US2978933A

US2978933A - Beambacked planetary rolling mill

Info

Publication number: US2978933A
Application number: US719315A
Authority: US
Inventors: Sendzimir Tadeusz
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-03-05
Filing date: 1958-03-05
Publication date: 1961-04-11
Anticipated expiration: 1978-04-11

Description

April ll, 1961 T. SENDZIMIR.

BEAMBACKED PLANETARY ROLLING MILL Filed March 5, 1958 s sheets-Sheet 1 ATTORNEYS.

Aprlll, 1961 T. sENDzlMlR 2,978,933

BEAMBACKED PLANETARY ROLLING MILL Filed March 5, 1958 3 Sheets-Sheet 2 AT1 QNEYS.

Apnl l1, 1961 T. sl-:NDZIMIR 2,978,933

BEAMBACKED PLANETARY ROLLING MILL Filed March 5, 1958 3 Sheets-Sheet 3 DEFORMTION ZONE 0F PLASTIC ZONE 0F" PLASTIC ATTORNEYS,

United States Patent' O f BEAMBACKED PLANETARY ROLLING MILL Tadeusz Sendzimir, The Sendzimir Co., Oxford Circle, Waterbury, Conn.

Filed Mar. 5, 1958, Ser. No. 719,315

28 Claims. (Cl. Sli-38) The invention has to do with mill structures designed to produce a very heavy reduction in gauge in a single pass through the apparatus. The metallic material being rolled is generally of slab thickness; and in a single pass such material is reduced either to sheet gauge or to such a gauge as will enable it to be converted to a sheet gauge product by a simple cold rolling operation.

Hitherto the type of mill employed for such -a purpose has utilized a pair of driven backing rolls journaled in appropriate bearings in a housing, there being arranged about the periphery of these backing rolls a plurality of working rolls of relatively small diameter. The ends of these working rolls may be engaged in bearings in suitable rings whereby the simultaneous contact of a pair of the working rolls with the slab at the start of their travel `against the work piece may be insured. The work piece is treated to the action of a large number of pairs of working rolls during a single pass between the backing rolls, the working rolls rolling forwardly on the work piece, i.e. in the direction of travel of the work piece. ln an exemplary form of such a mill, the working rolls are rotated by rictional contact between the backing rolls on one side and the work piece on the other. Since a high reduction is` made so that there is a great disparity in the entering and leaving speeds of the work piece, provision is usually made for precession of the working rolls i.e. for the forward movement of the working rolls at increasing speeds from the time they first contact the work piece until they leave the surface of it. Exemplary mills of this type are described in United States Patent No. 2,710,550, issued June 14, 1955.

In a planetary mill of the type hereinabove described, especially where provision is made for precession, the working rolls are essentially free-oating throughout their length, so that there is less tendency toward deflection of the working rolls in the working direction than would be encountered in a conventional four-high mill having working rolls of the same diameter engaged at their ends in fixed bearings. But in other respects such planetary mills have limitations similar to the limitations of the four-highmill in the matter of rigidity of the housing and of the backing. rolls. This circumscribes the construction of planetary mills for the rolling of materials in wide widths. For example, for aircraft wings and other structures sheet materials are required in widths from 60 inches to 120 inches and more.

It is a primary object of the present invention to provide a type of mill capable of performing the work of a planetary mill but useful for the rolling of slab-like materials to strip materials in `widths far beyond the practical limits of the hitherto known planetary mills.

It is an object of the invention to provide a mill capable of making large reductions, and in which the contour of the rolled piece can be much more exactly controlled.

It is an object of the invention to provide a mill construction which eliminates the greater part of all deflections which would affect the contour of the rolled material, the deections arising not only from the roll sepa- '2,978,933 Patented Apr. 11, 1961 ice rating pressure per se but also from the periodic variations of pressure which occur in cyclic rolling instrumentalities of the type of planetary mills. These periodic variations may occur at a rate as high as from 2,000 to 4,000 oscillations per minute. i

An object of the invention is to provide a mill structure in which the said oscillations of pressure will not coincide with some natural period of vibration of the mill structure and become accentuated thereby. The structures herein described are so rigid that they do not have natural periods of vibration within or near the2,000 to 4,000 oscillations per minute hereinabove set forth.

It is an object of the invention to provide a mill which not only is not subject to detiection as hereinabove set forth but is provided with means whereby the contour of the rolled material can be varied and adjusted as desired.

Other objects of the invention have to do with the provision of mechanical means whereby the above ad# vantages may be obtained in a mill structure; but these objects can best be understood in connection with the description, which follows, of an exemplary mechanism.

The various objects of the invention to which reference has been made, and others which will be pointed out hereinafter or will be apparent to one skilled in the art upon reading these specifications, are accomplished by that certain construction and arrangement of parts of which an exemplary embodiment will now be described in detail. Reference is made to the accompanying drawings wherein: s

Figure 1 is a partial cross section through the center of the mill taken in the direction of the extent of the work piece.

Figure 2 is an end elevational view of the mill with parts in section, the section being taken along the line A-A in Figure l.

Figure 3 is a side elevational view of the mill including an adjunctive rolling instrumentality as hereinafter described. i

Figure 4 is a transverse sectional view of a drive for the mill.

Figure 5 is a perspective View of a control device for transverse contour of the work piece. Y

Figure 6 is a diagrammatic representation indicating the way in which a particular contour of an anvil member permits precession of the working rolls.

Figure 7 is a similar diagrammatic showing of an improved mode of obtaining precession by means of the anvil contour.

