USRE20009E - Art of drawing - Google Patents

Description

. 1. M. HOTHERSALL R 20,009

June 16, 1936.

ART pr DRAWING Original Filed Feb. 20, 1931 ill/Ir! (/14!) I INVVTIKIJRY I I gjv/a ATTORNEY n in T A G 0 ,IA,

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June 16, 1936.

J. M. HOTHERSALL V ART 0? DRAWING Ofiginal Filed Feb. 20, 1951 4 Sheets-Sheet 4 W w W1 a ATTORN Lil Reissued Junel6, 1936 UNITED STATES PATENT "OFFICE ART or muwmc John m. Hothersall, Brooklyn, N. Y.,,,a a signor a American Can Company, New York, N. Y., a corporation of New Jersey Original No; 1,967,245, dated July 24, 1934, No. 517,244, February 20, 1931. Application for reissue April 13, 1936, Serial No. 74,393

28 Claims. (CL 11H) The present invention relates to drawing presses and has particular reference to a self-contained compensating and self-acting drawing and clamping device for shaping and holding the material being operated upon in all of its drawing stages. I

The present invention is directed to an improved method and apparatus for compensating or balancing the amount of clamping action'eflective upon the material in a series of slip grips in which the metal is held during each stage of drawing, tnis clamping force being automatically adjusted, at every stage of action, in direct ratio to the drawing resistance of the material being acted upon. A similar principle of clamping action as applied to a single drawing operation is disclosed in my pending application filed in the United States Patent Office, May 16, 1930, as Serial No. 452,852.

The-present invention relates to aseries of drawing ope-rations, the working forces of each stage being automatically controlled and applied in a unified compensating and balancing action.

The principalobject of the present invention is the provision of a method and mechanism for performing a series oi drawing operations upon sheet material while preventing the formation of wrinkles by holding the-work during each of the drawing actions in -a slip griphaving compensated clamping strength.

An important object of the invention is the provision of a method and mechanism adapted to uniformly draw an'article from sheet material in a series of stages by properly holding the same in a varying, self-compensating clamping action at the difierent stages, these clamping actions being-dependent in degree upon the resistance of the material being drawn.

An important object of the invention is the provision ofna mechanism adapted to uniformly draw an-article from sheet material in a series of steps or stages by utilizing a clamping-device at each stage which automatically adjusts itself to the proper degree of clamping action to prevent development of wrinklesin the' material. An' important object ofthe inventionis the provision of inter-acting elements hydraulically connected to perform a series of self-adjusting clamping actions in aseries of drawing operations.

An important object of the invention is theprovision of a die mechanism for holding sheet material in a series of slip grips while successively drawing the same over shaping members, the degree of clamping action in the slip grips varying directly with the force required in the drawing operations.

An important object of the present invention is the provision of a drawing mechanism wherein a single operating movement in one direction is transmitted through a liquid to parts or the mechanism to effect a corresponding series of resulting movements in the opposite direction.

An important object of the invention is the provision of a press mechanism for forming a drawn article in a series of operations by first cutting adisc irom sheet material and then successively holding the same in equalized slip grips while successively drawing intoshape.

Numerous other objects 01 the invention will be apparent as it is better understood from the following'descripti'on, which, taken in connection with the-accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawings:

Figure l'is a longitudinal sectional view through a cutting and drawing punch and die mechanism embodying the present invention, the view illustrating the parts'in position prior to operation;

Figure 2 is an enlarged fragmentary sectional view of the mechanism illustrated in Figure 1, this view illustrating the parts in the position assumed during the first drawing stage following the cutting operation; 1

Figure 3 is a view similar to Fig. 2 illustrating the second drawing stage;

Figure 4 is a view similar to Fig. 2 illustrating the'third drawing stage;

Figure 5 is a view similar to Fig. 2 illustrating the 4th drawing stage; and

Figure, 6 is a view similar to Fig. 1 showing the position ofthe parts at the end of the final drawing operation.

