US3714805A

US3714805A - Control system and method for concurrent automatic gage and crown control of a rolling mill

Info

Publication number: US3714805A
Application number: US00197715A
Authority: US
Inventors: M Stone
Original assignee: Wean United Inc
Current assignee: United Engineering Inc
Priority date: 1971-11-11
Filing date: 1971-11-11
Publication date: 1973-02-06
Anticipated expiration: 1990-02-06
Also published as: FR2161952A1; CA994453A; FR2161952B1; ES408244A1; GB1416175A; DE2253524A1

Abstract

A control system and method for concurrently controlling the delivery gage and crown of a workpiece while it is being processed in a rolling mill, preferably in the form of a 4-high rolling mill including a piston and cylinder assembly type of force applicator for adjusting the gap formed between the working rolls under the rolling load. The rolling mill further includes roll bending apparatus whereby bending forces are applied to extended journals of the backup rolls for changing the effective roll crown at the roll gap. The control system provides an automatic control designed to concurrently maintain a relationship between signals generated on the basis of rolling mill measurements to control the force applicator and the roll bending device. This concurrent relationship of signals equates a position change of the force applicator with the algebraic sum of signals representing roll gap changes due to a change in the rolling load and due to a change in the roll bending force, while concurrently the change in roll crown due to a change in roll bending force is equated to a rolling load change. The control system includes additional circuitry for an alternate form of concurrent gage and crown control.

Description

United States Patent 11 1 Stone 21 Appl. No.: 197,715

[52] U.S. Cl ..72/8, 72/19 [51] Int. Cl. ..B21b 37/08 [58] Field of Search ..72/79, 19, 20,

[56] References Cited UNITED STATES PATENTS 3,394,566 7/1968 O'Brien ..'...72/8 3,518,858 7/1970 Kamata ...72/l9 3,534,571 10/1970 Sivilotti et al. .....72/8 3,620,058 l l/l97l Sabatini et al ..72/8

Primary vExaminerMilton S. Mehr Attorney-Henry C. Westin 14 1 Feb. 6, 1973 5 7 ABSTRACT A control system and method for concurrently controlling the delivery gage and crown of a workpiece while it is being processed in a rolling mill, preferably in the form of a 4-high rolling mill including a piston and cylinder assembly type of force applicator for adjusting the gap formed between the working rolls under the rolling load. The rolling mill further includes roll bending apparatus whereby bending forces are applied to extended journals of the backup rolls for changing the effective roll crown at the roll gap. The control system provides an automatic control designed to concurrently maintain a relationship between signals generated on the basis of rolling mill measurements to control the force applicator and the roll bending device This concurrent relationship of signals equates a position change of the force applicator with the algebraic sum of signals representing roll gap changes due to a change in the rolling load and due to a change in the roll bending force, while concurrently the change in roll crown due to a change in roll bending force is equated to a rolling load change. The control system includes additional circuitry for an alternate form of concurrent gage and crown control.

20 Claims, 2 Drawing Figures SERVO J VA'LVE M as. M

PATENTEUFEB '6 I975 SHEET 10F 2 FIG.

CONTROL SYSTEM AND METHOD FOR CONCURRENT AUTOMATIC GATE AND CROWN CONTROL OF A ROLLING MILL FIELD OF THE INVENTION This invention relates to an automatic gage and crown control system for producing very accurate adjustments to the roll gap formed by a pair of rolls in a 1 DESCRIPTION OF THE PRIOR ART It is a well-known practice in the rolling mill art to provide an automatic gage control system for adjusting the gap formed by the working rolls of a rolling mill in an effort to maintain a constant delivery thickness of strip or plate while it is being processed in the rolling mill. One of the recent forms of automatic gage control, along with a rolling mill construction, is described in U.S. Pat. No. 3,496,743 which issued on Feb. 24, 1970. In this gage control system certain rolling mill parameters and load measurements taken during the actual rolling operation provide information which is used to form the basis for determining the necessary roll gap correction to be carried out by adjustments to the rolling force being developed by force applicator piston and cylinder assemblies. An important feature of this control system is that it produces the necessary roll gap correction more accurately and quickly to maintain a desired uniform delivery gage of the workpiece being rolled. The delivery gage as used herein with reference to a strip or plate after passing through a rolling mill is defined as a measure of the workpiece thickness which is taken at some preselected point across the width of the workpiece, such as at an edge, at the center, or at a quarter point.

ln hot strip or plate rolling mill installations, the employment of automatic gage control has the desirable effect of maintaining a uniform delivery gage, but concurrently therewith deviations, which in certain instances are very significant, were observed in the workpiece crown, particularly when a wide strip or plate underwent a substantial thickness reduction in the rolling mil. The crown of the workpiece, as used herein, is defined to mean the thickness differential, if any, of the workpiece as measured along the lines extending across the width of the workpiece. The occurrence ofa crown in a workpiece incident to a rolling operation is a wellknown characteristic which takes place when the large rolling forces incurred produce deflection in the rolling mill rolls. Moreover, when an adjustment is made to the roll gap during the actual rolling operation, there is concurrently produced a change in the magnitude of roll deflections. There are other factors that influence the crown of a workpiece, such as differences in the workpiece width, a lack of uniformity in the metallurgical composition of the workpiece, temperature deviations, and the everchanging condition of the rolling mill structure itself. Deviations in the crown of a metallic strip, for example, may occur in a uniform manner along its length or they may fluctuate in an erratic pattern along the strip length. Such a strip may have a wavy appearance and, in severe instances, the strip may be distorted and become unflat. However, the unflat condition is more prevalent in cold strip rolling operations wherein the strip is relatively thin and hardened due to rolling. A severe nonuniform crown condition in 0 such strip may result in its being declared unprime or even scrap because of its failure to meet the requirements set for its intended use.

In order to meet the requirements of the industry, numerous methods and apparatus have advanced the rolling mill art for the purpose of minimizing or eliminating deviations in the crown of the workpiece incident to processing in a rolling mill. One such method and apparatus that has been particularly successful is disclosed in U.S. Pat. No. 3,250,105 which issued on May 10, 1966 and will be referred to hereinafter as back-up roll bending. This method and apparatus is related to applying a contour controlling bending moment to extended journals of the back-up rolls in a 4-high rolling mill outboard of the main bearing chocks. The bending moment is applied to these rolls in such a direction and of such a magnitude so as to oppose and compensate for deflections of the working rolls at the roll gap. As an incident to employing back-up roll bending apparatus in a rolling mill for contour control of the working rolls, there was discovered a concurrent effect in the form of an overall gage variation in the strip or plate being processed. The magnitude of the gage variations is dependent not only upon the particular design of the back-up roll bending apparatus, but also upon the rolling mill design including the control system.

