Positive Resetting Latch for Electrical Switching Apparatus
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Solution Overview
Problem
Existing electrical switching apparatuses for low and medium voltage systems require numerous components, leading to increased wear and tear, especially due to exposure to considerable forces, and occupy significant space, necessitating a more efficient mechanism for closing contacts.
Innovation Solution
A spring-driven ram assembly directly engages the toggle assembly, reducing the number of components and space requirements, and incorporates a latch assembly with a reset mechanism to minimize wear and torque on the latch prop, allowing for a more compact and efficient closing latch assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a traditional cam shaft and multiple cams are used in the closing assembly, then the contacts can be closed with sufficient force, but the device occupies significant space and has increased complexity
Solution Approach 1:
The patent combines multiple cam functions into a single cam shaft with integrated cam profiles. The closing cam and toggle cam are disposed on the same cam shaft, eliminating the need for separate cam shafts and reducing overall space requirements while maintaining the necessary closing force and toggle action sequencing.
Solution Approach 2:
The single cam shaft serves multiple functions by incorporating different cam profiles at different locations. It simultaneously controls the closing cam roller to apply force to the closing spring and the toggle cam roller to actuate the toggle assembly, replacing what would traditionally require multiple dedicated cam mechanisms.
2Force
If traditional closing springs with diameter of 2 inches and length of 5-6 inches are used, then sufficient closing force of about 1,000 pounds can be applied, but the device occupies significant space
Solution Approach 1:
The patent changes the physical parameters of the closing spring by reducing its diameter and length while increasing its wire thickness. The closing spring has a diameter of about 1.25 inches and length of about 4 inches, with a wire thickness of about 0.375 inches, maintaining the required 1,000-pound closing force through optimized geometric parameters rather than simply scaling down the spring size.
3Volume of stationary object
If the latch prop is engaged by the latch lobe with radial force application, then the latch assembly can be compact, but torque and wear on the latch prop increase
Solution Approach 1:
Instead of applying force radially outward from the cam shaft center, the latch lobe applies force radially inward toward the cam shaft center. This inverted force direction creates a more favorable torque vector that reduces the rotational moment on the latch prop while maintaining effective latching engagement, thereby reducing wear and improving reliability.
4Reliability
If numerous components are used in the closing assembly, then the contacts can be reliably closed, but wear and tear on components increases due to exposure to considerable forces
Solution Approach 1:
The patent merges multiple components into fewer integrated elements. The cam shaft integrates the closing cam and toggle cam functions, the latch assembly combines the latch prop, latch lobe, and reset spring into a single unit, and the cam roller serves both to engage the cam and guide the toggle assembly motion, reducing the total component count while maintaining reliable contact closure.
Solution Approach 2:
Components are designed to perform multiple functions simultaneously. The cam shaft both controls spring compression and actuates the toggle assembly. The latch prop both engages the latch lobe for latching and serves as a lever for the reset spring. The cam roller both receives cam forces and guides toggle motion, reducing the number of dedicated components needed.
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 ram assembly reduces wear and tear on components, fits into a smaller space, and enables rapid contact closure with reduced torque and wear on the latch assembly, enhancing the operational efficiency and reliability of the electrical switching apparatus.
Implementation Method 1
The closing assembly, typically, included at least one stored energy device, such as a spring... Closing springs typically were about 2 inches (5,08 cm) in diameter and about 5 to 6 inches (12,7 to 15,24 cm) in length. These springs were structured to apply a force of about 1,000 pounds (453,59 Kg).
Implementation Method 2
Low and medium voltage selective electrical switching apparatus typically had a stored energy device, such as an opening spring... The spring biased the toggle assembly to the collapsed position.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A latch assembly (180) for an electrical switching apparatus operating mechanism (50) is provided. The latch assembly (180) is structured so that force from the closing spring is directed along a line extending through the pivot point of a latch prop (186). A reset assembly (200) for the latch prop (186) is also provided.