US2476254A - Method for working sheet metal - Google Patents

Description

July 12, 1949. -J. WINLOCK METHOD FOR WORKING SHEET METAL Filed Jan. 25, 1946 INVENTOR JOSEPH WINLOCK BY E f- ATTORNEY Patented July 12, 1949 METHOD FOR WORKING SHEET METAL Joseph Winlock, Philadel The Budd Company, P

phia, Pa., assignor to hiladclphia, Pa., a corporation of Pennsylvania Application January 25, 1946, Serial No. 643,247

2 Claims. 1 The invention relates to a method for cold working sheet metal and, more particularly, to the cold working of ferrous sheet metal.

The main object of the invention is to overcome a serious shortcoming of existing methods employed in preparing sheet metal for a subsequent cold forming operation, such as die forming, so as to avoid socalled stretcher strains or Liiders lines. Examples of the known methods used for the aforesaid purpose and for inducing the state of cold plasticity are disclosed in U. S. Patents Nos. 1,649,704; 1,649,705 and 1,649,706 issued November 15, 1927, to George L. Kelley and the present inventor, to said Kelley, and to said Kelley and C. L. Eksergian, respectively.

While the methods of the indicated type proved highly effective for certain types of sheet steel and were adopted practically universally by the industry, they show an unexpected shortcoming which renders them relatively ineffective in the cold working of the modern fine-grained sheet steels now generally in use and produced in what are commonly known in the industry as strip mills.

The method of producing this fine-grained stock from the strip mills is to roll the stock to sheet form hot and of a gauge very much greater than the ultimate gauge desired, to follow the hot strip rolling with reduction of the gauge on the way down to its ultimate gauge in three or four high mills operating upon the cold strip, and thereafter to subject the thus extremely highly cold worked strip to an annealing treatment at approximately 1200 F. as a result of which the extremely fine-grained-structure is produced.

The shortcoming of the aforementioned methods if applied to such fine-grained sheet material, resides in the fact that the sheets instead of flowing harmoniously and with symmetry over, that is, instead of hugging the so-called breaker rolls, (those through which the high degree of cold working is achieved) become creased transversely of the sheet at frequent intervals. These creases are known to the trade as coil breaks. The ensuing flattening operation of the remainder of the rolls in the leveler fails to, remove these creases and the surfaces of the products, as for example, high-grade automobile body panels stamped from such sheets, irremovably bear the configuration of these creases.

No ensuing flattening or straightening operation by one or more passages between ordinary leveler rolls is able to remove these creases which will show on the surfaces of the final product, as for example, high-grade automobile body panels stamped from such sheets, and they can be removed only by prohibitively expensive finishing operations. It is not clear why these creases occur in the annealed-last material whereas they do not occur, at least not frequently. in the previously used material which received in the mills a slight cold pass through a rolling mill following the annealing. On the other hand, it is obvious that the slight cold pass is objectionable inasmuch as it detracts from the ductility available for the subsequent forming of the sheet into the final desired shape.

Several attempts have been made to overcome the outlined disadvantages by forcing the sheet to hug the surface of the so-called breaker rolls. The known proposals included continuous webs or belts guiding between them the sheet to be treated or means exerting a tension on the sheet while passing over the breaker rolls. Such attempts have proved either ineffective or impractical for other reasons, so that they had to be abandoned.

According to the invention, the problem outlined hereinbefore is solved by methods which are extremely simple.

The invention resides in the fact that instead of at once subjecting a sheet of the type liable to develop creases to the severe bending by means of the breaker rolls, it is first subjected to a gentle back and forth bending prior to the passage over the breaker rolls. The back and forth bending, though the reasons of its effectiveness are not altogether clear, might be considered as a kind of softening up operation before subjecting the sheet to the severe bending caused by the breaker rolls.

In certain instances it was even found necessary to subject a sheet to the gentle back and forth movement in directions at about to each other prior to the passage over the breaker rolls. This last-named experience appears somewhat analogous to the sometimes encountered necessity of passing a sheet in two directions over the breaker rolls so as to avoid stretcher strains and endow the sheet with the cold plasticity.

The method according to the invention may be carried out by sending a sheet through one ordinary straightening roller leveler which bends the sheet slightly back and forth and straightens it, or it may be carried out on a machine according to the invention in which the breaker roll is preceded by a set of rolls which give this gentle back and forth motion.

