EP2036711B1

EP2036711B1 - Drive device for a bending press

Info

Publication number: EP2036711B1
Application number: EP08005440.6A
Authority: EP
Inventors: Markus Resch; Rudolf Scheidl; Peter Ladner; Karl Ladner
Original assignee: Trumpf Maschinen Austria GmbH and Co KG
Current assignee: Trumpf Maschinen Austria GmbH and Co KG
Priority date: 2007-09-12
Filing date: 2008-03-22
Publication date: 2016-08-17
Anticipated expiration: 2028-03-22
Also published as: CN101835601A; AT505724B1; US20100212521A1; CN101835601B; EP2036711A1; US8342086B2; AT505724A1; WO2009033199A1

Description

The invention relates to a drive device, as described in the preamble of claim 1.
a drive device for a bending press with a press frame and with a fixed press beam and a press beam adjustable relative thereto is known, the drive device consisting of a hydraulic system with a hydraulic pump and a ring line with control valves for a switchable flow circuit for a pressure medium for alternating pressurization of two pressure spaces at least a pressure cylinder for adjusting the press beam. The hydraulic system is an open system, supplied with the pressure medium from a tank, which excludes a pressure accumulator, since the compensation volume of the medium required for the different filling volumes of the pressure chambers of the hydraulic cylinder is conveyed into and out of the tank. This requires a correspondingly high total volume and delivery volume of the pressure medium for the alternating loading of the hydraulic cylinder. From the document JP 2002-147404 A is a drive device for a bending press with a press frame, and with a fixed press beam and a relatively adjustable press beam known, the drive means of a hydraulic system with a hydraulic pump and a ring line with control valves for a switchable flow circuit for a pressure medium for alternately pressurizing two pressure chambers at least a pressure cylinder for the adjustment of the press bar. The hydraulic system is an open, supplied with the pressure medium from a tank system, which excludes a pressure accumulator, since the different filling volumes of the pressure chambers of the hydraulic cylinder required equalization volume of the medium is conveyed into or out of the tank . This requires a correspondingly high total volume and delivery volume of the pressure medium for alternately pressurizing the hydraulic cylinder.
a hydraulic quick control with devices for avoiding control impacts for hydraulic presses, hydraulically operated machine tools or the like is known. In addition to a main valve, the quick control includes an additional control valve which, via a connecting line, establishes the connection between a pressure source, eg a pump, an accumulator, a press cylinder and the main control valve. It also includes a bypass line that leads directly from the pressure source to the main control valve, this having a smaller cross-section than the connecting line running through the additional control valve and, if necessary, a throttle valve can also be provided in this bypass line. In this way, the pressure surges caused by the control processes are counteracted in a regulating manner by the appropriate choice of cross section of the connecting line and the possibility of regulating by means of the throttle valve, and the greatest possible level of pressure is achieved. From the document DE 1 027 951 B For example, there is known a hydraulic high-speed controller with devices for avoiding control shocks for hydraulic presses, hydraulically operated machine tools or the like. In addition to a main valve, the rapid control comprises an additional control valve which establishes the connection between a pressure source, for example a pump, an accumulator, a press cylinder and the main control valve, via a connecting line. Furthermore, it comprises a bypass line which leads directly from the pressure source to the main control valve, which has a smaller cross-section than the connecting line running via the additional control valve and, if appropriate, also a throttle valve can be provided in this bypass line. Thus, the pressure surges caused by the control processes by corresponding cross-sectional selection of the connecting line and the Regulierbarkeit by means of the throttle valve is counteracted regulating and achieved the greatest possible pressure leveling.
From the document WO 2006/101156 A1 From the document WO 2006/101156 A1 a hydraulic drive device for a press brake and a method for operating such is known, according to which in an open hydraulic system for feeding working cylinders, a hydraulic pump with a variable speed motor is operated. The speed is variable depending on the movement processes, such as rapid traverse, press gear, emergency stop, return stroke, different requirements from a standstill up to a maximum speed controllable.
, a hydraulic drive device, in an open design, with a tank, pump and supply line for applying a pressure medium to a pressure chamber of a working cylinder is known. A discharge of the pressure medium from the further pressure chamber can optionally be fed to the supply line via a switching valve or, depending on a fixed pressure level in the supply line or the pressure chamber, returned to the tank via a drain line. Such an admixture of the outflowing pressure medium into the supply line leads to an increase in the adjustment speed of the press beam before the actual pressing process, i.e. a rapid delivery and thus a shortened cycle time, for a given delivery rate of the pump. From another document, DE 21 40 183 A1 , a hydraulic drive device, in open design, with a tank, pump and supply line for acting on a pressure chamber of a working cylinder with a pressure medium is known. A derivation of the pressure medium from the further pressure chamber can optionally be fed via a switching valve to the supply line or, depending on a defined pressure level in the supply line or the pressure chamber, can be returned to the tank via a discharge line . Such an admixing of the outflowing pressure medium into the supply line results in an increase in the adjustment speed of the press beam before the actual pressing process, ie an express delivery and thus a shortened cycle time, for a given delivery rate of the pump.
a hydraulic press with a double-acting hydraulic working cylinder with active surfaces of different sizes on both sides of a piston is known. The hydraulic drive device has a container for the pressure medium, which by means of an electric motor-driven pump into a conveying circuit and via control valves the working cylinder, optionally the pressure chambers separated by the piston for a movement of a press beam connected to the piston or a piston rod in order to carry out an adjustment for a press stroke and a return stroke. To reduce the working cycle, a suction line with a suction valve for a rapid equalization of the volume flows of the pressure chambers having a different receiving volume is provided between lines for the alternating loading of the pressure spaces of the working cylinder. From the document EP 0 967 028 A1 is a hydraulic press with a double-acting hydraulic cylinder with different sized effective surfaces on both sides of a piston known. The hydraulic drive device comprises a container for the pressure medium, which by means of an electric motor driven pump in a delivery circuit and control valves to the working cylinder, optionally the separate pressure chambers for a movement of a piston connected to the piston or a piston rod press ram for performing an adjustment for a press stroke and a return stroke is supplied. For a reduction of the duty cycle, a Nachsaugleitung with a Nachsaugventil for rapid compensation of the volume flows of a different receiving volume having pressure chambers is provided between lines for the alternating admission of the pressure chambers of the working cylinder.
, a hydraulic drive unit for a press, for example a press brake, is known for actuating a press beam by means of a double-acting hydraulic cylinder with different active surfaces. The hydraulic drive unit has a container for a pressure medium, an electric motor-driven pump and supply lines and control valves and a flow-connected, chargeable pressure accumulator by means of which a counterforce is brought about by the working cylinder to compensate for the weight of the press beam. Different piston effective areas are basically known in hydraulic drives and are, for example, in GB 749,571 A coat. From another document, AT 008 633 U1 A hydraulic drive unit for a press, for example, the bending press, for actuating a press bar by means of a double-acting hydraulic cylinder with different effective surfaces is known. The hydraulic drive unit comprises a reservoir for a pressure medium, an electric motor driven pump and supply lines and control valves and a flow-connected, rechargeable pressure accumulator by means of which to compensate for the dead weight of the press bar a counter force is caused by the working cylinder. Different piston active surfaces are basically known in hydraulic drives and, for example, in GB 749,571 A coat.
Conventional drive technologies for pressing the higher force categories use a hydraulic load-sensing principle for the operation and a hydraulically controlled falling of the pressure beam in rapid downwards. Since a control reserve of pressure loss is required in load-sensing mode and the movement is also regulated in the case of fast-down or high-resistance control via resistance control, there are inherent losses. The resulting oil heating must be reduced in some cases via oil cooler. Another disadvantage is that the electric drive motor and the connected hydraulic constant displacement pump run during the entire operating time, which causes losses and unnecessary noise. Such a drive design provides for a hydraulic supply unit per machine, which in addition to the pump, motor and tank connecting lines and various auxiliary equipment and in any case prevents a strictly modular design, in which each axis is completely separate and compact. Numerous hydraulic connections are to be made in the assembly process of the press. These are a risk of leaks due to leaks, hose breakage or replacement of hydraulic components.
Furthermore, today electric-hydraulic hybrid drives are known whose basic idea is to connect a hydraulic constant displacement pump with a variable speed electric motor so as to control the speed can electrically and the connected hydraulic circuit with a hydraulic cylinder at its end on the one hand for simple power transmission and on the other hand Manual transmission to use for rapid-speed changeover. Application finds an open hydraulic system, in addition to the actual working cylinder, designed as a catchy differential cylinder, another plunger cylinder used. Its hydraulically effective area is equal to the annular surface of the differential cylinder. The cylinder chambers associated with these two surfaces are connected in rapid traverse so that the effect of a synchronous cylinder, which is moved by the pump, is established. The piston-side chamber sucks out of the tank in rapid traverse. In the operation, the pump acts on the piston side of the differential cylinder, the ring side is to counter hold on a hydraulic accumulator.
The object of the invention is to provide a drive device for a bending press, with a high efficiency and thus energy-saving operation is achieved and the one compact, modular design allows.
This object of the invention is achieved by the features of claim 1. It is advantageous that the volume of a pressure medium required for operation and thus the power requirement for the supply of drive components to the medium can be kept low by means of a closed hydraulic system with a loop and medium reservoir. In addition, a stop / go operation is possible whereby the environmental load is kept low by reducing the noise emission.
Advantageous development but also describe the claims 2 to 7, because characterized the accumulator for a small storage volume of about a differential volume of the pressure chambers of the printing cylinder can be designed and dimensioned sufficiently, for example, with 0, 75-1 and this at an approximately required memory pressure of about 3 bar to 5 bar a complex memory safety block and a memory test can be omitted, and already at a small delivery volume of pressure medium and thus already at low pump performance very high rapid traverse speeds can be achieved.
According to the advantageous embodiment according to claim 8, cavitation in the impression cylinder is effectively avoided by the cartridge valve provided in the bypass line and designed for a high volume flow.
But are also advantageous embodiments according to claims 9 to 12, whereby a rapid response is achieved for a reversal process and an on demand controllable drive and braking effect is ensured by the controllable drive of the hydraulic pump.
It is also possible an embodiment according to claim 13 whereby different storage concepts can be achieved.
Finally, the embodiments according to claims 14 to 19 are advantageous, whereby different adaptable to the application machine designs can be realized and thus the range of applications is extended.
The invention will be explained in more detail below with reference to the exemplary embodiments illustrated in the figures.

