Abstract:
A pipetting system including a pipet ( 8 ) which can be hooked up to pressurizing source ( 9 ), the pipet being fitted with a discharge aperture ( 10 ) and having an inside volume sufficient to receive the full quantity of liquid ( 7 ) to be discharged is characterized in that the discharge aperture ( 10 ) is situated at one end part ( 16 ) of the pipet ( 8 ), the end part being connectable to a connector aperture ( 19 ) of a main part ( 15 ) of the pipet, the main part receiving all the liquid ( 7 ) that shall be discharged, the connector part aperture ( 19 ) being larger than the discharge aperture ( 10 ).

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 11/577,166, filed Apr. 12, 2007, which is a U.S. National Stage of PCT/EP2005/010666, filed Oct. 4, 2005, which claims priority to German Patent Application No. 102004050466.0 filed on Oct. 16, 2004, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Pipet systems are frequently required in very fine metering designs demanding exceedingly narrow pipet discharge apertures. Illustratively, such systems are needed to pipet tiny amounts of liquid in free fall into a reagent glass or also to deposit tiny amounts of liquid on carrier plates to carry out chemical, in particular biochemical reactions, or for instance also when microscopying. 
         [0003]    A further example are the means depositing inoculating solutions on nutrient media. They are used, for instance, to detect germs such as bacteria or fungi contained in the inoculating solution by means of incubation multiplication. This requires depositing at a given thickness the inoculating solution onto the surface of a nutrient medium, typically in a Petri dish. The pipet discharge aperture then must be very narrow. 
         [0004]    U.S. Pat. No. 5,294,325 A in its  FIG. 1  discloses a pipet system wherein a pipet designed as an injection needle may be connected to a pressurizing element designed as a plunger syringe. Such a design incurs the drawback that both the pipet and the pressurizing element must be discarded when dispensing contaminated substances which must be precluded from being carried from one sample to the next. 
         [0005]    In generic systems employed in the present state of the art, the pipet collects the full amount of the liquid which must be dispensed to prevent the liquid from making contact with the pressurizing element. As a result, the pipet may be designed as a disposable item whereas the uncontaminated pressurizing element can be re-used. 
         [0006]    Known systems of the above kind comprise an integral pipet. Such pipets are filled conventionally by aspiration, entailing a very long time due to the narrow discharge aperture. In serial testing requiring filling the pipets very quickly, this feature is a significant drawback. 
         [0007]    Accordingly it is the object of the present invention to create a system of the above kind allowing higher processing rates. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    According to the present invention, a pipet end part having a discharge aperture can be hooked up to a connector aperture of a main part of the pipet. When hooked up, the pipet may be operated conventionally when depositing a liquid. When disconnected, the main part of the pipet can be filled very rapidly by conventional aspiration through the much larger connector aperture. Accordingly the operational rate can be raised very substantially, especially in serial testing. 
         [0009]    The design of the connector may be conventional, for instance using a screw connection or the like. Conical plug-in connectors allow using in this field a widely conventional, simple and accurate connection means. 
         [0010]    The pipet end part may be of a rigid, conventional design. Advantageously, however, this end part shall be elongated and flexurally elastic. In this manner the end part may gently lie against the surface of a nutrient medium, its flexibility compensating any damage or change in spacing. This feature is especially advantageous as regards systems moving the pipet relative to the nutrient medium surface when liquid deposition is along lines. Higher accuracy of deposition is attained, and there is less risk of damaging the nutrient medium surface. 
         [0011]    An elastically flexuring end part may be conically tapering as is conventional with pipets. Using a hose element as the end part allows especially simple manufacture allowing the accurate selection of the elasticity parameters and the discharge aperture size. 
         [0012]    The present invention is shown in the appended drawings in illustrative and schematic manner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a top view of the system of the present invention together with nutrient medium and pipet, 
           [0014]      FIG. 2  is a section along line  2 - 2  of  FIG. 1 , 
           [0015]      FIG. 3  is a side view of a pipet rack together with the main pipet components before the pipets are removed, 
           [0016]      FIG. 4  is the side view of a removed, main pipet part being filled, 
           [0017]      FIG. 5  is the side view of a rack with pipet end parts, and 
           [0018]      FIG. 6  is the side view of a complete supported pipet. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIGS. 1 and 2  show a system of the invention used to deposit a inoculating solution on the surface  2  of a nutrient medium  1  configured on the base  3   a  of a Petri dish  3  consisting of its base  3   a  and a circumferential rim  3   b . Such a Petri dish  3  is conventionally also fitted with a cover sealed in a germ-free manner during the ensuing incubation. 
         [0020]    The Petri dish  3  rests by its base  3   a  on a turntable  4  of a drive means, not shown in further detail, whereby the Petri dish  3  and the nutrient medium  1  may be rotated about a vertical axis  5  in the direction of the arrow  6 . 
         [0021]    Inoculating solution  7  held in readiness in a pipet  8  shall be deposited on the surface  2  of a nutrient medium  1 . At one of its ends, pipet  8  is pressurized with compressed air, for instance through a hookup tube  9 , and by its other end it expels the inoculating solution  7  through a narrow discharge aperture  10  in form of a line  11  on the surface  2  of the nutrient medium  1 . 
         [0022]    In the process, the pipet  8  is held in place by a support arm  12  that is displaced and adjusted by an omitted drive means in a manner that it keeps the pipet  8  at a defined height above the surface  2  of the nutrient medium  1  and moves the discharge aperture  10  radially outward in the direction of the arrow  13  during the rotation of the nutrient medium  1 . The line  11  of inoculating solution deposited on the surface  2  of the nutrient medium  1  therefore forms a spiral line as indicated in  FIG. 1 . 