In the past, known attempts to provide an automatic control system to effect corrective adjustments to the roll gap of a rolling mill in order to produce a workpiece having a desired gage and crown have not achieved the degree of success demanded by the industry. One form of control known in the art is disclosed in U.S. Pat. No. 3,416,341, which issued on Dec. 17, 1968 in the names of C.'Dey et a1. and takes the form of rolling mill control arrangement for operating a roll bending fluid actuator and a roll push-up fluid actuator. A particular form of rolling mill construction is provided wherein the roll push-up fluid actuators resist the rolling loads and, at the same time, apply a parallel force to certain components of the mill structure, namely, rods and load cell combinations. A constant roll gap is said to be provided by maintaining the parallel force constant. The roll bending device has fluid actuators which are controlled in a proportionate manner by the force changes in the roll push-up fluid actuators. The controlling of the roll bending forces in a direct proportionate relation to changes in the push-up actuator forces, which also includes the rolling load, is considered to be insufficiently precise and accurate to provide either constant gage or desired crown of a workpiece.

Another form of control system known in the art is disclosed in U.S. Pat. No. 3,394,566 which issued on July 30, 1968 in the name of J. W. OBrien. This control system is directed to compensating for the influence that corrective roll bending has on a strip thickness controlling system, wherein the roll benders are tied in with a control circuit for determining the rolling loads of the mill so that the roll bending will be automatically operated in accordance with an increase or a decrease in the rolling loads.

Neither of these known control arrangements correctly recognize or attempt to compensate for the concurrent effects that a roll gap change per se and/or a roll crown change per se will induce in each other.

SUMMARY OF THE INVENTION It is the main object of this invention to accurately recognize the concurrent interaction of automatic gage control and back-up roll bending control in a rolling mill and to provide a control system to perform in such a way so as to provide both accurate gage and desired crown of a workpiece.

It is a further object of this invention to provide an automatic control system for a rolling mill designed to effect a gage correction on the basis that the gage of a workpiece is influenced by a concurrent correction by a crown control means.

A still further object of this invention is to provide in a 4-high rolling mill including force applicator piston and cylinder assemblies for adjusting the roll gap formed between the working rolls and roll bending piston and cylinder assemblies for changing the effective crown of the working rolls, a gage and crown control system for automatically providing a signal representing a roll gap change which includes the influence on the roll gap of a concurrent and precise change in effective roll crown. A complete lack of crown in the workpiece may be obtained according to this control system in such instances where it is desired.

Another object of this invention is to provide a control signal to anticipate a crown control correction included as a basis for gage control correction in an automatic control system for a rolling mill having rolling force applicators for gage control and back-up roll bending force applicators for crown control.

DESCRIPTION OF THE DRAWINGS These features, as well as others, will be better appreciated from the following description when con- DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a 4-high plate rolling mill having a preferred construction for carrying out the features of the present invention. The rolling mill includes a pair of housings 11 and 12, each having a window 13 into which there is received an upper work roll 14 with the usual bearing chock assemblies 15 carried on its journals. A lower work roll 16 has bearing chock assemblies 17 carried on its journals by which it is located in the housing window. The upper work roll 14 is supported by a large diameter back-up roll 18 having bearing chock assemblies 19 arranged within the housing window. The lower work roll 16 is supported by a large diameter back-up roll 21 having bearing chock assemblies 22 arranged within the housing window. At the top of the housing there is located a beam 23 which extends through both housing windows in a manner that it is engaged by the back-up chocks 19. A screw 24 in each housing adjustably positions the beam 23 along with the back-up roll 18 and work roll 14 with respect to the lower work roll 16. This is accomplished in a conventional manner by a screwdown drive, not shown, operatively coupled to each of the screws 24 to rotate it relative to a nut 25 which is held against rotation in a recess formed in the housing. Included in each of these recesses between the nut 25 and the housing is a load cell 26, the purpose of which will be more fully explained hereinafter. Balance means, not shown, are connected to arms 27 for urging the beam 23 upward into engagement with the lower ends of the screws 24. The beam 23 has projecting portions 23a which extend outward at each side of the housings where these extensions support a cylinder into which there is received a piston 29 forming a roil bending piston and cylinder assembly 30 that receives fluid under pressure through conduit lines 31. The forces generated by the piston and cylinder assemblies 30 are transmitted by the pistons 29 through load cells 32 to yokes 33 which have downwardly extending arms 33a in force transmitting contact with outboard bearing chock assemblies 34 that are mounted on extended journals 18a of the backup roll 18. The beam 23, including the projecting portions 23a, serves to equilibrate the roll bending forces generated by the piston and cylinder assemblies 33 and in a manner that is independent of the housings and screwdown assemblies.

With reference to the lower portion of the rolling mill, an elongated beam 35 is arranged in the housing windows such that at the top thereof the bearing chocks 22 engage the beam, and below the beam there are arranged cylinders 36 that receive pistons 37 which will be collectively referred to as force applicator piston and cylinder assemblies 38. Each of the assemblies 38 is constructed and arranged in the bottom of the housing window where there is provided a conduit line 39 for transmitting fluid under pressure according to the features of the present invention. The beam 35 has projecting portions 350 which extend outwardly beyond each side of the housing where there are mounted load cells 41. In contact with each load cell 41 is a piston 42 received in a cylinder 43 forming a roll bending piston and cylinder assembly 44 that receives fluid under pressure through a conduit line 45. The force generated by each roll bending piston and cylinder assembly 44 is transmitted by a yoke 46 which has upwardly extending arms 46a that engage in a force transmitting relation an outboard bearing chock assembly 47 mounted on an extended journal 21a of the back-up roll 21. The beam 35, including the projecting portions 35a, serves to equilibrate the roll bending forces generated by the piston and cylinder assemblies 44 and in a manner that is independent of the housings and the piston and cylinder assemblies 38.

As shown in FIGS. 1 and 2, attention is directed to the lower portion of the mill housings where there is formed a pair of housing projections 48 which extend toward each other in the window. Each of these projections forms a recess where there is supported a load cell 49. Below each of the load cells 49 is arranged a beam spring 51 in a manner that the spring is compressed between extensions 35b of the beam 35 and the load cell 49 in accordance with the teachings of US. Pat. No. 3,496,743.

FIG. 2 illustrates a control system incorporating the features of the present invention wherein the electrical signals generated by the previously described load cells are shown as originating from such load cells at their respective locations at the operators side of the rolling mill. It is to be understood with respect to the drive side of the rolling mill that either a duplicate control system will be provided or, alternatively, the control system now to be described will serve the entire rolling mill stand, in which event the various corresponding load cell signals from both of the mill housing assemblies will be averaged by additional circuitry that is per se well known in the art. The load cell 26 provides a signal proportional to the total rolling load P encountered between the work rolls during the actual rolling operation. The load cell 49 develops a signal Q proportional to the difference between the load F developed by the piston and cylinder assembly 38 and the rolling load P. This signal Q is also known as one of the signals forming part of a force type of position transducer. In the particular rolling mill construction shown in FIG. 1 the signal Q is employed in a proportional manner to represent a measure of the distance between the bottom of the housing window and the projection 35b of the beam 35. Alternate forms of position transducers known in the art, such as LVDTs, LVCTs, etc., may be employed to generate a signal Ah equivalent to AQ/M,,, which will be more fully described hereinafter. The

load cells

32 and 41 develop a signal B proportional to the roll bending force applied to the outboard bearing chocks mounted on the extended necks of the back-up rolls 18 and 21.

