WO2009026893A1

WO2009026893A1 - Drive system for hydraulic presses

Info

Publication number: WO2009026893A1
Application number: PCT/DE2008/001388
Authority: WO
Inventors: Christian Wieber
Original assignee: Christian Wieber
Priority date: 2007-08-24
Filing date: 2008-08-21
Publication date: 2009-03-05
Also published as: DE102007040286A1; EP2183096A1

Abstract

The invention relates to a drive system for hydraulic presses, which allows constant and symmetrical prestressing of the press frame (1), said prestressing being independent of the required forming force, and thus precise guidance of the slide (2), wherein the drive (20) must only apply the energy in fact required for the forming operation. By rigidly coupling (19c) a plurality of movable separating elements (18a, 18b) having a common drive (20), through an appropriate association of the counter-acting cylinders (9a, 9b) with the hydraulic coupling device (17a, 17b) passive and force-neutral parallelism control of the slide (2) can be achieved, whereby for one the maximum slide tilt during eccentric load is limited, and secondly the force to be applied by the drive (20) furthermore is proportional to the forming force in fact required. If increased requirements are placed on the parallelism of the slide (2), said parallelism control may be superimposed by an active parallelism control (25, 26), which has high dynamics due to the low volume currents. Due to the prestressing of the press frame (1) being constant during the entire press stroke, elastic deformations are minimized, and furthermore, as a result of the constant pressure in the slide cylinder (6), the hydraulic medium volume enclosed therein has no influence on efficiency and cycle times. By minimizing the hydraulic fluid volumes enclosed in the counter-acting cylinders (9a, 9b) and the pressure chambers directly connected thereto, particularly during short working strokes high efficiency and short cycle times are achieved, and during cutting and stamping operations low cutting impact energy is achieved.

Description

Drive system for hydraulic presses

The invention relates to a drive system for hydraulic presses. These are versatile because of their usually large working stroke and the forming force available throughout the stroke, but also have a number of disadvantages. For example, presses are used with a large stroke for forming tasks that require only a short stroke, such as cutting or punching, so make the compressibility of the hydraulic fluid and the elastic deformation of the press frame negative impact, which must be required to build up the required forming force additionally required pressure fluid volume provided by the pump, thus increasing the cycle time. The case additionally required energy remains for the forming process mostly unused, the board cutting for example, this causes the so-called cutting shock with the known negative influences on tools and press, in other forming processes such as embossing this energy must be before opening the press by relaxing the located in the ram cylinder Volume of hydraulic fluid can be specifically reduced in order to avoid relaxation shocks in the hydraulic system of the press when opening, this leads to an additional increase in the cycle time and a reduction in efficiency. For these reasons, therefore, the production of parts requiring only a short stroke usually takes place either on special hydraulic cutting and punching presses, which have only a relatively short ram stroke and a correspondingly rigid frame, or on mechanical presses. In hydraulic cutting and punching presses, however, the available short ram stroke limits the available forming path, poor tool accessibility, and a limited range of tool installation height, and efficiency and cycle time is dependent on the effective height of the pressure fluid column in the ram cylinder and thus directly dependent on the installation height of the tool. Furthermore, conventional hydraulic presses can only accommodate off-center loads up to a certain limit, otherwise additional parallel control devices are required, but in most cases are not force-neutral and thus further reduce the efficiency of the presses. Another disadvantage of conventional hydraulic presses is the depending on the respective forming force constriction of the side stand, which is not constant over the ram stroke and thus precludes a precise and smooth leadership of the ram. This problem, which also exists in mechanical presses, can only be countered by a correspondingly rigid and thus heavy press frame or by guide elements in the tools. From DE 196 43 396 Al a hydraulic control device is known in which the plunger are assigned counter-holding cylinder, which are connected to the working cylinder via a pressure medium line and in the fast closing and opening movements of the plunger, the prestressed pressure medium between these two pressure chambers and a Pressure accumulator is replaced, while the implementation of the Umformhubes this connection is canceled and the pressure chambers of the counter-holding cylinders are relieved in the tank, whereby the required forming force is generated. Although the effective compression volume is reduced here during short strokes, it is disadvantageous that the energy required for the forming stroke does not depend on the actual forming force required, but on the level of the prestressing pressure, this must therefore be adapted to the respectively required forming force to optimize the efficiency be, on the one hand requires a complex hydraulic system, on the other hand, no constant bias of the press frame allowed. Furthermore, this device has a low efficiency, especially when changing over the working stroke forming forces and off-center loads, the unused energy is supplied to the hydraulic fluid as heat energy.

From BE 10 16 706 A, a parallel control device is further known in the Gegenhaltezlinder are connected to the pressure chambers of two rigidly connected Gleichgangzylinder, whereby in this way in conjunction with a servo valve, a parallel movement of the plunger is achieved.

From DE 10 2006 039 463 Al a device for cutting impact damping on mechanical presses is also known, in which the plunger is supported at the beginning of the material tear on the piston rods of a hydraulic system. However, this device must first be set manually before the tool is put into operation; furthermore, with increasing wear on the tool, it may become necessary for the device to be readjusted. Furthermore, the use of this device on conventionally driven hydraulic presses would lead to an extension of the cycle time, since before opening the press in addition to the pressure fluid in the plunger cylinder and the displaced in the device pressure fluid volume would be relaxed, the energy contained therein would thus during the decompression unused converted into heat. In addition, this device ensures no constant bias of the press frame, both when used on mechanical presses and on hydraulic presses thus subject to the press frame during the stroke elastic deformations. The invention is based on the object to provide a drive system for hydraulic presses, which allows independent of the particular forming force constant bias of the press frame and thus precise guidance of the plunger, independent of the respective forming force high efficiency especially for short strokes offers , a force-neutral parallel control allows a high eccentric loading of the plunger allows, and in addition has a significantly reduced cutting energy. With appropriate design equipped with this drive system presses offer compared to prior art hydraulic presses thus a universal applicability for a variety of forming processes, reduced wear and good accessibility of the tools, reduced energy consumption and increased output, especially in short-stroke forming processes. It can be dispensed with a particularly rigid design of the press frame, which in addition material can be saved.

This object is achieved by the method described in claim 1

Drive system solved. In this case, at least serving for generating the closing force pressure chambers of the plunger or cylinder for operation with the drive system according to the invention during the entire stroke and during several successive strokes with a constant or at least approximately constant pressure is applied. The closing force generated by the pressure is at least as large as the required forming force, to simplify the hydraulic system and to ensure a constant bias of the press frame, this force should preferably be kept at a constant value, which usually corresponds to the Pressennennkraft.

In the press frame, in the tool installation space or in the tool itself, there is one or more counter-holding cylinders, the effective direction of which is opposite to the closing force acting on the ram. The transmission of the counter-holding forces on the plunger can be done, for example, by corresponding pressure-resistant force-transmitting components that allow easy replacement or by force and / or positive-acting adjustment adjustment to the respective tool installation height, by acting directly on the plunger piston rods of the counter-holding cylinder or, in the event that the counter-holding cylinders are an integral part of the tool, through the upper tool connected to them. - A -

Furthermore, the drive system according to the invention has at least one hydraulic coupling device, which has two pressure chambers which are separated from one another as free of leakage as possible, at least by a movable separating element. In addition, the hydraulic coupling device has at least one device for introducing an external force, which allows a transmission of this force to the movable separating elements or the. A pressure chamber of the hydraulic coupling device is connected to the pressurized space or chambers of the ram cylinder subjected to constant pressure, while the other pressure chamber is connected to the pressure space or chambers of the counter-holding cylinder or cylinders. Depending on the two the pressure chambers of the hydraulic coupling device associated active surfaces of the movable separating elements and of the in the

Pressure chambers prevailing pressures thus act two forces or force components on the one or more separators, and thus also on the associated device for introducing an external force. The respective pressure chambers do not necessarily have to be directly connected with each other here, this connection can also be indirectly, e.g. via additional pressure booster. This can e.g. be advantageous if the counter-holding cylinders are an integral part of the tool and they are to be operated to reduce the size of a higher pressure than the plunger cylinder, the pressure booster allow this the use of hydraulic coupling devices in which the movable separating element has the same effective areas for both pressure chambers.

For ease of explanation, it should be assumed here that only a hydraulic coupling device with a movable separating element is present and the press has a tappet cylinder and four located in the corner regions of the press bed counter holding cylinder, the effective area of the plunger cylinder and the sum of the effective areas of the counter holding cylinder the same size are, so these cause the same size but oppositely acting closing and Gegenhaltekräften pressures in the two pressure chambers of the hydraulic coupling device, and the pressure chambers of the cylinder are connected directly to the corresponding pressure chambers of the hydraulic coupling device. Furthermore, it should be assumed that the two pressure chambers of the hydraulic coupling device associated active surfaces of the movable separating element are the same size, and thus act at the same pressures in the two pressure chambers of the hydraulic coupling device equal but oppositely acting forces or force components on the movable partition. The assumptions made here are not absolutely necessary for the operation of the drive system according to the invention, a change in the Area ratios can definitely lead to desired effects, this will be discussed in more detail in the description of the embodiments.