- The mill housing While the housing of the mill may be made up of parts bolted or otherwise fastened together, it is preferably formed from a single block of metal i having a rectangular hole in the center of it. This hole is indicated at 2 in Figure 3. The housing thus has end members 4 and 5 and top and bottom transverse members 6 and 7 which constitute beams. These parts may be made of such size and mass as to be to all intents and purposes rigid against deliection due to the roll-separating forces generated in the mill. The slab 8 (Figure 1) passes through the hole 2 between the beams 6 `and 7, and in that zone is converted by plastic deformation into the strip 9.

The housing 1 is provided with lugs 10 and 11 bythe beam 6 and the other returning below the beam 7.

In a solid housing such as has been described, roll separating pressure tending to deect the beams 6 and 7 in directions at rightV angles to their axes, is further resisted by the rigidity of the vertical columns 4 and 5; and the portions ofthe columns 4 and 5 which are subject to tensional forces are quite short. Thus a mill housing may be made which is .to all intents and purposes completely rigid as respects the strains imposed by the reduction of the widest slabs. Moreover, the total weight of the housing, Vdue to the compactness of the structure, is normally less than the weight of a single housing of a conventional backing roll type of mill of comparable size, which makes the structure more practical to manufacture and transport and also less costly. Since the planetary. rolls in this type of mill travel Aaround backing beams 6 and 7 which are stationary, provision must be made for the driving of the working rolls. Also, since the distance between the backing beams 6 and 7 is fixed, it becomes necessary to provide suitable screw down means in order to adjust the thickness of the product.

: Planetary roll assemblies, mounting and driving means Referring now to Figure l, the two planetary assemblies comprise each a series of

working rolls

14 and 15 which are supported by pairs of rotary elements 16 and 17 mounted upon shafts 1S and 19 extending transversely ,of the mill. The shafts 18 and 19 are interconnected by `

link elements

20 and 21 so that each planetary assembly is inthev form of a chain, as shown. These chains are guided around the respective beams 6 and 7 in orbital paths which include their passage around sprockets such as the sprocket 22 in Figure l, the sprockets being located on driven roll-like shafts 23 and 24 positioned as closely as possible to the beams 6 and 7. In the plastic deformation zone within the housing opening 2, the rotary supporting elements 16 and 17 engage against anvil members and 26 which are supported by the beams and which cause the working rolls to move in a path suitable for the reduction of the slab 8 to the strip 9 within the plastic deformation zone ofthe mill. The shaft 23 is driven in a counterclockwise direction in Figure 1 while the shaft 24 is driven in a clockwise direction. This causes the working rolls to move through the plastic deformation zone in the same direction as the movement of the work piece. The chain assemblies are thus in tension in the zone of plastic deformation. The roll-separating forces yare transmitted through the

anvil members

25 and 26 to the beams 6 and 7. Y

As will be evident from Figure 2, the rotary supporting elements 16 and 17 for the working rolls 14 and .15 are not continuous rolls but instead are broken up into spaced portions mounted respectively on the shafts 18 and 19. Thus the lower rotary supporting elements are shown as constituting spaced portions 17 to f in Figure 2, all mounted on the shaft 19. The spaced rotary supporting elements will hereinafter be referred to for convenience Vas casters Adjacent ones of the shafts 19 are connected together by the link elements 21 between the sev- -eral casters. The sprocket elements 22 engage the chain link elements 21 as will be clear from Figure l; and as shown in Figure 2 the shaft 24 carries a plurality of these sprockets 22 to 22e so as to engage links of the chain at intervals throughout the width of the chain construction. The sprockets are of course splined or otherwise attached to the roll 24.

The shaft 24 is supported at either end in antifriction bearings 27 and 28 mounted in

brackets

29 and 30. These brackets are interconnected by a web 31 so as Vto Aprovide a rigid frame, which can be bolted to the mill yhousing by bolts 32 engaging in slots in the brackets. .Adjustment in height of the frame can be accomplished `,witll the aid of screw devices shown at 3 3.l

of the planetary arrangements "envases 4 The provision of the rigid frame aforesaid, makes possible the provision of intermediate bearings as at 34 (Figure 2) for the shaft 24, which contribute to the rigidity of the driving means and minimize the tendency to develop periodic vibrations, especially on wide mills.

The planetary mill, especially when operating as a hot mill, requires a large amount of energy, usually more than 5() horsepower per inch of slab Width. The transmission ef power from the shaft 24 to the chain through the several sprockets, therefore, involves an important problem. if the sprockets 22 engaged the casters 17, it is evident that the rotation ofthe casters would have to come to a stop at the drive point in each cycle. This in turn would stop the rotation of the working rolls at the high speed of the mill, entailing a large energy loss, and the possibility of scratching and damage to both the working rolls and the casters, because of the sudden stoppages.

The problem has been solved by causingthe sprockets 22 to engage the chain links 21 as is clearly illustrated in Figure l, the sprockets being so shaped that they clear the casters.

Since the engagement of the chain links by the sprockets results in some rubbing between these members, it is preferred to make the chain links of a material having a high surface hardness, and to use lubricants'that prevent galling.

The casters 16 and 17 support the working rolls 14 and 3.5 as will be evident from Figure 1, and in order to insure that the working rolls are urged toward the casters` at all time, use is made of spring yokes 35 which embrace end portions of the working rolls, and engage, by means of their inclined extremities, the ends of the caster shaft 18 and 19. The inclination aforesaid maintains the working rolls against the casters even after the rolls have been ground to a smaller diameter.

One end of the shaft 24 has a projection 36 to which a drive may be applied as hereinafter described.

The construction of the upper chain assembly and of the shaft 23, its sprockets, bearings and the like is similar.

