EP0300000B1 - Press drive - Google Patents

Abstract

To drive two toggle levers (29, 29') of a press, in particular a high frequency cutting press with at least 400 strokes per minute, two separate but mutually synchronized drives (101, 101') are provided to ensure a uniform, non-wobbling motion of the tool carrier (5). The drives (101, 101') can be shaped as rotary or as linear drives and are used to drive the toggle levers (29, 29') during at least part of their motion. The energy storage (200) ensures a low energy consumption, since it stores the braking energy and supplies it again to the drive during acceleration.

Description

The invention relates to a press drive, e.g. for deep-drawing, trimming or punching presses and in particular for high-frequency punching presses with at least 500 punching movements per minute (which, as is known, must be specially designed for this), according to the preamble of claim 1. In most cases there is only one tool carrier in such presses, as a rule the upper one is movable, but ultimately only the relative movement is important, which is why it would also be conceivable within the scope of the invention to make both tool carriers movable.

The demands on the drive of a punching machine are very special, because the highest precision is required in the range of less than a hundredth of a millimeter, and this - with their nature - of constantly vibrating machine parts and with high pressure forces.

Now, for example, in "Machine Tools" by Charcut / Tschätsch, Hauser-Verlag, 1984, p. 290, a drive with a crankshaft is shown and described (the same effect could also be with an eccentric shaft, be it in a version with a circular eccentric achieve it with a constant thickness), which has several advantages in this regard, since the - most generally the bottom - dead center determining the greatest approximation of the tool carrier is given by the vertex of a sine curve, so that small tolerances in the eccentric adjustment practically do not occur impact. However, this well-known drive did not meet the requirements in some respects. For example, its mass could not be reduced to the desired extent, since a flywheel had to be provided to provide the necessary punching force. The arrangement of a flywheel also requires the use of a controllable clutch, which involves an additional, sometimes repair-prone component brought himself. In addition, there are limits to the speed, since the drive must apply full acceleration every time, although part of the drive energy has to be braked again. Ultimately, this results in a correspondingly large drive dimension, which of course also results in high energy consumption.

The primary object of the invention is to provide a press drive which ensures an exactly corresponding movement sequence in every position, which dispenses with a flywheel and which manages with a reduced drive and a lower energy requirement. According to the invention, this is achieved by the characterizing features of claim 1.

Advantageous developments of the invention are described in the characteristics of the subclaims.

By using drive elements that allow driving (accelerating) and braking (pneumatically storing energy or feeding electricity back into the grid, with the so-called four-quadrant drive), it is possible to not only omit the clutch, but also any brakes. Only a few masses are moved during the lifting movement.

• 1) Statisch sehr steife Auführung im Vergleich zu Exzenter-Pressen, da im Bereich des unteren Totpunktes nur je zwei auf Druck beanspruchte Stangen im Kraftfluss stehen;
• 2) die Genauigkeit des unteren Totpunktes ist durch einfache Geometrie gut einzuhalten.
• 3) dynamische Stabilität: bei jeder Hubfrequenz (Hubzahl/ min.) herrschen gleiche dynamische Verhältnisse, d.h. es ist bei Veränderung der Hubfrequenz keine Nachstellung des unteren Totpunktes nötig;
• 4) "sanfter" Schlag beim Schneiden, da die Auftreffgeschwindigkeit auf das Band beim Kniehebelprinzip erheblich kleiner ist als bei Exzenterpressen; es entsteht ein "Schneiden" der Schnittstelle, kein Ausbrechen;
• 5) durch die Einstellbarkeit des Schwenkwinkels bzw. Kolbenweges kann ein stufenloser Stösselhub gewählt werden;
• 6) nur hin- und hergehender Massenausgleich (Ausgleich erster Ordnung);
• 7) Minimum an bewegten Teilen (einfache Mechanik);
• 8) gegenüber üblichen Kniehebel- bzw. Differenzpressen ist eine hohe Hubfrequenz möglich;
• 9) vorwählbarer Geschwindigkeitsablauf des Stössels;
• 10) vielseitigerer Einsatz (gegenüber Exzenterpressen);
• 11) es können grosse Presskräfte mit relativ kleinen Antriebskräften erreicht werden;
• 12) geringer Energiebedarf.

