Armored Cable Ferrule Connection for Watertight Thread Matching
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Solution Overview
Problem
Existing connectors fail to provide watertight seals for armored twisted-pair, fiber optic, and hybrid cables when connecting them to enclosures, as they do not match the thread pitch and taper of the armor, leading to inadequate protection in wet environments.
Innovation Solution
Modifying the armor pitch of the cables to match NPT threading, using a modified ferrule with non-NPT threading, or employing an adapter ferrule to facilitate connections with existing LFMC connectors, ensuring watertight seals and bonding of metallic armor to enclosures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common LFMC connectors with NPT threaded ferrules are used, then water-tight connections can be achieved, but the connector cannot be properly retained on the armor because the armor pitch does not match NPT threading
Solution Approach 1:
An adapter ferrule is introduced as an intermediary component between the NPT-threaded LFMC connector and the AC-armored cable. The adapter ferrule has dual threading: NPT external threads that mate with the connector's internal NPT threads, and AC internal threads that mate with the cable's armor. This intermediary resolves the thread pitch incompatibility while maintaining water-tight sealing capability.
Solution Approach 2:
The adapter ferrule changes the thread pitch parameter from NPT standard to AC armor standard, allowing the connection system to interface between two different thread pitch standards. This parameter transformation enables compatibility without modifying the original connector or cable designs.
2Ease of operation
If MC style connectors are used to attach armor to enclosure, then the connector can be installed, but it does not provide water-tight protection for wet locations
Solution Approach 1:
The adapter ferrule design allows a single LFMC connector system to serve multiple functions: it provides both the mechanical attachment capability of MC connectors and the water-tight sealing capability of LFMC connectors. By integrating the adapter ferrule, the system achieves universality across different connector types while maintaining the superior water-tight properties of LFMC connectors in wet locations.
3Reliability
If cable glands with larger opening sizes are used to fit around armored cables, then water-tight connections can be achieved, but the knockout sizes on NEMA rated enclosures are limited
Solution Approach 1:
The adapter ferrule is designed with a nested structure where the AC-threaded portion fits inside the NPT-threaded portion. This nesting allows the connector assembly to maintain a compact size that can pass through standard NEMA enclosure knockouts while still providing water-tight protection. The nested design avoids the need for larger opening sizes required by traditional cable glands.
Data Source
AI summary
A connection arrangement is provided for connecting an armored cable to a connection piece. The arrangement has a ferrule for fitting onto the end of the armored cable, that has an abutment flange, a washer and a threaded region. The threaded region has at least a portion threaded according to a first thread standard. A lock nut is configured to fit over the armored cable, and to connect with a nut thread on the connection piece. The lock nut and the connection piece are configured to compress the ferrule therebetween forming a watertight connection. An armor of the armored cable has a least a portion of the armor threaded to match the first thread standard.