Abstract:
A system is provided for sterilizing, by irradiation, a plurality of products, each product having an identification code. The products are carried on product carriers which include a carrier identification code. The system includes a product loading station, a product unloading station, an irradiation blocking containment, and an irradiation station location located within the containment. A conveyor passes from the loading station through the containment to the unloading station. Code readers are located along the conveyor for detecting and reading both the product identification code and the carrier identification code. A control and monitoring circuit receives the codes, and stores in memory an association between specific carriers and the products located on those carriers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an installation for the sterilization of medical products by irradiation. 
     2. Description of Related Art 
     It is known that tubes for extra-corporeal blood circulation, known as blood lines, which are used for extra-corporeal blood treatment, such as haemodialysis, undergo a sterilization process aimed at ensuring the complete elimination of germs. At the present time, this sterilization is carried out in various ways, for example by gamma-ray irradiation. However, this technique has various disadvantages linked to the dangerous nature of the material used for generating radiation, to the cost of shielding the irradiation equipment and to the difficulty in obtaining the official permits necessary for using it, in view of the growing awareness of environmental pollution. Moreover, high-temperature steam sterilization is unsuitable for PVC blood lines since, to ensure appropriate sterilization, it is necessary to employ a temperature near the softening point of PVC, thus entailing the risk of damage to the products. 
     At the present time, for further types of product, other irradiation methods are adopted, such as beta-ray irradiation, which do not cause the problems mentioned above. Beta-ray sterilization is, for example, used, with good results, for treating edible products or medical products of a non-critical nature. 
     However, where PVC blood lines are concerned, this sterilization treatment has not yet been used on a large scale due to the critical nature of the material and the stringent sterilization requirements demanded for such a use. In fact, on the one hand, the chemical and physical characteristics of PVC are extremely sensitive to irradiation doses and set strict upper limits to the doses which can be used and, on the other hand, the need for sufficient sterilization sets lower limits on these doses. Furthermore, irradiation installations which have not been designed specifically (such as third-party servicing installations) do not make it possible to ensure sufficient sterilization of the product as a whole, without some of the product being subjected to excessive exposure. In addition to this, the low unit price of the product makes it impossible to employ costly monitoring and management techniques if the competitiveness of blood lines sterilized by beta rays, as compared with lines sterilized by conventional methods, is to be maintained. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a sterilization installation which makes it possible to sterilize fragile products, such as PVC blood lines, efficiently and economically, without in any way damaging them. 
     In order to achieve this object, according to the invention an installation for the sterilization of medical products by irradiation is provided, characterized in that it comprises: 
     at least one product loading station, 
     at least one product unloading station, 
     an irradiation station located inside a containment having walls capable of stopping sterilizing radiation, 
     conveyance means for conveying the products to be sterilized from the loading station to the irradiation station and the sterilized products from the irradiation station to the unloading station, the conveyance means comprising grouping means for grouping the products to be sterilized in the vicinity of the irradiation station. Advantageously, the grouping means comprise a first conveyor and a second conveyor, the second conveyor being located immediately downstream of the first conveyor in relation to the direction of conveyance of the products and having a conveying speed lower than the conveying speed of the first conveyor. 
     According to a characteristic of the invention, the first and second conveyors comprise retractable drive members for catching the products and strictly subjecting their displacement to that of the corresponding conveyor. 
     According to a characteristic of the invention, the second conveyor comprises two half-conveyors separated by a gap located in a zone, towards which the irradiation station emits the sterilizing radiation. 
     According to a characteristic of the invention, the installation comprises a third conveyor located immediately downstream of the second conveyor in relation to the direction of conveyance of the products, the third conveyor having a conveying speed higher than the conveying speed of the second conveyor. 
     According to a characteristic of the invention, the conveyance means comprise 
     superposed conveyance sections, the conveyance sections located at a first level conveying the products to be sterilized from the loading station to the irradiation station and the conveyance sections located at a second level conveying the sterilized products from the irradiation station to the unloading station. 
     a vertical transporter for transferring the products from one conveyance level to the other conveyance level. 
