US3422655A - Prestressed rolling mill - Google Patents

Description

an 21, 9 M. DSTONE Em. 3,422 6 I PRESTRESSED ROLLING MILL She et Filed May 4, 1965 FIGI INVENTOR. MAURICE P. SIEGER BY MORRIS u. STONE m'fl ATTORNEY THEI Jan. 21 1969 M. D. STONE ET AL 3,422,655

PRESTRESSED ROLLING MILL Filed May 4, l95 Sheet g of 5 INVENTOR. MAURICE P. SIEGER BY MORRIS o. STONE.

THEIR ATTORNEY Jan. 21, 1969 STONE ETAL 3,422,655

PRESTRESSED ROLLING MILL Filed May 4, 1965 Sheet 3 of 5 Z4 2.4 29, J g g W28 9 27 26 F I I LQ I i 22 l l l I v I l INVENTOR.

MAURICE P SIEGER BY MORRIS D. STONE ATTORNEY Jan. 21, 1969 T NE ET'AL v 3,422,655

PRESTRESSED .ROLLING MILL Filed May 4, 1965 Sheet 4 of 5 III III! III OJ F IG. 6 :MAURICE e'iz BY MORRIS D. STONE THEIR ATTORNEY Jan. 21, 1969 M. D. STONE ETAL 3,422,655

PRESTRES SED ROLLING MILL Filed May 4, 1965 Sheet 5 of 5 v INVENTOR. 5 MAURICE P. SIEGER BY MORRIS 0. STONE ji e 774%; THEIR ATTORNEY United States Patent 7 Claims ABSTRACT OF THE DISCLOSURE A rod or bar rolling mill of the prestressed type wherein the prestressed pressure is maintained greater than the expected rolling load and the mill is constructed to subject the housing, bearing chock assemblies and roll separating means to the prestressed pressure. In this construction the mill is provided with cooperative rigid screws piston cylinder assemblies, the piston cylinder assemblies are employed initially and before rolling to apply the prestressed pressure and the screws are employed during rolling to apply the pressure once the piston cylinder assemblies are rendered inoperative. In combination with the prestressing feature anti-roll deflection means is also provided, thereby providing an extremely rigid mill construction.

The present invention relates to a rolling mill, and more particularly, to a rolling mill designed to roll extremely close tolerance products.

For the purpose of discussing the present invention its use in connection with a bar mill has been selected, although it will be appreciated that the invention may be employed in other types of mills, such as, rod mills, structural mills, etc.

Both with respect to the desire to increase the yield of the rolling mill and to meet the ever-increasing stiffer tolerance requirements, there is presently a great need for providing a rolling mill which will roll bars to one half present standard bar tolerances or better. Such an objective could not be obtained by conventional mills wherein the rolls are arranged to extend between the spaced-apart housings, in view of the fact that they inherently possessed considerable mill stretch or elastic deformation of parts and deflection of the rolls, which made it impossible to roll products within a predetermined narrow range of tolerances.

To illustrate this, reference will be made to one type of 2-high mill previously employed which was designed to produce a 1%" diameter steel bar, wherein the final pass developed a rolling force of the order of 135,000 lbs. Under this force, the inherent stretch or elastic deformation of the composite mill structure, that is to say, the elongation of the housing posts, the bending of the top and bottom housing separators, the compression of the mill screws, filler plates and chocks amounted to approximately .004 inch. Assuming that the particular mill in question employed cast iron metal rolls of 12" diameter by 24" long, under the above rolling force, each of the rolls would bend or deflect about .0095 inch, the total deflection amounting to .019 inch for both rolls. Therefore, the total mill stretch equals .023 inch which has a corresponding mill spring constant of the order of 5,900,000 lbs. per inch. It can be seen, therefore, from this analysis that 17% of the mill stretch is traceable to the mill proper, while the remaining, that is 83% of the mill stretch, is traceable to the rolls themselves.