In order to lead the chain assemblies about the beams 6 and 7 respectively, rail tracks may be provided at each end of each assembly. As shown most clearly in Figurel, these tracks may comprise a member 36 attached to an anvil member or to its beam, and

link members

37 and 38 pivoted together in succession. The end casters of the chain assemblies ride on these tracks from the place where the assemblies leave contact with the sprockets to the place where they contact the

anvils

25 and 26. Suitable expansion members, such as fluidpowered cylinders 39, connected between the track links 38 and the respective beams may be employed to tighten the chain assemblies by expanding the rail tracks, particularly in the event of stretching or wear of the chain. Other chain assembly supports are not ordinarily required, since the chains are under power drive only within the zone of plastic deformation and between that zone and the sprockets.

However, it has been found advantageous to` provide semi-flexible tensioned, outside strap-like members 40, to contact the chain assemblies in that part of the cycle outside the working zone of the mill. These members are mounted on supports 41 at one end, and at the other are provided with blocks or abutments 42 against which screw members 43 threaded in brackets 44 may engage for tensioning purposes. The strap members may be made of any suitable material, but if made of metal they are preferably faced inwardly with plastic to avoid marking of the working rolls 14 and 15. The strap members assist the spring retainers 35 in maintaining contact of the working rolls with the casters in spite of centrifugal force; but more importantly they serve to maintain the working rolls in continuous rotation so that sudden starts and stops (which might entail roll damage) `are not encountered. i

It will be clear from the description above that a rigid inill has been provided, amply dimensioned for 'the lowest deflections, together with a rigidly supported chain drive, andalso that synchronism can be attained by controlling the relative rotative positions of the shafts 23 and 24. The term synchronism as applied to a planetary mill implies such control of the working rolls that opposite ones thereof will contact the work piece simultaneously at either side. However, it has been found in the mill of this invention that there is a great advantage in providing for minute adjustment of the synchronization at all times during the rolling operation.

Whereas in theory the best results will be attained if each working roll rst contacts the slab in perfect synchronism with the opposite working roll, and then moves through the whole zone of plastic deformation in strict symmetry with it, experience has shown the need for adjustment even to the extent of creating small departures from exact synchronism. When the working rolls are close to the position of exact synchronism, the forces which tend to throw them out of synchronism are small in magnitude; but if and when a roll has been thrown out of synchronism, the de-synchronization forces tend to increase rapidly in magnitude.

Such conditions are particularly severe at the moment when the trailing end of a slab passes through the zone of plastic deformation, followed by the leading end of a succeeding slab. The slab ends are frequently at Vdifferent temperatures; and sometimes each is unevenly heated. Also the slab ends may not be square; and they also may have been bent by the shear.

By carefully observing such conditions, the milloperator may usually anticipate at tendency ofthe material being reduced to throw the rolls out of synchronism; and

6 connectors 50 and 53 hence of the mill shafts 23 and24.

The arrangement of the parts is preferably such that the shorter pinion 54 will lie about midway of the shaft 52'for the position of exact synchronism, providing by its movement for an adjustment of opposite working rolls in the mill of about a tenth of an inch, more or less, on either side of the position of exact synchronism, although ythe degree of adjustment may be varied with the size of the mill.

Means are provided to move the shaft 57 longitudinally in order to secure the desired adjustment. One such means may be a fluid cylinder 58. Indicating means attached to the fork 56 on the shaft 57 may be provided to show departures from synchronism. It will be understood that means other than those specifically hereinabove described may be used to adjust the synchronism.

Screwdown and contour control It isnecessary in the mill of this invention to provide a screwdown which will operate with precision and which will not impair the rigidity of the system. If the beams 6 and 7 were treated like the necks of backing rolls with their ends slidably journalled in openings in conventional mill housings, a conventional type of screwdown could be used. But in this event most of the advantages of an ultra rigid and compact mill housing would be lost. As has been explained, the beams 6 and 7 are either integral with the end members 4 and 5 of the housing or are rigidly bolted thereto. In the mill of this invention screwdown is accomplished by causing one or both of the anvils Y 25 `or 26 to move vertically with respect to the beams he may therefore counteract the tendency by making a brief counter-adjustment. Furthermore, during the rolling of any one slab, conditions may change so that a minute adjustment will be effective in establishing a quieter operation of the mill, 4and a more even surface on the rolled product. Adjustment of synchronization is simply attained in the mill of this invention by driving the shafts 23 and 24 individually through driving means which are adjustable as respects each other, both drives being mechanically interconnected by an indicating differential showing at all times .the exact degree of synchronization. A simple way of accomplishing the purpose, particularly where a single motor is to be used for driving both shaft 23 and shaft 24, involves the provision of a pinion stand having pinions with helical teeth, one of the pinions being axially slidable and adjustable as to position with respect to the other pinion.

This is illustrated in Figure 4 wherein there is shown a pinion stand comprising

end members

45 and 46. A

lower shaft 47 is journaled in the stand and bears an Aelongated helical pinion 48. -At one end the shaft 47 is provided with means 49 whereby it can be connected to 4'a motor (not shown). At the other end the shaft carries a preferably flexible coupling 5t) by which it may be ,connected to the lower drive shaft of the mill by a conventional mill spindle 51 which engages the driving neck 36.

