Turning – Process of turning
Reexamination Certificate
1998-06-11
2001-03-20
Tsai, Henry (Department: 3722)
Turning
Process of turning
C082S047000, C082S148000, C082S162000
Reexamination Certificate
active
06202520
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatus for machining one or more highly concentric diametral surfaces on a workpiece. However, certain applications of the present invention may lie outside this field.
It is conventional on some machining operations to machine a workpiece after applying compression to the workpiece. Often this compression force within the workpiece is applied through thrust bearings that are oriented so as to apply compression in the workpiece, but incapable of applying tension in the workpiece without degrading the reliability and safety of the thrust bearing. The compressive force tends to cause the workpiece to bow. Also, there is a natural tendency for the force from the cutting, grinding, milling or other operation, which is applied generally perpendicularly to the compressive force, to further increase the bowing of the workpiece. This bowing results in uneven machining of the workpiece, causing varying amounts of eccentricity among the one or more diameters machined along the length of the workpiece. For example, a diameter machined on a shaft may have excessive runout of the center of the machined diameter relative to the centerline of the shaft.
On workpieces where multiple outer diameters are being machined, the multiple outer diameters as first machined may not be sufficiently concentric with each other, or with the machining centers on the ends of the workpiece that may be used in subsequent operations. For example, two diameters may each be acceptably round, but their centerlines may be shifted from one another. In another example, one diameter may be acceptably round, but another diameter on the same workpiece may be out of round. It may be necessary to support the workpiece in the vicinity of the multiple outer diameters by a pair of rolls. It is often necessary to add a second machining operation to improve the relative concentricities of the multiple diameters. The present invention overcomes the limitations of conventional machining methods and apparatus in a novel and unobvious way.
SUMMARY OF THE INVENTION
One embodiment of the present invention provides for improved apparatus and methods for machining a workpiece with highly concentric diameters. One aspect of the present invention includes grabbing a workpiece at a first position intermediate of the ends of the workpiece. A first locating feature is machined on one end of the workpiece, and a second locating feature is machined on the other end of the workpiece. The workpiece is released at the first position. The first locating feature and the second locating feature are clamped, and tension is applied to the workpiece. The workpiece is machined during the application of tension.
Another embodiment of the present invention provides an apparatus for machining a workpiece. The apparatus includes a first rotatable spindle powered to rotate. The first rotatable spindle is coupled to first means for clamping the workpiece. The apparatus also includes a second rotatable spindle coupled to second means for clamping the workpiece. There is also means for urging the first rotatable spindle apart from the second rotatable spindle when the first clamping means and the second clamping means are clamping ends of the workpiece. The apparatus also includes a machining tool for machining the workplace.
Another embodiment of the present invention is an apparatus which includes a workpiece having two ends with a first locating feature on one end and a second locating feature on the other end. The first locating feature is concentric with the second locating feature. There is also a first means for clamping the workpiece on the first locating feature, the first clamping means being powered to rotate. There is also a second means for clamping the workpiece on the second locating feature, the second clamping means being rotatable. The apparatus also includes means for urging the first clamping means from the second clamping means, and a machining tool for machining the workpiece.
One object of the present invention to provide an improve method for machining a highly concentric part.
These and other objects will be apparent from the description of the preferred embodiment, the drawings, and the claims to follow.
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Car-Tec Company
Tsai Henry
Woodard Emhardt Naughton Moriarty & McNett
LandOfFree
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