Tamper-Resistant Electrical Wiring Device Shutter Mechanism
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Solution Overview
Problem
Conventional tamper-resistant electrical wiring devices have ineffective shutter mechanisms that can be easily dislodged by vibrations and foreign objects, leading to safety hazards and complex, costly installations.
Innovation Solution
A robust and simple shutter assembly for electrical wiring devices that operates smoothly even with foreign objects or uneven plug blades, featuring a frame with compression springs and moveable shutters that only open when a corded plug is inserted, ensuring safe operation and easy installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional shutter mechanisms are used in electrical receptacles, then foreign object protection is provided, but the shutters can be easily dislodged by vibrations and foreign objects leading to safety hazards
Solution Approach 1:
The shutter mechanism transitions from a static spring-loaded design to a dynamic cam-actuated system. The cam profile is specifically designed to engage the shutter in a closed position and require a specific pulling motion to open, making it resistant to random vibrations and foreign object insertion while remaining controllable by the user.
Solution Approach 2:
The cam mechanism is pre-configured to prevent the shutter from opening unless the specific opening action is performed. The cam profile creates a mechanical lock that must be deliberately disengaged, preventing premature or accidental opening by foreign objects or vibrations before the plug is properly inserted.
2Reliability
If complex shutter mechanisms with multiple parts are used, then protection is provided, but the cost and time of assembling increases and automated environments experience failure modes
Solution Approach 1:
The shutter, cam, and spring components are integrated into a single assembly unit that functions as one cohesive mechanism. The cam is directly mounted on the shutter assembly, and the spring is pre-compressed within the same housing, eliminating the need for separate adjustment mechanisms and reducing the total number of parts requiring assembly.
Solution Approach 2:
The shutter mechanism is divided into modular components (shutter blade, cam follower, cam lobe, spring assembly) that can be independently manufactured and then quickly assembled together. This modular design allows for automated assembly while maintaining the mechanical reliability of each individual component.
3Ease of operation
If delicate leaf spring elements are installed within the base platform, then shutter operation is enabled, but vibrations cause the spring to become dislodged or separated
Solution Approach 1:
The cam acts as an intermediary between the shutter and the spring mechanism. Instead of the spring directly supporting the shutter blade, the cam translates the spring's force into a controlled mechanical advantage, allowing the shutter to move smoothly while the spring remains securely positioned within the cam housing.
Solution Approach 2:
The spring is pre-compressed and secured within the cam assembly housing before final installation. The cam structure provides a rigid framework that cushions and protects the spring from external vibrations and forces, preventing dislodgement while maintaining the necessary elasticity for shutter operation.
4Ease of operation
If objects are inserted into the receptacle opening, then the shutter is forced to press against the leaf spring, but this increases the likelihood of the spring becoming dislodged
Solution Approach 1:
The cam mechanism transforms the static spring pressure into a dynamic force that is only applied to the shutter during the controlled opening motion. When objects are inserted, the cam profile directs the force through a specific path that opens the shutter without allowing excessive pressure that could dislodge the spring from its secured position.
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 shutter assembly effectively prevents foreign objects from entering electrical receptacles, enhancing safety by ensuring the shutter remains functional under mechanical stress and simplifying installation processes, reducing the risk of electrical shocks and improving device reliability.
Implementation Method 1
featuring a frame with compression springs and moveable shutters
Data Source
AI summary
An electrical wiring device including a housing including a front cover coupled to at least one body member, the front cover including a plurality of receptacle openings in a major front surface thereof, the plurality of receptacle openings being configured to receive a plurality of plug blades of a corded electrical plug, wherein the plurality of receptacle openings includes at least a ground prong opening and the at least one body member includes at least one set of receptacle contacts including a hot receptacle contact and a neutral receptacle contact; and a shutter assembly positioned within the housing and including a first shutter member coupled to a second shutter member, wherein the first shutter member is configured to move from a first position to a second position when a ground prong is inserted through the ground prong opening.