Patent Number: 
Section: abstract

A magnetic jack type control element drive mechanism for precision position control of a control element assembly, satisfies the following conditions:D1=D2=P+D5;D3=P×2;D4=D3×(N−½), (N is an arbitrary natural number),                wherein        D1 represents a lift gap of the upper motor assembly;        D2 represents a lift gap of the lower motor assembly;        D3 represents a space width between tips of adjacent teeth of the drive shaft;        D4 represents a gap between an upper latch and a lower latch;        P represents pitch that is a distance of ascent or descent of the drive shaft; and        D5 represents a margin which is a separation space between the teeth and the upper latch or the lower latch when the upper latch or the lower latch is inserted into the teeth of the drive shaft.