The inventive design of the machine with the synchronized double knee levers and the mass balance thus created a new, electronically controllable type of press. The press machine described according to the invention has the following advantages over the prior art:

• 1) Statically very stiff design compared to eccentric presses, since in the area of bottom dead center there are only two bars under pressure in the power flow;
• 2) The accuracy of the bottom dead center is easy to maintain by simple geometry.
• 3) dynamic stability: the same dynamic conditions prevail at every stroke frequency (number of strokes / min.), Ie no adjustment of the bottom dead center is necessary when changing the stroke frequency;
• 4) "gentle" stroke when cutting, since the speed of impact on the belt is considerably lower with the toggle lever principle than with eccentric presses; there is a "cutting" of the interface, no breaking out;
• 5) an infinitely variable ram stroke can be selected due to the adjustability of the swivel angle or piston travel;
• 6) only reciprocating mass balancing (first order balancing);
• 7) minimum of moving parts (simple mechanics);
• 8) a high stroke frequency is possible compared to conventional toggle lever or differential presses;
• 9) preselectable speed of the ram;
• 10) more versatile use (compared to eccentric presses);
• 11) large pressing forces can be achieved with relatively small driving forces;
• 12) low energy consumption.

Precise guidance and a wobble-free movement can be obtained by the features of claim 9, and if desired also with a single drive energy carrier, it being possible for the energy store to be fastened to the crossheads at a spatial distance from the toggle levers. It is noted here that the term "drive energy carrier" in the present description encompasses everything that drive energy is capable of delivering, even only in a partial area of the movement, i.e. also the energy storage.

Such an energy storage device can be used with advantage in general, regardless of how the drive may otherwise be designed, ie by means of a rotary drive or linear drive, and even quite independently of whether two Toggle lever systems are provided or not. A pressure accumulator is particularly suitable, however, if a fluidic drive, such as according to claim 7, is provided anyway.

The feature of claim 2 creates very precisely and easily that adjustment, especially for top dead center, which went off in the two references mentioned above. In connection with the features of claim 1, it is important that the reciprocating drives are low-mass, in particular in the case of an embodiment according to claim 9.

Practical tests have shown that hydraulic or asynchronous motors are particularly suitable for rotary drives because of their characteristics with regard to the starting torque.

Fig. 1

ein Prinzipschaltbild mit elektrischem Antrieb, wobei auch die sich bietenden Justiermöglichkeiten dargestellt werden;

Fig. 2

eine erste Ausführungsform mit zwei völlig symmetrisch aufgebauten Antrieben für beide Seiten eines beweglichen Werkzeugträgers, wobei eine Kreuzkopfführung an den Gelenkpunkten der beiden Kniehebel zusätzlich eine gleichmässige, taumelfreie Bewegung sichert;

Fig. 3

ein erstes Ausführungsbeispiel für die Verwirklichung der Erfindung mit Hilfe zentral angeordneter fluidischer Linearantriebe (Zylinder-Kolben-Aggregate); und

Fig. 4 und 5

weitere Varianten mit unterschiedlich placiertem Energiespeicher.

Further details emerge from the following description of exemplary embodiments shown schematically in the drawing. Show it:

Fig. 1

a basic circuit diagram with electric drive, the adjustment options are also presented;

Fig. 2

a first embodiment with two completely symmetrical drives for both sides of a movable tool holder, a crosshead guide at the articulation points of the two toggle levers additionally ensuring a smooth, wobble-free movement;

Fig. 3

a first embodiment for realizing the invention with the help of centrally arranged fluidic linear drives (cylinder-piston units); and

4 and 5

further variants with differently placed energy storage.

