US3496743A - Rolling mill for producing constant gauge - Google Patents

Description

Feb. 24, 1970 M. D. STONE ROLLING MILL FOR PRODUCING CONSTANT GAUGE 3 Sheets-Sheet 1 Filed Aug. 21. 1967 INVENTOR. MORR/S 0. arc/v5 J QM ATTORA/EV.

Feb. 24, 1970 M. D. STONE ROLLING MILL FOR PRODUCING CONSTANT GAUGE Filed Aug. 21. 1967 3 Sheets-Sheet 2 wm bw INVENTOR.

E W M m. M. 4 M

Feb. 24, 1970 M. D. STONE 3,496,743

ROLLING MILL FOR PRODUCING CONSTANT GAUGE Filed Aug. 21. 1967 :s Sheets-Sheet s INVENTOR. MORRIS 0. STONE ATTOR/VfY.

United States Patent C U.S. Cl. 728 14 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a rolling mill of the type designed to produce a constant thickness workpiece, such as metallic strip. The mill is provided with a piston cylinder assembly for subjecting a first group of mill parts, such as the bearing chock assemblies of one of the rolls, to a roll gap controlling force which is applied in a direction to resist the rolling force of the mill. The cylinder is constructed and arranged so that the force difference between its total force and the rolling force is applied to a second group of mill parts, which may include a tension or compression member. In this mill construction only a portion of the housing of the mill is subject to the rolling force.

In one form there is provided in a rolling mill having a housing, an elongated window in said housing, a pair of rolls between which a rolling force is developed, including mounting means for each roll received in said window of said housing, wherein a portion of the housing receiving the mounting means and said mounting means is subject only to the rolling force of the mill, means arranged at one end of said window of said housing and between one of the mounting means and housing for applying to a first group of mill parts, including one of said mounting means, a substantial part of a roll ga-p controlling force, said force being applied in a direction to resist the rolling force of the mill, the force applying means being constructed and arranged so that the force differential between its total force and the rolling force is applied to a second group of mill parts, which excludes at least said other mounting means, and wherein the elastic characteristics of said two groups of mill parts have a predetermined relationship.

This rolling mill can be employed in combination with a control means for continually measuring the force imposed on either said first or second group of parts and varying the applying force proportional to a change in the force being imposed on said first or second group of mill parts to maintain a predetermined relationship between either of these forces and the applied force.

In another form, the present invention provides in a rolling mill, or like apparatus, having a housing, a pair of rolls between which a rolling force is developed including means arranged in said housing at one side thereof for applying to a first group of mill parts, including said mounting means, a substantial part of a roll gap controlling force, said roll gap controlling force being applied in a direction to resist the rolling force of the mill, the force applying means being constructed and arranged so that the force difierential between its total force and the rolling force is applied to a second group of mill parts, which excludes at least one of said mounting means, and wherein the elastic characteristics of said two groups of mill parts have a predetermined relationship, means separate from said force applying means and associated with the mounting means arranged on the side of the housing opposite said force applying means for adjusting the associated mounting means and its roll to adjust the position of the roll independent of said force applying means.

This rolling mill can be employed in a combination with a control means for continually measuring the force imposed on either said first or second group of parts and varying the applying force proportional to a change in the force being imposed on said first or second group of mill parts to maintain a predetermined relationship between either of these forces and the applied force.

In a still further form of the invention said second group of mill parts comprises one or more tension rods associated with the lowest roll assembly of the mill, said tension rod subject to a tension force by said force applying means, and wherein the tension imposed on said tension rods is measured by a force measuring means. In certain cases a spring or equivalent device can be used in conjunction with the tension rods compressible by said rods to give added flexibility to the system.

In still another form of the present invention, there is provided alternately either a force measuring device associated with the tension rods or with the mill housing that receives the separating force from the roll assemblies.

A still further object of the present invention is to provide in a rolling mill of the above-described construction a readily yieldable means received in the housing of the mill and so associated with the force applying means to be subject to a compression force. In one form the housings are provided with projections having openings to which there are received a plurality of springs, one end of which engages one of the roll chocks of the roll assembly, this spring being compressed by the application of said force applying means and wherein said housing projections are in the vicinity of the work rolls of the mill.

