US2192778A - Drawing press - Google Patents

Description

March 5, 1940. STACY 2,192,778

DRAWING PRES 5 Filed Nov. 5, 1955 3 Sheets-Sheet l A TTOEA/EY5.

March 5, 1940. T. F. STACY 2,192,773

DRAWING PRESS Filed Nov. 5, 1935 3 Sheets-Sheet 2 March 5, 1940. STACY 2,192,778

DRAWING PRESS Filed Nov. 5, 1935 3 Sheets-Sheet 5 M m #2 W VAR/ABLE DEL/VERY PUMPS.

5/ QC4LWMZMM A TTORA E Yd.

Patented Mar. 5, 1940 UNITED STATES PATENT OFFICE DRAWING PRESS Application November 5, 1935, Serial No. 48,382

19 Claims.

This invention relates to metal drawing presses in which a blank sheet of metal is drawn and deformed into a desired form or configuration. In the drawing of sheet metal from blanks, when deep draws are made, a certain point is sometimes reached at which the metal will tear or rupture. If the speed of drawing is too great, there is further danger of tearing of the metal blank.

An object of the invention is to provide an improved method of drawing metal from blanks,

with which exceptionally deep draws will be possible; and with which losses from tearing and rupturing of the metal blanks will be reduced.

Another object of the invention is to provide improved means for controlling and varying the pressure on a metal blank during the drawing operation.

Another object of the invention is to provide an improved metal drawing press and control means therefor, with which deeper draws may be made with a minimum of loss from tearing and rupturing of the blanks in the drawing operation; with which the speed of the draw need not be objectionably lessened; and which will be rela tively simple, dependable, easily controlled, compact and inexpensive.

A further object is to provide improved means for controlling the speed of travel of a platen in accordance with a predetermined plan.

Various other objects and advantages will appear from the following description of an embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

Fig. l is a diagram of a drawing apparatus and control system constructed in accordance with this invention;

Fig. 2 is an elevation of part of the control mechanism for one of the parts;

Fig. 3 is a transverse sectional elevation through a pilot operated check valve, two of which are employed in the system shown in Fig. 1;

Fig. 4 is a sectional elevation through a control valve which may be used in the system of Fig. 1 for controlling the rate of travel of the main ram;

Fig. 5 is a sectional elevation through another control valve which may be used for maintaining a sustained pressure on the blank holding ring in the system of Fig. 1;

Figs. 6 and '7 are sectional elevations of a control valve used. in the system of Fig. 1 for controlling the activity of the auxiliary blank holding rams;

Figs. 8 and 9 are similar elevations of valve mechanism used in the system of Fig. 1 for controlling the activity of the main ram, and

Fig. 10 is a diagram similar to Fig. l but illustrating some modifications in the system.

While many features of the invention may be applied to presses of various types, including mechanical, crank and hydraulic presses, or combinations of them, the improved system is shown, by way of example, as utilized in connection with a hydraulic press having upon its base a relatively fixed die element ill with a suitable die cavity or recess H in its upper face. Supported above the base, as usual in hydraulic presses, is a platen f2 which is guided in the usual manner for reciprocation toward and from the base which mounts the die element Hi. This platen i2 is operated in both directions by a piston l3 projecting into a main cylinder id and forming therewith a double acting main ram, by which the platen if: is reciprocated in opposite directions. The platen i2 removably mounts a die element it which cooperates with the die cavity H to draw and deform a metal blank 15 into a desired configuration or shape.

The blank it is placed on the die element Ii] across the cavity H, and while it is confined in that position, the cooperating die element l5,

during the downward travel of the platen 12, Jill draw and deform the blank until it conforms to the shape of the cavity H. During the drawing operation it is desirable that the periphery of the blank be held under a sustained pressure in order to prevent wrinkling of the blank while being drawn. For this purpose a blank holding ring or member H is disposed beneath the platen l2 and is provided with an aperture or opening 18 through which the die element 95 projects. The ring or member ii is supported by a plurality of pistons 59, which extend upwardly therefrom through apertures 2!! in the platen l2, and into auxiliary cylinders 21 so as to form with the cylinders 2!, double acting rams that support and reciprocate the blank holding ring or member ll.

When the pistons 19 are lowered or forced downwardly, the member or ring I? will engage with the blank l6 and confine it against the die element 10 with a sustained pressure. The details of such drawing presses are well known in the art, and in themselves form no part of the invention, and while the blank holding means may be employed equally well with a mechanical all) or any other type of drawing press, the means for controlling the pressure of the blank holding ring onthe blank is particularly adaptable for use in connection with a hydraulic press in which the drawing platen is reciprocated by hydraulic rather than mechanical means.

