Apparatus for controlling machine tools

Claim 1

Apparatus for use in machining a crowned roll or the like wherein the shape of the crown can be expressed as a function of the longitudinal displacement of the tool relative to the workpiece, comprising: first means for moving a tool with respect to said roll in a direction generally parallel to the longitudinal axis of said roll; second means for moving said tool with respect to said roll in a direction parallel to a cross axis which is generally transverse to said longitudinal axis; means responsive to said first moving means for producing a first voltage which is dependent upon the position of the tool with respect to said roll as measured along said longitudinal axis, said first voltage producing means including at least two potentiometers, the wipers of said potentiometers being driven by said first moving means, with the voltage across one potentiometer being derived from the wiper of the other potentiometer, said first voltage being derived from the wiper of said one potentiometer; function generator means responsive to said first voltage for producing a continuously variable voltage which varies with the displacement of the tool relative to the roll along the longitudinal axis in accordance with said function; means for producing a second voltage which is an electrical analog of the position of said tool with respect to said roll as measured along said cross axis; and control means responsive to said variable and second voltages for causing said second moving means to move said tool relative to said roll to a position at which the cross axis displacement of the roll relative to the tool is equal to said preselected function of the roll position with respect to said tool as measured along said longitudinal axis, said control means comprising means for comparing the magnitudes of said first and second voltages, and means for causing said second moving means to continuously move said tool so as to maintain said first and second voltages equal.