Abstract:
A stirrer unit includes a reaction vessel having an inlet port, a shaft stirrer having a stirrer blade and a stirrer shaft connected to the stirrer blade, and an adapter defining a passage. The adapter is configured to be inserted into the inlet port and releasably fastened to the inlet port using a fastening device so that, in a connected state, the stirrer blade and a part of the stirrer shaft is disposed inside the reaction vessel. Furthermore, in the connected state, an immersion depth to which the stirrer shaft extends into the reaction vessel is adjustable and securable using a locking device in at least two positions that are spaced apart from one another.

Description:
Priority is claimed to European Patent Application No. EP 07119828.7, filed on Nov. 1, 2007, the entire disclosure of which is incorporated by reference herein. 
     The present invention relates to a stirrer unit with a reaction vessel and a height-adjustable shaft stirrer. 
     BACKGROUND 
     In many areas of chemistry, biochemistry, pharmacology and biology, shaft stirrers are used for the mixing of a reaction medium in a reaction vessel. The stirring is required for example in chemical and/or physical reactions with several phases, when a reaction component is being added, or if components in solid form are present. In heterogeneous reaction media, the stirring has the function of mixing the components thoroughly with each other. In homogeneous reaction media, stirring is often necessary in order to distribute an added substance quickly and thoroughly in the solution, in order to avoid high local concentrations, local overheating, or boiling delays. If a reaction is to be stirred over a longer time period or inside an enclosed reaction vessel, one can use for example a magnetic stirrer or a CPG (core-drawn precision glass) stirrer. 
     A magnetic stirrer consists of a coated iron element which is inserted into the reaction medium and a drive source which is located outside of the reaction vessel. The known state of the art includes iron elements with diverse shapes, with the shape and length of the iron element being selected to match the dimensions of the reaction vessel and the nature and viscosity of the reaction medium. These stirrers suffer from the drawback that the iron element is difficult to remove from the reaction vessel especially in complex laboratory setups and further that a magnetic stirrer cannot be used for reaction media of intermediate or high viscosity. 
     A CPG stirrer often consists of a stirrer shaft of glass, where one end of the shaft is configured as, or connected to, a stirrer blade, and the other end of the shaft is connected to an electric motor by way of a coupling. In laboratory applications, one uses for example simply a piece of vacuum hose for the coupling. CPG stirrers can also be used for the mixing of reaction media with higher viscosities. However, because of the electric motor, they characteristically require a large amount of space and can be used effectively only above a certain filling height of the reaction vessel. Furthermore, the reaction vessel as well as the electric motor need to be secured to a suitable post, and stirrer shafts made of glass can be used only in a laboratory environment, because due to the danger of breakage which is inherent in this material they should be continuously monitored. 
     Further developed versions therefore often have stirrer shafts that are made of other materials such as different metals, ceramics or polymers and are driven by a motor through a suitable coupling. 
     Shaft stirrers, which in the broadest sense also include the aforementioned CPG stirrers, have the advantage that they can be more easily removed from the reaction medium and that they are also capable of mixing highly viscose reaction media. 
     The mixing of the reaction medium is influenced on the one hand by the selection of the stirrer blade, the power of the motor, and the selected rate of rotation, but on the other hand also by the orientation of the stirrer blade in the reaction vessel. It has thus been found that if the volume of the reaction medium increases or if the fill level rises, for example if further reagents are added, the position of the stirrer blade should also be readjusted in order to ensure that the rate of mixing remains the same. A position readjustment of the stirrer blade in this context means not only a change of the distance between an inlet port on the reaction vessel and the stirrer blade which is arranged in the reaction vessel, but also a change of the immersion depth of the stirrer shaft into the reaction vessel. 
     The stirrer is normally fastened to the inlet port by means of a suitable adapter, and both the reaction vessel and the motor are secured on a support stand or a similar device. To provide the capability for adjusting the height of the stirrer blade, it is possible to use for example stirrer shafts of different lengths, and/or extension pieces. This has the disadvantage that, in order to adjust the position of the stirrer blade, it is necessary to either remove the entire stirrer from the reaction vessel, to disassemble and reassemble the stirrer, or to remove at least parts of the setup or of the stirrer. 
     SUMMARY OF THE INVENTION 
     It would be desirable if the immersion depth of the stirrer shaft could be adjusted in a simple, fast and reproducible manner, so as to keep interruptions of the stirring process as short as possible. The reaction medium should remain constantly in motion in order to suppress for example the occurrence of locally concentrated overheating or undesirable side reactions. Furthermore, some of the reaction medium could be removed from the reaction vessel in the course of uninstalling the stirrer, which can lead to a change in the relative proportions of the reagents and can in the final outcome affect the yield and/or the reaction products. 
     It is an object of the invention to develop a shaft stirrer wherein the immersion depth of the stirrer into a reaction vessel can be changed in a simple and fast manner without having to remove the stirrer from the reaction vessel. 
     The present invention provides a stirrer unit with a reaction vessel that has an inlet port and with a shaft stirrer. The shaft stirrer has a stirrer blade, a stirrer shaft fastened to the stirrer blade, and an adapter with a passage in which the stirrer shaft is guided. The adapter can be inserted with a precise fit into the inlet port and can be releasably fastened on the inlet port through a fastening means, so that the stirrer blade and a portion of the stirrer shaft are disposed inside the reaction vessel. The stirrer unit according to the present invention is distinguished in that the immersion depth of the stirrer shaft into the reaction vessel is adjustable and can be secured with a locking device in at least two positions that are spaced apart from each other, while the adapter remains connected to the inlet port. 
     An advantage of the stirrer according to the present invention is that it allows the immersion depth to be changed without disassembling and/or partially dismantling the stirrer unit, and to secure the immersion depth reproducibly in at least two position settings. 