         [0023]    The hookup tube  9  is connected to an omitted source of compressed air, assuring expulsion of the inoculating solution  7 . Said expulsion may be controlled in variable manner for instance by forming the line  11  from one end to the other at a monotonely decreasing deposition rate in order to dilute the deposited germ concentration. 
         [0024]    Instead of the design shown in  FIG. 1  comprising the system with a rotational drive for the nutrient medium  1  and linear advance of the pipet  8 , this pipet also may be displaced spirally across the nutrient medium  1  at rest or other shapes of the line  11  such as several parallel straight lines may be selected. 
         [0025]    The pipet  8  is fitted with a support  14  engaged by the supporting arm  12  and the hookup tube  9 . This support  14  also may be designed as a pump pressurizing the pipet  8 , in which case the hookup tube  9  would be replaced by electric control lines controlling pumping. 
         [0026]    The pipet  8  shown in  FIGS. 1 and 2  substantially consists of a main part  15  of which the considerable inside volume may receive all the quantity of inoculating solution  7  to be deposited. In the shown embodiment mode, the main part  15  can communicate by means of a conventional conical plug-in connector with the support  14 . 
         [0027]    At the end opposite the support  14 , the main part  15  also can communicate by means of a conventional conical plug-in connector to a terminal part  16  consisting of a connector part  17  and a hose element  18 . 
         [0028]    The connector part  17  allows hooking up the end part to the main part  15 , said main part  15  comprising a connector aperture  19  which is substantially larger than the very narrow discharge aperture  10  at the end of the end part  16 . 
         [0029]    In an alternative but omitted design, the end part  16  of the pipet  8  also may assume the conventional pointed, conical shape while however being flexurally elastic in a manner illustratively selecting the thickness of the material or the kind of material. Moreover said end part also may be integral with the main part  15 . 
         [0030]    Because of the flexurally elastic design of the end part  16 , implemented in this case by the thinness of the hose element  18 , the pipet  8  may be moved into the position of  FIG. 2  while its height is appropriately controlled using the support arm  12 . In the process, the hose element  18  rests in an elastic arc on the surface  2  of the nutrient medium  1 , whereby the end zone of the hose element  18  is parallel to the surface of the nutrient medium  1 . 
         [0031]    As shown by  FIG. 2 , a highly defined position of the discharge aperture  10  is attained in this manner relative to the surface of the nutrient medium  1 . If during pipet operation there should be deviations in height for instance caused by inaccurate displacements of the support arm  12  or also by varying thickness of the nutrient medium  1 , then said deviations shall be elastically compensated by the flexure of the elastic hose element  18  without the position of the discharge aperture  10  changing relative to the surface of the nutrient medium  1 . 
         [0032]    Even at high speeds of the pipet  8  across the surface of the nutrient medium  1 , the present design precludes fluctuations in deposition, and damages to the delicate surface of the nutrient medium  1 . 
         [0033]    In the shown embodiment, the end part  16  is detachable from the main part  15  of the pipet  8 , namely, the embodiment as shown, by means of a conical connector which also may be replaced by other kinds of connectors. 
         [0034]    For serial tests, where numerous inoculating solutions must be deposited on numerous nutrient mediums, a rack  20  shown in  FIG. 3  may be used, that receives several empty main parts  15 . The support  14  of the pipet  18  can be moved in position by means of the support arm  12  above the particular next main part  15  in the rack  20  and then be lowered to be connected to it. 
         [0035]    Thereupon, by appropriately displacing the support arm  12 , the support  14  together with the main part  15  which is connected to said main part and still empty, as shown in  FIG. 4 , may be moved above a test vial  21  containing the next inoculating solution  7  to be processed then be lowered until the connector aperture  19  of the main part  15  dips into said solution. The main part  15  then will fill up by a corresponding partial vacuum being applied through the hookup tube  9 . 
         [0036]    In the next step, shown in  FIG. 5 , the filled main part  15  is displaced by a commensurate displacement of the support arm  12  above a rack  22  containing a stock of end parts  16  and is connected to one of them. Then, the support arm  12  is raised again. The pipet  8 , which now is fully plugged together and filled with liquid, is moved into position as shown in  FIG. 6  where, by appropriate control of height and angle, it can be moved above a Petri dish  3  with a nutrient medium  1  in the processing position shown in  FIGS. 1 and 2 . 
         [0037]    In the shown embodiment mode, the pipet  8  is used in a system elucidated in relation to  FIGS. 1 and 2  and serving to deposit a inoculating solution on the surface  2  of a nutrient medium  1 . However the pipet  8  shown in  FIG. 6  also may be used for other purposes. 
         [0038]    Illustratively, the pipet  8  may be used to pipet minute amounts of liquid into reaction vials, for instance into microtitration trays. Moreover, said pipet may be used to deposit small amounts of liquid on carrier plates, namely the so-called spots for subsequent biochemical reactions. It also may be used to deposit small quantities of liquid on object supports for purposes of microscopying. Further applications are feasible wherein minute quantities of liquid must be pipeted and high processing speeds are required. 
         [0039]    None of such applications requires that the pipet tip as shown in the Figures be fitted with a long and thin end part  16 . The pipet tip also may be short provided that the discharge aperture  10  is very narrow.