Free Spin Fastener Assembly for Plastic Components
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Solution Overview
Problem
Existing fastener systems either require specialized tooling for assembly and disassembly, subject components to excessive stress, or are unreliable in vibrating environments, particularly when used with plastic components like in automotive bussed electrical connections.
Innovation Solution
A fastener system with a shank featuring a threaded leading portion, an annular recess, and abutment surfaces that allows for secure assembly without excessive torque, enabling easy servicing and resistance to vibration, using a design where the fastener can spin freely after assembly and the annular recess prevents uncoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded fastener is used to attach plastic components, then the components can be securely fastened, but excessive torque may damage the soft plastic components
Solution Approach 1:
The fastener system segments the fastening function into two independent parts: a threaded pin that provides secure attachment and a separate torque-limiting mechanism (snap ring or deformed portion) that prevents excessive stress. This segmentation allows each component to optimize its function without compromising the other.
Solution Approach 2:
The patent introduces an intermediary element (snap ring or deformed portion of the pin) that acts as a mediator between the threaded pin and the plastic component. This intermediary limits the torque transmitted to the plastic component while maintaining secure fastening, effectively protecting the soft material from damage.
2Device complexity
If an integrally formed lock is used to attach components, then the number of parts is reduced and stress control is improved, but the components cannot be separated for servicing and require replacement if damaged
Solution Approach 1:
The fastener system divides the locking function into separable components: a pin that can be removed and replaced, and a locking mechanism (snap ring or deformed portion) that secures the pin. This segmentation maintains low part count while enabling easy serviceability, as the pin can be independently replaced without replacing the entire fastening system.
Solution Approach 2:
The patent designs the pin as a disposable or replaceable element that can be easily discarded and replaced during servicing. The locking mechanism remains with the main assembly, allowing the pin to be recovered and replaced without replacing the entire fastening system, thus improving serviceability while maintaining simplicity.
3Reliability
If a threaded fastening system is used, then components can be attached securely, but specialized torque limiting equipment is required for assembly and disassembly
Solution Approach 1:
The fastener system incorporates a self-limiting torque mechanism where the snap ring or deformed portion automatically prevents excessive torque during assembly. This self-service feature eliminates the need for specialized torque limiting equipment, as the fastener itself controls the torque to protect plastic components from damage.
Solution Approach 2:
The patent uses a simple, inexpensive snap ring or deformed portion of the pin as a disposable torque-limiting element. This cheap component replaces expensive specialized torque limiting equipment, providing effective torque control without requiring complex tools or specialized assembly procedures.
Data Source
AI summary
A fastener and a fastener system using the fastener are disclosed. The fastener has an elongated shank having a thread formed at one end and a annular recess formed adjacent the threaded portion to define a leading and trailing abutment surface. The thread guides the fastener into engagement with one or more components having thread engagement features and the annular recess permits the free spinning of the fastener without further tightening after the thread engagement features have advanced past the thread. The fastening system includes the fastener and a component to be fastened having a passageway for accepting the fastener formed by at least two flanges engageable in the thread and engageable in the annular recess of the fastener.