EP2397315B1 - Drive unit for a punching machine or a press and process for machining a workpiece - Google Patents

Description

The subject of this invention is a drive unit for a punching machine or a press for moving a plunger, wherein the plunger movement composed of a Liftweg for removing and approaching the plunger from and to a workpiece and a working stroke for machining the workpiece.

The subject of this invention is also a method for processing a workpiece in which the drive unit according to the invention is used.

Actuators for the ram of stamping presses or presses are well known, these are usually spindle, eccentric or hydraulic drives. However, embodiments with linear drives are also known. These drives provide for the stroke movement of the plunger. On the plunger, a punching or forming tool is arranged, through which the workpiece processed, for example, punched or formed, is. For this machining process, a considerable pressing force of the plunger is required. On the other hand, the ram must be lifted with the tool from the sheet, so that the machined workpiece can be transported further or a new sheet can be inserted into the punching machine or in the press. The movement of the plunger from and to the workpiece is referred to as a lift path. The actual machining of the workpiece is carried out in the working stroke.

For the working stroke a much stronger drive power is required than for the Liftweg.

The JP 2001 113393A . DE 20 2006 004470 U1 , which discloses the preamble of claims 1 and 5, and US 1 007 792 A reveal each press, where the Liftweg is carried out via a toggle lever system and the working stroke via a separate drive.

In Fig. 1 a press or a punching machine according to the prior art is shown. The ram is driven by two high-performance spindle drives of high precision. These spindle drives realize here the Liftweg and the working stroke. Such a device has the disadvantage that the machining time for a workpiece is limited by the spindle drive, because a spindle drive can not be operated arbitrarily fast. The processing speed is limited on the one hand by the spindle drive itself, on the other hand, but also by the tool, which may not penetrate any arbitrary speed in the workpiece, otherwise it will be damaged.

In addition, in other conventional stamping presses and presses, a drive unit for the movement of the plunger is used, which is actually oversized for the pure Liftweg.

Often, a large total stroke of the plunger is required, but this great movability of the plunger has an unfavorable effect on the construction of the plunger drive. For example, reduces the buckling stiffness of the threaded spindle of a spindle drive by a higher ram stroke.

The invention is therefore based on the object to disclose a drive unit for a stamping press or a press, with a higher production speed than in conventional systems can be realized and in which the drive unit can be better tuned to the working stroke.

This object is achieved by a novel drive unit for a stamping press or a press having the features of claim 1.

The lifting height of the plunger is thus realized by the combination of a power take-off with a main drive. This has the advantage that for the Liftweg mainly the PTO is used, the PTO needed for this only a small drive torque and no complex measuring systems. Thus it is possible to realize a highly dynamic lift stroke.

The main drive is used for the actual machining process of the workpiece. Since the auxiliary drive primarily takes over the Liftweg, the speed of the main drive can optimally on the Machining be tuned, without causing the highest possible speed of the main drive is in the foreground.

According to the invention, the power take-off on a toggle lever system with upper and lower toggle arms, a toggle joint and a fixed stop, the toggle lever are mechanically locked by the fixed stop.

Due to the mechanical locking of the toggle lever system, the pressing forces occurring during machining are absorbed by the fixed stop and the headpiece bearing point of the upper toggle lever. The drive unit for the auxiliary drive is not loaded. Thus, it is possible to realize a high dynamic lift stroke with low cost and easy parts.

No complicated turning and grinding parts are required for the toggle lever system (eccentric shaft bearing, eccentric shaft, stroke adjustment, etc.).

It is advantageous if the toggle lever system is actuated via a rack drive or via a spindle drive. These drives have a simple structure and are inexpensive to produce.

The toggle lever system can also be actuated by a linear drive. Linear actuators work contact-free and are therefore very wear-resistant. In addition, high accelerations and high end speeds can be achieved with linear drives.

According to the invention form the upper and lower toggle leg on the side facing the fixed stop an angle of more than 181 ° when the toggle leg abut the fixed stop, since thereby the toggle lever system is automatically locked.

It is advantageous if the main drive is a spindle drive, preferably a servo-driven spindle drive. As a result, the spindle drive is free programmable and takes over the overload protection (current consumption measurement), the ram adjustment, the adjustment of the tool installation height and a part of the lifting height. The plunger is simplified and reduced weight by eliminating the ram adjustment and overload protection.

Since the spindle drive can not realize high speeds, the gear ratio and the size of the servo motor can be optimally adapted to the spindle drive. In comparison to conventional eccentric drives, the drive unit according to the invention with spindle drive requires considerably less lubricant.

In addition, reduces the length of the threaded spindle of the main drive to the part of the toggle lever path, this increases the buckling resistance of the main drive.

The invention also provides a method for machining a workpiece with a punching machine or a press with the features of claim 5, wherein a plunger is moved by a Liftweg to the workpiece and wherein the workpiece is processed by a subsequent working stroke of the plunger. According to the Liftweg are essentially carried out by a power take-off and the working stroke by a main drive.

