Key Fob Battery Retention Posts Preventing Corrosion
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Solution Overview
Problem
Existing key fobs experience reliability issues due to fretting corrosion caused by mechanical damage between the battery and electrical contacts, leading to electrical insulation and potential failure.
Innovation Solution
The key fob design incorporates flexible battery retention posts and a stop pillar to restrict movement of the battery and cover relative to the electrical contacts, preventing abrasion and corrosion by ensuring stable contact and secure battery positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the battery is enclosed in a compartment with a cover that can deflect relative to the battery, then the key fob structure allows for manufacturing flexibility and ease of assembly, but the battery moves relative to the electrical contacts causing fretting corrosion and reduced reliability
Solution Approach 1:
The patent applies preliminary action by pre-positioning the battery using retention posts that extend into the battery compartment bottom. These posts are configured to engage the battery before the cover is fully assembled, preventing movement and fretting corrosion from occurring during normal operation. The retention posts are formed as integral parts of the housing during molding, establishing the battery position in advance of final assembly.
Solution Approach 2:
The patent introduces retention posts as intermediary elements between the battery and the housing structure. These posts act as mediators that transfer and distribute the mechanical forces, preventing direct contact and friction between the battery and the housing walls. The posts extend upwardly from the housing bottom to engage the battery, serving as an intermediate support structure that eliminates harmful fretting while maintaining electrical contact.
2Stability of the object's composition
If the cover is allowed to deflect relative to the battery, then the key fob can accommodate assembly tolerances and structural flexibility, but the battery surface abrasion increases leading to faster corrosion
Solution Approach 1:
The retention posts are configured to pre-establish the battery position within the compartment, preventing relative movement between the battery and housing structures. By forming these posts as integral parts of the housing during the molding process, the design preliminarily establishes stable mechanical relationships that accommodate tolerances without causing abrasion during operation.
Solution Approach 2:
The retention posts serve as intermediary elements that buffer and distribute mechanical stresses between the battery and housing. Rather than allowing direct contact and friction between the battery surface and housing walls, the posts act as mediators that maintain separation while providing structural support, thereby eliminating harmful mechanical abrasion.
3Reliability
If the battery is secured with retention posts that extend into the compartment bottom, then the battery position is stabilized preventing movement, but the device complexity increases
Solution Approach 1:
The patent merges the retention posts with the housing structure by forming them as integral parts of the housing during the molding process. This combining of functions - where the housing simultaneously provides structural enclosure and battery retention through integrated posts - reduces the number of separate components and assembly steps, thereby reducing device complexity while maintaining reliable battery positioning.
Solution Approach 2:
The housing structure is designed with multi-functionality, serving both as the protective enclosure and as the battery retention mechanism through integrated posts. This universal design approach allows the same structural element to perform multiple functions - providing mechanical support, defining the compartment geometry, and securing the battery - thereby reducing overall device complexity.
Data Source
AI summary
Battery fretting or corrosion in a key fob is reduced or even eliminated by firmly holding the fob's battery against electrical contacts and holding the battery away from key fob components that are subject to deformation or deflection. Reduced battery movement relative to electrical contacts thus reduces or eliminates abrasion of the battery's electrically conductive surfaces.