Threaded Line Bushing Ignition Gap Design
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Solution Overview
Problem
Existing line bushings in dynamo-electric machines for explosive atmospheres require precise, high-tolerance cylindrical gaps for ignition protection, which are costly and complex to produce, and do not efficiently manage ignition gaps to prevent spark or flame escape.
Innovation Solution
A line bushing design featuring a threaded bush and terminal stud with threads on both components, increasing the length and number of ignition gaps for effective gas cooling, while reducing installation space and production costs through simpler thread production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a cylindrical gap is used for the ignition gap in existing line bushings, then the ignition gap width can be controlled, but the production complexity and cost increase due to high tolerance requirements
Solution Approach 1:
The ignition gap is segmented into multiple sections by dividing the single cylindrical gap into several smaller gaps created by the threaded structure. The terminal stud with external threads engages with the threaded bush, creating multiple ignition gap sections along the threaded engagement length, which collectively provide the required ignition protection while simplifying manufacturing tolerances.
Solution Approach 2:
The solution transitions from controlling ignition gap width in a single dimension (cylindrical gap) to utilizing multiple dimensions through the threaded structure. The ignition gap is distributed along the axial length of the threaded engagement, converting a single critical width dimension into multiple smaller gaps distributed over a longer axial dimension, thereby reducing the stringency of tolerance requirements.
2Reliability
If a cylindrical gap is used for the ignition gap, then ignition protection is provided, but the production cost increases due to high tolerance requirements
Solution Approach 1:
The ignition protection function is achieved through multiple segmented gaps created by the threaded engagement between the terminal stud and threaded bush. Each thread engagement section creates a small ignition gap, and the cumulative effect of multiple such gaps along the threaded length provides robust ignition protection while using standard, cost-effective threading processes.
Solution Approach 2:
The solution changes the geometric parameters from a single large cylindrical gap requiring tight width tolerances to multiple smaller gaps distributed along a threaded engagement. This parameter transformation allows the use of conventional threading operations with more relaxed tolerances, significantly reducing production cost while maintaining or enhancing ignition protection reliability.
3Length of stationary object
If a long cylindrical gap is used to increase ignition gap length, then ignition protection is improved, but the installation space increases
Solution Approach 1:
The threaded structure allows the ignition gap to be nested within the threaded engagement zone. The terminal stud with external threads is inserted into the threaded bush, and the ignition gaps are formed within the threaded engagement region. This nested arrangement achieves a long effective ignition gap length while containing the overall footprint within a compact cylindrical volume, efficiently utilizing the available installation space.
4Reliability
If a threaded joint is used instead of a cylindrical gap, then the number and length of ignition gaps are increased, but the structural complexity increases
Solution Approach 1:
The threaded structure serves multiple functions simultaneously: it provides mechanical fastening of the terminal stud to the housing, creates the ignition gaps along the threaded engagement, and enables electrical connection. By integrating these functions into a single threaded joint mechanism, the solution increases ignition gap effectiveness without proportionally increasing structural complexity, as the same structural feature accomplishes multiple objectives.
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 design effectively complies with explosion protection standards by increasing ignition gap length and reducing production complexity and costs, ensuring safe energy supply and reduced installation space.
Implementation Method 1
any gas ignited in the interior of the dynamo-electric machine is cooled via the gap until it is extinguished
Data Source
AI summary
The invention relates to a line bushing (1) in a housing (2) of an electrical machine (1) in explosive atmospheres, having a threaded bush (100) and a terminal stud (200), wherein the threaded bush (100) is an insulator and is located in, particularly screwed into, a recess in the housing (2), wherein the terminal stud (200) is made from an electrically conductive material and is provided, at least in sections, with a thread, wherein connection options (206) for lines and braids are provided at either end of the terminal stud (200), wherein the terminal stud (200) can be screwed into the threaded bush (100).