Work holders – With fluid means – Cylinder-piston means in series with additional positioning...
Reexamination Certificate
1999-11-03
2001-05-15
Watson, Robert C. (Department: 3723)
Work holders
With fluid means
Cylinder-piston means in series with additional positioning...
C269S134000
Reexamination Certificate
active
06231035
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a fixture for holding a workpiece, and more particularly, to a fixture which firmly holds the workpiece without deforming or displacing the workpiece.
Fixtures are commonly used to hold workpieces in desired locations and orientations when performing manufacturing operations. Such fixtures generally include a support having one or more reference points which engage points on the workpiece for locating and orienting the workpiece. These fixtures also include one or more clamps for clamping the workpiece against the reference points to hold the workpiece in the predetermined position. Any workpiece movement can adversely affect the manufacturing operation. For instance, if the workpiece moves during a grinding operation, surfaces on the workpiece may be ground to an improper shape.
Even if the clamps firmly hold the workpiece against the reference points, the workpiece may still deform (i.e., flex) between the clamps and thereby affect the manufacturing operation. To prevent the workpiece from deforming, one or more braces are sometimes mounted on the support between the clamps. Frequently, these braces are retractable so they do not interfere with the workpiece when it is located on the reference points. The braces are retracted when the workpiece is positioned on the reference points and extended into position after the workpiece is clamped in place. However, due to variations in dimensions from workpiece to workpiece, the braces may not precisely meet the workpiece when extended. There may be gaps between the braces and the workpiece which permit the workpiece to deform during the manufacturing operation. Further, the brace may interfere with the workpiece as it is extended, causing the workpiece to deform. Therefore, unless the brace precisely meets the workpiece, the workpiece can deform and adversely affect the manufacturing operation.
SUMMARY OF THE INVENTION
Briefly, apparatus of this invention is a fixture for holding a workpiece in a predetermined position during a manufacturing operation. The fixture includes a support having a surface for receiving the workpiece. The surface has a reference point for locating and orienting the workpiece in the predetermined position. The fixture also includes a clamp for clamping the workpiece in a fixed position with respect to the reference point to hold the workpiece in the predetermined position and a brace mounted on the support for bracing the workpiece to prevent the workpiece from deforming during the manufacturing operation. The brace has at least two jaws adapted for clamping the workpiece when received by the support to prevent movement of the workpiece toward or away from the support. The jaws have a closed position in which the jaws are spaced apart a first distance sufficiently small to grip the workpiece and an open position in which the jaws are spaced apart a second distance sufficiently large to release the workpiece to permit the workpiece to be removed from the support. The brace is mounted on the support so as to permit at least one of the jaws to move generally parallel to the surface when moving from the open position to the closed position to compensate for geometric variation in the workpiece thereby permitting the brace to align itself to the workpiece and preventing the brace from moving the workpiece out of the predetermined position when the workpiece is clamped against the reference point. Further, the brace is mounted on the support so as to prevent the jaws from moving substantially normal to the surface to prevent the workpiece from moving toward or away from the support when the jaws are in the closed position.
REFERENCES:
patent: 4558856 (1985-12-01), Shaffer
patent: 4901990 (1990-02-01), Frechette
patent: 5312094 (1994-05-01), Zera
de Graaff Willem T.
Kelly Allen L.
General Electric Company
Gressel Gerry S.
Hess Andrew C.
Watson Robert C.
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