EP2838719B1 - Machine press - Google Patents

Description

The present invention relates to a machine press comprising a machine frame, a lower tool carrier (preferably fixed to the machine frame), an upper tool carrier which is linearly movable up and down by one operating stroke by means of a hydraulic drive system relative to the lower tool carrier, and a numerical machine control ,

Machine presses of the type mentioned above can be found in various designs in the prior art. So are (cf. EP 231735 A1 ) Machine presses already known in which the hydraulic drive system comprises two piston-cylinder units, by means of which the upper tool carrier is moved, and a single, both piston-cylinder units together with hydraulic fluid supplying motor-pump unit (hydraulic unit). The loading of the two piston-cylinder units is controlled via actuatable by the machine control valves.

Furthermore, machine presses are known with two piston-cylinder units which together serve to move the upper tool carrier, in which case the hydraulic drive system also has two separate motor-pump units, each of which supplies only one associated piston-cylinder unit with hydraulic fluid. The speed of lifting and lowering the upper tool carrier typically depends on the engine speed, by reversing the direction of rotation of the pump (Reversible pump) is switched between lifting and lowering.

A machine press having the features of the preamble of claim 1 is known from EP0692327 A1 known.

The present invention has for its object to provide a machine press of the type mentioned, which is characterized by a very high energy efficiency at relatively low production costs and compact design of the hydraulic drive system.

This object is achieved by a machine press of the type described above, further characterized by the combination specified in claim 1 functionally synergetic interacting features distinguished. Accordingly, the upper tool carrier of a machine press, which may be in particular a press brake, with the aid of at least two front hydraulic drive system comprehensive hydraulic cylinder moves linearly up and down. In each case, at least one hydraulic cylinder, which is preferably designed in each case as a double-acting differential cylinder, part of a separate hydraulic drive unit, so that the hydraulic drive system comprises at least two separate, each having its own motor-pump unit having hydraulic drive units. Each of the motor-pump units draws hydraulic fluid from a tank and supplies it to a main pressure line. The hydraulic fluid is supplied from this via valves, which are preferably designed as proportional valves, controlled the at least one hydraulic cylinder of the respective hydraulic drive unit to - depending on the pressurization of the lifting-working space or the sink working space - to raise or lower the upper tool carrier, whereby by an appropriate hydraulic circuit (see below) can be carried out an express lowering of the upper tool carrier alone under its own weight, ie without pressurizing the sink working space.

The numerical machine control of the machine press contains a speed profile and a pressure profile. Both are defined by a work cycle of the machine press. The numerical machine control acts on the at least two mutually (hydraulically) independent hydraulic drive units, i. the engine of the respective motor-pump unit and each different valves controlling a.

On the one hand, the numerical machine control uses the speed profile to control the speed of the engine of the respective hydraulic drive unit. Thus, the motor drives the pumps with the speed specified by the numerical machine control phase-dependent speed, which is so dimensioned that the required for the desired movement of the upper tool carrier volumetric flow of hydraulic fluid - possibly plus a security surcharge (see below) - is provided. Depending on its displacement volume, the respective pump draws in an amount of hydraulic fluid corresponding to the rotational speed from the tank and feeds it to the main pressure line.