' An upper shaft 52 is journaled in the pinion stand and is connectible through a coupling 53 and a mill spindle to a driving neck on the upper mill shaft 23. The pinion shaft 52 bears a helical pinion 54 which is shorter than the pinion 48 on the lower shaft, and is splined to the upper shaft so as to be axially slidable but non-rotatable with respect thereto. The upper pinion 54 has an integral collar 55, the curve of which is engaged by a fork 56 attached to a shaft 57 slidably mounted in the frame of the pinion stand. It will be evident that movement of the shaft 57 will produce longitudinal movement of the pinion 54 on the shaft 52, and because the meshing pinions 54 and 58 have helical teeth, such longitudinal 'movement will vary the relative rotative positions ofthe In theory such movement could be accomplished by means of Wedge devices; but this is not generally practicable because of the large areas ofthe members, the friction involved, and the difficulty of actuation. The screwdown means provided in connection with the mill of this invention not only avoids the disadvantages hereinabove set forth but also provides important additional advantages not attainable either in wedge-actuation or in conventional screwdown where right and left hand screws can he operated independently.

As shown most clearly in Figure 2, the anvil 25 has spaced projections 59 which rest eccentrically against half-round spaced parallel shafts 60 which are journaled in a block 61 interposed between the anvil 25 and the lower edge of the beam 6. The block 61 is preferably faced in socket portions which engage the half-round shafts with materials which will preserve lubrication at the high pressures encountered; or roll or needle bearings may be provided between the shafts and the block as will be well understood by those skilled in the art. The projections 59 of the anvil 25 either rest directly against the shafts 60 or through the intermediary of an anti-friction means such as a small hardened roller 62. In an alternative construction, the upper surface of the anvil 25 may be flat and ridges may be provided eccentrically on the flat sides of the shafts 60.

In either event it will be apparent that if the shafts 60 are rocked, th-e anvil member 25 Will be caused to move vertically toward or away from the beam 6. The anvil member Z5 will be slidably mountedrfor vertical movement and restrained from horizontal movement in any direction by engagement with inner-machined surfaces of the vertical mill beams 4 and 5 and by engagement with

end keepers

63 and 64 in Figure 2.

' Vertical rods 65 and 66 may be journaled for sliding movement in or on the mill housing. At their bottoms, these rods may have

latches

67 and 68 for engagement with the anvil member 25, and at their tops they may be provided with washer-

like abutments

69 and 70, preferably adjustable by means of nuts, with compression springs 71 and 72 engaged between the abutments and the mill housing. Thus, the anvil member 25 is held `forwardly in the mill against the rocking shafts 60.

agresse j To rock the shafts 6G, lever members 73 to 73e are connected to their respective ends. The upper ends of theV levers may be forked or otherwise configured for attachment to nuts 74 to 74e threaded on a shaft 7S which may be connected by a coupling 76 to a motor 77, to a handwheel, or to some other means whereby the shaft 75 maybe turned. It will be clear that if the shaft 75 is restrained from longitudinal movement and is rotated, the various nuts 74 to 74e will be moved the same distance to the right or left, rocking the. various shafts 6d? by the same amounts and producing an over-all vertical movement of the anvil while maintaining its parallelism with the underside of the beam 6. Thus a general screwdown isv accomplished.

This type of screwdown gives opportunity for the provision of means for effecting supplementary individual movement of each of the levers 73 to 73e individually so as to control the proiile of the piece being rolled across its width. To accomplish this, instead of pivoting each lever arm directly to one of the nuts, the lever arms are pivoted to housings 78 each of which contains a small servo-motor which is geared to the nut.V The servomotors are connected respectively to servo-generators in Ways known to those skilled in the art. The servo-generators are individually connected to operating levers 79 to '79e of a control quadrant titl (Figure 5) which will be located upon the mill operators desk. The control quadrant is preferably provided with graduations Si to indicate Vthe positons of the several levers. When any lever of the control quadrant remains in a fixed position,

the increasing nut of the series 7d to 7de will be held against rotation by its servo-motor. Thus there is no interference with the over-all screwdown effecting the adjustment of the shaft 75. When, however, a lever of the series 79 to 79e is changed as to position, the servogenerator to which it is connected will rotate the corresponding servo-motor to a new position, rotating the nut to which that servo-motor is attached, and thus producing an independent change of position of the corresponding lever arm of the series 73 to 73e.

Since the lever arms 73 to 73e are now individually as well as concurrently adjustable, it will be seen that it is now possible to control the contour of the piece being rolled in the direction of its width. The operator not only can correct the thickness of the strip on the right side or left side, but also he can obtain any eiect which on a conventional 4-high mill or ou a roll backed planetary mill would require prole grinding of the backing rolls, the working rolls or both. He may produce or alleviate positive or vnegative crowns or tapers; and may compensate locally for any inequalities of rolling occurring across. the face of the strip. He may do this instantaneously and while the mill is rolling. This control is especially desirable since the mill proiile tends to change with heat, while the heat may itself vary from the beginningvof a rolling operation to the point at which heat equilibrium is reached inthe mill', and the heat may 'also vary due to the change in temperature in an individual slab or between slabs, or in the case of interruption of rollingv operations, or for other reasons. The operator can eliminate wavy edges, =a camber or deflections in the rolled material as soon as they appear.

It will be understood that abrupt proiile changes are not generally desirable; but the anvil member 25 will normally lbe flexible enough to permit not only the full correction of prole irregularities in the width of the rolled material but also the deliberate production of speciiic desired proles such as those mentioned above. The flexibility of the `anvil member 25 may be increased in various ways, although it should not be made too thin. One way of increasing the apparent flexibility of the anvil is to make it in a series ofV individual .section extending in the direction of rolling like the keys of a piano, the sections being held together by suitable tie rods.

