Burns, Doane, Swecker & Mathis
Multiple-purpose closed loop automatic control system
 A multiple-purpose, closed-loop, automatic control system is disclosed, having a system controlled, and means for detecting a controlled variable output from the system controlled and for converting the controlled variable into an electrical feedback signal. The system further includes signal converting means for receiving the feedback signal and for converting the signal into an angular displacement corresponding to the feedback signal; means for comparing the controlled variable with a preset desired value and for selectively opening or closing a forward or reverse controlling circuit; and controlling means for automatic control over the system controlled to keep the controlled variable within the preset desired value. The controlling means includes the forward and the reverse controlling circuits selectively opened or closed by the comparing means, a braking control circuit and a driving mechanism responsive to the forward and reverse control circuits and the braking control circuit. The driving mechanism includes a fluid-type electromagnetic pilot valve mechanism having a piston rod, and includes a solenoid at each end of the piston rod. The solenoids are selectively energized by the forward and reverse controlling circuits such that the piston rod is selectively moved in order to change the direction of flow of the fluid through the pilot valve. 
G
G05B
inventional
Yu-Kuang
Lee