EP0333052B1 - Drawing apparatus for shaping sheet metal blanks - Google Patents

Drawing apparatus for shaping sheet metal blanks Download PDF

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Publication number
EP0333052B1
EP0333052B1 EP89104248A EP89104248A EP0333052B1 EP 0333052 B1 EP0333052 B1 EP 0333052B1 EP 89104248 A EP89104248 A EP 89104248A EP 89104248 A EP89104248 A EP 89104248A EP 0333052 B1 EP0333052 B1 EP 0333052B1
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EP
European Patent Office
Prior art keywords
pressure
piston
cylinder
pressure medium
line
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EP89104248A
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German (de)
French (fr)
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EP0333052A2 (en
EP0333052A3 (en
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Erhardt Reitter
Karl Hehl
Herbert Dipl.-Ing. Kraibühler
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Individual
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Individual
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Priority to AT89104248T priority Critical patent/ATE91653T1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D24/00—Special deep-drawing arrangements in, or in connection with, presses
    • B21D24/10—Devices controlling or operating blank holders independently, or in conjunction with dies
    • B21D24/14—Devices controlling or operating blank holders independently, or in conjunction with dies pneumatically or hydraulically

Definitions

  • the invention relates to a drawing tool according to the preamble of claim 1.
  • Every change is triggered by a negative criterion, such as the risk of tearing on the drawing part, that the drawing speed is too low and brings the corresponding hydraulic elements into or out of action.
  • Changes in the sheet holding force, the pulling force and the pulling speed can also be alternated in order to achieve a rapid and at the same time energy-saving pulling process during this pulling process.
  • the basic requirements for a controlled discharge of pressure medium from the cylinder spaces of the hydraulic unit into a pressure accumulator or into the pressure medium reservoir as well as for re-feeding into the cylinder spaces from a pressure accumulator are present, whereby further possibilities of influencing the drawing process can be developed.
  • a drawing process or a time segment thereof can take place with the drawing ring stationary or with the drawing punch stationary.
  • a further embodiment according to claim 3 ensures that, with the construction of the hydraulic unit being favorable in terms of production engineering, the drawing tool can be returned to its starting position from the cylinder space delimited by the central piston after the drawing process has been completed.
  • the oil which is necessarily displaced from this cylinder chamber can be fed into the rear cylinder chamber of the working piston to accelerate the drawing process.
  • the sheet holding force can be adjusted in accordance with the respective drawing technical requirements before the start and during the drawing process by appropriately presetting the pressure of the pressure limiting valve 36, the optimum initial sheet holding force having been empirically determined beforehand.
  • the pressure in the hydraulic system is reduced thanks to the pressure booster if there is a risk of the pulling part tearing off.
  • a flow path change corresponding to the respective drawing-technical requirements leads to an optimization of the drawing process with regard to energy saving and drawing speed, while avoiding any risk of tearing off, the limiting pressures or cross-sections to be preset on the pressure-limiting valve and on the throttle valve generally being empirically determined beforehand.
  • the drawing speed can be increased with a corresponding adjustment of the sheet holding force.
  • the drawn part can be produced by opening the third flow path to the pressure accumulator while the drawing piston is stationary. If the flow path is only opened temporarily, there is a corresponding temporary pressure drop via the hydraulic system.
  • the drawing process can take place with the ring piston at a standstill.
  • the drawing tool is used for forming preferably flat sheets, for example in containers, pots, sinks and the like.
  • An external driving force A acts on the drawing tool from outside for forming. It usually comes from a hydraulic press, the press head of which drives the drawing ring 18 of the drawing tool. Together with the drawing ring 18, a sheet metal holder 15 is moved during the forming process.
  • a circuit board 47 is clamped between the drawing ring and the sheet metal holder at the beginning of the drawing process.
  • a drawing die arranged coaxially in the sheet metal holder can be moved into the drawing ring 18.
  • the movement of the movement unit 18, 15 carrying the respective circuit board 47 can be converted into a simultaneous but opposite movement of the drawing punch 17 with the aid of a hydraulic unit H of the drawing tool.
  • the hydraulic unit H comprises a central working piston 12, an annular piston 13 enclosing it and a cylinder 10d enclosing the annular piston, which is part of a cylinder housing 10 of the hydraulic unit H.
  • the annular piston 13, which can be driven indirectly by the driving force A, can be supported on the pressure medium of a cylinder space 48.
  • the working piston 12, which is designed as a differential piston, can be acted upon with pressure medium on both sides.
  • the pressure medium displaced from the cylinder space 48 during the drawing process by the annular piston 13 drives the working piston at least temporarily during the drawing process.
  • Cylinder spaces 51, 52 and 48 delimited from the base of the cylinder housing 10 are hydraulically separated from one another by a separation sleeve 10a projecting from this base.
  • the annular piston 13 guided on the cylinder 10d of the cylinder housing 10 is guided on the working piston 12 by means of a radial flange 13a which overlaps the separating sleeve 10a.
  • the inner circumferential surface 13b of the annular piston 13 is located at a distance from the outer circumferential surface of the separating sleeve 10a.
  • the working piston 12 which can be acted upon from the rear from the cylinder space 51 can be acted upon in the opposite manner from a cylinder space 49 which lies in a central recess of the cup-shaped working piston 12.
  • the cylinder chamber 49 is delimited by a central piston 10c anchored in the base of the cylinder housing 10 and an annular part 12b screwed to the working piston 12.
  • the ring part 12b encloses the shaft 10b of the central, stationary piston 10c sealing.
  • the rear cylinder space 51 communicates with a further cylinder space 52. This is delimited by the bottom 12a of the working piston 12 and by the central piston 10c.
  • the drawing punch 17 is received by the working piston 12 via a cylindrical intermediate piece 17a.
  • An adapter ring 14 between the sheet metal holder 15 and the upper edge of the annular piston 13 serves to transmit the driving force from the sheet metal holder 15 to the annular piston 13.
  • a knife ring 16 is arranged to be displaceable to a limited extent. When the remaining blank is bent from the edge of the finished drawn part, this knife ring 16 interacts with stationary stops 16a. These are supported on the end edge of the cylinder 10d of the cylinder housing 10 and, when the sheet metal holder moves downward, plunge into corresponding bores in this sheet metal holder.
  • Working pistons 12 and annular pistons 13 can be acted upon from the hydraulically separated cylinder spaces 51, 52 on the one hand and 48 on the other.
  • the cylinder spaces mentioned can be connected to one another via three alternative flow paths, which are each designed differently hydraulically.
  • the first flow path is via line 20.
  • the second flow path is via line 20a.
  • the third flow path is formed by line 20b.
  • the alternative flow paths in the * communicating cylinder spaces 51, 52 and 48 require a pressure curve at a different pressure level during the drawing process.
  • the flow path change can be triggered by a pressure sensor 21 which detects the pressure of the pressure medium in the communicating cylinder spaces 51, 52; 48 and which delivers switching impulses when preset limit pressures are exceeded.
  • a 2-way valve 34 and the pressure sensor 21 are arranged in the line 20 of the first flow path.
  • line 20a of the second flow path there is a controllable pressure relief valve that can be set to different limit pressures 36 with an upstream check valve 35.
  • a 2-way valve 40, a throttle valve 22 and a piston accumulator 24 acting as a hydraulic pressure intensifier are inserted in line 20b of the third flow path.
  • the pressure medium introduced into the cylinder spaces 51, 52 under pressure during the drawing process via the three alternative flow paths acts on the working piston 12 via an action surface which is larger than the cross-sectional area of the piston head 12a.
  • the working piston acts as a pressure intensifier, which is possible in that the stationary piston 10c projects radially beyond its shaft 10b, which results in the enlargement of the pressure area.
  • the driving force A can be converted into a larger force of the drawing piston (with a smaller drawing path). *) via connection channel 50
  • the pressure medium filling of the cylinder space 49 delimited by the ring part 12b and by the central piston 10c can be introduced into the rear cylinder space 51 of the working piston 12.
  • the pressure medium displaced from the cylinder space 49 during the drawing process reaches the line 45 into the cylinder spaces 51, 52 via channel 11.
  • the empty cylinder space 49 is refilled from a pressure accumulator 26. With this reset, a volume of pressure medium corresponding to the volume of the cylinder space 49 can be displaced from the cylinder spaces 50, 51, 48 into the pressure medium reservoir 27.
  • the right cylinder space 24b of the piston accumulator 24 can be connected to the pressure accumulator 26 via a line 41 provided with a 2-way valve 25, which in turn can be connected to all cylinder spaces of the hydraulic unit for recharging or for pressure relief.
  • the pressure accumulator 26 itself can be reloaded from the pressure medium reservoir 27 by means of a feed pump 39.
  • the working piston 12 can be driven by means of a pressure source P when the annular piston 13 is stationary, that is to say when the driving force A is switched off. That from the cylinder chamber 49 displaced pressure medium is discharged into the pressure medium reservoir 27 via a 2-way valve 28. The discharge can also take place via a valve 30 which opens when an upper pressure limit is exceeded.
  • the 2-way valve 40 and the throttle valve 22 in the line 20b of the third flow path can be bridged by means of a bypass line 20b.
  • a check valve 23 which releases a predetermined pressure in the flow direction in the flow direction is arranged in this.
  • the mass moved when folding the rest of the blank from the edge of the finished drawn part, which is represented in the illustrated embodiment by the drawing ring 18, the sheet metal holder 15, the adapter ring 14 and the annular piston 13, can be eliminated by throttling the outflow of the pressure medium from the bending resistance Cylinder chamber 48 are stopped. This is done with the help of the throttle valve 22 arranged in the line 20b of the third flow path in dependence on and the pressure drop triggered by the elimination of the folding resistor.
  • the pressure medium passes through the piston accumulator 24 into the pressure accumulator 26, the 2-way valve 33 being controlled in the closed position and the 2-way valve 25 in the open position.
  • Fig. 1 shows the out of operation drawing tool with the entire associated hydraulic system with the board inserted.
  • the figures 2-8 are used to explain specific different procedures in the operation of the drawing tool, which correspond to the different drawing requirements.
  • the lines and rooms through which the respective process flows are emphasized by a stronger line. All organs not included in the process sequence, in which there is consequently no pressure, are omitted.
  • the drawing tool is switched to the first flow path.
  • the pressure medium flows from the cylinder space 48 via the line 20 with a two-way valve 34 into the cylinder space 51 and additionally via the connecting channel 50 into the cylinder space 52.
  • Fig. 3 In this figure, the drawing tool is switched to the second flow path.
  • the pressure medium is displaced from the cylinder space 48 with the partial inclusion of the line 20 of the first flow path via a check valve 35 and an adjustable pressure relief valve 36 in a line 20a into the cylinder spaces 51, 52 in order to drive the drive piston 12.
  • the switching of this flow path makes sense if an adjusted setting of the sheet holding force is important before the drawing process begins or if a control of the sheet holding force is indicated during the drawing process.
  • the drawing process only begins when the sheet metal holding force, that is to say the pressure in the cylinder space 48, exceeds the limit pressure set in the pressure relief valve 36.
  • This limit pressure is adjustable or changeable depending on the pressure sensor 21, so that the sheet metal holder force can be adapted to the respective drawing requirements during the drawing process.
  • Fig. 4 When switching the third flow path according to Fig. 4, the pressure medium coming from the cylinder space 48, including the line 20 of the first flow path, via line 20b, via a two-way valve 40, a throttle valve 22 and via a piston accumulator 24 and via Another directional control valve 33 is pressed into the cylinder spaces 51, 52 in order to drive the working piston 12.
  • the piston accumulator 24 is designed as a pressure intensifier.
  • Fig. 8 It shows how the drawing tool is returned from its end position to the starting position after the drawing process.
  • pressure medium passes from a pressure accumulator 26 via the initial section of a line 42 and via line 43 and the directional control valve 32 as well as the channel 11 in the shaft 10b into the initially empty cylinder space 49, in order to drive the working piston 12 in one direction from there. which is opposite to the direction of pull.
  • the pressure medium displaced from the cylinder spaces 51, 52 when the working piston is returned to its starting position can, for example return to the cylinder space 48 via the first flow path.
  • the pressure medium is fed from the cylinder space 49 into the cylinder spaces 51, 52 during the drawing process to accelerate the drawing process, then when the drawing tool is reset, a to displace volume corresponding to the injected volume from the cylinder spaces 51, 52 into the pressure medium reservoir 27.
  • Such a partial exchange is advantageous because it prevents the temperature of the pressure medium in the cylinder spaces from rising above a critical limit and enables the pressure medium to be kept clean by filtering the portion that is exchanged.
  • FIGS. 5, 6 illustrate process sequences in which the drawing process takes place with the drawing punch 17 (FIG. 5) or with the sheet holder 15 stationary, so that there is no opposite movement of the sheet holder and drawing punch.
  • Such a procedure may be required for certain difficult drawn parts. It may also be necessary to allow such a procedure to take place only in a particularly critical section of the entire drawing process, with switching between the first, second or third flow path before and after this section of the drawing process in order to save energy and to accelerate the drawing process Flow paths are changed.
  • the drawing process driven by the external force A, is effected exclusively by the movement of the drawing ring 18, sheet metal holder 15, adapter ring 14 and annular piston 13, while the working piston is not being acted upon.
  • This is achieved in that the pressure medium displaced from the cylinder space 48 reaches the left storage space 24a of the pressure accumulator 24 via the line 20b, the directional control valve 40 and the throttle valve 22.
  • the piston 24c becomes shifted to the right and displaces pressure medium from the right storage space 24b of the piston accumulator.
  • the displaced pressure medium passes through the directional control valve 25, the line 41 into the pressure accumulator 26. If required, this can be reloaded from the pressure medium reservoir by means of the feed pump 39 via the check valve 38.
  • the sheet metal holder is stopped during the drawing process by shedding off the external force A, while the working piston 12 and thus the drawing punch 17 are driven and effect the drawing process.
  • pressure medium is pressed into the initially empty cylinder spaces 51, 52 from a separate pressure medium source P via a check valve 53 and via a line section of line 20 of the first flow path, in order to drive the working piston 12 in the direction of pull.
  • the pressure medium displaced from the cylinder chamber 49 reaches the pressure accumulator 26 via the directional valve 32.
  • the drawing tool is reset to the starting position, as described above, by introducing pressure medium from the pressure accumulator 26 into the initially empty cylinder space 49.
  • Fig. 7 illustrates the process for folding the remaining board 47 from the edge of the finished drawn part.
  • the drawing punch 17 with the working piston on the one hand and the moving unit consisting of drawing ring, sheet metal holder 15 adapter ring 14 and annular piston 13 are used moved down synchronously.
  • the knife ring 16 which is arranged to be displaceable to a limited extent in the sheet metal holder 15, runs onto bolt-shaped stationary stops 16a in order to be moved over a slight distance for the work process relative to the aforementioned movement unit and thus relative to the drawn part or to the plate 47.
  • the bending resistance in the hydraulic system suddenly disappears, which equates to a sudden drop in pressure.
  • the outflow of the pressure medium from the cylinder 48 is throttled with the aid of the throttle valve 22 at the moment of the pressure drop as a function of the pressure sensor 21, as described above.
  • the pressure medium filling of the cylinder space 48 (FIG. 5) or the pressure medium filling of the cylinder space 49 (FIG. 6) is displaced into the pressure accumulator 26, specifically against the pressure prevailing there.
  • the pressure accumulator 26 is raised to a correspondingly higher pressure level. This means that the energy additionally required for pressing the pressure medium into the pressure accumulator is stored in the pressure accumulator 26 and is available again for a subsequent operation (e.g. for an operation according to FIGS. 7 and 8).
  • a safety valve 30 in the * line 44 allows the pressure medium filling of the cylinder space 49 to flow into the pressure medium reservoir 27, so that no damage can occur in the hydraulic system.
  • the construction shown in the illustrative embodiment can be substantially shortened by omitting the cylindrical intermediate piece 17a and / or by omitting the adapter ring 14 in the direction of the axis of symmetry. In this sense, it may also be expedient under certain circumstances to design the drive piston 12 as such at the same time as a drawing punch, so that a separate drawing punch 17 is omitted. * provided with check valves 31,29
  • a major advantage of the drawing tool according to the invention is that the external force A acting on the drawing ring can be converted into a substantially larger, opposing drawing force.
  • the entire pressure surface of the working piston 12 is composed of a pressure surface on the rear and the end face of the central piston 10c. This also provides the prerequisite for the fact that, if necessary, the external force A can be converted into an opposing pulling force of the same size, but which pulling force acts on a smaller drawing piston or a smaller drawing tool.
  • the specific computer program initially determined empirically for each drawn part according to shape, material and depth of drawing gives the drawing device the endeavor to work at the highest possible drawing speeds without the risk of tearing.
  • the pulling part can be torn off by means of the pressure sensor 21 by transitioning to one of the numerous flow alternatives of lower pressure or lower pulling speed (e.g. from the second flow path to the first or third flow path or from the first flow path to the third flow path) or by partially releasing pressure medium from the Avoid cylinder space 48 or 51.52 or by stopping external force A or the plunger. If, after the pressure drop occurs, the pressure in the system rises again up to the critical pressure limit due to increasing drawing resistance (forming resistance), the hydraulic system can switch from the current flow alternative to a flow alternative of even lower pressure.
  • the interconnection of stationary pistons 10c, annular piston 13 and cylinder housing 10 or cylinder block leads to such a space-saving construction of the drawing tool that it can also be operated in extremely small presses, in particular in injection molding machines.
  • the hydraulic unit H is clamped in the one mold clamping plate of the injection molding machine and another unit of the drawing tool comprising the drawing ring and the sheet metal holder on the second mold clamping plate of the injection molding machine.
  • the drawing tool therefore works with a horizontal drawing axis. * at least temporarily

