US3595054A

US3595054A - Double three high planetary mill

Info

Publication number: US3595054A
Application number: US820719A
Authority: US
Inventors: Tadeusz Sendzimir
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-05-01
Filing date: 1969-05-01
Publication date: 1971-07-27
Anticipated expiration: 1988-07-27
Also published as: DE2123578A1; FR2135103B3; FR2135103A3; GB1342634A

Abstract

A planetary rolling mill with nonoverlapping rolling cycles, i.e. a pair of work rolls leaves contact with the strip before a succeeding pair of work rolls engages the strip, wherein torsional vibrations of the drive elements are minimized, in that torque stresses on the drive elements are relieved before the end of each rolling cycle, i.e. before each pair of work rolls leaves contact with the strip.

Description

United States Patent Inventor Tadeusz Sen dzimir do '1. Sendzimir, lnc. P.O. Box 1350, Waterbury, Conn. 06720 Appl. No. 820,719

Filed May 1, 1969 Patented July 27, 1971 DOUBLE THREE HIGH PLANETARY MILL 14 Claims, 9 Drawing Figs.

lnt.Cl B2lb 21/00 Field of Search 72/224,

[56] References Cited- UNITED STATES PATENTS 2,960,894 1 1/1960 Platzer 72/190 3,138,979 6/1964 Sendzimir 72/240 3,153,955 10/1964 Platzer 72/190 Primary Examiner-Milton S. Mehr Attorney-Melville, Strasser, Foster & Hoffman ABSTRACT: A planetary rolling mill with nonoverlapping rolling cycles, i.e. a pair of work rolls leaves contact with the strip before a succeeding pair of work rolls engages the strip, wherein torsional vibrations of the drive elements are minimized, in that torque stresses on the drive elements are relieved before the end of each rolling cycle, i.e. before each pair of work rolls leaves contact with the strip.

PATENTED m2? i97| SHEET 1 UP 2 INVENTOR. 8 7ZDEusz SENDZ/M/f? MELV/LLE, Siva/45552, FOSTER A/VD HOFFMAN ATTORNEYS DOUBLE THREE HIGH PLANETARY MILL BRIEF SUMMARY OF THE INVENTION A. Background Planetary mills having powerful feeding means such as rolls which force a slab into the bite of two cooperating planetary assemblies at uniform speed are known. Such mills are described, for example, in US. Pat. Nos. 2,710,550 and 2,932,997.

In such mills the planetary assemblies are composed of a backing roll surrounded by a plurality of spaced work rolls. Such mills are limited, so far as the choice of the number of work rolls is concerned, by the consideration that there must always be a pair of work rolls in contact with the workpiece, i.e. before each pair of work rolls leaves contact with the strip the succeeding pair of work rolls must already be in contact with the slab. Thus, while the driving torque requirements will vary between two and one pair of work rolls they never fall to zero. If this condition is not met, the entire driving mechanism including spindles, pinions, and couplings, is subjected to dangerous and destructive vibrations.

A driving spindle of a backing roll in some planetary mills will transmit a torque of say 5,000 horse power at 200 r.p.m., and in so doing is slightly twisted elastically like a torsion spring. All the other drive elements from the motor to the backing roll'arealso under elastic stress and unless a succeeding pair of rolls is also in contact with the work, all this potential energy is suddenly released when the work roll leaves contact with the workpiece and the torque momentarily drops nearly to zero. This recoil is very dangerous to the mill driving elements.

B. Solution According to the present invention, by means of a mill of great simplicity and ruggedness having large diameter work rolls and relatively few working rolls, the problems above described are solved. Whereas a conventional planetary mill will be provided with 20 to 24 work rolls per assembly, a mill according to the present invention can operate with as few as two work rolls whereby only one pair of work rolls is ever in contact with the strip at any given time.

The present invention provides a method and means whereby the torque stresses on the drive elements are relieved before the end of each rolling cycle, i.e. before each pair of work rolls leaves contact with the strip.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a transverse cross-sectional view of a mill accord ing to the invention.

