Pipette tip and mounting shaft

Abstract

A pipette tip configured to fit onto a mounting shaft, which includes a locking ring extending circumferentially outward onto which the pipette tip collar is mounted. When the pipette tip is fully mounted onto the mounting shaft, the locking ring on the inner surface of the tip collar engages with the lobe to provide an over-center engagement. The pipette tip includes a circular cantilever sealing ring that laterally seals the mounting shaft when the tip is fully mounted. The circular cantilever sealing ring has an annular wall surrounded by a gap. The annular wall has an inner surface that slopes inward to provide a lateral engagement with the mounting shaft. When the tip is mounted onto the mounting shaft, the annular wall bends radially outward toward the gap rather than stretching, thereby reducing the required insertion force.

Description

Technical Field

[0001] (Reference to Related Applications) This application claims the priority of U.S. Provisional Patent Application No. 63 / 490,891, filed on March 17, 2023, the content of which is hereby incorporated by reference in its entirety.

[0002] (Technical Field) The present invention relates to improvements in handheld pipettes and automated liquid handling systems. More specifically, the present invention relates to the configuration of disposable pipette tips and mounting shafts, providing a robust sealing engagement with low insertion and ejection forces while securely and stably maintaining the attached pipette tips on their respective mounting shafts during use.

Background Art

[0003] The use of disposable pipette tips with handheld pipettors and automated liquid handling systems is well known. Disposable pipette tips allow for repeated use of pipetting systems for transferring liquid reagents or liquid samples without carryover contamination. Disposable pipette tips are typically formed from plastic materials such as polypropylene and have a hollow, elongated, generally conical shape. The upper end of the pipette tip typically includes a collar that fits onto a mounting shaft on the pipette device. The mounting shaft is sometimes called the tip fitting. The mounting shaft or tip fitting contains an internal bore through which air is moved to draw liquid sample or reagent into the barrel of the pipette tip and then dispense the liquid sample or reagent from the pipette tip, usually to another location. The distal end of the pipette tip has a small opening through which the liquid sample or reagent is received when it is drawn into the barrel of the pipette tip and then dispensed.

[0004] Historically, disposable pipette tips have relied on tapered fits between the mounting shaft and the pipette collar, as well as a sealing ring on the inner circumference of the pipette collar, to secure and seal the pipette tip to the mounting shaft. In tapered fits, the seal between the mounting shaft and the disposable tip is achieved by pushing the tapered mounting shaft into the tapered collar until the mounting shaft is wedge-secured to the tip. At this point, a seal is achieved between the truncated conical tip collar and the mounting shaft as a result of crushing the sealing ring on the mounting shaft and / or stretching the diameter of the collar.

[0005] In addition to achieving a proper seal, it is also important that the position and orientation of the mounted pipette tip remain stable despite typical lateral momentum or slight knocking forces during normal use, such as when touching off against the side wall of the sample container. To ensure tip stability, users tend to forcefully pack the mounting shaft into the tip collar. In handheld pipetting, repeatedly using excessive force to mount and eject pipette tips is undesirable for ergonomic reasons. Reducing insertion and ejection forces is particularly important in multi-channel handheld pipettes. Minimizing insertion and ejection forces is also desirable in automated liquid handling systems, which are often configured to mount and eject 96 or 384 pipette tips simultaneously. Reducing insertion and ejection forces can reduce the size of the motor drive used in automated liquid handling systems, reduce system deformation, improve tip z-position accuracy, and otherwise improve the reliability of such systems.

[0006] Various systems have been devised to provide proper sealing and stability without requiring excessive insertion and discharging forces. Both U.S. Patent No. 6,955,077, “Pipette Tip with an Internal Sleeve and Method for Forming Same,” and U.S. Patent No. 7,047,828, “Pipette Tip with Internal Sleeve and Stabilizing Projections,” by Blazcak et al., are directed to pipette tips having branched or split sidewall portions that extend annularly upward to help seal the pipette tip against the mounting shaft. The branched portions that form the seal extend slightly inward from the tip wall in the relaxed position. When the conical mounting shaft is pushed into the pipette tip, the shaft engages with the branched portions, pressing them laterally and forming a seal between the pipette tip and the shaft. These patents claim to reduce the required insertion force. However, users can still pack pipette tips into the conical mounting shaft with excessive force. In other words, these patents describe a lateral seal, but the user naturally pushes the conical mounting shaft into the tapered tip until sufficient force is applied to feel that the tip is fixed and stable on the mounting shaft. These patents claim to reduce potential ejection force. However, ejection force depends on how much force was used to mount the pipette tip in the first place.

[0007] The assignee of this application is the assignee of U.S. Patent No. 7,662,343, entitled “Locking Pipette Tip and Mounting Shaft,” issued on 16 February 2010; U.S. Patent No. 7,662,344, entitled “Locking Pipette Tip and Mounting Shaft,” issued on 12 February 2010; U.S. Patent No. 8,277,757, entitled “Pipette Tip Mounting Shaft,” issued on 2 October 2012; U.S. Patent No. 8,501,118, entitled “Disposable Pipette Tip,” issued on 6 August 2013; U.S. Patent No. 8,877,513, entitled “Method of Using a Disposable Pipette Tip,” issued on 4 November 2014; and “Locking Pipette Tip and Mounting Shaft in a Handheld Manual,” issued on 1 May 2016, all of which are incorporated herein by reference. We have developed a reliable and ergonomic pipette tip mounting system, largely described in U.S. Patent No. 9,333,500, entitled “Pipette”. In these patents, owned by the assignee, the tip mounting shaft includes a locking section having a circumferentially spaced, outwardly extending locking loop, the locking loop positioned above a stop consisting of a step that spans between the locking section of the mounting shaft and a lower sealing section of the mounting shaft having a smaller diameter. When the mounting shaft is fully inserted into the collar of a compatible disposable pipette tip, the collar of the tip locks onto the mounting shaft. The bore of the pipette tip includes a circumferential shelf or shoulder that separates its upper collar from a tip sealing area located below the circumferential shelf of the tip barrel. The tip collar preferably includes a locking ring in or near the upper opening of the collar into which the mounting shaft is inserted. The dimensions of the collar, particularly the distance between the circumferential shoulder and the locking ring, are selected to match the dimensions of the mounting shaft between the stop and the catch surface at the upper end of the locking glove, thereby securely and reliably locking the pipette tip in a specific position and orientation.The locking lobe includes an inclined ramp portion, which, rather than stretching the tip collar, generally bends and deforms the pipette tip collar into a less rounded shape when the mounting shaft is inserted into the pipette tip, thereby reducing the amount of insertion force required to mount the tip. A preferred tip mounting shaft has three or more lobes evenly spaced around the mounting shaft, each having a concave relief portion spanning between the lobes to accommodate the inward strain of the tip collar between the lobes. As described above, the lobes include an inclined ramp that slopes gently between 10° and 20° with respect to the vertical axis of the mounting shaft. Each lobe extends outward along the ramp toward the top of the locking section of the mounting shaft until it rotates inward to form a catch surface. In some embodiments, the lobes have a ramp that decreases beyond the peak of the lobe, reducing the required discharge force compared to a steep catch surface. Once the mounting shaft is fully inserted into the pipette tip, the locking ring on the pipette collar engages with the catch surface or inclined ramp as it fits onto the lobe peaks, thereby providing a secure, snapped mounting. The peaks of each lobe are preferably slightly rounded to facilitate removal of the pipette tip.

