Numerically controlled contouring system

Claim 1

A numerically controlled contouring system comprising: first means for producing original command pulses ( Delta X, Delta Y) to follow an original curve X( Tau ), Y( Tau ) and tangential signals indicating the tangential direction (dX/d Tau , dY/d Tau ) of the original curve; second means for producing variable signals representIng variables (x,y), respectively, which vary along the circumference of a circle having a radius equal to a desired offset distance and a center lying on the original curve and offset pulses ( Delta x, Delta y) to follow the variables; offset setting means for producing initial signals representing initial values (xo, yo) of the variables in accordance with the desired offset distance and for supplying the initial signals to the second means so as to determine said radius with said initial values; gate means for controlling the direction of variation of the variable signals; third means for producing an inner product signal representing the inner product S (x)(dX/d Tau + dY/d Tau between the tangential signals and the variable signals supplied from said first and second means; control means for producing instruction signals (CW,CCW) representing the direction of variation of the variable signals in accordance with the inner product signal supplied form said third means and for supplying the instruction signal to the gate means so that the variable signals are controlled to vary in the direction indicated by the instruction signals so as to make the inner product zero; and fourth means for synthesizing said original command pulses and offset pulses so as to obtain offset command pulses ( Delta X + Delta x, Delta Y + Delta y) to follow an offset curve spaced apart by the offset distance from the original curve.