Rolling mill including means for compensating for roll bending
United States Patent [191 Marten [451 Apr. 15, 1975 [75] Inventor: Hans-Friedrich Marten, Kreuztal,  
 Germany [73] Assignee: Schloemann-Siemag Aktiengesellschaft [22] Filed: Dec. 28, I973 [21] Appl. No.: 429,424  
 [30] Foreign Application Priority Data Dec. 30, 1972 Germany 2264333 [52] US. Cl. 72/8; 72/21; 72/245 [51] Int. Cl B2lb 37/00 [58] Field of Search 72/8, 20, 19, 237, 241, 72/245, 21  
 [56] References Cited UNITED STATES PATENTS 2,903,926 9/1959 Reichl 72/8 3,416,341 12/1968 Dey et al. 72/21 X 3,518,858 7/1970 Kamata 72/19 3,620,058 11/1971 Sabatini et a1. 72/8 3,793,859 2/1974 Sterrett et al. 72/20 X Primary Exdm&#39;inerMilton S. Mehr Attorney, Agent, or Firm-Daniel Patch; Henry C. Westin [57] ABSTRACT The disclosure of this invention pertains to a rolling mill having an hydraulic piston cylinder assembly for bending the rolls to compensate for roll deflection caused by the separating force. One of the rolls is adjusted by other hydraulic piston cylinder assemblies and the separating force is measured by load cells. A control device is provided for receiving a separating force signal from the cells and for controlling the operation of the roll bending and roll adjusting piston cylinder assemblies to maintain the forces thereof at a desired relationship relative to a variation of the separating force.  
 9 Claims, 4 Drawing Figures PATENTEDAPRI 5:915 3, 877, 270  
 sum 2 9f &#39;3 ROLLING MILL INCLUDING MEANS FOR COMPENSATING FOR ROLL BENDING It is known to reduce the bending of rolls of a rolling mill stand caused by the roll separating forces by inducing counteracting bending forces with the aid of bending bearings installed on the extended necks of rolls. The systems known and applied and manufactured devices have the disadvantage that the range of control and adjustment is very limited due to the fact that the roll bending causes mainly a bending of the extended necks of rolls, and the actual roll bodies which are constructed with a large diameter and a high moment of inertia are only slightly elastically deformed by the moments transferred to them.  
  The high bending forces that must be produced to bend the rolls result in an additional load of the stand, causing an increased swelling of the stand, and are the cause for unwanted changes to the roll gap and, with this, of the thickness of the rolled stock. For the reason, the screwing down of rolls must be changed with each adjustment of the roll bending, if the thickness of the rolled stock is to be brought back to the desired thickness. Therefore, the known systems and devices for the adjustment or the control of the bending of rolls have not only the above-mentioned disadvantage of the limited range of control, but also an unwanted influence on the thickness of the rolled stock and a detrimental effect as far as the tolerance of the finished rolled stock is concerned.  
  It has been suggested not to use the spindle screwdown mechanism of a roll stand for the automatic control of the thickness of rolled strips, but instead to additionally change the roll bending force in proportion to the changes of the roll separating forces caused by the various thicknesses of rolled strips. This eliminates an increased bending of the rolls when harder or thicker lengths of rolled strips pass the stand so that the thickness measured in the center of the rolled strip shows less tolerances as would be the case without the application of such a control. The increased load of the stand causes an increased swelling of it which enlarges the roll gap itself. On principle, variations in the lengths cannot be compensated in this manner, and the application of strip tensions, differing over the width of the strip is favored.  
  The present invention has for one of its objects the consturcting of a roll stand in which the counteracting roll bending forces fro the roll or rolls can be derived from the changes of the roll separating forces, without the need of employing a control device.  
  With the application of such an arrangement these forces allow for a quick acting adjustment of the roll bending with only unimportant effects on the roll gap, and a roll gap which is largely constant over its entire length will be attained,and consequently, a uniform shape of the rolled stock as well as a uniform thickness of the rolled stock.  
  The invention has the further object of designing a simple control in a manner that an adjustment of the cross section of the roll gap according to specified cross sections of the entering strip is possible, in order to guarantee that the strip can be rolled free of tension.  
