| 摘要 |
A centering pin for use in a machine tool work table of the type in which a workpiece fixture is supported on a film of pressurized air thereby enabling substantially friction free movement of the fixture on the table surface. The centering pin comprises an outer pin mounted within the table and projecting above the table upper surface, an inner pin received within the outer pin for reciprocal movement along a direction generally normal to the table surface, a hydraulic actuator for causing the inner pin to project above the outer pin at a first vertical position, and a spring for causing the inner pin to retract to a second vertical position below the first vertical position when the fluid actuator is deactivated. The fixture has one or more slots which ride over the outer pin and a plurality of holes within the slots which are adapted to be engaged by the inner pin when it is extended to its upper vertical position, thereby enabling controlled translation and rotation of the fixture on the table. A safety feature is provided wherein if the slot is not engaged by the outer pin when the fixture is placed on the table, air floatation pressure cannot be supplied between the fixture and table surface.
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