This analysis demonstrates that in the type of mill under discussion the solution to the problem of manufacturing "'ice a mill that will produce bars within close tolerances must lie in a construction that not only will considerably reduce the mill stretch of the housings, but more important in a construction that will in combination therewith reduce appreciably the deflections of the rolls. The ultimate, of course, would be a mill construction that would in addition eliminate or considerably reduce the elastic deformation of the other components of the mill, such as the chocks and filler plates and the compression of the mill screws. In other words the optimum mill design would be a design that would greatly increase the rigidity of the mill and its component parts, together with the elimination or substantial reduction of the deflections of the rolls thereof.

It is an object of the present invention to provide a rolling mill, wherein the rigidity of the mill housing and the other component parts of the mill, such as the chocks, screws and filler plates, are subject to a predetermined prestressing pressure greater than the largest anticipated rolling force which will eliminate the elastic deformation of these parts from influencing the gauge of the bar.

The present invention is addressed to an open mill, that is to say, the rolls operate with a space between the opposite cooperative faces, in which connection the present invention employs wedges between the cooperative chocks of the rolls, thereby assuring that the prestressing pressure will pass through the roll chocks. In one form the roll deflection under rolling pressure is partly or wholly alleviated by providing a series of lands on the reducing rolls and wherein the rolls are each supported by backup rolls which engage the reducing roll intermittently along their entire lengths.

In another form the deflection of the roll under rolling pressure is eliminated or reduced by providing a roll with a central flat cylindrical portion, which portion outward from the rolling bite is engaged by a short-bodied backup roller, which is adjustable toward and away from the roll by a pressure-exerting means, such as, a piston cylinder assembly or screw arrangement.

In one preferred form of the present invention there is provided a housing, including a window, a pair of metal reducing rolls having a number of roll passes along their length, central load portions, bearing and chocks for the journals of the rolls received in the housing window, roll adjusting means carried by said housing for positioning one of the rolls relative to the other, cooperative pair of wedges for each roll journal engaging the chocks of the rolls, means for prestressing the housing, the bearing and chocks of the rolls, the wedges and the roll adjusting means, to an extent greater than the largest anticipated rolling force, and means for engaging said central load portions of each of the rolls to resist deflection of the rolls under the rolling forces.

These features and various other advantages of the present invention will become more apparent when the following description is read along with the accompanying drawings of which:

FIGURE 1 is an outside elevational view of a bar mill of one embodiment of the present invention;

FIGURE 2 is an elevational view, partly in section, of the mill illustrated in FIGURE 1;

FIGURE 3 is an enlarged view of the upper portion of the mill illustrated in FIGURES 1 and 2 showing two positions of certain components of the mill;

FIGURE 4 is a modification of the prestressing cylinders illustrated in FIGURE 3, showing two positions of certain components of the mill;

FIGURE 5 is an elevational view, partly in section, of a third embodiment of the present invention; and

FIGURE 6 is a modification of the construction of the housings shown in the previous figures.

With reference to the drawings, reference will first be made to FIGURES 1, 2 and 3 where there is shown a mill comprising two vertically arranged, spaced-apart interconnected housings 12 and 13 having windows 14 and 15 to which there is received a pair of cooperative rolls 16 and 17. The rolls have a number of grooves 18, as shown in FIGURE 2, through which a bar passes and is reduced in cross section. The journal portions of the rolls 16 and 17 are received in bearings 19, which in turn are contained in chocks 22 received in the windows 14 and 15 of the housings. The chocks 22 of the lower roll 17 rest upon the bottom of the windows 14 and 15, whereby the rolling forces are transmitted directly to the lower portions of the housings 12 and 13.

As shown in FIGURE 2, which illustrates one side of the mill in section, the chocks 22 of the upper roll 16 are engaged by the lower end of individual screws 23, the screws being received in nuts 24 mounted in the upper part of the housings and rotated by motors 25 through a worm-wheel set only generally shown. As FIGURE 3 shows, the top of the chocks have recesses 26 into which the lower ends of the screws extend. Cylindrical blocks 27 are also received in the recesses. Between the screws and chocks in the usual manner, there are provided breaker blocks 28.

