CN114786817B

CN114786817B - Electric external piston type distribution method

Info

Publication number: CN114786817B
Application number: CN202080084036.6A
Authority: CN
Inventors: 迈克尔·麦克纳尔; 汉斯·伯格曼; 理查德·希尔
Original assignee: Mettler Toledo Reining LLC
Current assignee: Mettler Toledo Reining LLC
Priority date: 2019-10-25
Filing date: 2020-10-26
Publication date: 2024-01-05
Anticipated expiration: 2040-10-26
Also published as: EP4149681A1; WO2021081534A1; KR20220088891A; CN114786817A; JP2022553735A; CA3158790C; CA3158790A1

Abstract

An exemplary method for dispensing liquid from an electric hand-held external piston pipette is described.

Description

Electric external piston type distribution method

Technical Field

Exemplary embodiments of the present general inventive concept relate to an electric hand-held external piston pipette and pipette assembly, including a novel syringe for the pipette, and associated mechanisms for releasably holding, ejecting and possibly automatically identifying the syringe.

Background

As will be appreciated by those skilled in the art, pipettes are typically of gas piston or external piston design. In contrast to gas piston pipettes, in which the aspirated liquid and the pipette piston are separated by a gas cushion, external piston pipettes are designed such that the pipette piston is in direct contact with the aspirated liquid.

The design of the external piston pipette eliminates potential gas piston pipette inaccuracies that may result from the effects of different liquid properties and/or environmental conditions on the gas cushion of the gas piston pipette. For example, height variations, evaporation, and other conditions that a gas piston pipette may experience may affect the accuracy of the gas piston pipette.

While external piston pipettes may provide the above-described advantages over gas piston pipettes, known external piston pipettes have their own drawbacks. A commonly known disadvantage is that external piston pipettes do not provide accurate, non-contact dispensing of very small liquid volumes, including volumes below 1 μl. More specifically, when dispensing very small volumes of liquid using known external piston pipettes, after the dispensing stroke, there is a certain amount of liquid that can adhere to the inside of the pipette tip, which requires subsequent physical contact ("contact") of the pipette tip with the liquid receiving container to expel the adhering liquid from the pipette tip.

In addition, during normal use, the direct contact between the piston of the external piston pipette and the liquid of interest means that the piston cannot be reused. Thus, external piston pipettes typically use a "consumable" in the form of a disposable syringe that includes not only a hollow barrel (capillary tube) having a tip portion, but also a piston that resides and seals within the capillary tube and is capable of reciprocating within the capillary tube by the pipette to aspirate and dispense a desired amount of liquid of interest when the capillary tube and piston are releasably attached to the pipette. After the pipetting operation is completed, the entire syringe is typically removed from the external piston pipettor and discarded.

The complexity associated with the insertion, retention and ejection of an external piston pipette syringe is greater than that associated with a typical gas piston pipette tip, which is much simpler in construction and typically held in place on the dispensing end of the gas piston pipette body by friction alone. In an external piston pipette, the syringe must be securely held on the pipette body until intentionally ejected, while the piston is properly positioned within the pipette for releasable engagement and reciprocal movement by the aspiration/dispense mechanism of the pipette.

There is a need for an external piston pipette that can provide accurate and repeatable non-contact dispensing of various volumes of liquid, including very small liquid volumes. There is also a need for an external piston pipette with an improved mechanism by which a syringe can be easily and reliably mounted to, releasably held by, and ejected from the pipette. The exemplary external piston pipettes according to the present general inventive concept and the various features of the exemplary external piston pipettes meet these needs.

Disclosure of Invention

An exemplary embodiment of an electric hand-held external piston pipette according to the present general inventive concept will generally include a substantially hollow body that is preferably shaped to be an ergonomic grip for a user and that serves as a housing for various internal components of the pipette. The proximal end of the body may include a user interface portion, while the distal end of the body is configured and serves as a connection end for a syringe.

Exemplary pipettes typically also include a motorized drive assembly, a dispensing solenoid assembly, a syringe retaining mechanism, a syringe plunger gripping mechanism, and a syringe ejection mechanism, all of which are housed within the pipette body. At least some of the above components may also reside within an inner housing that is also located within the pipette body.

A syringe is releasably mounted to the distal end of the pipette for aspirating and dispensing fluids of interest. The syringe may be provided in a number of different volumes. However, regardless of volume, each syringe typically includes a generally hollow outer barrel (capillary tube) that may be tubular in shape or some other shape, such as, but not limited to, oval or oblong. The capillary tube includes a tip having an orifice at a distal end thereof and is adapted to receive a fluid sample to be dispensed. At the top of each capillary there is a syringe retaining element, which may be an integral part of the capillary. The syringe retaining element is shaped and sized to mate with a syringe retaining mechanism of the pipette.

Each syringe further includes a piston having a first fluid contacting portion disposed within the capillary tube and a piston head connected thereto and located proximal to the syringe retaining element when the piston is in the capillary tube. The piston head is configured to releasably engage with a piston carrier of a syringe piston gripping mechanism of the pipette.

The motorized drive assembly is responsible for providing various positions of the syringe attached to the pipette for drawing the syringe piston in a proximal direction of the pipette to aspirate fluid into the syringe, for moving the syringe piston in a distal direction to dispense fluid from the syringe, and for generating a syringe ejection motion.

The dispensing solenoid assembly includes an armature that floats within a bore in the solenoid body and is linearly displaceable relative thereto. The armature includes a shaft that extends through an opening in the solenoid body and connects the armature to a plunger carrier that forms part of a syringe plunger retaining mechanism of the pipette and engages a piston head of the syringe plunger.

The dispense solenoid assembly and syringe plunger gripping mechanism reside substantially within a plunger carrier that is connected to the output of a drive motor of the electric drive assembly by a lead screw. In one exemplary embodiment, operation of the drive motor may rotate a drive nut coupled to the lead screw but limited in linear displacement, thereby converting the rotational output of the motor into linear displacement of the lead screw and the piston carrier and components such as a dispensing solenoid coupled to the piston carrier. In another exemplary embodiment, operation of the drive motor may rotate the lead screw within a drive nut that is linearly displaceable but rotation limited, thereby translating the rotational output of the motor into linear displacement of the lead screw, the piston carrier, and various components connected to the piston carrier. In other exemplary embodiments, the lead screw and/or drive nut may be replaced with other components that result in the desired controlled displacement of the piston carrier and the various components connected to the piston carrier.

The dispensing solenoid assembly of the exemplary pipette is configured to independently generate pulsed dispensing of selected volumes of fluid according to selected dispensing volumes and dispensing modes, or to assist the motorized drive assembly in dispensing functions by ensuring that each selected dispensing volume is actually dispensed from the syringe without touching the syringe tip to the sample receiving container. More specifically, the solenoid body (coil) is energized to produce a rapid and forceful displacement of the solenoid armature toward the distal end of the pipette, thereby causing a similar rapid movement of the plunger carrier and syringe plunger, and expelling a fluid jet from the syringe tip. The general concept of pulsed fluid dispensing with respect to a bench-top pipette instrument can be reviewed in european patent application EP1344565 A1. The displacement of the piston carriage may be repeated as necessary, and then the dispensing solenoid assembly actuated to dispense a plurality of aliquots, each aliquot representing a portion of the entire liquid volume held by the syringe.

Operation of the motorized drive assembly and the dispensing solenoid assembly is controlled by a controller that receives command signals from user inputs and/or from internal programming. The controller also receives a position information signal from the encoder.

The selected syringe is securely but releasably held on the pipette by the syringe holding mechanism and the syringe plunger is connected to the solenoid armature and to the motorized drive system via the plunger carrier of the syringe plunger gripping mechanism.

Upon completion of the aspirating and dispensing operations, the syringe ejection mechanism is operable to disengage the syringe retaining element of the syringe from the syringe retaining mechanism and to disengage the syringe piston head from the plunger carrier. The motorized drive system then drives the piston carriage toward the distal end of the pipette, which causes the syringe retaining mechanism to release the syringe capillary tube via a release element associated with the piston carriage and disengage the syringe piston gripping mechanism from the syringe piston head, after which the syringe will automatically pop out of the pipette.

Various dispensing operations using the exemplary pipettes may be implemented in either an automatic mode or a manual mode. The user can access and selectively initiate the desired automated pipetting procedure through the user interface portion of the pipettor.

The automatic mode allocation may include a number of different and alternative allocation procedures. For example, these allocation procedures may result in: aspiration of the full syringe volume of fluid, and then dispensing the entire aspirated fluid volume in one dispensing operation; aspirating a volume of fluid into the syringe, and then dispensing the aspirated fluid in a plurality of doses of equal volume; aspirating a volume of fluid into the syringe, and then dispensing the aspirated fluid in a variable volume of multiple doses; or aspirate a volume of fluid into the syringe and then dispense the aspirated fluid in multiple doses of equal or variable volume until a portion (e.g., 50%) of the aspirated volume has been dispensed and then perform another aspiration operation. The dispensing operation may also be performed by the user in manual mode, rather than by the controller of the pipette in automatic mode.

