Abstract:
The invention concerns a method and an apparatus for disinfecting a cuvette cover. The opening of a cuvette ( 14 ) containing a test fluid is temporarily covered while the cuvette is at a processing station. The surface of the cover facing the cuvette opening in the lifted condition of the cover is heated to a temperature suitable for the killing of microorganisms on the cover.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The priority of German Patent Application 10 2004 025 587.3 of May 25, 2004 is claimed, and the disclosure of the German Patent Application is incorporated by reference.  
       FIELD OF THE INVENTION  
       [0002]     The invention concerns a method for disinfecting a cover by means of which the opening of a cuvette containing a test fluid is temporarily covered while the cuvette is at a processing station.  
       BACKGROUND OF THE INVENTION  
       [0003]     The method according to the invention is designed for a known automatic machine in which a plurality of test fluids can be analyzed in sequence. These test fluids can contain microorganisms and usually are delivered to the automatic machine in cuvettes from which the automatic machine takes the test fluid with the help of a pipette in order to load them into the measuring chambers of so-called microtitration plates. The measuring chambers can be loaded with a nourishing solution and/or detection chemicals for certain microorganisms. Before the test fluid can be loaded into the microtitration plate it must among other things be preprocessed, for example be homogenized or thinned. The homogenization can for example take place with the help of an ultrasonic mixer. With this the danger exists of that a spray or mist of the test fluid escapes from the cuvette opening. Because of this the cuvette cover must be closed at least during the homogenization process. With this the problem arises that the cover itself becomes dirty and with a change of cuvettes microorganisms can be transmitted from one cuvette to the following cuvette by the cover. Naturally this must be avoided under all circumstances.  
         [0004]     One solution exists in that the cover surface is wiped off with each cuvette change. A wiping mechanism necessary for this is not only complicated but also does not solve the problem since the washing organ itself must also be disinfected in order to avoid a spreading of the microorganisms. With the use of disinfecting chemicals there exists the danger of a contamination of the test fluids and a damaging of the microorganisms contained in the fluids.  
         [0005]     The invention has as its object the provision of a method by means of which the cover surface can be disinfected reliably in a simple way.  
       SUMMARY OF THE INVENTION  
       [0006]     For the solution of the mentioned object in accordance with the invention it is proposed that the surface of the cover facing the cuvette opening in a lifted condition of the cover be heated to a temperature suitable for the killing of-microorganisms on the cover.  
         [0007]     The solution of the invention requires neither moving parts nor chemicals which could contaminate the test fluids. The temperature to which the cover surface is heated can be chosen to be so high that the microorganisms present on the cover surface are essentially burned.  
         [0008]     An especially simple solution exists for example in that at least one layer of the cover which includes the surface to be heated is electrically conductive and in that for heating the surface an electrical current is conducted through the layer. Such a solution is simple to realize and reliable to control. The electric heating of the cover surface offers also the possibility of measuring the electrical resistance of the layer for which the current flows and from the measured value determining the temperature of the heated surface in order to have a control assuring that the microorganisms are actually reliably destroyed. Another possibility for the temperature determination exists in that the infrared radiation emitted from the heated surface is measured and from that measurement the temperature is determined.  
         [0009]     The invention further concerns an apparatus for disinfecting a cover by means of which the opening of a test fluid containing cuvette is temporarily covered while the cuvette is in the a processing station. According to the invention, the cover which is movable relative to the cuvette opening has associated with it a heating device for heating the surface of the cover facing the cuvette opening.  
         [0010]     Preferably the cover includes a pressing element movable relative to the cuvette opening and a metal strip pressable by the pressing element onto the cuvette opening, which metal strip for example is part of a spring element which is baised toward a lifted position away from the cuvette opening. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Further features and advantages of the invention will be apparent from the claims below as well as from the following description which in combination with the accompanying drawings explain the invention by way of an exemplary embodiment.  
         [0012]      FIG. 1  is a partial schematic illustration of a mixing station for homogenizing a test fluid contained in a cuvette, wherein the cover for closing the cuvette opening is shown lifted from the cuvette,  
         [0013]      FIG. 2  is a figure corresponding to  FIG. 1  wherein a cuvette is shown to be closed by the cover, and  
         [0014]      FIG. 3  is a schematic plan view of an electrically heatable leaf spring arrangement which forms a part of the cuvette cover. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     The mixing apparatus shown in  FIGS. 1 and 2  for homogenizing a test fluid in a cuvette is part of an automatic analyzing machine for analyzing test fluids. Seen in these figures is a guide rail ( 10 ) fixedly connected with the chassis of the non-illustrated automatic analyzing machine for a cuvette rack ( 12 ) which can receive a plurality of cuvettes ( 14 ), which cuvettes are arranged behind one another in the viewing direction of  FIGS. 1 and 2 . While in this cuvette rack the cuvettes ( 14 ) are moved through the several processing stations of the automatic analyzing machine.  
