Transport Device for Reactor Fuel Rod Cladding Tubes

1. Field of the Invention

The present invention relates to a transport device for transporting reactor fuel rod cladding tubes transverse along a production line, comprising at least one member provided with a travel surface for said cladding tubes and a transport chain running in the direction of transport and parallel to the travel surface, said transport chain having a plurality of carriers arranged one after the other in the direction of transportation. More specifically, the invention relates to a conveyor having buffer storage between operating stations in a production line for reactor fuel rods which are transported in a direction perpendicular to the longitudinal axes of the fuel rods.

2. The Prior Art

In a device according to the invention, the transport chain can be driven with an even, invariable speed even if pauses or variations in the working pace occur at some operating station. This is achieved by applying the principle, known per se, of letting the space between two operating stations be used as a buffer storage for product units coming from one of the stations.

A transport device according to the invention is intended for transporting reactor fuel rods between operating stations representing different stages in the production.

According to the invention, a travel surface is provided for the tubes and a transport chain runs in the direction of transport parallel to the travel surface. The chain has carriers arranged one after another in the direction of its movement. Each of these carriers has rotatably mounted on it a two-armed carrier lever. Springs pull these levers around their pivots in the direction of travel of the chain. The springs are of such strength that they will only move rollers which are mounted on the ends of the levers up between the tubes when a predetermined small number of tubes is in front, whereas if the number of tubes is large the rollers cannot rise between the tubes but will roll on their bottom surfaces. This provides a storage system if the tubes are being fed along too rapidly.

The invention will be described in the following with reference to the accompanying drawings, in which FIG. 1 shows part of a production line for reactor fuel rods in a vertical view from above. FIGS. 2 and 3 show details of the same production line seen from the side, that is, in a direction perpendicular to the direction of transportation, and FIG. 4 shows a part of a section along the line IV--IV of FIG. 3.

In the drawings, A, B, C designate three different operating stations. At each station there is a long working table 1 adapted for placing almost equally long thin-walled fuel rod cladding tubes, which are not shown in FIG. 1. From operating station A the cladding tube is moved transversely and is placed at the end portions of a plurality of substantially horizontal, solid steel spars 3, which together provide sufficient travel surface for the cladding tubes. In FIGS. 2, 3, and 4 the cladding tubes are shown and designated 4. These are transported from station to station with the help of a transport chain 5, whose links are designated 6, 7 and 8. The direction of transportation is indicated by the arrow 9. Each pair of links 6 supports a shaft 10, on which a carrier arm 2 formed of two arms 11 is rotatably mounted at 2'. At the outer end of the carrier arm 2 a carrier roll 12 is mounted so as to be able to rotate about a horizontal shaft 13 which is transversely oriented in relation to the longitudinal direction of the transport chain 5.

Each carrier arm 2 is subjected to a torsional moment by means of a spring 14 and provided with a stop member 14', and turning in a counterclockwise direction past the limit position shown at the extreme right of FIG. 2 is not possible. At this limit position the roller 12 has its highest level in relation to the surface on which the cladding tubes 4 are positioned, that is, in relation to the supporting surface of the beams 3. The carrier arms 2 are held by the springs 14 in the above-mentioned limit position for as long as they are not in mechanical contact with the cladding tubes 4. According to the invention, the springs 14 are dimensioned and adjusted in such a manner that the torque exerted by the springs is only sufficient for carrying along a group of cladding tubes, if the number does not exceed a certain, relatively low value. In the example described in connection with the drawings this value is chosen to be equal to 1. As shown in FIG. 2, the carrier 2 is pulled backwards when it strikes against a group containing a plurality of adjacent cladding tubes 4 even when the group is free to move in the direction of travel. Then the carrier roller 12 rolls on the undersides of the tubes and finally sets the front tube in motion. If the spring 14 had been somewhat more taut, the carrier arm 2 would instead have moved in between the third and fourth or perhaps between the fourth and fifth cladding tubes and -- in agreement with the inventive idea -- even with the somewhat more taut spring the carrier would only have had to move a smaller part of the group of tubes, and unallowable stresses on the tubes would have been avoided.

The eight tubes shown in FIG. 2 constitute a buffer storage between two operating stations. By means of the carrier of the transport chain one tube at a time is moved on to a stop edge 16 located immediately in front of the next operating station, where it may be removed from the spars 3. If the tube is not removed quickly enough, a tube transported by the next carrier will add to the growth of a buffer storage.

The right-hand portion of FIG. 3 shows a chain section working at full transport capacity, whereas the left-hand portion shows a buffer storage which is building up. Feeding units from such a buffer storage by applying a force at the very back of the row is a well-known principle, but it is not very suitable when it is a question of sensitive object, for example reactor fuel rods, and it implies that the feeding force increases with the size of the buffer storage, so the allowable number of buffer-stored tubes will be far less than when using an arrangement according to the invention.

A transport device according to the present patent application can be constructed in many different ways within the scope of the invention.

Instead of a number of steel spars 3 a table provided with slits may be used, and in some cases only one spar may be sufficient. Instead of a chain it is possible to use an endless band of rubber or the like. The cladding tubes may be arranged with vertical shafts and with supports against a wall, the feeding then taking place by means of carrier arms which are rotatable in a horizontal plane.

Instead of a plurality of spars as a roll conveyor it is also possible to use a plane or a curved table, which does not have to be provided with longitudinal gaps for the carrier arms, and to use a transport chain or the like which is arranged across the table and the carrier arms of which are rotatable in a vertical plane.