US2603114A - Enclosed rolling mill - Google Patents

Description

y 15, 1952 R. D. COLINET 2,603,114

ENCLOSED ROLLING MILL 7 Filed March 21, 1945 9 Sheets-Sheet 1 3 rwe/wtw "PE/-15 D. COL/HE T July 15, R952 R. D. COLINET 2,603,114

ENCLQSED ROLLING MILL Filed March 21, 1945 e Sheets-Sheet 2 n 0 PEN: D CO y 1952 R. D. COLINET 2,603,114

ENCLOSED ROLLING MILL.

Filed March 21, 1945 9 Sheets-Sheet 5 3 MW PENE D. COL /NET R. D. COLINET ENCLOSED ROLLING MILL.

Filed March 21', 1945 9 Sheets-Shet 4 RENE D. COL/NE T y 1952 R. D. COLlNET $603,114

ENCLOSED ROLLING MILL Filed March 21, 1945 9 Sheets-Sheet 6 FIE/5 LEE/YE DJC'QL/MFT J y 1952 R. D. COLINET 2,603,114

ENCLOSED ROLLING MILL.

Filed March 21, 1945 9 Sheets-Sheet s F/E. 25. M7

A pa /40 o v o 'N V EN TOR.

REP/ D. 604 mar July 15, 1952 R. D. COLINET ENCLOSED ROLLING MILL 9 Sheets-Sheet 9 Filed March 21, 1945 &

INVENT FNBC0UN 7' BY W47: 1 I

Patented July 15, 1952 UNITED STATES PATENT OFFICE ENCLOSED ROLIJNG MILL Rene D. Colinet, Philadelphia, Pa., assignor to La Soudure Electrique Autogene S. A., Brussels, Belgium, a Belgian company Application March 21, 1945, Serial No. 583,887

2 Claims. 1

This application is a continuation-in-part of my copending application Serial No. 522,819, filed Februaryl'l, 1944, and now abandoned.

This invention relates to rolling mills of the type having forming rollers with cooperating spherical sealing surfaces and forming surfaces. It is therefore an object of the invention to provide the rollers with spherical sealing surfaces. A further object resides in profiling the'rollers with forming surfaces to form a funnel in front of or preceding the final restricted configuration of the shape to be produced by the rollers.

Further objects will be apparent from the following description when considered with the accompanying drawings which show a number of preferred forms of the invention and in which:

Figure 1 is a top plan view of an enclosed mill according to the invention showing certain parts in section; 4

Fig. 2 is a vertical cross section of the mill of Fig. 1 taken on line 2 -2 thereof V Fig. 3 is a horizontal section of the central portion of the mill taken on line 3-3 of Fig. '2;

Fig. 4 is a top plan view of a modified construc' tion;

Fig. 5 is a vertical section through the center of the cooperating rollers taken on line 55 of Fig. 4;

Fig. 6 is a horizontal section of the central portion of the mill taken on line 6-6 of Fig. 5;

Fig. 7 is a top plan view partly in section of the mill of Fig. 4 showing the drive connections;

Fig. 8 is a top plan view of another form of the invention for producing rectangularly-shaped bars;

Fig. 9 is a top plan view of a further modified mill for producing T-shaped bars;

Fig. 10 is a cross section of a portion of the rollers of Fig. 9 showing the cooperating rollers merging into the T-shape configuration;

Figs. 11 to 15 are diagrams pertaining to comparative rigidity of parts of the rollers subjected to pressure or strain.

Fig. 16 is a horizontal section of four rollers showing an example of non-rubbing sealing surfaces obtained by replacement of pure spherical surfaces by torus or ellipsoid surfaces;

Fig. 17 is a vertical section of the mill of Fig. 16;

Fig. 18 is a horizontal section taken on line I-I of Fig.

Fig. 19 is a horizontal section takenon line II-II of Fig. 20;

Fig. 2.0 is a side view of the mill;

Fig. 21 is a vertical section through the center of the cooperating rollers;

The invention is primarily directed to an improvement of the enclosed mill for use with hot or cold materials. By enclosed type is meant a? mill wherein the rollers are so formed as to contact each other in the plane of the axes,.leaving between them the shape of the product to be formed, which can be round, square, fiat, tubular or any other cross section.

