Clock Spring Circuit Breaker Actuator Reduces Bearing Stress
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Solution Overview
Problem
Conventional compression closing springs in circuit breaker operator mechanisms apply large spring forces, leading to operational issues such as undue stress on shaft bearings and potential misalignment in medium and high voltage switches and circuit breakers.
Innovation Solution
The use of clock springs with a cam shaft and drive cam, eliminating the need for compression closing springs, which are configured to drive a pinion associated with an electric motor and maintain open and closed energy status of the electrical circuit, reducing force imbalances and allowing for a more compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional compression closing springs are used to close the circuit breaker, then the closing force is sufficient to operate the switch, but the large spring force causes undue stress on shaft bearings and potential misalignment in operational components
Solution Approach 1:
The closing spring system is segmented into multiple clock springs (typically two or more) that are distributed around the cam shaft. Each clock spring independently provides closing force, which divides the total force requirement across multiple smaller units. This segmentation reduces the force burden on any single shaft bearing and distributes the mechanical stress more evenly, preventing misalignment while maintaining sufficient total closing force.
Solution Approach 2:
The patent transitions from a linear compression spring arrangement to a radial clock spring configuration around the cam shaft. This dimensional change allows the closing force to be applied in a distributed radial pattern rather than concentrated in one location. The clock springs engage with the cam profile in multiple zones, converting the force application from a single-point load to a distributed multi-point load, thereby reducing bearing stress and preventing misalignment.
2Reliability
If conventional compression closing springs are used, then the circuit breaker can be closed reliably, but the spring volume is large and the design is less compact
Solution Approach 1:
The closing spring function is segmented across multiple compact clock springs arranged radially around the cam shaft. Each clock spring is a smaller, more compact unit compared to a single large compression spring. The segmented configuration allows the springs to be distributed in a compact radial pattern, significantly reducing the overall volume occupied by the spring system while maintaining reliable closing operation through the combined force of multiple springs.
Solution Approach 2:
The clock springs are nested around the cam shaft in a concentric arrangement, with multiple springs occupying different radial zones. This nesting configuration allows the spring system to be packed into a compact cylindrical volume centered on the cam shaft, maximizing space utilization and reducing the overall footprint of the operator mechanism while ensuring reliable closing force is available.
3Force
If conventional compression closing springs are used, then the circuit breaker operates with high force, but the rotational stiffness is high which reduces operational precision
Solution Approach 1:
The high closing force is achieved through multiple clock springs working in parallel rather than a single high-force spring. This segmentation allows the total force to be distributed across multiple lower-stiffness springs, reducing the overall rotational stiffness of the system. The distributed force application improves operational precision by minimizing abrupt force changes and reducing the risk of misalignment during the closing operation.
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 reduces force imbalances and spring volume by over 50%, enabling a more precise and efficient operation with lower rotational stiffness, and allows for the same design to be scalable across different voltage and current ranges.
Implementation Method 1
at least one clock spring comprising a disc shaped body with gear teeth and a spiral spring
Data Source
AI summary
Spring operated actuator devices for an electrical circuit breaker and/or electrical switching device include at least one clock spring comprising a disc shaped body with gear teeth and a spiral spring, a cam shaft holding the at least one clock spring with an inner end portion of the spiral spring attached to the cam shaft, and a drive cam held by the cam shaft adapted to be in communication with a follower that directs an actuator to open or close a mobile contact to maintain open and closed energy status of the electrical circuit. The at least one clock spring is configured as a closing spring of the spring operated actuator.