Propeller Shutter Assembly for Tamper Resistant Receptacles
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Solution Overview
Problem
Conventional tamper-resistant electrical receptacles face issues with the translation of vertical force into lateral movement of shutters, leading to increased operational force requirements over time and higher costs due to complex shutter housing components.
Innovation Solution
A propeller shutter assembly with a central hub, radially extending arms, and wing blocks, secured by a torsion spring and barbed anchor, translates vertical force into rotational movement to overcome spring bias, allowing simultaneous plug blade insertion while preventing accidental access by children.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sliding shutter mechanism is used to block access to electrical contacts, then safety protection is improved, but the operational force increases over time and the device complexity increases
Solution Approach 1:
The shutter mechanism is divided into independent shutter members (first shutter member and second shutter member) that can move separately, each controlled by its own spring member. This segmentation reduces the complexity of the housing structure while maintaining safety functionality, as each shutter can operate independently without requiring a complex integrated housing system.
Solution Approach 2:
Instead of using a complex housing structure to guide and constrain the shutters, the patent inverts the approach by using simple guard walls that passively guide the shutters through their natural pivoting motion. The shutters are biased by springs to automatically return to the blocked position, eliminating the need for complex return mechanisms and reducing overall device complexity.
2Reliability
If a sliding shutter mechanism is used to block access to electrical contacts, then safety protection is improved, but the operational force increases over time
Solution Approach 1:
The shutter members are designed to pivot dynamically rather than slide linearly, allowing them to rotate on pivot points. This dynamic motion reduces friction and operational force compared to sliding mechanisms. The spring members provide continuous bias to maintain the blocked position, ensuring safety while requiring minimal force to operate during plug insertion and removal.
Solution Approach 2:
The patent changes the motion parameter from linear sliding to rotational pivoting, and modifies the force parameter by introducing spring bias. This allows the shutters to maintain a blocked state with minimal force while requiring only small forces to pivot open during normal operation, reducing the operational force burden over time.
3Reliability
If guard walls are added to prevent foreign object access, then safety protection is improved, but the device complexity increases
Solution Approach 1:
The guard walls are merged with the faceplate structure, forming an integrated component rather than separate add-on parts. This combining approach provides foreign object prevention functionality while minimizing additional complexity, as the guard walls are simply extensions of the existing faceplate that guide the pivoting shutters without requiring separate housing structures.
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 propeller shutter assembly extends the service life of tamper-resistant receptacles, reduces operational force, and lowers costs by simplifying the component structure, ensuring compliance with safety codes and preventing foreign object access.
Implementation Method 1
a spring member to bias the propeller in the 'closed' position
Implementation Method 2
translates vertical force into rotational movement to overcome spring bias
Data Source
AI summary
A tamper resistant receptacle having a propeller shutter assembly comprising a propeller shutter comprising a central hub with an annual opening, a pair of radially extending arms, and a wing block disposed on the end of each arm. The shutter assembly also includes an anchor for attaching the propeller to the receptacle body and a spring member to bias the propeller in the “closed” position. The wing blocks are sized to block a respect one of the hot and neutral openings of a standard 15-amp electrical receptacle. The wing blocks each include a ramp or inclined cam surface. These surfaces are juxtaposed such that when a plug blade hit one surface and cams past it to cause rotation of the propeller, the opposite plug blade cams down and past the other surface to cause rotation of the propeller in the same direction. This configuration causes the propeller to translate vertical force from the plug blades into rotational force in a direction and of sufficient force to overcome the spring bias of the spring and rotate the propeller wing block out of the way of the electrical contacts such that the blades can “plug in” to the device's electrical contacts.