Whenever such enclosed rolling mill is used with a compressible material, that is, onewhich 1 is soft or plastic enough to fiow laterally when subjected to pressure, it is necessary to providef means to oppose such lateral flow, and to direct the material closely and as deeply as possible intoI the rollers. Otherwise, instead of reducing all of the material to the desired shape, the rollers may allowsome of the material to spread. laterally between them, and then would force this excess material into an edge or burr which would remain attached to the final product.

This difiiculty becomes even greater with fluid materials which are supposed to solidify or coagulate in the rolling mill itself, such as hot liq uid metals, certain plastics, compressible powders,

quick-hardening pastes or mixtures, etc.

The means to oppose lateral fiowor-leakage between the rollers ahead of their contactplane,

as referred to above. are usually stationary wedges filling in all gaps between the-rollers. as far asthey can possibly go toward the contact plane of the rollers. Such wedges become exceedingly thin and fragile at the very point where the pressure reaches its peak. Also they are unfit to withstand successfully both wear and heat action and they cannot be properly cooled. In all cases, they must be interrupted ahead of the tangent point ofcontact of the rollers, leaving a narrow'gap unfilled between them. where lateral flow .canstill take place without restraint.

The provision of spherical sealing surfaces' on the rollers themselves is designed to create supporting surfaces which oppose any-lateralfiow.

or leakage of the material, from a point far ahead of the contact plane of the rollers and where pressure is still non-existent or. at least negligible, to the very center of the rolling mill where the material is forced into its final shape or configuration. Such a mill forms a funnel between the rollers, the inside walls of which are leakproof, yet move together toward the smaller orifice in a converging manner, thereby dragging the material along and forcing it through the outlet without any possible place of escape.

This result is obtained by assembling a number of rollers which, in addition to the usual shaping surfaces which join in the center to form the cross section of the final product, also have auxiliary surfaces which act as solid and tight walls all the way from a point aheadof where the material comes in contact with the rollers,'to a point beyond where the finished product leaves the rollers after being shaped. To assure mutual contact between the rollers in all cross sections perpendicular to the direction of travel of the product, and not only in the axes plane as it would be the case for the rollers of known constructions, the following geometrical conditions."

must be fulfilled: at least three rollers must be.

used, the axes of which intersect in at least two points at a finite distance from the axis of the work; and any two adjacent rollers must have a common surface of mutual contact which is a sphere, the center of which is located at. the junction of their respective axes of rotation. It is desirable, though not necessary, that these axes belocated in the same plane, but the'axes of adjacent rollers must always intersect. In a fourroller mill, for instance, withaxes in different planes, the bight of. two rollers diagonally opposed is at a level different from that of the bightv of 'the'other two rollers. Therefore, the product I8 have exactly the samedegree of curvature and the same diameter.

Figs. 4 to 7 illustrate an enclosed mill for producing round rods having four rollers 22, 23, 24 and 25 each rotatably mounted in a stationary bearing 25. Each roller has a head portion 21 and an integral shaft 28, and each head portion is provided with two spherical sealing surfaces 29; and 30 and the annular forming surface 3 I. The two surfaces 29 and 30 of each two adjacent roll-' ers cooperate with eachother so that, as shown in Fig. 6, the annular surfaces 2| merge into the round configuration 32 from the trough-like funnel 33. All rollers revolve at even speeds and in Y a converging manner.

Fig. 5 shows theliquid metal or plastic material 34 being poured from a crucible or container 35 into the funnel 33 formed by the head portions 21 of the rollers. The rolled rod 36 emerges from the bottom of the funnel after the revolving surfaces}! have profiled and formed the solidifying material into the finished rod.

