Patent Number: 042382882
Section: description

DETAILED DESCRIPTION OF THE INVENTION According to the invention, the drive of a nuclear reactor's control element comprises an electromotor 1 (FIG. 1) having a housing 2 which accommodates a stator 3 and a composite rotor 4. The stator 3 is insulated from the reactor's coolant by a shield 5. Lengthwise, the rotor 4 is composed of two parts whose total length is equal to the length of the active part of the stator 3. One part of the rotor 4 is a solid cylinder-shaped member 6, whereas the other comprises three double-arm rocking levers 7 (FIG. 2). Mounted on the outer surface of the solid cylindrical member 6 (FIG. 1) of the rotor 4 are rods 8, each having one of its ends secured in a ring 9, whereas their other ends are secured in a ring 10 mounted on a spindle 11 rotatable in bearings 12 and 13. The bearings 12 and 13 are arranged in housings 14 and 15, respectively, which, in turn, are accommodated in the housing 2 of the electromotor 1. Arranged inside the spindle 11 are centering bushings 16 through which there extends a drive screw 17 coupled to a control element (not shown). The rods 8 and rings 9 and 10 make up a grid for starting the electromotor 1. Pivot axles 18 (FIG. 3) of the double-arm levers 7 are parallel to the axis of the drive screw 17. One end of each of the pivot axles 18 is secured in the ring 10 (FIG. 1), whereas the opposite end is secured in a lug 19 (FIG. 3) provided in the spindle 11. First arms 20 of the double-arm rocking levers 7 act as poles of the rotor 4 (FIG. 1). Second arms 21 (FIG. 3) of the levers 7 are forked and carry rollers 22 whose rotation axles 23 are secured in the forks so that they are parallel to the axis of the drive screw 17. The rollers 22 (FIG. 2) form a detachable roller nut interacting with the drive screw 17 through apertures 24 provided in the spindle 11 due to the action of the electromagnetic field of the stator 3 (FIG. 1) upon the double-arm levers 7. Each arm 20 (FIG. 3) of the double-arm levers 7 has a lug 25 which accommodates a spring 26 (FIG. 4) intended to actuate a stop 27. The extent of displacement of the arm 20 (FIG. 3) of the double-arm lever 7 is limited by a stop 28 provided on the ring 10 (FIG. 1). The present invention has been described herein with reference to a preferred embodiment of a drive of a nuclear reactor's control element, wherein the rotor contains three double-arm rocking levers. It is apparent, however, that use can be made of a greater number of levers without altering the spirit of the invention. The operating principle of the proposed drive of a nuclear reactor's control element is as follows. As supply voltage is fed to the stator 3 (FIG. 1) of the electromotor 1, the resultant electromagnetic field interacts with the solid cylinder-shaped member 6 and rotates the composite rotor 4. At the same time the electromagnetic field of the stator 3 interacts with the arms 20 (FIG. 2) of the double-arm rocking levers 7 and pivots them in the radial direction about the axles 18; as a result, the rollers 22 of the detachable roller nut engage with the drive screw 17 which drives the control element. As the stator 3 (FIG. 1) of the electromotor 1 is deenergized, the double-arm rocking levers 7 (FIG. 2) are pivoted in the opposite direction by the stop 27 (FIG. 4) and the spring 26, whereby the rollers 22 (FIG. 2) are disengaged from the drive screw 17, and the control element is dropped under gravity by an emergency protection signal. By altering the sequence of connection of the supply voltage phases, one can change the direction of rotation of the rotor 4 (FIG. 1) and, consequently, the direction of motion of the drive screw 177 and the control element. Whenever it is necessary to stop the control element and keep it at any desired level, d.c. voltage is applied to the stator of the electromotor. The proposed drive of a nuclear reactor's control element is of a small size and simple to control; at the same time it guarantees a stable and failsafe operation of the reactor's control and protection system. While preferred forms and arrangements have been shown in illustrating the invention, it is to be clearly understood that various changes in detail and arrangement may be made without departing from the spirit and scope of this disclosure.