The activity of the auxiliary ram pistons i9 is controlled by a valve 22 illustrated in Figs. 1, 6 and 7, and the activity of the main ram piston I3 is controlled by a valve .23 which is similar in construction to the valve 22. The valve 22 is provided with a valve chamber i l in which a spool-shaped valve element 25 reciprocates, and reciprocation of the element 25 is obtained by a valve stem 26 extending from the element 25 downwardly through the bottom end of the easing of valve 22, and downwardly through a passage El provided in a lateral extension of the blank holding ring or member IT. The lower end of the stem 25 is pivotally connected to one end of a control lever 28, which is pivoted at 2Q on a suitable part of the press frame. Intermediate of its ends and above the ring ll, the stem 26 carries a collar 39 which is shiftable along the stern it into diiierent, desired, adjusted positions in any of which positions it may be secured in any suitable manner such as by a set screw. 1

In the particular illustrated example, the stem 26 also extends loosely through an aperture 3! in the platen l2. The neutral or intermediate position of the valve element 25 is shown in Fig. l, and the other operative positions are shown in Figs. 6 and '1, the element 25 being shiftable into the different positions by the control lever 28 and the collar 30. The liquid for the actuation of the auxiliary rains that control the blank holding ring ll may be obtained from any suitable source such as a tank 32 of any desired size, and preferably, although not essentially, the liquid in tank 32 is maintained under a pressure such as under a pneumatic pressure, or by the use of an accumulator, not shown. Various means for malntaining the liquid in the tank 32 under such pressure are well known and are omitted in the interest of clarity.

A unidirectional, continuously operating pump 33 is connected at its intake side by a pipe 34 to one portion of the tank 32, and at its outlet side is connected by a pipe 35 to a port 35 in the valve chamber 25: approximately midway between its ends and between the flanges 31 and 38 of the spool-shaped valve element 25. One end of the chamber TM is connected by pipes 33 and All to another part of the tank 32, and the opposite end of the chamber 24 is similarly connected by pipes M and 2 to the pipe 45 which leads to the tank 32.

When the valve element 25 is in a neutral or intermediate position, such as shown in Fig. l, the flange 3'! of one end of the spool, bridges and closes an annular port 43 in the side wall of the chamber 2t, and this port 43 is connected by a branched pipe 3 3 to the lower or pullback ends of the auxiliary cylinders 2!, that is to the ends of the cylinders 25 which are beneath the head of the piston 19. Any number of the cylinders 2| may be employed, but only two are shown for the sake of simplicity.

The opposite ends of the cylinders 2!, that is, the upper ends which extend across the entire end areas of the heads of the pistons iii, are connected by a pipe 55 with a port G6 which is aligned with the other flange 33 of the spool of the valve element 25, when the latter is in this intermediate or neutral position shown in Fig. 1. The flange 38, however, instead of bridging and closing the port t6, when aligned therewith, in the manner that the flange 37 closes the port Q3, is bevelled or chamfered on" on opposite sides of its peripheral edge so that when this flange 3? is aligned with this port 56, as shown'in Fig. 1, liquid in the chamber 25 may pass around the flange 33 as well as through the port 56. which, for convenience, is made annular.

When the valve element 25 is shifted into the position shown in Fig. 6, that is, when it is moved upwardly from the neutral position, such as occurs when the free end of the control lever 23 is depressed, the intermediate port 33 will be connected through the central annular space surrounding the valve element with the upper port ill, and at the same time the flange 31 has uncovered the port 3 so that communication is established between pipe ll leading to the lower end of the chamber 2 3 and the port 43. When the valve element 25 is in this upper position shown in Fig. 6, any liquid trapped in the auxiliary cylinders 25 below the heads of the piston, may escape through the pipe l l, port 43, the lower end of chamber 2 5 and pipes ll and 42, back to the tank 32. At the same time the pump 33 withdrawing liquid from the tank 32 through the pipe 3 and delivering it through the pipe 35, port central portion of the valve chamber 2%, port and the pipe 35 to the upper ends of the auxiliary cylinders i l.

The pistons 53 are now free to descend and the liquid delivered from the pump into the upper ie cylinders El will urge the pistons l3 5 ends of downwai ly. Until resistance is encountered, however, by the ring ll, its weight will tend to pull the pistons is downwardly, and in order to expedite this movement, a prefill check valve N is connected at one side through a pipe 48 to the pipe and at its other side by a pipe l9 to the pipe One type of such a check valve is shown in Fig. 3. The free check valve element 59 provided in this valve l'l, opens freely to pass fluid from the pipe as to the pipe is and automatically closes to prevent reverse flow. Thus as the pistons it start downwardly to place the blank holding ring ii on the blank it, the operating liquid will flow from the tank J2 through pipes M and lil to the valve ll, will open the check valve 53 and pass through the pipes 58 and 45 to the free ends of the cylinders 21 to ill the space created by descending pistons 59. When the auxiliary pistons iii are who raised, it is desirable to open the valve ll and allow the liquid displaced from the upper ends of the cylinders 2i by the pistons It to return easily and rapidly to the tank 32. For this purpose a pilot cylinder Ma (Fig. 3), operates a piston ll'b against the action of a helical compression spring Me to lift the valve element 53 forcibly. A branch of the pipe M is connected to the pilot cylinder ilo. Hence, whenever operating liquid is supplied to the lower ends of the cylinders ill to lift the pistons 13, the same operating liquid pressure is applied to the pilot device to lift valve element 58 and allow free return of liquid from the upper ends of cylinders 2| to tank 32, without passage of all or the displaced liquid through the valve 22.

When the blank holding ring ll engages with the blank 53, resistance is immediately offered to further downward travel of the pistons l 9, whereupon the pressure in the upper ends of the cylinders 2! immediately builds up because of the continued delivery thereto of the operating liquid from the pump 33, and this increased pressure ,with the teeth of a rack bar 6!.

.' platen tends to cause a reverse flow through the valve 47. The valve 4? thereupon automatically closes through the seating of its valve element 50, and thereafter continued delivery of the operating liquid from the pump 33 to the upper ends of the cylinders 2i will cause the building up of a high pressure on the pistons 19 acting in a downward direction, which pressure is transmitted to the blank holding ring l? and thus to the periphery of the blank 16.