     According to a characteristic of the invention, the installation comprises means for the detection of products, said detection means being arranged along the conveyance means, and control and monitoring means connected to the detection means in order to follow the travel of the products on the conveyance means. 
     According to a characteristic of the invention, the installation comprises a plurality of trays intended for supporting the products on the conveyance means, each tray being provided with an identification code, the means for the detection of products comprising code-reading means capable of reading the code affixed to each tray. 
     According to a characteristic of the invention, the means for the detection of products comprise code-reading means capable of reading an identification code affixed to each of the products arranged on each tray, and the control and monitoring unit is provided for combining and storing the identification code of each product and the identification code of the tray supporting this product. 
     According to a characteristic of the invention, the means for the detection of products comprise mechanical travel-limit detection means arranged inside the containment, in order to detect the position of the trays inside the containment and transmit a corresponding signal to the control and monitoring unit. 
     According to a characteristic of the invention, the invention comprises means for measuring the speed of the second conveyor which are connected to the control and monitoring means, and the control and monitoring means are provided for setting the irradiation emitted by the irradiation station as a function of the speed variations of the conveyor in such a way that the products receive a predetermined irradiation dose. 
     Another subject of the invention is a method for the sterilization of medical products by irradiation, comprising the steps of: 
     placing at least one product provided with a product identification code onto a tray provided with a tray identification code, 
     reading the tray identification code and the product identification code, 
     storing the combination of the tray and product identification codes, 
     conveying the tray along a definite path towards an irradiation station, and 
     locating the tray by reading the tray identification code at definite places along the path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages and characteristics of the invention will emerge from a reading of the following description. Reference will be made to the accompanying drawings, in which: 
     FIG. 1 shows a top view of the entire sterilization installation according to the invention; 
     FIG. 2 shows diagrammatically a blood line for once-only use; 
     FIG. 3 shows a perspective view of two boxes, each containing a plurality of blood lines; 
     FIG. 4 shows a perspective view of a tray for transporting the two boxes of FIG. 3; 
     FIG. 5 shows an enlarged detail of FIG. 1; 
     FIG. 6 shows a side view of part of the installation of FIG. 1; 
     FIG. 7 shows an enlarged detail of FIG. 6; 
     FIG. 8 shows another enlarged detail of FIG. 1; 
     FIG. 9 shows a cross-section through the installation along the line IX—IX of FIG. 1; 
     FIG. 10 shows another enlarged detail of FIG. 1; 
     FIG. 11 shows a side view of part of the installation of FIG. 1; 
     FIG. 12 shows a detail of the conveyors of FIG. 11; 
     FIGS. 13 and 14 show side views, in two different positions, of the drive members of the conveyors of FIG. 11; 
     FIG. 15 shows a cross-section through part of the conveyors of FIG. 11; 
     FIG. 16 shows a cross-section through the installation along the line XVI—XVI of FIG. 1; and 
     FIGS.  17   a  and  17   b  show a block diagram relating to the control functions of the control and monitoring unit. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to FIG. 1, the sterilization installation  1  comprises a main loading station  2 , an auxiliary loading station  3 , a main unloading station  4 , an auxiliary unloading station  5 , a containment or bunker  6 , an irradiation station  7  located inside the containment  6 , and conveyance means  8  connecting the loading station  2  to the unloading station  4 . 
     The conveyance means  8  comprise a plurality of conveyors, preferably of the roller type, with sections for the conveyance of products to be sterilized and sections for the conveyance of sterilized products, the said sections being superposed. In particular, the conveyance means  8  comprise the following successive sections: 
     a first section  10  arranged in the extension of the main loading station  2 , 
     a second section  11  perpendicular to the first section  10 , 
     a third section  12  perpendicular to the second section  11  and extending in a direction opposite to that of the first section  10 , 
     a fourth section  13  perpendicular to the third section  12  and extending in the same direction as the second section  11 , 
     a fifth section  14 , passing through the irradiation station  7 , perpendicular to the fourth section  13  and extending in a direction opposite to that of the third section  12 , 
     a sixth section  15  perpendicular to the fifth section  14  and extending in a direction opposite to that of the fourth section  13 , 
     a seventh section  16  of curved shape, with its concavity facing towards the irradiation station  7 , 
     an eighth station  17  of curved shape, with its concavity facing the opposite way to the irradiation station  7 , this eighth section  17  being in a plane located below a parallel plane containing the seven preceding sections, 
     a ninth section  18 , a tenth section  19  and an eleventh section  20  extending respectively below the fourth section  13 , the third section  12  and the second section  11 , and 
     a twelfth section  21  parallel to the first section  10  and extended by the main unloading station  4 . 