Titration procedures may also be performed. The titration program of an exemplary pipette may include a titration volume counter that represents the volume of titrant dispensed, and the counter may be resettable to allow for multiple titration operations on a single aspirated volume of titrant.

Exemplary pipettes may also include fluid viscosity detection capabilities, such as by, for example and without limitation, providing the pipette with appropriate circuitry or other means for monitoring increases in current consumption of the motorized drive assembly motor required to move the syringe piston relative to the syringe capillary tube during aspiration or dispensing operations; by using the provided load cell, it measures the force required to move the syringe piston relative to the syringe capillary tube during a aspirating or dispensing operation; by a mechanical spring; or by another technique as will be appreciated by those skilled in the art. The value of the current consumption may be used to classify the viscosity of the fluid, and the pipette controller may adjust the dispensing operating parameters of the pipette based on the identified fluid viscosity class.

The exemplary pipettor may also be provided with an automatic syringe identification system. Such a system would allow the controller of the pipette to automatically select the appropriate operating parameters for a given syringe volume, simplifying the setup process and possibly eliminating operator errors associated with erroneously identifying the volume of the syringe being used. Such a system may be implemented, for example, by associating each syringe volume with a different color, placing a region of the corresponding color on the syringe, positioning a color sensor in the pipette, and transmitting image data from the color sensor to the pipette controller, the color sensor being structured and positioned to image the colored region on the syringe. The signal of the pipette controller is representative of the color of the colored region on the syringe and the controller is programmed to analyze the signal and thereby ultimately identify the volume of the syringe installed.

Exemplary pipettes according to the present general inventive concept are capable of accurately and reproducibly dispensing sub-microliter (sub-microlite) volumes of fluid doses to milliliters or more volumes. The ability to automatically dispense a selected volume of fluid of interest without touching the syringe tip means that the dispensing operation is also user independent and thus isolated from possible user-introduced errors. These are significant improvements to the capabilities of known external piston pipettes.

Other aspects and features of the present general inventive concept will become apparent to those ordinarily skilled in the art upon review of the following detailed description of illustrative embodiments and the accompanying figures.

Drawings

In the following description of the drawings and exemplary embodiments, like reference numerals designate like or equivalent features throughout the several views, and:

FIG. 1 is a perspective view of an exemplary embodiment of a motor-driven external piston pipette according to the present general inventive concept, and includes a syringe shown prior to insertion of the pipette;

FIG. 2 illustrates an assembly of the exemplary pipette of FIG. 1 with a syringe installed into and held by the pipette;

FIG. 3 is an enlarged view of a user end of the exemplary pipette of FIGS. 1-2;

FIG. 4 illustrates an exemplary user interface provided on a user side of an exemplary pipette in accordance with the present general inventive concept;

FIG. 5A is a cross-sectional side view of the exemplary pipette assembly of FIG. 2 with various internal components of the pipette and the piston of the syringe shown in a aspirated position;

FIG. 5B is an enlarged transparent view of a portion of the pipette of FIG. 5A;

FIGS. 6A-6B are perspective and cross-sectional side views, respectively, of an exemplary 0.1ml syringe for use with an exemplary inventive pipette;

FIGS. 7A-7B are perspective and cross-sectional side views, respectively, of an exemplary 1.0ml syringe for use with an exemplary inventive pipette;

8A-8B are perspective and cross-sectional side views, respectively, of an exemplary 10ml syringe for use with an exemplary inventive pipette;

9A-9B are perspective and cross-sectional side views, respectively, of an exemplary 25ml syringe for use with an exemplary inventive pipette;

FIGS. 10A-10B are perspective and cross-sectional side views, respectively, of an exemplary 50ml syringe for use with an exemplary inventive pipette;

FIG. 11 is a cross-sectional side view of the exemplary pipette of FIG. 1A with a housing portion of the pipette removed to better show various internal components of the pipette;

FIG. 12 is an enlarged cross-sectional perspective view of various internal drive components of the exemplary pipette of FIG. 11;

FIG. 13 is an enlarged cross-sectional view of a distal portion of an exemplary motor-driven external piston pipette, illustrating various internal components forming an exemplary syringe retaining mechanism;

fig. 14A is a perspective view of a piston carrier element of an exemplary syringe piston gripping mechanism, and fig. 14B-14C are front views of the piston carrier element;

FIG. 15A is an exploded view showing the piston head of the exemplary syringe inserted into the piston carrier element of FIGS. 14A-14C, with some of the piston release elements of the exemplary syringe ejection mechanism also present;

FIG. 15B is a somewhat less exploded view of FIG. 15A, with additional elements of an exemplary syringe ejection mechanism;

FIG. 16 illustrates how an exemplary syringe may be inserted into an exemplary motor-driven external piston pipette;

FIG. 17A is an enlarged view showing the syringe and pipette of FIG. 16 with the syringe partially inserted into the pipette such that the piston head of the syringe is only partially engaged by the piston head grasping mechanism of the pipette;

FIG. 17B is an enlarged view showing the syringe and pipette of FIG. 17A with the syringe further inserted into the pipette but not yet fully engaged with its syringe retaining mechanism;

FIG. 18 shows the syringe and pipette of FIG. 17 with the syringe fully inserted into the pipette such that the syringe is engaged with the syringe retaining mechanism of the pipette and the piston head of the syringe is engaged with the syringe piston grasping mechanism of the pipette;

FIG. 19 is an enlarged cross-sectional view of a portion of FIG. 18 showing the interaction of various components of the syringe retaining mechanism and the syringe plunger gripping mechanism with elements of the syringe;

20A-20D illustrate various components of an exemplary syringe ejection mechanism of an exemplary motor-driven external piston pipette;

FIG. 21A illustrates the position of the various syringe ejection mechanism components of FIGS. 20A-20D, along with other related components of the pipette, shortly after the beginning of a syringe ejection operation;

21B-21E further illustrate the positions of the various syringe ejection mechanism components of FIGS. 20A-20D as the syringe ejection operation proceeds;

FIG. 21F illustrates a retracting movement of a plunger carrier portion of a pipette during a final stage of an exemplary syringe ejection operation;

FIG. 22 is an enlarged cross-sectional side view of a portion of an exemplary motor-driven external piston pipette, showing various internal components thereof when the pipette is in a home position;

23A-23B are cross-sectional side views of an exemplary motor-driven external piston pipette with an attached syringe according to the present general inventive concept and illustrating the change in position of various internal components of the pipette and syringe piston as the pipette is moved from a home position to a position ready for full aspiration (e.g., possibly caused by a fluid aspiration operation);

FIG. 24 depicts a change in position of various internal components of the exemplary pipette and syringe assembly from the fully aspirated position shown in FIG. 23B during one exemplary type of fluid dispensing operation; and

fig. 25 is a bottom perspective view of an exemplary motor-driven external piston pipette, with a color sensor visible along with various other components.

Detailed Description

Fig. 1 illustrates an exemplary embodiment of a hand-held motor-driven external piston pipette 5 (hereinafter, referred to as a "pipette" for brevity) according to the present general inventive concept. Also shown in fig. 1 is a consumable in the form of an exemplary disposable syringe 600 (see fig. 8A-8B) that is mounted to a pipette to perform a pipetting operation. Various exemplary syringes for use with the exemplary inventive pipettes are shown in fig. 6A-10B and described in more detail below. Fig. 2 shows the assembly of the pipette 5 and syringe 600 of fig. 1.

The exemplary pipette 5 of fig. 1-2 includes a body 10 for grasping by a user. The body 10 is typically a substantially hollow structure that also serves as a housing for various internal components of the pipette 5. In other embodiments, the body 10 may have a different shape and/or size, but the shape and size is generally dictated at least to some extent by the ergonomics of use.

The body 10 also includes a proximal end 10a that is proximal (user) and a distal end 10b that serves as a connecting end for the syringe 600. In this example, the proximal end 10a of the body 10 includes a user interface portion 15. Referring also to fig. 3-4, it may be observed that the user interface portion 15 of the exemplary pipette 5 further includes a display 20 and various actuators, such as input/select buttons 25a, 25b, and a joystick 27, the joystick 27 allowing a user to view and select pipette functions, view and change pipette settings, and engage in various other interactions with the programmable controller of the pipette, as will be appreciated by those skilled in the art. In this exemplary embodiment of the pipette 5, a trigger switch 30 is also provided for initiating a pipette operation, and an eject button 32 is provided for initiating a syringe eject operation.

