US2290743A - Blank-holder press - Google Patents

Description

July 21, 1942. w ERNST BLANKHOLDER PRESS 'Filed Dec. A11, 1939 4 sheets-sheet 1* 21, 1.942- w. ERNST 2,290,743

BLANKHDLDER PRESS FiledDec. 1l, 1939 4 Sheets-Sheet 2 Y y I 7- I l July 21, 1942- w. ERNST BLANKHOLDER PRESS Filed Dec. 11, 1939 4 Sheets-Sheet 3 July 21, 1942.

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W. ERNST BLANKHOLDER PRESS Filed Dec. ll, 1939 v FIB. 4

4 Sheets-Sheet 4 43A- l/4f/3 45a 45a /3 /4 sa /a 26 27- z2 Ill' Patented July 21, 1942 UNITE STAT ES PAT E erica BLANK-HOLDER. PRESS Application December 11, 1939, serial No. 308,594 s claims. (c1. 11H5) This invention relates to hydraulic presses and in particular to means and mechanism for'operating blankholders on hydraulic presses.

It is Particularly the object of this invention to provide means of operating and controlling a hydraulic press, and especially that part of the press dealing with blankholders.

It is an object of the invention to coordinate the operation of the hydraulic press with lthe operation of the blankholder and to operate both the press and the blankholder hydraulically in synchronism with one another.

It is an object of this invention to provide an independent source of hydraulic pressure for the blankholder cylinders, and means of regulating the application of that pressure to the respective cylinders of the blankholder.

It is a further object of-this invention to provide means of balancing the pressure between the respective cylinders of the blankholder.

It is a further object to provide means of hydraulically operating and hydraulically timing a blankholder inv connection with the hydraulic which diverted pressure was utilized for operating the blankholder.

It is an object of this invention to provide one source of h ydraulic pressure for the operation of the platen and an independent pressure source for operating the blankholder, but timed and coordinated so as to operate in synchronism with the platen. Y

It is a further object ofthis invention to utilize the separate source of pressure for the blankholder to prell the blankholder cylinders when the platen is elevated and to thereafter utilize the major pressure on the ram in the main cylinder so that when the platen is forced down to draw the metal, this same downward force will cause an increase of pressure in the blankholder cylinders so that the greater the pressure on the platen, there is proportionately greater coordinated application of pressure applied to the blankholder.

vide means of relieving the pressure in said blankholder cylinders as the platen descends in the course of the application of the drawing pressure Y on the metal being drawn.

It is a further object of this invention to provide means of increasing the pressure in the blankholder cylinders to facilitate stripping as the platen is withdrawn and to utilize the separate source of hydraulic pressure for this purpose, and to utilizey this blankholder pressure for stripping purposes as also the means of prelling the blankholder cylinders prior to another stroke of the platen.

It is a further object to vutilize the unloading -valve system, which unloads the pressure source Figure 1 is a diagrammatic vertical section through a` metal drawing press, showing one form of hydraulic operating system of this irlvention for controlling the action of the blankholder.

Figure 2 is a vertical section through the press showing the parts in position at the start of the pressing or drawing operation.

Figure 3 is a similar view showing the parts in position during the stripping and prelling operations.

Figure 4 is a horizontal section through the platen of the press shown in Figure 1, taken on the line 2-2 and looking in the direction of the arrows, and further illustrating the hydraulic operating system seen in Figure 1.

Figure 5 is a view simmer te Figure abut i1` lustrating a modied form of operating system wherein provision is made for adjustably determining the pressures in each of the blankholder cylinders;

Referring to the drawings in detail, and par-.

ticularly to Figures 1, 2 and 3, there is provided a main pressing plunger l, having at its upper end a double-acting hydraulic piston 2. This piston reciprocates within a cylinder 3l according as pressure fluid is delivered to lits upper pressing area, or to its lower pullback area. Fluid pressure for moving the piston 2 is generated by a pump shown diagrammatically at 4, this pump being of the variable delivery reversible type. One ofthe discharge ports of the pump is connected by the conduit 5 to the upper wall of the cylinder 3, for eiecting the downward pressing stroke of the piston 2, and the other discharge port of the pump is connected by the conduit 6 to a port in the return stroke of the piston 2. The flow controlling element of the pump 4 may be shifted by any suitable manual or automatic means, such means being omitted from the drawings since they form no part of thisinvention.

