JP7475440B2 - Powered positive displacement dispensing method - Google Patents

Description

An exemplary embodiment of the general inventive concept relates to a hand-held, powered, positive displacement pipette and pipette assembly, including a novel syringe for said pipette and associated mechanisms for releasable retention, ejection, and proper automatic identification of said syringe.

As one skilled in the art will appreciate, pipette designs are generally either air displacement or positive displacement. In contrast to air displacement pipettes, where a cushion of air separates the aspirated liquid from the pipette piston, positive displacement pipettes are designed so that there is direct contact between the pipette piston and the aspirated liquid.

The design of the positive displacement pipette eliminates potential inaccuracies of air displacement pipettes that may result from the effect of various liquid properties and/or environmental conditions on the air cushion of the air displacement pipette. For example, altitude changes, evaporation, and other conditions to which the air displacement pipette is subjected can affect the accuracy of the air displacement pipette.

Although positive displacement pipettes have the aforementioned advantages over air displacement pipettes, known positive displacement pipettes have drawbacks. One of these is their inability to accurately dispense small amounts of liquid, including less than 1 μl, in a non-contact manner. Specifically, when dispensing small amounts of liquid, the liquid tends to adhere to the inside of the pipette tip after the dispensing stroke, and the pipette tip must then be physically touched off of the liquid receptacle to expel the adhered liquid from the pipette tip.

Positive displacement pipettes also do not allow for the reuse of the pipette piston due to the direct contact between the pipette piston and the target liquid during normal use. As a result, positive displacement pipettes typically use "consumables" in the form of disposable syringes that contain not only a hollow barrel (capillary) with a tip portion, but also a piston that resides within and seals the capillary, such that the piston can be reciprocated within the capillary by the pipette to aspirate and dispense a desired amount of the target liquid while the capillary and piston are releasably attached to the pipette. Once the pipetting operation is completed, the syringe is typically detached from the positive displacement pipette and discarded.

The complexities involved in inserting, holding, and ejecting a positive displacement pipette syringe are greater than those involved with typical air displacement pipette tips, which are structurally much simpler and are generally held in the dispensing end of the air displacement pipette body by simple friction. In a positive displacement pipette, the syringe must be held securely in the pipette body until it is intended to be ejected, while the piston is appropriately positioned within the pipette for releasable engagement and reciprocation by the pipette's aspirating/dispensing mechanism.

There is a need for a positive displacement pipette that can accurately and repeatedly dispense various amounts of liquid, including minute amounts of liquid, without contact. There is also a need for a positive displacement pipette that has an improved mechanism by which a syringe can be easily and securely attached to the pipette, releasably retained by the pipette, and expelled from the pipette. An exemplary positive displacement pipette according to the general inventive concept, and various features of the exemplary positive displacement pipette, meet these needs.

An exemplary embodiment of a handheld powered positive displacement pipette in accordance with the general inventive concept will generally include a substantially hollow body, preferably shaped to be ergonomically grasped by a user and serving as a housing for the 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 connecting end for a syringe.

An exemplary pipette generally further includes a motorized drive assembly, a dispensing solenoid assembly, a syringe retention mechanism, a syringe piston gripping mechanism, and a syringe ejection mechanism, all of which are contained within the pipette body. At least a portion of the aforementioned components may also reside within an internal housing disposed within the pipette body.

At the distal end of the pipette is releasably attached a syringe for aspirating and dispensing the desired liquid. Syringes may be provided in a variety of capacities. However, regardless of volume, each syringe generally includes a hollow outer barrel (capillary) that may be tubular in shape or some other shape, including but not limited to oval or round. The capillary includes a tip having an orifice (hole) at the distal end and functions to contain the fluid sample to be dispensed. At the tip of each capillary is a syringe-retaining element, which may be an integral part of the capillary. The shape and dimensions of the syringe-retaining member are adapted to the syringe-retaining mechanism of the pipette.

Each syringe also includes a piston having a first fluid contacting portion disposed within the capillary and a piston head connected thereto and proximal to the syringe retaining element when the piston is disposed within the capillary. The piston head is configured for releasable engagement with a piston carrier of a syringe piston gripping mechanism of the pipette.

The electric drive unit is responsible for setting the position of the syringe attached to the pipette, pulling the syringe piston proximally to the pipette to draw liquid into the syringe, and moving the syringe piston distally to eject or discharge the liquid from the syringe.

The dispensing solenoid assembly includes an armature suspended within and linearly displaceable relative to a bore in the solenoid body. The armature includes a shaft that extends through an opening in the solenoid body and connects the armature to a piston carrier, which forms part of the syringe piston retention mechanism of the pipette and engages the piston head of the syringe piston.

The dispensing solenoid assembly and the syringe piston gripping mechanism are substantially within the piston carriage, which is coupled to the output of the drive motor of the motorized drive assembly by a lead screw. In one exemplary embodiment, the operation of the drive motor may rotate a drive nut that is engaged with the lead screw but constrained from linear displacement, thereby transmitting the rotational output of the motor to the linear displacement of the lead screw and piston carriage, and components coupled to the piston carriage, such as the dispensing solenoid. In another exemplary embodiment, the operation of the drive motor may rotate a lead screw within a linearly displaceable but rotationally constrained drive nut, thereby transmitting the rotational output of the motor to the linear displacement of the lead screw, piston carriage, and various components coupled to the piston carriage. In other exemplary embodiments, the lead screw and/or drive nut may be replaced with other components that provide the desired controlled displacement of the piston carriage and various components coupled to the piston carriage.

The dispense solenoid assembly of the exemplary pipette is configured to generate a pulse dispense of a selected amount of fluid by itself, depending on the selected dispense volume and dispense mode, or to assist the motorized drive assembly in the dispense function by ensuring that all of each selected dispense volume is actually dispensed from the syringe without the need to touch off the syringe tip against a sample receiving vessel. Specifically, energizing the solenoid body (coil) causes a rapid and forceful displacement of the solenoid armature toward the distal end of the pipette, which in turn causes a similarly rapid movement of the piston carrier and syringe piston, expelling a jet of fluid from the syringe tip. The general concept of pulsed fluid dispensing in the context of benchtop pipette instruments can be reviewed in European Patent Application EP1344565A1. The displacement of the piston carriage and actuation of the dispense solenoid assembly can be repeated as desired to dispense multiple aliquots, each representing a portion of the total liquid volume held by the syringe.

The operation of the motorized drive assembly and the dispensing solenoid assembly is controlled by a controller that receives instruction signals from user input and/or internal programming. The controller also receives position information signals from an encoder.

The selected syringe is securely and releasably held in the pipette by the syringe holding mechanism, and the syringe piston is coupled to a solenoid armature via a piston carrier of the syringe piston gripping mechanism, and is also coupled to an electric drive system.

Upon completion of the aspiration and dispensing operations, the syringe ejection mechanism operates to disengage the syringe retaining element of the syringe from the syringe retaining mechanism and to disengage the syringe piston head from the piston carriage. The motorized drive system drives the piston carriage toward the distal end of the pipette, causing the syringe retaining mechanism to release the syringe capillary via a release element associated with the piston carriage and the syringe piston gripping mechanism to disengage from the syringe piston head, and the syringe is automatically ejected from the pipette.

Various dispensing operations using the exemplary pipette can be accomplished via automatic or manual modes. A user can access and selectively initiate a desired automated dispensing program through the user interface portion of the pipette.

Automatic mode dispensing can include many different selectable dispensing procedures. For example, these dispensing procedures include: aspirating the entire amount of liquid in the syringe and dispensing the entire amount in one dispensing operation; aspirating an amount of liquid in the syringe and dispensing the aspirated liquid multiple times in the same amount; aspirating an amount of liquid in the syringe and dispensing the aspirated liquid multiple times in varying amounts; or aspirating an amount of liquid in the syringe and dispensing the aspirated liquid multiple times in the same or varying amounts until a portion of the aspirated liquid (e.g., 50%) has been dispensed, followed by another aspirating operation. Dispensing operations may be performed by a user in manual mode rather than by a controller of the pipette operating in automatic mode.