Fig. 5A is a cross-sectional side view of the exemplary pipette 5 and syringe 600 assembly of fig. 2, revealing various internal components of the pipette hidden by the body 10. As can be observed, the exemplary pipette 5 includes, among other components, a motorized drive assembly 40, a dispensing solenoid assembly 250, a syringe retaining mechanism 150, and a syringe plunger grasping mechanism 200, all of which are described in more detail below. The assembly of fig. 5A also includes a syringe 600 releasably held by the syringe holding mechanism 150 of the pipette 5 and shown in a post-aspiration and pre-dispense position. An enlarged and transparent view of a portion of the proximal end 10a of the pipette body 10 is shown in FIG. 5B and illustrates additional pipette components such as a printed circuit board and various electronic components including motor control circuitry including the controller 90.

Various exemplary syringes that may be used with exemplary pipettes according to the present general inventive concept are shown in perspective and cross-sectional elevation views in fig. 6A-10B. The example syringes 500-600 are arranged in increasing order of volume, with fig. 6A-6B representing an example syringe 500 having a volume of 0.1ml, fig. 7A-7B representing an example syringe 550 having a volume of 1.0ml, fig. 8A-8B representing an example syringe 600 having a volume of 10ml, fig. 9A-9B representing an example syringe 650 having a volume of 25ml, and fig. 10A-10B representing an example syringe 700 having a volume of 50 ml. Thus, while the exemplary syringe 600 of fig. 8A-8B has been arbitrarily selected as the syringe component of the exemplary pipette and syringe assembly for purposes of illustration, it should be understood that the exemplary inventive pipette may be used with a plurality of different syringes to accurately and reproducibly dispense samples over a wide range of volumes.

Each of the exemplary syringes 500, 550, 600 shown in fig. 6A-8B includes an outer barrel, referred to herein as a capillary tube 505, 555, 605, having a generally hollow and tubular configuration and for containing a fluid sample to be dispensed. The distal end of each capillary 505, 550, 605 includes a tip 510, 560, 610 having an orifice 515, 565, 615 through which fluid previously drawn into the capillary may be dispensed through the orifice 515, 565, 615. The top of each capillary 505, 555, 605 forms a syringe retaining element 520, 570, 620 of the same shape and size. The syringe retaining elements 520, 570, 620 are shaped and sized to allow engagement with the syringe retaining mechanism 150 located in the pipette 5. For example, in the particular syringe embodiment shown, each syringe retaining element 520, 570, 620 includes a circumferential edge 535, 585, 635 and a lower surface 540, 590, 640 that may be engaged by elements of the syringe retaining mechanism 150.

Each syringe 500, 550, 600 also includes a piston 525, 575, 625 (sometimes also referred to as a plunger) having a first fluid contacting portion concentrically disposed within the capillary 505, 555, 605 for aspirating and dispensing fluid, a head 530, 580, 630 portion proximal to the syringe retaining element 520, 570, 620, and a connecting portion passing through a slit in the syringe retaining element to connect the piston head with the fluid contacting portion. The piston heads 530, 580, 630 of the example syringes 500, 550, 600 illustrated herein are substantially bell-shaped and include opposing arms 530a-530b, 580a-580b, 630a-630b that permit at least some degree of elastic deformation thereof. In other embodiments, other piston head shapes and other numbers of arms are possible.

When the syringe 500, 550, 600 is properly mounted to the pipette 5, the syringe is held in a fixed position by engagement of the syringe retaining element 520, 570, 620 of the syringe and the syringe retaining mechanism 150 of the pipette, and the head 530, 580, 630 portion of the piston 525, 575, 625 is engaged by the piston gripping mechanism 200 of the pipette such that the fluid contacting portion of the piston is capable of reciprocating within the capillary tube 505, 555, 605 by the pipette. The syringe 500, 550, 600 may be ejected from the pipette 5 after use, as described in more detail below.

The exemplary syringes 650, 700 shown in fig. 9A-9B and fig. 10A-10B, respectively, are designed for use in pipetting of large fluid volumes. In these exemplary syringe embodiments, again including capillaries 655, 705 having tips 660, 710 with orifices 665, 715, and pistons 670, 720 are again arranged to reciprocate within the capillaries. However, unlike the exemplary syringe embodiments 500, 550, 600 shown in fig. 6A-8B, the capillaries 655, 705 of the syringes 650, 700 have open tops (proximal ends) and do not include syringe retaining elements. Instead, each syringe 650, 700 includes a reusable adapter 675, 725 for connecting the syringe to the pipette 5.

Each adapter 675, 725 has an open distal end sized to receive the proximal end of a syringe 650, 700. The retaining elements at the proximal ends of the capillaries 655, 705 and at the distal ends of the adapters 675, 725 cooperate to secure the capillaries to the adapters. The proximal ends of the adapters 675, 725 form syringe retaining elements 680, 730 shaped and sized to engage a syringe retaining mechanism in the pipette 5. For example, in the particular syringe embodiment shown, each syringe retaining element 680, 730 includes a circumferential edge 690, 740 and a lower surface 695, 745 that may be engaged by elements of the syringe retaining mechanism 150.

Each syringe 650, 700 includes: pistons 620, 720 having first fluid contacting portions concentrically disposed within capillaries 655, 705 for aspirating and dispensing fluids; portions of heads 685, 735 proximal to syringe retaining elements 680, 730 of adapters 675, 725; and a connecting portion passing through a slit in the syringe retaining member to connect the piston head with the fluid contact portion. The piston heads 685, 735 of the example syringes 650, 700 shown herein are also generally bell-shaped and include opposing arms 685a-685b, 735a-735b that allow for at least some elastic deformation thereof. In other embodiments, other piston head shapes and other numbers of arms are possible.

When the bulk syringe 650, 700 is properly mounted to the pipette 5, the syringe is held in a fixed position by engagement of the syringe retaining element 680, 730 of the adapter 675, 725 with the syringe retaining mechanism 150 of the pipette, and the piston head 685, 735 is engaged by the piston grasping mechanism 200 of the pipette, such that the fluid contacting portion of the piston can reciprocate within the capillary tube 655, 705 by the pipette. The syringe 650, 700 may be ejected from the pipette 5 after use, as described in more detail below.

It will be appreciated that the syringe of figures 6A to 10B is provided for illustrative purposes only and that variations are of course possible. For example, and without limitation, the piston head and piston of a given syringe may be separate engageable elements rather than an integral part of a single element as described herein.

Likewise, while only the example larger volume syringes 650, 700 of fig. 9A-10B are shown and described as employing an adapter with an open-topped capillary tube, it is equally possible that the smaller volume syringes 500, 550, 600 of fig. 6A-8B could have a similar design and also include an adapter. When a given syringe includes an adapter, the adapter may be a reusable component rather than a consumable component, which in most syringe embodiments will be the remainder of the syringe.

In fig. 11, a cross-sectional side view of the exemplary pipette 5 of fig. 1 is shown with its body 10 removed to better reveal various internal components of the pipette. As briefly described above, it can be seen that the pipette 5 includes a proximal motorized drive assembly 40, a distal syringe retaining mechanism 150, and a dispensing solenoid assembly 250 and syringe plunger grasping mechanism 200 disposed therebetween. The pipette 5 further includes an inner housing 35 that houses each of the dispensing solenoid assembly 250, the syringe plunger gripping mechanism 200, and the syringe retaining mechanism 150. A motorized drive assembly 40 is attached to the proximal end of the inner housing 35.

The motorized drive assembly 40 is responsible for providing various positions of the syringe 600 attached to the pipette 5 for moving the syringe piston in a distal-to-proximal direction to aspirate fluid into the syringe, for moving the syringe piston in a proximal-to-distal direction to dispense fluid from the syringe, and for producing the movement required to eject the syringe. Referring also to fig. 12, it can be observed that in this exemplary pipette 5, the motorized drive assembly 40 comprises a drive motor 45 whose output shaft is connected to a rotatable drive nut 50 by a drive belt 55, whereby rotation of the drive nut by the drive motor causes linear displacement of a lead screw 95, the lead screw 95 passing through and threadably engaging the drive nut. Other drive schemes may be used in other embodiments, such as a direct drive scheme, in which the output of the drive motor is directly connected to lead screw 95 through a connector, or possibly through a reduction gear assembly.

In this exemplary electric drive assembly 40, the drive belt 55 may connect an output pinion 60 fixed to the output shaft of the motor 45 to an input pinion 65, the input pinion 65 being connected to the drive nut 50 or integral with the drive nut 50. The drive nut 50 may be provided with bearings 70 to facilitate rotation of the drive nut, and the drive nut may also be preloaded with springs 75 (e.g., wave springs), which springs 75 bias the drive nut toward the proximal end of the pipette 5 to help account for any manufacturing (e.g., stacking) tolerance variations within the motorized drive assembly 40 and minimize gear backlash that may otherwise result in inaccuracies during dispensing operations. A mounting block 80 or similar structure/component may be provided for mounting the various components of the electric drive assembly 40.