VIt will be within the skill of the worker in the art t0 provide composite .thickness gauge means which willindicate to the mill operatorthe actual lateral profileV of the.

reduced material going through the mill, so that the mill operator may either make prolee corrections therein or` may'adjust the mill to Vroll a particular desired prole.

ltV is inherent in the profile adjustment which has been nuts 74 etc.; and these pinions may be connected by ilexi-` ble shafts with the operators desk where handwheels, cranks or thelike are provided for eiecting individualadjustment of the lever arms 73 etc.

Precesson Since the issuing strip 9 has a velocity many times high er than that of the entering slab 8, While the driving of the chain assemblies occurs at some selected linear speed, it will be evident that the linearv speed of the material being reduced cannot at all times be the same as the peripheral speed of the working rolls throughoutthe zone of plastic deformation, unless means are provided to meet this situation. PrecessionV of the working rolls` is easily accomplished in a roll-backed planetary mill as in United States Patent 2,710,550 by providing bearing chocks for the working rolls of a design which permits each working roll to advance slightly from its initial position in the rolll cage as it traverses the zone of plastic deformation,v the working roll returning to its original position Vafter it leaves the said zone. No similar provision for procession can be made in a chain assembly such as characterizes this invention.

However, it has been found that precession may be accomplished in the present case by relatively simple means which have to do with the shaping of the longitudinal proile of the zone of plastic deformation,

By wayof explanation, it would ordinarily be thought advantageous to cause the working rolls to follow a path in contact with the strip which would gradually bring them into a direction of motion parallel with the surfaces y of the reduced strip and which would gradually cause the rollfseparating pressure to decrease to zero. The reason for this is that this would in theory seem to afford' the best opportunity to produce a strip having no periodic variations in thickness, or surface markings indicating the termination of contact with the strip of each individual pair of working rolls. v

It has been found that much better results are obtained by disregarding this obvious principle, and purposely giving to the exit portion of the zone of plastic deformation (as determined by the shape of the anvil members 25 and Z6) a convex curvature particularly at the exit end. When this is done, advantage may be taken of the geometrical fact that the distance between adjacent working rolls 14 or 15 in each of the chain assemblies will be equal to or somemultiple .of the diierence between the adjacent chain shafts 1S or 19 in the chain assemblies only when the chain is llat, i.e. following a rectilinear plane. If the `chain is convexry curved on the working roll side, adjacent Working rolls will lie further from each other, and their distance apart will increase as the radius of curvature of the chain becomes smaller. Y

Figure 6 is a diagrammatic representation, exaggerated in depth', of the prole of one of the anvil members 25 or ze. The zone of plastic deformation is indicated in this diagram as extending from A to C; and the direction of rolling is indicated by a small arrow. Taking into account the 5:1 exaggeration of the vertical scale in this diagram, it can be seen that the first major portion 'of Vplastic deformation extending from the point A where a working roll iirst contacts the slab to about the point B has .a fairly uniform .curvature The waal P IQle .can

be a straight line or an arc of a circle.` Assume that the slab in the length AB of the zone of plastic deformation is reduced to about one-fourth or one-sixth of its original curvature.

It will be noted that from the point B to the point C in the zone of plastic deformation, the radius of curvature of the track gradually decreases so that the convexity of the chain becomes greater and the working rolls forming part of the chain increase their distance from each other. This is equivalent to precession, and it avoids or reduces the slipping of the working `rolls both with respect to the work piece and with respect to the casters.

AIt is preferred to decrease the radius of curvature even more than is indicated in the diagram, wherever this is possible for the reason that the forward working rolls are then caused to produce a slight forward drag upon the strip, `introducing tension into that portion of the strip which lies between the forwardworking rolls and the next succeeding working rolls. A strip under tension will be flatter and will roll easier. Tension applied to the strip beyond the mill will not aifect tension conditions in it behind the` foremost pair of working rolls which is in contact with `the strip. a

Figure 6 illustrates the principle that in a mill of the type in which working rolls are driven through a zone of plastic deformation while being supported by casters on shafts interconnected by links in a chain assembly, and where thepath of the working rolls is determined by the profile of an anvil member which establishes a track or path for the working rolls, the effect of precession can be` `attained by progressively decreasing the radius of curvature of the track` toward the exit end of thezone of plastic deformation. The. decreasing of the radius of curvature maytoccur progressively from one end of the zoneof plastic deformation to the other end, or it `may occur only in some limited areas thereof preferably adjacent the exit end. The effect of precession is attained not only because adjacent working rolls increase their actual distance from each other but also because in doing so the forward working roll increases its rate of rotation, these effects being cumulative.

In Figure `7 amoditied form of` track or profile is shown. The track `is generally shapedlike that shown in Figure 6, excepting that at the entrance end of the zone of plastic deformation a reverse curvature is indicated between A and A. In the rolling of some metals it is desirable to have the working rolls iirst contact the slab while they are moving in a path at a lesser angle to the plane of the slab than will obtain during the subsequent major reduction. f Certain defects in the surface of the slab, usually caused by imperfections in the ingot, can thus be ironed out with a consequent improvement in the surface of the resulting strip. Under these circumstances only a slight correction, such as achange of one or two degrees in inclination, is usually sucient to result in a substantially increased yield. p

While some slippage. of the working rolls with respect to the work piece is tolerable, particularly at the start of the reduction where the slab is thick and its speed isrelatively slow, Figure 7 is illustrative of another way in which precession may be attained throughout the extentof the zone of plastic deformation. The working rolls `will be closely together when the chain is concave outwardly; and thus a track characterized by a concave curvature at the entrance end of the zone of plastic deformation, followed throughout that zone by `both a gradualchange to a convex curvature and a gradual decrease in the radius of the convex curvature will providemcontinuous precession. As will be evident from the foregoing, the precession canV be made less than, equal to or more than sufficient to take care of the increase in speed of the surfaces of the material being worked upon in thezone of plastic deformation; and the precession need not be the same in all parts of that zone.

