EP0616882B1 - 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 after the Method according to the preamble of claim 1 and According to claim 5. Such processes are mainly used for Cutting and forming presses of modern design with hydromechanical Articulated lever drives applied. The applicant has for example under the name differential travel press (DWP) successfully launched a toggle plate cutting press in the Market introduced, 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 supporting them on the press frame and support of the working cylinder on the press ram apply for the purpose of constructive design one embodiment as disclosed herein.

Such a press has two - with their knee joints buckling towards the middle of the press - toggle lever systems, that of a piston rod one symmetrical to the toggle levers arranged cylinder piston assembly during a Lift cycle in the forward and then reverse direction be charged. In passing, the market also knows one as Differential printing press (DDP) introduced press that between the piston rod and the articulation points on the toggle levers has yet another linkage guided in roller tracks. Such a press became public in August 1987 presented and subsequently used.

Both known presses go into one in their origins Toggle press with crank drive back, which is the toggle lever operated to 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 further reduce and over a certain period or over a to keep certain distance as slow as possible. This is because because in the cutting or embossing or drawing area of the processing material a better cutting precision or Machining quality could reach that of a pure Crank drive without interposition of toggle levers. In addition could the power through the translation effect of the knee lever in the working area (cutting area) increased accordingly will.

The toggle levers also provide precision in the cutting direction (depth of cut) for sure what is under also for toggle presses with hydraulic piston drives took advantage of, such as shown in GB-A 707815.

In the past, it was particularly about obtaining the aforementioned Speed reduction in the work area and later the improvement in cutting precision, so became with increasing Automation of production processes the speed of work (Stroke rates) with maximum precision brought to the fore. 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 that of a toggle press (high forces in the work area and maximum precision with regard to the depth of cut). The DDP built later based on the DWP tried through additional mechanical effort of the roller rails and Intermediate linkages to increase the stroke rates of the press what however, due to the high wear additional components were bought expensive.

The present invention is therefore based on the object of providing a press and a simple method for driving the same, which, without losing the respective advantages and properties of the known presses, should enable a higher stroke rate and therefore greater profitability. 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 should 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 is achieved per workpiece. This task should also be made possible without significant additional control expenditure (by a large number of additional components for regulators or the like).

The speed of the press ram over the entire Work area (from cut contact with the workpiece to the Backward movement of the ram) to keep it as constant as possible is fundamental for other hydraulic press types already known. However, this usually requires big ones Pressure fluid drives, since these without - at the familiar nonexistent - beneficial effect of the toggle lever both the working pressure, as well as the considerable amount of oil flow for have to make a movement in overdrive. Size Oil flow quantities also mean large cross sections the pressure lines or increased flow velocities and thus a deteriorated efficiency the press as a whole and often even one increased cutting bang.

Such a comparable hydraulic press is for example described in DE-A 4036564, however does not aim at a constant ram speed, one but could make them possible with an appropriate design. To control important process variables such as paths (s), Speed (v) and forces (F) are complex there 4/5-way regulator valve with some peripheral equipment, electronic Displacement sensors, pressure sensors and ultimately even one electronic control required.

This goal is also new for articulated or toggle presses and actually exactly the opposite of the previous teaching that namely says that you can permanent speed reduction of the press ram in the work area strived for or the effect of the knee levers Speed reduction takes advantage.

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

The slowdown effect, which the toggle levers bring about in the work area partially weakened or compensated by the Crank speed in the work area according to the invention and is advantageously varied.

The tasks were also not solved by other constructions, which, however, appear to have similar solutions searched:

For example, U.S. Patent 3,926,033 shows a "series connection" of Cylinder piston arrangements (telescopic cylinders) with different effective areas, which in turn disadvantageously with correspondingly large, powerful pressure medium drives must be applied. A targeted one Switch from one piston to another inside a movement phase is not possible

The invention, on the other hand, solves the stated problems in a simple manner Art. In principle, the invention can with any conventional Pressurized articulated or toggle press be applied. The only requirement is that the drive the piston rod is speed controllable.

