EP1839844A2 - Hydraulic press for plastic and metal processing - Google Patents

Abstract

The press has a rapid motion cylinder (12) arranged with a tappet binding for the fast idle stroke of the plunger. The piston (6) or the working cylinder (7) is firmly arranged at the upper crosshead (11) of the press frame (1) to the press table. The piston has a centrically arranged cylindrical extension (18) for the sliding guidance of a shaft (3), and the shaft is connected with the press plunger (2).

Description

The invention relates to a hydraulic press according to the preamble of claim 1 for the plastics and metal processing.

Fast running hydraulically operated presses for the plastic and metal processing are known, these machines are designed for different tool heights and opening strokes so that the Arbeitszylinderhub is so large that depending on the tool in the installation space between the press table and press ram, the maximum expected tool height (large Gap between the platens of press table and press ram) with a required stroke and a very low tool height (small gap between the platens of press table and press ram) can be used equally. Such presses have because of a necessary oil column of up to 2.5 m, the corresponding work surface and the high specific processing pressures in the tools, a very large volume of oil in the working cylinders, what next a large compression volume also entails economic disadvantages during operation.
There are now various approaches to limit the idle stroke of the working cylinder with different tool application and yet to ensure a high flexibility of the press with short changeover times. For example, presses are known DE 36 37 544 A1 and DE 36 37 545 A1 in which the working stroke is to be reduced to a so-called short stroke with the lowest compression volume with frictional clamps on steel columns (round or square shape). However, these frictional connections have not proven in practice, or are too expensive.
Of course, there are also a variety of other mechanical solutions for height adjustment of long stroke in the prior art. Systems in which, similar to injection molding machines with retractable bars, or pressure plates, the force is also transmitted with short-stroke working cylinders have not been successful because of the large moving pressure plates and large ways and the resulting extension of the cycle time.
A possible remedy can be found in DE 10 2004 040 512 A1 in which in each case between a short-stroke piston and the web plates of the press ram, a turntable with rotary shaft and four stilts is provided, wherein the stilts by means of rotary drive of the rotary shaft and a twist angle either in power transmission position on the support surfaces of the web plates or in Opening position between the web plates of the press ram are arranged adjustable. This application has proven itself in principle.

With US 4,304,540 A has become known a press, which is designed in column construction, while the press ram moves on a plurality of externally arranged columns. The working cylinders are arranged in the press table and above the press ram jaws are mounted, which connect after bridging the idle stroke the press ram on the columns form-fitting and thus close the power flow for the pressing process. Predominantly disadvantageous has been the direction of the power flow, as the power flow redirection takes place in the screening of the columns and thus load peaks must be redirected in notched machine elements. Also, the screens of the columns are freely accessible and thus exposed to possible contamination. The clamping of the columns takes place at standstill.

In addition to the mechanical alternatives was trying to shorten the idle stroke using other drives, such as electrically operated intermediate drives.
This results in the disadvantage that power peaks of several hundred amperes in the drive motors occur because the drives used must move tons loads quickly and usually without intermediate translations (as in crane loads). Just such power peaks are measured by the utilities and high surcharges in the Billing of the power supply charged. The surcharges are so high in massive energy peaks as they occur here, that they significantly affect the economic efficiency of a press. In addition, it may be imposed on the operator by the competent electricity supplier to install devices for damping the power peaks for the supply network, which in turn entail high acquisition and maintenance costs.

