Device and method for adjusting the guides for the entry of the strip in a mill

Abstract: A device for adjusting the guides for the entry of the strip in a housing, the particularity of which is the fact that it comprises: at least one pair of mutually opposite guides which are suitable to adjust the correct alignment of the strip that enters the housing and are actuated, in terms of position and force, by respective actuation means; position and force/pressure transducer means which are connected to the actuation means; and an electronic adjustment unit, which is suitable to receive signals from the position and force/pressure transducer means for the closed-loop control of the actuation means, in order to keep the guides in the correct position with respect to the strip and apply to the edges of the strip a force which is controlled as a function of parameters related to the position, width and thickness of the strip, which are detected by the transducer means.

Description: The present invention relates to a device and a method for adjusting the guides for the entry of the strip in a mill, particularly for controlling the position and the centering of the ribbon at the inlet of housings. The guides for strips at the inlet of mill housings are currently generally controlled by virtue of a position presetting performed by a closed-loop position adjustment system. In this case, when the edge of the strip makes contact with one of the two guides, contact forces are generated to which the closed-loop position adjustment system reacts rigidly, so as to contrast the transverse movements of the strip. This produces the scraping of the strip against the guides, causing deformations of the strip edges and damage to the guides themselves. Another disadvantage of adjustment systems which operate with a simple position loop is the fact that if the edge of the strip returns to the correct position after a misalignment which has required a manually-actuated opening of the guides, they are unable to adapt automatically and accordingly return the guides to the appropriate position. One solution used to solve these drawbacks consists in presetting the position of the lateral guides with a rather wide tolerance with respect to the nominal width of the strip, so as to reduce the pressure applied by the edge of the strip on the guides in case of transverse movements of said strip. The greatest drawback of this solution is the fact that the application of a wide tolerance for the position of the guides with respect to the nominal width of the strip proportionally reduces the ability to correct strip misalignments, increasing errors and producing a telescopic effect in the winding of the strip on the takcup reel at the outlet of the housing in the presence of said errors. This entails poor quality of the roll, whose nonaligned edges are subject to damage during handling, packaging and transport. An example of a device of known type is disclosed in US-A-4 590 778. The aim of the present invention is therefore to provide a device for adjusting the guides for the entry of the strip in a housing which can automatically adapt to width variations of said strip and to any transverse movements thereof with respect to the direction in which the strip advances toward the housing. Another object of the present invention is to provide a device for adjusting the guides for the entry of the strip in a housing in which the force with which the edges of the strip slide against said guides is adjusted so as to avoid exceeding a preset maximum value. Within the scope of this aim, an object of the present invention is to provide a device for adjusting the guides for the entry of the strip in a housing which, in controlling the position and the contact force of the edges of the strip, allows to take into account the width, thickness and metallurgical characteristic of the strip in order to center the strip with respect to the guides. Another object of the present invention is to provide a device for adjusting the guides for the entry of the strip in a housing which allows more precise and accurate winding on the takeup reel, consequently improving the quality of the produced roll. Another object of the present invention is to provide a device for adjusting the guides for the entry of the strip in a housing which allows to reduce the damage and wear of said guides. Another object of the present invention is to provide a device for adjusting the guides for the entry of the strip in a housing which is highly reliable, relatively easy to provide and at competitive costs. This aim, these objects and others which will become apparent hereinafter are achieved by a device and a method for adjusting the guides for the entry of the strip in a housing as defined in claim 1 and 13, respectively. Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the device according to the invention, illustrated by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a schematic plan view of the travel of a strip through a housing, with the device according to the invention; figure 2 is a schematic view of a strip to be rolled and of the inlet guides provided with the device according to the present invention; figure 3 is a general block diagram of the adjustment device according to the present invention; and figure 4 is a detailed block diagram of the adjustment device according to the present invention. With reference to the above figures, and particularly to figures 1, 2 and 3, the reference numeral 1 designates a strip to be rolled, which is unwound from a feeder reel 100 and is guided to the inlet of a housing 200 by a pair of inlet guides 2 and 3, respectively an operator-side guide and a drive-side guide, where the expression "operator side" designates the side of the mill at which the control panels are located and the expression "drive side" designates the opposite side. The strip 1 that exits from the housing 200 is then wound on a takeup reel 200. A first adjustment and actuation element 4 and a second adjustment and actuation element 5 are coupled, by virtue of mechanical means, to mechanical elements to be actuated whose position and force applied to the strip is to be adjusted and controlled. The mechanical elements to be actuated are the guides 2 and 3 for the entry of the strip I in the housing 200. Advantageously, the first and second adjustment and actuation elements 4 and 5 comprise a first cylinder and a second cylinder in which the means that are mechanically coupled to the mechanical elements 2 and 3 to be actuated are corresponding pistons 17 and 18 of the cylinders 4 and 5 respectively. Each cylinder 4 and 5 has at least one transducer, designated by the reference numerals 6 and 7 respectively (one for each cylinder), for detecting the position of the corresponding pistons 17 and 18, and has a pair of transducers 8 and 9 (two transducers 8 for the cylinder 4 and two transducers 9 for the cylinder 5) for detecting the force/pressure applied by the pistons 17 and 18 to the guides 2 and 3 to be actuated. As an alternative, the force/pressure of each piston 17 and 18 can be detected by means of a single force/pressure transducer per cylinder, if the pressure of the line that feeds the cylinders 4 and 5 is known. The transducers 6 and 7 send feedback signals 21 and 22 related to the position of the pistons 17 and 18 of the cylinders 4 and 5 to an electronic adjustment unit 14. The transducers 8 and 9 instead send signals which are compared in transducer means 10 and 11 (for the cylinders 4 and 5 respectively), which in turn send force feedback signals 23 and 24 to the electronic adjustment unit 14. The electronic adjustment unit 14 also receives a position reference signal 25, related to the pistons 17 and 18 of the cylinders 4 and 5, and a maximum force reference signal 26. The position reference signal 25 corresponds to the nominal position of the strip 1 with respect to an ideal central line traced between the two guides 2 and 3 which defines an ideal path for the entry of the strip in the housing. The force reference signal 26 is generated by means of a correlation function 40, which takes into account the width 41 of the strip 1, the thickness 42 of the strip and the code of the alloy of the material 43 of which the strip is made. In turn, the electronic adjustment unit 14 is connected to a pair of electronic actuators 12 and 13 for actuating valves 15 and 16 operated by modulated electric control, which act on the respective cylinders 4 and 5. The actuators can be of the type with servovalve, proportional valve, hydraulic motor, pneumatic motor or electric motor. Finally, it is also possible to provide sensors for detecting the movement or the presence of the edge of the strip 1; said sensors are designated by the reference numerals 19 and 20, respectively, for the guides 2 and 3 in figure 2. Said sensors detect any displacement of the strip or the presence of the edge, allowing to send a signal which indicates the position of the strip 1 between the guides 2 and 3. The sensors 19 and 20 can be, for example, of the mechanical type, that is to say, probes with a control unit provided with a yielding rod (pneumatic or hydraulic cylinder) with an axial yielding detector, or of the optical type (using a normal-light or monochrome-light detector with an emitter and a receiver), or of the magnetic type. The electronic adjustment unit 14 furthermore receives force