On the other hand, the numerical machine control uses the pressure profile to supply the at least two hydraulic drive units each with a supply pressure which is the maximum prevailing in the respective main pressure line in a phase-dependent manner. This phase-dependent maximum pressure is typically based on the maximum pressure required in the respective working phase for a specific pressing operation to which the relevant pressure profile is tailored, possibly increased by a safety margin (see below), wherein the specification of the maximum pressure can additionally also fulfill a safety function, which protects the hydraulic drive unit from overpressure. Moreover, according to the invention, it is provided that in each of the at least two hydraulic drive units, the respective pressure limiting unit individually controls the supply pressure prevailing in the relevant main pressure line, at least during part of the work cycle (in particular in the phase of the so-called "force pressing", see below) Lowered predetermined phase-dependent maximum pressure, depending on demand. In this sense, the supply pressure by means of the respective pressure limiting unit for each of the hydraulic drive units is at least temporarily individually limited to the smaller pressure from the maximum pressure given by the pressure profile and the actually existing on the at least one hydraulic cylinder load pressure plus an additional charge, where the relevant load pressure, if the relevant period of load-dependent pressure limiting extends from the lowering phase into the lifting phase, depending on the working phase at the sink working space or else at the lifting working space of the at least a hydraulic cylinder is applied. This further limitation allows an adjustment of the supply pressure limited to the actual demand- and operation-dependent load pressure limited by the numerical machine control based on predicted required pressure values. Due to the system structure having at least two independent hydraulic drive units, the actual supply pressure in each of the at least two hydraulic drive units can thus advantageously be set individually to the respective load pressure of the relevant hydraulic drive unit. For typical practical applications of the machine press, this is an important aspect in terms of energy efficiency; because in asymmetric pressing tasks, where the different hydraulic cylinders of the hydraulic drive system have different forces to provide (eg off-centering of the workpiece in a mono press or centering of the workpiece in a tandem press), hydraulic power in each of the motor-pump units only becomes provided in the amount actually required (taking into account a security surcharge). In particular, there is no load-dependent - or even entirely independent of the actual load - provision of the identical supply pressure for all hydraulic cylinders, which relates to the greatest load of all the hydraulic cylinders of the entire hydraulic drive system. The above-described combination of synergistically interacting features with respect to supply side profile-controlled delivery rates and profile-controlled and load-dependent set pressure levels makes a significant contribution, the enormously increase the energy efficiency of the machine press with moderate use of resources. Due to the increased energy efficiency, because significantly less heat loss is dissipated, moreover, the tank volumes designed smaller and / or - in terms of the lowest possible technical effort - additional measures for cooling the hydraulic fluid can be avoided - in terms of a compact drive system.

In contrast to the state of the art presented in the introduction, it should be noted as special advantages of the machine press according to the invention that it can be operated particularly efficiently with little constructional effort, wherein, moreover, a modular construction is made possible, in particular with regard to the hydraulic cylinders provided. And even compared to known machine presses with load-sensing functionality in which the supplied by a common, all hydraulic cylinders supplying motor-pump unit supply pressure is adjusted load dependent on the highest prevailing in the system load pressure, as shown, significant energy benefits. In addition, in order to ensure the load-sensing function in known presses, piston-cylinder units equipped with pressure sensors are to be used, which are expensive custom-made products. The installation of simple cylinders of different manufacturing in the sense of a modular structure is not possible in such systems. In that regard, in the machine press according to the invention also the rather low manufacturing effort is emphasized. In this It proves to be favorable that a high outlay, as arises when using controllable asynchronous motors with feedback due to the necessarily complex integration into the hydraulic system, can be avoided in implementation of the present invention.

In a preferred embodiment, the pressure-limiting unit has a pressure limiter which can be controlled by the numerical machine control and a separate, hydraulically-mechanical pressure balance connected in parallel thereto for flow-related purposes. Through the numerical machine control, a pressure is set on the pressure limiter in phase-dependent manner / which prescribes the maximum pressure which is set phase-dependent in the main pressure line. The pressure compensator adopts the respective load-dependent regulation of the supply pressure to a pressure level which is more or less below the phase-dependent maximum pressure, depending on the respective actual load on the hydraulic cylinder. The latter results preferably from the respective actual momentary load pressure taking a surcharge. Particularly advantageous in such an embodiment / when the load pressure at the at least one hydraulic cylinder of each hydraulic drive unit is removed by a cost-effective shuttle valve and the pressure balance / ie a control input of the pressure compensator / is supplied / wherein the two inputs of the shuttle valve with the lifting workspace and the sink Working space are connected / whereby the higher of the pressure prevailing in the two said work spaces on the control input of the pressure compensator is switched. The same can for reasons the failure safety even be appropriate / if by special measures (see below) the pressure compensator is intended only effective in force pressing.

Furthermore, it is advantageous / if, upstream of a second control input of the pressure compensator, a pilot valve operable by the machine control is fluidically connected upstream / that - depending on the position of the pilot valve - either the supply pressure or the tank pressure is applied to the second control input of the pressure compensator. This can be targeted causes / that the pressure compensator is only temporarily effective / so that the pressure compensator can be put inoperative especially in those operating phases of the machine press in which they (eg by hydraulic vibration and / or resonance effects) adversely affect the performance would. Is in this way, i. ensured by influencing the machine control that the pressure compensator is effective only during lowering, especially the power lowering, loses the above-mentioned shuttle valve in importance. The said pilot valve may preferably also have a further function within the relevant hydraulic drive unit, for example the control of a lowering the working chamber of the respective hydraulic cylinder associated controllable Nachsaugventils in such a machine press, which is designed solely on the weight of the upper tool carrier rapid lowering is.

