US2479974A - Design and construction of rolling mills - Google Patents

Description

Aug. 23, 1949. T. SENDZIMIR ETAL 2,479,974

DESIGN AND CONSTKUCTIbN OF ROLLING MILLS Filed May 5} 1943 3 Sheets-Sheet 1 'g mmm's 'Pi t EaEusz SE'NOZINIR.

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DESIGN AND CONSTRUCTION OF ROLLING MILLS Filed May 5, 1943 3 Sheets-Sheet 2 45' 53 H HM. +6

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Patented Aug. 23, 1949 DESIGN AND CONSTRUCTION OF ROLLING MILLS Tadeusz Sendzimir and John E. Eckert, Middletown, Ohio, assignors to Armzen Company, Middletown, Ohio, a. corporation of Delaware Application May 5, 1943, Serial No. 485,750

23 Claims. (CI. 80-38) The present invention pertains to improvements in the arrangement and design of rolling mills of a type in which rotary elements or casters, acting substantially throughout the length of the working rolls, transmit the roll-separating force from small diameter work rolls to the housing beams. Such mills are. shown in U. S. Patents 2,169,711 and 2,187,250 to Sendzimir, one of the inventors herein.

The housing of such mills comprises, in addition to end members, transverse beams paralleling the axis of the work rolls, and the housings are usually though not necessarily formed in one piece. It is the housing itself which prevents deflection of the slender work rolls. The casters back the work rolls at many points, preferably along two generants, so that the work rolls can be fully floating, i. e., they requ re no other radial bearings to locate them. Each caster comprises a heavy ring of relatively narrow width in relation to its diameter, a shaft and a bearing (preferably of the oil-film or roller types) and, of course, a support for the shaft which contacts the housing beam. As distinguished from conventional backing rolls in the ordinary 4-high or cluster mills, which have a length substantially I housing-backed mills, to which this invention is addressed, take up any bending movements, and simply transmit their share of the roll-separating force directly to the housing beams, since they are disposed at close intervals entirely across the metal strip being rolled.

Our invention has for its object the provision of structural and operating improvements in such mills which have to do not only with the ge ometry of such mills, but also with the provis on of means whereby extraordinary variations in gauge or thickness of the work piece, or obstructions which would enforce a greater separation of the work rolls, can be accommodated without danger to the mechanism.

These and the more specific objects of our invention, which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, since they can be more clearly brought out in connection with the ensuing detype of rolling mill of the character to which reference has already been made.

Figure 2 is a similar partial sectional view of a modified mill, which is equipped with mill pressure release means;

Figure 3 is a diagrammatic representation of a mill equipped to do contour rolling.

Figure 4 is a partial sectional view taken through the .end of an intermediate roll and a drive spindle to show a thrust bearing arrangement.

Figure 5 is a diagrammatic v ew of a mill equipped with means for continuously indicating both the entering and leaving gauges of the piece being rolled, as well as the conditions to be encountered during rolling.

Figure 6 is a partial plan view showing a staggered arrangement of caster elements.

Figure 7 is a partial vertical section of a mill showing an arrangement of operating elements, and an automatic screw-down release mechanism.

Figure 8 is a partial vertical section through another type of mill in which staggered casters are journaled upon a beam member by means of a traveling bearing chain.

Figure 9 is a partial plan view of a wedge assembly for screw-down purposes.

Figure 10 is a partial plan view of one type of bearing chain.

Figure 11 is a partial sectional view showing the relation and coaction of a certain type of staggered casters with the chain of Figure 10 and trackways on a mill beam member.

Figure 12 is a partial plan view showing another type of bearing cha n.

Figure 13 is a partial sectional view showing the coaction of another type of caster with the chain of Figure 12 and with a mill beam element.

Figure 14 is a partial sectional view showing casters and sealing means for lubricant.

In Patent 2,187,250, Figures 6, 7 and 8 show a simple embodiment of a housing-backed mill having only two rows of casters for each work roll. Figure 8 of Patent 2,169,711 may be referred toas showing a longitudinal section through a shaft having a plurality of casters rotatably mounted on it by means of self-aligning roller bearings, and a plurality of supports, one between each pair of casters, the supports resting directly on the housing beam. Compared to a conventional mill, having a somewhat similar general arrangement (the so-called cluster mill, where each work roll is floating on a pair of backing rolls), it will be seen that entirely different factors govern the design of the two mill, where the backing rolls must sustain the roll-separating force through their inherent stinness, the backing rolls themselves must have a large diameter. In general, this diameter must be almost equal to themaximum width of the strip to be rolled if they are not to deflect too much under rolling pressure. This determines the minimum diameter of the work rolls. Thus,

for a strip mill which is intended to roll material 50" wide, the backing roll should have a diameter of about 44'', and the smallest possible work roll diameter would be around 18". This is too great a diameter for the efiiclent rolling of light gauge strip.

These limitations do not apply backed mills, since it is the housing itself that sustains the roll-separating force. The housing beams can be made as rigid as desired, while the diameter of the casters and, hence, the diameter of the work rolls becomes independent of the width of the strip. But there is another limitation peculiar to the housingrbacked which I has to do with the load carrying capacity or the If the diameter of the bearingafor the casters. work rolls is made small (in view of the iact that the casters for geometric reasons cannot ordinarily be made larger in diameter than two and one-half times the diameter of the work rolls),

in Figure oi the same patent, where each work roll has two first intermediate and three second intermediate rolls, and the total number of sets to the housingonly as much as may be required for the stationary supports or bearing members. When bearing members are made with their bores hardened and ground, or faced with a hard metal, and when the shafts are also hardened and ground, and preferably lapped in position (i. e., assuming ideal conditions), the practical limit is reached when the total axial length reserved for the casters is about 80%, leaving about 20% for the supports. If 20% of the axial length of the force-transmitting structure is not reserved forthe stationary supports, the unit pressure on those supports becomes too great. This is especially true when the shafts themselves are eccentric, and their axial position is changed from pass to pass by a suitable mechanism for screwdown purposes. 1

0n the other hand, the bearing capacity of the casters for any given diameter of work rolls is efiectively increased, and theoretically without limit, by increasing the number of sets of casters, by means of which the rolling force which is effective on one work roll is transmitted to its beam. Figure '7 of Patent 2,169,711 shows the first step in this direction in which each work roll has two intermediate rolls and three sets of casters. This arrangement might be called a 1-2-3-pyramid clearly noticeable in such a mill.

of casters becomes four. This might be termed a 1-2-3-4 arrangement. More elaborate arrangements along the same line might be made; but a mill with very many intermediate. rolls 'is more complicated, and rapidly becomes too complicated for economy. But such a mill also has the disadvantage of becoming less rigid because the high roll-separating force produces a flattening of the various rolls at their respective lines of contact, and these flattenings are cumulative in character, depending uponthe number of the rolls. Thus, a more complicated mill will be characterized by an increased deflection of the work rolls in spite of the rigidity of the housing beams. This increased deflection may be unevenly distributed over the length of the work rolls, as will be shown. I

An undesirable consequence of a mill overelaborated for reasons set forth above is that it becomes laterally unstable. This is especially true of mills for rolling relatively narrow strip. To illustrate this, assume a mill designed to roll strip 12 in width, which mill has a 1-2-3-4-arrangement and employs casters of about 9 in diameter. The effect of lateral'instability would be If the strip deviates from the center of the mill by as much as one-quarter of an inch, which is common in actual practice, this deviation throws more load on the side of the tall roll structure, and produces a slanting deflection of the work rolls due to the lack of rigidity aforesaid. This, in turn, tends to throw the strip still more to the side, and it to the rolling of relatively narrow strip, in spite of its great advantages in cold reduction, arising through the use of very small working rolls and the resistance of the roll-separating forces by means effective along the whole length of the working rolls.

