GB713105A - Improvements in and relating to the measurement of thickness in the production of sheet and strip material - Google Patents

Abstract

713,105. Electric analogne calculating systems. BRITISH IRON & STEEL RESEARCH ASSOCIATION. Nov. 25, 1952, [Nov. 27, 1951.] No. 27797/51. Class 37. [Also in Groups XXII and XXXVIII] A method of measuring the thickness of sheet or strip emergent from a rolling or drawing mill comprises the derivation of a 1st signal proportionate to the separating force on the rollers or dies, and a 2nd signal proportionate to the setting of the rollers or dies the proportionality factor of the 1st signal being a predetermined number of times greater than that of the 2nd signal and determined by the elasticity of the mill structure, and the signals being added to give a sum signal representative of the thickness of the emergent material. In Fig. i the slider of a potentiometer R 2 energized from a battery B 2 through a variable resistance P 2 determining the proportionality factor is adjusted in accordance with the required mean thickness h<SP>1</SP> of material emerging from a rolling mill (Fig. 3) wherein rollers 23, 24 may be set to a predetermined separation by a screw 27 co-operating with worm gearing 26 driven by a handwheel 25 to produce a representative voltage which is connected to a zeroizing slider 11 of potentiometer Ri energized through a variable resistance P I determining the proportionality factor from battery Bi; the operative slider 10 of which is adjusted in accordance with the roll setting So of the mill by e.g. rotating a drum 29 carrying the resistance winding 30 past a fixed sliding contact 31 engaging the wire. A stress indicator 28 such as that described in Specification 626,206 comprising four resistance strain gauges connected in a Wheatstone bridge 12 is supported in the mill structure to respond to the mean separating force F exerted on the rollers during passage of the material and is energized from a battery to produce an unbalance voltage (measurable by meter M 2 ) representing the quantity F - where M is a proportionality constant depen- M dent on the elasticity of the mill structure and a predetermined multiple of the constant affecting the roll setting. It is shown that if #h is the difference betewen the required mean thickness h<SP>1</SP> and the mean thicknesses produced, and the representative voltages are thus combined in appropriate polarities at the input of an interrupter type D.C. amplifier 16 whose output energizes a centre zero meter MI calibrated to indicate the difference in thickness #h. The apparatus is zeroised by adjusting slider 11 for zero difference indicating when the separating force, roller setting, and required thickness are alike zero. The resistance drum 3 o may be replaced by a disc, rotatable direct or through gearing or through a magslip transmission from screw 27, having a resistance wire round the periphery, while the output of amplifier 16 may operate a pen recorder inscribing the varying thickness of emergent strip over the length of a run. The signals which are to be combined may be derived in terms of other physical quantities e.g. fluid pressures or mechanical displacements whose values are derived in accordance with the requisite variables.