  Another purpose of the invention is to design a roll stand in such a manner that the desired roll bending can be attained with relatively low roll bending forces which load the stand only to an unimportant extent.  
  Another aim of the invention is to design a skin-pass stand which discharges a product which is free of tension when a skin-pass rate of elongation has been specified. This can be attained by providing an adjusting device which will keep the screwdown forces (P and the roll bending cylinder force (P always in proportion to each other, in which the proportional factor results from a distance a of a line which divides the first from the second adjacent quarters of the effective width of the rolled stock, from the center of the adjacent main bearing, and a distance b of the line of application of the restoring force, from the center of said adjacent main bearing according to the following equation:  
  m PA1 1/(b/a+ 1 The roll bending forces which are necessary for the bending of the back-up rolls are considerably reduced when the diameters of the necks of the back-up rolls for four-high roll stands are 0.8 of the diameters of the roll bodies. A control of the thickness of strips can be obtained when the parts of the opposed main bearings are equipped with motion or position pickups which measure their distance, and when a control device is provided for maintaining a specified distance of these parts. The motion or position pickups can be arranged ahead of the control device.  
  As noted, the invention can be applied advantageously to a skin-pass mill. Here it is practical to install pickups in front of and after the roll stand which work together with the strip and which pick up the speed of these strips, and a calculating device is provided to produce a quotient of the results of the pickups. This calculating device specifies its original datum as an actual value to a control device which changes the roll separating force in the sense of a return of the quotient to a specified nominal or desired value. With this, the operation of the roll bending cylinders is changed in proportion to the operation of the hydraulic cylinders which effect the roll separating force.  
  According to the invention, unwanted strip tensions can be avoided when pickups are installed ahead and following the roll gap of the stand, located over the width of the rolled stock, which pickup the thicknesses of the strip or its tensile stresses across the width of the stock. In this way, when differences in thickness or differences in the tensile stress are detected with the aid of a comparison device, values of which are fed to the entrance of a control loop of the control device, the control device influences the roll bending in the sense of reducing or abolishing the differences in thickness or the differences in tensile stress.  
  The invention can be applied to a two-high roll stand as well as other multi-roll stands, such as four-high and cluster stands, and it is explained by the following descriptions of examples of construction in connection with drawings showing two-high and four-high mills. The drawings show the following:  
  FIG. 1 is a side view of a two-high skin-pass mill stand equipped with counteracting bending bearings and roll bending cylinders in diagrammatic and partially sectioned representation;  
  FIG. 2 is one half of a section taken through the housing and the rolls of a four-high roll stand including pickups assigned to it, and a control device represented in block diagram form;  
  FIG. 3 is the skin-pass stand of FIG. 1 including rolls arranged in front of and behind the stand as well as speed and strip tension measuring devices, diagrammatically shown in side view; and  
  FIG. 4 is a control device in block diagram form employed in conjunction with FIGS. 1 and 3 t operate a skin-pass mill.  
  FIG. 1 shows a side view of a mill stand 100 partially sectioned in a plane which lies in front of one of its two identical housings 101 that make up the mill stand. Since the housing and their components are identical only one of the housings will be discussed. The housing 101 has a window 102 in which bearing chocks 103 and 104 of working rolls 105 and 106 are guided. The necks 107 and 108 of the rolls which are rotatably supported in the chocks 103 and 104 extend freely outward of roll bodies 105 and 106, and they are equipped with chocks 109 and 110 at their free ends as well as with roll bending bearings supported in these chocks. The chocks 109 and 110 are constructed each with two similar C- shaped notches into which the end pieces 111 of piston rods 112 engage. Levers 114 which are swingably around axes 113 connected with the housing 101 support hydraulic roll bending cylinders 115, each of which is equipped with two opposite pistons associated with the rods 112. The levers 114 are equipped with forks. Bolts 116 extend through the bores of each fork to which the piston rod of an hydraulic cylinder 117 is attached. Each hydraulic operating cylinder is swingably connected to the housing 101. The end pieces 111 are heldin their operative position in the C-shaped notches formed in the chocks 109 and l with the aid of the hydraulic operating cylinders 115. The hydraulic roll bending cylinders 115 may be swung outwardly by the operating of the hydraulic cylinders 117, and the end pieces 111 can be pulled out of the notches of the chocks 109 and 110 to allow for changing of rolls 105 and 106.  