To initiate the operation by means of the drive system according to the invention, the press, if necessary, initially closed so far until the plunger rests on the piston rods or other components of the counter-holding cylinder, which may be made by appropriate means a mechanical and / or hydraulic adjustment to the installation height of the tool can. Subsequently, the pressure build-up takes place in the ram circle, whereby this pressure is kept constant or at least approximately constant by corresponding devices during a complete stroke as well as over several successive strokes. The closing force generated thereby by the plunger cylinder now also acts on the pistons of the counter-holding cylinder, neglecting friction, gravitational and deformation forces and with the same active surfaces of the pressure in the ram circle thus generates an equal pressure in the counter-holding cylinders. These two pressures now act on the two sides of the movable separating element, due to the equal pressures and effective surfaces, the resulting forces or force components cancel, so it is in terms of strength in equilibrium. If a force is introduced into the movable separating element via the device for introducing an external force, a resulting movement of the separating element leads to a corresponding change in volume in the connected pressure chambers. The pressure in the ram circle and thus the closing force acting on the plunger is kept at least approximately constant by the corresponding devices, while the pressure in the counter-holding cylinders and thus the counter-holding forces change correspondingly due to the compression or decompression of the pressure fluid in the counter-holding cylinders. As a result, closing force and counter-holding forces are no longer balanced and there is a resultant force on the plunger, the direction of which depends on the direction of the force acting on the movable separating element. If the resultant force acting on the plunger exceeds the required forces, such as frictional, gravitational, forming or stripping forces, the force introduced from the outside into the movable separating element causes a further movement of the separating element and thus, due to the associated change in volume the connected pressure chambers of plunger cylinder and counter-holding cylinders, a movement of the plunger. For the case assumed here that the movable separating element has the same size effective areas in both pressure chambers and the effective areas of ram cylinder and counter-holding cylinders are also the same size is, apart from the pressure differences in the Counter-holding cylinders caused volume changes, the plunger circuit neither removed nor supplied pressurized fluid, whereby the design of the means for keeping constant the pressure in the ram circle simplified accordingly.

In this case, there is a hydraulic transmission ratio between the active surfaces of the movable separating element and the active surfaces of the counter-holding cylinder, thus, for example, with appropriate design of the active surfaces on the movable separating element acting small force at high lift generate a large force on the plunger with a correspondingly small stroke. The resultant force acting on the plunger depends only on the force introduced into the movable separating element and on the ratio of the active surfaces and is, assuming equal effective areas of plunger cylinder and counter-holding cylinders and neglecting the frictional forces occurring at the seals of the pressure in the Ram circle independent.

If the pressure fluid volume existing in the counter-holding cylinders and the associated pressure chambers is reduced to the extent that it is sufficient for the required working stroke, a very low compression volume and thus high efficiency and short cycle times result, in particular with short work strokes. Due to the constant pressure in the ram circle and the constant closing force of the ram cylinder generated thereby elastic deformations of the press frame during the press stroke are largely excluded, continue to exist in the ram cylinder, under constant pressure pressure fluid volume has no effect on efficiency and cycle time. As a result, presses with a large ram stroke and a low rigidity of the press frame, such as e.g. Conventional deep-drawing presses, when operating by means of the drive system according to the invention highly efficient for short-stroke forming processes such. to be used for board cutting.

Further advantageous embodiments of the drive system according to the invention will become apparent from the dependent claims claim 1. The invention is explained in more detail below with reference to the attached schematic drawings:

Fig. 1 shows an embodiment of the drive system in which the required force is hydraulically generated on the movable separating elements and which enables a force-neutral parallel control of the plunger;

Fig. 2 shows an exemplary embodiment of the drive system in which the force required on the movable separating elements is mechanically and / or hydraulically generated and in which the plunger movement can be effected by the superposition of the movements of multiple drives; Fig. 3 shows an embodiment of the drive system in which the required force is hydraulically generated on the movable separating elements, the press is used for deep drawing in return method and while the force introduced by the drawing punch in the plunger force can be at least partially compensated by the movable separating elements; Fig. 4 shows an embodiment of the drive system which is designed for large working strokes and also allows fast closing and opening movements of the plunger without the need for movement of the movable separating elements is required; Fig. 5 shows an embodiment of the drive system which is very efficient especially in the operation of cutting tools and also can easily be retrofitted to existing, single or multiple acting conventional hydraulic presses.

In the following descriptions, the same or the same parts are provided with the same reference numerals for the sake of simplicity.

The illustrated in Fig. 1 hydraulic press consists of a press frame 1, a movably guided in this plunger 2 and connected to this, located in the press main double-acting plunger cylinder 6, the forces required for the closing and Öffhungsbewegung and the forming operation in conventional operation generated and introduced into the plunger 2, while the control of the plunger cylinder 6 via a conventional hydraulic press control 7 in conjunction with a main pump 8, this control is shown here greatly simplified. Due to the long working stroke, the press shown here is basically also suitable for forming processes with a long forming path, such as thermoforming, the here usually on universally applicable hydraulic presses existing auxiliary equipment such as pulling device, ejector, etc. are not shown here for reasons of clarity. For the initiation of the operation by means of the drive system according to the invention, the plunger 2 is first lowered by means of the conventional press control 7 until it is supported by the force-transmitting components 10 on the piston rods of the counter-holding cylinders 9, wherein these are here in the press bed and their piston rods by appropriate Cutouts in the press table 3 protrude. Preferably, there are four counter-holding cylinders 9 in the corner regions of the press table 3, wherein the two left and two right counter-holding cylinders 9a, 9b are connected as a group to one of the two hydraulic coupling devices 17a, 17b. Because of the cut, here are only two counter-holding cylinders 9a, 9b shown. An adaptation to different mounting heights of the forming tools 4 can be done here, for example, by simple replacement or force and / or positive acting adjustment of the force-transmitting components 10, corresponding devices are known, for example, for adjusting the cutting impact damping from conventional press construction.

After the conventional press control 7 is separated from the plunger cylinder 6, which is represented here by the locked center position, the opening of the differential lock valve 11 and the main shut-off valve 12 takes place. The operation of the ram cylinder 6 in differential circuit is for operation by means of the drive system according to the invention Although not absolutely necessary and causes a reduction in the effective area for generating the closing force, but this has the advantage of rapid movements of the plunger. 2

Avoid cavitation damage to the seals of the annulus which could occur when the annulus side would be connected to the tank. After opening the check valves 11, 12, the pressure buildup now takes place in the ram 13 via the feed pump 14 and a pressure control device 15 shown here as a pressure relief valve, depending on the design of the pressure accumulator 16 holds this pressure even with changes in the compression volumes in the counter-holding cylinders 9 and 9 caused by pressure changes the associated pressure chambers, temperature changes, elastic deformations of components or otherwise caused volume fluctuations of the hydraulic fluid in the ram 13 largely constant, without this the ram 13 pressure fluid must be supplied or removed. The ruling in the ram 13 pressure now acts on the operated in differential circuit plunger cylinder 6, this initiates the closing force generated thereby on the plunger 2 connected to it. Furthermore, the closing force generated by the plunger cylinder 6 acts on the force-transmitting components 10 on the Piston rods of the counter-holding cylinder 9 shown here as a single-acting cylinder with spring return.

Both the pressure in the ram circle 13 and the pressures in the two groups of counter-holding cylinders 9a, 9b now also act on the two hydraulic coupling devices 17a, 17b connected to them. Here, these hydraulic coupling devices 17 consist of two flanged-parallel cylinders, which are connected via a common piston rod rigidly interconnected pistons same annular surfaces here as movable separating elements 18a, 18b, further serves the common piston rod as a device for the introduction of an external force 19c on the separating elements 18th In the embodiment shown here, the generation of external force on the movable separating elements 18 by a hydraulic drive cylinder 20, this is carried out here as Differentialzy cylinder and flanged directly to the two coupling devices 17 a, 17 b, resulting from the use of the common piston rod 19 c thus an advantageous, extremely compact and stiff drive unit. The control of the drive cylinder 20 via the control valve 21, the pressure fluid flow required for this is provided in the embodiment shown here by the already existing for the conventional operation of the press main pump 8 available.