As best shown in FIGURE 3, the upper surface of each of the blocks 27 is engaged by the lower end of a piston 29, it being noted that the nut 24 is provided with a cylindrical opening 31 which forms a single action cylinder into which the piston 29 is received. Also shown in FIGURE 3, the upper end of the cylinder has a port 32 which communicates with the passageway 33 formed in the housing, the passageway being connected to a fluid supply source not shown.

Returning to FIGURE 2, each of the rolls 16 and 17 is provided with a series of lands 34, 35 and 36, the lands 34 and 36 being arranged at the ends of the rolls whereas the land 35 is arranged at the center and is appreciably wider than the end lands. As indicated in FIGURE 2, and as previously noted, the lands of each roll are not in contact with each other which characterizes the mill an open mill. In engagement with the lands 35 of the rolls are narrow body freely rotatable backup rollers 37 which on occasion are referred to as antideflection rollers, the backup rollers being rotatably mounted on non-rotating shafts 38 by bearings 39, the ends of the shafts 38 being received in U-shaped yokes 41 which are guided in the housings 12 and 13 in a vertical direction. At the one end of the yokes, there is provided pressure block 42, the upper surface of which is engageable by the one end of a screw 43. The screws 43, in turn, are threadably received in nuts 44 nonrotatably mounted in the separators 45 that connect the housings 12 and 13 at the top and bottom. The outer ends of the screws carry gear wheels 46 which are rotated by gear worms 47 driven by motors 48.

The upper narrow body roller 37, as shown in FIG- URE 1, is urged upwardly by a balance mechanism comprising a cross bar 50, the ends of which are connected to rods 51. The upper ends of the rods 51 are associated with piston cylinder assemblies or springs 52.

With reference to FIGURE 1 and in referring to only one side of the mill, although a similar interconnected construction is provided on the other side, it will be observed that between the chocks 22 and in engagement therewith in the region of the passline of the mill there is provided a pair of adjustable wedges 53 and 54 on each side of the transverse vertical center line of the mill, that is, there is a pair of oppositely arranged spacedapart wedges for the opposed pairs of chocks which determine the opening between the rolls 16 and 17. As FIGURE 1 shows, each wedge is provided with an opening, a portion of which is threaded, into which is received a screw 55 which in turn is connected to a wormwheel gear set 56, the worm of which is secured to a vertically extending shaft 57 which terminates in and is secured to one of a set of bevel gears 58 and 59, the other bevel gear being connected to a horizontal shaft 61. This shaft has mounted on its other end a bevel gear 62 which meshes with a bevel gear 63. This gear, as FIGURE 1 shows, is secured to a vertical shaft 64 that is connected to a worm-wheel gear set 65. Returning to the shaft 61, its opposite end is connected to and driven by a motor 66.

One other characteristic of the mill illustrated in FIGURES 1 and 2 should be noted. As shown in FIGURE 2, as to one side of the mill, extending between the base of the housings 12 and 13 and passing through the window 14 is a shelf 67. The lower portion of the shelf rests on the housings. In the vicinity of each lower chock 22, a block 68 is provided having at its upper end a rocker plate 69, which contacts a similar rocker plate 71 secured to the chock 22 having its lower end formed with an inclined surface. In contact with the inclined surface of the block 68 is a wedge 72 being of suflicient height to give the necessary vertical displacement of the block 68 and chock 22. While not particularly shown in the drawings, the block and wedge are interconnected by an interfitting connection such as a T slot construction.

The one end of the wedge 72 is provided with a threaded opening into which is received a screw 73. The other end of the screw 73 is formed with two spaced collars and between which is received a bearing 74. The outer end of the screw is formed with a nut, whereby the screw can be rotated by a hand wrench, not shown. By this mechanism the passline of the mill can be maintained at a predetermined location even though the rolls are turned down and at the same time allowing the prestress pressure to pass through the block 68 and wedge 72 and into the housing.