One of the objects of our invention is the provision of a solution of the difiiculties hereinabove mentioned, in particular, of a means and mode of operation whereby small workin rolls may be employed without either an over-elaboration and consequent lack of rigidity in the mill on the one hand, or too sinall a bearing capacity on the other.

Considering first the normal arrangement of a 1-2-3-4 mill, as illustrated in Figure 1, where a work roll I is immediately backed by a pair of rolls 2 and 3, which in turn rest against second intermediate rolls 4, 5, and 6, and where casters .65 I, 8, 9 and I0 through their bearings and supports transmit the rolling forces to a rigid housing beam II, it will be evident that the axes of the work roll I, the outer intermediate rolls such as 3 and 6, and the outer casters such as l0 lie almost in a plane. The plane, however, has to be slightly concave, as observed from the plane of the work piece, since otherwise the intermediate rolls would be thrown out of the mill. But a very great concavity could not be tolerated for arrangement. The next step is that illustrated geometrical reasons.

proportionate division of the load makes it possible to do either one or both of two things: We

can make the inner series of casters 8 and 9 smaller (and with smaller bearings), roughly corresponding to their load bearing capacity.

Such an arrangement is illustrated in Figure 21 10 stead of plain bearings with hardened and ground of our copending application Serial No. 477,087, filed February 25, 1943. The chief advantage of such an arrangement 'is that it effectively increases the depth and, therefore, the rigidity of the beam II for a given height of the mill.

Again, we can bring the shafts of the caster sets 8 and 9 closer together than their outer diameters would permit, providing we stagger or interdlgitate the casters on these shafts. A large number of advantages fiows from this, as will hereinafter be set forth. One of these advantages is a geometrical one permitting the use of smaller working rolls, as will be seen from Figure 2. Here a work roll 12 is immediately backed by first intermediate rolls l3 and 14. These, in turn, rest against second intermediate rolls l5 l6 and H. The second intermediate rolls rest against caster series l8, I9, 20 and 2|, which in turn are supported by the housing beam 22. Due to the force distribution which has already been noted, it is possible to stagger the caster series i 9 and 20, which mechanically means that the total of the operating faces of the casters in each of these particular series may be about 50% of the length of the working rolls, leaving about 50% of that 3 length for the supports and the bearings which may be employed in connection with the supports. It will be noted that the roll I Ii ofthe second intermediate series is smaller than the rolls l5 and I1. Thus, the first intermediate rolls in the mills of the two figures, a minimum work roll size of about 1%" will be found for the mill of Figure 1. For the mill of Figure 2; however,

this size may be reduced to about 11 3".

The arrangement shown in Figure 2 involves smaller bearings for the casters I 9 and 20 on the shafts on which they are mounted, but this is tolerable, as explained, because of the force distribution. On the other'hand, considerably more axial space is provided for the stationary supports by means of which the shafts are mounted on the mill beam 22. This fact facilitates the provision of a further improvement. In the mills of the Sendzimir patents to which reference has been made, the casters are mounted on roller bearings or the like on shafts, which shafts in turn are mounted on supports in cradles bearing against hollows in the mill housing beams. For screw-down purposes, it is possible to make two different provisions. The cradles may have arcuate surfaces bearing against mating surfaces in the housing beams, while the shafts supporting the casters may have their axes eccentric to .the axes of the cradles. Ifthis construction is adopted, screw-down may be effected by rocking the cradles in the housing beams by suitable mechanical arrangements, such as those described in Patent 2,169,711. Instead of this, however, it is possible'to provide the shafts with portions engaging the supports,

which portions are eccentric to. those portions their bearings.

. 6 upon which the casters are mounted by means of Where this construction is adopted, screw-down is effected by rocking the shafts by means of a suitable mechanical arrangemnt, as described in ,Sendzimir Patent 2,170,732.

In mill structures embodying staggered casters the. greater possible width of the supports makes it possible to mount the eccentric shafts in them upon roll or needle bearings, in-

contacting surfaces. Where the eccentric shafts are then used, in part at least, for screw-down purposes, this construction attains, for the first time in the art so far as we are aware, the aspects of an antifriction screw-down system, and opens up certain additional possibilities, as will hereinafter be described.

Referring to Figure 2, we have shown an exemplary structure in which there is a common cradle 23 for the intermediate caster series 19 and 20. Thi cradle rests in an appropriate recess in the housing beam 22. and is provided with integral supports at suitable staggered intervals for the shafts 24 and 25. One such support is shown at 26. Shaft 25 has an eccentric portion mounted in this support by means of a needle bearing 21, ,and a cover or clamp member 28. It will be understood how similar bearings are provided for, each of the mounted portions of shafts 24 and 25, and that these mounted portions are eccentric with respect to those intermediate portions of the same shafts upon which casters l9 and 20 are mounted by means of their roller bearings, one such being illustrated As to the caster series I 8 and 2|; they may have no provision for screw-down movement, or as shown, they may be mounted respectively on shafts 30 and 3! which are eccentric, 0r again, their cradles 32 and 33 may be eccentrically mounted in the mill beam.

Mill screw-down mechanisms on cold strip mills have not only to bear enormous loads, but also have to be operated under such loads. Whether it be the conventional screw mechanism of the type used on ordinary 2- and 4-high mills, or eccentric shafts or cradles as shown in the Sendzimir patents, their overall mechanical efllciency is low, usually ranging between 5% and 10%. This is because of their high frictional characteristics, and the very great difference between stationary and running friction as encountered on all sliding bearings subjected to great pressures. During the operation of the mill, the screw-down mechanism may or may not remain stationary, but in any event, it has to be varied under a load at the end of each pass to bring the rolls close together for a subsequent pass on reversing mills. Where, in addition to this, the screw-down position must be moved in order to correct for variations in gauges, the screw-down has to be driven, again under full load, by minute amounts repeatedly during rolling, and such movement involves overcoming the initial stationary friction. Thus, in an instance where a Z-horsepower motor would be theoretically sufficient to drive the screw-down under running friction, it will be found that a 30-horsepower motor at least is required for operability. For this reason alone, overcoming of starting friction and the elimination of running friction in a screw-down mechanism is an important improvement in the structure and operation of a rolling mill.

