Abstract:
Pipetting device with a displacement device with a displacement chamber with a displaceable limiter, a attachment for connecting to a pipette tip and a connecting channel between the displacement chamber and the free end of the attachment, a drive device for driving the displaceable limiter of the displacement device with a drive member, which has a releasable cooperation with the displaceable limiter, and a bayonet connection between the drive device and the displacement device which can be established by creating the cooperation between the drive member and the displaceable limiter and can be released by releasing the cooperation between the drive member and the displaceable limiter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     Pipetting devices are in particular used in the laboratory for metering liquids. They are drawn into pipette tips through a tip orifice and dispensed. With air cushion pipettes a displacement device for a gas is incorporated in the pipetting device and communicatingly connected to the pipette tip by the attachment. An air cushion is displaced by means of the displacement device, so that liquid is suctioned into the pipette tip and ejected therefrom. The displacement device is generally a cylinder with a piston which can be displaced therein.  
         [0004]     The pipette tips are releasably connected to the attachment, so that they can be exchanged after use for a fresh pipette tip. As a result contamination can be avoided during subsequent metering. Single use pipette tips are available cheaply, made from plastics.  
         [0005]     The attachment for fastening pipette tips is frequently a cylindrical or conical projection relative to a base body or a housing, and onto which a pipette tip with a suitable mounting opening or receiver can be clamped. This can take place without grasping the pipette tip by pressing the attachment into the mounting opening of the pipette tip which is ready in a holder.  
         [0006]     To avoid contamination of the user, pipette devices comprise an ejection device with a drive device and a throw-off device. By actuating the drive device the throw-off device is displaced, such that it releases the pipette tip from the attachment, without it having to be grasped by the user. Frequently, the drive device has a mechanism which has to be manually actuated by means of an actuation button, in order to release the pipette tip from the attachment. Drive devices are also possible with an electromotive drive. Releasing the pipette tip from the attachment can require increased operating force, in particular with pipette tips which are rigidly clamped onto the attachment. Even with one-channel systems, ie pipetting devices which comprise a single attachment for a single pipette tip, this can make ejecting the pipette tip from the attachment difficult or impossible. Particularly high operating force can be required with multi-channel pipette systems which have a plurality of parallel attachments for mounting pipette tips, due to multiple tip ejection forces.  
         [0007]     A pipette system with an axially movable throw-off device for releasing a pipette tip from an attachment, a drive device to drive the axial movements of the throw-off device and a pull-means gear, push-means gear or linkage gear transferring an axial drive movement of the drive device into an axial movement of the throw-off device is known from EP 0 992 288 A2. The force exerted by the throw-off device on the pipette tip exceeds the force exerted by the user, whereby the ejection is facilitated.  
         [0008]     Air cushion pipettes can lead to contamination of the displacement device. Penetration of fluid due to improper handling or the rising of vapour or tiny droplets of the liquid to be pipetted into the displacement device can result therefrom. Moreover, it can be desirable to exchange the displacement device in order to prepare the pipetting device for use in a further area of the volume of liquids to be pipetted.  
         [0009]     Pipetting devices are already known in which the displacement device with the attachment for mounting the pipette tip can be separated from a drive device to drive the displacement device. In EP 0 428 500 B1 such a pipetting device is disclosed in which the displacement device can be screwed onto a shank of the drive device by means of a coupling nut. In principle, it is therefore possible to release the displacement device for cleaning or for exchanging the drive device. The fastening is nevertheless laborious, time-consuming and susceptible to faults.  
         [0010]     Proceeding from this, the object of the invention is to provide a pipetting device in which the displacement device and the drive device can be more easily and more rapidly connected to and separated from one another and in which the connection is less susceptible to faults.  
         [0011]     The object is achieved by a pipetting device with the features of claim  1 . Advantageous embodiments of the pipetting device are revealed in the sub-claims.  
       BRIEF SUMMARY OF THE INVENTION  
       [0012]     The pipetting device according to the invention has a displacement device with a displacement chamber with a displaceable limiter, an attachment for connecting to a pipette tip and a connection channel between the displacement chamber and the free end of the attachment, a drive device for driving the displaceable limiter of the displacement device with a drive member which cooperates releasably with the displaceable limiter, and a bayonet connection between the drive device and the displacement device which can be established by producing the cooperation between the drive member and the displaceable limiter and can be released by releasing the cooperation between the drive member and the displaceable limiter.  
