GB1188084A - A Linear Motion Device - Google Patents

Abstract

1,188,084. Electric motor driving arrangement. BORG-WARNER CORP. 5 April, 1968 [22 May, 1967], No. 16589/68. Heading H2A. [Also in Divisions F2 and G6] Relates to a linear actuator, e.g. for raising and lowering control rods of a nuclear reactor, comprising a disengageable screw-and-nut mechanism driven by an electric motor 12 having a stator 27 coaxially surrounding a reluctance type rotor formed of two rotor arms 34 pivoted at 37 to the inner race 39 of a bearing 41 to allow radial movement of the arms between an activated position (Fig. 2) in which the upper portions 74 of the arms are close to the stator and rollers 47 on the lower ends of the arms engage an axially movable, non-rotatable lead screw 11 and a deactivated position in which the portions 74 move inwardly from the stator and the rollers 47 disengage from the lead screw 11. A bearing 92 mounted in the upper part 19 of the motor frame 14 has its freely rotatable outer race 91 axially extended at 88 to form a stop limiting outward movement of the rotor portions 74 when activated, and bores 97 in the race 91 receive pins 94 on the ends of the rotor portions 74 to synchronize radial movement of the latter. Lugs 79 on the ends of the rotor portions 74 engage the race extension 88 in the activated position and a flange 84 of a fixed sleeve 63 in the deactivated position. Springs 57 between the lower portions 44 of the rotor arms 34 urge the latter towards their deactivated positions. The inner faces of the rotor arms are shaped to permit the lead screw 11 to extend between them. A ring (68) (Fig. 3, not shown) retains the pivot pins 37 in the bearing race 39. The stator 27 is surrounded by a cooling coil 26. The motor frame 14 forms a pressure vessel isolating the stator from any fluid around the lead screw. The stator is a four-pole assembly which may be energized by a multi-phase A.C. or a D.C. supply, in the latter case the poles being cyclically energized to form a D.C. step motor. While the stator is energized the rollers 47 engage the lead screw. On de-energization, e.g. for emergency shut-down of a reactor, the rollers release the lead screw, which is moved by springs and/or gravity to a " safe " position.