Again, where screw-down adjustments are to be made manuallyor automatically during the rolling operation, the elimination of friction makes possible a very much more accurate and rapid response to gauge variations, as will be clear.

Because of the substantial elimination of frictional characteristics in a screw-down, the eccentricity or wedging action of the coacting members may be made such that the holding force required is small. But this need not be done if suitable holding means are provided. Further, if the holding means are of such character that their holding action can be accurately correlated to various pressures, then the elimi- .na'tion of friction in the screw-down mechanism as such enables us to provide in rolling mills a mechanism for safety release.

It happens occasionally, especially to the less experienced rolling mill operators, that a strip" may become doubled within the roll bite, an cecurrence commonly known as a Again, there may be foreign bodies like bits of metal unintentionally caught in the roll bite. Yet again, atthe conclusion of a pass in a reversing mill operation, the operator may omit rolling operations, will, nevertheless, give or release if these normal working forces are much exceeded.

One way of accomplishing this object is illustrated in Figure 2 Where the eccentric shafts 2d and 25 at their ends are provided with keyed pinions, 34 and 35. A rack 36 simultaneouslyengages these two pinions, and the eccentricities of the shafts are arranged to have opposite hands,

so that movement of the rack in one direction will move the work roll into the work, while movement in the opposite direction willrelieve the screw-down pressure. The rack 36 is'part of or connected with the piston rod 36a. of the piston 31 of an hydraulic cylinder 38," by which the screw-down is moved and the screw-down pressure exerted.

There may be two sets of the mechanisms just described, one at each end of the eccentric shaft assembly, so as to minimize errors caused by the torsional deflection of the eccentric shafts. There may be a straight tooth rack and pinion at one end, and at the other spiral teeth may be employed. The object is to provide a screw-down mechanism wherein the forces will tend to produce an even screw-down across the entire width of the mill.

The hydraulic cylinders can obtain their fluid supply from a constant delivery volumetric pump capable of delivering a fixed volume of fluid for I equivalent of a mechanical screw-down system with suitable compensation for replacing leakages in the system. Or a variable delivery pump may be employed which can be kept running at all times by a motor. From such a pump, the delivery may also be varied from zero to the amount each revolution, and thus acting as the hydrauic 8 required by an appropriate mechanism in the operato'rs pulpit. The operation is the same as with the first alternative, except that the variable delivery pump provides in itself a compensation for leakages in the system.

The third possibility, as illustrated in Figure 2, takes high pressure oil (at a pressure higher than that needed in the system) from a constant pressure source, e. g. an accumulator, and uses an hydraulic valve system with a follow-up bushing and linkage, as at 40, which insures control of the exact position of the pistons 31 in their cylinders. Such an hydraulic valve 40 can be of the Servo-Valve Type as commercially known, for example, that valve manufactured by Vickers, Incorporated, Detroit. The relief feature is accomplished by the inclusion of a relief valve in the system (pressure relief valve 39), where the relief valve may be accurately adjusted for the particular relief pressure desired- By appropriately locating the relief valve, we may by the means described provide that relief occurs on excess pressure very rapidly because practically no inertia need be overcome.

For extreme accuracy of relief pressure, the relief valve 39 can be kept slightly open at all times during operation, the escaping oil being compensated for, together with other leakages. When pressure on the work rolls is suddenly increased, the flow through the relief valve 39 increases, thuspreventing increase of pressure in thesystem; but there is no additional pressure needed to lift valve 39 off its seat.

Other types of screw-down operating means may be employed. But it. should be noted that two general modes of operation are. possible with a mill such as that described in connection with Figure 2. With suitable apparatus, the screwdown may be so operated that upon adjustment, a fixed position of the working rolls within the resiliency limits of the 'mill will be maintained at all operating times, and will be relieved only if the roll-separating force exceeds a predetermined value above the normal roll-separating force. But it isalso possible to operate an hydraulic screwdown system, and certain mechanical counterparts, in such a way as to insure the maintenance of a desired resistance to the roll-separating force, irrespective of the actual position of theworkrolls. This also embodies a safety feature in that any obstructions, which would normally tend to increase the roll-separating force, will, in this latter system," be able to separate the rolls without imposing an increased stress on the operating part of the mill. Such a system lends itself better to the use of automatic means for maintaining an even gauge. In connection with known means for constantly measuring the gauge of the strip as it leaves the mill, we may employ means for responsively varying the screw-down pressure. Also, the exertion of a constant roll pressure, irrespective of the actual roll positions, eliminates such gauge variations as occur when using oil film bearing casters because of changes in the thickness of the oil film with increasing or decreasing speeds of rolling. In the light of these teachings, the skilled worker in the art will readily realize that a non-self-locking, antifrictibnal screwdown mechanism, such as we have described, can be employed for the exertion of constant roll pressure with any mechanical, electrical, or fiuid pressure means capable of exerting a constant force, in spite of variations in the position of the element upon which force is exerted.

Yet again, our teachings open new fields of rolling technique by extending the application of our mill to procedures in which a rapid and frequent movement of the screw-down mechanism is necessary as, by Way of example, where a strip of varying longitudinal section is required, as in taper rolling. With this type of rolling, several passes are usually necessary for the complete reduction of a blank, which initially may be either fiat or tapered. For this purpose, it may be required that the work piece be moved rapidly back and forth between the work rolls I and i2. This may be accomplished, as in Figure 3, by attaching the work piece 4! to a carriage 42, which is reciprocated back and forth in synchronism with the operation of the work rolls and the screwdown pistons 38, as by an hydraulic cylinder 43, or other means. It is preferable so to arrange the work stroke that it goes from the thicker to the thinner portions, although with suitable control mechanism, both the forward and the back strokes may be utilized, reversing the rotation of the work rolls as may be required. The operation of the screw-down mechanism will, of course, be correlated with the position of the piece during rolling.

Such a mode of operating a mill without an anti-friction screw-down would lead to premature wear of the eccentric shafts or other screwdown mechanism and, therefore, to loss of accuracy of the mill. It approaches in some aspects the Pilger system of rolling as used, for example, in seamless tubing mills. A relatively heavy slab can be reduced in one operation to light-gauge strip by reciprocating the slab in the mill back and forth while the screw-down mechanism moves the rolls up and down during each stroke. At the end of each stroke, the slab is fed forward a small distance independently of its normal reciprocating motion. It has heretofore been impossible to operate a strip mill in this manner unless eccentric or cam-shaped work rolls are employed.

While the geometric aspects of the mill which we have described in connection with Figure 2 makes it possible for us materially to decrease the diameter of the work rolls without at the same time pyramiding the rolls too high, it should be noted that the use of very small work rolls presents another problem in that they may not have enough torsional strength to be driven in the conventional way. To meet this problem, we have developed another mode of driving the mill which comprises simultaneously driving all of the intermediate rolls of one degree i. e., the four first intermediate or six second intermediate rolls, etc.), rather than attempting to drive the work rolls, or in addition to the direct drive of the Work rolls, the latter being however, limited to the torque transmitting capacity of said work rolls.