Fig. 1 Fig. 1: eine mögliche Abkantpresse in schematischer Darstellung, nach dem Stand der Technik; a possible press brake in a schematic representation, according to the prior art;
Fig. 2 Fig. 2: eine vereinfachte erfindungsgemäße hydraulische Antriebsvorrichtung für die Abkantpresse; a simplified hydraulic drive device according to the invention for the press brake;
Fig. 3 Fig. 3: eine bevorzugte Weiterbildung der erfindungsgemäßen hydraulischen Antriebsvorrichtung für die Abkantpresse; a preferred development of the hydraulic drive device according to the invention for the press brake;
Fig. 4 Fig. 4: ein Hydraulikschema zur bevorzugten Weiterbildung in einer Beschaltung für einen Betriebszustand "Eilgang- abwärts"; a hydraulic scheme for a preferred development in a circuit for an operating state "rapid traverse down";
Fig. 5 Fig. 5: das Hydraulikschema nach the hydraulic scheme according to Fig. 4 Fig. 4 in einer Beschaltung für einen Betriebszustand "Arbeitsgang- abwärts"; in a circuit for an operating state "work gear down";
Fig. 6 Fig. 6: das Hydraulikschema nach the hydraulic scheme according to Fig. 4 Fig. 4 in einer Beschaltung für einen Betriebszustand "Eilgang- aufwärts"; in a circuit for a "rapid traverse up" operating state;
Fig. 7 Fig. 7: das Hydraulikschema nach the hydraulic scheme Fig. 4 Fig. 4 in einer Beschaltung für einen Betriebszustand "Notstopp aus Eilgang- abwärts". in a circuit for an operating state "emergency stop from rapid traverse downwards".
Fig. 8 Fig. 8: eine andere Ausbildung der erfindungsgemäßen Antriebsvorrichtung mit einem am Pressengestellt befestigten Druckzylinder und einem vereinfachten Hydrauliksystem; another embodiment of the drive device according to the invention with a pressure cylinder attached to the press frame and a simplified hydraulic system;
Fig. 9 Fig. 9: die Ausbildung nach the training after Fig. 8 Fig. 8 mit einem erweiterten Hydrauliksystem; with an advanced hydraulic system;
Fig. 10 Fig. 10: eine weitere Ausbildung der Antriebsvorrichtung mit einem am verstellbaren Pressenbalken befestigten Druckzylinder und mit vereinfachtem Hydrauliksystem; a further embodiment of the drive device with a pressure cylinder attached to the adjustable press beam and with a simplified hydraulic system;
Fig. 11 Fig. 11: die Ausbildung nach the training after Fig. 10 Fig. 10 mit einem erweiterten Hydrauliksystem; with an advanced hydraulic system;
Fig. 12 Fig. 12: die Antriebsvorrichtung mit einer weiteren Ausführung des Hydrauliksystems mit Beschaltung für den Betriebszustand "Stillstand" ; the drive device with a further version of the hydraulic system with circuitry for the "standstill" operating state;
Fig. 13 Fig. 13: das Hydrauliksystem nach the hydraulic system Fig. 12 Fig. 12 mit Beschaltung für den Betriebszustand "Eilaufwärts" und "Eil-abwärts"; with wiring for the "rapid upward" and "rapid downward" operating states;
Fig. 14 Fig. 14: die Antriebsvorrichtung mit dem Hydrauliksystem nach the drive device with the hydraulic system Fig. 12 Fig. 12 mit Beschaltung für den Betriebszustand "Pressen". with wiring for the "pressing" operating state.