feedback signals 23', 24' (generated respectively by the sensors 19 and 20, which are provided analogically) and strip presence feedback signals 23" and 24" (generated by the sensors 19 and 20, which are provided in an ON/OFF mode, that is to say, of a kind suitable to detect the presence or absence of the edge of the strip proximate to each guide). The signals 23', 23", 24', 24" are actually an alternative to the signals 23 and 24, and in turn the signals 23', 23" and 24', 24" are also mutually alternative and depend of course on the type of sensor chosen (sensors 19 and 20). These signals are shown more clearly in figure 4, which describes, as a block diagram, the operation of the electronic adjustment unit 14. The reference numeral 44, in figure 4, designates a position reference enable signal which is sent to enabling means 45, which receive in input the signal produced by the sum of the strip width signal 41 and of a positional tolerance signal 46 for the strip 1 with respect to the guides 2 and 3; said signals merge in an adder block 47, forming a theoretical guide position reference. An actual position reference, which depends on the real alignment of the strip, is furthermore generated for each guide 2 and 3. In particular, the signal 44, sent to a block which generates a pulsed signal, generates a command for starting the closing motion of the guides by means of the memory blocks 257 and 258 for the hydraulic actuators 15 and 16 respectively. The start command (START) is sent to the ramp generator means 57 and 58 which, by receiving in input a maximum closure reference from the block 157 and 158, for the operator side and for the drive side respectively, generate a ramped position reference which is input to the adder means 57a and 58a respectively. The closure reference signal generated by the means 57 and 58 is stored at the value reached at force contact between each guide and the corresponding edge of the strip, as detected by the force feedback signals generated by the transducer means 10 and 11 or 19 and 20. In particular, the storage signals are EN1(OS) and EN1(DS) for the operator side and for the drive side respectively (if the force transducers are enabled with signals 23-23' and 24-24') or the signals Pb(OS) and Pb(DS), for the operator side and for the drive side respectively (if the strip proximity sensors 19 and 20 are enabled with reception signals 23" and 24"). Once the position in which contact occurs between the guides and the edges of the strip has been reached, the signals MEM(OS) and MEM(DS) generated by the memory blocks 257 and 258, respectively, generate, by means of a logic sum block 147, a RESET signal which enables the position/force-related adjustment of the guides by following and correcting the misalignment of the strip. The RESET signal enables in particular the blocks 69, 82 and 71a on the operator side and 70, 83 and 72a on the drive side. The force threshold signal 26 is a signal which is compared, in blocks 49 and 50, with the actual measured force signal 23 which arrives from the transducer means 8 of the cylinder 4 of the operator side (hereinafter termed OS) and with the actual measured force 24 which arrives from the transducer means 9 of the cylinder 5 of the drive side (hereinafter termed DS). The comparison of these signals in the blocks 49 and 50 produces force error signals, respectively e f (OS) for the operator side and e f (DS) for the drive side. The actual measured force is the reaction force of the edges of the strip 1 against the guides 2 and 3. Said force can be detected, as mentioned, with two types of transducer: force/pressure transducers 8 and 9, or analog transducers 19 and 20 which, by generating yield signals 23', 24' which are appropriately correlated, generate a signal which is equivalent to a force/pressure signal. In the diagram of figure 4, the blocks 51 and 52 indicate the above correlation by means of coefficients K1. The choice of the type of signal to be used (that is to say, of the type of force transducer to be used) is made in the switching blocks 53 and 54 by means of signals F SW /F. The transducers 23" and 24" instead emit signals of the ON/OFF type, designated by Pb(OS) and Pb(DS) respectively. Operation in detail is as follows. By means of the enable signal 44, a theoretical guide position reference is given which is equal to the sum of the width 41 of the strip 1 plus the tolerance 46; said reference is input to a divide-by-two block 55 in order to divide the reference between the operator-side actuator and the drive-side actuator. The signal for actuating the actual movement of the actuator 15 of the operator side is generated in the ramp generator means 57, which receives