hollow profile, which forms the braking surface is worn off, the strength of this profile is lost. This is especially due to the fact that the rim brake will push the braking surface inwards so that the inner wall of the hollow profile is not supported any more and will thus bend outwards under the pressure of the tyre. In a particular embodiment of the present invention, said longitudinal hole is a pinhole provided for forming a pin joint between the two extremities of the rim profile. In this embodiment no additional longitudinal holes have to be provided along the flanks of the bicycle rim. An advantage of this embodiment is further that it provides an additional indication of the fact that the braking surfaces are worn off. Indeed, when the braking surfaces are worn off down to the pins of the pin joint, this will be felt upon braking, i.e. a shocking braking effect will be obtained. In a preferred embodiment, a resilient element is pressed in said longitudinal hole, more particularly in the pinhole near the pin joint. In this way said shocking braking effect will be achieved by this resilient element and will even be more pronounced than the shocking effect caused by the pins of the pin joint due to the higher frictional forces between the resilient element and the rim brake. Further particularities and advantages of the present invention will become apparent from the follo¬ wing description of some particular embodiments of the bicycle rim according to the invention. This descrip- tion is only given as an example and is clearly not intended to limit the scope of the present invention. The reference numerals used in the description refer to the annexed drawings wherein : Figure 1 shows a cross-sectional view of a prior art light alloy bicycle rim and of a brake shoe cooperating therewith. Figure 2 shows a cross-sectional view of a light alloy bicycle rim according to the present inven¬ tion and of a brake shoe cooperating therewith. Figure 3 is a cross-sectional view analogous to Figure 2 but relating to another possible embodiment of the bicycle rim according to the invention ; and Figure 4 shows a perspective view of one extremity of the rim profile shown in Figure 2 compris¬ ing the pins of the pin joint. In these different figures, the same reference numerals refer to identical or analogous elements. As set forth hereinabove, prior art light alloy bicycle rims, in particular aluminium alloy rims, may cause dangerous situations since they wear off relatively quickly, especially when use is made of highly abrasive rim brake shoes. Figure 1 shows such a prior art bicycle rim and a rim brake shoe 1 cooperating therewith. The bicycle rim shown in the figures comprises a base portion 2 and two lateral flanks 3 adjacent to the base portion 2 so as to form a generally U-shaped cross-section. The lateral flanks 3 show an outer braking surface 4 destined for cooperating with the rim brake shoes 1. Further a so-called pinhole 5 is pro¬ vided for making a pin joint between both extremities of the normally extruded rim profile. Both pinholes 5 are mutually connected by a web 6 to reinforce the profile and they usually provide a seat 7 for the tyre beads. In Figures 1-3, the wear of the rim caused by the rim brake shoe 1 has been indicated schematically by a curved recess 9 in one of the lateral flanks 3. For clarity's sake, no brake shoe has been indicated at the other lateral flank 3 but it will be clear that this latter flank 3 will also cooperate with a brake shoe 1 and will thus also be subjected to wear. The curved recess 9 is only a schematic representation of the wear but is based on experimental data. The actual wear will in practice however depend on a number of factors, such as the abrasion resistance of the flanks, the rigidity and structure of the brake shoes, etc., and may thus show a more or less pronounced curvature which will generally not be as regular as shown in the figures. On the basis of this schematic representation, it will be clear that in the prior art bicycle rim of Figure 1, the lateral flanks 3 will bend outwards or may even break off before the braking surface 4 is worn off down to the pinhole 5. This prior art rim provides thus no visual indication of the dangerous situation which arises when the braking surface is worn off. In contrast to the shown prior art rim, the rim according to the invention does provide such a visual indication. In general, the pinhole 5, or another longitudinal hole provided along the lateral flanks 3 of the rim according to the invention extends only over a first portion H, of the height H of the braking surface 4. According to the invention, the second portion H 2 of the height H of the braking surface 4, situated radially outwards with respect to the first portion H,, has to have a thickness such that it main¬ tains its strength when the first portion H, is worn off down to the pinhole 5. This is schematically shown in Figures 2 and 3. The lateral flanks 3 should further be reinforced to prevent them from bending outwards under the pressure of the type when the braking surface 4 is worn off down to the pinhole 5. In the embodiment shown in Figure 2, this is achieved by the web 6 between the pinholes 5. This web 6 could however also be provided between the second portions of the flanks 3 themselves. The required reinforcement can further be obtained by an additional support between the pinhole 5 and the base portion 2 or by an increased wall thickness of the pinhole 5 as shown in Figure 3. In the rims