It is desirable to maintain a sustained pressure on the ring l? in this holding position, and this is accomplished in accordance with this invention by means in addition to the pump 33. For this purpose the port 45 is also connected by a pipe 5! through a valve seat to the valve chamber 52 of a pressure relief valve 53. This pressure relief valve, shown particularly in Fig. 5, has a free valve element 54 which is urged into closed position against its seat by a spring 55 which is compressed between the valve element 54 and a pressure head 55 also disposed in the chamber 52. The pressure head 56 is mounted on a stem 5'! which has threaded engagement with the casing of valve 53, so that when this stem or rod 5? is turned or rotated, it will be shifted endwise in the chamber 52 in a direction depending upon the direction of rotation of the stem. The pressure of the spring 55 on the valve element 54 will thus be varied by rotation of the stem or rod 5'1.

An outlet 58 of the chamber 52 is connected by a pipe 59 to the pipe #2, so that when the pressure in the pipe 5|, which is at all times in communication with the upper ends of the auxiliary cylinders 2i, becomes sufficient to overcome the pressure of the spring 55 on the valve element 56, the valve element 54 will open and liquid will pass through pipes 59 and 12 back to the tank 32. As soon as the excess pressure falls the spring 55 will again close the valve element 5d, and hence the pressure in the upper ends of the cylinders 25 and thus on the blank holding ring I 7 will be sustained, and will be directly proportional to the pressure of the spring 55 on the valve element 54. Thus the pressure on the ring 11 may be varied by rotating the stem or rod 51 in one direction or the other, depending upon whether an increase or decrease in the pressure of the ring I! on the blank i6 is desired.

In order to vary the pressure on the spring 55 and thus the pressure of the ring H on the blank Hi, the outwardly extending end of the rod or stem 57 is provided with a pinion 69 which meshes The bar 6| is rockably connected at its lower end to one arm of the bell crank lever 62, pivoted at 83, and mounts upon its other arm a cam follower or roller A spring urges the bell crank lever 82 yieldingly in a direction to force the cam follower B l against a cam surface 66 which is carried by the platen I2.

As the platen l2 moves toward the die element 10. the undulations of the cam surface cause a rocking of the bell crank lever 62, reciprocation of the rack bar 61, and rotation of the pinion 60 and of the stem or rod 57, to change the pressure on the blank holding ring l? in accordance with a predetermined plan under the control of the 12. Thus while the ring 1! remains clamped against the blank it under a sustained hydraulic pressure, the travel of the platen in a downward direction will cause a variation in this sustained presstue in accordance with a predetermined plan.

The connection between the rack bar El and the bell crank lever 62 is one which causes the rack bar to reciprocate vertically in both directions upon rocking of the bell crank lever 62. For example, the rack bar may have a shoulder or collar 6'! provided thereon at a short distance from the lower end of the bar and engaging with one side of the bell crank arm, and the bar, after passing loosely through an aperture or slot in the arm of the bell crank lever 62, carries a washer B8 and a nut 63. The collar 6'! and the washer 88 have semi-spherical or convex arcuate surfaces abutting opposite faces of the bell crank lever 62, so that the rack bar may rock laterally somewhat at its connection to the bell crank 82.

The valve 23 is similar in construction to the valve 22, and is provided with a central annular port I'll and intermediate ports H and 72. The valve element 13 is of spool shape, similar to the valve element 25 of valve 22, and has the flange 14 at one end, which corresponds to the flange 41 of valve 22, of such thickness that when in its neutral position shown in Fig. 1, it will bridge and close the port ii. The other flange 75, which corresponds to the flange 38 of valve 22, is bevelled or chamfered on both faces at its periphery for a similar purpose, so that when the valve element 13 is in a neutral or intermediate position, such as shown in Fig. l, in which the flange l4 closes the port H, the chamfered flange '15 will be aligned with the port 72. Liquid may thus pass from the port 10 around the flange at the port '12, through the upper end of the valve chamber It, and thence through the pipe 38 to the tank 32.

A unidirectional, continuously operating pump ll is connected at its intake side by a pipe 78 to a portion of the tank at a point spaced from the connection of the pipe 483 to the tank. The output or delivery side of the pump 7? is connected by a pipe '19 to the port Hi, so that when the valve element 13 is in the neutral position shown in Fig. 1, the liquid delivered by the pump 19 will flow around the periphery of flange l5 and back through the pipe 49 to the tank, thus circulating idly through the valve chamber '55. The port ii is connected by a pipe 83 to the lower end of the main cylinder 14, and thus liquid trapped in the cylinder M, below the head thereof, cannot escape through the port 7 l. which holds the platen l2 in raised position.

Pipe 48 is also connected by a branch pipe 81 to the lower end of the chamber 13 for a purpose which will appear presently. The valve element 73 is reciprocated endwise in the chamber '16 by means of a valve rod 82 which extends downwardly through the lower end of the chamber 76, passes through an aperture 83 in the platen l2, and at its lower end is pivotally connected by a pin 84 to one end of a control lever which in turn is pivoted at 88 to a suitable support.