         [0013]     The displacement device and the drive device of the pipetting device can be easily connected to one another by being pushed together along a longitudinal axis of the bayonet connection and rotating about the longitudinal axis of the bayonet connection and can be separated from one another in the reverse manner. When establishing the bayonet connection the cooperation between the drive member and the displaceable limiter is simultaneously produced without it requiring further particular actions therefor. When releasing the bayonet connection, the cooperation is released without particular further actions. The invention allows a particularly simple, rapid and secure connection and separation of the displacement device and the drive device, for example during assembly, before autoclaving or other cleaning of the lower part, before exchanging the lower part for the purpose of altering the working area, repairs, etc. The bayonet connection is not particularly susceptible to faults. These advantages are in particular effective when manually and automatically connecting and separating the displacement device and the drive device. The latter, for example, with automatic assembly or a workstation with automatic tool exchange.  
         [0014]     The drive device can be designed in different ways. It makes use of technical means to displace the drive member, such that it displaces the displaceable limiter of the displacement device. To this end, the drive member carries out, for example, a linear movement. Accordingly, the drive device comprises a linear drive. In this connection there is, for example, a lifting rod which can be manually actuated directly by actuating a button or a lifting rod which is linearly displaceable via an electric drive motor and a gear mechanism. A pneumatically or hydraulically operated pressure medium cylinder can also be considered as the drive for the lifting rod which is actuated via a pneumatic or hydraulic control mechanism and a pressure medium reservoir. If the drive member does not carry out a linear movement but a three-dimensional feed motion, the drive device comprises a corresponding drive.  
         [0015]     The drive device preferably comprises a housing in which the drive and the drive member are arranged. According to an embodiment, the drive member is a lifting rod of the drive device, displaceable parallel to the longitudinal axis of the bayonet connection and the displacement device comprises a contact surface connected to the limiter, oriented transversely to the lifting rod and which is pressed by a lift spring against the end of the lifting rod. In this embodiment the cooperation between the drive member and the displaceable limiter is automatically produced when the bayonet connection is established and automatically released when the bayonet connection is released.  
         [0016]     According to an embodiment the contact surface is constructed on a pressure piece connected to the displaceable limiter via a rod and the lift spring is designed as a coil spring which at one end is supported on the pressure piece and at the other end on the displacement chamber.  
         [0017]     The bayonet connection can be designed in different ways. Included in the invention in particular is the design of the drive device as a male part and the displacement device as a female part of the bayonet connection and vice versa. According to an embodiment the drive device has a cylindrical receiver which comprises an aperture at one end through which the cylindrical receiver is externally accessible in the axial direction which comprises at least one axially oriented longitudinal groove which is connected to an annular groove oriented in the peripheral direction of the cylindrical receiver and the displacement device on a cylindrical portion comprises at least one outwardly protruding projection, the cylindrical portion able to be inserted in the axial direction of the cylindrical receiver through the aperture into the receiver and with the projection into the longitudinal groove and can be screwed with the projection into the annular groove. In this embodiment the drive device is the female part and the displacement device the male part.  
         [0018]     According to an embodiment the annular groove comprises, at a distance from the longitudinal groove, a limiting wall extended in the axial direction of the receiver, as far as which the projection can be rotated. Reaching the limiter indicates to the user that the bayonet connection has been established.  
         [0019]     According to an embodiment, the annular groove is connected, at a distance from the longitudinal groove, to a longitudinal groove portion extending parallel thereto, which ends at a distance from the aperture. By engaging the projection into the longitudinal groove portion the reliability of the bayonet connection is effected.  
         [0020]     According to an embodiment, the annular groove has a limiting wall extending in a ramp-like manner, of which the distance from the aperture increases with increasing distance from the longitudinal groove. The ramp-like path of the limiting wall facilitates finding the connection position and the separation of the displacement device from the drive device.  
         [0021]     According to an embodiment the longitudinal groove, the annular groove and optionally the longitudinal groove portion are constructed in a cylindrical coupling piece which forms the receiver of the drive device and is fastened therein. As a result the manufacture, assembly and disassembly are facilitated.  
         [0022]     According to an embodiment the drive device comprises a spring which presses against the displacement device connected to the drive device via the bayonet connection. As a result the bayonet connection is secured.  
         [0023]     According to an embodiment, the spring is arranged on a further aperture of the receiver which is positioned opposite the aperture for axially inserting the displacement device. The displacement device and the spring act upon one another through this aperture. According to a further embodiment, the spring is a coil spring which is supported on an inner front face of the coupling piece.  
         [0024]     According to an embodiment the longitudinal groove and/or the annular groove and/or the longitudinal groove portion are opened toward the further aperture.  