It may also be possible to perform a titration procedure. The titration program of an exemplary pipette may include a titration counter that indicates the amount of titrant dispensed, and the counter may be resettable to allow multiple titration operations from a single aspiration of titrant.

An exemplary pipette may also include fluid viscosity detection capabilities, such as, but not limited to, by providing the pipette with appropriate circuitry or other means for monitoring the increase in current draw of the motorized drive assembly motor required to move the syringe piston relative to the syringe capillary during an aspiration or dispense operation; by use of a built-in load cell that measures the force required to move the syringe piston relative to the syringe capillary during an aspiration or dispense operation; by a mechanical spring; or by other techniques that will be understood by those skilled in the art. The value of the current draw may be used to classify the viscosity of the fluid, and the pipette controller may adjust the pipette's dispense operation parameters based on the identified fluid viscosity classification.

The exemplary pipette may further include an automatic syringe identification system. Such a system would enable the pipette's controller to automatically select the appropriate operating parameters for a given syringe volume, thereby simplifying the set-up process and eliminating operator error associated with misidentifying 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 areas of the corresponding color on the syringe, placing a color sensor in the pipette configured and arranged to image the colored areas on the syringe, and transmitting image data from the color sensor to the pipette controller. A signal to the pipette controller is indicative of the color of the colored area on the syringe, and the controller is programmed to analyze the signal and, as a result, identify the volume of the installed syringe.

Exemplary pipettes according to the general inventive concept are capable of accurately and repeatably dispensing sub-microliter to milliliter or greater volumes of fluid. The ability to automatically dispense selected amounts of the desired fluid without the need to touch off the syringe tip also means that the dispensing operation is independent of the user and therefore isolated from user-induced errors. These are significant improvements over the capabilities of conventional positive displacement pipettes.

Other aspects and features of the general inventive concept will become apparent to those skilled in the art upon review of the following detailed description of exemplary embodiments in conjunction with the accompanying drawing figures.

In the drawings and description of exemplary embodiments that follow, like reference numerals throughout the several views indicate the same or equivalent features.
FIG. 1 is a perspective view of an exemplary embodiment of a motorized positive displacement pipette in accordance with the general inventive concept, including a syringe shown prior to insertion into the pipette. FIG. 2 illustrates an assembly of the exemplary pipette of FIG. 1 with a syringe mounted and held in the pipette. FIG. 3 is an enlarged view of the user end of the exemplary pipette of FIGS. 1 depicts an exemplary user interface provided at a user end of an exemplary pipette in accordance with the general inventive concept. 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 the aspiration position. FIG. 5B is an enlarged perspective view of a portion of the pipette of FIG. 5A. 6A and 6B are perspective and cross-sectional side views, respectively, of an exemplary 0.1 ml syringe for use with an exemplary pipette of the present invention. 6A and 6B are perspective and cross-sectional side views, respectively, of an exemplary 0.1 ml syringe for use with an exemplary pipette of the present invention. 7A and 7B are perspective and cross-sectional side views, respectively, of an exemplary 1.0 ml syringe for use with an exemplary pipette of the present invention. 7A and 7B are perspective and cross-sectional side views, respectively, of an exemplary 1.0 ml syringe for use with an exemplary pipette of the present invention. 8A and 8B are perspective and cross-sectional side views, respectively, of an exemplary 10 ml syringe for use with an exemplary pipette of the present invention. 8A and 8B are perspective and cross-sectional side views, respectively, of an exemplary 10 ml syringe for use with an exemplary pipette of the present invention. 9A and 9B are perspective and cross-sectional side views, respectively, of an exemplary 25 ml syringe for use with an exemplary pipette of the present invention. 9A and 9B are perspective and cross-sectional side views, respectively, of an exemplary 25 ml syringe for use with an exemplary pipette of the present invention. 10A and 10B are perspective and cross-sectional side views, respectively, of an exemplary 50 ml syringe for use with an exemplary pipette of the present invention. 10A and 10B are perspective and cross-sectional side views, respectively, of an exemplary 50 ml syringe for use with an exemplary pipette of the present invention. FIG. 11 is a cross-sectional side view of the exemplary pipette of FIG. 1A with portions of the pipette's housing removed to better reveal various internal components of the pipette. 12 is an enlarged cross-sectional perspective view of various internal drive components of the exemplary pipette of FIG. FIG. 13 is an enlarged cross-sectional view of a distal portion of an exemplary motorized positive displacement pipette showing various internal components that form an exemplary syringe retention mechanism. FIG. 14A is a perspective view and FIGS. 14B-C are elevational views of a piston carrier element of an exemplary syringe piston gripping mechanism. FIG. 14A is a perspective view and FIGS. 14B-C are elevational views of a piston carrier element of an exemplary syringe piston gripping mechanism. FIG. 14A is a perspective view and FIGS. 14B-C are elevational views of a piston carrier element of an exemplary syringe piston gripping mechanism. FIG. 15A is an exploded view showing the piston head of an exemplary syringe inserted into the piston carrier element of FIGS. 14A-14C, in which certain piston release elements of an exemplary syringe ejection mechanism are also present. FIG. 15B is a slightly less exploded view of FIG. 15A in which additional elements of an exemplary syringe ejection mechanism are also present. FIG. 16 shows how an exemplary syringe is inserted into an exemplary motorized positive displacement pipette. 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 gripping mechanism of the pipette. FIG. 17B is a close-up view showing the syringe and pipette of FIG. 17A with the syringe further inserted into the pipette but not yet fully engaged by 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 by the syringe retaining feature of the pipette and the piston head of the syringe is engaged by the syringe piston gripping feature 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 piston gripping mechanism with elements of the syringe. 20A-20D show various components of an exemplary syringe ejection mechanism of an exemplary motorized positive displacement pipette. 20A-20D show various components of an exemplary syringe ejection mechanism of an exemplary motorized positive displacement pipette. 20A-20D show various components of an exemplary syringe ejection mechanism of an exemplary motorized positive displacement pipette. 20A-20D show various components of an exemplary syringe ejection mechanism of an exemplary motorized positive displacement pipette. FIG. 21A shows the positions of the various components of the syringe ejection mechanism of FIGS. 20A-20D, along with other associated components of the pipette, immediately after the start of a syringe ejection operation. 21B-21E further illustrate the positions of various components of the syringe ejection mechanism of FIGS. 20A-20D as the syringe ejection operation progresses. 21B-21E further illustrate the positions of various components of the syringe ejection mechanism of FIGS. 20A-20D as the syringe ejection operation progresses. 21B-21E further illustrate the positions of various components of the syringe ejection mechanism of FIGS. 20A-20D as the syringe ejection operation progresses. 21B-21E further illustrate the positions of various components of the syringe ejection mechanism of FIGS. 20A-20D as the syringe ejection operation progresses. FIG. 21F illustrates the retraction of the piston carrier portion of the pipette during the final stages of an exemplary syringe ejection operation. FIG. 22 is an enlarged cross-sectional side view of a portion of an exemplary motorized, positive displacement pipette, showing its various internal components when the pipette is in the home position. 23A-23B are cross-sectional side views of an exemplary motorized positive displacement pipette with attached syringe in accordance with the general inventive concepts, illustrating the positional changes of various internal components of the pipette and syringe piston as the pipette moves from a home position to a fully aspirating position, such as may occur as a result of a liquid aspiration operation. 23A-23B are cross-sectional side views of an exemplary motorized positive displacement pipette with attached syringe in accordance with the general inventive concepts, illustrating the positional changes of various internal components of the pipette and syringe piston as the pipette moves from a home position to a fully aspirating position, such as may occur as a result of a liquid aspiration operation. 23C illustrates the change in position of various internal components of an exemplary pipette and syringe assembly from the fully aspirated position shown in FIG. 23B during one exemplary type of fluid dispensing operation. FIG. 25 is a bottom perspective view of an exemplary motorized positive displacement pipette, showing the color sensor along with various other components.

