Cartridge Piston Centering Ribs for Sealing Lip Protection
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Solution Overview
Problem
Cartridge plungers often tilt during insertion, risking damage to the sensitive sealing lip and inadequate sealing due to one-sided contact with the cartridge wall, leading to air ingress and spoilage of the filling compound.
Innovation Solution
The design features radial centering ribs on the piston's front circumference, axially stepped near the transition to the peripheral wall, with closely spaced ribs that continue the top wall contour, providing uniform pre-centering and low frictional resistance to prevent tilting and ensure the sealing lip's protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a closed outer wall at the front end of the piston is used, then the piston structure is simple and rigid, but high one-sided friction occurs during insertion causing tilting and misalignment
Solution Approach 1:
The closed outer wall at the front end of the piston is segmented into multiple radial ribs spaced at specific angular intervals (e.g., 30° to 60°). This segmentation transforms the continuous contact surface into discrete contact points, distributing the insertion force evenly around the circumference and eliminating one-sided friction that causes tilting and misalignment.
2Reliability
If the sealing lip is made thin and flexible for proper sealing, then sealing performance is improved, but the sealing lip becomes delicate and prone to damage during insertion
Solution Approach 1:
The radial ribs perform preliminary centering action during insertion by making contact with the cartridge wall first. This pre-centering aligns the piston axially before the sealing lip encounters the cartridge wall, preventing uneven loading and damage to the thin, flexible sealing lip while maintaining its sealing effectiveness.
3Ease of manufacture
If radial ribs are spaced widely apart, then manufacturing is simpler, but uniform pre-centering cannot be achieved during insertion
Solution Approach 1:
The angular spacing between radial ribs is optimized to specific ranges (e.g., 30° to 60°, or more densely 20° to 30°). This parameter optimization ensures sufficient rib density for uniform pre-centering contact around the circumference while remaining manufacturable. The specific spacing creates multiple contact points that distribute insertion forces evenly, achieving precise centering without excessive manufacturing complexity.
Data Source
Figure 1~2
AI summary
A cartridge piston for dispensing viscous masses from a cartridge has a front cover wall (1), a rearwardly extending outer wall (2) adjoining its circumference, and a forward-projecting flexible sealing lip (4) connected to the outer wall (2) for sealing against a cartridge wall, wherein the cover wall (1) has an axial, backward-pointing step (6) near its circumference. On this step (6) is arranged a ring of radial ribs (7) with rotationally symmetrical small angular intervals, the forward-pointing edges of which follow the contour of the area of the cover wall (1) located radially within the step (6) and which project radially slightly beyond the front area of the outer wall (2), wherein the sealing lip (4) is located axially behind the ribs (7).