Patent Publication Number: US-3875775-A

Title: Device for automatic adjustment of strip thickness in rolling

Description:
United States Patent Daniljuk et al.  
 l l DEVICE FOR AUTOMATIC ADJUSTMENT OF STRIP THICKNESS IN ROLLING [76] Inventors: Valery Vladimirovich Daniljuk.  
 ulitsa Serebryannikovskaya. l6. kv. 39&#39;. Alim Ivanovieh Chahanov. ulitsa Zorge. l8l. kv. 1 I3. both of Novosibirsk. U.S.S.R.  
 [22l Filed: May 10. I974 [2 ll Appl. No.: 468.735  
 I52] US. Cl 72/8; 72/20 [Sll lnt. CI B2lb 37/08: BZIb 37/l2 [53] Field of Search 72/8. 20. 28  
 [Sol References Cited UNITED STATES PATENTS 3 55(l.-ll3 IZII HU Barackel 72/8 lhXhHlW 8/l972 Scholm et ul. 72/20 X Irinmry EXUHIIIHV-Mllltlll S. Mehr Attorney. Agent. or FirmWaters. Roditi. Schwartz &amp; Nissen {57] ABSTRACT A device for automatic adjustment of thickness of strip being rolled on units producing strip material. comprising a closed hydraulic system providing local enhancement of roll mill stand rigidity within a force range approximately equal to a range of deviations of the rolling pressure from a specified value. The system includes at least one hydraulic power cylinder disposed intermediate of work roll supports. a second bydraulic cylinder functioning as a damper whose piston is being fixed as the strip passes through the roll mill stand. said hydraulic cylinders being arranged symmetrically on both sides of the roll mill stand. and a controlled valve. The device comprises also a second closed hydraulic system providing local enhancement of roll mill stand rigidity within a force range sufficient to correct the deviations in the strip thickness from that specified. The second system includes at least one hydraulic power cylinder disposed intermediate of backup roll supports. a second hydraulic cylinder functioning as a damper whose piston is being fixed as the strip passes symmetrically the roll mill stand. said hydraulic cylinders being arranged symmetriclaly on both sides of the roll mill stand. and a controlled valve. In addition. the device is fitted with a circuit for stabilizing the thrust of the work rolls within a specified range and with a circuit for correcting deviations in the transverse profile of the strip being rolled from that specified. The latter circuit has a gauge for measuring the pressure within the second hydraulic system. a setter of the rated thrust force of the back up rolls and an adder connected with one input to the output of the gauge for measuring pressure within the first hydraulic system and with the second input to the output of the pressure gauge of the second hydraulic system. its third input being connected to the rated thrust force setter of the work rolls and a fourth input to the rated thrust force setter of the backup rolls with its output being connected through a variable gain amplifier to the input of a comparison element and through another amplifier also with a variable gain to the input of an initial pressure setting controller of the first hydraulic system.  
 2 Claims. 2 Drawing Figures 3 24 25 22 A a; UN  
 PATENIEUAPR&#39; ems DEVICE FOR AUTOMATIC ADJUSTMENT ()F STRIP THICKNESS IN ROLLING The present invention relates to devices for automatically adjusting. both in a transverse and longitudinal direction. the thickness of strip being rolled: it may prove to be most advantageous in units producing strip materials. such as paper. synthetic films. by rolling. preferably on hotand/or cold-rolling mills for processing fer rous and non-ferrous metals.  
  The process of rolling of a strip material. such as strip steel. is characterized by a number of disturbances affecting thickness accuracy ofthe strip both in a longitudinal and transverse direction. The disturbances are subdivided into external ones (i.e.. those brought in a mill by the strip! and internal ones (those produced by the instrumentation signal per se). Most important disturbances affecting parameter accuracy of rolled products are the following: the disturbances brought in by fluctuations of a rolling force. variations in thickness of rolled stock. changes in height and rigidity of an oil wedge in film lubrication bearings of backup rolls caused by changes in a rolling speed. backup roll runout. anisotropy of rolled stock material. temperature instability of the strip during hot rolling and so on.  
  Known in the art is a diversity of automatic control system adapted for stabilizing the thickness of rolled stock. the above systems differing in methods and deices for measuring deviations in strip thickness. procedures for effecting power action on rolling conditions in the course of their stabilization and in the nature of compensated components of the disturbing action.  