The operation of the mill illustrated in FIGURES 1 and 2 will now be briefly explained. It will be appreciated that the wedges 53 and 54 of each housing 12 and 13 will be adjusted to set the separation between the rolls 16 and 17 prior to a bar being introduced into one of the grooves 18. Also prior to the reception of the bar, the piston cylinder assemblies 29 will be operated to subject the housings 12 and 13, chocks 22, bearing 19, roll necks of the rolls 16 and 17 to a prestressed pressure which at all times will be controlled to exceed the expected rolling pressure. In this respect, as the arrows in FIGURE 2 indicate, the prestress pressure will pass through the top work roll chocks 22, through the wedges 53 and 54 and into the lower work roll chocks 22, into the blocks 68 and wedges 72 and into the housings thereby providing a closed circuit pressure system. The screws 43 will be adjusted to position the anti-deflection rollers 37 to offset the deflection of the rolls under the rolling loads. After the rolling mill has been prestressed in the aforesaid manner, the screws 23 are prestressed by being brought into engagement with the prestressed chocks 22 of the roll 16. Once this has been performed, the pressure in the cylinders 29 will be relieved. By using the screws in this manner a very rigid construction is provided and the prestressing condition of the mill is not subject to any losses in the hydraulic system or with providing a system to makeup for hydraulic losses.

Thus, the present invention provides an extremely rigid mill wherein the total rigidity of the mill is many times greater than that of conventional mills.

FIGURE 4 illustrates another embodiment of a piston cylinder assembly provided for prestressing the components of the mill, in which regard there is provided on either side of the screw 23 a pair of piston cylinder assemblies 75 having pistons 76 that engage projections 77 formed on the upper chock 22 of the upper roll 16.

Turning now to FIGURE 5, this mill in many respects is quite similar to the mill shown in FIGURES 1 and 2,

having for example wedges 78 between the metal reducing rolls 79 and 81, and therefore only the significant difference between the two mills will be pointed out. The mill shown in FIGURE 5 differs, primarily, in that the deflections of the reduced rolls 79 and 81 are resisted in an altogether diiferent manner. The rolls 79 and 81 of the mill in FIGURE 5 are provided with end lands 82 and 83 and a number of lands 84 intermediate the grooves 85 which serve to transmit the prestressing pressure to the chocks of the upper roll in the case of the upper roll 79 and the lower backup roll in the case of the lower roll 81. As just indicated, the rolls 79 and 81 are backed up by large stiff backup rolls 86 and 87 that engage the lands 82, 83 and 84 of the rolls 79 and 81. The backup rolls 86 and 87 are provided with bearing chock assemblies 88 at their journals, which, as to the upper roll 86, are engaged by the mill screws 89 and prestressing piston cylinders 91. The bearing chock assembly 88 of the lower backup roll 87 rests on a block 92 of the wedge pass adjustment mechanism 93. As FIGURE 5 illustrates by the arrowed lines, the prestressing pressure of the cylinder 91 subjects each of the following components to its pressure: the screws 89, bearing chocks 88 of the upper backup rolls 86, the upper backup rolls 86, the reducing roll 82, its bearing and chock, wedges 78, reducing roll 81, lower backup roll 87, its bearing chock assembly 88, block 92, wedge 93 and the housings, As the arrowed lines indicate, the prestress pressure is taken through a closed pressure circuit.

FIGURE 6 shows the arrangement whereby in order to facilitate quick roll changing, the housings of the mill are adapted to be pivotally mounted on trunnions at their bases. With reference to this figure, there is seen the lower portion of a housing 94 where its feet 95 are formed with openings 96 for receiving pins 97. The pins are contained in the base 98 through which construction the housing 94 is allowed to be swung in a direction toward and away from the ends of the roll 99.

In accordance with the provisions of the patent statutes, we have explained the principle and operation of our in vention and have illustrated and described what we consider to represent the best embodiment thereof. However, we desire to have it understood that within the scope of the appended claims, the invention may be practiced other wise than as specifically illustrated and described.

