Escapement device for timepiece

An escapement device of a clockwork movement with two active alternations between a balance plate and an escape wheel including:

• a first mobile having a first impulse face and a first locking face that cooperate with the escape wheel,
• a second mobile having a second impulse face and a second locking face that cooperate with the escape wheel and having gears linking the second mobile and the balance plate;
• gears linking the first mobile and the second mobile;
• wherein the escape wheel is subjected to an essentially constant torque, is arranged to alternately transmit mechanical energy to the first mobile and to the second mobile, and has an angle of rotation,
• the first locking face is arranged so that the force transmitted by the escape wheel in the first locking face passes substantially in proximity to the center of rotation of the first mobile,
• the second locking face is arranged so that the force transmitted by the escape wheel on the second locking face passes substantially in proximity to the center of rotation of the mobile,
• the first drive face is positioned adjacent to the first locking face in such a manner that an outside angle α2 running from the first locking face toward the first drive face has the same sign as that of the angle of rotation of the escape wheel,
• the second drive face is positioned adjacent to the second locking face in such a manner that an outside angle α3 running from the second locking face toward the second drive face has the same sign as that of the angle of rotation of the escape wheel,
• the first locking face and the second locking face have concave surfaces.