It must be observed that the spherical sealing surfaces have a sliding action against each other. They do not roll like gears meshing together. Therefore, any foreign matter like spatter from liquid metal, or any material particle that might adhere .to the surface of the roller would not be pinched and flattened by the adjoining roller, but would be cleared away by the edge of that roller, in scraper-like fashion. This assumes, of

w course, thatthe particle has not welded itself deep is first rolled one direction across its longitudinal axis, and then, a'littl'e later but in the same rolling operation, in the'direction perpen dicular to the first one. This'method of successive rolling in cross directionslis similar to the standard practice of hot rolling of round barsand rods, and may be preferred in some cases.' Rollers may, or may, not, be identical.

Each roller is provided with two separate spherical sealing surfaces extending to the forming or shaping surfaces- Referringnow to the drawings irrwhich like referencecharacters refer to corresponding parts,

throughout, Figs'l to 3, 9 and 10 showthreeroller mills and Figs..4 to 8 show four-roller mills. Furthermore, the mill of Figs. 1 to 3 producesa bar having a hexagonal configuration, Figs. 4 to '7, a round configuration, Fig. 8a. rectangular configuration and Figs. 9 and 10 a T-shaped 6011-.

figuration- It is of course, obvious that any de-.

sired shapecan be produced as it is only necessary to appropriately contour theindividual rollers.

Theijmillof Figs. 1 to 3 has 'threecooperating rollers. ll, l 2 and J3 eachrotatably mounted in a suitablebearing 14...,All three bearings are held I rigidly in place by a sturdy. frame not shown in the drawings. Each roller is a duplicate of the othertwuandinclu'des a head portion l5 with a shaft lfijshown as being integral for simplicity. Each headportion vI5 has two spherical sealing surfaces Hand 3, of which [-1 is an end concave surface and I8 is an annular convex surface. Be-

tween these two spherical surfaces on each roller is the; annular forming surface I19 of which for the hexagon configuration each roller will impress two sides. All three rollers'are made to revolve around their respective'axes, atequal speedand in a converging direction.

Fig. 3 illustrates how the rollers merge as a into the roller by melting it below its surface. For that reason, any liquid'steel being poured in a mill made of steel or iron rollers should never be overheated to such extent that spatter from it would be hot enough to melt the rollers locally.

' The rollers should be maintained as cool as possible through artificial cooling, for instance by a water jet or spray underneath the mill, directed toward the product and the rollers alike.

This sliding action of thenspherical sealing surfaces require that adjacent rollers revolve smoothly against each other, without appreciable clearance, but also without excessive pressure. Play would allow leakage, while pressure would mean undue wear or abrasion. It is preferable to 1 mild the rollers of a tough, wear-resisting material, such asa properly heat-treated tool steel,

also to grind them smoothly and exactly after heat treatment, and above all to secure enough rigidity in the bearings and theirsuppolting frame to eliminate relative motions under in-' ternal strain clue to compression-of the material in the .mill. Means of fine adjustment of the bearings in all directions should be provided to bring the spherical surfaces in good contact, yet-' without excessive pressure, when assembling the mill, and also compensating for possible-heat distortion by proper cooling, take-ups or releases, etc- Rollers should be easily -removable from their shafts, for quick change when worn or for replacement ofdifferent shapes or sizes.

The rollers. are self-lapping, and the quality of their contact improves with. usage. The

reason for this, is that the slidingaction, there-' fore the wear, is greater at the periphery of each roller than it is near the annular forming. surface,

where the best contact is required because of." higher pressure. At andnear the neck of. the.

mill, all. surfaces travel practically together,

parallelly and at the same speed, therefore with- The convex outerminimum friction and wear. spherical surfaces and the forming surfacesare the only ones coming in contact with the material.

The concave central spherical surfaces never touch it. They should however be protected against'spatter or other stray particles by'the use of convenient guards.

As outlined above, it is obviously difficult to maintain the rollers in good sealing contact, and yet to avoid at the same time pressure between them. One method of overcoming this difliculty consists in a slight alteration of one or both of the sealing surfaces, so that they will contact each other under relatively high pressure only in the region close to the center of the mill, where the relative motion of the rollers is substantially a rolling action, exempt from sliding or pivoting friction. In all other regions where such sliding or pivoting occurs, the sealing surfaces are no more in contact, but remain close enough so that surface tension in case of liquids, and particle size in case of powder or fibres, will prevent any introduction of material in the narrow gap between the sealing surfaces.

