US3534571A - Rolling mill control - Google Patents

Rolling mill control Download PDF

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US3534571A
US3534571A US713150A US3534571DA US3534571A US 3534571 A US3534571 A US 3534571A US 713150 A US713150 A US 713150A US 3534571D A US3534571D A US 3534571DA US 3534571 A US3534571 A US 3534571A
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Prior art keywords
strip
signal
roll
control
rolling load
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Olivo G Sivilotti
Maurice W Tulett
William E Davies
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Alcan Research and Development Ltd
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Alcan Research and Development Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/28—Control of flatness or profile during rolling of strip, sheets or plates
    • B21B37/38—Control of flatness or profile during rolling of strip, sheets or plates using roll bending
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/68—Camber or steering control for strip, sheets or plates, e.g. preventing meandering

Definitions

  • Means for sensing ilatness or off-flatness of the rolled strip may automatically provide part or all of the ⁇ first above-mentioned factor of bending jack force adjustment, advantageously at a slower rate than the rolling load control, and may include supplemental manual and signal-holding control arrangements as well as means to account for other or longer-term factors affecting strip shape, a further feature being means differentially responsive to off-flatness adjacent to the respective strip edges for adjusting the screwdowns on the chocks at opposite ends of the rolls in different directions to correct unbalance when it occurs between the screwdown load forces.
  • This invention relates to the rolling of metal strip, and in a special sense is concerned with apparatus and methods for regulating or governing rolling operations with a 4-high mill to achieve a predetermined cross-sectional configuration of the work roll gap or bite, particularly by automatic control of roll deflection, as for the purpose of attaining a desired flatness of the sheet product.
  • the present improvements are concerned with rolling reduction of metal in sheet form, as for example where a strip of aluminum (including aluminum alloys) having continuity over a relatively long length, is passed through the mill to reduce its thickness or gauge, by virtue of the rolling pressure exerted between the work rolls.
  • the invention is of advantage in cold rolling operations for aluminum strip and is therefore so exemplified below, it is conceived that the apparatus, systems and procedures are applicable to other metals and to other types of rolling such as hot rolling.
  • Particular aims of the invention are to provide means and methods for readily taking into account various circumstances which affect the shape or surface configuration of the rolled strip, including particularly factors which tend to deform or deflect the rolls and thus in turn to modify the flatness or other desired shape of the product, as well as its gauge.
  • the indicated factors tend to modify the roll gap, i.e., the space which is defined by the working surfaces of the rolls that engage the strip, to the extent that departures from parallelism of this gap, under rolling condition, will produce greater or less ofl-flatness.
  • the longitudinal bands or sections of the strip not only vary in actual thickness but are differently elongated by the rolling function, so that the areas of metal considered from place-to-place across the strip are nonuniform in length in the direction of rolling.
  • These lengthwise bands are generally longer at the thinner regions of the rolled sheet product.
  • Such nonuniformity of length is conventionally defined as off-flatness, being usually evidenced by waves, pockets or other detectable departures from straightness and flatness of the strip. 'In other words, this nonuniformity is exhibited by actual bends or waves in one portion or another of the sheet, as well as by varying thickness or gauge across the product.
  • the present improvements are designed to provide control of the rolling operation and especially of roll deflection, in a basically automatic manner and in such way as to minimize or essentially obviate undesired departures from ilatness or from uniformity of other selected configuration.
  • the rolling load must ordinarily be decreased substantially, i.e., by adjusting the screwdown pressure, as the mill is brought up to speed, and adjustments during the pass are often needed or occur in order to maintain gauge, Whether by automatic or manual gauge control.
  • Variations in hardness of the metal, or in thickness of the entering strip are also among the factors that require or may indeed occasion (for a given screwdown setting) change in rolling load. All of these and other factors alter the elastic deformation of the work rolls, in a manner which cannot be precompensated and which is detrimental to desired strip shape, eg., flatness.
  • the thermal effects may also vary, and although these changes are not of such rapid occurrence between the beginning and end of a single pass, there may be variations between passes.
  • a factor of similar eect is the surface wear of the work rolls.
  • Supplemental adjustments or control features have been proposed or used for aid in achieving llatness, such as various arrangements of special jacks, between the chocks of the several rolls, to apply supplemental forces to bend the rolls elastically.
  • so-called balance jacks have been placed between the chocks of the upper and lower work rolls at each end of the latter, so as to apply, at the roll axes, a bending force in opposite direction to the effect of rolling load on the strip in bending the rolls toward each other near their ends.
  • it has been proposed to change the pressure in these jacks in some automatic response to changes of screwdown load, but no way of achieving a properly proportional response, or of doing so conveniently, has been available.
  • response to changes of rolling load and for the purpose of maintaining strip shape can be effectuated by adjustment of bending force on the work rolls7 when such adjustment is provided as the sum of two factors, namely a basic shape adjustment that takes care of thermal effects and that may be achieved, for instance, when the mill is running slowly at the start, and a factor that can then depend automatically and proportionately on the actual rolling load, for example as sensed by load cell means between the chocks of the upper backup rolls and the screwdown or between the lower backup roll chocks and the frame or base of the mill stand.
  • the proportionality of change of work roll bending force to change of rolling load varies linearly with the width of the strip being rolled (a greater change of applied bending force being required to compensate a given increment of change in rolling load for narrower strip, and a lesser change for wider strip), and can therefore be so set for each pass, as by a control element reading in units of width.
  • change in roll bending force (as the difference of pressure of balance and contour jacks) can thereafter be effected in proportion to the proportioned rolling load signal, in a way that compensates or accommodates the effects of rolling load variation with unusual accuracy, for achieving a high degree of flatness or other uniformity of strip shape.
  • a useful embodiment of the present system thus includes bending jack means for the work rolls, means for sensing the rolling load and servo or like means for adjusting the pressure of the bending jack means from a control organization responsive to the sensed rolling load.
  • the control instrumentalities include two elements of bias or quantity that jointly coact in governing the servo means.
  • One such quantity is a first signal that is preliminarily, or from time to time, adjustable for the basic, desired shape of the roll gap.
  • This adjustment conveniently manual, affords a base or nominal setting of the bending f'orce of the jack means; it has been discovered that the setting of this rst signal remains effective at all rolling loads, although the actual value of bending force is changed by the second signal or control.
  • Such second signal being the principal and automatic control, is the reading of actual rolling load
  • the basic controlling quantity or signal is that of the rolling load, and the system and method are practicable simply in response to load cell determinations of screwdown force as noted above, greater accuracy and superior results have been achieved by a control effected in accordance with the rolling load as exerted at the line of contact between the backup rolls and the work rolls.
  • the load cell signal which measures the screwdown force can be utilized as diminished by a corresponding signal -derived from the pressure in the contour jacks.
  • the net rolling load signal (which is adjusted, in its proportional significance, according to strip width) is conveniently determined as the screwdown load minus the opposing load exerted by the contour jacks, the latter value, of course, being very substantially smaller than the screwdown load, particularly so at normal values of the latter in high speed operation.
  • general references herein to rolling load or rolling force as a control quantity are intended (unless otherwise expressed) to be understood in a generic sense, meaning such value whether or not it is diminished by the contour jack load; but as stated, optimum results have been achieved in the latter case.
  • the invention is also designed to accommodate automatically, in cooperation with the automatic control of work roll deflection, two conditions that occur successively at the end of a rolling pass.
  • the strip When the tail end of the strip leaves the supply reel, losing back tension, there is a tendency for the strip to move sidewise in one direction or the other, so as to be improperly aligned for passage between the rolls and for rewind in the finished coil.
  • a small signal is introduced in the control in opposition to the rolling load signal, whereby the servo system causes the bending jack means to function as if there were a reduction of rolling load.
  • the roll gap is caused to assume a crown rather than a parallel shape, with the effect of keeping the strip centered and preventing its wandering to either side.
  • the invention preferably includes a delayed response from the back tension sensing signal, timed to be effective shortly before the tail of the strip reaches the gap, so as to introduce a considerable attenuation in the signal circuit which controls the servo function, i.e., the circuit into which the rolling load signal is continuously supplied.
  • the control system would normally tend to operate the bending jacks as if to drive the work rolls toward each other, e.g., by increasing the pressure greatly in the contour jacks and reducing it in the balance jacks, but the attenuation which has now been inserted in the control circuit prevents any such rapid response and indeed only permits a very small or slow alteration of the bending jack forces.
  • a separate signal directly responsive to loss or to rapid reduction of rolling load, may operate to substitute a special control quantity for all of the automatic bias values, such as to drive the bending jack means in a direction to maintain the desired contact between each work roll and its backup roll. Tn this fashion, skidding or other malfunction at the very end of the pass is automatically averted and the balance jacks are brought into full and essentially sole play, so that the mill can be brought to rest in proper condition.
  • the described system affords an effective automatic control of roll deflection throughout a selected pass, in such fashion as to maintain the desired strip shape, e.g., a high degree of flatness, at all times.