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
  • Mounting, Exchange, And Manufacturing Of Dies (AREA)
  • Control Of Presses (AREA)
  • Press Drives And Press Lines (AREA)
  • Treatment Of Fiber Materials (AREA)
  • Pens And Brushes (AREA)

Abstract

The motion of the blank holder (15) can be converted by a hydraulic unit of the drawing apparatus into a simultaneous but opposite motion of the drawing punch (17). The hydraulic unit has a central working piston (12), an annular piston (13) surrounding the latter, and a cylinder (10d) surrounding the annular piston. The working piston (12) and the annular piston (17) can be pressurised from hydraulically separated cylinder spaces (51, 52; 48) which communicate with one another via at least two alternative flow paths (lines 20; 20a; 20b). Due to their different hydraulic design, the flow paths entail a pressure variation on a different pressure level in the intercommunicating cylinder spaces (51, 52; 48). A pressure transducer (21) detecting the pressure of the hydraulic fluid in the cylinder spaces (51, 52; 48) connects up the alternative flow paths when limiting pressures are exceeded. It is thereby possible to manufacture even drawn components which are extremely difficult as regards deformation profile and/or material and/or drawing depth without the necessity to sacrifice the cost- and space-saving construction of the drawing apparatus. <IMAGE>

Description

Die Erfindung bezieht sich auf ein Ziehwerkzeug entsprechend dem Oberbegriff des Patentanspruches 1.The invention relates to a drawing tool according to the preamble of claim 1.

Für ein bekanntes Ziehwerkzeug dieser Art ist charakteristisch, daß der Ziehvorgang in einen vom extern angetriebenen Ziehring bestimmten Teilzug und in einen vom Ziehstempel bewirkten, gleichzeitigen, jedoch gegenläufigen Teilzug zerlegt wird, indem der Arbeitskolben von dem vom Ringkolben verdrängten Druckmedium gegenläufig zum Blechhalter angetrieben wird. Dabei ist für den Ringkolben und den Antriebskolben ein gemeinsamer Zylinderraum vorgesehen. Nach dem Ziehvorgang ist das Ziehwerkzeug durch Beaufschlagung einer Differenzfläche des Antriebskolbens in seine Ausgangslage rückführbar (DE-OS 36 20 876 - vergleiche auch US-PS 2.609.775 und AU-OS 132.028 -). Im übrigen ist es auch bekannt, bei einem Ziehwerkzeug anderer Art die Ziehkraft und die Blechhaltekraft je mit Hilfe hydraulischer Steuerorgane zu verändern, indem Druckmedium aus den betreffenden Zylinderräumen in ein Reservoir abgelassen wird. Die für den üblichen Ziehvorgang erforderlichen Volumina an Druckmedium in den genannten Zylinderräumen können durch Nachfüllen aus einem Druckspeicher wieder reproduziert werden. Das Ziehwerkzeug kann wegen der Größe des 'Ziehkissens' nur in großen Pressen betrieben werden (DE-OS 36 03 107).
Ausgehend von dem genannten Stand der Technik liegt der Erfindung die Aufgabe zugrunde, ein Ziehwerkzeug der eingangs genannten Art derart weiterzubilden, daß hinsichtlich Verformungsprofil und/oder Werkstoff und/oder Ziehtiefe auch extrem schwierige Ziehteile hergestellt werden können, ohne daß der kosten- und raumsparende Aufbau preisgegeben werden müßte.For a known drawing tool of this type, it is characteristic that the drawing process is broken down into a partial pull determined by the externally driven drawing ring and into a simultaneous but opposite partial pull caused by the punch, in that the working piston is driven in the opposite direction to the sheet metal holder by the pressure medium displaced by the annular piston. A common cylinder space is provided for the ring piston and the drive piston. After the drawing process, the drawing tool can be returned to its starting position by acting on a differential surface of the drive piston (DE-OS 36 20 876 - see also US Pat. No. 2,609,775 and AU-OS 132,028). In addition, it is also known to change the drawing force and the sheet metal holding force in each case with the aid of hydraulic control elements in a drawing tool of another type, in that pressure medium is discharged from the relevant cylinder spaces into a reservoir. The volumes of pressure medium required for the usual drawing process in the cylinder spaces mentioned can be reproduced by refilling from a pressure accumulator. The drawing tool can only be operated in large presses due to the size of the 'drawing cushion' (DE-OS 36 03 107).
Based on the prior art mentioned, the invention has for its object to develop a drawing tool of the type mentioned in such a way that with respect to the deformation profile and / or material and / or drawing depth also extremely difficult drawn parts can be produced without the cost and space-saving structure would have to be revealed.

