US2395651A

US2395651A - Metal drawing die

Info

Publication number: US2395651A
Application number: US317830A
Authority: US
Inventors: Anderson Frohman
Original assignee: IDA KARL ADLER
Current assignee: IDA KARL ADLER
Priority date: 1940-02-08
Filing date: 1940-02-08
Publication date: 1946-02-26
Anticipated expiration: 1963-02-26

Description

Feb. 26, 1946. F, ANDERSON 2,395,651

METAL DRAWING DIE Filed Feb. 8, 1940 5 Sheets-Sheet 1 35 0 Jim I 38 O INVENTOR. FRO/{NAN fl/voaesozv BY HQ ATTORNEY.

Feb. 26, 1946. F. ANDERSON 12,395,651

METAL DRAWING DIE Filed Feb. 8. 1840 5 Sheets-Sheet 2 WV///////////////7//////////////////fl BY Id.

ATTORNEY.

Feb. 26, 1946.

F. ANDERSON METAL DRAWING DIE Filed Feb. 8, 1940 5 Sheets-Sheet 5 INVENIOR. Few/rm Amptesav ATTORNEY.

Feb. 26, 1948. F. ANDERSON 2,395,651

METAL DRAWING DIE Filed Feb. 8, 1940 5 Sheets-Sheet 4 ATTORNEY.

Feb. 26, 1946. F. ANDERSON METAL DRAWING DIE Filed Feb. 8, 1940 5 Sheets-Sheet 5 Patented Feb. 26, 1946 METAL DRAWING DIE Frohman Anderson, Brooklyn, N. Y., assignor of two-fifths to Ida Karl Adler, New York, N. Y.

Application February 8, 1940, Serial No. 317,830

4 Claims.

This invention relates to metal working and more particularly to dies for forming curved sheets of metal from iiat sheet stock, as required in the manufacture of automobile and airplane bodies, boats or other fabricated articles.

Heretoi'ore these curved sheets have been formed by die stamping or rolling machines which are of high initial cost due to the accurate machining required of their component parts, which are necessarily heavy, cumbersome, large. and the dies are adapted to make but a single shape. Also, there are many shapes desired in fabricated articles that do not lend themselves readily to die stamping and rolling from flat sheets, due to the metal required at different zones to maintain a generally uniform thickness and strength and without wrinkles. Furthermore, formation of shapes by die stamping is limited by the practical size of the punch presses. The production costs of sheets made by such machines have been high due to the extreme precision required in their operation and the high cost of replacement of the dies and the rolls themselves, shouid they become marred and produce surface scratches, which are undesirable especially in airplane bodies where skin resistance and corrosion is so greatly to be avoided.

In both the die stamping and rolling processes, flash or wastage is involved in every operation as metal must be available outside the desired shape for holding the sheet in the die press or at the edges of rolls. This flash must be removed by a further process of stamping or trimming.

The principal object 01' this invention is to provide a simple machine for forming a flat sheet of metal into a curved shape having predetermined transverse or longitudinal curvature or both.

Another object of the invention is to provide a simple die drawing unit which can be adjusted during the drawing of a sheet to vary the curvature of the sheet throughout its length.

Another object of the invention is to provide a die drawing unit by means of which curved sheets of metal may be duplicated even though each drawn sheet may have varying curved surfaces at different zones along its length.

Another object of the invention is to provide a die drawing unit that automatically produces through the length of the draw sheet, surfaces of varying curvatures.

Another object of the invention is to provide a simple die drawing machine adapted to form sheets of var ing curvature from sheet blanks cut to the configuration of the finally formed shape.

Another object of the invention is to provide a simple die drawing machine adapted to form sheets of varying curvature from sheet blanks without requiring trimming after the forming operation.

Another object of the invention is to provide a simple die drawing machine adapted to form sheets of varying curvature from sheet blanks without maintaining a transverse tension in the sheet as it passes through the die unit.

Further objects of the invention will be apparent from the specification and drawings forming a part of the application.