Show it:

Fig. 1 Fig. 1: a possible press brake in a schematic representation, according to the prior art; a possible press brake in a schematic representation, according to the prior art;
Fig. 2 Fig. 2: a simplified hydraulic drive device according to the invention for the press brake; a simplified hydraulic drive device according to the invention for the press brake;
Fig. 3 Fig. 3: a preferred embodiment of the hydraulic drive device according to the invention for the press brake; a preferred embodiment of the hydraulic drive device according to the invention for the press brake;
Fig. 4 Fig. 4: a hydraulic scheme for preferred development in a circuit for a state "rapid traverse down"; a hydraulic scheme for preferred development in a circuit for a state "rapid traverse down";
Fig. 5 Fig. 5: the hydraulic scheme after the hydraulic scheme after Fig. 4 Fig. 4 in a circuit for an operating state "operation downwards"; in a circuit for an operating state "operation downwards";
Fig. 6 Fig. 6: the hydraulic scheme after the hydraulic scheme after Fig. 4 Fig. 4 in a circuit for an operating state "rapid traverse upwards"; in a circuit for an operating state "rapid traverse upwards";
Fig. 7 Fig. 7: the hydraulic scheme after the hydraulic scheme after Fig. 4 Fig. 4 in a circuit for an operating state "emergency stop from rapid traverse downwards". in a circuit for an operating state "emergency stop from rapid traverse downwards".
Fig. 8 Fig. 8: another embodiment of the drive device according to the invention with a pressure cylinder attached to the press and a simplified hydraulic system; another embodiment of the drive device according to the invention with a pressure cylinder attached to the press and a simplified hydraulic system;
Fig. 9 Fig. 9: the training after the training after Fig. 8 Fig. 8 with an extended hydraulic system; with an extended hydraulic system;
Fig. 10 Fig. 10: a further embodiment of the drive device with a pressure cylinder attached to the adjustable press bar and simplified hydraulic system; a further embodiment of the drive device with a pressure cylinder attached to the adjustable press bar and simplified hydraulic system;
Fig. 11 Fig. 11: the training after the training after Fig. 10 Fig. 10 with an extended hydraulic system; with an extended hydraulic system;
Fig. 12 Fig. 12: the drive device with a further embodiment of the hydraulic system with wiring for the operating state "standstill"; the drive device with a further embodiment of the hydraulic system with wiring for the operating state "standstill";
Fig. 13 Fig. 13: the hydraulic system after the hydraulic system after Fig. 12 Fig. 12 with wiring for the operating state "Upright" and "Eil-down"; with wiring for the operating state "Upright" and "Eil-down";
Fig. 14 Fig. 14: the drive device with the hydraulic system after the drive device with the hydraulic system after Fig. 12 Fig. 12 with wiring for the operating state "pressing". with wiring for the operating state "pressing".

