Sensor, system and method for determining Z-directional properties of a sheet

A system for determining a physical property of a traveling sheet, said physical property being a function of sheet caliper measured at a plurality of pressures exerted on the sheet, the sheet having opposed, first and second major surfaces, the system comprising:

• a first sheet-contacting pad disposed adjacent to the first major surface;
• a second sheet-contacting pad opposing the first pad and disposed adjacent to the second major surface;
• a third sheet-contacting pad disposed upstream from the first pad adjacent to the first major surface;
• a fourth sheet-contacting pad opposing the third pad and disposed adjacent to the second major surface;
• means, operatively coupled to the first pad, for measuring and generating a signal indicative of the distance between the first and second pads;
• means, operatively coupled to the third pad, for measuring and generating a signal indicative of the distance between the third and fourth pads;
• means for pressing the first and second pads toward the sheet at a first predetermined pressure and for pressing the third and fourth pads toward the sheet at a second predetermined pressure and for generating signals indicative of said first and second pressures, wherein the first predetermined pressure is different than the second predetermined pressure;
• and
• a computer responsive to said generated signals for determining the caliper of said sheet and said physical property.

A method for determining a physical property of a sheet, said physical property being a function of sheet caliper measured at a plurality of pressures exerted on the sheet, the sheet having opposed, first and second major surfaces, the method comprising the steps of:

• pressing the first and second major surfaces on opposite sides of the sheet at a plurality of pressures;
• measuring the plurality of pressures;
• measuring the sheet caliper at the plurality of pressures;
• and
• computing the physical property based upon the pressure and caliper measurements.

A system for determining a z-directional physical property of a sheet having a sheet caliper and opposed, first and second major surfaces, the system comprising:

• means for pressing the first and second major surfaces on opposite sides of the sheet at a plurality of pressures;
• means for measuring the plurality of pressures;
• means for measuring the sheet caliper at said plurality of pressures;
• and
• means for computing the physical property based on the pressure and sheet caliper measurements.

A sensor for use in determining the caliper of a sheet, the sensor comprising:

• means for compressing the sheet in a z-direction at a first pressure at a first location relative to the traveling sheet;
• means for compressing the sheet in the z-direction at a second pressure at a second location relative to the traveling sheet, the second pressure being different than the first pressure;
• means for measuring the first and second pressures and generating signals indicative thereof;
• and
• means for measuring the sheet caliper at the first and second locations and generating signals indicative thereof.

A method for determining a z-directional physical property of a sheet traveling in a machine direction, the method comprising the steps of:

• compressing the sheet in the z-direction at a first location along the machine direction using a first pressure;
• measuring the first pressure;
• measuring the caliper of the compressed sheet at said first location;
• compressing the sheet in the z-direction at a second location in substantial alignment with the first location along the machine direction using a second pressure, the second pressure being different than the first pressure;
• measuring the second pressure;
• measuring the caliper of the compressed sheet at the second location;
• and
• calculating the physical property based on the pressure and caliper measurements.