The dies of one of my drawing units are characterized by at ieast one of the dies having a working edge of varying shape and sharpness throughout its length as it is mounted transversely in the unit, over which the drawn sheet is bent and worked as it passes over the die. The drawing or the sheet over this edge causes it to become elongated in varying amounts throughout its thickness depending upon the degree of sharpness of the bend. which in turn is dependent upon the shape and sharpness of the working edge of the individual die and its relative position from a second rigid surface, whether the latter be the working edge of another die or a straight edge of a guiding surface. The elongation of the sheet as it is drawn over the working edge of a die is greater at the relatively sharper points of the working edge and is caused by the adjustment of metal to its deformation as it passes over the working edge and, if the metal is stretched beyond its elastic limit, the sheet is given a permanently formed shape. At the same time the sheet is stretched and worked as it progressively passes between the working edges of the dies. In this manner an initially flat sheet is formed into one having a curvature.

In their more general aspects, die units embodying my invention include two dies with their working edges held in difl'erent planes and forming with guide block two throats through which the sheet passes over the working edges of the dies where the sheet is bent, stretched and worked into a desired curved shape. The second throat through which the sheet passes is so shaped that the distances between corresponding points on the two cooperating dies vary throughout the transverse lengths of the throats. These unequal distances cause unequal longitudinal stretching of the longitudinal portions of the sheet as it progressively passes between the throats, the greater the distance between corresponding points of the two dies, the greater the stretching. This stretching and working of the sheet is in addition to that resulting from the bending and working of sheet on the working edges of the throats. Either or both of the die throats may be curved to obtain predetermined forms of the drawn sheet.

The working edges of my dies are in general relatively sharp, at least throughout a portion of their lengths. The sharpness depends in general upon the degree of stretching desired by a particular section of the working edge of the die. The degree of sharpness of the working edge is also generally dependent upon the gauge and the physical characteristics of the material being drawn, the working edge being sharper for thinner gauges.

My invention also includes the feature of positioning the working edges of the dies relative to each other and changing the relative positions of the working edges during the drawing and thus form a sheet into a shape having varying degrees of curvature throughout its length.

In forming a die throat of one embodiment of my invention, a guide block is provided whose working surface is substantially parallel to the working edge of the die, and extending back from that edge a distance suificient to substantially keep the sheet in contact with the surface of die as it approaches and reaches the working edge. This block is necessary to overcome the tendency of the sheet to maintain its own plane when it is bent over the working edge of the die. It also prevents bulging of the sheet due to the difference in tension of the different longitudinal portions of the sheet as it is stretched unequally in those longitudinal portions. This unequal longitudinal stretching would manifest itself by creating other bulges behind the bulges caused by the sharp bending at the working edge of the die, which latter bulges would occur relatively near the working edge.

In the prior art, rolling machines have been disclosed showing changes in direction of a sheet as it passes through one or more pairs of rolls, wherein the gap between the rolls forms merely a line contact with the sheet and at which line the force of the rolls is exerted in equal amounts on both sides of the sheet. In my invention there i5 no such pressure placed on the sheet as it passes over the working edge of the die. The sheet of my invention develops a pressure against the working edge due to the resistance to bending of the sheet. In my invention there is a component of this pressure parallel to the working surface of the die, which provides the retarding force necessary for establishing tension in that portion of the sheet between two cooperating throats, which rolling machines do not have.

Furthermore, it is obvious that since the rotating rolls of the prior art are in contact through the sheet on only a very limited area, which approaches a line, unusually high pressures are required to exert any retarding force to a sheet being pulled through a pair of rolls. Also, this force is critical as the volume of the metal between the rolls is small and too much pressure extrudes the metal and too little pressure results in slippage at the transverse center of the rolls where the tension on the sheet is greatest, thus causing wrinkles to form behind the rolls. Also, it is well known that sheets received from rolling mills vary in thickness and such variations would naturally cause variations in the pressures of the rolls on the sheet, as the rolls are set rigidly in definite positions.

It is also well known in the rolling art that flanges must be turned up at each side of the sheet throughout its entire length, to engage holding surfaces at the sides of the rolls to prevent transverse slippage of the sheet during the rolling. It is apparent that the use of my drawing dies eliminates the operation of forming flanges on the sheets before passing them through a rolling machine and trimming the sheets after the rolling, as well as eliminates the cost of the scrapped material. Sheets may be drawn through my die units that are narrower than the width of the dies. The character of my invention is drawing and not rolling.

The throats in my die units may be staggered in parallel horizontal, vertical or transverse planes, so that the sheet is bent at an angle at the edge of the first die throat and then bent again as it passes through the second die throat. That portion of the sheet which at any instant is between the throats is under tension, causing the sheet to be stretched and worked. This stretching and working contributes to the final shape of the sheet.

