Method of and apparatus for measuring strip planarity

1. In a strip-treating system where a tensioned metal strip moves in a longitudinal direction, an apparatus comprising:

a roller rotatable about an axis transverse to the direction and having a substantially cylindrical outer surface engaged generally tangentially by the strip;

a radially shiftable tension-measuring bar set in the roller, extending generally only angularly of the axis so as to lie in a plane substantially perpendicular to the axis, and having an outer surface generally flush with the roller surface; and

sensor means between the bar and the roller for measuring radial deflection of the bar and thereby determining longitudinal strip tension.

2. The apparatus defined in claim 1 wherein the tension-measuring bar extends angularly all around the roller.

3. The apparatus defined in claim 2 wherein the tensioning-measuring bar is formed by a plurality of bar sections.

4. In a strip-treating system where a tensioned metal strip moves in a longitudinal direction, an apparatus comprising:

a roller rotatable about an axis transverse to the direction and having a substantially cylindrical outer surface engaged generally tangentially by the strip;

a radially shiftable tension-measuring bar set in the roller, extending generally only angularly of the axis so as to lie in a plane substantially perpendicular to the axis, and having an outer surface generally flush with the roller surface; and

sensor means between the bar and the roller for measuring radial deflection of the bar;

a planarity-measuring bar also set in the roller, extending at an acute angle to and across a respective plane perpendicular to the axis, and having an outer surface generally flush with the roller outer surface; and

sensor means between the planarity-measuring bar and the roller for measuring radial deflection of the planarity-measuring bar.

5. The apparatus defined in claim 4 wherein both the bars extend essentially over the same angular extent.

6. The apparatus defined in claim 4 wherein the tension-measuring bar is positioned generally centrally in the roller.

7. The apparatus defined in claim 4 , further comprising

control means connected to both of the sensors for comparing an output of the tension-measuring sensor from the output of the planarity-measuring sensor.

8. The apparatus defined in claim 7 wherein the control means subtracts the tension output form the planarity output.

9. A method of detecting planarity errors in a metal strip passing in a direction over a planarity-detecting roller rotatable about an axis transverse to the direction and having

a substantially cylindrical outer surface engaged generally tangentially by the strip,

a radially shiftable tension-measuring bar set in the roller, extending generally only angularly of the axis so as to lie in a plane substantially perpendicular to the axis, and having an outer surface generally flush with the roller surface, and

a planarity-measuring bar also set in the roller, extending at an acute angle to and across a respective plane perpendicular to the axis, and having an outer surface generally flush with the roller outer surface, the method comprising the steps of:

sensing radial inward deflection of the tension-measuring bar and generating an output corresponding thereto;

sensing radial inward deflection of the planarity-measuring bar and generating an output corresponding thereto;

comparing the outputs over time and thereby detecting defects in planarity over the strip.

10. The method defined in claim 9 wherein the outputs are compared by subtracting the output from the tension-detecting bar from the output of the planarity-detection bar.