Work holders – Relatively movable jaws – With means to fasten holder to support
Patent
1994-03-04
1996-03-26
Watson, Robert C.
Work holders
Relatively movable jaws
With means to fasten holder to support
269900, B23Q 306
Patent
active
055014372
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an adapter for use with clamping devices for clamping workpieces on perforated screen plates of machine tools.
2. Description of Prior Art
Machine tools, such as milling machines or drills, are often equipped with a clamping table for clamping workpieces. Previously, these tables mostly had T-grooves or dovetailed grooves, into which clamping screws or threaded bolts were inserted. The workpiece was fastened either by these threaded bolts or with other clamping elements, such as clamping straps and threaded clamps. This type of clamping table is increasingly being replaced by machine tables having a screen plate or a screen block. Both variants have threaded bores at defined distances in the perforated screen. Typical distances between holes of the perforated screen are 50 mm with an accuracy of a few micrometers. The workpiece can be fastened as before with the aid of clamping elements, which are mounted in the holes of the perforated screen with screws.
Situations occur where the position of the holes provided in the screen is unsatisfactory.
This is the case, for example, if it is necessary to clamp a workpiece in such a way that poor force transfer conditions are created. In such situations the lever arm between the clamping screw of the clamping element and the workpiece is larger than the lever arm of the clamping element on the opposite side of the clamping screw. Thus, the clamping force is transferred in an unfavorable manner to the workpiece. The workpiece is not securely clamped, and accuracy and the clamping force are reduced.
The locations of the screen holes provided often cause the clamping element to cover a portion of the workpiece surface to be treated. Thus, in these situations it is necessary to clamp the workpiece twice for treatment. This increases the amount of labor and therefore production costs and, in addition, greater production tolerances in the workpiece must be expected.
In both of the situation mentioned a threaded hole is needed exactly in a place where there is none, namely between two adjoining holes of the perforated screen plate.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a device for clamping a workpiece regardless of the distribution of holes in the machine table, so that the above mentioned disadvantages are avoided.
To attain this according to one embodiment of this invention, an adapter is fastened on a perforated screen plate or perforated screen block. The clamping element is not mounted on the perforated screen plate or the perforated screen block, but to the adapter. It is now possible to fix the clamping element holding the workpiece in any position, regardless of the distribution of the holes in the machine table. The adapter of this invention allows complete freedom in choosing the position in which the workpiece is to be clamped in relation to the machine table and in relation to the workpiece itself. In this way it is possible to transfer an optimal clamping force to the workpiece. The workpiece can also be clamped in such a way that the surfaces to be treated are not covered by clamping elements. Thus it is not necessary to interrupt the work process to clamp the workpiece in a different position.
All these requirements are achieved, according to one embodiment of this invention, by an adapter for use with clamping devices for clamping workpieces on a perforated screen plate or a perforated screen block. The adapter has a plurality of building block-like elements. One such element, a base plate, has at least two bases separated by a distance equal to the distance between the screen holes of the perforated screen plate. The two bores are used for fastening the base plate to the perforated screen plate. The base plate forms a first T-groove at a lateral distance away from the two bores. The first T-groove receives a transverse sliding element. The transverse sliding element forms a second T-groove, which is perpendicular to the first T-groove, for
REFERENCES:
patent: 1397771 (1921-11-01), Mort
patent: 2365079 (1943-08-01), Huber
patent: 4711437 (1987-12-01), Longenecker et al.
patent: 5026033 (1991-06-01), Roxy
patent: 5246217 (1993-09-01), Brot
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