Work holders – Work-underlying support – Support mounting means
Reexamination Certificate
2000-01-19
2001-09-04
Hail, III, Joseph J. (Department: 3723)
Work holders
Work-underlying support
Support mounting means
Reexamination Certificate
active
06283465
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a clamping device for fastening a draw-in bolt to a machine table, a baseplate, or the like, having a piston that is arranged axially displaceably in a recess of the machine table and is hydraulically actuable, and having a cover that is fastenable to the machine table in order to close off the recess, the piston and/or the cover forming a receptacle into which a draw-in bolt can be inserted through the cover and in which it can be fastened by way of a clamping mechanism that is actuable by displacement of the piston.
BACKGROUND OF THE INVENTION
The machining of workpieces is often very complex, and can comprise a plurality of chip-generating and non-chip-generating operations on different processing machines in order to produce the finished component from a blank. In all production sequences, it is essential in this context that the workpiece assume a defined position on the respective machine tool for each operation.
For this purpose, it is usual in practice first to clamp the unmachined workpiece onto a carrier pallet, and then to clamp the entire unit onto the respective machine tool, by way of multiple draw-in bolts that are provided on the back side of the carrier pallet and are configured as centering elements, by the fact that the draw-in bolts are inserted into corresponding quick clamping units that are provided on the machine table. In production, it is possible in this manner to regard the positions of the quick clamping devices as a fixed machine parameter, so that it is necessary in each case only to position the workpiece precisely on the carrier pallet. The actual clamping and reclamping of the unit comprising the workpiece and carrier pallet onto machines can then be accomplished very quickly and easily, with no need for further positioning.
The known mechanical/hydraulic clamping devices on which the present invention is based are configured either as so-called build-up cylinders—which form closed units and can be clamped onto a machine table, a baseplate, or the like—or as so-called built-in cylinders—which can be recessed into the machine tables, quick-release plates, dies, etc. The known built-in cylinders are inserted directly into a recess of the machine table or into a corresponding base element; a pressure space is then formed between the built-in cylinder and the recess of the machine table, and can be acted upon by a hydraulic medium in order to release the clamping device.
The use of such built-in cylinders often proves problematic because the machine tables often do not possess the necessary casting quality, so that the receptacles cannot be manufactured with the necessary accuracy and sealing problems thus occur. In addition, the formation of cavities can in some cases greatly degrade the service life of the pistons of the clamping devices or that of the seals. In addition, the clamping forces are directed into the machine table, base element, or the like, so that distortion can occur therein.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to describe a clamping device of the kind cited initially, suitable for mounting into a machine table or the like, which is configured so that it can easily be installed in the machine table without causing sealing problems, and which is easy to maintain.
This object is achieved, in a clamping device of the kind cited initially, in that the piston is guided displaceably in an integrally configured bushing with which it forms a pressure space; and that the cover is arranged centeredly—on the one hand on the bushing and on the other hand on the machine table.
The fact that the clamping device according to the present invention is configured as a closed unit means that the sealing problems which occur in the existing art can be eliminated. The clamping device can furthermore be configured as a standardized compact component, so that manufacturing costs can be reduced. Since positioning of the clamping device is accomplished by way of the cover, all that is necessary is to provide corresponding centers on the machine table and on the cover, with the result that machining inaccuracies in the remaining region of the receptacle play only a limited role. An annular gap that is possibly present between the receptacle and the bushing is sealed from below against oil or air by way of two O-rings.
The clamping device according to the present invention offers the further advantage that no distortions of the machine table occur during operation, since the clamping or release forces are absorbed entirely within the clamping device. In addition, the service life of the clamping devices is greatly extended because, for example, cavities in the machine table have no effect on the operation of the clamping device.
Centering of the cover on the machine table and of the bushing can be accomplished in various ways. It has proven advantageous to provide on the cover a centering extension which engages into the bushing, a sealing element then preferably being arranged between cover and bushing. For centering of the cover on the machine table, the outer rim of the cover can be configured as a centering rim which forms a fit with a depression provided on the machine table. The cover can be at least partially, but in particular completely, recessed into the machine bed, so that it terminates flush with the table surface. Provision of hydraulic medium and optionally air to the clamping device is preferably accomplished in the base region of the bushing, which is where the seal between bushing and receptacle can be accomplished most easily.
With regard to further advantageous embodiments of the invention, reference is made to the dependent claims and to the explanation below of an exemplary embodiment referring to the appended drawings. In the drawings, the single FIGURE shows in longitudinal section an embodiment of a clamping device according to the present invention having a draw-in bolt inserted and clamped in place.
REFERENCES:
patent: 5415384 (1995-05-01), Obrist
patent: 5918870 (1999-07-01), Stark
patent: 5961261 (1999-10-01), Stark
patent: 6073325 (2000-06-01), Stark
patent: 3322232A1 (1984-03-01), None
patent: 4135418 A1 (1993-05-01), None
patent: 2980473 (1998-07-01), None
patent: 2981699 (1998-10-01), None
patent: 0827805 A1 (1997-03-01), None
patent: 0858862 A1 (1998-02-01), None
Hail III Joseph J.
Liniak, Berenato, Longacre & White LLC
Shanley Daniel
Vischer & Bolli AG
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