[0008] When the mounting shaft is inserted into the pipette tip, the collar of the pipette tip bends and deforms into a non-rounded shape, but the circumferential shoulder on the pipette tip between the collar and the tip barrel isolates the sealing region at the upper end of the barrel from distortion. The structural isolation provided by the circumferential shoulder of the tip facilitates a reliable sealing engagement between the lower sealing section of the tip mounting shaft and the sealing region at the upper end of the tip barrel. In some embodiments, the sealing ring on the pipette tip extends inward from the upper end of the tip barrel below the circumferential shoulder and engages with the sealing region on the mounting shaft below the stop in an interference fit. In some embodiments, the sealing region on the mounting shaft is truncated cone-shaped. In other embodiments, the mounting shaft includes a groove below the stop that holds a sealing ring, such as an elastomer O-ring. The O-ring on the tip mounting shaft engages with the sealing region at the top of the tip barrel when the mounting shaft is fully inserted into the tip. O-rings are typically used to further reduce insertion force in larger tips, which generally have greater insertion force than smaller tips. In each of these cases, the sealing ring or area at the upper end of the tip barrel is isolated from strain by the structural integrity of the circumferential shoulder on the pipette tip, which is located between the distorted locking collar and the rounded tip barrel.

[0009] As described in the aforementioned patent owned by the assignee, the combination of the locking glove and the stop on the mounting shaft results in an ergonomic over-center locking engagement that provides tactile feedback to the user of the handheld pipette indicating that the disposable pipette tip is approaching and fully engaged with the mounting shaft. As the mounting shaft is pushed into the tip collar, the first point of contact is where the leading edge of the mounting shaft, i.e., the lower sealing section, enters through the circumferential shoulder of the pipette tip and contacts the sealing area of ​​the tip barrel. As the mounting shaft is further pushed into the pipette tip bore, the interference with the seal increases, and the inclined ramp area of ​​the locking glove on the mounting shaft engages with the tip collar, distorting the upper portion of the collar into a non-rounded shape. The overall insertion force is relatively light and ergonomic at that point compared to the prior art, but the force increases noticeably, providing the user with tactile feedback that the tip is nearly fully seated. This level of insertion force remains somewhat stable until the stopper on the mounting shaft engages with the circumferential shoulder on the pipette tip, abruptly stopping further movement of the mounting shaft into the tip. At this point, the lobe also snaps under the locking ring on the collar, thus warning the user not to use additional excessive force to mount the tip. These interrelated mounting conditions result in a secure and stable mounting with consistent sealing. In addition, bending the collar into a distorted shape stores energy within the collar when it is mounted. To eject the tip from the mounting shaft, a downward ejection force is required to release the locking ring on the collar from the locking lobe on the mounting shaft. Generally, a downward ejection force further deforms the collar outward on the lobe so that the locking ring slides down the peak of each lobe and is then released downward.When the tip is released from the lobe, the combination of the downward force from the pipette tip release mechanism and the energy stored within the distorted tip collar acting against the lobe's geometry tends to eject the tip from the mounting shaft, thereby facilitating the easy removal of the tip from the mounting shaft after use. [Overview of the project] [Problems that the invention aims to solve]

[0010] While the tip mounting systems described in the assignee's previous patents represent significant advances in the art in some circumstances, it is desirable to further reduce the tip insertion and ejection forces. The primary objective of the present invention is to reduce the required insertion and ejection forces without substantially affecting the stability of the mounted pipette tip. [Means for solving the problem]

[0011] The present invention relates to an improved seal on a pipette tip configured to be mounted on a tip fitting or mounting shaft having circumferentially spaced outward-extending locking lobes. In the above patent owned by the assignee, the pipette tip seals the mounting shaft below the circumferential shoulder of the tip between the tip collar and the barrel. That is, the seal occurs in the upper portion of the tip barrel. In the present invention, the pipette tip has a circular cantilever sealing ring on the circumferential shoulder between the tip collar and the barrel. The circular cantilever sealing ring has a laterally elastic annular sealing wall that extends from the circumferential shoulder on the pipette tip toward the collar opening and has a apex that abuts against a stop on the mounting shaft to provide tactile feedback that the pipette tip is fully mounted so that the user does not use excessive force when attempting to press the pipette tip onto the mounting shaft. The annular sealing wall of the cantilever sealing ring slopes slightly inward as it extends upward from the base. The upper portion of the annular sealing wall displaces laterally and radially outward when the mounting shaft is inserted, forming a lateral interference seal on the mounting shaft just below the stop on the mounting shaft. There is an annular gap between the annular sealing wall and the tip collar. The gap allows the annular sealing wall to move laterally outward without requiring the collar to stretch, which reduces the required insertion force compared to the pipette tips of the appropriator's prior art. In addition, the sealing region on the mounting shaft is preferably cylindrical, and the inner diameter just below the annular sealing wall of the cantilever ring seal is preferably selected to have zero interference with the cylindrical sealing region of the mounting shaft, which helps to further reduce the required insertion force.

[0012] Pipette tips incorporating a circular cantilever sealing ring have been found to require substantially less insertion and dispensing force than conventional pipette tips manufactured by the assignee. For larger tips, it is desirable to use an O-ring in the sealing area of ​​the mounting shaft to further reduce insertion force. However, since the circular cantilever sealing ring configuration significantly reduces insertion force compared to conventional sealing methods, it is conceivable that an O-ring may not be necessary even for larger tips.

