EP0616882A1 - Method for hydraulically controlling a link-type press or a toggle press and link-type press or toggle press with a control system adapted for carrying out the method - Google Patents

Abstract

The invention relates to a method for hydraulically controlling a link-type or a toggle press and a link-type or toggle press with a control system adapted for carrying out the method. An innovative feature is that in the operating region of the press ram (3), the speed of the driving piston rod (2) is increased at least once. The speed of the ram (3) is therefore kept relatively constant until the lower part is reached. <IMAGE>

Description

The invention relates to a method for controlling a and an articulated or toggle press controlled by the method according to the preamble of claim 1 and according to claim 3. Such methods are used above all in cutting and forming presses of modern design with hydromechanical articulated lever drives. For example, the applicant has successfully launched a toggle lever plate cutting press under the name Differential Path Press (DWP), which is described, for example, in DE-C 2925416 or EP-A1 250610. The description and drawing from DE-C and EP-A1 of the parts: toggle lever arrangement (one or more in parallel) and support thereof on the press frame and support of the working cylinder on the press ram apply to the purpose of constructing an embodiment as disclosed herein.

Such a press has two toggle lever systems - with their knee joints buckling towards the center of the press - which are acted upon by a piston rod of a cylinder-piston arrangement arranged symmetrically to the toggle levers during a lifting cycle in the forward and then backward direction. The market is also familiar with a press introduced as a differential pressure press (DDP), which has another linkage guided in roller rails between the piston rod and the articulation points on the toggle levers. Such a press was presented to the public in August 1987 and subsequently used.

Both known presses originate from a toggle lever press with crank drive which the toggle lever used to further increase the speed of the press ram in the area of the lower or upper (depending on whether the working area was below or above) dead center reduce and keep as slow as possible over a certain period of time or a certain distance. This is because, in the cutting or embossing or drawing area of the material to be processed, it was possible to achieve better cutting precision or processing quality than with a pure crank drive without the interposition of toggle levers. In addition, the power in the working area (cutting area) could be increased accordingly by the translation effect of the toggle lever.

The toggle levers in particular also ensure the precision in the cutting direction (depth of cut), which was also used, among other things, in toggle presses with hydraulic piston drives, such as shown in GB-A 707815.

In the past, the focus was on achieving the above-mentioned speed reduction in the work area and later on improving the cutting precision, but with increasing automation of the production processes, the working speed (number of strokes) was brought to the fore with maximum precision. The DWP achieved this by combining the advantages of an eccentric press (fast continuous running) with those of a hydraulic press (pressure control and speed variation) and those of a toggle press (high forces in the work area and maximum precision with regard to the depth of cut). The DDP, which was later built on the basis of the DWP, attempted to increase the number of strokes of the press by means of additional mechanical effort on the roller rails and intermediate linkage, but this was expensive due to the additional components subject to high wear.

The present invention is therefore based on the object of providing a press and a simple method for driving the same that, without losing the respective advantages and properties of the known presses, a higher stroke rate and therefore greater profitability should enable. The additional components required for the control effort should be kept as low as possible - not least to avoid inertia and control errors -. On the other hand, a conventional DWP or DDP is to be improved in such a way that a desired forming speed can be set which remains essentially constant over the entire forming process, as a result of which the optimum forming speed per workpiece is achieved. This task should also be made possible without significant additional control expenditure (by a large number of additional components for regulators or the like).

Maintaining the speed of the press ram as constant as possible over the entire working range (from cut contact with the workpiece to the backward movement of the ram) is already known in principle with other types of hydraulic presses. However, this generally requires large pressure medium drives, since without the advantageous effect of the toggle levers, which is not known to the known, they have to apply both the working pressure and the considerable amount of oil flow for a movement in overdrive. Large amounts of oil flow also mean large cross-sections of the pressure lines or increased flow velocities and thus a reduced efficiency of the press as a whole and often even an increased cutting bang.

Such a comparable hydraulic press is described, for example, in DE-A 4036564, which, however, does not set a constant ram speed as its goal, but could, however, be possible with the appropriate design. To control important process variables such as travel (s), speed (v) and forces (F), a complex 4/5 way control valve with some device peripherals, electronic travel sensors, pressure sensors and ultimately even an electronic control are required.