  • Initial setting of the control is only required in two respects, in accordance lwith the width of the strip being rolled, and by a separate instrumentality, in order to achieve desired fiatness or parallelism of the roll gap at the very beginning of rolling operation when the strip is moving slowly and the attendant can readily determine the attainment of the desired condition, e.g., by visual observation.
  • the deflection of the rwork rolls is automatically adjusted whenever necessary so as to preserve the desired strip shape or roll gap configuration, Changes in rolling speed, changes in hardness of the strip, adjustments whether manual or automatic to maintain gauge, and like Variations, are all compensated accurately by suitable change in the bending force on the ends of the work roll axes; guesswork by the operator is eliminated.
  • the thermal crown or thermal effects may vary, such change is of a very slow nature and ordinarily does not occur to a significant extent during a pass, unless the time between passes has been unduly long with corresponding significant cooling of the rolls.
  • the operator can adjust the initial shape control during the run, and indeed to do so he may reduce the tension or even slow the mill down for observation of the strip, without any interference whatever as to the automatic control function in response to change of rolling load.
  • the system may also, as described below, include automatic means that supplementarily alter the roll bending forces so as to compensate for changes of roll shape due to thermal drift, wear or other phenomena responsible for slow changes in strip flatness.
  • this system is further such as to compensate for the special requirements of loss of back tension and loss of rolling load as the tail end of the work approaches and leaves the mill.
  • the strip is steered in proper alignment and a balance function of mill operation is automatically assumed, replacing the regulating mode during this final brief period, whereby the work rolls are kept against the backup rolls when the mill is brought to a halt.
  • FIG. 1 is a diagrammatic view of basic elements of a system according to the invention, shown in simplified form;
  • FIG. 2 is a side view of a rolling mill for strip, simplified as to detail, including certain elements of the invention and also including circuit diagrams of supplemental control instrumentalities;
  • FIG. 3 is a hydraulic circuit diagram, in simplified form, appropriate for control of a mill as shown in FIG. 2 and employed with further instrumentalities as in other views;
  • FIG. 4 is a schematic diagram of electrical and electronic control arrangements, appropriate for governing the hydraulic system of FIG. 3, in association with instrumentalities as shown in FIG. 2;
  • FIG. 5 is a schematic diagram showing additional features of automatic strip shape control, exemplified as related to FIG. 4.
  • FIGS. 1 and 2 the invention is illustrated as applied to a 4-high mill 10 including upper and lower backup rolls 12, 14, having their necks or shafts respectively carried in conventional chocks 13, 15, and arranged to bear on upper and lower work rolls 16, 18, which in turn are respectively carried, at their necks or shafts, by chocks 17, 19.
  • the entire assembly is supported in the usual frame or housing 20, with conventional screwdowns indicated schematically at 22 and bearing on the upper backup roll chocks 13, with appropriate gearing or like drive as indicated at 23 for adjusting the pressure applied by the screwdowns to the rolls.
  • balance jacks 28 are interposed between the upper and lower work roll chocks 17, 19, and contour jacks are similarly interposed between the work roll chocks and the upper and lower backup roll chocks, i.e., jacks 30 between the upper work and backup rolls, and jacks 31 between the lower work and backup rolls.
  • All of these jacks may be of known, conventional nature such as heretofore sometimes employed (under manual control), being rugged hydraulic cylinders with heavy plungers, arranged to exert force between the associated roll chocks upon introduction of hydraulic liquid under pressure.
  • FIG. 1 indicates, for simplicity, a single jack on each side at each locality.
  • all jacks of a given situation are hydraulically connected in parallel, as for example in reference to FIG. 2, all of the four upper jacks 30 (including the opposite pair, not shown) are Supplied simultaneously from a single conduit for hydraulic liquid under pressure, the same being likewise true of the entire set of jacks 28 and the set of jacks 31. Identification of these devices as balance and contour jacks is 'in accordance with known terminology for jacks so situated.
  • This complete system of jacks constitutes means for applying bending force to the necks of the work rolls, relative to the entire stand of rolls as engaged by the screwdown, the direction and extent of such force being dependent on the relative values of initial pressure and resulting displacement of the jacks coacting on each work roll.
  • the pressure of the contour jacks predominates, the ends of the ⁇ work rolls tend to be bent toward each other, as to overcome a thermal crown of the rolls, or to create a crowned roll gap between what might otherwise be parallel roll surfaces, while predominance of pressure in the balance jacks, over the contour jacks, tends to bend the work rolls away from each other at their ends, as for example where desired to overcome a crowned or bulging roll gap that would otherwise exist.
  • the entire assembly is, as stated, maintained under rolling pressure, i.e., for desired reduction of the aluminum or other metal strip 35 traversing the bite of the work rolls 16, 18, by the screwdowns acting through the backup roll chocks and the rolls of the stand, against the base 36 of the mill.
  • the strip to be rolled is supplied from a coil 38 carried on a reel or shaft 39 provided with appropriate drag or mechanical resistance means (not shown) to maintain back tension on the portion of strip 35a traveling to the work rolls, while the rolled strip of desired reduced gauge, traveling from the mill as at 35h is rewound in a coil 40 on an appropriate reel on a shaft 41, which is driven by means of the usual sort, indicated by the legend at 41a.
  • the function of the present system and method is to maintain a desired uniformity of the roll gap, notably a configuration of parallelism appropriate to maintain flatness, the roll gap being the space between the work rolls 16, 18 that is occupied by the passing strip 3S while the latter is 1educed in gauge by the force or load between these ro s.
  • FIG. l Iwhere the roll stand 10 is shown schematically as indicated above, the hydraulic liquid connection to the upper and lower contour jacks 30, 31 is provided by conduit lines 40, 41, joining in a common pipe or conduit 42, while similar hydraulic connection to the balance jacks 28 is provided by a pipe or conduit ⁇ 44.
  • Hydraulic liquid e.g., suitable; oil, water or other liquid, oil of appropriate character being preferably employed as is known for jack systems of this sort, is supplied to or discharged from the balance and contour jack systems in appropriate manner (with the systems kept filled as required, when no flow of liquid is taking place) by a control valve assembly, as for instance an electro-hydraulic servo-valve 50 (an example being such a valve as manufactured by Moog, Inc., U.S.A.), having an electrical control coil 52 that is shown both in location in the valve and diagrammat ically in dotted lines for convenience of circuit illustration. Hydraulic liquid is supplied under high pressure to the valve through a conduit line 54 and such liquid is discharged as to an appropriate reservoir through a line 56.
  • a control valve assembly as for instance an electro-hydraulic servo-valve 50 (an example being such a valve as manufactured by Moog, Inc., U.S.A.), having an electrical control coil 52 that is shown both in location in the valve and diagrammat ically
  • the basic control of the invention is exerted in proportion to rolling load in the mill 10, or changes of such load, and is advantageously sensed in a continuous manner by suitable means for detecting pressure or force, as for example by load cells or load cell assemblies which can be embodied between the screwdown on each side and the upper backup roll chocks or between the lower backup roll chocks and the base or frame of the mill, FIG. 1 showing for example a pair of such load cells 60, 60 in the latter location.
  • load cells or load cell assemblies which can be embodied between the screwdown on each side and the upper backup roll chocks or between the lower backup roll chocks and the base or frame of the mill, FIG. 1 showing for example a pair of such load cells 60, 60 in the latter location.
  • These cells may be of any suitable, known character, as of the magneto-elastic type or as constituted by wire-type strain gauge assemblies, cells of the magnetic or magneto-elastic nature being selected for embodiment in the systems here described.
  • the cells 60 are suitably connected together, with appropriate summing means (not shown) if necessary, and their electrical response is applied through an appropriate readout circuit 62, of known, conventional character for such purposes, so as to yield an electrical signal at the terminals 63, 64 of the latter device that varies in magnitude in proportion to the total rolling load or force of the mill.
  • the positioning of the servo-valve 50 is effected by its electrical coil or winding 52 which in turn is controlled by the rolling load signal derived from the terminals 63, 64. While other types of control system can be used for operating this or other valve control for the bending jack assembly, notably effective results are attained with a feedback arrangement, i.e., wherein a signal from the bending jack means is supplied in opposition to the basic control signals in the circuit for the servo coil 52, and such system is therefore illustrated by way of example, the function being to cause the current in the coil to return to an appropriate value, eg., zero, after each change of bending jack situation has been brought about.
  • the coil 52 is shown as having a simple, series control circuit 65, which when unbalanced supplies an operating signal to the terminals 66, 67 of the coil, if desired through an appropriate amplifier 68 or like device, e.g., to supply current to the coil in accordance with the presence of a voltage signal in the circuit 65.
  • the terminals ⁇ 63, 64, carrying the primary rolling load signal, are connected across the input of a potentiometer 70, having an adjustable, reduced output at the terminals 71y 72, shown for simplicity as a part of the control circuit 65.
  • a separate bias signal is also applied in the same series circuit at the terminals 73, 74, being the output of an adjustable electrical source such as the voltage source 75, here shown as comprising an appropriate voltage supply 76 across the input of a potentiometer 77.