1. a) es müssen große hydraulische Ölmengen bei Langhubpressen bewegt werden, was zu einem erhöhten Energieaufwand und erhöhtem Verschleiß der hydraulischen Elemente (Ölverbrauch, Pumpen, Ventile) führt,
2. b) bei mechanischen Leerhubüberbrückungen zur Vermeidung der Nachteile aus a) finden sich umständliche Klemmungen die die Schließgeschwindigkeit der Presse beeinträchtigen und den Arbeitszyklus verlängern,
3. c) dabei unterliegen mechanische Leerhubüberbrückungen in der Regel erhöhtem Verschleiß durch ungünstige Kraftflüsse in der mechanischen Klemmung,
4. d) die Säulen oder Zahnstangen für den Eingriff der mechanischen Klemmelemente sind in der Regel ungeschützt und der üblichen Verschmutzung in Werkshallen zugänglich, und
5. e) bei Leerhubüberbrückung mittels elektrischer Antriebe ergeben sich hohe Leistungsspitzen, die Nachteile für die Wirtschaftlichkeit des Betriebes und erhöhten regelungstechnischen Bedarf in der Energieversorgung bewirken.

Thus, the following disadvantages arise in the known art:

1. a) it is necessary to move large amounts of hydraulic oil in long-stroke presses, resulting in increased energy consumption and increased wear of the hydraulic elements (oil consumption, pumps, valves),
2. b) mechanical Leerhubüberbrückungen to avoid the disadvantages of a) are cumbersome clamps that affect the closing speed of the press and extend the duty cycle,
3. c) mechanical Leerhubüberbrückungen are usually subject to increased wear due to unfavorable power flows in the mechanical clamping,
4. d) the columns or racks for the engagement of the mechanical clamping elements are usually unprotected and the usual pollution in factory buildings accessible, and
5. e) in Leerhubüberbrückung means of electric drives, high power peaks, which cause disadvantages for the efficiency of the operation and increased control technology needs in the energy supply.

The invention is an object of the invention to provide a hydraulic press with the possibility for short cycle times and a fast and variably adjustable Leerhubüberbrückung.

The solution for a hydraulic press consists of a press frame with press table disposed thereon and arranged therein press ram, being arranged for the fast idle stroke of the press ram rapid traction cylinder with a plunger connection, wherein at the upper crosshead of the press frame of the or the working cylinder with the press table directed piston are fixedly arranged, wherein on the piston in the direction of the press table, a coupling jaw and opposite thereto a traverse with positioning and synchronizing are arranged for the piston, wherein the piston has a centrally disposed cylindrical extension for sliding guidance of a rack, said rack connected to the press ram is.

The inventive design of the press allows a quick closing of the press, while still during the movement of the Press ram in the fast idle stroke or during the braking phase of the coupling process is performed and without delay, the working stroke can be performed. This means that for the coupling process, the press ram does not have to be stopped and this can change directly from a reduced rapid traverse speed to the main pressing phase. This is achieved in an advantageous manner by the hydraulic control of the closing movement between the rapid traverse cylinders of the press ram and the working cylinder for the working stroke and / or the positioning and synchronizing cylinders 9 and 9, which with the aid of the position and speed information of the respective position measuring systems, a simple synchronization of clutch claw to the rack allows. This results in an advantageous manner automatically adjustable adjustment options for the variably definable tool heights without intermediate pieces inserted or mechanical elements must be adapted to the tools. Accordingly, there is the possibility of full automation of a press line or a press for automatic feeding with different tools without manual adjustment of the Leerhubweges.

The short stroke of the working cylinder results in significant energy savings due to the low compression volume and compared to the prior art to be moved amount of hydraulic fluid. Since the working cylinders are usually designed large-volume must already be in an application with a short press ram idle stroke with small-volume rapid traverse high energy savings potentials. The saving effect is additionally reinforced by lower amounts of circulating oil, which has to be changed regularly. Also, a low cooling capacity, due to lower installed engine power and lower circulating hydraulic oil quantities contributes significantly to an economical operation of a hydraulic press. Furthermore, there are still advantages in terms of susceptibility to failure of the hydraulic elements, as well as the closure of the valve technology, the hydraulic lines and other machine elements involved is reduced. In this case, a short pressure build-up time in the working cylinder is achieved in an advantageous manner, since the low existing oil volume, this does not have to be compressed first for the pressure build-up.
The arrangement of the mechanical coupling with a coupling claw in conjunction with a centrally arranged in the piston of the working cylinder rack gives advantages in terms of power flow during the pressing. The power flow is not redirected in the coupling jaw or the locking elements of the rack, as is the case with tie rods, but can flow in a straight line in the form of continuous compressive stresses, resulting in a simplified geometric design in conjunction with a construction safe design of the locking elements for the mechanical Coupling possible.