When a downward movement of the platen is desired the operator pushes the free end of the control lever 35 downwardly, which elevates the rod 82 and through it shifts the valve element '13 from the neutral intermediate position shown in Fig. 1 to the upper position shown in When this occurs the flange l4 uncovers the port H and positively prevents communication between the ports '18 and H. Communication is, however, established between the pipes 36 and BI so that the fluid trapped in the lower end of the main ram cylinder l4 may escape through the pipe 80, the port H, the chamber '16, and pipes 81 and 40 back to the tank 32.

f of the chamber 92.

At the same time the flange it moves above the port '12 andthe liquid delivered by the pump 17 instead of passing upwardly and around the flange its to the pipe 48 will be compelled to pass through the port l2, and thence by means of pipes 81 and 68 to the upper end of the main cylinder it. The movement of operating fluid into the upper end of the cylinder i i and the weight of the platen I2 will cause the platen to descend as rapidly as fluid can enter the upper end of the cylinder M.

In order that the speed of the platen 52 may be rapid until the drawing operation starts, the pipe 88 is connectedthrough a prefill check valve 89 to the pipe lll and thus to the tank This valve Sl is identical with, except usually larger than, the valve 47 shown in 3 and it opens freely in a direction to pass fluid from the pipe ii to the pipe 88 and the main cylinder 2 so that as the descent of the platen creates a suction in the upper end of the cylinder operating liquid may flow from the tank 32 through the pipe Mi, the valve 89 and pipe 88 into the upper end of the cylinder is, thus supplementing the liquidvdelivered by the pump ii to the upper end of the cylinder M.

When the die it carried by the platen E2 engages with the blank 5, pressure resistance to further movement of the platen i2 is set up, and since the pump l'i continues to deliver liquid to the upper end of the cylinder i l, the pressure on the upper end of the piston is will build up, whereupon the liquid in the cylinder is will tend to flow outwardly through the pipe 83 and valve 89 to the pipe id, but thereupon the valve 89 closes automatically, so that the pressure on the upper end of thepiston l3 builds up in response to the continued delivery of liquid to the upper end of the cylinder i l from the pump ll.

It is desirable to vary the speed of downward travel of the platen during the drawing operation on the blank l6, and the means for varying this speed in accordance with a predetermined plan will next be described. The pipe 92] connects the pipe 31, leading from the port 12, to one end of a bypass valve 9! which is shown diagrammatically in Fig. l and in greater detail in Fig. In the chamber 92 of the valve 9i is a valve element 93 which is mounted on the end of stem or rod M. The rod 9 has threaded engagement with the inner end of a sleeve that closes one end Thus as the stem Qt is rotated, it will be threaded into and out of the chamber 92 to various extents, so as to shift the valve element t3 toward or from its valve seat in the chamber 92, depending upon the direction of rotation of the stem t l.

A pipe 96 connects the chamber $2 to the pipe til, from which it will be observed that a portion of the liquid delivered by the pump ll to the pipe 8'! may pass through the pipe tit and the valve 9i back to the pipe it, thus completing an idle circuit through the pump for a portion of the liquid. The proportion of the liquid which is bypassed through the valve st in this manner will vary with the setting of the valve element and this setting may be varied by rotating the stem or rod 9% in one direction or the other, deending upon whether an increase or decrease in the amount of bypass is desired. The outer end of the stem or rod 94 is provided with a pinion 9! which meshes with the teeth of a rack Q8. This rack bar depends from the pinion er and at its lower end is rockably connected to one arm of a bell crank lever 99, such as the manner explained for the connection of the rack bar 6| to the bell crank lever 52.

The bell crank lever 99 is pivoted at Mill, and its other arm carries an offset cam roller or 01- lower it! which engages with and rolls upon a cam surface 502 carried by the platen 12. A spring i833 that is connected to the horizontal arm of the bell crank 53B, urges the latter in a direction to press the roller illl against the undulating cam surface 592 at all times. The cam surface it? extends or undulates in the direction or" the travel of the platen, and thus as the platen i2 descends, the cam surface H32 thereof will cause a rocking of the bell crank 95 and through the resulting reciprocation of the rack bar 98,

the pinion 9'? and stem S t will be turned in one direction or the other to increase or decrease the amount of liquid bypassed. When more liquid is bypassed, the speed of travel of the platen l2 will be decreased, and vice versa.

Thus the platen 52 in its movement controls its own speed during the drawing stroke, and by selecting the undulations. of the cam surface I02, the speed of travel of the platen l2 may be decreased at those points or zones in the drawing operation, where there is danger of tearing or rupturing of the blank, with the result that deeper draws may be successfully made. By selecting the character of the cam surface lit, the pressure or the blank holding ring H on the periphery of the blank it may be decreased to the extent desired in the proper zone of the platen travel to allow more slippage of the blank It at the critical zones, which in some cases may be at the same time that the speed of the platen i2 is decreased. Any other control of the pressure of the blank holding ring on the blank or in the speed of the platen may be obtained merely by proper selection of the shapes of the cams 66 and i112.

