Servo control for movement of a device through successive steps

Claim 1

Electrical control apparatus for use with a machine having a regular internal law of operation, and including a tool for operating on a workpiece, means for so operating the tool, means for intermittently advancing the tool in a series of discrete steps through a range, and maintaining it in position between steps, the operating means being effective for performing an operation after each step while the advancing means is inactive, and thereby operative for so performing that operation effectively throughout the range, the advancing means including means for initiating the advancing movements, interrupting them, and again continuing them, to produce said steps, and finally terminating them at the end of the range, said control apparatus comprising: a first control means including an inductance means which includes coil means and a core movable therein to vary the inductance in the coil means, the core being operatively connected with the advancing means and continuously progressivelY movable in a first and controlling direction in response to movement of the advancing means; a plurality of second control means each including an inductance means which includes coil means and a core movable therein to vary the inductance in the respective coil means, the cores in the second control means being normally stationary but individually adjustable and individually operative for opposing the inductance of the first control means when the respective second control means is connected with the first control means, according to movement of the core in the first control means, the cores in the second control means being operative through their adjusted positions for predetermining the point of effective opposition of each second control means to the first control means, and when effectively opposing the first control means being operative for operating the interrupting means for thereby stopping the advancing means for predetermining said steps; a third control means including inductance means which includes coil means and a core movable therein, the core being stationary but manually adjustable for opposing the inductance of the first control means, when the third control member is connected thereto, and the third control means being operative when it effectively opposes the first control means for operating the advancing means for terminating said range; each inductance means including a single primary and single secondary, the core in the first inductance means is continuously movable throughout each step by the movement of the advancing means, and the inductance thereof is correspondingly continuously varied; and means for placing the second control means and the third control means successively in circuit with the first control means, the second control means and the third control means being operative independently of the advancing means according to the predetermined adjustment position of the respective ones of those control means.