An escapement device for a mechanical timepiece having an escapement wheel cooperating with a rocker and a mobile element, the rocker cooperates with the escapement wheel by blocking arms and with the balance plate by a release fork, the mobile element having a spring cooperating with the teeth of the escapement wheel by a winding arm and with the balance wheel plate by an impulse arm. This space-saving escapement device is able to supply the balance wheel with an almost constant quantity of energy within a variable barrel torque range.

An escapement device for a mechanical timepiece having an escapement wheel cooperating with a rocker and a mobile element, the rocker cooperates with the escapement wheel by blocking arms and with the balance plate by a release fork, the mobile element having a spring cooperating with the teeth of the escapement wheel by a winding arm and with the balance wheel plate by an impulse arm. This space-saving escapement device is able to supply the balance wheel with an almost constant quantity of energy within a variable barrel torque range.