Abstract:
A brake apparatus for a bicycle capable of applying a higher braking force on the front wheel ( 3 ) and a lower braking force on the rear wheel ( 4 ) given the same force exerted on the levers ( 7, 8 ) controlling the front brake ( 5 ) and the rear brake ( 6 ) so to prevent early locking of the rear wheel of the bicycle during braking while leaving the cyclist the possibility to separately control the front brake ( 5 ) and the rear brake ( 6 ).

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to brake apparatuses for bicycle, of the known type, comprising: 
     a front wheel braking device of the bicycle comprising: 
     a front brake, and 
     a front brake control device, comprising: 
     a supporting body, 
     a front brake control lever articulated around the supporting body and, 
     a transmission connecting the front brake and the front brake control lever, and 
     a rear wheel braking device of the bicycle comprising: 
     a rear brake, and 
     a rear brake control device, comprising: 
     a supporting body, 
     a rear brake control lever articulated around the supporting body and, 
     a transmission connecting the rear brake and the rear brake control lever. 
     In bicycles, as in all vehicles, the force by which the front wheel is pressed on the ground increases and the force by which the rear wheel is pressed on the ground decreases during braking, reason for which the grip of the rear wheel with respect to the ground is reduced with respect to the front wheel in equal conditions of friction. In other words, the maximum braking action which can be applied to the front wheel without locking it and causing it to slip on the ground is higher than that applicable to the rear wheel. Consequently, when braking to the limit of grip, the necessity of differentiating between the braking action of the front wheel and the rear wheel arises. On conventional bicycles, the front brake and the rear brake are controlled by means of two separate levers which are operated manually, reason for which, in theory, cyclists can employ their sensitivity and apply a different braking force on the front wheel and on the rear wheel. However, firstly, not all cyclists have the sensitivity to control the front wheel and the rear wheel in a differentiated fashion to obtain the maximum possible braking without locking the wheels. Secondly, in emergency conditions, i.e. when the maximum possible braking must be applied in the shortest possible time, this result is not achievable. 
     SUMMARY OF THE INVENTION 
     In order to account for these requirements, various braking systems for bicycles have been proposed in the past which comprise a centralised control device to operate the front brake and the rear brake at the same time. This device is connected to the two brakes by means of the respective conformed transmissions and arranged in such a way to obtain two different braking actions on the front wheel and on the rear wheel from a single control action. However, these devices are not very commonly implemented both because they are relatively complicated and because cyclists always prefer having two available separate brake controls for the front wheel and for the rear wheel, especially in the case of competition bicycles. 
     In order to solve all of the aforesaid problems, this invention relates to a brake apparatus for bicycle comprising: 
     a front wheel braking device of the bicycle comprising: 
     a front brake, and 
     a front brake control device, comprising: 
     a supporting body, 
     a front brake control lever articulated around the supporting body and, 
     a transmission connecting the front brake and the front brake control lever, and 
     a rear wheel braking device of the bicycle which is fully independent from the front wheel braking device comprising: 
     a rear brake, and 
     a rear brake control device, comprising: 
     a supporting body, 
     a rear brake control lever articulated around the supporting body and, 
     a transmission connecting the rear brake and the rear brake control lever characterised in that the front braking device is capable of applying a braking force on the front wheel which is higher than that applied on the rear wheel given the same force exerted on the levers controlling the front brake and the rear brake. 
     In order to achieve this, this invention moves against a technical prejudice which has existed to the current day. This is because, the proposed forms of embodiment aimed at obtaining differentiated braking of the two wheels of a bicycle always comprised a centralised control suitable for causing in any way a different braking action on the two wheels of the bicycle. Conversely, in the case of this invention, two fully separate braking devices for the front wheel and the rear wheel are still used, but these braking devices are conformed to exert two different braking actions (specifically, a higher braking action on the front wheel) given the same control force exerted on the control lever of the front brake and on the control lever of the rear brake. 
     In a first form of embodiment, this result is obtained by mutually differentiating the brake and the rear brake. Particularly, in the apparatus according to this invention, the front brake is a so-called “dual-pivot” brake. The term “dual-pivot” here is used to intend, for example, a brake of the type described and illustrated in U.S. Pat. No. 5,425,434 by the Applicant. This brake comprises two arms holding respective brake shoes, where a first arm is articulated around a first pivot pin, secured to the bicycle frame, and the second arm is articulated around a second pivot pin, spaced from the first pivot pin and held by an auxiliary support, which in turn is rigidly secured to the bicycle frame. Furthermore, a rocking member is arranged between the two arms to multiply the braking load. According to this first form of embodiment of the invention, the rear brake, on the contrary, is a conventional brake with a single pivot pin, where the two arms holding the brake shoes are mutually articulated around the same pin secured to the frame of the bicycle. Naturally, given equal dimensioning of the dual-pivot brake and of the single pivot brake, the braking action obtained on the wheel for the same force applied to the control wire of the brake is higher in the case of the dual pivot brake. In this way, cyclists can avail of a brake apparatus which always ensures higher braking of the front wheel easily permitting to obtain the maximum possible braking efficiency in all conditions of grip with ground, in all cases always offering cyclists the possibility to separately control the front brake and the rear brake. 
