An articulation mechanism for large scale mobile aggregate system equipment. The mechanism includes a screw device that is pivotally secured to an elongated portion of the equipment to drive its movement to and from a collapsed position. The screw device is driven by a screw jack and moved within a housing while the housing itself is pivotally secured to another portion of the equipment. Rollers within the housing may be used to stabilize the lateral movement of the screw device during the opening, closing or self-locking of the elongated portion by the mechanism.