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to the new situation mutatis mutandis when a change in position. Furthermore, individual features or combinations of features from the different exemplary embodiments shown and described can also represent independent, inventive or inventive solutions.
All statements on ranges of values in the description of the present invention should be understood to include any and all sub-ranges thereof, e.g. the indication 1 to 10 should be understood to include all sub-ranges, starting from the lower limit 1 and the upper limit 10, i. all subregions begin with a lower limit of 1 or greater and end at an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1 or 5.5 to 10.
In the Fig. 1 is a press brake 2 operated by means of hydraulic drive device 1, in a simplified representation with a press frame 3, consisting essentially of side uprights 4, 5, a cross-dressing 6 and a fixed, aligned in a footprint 7 vertical plane 8 aligned plate-shaped press table 9 shown.
In an upright to the footprint 7 direction an upper press bar 11 is mounted adjustably guided in linear guides 10 on the side stand 4. 5, which in the illustrated embodiment of two pressure cylinders 12 as drive means 13 of the hydraulic drive device 1 according to - double arrow 14 - between an upper end position and a lower controllable end position, for applying a forming force to a between bending tools 15 of the press table 9 and press bar 11 for a forming process introduced workpiece, eg a sheet metal blank, sheet metal part etc.
The arrangement of the printing cylinder 12 is in the illustrated embodiment for a tensile force application during the forming process on the workpiece part of the press bar 11 and a pressure force application designed at a reversal of movement or a stop or holding the press bar 11 wherein the power transmission via a housing bearing and a rod bearing 17 takes place.
the hydraulic drive device 1 for the press beam 11 is shown in detail using the example of a pressure cylinder 12 and a possible hydraulic system 18 in a simplified embodiment. In the Fig. 2 is shown in detail the hydraulic drive device 1 for the press bar 11 using the example of a pressure cylinder 12 and a possible hydraulic system 18 in a simplified embodiment.
To simplify the representation and description of the hydraulic drive device 1, this is explained in its design and effect on the example of only one, of several, preferably arranged symmetrically to a transverse median plane of the press 1 symmetrically to a transverse center plane of the press 1, operated via the hydraulic system 18 shown pressure cylinders 12.
For a reversible force application of the pressure cylinder 12 is designed as a so-called double-acting differential cylinder 19, with a cylinder housing 20 and therein adjustable by pressurization with a pressure medium, a cylinder chamber 21 in pressure chambers 22, 23 dividing piston 24th
The piston 24 is mounted on a piston rod 25 projecting from the cylinder housing 20 on one side and which is drive-connected in a protruding end region 26 to the press beam 11, e.g. by means of a bolt 27, which allows a tolerance of angular deviation.
In a bearing arrangement formed on the cylinder housing 20, the pressure cylinder 12 is attached according to the embodiment shown on a side surface 28 of the side stand 5, wherein the piston rod 25 protrudes from the cylinder housing 20 in a pressure-sealed rod feedthrough 29 of an end flange 30 facing away from the footprint 7 and as previously described in the end portion 26 is drivingly connected to the press bar 11 by means of the bolt 27.
By this arrangement, the pressure cylinder 12 is supported by the piston rod 25 of the press beam 11 in the rest against the action of a deadweight component - according to arrow 31 -, ie that the piston rod 25 is exposed in this operating condition of a compressive stress, the pressure load in addition to the own weight component - According to arrow 31 - by acceleration forces by the movement of the press bar 11 - according to double arrow 14 - both during braking as well as a reversal of motion varies and this is to be considered in the dimensioning of the piston rod 25.
During a forming process on the workpiece between the bending tools 15, 16 occurs in the piston rod 25, as soon as the required Umformkraftkomponente exceeds the net weight component of the press bar 11, a tensile load.
The pressure chambers 22,23 are 25 different piston active surfaces 32, 33 facing through the unilaterally led out from the cylinder chamber 21 piston, wherein the rod-side Kolbenwirkfläche 32 forms a circular ring surface of a circular surface with an inner diameter 34 of the cylinder chamber 21 minus a circular area of a piston rod diameter 35 and the opposite to the piston 24 opposite piston effective surface 33 of a circular area with the inner diameter 34 of the cylinder chamber 21 corresponds.
It is advantageous, as explained in more detail below, if a ratio of the piston effective areas 32, 33 is greater than 1 to less than 1.5, which is equivalent to the different volume flows for acting on the pressure chambers 22, 33 from the hydraulic system 18 to perform a work cycle, which comprises twice the adjustment path between an upper and lower end position of the press bar.
The hydraulic system 18 can now also be seen in a simplified embodiment in the form of a hydraulic diagram for controlling the hydraulic cylinder 12, which is a closed and essentially tankless hydraulic system 18. Of the Fig. 2 The hydraulic system 18 can now also be seen in a simplified form in the form of a hydraulic scheme for controlling the hydraulic cylinder 12, which is a closed and essentially tankless hydraulic system 18.
The pressure cylinder 12 is supplied from the hydraulic system 18 with the pressure medium via a pressure line 36 in the piston-side pressure chamber 23 for the opening movement and via a pressure line 37 in the rod-side pressure chamber 22 for the closing movement.
The pressure line 36 connects the pressure chamber 23 with a port 38 of a control valve 39 and the pressure line 37, the pressure chamber 22 with a port 40 of another control valve 41st
Connections 42, 43 of the control valves 39, 41 are fluidly connected to a ring line 44 in which a via a speed and Dreurichtungsregelbaren drive motor 45, in particular an electric motor 46, operated hydraulic pump 47 is arranged whereby a medium flow according to - arrows 48, 49 - corresponding to a selected Direction of rotation according to - double arrow 50 - of the drive motor 45 and thus the hydraulic pump 47 optionally between the control valves 39, 41 can be reversed.
The ring line 44 forms a first line strand 51 between a first port 52 of the hydraulic pump 47 and the port 42 of the control valve 39 and a second line strand 53 between a second port 54 of the hydraulic pump 47 and the port 43 of the control valve 41, wherein according to the selected direction of rotation of the electric motor 46 and a first or second switching position of the control valves 39, 41 is a flow connection between the hydraulic pump 47 and the piston-side pressure chamber 23 or the rod-side pressure chamber 22 of the pressure cylinder 12, or the flow connection between the ring line 44 and the pressure line 36 for the piston-side pressure chamber 23, or between the ring line 44 and the pressure line 37 for the rod-side pressure chamber 22 of the pressure cylinder 12, is interrupted.
From the first wiring harness 51, between the hydraulic pump 47 and the control valve 39, a bypass line 55 branches off, which leads to a second connection 56 of the control valve 41.
Furthermore, the ring line 44 is fluidly connected to a pressure accumulator 57 via a 3/2-way control valve 58 of which a port 59 of the control valve 58 via a line 60 to the wiring harness 51 and another port 61 of the control valve 58 via a line 62 to the wiring harness 53rd is connected and the pressure accumulator 57 is connected to a port 63 of the control valve 58. This flow connection of the pressure accumulator 57 by means of the lines 60, 62 in conjunction with corresponding switching positions of the control valve 58 allows a need-based storage or release of a proportion of the circulating pressure medium whereby short control operations are achieved and the required amount of pressure medium in the hydraulic system 18 is kept low.
The control valves 39, 41, 58 are in the illustrated embodiment Zweistellungs- electrical switching valves, preferably piston valves with spring return and are in the following Description of the function of each operating state different switch positions, with reference to cross-reference to the representation in the figures, with the letters (A) for a first switching position and (B) for a second switching position.
For the time being, the functional elements according to the in Fig. 2 illustrated hydraulic scheme explained.
In a hydraulic system 18 with a closed flow circuit is achieved that only a very small volume of the pressure medium is displaced - it corresponds to the displacement volume of the piston rod 24 or in the case of a both sides protruding piston rod - as explained later in detail - the difference in volume of the two rod elements ,
This displacement volume can be absorbed by a very small pressure accumulator 57, or hydraulic accumulator. The required pressure in this pressure accumulator 57 - he also exercises the hold function in the operation - is for a typical embodiment at 2 bar to 8 bar, preferably 3 bar to 5 bar and is of a storage volume of 0.5 1 to 2.5 1, preferably 0.75 to 1.0 1 go out. This provides the basis for getting along with no pressure storage block and no special memory check according to the pressure vessel guidelines.
The accumulator 57 performs two functions, such as hold function and tank function (pre-charged tank) for storing and dispensing a differential volume of the pressure medium due to the pressure chamber 22 retracting piston rod 24, or in the case of a both sides projecting piston rod - as explained in more detail later - the difference in volume of the two rod elements.
The pressure cylinder 12 is a differential cylinder with a relatively small surface area of the piston rod 25. The piston rod 25 is directed upward and suitably drivingly connected to the press beam 11 and supports it or pulls it down during a forming process. In this case, the working pressure of the medium acts in the rod-side pressure chamber 22, ie, on the annular surface of the piston 24. Since in the case of a Werkteilumformung the piston rod 25 is claimed to train, there is no risk of buckling. Compressive stress exists only by the proportionate weight of the press bar 11 while holding the press bar 11 and in addition by an acceleration component when stopping or during the movement of the press bar upwards.
Only with a pressure cylinder 12, the lower pressure chamber 23 has a larger effective area than the upper, a controlled lowering or holding up of the press bar 11 in the rapid traverse circuit is possible. In the rapid traverse circuit, i. when the two pressure chambers 22, 23 are hydraulically substantially short-circuited, the pressure cylinder 12 corresponds to a pure plunger cylinder with the surface of the piston rod 25 as a hydraulic active surface. Only an upwardly directed plunger can compensate for a downwardly directed weight force.
In the hydraulic pump 47 is in principle a hydraulic four-quadrant machine. However, the main stress under pressure occurs during the working process, ie when the work piece is re-shaped, so that it can be designed as a one-sided pump operated in the other quadrants at substantially lower pressures.
With the variable speed electric motor 46, the speed and positioning of the press bar 11 is controlled. He works in both directions to the press bar 11 to move up and down.
The control valve 39 is a 2/2-way valve and serves to hold up the press bar 11 and to realize an emergency stop, wherein it is switched to position (A).
The control valve 41 is a 3/2-way valve and is used for rapid traverse operation. In the operation it is in position (A), in rapid traverse in position (B).
The control valve 58 is a 3/2-way valve and also serves the rapid traverse operation switching. In the operation it is in position (B), in rapid traverse in position (A).
The pressure accumulator 57 is a low-pressure accumulator with a relatively small volume. With his pressure he holds the press bar 11 in the operation over the effective surface of the piston 24 against the weight of the press bar 11 high. In rapid traverse downwards, it absorbs the volume of oil displaced by the piston rod 25 when the pressure cylinder 12 retracts. He acts as a tank in this phase.
Below is the description of how to work in the Fig. 2 illustrated hydraulic drive device 1, broken down into the phases of a typical Abkantprozesses, ie, starting from an upper rest position of the press bar 11 in a lower dead center position and subsequent upward movement in the rest position. Below is the description of how to work in the Fig. 2 illustrated hydraulic drive device 1, broken down into the phases of a typical Abkantprozesses, ie, starting from an upper rest position of the press bar 11 in a lower dead center position and subsequent upward movement in the rest position. Below is the description of how to work in the Fig. 2 illustrated hydraulic drive device 1, broken down into the phases of a typical Abkantprozesses, ie, starting from an upper rest position of the press bar 11 in a lower dead center position and subsequent upward movement in the rest position.