The figures are described together. The same parts have the same reference numbers. Repetitive parts are partly not shown (e.g. energy storage in Fig. 2).

Fig. 2 shows a completely symmetrical drive 1, which is also particularly suitable for a reciprocating rotary drive. Two parallel crank or eccentric shafts (only one of which is shown schematically as drive 1), which are designed as flywheel-free motor shafts of a hydraulic or electric motor, ensure the drive of the toggle levers 29, 29 '. Care is taken to ensure that the movement of the two shafts or drives 1 takes place synchronously with one another, so that the movement of the two toggle levers 29, 29 'is uniform. The synchronization can be electrical, which is easily possible due to the pulse-dependent position of the rotor of synchronous or asynchronous motors. Additionally or alternatively, mechanical coupling can also be provided. Even a single crankshaft (drive 1) could even be provided.

The construction shown in FIG. 2 is also particularly suitable for a to-and-fro rotary drive because a certain simplification results from the fact that for two strokes of the tool carrier 5, the angle α is on both sides of the crank dead center T (corresponding to the top dead center) the tool holder 5) is passed through, which is favorable in terms of smoothness and energy consumption. Of course, the movement to both sides must then be limited by a corresponding limiter device, as will be discussed with reference to FIG. 1.

Two toggle levers 29, 29 'form a scissor system for a straight guide construction. They are hinged at one end via a bearing 26, 26 'to a balance weight 31. On the other hand, the toggle levers 29, 29 'are articulated on a tool carrier 5. To support the guide are the tool holder Assigned to 5 columns 106 in guides 30, and analogously, a guide column 32 can pass through an opening 33 in a counterweight 31 (FIG. 5).

The knees of the toggle levers 29, 29 'are mounted on cross heads 25, 25', whereby the upward and downward movement transmitted by connecting rods 104, 104 ', i.e. divided on the weight 31 and the tool carrier 5 and thus halved.

The essential difference of the construction according to Figures 3 to 5 compared to that of Figure 2 is that instead of the bearing 26, 26 'in the counterweight 31, a fixed pivot bearing 126, 126' for each toggle lever 129, 129 '; 229, 229 'is provided. Thus, the entire effect, from the connecting rods 404, 404 '; 504, 504 'transferred stroke to the tool carrier 5, which can also be provided in the example shown in FIG. 3 with an additional guide column 34 on its top, which cooperates with a fixed guide 35.

However, in order not to have to do without a counterweight 31, the upper legs 128, 128 '; 228, 228 'of the toggle lever 129, 129'; 229, 229 'beyond the fixed pivot point 126, 126' be extended and have a short extension arm 36, 36 '. On this arm 36 and 36 ', a link 37 or 37' is pivotable, which theoretically represents only a pressure member, but is exposed to both tensile and compressive loads in view of the high stroke frequencies of the punch press.

Again, a guide column 32 is provided for the counterweight 31. It cannot be seen in more detail that this column 32 is fastened to a frame in holding bushes 39. The frame has a recess to enable the free movement of the weight 31 up and down.

In Fig. 1, an adjusting device 22 is indicated, through which not only the upper reversal point of the movable tool carrier 5, but also its bottom dead center is adjustable in height.

Another adjustment device, not shown in detail, can e.g. be formed as follows: nuts with a thread are arranged above guide columns, the frame being provided with guide sleeves, each of which has a bore for receiving the guide columns. In cross section, the sleeves can have an approximately rectangular outer contour, the longer side of which runs in one plane, the shorter side, however, perpendicular to this plane. A cutout thus penetrates at least one outer surface of the sleeves, for example only the front surface, but possibly also the rear surface, so that the nuts partially protrude outwards and can be actuated from the outside.

The height of the frame can now be adjusted by turning the nuts, the nuts of course having to be adjusted in the same direction and by the same amount. In order to facilitate this, they can have a common adjustment drive which, for example, has a toothing with which e.g. a chain, rack or swivel drive is engaged.

