Electric-powered spring-return actuating device

Electric actuating means comprising:

• (a) electric motor means with output shaft, said shaft capable of being rotary motivated by suitably switched electric currents to said motor and further being capable of retaining a fixed position when said motor is subjected to polarity-fixed electric currents;
• (b) electrical amplifying circuit means capable of first switching electric current to said motor capable to rotate the shaft in one direction, secondly to generate a sufficiently constant current for holding said shaft in a desired position, and thirdly to de-energize the motor completely if rotating of said motor shaft in the opposite direction is desired;
• (c) mechanical means motivated by said electric motor shaft and capable of converting more than fifty percent of the motor's mechanical rotary power output into reciprocating mechanical power, said mechanical means coupled to at least one stem and at least one mechanical spring, the latter capable of overcoming mechanical or electrical resistance forces and further being able, together with said mechanical means, to rotate said electric motor shaft whenever said electric motor is substantially de-energized and wherein said mechanical means comprises a suitably supported spindle having two seperate threaded sections with differing pitch diameters, at least one cable, portions of which being wound around each threaded section of said spindle, and one or more pulleys capable of engaging said cable and motivating said stem.