Rapid traverse downwards:

The control valves 39, 41 switch to the state (B), the control valve 58 switches to the state (A), whereby the connection 54 of the hydraulic pump 47 is connected to the pressure accumulator 57. The electric motor 46 and thus the hydraulic pump 47 are rotated, the press bar 11 moves down. In a typical design, about 90% of the volume displaced from the piston-side pressure chamber 23 is received by the rod-side pressure chamber 22. The corresponding oil flow flows via the bypass line 55 and the control valve 41. The oil flow delivered by the hydraulic pump 47 into the pressure accumulator 57 corresponds to the displaced relatively small rod volume relative to the ring side volume, therefore a very high rapid traverse speed is achieved.

Operation downwards:

The control valve 41 switches to the positions (A), while the control valve 58 switches to state (B) whereby the line 51 is connected to the pressure accumulator 57. The hydraulic pump 47 conveys into the rod-side pressure chamber 22 and obtains a large force over the annular surface of the pressure cylinder 12. The applied pressure from the accumulator 57 pressure in the piston-side pressure chamber 23 keeps the press bar 11 high even if no pressing forces acting on the press bar 11.

Operation upwards with decompression phase:

The control valves 39,41 and the control valve 58 remain in the same positions as in the case of operation down. However, the electric motor 46 and the hydraulic pump 47 rotate in the other direction. The medium pressure in the accumulator 57 raises the press bar 11 high, the engine speed controls the lifting speed whereby a controlled decompression is possible, ie reduction of reaction forces by spring force of the workpiece, Deformation of the deformation occurring during bending of the press bar 11 and the press frame 3, in particular the side stand.

Rapid up:

The switching positions of the control valves 399 41, 58 are as in the case of rapid down but upon reversal of the conveying direction of the hydraulic pump 47. The hydraulic pump 47 presses over the differential surface is equal to the piston rod surface the piston 24 and thus the press bar 11 upwards.

Hold up at rest:

The control valve 39 is in the switching position (A) whereby the press bar is held by the medium pressure in the pressure chamber 23.

Emergency stop in rapid down:

By rapidly switching the control valve 39 in the switching state (A) of the piston-side pressure chamber 23 is locked, the press bar 11 comes to a stop quickly.
The hold-up and emergency stop, controlled by the control valve 39, provides a cost-effective solution, eg, as compared to mechanical brakes acting on the electric motor 46 or the press beam 11, eg by the application of a cost-effective, powered by a frequency converter asynchronous motor as an electric motor 46th
Another embodiment of the hydraulic control device with a preferred variant of the pressure cylinder 12 as the differential cylinder 19 of the press brake 2 and the hydraulic system 18 is shown. In the Fig. 3 Another embodiment of the hydraulic control device with a preferred variant of the pressure cylinder 12 as a differential cylinder 19 of the press brake 2 and the hydraulic system 18 is shown.
The pressure cylinder 12, in the illustrated embodiment, for example, stationary relative to the press table 9, has a continuous piston rod 25, with a projecting upwards in the direction of the press bar 11, the cylinder housing 20 rod member 64 and a in the direction of the footprint 7, the cylinder housing 20 by projecting rod member 65. The press beam 11 is drivingly connected to the rod member 64. The rod member 65 is to achieve a predetermined area ratio on the piston 24 of the pressure chamber 23 for raising the press beam 11 facing annular surface 66 and the pressure chamber 22 for the operation facing pressure surface 67. A rod diameter 68 of the rod member 64 is greater than a rod diameter 69 of the rod member 65, whereby the annular surface 66 is larger than the annular surface 67 and wherein the area ratio is in a preferred embodiment, approximately greater than 1 to less than 1.5. The application of the downwardly led rod member 65 ensures a preferred area ratio to comply even with a required larger rod diameter 68, to avoid too high buckling load by a high weight of the press bar 11 and high acceleration forces.
The hydraulic system 18 according to the preferred embodiment provides for the control valve 39 and control valve 41 a plurality of control and regulating elements 70 and control lines 71, as described in detail later.
By means of the control valves 39, 41, relatively high volume flows flow at rapid traverse which produce appreciable pressure losses on directly actuated industrial switching valves of nominal size 6. As a result, cavitation in the upper pressure chamber 22 would occur in any case during rapid traverse downwards. Therefore, hydraulically pilot operated valves are preferably used, which allow such flow rates at acceptable pressure drops. In the case of the control valve 41, this is a pilot-operated cartridge valve 72 and, in the case of the control valve 39, a pilot operated, non-returnable check valve 73. If the pilot stage is designed to be redundant, the functions provided for the control valve 39 are emergency redundant and redundant.

a) a safe holding open of the valves in the operating states;
b) a quick emergency stop at Eilab - this is the most critical case for reaching the required stopping distance;
c) In order to be able to switch the drive from the rapid downward operating state to the press circuit quickly and without stopping the pressure bar, a throttle valve 76 is arranged in a line 77 leading from the line 51 to the control valve 58 - in this embodiment a 4/2-way valve and thus ensures a quick and steady transition between the two operating states without completely slowing down the pressure bar, which contributes to reducing cycle times;
d) Another throttle valve 78 in the pilot stage to control valve 41 allows a smooth transition without rapid pressure equalization from working to rapid traverse and thus ensures a quick and steady transition between the two operating states without completely braking the pressure beam. This makes a contribution to reducing cycle times.