In another form the housing projections are at the base of the mill wherein the springs engage a member associated with said force applying means and is compressible upon the movement thereof.

In one form the yieldable means is arranged between the mill screw and a crosshead against which a compression force is exerted.

A still further embodiment of the present invention comprises, either at the top or bottom of a rolling mill, a pair of substantially parallel arms connectable to one of the roll chocks of the mill and extending through or alongside the housing at which place they are connected with a cross member, means for adjusting the cross member relative to the pass line of the mill in which construction the force applying means in applying a force on the roll chock to which the arms are associated imposes a tension force on said arms, a portion of which is taken into the cross member and into the housing.

As noted above, the present invention relates to a rolling mill for producing constant gauge and, more particularly, uniformity of longitudinal gauge, such as, metallic sheet or strip. It has been well recognized for many years that the degree of gauge accuracy in a rolling mill is dependent upon the stiffness of the mill, i.e. to say, the resistance the mill has to stretch under the rolling load generated in the rolling of the material. ln this regard the art early in its history sought to add stiffness to the mill by providing one or more backup rolls for the reducing rolls. The most common for-m of such a mill is the well known and universally employed 4-high mill. While the multi-high mill improved the stillness of the rolls and, hence, of the mill and yielded a more uniform product, it leaves much to be desired. This is by reason of the fact that, notwithstanding the added stillness afforded by the backup rolls, the rolls and housing and other components stretch considerably under the rolling load, which stretch varies as the rolling load varies, resulting in a product having a non-uniform gauge.

Since the housing itself represents a substantial amount of the elastic stretch of the mill, the prior art sought to eliminate the housing as a factor in the obtaining of uniform gauge by providing a prestressing means, an example of which is shown in U.S. Patent No. 581,078 issued to F. Menne on Apr. 20, 1897. This, too, was an improvement in obtaining more uniform gauge. However, since it did not compensate for the elastic deformation of the other components of the mill, such as, roll body and neck deflection, chock deflection, screw compression, roll compression, which in the aggregate far exceeded the clastic influence of the housings themselves, the result was that objectionable gauge variations were experienced.

To further improve the performance of a rolling mill with respect to obtaining constant gauge, the art then developed an automatic gauge control means, whereby, as the rolling load changes, the position of the rolls was changed to compensate for variation in the rolling load. An illustration of this is U.S. Patent No. 2,680,978 issued W. C. F. Hessenberg et al. on June 15, 1954. It is of interest to note that in the Hessenberg patent reference is made to still other automatic gauge control approaches which were found unsuccessful.

The most recent attempt to obtain automatic gauge control was to combine the prestressed concept with an automatic gauge control concept whereby, as the rolling load changes, the distance between the rolls would be maintained constant. This approach has taken two forms; one of which is illustrated in British Patent No. 955,164 for Improvements in and Relating to Rolling Mills, published on Apr. 15, 1964, and the other, as illustrated, in U.S. Patent No. 2,736,217 for Adjusting Device in Rolling Mills, issued to P. Blain on Feb. 28, 1956.

In the first patent the attempt is made to maintain the distance between the axes of the backup rolls or the distance between the backup chocks of a 4-high mill constant. In this construction a change in the rolling load will, if appropriate correction is not effected, change the distance between the axes of the backup rolls. Hence, this patent teaches making an appropriate correction. The second attempt is to literally measure the distance between the axes of the work rolls of the 4-high mill and to adjust continually the rolls as the measured distance is detected to have varied from a predetermined distance. In the first case, it will be noted that while the invention has eliminated not only the housing but the backup chocks, there still remains the elastic characteristics to be reckoned with, having to do with roll bending, roll compression and roll flattening. These factors are substantial and, therefore, cannot be overlooked. The second form, where the actual distance is measured between the work rolls, has been found unacceptable as being unreliable and very cumbersome in addition to the limitations it imposes upon the operation of the mill, say, for example, from the standpoint of changing the rolls.