The ram speed is reduced by the method according to the invention not as before (e.g. with the DWP or DDP) reduced to the UT (bottom dead center), but rather almost constant at the expense of the driving force of the piston rod held. You can allow yourself this because of the movement physics of the toggle principle, which because of its always higher translation in the UT area (work area) anyway only a part of the driving force is needed, which continues above the UT was still required for deformation to apply the required press force. Will with a workpiece according to an arrangement according to the invention cut, the effect according to the invention comes to that Workpiece in the opposite direction: only during first contact of the cutting tool with the workpiece are high forces second hand; these generally decrease in the flow area.

The invention advantageously changes other desired ones Properties of a DWP or DDP not, e.g. Stop times under 50ms, practically no cutting bang due to under high Pressure of clamped oil quantities, long tool life, possibility any reprint settings in the range from UT, no need for shock absorption, etc. Well but the invention is by the simplest hydraulic Circuits possible. Compared to the known circuit according to DE-A1 4036564, it can according to the exemplary embodiments shown with a minimal mechanical-hydraulic Regular effort to find enough.

A preferred embodiment of a press according to the invention is however with at least one stepped piston cylinder or Differential cylinder with integrated plunger cylinder as Main working power source equipped. Together with the According to the method according to the invention, this structure offers the advantage great compactness and a reduction of sealing problems compared to arrangements of multiple drive cylinders with different ones working parallel to each other Printing areas. As another advantage, this offers preferred Solution that one in the sense of a high hydraulic efficiency with high pressures but low oil flows can work.

In the device claims is on the speed the piston rod is turned off. of course lie within the scope of the invention, however, also variants whose toggle levers not directly through a piston rod but e.g. are driven by an electromechanical drive. In such cases, the piston rod is only a thrust piece understand that right at the knee levers attacks.

The method according to the invention deals with the basic principle forth with the control of a press ram one hydromechanical toggle press in its working area. The basic idea, as mentioned, is the speed of work of the ram there as constant as possible on the as optimal recognized speed that he was at the time of first cut contact (at the beginning of the work area) has reached. There is one for each material or workpiece optimal forming speed, according to the invention selected and essentially constant during the forming remains. However, it is also within the scope of the invention the piston rod speed after reaching the To increase the intersection point so that after redirection of this Speed through the toggle or even one Increase in ram speed results if for the workpiece in question, for example, from deformation technology Reasons is desirable.

As a rule, all switching or control processes can be carried out in stages can be done for special versions however also - if necessary even electronically regulated, e.g. using the complex controller circuit according to DE-A 4036564, the detailed circuit structure as in the frame this application is disclosed horizontally - take place continuously, possibly even via the non-preferred route of oversized or parallel pressure oil pumps, which by increasing their output also become one Acceleration of the piston rod in the working area of the ram could be used.

However, a purely mechanical positive control is preferred of the valves depending on the path of the piston rod, because highest stroke rates can be achieved. The principle of the step piston shown in the drawing can course within the scope of the invention to increase the Use the number of stages several times, provided the cylinder piston arrangement is chosen accordingly.

Another variant could be between the piston rod and a suitable lever ratio at the articulation points on the toggle levers or a gear or the like. be arranged that way is designed so that it corresponds to the inventive Procedure with constant piston speed Articulation points accelerated in the forward direction.

Identify the remaining dependent and independent claims or describe embodiment variants of the invention. Other variants also result from the Combination of the different embodiments below each other to perform more specific or detailed tasks, if necessary to be able to solve. In particular, this affects the arrangement a master cylinder on the ram and at least an auxiliary working cylinder on the press frame, the piston of the main working cylinder on the toggle levers and the piston of the auxiliary cylinder only on the tappet attacks.