Diese Aufgabe wird erfindungsgemäß durch die im Kennzeichen des Patentanspruches 1 genannten Merkmale gelöst.This object is achieved by the features mentioned in the characterizing part of claim 1.

Bei einer solchen Ausbildung eröffnet die hydraulische Trennung der an den Ringkolben und den Arbeitskolben angrenzenden Zylinderräume zahlreiche Möglichkeiten einer Einflußnahme auf den Ablauf des Ziehvorganges, wobei das raumsparende bauliche Prinzip einer koaxialen Ineinanderfügung mehrerer Kolben (zentraler Kolben 10c; Arbeitskolben 12; Ringkolben 13) grundsätzlich beibehalten werden kann; Ebenso eine einfache Auswechselbarkeit von Ziehring, Blechhalter und/oder Ziehstempel zwecks Anpassung an unterschiedliche Ziehteile. Bei der erfindungsgemäßen Lösung kann der sich bei energiesparender gegenläufiger Ziehbewegung von Ziehring und Ziehstempel vollziehende Ziehvorgang an die jeweiligen ziehtechnischen Erfordernisse durch den bedarfsweisen, druckabhängigen Strömungsweg-Wechsel angepaßt werden. Jeder Wechsel wird durch ein negatives Kriterium, wie z.B. beginnende Abreißgefahr am Ziehteil, zu geringe Ziehgeschwindigkeit ausgelöst und bringt entsprechende hydraulische Organe in oder außer Wirkung. Dabei können auch Änderung in der Blechhaltekraft, der Ziehkraft und der Ziehgeschwindigkeit zur Erzielung eines raschen und zugleich energiesparenden Ziehvorganges während dieses Ziehvorganges abwechseln. Im übrigen liegen die prinzipiellen Voraussetzungen für ein gesteuertes Ablassen von Druckmedium aus den Zylinderräumen der hydraulischen Einheit in einen Druckspeicher oder in das Druckmedium-Reservoir sowie zum Wiedereinspeisen in die Zylinderräume aus einem Druckspeicher vor, wodurch weitere Möglichkeiten einer Einflußnahme auf den Ziehvorgang erschlossen werden können. So kann insbesondere ein Ziehvorgang oder ein zeitlicher Abschnitt desselben bei stillstehendem Ziehring oder bei stillstehendem Ziehstempel erfolgen. Andererseits ist es auch möglich, sehr einfache Ziehteile ohne Strömungsweg-Wechsel bei verhältnismäßig rascher Taktfolge unter Einschaltung eines Strömungsweges von geringstmöglichem Strömungswiderstand zu fertigen (erster Strömungsweg). Insgesamt liegen die steuerungstechnischen Voraussetzungen dafür vor, daß nahezu ausschließlich das energiesparende Verfahren einer gegenläufigen Bewegung von Ziehring und Ziehstempel angewandt werden kann. Somit wird nur bei extrem schwierigen Ziehteilen bzw. in kritischen Ziehabschnitten eines Ziehvorganges bei stillstehendem Ziehstempel oder Ziehring umgeformt. Bei einer Ausbildung nach Patentanspruch 2 ergibt sich trotz Trennung der Zylinderräume für Arbeitskolben und Ringkolben ein besonders kompakter Aufbau der Hydraulikeinheit, was einen Einsatz des Ziehwerkzeuges in unterschiedlichen, die externe Antriebskraft liefernden Pressen, insbesondere in kleinen Pressen, von Bedeutung ist.With such a design, the hydraulic separation of the cylinder spaces adjoining the annular piston and the working piston opens up numerous possibilities for influencing the sequence of the drawing process, the space-saving structural principle of coaxially intermeshing several pistons (central piston 10c; working piston 12; annular piston 13) basically being retained can be; Likewise, a simple interchangeability of the drawing ring, sheet holder and / or drawing punch for adaptation to different drawn parts. In the solution according to the invention, the pulling process taking place with the energy-saving pulling movement of the pulling ring and the pulling punch can be adapted to the respective drawing requirements by the need-dependent, pressure-dependent flow path change. Every change is triggered by a negative criterion, such as the risk of tearing on the drawing part, that the drawing speed is too low and brings the corresponding hydraulic elements into or out of action. Changes in the sheet holding force, the pulling force and the pulling speed can also be alternated in order to achieve a rapid and at the same time energy-saving pulling process during this pulling process. Otherwise, the basic requirements for a controlled discharge of pressure medium from the cylinder spaces of the hydraulic unit into a pressure accumulator or into the pressure medium reservoir as well as for re-feeding into the cylinder spaces from a pressure accumulator are present, whereby further possibilities of influencing the drawing process can be developed. In particular, a drawing process or a time segment thereof can take place with the drawing ring stationary or with the drawing punch stationary. On the other hand, it is also possible to manufacture very simple drawn parts without changing the flow path with a relatively rapid cycle sequence by switching on a flow path with the lowest possible flow resistance (first flow path). Overall, the control engineering requirements exist for the fact that almost exclusively energy-saving process of an opposite movement of the drawing ring and drawing punch can be used. This means that only in the case of extremely difficult drawn parts or in critical drawing sections of a drawing process, when the punch or drawing ring is at a standstill. In an embodiment according to claim 2, despite the separation of the cylinder chambers for the working piston and the annular piston, the hydraulic unit has a particularly compact structure, which means that the drawing tool is used in different presses that supply the external driving force, especially in small presses.

Durch eine weitere Ausgestaltung entsprechend Patentanspruch 3 wird erreicht, daß bei fertigungstechnischem günstigen Aufbau der Hydraulikeinheit das Ziehwerkzeug nach Beendigung des Ziehvorganges durch Beaufschlagung des Arbeitskolbens aus dem vom zentralen Kolben begrenzten Zylinderraum in seine Ausgangslage rückführbar ist. Darüberhinaus kann während des Ziehvorganges das aus diesem Zylinderraum notwendigerweise verdrängt Öl zur Beschleunigung des Ziehvorganges in den rückseitigen Zylinderraum des Arbeitskolbens eingespeist werden.A further embodiment according to claim 3 ensures that, with the construction of the hydraulic unit being favorable in terms of production engineering, the drawing tool can be returned to its starting position from the cylinder space delimited by the central piston after the drawing process has been completed. In addition, during the drawing process, the oil which is necessarily displaced from this cylinder chamber can be fed into the rear cylinder chamber of the working piston to accelerate the drawing process.

Bei einer Weiterbildung nach Patentanspruch 4 können bei Einschaltung des ersten Strömungsweges (Leitung 20) relativ einfache Ziehteile gefertigt werden.In a further development according to claim 4, relatively simple drawn parts can be manufactured when the first flow path (line 20) is switched on.

Mit dem zweiten Strömungsweg (Leitung 20a) kann durch entsprechende Voreinstellung des Druckes des Druckbegrenzungsventils 36 die Blechhaltekraft vor Beginn und während des Ziehvorganges entsprechend den jeweiligen ziehtechnischen Erfordernissen eingestellt werden, wobei die optimale anfängliche Blechhaltekraft zuvor empirisch ermittelt wurde. Beim Übergang auf den dritten Strömungsweg (Leitung 20b) wird der Druck im hydraulischen System dank des Druckübersetzers abgesenkt, wenn ein Abreißen des Ziehteiles zu befürchten ist. Ein den jeweiligen ziehtechnischen Erfordernissen entsprechender Strömungswegwechsel führt bei Vermeidung jeglicher Abreißgefahr zu einer Optimierung des Ziehvorganges hinsichtlich Energieeinsparung und Ziehgeschwindigkeit, wobei die am Druckbegrenzungsventil und am Drosselventil voreinzustellenden Grenzdrücke bzw. Querschnitte in der Regel zuvor empirisch ermittelt sind.With the second flow path (line 20a), the sheet holding force can be adjusted in accordance with the respective drawing technical requirements before the start and during the drawing process by appropriately presetting the pressure of the pressure limiting valve 36, the optimum initial sheet holding force having been empirically determined beforehand. At the transition to the third flow path (line 20b), the pressure in the hydraulic system is reduced thanks to the pressure booster if there is a risk of the pulling part tearing off. A flow path change corresponding to the respective drawing-technical requirements leads to an optimization of the drawing process with regard to energy saving and drawing speed, while avoiding any risk of tearing off, the limiting pressures or cross-sections to be preset on the pressure-limiting valve and on the throttle valve generally being empirically determined beforehand.

Nach Anspruch 5 kann die Ziehgeschwindigkeit bei entsprechender Anpassung der Blechhaltekraft erhöht werden.According to claim 5, the drawing speed can be increased with a corresponding adjustment of the sheet holding force.

Bei einer Ausgestaltung nach Patentanspruch 6 kann durch Öffnen des dritten Strömungsweges zum Druckspeicher bei stillstehendem Ziehkolben das Ziehteil hergestellt werden. Bei einem nur zeitweisen Öffnen des Strömungsweges ergibt sich eine entsprechende zeitweise Druckabsenkung über hydraulisches System.In one embodiment according to claim 6, the drawn part can be produced by opening the third flow path to the pressure accumulator while the drawing piston is stationary. If the flow path is only opened temporarily, there is a corresponding temporary pressure drop via the hydraulic system.

Nach Patentanspruch 7 kann der Ziehvorgang bei stillstehendem Ringkolben ablaufen.According to claim 7, the drawing process can take place with the ring piston at a standstill.

Bei einer weiteren Ausgestaltung nach Patentanspruch 8 ist es möglich, die Druckmedium-Füllungen in den Zylinderräumen der Hydraulikeinheit wieder exakt zu reproduzieren, wenn zuvor aus diesen Zylinderräumen in den linken Speicherraum des Kolbenspeichers aus diesen Zylinderräumen Druckmedium abgelassen worden ist.In a further embodiment according to claim 8, it is possible to exactly reproduce the pressure medium fillings in the cylinder spaces of the hydraulic unit if pressure medium has previously been discharged from these cylinder spaces into the left storage space of the piston accumulator from these cylinder spaces.