By shaping the track surfaces of the anvils 25"and 26` crepes i beyond the zone of vplastic deformation, another problem may be solved, namely the guiding of the leading end of the rolled strip. Because of heat differences between top and bottom portions of the material being rolled,` sometimes coupled with minute errors in synchronization between the top and bottom working rolls, the leading end of a rolled strip may have a tende-ncy to curl upwardly or downwardly as the planetary roll pressure relaxes. The curled end of the strip may have some' Springiness, so that if a separating means of chisel-likeform is used it may happen that the end of the strip will enter between the separating means and the rolls. This necessitates stopping the mill, with loss of time in clearing it.

The di'culty may be avoided by extending the paths:

of the working rolls 14 and 15, beyond the zone of plastic deformation,

exert little or no pressure on the strip; and the length.

of this portion of the path need not be long, .e. it needi not exceed the distance between two pairs of the working rolls. However, if the working rolls, after the reduction is completed maintain brief contact with the rolled strip, they act as a roller leveler because their speed of translation is considerably higher than the linear speed of the strip. Thus they tend to straighten the leading end of the strip so that it issues out of the mill in a substantially rectilinear path and does not end to follow the rolls. Separation devices are rendered unnecessary.

The attainment of precession in the way indicated, particularly where a decreasing radius of convex curvature of the track is employed in the exit end of the zone of plastic deformation, the periodic variations in thickness of the rolled material may tend to be somewhat greater; but they are easily removed by subsequent rolling in an `ordinary mill, either hot, i.e. immediately upon leaving the planetary mill or at a later period by `cold rolling.

It has been found after long experiment that it is advantageous to have the planetary working rolls enter the zone of plastic deformation in a path at a rather slight angle (preferably not more than 5 to 10 to the plane of the slab). The later reduction of the slab in the zone of plastic deformation may be effected by the working rolls moving in paths having an inclination to the plane of the slab greater than the above by a few deing alloy steel was being rolled, the best surface and excellent metallurgical conditions were obtained by causing the working rolls to follow a substantially rectilinear path during the rst major portion of the deformation, i.e. until the slab was reduced to less than one-third of its original thickness. The angularity between these rectilinear paths was between 5 and 9, i.e. each path had a slope of 21/2 inches to 41/2 inches to the horizontal approximately. Provision was made in this instance for a reduced angle at the entry point of the working rolls into the zone of plastic deformation by about lil/2 to 2. However, other angularities may be chosen for particular purposes; and as compared with a roll-backed planetary mill, where the working rolls travel in paths which are the arcs of fixed surfaces, the beambacked mill of the present invention has the obvious advantage of free choice of the longitudinal contour of the paths of the Working rolls in the zone of plastic deformation.

Chain assembly and operation In Figure 3 the planetary mill is shown mounted on the foundation supports 12 as has hereinabove been described. Casing members 82 and 83 may be used to enclose the planetary instrumentality. The slab 8, as in 4 other planetary mills, must be positively fed forwardly into the zone of plastic deformation. This may be accom`V in a direction parallel with the desired'A plane of the strip, for a relatively short distance. The' paths are such in this portion of the track that the rollsl dei. plished in various ways, but is conveniently accomplished by a pair. of driven pinch rolls 84 and 85. At either side, on the foundation or bed a frame member 85. is mounted. rlhe pinch roll 84 is journaled in this member as at 87. The member has a forward extension 8S which is bolted to the housing of the planetary mill as at 89 and 90 so that the thrust of the pinch rolls will be transmitted tothe material in the Zone of plastic deformation.A To the upward extensions ofthe frame members lever arms are pivoted. One of these lever arms is shown at S1 in` Figure 3. The upper pinch roll is journaled in bearings in these lever arms, one of the bearings being indicated at 92. To control the pressure exerted by' the pinch rolls on the slab 8, the outer ends of the lever arms are connected to the lower ends ofthe frame members by some suitable (preferably adjustable) ten.- sioning means such as huid pressure cylinder assemblies, onetof which is shown at 93. Other means may be employed such asscrews.

The pinch rolls 84 and S5 are driven by variable speed means, not shown; and they are arranged to make a slight reduction in the slab 8, usually from 5% to 10% or even as much as 15%, at which reductions they are capable of exerting a strong pushing force on the slab 8 and thus control its passage at a predetermined forward speed through the zone of plastic deformation.

The rolling will normally be done at elevated temperatures, and the conditions obtaining in roll-backed planetary mills can be achieved in the mill of this invention. For example, the reduction of the slab may be so effected that the initial heat is preserved, or the rolling can be conducted with a net rise or net fall of temperature, byV controlling such factors as the speed of translation of the working rolls. The slab 8 will normally be delivered to the mill from a heating furnace (notshown) along a roll table 94. If desired the slab may be supported and prevented from buckling between the bite of the pinch rolls 84 and 85 and the zone of plastic deformation of the planetary mill by one or more sets of pinch rolls such as the rolls 95 and 96.

An independent mill stand, which may be of Z-hgh, 4-high, or any other type may be mounted on the foundation plates at the opposite side of the planetary mill. Such an independent mill has been indicated in Figure 3 as an ordinary 2-high mill. One of its end housings is indicated at 97. The mill has rolls 98 and 99 mounted in the usual bearings which are vertically slidable in the housings. A screwdown is indicated at 100. The mill will be driven by variable speed means, not shown. Where sucli'a. mill is provided as a part of the installation, it will be used toact upon the strip 9 issuing from the planetary mill vand exert uponit a controllable'tension. If desired it may be employed also to make a reduction in the strip 9, usually of the order of 5% to 2,5%. It can thus act as a planishing mill to eliminate periodic variations in the thickness of the strip 9.

