Self-Fixturing Nutplate Heater With Friction-Fit Thermal Compression
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Solution Overview
Problem
The existing nutplate fastener assemblies require a lengthy curing time for adhesive bonding agents, typically taking up to 24 hours, which hampers aircraft availability and maintenance efficiency due to the need for secure adhesion before other components can be tightened.
Innovation Solution
A self-fixturing heater with a central channel and heat transfer surface is used to accelerate the curing process by applying controlled elevated temperatures to the adhesive bondline, allowing the elastomeric fixture to sandwich the substrate and apply heat uniformly, reducing curing time to four hours or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive bonding agent is used to secure nutplate fastener assembly to substrate, then strong adhesion is achieved, but curing time is excessively long (up to 24 hours)
Solution Approach 1:
The patent applies thermal energy to change the temperature parameter of the adhesive bonding agent, accelerating the chemical curing reaction. By controlling the heating process, the adhesive cures in 4 hours or less instead of requiring 24 hours at room temperature, while maintaining the required bond strength.
Solution Approach 2:
The curing process uses periodic or controlled thermal application through the heater assembly, applying heat at specific intervals or maintaining controlled temperature conditions to optimize the curing rate while preventing degradation, thereby reducing total curing time.
2Loss of time
If heater is added to accelerate curing, then curing time is reduced, but device complexity increases
Solution Approach 1:
The heater assembly is merged with the existing fixturing components, combining the heating function with the clamping and positioning functions. The elastomeric fixture with compression springs serves dual purposes: mechanical compression for alignment and thermal transfer for curing acceleration, reducing overall device complexity.
Solution Approach 2:
The elastomeric fixture serves multiple functions: it provides mechanical compression to hold the nutplate assembly against the substrate, acts as a thermal conductor to transfer heat from the heater to the adhesive bondline, and maintains alignment during curing. This multi-functionality eliminates the need for separate heating and fixturing devices.
3Strength
If compression force is applied during curing, then adhesive bond strength is improved, but fixture design complexity increases
Solution Approach 1:
The fixture uses compression springs that provide dynamic, self-adjusting compression force during curing. The springs automatically maintain optimal pressure as the adhesive shrinks or expands during the curing process, ensuring consistent bond strength without requiring complex pressure control mechanisms.
Solution Approach 2:
The compression springs are self-regulating, automatically adjusting the compression force applied to the adhesive bondline during curing. The fixture design uses the inherent elastic properties of the springs to maintain optimal pressure without external control, simplifying the overall system design.
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 self-fixturing heater effectively accelerates the curing process of adhesive bonding agents under the nutplate baseplate, ensuring strong adhesion within a shorter timeframe, enhancing maintenance efficiency and aircraft availability.
Implementation Method 1
a heating element therein
Implementation Method 2
a heat transfer surface positioned relative to the heating element for receiving generated heat therefrom
Implementation Method 3
the elastomeric fixture 20 may stretch and deform to permit insertion and pull through engagement into and through the aperture 22
Implementation Method 4
the elastomeric fixture 20 helps provide a positive force drawing the baseplate 14 in against the substrate 18 during at least an initial period of time for curing
Data Source
AI summary
The self fixturing heater includes an outer casing having a central channel therein for selectively receiving and retaining in friction-fit relation an elastomeric fixture from a nutplate fastener assembly that axially aligns the self fixturing heater with a nutplate fastener assembly. The outer casing encloses a heater element generally disposed circumferentially around the central channel and includes a thermal insulated cover to direct heat energy toward a heat transfer surface that includes a thermally conductive pressure pad in engagement with a substrate underneath a baseplate of a nutplate having an adhesive bonding agent thereon, the heat transfer surface imparting heat energy to the adhesive bonding agent thereby curing the adhesive in four hours or less.