  The bearing chock 104 is engaged by an hydraulic screwdown cylinder 118 which is mounted on a pressure or load cell 119 supported by the housing 101 and which in turn reproduces a signal proportional to the roll separating force of the mill. The coarse adjustment of the roll gap is done with the aid of a screwdown spindle 120 arranged at the top of the housing 101, which is associated with a common constructed mechanical screwdown device 122 which engages a worm gear 121 secured to the screwdown spindle.  
  A two-high stand has so far been described in which the necks of the working rolls 105 and 106 are supported in bearing chocks in accordance with common mill practice. The rolls are constructed with extended necks and equipped with roll bending bearings on their free ends in such a manner that expanding forces can be applied with the aid of roll bending cylinders 115 which are capable of causing additional bending moments to the working rolls while they are subject to bending caused by the roll separating forces.  
  The effect, as well as the control of the screwdown cylinder 118 and of the roll bending cylinder 115, will be explained in detail by referring to FIG. 2 which shows a vertical section through the roll axes of a fourhigh mill stand in connection with a control device assigned to it which is shown in block diagram form. For the sake of brevity, only the left side of the mill stand from the mean vertical plane is shown in the drawing. The right side while not shown is constructed identical to the left side. The upper and lower yokes of the housing 1 are cut in this particular representation. The main bearings 3 and 4 of the backing rolls 5 and 6 are guided in chocks 7 and 8 in the housing window 2 of the housing 1. The backing rolls back up the working rolls 9 and 10, the necks, bearings, and the chocks of which are not shown in this drawing for simplicity sake. Backing rolls and working rolls enclose a roll gap 11 in which rolled stock 12 is shown in this particular stand. While the chock 8 braces itself against the bottom of the housing window 2- which is formed by the lower yoke of the housing, the chock 7 is screwed down with the aid of an hydraulic screwdown cylinder 13. The screwdown cylinder 13 is associated with a pressure cell 14 which measures the supporting forces which have to be produced by the screwdown device. The screwdown cylinder 13 is supported against the upper yoke of the housing 1 with the aid of a removable block which can be replaced with blocks of different dimensions, and which allows for a coarse adjustment of the screwdown mechanism. Wedge type or screwdown mechanisms using screwdown spindles can be applied instead of these blocks. The distance between the chocks 7 and 8 caused by the blocks and screwdown cylinders 13 is constantly measured by a motion or position pickup device 15 which is inductively active in the given example and which can be built as a magnetic amplifier.  
  In order to attain the dimensions of the main bearings 3 and 4 which are necessary to transfer the high supporting forces, the necks 16 and 17 of the rolls 5 and 6 are constructed with a larger diameter in their root area 36 than in their other areas. For the reasons described later, the diameters of the bodies of the backing rolls 5 and 6 correspond to the diameters of the necks l6 and 17 of these rolls.  
  The free ends of the necks 16 and 17 of the backing rolls are equipped with bending bearing assemblies 18 and 19 which are hydraulically expandable with the aid of a back up roll bending cylinder 20. A motion or position pickup device 21 is arranged between the bearing 18 and 19 and parallel to the back up roll bending cylinder 20, which can be constructed inductively active, similar to the motion pickup device 15.  
  A pressure reservoir 22 is provided to operate the hydraulic screwdown devices 13 of the stand as well as the back up roll bending cylinder 20. The pressure supply system for the pressure reservoir will follow common mill practice, for which reason it has not been I shown in the drawing. It will be noted that the pressure reservoir 22 feeds servo valves 23 and 24 inserted after it.  
  The working rolls 9 and 10 are screwed down with the aid of a control device 25 and a potentiometer 26 arranged ahead of the control device employed to set the appropriate roll gap. The motion pickup 15 is connected to the entrance 27 of the control device 25 and functions as a potentiometer The control device effects the servo valve 23 arranged following it and determines the admission of the compressive volume of the screwdown device 13 with the aid of the connection 28.  
