AT507110A1 - Press for material shaping, has head piece with plunger moved up and down with respect to table, where head piece is moveable platform of parallel kinematic device, whose stationary platform is fixed in position with respect to table - Google Patents

Abstract

The press has a table (105), and a head piece (104) with a plunger that is moved up and down with respect to the table in a pressing direction using a press drive. The head piece is a moveable platform of a parallel kinematic device, and a stationary platform of the parallel kinematic device is fixed in a position with respect to the table. The parallel kinematic device comprises actuators (112, 113) that are oriented parallel to the pressing direction, A guide is provided for binding the head piece with respect to the head, where the guide is oriented parallel to the pressing direction. An independent claim is also included for a method for operating a hydraulic cylinder-piston-unit in a press.

Description

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P43496

Press for forming material

The invention relates to a press for forming material with a table and a press ram, which is opposite to the table by means of a press drive up and down 5 movable.

Such hydraulic or mechanical presses for forming are built for decades according to the same mechanical principle, while the base ("the table) by one, two or four stands (in special form also three stands) connected to a head piece to 10 a frame. From the head piece a press ram or slide is driven by a mechanical, hydraulic or pneumatic drive, which is usually performed on the uprights.

The power flow or power line through the press takes place in the " detour ", that is, the 15 force is passed from the base via the stator in the head piece and from there via the drives in the press ram the table. This leads to two major disadvantages:

The press builds very hard through the stands and the massive head piece;

The press deforms in all components, including header and stand. 20

The moments and transverse forces created by the pressing force must be dissipated via the stand guide. That is, these guides need to be in order to get a " tilt " of the press carriage to be set without play. Since these components have to absorb high forces 25 in the case of asymmetrical pressure force distribution (which corresponds to the normal case), they are deformed and, even with optimally adjusted guides, lead to premature wear of the pressing tool and to a poor pressing result. Since these forces also lead to wear of the sliding guide and this wear leads to internal clearance, the quality of the press with increasing operating time is worse.

Since the press controls only one direction of movement, the possibilities of optimizing the pressing process are solely based on the structural design of the pressing tool 30 2

··

• · · · ··· ·· ··· • · limited. On the one hand, this is only possible to a limited extent, and on the other hand, these measures substantially increase the cost of this tool.

When punching (also the relevant devices are in the application, as 5 commonly used, reckoned to the presses) by biasing the press body enormous residual energy is present. This leads to enormous sudden loads of the machine and the foundations when cutting (breaking through) the punching tool by the material. Furthermore, these "blows" lead to extreme noise pollution for people working in the environment. 10

In addition, it is difficult to impossible, the energy consumption and Hamit the network load in particular hydraulic presses even close to even and that there are difficulties to optimize the movement of the pressing tools so that no long dead times occur. Dead times are understood to mean the times 15, which pass for the movement of the head piece between the end of the pressing operation and the top dead center and back again.

It is the object of the invention, a forming machine, hereinafter referred to as "press" to build, which does not have the disadvantages mentioned at least in various embodiments 20 and thereby requires no higher investment costs than presses of the prior art.

According to the invention, these objects are fundamentally achieved in that the head piece is the movable platform of a parallel kinematic device whose fixed platform is stationary relative to the table. With regard to the construction and special properties of the invention, in particular the advantages of parallel kinematic devices, reference is made to the following publications: Cinematics, dynamics, and design of machinery by Kenneth J. Waldron and Gary L. Kinzel, New 6-DOF parallel robotic structure actuated by wires, Coordinate free formulation of a 3-2-1-wire-based tracking device by Federico Thjomas, Erika Ottaviano, Lluis Ros and Marco Ceccarelli, Uncertainty model 30 and singularities of 3-2-1 wire-based tracking systems of the same Authors such as the above document, DE 102 57 108 A, EP 1 106 563 A, DE 101 00 377 A, DE 101 03 837 A, WO 03/004223 A and WO 03/059581 A, the content of which by reference to the content of the present Registration is made. This means for the invention: ·· ·· ·· · · · ····

• φ ······································································································ A · · ····· -3-

Neither a conventional header nor a related stand is needed; As a result, on the one hand the weight of the press and their costs are reduced, on the other hand, this reduces the overall deformation of the press.

In Ausfährungsformen the invention, no Ständerföhrungen needed, thereby 5 there is also no wear of these components, in turn, the pressing tools are spared.

In addition to the vertical movement, further small movements of the press ram in relation to the lifting movement are made possible, as a result of which the total pressing force or the maximum pressing force can be reduced, e.g. by deliberate intended and controlled 10 slight inclination of the guide tappet; As a result, the energy stored in the press structure can also be optimally optimized in terms of control during punching operations (by deliberately intended and controlled slight inclination of the guide tappet), thereby reducing the development and production costs of the pressing tools.

Finally, a control-technical compensation of the press deformation 15 is made possible, as a result of which the press can optimally exert and distribute the required force on the pressing tool.

There are thus inventively provided instead of the head piece, the stand and the StänderfÜhrungen, actuators, which provide the pressing forces and record the auftre-20 border moments and transverse forces. Actuators are in the parallel kinematics, as stated in the literature to the above overview, understood rod-shaped structures that are either variable in length and / or have a movable base and (in the technical sense) only on train and / or pressure, but not on bending or Torsion be claimed. The principle possible rotary parallel kinematic devices are not considered here. Preferably, as far as possible all components of the press are disassembled into frameworks, wherein the press ram is supported by such a framework. All this makes the following possible;

By supporting the upper and lower connection bearings of the actuators without play and a measuring system measuring the distance between these connection layers, it is possible to significantly reduce the deformation of the press; , -4- ·· ·· ··· ·· ···· • ··································

Quality loss of the pressing process or the product due to the wear of the stator guide due to the auflretenden moments and shear loads can be excluded;

The freely programmable actuators, a movement of the guide plunger on the vertical movement is also possible, whereby the process of pressing itself can be influenced in previously impossible manner, for example, the simultaneous impact of the tool on the workpiece on the entire surface or line and thus the energy peak can be prevented;

A control-technical compensation of the deformation of the base and the guide-10 plunger is possible;

By dissolving the movable components into a framework, the individual components can be arranged with respect to the table in an optimal position for the supply and removal of the workpieces. 15 Since mass production is carried out with such presses, it is possible to detect by means of sensors the actual state of the first manufactured parts then to optimize the movement of the press ram in all subsequent parts, so that the quality of the manufactured parts increases and the stress of the tool as well as the energy consumption per manufactured part decreases. 20

In addition, in embodiments of the invention, which manage without guides, by arranging more than the required 6 actuators (to come to a statically determined parallel kinematic structure) on the one hand, the pressing force are even better distributed to the tool and the other Storage of 25 terminal bearing of the actuators can be braced control technology, so that a usually expensive play-free storage is unnecessary.