[0013] The presence of a circumferential shoulder on the pipette tip maintains its circular shape at the base of the circular cantilever sealing ring, even if the collar is otherwise distorted into a non-rounded shape to cover and lock onto the lobes on the mounting shaft. As with the assignee's conventional pipettes, each of the locking lobes on the pipette tip mounting shaft includes a sloping ramp portion that slopes outward as the sloping ramp extends upward along the mounting shaft. The purpose of the sloping ramp portion of the lobe is to facilitate the distortion of the pipette tip collar into a non-rounded shape when the mounting shaft is inserted into the pipette tip. Relief portions that span between the outward-extending lobes and are recessed relative to the lobes accommodate the inward distortion of the pipette tip collar between the lobes, as in the prior art. Thus, when the pipette tip is mounted on the mounting shaft of the present invention, the pipette tip collar is distorted into a non-rounded shape, but the circumferential shoulder of the pipette tip between the collar and the barrel remains substantially circular and undistorted. The structural integrity of the circumferential shoulder on the tip, in turn, maintains the circular and distortion-free shape of the base of the circular cantilever sealing ring.

[0014] Preferably, each locking lobe includes a peak portion positioned at the maximum outward distance from the longitudinal axis of the mounting shaft, and a descending ramp portion that extends upward along the mounting shaft away from the peak of the lobe and is angled inward toward the longitudinal axis of the mounting shaft. However, the present invention can be implemented using a mounting shaft having a steeper catch surface on the locking lobe rather than a gently descending ramp. Preferably, the mounting shaft has three or more locking lobes. Preferably, the lobes constitute less than 15% of the outer circumference of the mounting shaft at the peak portion of the lobe, and the remaining portion of the outer circumference of the mounting shaft is consumed by the relief portions between the lobes. This configuration with relatively thin lobes helps reduce friction between the tip collar and the mounting shaft, reducing insertion and ejection forces, while simultaneously providing stable over-center mounting of the tip on the lobes.

[0015] The present invention can be used in connection with handheld, single-channel and multi-channel pipettes, as well as automated and semi-automated liquid handling equipment using arrays or matrices of multiple disposable pipette tips. The use of the aforementioned lobes and stops on the mounting shaft also ensures that each pipette tip in multi-channel applications is mounted at the same height and properly aligned. As will be described in more detail below with reference to the drawings, the pipette tip and mounting shaft configuration of the present invention reduces the required insertion and dispensing forces without substantially affecting the stability of the tip mounted on the mounting shaft under normal operating conditions.

[0016] These and other aspects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawing]

[0017] [Figure 1] This is a perspective view of a handheld electronic air replacement pipette incorporating the concept of the present invention.

[0018] [Figure 2] A perspective view showing a disposable pipette tip and a tip mounting shaft configured according to an exemplary embodiment of the present invention.

[0019] [Figure 3] A side view of the mounting shaft and the pipette tip shown in FIG. 2.

[0020] [Figure 4] A longitudinal sectional view taken along line 4-4 of FIG. 3.

[0021] [Figure 5] A detailed view of the area enclosed by line 5-5 of FIG. 4 showing the upper locking collar, circumferential shoulder and circular cantilever sealing ring on the disposable pipette tip shown in FIGS. 2 and 4.

[0022] [Figure 6] A detailed view of the area enclosed by line 6-6 of FIG. 4 showing the locking section, cylindrical sealing section and stop of the tip mounting shaft shown in FIGS. 2 and 4.

[0023] [Figure 7] A side view showing the mounting shaft inserted into the disposable pipette tip.

[0024] [Figure 8] A longitudinal sectional view taken along line 8-8 of FIG. 7.

[0025] <​​​​​​​​ [Figure 11] This is a cross-sectional view along line 11-11 in Figure 10, showing the pipette tip collar and locking ring, which are distorted into a non-rounded shape when the pipette tip is fully mounted on the mounting shaft.

[0028] [Figure 12] This diagram is similar to Figure 10, which shows the pipette tip being discharged from the mounting shaft.

[0029] [Figure 13a] This is a schematic diagram illustrating the interaction between the cylindrical sealing region on the pipette mounting shaft and the annular wall of the circular cantilever sealing ring on the pipette tip when the mounting shaft is inserted into the tip collar. [Figure 13b] This is a schematic diagram illustrating the interaction between the cylindrical sealing region on the pipette mounting shaft and the annular wall of the circular cantilever sealing ring on the pipette tip when the mounting shaft is inserted into the tip collar. [Figure 13c] This is a schematic diagram illustrating the interaction between the cylindrical sealing region on the pipette mounting shaft and the annular wall of the circular cantilever sealing ring on the pipette tip when the mounting shaft is inserted into the tip collar.

[0030] [Figure 14] This is an enlarged cross-sectional view of a circular cantilever sealing ring and stabilizing ring in a disposable pipette tip molded according to an exemplary embodiment of the present invention.

[0031] [Figure 15] The present invention includes data demonstrating that using disposable pipette tips and tip-mounted shafts configured according to the present invention substantially reduces insertion and dispensing forces.

[0032] [Figure 16] An alternative embodiment of a mounting shaft having an O-ring in the sealing region on the mounting shaft is shown.

[0033] [Figure 17] This is a perspective view of an exemplary handheld multichannel pipette using the present invention.

[0034] [Figure 18] This is a manually assisted 96-well pipetting device using the present invention.

[0035] [Figure 19] This shows a structural analysis of a tip configured according to an exemplary embodiment of the present invention, which is subject to lateral displacement at the dispensing end of the tip, such as during a standard pipetting operation when the tip touches off. [Modes for carrying out the invention]

[0036] Figure 1 shows a handheld electronic air displacement pipette 10 incorporating a tip mounting shaft 12 configured according to an exemplary embodiment of the present invention. A disposable pipette tip 14, similarly configured according to the present invention, is attached to the pipette tip mounting shaft 12. The pipette tip mounting shaft 12 is also commonly referred to as tip fittings.

[0037] The handheld pipette 10 includes a housing 16 designed to be held in the palm of the user's hand. Internal components of the pipette (not shown) drive a piston extending through a sealing assembly to move air within the aspiration and dispensing cylinder. The tip mounting shaft 12 is screwed into or otherwise attached to the lower end of the pipette 10 to fluidly communicate with the aspiration and dispensing chamber. The attachment of the mounting shaft 12 to the pipette is not particularly relevant to the idea of ​​the present invention and is well known in the art. A run button 18 is provided for the user to command the pipette to aspiration and dispensing. The pipette 10 also includes a lever or dispensing button 20 which is actuated in the direction of arrow 22 to move a dispensing mechanism sleeve 24 downward and dispensing a disposable pipette tip 14 from the mounting shaft 12. The disposable pipette tip 14 is mounted for use by inserting the mounting shaft 12 on the pipette 10 into the collar of the disposable tip 14.