With this in mind, attention is now directed to the present invention which presents a substantial improvement over the previous mills in obtaining constant gauge, several forms of which are illustrated in the accompanying drawings of which:

FIGURE 1 is an elevational view, partly in section, of a 4-high rolling mill incorporating the features of the present invention;

FIGURE 2 is a similar view of a second embodiment of the present invention;

FIGURE 3 is a further embodiment of the form illustrated in FIGURE 2;

FIGURE 4 is an elevational view, partly in section, of a still further embodiment of the present invention;

FIGURE 5 is a further embodiment of the present in vention; and

FIGURE 6 is a typical control circuit for the mill shown in FIGURES 1-5.

With reference now to FIGURE 1, there is shown one of the housings 10 of a 4-high mill, it being appreciated that according to normal mill construction a similar housing will be provided for the other side of the mill and that it will contain all the components of the illustrated housing. The housing 10 has a window 11 into which there is received backup chocks 13 and 14 which rotatably support backup rolls 15, the backup chocks have recesses into which there is received work roll chocks 17 and 18 that rotatably support work rolls 19 and 21. The upper backup chock 13 is adjustable relative to the pass line of the mill by a conventional mill screw 22 received in a nut 23 secured to the housing. The motor and gear for rotating the screw are not shown since they follow conventional designs. Between the upper chock 13 and screw 22, as further noted hereinafter, there may be provided in one alternative form a load cell 24 for measuring the separating force of the mill. According to usual mill designs, the backup and work roll chocks are separated by balance cylinder assemblies 25 and 26.

Attention is now directed to the lower backup chock 14. It will be noted that immediately below the chock there is provided a block in the form of a variable spacer and below the spacer there is provided a crosshead 27. The crosshead, at its underneath surface, is engaged by the piston 28 of a piston cylinder assembly 29 which is positioned betwen the bottom of the housing and the' crosshead. The cylinder is adapted to be fed by a variable pressure which, at all times, either equals or exceeds the separating force of the mill. On the two opposite sides of the crosshead there is connected a tension rod 31 which extends downward through or alongside the mill housing and at their lower ends carry spring retainer elements 32, into which there are received compression springs 33 The tension rods at their lower ends and beyond the retaining elements are either enlarged to form heads, or threaded to receive nuts 34, and between the lower surfaces of the spring retainers and nuts are provided load cells 35. The load cells 35 may be employed in place of the load cells 24, and are designed to measure the tension force imposed on the rods 31, and could take the form of conventional strain gauges, if such were desirable.

As noted above, the piston cylinder assembly 29 is adapted to apply to the bottom roll 15 a force which may be identified as F. It will be noted that during rolling, the force F is divided into two components, one component being identified as P (the rolling force) and the other component as Q (the by-pass component) which is imposed on the rods 31 as a tension force, and which force eventually is transmitted to the housing and is resisted by the reaction force of the cylinder. Thus, we find in the illustrated mill that In the operation of the mill the initial no-load gap condition rolls h is set by the mill screw 22, and the force of the piston cylinder assembly 29 will act to stretch the rods 31, bend the crosshead 27 and compress the springs 33, wherein the initial hydraulic force may be identified as F and the initial force on the rods as Q so that Q =F since P =no-load rolling force =0.

The gauge of the outgoing strip which, for purposes of description, will be identified as t is determined by the following relationship:

P Q 114... M.

where M,,, equals the spring constant of the mill composed of rolls, backup chocks, screws, and housings, and M equals the spring constant for the crosshead, rods, and springs. It is an object of the present invention, as will be later emphasized, to make the value M small by proper design of the springs with respect to M With the above remarks in mind, consideration will now be given to what takes place when a heavy or hard spot appears in the strip as it enters the roll gap. This will result in a change in the delivery gauge of the material as represented by a change in the force P and Q,

since no change in It moving the screws takes place, such that In subtracting Equation 2 from Equation 3 it can be seen that the change in gauge is:

M=AP (4) For Equation 4, the relationship of the change in the rolling force P and the spring force Q to the cylinder force F in terms of Equation 1 can be written:

which, by subtracting Equation 1 from Equation 5 the following is derived:

AF=AP+AQ Therefore, it is the prime object of the present invention to provide a mill control wherein the variation in t=0, i.e., the roll gap of the mill is maintained constant, except for some minor factors such as roll eccentricities. This is objective is achieved by the present invention by making At equal zero, in Equation 4, i.e.,