For further explanation, the resting state with open forming tool 4 and locked control valve 21 for the drive cylinder 20 will now be considered first, frictional forces are neglected. Assuming that the introduction of force into the counter-holding cylinders 9 takes place symmetrically and the sum of the active surfaces of the existing counter-holding cylinders 9 is equal to the effective effective area of the ram cylinder 6, the pressure in the ram circle 13 and the closing force generated thereby by the ram cylinder 6 and introduced into the ram 2 causes Equally high pressures in the counter-holding cylinders 9. Furthermore, the gravitational force acts on the plunger 2 in the illustrated here upper piston press, this is additionally introduced via the force-transmitting components 10 in the counter-holding cylinder 9, whereby the pressure in the counter-holding cylinders 9 by a certain amount the pressure in the ram 13 increases. The pressures in the counter-holding cylinder 9 now act respectively on the left sides of the two pistons 18a, 18b, while the pressure in the ram circle 13 acts on the right sides. As a result of the higher pressure in the counter-holding cylinders 9 caused by the gravitational force, a resultant force thus results on the common piston rod 19c in the direction d1, this force acts via the common piston rod 19c also on the piston of the drive cylinder 20 and causes locked control valve 21 a corresponding pressure on the annulus side, which counteracts this force. For fast closing of the press, it is therefore sufficient first to relieve the annular space side of the drive cylinder 20 via the control valve 21 against the tank, the forces acting on the common piston rod 19c force moves them in the direction dl, by the resulting volume change in the connected pressure chambers moves Tappet 2 down until the gravitational force acting on him on the upper tool part 4a, 4b and lower tool part 4b is introduced into the press table 3, this case on the piston side of the drive cylinder 20 required hydraulic fluid volume can be removed via the unlockable Nachsaugventil 23 depressurized the tank. For a given ram stroke, the pressure fluid volumes removed by the movement of the movable separating elements 18 from the counter-holding cylinders 9 and supplied to the ram circle 13 correspond exactly to the product of the respectively connected active surfaces and this stroke, with the given design of the active surfaces of the ram cylinder 6, counter-holding cylinders 9 and movable Separating elements 18 is the pressure accumulator 16 thus removed at constant pressures neither pressure fluid nor supplied. If a force acting in the direction dl is exerted on the common piston rod 19c by corresponding activation of the control valve 21 by the drive cylinder 20, this force leads to an increase in volume and thus to a relaxation or pressure reduction of the pressure fluid in the counter-holding cylinders 9, the pressure accumulator 16 takes while the the

Plunger circuit supplied pressure fluid quantity and thus keeps the pressure in the ram circuit 13 at least approximately constant. Here, the height of the pressure difference depends on the active surfaces of the piston 18 and the force introduced by the drive cylinder 20, while the force exerted on the forming tool 4 and thus on the workpiece S force of the difference between the closing force and counter-holding force and thus the product of the generated pressure difference and the active surfaces of the counter-holding cylinder 9 depends. If the force exerted on the workpiece 5 now exceeds the required forming force, the force generated by the drive cylinder 20 shifts the common piston rod 19c further in the direction d1, and the plunger 2 carries out the working stroke. The retraction of the plunger 2 is now carried out by appropriate reversal of the control valve 21, by pressurizing the annular space side of the drive cylinder 20 generates this acting in the direction d2 force on the common piston rod 19c, resulting in a corresponding pressure increase in the counter-holding cylinders 9 against the pressure in the ram circle 13 for Episode has. Exceeds the resulting common force of the counter-holding cylinder 9, the sum of the generated by the plunger cylinder 6 Closing force, weight of the plunger 2, frictional forces and possibly required stripping forces of the forming tool 4, the common piston rod 19c moves further in the direction d2 and the opening stroke takes place.

It should again be noted that between the active surfaces of the movable separating elements 18 and the active surfaces of the counter-holding cylinder 9 is a hydraulic translation, thus, for example. a small force introduced from outside into the movable separating elements 18 with a large stroke produces a correspondingly large ram force with a short stroke. The force exerted on the forming tool 4 and thus on the workpiece 5 in this case depends only on the hydraulic Übersetzungsverhältniss and the force introduced into the movable separating elements 18 force, a regulation and limitation of the force exerted on the workpiece 5 force can thus via a corresponding control of Forces of the drive cylinder 20 take place, the pressure in the ram circle 13 and thus the closing force generated by the plunger cylinder 6 has no influence and can thus be kept at a constant, at least sufficiently high value for the forming process, causing the

Design of the hydraulic system significantly simplified and the press frame 1 is independent of the required forming independent constant bias. Furthermore, in the embodiment shown here, the ratio of closing force and retraction force of the plunger 2 and the achievable closing and opening speeds at given volume flow during operation by means of the invention

Drive system of the ratio of piston area and annular surface of the drive cylinder 20, these are thus independent of the area ratios of the plunger cylinder 6 and thus can be optimized according to the requirements of the forming process, so as e.g. for cutting tools to provide the necessary stripping forces, while driving the plunger via the conventional press control 7, e.g. during deep drawing, the available retraction force of the annular surface of the plunger cylinder 6 is dependent.

Another significant advantage of the embodiment shown here is the use of two hydraulic coupling devices 17a, 17b with rigid coupling and common drive 20 for generating the external force and the separate assignment of a group of counter-holding cylinders 9a, 9b to each of these hydraulic coupling devices 17, this arrangement ensures a largely parallel closing of the plunger 2 during the forming process. To explain the case to be considered, which is the point of application of the forming force from the ram center to the piston centers of the cylinder group 9a shifts and the forming tool 4, for example, a composite tool, while one-sided is driven to block, gravitational and frictional forces are neglected. The maximum forming force at this point is reached when the pressure in the counter-holding cylinders 9a drops to zero, due to the area ratios, this force is thus 50% of the closing force generated by the ram cylinder 2, the pressure acting in the counter-holding cylinders 9b corresponds to the pressure in the ram circle 13 there they do not have to generate a forming force. The maximum ram tilting, neglecting elastic deformations in the hydraulic coupling devices 17, force-transmitting components, etc., thus results from the distance between the two cylinder groups 9a, 9b and the difference in the compression height caused by the pressure difference in the two cylinder groups

Pressure fluid columns, by corresponding minimization of existing in the counter-holding cylinder 9 and the associated pressure chambers pressure fluid volumes thus the maximum ram tilt can be minimized. Compared with a drive system according to the invention with two separate hydraulic coupling devices 17 each with its own drives 20 in this case the compression volume of the drive cylinder 20 has no influence on the tappet tilting. Although reduced in this passive form of parallel control the available forming force with increasing eccentric load of the plunger 2, this requires the form of parallel control no measurement and control devices, control valves or hydraulic fluid supply, is extremely inexpensive, fast and efficient, it also ensures a symmetrical bias of the press frame independent of off-center loads. Furthermore, this form of parallel control operates force neutral, i. the force to be applied by the drive cylinder 20, regardless of the degree of off-center loading, continues to be proportional to the actual forming force required. For example, as in the example given above, the forming force to be applied by the counter-holding cylinders 9a is 50% and that of the

Counteracting cylinders 9b applied forming force 0% of the press nominal force, so the force acting on the movable partition member 18a pressure difference reaches its maximum value, while the acting on the movable partition member 18b pressure difference is zero. The applied by the drive cylinder 20 and introduced into the common piston rod 19c force is thus also only 50% of the force required to generate the press rating, resulting in optimum efficiency.

For applications in which the plunger tilt caused by the compressibility of the hydraulic fluid interferes with this passive form of parallel control, can These are additionally supported by an active parallel regulation. This is done in the embodiment shown here by a compensation cylinder 25 in conjunction with a control valve 26, the additionally required control device and Wegmesssysteme are not shown here for reasons of clarity. The compensation cylinder 25 here consists of two piston rod side fixedly interconnected differential cylinders with a common piston rod 25b, the two sealed annular spaces are each connected to a group of Gegenhaltezylindern 9a, 9b, while the two piston-side connections are guided to the corresponding terminals 26 of the control valve , If an off-center load now leads to different pressures in the groups of counter-holding cylinders 9a, 9b, the resulting different compression of the

Pressure fluid columns to a plunger tilt. The control electronics detects this ram tilting and compensates for the difference in volume caused by the pressure difference by a corresponding displacement of the piston 25a connected via the common piston rod 25b of the compensation cylinder 25. Decreases due to off-center loading e.g. the pressure in the two left counter-holding cylinders 9a, there is a displacement of the piston 25a in direction d2, the two right Gegenhaltezylindern 9b is thus supplied to a certain pressure fluid volume, while the two left Gegenhaltezylindern 9a at the same time a corresponding amount is removed, by the different pressure In the two groups of counter-holding cylinders 9a, 9b caused plunger tilt is thus compensated. The active parallel control must compensate only in the groups of counter-holding cylinders 9a, 9b and the associated pressure chambers caused by compression or decompression volume changes, with correspondingly low pressure fluid volumes thus only small compensation volumes are needed, creating a highly dynamic control is possible. The pressure fluid supply for the control valve 26 takes place in the embodiment shown here from the ram 13, by the large compression volume and the already existing pressure accumulator 16 this supports the dynamics of the control process, the feed pump 14 in this case consumes the consumed during the control process pressure fluid to the ram circuit 13 again ,

It is of course this that, with a corresponding number of hydraulic coupling devices 17, compensation devices 25, 26 and counter-holding cylinders 9 and a corresponding arrangement and assignment of the counter-holding cylinder 9, both the passive and the active parallel control can act in more than one plane. Particularly in the case of short-stroke forming processes, it is advantageous if the pressure fluid volumes present in the counter-holding cylinders 9 and the associated pressure chambers are reduced to a minimum, since a shorter cycle time and higher efficiency are achieved due to the reduced compression volumes. In the embodiment shown here, this is done by the common

Piston rod 19 is first moved through the drive cylinder 20 until it stops in direction d2. After opening the check valves 24, the pressure fluid present in the counter-holding cylinders 9 is now displaced into the tank by the force acting on the plunger 2 gravitational force or the spring return, until the pistons are at the bottom stop. Will now, with still open check valves 24, the common

Piston rod 19 as far as in the direction dl process by the drive cylinder 20, as is required for each required ram stroke, the required pressure fluid is sucked through the open check valves 24 from the tank, after closing the check valves 24 is thus a defined, for the required ram stroke just sufficient amount of pressure fluid in the counter-holding cylinders 9 and the associated pressure chambers. The required e.g. located on the drive cylinder 20 displacement sensor and the corresponding control device for controlling the control valve 21 are not shown here for reasons of clarity. Any necessary adaptation to different tool installation heights can be done by replacing or adjusting the force-transmitting components 10. It is also understood that the pressure fluid volumes in the pressure medium lines between the counter-holding cylinders 9 and the hydraulic coupling devices 17 should also be reduced to a minimum.