The signal P provided by the load cell 26 is transmitted by a line 58 to an amplifier 59. The signal P is also supplied to a memory storage device 61 employed to develop a signal P which represents the rolling load developed between the work rolls at the instant the workpiece enters the roll gap and used as a lock on reference rolling load signal. A potentiometer 62 generates a signal P representative of a predetermined rolling load signal that may be selected by the setting of the potentiometer. The potentiometer 62 is connected by line 63 to one of the contacts of a manual switch 64. The other contact of the switch 64 receives the P signal delivered along line 65. The switch 64, shown in its normal operating position, delivers the signal P to a line 66 and, upon actuation of the switch to the phantom line position, the line 66 receives the signal P The line 66 is connected to the amplifier 59 and to an amplifier 67.

The signals P and P or P depending upon the position switch 61, are combined by the amplifier 59 to derive a signal AP representative of the change in the rolling load developed between the work rolls. The signal AP is combined by an amplifier 68 with a signal M p generated by a potentiometer 69 to represent in a proportional manner the modulus of the rolling mill parts, which modulus is a measure of the change of roll gap due to a change in the rolling load. The signal M is fed over line 70 to the amplifier 68, the output of which is a signal in a line 71 proportional to the factor APIM which represents the change in the work roll gap as a function of a change in the rolling load. The

signal AP/M p is fed by line 71 to an amplifier 72 where it is combined with a signal from a variable modulus control 73 that is per se well known in the art. The signal APIM which may have a bias due to the control 73, is fed to an amplifier 74 where it is combined with other component control signals generated in a manner next to be described.

The signal Q from the load cell 49 is transmitted by line 75 to an amplifier 76 and to a memory storage device 77. The output of the device 77 is denoted as Q, and represents a magnitude of the Q load cell signal taken at the instant the workpiece enters the roll gap and used as the lock on reference Q load cell force. A line 78 transmits the Q signal to an amplifier 79 where it is combined with a signal from a line 80 produced by an acceleration and deceleration signal program 81 designed to introduce a compensating factor into the control system for overcoming abnormal conditions in the rolling mill during the time when it is accelerated and decelerated from a preselected operating speed. The output of the amplifier 79 is fed along line 82 to the amplifier 76 from which there is derived a signal in line 83 proportional to AQ representing a change in the Q load cell reading. The AQ signal is fed to an amplifier 84 where it is combined with a signal M, transmitted by a line 85 from a potentiometer 86 designed to generate by a manual setting a signal proportional to the modulus of the spring 51. The output of the amplifier 84 is a signal representing (AQ/M Ah which is proportional to a change in distance between the beam projection 35b and the bottom of the housing window which will now be denoted as 1311. This change in distance includes any movement that may occur between the .piston 37 and cylinder 36.

The

load cells

32 and 41 each provide signals that are combined to form a signal B representative of the outboard bending force applied to the extended necks of the back-up rolls. The signal B is delivered by a line 87 to an amplifier 88 and also to a memory storage device 89. Output signal 8,, from the device 89 is produced in a line 90 and represents a measurement of the outboard bending force taken at the instant the workpiece enters the roll gap and used as the lock on reference roll bending force signal. The line 90 is connected to one contact of a two-position manual switch 91 which also has a contact receiving a signal B along line 92 from a manually set potentiometer 93. The signal fed along line 94 from switch 91 during normal rolling operations is the value 8,, as shown by the position of the switch 91, or upon actuation of the switch to the phantom line position, the line 94 receives the signal B the value of which is selected to represent a predetermined roll bending force. The line 94'is connected to an amplifier 95 where it is divided by a signal M received along a line 96 from a potentiometer 97. The signal M is manually selected to represent the modulus of the rolling mill rolls 14, 16, 18 and 21 and mill parts directly associated therewith, which modulus is a measure of the change in the effective crown of the work rolls due to a change in the outboard bending force applied to the extended necks of the back-up rolls. The amplifier 95 produces a signal equivalent to B /M which is connected by a line 98 to

amplifiers

99 and 100. The amplifier 100 combines the signal (B /M with the signal B/M delivered from amplifier 88 to produce a signal in line 101 having a value proportional to AB/M B representing the change in the roll crown as a function of the change in the bending load. The line 101 transmits the signal AB/M to an amplifier 102 and the same signal is fed to one contact of a two-position switch 103 shown in its normal operating position.

in accordance with the features of the present invention, the signal AB/M described above is compared with a signal to be denoted as AP/M and defined as a change in the mill roll crown that will concurrently take place with a change in the rolling force. The signal AP/M is developed by providing a manually set potentiometer 104 for generating a signal M representing the modulus of the work rolls and the back-up rolls and mill parts directly associated therewith which modulus is a measure of a change in the effective crown of the working rolls due to a change in the rolling load P. The signal M is transmitted by line 105 to an amplifier 106 where it is combined with the signal P in line 58 to produce an output signal P/M in line 107. Amplifier 67 combines the signal M with the signal in line 66 and produces a signal P /M or Pp /M p, depending upon the position of switch 64 in a line 108. The line 108 is connected to an amplifier 109, the output of which is a signal AP/M p in line 110. This signal is transmitted to amplifier 102 and it is also connected to the second contact of the switch 103. The output from the amplifier 102 is a signal in line 111 representing the quantity to operate a servo-valve 114 according to the equation [AP/M6,; /Mmi 1 whereby a precise fluid pressure delivered from a pump, not shown, is caused to exist in

conduit lines

31 and 45 to bring about the change in the bending force applied to the back-up rolls, as prescribed by this equation, to produced an exact correction to the effective crown of the work rolls that is necessary to yield the desired crown in the workpiece in a manner concurrent with a gage correction to be more fully described.

In order to establish an initial relationship between the lock on signal B, with respect to the lock on signal P,,, which are denoted in FIG. 2, an alternate control for the servo valve 114 is used to satisfy the equation iz ela a/ C/P) a4+ 1+ man This is accomplished by positioning the switch 112 in the phantom line position thereby interconnecting line 113 with a line 1 containing the output signal from an amplifier 116. The signals fed into amplifier 116 are the output signal P /M (B /M from amplifier 99 in line 117 and the output signal (C C C from an amplifier 118 in line 119. The output signal from amplifier 99 is derived by combining the signal P IM p from amplifier 67 and the signal B /M B from amplifier which have been formed in the previously described manner. The signal P IM is an initial lock-on reference signal representing an effective crown of the work rolls due to the rolling load. The signal B /M is an initial lock-on reference signal representing an effective crown of the work rolls due to the roll bending force produced by the piston and

cylinder assemblies

30 and 44. The signal representing (C C C is derived from amplifier 118 which combines the signals produced by

potentiometers

121, 122 and 123. The potentiometer 121 is set by manual adjustment to represent the amount of mechanical crown that is ground on the mill rolls, C The potentiometer 122 is manually set to represent the amount of thermal crown in the mill rolls that is induced as a function of the rolling operation and, particularly, the heat generated in the rolls C The potentiometer 123 is set to represent the desired amount of crown in the plate after rolling, C