The cylinder 3 is rigidly mounted in the head of the press, designated 1, this head being supported upon, and spaced from a base 8 by means of strain rods 9.

Attached to the pressing plunger I and moving integrally with it is the main platen I0, to which, in turn, is attached the upper member of a die shown in the drawings as the male member II adapted to mate with the lower member I2 of the die which is mounted upon the bed of the press. Within the platen there is formed a plurality of secondary pressing cylinders I3, these cylinders receiving pressure fluid from a secondary source for the purpose of exerting a clamping force through the plungers I4 to the blankholder platen I5. The plungers I4 may be attached by any suitable means, such as threads I6, to the blankholder platen I5. The blankholder platen is adapted to engage the work` piece, shown in the drawings as a flat blank I1, transmitting to the workpiece the clamping pressure generated in the blankholder cylinders I3, for the purpose of preventing the formation of tears and wrinkles.

As seen in Figures 1 to 4, pressure fluid to the y blankholder cylinders I3 is supplied by the auxiliary pump I8 which is of the common vane or gear type having a constant displacement. This` shoulder 33, which, in response to fluid pressure within the annular chamber 34, urges the plunger upwardly in opposition to the compression of the spring 35. At one end this spring bears against the head 36 of the plunger 3| and at the other end against the retainer 31, the position of which is set by the conical end of the adjusting screw 38. This adjusting screw is threaded into the top wall of the spring barrel 38, and is locked in place by the nut 40. It will be readily apparent that different settings of the adjusting screw 38, by varying the compression of the spring 35, will require correspondingly different fluid pressures within the annular chamber 34, acting against the area presented by the shoulder 33, to lift the plunger 3| and consequently to open the passage between the incoming conduit 22a and the exhaust conduit 28. Pressure is communicated to the chamber 34 through the control conduit 4I from anyone of the blankholder cylinders I3. The unloading of the pump I8 through the valve 2| is thus responsive to pressures within the cylinders I3, and these pressures, in turn, are determined by the setting of the adjustment 38 of the valve 2|. At the entrance of the conduit 4I into the chamber 34, there is provided an adjustable needle valve 42, which, by

l presenting a choke or resistance to the fluid flow into or out of chamber 34, determines the repump draws its fluid through the conduit I9 from the tank 20 and delivers it to an unloading valve, generally designated 2|, through a conduit 22. Interposed between the valve 2| and conduit 22 is a flexible connection 23, shown in Figure 1. 'Ihis connection is in the form of a stationary cylinder within which telescopes the conduit 22a, the latter being mounted, along with the valve 2|, upon the press platen I0, and moving with it as it reciprocates in its pressing and return strokes.

Since the pump I8 is of the constant displacement type, fluid will at all times be delivered to the valve 2|, from which it will be discharged in one of two directions, depending upon the requirements of the blankholder cylinders I3.` If these cylinders are under relatively low pressure, which condition occurs at the beginning of a retraction stroke of the press, fluid will pass from the valve 2| into the conduit 24, past the ball check valve 25, into a common blankholder supply conduit 26, and finally-through blankholder supply conduits 21 to the cylinders I3. If, on the other hand, the pressure within theblankholder cylinders is relatively high,`such asy occurs during a drawing operation. then the valve 2| will be actuated to exhaust through the line 28 and back to the tank 20. At this time the total delivery of the pump I8 will be vby-passed or unloaded through the valve 21|.

As shown in Figure 6, this valve consists of a valve body 29, having a bore 30, within which reciprocates a plunger 3|. adapted to fit snugly within the bore 30 so that when it enters this bore. as shown in Figure 4, no fluid passage is permitted between the line v 22a and the conduit 28. Surrounding the plunger 3|, and located centrally of the valve body 29,

there is provided an annular chamber 32, which at all times maintains fluid communication between conduit 22a and conduit 24. Toward its upper end, the plunger 3| is provided with a The plunger 3| isaction time of the valve 2l.

