|Publication number||US3596485 A|
|Publication date||Aug 3, 1971|
|Filing date||Sep 11, 1969|
|Priority date||Sep 12, 1968|
|Also published as||DE1777153A1, DE1777153B2, DE1777153C3|
|Publication number||US 3596485 A, US 3596485A, US-A-3596485, US3596485 A, US3596485A|
|Original Assignee||Siemens Elektrogeraete Gmbh|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (16), Classifications (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent  inventor Eugen Burk Traunstein, Germany ] Appl: No. 857,030
 Filed Sept. 11,1969
 Patented Aug. 3, 197i Siemens-Electrogerate G.m.b.H. Berlin & Munich, Germany  Priority Sept. 12, 1968  Germany  Assignee  HYDROMECHANICAL METHOD AND DEVICE FOR THE REVERSE REDRAWING OF SHEET METAL 7 Claims, 4 Drawing Figs.
 U.S.Cl 72/57, 29/42]  Int. Cl B211! 26/04  Field Of Search 7267,60;
 References Cited UNITED STATES PATENTS 3,208,255 9/l'965 Burk 72/57 3,504,070 3/1970 Zaharskl 18/19 Primary Examiner-Richard J. Herbst Alrorne vsCurt M. Avery, Arthur E. Wilfond, Herbert L.
Lerner and Daniel J Tick ABSTRACT: Blanks for sheet metal are drawn with the aid of a pressure container, a liquid displacing annular plunger pres sure tightly glidable in the container and having a top adapted for accommodating the blank, a holddown for pressing the blank against the top, and a draw punch passing through the holddown. The container and plunger are first filled with liquid up to the top. Then the blank is placed onto the top, whereafter the holddown is forced downwardly against the blank, thereby pressing the plunger into the container. The increasing liquid pressure in the container draws the blank to a shape bulging upwardly into the holddown. Thereafter, the blank is reversely redrawn into the pressure container by pressing the punch from above against the blank and downwardly into the container.
, msqnmjnmcn ME'rnonANu Device iron T e a container and adapted for receiving the sheet-metal blank, a
holddown which presses the blank against the plunger top, and a drawing punchwhich passes through the holddown.
It is known to shape a blank of sheet metal hydromechanically by first predrawing a blank with the aid of the conventional drawing method, using an ordinary dieandpunch blank 7 been placed upon the top of the plunger i. When the tool assembly closes; the holddown '8 moves'against the blank 14 and presses it onto the seal ii, the downward travel of the holddown relative to the plunger 4 being limited by spacers l4. Thereafter, the downwardly travelling plunger Al is forced into the tool bottom portion ll. The spacers 114 are so dimensioned'that, while permitting a slight deformation of the blank 7, they receive the pressing force from the holddown 8 and transmit it to the displacing plunger 4. The displacing plunger 4 thus is pressed into contact of its top flange with the tool bottom portion 1 (FIG. 2), while the correspondingly in-, creasing liquid pressure draws the blank 7 to the cup shape ap' parent from FIG. 2. The bottom of the draw punch 9 may then form a limiting stop. However, additional stops or abutments may also be inserted so as to form part of the holddown member.
press. Thereafter, the. preshaped workpiece is reversely,
redrawn by the hydrornechanical method. The two assemblies known for such purposes have the disadvantage that due to the necessity of first applying a conventional drawing operation,the equipment is rather complicated and expensive whilestill falling short of providing for optimal drawing conditions during the predrawing operation.
, It is an object of my invention to provide a reverse redrawing methodv and device with whose aid'a double-acting drawing press affords predrawing and reversely redrawing the workpiece on the hydromechanical drawing principle.
To this end, and according to my invention, the pressure container and the annular plunger glidable in the container are filled with liquid up to the top rim, whereafter the blank is placedupon theannular top of the displacement plunger and so loaded by the holddown'as to press the displacement plunger into the pressure container. The liquid pressure thus belng increased in the interior of the container and plunger is deformed into the hollow space formed within the annular holddown and, as the case may be, also by the withdrawn drawing punch. This results in preshaping the blank to a bulging or cup shape by the hydromechanical action. The blank,
thus preshaped, is then subjected to the downward drawing pressure of the punch which turns the bulging shape inside out and forces it into the interior of the holddown or container.
