Pipette Throttle Point for Consistent Dosing
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Solution Overview
Problem
Pipetting devices, particularly washing heads, experience changes in dosing behavior due to deposits forming on the pipetting opening or channels, leading to inconsistent dispensing of liquids, even when operated under identical conditions.
Innovation Solution
Incorporating a throttle point with a flow resistance ratio less than 0.5 between the dosing liquid receiving space and the pressure-changing device, ensuring a gradual pressure change and reducing the impact of deposits on dosing behavior by maintaining consistent dispensing across different flow cross-section changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pipetting opening is used to dispense dosing liquid by pressure increase, then dosing liquid can be delivered through the constriction, but deposits form on the pipetting opening reducing flow cross-section and changing dosing behavior
Solution Approach 1:
A throttle point is introduced as an intermediary element in the working fluid path between the pressure-changing device and the dosing liquid receiving space. This throttle point has a specifically dimensioned flow cross-section that creates a pressure buffer, decoupling the pressure transmission from the dosing opening. The throttle point acts as a mediator that smooths pressure changes and reduces the impact of deposits on dosing consistency.
Solution Approach 2:
The invention changes the flow resistance parameter by introducing a throttle point with a specific flow cross-section ratio (less than 0.5) relative to the dosing opening. This parameter change creates a pressure buffer that stabilizes the dosing process. By adjusting the flow resistance at the throttle point, the system compensates for variations caused by deposits on the dosing opening, maintaining consistent dosing behavior.
2Manufacturing precision
If the flow cross-section of the pipetting opening changes due to deposits, then dosing behavior changes, but maintaining identical dosing behavior requires compensating for these changes
Solution Approach 1:
The throttle point serves as a passive intermediary that automatically compensates for flow cross-section changes without requiring active control mechanisms. The specific dimensioning of the throttle point creates a pressure buffer that naturally stabilizes dosing behavior, eliminating the need for complex active compensation systems while maintaining manufacturing precision.
3Productivity
If pressure is increased to dispense dosing liquid, then dosing liquid flows out through the pipetting opening, but pressure changes are transmitted suddenly causing dosing instability
Solution Approach 1:
The throttle point creates a pressure buffer that cushions sudden pressure changes before they reach the dosing liquid receiving space. This beforehand cushioning effect stabilizes the dosing process by preventing abrupt pressure transmissions, ensuring reliable and stable dosing while maintaining adequate dispensing rate.
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
This solution ensures that pipetting devices maintain consistent dosing behavior despite deposits, allowing for precise and identical dispensing of liquids across multiple channels, regardless of manufacturing tolerances or deposit thicknesses, and is applicable to both dispensing and aspiration processes.
Implementation Method 1
a ratio of a flow resistance (R1) of the pipetting opening for dispensed dosing liquid to a flow resistance (R2) of the throttle point for working fluid, which flows through the throttle point when dispensing the dosing fluid
Implementation Method 2
a pressure changing device which is designed to change the pressure of the working fluid in the dosing liquid receiving space
Data Source
Figure 1
AI summary
Pipetting device (10) at least for dispensing metered liquid by increasing the pressure of a working fluid, comprising a metered liquid receiving chamber (38) at least partially filled with working fluid with a pipetting orifice (36) as a first flow cross-sectional constriction through which metered liquid can be dispensed from the metered liquid receiving chamber (38) depending on the pressure of the working fluid, and a pressure changing device (40) which is configured to change the pressure of the working fluid in the metered liquid receiving chamber (38), wherein the pipetting device (10) has a throttling point (42) as a further flow cross-sectional constriction in a pipetting channel (12) filled with working fluid between the metered liquid receiving chamber (38) and the pressure changing device (40), which is dimensioned as follows:that the ratio of a flow resistance (R1) of the pipetting orifice (36) for dispensed metering fluid to a flow resistance (R2) of the throttling point (42) for working fluid, which flows through the throttling point (42) during dispensing of the metering fluid, is less than 0.5, preferably less than 0.3, particularly preferably less than 0.225, wherein the flow resistances of the respective flow cross-sectional constrictions (36 or 42) are calculated taking into account the product of the viscosity of the medium of working fluid and metering fluid associated with the respective flow cross-sectional constriction (36 or 42) and the characteristic length (lDst, lPof) of the associated flow cross-sectional constriction (36 or 42), divided by the fourth power of the characteristic dimension (dDst, dPof) of the flow cross-section of the associated flow cross-sectional constriction (36 or 42).,