Press with a hydraulic drive device without an accumulator, and a method for operating a press with a hydraulic drive device

Abstract

In the case of an, in particular, pressure-accumulator-free hydraulic drive arrangement (10) for and comprising a consumer, in particular for presses, having a double action piston / cylinder arrangement (20) which comprises at least one reversibly movable operating piston (21) and at least one cylinder chamber, in which the at least one cylinder chamber or the cylinder chambers comprises / comprise at least one first piston chamber (23A) which loads the operating piston (21) with fluid pressure and possibly at least one second piston chamber (23C), having pressure lines (D1,…) which supply the piston chambers with a pressure medium, having at least one pump arrangement (30; 30A, 30B) which has at least one pump (31; 32) which is driven at least in a variable-speed manner and at least one variable-speed drive (33) which drives the at least one pump (31, 32), having at least one pressure medium supply which is connected or can be connected hydraulically to the piston / cylinder arrangement (20) and the pump arrangement (30; 30A, 30B), in which the at least one pump (31) is connected or can be connected to the first piston chamber (23A) via a first pressure line (D1), with the result that the hydraulic drive arrangement (10) can both be operated in at least one movement direction by means of a single one-motor drive train and achieves high operating pressures in the operation, an improved load of the drive motor and as far as possible also of its inverter is achieved by way of at least in each case one hydromechanic actuating cylinder (51; 51 A) which has at least one pump (32), a hydraulic connection / connecting line (D1') which is active between the actuating cylinder (51; 51 A) and the pressure line (D1) which is provided between the at least one pump (32) and the piston chamber (23A) which is assigned to it, and at least one hydraulic valve, in particular a proportional valve (50; 50A), wherein the at least one hydraulic valve is hydraulically active in the at least one connecting line (D1') between the actuating cylinder (51; 51 A) and the pressure line (D1) in such a way that the actuating cylinder (51; 51 A) can be loaded with a variable pressure by way of a variation of the position of said hydraulic valve by means of an external, in particular electric actuating signal which influences the position of the hydraulic valve.

Description

AREA OF INVENTION

[0001] The invention relates to a press with a hydraulic, in particular pressure-accumulator-free, drive arrangement having the features of the preamble of claim 1 and to a method for operating a press with a hydraulic drive arrangement having the features of the preamble of claim 5.

[0002] Accordingly, the invention relates to a hydraulic drive arrangement with at least one working piston and, optionally, a supplementary rapid traverse piston and, optionally, an annular return piston, particularly when it comprises a double-acting piston / cylinder arrangement comprising at least one reversibly movable working piston and at least one cylinder chamber, in which the at least one cylinder chamber or chambers comprise at least one (first) piston chamber pressurizing the working piston with fluid pressure and, preferably, at least one second piston chamber. The piston chambers can be supplied with a pressure medium via pressure lines. At least one pump arrangement is provided with at least one pump, preferably driven at least at variable speed, and with at least one drive, preferably also variable speed, driving the at least one pump.At least one hydraulically connected or connectable pressure medium tank can be provided with the piston / cylinder assembly and the pump assembly. The at least one pump can be connected or connectable to the first piston chamber via a first pressure line, so that the hydraulic drive assembly can be operated in both directions of movement by means of at least one single-motor drive train and, preferably, also achieves high operating pressures during operation. An adjustment device for the at least one pump with an actuating means for this pump can be provided, wherein the delivery flow of the at least one pump can be changed by means of the adjustment device actuated by the actuating means. The pressure-accumulator-free hydraulic drive assembly can include a third piston chamber supplementing the first piston chamber, which is supplied by a pressure line.The pump(s) supplying the piston chamber(s) with pressure medium can be driven or operated with variable speed and, if desired, also variable direction of rotation. TECHNOLOGICAL BACKGROUND

[0003] Variable-speed hydraulic drives, especially for large cylinders, are designed according to WO 2010 / 020427 or WO 2012 / 110259. The former uses two separate pump drive arrangements for the working stroke and the return stroke to save on large-volume pressure accumulators. The hydraulic cylinder can be equipped with an additional rapid traverse piston chamber. A disadvantage is the high construction cost for the two motor-pump stations. Particularly with large loads, the inverter controls and power supplies used for the motor drive are quite expensive. The large directional control valves for switching the pump flow from the rapid traverse piston to the large piston area are also costly.

[0004] The latter, based on WO2010 / 020427, is based on the concept of providing a direction-of-rotation variable pump arrangement consisting of a variable-speed motor with at least two pumps in a pressure-storage-free hydraulic drive arrangement with working piston, supplementary rapid traverse piston and ring-shaped return piston, and connecting the three cylinder (or piston) chambers individually and directly to the pumps via three pressure lines in such a way that rapid traverse takes place in both directions.