  The control system for adjusting the parameters of the rolled stock. based on direct gauging of roll support thrust as well as those comprising a hydromechanical or an electrohydraulic actuating mechanism in a highspeed compensating channel are considered to be most advanced.  
  Thus. known in the art is a device for effecting fine control action on the profile of the strip being rolled by adjusting hydraulic forces applied to work roll supports either manually or by a signal from rolled stock thickness gauges set up at the exit side of a rolling mill.  
  Also known is a device for automatic adjustment of the thickness of strip being rolled. based on the principle of local enhancement of stand rigidity (see. e.g.. US Pat. No. 3686907. Cl. 73-6 granted in 1972). The above device comprises closed hydraulic systems for controlling the thrust of work and backup roll supports, and a housing screw electric drive. acting on the backup rolls and utilized as a third power action channel during the adjustment process. The first closed hydraulic system for controlling the thrust and ensuring local enhancement of roll mill stand rigidity within a force range approximately equal to a deviation range of the rolling pressure from that specified. comprises at least one hydraulic power cylinder mounted intermediate ofthe work roll supports. a second hydraulic cylinder functioning as a damper whose piston is being fixed as the strip passes through the stand. said cylinders being disposed symmetrically on both sides of the roll mill stand. and a controlled valve, and acts simultaneously as an actuating mechanism and as a gauge for measuring \ariations in strip thickness depending on the position of hydraulic cylinder pistons. The second closed hydra ulic system for controlling the thrust ofthe backup roll supports ensures local enhancement of rigidity of the roll mill stand within a force range sufficient to correct deviations of the strip thickness from that specified and includes at least one hydraulic power cylinder disposed intermediate of the backup roll supports. a second hydraulic cylinder functioning as a damper whose piston is being fixed as the strip passes through the roll mill stand. and a controlled valve.  
  The device comprises also a circuit for stabilizing the thrust of the work roll supports within the specified range. said circuit including a pressure gauge of the first closed hydraulic system. a setter of a rated thrust of the work roll supports. and an element for comparing an actual pressure with its rated value. The above device enables high-precision thickness stabilization of the strip being rolled only in a longitudinal direction.  
  With the above-mentioned prior-art devices the pressure within the hydraulic systems controlling the thrust of the work and backup roll supports can be adjusted either manually or by a signal from the strip profile meter arranged at the mill exit. This results in:  
  a. principal impossibility to correct the errors in the profile of the strip being rolled brought about by the backup roll runout. insofar as the frequence of this disturbance exceeds the natural frequency of controllers by order of magnitude;  
  b. a need for accurate gauging the strip thickness in a transverse direction at least at three points with the ensuring substantial increase in both the device cost and overall dimensions;  
  c. insufficiently fast control system response to compensate deviations in the strip profile brought about by rapid variations of the roll force.  
  The above-listed disadvantages restrict the control accuracy of the strip profile. e.g. of a strip in hotand- /or cold-rolling. within a range of $0.03 to 10.05 mm even when using a precision system for adjusting the thickness variations in the longitudinal direction.  
  The principal object of the invention is the provision of a device for automatic adjustment of the thickness of strip rolled stock. which would allow obtaining a preset profile of material being rolled within an accuracy range of iOIlOZ to $0.005 mm.  
  Another object of the invention is the provision of a device featuring a sufficiently fast response to correct thickness variations of the strip being rolled both in a longitudinal and transverse direction within the entire frequency range of disturbing actions.  
  A further object of the invention is to provide a device whose embodiment would require neither high layouts nor longterm shutdowns of the rolling mill.  
  Still another object of the present invention is the provision of a device of the type described featuring high reliability.  