The machine employed according to my invention comprises a standard roller leveler, e. g., of the type disclosed in the aforesaid patents, bearing in its forefront in position to feed into its breaker rolls a set of rolls of the type of ordinary flattening rolls which may be arranged in reverse, to wit, the rolls at the feeding-in end doing comparatively little and those: at the feeding-out end adjoining the breaker rolls doing more bending even though still less than the bending done on the sheet by the breaker rolls.

A number of different arrangements and mechanisms for control enter into various possible modifications of the invention, but in the accompanying drawing but one form of the invention is illustrated as being sufficient for the instruction of those skilled in the art, and to constitute foundation for the award of claims of the breadth which are sought.

In the drawing,

Figure 1 is a diagrammatic plan view of a machine built in accordance with the invention and adapted to carry out the inventive method;

Figure 2 is a diagrammatic section through the rollers of the main part of the machine shown in Figure 1, the section being taken substantially along line 2-2 of Figure 1;

Figure 3 is a diagrammatic section taken along line 3-3 of Figure 1 and illustrating diagrammatically in elevation the driving gear for the rollers shown in Figure 4; and

Figure 4 is a fragmentary section along line l4 of Figure 3 on a larger scale and illustrating a free-wheel drive.

Referring now to this diagrammatical drawing, the rolls comprehended within the elongated bracket I delineate the rolls of a standard flattening roller leveler arranged in series with a gripping pair of rolls I i, a breaker roll i2 for achieving high degrees of cold plasticity, drawing rolls i3. and flattening rolls comprehended within the bracket M, the function of the latter being principally to take out of the sheet the heavy curvature which results from the high degree of bending effected by the breaker roll in carrying out the high degree of cold work upon the sheet.

As is well known and explained in the patents referred to hereinbefore, the breaker roll 12 soon after the sheet traverses the space between the entering and the gripping pairs of rolls I i and i3 is projected upwardly to achieve the initial bend, and thereafter as the roll rotates in the direction of the arrows the main body of the sheet is progressively carried over the top of the breaker roll and is progressively subjected to the same degree of bending.

It is over the top of this breaker roll l2 that the difficulties with the fine-grained finally annealed stock with the pre-cold working is encountered. The sheet instead of taking the bend uniformly over its length, that is, instead of hugging the surface of the break roll, is creased at frequent intervals, a fraction each of the circumference of the breaker roll l2.

The set of rolls comprehended by the bracket I0 is the setof reversed ordinary flattening roller leveler rolls which, according to the invention, are combined with the rolls of the standard roller leveler II to [4 of the breaker roll type. The ordinary roller leveler used principally for flattening sheet stock does not comprehend a breaker roll such as [2.

As will be clearly seen by the increasing proximity of the axes of the rolls of the group In to the central plane of the machine, the arrangement of this set of rolls which is established in front of the group l2, I3 is in reverse to those of the group I 4 which in the standard roller leveler follow the breaker roll. In other words, the amount of reverse bending and consequently the amount of cold working increases from the entering end of the series toward the leaving end in the direction of the arrows instead of decreasing as in the instance of the series M. A greater or lesser number of rolls within group I0 may be used, depending on the amount of work desired to be done.

From the foregoing discussion, it will be evident that the break roller treatment of the roller I2, by which the desired cold plasticity is imparted to the blank, is preceded by treatment upon the group of rollers I0. and that this pre-treatment of the blanks by the'rollers l0 imparts to them a condition in which the break roller treatment can be effected without creating the undesired transverse creases heretofore encountered when a blank of the annealed-last type was subjected to the break roller cold plasticity treatment.

The pair of rolls [3 in advance of the group M is a pair of feeding-in rollers of the type commonly used in feeding roller levelers.

The lower rolls of the groups l0 and I4 and the upper and lower rolls H and 13 are driven by an electric motor i5 through a reduction gear 16. a shaft ll carrying a pair of gears i8 and I9, and a train of gears presently to be described.

The gear 18 is a free-wheel drive having a hub 20 keyed to the shaft i'l, an outer toothed member 2| and intermediate members. such as in the form of small rolls 22, which are wedged between the members 20 and 2| if the former is driven by the shaft I! in the direction of the arrow 23 but which will disrupt the driving connection between the members 20 and 2| if the member 21 is driven in the same direction, that is, in the direction of the arrow 24, at an angular speed greater than that of shaft [1 with its body 20.