Even if such an alternative arrangement as last described not operated with the method according to the invention it brings advantages over conventional designs with only one master cylinder e.g. at a DWP or DDP. If the auxiliary working cylinders e.g. only for them Used backwards movement of the ram, they work optimally in accordance with the overall physical concept a DWP, which is also designed to minimize pumping Pressure oil quantities is designed. When moving forward can a small sized master cylinder for feed ensure (less oil to be pumped). When moving backwards (in this case when lifting the ram) is initially only little and slow flowing oil in the auxiliary cylinders used that simply sucked in even without pump power or can be refilled with or without pressure. in the The area of the UT helps the knee lever translation Main working cylinder, so that this despite smaller dimensions can lift the ram. Only in the upper area, where the toggle effect can then wear off temporarily Auxiliary cylinders are helped, whereby in OT (OBERER TOTPUNKT) Area again the movement of the main piston is slowed down and therefore less there again Pressure oil delivery is necessary.

The two cylinder systems therefore complement each other perfectly In order to minimize pressure oil consumption with good press performance. Together with the method according to the invention (if necessary with the help of a stepped piston) such a variant also works faster than so far.

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 lever press with a simple (large-sized) 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 step cylinder piston arrangement modified, but not shown, engages, which is connected to a control, not shown, which operates according to the method according to the invention.

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.

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

Fig. 2 shows a press with two counter-acting toggle lever systems 10, 12, 16 by a cylinder-piston arrangement 10,11 are driven. The latter becomes corresponding the press of Figure 1 with a control line 21 Compressed air or another pressure medium. Of the The remaining structure of this press is described in GB-A-804352 described as being 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 here thus understandable for the OT.

The press according to Figure 3 is the one according to Figures 1 and 2 to the extent that the working cylinder 1 is not on Housing G, but is supported on the plunger 3, it corresponds thus a DWP. The detailed structure of such Press is described for example in EP-A1 250610.

The further details of the construction according to the invention result as follows:

A pump delivers pressure oil through a pressure line 30 a cam-operated 3-position valve 14a, which in its Position b promotes the oil in a line 31. The cam control is coupled to the piston position and symbolic indicated at 15. Line 31 becomes the pressure oil via the 3-position valve 16a in its position a via the 2-position valve 21 in its position b in the innermost Cylinder chamber 11 promoted. Because this is a relatively small volume has resulted in a relatively rapid downward movement of the piston 2 and thus via the pressure piece 4 and Toggle lever 5,6,7 a rapid downward movement of the ram 3. The cylinder chamber 13 is simultaneously via the line 36 emptied, this via the valve 14a (position b) in the reservoir 25 is emptied.

From the memory 18 can be depressurized and sufficient at the same time Quantity of oil flow into the cylinder chamber 12 without to brake the feed speed of the piston 2.

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

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

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

After reaching the UT, valve 16a switches to position a and valve 14a in its position a, whereby the pressure oil out the line 30 is promoted to line 36 to from there to apply pressure to the annular cylinder space 13, which moves the piston 2 quickly upwards. In the beginning is the the pressure required for this is still low since the toggle lever ratio helps. At the same time, valve 16a switches on its position a, whereby the oil from the room 12 in the Pressure accumulator 18 and the oil from space 11 via the valve 14a can flow 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 one selects the effective piston area 8 of the plunger cylinder smaller than the effective piston ring area 10, a differential circuit can be used for the backward movement (upwards in phase 3) between these two areas. 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 shift The differential shift 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). If the gear ratio drops, the gearshift must 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 the case of simpler variants of the invention as an independent solution.

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

About the pump 50 and valve 51 (Fig.3; position a) constantly conveyed a small amount of oil into the memory 18. This ensures that between memory 18 and Container 25 an oil exchange takes place.

Excess oil in the reservoir 18 (when the Tappet 3) is in the container 25 via pressure valve 52 reduced.

Compared to the solution according to Figure 3, the variant according to Fig.4 dispenses with the differential circuit option.