An embodiment according to FIG. 2 is preferred for a punch press of extremely high punch frequency. The connecting rods 104, 104 'are relatively long and overlap or overlap each other during their passage through the dead center T. For this purpose, the two connecting rods 104, 104' are axially offset from one another.

It is clear that the arrangement of two mutually parallel and mutually synchronized crank or eccentric shafts 1, with regard to the accommodation of the units for an increased drive power has special advantages, regardless of whether the reciprocating drive is realized or not. The arrangement in pairs also results in a horizontal compensation of the vibrating masses, so that there is also a smoother run or higher speeds are possible and the effect of the energy store or is fully effective. In the embodiment shown, this is further supported by the small number of force transmission members and articulation points, which on the one hand results in low masses and on the other hand high precision, especially since there are no parts subjected to bending in all of the versions.

To explain the reciprocating rotary drive according to FIG. 1, which has already been mentioned several times, only a crankshaft (drive 1) is shown there, which can be rotated about a geometric axis 2, a connecting rod 4 being articulated on a crank pin 3. On the opposite. lower end of the connecting rod 4, a movable tool carrier is shown directly connected for the sake of simplicity; in practice, a toggle lever system is also connected in between. The tool carrier 5 can be moved up and down along guide columns 6 which are connected to a stationary tool carrier 7. Both tool carriers 5, 7 are designed in a manner known per se, not shown here, for fastening tools 8 indicated by dash-dotted lines. These tools 8 lie against one another in the lowest dead center position of the crank pin 3, or have the greatest approximation to one another.

An eccentric shaft (drive 1) can be driven by an electric motor 9. The shaft 1 is dimensioned in terms of its diameter or provided with a wheel of such a diameter that a rotation of 180 ° from the bottom dead center position shown results in the maximum possible stroke in this punch press, which is only required for certain tools is, whereas in most cases a smaller stroke is sufficient.

In order to save on stroke on the one hand and thereby also enable a higher punching frequency and on the other hand to be able to adapt the upper reversal point for the movable tool carrier plate to the requirements, the motor 9 operating in motor and braking mode is provided with a reversing device 10 for the direction of rotation. In this way, it is possible to reverse the direction of rotation of the shaft (drive) 1 at a certain point.

It is now important to determine this point as precisely as possible, the requirements for accuracy being lower in the case of the upper “dead” or reversal point than for the lower dead center position shown in FIG. For this purpose, the motor 9 has a rotor, the position of which is determined by the respective number of pulses that are supplied to the motor 9. Such motors are either stepper motors or - which is preferred because of the better drive properties - are synchronous or asynchronous motors.

Accordingly, the motor 9 is preceded by a limiter device 11, via which a predetermined number of pulses can be fed to it. In order to determine this number exactly, a pulse generator 12 is provided for delivering this predetermined number of pulses. Such an assembly can be constructed from mechanical-galvanic elements (e.g. a switch cam which interacts with a switch and is stopped after the predetermined number of pulses), it can be a relay technology structure, or - as shown - a clock generator 13, to which a counter stage 14 is connected.

The counter stage 14 has in the usual way a number of only indicated outputs and can be a decade counter or a binary counter. One of its outputs, the output nx, is connected to a shutdown input A of the limiter device 11. This is the case if the counter 14 is a decadal counter, whereas in the case of a binary counter, the number corresponding to the predetermined number of pulses is logically L at some outputs and "O" at other outputs. In the latter case, it is necessary to connect all outputs to the limiter device 11 via an AND gate, for example all outputs with the signal "L" directly, all outputs with the signal "O" via an inverter, so that the AND gates are only supplied "L" signals when the predetermined number is reached.

As soon as the counter 14 has reached the predetermined number, the motor current of the motor is switched off via the output nx. The arrangement can now be such that a braking device in the form of a braking circuit 15 is switched on at the same time, by means of which the motor 9 is switched over to generator operation. However, it is also possible to let the press continue to operate under the effect of its inertia and to initiate braking only a short time later. This means that the current is switched off before the upper reversal point is reached, with braking only being initiated when this reversal point is reached.