In a further, alternative preferred embodiment, the respective pressure-limiting unit comprises in one Unit integrates a controllable by the numerical machine control electronic pressure compensator with also adjustable by the machine control pressure limiter, with a control technical superposition of both functionalities takes place. The advantage here is the combination of the pressure balance and the pressure limiter in a compact component.

• der Arbeitszyklus, für den das Drehzahlprofil und das Druckprofil phasenabhängig die Drehzahl des Motors bzw. den maximalen Versorgungsdruck vorgeben, mindestens die Phasen Eil-Senken, Kraft-Senken und Heben des oberen Werkzeugträgers umfasst,
• sich der Motor gemäß Drehzahlprofil in der Phase Eil-Senken des oberen Werkzeugträgers nicht dreht,
• gemäß dem Drehzahlprofil die Motordrehzahl in der Phase Heben des oberen Werkzeugträgers die Motordrehzahl in der Phase Kraft-Senken überschreitet,
• die numerische Steuerung eine Eingabeeinheit umfasst, an der mindestens die Drehzahlen des Drehzahlprofils und die Drücke des Druckprofils eingebbar sind, und/oder
• jede Hydraulikantriebseinheit genau einen als Differentialzylinder ausgeführten Hydraulikzylinder aufweist, wobei idealerweise der Differentialzylinder ein Flächenverhältnis des Heben-Arbeitsraums zum Senken-Arbeitsraum kleiner als 0,1 aufweist.

Diverse preferred developments and other advantageous aspects of the invention will become apparent from the following description and explanation of an embodiment of the invention and the dependent claims, according to which - for the operation of the machine press according to the invention - in particular an open tank, which is under atmospheric pressure, is particularly favorable, and - In cost aspects - the use of a pump with a constant displacement volume, a conveying direction and a direction of rotation and / or frequency-controlled asynchronous motors without feedback is particularly advantageous. Furthermore, such embodiments are particularly useful in which

• the duty cycle, for which the speed profile and the pressure profile, depending on the phase, predetermine the speed of the motor or the maximum supply pressure, comprises at least the phases sinking, lowering and lifting the upper tool carrier,
• the motor does not rotate according to the speed profile in the Eil-lowering phase of the upper tool carrier,
• according to the speed profile, the engine speed in the phase of lifting the upper tool carrier exceeds the engine speed in the power-lowering phase,
• the numerical control comprises an input unit on which at least the rotational speeds of the rotational speed profile and the pressures of the pressure profile can be entered, and / or
• each hydraulic drive unit has exactly one hydraulic cylinder designed as a differential cylinder, wherein ideally the differential cylinder has an area ratio of the lift working space to the sink working space smaller than 0.1.

Fig. 1

schematisch eine erste als Abkantpresse ausgeführte Maschinenpresse nach der vorliegenden Erfindung,

Fig. 2

schematisch eine zweite als Abkantpresse ausgeführte Maschinenpresse nach der vorliegenden Erfindung und

Fig. 3

anhand eines Hydraulikschaltplans die Ausführung einer der beiden Hydraulikantriebseinheiten der Abkantpressen nach Figuren 1 und 2.

The invention will be explained in more detail with reference to an embodiment illustrated in the drawing. It shows

Fig. 1

1 schematically shows a first machine press according to the present invention, which is designed as a press brake,

Fig. 2

schematically a second designed as a press brake machine press according to the present invention and

Fig. 3

on the basis of a hydraulic circuit diagram, the execution of one of the two hydraulic drive units of the press brake after FIGS. 1 and 2 ,

In the Fig. 1 machine press 1 shown as a press brake has a machine frame 3 comprising two C-frames 2. In a fixed spatial relationship to the machine frame 3, namely each fixed to the lower profile leg of the two C-frame 2, a lower tool carrier 4 with a lower tool 5 is arranged on this. A stocked with an upper tool 6, in Fig. 1 in its uppermost position shown upper tool carrier 7 is linearly movable up and down relative to the lower tool carrier 4 by an operating stroke H. Since the in Fig. 1 shown press brake to this extent corresponds to the well-known state of the art, further explanations are unnecessary in this respect.