Referring again tothe modification of Figures 1 to 4, there is provided a conduit 43 leading from one of the blankholder cylinders to the intake port of a' relief valve 44 and a safety valve 45. It is through this conduit that all fluid trapped within the cylinders I3 is exhausted.

l It will be observed that, because of the provision of the check valve 25 between conduits 24 and 25, fluid within the cylinders I3 cannot escape through said conduits, but must escape through conduit 43. It will also be observed, that in this modification, since all the blankholder cylinders are in open communication with one another through the supply conduit 25 and branches 21, no outlet, other than conduit 43, is necessary.`

Exhaust from the blankholder cylinders normally passes through the relief valve 44, and takes place during the pressing stroke when the blankholder I5 has exerted upon the work piece the maximum pressure permitted by a given setting of the adjustment 46 of the relief valve 44. The safety valve 45 is normally inoperative and acts only in the event of failure of the valve 44 to open, resulting in the development of excessive pressure in the blankholder system. The valves 45 and 46 are both of the usual type in which pressure fluid acts against a spring-loaded plunger, the valve spring opposing the fluid pressure in accordance with the setting of a screw-threaded adjusting nut. Both of the valves 44 and 45 empty into the conduit 41 which returns to the tank 28. As seen in Figure 1, there is provided in the line 41 a telescoping joint similar to the one shown in the pump discharge line 22, and provided for the same purpose, namely, to permit valves 44 and 45 ,with their piping to reciprocate with the platen I0- of the press. This telescoping joint is designated 48.

It will be noted by referring to Figure -1 that the lower surface of the blankholder platen I5 stands slightly in advance of the lower surface' under predetermined pressure before the workpiece is contacted by the upper die member. In this invention the exact spacing of the blankholder platen I relative to the upper die member I I is controlled by the adjustment of spacing rods 49 which are fastened, as by threading, into the blankholder platen I5, and which are threaded at their upper ends to receive adjusting nuts 58, which act as stops against the upper surface of the main press platen I0, thus` limiting the extent to which the pressure within the blankholder cylinders I3 vmay extend the blankholder platen I5 upon the retraction stroke of the press. The spacing rods 49 slide freely within bores 5I in the platen I0. f

, Operation The operation of the press, having the circuit arrangement shown in Figures 1 to 4, is as follows. Let it be assumed that thepress is idling;

that is, that both the pump I8, and the main nuid, the pressure of which, in addition to the weight of the blankholder platen I5 and the parts mounted uponv it. is holding the blankholder platen I5 in its fully extended position with the adjusting nuts 5I) bearing against the upper surface of` the main platen I0. The particular pressure existing within the cylinders I3 has been predetermined by, the setting of the valve 2I. Pressure within all of the cylinders I3 is identical because of their interconnection by' means of the lines 26 and 21, and this pressureiscommunicated to the annular compartment 34 of the valve 2l through the control conduit 4I. During the idling position of the press, now under consideration, this pressure within the cylinders is 'sufficient to move the plunge/1` 3| of the unloading valve upwardly against the opposing spring 35,v so that the total delivery of the pump I8 is being by-passed from the line 22a through the unloading valve to the line 28 and back to the tank 20. So long as the press continues to idle, this by-passing or unloading of the pump i8 will continue.

When the operator initiates a pressing cycle by actuating the` controls to the pump 4 so as to deliver pressure fluid into the conduit 5, withdrawing uid from the pullback side of the piston 2 through the conduit B, the main pressing piston 2, ram I, and main platen I0, will vstart their downward movement, carrying lwith them the upper die member I I and the blankholder platen I5 with its plunger I4 and spacer rods 49. Valves 2I,'44 4,and 45, being mounted upon the main platen,`wil1 also move downwardly carrying the piping associated Y with them, the telescoping joints 23 and 48'perin'itting this movement relative tothe stationary piping while at the same time lI'naintainingl Vintact the' hydraulic connection fjfthe parts. During this downward traverse of the'fpre's'sing members, and before the engagement of the work piece bythe blankholder platen I5, the spatial relationship of this platen with the main presslplaten does not change from the idling position-.of these parts, ythe predetermined pressure in the cylinders I3 remainingat the same level, this pressure continuing to hold the unloading valve 2I in its open position, and the pump I8 continuing to by-pass to the tank 20.