         [0025]     According to an embodiment, the displacement device is a piston-cylinder-unit with a cylinder and a piston displaceable therein and the piston comprises the displaceable limiter. Other displacement devices are also included in the invention, for example a displacement chamber with a resilient wall forming the displaceable limiter. A piston-cylinder-unit is, for example actuated by a linear drive device. A corresponding actuation is possible with a displacement chamber with a resilient wall. The latter can also however be controlled via a drive device with a three-dimensional drive motion. Thus it is possible, for example, to control the resilient wall externally by acting upon a hydraulic or pneumatic pressure means.  
         [0026]     According to an embodiment the attachment is aligned coaxially to the longitudinal axis of the bayonet connection. According to a further embodiment the attachment is rigidly connected to the displacement device.  
         [0027]     According to an embodiment the pipetting device has an ejection device for ejecting a pipette tip from the attachment which comprises an ejection drive arranged on the drive device, a throw-off device arranged on the displacement device and a releasable axial clamping connection between the ejection drive and the throw-off device oriented in the direction of the longitudinal axis of the bayonet connection. The clamping connection can be established at the same time as the creation of the bayonet connection at the stage of the displacement device and the drive device being axially pushed together and can be released in the reverse direction.  
         [0028]     According to an embodiment the ejection drive comprises an ejection rod protruding from the drive device parallel to the bayonet connection and the throw-off device comprises an axial bore parallel to the attachment and with which the ejection rod has an interference fit.  
         [0029]     According to an embodiment, the throw-off device is carried on the displacement device.  
         [0030]     According to an embodiment, the throw-off device is a sleeve carried on the displacement device.  
         [0031]     According to an embodiment, the pipetting device is a hand-held device and/or a stationary device and/or an electrically driven device and/or a (semi) automatic machine. In the embodiments as a hand-held device the pipetting device is manually taken to the point where samples are taken and dispensed and the suctioning and dispensing of liquid and the actuation of the ejection device controlled manually. The drive devices for the displacement device and/or the throw-off device are of mechanical and/or electromechanical design. The latter also applies to the design of the pipetting devices as stationary devices. When designing the pipetting device as a (semi) automatic machine all functions or a portion of the functions of the pipetting devices (suctioning and dispensing liquid, movement of the pipetting devices into positions for receiving and dispensing liquid or pipette tips, receiving and dispensing of pipette tips) are carried out automatically.  
         [0032]     According to an embodiment, the pipetting device comprises a row of parallel attachments to receive pipette tips. In this case it is a multi-channel pipetting system. A special or common displacement device is associated with each attachment of the pipetting device which is connected to the drive device via a bayonet connection. In addition, there can be a common drive device for all the displacement devices. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0033]     The invention will be described in more detail hereinafter with reference to the accompanying drawings of embodiments, in which:  
         [0034]      FIG. 1  is a hand-operated pipetting device with separate piston-cylinder-unit and throw-off device in longitudinal section;  
         [0035]      FIG. 2  is the same pipetting device with attached piston-cylinder-unit and throw-off device in longitudinal section. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]     While this invention may be embodied in many different forms, there are described in detail herein a specific preferred embodiment of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiment illustrated  
         [0037]     The terms ‘above’, ‘below’, ‘horizontally’ and ‘vertically’ refer to the alignment of the pipetting device according to the drawings. In this connection it refers to an alignment of the pipetting device in which the pipette tip is arranged with its tip orifice below, in order to draw in liquid from a container located below the pipetting device and to dispense it into such a container.  
         [0038]     The pipetting device according to  FIGS. 1 and 2  has an elongate housing  1  formed as a grip with a housing upper part  2  and a housing lower part  3 . The housing upper part  2  with all the parts contained therein forms a drive device and the housing lower part  3  with all the parts contained therein forms a displacement device. The housing upper part  2  has a screw cap  4  above. An adjustable sleeve  5  protrudes upwardly therefrom. The adjustable sleeve  5  is axially fixedly and rotatably mounted in the housing upper part  2 .  
         [0039]     In the adjustable sleeve  5  a push button  6  is arranged which protrudes even further upwardly.  
         [0040]     The push button  6  is connected to a lifting rod  7  through which a spindle  8  is passed in the housing upper part  2 . The spindle  8  is screwed into an internal thread  9  of a bearing body  10  fixed in the housing upper part  2 .  
         [0041]     Above, the spindle  8  comprises a tappet  11  connected rotationally fixedly thereto. The tappet  11  has on the periphery two diametrically opposing radial projections  12 . The radial projections  12  engage in axially extending grooves—not shown—of the adjustable sleeve  5 .  
