A BRAKE FOR A BICYCLE WHEEL WITH OPPOSED FRICTION BLOCK LEVERS DISPOSED TANGENTIALLY TO THE WHEEL

Abstract: A bicycle wheel brake (10) consisting of a pair of opposed friction blocks (18) carried by respective levers (16) pivoted, either directly or through a support (11), to the bicycle frame, so as to be controllable against the action of antagonists (17) to lock the blocks against the wheel rim (13). Each lever is pivoted at one side of the wheel so as to move on a plane substantially parallel to the plane tangential to the wheel.

Description: Brakes for bicycles -particularly racing bicycles- are known which consist of a pair of opposed friction blocks which can be controlled to lock against the wheel rim. The blocks are rigidly fixed to a caliper the levers of which are pivoted to the fork or the frame of the bicycle, by means of a central pin, so as to move on a plane radial to the wheel. The said levers extend beyond the central pin from the part opposite the extremities which carry the blocks, and a Bowden cable within a guide is secured to such extensions. The Bowden cable, when operated, closes the caliper against the action of counter spring, usually of the wire type, acting between the said two levers. Brakes having the above described general structure entail various problems which have not thus far been fully solved. Firstly, when stressed, i.e. when the brakes are applied, they are not sufficiently rigid on account of the structure and disposition of the caliper and the friction blocks. More specifically, the lack of rigidity is due to the co-existence of the clearance which must perforce exist between the levers and their pin and the disposition of such levers on a plane transversal to the bicycle wheel. In consequence, when the brakes are applied, the stresses transmitted to the caliper flexurally stress the levers and their pivoting to the frame. To achieve a good degree of resistance and rigidity of the brake caliper, the flexurally operating levers must be made of material adequate for the purpose, with a section such as well lends itself to resist such kind of stress. The pivoting of the levers must also be of sturdy configuration, since such pivoting is subject to a fairly high deflecting torque. The length of the two arms of the caliper cannot in fact be reduced beyond the limit necessary for them, overreaching the height of the tyre, to bring the friction blocks proximal to the lateral faces of the rim. It is, moreover, evident that much friction is caused to pivoting arrangements subject to flexural stress, and this impedes the manually-applied closure of the caliper, which becomes stiff and not readily modulated. US-A-3.921.764 discloses a bicycle wheel brake comprising a pair of opposed friction blocks carried by respective levers pivoted to the bicycle frame and controllable against the action of elastic springs to press said blocks against the wheel rim in which said levers are each pivoted at one side of the wheel so as to move on a plane substantially parallel to the tangential plane of the wheel itself. This is a self-energizing bicycle brake which, upon engagement with the wheel rim, is energized by the frictional drag between the wheel rim and brake into more firm engagement with the wheel, thus requiring less effort on the part of the person riding the bicycle to energize the brakes of the bicycle to stop or slow forward motion of the bicycle. However, because of the complexity of the system of mounting the friction blocks to the fork fixed to the bicycle frame, which system comprises -for each friction block- an articulated parallelogram and a further pivoting, the brake proposed in the aforesaid U.S. patent 3.921.764 does not achieve the rigidity necessary under stress, i.e. at the time or breaking. The French Patent FR-A-935 044 discloses a bicycle wheel brake comprising a support on either side of the wheel, and a pivot shaft pivotally mounted on the support and bearing two levers near its free ends. One lever supports a friction block and the other additional lever is moved to engage the wheel rim by a Bowden control cable acting between the two additional levers. This structure involves high torsional stresses in the pivot shaft, flexional stresses in the lever and a lack of rigidity of the brake. Another keenly felt problem relating to brakes of the type described above is the elevated aerodynamic resistance they offer when the bicycle is in motion, as a result of the sizing the different parts have to be given in order to resist the aforesaid stresses. The aerodynamic resistance factor is not a negligible one, given that in bicycles, especially racing bicycles, each component is required to assure the maximum aerodynamic penetration. A last but not least difficulty is abnormal (irregular) wear of the fixed friction blocks caused by errors of parallelism between these and the rim, both during mounting and owing to the elastic deformation of the brake during use. The principal object of the present invention is to solve the above-mentioned technical problems by embodying a brake having a structure which causes minimal torsional and flexural stresses to the components, so as to prove rigid and easily operated without calling for excessive manually applied force. Another object of the invention is to embody a brake having improved aerodynamic penetration. A further object of the invention is to embody such a brake for fixing to the bicycle frame in the same place as a traditional brake is fixed, so as to be mountable if necessary without any local modifications thereto. These objects are attained by bicycle wheel brake according claim 1. In the hereto appended drawings: Figure 1 is a front elevation, partially sectioned, illustrating a brake embodied according to the principles of the invention; Figure 2 is a side elevation, partially sectioned, illustrating the same brake as a Figure 1; Figure 3 is a plan view; and Figures 4, 5 and 6 are views the same as the previous views but illustrating another possible form of embodiment of the invention. With reference firstly to the Figure 1 and 3 of the drawings, the bicycle wheel brake according to the invention therein shown is indicated overall by 10, and consist structurally of a support body 11 preferably having an aerodynamic form such as offers negligible air-resistance. To such end, the body 11 can advantageously have a general "C"-shaped configuration, with the wings 12 interconnected so as to give an aerodynamic profile. The support 11 is centrally traversed by a bore 14 adapted to receive a means for securing the brake to the bicycle frame. Characteristically, there are pivoted to the wings 12 of the body 11, by pins 15, respective levers 16 oscillating against the action of a counter spring 17 acting between them and the body 11. At the free end of levers 16 there also mounted, through block holders 19, a pair of friction blocks 18 facing the rim of the wheel 13, which rim is shown by dash-and-dot lines in Figure 1. The block holders 19 are pivoted to the levers 16 by pins 20 parallel to the pins 15 restrained in place axially by radial dowels 21. The pins 20 protrude upwardly from the levers 16 with respective tangs 22 which are operatively interconnected for the actuation of the brake by means of a traditional Bowden cable 23, cable guide 24, adjusting screw 25 and nut 26. Worthy of note is the concealed disposition of the cable 23, which passes through the body 11. Figures 4, 5 and 6 show another possible form of embodiment of the invention which is conceptually identical to that described above with reference to Figures 1, 2 and 3, and in which the identical or equivalent parts are indicated by the same reference numerals. The brake shown in Figures 4, 5 and 6 differs from the first described brake only in point of simplification of configuration of the components, less attention being paid to the connections between the parts as regards their aerodynamic penetration. The body 11 is in effect a simple "C" and the levers 16 are countered by an unconcealed single spring mounted on the cable 23 which acts directly between the tangs 22 of the articulation pins 20. The advantages of the brake according to the invention are apparent from what has been described heretofore with reference to the Figures. The great rigidity of the structure under stress will prove particularly clear, such rigidity being due to the possibility of stably fixing the support body 11 to the frame or fork of the bicycle and also due to the disposition of the levers 16 in a plane tangential to the wheel, so that the levers 16 are chiefly stressed by traction or compression. There needs to be noted the minimal arm indicated by A existing between the friction blocks and the lever articulation pins, whereby the levers and the pins undergo only moderate flexural and torsional stress. The fact that the pins of the linkage levers work chiefly shear-wise prevents the occurence of friction and jibbing such as impede the manual operation of the brake, and thus braking is easily modulated and calls for no excessive effort. With the brake according to the invention, moreover, it is possible to obtain a self-braking action, when the brake is mounted according to an appropriate orientation. This can be seen from Figure 6: if the leverage configuration is such that, when the blocks rests on the wheel rim, the pin 20 is of smaller (by a value shown as B) radial distance than the pin 15, and the mounting orientation of the brakes is such that the braking action brings about a force F on the block, there is induced a corresponding moment on the levers 16, about the pin 20, which thrusts the brake to closure. A suitable sizing of the value B permits the desired extent of self-braking effect that facilitates manual operation of the brake. Additionally, the free-float mounting of the blocks on the levers allows the former to self-adapt perfectly to the rim, which means that wear of the friction material is uniform and that thus there is an even distribution of stresses. To this end, the axis of the pin 20 can lie outside the median geometrical plane of the block so that, when braking is applied, the pressure of the different zones on the rim is averagely uniform.