An important aspect of the present invention is an improved automatic gage control system designed to operate on a basis which includes a recognition and compensation for the influence that a concurrent crown control correction has on the gage of the plate being rolled in the rolling mill. The control system illustrated in FIG. 2 includes for this purpose an amplifier 125 employed to divide the modulus signal M in line 96 by a modulus signal M delivered by a line 126 from a potentiometer 127 which is manually set to provide a signal representing the modulus of the backup rolls, the work rolls and certain other rolling mill parts, which modulus is a measure of a change in the roll gap due to a change in the roll bending force. Amplifier 12S produces a signal in line 128 proportional to the factor M /M Amplifier 129 multiplies this signal by the signal in a line 130 passed through the switch 103. in the preferred mode of operation the line 130 receives the signal AB/M and when the switch 103 is positioned in the phantom line position, the signal [AP/M }[M ,,,/M is transmitted by line 130. The output from amplifier 129 in the preferred mode is a signal AB/M B which is proportional to a change in the work roll gap due to a change in the roll bending force. The signal AB/M is transmitted by line 131 to amplifier 132, which also receives the previously described signal AQ/M, from amplifier 84. The output from amplifier 132 is a signalrepresenting AQ/M, AB/M which is transmitted by a line 133 to the previously described amplifier 74 where it is combined with the signal AP/M to provide a control signal in line 134 for the operation of a servo-valve 135 according to the relationship- The servo-valve 135 controls the fluid delivered. by a pump, not shown, in conduit line 39'to the force applicator piston and cylinder assemblies 38.

Having described the component parts and their relationships in the control system illustrated in FIG. 2, a brief description of the underlying theory along with the operation of this control will now be given wherein a plate mill will be referred to for the purpose of the description only. The control system previously described may be used to operate the plate mill in any one of a number of various modes depending upon the position of the

switches

64, 91, 103 and 112. The thickness of the plate delivered from the rolling mill can be expressed as a function of the cooperating forces produced during operation of the mill by the following expression 2 o GlP) (Q/ g) G/B) (Equation 1) where h, no-load roll gap between the work rolls P= rolling load M the modulus of the rolling mill parts, which modulus is a measure of a change in the roll gap due to a change in rolling load Q load acting on the position transducer beam spring M, modulus of beam spring of the position transducer B back-up roll bending force M modulus of the working rolls, back-up rolls and associated mill parts, which modulus is a measure of a change in the roll gap to a change in the back-up roll bending force. Equation 1 is an expression for the delivery gage of the mill that describes the relationship that, as P increases, the roll gap opens up and the delivery gage increases; as Q increases, the roll gap decreases; and as B increases, the roll gap decreases.

We can now write the equation for the actual crown in a plate after rolling, denoted as C which, as indicated heretofore, is defined as that amount that the plate is thicker in the middle than at the edges (Equation 2) where C 1,, actual crown in the plate P, B as before M the modulus of the work rolls, back-up rolls and associated mill parts which modulus is a measure of a change in effective crown in the work rolls due to a change in the rolling load M the modulus of the work rolls, back-up rolls and associated mill parts, which modulus is a measure of a change in effective crown of the work rolls due to a change in the back-up roll bending force.

C the effective mechanical crown in the work rolls C the effective thermally induced crown in the work rolls Equation 2 describes the relationship that, as the rolling pressure P increases, the rolls will bend more and, hence, the resulting crown on the plate will be greater; as the back-up roll bending forces are increased, the resulting plate crown will decrease; and the greater the mechanically ground crown on the rolls and/or the greater the thermally induced crown, the resulting crown in the plate will be reduced.

Now, during each pass of a plate through the rolling mill, the value of h, given by the position of the screws 24 will not be changed and the values of mechanical and thermal crown of the rolls essentially will not change. As the entry gage of the plate, its hardness, temperature, or the like change, the rolling pressure necessarily changes and the control system will then rapidly introduce changes in the Q and B forces, which will further change P, in such a way as to maintain the values of and C A constant. 7

These changes are numerically given by taking the differentials of equations 1 and 2 to give (Equation 3) I AC HJA (AP/MC/P) ew) A(CM+ CT) (Equation 4) During a required action by the control system for uniform gage and control control, the quantities h,,, C and C do not change so that we can write Ah 0 (Equation 5) AC 0 (Equation 6) AC 0 (Equation 7) Furthermore, since the object of the automatic control system is to maintain the delivery gage. t at a prescribed value and constant while concurrently maintaining the delivery plate crown C R controllably small and constant for the production of high-quality plate products, it follows that these quantities must not deviate from a prescribed value, which can be written AP/M p AB/M B=0 (Equation ll) as the condition for a uniformly constant crown that is required in the plate.

Equations 10 and ll, therefore, set down the force change relationships that must be maintained concurrently during rolling operation. The interrelations between the changes in P, Q and B forces, given as AP, AQ, and AB, must be rapidly and continuously controlled and maintained to produce the high-grade plate product desired, namely, one having constant gage and constant crown end to end, including the possible condition of zero crown in product.

Since each of the terms expressed in equations 10 and ll involve a force change or, more particularly, a change in a force divided by a modulus factor, according to Hookes law the substance to these equations can be expressed in an equivalent manner as dimensional changes whereby, with respect to equation 10, we can write (Equation 12) where AG 1 a change in the roll gap due to a change in the rolling load AG, a change in the roll gap due to a position change of said force applicator piston and cylinder means AC a change in the roll gap due to a change in the roll bending force and, with respect to equation 1 1, we can write no (Equation 13) where AC a change in the effective crown of the working rolls due to a change in the rolling load AC a change in the effective crown of the working rolls due to a change in the roll bending force.

By employing the control system illustrated in FIG. 2 on the basis of equations and 11, when an increase in the entry thickness of the plate occurs, there will be an increase in the rolling pressure P as the thicker material starts to go through the roll bite, resulting in an increase in mill stretch and an increase in bending of the back-up rolls which will cause an increase in the delivery plate gage as well as an increase in the delivery plate crown. The instantaneous action on the mill will be to decrease the bending of the beam springs 51 ac conipanied by a decreased Q force measurement by the load cell 49. The immediate action of the control circuits will be to concurrently introduce oil into the force applicator piston and cylinder assemblies 38 and into the piston and cylinder assemblies and 44 of the back-up roll bending system in response to required increases in the Q load cell forces and in the B load cell forces, respectively, which, in turn, will result in further increases in P load cell force. The resulting increases AP, AQ, AB, will be so controlled as to satisfy equations 10 and 11 concurrently, which are given in lines 134 and 113, respectively, of FIG. 2.