  • suitable pressure transducers 80, 81 have liquid pressure sensing connections, indicated by the lines 82, 83, respectively extending to the liquid supply system 40, 41, 42 of the contour jacks and to the liquid supply line 44 of the balance jacks.
  • Devices Suitable for this purpose are known, and need not be described in detail, each being adapted to yield an electrical signal across its output terminals, proportional to the sensed pressure.
  • all of the signal-delivering means are shown as direct current devices, e.g., interposing a corresponding D.C. signal voltage in the control circuit 65.
  • the outputs of the pressure transducers are illustrated as connected in series but in opposed relation respecting their electrical polarity, thus providing at the terminals 86, 87 a signal which, in effect, varies in accordance with the difference of pressures in the contour and balance jack systems to represent a totalized measure of the bending force (in direction and value) applied to the necks of the work rolls.
  • These terminals 86, 87 form part of the circuit 65, serving to introduce the feedback signal, in generally opposing relation to the control signals, or their net result, as derived across the terminals 71, 72 and 73, 74.
  • the :rolling load signal is a varying D.C.
  • the shape bias signal is in this instance selected as a D.C. voltage of polarity opposite to the load signal, i.e., its terminal 73, on the side toward the opposite terminal 67 of the coil 52, being positive in polarity.
  • the feedback signal will be of positive polarity at the terminal 87, nearest the terminal 67 of the coil 52, while it will be of negative polarity at such terminals (and positive at the terminal 86) if the contour jack forces predominate, e.g., if the necks of the work rolls are bent more or less toward each other.
  • the function of the complete circuit extending to the servo coil 52 is to establish a current in this coil upon unbalance of the circuit 65, of direction and extent corresponding to the direction and extent of unbalance.
  • the valve 50 is then actuated in corrective direction and amount, i.e., so as to increase the pressure in one of the contour and balance jack sets and decrease it in the other, until change of reading of the transducers 80, 81 restores balance to the circuit.
  • the system is also self-correcting, in that if an error signal appears because of leakage or other departure of the balance jack means from desired condition, the coil 52 and valve 50 will function to restore such condition in the same manner.
  • the device 50 shown for example is suitable, being a known structure of electromagnetically actuated character, including a hydraulic amplifying stage for shifting the valve.
  • the device has a sliding spool assembly 90 which carries three spaced closure rings 91, 92 and 93 normally disposed in closing relation, respectively, to a discharge port 95, a liquid supply port 96 and another discharge port 97, the discharge ports being connected together and to the outlet conduit 56.
  • a sliding spool assembly 90 which carries three spaced closure rings 91, 92 and 93 normally disposed in closing relation, respectively, to a discharge port 95, a liquid supply port 96 and another discharge port 97, the discharge ports being connected together and to the outlet conduit 56.
  • ports 95, 96 and 97 are ports 98 and 100 respectively connected to the contour and balance jack lines 42 and 44, and closed from either the inlet port 96 or the outlet ports 95, 97 by the adjacent rings 91, 92 and 93 in their null or balanced position.
  • the coil 52 is an annular winding suspended in the manner of the voice coil of a permanent-magnet speaker in an annular space between opposite poles 102, 103 of a permanent-magnet assembly, the pole 102 being a circular ring around the outside of the coil and the pole 103 being a central, cylindrical element within the coil, the magnet structure being completed by a central portion 104 eX- tending to the pole 103 and connecting portions 105, 106 which may be the permanently magnetized parts, the magnetic circuit thus providing an annular gap in which the coil 52 may float.
  • the coil 52 carries a supporting spider or cone 108 which extends to a centering pin or target element 110, that in turn, through a diaphragm 112, is urged by pressure of a coil spring 113 toward the opening of a nozzle 115.
  • the nozzle leads from a chamber 116 continuously supplied with fluid under pressure (through a suitable inlet orifice) from a bypass 118 leading around the closure ring 92 to the inlet port 96. From the outer side of the orifice, i.e., beyond the nozzle, a passage 120 including an outlet orifice, leads to the discharge port 97.
  • the chamber 116 also communicates, through a small passage, with the end portion 122 of the chamber in which the spool 90 slides, whereby the pressure of the liquid in the chamber 116 in effect continuously urges the spool in one direction, being to the left as shown, such force being normally balanced by a spring 124 which is under compression at the other end 0f the spool and is adjustable for balance (with zero current in the coil 52) by turning the screw 125 against the opposite end of the spring.
  • the design and adjustment of the parts including the 1 1 force of the spring 113 and the setting of the spring 124 are such that when the coil 52 exerts no force, the target assembly 110-112 limits the discharge of fluid from the chamber 116 through the nozzle 115 sufficiently to maintain just enough pressure in the chamber space 116-122 to keep the valve spool 90 in the neutral position illustrated. If current fiows through the coil in a direction to urge it to the left, for example, the target assembly tends to close the nozzle, correspondingly increasing the pressure in the chamber 116-122 and thus moving the spool to the left against the spring 124. This action brings the liquid inlet port 96 into communication with the balance jack port 100, while similarly opening a passage between the contour jack port 98 and the discharge port 95.
  • control device 77 By observation of the slowly issuing strip, or other measurement as may be available to the operator, the control device 77 is now set until, through the instrumentality of the coil 52 and the servovalve 50, the bending jack means have been adjusted to establish a desirably fiat condition, e.g., an effective parallelism of the work roll surfaces along the lines of engagement with the strip at the bite or gap. The adjustment is thus completed when the slow-moving strip is observed to be appropriately flat.
  • a desirably fiat condition e.g., an effective parallelism of the work roll surfaces along the lines of engagement with the strip at the bite or gap.
  • the work rolls are highly heated, as from an immediately preceding pass and thus tend to have a fully developed thermal crown. It may also be assumed that the rolls have been ground with a slight concave, so that the thermal crown is partially compensated by the initial roll shape, there still remaining (with no load) a small roll crown, in effect.
  • the mill being threaded with strip and running slowly, the rolling load (applied screwdown force) may be considerable, as is usual in starting, and a correspondingly high signal from the rolling load appears at terminals 71, 72.
  • this high rolling load bends the ends of the work rolls toward each other, not only overcoming the residual thermal crown but in fact producing a concave, causing a central bulge of the roll gap.
  • the shape control 77 is then adjusted to provide a fiat configuration of the issuing strip, i.e., to bring the roll surfaces at the bite into parallelism. Under the conditions of this example, the adjustment will be such as to produce some predominance of pressure in the balance jacks, over the contour jacks.
  • the bias signal at the terminals 73, 74, resulting from the shape control will be equal to the algebraic sum of the magnitudes of the rolling load -signal at 71, 72 and the feedback signal (then neagtive at the terminal 86) from the pressure transducers 80, 81.
  • the shape bias signal is the amount by which the load signal (71, 72) must be diminished to equal, arithmetically, the feedback signal that represents the jack-applied bending force required for parallelism.
  • the shape bias signal will thereafter remain at this value, unless the operator finds, as he may, that thermal conditions have changed to a point requiring readjustment of the shape control 77.
  • the operator may then bring the mill up to speed, with accompanying decrease of the screwdown load, as may be conventional.
  • the decrease of rolling load is sensed by the load cells 60 and results in a corresponding decrease of rolling load signal at the terminals 71, 72.
  • This unbalance of the circuit causes operation of the servo valve 50 in the manner described above, specifically in a direction to increase the pressure in the contour jacks and to decrease it in the balance jacks.
  • FIG. 3 A more detailed diagram of a suitable hydraulic circuit is shown in FIG. 3, but nevertheless simplified with respect to conventional structure or features of a hydraulic system that are not a part of the present invention.
  • Suitable hydraulic liquid is stored in a tank from which it is withdrawn by a pump 131 to be delivered in the high pressure conduit 132 through appropriate valves including a check valve 133.
  • the line 132 extends to the inlet 54 for the servo valve, from which the output line 56 runs through a spring-opposed check valve 134 to a main return conduit 135, whereby the liquid can be discharged to the tank.
  • the pressure of liquid in the supply lines 132, 54 is kept at a constant, high value by cooperation of a conventional accumulator 137 functioning to accommodate transient changes, and a pressure relief valve 138 which extends from line 132 to the return line and which is set to maintain a preselected maximum supply pressure.
  • Line 44 extends from the servo valve 50 toward the balance jacks through a manual, normally open valve 140 and a remotely controllable valve 141, the latter being operable, when desired, by deenergization of a solenoid 142, to shift the work roll balance jack input 44a to drain into the line 135.
  • the contour jack supply line 42 extends through a manual valve 144, normally open, to the lines and 41 respectively leading to the top and bottom contour jacks, through remotely controllable valves 146, 147, similar to the valve 141.
  • the valves 146, 147 are normally held in position connecting the lines 40, 41 to the contour jack feed lines 40a, 41a.
  • the pressure transducers 80, 81 see also FIG.
  • a check valve 134 advantageously functions to prevent complete draining of the jacks when the line 56 is connected to one or the other of the lines 42 and 44; the spring of this check valve is set to allow opening of the valve only at some low minimum pressure suticient to keep the jacks from collapsing when the system is not in use, but nevertheless of such character as to permit desired drainage from the jacks for the described automatic operation.