In addition, the leadership of the rack in the cylindrical bore of the piston of the master cylinder simultaneously provides an encapsulation of the locking elements and provides protection against harmful environmental influences. In the open state of the press, during maintenance or standstill, the rack is completely protected inside the piston and its extension and is also exposed to unnecessary contamination even when changing tools or operational standstill. To ensure this effect during operation there is still the possibility between press ram and coupling claw provide a telescopic encapsulation or the like. With a complete encapsulation of the rack and its guide, it would be necessary to filter the entering into this enclosure air due to the different gas volumes with open and closed press.

Further advantageous measures and embodiments of the subject matter of the invention will become apparent from the dependent claims and the following description with the drawing.

Figur 1

ein schematisch Schnitt einer hydraulischen Presse mit zwei Arbeitszylindern,

Figur 2

einen Teilschnitt nach Figur 1 Stellung des Arbeitszylinders im oberen Totpunkt bei geöffneter Kupplungsklaue,

Figur 3

einen Teilschnitt nach Figur 1 mit Stellung des Arbeitszylinders im unteren Totpunkt mit geschlossener Kupplungsklaue und

Figur 4

ein Schnitt durch eine geöffnete Kupplungsklaue mit Darstellung der Rastelemente nach Figur 2.

Show it:

FIG. 1

a schematic section of a hydraulic press with two working cylinders,

FIG. 2

a partial section of Figure 1 position of the working cylinder at top dead center with open clutch claw,

FIG. 3

a partial section of Figure 1 with the position of the working cylinder at bottom dead center with closed clutch claw and

FIG. 4

a section through an open coupling claw showing the locking elements of Figure 2.

Figure 1 shows a schematic section of a hydraulic press in the open state with a press frame 1, a fixed therein press table 20 and movably arranged above press ram 2. For the movement of the press ram 2 in rapid traverse 13 rapid traverse cylinder 12 are arranged laterally via plunger connections. Above the press ram 2 a rack 3 is articulated depending on the design and necessity of a hydrostatic bearing 4, which is guided in a central bore of the piston 6 of the working cylinder 7. In this case, the piston 6 has an extension 18 for a secure guidance of the rack 3 and at the same time protects the rack 3 from environmental influences.
In Figure 2 is found in an enlarged view of the open press state again. The clutch claw 5 is opened and the piston 6 of the master cylinder 7 is at top dead center. This is achieved in that over the piston chamber 8 of the positioning and synchronizing cylinder 9, the cross member 10 pulls the permanently connected thereto extension 18 of the piston 6 upwards. The working cylinder 7 is fixed to the upper crosshead 11 and the coupling claw 5 is fixedly connected to the piston 6. The closing of the press via the rapid traverse cylinder 12, via the tappet connection 13th the press ram 2 moves downward. Before tool or material contact or before reaching the parallel position, consisting of parallel holding cylinders 14 and the spacer elements 15, the piston 6 is accelerated in advance in order to synchronize with the speed of the rack 3. This is controlled by the positioning and synchronizing cylinder 9 and the rapid traverse cylinders 12 in conjunction with the associated Wegmeßsystemen. As soon as a synchronization via the displacement measuring devices 21 and 22 is confirmed, the coupling claw 5 is closed. This engages with the screening of the locking elements 19 in the teeth of the rack 3 (see Figure 4). This process must be completed before the system is clamped on the parallel holding cylinder 14 with the working cylinder 7 and the working cylinder 7 initiates the pressing process and in the piston chamber 16 via the port 17 pressure builds up (see Figure 3). Accordingly, hydraulic core elements such as hydraulic supply, hydraulic pumps, controls and much more must be provided, which are not relevant according to the invention and thus not further illustrated.
After the pressing process and relief of the piston chamber 16, the clutch claw 5 is opened again and the rapid transfer cylinder 12 and the associated plunger connection 13 of the press ram 2 is again moved to the position of the top dead center. At the same time, the piston 6 is transported back to its upper end position via the positioning and synchronizing cylinder 9.