Fig. 16 shows by way of example how such result may be practically obtained. This figure is a horizontal section on the plane of the axes of the roller in a mill as shown in Fig. 4, while Fig. 1'7 is a vertical section through the same mill on the axial plane of roller 23. The internal or concave surfaces 30 of all rollers remain unchanged. They are purely spherical with center 81 and" radius 31-98. By the external or convex spherical surfaces 29 of all rollers have been replaced by torus surfaces. One of them'is defined by a portion of circle of radius 99IIIB and center 99 rotating around axis BL-HII while remaining rigidly attached to that axis. .In the position shown, center 99 is on a straight line with 81 and the center of the mill, and at such distance from. axis 8I-IIII as defined by the quantity: clearance/ /21). By clearance is meant the distance considered desirable between the rollers, measured as I03--I04 on axis 87-81 of roller 23. In case of steel casting, a fair and satisfactory value of the clearance is & inch to inch.

From the vertical section, Fig. 17, it can readily be seen that the clearance is constant in each vertical section parallel to axis 81-87, although it gets smaller from one vertical plane to another when approaching the center of the mill. This is as it should be, since the pressure exerted by the rollers on the material increases toward that region, and also because the relative motion of rollers 23 and 24 becomes more and more a slideless rolling nearer to the center of the mill. Near the very center, positive contact is obtained between the rollers which can now be actually pressed hard against each other. They will not separate, regardless of the flexibility of the bearings and their supporting frames, as long as the operating pressure on the product remains inferior to the pre-set pressure put on the rollers during assembly.

A similar result would be obtained, either by the use of an ellipsoid of revolution defined by an ellipse rotating around its longer axis 8I-IOI, or by'a roller having a narrow portion of spherical sealing surface, adjacent to the forming grooved surface, and followed by a wider spherical quasi-sealing surface of same center, but with a slightly reduced radius.

It is obvious that theshafts of the rollers can be driven by any suitable means. Preferably, all rollers should be power-driven at equal peripheral speed, measured on the annular forming surface. Sometimes, however, idler rollers are acceptable, as in Fig. 8. Fig. 7 illustrates 6 various details of one way for driving the rollers 22 to 25. As shown, the main shaft 3'! is driven by any suitable means such as a motor, not shown. Two sprocket wheels or pulleys 38 and 39, bevel gear 40 and pinion M are mounted to. rotate with and on the shaft 31. Sprocket wheel. or pulley 38 drives a chain or belt 42 which in turn drives a sprocket wheel or pulley 43, the latter being mounted to rotate-the shaft of the roller 23. Also sprocket wheel or pulley 39 drives a chain or belt 44 which drives a sprocket wheel or pulley 45. This wheel 45 drives the shaft of the roller 24 through the intermediary of bevel gears 46 and 41 and shaft 48. Bevel gear 4|] meshes with a bevel gear 49 secured on the shaft of the roller 22. Pinion 4I drives another pinion 59 secured on the shaft of the roller 25. All drives are proportioned to insure equal speed of rotation for all four rollers. As shown in Fig. 7 the shaft 31 rotates in the direction of the arrow which will impart a direction of motion to each of the rollers as indicated by the arrows so that they shall all rotate toward the funnel and forming center for the bar to be produced. An-

other way, shown in Figs. 23 and 24, of driving the rollers would involve four auxiliary shafts forming a square around the mill, connected;

together through bevel or spiral gears. Each one of these shafts, in turn, would operate its corresponding roller, through a chain drive or a pair of spur gears.