Bei einer weiteren Ausgestaltung nach den Patentansprüchen 9 und 10 werden übermäßige Beanspruchungen des Ziehwerkzeuges beim Abkanten der Restplatine vom Rand des Ziehteiles vermieden.In a further embodiment according to claims 9 and 10, excessive stresses on the drawing tool when bending the remaining blank from the edge of the drawn part are avoided.

Nachstehend wird die Erfindung anhand der Zeichnung beschrieben.The invention is described below with reference to the drawing.

Es zeigen in schematischer Darstellung:

Fig. 1
Das Ziehwerkzeug im Schnitt durch seine Symmetrieachse mit den zugehörigen hydraulischen Steuerorganen und
Fig. 2-8
das Ziehwerkzeug in einer Darstellung gemäß Fig. 1 in unterschiedlichen Arbeitspositionen bzw. bei unterschiedlichen Arbeitsweisen, wobei die Fig. 1,2,4 das Ziehwerkzeug bei Beginn und die Fig. 3,5-8 bei Ende des Ziehvorganges zeigen.
In a schematic representation:
Fig. 1
The drawing tool in section through its axis of symmetry with the associated hydraulic control elements and
Fig. 2-8
the drawing tool in a representation according to FIG. 1 in different working positions or with different working methods, with FIGS. 1,2,4 showing the drawing tool at the beginning and FIGS. 3,5-8 at the end of the drawing process.

Das Ziehwerkzeug dient zum Umformen von vorzugsweise ebenen Blechen, z.B. in Behälter, Töpfe, Spülen und dergleichen. Zum Umformen wirkt eine externe Antriebskraft A von außen auf das Ziehwerkzeug ein. Sie kommt in der Regel von einer hydraulischen Presse, deren Preßhaupt den Ziehring 18 des Ziehwerkzeuges antreibt. Zusammen mit dem Ziehring 18 wird beim Umformen ein Blechhalter 15 bewegt. Zwischen Ziehring und Blechhalter ist bei Beginn des Ziehvorganges eine Platine 47 festgeklemmt. Zur Verformung der Platine 47 ist ein koaxial im Blechhalter angeordneter Ziehstempel in den Ziehring 18 einfahrbar. Die Bewegung der die jeweilige Platine 47 mitführenden Bewegungseinheit 18,15 ist mit Hilfe einer Hydraulikeinheit H des Ziehwerkzeuges in eine gleichzeitige, jedoch gegenläufige Bewegung des Ziehstempels 17 umsetzbar. Die Hydraulikeinheit H umfaßt einen zentralen Arbeitskolben 12, einen diesen umschließenden Ringkolben 13 sowie einen den Ringkolben umschließenden Zylinder 10d, der Bestandteil eines Zylindergehäuses 10 der Hydraulikeinheit H ist. Der mittelbar von der Antriebskraft A antreibbar Ringkolben 13 ist auf dem Druckmedium eines Zylinderraumes 48 abstützbar. Der als Differentialkolben ausgebildete Arbeitskolben 12 ist beidseits mit Druckmedium beaufschlagbar. Das beim Ziehvorgang vom Ringkolben 13 aus dem Zylinderraum 48 verdrängte Druckmedium treibt den Arbeitskolben beim Ziehvorgang wenigstens zeitweise an. Vom Boden des Zylindergehäuses 10 begrenzte Zylinderräume 51,52 und 48 sind durch eine aus diesem Boden vorspringende Trennungshülse 10a hydraulisch voneinander getrennt. Der am Zylinder 10d des Zylindergehäuses 10 geführte Ringkolben 13 ist mittels eines die Trennungshülse 10a übergreifenden Radialflansches 13a am Arbeitskolben 12 geführt. Dabei befindet sich die innere Mantelfläche 13b des Ringkolbens 13 im Abstand von der äußeren Mantelfläche der Trennungshülse 10a. Der rückseitig aus dem Zylinderraum 51 beaufschlagbare Arbeitskolben 12 ist gegensätzlich aus einem Zylinderraum 49 beaufschlagbar, der in einer zentralen Ausnehmung des topfförmigen Arbeitskolbens 12 liegt. Der Zylinderraum 49 ist von einem im Boden des Zylindergehäuses 10 verankerten zentralen Kolben 10c und einem mit dem Arbeitskolben 12 verschraubten Ringteil 12b begrenzt. Das Ringteil 12b umschließt den Schaft 10b des zentralen, stationären Kolbens 10c dichtend. Der rückseitige Zylinderraum 51 kommuniziert mit einem weiteren Zylinderraum 52. Dieser ist vom Boden 12a des Arbeitskolbens 12 und vom zentralen Kolben 10c begrenzt. Wie aus Figur 1 ersichtlich, ist der Ziehstempel 17 über ein zylindrisches Zwischenstück 17a vom Arbeitskolben 12 aufgenommen. Ein Adapterring 14 zwischen dem Blechhalter 15 und der Oberkante des Ringkolbens 13 dient der Übertragung der Antriebskraft von Blechhalter 15 auf den Ringkolben 13. Im Blechhalter 15 ist ein Messerring 16 begrenzt verschieblich angeordnet. Beim Abkanten der Restplatine vom Rand des fertigen Ziehteils wirkt dieser Messerring 16 mit stationären Anschlägen 16a zusammen. Diese sind auf der Stirnkante des Zylinders 10d des Zylindergehäuses 10 abgestützt und tauchen bei Abwärtsbewegung des Blechhalters in korrespondierende Bohrungen dieses Blechhalters ein.The drawing tool is used for forming preferably flat sheets, for example in containers, pots, sinks and the like. An external driving force A acts on the drawing tool from outside for forming. It usually comes from a hydraulic press, the press head of which drives the drawing ring 18 of the drawing tool. Together with the drawing ring 18, a sheet metal holder 15 is moved during the forming process. A circuit board 47 is clamped between the drawing ring and the sheet metal holder at the beginning of the drawing process. To deform the circuit board 47, a drawing die arranged coaxially in the sheet metal holder can be moved into the drawing ring 18. The movement of the movement unit 18, 15 carrying the respective circuit board 47 can be converted into a simultaneous but opposite movement of the drawing punch 17 with the aid of a hydraulic unit H of the drawing tool. The hydraulic unit H comprises a central working piston 12, an annular piston 13 enclosing it and a cylinder 10d enclosing the annular piston, which is part of a cylinder housing 10 of the hydraulic unit H. The annular piston 13, which can be driven indirectly by the driving force A, can be supported on the pressure medium of a cylinder space 48. The working piston 12, which is designed as a differential piston, can be acted upon with pressure medium on both sides. The pressure medium displaced from the cylinder space 48 during the drawing process by the annular piston 13 drives the working piston at least temporarily during the drawing process. Cylinder spaces 51, 52 and 48 delimited from the base of the cylinder housing 10 are hydraulically separated from one another by a separation sleeve 10a projecting from this base. The annular piston 13 guided on the cylinder 10d of the cylinder housing 10 is guided on the working piston 12 by means of a radial flange 13a which overlaps the separating sleeve 10a. The inner circumferential surface 13b of the annular piston 13 is located at a distance from the outer circumferential surface of the separating sleeve 10a. The working piston 12 which can be acted upon from the rear from the cylinder space 51 can be acted upon in the opposite manner from a cylinder space 49 which lies in a central recess of the cup-shaped working piston 12. The cylinder chamber 49 is delimited by a central piston 10c anchored in the base of the cylinder housing 10 and an annular part 12b screwed to the working piston 12. The ring part 12b encloses the shaft 10b of the central, stationary piston 10c sealing. The rear cylinder space 51 communicates with a further cylinder space 52. This is delimited by the bottom 12a of the working piston 12 and by the central piston 10c. As can be seen from FIG. 1, the drawing punch 17 is received by the working piston 12 via a cylindrical intermediate piece 17a. An adapter ring 14 between the sheet metal holder 15 and the upper edge of the annular piston 13 serves to transmit the driving force from the sheet metal holder 15 to the annular piston 13. In the sheet metal holder 15, a knife ring 16 is arranged to be displaceable to a limited extent. When the remaining blank is bent from the edge of the finished drawn part, this knife ring 16 interacts with stationary stops 16a. These are supported on the end edge of the cylinder 10d of the cylinder housing 10 and, when the sheet metal holder moves downward, plunge into corresponding bores in this sheet metal holder.

Arbeitskolben 12 und Ringkolben 13 sind aus den hydraulisch voneinander getrennten Zylinderräumen 51,52 einerseit und 48 andererseits beaufschlagbar. Die genannten Zylinderräume sind im zeichnerisch dargestellten Ausführungsbeispiel über drei alternative Strömungswege miteinander verbindbar, die je unterschiedlich hydraulisch ausgelegt sind. Der erste Strömungsweg geht über die Leitung 20. Der zweite Strömungsweg führt über die Leitung 20a. Der dritte Strömungsweg wird durch die Leitung 20b gebildet.Working pistons 12 and annular pistons 13 can be acted upon from the hydraulically separated cylinder spaces 51, 52 on the one hand and 48 on the other. In the exemplary embodiment shown in the drawing, the cylinder spaces mentioned can be connected to one another via three alternative flow paths, which are each designed differently hydraulically. The first flow path is via line 20. The second flow path is via line 20a. The third flow path is formed by line 20b.

