Cap Assembly Sealant Displacement for Aircraft Isolation
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Solution Overview
Problem
Existing cap assemblies used for electrical isolation of metallic fasteners in aircraft assemblies face issues with uncured sealant expansion causing lift-off, resulting in increased costs and weight due to the need for reinstallation and the use of high-density sealants.
Innovation Solution
A containment cap assembly design featuring an inner cap with a projection that fits within a slot on an outer cap, allowing for the displacement of uncured sealant within a limited space, preventing lift-off and reducing the amount of sealant required, thereby minimizing weight and operational costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cap assembly is filled with uncured sealant to provide electrical isolation, then the electrical isolation effectiveness is improved, but the weight of the assembly increases
Solution Approach 1:
The patent applies partial action by filling only a portion of the cap assembly volume with uncured sealant rather than completely filling it. The sealant is applied to the interior surface of the cap assembly to a程度 that provides adequate electrical isolation of the metallic fastener while avoiding excessive sealant volume that would cause expansion lift-off and unnecessary weight increase.
2Reliability
If uncured sealant is used to enclose the metallic fastener, then the electrical isolation is achieved, but the sealant expansion causes lift-off of the cap assembly
Solution Approach 1:
The patent applies preliminary anti-action by providing a lift-off prevention mechanism that counteracts the expansion force of the uncured sealant before it can cause the cap assembly to lift off. The mechanism includes a resilient member that biases the cap assembly against the structure, preemptively counteracting the upward expansion force generated by the curing sealant.
Solution Approach 2:
The patent applies beforehand cushioning by incorporating a resilient member that absorbs and cushions the expansion force of the uncured sealant during curing. This resilient member acts as a buffer that accommodates the volume expansion of the sealant without transmitting the full expansion force to the cap assembly, thereby preventing lift-off.
3Reliability
If high density sealant material is used to fill the cap assembly, then the electrical isolation is enhanced, but the operational cost increases due to additional weight
Solution Approach 1:
The patent applies partial action by using high density sealant material only to the extent necessary for effective electrical isolation rather than filling the entire cap assembly volume. This selective application provides adequate insulation while minimizing the total amount of high-density material used, thereby reducing the weight penalty and associated operational costs.
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 containment cap assembly effectively isolates metallic fasteners from electromagnetic effects while reducing the need for additional sealant, minimizing weight and installation costs by controlling sealant extrusion and preventing lift-off, thus enhancing the efficiency and cost-effectiveness of electrical isolation in aircraft assemblies.
Implementation Method 1
The uncured sealant tends to expand with the cap assembly installed over the metallic fastener
Data Source
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AI summary
A containment cap assembly for enclosing a metallic fastener extending through a structure includes an inner cap with a projection extending from an outer surface of the inner cap and an outer cap includes a first end which defines an opening and includes an inner surface which defines a first space within the outer cap in communication with the opening. A dimension of the opening and of the first space defined by the inner surface of the outer cap are each greater than a dimension defined by the outer surface of the inner cap such that with positioning the inner cap within the outer cap, a second space is defined between the outer cap and the inner cap. A slot of the outer cap extends first curvilinear direction such that the projection positioned within the slot moves along first curvilinear direction with moving the inner cap into the outer cap.