EP-3684513-A1 - PIPETTE CALIBRATION AND VOLUME OFFSET MECHANISM

Abstract

A pipette calibration and volume offset mechanism. The calibration and volume offset mechanism is provided to facilitate user selectable calibration or volume offset operations of a pipette to which the calibration and volume offset mechanism is installed, through axial displacement of a threaded element that effectively moves the home position of the pipette. An offset counter of the calibration and volume offset mechanism is rotationally coupled to the threaded element during a volume offset operation to indicate offset magnitude, but decoupled from threaded element during a calibration or recalibration operation.

Inventors

• SCHIRAGA SETON

Assignees

• METTLER TOLEDO RAININ LLC

Dates

Publication Date

20200729

Application Date

20180919

Priority Date

20170919

Claims (1)

1. WHAT IS CLAIMED IS: 1 . A pipette calibration and volume offset mechanism (250), comprising: a housing (280); a mode selection mechanism (255) having a mode selector element (285) movable between a first and second position, the mode selection mechanism (255) being axially and rotationally constrained at a proximal end of the housing (280); an axially displaceable follower element (260) interposed between the mode selection mechanism (255) and the housing (280) and coupled to the mode selection mechanism (255); an offset counter (265) located within the housing (285) and axially movable with the follower element (260); a threaded element (510) located within the housing (285) and having an axial position that is adjustable to define the home position of a pipette to which the calibration and volume offset mechanism (250) is installed; a coupling (275) located within the housing (280), the coupling (275) rotationally coupled to the threaded element (51 0) and operative to selectively rotationally couple the offset counter (265) to or decouple the offset counter (265) from the threaded element (510); and a user rotatable input mechanism (270) that is rotationally coupled to the coupling (275); wherein, the offset counter (265) will not rotate with the input mechanism (270) and the coupling (275) when the mode selector element (285) of the mode selection mechanism (255) is in the first position; and wherein, the offset counter (265) will rotate with the input mechanism (270) and the coupling (275) when the mode selector element (285) of the mode selection mechanism (255) is in the second position. 2. The pipette calibration and volume offset mechanism (250) of claim 1 , wherein: a mounting plate (405) is coupled to the proximal end of the housing (280); and the mode selection mechanism (255) is interposed between the mounting plate (405) and the housing (280). 3. The pipette calibration and volume offset mechanism (250) of claim 1 or 2, wherein the mode selection mechanism (255) and the follower element (260) are both barrel cams. 4. The pipette calibration and volume offset mechanism (250) of claim 3, wherein the mode selection barrel cam (255) is at least partially nested within the follower barrel cam (260). 5. The pipette calibration and volume offset mechanism (250) of claim 4, wherein the coupling of the follower barrel cam (260) to the mode selection barrel cam (255) comprises: at least one arcuate or sloped cam slot (295) on an outside surface of the mode selection barrel cam (255); and at least one cam follower pin (300) extending inward from the follower barrel cam (260) and engaging the at least one cam slot (295) in the mode selection barrel cam (255); such that rotation of the mode selection barrel cam (255) will produce an axial displacement of the follower barrel cam (260). 6. The pipette calibration and volume offset mechanism (250) of claim 1 , wherein the offset counter (265) is rotationally coupled to the coupling (275) by a mechanism selected from the group consisting of the engagement of gear teeth or splines, and the engagement of corresponding tapers. 7. The pipette calibration and volume offset mechanism (250) of claim 1 , wherein the user rotatable input mechanism (270) is a pinion gear. 8. The pipette calibration and volume offset mechanism (250) of claim 7, wherein the coupling (275) is provided with a miter gear (330) that engages with the pinion gear (270) to translate user rotation of the pinion gear (270) into rotation of the coupling (275). 9. The pipette calibration and volume offset mechanism (250) of claim 1 , further comprising a viewport (340) in the housing (280) for observing numerals or other indicators located on the offset counter (265). 10. The pipette calibration and volume offset mechanism (250) of claim 1 , further comprising a user input mechanism access opening (345) in the housing (280) for allowing engagement and rotation of the user input mechanism (270). 1 1 . The pipette calibration and volume offset mechanism (250) of claim 1 , wherein upward axial movement of the offset counter (265) is prohibited if the offset counter (265) is in an offset position. 12. The pipette calibration and volume offset mechanism (250) of claim 1 , wherein: the threaded element (510) and the housing (280) are in threaded engagement; and rotation of the input mechanism (270) will result in rotation of the threaded element (510) and axial displacement of the threaded element (510) relative to the housing (280). 13. The pipette calibration and volume offset mechanism (250) of claim 12, wherein: the threaded element (510) forms a housing of a blowout assembly (500); the blowout assembly (500) further includes a blowout piston (505) located in the blowout assembly housing (510); and a blowout spring (45) is located in the blowout assembly housing (51 0), distally of the blowout piston (505), such that the blowout piston (505) is biased toward a proximal end of the housing (510).

