Thrust chain device having a toothed sprocket with long asymmetrical teeth

A thrust chain device, comprising a thrust chain (10) comprising a straight portion (10a) along an axis and a curved portion (10b), the thrust chain comprising links (12) hinged on axes, a thrust chain guide (20), a driving sprocket (1) provided with teeth (2) engaging the thrust chain, the driving sprocket (1) being in contact with the thrust chain through involute contact surfaces (2a), said contact surfaces (2a) belonging to the teeth (2), a tooth (2) meshing with the chain (10) by defining a line of action having an angle with the axis of the straight portion (10a) of between −10° and 10°, the line of action being offset with respect to the hinge axes of links (12), the driving sprocket (1) is in contact with the straight portion (10a) and without contact with the curved portion (10b), the driving sprocket (1) is rotatably mounted to an axis located on an opposite side of the thrust chain to the center of curvature of the curved portion (10b), and said contact surfaces (2a) of each tooth (2) comprise a convex front surface directed towards the straight portion (10a) when the tooth (2) is engaged and a rear surface directed towards the curved portion when the tooth (2) is engaged, the convex front surface occupying an angle greater than one half the angle occupied by the tooth (2) and the axis of the sprocket (1) is disposed, along the axis of the straight portion (10a), in a zone between a boundary between the curved portion (10b) and the straight portion (10a) and a maximum distance from said boundary (30), a tooth (2) exerting a thrust force on an angle of rotation epsilon of the sprocket (1) and having an angle sigma from one tooth to a next tooth with sigma equal to 360°/n, n being the number of teeth of the sprocket (1), and the epsilon-sigma difference is greater than 30°.