  A control device 29 is equipped with two constant or pre-set potentiometers 30 and 31, and it is designed to control the servo valves 24, and with it, the admission of the backup roll bending cylinder 20. A value is specified with the aid of the constant or pre-set potentiometer 30 which corresponds with a specified roll separating force and which causes a base admission to the backup roll bending cylinder 20 which in turn corresponds with this roll separating force. The roll separating force which has to be intercepted by the housing 1 is determined by the pressure cell 14 and then delivered to the control device 29 as an actual value. The control device causes an increase or decrease of the back up roll bending force brought about with the aid of the back up roll beding cylinder 20 in proportion to each increase or decrease respectively of the roll separating force, at which the proportional factor is specified by the constant or pre-set potentiometer 31.  
  The proportional factor can be calculated based on the following considerations: Starting from the assumption that the entire roll separating force P is transferred pro rata to both housings; the roll separating force P induced into the left half of the rolled stock 12 is transmitted by the housing 1 and represents a component of the supporting force P A1 acting upon the pressure cell 14. With this, a moment is applied into the left halves of the working rolls 9 and 10, the sum of which results from the product of the one half of the roll separating force P and the lever arm. The mean lever arm corresponds to the distance a taken from the center of the main bearings 3 and 4, and the center of the half width of the rolled stock; in other words, from a point taken from between the adjacent first and second quarters of the entire width of the rolled stock. This moment is to be compensated for by a counter moment produced by the roll bending cylinders. The counter moment is determined by the restoring force P as well as by the lever arm b by which this force is applied at the distance between the center of the roll bending bearings 18 and 19 and the center of the main bearings 3 and 4.  
  Accordingly, an equilibrium is guaranteed as long as P a equals P b, and the roll bending due to the rolling force will be totally compensated for. There is a tendency for a change to occur in the distance 0 of the main bearings 3 and 4 when the roll separating force changes, but these changes will be picked up by the motion pickup device and immediately stabilized with the aid of the control device 25 and the quick acting hydraulic screwdown device 13, and the distance 0 will be maintained practically constant. With this, a control of the roll bending is also obtained since when the roll separating force changes, the distance c is maintained constant and so is the distance d of the back up roll bending bearings 18 and 19 until the control device 29 acts.  
  In order to strengthen this effect, the control device 29 is equipped with a second control loop which keeps this distance specified by the potentiometer 32 and/or by the connection 33 of the exit 34 of the control device 25 constant: the distance d is picked up by the motion pickup 21 which is connected with the control device 29 as an input signal. For instance, an increase of the roll separating force which would cause the distance c to increase and the distance d to decrease will be picked up by the control devices 25 and 29 which hold these distances constant. With this, not only the moment occurring in the roll body is increased, but also the bending moment which is forced upon the necks of rolls. In other words, when the roll separating force increases, the back up roll bending force increases at the same time, and the distances or the settings of the motion pickups l5 and 31 will be maintained. Changes of the roll bending as well as changes of the mean roll gap as a result of changes of the roll separating force will be corrected automatically and without any time loss, and the shape of the strip and the thickness of the rolled stock as well as the skin pass degree, as it will be explained in detail in connection with FIGS. 3 and 4, will be maintained at a constant level.  
  Changes of the desired thickness of rolled stock as well as adjusting to changed widths of rolled stock can be obtained by changing the specification of the actual value 26 of the pickup 15 as well as by adjusting the roll bending force P according to the changed roll separating force P in relation to the lever arms a/b. This can be done for one side of the stand as well as for both sides at the same time.  
  The roll bending can also be changed by introducing an additional correction factor K in addition to the change with the aid of the proportional relation P P a/b. This too is possible for one side of the stand as well as for both sides at the same time, in order to make an adjustment to changes of rolling procedures such as variations of the roll body caused by roll etching, temperature variations, wear, changes of the entering strip sections, or changes of the lever arm a, as well as of the resulting roll separating force P during rolling operation.  