In the case of a single die throat, the angle of approach of the sheet to the working edge may be adjusted to produce varied effects in the drawn sheet by providing a guide block adjustable in its position relative to the working edge. When using only one throat, it is preferable at times to make the portion of a guide block near the throat of a form generally complementary to the working edge of the die.

For sheet metal of medium or heavy gauge, or of high tensile strength, the working edges of the dies may be made of hard metal. However, the working faces may be made of such materials as a hard wood or fiber, for shaping sheets of low tensile strength. In all cases, the working edges of the dies should be smooth so as to exert an ironing effect on the sheets and without scratching or otherwise marring the drawn surfaces. However, should rough surfaces corrugated or otherwise irregular shapes be desired, the working edges may be made up of irregular curves or of curves and straight lines.

With dies of the type generally described herein, it is possible to form sheets with longitudinal curvatures such that the sheets will tend to form comparatively tight spirals after passing through the unit. In this condition, sheets having compound curvatures imparted to them may be coiled and shipped or handled in a small container. When unpacked and uncoiled, they will assume the desired form.

Such metals as aluminum, magnesium, Monel and stainless steel have been handled successfully with drawing dies of my type without the drawn sheets being cracked, torn, wrinkled or otherwise damaged.

Reference is had to the accompanying drawings forming a part of this specification, in which:

Fig. 1 is a top plan view, partly broken away, of a typical form of a single die throat type of drawing unit embodying the invention;

Fig. 2 is a view in section taken on line 2-2 of Fig. 1;

Fig. 3 is an enlarged view in perspective oi the male die used in arrangement shown in Figs. 1 and 2;

Fig. 4 is an enlarged view in perspective oi the assaou female die used in the arrangement shown in Figs. 1 and 2:

Fig. 5 is an enlarged view in perspective of a metal sheet as it assumes a iorm in passing through the die unit shown in Figs. 1 andz:

Fig. 6 is a top plan view. partly broken away of a typical form oi a two throat drawing unit embodying the invention:

Fig. '1 is a view in section taken on line 1-1 of Fi 6:

Fig. 8 is a view in section taken on line 8-8 of Fig. 6; v

Fig. 9 is a view in section taken on line 8-8 oi Fig. 6 but in position 01 maximum gap between throats and with the machine in position for loading the sheet;

Fig. 10 is a view in section similar to Fig. 8 but showing a vertically adjustable auxiliary creasing edge;

Fig. 11 is an enlarged view in perspective of a metal sheet showing its form at the bends as it passes through the drawing dies of Figs. 6-7 and 8:

Fig. 12 is a view in side elevation oi a typical form oi device embodying the invention, for imparting compound curvatures to sheets of metal;

Fig. 13 is a view in perspective of a metal sheet showing its form and its two bends as it passes through a pair of drawing dies, to produce greater elongations at the sides of the sheet than in its center;

Fig. 14 is a view in perspective of ametal sheet having a curvature given it as it passes through a die throat having a curved working edge and through a second die throat having a diiierent curved working edge;

Fig. 15 is a view in perspective 01' a metal sheet showing its form at its four bends as it passes through four throats, the first two being similar to those in Fig. 11 and the last two being similar to those of Fig. 14:

Fig. 16 is a view in perspective of a metal sheet showing its form at its four bends as it passes through four throats, the working edges of which are similar to the form shown in Fig. 3:

Fig. 1'? is an isometric sectional view of a four throat die unit taken on its central longitudinal plane to form the sheet shown diagrammatically in Fig. 15;

Fig.18 is an isometric view showing the holding construction of the slides shown in Fig. 17 and Fig. 19 is an isometric view of the actuating mechanism of the slides, the view being partially broken away to show the position of the sheet being drawn when the slides are somewhat extended from each other.

Dies embodying the invention may be used with any desired type of mechanism capable oi drawing a sheet of metal through the die throats. As shown in Fig. 12, one form of drawing mechanism may suitably consist of a frame I, along which moves table 2 having grooved sliding surfaces 3. The table 2 is provided with a rack 4, with which meshes a system of reduction gears 6 driven by an electric motor 8, whereby upon operation of the motor the table 2 travels along the frame I. At the right hand end of the table 2, as viewed in Fig. 12, there is provided a standard I, with a clamping head 8 having at the inner end of groove 9 a pair of jaws ill for gripping the end of a sheet of metal H. Standard 1 also has means for mounting one end of a replaceable cam unit or plate l2, to be described later. The sheet of metal is drawn by means of jaws l0 through a die unit I! mounted on a bed plate la secured to up of trains i. Uprights lb support at their upper extremities a head unit to which houses a conventional actuating mechanism for toggles id. Toggles Id adjust the position of ram 42 to which the upper part of die I! is attached. The lower part of die I3 is attached to bed la.