A particularly preferred form of mill frame consists in a number of panels, equal to the number of rolls, which arehinged to each other like a multiple panel door. Each panel holds one roll, its bearings, drive and accessories. To

open the mill, for inspection, cleaning or rollchanging purposes, it is only necessary to remove one of the hinge-pins and to spread the panels open, without losing in that operation any of the fine adjustments which have been made to bring the rolls in proper contact with each other in a previous assembling. Fig. 23 illustrates this design in the case of a four-roll mill,

shownclosed and ready for operation. Fig. 24 represents the same mill as opened for inspection. One of the panels, marked I33 in Fig. 24, is rigidly afiixed to the basejl34. Its shaft I35 extends backwards where it is driven'byamotor, not shown, preferably through, a speed variator. The corresponding roll I36 is operated by a chain drive I31. That same shaft I35 holds two spiral gears I38 and I39, which will mesh at degrees with similar gears on the other panels, when the frame closes. relative displacements of the shafts as long as they remain at right angles. When in mesh,

all four rolls revolve together at identical speeds,

from the outside drive on shaft I35, through the spiral gears, the other shafts and the chain drives.

A further improvement consists in using hingepins which are eccentric in design, and which are interconnected so as to rotate with equal This type of gears permit slight to move only at right angle to the roll axis of permits to use various sets of rolls 'with slightly different diameters, provided all rolls'in each particular set remain identical in size. Such would be the case, practically, for rolls'which have been re-dressed after wear. Re-dressing a set of :rolls consists in machining or grinding alloutside convex sealing surfaces to a diameter slightly smaller than the original one, and doing the same to the inside concave surfaces; Since the inside concave sealing surfaces must be res duced *in diameter to the same extent as the convex ones, the re-dressing operation requires of necessity a transfer of the centers of'the sealing. surfaces toward the shaft end of each roll.

Reedressing. while keeping the centers where originally located would wrongly result in a reduction of the diameter of the convex surfaces, and an increase of diameter for the concave surfaces, destroying the good mating of adjacent rolls. The displacement of the centers in each successive-re-dressing depends on the depth of metal to remove from the sealing surfaces, and should best be determined from a full-size draw ing. The distances between both centers (convex and concave sealing surfaces) of each roll are also reduced in a re-dressing operation, in proportion with the reduction of diameters. Therefore,xthe polygon of the rolls axes in the mill also becomes smaller with each re-dressing, al-

through this polygon remains unchanged in shape or symmetry.

The panel-type mill frame, with its inter-related eccentric hinge-pins, precisely provides for such contraction of the polygon of the axes, and

Theform or configuration of the bar produced in the mill shown in Fig. 8 isindicateda ttf65f-v which shows the actual forming or pressing con tour for the work as confined by'the surfaces '5l' and60.

The mill of Figs. 9 and 10 is designed to produce. a profiled bar of approximately T shape; I mill has a main roller 66 rotatably mounted in bearings 61 by means of a drive shaft or shafts 68. Two auxiliary rollers 69 and 70 are rotatablymounted in bearings H and 12 respectively by means of drive shafts I3 and 14 respectively. The roller 66 has annular forming surfaces 15 and; annular spherical sealing surfaces 16 and" one. on each side of the surfaces 15. The roller 69 has an end spherical sealing surface ,18 and annular] forming surfaces 19.. The roller lfl'also halsia I similar end spherical sealing surface 80 andfs'imilar annular forming surfaces 8 I. 1 Roller 10 "how ever has an integral annular abutment flange 82 of which the side or forming surface 83 abuts and contacts a side surface84 of roller 69; All three rollers are made to revolve at substantially equal peripheral speeds. Fig. 10 shows the ultimate .T i shape 85 produced by the merging surfaces 15 and 19 together with surface 83. i In Fig. 1 the axes of adjacent rollers II to [3 intersect in points 86 which are also the centers of the spherical surfaces l1 and I8. Theshapin'glf surfaces [9 are surfaces of revolution generated by a portion of the cross section of the product revolving around the axis of the'corre'spondin'g roller. In Figs. 4 and '7 the axes of adjacent rollers 22 to 25 intersect in points 81 which are the centersof the spherical surfaces 29 and 30. In Fig. .8 the axes intersect in points 88 which are'the centers of the spherical surfaces 55, 56, 58 and 59.