FIG. 2 is a longitudinal cross-sectional view on the line Il-Il of FIG. ll.

FIG. 3 is a fragmentary schematic view ofa workpiece during reduction by a pair of work rolls.

FIG. 4 is a cross-sectional view on a greatly enlarged scale ofan edge retaining roll and its mounting.

FIG. 5 is a schematic front elevational view of the mill and its drive.

FIG. 6 is a schematic side view of a torque compensating mechanism.

FIG. 7 is a schematic cross-sectional view of a modification ofthe invention.

FIG. 8 is a longitudinal cross-sectional view of another embodiment of the invention; and

FIG. 9 is a schematic cross-sectional view of the embodiment of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION The pair of coacting planetary assemblies shown in FIGS. 1 and 2 consist of the two backing rolls 1 and 1 each having as sociated therewith two

work rolls

2, 2 and 3, 3'. The backing rolls l, I are mounted in chocks t, 4' and 5, 5' located in openings in the mill housing 6.

While any suitable screw-down system may be employed the one illustrated here provides that the outside peripheries of the chocks l, 4' and 5,5 are eccentric with respect to the axis of the backing rolls so that the roll gap can be increased or decreased by rotating the chocks by a certain angle substantially as described in U.S. Pat. No. 3,138,979.

The path described by each

work roll

2, 2' and 3, 3 around the respective backing rolls 1 and I is substantially circular; yet if the diameters of the work rolls with respect to the diameters of the backing rolls correspond to certain specific ratios and the speeds of rotation of the backing rolls and the cages 7,

7 which carry the work

roll bearing chocks

7a, 7a are related in the same ratio, then it will be clear that the angular positions of the backing rolls 1, 1', when a work roll engages the workpiece and when it leaves the workpiece, will always be the same. The importance of this resides in the fact that the backing roll instead of being cylindrical can now be slightly profiled to cause the work roll to deviate from its circular path and providing the substantial advantages which will be explained in more detail hereinafter.

Any suitable means may be employed to drive the cages7, 7' in the appropriate ratio to the speed. of the backing rolls 1, 1. Preferably, for example, the cage 7 is driven from the backing roll 1, 1' through a pair of

gears

35, 36 and the cage 7' is similarly driven through an identical pair of gears from the backing roll 1. The

gears

35 and 36, best seen in FIGS. 2 and 8, are mounted on splines or bolted onto their respective shafts. They preferably have large teeth of suitable profile to permit variation in the center distance as necessitated by the screwdown. Where larger adjustments in the center distance are desired it is, of course, within the scope of the present invention to use variable center mountings such as the well known Oldham couplings for mounting the gears, or even to use intermediate gears. On larger mills such a simple drive may not suffice to permit the full utilization of roll diameters, and a suitable compensating drive may be employed.

Referring now to FIG. 3, the lower portion of this Figure shows the path of a work roll 3 backed by a truly cylindrical backing roll, whereas the upper half shows the path of a work roll 2 when backed by a profiled backing roll 1. In the lower half of the Figure it will be observed that the work roll 3 first contacts the slab 10 at the point A, and leaves contact just after passing the point D, which is the highest point of its trajectory, where the slab 10 is already reduced to strip gauge 11. The orbiting velocity of the work roll 3 around the backing roll I, and therefore the theoretical angular velocity of the cage 7, as the work roll 3 moves down the roll bite from the point A, to the point D,, is increasing because the surface velocity of the workpiece increases roughly in inverse ratio to the thickness of the workpiece. This precession is very small; but as will readily be understood it tends slightly to unload the potential energy stored in the spindles 9, 9 and the driving mechanism of the mill because it causes the backing roll to turn faster than its drive before the moment when the torque demand suddenly disappears as the work roll 3 leaves contact with the workpiece after passing point D,.