  The principle of the control by applying the equality of moments and by maintaining the distance 0 of the main bearings constant which can be considered as the point of rotaton of a scale balance system&#34; has proven to be of great advantage. It has proven to be of special advantage for four-high roll stands to make the necks of the backup rolls-as far as they are involved for backup bending-the same diameter as the roll bodies, and hence, with approximately the same moment of inertia, in order to obtain the same characteristics for backup bending. Furthermore, it has proven to be of advantage when the diameters of the roll bodies and the necks of the rolls are maintained small. In this way, very high expanding forces will be avoided in obtaining the desired bending effect of the rolls as would otherwise be needed due to their high moment of inertia, and, the fact that the necks of rolls must be subject to corresponding high bending stress by the expanding forces. It is recommended to keep the difference between the diameters of the necks of the rolls and the roll bodies at no greater than 0.2.  
  Due to the compensation of the roll bending as described above, the roll body can be kept considerably smaller in its diameter than what has been the case in the past. The large diameter of the roll body has been necessary in the past to obtain a high inherent rigidity. In addition to this, the strain of the roll bodies is greatly reduced by the application of the backup roll bending.  
  The system and the device of the present invention can be applied to a two-high roll stand as well as fourhigh and cluster stands. As shown in the drawing, the following relations of forces and moments result from the application of this system:  
 -Continued Since the proportioned roll separating force cannot be determined directly, and only the corresponding supporting force which is the sum of the roll separating force and of the roll bending force can be determined with the aid of the pressure cell 14, the roll bending force can be calculated, adjusted and constantly controlled with the aid of the following equation:  
 In this case, as noted earlier, K represents the correction factor for the adjusting of the roll bending to certain changes that take place in the roll body and in the roll gap and preferably is 0.5 is than K 2. Changes of the roll separating force due to changes of the thickness of the entering rolled stock or changes of the deformation stability, and of the lubricating conditions, etc., will be automatically corrected accordingly with the aid of a proportional change of the roll bending P in addition to the pickup of the deviations of the load of the main bearings P With this, a system for the bending of rolls is invented which can be applied in many different ways. As long as the set or desired distances c and d are maintained-- -and that applies especially for rolls having roll bodies approximately equal in thickness with the necks of the rolls--variations of the roll separating force are automatically balanced without making a control device necessary. The arrangements described which keep the distances constant assure this result. Furthermore, there is a simple procedure for determining the counter moment, which has to be produced, beforehand. The application can be further extended when the corresponding actual values can be made to influence a controlled system and a simple operation in combination with the widest range of control can be guaranteed due to the combination of the distance control and the control of the supporting force.  
  Furthermore, it could prove to be practical to equip the exit side of the stand with monitors arranged over the width of the rolled stock. The thickness distribution and/or the distribution of the tensile stress of the rolled stock can be determined with the aid of these monitors or with the aid of measuring devices measuring the distribution of the tensile stress over the width of the strip, and further, corrections of the roll bending could be made manually or automatically with the aid of another control loop of the control device 29 which reached over the entrance 35 of the control device. A very low regulating speed is desired for this control loop corresponding with the indirect control which is brought about in this case.  
  Monitors, for instance, gauge measuring devices for the rolled stock, which may be constructed as X-ray devices, can also be used in order to measure the outgoing and/or the entering thickness of the rolled stock as actual value or as reference input to the control device 25 as a further aid to maintain uniform thickness of the outgoing rolled stock which can be added to the control process and, with this, the tolerances are further narrowed down. The monitors mentioned above can do this task in which actual value can either be derived from only one of the monitors or an average can be taken from the measuring results of several monitors.  
