Abstract:
A sterilizing tunnel for pharmaceutical containers has an entry zone, a heating zone, and two cooling zones. The individual zones contain ventilating fan units that generate air currents, which serve to heat and cool the containers that a transport apparatus conveys through the sterilizing tunnel. The heating and cooling units, which operate using the principle of heated and cooled air flow, is supplemented with radiant heat-generating unit. The sterilizing tunnel makes it possible to achieve a uniform heating and cooling of the containers, preventing stress cracks in the containers and permitting intentional heating that makes it possible, for example, for the containers to be coated with a substance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of Ser. No. 10/470,343 filed on Jan. 12, 2004 now abandoned, which is based on a 35 USC 371 application of PCT/DE 02/02793 filed on Jul. 30, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an improved sterilizing tunnel for pharmaceutical containers. 
     2. Description of the Prior Art 
     One sterilizing tunnel of the type with which this invention is concerned is known from DE 198 46 277 C2. Sterilizing tunnels of this kind, which are used in the pharmaceutical industry, particularly for sterilizing ampules, vials, or the like, have ventilating fans in the individual zones along which the containers are conveyed, which produce an air flow that circulates around the containers in a laminar fashion from top toward the bottom. Depending on the zone, the circulated air is scrubbed by means of clean air filters (so-called HEPA filters) disposed above the containers and is heated and cooled by means of heating and cooling units. Due to the flow direction of the air, the heating and cooling of the containers occurs from the direction of the container mouth toward the container bottom, i.e. unevenly over the height of the container, which can damage the containers or produce stress cracks in them, particularly in relatively thin containers or when a container has walls of different thicknesses. 
     It is also known to coat the containers with emulsion-like substances (e.g. silicone) before entry into the sterilizing tunnel. In this case, the sterilizing tunnel is also used for fixing and baking the substance into the surface of the containers. In the sterilizing tunnels of the prior art in which hot air is circulated through filters, the filters can become clogged with baking residues of the substances, consequently reducing the service life of these filters. 
     There are also known sterilizing tunnels whose heating units are operated solely by means of radiant heat generators (e.g. infrared radiators). 
     SUMMARY AND ADVANTAGES OF THE INVENTION 
     The sterilizing tunnel for pharmaceutical containers according to the invention, has the advantage over the prior art that the containers are thermally treated in a particularly gentle way so that the probability of stress cracks is reduced. This is achieved according to the invention through the additional use of radiant heat-generating heating units that act on the container bottoms so that in concert with the hot air from the ventilating fan units, it is possible to produce a uniform heating of the containers over their entire height. 
     In order to improve the action of the radiant heat on the container bottoms, it is advantageous for the transport apparatus on which the containers are conveyed to be embodied in the form of a radiation-permeable wire mesh belt. 
     If the sterilizing tunnel is also intended to be used for coating and baking-on emulsion-like substances, then the invention provides for the use of heating units that generate additional radiant heat in the heating zone, which units are disposed above and/or to the side of the containers. As a result, the coating and baking-on process is at least for the most part already finished by the next time hot air is circulated around the containers, thus reducing the percentage of baking residues in the air that is circulated through the filters. 
     In order to reduce the susceptibility of the containers to stress cracks, it is likewise advantageous to also provide radiant heat-generating heating units in the cooling zone, at least above the container mouths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Two exemplary embodiments of the invention are described in detail herein below, in conjunction with the drawings, in which: 
         FIG. 1  shows a simplified longitudinal section through a first sterilizing tunnel according to the invention, 
         FIG. 2  shows a partial section in the plane II-II of  FIG. 1  during operation of the first sterilizing tunnel, 
         FIG. 3  shows a simplified longitudinal section through a second sterilizing tunnel according to the invention, and 
         FIG. 4  shows a partial section in the plane IV-IV of  FIG. 3  during operation of the second sterilizing tunnel. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first sterilizing tunnel  10  according to the invention schematically depicted in  FIG. 1  is essentially comprised of an entry zone  11 , a heating zone  12 , and two cooling zones  13 ,  14 . Pharmaceutical containers  1  such as ampules, vials, or the like, which come from a cleaning machine, not shown, are supplied into the sterilizing tunnel  10  from the entry zone  11  and leave the tunnel at its opposite end  15  after the cooling zone  14 , in order to then be further processed in the subsequent filling and closing machines, which are not shown. 
     A horizontal, preferably continuously driven, endless conveyor belt  17  serves to transport the containers  1  through the individual zones inside the sterilizing tunnel  10 . Preferably, the conveyor belt  17  is embodied as an air-permeable wire mesh belt made of stainless steel. 
     Large-area filter elements  18 ,  19 , and  20  are disposed above the conveyor belt  17  in the different zones of the sterilizing tunnel  10 . The filter elements  18 ,  19 , and  20  cooperate with ventilating fan units  22 ,  23 , and  24 , which are each associated with a respective zone and each serve to circulate the air in a respectively closed circuit. The air flows generated by the ventilating fan units  22 ,  23 , and  24 , which circulate in the form of so-called laminar flow currents (flow arrows  25 ) around the containers  1  essentially from top to bottom during their transport through the sterilizing tunnel  10 , are temperature-controlled by means of heating and cooling units that are not shown. To that end, temperature sensors are placed in the individual zones, which supply the measured temperatures as input values to the control unit of the sterilizing tunnel  10 . The control unit then appropriately regulates the heating and cooling units, and is assisted by inlet and outlet air flaps, not shown, that are also disposed in the zones, which additionally serve to compensate for leakage and overflow losses. Furthermore, vertically adjustable sluices  26 ,  27 , and  28 , whose position is adapted to the respective container height, are positioned both between zones and within zones in order to reduce the above-mentioned overflow losses between the individual zones. 