[0038] Although the present invention is illustrated and described in Figures 1 to 13 with respect to its use in a single-channel handheld electronic air-displacement pipette 10, the present invention is also useful with respect to manual pipettes, electronic or manual multi-channel handheld pipettes (see Figure 17), and automated liquid processing systems and semi-automated liquid processing machines using disposable pipette tips (see Figure 18). The present invention provides a robust and stable sealing engagement of each pipette tip to each mounting shaft in automated or semi-automated liquid processing systems, as well as a robust and stable sealing engagement with handheld pipettes. The reduction in insertion and dispensing forces provided by the present invention is useful not only for handheld pipettes, but also in automated or semi-automated systems having 96 or 384 channels.

[0039] As shown in Figure 2, the mounting shaft 12 of this exemplary embodiment has threads 26 for mounting on the lower end of a suction and dispensing cylinder (not shown) on the pipette 10. The dimensions of the mounting shaft 12 match the dimensions of the pipette tip 14, so that only pipette tips 14 with the appropriate dimensions will fit and engage properly with the mounting shaft 12. For example, if you choose to use a pipette tip with a different bore dimension in the collar or seal area, even if the pipette tip is configured according to the present invention, you will need to replace the mounting shaft 12 and / or the tubular peel shaft sleeve 24 with one of the appropriate dimensions. In a laboratory bench where multiple color sizes of pipette tips are used, it is common to have multiple handheld pipettes, each with a different sized mounting shaft. The pipettes and racks that house the tips are preferably color-coded so that the user can easily identify the tip to which it is assigned and that each has the appropriate color to fit the respective mounting shaft. In an automated or semi-automated system as shown in Figure 16, a removable multi-channel pipetting head has a mounting shaft that is sized and color-coded for each color on the disposable pipette tip.

[0040] Referring here to Figures 2 to 6 in general, the mounting shaft 12 includes a central bore 28 (Figure 6) for air to pass between the aspiration and dispensing cylinder in the pipette 10 and the pipette tip 14, as is well known in the art. The pipette mounting shaft 12 has an upper locking section 30, a lower section 32, and a stop 34 positioned between the upper locking section 30 and the lower section 32. Sealing occurs in a region 55 of the lower section 32 just below the stop 34 (see Figure 6). The locking section 30 of the mounting shaft 12 has an outwardly extending locking glove 50 and a spanning recessed region 58 (see, for example, Figure 6) between the locking glove 50.

[0041] A pipette tip 14 generally consists of a collar 36, a barrel 38, and a circumferential shoulder 40 (see, for example, Figures 4 and 5) that extends around the inner bore of the tip 14 and connects the lower end of the collar 36 to the upper end of the barrel 38. The upper end of the collar 36 has an opening 42 for receiving the pipette mounting shaft 12. The lower end of the barrel 38 has a small opening 44 through which, during normal operation of the pipette 10, liquid is drawn into the tip barrel 38 and dispensed from the tip barrel 38. Support ribs 46 (Figure 3) extend downward from the collar 36 onto the outer surface of the disposable pipette tip 14. The support ribs 46 function to hold the tip 14 or an array of tips 14 in a rack for subsequent use and mounting, as is known in the art.

[0042] A preferred configuration of the pipette tip 14 is described here with reference to Figure 5. A circumferential locking ring 48 is preferably located on the inner surface of the collar 36 of the pipette tip 14. The locking ring 48 is located at or slightly below the position of the opening 42 in the collar 36 into which the mounting shaft 12 is inserted. The locking ring 48 extends slightly inward from the inner wall of the collar 36, preferably within a range of 0.025 to 0.25 mm, to provide an overcenter locking fit across the peak 61 of the lobe 50 on the mounting shaft 12 (see Figure 6). The locking ring 48 may include an optional air bleed 52, but such an air bleed is not necessary in most situations, because the deformation of the collar 36 when the tip is mounted should normally provide sufficient clearance to cover the recessed area 58 of the mounting shaft 12. The inner surface of the collar 36 is preferably slightly tapered or slightly truncated cone, but can also be cylindrical. The preferred taper is between 0° and 10°. In any case, the horizontal section through the main compartment of collar 36 is circular.

[0043] As previously described, the circumferential shoulder 40 of the tip 14 connects the lower end of the collar 36 to the upper end of the barrel 38. The circular cantilever sealing 100 includes an elastic annular wall 101 extending from the tip shoulder 40 toward the collar opening 42. The purpose of the laterally elastic annular wall 101 is to laterally engage with and seal the cylindrical sealing area 55 (see Figure 6) on the mounting shaft 12 when the tip 14 is fully mounted on the mounting shaft 12. The annular wall 100 has an upper free end 102 that abuts against the stop 34 on the pipette mounting shaft 12 when the tip 14 is fully mounted on the mounting shaft 12. See, for example, Figures 9 and 10.

[0044] The collar 36 of the disposable pipette tip 14 is sufficiently flexible so that when the pipette tip 14 is mounted on the tip mounting shaft 12, it deforms outward at the lobes 50 on the mounting shaft 12 and inward at the recessed relief portion 58 (relief portion) on the mounting shaft between the lobes. However, the circumferential shoulder 40 has sufficient structural integrity to maintain the roundness of the circular cantilever sealing ring 100 so that the inner surface 104 of the annular wall 101 laterally seals the sealing area 55 of the mounting shaft 12.

[0045] The circumferential shoulder 40, as shown in Figure 5, is continuous around the outer circumference of the tip 14. In the exemplary embodiment, the shoulder 40 has an angle in cross-section, but it is not required to have an angle. The circumferential shoulder 40 provides structural integrity that helps separate and isolate the distortion of the collar 36 from the circular cantilever sealing ring 100. As best shown in Figure 11, when the mounting shaft 12 is fully inserted into the pipette tip 14, the collar 36 is deformed into a non-rounded shape. The circumferential shoulder 40 of the tip 14 isolates the circular cantilever sealing ring 100 from this distortion, thereby facilitating an effective lateral seal between the inner surface 104 of the annular wall 101 of the circular cantilever sealing ring 100 on the pipette tip 14 and the sealing area 55 (not shown in Figure 11). The mounting shaft 12 is around the entire outer circumference.