  The invention can be further altered. FIG. 3 shows in side view an arrangement as it can be used for surface dressing cold rolled strip. The strip 42 is drawn off from the strip coil 41 and conveyed over a measuring roll 43 coupled with a tachometer 44 to the mill stand which corresponds with the stand shown in FIG. 1 as far as its structure is concerned. After the strip has passed the roll gap of the stand, it is guided over another measuring roll 45 which is coupled with a tachometer 46. A guide roller 47 finally conveys the strip to a reel 49 where it is coiled. A measuring roll 48 is employed on the strip section between the measuring roll 46 and the guide roller 47, which is equipped with rings supported flexibly in an axial direction, the radial compressive load application of which can be determined with the aid of measuring systems, in order to determine the strip tension in various sections of the width. The construction and operation of the rolls 43, 45 and 48, can follow several well-known devices, al though the type disclosed in US. Pat. No. 3,538,765 is preferred. The measuring rolls arranged ahead and following the roll gap in connection with the tachometer represent speed indicators with the aid of which it is possible to determine the quotient between the speed of the entering strip and the outgoing strip, and consequently, to determine the skin-pass rate of elongation.  
  A control arrangement to operate this skin-pass mill arrangement is shown in block diagram form in FIG. 4. The tachometers 44 and 46 transfer signals of the tensions they measure to a comparison device 61. A potentiometer 62 is assigned to the tachometer 44 which is able to increase the excitation of the tachometer 44 against the excitation of the tachometer 46. Its scale is gauged in percents of the excitation of the tachometer 46 so that by increasing the excitation of the tachometer 44 for practically each existing skin-pass rate, uniform output voltages of the tachometer may be set. The desired skin-pass rate will be set with the aid of the potentiometer 62. Due to the increased excitation of the tachometer 44 which occurs with this, uniform output voltages of both tachometers are obtained. Meanwhile both the desired strip tension and the outgoing speed which exceeds the entering speed by the desired percentage are maintained.  
  These output voltages can be compared by the following comparison device 61 and the result will then be forwarded to a control device 63. If the skin-pass rate determined by measuring the speed and the formation of quotients have proven to be too low, the servo valve 66 which is fed by a pressure reservoir 65 will be activated with the aid of the following control loop 64 including an intensifier, and the admission of the screwdown cylinder 118 of the stand 100 shown in FIGS. 1 and 3 will be increased to produce a higher screwdown force, which increases the skin-pass rate. Not until the roll separating force increases, due to the increasing admission to the screwdown cylinder 118 to such an extent that the desired skin-pass rate is obtained as determined by the voltage received by the comparison device 61 moving toward zero, will further admission of the screwdown cylinder 118 be terminated. In order to obtain a more sensitive setting the regulating loop which activates the screwdown cylinder 118 is constructed as control loop 64 which picks up the voltage produced by the control device 63 as nominal value. This control loop 64 receives in addition a signal in the form of the actual value of the separation force of the mill as determined by the pressure cell 119.  
  The roll bending cylinders 1 will admit fluid in proportion to the admission to the screwdown cylinders 118. Principally, the admission control could also be taken off from the exit of the control device 63. For this purpose, a control loop 67 is provided which is directly controlled by the pressure signal of the pressure cell 119, in order to immediately bring about an accurate and sensitive expanding force which follows every change of the roll separating force. The control loop 67 influences a servo valve 69 which also is fed by the pressure reservoir 65. The exits of this servo valve are connected with the hydraulic roll bending cylinders 115 shown in the FIGS. 1 and 3. The pressure in these servo valves is picked up by a pressure pick-off 68 and transferred to the control loop 67 as actual value, in  
 another comparison device 72. In case an asymmetry has been detected, this asymmetry will be transferred to the control loop 67 as an electrical signal and, as another limiting quantity, it causes an additional change of the admission of the roll bending cylinders until the expanding force reaches values that will cause the roll bending to guarantee a product with a constant tension distribution over the width of the strip. In this case, it is not sufficient to keep the roll gap completely parallel and in uniform gauge over its length. For instance, it is not possible to obtain an outgoing material free of tension with a uniform thickness over the length of the gap, when the entering strip is thicker in its center than on its edges. It is practical in this case, to change the roll bending expanding force slightly until a material is obtained which is free of tension. On the other hand, in a case of surface dressing a strip with slightly keystone or concave shaped section, it could also be practical to subject the necks of the rolls of both housings of a stand with different expanding forces or, to let potentiometers of the measuring roll act upon the control loops 64 of a stand with the aid of comparison devices which are interpolated in a different arrangement so that not only different expanding forces can be brought about but also different screwdown forces which are guided or controlled in such a manner that material with constant tensions over the entire width of the strip leaves the roll gap.  