The condition just described obtains until the work piece is engaged. Since the blankholder platen precedes the die member II, as determined by the setting of the adjusting screws 50, it rst engages the work piece Il. Although this action brings the blankholder platen to rest, the main platen III and the upper die member continue to advance toward the work, perhaps at a decelerated -rate as governed by the controls to the main pump 4. It is this relative motion between the main platen and the blankholder platen I 5 which builds up the blankholder pressure within the cylinders I3 by carrying these cylinders downwardly over their respective plungers I4, these plungers having now become stationary. Since these blankholder cylinders have previously been lled with fluid alongwith the conduits leading to and from the cylinders, this telescoping motion of the cylinders over their respective plungers I4 causes pressure to be built up rapidly, and this pressure, acting upon the upper ends of the plungers, and being transmitted by .them to the blankholder .,platen, results in the clamping of the margin of the workpiece against the lower die member I2. The maximum point to which this clamping force may be raised is determined by the setting of the adjusting nuts 46 of the relief valve 44. It will be recalled that pressure, trapped within the blankholder cylinders I3, may escape only by Way of this relief valve through the conduit 43, due to the presence of the ball check valves 25 in the supply line to these cylinders. Consequently, upon the attainment of the desired pressure within the blankholder cylinders, further motion of the main platen Ill relative to \the blankholder platen I5, willcause fluid displaced by the plungers I4 to escape through the relief valve 44 and to return to the tank 20 (for illustration of this action see Figure 2). Once this escape of fluid takes place, the pressure within the cylinders I3 will rise no higher, but, on the other hand, will be maintained at the levels reached. Since, in the modification shown in Figures 1 to 4, the several blankholder cylinders are in open communication with one another, the single relief valve 44 will serve to maintain allof these cylinders at identical pressure. This condition is applicable where the nature of the operation to be performed upon the.' workpiece -I1 is such as'to require'"equal clamping pressure at all points about the margin of the workpiece.

Appropriate blankholder pressure having been built up, the-male die member II engages the workpiece I1 as the main press ram I continues to drive this die member toward the lower mating die member I2. As the workpiece I'I ispressed into the cavity of the die member I2, its marginal portion slips under the pressure of the blankholder platen to supply the metal necessary for the drawing operation; and upon the termination of this operation, the return movement of the press will be initiated either in response to the pressure built up 4above the main pressing area of the piston 2, or by the position reached by the 'die member I I. In either case, the control mechato the action of the pump I8 and valve 2I during the actual pressing operation, it will be observed that, since the pressure within the cylinders' I3 prior to this pressing operation was sufcient 'ingoperations.

to cause opening of the valve 2I and unloading of the delivery of pump I8,` the higher pressures developed within these cylinders during the working stage are, of course, sufficient to maintain valve 2I and pump I8 in their unloading relation.

As soon as the return stroke of the press is begun, the function of the die II has been completed for one cycle. The blankholder platen, however, as illustrated in Figure 3, now enters upon the second phase of its function, namely, to serve as a stripper plate for removing the nished article as it clings tothe male member II of the die. This stripping action of the blankholder platen I is brought about and controlled by a change of conditionswithin the cylinders I3. As

' the platen I0 starts upwardly and is lifted away from the blankholder platen I5, a rapid drop in pressure occurs within the cylinders I3, whereupon the relief valve 44 closes, and, for the first time in the cycle, the pump I8 begins to supply fluid to the cylinders I3. This latter event is due to the lowering of the pressure within the annular chamber 34 of the unloading valve 2| correspondingly with the `lowering of pressure within the blankholder cylinders, and the consequent closing of the passage between'conduits 22a and 28 by the compression of the valve spring 35. The output of pump I8 is thus no longer by-passed to the tank, but, instead, is utilized to perform. the stripping action described above, and simultaneously, to prefill the blankholder cylinders I3 to the fullextent permitted by the location of adjusting nuts 50 upon spacer rods 49, preparatory to the next pressing cycle. During the first portion of the return stroke of thepress, the main platen I0 rises while the blankholder platen I5 remains stationary upon the margin of the workpiece, this separating action of the two platens being the result of the ow of pressure uid from pump I8 into the cylinders I3. It is by causing this separation of the platens I0 and I5 that pressure uid from the pump I8 results in stripping the work from the upper die member I I.