Dispensing solenoid assembly 250 is configured to independently dispense a selected volume of fluid according to the selected dispense volume or to assist motorized drive assembly 40 in a dispensing function (described below) by ensuring that all selected dispense volumes are actually dispensed from syringe 600 without having syringe tip 610 contact the sample receiving container. Dispensing solenoid assembly 250 includes a solenoid body (coil) 255, solenoid body 255 being located within plunger carrier 100 and connected to plunger carrier 100 such that the solenoid body moves axially with the plunger carrier. The solenoid body 255 includes an axial bore 270, the axial bore 270 extending a distance into the solenoid body from an axial end of the solenoid body. The armature 260 is located concentrically within the bore 270 and is capable of linear reciprocation within the bore and relative to the pipette 5 by a magnetic field generated within the bore, as will be appreciated by those skilled in the art. When the armature 260 floats within the aperture 270 rather than being connected to the piston carrier 100 as with the solenoid body 255, the armature is not constrained (within a distance) to move linearly with the piston carrier. The bottom wall of the aperture 270 acts as an armature hard stop 275 during proximal to distal movement of the armature 260. In the example dispensing solenoid assembly 250 shown, the armature 260 includes a shaft 265, the shaft 265 extending through an opening in the bottom wall of the bore 270 toward the distal end of the pipette 5.

Operation of the motorized drive assembly 40 and the dispensing solenoid assembly 250 is controlled by the controller 90 (see fig. 5B). The controller 90 receives command signals from user inputs such as the actuators 25, 30 and/or from internal programming. The controller 90 also receives a position information signal from an encoder 85 connected to the drive nut 50.

The rotational motion of the drive nut 50 is converted to linear (axial) motion by a lead screw 95, which lead screw 95 passes through and is threadably engaged with the drive nut. Drive nut 50 is free to rotate while lead screw 95 is limited in rotation but linearly displaceable. Thus, rotation of the drive nut 50 by the drive motor 45 will cause the lead screw 95 to move in a proximal or distal direction along the longitudinal axis of the pipette 5.

Distal end 95b of lead screw 95 is attached to the proximal end of piston carrier 100 in a manner that prevents rotation of lead screw 95. The piston carrier 100 is located in a carrier holder 105, the carrier holder 105 being mounted within the inner housing 35 to be restrained from movement relative thereto. The piston carrier 100 is axially displaceable and reciprocally movable within the carrier holder 105 and relative to the longitudinal axis of the pipette 5, but limited in rotation.

The dispensing solenoid assembly 250 and the syringe plunger gripping mechanism 200 (both described in detail below) are located substantially within the plunger carrier 100. Thus, during linear displacement of the plunger carrier within the pipette 5, both the dispensing solenoid assembly 250 and the syringe plunger gripping mechanism 200 move with the plunger carrier 100.

For proper pipetting, the syringe 600 must be held securely on the pipette 5 and the motorized drive system 40 of the pipette 5 must be connected to the syringe piston 625 to reciprocate the syringe piston within the syringe capillary 605. These syringe retaining and plunger coupling functions are performed by the exemplary syringe retaining mechanism 150 and syringe plunger gripping mechanism 200 of the pipette 5, respectively.

The example syringe retaining mechanism 150 of the example pipette 5 may be better understood by additionally referring to fig. 13, which provides an enlarged cross-sectional view of the distal end of the example pipette 5. The exemplary syringe retaining mechanism 150 is shown as including a plurality of spaced apart syringe latch elements 155 that are secured within the distal end of the pipette 5, such as by a pin connection 185, so as to be pivotable over some range of rotational movement, but limited to axial movement. In this exemplary pipette 5, there are three syringe latch elements 155 (only two are visible in fig. 11), but in other embodiments a different number of latch elements may be used.

The syringe latch elements 155 of the syringe retaining mechanism 150 are shown in the closed position in fig. 11 and are held in the normally closed position by a resilient O-ring 160 or similar resilient element which encircles three syringe latch elements 155 and is located within a slot 165 provided in each latch element. The syringe latch element 155 is connected to the plunger carrier 205 using a mounting pin 185 (see fig. 20D), which allows the syringe latch mechanism to pivot during a syringe insertion procedure, as will be explained more fully below.

Each syringe latch element 155 of the syringe retaining mechanism 150 also includes a latch hook 170 at its distal end. The latch hooks 170 of the syringe latch element 155 are designed to engage the syringe retaining element on the syringe capillary when the syringe is inserted into the distal end of the pipette 5. For example, with respect to the arrangement of pipette 5 and syringe 600 shown in fig. 5, latch hooks 170 of syringe latch element 155 are designed to engage syringe retaining element 620 on syringe capillary 605 (e.g., along lower surface 640).

When the syringe retaining mechanism 150 secures the capillary tube of the syringe 600 to the pipette 5 and retains the capillary tube in a fixed position relative thereto, the syringe piston gripping mechanism 200 engages and releasably retains the head 630 of the syringe piston 625. To this end, the syringe plunger gripping mechanism 200 includes a plunger carrier 205 located substantially within the plunger carrier 100. As seen in greater detail in fig. 14A-14C, at least the interior shape of the plunger carrier 205 may substantially conform to the exterior shape of the syringe piston head 630. The example piston carrier 205 also includes a distally located actuation collar 285, the actuation collar 285 having a piston head retaining lip 210 and a plurality of radially spaced slits 215, the apertures 215 allowing passage of the piston head release element 305 of the example syringe ejection mechanism through the wall of the piston carrier into the arms 630a, 630b of the piston head 630, as described further below.

A plurality of spaced apart piston head release member guides 220 extend laterally outwardly from the actuation collar 285 of the piston carrier 205. As can be seen (see also fig. 17A-17B and 21A-21E), the inwardly facing face 220a of each piston head release element guide 220 has an inclined (cam) shape that guides movement of the distal portion of a respective one of the piston head release elements 305 during a syringe ejection operation. The outward facing surface 220b of each piston head release member guide 220 may facilitate axial movement of the piston carrier 205 within the inner housing 35 and/or may function to limit piston carrier rotation.

The proximal end 205a of plunger carrier 205 is configured to facilitate coupling of the plunger carrier to the distal end of armature shaft 265 of dispensing solenoid assembly 250. Thus, in the assembled pipette 5, the piston carrier 205 is capable of reciprocating with the piston carrier 100 by the motorized drive assembly 40 and is also capable of independently reciprocating within the piston carrier by the dispensing solenoid assembly 250.

The operation of the piston carrier 205 may be better understood by reference to the exploded views of fig. 15A-15B. Fig. 15A shows an exemplary syringe 600 with a piston head 630 inserted into the piston carrier 205 of fig. 13 and 14A-14C, wherein the piston head release element 305 of the exemplary syringe ejection mechanism is pivotably located in the slot 215 in the piston carrier. The piston head 630 preferably fits snugly within the interior of the piston carrier, and it is observed that the distal ends of the piston head arms 630a, 630b engage the piston head retaining lip 210 in the piston carrier 205, thereby preventing removal of the piston head 630 from the piston carrier. Thus, the piston head 630 is firmly grasped by the piston carrier 205 and ensures that the piston 625 of the syringe 600 will move axially with any axial movement of the piston carrier.

Referring now to fig. 16-17B, the process of inserting the exemplary syringe 600 into the exemplary pipette 5 may be observed. Fig. 16 shows a syringe 600 positioned below the distal end of the pipette 5 and substantially axially aligned therewith. The arrow indicates the direction of the engagement movement of the syringe 600 towards the pipette 5.

In fig. 17A, the syringe 600 has been partially inserted into the pipette 5. During insertion of the syringe 600, the piston head 630 of the syringe piston 625 begins to engage the piston carrier 205 of the syringe piston grasping mechanism 200. As can be seen in fig. 17A, during the syringe insertion process, the piston head arms 630a, 630b of the piston head 630 compress inwardly (i.e., undergo inwardly directed elastic deformation) via contact with the wall formed by the distal opening 290 in the actuation collar 285 of the piston carrier 205. The inward compression of the piston head arms 630a, 630b allows the syringe piston head 630 to pass through a distal opening in the actuation collar 285.

Fig. 17B depicts the partial engagement of the syringe 600 and the pipette 5 as the proximal end of the syringe 600 continues to be inserted into the distal end of the pipette 5 beyond the point shown in fig. 17A. This continued insertion of the syringe 600 results in the distal end of the syringe latch element 155 pivotally moving outwardly under the insertion force applied to the syringe 600. More specifically, when the syringe 600 is inserted into the pipette 5, the syringe retaining element 620 exerts a resulting outwardly directed force on the distal end of the syringe latch element 155 that is sufficient to overcome the inwardly directed force exerted on the syringe latch element by the O-ring 160.