In the case of articulated or toggle presses, this goal is just as new and actually exactly the opposite of the previous teaching, which states that the aim was to permanently reduce the speed of the press ram in the work area or to use the effect of the toggle lever to reduce the speed.

The tasks are solved for the first time by adding the features of the characterizing part of claim 1 or by a press with the features of claim 5.

The method according to the invention partially weakens or compensates for the slowing effect which the toggle levers bring about in the work area by varying the crank speed in the work area according to the invention and advantageously.

The tasks were also not solved by other constructions, which, however, appeared to be looking for similar solutions:
For example, US Pat. No. 3,926,033 shows a "series connection" of cylinder piston assemblies (telescopic cylinders) with different effective surfaces, which in turn have to be adversely affected by correspondingly large, powerful pressure medium drives. A targeted switch from one piston to another within a movement phase is not possible
The invention, on the other hand, solves the problems in a simple manner. In principle, the invention can be applied to any conventional pressurized articulated or toggle press. The only requirement is that the drive of the piston rod can be speed-controlled.

The ram speed is not as before by the method according to the invention (for example in the DWP or DDP) reduced to the UT (bottom dead center), but rather kept almost constant at the expense of the driving force of the piston rod. This can be allowed due to the movement physics of the toggle principle, which due to its ever increasing translation in the UT area (work area) only requires a portion of the driving force that was still required above the UT in order to apply the press force required for the deformation. If a workpiece is also cut with an arrangement according to the invention, the effect according to the invention particularly suits the workpiece: high forces are only needed when the cutting tool first comes into contact with the workpiece; these generally decrease in the flow area.

Advantageously, the invention does not change other desired properties of a DWP or DDP, such as Stopping times under 50ms, practically no cutting bang due to the oil quantities clamped under high pressure, long tool life, possibility of subsequent press settings in the area of the UT, unnecessary damping of cut impact etc. However, the invention can be realized by simple hydraulic circuits. Compared to the known circuit according to DE-A1 4036564, according to the exemplary embodiments shown, it can find its end with a minimal mechanical-hydraulic control effort.

A preferred embodiment of a press according to the invention is, however, equipped with at least one stepped piston cylinder or differential cylinder with an integrated plunger cylinder as the main working drive source. Together with the method according to the invention, this structure offers the advantage of great compactness and a reduction in sealing problems in comparison to arrangements of a plurality of drive cylinders with different pressure surfaces acting parallel to one another. As a further advantage, this preferred solution offers the possibility of high hydraulic efficiency can work with high pressures but low oil flows.

The device claims are based on the speed of the piston rod. Of course, there are also variants within the scope of the invention, the toggle levers of which are not directly connected by a piston rod, but e.g. are driven by an electromechanical drive. In such cases, the piston rod is only to be understood as a pressure piece that acts directly on the toggle levers.

The basic principle of the method according to the invention is concerned with the control of a press ram of a hydromechanical toggle press in its working area. The basic idea is, as mentioned, to keep the working speed of the ram as constant as possible there at the speed recognized as optimal that it reached at the time of the first cut contact (at the beginning of the working area). For each material or workpiece there is an optimal forming speed, which is chosen according to the invention and remains essentially constant during the forming. However, it is also within the scope of the invention to increase the piston rod speed after reaching the point of intersection in such a way that after deflection of this speed by the toggle lever or levers there is even an increase in the ram speed, if this is desirable for the workpiece in question, for example for reasons of deformation technology .

As a rule, all switching and control processes can be carried out in stages, but for special versions these can also - if necessary even electronically controlled, for example using the complex control circuit according to DE-A 4036564, the detailed circuit structure of which is disclosed as being within the scope of this application - be carried out continuously, possibly even via the non-preferred route of Oversized or parallel-connected pressure oil pumps, which could also be used to accelerate the piston rod in the working area of the ram by increasing their delivery capacity.

However, preference is given to purely mechanical positive control of the valves depending on the travel of the piston rod, since this enables the highest number of strokes to be achieved. The principle of the step piston shown in the drawing can of course also be used several times within the scope of the invention to increase the number of steps, provided the cylinder piston arrangement is selected accordingly.

As a further variant, a suitable lever transmission or a gear or the like could be located between the piston rod and the articulation points on the toggle levers. be arranged, which is designed such that it accelerates the articulation points in the forward direction according to the inventive method at a constant piston speed.

