Medical Syringe Plunger With Radial Thickness Gradient Cover Layer
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Solution Overview
Problem
Existing plungers for medical syringes do not adequately ensure a liquid-tight seal and effective separation of the plunger material from the medical substance, particularly in terms of sliding properties and contact area with the syringe cylinder.
Innovation Solution
A plunger design featuring a film-like cover layer with varying thicknesses, where the thickness is greatest at the longitudinal axis and decreases radially, combined with one or more sealing beads that maintain contact with the syringe cylinder, ensuring a secure seal and improved sliding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a uniform thickness cover layer is applied to the plunger, then the separation from medical substance is improved, but the sliding properties and sealing efficiency deteriorate due to excessive friction and contact area
Solution Approach 1:
The cover layer is designed with non-uniform thickness, being thinnest in the radial outer region where it contacts the syringe cylinder wall during sliding, and thicker in the central region. This local variation in thickness optimizes both separation and sliding properties by reducing friction at the contact interface while maintaining adequate separation elsewhere.
Solution Approach 2:
The thickness parameter of the cover layer is varied continuously or in steps from the central region to the radial outer region. This parameter change allows the cover layer to transition from providing maximum separation in the center to providing minimal, low-friction contact at the periphery, thereby resolving the contradiction between separation and sliding properties.
2Object-affected harmful factors
If a thicker cover layer is applied to ensure adequate separation, then the separation from medical substance is improved, but the sealing efficiency deteriorates due to increased contact area and friction
Solution Approach 1:
The cover layer thickness is locally optimized to be minimal in the radial outer region where sealing contact with the cylinder wall occurs. This ensures low-friction sealing while maintaining adequate thickness in the central region for effective separation from the medical substance, thereby resolving the contradiction between separation and sealing efficiency.
Solution Approach 2:
The thickness parameter of the cover layer is systematically varied across its surface, creating a gradient from thicker central regions to thinner peripheral regions. This parameter variation allows the structure to simultaneously achieve adequate separation (where thickness is greater) and efficient sealing (where thickness is minimal at the contact interface).
3Object-affected harmful factors
If the cover layer extends beyond the sealing bead region, then the separation from medical substance is improved, but the device complexity increases due to additional material and processing
Solution Approach 1:
The cover layer thickness parameter is varied in a controlled manner from the central region toward the radial periphery, naturally tapering to minimal thickness at the edges. This parameter variation allows the cover layer to extend where needed for separation while automatically reducing material usage and complexity at the boundaries, eliminating the need for additional structural elements.
Data Source
AI summary
A plunger for a medical syringe includes a plunger body having a longitudinal axis, a lateral surface, a front side and a rear side, wherein a first sealing bead is associated with the front side of the plunger, the rear side is used for connecting to a plunger rod and, in addition, a front part of the plunger including the front side is covered with a film-like cover layer for otherwise separating the plunger from the medical substance in the use position. In addition, the cover layer be configured with different thicknesses, wherein the thickness is greatest in the region of the longitudinal axis and decreases radially outwards from the longitudinal axis.