Split Locknut Grounding Bushing for Insufficient Thread Exposure
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Solution Overview
Problem
In electrical installations, when a locknut securing an electrical connector or conduit to a panel box leaves insufficient exposed threads, it becomes difficult to use conventional split electrical grounding bushings, as they are typically threadless and cannot be properly secured.
Innovation Solution
A split, locknut grounding bushing that combines the functions of a locknut, bushing, and grounding bushing, featuring pivotable metal bushing portions with threaded engagement and insulators for secure attachment to the panel box, allowing for proper grounding and thread engagement with existing connectors or conduits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional split electrical grounding bushing is used, then grounding function is provided, but it cannot be properly secured when exposed threads are insufficient
Solution Approach 1:
The patent combines the functions of a locknut and a grounding bushing into a single integrated component. The locknut body includes threaded interior surfaces that engage with conduit threads, while simultaneously providing exterior threaded bosses for grounding conductor attachment. This merging eliminates the need for separate locknut and grounding bushing components, allowing secure installation even when exposed threads are limited.
Solution Approach 2:
The locknut grounding bushing serves multiple functions: it acts as a locking mechanism to secure the conduit to the panel box, provides a grounding point for electrical connection, and protects the conduit threads. This multi-functionality allows a single component to replace what would traditionally require multiple separate components, resolving the contradiction between providing reliable grounding and ease of installation.
2Strength
If a locknut is used to secure the electrical connector or conduit, then mechanical attachment is achieved, but sufficient exposed threads are not available for grounding bushing installation
Solution Approach 1:
The patent integrates the locknut and grounding bushing functions into one component. The locknut's threaded interior engages with the conduit to provide mechanical attachment, while the same component provides exterior threaded bosses for grounding conductor attachment. This eliminates the need for additional thread exposure beyond what the locknut requires.
Solution Approach 2:
The grounding attachment points are positioned on the exterior surface of the locknut body rather than requiring additional linear thread exposure. This spatial arrangement in another dimension (radial direction from the thread engagement) allows grounding attachment without requiring additional axial thread length.
3Reliability
If a split grounding bushing is used, then grounding capability is provided, but it requires sufficient exposed threads for proper installation
Solution Approach 1:
The locknut grounding bushing is designed to work in situations where conventional grounding bushings cannot be installed. By integrating the grounding function into the locknut structure itself, it becomes universally applicable to installations with limited thread exposure, while still providing reliable grounding capability.
Solution Approach 2:
The locknut body is segmented to include distinct functional zones: an interior threaded surface for conduit engagement, exterior threaded bosses for grounding conductor attachment, and flat surfaces for panel box contact. This segmentation allows each function to be optimized independently while contained within a single component.
Data Source
AI summary
A split, locknut grounding bushing has a first metal bushing portion with first and second ends, a top, a bottom with teeth, an exterior surface with a boss for receipt of a lug, and an interior surface with threads; a second metal bushing portion similar to the first bushing portion, first and second insulators respectively connected to the top of the first and second metal bushing portions. The first and second metal bushing portions pivot with respect to each other at one end and can be fastened to each other at the second end. The threads of the first and second bushing portions can thread onto the threads of a conduit or connector passing through a hole in an electrical enclosure so as to engage the teeth on the bottom of the first and second bushing portions with an interior surface of the enclosure.