A reduction gear of angular velocity comprising: - an input shaft configured to be coupled with a drive shaft; - an output shaft configured to transmit an angular velocity to a mechanism, the output shaft being coaxial with the input shaft, and - mechanical system adapted to convert an input angular velocity of the input shaft into an output angular velocity of the output shaft, the output angular velocity being lower than the input angular velocity, wherein the input shaft comprises a first cam and a second cam having circular cross-sections that are mutually separated along a main axis of the input shaft from an intermediate portion, the first cam having an axis spaced apart from a main axis of the input shaft of a first distance (ΔX1) in a first direction transversal to said main axis, the second cam having an axis spaced apart from the main axis of the input shaft of a second distance (ΔX2) in a second direction different from the first direction, and wherein the mechanical system comprises: - an input gear wheel mounted on the first cam, and - an output gear wheel mounted on the second cam, characterized in that the input gear wheel comprises a plurality of first housings arranged radially with respect to a center of the input gear wheel, each first housing having a respective extension axis (H1-6), and the output gear wheel comprising a plurality of second housings arranged radially with respect to a center of the output gear wheel, each second housing having a respective extension axis (J1-6), and by comprising - a plurality of pins, each having a first end inserted into a respective first housing of the input gear wheel and a second end opposite the first end inserted into a respective second housing of the output gear wheel, the first end and the second end of each pin being free to move within the first housing and the second housing, respectively, thus tilting an axis of the pin with respect to the extension axes (H1-6) of the first housings and the extension axes (J1-6) of the second housings, and wherein the rotation of the input gear wheel drives the output gear wheel through the pins. - an input shaft configured to be coupled with a drive shaft; - an output shaft configured to transmit an angular velocity to a mechanism, the output shaft being coaxial with the input shaft, and - mechanical system adapted to convert an input angular velocity of the input shaft into an output angular velocity of the output shaft, the output angular velocity being lower than the input angular velocity, - an input gear wheel mounted on the first cam, and - an output gear wheel mounted on the second cam, characterized in that the input gear wheel comprises a plurality of first housings arranged radially with respect to a center of the input gear wheel, each first housing having a respective extension axis (H1-6), and the output gear wheel comprising a plurality of second housings arranged radially with respect to a center of the output gear wheel, each second housing having a respective extension axis (J1-6), and by comprising the input gear wheel comprises a plurality of first housings arranged radially with respect to a center of the input gear wheel, each first housing having a respective extension axis (H1-6), and the output gear wheel comprising a plurality of second housings arranged radially with respect to a center of the output gear wheel, each second housing having a respective extension axis (J1-6), and by comprising - a plurality of pins, each having a first end inserted into a respective first housing of the input gear wheel and a second end opposite the first end inserted into a respective second housing of the output gear wheel, the first end and the second end of each pin being free to move within the first housing and the second housing, respectively, thus tilting an axis of the pin with respect to the extension axes (H1-6) of the first housings and the extension axes (J1-6) of the second housings, and