Patent Application
20080127839
This application claims the priority benefits of German Application No. 10 2006 056 520.7 filed Nov. 30, 2006.
The invention relates to a press with a drive arrangement connecting the operating movement of the press plunger.
Press drives, for example, for cutting presses, draw presses, or stamping presses for the deformation of bodies, such as transverse flux presses, often include a lever drive arrangement which generates a travel-time curve which deviates from the normal sine form of movement. Such a lever drive is generally designed to generate near the bottom dead center portion of the plunger movement which flattens the plunger movement curve so as to approach a straight line. To achieve this, various lever kinematics are known in the art.
Furthermore, presses are known which include adjustment mechanisms. DE 695 18 899 T2, for example, discloses a press with an eccentric member which acts on a lever drive. The eccentric member forms a first input for the lever drive whose output is connected to a plunger. A lever, of the lever drive, forms a second input which is connected to an air cylinder. This makes it possible to adjust the lower dead center position of the press plunger.
With the initially presented movement arrangements, the tool has a certain non-negligible speed when hitting the workpiece, which increases as the number of strokes increases. This cases substantial stresses on the tool and a substantial noise in the operation of the tool.
Generally, a plunger movement would be desirable which, with a uniformly running drive source and a lever drive arrangement is difficult to achieve. In addition, the plunger movement should also be adjustable.
To achieve this DE 1982 1159 proposes to drive the plunger by means of several servo-motors. To achieve this, the servo-motors need to generate, on one hand, all the required maximum press force and, on the other hand, need to be able to reach a high adjustment speed. The servo-motors are connected to the plungers by way of spindle stroke drives. If such a drive has a transmission ratio, a high press force can be achieved, but the adjustment speed is relatively low. If it has a low transmission ratio, the achievable adjustment speed is relatively high, but the maximum press force is limited. For achieving high press forces then, very large servo-motors must be used.
It is the object of the present invention, to provide a press with a drive arrangement by which in a simple and energetically advantageous manner variable travel/press-angle arrangements of the press can be achieved.
In a press with an adjustable drive arrangement including, in addition to a main drive, an adjustment drive for dynamically changing the press kinematics of the manually predetermined press angle-plunger stroke. Means are provided, whereby, driving a transforming process, the speed of a movable plunger of the tool part which engages the workpiece for the transformation thereof, is reduced, essentially to zero for the moment of engagement between the plunger and the workpiece, so as to provide for a smooth impact force engagement between the plunger and the workpiece.
The first drive input has a uniform drive movement in that it rotates, for example, at essentially a constant speed. The second input of the drive is connected to a second drive source with a modulated drive movement. This means that the drive movement of the second drive source is controllable, that is adjustable in a time-dependent manner. As a result, a second movement is imposed over the movement caused by the first drive source which may be considered a correcting movement. The correcting movement may be used, for example, to slow the movement of the plunger just before it engages the workpiece to such an extent that it contacts the workpiece smoothly. After that, the second drive source again contributes to the acceleration of the plunger.
The second drive source may be a linear drive, an eccentric member drive, a rotational drive, a hydraulic cylinder, a pneumatic cylinder, a servo-drive or any other drive which can be operated in travel distance—controllable manner. In addition, it must be connected to an energy storage device in order to recuperate the energy gained and stored during slowing of plunger movement for again accelerating the plunger. The energy storage device may be a pneumatic pressure store, a spring, a flywheel device or a similar device
The drive is preferably a lever drive which is driven by the first drive source via an eccentric member. In addition, it preferably includes a support point which forms the second input and is connected to the second drive source. The support point may, for example, be the end of a support member of an elbow lever drive.
For the control of the press preferably a control arrangement is provided which controls at least the second drive arrangement, but preferably also the first drive arrangement. By the control of the second drive arrangement, the travel-time curve of the plunger movement can be relatively freely adjusted within given limits. It is, for example, possible to select a certain travel/time curve for the plunger movement. The second drive arrangement may be in a rest position during operation of the press. It is, however, preferred if the second drive arrangement is actively controlled for superimposing another movement on the plunger movement, in order to obtain the desired travel/time curve for the plunger movement.
The second drive source can be controlled dependent on plunger position or on the eccentric member position. The plunger position or eccentric member position can be determined, for example, by means of corresponding sensors. The second drive source can then be operated in accordance with a fixed travel/time profile. For example, the control arrangement includes a certain program via which each eccentric member position is assigned a control position of the second drive source.
