Torque Controlling Break Screw for Medium Voltage Connectors
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Solution Overview
Problem
Current shear bolts and screws used in connectors are expensive to manufacture, require special tools, and have a fixed length, making them unsuitable for medium voltage applications where the screw must break at or below the connector surface and only apply the required force to the conductor.
Innovation Solution
A torque controlling break screw with a thin-walled, hollow design featuring a torque limiting mechanism between the nut and screw, allowing the nut to break loose and travel down the screw shaft to shear off excess length, ensuring the screw is flush with the connector surface, and optionally allowing removal with a hex key recess.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed-length shear bolt or screw is used, then the screw can break at a predetermined position, but it cannot adapt to medium voltage connectors that require the screw to break at or below the connector surface
Solution Approach 1:
The screw design transitions from a static fixed-length configuration to a dynamic system where the effective length is controlled by the nut's travel distance. The nut moves along the screw shaft until it contacts the connector surface, at which point further tightening shears the screw. This dynamic adjustment allows the same screw to adapt to different connector types and surface requirements.
Solution Approach 2:
The invention changes the critical parameter from fixed screw length to variable engagement length determined by nut position. By making the effective screw length a variable parameter controlled by the tightening process rather than a fixed manufacturing parameter, the system can adapt to different application requirements including medium voltage connectors.
2Adaptability or versatility
If multiple break points are added to the screw body to enable breaking at different positions, then adaptability improves, but manufacturing complexity and cost increase
Solution Approach 1:
The invention extracts the break point determination function from the screw body itself and relocates it to the nut-screw interface. Instead of incorporating multiple break points into the screw, the system uses the nut's position and the torque limiting mechanism to determine where the screw will break, simplifying screw manufacturing while maintaining adaptability.
Solution Approach 2:
The nut serves as an intermediary mechanism that controls the breaking position. Rather than modifying the screw to have multiple break points, the nut's travel along the screw shaft and its interaction with the torque limiting feature determine the effective break point, eliminating the need for complex screw designs.
3Measurement precision
If special tools are used to achieve precise breaking and force control, then force application precision improves, but operational complexity and cost increase
Solution Approach 1:
The system performs self-regulation of force application through the torque limiting feature. As the nut travels down the screw shaft and contacts the connector surface, the torque required to continue tightening automatically increases until it reaches the limiting value, at which point the screw breaks. This self-limiting mechanism eliminates the need for special tools to control the breaking force.
Solution Approach 2:
The tightening process incorporates inherent feedback through the torque limiting mechanism. As the nut progresses along the screw, the resistance increases until the torque limit is reached, providing automatic feedback that controls the breaking point without requiring external measurement or special tools.
4Weight of moving object
If a thin-walled hollow screw design is used, then material cost and weight decrease, but the screw requires higher force to shear off excess length
Solution Approach 1:
The torque limiting feature performs a preliminary action by controlling the nut's detachment from the screw. The nut is initially secured to the distal end with a torque limit that allows it to break loose and travel down the shaft. This preliminary controlled detachment enables the system to accumulate the necessary force through the travel distance before the final shear occurs, managing the force requirement for the thin-walled design.
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
Enables secure conductor connection with controlled force application and flush screw installation, suitable for medium voltage connectors without the need for multiple break points or special tools, while allowing for easy removal if necessary.
Implementation Method 1
There is a torque limiting feature between a thin-walled, hollow screw and a nut
Implementation Method 2
Once the strength of the torque limiting feature that secures the nut onto the distal end of the screw is exceeded, the nut breaks loose from the distal end of the screw
Data Source
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AI summary
A torque controlling break screw is provided for securing a wire or cable within a connector. The break screw comprises a nut, a thin-walled, hollow screw and a torque limiting feature between the nut and the screw.