Description of the embodiments

Figure 1 illustrates one exemplary embodiment of a handheld, motorized, positive displacement pipette 5 (hereafter simply "pipette") in accordance with the general inventive concept. Also illustrated in Figure 1 is a consumable in the form of an exemplary disposable syringe 600 (see Figures 8A-8B) that is attached to the pipette for performing pipetting operations. Various exemplary syringes for use with the exemplary inventive pipette are illustrated in Figures 6A-10B and described in more detail below. Figure 2 illustrates an assembly of the pipette 5 and syringe 600 of Figure 1.

The exemplary pipette 5 of FIGS. 1-2 includes a body 10 for being grasped by a user. The body 10 is generally a substantially hollow structure that also serves as an external housing for the various internal components of the pipette 5. The body 10 may be of different shapes and/or sizes in other embodiments, although the shape and size will typically be dictated, at least to some extent, by the ergonomics of use.

The body 10 further includes a proximal (user) end 10a 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. With reference to FIGS. 3-4, the user interface portion 15 of this exemplary pipette 5 may further include a display 20 and various actuators, such as input/selection buttons 25a, 25b, and a joystick 27, that allow a user to view and select pipette functions, view and change pipette settings, and engage in various other interactions with the pipette's programmable controller, 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 ejection operation.

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 that are hidden by the body 10. As can be seen, the exemplary pipette 5 includes, among other components, a motorized drive assembly 40, a dispensing solenoid assembly 250, a syringe retention mechanism 150, and a syringe piston gripping mechanism 200, all of which are described in more detail below. The assembly of FIG. 5A also includes a syringe 600 that is releasably retained by the syringe retention mechanism 150 of the pipette 5, the syringe 600 being shown in a post-aspiration and pre-dispense position. An enlarged transparent view of a portion of the proximal end 10a of the pipette body 10 is shown in FIG. 5B, revealing additional pipette components, such as a printed circuit board and various electronic components, including the motor control circuitry that makes up the controller 90.

Various exemplary syringes usable with exemplary pipettes according to the general inventive concept are depicted in perspective and cross-sectional elevation views in Figures 6A-10B. The exemplary syringes 500-600 are arranged in order of increasing volume, with Figures 6A-6B depicting an exemplary syringe 500 having a 0.1 ml capacity, Figures 7A-7B depicting an exemplary syringe 550 having a 1.0 ml capacity, Figures 8A-8B depicting an exemplary syringe 600 having a 10 ml capacity, Figures 9A-9B depicting an exemplary syringe 650 having a 25 ml capacity, and Figures 10A-10B depicting an exemplary syringe 700 having a 50 ml capacity. Thus, while the exemplary syringe 600 of FIGS. 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 pipette of the present invention can be used with a number of different syringes to accurately and repeatably dispense samples over a wide range of volumes.

Each of the exemplary syringes 500, 550, 600 shown in FIGS. 6A-8B includes an outer barrel, referred to herein as a capillary 505, 555, 605, which is a generally hollow and tubular structure and functions to contain the fluid specimen to be dispensed. The distal end of each capillary 505, 555, 605 includes a tip 510, 560, 610 having an orifice 515, 565, 615 through which fluid previously aspirated into the capillary can be dispensed. The top of each capillary 505, 555, 605 forms a syringe retaining element 520, 570, 620 of similar shape and dimensions. The shape and dimensions of the syringe retaining element 520, 570, 620 permit its engagement by a syringe retaining mechanism 150 disposed within 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 can be engaged by an element of the syringe retaining mechanism 150.

Each syringe 500, 550, 600 also includes a piston 525, 575, 625 (sometimes called 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 holding element 520, 570, 620, and a connecting portion passing through an opening in the syringe holding element to connect the piston head and the fluid contacting portion. The piston head 530, 580, 630 of the exemplary syringe 500, 550, 600 shown herein is substantially bell-shaped and includes opposing arms 530a-530b, 580a-580b, 630a-630b that allow at least some degree of elastic deformation. In other embodiments, other piston head shapes and other numbers of arms may be implemented.

When the syringe 500, 550, 600 is properly attached to the pipette 5, the syringe is held in a stationary position by engagement of the syringe retaining element 520, 570, 620 of the syringe with 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 to allow the liquid contacting portion of the piston to be reciprocated within the capillary 505, 555, 605 by the pipette. The syringe 500, 550, 600 can be expelled from the pipette 5 after use, as described in more detail below.

The exemplary syringes 650,700 shown in Figures 9A-9B and 10A-10B, respectively, are designed for use in pipetting larger fluid volumes. In these exemplary syringe embodiments, a capillary 655,705 is again included having a tip 660,710 with an orifice 665,715, and a piston 670,720 is again positioned to reciprocate within the capillary. However, unlike the exemplary syringe embodiments 500,550,600 depicted in Figures 6A-8B, the capillary 655,705 of the syringe 650,700 has an open top (proximal end) and does not include a syringe retaining element. Instead, each syringe 650,700 includes a reusable adapter 675,725 for connecting the syringe to a pipette 5.

Each adapter 675,725 has an open distal end dimensioned to receive the proximal end of the syringe 650,700. The proximal end of the capillary 655,705 and a retaining element at the distal end of the adapter 675,725 cooperate to secure the capillary to the adapter. The proximal end of the adapter 675,725 forms a syringe retaining element 680,730 having a shape and dimensions to engage a syringe retaining feature 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 can be engaged by an element of the syringe retaining feature 150.

Each syringe 650,700 includes a piston 620,720 having a first fluid contact portion concentrically disposed within the capillary 655,705 for aspirating and dispensing fluid, a head 685,735 portion proximal to the syringe holding element 680,730 of the adapter 675,725, and a connecting portion passing through an opening in the syringe holding element to connect the piston head and the fluid contact portion. The piston head 685,735 of the exemplary syringe 650,700 shown herein is again substantially bell-shaped and includes opposing arms 685a-685b,735a-735b that allow at least some elastic deformation. Other piston head shapes and other numbers of arms may be implemented in other embodiments.

When the large volume syringe 650,700 is properly attached to the pipette 5, the syringe is held in a stationary 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 gripping mechanism 200 of the pipette, allowing the liquid contacting portion of the piston to be reciprocated within the capillary 655,705 by the pipette. The syringe 650,700 can be expelled from the pipette 5 after use, as described in more detail below.

The syringes of FIGS. 6A-10B are provided for illustrative purposes only, and it is understood that variations are certainly possible. For example, but not by way of limitation, the piston head and piston of a given syringe may be separate, engageable elements rather than a single, integral part as described herein.

Similarly, while only the exemplary large volume syringes 650, 700 of FIGS. 9A-10B are shown and described as employing an adapter having an open-top capillary, the small volume syringes 500, 550, 600 of FIGS. 6A-8B may be of a similar design and may also include an adapter. If a given syringe includes an adapter, the adapter may be a reusable component rather than a consumable item like the remainder of the syringe in most syringe embodiments.

11, a cross-sectional side view of the exemplary pipette 5 of FIG. 1 is shown with its body 10 removed to better reveal the various internal components of the pipette. As briefly described above, the pipette 5 is seen to include a motorized drive assembly 40 at a proximal end, a syringe retaining mechanism 150 at a distal end, and a dispensing solenoid assembly 250 and a syringe piston gripping mechanism 200 interposed therebetween. The pipette 5 also includes an internal housing 35 that houses each of the dispensing solenoid assembly 250, the syringe piston gripping mechanism 200, and the syringe retaining mechanism 150. The motorized drive assembly 40 is attached to the proximal end of the internal housing 35.

The motorized drive assembly 40 is responsible for setting various positions of the syringe 600 attached to the pipette 5, moving the syringe piston from distal to proximal to aspirate fluid into the syringe, moving the syringe piston from proximal to distal to expel fluid from the syringe, and producing the necessary motions to expel the syringe. With reference also to FIG. 12, it can be seen that in this exemplary pipette 5, the motorized drive assembly 40 includes a drive motor 45 having an output shaft coupled 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 that threadably engages through the drive nut. Other drive schemes, such as a direct drive scheme in which the output of the drive motor is connected to the lead screw 95 directly by a coupling or possibly through a reduction gear assembly, may be utilized in other embodiments.