according to the present invention, a visible slit will thus be formed in the braking surface 4 when this surface is worn off, providing a clear warning in case the rim has been worn off. The location where the visible slit will be formed has been indicated in Figures 2 and 3 by arrow 8. In the embodiments shown in Figures 2 and 3 , the thickness of the second portion H 2 of the braking surface 4 increases towards the pinhole 5. As set forth hereinabove, it has been found experimentally that due to the wear, a generally curved recess will be formed in the braking surface 4 so that less material is required in these embodiments to retain the strength of the second portion H 2 . The thickness of this second portion H 2 of the braking surface 4, measured near the pinhole 5, will in particular comprise at least 120 percent of the thick¬ ness at the level of the pinhole 5 and preferably from about 140 to about 160 percent of this latter thickness. These thicknesses may be smaller in case one would consider to use a hollow structure for the second portion. In such a case, the second portion of the braking surface, i.e. the outer wall of this hollow structure, may be for example 0.1 to 0.3 mm thicker near the pinhole 5 than the first portion at the level of the pinhole. Without additional reinforcement of the second portion of the braking surface, this second portion should for example be 0.4 to 1.0 mm, and more particu¬ larly 0.6 to 0.8 mm thicker near the pinhole 5 than the first portion at the level of the pinhole. In view of the generally curved recess which will be formed upon prolonged wear of the braking surface, the pinhole 5 or another longitudinal hole is located ideally such that the slit which will be formed into this longitudinal hole will be situated at a level of about 50 % of the height of the braking surface. In this way, the amount of material required to achieve the required thickness of the second portion H 2 of the braking surface 4 and of a third portion H 3 of the braking surface 4, situated radially inwards with respect to the first portion H, can be kept to a mini¬ mum. In general, the slit formed upon prolonged wear of the braking surface 4, will be located at a distance of 20 to 80 % and more particularly of 25 to 65 % of the height H of the braking surface from the edge 10 thereof situated adjacent to the base portion 2. In a preferred embodiment, the slit 8 will be located at a distance of 25 to 40 % of the height of the braking surface 4 from the edge 10. An advantage of this preferred embodiment is that, in view of the standard height of the flanks 3 above the tyre seat 6 usually formed by the pinhole 7, no important increase of the height of the braking surface 4 is involved as can be seen in Figure 2. Figure 3 shows a variant embodiment of the bicycle rim according to the invention. In this embodi¬ ment, the pinhole 5 is situated, just as in the prior art, in the corner between the base portion 2 and the lateral flank 3 but shows an extension 11 which extends towards the middle of the braking surface 4. In this way, a visible slit 8 will be formed into this extension 11 upon prolonged wear before the lateral flanks 3 loose their required strength. In the above described embodiments, a further indication of the fact that the rim is worn off can be felt upon breaking. Indeed, the pins of the pin joint will act on the brake shoes 1 and will thus cause a shocking braking effect. In order to enhance this effect, a resilient element may be pressed in the longitudinal hole, in particular in the pinhole 5 near the pin joint as shown in Figure 4. Such a resilient element can also be pressed in the longitudinal hole 5 in case this is not used as a pinhole, for example in case both extremities of the rim are welded together. In the embodiment shown in Figure 4, the pins 12 are arranged to carry a resil¬ ient element 13, for example a rubber sleeve or a rubber cap, and to push this element 13 into the pinhole 5 when making the pin joint. The free extremity of the pins 12 have for example a reduced diameter so that the resil¬ ient element 13 can be slid thereover. By the force exerted by the pins 12 when pushing the elements 13 into the pinhole 5, these elements will be compressed between the wall of the pinhole 5 and the pins 12. When a slit 8 will be formed in the braking surface 4 due to pro¬ longed wear, the presence of the resilient element 13 projecting somewhat out of the slit 8 will cause an irregular braking or in other words a shocking effect. This effect can be felt very clearly and is thus a further indication of a prolonged wear of the braking surfaces 4. From the above description it will be clear that the invention is not limited to the described embodiments but that all kinds of modifications could on the contrary be applied thereto without leaving the scope of the annexed claims, in particular as to the possible shapes of the rim. In the shown embodiments, the braking surfaces 4 on the rim define for example a mutual angle of 0°, or are in other words parallel to one another. These braking surfaces may however be disposed under an angle with respect to one another which will normally be smaller than 15°, and preferably smaller than 10°, to achieve the desired braking effect. Further, as already indicated hereinabove, the longitudinal hole does not necessarily have to be formed by a pinhole, for example in case the rim comprises one or two further holes for making the pin joint or in case both extremities of the rim are welded together.