To effect the downward movement of the upper tool carrier, a hydraulic drive system is provided. This comprises two hydraulic drive units, namely a left hydraulic drive unit 8 and a right hydraulic drive unit 9, which together form the hydraulic drive system 10 acting on the upper tool carrier 7. The two hydraulic drive units 8 and 9 are closed and self-sufficient, i. they have no hydraulic connection to each other. They are designed in the form of complete drives 11.

In the Fig. 2 illustrated press brake corresponds in terms of essential design features of those of FIG. I, so that reference is made to the above explanations. However, the two hydraulic drive units 8 and 9 are not executed here as a structural unit forming a complete drive solution, but rather in a dissolved design. Thus, in each case the hydraulic cylinder-piston unit 12 is spatially separated from the associated, the tank and the flanged-on motor-pump unit 15 comprehensive assembly 46 with the flanged to the respective cylinder 13 valve block 45.

Each of the two complete drives 11 (mirror-inverted) 11 ( Fig. 1 ) or each of the two - also mirror-inverted - hydraulic drive units 8 and 9 ( Fig. 2 ) includes in particular (see also the hydraulic circuit diagram Fig. 3 ) designed as a differential cylinder hydraulic cylinder-piston unit ("hydraulic cylinder") 12 with a cylinder 13 and a guided therein piston 14, the piston rod is fixedly connected to the upper tool carrier 7, a hydraulic cylinder 12 acting on hydraulic unit 15 with a constant pump with a direction of rotation running hydraulic pump 16, which is driven by a frequency-controlled asynchronous motor (without feedback) running electric motor 17, and a hydraulic fluid-storing tank 18. The speed of the motor 17 and thus the flow rate of the 12 pump 16 is phase-dependent on the machine control 21 adjustable, for which purpose in the numerical machine control 21 a speed profile is stored.

The loading of the hydraulic cylinder 12 by the hydraulic unit 15 for the purpose of downward movement ("lowering") and the upward movement ("lifting") of the upper tool carrier 7 via a conventional filter unit 19, a main pressure line 20 and a proportional, from the numerical machine controller 21st controlled 4/3-way valve 22. The latter is equipped with a position switch 23, which in turn returns the actual position of the valve 22 to the machine controller 21. The three positions of the valve 22 correspond to the Operating states "hold" (as in Fig. 2 shown), "lowering" and "lifting". In the "lower" position, the main pressure line 20 is connected to the piston working space 24, which represents the sink working space, while in the position "lifting" with the lifting working space forming piston rod working space 25, in this position "lifting" the Piston working chamber 24 (also, see below) is connected via the valve 22 to the tank 18.

Between the piston rod working space 25 and the valve 22, two further valves 26 and 27 are connected in parallel to each other, which become differently effective in the "lowering" position of the valve 22 depending on the working phase ("rapid traverse" or "force pressing"; For lowering the upper tool carrier 7 in rapid traverse, in which the upper tool carrier 7 relatively quickly approaches the lower tool carrier 4 due to its own weight and the Nachsaugventil 28 to fill the increasing piston working chamber 24 from the tank 18, is open, is also the seat valve 26 is opened with integrated check valve, wherein the speed of the downward movement of the upper tool carrier 7 is controlled via the proportional valve 22. The opening of the (hydraulically operated) Nachsaugventils worried the connected to the main pressure line 20, controlled by the machine control 21, equipped with a position switch 30 pilot valve 29 via the control line 31st

Before the upper tool 6 reaches the workpiece, the downward movement of the upper tool carrier 7 in rapid traverse - by appropriate control of the valve 22 - braked. It is switched to power presses by both the poppet valve 26 and - by appropriate reversal of the pilot valve 29 - the suction valve 28 are closed so that the piston working chamber 24 via the main pressure line 20, the valve 22 and the line 32 for force pressing controlled with hydraulic fluid is charged. The counter-holding valve 27, which is connected between the piston rod working chamber 25 and the valve 22, prevents uncontrolled lowering of the upper tool carrier 7 by setting it to such a holding pressure that only active loading of the piston working chamber 24 with hydraulic fluid from the main pressure line with an above the Tank 18 prevailing pressure causes a lowering of the upper tool carrier 7.