In this exemplary motorized drive assembly 40, a drive belt 55 may connect an output pinion 60 mounted on the output shaft of the motor 45 to an input pinion 65 coupled to or integral with the drive nut 50. The drive nut 50 may include bearings 70 to facilitate rotation of the drive nut. To help account for any manufacturing (e.g., stacking) tolerance variations within the motorized drive assembly 40 and to minimize backlash that may cause inaccuracies during dispensing operations, the drive nut may also be preloaded with a spring 75 (e.g., a wave spring) that biases the drive nut toward the proximal end of the pipette 5. A mounting block 80 or similar structure/component may be provided to facilitate mounting of the various components of the motorized drive assembly 40.

Dispense solenoid assembly 250 is configured to dispense a selected amount of fluid by itself, depending on the selected dispense volume, or to assist motorized drive assembly 40 in the dispense function by ensuring that all of the selected dispense volume is actually dispensed from syringe 600 without the need to touch syringe tip 610 to a sample receiving vessel (as described below). Dispense solenoid assembly 250 includes a solenoid body (coil) 255 that resides within and is coupled to piston carriage 100 such that the solenoid body moves axially with the piston carriage. Solenoid body 255 includes an axial bore 270 that extends from its axial end a distance within the solenoid body. Armature 260 is concentrically disposed within bore 270 and is linearly reciprocable within the bore relative to pipette 5 by a magnetic field generated within the bore, as will be appreciated by those skilled in the art. Because the armature 260 floats within the bore 270, as opposed to being coupled to the piston carriage 100 as the solenoid body 255 is, the armature is not constrained (a distance) to move linearly with the piston carriage. The bottom wall of the bore 270 acts as an armature hard stop 275 during the proximal-to-distal movement of the armature 260. In the illustrated exemplary dispensing solenoid assembly 250, the armature 260 includes a shaft 265 that extends through an opening in the bottom wall of the bore 270 toward the distal end of the pipette 5.

The operation of the motorized drive assembly 40 and the dispensing solenoid assembly 250 is governed by a 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 position information signals from an encoder 85 coupled to the drive nut 50.

The rotational motion of the drive nut 50 is converted to linear (axial) motion by the lead screw 95 which passes through and threadedly engages the drive nut. While the drive nut 50 is freely rotatable, the lead screw 95 is rotationally constrained but linearly displaceable. Thus, rotation of the drive nut 50 by the drive motor 45 moves the lead screw 95 proximally or distally along the longitudinal axis of the pipette 5.

The distal end 95b of the lead screw 95 is attached to the proximal end of the piston carriage 100 in a manner that prevents rotation of the lead screw 95. The piston carriage 100 is disposed within a carriage holder 105 that is mounted within the internal housing 35 in such a manner that relative movement is constrained. Within the carriage holder 105, the piston carriage 100 is axially displaceable and reciprocable relative to the longitudinal axis of the pipette 5, but is constrained from rotation.

The dispense solenoid assembly 250 and the syringe piston gripping mechanism 200 (both described in more detail below) reside substantially within the piston carriage 100. Thus, both the dispense solenoid assembly 250 and the syringe piston gripping mechanism 200 move with the piston carriage 100 during linear displacement of the piston carriage within the pipette 5.

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

A better understanding of the exemplary syringe retention mechanism 150 of the pipette 5 can be obtained by further reference to FIG. 13, which provides an enlarged cross-sectional view of the distal end of the exemplary pipette 5. The illustrated exemplary syringe retention mechanism 150 includes a plurality of spaced apart syringe latch elements 155 secured within the distal end of the pipette 5, such as by pin connections 185 (see, e.g., FIG. 20C) to the body 10, such that the syringe latch elements 155 are pivotable within some range of rotational motion but constrained against axial motion. In this exemplary pipette 5, there are three syringe latch elements 155 (only two are visible in FIG. 11), although other embodiments may utilize a different number of latch elements.

The syringe latch elements 155 of the syringe retention mechanism 150 are shown in the closed position in FIG. 11 and are normally maintained in the closed position by an elastomeric O-ring 160 or similar elastomeric element that surrounds the three syringe latch elements 155 and resides in a slot 165 in each latch element. The syringe latch elements 155 are coupled to the piston carrier 205 with a mounting pin 185 (see FIG. 20D), which allows the syringe latch mechanism to pivot during the syringe insertion procedure, as described 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 hook 170 of the syringe latch element 155 is designed to engage a 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 the pipette 5 and syringe 600 shown in FIG. 5, the latch hook 170 of the syringe latch element 155 is designed to engage (e.g., along the lower surface 640) with the syringe retaining element 620 on the syringe capillary 605.

While the syringe retaining mechanism 150 secures the capillary of the syringe 600 to the pipette 5 and maintains the capillary in a stationary position relative thereto, the syringe piston gripping mechanism 200 engages and releasably holds the head 630 of the syringe piston 625. To this end, the syringe piston gripping mechanism 200 includes a piston carrier 205 disposed substantially within the piston carriage 100. As can be seen in more detail in FIGS. 14A-14C, at least the internal shape of the piston carrier 205 can substantially match the external shape of the syringe piston head 630. The exemplary piston carrier 205 further includes a distally located actuation collar 285 having a piston head retaining lip 210, and a plurality of radially spaced apart openings 215 that allow access through the walls of the piston carrier to the arms 630a, 630b of the piston head 630 by a piston head release element 305 of the exemplary syringe ejection mechanism, as will be described further below.

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

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

A better understanding of the operation of the piston carrier 205 can be obtained by referring to the exploded views of FIGS. 15A-15B. In the exemplary syringe 600 shown in FIG. 15A, the piston head 630 is inserted into the piston carrier 205 of FIGS. 13 and 14A-14C, and the piston head release element 305 of the exemplary syringe ejection mechanism is pivotally disposed in an opening 215 in the piston carrier. The piston head 630 preferably fits snugly inside the piston carrier, and as can be observed, the distal ends of the piston head arms 630a, 630b engage the piston head retaining lip 210 in the piston carrier 205, thereby preventing the piston head 630 from being pulled out of the piston carrier. As a result, the piston head 630 is securely gripped by the piston carrier 205, ensuring that the piston 625 of the syringe 600 moves axially along the axial movement of the piston carrier.

Referring now to Figures 16-17B, the process of inserting an exemplary syringe 600 into an exemplary pipette 5 can be seen. Figure 16 shows the syringe 600 positioned below and substantially axially aligned with the distal end of the pipette 5. The arrow indicates the direction of engagement movement of the syringe 600 towards the pipette 5.

In FIG. 17A, the syringe 600 is partially inserted into the pipette 5. During the insertion of the syringe 600, the piston head 630 of the syringe piston 625 begins to engage with the piston carrier 205 of the syringe piston gripping mechanism 200. In FIG. 17A, it can be observed that during the syringe insertion process, the piston head arms 630a, 630b of the piston head 630 are compressed inward (i.e., undergo inwardly directed elastic deformation) through contact with the wall formed by the distal opening 290 of 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 the distal opening of the actuation collar 285.

17B depicts partial engagement of the syringe 600 with the pipette 5 resulting from continued insertion of the proximal end of the syringe 600 into the distal end of the pipette 5 beyond the point shown in FIG. 17A. Such continued insertion of the syringe 600 results in outward pivotal movement of the distal end of the syringe latch element 155 in response to an insertion force applied to the syringe 600. More specifically, as the syringe 600 is inserted into the pipette 5, an outward force is exerted by the syringe retaining element 620 on the distal end of the syringe latch element 155 that is sufficient to overcome the inward force exerted on the syringe latch element by the O-ring 160.

As insertion of the syringe 600 into the pipette 5 continues, the proximal (top) surface of the syringe retaining element 620 of the syringe capillary 605 comes into approximate contact with the spring(s) 300 retained within the pipette 5. As can be seen in FIG. 17B, at the point of contact between the proximal (top) surface of the syringe retaining element 620 and the spring(s) 300, the syringe retaining element 620 preferably moves past the latch hook 170 of the syringe latch element 155 (although reaching that point may alternatively require the spring(s) to be compressed slightly), thereby allowing the syringe latch element 155 to be returned to its normal closed position by the contraction force of the O-ring 160. When the syringe latch element 155 returns to its normal closed position (see also FIGS. 18-19), the flat surface 175 on each syringe latch element hook 170 engages over the underside 640 of the syringe retaining element 620, while the inwardly facing surface 180 of each syringe latch element 155 is preferably pressed against the circumferential edge 635 of the syringe retaining element by the contraction spring force of the O-ring 160. The syringe capillary 605 is thereby captured and releasably locked to the pipette 5, which means that the syringe capillary is also securely held in a stationary position relative to the pipette.