  It will be appreciated that the invention is not limited to the example of the construction illustrated. For instance, monitors can be used to additionally pick up the width of the strip and the determination of the tensile stress of the strip could be useful for reduction rolling of cold strips, for instance, in combination with a roll stand as shown in FIG. 2. It is also possible to provide for roll bending expanding forces to be made proportional to the roll separating forces, when a thickness control and/or an adjustment of an advanced skin-pass rate is not employed. In this case, it is practical to use the control loops determining the expanding force in combination with measuring devices which measure the tension distribution over the width of the outgoing strip, and to control the expanding forces in such a manner that material will be obtained which is free of tension or which has a constant tension over the entire width of the strip.  
  In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof.  
 I claim:  
  1. In a rolling mill having a housing and a pair of rolls between which is formed a roll gap,  
 said pairs of rolls having bearing chock assemblies mounted on their ends received in said housing,  
 position indicating means arranged between at least one of said cooperative opposed pair of bearing chock assemblies and capable of producing a signal representing the distance between said cooperative opposed pair of bearing chock assemblies,  
 at least one of said rolls having free ends which are subject to roll bending forces of hydraulic roll bending piston cylinder assemblies, for the purpose of compensating for at least some of the deflections of said one roll caused by the separating force generated by said rolls during rolling.  
 one of said rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing,  
 a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relationship relative to variations of the separating force, and  
 said control means receiving said distance signal and producing a control signal for effecting an operation of said screwdown to maintain substantially constant the distance between said cooperative opposed pair of bearing chock assemblies.  
 2. In a rolling mill having a housing and a pair of rolls between which is formed a roll gap,  
 at least one of said rolls having free ends which are subject to roll bending forces of hydraulic roll bending piston cylinder assemblies, for the purpose of compensating for at least some of the deflections of said one roll caused by the separating force generated by said rolls during rolling,  
 one of said rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relationship relative to variations of the separating force, and  
 said pair of rolls having bearing chock assemblies mounted on their ends received in said housing and wherein said proportional relationship is determined by a distance a drawn from a line dividing the adjacent first quarter from the second quarter of the effective width of the roll stock and the center of the adjacent bearing chock assemblies on the one hand and a distance b from a line coincident with the application of the roll bending force and the center of said adjacent bearing chock assemblies according to the equation:  
 where P represents the roll bending force, and P represents the separating force.  
  3. In a rolling mill according to claim 2, wherein said proportional factor is modified by another factor K in which said K factor is greater than 0.5, but less than 2.  
 4. In a 4-high rolling mill having a housing including a pair of work rolls between which is formed a roll gap,  
 at least one of said backup rolls thereof having free ends which are subject to roll bending forces of hydraulic roll bending piston cylinder assemblies, for  
 the purpose of compensating for at least some of the deflections of said one roll caused by the separating force generated by said rolls during rolling, and  
 wherein the diameters of the necks of said one backup roll is at least 0.8 of the diameter of the roll body of said one backup roll,  
 one of said rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing,  
 a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relatonship relative to variations of the separating force.  
 5. In a 4-high rolling mill having a housing including a pair of work rolls between which is formed a roll gap, at least one of said backup rolls thereof having free ends which are subject to roll bending forces of hydraulic rollbending piston cylinder assemblies, for the purpose of compensating for at least some of the deflections of said one roll caused by the separating force generated by said rolls during rolling. said backup rolls having bearing chock assemblies received in said housing, and  
 the necks of the said one backup roll being constructed with diameters in the areas at which said bearing chock assemblies are mounted which exceed the diameters of the necks and/or the diameters of the roll bodies of said one backup roll,  
 one of said rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing,  
 a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relationship relative to variations of the separating force.  
