Neutronic reactor control rod drive apparatus

Claim 1

IN A NEUTRONIC REACTOR CONTROL SYSTEM, IN COMBINATION, A VERTICALLY ELONGATED CONTROL ROD ADAPTED TO BE VARIABLY INSERTED INTO A NEUTRONIC REACTOR AND HAVING A LOWERMOST POSITION WHEREIN IT IS SUPPORTED WITHIN AND BY THE RECTOR, A CONTROL ROD EXTENSION DISPOSED ABOVE SAID CONTROL ROD AND ENGAGEABLE THEREWITH, ELECTROMAGNETIC MEANS FORMING A RELEASABLE COUPLING BETWEEN SAID CONTROL ROD AND SAID EXTENSION, A VERTICALLY MOVABLE DRIVE SHAFT, A SPRING INTERCONNECTING SAID EXTENSION AND SAID DRIVE SHAFT WHEREBY SAID EXTENSION IS NORMALLY SUPPORTED FROM SAID DRIVE SHAFT THROUGH SAID SPRING, MOTIVE MEANS FOR CONTROLLING THE VERTICAL POSITION OF SAID DRIVE SHAFT, AND THREE POSITION ELECTRICAL SWITCHING MEANS ACTUATABLE BY RELATIVE VERTICAL MOVEMENT OF SAID EXTENSION WITH RESPECT TO SAID DRIVE SHAFT, SAID SPRING BEING OF SUCH STRENGTH THAT THE WEIGHT OF SAID EXTENSION AND SAID CONTROL ROD TOGETHER CAUSES SAID SWITCHING MEANS TO ASSUME THE FIRST OF ITS THREE POSITIONS, THE WEIGHT OF SAID EXTENSION ALONE CAUSES SAID SWITCHING MEANS TO ASSUME THE SECOND OF ITS THREE POSITIONS, AND THE ABSENCE OF ANY WEIGHT LOAD ON SAID SPRING CAUSES AND SWITCHING MEANS TO ASSUME THE THIRD OF ITS THREE POSITIONS.