The invention and its multiple developments and refinements will be explained in more detail below with reference to the drawing. 1 shows, purely schematically, a typical press according to the prior art, Figs. 2 and 3, the deformations of two presses according to the prior art, Fig. 4 shows an inventive single-stand press in 5 is a perspective view of a multi-column press according to the invention, FIG.

FIGS. 6 and 7 show the deformations of the presses according to FIGS. 4 and 5 in views analogous to FIGS. 2 and 3, FIG. 8 shows a variant of a multi-stand press according to the invention in a perspective view, FIG FIG. 10 shows a press line, FIG. 11 a and subsidiary figure 11 b show an embodiment of the invention for better adjustment or distribution of the pressing forces, partly in section, FIGS. 12 to 14 show a development of the invention FIGS. 15 to 17 show another embodiment of the invention for increasing the clock rate, and FIGS. 18 to 23 show various embodiments of the invention for equalizing energy consumption. FIG. 24 shows an embodiment of a press according to the invention, FIG a press with 15 guides extending between the table and the head piece, FIG. 26 a guide from FIG. 25 in detail, FIG. 27 a side view of the press from FIG. 25, the F 28 shows the press from FIG. 27 in section AA together with detail, FIG. 29 shows a press in which an actuator is clamped on the table, FIG. 20 shows the press from FIG. 29 from another direction, FIG a side view of the press of Fig. 30, Fig. 32, the press of Fig. 31 in section AA including details.

Fig. 1 shows a typical press 1 of the prior art in front view and 25 plan view. Four arranged at the corners of the table 5 vertical posts 2 each carry guides 3, where a head piece 4 can slide. The head piece 4 is under the influence of a plunger 6, which also transmits the plunger force F (ultimately also the pressing force). Clearly, the relatively narrow access 7 of vome and 8 can be seen laterally. FIG. 2 shows the deformation of a so-called single-column press under the pressing force in dotted lines; FIG. FIG. 3 shows the corresponding deformation of a multistage press such as, for example, the one shown in FIG. 1. The problem of detecting the -6- • t «· • · · · · · · · · ff • ff ff • ff ff ffffffffffffff «· ··· ·· ···· • • • • 9 ffffff • • 9 · • - * ·· ···

Deformation, the impossibility of compensation and, above all, the burden on the guides are immediately apparent from these representations.

FIG. 4 shows, purely schematically, a press 101 according to the invention in a perspective view. In this case, the table 105 is connected via a framework 109 and actuators 110 with a head piece 104 belonging to the framework 111. The frameworks 109, 111 are designed statically determined, the rods are charged only to train or pressure, all deformations due to the pressing force are easy and accurate to calculate. The nodes of the frameworks are commercial structures. 10

The six actuators 110 (statically determined design), which form the actual parallel kinematics, are divided into two groups in the illustrated embodiment, three actuators 112 are arranged virtually exactly in the pressing direction and are for this reason called main actuators, three further actuators 113, the 15 Nebenaktuatoren , establish the static certainty, as explained in more detail below. The points of attack of the actuators 110 are known in their training in the field of parallel kinematic, it is referred to the above-mentioned literature. In the description, for the sake of clarity, the attack points on the table side as the foot points and the attack points on the side of the head piece are referred to as 20 head points, of course, the entire device is kinematically completely and dynamically virtually completely reversible. The head piece 104 is, already to illustrate this, constructed completely analogous to the table. As bearing for the entire device three bearing stub 114 are provided. 25 The parallel kinematics, consisting of the actuators 110, now allows a movement between the table and the head piece, which is not limited to a completely linear movement. This means that the vertical main movement during the pressing process (or the punching process), for example, a rotational movement about a horizontal axis can be superimposed, passes through the usual beating machining in a cutting machining of the workpiece, whereby a much gentler work is achieved as before.

FIG. 5 shows, in a nearly complete analogy to FIG. 4, a multi-stand press in which the same reference numerals have been used for parts acting in the same way. However, the press according to FIG. 5 has eight actuators, is thus statically overdetermined. This can, as explained below, bring about various advantages. As can be seen directly from a comparison of FIG. 1 on the one hand and FIGS. 4 and 5 on the other hand, in the presses according to the invention the access to the table and thus to the workpiece is substantially greater and easier from all sides. This is illustrated in particular by FIGS. 8 and 9, which shows the press according to FIG. 5 in matching casing 1114 and with tool plates 115, once installed on their own: Once around table 115, 10 is a substantially free space. the horizontal bars 116 interconnecting the bases of the slave actuators are below the plane of the table 115, as shown in FIG.

The advantageous situation when using such presses in a press line is shown in FIG. 10, from which the good accessibility to all presses and tables can be seen. In particular, here, if necessary automatic tool change in the automotive industry is favored by the side, but also in other manufacturing maintenance and tool change is much easier. 20 A comparison of Figs. 2 and 3 on the one hand with Figs. 6 and 7 on the other hand shows the significantly reduced deformation under the action of the pressing force, including the by the framework (also the parallel kinematic is ultimately one) enabled easy and accurate calculation of the deformation comes, which makes a compensation possible. An embodiment of the invention, which can also be advantageously used in presses according to the prior art, can be seen from FIG. 11 together with the subordinate figure:

In the presses according to the invention, a maximum of as many positional points of the press ram can be positioned exactly as directional cylinders (main actuators) 30 are present (thus minimally 3x2 = 6 points for statically determined designs, corresponding more to the above-mentioned variants with the desired bracing); in presses according to the prior art, this depends on the guides, but usually not a point of the press ram is exactly positioned. -8th- • ·· ·· ·· · ·· • · · ·· ··· · ···· • · · · ··· ···· ··· · ···· · · · · • ····· ·······

For long (wide) tools (press ram) these are usually not stiff enough to be able to distribute the force across the length (width) of the tool. Therefore, the embodiment of the invention proposes, at certain points of the framework, to provide short-stroke cylinders 209, 211 (or the like, below), which are controlled according to the application, force or position.

