Chucks or sockets – Socket type – Spring biased jaws
Reexamination Certificate
1999-09-02
2001-07-10
Bishop, Steven C. (Department: 3722)
Chucks or sockets
Socket type
Spring biased jaws
C279S057000
Reexamination Certificate
active
06257595
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a collet chuck assembly for holding a tool or workpiece on a spindle of a turning machine and particularly to a collet chuck that can be changed quickly and easily.
Collets are sleeves or collars used in various machine tools such as lathes for clamping or gripping workpieces or tools. Collets include a plurality of circumferentially-spaced, workpiece-gripping segments and conical surfaces or cams, which, when the collet is moved axially, interact with corresponding, opposing surfaces or cams on a mounting fixture or on the spindle. This interaction causes the workpiece-gripping segments of the collet to contract or expand to grasp or release a workpiece or tool, depending on the direction of movement. Collet chucks have commonly been used in machine tools in place of other types of chucks. Collet chucks are typically more accurate and have a greater gripping characteristic than a typical jaw chuck, for example. An advantage of collets is that they continue to grasp the workpiece or tool even at high rotational speeds when jaw chucks would have a tendency to loosen their grip due to centrifugal force.
One problem encountered with collet chucks is that slight variations in the diameter of the workpiece or stock could cause the collet to position the workpiece differently. When and where a collet will grasp a work piece depends on the difference in diameter between the open collet and the diameter of the workpiece. Precise workpiece diameter is therefore required if the workpiece is to be positioned precisely and consistently in machining operations such as facing, side finishing or cutting to precise lengths.
Another problem encountered with conventional collet assemblies is that collet cannot be easily and quickly removed from the spindle. Accordingly, changing collets can be time consuming.
For example U.S. Pat. Nos. 5,096,213 and 5,330,224, the respective disclosures of which are hereby incorporated by reference, disclose collet chucks in which a collet body includes an annular groove and hook portion on a rear end of the body which engages an annular flange portion of a spindle of the turning machine or a drawbar adapter of the collet assembly. A collet is installed by engaging the hook portion of the collet to the flange portion of the spindle or adapter, a special tool, such as those disclosed in U.S. Pat. Nos. 4,589,938 or 5,087,059, the respective disclosures of which are hereby incorporated by reference, is needed to compress the rear portions of the collet segments a sufficient distance radially inwardly so that the hook portion of the collet clears the annular flange portion. Similarly, to remove the collet from the turning machine, the tool must again be used to compress the rear portions of the segments so that the hook portions clear the flange portions so that the collet can be disengaged.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the forgoing disadvantages which accompany prior art collets. This object is achieved by a collet chuck assembly for holding a tool or workpiece on a spindle of a turning machine constructed in accordance with principles of the present invention. The collet chuck assembly comprises a mount, a collet assembly, and a cap.
The mount has a rear end adapted to be connected to the spindle and cap engaging structure. The collet assembly includes a collet structure for holding a tool or workpiece and operatively interacting cam surfaces. The collet assembly permits relative movement between the cam surfaces, whereby relative movement between the cam surfaces in one direction closes the collet structure to hold the tool or workpiece and relative movement between the cam surfaces in another direction opens the collet structure to release the tool or workpiece. The cap is secured to the mount and engages a front end of the collet structure to maintain the front end at a fixed axial position with respect to the cap and the mount during the relative movement between the cam surfaces of the collet assembly. The cap includes mount engaging structure adapted to coact with the cap engaging structure of the mount to prevent relative axial displacement between the cap and the mount when the cap is in a cap-locked position with respect to the mount. The cap is placed in the cap-locked position by coupling the cap to the mount with the cap-engaging structure of the mount and the mount-engaging structure of the cap disengaged from one another and then rotating the cap less than one revolution with respect to the mount to interengage the cap-engaging structure of the mount with the mount-engaging structure of the cap.
Accordingly, the collet structure does not move axially with respect to the assembly so that tools and workpieces can be gripped and positioned consistently. Furthermore, installing a collet is easily accomplished by merely inserting a collet structure into the collet assembly, engaging a cap over the collet structure onto the mount, and rotating the cap into the cap-locked position.
Other objects, features, and characteristics of the present invention, as well as the methods of operation of the invention and the function and interrelation of the elements of structure, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this disclosure, wherein like reference numerals designate corresponding parts in the various figures.
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Difasi Anthony J.
Terwilliger Donald N.
Bishop Steven C.
Hardinge Inc.
Pillsbury & Winthrop LLP
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