Aufgrund unterschiedlicher hydraulischer Auslegung bedingen die alternativen Strömungswege in den* miteinander kommunizierenden Zylinderräumen 51,52 und 48 beim Ziehvorgang einen Druckverlauf auf anderem Druckniveau. Der Strömungswegwechsel ist durch ein den Druck des Druckmediums in den miteinander kommunizierenden Zylinderräumen 51,52;48 erfassenden Druckfühler 21 auslösbar, der bei Überschreiten voreingestellter Grenzdrücke Schaltimpulse liefert. In der Leitung 20 des ersten Strömungsweges sind ein 2-Wegeventil 34 und der Druckfühler 21 angeordnet. In der Leitung 20a des zweiten Strömungsweges befindet sich ein auf unterschiedliche Grenzdrücke einstellbares, steuerbares Druckbegrenzungsventil 36 mit vorgeschaltetem Rückschlagventil 35. In der Leitung 20b des dritten Strömungsweges sind ein 2-Wegeventil 40, ein Drosselventil 22 und ein als hydraulischer Druckübersetzer wirkender Kolbenspeicher 24 eingefügt. Das über die drei alternativen Strömungswege beim Ziehvorgang in die Zylinderräume 51,52 unter Druck eingeführte Druckmedium wirkt über eine Beaufschlagungsfläche auf den Arbeitskolben 12 ein, der größer ist als die Querschnittsfläche des Kolbenbodens 12a. Insoweit wirkt der Arbeitskolben als Druckübersetzer, was dadurch möglich ist, daß der stationäre Kolben 10c seinen Schaft 10b radial überragt, woraus sich die Vergrößerung der Beaufschlagungsfläche ergibt. Durch diese Ausbildung kann die Antriebskraft A in eine größere Kraft des Ziehkolbens (bei geringerem Ziehweg) umgesetzt werden.
*) über Verbindungskanal 50Due to the different hydraulic design, the alternative flow paths in the * communicating cylinder spaces 51, 52 and 48 require a pressure curve at a different pressure level during the drawing process. The flow path change can be triggered by a pressure sensor 21 which detects the pressure of the pressure medium in the communicating cylinder spaces 51, 52; 48 and which delivers switching impulses when preset limit pressures are exceeded. A 2-way valve 34 and the pressure sensor 21 are arranged in the line 20 of the first flow path. In line 20a of the second flow path there is a controllable pressure relief valve that can be set to different limit pressures 36 with an upstream check valve 35. A 2-way valve 40, a throttle valve 22 and a piston accumulator 24 acting as a hydraulic pressure intensifier are inserted in line 20b of the third flow path. The pressure medium introduced into the cylinder spaces 51, 52 under pressure during the drawing process via the three alternative flow paths acts on the working piston 12 via an action surface which is larger than the cross-sectional area of the piston head 12a. In this respect, the working piston acts as a pressure intensifier, which is possible in that the stationary piston 10c projects radially beyond its shaft 10b, which results in the enlargement of the pressure area. With this design, the driving force A can be converted into a larger force of the drawing piston (with a smaller drawing path).
*) via connection channel 50

Zur Erhöhung der Geschwindigkeit des Ziehvorganges kann die Druckmediumfüllung des vom Ringteil 12b und vom zentralen Kolben 10c begrenzten Zylinderraumes 49 in den rückseitigen Zylinderraum 51 des Arbeitskolbens 12 eingeführt werden. Dabei gelangt das beim Ziehvorgang aus dem Zylinderraum 49 verdrängte Druckmedium bei offenem Wegeventil 19 über Kanal 11 die Leitung 45 in die Zylinderräume 51,52. Zwecks Rückstellung des Ziehwerkzeuges in Ausgangsposition nach dem Ziehvorgang wird der leere Zylinderraum 49 aus einem Druckspeicher 26 wieder aufgefüllt. Bei dieser Rückstellung ist ein dem Volumen des Zylinderraumes 49 entsprechendes Volumen an Druckmedium aus den Zylinderräumen 50,51;48 in das Druckmedium-Reservoir 27 verdrängbar. Der rechte Zylinderraum 24b des Kolbenspeichers 24 ist über eine mit einem 2-Wegeventil 25 versehene Leitung 41 mit dem Druckspeicher 26 verbindbar, der seinerseits mit sämtlichen Zylinderräumen der Hydraulikeinheit zur Nachladung oder zur Druckentlastung in Verbindung gesetzt werden kann. Der Druckspeicher 26 selbst ist mittels einer Förderpumpe 39 aus dem Druckmittel-Reservoir 27 nachladbar.In order to increase the speed of the drawing process, the pressure medium filling of the cylinder space 49 delimited by the ring part 12b and by the central piston 10c can be introduced into the rear cylinder space 51 of the working piston 12. When the directional control valve 19 is open, the pressure medium displaced from the cylinder space 49 during the drawing process reaches the line 45 into the cylinder spaces 51, 52 via channel 11. For the purpose of resetting the drawing tool in the starting position after the drawing process, the empty cylinder space 49 is refilled from a pressure accumulator 26. With this reset, a volume of pressure medium corresponding to the volume of the cylinder space 49 can be displaced from the cylinder spaces 50, 51, 48 into the pressure medium reservoir 27. The right cylinder space 24b of the piston accumulator 24 can be connected to the pressure accumulator 26 via a line 41 provided with a 2-way valve 25, which in turn can be connected to all cylinder spaces of the hydraulic unit for recharging or for pressure relief. The pressure accumulator 26 itself can be reloaded from the pressure medium reservoir 27 by means of a feed pump 39.

Schließlich ist der Arbeitskolben 12 mittels einer Druckquelle P bei stillstehendem Ringkolben 13, also bei abgeschalteter Antriebskraft A antreibbar. Das aus dem Zylinderraum 49 dabei verdrängte Druckmedium wird über ein 2-Wegeventil 28 in das Druckmedium-Reservoir 27 abgeführt. Die Abführung kann aber auch über ein bei Überschreiten einer oberen Druckgrenze öffnendes Ventil 30 erfolgen.Finally, the working piston 12 can be driven by means of a pressure source P when the annular piston 13 is stationary, that is to say when the driving force A is switched off. That from the cylinder chamber 49 displaced pressure medium is discharged into the pressure medium reservoir 27 via a 2-way valve 28. The discharge can also take place via a valve 30 which opens when an upper pressure limit is exceeded.

Das 2-Wegeventil 40 und das Drosselventil 22 in der Leitung 20b des dritten Strömungsweges sind mittels einer Überbrückungsleitung 20b′ überbrückbar. In dieser ist ein im Durchfluß in Strömungsrichtung einem vorbestimmten Druck freigebendes Rückschlagventil 23 angeordnet. Die beim Abkanten der Restplatine vom Rand des fertigen Ziehteils bewegte Masse, die im zeichnerisch dargestellten Ausführungsbeispiel durch den Ziehring 18, den Blechhalter 15, den Adapterring 14 und den Ringkolben 13 repräsentiert wird, kann bei Wegfall des Abkantwiderstandes durch Drosselung des Abflusses des Druckmediums aus dem Zylinderraum 48 abgestoppt werden. Dies geschieht mit Hilfe des in der Leitung 20b des dritten Strömungsweges angeordneten Drosselventils 22 in Abhängigkeit und dem durch den Wegfall des Abkantwiderstandes ausgelösten Druckabfall. Dabei gelangt das Druckmedium über den Kolbenspeicher 24 in den Druckspeicher 26, wobei das 2-Wegeventil 33 in Schließstellung und das 2-Wegeventil 25 in Offenstellung gesteuert ist.The 2-way valve 40 and the throttle valve 22 in the line 20b of the third flow path can be bridged by means of a bypass line 20b. A check valve 23 which releases a predetermined pressure in the flow direction in the flow direction is arranged in this. The mass moved when folding the rest of the blank from the edge of the finished drawn part, which is represented in the illustrated embodiment by the drawing ring 18, the sheet metal holder 15, the adapter ring 14 and the annular piston 13, can be eliminated by throttling the outflow of the pressure medium from the bending resistance Cylinder chamber 48 are stopped. This is done with the help of the throttle valve 22 arranged in the line 20b of the third flow path in dependence on and the pressure drop triggered by the elimination of the folding resistor. The pressure medium passes through the piston accumulator 24 into the pressure accumulator 26, the 2-way valve 33 being controlled in the closed position and the 2-way valve 25 in the open position.

Fig. 1 zeigt das außer Betrieb befindliche Ziehwerkzeug mit dem gesamten zugehörigen Hydrauliksystem bei eingelegter Platine.Fig. 1 shows the out of operation drawing tool with the entire associated hydraulic system with the board inserted.

Die Fign. 2-8 dienen der Erläuterung konkreter unterschiedlicher Verfahrensabläufe beim Betrieb des Ziehwerkzeuges, die den jeweiligen unterschiedlichen Zieherfordernissen entsprechen. Dabei sind die im jeweiligen Verfahrensablauf durchströmten Leitungen und Räume durch eine stärkere Linienführung hervorgehoben. Alle nicht in den Verfahrensablauf einbezogenen Organe, in welchen demzufolge kein Druck ansteht, sind dabei weggelassen.The figures 2-8 are used to explain specific different procedures in the operation of the drawing tool, which correspond to the different drawing requirements. The lines and rooms through which the respective process flows are emphasized by a stronger line. All organs not included in the process sequence, in which there is consequently no pressure, are omitted.

Verfahrensablauf gemäß Fig. 2: Zur Herstellung einfacher Ziehteile bei relativ schneller Taktfolge ist das Ziehwerkzeug auf den ersten Strömungsweg geschaltet. Beim Ziehvorgang strömt das Druckmedium aus dem Zylinderraum 48 über die Leitung 20 mit Zweiwegeventil 34 in den Zylinderraum 51 und zusätzlich über den Verbindungskanal 50 in den Zylinderraum 52.2: To produce simple drawn parts with a relatively fast cycle sequence, the drawing tool is switched to the first flow path. During the drawing process, the pressure medium flows from the cylinder space 48 via the line 20 with a two-way valve 34 into the cylinder space 51 and additionally via the connecting channel 50 into the cylinder space 52.

Fig. 3: In dieser Figur ist das Ziehwerkzeug auf den zweiten Strömungsweg geschaltet. Das Druckmedium wird aus dem Zylinderraum 48 unter teilweiser Einbeziehung der Leitung 20 des ersten Strömungsweges über ein Rückschlagventil 35 und ein einstellbares Druckbegrenzungsventil 36 in einer Leitung 20a in die Zylinderräume 51, 52 verdrängt, um den Antriebskolben 12 anzutreiben. Die Schaltung dieses Strömungsweges ist sinnvoll, wenn es auf eine angepaßte Einstellung der Blechhaltekraft vor Beginn des Ziehvorganges ankommt bzw. eine Steuerung der Blechhaltekraft während des Ziehvorganges angezeigt ist. Der Ziehvorgang beginnt erst, wenn die Blechhaltekraft, das heißt der Druck im Zylinderraum 48 den im Druckbegrenzungsventil 36 eingestellten Grenzdruck überschreitet. Dieser Grenzdruck ist in Abhängigkeit vom Druckfühler 21 einstellbar bzw. veränderbar, so daß die Blechhalterkraft während des Ziehvorganges den jeweiligen ziehtechnischen Erfordernissen angepaßt werden kann.Fig. 3: In this figure, the drawing tool is switched to the second flow path. The pressure medium is displaced from the cylinder space 48 with the partial inclusion of the line 20 of the first flow path via a check valve 35 and an adjustable pressure relief valve 36 in a line 20a into the cylinder spaces 51, 52 in order to drive the drive piston 12. The switching of this flow path makes sense if an adjusted setting of the sheet holding force is important before the drawing process begins or if a control of the sheet holding force is indicated during the drawing process. The drawing process only begins when the sheet metal holding force, that is to say the pressure in the cylinder space 48, exceeds the limit pressure set in the pressure relief valve 36. This limit pressure is adjustable or changeable depending on the pressure sensor 21, so that the sheet metal holder force can be adapted to the respective drawing requirements during the drawing process.