in input a START signal, generated as described earlier by the enable signal 44, which activates a memory block 257 which is reset by the presence of the minimum-threshold-exceeded signal EN1(ops) or, as an alternative, Pb(OS). The reset signal stores the last reference generated by the means 57. locking the ramp, and enables adjustment with force limit control. The block 57 is driven for maximum CLOSURE or maximum OPENING by suitable signals which are switched by the switching means 157 as a function of the signal 44. The signal in output from the ramp generator block 57 is sent to a position reference adder block 57a. Position adjustment blocks 59, limiter blocks 61 and amplifier blocks 63 for controlling the valve 15 operated by modulated electric control are cascade-connected to said blocks 57 and 57a. The same control circuit is provided for the drive side DS by means of blocks 58, 58a, 60, 62, 64, 16. The signals e f (OS) and e f (DS), obtained as described earlier, arc sent to enabling means 65 and 66, which in the presence of the enable signal, respectively EN2(OS) and EN2(DS), generated by the threshold means 67 and 68, enable the input of the signals e f (OS) and e f (DS) into the increment/decrement means 69 and 70. The threshold means having a double threshold S1, S2 and designated by the reference numerals 67 and 68 compare the current force/pressure signals 23 and 24 with two limit values S1 and S2 which can also be programmed as a function of the signal 26, generating logic enable signals EN2 and EN1 when the current force signal is greater than S2 and smaller than S1, respectively. Accordingly, when the signal 23, 24 is greater than S2, the signal EN2 for enabling the force error signal e f (OS) and e f (DS) is generated and is then processed by an increment/decrement block 69, 70, which generates a position correction signal which is proportional to the force error signal and is added in the adder block 57a, 58a for the OS and DS respectively. The position increment signal allows one of the guides, subjected to a reaction force by the edge of the strip 1, to retract by a value which is proportional to the extent of the measured force error with respect to the threshold S2. The same position correction signal is also transmitted to the block 72 and 71, which inverts the sign of the signal, and then to the blocks 72a 71a, which enable the [delta] inc/dec of said signal (that is to say, the incremental opening or closure position change) only if the affected guide is not subjected to a force/pressure value which is higher than the minimum allowed threshold EN1. Said incremental position correction signal enters the adder blocks 58a, 57a, which have already been described, and then enters the position adjustment means (60 and 59), which controls the valve operated by modulated electric control, which drives the opposite guide so that any outward motion of one of the two guides 2 and 3 with respect to the edge of the strip is associated with an inward motion of the other guide by an equal extent, provided it is subjected to a force which is smaller than S1. This reference, with its sign changed, enters the adder block 57a, 58a, which is enabled only in the presence of signals EN1(OS), EN1(DS); this means that the opposite edge of the strip is not subjected to a force or in any case is subjected to a minimal force which is monitored by the threshold S1. The signal EN1(OS), EN1(DS) is then sent in input to an enable block 74, 73, which enables the blocks 72a and 71a, which generate a [delta] for the movement, with opposite signs, of the two guides. The blocks 71a and 72a are enabled by the OR blocks 73 and 74, which in turn receive in input signals obtained from logic AND means 200-204, which receive in input the inverted signal Pb(OS), the signals EN1(OS), EN2(DS), MIN-F(DS & OS), the A/D signal SW, the inverted signal Pb(DS), and the signals EN1(DS) and EN2(OS). The A/D signal SW is inverted and input to the blocks 200 and 203 and allows to select the type of sensor (analog or digital) used in the control system. If the lower threshold signal EN1 prevails, that is to say, if the force threshold 26 is smaller than the threshold value S1, the actual position signal 21 and 22 generated by the position transducer 6 and 7, respectively for the OS and the DS, is considered and sent to a subtractor block 75. 