Claims: A bicycle wheel brake comprising: a) an elongate support body (11) mountable on a bicycle frame member and being of sufficient lenght to transgress the width of the wheel, b) wings (12) extending downwardly from said body to be positionable on either side of the wheel, c) a pivot pin (15) vertically mounted on each wing (12), d) a lever (16) pivotally mounted on each pivot pin (15) to be movable only in a plane substantially parallel to the closest tangential plane of the wheel, e) an oscillatable pin (20) mounted near the free end of each lever (16) parallel to the pivot pin (15) thereof and having a length sufficient to transgress the rolling height of the wheel, f) a friction block (18) mounted on the lower end of each oscillatable pin (20) below the respective lever (16) to frictionally engage the wheel rim when braking, g) elastic spring means (17) urging the free ends of the levers (16) away from the wheel and h) a Bowden control cable acting directly between the upper ends of the oscillatable pins (20). The bicycle wheel brake of claim 1 wherein said means to bias the friction blocks away from said wheel rim constitutes a spring mounted around said cable between said oscillatable pins. The bicycle wheel brake of claim 1 wherein said means to bias the friction blocks away from said wheel constitues two springs, each spring being mounted between said wing and said lever. The bicycle wheel brake of claim 1 wherein said oscillatable pins are spaced a distance apart less than the distance between the pins mounted in the wings. The bicycle wheel brake of claim 1 wherein said support body extends between said oscillatable pins and said cable passes through said support body extending between said pins.

Inventors: ANCARANI RESTELLI, AMEDEO
Applicants: SOCIETA' ITALIANA CATENE CALIBRATE REGINA S.P.A.
Application year: 1985
Main classification: B62L1
IPC codes: F16D65, B62L1