When operating cutting tools, the drive cylinder 20 can continue to be used for a controlled reduction of the cutting impact energy. Is brought as soon as possible after the material has broken off, for example, by corresponding, not shown, or acceleration sensors, the control valve 21 for the drive cylinder 20 in the locked center position, then increases as the displacement of the common piston rod 19 in the direction dl the pressure on the annulus side of Drive cylinder 20 except for the pressure set on the pressure relief valve 22, while at the same time the pressure drops on the piston side. By thus introduced into the common piston rod 19c, acting in the direction d2 force takes place corresponding to the area ratio increase in the pressure in the counter-holding cylinder 9 relative to the ram circle 13, the resulting Force in the opposite direction can now selectively brake the plunger 2, the energy released as heat energy is supplied to the hydraulic fluid. Here, the delay of the plunger movement of the height of the force difference between the closing force generated by the plunger cylinder 6 and the counter-holding force generated by the counter-holding cylinders 9, and thus by the increase in the pressure in the counter-holding cylinders 9 against the pressure in the ram circle 13 is dependent. It is thus advantageous to design both the hydraulic coupling devices 17, the counter-holding cylinders 9 and the drive cylinder 20 for an operating pressure which is as high as possible in relation to the pressure in the ram circle 13 in order to have as high a force as possible for selectively delaying the ram movement.

In the embodiment of the inventive drive system shown in Fig. 2, the generation of external force via a mechanical eccentric 28 and, as explained later, the actively operated Kraftbegrenzungszylinder 29. The eccentric 28 is shown here simplified, the other components such. Drive motor, flywheel, clutch and brake unit are not shown here for reasons of clarity, as well as the shown in Fig. 1 active parallel control 25, 26. The stationary mounted eccentric 28a is connected via the connecting rod 28b with the connecting rod 28c, this passes the caused by the rotational movement of the eccentric wheel movement via a crosshead 28d in the common piston rod 19c of the two hydraulic coupling devices 17a, 17b, which again consist of two flanged together Gleichzzylindern. The common housing of the two hydraulic coupling devices 17a, 17b is supported here also on the piston rod 29a of a double-acting, also fixedly mounted and here designed as a differential cylinder force limiting cylinder 29, whereby a common piston rod 19c axial displacement of the hydraulic coupling devices 17 is made possible. The movement of the common wheel caused by the eccentric wheel 28a

Piston rod 19c is now transmitted by the two associated movable separating elements 18 on the counter-holding cylinder 9 and thus on the plunger 2, the path-time diagram of the plunger movement, the energy available per stroke and the dependent on the position of the eccentric 28a on the plunger. 2 available power thus largely correspond to a mechanical eccentric press. By the hydraulic transmission ratio between the movable separating elements 18 and the counter-holding cylinders 9, a favorable ratio between the force generated by the eccentric 28 and the plunger 2 available force can be achieved in this case, designed for the case of the eccentric 28 for a large stroke at relatively small forces this can be designed according to cost Nevertheless, the hydraulic transmission ratio still allows a high forming force at a correspondingly shorter ram stroke.

In order to limit the deformation force introduced into the forming tool 4 and to protect the eccentric drive 28 against overloading, the force limiting cylinder 29 serves in this case.

Located in the associated directional control valve 32 in the middle position, the annular space side is connected to the tank, to limit the force this is thus operated here as a single-acting cylinder. The force introduced via the connecting rod 28c into the common piston rod 19c of the two hydraulic coupling devices 17a, 17b also acts on the common housing and, via the piston rod 29a connected thereto, on the pressure differences caused thereby at the movable separating elements 18a, 18b Piston of the force limiting cylinder 29. If this force exceeds the product of the piston surface and the pressure set on the pressure limiting valve 30, then the piston displaces the hydraulic fluid contained therein, and the piston rod 29a moves in the direction dl. If there is a further movement of the common piston rod 19c driven by the connecting rod 28c in the direction d1, then the pressure difference at the movable separating elements 18 and thus the force acting on the plunger 2 and thus on the workpiece 5 corresponding to the hydraulic transmission ratio to a constant value limited, further movement of the plunger 2 does not take place due to the lack of relative movement between the movable separating elements 18 and the housing of the hydraulic coupling device 17. Of course, it is also possible here prior to initiation of the stroke located on the piston side of the force limiting cylinder 29 pressure fluid via a corresponding hydraulic device to a certain pressure, so as to avoid the part of the eccentric 28 available stroke for compression in the Force limiting cylinder 29 located pressure fluid is needed. After the reversal of direction of the connecting rod 28c then takes place a movement of the common piston rod 19c in direction d2, by the force acting on the plunger 2 gravitational force now increases the pressure in the counter-holding cylinders 9 against the pressure in the ram circle 13, thereby acting on the housing of the hydraulic Coupling 17 a force in the direction d2. This force now acts via the piston rod 29a also on the piston of the force limiting cylinder 29, this is thereby moved in the direction d2 and can take, for example via a suction valve 31 pressure fluid from the tank. Reached the piston of the force limiting cylinder 29, the end position in the direction d2, so again finds a relative movement between the movable Separating elements 18 and the housings of the hydraulic coupling devices 17 instead, caused by the resulting volume changes in the connected pressure chambers thus Öfmungsbewegung the plunger 2 is initiated. The Kraftbegrenzungszylinder 29 must be designed only for the maximum force on the connecting rod 28c and the common piston rod 19c, this depends on the hydraulic Übersetzungsverhältniss between the movable separating elements 18 and the counter-holding cylinders 9, while in mechanical presses, these cylinders for the Pressennennkraft must be designed as moving parts in the drive train of the press and usually offer only a very limited stroke. In the embodiment of the drive system according to the invention shown here, the effect of the force limit can also be used particularly advantageous for certain forming processes, such as a displacement of the bottom dead center in the direction of the closed forming tool 4 can be achieved when embossing by adapting the force-transmitting components 10, thereby in the eccentric drive 28 shown here, the forming tool 4 are kept closed for a determinable time with a constant force. If in this case the piston side of the force limiting cylinder 29 connected to a corresponding biased pressure accumulator, not shown, the force applied during the closing phase by the eccentric 28 energy for displacement of the piston rod 29a in the direction dl this can be supplied again during the opening phase. Except by the force limiting cylinder 29 shown here, the limit of the

Eccentric drive 28 in the hydraulic coupling devices 17 introduced force also carried elsewhere, e.g. by mechanical friction clutches.

Furthermore, it is particularly advantageous in the embodiment shown here that can be completely dispensed both for the control of the ram stroke and for the passive parallel control on the use of hydraulic switching or proportional valves and corresponding control and regulating devices, thereby eliminating switching times and flow losses This embodiment of the drive system according to the invention can thus achieve high stroke rates with simultaneously high efficiency. If the eccentric drive 28 has a corresponding adjusting device for changing the eccentricity, then the ram stroke can be adapted to the respectively required working stroke, this being illustrated here by the connecting rods 28b and the connecting rod 28c shown by dashed lines. Can continue the position of one of the stationary bearings 27a, 27b by a corresponding, not shown adjusting in the axial direction to the common piston rod 19c be moved, it can be achieved via the check valves 24 an adjustment of the pressure in the holding cylinders 9 and the associated pressure chambers volume of the required ram stroke and thus in turn an increase in efficiency and a reduction of the incipient cutting energy.

Another advantage of Ausführungsbeipieles shown here is achieved in that the force limiting cylinder 29 is actively operated by driving the directional control valve 32, and thus practically takes over the function of the double-acting drive cylinder 20 of the exemplary embodiment of FIG. 1, in which case the introduction of the external force in the hydraulic coupling devices 17 but not via the common piston rod 19c, but via the interconnected housing of the hydraulic coupling devices 17 takes place. Thus, on the one hand, a superposition of the movements of eccentric 28 and force limiting cylinder 29 can be achieved, the function is similar to the known hybrid presses, with the difference that the hydraulic cylinder or the change of the movement characteristics, the power limit and the parallel control in the drive system according to the invention not on Tappet or in the drive train, and thus allow a simpler and more cost-effective design of the press. On the other hand, with appropriate control of the two drives 28, 29 also an optional drive of the plunger 2 take place, with a suitable design of the plunger stroke, the press can thus be used for example during operation on the conventional press control 7 for deep drawing, while in operation by means of the drive system according to the invention the ram drive either via the eccentric 28 with additional force limit, the eccentric 28 with superimposed movement of the actively operated force limiting cylinder 29 or, by setting the eccentric 28a, for example in the 180 ° position, can be done only on the actively operated force limiting cylinder 29. The stroke rate, stroke, ram kinematics as well as the force available on the plunger 2 can thus be optimally adapted to the particular forming task and enable maximum output with simultaneously high efficiency. It is also possible to replace the force limiting cylinder 29 by a second mechanical drive, whereby the plunger movement of the superimposed movement of these two drives corresponds, and thus, for example, a corresponding change in the ram kinematics or the ram stroke can be done. In addition to the eccentric drive 28 shown here, the required external force can also be introduced by other known from the mechanical press construction types of drive in the movable separating elements 18, for example by Articulated drives, toggle or modified toggle drives, etc., whereby the kinematics of the plunger movement can be optimized for the respective forming task.

