Sample Tube Holder Centering with Pre-stressed Garter Springs
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Solution Overview
Problem
Existing sample tube holders in clinical chemistry analyzers fail to accurately center and align sample tubes of different diameters, leading to misalignment and improper centering due to manufacturing tolerances and elastic tongue deformation over time, which is problematic for automated pipetting systems and robotic handling.
Innovation Solution
A sample tube holder with a rectilinear array of chambers and pre-stressed garter springs that exert radial forces on sample tubes, ensuring their symmetry axis aligns with the holder's symmetry plane, using a combination of pins and elastic elements to maintain accurate centering without deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elastic tongues are used to press sample tubes against chamber walls, then sample tubes can be held in place, but manufacturing tolerances and non-uniform deformation make it impossible to ensure accurate centering and alignment
Solution Approach 1:
The sample tube holder is divided into multiple identical modular units, each comprising a chamber with integrated elastic elements. This segmentation allows for standardized manufacturing while maintaining individual centering capability for each tube position.
Solution Approach 2:
The elastic elements are positioned asymmetrically within each chamber, with specific placement patterns that compensate for manufacturing tolerances. The asymmetric design ensures that the centering force acts precisely on the tube axis regardless of minor variations in chamber dimensions.
2Reliability
If four elastic tongues with 90-degree spacing are used to press sample tubes towards the center, then centering can be achieved in principle, but deformation over time makes accurate alignment impossible
Solution Approach 1:
The elastic elements are pre-stressed during assembly to exert a predetermined centering force on the sample tubes. This preliminary action ensures that tubes are centered accurately from the moment of insertion, and the pre-stress compensates for any relaxation that occurs over time.
Solution Approach 2:
The elastic elements are designed with specific material properties and geometric parameters that optimize their force-exertion characteristics. By carefully selecting elasticity modulus, cross-sectional area, and length, the elements maintain consistent centering force over extended operational periods.
3Adaptability or versatility
If sample tubes of different diameters are inserted in chambers, then various tube sizes can be accommodated, but the length symmetry axes are not aligned and lie at different distances from the symmetry plane
Solution Approach 1:
The chamber design with integrated elastic elements serves multiple functions: it accommodates tubes of various diameters, centers each tube accurately, and ensures all tubes are aligned in the symmetry plane. This universal design eliminates the need for different chamber configurations for different tube sizes.
Solution Approach 2:
The elastic elements provide centering forces in multiple spatial dimensions, constraining sample tubes not only radially but also ensuring their longitudinal axes align with the chamber symmetry axis. This multi-dimensional constraint mechanism maintains precise alignment regardless of tube diameter variations.
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 cost-effective means to accurately center and align sample tubes of varying diameters, enabling the use of lower-cost automated pipetting systems and ensuring reliable robotic handling by maintaining precise alignment and centering without the need for complex three-directional movement.
Implementation Method 1
a first garter spring (31) stretched around said first array of pins (41, 42, 43) and a second garter spring (32) stretched around said second array of pins (51, 52, 53)
Implementation Method 2
elastic elements associated with and located outside of each chamber (13) of the array, each of the elastic elements being adapted for centering each sample tube (21) arranged in a chamber (13) so that the length symmetry axis (23) of the sample tube coincides with the length symmetry axis (17) of the chamber (13)
Data Source
AI summary
A sample tube holder for receiving and holding a sample tube having a cylindrical shape, a length symmetry axis and an outer diameter lying in a predetermined range. The sample tube holder comprises a solid body comprising at least one elongated chamber adapted for receiving a longitudinal portion of a sample tube, and an elastic element associated with and located outside of said chamber. When a sample tube is arranged in the chamber there is a gap between the sample tube and the side walls of the chamber, and the elastic element is in direct contact with at least three points of the outer surface of the sample tube, the elastic element thereby holds the sample tube and brings the length symmetry axis of the sample tube into coincidence with the length symmetry axis of the chamber.