57a which, by comparing it with the theoretical position reference in output from the block 55, yields a position error signal epos(OS), epos(DS) which is displayed at the block 76, 76a and is furthermore sent to switching means 77, 77a enabled by the fact that in both sides of the strip the reaction force is smaller than the threshold S1. This means that the strip 1 is not in contact with the guides 2 and 3 or is in contact with a very low force. The position error signal epos(OS) and epos(DS) then enters the increment/decrement block 69 and 70, which generates a position correction signal which is proportional to epos(OS), epos(DS), so as to correct the position of the guide 2 on the operator side or 3 on the drive side in order to again move it into contact with the edge of the strip 1. When there is no force, it is in fact necessary to actuate the return of the guide toward the theoretical reference position (output of block 55) in order to guide the strip to the centerline of the mill. The position reference signal generated by the error epos(OS), epos(DS) therefore has a function which is practically the opposite of the function of the force error signal e f (OS) and e f (DS), respectively, and is always added, by means of an adder block 57a and 58a, to the position reference and, with its sign inverted, drives the other guide, provided that the conditions for enabling the blocks 72a and 71 a [delta] INCR/DECR are met. The blocks 78 and 79 are additional switching blocks which allow to select, by means of appropriate selection signals F/D SW (signal from analog or digital ON/OFF transducers), whether one type of transducer or the other is active, that is to say, the signals 23-23' (24-24') or the signals 23"-24" are active. The operation of the operator side (OS) and of the drive side (DS) are mirror-symmetrical and are sometimes independent (for example, both are subjected to a sliding force) and sometimes paired (for example, one side is subjected to force whilst the other one is not loaded). Consider now the case in which transducers of the ON/OFF type are provided and there are no force/pressure transducers and/or yield transducers. By means of a suitable rigidity coefficient K2 input to blocks 80 and 81, the signals Pb(OS) and Pb(DS) are respectively input to integrator blocks 82 and 83, which are meant to integrate the ON/OFF signal, and the value of the integration is sent as a correction to the position reference signal in output from the ramp block 57 and 58 respectively for the OS and the DS, passing through the blocks 78 and 79. The two guides 2 and 3 can both move so as to open independently of each other and drive the opposite guide to close only if said guide does not detect, from the associated transducer 19 or 20, a signal indicating the presence of the strip at that moment. The reference numerals 84 and 85 designate blocks for compensating for the nonlinear gain of the valves 15 and 16 operated by modulated electric control as a function of force/pressure, respectively. If the strip presence signal Pb(OS), Pb(DS) is present, it is necessary to open the guides 2 and 3. When the signal 23"-24" indicating the presence of the strip at a respective guide is detected, a correction signal is generated to open out the corresponding guide and to close the guide on the opposite side (if there is no strip presence signal on that side). This correction is performed by sending the increment calculated in one of the integrator blocks 82 and 83 to the opposite guide with its sign changed in the blocks 71 a and 72a enabled by the signals Pb(DS) and Pb(OS), respectively, so that the opening of one guide corresponds to the approach of the other side by a same value. The inverted signals Pb(OS) and Pb(DS) are then sent to the blocks 73 and 74 respectively, so as to allow to enable the sending of the movement correction signal, with the opposite sign, to the guides. In practice it has been found that the adjustment device according to the invention fully achieves the intended aim, since it allows to perform a dual closed-loop position and force/pressure adjustment, automatically adapting to the movements of the strip to realign the guides with the position of the edges of said strip. The device thus conceived ensures that the value of the force with which the edges of the strip slide on the inlet guides does not exceed a preset value, so as to avoid damaging the edges of the strip and reduce guide wear. The device according to the invention furthermore allows to position the guides more accurately, reducing tolerances with respect to the nominal width of the strip being processed, since there is an automatic adaptation to the width variations of said strip and to any transverse movements thereof, allowing greater precision in processing. The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims all the details may furthermore be replaced with other technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, as well as the dimensions, may be any according to the requirements and the state of the art.

