Direct-Driven Latch Assembly for Switch Shaft Rebound Prevention
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Solution Overview
Problem
Latching mechanisms in circuit interrupters face challenges with malfunctions due to the substantial mass of movable conductor assemblies and drive assemblies, leading to significant force requirements for opening, which can cause rebound and unintended re-closure of separable contacts, potentially damaging components.
Innovation Solution
A streamlined latching assembly with a driven latch and a pivoting hammer featuring a square pin that engages a groove in the switch shaft to prevent rebound, ensuring the switch shaft remains in an open state by being biased towards the open position after the opening stroke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional latching mechanism is used to hold the movable conductor assembly in the open state, then the separable contacts remain open to prevent fault current, but the substantial mass of the movable conductor assembly creates significant rebound force that can cause latching malfunction and unintended re-closure
Solution Approach 1:
The latching assembly is engaged by the switch shaft before the opening stroke completes, proactively preventing rebound rather than reacting to it. The latch engages the groove in the switch shaft at the initiation of the opening stroke, holding the movable conductor assembly in place against the substantial rebound force generated by its mass.
Solution Approach 2:
The latching assembly is divided into distinct functional components: a latch member with a latch arm that engages the groove, a hammer member that provides the latching force, and a spring member that biases the system. This segmentation allows each component to be optimized for its specific function while working together to overcome the rebound force.
2Reliability
If multiple latching components move in coordinated sequence during the opening stroke, then the separable contacts can be opened reliably, but any malfunction in component positioning causes impact damage due to rebound
Solution Approach 1:
The latch member and hammer member are combined into a single integrated assembly that rotates as one unit about the pin axis. This merging eliminates the need for separate coordinated movements of multiple independent components, reducing complexity while maintaining reliable latching function. The integrated assembly engages the groove and provides latching force through a single rotational motion.
Solution Approach 2:
The latch member serves multiple functions: it engages the groove in the switch shaft to prevent rebound, provides a seating surface for the spring member to store energy, and transfers force from the hammer member to hold the movable conductor assembly in the open state. This multi-functionality reduces the number of components needed while maintaining reliability.
3Device complexity
If a streamlined latching assembly with fewer components is used, then the chance of malfunction is reduced, but the ability to handle substantial mass and prevent rebound must be maintained
Solution Approach 1:
The spring member is designed with specific force characteristics to provide sufficient biasing force that, when combined with the hammer member's weight, generates adequate latching force to hold the movable conductor assembly against substantial rebound. The geometric parameters of the latch arm and groove engagement are optimized to maximize mechanical advantage and latching force with minimal components.
Solution Approach 2:
The groove in the switch shaft serves as an intermediary element that translates the linear motion of the switch shaft into rotational engagement of the latch member. This intermediary mechanism allows the streamlined latching assembly to effectively capture and hold the substantial mass of the movable conductor assembly without requiring complex mechanical 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 latching assembly effectively reduces the likelihood of malfunctions and damage by ensuring precise engagement and maintaining the open state of the switch shaft, preventing unintended re-closure and enhancing the reliability of circuit interrupters.
Implementation Method 1
The square pin of the hammer is configured to push the driven latch into engagement with a groove formed in the switch shaft once the switch shaft engages the latching assembly, which prevents the switch shaft from rebounding after the opening stroke concludes.
Implementation Method 2
the hammer is structured to be biased toward the open state when the driven latch has engaged the switch shaft, thus further preventing rebounding of the switch shaft.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A latching assembly for latching the moving conductor assembly of a circuit interrupter after an opening stroke includes a streamlined latch that omits components commonly prone to damage during latching operations in existing latching assemblies. The disclosed latching assembly comprises a fixed latch block, a driven latch rotatably coupled to the latch block, and a pivoting hammer with a square pin positioned to always be engaged with the driven latch. The latching assembly is structured to be engaged by a switch shaft once an opening stroke is initiated. When the latching assembly engages, the hammer square pin pushes the driven latch into engagement with a shelf formed in the switch shaft, which prevents the switch shaft from rebounding after the opening stroke. Rebounding is further prevented due to the hammer being structured to be biased toward the open state once the driven latch has engaged the switch shaft shelf.