After the main principle of this circuit, however, the Circuit corresponds to Figure 3, their description is only stated in key words. The brackets behind a reference sign means the position of the corresponding one 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 in the cylinder chamber 11. In the cylinder chamber 12 Oil from reservoir 15 via line 34, valve 16b (c), line 35 sucked up or refilled. From the cylinder room 13 becomes oil via line 36, valve 19 (b), line 37, valve 14b (a) and line 38 into container 25 promoted back.

Phase 2A:

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

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

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 in the cylinder space 12. In the cylinder space 11 Oil from reservoir 15 via line 34, valve 16b (a), Line 33 sucked or refilled. From the cylinder room 13 oil flows through line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into 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). management 33 in the cylinder space 11. In the cylinder space 12 Oil from reservoir 15 via line 34, valve 16b (c), line 35 sucked up or refilled. From the cylinder room 13 oil flows through line 36, valve 19 (b), line 37, Valve 14b (a), line 38 back into 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. That from the cylinder space 11 displaced oil flows via line 33, valve 16b (c), line 32, valve 14b (c), line 38 into the container 25. Das Oil displaced from the cylinder chamber 12 flows via the line 35, valve 16b (c), line 34 into container 15.

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

Stellung a: Presse Stop

Stellung b: Presse in Betrieb

The valve 19 serves as a safety valve:

Position a: press stop

Position b: press in operation

Description of the embodiment according to Fig. 5, the - different from the previous - auxiliary cylinder 44 for the Has upward movement, which are fixed to the housing.

Annotation:

The hydraulically effective piston surface in the cylinder chamber 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 chamber 11. At the same time, pressure oil displaced from the cylinder chamber 13 and flows via line 36 and valve 18 (a) in line 31. In the cylinder space 12 becomes oil from the reservoir 15 via line 34, valve 16b (c). Line 35 sucked or refilled.

The oil displaced from the cylinders 44 flows through the 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. From the cylinder space 13 oil flows through line 36, valve 18 (b), line 38 back into the tank 25. That from cylinders 44 displaced oil flows via lines 39, 40, valve 19 (b) line 41, valve 17 (b), line 42 into 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 in the cylinder space 12. In the cylinder space 11 Oil from reservoir 15 via line 34, valve 16b (a), line 33 sucked up or refilled. From the cylinder room 13 oil flows through line 36, valve 18 (b), line 38 in the tank 25 back.

The oil displaced from the cylinder 44 flows through the 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 in the cylinder space 11. In the cylinder space 12 Oil from reservoir 15 via line 34, valve 16b (c), line 35 sucked up or refilled. From the cylinder room 13 oil flows through line 36, valve 18 (b), line 38 in the tank 25 back.

The oil displaced from the cylinders 44 flows through the 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 chamber 11 flows through the 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 cylinders 44 are with their upper hydraulic room with ambient air connected.

The effective piston ring area of the annular space 13 is smaller than that of the effective cylinder space 11. The space 13 stands constantly under pump pressure. But there is a forward movement nevertheless possible due to the above area ratio. The Auxiliary cylinders therefore support the backward movement, to the small force of the small effective area in the Make up for space 13. At the beginning of the backward movement the performance of 13 is still completely sufficient, since there the Lever translation of the toggle lever still helps. First against This support is needed at the end of the backward movement.

Description of the hydraulic circuit according to Fig. 6:

Annotation:

The hydraulically effective piston surface in the cylinder chamber 11 is smaller than the piston area in the cylinder chamber 13. Parenthetical expressions 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 in the cylinder chamber 11. Valve 21 is in Position b. Oil from the container becomes in the cylinder chamber 12 15 sucked in via line 34, valve 23, line 35 or refilled. Oil flows from the cylinder space 13 via a line 36, valve 19 (b), line 37, valve 14b (a), line 38 in the tank 25 back.

