MEANS FOR DETERMINING FORCE APPLIED TO A ROLL BY STRIP MATERIAL

Abstract: A roll for determining the force applied to it by strip material moving in the direction of its length and engaging part of the periphery of the roll comprises an arbor having a body of elastic material mounted on it. The elastic material is one whose resistance varies in a predictable manner when subjected to compressive forces.

Description: MEANS FOR DETERMINING FORCE APPLIED TO A ROLL BY STRIP MATERIAL This invention relates to a roll for determining the force or distribution of force applied to it by strip material moving in the direction of its length, and. engaging part of the periphery of the roll. The strip material may be paper, plastics or metal and the roll may be used to determine the width, shape, or the force distribution of the strip material or the position of the strip on the roll. It is well known that the shape of strip material can be determined by detecting the variations in tension across the width of the strip as the strip is moved, under tension, in the direction of its length. To this end, a "shapemeter" roll is positioned with its longitudinal axis normal to the direction of movement of the strip and part of its periphery is caused: to engage with a face of the strip as the strip is irrorved under tension in the direction of its length. The coll is rotated as a result of its engagement with the; moving strip and detectors are provided at positions along the length of the roll to detect the forces which are applied to the roll by the strip at these: positions. These forces are representative of tiiei tension- in the strip at the corresponding positions across its width. From a consideration of the tension variation across the width of the strip, it is possible to determine the latent or residual stresses and hence the shape of the strip material. It has been proposed in EP-A-0241280 for a shapemeter roll to comprise a plurality of annular rings fitted side-by-side around a rotatable arbor but separated therefrom by elastic material which permits displacement of the rings towards and away from the az±>xzfτ:.. Means; a provided for determining the displacement of each ring relative to the arbor. According to the present invention, a roll for determining the force applied to it by strip material moving in the direction of its length and engaging part of the periphery of the roll includes an elongate arbor and a body of elastic material mounted on the arbor and located between the arbor and the cylindrical peripheral surface of the roll, characterised in that the elastic material is pressure sensitive and has an electrical resistance which varies in aipredictable manner when subjected to compressive forces. I use r the roll is arranged with its longitudinal axis at right angles to the direction of movement of the strip material. The roll is urged into engagement with one face of the strip material so that the strip material, passes around part of the periphery oifthe; nor .. Εfci∑sy by determining the resistance of the body of elastic material it is possible to determine the force which is applied to the roll by the strip material. Furthermore, from a consideration of the variation in forces applied across the width of the strip, it is possible to determine the latent stresses in and hence the shape of the strip. A sleeve of material, such as plyur.ethane, or metal, or a composite sleeve of polyurethane and metal may be fitted to the peripheral surface of the body of elastic material to protect it from the effects of the strip material continuously bearing against it. In an alternative form of the invention, the body of elastic material is in the form of a plurality of separate portions arranged circumferentially of the arbor. Again, a sleeve may be fitted to the peripheral surface of each portion of the body. The elastic material may be one of a range of piezo-resistive elastomers (PRE) or piezo-electric plastics; (PEP). They form part of a formulated polymer system", who-se electrical resistance or voltage generated varies- as they are subjected to load which gives rise to deformation. The resistance change of the PRE (and PEP) depends on many factors, not only the pressure applied to them, but the factors are such that the change. ozH resistance is predictable. R supplier of one such material is THE GATES RUBBER COMPANY LIMITED of Dumfries, Scotland Alternatively, the material may be a polymer film device sold under the trade mark FORCE' SENSING RESISTOR and available from SERVO DATA COMPONENTS LIMITED of Newbury, Berkshire, England. In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings,, in. whic :- Figures 1, 3, 5, 7 and 9 are sectional side elevations of part of a roll in accordance with alternative embodiments of the invention; and Figures 2, 4, 6, 8 and 10 are end elevations on the line X-x of Figures 1, 3, 5, 7 and 9, respectively. Referring to Figures 1 to 4, a rigid metal arbor 1 is mounted in bearings (not shown) which permit the arbor to rotate about its longitudinal axis 1'. On the periphery of the arbor, and extending parallel to the. longitudinal axis thereof, there are a multiplicity of strips of pressure sensitive elastically deformable mateadial 3. These strips are arranged side-by-side on thes periphery of the arbor and the material is one which has an electrical resistance which varies in a predictable manner when subjected to compressive forces. Surrounding the strips 3 is a sleeve 2 of deformable material, such as polyurethane, and this sleeve p øv.ides an outer cylindrical peripheral surface 5. The sleeve is divided into a plurality of separate portions, each of which is arranged circumferentially of the arbor . In use, strip material moving in the direction of its length is caused to engage part of the peripheral surface 5 and this causes the roll to rotate about its longitudinal axis 1'. The strip applies forces to the sleeve 2 along the length of the roll and the. forces have a component which compress the sleeve 2 aro : apply pressure to the pressure sensitive material 3 " . The changes in resistance of this material is an indication of the co pressive force applied to the peripheral surface 5. The strips of material 3 are provided with electrodes (not shown) which enable the strips, which have the variable resistance, to be connected, for example, in series with a fixed resistor across a source of electrical energy. The variable resistor and the fixed resistor serve as a potential divider and an output can be taken which indicates the change of resistance of the material. The arrangement shown in Figures 3 and 4 is particularly suitable for use when the strip material is likely to damage the flexible material 2 and, consequently, a protective sleeve 4 of a hard material, such as polyurethane or metal or a composite material of polyurethane and metal, is provided in order to protect the material 2 from damage. The peripheral surface of the roll which is engaged by the strip material is thus the outer surface of the protective material 4. In the arrangement shown in Figures 5 and 6, the pressure sensitive material 3 is in the form of separate bands which extend circumferentially around the arbor 1. The bands are covered with a sheath 2 of resilient material, such as polyurethane, and, again, an outer protective sheath 4 is provided. Whether or not this outer sheath is provided depends on the material which will engage the roll and the protective sheath may be omitted if the material is unlikely to cause damage to the material 2. The embodiments shown in Figures 7 and 8, and 9 and 10 are particularly suitable where the strip material is a metal, such as steel. In Figures 7 and 8, the material 3, whose resistance changes with the compressive forces applied to it, is in the form of continuous bands extending circumferentially around the periphery of the arbor and each band has a separate sleeve 2 of polyurethane mounted: a uπxE it. Err. the arrangement shown in Figures 9 and 10, the material 3 is arranged in strips on the surface of the arbor extending in the direction of the length of the arbor and a sleeve 4 of material, such as polyurethane, surrounds the strips. In both embodiments, there are separate roller: car bas l bearings 7 between the outer surface 5 of the material 2 and the strip material that passes over the roll. The arbor 1, the pressure sensitive material 3, the flexible material 2 and the inner race of eaσtr roller or ball bearing do not rotate. They may, however, slowly oscillate to overcome creep effects of the material 3. The outer race of the roller or ball bearings rotate due to the motion of the strip. Downward loads due to tension in the strip will be transmitted through the bearings to exert a pressure on- the. material 3. As before, its electrical resistance change is determined. In use, movement of the strip in the direction of its length causes the outer race of each bearing to rotate about its longitudinal axis and the strip applies forces to each outer race. The forces have a component which displace the race downwardly with respect to the arbor so that axis of the outer race is no longer coincident with that of the arbor. The forces applied to the outer races are a measure of the tension in that part of the strip which engages with each, outer race and, consequently, the displacement of the races, measured by a change in the electrical resistivity of the material 3 as it is compressed, is an indication of the tension across the width of the strip. In some of the ilύstrated embodiments of the invention,.- the roll has been used as a shapemeter roll to determine the shape of the strip, usually metal strip, moving in the direction of its length. In some applications, however, it may not be necessary to determine the shape, but what is more important is to determine the total load or distribution of the load applied to the roll by the strip material or the distribution of the load along the length of the roll. This may be used in a calendering process for direct measurement of force or force distribution. If it is desired to know accurately the width of the strip that is-passed: over the roll, then, by determining the signals from the various strips of material 3, it is clear where the edges of the strip material engage with the outer periphery of the roll and, in this way, the width of the strip can be determined. In all embodiments of the invention the material 3 can be of the form described above and sold by the named manufacturers. Electrodes (not shown) are provided to enable the material to be included in electrical circuits for determining the change of resistance as the pressure applied to the material is varied. The or each body of pressure sensitive mateartsl 3T may be wound in a spiral on the surface of he^ sri∑or. One or more bodies of pressure sensitive material positioned longitudinally of the arbor and one or more bodies of pressure sensitive material positioned circumferentially may be provided on the arbor. These bodies given an indication of the position on the roll of forces applied thereto.