Another advantage of the drive system according to the invention can be achieved in that the ratio of the active surfaces between plunger cylinder 6 and counter-holding cylinders 9 is changed. In the case of the upper-piston press shown here, in addition to the closing force, the gravitational force also acts on the plunger 2 and thus on the counter-holding cylinders 9, which leads to an increase in pressure in the pressure chambers of the counter-holding cylinders 9. As explained in the description of the exemplary embodiment according to FIG. 1, this leads to a force in the direction d 1 on the common piston rod 19 c, which was used there for rapid closing of the tappet 2 in the case of corresponding area ratios. However, if the effective surfaces of the counter-holding cylinders 9 are enlarged to such an extent that the pressure generated in the ram circle 13 by the closing force and the gravitational force corresponds to the pressure in the ram circle 13, then the forces on the movable separating elements 18 are compensated for the same active surfaces, a rapid closing movement takes place without initiation an external force no longer takes place, the plunger 2 remains in the open position without the eccentric 28 must initiate a force in the hydraulic coupling devices 17. If the common piston rod 19c is now displaced in the direction d1 by introduction of an external force, the counter-holding cylinders 9 due to the larger effective surfaces provide a larger exchange volume for the same path than required by the plunger cylinder 6, the excess amount of draining liquid supplied to the ram circuit 13 being discharged from the pressure accumulator 16 taken, with appropriate design holds this while the pressure around ram circle 13 continues to be at least approximately constant. If now the opening movement is initiated, the additional exchange volume required by the counter-holding cylinders 9 is again taken from the pressure accumulator 16, the gravitational force acting on the plunger 2 is thus compensated.

By a corresponding change in the effective surfaces of plunger cylinder 6 and counter-holding cylinders 9 can also be achieved that the plunger 2 assumes a preferred position in the absence of initiation of an external force in the hydraulic coupling devices 17. If, for example, the active surfaces of the counter-holding cylinders 9 are further increased, the movable separating elements 18 move in the absence of external force due to the internal forces caused by the pressure ratios in direction d2, the plunger 2 thus moves in the opening direction, the fully extended counter-holding cylinder 9 or in Direction d2 located on stop piston 18 limit this movement in Opening direction. Thus, for example, can be achieved that the plunger occupies a safe position in a malfunction of the drive 28. The above-mentioned effects can be achieved with the same active surfaces of plunger cylinder 6 and counter-holding cylinders 9, also by a corresponding difference of the active surfaces of the movable separating elements 18, which is particularly apparent from Fig. 5.

Fig. 3 illustrates a further advantageous embodiment of the drive system according to the invention. This press shown here is equipped with a forming tool 4 for the combined cutting-train process, the drawing die 4c serves as a cutting punch, while the lower die 4a the function of cutting die and Sheet holder takes over. in the

Press bed is the drawing device 33, which is shown here as a differential cylinder, which is connected via the piston rod with the drawing punch 34, the control via the associated directional control valve 35, the auxiliary devices shown in the other embodiments, such as active parallel control 25, 26, check valves 24 for the counter-holding cylinder 9, etc. are not shown here for reasons of clarity, but an additional hydraulic device for cutting impact damping, consisting of the two creeper valves 37 for flow limitation and the associated pressure relief valves 38. In the off state, the creep valves 37 allow free flow in both Directions and have no influence on the operation. But if these, e.g. before the initiation of the cutting process, so they limit regardless of the pressure difference, the flow from the counter-holding cylinders 9 to the hydraulic coupling devices 17 to the set value, which should be as close to the required for the corresponding cutting speed flow rate. Now finds the material tear instead, the difference between closing force and counter-holding force leads to an acceleration of the plunger 2 and thus to an increase in the

Volume flow from the counter-holding cylinders 9 to the hydraulic coupling devices 17. Due to the flow limitation by the creep valves 37 now increases the pressure in the counter-holding cylinders 9 up to the value set at the pressure relief valves 38, this is above the pressure in the ram circle at the assumed here effective effective areas 13, the opposing force exceeds the closing force, and the plunger 2 is braked controlled until the volume flow caused by the plunger speed again falls below the value set at the slow speed valves 37. Here, in the hydraulic coupling devices 17 and in the pressure medium lines between the valves 37, 38 and the hydraulic coupling devices 17 existing pressure fluid volumes no Eiπfluss on the height of the cutting impact energy. In order to keep the effective compression volumes as low as possible, the valves 37, 38 should be connected via the shortest possible pressure medium lines with the counter-holding cylinders 9, preferably therefore each counter-holding cylinder 9 own valves 37, 38 are assigned, the pressure build-up in the counter-holding cylinders 9 and thus the delay of the plunger 2 thus happens almost immediately after the material is broken. Particularly advantageous is this type of cutting shock damping if after cutting further forming operations are to take place, such as here the deep drawing.

Furthermore, in the embodiment shown here, the piston-side pressure chamber of the pulling device 33 is connected to the annulus of the device for compensating the punching force 36, this is designed as a differential cylinder wherein the piston 36a is connected to the common piston rod 19c of the hydraulic coupling devices 17, the piston-side pressure chamber the device for compensating the punching force 36 is connected to the surrounding atmosphere and can therefore be neglected in terms of power.

As shown, the cutting operation by means of the counter-holding cylinders 9 has already taken place, the cut-out blank 5a is located between the drawing die 4c and the lower tool 4b serving as a blank holder. For ease of explanation, it is assumed here that the pistons 18a, 18b, 36a have the same annular surfaces, the sum of the active surfaces of the counter-holding cylinders 9 in the counter-holding direction equal to the effective area of the plunger cylinder 6 in the closing direction, as well as the effective surface of the pulling device 33 in the drawing direction equal Half of the effective surface of the plunger cylinder 6 in the closing direction. In the absence of external forces on the common piston rod 19, the pressure in the ram circle 13 now acts on the counter-holding cylinders 9 via the movable separating elements 18 and thus causes a counter-holding force of the same size, while the gravitational force acting on the ram 2 acts on the drawing die 4c and the round plate 5a in FIG the lower tool 4b and thus introduced into the press table 3. Now, if the drawing process is initiated by appropriate control of the directional control valve 35, the pulling device 33 moves the drawing punch 34 against the blank 5a, the forming forces occurring cause a corresponding increase in pressure in the piston-side pressure chamber of the pulling device 33. This pressure now also acts on the annular surface of the Piston 36a and thus generates in the common piston rod 19c a force in the direction dl which, in still missing introduction of an external force, a pressure drop in the counter-holding cylinder 9 and thus a reduction in the Holding force causes. If the pressure in the pulling device 33 caused by the drawing process increases, for example, to the value of the pressure in the ram circle 13, the pressure in the counter-holding cylinders 9 drops to half the pressure in the ram circle 13 at the given active surfaces, as a result of which the counter-holding force is exactly equal to that of the drawing device 33 generated stamping force is reduced. This results in the advantage of the

Drive cylinder 20 only has to generate the force required to produce the Blechhaltekräfte, the force introduced by the pulling device 33 in the plunger 2 force can be compensated by the force on the piston 36 a. This can also be achieved, for example, by enlarging the annular surface of the piston 36a, that the reduction in the counter-holding force caused by the pressure in the pulling device 33 is greater than the stamping force generated by the pulling device, characterized practicing the plunger 2 during the drawing process additionally one of Stamping force proportional sheet holding force on the blank 5a, without the introduction of an external force by the drive cylinder 20 is required here.

If the active parallel control 25, 26 shown in the exemplary embodiment according to FIG. 1 is furthermore used, this can be used to specifically change the pressures and thus the sheet holding forces in the individual groups of counter-holding cylinders 9a, 9b and thus, for example, the deep-drawing of asymmetrical To enable sharing. Due to the small compression volumes, rapid pressure changes are possible with small volume flows. The press shown here can thus, with a suitable design of the hydraulic control 35 for the pulling device 33 and the stroke of the ram cylinder 6, both for conventional deep drawing me passive die cushion, deep drawing in Gegenzugverfahren with active die cushion, deep drawing in the cutting-train process , as well as for the operation of cutting, punching, compounding, progressive tools, etc., ensuring in all applications high efficiency, high output and high flexibility in terms of permissible installation heights and good accessibility of the forming tools 4.

