Backup Ring Edge Hardening for Roller Cone Drill Bit Seals
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Solution Overview
Problem
The backup ring in roller cone drill bits often fails due to tearing and wear, particularly at the outer diameter, caused by exposure to drilling fluids and mud, leading to seal failure.
Innovation Solution
The backup ring is modified by increasing its hardness while maintaining flexibility, achieved through material removal at the exposed edge in shapes like U or V configurations, or by using electron beam radiation to increase crosslink density at the edges, and incorporating springs or honeycomb structures to enhance durability and sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low Shore A hardness elastomeric compound is used in the backup ring, then the backup ring can be easily manufactured and installed, but it degrades over time and suffers tear and wear failure at the outer diameter
Solution Approach 1:
The patent applies local quality by creating a dual-hardness structure where the bulk of the backup ring maintains low Shore A hardness for flexibility and ease of manufacture, while the outer diameter edge is hardened to resist wear and tear. This is achieved through selective material application or surface treatment that differentiates the properties of different regions of the same component.
Solution Approach 2:
The patent employs composite materials by combining a soft elastomeric base material with a harder material layer or reinforcement at the critical outer diameter edge. This composite structure allows the backup ring to simultaneously exhibit the flexibility needed for sealing and the hardness required for wear resistance.
2Strength
If the hardness of the backup ring is increased to reduce wear, then wear resistance improves, but the backup ring loses flexibility and sealing effectiveness
Solution Approach 1:
The patent resolves this contradiction by applying local quality - the bulk material remains soft and flexible to maintain sealing effectiveness, while only the outer diameter edge is hardened to provide wear resistance. This localized property differentiation allows both requirements to be satisfied simultaneously in different regions.
Solution Approach 2:
The patent segments the backup ring into functionally distinct zones: a soft elastomeric core for flexibility and sealing, and a hardened outer edge for wear resistance. This segmentation allows each zone to perform its specific function optimally without compromising the other.
3Strength
If material is removed from the exposed edge of the backup ring, then wear resistance is improved through reduced stress concentration, but the structural integrity may be compromised
Solution Approach 1:
The patent applies curvature by replacing sharp edges with radiused or rounded edges on the backup ring. This geometric modification reduces stress concentration at the outer diameter while maintaining structural integrity, as the curved transition distributes stresses more evenly throughout the material.
Solution Approach 2:
The patent applies preliminary action by pre-modifying the edge geometry (adding radiuses or removing material) during manufacturing to prevent future stress concentration and wear initiation. This preventive modification is performed before the component enters service, eliminating the need for corrective actions later.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified backup ring design significantly reduces wear and tear, maintaining effective sealing force and contact pressure, thereby enhancing the durability and reliability of the face seal assembly.
Implementation Method 1
using electron beam radiation to increase crosslink density at the edges
Implementation Method 2
incorporating springs or honeycomb structures to enhance durability and sealing performance
Data Source
Figure 1~4
Figure 2~3
Figure 5~8
AI summary
A backup ring for a face seal in a roller cone bit is configured to resist wear from drilling fluids present adjacent exposed faces of the backup ring. Portions are removed from an exposed end face in a variety of shapes while the hardness of the material is increased. The removal of material offsets an increase in force that would be transmitted through the backup ring on face seal assembly due to flexing. A spring can optionally be included in the removed material location. Another way is to increase the edge density of all or part of the exposed edges while leaving the interior portions unaffected by using electron beam radiation to increase the crosslink density or by other techniques that allow a unitary structure with a more durable edge region.