GB2181852A - Measuring distribution of tension in strip - Google Patents

Abstract

In a driven or driving roll in a strip mill, for measuring the distribution of strip tension across the width, the roll deflects the strip path and is divided axially into a number of sections (2) resiliently mounted on a central roll-support shaft (8), any defections of said sections being measured by sensitive displacement transducers (5). The transducers may be disposed in a contacting or non-contacting relationship with the sections of the roll. <IMAGE>

Description

SPECIFICATION Strip shape measurement The present invention relates to strip shape measurement and more particularly relates to a segmented roll for measuring the transverse distribution of strip tension over the width of the strip in a hot or cold strip mill.

In the hot or cold processing of metal strip the line tension in the process is often large enough to conceal the small transverse length differences in elastic strain and stress. The high elastic modulus of metals generates large elastic stress differences for very low strains and facilitates the measurement of elastic strain or elongation differentials from differential tension measurements. Deflecting the strip through an angle around a roll or roller imposes load components on the roll which can be measured by a number of methods on axially adjacent segments of the roll. The resolved forces on the various segments reflect the transverse variation of elastic stress and elongation across the strip width.

Several such rolls with load sensing segments have been used in metal strip processing for some years, generaiiy with the load sensing incorporated in the roll itself. All such rolls are limited by the temperature or load level which the load sensing technique can withstand. More recently rolls with their segments supported by wheels or rollers mounted on load sensing elements have been proposed in order to move the load sensing elements to a less hostile environment. This benefit is obtained in most cases at the expense of increasing the number and cost of load sensing elements involved or of distorting the load sensing when two or more support rollers bear on the same sensing element.

The present invention seeks to avoid the disadvantages of the prior art and to widen the application and usefulness of differential tension sensing for shape measurement.

The present invention provides a driven or driving roll in a strip mill for measuring the distribution of strip tension across its width, said roll deflecting the strip path and being divided axially into a number of segments resiliently mounted on a central roll-support shaft, any deflections of said segments being measured by sensitive displacement transducers.

The transducers may be disposed in a noncontacting relationship with the segments.

Preferably the transducers are calibrated to yield load measurements. The transducers measure the deflection of the surface of each segment in the direction of the resolved load or along mutually perpendicular axes. The displacement signals are processed by suitable circuits or microprocessors to measure the tension in the strip over each segment and, provided either the angle of approach or departure of the strip is fixed, a variable angle of deflection over the sensing roll can also be evaluated. Indeed where the angle of the strip is measured this may be effected to calculate coil diameter or weight. Additional displacement transducers may be used to monitor thermal expansion.

The limited elastic deflection of the segments, obtained by employing a resilient mounting material suitable to the loading involved, allows the segments to be driven by the central arbor without excessive torsional deflection. The sensing roll may thus act as a pinch or driving roll as well as an idle driven roll.

In order that the invention may be fully understood, some embodiments thereof will now be described, by way of example, with reference to the accompanying drawings which: Figures 1 and 2 show schematic side and end elevations, respectively, of one form of the invention; Figures 3 and 4 show end elevations of two other forms of the invention; Figure 5 shows a detail of a roll segment; Figures 6 and 7 shows facilities for nuilifying thermal effects in respect of the Fig. 1 and Fig. 2 embodiments, respectively; and Figure 8 shows a yet further form of this invention.

Referring now to Figs. 1 and 2 there is shown one embodiment of a tension sensing roll where the strip geometry does not vary.

The roll is divided axially into a number of segments the barrel 1 of each being mounted on a resilient elastic annulus 2 surrounding a central arbor 8. The deflection of each segment along the direction of the resolved force due to the tension in the strip 4 is measured by one or two sensitive displacement transducers 5, according to the width of the segment. To prevent excessive deflection and possible damage due to over-load, end plates 6 are fitted to both ends of each segment with a predetermined clearance 7 from the central arbor. The clearance is set at a value which transfers the imposed load on the barrel 1 via the end plates 7 to the arbor when the imposed load exceeds the range of measurement required.

Fig. 3 shows a second embodiment of the tension sensing roll where either the angle of approach or of departure of the strip changes.

Two rows of displacement transducers 9 and 10 with their measurement axes mutually perpendicular measure the displacements of the barrel of each segment to assess the strip tension and the angle of deflection of the strip.

Fig. 4 shows a third embodiment, where the barrel 1 of the segments is separated by radial webs 11 from an inner sleeve 12 which encloses the elastic annulus 2, in order to limit the heat conducted from hot strip to the elastic material 2.

Fig. 5 shows a typical chamfer of radius 13 at each end of the barrel 1 of the segments, to reduce the risk of marking the strip when the differential deflection of adjacent segments is large.

In all cases deflections of the barrel due to thermal effects may be detected and nullified by measuring such effects by a diametrically opposed pair of displacement transducers 14, 15 as in Fig. 6 for a roll operating under constant strip geometry, or by one or more such transducers 16 disposed diametrically opposite to one of the rows of transducers (9) used for load sensing as in Fig. 7.

The displacement transducers which are used to measure the deflections may be of any suitable type such as inductive, capacitive or air gauge, e.g. as described in out patent application publication No. 2136128A.

The use of certain types of displacement transducers of small size, permits the width of the individual roll segments to be made correspondingly small, allowing fine discrimination of the transverse tension distribution in the strip. Transducers suitable for a segment width of 15mm already exist and even smaller sizes may ultimately be accommodated.

Finally, when the deflection is necessarily very limited it may be measured by stiff load sensing cantilevers as in Fig. 9, cantilevers 17-constituting bending beam load cells-holding rollers 18 in contact with the barrel segments.

Claims (11)

1. A driven or driving roll assembly in a strip mill for measuring the distribution of strip tension across its width, said roll deflecting the strip path and being divided axially into a number of segments resiliently mounted on a central roli-support shaft any deflections of said segments being measured by sensitive displacement transducers.

2. A roll assembly according to Claim 1, in which the transducers are sited to measure deflection in the direction of the resolved load.

3. A roll assembly according to Claim 1, in which the transducers are sited to measure deflection along mutually perpendicular axes whereby to assess both strip tension and the angle of deflection of the strip.

4. A roll assembly according to Claim 3, in which the transducers include a pair sited parallel to the tangent to the line of strip/roll contact whereby to monitor and or compensate for thermal changes.

5. A roll assembly according to any one of Claims 1 to 4, in which the transducers measure the angle of deflection of the strip over the roll.

6. A roll assembly according to any one of Claims 1 to 5, in which the transducers are disposed in a non-contacting relationship with the segments.

7. A roll assembly according to Claim 6, in which the transducers are air gauge devices according to the disclosure in patent publication No. 2136128.

8. A roll assembly according to any one of Claims 1 to 5, in which the transducers are in contact with the segments.

9. A roll assembly according to Claim 8, in which the transducers are mounted as stiff load-sensing cantilevers constituting bending beam load cells.

10. A roll assembly, according to any one of Claims 1 to 9, in which the resilient mounting is housed within an inner sleeve, the roll surface proper being supported on this sleeve by radially extending webs whereby to reduce heat transfer to the resilient mounting.

11. A roll assembly, substantially is herein described with reference to Figs. 1 to 8 in the accompanying drawings.