As syringe 600 continues to be inserted into pipette 5, the proximal (upper) face of syringe retaining element 620 of syringe capillary 605 is in abutting contact with one or more springs 300 retained within pipette 5. As can be seen in fig. 17B, at the point of contact between the proximal (upper) face of the syringe retaining element 620 and the spring 300, the syringe retaining element 620 has preferably moved past the latch hook 170 of the syringe latch element 155 (although or admittedly slight compression of the spring may be required to reach that point), which allows the syringe latch element 155 to return to their normally closed position by the contractive force of the O-ring 160. As the syringe latch elements 155 return to their normally closed position (see also fig. 18-19), the flats 175 on each syringe latch hook 170 overlie and engage the lower surface 640 of the syringe retaining element 620, while the inwardly facing surface 180 of each syringe latch element 155 is pressed against the peripheral edge 635 of the syringe retaining element, preferably by the contractive spring force of the O-ring 160. The syringe capillary 605 is thereby trapped against the pipette 5 and releasably locked to the pipette 5, which means that the syringe capillary is also held firmly in a fixed position relative to the pipette.

After releasably locking the syringe 600 to the pipette 5, continued application of an insertion force on the syringe causes the syringe to move slightly but additionally proximally into the pipette as shown in fig. 17B and described above. This additional movement of the syringe 600 is due to the insertion force exerted on the syringe compressing the spring 300 in the pipette.

As shown in fig. 18, additional proximal movement of the syringe 600 into the pipette 5 allows the syringe's piston head 630 to become fully inserted into the plunger carrier, after which the piston head arms 630a, 630b will resiliently return to their normal resting position and engage with the piston head retaining lip 210 located in the actuation collar 285 of the plunger carrier, as shown in fig. 18. The engagement of the piston head arms 630, 630b with the actuation collar 285 retains the piston head 630 in the piston carrier 205. It can also be seen in fig. 18 that in this exemplary embodiment of the pipette 205, the piston head 630 fits snugly inside the piston carrier 205.

In fig. 18-19, the syringe 600 is fully mounted to the pipette 5. In the fully installed position, the syringe 600 is releasably locked to the pipette 5 as described above, and the syringe's plunger head is fully engaged by the syringe plunger gripping mechanism 200 of the pipette. Once placed in the fully installed position shown, the syringe 600 may be used to aspirate and dispense fluid.

In addition to providing additional insertion of the syringe 600 into the pipette 5 after the syringe retaining element 620 of the syringe capillary 605 has reached the engaged position with the syringe retaining mechanism 150 of the pipette, the spring 300 also provides increased retention safety and secure engagement of the syringe 600 into the pipette 5. More specifically, with the syringe 600 mounted to the pipette 5, the spring 300 abuts the upper surface of the syringe retaining element 620 and applies a distally directed force, which presses the lower surface 640 of the syringe retaining element tightly against the flats 175 of the hooks 170 of the syringe latch element 155. The distally directed force exerted by the spring 300 also pushes the piston head 630 toward the distal end of the pipette 5, which presses the distal ends of the piston head arms 630a, 630b tightly against the piston head retaining lip 210 in the actuating collar 285 portion of the piston carrier 205. Thus, any possible accidental movement of the syringe retaining element 620 relative to the syringe latch element 155 of the syringe retaining mechanism 150 and/or movement of the piston head 630 relative to the piston carrier 205 is resisted by the axial force exerted by the spring 300, thereby further securing the syringe 600 to the pipette 5. Spring 300 may be, for example, but is not limited to, a sheet metal spring. Other types of springs may also be used.

Because the external piston pipette syringe is disposable, i.e., intended to be discarded after completion of the relevant pipetting operation, the exemplary syringe 600 must be capable of being ejected from the pipette 5. As can be best appreciated from an exploded perspective view of fig. 20A-20D and a review of the cross-sectional views of fig. 21A-21F (see also fig. 13, 15A-15B, and 17A-19), the pipette 5 is provided with an exemplary syringe ejection mechanism for this purpose. In general, the syringe ejection mechanism is operable to disengage the syringe retaining element 620 of the syringe 600 from the syringe retaining mechanism 150 and to disengage the syringe piston head 630 from the plunger carrier 205, after which the syringe will automatically be ejected from the pipette 5. As explained in more detail below, the syringe ejection mechanism of the exemplary pipette 5 generally includes a motorized drive assembly 40 and lead screw 95, a plunger carrier 100 and wedge syringe latch element release portion 335 thereof, a syringe latch element 155, a plunger head release element guide 220 on an actuation collar portion 285 of a plunger carrier 205, and a plurality of plunger head release elements 305.

Fig. 20A provides substantially the same view of the piston head 630 of the exemplary syringe 600 inserted into the piston carrier 205 shown in fig. 15A, except that the piston carrier 205 has been removed in fig. 20A for further clarity. It can be seen in fig. 20A that the piston head release element 305 of the syringe ejection mechanism (which is shown in fig. 15A as being aligned with the slot 215 in the plunger carrier 205) is arranged to at least partially cover the opposing arms 630A, 630b of the syringe piston head 630 when the piston head is inserted into the plunger carrier 205. Each exemplary piston head release member 305 may include a roller 310 at its distal end. The rollers 310 serve to reduce friction between the piston head release member 305 and the inwardly facing inclined surface 220a of each piston head release member guide 220 of the piston carrier 205 and between the piston head release member and the arms 630a, 630b of the syringe piston head 630. However, in other syringe ejection mechanism embodiments, roller 310 may be eliminated, for example, by using a low friction material or the like.

The piston head release member 305 is pivotally secured within the piston carrier 100 by a pin 315 such that inward movement of the proximal end of the piston head release member will cause outward movement of the distal end of the piston head release member. Although not shown in fig. 20A-20D for clarity, the piston head release members 305 are maintained in a normally open position by an O-ring 320 or another similar resilient member (see, e.g., fig. 13, 16-19, 21A-21B, 22 and 24), the O-ring 320 or another similar resilient member encircling the piston head release members 305 and being located within a groove 325 provided in each piston head release member. The O-ring 320 applies an inwardly directed force to the proximal end of each piston head release member 305 such that the normally open position of the piston head release members is the position where the distal ends of the piston head release members are pushed away from the piston carrier 205.

An exemplary syringe ejection operation is shown in fig. 21A-21F. During a syringe ejection operation, the plunger carrier 205 is placed against the hard stop 225 and the motorized drive assembly 40 is commanded to cause the plunger carrier 100 to move distally a predetermined distance. In this exemplary embodiment of the pipette 5, the piston carriage moves about 3.25mm in the distal direction during the syringe ejection operation, but the distance may be different in other embodiments.

Because the piston carrier 205 is constrained against further distal axial movement when against the hard stop 225, such distal axial displacement of the piston carrier 100 will result in distal axial displacement of its latch element release portion 335 relative to the piston carrier and piston head release element 305 pivotably connected to the piston carrier 100.

Referring to fig. 21A, it can be observed that as the plunger carrier 100 moves distally, the syringe latch element release portion 335 of the plunger carrier comes into contact with the proximal end of the syringe latch element, which syringe latch element release portion 335 is arranged to align with the syringe latch element 155 and is positioned to move in the space between the syringe latch element and the plunger carrier 205. Likewise, distal movement of the piston carrier 100 creates contact between the roller 310 of the piston head release element 305 and the inwardly directed angled face 220a of each piston head release element guide 220 associated with the actuation collar 285 of the piston carrier 205.

Fig. 21B shows that continued distal movement of the piston carrier 100 ultimately results in sufficient contact between its wedge-shaped syringe latch element release portion 335 and the proximal end of the syringe latch element 155 to cause the distal end of the syringe latch element to pivot outwardly about the mounting pin 185 and resist the counteracting contractive force of the O-ring 160 and the axial force of the spring 300. As shown above, this pivotal movement of the syringe latch element 155 causes its latch hook 170 to disengage from the syringe retaining element 620 of the syringe 600 (also shown in fig. 20D), thereby releasing the syringe retaining element and syringe capillary 605 from retaining engagement with the pipette 5.

Referring now to fig. 21C-21E, it can be further observed that additional distal movement of the piston carrier 100 causes the rollers 310 of the piston head release element 305 to follow the correspondingly aligned inclined faces 220a of the piston head release element guide 220 of the piston carrier actuation collar 285. Thus, the distal end of the piston head release member 305 pivots inwardly toward the piston carrier 205. As shown in fig. 21D-21E, this inward movement of the distal end of the piston head release member 305 causes the roller 310 attached thereto to enter the plunger carrier 205 through the slit 215 therein and contact and begin to compress (deform) the opposing arms 630a, 630b of the syringe piston head 630 inwardly.

As shown in fig. 21E, the amount of inward deformation of the syringe piston head arms 630a, 630b by the piston head release element 305 is ultimately sufficient to disengage the arms from the piston head retaining lip 210 in the actuation collar 285 of the piston carrier 205. This disengagement of the syringe piston head arms 630a, 630b releases the piston head 630 from the piston carrier 205 and allows the syringe piston head 630 to thereafter return in a proximal-to-distal direction through the distal opening 290 in the piston carrier.