     The air flows generated by the ventilating fan units  22 ,  23 , and  24 , which circulate around the containers  1  from above, i.e. from the container mouth  2  toward the container bottom  3 , result in an uneven temperature distribution over the height of the containers. As a result, the container mouths  2  have a higher temperature than the container bottoms  3  as they pass through the heating zone  12 . This is because the hot air in the heating zone  12  comes into contact with the container mouth  2  first. 
     The sterilizing tunnel  10  is particularly designed to permit deliberate influence to be exerted on the temperature distribution along the height of the containers  1  in order to thus prevent thermal stresses that can damage the containers  1  and is also designed to permit favorable influence to be exerted on the baking of emulsion-like particles into the inner walls of the containers. In order to accomplish this, the heating zone  12  is divided into two regions  33  and  34  by means of a dividing wall  31 , whose end oriented toward the conveyor belt  17  is embodied as a vertically adjustable intermediary way  32 . In the one region  33 , the ventilating fan unit  22  provides a heated air flow, whereas the other region  34  situated on the side oriented toward the entry zone  11  is provided with a number of radiant heat-generating heating units  35 ,  36 ,  37 . This region  34  includes a forward section which is where the containers enter the heating zone  12 . 
     The heating units  35 ,  36 ,  37 , which are in particular embodied in the form of infrared radiators and in the exemplary embodiment are embodied as rod-shaped, are disposed underneath the radiation-permeable conveyor belt  17  close to the container bottoms  3 , above the conveyor belt  17  close to the container mouths  2 , and if need be, beside the conveyor belt  17  at the same height as the container mouths  2  outside of stationary or mobile lateral guides  38  for the conveyor belt  17 ; in the exemplary embodiment, the heating units  35 ,  36  extend lateral to the travel direction of the containers  1  through the sterilizing tunnel  10  and the heating units  37  extend along this travel direction. At least some of the units  35  are positioned in the forward section so as to provide a controlled and precise heating of the bottoms of the containers so that during their heating up phase thermal stress cracks are avoided. Furthermore, in the region  34 , there is also at least one temperature sensor  39 , which is coupled to the control unit of the sterilizing tunnel  10  so as to help to accurately control the heating of the containers. 
     Depending on the intended use, the heating units  35 ,  36 ,  37  make it possible to provide an intentionally more intense preheating of particular container regions, for example the container bottoms  3 , in order to prevent thermal stresses in the containers  1  in the subsequent further heating by means of the air flow in region  33 . In this instance, the heating units  35  oriented toward the container bottoms  3  are set to a higher temperature than the other heating units  36 ,  37 . 
     In addition, if an emulsion-like substance (e.g. silicone), is used to coat the container  1 , it should already be baked-on in the region  34  so that possible baking residues place as little subsequent strain as possible on the filter element  18  in the region  33 . In this instance, the radiant heat of the heating units  35 ,  36 ,  37  can be set very aggressively, so that the temperature inside the containers  1 , which is required for coating them, is reached within an extremely short period of time and is then reduced again if need be in the region  33 . 
     By contrast with the sterilizing tunnel  10 , in the second sterilizing tunnel  10   a  shown in  FIGS. 3 and 4 , the heating zone  12  is only provided with additional heating units  35  underneath the radiation-permeable conveyor belt  17  and with heating units  37  disposed to the side, outside the lateral guides  38  in a manner analogous to the sterilizing tunnel  10 , but no radiant heat-generating heating units are provided above the containers  1 . Instead, the containers  1  are heated with hot air from above by means of the ventilating fan unit  22  in the entire heating zone  12 , from which it also follows that the sterilizing tunnel  10   a  does not contain a dividing wall  31  of the type provided in the sterilizing tunnel  10  that divides the heating zone  12  into different regions. 
     In addition, in the sterilizing tunnel  10   a , the first cooling zone  13  is provided with additional heating units  40 ,  41 , which also generate radiant heat. These heating units  40 ,  41 , which are also rod-shaped, are provided above the container mouths  2  on the side oriented toward the heating zone  12 , as well as laterally, outside the lateral guides  38 , at the same height as the container mouths  2 , and are controlled by means of a temperature sensor, not shown, which is disposed in the cooling zone  13  close to the heating units  40  and is coupled to the control unit of the sterilizing tunnel  10 . 
     The heating units  40 ,  41  make it possible for the containers  1 , which are transferred out of the heating zone  12  and have a relatively high temperature, to be cooled down somewhat less rapidly in the vicinity of their container mouths  2 , thus permitting a more uniform cooling of the containers  1  on the whole. The arrangement of additional heating units  35 ,  37 ,  40 ,  41  embodied in the sterilizing tunnel  10   a  consequently makes it possible to achieve a heating and cooling of the containers  1  that is gentle to the material in order to avoid thermal stresses and prevent heat cracks in the containers  1 . 
     The two sterilizing tunnels  10 ,  10   a  according to the invention can be modified in numerous ways without going beyond essence of the invention, which is comprised of providing additional radiant heat-generating heating units in the sterilizing tunnel  10 , which in cooperation with air flows generated by the ventilation fan units, produce a uniform heating and uniform cooling of the containers  1 . It is therefore conceivable, for example, to omit the heating units  36 ,  37  at the top and at the sides. Furthermore, the sterilizing tunnel  10  can also have the heating units  40 ,  41  disposed in the cooling zone  13  of the sterilizing tunnel  10   a , in order to treat the containers  1  in a particularly gentle fashion with regard to thermal stresses. 
     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.