TORQUE AMPLIFIER. The torque amplifier consists of a mechanism provided with a control-shaft at one end and a work shaft at the other, the control-shaft requiring only a feeble torque to operate it in either direction, while the work-shaft yields a torque of sufficient amount to accomplish any purpose desired, at the same time accurately following the control-shaft in all its angular movements. Its broad purpose is to perform the functions of an electrical or hydraulic servo-motor.
The torque amplifier was invented by Henry W. Nieman, an engineer for the Bethlehem Steel Co. It was originally developed for the control of anti-aircraft gun batteries from a remote con trol station. The torque amplifier has three elements : "work shaft," "control-shaft" and "drive-shaft." The drive-shaft is driven by any outside source of power, and revolves continuously in one direction. The control-shaft is actuated by any mechanical or manual control means, or by such weak forces as can be de livered through electrical recording instruments or telemetric transmission systems. The work-shaft is directly coupled to the work to be done, as for instance the elevating or training gears of a gun, a ship's rudder or the steering gear of an automobile.
The control-shaft can be freely revolved in either direction, with only a small amount of effort ; the work-shaft maintains at all times its angular synchronism with the control-shaft, and in addi tion exerts a heavy torque to overcome outside resistance. Un like other forms of servo-motor, there is always a definite ratio between the torque applied at the control-shaft and that delivered at the work-shaft, this ratio being known as the "amplification " Fundamentally, the torque amplifier consists of two oppositely rotating drums provided with friction bands which may be brought into contact with the drums through actuation of the control shaft, this frictional contact causing the friction bands to exert pressure on the work-shaft. The force applied to the control-shaft is thus enhanced, or amplified, when it reaches the work-shaft by the extent to which the bands are urged forward because of their frictional contact with the rotating drums.