The method of driving rolls by friction is not itself new, but it is new as applied to this type ofmill, and it offers some special advantages. First, the driving force frictionally applied to the surface of the work rolls is applied along two generants corresponding to the two intermediate rolls, which cuts down wear and scratching, as compared to driving a backing rod on a 1-inch mill, where only one contact line transmits the whole torque. Second, there is a more abundant reserve of driving power. The efiiciency of a frictional drive depends upon the coefiicient of friction. Where a work roll is contacted by two intermediate rolls in approximately the positions shown in Figure 2, each work rollsustains a reaction force which is just about 70% of the rollseparating force effective on the work roll. Thus, for each ton of roll-separating force, there are two reaction forces of .7 ton each each, or a total of 1.4 tons which, multiplied by the coefficient of friction, produces a 40% better frictional drive than could be obtained along a single line in a 4-high mill, for example.

The use of driven intermediate rolls, however, is coupled with another difliculty because unless some way is provided for taking up the thrust of the intermediate rolls, the mill cannot be operated. We solve this difficulty in a simple fashion by providing flexible spindles which not only transmit the torque of driving means to the intermediate rolls, but take up the thrust of such rolls, as for example, against a pinion stand. These spindles also provide for such up and down movement as the screw-down requires. In Figure 4, we have shown the end of an intermediate roll at 44, and the end of one of our spindles at 45. The spindle is hollow at its end so as to accept a reduced portion of the intermediate roll, and is provided within with teeth 46, which mate with other teeth 41 on the intermediate roll. This provides for the transmission of torque, irrespective of changes in the relative angularity of the axes of the roll and the spindle.

The same spindle 45 is also used to transmit thrust from the driven roll 44 to the pinion stand by means of a ball and socket coupling. Ball 5!! has a shank 48 connected to spindle 45, and takes thrust in either direction from driven roll 44 through a suitable recess in said roll, or through a recess in the nut 5i. The connection between shank 48 and spindle 45 can be accomplished by any known means, such as a pin, setscrews, etc. A cannon lock connection is a very serviceable one for this purpose, and is illustrated in Figure 4. It comprises quadrant thread teeth provided in the shank 48, engaging with similar quadrant thread teeth provided in the spindle 45 and held in angular position by spring-pressed block 55 urged against a fiat on the shank 48.

To disengage such a cannon lock coupling, as when changing rolls, all it is necessary to do is to turn shank 48 one-quarter turn in the spindle 45 so that the quadrant thread teeth come out of engagement and the shank 48 is free to be pulled out axially. This is accomplished by inserting a toothed wrench 53 into engagement with tapered teeth 52 provided on said shank 48, and turning the wrench 53 so as to overcome the pressure of the spring 56, and rotate the shank 48 in the spindle 45. A similar arrangement may be provided on the other end of the spindle for engagement with a shaft in a pinion stand.

Other type flexible joints, like the automobile type universal joint, which can transmit torque and thrust simultaneously, can be used instead of the coupling shown in Figure 4, but their capacity for torque is usually inferior to that of the coupling described.

In a copending application, serial No. 477,087, filed February 25, 1943, we have dealt with problems connected with lubricating and cooling mills of this general type. The teachings in this application apply, of course, to the mills of our present invention, and will not here be repeated. It may be noted, however, that where the intermediate rolls are to be driven, as by spindles which we have just described, there may be a problem of sealing the general lubricant bath on the drive side of the mill, in view of the fact that the rolls move vertically for screw-down purposes. In the solving of this problem, we have found that it is practicable to extend the bath of lubricant on the one side of the mill up to the pinion stand by surrounding the various driving spindles with a housing (not shown) connected to the mill at one end and at the other connected to the pinion stand.

The combined effect of relieving the work rolls of the driving torque and at the same time backing them in a floating manner adapts our mill in a superior way to the use of work rolls of extremely hard and abrasion-resistant material, such as for example sintered tungsten carbide (Carboloy) and some other products of the pow-,

der metallurgy. Such materials have in addition to extreme hardness a modulus of elasticity much higher than that of steel, so that they are more efilcient as work rolls. They exhibit markedly less elastic flattening than steel rolls, especially when rolling light gauges. But such materials are very brittle and cannot stand the torque of driving. They also cannot withstand any appreciable bending or shearing stresses as are encountered in the conventional 4-high mill. In such a mill, even if the work rolls were not driven, and the force were applied to the strip only, the work rolls would have to withstand bending moments in the horizontal as well as the vertical planes, and they would break unless their diameters were made quite large. None of these disadvantages is encountered in the mill of our invention when using'such rolls. The fact that our mill makes possible the use of Carboloy or similar work rolls affords a further advantage in economy because of the extremely small diameter of our work rolls. In spite of the high cost of the material, such rolls are not relatively expensive, though they would be if greatly increased in diameter. Even the first intermediate rolls are small in our mill, and they may also be made of Carboloy or similar material in cases where it is desired to take heavy passes on light-gauge, workhardened stock, and where the pressure at the lines of contact of the work roll with the first intermediate rolls might be high enough to cause fatigue and spalling. Where the first intermediate rolls are also made of Carboloy or similar material, the drive, of course, will preferably be applied to the second intermediate rolls.

As we have indicated, the provision of an antifriction screw-down mechanism eliminates completely the vibration and jolting involved in overcoming the initial static friction when starting a screw-down motor. This is especially true where an anti-friction screw-down is operated by a highly sensitive and precise hydraulic system.

The gauge of the piece being rolled may be controlled much more constantly by the operator or may be made responsive to an automatic gauge control system with superior efiects. In Figure 5, 58 represents a mill of the type hereinafter described, being operated as a reversing mill with coilers 59 and 60 on either side. Flying micrometers BI and 62 are arranged to contact the strip as it enters and as it leaves the mill, and these may be connected with electric gauge indicators diagrammatically shown at 63 and 64. Ifthese indicators are located in the operator's pulpit, together with a control for the screw-down, the operator can constantly watch the gauge and correct it.

Systems of gauge control hitherto proposed have (quite aside from any question of rapidity of response) neglected an important factor. If, for example, the gauge of a strip being rolled shows an increase, the effect has hitherto been to adjust the mill to decrease the gauge, irrespective of any other factor. But at the time when such a correction is made, the actual conditions in the mill may have varied or may be about to vary in the opposite direction, so that the actual effect of the correction may be the reverse of that desired.

