Patent GB-936453-A (GB)
Title: Improvements in grabs
Inventor: HILLIARD PETER THOMAS
IPC: G21C19/105
Filed: 1959-07-03
Abstract: 936,453. Fuelling reactors. BABCOCK & WILCOX Ltd. July 4, 1960 [July 3, 1959; Nov. 4, 1959], No. 22936/59. Class 39 (4). [Also in Group XXX] A grab intended for handling fuel elements in a reactor has jaws 77, Fig. 1, movable by a cam member 61 between load engaging and releasing positions, the cam member being moved by reciprocating movements of a member 25 controlled by a lifting cable 27. The grab operates as follows. As the grab is lowered a conical spigot 83D on the load 83 enters a hole 7C and aligns the grab. On further downward movement of the cable 27 the member 25 and the cam member 61 move downwards under gravity to the position shown in Fig. 1. During this movement cam rollers 59, Fig. 2; which are engaged in a cam track in the member 61 cause a cam roller ring 55, in which rollers 59 are mounted, to rotate. The member 25 is now raised by the cable 27 and, due to the shape of the cam track, moves a smaller distance up inside the cam member 61, thus raising the cam member 61 until a surface 76B thereof closes the three jaws 77 by abutting projections 81A thereon. When the load is lowered on to a support the cam member 61 moves downwards with the member 25 and opens jaws 77. Further downward movement of member 25 rotates the ring 55 to a different part of the cam-track so that when the member 25 is raised the cam member 61 is lifted only a small amount which is insufficient to close the jaws. Thus, alternate reciprocations of the member 25 open and close the jaws 77. Instead of two rollers 59 one only may be provided. The locations of the spigot 83D and socket 7C may be reversed. In a second embodiment, Fig. 8, a grab body 101 has three slots 105 which are lowered on to co-operating pins on a load, the lower ends 105A being flared to facilitate this. A sleeve 111 having a continuous cam track 115, Fig. 10, on its inner surface and flared recesses 107, similar to flared portions 105, is rotatably mounted on the body 101. The recesses 107 have vertical slots 119 which lead into the camtrack 115. In operation, when the grab is lowered on to a load, the pins thereof are received through aligned portions 107, 105 into slots 105 and also into the cam-track 115. The slope of the cam-track causes the sleeve 111 to rotate, thus holding the pins captive. As the grab is raised the sleeve rotates further and then stops, at which point the load is lifted. When the load is set down the sleeve rotates further in the same direction and continues to do so as the grab is again raised. As the upward movement of the grab continues the portions 107, 105 again become aligned so that the grab can be lifted off the pins on the load. In a third embodiment, Fig. 13, a load 331 is located inside a pipe 332 and is gripped by three jaws 323 operated by cam surfaces 327, 329 on a rotatable member 317. This member 317 cannot be rotated until pins 341 are withdrawn from holes 351 by levers 335, which are rocked when wheels 336 abut the sides 332B of the pipe 332. Thus, the load cannot be set down in an unsuitable position. The member 317 is rotated by cam-wheels 315 which run in a cam-track 313 when a member 305 is reciprocated by a lifting cable 301. The cam surfaces 327, 329 are so shaped that successive reciprocations of the member 305 alternately open and close the jaws 323 provided the pins 341 are withdrawn. A shroud 353 protects the levers 335. Similar latching devices may be applied to the other embodiments described. The invention may be applied to grabs moving in directions other than the vertical, the gravity biasing force required on the reciprocating members being replaced by springs, and the lifting cables by rigid members.