     In a second form of embodiment of this invention, the front braking device and the rear braking device is differentiated by means of a different positioning of the point of the brake control lever to which the respective control wire is connected. This solution naturally refers to the conventional case in which the transmission connecting each control lever to the respective brake consists of a flexible wire, with one extremity connected to the control lever in a point of the lever which is situated on the opposite side of the pivoting axis of the lever with respect to the actuation end of the lever. In the case of this invention, the control lever of the front brake is connected to the respective flexible wire in a point which is closer to the pivoting axis of the lever with respect to the case of the rear brake control lever. Thanks to this characteristic, given the same force exerted on the actuation end of the control lever, the control lever of the front wheel generates on the flexible wire a higher force with respect to the case of the control lever of the rear brake. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Studies and experiments conducted by the Applicant have ascertained that the optimal differentiation of load on the front brake and load on the rear brake corresponds to a ratio of approximately 1.3:1. 
     Characteristics and advantages of this invention will be illustrated with reference to a preferred embodiment as non-limiting examples in the enclosed drawings, whereas: 
     FIG. 1 is a schematic view of a competition bicycle employing a brake apparatus according to this invention, 
     FIGS. 2 and 3 are prospective views of the front brake and the rear brake of a first form of embodiment of the braking device according to this invention and 
     FIGS. 4 and 5 are a cross-section view of the control levers of the front brake and the rear brake in a second form of embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, number  1  indicates generally denotes a competition bicycle comprising a frame  2 , a front wheel  3  and a rear wheel  4  to which a front brake  5  and a rear brake  6  are associated and controlled by means of the respective flexible wires by a lever  7  controlling the front brake  5  and a lever  8  controlling the rear brake  6 , associated to the handlebar  9  of the bicycle. 
     In the first form of embodiment of this invention, the structure and conformation of the front brake  5  and the rear brake  6  are illustrated in accompanying figures  2  and  3 . As shown, the front brake  5  is of the “dual-pivot” type which first arm  10  holds a first braking shoe  11  and is articulated around a first pivot pin  12  which is secured to the frame of the bicycle. A second arm  13  holds a second braking shoe  14  and is articulated around a second pivot pin (of which the axis  15  only is illustrated in figure 2) and is connected to an auxiliary support  16 , which is also rigidly secured to the bicycle frame. Furthermore, as described, for example, in U.S. Pat. No. 5,425,434, a rocker member (not visible in FIG. 2) is articulated around the axis  15  which is used to multiply the braking load. The brake  5  is operated by a flexible metallic wire  17  one extremity of which is secured to an end of the arm  13  opposite to the shoe  14  and the other extremity is connected to the respective brake control lever, the arm  10  conversely being secured to a sheath  17   a  of the wire. Always according to the first form of embodiment of this invention, the rear brake  6  is on the other hand of the type illustrated in figure 3, simply including two arms  10 ,  13  mutually articulated around the same pin  12  to be secured to the bicycle frame and holding respective braking shoes  11 ,  14 . The arrangement is such that the two brakes  5 ,  6  are substantially of equal dimensions and have arms  10 ,  13  which are also substantially similar to each other. However, the dual-pivot brake is able to generate a higher braking action from the same value of force applied to the control lever  7 . Consequently, the cyclist can separately control the front brake and the rear brake with two levers  7 ,  8  by exerting the same force on the two levers, but obtaining a higher braking action on the front brake and a lower braking action on the rear brake. 
     The FIGS. 4,  5  refer to a second form of embodiment, in which the braking action is differentiated between the front brake  5  and the rear brake  6  by means of a different design of the control levers  7 ,  8 . 
     With references to the FIGS. 4,  5 , each lever comprises a body articulated around an axis  18  on a supporting structure  19  secured to the handlebar of the bicycle. The lever is connected at point  20  to the extremity of the respective flexible control wire  17  on the side opposite to the pivoting axis  18  with respect to the portion of the brake lever actuation end  21 . In this form of embodiment of the invention, the point  20 , in the case of the lever  7  controlling the front brake is closer to the axis  18  with respect to the case of the lever  8  controlling the rear brake. Consequently, the same force applied to the actuation end  21  of the two levers  7  and  8  a higher force is transmitted in the case of the front brake and a lower force in the case of the rear brake. 
     In the description above, it is apparent how the brake apparatus according to this invention makes the cyclist able to obtain a differentiated braking effect, particularly a higher braking on the front wheel and a lower braking on the rear wheel from a same load applied to the control levers of the front brake and of the rear brake, so to constantly ensure braking in the best safety conditions and at the same time giving the cyclist the possibility of controlling the front brake and the rear brake separately. 
     Naturally, numerous changes can be implemented to the construction and forms of embodiment of the invention herein envisaged, all comprised within the context of the concept characterising this invention. 
     This is because, obviously, the principle underlying this invention pertains to mutually differentiating the front braking device and the rear braking device so to obtain the result illustrated above. In the forms of embodiment herein illustrated, this purpose was obtained by mutually differentiating either the front brake and the rear brake, or the lever controlling the front brake and the lever controlling the rear brake. However, such differentiation may be implemented in any point of the braking device, which is the brake apparatus in total, of the brake control device and of the transmission connecting the parts.