The remaining dependent and independent claims characterize or describe embodiment variants of the invention. Other design variants also result from the combination of the different exemplary embodiments with one another, in order, if necessary, to be able to solve more specific or detailed tasks. In particular, this relates to the arrangement of a main working cylinder on the ram and at least one auxiliary working cylinder on the press frame, the piston of the main working cylinder acting on the toggle levers and the piston of the auxiliary working cylinder acting only on the ram.

Even if such an alternative arrangement as described last is not operated with the method according to the invention, it brings advantages over conventional designs with only one main working cylinder, for example in a DWP or DDP. Are the auxiliary cylinders only for the Used backwards movement of the ram, they work optimally in accordance with the overall physical concept of a DWP, which is also designed to minimize the amount of pressure oil to be pumped. When moving forward, a small master cylinder can provide feed (less oil to be pumped). When moving backwards (in this case when lifting the plunger) only a little and slowly flowing oil is needed in the auxiliary working cylinders, which can be easily refilled or refilled with or without pressure, even without pumping power. In the area of the UT, the toggle lever transmission helps the main working cylinder, so that it can lift the ram despite its smaller dimensions. Only in the upper area, where the toggle action wears off, can the auxiliary cylinders help briefly, but in the TDC (UPPER TOTPUNKT) area the movement of the main working piston is slowed down again and less pressure oil delivery is required there again.

The two cylinder systems complement each other optimally in terms of minimizing pressure oil consumption with good press performance. Together with the method according to the invention (possibly with the aid of a stepped piston), such a variant also works faster than before.

Fig.1

ein Beispiel einer bekannten Kniehebelpresse mit einfachem (gross dimensioniertem) Antriebszylinder, der entsprechend dem erfindungsgemässen Verfahren mittels nicht näher dargestellter Steuerung angesteuert sein kann.

Fig.2

eine Variante dazu mit zwei symmetrisch angeordneten Kniehebeln, bei denen eine erfindungsgemäss modifizierte, jedoch nicht näher dargestellter Stufenzylinderkolbenanordnung angreift, die mit einer nicht dargestellten Steuerung verbunden ist, die nach dem erfindungsgemässen Verfahren arbeitet.

Fig.3

eine schematisch dargestellte Variante an einer DWP mit Hydraulikschaltkreis, der zur besseren Ausnutzung der fliessenden Ölmengen eine Differntialschaltung für den Differentialzylinder aufweist.

Fig.4

eine Variante dazu ohne Differntialschaltung für den Differntialzylinder;

Fig.5

eine Variante mit Hilfsarbeitszylindern;

Fig.6

eine Variante mit getrennten einfachen Ventilen;

Fig.7

eine symbolische Weg/Zeit-Kurve einer erfindungsgemässen Presse;

Fig.8

eine andere Weg/Zeit-Kurve bei anders ausgelegter Presse;

Fig.9

die schematische Geschwindigkeits/Zeit-Kurve der Kolbenstange zum Vergleich eines herkömmlichen einstufigen Zylinders mit einem erfindungsgemässen mehrstufigen Zylinder und

Fig.10

eine entsprechende Kurvenvergleichsdarstellung für den Pressenstössel.

Further examples result from the figures and their description. Show:

Fig. 1

an example of a known toggle press with a simple (large dimensioned) drive cylinder, which can be controlled according to the inventive method by means of a control, not shown.

Fig. 2

a variant of this with two symmetrically arranged toggle levers, in which a modified according to the invention, but not shown in detail Stepped cylinder piston arrangement attacks, which is connected to a control, not shown, which operates according to the inventive method.

Fig. 3

a schematically illustrated variant on a DWP with hydraulic circuit, which has a differential circuit for the differential cylinder for better utilization of the flowing oil quantities.

Fig. 4

a variant of this without differential gear for the differential cylinder;

Fig. 5

a variant with auxiliary cylinders;

Fig. 6

a variant with separate simple valves;

Fig. 7

a symbolic path / time curve of a press according to the invention;

Fig. 8

another path / time curve with a different press;

Fig. 9

the schematic speed / time curve of the piston rod for comparing a conventional single-stage cylinder with an inventive multi-stage cylinder and

Fig. 10

a corresponding curve comparison representation for the press ram.

