General Description of the Previous State of the Art.

In the field of sport or recreational equipments, industries are obliged to look for innovative solutions in order to optimize their products under a functional point of view. A typical goal of innovation efforts is maximizing human output. In the field of bicycle industry, in particular, a continuous improvement of ergonomic and functional performances has been achieved. For this purpose, ultra-light alloys are used to minimize the weight of high- performance bicycles, while the design process is subject to ergonomic requirements in order to make bicycles more and more fitted on various anatomic characteristics of users. Different solutions are commonly employed in race or high-speed bicycles. For instance, flywheels are used in order to maximize sportsman's performances. As a consequence of the loading actions of cyclist's pedaling, a fluctuating torque curve is produced at the pedal axis. Each leg, in fact, generates a typical torque curve with a peak value occurring when the applied force is maximum, while the other leg is passively driven. The resultant torque curve is characterized by two peak values shifted about 180 degrees out of phase from each other, corresponding to the maximum torque produced on each pedal. Since the resisting moment is usually almost constant, the vehicle behavior is not regular, especially during a low-speed motion. In order to reduce such a problem, the use of an elliptical ring has been recently proposed. This solution improves the situation, but the torque regularization is poor. In order to overcome this problem, an innovation is here proposed, consisting of an innovative mechanism, based on the use of non-circular gears, which is used to transmit power from pedals to the output element of the vehicle (i.e., the driving gear in a bicycle). The purpose of the present invention is to perform a variable transmission-ratio curve, so that the fluctuations of the output torque are effectivelv reduced.

Basically, the proposed mechanical system consists of an ordinary or epicyclical gear train mechanism, using non-circular gears to perform a suitable input-output relationship. This function is designed to lower the irregularity of the output torque curve and, as a consequence, to improve the vehicle motion, especially in low-speed conditions. Since the present invention can be combined with traditional single- or multi-ratio transmission mechanisms, it can be effectively and simply employed in any kind of bicycle or other pedal vehicle.

Description of the preferred embodiment

The general configuration of the proposed transmission mechanism consists of a set of non- circular gears, arranged in an ordinary or epicyclical gear train configuration. The simplest mechanism can be formed by a pair of non-circular gears, where the bigger one is an internal gear. By referring to figure 1, the innovative transmission is formed by an internal non-circular gear (2) and an external non-circular gear (3). Such a mechanism is driven by the pedals (1) and operates a torque modulation. In particular, the transmission ratio curve is designed to reduce torque fluctuations, so that the output torque is more regular. A traditional transmission mechanism, formed by a set of rings (4) a chain (5) and a set of sprockets (6), can be used to transmit and further transform the regularized torque to the output element of the vehicle, typically the driving wheel (7). The sprocket-chain mechanism can be designed as a single or multi-ratio transmission mechanism, so that a further modulation of the output torque can be performed, according to different motion conditions.

A different, less simple but probably more effective configuration is a set of non-circular gears, coupled as in an ordinary or epicyclical (i.e., planetary configuration) gear train arrangement. The ϋroposed innovative transmission mechanism can be easilv combined with traditional

single or multi-ratio transmission mechanisms using sprocket-chain systems. Therefore, it can be effectively employed in any kind of bicycle or other pedal vehicle.