In the system diagrammatically indicated in Figure 5, two recording gauges or indicators, 63 and 64, are connected respectively with the two flying micrometers. The one recording indicator draws a curve representative-of the strip gauge on the exit side of the mill, while the other indicator is for the moment inoperative. When the mill is reversed, the last mentioned indicator is placed in operation, and the first rendered inoperative, But the charts of both indicators are advanced by suitable feeding mechanism, which causes them at all times to follow the movement of the strip through the mill. Consequently, the curve on the presently inoperative-indicator will represent the gauges produced by the mill on the frictionless f preceding pass, and since the chart is moving, the operator can tell from it the entering gauge of the material and thegauge trend of the material about to enter the mill. The operating indicator gives him a picture of the gauge actually being produced by the mill on the present pass. The operator is informed not only of any gauge variations currently being produced in the mill, but

also of the starting gauges which the mill is encountering on the present pass. The operator will, therefore, operate his screw-down knowing exactly what variation he has to compensate for, knowing how thick the strip is, and how much material of that thickness is approaching the mill.

The presently inoperative indicator also currently informs the operator'how much more strip there is on the pay-ofi coiler, so that he knows exactly when to stop the mill. This eliminates the necessity of wrap counters which are a complication in the already complicated operators pulpit. 1

The gauge correction system which-we have just described'lends itself to. fully automatic oper'ation. Means for automatically operating the screw-down can be connected to means to ollowing both charts in such a way as to be acted upon by the differential of the observations of each chart follower. There are various ways both electrical and mechanical in which the charts or other records can be followed. For

example, electric eye devices may be employed for this purpose. Using such devices as exemplary, it is better to use two electric eyes at each side of the mill, one of them responsive to the spot on the chart corresponding to the strip as it enters or leaves the mill, while the other is responsive to a spot on the chart a certain distance behind or ahead of the first mentioned spots, as the case may be. The actual screw-down corrections may then be obtained through the combined action of all of these electric eyes, so as to dampen oscillations and produce a very accurate response to the actual and expected conditions encountered in the mill.

It may be noted, however, that through the use of our frictionless screw-down mechanism with any type of automatic or manual gauge control, a superior result is achieved because of the extreme sensitiveness and smoothness of operation of our screw-down.

In the type of mill under discussion, some slight deflection of the housing beams is, of course, en-

countered, and while that deflection is very much less than the roll deflection in 2-high or 4-high mills, it can be compensated for exactly so that the flatness and uniformity of the strip do not vary across the strip with varying roll pressure once the mill has been properly calibrated. Modes of accomplishing this are set forth in the patent to Sendzimir, No. 2,187,250. In combination with the characteristic features of the present invention,-this feature of automatic compensation may take on certain new forms, It consists in balancing off any deflection of the housing beams by an opposite deflection of another member or members, which will be equivalent for the same pressure. The several shaft supports formed on one cradle in our present mill will compress elastically under the influence of the roll pressure by a very small amount, but substantially uniformly for all supports, since the loads they bear are uniform. Deflection of the housing beam will be greater at the center of the beam than at the ends. It can be compensated for if the compressibility of the cradle supports is made non-uniform by varying in the opposite direction, i. e., if the supports are made least compressible near the center of the mill, and most compressible near the sides of the mill. This may be accomplished by reducing the section of the supports on the cradles progressively from the center toward the ends. Again, a varying number of holes in a uniformpattern may be drilled through such supports, or some of them, since this is equivalent to increasing the'elasticity of the web portions so drilled, but does not diminish their stability in the other direction in their action as plates. i

This feature of compensation should not be confused with means for deliberately varying the cross-sectional contour of the piece being rolled.

In Patent 2,169,711, Sendzimir has described the use of cradles which are essentially separate for each support, which are eccentrically mounted in arcuate recesses in the housing beams, and which are provided with independent control means, whereby the several cradles may be moved with respect to each other. This may also be done in the mills of the present invention, as will be evident.

Hereinabove we have indicated that we are not restricted to the use of frictionless screw-down means employing hydraulic elements. Purely mechanical relief mechanism may be employed. Nor again, are we restricted to the particular arrangement of staggered or interdigitat'ed casters which we have described in connection with Figure 2. The features of our mill may be widely varied without departing from the spirit of our invention. By way of example, another arrangement is shown in Figures 6 and '1. The work roll 65 rests upon two intermediate rolls, 68 and 61, which in turn rest upon three sets of staggered casters indicated at 68, B9 and Hi. These casters are rotatab y mounted on shafts 1|, I2 and 13, which are mounted in supports on a single cradle The load on the center series of casters 69 in this mill is less than one-quarter of the load imposed upon the two outer sets of casters so that, especially when using self-aligning roller bearings for the casters, it is possible to provide more bearing area for the outer caster series than for the central one. Thus, the outer casters, 68 and 10, may be arranged in groups of two each, while the inner casters, 69, are individually interdigitated between the groups of two outer casters, as clearly shown in Figure 6.

The cradle 14 has a cylindrical outer surface eccentric, however, to the axis of the work roll El. It is rotatably journaled in a semi-cylindrical recess in the mill beam 15, and it may be given an anti-frictional mounting by means of a series of roller bearing members 16. At one side of the beam, we provide a fixed stop 11, while at the other side we pivot a lever orseries of levers, 18, on ears 19 aflixed to the mill beam. One end of the lever or levers engages aslot or depression formed in the cradle 14 as illustrated, while at the other end of the lever or levers, we. provide some constant force means, such as compression springs Oil engaged between the levers and sockets 8| on adjusting screws 82, threaded into ears 83 on the beam. The effect of the springs is to force the cradle 14 in a clockwise direction against the stop TI, and the force exerted by the springs is adjusted to counteract the expected or desired rolling pressures. It will be understood, of course, that the eccentric arrangement greatly diminishes the necessary value of the counterbalancing force. The upper part of the mill, which is not illustrated excepting for the upper working roll, may have a similar construction.

For screw-down purposes in this mill, we may provide one or more of the shafts H, 12 and I! with eccentric portions and obtain screw-down adiustment by rocking these shafts, as will be understood from the description above.

Or else, instead ,of a fixed block 11, an adjustable (e. g., by screws) stop may be provided so that cradle 14 itself can be oscillated for screwdown purposes. Instead of the lever I8 and spring 85!, it would be preferable in this case to employ an air cylinder or similar known means for maintaining the same pressure regardless of position.

So long as the roll-separating force does not exceed a given value as determined by the adjustment of springs 80, the mill will act as a rigid mill. But when the working rolls encounter an obstruction and the roll-separating force is suddenly increased beyond the predetermined value, the cradle 14 will rock in a counter-clockwise direction against the force exerted by the springs. This is because of-the eccentricity of the cradle with respect to the axis of the work roll; and this eccentricity permits a separation of the working rolls when the cradle rocks as aforesaid, so that the obstruction can pass through without damage to the rolls. In Figure 7, the strip being rolled is indicated at 84.

A similar effect might be obtained by providing a corresponding spring and lever arrangement in connection with one of the eccentric shafts of the mill (one that is not used-for screw-down) Such a pressure relief system would be less accurate and effective, however, because of the static friction in the shaft journals.

The mill of Figures 6 and 7 is suitable for relatively light rolling pressures, yet it has an arrangement in which it is possible to mount 1" work rolls upon 9* diameter casters in a simple 1-2 3 pyramid, so that for all rolling applications where the bearing capacity thus obtained'is adequate, this mill has the advantage of greater simplicity, combined with morelateral stability.