In connection with the stripping of the work piece and the prefllling of the-blankholder cylinders, two advantages of the present invention over previous arrangements should benoted. The first of these concerns the widely varying stripping pressures demanded .by different press- The inclusion of the unloading valve 2I in the present invention provides for meeting these demands by making available, through the setting of the adjusting screw 38, any stripping pressure up to the pressure capacity of the pump I8. The second advantage lies in the provision of pump I8 in addition to the main operating pump 4 for the purpose of providing stripping pressure in the blankholder' cylinders and of prefilling these cylinders. In previous hydraulic arrangements, the pullback discharge of the main operating pump has been` partly diverted to the blankholder cylinders to perform these functions. Since it is desirable for the opening stroke of the press to be eected without delay, such an arrangement has necessarily introduced aproblem which can be solved only by supplying a main operating pump having greater capacity, with an attendant considerable increase in cost. By providing the simpler constant delivery vane or gear type pump I8 of vthis invention, the main operating pump is relieved of its stripping and prefilling functions, so that its full discharge may be devoted to effecting a speedy return of the press platen. Thus, a raster press is provided at lower cost.

After the stripping and preiilling functions have been completed by iluid pressure in the cylinders I3, there remains to the completion of the press cycle only the retraction/of the blankholder platen I5 from its clamping engagement with the workpiece I1 and die member I2. This is accomplished by the contacting of the nuts 50 by the main platen` III in its upward movement, the spacer rods 48 then lifting the blankholder platen. Platens I 8 and I5 then move upwardly as a unit until suitable control means actuate the flow control element of pump 4 moving it to neutral position, at which time the return movement is terminated, and the press again stands in the idling state of Figure 1, in readiness for the beginning of another cycle.

In the modification shown in Figure 5 of the drawings, the hydraulic operating system associated with the blank holder cylinders I3 is similar `to that shown in Figures 1 to 4, but provision is made therein for independent control of the pressure generated within the cylinders I3 during the pressing operation.- This consists in placing, in the branch lines 21, separate ball check valves 25a for each of the blankholder cylinders; in providing separate exhaust conduits 43a for each of these cylinders; and in interposing between these exhaust conduits and the return conduit 41 separate relief and safety valves 44a and 45a. The check valves 25a, while permitting the flow of fluid into the blankholder cylinders from the pump I8, prevent the pressure developed in the cylinders during an actual pressing operation from being communicated to one another through the supply conduits 28 and 21 and thereby equalizing with one another. The precise pressure developed in each blankholder cylinder and conilned within it by the associated check valve 25a, is determined by the setting of the manual adjustment of the associated relief valve 44a. It will be apparent that with this arrangement independent pressures may be generated within each of the several blankholder cylinders, and transmitted through the respective plungers I4 to the blank-y hend within'my invention such modifications as come within the scope of the claims andthe invention.

Having thus fully described my invention what `I claim as new and desire to secure by Letters Patent, is: I

1. In combination in a hydraulic press, a platen, ram and main cylinder, a source of hydraulic fluid pressure for exclusively supplying pressure fluid to said ram for reciprocatingsaid platen 'a plurality of blankholder cylinders in said platen, a blankholder, pistons on said blankholder arranged for reciprocation in said blankholder cylinders, a second and independent source of Vhydraulic fluid pressure for exclusively supplying pressure fluid to said blankholder cylinders during the retraction stroke of said platen to completely lill said cylinders and provide a constant positive pressure therein to maintain said blankholder separated from said platen.

2. In combination in a hydraulic press, a platen,

ram and main cylinder, a source of hydraulic fluid pressure for exclusively supplying pressure fluid to said ramfor reciprocating said platen, a plurality of blankholder cylinders in said platen, a blankholder, pistons on said blankholder arranged for reciprocation in said blankholder' cylinders, a second and independent source of hydraulic fluid pressure for exclusively supplying pressure fluid to said blankholder cylinders during the retraction stroke of said piston to completely iill said cylinders and provide a-` constant positive pressure therein to maintainisaid blankholder separated from said platen, saidplaten and blankholder being arranged to advance in unison upon a pressing stroke with the blankholder in advance of the die carried by the platen,

the uid pressure in said'blankholder cylinders providing for initial pressure contact of the blankholder upon the work in the vpress and providing means for developing. full clamping pressure upon continued advancement ofthe platen.'

