Pipette Tip Snap Engagement and Spring Ejection Mechanism
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Solution Overview
Problem
Existing air displacement pipettes face challenges in securely retaining and ejecting pipette tips due to uncertainty in the force required for friction fit, leading to premature dislodging or jamming, especially in multi-channel pipettes, and dimensional variations affecting engagement and release forces.
Innovation Solution
A tubular pipette tip with a locking chamber and a spring-loaded ejection sleeve, featuring resilient fingers for snap engagement and a spring-loaded collar for forcible ejection, allowing for secure retention and ergonomic ejection with reduced user force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction fit is used to retain pipette tip on mounting shaft, then retention is achieved, but user uncertainty about force level causes premature dislodging or jamming
Solution Approach 1:
The patent uses audible feedback (click sound) as a sensory indicator to replace visual color changes. The resilient fingers snapping into engagement with the mounting shaft produce a distinct audible click that signals proper retention, eliminating user uncertainty about whether the tip is securely retained without requiring visual inspection or complex force measurement.
Solution Approach 2:
The resilient fingers provide immediate tactile and audible feedback when they snap into engagement with the mounting shaft. This feedback mechanism allows users to know definitively when proper retention force has been applied, eliminating the uncertainty inherent in friction-fit systems where users cannot sense whether adequate force has been applied.
2Reliability
If excessive force is applied to achieve secure friction fit, then retention security is improved, but ejection force requirement increases
Solution Approach 1:
The resilient fingers transition from a deflected state during insertion to a locked state during retention, and then to a deflected state again during ejection. This dynamic behavior allows the system to accept high insertion force for secure retention while requiring minimal ejection force, as the spring-loaded fingers naturally return to their deflected position when the mounting shaft is withdrawn, automatically facilitating tip release.
Solution Approach 2:
The ejection mechanism uses periodic or repeated minor forces rather than a single large force. The resilient fingers are designed to release in a controlled manner, potentially with multiple small movements or vibrations that progressively disengage the tip from the mounting shaft, reducing the peak force requirement compared to overcoming static friction in a single action.
3Reliability
If snap engagement with radial expansion is used, then secure retention is achieved, but insertion force becomes unacceptably high
Solution Approach 1:
The resilient fingers are pre-loaded in a deflected position and only require minimal axial force to allow them to snap into engagement with the mounting shaft. The elastic deformation of the fingers during insertion absorbs the expansion energy, requiring far less insertion force than rigid radial expansion systems where the full expansion force must be applied axially.
Solution Approach 2:
The system changes the mechanical parameters of engagement from rigid radial expansion to elastic deflection and snap-back. The resilient fingers utilize elastic deformation as an intermediate state, transforming the insertion process from direct radial expansion (high force) to controlled deflection and snapping (low force), while achieving the same secure retention outcome.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a secure and reliable retention mechanism with audible feedback for proper insertion and a modest ejection force, ensuring consistent and efficient pipette tip handling across various pipette designs.
Implementation Method 1
A spring loaded ejection sleeve is manually shiftable on the pipette mounting shaft between a retracted position accommodating establishment of the aforesaid axially interengaged relationship, and an advanced position disrupting that relationship to thereby accommodate axial ejection of the pipette tip from the pipette mounting shaft
Implementation Method 2
A spring loaded collar on the ejection sleeve serves to forcibly eject the pipette tip from the mounting shaft when the axially interengaged relationship is disrupted. The spring loaded collar also serves to eject a pipette tip that has not been fully inserted to establish its axially interengaged relationship with the mounting shaft
Implementation Method 3
The upper section of the pipette tip is provided with at least one and preferably a plurality of integral circumferentially spaced resilient fingers that project inwardly into the locking chamber to coact in snap engagement with a complimentary surface on the distal end of the mounting shaft
Data Source
AI summary
An air displacement pipette has a tubular pipette tip with an upper section surrounding a locking chamber, and a body section leading from the upper section and tapering downwardly to a reduced diameter end. A tubular mounting shaft on the pipette has a distal end configured and dimensioned for axial insertion into the locking chamber of the pipette tip. Coacting surfaces on the distal end of the mounting shaft and the upper section of the pipette tip establish an axially interengaged relationship between the pipette tip and the mounting shaft in response to insertion of the distal end of the mounting shaft into the locking chamber. A sleeve is axially shiftable on the mounting shaft between a retracted position accommodating the establishment of the axially interengaged relationship, and an advanced position disrupting the axially interengaged relationship to thereby accommodate axial ejection of the pipette tip from the mounting shaft.