In the case of a position or path control, the position of the nodes of the truss can be calculated via the controller / software of the press and the difference to the optimum position of the tool can be corrected; In a force control, this is particularly useful in prior art presses, the force required at the point of control is either pre-set, e.g. in the finite element calculation of the pressing process, calculated and taken into account, or it is concluded on the basis of the first results from the finished workpiece and / or the data from sensors to necessary changes in the locally acting forces.

The Kurzhubzylinder can be connected to the uniform application of the pressing force in the simplest form only in the manner of corresponding vessels with each other, so that during the pressing process, a compensation of the forces acting locally on the workpiece occurs. If a progressive start of the pressing process is desired in presses according to the invention, for example, by appropriate movement of the press ram, this can be ensured by appropriate throttling in the connecting lines, so that the individual Kurzhubzylinder not hitting the workpiece until it hits evenly, but the pass on cutting movement.

An essential optimization goal of the presses is their output of pressed parts per unit of time. For this purpose, the standstill of the press must be optimized for conveying the board or the pressed part. This can not be influenced by the press.

To influence by the press are: the period that the press takes to get between the upper breakpoint and the first one

Contact of tool to board / sheet metal part to come (infeed motion), the period the press needs to perform the pressing operation (power stroke) and -9- • · • · -9- • · • ·

• ··· ··· fl is the time it takes for the press to move from the lower press point to the upper break point (free movement); In this case, feed movement and free movement together form the idle stroke.

In order to optimize the times for these movements, the invention provides, as shown in FIGS. 12 to 14, in one embodiment, a press which combines mechanically effected and hydraulically effected movements with surprising results. It is also this variant of the invention for presses according to the prior art suitable, albeit with the restriction that in such presses compared to presses according to the invention very high dead loads (the posts 2, including all components and drives thereon) must be moved. For the static certainty of this variant, the above applies.

As can be seen in FIGS. 12 and 13, this shortening of the pressing cycle can be achieved in a first variant by a combination of vertical movements by movement of the foot points 302 of the (in this case exactly) vertically extending actuators, the main actuators 112. It is exploited according to the invention that the drives 301 for the mechanical lifting movement can be very small (weak), since they only during the feed movement and the free movement (does not have to be during the whole movement) must accelerate the masses of press ram and upper mold half but not participating in the power stroke. During the pressing process (power stroke) itself, only the hydraulic cylinders 112, 113 are in use and the mechanism is in "singular position". and transmits " no " Force on the drives, this is derived through the bearings and / or own blocks in the framework 109.

In particular, from Fig. 13, a partially sectioned perspective view, the kinematics of such a hybrid press is apparent: A drive 301 moves via suitable angle gear 303 swing 304 in time by 180 ° between an upper (shown) and a bottom dead center. On the wings are the bases 302 of the main actuators 112, which are thus brought in the idle stroke quickly and synchronously with the rest, hydraulically effected movement, which takes place simultaneously, either in the upper rest position or in the position just before the power stroke. During the idle stroke, the axes of the main actuators move as a result of the movement of their foot • • · · · · · · · ················································································ ···························································································································································· During the entire duration of the power stroke base point 302, head point 305 and 5 rotation axis 307 of the rocker 304 lie on a straight line (singular position), there is no mechanically induced movement; the rocker is in this position, thus during the power stroke, either by a solid bearing on the framework 109 (this also includes the associated with him panel 306), or by attached to the framework 109, own (not shown) shoulder under discharge of the Bearing, supported. 10

Of course, it is also possible to carry out the lifting movement purely mechanically (rocker arm, four-link chain ...) and / or to design the actuators as spindles or other mechanical linear drives, as shown in FIG. 14. In this case, the actuators 14 'simple rods that act as an actuator 15 by the Fußpunktverschiebung and supported in their pressing action by the Nebenaktuatoren that are suitable as spindles. Of course, spindles and even ropes with matching baffles and drives may be used instead of the rods, as long as the slave actuators provide movement of the header and the extraction of the ropes of the main actuators against gravity without their assistance. 20

The movement of the entire device can be mathematically well calculated and thus also easily controlled, the non-vertically extending side actuators, whose bases are still fixed with respect to the frame 109 are arranged, can therefore be tracked with aiisreichender accuracy the main actuators. By this combination of movements it is possible to advantageously reduce the lifting height of the hydraulic movement.

For the design of the kinematics is to say in principle that the arrangement of the actuators does not necessarily have to be as shown, it can be chosen many other arrangements 30, in particular the favorable for the calculation of the movements 3-2-1 kinematics. In this attack at a common head on the movable platform, the head piece 104, three actuators, at another common head point two actuators and finally the sixth actuator by itself at a -11 -

• · · · · · · · · · · · ♦ φφφ

third head point. The advantages and the possible embodiments of this variant of the parallel kinematics are described in detail in the literature mentioned above and can be easily applied to presses by those skilled in the field of presses with knowledge of the invention. 5

As an additional advantage, it is achieved that the mechanism stores the energy like a flywheel and thus the pressing movement can be carried out very quickly; as a certain disadvantage, it can be noted that the press ram can not perform any pivoting movements about horizontal axes during the pressing process; The axes of the 10 main actuators run parallel to the pressing direction during the entire power stroke.

In the following, starting from FIG. 24, which represents a press according to the parallel kinematics described above, further embodiments are described with reference to FIGS. 25 to 32 described. 15

FIG. 24 shows a press 600 having a table 605 and a head 604 connected together by generally vertically oriented main actuators 612 and other side-by-side slanted actuators 613. The

Actuators are cylinder-piston units connected to the table 605 via a universal joint 620, respectively. The connection of the actuators 612, 613 with the head piece 604 via universal joints 621, which, as in the illustrated embodiment, the ends of two mutually inclined actuators 612, 613 may open in a common universal joint 621. 25 The system consists of four vertical and four oblique actuators and is thus twice as overburdened, once by a vertical actuator 612 and once by an inclined actuator 613. Due to the over-determination, the pressing force can be better distributed to the tool. In addition, can be dispensed with by a control technology caused slight tension of the actuators on a complex backlash-free storage of 30 actuators on the table and on the head, without having to accept a geometric offset between the tool and workpiece in purchasing. • ······· ··· ·· ··· -12-

As the embodiments of Figs. 25 to 32 can also be used within the scope of the invention, less than six actuators for the lifting or pulling movement of the head piece relative to the table. For the binding of degrees of freedom 612 guides 603 are provided in addition to vertical actuators in the press of FIG. The five four, arranged at the corners of a rectangle vertically oriented cylinder-piston units are connected to both the table 605 and the head piece 604 via a universal joint 620, 621, respectively. The parallel to the actuators extending guides 603 prevent the headpiece twists about the vertical axis and movements in the horizontal plane. In this system, the degrees of freedom of the head 10 are bound by cooperation of the parallel kinematic with guides 603. The present embodiment is overdetermined twice, once active by a vertical actuator 612 and once passively by a vertical guide 603.