Claims: A device for adjusting the guides for the entry of the strip in a mill housing, comprising: at least one pair of mutually opposite guides (2, 3) which are suitable to adjust the position of the strip that enters the housing and are actuated, in terms of position and force, by respective actuation means; position and force/pressure transducer means (6, 7; 8, 9), which are connected to said actuation means; and an electronic adjustment unit (14), which is suitable to receive signals from said position and force/pressure transducer means for the closed-loop control of said actuation means, in order to keep said guides in the correct position with respect to the strip and apply to the edges of the strip a force which is controlled as a function of parameters related to the position, width and thickness of said strip, which are detected by the transducer means; each one of said guides comprising a cylinder with a corresponding piston, said actuation means being constituted by the piston (17, 18) of said cylinder (4, 5), each one of said guides being connected, by virtue of the interposition of said force/pressure transducer means, to force/pressure comparison means which in turn emit a force/pressure feedback signal for the corresponding guide (2, 3) to be actuated said electronic adjustment unit (14) receiving in input, for each actuation cylinder (4, 5), a position feedback signal related to the piston of said cylinder which arrives from said position transducer means (6, 7), a maximum force reference signal; and a force feedback signal arriving from said comparison means, which are connected to the pressure/force transducer means; said electronic adjustment unit furthermore receiving a position reference signal obtained by dividing by two the sum of the signals related to strip width and tolerance or from the maximum guide opening reference signal, and signals indicating the presence/absence of the edges of the strip and/or signals indicating the yielding of sensors (19, 20) for detecting the movement or presence of said strip. A device according to claim 1, characterized in that said controlled force is furthermore determined as a function of a parameter which distinguishes the type of material of which said strip is made. A device according to claim 1, characterized in that said guides act alternatively so as to close or open, according to the position of the strip with respect to a central line which defines an ideal path for the entry of the strip in the housing. A device according to claim 1, characterized in that each one of said guides furthermore comprises a servovalve, a proportional valve, a pneumatic, hydraulic or electric motor. A device according to one of the preceding claims, characterized in that said adjustment unit is connected, by means of actuators, to respective valves with modulated electric control for the control of said guides. A device according to one of the preceding claims, characterized in that each one of said guides comprises and at least one sensor (19, 20) for detecting the movement or presence of said strip, arranged so as to face the edges of the strip. A device according to one or more of the preceding claims, characterized in that said adjustment unit comprises ramp generator means which receive in input said position reference signal and are connected to means for adjusting the position of the piston of said actuation cylinder, which are in turn connected to limiting means which are suitable to drive first actuation means for controlling the corresponding valve operated by modulated electric control. A device according to one of the preceding claims, characterized in that said signals are related to strip width, strip thickness and type of material of the strip and determine, by means of a correlation function, a force threshold signal, said force threshold signal being subtracted from the actual measured force/pressure signals, in order to obtain a force error signal for each one of said guides. A device according to claim 8, characterized in that it comprises enabling means which are suitable to enable the sending of said force error signal to the strip position adjustment means, according to a threshold which is set by double-threshold means in order to determine the direction of the movement of one guide and of the guide that lies mutually opposite thereto with respect to said central line. A device according to claim 8 or 9, characterized in that said force error signal is sent, with its sign changed, to the means for adjusting the guide that lies opposite to the one from which the force error signal has been obtained, in order to produce a movement of said guide by the same extent but in the opposite direction with respect to said central line. A device according to one of claims 5 to 10, characterized in that it comprises means for compensating the gain of said valves operated by modulated electric control as a function of the force, said means receiving in input actual measured force/pressure signals and being connected to said means for adjusting the position of said guides. A device according to one of the preceding claims, characterized in that said sensors for detecting the presence of the edges of the strip emit edge presence signals which are sent to integrator means in order to drive said means for adjusting the position of the guides and determine their movement in one direction or the other with respect to said central line as a function of the movement of the strip. A method for adjusting guides for the inlet of the strip in a mill housing, comprising the steps that consist in: arranging a first guide (2) and a second guide (3) at the edges of a strip (1) to be rolled, with corresponding actuation means (4, 5, 17, 18) arranged mechanically in contact with said guides (2, 3), controlling the position of said strip with respect to said guides, so as to keep it centered with respect to a central line which defines an ideal path for the entry of the strip in the housing; controlling the position of said guides so as to open or close them with respect to the edges of the strip according to signals related to the pressure/force applied by said strip to the guides and to a position reference signal, said position reference signal being obtained by dividing by two the sum of the width of the strip and of the position tolerance with respect to said guides (2, 3), or a value for the maximum opening of said guides, said force/pressure signal being derived by means of a function for correlating the width of the strip, its thickness and the code of the material of which the strip is made. A method according to claim 13, characterized in that the opening or closing of said guides is performed in a coordinated manner for each guide, the direction of movement of the two guides being mutually opposite with respect to said central line.

Inventors: ANDREOLII MARCO, PEREGO CARLO, ANDREOLII, MARCO, PEREGO, CARLO
Applicants: ABB PROCESS SOLUTIONS & SERVIC, ABB PROCESS SOLUTIONS & SERVICES S.P.A.
Application year: 1998
Main classification: B21B39
IPC codes: B21B39