As the piston head arms 630a, 630b are compressed inwardly by the distal end of the piston head release member 305 during downward movement of the piston carrier 100, the proximally located ejection tab 340 of each piston head release member simultaneously exerts a distally directed (ejection force) on the top of the piston head 630. This distally directed force results in a similar displacement of the piston head 630 and capillary 605 and also results in the free ends of the piston head arms 630a, 630b entering the distal opening 290 in the piston carrier 205.

With the syringe elements positioned as described above, the entire syringe 600 may be ejected from the pipette 5. In this exemplary embodiment, the actual ejection of the syringe 600 occurs by first retracting the piston carrier 100 (see fig. 21F) to its original position, which retraction movement allows the piston head arms 630a, 630b to clear the roller 310 of the piston head release element 305 during ejection. Thereafter, physical ejection may occur automatically due to gravity in combination with the axial force exerted by spring 300 on syringe retaining element 620, and/or syringe 600 may be removed from pipette 5 by a user. The ejection movement and return movement of the piston carriage 100 may occur automatically in accordance with an ejection operation program command from the pipette controller 90.

Various states and operations of the exemplary pipette 5 will now be described with reference to fig. 22-24. Fig. 22 shows the home position of the exemplary pipette 5. In the home position, the distal end of the piston carrier 205 is substantially held against the hard stop 225, it being understood that the holding against the hard stop allows for a minimum assembly gap between the hard stop and the piston carrier. Likewise, in the home position of pipette 5, armature 260 of dispensing solenoid assembly 250 abuts against the bottom wall of core 270 at its distal hard stop, and coil 260 of dispensing solenoid assembly is not energized. In the home position of the pipette 5, the piston carrier 100 is distally positioned such that there is a slight gap 400 between the piston carrier 205 and the roller 310 of the piston head release element 305, such that there is no unintended interference between the roller and the piston head 630 when inserting a syringe into the pipette 5. A home position sensor 405 may be provided to indicate to the controller 90 that the piston carriage is in a home position.

The aspiration function of the exemplary pipette is illustrated in fig. 23A-23B by using the exemplary pipette 5 and syringe 600 assembly of fig. 2. Fig. 23A shows an exemplary pipette 5 in the home position, described immediately above. It can further be observed that when the pipette 5 is in the home position and the syringe 600 is mounted thereto, the piston head 630 of the syringe piston 625 is engaged with the piston carrier 205 of the pipette, but the piston has not been intentionally moved toward the proximal end of the pipette (except for any occasional axial movement necessary to engage the piston head with the piston carrier). Thus, the piston 625 remains substantially against the distal interior of the syringe capillary 605.

The pipette assembly of fig. 23B is depicted in a ready-to-dispense or full aspirate position, i.e., the pipette 5 is shown as having performed an aspiration function by which a full syringe volume of a fluid of interest is aspirated into the syringe 600. It is also possible to aspirate less than the full syringe volume. To aspirate fluid, the tip 610 of the syringe 600 is placed in the fluid and an aspiration procedure is initiated via the user interface portion 15 of the pipette or a user manipulating the actuator to energize the motor 45 of the motorized drive assembly 40 to drive the piston carriage 100 and associated components connected thereto a desired distance toward the proximal end of the pipette 5. This proximal axial movement of the plunger carrier 100 produces a similar movement of the solenoid body 260, which in turn produces a similar movement of the armature 260 and the plunger carrier 205 attached to the armature shaft 265. Since the head 630 of the syringe piston 625 is engaged with the piston carrier 205, the syringe piston also moves proximally an equal distance within the syringe capillary 610, which draws the fluid of interest into the now evacuated capillary.

When the example pipette 5 is in the full aspiration position, such as shown in fig. 23B, various ones of the pipette components will still reside in the same position relative to the other components as when the pipette was in the home position. For example, the armature 260 of the dispensing solenoid assembly 250 is held against the bottom wall of the bore 270 at its distal hard stop 275 and the coil 260 of the dispensing solenoid assembly is not energized. Likewise, when the pipette 5 is in the aspiration position, the gap 400 between the piston carrier 205 and the roller 310 of the piston head release member 305 is also maintained.

The actions of the various pipette components during the dispense operation are described with reference to fig. 23B and 24. The specific manner in which the dispensing member of the pipette 5 is actuated during the dispensing operation depends on the selected dispensing volume. That is, it is preferable to perform small volume dispensing using solenoid assembly 250, while it is preferable to perform large volume dispensing using electric drive assembly 40 alone or in combination with solenoid assembly 250 using electric drive assembly 40.

In different pipette embodiments, the limit between the small dispensing volume and the large dispensing volume may vary, as the maximum volume of fluid that may be dispensed by solenoid assembly 250 alone depends on the maximum stroke of solenoid armature 260, which in turn is determined by the maximum distance piston carriage 100 moves from the full aspiration position toward the distal end of pipette 5 before causing accidental dispensing of fluid from syringe 600. For purposes of illustration and not limitation, in this exemplary embodiment of the pipette 5, the maximum piston carrier displacement that can occur without causing unintended dispensing is 0.5mm.

Because the solenoid body 255 is connected to the plunger carrier 100, the solenoid body moves toward the distal end of the pipette 5 during similar movement of the plunger carrier. However, because the solenoid armature 260 is free floating within the bore in the solenoid body 255, because the solenoid armature is also connected to the plunger carrier 205 through the armature shaft 265, and because the plunger carrier is biased toward the proximal end of the pipette 5 by the pressure of the aspiration fluid in the syringe 600 pushing the syringe plunger 670, the solenoid armature remains in its current position and does not move with the plunger carrier and solenoid body during the foregoing movement of the plunger carrier. This creates a solenoid stroke gap 280 between the distal face 260b of the armature 260 and the bottom wall of the bore 270 in the solenoid body 255, the distance of the solenoid stroke gap 280 being comparable to the aforementioned distal movement of the plunger carrier 100 (up to 0.5mm in this example). The solenoid stroke gap 280 is the maximum stroke of the solenoid armature 260 and is thus also 0.5mm in this exemplary embodiment of the pipette 5.

A maximum stroke of 0.5mm of solenoid armature 260 results in a corresponding dispensed volume of about 0.01 (1%) of the total volume of a given syringe mounted to the pipette. Thus, for this particular example, a small dispense volume would be considered to be about 0.001ml or less of 0.1ml volume syringe 500, about 0.01ml or less of 1.0ml volume syringe 550, about 0.1ml or less of 10ml volume syringe 600, about 0.25ml or less of 25ml volume syringe 650, and about 0.5ml or less of 50ml volume syringe 700. In this particular example, dispense volumes that are greater than these approximately small dispense volumes will be considered large dispense volumes. Note that the minimum deliverable dispense volume of motor drive assembly 40 alone or motor drive assembly 40 in combination with solenoid assembly 250 is generally the same as the maximum deliverable dispense volume of solenoid assembly alone (although some overlap may exist).

At the beginning of the small volume dispense operation, the controller 90 of the pipette 5 instructs the motorized drive assembly 40 to move the piston carriage 100 a distance (less than or equal to 0.5mm, depending on the selected small volume to be dispensed) toward the distal end of the pipette. The specific distance the piston carrier 100 moves depends on the selected small volume of fluid to be dispensed. In this exemplary pipette 5, the maximum piston carrier 100 displacement distance and resulting solenoid armature 260 stroke is 0.5mm.

With the piston carriage 100 moved to the low volume dispensing position and thus creating a gap 280 in the solenoid assembly, the controller 90 temporarily energizes the solenoid body 255, as will be appreciated by those skilled in the art, the solenoid body 255 generates a magnetic field that rapidly and forcefully triggers the armature 260 toward the distal end of the pipette 5 and ceases to contact the armature hard stop 275. This rapid and distally directed movement of the solenoid assembly armature 260 produces a similar movement of the plunger carrier 205 and syringe plunger 625 connected thereto, which causes a selected dispense volume of fluid to be ejected from the tip 610 of the syringe 600 at a sufficient velocity to break any surface tension between the fluid and the inner wall surface of the syringe capillary 610, thereby ensuring that the last drop of fluid is dispensed without touching the syringe tip 610 on the receiving container. The process of moving the piston carriage 100 and dispensing a small fluid volume by triggering the solenoid assembly 250 may be repeated until the aspiration volume is completely dispensed or until the desired number of dispensing operations have been completed.

