Segmented Scroll Pump Tip Seal for Radioactive Environments
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Solution Overview
Problem
Existing scroll pump tip seals made of PTFE are not suitable for applications involving radioactivity, and their square cross-section design makes them relatively stiff, increasing leakage due to manufacturing and operational tolerances.
Innovation Solution
A segmented tip seal design using elongate seal segments with interengagable end formations, allowing for increased flexibility and surface contact area, which can be made from high-performance polymers or metals like bronze, suitable for environments where PTFE is not acceptable, and accommodating varying pressures and curvatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a square cross-section tip seal with aspect ratio 1:1 is used, then the tip seal is relatively stiff in the radial direction, but this relative stiffness slows the movement of the tip seal between sidewalls, thereby increasing leakage
Solution Approach 1:
The tip seal is divided into multiple longitudinal segments that can move independently relative to each other. This segmentation allows the seal to flex and adapt to the channel sidewalls more effectively, reducing leakage paths while maintaining structural integrity. The segments can deform to accommodate the back-and-forth motion between sidewalls without being constrained by the stiffness of a solid square cross-section.
Solution Approach 2:
The tip seal transitions from a static, rigid square cross-section to a dynamic structure with segments that can move and deform. The longitudinal segments are configured to allow relative movement between them, enabling the seal to dynamically adjust its shape and position during operation, thereby maintaining effective sealing contact with the sidewalls throughout the orbital motion cycle.
2Reliability
If PTFE material is used for tip seals, then sealing performance is improved, but it is not possible to use PTFE as the tip seal material in applications involving radioactivity
Solution Approach 1:
The invention changes the material parameter of the tip seal from PTFE to alternative materials such as polymers with flexural moduli greater than 1.5 GPa or metals like bronze. These material substitutions maintain the functional requirements for sealing while expanding adaptability to environments where PTFE is unsuitable, such as radioactive applications. The segmented design compensates for material property differences by enabling flexibility through structural configuration rather than relying solely on material elasticity.
3Ease of operation
If the tip seal is narrower than its channel with radial clearance, then the tip seal can move between sidewalls, but leakage is increased because there is a leakage path formed from one side of the seal to the other side
Solution Approach 1:
By dividing the tip seal into multiple longitudinal segments, the invention creates multiple narrow gaps between adjacent segments rather than one wide radial clearance. This segmentation effectively blocks leakage paths that would otherwise form through the radial clearance, as fluid must pass through multiple restricted interfaces between segments. The segments maintain lateral movement capability while preventing through-leakage.
Solution Approach 2:
The invention addresses the leakage problem by moving from a two-dimensional sealing approach (radial clearance between sidewalls) to a three-dimensional solution where multiple longitudinal segments create a series of stacked sealing interfaces. This adds the dimension of longitudinal segmentation, transforming a single radial leakage path into multiple restricted pathways that collectively prevent effective leakage while preserving movement freedom.
Data Source
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AI summary
A scroll pump tip seal to seal a single stage of a scroll pump that includes a first scroll (22) and a second scroll (20). The tip seal is formed of a plurality of seal segments (46(1) to 46(n)) fitted contiguously end to end to a tip face (34) the scroll wall (28) of the scroll (22) to form a continuous seal between the tip face (34) and a base plate (38) of the second scroll (20).