[0046] Referring again to Figure 5, when the tip 14 is fully mounted on the mounting shaft 12, a stop 34 on the mounting shaft 12 engages with the upper edge 102 of the annular wall 101 of the circular cantilever sealing ring 100 to precisely position the mounting height of the tip 14 on the mounting shaft 12. In a multi-channel device, this configuration ensures the same vertical mounting distance from tip to tip, which facilitates accurate and consistent tip positioning during pipetting. When the tip 14 is in a relaxed state, the inner surface 104 of the annular wall 101 has a slight inward angle as the annular wall 100 extends upward toward the collar opening 42. This slight inward inclination results in a lateral interference fit between the inner surface 104 of the annular wall 101 and the cylindrical sealing region 55 of the mounting shaft 12 when the mounting shaft 12 is fully inserted. The annular wall 101 extends above the circumferential shoulder 40 such that a gap 106 exists between the annular wall 100 and the collar side wall 36. The gap 106 allows the annular wall 100 to pivot laterally outward when the pipette mounting shaft 12 is inserted into the tip 14. The inner diameter immediately below the annular wall 101 is selected to have zero interference with the mounting shaft 14. Rather, the lateral interference fit of the annular wall 101 of the circular cantilever sealing ring 100 above the shoulder 40 of the tip 14 results in a sealing engagement of the tip 14 with respect to the mounting shaft 12.

[0047] Referring to Figures 6, 9, and 10, the locking section 30 of the mounting shaft 12 has a central cylindrical alignment section 56 located directly above and adjacent to the stop 34. When the pipette tip 14 is mounted on the mounting shaft 12, the central cylindrical alignment section 56 on the mounting shaft 12 helps to keep the tip 14 in a straight line, however, when the tip 14 is mounted on the mounting shaft 12, it is preferable that there is a gap (clearance) between the collar sidewall 36 of the tip 14 and the central cylindrical alignment section 56. The diameter of the mounting shaft 12 decreases (e.g., steps down) at the stop 34 between the cylindrical compartment 56 above the stop 34 and the sealing compartment 55 below the stop 34. The decrease in the shaft diameter at the stop 34 is roughly balanced by the decrease in the diameter of the fitted pipette tip 14 on its circumferential shelf 40. This decrease is preferably in the range of about 0.1 to 1.0 mm. Since the purpose of these components is to provide a secure and stable locking engagement of the pipette tip 14 on the mounting shaft 12, and not to provide a seal, the cylindrical matching compartment 56 and the stop 34 do not need to be continuous around the outer circumference of the mounting shaft 12. In this regard, the configuration of the mounting shaft 12 in the exemplary embodiment is similar to that disclosed in the above incorporated patent application.

[0048] Above the cylindrical alignment section 56, the diameter of the mounting shaft 12 decreases, which may result in an additional gap between the mounting shaft 12 and the collar of the pipette tip 14. Referring to Figure 6, as previously described, the upper part of the locking section 30 of the mounting shaft 12 includes two or more locking lobes 50 evenly spaced circumferentially around the mounting shaft 12, and a corresponding concave region 58 spanning between the locking lobes 50. The lobes 50 include inclined ramps 60 that slope relatively gently. A preferred inclination of the inclined ramps 60 with respect to the vertical axis of the mounting shaft is between 10° and 20°. The lobes 50 have an outward angle as the inclined ramps 60 extend toward the peak portion 61 of the lobes 50. Each lobe 50 also includes an inclined ramp 62 that slopes inward as the inclined ramp 62 extends upward from the peak portion 61. Preferably, the inward slope of the inclined ramp 62 is the same as the outward slope of the inclined ramp 60, but such symmetry is not required. The peak portion 61 is preferably curved and has a radius between 0.15 and 0.38 mm. In the peak portion 61, the lobe 50 preferably extends outward beyond the outer surface of the cylindrical alignment section 56, although the exact preferred dimensions depend on the amount of taper of the collar 36 in the corresponding fitted pipette tip and the thickness of the tip wall. The mounting shaft 12 is preferably made of a material that reduces rough edges and friction.

[0049] Preferably, the recessed portions 58 between the lobes 50 consume substantial portions around the mounting shaft 12 along the inclined ramp 62 where the locking ring 48 on the pipette tip 14 normally engages when the mounting shaft 12 is fully inserted into the pipette tip 14, and at the peak portion 61. According to an exemplary embodiment of the present invention, the lobes 50 at the peak portion 61 consume less than 15% of the outer circumference of the mounting shaft. The narrow locking lobes 50 reduce friction associated with mounting and ejecting the pipette tip 14. The recesses 58 extend downward along the mounting shaft 12 below the height of the lobes 50 to accommodate the inward strain of the tip collar 36 when the tip is mounted on the mounting shaft 12.

[0050] Referring here to Figures 13a and 13c, when the mounting shaft 12 is pushed into the tip 14, the first contact point occurs when the leading edge 110 of the mounting shaft 12 passes through the opening formed by the upper edge 102 of the annular wall 101 of the circular cantilever sealing ring 100 (Figure 13a). The leading edge 110 of the mounting shaft 12 is substantially tapered to facilitate secure insertion of the leading edge 110 through the upper edge 102 of the annular wall 101.

[0051] The corner between the upper edge 102 and the inner surface 104 is rounded to facilitate proper insertion. As the mounting shaft 12 continues along its insertion path, the inner surface 104 of the annular wall 100 is bent outward as the diameter of the mounting shaft 12 increases. Figure 13b shows the lateral inner surface 104 engaging with the sealing region 55 of the mounting shaft 12 to provide a lateral sealing engagement. The sealing region 55 on the mounting shaft 12 is preferably cylindrical so that the lateral seal is cylindrical and vertical. This configuration is particularly advantageous with a cylindrical sealing region 55 on the mounting shaft 12 because a lateral cylindrical seal provides a robust seal, and does so with relatively low insertion force. In Figure 13b, the annular wall 101 and its inner surface 104 are depicted as if the annular wall 104 were theoretically not bent outward when the mounting shaft 12 is inserted. Figure 13b shows the amount of interference between the inner surface 104 of the annular wall 101 and the cylindrical sealing region 55 on the mounting shaft 12, as illustrated. Figure 13c is drawn in a similar manner.