Fig. 4 shows an embodiment of the drive system according to the invention, which is also suitable for large forming paths and in which fast closing and / or opening movements of the plunger 2 can be done without the movement of the movable separating elements 18 is required for this purpose. The generation of the external force, in this case a torque, is effected here by two electric motors 39, wherein each motor is associated with a respective hydraulic coupling device 17a, 17b. The two coupling devices 17a, 17b exist here from two adjustable axial piston pumps for the closed circuit, the volume flow and conveying direction can be controlled by a corresponding adjustment. The movable separating elements 18 thus consist of the piston of the axial pump engines, not shown here, the introduction of external force on the separating elements via the introduced into the drive shafts 19 a, 19 b torque in conjunction with the swash plates, shoes, etc. also not shown here In this embodiment, the differential check valve 11, instead, this embodiment has a proportional control valve 40 for controlling the fast closing and opening movements, which takes place here via the annulus side of the plunger cylinder 6. Furthermore, this embodiment has two lock-up valves for the hydraulic coupling devices 42 which produce a direct connection between the ram circle 13 and the counter-holding cylinders 9 in the controlled state, and two pressure relief valves 41, which the maximum difference between the pressure in the ram circle 13 and the pressure in the Limit counter-holding cylinders 9.

For ease of explanation, equipped with the drive system according to the invention here press additionally shown cut vertically. The left side of section I shows the press in a wide open condition, as may be required for insertion or transfer operations. The lock-up valve 42 is opened here, whereby the pressure fluid between the ram circle 13 and the counter-holding cylinders 9 regardless of the hydraulic

Coupling devices 17 can be freely exchanged. At the same area ratios of plunger cylinder 6 and counter-holding cylinders 9, the forces generated by them are in equilibrium, which in addition to the plunger 2 and the parts connected to it such as upper tool 4a and piston rod and piston of the plunger cylinder 6 acting gravitational force generated at locked control valve 40, a pressure increase in the annular space of the plunger cylinder 6, the plunger 2 is thereby held in the open position. If the annular space side of the plunger cylinder 6 is now relieved via the control valve 40 to the tank, the gravitational force causes a circulation of the pressure fluid from the counter-holding cylinders 9 via the open lock-up valves 42 in the plunger cylinder 6, the rapid closing movement of the plunger takes place, the pressure accumulator 16 is neither

Pressure fluid taken still supplied. Shortly before reaching the starting position for the working stroke of the plunger 2 can then be braked by the control valve 40 to forming speed. Advantageously, in this case, the volume flow of the hydraulic Coupling devices 17 are already controlled to the desired forming speed, thus giving a smooth plunger movement when closing the lock-up valves 42nd

The right side II of the section now shows the position just before the start of the forming stroke, the lock-up valve 42 is already closed. The further closing movement of the plunger 2 is now carried out by the hydraulic coupling devices 17 which remove the counter-holding cylinders 9 hydraulic fluid and feed them to the ram circle. When placing the upper tool 4a on the workpiece 5 thereby drops the pressure in the counter-holding cylinders 9 so far until the required forming force is achieved and takes place by the further plunger movement of the forming process. During the forming process, the two meet

Pressure limiting valves 41 here two functions. On the one hand they limit the maximum pressure difference between ram circle 13 and counter-holding cylinders 9 and thus, regardless of the pressure in the ram circle 13, the maximum forming force, on the other hand they prevent cavitation in the axial piston pumps used here as hydraulic coupling 17 cavitation due to a low pressure in the counter-holding cylinders 9 occurs.

After the forming process, the opening of the press can be done in two ways. If greater forces are required for opening, e.g. due to existing Abstreifkräfte, first, the conveying direction of the hydraulic coupling devices 17 can be reversed, the opening force is generated by the resulting pressure increase in the counter-holding cylinders 9, after the stripping operation then the lock-up valves 42 are opened again and the rapid opening stroke takes place by the pressurization of the annulus side the plunger cylinder 6 via the control valve 40, the hydraulic fluid is thereby circulated again by the plunger cylinder 6 via the lock-up valves 42 in the counter-holding cylinder 9. If these forces are not required, the rapid opening movement can be initiated directly by opening the lock-up valves 42 and pressurizing the annular space side of the ram cylinder 6, in which case a reversal of the conveying direction of the hydraulic coupling devices 17 is not required.

In contrast to the previous embodiments, in which a passive parallel control of the plunger movement is achieved by the mechanical coupling of the hydraulic coupling devices 17, this takes place here purely actively via the electronic Regelvorrichrung 44 in conjunction with the two position sensors 43a, 43b and Adjustment of the two hydraulic coupling devices 17a, 17b, whereby the flow rate is controlled so that any plunger tilt is compensated. Since the torque required by the hydraulic coupling devices 17 consisting of axial piston pumps here is proportional to the product of the displacement volume and the pressure difference, the parallel control is again force-neutral and therefore offers optimum efficiency.

Further advantages of the embodiment shown here are, firstly, that the high volume flows occurring during the rapid closing and opening movements do not have to be conducted via the hydraulic coupling devices 17, these flow only in the bridging valves 42 and their connecting lines to the ram circle 13 and to the counter-holding cylinders 9. As a result, the pressure medium lines between the counter-holding cylinders 9 and the hydraulic coupling devices 17 and the hydraulic coupling devices themselves must be designed only for the volume flows occurring at maximum forming speed, thereby reducing the additional compression volumes accordingly. This is supported by the use of separate drives 39 for the two hydraulic coupling devices 17a, 17b, especially for presses with large table dimensions, the hydraulic coupling devices 17a, 17b can thus be positioned closer to the respective counter-holding cylinder or the groups of counter-holding cylinders 9a, 9b, which a further reduction of the compression volume leads. Furthermore, in this embodiment, the maximum available replacement volume of the hydraulic coupling devices 17 is not limited by the mechanical dimensions of the coupling devices, as e.g. when using hydraulic cylinders is the case. This allows a correspondingly compact construction of the hydraulic coupling devices 17, in particular for large forming paths, a conventional press control 7 can therefore be omitted in this embodiment, even when used for forming operations with a long stroke.

Of course, as hydraulic coupling devices 17, constant pumps, e.g. Gear pumps, to be used in conjunction with servomotors, wherein

Volumetric flow and conveying direction can be controlled by appropriate control of the servo motors and these can be used simultaneously for the compensation of leaks between the two pressure chambers of the hydraulic coupling device 17. Furthermore, there is the possibility, as already mentioned in the description of Fig.2, by appropriate Changing the area ratios between the plunger cylinder 6 and the counter-holding cylinders 9 to vary the forces generated thereby. For example, can be compensated by a corresponding increase in the effective surfaces of the counter-holding cylinder 9 on the movable masses, ie plunger 2, upper tool 4a and piston rod and piston of the plunger cylinder 6, acting gravitational forces, thus need only fast at closing and Öffhungsbewegungen the acceleration occurring Friction and flow forces are overcome, thereby, for example, the forces required for these movements can be generated by acting directly on the plunger 6 linear motors or similar drives.

Fig. 5 shows a further embodiment of the drive system according to the invention, which has a very high efficiency, especially when using cutting tools. The hydraulic coupling device 17 here consists of two stationary mounted single-acting differential cylinders, serving as movable separating elements piston 18a, 18b are firmly connected to each other by means of the piston rod 19. The generation of the external force is done here by a likewise fixedly mounted and designed as a servo motor electric drive 45, wherein the torque generated by it is introduced here via the pinion in the toothing serving here as means for introducing an external force piston rod 19 and so on corresponding force in the movable separating elements, that is, the two pistons 18a, 18b, is introduced, the limitation of the maximum forming force can thus be effected by a corresponding limitation of the torque of the servomotor 45. The generation and transmission of the force can of course be done differently, for example by means of a torque motor in conjunction with a ball screw and a corresponding nut. As in the embodiment of FIG. 4, the movable dividing elements 18 are here only on one side pressurized, the force balance is in this case via the piston rod 19. As in this embodiment can be easily seen by a corresponding change in the area ratios of the two pistons 18 a, 18b can be achieved, for example, the two of the pistons 18a, 18b generated and acting on the piston rod 19 forces cancel each other at different effective surfaces of plunger cylinder 6 and counter-holding cylinders 9 and the associated different pressures at the same closing and Gegenhaltekräften, an additional pressure booster is not needed in this case. The counter-holding cylinders 9 are in this embodiment an integral part of the tool, so are located between the upper tool 4a and lower tool 4b, preferably here again four counter-holding cylinder 9 to install in the corner regions of the tool. Since only one hydraulic coupling device 17 is present here, the passive parallel control is also omitted in this exemplary embodiment. Furthermore, there are in the pressure lines between the coupling device 17 and those associated with their counter-holding cylinders 9 each a burst safety valve 46 and, in parallel, depending a pilot-operated check valve 47, only two counter-holding cylinder 9 and two respective valves 46, 47 shown due to the section here , The burst safety valves 46 are set so that they just do not trigger at the desired forming speed, they can be bridged by controlling the pilot-operated check valves 47, which allows a fast closing of the tool 4 without a premature response of the pipe safety valves 46. In this case, the valves 46, 47 are to be arranged as close as possible to the respective counter-holding cylinders 9 in order to reduce the incipient cutting energy.

