Method and apparatus for quantitatively evaluating roll hardness

Abstract

A method and apparatus for testing the hardness of wound rolls, such as paper rolls, which yields quantitative information which is reproducible from roll to roll and under various conditions of testing. The apparatus can be operated much like a backtender's stick, to simply strike the roll at a point where hardness is to be determined with a force variable between certain limits as determined by the operator using the stick. The apparatus includes an accelerometer mounted in a striker associated with circuitry for producing signals relating to (a) the energy of the impact between the striker and roll and (b) the peak deceleration of the striker. Those signals are processed to produce a roll hardness measure, which can be correlated to a commonly used Rho scale if desired, and which is repeatable irrespective of the force used by the operator to cause the impact.