Threaded Collar Cover for Field Device Circuit Protection
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Solution Overview
Problem
Field devices in industrial process facilities face challenges in providing a local operator interface without exposing sensitive circuitry to harsh environments, as conventional threaded covers can disrupt or damage circuitry during engagement or disengagement and are difficult to configure without removing covers, which are hard to reinstall and expose internal components to the environment.
Innovation Solution
A field device system with a housing body, a first circuitry subassembly, a cover chassis, and a threaded collar that allows rotation relative to the cover, along with a second circuitry subassembly secured to the cover, featuring an electrical connector for linear insertion engagement with the housing body to secure the cover and prevent rotation, ensuring an explosion-proof and flameproof enclosure while minimizing risk to circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional threaded cover is used to secure the transmitter housing, then the explosion-proof enclosure is achieved, but the torque and vibrations during operation can disrupt or damage sensitive circuitry
Solution Approach 1:
The cover assembly is segmented into distinct functional components: a non-rotating cover body that maintains explosion-proof sealing, and a rotating collar that provides electrical connection and mechanical fastening. This segmentation allows the cover body to remain stationary and protect circuitry while the collar handles rotational engagement.
Solution Approach 2:
The electrical connector serves as an intermediary element between the cover and housing body. It provides both electrical connection and mechanical coupling, allowing the cover to be secured without direct threaded engagement that would transmit damaging torque to circuitry.
2Ease of operation
If the cover is removed to configure the field device, then the operator interface can be accessed, but the interior regions are exposed to the harsh environment and the cover is difficult to reinstall
Solution Approach 1:
The mechanical threaded fastening system is replaced with a collar-based retention system that uses linear engagement rather than rotation. This allows the cover to remain sealed and protected while enabling configuration access through the transparent portion without removal.
Solution Approach 2:
The transparent cover portion acts as a protective barrier that allows optical access to the operator interface while maintaining the explosion-proof enclosure. The transparent material enables viewing and interaction with display elements without compromising structural integrity or environmental protection.
3Object-affected harmful factors
If the cover is made secure and rotationally fixed to protect circuitry, then circuitry damage is prevented, but the cover cannot be easily removed for configuration
Solution Approach 1:
The collar is designed with dynamic characteristics that allow it to be easily engaged and disengaged through linear motion, while once engaged, it provides secure retention of the cover. The anti-rotation structure ensures the cover remains fixed during operation but can be removed when needed for configuration or maintenance.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A field device assembly (40; 40'; 40") includes a housing body (48), a first circuitry subassembly (54) mounted to the housing body (48) and positioned at least partially within the housing body (48), a first cover chassis (50A; 50B; 92) having a shoulder (94), mating flame path restricting structures (96A, 96B) positioned on the first cover chassis (50A; 50B; 92) and the housing body (48), a first threaded collar (52A; 52B) configured to fit about the first cover chassis (50A; 50B; 92) and to permit rotation relative to the first cover chassis (50A; 50B; 92), and a second circuitry subassembly (58A; 58B) secured to the first cover chassis (50A; 50B; 92). The first threaded collar (52A; 52B) is threadably engaged with the housing body (48), and includes an engagement structure (90) engaged with the shoulder (94) of the first cover chassis (50A; 50B; 92) to secure the first cover chassis (50A; 50B; 92) to the housing body (48). The second circuitry subassembly (58A; 58B) includes an electrical connector (60A; 62A) configured for linear insertion engagement with a mating electrical connector (60B; 62B) within the housing body (48) to electrically connect the first and second circuitry subassemblies.