To achieve this, it follows from Equation 4 and Equation 7 that the following relationship must be maintained:

s *(Mm) AP (8) Looked at another way, by defining the operating equivalent mill stiffness as AP/ At, it follows from Equation 7 and Equation 8 that Alternatively, Equation 8 may be transformed to give s Mm which, substituted in Equation 6', gives s O MJ 2) The above shows that to make At=0, AF must be varied as AP or AQ varies to keep the ratio between either AF and AP or AF and AQ constant at all times, that is,

AF M F( Mm) A F M m A Q M t As noted above, the spring load cells 35 will read AQ or the alternate load cell 24 under the screw will read AP, so that either one may be used during rolling as the actuating signal and the ratio of a change in force represented by AF/AP or AF/AQ must be maintained, as stated in Equation 13 to obtain constant gage control.

It will be noted at this point that one of the operational advantages of the arrangement shown in FIGURE 1 is that the action involves no machine elements between the backup chocks since the tension rods, springs, etc., are arranged below the chocks and yield the very significant advantage of allowing roll changing to be handled as it is presently done in conventional mills.

6 With reference now to the electrical-hydraulic circuit provided for solving Equation 14 stated below, it will be noted that this formula can be expressed in terms of a gauge error which takes the following form:

ws Q (Mm J] t where 2' equals the thickness, and e the gauge error, that is the departure of the thickness of the rolled material from the desired thickness, t.

It Will be appreciated that the reduction of the error in accordance with the Equation 14 is based upon the relationship set out in Equation 13, in which the relationship between the AF and AP or AQ is held constant when the error is made to be zero.

The control circuit illustrated in FIGURE 6 is designed to solve Equation 14, the value Q being derived from the load cells 35, the value F from a pressure transducer 40 connected to the cylinder 29, and the value h from the potentiometer 41 coupled to the mill screw 22 (in FIG- URE 6 the potentiometer is shown as coupled to the motor 42 that drives the screw 22). The required material gauge t is set up on a manually controlled potentiometer 43. Electrical signals representing h F/M 1 1 Q (MEWS) and t are summer in a summing circuit 44 to produce an error signal e, which is amplified in amplifier 45 and sent to a differentiating circuit 49, the difference signal being applied to a pressure control valve 51 in the supply line 52 of the cylinder to reduce the error signal to equal zero.

In referring to the other embodiments of the present invention, reference is made to FIGURE 2 where there is illustrated a housing 55 having a window in which there is received backup chocks 56, the chocks adapted to rotatably support backup rolls 57, the lower chock, it being noted, is in engagement with a force applying piston cylinder assembly 58 which exerts a force greater than the rolling load. The upper chock 56 is engageable by the bottom end of a screw 59 being received in a housing via a nut 61 in which the screw is driven in the usual Way. The housing is provided midway between its upper and lower portion with projections 62 forming in a reduced window section to which there is received the work roll chocks 63 and, accordingly, the work rolls 64 which constitute the mill.

In the usual manner, balance piston cylinder assemblies, such as 65, are provided for the backup chocks and the work roll chocks so as to take up clearances prior to the material being introduced into the mill. In the lower portion of the projections 62 of the housing there are provided cavities 66 into which there are received readily yieldable means, such as springs 67, the bottom surface of the springs engaging enlarged heads of plunger 68 which rest on the lower backup roll chock 56. The relationship of the parts and the applied forces on this mill are similar to the mill of FIGURE 1 and may be represented as F =P+Q Where F is the cylinder force, P, the rolling force, and Q, the compression force on the spring. A AP signal will be developed as in the alternate form illustarted in FIGURE 1 from a load cell 69 arranged between the screw 59 and the upper chock 56.

Aside from these distinctions the embodiments in FIG- URE 2 will be similar to the arrangement in FIGURE 1.