     The stirrer shaft is held in a guide sleeve which is position-adjustable relative to the adapter. By moving the guide sleeve relative to the adapter along the lengthwise axis of the shaft stirrer, the stirrer shaft is pulled out of, or pushed into, the reaction vessel by a certain distance, so that the immersion depth can be changed in this manner. 
     The distance between the adapter and the guide sleeve can be changed for example by twisting, in conjunction with a simultaneous movement of the guide sleeve along the lengthwise axis of the shaft stirrer, which allows a continuous adjustment of the immersion depth. 
     This can be achieved in particular through a design where the adapter and the guide sleeve are provided with adjustment screw threads that cooperate with each other. The adapter is equipped with an external screw thread that is capable of engaging an internal screw thread of the guide sleeve. This allows a stepless adjustment of the immersion depth. 
     For the fixation of the desired immersion depth, the guide sleeve can be secured on the adapter by means of the locking device. In a continuously adjustable guide sleeve, the locking device can be configured for example in the form of screws, springs or similar elements which secure the guide sleeve on the adapter. 
     In a preferred embodiment the locking device takes the form of a locking lever which is arranged on the guide sleeve and which cooperates with at least two recesses that are arranged apart from each other on the outside of the adapter. The locking lever can have one end configured so that it can engage and/or snap into the recesses. The locked position can be secured by an elastic element which in the case of the locking lever pushes one end of the locking lever into one of the recesses and thereby secures the end of the lever in the recess. 
     The design of the locking element as a locking lever has the advantage that a lever is simple to operate and in particular capable of being operated with one hand, and that it can be tilted about a fulcrum. The elastic element can set the locking lever back again into its original position. 
     In a further embodiment, the locking device can be configured as a counter nut. The locking device can further be configured as a screw, in particular as a grub screw. These two embodiments of the locking device are advantageous in particular in combination with the adjustment screw threads. 
     The counter nut can easily be loosened manually, whereupon the immersion depth can be changed and then secured again by manually tightening the counter nut. 
     A locking device in the form of a screw can for example protrude on the outside from the guide sleeve, for simple manual loosening and tightening. As an alternative, it is also possible to use a grub screw which can be loosened or tightened with a suitable utensil. 
     One end of the stirrer shaft is connected to the stirrer blade or configured as a stirrer blade, and the other end can be connected to a first coupling element or can be configured as a coupling element. 
     As a drive source, the stirrer unit can have a motor and, connected to the latter, a motor shaft whose free end is connected to a second coupling element or is configured as a second coupling element. The second coupling element can be coupled to the first coupling element, so that for example a torque generated by the motor can be transmitted to the stirrer shaft. 
     The coupling elements should have the distinguishing trait that the coupling can be released or connected rapidly and without using any utensils, with the configuration of the coupling elements not being limited to a specific form, but encompassing any state-of-the-art elements which can provide a coupling connection. 
     It is advantageous if the motor can be connected to the guide sleeve in a releasable manner, so that the motor can be separated in a simple way, preferably manually and/or without using tools or other auxiliary means, and the stirrer unit can for example be put in another place in the laboratory and/or can be cooled. In order to accomplish this, the motor can be connected to the guide sleeve for example by means of a motor flange. 
     Preferred is a clamping connection between the motor and the guide sleeve wherein, when the reaction vessel, the adapter and the guide sleeve have a fixed connection, said clamping connection can be released with one hand without thereby changing the immersion depth of the stirrer shaft. Thus, the motor and the stirrer shaft can be released from each other without causing a change of the immersion depth. 
     Further embodiments can have a snap connection, a detent connection, or a bayonet connection between the motor and the guide sleeve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A stirrer unit according to the invention is described with the help of the following drawing figures wherein identical elements are identified with the same reference symbols, and wherein: 
         FIG. 1  represents a stirrer unit with a reaction vessel and a shaft stirrer shown in a sectional view; 
         FIG. 2  represents the shaft stirrer of  FIG. 1  in the disassembled state without stirrer shaft and stirrer blade, shown in a sectional view; 
         FIG. 3  shows the shaft stirrer of  FIG. 2  in a three-dimensional exploded representation; 
         FIG. 4  represents a further embodiment of the guide sleeve, the adapter and the locking device, shown in a sectional view; and 
         FIG. 5  illustrates a further embodiment of the guide sleeve, the adapter and the locking device, shown in a sectional view. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a stirrer unit with a reaction vessel  1  and a shaft stirrer  2 . The reaction vessel  1  has an inlet port  3  in which an adapter  4  of the shaft stirrer  2  is inserted with a precise fit. The adapter  4  is releasable connected to the inlet port  3  by means of a suitable fastening means  5 , for example a clamp as shown here. The adapter  4  is configured in such a way that it fills out the inlet port  3  and thus closes off the reaction vessel  1 . 
     The adapter  4  has a central passage in which a stirrer shaft  6  is mounted. The stirrer shaft  6  is connected to a stirrer blade  7  which is located in the reaction vessel  1 . The size of the stirrer blade  7  can be adapted to the diameter of the reaction vessel  1 . In order to move the shaft stirrer more easily out of and into the reaction vessel  1 , the stirrer blade  7  can be of a foldable or flexible configuration so that it fits through the inlet port  3 . The end of the adapter  4  that faces away from the reaction vessel  1  is sealed by a sealing means  8  towards the stirrer shaft  6 . On the outside of the adapter  4  there are further a plurality of recesses  9  which can be engaged by a lever-like locking device  10 . The locking device  10  is arranged on a guide sleeve  11  which is movable relative to the adapter  4  along the lengthwise axis of the shaft stirrer. The locking device  10  has a fulcrum  12  about which the lever-like locking device can be pivoted. 