1 shows a toggle press, the structure of which is described in more detail in US-A-707815 (corresponding parts of the description are deemed to be disclosed herein). The press ram 1 is driven by the toggle lever arrangement 18, which is driven by a cylinder-piston arrangement 10, 11. This arrangement is controlled by a hydraulic control 3 via pressure lines 2. the control works according to the principle of the invention. In the area of the UT, the oil flow quantity is increased and the piston 10 is accelerated accordingly, so that the press ram or ram 1 has a constant working speed in the working area.

2 shows a press with two counter-acting toggle lever systems 10, 12, 16, which have a cylinder-piston arrangement 10,11 are driven. The latter is supplied with compressed air or another pressure medium according to the press according to FIG. 1 via a control line 21. The rest of the structure of this press is further described in GB-A-804352, which is believed to be disclosed herein. The press ram 20 of this press works from the bottom up. The meaning of the UT area according to the invention is therefore to be understood here for the OT.

The press according to FIG. 3 differs from those according to FIGS. 1 and 2 in that the working cylinder 1 is not supported on the housing G but on the ram 3, and thus corresponds to a DWP. The more detailed structure of such a press is described for example in EP-A1 250610.

The further details of the structure according to the invention are as follows:
A pump delivers pressure oil through a pressure line 30 to a cam-actuated 3-position valve 14a, which in its position b conveys the oil into a line 31. The cam control is coupled to the piston position and is symbolically indicated at 15. The pressure oil is conveyed from line 31 via the 3-position valve 16a in its position a to the innermost cylinder chamber 11 via the 2-position valve 21 in its position b. Since this has a relatively small volume, this results in a relatively rapid downward movement of the piston 2 and thus, via the pressure piece 4 and the toggle levers 5, 6, 7, a rapid downward movement of the plunger 3. The cylinder space 13 is emptied simultaneously via the line 36, this is emptied into the reservoir 25 via the valve 14a (position b).

At the same time, oil can flow from the reservoir 18 without pressure and in sufficient quantity into the cylinder space 12 without braking the feed speed of the piston 2.

By switching the valve 16a to its position 0 (phase 2A), starting with phase 2 (cf. FIG. 7), pressure oil is now conveyed from line 31 into both cylinder chambers 11 and 12, whereby the nominal working pressure for plunger 3 is applied. The feed speed of the piston rod 2 is now the lowest, your force the greatest.

By switching the valve 16a into its position b (phase 2B), pressure oil is only fed into the cylinder space 12. Unpressurized oil enters the cylinder chamber 11 from the reservoir 18. The speed of the piston rod 2 is accelerated again, the speed of the plunger 3 is not delayed.

By switching the valve 16a back to its position a, phase 2C is reached, in which pressure oil is again only fed into the cylinder chamber 11, which has the consequence that the piston rod is accelerated further and the speed reduction of the tappet - caused by the toggle effect - is compensated.

After reaching the UT, valve 16a switches to position a and valve 14a to position a, whereby the pressure oil is conveyed from line 30 into line 36 in order to pressurize annular cylinder space 13 from there, which piston 2 rapidly moved up. At the beginning, the pressure required for this is still low because the knee lever transmission helps. At the same time, the valve 16a switches to its position a, as a result of which the oil can flow from the space 12 into the pressure accumulator 18 and the oil from the space 11 via the valve 14a into the line 42 or the container 25.

• Phase 1 (schnelle Vorwärtsbewegung des Pressenstössels bis zum Beginn des Arbeitsbereiches - Schnittpunktes): Stellung a;
• Phase 2A (abgebremste Bewegung mit grösster Hydraulikkraft an der Kolbenstange 2): Stellung 0;
• Phase 2B (erste Erhöhung der Kolbengeschwindigkeit bei gleichzeitiger Druckkraftreduktion): Stellung b;
• Phase 2C (zweite Erhöhung der Kolbengeschwindigkeit bei weiterer Druckkraftreduktion): Stellung a;
• Phase 3 (beschleunigte Rückwärtsbewegung des Stössels):
  Stellung a
  Gegen Ende der Phase 3 gegebenenfalls wieder Stellung 0.

Summary of the control sequence at valve 16a:

• Phase 1 (rapid forward movement of the press ram to the start of the work area - intersection): position a ;
• Phase 2A (slowed down movement with the greatest hydraulic force on piston rod 2): position 0;
• Phase 2B (first increase in piston speed with simultaneous reduction in pressure): position b;
• Phase 2C (second increase in piston speed with further pressure reduction): position a;
• Phase 3 (accelerated backward movement of the ram):
  Position a
  At the end of phase 3 , position 0 again if necessary .

