A kinematic chain comprising: - a first pulley arranged to rotate about a rotation axis x; - a second pulley arranged to rotate about a rotation axis y; - at least one connecting element comprising at least one passage having at least one rotating element having a rotation axis u, said or each connecting element also comprising at least one interface arranged to connect said or each connecting element to an adjacent connecting element or to a pulley , generating a rotational constraint about a rotation axis z; - a transmission element arranged to evolve along a determined path for transmitting a rotational motion between said first pulley and said second pulley , said transmission element arranged to pass through said or each passage generating a rotation of said or each rotating element about said rotation axis u; said kinematic chain being arranged to pass between an adjusting configuration, wherein said or each connecting element is adapted to rotate about said rotation axis z for adjusting its own angular position with respect to an adjacent connecting element or to a pulley , and a transmission configuration, wherein, when said first pulley rotates about said rotation axis x, said second pulley rotates proportionally about said rotation axis y, in said transmission configuration said or each connecting element being adapted to not rotate about said rotation axis z, said kinematic chain characterized in that said or each connecting element comprises a first interface and a second interface , said first and said second interface comprising alternatively: - a first protrusion ; - a first protrusion and a second protrusion ; - a first protrusion and a second protrusion and a third protrusion ; - a combining the previous; said protrusions arranged to create hinge constraints between said connecting element and an adjacent connecting element or between said connecting element and a pulley . - a first pulley arranged to rotate about a rotation axis x; - a second pulley arranged to rotate about a rotation axis y; - at least one connecting element comprising at least one passage having at least one rotating element having a rotation axis u, said or each connecting element also comprising at least one interface arranged to connect said or each connecting element to an adjacent connecting element or to a pulley , generating a rotational constraint about a rotation axis z; - a transmission element arranged to evolve along a determined path for transmitting a rotational motion between said first pulley and said second pulley , said transmission element arranged to pass through said or each passage generating a rotation of said or each rotating element about said rotation axis u; in said transmission configuration said or each connecting element being adapted to not rotate about said rotation axis z, said kinematic chain characterized in that said or each connecting element comprises a first interface and a second interface , said first and said second interface comprising alternatively: - a first protrusion ; - a first protrusion and a second protrusion ; - a first protrusion and a second protrusion and a third protrusion ; - a combining the previous; - a first protrusion ; - a first protrusion and a second protrusion ; - a first protrusion and a second protrusion and a third protrusion ; - a combining the previous; said protrusions arranged to create hinge constraints between said connecting element and an adjacent connecting element or between said connecting element and a pulley . <EOS>