Canted Coil Spring Fastener Resists Loosening
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Solution Overview
Problem
Threaded fastening devices often loosen due to vibration, thermo-cycling, or physical contact in applications like aerospace, automotive, and medical fields, where secure fixation is critical.
Innovation Solution
The use of canted coil springs and ridged surfaces in screw fastening devices, where a spring element engages with a lock washer or ring to provide a biasing force, preventing rotation and ensuring secure engagement between the screw and the body it is fastened to, thereby resisting loosening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded fasteners are used, then the device structure is simple, but the fastener becomes loose due to vibration, thermo-cycling, or physical contact
Solution Approach 1:
The spring element is nested within the fastening device assembly, positioned between the fastener head and the lock element. This nested configuration allows the spring to provide continuous biasing force without significantly increasing the overall device footprint or structural complexity.
Solution Approach 2:
The spring element introduces dynamic characteristics to the fastening system by providing continuous elastic biasing force that adapts to varying loads and vibrations. This dynamic mechanism maintains constant contact pressure between the lock element and fastener head, preventing loosening under vibrational or thermal conditions.
2Reliability
If a spring element is added to prevent loosening, then the fastener security is improved, but the device complexity increases
Solution Approach 1:
The spring element serves multiple functions simultaneously: it provides biasing force to maintain engagement, absorbs vibrational energy, compensates for thermal expansion/contraction, and ensures continuous contact between mating surfaces. This multi-functionality justifies the addition of a single component that addresses multiple failure modes.
Solution Approach 2:
The spring element acts as an intermediary component between the fastener head and the lock element, mediating the interaction by providing continuous elastic force. This intermediary mechanism ensures that the engagement force is maintained even under varying operational conditions without requiring complex active control systems.
3Reliability
If ridged surfaces are engaged with spring biasing, then the engagement security is improved, but the manufacturing complexity increases
Solution Approach 1:
The engagement interface is segmented into discrete ridged features on both the fastener head and lock element. These segmented ridges provide multiple contact points that distribute loads and enhance engagement security while being manufacturable using conventional machining or forming processes.
Solution Approach 2:
The ridged surfaces are designed with specific geometric parameters (ridge height, spacing, angle) that optimize engagement security while remaining compatible with standard manufacturing capabilities. The spring element's wire diameter, coil density, and material properties are also parameterized to achieve the desired biasing force without excessive manufacturing complexity.
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 solution effectively prevents screw loosening by applying a constant load and eliminating vibration play, ensuring reliable fixation in applications prone to movement or stress.
Implementation Method 1
The spring element is configured to bias the lock element towards the head
Implementation Method 2
The screw element and the lock element both comprise ridged surfaces that, at least in part, engage
Data Source
AI summary
Fastening devices are disclosed herein with variations on how said devices resist loosening or un-fastening from a structure or structures. In some examples, the fastening devices accomplish the removal resistant condition by using a spring component engaging ridged surfaces. The spring component generally consists of a spring ring conveniently coiled to a canting position. One exemplary design is characterized by incorporating a screw element with its head underside surface being ridged and a lock element with a ridged topside surface and engaging the two ridges surfaces. Another exemplary design is characterized by a screw element having a head outer sidewall being ridged for cooperating with a bore having a ridged inner sidewall. The bore can be part of a first body or structure or a lock element.