The ram can be lowered by a very fast PTO. Thereafter, with the help of the main drive, the actual machining of the workpiece can be performed, this can be done with a lower stroke speed than during the lowering movement.

According to the invention the Liftweg is executed by a toggle lever system with fixed stop in the inventive method. The toggle lever system is already mechanically locked by the fixed stop before running the working stroke for machining the workpiece. This prevents buckling of the toggle lever.

It is also possible if after the machining of the workpiece for the return stroke of the ram of the power take-off and the main drive are operated simultaneously to remove the plunger from the workpiece. The Total movement of the plunger away from the workpiece is thus faster than the total plunger movement to the workpiece. The processing time per workpiece can be significantly reduced.

• Fig. 1 eine Presse bzw. einen Stanzautomat mit Spindelantrieb nach dem Stand der Technik;
• Fig. 2 eine schematische perspektivische Ansicht einer erfindungsgemäßen Antriebseinheit, bei der beispielhaft der Nebenantrieb über ein Kniehebelsystem und der Hauptantrieb über einen Spindelantrieb realisiert wurde;
• Fig. 3 eine Presse oder einen Stanzautomaten mit der erfindungsgemäßen Antriebseinheit aus Fig. 2, wobei sich der Nebenantrieb im oberen Totpunkt befindet;
• Fig. 4 eine Presse oder einen Stanzautomaten mit der erfindungsgemäßen Antriebseinheit aus Fig. 2, wobei sich der Nebenantrieb im unteren Totpunkt befindet;

In the following the invention will be described with reference to drawings. Show it:

• Fig. 1 a press or a punching machine with spindle drive according to the prior art;
• Fig. 2 a schematic perspective view of a drive unit according to the invention, in which, for example, the auxiliary drive has been implemented via a toggle lever system and the main drive via a spindle drive;
• Fig. 3 a press or a stamping machine with the drive unit according to the invention Fig. 2 with the PTO at top dead center;
• Fig. 4 a press or a stamping machine with the drive unit according to the invention Fig. 2 with the PTO at bottom dead center;

In FIG. 1 a conventional punching machine or a press is shown. In this case, a plunger 5 is guided via plunger guides 4 in a press frame 3. The ram stroke is realized here by a spindle drive, it consists in the present example of two spindles 1, which are each driven by a spindle motor 2. On the plunger 5 is a tool 6 for the machining of a workpiece 8, for example, a sheet attached. Below the workpiece 8 is a table top 7, which is firmly connected to the press frame 3. The tool 6 may be a punching tool or a forming tool.

In most cases, such a device is used to machine a sheet metal in strip form, wherein, for example, shaped pieces are punched out of the sheet metal. So that the sheet metal strip can be transported further for the subsequent punching or forming process, the tool 6 must be lifted sufficiently high from the sheet metal strip. This movement of the tool 6 from and to the workpiece is referred to as a lift path. In the actual working stroke, the machining of the workpiece 8 takes place.

In Fig. 2 Now, an embodiment of the drive unit according to the invention for a punching machine or a press is shown. It basically consists of a main drive and a PTO. The main drive is designed here as a spindle drive 20 with a motor 28 and a spindle 21. At the end of the spindle 21 is the spindle eye 22 in which the bolt 23 for connecting the spindle 21 with the plunger 27 (in Fig. 2 not shown) is stored.

Preferably, it is a servo-driven spindle drive 20, which is freely programmable.

The auxiliary drive is designed here as a toggle lever system 11. The lifting height of the plunger 27 is realized by the combination of the toggle lever system 11 and the spindle drive 20. The toggle lever system 11 consists essentially of an upper toggle leg 12 and a lower toggle leg 13, which are hinged together via the toggle joint 14. The upper knee lever leg 12 is mounted at the upper end via a head piece bearing pin 10 in a head piece bearing 9. The headstock bearing 9 is fixed to the press frame 30 (in Fig. 2 not shown).

The lower toggle leg 13 has at the lower end an adapter plate 19, via which the toggle lever system 11 is connected to the spindle drive 20. The knee lever is actuated via a rack drive. The rack drive consists of a rack motor 16 and a rack 17, via the rack eye 18 with the toggle joint 14th connected is. With the help of the rack and pinion drive 16, 17 of the toggle lever can be bent in a simple manner and durchgestreckt. Of course, but instead of the rack drive 16, 17, a spindle drive, a rotating eccentric drive or a linear drive can be used.

The toggle lever system 11 also has a fixed stop 15 against which the toggle leg 12, 13 strike when the toggle lever is extended. The fixed stop is adjusted so that the toggle lever is moved in operation to an angle α of more than 181 ° before it abuts against the fixed stop 15. The angle α is the angle which is formed by the upper knee lever leg 12 and the lower knee lever leg 13 on the side of the fixed stop 15. Due to the deflections of the knee lever to over 181 ° ° against the fixed stop 15, this is mechanically locked. Pressing forces exerted by the main drive are thus received via the headstock bearing 9 and the fixed stop 15.