The concurrent gage and crown control for a rolling mill according to the present invention may be further illustrated by the following example. Let us consider a rolling mill construction according to FIG. 1 for a plate mill having 42 inch diameter work rolls and 80 inch diameter back-up rolls, all of which have a 190 inch roll face length. When such a rolling mill is employed to reduce a 100 inch wide plate, the values of the moduli for this mill are:

M 302 X 10 lb./in

M 31.2 X 10 lb./in

M 41.2 X 10 lb./in

When a plate 1.370 inches thick by 100 inches wide is reduced by rolling to 1.0000 inch thick, the nominal or lock-on reference rolling load P, may be assumed to have a value of 7,000,000 pounds. Under these rolling mill conditions, the various crowns over the plate width are as follows:

mechanical crown, C 0.00195 inches thermal crown, C 0.01551 inch The crown due to roll deflection under the rolling load is given by the expression P lM 7 X l0 lb./39l X l0lb./in 0.01793 inch (crown loss) Thus, for the desired plate crown C MD 0.0000 inches we require a back-up roll bending force of 144,000 pounds to produce an effective roll crown due to the bending of 0.00047 inch according to the expression:

B IM 144 X l0 lb./302 X 10 lb./in 0.00047 inch in order to produce a balanced crown condition given by the equation:

wherein the numerical values are 0.00047 inch [0.01793 inch (0.00195 inch 0.01551 inch 0.0000 inches)] i.e., 0.00047 inch 0.00047 inch Let it be assumed further that an increased plate thickness of 1.481 inches enters the mill which requires a rolling load of P 8,050,000 lb. to roll the plate down to the desired delivery gage of 1.000 inch as before. This corresponds to a AP of 1,050,000 pounds. According to the teachings of the present invention, constant plate crown is automatically maintained by a roll bending force increase of AB 811,000 lb. according to equation 1 l:

7 0.00268 inch 0.00268 inch 0.00000 inches which means that the initial desired plate crown of 0.00000 inches is maintained. Concurrently, according to this invention, a precise gage control correction is made according to equation 10 cm (AQ/MS+ cm) =0 from which it follows that the force applicator system automatically moves to make AQ 23,000 1b., as is seen by (1,050,000 lb./3 1 .2X 10 ]b./in) (23,000 lb./l .6 X

l0 lb./in) (81 l,000lb./4l .2 X 10 lb./in)

=0.00000 inch or 0.03362 inches (0.01420 inch +0.0l942 inch) 0.00000 inches which means that the initial desired plate delivery thickness of 1.0000 inch is maintained.

It is significant to observe that in the given example of the plate mill only 42 per cent of the gage correction stems from the force applicator system and 58 per cent of the gage correction is contributed by the back-up roll bending system while concurrently maintaining constant plate crown.

An alternate method of control, differing from that previously described, is to anticipate the effect of a change in the bending force AB on the gage of the plate by feeding a second AP signal directly into the amplifier 129, which signal is related to the AB signal by the form of a signal [AP/M ][M /M when the switch 103 is actuated to the phantom line position, and is the equivalent of AB/M One skilled in the art will appreciate that the basic mathematical expressions given by equations 1 and 2 may be rewritten in terms of additional and/or other forces developed within a given rolling mill construction. Thus, for example, let us consider an assumed mill construction which does not include the reaction beam extensions 23a and 35a, shown in FIG. 1, for absorbing the reaction forces to the roll bending forces, and, furthermore, that the back-up roll bending piston and cylinder assemblies are arranged directly between the extended journals of the back-up rolls according to the teachings of U. S. Pat. No. 3,373,589. According to the present invention, the basic equations of this assumed mill construction take the form given as (Equation 14) for the delivery gage of this mill wherein the rolling load P is determined according to the equation P= F- Q B. The crown in the plate after rolling may be written by the equation (Equation 15) For the purpose of disclosing the present invention, reference has been made to a 4-high plate rolling mill and, in FIG. 1, there is illustrated such a mill having a preferred construction to carry out the features of the present invention. Other rolling mill constructions known in the art may be employed in combination with the control features disclosed herein for rolling strip, plate and like workpieces without departing from the spirit of the present invention.

In accordance with the provisions of the patent statutes, l have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof.

lclaim:

l. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition,

and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including roll bending means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of:

generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending means, forming in a predetermined manner concurrent interrelationships between said signals in ac cordance with the simultaneous influence said signals have on the delivery thickness and crown of a workpiece, and controlling said force applicator means and said roll bending means according to said concurrent interrelationships to yield a constant thickness and crown of a workpiece delivered from said rolling mill.

2. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including roll bending means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of:

generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending means,

forming in a predetermined manner concurrent interrelationships between said signals in accordance with the simultaneous influence said signals have on the delivery thickness and crown of aworkpiece,

controlling said force applicator means and said roll bending means in accordance with said concurrent interrelationships in such a manner that the algebraic sum of the changes in the roll gap due to variations in the rolling load, variations in the position of said force applicator means, and-variations in said roll bending force is reduced to zero and concurrently the algebraic sum of the changes in the effective roll crown due to variations in the rolling load and variations in said roll bending force is reduced to zero.

3. A methodof automaticallycontrolling the delivery H thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure, which includes a pair of working rolls, each of which are supported by a back-up roll in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said working rolls, said rolling mill further including roll bending piston and cylinder means for exerting a roll bending force to apply bending moments to extended journals of the back-up rolls for changing the effective crown of said working rolls, said method comprising the steps of: generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending piston and cylinder means,

controlling said force applicator means and said roll bending piston and cylinder means in such a manner that said interrelationships given by the following expressions are concurrently reduced to zero:

3 2 AG, i=1 and AU; 0 =1 l where 7 AG, a change in the roll gap due to a change in the rolling load AC a change in the roll gap due to a position change of said force applicator means AC a change in the roll gap due to a change in the roll bending force AC, a change in the effective roll crown due to a change in the rolling load AC a change in the effective roll crown due to a change in the roll bending force. 4. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure, which includes a pair of working rolls, each of which are supported by a back-up roll in a mill housing having force applicator piston and cylinder means for adjusting under the rolling load the gap formed between said working rolls, position transducer means for sensing change of said force applicator piston and cylinder means, said rolling mill further including roll bending piston and cylinder means for exerting a roll bending force to apply bending moments to extended journals of the back-up rolls for changing the effective crown of said working rolls, said method comprising the steps of:

generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator piston and cylinder means, and from changes in said roll bending piston and cylinder means, forming in a predetermined manner concurrent interrelationships between said signals in accordance with the simultaneous influence said signals have on the delivery thickness and crown of a workpiece,

controlling said force applicator piston and cylinder means and said roll bending piston and cylinder means according to said interrelationships of said signals such that the following expressions are concurrently reduced to zero:

5 and AP/M p' AB/Mc 0 where AP/M a change in said gap formed between said working rolls due to a change in the rolling load AQ/M, a change in the displacement of said force applicator means as sensed by said position transducers AB/M B a change in said gap formed between said working rolls due to a change in said roll bending force AP/M a change in the effective crown of said working rolls due to a change in the rolling load AB/M a change in the effective crown of said working rolls due to a change in said roll bending force.

5. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill according to claim 4 comprising the additional steps of:

controlling said roll bending piston and cylinder means during the momentary period of time when 30 the workpiece first enters the rolling mill, according to the equation or clB P0MCIP (CM+CT+ C are) where B0] MCIB crown force P M an initial, lock-on reference effective crown in the work rolls due to said rolling load C the effective mechanical crown in said working C the thermally induced effective crown in said working rolls C the desired crown in the workpiece after a thickness reduction in the rolling mill.

