GB1080361A - Improvements relating to grabs - Google Patents

Abstract

1,080,361. Grabs for nuclear fuel elements. FAIREY ENGINEERING Ltd. March 11,1964 [Dec. 12, 1962], No. 47004/62. Heading B8H. The invention concerns the combination of a canister type T.V. camera and a grab mounted on the forward end of the camera, the combination being intended for use in the core channels of a nuclear reactor. As shown, Fig. 2, the forward end of a T.V. camera 10 having an optical centre at 13 is detachably connected by locking balls 20 to a sleeve 16 of the grab 12, this sleeve sliding over the camera wall 21. The balls 20 are movable into engagement with recesses 22 in the sleeve 16 by a ring 18 rotatable in the wall 21 and having cam grooves 19 for moving the balls, the ring being rotated by a pinion 24 driven by a shaft 23 controlled by an electric motor within the camera. The other end of the camera (Fig. 1, not shown) is connected to a flexible hose containing the power and output leads. A grab body 15 mounted on bearings 14 in the sleeve 16 is rotatable by a pinion 27 engaging an internal gear 28 on the body, this pinion being driven by a shaft 26 controlled by a further motor in the camera 10 whereby the grab 12 may be orientated relatively to the camera. A cam ring 32 for operating the grab fingers or other tools is rotatable on bearings 33 in the body 15 by a pinion 30 engaging a gear ring 31, this pinion being driven by a shaft 29 controlled by a third motor in the camera. The fingers may be of the type which move radially with respect to the grab axis 36 to engage or disengage the load and in this instance the forward end 39 of the body 15 has three radial slideways 40 each formed by a pair of lugs 41, Fig. 4. The grab fingers have slide blocks 42 movable in the slideways 40 by scroll cam teeth 44 co-operating with similar toothed sectors 38 formed on the cam ring 32. The blocks 42 may have different types of fingers and, as shown in Fig. 2, the upper block has an outwardly hooked finger 52 for engaging an annular groove 59 formed in the end of a reactor control rod 53. The lower block 42 has an inwardly hooked finger 66 for grabbing the grooved head of a reactor fuel element 67. Further, concave channels 60 may be formed in the backs of the fingers 62 to grip the end fitting 61 of a cable, and back surfaces 69 may be formed on the fingers 66 for gripping the surface 70 of a shut-down rod 71. In order to guide the grab on to the load, a sleeve 54 having a flared leading end is attached by pins 56 to the lugs 41. The detached head of a fuel can may be removed by inserting in the three slideways 40, a finger 52, a finger 66, and a fixed bolster not provided with scroll cam teeth (Fig. 8, not shown) secured to the lugs 41 by a pin. In another gripping arrangement, Fig. 9, a grab finger 80 pivoted at 84 to the lugs 41 has an end 86 engaged in a recess 87 formed in a slide block 88 having scroll teeth 89 cooperating with the teeth on the cam ring 32. The finger 80 co-operates with a fixed bolster 82 to grab the broken head 67 of a fuel element 68. In a modified grab, Fig. 11, the grab body 15A has four axially-extending guides 100 each formed with a slot 101 receiving a jaw 102. Each jaw has two oblique grooves 103 registering with oblique grooves 104 in the sides ofthe associated guide 100, the pairs of grooves 104, 105 trapping a ball 105. Thus forward motion of the jaws 102 also causes them to move inwardly relatively to the body 15A. The rearward ends of the jaws have yokes 107 receiving heads 108 formed on a cam nut 109. The nut has a helical screw thread 110 cooperating with a similar thread on the cam ring 32A whereby when the ring is rotated by the pinion 30 the nut 109 is moved axially and the jaws 102 are operated.