Description

PIPETTE CALIBRATION AND VOLUME OFFSET MECHANISM Inventor: Seton Schiraga TECHNICAL FIELD [0001] Exemplary embodiments described herein are directed generally to a calibration and volume offset adjustment mechanism for a volume adjustable pipette. BACKGROUND [0002] As would be understood by one of skill in the art, a pipette is a device that is normally used in conjunction with a pipette tip to transfer or distribute a measured volume of liquid from one location to another. Manually-operated air-displacement pipettes, which are of the most interest with respect to this application, operate generally by creating a vacuum via the retraction of a piston located in the pipette body. Thus, when the open end of an associated pipette tip is submersed in a liquid, the resulting vacuum draws air from the pipette tip and an amount of the liquid is consequently drawn into the tip to replace the evacuated air. Movement of the pipette piston is regulated such that a desired measured amount of liquid is drawn into the tip during the aspiration phase of the pipetting operation. [0003] Manually-operated air-displacement pipettes are available in a wide volume range of between about 0.2μΙ_ to several thousand μΙ_. Because a user may need to pipette a multitude of different liquid volumes, such pipettes are frequently offered with different volume ranges (e.g., 0.5-10 μΙ_, 10-1 15 μΙ_, 1 1 5-1 ,000 μΙ_) and with volume adjustability within the selected volume range. Volume adjustability is commonly accomplished, for example, by manually rotating a provided volume setting shaft or manually rotating the plunger button and associated plunger of the pipette which, through one of various possible associated mechanisms, results in a change in the volume setting of the pipette. [0004] A common drawback to known volume-adjustable pipettes has been the time and effort required to make volume adjustments - particularly when the difference between the current volume setting and a desired volume setting is large. For example, in the case of known volume-adjustable pipettes, a full rotation of the pipette volume adjusting device may result in a volume change of only 5%-1 0% of the total volume of the pipette. Thus, making a large change in volume may require significant and time consuming effort on the part of a user. [0005] Volume adjustable pipettes with speed-increased volume adjustment functionality are known. However, these know pipettes suffer from various deficiencies including, but not limited to, complex and/or inaccurate volume adjustment mechanisms, the need to employ separate volume adjustment inputs for low speed and high speed volume adjustment; and/or the need to provide a volume adjustment input that is separate from the pipette plunger rod or plunger button. [0006] As would also be understood by one of skill in the art, calibration of the dispensed fluid volume is required for accurate pipetting. Consequently, pipettes are typically calibrated at the factory and may also be calibrated during servicing operations. [0007] In one known pipette design, calibration is accomplished by disconnecting a volume display from an associated volume screw, and volume offset is separately accomplished by moving a bottom stop. In another known pipette design, calibration is accomplished by disengaging a volume display from an associated volume screw using a spline-type coupling located within the counter wheels of the volume display, and subsequently adjusting the position of the volume screw. In yet another known pipette design, calibration and volume offset are accomplished by moving an upper stop of the pipette without changing the pipette volume display. [0008] It is evident from the foregoing description that adjustable volume pipettes and pipettes that permit user calibration or volume offset are known. However, when the identified drawbacks of known volume-adjustable pipettes are considered in the context of the numerous pipetting operations and associated volume adjustments made by many pipette users over the course of a typical work day, the benefits of providing an improved design that facilitates more efficient pipette volume adjustment should be readily apparent. Similarly, while mechanisms and techniques for pipette calibration and volume offset are known, it would nonetheless be desirable to provide a simplified and compact pipette calibration/volume offset mechanism that may be used in conjunction with an improved pipette volume adjustment mechanism in a new manually operated pipette. SUMMARY [0009] Exemplary embodiments described herein are directed to a quickset mechanism for easily and rapidly adjusting the liquid volume of a manually-operated (manual) volume-adjustable pipette. Other exemplary embodiments described herein are directed to a combined pipette calibration and volume offset mechanism that may be used in a manual pipette, such as but not limited to a volume-adjustable manual pipette having quickset volume