Referring particularly to Figs. 1 and 2, a typical form of a single die throat may consist 0! a base plate l4 having at two corners thereof guide pin bosses It for guide pins i8. Spaced from base plate II but guided by guide pins II is top plate i1 which, together with the base plate I4 defines a cavity IS, in which are located elements defining a gap or throat it. The die throat it is defined by a male die 20 and female die 2i. On die 20 is formed the working surface or edge over which the sheet H is bent and stretched. Die 20 is dependent from top plate i1 and the vertical gap 22 of the throat is controlled by shimmed stop blocks 23.

Die 2i is mounted on slide element 24 which is slidable along the base plate l4, in order to vary the character of the bend at throat l9. When the die is in operation, the horizontal thrust is received by heel plates 25 mounted on the inner side of guide pin bosses ii. Plates 2t engage the vertical finished surfaces 26 of top plate ii.

The slide 24, as previously indicated. is shiftable toward and away from die 20 shown in this instance as being shiftable in a horizontal plane. Slide 24 is guided at its sides by gibs 21 mounted on plate H. The purpose of changing the position of the die 2| is to vary the angular approach of the sheetagainst the edge 28 oi die 20. Thus, when the slide 24 moves die 2i closely adjacent to die 20, as shown in Fig. 2, so that an acute bend is, made in sheet II. a greater amount of stretch is imparted to the sheet I i for the reason that the diiferent layers of the sheet throughout its thickness are caused to stretch beyond their elastic limit in greater amounts than would be the case were die 2| further away from die 20.

Fig. 3 shows an enlarged view in perspective oi the die 20. The working edge 28 varies in sharpness from its longitudinal center as it is mounted transversely in the unit, until at the ends oi the die the edges become curved surfaces 28 of relatively large radii. In other words the working edge is rounded to a variable radius along its length, in the case shown there being virtually zero radius at the center and the radius increasing progressively from the center oppositely to each end where there is substantial radius. It will be apparent that a greater elongation will be imparted to the sheet at the point of greatest sharpness of die. for the drag imposed upon the sheet will be a function of the radius of curvature of the edge. The shifting of the die 2i toward and away from die 20 during the operation of the machine, as for example to the dotted line position 30 in Fig. 2, will vary the curvature imparted on the sheet ll along its length.

In order to control the movement and position of the slide 24, a toggle link construction has been provided, as best shown in Figs. 1 and 2. The toggle construction consists of a pair of pivotally connected links 3i and 32, having their opposite ends pivotally connected to the slide 24 and to a rearward extension 33 on the base plate [4, respectively. At the opposite ends of slide 24. a

similar toggle construction

34 and 35 is arranged except that link 35, pivotally connected to extension 36 of base plate I 4, has a handle extension 31 for imparting angular movement to the toggles. A cross link 36 connects the pivotally connected ends of

links

34 and 36 to the pivotally connected ends of links 3| and 32. Thus by operating handle 31, the links may be moved from an in-line position, as shown in Fig. 1, into angular relation, thereby retracting the slide 24. As stated before, the effect of moving the slide 24 is to vary the curvature of the drawn sheet. Other means for moving slide 24 will be described hereinafter in relation to Figs. 6 to 9 inelusive.

As shown in Figs. 6 to 9 inclusive, a typical form of a two die throat machine may consist of a base plate M which is mounted on a bed |a, as shown in Fig. 12. Spaced from the base plate l4 but connected rigidly thereto by means of guide pins l6, heel plates 25 and stop blocks 23, is a top plate H, which, together with the base plate |4 define a cavity IS, in which are located dies defining a pair of