At the end of the power pressing, ie at the end of the lowering movement, the valve 22 is reversed to "lifting". Initially, a so-called "decompression" takes place in order to control the high pressure in the piston working chambers 24, whereby in the decompression phase with the said pressure reduction, the reduction of possible deformations of the machine structure which has occurred during force pressing is accompanied. Typically, the decompression phase involves a controlled upward movement of the upper tool carrier 7 over a predetermined path at (slow) operating speed by correspondingly loading the lifting work spaces 25 of the two hydraulic drive units 8 and 9. Subsequently, the piston rod working space 25 is acted upon via the valve 22 and the line 33 (with the poppet valve 26 open or the check valve open of the poppet valve 26) with hydraulic fluid from the main pressure line 20, wherein the increased speed of the upward movement of the upper tool carrier 7 on the Proportional function of the valve 22 is controlled. The thereby displaced from the piston working space 24 hydraulic fluid passes through the - now again - opened suction valve 28 to the tank 18th

The existing pressure in the main pressure line 20 is controlled both phase-dependent and load-dependent during the work cycle 'by a complex pressure limiting unit, the load-dependent control takes into account a different stress on the at least two hydraulic drive units of the hydraulic drive system. For this purpose, on the one hand, a pressure limiter 34 connected between the main pressure line 20 and the tank 18 is provided. This comprises a known as such cartridge 35, the pressure threshold, in which the connection between the main pressure line 20 and the tank 18 is opened, is adjustable over the pressure prevailing in a control line 36 pressure. The prevailing in the control line 36 pressure is limited by a switched between the control line 36 and the tank 18 pressure relief valve 37, the set value thus dictates the maximum in the main pressure line 20 prevailing pressure. A (via a stored in the machine control phase-dependent pressure profile) via the machine control 21 controlled lowering of the in Control line 36 existing pressure levels is about the - to the pressure relief valve 37 fluidly connected in parallel - controllable by the machine control 21 adjustable pressure relief valve 38 possible. Such a lowering of the pressure level in the control line 36 causes a corresponding reduction of the pressure threshold, in which a connection between the main pressure line 20 and the tank 18 is made via the cartridge 35, and accordingly a (profile-controlled) setting of the maximum in the main pressure line 20 pressure.

Fluidically parallel to the pressure limiter 34, a hydraulic-mechanical pressure compensator 39 is connected between the main pressure line 20 and the tank 18, which in turn - in the active phase of the pressure compensator 39 - limits the maximum setting in the main pressure line 20 pressure, namely to a value , which is a predetermined amount ("supplement") above the currently prevailing at the hydraulic cylinder 13 load pressure. For this purpose, the control input 40 of the pressure compensator 39 is connected via the control line 41 with a shuttle valve 42, which in turn switches the higher of the applied pressure at its two inputs to the control line 41. The one input of the shuttle valve 42 is in communication with the piston working space 24 and the line 32 connected thereto; the other is connected to the piston rod working space 25 associated line 33, in which the valves 26 and 27 are connected.

The pressure compensator 39 can be controlled via the machine control 21 switched on and off by the control line 31, via which the suction valve 28 is switched, is also connected to a second control input 43 of the pressure compensator 39. In this way, with the suction valve 28 open, the pressure compensator 39 is inoperative, i. a connection of the main pressure line 20 to the tank 18 via the pressure compensator 39 is excluded.

Provided in both in each case according to the circuit diagram Fig. 3 This also takes into account that the hydraulic cylinder 13 acts as a pressure booster during force pressing and prevents severe damage to the hydraulic system in the event of failure of the pressure holding valve 27.

According to the above-mentioned speed profile, the motor 17 can stand, for example, in the phase of rapid downward movement of the upper tool carrier, so that the pump 16 promotes no hydraulic fluid. When force pressing, depending on the particular pressing task, the pump speed can be set for example to a value between 10% and 100% of the design speed, the speed is set so that the calculated for the movement of the upper tool carrier 7 flow rate always a Safety margin (eg 5%) is exceeded. The relevant reserve will be over the above-described pressure limiting unit is regulated and returned to the tank 18. For the phase of lifting the upper tool carrier 7, since there is less load (over a shorter period of time), the pump speed may even be raised beyond the design speed, eg to a value of 130% of the design speed.