It will be appreciated from the foregoing description that bulk dispensing in the context of an exemplary pipette is simply dispensing a volume of fluid that is greater than the maximum possible volume of fluid that can be dispensed by actuation of the solenoid assembly alone. Thus, with respect to the example pipettes 5 and example syringes 500, 550, 600, 650, 700 shown and described herein, the bulk volume dispensing encompasses greater than about 0.001ml of the 0.1ml volume syringe 500, 0.01ml of the 1.0ml volume syringe 550, greater than about 0.1ml of the 10ml volume syringe 600, greater than about 0.25ml of the 25ml volume syringe 650, greater than about 0.5ml of the 50ml volume syringe 700. The maximum volume that can be dispensed during a single large volume dispense operation is the entire volume of a given syringe 500, 550, 600, 650, 700.

As mentioned above, two methods of bulk dispensing are possible. According to the first method, the bulk dispensing is performed using only the electric drive assembly 40, while according to the second method, the bulk dispensing is performed using the electric drive assembly 40 in combination with the solenoid assembly 250. The general volume integration method employed may depend on the specific configuration of the pipette and may also depend on the characteristics of the fluid to be dispensed.

According to the first method of the bulk volumetric dispensing method described above, it has been found that dispensing may be performed without assistance from solenoid assembly 250 when dispensing large fluid volumes, or at least when dispensing fluid volumes that fall within a certain volume range of the entire large volume dispensing range of exemplary pipette 5. More specifically, it has been found that when dispensing large volumes of fluid, the piston carrier 100 alone, plus the increase in fluid velocity due to the fluid in the syringe 600 being forced from the larger diameter capillary 605 through the much smaller diameter tip 610 and orifice 615, can be sufficient to produce a fluid dispensing velocity large enough to overcome any surface tension between the fluid and the inner wall surface of the syringe capillary to ensure that the last drop of fluid is dispensed from the syringe without touching the syringe tip on the receiving container.

The pipette controller 90 may automatically direct bulk dispensing solely by movement of the piston carriage 100 according to a user selected dispensing program, a syringe mounted to the pipette 5, a dispensing volume associated with the selected dispensing program, and the like. In any event, upon initiation of a bulk dispense operation solely by movement of the piston carrier 100, the controller 90 determines the displacement of the piston carrier required to eject the selected bulk fluid to be dispensed. The motorized drive assembly 40 then rotates the drive nut 50 to linearly displace the lead screw 95 and the piston carrier 100 until the gap 400 between the piston carrier 205 and the roller 310 of the piston head release member 305 is closed, which results in a similar displacement of the piston carrier 205 and the syringe piston 625 engaged therewith. Thus achieving the dispensing of the selected large fluid volumes.

Alternatively, bulk dispensing may be achieved by a combination of piston carriage movement and triggering of solenoid assembly 250. As with the first bulk volume fitting method, the second bulk volume fitting method may be automatically selected by the pipette controller 90 based on a user-selected dispensing program, a syringe mounted to the pipette 5, a dispensing volume associated with the selected dispensing program, and the like. In any event, upon commencing the second high volume dispensing operation, the controller 90 again determines the displacement of the piston carrier required to eject the selected high volume of fluid to be dispensed. The motorized drive assembly 40 then rotates the drive nut 50 to linearly displace the lead screw 95 and the piston carrier 100 a desired distance, which results in a similar displacement of the piston carrier 205 and syringe piston 625 engaged therewith, and a corresponding dispensing of fluid from the syringe.

Upon completion of the movement of the plunger carrier 100 and the corresponding dispensing of fluid from the syringe 600, the controller 90 temporarily energizes the solenoid body 255, which triggers the armature 260 of the solenoid assembly 250 toward the distal end of the pipette 5 and ceases contact with the armature hard stop 275. This rapid and distally directed movement of solenoid assembly armature 260 produces a similar movement of plunger carrier 205 and syringe plunger 625, which will dispense any undispensed fluid that remains in syringe tip 610 due to surface tension between the fluid and the inner wall surface of syringe capillary 610. Thus, it may be ensured that the last drop of the volume of fluid intended to be dispensed is actually dispensed and does not inadvertently remain in the syringe tip 610. When the volume of fluid dispensed during a bulk fluid dispensing operation is less than the total volume of fluid in syringe 600, the dispensing operation may be repeated until the desired number of dispensing operations have been completed, until the fluid volume is exhausted, or until the remaining fluid volume is insufficient to perform another dispensing operation of the desired fluid volume.

The dispensing operation using the exemplary pipette 5 may be accomplished via a selected pipetting program that operates the pipette in an automated (automatic) mode or via a manual mode. As described above, the user can access and selectively activate the desired suction measuring range via the user interface portion 15 of the pipette 5.

The automatic mode allocation may include a number of different and alternative allocation procedures. A simple example of such a dispensing process results in aspiration of the entire syringe volume of fluid followed by dispensing of the entire aspirated fluid volume in one dispensing operation.

In another example automatic mode dispensing sequence, a volume of fluid is aspirated into the syringe 600, as previously described, and then dispensed in multiple doses of equal volume until the desired number of dispensing operations have been completed, until the fluid volume is exhausted, or until the remaining fluid volume is insufficient to perform another dispensing operation of the selected fluid volume. In yet another example automatic mode dispensing procedure, a volume of fluid is aspirated into the syringe 600, as previously described, and then dispensed in multiple doses of variable volume until the desired number of dispensing operations have been completed, until the fluid volume is exhausted, or until the remaining fluid volume is insufficient to perform another dispensing operation of the desired fluid volume. In yet another example automatic mode dispensing process, as previously described, a volume of fluid is aspirated into the syringe 600 and then dispensed in multiple doses of equal or variable volume until some fraction (e.g., 50%) of the aspirated volume has been dispensed. At this time, another aspiration operation is performed to increase the volume of fluid in the syringe 600, and dispensing is performed again. This process may be repeated until the desired number of dispense operations have been completed, until the fluid volume is exhausted, or until the remaining fluid volume is insufficient to perform another dispense operation of the selected fluid volume.

In any of the above exemplary automatic mode dispensing procedures, the aspirated fluid volume may be the entire fluid volume of the installed syringe, or some smaller volume. The dispensing of fluid may be accomplished by activating solenoid assembly 250 alone, by moving piston carrier 100 alone, or by a combination thereof. As described above, the dispensing method used may be selected based on the pipette configuration (e.g., resolution), the syringe installed, the volume of dispense required, some combination thereof, and/or other factors.

The menu of exemplary procedures that may be performed in the automatic mode of the exemplary pipette may also include a titration procedure. As will be appreciated by those skilled in the art, a titration procedure using the exemplary pipette 5 generally involves adding a quantity of titrant that has been aspirated into the syringe 600 to a container of analyte and indicator until the indicator changes color or some other observable property is achieved, indicating that the reaction has reached a neutralized state. Since the amount of titrant that needs to be added to the analyte solution to achieve neutralization is typically unknown, the titration procedure may include a titration volume counter that indicates the volume of titrant that has been dispensed. The counter may be resettable to allow for multiple titration operations of titrant from a single inhalation volume.

The dispensing operation may also be performed by the user in manual mode instead of the controller 90 of the pipette 5 in automatic mode. In manual mode, a user operates the motorized drive assembly 40 to create a rapid or slow aspiration and/or dispense of fluid from the syringe 600.

An exemplary pipette may also have fluid viscosity detection capabilities. More specifically, the viscosity of the fluid of interest may be determined indirectly, such as by providing the pipette with an appropriate electrical circuit 350 (see fig. 5B) or other means for monitoring and analyzing the increased current consumption caused by the drive motor due to the increased motor torque required to move the syringe piston relative to the syringe capillary tube during a aspiration or dispense operation; by using a load cell 355 (see fig. 5B) provided, it measures the force required to move the syringe piston relative to the syringe capillary tube during a aspirating or dispensing operation; by a mechanical spring; or via another technique as will be appreciated by those skilled in the art.

When utilizing current consumption monitoring techniques, the value of current consumption may be used to classify the viscosity of the fluid, and the pipette controller may adjust the dispensing operating parameters of the pipette based on the identified fluid viscosity class. For example, but not limiting of, if it is determined that the fluid of interest has a low viscosity, the controller may apply the normal dispense settings during the fluid dispense operation. If it is determined that the fluid of interest has a medium viscosity, the controller may increase the voltage of the drive motor and solenoid assembly, and may also implement a suck back mode (retraction of the lead screw that draws air into the syringe capillary), typically without requiring a suck back aliquot during dispensing of the low viscosity fluid. If the fluid of interest is determined to have a high viscosity, the controller may disable the solenoid assembly, so dispensing may be performed only via movement of the piston carriage, and may also inform the user that syringe tip contact will be required to ensure that no liquid remains in the syringe tip. The exemplary categories of what viscosity levels fall into "low," "medium," and "high" will depend on the characteristics of the solenoid assembly 250 (e.g., maximum drive strength) and the size of the possible tip orifices 515, 565, 615, the diameter of the capillary 605, and the sealing resistance associated with the piston 625 in the capillary 605. Other factors may also be relevant.