17B and described above, following releasable locking of the syringe 600 onto the pipette 5, continued application of an insertion force to the syringe results in a small but additional proximal movement of the syringe into the pipette. This additional movement of the syringe 600 is due to compression of the spring(s) 300 within the pipette due to the insertion force being exerted on the syringe.

As shown in FIG. 18, further proximal movement of the syringe 600 to the pipette 5 causes the piston head 630 of the syringe to be fully inserted into the piston carrier, after which the piston head arms 630a, 630b resiliently return toward their normal static position and engage with the piston head retaining lip 210 located on the actuation collar 285 of the piston carrier. The engagement of the piston head arms 630, 630b with the actuation collar 285 retains the piston head 630 within the piston carrier 205. Also, from inspection of FIG. 18, it can be seen that the piston head 630 fits snugly within the piston carrier 205 in this exemplary embodiment of the pipette 205.

In Figures 18-19, the syringe 600 is fully attached to the pipette 5. In the fully attached position, the syringe 600 is releasably locked to the pipette 5 as described above, and the syringe's piston head is fully engaged by the pipette's syringe piston gripping mechanism 200. Once the syringe 600 is in the fully installed position shown, it can be used to aspirate and dispense fluid.

In addition to providing for further insertion of the syringe 600 into the pipette 5 after the syringe retaining element 620 of the syringe capillary 605 reaches an engagement position with the syringe retaining mechanism 150 of the pipette, the spring(s) 300 also provide for improved retention security and static engagement of the syringe 600 to the pipette 5. More specifically, with the syringe 600 attached to the pipette 5, the spring(s) 300 exert a distally directed force against the upper surface of the syringe retaining element 620, which presses the lower surface 640 of the syringe retaining element firmly against the flat 175 of the hook 170 of the syringe latch element 155. The distally directed force exerted by the spring(s) 300 also urges the piston head 630 towards 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 of the actuation collar 285 portion of the piston carrier 205. Thus, unintended 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 prevented by the axially directed force exerted by the spring(s) 300, thereby further securing the syringe 600 to the pipette 5. The spring(s) 300 may be, for example, but not limited to, a metal leaf spring(s). Other types of springs are also possible.

Because positive displacement pipette syringes are intended to be disposable, i.e., discarded after completion of the associated pipetting operation, the exemplary syringe 600 must be capable of being expelled from the pipette 5. As can best be seen from a consideration of the exploded perspective views of FIGS. 20A-20D and the cross-sectional views of FIGS. 21A-21F (see also FIGS. 13, 15A-15B, and 19A-19), the pipette 5 includes an exemplary syringe ejection mechanism for this purpose. Generally speaking, the syringe ejection mechanism operates to decouple the syringe retaining element 620 of the syringe 600 from the syringe retaining mechanism 150 and to decouple the syringe piston head 630 from the piston carrier 205, after which the syringe will be automatically ejected from the pipette 5. As described in more detail below, the syringe ejection mechanism of the exemplary pipette 5 is generally comprised of the motorized drive assembly 40 and lead screw 95, the piston carriage 100 and its wedge-shaped syringe latch element release portion 335, the syringe latch element 155, the piston head release element guide 220 on the actuation collar portion 285 of the piston carrier 205, and a plurality of piston head release elements 305.

20A essentially provides the same view of the piston head 630 of the exemplary syringe 600 inserted into the piston carrier 205 shown in FIG. 15A, but in FIG. 20A, the piston carrier 205 has been removed for clarity. As can be seen in FIG. 20A, the piston head release element 305 of the syringe ejection mechanism (which is shown aligned with the opening 215 of the piston carrier 205 in FIG. 15A) is positioned to at least partially overlap the opposing arms 630a, 630b of the syringe piston head 630 when the piston head is inserted into the piston carrier 205. Each of the exemplary piston head release elements 305 may include a roller 310 at its distal end. The rollers 310 function to reduce friction between the piston head release element 305 and the inwardly directed ramp surfaces 220a of each piston head release element guide 220 of the piston carrier 205, and between the piston head release element and the arms 630a, 630b of the syringe piston head 630. However, in other syringe ejection mechanism embodiments, such as using low friction materials, it may be possible to eliminate the rollers 310.

The piston head release elements 305 are pivotally secured within the piston carriage 100 by pins 315 such that inwardly directed movement of the proximal ends of the piston head release elements results in outwardly directed movement of the distal ends of the piston head release elements. Although not shown in FIGS. 20A-20D for clarity, the piston head release elements 305 are normally maintained in an open position (see, e.g., FIGS. 13, 16-19, 21A-21B, 22 and 24) by an O-ring 320 or another similar resilient element that surrounds the piston head release elements 305 and resides in a slot 325 provided in each piston head release element. The O-ring 320 exerts an inwardly directed force against the proximal end of each piston head release element 305 such that the normally open position of the piston head release elements urges the distal ends of the piston head release elements away from the piston carrier 205.

An exemplary syringe ejection operation is shown in Figures 21A-21F. During a syringe ejection operation, the piston carrier 205 is positioned against the hard stop 225 and the motorized drive assembly 40 is commanded to cause distal movement of the piston carriage 100 a predetermined distance. In this exemplary embodiment of the pipette 5, the piston carriage moves distally approximately 3.25 mm during a syringe ejection operation, although this distance may vary in other embodiments.

Because the piston carrier 205 is constrained against further distal axial movement upon striking the hard stop 225, the aforementioned distal axial displacement of the piston carriage 100 causes distal axial displacement of the syringe latch element release portion 335 relative to the piston carrier, as well as the piston head release element 305, which is pivotally coupled to the piston carriage 100.

21A, as the piston carriage 100 moves distally, the syringe latch element release portion 335 of the piston carriage begins to contact the proximal end of the syringe latch element, where the syringe latch element release portion 335 is positioned to align with the syringe latch element 155 and to move within the space between the syringe latch element and the piston carrier 205. Similarly, distal movement of the piston carriage 100 creates contact between the roller 310 of the piston head release element 305 and the inwardly directed ramp surface 220a of each piston head release element guide 220 associated with the actuation collar 285 of the piston carrier 205.

21B, continued distal movement of the piston carriage 100 eventually results in sufficient contact between the wedge-shaped syringe latch element release portion 335 and the proximal end of the syringe latch element 155 to pivot the distal end of the syringe latch element outwardly about the mounting pin 185 against the opposing contraction force of the O-ring 160 and the axially directed force of the spring(s) 300. As shown, the pivoting movement of the syringe latch element 155 disengages the latch hook 170 from the syringe retaining element 620 of the syringe 600 (as also shown in FIG. 20D), thereby disengaging the syringe retaining element and the syringe capillary 605 from retaining engagement with the pipette 5.

21C-21E, further distal movement of the piston carriage 100 causes the rollers 310 of the piston head release element 305 to follow the correspondingly aligned inclined surfaces 220a of the piston head release element guides 220 of the piston carrier actuation collar 285. As a result, the distal end of the piston head release element 305 is pivoted inwardly toward the piston carrier 205. As shown in FIGS. 21D-21E, this inward movement of the distal end of the piston head release element 305 causes the rollers 310 attached thereto to enter the piston carrier 205 through the openings 215 therein and begin to compress inwardly against the opposing arms 630a, 630b of the syringe piston head 630.

As depicted in FIG. 21E, the amount of inward deformation of the syringe piston head arms 630a, 630b caused by the piston head release element 305 is sufficient to eventually 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 then be withdrawn in a proximal to distal direction through the distal opening 290 in the piston carrier.