If and when the axes of two adjacent rollers are parallel as axes 89 in Fig. 9, their correspond- *ing point of intersection is at infinity and the fl'i common spherical surface becomes a plane'surface 83 and 84 perpendicular to these axes 89.

The points 90 are spaced and accessible but the accommodates for a number of sets of rolls, differas other int is at infinity. The exact radius of the ing in dimensions from set to set, but not within Sphere; or the exact location of e pla e when Y each set. No modification is required to the fine the Point of intersection 18.31? infinity; is l d adjustment originally made'to positi th first by the geometrical condition that the sphere or set of rolls correctly in the mill. 7 The simplified Plane 5 contain the. point whelewhelshagping procedure to change rolls includes the-following surfaces of the correspQnding r t n steps: first, release all roll pressure by moving all Plane of the these rollels- ,FQ instance. panels awayfrom center, through a single drive In 61 the Spherical s. 1' 5 Co ain lever or-crank; then remove one "of the hinge-pins point 9! Where forming aceil' Of roller 23 v and spread the panels open. Unfasten all rolls meets forming Surface 3 of er 2- and fasten the rolls of the new set. Close the At h j o of e annular forming u face panels re-engage thehinge;pj n.and apply pres; With the spherical sealing surfaces the rollers surethrough th leverer k. 1 present a sharp edge. The mechanical strength In th forms of. the in ho n in Figs, 1 t 7 of that edge under pressure or strain from the all of the rollers of each mill are identical as to compressed r can be measured by the n size and shape. It is; however, possible to have a between he fi sl both profiles meefiiilg it V the edge considered. In Fig; 3,'such angle would be 929l- 93 for one edge, and 92 9I 9'4 for the other edge. For constructive reasons, it is obvious that these angles should be as large'as different sizes and shapes of forming-rollers'in' the mill as, for instance, shown in Fig. 8 which has two larges rollers 5| and 52 and two smaller rollers 53 and 54. Each of the rollers '5l'and 52 has two spherical sealing surfaces 55 and 56 with (is possible, and inno case smaller than 30 deg. for

a cylindrical surface 51 between "the two. Each of the rollers 53 and 54 has two" side spherical sealing surfaces 58- and 59 and a cylindrical peripheral surface 605- Suitable shafts 6|, '63 and 64 drive and rotate the respective rollers 5!, 53 7 0 desired shape of the product. .A three-roller mm} and 54 in directions indicated by the arrows and is particularly well adapted for hexagon shapes... at substantially equal peripheral speed, while rolbecause, as Fig. 3 shows, angle 92'9|-9'31s"90 ler 52 revolves as an idleraround stationary deg. while angle-92 9 9 is 5 s shaft .62 which is eye-shaped at the ends to per-- mit passage of shafts 63 and 6d; 1

soft compressed materials'and 45 deg. for hard materials, with preferred values at or above deg. This condition will bea decisive factor inthe' choice of'the number of rollers with respect to the; 4 I

three-roller mill, however, would not be recom-. mended for a circular shaped product because. as;

9 Fig. 11 shows, angle 92-9l-93 would'be only 30 deg. Figs. 12, 13 and 14 indicate'that this angle for a circular shape becomes 45 deg. for a four-roller mill, 54 deg. for a five-roller mill, and Y 95-96-91, forwhich a preferred value would be 30 deg., thus obtaining 60 deg., 75 deg.,"84;deg.. and 90 deg. for 3, 4, 5, and 6 rollers respectively.

This alteration of the circular shape has another important function, which becomes apparent in Figs. 18 and 19 showing therollers, first when completely closed h in the center of the mill; second, after they have started to disengage themselves from the rolled product-a little belowcenter. It will be noted that opposite rollers move outwardly and parallelly as indicated by the arrows N11. The plane surface 9I-95 in each roller, therefore, moves in its own plane, forcing the product to rotate clockwise as shown by arrow I08. In that motion, the excess material of the triangle 9l-95-I05 in Fig. 18 is rolled down transversely to the correct circular shape l-l06 in Fig. 19.