As can be seen from the detail view of FIG. 26, the part 602 of the head piece 604 which bears against the sliding guide 603 15 is not flat, but is cambered inwards, so that only a small contact surface is formed. This allows slight tilting of the head piece by appropriate control of the individual lifting cylinder. Corresponding effect could also be provided by differently shaped - inwardly or outwardly arched - guide support surfaces, e.g. spherical, cylindrical, etc., can be achieved. The 20 caused by the shape softness of the guide surface can be reinforced by appropriate choice of material.

In addition to the vertical movement can be caused by 25 horizontal axes of rotation due to the curved bearing surfaces on the guide even minor movements of the headpiece attached tool, which is deliberately targeted and controlled skew of the tool pressing on the edges and the pressing force can be reduced. Despite the presence of guides these are not crushed, while at the same time achievable by conventional tumbling the achievable with conventional tumble press advantages.

27 and 28 show the press of FIG. 25 in a side view and in a section according to A-A, wherein the gimbal 620 of the cylinder base is highlighted at the table 605 closer. The universal joint is oriented in such a way that it rotates 30 -13- • · ··· ····

• · · allows the actuator to move horizontally. Generally speaking, the universal joint allows rotations about axes that are normal to the effective direction of the respective actuator. The same applies to the cardan joints that connect the actuators with the head piece. 5

At this point, it should be mentioned that other types of guides can be used, it is basically a matter of freezing the degrees of freedom of the head with respect to the table. For example, the guide can be made by a single tube with a rectangular cross-section, on the lateral surfaces of each corresponding contact surfaces 10 of the other part - table or head piece - abut and can slide on it. This would be an example that can be prevented with a single guide both movements in the horizontal plane and pivoting about the vertical axis. The difference with the stator guides of the presses known from the prior art is that only slight lateral forces occur in the present invention. On the other hand - as described above - in presses of the prior art due to the fact that the guides must be adjusted without play, and due to the asymmetry of the press force distribution, the load moments occurring over 20 the guides removed. This leads to deformation and early wear. In the present invention, however, the resulting load moments are determined by the arrangement and control of the actuators as parallel kinematic, whereby the lateral forces are orders of magnitude smaller than in the prior art. In addition, in the invention, the guides can be adjusted without play. 25

FIG. 29 shows a further variant of the invention in which, instead of the guides 603 from FIG. 26, at least one of the actuators 612a is firmly clamped to the table 605. Another actuator 612b is secured to the table against pivoting about a horizontal axis while pivoting about the horizontal axis 30 normal thereto is possible. These actuators 612a, 612b additionally assume the function of a guide and bind three degrees of freedom of the head piece or the attached tool, namely two translational in the horizontal plane and one against • • • • ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• ···········································································

Swiveling around the vertical axis. The remaining actuators 612 are mounted like those of the example of FIG. 25 with a single universal joint 620 at the table.

The clamping of the lifting cylinder is e.g. by supporting the lifting cylinder at the table by two cardan joints 620, 622 spaced vertically from one another. Securing the other lifting cylinder against pivoting about a horizontal axis is e.g. by two vertically spaced joints 620, 623, one of which, 620, is a universal joint and the other a simple pivot 623 which allows rotation about a single horizontal axis. At this time, the hinge 623 itself is movable in a horizontal direction, e.g. as part of a cylinder-piston guide. This translational movement is indicated in the figures with an arrow P, while the axis of rotation of the rotary joint is shown with a dashed line. The details of these hinges are shown in FIG. 32, wherein the main illustration of FIG. 32 is a sectional view A-A of FIG. 31 (side view). 15

The other two actuators 612 of the total of four actuators are each connected to the table 605 only via a single universal joint 620. This system with four actuators is simply overdetermined, namely by one of these simple mounted actuators. Thus, in order to be certain, these examples require at least 20 three actuators. In such embodiments, at least three actuators are required whose bases (or head points) are not all arranged on a straight line.

Of course it is also possible to clamp more than one, even all cylinders in the table. 25 The system is then overdetermined several times. The softness of the elements nevertheless allows a lifting movement - however, should the cylinders be e.g. for control reasons, not run the same and tilt the head, this could lead to permanent deformation of the cylinder. The lifting cylinders described below, which are designed in the form of long step cylinders, offer a particularly good guide ratio, so that the above-described function of the guide can be reliably taken over by the actuators. 15 • ············ · ···········································

can. Of course, the sliding guides of the cylinder must be adapted to the intended use.

It should be noted at this point that terms such as "vertical" and "horizontal" were used only to describe the concrete representations. However, since basically the

Pressing direction can be in any direction, are for generalization instead of the "vertical direction" to replace the pressing direction or the effective direction of the actuators and instead of the "horizontal directions" the normal direction to the pressing direction or effective directions. 10

Another aspect of the invention relates to the interaction of separate tool guides with the rest of the drive and possibly guide system. Press tools usually have their own, separate guide systems, which determine the position of the upper tool part (attached to the head piece) and the lower tool part (fixed to the table 15). This tool guide can now lead to undesirable stresses within the entire press, since they lead to a multiple over-determination of the system.

The invention proposes that, as soon as the upper and lower tool guide 20 engage with each other (this is done, for example, by chamfers, funnel-shaped Veijüngungen, rails, etc.), the (clamped or against pivoting securing) actuators 612a, 612b, the otherwise take on the role of leadership to take their leadership. By this unlocking the otherwise occurring over-determination is canceled, whereby tension 25 and consequently wear on the tools can be prevented.

