US760921A - Drawing-press. - Google Patents

Description

No. 760,921. PATENTED MAY 24,1904.

J..J. RIGBY. DRAWING PRESS.

APPLICATION FILED .TLAN. 29, 1902.

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INVENTOR:

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No. 760,921. PATENTED MAY 24, 1904.

J. J. RIGBY.

DRAWING PRESS.

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UNITED STATES v Patented May 24, 1904.

PATENT OEEIcE.

JOHN J. RFGBY, OF BROOKLYN, NEW YORK, ASSIGNOR TO E. W. BLISS COMPANY, OF BROOKLYN, NEW YORK, A CORPORATION OF WEST VIRGINIA.

DRAWING-PRESS.

SPECIFICATION forming part of Letters Patent No. 760,921, dated May 24, 1904.

Application filed January 29, 1902. Serial No. 91,731. (No model.)

To all whom, it may concern:

Be it known that I, JOHN J. RIGBY, a citizen of the United States, residing in the borough of Brooklyn, county of Kings, city and State of New York, have invented certain new and useful Improvements in Drawing-Presses, of which the following is a specification.

This invention relates to presses for drawing sheet metal into cup form. In such presses it is customary to stamp out a disk or blank of suitable shape from a sheet of metal, as tinned iron or steel, and by gripping the edge or marginal portion between an annular die and blank-holder with a graduated pressure to force down the central portion by means of aplunger or punch, thereby forcing the metal into dished or cupped form while drawing its marginal portion out from between the blank holding or gripping dies. For forming any but shallow cups it is necessary to repeat this operation two or more times by successively-acting dies, drawing the blank each time to a smaller diameter and to a greater depth. This drawing operation has the efiect of stiffening the metal, rendering it brittle and liable to crack, so that afteracertain number of drawing operations it is necessary to anneal the metal before it can be further drawn. Such annealing is admissible with certain metalsas gold, silver, copper, and

brass-or with iron or steel if not coated or tinned; but it is not possible with so-called tin or tinned iron or steel-plate, be-

cause the annealing requires a temperature so high as to fuse off the coating of tin. For this reason in drawing cups from tinned plate such depth as can be produced ordinarily by of practicability, and all efforts to draw cups beyond a certain depth have failed. The extreme depth heretofore attainable cannot be exactly stated; but the limit of practicable depth has rarely exceeded two-thirds the diameter of the cup. In most arts wherein such sibility heretofore of drawing such deep cups or cans it has been necessary to construct them with seamed joints of a body consisting of a sheet of tin bent into tubular form, with its edges united by a side seam to form a tube and a bottom stamped out of a sheet of tin and seamed to the lower end of such tube, these seams being soldered wherever the can is to contain liquids. Such seamed cans are necessarily produced by a complicated series of operations, requiring several machines and much handling, so that the product is expensive, and they have the disadvantage of presenting an unsightly seam along one side and a seam around the bottom. The desirability of producing seamless cans by a drawing operation has long been obvious.

My present invention provides dies for a drawing-press whereby it is rendered feasible to draw the cups or cans toa much greater depth than heretofore and to such depth as to serve many of the purposes for which seamed cans have heretofore had to be supplied.

' My invention is also applicable with advantage for drawing cups or cans of other metal than tinned iron or steel.

The nature and novel features of my invention will be made apparent in the course of the following description.

Figure 1 of the accompanying drawings is a section of a sheet or plate of metal from which the blank is to be struck out. Fig. 2 is a section thereof, showing the usual first operation of stamping out the blank or disk. Fig. 3 is a diametrical section of the blank after undergoing the firstdrawing operationas heretofore practiced. Fig. 4 is a similar section after undergoing the second drawing opera- .tion, and Fig. 5 is a similar section of the product of the third drawing operation. Fig. 6 is a diametrical section of the dies constructed according to my invention adapted for receiving the blank shown in Fig. 3 and drawing it into that shown in Fig. 4:. Fig. 7 is a similar section of dies constructed according to my invention for receiving the blank shown in Fig. 4 and drawing it into that shown in Fig. 5. Fig. 8 is an ideal or exaggerated section illustrating the drawing operation, showing the active elements of the dies, and showing the sheet metal being operated upon. Fig. 9 is a similar section showing a modified arrangement of dies. Figs. 10 and 11 are similar sections showing other modified arrangements. I