[0005] The servomotors and associated frequency converters currently used as drives are very expensive; reducing the drive torque would significantly lower the costs of using variable displacement pumps in variable-speed hydraulic drives. The variable displacement pumps implemented so far are based on an internal, usually purely hydromechanical, torque or pressure control of the flow rate. The adjustment mechanism (the adjustment system) of the variable displacement pump(s) for the piston and, if applicable, the annular space of the working cylinder is characterized by an actuating element in the form of a hydraulic cylinder with spring return. As the operating pressure of the variable displacement pump increases, the pump pivots forward against the spring and then pivots back, thus reducing the flow rate per pump revolution (displacement). The drive torque of the drive motor is proportional to the product of the hydraulic pressure and the displacement of the driven working piston.By appropriately selecting the spring characteristics, it is possible to keep the motor drive torque almost constant, independent of pressure, and to avoid exceeding the motor's rated torque. As the operating pressure of the (variable) pump increases, its flow rate is reduced to such an extent that the drive torque of its motor remains largely constant. Alternatively, an electric adjustment mechanism for the variable displacement pump is known.

[0006] It was further found that most applications of hydraulic drive systems require long rapid traverse distances with low load, while phases of high load constitute only a small proportion of the time. Examples of such processes include forming or straightening operations, where high process forces are required for less than 10 percent of the total cycle time. Improved utilization of the motor's available drive torque would therefore also be desirable. PRESENTATION OF THE INVENTION

[0007] The object of the invention is therefore to further develop a press of the generic type in such a way that the utilization of the drive motor and, if possible, also of its inverter can be improved.

[0008] To solve the problem, a press with the features of claim 1 and a method with the features of claim 5 are proposed. Accordingly, the invention, based on WO 2010 / 020427, is based on the method concept (claim 5) whereby, in a generic hydraulic drive arrangement, a change, in particular a reduction, in the delivery flow of the at least one pump caused by a hydromechanical pump control or adjustment is delayed by means of an externally controllable hydraulic drive device that superimposes the hydromechanical pump control or effects the pump adjustment until the drive torque of the motor is utilized to the desired extent.

[0009] The invention allows, among other things, the pump's flow rate to be adjusted over time to the current state of the motor or inverter. In particular, the motor's drive torque and the thermal or electrical limits of the motor or inverter can be utilized as desired. For example, a reduction in the pump's flow rate can be delayed until the thermal or electrical limits of the motor or inverter are fully utilized. A combination of drive arrangement and downstream valve controls can also be provided. Variable speed can be achieved with at least one asynchronous motor and at least one frequency converter. If desired, the pump's direction of rotation can be reversed without the motor itself having to reverse its direction.If desired, the swivel disc of the (axial piston) pump can also be rotated beyond the angle "0°", especially into the negative angle range, so that the (thread and pressure) connections of the pump each reverse their function.

[0010] According to a (first) implementation of the invention, in a known self-contained, purely hydromechanical control of the delivery flow of at least one pump, comprising a pump adjustment device, in particular a pivoting device, and a control piston for this purpose, it is provided that the input pressure of the control piston is changed superimposed by means of an electrically controlled proportional valve in such a way that, by varying the position of this hydraulic valve, the control piston of the pump adjustment device is subjected to a variable pressure by means of the electrical control signal.

[0011] The pump's adjustment system can therefore include a hydraulic cylinder, possibly with a (spring-loaded) return mechanism. As the operating pressure increases, the pump pivots against the return spring. During this forward and / or backward pivoting, the flow rate is changed with each pump revolution (displacement).

[0012] The use of the inventive flow control technology can be implemented with a wide variety of circuit concepts for variable-speed motor-pump combinations, such as with a single motor-pump station with one or more pumps, at least one of which has an adjustment according to the invention, or with several motor-pump stations, each with one or more pumps, wherein at least one motor-pump station has a flow control according to the invention.

[0013] Known variable-speed hydraulic drives have drive motors that can be subjected to significantly higher torque loads for short periods. For example, a torque four times higher can be accessed for approximately two seconds, and a 10 percent overrun is permissible for several minutes. These higher limits are determined by the thermal capacity of the motor windings and the power semiconductors of the inverter. The current I is a quadratic factor, while the duration t of the current is linear. The respective load spectrum is evaluated to assess the system's limits ("I 2 < t calculation"). This potential can be utilized simply and cost-effectively by the invention, whereas known hydraulic drives automatically limit the motor torque by adjusting the pump's oscillation, meaning that a higher torque can only be used to a limited extent, even briefly, without utilizing the full capacity of the inverter and motor.

