Measuring unit for measuring the bending radius and the forwarding of a workpiece in a bending machine

A measuring unit for measuring a bending radius and a forwarding of a workpiece while the workpiece is being bent in a given bending plane by a bending machine,

• wherein the measuring unit comprises a first carriage which is arranged to be connected to the bending machine and to be passed through by the workpiece, wherein the first carriage comprises
• a main body;
• a pair of support bodies carried by the main body;
• a pair of measure rollers mounted each on a respective support body so as to be idly rotatable each about a respective axis of rotation, the axes of rotation of the measure rollers being parallel to each other and perpendicular to the bending plane;
• a first measuring device arranged to provide a signal indicative of an angular position of each of the measure rollers about the respective axis of rotation;
• a guide device mounted on the main body so as to guide the support bodies along a straight direction perpendicular to, and passing through, the axes of rotation of the measure rollers;
• an elastic device arranged to apply on the support bodies an elastic force tending to urge the support bodies towards each other, and therefore to urge each measure roller against the workpiece when the workpiece is moved forward between the measure rollers, so as to cause each measure roller to roll on a respective intrados surface or extrados surface of the workpiece while the workpiece is moved forward through the first carriage;
• a second measuring device arranged to provide a signal indicative of a distance between the axes of rotation of the measure rollers;
• and
• a positioning device arranged to define a positioning of the main body, and hence of the guide device, relative to the workpiece, in such a manner that during bending with a constant bending radius a tangent to the longitudinal axis of the workpiece in a point of intersection between the longitudinal axis of the workpiece and the straight direction of the guide device is perpendicular to said straight direction;
• wherein said elastic device comprises at least one spring which is connected at one end thereof to one of the two support bodies and at an opposite end thereof to the other one of the two support bodies, whereby a resulting normal force applied by said elastic device on the workpiece is zero, and
• wherein said positioning device comprises a first pair of guide rollers and a second pair of guide rollers which are arranged upstream and downstream of the measure rollers, respectively, and are supported by the main body so as to be idly rotatable about respective axes of rotation parallel to the axes of rotation of the measure rollers.