We claim:

1. In a rolling mill comprising a housing having a window for receiving a pair of cooperative metal reducing rolls,

said rolls having a number of complementary pass openings formed along their lengths,

bearing chock assemblies mounted on the opposite ends of the rolls and received in the window of said housing,

a roll separating means arranged between each pair of opposed bearing chock assemblies of said rolls,

a rigid screw for each bearing chock assembly of one of the rolls of said pair of rolls mounted in said housing and engageable with said bearing chock assemblies of the said one roll,

a piston cylinder assembly associated with each of said screws and engageable with different chocks of the said one roll adapted to exert a prestressing pressure thereon greater than the largest anticipated rolling force developed between said rolls and in a direction to force said one roll towards the other roll,

said pressure being transmitted by said roll separating means to the chocks of the other roll whereby the housing, bearing chock assemblies and roll separating means are all subject to said prestressed pressure, and

means for bringing said screws into engagement with said chocks of said one roll after the prestressing pressure has been applied thereto to hold the chocks of the said one roll in the prestressed condition when the prestressing pressure of said piston cylinder assemblies are relieved.

2. In a rolling mill according to claim 1, wherein said prestressing piston cylinder assemblies are formed in the housing and concentric with the screws, and wherein the pistons thereof extend around the screws, the lower end of the screws passing through the cylinders of said piston cylinder assemblies.

3. In a rolling mill according to claim 1, wherein for each screw there is provided at least two separate piston cylinder assemblies, each pair arranged equal distance around the relative screw and engageable with the adja' cent chocks of the uppermost roll.

4. In a rolling mill according to claim 1, wherein said roll separating means includes a wedge arranged between the opposed chocks of said reduced rolls, and

means for moving said wedges between the chocks of said rolls.

5. In a rolling mill according to claim 1, including means for engaging the chocks of the roll not engaged by said rigid screws to position the roll relative to a predetermined pass line of the mill.

6. In a rolling mill according to claim 5, wherein said means for positioning the roll relative to the pass line of the mill includes a beam extending between the chocks of the lowermost roll, a pair of wedges between each chock and the beam,

means for moving one of said wedges of each pair in a first direction to impart movement of the other wedge of each pair in a second direction thereby to move the lowermost roll toward and away from said pass line.

7. In a rolling mill comprising a housing having a window for receiving at least three cooperative rolls,

two of said rolls comprising cooperative working rolls having complementary pass openings formed along their lengths,

the remaining roll comprising a backing up roll for one of said working rolls adapted to engage said one working roll along a substantial portion of its length.

bearing chock assemblies mounted on the opposite ends of each roll and received in the window of said housing,

a roll separating means arranged between each pair of opposed bearing chock assemblies of said working rolls,

a rigid screw for each bearing chock assembly of said backup roll mounted in said housing and engageable with said bearing chock assemblies of the backup roll,

a piston cylinder assembly associated with each of said screws and engageable with different chock of the said backup roll adapted to exert a prestressing pressure thereon greater than the largest anticipated rolling force developed between said working rolls and in a direction to force said backup roll towards said working rolls,

said pressure being transmitted by the bearing chock assembly of one of said working rolls to the roll separating means and by the roll separating means to the other working roll bearing chock assembly whereby the housing, working roll bearing chock assemblies, and roll separating means are all subject to said prestressed pressure, and

means for bringing said screws into engagement with the bearing chock assemblies of the said backup roll after the prestressing pressure has been applied thereto to hold the bearing chock assemblies of the said backup roll in the prestressed condition when the prestressing pressure of said piston cylinder assemblies are relieved.

(References on following page) 7 8 References Cited FOREIGN PATENTS UNITED STATES PATENTS 1,430,038 1/1966 France.

1935091 11/1933 Iversen 72'245 CHARLES W. LANHAM, Primary Examiner, 2,363,656 1/1944 Dawson 72237 5 2 410 11 Pauls 245 A. RUDERMAN, Assistant Exammer. 2,985,042 5/1961 Talbot 72-243 3,217,525 1/1965 Howard 72 237

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