3. In combination in a hydraulic` press, a platen,

' draulicfiuid pressure for exclusively supplying pressure fluid to said blankholdercylinders durram and main cylinder, asource of hydraulic to maintain said blankholder separated from said platen, and a pressure relief valve responsive to the pressure in the blankholder cylinders associated with said pump and arranged to open a uid return circuit to said pump to by-pass said blankholder cylinder upon attainment of a predetermined pressure in said cylinders.

6. In combination-'in a hydraulic press, aplaten, ram and main cylinder, a'source of hydraulic iiuid pressure for exclusively. su'pr'ilyingy pressure uid to said ram for-reciprocating said platen, a plurality of blankholder cylindrs'in said platen, a blankholder, pistons-on said blankholder arranged for reciprocation in ,said blankholder cylinders, Va constant delivery fluid pump for exclusively supplying pressuregiluid to said blankholder cylinders during the retraction stroke of said platen to -completely ll'fsaid'cylinders and provide a constantA `positive .pressure therein to maintain said blankholder separated,from-said platen, and a pressure relief valve responsive to the .pressure irii theblankholder cylinders asso- -ciated with said-pumpend arranged to open a fluid return circuit to said pump to by-pass said .25 .blankholder cylinder-upon attainment of a predetermined pressure in said cylinders, saidplaten and `blankholder being arranged to advance in unison upon a-.pre'ssing stroke with the blankholder in advance of the die carried by the platen,- gg-the-iiuid lpressure established and maintained in ing the retraction stroke of said piston to completely llsaid cylinders and provide a constant positive pressure-therein tomaintai'nsaid blank-` blankholder upon the work in the lpress and pro` viding fordeveloping full clamping pressurev ,upon

continuedV advancement of the platen, "and relief n means associated with said blankholder cylinders for relieving pressure developed therein above a predetermined maximum, f 4. In combination in a hydraulic press. a platen, ram and main cylinder, a source of hydraulic fluid pressure for exclusively supplying pressure said-blankholder cylinders by -said ,pump pro- -viding ,for initial pressure contact of the blankholderf-upon-the work in the press, the-pressure ffluid providingmeansfor developing full clampjs ing pressure upon continued advancement of the fluid to said ram for reciprocating said platen, a

pluralitv of vblankholder cylinders in said platen, a blankholder, pistons onsaid blankholder arranged for reciprocation in said blankholder cylinders, a constant I'delivery fluid pump for exclusively supplying pressure iiuid to said blankholder cylinders during the retraction stroke of said platen to completely fill said cylinders and provide a constant positive pressuretherein to maintain said blankholder separated from said platen. and a pressure relief valve associated with said pump arranged to open a fluid return draulic uid pressure for exclusively supplying f pressure'uid to said ram for reciprocating said platen, a plurality of blankholder cylinders in said platen` a blankholder. pistons on said blankholder arranged for reciprocation in said blankholder cylinders. a constant delivery fluid pump fnr exclusively supplying pressure uid to said 70 blankholder cylinders during the retraction stroke of said platen to completely fill said cylinders and provide a constant positive pressure therein platen, and relief 1 means vassociated with said blankholder cylinders for relieving pressure -developed therein above a predetermined maximum. fl.. A method of operating a hydraulic press which consists of applying hydraulic pressure `onthe press platen fto advance the saine and a blankholder carried thereby iniunison, of applying hydraulic clamping pressure on the blankholder by the continued forward advancement of the press platen after the blankholder-'has reached a stationary position, of "hydraulically retracting the press platen, and of establishing and maintaining a positive predetermined hydraulic pressure in the hydraulic cylinders of the blankholder through means of an independent iiuid pressure source upon initiation of the retraction strokeI of the platen and untilthe j blankholder again reaches its clamping position.

8. In combination in a hydraulic press, a platen, ram and main cylinder, a source of hydraulic. fluid pressure for exclusively supplying pressure vfluid to saidram for reciprocating said platen,

a plurality of blankholder cylinders in said platen, a blankholder, pistons on said blankholder arranged for reciprocation in said blankholder cylinders, a constant delivery iiuid pump for vexclusively supplying pressure fluid to said blankholder cylinders during the retraction stroke of said platen to completely fill said cylinders and provide a constant positive pressure therein to maintain said blankholder separated from said platen. and a pressure .relief valve associated with said pump arranged to open a uid return circuit to said pump to by-pass said pump upon attainment of a predetermined pressure in said cylinders. a

WALTER ERNST.'

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