In the ordinary drawing operation a sheet or plate of suitable metal, as tin, (tinned iron or steel,) a, Fig. 1, is placed in a combined stamping and drawing press, whereby at one stroke a blank, usually a circular disk, is cut out from the sheet, as shown at Z) in Fig. 2, and this blank is then drawn into a shallow cup, as shown at 6 in Fig. 3. If it is required to be of no greater depth, its bottom may be made square or with a slightly-rounded corner; but if it is to be subjected toa further drawing operation it is customary to form it with a conical portion 0 between the sides and bottom. At the next drawing operation this blank I) is put in a press having blank-holding dies which engage the conical portion 0, while a plunger or punch descends through such blank-holder and forces down the bottom of the blank, drawing the side portions thereof through the conical space between the blank-holding surfaces, and thereby reducing the blank to a cup of substantially the proportions shown in Fig. 4, the cup being of smaller diameter and of greater depth than the previous blank. In Fig. 4 I have shown the blank 5 as having a conical portion 0 between its sides and bottom. It will be understood that in ordinary drawing the product of the last drawing operation has a substantially square or slightly-rounded corner or any other shape that may be desired within the limits of practicability and that ordinarily only the intermediate or preceding blanks have the conical portion cor c. Heretofore in drawing tin a cup of substantially the depth of that shown in Fig. 4 represents about the extreme of practicability. By my invention, however, I enable much deeper cups to be made such, for example, as that shown in Fig. 5, where the cup or finished product of the drawing operation is designated at I)". r

In an ordinary drawing-press the blank is gripped between annular blank-holding surfaces, which for the first operation are flat and for the succeeding operations are ordinarily conical for fitting the cones 0 or 0. Ordinarily the lower blank-holding surface is formed on a ring or die, which ordinarily is supported on the bed of the press, while the upper blank-holding surface is formed on a blankholder, which ordinarily is movable vertically, being carried upon the movable head or platen of the press. Essentially either the blank-holding die or the blank-holder may be movable the one toward and from the other, or both may be movable. It is practically necessary that means he provided for pressing them together adJustably to grip the blank with a graduated pressure, so as to hold it just firmly enough to permit it to be drawn through between them, their pinch upon the blank being not so great as to tear or break the sheet metal nor so slight as to permit the sheet metal to wrinkle or corrugate while being drawn through between them.

In the ordinary drawing operation the middle portion of the blank is forced down by the male die or plunger (commonly called the punch through an annular female die, (commonly called the reducing-die) which is formed ordinarily on its upper side with the blank-holding surface, and on its inner face it conforms to the plunger and approaches it so closely as to allow room between them only for the thickness of the metal being drawn, so that the drawing operation carries the metal into a diameter determined interiorly by the plunger and exteriorly by the reducing-die. Ordinarily the intervening space is of a thickness closely approximating that of the sheet metal being operated on, so that as the blank tends to thicken or corrugate by being drawn from a larger to a smaller circumference it is elongated sufficiently to preserve approximately its original or normal thickness.

The usual cutting and drawing dies which perform the operations indicated in Figs. 2 and 3 being well understood, I illustrate only the dies used for drawing the blank to the forms shown, respectively, in Figs. 4 and 5. Referring to Figs. (Sand 7 and also in part to Figs. 8 and 9, let A designate the bed or fixed die-support of the press and let B designate a portion of the movable head or platen thereof, while C designates the vertically-reciprocating spindle carrying the male die or plunger. It is well understood that in drawing-presses the bed A is stationary, the head B has a limited movement sufficient to bring the blank-holding surfaces together, and the spindle G has a greater vertical movement sufiicient to carry the plunger down through the dies. These parts being Well understood require no special illustration. On the bed A is mounted the usual die-block D, in which is carried an annular die E, resembling the ordinary blank holding and reducing die. In the same block and lower down is placed a secondary die F, which I call the burnishing-die. Beneath the latter is the usual stripper-ring G, which is a split ring pressed inwardly by springs d, so that when the blank is forced down through it it contracts and hugs the plunger just above the blank, so that on the upstroke of the plunger the blank is stripped off therefrom and caused to drop through the central opening a in the bed.

H is the plunger or punch, having its exterior conformed to the interior of the blank or cup to be drawn and carried in the usual manner on the spindle G.

