Kenter Shackle Tooth Geometry for Fatigue-Resistant Chain Coupling
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Solution Overview
Problem
Existing capsizing shackles suffer from high notch stresses and fatigue fractures due to sharp edges in the transition zones, which cannot be strengthened by increasing wall thickness without altering the outer shape to maintain compatibility with anchor chain links.
Innovation Solution
The design incorporates a circumferential groove or pocket above the uppermost toothing with rounded flanks and a coupling stone that distributes tensile stresses around the toothing receptacle, and uses a coupling block with bolts and an expanding element to secure and disassemble the shackle, reducing stress concentrations and allowing for easy disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wall thickness is increased to strengthen the transition zones, then the strength is improved, but the outer shape changes significantly which compromises compatibility with anchor chain links
Solution Approach 1:
The patent applies curvature by rounding all tooth flanks with a large radius (at least 3% of the nominal core diameter) and providing an empty space above the uppermost toothing with rounded outer circumference. This eliminates sharp edges and stress concentrations while maintaining the overall outer shape and dimensions of the shackle, ensuring compatibility with anchor chain links and winch components.
2Ease of manufacture
If sharp edges are used in the teeth design, then the manufacturing is simpler, but high notch stresses occur leading to fatigue fractures
Solution Approach 1:
All tooth flanks are rounded with a large radius, both on the outside and inside fillets. This eliminates sharp edges that cause stress concentrations while maintaining manufacturability through standard rounding processes.
Solution Approach 2:
The patent changes the geometric parameters of the tooth design by specifying rounding radii of at least 3% of the nominal core diameter (e.g., R3 for D=76). This parameter change reduces stress concentrations significantly while remaining compatible with manufacturing capabilities.
3Device complexity
If the shackle is designed as a single solid piece, then the structure is simpler, but stress concentrations cannot be effectively distributed
Solution Approach 1:
The patent segments the shackle into two separate half-elements that can be pushed into one another laterally. This segmentation allows for better stress distribution through the intermeshing teeth and the empty space design, while the overall structure remains relatively simple. The coupling block with coupling elements further divides the load path.
Solution Approach 2:
The patent introduces coupling elements (bolts or pins) as intermediaries between the two half-elements. These coupling elements distribute tensile stresses across multiple contact points and prevent concentration at single critical locations, thereby improving overall structural strength.
Data Source
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AI summary
The invention relates to a kenter shackle (100) for anchor chains, at least comprising two half-elements (10) that can be coupled to one another and a coupling stone element (20) that can be introduced between the half-elements (10), wherein the half-elements (10) each have an L-shaped or J-shaped configuration, wherein an outer toothing (12.1) with multiple parallel toothing planes is formed at the end of a short connection limb (12) and wherein a receiving chamber (16) is formed at the end of a long connection limb (11), having an inner toothing (16.1) with multiple parallel toothing planes, into which the outer toothing (12.1) of the short connection limb (12) engages, and wherein the connection limbs (11, 12) are connected to one another via a curved clasp (13). In addition, the receiving chamber (16) in the long limb (11) is extended by means of a cavity (17) above the end side of the outer toothing (12.1) of the short limb (12) and/or above the uppermost toothing plane of the inner toothing (16.1) pointing towards the clasp (13).