As we have explained'the use of-staggered casters cuts down the effective total width of each of the staggered sets across the face' ofthe strip being rolled, and by-the same token, cuts down the width of the bearings for the casters on the shafts on which they are mounted, although at the same time, it increases the width maintaining the casters in position and, there-z fore, can be made quite thin. The interdigitation of the casters can thus be increased, and it is possible to support very thin working rolls directly upon large casters.

Perhaps the simplest mill embodying features of the present invention is that shown in Figures 8 to 13, inclusive. Figure 8 is a cross-sectional view of the lower half of such a mill. It comprises a lower housing beam 85, upon which is supported a movable section 88, upon a screwdown mechanism presently to be described. Interdigitated caster sets, 81 and 88, are J'ournaled upon a configured upper surface of the movable beam section 88, and awork roll 88 is shown as resting directly upon the caster sets. The casters themselves are connected by thin shafts, indicated at 88 in Figures 11 and 13. The outer surfaces of the casters in the caster sets 81 and 88 rest upon rollers 8| interposed between them and the movable beam section 88. These rollers are bearing members; but they also are preferably interconnected to form a chain, 8 la, which passes over sprockets 82 and 88 and returns beneath the beam 85 on a larger sprocket 88. In a mill of this type. the driving force may be applied to the chain 8Ia, asby means of the sprocket 84, or by one of the two sprockets 82, 83, depending on the direction of rolling, and where this is done, no other driving means need be supplied. However, the mill may be otherwise driven, if desired.

The movable beam section 88 rests upon the fixed beam 85 through wedges 85 and 88. The under surface of the movable section 88 may be flat, as shown, excepting for a depending rib 81, while the upper surface of the fixed beam 85 may be formed of two slanting surfaces inclined toward each other and meeting at the center of the beam. It will be clear that by moving the wedges 85 and 88 toward and away from each other, the movable section 88 is respectively lowered and raised on the fixed beam 85. This movement is employed for a screw-down. Segment plates 88, 88, I88 and IM are mounted in arcuate hollows in the wedges 85 and 88, and these segment plates are, in turn, engaged by internal wedges I82 and I83 which are grooved as shown and are guided by the rib 81 on the movable part 88.

The wedges I82 and I88 may be interconnected and moved by suitable mechanism such as screws, hydraulic cylinders, or other means. When the wedges are moved symmetrically away from each other, the movable portion 88 is raised with respect to the stationary housing beam 85, and the gauge of the rolled strip is uniformly decreased. If, on the other. hand, the wedges I82 and I83 are not moved symmetrically, but one is moved a greater distance than the other, the portion 88 becomes tilted with respect to the beam 85 and a non-parallel screw-down movement may thus be achieved.

For obtaining the maximum backing capacity from the chain 8Ia, its type may be that illustrated in Figures 12 and 13. The rollers I88 are mounted upon shafts I85, and the shafts are in- .thus practically filling the whole length of the 16 terconnected with relatively thin staggered links I88, so that the links need not be doubled, and the minimum spacing between the rollers I84 is achieved. With such a chain, the width of the casters 81 and 88 can be almost as much as the distance between casters in any given set, leavin only a small clearance between them, and

work roll.

If the centers of the casters permit this, then a set'of casters and its sliaft can be turned from one piece of metal, or the casters can be snugly fitted to a shaft otherwise made. Where shafts ride.

may be employed as illustrated, no further support or bearing members for the caster assemblies need be employed; but where the interdigitation of the casters is such as to leave no room for shafts, then the spaces between the casters will be filled in with suitable guide means so as to maintain the casters in anupright position, to keep them accurately spaced, and to prevent tilting.

In many instances, when it is not essential that the additive widths of the casters in the caster sets 81 and 88 be so nearly equal to the length of the work roll 88, then the operating faces of the casters may be made narrower and a regular "roller type chain employed, as illustrated in Figures 10 and 11. The rollers I81 may be mounted upon shafts I88, and we may employ roller chain type links I88 which encircle the rollers I81 and are double. Such achain can stand a considerably greater pulling force, and this construction is of advantage where, as hereinabove mentioned, the drive is applied through the chain 8Ia. The contact area between the casters "sand 88:: and the chain rollers I81 will necessarily be reduced, as will the axial length of the contact between any individual caster and the work roll, so that a lesser roll-separatin force must be contemplated. Also, since the ends of the links themselves are of greater diameter than the rollers I81 which they embrace, it will be necessary to provide the movable beam portion 88 with spaced trackways II8 (Figure 11), between which are grooves in which the links may This construction also prevents sidewise displacement of the chains.

In cases where a work roll is to be supported directly on casters, the total width of the faces of which is substantially less than the length of the work roll, grooving of the work roll can be eliminated or minimized by slightly relieving the edges of the casters. We have found, however,

that adequate support for a work roll can be provided by spaced elements, such as the operating surfaces of the casters 81a and 88a in Figure 11, providing the spaces between the operating surfaces are not substantially greater than the diameter of the work roll. In a mill where on either side of the strip being rolled there arebut two sets of casters, it will be evident that the work roll must be supported directly on the casters. This makes for simplicity of mill construction, but in the embodiment shown, gives us a mill which is not capable of withstanding as great a roll-separating force as some of the other embodiments herein disclosed. It will be evident, however, that the structure described in connection with Figures 8 to 13, inclusive, can be modified (with suitable reshaping of the operating face of the movable beam portion 88 and suitable reshaping of the elements), to accommodate three or more sets of casters, in which 15 event intermediate rolls may be employed, e. g.,

. 17 in such an arrangement as is illustrated in Figure 7. While Figure 8'shows the lower half of a mill,

it will be understood that the upper half may have may be desirable. This of course, involves sealing.

Figure 14 shows a cross section in part of two adjacent backing casters I II and H2 mounted on eccentric shaft H3 and the top cap H4 or the corresponding support or bearing member." The cap I must have a small clearance where it faces the casters, or dangerous rubbing would occur. To prevent oil leakage through said clearance and also to prevent dirt and foreign matter from entering the inside of roller or other bearings H5 and M6 on which the casters rotate, special sealing rings H1 and H8 are provided.

These are split elastic rings, preferably metallic, with the outer or inner face tapering so that they have a tendency to slide in a suitable taper surface provided in the saddle and its cap, towards the side faces of the casters, but only with a small force, compared to the radial pressure they exert on said taper surface in the saddle, owing to the angle of the taper.

Small oil channels, straight or spiral, may be provided on the sealing rings to insure complete lubrication of the interface with the casters, the faces of which are preferably polished after grinding. Oil leakage through such lubrication channels and also through the slot in the ring itself is immaterial, as oil is steadily supplied and circulated under pressure.

In case of poor lubricationon said interface between casters and the sealing rings, so called rubbing cracks" would develop in the casters, causing their premature failure. To make the danger from this source still more remote, it is preferable so to dispose the sealing rings that they contact the casters in the middle, 1. e., close to the neutral axis of theirsection, where stresses due to bending moments are small.