With check valves 74, 75, the highest pressure is placed on one of the control lines. Access to the memory pressure provides the minimum pressure in the system. This circuit variant ensures

a) a safe keeping open the valves in the operating conditions;
b) a rapid emergency stop at Eilab - this is the most critical case for reaching the required stopping distance;
c) to quickly and smoothly switch the drive from the operating state rapid traverse down in press circuit without stopping the pressure bar, a throttle valve 76 is arranged in one of the wiring harness 51 to the control valve 58 - in this embodiment, a 4 / 2-way valve - leading line 77 and thus ensures a rapid and steady transition between the two operating states, without completely slowing down the pressure bar, thereby contributing to the reduction of the cycle times;
d) a further throttle valve 78 at the pilot stage to the control valve 41 allows a smooth transition without rapid pressure equalization from working to rapid traverse and thus ensures a rapid and steady transition between two operating conditions, without completely decelerating the pressure bar. This contributes to the reduction of the cycle times.

In contrast to the embodiment described in the preceding figure, in this case the control valve 41 is a 2/2-way valve and the control valve 58 is a 4/2-way valve.

In the Fig. 4 the hydraulic system 18 already described in its components in the switching state of the control valves 39, 41 and the control valve 58 for the operating state "rapid traverse downwards" of the press bar 11 is shown. In the Fig. 4 the hydraulic system 18 already described in its components in the switching state of the control valves 39, 41 and the control valve 58 for the operating state "rapid traverse downwards" of the press bar 11 is shown. In the Fig. 4 the hydraulic system 18 already described in its components in the switching state of the control valves 39, 41 and the control valve 58 for the operating state "rapid traverse downwards" of the press bar 11 is shown.

In this operating state, the hydraulic pump 47 delivers the corresponding oil volume of the retracting rod element 64 minus the volume of the extending rod element 65, ie a differential volume via the control valve 58 into the pressure accumulator 57. The remaining oil volume flows via the bypass line 55 and the pressure line 37 into the pressure chamber 22 the printing cylinder 12th

the hydraulic system 18 with the control valves 39, 41 and the control valve 58 is shown in the switching positions for the operating state "work gear down" of the press beam 11. In the Fig. 5 the hydraulic system 18 is shown with the control valves 39, 41 and the control valve 58 in the switch positions for the operating state "operation down" of the press bar 11.

To prevent jerky switching when the pressure level in the pressure chamber 23 of Pressure cylinder 12 does not exactly equal to the pressure level in the pressure accumulator 57, the throttle valve 76 is provided in the leading from the wiring harness 51, bypassing the hydraulic pump 47 to the control valve 58 line 77.

During the operation downwards, a volume flow from the pressure chamber 23 via the control valve 58 and the line section 53 of the ring line 44 is conveyed by the hydraulic pump 47 into the pressure chamber 22 of the pressure cylinder 12. The remaining displaced oil volume from the pressure chamber 23 is passed via the line 67 and the control valve 58 into the pressure accumulator 57 and received by this.

Before the switching of the movement of the press bar 11 in the operation "rapid traverse" is carried out a decompression phase in which a controlled relaxation of the pressing force occurred deformations of the press bar 11 and the press frame, in particular the side stand as well as degradation of the return spring force of the workpiece is initiated In this decompression phase, the wiring of the control valves 39, 41 and the control valve 58 is the same as in the operating state "down" but with a reversal of the direction of rotation of the drive motor 45 and the hydraulic pump 47, whereby the flow of the hydraulic pump 47 against the conveying direction for the "operation - downwards "is reversed.

In the Fig. 6 the hydraulic system 18 is shown with the switching positions of the control valves 39, 41 and the control valve 58 in the operating state "rapid traverse upwards" of the pressure bar 11.

In this operating state, the hydraulic pump 47 conveys the oil volume corresponding to the extending rod element 64 from the pressure accumulator 57 via the line branch 51 into the pressure chamber 23 of the pressure cylinder 12. The oil volume displaced from the pressure chamber 22 is discharged directly via the control valves 41 and 39 located in this switching state Pressure chamber 23 fed, whereby the funded by the hydraulic pump 47 oil volume is relatively small.

In the Fig. 7 is the hydraulic system 18 for the operating state "emergency stop" of the press bar 11 during a rapid traverse movement down - shown in accordance with arrow 80 - with the corresponding switching positions of the control valves 39, 41 and the control valve 58.

In an emergency stop, the hydraulically releasable check valve 73 in the wiring harness 51 by switching the control valve 39, a control line 81 is driven by the accumulator pressure and closed. In parallel, the drive motor 45 and thus the hydraulic pump 47 is stopped. At the same time the control valves 39,41 and the control valve 58 are switched to position (A), whereby a security guidelines and the resulting requirements of the corresponding Anhalterwege in the downward movement - as indicated by arrow 80 - of the press bar 11 is achieved.

In the Fig. 8 and 9 is another embodiment of the drive device 1 for the opposite of the fixed press table 9 adjustable press bar 11, with the different design hydraulic systems 18, as already detailed in the Fig. 2 and 3 are shown.

According to this embodiment, the differential cylinder 19 is secured immovably to the press frame 3, in particular to the cylinder housing 20, on the side stand 4 and has the continuous piston rod 25, which is formed from the rod elements 64, 65 provided with different diameters.

The arrangement is chosen so that exerted on the piston rod 25 on the adjustable press beam 11 in an adjustment of the press bar 11 in the direction of the press table 9 - according to arrow 31 - a compressive force or a dependent on the weight of the press bar 11 supporting force. With the press bar 11 in the rod bearing 17, the smaller rod diameter 68 having rod member 64 is coupled.

By the pressure chambers 22, 23 thereby associated different annular surfaces 66, 67 of the piston 24 are with the hydraulic systems 18 shown by way of example, the previously described advantages of optimizing the movement of the press bar 11 for the respective operating conditions in conjunction with the closed hydraulic system 18, with adjustable and conveying direction reversible hydraulic pump 47 and pressure accumulator 57 and the line formed from the line strands 51, 53 ring 44 reaches.

