Tamper Resistant Receptacle Shutter Friction Reduction

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Solution Overview

Problem

Conventional tamper-resistant (TR) electrical receptacles face issues with the sharpness of plug blades causing deformation and increased friction on the camming surface, leading to reduced functionality and a shorter service life due to scratches and increased force requirements for plug insertion.

Innovation Solution

The TR receptacle design incorporates a camming surface with a steep initial point of contact transitioning to a flatter, curved, or roller-based surface to reduce frictional force and point of impact damage, enhancing the lateral movement of shutters and extending the device's useful life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional camming surface with a single point of contact is used, then the initial lateral displacement of the shutter is effective, but the sharp plug blades cause deformation and increased friction on the camming surface over time, leading to a shorter service life

Engineering Contradiction:

Improveservice lifeVSAvoidfriction and wear on camming surface

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies curvature by replacing the conventional flat camming surface with a roller element that has a curved, cylindrical surface. This roller rotates as the plug blade inserts, converting the linear sliding motion into rotational motion. The curved surface of the roller distributes the contact force along its circumference rather than concentrating it at a single point, thereby reducing wear and friction on the camming surface while maintaining effective lateral displacement of the shutter blocking portion.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Ease of operation

If a steep camming surface is used to provide initial contact, then the shutter unblocks quickly, but the point of impact causes deformation and increased friction

Engineering Contradiction:

Improveshutter unblocking speedVSAvoidimpact damage and friction

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces the roller as an intermediary element between the plug blade and the camming surface. The roller mediates the interaction by providing a rolling contact interface that reduces direct impact and friction. As the plug blade pushes against the roller, the roller rotates and gradually translates the vertical insertion force into lateral shutter movement, softening the impact and distributing the mechanical stress over the roller's surface rather than concentrating it at a single contact point.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If force is applied to overcome spring bias for shutter movement, then the shutter blocks effectively, but excessive force is required due to friction on the camming surface

Engineering Contradiction:

Improveblocking effectivenessVSAvoidinsertion force requirement

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent substitutes the conventional sliding mechanical system with a rolling mechanical system. Instead of the plug blade sliding directly against the camming surface with high friction, the roller rotates as it contacts the blade, converting the high-friction sliding interface into a low-friction rolling interface. This mechanical substitution significantly reduces the force required to overcome spring bias and move the shutter, while maintaining the effectiveness of the blocking function when the shutter is in the closed position.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This configuration reduces wear and tear on the camming surface, making plug insertion easier and extending the receptacle's service life while maintaining safety features, thus addressing the limitations of prior art TR receptacles.

Implementation Method 1

a sliding shutter mechanism is spring-biased into a position blocking (or 'shuttering') the blade opening from underneath the faceplate

Methodology Applied

Scientific EffectSpring bias: Spring

Implementation Method 2

the spring-bias must be overcome by a camming action caused by the other plug blade during insertion in the other blade opening

Methodology Applied

Scientific EffectCamming action: Cam

Implementation Method 3

camming surface with a steep initial point of contact transitioning to a flatter, curved, or roller-based surface to reduce frictional force

Methodology Applied

Scientific EffectFriction reduction: Friction

Data Source

PatentUS9502806B2Tamper resistant receptacle shutter with friction reducing lead in configuration

Publication Date: 2016.11.22 HUBBELL INC

AI summary

A tamper resistant receptacle having cooperating shutter mechanisms wherein each shutter member has a lead-in cam surface having a steep initial point of contact and a flatter sliding surface (tangent fillets) to provide both an advantageous point of contact while also providing sufficient lateral clearance to un-shutter a blade opening, or lead-in cam surface having a continuously convex radius thereby providing a curved surface for the entire length of the camming operation, or a lead-in surface comprising a roller disposed in a fillet of a slide block cam surface.