Pipette Calibration Mechanism with Decoupled Counter Drive
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Solution Overview
Problem
Existing mechanical pipettes face challenges in accurate calibration due to design limitations, leading to inaccuracies in liquid volume measurement, and require complex calculations and additional tools for correcting pipette accuracy deviations, making the calibration process cumbersome and prone to errors.
Innovation Solution
A mechanical pipette with a calibration mechanism that includes releasable coupling means and a two-stage torque differentiation system, allowing for easy disengagement of the mechanical counter drive mechanism in CALIBRATION MODE, ensuring accurate counter indications and preventing accidental changes in liquid volume settings during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mechanical counter drive mechanism remains engaged during calibration, then the counter indication changes automatically with plunger stroke adjustments, but this causes inaccurate calibration because the counter indication must be independently adjustable without changing the plunger stroke setting
Solution Approach 1:
The patent segments the coupling between the plunger working stroke adjustment mechanism and the mechanical counter drive mechanism by introducing a releasable coupling means. This allows the two mechanisms to be decoupled during calibration mode, enabling independent adjustment of the counter indication without affecting the plunger stroke setting. The coupling means can be engaged during normal operation to link the mechanisms and disengaged during calibration to allow independent counter adjustment.
Solution Approach 2:
The patent implements a dynamic coupling system that can transition between engaged and disengaged states based on operational mode. The releasable coupling means allows the system to adapt its connectivity: during normal pipetting operation, the coupling is engaged to ensure counter indication reflects actual plunger stroke; during calibration, the coupling is disengaged to allow independent counter adjustment. This dynamic reconfiguration resolves the contradiction by providing the appropriate mechanical relationship for each operational phase.
2Reliability
If the lock mechanism provides strong braking torque to prevent accidental resetting, then volume setting stability improves, but adjustment element resetting becomes difficult requiring excessive force
Solution Approach 1:
The lock mechanism employs a dynamic friction brake system where the braking torque can be modulated. During normal operation, the brake provides strong holding torque to prevent accidental resetting of the volume setting. During intentional adjustment, the user can apply sufficient force to overcome the brake and reset the adjustment elements. The brake is designed with appropriate friction characteristics that allow controlled slipping under excessive force, enabling resetting when deliberately intended while maintaining stability during normal use.
Solution Approach 2:
The friction brake in the lock mechanism changes its braking characteristics based on the applied force. When small forces are applied during normal operation, the brake maintains high friction to prevent movement. When large forces are applied during intentional resetting, the brake allows controlled slipping. This parameter change in friction behavior resolves the contradiction by providing both strong holding torque for stability and controlled release for adjustment resetting.
3Measurement precision
If complex calibration procedures with additional tools are used, then calibration accuracy can be achieved, but operational convenience deteriorates and error risk increases
Solution Approach 1:
The calibration mechanism is designed to be self-contained within the pipette body, eliminating the need for external calibration tools. The releasable coupling means, changeover means, and resetting means are all integrated into the pipette structure, allowing the user to perform calibration using only the pipette itself. The mechanical counter and its drive mechanism serve dual purposes: indicating volume during normal operation and providing calibration adjustment capability when decoupled. This self-service design resolves the contradiction by achieving calibration accuracy through integrated mechanical means without requiring additional tools or complex external procedures.
Solution Approach 2:
The mechanical counter and its drive mechanism serve multiple functions: they indicate the plunger working stroke during normal pipetting operation and provide the calibration adjustment mechanism when decoupled. The same counter that displays volume during operation becomes the calibration reference when the coupling is released. This multi-functionality resolves the contradiction by using existing components for dual purposes, eliminating the need for separate calibration tools while maintaining calibration accuracy.
Data Source
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AI summary
Mechanical pipette with adjustable volume value of aspirated liquid is built of a handle (1) and a nozzle (3) and coupled with them: an ejection mechanism of a pipette exchangeable tip (8), a drawing up and discharging mechanism with a plunger (33) mounted in said pipette nozzle (3), a plunger working stroke adjustment mechanism, a manually actuated lock mechanism of a drive assembly of an adjustment screw of the plunger working stroke, a mechanical counter, a drive mechanism of a mechanical counter and a calibration mechanism for correction of the pipette accuracy deviation. The ejection mechanism applied in the pipette constitutes a hand operated second-class lever the rotating axis of which is perpendicular to the pipette axis and is situated on the other side of the pipette axis than the point of application by the user to a push button (4) of a force actuating via intermediate means the ejector (2). The points of force transfer from the push button (4) to the intermediate means during the angle movement of the push button (4) displace along rectilinear contact surfaces (4c) of the push button (4). The calibration mechanism, preferably, comprises, mounted in the mechanical counter, releasable coupling means for complete disengagement of a revolvers assembly from the mechanical counter drive mechanism in CALIBRATION MODE, further, engaged with them, changeover means for changing over the pipette into CALIBRATION MODE and resetting means of the indication of the liquid volume value on the counter in CALIBRATION MODE. The subject-matter invention relates also to an electric pipette for transferring a liquid, which is provided with the above mentioned ejection mechanism.