US2784620A - Rolling mill - Google Patents

Description

March 12, 1957 r L. IVERSEN 2,734,62@

ROLLING MILL Original Filed Aug. 3, 1945 4 Sheet-Sheet l in; la -a INVENTOR 402/72 Wersen March 12, 1957 L. NERSEN ROLLING MILL Original Filed Aug. 3. 1945 4 Sheets-Sheet 2 w oeoo wwnlo 0 INV ENTOR L 0/ 9/72 /1/e/1sen BY M x 1m ATTORNEYS L. EVERSEN ROLLING MILL Marci: 12, T1937 4 Sheets-Sheet 5 Original Filed Aug, 3, 1945 R O T N E V m A ore/72 Axe/"Jen ATTORNEYS March 32,, 1W5? a... WERSEN 238mm ROLLING MILL Original Filed Aug. 3, 1945 4 Sheets-Sheet 4 r INVENTOR Lore/72 /1/e/-1s-ev7 ATTORN EYS Un W1 Pram EROLLING MILL Lorenz Iv'erseii, Pittsbili'gh, ra asstgner to MestaMachineCbmpauhPittsburgh, Pa., a corporation of Penneylvania Continuation of abandoned QPPlication Serial No. ,08,628, August 3, 1945. This application November '30, 1954],Sefil No. 198,399

1 Claim. (Ci. 80-38) Thi sinventio n relates to rolling mills. It is of particular value as embodied in a mill for the cold rolling of wide, thin strip. This application is a continuation of my application Serial No. 608,628, filed August 3, 1945, now abandoned.

There has been, and is, an insistent demand in the steel industry for higher rolling speeds particularly in cold strip mills. Thecapital investment in such a mill is veryliigh, and any increase in the production rate is of substantial economic importance. The industry requires, however, .that increased production shall not be achieved at the ex ense of quality. Cold reduced strip, to be acceptalile, must be accurate to gage within close tolerances and must have surfaces of high quality.

Steel strip is preferably cold-rolled in a 4-high mill having a pair of small diameter working rolls mounted between a pair of substantially larger diameter backing rolls, with power supplied directly to the working rolls and with backing rolls driven only by frictional engagement with the working rolls. In modern .mills of this description considerable power is required to make the desired reduction of the cold-rolled steel strip and a pair of motors furnishing the required power are necessarily of relatively large diameter compared with the working rolls, especially when high rolling speeds are to be attained. The necessary spacing between the axes of a pair of motors for driving the respective working rolls has to be so much greater than the spacing between the axes of 'the Working rolls that it is impossible to mount a pair of motors of the desired size on the same side of the roll housing with a direct coaxial drive to the working rolls, and a direct coaxial drive between the working rolls and a pair of motors mounted on opposite sides of the roll stand is not a practical driving arrangement because it interferes with removal of the working rolls from both sides of the roll housing and also wastes plant space and obstructs passage on both sides of the mill. A drive system involving any substantial angularity of universal joints is likewise impractical because the universal joints would soon wear out in transmitting the required power for cold rolling at even conventional speeds.

These considerations have resultedheretofore in general acceptance of the conventional driving arrangement which employs a single motor with a motor drive shaft which has a direct coaxial driving connection with one of the working rolls and which mounts a gear meshing with a gear on the drive shaft of the other working roll. While this arrangement avoids blocking both sides of the roll housing it has serious inherent limitations, especially at higher rolling speeds. One limitationis that the relative speeds of the working rolls cannot be adjusted in order to maintain equal peripheral surface speeds against the strip being rolled, With the result that inequalities of the diameters of the working rolls tend to cause surface markings on the rolled strip. Another limitation is the relatively unfavorable rotary inertia characteristics of a single motor driving both working rolls, especially when "ice comes increasingly important to offset this effect as rolling speeds are increased by increasing the rate of acceleration and deceleration. Moreover, the effects of rotary inertia vary as the square of the speed of rotation. Re-

duction of he effects of rotary inertia is therefore an increasingly important factor in the practical attainment of higher rolling speeds.

By the present invention, I achieve the improved new result of increased production from a mill, but with sustained high quality, by a driving arrangement which reduces rotary inertia, reduces motor speed relative to working roll speed, permits of adjusting relative speeds of the working rolls, and disposes the driving means entirely on one side of the roll housing. The novel combination of features which I employ will best be appreciated from a specific description of the mill illustrated in the accompanying drawings, in which:

Figure 1 is a top plan view, partly broken away, of a S-stand continuous cold-reducing mill with certain parts of the rolling mill stands omitted for clarity of illustration;

Figure 2 is a top plan view to enlarged scale showing a portion of thedrive mechanism for the last stand of the mill shown in Figure 1;

Figure 3 is a vertical section generally on the line III-III of Figure 2, but extended to include a portion ofthe mill housing;

Figure 4 is a vertical section on the line IVIV of Figure 3; and a Figure 5 is a simplified wiring diagram indicating the electrical driving meehanism and control for one of the stands.

the delivery end.