But, if, as suggested above, advantage is taken of the fixedratio mill geometry, and if instead of using-a circular cross section backing roll 1, the backing roll is given a slight profile, the roll 2 instead of describing an are or a circle with its lowest point at D, may be caused to move along a straight line from C to D during the last part of its contact with the workpiece and thus produces a parallel piece of strip 11 instead of an arcuate one. As a result of this, not only is a better product produced but it makes possible the unloading of a considerably larger proportion of the elastic energy stored in the mill spindles. This is because the work roll 2 contacts the light gauge finished strip over a much longer distance, i.e. from the point C to the point D, and therefor the precession of the work roll is much greater than if the backing roll 1 were cylindrical.

If the part of the backing roll 1 corresponding to the entry of the work roll 2 into the roll bite, i.e. at the point A,, is also profiled, an additional advantage is obtained in that a thicker slab such as it) can be fed into the mill without exceeding the critical angle of entry of the roll 2 into the roll bite at A As is clearly explained in the two United States patents above noted, an entry angle of about must not be exceeded. Above that angle the work roll 2 has a tendency to throw back a part of the surface layer of the workpiece, creating surface defects called back fins." It is clear that if the work roll 2 can be caused to deviate from its circular path, this angle of entry can be maintained, reduced or even rounded off, thus permitting considerably thicker slabs to be fed into the mill. This measure makes it possible to increase the ratio between the thickness of the slab entering the mill at It) and the thickness of the strip leaving the mill at 11, whereby the precession achieved between the points C and D is of still greater magnitude and in most cases permits a reduction of the potential energy stored in the spindle and the drive mechanism at the end ofeach rolling cycle to within tolerable limits.

In some cases, particularly in planetary mills of very large proportions, the above described means for extending the precession of the work rolls ahead of their geometric angular positions are not sufficient. It is possible, however, to insert an independent element in the driving means for positively controlling the angular position so as to eliminate considerably the dangerous shocks to the driving mechanism. Such an arrangement is shown in FIGS. 5 and 6. The driving motor 19 drives the planetary mill 22 through a planetary reduction gear 23, a pinion stand and flexible spindles 9, 9. In the planetary gear 23 (as best seen in FIG. 6), the motor 19 is keyed to the central or sun pinion 24 and the lower pinion of the pinion stand 20 is keyed to the satellite carrier 25 of the planetary gear 23. Very precise and minute alterations of the angular position of the work rolls 2, 2, 3, 3' at their point of exit from the working cycle are produced by an angular movement of the ring gear 26 of the planetary reduction gear 23. For this purpose the housing of the ring gear 26 is provided with a lever 27 and a roller 28 is mounted at the extremity of the lever 27. The roller 28 rides over a cam 29 which rotates in a fixed angular relation to the rotation of the planetary cages by any conventional driving means (not shown). By providing the cam 29 with a suitable profile, the required alteration of the angular position of the drive ends of the mill spindles can be achieved to coincide with a definite position of the work rolls 2, 2, 3, 3, particularly the point at which the work rolls leave contact with the workpiece, to insure that the elastically stored energy is relieved at this point.

While the mill thus far described comprises planetary assemblies with two diametrically opposed work rolls, modifications are possible, and one of these is shown in FIG. 7 where each backing roll is provided with three work rolls. The backing rolls have a diameter twice that of the work rolls. Since with a 2:1 ratio of diameters, the gear ratio for driving the respective rolls is 3:l, it will be observed that only one profiled relief of the backing rolls is required to assure entry and exit of all three work rolls.

FIGS. 8 and 9 show a further modification wherein each backing roll has four work rolls, and the backing roll is four times the diameter of the working roll. With a 4:1 ratio of diameters, a ratio between speeds of the backing rolls and the cages 7, of 25:1 is required. This configuration makes it possible to obtain twice the production obtainable by a mill according to FIGS. land 2 without too great a sacrifice in the rigidity of the cages, the importance ofwhich is explained below.

The above-noted ratios are given as examples of possible diameter and speed combinations. In some cases, for example, for softer metals it may be advantageous to use even larger work rolls in relation to the backing rolls, such as work rolls of the same diameter as the backing rolls. With such an arrangement, it is possible to use six work rolls with three profiles on the backing roll, or four work rolls in each cage with only one profile on the backing roll. In the latter case, the other work rolls coact with the backing roll in supporting that particular work roll, which is in the roll bite, against deflection.