The compact design of the locking system can be designed independently of the press frame 1 or its crosshead 11. With regard to opening stroke, working stroke and number of master cylinders, the locking system is also independent. The coupling device 5 is seated directly on the piston 6, which is designed with its extension 18 as a hollow piston and arranged in the working cylinder 7. The positioning and synchronizing cylinder 9 are seated on the working cylinder 7. The piston 6 is brought in operation as needed on the positioning and synchronizing cylinder 9, depending on the position of the press ram 2 and the rapid traverse cylinder 12 in the clutch position. This makes it a prerequisite for the automatic adjustment of the press to different predefined tool heights, without having to manually change the press during a tool change. In this case, energy savings are possible by the short stroke of the working cylinder 6 with low compression volume in a hydraulic long-stroke press of more than 50% compared to a fully hydraulic solution in which the stroke of the working piston corresponds to the opening stroke of the press ram.
Next results in a fast closing operation of the press ram 2 by high closing speed in conjunction with the pre-acceleration of the piston 6 of the working cylinder 7 to synchronous drive with the rack 3 for the dome operation and short pressure build-up time due to lower hydraulic oil compression. The coupling claw 5 and the rack 3 are claimed only on pressure. As a result, only small Deviations of the profile division under force and there is no compensation required by different column or division of the components. This is accompanied by a high possible power density.

The arrangement of the hydrostatic bearing 4 between the rack 3 and press ram 2 results in a decoupling of the locking system with respect to eccentric moments. Moments that act on the press ram 2 from the process are not transferred to the locking system. Furthermore, there is a compensation of the offset of the rack connection of the rack 3 on the press ram 2 at plunger inclination because of the short guide length on the working cylinder 7 and the hydrostatic bearing 4. The synchronization between the two moving main elements (press ram 2 and piston 6 of the working cylinder 7) is as follows regulated: and monitors: The stroke of the working cylinder 7 and thus the vertical position of the locking elements 19 of the clutch claw 5 is detected by the path measuring device 22. The stroke of the press ram 2 and thus the vertical position of the rack 3 is detected by the path measuring device 21. On the one hand, the positioning and synchronizing 9 on. Working cylinder 7 together with the path measuring device 22 and the corresponding necessary and interconnected hydraulic and electrical components form a control loop, on the other hand creates a control loop on the rapid traverse cylinder 12 on the press ram 2 together with the Path measuring device 21 and the corresponding necessary and interconnected hydraulic and electrical components. By means of the machine control, by means of the control circuits and the position information by the distance measuring devices 21, 22, the predetermined coupling position is approached, depending on the tool height and product information and the corresponding waypoints for braking or acceleration and over the distance necessary for coupling kept synchronous with each other at a dome time of less than 0.4 s.
Preferably, the locking elements 19 to the rack 3 according to Figure 4 in the vertical direction game in order to be able to securely couple even with occurring positional deviations from the determined actual values. Deviations of the actual values from the information of the travel measuring devices 21, 22 from toothed rack 3 to the respective latching elements 19 over the permitted tolerance range are monitored and recognized by a sensor (not shown).
In a further possible application of the press, it is conceivable that the piston 6 in the working cylinder 7 in the direction of movement of the rack 3 just before contact of acting on the closing movement of the press ram 2 parallel holding consisting of parallel holding cylinder 14 on the press frame 1 and arranged on the press ram 2 spacer elements 15th , is accelerated while the press ram 2 is braked. Depending on the requirements, the remaining speed of the press ram 2 before the beginning of the power flow over the tool halves on press table 20 and Press ram 2 is reduced to almost zero. The rapid traverse cylinders 12 and / or the parallel holding cylinders 14 can be used.
In an advantageous further application of the piston 6 in the working cylinder 7 in the direction of movement of the rack 3 just before contact of acting on the closing movement of the press ram 2 parallel position consisting of parallel holding cylinder 14 on the press frame 1 and arranged on the press ram 2 spacers 15 are accelerated, at the same time the press ram 2 is braked and the clutch claw is closed after synchronization. In an alternative application to the closing movement of the press ram 2 is slowed down shortly after contact the delaying parallel holding consisting of parallel holding cylinder 14 on the press frame 1 and arranged on the press ram 2 spacers 15, simultaneously accelerates the piston 6 in the working cylinder in the direction of movement of the rack 3 and the Clutch claw closed after synchronization.
The parallel attitude here can take over the function of a damper and brake the press ram 2 controlled. It can also happen that the remaining speed of the press ram 2 is reduced to almost zero before the beginning of the power flow over the tool halves on press table 20 and press ram 2.