 6. In a 4-high rolling mill having a housing including a pair of backup rolls and a pair of work rolls, said work rolls forming a roll gap and wherein said backup rolls have bearing chock assemblies received in said housmg,  
 said backup roll having other bearing chock assemblies which are subject to roll bending forces of hydraulic roll bending piston cylinder assemblies for the purpose of compensating at least some of the deflections of said backup rolls caused by the separating forces generated by said rolls during rolling,  
 position indicating means arranged between cooperative opposed bearing chock assemblies associated with said roll bending piston cylinder assemblies for measuring the distance between said opposed bearing chock assemblies,  
 said indicating means adapted to produce a signal representative of said distance,  
 one of said backup rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing,  
 a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relationship relative to variations of the separating force, and  
 said control means receiving said distance signal and including means for maintaining substantially constant said distance between said cooperative opposed bearing chock assemblies associated with said roll bending piston cylinder assemblies.  
 7. In a rolling mill having a housing for receiving a pair of rolls between which is formed a roll gap,  
 at least one of said rolls having free ends which are subject to roll bending forces of hydraulic roll bending piston cylinder assemblies, for the purpose of compensating for at least some of the deflections of said one roll caused by the separating force generated by said rolls during rolling,&#39;  
 one of said rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing,  
 a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relationship relative to variations of the separating force,  
 roll stock engaging means arranged on the entry and delivery sides of said roll gap for measuring the differences in thickness or in tensile stress transversely of the roll stock,  
 a thickness comparison means associated with said control means, and  
 said thickness comparison means being in the form of a control loop adapted to effect an adjustment of said roll bending in order to reduce or eliminate any detected difference in transverse thickness or tensile stress of said roll stock.  
  8. In a rolling mill according to claim 7 including a device for regionally measuring transversely the roll stock tension on the delivery side of said mill,  
 said device including means for feeding a signal to a second control loop,  
 said second control loop adapted to adjust said roll bending in a manner that differences in roll stock tension occurring over the width of the roll stock are maintained at a desired low level.  
  9. In a rolling mill having a housing for receiving a pair of rolls between which is formed a roll gap,  
 at least one of said rolls having free ends which are subject to roll bending forces of hydraulic roll bending piston cylinder assemblies, for the purpose of compensating for at least some of the deflections of said one roll caused by the separating force generated by said rolls during rolling,  
 one of said rolls being adjusted by an hydraulic piston cylinder assembly screwdown arranged in said housing,  
 a pressure detecting means for producing a signal proportional to the separating force, which signal is received by a control means,  
 means for connecting said control means with said roll bending piston cylinder assemblies in a manner that the forces of said roll bending and screwdown piston cylinder assemblies are maintained in a desired proportional relationship relative to variations of the separating force,  
 speed determining means arranged on the entry and delivery side of said mill and means associated therewith for determining the difference between the entry speed and the delivery speed of the said rolled stock and control speed means for producing a datum value of a desired speed difference of the rolled stock and comparing it with said determined difference in speed,  
 said control speed means including means for effecting operation of said screwdown piston cylinder assembly in order to return said determined speed difference to said desired value, and  
 said control speed means also including means for changing said roll bending piston cylinder assemblies in proportion to the change effected in said screwdown piston cylinder assemblies.  
  UNITED arrrENT oFFIcE CERTIFICATE CORRECTION PAlENl&#39; NO 3 8&#39;77 270 DATED April 15, 1975 Hans-Friedrich Marten iiw&#39;VENTOKiS:  
  It s certified t&#39;r a r error appears in the above-Identified patent and that said Letters Patent are hereby corrected as shown below- Column 1, line 48, &#34;consturcting&#34; should readconstructing; and  
 line 49, &#34;fro&#34; should readfor.,  
 Column 3, line 6, &#34;ot&#34; should readto-.  
 Column 5, line 8, &#34;beding should readbending.  
 Column 7, lines &#39;7 to 9, formula 6, that the two portions of the formula reading &#34;p 1 and &#34;iAP 1 H +1 1 a a should read PA1 1 l 0 19 +1 b 1 a E Signed and Scaled this twenty-second Day of July 1975 [SEAL] A nest:  
 RUTH C MASON Allesling Officer C. MARSHALL DANN Commissioner of Parents and Trademarks