     When the locking device  10  is in a released state, the guide sleeve  11  can be moved along the lengthwise axis of the shaft stirrer and can be secured at several different distances from the adapter  4  which are defined by the recesses  9 . The adapter  4  and the guide sleeve  11  consist of a smooth material in order to allow a movement that is substantially free of friction, and in addition the material used for the adapter  4  has to be chemically inert. PTFE (polytetra-fluoroethylene), for example, lends itself to manufacture of these elements. 
     By releasing the locking device  10 , moving the guide sleeve  11 , and letting the locking device  10  reengage another recess  9 , it is possible to change the immersion depth h of the stirrer blade  7  in the reaction vessel  1 . 
     In  FIG. 1 , the locking device  10  is engaged in the middle one of the recesses  9 . Starting from this position, the immersion depth h could be changed by Δh along the lengthwise axis of the shaft stirrer  2 , as indicated by the stirrer blades  7   a  and  7   b  which are drawn in broken lines. 
     For the engagement of the locking device  10 , the latter is held in resilient contact with the guide sleeve  11  by means of an elastic element  13  which is arranged in a groove of the guide sleeve  11 . If pressure is applied to what is drawn in  FIG. 1  as the upper and wider part of the locking device  10 , this will cause the locking device to be pushed out of one of the recesses  9 . When the pressure is taken off, the locking device will be pushed against the guide sleeve  11  again by the elastic element  13  and will seat itself either in another or the same recess  9 , depending on the desired immersion depth h. 
     The guide sleeve  11  is further releasably connected to the housing of a motor  15  by way of a motor flange  14 . The motor  15  has a motor shaft  16  which is connected at its free end to a second coupling element  17 . The motor  15  further has a connector  20  for a power- and/or data cable. The second coupling element  17  engages a first coupling element  18  which is connected to the stirrer shaft  6 . 
     The motor  15  can transmit a torque to the stirrer shaft  6  by way of the motor shaft  16  and the coupling elements  17 ,  18 . If the reaction vessel  1  is secured on a stand  19  or in any other suitable manner, then the reaction to the torque generated by the motor  15  can be transmitted to the reaction vessel  1  and/or to the holder stand  19  by way of the fastening means  5 . This makes an additional fixation of the shaft stirrer  2 , for example an attachment of the motor  15 , unnecessary, and it is possible to change the immersion depth h of the stirrer blade  7  in the reaction vessel with one hand. 
     Besides the illustrated securing arrangement for the reaction vessel  1  on the holder stand  19 , the reaction vessel  2  can for example also be a part of an analytical instrument and can be fastened in or attached to the latter. 
       FIG. 2  illustrates in sectional view the shaft stirrer  2  in the uninstalled state. The motor  15  together with the motor flange  14 , the motor shaft  16  and the second coupling element  17  can be separated from the guide sleeve  11  by a simple pulling movement, as the motor flange  14  is connected to the guide sleeve  11  through a spring-clamp connection. The spring-clamp connection is formed by the partially elastic, fork-like extensions or clamping springs  21  of the motor flange which on the one hand embrace the guide sleeve  11  and on the other hand, with their cutout openings  22 , enter into engagement with seating guides that are arranged on the outside of the guide sleeve (see  FIG. 3 ). 
     Besides the motor  15 , the first coupling element  18  can also be removed from the stirrer shaft (not shown here). 
     The guide sleeve  11  and the adapter  4  are shown in  FIG. 2  at the limit of their mutual position-adjustment range and have a distance Δh max  from each other which is defined by the distance of the recesses  9   a  and  9   d  from each other. This maximum distance Δh max  represents the maximum amount by which the stirrer blade and/or the stirrer shaft can be moved in the reaction vessel and thus the maximum change of the immersion depth (see  FIG. 1 ). 
     The stirrer shaft with the stirrer blade that is attached to it is not shown here (see  FIG. 1 ). The stirrer shaft can be held in the passages  23 ,  28  in the adapter  4  and in the guide sleeve  11 , respectively. 
       FIG. 3  illustrates the shaft stirrer  2  in a three-dimensional exploded view. In addition to the elements shown already in  FIGS. 1 and 2 , this drawing shows a power- and/or data cable  24  which can be connected to the motor  15 , as well as the seating guides  27  which are arranged on the outside of the guide sleeve  11  and each of which in the installed state engages a cutout  22  of one of the fork-shaped extension  21  of the motor flange  14 . 
     One can further see the adapter  4  which is made of one piece and consists of a connector portion  25  for the connection to the reaction vessel, and of an adjustor sleeve  26 . Arranged on the outside of the adjustor sleeve  26  are several recesses  9  which can cooperate with the locking device  10 . 
     The coupling elements  17 ,  18  in the installed condition are engaged in each other. Dependent on the material of the stirrer shaft being used, it is possible to use different first coupling elements such as for example clamp couplings, clamp plugs, screw-treaded connections and other solutions which are well known to any professional in this field. 
       FIG. 4  shows a further design of an adapter  104  and a guide sleeve  111 . The adapter  104  has an external screw thread which cooperates with an internal screw thread of the guide sleeve  111 . The screw threads form a screw-adjustment device which allows the guide sleeve  111  to be moved relative to the adapter  104  along the lengthwise axis of the shaft stirrer. The stirrer shaft  6  is constrained in the adapter  104  and in the guide sleeve  111 . As a locking device  110 , this design has a counter nut  110  which is arranged on the adapter  104 . 
     The example of an embodiment which is shown in  FIG. 5  has a guide sleeve  211  with an internal screw thread and an adapter  204  with an external screw thread, wherein the screw threads cooperate so as to allow a movement of the guide sleeve  211  relative to the adapter  204  along the lengthwise axis of the shaft stirrer  2 . The function of a locking device  210  is performed by a screw, for example a grub screw or a thumb wheel screw, whereby the guide sleeve  211  is locked in position on the adapter  204  when the screw is turned into the guide sleeve  211  and tightened against the adapter  104 . 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 LIST OF REFERENCE SYMBOLS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 reaction vessel 
               