I is the blank-holder, carried, as usual, by

the headB and having its lower end formed with a blank-holding surface, which in these perceptible in Figs. 6 and 7. Instead of drawing the blank at once tothe requisite thinness this die is large enough on its inner face to leave the metal of a somewhat greater thickness than it should have in the finished product, and the metal is subsequently reduced by the secondary die F, which I call the burnishing-die, and the inner faceof which has a very slightly smaller diameter than that of the reducing-die E. The diiference between these two dies is shown to a greatly exaggerated scale in Fig. 8. In operation the blank as it is drawn from the larger diameter 10 to the smaller diameter 11 is thickened, notwithstanding the elongating action of the dies, this thickening at 11 being much exaggerated in Fig. 8. Subsequently as the blank is drawn through the die F, which more closely approaches the plunger, the metal is reduced in thickness, as indicated, so that the portion 12 is brought down to the required gage, which ordinarily will be the same as that of the original metal sheet a. The burnishing-die F is mounted loosely in a cavity in the block D, this looseness being shown to a somewhat exaggerated extent in Figs. 6 and 7, a free space being left above and surrounding the die F, so that it is capable of slight vertical and horizontal movements. The die F is made of comparatively thin metal, which I believe in practice permits it to dish or bend slightly as the heavy pressure of the punch is received by it, this movement being permitted by the free space above the die. The effect of this is apparently to relieve the blank of a portion of the strain upon it, perhaps by a slight increase in the working diameter of the opening of the die, although I am unable to state positively that this is the fact. I find, however, that it is practically essential that the die be made of comparatively thin metal and that it be unconfined upon its upper face either by a retaining-wall or by the upper die. In the construction shown I provide a heavy wall or flange J, which serves to rigidly support the die E, so that the heavy pressure which is brought to bear upon this die shall not be transmitted to the burnishing-die. The latter, as before stated, is so mounted in its cavity that it is also capable of a slight horizontal movement therein. This free horizontal play has the effect of enabling the die F to center itself so as to embrace the-plunger with uniform pressure on all sides, so that with homogeneous metal it automatically assumes a position exactly concentric with that of' the 7 plunger, while in the event of a slight inequality in the metal of the blank this die is enabled to shift its position so as to compensate therefor and distribute the pressure or resistance equally around its entire circumference.

Practical experience with dies constructed according to my invention, as thus described,

has demonstrated that cups or integral cans may be successfully drawn of a height or diameter, but also brings it down to the required thinness oftwo dies separated by a suitable interval, whereof the first, which I call the reducing-die, serves merely to reduce the diameter of the blank without attempting to bring the metal to the requisite thinness, whereas the second, which I call the burnishing-die, has the sole function of diminishing the thickness of the metal. The remarkable result attained by my invention may be due to some extent to an annealing or partial annealing effect, since the friction and molecular disturbance due to the reducing and burnishing of the blank heats it to such extent that when it drops out beneath the pressthe blank is much too hot for handling.

It is found to be practically essential that the reducing and burnishing dies shall act upon the blank in rapid succession and during one operation of the drawing-press. It has been attempted to reduce the blank by one operation by forcing it through a die like the die E and afterward in another press or by a separate operation to reduce the thickness of the blank by forcing it through a burnishing-die like the die F; but this has resulted in the cracking of the metal of the blank longitudinally after the reducing and before the burnishing operation, owing apparently to the release of the metal from strain or, perhaps, to permitting it to cool before forcing it through the burnishing-die. On the other hand, it has been attempted and is the customary practice in drawing tin to make the one die perform the functions of my reducing-die E and burnishing-die F by forming its inner face to so .closely conform to the plunger as to at once reduce the metal to the final gage. This operates successfully with short or shallow blanks; but in attempting to draw deeper cups or cans than those heretofore successfully produced it is found that the blank almost invariably breaks either close to the bottom or around the side and tion not only reduces the blank to a smaller K IIO approximately parallel to the bottom, so that the metal frequently parts before being drawn through the die, or if it is successfully drawn through is commonly found to be cracked or ruptured, so as to render it worthless. In my invention by separating these functions and performing them by dies spaced somewhat apart the strain upon the metal, which with a single die would break it, is distributed so that the descending punch first draws the blank down through the larger die E and after having partially drawn out the blank then commences to force it through the smaller die F. Thus the shock or initial blow is diminished and distributed over two points in the stroke of the plunger, thereby reducing the liability to fracture at or near the bend where the bottom joins the sides of the blank, while toward the lower portion of the stroke, Where the blank offers the greater resistance to reduction by reason of the tendency to thicken toward its upper portion, this portion of the blank is relieved of. the strain of final reduction of thickness until it is drawn down into the lower die F. It has also been attempted to employ two successive rigidlymounted dies having their active faces spaced somewhat apart, so that the upper one shall reduce the blank to the desired diameter, and the lower one shall then reduce it in thickness; but this has resulted with deep cups in the rupturing of the metal. The mounting of the lower or burnishing die loosely in the manner set forth herein has successfully solved the problem of drawing such deep cups of tin-plate.

