System for precise valve control

A system for precise position control of a fluid control valve which is operated by rotary movement of an actuating shaft, said control system comprising:

• rotary motion transmitting means, including an input shaft, for turning said actuating shaft;
• opposing first and second rotary transmission members having output ends thereof connected to opposite ends of said input shaft and input ends to be rotatably driven;
• first and second reciprocable driving means at the input ends of said rotary transmission members;
• interengagable means on each of said driving means and the input end of a rotary transmission member for imparting an increment of rotation to said rotary transmission member in response to a stroke of said driving means in one direction only;
• a pressure-actuated member in each of said driving means operative when pressurized to move said driving means in said one direction;
• biasing means opposing said pressure-actuated member;
• a source of pressure fluid;
• a pair of actuating means, each operative when activated to deliver a pulse of pressure fluid to one of said driving means;
• clutch means in each of said rotary transmission members operative when engaged to transmit rotary motion from said input end thereof;
• energizing means for engaging said clutch means;
• continuous energy supply means connected to said energizing means for activation thereof;
• a two-position switch device in said supply means operative in each of two positions to activate one only of said clutch energizing means;
• and
• means associated with each of said actuating means for moving said switch device to activate the clutch actuating means associated with said actuating means upon activation of said actuating means.