For controlling tension, a rollltl adapted to contact the strip 9 between the planetary mill and the planishing mill can be arranged to be movable transverselyy of the strip so as to deflect it between the mills. The nal product can be delivered onto a roll table 102 whereby it can be transported to a shear or coiler.

The mill assembly may be operated in various ways. For high production it is preferred to havethe strip 9 issue from the planetary mill ata relatively heavy gauge 'such for example as 0.250 or 0.30 inch, and to employ` two or three independent mills'as finishing mills in aconf ventional manner. Since the finishing speed of the'planetary mill, for a given gauge, will depend (other things being equal) upon the largest tolerable gauge variations arising. from the passageV of individual roll pairs in the zone of plastic deformation, itwill be evident that when the strip issues at the relatively heavy gauges mentioned above, the planetary mill will be capable of producing much heavier tonnages. For example, inrolling steel a lf2 Y suitable planetarymill constructed in accordancey with this invention will be capable of producing 300 tons per -hour of a 40 inch wide strip at a gauge of 0.30 inch at the point where the strip leaves the zone of plastic deformation.

It will be evident from the construction hereinabove described thatV deflection can be avoidedas wellY as.com pensated for, and that the transverse contour of the rolled material can be controlled. Thus there is no essential` limitationV on the width of the planetary mill of this invention. While a mill has been shown in a preferred form in which each working roll is supported by an independentV pair of adjacent caster assemblies, additional working rolls may be. added in the intermediate positions as desired.4 Y. VModifications may bemade in the invention without departingfrom thespiritof it. The invention having been described in an exemplaryembodiment, what is claimed as new and. desired to be secured by Letters Patent is:

1. In a planetary mill, a transverse beam bearing an anvil member. on one of its surfaces, afplanetary roll chain assembly surrounding said beam, said chain assembly made up of shafts extending in the direction of the length of said beam, casters mounted onV said shaftsV in spaced relationship, links interconnecting said shafts in the spaces between. said casters,.whereby said shafts are interconnected by said links at spaced intervals throughout the length of said shafts, working rolls resting on and supported by the casters on adjacent shafts, a driven shaft, means for mounting said, driven shaft in a position adjacent said beam, said driven shaft having a plurality of sprockets spaced along its length, said sprockets having recesses shapedto engage the links and teeth engaging thel ends of the links, said sprockets engaging and. driving directly said chain links whereby said chain assembly is driven'throughout its width, and caused to traverse the surface of said` anvil member under tension, and `guide means for carrying said chain from said driven shaft, around saidbeam and to said anvil member.

2. Thestructure claimed in claim. 1 including means for retaining said working rolls in contact with the casters on said chain. Y Y Y 3. The structure claimed in claim 2 wherein said driven shaft is journaledin means attached to said beams.

4. The structure claimed in claim 3- wherein said driven shaft is supported from said beam at positions throughout the length Vof said driven shaft between `said sprockets n whereby torprovidev a.. rigid driving means for said chain assembly.

5. The structure claimed in claim 4 including an outer strap member engagingV the working rolls of said chain assembly andserving tokeep said working rolls in a state of continuous rotation during thedriving of said chain assembly.

6,. In a planetary vmill structure spaced parallel beams extending transverse the direction of rolling, approachingV surfaces of'said beams carrying anvil members defining a path of travel of working rolls in a zone of plastic deformation in said mill, a driven shaft journaled in means attached to each offsaid beams, a chain assembly'surrounding each of said beams, said chain assemblies each comprising a series ofshafts extending in the direction of thelength of said beams, spaced casters for contacting,

said anvil members mounted on each of said shafts, said` shafts being interconnected by link membersrin the intervals vbetween said casters, said driven shafts bearingY spaced sprockets located and coniigured to-engage said links and thereby drive said chain assemblies throughout` their width, said sprockets having recesses shaped to engage the links andteeth engaging the ends of thelinks,

working rolls engaging the casters von adjacent shafts of..

saidchain assemblies, means for maintaining said working rol1sin contactwithsaid casters and means for conbeamstosaidanvil members.

'7.The lstructure claimed in claim 6- wherein said beams are rigidly connected togetherat their ends `beyond said chain assemblies by transverse members, said beams and said last mentioned members constituting a rigid housing.

8. The structure claimed in claim 7 wherein one at least of said anvil members is mounted withrespect to its beam on adjustable means for moving said anvil member toward and away from its beam for screwdown purposes.

9. The structure claimed in claim 8 wherein said driven shafts are respectively supported from said beams at` intervals throughout their length and at positions located between said sprockets, whereby to provide rigid drives yfor said chain assemblies.

10. The structure claimed in claim 9 including driving means for said driven shafts, said driving means including means whereby the rotative position of said shafts with relation to each other may be adjusted whereby to control synchronous action of the` working rolls of each chain assembly as they pass through said zone of plastic deformation.

11. The structure claimed in claim 10 including strap members engaging the said working rolls elsewhere than in the zone of plastic deformation and serving to keep said working rolls in a state of rotation so long as said chain assemblies are being driven.

12. The structure claimed in claim 11 wherein said means for conducting said chain assemblies about said beams comprises inner track members in the form of link elements and provided with means for tensioning said chains.

13. The structure claimed in claim 11 wherein said anvil members have working surfaces so shaped as to provide precession of the working rolls in the zone of plastic deformation.

