GB1056413A - Lifting devices - Google Patents

Abstract

1,056,413. Article engaging devices for lifting and lowering. ENGLISH ELECTRIC CO. Ltd. Feb. 25, 1965 [Feb. 27, 1964], No. 8297/64. Heading B8H. A grab for moving fuel elements into or out of nuclear reactors comprises a hollow body 10, Fig. 1, attached to a rope 37 and having pivoted thereon jaws 12 and a probe 18 movable longitudinally in the body between an extended position and a retracted position for endwise engagement with the element, the probe having cam portions 20B, 20C, 20D for engaging projections 15, 16 on the jaws 12 to move the latter between its open and closed positions. The body is in three parts 10A, 10B, 10C and the part 10C is formed with four radial slots 11, each of which has disposed therein a jaw 12 provided with a gripping lug 14 and a radial locating fin 17. The probe 18 comprises a solid core 19 around which is rigidly secured a sleeve 20 having a nose 20A and the cam portions 20B, 20C, 20D, the portion 20D having lateral surfaces 20E and a lower surface 20F which normally rests on the jaws 12 to support the probe in the body 10. The body part 10A houses a solenoid coil 24 in which is movably disposed a plunger 25, the latter having secured thereto a cylindrical locking sleeve 26 which is spring-biased downwardly and has an annular recess 26B. Disposed within the sleeve 26 is a sleeve portion 28 of the body part 10C having three radial holes 30 in which are housed balls 29, the latter being prevented from moving radially by engagement with either the cylindrical surface of the sleeve 20 and the recess 26B or with the inner surface of the sleeve 26 and one of two annular grooves 31, 32 formed in the sleeve 20. The coil 24 is electrically connected at one end to the body 10 and at its other end to contacts 33, Fig. 2 (not shown), fixed relative to the body 10 and engageable by contacts 34 attached to a movable plunger 35 and electrically connected to a cable 36 passing through the rope 37 which is rigidly attached to the plunger 35. The latter has a shoulder 35A for engaging with a shoulder 10D on the body part 10A. In operation to remove a fuel element 40, the grab in the position shown in Fig. 1 is lowered towards the element. An electric signal current which is not sufficient to energize the coil 24 is passed through the latter so that any change in the axial position of the plunger 25 which will cause a consequent change in the inductance of the solenoid can be detected by the resultant change in the signal current. If the grab touches an obstruction the plunger 35 moves downward separating the contacts 33, 34 to interrupt the signal current and so operate remote indicating and warning means. As the grab approaches the element 40 its speed is decreased and the current through the coil 24 is increased to a value at which the coil is energized to raise the plunger 25 so that the recesses 26B in the sleeve 26 is placed opposite the balls 29 so unlocking the probe 18. When the nose 20A of the latter engages a lifting button 41 of the element 40 further downward movement of the body 10 will cause the probe 18 to first open the jaws 12 and then close them into engagement with the lifting button 41 with the projections 16 engaged with the surfaces 20E of the cam portion 20D, Fig. 3 (not shown). At the same time the groove 32 comes opposite the balls 29 so that upon further lowering of the rope 37 the plunger 35 moves to open the contacts 33, 34 so de-energizing the coil 24 to permit the sleeve 26 to be spring-moved to lock the balls 29. The energizing current is then switched off so that the coil 24 will not be energized when the contacts 33, 34 are re-engaged during lifting of the element; the weight of the latter locks the projections 16 in engagement with the surfaces 20E preventing movement of the probe 18 even if it were not locked by the balls 29. A fuel element is lowered into a nuclear reactor in a similar manner. In a second embodiment, Fig. 4 (not shown), the probe 50 has a further groove 51 at its upper end and the locking sleeve 26 has two adjacent grooves 53, 54 at its upper end, the grooves coacting with further balls 57 to prevent axial movement of the sleeve 26 to release the balls 29 when a fuel element is engaged. The grab may have only two or three jaws 12.