This can be done via an output ny of the counter 14, which is connected on the one hand, expediently via a gate circuit 16, to the braking device 15, and on the other hand to a reset input R, which causes the counter 14 to be switched back to zero and then with a new count begins. Furthermore, the last output of the counter 14, ie the output ny, which corresponds to the highest number and thus the predetermined top position of the tool carrier 5, also connected to the reversing device 10 in the form of a reversing stage, so that when the counter 14 continues to count, the same distance from the eccentric shaft is now covered in the opposite direction.

If the "same path" is mentioned here, every specialist knows that precise positioning is possible, especially with stepper motors. Such motors could theoretically be used here, but they generally have smaller starting torques than synchronous or asynchronous motors. It is now possible to ensure that the very critical bottom dead center position in the construction shown is given by the lowest position of the crank pin 3, with small deviations along the curve hardly resulting in a change in the position of the movable tool carrier 5 in the region of the culmination point of a sinusoidal curve. Therefore, the synchronous or asynchronous motors, which can be braked less precisely but are equipped with better torque characteristics, can be used.

The path that the crankshaft (drive) 1 travels back and forth is entered as angle α. It is understood that in many cases (not all) it will be desirable to be able to set this angle α. To variably limit the stroke of the tool carrier 5, an adjusting device is therefore expediently provided. In the embodiment shown, such an adjustment device can be created in that the outputs of the counter 14 can optionally be connected to the stages 10, 11 and 15, so that they are activated depending on the respectively connected output and the corresponding counter reading. It would also be possible to provide a plurality of counting stages instead of a single counter 14, each counting stage corresponding to a different maximum counting value and thus a different angle α.

In any case, it is indicated in FIG. 1 that the shutdown input A of the limiter device 11 can be connected to various outputs of the counter 14 via an adjusting device 17 designed as a sliding contact, and analogously the reset input R, the input of the reversing device 10 and the braking device 15 can be connected via one another (not shown) sliding contact can be optionally connected to different outputs.

The gate circuit 16 has already been mentioned, one input of which is formed by the output ny of the counter stage 14. The other input may be led via a switch tongue S1 connected to the main switch 18 for the motor current of the motor 9, or a switch tongue S2 may be connected to this main switch 18 (in a manner not shown) via which the clock generator 13 also connects to the motor 9 can be switched on. The braking device 15 can also be tilted into its braking state only when the motor 9 is switched on.

The following should also be emphasized from the above explanation: It can be seen that the circuit shown creates a reciprocating drive by means of which the top dead center of the tool carrier 5 can be easily adjusted. It goes without saying that this drive itself can be replaced by equivalent drives, although the drive shown or described is also characterized by low mass and high performance, primarily because of the good interaction with the energy store. The various stages 10, 11 and 15 are controlled by an electronic program control unit, but other known program control units can of course also be used for this purpose. For example, a microprocessor could be provided for this purpose, which could then possibly take on additional control tasks. The input of the desired angle α can then be carried out particularly easily using a keyboard device.

While in step control, as described above, feedback via sensors is not required, a program control unit can also include such sensors in the form of position sensors. For this purpose, a switch S3 can interrupt the control of the braking device 15 via the counter 14. A selection device 19 is also provided, to which three switching positions are assigned. In the position I shown, the function takes place in the manner described above; in position II it is not possible to reverse the direction of rotation, i.e. the motor 9 rotates continuously in one direction, ie makes at least one rotation through 360 °.

The adjusting device 17 designed as a sliding contact is placed in a position 20 for this function, so that the stage 11 can no longer receive a switch-off signal, while on the other hand it continues (as in the function according to position I of the adjusting device 19) via a terminal B with the Clock generator 13 is connected and can receive pulses from it. This circuit with terminal B can, however, possibly prevent the clock frequency of the clock generator 13 from being matched to the mains frequency or even being synchronized, so that the number of pulses supplied to the motor 9 - in accordance with that of the clock generator 13 - actually comes from the network.