  • Appropriate filters are included in the supply line 132, e.g., as indicated at 448 and 449.
  • valves 140, 144 When the automatic system is not operating, the valves 140, 144 can be closed, and normally closed valves 140a, 144:1 can be opened, connecting the high pressure line 132 to the several lines to the remote-controlled valves 141, 147, 146; the latter can then be employed for manual control of the condition of the several jacks, as for example at a time of changing rolls.
  • the servo valve is indicated schematically in FIG. 3 as any suitable device for attaining the desired function, for example the valve so designated in FIG. 1 and arranged, under control of the coil 52, to shift the valve spool or like element in one direction, e.g to the right, to connect the contour jack line 42 with the high pressure line 54 and the balance jack line 44 to the return 56, and in the opposite direction, e.g., to the left, for reverse connection of the lines.
  • the valve spool or like element in one direction, e.g to the right, to connect the contour jack line 42 with the high pressure line 54 and the balance jack line 44 to the return 56, and in the opposite direction, e.g., to the left, for reverse connection of the lines.
  • the displacement of the valve spool 90 is proportioned in amount as well as in direction to the error signal appearing across the coil, so that the rate at which pressure builds up inone of the two groups of jacks (balance and contour) and falls in the other of them is proportioned to the magnitude of change required.
  • the feedback signal from the pressure transducers has changed by the required amount to balance the error signal, reaching a null condition of the circuit 65, the current in coil 52 falls to zero and the valve spool 90 returns to its null position, closing all of the jack hydraulic lines.
  • the hydraulic supply pressure set, by the relief valve 138, to be available in the line 132-54, is selected at a high enough value whereby the difference of contour and balance jack pressures can reach a desired maximum in either direction, corresponding to the contemplated maximum bending of the work rolls at their necks, both toward and away from each other. If the control of the valve 50 happens to require no forcible deflection either way, the contour and balance jack pressures are equal with the Valve in null position; as the desired magnitude of deflection varies in either direction, the difference of jack pressures reached at corresponding balanced conditions of the servo system is necessarily proportional to such magnitude. Maximum deection is obtained when the pressure in one of the sets of jacks reaches the full value of the hydraulic supply and at the same time the pressure in the other set is at minimum, e.g., as determined by the check valve 134.
  • Biased check valves 148, 149 are respectively located in bypass lines between the contour and balance jack conduits 42, 44 and the liquid pressure line 132-54; these valves are strongly biased to remain closed up to a pressure above that of the supply, but if a large pressure surge in the lines 42, 44 (or either of them) occurs, as is possible, at the end of a pass, the servo valve is bypassed and the pressure surge is contained below a safe value.
  • the mill is of prestressed design, involving a special counterforce between the top backup chocks and the bottom backup chocks which is applied, as by jacks, wedges or other means, to put the mill frame and its parts under stress opposing the screwdown force to a minor extent, and which functions to achieve a more rigid assembly, it is necessary to substract this prestress force, in effect, from the signal of the load cells or equivalent means responsive to total screwdown force, in order to have a net rolling load signal for the present control system and method.
  • the mill 10 is shown as prestressed by the use of backup roll balance jacks 150, between the upper backup chock 13 and the lower backup chock 15, it being understood that these and all other jacks shown in FIG.
  • FIG. 2 are duplicated at the other side of the mill.
  • These jacks are connected to the hydraulic system by a manifold conduit 152 (FIG. 3) that has branches which lead to the several jacks 150 (being one, or as shown in FIG. 2, two on each side) in a conventional manner, not shown.
  • a remotely controllable valve 154 similar to the valve 141, hydraulic liquid is supplied to the line 152 by a line 155 from the liquid pressure supply line 132.
  • the system is shown for simplicity (in FIG. 3) as keeping these jacks under full pressure of the system, applied as or before screwdown force is initiated at the beginning of a rolling pass.
  • means for producing a net rolling load signal across a pair of electrical conductors 156, 157 are schematically shown as including an instrumentality 158 that provides a readout to total backup balance jack force in suitable electrical terms, shown for simple illustration as a voltage across conductors 159, 160.
  • the device 158 may include pressure transducers of conventional sort (not shown) connected through hydraulic pressure-conducting lines 162 to the backup jacks 150 or their supply conduits, and appropriate electronic or other electrical means which may involve appropriate circuits of known character (likewise not shown) for producing an output voltage that is representative of the sum of the backup jack forces.
  • a suitable readout device 164 is controlled by the load cells or load cell assemblies, of which one is indicated at 60 Jn the side of the mill shown in FIG.
  • this device may be of known character (and is therefore not shown in detail) for producing an electrical signal, illustrated as a varying voltage across conductors 167, 168, that represents the total of the load cell readings as total force exerted by the screwdown on the backup chocks.
  • the signal from the device 158, across conductors 159, 160, is appropriately subtracted from the signal dilevered by the device 164 across conductors 167, 168, as in suitable electrical means 170, to yield the desired net rolling load signal, for exan'17ple as a varying voltage, across the conductors 156, 15
  • F-IG. 2 shows a gauge control system, simply indicated as a device 172 for detecting the actual thickness or gauge of the issuing, product strip 35h, and control means 173 that may be operated in response to the gauge detector 172 for adjusting the screwdown drive, and therefore the rolling load force, in order to maintain uniform gauge of the strip at a selected value.
  • Means of this sort are known, including automatic systems, and are therefore not shown in detail, but they are significant in the present combinations of system and procedure, in that when the screwdown is adjusted for gauge regulation, the instrumentalities of the present invention automatically correct the deflection of the work rolls as required by the change of rolling load, to maintain atness.
  • FIG. 4 a somewhat more complete control system is schematically indicated, but nevertheless embodying the basic elements of preceding views and being understood to function, of course, with a 4-high mill and a hydraulic system of bending jacks as shown and described in connection with preceding views.
  • the servo coil 52 will be understood as functioning to control the value 50 of FIGS. l and 3, for adjustment of the balance and contour jacks
  • the device 17011 will be understood as corresponding to the device 170 of FIG. 2 for delivering a continuous signal eg., a D.C. voltage, varying in accordance with net rolling load, across the conductors 156, 157.
  • a direct readout from the load cell system may be employed as at 62 in FIG. 1.
  • the circuit of FIG. 4 is exemplified as including certain known servo control units 175, 176 and 177, each being an electronic system which is designed to receive both an A.C. input signal and one or more D.C. signals of the nature of a control bias, to yield an amplified electrical output, in the form of a supply of current, as for example to the servo coil 52 (from the device 176) which will depend on the relation of the input signals, in a manner analogous to the description of the circuit of FIG. 1.
  • the specific arrangement of elements in the controllers 175, 176 and 177 forms no part of the present invention, and devices of this sort are known and available.
  • the pressure transducers 80a, 81a (of conventional type), that are connected to the hydraulic lines of the contour and balance jacks in exactly the same fashion as the elements 80, 81 in FIGS. 1 and 3, are here shown as yielding an alternating current signal, the indicated opposition of polarity of these devices being thus actually an opposition of phase in their A.C. outputs, which can also be characterized as a phase difference of 180.
  • the devices 80a, 81a are energized from a suitable A.C. source, as indicated at 178, 179, with appropriately adjustable resistors 180, 181 for initial sensitivity setting.
  • the combined output from the series-opposed connection of the transducers is delivered across conductors 183 and 184 (the circuit being simplified by showing ground connections Where convenient, as at 184) and extends as an input at 185 to the servo controller 176.
  • the output at the line 188 can be an alternating current signal which may be taken as a measure of the value and direction of difference of the signals from the balance and contour jack systems.
  • the net feedback signal was indicated as a D.C. quantity which would be zero at equal jack forces and would have a polarity and magnitude, dependent in one direction or the other, on a difference of such forces
  • the signal at 188 may be an alternating current value which has a phase and an amplitude dependent on the direction and magnitude of the bending jack forces.
  • this signal may be converted to a D.C. quantity in the line 191 to a D.C. amplifier 192, i.e., being a voltage which represents the difference of balance and contour jack forces. While this signal may have a range into values of opposite polarity, as at 86, 87 in FIG.
  • an alternative and equally effective arrangement providing the control circuit is otherwise suitably biased, is to utilize a signal varying only in quantity as indicated above, for example being zero when the contour jack pressure is maximum in respect to the balance jack pressure, and being maximum when the balance jack pressure correspondingly predominates at maximum difference of the latter system, and having a settable intermediate value representative of zero force difference, i.e., representative of equality of the feedback signals from the balance and contour jack systems at the transducers a, 81a.
  • the input circuit supplying the control or operating bias to the D.C. amplifier 192 also includes a continuing signal from the manually adjusted shape control potentiometer 77a, via the conductor 194, and a continuing signal from the Width control potentiometer 70a, via a conductor 195.