Fig. 4: Bei Schaltung des dritten Strömungsweges gemäß Fig. 4 wird das aus dem Zylinderraum 48 unter Einbeziehung der Leitung 20 des ersten Strömungsweges kommende Druckmedium über die Leitung 20b, über ein Zweiwegeventil 40, ein Drosselventil 22 und über einen Kolbenspeicher 24 sowie über ein weiteres Wegeventil 33 in die Zylinderräume 51, 52 eingedrückt, um den Arbeitskolben 12 anzutreiben. Wie aus der Figur ersichtlich, ist der Kolbenspeicher 24 als Druckübersetzer ausgebildet. Bei Schaltung auf den dritten Strömungsweg wird daher der Druck im hydraulischen System abgesenkt* wenn dieser Druck eine obere Grenze überschritten hat, der mit Bezug auf das in Arbeit befindliche Ziehteil die Gefahr eines Abreißens in sich birgt. Der Druckfühler schaltet also bei einem zuvor empirisch ermittelten kritischen Grenzdruck.
* und die Ziehgeschwindigkeit dementsprechend vermindertFig. 4: When switching the third flow path according to Fig. 4, the pressure medium coming from the cylinder space 48, including the line 20 of the first flow path, via line 20b, via a two-way valve 40, a throttle valve 22 and via a piston accumulator 24 and via Another directional control valve 33 is pressed into the cylinder spaces 51, 52 in order to drive the working piston 12. As can be seen from the figure, the piston accumulator 24 is designed as a pressure intensifier. When switching to the third flow path, the pressure in the hydraulic system is therefore reduced * when this pressure has exceeded an upper limit, which, with respect to the drawn part in work, entails the risk of tearing off. The pressure sensor therefore switches at a critical limit pressure previously determined empirically.
* and the pulling speed is reduced accordingly

Unabhängig davon, ob das Druckmedium über den ersten, zweiten oder dritten Strömungsweg in die Zylinderräume 51, 52 einströmt, kann das beim Ziehvorgang aus dem Zylinderraum 49 verdrängte Druckmedium über unterschiedliche Wege abgeführt werden. Diese unterschiedlichen Wege entsprechen den jeweiligen ziehtechnischen Erfordernissen:

  • 1. Das Druckmedium kann zur Beschleunigung des Ziehvorgangs über das Wegeventil 19 in der Leitung 45 in die Zylinderräume 51,52 eingespeist werden. In diesem Falle wird nach dem Ziehvorgang bei Rückstellung des Ziehwerkzeuges in Ausgangsstellung (welche Rückstellung weiter unten erläutert wird) aus den Zylinderräumen 51, 52 ein Volumen an Druckmedium in das Druckmittel-Reservoir 27 verdrängt, das dem zuvor beim Ziehvorgang in die Zylinderräume 51, 52 eingespeiste Volumen an Druckmedium entspricht. Dabei gelangt das Druckmedium aus den vorgenannten Zylinderräumen 51, 52 über einen Abschnitt der Leitung 20 und über das Wegeventil 28 in das Druckmittel-Reservoir 27.
  • 2. Das beim Ziehvorgang aus dem Zylinderraum 49 verdrängte Druckmedium gelangt über die Leitungen 43,42,46 mit Wegeventilen 32,37,28 direkt in das Druckmittel-Reservoir 27.
Regardless of whether the pressure medium flows into the cylinder spaces 51, 52 via the first, second or third flow path, the pressure medium displaced from the cylinder space 49 during the drawing process can be discharged in different ways. These different paths correspond to the respective drawing requirements:
  • 1. To accelerate the drawing process, the pressure medium can be fed into the cylinder spaces 51, 52 in the line 45 via the directional valve 19. In this case, a volume of pressure medium is displaced from the cylinder spaces 51, 52 into the pressure medium reservoir 27 after the drawing process when the drawing tool is returned to the starting position (which provision will be explained below), which volume previously was during the drawing process into the cylinder spaces 51, 52 volume of pressure medium fed corresponds. In this case, the pressure medium passes from the aforementioned cylinder spaces 51, 52 via a section of the line 20 and via the directional valve 28 into the pressure medium reservoir 27.
  • 2. The pressure medium displaced from the cylinder chamber 49 during the drawing process passes directly into the pressure medium reservoir 27 via the lines 43, 42, 46 with directional valves 32, 37, 28.

Fig. 8: Dort ist verdeutlicht, wie das Ziehwerkzeug nach dem Ziehvorgang aus seiner Endstellung in die Ausgangsstellung zurückgeführt wird. Bei diesem Verfahrensablauf gelangt aus einem Druckspeicher 26 Druckmedium über den Anfangsabschnitt einer Leitung 42 sowie über die Leitung 43 und das Wegeventil 32 sowie den Kanal 11 im Schaft 10b in den zunächst leeren Zylinderraum 49, um von dort aus den Arbeitskolben 12 in einer Richtung anzutreiben, die gegenläufig zur Ziehrichtung ist. Das bei Rückführung des Arbeitskolbens in seine Ausgangsstellung aus den Zylinderräumen 51, 52 verdrängte Druckmedium kann z.B. über den ersten Strömungsweg in den Zylinderraum 48 zurückgelangen. In diesem Zusammenhang ist auf folgendes hinzuweisen: Wird, wie oben dargelegt (S. ¹⁰, Zn⁸⁻¹⁰), beim Ziehvorgang das Druckmedium aus dem Zylinderraum 49 in die Zylinderräume 51, 52 zur Beschleunigung des Ziehvorganges eingespeist, so ist bei Rückstellung des Ziehwerkzeuges ein dem eingespeisten Volumen entsprechendes Volumen aus den Zylinderräumen 51, 52 in das Druckmittel-Reservoir 27 zu verdrängen. Dies bedeutet, daß bei jedem Ziehvorgang ein Teil des in den Zylinderräumen 50, 51, 48, also in einem inneren kommunizierenden System befindliche Druckmedium ausgetauscht wird. Ein solcher partieller Austausch ist vorteilhaft, weil er ein Ansteigen der Temperatur des Druckmediums in den Zylinderräumen über eine kritische Grenze verhindert und die Möglichkeit der Reinhaltung des Druckmediums durch Filtern des jeweils getauschten Anteils gibt.Fig. 8: It shows how the drawing tool is returned from its end position to the starting position after the drawing process. In this course of the process, pressure medium passes from a pressure accumulator 26 via the initial section of a line 42 and via line 43 and the directional control valve 32 as well as the channel 11 in the shaft 10b into the initially empty cylinder space 49, in order to drive the working piston 12 in one direction from there. which is opposite to the direction of pull. The pressure medium displaced from the cylinder spaces 51, 52 when the working piston is returned to its starting position can, for example return to the cylinder space 48 via the first flow path. In this context, the following should be pointed out: If, as explained above (S. ¹⁰, Zn⁸⁻¹⁰), the pressure medium is fed from the cylinder space 49 into the cylinder spaces 51, 52 during the drawing process to accelerate the drawing process, then when the drawing tool is reset, a to displace volume corresponding to the injected volume from the cylinder spaces 51, 52 into the pressure medium reservoir 27. This means that part of the pressure medium located in the cylinder spaces 50, 51, 48, that is to say in an internal communicating system, is exchanged during each drawing process. Such a partial exchange is advantageous because it prevents the temperature of the pressure medium in the cylinder spaces from rising above a critical limit and enables the pressure medium to be kept clean by filtering the portion that is exchanged.

In den Figuren 5, 6 sind Verfahrensabläufe verdeutlicht, bei welchen der Ziehvorgang bei stillstehendem Ziehstempel 17 (Fig. 5) bzw. bei stillstehendem Blechhalter 15 erfolgt, so daß also keine gegenläufige Bewegung von Blechhalter und Ziehstempel stattfindet. Eine solche Verfahrensweise kann bei bestimmten schwierigen Ziehteilen erforderlich sein. Auch kann es geboten sein, eine solche Verfahrensweise nur in einem besonders kritischen Abschnitt des gesamten Ziehvorganges ablaufen zu lassen, wobei vor und nach diesem Abschnitt des Ziehvorganges zur Energieeinsparung und zur Beschleunigung des Ziehvorganges auf den ersten, zweiten oder dritten Strömungsweg geschaltet ist oder zwischen diesen Strömungswegen gewechselt wird.FIGS. 5, 6 illustrate process sequences in which the drawing process takes place with the drawing punch 17 (FIG. 5) or with the sheet holder 15 stationary, so that there is no opposite movement of the sheet holder and drawing punch. Such a procedure may be required for certain difficult drawn parts. It may also be necessary to allow such a procedure to take place only in a particularly critical section of the entire drawing process, with switching between the first, second or third flow path before and after this section of the drawing process in order to save energy and to accelerate the drawing process Flow paths are changed.