In the embodiment shown here, the press is just at the beginning of Umformhubes, the pilot-operated check valves 47 are closed, the servo motor 45 rotates clockwise, thus generating a force on the piston rod 19, which moves the two movable separating elements 18a, 18b in the direction d2 , The counter-holding cylinders 9 is thereby removed via the still open pipe safety valves 46 pressure fluid, the pressure difference thus generated reaches a sufficient value of the associated with the upper tool 4a cutting punch in the material. In the course of the cutting process, the material is now torn off, due to the force difference acting on the tappet 2, it is abruptly accelerated and the cutting stroke takes place. As a result of the abrupt acceleration of the plunger 2, the volume flows flowing through the bursting safety valves 46 abruptly increase, thereby closing them almost instantaneously. As a result of the plunger 2 accelerating in the closing direction, the pressure fluid enclosed in the counter-holding cylinders 9 is increasingly compressed until the sum of the closing and gravitational forces acting on the plunger 2 and the counter-holding forces generated by the counter-holding cylinders 9 are again in equilibrium, further acceleration of the plunger 9 Now no longer takes place, by correspondingly small compression volumes in the counter-holding cylinders 9 thus introduced into the plunger 2 cutting energy impact can be minimized. By moving further in the closing direction Plunger 2 is now the pressurized fluid in the counter-holding cylinders 9 further compressed, causing an increase of the counter-holding forces against the closing force and thus an increasing delay of the plunger movement. As a result of the increase in pressure in the counter-holding cylinders 9, the cutting impact energy introduced into the plunger 2 is reduced, the pressure in the counter-holding cylinders 9 reaches a maximum value at the end of the closing movement, then the plunger 2 is again in the opening direction due to the overpressure now prevailing in the counter-holding cylinders 9 accelerates until the forces acting on the plunger 2 closing and gravitational forces and the counter-forces generated by the pressure in the counter-holding cylinders 9 are in equilibrium again.

The maximum pressure occurring in the counter-holding cylinders 9 depends mainly on the pressure in the ram circle 13, the pressure difference required between the pressure in the ram circle 13 and the pressure in the counter-holding cylinders 9 and the response speed of the burst safety valves 46 to generate the forming force. In unfavorable cases, the occurring maximum pressure can exceed the operating pressure of the components acted upon therewith, that is to say counter-holding cylinders 9, burst-break safety valves 46 as well as unlockable check valves 47. To avoid this in the embodiment shown here each counter-holding cylinder 9 is assigned a respective differential cylinder 48, due to the sectional view here again only two differential cylinders 48 are shown. To reduce the occurring cutting impact energy, these are to be arranged as close as possible to the corresponding counter-holding cylinders 9. These serve in conjunction with the already existing pressure accumulator of the ram circle 16 as a pressure accumulator with pressure transmission function and could be replaced with the same function by appropriately biased pressure accumulator. The surfaces of the differential cylinders 48, ie the annular space surfaces A1 and the piston surfaces A2 are now designed according to the constant pressure in the ram circle p _s t and the maximum permissible pressure in the counter-holding cylinders 9 p _m ax, ie Al> (p _s t / Pmax) ^x A2 ,

In normal operation, the pistons of the differential cylinder 48 are at the stop in the direction dl and have no influence on the operation of the inventive drive system. However, if, due to a cutting stroke, an increase in the pressure exceeds the value calculated above, the pressure fluid is displaced from the counter-holding cylinders 9 into the two differential cylinders 48, with the pistons moving in the direction d2. The occurring in the counter-holding cylinders 9 maximum pressure is thus on a limited fixed value and the plunger 2 with a constant force further delayed. After the reduction of the cutting energy and the associated stoppage of the plunger 2, the pressure fluid from the differential cylinders 48 is now pushed back into the counter-holding cylinder 9 due to the prevailing pressure in the ram circle 13, whereby the opening movement of the plunger 2 is initiated. After the differential cylinders 48 have reached their stop in the direction dl again takes place, as described previously, a reduction in the pressure in the counter-holding cylinders 9 to closing and gravitational forces and counter-holding forces are back in equilibrium. The energy released in breaking down the cutting energy impact energy is therefore not converted into heat as in conventional hydraulic presses, but stored and reused to initiate the opening movement of the plunger 2, further adjustment of the cutting impact damping is not required here.

Furthermore, the combination of servo motor 45 and hydraulic coupling device 17 should be considered. To build up the required cutting force, the servomotor 45 first initiates a force in the direction d2 via the piston rod 19 into the two movable separating elements 18a, 18b. By the movement of the separating element 18b in the direction d2 thus takes place a decompression of the hydraulic fluid in the right pressure chamber of the hydraulic coupling device 17 and the associated counter-holding cylinders 9, for which a corresponding energy is needed. Now finds the cutting blow instead, so is on the

Pipe burst safety valves 46, the connection between the counter-holding cylinders 9 and the hydraulic coupling device 17 is suddenly blocked, which leads to a sudden increase in pressure in the counter-holding cylinders 9. By a suitable, not shown here device, the cut cut can now be detected and the servo motor are switched off, this can be done simply via a differential pressure measurement, the pressure in the counter-holding cylinders 9 exceeds the pressure in the right pressure chamber of the hydraulic coupling device 17 by a corresponding value , this means that the pipe burst safety valves 46 are closed and thus the cutting stroke is done. While the pressure in the ram circle 13 now acts on the piston 18a, the pressure acting on the piston 18b is lower by the pressure difference required to produce the cutting force, thus acting on the piston rod 19 in the direction d1. After switching off the servomotor 45, the two pistons 18a, 18b and the piston rod 19 connected to them are now accelerated in the direction d1, the energy previously required for the decompression of the pressurized fluid is thus, apart from the existing ones Frictional losses, reused for compression. After pressure equalization can now by appropriate control of the servo motor 45, a force in the direction dl are introduced into the piston rod 19, by the resulting pressure difference now pressure fluid from the hydraulic coupling device 17 is displaced in the counter-holding cylinder 9, resulting from the movement of the piston 18b Volumetric flow flows via the pilot-operated check valves 47 and via the reopening burst safety valves 46, the opening movement of the plunger 2 takes place.

The installation of the counter-holding cylinder 9 in the tool 4 offers two additional advantages in the embodiment shown here. For one, especially for small

Dimensions of the tool 4 relative to the dimensions of plunger 2 and press table 3, the deflection of plunger 2 and press table 3 is reduced, which leads to a further increase in the efficiency and shortening of the cycle times. On the other hand, with a corresponding modification of the hydraulics and control, the drive system according to the invention can be easily retrofitted to existing single or multiple-acting presses, without the need for modification on the press frame are necessary.

Also, other types of drive than shown in the embodiments illustrated herein may be used to generate the external force, e.g. Linear motors, in particular, the hydraulic transmission ratio between the movable separating elements 18 and the counter-holding cylinders 9 is advantageous, whereby e.g. acting on the movable separating elements 18 small forces at a large stroke can produce a large forming force at a correspondingly small stroke. Furthermore, the transfer of external force to the movable dividers 18 can not only be mechanical but also otherwise, e.g. magnetic or electromagnetic. The volume changes required for the plunger movement in the pressure chambers connected to the hydraulic coupling device 17 can also be achieved by an elastic deformation of the separating element 18, e.g. a pressure-resistant membrane can be achieved. Furthermore, there is the possibility that, with a sufficiently large volume of the pressure fluid in the ram circle or a low rigidity of the press frame and relatively small volumes of pressure fluid in the

Counter-holding cylinders, can be dispensed with the accumulator 16. In addition, the erfϊndungsgemäße drive system could in the presence of several plunger cylinder 6 also have a plurality of ram circuits 13, each ram circuit 13 with its own hydraulic Coupling device 17 could be connected. However, this has the disadvantage over the parallel connection of the plunger cylinders 6, which would also require a plurality of pressure accumulators 16.

The drive system according to the invention can also be operated instead of liquids with other pressure means, e.g. with gases or gas mixtures. A particularly advantageous embodiment results here, when the drive of the plunger cylinder 6 is pneumatic, which is in the counter-holding cylinders 9 and the associated pressure chambers pressure fluid is a liquid, and the generation of external force for the drive system according to the invention by a mechanical drive 28 according to In Fig. 2 illustrated embodiment takes place. With appropriate design of the plunger cylinder 6 is thus a large travel for the plunger 2 available, resulting in a good accessibility of the forming tools 4 and a large range for the allowable installation height. After completion of pressure build-up in the ram circle 13 no further pressure medium supply is now required during operation by means of the drive system according to the invention due to the hermetically sealed pressure chambers, the ram drive can be done alone by the mechanical drive 28 without this pneumatic valves are necessary, a hydraulic pump 8, 14 is also not needed. Due to the low compressibility of the hydraulic fluid in the counter-holding cylinders 9 and the associated pressure chambers, the press operates in a highly efficient manner and can be operated with high stroke rates. Furthermore, the passive parallel control described in the exemplary embodiment according to FIG.

The invention is not limited to the embodiments illustrated and described here, it also includes all expert embodiments within the scope of the current claim 1.

