Luneta with electric drive

Window (1) for fixing centered workpieces, with three holding members (3, 30) arranged in unplano and having rollers (2), the two members outer retaining (30) they are associated hugs fixing (4), which they are pivotable about bolts joint (6) arranged in the body laluneta (5) and the center holding member (3) is adjustable linearly with respect to the workpiece, laque member central retaining (3) is adjustable by means of a rod formed as a spindle (9), cuyoaccionamiento is performed by means of an electric motor (7) and which is adjustable by a dehusillo member (10) actuable by the electric motor (7), and in laque on the side axially traseroentre spindle member (10) and the body of the bezel (5) is arranged a spring element (16), characterized in that between the spindle member ( 10) and the spring element (16) is pre seen discodistanciador (19) having a distance indicator (18) and in that a distance sensor (20) for measuring the variable distance from the distance indicator (18) is provided.