         [0016]     On a carrier ( 16 ), likewise rigidly fixed to the chassis of the automatic analyzing machine, there is arranged below the guide rail ( 10 ) by means of a bracket ( 18 ) an ultrasonic mixing head ( 20 ) whose sonotrode ( 22 ) through a corresponding opening in the guide rail ( 10 ) and in the cuvette rack ( 12 ) comes in contact with the bottom of each cuvette ( 14 ) brought to the mixing position to introduce ultrasonic energy through the cuvette bottom into the test fluid in the cuvette ( 14 ).  
         [0017]     A stand ( 24 ) is further fixed to the carrier ( 16 ) on which a pressing arm ( 26 ) is movable between a lifted open position illustrated in  FIG. 1  and a returned lowered closed position illustrated in  FIG. 2 . The movement mechanism includes a motor ( 28 ) fastened to the lower end of the stand which motor by means of a drive belt ( 30 ) drives a belt pulley ( 32 ) supported in the stand ( 24 ). The shaft ( 34 ) is non-rotatably fixed to one end of a crank arm ( 36 ) whose other end is pivotably connected with the lower end of a double link ( 38 ). The upper end of the double link ( 38 ) is pivotably linked to the pressing arm ( 28 ) for movement about an axis of ( 40 ), in order to move the pressing arm about it&#39;s pivot axis ( 42 ) between the positions illustrated in  FIGS. 1 and 2 .  
         [0018]     An angularly shaped pressing element ( 44 ) is linked to the pressing arm near the free end of the pressing arm for a moment about an axis of ( 46 ), which pressing element is moved by a lever ( 48 ) pivotably connected at one end to the stand ( 24 ) and at its other end to the pressing element ( 44 ) so as to move the pressing element ( 26 ) between the positions illustrated in the  FIGS. 1 and 2  upon pivoting movement of the pressing arm ( 26 ). A spring element ( 50 ) is fastened to the upper end of the stand ( 24 ) and forms a part of the cover for the cuvette opening. The spring element ( 50 ) is illustrated in more detail in  FIG. 3  and includes two strip shaped leaf spring arms ( 52 ) which at their one ends are connected together by a thin metallic heating foil ( 54 ) and which at their other ends are connected to the stand by rivets or screws. These two ends are connected through a switch ( 55 ) to a current source ( 56 ). The leaf spring arms ( 52 ) are so biased that the spring-element ( 50 ) in its unloaded condition takes on the position illustrated in  FIG. 1 . With a lowering of the pressing arm ( 26 ) the pressing element ( 44 ) takes along with it the spring element ( 50 ) and presses its metal foil ( 54 ) against the opening of the cuvette ( 12 ) so that the cuvette becomes closed, as is illustrated in  FIG. 2 . At the same time the pressing arm serves in its closed position to provide a good contact between the cuvette ( 14 ) and the sonotrode ( 22 ) of the ultrasonic mixer ( 20 ). The arrangement can be so designed that the switch ( 55 ) is controlled by the positioning movement of the pressing arm ( 26 ).  
         [0019]     To free the metal foil ( 54 ) from possible microorganisms after the mixing, the foil ( 54 ) is heated by connection with the voltage source ( 56 ), so that microorganisms possibly clinging to the foil are destroyed. As seen in  FIG. 1  the spring element ( 50 ) and especially its foil ( 54 ) is lifted entirely free from the pressing element ( 44 ). Because of its small mass, the foil ( 54 ) can quickly and with little consumption of energy be heated to a relatively high temperature, and after turning off the voltage source it can therefore also likewise be again quickly cooled. The small thermal inertia of the element ( 54 ) makes possible a high repetition rate in the processing of the cuvettes.  
         [0020]     As is further seen in  FIGS. 1 and 2 , the doublelink ( 38 ) is connected with a fork arm ( 58 ) which by means of a sleeve ( 60 ) surrounding the sonotrode ( 22 ) can lift the cuvette ( 12 ) from the position illustrated in  FIG. 2  to the position illustrated in  FIG. 1  when the pressing arm ( 26 ) is moved to its open position. This provides the possibility of optically measuring the cuvette ( 14 ) at different elevations of the cuvette, preferably with the help of an optical measuring device including a light emitter ( 61 ) and a light receiver ( 62 ).