LIST OF REFERENCE NUMBERS

1 press frame

2 plungers 3 press table

4 forming tool

4a tool upper part

4b lower tool part

4c drawing die 5 workpiece

5a round plate

6 ram cylinders

7 conventional hydraulic press control (simplified)

8 Main pump 9 Counter-holding cylinder

9a counter-holding cylinder left

9b counter-holding cylinder on the right

10 force-transmitting component

11 Differential check valve Plunger cylinder 12 Main check valve Plunger cylinder

13 ram circle

14 Feed pump ram circle

15 Pressure control device ram circle

16 accumulator ram circle 17 hydraulic coupling device

17a hydraulic coupling device I

17b hydraulic coupling device II

18 movable partition 18a movable partition I 18b movable partition II

19 Device for introducing an external force

19a Device for introducing an external force I

19b Device for introducing an external force II

19c common device for introducing an external force 20 drive cylinders (hydraulic drive)

21 control valve drive cylinder

22 Pressure relief valve drive cylinder

23 unlockable suction valve drive cylinder 24 check valve counter hold cylinder

25 compensation cylinders

25a piston compensation cylinder

25b piston rod compensation cylinder

26 control valve compensating cylinder 27 fixed bearing

27a stationary bearing eccentric wheel

27b fixed bearing force limiting cylinder

28 Eccentric drive (mechanical drive) 28a Eccentric wheel 28b Connecting rod

28c connecting rod

28d crosshead

29 force limiting cylinder

29a Piston rod Force limiting cylinder 30 Pressure limiting valve Force limiting cylinder

31 Suction valve Force limiting cylinder

32 directional valve force limiting cylinder

33 pulling device

34 Drawing punch 35 Directional valve pulling device

36 Piston force compensation device 36a Piston

37 slow speed valve

38 pressure relief valve 39 electric motor (electric drive)

40 control valve for rapid traverse ram cylinder

41 Pressure relief valve hydraulic coupling device

42 lock-up valve hydraulic coupling device

43 Position sensor plunger a Positioner Plunger leftb Positioner Plunger right electronic control unit servomotor (electric drive) Pipe Break Safety Valve unlockable check valve Differential Cylinder

Claims

claims

1. Drive system for hydraulic presses with one or more plunger cylinders (6) for generating the required closing force, a connected thereto and in the press frame (1) movably guided plunger (2), and one or more in the press frame (1), in the tool installation space or in the tool (4) located counter-holding cylinders (9), the effective direction of the closing force of the plunger or cylinder (6) is directed opposite and the counter holding force is introduced directly or via corresponding means (4a, 10) in the plunger, characterized in that the pressure at least the surfaces acting in the closing direction of the plunger or cylinder (6) by means of suitable devices (16) during the entire Pressenzyklusses and between several consecutive press cycles is kept constant or at least approximately constant, at least acting in the closing direction pressure chambers of the plunger cylinder (6) and the in Gegenhalterich tion acting pressure chambers of the or the counter holding cylinder (9), directly or indirectly and individually or in groups, each with the two pressure chambers at least one hydraulic

Coupling device (17) are connected, this at least one movable separating element (18) for as leak-free separation of the different pressure chambers and at least one directly or indirectly connected to this device for introducing an external force (19), as well as by a corresponding drive (20 , 28, 39, 45) and acting on the means for introducing an external force (19) acts on the force acting on the movable separating elements or elements (18), this force acting on one of the effective surfaces of the movable separating element or elements (18 ) And the direction of action of the force corresponding pressure change in the counter-holding cylinders (9) and thus causes a change in the counter-holding force, and the respective difference between the force acting on the plunger (2) closing force and counter-holding force at least provides the forces required for the forming process, and a by internal and / or external forces caused movement tion of the movable separating elements (18) leads to a corresponding change in the pressure fluid volume in the connected pressure chambers of plunger cylinders (6) and counter-holding cylinders (9) and thus allows movement of the plunger (2).

2. Drive system according to claim 1, characterized in that by appropriate design of the active surfaces of the movable separating elements (18) on the one hand and the active surfaces of the counter-holding cylinder (9) on the other hand, the hydraulic transmission ratio and thus the ratio between the introduced into the hydraulic coupling devices (17) forces and the resulting pressure changes in the counter-holding cylinders (9) can be freely selected.

3. Drive system according to claim 1 or 2, characterized in that the hydraulic coupling devices (17) can be bridged by suitable valves (42), thereby a direct connection between counter-holding cylinders (9) and ram circle (13) is produced and thus at the initiation of a by an additional device (6, 40) generated force in the plunger (2) can be moved without this, the introduction of an external force in the hydraulic coupling devices (17) or a movement of the movable separating elements (18) is necessary.

4. Drive system according to one of the preceding claims, characterized in that by appropriate design of the active surfaces of plunger cylinder (6), counter-holding cylinders (9) and / or movable separating elements (18) is achieved in the absence of external forces on the movable separating elements (18) a difference between closing and holding force arises, and this difference in force either to at least partially

Compensation of the force acting on the plunger (2) acts gravitational forces or makes it possible that the plunger (2) assumes a preferred position in the absence of external forces on the movable separating elements (18).

5. Drive system according to one of the preceding claims, characterized in that in the counter-holding cylinders (9) and the associated pressure chambers located pressure fluid volumes by suitable devices (24), also in conjunction with mechanical adjusting devices (10), to those required for each Working volume necessary volumes can be adjusted and thus the effective compression volumes can be minimized.

6. Drive system according to one of the preceding claims, characterized in that at least two or more hydraulic coupling devices (17a, 17b) and their devices for introducing an external force (19c) with each other as well as with a common drive for generating the external force ( 20, 28), thereby synchronized the movement of the movable separating elements (18a, 18b) and thus the movement of the associated counter-holding cylinders (9a, 9b) or groups of counter-holding cylinders and thereby, with a corresponding arrangement of the counter-holding cylinders (9a, 9b ) in the press frame (1), the tilting of the plunger (2) can be limited due to eccentric load.

7. Drive system according to claim 6, characterized in that the pressure fluid volumes in the counter-holding cylinders (9a, 9b) or groups of counter-holding cylinders by suitable devices (25, 26) can be changed so that the resulting eccentric load by different compression of the hydraulic fluid tilting the plunger (2) can be compensated and / or the pressures and thus the forces generated by the individual counter-holding cylinders (9a, 9b) or groups of counter-holding cylinders can be selectively changed.

8. Drive system according to one of claims 1 to 5, characterized in that at least two hydraulic coupling devices (17a, 17b) are present, a tilting of the plunger

(2) is detected by appropriate control devices (44) in conjunction with suitable metrological devices (43a, 43b) and the control devices (44) in this way act on corresponding adjusting devices of the hydraulic coupling devices (17a, 17b) and / or their drives (39), the thereby, with a corresponding arrangement of the counter-holding cylinders (9a, 9b) in the press frame (1), a parallel closing of the plunger (2) is made possible.

9. Drive system according to one of the preceding claims, characterized in that by increasing the pressure in the counter-holding cylinders (9) an increase of the resulting counter-holding force against the on the plunger (2) acting closing force is achieved and thereby resulting force difference to the targeted Dismantling of the ram (2) initiated cutting impact energy is used.

10. Drive system according to claim 9, characterized in that by means of corresponding means (46, 48) at least a part of the plunger (2) introduced cutting energy impact can be reused to initiate the Öffhungsbewegung.

11. Drive system according to one of the preceding claims, characterized in that on the movable separating elements (18) acting external forces by suitable mechanical or electromechanically acting drives (28, 39, 45) are generated.

12. Drive system according to claim 11, characterized in that by suitable devices for force limiting (29) by the drives (28) generated and on the movable separating elements (18) acting forces and thus also in the workpiece (5) introduced force limits can be.

13. Drive system according to one of claims 1 to 10, characterized in that on the movable separating elements (18) acting external forces are generated by suitable hydraulically acting drives (20).

14. Drive system according to one of the preceding claims, characterized in that this is used in presses which have a hydraulic pulling device (33) which is suitable for the active Gegenzugverfahren, wherein the pulling direction in the pulling direction in the pulling device (33) to at least one suitable Acts to compensate for the punch force (36) which exerts a force corresponding to the pressure on the movable separating elements (18), this force leads to a corresponding reduction in pressure in the counter-holding cylinders (9) and thus, with a corresponding design of the effective surfaces of pulling device (33 ), Counter - holding cylinders (9), movable separating elements (18) and the

Device for compensating the stamping force (36), an at least partial compensation of the by the pulling device (33) via the drawing die (4c) in the plunger (2) introduced force is achieved.

15. Drive system according to one of the preceding claims, characterized in that the hydraulic coupling devices (17) consist of hydraulic cylinders.

16. Drive system according to one of the preceding claims, characterized in that on the hydraulic coupling devices (17) at least two, by separate drives (28, 29) generated forces can act, wherein the movement of the movable separating elements (18) and thus the resulting Movement of the plunger (2) either by appropriate selection of one of the drives (28, 29) or by the superposition of the movements of several of these drives (28, 29) can take place.

17. Drive system according to one of the preceding claims, characterized in that at least the pressure means used in the ram circle (13) is a gas or gas mixture.

18. Drive system according to one of claims 1 to 13, characterized in that the hydraulic coupling devices (17) consist of hydraulic pumps.

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