• Stellung a: Differntialschaltung zwischen Fläche 8 und Fläche 10; die vom Zylinderraum 11 zurückbeförderte Ölmenge wird direkt in den Raum 13 gefördert, was den Ölmengenfluss erhöht und derart die Befüllung beschleunigt.
• Stellung b: Direktschaltung
  Die Differntialschaltung lässt sich sinnvoll zu Beginn der Phase 3 einsetzen, weil dort das Übersetzungsverhältnis zwischen Druckstück 4 und Stössel 3 gross ist (geringer Kraftbedarf an der Kolbenstange 2). Mit fallendem Übersetzungsverhältnis muss dann auf Direktschaltung (Ventil 21 in Stellung b) umgeschaltet werden. Durch die Differntialschaltung lässt sich somit Phase 3 am Beginn beschleunigen, was eine weitere Hubzahlsteigerung erlaubt, zumal die Zeit für die Rückwärtsbewegung vorteilhafterweise reduziert. Auch diese technische Lösung könnte bei einfacheren Varianten der Erfindung als selbständige Lösung unabhängig zum Einsatz gelangen.

If the effective piston surface 8 of the plunger cylinder is selected to be smaller than the effective piston ring surface 10, a differential circuit can be used for the backward movement (upwards in phase 3) between these two surfaces. Valve 21 serves the following functions:

• Position a : differential circuit between surface 8 and surface 10; the oil quantity conveyed back from the cylinder space 11 is conveyed directly into the space 13, which increases the oil quantity flow and thus accelerates the filling.
• Position b: direct switching
  The differential circuit can be used sensibly at the beginning of phase 3, because there the gear ratio between pressure piece 4 and plunger 3 is large (low power requirement on piston rod 2). When the gear ratio drops, the gearshift must then be switched to direct (valve 21 in position b). The differential circuit allows phase 3 to be accelerated at the beginning, which allows a further increase in the number of strokes, especially since the time for the backward movement is advantageously reduced. This technical solution could also be used independently in simpler variants of the invention as an independent solution.

The container 18 shown as a pressure accumulator reduces the relaxation problems of the pressure oil during the transition from the unpressurized to the pressure state. As a rule, however, it will only have a low pressure compared to the working pressure in the cylinder and - as shown in other examples (e.g. Fig. 4) - can even be replaced by a pure refill container with ambient pressure.

A small amount of oil is continuously pumped into the reservoir 18 via the pump 50 and valve 51 (FIG. 3; position a). This ensures that an oil exchange takes place between the reservoir 18 and the container 25.

Excess oil in the reservoir 18 (during the upward movement of the plunger 3) is reduced into the container 25 via the pressure valve 52.

Compared to the solution according to FIG. 3, the differential circuit option is dispensed with in the variant according to FIG.

However, since the main principle of this circuit also corresponds to the circuit according to FIG. 3, its description is only given in key words. The name in brackets behind a reference sign means the position of the corresponding valve.

Phase 1:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (a), line 32, valve 16b (c), line 33 into cylinder chamber 11. Oil from container 15 is transferred into cylinder chamber 12 Line 34, valve 16b (c), line 35 sucked or refilled. Oil is conveyed back from the cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a) and line 38 into the container 25.

Phase 2A:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (a), line 32, valve 16b (b), lines 33 and 35 into rooms 11 and 12.

Oil flows out of cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into the container 25.

Phase 2B:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (a), line 32, valve 16b (a), line 35 into the cylinder space 12. Oil from the container 15 is in the cylinder space 11 suctioned or refilled via line 34, valve 16b (a), line 33. Oil flows out of the cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into the container 25.

Phase 2C:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (a), line 32, valve 16b (c). Line 33 into the cylinder space 11. Oil is added or refilled into the cylinder space 12 from the container 15 via line 34, valve 16b (c), line 35. Oil flows out of the cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into the container 25.

Phase 3:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (c), line 37, valve 19 (b), line 36 into the cylinder space 13. The oil displaced from the cylinder space 11 flows via line 33, valve 16b (c), line 32, valve 14b (c), line 38 into the container 25. The oil displaced from the cylinder space 12 flows via line 35, valve 16b (c), line 34 into the container 15.

