Auxiliary Trip Device Positive Latching Mechanism
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Solution Overview
Problem
Existing auxiliary trip units for circuit breakers face challenges in manufacturing due to the difficulty in mastering the combination of parameters affecting the strength of the releasable latching mechanism, leading to adjustment problems and potential issues with accidental tripping or failure to trip.
Innovation Solution
The auxiliary trip unit incorporates a drive part with a blade, a swiveling latch, and a combination of bias springs and an electromagnetic coil to securely latch and unlatch the blade, ensuring stable latching and reliable tripping, with a design that simplifies manufacturing by reducing the need for precise adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the latching strength is increased to prevent accidental unlatching, then the reliability of the circuit breaker is improved, but the device complexity increases due to the need for precise parameter control and adjustments
Solution Approach 1:
The patent changes the latching mechanism from a friction-based system requiring precise parameter control to a positive engagement system using a pawl and ratchet tooth geometry. The latching strength is determined by the mechanical geometry of the tooth engagement rather than by adjusting friction parameters, eliminating the need for complex parameter control while maintaining high reliability
Solution Approach 2:
The patent replaces the flexible bias spring system with a mechanical ratchet and pawl system. The spring system required precise balancing of multiple parameters to achieve stable latching, while the ratchet mechanism provides inherent mechanical stability through its geometric tooth engagement, substituting a complex mechanical system with a simpler, more reliable one
2Ease of operation
If the latching strength is decreased to allow easier unlatching, then the ease of operation is improved, but the reliability deteriorates due to risk of accidental tripping
Solution Approach 1:
The patent segments the latching function into two distinct modes: a strong latched state secured by positive mechanical engagement of the pawl with the ratchet tooth, and an unlatched state achieved by applying force to overcome the mechanical engagement. This segmentation allows the system to provide both strong holding capability and controlled release capability without compromising either reliability or ease of operation
Solution Approach 2:
The patent introduces dynamic characteristics to the latching system through the movable pawl that can be held in a latched position by normal operating forces but can be deliberately moved to an unlatched position by applying sufficient force in the opposite direction. This dynamic design allows the system to adapt between strong latching and easy unlatching based on operational requirements
3Reliability
If precise latching parameters are used to achieve stable latching, then the reliability is improved, but the manufacturing precision requirements increase leading to adjustment problems
Solution Approach 1:
The patent changes the critical parameters from friction-based properties (coefficient of friction, spring constants) that require high manufacturing precision to geometric parameters (tooth angle, engagement depth) that are inherently more tolerant of manufacturing variations. The positive mechanical engagement provides a clear, unambiguous latching state that does not depend on precise friction control
Solution Approach 2:
The patent substitutes the friction-based latching mechanism with a positive mechanical engagement system using ratchet teeth. This substitution eliminates the need for high-precision control of friction parameters and spring forces, replacing them with a geometrically-defined mechanical engagement that is more robust to manufacturing tolerances and does not require complex adjustments
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 solution provides a dependable and stable latching mechanism that is insensitive to variations in construction parameters, ensuring reliable tripping of the circuit breaker without accidental releases, and simplifies the manufacturing process by reducing the complexity of parameter adjustments.
Implementation Method 1
an electric coil generating an electromagnetic force to drive the slide against the second bias spring, in a second direction opposite to the first direction, when this coil is supplied by said electric command
Implementation Method 2
a second bias spring fitted to bias the slide in a first direction
Data Source
AI summary
An auxiliary trip unit for a circuit breaker comprises:a drive part with a movable blade,a latch fitted pivoting around a swivelling axis and designed to secure the blade in a neutral position, against a flexible bias force, until movement of the latch takes place to a released position,a nose of the latch salient in a direction passing through the swivelling axis so as to comprise a salient end where positive latching of the blade on the latch takes place in the neutral position.The latch collaborates with the blade to receive a thrust force acting in the direction of resetting of the latch to its latching position.