Claims: Claims : 1. A roll for determining the force applied to it by strip material moving in the direction of its length and engaging part of the periphery of the roll, said roll comprising an elongate arbor and a body of elastic material mounted on the arbor and located between the arbor and the cylindrical peripheral surface of the roll, characterised in that the elastic material is pressure sensitive and has an electrical resistance which varies in a predictable manner when subjected to compressive force. 2. A roll as claimed in claim 1, characterised in that a protective sleeve is fitted to the peripheral surface of the body. 3. A roll as claimed in claim 1, characterised in that the body of elastic material is in the form of a plurality of separate portions arranged circumferentially of the arbor. 4. A roll as claimed in claim 3, characterised in that a protective sleeve is fitted to the peripheral surface of each portion of the body. 5. A roll as claimed in claim 2, 3 or 4, characterised in that the protective sleeve is of polyurethane or metal or a combination of polyurethane and metal. 6. A roll as claimed in claim 1, characterised in that the body of elastic material is in the form of a plurality of portions extending in the direction of the length of the arbor. 7. A roll as claimed in claim 6, characterised in that an additional body of pressure sensitive elastic material is arranged on the arbor, said additional body having an electrical resistance which varies in a predictable manner when subjected to compressive force, said additional body being in the form of a plurality of separate portions arranged circumferentially of the arbor. 8. A roll as claimed in claim 1, characterised in that the body of elastic material comprises one or more portions wound spirally on the arbor. 9. A roll as claimed in any preceding claim, characterised in that the arbor is rotatable about its longitudinal length. 10. A roll as claimed in claim 3, characterised in that a ball or roller bearing having inner and outer races is mounted on each portion of the body and where the inner race of the bearing and the arbor are non- rotatable while the outer race is rotatable with respect to the inner race.

Inventors: DOBSON JOHN CLIFFORD, HOPE THOMAS, LAWSON KENNETH THOMAS, SHERMAN PAUL, SWIFT COLIN, DOBSON, JOHN, CLIFFORD, HOPE, THOMAS, LAWSON, KENNETH, THOMAS, SHERMAN, PAUL, SWIFT, COLIN
Applicants: DAVY MCKEE SHEFFIELD, DAVY MCKEE (SHEFFIELD) LIMITED
Application year: 1989
Main classification: G01L5
IPC codes: G01B7, G01L5