Overshot Grapple Tension Ring Local Quality Design
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Solution Overview
Problem
Existing overshots in fishing operations face challenges in engaging a larger range of fish due to unknown wear, leading to increased costs and time, and high stress on grapple components, which can result in mechanical failure.
Innovation Solution
The overshot is modified by reducing the helix diameter of the tension ring while maintaining it on both sides of the control finger slot to reduce stress and allow torque transfer, and incorporating expansion blades and grooves to alleviate cantilever effects, along with an offset control finger and compliant grapple control designs to manage contact forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the catch range of the overshot is increased, then the ability to engage worn fish is improved, but the stress on tension rings increases leading to yielding
Solution Approach 1:
The patent applies local quality by varying the wall thickness of the bowl in different regions. The bowl has reduced wall thickness in areas where the grapple expands to engage larger fish, while maintaining sufficient thickness in other areas to support structural loads. This localized modification allows the grapple to expand fully for increased catch range without compromising overall structural integrity.
2Adaptability or versatility
If the wall thickness of the bowl is decreased to allow grapple expansion, then the catch range is increased, but the bowl wall may fail
Solution Approach 1:
The bowl is designed with non-uniform wall thickness, being thinner in regions where grapple expansion is needed and thicker in regions requiring structural support. This localized variation enables the grapple to expand to larger diameters for increased catch range while preventing bowl wall failure in critical areas.
Solution Approach 2:
The bowl structure is effectively segmented into regions with different thickness characteristics. The transition zones between thin and thick sections are designed to manage stress distribution, allowing the grapple to expand in designated areas without compromising the overall structural integrity of the bowl.
3Strength
If the helix diameter is reduced to reduce stress, then the stress on the ring is reduced, but the grapple may lose contact with the control finger
Solution Approach 1:
The helix diameter is varied locally along the tension ring. In regions where stress reduction is needed, the helix diameter is reduced. In regions where torque transfer to the control finger is critical, the helix diameter is maintained at larger values. This localized variation allows simultaneous stress reduction and torque transfer capability.
Data Source
AI summary
A grapple for use in an overshot has a tension ring with a reduced helix diameter but the helix diameter is not reduced on either sides of the control finger slot. One embodiment includes expansion blades on the inner diameter (“ID”) of the tension ring to allow the grapple to expand substantially before the fish reaches the segments. An embodiment provides for a control with an offset finger to allow the guide thread ID to be smaller than the bowl helix major ID. Also provided is grapple control for a spiral grapple that has at least one gap to allow the grapple control to be more compliant during fishing operations. The control may include one or more bridges of reduced thickness. Alternate embodiments include gaps and support bands with or without bridges and/or a backup ring to help eliminate misalignment of the grapple control with the support shoulder of the overshot guide.