     In other words, the sections  13  to  17  form a ring inside the containment  6  and are preceded and followed by superposed sections for conveying the boxes of products to be irradiated and irradiated boxes. 
     All the conveyance sections form an angle with one another, with the exception of sections  13  to  15 , which are connected to one another by means of curved portions. 
     The containment  6  is produced from masonry, and it delimits three zones which communicate with one another: 
     a first entry and exit zone  25  containing part of the sections  11 ,  20 , the sections  12 ,  19  and part of the sections  13 ,  18 , 
     an intermediate second zone  26  containing part of the sections  13 ,  18  and the sections  15  to  17 , and 
     a third zone  27  containing the section  14  and the irradiation station  7 . 
     The third zone  27  does not contain any electrical or electronic equipment which could be damaged by the ionizing radiations generated in the irradiation station  7 . Moreover, the mechanical members which are located there are produced from materials highly resistant to ionization, such as stainless steel, and lubricated by means of specific products. 
     Those sections of the conveyance means which are located outside the containment  6  are enclosed in a metal trelliswork cage  43  preventing access (see FIG.  6 ). 
     The installation  1  is intended for the sterilization of blood lines, for example of the type illustrated in FIG.  2  and identified by the reference numeral  30 . A plurality of blood lines  30  are arranged in a box  31  (FIG. 3) provided with a box label  32  bearing a product identification code (for example, a bar code). Two boxes  31  are arranged side by side on a rectangular tray  33  (see, in particular, FIG.  4 ), preferably made of metal, which comprises a flat bottom  34  equipped with a peripheral rim  35 . Fastened to the lower face of the bottom  34  is a frame  36 , the sides of which are set back slightly relative to the corresponding rims of the bottom  34 . A tray label  37  is glued to the rim  35  of the tray  34  and bears an identification code (typically, a number specific to the tray or a bar-code). 
     At the main loading station  2  (see FIG. 5) the trays  33  are loaded in such a way that the two boxes  31  advance one behind the other on the conveyance means. The main loading station  2  comprises a group of code readers  40 ,  41 ,  44  of the optical type which are arranged laterally relative to the conveyor and are oriented in such a way that each of them can read the identification code of the two boxes and the identification code of the tray from the respective labels  32 ,  37  and emit corresponding identification signals. The code readers  40 ,  41 ,  44 , as well as the other code readers mentioned below, are connected to a control and monitoring unit  42  (see FIG. 1) located in a room  39  contiguous to the containment  6 . The control and monitoring unit  42  is connected to a memory  54  and, if appropriate, to a processing unit, placed at a suitable location along the conveyance means  8 , and to optical and/or acoustic signaling devices not illustrated in detail. 
     An auxiliary loading station  3  is arranged laterally relative to the first section  10  of the conveyance means. This auxiliary station  3  is provided with a code reader  45  for the label of a tray, the said code reader being intended to emit a corresponding code signal. 
     As illustrated in FIGS. 5 to  7 , the first and the twelfth conveyance sections  10  and  21  each comprise three different conveyors  46   a ,  46   b ,  46   c , respectively, and  47   a ,  47   b ,  47   c , each of them defining an initial path, an intermediate path and a final path in the respective conveying direction. Since the main loading station  2  and the main unloading station  4  are arranged side by side, the conveyors  46   a  and  47   c  are at the same level. The intermediate conveyors  46   b ,  47   b  define ramps which both ascend in the direction of travel of the trays  33 . The conveyor  47   a  is arranged laterally relative to the conveyor  46   c , at a lower level. The conveyors  46   a  and  47   c  are equipped with blocking devices  58   a ,  58   b  which are illustrated diagrammatically and are not described in detail. The main unloading station  4  comprises, furthermore, a code reader  38  arranged so as to make it possible to read the label  37  of the tray  33  reaching the end of its travel. 