But it is also possible to optimize this movement profile depending on the recorded acceleration values. To this end, the plunger and/or the moving part of the tool may be provided with acceleration sensors. Furthermore, the moving tool part, the plunger or another part of the drive may be provided with force sensors in order to determine the point in time when the tool part comes into contact with the workpiece and to change in this way the profile of the movement of the second drive source in such a way that the impulse occurring thereby is minimized.
The invention will become more readily apparent from the following description of preferred embodiments, thereof, on the basis of the accompanying drawings.
For driving the plunger 6, a plunger drive 9 is provided which, like in the embodiment shown, may be a lever drive 10, a first drive source 11 and a second drive source 12. The lever drive 10 includes in the present embodiment a joint carrier 13 in the form of a double arm lever. The first lever arm 14 is pivotally connected to the second drive source 12 by way of a link 15. The end 15a of the link 15 is pivotally connected to the second drive source 12. The second lever arm 16 is pivotally connected via a second link 17 to the plunger 6. The joint carrier 14 is supported on an eccentric member 18 which forms a first input of the lever drive 10 and is connected with a drive output 20 of the first rotational drive source 11, for example, via a gear 19. The gear 19 may additionally form a flywheel. The drive output 20 may be a spur gear which is in engagement with the gear 19.
The end of 15a of the link 15 which is remote from the lever arm 14 represents a second input of the lever gear 10 which is connected to the second drive source 12. The second drive source 12 may be, for example, a linear drive arrangement by which via an adjustment of the drive source 12 the connecting point of the link 15 is adjustable in the space; particularly with regard to the axis of rotation of the eccentric member 18.
The press 1 preferably includes a control arrangement 21, which is provided particularly for controlling the second drive source 12. The second drive source 12 is, for example, an electric servo-motor with a spindle drive forming an electric linear drive arrangement, a hydraulic servo-drive or a drive provided with another type of travel control arrangement.
The control arrangement 21 may also be connected to angular position sensor 22 for the determination of the angular position of the gear 19 or, respectively, the eccentric member 18. In addition, or alternatively, the control arrangement 21 may be connected to a travel sensor 23 for determining the position of the plunger 6. Furthermore, the control arrangement 21 may be connected to the first drive source 11 for controlling the operation thereof. In addition, there may be an acceleration sensor 24 for determining the acceleration of the plunger 6 and/or the acceleration of the tool 4 and to report it to the control arrangement 21. Optionally, furthermore, one or more force sensors may be provided at the tool 4, the plunger 6, the link 17 or another part of the force transmission path from the drive source 11 to the tool 4 in order to determine the force applied by the tool 4 to the workpiece 5. Those sensors are then all also connected to the control arrangement 21.
The press described above operates as follows:
In
The second drive source 12 is, for example, a servo-motor which operates in the section 28 of the curve 25 as a generator and feeds energy back into the power supply or into a flywheel storage device. Using this energy, the servo-motor can again be accelerated using the energy previously saved for the transforming of the workpiece 5.
The second drive source 12 includes an operating range 29 which is indicated in
The control arrangement 21 can perform the process described above on the basis of a predetermined curve of movement provided for the second drive source 12. It is also possible to optimize the movement, for example, by leaving as the forces effective on the plunger 6 and/or the acceleration forces effective thereon are recorded. For example, this acceleration sensor 24 can be used to measure impulses as they occur upon contact of the upper tool 4 with the workpiece 5. The control arrangement 21 can then coordinate the operation resulting in the delay of the plunger movement timely in such a way that is, it can reduce or increase the speed of the plunger such that the impact of the plunger on the workpiece is minimized. This can be done during initial operation of the press or constantly during operation of the press in a continuing optimizing procedure.
The drive source 12 is in the form of an eccentric member drive, Whereas the drive 12 in accordance with
Another possible embodiment is shown in
In the press 1 shown in
Another modified embodiment of the press 1, according to the invention, is shown in
In the embodiment according to
In addition, to the main drive source 11, a press 1 includes a second drive source 12 which can be used to dynamically control the press angle 1 plunger-stroke curve otherwise predetermined by the press kinematics. Particularly, a transformation process can be performed in this way, wherein the movable tool part of a transformation tool, engages the workpiece 5 at a speed of zero or almost zero, that is smoothly without sudden impact.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 056 520.7 | Nov 2006 | DE | national |