[0014] Adjustable pump controllers according to the invention can be controlled directly by the frequency converter, for example, without additional control modules or sensors. The control should preferably be configured such that, based on the current utilization factor of the motor and drive determined by the frequency converter's internal I²<t calculation, the pump is operated at a high oscillation angle for as long as possible to optimize the utilization of the motor and frequency converter. The resulting increased flow rate allows for a significant reduction in the system cycle time or, alternatively, the selection of a smaller drive motor. Furthermore, it has been recognized that the aforementioned typical load profiles of a press, with their only briefly higher forces, allow for significantly higher torques to be applied during the work process if the subsequent rapid traverse and pauses for loading and unloading the system are used for cooling.

[0015] According to the invention, it can therefore be advantageous to use the current utilization rate as a control variable. Preferably, the utilization value of the motor and inverter is considered on the one hand, and on the other hand, the rate of change of this value is also taken into account. With a rapidly increasing utilization value, the adjustment of the pump, such as the swivel angle, is reduced relatively quickly to lower the motor torque, whereas with a slowly increasing utilization value, an adjustment can be made more slowly or even omitted entirely.

[0016] In addition to the utilization factor for the motor and drive, the invention allows the knowledge of the respective operating process of the entire system to be considered as a further control variable for adjusting the pump. For example, if it is known that a particularly high power demand will only be required for a short period, a high degree of adjustment, such as a large swivel angle, can be maintained even though the utilization factor indicates an imminent emergency shutdown.

[0017] In contrast, the variable-speed drives implemented according to the prior art, upon which the invention is based, rely—as already mentioned—solely on an internal, mostly purely hydromechanical control of the flow rate within the pump. As the pressure increases, the pump's flow rate is automatically reduced to such an extent that the motor's drive torque, which is proportional to the product of hydraulic pressure and displacement, remains largely constant. Thus, by appropriately selecting the spring characteristics, it was possible to keep the motor's drive torque almost constant regardless of pressure and to avoid exceeding the motor's rated torque. An example of such a hydromechanically torque-controlled pump is the Bosch Rexroth A4VSO-LR2. A characteristic feature of this known control system is that the adjustment is made internally within the pump and the frequency converter responsible for motion control has no influence on it.These self-contained, purely hydromechanical regulators could alternatively be designed, for example, to keep the operating pressure constant as the control variable for varying the displacement (pressure regulator). This was advantageous for the pump connected to the cylinder's annular space. Its sole function was to support the cylinder and any attached masses against gravity and to prevent cavitation of the pump connected to the annular space during upward movement.

[0018] In addition to these hydromechanical controllers, electrically controlled controllers are also currently available. For example, modern frequency converters can continuously monitor the load of the motor and the converter itself, and they automatically limit the current as soon as thermal limits are reached. The respective load level of the converter and motor can also be provided as a numerical value for the machine control system via an electrical interface. Controllers such as the DFE1 type are also available for the pump mentioned above, allowing the pump to be controlled by external signals for flow rate or pressure. These electrically controlled controllers require their own control electronics and have sensors for actual values ​​such as swivel angle and pressure. However, the additional components and costs of the control system significantly increase the pump's price.

[0019] In contrast, the invention offers, among other things, the following advantages: Improved utilization of motor and inverter; Lower purchase price due to the elimination of a separate pump control system and sensors for swivel angle and pressure; More favorable cycle times; Selection of energy-optimized operating points for motor and pump possible (poor efficiency at very low speeds); Increased machine safety: Targeted swiveling of the pumps to "0" reduces the risk of unintended movement; Possibly eliminating the need to reverse the motor's direction of rotation, especially by swiveling the pump beyond "0°".

[0020] The aforementioned components, as well as those claimed and described in the exemplary embodiments, to be used according to the invention are not subject to any special exceptional conditions with regard to their size, shape, material selection and technical conception, so that the selection criteria known in the field of application can be applied without restriction.