The advantages of this design are self -evident: a perfectly circular shaped product is obtainable although the rollers are given a non-circular shape at the bight, in a view'to' reinforce the mechanical strength of their edges. Another advantage is that the product is positively guided out of the mill by parallel planes. It will therefore be delivered perfectly straight and could not adhere to any roller in particular.

The rotation of the product combined with the longitudinal motion of the wire, result in a continuous twisting or helical motion of the product. Such motion may either be neutralized, or it may be preserved.

In the first case, it will only be necessary to reel the. product in a stationary reeling device, and the wire will untwist itself after leaving the mill, while still in a plastic stage. In the second case,- the twist can be preserved all along;the product by giving the reeling device a continuous rotation around the axis of the wire or rod, in such direction and at such speed as to correspond to the rotation of the rod shown by arrow I08. Any burr or marking will then appear as a helix all along the wire which is a decisive advantage when subsequent cold drawing operations are involved, because of a more even wear of the dies.

Figs. 3, 6 and actually illustrate the fun nel created by the forming surfaces of the rollers. There are no open gaps in the funnel and thus no leakage of metal or plastic when used in the fluid state. It is not only possible to use the mills for metals in molten, hot or cold state but for quick-setting fluids and substances or plastics as well as for compressing fibers or powders. The products produced by the mills are in the shape of bars and slabs of any rollable cross section and indefinite length.

When used with hot liquid metal or alloy, these mills can operate either as a continuous mould, or casting machine, Or as a regular rolling mill. In the first case, the metal would be permitted to cool just enough to acquire sufficient cohesion to hold itself together in bar form under the mill, where it would be cooled subsequently by water spray or otherwise. Very little pressure would be imposed on the machine 7 in that case, ensuring'little wear and low power consumption In the second case, the cooling would be more pronounced, and thematerial would come out under appreciable side pressure from the rollers. Some pre-cooling. could be provided also by provision of, a refractory tube standing above the mill and shaped at the bottom to contact the ;r'ollers without excessive clearancej In such a" case, 'hotmetal poured in the tube would setor solidify. partly in hot ingot form which, in turn; would be worked by the mill and rolled tothe final shape. This process could be continuous, the ingot beingfed at the top while dropping steadilytoward the mill. Any of the above-mentioned products could bere rolled or otl'l'erwiseitreated.

I Means of feeding hot metal'iat,constant level, either in the mill itself, or. in the ltubeyshould be provided. .With light-emitting. fluid metals, like steel, photoelectric devices could maintain a correct flow, while pyrom'etricv ormec'hanical feelers would operate better on, dark metals like lead or other low: melting alloys and for'fpastes or plastics." The mills, can also be used-as frictionless outlet dies for extruding presses, being either power-driven or idle, with or without the usual central core or I mandrel for tubular or hollow shapes or for. covered wire, cables and welding electrodes? sheathed with a protective t n 1 Ladles with abottom -pouring nozzle arepreferred because of the lengthjof the jet. of liquid metal, measured between the nozzle and the spherical rolls,'can beheld short andv vertical regardless of the size of the ladle. Also, such jet will respond immediately to any motion of the stopper, in incr,ease. or decrease of the out put, under control of. photoelectric or'other devices depending upon the levelgof the liquid bath between the rolls of the mill,

Greater steadiness. and. stability of thatjlevel can be achieved if the servo-motor acting on the stopper of a bottom-pouring ladle, or on the tilting of a top-pouring ladle,.is.made to be sensitive, not only to the levelof liquid metal between the rolls but also to the firstderivative of thatjfu'nction, namely the speed by which such level rises or lowers. In casesof extreme inertia (heavy ladle of the tilting-type) it may be, indicated to. render the servo-motor sensitive also to the sec-' ond derivative of the level function, namely the rate of acceleration or deceleration of its variation or, in other words, the variation of the speed by which such level changes. This method is highly effective in the prevention of hunting around the position of ideal equilibrium, and in reducing the magnitude of the deviations from the optimum level.