6. A method of concurrently controlling the delivery thickness and crown of a workpiece while it is being processed in a rolling mill which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of:

generating a first signal representing a change in the roll gap due to a change in rolling load, I generating a second signal representing a change in the position of said force applicator means, generating a third signal representing a change in the roll gap due to a change in the roll bending force, generating a fourth signal representing a change in the roll crown due to a change in rolling load, generating a fifth signal representing a change in the roll crown due to a change in said roll bending force, and controlling said force applicator means and said means for exerting a roll bending force in such a an initial, lock-on reference effective the work rolls due to said roll bending way that the algebraic sum of said first, second and third signals and the algebraic sum of said fourth and fifth signals are concurrently reduced to zero or substantially zero to thereby produce a workpiece having constant thickness and crown. 7. A method of concurrently controlling the delivery thickness and crown of a workpiecewhile it is being processed in a rolling mill which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of:

generating a first signal representing a change in the roll gap and due to a change in rolling load which includes the influence of said roll bending force,

generating a second signal representing a change in the position of said force applicator means,

generating a third signal representing a change in the roll crown due to a change in rolling load,

generating a fourth signal representing a change in the roll crown due to a change in said roll bending force, and

controlling said force applicator means and said means for exerting a roll bending force in such a way that the algebraic sum of said first and second signals and the algebraic sum of said third and fourth signals are concurrently reduced to zero or substantially zero thereby to produce a workpiece having constant thickness and crown.

8. A method of concurrently controlling the delivery thickness and crown of a workpiece while it is being processed in a rolling mill which includes a pair of working rolls, each of which are supported by a backup roll in a mill housing force applicator piston and cylinder means for adjusting under the rolling load the gap formed between said working rolls, said rolling mill further including roll bending piston and cylinder assemblies for exerting a roll bending force to apply bending moments to extended journals of the back-up rolls for changing the effective crown of said working rolls, said method comprising the steps of:

generating a first signal representing a change in the roll gap due to a change in rolling load developed between said working rolls,

generating a second signal representing a change in the relative position of the piston with respect to the cylinder of said force applicator,

generating a third signal representing a change in the roll gap due to achange in said roll bending force, generating a fourth signal representing a change in the roll crown due to a change in rolling load, generating a fifth signal representing a change in the roll crown due to a change in said roll bending force, and

controlling said force applicator piston and cylinder assembly and said roll bending piston and cylinder assemblies in such a way that the algebraic sum of said first, second, and third signals and the algebraic sum of said fourth and fifth signals are concurrently reduced to zero of substantially zero to thereby produce a workpiece having constant thickness and crown.

9. An automatic control system for accurate concurrent control of the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the enteringworkpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including roll bending means for exerting a roll bending force to change the effective crown of said working rolls, said control system comprising: means for generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending means,

means for computing the simultaneous influence said signals have on the delivery thickness and crown of a workpiece according to concurrent interrelationships between said signals, and

control means associated with said force applicator means and said roll bending means formaintaining said concurrent interrelationships between said signals to yield a constant thickness and crown of a workpiece delivered from said rolling mill.

10. In a rolling mill or the like apparatus having a housing for supporting a pair of processing rolls forming a roll gap which is subject to thickness and deflection variations due to the forces developed between the rolls during the processing of a workpiece, said rolling mill further including: 7

force applicator means supported in said housing for adjusting the roll gap under the rolling load,

roll bending means for exerting roll bending forces to change the effective crown of said processing rolls,

a control including means for generating a first signal representing a change in the roll gap due toa change in the rolling load,

position transducer means for generating a second signal representing a position change of said force applicator means,

means for generating a third signal representing a change in said roll gap due to a change in the roll bending force,

means for generating a fourth signal representing a change in effective roll crown due to a change in the rolling load,

means for generating a fifth signal representing a change in the effective roll crown due to a change in the said roll bending forces,

a first control means associated with said force applicator means for maintaining a predetermined relationship between said first, second and third signals, and a second control means associated with said roll bending means for maintaining a predetermined relationship between said fourth and fifth signals. 11. In a rolling mill or the like apparatus according to claim 10 wherein said force applicator means includes fluid actuated piston and cylinder assemblies.

12. ln a rolling mill or the like apparatus according to claim ll wherein said position transducer means includes a load cell and spring assembly for detecting a displacement of said force applicator means.

13 In a rolling mill or the like apparatus according to claim 12 wherein said rolling mill further comprises:

a back-up roll including extended journals for supporting each of said processing rolls, and

outboard bearing chocks mounted on said extended journals in a force transmitting relationship with said roll bending means for applying bending moments to said backup roll to change the effective crown of the processing roll supported thereby.

14. In a rolling mill or like apparatus according to claim 13 wherein said rolling mill further comprises a beam member for each of said back-up rolls constructed and arranged to equilibrate said roll bending forces in a manner independent of said force applicator means.

15. In a rolling mill or the like apparatus according to claim 14 further comprising means for combining said first, second and third signals according to the first expression wherein said first control means reduces said first expression to zero and where said first signal represents AP/M said second signal represents AQ/M and said third signal represents AB/M and where AP a change in the rolling load M the modulus of the rolling mill parts, which modulus is a measure of the change in the roll gap due to a change in the rolling load AQ a change in the load acting on said position transducer means M, modulus of said spring of said position transducer means AB a change in said roll bending force M modulus of said processing and back-up rolls and associated mill parts which modulus is a measure of a change in the roll gap due to a change in said roll bending force.

16. In a rolling mill or the like apparatus according to claim 15 further comprising means for combining said fourth and fifth signals according to the second expression wherein said second control means reduces said second expression to zero and where said fourth signal represents AP/M and said fifth signal represents AB/M and where M :the modulus of said processing and back-up rolls and associated mill parts, which modulus is a measure of a change in the effective crown of the processing rolls due to a change in the rolling load My, the modulus of said processing and back-up rolls and associated mill parts, which modulus is a measure of a change in the effective crown of the processing rolls due to a change in said roll bending force.

17. In a rolling mill or the like apparatus according to claim 16 further comprising:

means for generating a sixth signal representing an initial, lock-on reference effective crown of the processing rolls due to said roll bending force according to the equation where B, an initial, lock-on reference roll bending force signal P an initial, lock-on reference rolling load signal C the effective mechanical crown in said processing rolls C the thermally induced effective crown in said processing rolls,

C 11.11: the desired crown in the workpiece after a thickness reduction in the rolling mill,

and

switching means operatively arranged for feeding said sixth signal to said second control means during a momentary period of tie when the workpiece first enter the rolling mill.

18. In a rolling mill or the like apparatus having a housing for supporting a pair of processing rolls forming a roll gap which is subject to thickness and deflection variations due to the forces developed between the rolls during the processing of a workpiece, said rolling mill further including:

a control including means for generating a first signal representing a change in the roll gap and due to a change in he rolling load in which includes the influence of said roll bending force,

means for generating a third signal representing a change in effective roll crown due to a change in the rolling load,

means for generating a fourth signal representing a change in the effective roll crown due to a change in the said roll bending forces,

a'tirst control means associated with said force applicator means for maintaining a predetermined relationship between said first and second signals, and

a second control means associated with said roll bending means for maintaining a predetermined relationship between said third and fourth signals.