die throats

40 and 4|. Top plate H is fixed to ram 42 of draw bench (see Fig. 12). The die throat 4|! is defined by a slide element 43 of generally rectangular cross-sectional shape, which is slidable along the base plate and a superimposed pressure plate 44, which is supported by the top plate As illustrated in Figs. 6 to 10 inclusive, the slide 43 and plate 44 may be reduced in weight by making them hollow. The plate 44 is supported on the top plate I? by means of a plurality of retainer screws 45, which are provided with reduced threaded ends 46 and enlarged heads 41. The threaded ends 46 are screwed into the plate 44 and the heads 41 retain it against separation from the top plate while allowing relative movement therebetween. The pressure plate 44 is normally forced downwardly into spaced engagement with the slide 43, by means of springs 48 disposed in holes 49 in the top plate H. Top plate ll when raised, brings with it die and permits the sheet H to be threaded through or loaded in the die unit. The raising of die 5| permits the sheet to extend between slide 43 and plate 44 and beyond the die unit, where it can be gripped by jaws Ill. (See Fig. 9.) The springs 46 together with the weight of the plate 44, assure that the sheet II will remain fiat when top plate H and die 5! are lowered and die 5| and block 53 form throat 4|. A proper spacing of throat 4|] is made by adjusting the height of stop blocks 23 by shims.

At the left hand edge of the slide 43, as viewed in Figs. 8 to 10 inclusive, die 50, which may be made of hardened metal or wood or fiber, forms a working surface and a working edge over which the sheet of metal II is bent. As shown in Fig. 7 the die throat 40 is straight from end to end and therefore the sheet of metal is only bent at an angle relative to the throat 40. While die throat 4D is illustrated as being straight, it will be understood that it may be of irregular shape according to the results desired, as illustrated in Figs. 14 and 16. To resist excessive wear plate 44 is provided with an interchangeable insert 500..

The die throat 4| is defined by die 5| in the lower right hand edge of a flange 52 which depends from and is a part of the top plate I1. The lower face of the die 5| is formed on a curve which extends from end to end, as shown in Fig. 7. While the die 5| is illustrated as being a smooth, continuous curvature, it will be under stood that it can he an irregularly curved die, ii. it is desired to impart an irregular or isometric curvature to the sheet of metal, inasmuch as the curvature of this edge determines the degree of elongation at different stations on the width of the sheets in conjunction with the particular die throat 4|) as described. The die throat 4| may take the form of a curve with outer edges below the mid point, which would deform the sheet as illustrated in Fig. 13.

Cooperating with the die 5|, in defining the die throat 4|, is a block 53 which is fixed to the base plate I4 and retained in position by means of a rail 54 extending across the plate I4. The block 53 has its upper edge curved substantially complementarily to the curvature of the die 5|, and thus defines the transversely curved die throat The slide 43, as previously indicated, is shiftable toward and away from the die throat 4|, as shown in this particular instance, in a horizontal plane. The purpose of changing the position of the die throat is to vary the amount of curvature to be imparted to the sheet throughout its length. Thus, when the die throat 40 terminates closely adjacent to the die throat 4|, as disclosed in Fig. 8, so that an abrupt bend is made in the sheet II, the greatest longitudinal curvature may be imparted to the sheet H as will be apparent from consideration of Fig. 11.

Fig. 11 represents sheet marked with longitudinally and transverse parallel lines. Line YWY represents the die throat 4|. Line YVY represents the die throat 43 when slide 43 is close to die throat 4| as in Fig. 8. Dotted line ZUZ represents the position of the die throat 4|) when it is removed away from die throat 4| as in Fig. 10. Assuming that the distance KY and TW are equal, we have: The ratio UWT/ZYX is greater than 1 but approaches 1 when YZ becomes inflnite, so that the further away the die throat 40 is removed from die throat 4| the less stretch the sheet will be subjected to along its center. Also, it will be seen, the ratio UWT/ZYX becomes a maximum when YZ becomes 0, when the maximum stretch is obtained. The second effect that produces elongation is that of the angular approach at the working edges of the throats. Again, looking at Fig. 11 it may be seen that the sheet would be given less elongation when moving along path UWT than when moving along path UVWT. It may also be observed that the path ZYX would have no angular deflections and therefore no elongation. Thus it will be apparent that by shifting the slide 43 toward and away from the dies 5| and block 53 during operation of the machine, the curvature imparted to the sheet throughout its length may be varied as may be desired.