  • -Return conductors of these bias input signals are omitted for the sake of clarity, except by indication of the other side of the shape control bias at 196. While the latter bias may be a single magnitude, it may be convenient, where the bias or feedback signal from the pressure transducers (in line 191) in a varying single magnitude, to provide for adjustment of the shape bias over a range extending to opposite polarities, e.g., a plus or minus D.C. voltage. Simply to indicate this alternative mode of signal presentation, the other line 196 of the shape bias signal is shown as connected to the center tap 198 of a voltage dividing resistor 199 across the D.C. supply voltage 200 for the shape control potentiometer 77a.
  • the basic function of the system is the same as above explained relative to FIG. l, namely that the main controlling signals reaching the input of the D C.
  • amplifier 192 are those of the initial shape control potentiometer 77a, represented at the conductor 194, the controlling signal of rolling load supplied as indicated by conductor from the output of the width-adjusted control 70a, and the feedback signal representing the pressure difference of the contour and balance jack systems, derived as explained above, and supplied as represented by the conductor 191.
  • the polarities and mutual arrangement of these signals for the control of the amplier may assume various forms, including the aid of fixed or preliminarily adjustable bias as necessary and can be basically explained as accomplishing the functions already described.
  • the input to the D.C. amplifier should be such as to produce zero current in the servo coil circuit 66a, 67a when the shape controller 77a has been adjusted for observed proper flatness of the strip, the balance and contour jack system then providing a feedback signal of necessary opposing effect, i.e., such that the combined shape and feedback signals balance the rolling load signal, the combination of the shape and feedback values being additive or subtractive depending on the mutual situation of polarity and magnitude of these signals.
  • the result should be a decrease of balance jack pressure relative to contour jack pressure, to reach a null control point at each condition of rolling load.
  • the net effect of the combined feedback and shape adjustment signals should be of opposite polarity to the rolling load signal derived from the control device 70a, throughout the operating range of rolling loads.
  • the bending force difference signal supplied at 191
  • the polarity of the rolling load signal is of a single polarity varying from zero magnitude at maximum prevalence of contour jack bending force to maximum magnitude at maximum prevalence of balance jack bending force, the polarity of the rolling load signal,
  • the shape control device 77a can then be set, eg., at the outset of a given rolling pass, to supply a signal through the line 194 which is of a polarity and magnitude as required for balancing the circuit to provide the desired condition of the strip.
  • the system of FIG. 4 is designed to function similarly to the system of FIG. l, in permitting initial or presettable shape adjustment at initial (e.g., high) rolling load, and thereafter in providing automatic adjustment of roll deflection, in proportion to decrease and other changes of rolling load throughout the pass, for maintaining the desired strip atness.
  • the rolling load signal as being the net screwdown force determined in the manner of FIG. 1 or FIG. 2, it is found that more accurate and strictly proportional results, in maintaining the precise requirements of roll defiection over a large operating range of rolling loads, are achieved by subtracting, in effect, from the rolling load signal the actual opposing force of the contour jack system.
  • this arrangement means that the actual rolling load response is then effected with respect to the load that the backup rolls exert by contact with the work roll; in other Words the preferred control by rolling load signal is with respect to the rolling load determined at the line between the backup and work rolls.
  • the contour jack signal is amplified in the A.C. amplifier 202, in effect with modulation of an A.C. supply of the same frequency, and the A.C. signal at conductor 204 then controls the demodulating amplifier 205, to yield a D'.C. signal at the conductor 206 appropriately opposing and reducing the net rolling load signal, indicated at the conductor 156, both of these signals being supplied as control bias to the D.C. amplifier 208.
  • the output at 210, 211 of the unit 177 represents a current through the potentiometer 70a that varies with the adjusted rolling load signal, i.e., being a measure of the rolling load as applied by the backup rolls to the work rolls.
  • the magnitudes of the signals supplied at 206 and 156 to the amplifier 208 may be readily calibrated in proportion to values of force, so that the net input bias signal is a measure of the force of the rolling load, adjusted in the manner indicated.
  • the function of the principal control effected for the output of the amplifier 192 and for energization of the servo coil 52 is, of course, exactly the same in principle, as before, for the last-described special or adjusted of rolling load force.
  • the system may also include, if desired, automatic shape controlling means, for example cooperating with the initially set manual shape control 77a, to provide compensation for changes of thermal crown or other slow variation of roll gap configuration, such means being indicated at 212 and detailed in FIG. 5, as described hereinbelow.
  • automatic shape controlling means for example cooperating with the initially set manual shape control 77a, to provide compensation for changes of thermal crown or other slow variation of roll gap configuration, such means being indicated at 212 and detailed in FIG. 5, as described hereinbelow.
  • the signal from the combined balance and contour transducers 80a, 81a may also be supplied, as indicated at conductor 214, to another servo control unit 175, conveniently indentical with the units 176 and 177, so adjusted that its output circuit at conductors 215, 216 may include an electrical meter 218, eg., a voltmeter, that can be calibrated to provide a continuing indication of the difference of bending jack forces at all times.
  • another servo control unit 175 conveniently indentical with the units 176 and 177, so adjusted that its output circuit at conductors 215, 216 may include an electrical meter 218, eg., a voltmeter, that can be calibrated to provide a continuing indication of the difference of bending jack forces at all times.
  • the system provides automatic adjustment to increase the bending jack differential in the direction of greater contour jack pressure, for guiding the trailing portion of the strip against sidewise movement.
  • such action may be controlled by any suitable means for sensing tension loss in the entering strip 35a.
  • a torque-sensitive device 220 is schematically indicated as suitable to detect loss of tension, for example by decrease or absence of opposing torque in the shaft 39.
  • This may be a conventional device operating on magneto-elastic principles, or other known instrumentality, which need not be detailed here, but which supplies, as in the conductor 222, an appropriate signal to a control means 223 that is adapted to close a switch 225 when tension is lost in the entering strip 35a. As shown, closure of the switch 225 closes the energizing circuit 227 of the winding of a relay 228, and in turn causes immediate closure of the relay contacts 230.
  • the relay contacts 230 which are normally open but close under circumstances described above, are arranged to supply a special bias signal, as indicated by the conductor 232, to the control system for the servo coil, conveniently by introduction with the signals supplied to the D.C. amplifier 208 that is primarily designed to yield the net or adjusted rolling load signal.
  • this tension-loss signal can be introduced to like effect elsewhere in the control circuits for the servo coil.
  • the special bias value inserted by closure of contacts 230 is basically a signal of opposite sense to that of the rolling load or of increase in rolling load, and may be derived from the same Voltage source 200 that supplies the basic shape bias from the potentiometer 77a.
  • the signal may be derived from a suitable tap on a voltage dividing resistor 235 across the source 200.
  • the voltage in line 232, 234 is indicated as positive (relative to its return conductor 236) and thus arranged in opposing polarity to the indicated negative value of rolling load signal in the lead 156.
  • this special bias signal is to create a bending force on the work rolls toward each other at their necks, more specifically to provide at least some small concavity at central regions of the rolls; the polarity of the signal being in a direction to increase the pressure in the contour jacks and decrease it in the balance jacks.
  • the slightly crowned gap provides desired tail guidance, preventing movement or oscillation sidewise and keeping the strip properly centered.
  • the tension-loss-responsive relay 228 also includes a pair of normally closed contacts 240, which upon energization of the relay are caused to open after a small, predetermined delay, as for instance such that these contacts open just before the end of the strip reaches the roll gap.
  • a convenient delay time for a conventional 4- high mill is about one-half second.
  • the contacts 240 are normally closed to short-circuit a resistor 242 in the circuit of the servo coil 52, but when these contacts open, this resistance is incorporated in series, and has the effect of greatly reducing or attenuating the response of the servo coil and its valve to changes of control signals.
  • the amplifier may be such that it is capable of supplying, in effect, an output voltage proportional to the error signal at its input, until the amplifier reaches a saturation value.
  • This saturation value of voltage is conveniently chosen as such that the current in the servo coil 52 is then sufficient to move the spool 90 (FIG. l) to the limit of its motion in one direction or the other, depending on the direction of servo coil current.
  • the valve is in effect opened fully, to allow full flow to either the roll balance or the roll contour line.
  • the servo coil being a relatively low impedance element, this full flow current is in effect matched by a resistor 244 in series with the coil 52.
  • FIGS. 2 and 4 indicate a further, automatic feature of the present system for this purpose.
  • a suitable device 250 which is actuated by release of the rolling load and which can, for example, be controlled from the rolling load signal lines 156, 157 as indicated at 251, closes its contacts 252 and thereby causes energization of a relay 253, shifting its Contact arm 254 from a normal position of closure with contact 255, so as to open the circuit at the latter point and to close a circuit between the arm 254 and a contact 256.
  • the normally closed contact means 254, 255 is a part of the control circuit of the servo coil 52, and when the arm 254 engages contact 256, the servo coil is now energized directly by a separate source of current indicated by the negative voltage terminal 258.
  • the polarity of the lastmentioned source is such that the servo coil drives the valve S0 to a position (c g., to the left in FIGS. 1 and 3) where full flow of liquid under pressure is supplied to the balance jacks lwhile the contour jacks are allowed to discharge to a minimum pressure value.