     The sections  10  and  21  are connected to the contiguous sections  11 ,  20  by means of curved connecting portions  48 ,  49 , respectively (see FIG.  8 ), in such a way that the sections  11  and  20  are exactly superposed. 
     As shown in detail in FIG. 8, the conveyance section  20  is connected to the auxiliary unloading station  5  by means of a junction section  50  perpendicular to the conveyance section  20 . Each conveyance section  11 ,  20  is equipped with a respective code reader  51 , 52  (FIG.  1 ). 
     Inside the containment  6 , the conveyors defining the section  14  are driven by means of a single motor  55  (see FIGS. 1 and 15) which is arranged in the entry and exit zone  25  and therefore outside the critical zone  27 . The motor  55  is connected to the conveyors of the section  14  by means of a shaft  57  passing through a wall of the containment  6 . The motor  55  comprises a pulse transmitter  56  which accurately controls the speed of the said motor and emits signals which are supplied to the control and monitoring unit  42 , in order to check that the conveyor system is functioning correctly and, if appropriate, that the process parameters are appropriate. 
     The conveyance section  13  extending from the entry and exit zone  25  to the sterilization zone  27  comprises a stainless-steel roller conveyor  60  and, at its end contiguous to the section  14 , a travel-limit detector  61  of the mechanical-arm type, shown diagrammatically in FIG.  10 . The travel-limit detector  61  is connected to the control and monitoring unit  42  by means of a rod assembly and transducers. 
     The section  14  comprises three chain conveyors  62 ,  63 ,  64 . The end conveyors  62  and  64  have a high conveying speed, whilst the speed of the central conveyor  63  is lower. Guide rails  67  are arranged on each side of the section  14 , outside the chain conveyors  62  to  64 , in order to support and guide the trays  33 . A mechanical arm-type detector (not shown) is mounted level with the central conveyor  63  in order to detect the presence of the trays  33 . A travel-limit detector  65  is mounted at that end of the conveyor  64  which is contiguous with the conveyance section  15 , in order to detect the arrival of a tray  33  and trigger the functioning of the roller conveyor  66  of the conveyance section  15 . 
     As may be seen in FIG. 11, the central conveyor  63  comprises two half-conveyors  63   a ,  63   b  separated by a gap located in the irradiation station  7 . This station comprises a particle accelerator  70  provided with a scanning head (not shown) which is arranged above the path of the products to be sterilized, vertically in line with the gap separating the two half-conveyors  63   a ,  63   b , and an absorbing well  71  arranged vertically in line with the scanning head, below the level of the conveyors  63   a ,  63   b , in order to absorb and dissipate the excess beta radiation energy. 
     As shown diagrammatically in FIGS. 10 and 11, the conveyor  62  consists of a pair of chains  72 , the half-conveyor  63   a  consists of a pair of chains  73 , the half-conveyor  63   b  consists of a pair of chains  74  and the conveyor  64  consists of a pair of chains  75 . For actuating these conveyors, the shaft  57  drives the pair of chains  75  by means of a chain transmission  76 , a drive shaft  77  and a gearwheel  78 ; the pair of chains  75  drives the pair of chains  74  by means of a reduction gear train  79  located below the conveyors; the pair of chains  74  drives the pair of chains  73  by means of a transmission mechanism  80  located above the conveyors; and the pair of chains  73  drives the pair of chains  72  by means of a step-up gear train  81  located below the conveyors. 