In order to control the movement and position of the slide 43, a toggle link construction has been provided, as best shown in Fig. 6. The toggle construction is similar to that described in Fig. 1 but with certain modifications. Link 35 instead of having a handle extension, as in the previous case, has a bevel gear extension 55 which meshes with a bevel pinion 56 which is fixed to the end of a shaft 51 journaled in standard 56 mounted on extension 36 of the base plate l4. The shaft 51 is rotated by the crank 59 whereby the links 3|, 32 and 34, 35 may be moved from inline position, as shown in Fig. 6, into angular relation, thereby retracting the slide 43. Thus, by rotating the crank 59, it is possible to advance and retract the slide 43 to vary the spacing of the working faces of the

die throats

40 and 4| and thereby vary the curvature of the sheets. While a lever, crank and gear drive have been illus-- trated for shifting slide 43, it will be understood that any other desired actuating'mechanism may be used, such as a cam plate I! which is provided with slot Oil of predetermined shape for regulating e movement or the slide during the possage oi a sheet through the drawing die. Blot iace ti oi cam groove 80 engages cam follower e: which is connected to cross link Iii. It is apparent that with the same cam plate in position, the curvatures applied to sheet H may be duplicated.

In drawing the sheet over a working edge of the die, there is unequal elongation of the sheet throughout its thickness, and there is created a tendency for the sheet to curl up in a spiral. It the worked sheet passes over a second working edge in a bend in an opposite direction, this tendency to curl may be lessened or eliminated according to the degree 01' bend at the second working edge. Where there has been unequal bending at a plurality of working edges and it is desired to eliminate the over-all tendency for the sheet to curl, there is provided, as shown in Fig. 10, a sharp edged block 03, of the general form of block 53, positioned to exert a pressure on the sheet after it has passed through the last die throat. Block 63 is held in position by rail 84 and may be adjusted in position by shims 65. Thus by drawing the sheet over block 83, the tendency of the sheet to curl may be eliminated.

This final working edge provided by the block 83 thus iunctions to determine the amount of longitudinal curvature left in the drawn sheet under condition of equilibrium. The transverse curvature imparted by a given set of dies depends upon the longitudinal curvature, the transverse curvature varying inversely with the longitudinal curvature. The block 63 will therefore be so adiusted that it will leave Just the right amount oi inherent longitudinal curvature. This will in all normal circumstances be considerably less than a coiled up or spiral condition, such as would result upon release of the sheet ii the unbalance in inherent stresses produced at the last drawing die were not in part at least overcome.

In operation, the table 2 is moved to its lefthand position (see Fig. 12) and top plate I! and the parts attached thereto are raised by vertically moving the ram 42 to the position shown in Fig. 9. Pressure plate 44 is now separated from slide 43 sufficiently to permit the sheet ii to pass therebetween and beyond die 5i, which is also in its raised position, and to the Jaws lli. where it is clamped. Ram 42 is then lowered until plate i1 rests on pressure plate 44. This movement also lowers die 6! and in its lower position forms throat 4| with the sheet I I in position for drawing. The motor Ii is then started and the table 2 travels along the frame i, in the direction of the arrow, pulling the sheet through the die unit. As the sheet passes through the die unit, it is bent over the working edges of the dies as described. While the sheet is moving through the die unit, the herizontal spacing between the die throats 4|) and ll may be varied by rotating the crank 59, or by the action of cam slot Bil, thereby varying the radius of curvature of the sheet to cause it to be curved in a predetermined way.

My arrangement is adapted to draw a large variety of curved sheets from one set oi die throats and with other sets of die throats of other characteristics, a few oi which have been described. an extremely large number of shapes may be obtained from a single die unit. Thus, for example, it it is desired to curve a sheet longitudinally in the same direction and transversely in the direction opposite to the curvatures disclosed in Figs. 7 and 8, the die 5i and block 53 can be replaced by another set having upwardly curved, rather thandownwardly curved, complementary edges, the working edge or which is indicated in Fig. 18 by the line b, so that the center oi the sheet is substantially in alignment with the die throat l0,

the working edge of which is indicated in Fig. 18

by the line a, and the ends of the throat II are disposed below the die throat I. With this type of construction, the edges of the sheet will be stretched to a greater extent than the center portion, and thus a concavely curved sheet will be produced, as shown in Fig. 13.

Likewise, the working edges of both of the die throats may be downwardly curved, as indicated by lines a and b in Fig. 14. Four die throats may also be used, the working edge of one or which may be straight and the others may be curved. as shown by lines a, b, c and d in Fig. 15, or as shown by lines a, b, c and d in Fig. 16.