A mill according to the present invention having composite cages requires that the right and left cages be rigidly joined together to form one body which is rigid as to torsional as well as to bending stresses. Torsional rigidity is essential since driving torque can be applied conveniently at one end only, while the cage applies the drive to the

work roll chocks

7a, 7a, which must stay parallel.

The cage 7 is a tubular body, the diameter of which is usually somewhat reduced at the two ends where the

main chock bearings

4, 5 are located. In the embodiment of FIGS. 1 and 2, the cage is split for assembly reasons and the two halves are tightly held together by the bearings 30 and spacers 31 which are shrunk into them.

In the embodiment of FIGS. 8 and 9, each cage is a onepiece body. The assembly of the cage over the backing roll 1 is made possible by shrinking bushings 32 of bronze or other suitable material upon the backing roll necks so that the outer periphery thereof acts as a bearing surface.

The provision of rigid cages 7 as described herein makes possible other benefits which could not be foreseen. l. The rigid cages can be used as rotary housings on which to mount small edge retaining rolls 33, 33 which contact the upper and lower edge corners of the workpiece respectively. One of the big problems connected with-planetary mills is side spreading of the workpiece, which finally results in a strip with edge cracks and reduced gauge in the edge area. The provision of the edge retaining rolls 33, 33, which press upon the protruding edge corners after the passage of each work roll 2, effectively stops the progress of side spreading, so that even materials having little ductility can be rolled successfully from a slab down to strip gauges without sidecracks.

Since these edge retaining rolls 33 and 33' protrude beyond the plane of symmetry of the mill, they are disposed in such manner that the rolls 33 and the rolls 33 never meet. Corresponding to the positions of the rolls 33 there are provided the cavities 37 in the cage 7 and the cavities 37 in the cage 7, whereby interference is avoided (FIG. 1). Adjustment for strip width is provided, as best seen in FIG. 4, by the eccentric trunnion 39 upon which the roll 33 is mounted; and the angular position is maintained by engaging a pin 40 in a suitable slot in the flange 38. Since this adjustment has quite a narrow range, several pairs of recesses 37 are provided for the flanges 38 to take care of the whole range of widths to be rolled on a given mill. 2. The usefulness of the mill can be extended in that the cages 7 can be stopped and their drive disconnected and the whole rnill can then be used as a four-high mill, where the work rolls 2 and 3 are both driven, and supported by the backing rolls ll, 1. When used in this manner as a four-high mill, the

rolls

2, 3 may have a rough finish and the other rolls 2', 3' a fine finish for use in a finishing pass or passes. To switch from a roughing to a finishing pass it is only necessary to turn the cages 7, 7'

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of reducing vibrations in the operation of a planetary mill having rotating driven backing rolls and work rolls mounted in cages, which includes the step of intermittently varying the angular velocity of the driving means for said backing rolls in timed relation to the working cycle of the said work rolls, so as to reduce stresses in said driving means near the end of each rolling cycle.

2. The method of claim 1, wherein said variations in angular velocity are produced by causing said work rolls to deviate from their circular paths and to move parallel to each other during the final portion of the working cycle.

3. The method according to claim 2, wherein the deviation is produced by driving the said roll cages at such a speed ratio with respect to the backing rolls that each work roll, during its operating cycle, is backed by the same are of the circumference of the backing roll, and profiling said are to produce the required deviation.

4. The method according to claim 3, wherein said work rolls are also caused to deviate from their circular paths near their point of engagement with the workpiece, to reduce the angle at which the work rolls meet the workpiece.

5. The method according to claim 1, wherein said variation in angular velocity is produced by retarding the driving ends of the spindles during said last portion of the working cycle.

6. The method according to claim 5, wherein said variation is produced by driving said backing rolls through a planetary reduction gear having a free element to oscillate in synchronism with the working cycles of the mill, so as further to relieve spindle stresses by retarding the driving ends of said spindles in relation to their driven ends near the end of each working cycle.

