Patent Number: 053234332
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for arranging short cylindrical bodies in general, and relates in particular to its application to a drying apparatus capable of changing the direction of transport of a plurality of pellets, and an associated inspection apparatus for inspecting the external surface quality of each pellet. 2. Technical Background of the Invention In general, the pellets which are charged into nuclear fuel rods are made by pressing a fuel powder, such as uranium dioxide, into cylindrical pellets of a short rod shape, and sintering the pressed pellets. In the process of producing such pellets, surface chips and other surface defects are sometimes produced on the external surfaces of the pellets. It is therefore necessary to inspect the surface quality of the pellets for the presence of surface defects. Conventionally, such inspections have been performed visually on every sintered pellet to eliminate defective pellets so as to assure the reliability of the reactor operation. However, such a manual inspection method is not only labor-intensive and time-consuming but also places a large mental stresses on the inspectors who carry out such tasks on a daily basis. To alleviate such problems, the present inventors have previously presented an inspection apparatus for inspecting the surface quality of the pellets based on image processing technology (U.S. Pat. No. 5,019,326). The inspection apparatus is usually associated with a wet grinding device. The pellets subjected to wet grinding are discharged continuously from the wet grinder with the axis of the short rod-shaped pellets aligned in the transport direction. To inspect the surface quality of the pellets efficiently, it is necessary to quickly change the direction of movement of the pellet from its axial direction to its radial direction in the inspection apparatus so that both the end surfaces and the side surface of the short rod-shaped pellets can be inspected. Also, for pellet handling purposes, the planar end surfaces of the pellets are provided with a pair of depressions (dish sections), which are prone to collecting moisture from the wet grinding operation. The moisture sometimes affects optical recording of the surface images, because of false surface signals from abnormal reflections and refractions caused by droplets of water collecting in the dish sections. The presence of water thus interferes with the proper optical inspection of the wet ground pellets, and it is necessary that the pellets be dried completely before optical inspection. SUMMARY OF THE INVENTION The present invention was made in view of the technological background presented above, and an object is to present an application of an apparatus for arranging short cylindrical bodies to drying of a plurality of pellets, in which the apparatus also serves as a device for changing the direction of transport of each pellet from an axial direction to a radial direction, so as to facilitate surface inspection of each pellet. The apparatus further includes a device for efficiently transferring the accepted pellets from surface inspection and arranging on a tray for storage. To achieve the above object, the present invention presents a drying apparatus comprising: a rotation disc of an approximately circular shape rotatable about a disc axis for redirecting each pellet of the plurality of pellets from an axial direction to a radial upward direction; a plurality of pellet pockets formed on the outer periphery of the rotation disc for housing each pellet of the plurality of pellets with the pellet axis lying in the axial direction; and a plurality of gas circulation devices having a plurality of gas circulation paths communicating with the plurality of pellet pockets. In the apparatus of such a construction, the pellets which are transported horizontally with the axis lying in the direction of the transport are housed in the pellet pocket formed around the periphery of the rotation disc. Accordingly, the direction of transport of the pellets can be changed quickly to a radial upward direction. At the same time, the gas circulation device circulates air flow around each pellet housed in the pellet pocket, thereby drying the pellets completely and efficiently, and promoting efficient inspection of the surfaces of the pellets. The apparatus further comprises: a pellet displacement monitor which determines changes in the position of the end surface of a pellet being transported in an axial direction; and a pellet transport control device for placing the pellet in a pellet direction change position so as to be housed in a pellet pocket of the rotation disc. Therefore, the speed of transporting the pellets is determined on the basis of the position of the end surface of a pellet being transported in the axial direction. The pellet is stopped at the pellet direction change position of the rotation disc. The direction of the transport of the pellet is thus efficiently changed from the axial direction to the radial upward direction. The apparatus is further provided with a control device for rotating the rotation disc through a specific angle when the pellet displacement monitor determines that the pellet has been placed in the pellet direction change position. Accordingly, when the pellet displacement monitor determines that the pellet has been placed in the pellet direction change position, the control device rotates the rotation disc through a specific angle so as to correctly house the pellet in the pellet pocket of the rotation device, and thereby changing the direction of transport of the pellet for further processing. The apparatus is further provided with a pellet position sensor which determines that a pellet to be housed in the pellet pocket of the rotation disc has been disposed in the pellet direction change position; and a control device for rotating the rotation disc through a specific angle when the pellet position sensor determines that the pellet has been placed in the pellet direction change position. Accordingly, it is doubly confirmed that the pellet which has been transported with the pellet axis lying in the axial direction has been placed in the pellet direction change position, thereby assuring that the position change step is performed efficiently without any potential error. The apparatus is further provided with equidistantly disposed pellet pockets on the circumferential periphery of the rotation disc. Accordingly, it is possible to transport a plurality of pellets in the radial upward direction at the specific timing. The apparatus is further provided with a plurality of ratchet devices between two neighboring pellet pockets equidistantly around the circumferential periphery with sharp teeth of the ratchet devices facing in the forward rotational direction of the rotation disc. Accordingly, the pellet stopped at the pellet direction change position is positively housed in a pellet pocket of the rotation disc. The apparatus is further provided with a plurality of gas circulation paths comprising a plurality of gas in-ports which direct a gas flow to end surfaces of the plurality of pellets. Accordingly, both end surfaces of the pellets which are difficult to dry completely can be dried efficiently by the directed air flow. The apparatus is further provided with a plurality of gas circulation paths comprise a plurality of gas out-ports so as to enable gas to sweep over the end surfaces of pellets. Accordingly, moisture collecting in the end surface of the pellets and particulate matters in the pellet pockets are exhausted and expelled out the rotation