Claims: CLAIMS 1. A light alloy bicycle rim comprising a base portion (2) , two lateral flanks (3) forming an outer braking surface (4) , and a longitudinal hole (5) provided along said lateral flanks (3) and extending over a first portion (H j ) of the height (H) of the braking surface (4) , characterized in that said first portion (H^ of the braking surface (4) is arranged to be worn off down to the longitudinal hole (5) so as to form a visible slit (8) whilst a second portion (H 2 ) of the height (H) of the braking surface (4) , situated radially outwards with respect to the first portion (H,) , has a thickness such that it maintains its strength when said first portion (H,) is worn off, said lateral flanks (3) being further reinforced to prevent them from bending outwards when the braking surface (4) is worn off down to the longitudinal hole (5) . 2. A bicycle rim according to claim 1, characterized in that when said first portion (H,) is worn off down to the longitudinal hole (5) , the formed slit (8) is located at a distance of 20 to 80 % of the height (8) of the braking surface (4) from the edge (10) thereof situated adjacent the base portion (2) . 3. A bicycle rim according to claim 2, characterized in that when said first portion (H,) is worn off down to the longitudinal hole (5) , the formed slit (8) is located at a distance of 25 to 65 % of the height of the braking surface (4) from the edge (10) thereof situated adjacent the base portion (2) . 4. A bicycle rim according to claim 3, characterized in that when said first portion (H,) is worn off down to the longitudinal hole (5) , the formed slit (8) is located at a distance of 25 to 40 % of the height (H) of the braking surface (4) from the edge (10) thereof situated adjacent the base portion (2) . 5. A bicycle rim according to any one of the claims 1 to 4, characterized in that the thickness of said second portion (H 2 ) of the braking surface (4) increases towards the longitudinal hole (5) . 6. A bicycle rim according to any one of the claims 1 to 5, characterized in that the thickness of said second portion (H 2 ) of the braking surface (4) com¬ prises near said longitudinal hole (5) at least 120 percent of the thickness at the level of said longitudi- nal hole (5) and preferably from about 140 to about 160 percent of this latter thickness. 7. A bicycle rim according to any one of the claims 1 to 6, characterized in that said second portion (H 2 ) of the braking surface (4) is 0.4 to 1.0 mm, and more particularly 0.6 to 0.8 mm, thicker near said longitudinal hole (5) than the first portion (H,) at the level of the longitudinal hole (5) . 8. A bicycle rim according to any one of the claims 1 to 7, characterized in that said longitudinal hole (5) has an increased wall thickness to reinforce the flanks (3) so as to prevent them from bending outwards when the braking surface (4) is worn off down to the longitudinal hole (5) . 9. A bicycle rim according to any one of the claims 1 to 8, characterized in that the flanks (3) of the rim are reinforced by means of a reinforcing web (6) provided transversally between said flanks (3) , in particular between said longitudinal holes (5) .

Inventors: CLAES IVO JOANNA HUBERT, CLAES, IVO, JOANNA, HUBERT
Applicants: ALESA, CLAES IVO JOANNA HUBERT, "ALESA", "L'ALLIAGE LEGER ET SES APPLICATIONS", CLAES, IVO, JOANNA, HUBERT
Application year: 1996
Main classification: B60B21
IPC codes: B60B21