Rotatable Grounding Bushing for Post-Wiring Raceway Access
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Solution Overview
Problem
Conventional grounding bushings are cumbersome to remove and reassemble from conduits, often requiring the removal of multiple fasteners and are prone to misplacement, and they do not provide adequate protection against chafing or abrasion of electrical cables.
Innovation Solution
A grounding bushing with a stationary and rotatable portion held together by mounting fasteners, featuring slotted ends for easy rotation and removal, and an electrically insulated liner to prevent abrasion, allowing for easy installation and reinstallation without losing fasteners and ensuring secure attachment to meet UL grounding requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hinged assembly with screw fasteners is used, then the bushing can be assembled and disassembled, but it is cumbersome to remove and reassemble requiring complete removal of screws and radial rotation
Solution Approach 1:
The bushing is divided into two separate bushing portions (first and second portions) that can be independently manipulated. Each portion has its own fastener, allowing selective loosening and rotation of individual portions to open the assembly and access the conduit opening without removing entire screw assemblies.
Solution Approach 2:
The bushing portions are designed to be rotatable relative to each other about the conduit opening. The fasteners can be loosened to permit rotation, transforming the static closed bushing into a dynamic open configuration for wire installation, then rotated back to closed position for grounding.
2Reliability
If multiple screws are used to secure bushing portions, then the bushing can be tightly secured to conduit, but the screws are easy to drop, lose, or misplace hampering reassembly
Solution Approach 1:
The bushing portions and fasteners are designed as an integrated assembly where the fasteners remain attached to their respective bushing portions throughout the disassembly and reassembly process. This merging prevents loss of fasteners and simplifies reassembly by maintaining the association between each fastener and its bushing portion.
3Object-affected harmful factors
If a conventional bushing without liner is used, then the structure is simpler, but electrical cables are subjected to chafing or abrasion by conduit edges
Solution Approach 1:
An electrically insulated liner is introduced as an intermediary component between the conductive bushing portions and the electrical cables. The liner extends around the inner periphery of both bushing portions, providing a non-abrasive protective surface that prevents chafing and abrasion of cables while the bushing portions provide structural support and grounding function.
Data Source
AI summary
A grounding bushing with a central opening for electrically grounding a conduit, electrical metal tubing (EMT), or a pipe. The grounding bushing includes a stationary bushing portion and a rotatable bushing portion having slotted ends held together by mounting fasteners. The slotted ends permit rotation of the rotatable bushing portion away from the stationary bushing portion. After attachment to a conduit or similar structure, one or more mounting fasteners can be loosened to allow installation of additional wires through the central opening and into the conduit, EMT, or pipe. An electrically insulated liner extending around the entire inner periphery of the bushing prevents chafing or abrasion of any electrical wires by the end of the conduit.