7. A planetary rolling mill having a pair of backing rolls, and a number of work rolls symmetrically associated with each backing roll, the number of work rolls associated with each backing roll being such that a given pair of work rolls leaves contact with the strip before a succeeding pair engages the strip, said work rolls being mounted in roll cages, said roll cages being geared to the respective rotating, driven backing rolls in such a ratio that each work roll, during its working cycle, is backed by the same angular portion of the circumference of the backing roll, said angular portion of the backing roll circumference being profiled to produce a deviation ofthe working roll from a true circular path during its working cycle.

8. A mill according to claim 7, wherein the ratio of the diameters of the backing roll to the work rolls is 2:1 and the gearing is such as to produce a ratio of the speeds of the backing roll to the work roll cage of 3:1, and wherein each cage is provided with two work rolls and each backing roll is provided with two profiled portions.

9. A mill according to claim 7, wherein the ratio of the diameters of the backing roll to the work rolls is 2:1 and the gearing is such as to produce a ratio of the speeds of the backing roll to the work roll cage of 3:1, and wherein each cage is provided with one work roll and each backing roll is provided with one profiled portion.

10. A mill according to claim 7, wherein the ratio of the diameters of the backing roll to the work rolls is 4:1 and the gearing is such as to produce a ratio of the speeds of the backing roll to the work roll cage of 2.511, and having two work rolls in each cage, and four profiled portions on each backing roll.

11. A mill according to claim 7, wherein the ratio of the diameters of the backing roll to the work rolls is 4:1 and the gearing is such as to produce a ratio of the speeds of the backing rolls to the work roll cage of 2.5:1, and having four work rolls in each cage, and eight profiled portions on each backing roll.

12. A mill according to claim 7, wherein the backing rolls and work rolls are of equal diameter, and the gearing is such as to produce a ratio ofspeeds of the backing roll to the work roll cage of 4:1, and having siir work rolls in each cage and three profiled portions on each backing roll.

13. A mill according to claim 7, wherein the backing rolls and work rolls are of equal diameter, and the gearing is such as to produce a ratio of speeds of the backing roll to the work roll cage of 4: l, and having four work rolls in each cage and one profiled portion on each backing roll,

14. A mill according to claim 7, in which edge retaining rollers are mounted on the periphery of the roll cages, each contacting one corner of the roughly rectangular section of the workpiece in the roll bite.

Claims

3. The method according to claim 2, wherein the deviation is produced by driving the said roll cages at such a speed ratio with respect to the backing rolls that each work roll, during its operating cycle, is backed by the same arc of the circumference of the backing roll, and profiling said arc to produce the required deviation.

7. A planetary rolling mill having a pair of backing rolls, and a number of work rolls symmetrically associated with each backing roll, the number of work rolls associated with each backing roll being such that a given pair of work rolls leaves contact with the strip before a succeeding pair engages the strip, said work rolls being mounted in roll cages, said roll cages being geared to the respective rotating, driven backing rolls in such a ratio that each work roll, during its working cycle, is backed by the same angular portion of the circumference of the backing roll, said angular portion of the backing roll circumference being profiled to produce a deviation of the working roll from a true circular path during its working cycle.

10. A mill according to claim 7, wherein the ratio of the diameters of the backing roll to the work rolls is 4:1 and the gearing is such as to produce a ratio of the speeds of the backing roll to the work roll cage of 2.5:1, and having two work rolls in each cage, and four profiled portions on each backing roll.

12. A mill according to claim 7, wherein the backing rolls and work rolls are of equal diameter, and the gearing is such as to produce a ratio of speeds of the backing roll to the work roll cage of 4:1, and having six work rolls in each cage and three profiled portions on each backing roll.

13. A mill according to claim 7, wherein the backing rolls and work rolls are of equal diameter, and the gearing is such as to produce a ratio of speeds of the backing roll to the work roll cage of 4:1, and having four work rolls in each cage and one profiled portion on each backing roll.