Figure 21 shows a photo-electric control system for a tilting ladle, also adaptable to a bottompouring ladle or furnace. The ladle 35 is hinged at the lip I09 and its bottom is raised by a cable I l 0 pulled by a winch l H driven by one or more electric motors H2. A photo-electric cell H3, fitted with a cone-shaped visor H4, receives the light emitted by the bath of molten steel H5 laying between the rolls of the mill. The higher the level of that bath, the wider the bath, the more light emitted and the greater the current generated by the cell. This current is amplified and automatically analyzed as shown in Fig. 22, by way of example only. Three direct current electric motors H6, H1 and H8 are used, all mechanically coupled to the same shaft H2 in Fig. 21. All three have independent magnetic ,etficient of self-induction.

racoau-r the com bined torque of all threermotors acting onwinch III.

The current generated by photo-cell I I3 is first amplifiedbya triode H9 and then sent through a. Wheatstone bridge, I20 before energizing motor IIB. All four branches of the bridge have equal ohmic resistance, buttwo of them, I22 and I23, are strictly non-inductive resistors, .while .the

other two I24 and I25 are coils witha-high co- The armature of motor II 6 is connected between the junction point of bridge I20 andresistor I2I, and anad- 'justablecontact I26 on potentiometer I21. .This

contact isepositionedto nullify the .voltage applied to motor II6 whenthe level of bath Iliis normal. Iheladle 35 will be raised and thefiow of metal 34 increased if the .level is subnormah or the ladle will be lowered and the vflow decreased if the level is over-normalwith, however, a double corrective action from 'motors- II I and H3.

Motor H1 is connected, through amplifying triode I28, to junctions vI23-.-I24 and I22-I25 of the bridge I20. These points are at equal voltage for any current emitted by triode I I9,,as long as that current does not vary. But if it does, the retarding effect of coils I24 and 125 results in a temporary unbalance of bridge I20. Motor -I I! will tend to increase the metal flow 34 when the .bath H is going down, regardless of its position. inversely, it will tend toreduce the flow when the level is going up.. Similarly, motor H8 is made sensitive to the variation only of the current emitted by triode I28, by the use of a. triode I3I and a second Wheatstone bridge I32 identical to the first one. This motor II 8 will tend to increase the flow of metal 34 when the downward speed of the level H5 is increasing, or the upward speed decreasing. It will reduce that flow if the downward speed of the level decreases, or the upward speed increases. In order to render bothmotors II! and H8. responsive to positive as well as negative unbalance of bridges I20 and I32, despite the unidirectional properties of triodes, some compensating device must be used, ifor instance a polarizing battery I29 in the grid of triode I28, the effect of which is exactly compensated when the bridge I20 is balanced,

- through another. polarizing battery I 30 shunting M-rnotorII'I. H

.. .I claim .as my inventioni 1. :A rolling mill comprising at least three rollerseach rotatably mountedin sealing, contact swithone another havingsealing and forming surfaces and all rotating -atsubstantially equal peripheral speed in a converging directiom-said rollers: having their axes of revolution in-a c'oinrnontplane. and QImin a funnel-shaped o'penin'g closed on all sides; each rollerhavinga. concave sealing surface of revolution closely-enveloping ,a corresponding convexsealing surface of r'ev'olu- ..tion of the adjacent roller, and said two surfaces intersecting the plane of the axes of the rolle'rs :alongtwodistinct curves tangent to each other where they. join the forming'profile of'the rollers and then extending outwardly in' close conform- .ity, but progressively'divergingslightlyfrorn' each other. 1

.2. .A .rolling mill comprising. at least three rollerseach rotatably mounted in'sealin'g contact with oneanother and all rotating at substantially equal peripheral speed in a converging'direction,

'eachroller having a concave sealing surface'of .revolution closely enveloping a corresponding convex sealing torus surface on the adjacent roller, said two vsurfacesintersecting the plane of the axes of the rollers respectively along'a curve and a circle tangent to each other where they join the forming profile of the rollers, and then extending outwardly in close conformityjbut pro gressively diverging slightly from each other.

-. RENE ncoLI'NE'r.

REFERENCES CITED The following references are of record in the file of this patent: 1

UNITED STATES PATENTS

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