Patent GB-994029-A (GB)
Title: A grab
Inventor: ALLIOT PAUL
IPC: G21C19/11
Filed: 1962-09-06
Abstract: 994,029. Article engaging devices. L'ELECTRICITE DE FRANCE (SERVICE NATIONAL). Sept. 6, 1962 [Sept. 18, 1961], No. 34168/62. Heading B84. [Also in Division G6] A grab for operating in the fuel element channels of a reactor has jaws which automatically grip the load by a mechanical action consequent upon the lowering of the grab thereonto, the load being subsequently released automatically by a further mechanical action consequent upon the lowering of the load on to a support; however, this lowering operation to release the load must be performed twice with a raising operation intervening. This double action to release the load acts as a safety arrangement to prevent unwanted release should the load meet an obstruction during lowering. As shown the grab comprises a head 1 supported by a cable 4, this head having arms 27 connected to a ring member 5 provided with a sleeve extension 6 whereby the coolant flow in the reactor channel is not obstructed. A sleeve 10 slidably and non- rotatably mounted on the sleeve 6 by balls 8 in grooves 7, 11 carries four jaws 15 on pivot pins 14, the upper ends 24 of the jaws engaging an annular cam groove 21 in the bottom surface of an annular member 19. The member 19 is rotatably mounted on the sleeve 10 by balls 25 housed in circular grooves and is connected by a casing 26 to an annular member 18. The members 18, 19 have saw-tooth cam teeth 47, 50, Fig. 5, co-operating with studs 17 formed on the sleeve 6, there being twelve teeth on each member 18, 19 and twelve studs. The cam groove 21 is divided into four identical sections, Fig. 6, each section comprising a portion A . . . D in which the lower ends of the jaws 15 are held outwards to grip the load 52 by a groove 51 and a portion D ... G in which the jaws are moved inwards to release the load. When the grab is lowered to pick up a load the studs 17 are located between the teeth of cam 18 as shown in Fig. 5 and the jaw ends 24 have the position O, Fig. 6. The bottom 12 of the sleeve 10 is arrested by the load 52 and the sleeve 6 continues to be lowered whereby the studs 17 engage the teeth 50 and move the unit 18, 19 in the direction F through and angle # of 15 degrees. The ends 24 now have the position A in the groove 21 and the jaws have closed to grip the load. On raising the grab the sleeve 6 again moves axially relatively to the sleeve 10 whereby the studs 17 engage the teeth 47 and a further movement in the direction F through an angle # of the unit 18, 19 takes place and the ends 24 have the position B. If the grab is lowered and the weight of the load is taken by a support the studs 17 cause a further movement through an angle # of the unit 18, 19 and the ends 24 occupy position C and the jaws 15 continue to grip the load. On raising the grab the studs cause another movement through angle # so that the ends 24 occupy position D. On a further lowering to position the load on a support the unit 18, 19 is moved by the studs through a further angle # and the ends 24 occupy the position E in which the jaws are open to release the load. On finally lifting the grab the studs move the unit a further angle # so that the ends 24 take up position F and the jaws remain open. The cable 4 is detachably connected to the head 1 by a ball 3 held by pivoted clamp members 2, these members being movable to the release position by rotating a cam member 35 through 180 degrees. A modified jaw is described with reference to Figs. 7, 8 (not shown) this jaw having an open rectangular frame to permit the passage of coolant gas.