[0021] Further details, features and advantages of the subject matter of the invention will become apparent from the dependent claims, as well as from the following description of the associated drawing and table, in which - by way of example - an embodiment of a pressure-storage-free hydraulic drive arrangement is shown. FIGURE DESCRIPTION

[0022] The drawing shows: Fig. 1a (first) embodiment of a pressure-accumulator-free hydraulic drive arrangement with an external, in particular electrically controlled, drive device for influencing the position of a hydromechanical drive element (actuator) of the adjustment device of the at least one pump of the drive arrangement, wherein the drive device changes the position of the actuator to influence the delivery flow of the at least one pump by means of the working pressure of the drive arrangement in a hydraulically superimposed manner - as a block diagram; and Fig. 2a (second) embodiment of a pressure-storage-free hydraulic drive arrangement with an external, in particular electrically controlled, drive device for influencing the position of a hydromechanical drive element (actuating means) of the adjusting device of the at least one pump of the drive arrangement, wherein the drive device changes the position of the actuating means for influencing the delivery flow of the at least one pump by means of the working pressure of the drive arrangement hydraulically superimposed - as a block diagram; Fig. 3an alternative, non-inventive realization of a hydraulic drive arrangement with an external, in particular electrically controlled, drive device for influencing the position of a hydromechanical drive element (actuating means) of the adjusting device of the at least one pump of the drive arrangement, wherein the drive device hydraulically changes the position of the actuating means to influence the delivery flow of the at least one pump by means of the working pressure of a separate pump - as a block diagram; Fig. 4Another alternative, non-inventive realization of a hydraulic drive arrangement with an external, in particular electrically controlled, drive device for influencing the position of a mechanical drive element (actuating means) of the adjusting device of the at least one pump of the drive arrangement, wherein the drive device mechanically changes the position of the mechanical drive element to influence the delivery flow of the at least one pump by means of a drive means associated with the mechanical drive element - as a block diagram; Fig. 5 one compared to the further alternative realization according to Fig. 4 modified (second) embodiment - as a block diagram, Fig. 6 one compared to the further alternative realization according to Fig. 4 or 5 modified (third) embodiment - as a block diagram Fig. 7 one compared to the further alternative realization according to Fig. 4 ,5 or 6 modified (fourth) embodiment - as a block diagram. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0023] From the Figure 1A double-acting piston / cylinder assembly 20, comprising a working piston 21, a piston rod 22, and a cylinder chamber, is shown. The reversibly movable working piston 21 divides the cylinder chamber into a first piston chamber 23A (or working cylinder) and a second piston chamber 23C (or annular chamber or return cylinder) surrounding the piston rod 22. A rapid-travel piston, not shown in this or the subsequent figures, can be oriented in a direction opposite to the piston rod 22 or in the same direction as the piston rod. The piston / cylinder assembly 20 is connected to a first pressure line D1, which supplies the first piston chamber 23A with a pressure medium, and to an optional second pressure line D3, which supplies the optional annular chamber 23C with pressure medium.

[0024] A single drive 33, designed as a servo motor, drives a double pump in the form of two, in particular variable-speed, pumps 31, 32 on a single drive shaft 33A. Both pumps are each equipped with a device (50, 51, D1'; D3') for adjusting their delivery volume. The adjustment is effected, in particular internally within the pumps, by a control device (adjustment device 38; 38A, 38B), in particular in the form of actuating cylinders 51; 51A, 51B, which changes the delivery rate in a known manner according to the current operating pressure of the respective pump 31 or 32, which is applied to it via the connecting lines D1' or D3', e.g. by means of a pump pivoting mechanism 52.In addition, according to the invention, a hydraulically upstream adjusting device 50 (hydraulic valve) in the form of a proportional valve 50A, 50B is used for each pump, which reacts to hydraulic or, in particular, electrical control signals from an external controller, such as an inverter. This allows the pump flow rate to be hydraulically adjusted up to the maximum flow rate – superimposed on the operating pressure of the associated pump 31 and / or 32 – depending on an external input signal. The drive device 60 for this superimposed flow rate adjustment is accordingly hydromechanical in nature and comprises – in addition to the connecting lines D1' and D3' for supplying the hydraulic valves 50 with pressure fluid – the electrically adjustable hydraulic valves 50, which are controlled externally via signal lines 150A and 150B, respectively.The latter throttle - as described in more detail below - depending on the state of the drive 33 and / or the converter U, the fluid quantity for adjusting the delivery rate of the associated pump 31 or 32 by means of the hydromechanical drive element 51A or 51B.

[0025] In this embodiment, the pump 32 closest to the servomotor 33 is hydraulically connected to the piston chamber 23A, which serves as the working cylinder, and the other pump 31 is hydraulically connected to the opposite piston chamber 23C. Pumps 31 and 32 are fluidically connected on one side to a tank 40 and on the other side to the piston chamber 23A and the annular chamber 23C, respectively. The position sensor 36, installed on the piston rod 22, transmits the current piston position to a frequency converter U, which supplies the drive 33 with electrical voltage.