Modifications of our invention may be made without departing from the spirit of it. Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. In a rolling mill having small diameter work rolls and mill housing beams extending in the direction of the work roll axes, to which beams the roll-separating force is transmitted substantially uniformly throughout the length of the work rolls by means including casters supported on the beams, a caster construction including at l t t f th t east W Se o casters 8 cas ers of one set as housing beams extending in the direction of the being interdigitated with the casters of another set, whereby to support a roll substantially smaller in diameter than the casters in a position in which a portion of said roll extends beyond the tangent to the casters.

2. In a rolling mill having work rolls and mill housing beams extending in the direction of the work roll axes, to which beams the roll-separating force is transmitted substantially uniformly throughout the length of the work rolls by means 18 ter construction including at least two sets of casters, the casters of one set being interdlgitated with the casters oi another set, there being for one beam two sets of casters interdigitated with each other, said beam configured to form a supporting surface for the operating faces of said casters, and a movable chain of bearing rollers interposed between said beam and said faces of i the said casters.

3. Ina rolling mill having work rolls and mill housing beams extending in the direction of the work roll axes, to which beams the roll-separating force is transmitted substantially uniformly throughout the length of the work rolls by means including casters supported on the beams, a caster construction including at least two sets of casters, the casters of one set being interd gitated with the casters of another set, there being for one beam two sets of casters interdigitated with each other, said beam configured to form a supporting surface for the operating faces of said casters, and a movable chain of bearing rollers interposed between said beam and said faces of the said casters, said chain being an endless chain, and sprockets over which said chain moves in a continuous path surrounding said beam.

4. In a rolling mill having work rolls and mill housing beams extending in the direction of the work roll axes, to which beams the roll-separating force is transmitted substantially uniformly throughout the length of the work rolls by means f including casters supported on the beams, a caster construction including at least two sets of casters, the casters of one set being interdigitated with the casters of another set, there being for one beam two sets of casters interdigitated with each other, said beam configured to form a supporting surface for the operating faces of said casters, and a movable chain of bearing rollers interposed between said beam and said faces of the said casters, said chain being an endless chain, and sprockets over which said chain moves in a continuous path surrounding said beam, one at least of said sprockets being capable of being driven whereby to supply power to said casters and through said casters to a work roll supported thereon.

5. The structure claimed in claim 4 wherein the operating faces of all of said casters are of less total width than the length of said work roll. in which said chain comprises links for said rollers having portions of greater diameter than said rollers, and in which the beam is grooved to provide trackways for the roller portions of said chain lying between said links.

6. The structure claimed in claim 4 wherein said beam is divided into two parts, one part constituting a fixed portion of the mill housing and a second part movable with respect to the first co and mounted thereon by means of opposed wedges whereby said second part may be moved for screw-down purposes by movement of said wedges.

7. In a rolling mill having work rolls and mill caster construction including at least two sets of casters, the casters of one set being int'erdigitated with the casters of another set, there being as to one of said mill beams at least two sets of casters in interdigitated relationship and two outincluding casters supported on the beams, a cas- 7 lying Sets Of non-interdigita-ted r n r throughout the length of the work rolls by means including casters supported on the beams, a caster construction including at'least two sets of casters, the casters of one set being interdigitated with the casters of another set, there being as to one of said mill beams at least two sets of casters in interdigitated relationship and two outlying sets of non-interdigitated casters, intermediate roll sets interposed between said casters and a work roll, one of said sets of intermediate rolls comprising three rolls of which the center one is smaller than the outlying ones, whereby a geometrical advantage is obtained in said mill permitting the use of a smaller diameter work roll with casters of a given diameter, said smaller intermediate roll of the set of three resting concurrently on the certain interdigitated casters, the

arrangement being such that the greater part of the eifective roll-separating force is sustained by the outlying sets of non-interdigitated casters, said casters having greater bearing capacity than the interdigitated casters.

9. The structure claimed in claim 8 including means for applying a driving force to one of the sets of intermediate rolls.

10. The structure claimed in claim 8 including means for applying a driving force to one of the sets of intermediate rolls, said means comprising drive spindles having both a universal joint action to permit drive in spite of screw-down movement and a thrust bearing action for preventing axial movement of the driven intermediate rolls.

11. The structure claimed in claim 8 wherein the casters of each intermediate set have a total width approximately equal to half the length of the working roll with allowance for clearance, providing substantially equivalent bearing space between casters, said casters being mounted by means of anti-friction bearings on shafts having eccentric portions, said shafts also being mounted on anti-friction bearings on supports on said housing beam whereby said shafts maybe employed as an anti-friction screw-down mechanism, and means for rocking said shafts for screw-down purposes.

12. The structure claimed in claim 8 wherein the casters of each intermediate set have a total width approximately equal to half the length of the working roll with allowance for clearance, providing substantially equivalent bearing space between casters, said casters being mounted by means of anti-friction hearings on shafts having eccentric portions, said shafts also being mounted on anti-friction bearings on supports on said housing beam whereby said shafts may be employed as an anti-friction screw-down mechanism, and means for rocking said shafts for screwdown purposes, said last mentioned means comprising a release mechanism operative to permit rocking of said shafts under the roll-separating force when the roll-separating force exceeds a.

predetermined maximum.

width approximately equal to half the length of the working roll with allowance for clearance, providing substantially equivalent bearing space between casters, said casters being mounted by means of anti-friction bearings 0n shafts having eccentric portions, said shafts also being mounted on anti-friction hearings on supports on said housing beam whereby said shafts may be employed as an anti-friction screw-down mechanism, and means for rocking said shafts for screw-down purposes, said last mentioned means comprising a release mechanism operative to permit rocking of said shafts under the roll-separating force when the roll-separating force exceeds a predetermined maximum, said screw-down 'mechanism comprising an hydraulic cylinder and automatically acting pressure release means in connection with said hydraulic cylinder.

14. The structure claimed in claim 8 wherein the casters of each intermediate set have a total width approximately equal to half the length of the working roll with allowance for clearance, providin substantially equivalent bearing space between casters, said casters being mounted by means of anti-friction bearings on shafts having eccentric portions, said shafts also being mounted on anti-friction bearings on supports on said housing beam whereby said shafts may be employed as an anti-friction screw-down mechanism, and means {or rocking said shafts for screw-down purposes, said last mentioned means comprising a release mechanism operative to permit rocking of said shafts under the roll-separating force when theroll-separating force exceeds a predetermined maximum, said screwdown mechanism comprising an hydraulic cylinder and automatically acting pressure release means in connection with said hydraulic cylinder, means for supplying fluid under pressure to said cylinder, and means in connection with said fluid means for controlling the operation of a piston in said cylinder so as to determine by fluid pressure means the position of said piston therein.