With reference to FIGURE 3, which illustrates a further embodiment and a second embodiment of the principle illustrated in FIGURE 2, and in which only the lower half of the mill in FIGURE 2 is illustrated, wherein it will be noted that the projections 71 of the housing are located at the bottom of the housing. In these projections there are provided cavities 72 for receiving springs 73 as in the case of FIGURE 2. The lower end of the springs engage enlarged heads of plunger 74 which are carried by a crosshead 75 forming the cylinder of a piston cylinder assembly 76, the piston being in engagement with the bottom of the housing. Between the crosshead and the bottom chock there are provided variable spacers 77 to take care of a change in the diameter of the roll. The mill arrangement in FIGURE 3, aside from the structural dilterences, is similar in operation as that disclosed with respect to the FIGURE 2 embodiment.

The embodiment of the present invention illustrated in FIGURE 4 will now be described. It will be appreciated that while the equipment to be discussed is arranged at the bottom of the mill, it can be just as well arranged at the top. With reference to this figure there is provided a housing 81 which has a window 82 into which there is received backup chocks 83 of a 4-high mill, backup chocks rotatably supporting backup rolls 84. The backup chocks, as in the case of FIGURE 1, are provided with cavities 85 into which there are received work roll chocks 86 which rotatably support work rolls 87. The backup and work roll chocks are provided with the usual balance cylinder assemblies 88 and 89. The upper backup chock is adapted to be adjusted by a mill screw, not shown, which is driven in the usual way. With respect to the lower backup chock 83, it will be noted that it is provided with projections 91 that provide an opening for receiving the ends of the tension bars 92, the tension bars extending downward through or alongside the mill and are connected to a common crosspiece 93. The crosspiece itself is movable towards and away from the rolls by a power-driven screw '94 which is connected to a worm wheel 95 driven by a worm 96, the drive for the worm not being shown. The screw 94, it will be noted, engages the bottom of the housing 81. The screw can be operated to maintain the pass line, set the initial roll gap, or change the gap during rolling. Between the lower backup chock and the housing is provided a piston cylinder assembly 97 adapted as in the other embodiments to deliver a force greater than the rolling load and which pressure is changed pursuant to the formula F =P+Q.

As pointed out above, while the present invention and the novel mechanism illustrated and described have been set forth as a procedure for obtaining constant roll gap, should for any reason the rolling mill illustrated be desired to be operated with a constant cylinder pressure, this can be performed. Also, should it be desired, in accordance with present practice, to operate the mill whereby the Q force in the formula F=P+Q (Equation 1) is maintained constant, thereby, as for example in FIGURE 1, maintain the distance between the backup rolls constant, this method can also be carried out in the present invention without necessitating any change aside from what is required to control the cylinder in FIGURE 6 to maintain the cell reading constant. It will also be noted, as illustrated in FIGURES 1 and that while in a given construction it may be desirable to provide readily yieldable means, such as springs, for maintaining a desired relationship between the moduli of the rolling mill parts subject to the rolling pressure, and the rolling mill parts subject to the Q force, this is not necessary in certain applications as illustrated in FIGURE 4.

It will be appreciated that the relationship of the spring or other yieldable means, such as tension rods, with reference to the cylinder can be changed from what is shown in FIGURES 1 and 4, so that the spring force acts in the same direction as the force of the cylinder. In this construction the cylinder force will be less than the rolling force by an amount equal to the spring force. In FIG- URE 5 there is illustrated such an arrangement, wherein there is shown a housing 101 having a window 102 that receives the rolls shocks of a 4-high mill. The upper chock is engaged by a cross member which is urged downward by a pair of force applying cylinders 104. At the center of the cross member a spring 105 is rotated between the cross member and a screw 106, which is driven by a motor wheel set 107. In this arrangement the spring and cylinder act in concert, the force of the cylinder being controlled by the signal of a load cell 108 as in the other embodiments.

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. However, I desire to have it understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim: 1. In a rolling mill, or like apparatus having a housing, an elongated window in said housing, and

a pair of rolls between which a rolling force is developed, including mounting means for each roll received in said window of said housing, wherein a portion of the housing receiving the mounting means and at least one of said mounting means is subject only to the rolling force of the mill,

means arranged at one end of said window of said housing and between one of the mounting means and housing for applying to a first group of mill parts, including one of said mounting means, a substantial part of a roll gap controlling force, said force being applied in a direction to resist the rolling force of the mill,

the force applying means being constructed and arranged so that the force differential between its total force and the rolling force is applied to a second group of mill parts, which excludes at least said other mounting means, and wherein the elastic characteristics of said two groups of mill parts have a predetermined relationship.