The drawing press mechanism illustrated as a preferred embodiment of the present invention is carried in a suitable press frame in the usual manner. These parts which are concerned particularly with the present invention comprise upper movable punch members and lower die members. The die member parts are supported on a bolster plate I I (Figs. 1 and 6) and comprise a cutedge member l2 secured to the bolster plate by bolts l3.

This cutedge member is provided with an annular cutting edge I 4, the wall of which is under cut to provide a shoulder l5 which forms a termination for a vertical wall l6, extending downwardly in a tubular section l1 which encloses achamber 18. The lower part of the tubular wall I! is threaded at 2| to provide engagement with the upper end of a cylindrical wall 22 of a cup bowl member 23. Y l

A draw ring 28 is located for sliding movement within the cutting wall I 4 of the cutedge H and is provided with an annular projecting shoulder 21 which engages beneath the shoulder ii of the cutedge I 2 when the draw ring is in its uppermost position. The ring 26 has adownwardly extending tubular section 28 which slidingly engages inside of the inner part of the'cup member 23 adjacent its upper end and this Joint is rendered liquid-tight by the use of a cup washer 29 seated in a groove formed on the bottom face of the wall 28.

A second tubular ring 3| is provided, being located interior of and having sliding movement within the draw ring 26, the sliding joint so formed being rendered liquid-tight by a washer 32 carried on the lower end of the tubular wall of the ring 3|. The ring 3|, when in its lowermost position (Fig. 1) engages a stop shoulder 33 formed in the wall 28 of the draw ring 26, the upper part of the ring 3| being of a larger diameter, as illustrated, to insure such engagement.

A third tubular ring 35 is used, being located for sliding movement within the ring 3|, its outer wall being of larger diameter above than a lower tubular wall 35. The juncture between these two outside diameters provides a stop for a shoulder 31 formed on the inside of the ring 3| and insures a definite relation of. the rings 3|, 35 when the latter is in its lowermost position.

A fourth ring 4| is provided, being located inside of the ring 35 and extending downwardly in a tubular wall 42, the outer diameter of which is less than the outer diameter of the upper part of the .ring, this for engagement with a shoulder 43 formed in the ring 35 when the ring 4| is in its lowermost position, (Fig. 1). The ring 4| has sliding movement in the ring 35 and a liquid-tight sliding joint is provided by a cup washer 44 inserted in an annular groove formed on the lower end of the tubular extension 42 of the ring 4|.

An anvil block 5| is located and has sliding movement within the ring 4| and is formed with a downwardly extending part 52, the outer diameter of which is less than the outer diameter of the upper part ofthe block. The junction between the diameters provides a stop for engagement with a shoulder 53 formed in the part 42 of the ring 4| when the anvil block is in its normal or lowermost position, as shown in Fig. 1. A liquid-tight sliding joint is maintained therebetween by a cup washer 54 carried on the lower surface 01' the extension 52. v

The anvil block 5| and its surrounding rings,

4|, 35, 3|, 26, are held in a normal or lowered position by a spring 56 located within a central vertical bore 51 formed in the anvil block 5|, the lower part of the spring extending downwardly within the cup member 23. The'upper end of the spring is engaged. by an eye 6| carried in a screw plug 62 threadedly engaged in the upper end of the anvil block 5|, this plug closing the upper quantity of liquid is through a check bottom of the bowl. When the construction providing a stop.

' block 5| which are in .the third recess formed nested positions (Fig. 1), the plug 62 at that time,

with the spring 56 hanging from its eyell, being threaded in position anvil block 5|. The lower end of the spring is thereupon engaged by a' wire or cord and is stretched outside of and pulled beyond the bottom wall of the cup sembled with the washer I4, is then hooked over the lower end of the spring- 55 and the spring is allowed to retract until the washer 84 is seated within its counterbore 65. The eye 64 provides a hold or handle to allow this seating action.

