Fluid operated workholder

Apparatus for holding a workpiece having a locating surface in a precise predetermined position during multiple machining operations occurring at plural work stations circularly arranged about a central axis with each machining operation causing displacing forces in the workpiece tending to move the workpiece toward the central axis, comprising:

• (a) a base;
• (b) an indexing table mounted on said base for intermittent rotation about the central axis around which the plural work stations are arranged;
• (c) plural workholders mounted on said indexing table equal in number to the number of work stations plus one, each said workholder including:
• (1) fixture means for supporting a workpiece when inserted into the workholder, said fixture means including at least one fixed abutment for engaging the workpiece locating surface in a manner that forces imparted to the workpiece during each machining operation will tend to move the locating surface of the workpiece away from said fixed abutment,
• (2) an adjustable stop means mounted for movement toward and away from said fixed abutment between a retracted position in which workpieces may be removed and inserted into the workholder and an advanced position in which the locating surface of the inserted workpiece is maintained in contact with said fixed abutment, and
• (3) operator means for moving said adjustable stop means for said retracted position to said advanced position by a distance which depends on the size of the inserted workpiece and for holding the locating surface of the workpiece against said fixed abutment by preventing movement of said adjustable stop means during all such machining operation, said operator means including control means positioned adjacent the radial outermost portion of said worktable for effecting movement of said ajustable stop means between the retracted and advanced positions and for initially controlling the amount of force applied to the workpiece by the adjustable stop means, and hydraulic link means for responding to movement of said control means to effect movement of said adjustable stop means, said hydraulic link means including a fluid flow path and an incompressible fluid filling said fluid flow path and wherein each said workholder includes a support body having a first fluid cavity and a first piston connected with said adjustable stop means, said first piston being disposed for movement within said first fluid cavity and wherein said operator means includes an operator body containing a second fluid cavity, a second piston mounted for movement within said second fluid cavity between a retracted position and an adjustable advanced position and further wherein said fluid flow path is connected with said first and second fluid cavities to cause said first and second pistons to move simultaneously between corresponding advanced and retracted positions and further wherein said support body and said operator body are integrally connected to form an L-shaped member, said first and second fluid cavities having parallel longitudinal axes oriented, respectively, to interesect the lateral side of one leg portion of said L-shaped member and the end surface of the other leg of said L-shaped member.

Positioning apparatus for maintaining the locating surface of a workpiece in contact with a fixed abutment of a workholder designed to receive workpieces subject to substantial manufacturing tolerances in which primary forces are imparted to each workpiece during machining operations which tend to move the locating surface of the workpiece away from the fixed abutment of the workholder and in which secondary forces less than said primary forces are imparted to the workpiece which tend to move the workpiece parallel to the fixed abutment, comprising

• (a) fixture means for supporting a workpiece when inserted into the workholder for contact with the fixed abutment;
• (b) primary holding means for retaining a workpiece in said fixture means, said primary holding means including
• (1) a body containing first and second fluid cavities, said body has a generally L-shape with one leg containing said first cavity and the other leg containing said second cavity and wherein said fixture means is mounted directly on said other leg,
• (2) first and second pistons mounted for reciprocal movement within said fluid cavities, respectively,
• (3) hydraulic link means for causing said first piston to move in response to movement of said second piston, said hydraulic link means including a fluid flow path between said first and second fluid cavities and an incompressible fluid filling said fluid flow path,
• (4) an adjustable stop means connected with said first piston for movement toward and away from the fixed abutment of the workholder between a retracted position in which workpieces may be removed from and inserted into the workholder and an advanced position in which the locating surface of the inserted workpiece is maintained in contact with the fixed abutment of the workholder, and
• (5) control means for moving said second piston to control initially the amount of force applied to the workpiece by the adjustable stop means and for fixing said second piston in said advanced position during all machining operations on an inserted workpiece;
• and
• (c) secondary holding means for assisting said primary holding means to retain a workpiece in said fixture means, said secondary holding means includes clamping means separate from said adjustable stop means for clamping a workpiece in said fixture means to prevent the workpiece from moving parallel with respect to the fixed abutment.