     As may be seen in FIGS. 12 to  16 , the chains  72  to  75  comprise pairs of aligned drive members  84  (FIG.  12 ). Each drive member  84  consists of a pair of elements  85  in the form of an angle piece which are connected rigidly to one another at a first end  86  and are connected pivotally to the chain at a second end  87  (FIG.  15 ). A roller  88  is mounted pivotally on the outside face of each element  85  in the form of an angle piece, level with the bent part of the latter. In predetermined sections of the upper portion of each chain  72  to  75 , the rollers  88  of a drive member  84  come into engagement with corresponding parallel straight guides  90  (see FIGS.  11  and  15 ), the effect of this being to cause the drive member  84  to pass from a retracted position, in which it is below the level of the guide rails  67  of the trays  33  (see FIG.  13 ), into a projecting position (see FIG.  14 ), in which it can engage into the frame  36  fastened under each tray  33 . The position of the drive members  84  on each chain  72  to  75 , the synchronization of the chains and the length and arrangement of the straight guides  90  are suitably calculated to ensure that each tray  33  is driven by the chains  72  to  75  at the desired moment and that the trays  33  are grouped correctly, as described below in more detail. 
     FIG. 11, furthermore, shows diagrammatically the travellimit detector  65  and the corresponding rod assembly  91  which serves for actuating the roller conveyor  66  of the conveyance sections  15  and  16 . The connection between the conveyance sections  16  and  17  which are not at the same level is made by means of a vertical transporter  92  (see FIG. 10) which is provided for picking up a tray  33  arriving at the end of the roller conveyor  66  and for transferring it onto the roller conveyor  97  of the conveyance sections  17  and  18 . The vertical transporter  92 , which is arranged in the zone  26  of the containment  6 , comprises a motor  93  for conveying the trays  33  vertically, a motor  94  for conveying them horizontally and specific control means  95  for ensuring synchronization with the roller conveyors  66  and  97 . 
     The installation just described functions as follows. At the main loading station  2 , the operator places two boxes  31  containing blood lines  30  onto a tray  33 , one in front of the other. As illustrated in the flow chart in FIGS.  17   a ,  17   b , the code readers  40 ,  41  and  44  read the labels  32  and  37  of the boxes  31  and of the tray  33  (block  100 ) and emit the corresponding signals which are transmitted to the control and monitoring unit  42  which combines (block  101 ) the data relating to the products and read from the label on the box  31  with the identification number of the tray, read from the label on the tray  33 . For the entire time that the boxes  31  dwell inside the installation  1 , the said boxes are identified and followed on the conveyance means solely from the identification code of the corresponding tray  33 , with which they are combined without any risk of exchange or error: it may be recalled that the conveyance means as a whole are inaccessible to the operators, since the said means are isolated from outside by the metal trelliswork cage  43  and by the containment  6 . 
     Furthermore, the control and monitoring unit  42  checks whether the product code read from the label on the boxes  31  corresponds to that of the previously loaded and processed products (block  102 ); if not (different products requiring a variation of the processing parameters, such as the intensity of the irradiation generated by the accelerator  70  or the conveying speed of the conveyor  14 ), the control unit  42  actuates the blocking devices  58   a , thus causing the trays  33 , already introduced into the main loading station  2 , to stop (block  103 ), and requiring the operator to introduce a test tray  33   a  at the auxiliary loading station  3  (block  104 ). For this purpose, suitable signaling means (not shown) may be provided at the station  3 . The operator then introduces into the installation a test tray  33   a  containing devices for controlling the operation. The test tray  33   a  consists of two test boxes  31   a ,  31   b  (FIG.  5 ), the box  31   a  arranged first in the direction of travel being empty, and the second box  31   b  containing means for measuring the irradiation, such as a calorimeter  96 . Subsequently, at the operator&#39;s command or automatically, after the code of the tray has been read by the reader  45  (block  105 ), after the operator has depressed an identification code key of the control and monitoring device (block  106 ) and after the code of the tray and the code introduced manually have been combined (block  107 ), the blocking devices  58   a  (block  108 ) are deactivated by the advance of the tray introduced manually in the auxiliary station  3  and of the test tray  33   a  and the trays  33  previously loaded at the main loading station  2 . 