The washer and its parts are then'sealed by a screw plug 51 threadedly secured into thebottom wall of the bowl 25. J

'A liquid, designated by the numeral H, which member. The eye", as

within the upper end of the may be oil, glycerine, or the like, is contained within the bowl 22" (Figs. 1 and 6). A sumcient used to completely fill the chamber below the lower ends of the anvil'block and the surrounding rings. The vertical bore 51 v of the anvil block is also completely filled with liquid.

This liquid may be conveniently inserted valve nipple 12 of any usual construction which is threadedly securedin the chamber with the assembled die parts is ready to be filled with liquid the entire unit is inverted, this being before the unit is inserted on the bolster plate II and before it is. put in the press. The nipple 12 is entirely removed and the parts are held in their normal or locked positions.

The liquid is then filled into the chamber through the nipple opening, air escaping therethrough as the filling takes place. When the chamber is completely filled with liquid running over, the nipple 12 is screwed home, entirely closing the chamber and preventing displacement of the liquid. The check valve is subsequently used from time to time to permit insertion of added charges of the liquid to maintain a full capacity within the chamber.

A strip of sheet material 15 may constitute the work being operated upon by the press mechanism and this strip is first positioned in the die where it rests on the upper surfaces of the rings 26, 3|, 35, 4| and the upper surface of the anvil the same horizontal plane as illustrated in Fig. l.

The upper movable punch members which also constitute the actuating elements for the cutting and drawing operations, comprise a punch head 8| having a stem 82. This punch head moves up and down along a vertical axis in the usual and preferred manner, as in apress slide with which the stem is connected.

The punch head 8| is centrally recessed in a series of counterbores of different diameters, the larger recess being located adjacent the lower end and constitutinga chamber 85. This chamber is enclosed by a cylindrical wall 86 which joins at its top with an annular inclined wall 81 leading into the secondrecess formed as a chamber 88. A cylindrical wall 89 encloses this chamber and joins with an inclined wall 9| above which leads into as a chamber 92. chamber is enclosed by a cylindrical wall 93 and the upper end of the with a fourth recess or chamber 94 which is enclosed by a cylindrical wall 95, this being the smallest of the chambers.

.A knockout pad 96 is located within the chamber 94 and is This I chamber communicates provided with an upwardly extendshouldered connections.

lng knockout rod or stem 91 normally held in raised position (Figs. 1 and 6). by a spring 38 surrounding the upper end of the stem and resting at its lower end within a counterbore 99 formed in the stem 82. An adjusting nut and a 'locknut-IOZ threadedly engage the upper end of the stem and confine the spring 98 in operating position. I

In operation the punch head 8| and the draw ring 25 constitute the proper instrumentalities for clamping the strip of sheet material 15 just prior to a disc being severed therefrom and, followingthis cutting action they provide the first slip grip on the edge of the disc while it is being drawn in the first drawing stage.

To bring these instrumentalities into action, the punch head 8| is lowered, the sheet material 15 being then clainped between the upper surface of the draw ring 28 and a lower face I of the head and the disc is cut out. Continued downward movement of the head from this point of engagement is resisted by the liquid 1| acting against the lower end of the draw ring 28 and the reaction resulting therefrom provides the proper clamping grip on the outer edge of the disc as the first drawing begins.

In this drawing operation, the draw ring 26 is forced down into the liquid which is non-compressible and this force is transmitted upwardly thereby against the bottom faces of therings 3|, 35, II, and the block 5| forcing these parts upwardly and into the disc altering its shape by drawing it into ashell I06 (Fig. 2) having a flange It". The fia'nge I1 is the part engaged between the instrumentalities 8 I, 26, being gradually pulled out of the slip grip formed thereby. The central part of the shell is drawn over the anvil block 5| and over the draw rings 4|, 35, 3|, which are held locked together by their respective The four parts all constitute anvil elements for this drawing stage.