The wiring of the control valves 39, 41, 58 is shown for the operating state "standstill of the press bar 11" as on the one hand for holding the press bar 11 in one upper death position or an intermediate position z. B. is provided an Eilstopp.

In the Fig. 10 and 11 In the Fig. 10 and 11 In the Fig. 10 and 11 In the Fig. 10 and 11 is another arrangement of the pressure cylinder 12 of the drive device 1 and the previously described differently designed hydraulic systems 18, which is therefore not discussed in detail shown.

The pressure cylinder 12 has in this embodiment, the one-sided protruding piston rod 25 and is eg connected immovably to the housing 20 and the housing bearing with the adjustable press beam 11.

The projecting piston rod 25 is coupled immovably in a firmly connected to the press table 9 or the press frame 3 abutment 85. This results in an adjustment of the press bar 11 in the direction of the press table 9 - according to arrow 31 - a tensile load in the piston rod 25 or a pressure load by a conditional by the weight of the press table 11-force when holding the press table 11 in an upper dead or intermediate layer plus a force such as occurs during braking of the press bar 11 in an emergency stop, as also already described in the preceding figures.

The optimization of the movement results in this arrangement of the printing cylinder 12 also by the different surface areas of the piston effective surface 33 corresponding to the diameter of the piston 24 on the one hand and the piston ring surface 32 on the other.

The wiring of the control valves is, as already described in the preceding figures, for the operating state "standstill of the press bar" shown.

In the Fig. 12 to 14 In the Fig. 12 to 14 The drive device 1 is shown with a further variant of the hydraulic system 18. The pressure cylinder 12 has the one-sided protruding piston rod 25. In the illustrated arrangement, a tensile load acts in the piston rod 25 during a pressing operation.

The hydraulic system 18 has the ring line 44 with the line strands 51, 53. The wiring harness 51 connects the hydraulic pump 47 with the pressure chamber 23 for acting on the piston effective surface 33. The wiring harness 53 connects the hydraulic pump 47 with the pressure chamber 22 with the piston ring surface 32nd

The pressure accumulator 57 is selectively activated or deactivated via a line 83 and a control valve 84 to the wiring harness 51, or via a line 85 and a control valve 86 to the wiring harness 53, and switching positions of the control valves 84 according to the respective operating state.

In the line strands 51, 53 a control valve 87, 88 is arranged in each case. In the bypass line 55, which connects the wiring harness 51 with the wiring harness 53, a further control valve 89 is arranged.

As already described in the preceding examples, the hydraulic pump is designed for direction-reversible conveying and is operated with the variable-speed drive motor 45.

As control valves 84, 86, 87, 88, 89 18 2/2-way valves are provided according to this variant of the hydraulic system.

In the Fig. 12 now the switching states for the operating state "standstill" or "emergency stop" are shown, after which all the control valves 84, 86, 87, 88, 89 are switched to blocking position or are and the hydraulic pump 47 is turned off. In the Fig. 12 now the switching states for the operating state "standstill" or "emergency stop" are shown, after which all the control valves 84, 86, 87, 88, 89 are switched to blocking position or are and the hydraulic pump 47 is turned off. In the Fig. 12 now the switching states for the operating state "standstill" or "emergency stop" are shown, after which all the control valves 84, 86, 87, 88, 89 are switched to blocking position or are and the hydraulic pump 47 is turned off.

Fig. 13 the switching states for the operating states "rapid traverse down" and "rapid traverse up" are shown. In this operating state, the pressure chambers 22, 23 of the pressure cylinder 12 are line-connected via the bypass line 55 and the control valves 87, 89 switched to passage, whereby a low volume flow, which corresponds to the difference volume of the pressure chambers 22, 23, from the also switched to passage via the Control valve 86 and line 85, depending on the direction of movement of the press beam 11, are conveyed into the pressure accumulator 57 or fed into the ring line 44 from there. In the Fig. 13 the switching states for the operating states "rapid traverse downward" and "rapid traverse upward" are shown. In this operating state, the pressure chambers 22, 23 of the pressure cylinder 12 via the bypass line 55 and the control valves connected to passage 87, 89 conductively connected, whereby a small volume flow corresponding to theiefevolumcn the pressure chambers 22, 23, from the also connected to the passage control valve 86 and line 85 is conveyed depending on the direction of movement of the press bar 11 in the pressure accumulator 57 or fed from this into the ring line 44.

This allows, as already described for the preceding figures, an energy-efficient design of the hydraulic pump 47 and the drive motor 45 and also the lines and control valves.

the switching states of the control valves are now shown for the immediate "pressing process" operating state, in which the forming force is to be applied by the press beam 11 during an adjustment movement in the direction of the press table 9 - according to arrow 31 - for forming a workpiece not shown in further detail. For this operating state, the control valve 87 of the line strand 51 and the control valve 88 of the line strand 53 are switched to passage and thus there is a direct flow connection between the pressure chambers 23, 22. In the Fig. 14 now the switching states of the control valves for the immediate operating state "pressing operation" are shown, in which the forming force of the press bar 11 at an adjustment in the direction of the press table 9 - according to arrow 31 - is applied for the forming of a not shown in detail workpiece. For this operating state, the control valve 87 of the wiring harness 51 and the control valve 88 of the wiring harness 53 is switched to passage and thus there is a direct flow connection between the pressure chambers 23, 22nd

At the same time there is a flow connection of the line strand 51 via the line 83 and the control valve connected to passage 84 for restoring the additional volume of the medium, due to the one-sided piston rod 25 caused volume differences of the pressure chambers 22,23, in the pressure accumulator 57th

The bypass line 55 with the control valve 89 is locked in this operating state, as well as the line 85 between the wiring harness 53 and the pressure accumulator 57 by the locking position of the control valve 86th

The embodiments show possible embodiments of the drive device, it being noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but also various combinations of the individual embodiments are possible with each other and this variation possibility due to the teaching of technical action by representational Invention in the skill of those skilled in this technical field. So are all conceivable embodiments, which are possible by combinations of individual details of the illustrated and described embodiment variant, includes the scope of protection.