In the pipette according to the invention, a DC motor is used in the electric drive assembly 40; in general, DC motors consume more current during pumping operations to obtain a more viscous liquid. In particular, it has been found that the relationship between viscosity and current consumption is strongest near the bottom position of the piston 625 in the capillary 605, because the flow path there is the most severely constrained, so in embodiments of the pipettor, during aspiration operations, current measurements are taken over the first thirty percent of travel segment representing the maximum travel of the piston and integrated therewith to identify the load characteristics associated with the viscosity of the aspirated liquid and the syringe 600 in use. The load characteristics are then used to reference a look-up table that determines the piston speed requirements that allow for the application of the non-contact dispensing, the optimal solenoid voltage to be applied, and ultimately whether the non-contact dispensing can be performed. If no contactless dispensing can be performed, the user will typically be notified as described above, and the pipette 5 will switch to a "touch required" dispensing operation mode, in which a trigger shut down is required.

Accurate switching between contact and non-contact dispensing is particularly important for pipettes according to the present invention, as non-contact dispensing starvation may tend to accumulate from one aliquot to the next when the solenoid assembly is driven with insufficient force to completely eject the desired amount of liquid and strike its hard stop. Thus, the pipette preferably uses a relatively conservative setting for contact/non-contact determination and solenoid voltage, and defaults to dispensing of the required contact when there is any reasonable likelihood that the solenoid cannot be driven with sufficient force. It should be noted that if the solenoid is not used to dispense the desired aliquot, it is often necessary to adjust the movement of the plunger via the motorized drive assembly to compensate for the stroke length that would otherwise be driven by the solenoid assembly.

Overdriving solenoid assembly 250 is also disadvantageous because it may result in undesirable aerosolization of the dispensed aliquot. Thus, the load characteristics and the look-up table may be advantageously used to ensure that the solenoid is properly driven, even for samples having low viscosity.

An exemplary pipette, such as exemplary pipette 5, may also be programmed to perform a discard dispensing function. The discard dispensing function is preferably part of a pipetting process when using the exemplary pipettor 5 and may be implemented by the controller 90. In general, the discard dispensing function is operable to remove any backlash and address any manufacturing and/or assembly tolerance issues in the drive, solenoid, and overall system, and may also remove any air trapped near the distal end of the syringe tip. The controller 90 may be programmed to activate the discard dispensing function after each aspiration operation. The waste dispense function may also be activated at any time that all fluid previously aspirated into the syringe is fully dispensed. The dispensed volume that is discarded will vary based on the viscosity of the liquid used and the syringe configuration.

Another possible exemplary pipette feature that may be provided according to the present general inventive concept is an automatic syringe identification function. Because the exemplary pipettes may be used with many different volumes of syringes, it should be appreciated that it would be beneficial if the exemplary pipettes could automatically identify syringe volumes when the syringes are mounted to the pipettes. This capability would allow the controller of the pipette to automatically select the appropriate operating parameters for a given syringe volume, simplifying the setup process and potentially eliminating operator errors associated with erroneously identifying the volume of the syringe being used.

In one exemplary embodiment, color coding is used as a mechanism for syringe identification. More specifically, each syringe volume is associated with a different color, and the area of the corresponding color is located on the syringe.

Using the exemplary syringes 500, 550, 600, 650, 700 depicted in fig. 6A-10B as an example, color bands 450, 455, 460, 465, 470 corresponding to the volume of each given syringe are placed along the upper shoulders 520a, 570a, 620a, 680a, 730a of the syringe retaining elements 520, 570, 620, 680, 730. In some embodiments, the color band of a given syringe may extend only partially around the syringe retaining element, while in other embodiments the color band may extend around the entire circumference of the syringe retaining element. Color coding may also be provided in the form of continuous blocks of color, discrete blocks of color, or any other readable form (such as, but not limited to, a collection of dots, segment lines, etc.). Colors may also be molded into the material from which a given syringe retaining element is made. Furthermore, in alternative embodiments, color coding may be placed on the syringe piston instead of or in addition to the syringe retaining element of a given syringe.

As shown in fig. 24, one or more color sensors 475 may be located within the distal end of exemplary pipette 5 and may be configured and positioned to image color bands on syringe retaining elements 520, 570, 620, 680, 730 of exemplary syringes 500, 550, 600, 650, 700. Upon mounting the exemplary syringe 500, 550, 600, 650, 700 to the pipette 5, the color sensor 475 images the color bands 450, 455, 460, 465, 470 and sends a signal to the pipette controller 90 indicating the color of the color bands. The controller 90 is provided with appropriate data (e.g., a look-up table, etc.) -for example, through a process of preliminary and offline color identification and registration operations using the color sensor 475-analyzing the signals received from the color sensor 475 to identify the color of the color bands 450, 455, 460, 465, 470 and, thus, the volume of the installed syringes 500, 550, 600, 650, 700. As described above, in the case of identifying syringe volume, the controller 90 may continue to automatically set any of a variety of pipetting parameters and/or indicate syringe volume to the user of the pipetter 5.

In the exemplary pipette and syringe embodiments presented herein, the upper shoulders 520a, 570a, 620a, 680a, 730a of the syringe retaining elements 520, 570, 620, 680, 730 are preferably chamfered at an angle (e.g., between 30 ° and 60 ° relative to the upper surface of the retaining elements). The chamfered upper shoulders 520a, 570a, 620a, 680a, 730a of the syringe retaining element 520, 570, 620, 680, 730 facilitate insertion of the syringe retaining element into the pipette 5. In addition, the chamfered upper shoulders 520a, 570a, 620a, 680a, 730a of each syringe retaining element provide an angled surface from which light emitted by the emitter portion (illumination source) 480 of the color sensor 475 may reflect toward the detection face 485 of the color sensor 475, which detection face 485 may be mounted to a pipette at a corresponding angle. The use of such a chamfered shoulder also allows the use of a vertical pad printing process to apply the ink ribbon, which is the most efficient printing mode.

While color sensing using a color sensor 475 to read color codes on the chamfered upper shoulders 520a, 570a, 620a, 680a, 730a of the syringe retaining elements 520, 570, 620, 680, 730 is shown and described herein for purposes of illustration, it should be understood that the exemplary pipette embodiments are not limited to such an arrangement. For example, but not limited to, the sensor may alternatively be positioned to read color coding, printing, etc. on other areas of the syringe.

Although certain embodiments of the present inventive concept have been described in detail above for the purpose of illustration, the scope of the present inventive concept is not to be considered limited by such disclosure and modifications may be made without departing from the spirit of the inventive concept as evidenced by the appended claims.

Claims

1. A method of operating an electric hand-held, external piston pipette comprising a solenoid assembly, a syringe and a piston, comprising the steps of:

operating an electrically driven assembly to move the piston in the syringe and perform a pumping operation to pump a liquid sample into the syringe;

measuring a characteristic of the electric drive assembly during at least a portion of the pumping operation;

Determining a dispensing operation parameter comprising a voltage applied to the solenoid assembly to effect non-contact dispensing of an aliquot of a liquid sample from the characteristics by applying a look-up table to the characteristics of the electrically driven assembly; and

an aliquot is dispensed from the liquid sample according to the dispensing operating parameter.

2. The method of claim 1, wherein the electric drive assembly comprises a DC motor, and wherein the characteristic of the electric drive assembly comprises a drive current of the DC motor measured during the pumping operation.

3. The method of claim 2, wherein the characteristics of the electric drive assembly include a drive current of the DC motor integrated over a portion of the pumping operation.

4. A method according to claim 3, wherein the portion comprises a first length of travel from a bottom position of the piston in the syringe.

5. The method of claim 4, wherein the portion comprises a first thirty percent travel from a bottom position of the piston in the syringe.

6. The method of claim 2, wherein characteristics of the electric drive assembly are used to determine load characteristics of the DC motor, the load characteristics being used in the step of determining the dispensing operating parameters from the characteristics.

7. A method of operating an electric hand-held, external piston pipette comprising a solenoid assembly, a syringe and a piston, the method comprising the steps of:

determining a dispensing operation parameter by applying a look-up table to a characteristic of the electrically driven assembly based on the characteristic, wherein determining the dispensing operation parameter comprises determining whether an aliquot of liquid sample can be dispensed contactlessly using the solenoid assembly; and

8. The method according to claim 7, wherein if non-contact allocation is not possible, the method comprises the further step of:

notifying a user of the electric hand-held external piston type pipette that non-contact distribution cannot be performed; and

the power hand-held external piston pipette is switched to a dispensing mode requiring contact prior to dispensing an aliquot.

9. The method of claim 8, wherein if non-contact dispensing is not possible, the step of dispensing an aliquot includes operating the motorized drive assembly and leaving the solenoid assembly de-energized to dispense the aliquot.

10. The method of claim 7, wherein if non-contact dispensing is enabled, the step of dispensing an aliquot includes operating the motorized drive assembly and energizing the solenoid assembly to dispense the aliquot.