Auto-sampler Needle Pipe Connector Reducing Dead Volume
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Solution Overview
Problem
The existing connecting methods between the sampling needle and pipe in auto-samplers for chromatographs result in dead volume due to gaps caused by surface roughness and improper alignment, leading to diffusion or peak broadening of samples, which adversely affect analysis results.
Innovation Solution
A connecting mechanism with a first and second component, each with seal surfaces, and a packing interposed between them, where the fixing component ensures the end surfaces of the needle and pipe are in contact with the packing, reducing dead volume by ensuring proper alignment and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the needle is connected to the joint member using male nut and ferrule, then the connection can withstand high pressure, but dead volume is generated due to gaps between sealing surfaces
Solution Approach 1:
The patent introduces a dedicated sealing structure (ferrule with sealing ring) as an intermediary element between the needle and joint member. This sealing ring creates a precise sealing interface that eliminates gaps while maintaining pressure resistance, thereby reducing dead volume without compromising pressure handling capability
Solution Approach 2:
The patent applies local quality by creating a specialized sealing zone at the connection interface. The ferrule structure concentrates the sealing function in a specific localized area with precise geometric features, ensuring minimal dead volume at the critical connection point while maintaining overall structural integrity for pressure resistance
2Ease of operation
If the needle end surface does not reach the sealing surface due to improper alignment, then assembly is easier, but dead volume increases affecting analysis accuracy
Solution Approach 1:
The patent incorporates preliminary alignment features (such as guide surfaces or positioning structures) on the needle and joint member that automatically ensure proper alignment during assembly. This preliminary action prevents misalignment before the sealing contact is made, ensuring accurate positioning without requiring complex assembly procedures
Solution Approach 2:
The sealing structure serves as a mediator that facilitates proper alignment during assembly. The geometric features of the ferrule and sealing ring guide the needle into correct positioning, making the assembly process easier while ensuring the needle end surface reaches the sealing surface accurately, thereby maintaining analysis precision
Data Source
AI summary
The auto-sampler for chromatographs includes a sampling needle, a pipe, a pump portion, and a connecting mechanism configured to connect the sampling needle and the pipe. The connecting mechanism includes a first component fixed to the sampling needle, a second component fixed to the pipe, a fixing component, and a packing. The fixing component fixes the first component and the second component using screwing of screws while the end surface of the sampling needle and the end surface of the pipe are in contact with the packing. As a result, dead volume at the connecting portion between the sampling needle and the pipe is reduced.