Method and device for controlling contact pressure on touch roller in sheet winder

Claim 1

In a sheet winder of the type wherein the sheet roll being wound is supported at the free end of a rocking arm and held in contact with a touch roller at a constant pressure determined by the difference between the component of the combined weight of the rocking arm and the sheet roll acting in the direction of the axis of the touch roller and a component of force acting in the opposite direction applied to the rocking arm by a servo mechanism, a method for the control of the contact pressure between the sheet roll and the touch roller, which method comprises: programming a first arithmetic circuit to perform arithmetic operations in accordance with the formula: F = F.sub.o {1 + γ.sup.· ƒ(x).sup.θ } wherein F is the desired contact pressure, F o is the contact pressure at the beginning of the winding operation, x is a variable whose value changes in proportion to the increasing weight of the sheet roll γ and θ are numerical values predetermined empirically for the sheet material to be wound, feeding the value of F o , the values of γ and θ determined for the sheet to be wound and the value of x to the first arithmetic circuit to obtain the value F, feeding the value of x, the value of ρ representing the angle of inclination of the rocking arm and values representing the unit weight of the sheet material, the weight of the rocking arm and its geometric relationship to the touch roll to a second arithmetic circuit programmed to calculate the uncompensated contact pressure between the sheet roll and the touch roll and obtaining the uncompensated contact pressure as the value F', feeding the values of F and F' to a comparator circuit to obtain a signal corresponding to the difference therebetween, and feeding the difference signal to the servo mechanism to control the force it exerts on the rocking arm, whereby the contact pressure between the sheet roll and the touch roll is adjusted to the desired contact pressure.