[0026] A mechanical gearbox 37, if present, for torque transmission from the drive 33, as also shown as an option in the other figures, is assigned to both pumps of the same drive train, in particular to allow the use of motors with relatively higher speeds compared to the pumps. It is also helpful if the pump arrangement includes a brake, especially to facilitate operation without a switching valve. The following working methods / structures are preferred: A) Pump, in particular swivel angle adjustment system

[0027] Based on the hydraulic drive system according to WO 2012 / 110259, at least one hydraulic valve, in particular a proportional valve 50A or 50B, is hydraulically connected in or, for example, at the ends of at least one connecting line D1', D3'. The at least one connecting line D1', D3' is provided between the actuator(s) 51A or 51B assigned to at least one of the pumps 32 or 31 and the pressure lines D1 or D3 of the pumps 32 or 31. The actuators 51A or 51B can be integrated into their respective assigned pumps 32 or 31. By varying the piston position of these hydraulic valves, the actuators 51A or 51B can be pressurized with a variable pressure, which can be adjusted from 0 to the applied pump pressure. This allows the respective pump to be adjusted externally via the proportional valves 50A and 50B, in particular with one control signal each, e.g. electrical.For controlling the two hydraulic / proportional valves, freely programmable control systems, which are standard in currently available frequency converters, can be used. The control algorithm can access all system parameters of the drive (e.g., motor load, motor temperature, plunger position, torque, and motor speed) to optimize control of the pump adjustment, especially the pump swashplate angle. The position sensors, particularly the swashplate angle, and pressure sensors found in conventional controllers can be omitted because the swashplate angle and system pressure can be indirectly calculated using the current signals from the cylinder position sensor, the internally available values ​​for motor current and speed, and, if required, a computational model of the pump behavior.Furthermore, it becomes possible, and therefore preferable, to install the pump below the oil level in a space-saving and noise-dampening manner, without maintenance problems.

[0028] The pump 32 connected to the piston chamber 23A is only adjusted, in particular pivoted back, when the load level of the motor 33 requires it. The pump 31 connected to the annular chamber 23C is pivoted, for example, so that the annular chamber pressure is approximately 20 bar to compensate for gravity.

[0029] For controlling the two proportional valves, freely programmable systems, which are standard features in currently available frequency converters, can be used. The control algorithm can, in particular, access all system parameters of the drive 33 (e.g., motor load, motor temperature, plunger position, torque, and motor speed) to use them for optimal control of the pump position, especially the pump swashplate angle.

[0030] For the ExitThe piston rod 22, attached to the working piston 21, moves at rapid traverse speed, and when the servomotor 33 rotates, pump 32 delivers oil into the piston chamber 23A. Simultaneously, pump 31 draws oil from the annular chamber 23C. The oil flow required to fill the piston chamber 23A, which serves as the working cylinder, can be drawn from the tank 40. Pump 31 is driven, for example, by the servomotor 33 via the common shaft 33A to pump 32, at the same speed as pump 32 but in the opposite direction of rotation. The delivery flow is preferably adjusted to the maximum via the adjusting device of each pump. This occurs at a comparatively low pump pressure.

[0031] For the Switch to operating speed The pump 32 fills the large piston chamber 23A on its own. The delivery volume of the pump 32 is reduced, optionally depending on the pressure or with the superimposed assistance of the proportional valve 50A, which is controlled via the inverter, to a predefinable value.

[0032] The positioning process is carried out in the usual way by stopping the servomotor 33.

[0033] For the Decompress The direction of rotation of the servomotor 33 is reversed. The pressurized oil drives the servomotor, which now acts as a generator. The resulting electrical energy can be fed back into the electrical grid.

[0034] For the Upward journey If a filling valve is opened, the reversed pump 31 now pumps into the annular space 23C of the piston / cylinder assembly 20, causing the piston rod 22 to retract at rapid traverse speed. Additionally, the pump 32 draws the oil from the piston chamber 23A. The pump 31 is preferably operated at full flow to assist any switchable filling valve during the emptying of the working cylinder. B) Pump control, in particular swivel angle control, according to drive load

[0035] This involves considering both the load value of the motor and inverter, and the rate of change of this value. With a rapidly increasing load value, the swivel angle must be reduced relatively quickly to lower the motor torque, whereas with a slowly increasing load value, adjustments can be made more slowly or even omitted entirely. C) Optimized pump control, especially swivel angle control, based on process data

[0036] An additional method for controlling the pump's position, particularly its swivel angle, is possible when the actual process sequence for the individual work cycles of the entire system repeats itself in a very similar form with regard to the force-velocity profile. This is the case, for example, with forming or straightening processes. In this case, in addition to the current measurement data, knowledge of the next time intervals can provide valuable information for the optimal swivel angle setting of the pump. This knowledge of the process sequence can be obtained, for example, from parameter lists created for the respective process.