  The present invention resides essentially in that a device for automatic adjustment of the thickness of strip being rolled on units for the production of strip materials. comprising a first closed hydraulic system providing local enhancement of roll mill stand rigidity within a force range approximately equal to that of deviations of the roll force from the specified value. and including at least one hydraulic power cylinder disposed intermediate of work roll supports. a second hydraulic cylinder functioning as a damper whose piston is being fixed as the strip passes through the roll mill stand. said hydraulic cylinders being arranged symmetrically on both sides of the roll mill stand. and a controlled valve. a second closed hydraulic system ensuring local enhancement of rigidity of the roll mill stand within a force range sufficient to correct deviations of the strip thickness from that specified and including at least one hydraulic power cylinder and disposed intermediate of the roll supports. a second hydraulic cylinder functioning as a damper whose piston is being fixed as the strip passes through the roll mill stand. said hydraulic cylin ders being arranged symmetrically on both sides of the roll mill stand. and a controlled valve. said device comprising also a circuit for stabilizing the thrust of the work rolls within the specified, range. the above circuit including a pressure gauge of the first closed hydraulic system. a setter of the rated thrust of the work rolls. an element for comparing the actual pressure with its specific value. and an actuating member communicated hydraulic with the second hydraulic system. said device being provided. according to the invention. with a cir cuit for correcting deviations of the transverse profile of the strip being rolled from a preset value. including a pressure gauge of the second hydraulic system. a setter ofthe rated thrust ofthe backup rolls, an adder connected with one its input to the output of the pressure gauge of the first hydraulic system. its second input being connected to the output of the pressure gauge of the second hydraulic system. third input to the setter of the rated thrust of the work rolls. fourth input to the setter of the rated thrust of the backup rolls and its out put being connected through a variable gain amplifier to the input ofthe comparison element and through an other variable gain amplifier to the input of a controller setting the initial \alue of the pressure within the first hydraulic system.  
  It is expedient that the correction circuit be fitted with a gate connected to a strip presence sensor and controlled by a signal therefrom The device for automatic adjustment of the thickness of strip being rolled according to the present invention ensures stabilization of the thickness of rolled stock both in a longitudinal and a transverse direction and a substantially higher lby an order of magnitut&#39;le) accu&#39; racy of adjusting the profile of the rolled stock as compared with the similar prion-art systems.  
  The hercinproposed device features of sufficiently fast response and ensures compensation of such dis turbances as the runout of the backup rolls.  
  Moreover. the device has an adequate reliability and does not necessitate extensive modernization ofthe roll mill stands. long-term shutdowns and high outlays to be realized on existing rolling mills Other objects and advantages of the invention will hereinafter become fully apparent from a consideration of a detailed description ofexemplary embodiments to be has in conjunction with the accompanying drawings. wherein:  
  FIG. 1 is a block diagram of a device for automatic adjustment of thickness of strip being rolled. according to the imention;  
  H6. 2 is a block diagram of the same device with an electromechanical controller of pressure within the first hydraulic system. according to the inicntion.  
  Considered hereinbelow is an exemplary embodiment of a de\ ice for automatic adjustment of thickness of strip being rolled on hotand/or cold-rolling mills.  
  Mounted in a roll housing I (FIG. 1) are chucks 2 acting as supports of backup rolls. chucks 3 which some as supports of work rolls. and housing screws 4 dri en by an electric drive 5.  
  One each side of the roll mill stand (shown in the drawing are the elements. devices and their interconnections only for one side of the stand) provision is made for hydraulic cylinders 6 and 7 with builtin pistons 8 and 9 set up intermediate of the work and backup roll supports so that a pressure built-up in the hydraulic cylinders 6 and 7 with the aid of a pumping unit 10 and open remote-controlled shutoff valves 1] and 12 would provide a thrust acting on said supports.  
  The device is also provided with hydraulic cylinders l3 and 14 functioning as dampers whose pistons 15 and 16 accordingly are being fixed during the rolling pro cess in their extreme positions with the aid of appropriate springs 17 and Is.  
  Said hydraulic cylinders 6 and 13 and the remotecontrolled shutoff valve 11 are connected to form a first closed hydraulic system for controlling the thrust of the work roll supports ensuring local enhancement of rigidity of the roll mill stand within a force range approximately equal to that of deviations of the roll pressure from the specified value. The hydraulic cylinders 7 and 14 and the remote-controlled shutoff valve 12 form a second closed hydraulic system for controlling the thrust ofthe backup roll supports ensuring local en hancement of rigidity of the roll mill stand within a force range sufficient to correct the strip thickness deviations from that specified.  