Referring particularly to Figs. 1'7, 18 and 19, the sheet II is shown passing between slides ll and a, which are constrained to move together by guide pins it. The two slides are kept separated by shimmed stop blocks 23. One edge of die 80 and insert a form the first die throat ll. Die throat II is formed by one edge of die iii and the flat surface insert 53. Die throat Ha is formed by another portion of the edge of die Ii and the working edge of insert 58. Die throat lib is formed by die Bio and the insert "a.

Slides 3 and 43a move between slides 88 and 61. which in turn move between upper plate I! and lower plate It. Upper slide 61 is guided at its sides by gib blocks 68, which have flanges 89 to engage with flanges iii of upper slide 61 when upper plate i1 is raised to position sheet ll preparatory to drawing.

Slides

66 and 61 and die plates I5 and 11 are also provided with stop blocks (not shown) similar to blocks 28.

The slides are moved relative to each other and to the stationary throat lib by a double link system consisting 01' links SI and 8| and links H and 12, which actuate slides 43 and 43a. Links H and I2 have also'pivots I3 and II mounted at their longitudinal center and connected to links I! and 1B, which are pivotally connected to slides 68 and 81. Motion is transmitted from cam follower 62, moving in cam groove in cam l2 by means of tie rods 38 connected to

pivots

13 and 14.

It is apparent that the die throats may be moved during the drawing of a sheet through the unit either in a direction parallel, transversely or vertically to the direction of the draw, or any combination of them.

Inasmuch as only the dies need be replaced. it will be evident that the expense of adapting the machine to any type of work is extremely small while its versatility by reason of the ready replacement of the dies is correspondingly great.

While the invention has been disclosed as applying to the drawing of metal sheets, it will be understood that it applies to sheets of other materials, such as fiber sheets, that are adapted to drawing and working processes.

In view of the many variations to which these dies are susceptible, the specific embodiment oi the die described above should be considered as illustrative and not as limiting the scope of the following claims.

I claim:

1. Apparatus tor shaping sheet metal comprising, in combination with means for pulling the sheet edgewise, a die member having a working edge and an opposing member cooperating with the die member to form a die throat through which the sheet is pulled, and guide means for the sheet in advance oi the die member positioned to direct the sheet to the throat at an angle to its direction of pull through the throat, the working edge of the die member being variably rounded along its length so as to effect a differential drag upon the sheet.

2. Apparatus for shaping sheet metal comprising, in combination with means for pulling the sheet edgewise, a die member having a working edge and an opposing member cooperating with the die member to form a die throat through which the sheet is pulled, guide means for the sheet in advance of the die member positioned to direct the sheet to the throat at an angle to its direction of pull through the throat, the working edge of the die member being variably rounded along its length so as to effect a difierentlal drag upon the sheet, the guide means being adjustable toward and away from the transverse plane including the die throat, and means to effect said adjustment.

3. Apparatus for shaping sheet metal comprising, in combination with means for pulling the sheet edgewise, a die member having a working edge that is variably rounded along its length and an opposing member of complementary shape cooperating with the die member to tom 9. throat through which the sheet is pulled, and uide means for the sheet in advance of the die member transversely oflset from the throat on the side including the die member so as to direct the sheet to the throat at an angle to its direction of pull through the throat and thereby 10 cause it to be drawn over the working edge.

4. Apparatus for shaping sheet metal comprising, in combination with means for pulling the sheet edgewise, a die member having a working edge that is variably rounded along its length and an opposing member oi complementary shape cooperating with the die member to term a throat through which the sheet is pulled, guide means for the sheet in advance of the die member transversely offset from the throat on the side including the die member so as to direct the sheet to the throat at an angle to its direction of pull through the throat and thereby cause it to be drawn over the working edge, the guide means being adjustable toward and away from the transverse plane including the die throat.

and means to effect said adjustment.

FROHMAN ANDERSON.

Certificate of Correction Patent No. 2,395,651.

FROHMAN February 26, 1946. ANDERSON It is hereby certified that the above numbered patent was erroneously issued to the inventor, said Anderson assignor of two-fifths to Ida Karl Adler, of New York,

N. Y., whereas said patent should have been issued to the inventor, as sole owner thereof; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of Pecember, A. D. 1946.

LESLIE FRAZER,

First Assistant Gammz'sst'oner of Patents.