During downward movement of the piston carrier 100, when the piston head arms 630a, 630b are compressed inwardly by the distal ends of the piston head release elements 305, the proximal ejection tabs 340 of each piston head release element simultaneously exert 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 the capillary 605, and also causes the free ends of the piston head arms 630a, 630b to enter the distal openings 290 of 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 carriage 100 (see FIG. 21F) to its home position, which allows the piston head arms 630a, 630b to clear the rollers 310 of the piston head release element 305 during ejection. Physical ejection may then occur automatically as a result of gravity combined with the axially directed force exerted by the spring(s) 300 on the syringe holding element 620, and/or the syringe 600 may be removed from the pipette 5 by the user. The ejection operation and the return movement of the piston carriage 100 may occur automatically according to an ejection operation program command from the pipette controller 90.

22-24, various states and operations of the exemplary pipette 5 will now be described. FIG. 22 depicts the home position of the exemplary pipette 5. In the home position, the distal end of the piston carrier 205 essentially rests against the hard stop 225, and resting "against" the hard stop can be understood to allow for minimal assembly clearance between the hard stop and the piston carrier. Similarly, in the home position of the pipette 5, the armature 260 of the dispense solenoid assembly 250 rests at its distal hard stop against the bottom wall of the core 270, and the coil 260 of the dispense solenoid assembly is not energized. In the home position of the pipette 5, the piston carriage 100 is positioned distally such that there is a slight gap 400 between the piston carrier 205 and the roller 310 of the piston head release element 305. This is to ensure that there is no unintended interference between the roller and the piston head 630 when a syringe is inserted into the pipette 5. A home position sensor 405 may be provided to indicate to the controller 90 that the piston carriage is in the home position.

The aspiration function of an exemplary pipette is depicted in FIGS. 23A-23B through the use of the exemplary pipette 5 and syringe 600 assembly of FIG. 2. FIG. 23A shows the exemplary pipette 5 in a home position, as described immediately above. It can be further observed that when the pipette 5 is in the home position with the syringe 600 attached to it, the piston head 630 of the syringe piston 625 engages with the piston carrier 205 of the pipette, but the piston has not yet been purposefully moved toward the proximal end of the pipette (beyond the concomitant axial movement required to engage the piston head with the piston carrier). As a result, the piston 625 still resides substantially against the distal interior of the syringe capillary 605.

The pipette assembly in FIG. 23B is shown in a ready-to-dispense or full aspirate position, i.e., the pipette 5 is shown as having performed an aspirate function by aspirating the entire syringe volume of the desired fluid into the syringe 600. It is also possible to aspirate less than the entire syringe volume of fluid. To aspirate fluid, the tip 610 of the syringe 600 is placed in the fluid and an aspirate program is initiated via the user interface portion 15 of the pipette, or the user operates an actuator to energize the motor 45 of the motorized drive assembly 40 to drive the piston carriage 100 and associated components coupled thereto a desired distance toward the proximal end of the pipette 5. This proximal axial movement of the piston carriage 100 causes a similar movement of the solenoid body 260, which causes a similar movement of the armature 260 and piston carrier 205, which are attached to the armature shaft 265. With the head 630 of the syringe piston 625 engaged with the piston carrier 205, the syringe piston moves an equal distance proximally within the syringe capillary 610, thereby drawing the desired fluid into the now emptied capillary.

When the exemplary pipette 5 is in the fully aspirated position as shown in FIG. 23B, the various elements of the pipette components remain in the same positions relative to one another as when the pipette is in the home position. For example, the armature 260 of the dispense solenoid assembly 250 remains at the distal hard stop 275 against the bottom wall of the bore 270, and the coil 260 of the dispense solenoid assembly is not energized. Similarly, the gap 400 between the piston carrier 205 and the roller 310 of the piston head release element 305 is also maintained when the pipette 5 is in the aspirated position.

The operation of the various pipette components during a dispensing operation is described with reference to Figures 23B and 24. The particular manner in which the dispensing components of the pipette 5 operate during a dispensing operation depends on the selected dispensing volume. That is, small volume dispensing is preferably performed using the solenoid assembly 250, while large volume dispensing is preferably performed using the motorized drive assembly 40 alone or a combination of the motorized drive assembly 40 and the solenoid assembly 250.

The boundary between small and large dispense volumes may vary across different pipette embodiments because the maximum volume of fluid that can be dispensed by the solenoid assembly 250 alone depends on the maximum stroke of the solenoid armature 260. This, in turn, is determined by the maximum distance the piston carriage 100 can travel from a full aspiration position toward the distal end of the pipette 5 before causing an unintended dispense of fluid from the syringe 600. For purposes of illustration, but not limitation, the maximum piston carriage displacement that can occur without causing an unintended dispense is 0.5 mm in this exemplary embodiment of the pipette 5.

Because the solenoid body 255 is coupled to the piston carriage 100, the solenoid body moves toward the distal end of the pipette 5 during such piston-carriage movement. However, because the solenoid armature 260 is free floating within the bore in the solenoid body 255, because the solenoid armature is also coupled to the piston carrier 205 by the armature shaft 265, and because the piston carrier is biased toward the proximal end of the pipette 5 by the pressure of the aspirated fluid in the syringe 600 pushing against the syringe piston 670, the solenoid armature remains in its current position and does not move with the piston carrier and solenoid body during such piston-carriage movement. 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, a distance commensurate with the aforementioned distal movement of the piston carriage 100 (maximum 0.5 mm in this example). This solenoid stroke gap 280 is the maximum stroke of the solenoid armature 260 and is therefore 0.5 mm in this exemplary embodiment of the pipette 5.

The 0.5 mm maximum stroke of the solenoid armature 260 results in a corresponding dispense volume of approximately 0.01 (1%) of the total volume of a given syringe attached to the pipette. As a result, in this particular example, small dispense volumes would be considered to be approximately 0.001 ml or less for the 0.1 ml syringe 500, approximately 0.01 ml or less for the 1.0 ml syringe 550, approximately 0.1 ml or less for the 10 ml syringe 600, approximately 0.25 ml or less for the 25 ml syringe 650, and approximately 0.5 ml or less for the 50 ml syringe 700. Dispense volumes greater than these approximate small volume dispense volumes would be considered large volume dispense volumes in this particular example. It should be noted that the minimum dispenseable volume using the motorized drive assembly 40 alone, or using the motorized drive assembly 40 in combination with the solenoid assembly 250, is generally the same as the maximum dispenseable volume using the solenoid assembly alone (although there may be some overlap).

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

With the piston carriage 100 moved to the small volume dispense position, resulting in a gap 280 in the solenoid assembly, the controller 90 momentarily energizes the solenoid body 255, which generates a magnetic field that rapidly and forcefully ejects the armature 260 toward the distal end of the pipette 5 and out of contact with the armature hard stop 275, as will be understood by those skilled in the art. This rapid distal movement of the solenoid assembly armature 260 causes a similar movement of the piston carrier 205 and associated syringe piston 625, thereby breaking the surface tension between the fluid and the inner wall surface of the syringe capillary 605, thereby ejecting the selected dispensed volume of fluid from the tip 610 of the syringe 600 at a sufficient velocity such that the last drops of fluid are dispensed without the need to touch off the syringe tip 610 on a receiving vessel. The process of moving the piston carriage 100 and firing the solenoid assembly 250 to dispense small amounts of fluid can be repeated until the entire aspirated volume has been dispensed or until the desired number of dispense operations have been completed.

As can be seen from the foregoing description, large volume dispensing in the exemplary pipette is simply dispensing a volume of fluid that is greater than the maximum possible volume of fluid that can be dispensed by the action of the solenoid assembly alone. Thus, with respect to the exemplary pipette 5 and exemplary syringes 500, 550, 600, 650, 700 shown and described herein, large volume dispensing includes a dispensing volume of greater than about 0.001 ml of the 0.1 ml syringe 500, a dispensing volume of greater than about 0.01 ml of the 1.0 ml syringe 550, a dispensing volume of greater than about 0.1 ml of the 10 ml syringe 600, a dispensing volume of greater than about 0.25 ml of the 25 ml syringe 650, and a dispensing volume of greater than about 0.5 ml of the 50 ml syringe 700. The maximum volume that can be dispensed during a single large volume dispensing operation is the total volume of a given syringe 500, 550, 600, 650, 700.