At the end of a drawing operation the operator elevates the upper end of the control lever 85, which pulls the valve rod 32 downwardly and moves the valve element 73 from the position shown in Fig. 8 to the position shown in Fig. 9. When this occurs the flange is will out ch communication between the ports l and '52, thus interrupting delivery from the pump ll to the upper end of the main cylinder M, and the flange 'Hl will move concomitantly to a position between the port it and the outlet pipe Bl, so that escape of further liquid from the lower end of the cylinder i l will be prevented. The central port it is now connected to the port i l, and thus the liquid delivered by the pump ll to the valve chamber it will now pass through the port ii to the pipe 88, and thence to the lower end of the cylinder 14, so as. to exert a lifting pressure on the piston l3. The flange 15 has moved from a position in which it interrupted communication between the port 52' andthe pipe so that the liquid previously delivered to the upper end of the cylinder 1 3 may now pass through the ipes 88 and 3'2, the port 72 and the pipe it back to the tank 322. The pressure in the upper end of the cylinder i l thus immediately falls and permits an upward movement of the piston 13.

In order to expedite the upward movement of the platen l2, provision is made for forcibly opening the check valve of the prefill valve 39. For this purpose a branch pipe i04- leads from the pipe 89 to the pilot cylinder of the prefill valve 8? so as to forcibly open the check valve element 51! thereof in the manner hereinbefore explained in con-f nection with the opening of the preiill valvev 47.

As the platen l2 moves upwardly and approaches its upper limit of movement, it will engage with a collar it??? provided on the valve rod 82, so that further upward movement of the platen l2 will elevate the rod 82 and shift the valve element (3 from the position shown in Fig. 9 to the neutral or idle position shown in Fig. 1. When the valve element 73 moves back into this neutral position, the flange M again bridges the port I! and thus disconnects the pump 7'! from the pipe 3%, and also prevents escape of liquid from the pipe 8!], thus locking the main piston l3 in its elevated position. The flange T at the same time opens communication from the port to the port l2 and the pipe All, thus conducting the liquid delivered by the pump 7! back to the tank 32. This idle circulation of liquid through the pump ll will continue and the piston !3 will be effectively held in its elevated position. The collar M95 is mounted on the rod 82 for adjustment endwise along it, and it may be secured in different adjusted positions in any suitable manner such as by a set screw which is carried by the collar and is engageable with the rod 82.

When the platen Ill starts upwardly the blank holding ring I! will continue to hold the blank It against the die element l9, so as to strip the formed blank from the die element l5, and after that occurs the operator elevates the free end of the control lever 28 which shifts the valve element 25 from the position shown in Fig. 6 to the position shown in Fig. 7. When this occurs, the intermediate port 36 to which the pump delivers operating liquid will be connected with the port 43, and thus the liquid from the pump will be delivered through the pipe 44 to the lower ends of the auxiliary cylinders 2 l. At this time the flange 38 is disposed between the ports 36 and 4E and shuts oil communication between them, but places the port it in communication with the pipes 39 and 48.

The liquid in the upper ends of the auxiliary cylinders 25 may then pass through the pipe 45, through the port and pipes 39 and All back to the tank 32, and thus as the liquid is delivered under pressure to the lower ends of the auxiliary cylinders the auxiliary pistons lo will be elevated and thus will elevate the blank holding ring or element ll and release the blank IS.

The pressure of the liquid from the pump 33 is transmitted through the pipe to the pilot cylinder filo. and will force the pilot piston ill) upwardly against the action of the spring 470. This forcibly opens or lifts the check valve element 5! so to allow the liquid to pass directly from the upper ends of the auxiliary cylinders 13! to the pipe Ml and back to the tank. After the blank holding ring ll has been elevated, the formed blank l3 may then be ejected from the die recess il in any suitable manner which is common in the art, such as by a spring ejector or air or hydraulic mechanism, not shown, and which in itself forms no part of this invention.

As the ring ll approaches its upper limit of movement it engages the collar shifts the valve stem or rod 2 3 upwardly, and thus returns the valve element 25 from the Fig. '7 position to the Fig. 1 position which is the idle or neutral position occupied when the press is idle. At this time the pump 33 circulates liquid idly through the valve 22 and pipes 39 and 4G back to the tank 32, and the pistons l S are held in their upper positions by the liquid trapped in the lower portions of the auxiliary cylinders 2!. due to the bridging of the port 43 by the flange 31 of the valve element 25.

The operation of the press and system will be clear from the foregoing description, but may be briefly summarized as follows:

Assuming that the parts are in the idle position shown in Fig. 1, let it be assumed that a blank 18 has been placed on the die element H] across the die recess H. The operator then depresses the free end of the control. lever 28, which elevates the valve element 25 an initiates a downward movement of the auxiliary pistons I9 and ring l1. At the start of this downward movement of ring ll, the pressure on the pipe 44 is released, and thus the pressure on the pilot piston 41b is decreased, whereupon the spring 470 forces the pilot piston no downwardly to release the check valve element Ell, and permit it to close. When the ring I! engages with the blank iii, the pressure then built up in the upper ends of cylinders 2i causes the prefill valve ll to close, and the continued delivery of liquid from the pump 33 to the upper ends of the auxiliary cylinders 2! will build up a sustained pressure upon the blank holding ring '5, until the pressure is suificient to overcome the force of spring 55. whereupon the valve element 54 opens sufficiently to maintain the pressure at that determined by the setting of the pressure head 56.

When the blank holding ring has progressed far enough so that it will engage and hold the blank 96 before the platen !2 can carry the die element into engagement with the blank, the operator depresses the fr e end of the control lever which elevates the valve element 13 from the Fig. 1 position to the Fig. 8 position, and initiates a downward movem nt of platen l2. The downward movement of the platen l2 will be controlled at intervals in its descent as to speed by the cam surface H32 and the bypass valve 9!, the latter being set into difierent degrees of open ing by successive changes in the character of the surface 62 as the platen l2 descends. At the same time the pressure on the blank holding ring will vary in accordance with the successive positions of the platen l2 under the control of the cam surface 56.