The valve 14b can be designed as a 4-edge regulator (FIGS. 4 and 6) or as a 2-edge regulator 14c (FIG. 5). In an embodiment according to FIGS. 4 and 5, the valve 16b can be replaced by individual valves 20, 21, 22, 23 (corresponding to FIG. 6). On the valves 16b, 20, 21, the electrohydraulic actuation can take place by mechanical actuation depending on the piston 2 via cams.

• Stellung a: Presse Stop
• Stellung b: Presse in Betrieb

Beschreibung des Ausführungbeispieles nach Fig.5, das - unterschiedlich zum bisherigen - Hilfszylinder 44 für die Aufwärtsbewegung aufweist, die gehäusefest montiert sind. Anmerkung:
   Die hydraulisch wirksame Kolbenfläche im Zylinderraum 11 ist grösser als die wirksame Kolbenfläche im Zylinderraum 13.The valve 19 serves as a safety valve:

• Position a: press stop
• Position b: press in operation

Description of the embodiment according to Figure 5, which - different from the previous - auxiliary cylinder 44 for the upward movement, which are fixed to the housing. Annotation:
The hydraulically effective piston area in the cylinder space 11 is larger than the effective piston area in the cylinder space 13.

Phase 1:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14c (a), line 32, valve 16b (c), line 33 into the cylinder space 11. At the same time, pressure oil is displaced from the cylinder space 13 and flows via line 36 and valve 18 (a) in line 31. In the cylinder chamber 12, oil from the container 15 via line 34, valve 16b (c). Line 35 sucked or refilled.

The oil displaced from the cylinders 44 flows via lines 39, 40, valve 19 (b), line 41, valve 17 (b), line 42 into the tank 25.

Phase 2A:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14c (a), line 32, valve 16 (b), lines 33, 35 into the cylinder spaces 12, 11. Oil flows out of the cylinder space 13 via line 36, valve 18 (b), line 38 back into the tank 25. The oil displaced from the cylinders 44 flows via lines 39, 40, valve 19 (b), line 41, valve 17 (b), line 42 into the tank 25.

Phase 2B:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14c (a), line 32, valve 16b (a), line 35 into the cylinder chamber 12. Oil from the container 15 becomes cylinder chamber 11 suctioned or refilled via line 34, valve 16b (a), line 33. Oil flows out of the cylinder space 13 via line 36, valve 18 (b), line 38 back into the tank 25.

The oil displaced from the cylinder 44 flows via lines 39 and 40, valve 19 (b), line 41, valve 17 (b), line 42 into the tank 25.

Phase 2C:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14c (a), line 32, valve 16b (c), line 33 into the cylinder chamber 11. Oil from the container 15 is in the cylinder chamber 12 suctioned or refilled via line 34, valve 16b (c), line 35. Oil flows out of the cylinder space 13 via line 36, valve 18 (b), line 38 back into the tank 25.

The oil displaced from the cylinders 44 flows via lines 39, 40, valve 19 (b), line 41, valve 17 (b), line 42 into the tank 25.

Phase 3:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 18 (a), line 36 into the cylinder space 13. At the same time, pressure oil flows from pump 24 via valve 17 (a), line 41, valve 19 ( b), lines 39, 40 to the cylinders 44.

The oil displaced from the cylinder space 11 flows via line 33, valve 16b (c), line 32, valve 14 (c), line 38 into the tank 25. The oil displaced from the cylinder space 12 flows via line 35, valve 16b (c ), Line 34 into the container 15. The upper chambers of the auxiliary working cylinders 44 are connected with their upper hydraulic space to ambient air.

The effective piston ring area of the annular space 13 is less than that of the effective cylinder space 11. The space 13 is constantly under pump pressure. However, a forward movement is still possible due to the above surface conditions. The auxiliary cylinders therefore support the backward movement in order to compensate for the small force of the small effective area in the annular space 13. At the beginning of the backward movement, the power of 13 is still completely sufficient, since the lever transmission of the knee levers still helps. This support is only necessary towards the end of the backward movement.

Description of the hydraulic circuit according to Fig. 6: Note:
The hydraulically effective piston area in the cylinder chamber 11 is smaller than the piston area in the cylinder chamber 13. Parentheses mean the position of the respective valve.