This unlocking is particularly easy to perform in the variant shown in FIGS. 29, 30. Here, only the two counter-holders of the corresponding guide cylinder, that is in one case (firmly clamped actuator 612a) one of the two universal joints 620, 622 and in the other case (the anti-pivot about a horizontal axis secured actuator 612b), the simple pivot 623 opened become. This means that at the point of the joint, the connection between the actuator and the table is released. This is done e.g. by pulling out the connecting bolt or • ·································································································· · Μ ·· * -16-

Joint pin by another, not involved in the parallel kinematics invention actuator. By this measure, a significantly longer life can be achieved on the tools, because a multiple overdetermination is avoided from the outset. 5

The invention is not limited to the described embodiments. Thus, instead of universal joints also ball joints can be used, or other joints or combinations thereof, which have the same effect in relation to the storage, clamping and securing described above. It is only important that the degrees of freedom of the 10 head piece be restricted accordingly.

It should be noted that the basic principle is realized even when head and table are reversed, or the cylinder head. Even if in the last described embodiments table and head are shown as box girders, it is of course possible - as described above - form them as frameworks.

Since the hydraulics for the described press assemblies is an essential element 20, the invention proposes in further embodiments the measures explained below, which are also advantageous for presses according to the prior art; wherein first the actual tasks of the individual parts of the hydraulic system are discussed: 25 On the structure: The function of the hydraulic cylinders in forming machines according to the invention can be divided into two groups:

The supporting cylinders for the lateral force, these must hold the lifting carriage (press ram) in a horizontal position and take over the moment about the vertical axis. Here there is no preferred direction of movement - in the optimal case, they must provide equally large forces on both sides. Here, conventional double-acting cylinders are good and those, as described in the not yet published Austrian patent applications A 603/2008 and A 937/2008, optimal, can be used. -17- -17- ··· ** · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ······························································· ···············································

The lifting cylinders for the lifting force and the pressing force - master cylinder - must move the lifting carriage (press ram) vertically and record the moments around the horizontal axes. During the downward movement of the cylinders, in addition to the force for the movement of the own masses (feed movement), they must also provide the force for the pressing process (power stroke). During the upward movement (free movement), the cylinders only have to move their own masses. Therefore, it makes sense to use multi-chamber cylinder to provide more effective area and thus more force in the downward movement and to require less stroke volume in the upward movement and thus to achieve higher speed. This is easily possible, in particular in presses according to the invention, since more height is available as a result of the specific arrangement of the cylinders than in presses according to the prior art.

The invention makes it possible, in a further development, to go beyond 15 optimization possibilities for the master cylinder, which is likewise advantageously usable in presses according to the prior art:

In order to further increase the cycle time of the press, one must realize the following: The power requirement during the pressing process is determined by the pressing force and the pressing speed 20. Here you need up to several 10001 press force (a few meganewtons) for large presses. Therefore, the effective area for the hydraulically applied pressure for this process (power stroke) must be very large, which means a large volume of oil. During the other lifting and lowering movements during the pressing process (idle stroke), only the mass of the moving parts has to be moved by the tool and ram. So you need 25 orders of magnitude less force, therefore also less effective area. A stroke cycle now consists of starting from the top dead center position of the press ram: 1: Acceleration to rapid traverse speed down 2: Constant rapid traverse speed down 30 3: Deceleration to press speed 4: Constant press speed 5: Deceleration to standstill (reversal point) 6: Acceleration to Rapid traverse speed upwards 7: Constant rapid traverse speed upwards 8: Deceleration to standstill (top dead center) 9: Standstill of the press for changing the workpieces. 5 Except for the pressing (4, and at least partly 5), only very small forces are required for the movement of the moving parts against gravity (6, 7 + 8) or no forces at standstill (9 ) and when moving with gravity (1,2 + 3), it even needs to be braked. 10 With this in mind, it is the aim and the task to specify a cylinder, which provides the force for the pressing process during the idle stroke as far as possible only the force for mass acceleration and possibly only during the power stroke. This allows you to optimize the performance of the press at a constant flow of oil. Various cylinder-piston units suitable for accomplishing this task, often referred to simply as cylinders for the sake of simplicity, are shown in FIGS. 15-17. It is, as stated, to be considered that in the erfmdungsge-proper arrangement of the actuators by far the largest power requirement (load stroke) occurs during a small part of the pulling movement of the cylinder-piston units, whereas 20 during most of the pulling movement and the entire pressure movement only a much lower power requirement (idle, Eilhub) exists

It shows the Fig. 15 purely schematically as a first embodiment of a cylinder 401 with two power levels, the Zugkammem 402 for the load stroke and a stage, the pressure chamber 403, for the idle stroke. This means that at least two Zugkammem 402 axially seen one behind the other are provided in the cylinder, and that on a continuous, common piston rod 404 two associated pistons 405, each left or right (above and below) sit an inner cylinder bottom 406. It is thus constructed this cylinder 401 as two successively arranged with a common piston rod 30 cylinder. During the power stroke both Zugkammem 402 are acted on, whereby high force is generated, the idle stroke (= rapid stroke) is applied only to the pressure chamber 403, and on the assumption of a substantially constant oil pressure and a substantially constant flow of oil can be achieved here • · · · · ···· ························································································································································································································ the piston rod whose about twice the speed, otherwise constant conditions presupposed.

This cylinder 401 is much better suited for pressing than those used in the prior art 5, but still has disadvantages that are avoided by the cylinder 411 of FIG. 16: In this cylinder 411 with basically the same basic structure as in the cylinder 401, at the same reference numerals are used for analog components, Leerhubkammem 408 and 413 are provided with greatly reduced cross-section and with a Leerhubkolben 414 of the piston rod 404 cooperatively. 10

This double-acting Leerhubzylinder can now cause all movements of the head piece 4 during the idle stroke and is either used during the load stroke to support or it will be the two chambers 407 and 413 short-circuited. It may be the Leerhubzylinder 408, 413, 414 optionally provided with its own 15 oil circuit with its own pump, but it can also be supplied by the pump that supplies the load cylinder.

In order to drive the cross-sectional reduction of the Leerhubkammem 408, 413 and thus the extension speed of the cylinder-piston unit 411 to the top, the 20 cylinder 401 has a central rod 409 and the piston rod 404 is hollow at its free end and takes the central rod 409th sealing up. Since a dead volume 410 of variable volume is thereby formed inside the hollow piston rod 404, it must be connected to the environment by means of a vent line 412 for the purpose of pressure equalization. 25

If, starting from the position of the piston rod 404 shown in FIG. 16, oil is applied to the idle stroke cylinder 408 and the piston rod 404 is extended, oil is forced out of the idle stroke chamber 413 to the pump without the need for a large supply vessel. Similarly, oil is pressed out of the 30 Zugkammem 402, but according to the invention not back into a storage vessel, but, by appropriately switched valves, in the Leerkammem 407, whose volume corresponds to the volume of Zugkammem 402. Possible small differences, for example, due to thermal expansion, can be dissipated in the usual way and fed to a storage vessel.