In Fig. 3 is now a press or a punching machine with two drive units according to the invention Fig. 2 and with a plunger 27, which is guided by plunger guides 25 in the press frame 30 shown. The toggle lever system 11 is here in the maximum bent position. The auxiliary drive is thus at top dead center. The plunger 27 is guided over the plunger guide 25 in the press frame.

In Fig. 4 is the same device as in Fig. 3 shown, but here is the PTO in the bottom dead center or approximately at the bottom dead center. In this position, the knee lever legs 12,13 to the fixed stop 15 and form an angle α of about 181 °. Now, if the spindle drives 20 exert a pressing force on the plunger 27 in the direction of the table top 26 for machining a workpiece, the pressing forces occurring on the knee lever legs 12, 13 and the head piece bearing 9 are transmitted to the press frame 30. Part of the press forces is also by the fixed stop 15 However, these forces are relatively low, since the knee lever legs 12, 13 are only in a slightly bent position. It can be seen clearly that no forces can be transmitted to the rack drive 16, 17 by this slight bending of the knee lever legs 12, 13 and by the concerns of the toggle on the fixed stop 15.

Noise emissions caused by the stop of the knee lever legs 12, 13 on the stop surface 24 of the fixed stop 15 can be reduced by a cutting impact damping, by elastomeric elements or by gas pressure shock absorbers.

In operation, the auxiliary drive is used to move the plunger 27 in Liftweg, in addition, the complete drive system can be compensated by ram weight compensation cylinder. The power take-off only needs to have a small drive torque and does not require complex measuring systems. Thus, it is possible to realize a high dynamic lift stroke with low cost and simple parts.

Once the PTO is at bottom dead center, the main drive for the actual forming or punching movement of the plunger 27 can be actuated. Since the knee lever legs 12, 13 are supported in an angular position of more than 181 ° on the fixed stop 15, the system is mechanically locked and the high caused by the main drive pressing forces can not lead to buckling of the toggle leg 12, 13.

Through this interaction of lift stroke and working stroke, it is possible to combine the advantage of a highly dynamic press with the precision of a spindle-driven tray-out press.

During the return stroke of the plunger 27 of the main drive and the PTO can be operated simultaneously, thereby requires the plunger 27 for the return stroke less time than for the lowering stroke, thus more parts can be processed per time unit.

The complete combination drive can be pre-assembled and available as a service part. In the event of a breakdown, the defective system with the service part can be exchanged and repaired without much effort on the part of the demo.

The position and amount of the drive units according to the invention consisting of main and auxiliary drive can be freely selected in a stamping machine or a press. It is structurally conceivable to integrate the drive unit as a single drive or as a two-, three-, four- or five-speed drive, since the system can be realized as a transverse or longitudinal drive.

The invention results in addition to the lead time reduction and cost advantages, since no complexed parts are needed. The production and assembly are easy. The header complexity is reduced to a minimum, also can be realized a lower overall height of the stamping presses or presses.

The embodiments shown in the drawings represent only a preferred embodiment of the invention. The invention also includes other embodiments in which, for example, instead of the spindle drive 20, a hydraulic drive is used as the main drive. The auxiliary drive can be realized as a centric single drive or as a double executed external drive.

Claims (6)

1. Drive unit for an automatic punching machine or press for moving a ram (27), where the ram movement consists of a lifting movement to move the ram (27) away from and towards a workpiece and a working stroke for machining the workpiece, where the drive unit has an auxiliary drive and a main drive, and where the working stroke is only executed by the main drive and the auxiliary drive has a knee lever system (11) with top and bottom knee lever legs (12, 13) and a toggle joint (14), characterized in that the knee lever legs (12, 13) can be locked in position mechanically by means of a fixed stop (15), where the top and bottom knee lever legs (12, 13) form an angle (α) of more than 181° on the side facing the fixed stop (15) when the knee lever legs (12, 13) hit the fixed stop (15) so that the knee lever system (11) is locked in place mechanically.
2. Drive unit according to Claim 1, characterized in that the knee lever system (11) is actuated via a rack-and-pinion (16, 17) or a spindle drive.
3. Drive unit according to Claim 1, characterized in that the knee lever system (11) is actuated via a linear drive.
4. Drive unit according to one of Claims 1 to 3, characterized in that the main drive is a spindle drive (20).
5. Method for machining a workpiece with an automatic punching machine or a press, where a ram (27) is moved towards the workpiece by a lifting movement and where the workpiece is machined by means of a subsequent working stroke by the ram (27), where the lifting movement is executed essentially by an auxiliary drive and the working stroke by a main drive, and where the lifting movement is executed by a knee lever system (11) that has a top and a bottom knee lever leg (12, 13) and a toggle joint (14), characterized in that the knee lever legs (12, 13) are locked in position mechanically by a fixed stop (15) before the working stroke to machine the workpiece is executed.
6. Method according to Claim 5, characterized in that the auxiliary drive and the main drive are actuated simultaneously to move the ram (27) away from the workpiece.

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