At the end of the drawing operation, the opera tor elevates the free end of the control lever 85 and initiates an upward travel of the platen I2 that is terminated automatically by engagement of the platen with the collar 35, through which the rod 52 is elevated to return the valve element it to the neutral position shown in Fig. l. The upward movement of the blank holding ring I! is initiated after the platen 12 has started upwardly, by tilting upwardly the free end of the control lever 23, and the upward movement of the ring H is terminated when it engages the collar and elevates the rod 26 sufficiently to return the valve element 25 to the neutral position shown in Fig. 1.

The shape and configuration of the cam surfaces 55 and H12 will vary with different dies employed, because the slippage and speed of travel must be varied at just the critical points in the drawing operation. These critical points will vary with different types of blanks being drawn and difierent dies that are used, and must be determined for each different die or blank employed.

In Fig. 10 a slight modification of the controls of the pressure on the blank and of the travel of the platen have been illustrated with so much of the remainder of the press and system as is necessary to show the relation of the modified parts to the other parts. In this modification of Fig. 10, the pressure opened valve 53 and the pipes El and 59 shown in Fig. 1 are omitted, and the pump 33 is replaced by a pump H35 which is of the variable delivery reversible type, but continuously operating. Such pumps are well known in the art and by way of example, one of this general type is illustrated in U. S. patent to Landenberger et al. 411,863,448 issued June 14, 1.932. The pump at its intake side is connected by the pipe 34 to the tank or source 32 of operating liquid, and its output side is connected by the pipe 35 to the valve 22, as in Fig. 1.

The pump I05 is adjustable in order to vary its delivery or to reverse its delivery by means of a yoke I05 which is shifted in alternate directions by a lever IIl'I pivoted at I518. The lever II): is pivoted to a block I03 which is mounted on a rod I I I) to slide in a direction endwise ther on. A nut or collar III is provided on an end of the rod I If) so as to limit movement of the rod HE! through the block H39 in one direction, and a helical spring I !2, disposed on the rod IIB and acting against a washer or collar HS that is slidably mounted on the rod I Iii, forces the block H19 yieldingly against the nut or collar lII. Pressure is provided on the spring I I2 by a washer I I4 which is slidable on the rod I It and abuts endwise against a pinion H5 that is threaded on the rod III). Thus, by rotating the pinion H5, it will be threaded along the rod IIFJ so as to further compress or release the spring H2, and thus vary the pressure with which the lever I0! is held against the collar or nut II I.

A lever H6, pivotally mounted at II 1, is pivoted at one end by a pin IIB to a block H9 that is also threaded or fixed on the rod Ht. so that the rod I Ill may be forcibly operated in alternate directions to change the direction of delivery of the pump, or the rate of delivery, in a manner which is well known in the variable delivery reversible type of pumps. The pressure in the pipe 35, which is the output side of the pump as connected, is operable upon the lever it? through a small ram, not shown, but which is common in this type of pump, in a manner to rock the lever H31 clockwise in Fig, 10, against the action of the spring I22, while the rod H9 remains in set position. Thus, when the pressure'in pipe 35 equals or exceeds a predetermined pressure, determined by the pressure of spring 1 I2, the lever an will be rocked clockwise in Fig. 10 against the action of spring IIZ so as to shift the yoke I96 in a direction to set the pump for neutral delivery position.

If the pressure falls, the spring I I?! will return the lever I0! and yoke I 36 to delivery position,

and the pressure in pipe 35 will built up until it is again suihcient to overcome the pressure on spring M2. By rotating the pinion H5, one may therefore determine the pressure which will be maintained automatically in the pipe 35, and this pressure may be varied merely by rotating the pinion H5 in one direction or other, depending upon whether an increase or decrease of pressure is desired. The pinion II? meshes with the rack bar Ii! corresponding to the rack bar 5! of Fig. 1, and thus, as the platen I2 moves downwardly the cam surface 65 will operate the rack bar EI to change the pressure on the spring H2 in accordance with a predetermined plan and controlled by the travel of the platen, thereby determining the pressure on the blank during the drawing operation, which pressure varies with the different positions of the platen in accordance with a predetermined plan. The lever H6 is operated merely to change the maximum rate of delivery of the pump, and the reversing feature of the pump need not be utilized. In controlling the rate of travel of the plate in the working stroke under the system as modified in Fig. 10, the valve SI and pipes 98 and 96 of Fig. 1 may be omitted, and the pump ll of Fig. 1 is replaced by a pump I20 of the variable delivery reversible type in Fig. 10. The reversible feature need not be utilized in the system. The intake side of the pump is connected to the pipe I8, as in Fig. 1, and the output side of pump is connected by the pipe IS to the valve also as in Fig. 1. The pump I29 is identical with the pump I05 except that instead of the pinion H5 in the control for the pump Hi5, I have substituted a hand wheel I2I which is threaded on the rod l H] for varying the pressure on the spring H2. The rod III) which varies the rate of delivery of the pump is connected to a lever I22 which corresponds to the lever H6 of the pump I 55 except that the lever IE2 is a bell crank lever and is pivotally connected by a pin I23 to one end of a link I24 which corresponds to the rack bar 88 of Fig. 1. Thus, as the platen l2 moves downwardly, the cam surface I 02 thereof will act through the roller IUI and link I24 to shift the rod III! endwise and thus change the rate of delivery lustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim as my invention:

1.111 a drawing press, a fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a blank holding member also movable toward and from said element entirely separately from the 1novement of said platen, hydraulic means for actuating said holding member toward and from said element and for holding it under pressure against said element, and means controlled by the platen forpartiallybut not fully releasing the liquid pressure of said hydraulic means on said member and thus the pressure of said member against said element, automatically during a predetermined critical interval of the drawing operation during the travel of said platen toward-s said element, so as to allow regulated slippage of the blank during said critical interval.

