Mechanical system for transmitting motion and an aircraft fitted with a corresponding system

A mechanical system for transmitting rotary motion between at least two shafts movable in rotation respectively about a first axis and a second axis, the first and second axes intersecting, the mechanical system including a bevel gear set made up of a first bevel gear having teeth and movable in rotation about the first axis and a bevel wheel having teeth and movable in rotation about the second axis, the teeth of the first bevel gear and of the bevel wheel respectively being suitable for co-operating in complementary manner with one another, the first bevel gear, referred to as a “power” gear, presenting a first defining pitch surface of conical shape, and the bevel wheel presenting a second defining pitch surface of conical shape, the intersecting first and second axes being relatively positioned so as to define, during meshing between the power gear and the bevel wheel, a first operating pitch surface of conical shape relating to the power gear and a second operating pitch surface of conical shape relating to the bevel wheel, the first and second operating pitch surfaces being defined respectively by a common vertex arranged at the intersection between the first and second axes and by a circle corresponding to one of the respective pitch circles of the power gear and of the bevel wheel, the pitch circles being formed respectively by tangential circles centered on the first and second axes, the first operating pitch surface being selected to be identical to the first defining pitch surface and the second operating pitch surface being selected to be identical to the second defining pitch surface, the mechanical system including another bevel gear, referred to as an “accessory” gear, having teeth meshing with the teeth of the bevel wheel to transmit rotary motion to a third shaft movable in rotation about a third axis, the accessory gear presenting a third defining pitch surface of conical shape;

• wherein the accessory gear presents a third operating pitch surface obtained by the second and third axes being relatively positioned so as to enable the accessory gear to mesh with the bevel wheel, the third operating pitch surface of the accessory gear being selected to be different from the third defining pitch surface of the accessory gear, the third operating pitch surface being defined firstly by a third vertex arranged at an intersection between the third axis and the second axis and secondly by a pitch circle of the accessory gear, the third vertex being separate from the common vertex.