1. Field of the Invention
The present invention relates to an apparatus for retaining a tool in cutting and drilling machinery and the like, especially for propulsion and production machinery, comprising a tool holder which may be fastened to the machine and having a cylindrical accommodation into which a cylindrical tool shaft may be inserted and retained rotatably and removably. The tool holder is detachably and rigidly connectable to a base plate which is rigidly connected to the machine whereby the releasable connection between the tool holder and the base plate is provided by a self-locking dovetail connection wherein the dovetail tenon and the dovetail groove taper in the insertion direction at a small angle to provide self-locking; and the plane of connection between the tool holder and base plate is oriented with respect to the central axis of the receptacle so that when the tool is stressed, at least one force component acts in the insertion direction to enhance the self-locking connection.
2. Description of the Prior Art
Tool holders are known which are usually welded to the machine, such as taught by German Patent Publication Nos. DE-OS 26 30 276 and DE-OS 33 46 014. German Patent Publication No. DE-OS 33 12 514 and U.S. Pat. No. 3,749,449 show attachment of a tool holder to a machine in a detachable manner using screws or bolts.
Tool holders are known in which various embodiments differ especially in the holding and the positioning of the tool in the tool holder, as described, for example, in German Patent Publication No. DE-OS 33 12 514. Replacement of the tool holder in this prior art device is always in addition very time consuming and expensive, since in order to achieve rigidity with the base plate, additional tight screwing is necessary.
This prior art device does make it possible to replace the tool holder without severing and welding operations, but the tool holder has a certain amount of play in the area of the screw or bolt attachment which leads to the misalignment of interconnected parts during machine operation which places constant stress on the tool, so that, in addition to the tool holder, the part attached to the machine with the connected base plate must be replaced from time to time. The advantage of the detachable connection of the tool to the machine is therefore limited, since the stress is shifted to the part rigidly connected to the machine with the base plate.