2. In a drawing press, a fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a blank holding member also movable entirely separately from said platen toward and from said element, hydraulic means for actuating said holding 111cm. ber separately from said platen toward and from said element and for holding it under pressure against said element, a source of actuating liquid under pressure connected to said hydraulic means to operate it, an adjustable regulator for controlling the pressure of said member said element by controlling the admission of liquid under pressure to said means from said source, mechanism operated by said platen during its travel towards said element for adjusting said regulator to vary the pressure of said memher on said element in accordance with a predetermined plan under the control of said platen.

3. In a drawing press, a fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a blank holding member also movable toward and from said element entirely separately from the platen, fluid actuated means for actuating said member against said element and holding it thereagainst during the travel of said platen while in contact with a blank being operated upon, a source of fluid under pressure connected to said actuated means for moving it and holding it in clamping position, and means controlled by said platen during its travel towards said element for varying the passage of actuating fluid between said source and said actuated means and thereby decreasing and increasing the pressure of said fluid actuated means on said member in accordance with a predetermined plan and dependent upon the successive positions of said platen.

4. In a drawing press, a fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a blank holding member also movable toward and from said element, hydraulic means for actuating holding member toward and from said element and for holding it under pressure against said element during travel or" said platen, a source or" fluid under pressure connected to said hydraulic means for operating said holding means in both directions, and for providing the holding pressure, a cam part and a follower part, one of said parts being mounted on the platen. for travel therewith and the other part being operated thereby, and means controlled by said operated part for varying the passage of actuating liquid between said source and said hydraulic means and thereby regulat ng the pressure on said member in accordance with a predetermined plan dependent upon the successive positions of said platen in its travel towards said element.

5 In a drawing press, a fixed die holding element, a die-mounting platen mounted for movement toward and from element, fluid actuated means for moving said platen toward and from said element, means controlled by said platen in its travel towards said element for selectively controlling said fluid actuated means and varying the rate of travel of said platen in accordance with a predetermined plan, a blank holding member for holding a blank against said fixed element, and means also controlled by said platen for varying the pressure of said member against said element in accordance with a me determined plan dependent upon the successive positions of said platen.

6. In a drawing press, a fixed die carrying element, a mounting platen mounted for movement toward and from said element, fluid actuated means for moving said platen toward and from said el ment, pumping means for delivering an operatin fluid to said means including a fluid bypass controlled by said platen in its travel towards said element for bypassing portions of the operating fluid delivered to said actuated means around said actuated means in different proportions determined by the successive positions of said platen, for varying the rate of travel of said platen towards said element in accordance with a predetermined plan dependent upon the successive positions of the platen.

7. In a drawing press, a die-mounting, fixed element, a die-mounting platen mounted for movement toward and from said element, a fluid operated device for moving said platen in alternate directions towards and from said element, a fluid circuit including a pump connected to said device for operating said platen in opposite direcions, controlling means for said circuit for regulating the direction of travel of said platen, and means including a fluid bypass for said circuit from said pump past said device and operable automatically during the travel of said platen towards said element and controlled by the platen for bypassing varying proportions of the fluid delivered to said device, past said device, and thus varying the speed of travel of said platen in different successive zones of its travel in accordance with different successive positions of said platen.

8. In a drawing press, a fixed die holding element, a platen r ounted for movement toward and from said element, ram means connected to said platen for operating it toward and from said element, a source of actuating fluid, a continuously operating pump, a ci cuit including said source, pump and said ram means for causoperation of said ram means in one direction or the other, a bypass forming a part of said circuit and operable to bypass a portion of said actuating fluid around said ram means while said ram means is operating the platen towards said fixed element, and means controlled by said platen. in its travel towards said fixed element for operating the bypass to vary the quantity of fluid bypassed and thereby regulate the rate of advancement of platen towards said element accordance with intermediate successive positions of the platen.

9. In a drawing a fixed die holding element, a platen mounted for movement toward and from said element, ram means connected to said platen for operating it toward and from said element, a source of actuating fluid, a continuously operating a circuit including said source, said pump and said ram means for causing operation of said ram means in one direction or the other, a bypass forming a part of said circuit and operable to bypass a portion of said actuating fluid being delivered by said pump to said ram means around said ram means while said ram means is operating the platen towards said fixed element, a cam part and a follower part, one of said parts being mounted on the platen for travel therewith and the other part being positioned adjacent thereto for operation from the other part during the travel of the platen, and means controlled by said other part for operating said bypass to vary the quantity of fluid bypassed and thereby control the speed of travel of the platen as determined by said cam part, during the travel of said platen towards said fixed element.