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. From the cylinder space 13 oil flows through line 36, valve 19 (b), line 37, valve 14b (a), line 38 back into 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 in the cylinder chamber 12. Valve 20 is in Position b. In the cylinder chamber 11 oil from the container 15 sucked in via line 34, valve 22, line 33 or refilled. Oil flows from the cylinder space 13 via a line 36, valve 19 (b), line 37, valve 14b (a), line 38 in the tank 25 back.

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 in the cylinder chamber 11. Valve 21 is in Position b. Oil from the container becomes in the cylinder chamber 12 15 sucked in via line 34, valve 23, line 35 or refilled. Oil flows from the cylinder space 13 via a line 36, valve 19 (b), line 37, valve 14b (a), line 38 in the tank 25 back.

Phase 3A:

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

The pressure oil displaced from the cylinder chamber 11 overflows Line 33, valve 18 (b) in line 37. That from the cylinder room 12 displaced oil flows through line 35, valve 21 (a), line 32, valve 14b (c), line 38 into the tank 25th

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 in the cylinder chamber 13. Valve 18 is in Position a.

The oil displaced from the cylinder chamber 12, 11 overflows 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 functional Similar components can be replaced without the frame to leave the invention, provided that the invention Procedure apply.

The outer structure of the press preferably includes one Partially closed two-stand frame on the front and front according to the well-known DWP. A multi-joint lever construction according to WO 87/07870 A1 is also possible be realized constructively within the scope of the invention. On the relevant parts of the description in the cited Publication is referenced.

Claims (10)

1. A method of hydraulically controlling a piston rod (2) of a working cylinder (1) of a toggle-joint or knuckle-joint system of a toggle-joint or knuckle-joint press, in which the press ram speed is reduced before reaching the cutting phase (contact of the tool with the workpiece) and the press force of the ram (3) is increased, characterized in that the speed of advancing movement of the piston rod (2) is increased at least once after reaching the cutting point and before initiating the return movement.
2. A method according to claim 1, characterized in that the speed of the advancing and return movement of the piston rod (2) is controlled - preferably through mechanical contact elements - in dependence on the stroke of the press ram (30, wherein the piston rod (2) is optionally moved also in its return movement with different drive speeds.
3. A method according to claim 1 or 2, characterized in that the speed of the piston rod (2) is increased at least twice after reaching the cutting point.
4. A method according to any one of the preceding claims, characterized in that the speed variation is effected through the - optionally stepless - switching out or in of hydraulically acting piston surfaces (8 - 10).
5. A toggle-joint or knuckle-joint press with a hydraulically controlled cylinder and piston arrangement, in which the press ram speed is reduced before reaching the cutting phase (contact of the tool with the workpiece) and the press force of the ram (3) is increased, characterized in that hydraulic valves are provided for the control and are connected indirectly or directly from a stroke-dependent feedback element (14; 115) which detects the stroke of the piston rod (2) or the press ram (3), wherein the speed of advancing movement of the piston rod (2) is increased at least once after reaching the cutting point and before initiating the return movement.
6. A 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 and piston arrangement.
7. A press according to claim 5, characterized in that the speed variation is effected through the - optionally stepless - switching out or in of hydraulically acting piston surfaces (8 - 10).
8. A press according to any one of the preceding claims 5 to 7, characterized in that at least one cylinder of the cylinder and piston arrangement (1) is fixed to the ram.
9. A press according to any of the preceding claims 5 to 8, characterized in that at least one working cylinder - especially for the return movement of the press ram (3) - is provided alongside a differential cylinder with at least one integrated plunger/cylinder (11).
10. A press according to any of the preceding claims 5 to 9, characterized in that at least one auxiliary working cylinder (44) with its piston rod connected to the press arm (3) is disposed alongside at least one main working cylinder (13) - preferably a differential cylinder with integrated plunger/cylinder (11) - fixed to the ram, with its piston rod (2) connected to the knuckle joint (5 - 7).

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