Each stand consists of housings 9 and iii secured to bed-rails 11. Each of the stands is of the 4-high type embodying a pair of working rolls 12, one above the other with parallel axes of rotation, each working roll having a larger diameter backing roll 13. The Working rolls are driven and the backing'i'olls are undriven. Each of the rolls has a body of substantially uniform diameter (a certain amount of crown may be provided, according to known practice) and has a very high surface finish.

In the operation of the mill, a coil of hot rolled strip is placed in the feed reel 6 and the leading end entered between the working rolls of stand 1, while the rolls are rotating at a low speed. As the leading end of the strip leaves stand 1, his directed between the Working rolls of stand 2, and so on, successively through stands 3, 4 and 5 for attachment to the head of the reel 7. The setting of the working rolls in each of the stands will have been made by the screw-downs to effect the desired amount of reduction in each stand. The mill being thus threaded, it is ready to be brought up to speed. This is done as rapidly as possible and the rolling continues at high speed. When the coil has been rolled the stands operate at progressively higher speeds. My invention is of particular importance as applied to the higher speed stands, and in many cases, as for instance in the case of the mill illustrated in the drawings, it need not be applied to all of the stands.

The working rolls for stand 1 are driven by a motor 14 through a reducing gear 15 and a pinion set 16. The working rolls for stand 2 are driven by a motor 17 through well known in the art.

Each of stands 3, 4 and 5 is provided with two motors, 19 and 20, one (19) for driving the upper working roll and one (20) for driving the lower working roll. The motors 19 and 20 are connected by couplings 21 to shafts 22 and 23, respectively. These shafts rotate coaxially with the motors 22 and 23 and are journaled in a gear case 24 having two compartments 24a and 24b.

The shaft 22 extends through the compartment 24b to the compartment 24a and there carries a drive gear 25 meshing with a pinion 26. The pinion 26 is carried by a shaft 27 journaled in the gear case 24, one end of the shaft projecting outside the case and terminating in a coupling 28. The coupling drives a spindle 29 which in turn is connected through a coupling 30 to the neck 12;: of the lower working roll.

The shaft 23 carries a gear 31 in the compartment 241), this gear meshing with a pinion 32. The pinion 32 is mounted on a shaft 33 which extends through the chamber 24a and beyond the casing 24 where it terminates in a coupling 34 lying above the coupling 28. The coupling 34 is connected through a spindle 35 and coupling 36 to the neck of the upper working roll. The spindles and couplings permit of adjusting the relative setting of the working rolls by the mill screw-down; but in any adjusted position, the working rolls will be generally coaxial with their respective drive shafts.

That portion of the shaft 33 which extends through the compartment 24a is of reduced diameter, as best shown in Figure 3, to provide clearance with the pinion 26.

The couplings 28 and 34 and the spindles 29 and 35 are protected by a housing 37. Bearings 38 are provided for supporting the spindles at their mid-points.

In the operation of a strip mill, very high pressures are developed and both rolls will frictionally engage the strip. In some stands, the setting of the rolls may be such that they are in face contact when there is no steel in the mill, the spring of the housings being relied upon to provide the proper pass setting when steel is being rolled. The two Working rolls are not interconnected by gearing, and except as the drive shafts for the rolls are relatively restrained by the interaction of the work rolls in contact with the work-piece or in face contact with one another, they rotate independently. In the mill drives customarily employed for cold strip mills the relative rotation of the rolls and their drive shafts is fixed by the intermeshing pinions of the pinion set.

In Figure 5, I have shown an electrical diagram indicating a control for one of the stands. I have illustrated the two motors 19 and 20 as receiving their armature current from the generator 38 of a motor-generator set 3839. The field winding 40 of the generator 38 is energized by an exciter 41 and a variable resistance 42 in series with the field winding 40 permits of varying the voltage impressed on the current by the generator 38, thereby to effect a simultaneous adjustment of the speeds of the motors 19 and 20. A handwheel 43 on a control panel 44 is provided for adjusting the variable resistance 42.

The exciter 41 also supplies the current for the field windings 45 and 46, respectively, of the motors 19 and 20. A variable resistance 47 is placed in series with the field Winding 45 and a like resistance 43 is placed in series with the field winding 46, these two resistances a pinion set 18. These two types of drive are old and being individually controllable by handwheels 49 and 50, respectively, on the control panel 44. Adjustment of the handwheels 49 and 50 will effect an adjustment in the relative speeds of the motors 19 and 20 while leaving them both subject to the general speed control of the handwheel 43.

A shunt 51 is provided in the armature circuit for the motor 19 and a shunt 52 is provided in the armature circuit for the motor 20. These shunts are cross-connected by wires 53 leading to an indicator 54, the arrangement being such that the pointer of the indicator 54 will be stationary in a central position if both motors are drawing the same amount of current, but will move if they draw different amounts of current, the movement being to the right or to the left, depending uponwhich motor is carrying the greater load.