For reasons of clarity of the drawing, the various control lines, with which the numerical machine control 21 is connected to the components controlled by it or the various position switches, are not drawn continuously, but rather are indicated only at their two ends. It should also be pointed out that, as already explained above, one of the above-mentioned functions of the pressure limiting unit has the same function, for example also via an assembly with superimposed functionalities of the pressure limitation (in the respective main pressure line) according to a phase-dependent pressure profile on the one hand and according to a load dependency on the other can.

Claims (14)

1. An automatic press (1), in particular a press brake, with a machine frame (3), a lower tool holder (4), an upper tool holder (7), which can be linearly moved up and down by a stroke (H) relative to the lower tool holder by means of a hydraulic drive system, and a numeric machine control (21), wherein the automatic press further comprises the following features: The hydraulic drive system comprises at least two mutually independent hydraulic drive units (8, 9), wherein each of the hydraulic drive units in turn comprises the following features:

   - at least one hydraulic cylinder (12) causes the upper tool holder (7) to move linearly up and down and is connected, via valves (22, 26, 27) and a main pressure line (20) under supply pressure, to a pump (16) driven by a motor (17), which draws hydraulic fluid from a tank (18);

   - the speed of the motor (17) can be adjusted via the numeric machine control (21), characterised in that a speed profile defined via the work cycle is stored in the numeric machine control;

   - and in that a pressure-limiting unit, at least during part of the work cycle, limits the supply pressure level to whichever is the lesser pressure from a pressure profile defined via the work cycle and stored in the numeric machine control (21), and the actual load pressure increased by an extra amount on the at least one hydraulic cylinder (12).
2. The automatic press according to claim 1, characterised in that the pressure-limiting unit comprises a pressure limiter (34) which can be controlled by the numeric machine control and a separate mechanical hydraulic pressure balance (39) fluidically connected in parallel thereto.
3. The automatic press according to claim 2, characterised in that the load pressure applied to the at least one hydraulic cylinder (12) and to the raising workspace (25) and the lowering workspace (24) is taken off by a shuttle valve (42) and the higher of the two pressure values is supplied to a control input (40) of the pressure balance (39).
4. The automatic press according to claim 2 or 3, characterised in that a pilot valve (29), which can be controlled by the numeric machine control (21), is connected upstream of the second control input (43) of the pressure balance (39), so that either the supply pressure or the tank pressure is applied to the second control input of the pressure balance.
5. The automatic press according to claim 1, characterised in that the pressure-limiting unit comprises an electronic pressure balance controllable by the numeric machine control (21) with a pressure limiter adjustable by the numeric machine control, integrated into one constructional unit.
6. The automatic press according to one of the preceding claims, characterised in that the tank (18) is open and under atmospheric pressure.
7. The automatic press according to one of the preceding claims, characterised in that the pump (16) is a pump with constant displacement volume, one delivery direction and one rotational direction.
8. The automatic press according to one of the preceding claims, characterised in that the motor (17) is a frequency-controlled asynchronous motor without feedback.
9. The automatic press according to one of the preceding claims, characterised in that the work cycle, for which the speed of the motor (17) / the maximum supply pressure is specified by the speed profile and the pressure profile depending on phase, comprises at least the phases: quick-lowering, force-lowering and raising of the upper tool holder (7).
10. The automatic press according to claim 9, characterised in that the motor (17), according to the speed profile in the quick-lowering phase of the upper tool holder (7), is not rotating.
11. The automatic press according to claim 9 or 10, characterised in that according to the speed profile the motor speed in the raising phase of the upper tool holder (7) exceeds the motor speed in the force-lowering phase.
12. The automatic press according to one of claims 9 to 11, characterised in that the numeric control (21) comprises an input unit for inputting at least the speeds of the speed profile and the pressures of the pressure profile.
13. The automatic press according to one of the preceding claims, characterised in that each hydraulic drive unit (8, 9) comprises exactly one hydraulic cylinder (12) configured as a differential cylinder.
14. The automatic press according to claim 13, characterised in that the differential cylinder has a surface ratio of raising workspace (25) to lowering workspace (24) which is smaller than 0.1.

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