  The initial forces of the springs 17 and 18 determine the values corresponding to maximum permissible pressures of working medium within the closed hydraulic systems and. hence. the thrust of the work and backup roll supports at the moment the strip being rolled leaves the stand.  
  Pressure fluctuations in the thrust hydraulic system of the backup roll supports are recorded by a gauge 19 and those within the thrust hydraulic system of the work roll supports by a gauge 20 which are in this instant magnetoanisotropic force pickups. During the rolling process the output signal of the gauge 20 is proportionate to a strip thickness deviation from the value at which the remote-controlled shutoff valve 11 is closed. This signal is used for automatic stabilization of the strip thickness during rolling.  
  The output of the gauge 20 is connected to the input of an amplifier 21 coupled in turn with its output to one of the inputs of a comparison element. in this instant. of an adder amplifier 22. The output of the amplifier 22 is connected to the input of an electrohydrualic drive comprising a thyristor converter 23 which controls an electric motor 24 whose shaft is rigidly coupled to a pltlngerdistributor of a rotary slide valve 25. With the help of the rotary slide valve 25 a high-pressure pumping unit 26 creates a pressure in the thrust hydraulic system of the backup roll supports.  
  The device includes also a rated thrust setter 27 of the work roll supports. the output of said setter being connected to the second input of the amplifier 22.  
  hi this case a potentiometer is employed as the setter 27.  
  The device elements 20 through 27 form a circuit for stabilizing the work roll thrust within the specified range with the electrohydraulic drive 23- 25 acting as an actuating member.  
  The outputs of the gauges 19 and 20 are connected to corresponding inputs of an adder through inverting amplifiers 28 and 29. Two other inputs of the adder 30 are coupled as follows: one input is connected to the above-mentioned rated thrust setter 27 of the work roll supports and the other to a rated thrust setter 31 of the backup roll supports in the thrust hydraulic system of the backup roll supports. The output of the adder is connected through a low-pass filter 32 and a transistorized gate 33 controlled by a roll mill stand strip presence sensor 34 and a variable gain amplifier 35 to the third input ofthe amplifier 22 and through an amplifier 36 also having a variable gain to the input of a controller setting the pressure within the thrust hydraulic system of the work roll supports comprising an amplifier 37. a thyristor converter 38 and an electric motor 39 connected in series. with the output of the electric motor 39 being coupled through a screw pair 40 with a piston 41 travelling within the interior ofa correcting hydraulic cylinder 42. The interior of the correcting hydraulic cylinder 42 communicates with the thrust hydraulic system of the work roll supports.  
  FIG. 2 shows a device which differs from that presented in FIG. 1 in that the controller setting the pressure in the thrust hydraulic system of the work roll supports is of an electromechanical type.  
  The device elements 19. 20. 27, 30, 31, 35 through 42 form a circuit for correcting deviations of a trans verse profile of the strip being rolled from that specified.  
  hi this embodiment the controller setting the pressure of the thrust hydraulic system ofthe work roll supports comprises an electronic amplifier 43 with an ex citing winding 44 of a reversible motor 45 being connected to the output of said amplifier 43. Another ninding 46 of the motor 45 is always connected to a power supply source drawing from industrial power mains. The shaft of the motor 45 is rigidly connected to a slider 48 of a rheochord 49. The latter is also provided with a rigidly fixed slider 50. An output signal from the rheochord 49 is added algebraically with the rated pressure value of the rated thurst setter 27 of the work roll supports.  
  The input of the electronic amplifier 43 is connected to the output of the amplifier 36.  
  The operation ofthe device for automatic adjustment of the thickness ofstrip being rolled will now be considered for the case of the device shown in FIG. 1.  
  in the course of adjustment of the rolling mill after changing the rolls or when readjusting the roll milI stands for new parameters of strip being rolled. the valves 1] and i2 and the transistorized gate 33 are open. The signal from the output of the adder 30 does not pass to the amplifiers 35 and 36 through the filter 32.  
  With the aid of a local feedback circuit [not shown in FIG. it the electric motor 24 sets the rotary slide valve 25 with the end face plungendistributor to a neutral position shutting off thereby the high-pressure pumping unit 26 from the thrust hydraulic system of the backup roll supports.  