In position III, however, the limiter device 11 is connected to a position transmitter switch S4. Another position transmitter switch S5 is arranged upstream of the switch S4 at an adjustable distance. In principle, however, both switches S4, S5 are connected to one another by a bracket 21 and can be displaced together along an adjustment device 22, designed as a guide indicated by a broken line, for adjusting the angle α. If such a control is desired, the drive 1 is provided with a radial stop extension 23 which actuates the switch S5 in the course of its travel and via him a signal on the one hand to a shutdown input A '(it can also be A) of the limiter device 11 for the motor 9 to interrupt its power supply, on the other hand also brings the braking device 15 for switching the motor 9 to generator operation.

The braking device 15 switches in the manner of a monostable multivibrator after the motor 9 has come to a standstill, i.e. when this no longer delivers current, it automatically switches back to "motor operation" without the need for a separate signal. For example, it can be equipped with a latching circuit for this purpose, which is powered by a relay (which is fed by the current of the motor 9) is held long until this current drops to zero.

As soon as braking is initiated via switch S5, the crankshaft may move a little further under the influence of the inertial forces, although this distance can be very short, especially if a mechanical brake is provided in addition to the electrical braking device 15. If the crank pin 3 is fastened on a disk which can be rotated about the axis 2, a disk brake, which is magnetically controlled and triggered via the switch S5 (or the output ny of the counter 14) can act on this disk.

For safety's sake, the stop extension 23 may strike an adjustable stop 24 at the end of its movement, while at the same time the direction of rotation is reversed via the switch S4. A similar arrangement with two switches can then be provided for the backward movement, not shown, which correspond to the switches S4, S5.

Instead of a back-and-forth rotary drive, a linear drive of the same kind can also be used, in particular with fluidic (usually hydraulic) cylinder-piston units 101, 101 ′; 301 (Fig. 3-5) can be used, which also results in a wobble-free movement characteristic when the two drives are synchronized with one another.

3, two toggle levers 229, 229 'are provided, each of which consists of a leg 227, 227' articulated in a bearing 126, 126 '. The movable tool carrier 5 is guided with the aid of frame-fixed guides 30, 30 'and guide columns 106 with narrow tolerances. The fixedly articulated toggle legs 228, 228 'are extended beyond their hinge points 126, 126' to tooth segments 151, 151 'or angled and widened, the tooth segments 151, 151' ensuring synchronization even when the cylinders 101, 101 'With hydraulic medium supplying, from a control valve PV (e.g. a proportional valve) control line 60 should have slight non-uniformities or would be partially blocked.

As shown, the control line 60 opens into the cylinders 101, 101 'on the side facing away from the piston rod 404 or 404', but control would also be possible on the opposite side or on both sides. A connection for a pressure accumulator 200 is provided on the other side.

A balance weight 31, which is practically indispensable in high-frequency punching presses with a stroke frequency of approximately 400 strokes / min, can be attached to the extensions of the legs 228, 228 ', i.e. So be attached to the segments 151, 151 ', conveniently via the handlebars 37, 37', similar to the case in Fig. 4. or 5 with the upwardly extending extensions of the fixed articulated legs of the toggle lever.

The control valve PV can be of a type known per se and there are numerous valves for such purposes on the market. Not only can this be an even, wobble-free one Achieve motion sequence, but it can also be varied by varying the inflow amount of hydraulic medium during the stroke, so as to obtain a desired overall characteristic of the movement. This is particularly important if smooth punch-cut edges are to be achieved, for which numerous coupling gears have been proposed in fine punching technology, which are not required in the drive design shown.

It has been pointed out several times above that certain disadvantages of flywheels, which are usually provided in punching machines, in order to provide the necessary energy for the punch cut. The flywheels were always justified by the fact that the drives can be kept small. The application of the principle according to the invention saves the flywheels without having to oversize the drive, which - because of the mass involved - would have disadvantages with regard to the maximum acceleration of this mass to be achieved. Fig. 4 and 5 illustrate how fluidic energy storage 201, 201 'can still be used for this purpose, which on the one hand can be easily formed with a small mass, on the other hand do not require a clutch.