19. In a rolling mill or the like apparatus according to claim 18 further comprising means for combining said first and second signals according to the first expression wherein said first control means reduces said first expression to zero, and where said first signal represents am X MCIB/MGIB X cu-Ol' and Said Second signal represents AQ/M, and further where AP a change in the rolling load M the modulus of the rolling mill parts which modulus is a measure of the change in the roll gap due to a change in the rolling load,

M the modulus of said rolls and associated mill parts, which modulus is a measure of a change in the roll gap due to a change in said roll bending forces M the modulus of said rolls and associated mill parts which modulus is a measure of a change in the effective crown of the processing rolls due to a change in said roll bending forces M the modulus of said rolls and associated mill parts which modulus is a measure of a change in the effective crown of the processing rolls due to a change in the rolling load AQ/M a change in the displacement of said force applicator means as sensed by said position transducer means. 20. In a rolling mill or the like apparatus according to claim 19 further comprising means for combining said third and fourth signals according to the second expres- SlOn AP/MCIP cm UNITED STATES PATENT oFFIc QERTWECATE OF fiORRECTION patent 3,714,8G5 Dated February 6, 1973 Inventor It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as Shown below:

Column 1, line 2, "GATE" should read GAGE Column 10, line 19, uniform gage and c zontro]. control,"

should read uniform gage and crown control, Column 20, line 19, "tie" should reaa time Signed and sealed this 20th flay of November 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE n. TEGTMEYER Attestin'g Officer Acting Comissioner of Patents ORM P04 050 (10-69) USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE: 1969 0-366-334.

Claims

1. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including roll bending means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of: generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending means, forming in a predetermined manner concurrent interrelationships between said signals in accordance with the simultaneous influence said signals have on the delivery thickness and crown of a workpiece, and controlling said force applicator means and said roll bending means according to said concurrent interrelationships to yield a constant thickness and crown of a workpiece delivered from said rolling mill.

2. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including roll bending means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of: generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending means, forming in a predetermined manner concurrent interrelationships between said signals in accordance with the simultaneous influence said signals have on the delivery thickness and crown of a workpiece, controlling said force applicator means and said roll bending means in accordance with saiD concurrent interrelationships in such a manner that the algebraic sum of the changes in the roll gap due to variations in the rolling load, variations in the position of said force applicator means, and variations in said roll bending force is reduced to zero and concurrently the algebraic sum of the changes in the effective roll crown due to variations in the rolling load and variations in said roll bending force is reduced to zero.

3. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure, which includes a pair of working rolls, each of which are supported by a back-up roll in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said working rolls, said rolling mill further including roll bending piston and cylinder means for exerting a roll bending force to apply bending moments to extended journals of the back-up rolls for changing the effective crown of said working rolls, said method comprising the steps of: generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending piston and cylinder means, forming in a predetermined manner concurrent interrelationships between said signals in accordance with the simultaneous influence said signals have on the delivery thickness and crown of a workpiece, controlling said force applicator means and said roll bending piston and cylinder means in such a manner that said interrelationships given by the following expressions are concurrently reduced to zero:

4. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure, which includes a pair of working rolls, each of which are supported by a back-up roll in a mill housing having force applicator piston and cylinder means for adjusting under the rolling load the gap formed between said working rolls, position transducer means for sensing change of said force applicator piston and cylinder means, said rolling mill further including roll bending piston and cylinder means for exerting a roll bending force to apply bending moments to extended journals of the back-up rolls for changing the effective crown of said working rolls, said method comprising the steps of: generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator piston and cylinder means, and from changes in said roll bending piston and cylinder means, forming in a predetermined manner concurrent interrelationships between said signals in accordance with the simultaneous influence saiD signals have on the delivery thickness and crown of a workpiece, controlling said force applicator piston and cylinder means and said roll bending piston and cylinder means according to said interrelationships of said signals such that the following expressions are concurrently reduced to zero: Delta P/MG/P -( Delta Q/Ms + Delta B/MG/B) -> 0 and Delta P/MC/P - Delta B/MC/B -> 0 where Delta P/MG/P a change in said gap formed between said working rolls due to a change in the rolling load Delta Q/Ms a change in the displacement of said force applicator means as sensed by said position transducers Delta B/MG/B a change in said gap formed between said working rolls due to a change in said roll bending force Delta P/MC/P a change in the effective crown of said working rolls due to a change in the rolling load Delta B/MC/B a change in the effective crown of said working rolls due to a change in said roll bending force.

5. A method of automatically controlling the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill according to claim 4 comprising the additional steps of: controlling said roll bending piston and cylinder means during the momentary period of time when the workpiece first enters the rolling mill, according to the equation Bo/MC/B PoMC/P -(CM + CT + C /D) where Bo/MC/B an initial, lock-on reference effective crown in the work rolls due to said roll bending force Po/MC/P an initial, lock-on reference effective crown in the work rolls due to said rolling load CM the effective mechanical crown in said working CT the thermally induced effective crown in said working rolls C /D the desired crown in the workpiece after a thickness reduction in the rolling mill.

6. A method of concurrently controlling the delivery thickness and crown of a workpiece while it is being processed in a rolling mill which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the steps of: generating a first signal representing a change in the roll gap due to a change in rolling load, generating a second signal representing a change in the position of said force applicator means, generating a third signal representing a change in the roll gap due to a change in the roll bending force, generating a fourth signal representing a change in the roll crown due to a change in rolling load, generating a fifth signal representing a change in the roll crown due to a change in said roll bending force, and controlling said force applicator means and said means for exerting a roll bending force in such a way that the algebraic sum of said first, second and third signals and the algebraic sum of said fourth and fifth signals are concurrently reduced to zero or substantially zero to thereby produce a workpiece having constant thickness and crown.

7. A method of concurrently controlling the delivery thickness and crown of a workpiece while it is being processed in a rolling mill which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including means for exerting a roll bending force to change the effective crown of said working rolls, said method comprising the stePs of: generating a first signal representing a change in the roll gap and due to a change in rolling load which includes the influence of said roll bending force, generating a second signal representing a change in the position of said force applicator means, generating a third signal representing a change in the roll crown due to a change in rolling load, generating a fourth signal representing a change in the roll crown due to a change in said roll bending force, and controlling said force applicator means and said means for exerting a roll bending force in such a way that the algebraic sum of said first and second signals and the algebraic sum of said third and fourth signals are concurrently reduced to zero or substantially zero thereby to produce a workpiece having constant thickness and crown.

