Patent ID: 7357022

Claim:
A method of determining planarity defects in strip, the method comprising the steps of: (a) providing a surface unevenness measurement roller centered on an axis and having two measuring units spaced apart angularly of the axis on the roller by 180° and each including a member set in the roller with peripheral clearance and bearing upon said strip as said strip passes over a surface of said roller and said roller is rotated about the axis in contact with the strip, and a respective force transmitter responsive over the width of the strip to tensile stress distribution in the strip; (b) interconnecting said members of said measuring units spaced apart by 180° by at least one generally diametrally extending tie rod such that force is transferred between the measuring units via said tie rod; and (c) evaluating surface unevenness of the strip from a measured force obtained by summing values from the force transmitters of each of the measuring units to respective sums, subtracting one of the sums from the other to obtain a differential force, and subtracting from said differential force a weight of said measuring units to provide said measured force.