  • the balance jacks keep the work rolls in the desired contact with the backup rolls, avoiding skidding or other dificulty as the mill is brought to rest.
  • the system functions at the end of a rolling pass to provide suitable guidance for the tail end of the strip, i.e., keeping it aligned with the center line of the mill by changing the geometry of the roll gap from parallel to convex.
  • the system is 2t) automatically conditioned to avoid any immediate response of the bending jack system to loss of rolling load, affording time for a separate release-of-load signal (at the device 250) to bring the jack system into special function and thereafter keep the work rolls appropriately engaged with the backup rolls.
  • the system may also include a manual switch 260, which can be moved from its off position either to a contact 262 for continuously energizing the relay 253 and maintaining full balance jack force yby the bias voltage supply 258 (as explained above; FIG. 4), or to a contact 264 for energization of a relay 266, which opens the servo coil circuit at 267 and closes a connection at contact 268 for impressing a positive voltage 269 on the servo coil. In the latter situation, full contour jack force is exerted, as may be desirable in the course of roll changing operations or other work of adjusting or setting up the mill.
  • the automatic shape control indicated at 212 in FIG. 4 may employ a strip liatness sensor of a previously devised type, having a multiplicity of pressure sensing elements carried in or by a billy roll 270, i.e., a supplemental, free-running roll.
  • a billy roll 270 i.e., a supplemental, free-running roll.
  • the strip 35C issuing under tension from the work rolls 16, 18 bends over the roll 270 in rolling contact, where the individual pressure sensing devices 271 detect the atness condition of the strip, there being less or more pressure in acocrdance with lessening or localization of strip contact, at each given place, as may be due to waves, Valleys, peaks or other departure of the strip from complete flatwise engagement.
  • signals are transmitted through suitable collecting and multiple conducting means 273, 274 to individual signal output circuits represented at 275, 275 in the wiring diagram.
  • suitable collecting and multiple conducting means 273, 274 to individual signal output circuits represented at 275, 275 in the wiring diagram.
  • the mill shown schematically in FIG. 5 can be such as to correspond with the mills in FIGS. 1 and 2 and to include the balance and contour jack systems, with related instrumentalities as illustrated in FIGS. 2, 3 and 4.
  • the strip flatness sensor 270-275 which is in itself another invention and which is not here claimed per se, as likewise alternative arrangements of such means that may also be available or proposed, is thus adapted to deliver a multiplicity of output signals, as shown at 275 and respectively related to successive localities across the width of the mill.
  • Each such signal may be a voltage proportional to the off-flatness of the strip in the corresponding location, as for instance signals having a range of plus or minus 10 volts D.C., which for cold rolling of aluminum strip may conveniently correspond to tensile strength differences of plus or minus 5000l p.s.i.
  • interest is preferably conlined to the areas of the strip nearest its lateral edges.
  • a pair of movable gangswitch assemblies 277, 279 are provided, each adapted to connect with a selected three adjacent sensor terminals.
  • the switch devices 277, 279 are positioned to read the outermost portions of the strip, i.e., over three sensing units in each case, corresponding, for example, to a band totaling 10 inches wide, more or less, adjacent the strip edge.
  • the signals from each side of the strip are summed separately by the networks 281, 283 and brought together electrically via conductors 284, 285 and resistors 286, 287 to a line 288 extending to the input of a summing amplifier 290.
  • the significance or importance of the signals decreases inwardly from the edge of the strip, and in consequence in each group of signal elements collected by the networks 281, 283 the signals are progressively attenuated for the pressure sensing elements l0- cated inward of the strip edge, this function being indicated by the individual resistors 291, 292 and 293 in the lines extending from the switch unit 277.
  • resistor 21 292 may have, for example, twice the resistance of element 291
  • resistor 293 may have four times the resistance of element 291.
  • a similar relationship can be embodied in the resistors 29161, 292a and 293:1 in the signal lines from the switch unit 279.
  • the output of the amplifier 290, at 295, thus delivers a signal proportional to the sum of the off-flatness condition at the regions of the two strip edges.
  • This signal can be supplied to appropriate roll deflection control means Such as the instrumentalities hereinabove described; for example the amplifier output line, indicated at B, may be connected as similarly marked B for this complete unit 212 in the circuit of FIG. 4, thereby supplying such signal as a bias in the input of amplifier 192 for control of the bending jack system through the servo coil S2.
  • Such bias may be proportioned, as will now be understood, for summation with the manual shape bias supply through the line 194, or if appropriately set at a suitable level, can supplant such bias.
  • the signal supplied to amplifier 192 is furnished at appropriate polarity for coaction with the rolling load signal in line 195 and the bending jack feedback signal in line 191, in the same manner as previously explained relative to the bias signal derived from the manual shape controller 77a.
  • the proportionality constant, of the signal in line 295 relative to the off-fiatness condition adjacent to the strip edges depends on the width of the strip, since larger roll bending forces are required to compensate for a given off-flatness condition detected on narrower strips.
  • the required adjustment may be conveniently obtained, for example, by a variable resistor 296 in the line 297 representing a component of a feedback circuit of amplifier 290, e.g., a conventional negative feedback.
  • the proportionality constant is reduced by adjustment of the resistor 296 to a low value of effective resistance, while for narrower strips, greater gain and larger proportionality constant is achieved with the resistor 296 at a larger value of resistance.
  • the feedback circuit of the amplifier 290 also includes a capacitor 298 of suitably large value at least to allow for the time lag of the sensor 270-271 in detecting the effect of a correction, which it initiates, in roll deflection. More particularly an advantageous function of the circuit including condenser 298 is that the output signal in the line 295 cannot change very rapidly, and thus as delivered at locality B in the circuit of FIG. 4, is characterized by only slow or delayed changes in contrast with the relatively fast action of the rolling load signal. Hence in the arrangement of strip shape controller of FIG. 5, the function of the signal at locality B is to provide .a bias for control of the roll bending forces, sufficient to compensate for changes of roll shape due to thermal drift, wear or other phenomena responsible for slow changes in strip fiatness.
  • the ⁇ controller of FIG. 5 further coacts in the complete combined system, in that it effects compensation, but only at a very slow rate, for such minor part of the rapid changes of strip fiatness (that are brought about by changes of rolling load) as may be due to residual errors in the automatic roll deflection control system.
  • Such errors are ordinarily slight but the cooperative effect of the supplemental circuit of FIG. 5 is to minimize them, at least over extended periods.
  • a residual off-atness condition may be desired for strip regions adjacent the edge, as to relieve tensions in such localities and thereby prevent edge cracks or strip breaks.
  • a manually adjustable bias may be introduced as input to the amplifier 290 from a voltage divider 299, which can conveniently be supplied with its base potential from a branch 194er of the bias line 194 from the manual shape controlled 77a (FIG. 4), such connection being indicated by the letter A in both views.
  • a further coacting feature is indicated by the amplifier 300 having its output line 302 connected through the resistor 303 to provide an additional bias signal in the input of the basic shape control amplifier 290.
  • the amplifier 300 is supplied by a signal proportional to the roll bending force exerted by the bending jacks, eg., by connection of the amplifier input line 304 to the point C of line 191, as indicated in FIG. 4, e.g., the bending force feedback signal which is delivered as a bias to the servo control amplifier 192.
  • the amplifier 300 has a feedback circuit comprising the resistor 306 and a condenser 308, so proportioned, especially with a large value of capacity for the condenser, that the amplifier output in the line 302 can only change in an extremely slow manner, the capacitor thus affording a time constant which in effect is substantially larger than that of roll shape changes due to thermal drift, i.e., the signal changes which are produced in the line 295 as a result of readings of the flatness sensor 270271.
  • the supplemental input into amplifier 290 from the circuit including the amplifier 300 has the effect of producing a controlled drift of the roll bending forces toward a balanced condition in a very slow way.
  • a normally energized relay 310 is deenergized to open the input circuits of both amplifiers 290 and 300 at the contacts 312, 314, respectively.
  • the condition of relay 310 may be controlled from a suitable main governing circuit (not shown) for this automatic flatness control system, and thus may be responsive to loss of back tension on the strip or other appropriate signal; for simplicity this control, which can of course be manual, is indicated as an on-off device 315, arranged to provide the above contact release by relay 310 when shifted to the off position.
  • the condensers 298 and 308 serve as a long-term memory, maintaining the output signal levels at their last-established values, e.g., until connection of the input signals is again restored at the beginning of the next rolling pass.
  • Circumstances may also make it desirable to change the shape control to a manual mode.
  • a selector switch 318 is arranged for simultaneous control of the input circuits of the amplifiers 290 and 300, having a first position with closure of contacts 320, 322 in the respective circuits for maintaining automatic operation, and a second, open position indicated at 324, 326
  • the primary function of the shape control instrumentalities of FIG. is to account automatically for roll shape changes due to thermal conditions, e.g., heating or cooling of the rolls, that may be significant but occur over relatively longer periods than the rolling load variations which are accommodated by the deflection control system of FIGS. l to 4.
