Patent ID: 8831841

Claim:
An automatic steering device for a self-propelled straddle carrier for lifting and transporting manufactures that includes a spatial portal structure ( 1 ) resting on the ground on a plurality of steering wheel units ( 4 ): wherein each of said steering wheel units ( 4 ) comprises two tired wheels ( 8 , 8 ′) each of which is associated with its own electric motor means ( 10 , 10 ′) that is independent of other said electric motor means; each of said steering wheel units is connected to said structure above by a respective fifth wheel that has a vertical axis and that rotates with a respective one of said steering wheel units about the vertical axis; each said electric motor means is supplied by its own vector frequency converter controlled by a control unit provided with a control microprocessor; angular rotation of each wheel unit ( 4 ) about the vertical axis is measured by an incremental encoder integral with said upper structure and with the fifth wheel ( 14 ) and connected to said microprocessor; and said control unit tracks a steering angle of each of said steering wheel units and modifies a trajectory of the self-propelled straddle carrier by modifying an order sent to a respective said vector frequency converter by which a respective said electric motor means is operated to modify a rotational speed of a respective one of said tired wheels thereby to turn a respective one of said steering wheel units about the vertical axis.