Stern Tube Seal Ring Reversed V-Shape Key Part Design
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Solution Overview
Problem
Conventional seal rings in stern tube sealing devices face issues with deformation under torsion or temperature changes, leading to reduced sealing performance, abnormal wear, and potential leakage due to inadequate contact pressure and stiffness, which affects durability and sealing efficiency.
Innovation Solution
The seal ring design features a key part with a reversed V-shape cross-section, a heel part, an arm part with a taper angle, and a lip part with a V-shaped tip and semicircular spring groove, optimized to maintain contact pressure and prevent deformation, ensuring stable fitting and enhanced sealing performance without abnormal wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer periphery seal-part is tightly fitted in the annular groove, then the sealing performance is improved, but deformation under torsion or temperature change occurs, causing contact stress changes and deteriorating sealing performance
Solution Approach 1:
The seal ring is divided into multiple functional parts: an outer periphery seal-part for sealing, a lip seal-part for contact sealing, and an arm part connecting them. This segmentation allows each part to perform its specific function independently, reducing mutual interference and deformation transmission between parts.
Solution Approach 2:
Different regions of the seal ring are designed with different properties: the outer periphery seal-part has specific hardness for groove fitting, the lip seal-part has softer material for conforming to the shaft surface, and the arm part has optimized stiffness. This local differentiation allows each region to optimize its performance without compromising other areas.
2Reliability
If the arm part stiffness is increased to maintain contact pressure, then sealing performance is improved, but the sliding surface area increases causing abnormal wear and material softening
Solution Approach 1:
The arm part is designed with specific dimensional parameters (length, thickness, cross-sectional area) that optimize the stiffness-to-contact-pressure ratio. By carefully controlling these parameters, the arm part maintains adequate contact pressure while limiting the sliding surface area to prevent abnormal wear and material softening.
3Object-affected harmful factors
If the lip seal-part contact pressure is reduced, then abnormal wear is prevented, but sealing performance deteriorates due to insufficient contact with the propeller shaft
Solution Approach 1:
The seal ring utilizes composite material properties, combining rubber or elastomer materials with different durometers in different regions. The lip seal-part uses softer material for gentle contact that prevents wear, while the outer periphery seal-part uses harder material for stable groove fitting, achieving both wear prevention and sealing performance.
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
This design enhances the fitting performance of the seal ring, maintains contact stress, prevents leakage and abnormal wear, and improves durability while allowing easy installation and replacement without disassembling the propeller shaft, thereby maintaining effective sealing performance.
Implementation Method 1
a spring groove (43) having a semicircular cross-section in which a ringed spring (41) is fitted so as to thrust the lip part (35) toward the propeller shaft (5)
Data Source
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AI summary
(Means) A seal ring in which an apex part of the key part is formed so that the cross-section profile regarding the apex part forms a reversed V-shape toward the outside in the radial direction; the summit T of the reversed V-shape is formed as the middle center T of the apex part; a step part on the front surface side of the key part and a step part on the back surface side of the key part are formed so that the width of the seal ring in the axis direction of the ship propulsion shaft becomes thinner in the transition area from the key part toward the heel part; the inner diameter of the key part at the step part on the back surface side of the key part is greater than the inner diameter of the key part at the step part on the front surface side of the key part; a lip tip of the lip part forms a V-shape protruding inward in the radial direction and a spring groove having a semicircular cross-section in which a ringed spring is formed in the lip part; the center regarding the spring groove is arranged so as to be nearer to the inboard side than the position of the lip tip, by an offset in the ship propulsion shaft axis direction, the offset being within approximately 10% of the orthogonal projection length of the lip back width.