Maintenance-Free Electrical Bus Assembly Threaded Fastener
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Solution Overview
Problem
Electrical bus assemblies in switchgear devices require frequent maintenance to prevent loosening of fasteners, which can lead to equipment damage and safety issues, especially when access is limited, and existing solutions like welding increase costs and complexity while making modifications difficult.
Innovation Solution
A maintenance-free electrical bus assembly using a fastener assembly with first and second fastening elements featuring threaded engagements, where the second threads perpetually secure the first threads to resist loosening, employing SPIRALOCK® thread form for secure and long-lasting connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fastener assemblies are used to connect bus members, then the electrical bus assembly can be assembled and disassembled, but the fasteners loosen over time requiring frequent maintenance inspections
Solution Approach 1:
The patent changes the geometric parameters of the thread form itself, creating a non-standard thread profile that inherently prevents loosening. The modified thread geometry creates asymmetric engagement where the fastener can be tightened but not loosened without damage, eliminating the need for maintenance while preserving assemblability.
Solution Approach 2:
The patent combines standard threaded fasteners with bus members that have modified thread forms, creating a composite connection system. The bus member incorporates a specially designed thread profile that works with conventional fasteners to provide maintenance-free operation, merging the benefits of standard components with custom geometry.
2Reliability
If welding is used to permanently secure bus joints, then maintenance-free operation is achieved, but manufacturing costs and complexity increase and future modifications become difficult
Solution Approach 1:
The patent divides the connection system into separable components: standard fasteners and bus members with modified threads. This segmentation allows the assembly to be disassembled and reassembled without welding, maintaining maintenance-free operation while enabling future modifications and reducing manufacturing complexity compared to welded joints.
Solution Approach 2:
The patent replaces the welding process (thermal/mechanical system) with a specialized mechanical thread-form system. The modified thread geometry provides permanent-like security through mechanical interlocking and asymmetric engagement, achieving welding-level reliability without the complexity and irreversibility of welding operations.
3Reliability
If prevailing torque-type nuts with nylon inserts are used to prevent loosening, then fastener security is improved, but the nuts become soft when heated and plastically deform losing their locking function
Solution Approach 1:
The patent changes the fundamental parameter of the thread form geometry rather than relying on material properties like nylon inserts. The modified thread profile provides thermal stability because it depends on geometric interlocking and asymmetric engagement, not on materials that soften at elevated temperatures, ensuring reliable fastener security in high-temperature electrical applications.
4Reliability
If chemical additives like LOCTITE are used to secure fasteners, then fastener loosening is prevented, but electrical conductivity is disrupted and the additives break down at elevated temperatures
Solution Approach 1:
The patent replaces chemical locking mechanisms (like LOCTITE) with a purely mechanical thread-form system. The modified thread geometry provides fastener security through asymmetric mechanical engagement, eliminating the need for chemical additives that would disrupt electrical conductivity or break down at elevated temperatures, thus preserving both electrical performance and thermal stability.
Data Source
AI summary
A maintenance-free electrical bus assembly is provided for a switchgear cabinet. The maintenance-free electrical bus assembly is coupled to a switchgear device in the cabinet, and includes electrical bus members, at least one bus joint comprising an electrical connection of two or more electrical bus members, and a fastener assembly fastening the bus joint and maintaining the electrical connection between the electrical bus members thereof. The fastener assembly includes at least one first fastening element having a plurality of first threads, and at least one second fastening element having a plurality of second threads. The second threads threadably engage the first threads of a corresponding first fastening element, in order to perpetually secure the first threads and the corresponding first fastening element, and to resist undesirable loosening of the bus joint once the fastener assembly has been fastened. Thus, inaccessible bus joints within the cabinet do not need to be inspected.