As mentioned above, there are two possible approaches to dispensing large volumes. According to the first approach, large volume dispensing is performed using the motorized drive assembly 40 alone, and according to the second approach, large volume dispensing is performed using the motorized drive assembly 40 in combination with the solenoid assembly 250. The method of large volume dispensing employed will depend on the particular construction of the pipette and may also depend on the properties of the fluid being dispensed.

In accordance with the first method of large volume dispensing described above, it has been found that when dispensing large volumes of fluid, or at least when dispensing fluid volumes that fall within a certain volume range of the overall large volume dispensing range of the exemplary pipette 5, dispensing can occur without the need for assistance from the solenoid assembly 250. More specifically, it has been found that: When dispensing large volumes of fluid, the movement of the piston carriage 100 alone, coupled with the increase in fluid velocity resulting from the fluid in the syringe 600 being forced from the larger diameter capillary 605 through the much smaller diameter tip 610 and orifice 615, produces a fluid dispensing velocity sufficient to overcome the surface tension between the fluid and the inner wall surface of the syringe capillary, thereby ensuring that every last drop of fluid is dispensed from the syringe without the need for the syringe tip to touch the receiving vessel.

Large volume dispensing by piston carriage 100 movement alone may be automatically commanded by pipette controller 90 based on the user-selected dispensing program, the syringe attached to pipette 5, the dispense volume associated with the selected dispensing program, and the like. In any event, upon initiation of a large volume dispensing operation by piston carriage 100 movement alone, controller 90 determines the piston carriage displacement required to eject the selected large volume of dispensed fluid. Motorized drive assembly 40 then rotates drive nut 50 to linearly displace lead screw 95 and piston carriage 100 until gap 400 between piston carrier 205 and roller 310 of piston head release element 305 is closed, which produces a similar displacement of piston carrier 205 and associated syringe piston 625. Dispensing of the selected large volume of fluid is thus accomplished.

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

Upon completion of movement of the piston carriage 100 and corresponding dispensing of fluid from the syringe 600, the controller 90 momentarily energizes the solenoid body 255, which fires the armature 260 of the solenoid assembly 250 toward the distal end of the pipette 5 and out of contact with the armature hard stop 275. This rapid, distal movement of the solenoid assembly armature 260 causes a similar movement of the piston carrier 205 and the syringe piston 625, which dispenses any unsecreted fluid remaining within the syringe tip 610 due to surface tension between the fluid and the inner wall surface of the syringe capillary 605. Thus, ensuring that every last drop of the volume of fluid intended to be dispensed is actually dispensed and is not inadvertently retained within the syringe tip 610. If the fluid volume dispensed during a large volume fluid dispensing operation is less than the total volume of fluid in the syringe 600, the dispensing operation may be repeated until the desired number of dispensing operations is completed, until the fluid volume is exhausted, or until the remaining fluid volume is insufficient to perform another dispensing operation of the desired volume.

Dispensing operations with the exemplary pipette 5 may be accomplished via a selected pipetting program that operates the pipette in an automatic or manual mode. As briefly described above, a user may access and selectively initiate a desired pipetting program via the user interface portion 15 of the pipette 5.

Automatic mode dispensing can include many different selectable dispensing procedures. One simplified example of such a dispensing procedure is aspirating the entire amount of liquid in a syringe and then dispensing the entire amount of aspirated liquid in one dispense operation.

In another example of an automatic mode dispensing procedure, as described above, fluid is aspirated into the syringe 600, followed by multiple dispenses of equal amounts until the desired number of dispense operations is 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 yet another example of an automatic mode dispensing procedure, as described above, fluid is aspirated into the syringe 600, followed by multiple dispenses of variable amounts until the desired number of dispense operations is completed, until the fluid volume is exhausted, or until the remaining fluid volume is insufficient to perform another dispense operation of the desired fluid volume. In yet another example of an automatic mode dispensing procedure, as described above, fluid is aspirated into the syringe 600, followed by multiple dispenses of equal or variable amounts until a portion of the aspirated fluid volume (e.g., 50%) is dispensed. At this point, another aspirating operation is performed to increase the fluid volume in the syringe 600, and dispensing is performed again. This process can be repeated until the desired number of dispense operations is completed, until the fluid volume is depleted, or until the remaining fluid volume is insufficient to perform another dispense operation of the selected fluid volume.

In any of the exemplary automatic mode dispensing procedures described above, the aspirated fluid volume may be the full fluid capacity of the installed syringe, or may be a lesser volume. Dispensing of fluid may be accomplished solely by firing of the solenoid assembly 250, solely by movement of the piston carriage 100, or by a combination thereof. As described above, the dispensing method used may be selected based on the pipette configuration (e.g., resolution), the installed syringe, the desired dispense volume, some combination of these, and/or other factors.

The menu of exemplary procedures that may be performed under the automatic mode of the exemplary pipette may further include a titration procedure. As one skilled in the art would appreciate, a titration procedure using the exemplary pipette 5 generally involves adding a quantity of titrant aspirated into the syringe 600 to a container of analyte and indicator until the indicator changes color or achieves some other observable characteristic that indicates that the reaction has reached a neutral state. Because the amount of titrant that needs to be added to the analyte solution to reach neutrality is generally unknown, the titration program may include a titration counter that indicates the amount of titrant dispensed. The counter may be resettable to allow multiple titration operations from a single aspirated volume of titrant.

Dispensing operations may also be performed by a user in a manual mode rather than by the controller 90 of the pipette 5 operating in an automatic mode. In the manual mode, the user operates the motorized drive assembly 40 to cause fast or slow aspiration and/or dispensing of fluid from the syringe 600.

The exemplary pipette may also be equipped with a fluid viscosity detection feature. More specifically, the viscosity of the fluid of interest may be determined indirectly; through the use of a provided load cell 355 (see FIG. 5B); by a mechanical spring; or through other techniques understood by those skilled in the art; such as by providing the pipette with appropriate circuitry 350 (see FIG. 5B) or other means for monitoring and analyzing the increase in current drawn by the drive motor resulting from an increase in motor torque required to move the syringe piston relative to the syringe capillary during an aspiration or dispensing operation.

When utilizing current monitoring techniques, the current value can be used to classify the viscosity of the fluid, and the pipette controller can adjust the pipette's dispensing operation parameters based on the identified fluid viscosity category. For example, but not by way of limitation, if the target fluid is determined to have a low viscosity, the controller may apply normal dispensing settings during the fluid dispensing operation. If the target liquid is determined to be of medium viscosity, the controller may increase the voltage to the drive motor and solenoid assembly and also force a suck-back mode (retraction of the lead screw that draws air into the syringe capillary) for aliquots that do not normally require a suck-back during dispensing of low viscosity liquids. If the target liquid is determined to be of high viscosity, the controller may disable the solenoid assembly so that dispensing is only possible through piston carriage movement and may notify the user that a syringe tip touch-off is required to ensure that no liquid remains in the syringe tip. What levels of viscosity fall into the exemplary categories of "low," "medium," and "high" will depend on the characteristics of the solenoid assembly 250 (e.g., maximum drive strength), and potentially the size of the tip orifice 515, 565, 615, the diameter of the capillary 605, and the sealing drag associated with the piston 625 within the capillary. Other factors may also be relevant.

In the pipette according to the invention, a DC motor is used for the motorized drive assembly 40, and typically, a DC motor draws more current during an aspiration operation for more viscous liquids. In particular, it has been found that the relationship between viscosity and current is strongest near the bottom position of the piston 625 in the capillary 605, where the flow path is most tightly constrained. Thus, in one embodiment of the pipette, current measurements are taken and integrated over a segment representing the first 30 percent of the maximum piston travel during an aspiration operation to identify a load characteristic associated with the viscosity of the liquid being aspirated and the syringe 600 being used. From this load characteristic, a lookup table can be referenced that determines the piston speed required for non-contact dispensing, the optimal solenoid voltage, and ultimately whether or not non-contact dispensing is possible. If non-contact dispensing is not possible, typically the user will be notified as described above, and the pipette 5 will switch to a "contact required" dispensing mode of operation that requires a touch off.

