| 摘要 |
A method and apparatus for positioning the top surface of a workpiece in proper relationship with respect to tooling including a fully extended upper clamp bushing, or for positioning the fully extended upper clamp bushing in proper relationship with respect to the top surface of a workpiece, which establishes a desired workplane wherein the top surface of the workpiece is always disposed in a normal position with respect to the lowermost surface of the upper clamp bushing and just in contact with the lowermost surface even though the top surface was disposed either below or above the desired workplane at the commencement of the clamping operation. The method and apparatus is capable of moving the top surface of the workpiece or the tooling into a desired workplane and also of determining whether or not the top surface of the workpiece adjacent the area which is to be fastened lies within the desired workplane. The apparatus including a plurality of position sensors associated with the upper clamp bushing, which sensors are capable of sensing when the upper clamp bushing contacts the top surface of the workpiece or is contacted by it, the apparatus further including a control for moving the workpiece to the desired position in response to the position sensors.
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