2. In a rolling mill according to claim 1, wherein said second group is located in the one extreme of said window and outside the area defined by said mounting means and having a tension member for transmitting said differential force between said force applying means and said housing.

3. In a rolling mill according to claim 1, including a control means for continually measuring the force imposed on either said first or second group of parts and varying the applying force proportional to a change in the force being imposed on said first or second group of mill parts to maintain a predetermined relationship be tween either of these forces and the applied force.

4. In a rolling mill, or like apparatus, having housings, and

a pair of rolls between which a rolling force is developed including mounting means for each roll,

means arranged in said housings at one side thereof for applying to a first group of mill parts, including said mounting means, a substantial part of a roll gap controlling force, said force being applied in a direction to resist the rolling force of the mill,

the force applying means being constructed and arranged so that the force difierential between its total force and the rolling force is applied to a second group of mill parts, which excludes at least one of said mounting means, and wherein the elastic characteristics of said two groups of mill parts have a predetermined relationship,

means separate from said force applying means and associated with the mounting means arranged on the sides of the housings opposite said force applying means for adjusting the associated mounting means and its roll to adjust the position of the roll independent of said force applying means.

5. In a rolling mill according to claim 4, including a control means for continually measuring the force imposed on either said first or second group of parts and varying the applying force proportional to a change in the force being imposed on said first or second group of mill parts to maintain a predetermined relationship between either of these forces and the applied force.

6. In a rolling mill according to claim 1, said second group of mill parts comprises one or more tension rods associated with the lowest roll assembly of the mill, said tension rod subject to a tension force by said force applying means, and wherein the tension imposed on said tension rods is measured by a force measuring means.

7. In a rolling mill according to claim 6, wherein a readily yieldable means is associated with said tension rods and arranged to be compressed thereby to give added flexibility to said second group of mill parts.

8. In a rolling mill according to claim 6, including a force measuring device associated with said housing arranged to receive and measure the separating force of said roll assemblies.

9. In a rolling mill according to claim 1, including readily yieldable means received in the housing of said mill and so associated with the force applying means to be subject to a compression force.

10. In a rolling mill according to claim 9, wherein said housing is provided with projections, openings in said projections for receiving a plurality of springs, one end of said springs engaging one of said roll chocks of the roll assembly, said springs being compressed by the application of said force applying means and wherein said housing projections are in the vicinity of the work rolls of the mill.

11. In a rolling mill according to claim 1, including a rotatable screw associated with one of said rolls for adjusting the initial gap of said roll assemblies.

12. In a rolling mill according to claim 9, in which said housing is provided with projections located at the base of the mill, the projections including openings for receiving springs and wherein said springs engage a member associated with said force applying means and are compressed upon movement thereof.

13. In a rolling mill according to claim 1, comprising a pair of substantially parallel arms connectable at one of their ends to one of the roll chocks of the mill and at the other of their ends to a cross member, means for adjusting the cross member relative to the pass line of the mill in which construction the force applying means in applying a force on the roll chock to which the arms are associated imposes a tension force on said arms, a'portion of which is taken into the cross member and into the housing.

14. In a rolling mill according to claim 1, including a cross member arranged in said window and between a mounting means of one of said rolls and said housing,

said force applying means arranged between said cross member and said housing,

a rotable screw mounted in said housing on the same said thereof that said force applying means is located, and

a yieldable means arranged between the screw and said cross member.

References Cited UNITED STATES PATENTS 3,327,508 6/1967 Brown 72-243 CHARLES W. LANHAM, Primary Examiner L. A. LARSON, Assistant Examiner US. Cl. X.R. 712 1, 245

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,496,743 February 24, 1970 Morris Denor Stone It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 45,"(the bypass component)" should read (the by-pass force component) Column 5, equation 11, should appear as shown below:

AP vAQ equation 12, should appear as shown below:

M AP 6 AQ Column 6, line 34, "summer" should read summed Column 10, line 22, "said" should read side Signed and sealed this 16th day of February 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

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