  The electric motor 39 by making use also of a local feed-back circuit (not shown in FIG. 1) placs the correcting piston 41 of the hydraulic cylinder 42 adjusting the pressure setting within the thrust hydraulic system of the work roll supports in an intermediate position in the function ofthe signal ofa setter 51 of the initial position of the piston 41 actuated by the signal from the sensor 34 in case of no strip being in the roll mill stand.  
  Under the pressure of the working medium delivered beneath the pistons 7 and 8 by the pumping unit 10. the  
 pistons 7 and 8 create the thrust forces F, and F of the supports of the backup and work rolls accordingly.  
  As the strip being rolled enters the roll mill stand. it exerts an influence of the work rolls building up a roll ing pressure P. The total force R acting on one stand side is equal to:  
  The rolling pressure results in an additional strain of the stand. increasing the roll thrust so that the pistons Sand 9 will shift augmenting the volume ofthe working medium within the hydraulic system.  
  The stand is adjusted for a preset thckness of rolled stock with the help of the housing screws 4 actuated by the electric drive 5. The pressure of the pumping unit 10 is set up either manually or automatically in accordance with the signals from the setter 27 (a circuit for transmitting and executing the above command is not shown in FIG. I).  
  The stand adjustment completed. i.e.. the strip pa rameters having acquired a requisite value. the valves 11 and 12 are closed either manually or automatically a supply voltage U,, is applied to the input of the strip pressence sensor 34 and the gate 33 closes.  
  Variations in the strip thickness caused. for example. by changes in the thickness of rolled stock stipulate a propriate pressure fluctuation in the closed thrust hydraulic system of the work roll supports and. hence. in the output signal of the inverting amplifier 21 which then comes to the input of the amplifier 22 where it is compared with the signal from the setter 27. A mismatch signal from the output of the amplfier 22 causes the displacement of the plutiger-distributor of the rotary slide valve 25 which ensures a rise (drop) in the pressure on the piston 9 and an appropriate decrease (increase) in the pressure on the piston 8 so that a constant pressure is maintained within the thrust hydraulic system of the work roll supports which provides for high-precision stabilizing of the thickness of the strip being rolled in a direction longitudinal to the rolling axis. However. insofar as an increment of the rolling pressure changes the profile of a roll system. the strip thickness alters in a transverse direction: at arise in the rolling pressure. e.g.. at a change in parameters of the strip entering the roll mill stand, the thicknes of the strip edges decreases in relation to its midportion, and vice versa. Therefore if the rolling pressure rises. a higher pressure should be provided in the thrust hydraulic system ofthe work roll supports which may re establish the roll and strip profiles.  
  The above-stated will be illustrated by a specified example.  
 Assume that the rolling pressure increases.  
  A rise in the rolling presure P and a corresponding decrease in the force F result in a diminution of the output signal of the gauge 19 measuring the pressure within the thrust hydraulic system of the backup roll supports which in turn leads to the appearance of a signal at the input ofthe amplifier 22 having the same signal as the signal from the setter 27. The electrohydraulic drive 23-25 installed in the hydraulic thrust channel of the backup roll supports responds to said signal so that the force F diminishes still further. while the force F- grows up.  
  In case the thrust hydraulic system of the work roll supports was absolutely rigid. the signal appeared at the output of the amplifier 35 would result in similar as to their modulus but dissimilar as to their polarity increments of the forces F and F andhence. a signal coming to the input of the amplifier 35 would be proportionate to the rolling pressure fluctuations. However the rigidity of a closed hydraulic system is finite and the system of the above type is not therefore feasible in practice owing to a small stability margin (the circuit comprising the adder 30, filter 32, gate 33 and amplifier 35 constitutes a positive pressure feedback in the thrust hydraulic system of the backup roll supports) which leads to still larger variations in the strip thickness in a longitudinal direction.  
