Patent Number: 050248030
Section: claims

1. An emergency device for control of displacement of a conveying carrier for a nuclear fuel assembly, in which said conveying carrier moves under the effect of a push-pull chain actuated by a driving mechanism selectively causing winding of said chain on itself in spiral so as to pull said carrier, and unwinding of said chain by forming a rigid carrier pushing element, including a connecting member between said chain and said carrier, said connecting member being formed of two portions connected to each other by a pin adapted to be broken when required for disconnecting the two portions and to free the carrier from the chain, wherein the breaking of said pin is due to the effect of traction exerted remotely from said carrier on a control cable, such that, after breaking, the cable can apply a traction on said carrier so as to bring it back freely, independently of said chain, to a predetermined position, the connecting member between said chain and said carrier including a fastening member attached to said carrier and connected to two parallel flanges of a link of said chain by means of a transverse spindle, said fastening member and said spindle being connected by said pin, said pin being parallel to said flanges. 2. An emergency device according to claim 1, wherein the transverse spindle extends freely through passages formed in alignment in said flanges and said fastening member, respectively. 3. An emergency device according to claim 1, wherein said transverse spindle is slidably mounted in a first housing of a support block, carried by said carrier and including a rack actuated by a flat pinion mounted so as to rotate freely on an axis perpendicular to the pinion and rigidly connected to the support block. 4. An emergency device according to claim 3, wherein said pinion actuating said rack of said spindle is driven in rotation by a second spindle mounted in the support block inside a second housing located in a plane of said first housing but perpendicularly to it, said second spindle also including a rack in mesh with the pinion in such manner that the rotation of the latter causes simultaneous and opposite displacement of the spindles, respectively toward the inside and the outside of the support block. 5. An emergency device according to claim 4, wherein said second spindle is rigidly connected at its end outside said support block to a member connecting with said traction cable. 6. An emergency device according to claim 5, wherein said connecting member includes a whorl adapted to bear at the end of the stroke of the second spindle under the effect of the pinion on an abutment rigidly connected to said carrier, in such manner that a traction effort exerted on said cable once said pin is broken brings said whorl against the abutment, thereby causing entrainment of said carrier by said cable. 7. An emergency device according to claim 3, wherein said support block of said pinion is mounted inside a tight casing which is supported by said axis of rotation pinion, said pinion being in turn disposed underneath a lower face of said carrier. 8. An emergency device according to claim 1, wherein said control cable is actuated by a winch located at a distance from said carrier and on a drum on which is wound said cable, guided toward said carrier by return pulleys. 9. An emergency device according to claim 8, wherein said cable winds itself on a mobile pulley provided with a counterweight exerting constant tension on said cable, which remains permanently taut in all positions of said carrier. 10. An emergency device according to claim 1, wherein said carrier includes wheels moving on rails extending parallel to a working plane of said push-pull chain. 11. An emergency device according to claim 10, wherein said chain winds itself on a toothed control driven by a return mechanism from a motor reduction unit.