The predrawing operation does not require any particular control or regulation of the liquid quantity because the volume er liquid displaced can readily be so dimensioned as to render further control unnecessary. However, the reverse redrawing operation requires controlling the liquid to obtain a predetermined pressure because the volume of liquid in the pressure container must become reduced during redrawing.
Theinvention will be further explained with reference to an embodiment of a hydromechanical device according to the invention illustrated schematically on the accompanying draw ing, in which:
FIG. 1, 2 and 3 illustrate the reverse redrawing device in diametrical section through the essential components and in three different drawing stages respectively; and FIG. 4 shows a modified detail of the same device.
The bottom portion 1 of the tool assembly, to be used in, or as part of, a punch press, is designed as a pressure container in whose interior 2 an annular displacement plunger 4 is glidably displaceable. The plunger 4 is provided with sealing rings at its periphery for maintaining a liquidtight and pressuretight seal.
. The top of the plunger 4 forms a flange above the container 1 and has a top face 5 for accommodating a blank '7. A sealing ring 6 surrounding the tubular hollow of the plunger t is in workpiece. This can be done, for example, by providing cor-- respondingly' adjustable or exchangeable stops between the bottom portion l and the displacing plunger 4, such as the inserted stop 15 shown in FIG. 4.
FIG. 3 shows how thereafter the punch 9 reversely draws the predrawn workpiece '7 into the pressure container. During this operation, liquid is issued from the pressure container into the tank 12 in accordance with the predetermined pressure set by the control valve ill.
The liquid used for the method and device according to the invention may be water.
It will be obvious that the device for performing the method according to the invention is not limited to the embodiment illustrated but that a variety of shapes can be drawn during the predrawing stroke as well as during the reverse redrawing stroke. For predrawing it is merely to be taken into account redrawing operation.
s'erted for securing a liquidtight and pressur'etight seal during j operation of the device. The blank 7 is pressed against the seal 6 by meansof an holddown member 8 whose hollow is traversed by a drawing plunger 9. The pressure space 2 within the tool bottorn portion 1 is connected through pipes and a V check valve 10 as well as an overpressure valve lll to a tank 12.
which receives compressed air through an inlet duct 13.
FIG. ,1 shows the tool assembly open. The interior of the pressure space 2 within the tool bottom portion 1 and within the plunger 4 has been completely'filled with liquid and a invention.
1. A hydromechanical reverse redrawing method for shaping blanks of sheet metal with the aid of a pressure container, a liquid displacing annular plunger pressure tightly glidable in said container and having outside said container a top adapted for accommodating a blank, 21 holddown for pressing the blank against the top and a draw punch passing through the holddown, which method comprises the steps of filling the container and plunger with liquid up to the top, placing the blank onto the top, forcing the holddown against the blank and thereby pressing the plunger into the containerwhereby the increasing liquid pressure draws the blank to a preshape bulging upwardly into the holddown, and thereafter reversely redrawing the blank into the pressure container by pressing the punch from above against the preshaped blank and downwardly into the container.
2. The method according to claim 1, which comprises maintaining the pressure in the pressure container during reverse redrawing substantially constant and simultaneously discharg ing from the container a quantity of liquid corresponding to the reduction in liquid volume displaced by the workpiece being reversely redrawn.
3. A hydromechanical reverse redrawing device for shaping blanks of sheet metal, comprising an upwardly open container for pressure liquid having liquid supply ducts, a plunger having a hollow and being glidably and pressure tightly displaceable in said container, said plunger having a flange with a top outside and above said container and having scalable means on said top for receiving the workpiece blank across the hollow so that the blank when pressed against the plunger forms a closure of said container, an holddown movable under pressure toward the container to force the plunger into the container whereby the increasing liquid pressure draws the workpiece blank to a shape bulging upwardly into the holddown, and a draw punch vertically movable in the hollow of said holddown for reversely redrawing the preshaped workpiece by pressing it from above into the container.
4. In a device according to claim 3, said punch, when in its top position, forming within the hollow of said holddown an
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