               
                   
                  2 
                 shaft stirrer 
               
               
                   
                  3 
                 inlet port 
               
               
                   
                  4, 104, 204 
                 adapter 
               
               
                   
                  5 
                 fastening means 
               
               
                   
                  6 
                 stirrer shaft 
               
               
                   
                  7, 7a, 7b 
                 stirrer blade 
               
               
                   
                  8 
                 sealing means 
               
               
                   
                  9, 9a, 9d 
                 recesses 
               
               
                   
                 10, 110, 210 
                 locking device 
               
               
                   
                 11, 111, 211 
                 guide sleeve 
               
               
                   
                 12 
                 fulcrum 
               
               
                   
                 13 
                 elastic element 
               
               
                   
                 14 
                 motor flange 
               
               
                   
                 15 
                 motor 
               
               
                   
                 16 
                 motor shaft 
               
               
                   
                 17 
                 second coupling element 
               
               
                   
                 18 
                 first coupling element 
               
               
                   
                 19 
                 support stand/stand 
               
               
                   
                 20 
                 connector 
               
               
                   
                 21 
                 fork-shaped extensions/clamping springs 
               
               
                   
                 22 
                 cutout opening 
               
               
                   
                 23 
                 passage in 4 
               
               
                   
                 24 
                 power- or data cable 
               
               
                   
                 25 
                 connector portion 
               
               
                   
                 26 
                 adjustor sleeve 
               
               
                   
                 27 
                 seating guide 
               
               
                   
                 28 
                 passage in 11