Backup Ring Tolerance Layout to Eliminate Seal Groove Gaps
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Solution Overview
Problem
The existing backup rings in seal structures for high-pressure gases suffer from gaps between the backup ring and the seal groove due to dimensional tolerances, leading to potential breakage and reduced reliability of the seal mechanism.
Innovation Solution
A backup ring design with specific cross-sectional shapes and dimensional tolerances, including outer and inner vertical surfaces with inclined surfaces, ensures a tight fit without gaps, using first and second tolerance settings to match the shaft and seal groove dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dimensional tolerance is set according to JIS standards with outer diameter smaller than shaft inner diameter and inner diameter larger than seal groove outer diameter, then the backup ring can be manufactured with standard tolerances, but gaps are formed between the backup ring and seal groove
Solution Approach 1:
The patent applies parameter changes by inverting the conventional tolerance relationship. Instead of setting outer diameter smaller than shaft inner diameter and inner diameter larger than seal groove outer diameter (conventional JIS standards), the patent sets the outer diameter larger than the shaft inner diameter and the inner diameter smaller than the seal groove outer diameter. This parameter inversion eliminates gaps between the backup ring and both the shaft and seal groove, directly resolving the technical contradiction between manufacturability and dimensional precision.
2Ease of manufacture
If standard dimensional tolerance is applied to backup ring, then manufacturing cost is reduced, but gaps cause O-ring protrusion and potential breakage reducing reliability
Solution Approach 1:
The patent changes the tolerance parameters from conventional JIS standards to an inverted relationship where outer diameter > shaft inner diameter and inner diameter < seal groove outer diameter. This parameter change eliminates the formation of gaps that would otherwise cause O-ring protrusion and breakage, thereby improving reliability while maintaining manufacturing feasibility through precise but achievable tolerance control.
Solution Approach 2:
The patent applies preliminary anti-action by designing the backup ring dimensions and tolerances in advance to prevent gap formation before operation begins. By setting the outer diameter larger than the shaft inner diameter and inner diameter smaller than the seal groove outer diameter from the design stage, the patent prevents the harmful effect of O-ring protrusion and breakage before it can occur during operation.
3Device complexity
If gap exists between backup ring and seal groove, then standard tolerance can be used simplifying design, but high-pressure gas causes O-ring deformation into gap leading to breakage
Solution Approach 1:
The patent applies parameter changes by inverting the conventional tolerance relationship to eliminate gaps. Instead of accepting gaps as a result of standard tolerances (which would require complex compensatory designs), the patent sets outer diameter > shaft inner diameter and inner diameter < seal groove outer diameter. This simplifies the design by eliminating the need for gap-management mechanisms while simultaneously improving reliability by preventing O-ring deformation and breakage.
Data Source
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AI summary
In a backup ring (20), an outer diameter dimension (L21) between outer vertical surfaces (20b) in a radial direction is set to be larger than an inner diameter dimension of a cylindrical groove in a first tolerance setting, the outer diameter dimension (L21) between the outer vertical surfaces (20b) in the radial direction corresponding to an outer diameter of the backup ring (20), and an inner diameter dimension (L22) between inner vertical surfaces (20c) in the radial direction is set to be smaller than an outer diameter dimension of a bottom surface of a seal groove in a second tolerance setting, the inner diameter dimension (L22) between the inner vertical surfaces (20c) in the radial direction corresponding to an inner diameter of the backup ring (20). According to the backup ring (20) having this configuration, it is possible to provide a backup ring including a configuration that causes no gap between the backup ring and a seal groove.