In Fig. 5 wird also der Ziehvorgang, angetrieben durch die externe Kraft A, ausschließlich durch die Bewegung von Ziehring 18, Blechhalter 15, Adapterring 14 und Ringkolben 13 bewirkt, während der Arbeitskolben nicht beaufschlagt wird. Dies wird dadurch erreicht, daß das aus dem Zylinderraum 48 verdrängte Druckmedium über die Leitung 20b, das Wegeventil 40, das Drosselventil 22 in den linken Speicherraum 24a des Druckspeichers 24 gelangt. Durch diese Einspeisung wird der Kolben 24c nach rechts verschoben und verdrängt Druckmedium aus dem rechten Speicherraum 24b des Kolbenspeichers. Das verdrängte Druckmedium gelangt über das Wegeventil 25, die Leitung 41 in den Druckspeicher 26. Dieser ist bei Bedarf aus dem Druckmedium-Reservoir mittels der Förderpumpe 39 über das Rückschlagventil 38 nachladbar. Bei dieser Verfahrensweise ist es erforderlich, nach jedem Ziehvorgang den Zylinderraum 48 wieder aufzufüllen. Dies wird im Verlauf eines Rückstellvorganges bewirkt, bei welchem aus dem Druckspeicher 26 über die Leitung 41 und das Wegeventil 25 in den rechten Speicherraum 24b des Kolbenspeichers 24 eingespeist wird. Dadurch wird unter dem Druck des Druckmediums auf den Druckspeicher der Kolben 24c in seine Ausgangslage zurückgeführt, um ein Volumen an Druckmedium aus dem linken Speicherraum 24a zu verdrängen, der exakt dem zuvor beim Ziehvorgang dort eingespeisten Druckmedium-Volumen entspricht. Dadurch ist es möglich, das ursprüngliche Druckmedium-Volumen im Zylinderraum 48 bei Rückstellung des Ringkolbens zu reproduzieren. Bei einer Arbeitsweise gemäß Fig. 6 ist beim Ziehvorgang der Blechhalter durch Abschlaten der externen Kraft A stillgesetzt, während der Arbeitskolben 12 und damit der Ziehstempel 17 angetrieben wird und den Ziehvorgang bewirkt. Bei dieser Verfahrensweise wird aus einer gesonderten Druckmittelquelle P über ein Rückschlagventil 53 sowie über einen Leitungsabschnitt der Leitung 20 des ersten Strömungsweges Druckmedium in die anfänglich leeren Zylinderräume 51,52 eingedrückt, um den Arbeitskolben 12 in Ziehrichtung anzutreiben. Das dabei aus dem Zylinderraum 49 verdrängte Druckmedium gelangt über das Wegeventil 32 in den Druckspeicher 26.5, the drawing process, driven by the external force A, is effected exclusively by the movement of the drawing ring 18, sheet metal holder 15, adapter ring 14 and annular piston 13, while the working piston is not being acted upon. This is achieved in that the pressure medium displaced from the cylinder space 48 reaches the left storage space 24a of the pressure accumulator 24 via the line 20b, the directional control valve 40 and the throttle valve 22. As a result of this feed, the piston 24c becomes shifted to the right and displaces pressure medium from the right storage space 24b of the piston accumulator. The displaced pressure medium passes through the directional control valve 25, the line 41 into the pressure accumulator 26. If required, this can be reloaded from the pressure medium reservoir by means of the feed pump 39 via the check valve 38. With this procedure, it is necessary to refill the cylinder space 48 after each drawing operation. This is brought about in the course of a resetting process in which the pressure accumulator 26 feeds via line 41 and directional control valve 25 into the right-hand storage space 24b of the piston accumulator 24. As a result, the piston 24c is returned to its starting position under the pressure of the pressure medium on the pressure accumulator in order to displace a volume of pressure medium from the left storage space 24a which corresponds exactly to the volume of pressure medium fed there previously during the drawing process. This makes it possible to reproduce the original pressure medium volume in the cylinder space 48 when the annular piston is reset. 6, the sheet metal holder is stopped during the drawing process by shedding off the external force A, while the working piston 12 and thus the drawing punch 17 are driven and effect the drawing process. In this procedure, pressure medium is pressed into the initially empty cylinder spaces 51, 52 from a separate pressure medium source P via a check valve 53 and via a line section of line 20 of the first flow path, in order to drive the working piston 12 in the direction of pull. The pressure medium displaced from the cylinder chamber 49 reaches the pressure accumulator 26 via the directional valve 32.

Die Rückstellung des Ziehwerkzeuges in Ausgangsstellung geschieht, wie oben beschrieben, durch Einführung von Druckmedium aus dem Druckspeicher 26 in den zunächst leeren Zylinderraum 49.The drawing tool is reset to the starting position, as described above, by introducing pressure medium from the pressure accumulator 26 into the initially empty cylinder space 49.

Fig. 7 veranschaulicht das Verfahren zum Abkanten der Restplatine 47 vom Rand des fertigen Ziehteils. Zum Abkanten wird der Ziehstempel 17 mit dem Arbeitskolben einerseits und die aus Ziehring, Blechhalter 15 Adapterring 14 und Ringkolben 13 bestehende Bewegungseinheit synchron nach unten gefahren. Dabei läuft der begrenzt verschieblich im Blechhalter 15 angeordnete Messerring 16 auf bolzenförmige stationäre Anschläge 16a auf, um über eine geringfügige Wegstrecke für den Arbeitsvorgang relativ zur vorgenannten Bewegungseinheit und damit relativ zum Ziehteil bzw. zur Platine 47 bewegt zu werden. Nach dem Abkanten entfällt der Abkantwiderstand im hydraulischen System schlagartig, was einem plötzlichen Druckabfall gleichkommt. Zur Dämpfung diesbezüglicher Erschütterungen des Ziehwerkzeuges wird im Moment des Druckabfalles in Abhängigkeit vom Druckfühler 21 der Abfluß des Druckmediums aus dem Zylinder 48 mit Hilfe des Drosselventils 22 gedrosselt, wie weiter oben beschrieben ist.Fig. 7 illustrates the process for folding the remaining board 47 from the edge of the finished drawn part. For folding, the drawing punch 17 with the working piston on the one hand and the moving unit consisting of drawing ring, sheet metal holder 15 adapter ring 14 and annular piston 13 are used moved down synchronously. Here, the knife ring 16, which is arranged to be displaceable to a limited extent in the sheet metal holder 15, runs onto bolt-shaped stationary stops 16a in order to be moved over a slight distance for the work process relative to the aforementioned movement unit and thus relative to the drawn part or to the plate 47. After folding, the bending resistance in the hydraulic system suddenly disappears, which equates to a sudden drop in pressure. To dampen vibrations of the drawing tool in this regard, the outflow of the pressure medium from the cylinder 48 is throttled with the aid of the throttle valve 22 at the moment of the pressure drop as a function of the pressure sensor 21, as described above.

Bei den in Figuren 5,6 dargestellten Arbeitsweisen wird die Druckmedium-Füllung des Zylinderraumes 48 (Fig. 5) bzw. die Druckmedium-Füllung des Zylinderraumes 49 (Fig. 6) in den Druckspeicher 26 und zwar gegen den dort herrschenden Druck verdrängt. Dabei wird der Druckspeicher 26 auf ein entsprechend höheres Druckniveau angehoben. Dies bedeutet, daß die für das Eindrücken des Druckmediums in den Druckspeicher zusätzlich aufgewendete Energie im Druckspeicher 26 gespeichert ist und für eine nachfolgende Operation (z.B. für eine Operation gemäß Fign. 7 und 8) wieder zur Verfügung steht.In the working methods shown in FIGS. 5, 6, the pressure medium filling of the cylinder space 48 (FIG. 5) or the pressure medium filling of the cylinder space 49 (FIG. 6) is displaced into the pressure accumulator 26, specifically against the pressure prevailing there. The pressure accumulator 26 is raised to a correspondingly higher pressure level. This means that the energy additionally required for pressing the pressure medium into the pressure accumulator is stored in the pressure accumulator 26 and is available again for a subsequent operation (e.g. for an operation according to FIGS. 7 and 8).

Bei eventuellen Fehlsteuerungen der Wegeventile 19 bzw. 32 bzw. 28 ermöglicht ein Sicherheitsventil 30 in der* Leitung 44 ein Abfließen der Druckmedium-Füllung des Zylinderraumes 49 in das Druckmedium-Reservoir 27, so daß keine Schäden im hydraulischen System entstehen können. Abschließend ist darauf hinzuweisen, daß der im zeichnerischen Ausführungsbeispiel dargestellte Aufbau durch Wegfall des zylindrischen Zwischenstückes 17a und/oder durch Weglassen des Adapterringes 14 in Richtung der Symmetrieachse wesentlich verkürzt werden kann. In diesem Sinne kann es unter Umständen auch zweckmäßig sein, den Antriebskolben 12 als solchen zugleich als Ziehstempel auszubilden, so daß ein gesonderter Ziehstempel 17 entfällt.
* mit Rückschlagventilen 31,29 versehenenIn the event of incorrect control of the directional control valves 19 or 32 or 28, a safety valve 30 in the * line 44 allows the pressure medium filling of the cylinder space 49 to flow into the pressure medium reservoir 27, so that no damage can occur in the hydraulic system. In conclusion, it should be pointed out that the construction shown in the illustrative embodiment can be substantially shortened by omitting the cylindrical intermediate piece 17a and / or by omitting the adapter ring 14 in the direction of the axis of symmetry. In this sense, it may also be expedient under certain circumstances to design the drive piston 12 as such at the same time as a drawing punch, so that a separate drawing punch 17 is omitted.
* provided with check valves 31,29

Ein wesentlicher Vorteil des erfindungsgemäßen Ziehwerkzeuges besteht darin, daß die auf den Ziehring einwirkende externe Kraft A in eine wesentlich größere, gegenläufige Ziehkraft umgewandelt werden kann. Dies resultiert daraus, daß das vom Ringkolben verdrängte Druckmedium über eine Beaufschlagungsfläche auf den Arbeitskolben 12 einwirken kann, die größer ist als der Querschnitt des Arbeitskolbens, weil der zentrale stationäre Kolben 10c die aus dem rückseitigen Zylinderraum 51 des Arbeitskolbens 12 beaufschlagbare Fläche radial übergreift. Insoweit setzt sich die gesamte Beaufschlagungsfläche des Arbeitskolbens 12 aus einer rückseitigen Beaufschlagungsfläche und der Stirnfläche des zentralen Kolbens 10c zusammen. Dadurch liegt auch die Voraussetzung dafür vor, daß erforderlichenfalls die externe Kraft A in eine gegenläufige Ziehkraft gleicher Größe umgewandelt werden kann, welche Ziehkraft jedoch auf einen kleineren Ziehkolben bzw. ein kleineres Ziehwerkzeug einwirkt.A major advantage of the drawing tool according to the invention is that the external force A acting on the drawing ring can be converted into a substantially larger, opposing drawing force. This results from the fact that the pressure medium displaced by the annular piston can act on the working piston 12 via an action surface which is larger than the cross section of the working piston, because the central stationary piston 10c radially overlaps the surface which can be acted upon from the rear cylinder space 51 of the working piston 12. In this respect, the entire pressure surface of the working piston 12 is composed of a pressure surface on the rear and the end face of the central piston 10c. This also provides the prerequisite for the fact that, if necessary, the external force A can be converted into an opposing pulling force of the same size, but which pulling force acts on a smaller drawing piston or a smaller drawing tool.

Das für jedes Ziehteil nach Gestalt, Werkstoff und Ziehtiefe zunächst empirisch ermittelte spezifische Rechnerprogramm verleiht dem Ziehgerät das Bestreben, insgesamt bei möglichst hohen Ziehgeschwindigkeiten ohne Abrißgefahr zu arbeiten. Ein Abreißen des Ziehteils ist mittels des Druckfühlers 21 durch Übergang auf eine der zahlreichen Strömungsalternativen geringeren Drucks bzw. geringerer Ziehgeschwindigkeit (z.B. vom zweiten Strömungsweg auf den ersten oder dritten Strömungsweg oder vom ersten Strömungsweg auf den dritten Strömungsweg) oder durch partielles Ablassen von Druckmedium aus dem Zylinderraum 48 bzw. 51,52 oder durch Stillsetzen der externen Kraft A oder des Ziehstempels zuverlässig zu vermeiden. Steigt nach dem eingetretenen Druckabfall der Druck im System durch einen zunehmenden Ziehwiderstand (Umformwiderstand) erneut bis zur kritischen Druckgrenze an, so kann das hydraulische System von der aktuellen Strömungsalternative auf eine Strömungsalternative noch geringeren Druckes übergehen. Fällt jedoch der Druck im System unter eine im Druckfühler 21 voreingestellte Druckgrenze, so geht das System wieder auf eine Strömungsalternative höheren Drucks bzw. höherer Ziehgeschwindigkeit über. Dabei kann es zu einem relativ raschen Wechsel der Strömungsalternativen als Voraussetzung für eine rasche Taktfolge beim Ziehen der Ziehteile kommen.The specific computer program initially determined empirically for each drawn part according to shape, material and depth of drawing gives the drawing device the endeavor to work at the highest possible drawing speeds without the risk of tearing. The pulling part can be torn off by means of the pressure sensor 21 by transitioning to one of the numerous flow alternatives of lower pressure or lower pulling speed (e.g. from the second flow path to the first or third flow path or from the first flow path to the third flow path) or by partially releasing pressure medium from the Avoid cylinder space 48 or 51.52 or by stopping external force A or the plunger. If, after the pressure drop occurs, the pressure in the system rises again up to the critical pressure limit due to increasing drawing resistance (forming resistance), the hydraulic system can switch from the current flow alternative to a flow alternative of even lower pressure. However, if the pressure in the system falls below a pressure limit preset in the pressure sensor 21, the system goes back to a flow alternative of higher pressure or higher drawing speed about. This can lead to a relatively rapid change in the flow alternatives as a prerequisite for a rapid cycle sequence when pulling the drawn parts.