It is the resistance against bending of the metal in the work being drawn which determines the amount of clamping action in the slip grip holding the edges of the work, the liquid acting merely as a freely flowing connection. Such resistance must be overcome to change the disc and draw it into shell form and this necessary force is applied by the descending punch head acting as drawing takes through the slip grip as soon place. The improved slip grip in this way is self-acting and self-compensating at all stages of drawing. This will be observed throughout the operationsthat follow.

The upper end of the draw ring- 3| is tapered at its outer edge to provide a conicalwall I05 and the shell "15 as it is being tightly drawn over the anvil elements in this'stage of the first operation assumes the same shape adjacent the conical wall, as illustrated in the drawings being thus formed into a conical wall Downward movement of the head 8| with the corresponding upward movement of the anvil parts continues until the entire flange I01 is drawn (iii and there then results a the conical wall I of the shell H2 is brought the shell is drawn up shell H2 (Fig. 33 having a cylindrical wall 3 located exterior The diameters of these the second stage of the drawing operation whichimmediately follows.

In this second stage of drawing, the walls I09, 81 of the respective parts 3|, 8| constitute the instrumentalities for clamping the shell 2 in a slip grip, effective at its inclined wall I, while into the chamber 88. The

ring 3! ceases to bean anvil and becomes a draw ring. The active moving member is still the head 8| but with it now travels downwardly the draw'rings 26 and 3| which push down into the liquid displacing it and causing a corresponding upward movement of the rings 35, 4| and the anvil block 5|, ail of these now being anvil elements, the upper faces of these members being still maintained in a horizontal plane as they are bodily lifted.

I The wall ||3thus slips through the slip grip passage between the walls I I! being altered in shape as it is drawn from the position illustrated in Fig. 3 into the position 11- lustrated in Fig. 4, this view showing the completion of the second drawing operation. A shell 5 is thus produced.

The upper end of the ring 35 adjacent its outer edge is formed as a conicalwall H6 and it is over this wall that the metal of the shell is -formedto produce a wall 1. The uppermost position of the drawring 35 and the other anvil parts at the end of the second drawing stage brings the conical surface H5 so that it clamps the'wall ii! of the shell 5 tightly against the wall 9|. the shell being fully within the chamber 88 and a cylindrical wall B being formed. The draw ring 35 is thus in position to provide a clamping instrumentality for the next succeeding or third stage of drawing operatic During the third drawing stage the ring 35 ceases to act as an anvil element and functions as a draw ring while the shell 5 is further reduced in diameter and altered in shape by movement of the parts from the position illustrated in Fig. 4, to that illustrated in Fig. 5. The latter view shows the relation of the die parts at the completion of the third drawing operation and shows a shell |2| formed thereby.

For this drawing of the shell the, head 8| and draw rings 28, 3| and 35 are moved downwardly. this force reacting through theliquid 1| to 'lift the draw ring 4| and the anvil block 5|, these parts constituting the anvil elements. The walls Ill and H801 the shell 5 are drawn throu h the proper slip grip afiorded by the walls H8, 9|

during the formation of the shell |2|. Such a shell is drawn over an upper rounded edge I22 vformed in, the ring II and is, therefore, formed constituting instrumentalities for this clamping of the metal in the slip grip. In the final drawing operation which immediately follows, the'shell l2| is further reduced and 81 and I89, the shellaltered in shape to provide a cup member Ill set wall I34 which is of the same diameter as the diameter of thewall I 24 of the shell I2 I, being in fact a remnant of that wall not drawn through v the slip grip.

In such a final drawing movement the draw rings 26, 3|, 35, 4| move with the head ill, the anvil function being solely performed by the anvil block 5|. Again, it is the downward movement of the draw ring parts and their pressure against the liquid II that reacts as a lifting force on the anvil block 5|. The cup member |3| is now completely formed, its upper wall being in contact with the knockout pad 95.

Fig. 6 shows'the posi tion of the parts at the completion of the drawing operations.

It will be understood that thefour distinct drawing operations which have been separately Upon the ascent of the die 8| the spring 55 pull- I ing down upon the anvil 5| through the hydraulic medium returns all of the parts to their normal position in readiness for the drawing of the next succeeding disc to be cut from the sheet.