After reaching the largest stroke and changing the workpiece, the 5 working stroke (pulling movement) begins, which, as will be explained in detail below, first begins with the feed movement, which does not yet require a large force. Therefore, oil is forced into the Leerhubkammer 413 and presses the oil in Leerhubkammer 408 through the now switched valves towards the pump (which also includes a small reservoir for oil, possibly with a cooling and / or cleaning device), the movement takes place accordingly quickly. Similarly, oil from the empty chambers 407 is directly forced into the draft chambers 402 by shorting the valves in the fluid lines (FIG. 23), that is, without passing through the pump or a reservoir (short circuit). When the piston rod 404 reaches the position corresponding to the beginning of the power stroke (step 4), both Zugkammem 402 are pressurized, it is the full force available, of course at a correspondingly reduced speed. The Leerhubzylinder 408, 413, 414 can support this movement or is shorted. 20

If parts are produced on the press in which the necessary pressing force is (relatively) small, this can be taken into account simply by pressurizing only one of the two chambers 402 during the power stroke (steps 4 + 5), which as with the feed motion, with the same flow of oil to an increase (in this example, about a doubling) of the press speed at deliberately reduced (about halved) pressing force, while the oil between the non-activated chambers is simply pushed back and forth ( closed-circuit).

If the installation height of the press is insufficient, a " idle stroke cylinder " 408, 413 30 to switch geometrically in series, it is also possible to integrate this, as shown in Fig. 17, in the free end of the piston rod 404 of the power cylinder. For this purpose, the free end of the piston rod 404 is hollow and slides sealed over a central rod 409 which carries the piston 414. The idle stroke thus formed in the piston rod •······························································································ • · · · * * · · ····· ·· ··· -21 -

Cylinder 408, 413, 414 is supplied via leads 410 inside the central rod 409 with oil.

This embodiment has the disadvantage that the Leerhubzylinder 408, 413, 414 because of 5 of the different cross-sections of the chambers 408 and 413 is no longer to build as a constant-cylinder run. Thus, an oil flow from and to an oil reservoir of only limited dimensions must be taken into account during the rapid stroke.

Another concern of the invention is the following: With simultaneous presses 10 (eg heat press) the energy requirement at the same time (when all 5-6 presses simultaneously exercise the full pressing force in the working stroke) is the highest, the required electrical maximum load must of the Power plants are provided, which means a considerable effort and leads to high energy consumption costs of the operator of such systems. The invention, in an embodiment which is equally applicable to the presses of any of the variants described above and to presses of the prior art, provides a new system of power supply and energy storage for presses.

The following background: advantages of mechanically driven presses are besides 20 of the many disadvantages: they are loud, form a rigid system, they are dangerous, there is the danger of self-destruction, etc., which compared to hydraulic presses shorter cycle time and the lower Energy peaks and thus a lower load on the electrical network, which is particularly evident in press lines, as they clock bound approximately synchronously perform their hub and thus burden the network together. 25

Mechanical drives have the ability to store energy in the flywheel. That is, these presses not only make the idle stroke faster than hydraulic presses, but also the power stroke. This is because the hydraulics at the same Kraflhub speed requires a huge engine power; e.g. requires a 1000t press 30 at a forming speed of 100 mm / sec. more than 1 000 KW drive power.

In order to prevent a multiplication of these enormous achievements by the simultaneity of the movement of the different presses of a line, today the -22- • ··· ··· · «·· ··· • ·

Motor power limited to keep the network load in the frame. Since only small forces are required in the idle stroke, an oil pump is installed, which allows a high Eilge-speed (pump outputs of quite several 100 kW). This high oil flow rate of the pump, the associated electric motor but only in the Leerhub 5 implement, so that forced in the power stroke, the lifting speed according to the available engine power according to the formula:

Force x speed = power 10 significantly reduced.

As already mentioned above, a stroke cycle consists of starting from the top dead center of the press ram: 15 1: Acceleration to rapid traverse speed down 2: Constant rapid traverse speed down 3: Deceleration to press speed 4: Constant press speed 5: Deceleration to standstill (reversal point ) 20 6: Acceleration to rapid traverse speed upwards 7: Constant rapid traverse speed upwards 8: Deceleration to standstill (top dead center) 9: Standstill of the press for changing the workpieces. 25 In this case, energy is "delivered" from the press to the drive in steps 1, 2 + 3; in steps 4, 5, 6, 7 + 8 energy is needed to move the press; and in step 9 no energy is needed. It should be said that the acceleration / deceleration (significantly) are smaller than the gravitational acceleration, otherwise the energy requirements would be different. Since the step 5 still takes place during the load stroke, the forming, 30 energy is generally required in spite of the delay due to the material deformation. • ♦ · ♦ · ······ ··· ·· ··· • -23-

Since this cycle is usually repeated continuously in the series production of parts and takes place in a relatively short period of time, the use of an energy storage to achieve the highest possible speed / acceleration at steps 1, 2, 3, 6, 7 and 8 offers and It is a flywheel especially for this 5 application. The advantages here are the high energy storage capacity and the high efficiency of flywheels.

This idea is not fundamentally new, DE 32 16 563 C, DE 33 18 188 A, which relates to an additional application of the first-mentioned document, EP 588 845 A, 10 US 5,526,738 A and the other technical field, namely EP 271 744 B, which concerns an aircraft rudder operation, discloses all of the various combinations of engine (s), flywheels, and pumps for hydraulic drives.

The idea of the invention is now the use of a flywheel which is rotated by a drive source (e.g., electric motor, hydraulic motor, etc.) which outputs a constant torque to the flywheel. A controllable hydraulic pump (motor) now decreases power at this flywheel according to demand, which is appropriately translated into oil speed and oil pressure in the pump according to the desired speed of the press ram and the required pressing force. In addition, energy is available during downhill travel and braking during braking and is delivered to the flywheel via the pump, which then operates as a motor. During the pressing process, during acceleration and during the upstroke (steps 4, 5, 6, 7 + 8) energy is required and removed from the flywheel by means of the pump and delivered to the hydraulic cylinders. 25

Since usually forming processes are always repeated and the parts produced mostly medium to high batch sizes, the following procedure to achieve a particularly economical operation is low: When adjusting the press after accelerating the flywheel (about 80% of the maximum speed), the first pressure 30th carried out slowly and thereby determined the exact energy demand on the pressing process. The calculated amount of energy plus the power loss is to be applied permanently by the motor mm. This is preferably controlled so that at the beginning of the pressing process (step 4), the flywheel with about 95% of the maximum allowable

Speed is rotating. The control circuit of the electric motor can be realized by the flywheel speed.

