Surge Arrester End Fitting with Overlapping Threads
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Solution Overview
Problem
The existing surge arresters with cage designs face challenges in achieving a compact terminal fitting due to the minimum length requirements of threads for connecting bolts and pressure screws, which hinder efforts to reduce the overall length of the surge arrester.
Innovation Solution
The design incorporates overlapping first and second threads arranged coaxially along an axial section, allowing for a shorter height of the end fitting by intersecting in a radial plane, enabling better contact between varistor blocks and facilitating compactness, with a pot-shaped pressure screw and injection openings for simplified sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the end fitting is designed with separate first and second threads for connecting bolt and pressure screw, then the surge arrester can maintain mechanical stability and proper electrical connection, but the overall length of the surge arrester increases due to the minimum length requirements of both threads
Solution Approach 1:
The patent merges the first thread (for connecting bolt) and the second thread (for pressure screw) into an overlapping axial section, allowing both threads to occupy the same axial space rather than requiring separate sequential spaces. This combining of thread functions into an overlapping region directly reduces the overall length of the end fitting while maintaining both mechanical stability and electrical connection capabilities.
Solution Approach 2:
The patent transitions from a sequential axial arrangement of threads to an overlapping spatial arrangement where threads are distributed around the circumference in the same axial region. This dimensional reorganization allows the end fitting to accommodate both connecting and pressing functions within a shorter axial length by utilizing radial distribution combined with axial overlap.
2Length of moving object
If the end fitting length is reduced to make the surge arrester more compact, then the overall length decreases, but the minimum length required for threads to transmit necessary forces cannot be satisfied
Solution Approach 1:
The patent combines multiple threads (first thread for connecting bolt, second thread for pressure screw) into an overlapping axial section, allowing force transmission functions to be achieved within a shorter axial length. The overlapping arrangement ensures that both threads have sufficient engagement length to transmit their respective forces while occupying the same axial space.
Solution Approach 2:
The patent applies different thread characteristics and distributions within the overlapping axial section to optimize local force transmission. The first and second threads can have different pitch, depth, or angular positions, allowing each to be optimized for its specific force transmission requirement while maintaining compact overall dimensions.
3Device complexity
If traditional separate thread arrangements are used, then adequate sealing length is available, but elaborate sealing measures are still required and the design is less compact
Solution Approach 1:
The patent merges the thread arrangements into an overlapping axial section that naturally provides adequate sealing length without requiring separate dedicated sealing sections. This integrated design reduces the need for elaborate separate sealing measures while maintaining compact dimensions.
Solution Approach 2:
The overlapping thread arrangement itself creates a natural sealing configuration where the threaded structures and associated features (such as sealing surfaces and gland structures) are integrated into the compact design, making the sealing function self-contained within the shortened end fitting without requiring additional elaborate sealing components.
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 configuration allows for a more compact surge arrester design while maintaining mechanical stability and ease of assembly, reducing the overall length and eliminating the need for elaborate sealing measures.
Implementation Method 1
a first thread for attaching a connecting bolt used for connecting the surge arrester to an overhead line of a power transmission network. In addition, the end fitting has a fitting body with a second thread for receiving a pressure screw for generating an axial force on the discharge column
Implementation Method 2
The discharge column is pressed together axially by means of the pressure screw in order to enable the best possible contact between the varistor blocks forming the discharge column
Implementation Method 3
the surge arrester has a discharge column with a voltage-dependent electrical resistance, a so-called varistor. Below a threshold voltage, which is a material property of the varistor, the discharge column has a high resistance and acts as an insulator. If the threshold voltage is exceeded, the resistance of the varistor decreases, the discharge column becomes conductive and discharges the overvoltage to earth
Data Source
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AI summary
The invention relates to surge arresters used for protection against overvoltages in electrical power transmission networks. Such a surge arrester (1) has a discharge column extending along a longitudinal axis (40), which is clamped between the end fittings (3) by means of several tension elements (4) radially surrounding the discharge column (2) and fixed in end fittings (3). At least one of the end fittings has a first thread (7) for attaching a connecting bolt (15). The end fitting (3) also has a fitting body (10) with a second thread (8) for receiving a pressure screw (14) to generate an axial force on the discharge column (2). According to the invention, the first and second threads (7, 8) overlap along an axial section (9).