  • a further automatic control embraced by the system of FIG. 5 is advantageously related to the relative position or adjustment of the two sides of the screwdown mechanism of the mill, specifically for controlling the effective condition of the two screws, that respectively bear on chocks at opposite ends of the rolls, to maintain symmetrical flatness of the strip across its width.
  • the summed signal from the fiatness sensors at one side is transmitted by a line 340 to an amplifier 342 while the signal from the sensors at the other side of the strip (switch 279) is carried by a line 344 to an inverter device 346, e.g., an electronic circuit of known character adapted to reverse the polarity of the signal, such signal being then also transmitted by line 348 to the amplifier 342.
  • inverter device 346 e.g., an electronic circuit of known character adapted to reverse the polarity of the signal, such signal being then also transmitted by line 348 to the amplifier 342.
  • these signals are algebraically summed, e.g., to yield an output in line 350, which is proportional to the arithmetical difference of the input signals.
  • a signal proportional to shape imbalance if such exists, is delivered in the line 350 and is arranged to actuate a polarized relay 352 in one direction or the other, conveniently when such signal exceeds a calibrated threshold value and therefore represents a significant departure from symmetry of any nonfiatness conditions adjacent to the strip edges.
  • the polarized relay When energized in one direction, the polarized relay thus closes the circuit to a contact 354 and when energized in the other direction, to a contact 356, such circuits extending to a screwdown control instrumentality 358 which may be of conventional sort for differentially adjusting the screws as well as for other purposes of maintaining effective balance of screwdown force on the roll chocks.
  • control system 358 is shown as extending to lefthand and righthand drive instrumentalities 360, 362 for the corresponding screwdown assemblies 364, 366 of the mill, all of these parts being shown merely in diagrammatic fashion, as constituted by known elements and connections, otherwise available for rolling mill control.
  • the system 358 may also, of course, provide for the usual identical, simultaneous adjustment of the screwdowns when desired, such as for various conventional purposes.
  • a special feature is the utilization of a rolling load signal, taken from the point D in the circuit of FIG. 4 and so designated at the line 368 of FIG. 5, leading to the movable contact 370 of the relay 352.
  • a rolling load signal taken from the point D in the circuit of FIG. 4 and so designated at the line 368 of FIG. 5, leading to the movable contact 370 of the relay 352.
  • the screws are caused to move at a speed proportional to the adjusted rolling load signal from the load cells.
  • the screwdown transfer function being the extent of strip gauge correction effected per unit of screw displacement, is a function of net rolling load and of the width of the strip. It is correspondingly preferable to compensate for such variation of the stated transfer function, in order to avoid extreme conditions of instability or to avoid unsatisfactorily slow response, in the presently described differential screwdown adjustment. Since the signal (locality D, FIG.
  • the special screwdown control thus automatically maintains symmetry, by operation of the polarized relay when significant departure from such condition arises. If the flatness condition as developed by the roll gap is in fact symmetrical, whether because of equal offflatness or because the desired good fiatness is present across the entirety of the strip, the relay 352 remains deenergized and no screwdown adjustment by the instrumentality 358 is required.
  • the transfer function that relates the proportionality of roll deflecting force to rolling load i.e., the variation of the proportionality constant by which the ratio of change in jack pressure difference to change in rolling load varies with strip width
  • this variation of proportionality constant has been found to be a straight-line function, which can be plotted linearly from a high value for narrow strips to a low value for the widest strip (approaching zero at full width of the work rolls) and can thus be determined; for example, in FIG.
  • the basic, nonsignal bias of amplifier 208 can be adjusted, with simple test of the mill in operations using different widths of strip if necessary, to afford attainment of a proper slope of the linear graph of proportionality constant pursuant to adjustment of the widthsetting potentiometer 70a, and similar basic calibration is attainable in the simplified system of FIG. l, respecting the output of potentiometer 70.
  • the desired controlled bending force represented by the feedback signal at 86, 87 can be considered as equal to the algebraic sum of the shape bias, being one parameter, and a second bias or signal that is derived from the rolling load and that equals, in effect, the product of the rolling load signal (at 63, 64) and a second parameter, such second parameter being the proportionality constant which is in efiect adjusted by the width control potentiometer 70.
  • both the last-mentioned product (the signal at 71, 72) and the algebraic sum of the bias values (i.e., the sum of such product and the shape bias) which is equated to the required bending force are essentially linear functions of the rolling load.
  • the actual value for setting the shape bias control (as the constant term of the binomial) is determinable by extrapolation and thereupon the value of width control setting (at 70) needed for maintenance of the individual straight-line function of the output 71, 72 (the other term) can be determined from the rolling load Values with the aid of adjustment, if necessary, of the proportionality in the load cell readout (or in the amplifier 208 of FIG. 4).
  • Final calibration of the potentiometer 70 in units of width is then attainable (in view of its own straight-line function as explained) upon similarly determining another setting of this device by like tests of the mill with a strip of another width.
  • the system is readily applicable to any desired rolling mill, for ultimate operation in the stated manner, whereby for rolling any given strip, the attendant first sets the device 70 (or 70a) to the strip width, and then as the rolling operation is initiated at slow speed, sets the shape control 77 (or 77a) to achieve desired fiatness as observed.
  • the bending jack system is thus automatically brought into function and as rolling proceeds, the necessary changes of bending force to accommodate changes of rolling load for maintained atness are automatically achieved.
  • the method and control system having the desired linear relationships, is notably applicable to mills wherein the length of the Contact line between each work roll and its backup roll is not greater than about 4.5 times the work roll diameter.
  • highly effective results have been achieved in a 4-high mill, employed for cold rolling aluminum strip to gauges of 0.200 to 0.010 inch, wherein the diameter of each work roll was 2l inches, the backup roll diameter was 54 inches and the effective work roll length, i.e., its contact line with the backup roll, was 78 inches.
  • the invention has been exemplified in cold rolling aluminum, the systems and method are applicable to such rolling of other metals, e.g., steel, brass, copper and the like. It is conceived that the apparatus and procedure are useful for hot mills, but maximum advantage of the invention, and indeed chief need for it, is at present understood to reside in the situation of the cold rolling of metal strip, i.e., to various intermediate and finish gauges.
  • a rolling mill control system in combination with a 4-high mill having upper and lower Ibackup rolls, upper and lower work rolls between the backup rolls, providing a roll gap for a strip of metal being rolled, chocks at the ends of each of said backup and work rolls, and supporting means for the backup roll chocks including screwdown means for maintaining rolling load on the backup rolls: means associated with said supporting means for detecting changes in rolling load, bending jack means for the work rolls including bending jacks ⁇ between the upper work roll chocks and the lower work roll chocks, means controlled by the load-detecting means for adjusting the rollbending force of the bending jack means in proportion to changes in rolling load, to counteract changes in roll gap shape due to changes in rolling load, means controlling said adjusting means for varying substantially only the proportionality thereof, settable to provide a desired proportion between changes in rolling load and the changes in bending jack force produced Iby said adjusting means, and separate means controlling the bending jack means for adjusting the bending force thereof, settable to provide a desired base
  • controllable roll-bending means applying bending forces at the necks of the work rolls for coaction with forces exerted by rolling load to provide bending effect on the work rolls which is adjustably directed to vary the separation between said work rolls at their ends relative to central regions thereof, for altering the shape of said roll gap as traversed by a strip under rolling load, a plurality of control means in controlling relation to said roll-bending means, independently operative to adjust said bending forces and conjointly operative to determine said bending effect, for maintaining a predetermined roll gap shape,
  • a first one of said control means being controlled by said detecting means, for adjusting said bending forces in proportion to changes of rolling load, and including independently controllable means for varying the proportionality of said last-mentioned adjustments to rolling load changes, and a second of said control means being adjustable to establish said predetermined gap shape which is subject to being maintained by operation of said first control means in response to changes of rolling load.
  • controllable roll-bending means applying forces at the necks of the ⁇ work rolls, differentially exerted in directions to push said work rolls apart and together at their ends, for altering the shape of said roll gap as traversed by a strip under rolling load
  • controllable roll-bending means applying forces at the necks of the ⁇ work rolls, differentially exerted in directions to push said work rolls apart and together at their ends, for altering the shape of said roll gap as traversed by a strip under rolling load
  • a plurality of control means in controlling relation to said roll bending means, independently operative to adjust the differential effectiveness of said forces and conjointly operative to determine said differential effectiveness, for maintaining a predetermined roll gap shape, and means for detecting changes in rolling load, a first one of said control means being controlled by said detecting means, for adjusting said differential effectiveness of forces in proportion to changes of rolling load, and including independently controllable means for varying the proportionality of said last-mentioned adjustments to rolling load changes, to accommodate said proportionality to strips of different width
  • a system as defined in claim 9, which includes means associated with said tension-loss-responsive means and operative in delayed response to said loss of tension, for attenuating the operation of the first-mentioned control means in control of the roll-bending means pursuant to change of rolling load, whereby upon subsequent departure of the strip from the roll gap and corresponding decrease of rolling load, said gap is maintained against rapid closure as would otherwise be caused by said first control means.