For this purpose, Figs. 18-23 show purely schematically (real arrangements are preferred with 5 aligned shafts with shaft couplings without any teeth) and unrealistically arranged next to the drive cylinder-piston units, but clearly and vividly some embodiments of this further development of the invention; namely, FIGS. 18, 19 a simple variant, FIGS. 20, 21 an embodiment, and FIGS. 22, and 23 a preferred variant. 10

18 and 19 show a first variant of the embodiment of the invention with an electric drive 501, which sets a flywheel 502 in rotation, which in turn drives an oil pump 504, which is connected by means of a hydraulic 503 with a cylinder-piston unit 401 , The flywheel 502 has, for example, for a press with 600 tons 15 pressing pressure and a load stroke of 500 mm a mass of 750 kg with a diameter of 1000 mm and a maximum allowable speed of 3500 U / min. The actuator 501 provides 120 kW, the pump 504 delivers 2.10'2 m3 oil / s at a pressure of 350 bar. The cylinder-piston unit 401 corresponds to that of FIG. 15, the leadership of the individual lines of the hydraulic 503 is such that the individual chambers are alternately under 20 pressure, move the piston rod and thereby empty the respective Gegenkammem direction pump so that a nearly uniform flow of oil is achieved with the need for a small reservoir which may be housed in the foot of the pump.

As shown, the hydraulic lines have no valves, the throttling when passing through valves and the associated destruction of useful energy (pressure energy is converted into heat) is completely avoided, as the following examples show.

20 and 21 show a variant of the embodiment explained above, in which the hydraulic 503 has its own circuit 505 and a cylinder-piston unit 401 is used as before. The circuit 505 makes it possible, by valves not shown in detail, to determine the flow of the oil depending on the respective operating state: the circuit 505 is in the load stroke, while the

Pressing movement (steps 4 + 5) shown: oil is pressed into the two Zugkammem 402, the pressure chamber 403 and the empty chamber 407 give the oil contained in them to the suction side of the pump. 5 During the idle stroke in the pressure direction, the circuit 505 is switched, the rear tension chamber 402 is then directly connected to the empty chamber 407, another connection to a reservoir creates the possibility of volume compensation in all directions; In the pressure chamber 403 oil is pressed, the front tension chamber 402 is the oil in her direction pump and is also connected to the reservoir in 10 connection. Thus, a substantially twice as fast extension compared to retraction is achieved, but a consideration for the details given above is not yet possible. However, it is also here in the operation no valve in throttle position to flow through, thus occur here in the prior art, the efficiency so degrading effects not on. 15

A particularly preferred embodiment, Figs. 22 and 23, which shows an arrangement with a cylinder-piston unit 411 according to FIG. 16. In order to take the best possible account of the actual load conditions and in this case also to manage without valves, which are flowed through throttle position in the operating state, two separate pumps 504 and 506 are in engagement with the flywheel 502, in operation the following operating states are to be distinguished:

If the piston rod 404 is extended from the position shown (steps 6, 7, 8 + 9), then the idle stroke cylinder 408 is acted upon by the pump 506 and moves the piston rod 25; at the same time the counter chamber 413 is emptied, the pump 506 requires only a minimal reservoir; It may be a separate hydraulic circuit or connected to the load circuit (pump 504). In this load cycle with the pump 504, the Zugkammem 402 are emptied, while the oil of Zugkammem 402 flows directly into the Leerkammem 407; The load circuit also requires only a minimal reservoir, which it optionally shares with the Leerhubkreislaufes.

After reaching top dead center (= piston rod 404 fully extended, step 9), when the piston rod retracts (steps 1, 2, 3), the idle stroke circle is first opened. ·· ···· ·· ···· Λ · · · · ··············· run applied accordingly (usually this is done by the fittings of the pump 506); the oil flows into the Leerhubkammer 413, moves the piston 404 and pushes oil from the Leerhubkammer 408 to the pump 506. Similarly, oil from the Leerkammem 407 is pressed directly into the Zugkammem 402. 5

With the beginning of the pressing step 4, the circuit 505 is changed, from this point on both Zugkammem 402 are pressurized, the speed of the piston rod 404 decreases, the available power increases against the idle stroke strongly. The Leerhubkreislauf 408, 413, 414 remains preferably activated to support the movement 10 on, but can also be switched off by short-circuiting of the chambers 408, 413 virtually lossless.

After reaching the bottom dead center, the circuit and the operation of the hydraulic circuits are changed over again, the Leerhubkreislauf remains / is activated, of course 15 in the opposite direction, the game restarts.

Depending on the friction and the other boundary conditions, the drive 501 permanently provides for the application of drive torque to the flywheel 502, at least as long as it is not switched off by a speed monitor. During the 20 individual steps now remove the pump 504 and possibly the pump 506 power from the flywheel, which reduces its speed. In individual operating states (deceleration, downward movement) falls, as already stated above, also on the pump side power, this can also be delivered by switching the pump to the flywheel; which further saves energy. 25

Of course, in the knowledge of these relationships a variety of hydraulic variants with rapid traverse, with one or more pumps, etc. are possible; e.g. Flywheel press drive with separately switchable Teilzylindem to realize correspondingly higher speeds in the partial load range and the like, but it is always essential that through the inventive measures the flow of only partially open valves and the concomitant throttle loss completely or almost completely is avoided.