8. A method of concurrently controlling the delivery thickness and crown of a workpiece while it is being processed in a rolling mill which includes a pair of working rolls, each of which are supported by a back-up roll in a mill housing force applicator piston and cylinder means for adjusting under the rolling load the gap formed between said working rolls, said rolling mill further including roll bending piston and cylinder assemblies for exerting a roll bending force to apply bending moments to extended journals of the back-up rolls for changing the effective crown of said working rolls, said method comprising the steps of: generating a first signal representing a change in the roll gap due to a change in rolling load developed between said working rolls, generating a second signal representing a change in the relative position of the piston with respect to the cylinder of said force applicator, generating a third signal representing a change in the roll gap due to a change in said roll bending force, generating a fourth signal representing a change in the roll crown due to a change in rolling load, generating a fifth signal representing a change in the roll crown due to a change in said roll bending force, and controlling said force applicator piston and cylinder assembly and said roll bending piston and cylinder assemblies in such a way that the algebraic sum of said first, second, and third signals and the algebraic sum of said fourth and fifth signals are concurrently reduced to zero of substantially zero to thereby produce a workpiece having constant thickness and crown.

9. An automatic control system for accurate concurrent control of the delivery thickness and crown of a workpiece undergoing a thickness reduction in a rolling mill wherein, as incident to which the crown and thickness of the delivery workpiece normally change due to nonuniform characteristics of the entering workpiece, such as a change in the entry thickness, in the metallurgical composition, and in the workpiece crown, thereby producing changes in the elastic deformation of the rolling mill structure which includes a pair of working rolls supported in a mill housing having force applicator means for adjusting under the rolling load the gap formed between said rolls, said rolling mill further including roll bending means for exerting a roll bending force to change the effective crown of said working rolls, said control system comprising: means for generating a plurality of signals resulting from said nonuniform characteristics of the entering workpiece, from changes in said force applicator means, and from changes in said roll bending means, means for computing the simultaneous influence said signals have on the delivery thickness and crown of a workpiece according to concurrent interrelationships between said signals, and control means associated with said force applicator means and said roll bending means for maintaining said concurrent interrelationships between said signals to yield a constant thickness and crown of a workpiece delivered from said rolling mill.

10. In a rolling mill or the like apparatus having a housing for sUpporting a pair of processing rolls forming a roll gap which is subject to thickness and deflection variations due to the forces developed between the rolls during the processing of a workpiece, said rolling mill further including: force applicator means supported in said housing for adjusting the roll gap under the rolling load, roll bending means for exerting roll bending forces to change the effective crown of said processing rolls, a control including means for generating a first signal representing a change in the roll gap due to a change in the rolling load, position transducer means for generating a second signal representing a position change of said force applicator means, means for generating a third signal representing a change in said roll gap due to a change in the roll bending force, means for generating a fourth signal representing a change in effective roll crown due to a change in the rolling load, means for generating a fifth signal representing a change in the effective roll crown due to a change in the said roll bending forces, a first control means associated with said force applicator means for maintaining a predetermined relationship between said first, second and third signals, and a second control means associated with said roll bending means for maintaining a predetermined relationship between said fourth and fifth signals.

11. In a rolling mill or the like apparatus according to claim 10 wherein said force applicator means includes fluid actuated piston and cylinder assemblies.

12. In a rolling mill or the like apparatus according to claim 11 wherein said position transducer means includes a load cell and spring assembly for detecting a displacement of said force applicator means.

13. In a rolling mill or the like apparatus according to claim 12 wherein said rolling mill further comprises: a back-up roll including extended journals for supporting each of said processing rolls, and outboard bearing chocks mounted on said extended journals in a force transmitting relationship with said roll bending means for applying bending moments to said back-up roll to change the effective crown of the processing roll supported thereby.

15. In a rolling mill or the like apparatus according to claim 14 further comprising means for combining said first, second and third signals according to the first expression Delta P/MG/P - ( Delta Q/Ms + Delta B/MG/B ) wherein said first control means reduces said first expression to zero and where said first signal represents Delta P/MG/P , said second signal represents Delta Q/Ms , and said third signal represents Delta B/MG/B , and where Delta P a change in the rolling load MG/P the modulus of the rolling mill parts, which modulus is a measure of the change in the roll gap due to a change in the rolling load Delta Q a change in the load acting on said position transducer means Ms modulus of said spring of said position transducer means Delta B a change in said roll bending force MG/B modulus of said processing and back-up rolls and associated mill parts which modulus is a measure of a change in the roll gap due to a change in said roll bending force.

16. In a rolling mill or the like apparatus according to claim 15 further comprising means for combining said fourth and fifth signals according to the second expression Delta P/MC/P -Delta B/MC/B wherein said second control means reduces said second expression to zero and where said fourth signal represenTs Delta P/MC/P , and said fifth signal represents Delta B/MC/B , and where MC/P the modulus of said processing and back-up rolls and associated mill parts, which modulus is a measure of a change in the effective crown of the processing rolls due to a change in the rolling load MC/B the modulus of said processing and back-up rolls and associated mill parts, which modulus is a measure of a change in the effective crown of the processing rolls due to a change in said roll bending force.

17. In a rolling mill or the like apparatus according to claim 16 further comprising: means for generating a sixth signal representing an initial, lock-on reference effective crown of the processing rolls due to said roll bending force according to the equation Bo/MC/B Po/MC/P - (CM + CT + C /D ) where Bo an initial, lock-on reference roll bending force signal Po an initial, lock-on reference rolling load signal CM the effective mechanical crown in said processing rolls CT the thermally induced effective crown in said processing rolls, C /D the desired crown in the workpiece after a thickness reduction in the rolling mill, and switching means operatively arranged for feeding said sixth signal to said second control means during a momentary period of tie when the workpiece first enter the rolling mill.

18. In a rolling mill or the like apparatus having a housing for supporting a pair of processing rolls forming a roll gap which is subject to thickness and deflection variations due to the forces developed between the rolls during the processing of a workpiece, said rolling mill further including: force applicator means supported in said housing for adjusting the roll gap under the rolling load, roll bending means for exerting roll bending forces to change the effective crown of said processing rolls, a control including means for generating a first signal representing a change in the roll gap and due to a change in he rolling load in which includes the influence of said roll bending force, position transducer means for generating a second signal representing a position change of said force applicator means, means for generating a third signal representing a change in effective roll crown due to a change in the rolling load, means for generating a fourth signal representing a change in the effective roll crown due to a change in the said roll bending forces, a first control means associated with said force applicator means for maintaining a predetermined relationship between said first and second signals, and a second control means associated with said roll bending means for maintaining a predetermined relationship between said third and fourth signals.

19. In a rolling mill or the like apparatus according to claim 18 further comprising means for combining said first and second signals according to the first expression wherein said first control means reduces said first expression to zero, and where said first signal represents ( Delta P/MG/P -( Delta P X MC/B/MG/B X MC/P)), and said second signal represents Delta Q/Ms , and further where Delta P a change in the rolling load MG/P the modulus of the rolling mill parts which modulus is a measure of the change in the roll gap due to a change in the rolling load, MG/B the modulus of said rolls and associated mill parts, which modulus is a measure of a change in the roll gap due to a change in said roll bending forces MC/B the modulus of said rolls and associated mill parts which modulus is a measure of a change in the effecTive crown of the processing rolls due to a change in said roll bending forces MC/P the modulus of said rolls and associated mill parts which modulus is a measure of a change in the effective crown of the processing rolls due to a change in the rolling load Delta Q/Ms a change in the displacement of said force applicator means as sensed by said position transducer means.