[0037] It is also possible to use self-learning algorithms for optimization, which continuously improve the swivel angle setting from a rather "cautious" setting to the optimum utilization. For example, the pump connected to the annular space is swivelled so that the pressure on the annular space side is around 20 bar to compensate for gravity.

[0038] The embodiment according to Figure 2Each unit contains a motor-pump station for the piston chamber and the annular chamber. A first and a second drive motor 33C and 33B, respectively, including an inverter, are provided. The significantly lower requirements for flow rate and pressure on the annular chamber side 23C necessitate only low motor power and small pumps. Furthermore, a simple constant-displacement pump 34 can be used for the annular chamber side 23C. The variation of the flow rate to the annular chamber side 23C is achieved solely via the motor speed. With a vertically arranged cylinder chamber, it is particularly advantageous to keep the annular chamber pressure constant by regulating the motor torque. - In detail, from Figure 2A double-acting piston / cylinder assembly 20, comprising a working piston 21, a piston rod 22, and a cylinder chamber, is shown. The reversibly movable working piston 21 divides the cylinder chamber into a first piston chamber 23A (or working cylinder) and an annular chamber 23C (or return cylinder) surrounding the piston rod 22. A rapid-travel piston, if provided, can be oriented in a direction opposite to the piston rod or in the same direction as the piston rod, as not shown. The piston / cylinder assembly 20 is connected to a first pressure line D1, which supplies the first piston chamber 23A with a pressure medium, and to a pressure line D3, which supplies the annular chamber 23C with a pressure medium.

[0039] Two drives 33B and 33C, each designed with variable-speed motors, each drive a variable-speed pump 32 or 34, respectively. Pump 33C alone is equipped with a device 50, 51 for adjusting its delivery volume. The adjustment is achieved, firstly, internally within the pump, by a control device, specifically in the form of an actuating cylinder 51A, which changes the delivery rate in a known manner according to the current pressure. Additionally, a hydraulically upstream adjustment device (hydraulic valve) in the form of a proportional valve 50 is used, which responds to hydraulic or, in particular, electrical control signals from an external controller, such as a frequency converter U. This allows the pump delivery flow to be hydraulically adjusted up to the maximum delivery flow rate, depending on an external input signal.

[0040] In the present embodiment, the pump 32 associated with the motor 33C is hydraulically connected to the piston chamber 23A, which serves as the working cylinder. Both pumps 32 and 34 are fluidically connected on one side to a tank 40 and on the other side to the piston chamber 23A and the annular chamber 23C, respectively. The position sensor 36, installed on the piston rod 22, reports the current piston position to an inverter U, which supplies the drive 33B and 33C with electrical voltage.

[0041] Equipping both motors 33C and 30 with suitable (optional, not shown in any of the figures) brakes can prevent the piston 21 from dangerously dropping under the influence of gravity when the cylinder unit 20 is installed vertically, for example, in the event of a power failure. This eliminates the need for switching valves previously used in such cases.

[0042] While the adjustment of the at least one pump 31; 32 according to the preceding implementation of the invention ( Figure 1 and 2 ) is implemented via a proportional valve, according to the implementations according to Figures 3 to 7 A small, in particular mechanical, drive element 62; 62A, 62B, preferably in the form of a servomotor, is used for the adjustment operation. It acts either via a further pump 61, preferably in the form of a small gear pump, on the adjusting piston, i.e. on a hydromechanical drive element 51A, 51B, which is preferably designed as an actuating cylinder ( Figure 3 ), or it acts on a mechanical drive element 51C, which is preferably designed as an adjusting spindle ( Figures 4 to 7).

[0043] The realizations after Figures 3 to 7These advantages do not affect the protected area; nevertheless, a number of benefits can be achieved: For example, at least one pump 31, 32 can be swivelled even without applied hydraulic pressure. Energy consumption is significantly lower. The control (x motor revolutions generate y degrees of pump swivel angle) is simpler. Using the targeted swivel to "0" as a monitored safety function is possible. The pump swivel angle can be fixed by means of a motor-side brake. Furthermore, in all embodiments according to Figures 1 to 7 With electrically swiveling pumps, it is possible to swivel them beyond the zero point. The suction and discharge sides then reverse. This also avoids reversing the motor's direction of rotation and instead allows the pump to be swiveled, in particular, through its entire rotation. In this case, a simple asynchronous motor with a frequency converter can be used instead of a servo motor.