Abschließend ist noch auf folgendes hinzuweisen: Im zeichnerisch dargestellten Ausführungsbeispiel der Hydraulikeinheit H ist der zentrale, stationäre Kolben 10c vom Ringkolben 13 und dieser von einem Zylindergehäuse 10 umschlossen, welches Zylindergehäuse 10 auch als Zylinderblock im Sinne des Ausführungsbeispiels der Fign. 3,4 der gattungsgemäßen DE-OS 36 20 876 (= US-PS 4,796,453) ausgebildet sein kann, welcher Zylinderblock wenigstens zwei Ringkolben umschließt. In jedem Falle führt das Ineinanderfügen von stationären Kolben 10c, Ringkolben 13 und Zylindergehäuse 10 bzw. Zylinderblock zu einem derartigen raumsparenden Aufbau des Ziehwerkzeuges, daß dieses auch in extrem kleinen Pressen, insbesondere in Spritzgießmaschinen betrieben werden kann. Zu diesem Zweck wird die Hydraulikeinheit H in der einen Formaufspannplatte der Spritzgießmaschine und eine den Ziehring und den Blechhalter umfassende andere Einheit des Ziehwerkzeuges an der zweiten Formaufspannplatte der Spritzgießmaschine aufgespannt. Das Ziehwerkzeug arbeitet demzufolge bei horizontaler Ziehachse.
* wenigstens zeitweiseFinally, the following should also be pointed out: in the illustrated embodiment of the hydraulic unit H, the central, stationary piston 10c is enclosed by the annular piston 13 and this by a cylinder housing 10, which cylinder housing 10 also as a cylinder block in the sense of the embodiment of FIGS. 3.4 of the generic DE-OS 36 20 876 (= US-PS 4,796,453) can be formed, which cylinder block encloses at least two ring pistons. In any case, the interconnection of stationary pistons 10c, annular piston 13 and cylinder housing 10 or cylinder block leads to such a space-saving construction of the drawing tool that it can also be operated in extremely small presses, in particular in injection molding machines. For this purpose, the hydraulic unit H is clamped in the one mold clamping plate of the injection molding machine and another unit of the drawing tool comprising the drawing ring and the sheet metal holder on the second mold clamping plate of the injection molding machine. The drawing tool therefore works with a horizontal drawing axis.
* at least temporarily

Claims (10)

  1. Drawing tool for deforming preferably planar sheets (blanks 47), including a drawing die (18), which is drivable by an external driving force (A), a sheet holder (15), which is displaceable together with the drawing die (18) as displacement unit (18, 15), and a drawing punch (17), which is insertable into the drawing die (18) in order to deform the blanks (47), and including a hydraulic unit, by means of which the movement of the displacement unit (18, 15), which entrains the respective blank (47), is convertible into a simultaneous, but oppositely directed movement of the drawing punch (17), which hydraulic unit includes a central working piston (12), an annular piston (13) surrounding said working piston, and a cylinder housing, which surrounds the annular piston, the annular piston (13), which is indirectly drivable by the driving force (A) and is supportable by the pressure medium of a cylinder chamber (48), being adapted to be supplied with pressure medium at one end, and the working piston (12), which is in the form of a differential piston (annular member 12b), being adapted to be supplied with pressure medium at both ends, and the pressure medium, which is displaced by the annular piston (13) from the cylinder chamber (48) during the drawing operation, drives the working piston (12) at least temporarily, characterised in that working piston (12) and annular piston (13) are adapted to be supplied from cylinder chambers (51, 52, on the one hand, and 48, on the other hand) hydraulically separated from one another, which chambers intercommunicate at least temporarily via at least two alternative flow paths (first flow path via line 20; second flow path via line 20a; third flow path via line 20b), and which chambers necessitate a pressure variation on another pressure level during the drawing operation because of a different hydraulic arrangement in the intercommunicating cylinder chambers (51, 52; 48), in that a pressure detector (21) is provided, which detects the pressure of the pressure medium in at least one of the two cylinder chambers (51, 52; 48) and generates control pulses if predetermined limit pressures are exceeded, and in that the alternative flow paths are controllable by the control pulses of the pressure detector (21).
  2. Drawing tool according to claim 1, characterised in that the cylinder chambers (51, 52; 48), which are defined by the base of a cylinder housing (10), are hydraulically separated from one another by a tubular partition (10a), which protrudes from this base, and in that the annular piston (13), which is guided by the cylinder (10d) of the cylinder housing (10), is guided on the working piston (12) by means of a radial flange (13a), which overlaps the tubular partition (10a), the internal surface (13b) of the annular piston (13) being spaced from the external surface of the tubular partition (10a).
  3. Drawing tool according to claim 1 or 2, characterised in that the working piston (12), which is adapted to be supplied at its rear end from the cylinder chamber (51), is adapted to be supplied in the opposite direction from a cylinder chamber (49), which is situated in a central recess in the cup-shaped working cylinder (12) and is defined by a central piston (10c), which is secured in the base of the cylinder housing (10), and by an annular member (12b), which is connected to the working piston (12), the cylinder chamber (51) at the rear end communicating with an additional cylinder chamber (52), which is defined by the base (12a) of the working piston (12) and by the central piston (10c).
  4. Drawing tool according to one of the preceding claims, characterised in that a directional valve (34) and a pressure detector (21) are disposed in the line (20) of the first flow path, a controllable pressure relief valve (36), which can be set to different limit pressures and has a preceding check valve (35), is disposed in the line (20a) of the second flow path, and a directional valve (40), a throttle valve (22) and a piston-type accumulator (24), which acts as a hydraulic pressure transmitter, are disposed in the line (20b) of the third flow path.
  5. Drawing tool according to one of the preceding claims, characterised in that (in order to increase the speed of the drawing operation) the pressure medium filling of the cylinder chamber (49), defined by the annular member (12b) and by the central piston (10c), is feedable into the rear cylinder chamber (51) of the working piston (12) via a line (45) provided with directional valve (19), and the empty cylinder chamber (49) is refillable from a pressure accumulator (26) for the purpose of returning the drawing tool into its initial position, during which return movement a volume of pressure medium, corresponding to the volume of the cylinder chamber (49), is displaceable into a pressure medium reservoir (27) from the cylinder chambers (50, 51; 48).
  6. Drawing tool according to claim 5, characterised in that the right-hand cylinder chamber (24b) of the piston-type accumulator (24) is connectable to the pressure accumulator (26), which is connectable to all of the cylinder chambers of the hydraulic unit, via a line (41) provided with directional valve (25), which pressure accumulator (26) is rechargeable from the pressure medium reservoir (27) by means of feed pump (39).
  7. Drawing tool according to one of the preceding claims, characterised in that the working piston (12) is drivable by means of a pressure source (P) when annular piston (13) is stationary, and the pressure medium, which is displaced from the cylinder chamber (49), is dischargeable into the pressure accumulator (26) via a directional valve (32) (Fig. 6).
  8. Drawing tool according to one of claims 4 to 7, characterised in that the directional valve (40) and the throttle valve (22) in the line (20b) of the third flow path can be by-passed by means of a by-pass line (20b'), in which by-pass line there is disposed a check valve (23), which releases the throughflow in the direction of flow at a predetermined pressure.
  9. Drawing tool according to one of the preceding claims, including a trimming cutter (16), which is displaceable to a limited extent in the sheet holder (15), for trimming the remainder of the sheet from the edge of the finished drawn part, characterised in that the component parts (drawing die 18, sheet holder 15, annular piston 13), which are displaced during the trimming process, are stoppable, in the absence of any resistance to trimming, by throttling the discharge flow of the pressure medium from the cylinder chamber (48) of the annular piston into the pressure accumulator (26) (Fig. 7).
  10. Drawing tool according to claim 9, characterised in that the discharge flow of the pressure medium from the cylinder chamber (48) can be throttled by means of the throttle valve (22), which is disposed in the line (20b) of the third flow path, in dependence on the pressure drop, released by the absence of any resistance to trimming, when the directional valve (33) is closed and the directional valve (25) is open.
EP89104248A 1988-03-12 1989-03-10 Drawing apparatus for shaping sheet metal blanks Expired - Lifetime EP0333052B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89104248T ATE91653T1 (en) 1988-03-12 1989-03-10 DRAWING TOOL FOR FORMING SHEET METAL.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3808262 1988-03-12
DE3808262 1988-03-12

Publications (3)

Publication Number Publication Date
EP0333052A2 EP0333052A2 (en) 1989-09-20
EP0333052A3 EP0333052A3 (en) 1990-09-26
EP0333052B1 true EP0333052B1 (en) 1993-07-21

Family

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Application Number Title Priority Date Filing Date
EP89104248A Expired - Lifetime EP0333052B1 (en) 1988-03-12 1989-03-10 Drawing apparatus for shaping sheet metal blanks

Country Status (6)

Country Link
US (1) US4909061A (en)
EP (1) EP0333052B1 (en)
JP (1) JPH01309798A (en)
AT (1) ATE91653T1 (en)
DE (1) DE58904930D1 (en)
ES (1) ES2043917T3 (en)

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CN111322282A (en) * 2020-03-31 2020-06-23 西安麦特沃金液控技术有限公司 Hydraulic drawing system

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Also Published As

Publication number Publication date
ATE91653T1 (en) 1993-08-15
ES2043917T3 (en) 1994-01-01
JPH01309798A (en) 1989-12-14
EP0333052A2 (en) 1989-09-20
DE58904930D1 (en) 1993-08-26
US4909061A (en) 1990-03-20
EP0333052A3 (en) 1990-09-26

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