Tamper Resistant Electrical Receptacle Shutter Mechanism
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Solution Overview
Problem
Conventional tamper-resistant electrical receptacles do not effectively prevent insertion of foreign objects or 20 amp plugs with perpendicular blades, as the shutter mechanisms in existing designs are suited only for parallel-bladed plugs.
Innovation Solution
A tamper-resistant assembly with a first shutter member having a semi-living hinge and a second shutter member with a blocking body, both movable between open and closed positions, biased by springs to ensure secure closure and prevent foreign object access, adapted to receive both 15 and 20 amp plugs by accommodating different blade orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional slideable shutter members are used, then tamper resistance is provided for parallel-bladed plugs, but the receptacle cannot receive 20 amp plugs with perpendicular blades
Solution Approach 1:
The shutter mechanism is divided into two separate shutter members (first shutter member with first arm and second arm, second shutter member with third arm and fourth arm) that can move independently. This segmentation allows each shutter to respond to different insertion scenarios - one shutter handles parallel-bladed plug insertion while the other handles perpendicular-bladed plug insertion, thereby achieving compatibility with both 15 amp and 20 amp plugs while maintaining tamper resistance
Solution Approach 2:
The shutter members are designed to be movable between blocked and unblocked positions based on the insertion force and direction of the plug blades. The first and second arms of the first shutter member can pivot independently, and the third and fourth arms of the second shutter member can pivot independently, allowing the mechanism to dynamically adapt to different plug configurations while maintaining security against tampering
2Ease of operation
If the first arm of the first shutter member is made resilient, then the shutter can respond to insertion forces, but the pivoted spring arm experiences stress that reduces its lifespan
Solution Approach 1:
The first arm of the first shutter member is made resilient by modifying its material properties or structural parameters to provide flexibility. This allows the arm to bend and respond to insertion forces without requiring a separate spring mechanism, thereby reducing stress concentration points and potentially extending the lifespan of the spring arm while maintaining shutter responsiveness
3Reliability
If a stop on the front cover prevents pivotal movement of the second arm, then the shutter maintains secure closure, but the mechanism becomes more complex
Solution Approach 1:
The stop feature is integrated directly into the front cover structure rather than being a separate component. This merging of functions allows the front cover to serve both as the structural housing and as the limiting element for shutter movement, thereby maintaining secure closure while minimizing the number of discrete parts and reducing overall mechanism 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 provides enhanced tamper resistance for electrical receptacles, ensuring safe operation by preventing foreign object insertion and allowing secure engagement of both 15 and 20 amp plugs, thereby enhancing safety and usability.
Implementation Method 1
A first spring is disposed between and biases the first and second shutter members toward closed positions thereof
Data Source
AI summary
An electrical receptacle includes a front cover having a rib and a protrusion connected thereto, a back housing secured to the front cover and a tamper resistant assembly disposed between the front cover and the back housing. The tamper resistant assembly includes a slide pad member, first and second shutter members, a first spring disposed between and biasing the first and second shutter members toward closed positions thereof, and a second spring disposed between and biasing the first shutter member away from the front cover. The slide pad member is connected to the back housing. The first shutter member is slidably disposed on the slide pad member and has first and second arms extending from a first cam surface. A second shutter member is slidably disposed on the slide pad member and has a blocking body connected to a second cam surface. The first and second shutter members are movable between open and closed positions.