It is particularly important for pipettes according to the invention to be able to accurately switch between contact and non-contact dispensing because non-contact dispensing shortfalls tend to accumulate from one aliquot to the next if the solenoid assembly is driven with insufficient force to fully expel the desired volume of liquid and hit its hard stop. Therefore, the contact/non-contact determination and solenoid voltage are preferably set relatively conservatively, and contact dispensing is preferably used by default if the solenoid cannot be driven with sufficient force. Note that if a solenoid is not used for the desired dispense, the movement of the piston through the motorized drive assembly will generally need to be adjusted to compensate for the stroke length that would have been driven by the solenoid assembly.

Also, overdriving the solenoid assembly 250 is disadvantageous as it can lead to undesirable aerosolization of the dispensed aliquot. Therefore, the load characteristics and lookup tables can then be advantageously used to ensure that the solenoid is adequately driven even for low viscosity samples.

An exemplary pipette, such as the exemplary pipette 5, may also be programmed to perform a waste dispense function. The waste dispense function is preferably part of the pipetting process when using the exemplary pipette 5 and may be implemented by the controller 90. In general, the waste dispense function operates to eliminate backlash, account for manufacturing and/or assembly tolerance issues in the drive, solenoids, and the overall system, and may also remove air trapped near the distal end of the syringe tip. The controller 90 may be programmed to initiate a waste dispense function after each aspirate operation. The waste dispense function may also be initiated whenever all of the fluid previously aspirated into the syringe has been completely dispensed. The waste dispense volume is variable based on the viscosity of the liquid being worked with and the configuration of the syringe.

Another exemplary pipette feature that may be provided in accordance with the general inventive concept is an automatic syringe identification feature. Because the exemplary pipette may be usable with syringes of many different capacities, it will be appreciated that it would be beneficial for the exemplary pipette to automatically identify the volume of the syringe when the syringe is attached to the pipette. Such a feature may enable the pipette's controller to automatically select the appropriate operating parameters for a given syringe volume, thereby simplifying the setup process and eliminating operator error associated with misidentifying 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 capacity is associated with a different color and a corresponding colored area is placed on the syringe.

Using the exemplary syringes 500, 550, 600, 650, 700 depicted in FIGS. 6A-10B as an example, the color bands 450, 455, 460, 465, 470 corresponding to each given syringe capacity are disposed along the upper shoulders 520a, 570a, 680a, 730a of the syringe-retaining elements 520, 570, 620, 680, 730. In some embodiments, the color bands of a given syringe may extend only partially around the circumference of the syringe-retaining element, while in other embodiments, the color bands may extend the entire circumference of the syringe-retaining element. The color coding may also be provided as continuous patches of color, discrete patches of color, or in other readable forms such as, but not limited to, a collection of dots, segmented lines, etc. The colors may also be molded into the material from which a given syringe-retaining element is made. Additionally, in alternative embodiments, color coding may be located on the syringe piston instead of or in addition to the syringe retaining element of a given syringe.

24, one or more color sensors 475 may be present in the distal end of the exemplary pipette 5 and may be configured and arranged to image color bands on the syringe retaining elements 520, 570, 620, 680, 730 of the exemplary syringes 500, 550, 600, 650, 700. When the exemplary syringes 500, 550, 600, 650, 700 are attached to the pipette 5, the color sensor(s) 475 image the color bands 450, 455, 460, 465, 470 and transmit signals to the pipette controller 90 indicative of the color of the color bands. The controller 90, equipped with appropriate data (e.g., look-up tables, etc.) such as a process for preliminary and offline color recognition and registration operations using the color sensor(s) 475, can analyze the signals received from the color sensor(s) 475 to identify the color of the color bands 450, 455, 460, 465, 470, and thus the volume 500, 550, 600, 650, 700 of the installed syringe. As described above, once the syringe volume has been identified, the controller 90 can proceed to automatically set various pipetting parameters and/or indicate the syringe volume to the user of the pipette 5.

In the exemplary pipette and syringe embodiments presented herein, the upper shoulders 520a, 570a, 620a, 680a, 730a of the syringe holding elements 520, 570, 620, 680, 730 are preferably chamfered at an angle (e.g., 30°-60° relative to the top surface of the holding element). The chamfered upper shoulders 520a, 570a, 620a, 680a, 730a of the syringe holding elements 520, 570, 620, 680, 730 facilitate insertion of the syringe holding elements into the pipette 5. Additionally, the chamfered upper shoulders 520a, 570a, 620a, 680a, 730a of each syringe-retaining element provide an angled surface along which light emitted by the emitter portion (illumination source) 480 of the color sensor 475 may be reflected toward a detection surface 485 of the color sensor 475, which may be attached to a pipette at a corresponding angle. The use of such chamfered shoulders further allows for the use of vertical pad printing, which is the most efficient printing method for the color bands.

Although color sensing using a color sensor 475 to read color coding 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 illustrative purposes, it should be understood that the exemplary pipette embodiments are not limited to this arrangement. For example, but not limited to, the sensor(s) may be alternatively positioned to read color coding, printing, etc. on other areas of the syringe.

While particular embodiments of the general inventive concept have been described in detail above for purposes of illustration, the scope of the general inventive concept is not to be deemed limited by such disclosure, and modifications may be made without departing from the spirit of the general inventive concept, as evidenced by the appended claims.

Claims (13)

1. A method of operating a powered handheld positive displacement pipette including a solenoid assembly, a syringe, and a piston, comprising:
operating a motorized drive assembly to move the piston within the syringe to perform an aspiration operation to draw a liquid sample into the syringe;
measuring a characteristic of the motorized drive assembly during at least a portion of the aspirating operation;
determining dispensing operational parameters from the characteristics of the motorized drive assembly by applying a look-up table to the characteristics, the dispensing operational parameters including the voltage to apply to the solenoid assembly to enable non-contact dispensing of an aliquot of the liquid sample;
dispensing said aliquots from said liquid sample according to said dispensing operational parameters;
The method includes: the motorized drive assembly includes a DC motor, and the characteristic of the motorized drive assembly comprises a drive current of the DC motor measured during the aspiration operation.
The method of claim 1. the characteristic of the motorized drive assembly is comprised of the drive current of the DC motor integrated over a portion of the suction stroke;
The method of claim 2. the portion comprises a first section of travel originating from a bottom position of the piston within the syringe;
The method according to claim 3. the portion consisting of 30% of the travel from a bottom position of the piston within the syringe;
The method according to claim 4. the characteristics of the electric drive assembly are used to determine load characteristics of the DC motor;
The method of claim 2. The load characteristic is affected by the viscosity of the liquid sample.
The method according to claim 6. The load characteristics are further affected by the size of the syringe.
The method according to claim 7. The load characteristic is further affected by the size of the orifice of the syringe.
The method according to claim 7. 1. A method of operating a powered handheld positive displacement pipette including a solenoid assembly, a syringe, and a piston, comprising:
operating a motorized drive assembly to move the piston within the syringe to perform an aspiration operation to draw a liquid sample into the syringe;
measuring a characteristic of the motorized drive assembly during at least a portion of the aspirating operation;
determining a dispensing operational parameter from the characteristic of the motorized drive assembly by applying a look-up table to the characteristic , the dispensing operational parameter including an indication of whether non-contact dispensing of an aliquot of the liquid sample using the solenoid assembly is either enabled or disabled;
dispensing said aliquots from said liquid sample according to said dispensing operational parameters;
The method includes : If the non-contact dispensing is not possible,
notifying a user of the powered handheld positive displacement pipette that non -contact dispensing is not possible;
switching the powered handheld positive displacement pipette to a contact-required dispensing mode prior to dispensing the aliquot;
The method of claim 10 further comprising: and dispensing the aliquot comprises operating the motorized drive assembly and dispensing the aliquot while leaving the solenoid assembly de-energized.
The method of claim 11 . and if the non-contact dispensing is enabled, dispensing the aliquot comprises operating the motorized drive assembly and energizing the solenoid assembly to dispense the aliquot.
The method of claim 10 .

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