Method and apparatus for measuring and removing rotational variability from a nip pressure profile of a covered roll of a nip press

A system for calculating and displaying a nip pressure profile for a nip press, comprising:

• a sensing roll configured with a second roll in a nip press, the sensing roll and the second roll adapted to rotatingly press matter therebetween in a nip region,
• the sensing roll comprising a plurality of cross-directional positions along its length,
• the sensing roll comprising a plurality of sets of pressure-measuring sensors,
• each sensor of the plurality of sets of sensors being disposed at a cross-directional position along the sensing roll,
• each sensor configured to sense and measure pressure when the sensor enters the nip region of the nip press,
• wherein the plurality of sets of pressure-measuring sensors comprises n sets of sensors, wherein each sensor of a one of the n sets has a corresponding sensor in each of the remaining n−1 sets, each corresponding sensor being located at the same cross-directional position and spaced 360°/n apart circumferentially from an adjacent sensor on the sensing roll, each set of sensors forming a partial helix which extends about 360°/n around the sensing roll,
• each of the corresponding sensors of the plurality of sets providing a measurement of pressure at the respective cross-directional position which is averaged to supply an average measurement to processing equipment which calculates and displays a nip pressure profile for the nip press.

A method for determining a nip pressure profile of a sensing roll of a nip press, comprising:

• measuring a pressure exerted on a first sensor disposed at a particular cross-directional position on the sensing roll as the first sensor enters a nip region of the nip press;
• measuring a respective pressure exerted on one or more additional sensors at the particular cross-directional position as they enter the nip region of the nip press,
• each of the one or more additional sensors being located at the particular cross-directional position as the first sensor and spaced apart circumferentially from the first sensor;
• and
• averaging the pressure measurement of the first sensor and the pressure measurement of the one or more additional sensors and determining a nip pressure profile,
• wherein the first sensor, the one or more additional sensors and a plurality of further sensors, the further sensors being located at one or more other cross-directional positions along the sensing roll, comprise a plurality of sensors arranged as n sets of sensors, wherein each sensor of a one of the n sets has a corresponding sensor in the remaining n−1 sets, each corresponding sensor being located at a same cross sectional position and spaced 360°/n apart circumferentially from an adjacent sensor, each set of sensors forming a partial helix which extends about 360°/n around the sensing roll.

A method for determining a nip pressure profile of a sensing roll of a nip press, comprising:

• placing n sets of sensors on the sensing roll, wherein n is an integer greater than one,
• each sensor of the n sets of sensors being disposed around the sensing roll for sensing pressure exhibited on the sensing roll at that sensor's location and for providing a pressure signal representative thereof,
• each of the sensors of the n sets being disposed at a particular cross-directional position out of a plurality of cross-directional positions along the sensing roll,
• each sensor of a one of the n sets having a corresponding sensor in the remaining n−1 sets, each corresponding sensor being located at the same cross-directional position and spaced 360°/n apart circumferentially from an adjacent sensor on the sensing roll, each set of sensors forming a partial helix which extends about 360°/n around the sensing roll;
• measuring the pressure exerted on each sensor of the n sets when the sensing roll is rotating and the sensors are in the nip region of the nip press;
• and
• at each of the plurality of cross-directional positions, averaging the pressure readings of each sensor of the n sets located at that cross-directional position.

A method for providing a nip pressure profile of a sensing roll of a nip press, comprising:

• providing a sensing roll having a working length and a plurality of cross-directional positions disposed along the working length;
• placing multiple pressure-measuring sensors at each cross-directional position,
• the sensors at each cross directional position being spaced apart circumferentially from the other;
• measuring the pressure exerted on each sensor at each cross-directional location as the sensor moves into the nip region of the nip press;
• at each cross-directional position, averaging the pressure measurements from all sensors at that cross-directional position to determine an average pressure measurement at each cross-directional position;
• and
• utilizing the average pressure measurements from each cross-directional position to provide a nip pressure profile for the nip press,
• wherein the multiple pressure-measuring sensors at each cross-directional position are arranged as n sets of sensors, wherein each sensor of a one of the n sets has a corresponding sensor in the remaining n−1 sets, each corresponding sensor being located at a same cross sectional position and spaced 360°/n apart circumferentially from an adjacent sensor, each set of sensors forming a partial helix which extends about 360°/n around the sensing roll.