In operation, the speed of a mill stand will be adjusted by the handwheel 43 and the load will be divided equally between its two motors 19 and 20 by adjustment of one or both of the handwheels 49 and 50.

My invention has many advantages. The mill is suited for operation at speeds in excess of a mile a minute, e. g., 5500 or more feet per minute. But, while these high speeds are of importance, I regard the time during which the mill is not operated at full speed as a major factor also, and my invention effects material time savings, and hence effects material improvements in output, by reducing this time factor to a minimum. In mills made according to my invention, there being two motors for a stand, each may be of relatively small diameter. In consequence, smaller inertia effects are encountered. It is therefore possible to accelerate and decelerate the mill more rapidly, the mill may be threaded and the maximum mill speed achieved more quickly, and the mill may be slowed down to a pace suitable for threading in a lesser time after the rolling of a strip, all contributing to an increase in the percentage of operating time in which the mill operates at full speed.

The improvement from reduced inertia effect is particularly notable if the gearing is such as to operate the rolls at a higher rotative speed than the motors, as in the mill herein illustrated and described. It will be understood, however, that other gear ratios may be employed.

Another advantage is that the mechanism permits driving of the mill at the highest speeds smoothly, with a minimum of strip breakage and a minimum of wear on mill parts. 7

Another advantage is that, while the assemblage is compact, well enclosed, and in all respects suitable for service under the conditions existing in a rolling mill plant, it is simple in construction, and highly accessible. The motors and all of the driving mechanism are on one and the same side of the housings, and roll changing is not hampered as would be the case if the drive were in part on one side and in part on the other side of the housing. The use of the gear drives between the motors and their respective working rolls permits of placing the motors side by side with their axes of rotation disposed in a horizontal plane parallel to each other and to the working roll axes, and spaced several times further apart than the axes of rotation of the working rolls are spaced in a vertical plane (Figure 4). Such spacing of the motor axes makes it possible to accommodate motors sufficiently large to deliver the required power. A motor may be readily replaced, if this becomes necessary, at minimum cost.

Another advantage lies in the fact that the working rolls need not be precisely matched. In present day practice, extreme care is taken to pair the working rolls so that the two rolls of any one stand are exactly alike. With my invention this is not necessary, because the relative speeds of rotation can be adjusted to give the same surface speed, even though the two rolls differ somewhat in diameter. (When so adjusted that the load is divided substantially equally between the motors, the surface speeds of the two working rolls will be substantially the same, even though the rotative speeds may be difierent. It is thus possible to roll at highest speeds with working rolls which are not precisely paired, but without impairing the surface of the strip or undue wear on either roll.

Another advantage, indicated in some measure in the preceding paragraph, is that surface marking of the strip is minimized and a high-quality product is obtained.

1 have illustrated and described a present preferred embodiment of the invention. I will be understood, however, that this is by way of illustration and that the invention may be otherwise embodied within the scope of the following claim.

I claim:

A mill for cold rolling of wide, thin strips of steel and the like at high speeds with rapid acceleration and deceleration, comprising a housing, a pair of working rolls journaled in the housing one above the other with parallel axes of rotation to roll strip therebetween, a pair of backing rolls of substantially larger diameter than the working rolls, each backing roll being driven by frictional engagement of the corresponding working roll, a pair of separately complete and independently rotatable motors mounted side-by-side on one side of the housing with their axes of rotation parallel to but spaced several times further apart than the axes of the working rolls, power means separately connected to each motor,

means for separately regulating the power supply to each ing roll drive shafts extending substantially axially from the respective working rolls, and a pair of separate gear sets between the motors and working rolls, one gear set connecting one motor drive shaft with one working roll drive shaft and the other gear set connecting the other motor drive shaft with the other Working roll drive shaft, with one gear set offset from the other toward the housing, and with each gear set comprising a pair of gears, one mounted on the associated motor drive shaft and a smaller gear mounted on the associated working roll drive shaft so that the working roll drive shaft rotates at a relatively higher speed than the motor drive shaft, said separate motors independently driving relatively small diameter Working rolls in a high-speed 4-high coldrolling mill at a speed higher than that of the motors through the drive shaft and the gear sets with equalized surface speeds against the strip from the same side of the housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,779,195 Steckel Oct. 21, 1930 1,813,129 White July 7, 1931 1,907,596 Shirk May 9, 1933 2,038,783 Gassen Apr. 28, 1936 2,047,509 Iversen July 14, 1936 2,068,260 Biggert Jan. 19, 1937 2,102,355 Cummins Dec. 14, 1937 FOREIGN PATENTS 382,081 Great Britain Oct. 20, 1932 839,487 France Apr. 4, 1939

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