[0052] Figure 13c shows a mounting shaft 12 fully inserted into a pipette tip 14, with a circumferential stop 34 on the mounting shaft 12 in contact with the annular wall 101 and upper edge 102 of the circular cantilever sealing ring 100 on the tip 14. As previously described, in the exemplary embodiment, the stop 34 is angled so that it contacts a corner 108 between the inner surface 104 of the annular wall 101 and the upper edge 102. The stop 34 is not intended to seal at this location and may optionally contain one or more voids around its outer circumference to ensure that no seal is made against the stop 34. Having a stop 34 at a certain angle is advantageous because it accommodates manufacturing tolerances within the mounting shaft 12 or pipette tip 14.

[0053] Reference numeral 114 in Figure 13c identifies the zero-interference threshold location between the inner surface 104 of the annular wall 101 of the circular cantilever sealing ring 100 on the pipette tip 14 and the cylindrical sealing region 55 of the mounting shaft 12. Lateral interference seal occurs on the inner surface 104 above the zero-interference threshold location 114 and corner 108. In this exemplary embodiment, the vertical length of the interference is preferably 0.20–0.30 mm. The maximum interference is preferably 0.08 mm, which has been shown to provide a robust seal even when normal machining and forming tolerances are taken into account. The annular wall 101 bends radially outward into a gap 106 to accommodate the interference between the cylindrical sealing region 55 on the mounting shaft 14 and the inner surface 104 of the annular wall 104. In this exemplary embodiment, the height of the gap 106 is 0.30 mm and its maximum width is 0.30 mm.

[0054] The diameter of the mounting shaft 12 is slightly tapered between the cylindrical sealing region 55 and the more aggressively tapered leading edge 110. At the same time, the inner diameter of the pipette tip 14 below the zero interference threshold position 114 continues to slightly enlarge to ensure that there is clearance and very little friction below the threshold position 114. Still referring to Figure 13c, just above the aggressively tapered leading edge 110, the mounting shaft 14 abuts against the stabilizing ring 112 at the upper end of the barrel 38 of the pipette tip 14. The stabilizing ring 112 aligns the tip 14 on the mounting shaft 12 so that the circular cantilever sealing ring 100 does not need to align the tip 14, thereby improving both the symmetry of the interference fit in the lateral seal 104 and the alignment of the tip opening 44 (Figure 2). Structural modeling of the chip (Figure 19) showed that the removal of the stabilization ring 112 increased the force on the sealing ring 100 by 72%, increasing the risk of fluid leakage (e.g., during touch-off). This was empirically confirmed in experiments demonstrating that chips without the stabilization ring 112 consistently leaked when lateral displacement was applied, whereas chips with the stabilization ring did not leak even when equivalent lateral displacement was applied.

[0055] Referring to Figures 9 and 10, as the mounting shaft 12 is inserted into the tip 14, the inclined ramp 60 of the locking lobe 50 begins to engage with the top of the tip collar 36 just before the circumferential stop 34 on the mounting shaft 12 contacts the upper edge 102 of the annular wall 101 of the circular cantilever sealing ring 100 on the tip 14. As the mounting shaft 12 is further inserted into the tip, the inclined ramp 60 of the lobe 50 presses against the locking ring 48 of the tip collar 36, gently bending the collar 36 and deforming it into a non-rounded shape. The recessed area 58 on the mounting shaft 12 provides sufficient clearance for the straightening of the collar 36 that occurs between the lobes 50. The intention is that the lobes 50 on the mounting shaft 12 bend the collar into a non-rounded shape rather than straighten it. When the mounting shaft 12 is fully inserted into the pipette tip collar 36 (see Figure 10), the stop 34 on the mounting shaft 12 abuts against the corner 108 of the annular wall 100 of the circular cantilever sealing ring 100 on the pipette tip 14, thereby preventing further movement of the shaft 12 into the tip 14. At the engagement point, the locking ring 48 on the inner surface of the tip collar 36 slides more or less simultaneously over the peak portion 61 of the lobe 50 on the mounting shaft 12 so that the locking ring 48 engages with the descending inclined portion 62 of the lobe 50. Thus, the pipette tip 14 is firmly locked in place on the mounting shaft 12, with positive engagement between the stop 34 on the mounting shaft 12 and the corner 108 of the annular wall 104 on the pipette tip 14, and between the descending inclined portion 62 of the lobe 50 on the mounting shaft 12 and the underside of the locking ring 48 on the tip collar 36. As previously mentioned, the stabilizing ring 112 at the top of the tip barrel 38 aligns the tip 14 below the circular cantilever sealing ring 100, while the interaction between the lobe 50 on the mounting shaft 12 and the locking ring 48 on the tip collar 36 results in alignment above the circular cantilever sealing ring 100.

[0056] Figure 11 shows a cross-sectional view looking down at the tip collar 36 locked to the mounting shaft 12 above the lobe 50. The collar 36 is bent and deformed into a non-rounded shape. The dashed line 70 indicates the outer surface of the collar opening in a loose, rounded state before being mounted on the mounting shaft 12. The dashed line 72 indicates the position of the inner surface of the locking ring 48 on the collar 36 in a loose, rounded state before being mounted on the lobe 50 on the mounting shaft 12. Although the mounted collar 36 is bent and deformed into a non-rounded shape, the circumferential shoulder 40 and the circular cantilever sealing ring 100 remain circular due to the structural integrity of the circumferential shoulder 40.

[0057] By bending and deforming the tip collar 36 rather than stretching it to mount the tip 14, less insertion force is required compared to tip mounting configurations that require a tight interference fit or stretching of the tip collar. In addition, as described above, bending the annular wall 101 of the circular cantilever sealing ring 100 when providing a lateral interference seal further reduces the required insertion force compared to stretching the tip or crushing the annular seal on the pipette tip. Nevertheless, the user receives clear tactile feedback that full engagement has occurred when the stop 34 engages with the circular cantilever sealing ring 100 on the tip 14, the locking ring 48 on the tip 14 slides along the lobe 50, and the mounting shaft 12 contacts the stabilizing ring 112. The locking engagement is robust and prevents unintended tip detachment when lateral forces are applied to the tip, such as during a touch-off procedure. Furthermore, the seal is robust despite the required low insertion force.