         [0042]     Below, the spindle  8  has an end stop  13  in the form of radially outwardly protruding ribs. In the position shown, the end stop  13  is located a small distance below a shoulder  14  of the bearing body  10 , with which it cooperates.  
         [0043]     The lifting rod  7  has a flange  15  which bears against the spindle  8  below in the position shown.  
         [0044]     At the lower end of the bearing body  10  a spring retainer  16  is arranged, which engages in the bearing body  10  with a collar  17 . Below, the spring retainer  16  has an axially protruding sleeve-shaped bearing portion  18  through which the lifting rod  7  is passed.  
         [0045]     Moreover, the pipetting device comprises a spring, not shown, which presses the lifting rod  7  upwardly, so that the flange  15  bears against the lower face of the spindle  8 . For example, a coil spring is arranged between the flange  15  and the spring retainer  16 .  
         [0046]     At a distance below the spring retainer  16  a coupling piece  19  is fastened in the housing. This has a plurality of pockets  20  inside. These have a longitudinal groove  21  extended axially over the entire length of the coupling piece  19 . Moreover, they have on the upper end of the coupling piece  19  an annular groove  22  extended over a small part of the periphery of the coupling piece  19 . Below, it has a limiting wall extending in a ramp-like manner at a distance from the upper end of the coupling piece  19 , which from the longitudinal groove  21  increasingly approaches the upper end of the coupling piece  19 . Finally, the pockets  20  have at the other end of the annular groove  22  a short axial longitudinal groove portion  23  which ends at a distance from the upper end of the coupling piece  19  in the coupling piece  19 .  
         [0047]     Between the spring retainer  16  and the coupling piece  19  a spring  24  is arranged under preload which is designed as a coil spring.  
         [0048]     The adjustable sleeve  5  has on its periphery a sprocket  25  which cooperates with a gear  26  which drives a counter  27  with a plurality of counter wheels  29  arranged over one another on an axis  28 . The counter wheels  29  are respectively numbered from 0 to 9. The lower counter wheel  29  is driven by the gear wheel  26 . The counter wheels  29  arranged thereover are respectively rotated further by a number when the counter wheel  29  arranged thereunder moves from 9 to 0.  
         [0049]     The housing lower part  3  can be releasably connected to the housing upper part  2 . To this end the housing lower part  3  comprises on the casing of an upper, cylindrical portion  30  a plurality of outwardly protruding projections or ribs  31  which extend in the axial direction of the cylindrical portion  30 .  
         [0050]     The housing lower part  3  has a plurality of conical portions  31  to  33  of varying lengths and taper below the cylindrical portion  30  which are revealed in the drawings. The conical portion  33  is connected below to a long, slightly conical attachment  34  for mounting a pipette tip. This again has a short, more conical mounting end  35  below.  
         [0051]     The housing lower part  3  houses a displacement device in the form of a piston-cylinder-unit  36 . This has a cylinder  37  arranged in the conical portion  32  and in which a piston  38  dips. The piston  38  is connected above to a pressure piece  40  via a piston rod  39 . The piston  38  forms a displaceable limiter of the cylinder  37 .  
         [0052]     Above the pressure piece  40  the housing lower part  3  has a piston holder  41  which spans the cylindrical portion  30  above. The piston holder  41  has a central through passage  42  above, through which a lower portion of the reciprocating piston  7  can be axially passed. Between the pressure piece  40  and the conical portion  31  a lift spring  43  is arranged which is designed as a coil spring. The piston  38  and the piston rod  39  are passed through the lift spring  43 .  
         [0053]     The lift spring  43  is biased and presses the pressure piece  40  against the piston holder  41 , so that the piston  38  is pulled out to a maximum extent from the cylinder  37 .  
         [0054]     A connection channel  44  extends through the attachment  34  and connects the cylinder  37  with an orifice in the mounting end  35 .  
         [0055]     Moreover, the pipetting device has an ejection device  45 . The ejection device  45  has an actuation button  46  in the housing upper part  2  in addition to the adjustment button  5 . The actuation button  46  is connected to an ejection rod  47  which extends parallel to the lifting rod  7  through the housing upper part  2 .  
         [0056]     A gear mechanism  48  is incorporated in the ejection rod  47 . The gear mechanism  48  converts an axial actuation stroke of the actuation button  46  into a smaller drive stroke with increased force. Suitable gear mechanisms  48  are disclosed in EP 0 992 288 A and namely generally in the main part of the description and especially in the description of the Figures which are included in the present application by reference.  