Phase 1:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (a), line 32, valve 20 (a), line 33 into the cylinder chamber 11. Valve 21 is in position b. Oil is sucked into the cylinder space 12 from the container 15 via line 34, valve 23, line 35 or refilled. Oil flows out of the cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into the tank 25.

Phase 2A:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (a), line 32, valves 20 (a), 21 (a), lines 33, 35 into the cylinder spaces 11, 12. Off Oil flows back into the cylinder chamber 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 into the tank 25.

Phase 2B:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31 valve 14b (a), line 32, valve 21 (a), line 35 into the cylinder chamber 12. Valve 20 is in position b. Oil is sucked in or refilled from the cylinder 15 into the cylinder space 11 via line 34, valve 22, line 33. Oil flows out of the cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into the tank 25.

Phase 2C:

Pressure oil flows from pump 24 via line 30, valve 19 (b). Line 31, valve 14b (a), line 32, valve 20 (a), line 33 into the cylinder chamber 11. Valve 21 is in position b. Oil from the tank 15 is sucked in or refilled into the cylinder space 12 via line 34, valve 23, line 35. Oil flows out of the cylinder space 13 via line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into the tank 25.

Phase 3A:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (c), line 37, valve 19 (b). Line 36 into the cylinder chamber 13. Valve 20 is in position b.

The pressure oil displaced from the cylinder chamber 11 flows via line 33, valve 18 (b) into line 37. The oil displaced from the cylinder chamber 12 flows via line 35, valve 21 (a), line 32, valve 14b (c), line 38 into the tank 25.

Phase 3B:

Pressure oil flows from pump 24 via line 30, valve 19 (b), line 31, valve 14b (c), line 37, valve 19 (b), line 36 into the cylinder space 13. Valve 18 is in position a.

The oil displaced from the cylinder chamber 12, 11 flows via lines 33, 35, valves 20 (a), 21 (a), line 32, valve 14b (c), line 38 into the tank 25.

The valves and lines shown can be replaced by functionally similar components without leaving the scope of the invention, provided the methods according to the invention are used.

The outer structure of the press preferably comprises a two-stand frame which is partially closed on the front and end sides in accordance with the known DWP. A multi-joint lever construction according to WO 87/07870 A1 can also be implemented constructively within the scope of the invention. Reference is made to the relevant parts of the description in the cited publication.

Claims (10)

Method for the hydraulic control of a piston rod (2) of a working cylinder (1) of an articulated lever or toggle lever system of an articulated lever or toggle press, in which, before reaching the cutting phase (contact of the tool with the workpiece), the press ram speed is reduced and the press force of the ram ( 3) is increased, characterized in that the speed of the forward movement of the piston rod (2) after reaching the intersection point and before initiating the backward movement is increased at least once. A method according to claim 1, characterized in that the speed of the forward and backward movement of the piston rod (2) - preferably via mechanical control elements - is controlled depending on the path of the press ram (3), said piston rod (2) possibly also during the backward movement is moved with different drive speeds. A method according to claim 1 or 2, characterized in that the speed of the piston rod (2) in the forward direction is increased at least twice after reaching the intersection. Method according to one of the preceding claims, characterized in that the speed variation by the - possibly stepless - distance or Hydraulic piston surfaces (8-10) are connected. Articulated lever or toggle press with a hydraulically controlled cylinder piston arrangement characterized by a control with a predetermined control method according to one of the preceding claims. Press according to claim 5, characterized in that at least one differential cylinder with at least one integrated plunger cylinder (11) is provided as the cylinder piston arrangement. Press according to claim 5 or 6, characterized in that hydraulic valves are provided for the control, which are connected directly or indirectly by a path-dependent feedback member (14; 115) which picks up the path of the piston rod (2) or the press ram (3) . Press according to one of the preceding claims 5 to 7, characterized in that at least one cylinder of the cylinder piston arrangement (1) is arranged in a ram-fixed manner. Press according to one of the preceding claims 5 to 8, characterized in that a differential cylinder with at least one integrated plunger cylinder (11) is provided with at least one working cylinder - in particular for the backward movement of the press ram (3). Press according to one of the preceding claims 5 to 9, characterized in that at least one ram-fixed main working cylinder (13) - preferably a differential cylinder with integrated plunger cylinder (11) - whose piston rod (2) is connected to the toggle levers (5-7) an auxiliary working cylinder (44) fixed to the press frame is set aside, the piston rod of which is connected to the press ram (3).

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