[0044] In the implementations after Figures 5 and 7 (Exemplary and thus preferred representations) it is advantageously possible to use the pump (pump 31) supplying the annular space 23C also for filling the first piston chamber 23A. Previously, the annular space and the first piston chamber were each equipped with their own pump. This was necessary because the two chambers have different surface areas. If the second pressure fluid outlet 31B of the annular space pump 31 is connected to the first piston chamber 23A via a pipeline, instead of to the pressure fluid tank, the different surface area ratios can be compensated for, among other things, by adjusting the delivery volume of the pumps 31 and / or 32 to these (surface area ratios).

[0045] Example: For a cylinder with a piston / ring area ratio of 2:1, two identical pumps with a maximum delivery volume of, for example, 40 cm³ would be chosen. When the piston extends, the delivery volume on the piston side is 40 + 40 = 80 cm³. The piston pump can therefore be significantly smaller. By changing the swivel angle of the pump connected to the annular space, the delivery volume can be adjusted so that the pressure in the annular space reaches the desired value (e.g., approximately 5 bar during downward movement, 20 bar during upward movement). Since both pumps can be swiveled independently of each other – as, for example, in Figure 6As shown, the swivel angle can also be adjusted as the motor load increases. Temporary changes in the piston / ring flow rate, for example during compression or decompression, can also be compensated for by swivel angle corrections. Key advantages include: smaller pump sizes (40 + 40 instead of 80 + 40), reduced noise levels, power losses, and pump costs.

[0046] In the to Figure 6 alternative embodiment according to Figure 7A separately controlled motor for the second drive unit 60B is omitted. Instead, a gearbox 63 is provided that couples the (single) motor 62A and the associated drive element, such as an adjusting spindle, with the other drive element in a speed ratio, which is particularly fixed. The adjustment of the pump 31, which acts, for example, on the annular space 23C, then follows, in particular according to the area ratios on the working piston 21, the adjustment of the pump 32, which acts, for example, on the first piston chamber 23A.

[0047] It is important to emphasize that it is readily possible for a specialist in the present field to also identify the other characteristics of the realizations according to Figure 1 and 2 and the other characteristics of the realizations according to Figures 3 to 7 essentially also applicable to the other implementations. REFERENCE MARK LIST 10 Drive arrangement 51 Positioning device 20 Piston / cylinder arrangement 51A, 51B hydromechanical drive element, such as actuator cylinder 21 working piston 22 piston rod 51C mechanical drive element, such as adjusting spindle 23A (first) piston chamber or working cylinder 51C' mechanical drive element, such as adjusting spindle 23C (second) piston chamber or annular chamber or return cylinder 51C" mechanical drive element, such as adjusting spindle 30 Pump arrangement 31 (first) pump 52 Pump swivel mechanism 31A (first) pressurized fluid outlet 60 drive unit 31B (second) pressurized fluid outlet 60A drive unit 32 second pump 60B drive unit 33 drive 61 additional pump 33A drive shaft 62 propulsion system 33B drive 63 transmission 33C drive 150 Signal line 34 pump 150A Signal line 36 Wayfinder 150B Signal line 37 transmission 38 Adjustment device D1 (first) pressure line 38A Adjustment device D1' Connection line 38B Adjustment device D3 (second) pressure line 40 Pressure medium tank D3' Connection line 50 hydraulic valve U inverter 50A, 50B Proportional valve(s)

Claims

1. A press with a hydraulic drive arrangement (10) without a pressure accumulator, with a double-acting piston / cylinder arrangement (20), which comprises at least one reversibly movable working piston (21) and at least one cylinder chamber and in which the at least one cylinder chamber or the cylinder chambers comprise / s at least one first piston chamber (23A) that acts upon the working piston (21) with fluid pressure and at least one second piston chamber (23C), with pressure lines (D1, D3) that supply the piston chambers with a pressure medium, with at least one pump arrangement (30), which comprises at least one pump (31; 32) that is driven with variable speed and in variable rotating directions and at least one variable-speed drive (33) that drives the at least one pump (31, 32), with at least one pressure medium reservoir that is or can be hydraulically connected to the piston / cylinder arrangement (20) and the pump arrangement (30), wherein the at least one pump (32) is connected to the first piston chamber (23A) by means of a first pressure line (D1) such that the hydraulic drive arrangement (10) can be operated in at least one direction of movement, preferably by means of a single one-motor drivetrain, and also reaches high operating pressures during working operation, characterized by an adjustment device (38) with at least one hydromechanical actuating cylinder (51; 51A) of the at least one pump (32), a hydraulic connection / connecting line (D1'), which is active between the actuating cylinder (51; 51A) and the pressure line (D1) provided between the at least one pump (32) and the piston chamber (23A) assigned thereto, and at least one hydraulic valve that is realized in the form of a proportional valve (50; 50A), wherein the at least one hydraulic valve is hydraulically active in the at least one connecting line (D1') between the actuating cylinder (51; 51A) and the pressure line (D1) in such a way that the actuating cylinder (51; 51A) can be acted upon with a variable pressure by varying the position of this hydraulic valve with the aid of an electrical control signal that influences the position of the hydraulic valve.