As stated in detail, various of the measures according to the invention can be used advantageously without it being necessary to take the other measures; For the expert in the field of presses and in particular of the hydraulically operated presses this is readily apparent in the knowledge of the invention and 5 applicable. In particular, the energy storage device according to the invention for pressing of all kinds

Claims (23)

Claims 1. Press for uniforming material with a table (5) and a head (4) with a press ram, which is movable up and down in the pressing direction relative to the table by means of a press drive, characterized in that the head piece (4) movable platform of a parallel kinematic device (101) whose fixed platform is stationary relative to the table (5). 2. Press according to claim 1, characterized in that the press drive of the parallel kinematic device (101, 600) comprises actuators (112, 612, 612a, 612b) which are oriented substantially parallel to the pressing direction. 3. Press according to claim 2, characterized in that for binding degrees of freedom of the head piece (604) with respect to the table (605) at least one guide (603) is provided, which is oriented substantially parallel to the pressing direction. (Fig. 25) 4. Press according to one of claims 1 or 2, characterized in that the press drive of the parallel kinematic device (101) main actuators (112) which are oriented substantially parallel to the pressing direction and differently oriented side actuators (113), wherein the base points (302 ) of the actuators (112, 113) on the table side and the head points (305) of the actuators (112, 113) are arranged on the head piece side. 5. Press according to one of claims 2 to 4, characterized in that the bases of the actuators (612, 613) sitting on universal joints (620), which connect the actuators (612,613) with the table (605). 6. Press according to one of claims 2 to 5, characterized in that the head points of the actuators (612, 613) sitting on universal joints (621) which connect the actuators (612,613) with the head piece (604). 29 ·· · · · · · · · · »· ···· · · · · · ··· 7. Press according to one of claims 2 to 6, characterized in that at least one actuator (612 a) on the table (605) or on the head piece (604) is firmly clamped. 8. Press according to claim 7, characterized in that the clamping of an actuator (612 a) on the table (605) or on the head piece (604) via two spaced apart in the pressing direction Kardangelenke (620, 622) takes place, each of the actuator (612 a) connect to the table (605) or the head piece (604). 9. Press according to one of claims 2 to 8, characterized in that at least one actuator (612b) on the table (605) or on the head piece (604) is mounted such that it secured against pivoting about an axis normal to the pressing direction (630) is and about an axis (630) normal axis (631) is pivotable. 10. Press according to claim 9, characterized in that the securing against pivoting of the actuator (612b) about an axis normal to the pressing direction (630) on the table (605) or on the head piece (604) via two spaced from each other in the pressing direction joints (620 , 623) each connecting the actuator (612) to the table (605) and the header (604), respectively, where one hinge is a universal joint (620) and the other hinge is a simple pivot (623) guided in a direction normal to the pressing direction is displaceable. 11. Press according to one of claims 8 and 10, characterized in that one of the two joints, with which the actuator (612 a, 612 b) on the table (605) or on the head piece (604) is clamped or secured, as a releasable connection of the Actuator (612) with the table (605) and the head piece (604) is formed. 12. Press according to one of claims 1 to 11, characterized in that the parallel kinematic device (101) is formed statically overdetermined. •······ • • • • • • • • • • • • • · · · · · · · · · · · · · · · · · 13. Press according to one of the preceding claims, characterized in that the head piece (4) and / or the table (5) as a framework (109, 111), optionally with a lining (114) is formed. 14. Press according to one of the preceding claims, characterized in that a plurality of short-stroke cylinders (201, 209) are provided on the head piece (4) and / or on the table (5), the position of the tool even with elastic deformation of the head piece (4). and / or the table (5). 15. Press according to one of the preceding claims, characterized in that the parallel kinematic device (101) comprises actuators, of which at least one is a hydraulic cylinder-piston unit (401,411). 16. Press according to one of claims 2 to 15, characterized in that in the substantially parallel to the pressing direction oriented actuators 19 are hydraulic cylinder-piston units (401,411) whose base points (302) are movable. 17. Press according to claim 16, characterized in that the foot points (302) sit on rockers (304) and that in the position of the rockers, in which the head 20 (4) is closest to the table (5), the axis ( 307) of the rocker (404) intersects the axis of the actuator (401, 411), and that this intersection, the base point (302) and the head point (305) lie on a straight line. Hydraulic cylinder-piston unit (401, 411) for use in a press 25 according to one of claims 1 to 17, characterized in that its piston rod (404) carries two pistons (405) and that the cylinder has an intermediate bottom (406 ) so that it has four chambers (402,403). 19. Hydraulic cylinder-piston unit (401, 411) according to claim 18, characterized 30 characterized in that the cross-sectional areas of at least three of the four Kam numbers (402,403) are equal to each other. -31 - -31 - * · • · ··· ···· ··················································· 20. Hydraulic cylinder-piston unit (411) according to claim 18 or 19, characterized in that the piston rod (404) further comprises a Leerhubkolben (414) and the cylinder has a Leerhubabschnitt with veijüngtem cross section, the double-acting Leerhub cylinder Piston unit (408,413,414) represents. 5 21. Hydraulic cylinder-piston unit (411) according to claim 20, characterized in that the piston rod (404) is hollow at its free end and a cylinder-fixed central rod (409) sealingly, and that the central rod (409) at its free end with a piston plate (414) sealingly against the inner shell 10 of the hollow piston rod (404) and thus forms the Leerhub cylinder piston unit (408.413.414). 22. A method for operating hydraulic cylinder-piston units (411) in a press according to one of claims 1 to 17 with a duty cycle of, starting from 15 of the top dead center of the press ram, from: 1: acceleration at rapid traverse speed down 2: Constant rapid traverse speed downwards 3: Deceleration to press speed 4: Constant press speed 20 5: Deceleration to standstill (reversal point) 6: Acceleration to rapid traverse speed upwards 7: Constant rapid traverse speed up 8: Deceleration to standstill (top dead center) 9: Standstill of the press to Change of workpieces; 25, characterized in that during the idle stroke, comprising the steps (1, 2, 3, 6, 7 and 8) the Leerhub cylinder piston unit (408, 413, 414) is pressurized in the appropriate direction, while the four chambers (402, 403) are short-circuited in pairs and possibly connected to a reservoir, and during the load stroke comprising steps 30 (4 + 5), the compression chambers (402) are pressurized and the pressure chambers (403 ) are associated with the suction side of the pressure source and optionally with a reservoir. φ φ · t · φ · · φ · · φ · φ φ φφ φφ φφ φ φ φ φ »φφ * φ φ φφ φφφφ φ φ φ φ φ φ · φ φφφ · φ φ φφ φφφ -32- 23. Energy storage for use in a press, wherein the energy storage consists of a flywheel (502), which is driven by a drive (501) and at least one pump (504, 506) for hydraulic fluid drives, characterized in that for always the same acted upon Pairs of chambers (402,403; 408,413) are each provided with a pump. 5