Metal working – Plural diverse manufacturing apparatus including means for... – Binding or covering and cutting
Reexamination Certificate
1998-10-30
2001-03-27
Hughes, S. Thomas (Department: 3726)
Metal working
Plural diverse manufacturing apparatus including means for...
Binding or covering and cutting
C198S345100, C409S163000, C409S164000, C409S202000, C409S212000, C409S224000, C483S014000, C483S015000, C082S124000, C414S225010
Reexamination Certificate
active
06205631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a machining center having a number of machine tools which each have a working space for machining workpieces, a clamping station in which workpieces to be machined are clamped into workpiece holders, and a loading device which transports the workpiece holders between the clamping station and the working space of at least one machine tool.
2. Related Prior Art
A machining center of this kind is known from DE 195 16 849 A1.
In the known machining center, machine tools are arranged next to one another, a loading/unloading station in which a clamping station is located being provided next to that row of machine tools. In the clamping station, workpieces are inserted into workpiece holders which are held by a pivot arm of a loading device.
After the workpiece holder has been loaded with a new workpiece, the pivot arm is pivoted in and the loading device travels to one of the machine tools, where the pivot arm pivots back out and the workpiece holder is clamped in a fixture holder which is provided in the working space of that machine tool. After machining of the workpiece, the workpiece holder is transported either to another machine tool for a further machining operation or back to the loading/unloading station where the machine workpiece is replaced with a workpiece that is yet to be machined.
The pivot arm of the loading device grasps the workpiece holder on one side, the latter also grasping the workpiece to be machined on one side. The fixture holder in the working spaces also grasps the workpiece holder on one side; a buttress can selectably be provided so that clamped workpieces can be better centered.
It has been found that with the known machining center, the handling of the workpieces and workpiece holders is disadvantageous particularly when bulky and/or heavy workpieces are to be machined. On the one hand, surprisingly, the machining accuracy and the reproducibility of the machining operation decrease when heavier and/or more bulky workpieces are used. These disadvantages can be partially eliminated or at least diminished by performing workpiece handling in general at lower velocities. This means, however, that in order to achieve high machining accuracy and reproducibility in the machining of heavy and/or bulky workpieces, the workpiece-to-workpiece time is reduced with the known machining center, which of course is disadvantageous.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to improve the machining center mentioned at the outset in such a way that enhanced machining speed and machining accuracy are achieved by means of a simple design, in particular with heavy and/or bulky workpieces.
In the case of the machining center mentioned at the outset, this object is achieved in that a multiple coupling for transferring fluidic energy, which is selectably docked in the clamping station, is provided on the workpiece holder.
The object underlying the invention is completely achieved thereby.
Specifically, the inventors of the present application have recognized that the impairment in machining accuracy with heavy workpieces is attributable, inter alia, to the fact that the holding forces in the workpiece holders are not sufficient, and further that the position of the workpieces cannot be sufficiently monitored. By means of the multiple coupling, fluidic energy can now be used on the one hand to actuate self-locking clamping elements and on the other hand to interrogate back pressure sensors which indicate the position of the workpiece via stops, etc. A considerable improvement in machining accuracy can be achieved by setting the workpieces in positionally accurate fashion into the workpiece holders, and optionally by increasing the holding force in the working space; the self-locking clamping elements allow rapid displacement of the loading device, thus also increasing the machining speed.
It is preferred in this context if a cover for coupling elements of the multiple coupling is provided.
The advantage here is that the coupling elements cannot become soiled where they are not needed. This once again increases the machining speed, since it is not necessary to flush the coupling elements before using the multiple coupling in order to ensure reliable operation. The cover can, for example, be spring-loaded and self-closing, so that it is opened only when the multiple coupling is docked.
On the other hand, however, it is preferred if a handling system is provided for removing and attaching the cover.
The advantage here is that reliable operation of the cover, which is not always guaranteed with spring-loaded covers, is ensured. A high level of reliability enhances the overall machining accuracy, since malfunctions due to soiled coupling elements as a result of covers which fail to close are prevented.
It is further preferred in this context if the handling system is arranged on the loading device, and attaches and removes the covers as the tool holder is being transported.
This feature is advantageous in terms of design on the one hand because it dispenses with a handling system in each working space. It may be noted here that the coupling elements need to be covered in particular in the working space, where on the one hand they are not needed, and on the other hand a particular risk of soiling exists. It would thus be conceivable to provide in each working space a separate handling system having its own cover which protects the unnecessary coupling elements. A simpler design, on the other hand, would be to provide only one handling system in the clamping station, in which the cover is in each case removed from the multiple coupling before use, and later attached again, so that each fixture has its own cover. The time saving with this approach is not yet sufficient, however, since in this case the removal and attachment of the cover further increases the workpiece-to-workpiece time. If, however, the handling system is now arranged on the loading device, the cover can be attached or removed simultaneously with displacement of the loading device between the working space and clamping station, so that the workpiece-to-workpiece time does not change as a result of this cover handling.
It is further preferred in this context if, for transporting the workpiece holder, the loading device has a pivot arm which pivots in during displacement of the loading device and for workpiece changing is pivoted into the working space or into the clamping station; and if the handling system is arranged on a support part for the pivot arm in such a way that when the pivot arm is pivoted in, the multiple coupling ends up located opposite the handling system.
This feature is advantageous in terms of design: the handling system needs only to perform a linear movement toward or away from the multiple coupling and grasp the cover in order to pull it off, or release it so that it can be pivoted into the working space together with the multiple coupling.
It is preferred in general if the workpiece holder comprises a fixture having self-locking clamping elements for positionally accurate clamping of a workpiece, the fixture comprising a coupling module for supplying the clamping elements with fluidic energy.
This feature makes it possible once again to increase the machining accuracy appreciably, since part of the accuracy loss with heavier workpieces in the prior art is attributable to the fact that these workpieces are not held securely enough in the workpiece holder. By way of the coupling module, the clamping elements are now supplied with fluidic energy both in the clamping station and in the working space, so that the workpieces can be held securely during both machining and positioning. The coupling module moreover makes it possible to use self-locking clamping elements whose clamping force in the working space is enhanced by the fluidic energy and which can be actively opened in the clamping station. These self-locking clamping elements hold the workpieces so securely dur
Chiron-Werke GmbH & Co. KG
Cummings & Lockwood
Hong John C.
Hughes S. Thomas
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