Thread Locking Fastener With Deflectable Addendum
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Solution Overview
Problem
Existing thread locking fastener assemblies rely solely on mating thread interference for locking, which degrades over time due to wear, leading to potential loosening under externally applied forces and inadequate joint integrity.
Innovation Solution
A fastener with a specially designed thread profile featuring a radially outer addendum that deflects to store residual energy when tightened, enhancing joint integrity and clamp load retention by increasing the included angle between thread faces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mating thread interference is used to achieve thread locking, then thread locking capability is obtained, but thread locking capability degrades over time due to wear
Solution Approach 1:
The addendum is pre-deflected during assembly to store residual energy before the fastener is subjected to external forces. This preliminary action ensures that the energy is available to maintain clamp load during service, preventing loosening without requiring continuous thread interference.
Solution Approach 2:
The patent converts the harmful effect of thread wear into a benefit by using residual energy stored in the deflected addendum to compensate for wear-induced loosening. The stored energy actively counteracts the degradation from wear, maintaining joint integrity over time.
2Reliability
If thread interference is increased to improve locking, then thread locking capability improves, but clamp load retention decreases under external forces
Solution Approach 1:
The addendum is pre-deflected during assembly to store residual energy before external forces are applied. This stored energy is released to maintain clamp load retention when the fastener is subjected to external forces, solving the contradiction between locking capability and clamp load retention.
Solution Approach 2:
The patent changes the physical state of the addendum from undeflected to deflected, storing residual energy in the process. This parameter change (deflection) enables the addendum to provide additional clamp load retention under external forces while maintaining thread locking capability.
3Ease of manufacture
If a conventional thread profile is used, then manufacturing is simple, but assembly joint integrity is insufficient under external forces
Solution Approach 1:
The patent modifies only the addendum portion of the thread profile while keeping the base zone conforming to standard thread forms. This localized modification maintains ease of manufacture for the majority of the thread while providing enhanced joint integrity through the deflected addendum's stored residual energy.
Solution Approach 2:
The patent changes the geometry parameters of the addendum (height, width, deflection angle) to enable residual energy storage. These parameter changes are made in a controlled manner that maintains compatibility with standard manufacturing processes while significantly improving assembly joint integrity.
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 stored energy in the deflected addendum maintains clamp load forces beyond conventional assemblies, ensuring superior assembly joint integrity and preventing loosening under external forces without permanent deformation.
Implementation Method 1
a radially outer addendum which is deflectable... the addendum is deflected so as to increase the included angle thereby storing residual energy in the fastener thread
Data Source
Figure 1A~1C
Figure 2
Figure 3
AI summary
A thread locking fastener assembly comprising a nut anchor (N) defining an internal thread having a longitudinal axis, a leading face and a trailing face, the internal thread, in axial section, having a profile which is symmetric about a first imaginary line extending radially out from the axis, and a fastener shank (24) having an external thread (28) with a longitudinal axis, a leading face (46) and trailing face (48), the external thread (28) being received in said internal thread so that said axes are substantially coincident. The external thread (28), in axial section, has a profile with a radially inner base zone (40) which is symmetric about a second imaginary line extending radially from the shank axis and a radially outer deflectable addendum (42) which is not symmetric about that line so that the addendum (42) prevents axial centralization of the external thread profile (28) in the internal thread profile unless a sufficient axial force is applied to the shank to deflect the addendum.