15. In a mill having a housing beam and a work roll and in which the roll-separating force is transmitted from said work roll to said housing beam throughout the length of said work roll by means of casters, three sets of interdigitated casters in which the outer sets of casters have substantially twice as much effective face width as the inner set of casters. and a, pair of intermediate rolls supporting said work roll on said casters in such manner that the work roll is from approximately /8 to b the diameter of the casters, the arrangement being such that the outer caster sets which have a larger bearing capacity sustain the greater part of the effective roll-separating force.

16. In a mill having a housing beam and a work roll and in which the roll-separating force is transmitted from said work roll to said housing beam throughout the length of said work roll by means of casters, three sets of interdigitated casters in which the outer sets of casters have substantially twice as much effective face width as the inner set of casters, and a pair of intermediate rolls supporting said work rol1 on said casters in such manner that the Work roll is from approximately $4, to the diameter of the casters, the arrangement being such that the outer caster sets which have a larger bearing capacity sustain the greater part of the effective roll-separating force, said caster sets being rotatably journaled on shafts which in turn are mounted on having an axis displaced from the axis of the work roll whereby the roll-separating force will tend tov rock said cradle in said beam to sheet a movement of the work roll away from the center plane of the piece being rolled, and resilient means for urging said cradle posite rotative direction.

17. In a. mill having a housing beam and a work roll and in which the roll-separating force is transmitted from said work roll to said housing beam throughout the length of said work roll by means of casters, three sets of interdigitated casters in which the outer sets of casters have substantially twice as much effective face width as the inner set of casters, and a pair of intermediate rolls supporting said work roll on said casters in such manner that the work roll is from approximately to the diameter of the casters, the arrangement being such that the outer caster sets which have a larger bearing capacity sustain the greater part of the efl'ective rollseparating force, said caster sets being rotatably iournaled on shafts which in turn are mounted on a common cradle having an arcuate outer surface engaged in an arcuate depression in the mill housing beam with anti-friction means interposed therebetween, the said arcuate surfaces having an axis displaced from the axis of the in the .op-

work roll whereby the roll-separating force will.

tend to rock said cradle in said beam to eifect a movement of the work roll away from the center plane of the piece being rolled, and resilient means for urging said cradle in the opposite rotative direction, there being a stop on said beam to limit the rocking of said cradle in said opposite direction and said urging means comprising a leverage and means for applying force to said leverage in a resilient manner.

18. The structure claimed in claim 17 in which said stop means is adjustable as to position for screw-down purposes, and in which said means for applying force is a means for applying a constant force irrespective of the position of said cradle.

19. In a mill, work rolls, a housing having end members and rigid, non-rotative beams extending axially of the work rolls and between said end members, means for transmitting the rollseparating force from said work rolls to said beams, said means including sets of intermediate rolls of substantially the same length as said work rolls and casters of substantially lesser length rotatably journaled on supports in connection with said beams and acting in groups to support said intermediate rolls, and means for driving said mill comprising means for transmitting torque to a set of intermediate rolls for each of said work rolls, said means for transmitting torque comprising spindles having both a universal connection with said intermediate rolls to permit roll separation and an end thrust connection therewith.

20. In a mill, work rolls, a housing having rigid beams extending axially of the work rolls, means for transmitting the roll-separating force from said work rolls to said beams, said means including sets of intermediate rolls and casters rotatably journaled on supports in connection with said beams and acting to support said intermediate rolls, and means for driving said mill comprising means for transmitting torque to a set i 22 of intermediate rolls for each of said work rolls,

- said last mentioned means comprising spindles of hollow character, said spindles having a rockable toothed engagement with portions of said intermediate rolls, said spindles within their hollows carrying balls on the ends of arms, said balls esting within sockets in the ends of said rolls and held therein by means of threaded collars, so that said spindles are capable of preventing endwise movement of said intermediate rolls, said balls and arms being mounted upon threaded members in the hollows of said spindles whereby said'members may be both adjusted and dlsen-.

gaged for disassembly.

21. In combination, a reversible rolling mill having work rolls and a screw-down, coilers on each side of the mill, means on each side of said mill for measuring the gauge of a work piece as it leaves said mill, means in connection with said last mentioned means for making a continuous record of said gauges and including record strips, and means for moving said record strips at all times in accordance with the movements of the work piece being rolled, whereby an indication is presented not only of the gauge of the work piece as it leaves the mill on each pass, but of the gauges of the work piece as it approaches the mill during said pass, and means for operating said screw-down so that gauge corrections may be made during rolling not only in accordance with the gauge being produced by the mill, but also in accordance with the known variations of gauge of the material as it approaches said mill.

22. In combination, a reversible rolling mill having work rolls and a screw-down, coilers on each side of the mill, means on each side or said mill for measuring the gauge of a work piece as it leaves said mill, means in connection with said last mentioned means for making a continuous record of said gauges and including record strips, and means for moving said record strips at all times in accordance with the movements of the work piece being rolled, whereby an indication is presented not only of the gauge of the work piece as it leaves the mill on each pass, but of the gauges of the work piece as it approaches the mill during said pass, and means for operating said screw-down so that gauge corrections may be made during rolling not only in accord- -ance with the gauge being produced by the mill,

but also in accordance with the known variations of gauge of the material as it approaches said mill, said screw-down being an anti-frictional, non-self-locking screw-down, and said means for operating it including means for applying to it a controlled force which may be varied as desired.

23. In a beam backed mill having work rolls and means for transmitting the roll-separating force from the working rolls to beams extending axially thereof, casters forming part of said force transmitting means, said casters being mounted on self-aligning bearings on a shaft, said shaft in turn being mounted in supports on one of said beams, said supports extending between said casters, and means for isolating lubricant in said bearings comprising sealing rings mounted in annular recesses in said supports, said sealing rings having an annular tapered face mating with a similarly tapered face in said supports, said rings so constructed as to provide resilient pressure against the tapered faces of said grooves whereby said sealing rings tend to move upwardly 23 I 24 in sold grooves until the! but adult add vNumb. Hm Date 1,914,429 Coe Jan. 11, 1927 gsggg 1,921,499 Shower et a1. Sept. 1, 1991 1.89%.: Shovel Dec. 27, 1932 1,99 :1: Rohn Apr. 11, 1939 ammo mm 1,977,919 Boyer at 9.1. Oct. 29, 1934 The following references are of record in the 2,019,141 Stake! at 9.1 Nov. 5. 1935 me of this patent: 3,099,409 Ross Oct. 6, 1936 .rzonsz Sendzlmir Aug. 22, 1999 N UNHEDNBTAHB Imus 2,919,999 Dahlstrom Mar. 10, 1942 m r 77 me am 151,449 Swan ....i......... an 29, 1914 mama PATENTS v 188,741 Kloman Mar. 87, 187! Number Country mm 651,441 Kuhlewind i-- June 12, 1900 418,004 Germany Aug. 24, 1925 1,911,949 Wflmot Sept. 2. 1919 1 929,777 Great Britain July 29, 1940 1,446,300 Iawrence at 81. Feb. M, 1m

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