.The exact separation of the dies E and F cannot be definitely stated, as it would probably vary for blanks of different sizes or thickness. The proportions shown in Figs. 6 and 7 have operated successfully for producing cups of two and one-half inches to three inches diameter and of a length or depth somewhat in excess of their diameter. I prefer to separate the dies as widely as the stroke of the press will allow. For a press of long stroke a separation as great as that shown'in Fig. 9 would probably be advantageous. In this figure the die F is located so low down that it engages the blank just before the upper margin thereof is pulled through the blank-holding surfaces. It is probably advantageous to hold the blank in the blank-holder or at least between the plunger and the inner margin of 5 5= the reducing-die E until it begins to enter within the die F, although this is not certainly necessary to success. I contemplate adopting the relative spacing shown in Fig. 10, where the blank enters the die F after it has been reduced by the die E and preferably just before its margin passes out from within the latter. With a smaller blanksuch, for example, that its top would come to the point 13 in this figurethe blank will have passed entirely out from the die E before entering the die F. I believe it to be essential that the blank shall be held on theplunger so as to be subjected during the one stroke to the action of the respective dies in order that the blank while still heated from the reducing operation may be subjected to the action of the burnishing-die.

My invention may by a further development be applied in connection with a greater number of dies than the two dies E and F. For example, I have indicated in Fig. 11 the use of three dies, of which the upper one, E, is the reducing-die. a partial diminution in thickness of the metal, while the third, F throws it to the final thickness or gage. Asan example of proportions that may be followed I would state that in practice with dies E and F, as in Figs. 6, 7, and 8, I have made the die E with an internal diameter of .006 inch larger than that of the die F. With the arrangement shown in Fig. ll the reducing-die E may be of the same in- The next, F, accomplishes ternal diameter as before, while the successive dies F F may each be, for example, .003 inch smaller, or in Fig. 11 the die E may be of larger internal diameter than that shown in Figs. 6, 7 and 8, being, for example, just'suffieiently smaller to prevent the metal crimping or corrugating in drawing through it, in which case the die F may be about .006 inch smaller and the die F .006 still smaller. These proportions are given only by way of example and not as limiting me to anydefinite proportions.

Ordinarily the reducing-die E is fixedly mounted in the-block D,while the burnishingdie F is freely mounted as described, so as to be able to automatically center itself or accommodate itself to varying thicknesses of metal being drawn. In some cases, however, it may be desirable to make the reducing-die E also free or self-adjusting. This is shown to an exaggerated extent in Fig. 7. To thus mount the die E is practically advantageous, although it has not the same degree of advantage as in the case of the burnishing-die F.

What I claim is 1. In a press for drawing metal of low duetility, the combination of a plunger, and an annular die, the latter mounted loosely, so as to be capable of independent vertical and horizontal movements.

2. In a press for drawing metal of low duetility, the combination of a plunger, a reducing-die and a burnishing-die, the latter mountformed of thin metal so as to be capable of slight distortion during the drawing operation, with means for mounting said die having a space above the die, whereby the latter is unconfined upon its upper face, so as to permit such distortion.

5. In a drawing-press, the combination of a plunger and an annular die, the latter being formed of thin metal so as to be capable of slight distortion during the drawing operation, with means for mounting said die having a space above and surrounding said die, so as to permit vertical and horizontal movements of the latter.

6. In a drawing-press, the combination of a plunger, a reducing-die, aburnishing-die, and

JOHN J. RIGBY.

Witnesses:

OTTO J. BEYER, W. E. MURDOGK.

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