disc, thereby providing efficient drying of the pellets. The apparatus is constructed such that a plurality of gas in-ports are provided which direct a gas flow to end surfaces of pellets; and a plurality of gas out-ports which exhaust gas from opposing end surfaces of the plurality of pellets; wherein the gas in-ports and the gas out-ports are disposed on both end covers of the rotation disc in the radial direction of the rotation disc, and perform intaking and exhausting of gas so as to alternatingly direct the gas flow to both end surfaces of the plurality of pellets. Accordingly, the pellets which are being transported through a specific angle are moved from the left end cover to the right end cover alternatingly and subjected to the air flow so as to expose both end surfaces of the pellets to the air flow, thereby promoting to dry both end surfaces positively and efficiently. The apparatus is further provided with a gas passage groove having a length longer than a diameter of the end surface of the pellets. Accordingly, the pellet attaching to the end covers do not present barrier to removal of particular matters, thereby promoting the removal of moisture as well as particulate matters. The apparatus is further provided with a plurality of outflow ports which direct air flow against the side surfaces of the plurality of pellets housed in the pellet pockets. Accordingly, the air flow is directed to the side surfaces of the pellets, thereby promoting to dry the side surfaces of the pellets efficiently. In the apparatus of the present construction, the outflow ports are aimed at a bottom region of the pellets housed in the pellet housing pockets. The pellet in the pellet pocket is thus floated in the air flow, thereby facilitating the sideways movement of the pellets as well a the drying of the underside of the pellets. The apparatus for arranging short cylindrical bodies (represented by pellets), each pellet having two end surfaces and a side surface and moving from upstream process to downstream process, comprises: a pellet drying section comprising a rotation disc of an approximately circular shape rotatable about a disc axis for redirecting each of a plurality of pellets being transported from an axial direction to a radial upward direction; a plurality of pellet pockets formed on the outer periphery of the rotation disc for housing each pellet of the plurality of pellets in each of the plurality of pellet pockets; and a plurality of gas circulation devices having a plurality of gas circulation paths communicating with the plurality of pellet pockets; a pellet inspection section for recording surface conditions of the two end surfaces and the side surface of each of the plurality of pellets which have been dried in the pellet drying section and have been redirected from an axial direction to a radial upward direction, and for determining acceptance or rejection of each of the plurality of pellets based on recorded images; and grip transporting devices for transporting a plurality of pellets which have been determined to be acceptable in the pellet inspection section; a visual confirmation section for visually inspecting the external appearance of the plurality of pellets transported by the grip transporting devices; and a tray loading device for inserting a tray fully loaded with a plurality of pellets transported from the visual confirmation section by the grip transporting devices into a tray storage rack. According to the apparatus for arranging pellets of the above configuration, the pellets are dried as well as the direction of their transport is changed. In the inspection section, the end and side surfaces of the pellets are inspected, and the defective pellets are removed, leaving only the defect-free pellets to be transported further. The accepted pellets are inspected once more visually to confirm that the pellets are completely acceptable. The grip transporting device moves the pellets quickly and swiftly to a tray, and when the tray is fully loaded, it is stored by the tray loading device in a tray storage rack. Therefore, the pellets are accurately and efficiently changed in the direction of transport from an axial direction to a radial upward direction, and the accepted pellets are transferred to the tray and the loaded tray is simply stored in the tray storage rack. The pellet inspection section of the apparatus further comprises: an end-surface recording device which transports each of the plurality of pellets at a specific time interval, record end surface conditions of the two end surfaces and determines acceptance or rejection of each of the plurality of pellets; and a side-surface recording device comprising a pellet rotation device having a small diameter roller rotating in the same direction and at the same peripheral speed as a proximally-disposed large diameter roller having pellet discharge pockets, for supplying each pellet of the plurality of pellets between the small diameter roller and the large diameter roller at a specific time interval, recording the side surface condition of the side surface of each pellet of the plurality of pellets, and determines acceptance or rejection of each pellet of the plurality of pellets based on an linearly translated image of the side surface of each pellet. Accordingly, pellets are transported periodically and the end surface of the pellet is recorded successively for determining acceptance/rejection of the pellets. The pellet is then supplied periodically to a space between the small diameter roller and the large diameter roller which are rotating in the same direction and at the same peripheral speed, thereby rotating the pellet. The side surface of the rotating pellet is recorded from above with a side surface recording device, and the pellet is accepted/rejected on the basis of a linearly translated recording image. The surfaces of the pellet can thus be inspected efficiently and accurately to perform quality control of the pellets. The pellet inspection section of the apparatus is further provided with a vacuum suction device disposed between the small diameter roller and the large diameter roller. Accordingly, the pellet is firmly and stably held in place against the rollers by the suction force, thereby enabling to exhaust particulate matters and perform side surface inspection stably. The apparatus further comprises a pellet collection device, disposed upstream of the pellet drying section in a plurality of pellet transport routes, for collecting a plurality of pellets being transported horizontally, and a spacer device for separating a plurality of pellets being transported horizontally in close contact with each other. Accordingly, it is possible to collect pellets being transported in the axial direction before forwarding them to the pellet drying section. The spacer device permits the closely disposed pellets to become spaced apart, thereby enabling to send each pellet separately and periodically to the drying section. The apparatus is constructed so that the pellet collection device becomes activated when an operational problem arises in a downstream section of the pellet drying section. Accordingly, if an operational problem should arise in a region upstream to the drying section, the operation of the sections downstream to the drying section is stopped, and the collection operation of the pellets is commenced, thereby stopping the supply of pellets to a downstream section of the apparatus. In the upstream of the pellet drying section, the flow of pellets is not disturbed, and the productivity in the upstream of the pellet drying section is not affected.