  To stabilize the thickness of rolled stock the setting of the rated thrust pressure ofthe backup roll supports must be changed. To this end the signal from the output of the adder 30 is passed through the amplifier 36 to the controller 37 through 42 providing thereby a corresponding displacement ofthe piston 41 ofthe hydraulic cylinder 42 in the thrust system of the work roll supports. By selecting (adjusting during both setting up and operation) the gains of the amplifiers 35 and 36 approximate equality of the increment modulus of the forces F and F is provided in the function of the output signal of the adder 30. in this case the attaining of stability in the strip profile control channel with again needed under given accuracy conditions presents no problems and the strip thickness stability in a longitudinal direction is not disturbed.  
  ln a possible emodiment ofthe device shown in FIG. 2. the signal from the output ofthe amplifier 36 in con trast to the device presented in FIG, I. comes to the input ofthe electronic amplifier 43. The electronic aniplifier 43 is made phaseresponsive so that the sign of the input signal would determine the direction of rotation of the motor 45 and. hence, the displacement of the slider 48 of the rheochord 49 rigidly connected to the shaft of the motor 45. The slider 48 shifting along the rheochord 49 with respect to the stationary fixed slider 50. a voltage appears at the output of the rheo chord 49 and this voltage upon being added with the voltage of the setter 27 changes the pressure setting within the thrust hydraulic system of the work roll supports which restores the strip profile.  
  To provide the device stability the low-pass filter 32 adds to the system response when compensating the variations in the longitudinal thickness over that of the strip profile stabilization system.  
  When the strip being rolled leaves the stand. the signal from the strip presence sensor 34 opens the gate 33 interrupting thereby the functioning of the strip profile stabilizing channel since at this moment the pressure within the thrust hydraulic system of the work and backup roll supports attains its limit values The interconnection of the proposed device with the electric drive 5 ofthe housing screws 4 is not shown in y the accompanying drawings. since it adds nothing new to the invention; it necessitates only an additional leadout from the gauge 19 measuring the pressure within the thrust hydraulic system of the backup roll supports running to the followup electric drive 5 of the housing screws 4 and an additional input to the adder 30 from a screw position transducer (the housing screw position transducer is not shown in FIG lit The circuits intended for correcting the strip thickness and profile running from the meters set up at the exit of the rolling mill are not presented in the drawings for the same reason.  
 What we claim is:  
  l. A device for automatic adjustments of thickness of strip being rolled on units producing strip materials, comprising: a first closed hydraulic system providing local enhancement of roll mill stand rigidity within a force range approximately equal to a range of deviations of the roll pressure from that specified; at least two hydraulic power cylinders of said first hydraulic system arranged singly and symmetrically on both sides of the roll mill stand intermediate of work roll supports of the stand; at least one damping hydraulic cylinder in said first hydraulic system: a piston of said damping hydraulic cylinder which is being fixed as the strip passes through said stand; a controlled valve in the first said hydraulic system; a second closed hydraulic system providing local enhancement of roll mill stand rigidity within a force range sufficient to correct deviations in the strip thickness from that specified; at least two other hydraulic power cylinders of said second hydraulic system arranged singly and symmetrically on both sides of the roll mill stand intermediate of the backup roll supports ofthe stand: at least one another damping hydraulic cylinder in said second hydraulic system: a piston of said other damping hydraulic cylinder which is being fixed as the strip passes through the roll mill stand; another controlled valve in the second hydraulic system; a circuit for stabilizing the thrust of the work rolls within a specified range; a setter ofthe rated thrust of the work rolls in said stabilizing circuit; a gauge for measuring the pressure within said first hydraulic system; a comparison element in said stabilizing circuit connected with one its input to the output of said pressure gauge and with another input to the output of said setter; an actuating element whose input is coupled to the output of said comparison element. its output being hydraulically associated with said second hydraulic sys term a circuit for correcting thickness deviations of the transverse profile of the strip being rolled from that specified another gauge for measuring the pressure within said second hydraulic system; a setter of the rated thrust of the backup rolls. an adder in said correcting circuit whose first input is connected to the output of said pressure gauge of the first hydraulic system; a second input to the output of said another pressure gauge of the second hydraulic system; a third input to said setter of the rated thrust of the work rolls and fourth input to said setter of the rated thrust of the backup rolls; a controller of the setting of initial pressure of said first hydraulic system; a first variable gain amplifier; a second variable gain amplifier; said adder whose output is connected through said first amplifier to the third input of said comparison element and through said second amplifier to the input of said controller of the initial pressure setting in the first hydraulic system 2. A device for automatic adjustment of thickness of strip being rolled on units producing strip materials. of claim 1, comprising: a gate set up in said correcting cir cuit; a strip presence sensor of the roll mill stand controlling said gatev