The pressure accumulators 201, 201 'have in the usual way compressed gas-filled cylinder spaces 61 and 62 (Fig. 4). The gas is compressed in rooms 61 and expanded in rooms 62 when the pistons of drives 101, 101 'move from the center into the interior of the machine. The compressed gas then drives the toggle levers or the tool carrier 5 again when relaxing in the opposite direction.

The use of such energy storage 201, 201 'is not limited to the arrangement of fluid drives or linear drives; rather, they can also be used with advantage in general for rotary drives, ie both for drives according to the previously discussed embodiments, as well as with any rotary drives. Such energy stores are particularly recommended for a linear drive.

With rotating drives, it is therefore advantageous to use an electric motor that operates in so-called four-quadrant operation.

It should also be mentioned that the counterweight 31 is only shown symbolically here and, of course, could of course be arranged as desired.

The above-described more favorable arrangement of two pressure accumulators 201, 201 'can be seen from Fig. 5, since it is preferred if the drive is moved in the middle between the two toggle levers 129, 129', in order to obtain a more compact structure. 5, the two pressure accumulators 201, 201 'serve during the lifting movement as a drive for accelerating the masses and for absorbing braking energy after punching until the tool carrier 5 stops; but also a control drive in the form of a cylinder-piston drive 301 is provided, which is arranged between the two toggle levers 129, 129 '. Its task is to reverse the piston movement at pre-selected stops, i.e. to determine the stroke by suitable control. This drive 301 has only a single piston rod 704, but two rods 604, 604 'are mechanically coupled by a pivot pin 63, so that a synchronous drive of the toothed segments 151, 151' is secured from this side. The toothed segments 151, 151 'here also ensure the synchronous movement during the stroke movement supported by the pressure accumulators 201, 201'.

The top dead center is preferably reached by pivoting the toggle levers to the left and right from the extended position (bottom dead center).

Numerous combinations of the described features with one another and with features according to the prior art are possible within the scope of the invention; since each tool carrier is generally rectangular in plan view, instead of two toggle levers, four of them can be provided, for example, which each engage one corner of the rectangle or in the area thereof. Furthermore, it is also possible in the case of FIGS. 3 to 5 to provide arc-shaped cross-head guides instead of the straight guides. Theoretically, a horizontal arrangement of the guide columns 6 would also be conceivable, which is why the terms “above” or “below” used in the description are only of relative importance and relate only to the examples, especially since an inverted arrangement would also be possible.

Of course, the step circuit shown in Fig. 1 is only an example. Alternatively, incremental encoders can be attached to the respective shaft and used to form a feedback signal. Another possibility is to use hydraulic motors for the reciprocating drive, the work force of the tool holder also being able to be set by adjusting the pressure. Likewise, the current supplied to the electric motors can be adjustable to adjust the work force.

Claims (11)

1. A press drive for two tool supports (5, 7) which are displaceable relative to one another, at least one of which can be driven by means of at least two toggle levers (29, 29′; 129, 129′; 229, 229′), each having two dead centers, to which toggle levers (29, 29′; 129, 129′; 229, 229′) drive energy can be transmitted from one drive energy carrier in each case by means of at least one rod (4; 104, 104′; 404, 404′; 504, 504′; 604, 604′; 704), one dead center of the toggle levers (29, 29′; 129, 129′; 229, 229′) determining the closest approach of the two tool supports (5, 7) which are displaceable relative to one another the toggle levers (29, 29′; 129, 129′; 229, 229′) bending in opposite directions, and the drive energy carriers being synchronized with one another via a synchronizing arrangement, wherein the drive energy carriers comprise an energy store formed by a four-quadrant operation system or by an accumulator which releases stored energy in order to accelerate the masses or removes energy from the energy supply and stores the braking energy during braking of the masses or feeds the energy back to the energy supply.

