Plunger Rod Annular Elements Prevent Syringe Tilting
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Solution Overview
Problem
Existing syringe designs face issues with leakage due to tilting of the plunger rod during insertion and lack effective guidance when used in syringe pumps, particularly during the screwing process.
Innovation Solution
The design incorporates three annular elements on the plunger rod that provide a coaxial connection with the syringe body, offering haptic and acoustic feedback to ensure correct alignment, and wing elements for improved guidance, preventing tilting and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plunger rod is screwed into the plunger without guidance elements, then the assembly process is simpler, but tilting occurs during insertion causing leakage
Solution Approach 1:
The plunger rod is segmented into multiple functional zones: a connecting portion with screw threads for attachment to the plunger, and multiple annular elements (guiding portions) distributed along its length. These segments perform distinct functions - the connecting portion enables secure attachment while the annular elements provide guidance and prevent tilting during insertion, resolving the contradiction between simple assembly and reliable connection.
Solution Approach 2:
The annular elements act as intermediary structures between the plunger rod and the syringe body/plunger interface. They mediate the insertion process by providing contact surfaces that guide the plunger rod into correct alignment, preventing direct contact that would cause tilting, thus ensuring leak-free connection without complicating the overall assembly process.
2Reliability
If annular elements are added to guide the plunger rod, then tilting is prevented and leakage is avoided, but the device becomes more complex
Solution Approach 1:
The annular elements are merged into a single integrated plunger rod structure rather than being separate components. Multiple guiding surfaces are combined along the length of the plunger rod, creating a unified component that provides continuous guidance throughout the insertion process, maintaining reliability while minimizing device complexity.
Solution Approach 2:
The plunger rod is designed with multi-functionality: it simultaneously serves as the attachment mechanism (connecting portion with threads), the guidance system (multiple annular elements), and the actuating component. This universal design ensures coaxial connection and prevents tilting without requiring additional separate components, resolving the contradiction between reliability and complexity.
3Ease of operation
If multiple annular elements are positioned along the plunger rod, then guidance is improved during insertion, but manufacturing precision requirements increase
Solution Approach 1:
Different regions of the plunger rod are assigned different local qualities: the connecting portion has screw threads for attachment, while specific annular elements at strategic positions provide guidance surfaces. Each local region is optimized for its specific function, with annular elements positioned where they most effectively prevent tilting during insertion, improving ease of operation while managing manufacturing precision through localized design.
Data Source
AI summary
A prefilled syringe includes a syringe body filled with a medical fluid, which has a nozzle at a front side, the nozzle being closed with a cap, and which is closed at a rear side with a displaceable plunger; and a plunger rod that can be inserted into the syringe body via the rear side. The plunger rod has a connecting portion at a front side, via whi9ch the plunger rod can be connected to the plunger. At least three annular elements, which extend at least in some sections about a longitudinal axis of the rod, are arranged on a rear side of the connecting portion on the plunger rod in such a manner that they are located in the syringe body when the plunger rod is fully connected to the plunger. The three annular elements support a coaxial connection of the rod to the plunger positioned in the syringe.