[0058] Another advantage of the present invention is lower ejection forces, which is advantageous not only for handheld single-channel and multi-channel pipettes but also for automated or semi-automated systems. Referring to Figure 12, as is common in the art, the stripping sleeve 24 is shown to move downward (arrow 22a), pushing the top of the collar 36 to eject the tip 14. As the locking ring 48 clears over the peak portion 61 on the lobe 50, the energy accumulated in the distorted collar 36 is released, facilitating the efficient ejection of the tip 14 from the mounting shaft 12. The use of the lobe 50 having a gently sloping descending ramp 62 and a curved peak portion 61 connecting the sloping ramp 60 to the descending ramp 62 provides sufficient lateral stability despite reducing the required ejection force. Furthermore, this configuration (i.e., the use of stop 34) prevents excessive insertion of the mounting shaft 12 into the tip 14, so the required ejection force is consistent and does not depend on how deeply the mounting shaft 12 is inserted, as in some prior art pipette tips. In addition, releasing the tip 14 from the circular cantilever sealing ring 100 requires less force than prior art annular sealing rings, which rely on stretching the tip or crushing the sealing ring.

[0059] Disposable pipette tips 14 are typically manufactured by injection molding virgin polypropylene. Figure 14 is an enlarged cross-sectional view of a portion of a polypropylene pipette tip 14 molded to have the configuration according to exemplary embodiments of the present invention described in Figures 1 to 13. Figure 14 shows a cross-section of a circular cantilever sealing ring 100 and a stabilizing ring 112. The pipette tip is for a 125 μl fitting. The minimum diameter of the inner surface 104 of the annular wall 101 of the circular cantilever sealing ring 100 is 2.58 mm ± molding tolerance. The height of the gap 106 around the annular wall 101 is 0.30 mm ± molding tolerance. The inner diameter of the stabilizing ring 112 is 2.58 mm ± molding tolerance. Figure 15 includes data comparing the insertion force for a tip photographed in Figure 14 and constructed according to the present invention with the insertion force for a tip constructed according to the assignee's previous design, which was sealed using a sealing ring in the barrel of the tip. The data in Figure 15 shows that the maximum force required to insert the mounting shaft 12 into the pipette tip 14 constructed according to the present invention is substantially less than the maximum force required to insert the mounting shaft 12 into the pipette tip 14 constructed according to the present invention, which is of a similar size (125 μl) and according to the assignee's previous design. The y-axis in Figure 15 plots the insertion force as a percentage of the maximum insertion force of the previous design, and the x-axis plots the insertion distance as a percentage of the end of the insertion process. In both cases, the required insertion force has a local peak because the locking ring 48 on the pipette tip 14 is deformed when the inclined ramp 60 on the lobe 50 of the mounting shaft 12 is pressed against the locking ring 48. The local maximum for the tip constructed according to the present invention is approximately 50%, compared to approximately 89% for the assignee's previous design. As the mounting shaft 12 is further inserted, the insertion force decreases slightly as the peak of the lobe 50 passes the locking ring 48 on the tip collar. Next, in both cases, the insertion force tends to be slightly upward until the stop 34 on the mounting shaft 12 reaches its moving end.While the assignee's previous chips required approximately 100% at the end of the insertion process, the chips constructed according to the present invention require approximately 58% at the end of the insertion process. The reduction in insertion force is due to the use of a circular cantilever sealing ring 100 instead of a sealing ring in the barrel that would require the barrel to stretch or the sealing ring to break.

[0060] The data in Figure 15 is for a 125 μl pipette tip, but the present invention is useful for pipette tips with different sizes of collars. For tips with larger tip collars, it may be desirable to modify the design as shown in Figure 16 to incorporate the O-ring 120 into the sealing region 155 of the mounting shaft 112. The configuration of the circular cantilever sealing ring 100 is conceptually invariant, but the O-ring 120 engages with the inner surface of the annular wall 101 instead of the cylindrical portion of the mounting shaft 112. Despite its ability to work effectively with the mounting shaft 112 having the O-ring 120, the present invention significantly reduces the insertion force, and it is considered that the present invention eliminates the need to use the O-ring 120 in most practical situations.

[0061] Although the above embodiments of the present invention have been described in relation to single-channel handheld pipettes, the present invention is also extremely useful for multi-channel handheld pipettes, an example of which is shown in Figure 17. The present invention is also useful for automated and semi-automated liquid processing systems. Figure 18 shows an exemplary manually oriented 96-channel semi-automated pipetting system that can be configured to use pipette tips configured according to the present invention.

[0062] While exemplary embodiments of the present invention have been described with reference to the drawings, it should be understood by those skilled in the art that various aspects and configurations of the present invention can be carried out in other forms. For example, although the mounting shaft is described as having three lobes, it may not be necessary for it to have more than two lobes.

Claims

1. A tip mounting shaft includes an upper locking section with a stop; a plurality of outwardly extending lobes positioned above the stop and spaced circumferentially around the locking section of the mounting shaft; and recessed relief sections spanning circumferentially between the lobes and recessed relative to the lobes, each of which has a peak spaced longitudinally above the stop on the mounting shaft by a predetermined distance; and the tip mounting shaft also includes a sealing section positioned below the stop. Disposable pipette tips for use with pipetting systems, A barrel having a downward opening, wherein a liquid is drawn into the barrel through the downward opening and dispensed from the barrel, and the diameter of the downward opening is less than the diameter of the barrel at the upper end of the barrel, In its relaxed state, the collar has a continuous inner surface with a circular outer circumference, an upper opening for receiving the tip mounting shaft, and a lower end having an inner diameter larger than the inner diameter of the upper end of the barrel. A circumferential tip shoulder connects the lower end of the collar to the upper end of the barrel, The invention includes a circular cantilever sealing ring having an annular wall extending from the tip shoulder toward the collar opening, which laterally engages with and seals the sealing area of ​​the mounting shaft when the tip is fully mounted on the mounting shaft, The annular wall has an upper edge that abuts against the stop on the pipette mounting shaft when the tip is fully mounted on the mounting shaft. The collar of the disposable pipette tip is sufficiently flexible to deform outward at the lobes on the mounting shaft and inward at the recessed relief portion on the mounting shaft between the lobes when the pipette tip is mounted on the tip mounting shaft, and the circumferential shoulder has sufficient structural integrity to maintain sufficient curvature of the circular cantilever sealing ring so that the annular wall seals the sealing area of ​​the mounting shaft laterally. Disposable pipette tips.

2. The disposable pipette tip according to claim 1, further comprising means for engaging with the respective locking lobes on the mounting shaft after the collar has been distorted outward by the lobe and inward by the recessed relief portion when the disposable pipette tip is mounted on the tip mounting shaft and the annular wall engages with the stop on the mounting shaft.