2. The press according to claim 1, characterized by at least two separate motor-pump stations, which respectively consist of at least one pump (32; 34) and a drive (33C; 33B), for the first piston chamber (23A) and for the second piston chamber (23C).

3. The press according to claim 1 or 2, characterized in that the first pump (31) is connected to the first piston chamber (23A) of the piston / cylinder arrangement (20) by means of a second pressure medium outlet (31B) for the purpose of acting upon said first piston chamber with additional pressure medium.

4. The press according to one of claims 1 to 3, in which the second piston chamber (23C) is supplied by a first pump (31) of the pump arrangement (30), characterized in that a transmission (63) is provided while forgoing an independently controlled driving means for a second drive device (60B), wherein said transmission couples the driving means of the associated driving member of the first drive device (60A) to the other driving member at a fixed speed ratio.

5. A method for operating a press with a hydraulic drive arrangement without a pressure accumulator, with a double-acting piston / cylinder arrangement (20), which comprises at least one reversibly movable working piston (21) and at least one cylinder chamber and in which the at least one cylinder chamber or the cylinder chambers comprise / s at least one first piston chamber (23A) that acts upon the working piston (21) with fluid pressure and at least one second piston chamber (23C), with pressure lines (D1, D3) that supply the piston chambers with a pressure medium, with at least one pump arrangement (30), which comprises at least one pump (31; 32) that is driven with variable speed and in variable rotating directions and at least one variable-speed drive (33) that drives the at least one pump (31, 32), namely if an adjustment device (38) of the at least one pump and an actuating means (51) for said adjustment device are provided, wherein the delivery rate of the at least one pump can be varied by means of the adjustment device (38) that can be actuated with the aid of the actuating means (51), with at least one pressure medium reservoir that is or can be hydraulically connected to the piston / cylinder arrangement (20) and the pump arrangement (30), wherein the at least one pump (32) is connected to the first piston chamber (23A) by means of a first pressure line (D1) such that the hydraulic drive arrangement (10) can be operated in at least one direction of movement, preferably by means of a single one-motor drivetrain, and also reaches high operating pressures during working operation, characterized in that at least one hydromechanical actuating cylinder (51; 51A) of the at least one pump (32) is provided, a hydraulic connection / connecting line (D1') is provided and active between the actuating cylinder (51; 51A) and the pressure line (D1) provided between the at least one pump (32) and the piston chamber (23A) assigned thereto, and at least one hydraulic valve is provided and realized in the form of a proportional valve (50; 50A), wherein the at least one hydraulic valve is hydraulically active in the at least one connecting line (D1') between the actuating cylinder (51; 51A) and the pressure line (D1) in such a way that the actuating cylinder (51; 51A) can be acted upon with a variable pressure by varying the position of this hydraulic valve with the aid of an electrical control signal that influences the position of the hydraulic valve.

6. The method according to claim 5, characterized in that a reduction of the delivery rate of the at least one pump, which is caused by a hydromechanical pump adjustment or control, is delayed by means of a hydraulic drive device (60) that causes the hydromechanical pump adjustment or overrides the pump control until the driving torque of the motor is fully utilized.

7. The method according to claim 6, characterized in that the driving motor of the variable-speed hydraulic drive is briefly and purposefully subjected to a load beyond its nominal torque by means of the drive device (60).

8. The method according to one of claims 5 to 7, characterized by using the current degree of utilization of the driving motor as control variable for the assigned pump.

9. The method according to claim 7 or 8, characterized in that a high-speed run and / or pauses for loading and unloading the consumer are used for once again cooling down the driving motor, which previously was purposefully overloaded.

10. The method according to one of claims 5 to 9, characterized in that a high pivoting angle of the at least one pump is maintained although the progression of the utilization factor indicates an imminent emergency shutdown.

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