     During travel along the conveyance means, the readers  51  and  52  (and, if appropriate, other readers not shown) read the identification code of the trays in order to follow the travel of the transported trays and products along the entire path outside the containment (blocks  110 ,  111 ). The information supplied by the readers, the data relating to the synchronization of the motor  55  and, if appropriate, the data supplied by the mechanical travel-limit devices  61 ,  65  with regard to the interior of the containment  6  (block  112 ) are used by the control unit  42  in order to locate or identify the exact position of each tray  33  inside the containment accurately at any moment. In the event of an anomaly or when the functioning of the installation is interrupted, the product boxes processed in full, those processed partially and those of which the state is not known perfectly can thus be identified. Furthermore, in the event of a serious anomaly, the control and monitoring unit  42  can stop processing directly by stopping the accelerator  70  (block  114 ), sending the corresponding error signals to the operator ( 115 ) and unloading the trays  33  present on the conveyance means  8  ( 116 ). 
     As mentioned above, the conveyor  62  of the conveyance section  14  is faster than the conveyor  63  (the two parts  63   a  and  63   b  of which are displaced at the same speed). The conveyor  62  quickly moves the trays  33  brought by the conveyor  60  away from the latter and causes the trays  33  to be regrouped in the direction of travel, so as to reduce the distance between two successive trays. Furthermore, the start of the guide rails  67  of the trays (the said start not being shown in the figures) and the position of the drive members  84  of the chains  72  are designed in such a way that the drive members come into contact with the lower frame  36  of each tray  33  only when the latter has reached the end of the conveyance section  13 , the purpose of this being to prevent the tray  33  from rotating. 
     The conveyors  62  and  63   a  are synchronized exactly, in such a way that, when a tray  33  reaches the conveyor  63   a , a pair of drive members  84  of the chains  73  engages into the lower frame  36  of the tray  33 , after pivoting from the retracted position, shown in FIG. 13, into the projecting position, shown in FIG.  14 . The pivoting of the drive members  84  has the effect of imparting to them a horizontal movement which is added to the displacement resulting from the drive by the chains  73 ; this pivoting therefore causes a slight increase in the speed of the members  84  in relation to the speed of the conveyor  63   a . Consequently, at the moment when a tray  33  is driven by the conveyor  63   a , this tray undergoes a slight forward push, thus further reducing the distance separating it from the preceding tray (of the order of a few millimeters), without the following tray bumping the one preceding it. The straight guides  90  combined with the conveyor  62  are not as long as this conveyor, so that a tray  33  is released by the conveyor  62 , before being driven by the conveyor  63   a , and the said tray does not undergo any push despite the difference in speed of the two conveyors. 
     In the central part of the conveyance section  14 , the trays  33  are very close together and travel at a constant speed, thus ensuring uniform irradiation in the irradiation station  7 . In this zone, the conveyors  63   a ,  63   b  behave in the same way as a single conveyor, since their speeds are equal, and, due to the gap separating them, they are not damaged by irradiation. 
     When a test tray  33   a  has been introduced on the conveyance means at the auxiliary loading station  3  (block  120 ), the control and monitoring unit  42  determines the moment when this tray  33   a  will reach the irradiation station  7 , stores the corresponding processing parameters (block  121 ) and controls the modification of the irradiation parameters in order to adapt them to the new product to be processed (block  122 ). Thus, when the test tray  33   a  reaches the irradiation station  7 , the accelerator  70  sets the irradiation parameters at the moment when the first box  31   a  (empty) passes, and, during the passage of the second box  31   b , the calorimeter  96  which the latter contains measures the dose received. The test tray  33   a  is subsequently unloaded at the auxiliary unloading station  5 , and a check is made as to whether the dose received corresponds to the controlled value (blocks  123 ,  124 ,  125 ). A code reader may, if appropriate, be provided at the auxiliary unloading station  5 , in order to make it possible to confirm the correct travel of the test trays. 
     Furthermore, the control and monitoring unit  42  continues to monitor the conveying speed of the trays in the irradiation station  7  by means of a signal sent to the pulse transmitter  56  (block  126 ), and, if an anomaly occurs in the speed of the motor  55 , the said anomaly being capable of being compensated by adjusting the irradiated dose, the said unit controls the modification of the operating parameters of the accelerator  70  (block  127 ). 