3. Disposable pipette tip according to claim 2, the means for engaging with the pipette surface on each of the locking gloves includes a locking ring that extends inward from the continuous inner surface of the collar and around the entire outer circumference of the collar or substantially around the entire outer circumference of the collar, and is positioned on the rim of the upper opening of the collar and above the circumferential shoulder at a distance corresponding to the longitudinal distance between the stop on the mounting shaft and the peak of each of the locking gloves on the mounting shaft.

4. The disposable pipette tip according to claim 1, wherein the circumferential shoulder reduces the internal bore diameter of the pipette tip by 0.1 to 1.0 mm.

5. The disposable pipette tip according to claim 1, wherein the inner surface of the annular wall inclines inward in its relaxed state as it extends from the circumferential shoulder toward the opening of the collar.

6. The disposable pipette tip according to claim 5, wherein the inner surface of the annular wall forms an interference of 0.05 to 0.11 mm with the cylindrical sealing region on the mounting shaft.

7. The disposable pipette tip according to claim 5, wherein the inclination of the inner surface continues as the surface extends downward toward a threshold location for a zero interference location and beyond the threshold location, providing sufficient clearance between the inner surface of the pipette tip and the mounting shaft below the threshold location.

8. The disposable pipette tip according to claim 7, further comprising a stabilizing ring positioned in the upper portion of the tip barrel extending inward from the inner surface of the barrel.

9. The disposable pipette tip according to claim 1, further comprising a stabilizing ring positioned on the upper portion of the tip barrel.

10. The disposable pipette tip according to claim 1, wherein the circular cantilever sealing ring on the pipette tip further includes a circumferential gap above the circumferential shoulder between the annular wall of the circular cantilever sealing ring and the tip collar.

11. The disposable pipette tip according to claim 8, wherein the height of the circumferential gap is in the range of 0.28 to 0.38 mm.

12. The disposable pipette tip according to claim 2, wherein the means for engaging with each of the locking gloves on the mounting shaft includes a circumferential locking ring in the opening of the collar or near the opening of the collar.

13. The disposable pipette tip according to claim 9, wherein the circumferential locking ring includes a void.

14. The disposable pipette tip according to claim 1, wherein the pipette tip is made of molded polypropylene.

15. Disposable pipette tips, Includes a pipette tip mounting shaft, It is a pipette system, The aforementioned disposable pipette tip is A barrel having a downward opening, through which a liquid is drawn and dispensed from the barrel, A collar having an upward opening for receiving a pipette tip mounting shaft, wherein the lower end of the collar has an inner diameter larger than the inner diameter at the upper end of the barrel, and a circumferential shoulder connects the lower end of the collar to the upper end of the barrel, A circular cantilever sealing ring having an annular wall extending from the tip shoulder toward the collar opening, and having an inner surface, an upper edge, and a corner between the inner surface and the upper edge, wherein the inner surface is a circular cantilever sealing ring that inclins inward as it extends upward toward the collar opening, The aforementioned pipette mounting shaft is An upper locking section having a stop that engages with and abuts against the annular wall of the circular cantilever sealing ring when the mounting shaft is fully inserted into the collar of the pipette tip, To seal the mounting shaft against the pipette tip when the mounting shaft is fully inserted into the collar of the pipette tip, a sealing section below the stop engages laterally with the inner surface of the annular wall of the circular cantilever sealing ring on the pipette tip, A plurality of outwardly extending lobes are spaced circumferentially around the upper locking section of the mounting shaft and positioned above the stop on the mounting shaft to engage with the inner surface of the collar, When the pipette tip is mounted on the mounting shaft over the stop and the lobes, the collar includes a recessed relief portion that spans between the lobes and is recessed relative to the lobes, such that the collar deforms outward at the lobes and inward at the relief portion. Pipette system.

16. The pipette system according to claim 15, wherein the sealing region of the mounting shaft is cylindrical.

17. The pipette system according to claim 15, wherein the sealing region of the mounting shaft includes an O-ring.

18. The pipette system according to claim 15, wherein the stop on the mounting shaft is angled, and the angled stop engages with the corner of the annular wall of the circular cantilever sealing ring when the mounting shaft is fully inserted into the pipette tip.

19. The pipette system according to claim 15, wherein each lobe includes a peak portion located at the maximum outward distance from the longitudinal axis of the mounting shaft; an inclined ramp portion, the inclined ramp portion which inclins outward as the inclined ramp extends upward along the mounting shaft toward the peak portion to facilitate distortion of the pipette tip collar as the mounting shaft is inserted into the pipette tip; and a descending ramp portion, the descending ramp portion which inclins inward as the descending ramp extends upward along the mounting shaft toward the peak.

20. The pipette system according to claim 15, wherein the inner surface of the collar of the pipette tip includes a substantially circumferential locking ring extending inward from the inner surface of the collar, which engages with two or more outwardly extending lobes on the mounting shaft when the pipette tip is fully mounted on the mounting shaft.

21. The pipette system according to claim 20, wherein the circumferential locking ring includes a void.

22. The pipette system according to claim 15, wherein the mounting shaft has lobes for engaging with the inner surface of the collar of the pipette tip.

23. The pipette system according to claim 15, wherein the mounting shaft further includes a leading tapered region below the sealing region, the outer diameter of the leading tapered region being less than the inner diameter of the inner surface of the annular wall of the circular cantilever sealing ring on the pipette tip.

24. The pipette system according to claim 15, wherein the inner surface of the annular wall is inclined inward in its relaxed state as it extends from the circumferential shoulder toward the opening of the tip collar.

25. The pipette system according to claim 16, wherein the inner surface of the annular wall forms an interference of 0.04 to 0.12 mm with the cylindrical sealing region on the mounting shaft.

26. The pipette system according to claim 16, wherein the inclination of the inner surface continues as the surface extends downward to and beyond a threshold location for zero interference, thereby providing sufficient clearance between the inner surface of the pipette tip and the mounting shaft below the threshold location.

27. The pipette system according to claim 15, wherein the disposable pipette tip includes a stabilizing ring positioned in the upper portion of the tip barrel that extends downward from the inner surface of the barrel.

28. The pipette system according to claim 15, wherein the circular cantilever sealing ring on the pipette tip further includes a circumferential gap above the circumferential shoulder between the annular wall of the circular cantilever sealing ring and the tip collar.

29. The pipette system according to claim 28, wherein the height of the circumferential gap is in the range of 0.28 to 0.38 mm.

30. The pipette system according to claim 15, wherein the pipette system includes a plurality of pipette mounting shafts, each pipette mounting shaft being subject to the limitations set forth in claim 15 with respect to the pipette mounting shaft.

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