14. The structure claimed in claim 13 wherein the parts are so configured as to maintain light contact of said working rolls with the work piece beyond the exit end of said zone of plastic deformation whereby to atten the rolled material for stripping purposes.

15. The structure claimed in claim 11 wherein the means for causing said anvil member to move toward and away from its beam comprises a plurality of means spaced in the direction of the length of said beam, said means being concurrently adjustable for screwdown purposes and independently adjustable to control the transverse profile of the material being rolled in the zone of plastic deformation.

16. In a planetary mill, a beam, an anvil member mounted with respect to one face of said beam, a chain assembly comprising casters and working rolls, means for driving said chain assembly to cause said casters to move over the face of said anvil member in a zone of plastic deformation, means for moving said anvil member with respect to said beam for screwdown purposes and comprising a block member attached to said beam and grooved for the rotative mounting of a plurality of half-round shafts extending transversely of said beam, means for causing said anvil member to engage said halfround shafts along eccentric lines, whereby the rotative movement of said half-round shafts will produce movement of said anvil member toward and away from said beam, lever arms afxed to the ends of said half-round shafts and means for moving said lever arms concurrently for screwdown purposes.

17. The structure claimed in claim 16 in which said last mentioned means comprise a threaded shaft mounted for rotative movement but held against axial movement, and means in pivotal engagement with each of said lever arms threaded on said shaft.

18. The structure claimed in claim 17 wherein said threaded means on said shaft are rotatably mounted with respect to said lever arms a'nd are provided with means whereby they may be independently rotated to adjust the positions of said lever arms individually whereby'to control the transverse contour of said anvil member in said zone of plastic deformation, said anvil member being suciently flexible to permit the said adjustment. y

19. The structure claimed in claim 18 wherein the means for individually rotating said threaded members constitute a servo-motor for each threaded member, said servo-motors being connected respectively to servogenerators, and means for controlling said servo-generators and for indicating the positions thereof so that said transverse profile may be caused to conform'to a predetermined pattern. t

20. In a planetary mill of the type set forth having a rigid housing comprising spaced parallel beams interconnected by members at their ends, in which chain as-r semblies including working rolls supported by spaced casters, are driven around said beams and through a zone of plastic deformation between said beams, anvil members attached to the approaching surfaces of each beam and contoured to determine the path of travel of the working rolls of said chain assemblies in the said zone of plastic deformation by contact with said casters, that improvement which consists in so con'touring the t working surfaces of said anvil members as to provide for working roll precession, the said working surfaces being characterized by a convex curvature of progressively smaller radius approaching the exit end of the zone of plastic deformation.

21. 'Ihe structure claimed in claim 20 in which the said surfaces of the said anvil members are further characterized by a slightly concave curvature adjacent the entrance end of said zone of plastic deformation.

22. The structure claimed in claim 2Ol wherein one of said anvil members is provided with means for `moving it toward and away from the beam on which it is mounted for screwdown purposes. Y

23. The structure claimed in claim 20 wherein one of said anvil members is provided with means for moving it toward and away from the beam on which it is mounted for screwdown purposes, said last mentioned means being differentially adjustable along the length of its beam whereby to control the transverse proiile of the said anvil member in the zone of plastic deformation.

24. A planetary mill comprising a substantially rectangular integral housing having a central transverse opening whereby upper and lower portions of said housing constitute beams interconnected at their ends, said housing being fastened adjacent its ends to spaced foundation supports, chain assemblies surrounding each of said beams and passing through said housing openings, said chain assemblies including spaced shafts extending in the direction of said beams, each of said shafts bearing a plurality of spaced casters, vsaid shafts being interconnected by link elements in the intervals between said casters, working rolls resting on the casters of adjacent shafts, means for holding said working rolls in contact with said casters, driven shafts journaled in brackets on each of said beams and supported at intervals throughout their lengths from said beams, said shafts bearing sprockets spaced to contact said links whereby said chains may be driven throughout their width, anvil means on the approaching faces of said beams within said opening to define a path of travel of casters and hence of said working rolls, brackets on said spaced foundation members, attached thereto and to said housing, said brackets providing means for journaling a lower pinch roll, lever arms pivoted to said brackets, an upper pinch roll journaled in said lever arms, means for applying force to the ends of said lever arms whereby to cause said pinch rolls to coact forcibly on a roll piece in the form of a slab, means for driving said pinch rolls so as to force said rolling piece into said zone of plastic deformation, means for driving the said driven shafts so as to produce movement of said chain assemblies causing said chain assemblies to move through said zone of plastic deformation with said working rolls in contact with said rolling piece whereby to reduce it, means in connection with said last mentioned driving means for adjusting the rotative position ofV said driven shafts to provide synchronism of said working rolls, and means for moving at least one of said anvil members toward and away from its beam for screwdown purposes.

25. The structure claimed in claim 24 in which said last mentioned screwdown means comprises a plurality of individually adjustable elements whereby to control the contour of said anvil member in said zone of plastic deformation transversely to the material being rolled.

26. The structure claimed in claim 1 wherein said sprockets have relatively staggered teeth in order to engage relatively staggered chain links interconnecting said shafts.

27. The structure claimed in claim 26 including a track element located'within said' chain so'as to be engaged by said casters to conduct said chain in a prede termined path, said track element having a movable portion for adjusting the tension of saidchain.

28. The structure claimed in claim 27 including a relatively exible Vand adjustable outer strapv member for engagingl the Working rolls' of said chain assembly and serving to keep said working rolls in ags'tate ofV continuous rotation during the driving of said chain'assernbly.

References Cited in the ile of this patent FOREIGN PATENTS 1,005,919 Germany Apr. 1*1`, 1957