Of course, the embodiment according to the invention is not limited by the comments suggested in the description of the figures.

LIST OF REFERENCE NUMBERS

1.

press frame

Second

press ram

Third

rack

4th

hydrostatic bearing

5th

coupling claw

6th

piston

7th

working cylinder

8th.

piston chamber

9th

Positioning and synchronizing cylinder

10th

traverse

11th

upper crosshead

12th

Eilgangzylinder

13th

ram connection

14th

Parallel holding cylinders

15th

spacers

16th

piston chamber

17th

connection

18th

renewal

19th

locking elements

20th

press table

21st

Distance measuring device for 2

22nd

Distance measuring device for 7

Claims (8)

Hydraulic press for plastic or metal processing, consisting of a press frame (1) with press table (20) arranged thereon and press ram (2) movably arranged therein, rapid traverse cylinder (12) with a ram connection (2) being provided for the fast idle stroke of the press ram (2). 13) are arranged, wherein on the upper crosshead (11) of the press frame (1) or the working cylinder (7) with the press table (20) directed piston (6) are fixed, wherein the piston (6) in the direction of press table ( 20) a coupling jaw (5) and opposite thereto a traverse (10) with positioning and synchronizing cylinder (9) for the piston (6) are arranged, wherein the piston (6) has a centrally arranged cylindrical extension (18) for sliding guidance of a Rack (3), said rack (3) with the press ram (2) is connected. Hydraulic press according to claim 1, characterized in that for the connection of the rack (3) to the press ram (2) a hydrostatic bearing (4) is arranged for the moment compensation. Hydraulic press according to claim 1, characterized in that for parallel holding the press ram (2) to the press table (20) parallel holding cylinder (14) on the press frame (1) and corresponding thereto on the press ram (2) spacer elements (15) are arranged. Hydraulic press according to one or more of the preceding claims, characterized in that the working cylinder (7) is designed as a differential cylinder. Hydraulic press according to one or more of the preceding claims, characterized in that between the coupling claw (5) and press ram (2) a sheath, preferably telescopic or foldable, for the rack (3) is arranged. Hydraulic press according to one or more of the preceding claims, characterized in that for the protection of the rack (3) and the associated guide in the piston (6) and whose extension (18) this area is encapsulated and provided with air filters. Hydraulic press according to one or more of the preceding claims, characterized in that for controlling the synchronization at least two control loops are arranged, wherein a control loop of positioning and synchronizing cylinder (9) per working cylinder (7) together with the associated path measuring device (22) per working cylinder (7) is formed and the second control loop from the rapid traverse cylinder (12) on the press ram (2) is formed together with the path measuring device (21). Hydraulic press according to one or more of the preceding claims, characterized in that for controlling the synchronization at least two control loops are arranged, wherein each one control loop per cylinder (7) together with the associated path measuring device (22) per working cylinder (7) is formed and the second control loop from the rapid traverse cylinder (12) on the press ram (2) is formed together with the path measuring device (21).

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