Patent Number: 048662810
Section: summary

The invention relates to an irradiation plant comprising an irradiation chamber and a conveyor system for conveyor units bearing articles for irradiation and moved past a radiation source the system comprising an even number of irradiation tracks disposed symmetrically to the radiation source and extending between a first transverse track and a second track each connecting the irradiation tracks at a respective end, and one transverse track being connected to the entry section and the exit section of the conveyor system to and from the irradiation chamber. CH-PSS 536 544 and 537 076 disclose an irradiation plant in which articles are irradiated with .gamma.-rays, e.g. for disinfection or for changing their physical properties. In the known plant, the conveyor units are moved around a radiating wall in batches, during a time preset for each batch and along the same preset path for all conveyor units. If the quantities of articles receiving the same dose of radiation are relatively large, the known device serves its purpose satisfactorily. In this case, since the change from one to another irradiation program does not have to occur too frequently, the operating costs are not excessively burdened by the change-over costs. It has been found in practice, however, that in many irradiation operations, e.g. in medicine or in the food industry or the treatment of plastics and glass, the article for irradiation often comes in small quantities, so that the irradiation plant can only be inefficiently used and loaded. In cases where the amounts of irradiated articles are small, the change-over times, as a proportion of the operating times, have a very adverse economic effect on the irradiation plant. A pamphlet dated June 1983 of Messrs. Atomic Energy of Canada Limited, PO Box 13500, Kanata, Ontaria, Canada discloses a .gamma.-irradiation plant with a suspended rail track on which the conveyor carriages carrying articles for irradiation are moved batchwise and manually to and from the irradiation chamber. The conveyor carriages and articles are all moved individually through the labyrinth along a single fixed path. A plant of this kind can be dangerous for the operator and requires expensive safety equipment. It is very complicated and uneconomic for the irradiation chamber to be simultaneously filled with articles which have to be irradiated differently. Although the residence time in the radiation area can be controlled by a dosimeter, there is a serious risk in this manually-operated plant that articles will be given the wrong doses of radiation. An object of the invention is to devise an irradiation plant in which relatively small quantities of differently-irradiated articles can be simultaneously irradiated, so that the irradiation chamber can be efficiently occupied and used even in these cases and the change-over work and time is reduced to an economically acceptable minimum. The irradiation plant must also provide high security for the operating staff. The plant must not need to be entered by staff during operation. This problem according to the invention is solved by an irradiation plant characterised in that each transverse track comprises a shift device for loading, unloading and changing over the conveyor units on the irradiation tracks and the conveyor units have control elements for presetting the path of the conveyor unit in the conveyor system and acting on sensors of a conveyor-system control means, and the control means is constructed so that whenever a conveyor unit is loaded on to or unloaded from an irradiation track, a shift device is disposed on each side of the conveyor unit, and at the end of each loading or unloading process, not more than one of the two facing shift devices is loaded with a conveyor unit. The dependent claims relate to advantageous further features of the irradiation plant. The path travelled in the irradiation chamber can be individually preset for each conveyor unit, thus enabling a number of differently-irradiated articles to travel through the irradiation chamber along various tracks depending on the preset irradiation requirement. During the loading and unloading process, only one of the two facing shift devices on the transverse tracks is occupied at one time by a conveyor unit, thus ensuring that the conveyor units run unimpeded along their individual paths through the irradiation chamber.