GB929174A - Improvements in and relating to nuclear reactor control rod winding mechanisms - Google Patents

Abstract

929,174. Nuclear reactor control rods. ENGLISH ELECTRIC CO. Ltd. Sept. 14, 1959 [Sept. 19, 1958], No. 30052/58. Class 39 (4). [Also in Group XXX] A nuclear reactor control rod winding mechanism comprises a winding drum journalled in a supporting structure for winding a cable supporting a control rod on to and off a spirally grooved outer surface of the drum, drum driving means mounted on the supporting structure for rotating the drum, means for causing the drum to move along its axis of rotation as it rotates so as to maintain the cable pay-off position at substantially the same position relative to the supporting structure, and guide pulley means for guiding the cable on to and off the drum at the pay-off position. In Fig. 2 the winding drum 45 carrying the cable 22 rotates about a spirally grooved shaft 46 and is secured to the shaft by a nut 49 of the recirculating ball type so that as the drum rotates it moves axially as the nut 49 rides up the groove in the shaft 46 and the cable pay-off position remains fixed. To facilitate deceleration as the drum reaches its lowest position a compression spring 60 is provided between collars 52, 61 mounted on the drum and the splined driving shaft 53 respectively. The driving means comprises a constant speed motor 62 carrying a gear pinion 63 which engages gear teeth on the circumference of a disc member 65 which drives a cylindrical member 72 through a captive ball 71; at the other end of the shaft carrying the cylindrical member 72 is a worm gear driving the splined driving shaft 53 which rotates the drum. The cage constraining the ball 71 is mounted on one end of a shaft 77 and is urged towards the central position by a compression spring 79; the other end of shaft 77 carries a roller which bears on a cam 81. Thus the position of the ball, and therefore the speed of the driving shaft 53, depends on the profile of the cam 81. The cam 81 is moved vertically up and down with the drum 45 and is so shaped that the rate of change of the reactivity of the reactor with movement of the control rod is substantially constant for all positions of the control rod. To allow the control rod to be released in an emergency an electromagnetic clutch (not shown) may be inserted in the driving shaft 53.