It will be understood that the spring 55 is sufliciently strong to restore these parts to their locked positions while the draw ring 26 follows up with the rising head 8|. At the time the surface I05 of the punch head 8| leaves the upper surface of the draw ring 25, the parts 26, 3|, 35, II and 5| have reached their normal lowered positions, as illustrated in Fig. 1.

During this restoring of the parts to normal position and during the downward movement of the anvil block 5|, the drawn cup member |3| remains in the chamber 94. As the punch head 8| nears the upward end of its travel, this bing after the head is above and clear of the lower die mechanism, the upper end of the rod 91 is engaged by any suitable stationary part on the machine. The pad 96 being thus held against further movement, with the head 8| continually rising, the upper wall of thechamber 94 moves away from the pad 98 until the pad is at the lower end of the chamber. The cup member |3| is in this way stripped or ejected from the chamber 94 and falls through the other chambers and out of the head 8|.

It isthought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

Claims 16 to 28 inclusive hereof were held allowable to me in my copending application Serial No. 452,852, filed May 16, 1930, constituting claims 1 to 8 inclusive, 25, 29, 30, 31 and 32 in said application, and are made in this reissue application to preserve the line of division between the claims of this reissue application and the 20,009 I (Fig. 6) having a cylindrical wall I32 and an onclaims of the aforesaid copending application, the above mentioned claims 16 to 23 inclusive relating to the same subject matter as claim 15 of this application. i

I claim:

1. The art of drawing metal, which comprises drawing sheet material over a plurality of nested anvil elements while holding its outer edges in a succession of'slip grips having their clamping pressures hydraulically transmitted by drawing resistance on said anvils and pulling the inner- 'most anvil elements in a direction opposite to said pressures.

2. The art of drawing metal, which comprises drawing sheet material in stages over a plurality of concentric anvil elements while holding its.

outer edges at each stage in hydraulic self-compensating slip grips, asaid anvil element'of one drawing stage providing a slip grip for the next succeeding stage at the same time pulling the innermost anvil element in a direction opposite to the hydraulic gripping.

3. The art of drawing metal, which comprises drawing sheet material in a series of drawing operations over a plurality of anvils formed of nested anvil elements by utilizing a different size of anvil for each stage of operation beginning with thelarger anvil made up of the greatest number of elements whileholding the outer edges of the material at each stage in a slip grip having its clamping pressure hydraulically transmitted thereto by the anvil in use, and pulling said anvils rial over one of a plurality of nested anvil ele-' ments while holding the outer edge of the mate.- rial at each stage in a slip grip, a part of the anvil of one stage becoming an element in the slip grip for the next succeeding stage, the

clamping pressure of each slip grip being hydraulically transmitted thereto by the anvil in use, and pulling said anvils successively one by the other in a direction opposite to said clamping pressures.

5. In a drawing press mechanism, the combination of punch head and a plurality of pairs of opposed substantially concentric inner and outer instrumentalities clamping material to be drawn in successive slip grips, a plurality of anvils over which the inaterial is drawn in stages as it is successively removed from its slip grips, means for moving said instrumentalities to effect the drawing of said .material, and hydraulic connecting means in which the lower parts of the anvils are directly immersed, and operating between said anvils and one of each pair of said instrumentalities whereby movement of the latter is transmitted through the liquidto said anvils causing them to move in an opposing direction, hydraulic means being closed to external pressure and the operative hydraulic pressure on the inner instrumentalities being caused by-the contrary movement of an outer said lnstrumentality.

6. In a drawing press mechanism the combination of a plurality of die members located conmember adapted to progressively clamp the edges centrically of each other, an actuating punch.

of a sheet material d.sc being drawn-against said to force the central part of said disc'through said slip grips and draw it into shell form, shoulders formed on said die members, and a spring drawing-the inner die member in a direction away, from said punch member.