2. A drive as claimed in claim 1, wherein the drive energy carriers comprise a reciprocating drive (1; 101, 101′; 301).

3. A drive as claimed in claim 2, wherein each drive (1; 102) has a shaft which is rotatable by at least one, preferably two, limiting means (11 and S4, S5) alternately only in the one or other direction over a predetermined angular range (α) to both sides of the dead center corresponding to the closest approach of the tool supports (5, 7), the limiting means (11, and S4, S5) preferably being coordinated with an adjusting means (17 or 22), and the limiting means (11 or S4, S5), if required, having a braking means which is, in particular, electrical and/or mechanical.

4. A drive as claimed in claim 2 or 3, which is formed by at least one reversible - in particular synchronous or asynchronous  - electric motor (9) which has a rotor with a pulse-dependent position and a pulse generator (12) which is preferably coordinated with a reversal means (10) for the direction of rotation.

5. A drive as claimed in claim 4, wherein the pulse generator (12) has an adjusting means (17) for changing the number of pulses and preferably a counter (14), a time pulse generator (13) expediently being upcircuit of the said counter.

6. A drive as claimed in claim 4, wherein the reversal means (10) has a switching means for switching over the electric motor (9) to the generator mode to brake it, a selector (19) for optional rotation in only one direction over a full 360° in each case preferably being connected to the switching means.

7. A drive as claimed in claim 2 or 3, wherein at least one reversible hydraulic motor or a fluid, in particular, hydraulic cylinder/piston unit (101, 101′; 301) - coordinated with the accumulator (200; 201, 201′) - is provided, and is controlable by means of the least one valve arrangement (PV).

8. A drive as claimed in any of the preceding claims, wherein the drive energy carrier or the drive (101, 101′; 102; 301) is arranged in the middle between two toggle levers (29, 29′; 129, 129′; 229, 229′).

9. A drive as claimed in any of the preceding claims, wherein the knee hinge points of the two symmetrically arranged toggle levers (29, 29′) are guided by means of crossheads (25, 25′) which are engaged by the energy store.

10. A drive as claimed in any of the preceding claims, wherein the toggle levers (129, 129′; 229, 229′) are mounted essentially stationary in a region of a toggle lever limb (128, 128′; 228, 228′) and are connected to one of the two tool supports (5) via the free end of the other limb (127, 127′; 227, 227′), and at least one of the following features is realized:

a) The limb (128, 128′; 228, 228′) which is hinged in an essentially stationary position is extended beyond its stationary hinge point (126, 126′) and engages, expediently via a guide rod (37, 37′; 137, 137′), a balancing weight (31) which is movable along a linear guide, which in particular is vertical, for example a guide column (32);

b) The toggle lever limbs (228, 228′) which are mounted in a stationary position are connected to a common balancing weight (31), the centers of pressure (138, 138′) of the toggle levers (129, 129′; 229, 229′) being symmetrical with respect to the center of gravity of the said weight; and

c) The stationary bearing (126, 126′) and the drive energy carriers or drives (101, 101′; 301) are arranged on a common frame which is adjustable by an adjusting means for adjusting the closest approach of the two tool supports (5) - in their direction of movement.

11. A drive as claimed in any of the preceding claims, having rods (104, 104′) in the form of connecting rods on a rotary drive (102) and one or two crankshaft or crankshafts or eccentric shaft or eccentric shafts, wherein the rods (104, 104′) overlap one another, are axially offset and are arranged symmetrically with respect to a plane passing through the crankshaft or crankshafts or eccentric shaft or eccentric shafts of the rotary drive (102), the said rods preferably each being connected to that crankshaft or eccentric shaft which faces away from the particular toggle lever (29, 29′), and at least one of the said shafts, but in particular both, being directly in the form of a motor shaft or motor shafts preferably without a flywheel and expediently of a hydraulic or electric motor (9).

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