Segmented Sealing Joint for Liquid Metering Pipettes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing liquid metering devices, such as pipettes, cause user fatigue and musculoskeletal disorders due to high friction forces required for sealing, which can lead to leakage issues when attempting to reduce spring strength for easier operation.
Innovation Solution
A novel sealing joint with distinct parts optimized for sliding and sealing functions, featuring a peripheral part for stationary fastening to the cylinder and an internal part for continuous sliding against the piston, reducing friction forces while maintaining effective sealing, even in small diameter devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a strong spring is used to maintain sealing contact force, then sealing reliability is improved, but user fatigue increases due to higher activation force required
Solution Approach 1:
The joint is divided into multiple functional parts: a first part for sealing against the cylinder wall and a second part for sealing against the piston. This segmentation allows each part to be optimized independently - the first part can provide strong contact for reliable sealing while the second part is optimized for low friction, resolving the contradiction between sealing reliability and ease of operation
Solution Approach 2:
Different parts of the joint have different geometric characteristics and material properties tailored to their specific functions. The first part has properties optimized for sealing against the cylinder, while the second part has properties optimized for sliding against the piston with minimal friction. This local optimization allows strong sealing without proportionally increasing friction across the entire joint
2Ease of operation
If contact force is reduced to decrease friction, then ease of operation is improved, but sealing reliability deteriorates due to increased leakage risk
Solution Approach 1:
The joint is segmented into a first part that maintains strong contact for sealing and a second part with optimized geometry for low-friction sliding. This allows the sealing function to be decoupled from the sliding function, enabling reduced overall friction while maintaining adequate sealing contact force
Solution Approach 2:
The joint design allows for dynamic adaptation of contact forces during operation. The geometric characteristics enable the joint to maintain optimal contact pressure during sealing while reducing frictional resistance during piston movement, effectively adapting to different operational phases
3Reliability
If joint tolerances are reduced to maintain sealing, then sealing reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The joint design implements different geometric characteristics and tolerance requirements for different parts. The first part has tolerances optimized for sealing against the cylinder, while the second part has tolerances optimized for sliding contact. This localized tolerance specification reduces overall manufacturing complexity compared to uniformly tight tolerances across the entire joint
Solution Approach 2:
By segmenting the joint into functionally distinct parts, each with specific geometric characteristics, the design allows for targeted manufacturing approaches. Each part can be manufactured and assembled with tolerances appropriate to its function, rather than requiring uniformly high precision across all components
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 significantly reduces user fatigue and the risk of leakage by minimizing friction forces, allowing for more efficient and ergonomic liquid metering across various device sizes, including small volume pipettes, and enabling the use of lower power motors in electronic devices.
Implementation Method 1
the user slowly releases the pressure exerted on the metering button which returns to its initial position while sucking in the liquid into the disposable nozzle, as it is pushed by the action of the spring
Implementation Method 2
The liquid is sucked in using the vacuum which is created, when the piston, which is housed inside the pipette and pushed by the metering button, goes up back inside the body of the pipette
Implementation Method 3
the contact force generates a friction force (F=μ.N, with μ being the friction coefficient and N the normal contact force) created between the joint and the piston, with the friction being the resultant of N required for preserving the sealing
Data Source
AI summary
The present invention relates to a device for manually metering liquids, for example a pipette or a metering button. The device comprises a joint forming a seal between a hollow cylinder and a piston housed inside the cylinder, the piston being moved vertically so as to suck in or expel the liquid. During the metering operation, the joint remains fixed with respect to the movement of the piston and comprises parts formed by portions having dedicated geometric and mechanical characteristics which make it possible to locally optimize the functions of sliding, sealing and fastening in the cylinder.