  • a system as defined in claim 10 which includes means responsive to departure of a strip from the roll gap and arranged in controlling relation to said roll-bending means, for adjusting said differential effectiveness of 13.
  • said atness-sensing means includes means retarding its controlling operation over said second control means, whereby said second control means responds substantially more slowly to departures of the strip from atness than the response of said roll-bending means to control by the rst control means upon change of rolling load.
  • a rolling mill control system in combination with a 4-high mill having upper and lower backup rolls, upper and lower work rolls between the backup rolls, providing a roll gap for a strip of metal being rolled, chocks at the end of each of said backup and work rolls, and supporting means for the backup roll chocks including screwdown means for maintaining rolling load on the backup rolls: means associated with said supporting means for detecting changes in rolling load, bending jack means acting on the work roll chocks for adjustably exerting forces on the work rolls to control the shape of the roll gap, means controlled by the load-detecting means for controlling the bending ⁇ jack means to adjust said forces to counteract changes in roll gap shape due to changes in rolling load, and means responsive to departure of a strip from the roll gap and arranged in controlling relation to the bending jack means, for effecting adjustment of said forces to keep said work rolls respectively in firm contact with the backup rolls.
  • a system as defined in claim 17, which includes means responsive to release of engagement of a tail portion of the strip while said strip is traversing the roll gap and operative in anticipation of actual departure of the strip from the gap, for attenuating the operation of the first-mentioned controlling means in control of the bending jack means pursuant to change of rolling load.
  • a rolling mill control system in combination with a 4-high mill having upper and lower backup rolls, upper and lower work rolls between the backup rolls, providing a roll gap for a strip of metal being rolled, chocks at the ends of each of said backup and work rolls, and supporting means for the backup roll chocks including screwdown means for maintaining rolling load on the -backup rolls: means associated with said supporting means for detecting changes in rolling load, bending jack means for the work rolls including balance jacks between the upper work roll chocks and the lower work roll chocks and contour jacks between the backup roll chocks and the respectively adjacent work roll chocks, means controlled by the load-detecting means for adjusting the difference in pressures of said balance jacks and contour jacks to change the roll-bending force of the bending jack means in proportion to changes in rolling load, for counteracting changes in roll gap shape, means in controlling relation to said bending jack means and adjustable to provide a base pressure difference of said balance and contour jacks for establishing a base condition of bending force on
  • said pressure-diiTerence-adjusting means comprises electrically controlled valve means for controlling supply of fluid under pressure to said balance jacks and contour jacks, electrical circuit means for controlling said valve means, means for supplying a first electrical signal to said circuit means in response to said rolling load detecting means, varying in proportion to changes of load, and means for supplying a feedback electrical signal to said circuit means in accordance with the difference in pressures of said balance and contour jacks, said means adjustable to provide a base pressure dierence comprising means for supplying a third electrical signal to said circuit means, said means settable to provide a desired proportion as to changes in rolling load comprising means settable to modify the first-mentioned electrical signal for said desired proportionality to changes in rolling load, and said circuit means being constructed and arranged to effect operation of said valve means in response to unbalance between said feedback signal and the conjoint effect of said first and third signals, for changing the pressure difference of said balance and contour jacks to restore balance in said circuit means by said feedback signal, for
  • said feedback signal supplying means includes means establishing a signal in accordance with the pressure in said contour jacks
  • said rolling load detecting means comprises means responsive to the force between the upper work roll chocks and the lower work roll chocks, said signal-establishing means being associated with said means supplying the aforesaid first signal for modifying the response of the latter to the load detecting means, to effect supply of said first signal as representing the rolling load folce directly exerted on the work rolls by the backup ro s.
  • said mill includes backup jacks between said backup roll chocks for prestressing the mill and means establishing a signal in accordance with the pressure in said backup jacks
  • said load detecting means including means measuring the total screwdown force on the bac-kup roll chocks, arranged in association with last-mentioned signal establishing means to supply a load signal representative of said total screwdown force diminished by the force of said back-up jacks.

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648496A (en) * 1969-06-16 1972-03-14 Marotta Valve Corp Apparatus for controlling rolling mill
US3714805A (en) * 1971-11-11 1973-02-06 Wean United Inc Control system and method for concurrent automatic gage and crown control of a rolling mill
US3782152A (en) * 1971-04-22 1974-01-01 Centro Speriment Metallurg Apparatus for improving the flatness of rolled strips
US3852888A (en) * 1972-07-20 1974-12-10 Inland Steel Co Roll level checking device
US4262511A (en) * 1978-09-08 1981-04-21 Reycan Research Limited Process for automatically controlling the shape of sheet metal produced in a rolling mill
US20120246917A1 (en) * 2011-04-01 2012-10-04 Ihi Corporation Continuous press apparatus for electrode band plate
CN112317538A (zh) * 2020-09-21 2021-02-05 山西太钢不锈钢股份有限公司 二十辊可逆冷轧机不锈钢轧制控制方法
CN116078829A (zh) * 2023-03-08 2023-05-09 中铝瑞闽股份有限公司 一种解决铝冷轧机起车纹的自动起车控制系统及应用方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115338268B (zh) * 2022-08-03 2025-09-30 首钢京唐钢铁联合有限责任公司 一种十八辊轧机穿带控制方法、装置、电子设备及介质

Citations (7)

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Publication number Priority date Publication date Assignee Title
US2903926A (en) * 1956-01-11 1959-09-15 Baldwin Lima Hamilton Corp Method and apparatus for controlling the contour of rolls in a rolling mill
US3024679A (en) * 1957-07-01 1962-03-13 Thomas A Fox Skin pass mills and methods of rolling
US3157073A (en) * 1958-10-31 1964-11-17 Siderurgie Fse Inst Rech Compensated screwdown mechanism for a rolling mill
US3248916A (en) * 1962-09-21 1966-05-03 Westinghouse Electric Corp Workpiece shape control with a rolling mill
US3250105A (en) * 1958-08-25 1966-05-10 United Eng Foundry Co Method of and apparatus for processing metal strip
US3318124A (en) * 1964-12-10 1967-05-09 Westinghouse Electric Corp Workpiece shape control
US3459019A (en) * 1965-09-13 1969-08-05 United Eng Foundry Co Method of and apparatus for rolling flat strip

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2903926A (en) * 1956-01-11 1959-09-15 Baldwin Lima Hamilton Corp Method and apparatus for controlling the contour of rolls in a rolling mill
US3024679A (en) * 1957-07-01 1962-03-13 Thomas A Fox Skin pass mills and methods of rolling
US3250105A (en) * 1958-08-25 1966-05-10 United Eng Foundry Co Method of and apparatus for processing metal strip
US3157073A (en) * 1958-10-31 1964-11-17 Siderurgie Fse Inst Rech Compensated screwdown mechanism for a rolling mill
US3248916A (en) * 1962-09-21 1966-05-03 Westinghouse Electric Corp Workpiece shape control with a rolling mill
US3318124A (en) * 1964-12-10 1967-05-09 Westinghouse Electric Corp Workpiece shape control
US3459019A (en) * 1965-09-13 1969-08-05 United Eng Foundry Co Method of and apparatus for rolling flat strip

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3648496A (en) * 1969-06-16 1972-03-14 Marotta Valve Corp Apparatus for controlling rolling mill
US3782152A (en) * 1971-04-22 1974-01-01 Centro Speriment Metallurg Apparatus for improving the flatness of rolled strips
US3714805A (en) * 1971-11-11 1973-02-06 Wean United Inc Control system and method for concurrent automatic gage and crown control of a rolling mill
US3852888A (en) * 1972-07-20 1974-12-10 Inland Steel Co Roll level checking device
US4262511A (en) * 1978-09-08 1981-04-21 Reycan Research Limited Process for automatically controlling the shape of sheet metal produced in a rolling mill
US20120246917A1 (en) * 2011-04-01 2012-10-04 Ihi Corporation Continuous press apparatus for electrode band plate
CN112317538A (zh) * 2020-09-21 2021-02-05 山西太钢不锈钢股份有限公司 二十辊可逆冷轧机不锈钢轧制控制方法
CN112317538B (zh) * 2020-09-21 2023-03-17 山西太钢不锈钢股份有限公司 二十辊可逆冷轧机不锈钢轧制控制方法
CN116078829A (zh) * 2023-03-08 2023-05-09 中铝瑞闽股份有限公司 一种解决铝冷轧机起车纹的自动起车控制系统及应用方法

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DE1913105A1 (de) 1969-12-11
NO136394B (show.php) 1977-05-23
CH518751A (fr) 1972-02-15
NL165957C (nl) 1981-06-15
NL165957B (nl) 1981-01-15
FR2003865A1 (show.php) 1969-11-14
SE354424B (show.php) 1973-03-12
NL6903887A (show.php) 1969-09-16
DE1913105B2 (de) 1976-12-02
GB1267581A (en) 1972-03-22
NO136394C (no) 1977-08-31
SU479276A3 (ru) 1975-07-30
BE729796A (show.php) 1969-09-15

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