The toothed ortion 2! of the gear l8 engages a pinion 25 keyed to the upper roll H and in engagement with another pinion 26 keyed to the lower roll II. Connected with the pinion 26 is a bevel gear 21 meshing with a bevel gear 28 keyed to a shaft 29. The shaft 29 is supported in bearings 30 of the machinegframe and carries a number of bevel gears 3! which mesh withcorresponding bevel gears 32 keyed to the respective lower rolls of the group ill.

The rolls i3 and the lower rolls of the group N are driven in a similar manner by the gear l9, pinions 33, pairs of bevel gears 34, 35 and a shaft 36 supported in bearings 31. It will be noted that the gear i9 is keyed to the shaft l1 and is not formed as a free wheel.

The sheets to be treated are fed into the machine so far described from the location 31' in the direction of the arrows 38 between the upper and the lower rolls while the break roll I2 is in the lowered position illustrated by dot-and-dash lines in Figure 2, While passing between the rolls of the group Ill, the sheet illustrated at 39 is gently bent back and forth. As soon as the leading edge of the sheet enters between the rolls l3, the break roll I2 is automatically pushed upward by means well known in the art. This upward movement causes the loop 40 to be formed in the sheet.

It is obvious that the loop cannot be formed if the rolls II and I3 firmly hold the sheet and are both positively driven with the same speed, or that the sheet would have to slip relative to the rolls in advance and/or in back or the breaker roll l2, which would cause scratches. The free wheel I8 described hereinbefore permits, however, the sheet to be drawn in between the upper and lower rolls In and II at a speed greater than the speed with which all the rolls are driven from the motor IS.

The action of the break roll and the effect of the subsequent flattening rolls ll need not be described because in this respect the new machine does not differ from the customary machines and procedures, as for instance disclosed in the patents cited hereinbefore.

In regard to the driving gear, it is emphasized that the illustration of the same is purely diagrammatic and in the nature of an example;

Any other suitable drive may be employed. It is not important whether the upper or the lower rolls or both are driven. The illustration and the arrangement of the free wheel is purely diagrammatic and may be substituted by any other well known free wheel device. Moreover, other means may be employed for permitting the formation of the loop 40 during the upward movement of the break roll I2.

If it is desired to give the sheets two flat passes, that is, treatments on a flattening roller leveler, at right angles to each other preceding the passage of the sheets over the break roll, then an ordinary flattening roller leveler diagrammatically illustrated-at II in Figure 1 may be employed and the direction of the passage of the sheets therethrough as indicated by the arrows 42, may be arranged at right angles to the direction 38 in which the sheets pass through the roller leveler according to the invention as described hereinbefore. Of course, in such case the length of the sheetcannot surpass the effective width of the leveler 4|.

The invention is not restricted to the specifically illustrated and described embodiment but is liable. to such modifications and adaptations as comprehended by the language and the spirit of the attached claims;

What is claimed is:

1. In the treatment of fine-grained annealedlast sheet steel to impart thereto cold plasticity and prevent occurrence of stretcher strains upon subsequent stamping, while avoiding formation of transverse creases, the process comprising pretreating the sheet by gentle back and forth bending action to impant to said sheet a condition in which it may be intensively bent over a breaker roll without formation of objectionable creases incident to such bending, and thereafter subjecting said pretreated sheet by passage thereof around a portion of such breaker roll to bending action sufliciently intense to impart the desired cold plasticity thereto, and finally straightening the pretreated and intensively worked sheet.

2. In the treatment of fine-grained annealedlast sheet steel to impant thereto cold plasticity and prevent occurrence of stretcher strains upon subsequent stamping, while avoiding formation of transverse creases, the process comprising pretreating the sheet by gentle back and forth bending action by passage of said sheet successively over roller portions offset in opposite directions to impart to said sheet a condition in which it may be intensively bent over a breaker roll without formation of objectionable creases incident to such bending, and thereafter subjecting said pretreated sheet to intensive bending action by passage thereof around a portion of such last mentioned breaker roll to impart the desired cold plasticity thereto, and thereafter lpasslng the pretreated and intensively worked sheet across portions of further rollers providing gentle back and forth bending action and finally through rollers spaced to provide a straightening passage for the sheet.

JOSEPH WINLOCK.

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

UNITED STATES PATENTS

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