Externally Calibrated Valve Limit Switch Assembly
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Solution Overview
Problem
Conventional limit switch assemblies in valve assemblies require opening the housing for calibration, which is inconvenient and may disrupt the installation, especially when redundant feedback is needed for valve position verification.
Innovation Solution
A limit switch assembly with a calibration mechanism that allows adjustment of limit positions using an input member accessible from outside the housing, enabling calibration without disassembly, and is mounted between the valve positioner and actuator to provide redundant feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional limit switch assembly calibration requires opening the housing, then calibration can be performed, but it is inconvenient and may disrupt the installation
Solution Approach 1:
The calibration mechanism is segmented into two parts: an input member accessible from outside the housing and internal calibration components. This allows the calibration function to be accessed externally without opening the housing, resolving the contradiction between calibration convenience and housing integrity.
Solution Approach 2:
A calibration linkage acts as an intermediary mechanism that transmits the adjustment input from the externally accessible input member to the internal position sensor. This mediator enables calibration without direct access to internal components, eliminating the need to open the housing while maintaining calibration functionality.
2Reliability
If limit switch assembly is installed between positioner and actuator, then redundant feedback is provided, but calibration becomes more difficult
Solution Approach 1:
Instead of making the calibration mechanism accessible from inside the housing (traditional approach), the input member is inverted to be accessible from outside the housing. This reversal allows calibration to be performed conveniently even when the assembly is installed between the positioner and actuator, maintaining both feedback redundancy and calibration accessibility.
Data Source
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AI summary
A valve assembly includes a valve, an actuator for opening and closing the valve, and a positioner for controlling the actuator. At least one limit switch assembly is mounted between the positioner and the actuator. The limit switch assembly connects the actuator and positioner so that movement of the actuator valve is conveyed to the positioner through the limit switch assembly. The limit switch assembly is configured to provide a limit signal when the valve is in one or more limit positions. The limit switch assembly has a calibration mechanism for adjusting the one or more limit positions using an input member accessible from outside of the limit switch housing when the limit switch is installed in the valve assembly.