Armored Cable Sheath Profile for Lower Pulling Resistance
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Solution Overview
Problem
Conventional armored cable designs fail to reduce pulling force during installation, despite efforts to minimize hang-ups and installer fatigue, as demonstrated by independent pull force testing which showed no significant decrease in pulling force compared to conventional designs.
Innovation Solution
The armored cable design features a metal sheath with a specific cross-sectional profile comprising an interlock, an interlock receiver, and an intermediate segment with a maximum incline angle less than 35° and a width ranging from two to ten times the interlock height, allowing for reduced pulling resistance while maintaining crush resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional armored cable designs with maximal crush resistance are used, then the cable can withstand significant pulling forces and maintain structural integrity, but the pulling force during installation remains high causing installer fatigue and potential damage
Solution Approach 1:
The armor layer cross-sectional profile is designed with non-uniform geometry featuring a flattened portion and a rounded portion with different curvature radii. The flattened portion has a larger curvature radius while the rounded portion has a smaller curvature radius, creating local variations in the profile that reduce pulling resistance while maintaining overall crush resistance through strategic geometric distribution
Solution Approach 2:
The invention changes the geometric parameters of the armor layer profile by specifying that the flattened portion extends along the cable axis with a width of 2-10 times the interlock height, and the maximum incline angle of the intermediate segment is less than 35 degrees. These parameter modifications optimize the balance between pulling force reduction and structural strength
2Ease of operation
If the armor layer profile is modified to reduce pulling force, then installation becomes easier with reduced installer fatigue, but the crush resistance may be compromised
Solution Approach 1:
The profile design strategically places a flattened portion and a rounded portion at different locations along the cable axis. The flattened portion reduces pulling resistance by creating a smoother transition, while the rounded portion with appropriate curvature maintains local structural strength to resist crushing forces, achieving both installation ease and structural integrity
Solution Approach 2:
The invention addresses the strength-pulling force trade-off by introducing dimensional variations in the cross-sectional profile along the cable axis. The flattened portion width is specified as 2-10 times the interlock height, creating a dimensional relationship that optimizes both pulling characteristics and crush resistance through geometric scaling
3Device complexity
If the intermediate segment has a steep incline angle, then the interlock structure is more compact, but the pulling resistance increases due to greater friction and contact with wall structures
Solution Approach 1:
The invention directly controls the pulling resistance by limiting the maximum incline angle of the intermediate segment to less than 35 degrees. This parameter constraint creates a gentler slope that reduces friction and contact pressure with wall structures during installation, thereby lowering pulling resistance while maintaining interlock functionality
Data Source
AI summary
Disclosed herein are armored cable sheaths that demonstrate decreased pull resistance in an aluminum stud pull test. Armored cables disclosed herein also demonstrate adequate crush resistance to meet UL 1569 requirements.