10. In a drawing press, a fixed die holding element a platen mounted for niovement toward and from said element, means for confining a blank against said fixed element, means for actuati g said platen toward and from said element. means for pressing said blank confining member against said element, cam means operated by said platen in its vement toward said element for varying the speed of travel of said platen through intermediate zones of travel while in contact with said ble. and cam means also operated by said platen ror concomitantly varying the pressure of said blank confining member against said element.

11. In a drawing press, a fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said plate-n toward and from said element, a member for holding a blank against said element, a fluid circuit including fluid actuated means for presssaid blank holding member against said element, a pressure release valve included in said circuit for bypassing the fluid that presses said member against said'element Whenever the pressure exceeds the setting of said release valve, and means controlled by said platen for varying the setting of said pressure release valve at an intermediate point in the travel of said platen toward element while in contact with said blank.

12. In drawing press, a fixed die holding eloincnt, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a member for holding a blank against said element, a fiuid circuit including fluid actuated means for pressing said blank holding member against said element, a pressure opened but spring closed valve forking a part of said circuit, and opened by the fluid pressure which confines said member to said element, and means controlled by said'platen for changing the pressure on said spring at an intermediate point in the travel of said platen toward said element.

13. In a drawing press or the like, a relatively fixed die holding element, a platen mounted for movement toward and from said element, a blank holding member also movable toward and from said element, means including a variable delivery pump anda iluid circuit including said pump for actuating said platen toward and from said element, means including a cam device operated by the travel of said platen for varying the delivery of said pump and thereby varying the rate of travel of said platen in accordance with a predetermined plan represented by said cam device and its relation to said platen, means including a variable delivery pump and a fluid circuit ineluding said pump for actuating said blank hold;

ing member toward and from said element, said second pump having pressure responsive means for an Jomatically set-ting it to approximately neu tral delivery condition when the pressure at the delivery side of said second pump exceeds a predetermined pressure and adjustable for varying the pressure at which it sets itself to approximately neutral delivery condition, and means operable in a predetermined speed ratio to the travel of said platen and concurrently therewith for varying the pressure regulating means in a manner to vary the pressure at which said second pump will set itself to approximately neutral delivery position, in accordance with a sequence having a definite predetermined relation to the successive positions of the platen.

14. In a drawing press, a relatively fixed die holding element having an unyielding blank clamping a platen mounted for movement toward and from said element, hydraulic means for actuating said platen toward and from said element, a member for holding a blankagainst said unyielding area on said element, additional separate hydraulic means for exerting independen y of the platen travel a holding pressure on member, and means responsive to the successive positions of the platen in its movement toward said element for partially but not fully releasing the hydraulic holding pressure of said member on said blank when said platen reaches a predetermined, critical drawing position, intermediate of the start and finish of the drawing operation.

15. In a drawing press, a relatively fixed die holding element having a clamping area rigid with the remainder of the die, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a member for holding a blank against said clamping area of element, hydraulic means for exerting a holding pressure on said member independently of the platen travel, a source of liquid under pressure connected to said hydraulic means to supply the holding ressure thereto, and means including cam device operated conciurently with said platen toward said element for decreasing and increasing the delivery of liquid from said source to said hydraulic means and hence decreasing and increasing the pressure of said holding member against said element selectively in a predeterm ned sequence of pressures bearing a definite timed re" laticn to successive positions of said platen in its travel toward said fixed element.

16. In a drawing press, a relatively fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said ele-' ment, a member for holding a blank against said element, a fluid actuated device for exerting a holding pressure on said member, means for deliering a holding fiuid under pressure to said device, pressure responsive means for releasing the fluid delivered to said device when a predetermined pressure has been reached, and means responsive to the travel of said platen toward said element for adjusting said pressure responsive means in a manner to vary the quantity of fluid delivered to said device in different successive positions of said platen in its travel toward said element.

17. In a drawing press, a relatively fixed die holding element, a platen mounted for movement toward and from said element, means for actuating said platen toward and from said element, a member for holding a blank against said element, a fluid actuated device for exerting a hold ing pressure on said member, means for delivering aholding fluid under pressure to said device, a pressure opened valve connected to said device for releasing the fluid pressure thereon when a predetermined pressure on said member has been reached, and means responsive to the travel of said platen towards said element for adjusting the pressure at which said valve opens at a plurality of different successive positions of said platen in its travel towards said element.

18. In a drawing press, a pair of relatively movable drawing dies, a blank holding member for clamping a blank against one of said dies, fluid pressiu'e actuated means for holding said member in blank clamping position exerting a clamping pressure on a portion of a clamped blank independently of the relative movement of the dies, means independent of the pressure of the dies on the blank for delivering a fiuid under pressure to said holding means for furnishing the holding pressure and means controlled by the relative movement of said dies during a drawing operation for increasing and decreasing the fluid pressure on said holding means in accordance with a predetermined plan determined by the relative positions of the dies.

19. In a drawing press, a pair of relatively movable drawing dies, a blank holding member for clamping a blank against one of said dies, fluid pressure actuated means for holding said memher in blank clamping position and exerting a clamping pressure on a portion of a clamped blank independently of the relative movement of the dies, means independent of the pressure of the dies on the blank for delivering a fluid under pressure to said holding means for furnishing the holding pressure and means controlled by the relative movement of said dies during a drawing operation for releasing fluid from and adding fluid to said holding means in accordance with a predetermined plan, whereby the holding pressure on a blank being drawn will be decreased and increased in a definite relation to the relative positions of the dies.

THOMAS F. STACY.

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