     After being irradiated in the station  7 , the trays  33  are transferred from the conveyor  63   b  to the conveyor  64 , the speed of which has been selected higher than that of the conveyors  63   a ,  63   b , so that processed trays  33  are conveyed quickly towards the end of the conveyance section  14 . As soon as the tray  33  reaches the travel limit detector  65 , the latter actuates the roller conveyor  66  which drives the tray  33  out of the section  14 , without changing its orientation. The conveyor  66  conveys the trays  33  as far as the vertical transporter  92  which picks them up one after the other on the conveyor  66 , causes them to descend to the level of the conveyor  97  and transfers them onto the latter. 
     The trays  33  loaded with irradiated boxes  31  are thus conveyed on the conveyance sections  17 - 20  below the conveyance sections for the trays loaded with boxes  31  of products to be processed. If they do not contain any test boxes  31   a ,  31   b , the trays are conveyed by means of the conveyors  47 ,  47   b ,  47   c  towards the main unloading station  4  (block  128 ). There, the reader  38  reads the label  37  of the tray  33  and communicates to the control and processing unit  42  the correct arrival of the trays  33  at the exit of the installation. 
     The installation described above has the following advantages. It is reliable and efficient, particularly because, in the central part of the section  14 , the spaces between the trays are reduced to a few millimeters (thus reducing the idle operating time of the accelerator virtually to zero). Its high performance is attributable, furthermore, to the fact that it makes it possible to modify the irradiation parameters required by different products, without the installation having to be stopped. 
     The constant conveying speed, particularly in the conveyance section  14 , ensures that the irradiation received by the products is uniform and makes it possible to process delicate products, such as PVC blood lines, for which there is a small difference between the admissible maximum and minimum doses for ensuring the sterilization of the products and avoiding damage to them. The monitoring of the entire conveyance, including inside the containment (by means of the pulse transmitter combined with the motor) contributes to ensuring the reliability of the installation and makes it possible to compensate slight speed irregularities, as described above. Moreover, the control and monitoring unit is capable of detecting any anomaly liable to affect sterilization efficiency, of interrupting the processing, and of distinguishing the boxes which have been processed from those which have not been or have been insufficiently processed. 
     Superposing a plurality of conveyance sections of the products to be processed and for the processed products makes it possible to limit the space occupied by the installation; the use of a vertical transporter makes it possible to reduce the space occupied inside the containment, the manufacturing cost of which is high. 
     Combining the product boxes  31  with the trays  33  and monitoring, carried out only on the trays inside the installation, make it possible to reduce the periodic checks of the conveyance of the products, even when ambient conditions are not helping the reading of the labels. In fact, the codes printed on the trays may have a better printing quality (thus making reading easier) than the codes printed on the cardboard of the product boxes. Stoppages of the installation which occur as a result of the problem of reading the codes are thus avoided. The presence of the mechanical travel-limit detectors in the critical inner zone  27  and the drive of the trays by means of a catch system which makes the trays  33  integral with the conveyors ensure, on the one hand, the possibility of monitoring the conveyance, even in the critical zone  27 , and, on the other hand, safety in the conveyance of the trays. Furthermore, the identification of all the trays and of the boxes which they support is ensured, even when the accelerator is switched off, without the conveyance of the trays being interrupted. Moreover, the inaccessibility of the conveyance means as a whole owing to the trelliswork cage  43  and the containment  6  ensures that it is impossible to change the box/tray combinations established on entry into the installation. 
     The use of materials resistant to ionizing radiations and the absence of electronic equipment inside the critical zone  27  ensure that the installation functions appropriately and has a long service life. By virtue of all the advantageous characteristics which have just been mentioned, it is possible to reduce the unit cost of processing the products and to subject products having a low unit cost to sterilization by beta-ray irradiation. 
     The invention is not limited to the embodiments described and illustrated, and it is capable of having variants.