7. In a drawing press mechanism, the combination of a plurality of die members located concentrically of each other, an actuating punch member adapted to progressively clamp the edges 01' a sheet material disc being drawn against said die members during a single working stroke to form a slip grip at each engagement, and hydraulic means for transmittingthe moving force 'of said actuating punch member to said die members to move them in an opposite direction and to forcethe central part of said disc through said slip grips and draw it into shellform, said punch member preventing an opposite movement.

of a said die member after it ceases to function ,as a slip grip, shoulders formed on said die members, anda spring drawing the inner die memher in a direction away from said punch member.

8; In a drawing press mechanism, the combination of a plurality of die memberslocatedconcentrically 01'' each other and having shoulders whereby each inner die member holds each outer die member from individual upward movement, an actuating punch member adapted to progressively clamp the edges of a sheet material disc being drawn against said die members during a single working stroke to form a slip grip at each engagement, hydraulic means for transmitting the moving force of said actuating punch member to said die members to move them in an opposite direction'and to force the central part of said disc through said slip grips and draw it into shell form, and devices including a spring connected with the, innermostdie member for restoring said die parts to normal position when disengaged by said punch member.

9. A drawing press mechanism comprising, in-

combination a plurality-of die members located onewithin the other and having-sliding movement therebetweemgan actuating punch memher having movement toward said die membersand adapted to perform a succession of drawing operations during its working stroke by first en gaging the edges'of a disc of sheet material and clamping it against the outer of said dies in a slip grip forcing the said die downwardly while drawing said disc into shell form over the other inner dies and withdrawing'its said edges from said slip grip and then further engaging in succession the other of said die members and forming other slip grips while progressively drawing the said shell into smaller form over the remaining inner die members, and hydraulic means in -which the lower part of each die member is directly immersed for transmitting the force of movement of each engaged die member to'the other non-engaged die members forcing them upwardly against the work to produce the said shell forms.- I

10. In a drawing press mechanism, the comblnation of a plurality of die members located I concentrically 01 each other, an actuating punch member adapted to progressively clamp the edges of asheet material disc being drawn against said die members during a single working stroke to form a slip grip at each engagement, and hydraulic means closed to external hydraulic pressure for transmitting the moving iorceoi said actuating punch member to said die members to move them in an opposite direction and to force 5 the central part 01' said disc through said slip grips and draw it into shell form.

'11, The combinationof a punch, an opposed cutting and gripping die, inner drawing dies lconcentric within said cutting die, and a bowl filled with a fluid in which the lower ends of said dies are immersed, said bowl being closed to external hydraulic pressure. I

12'. The art of drawing metal, which comprises drawing sheet material in stages over outer and inner anvil elements while holding its outer edges in hydraulic self-compensating slip grips, a said anvil element of one drawingstage providing a slip grip for the next succeeding stage, such clamping pressure of each slip grip at any given stage in the drawing operation being determined 7 single confined body of the same, so that the displaced fluid propels and gives drawing movement to an inner die element.

14. The art of drawing sheet metal to cup formation, which consists in drawing it successively to cup shapes of decreasing diameter, the while maintaining an hydraulic pressure on the drawing. elements and on the material in amount proportionate to the resistance said material progressively reposes to the drawing, by causing an outer die element to displace a substantially non-compressible fluid in a single confined body oi'the same, sothat the displaced fluid propels and gives drawing movement to an inner die element. 7 4

15. The art of drawing sheet metal to cup formation, which consists in applying pressure to the sheet metal and thereby gripping the metal against an outer gripping element, and-causing the movement of the outer gripping element, and thereby displacing a confined. practically noncompressible fluid, and causing said displaced fluid to apply drawing pressure in an opposite direction to an inner die or dies.

