Patent GB-997413-A (GB)
Title: Improvements in or relating to grabs
Inventor: BELLINGER RONALD
IPC: G21C19/10
Filed: 1961-01-27
Abstract: 997,413. Article engaging devices. STRACHAN & HENSHAW Ltd. March 27, 1962 [Jan. 27, 1961], No. 3315/61. Heading B8H. [Also in Division G6] A grab which automatically couples itself to or uncouples itself from a nuclear reactor fuel element by a purely mechanical action comprises a cylindrical actuating member 2 having at its lower end an extension 4 and attached at its upper end to hoist means (not shown). A slot 6 in the extension 4 receives a pin 20 carried by a grab nose 16, this nose being rigid with a sleeve 14 and guide fins 18, the pin 20 limiting the amount of sliding movement of the nose relatively to the member 2. Three jaws 24 (only one shown) are carried on pivot pins 26 supported by the nose 16 and operate in nose slots 22, hooked ends 28 of the jaws being able to engage the head 62 of a fuel element (shown in dotted lines). The jaws have cam surfaces 34, 36 whereby they may be rocked to the engaged or disengaged positions by cam surfaces 37, 38 on the extension 4. The relative movement between the nose 16 and member 2 when the latter is lifted is also controlled by a pawl 40 pivoted at 42 on the nose 16 and itself having a nose 41 engageable with a recess 60 in the extension 4. The pawl 40 is actuated by a link 49 having a slotted end carried by a pin 53 secured to the nose 16, the other end of the link engaging a cam surface 57 on the pawl. The slotted end of the link 49 co-operates with a cam surface 55 on the extension 4, whereby a thrust may be transmitted from the extension to the pawl 40 to rock the latter between the positions shown in Figs. 1 and 3. A pin 47 on the link 49 is received in a slot in an arm 45 of a lever pivoted on the pin 42, a further arm 51 of this lever being engageable by a resetting arm 58 and by a member 10 on the extension 4. Rocking of the arm 51 by the member 10 or arm 58 causes the link 49 to be rocked between the two positions shown in Figs. 2 and 4. The arm 58 is rigid with a resetting member 54 slidable in the nose 16 between stops (not shown). Fig. 1 shows the grab with the jaws 24 released from the element head 62, the weight of the grab being carried by the head 62 through the member 54. In operation, as the member 2 is raised away from the fuel element the pawl nose 41 engages the recess 60 to lift the nose 16, the jaws being maintained in the released position by the engagement of the cam surfaces 34, 37. The member 54 moves down against its lower stop so that arm 58 engages lever arm 51 and the link 49 is moved to the Fig. 2 position. Upon lowering the grab on to another fuel element the member 54 moves against its upper stop, further lowering of the member 2 moving the recess 60 clear of the nose 41 and causing the cam surface 55 to engage the link 49 and rock the pawl 40 to the Fig. 3 position. The grab is now raised so that pin 20 moves to the bottom of slot 6 and the cam surfaces 36, 38 engage to rock the jaws 24 to the engaged position, Fig. 4; also, the member 10 resets the link 49. On depositing this second fuel element the member 2 moves down relatively to the nose 16 so that cam surface 55 engages the link 49 and the cam surfaces 34, 37 engage whereby the pawl 40 and jaws 24 are restored to the Fig. 1 position. The grab may also incorporate the following safety features: (a) supplemental claws 80 pivoted at 82 on the member 54 engage the fuel element head when the member 2 is lifted and serve to drag down the member 54 should the latter fail to drop by its own weight, the claws 80 being subsequently swung to their disengaged position by engagement of cam-shaped recess 81 thereon with pins 84 on the jaws 24; (b) a gravity latch 72 pivoted at 70 to the nose 16 is held in a recess 76 in the extension 4 by the arm 58 when the parts are in the Fig. 4 position, whereby downward movement of the member 2 relatively to the nose 16 cannot take place until the fuel element carried in the grab has been deposited on a support surface to raise the member 54; (c) an electrical interlock comprising a solenoid 90 controlling an armature 92 having a groove 94 is energized to maintain the member 2 in the raised position relatively to the nose 16 by holding a ball 96 in engagement with a cam surface 100 on the sleeve 14, the solenoid not being de-energized until the grab as shown in Fig. 4 has been lowered to the position at which it is required to deposit the fuel element and thus inadvertent release due to the element meeting an obstruction is prevented. Another form of grab is described with reference to Figs. 5-8 (not shown) in which the jaws are moved outwardly to engage the interior of an element, a pawl corresponding to the pawl 40 of Figs. 1-4 being carried by the extension 4 and a recess corresponding to the recess 60 being formed in the nose 16.