         [0057]     The ejection rod  47  is supported in the housing upper part  2  via a further coil spring  49 , so that the actuation button  46  is pressed into the shown initial position into which it can be pressed against the effect of the further coil spring  49 .  
         [0058]     The lower end of the ejection rod  47  protrudes into a receiver  50  at the lower end of the housing upper part  2 .  
         [0059]     The ejection device  45  has an ejection sleeve  51  on the housing lower part  3 . This is carried on the cylindrical portion  30 , the conical portion  32  and the attachment  34 . Accordingly, the contour of the ejection sleeve  51  is similar to the contours of the aforementioned portions of the housing lower part  3 . In this connection the ejection sleeve  51  has inner steps  52 ,  53  which upwardly limit the pushing up of the ejection sleeve  5   1 , as they bear against conical portions  31 ,  33  of the housing lower part  3 .  
         [0060]     Moreover, the ejection sleeve  51  has a lateral projection  54  on the upper edge which comprises an axial bore  55  for pressing in the lower end of the ejection rod  47 .  
         [0061]     The pipetting device can be used in the following manner:  
         [0062]     The housing upper part  2  and the housing lower part  3  can be connected by axially inserting and rotating the lower part  3  in the coupling piece  19 . As a result, a bayonet connection is established. Then the ribs  31  are pushed into the longitudinal grooves  21 , rotated through the annular grooves  22  and pushed into the short longitudinal groove portions  23 . In this connection, the spring  24  presses against the upper edge of the cylindrical portion  30 , whereby the housing lower part  3  is fixed in its fastening position, in which the ribs  31  bear against the lower ends of the longitudinal groove portions  23  which form a stop. Moreover, the ejection sleeve  51  with the bore  55  is pressed onto the lower region of the ejection rod  47 . The housing upper part  2  and the housing lower part  3  can be disassembled in the reverse manner.  
         [0063]     After connecting the housing upper part  2  and the housing lower part  3  the lifting rod  7  engages through the through passage  42  and bears with its lower end against the pressure piece  40 .  
         [0064]     To adjust a volume to be pipetted, the adjustable sleeve  5  is rotated until the counter  27  indicates the desired volume. When rotating the adjustable sleeve  5  the tappet  11  is rotated therewith due to the radial projections  12 . As a result the spindle  8  rotates in the internal thread  9  and is displaced axially in the housing upper part  2  by driving the flange  15  and therefore the lifting rod  7 . The radial projections  12  are therefore axially displaced along the grooves on the inner face of the adjustable sleeve  5 . As a result, the stroke of the lifting rod  7  is altered, which can take place during actuation of the push button  6 .  
         [0065]     Moreover, on the lower end of the attachment  34  a pipette tip  56  is clamped. The pipette tip  56  has a lower tip aperture  57  for suctioning and dispensing liquid.  
         [0066]     When mounting the pipette tip  56  on the attachment  34 , the mounting force increases as it is mounted further. If the mounting force exceeds the force with which the spring  24  is biased, the attachment  34  and thus the entire housing lower part  3  is pressed upwardly against the effect of the spring  24 . When the upper edge  58  of the pipette tip  56  presses the lower edge forming a stop  59  of the ejection sleeve  51 , a further raising of the housing lower part  3  is prevented, as the ejection sleeve  51  bears against a limiter  60  in the receiver  50  of the housing upper part  2  above. The mounting force and thus the ejection force required for ejection are thus limited to a specific value.  
         [0067]     For pipetting, the push button  6  is pressed down, so that the piston  38  forces air out of the cylinder  37 . Then the pipette tip  56  is dipped with its lower tip orifice  57  into the liquid to be pipetted. Then, the push button  6  is released and the lifting rod  7  returns into its initial position under the action of the spring. The piston  38  also returns into its initial position under the action of the spring  43 . Then the piston  38  suctions liquid through the lower tip orifice  57  into the pipette tip  56 .  
         [0068]     Afterwards, the lower tip orifice  57  of the pipetting device is aligned with a dispensing position. The liquid contained in the pipette tip  56  is dispensed by pressing in the push button  6 , further dipping of the piston  38  into the cylinder  37  and pressing air out through the connection channel  44 . After releasing the actuation button  6 , the lifting rod  7  and the piston  38  return again to the initial position by spring force.  
         [0069]     To eject the pipette tip  56 , the actuation button  46  is pressed. As a result the ejection sleeve  51  moves downwardly and pushes the pipette tip  56  away from the attachment  34 .  
         [0070]     The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.  
         [0071]     Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim  1  should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.  
         [0072]     This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.