Screwless Wire Terminal Assembly for Constant-Force Clamping
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Solution Overview
Problem
Existing electrical wire terminations, particularly direct pressure and screw and clamp types, are prone to issues such as wire damage, poor connections, and strand relaxation, leading to increased resistance and overheating, especially with stranded wires, which necessitate re-torquing of terminal screws over time, thereby increasing costs.
Innovation Solution
The development of screwless wire terminals with a twist lock mechanism that includes a wire terminal and an activating member, where the activating member moves between open and closed positions to securely clamp wires using a force applying member, providing a constant mechanical force to maintain electrical connection without the need for screws.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct pressure type terminations are used, then the wire terminal structure is simple, but the wire can be cut or nicked resulting in poor electrical connections
Solution Approach 1:
The patent introduces a clamp member as an intermediary component between the terminal screw and the wire. The clamp member has a curved configuration that cradles the wire, preventing direct cutting or nicking by the screw, while still providing secure mechanical and electrical connection. This mediator resolves the contradiction by maintaining connection reliability without requiring complex multi-component structures.
2Reliability
If screw and clamp type terminations are used, then the wire connection is secure, but strand relaxation occurs causing increased resistance and overheating
Solution Approach 1:
The clamp member is designed with a curved configuration that pre-positions the wire strands in a stable arrangement before the terminal screw is tightened. The curved shape naturally cradles and supports the stranded wire, preventing the strands from relaxing or shifting under thermal cycling stresses. This preliminary anti-action against strand relaxation occurs before the connection is fully made, eliminating the need for re-torquing.
3Reliability
If terminal screws are re-torqued to alleviate strand relaxation, then connection reliability is maintained, but installation time and costs increase
Solution Approach 1:
The curved clamp member design provides self-service by automatically maintaining proper wire positioning and connection integrity throughout the product lifecycle. The geometric configuration of the clamp member inherently prevents strand relaxation without requiring any maintenance or re-torquing operations. This eliminates the need for follow-up service visits and re-torquing, making the installation complete in a single step while maintaining long-term reliability.
4Device complexity
If direct pressure type terminations are used, then the device complexity is low, but the electrical connection resistance increases due to poor connections
Solution Approach 1:
The clamp member serves as an intermediary that improves electrical connection quality without adding significant complexity. By cradling the wire strands in its curved configuration, the clamp member ensures optimal contact between the wire and terminal screw, minimizing contact resistance. This mediator component prevents the energy losses associated with poor direct pressure connections while maintaining a relatively simple overall terminal structure.
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 solution ensures reliable and durable electrical connections by preventing wire damage and strand relaxation, reducing resistance, and eliminating the need for re-torquing, thus enhancing safety and reducing maintenance costs.
Implementation Method 1
a force applying member secured to the clamp brace... where the force applying member is movable between a closed position where a wire can be clamped between the force applying member and the clamp brace
Data Source
AI summary
Electrical wiring devices that incorporate screwless wire terminal connections are described. The electrical wiring devices include for example, single and duplex blade-type electrical receptacles, blade-type locking electrical receptacles, single or multi-pole electrical switches, combination switches and blade-type receptacles, blade-type plugs for electrical cords, blade-type connectors for electrical cords, male and female inlet connectors and pin-in-sleeve connectors. The electrical wiring devices include a plurality of contact assemblies and a pushbutton type activating member that interacts with the contact assemblies.