16. In a drawing press mechanism, the combination, with cutting parts, or a pair of opposed substantially'concentric instrumentalities clamp ing material to be drawn in a slip grip, an anvil over which the material is drawn as it is removed from its slip grip, means for moving said instrumentalities to efl'ect the drawing of said material cooperating with one of said instrumentalities to cut a disc from said strip, an anvil over which the disc is drawn as it is removed from its slip grip, means for'mov'ing. said instrumentalities to effect the cutting and drawing actions and hydraulic connecting means between said anvil and a said instrumentality and operating throughout the cutting and the drawing operations .to transmit the movement of said instrumentality to said anvil causing it to move in an opposing direction.

18. In a drawing press mechanism, the combination, with cutting parts, of a pair of opposed, Substantially concentric instrumentalities clamping material to be drawn in a slip grip, an anvil over which said material is drawn, and an hydraulic device embodying a cylinder and piston members movable therein, said members moving with said anvil and with a said instrumentality movement of one of said pistons is transmitted through the liquid to the other.

19. A compensating hydraulic device for a drawing press mechanism comprising in combination, with cutting parts, of a pair of opposed substantially concentric instrumentalities for clamping material in a slip grip while performing a drawing operation thereon, an anvil over which said material is drawn, and means acting during the drawing operation for exerting a clamping pressure on said material in said slip grip in direct proportion to the drawing resistance offered by the material being drawn.

20. A compensating hydraulic device for a drawing press mechanism comprising in. combination, with cutting parts, of a pair of opposed substantially concentric instrumentalities for clamping material in a slip grip while performing a drawing operation thereon, an anvil over which said material is drawn, means acting during the drawing operation for exerting a clamping pressure on said material in said slip grip in direct proportion to the drawing resistance offered by the material being drawn, and devices for returningthe parts to normal position after the drawing operation.

21. In a drawing press mechanism, the combination, with cutting parts, of a pair of opposed, substantially concentric instrumentalities clamping material to be drawn in'a slip grip, an anvil over which said material is drawn, an hydraulic unit interposed between said anvil and a said instrumentality for transmitting pressure from one to the other'as such pressure is developed by the drawing resistance in said material, said pressure being manifested as a clamping pressure in said slip grip and bearing a predetermined relation to said drawing resistance.

22. In a drawing press mechanism, the combination, with cutting parts, of a pair of opposed,

substantially concentric instrumentalities clamping material to be drawn in a slip grip, an anvil over which said material is drawn, an hydraulic unit interposed between said anvil and a said instrumentality for transmitting pressure fromone to the other during the drawing operation, and means for removably connecting said anv with said hydraulic unit.

23. In adrawing press mechanism, the com- -bination, with cutting parts, of a pair of opposed, substantially concentric instrumentalities clampdirections of travel and operating against the. material being drawn to establish clamping pressure in. said slip grip.

24. In a sheet metal press, the combination of a fixed die, a chamber having a liquid therein,

oppositely movable ring and block elements cooperating with said die, meansmovable with said ring and disposed in the liquid, means rigid with said block and also disposed in the liquid, and a movable die for urging said ring in one direction,

' whereby to move said block in the opposite direction.

'25. A method for shaping articles from metal blanks which consists in placing a blank to be shaped over a die and supporting said blank upon a blank holder positioned. in the path of a. second die arranged to move toward the first die, so that upon movement of thesecond die to efiect drawing of the blank the latter will be clamped between the blank holder and the second die by a pressure'which bears a constant ratio to the drawing pressure. 26. A method for shaping metal blanks which consists in drawing the blank to be shaped between cooperating dies by hydraulic means, clamping a portion of the blank against only one of the dies by hydraulic means, and maintaining a free andv direct interflow of pressure fluid be- ,tween the hydraulic drawing means and the hydraulic clamping means, whereby to transmit pressure therebetween in substantially undiminished condition, said interfiow of pressure fluid serving to clamp said blank during the drawing operation by a pressure which bears aconstant ratio to the drawing pressure.

27. The art of forming articles, which comprises, drawing sheet material over an anvil while holding its outer edges in a slip grip and hydraulically transmitting the resulting clampingpressure to said anvil, said clamping pressure being substantially determined at any given drawing time by the drawing resistance oii'ered by the 'sheet material.

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