For the sake of order, it should finally be pointed out that, for a better understanding of the structure of the drive device, these or their components have been shown partly unevenly and / or enlarged and / or reduced in size.

connection 8th level 43 connection 9 Press table 44 Ring line 10 Linear guide 45 Drive motor 11 Press beam 46 Electric motor 12th Printing cylinder 47 hydraulic pump 13 Drive device 48 arrow 14th Double arrow 49 arrow 15th Accessory tool 50 Double arrow 16 Housing bearings 51 Wiring harness 17th Rod bearings 52 connection 18th Hydraulic system 53 Wiring harness 19th Differential cylinder 54 connection 20th Cylinder housing 55 Bypass line 21st Cylinder space 56 connection 22nd Printing room 57 Pressure accumulator 23 Printing room 58 Control valve 24 piston 59 connection 25th Piston rod 60 management 26th End area 61 connection 27 bolt 62 management 28 Side face 63 connection 29 Rod feedthrough 64 Bar element 30th Front flange 65 Bar element 31 arrow 66 Ring surface 32 Piston ring area 67 Ring surface 33 Effective piston area 68 Rod diameter 34 Inside diameter 69 Rod diameter 35 Piston rod diameter 70 Control and regulation element 71 Control line 72 Cartridge valve 73 check valve 74 check valve 75 check valve 76 Throttle valve 77 management 78 Throttle valve 79 80 arrow 81 Control line 82 Abutment 83 management 84 Control valve 85 management 86 Control valve 87 Control valve 88 Control valve 89 Control valve

The problem underlying the independent inventive solutions can be taken from the description. <B> Reference Numbers </b> 1 driving device 36 pressure line 2 press brake 37 pressure line 3 press frame 38 connection 4th kickstand 39 control valve 5 kickstand 40 connection 6th cross dressing 41 control valve 7th footprint 42 connection 8th level 43 connection 9 press table 44 loop 10 linear guide 45 drive motor 11 press beams 46 electric motor 12th pressure cylinder 47 hydraulic pump 13th driving device 48 arrow 14th double arrow 49 arrow 15th beige tool 50 double arrow 16 bearing units 51 wiring harness 17th rod bearings 52 connection 18th hydraulic system 53 wiring harness 19th differential cylinder 54 connection 20th cylinder housing 55 bypass line 21st cylinder space 56 connection 22nd pressure chamber 57 accumulator 23 pressure chamber 58 control valve 24 piston 59 connection 25th piston rod 60 management 26th end 61 connection 27 bolt 62 management 28 side surface 63 connection 29 Lead-through 64 bar member 30th end flange 65 bar member 31 arrow 66 ring surface 32 Piston ring 67 ring surface 33 Effective piston area 68 Rod diameter 34 Inner diameter 69 Rod diameter 35 Piston rod diameter 70 Control element 71 control line 72 Cartridge valve 73 check valve 74 check valve 75 check valve 76 throttle valve 77 management 78 throttle valve 79 80 arrow 81 control line 82 abutment 83 management 84 control valve 85 management 86 control valve 87 control valve 88 control valve 89 control valve

Claims

A drive device (1) for a bending press comprising a press frame (3) with a press table (9) and a press beam (11) which is adjustable relative to the press table (9) via a hydraulic system (18) comprising a hydraulic pump (47) with a controllable drive motor (45), switching and control means and pressure lines and a pressure store (57) with pressure cylinders (12) chargeable by a pressure medium, and that the hydraulic system (18) with a ring line (44) comprising the hydraulic pump (47) forms a switchable flow circuit closed by control valves (39, 41, 58, 84, 86, 87, 88, 89) for the pressure medium with a first line section (51) of the ring line (44) between a pressure chamber (23) of at least one pressure cylinder (12) and the hydraulic pump (47) and with a second line section (53) of the ring line (44) between an additional pressure chamber (22) of the pressure cylinder (12) and the hydraulic pump (47) and the pressure store (57) is flow-connected via at least one of the control valves (58, 84, 86) optionally to the first line section (51) or the second line section (53) of the ring line (44) for holding or releasing a stored volume of the pressure medium, characterized in that a piston active surface (32) crucial for applying the pressing force onto the press beam (11) of a piston (24) separating a cylinder chamber (21) into the pressure chambers (22, 23) is smaller than a piston active surface (33) opposite said piston active surface and a surface ratio of the piston active surfaces (32, 33) is greater than 1 to less than 1.5 and the line sections (51, 53) are flow-connected to the pressure chambers (22, 23) of the pressure cylinder (12) directly via a bypass line (55) by means of suitable hydraulic valve combinations.
The drive device according to claim 1, characterised in that the pressure store (57) is connected by a line (83) and the control valve (84) to the line section (51) of the ring line (44) and a line (85) and the control valve (86) to the line section (53) of the ring line (44).
The drive device according to claim 1, characterised in that the pressure cylinder (12) is designed to have a piston rod (24) projecting on one side.
The drive device according to claim 3, characterised in that a cross sectional area of the piston rod (25) is 1/5 to 1/20 of the piston active surface (32) surrounding the piston rod (24).
The drive device according to claim 1, characterised in that the pressure cylinder (12) is formed by rod elements (64, 65) projecting on both sides.
The drive device according to claim 5, characterised in that diameters (68, 69) of the rod elements (64, 65) are different, wherein the diameter (68) of the rod element (64) drive-connected to the adjustable press beam (11) is greater than the diameter (69) of the additional rod element (65).
The drive device according to claim 5, characterised in that diameters (68, 96) of the rod elements (64, 65) are different, wherein the diameter (68) of the rod element (64) drive-connected to the adjustable press beam (11) is smaller than the diameter (69) of the additional rod element (65).
The drive device according to claim 1, characterised in that a hydraulically servo-controlled cartridge-valve (72) is arranged in the bypass line (55).
The drive device according to claim 1, characterised in that the hydraulic pump (47) and a drive motor (45) of the hydraulic pump (47) are designed for conveying the pressure medium in two directions.
The drive device according to claim 9, characterised in that the drive motor (45) for the hydraulic pump (47) is formed by an electric motor (46).
The drive device according to claim 10, characterised in that the electric motor (46) is supplied with power via a speed control member.
The drive device according to claim 11, characterised in that the speed control member is formed by a frequency converter.
The drive device according to claim 1, characterised in that the energy store (57) is formed by a low pressure store, e.g. blister, membrane or piston store.
The drive device according to claim 1, characterised in that the piston rod (25) is connected via a workpiece (17) to the adjustable press beam (11).
The drive device according to claim 1, characterised in that the piston rod (25) is connected via an abutment (82) to the press frame (3).
The drive device according to claim 1, characterised in that the piston rod (25) is connected to the press table (9).
The drive device according to claim 1, characterised in that the pressure cylinder (12) is secured via a housing bearing (16) onto the press frame (3).
The drive device according to claim 1, characterised in that the pressure cylinder (12) is secured onto the side stand (4, 5).
The drive device according to claim 1, characterised in that the pressure cylinder (12) is secured via a housing bearing (16) onto the press beam (11).