Polychotomous Cable Pull Switch with Adaptive Thresholds

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Solution Overview

Problem

Existing cable pull switches in industrial settings face challenges such as inflexible binary operation, susceptibility to jamming, and the need for frequent tension adjustments due to thermal changes, which can lead to false triggers and require cumbersome maintenance procedures.

Innovation Solution

The implementation of a polychotomous sensor-based cable pull switch that uses strain gauges, inductance sensors, or linear optical sensors to provide a variable output, allowing for continuous tension monitoring and adjustment, and includes a processing device to manage thresholds and detect cable pull events, slack conditions, and thermal changes, thereby enhancing operational flexibility and reducing maintenance needs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If binary contact blocks are used for cable pull switch operation, then the switch provides simple on/off emergency stop function, but the operation is inflexible and requires frequent tension adjustments due to thermal changes

Engineering Contradiction:
Improveoperational flexibilityVSAvoidsystem complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces the traditional mechanical binary contact block system with an optical sensing system. Optical sensors detect cable displacement and tension changes without mechanical contact, eliminating the need for mechanical adjustment due to thermal expansion and contraction. This substitution provides continuous variable output for adaptive threshold adjustment while maintaining simple operation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements dynamic threshold adjustment based on real-time cable tension monitoring. The system adapts the activation threshold according to actual cable conditions, allowing the switch to respond flexibly to varying tension requirements while preventing false triggers from thermal changes. This dynamic adaptation resolves the contradiction between operational flexibility and system complexity.

Inventive Principle:
Principle #15Dynamics

2Ease of operation

If mechanical contact blocks with fixed thresholds are used, then the switch structure is simple, but the thresholds cannot be easily altered and require careful adjustment during operation

Engineering Contradiction:
Improveadjustment easeVSAvoidadjustment mechanism complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces mechanical threshold adjustment mechanisms with electronic/software-based threshold configuration. The optical sensing system allows thresholds to be programmed and adjusted without physical manipulation of mechanical components, making adjustment easier and more flexible while reducing mechanical complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent enables easy alteration of activation thresholds by changing software parameters rather than physical adjustments. The system allows operators to modify threshold values through programming or configuration interfaces, eliminating the need for mechanical repositioning and simplifying the adjustment process while adapting to different operational requirements.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If close activation thresholds are used for easy detection, then cable pull events are easily detected, but false triggers occur due to thermal expansion and contraction

Engineering Contradiction:
Improvecable pull detection precisionVSAvoidfalse trigger rate
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent implements continuous feedback monitoring of cable tension and environmental conditions. The optical sensing system constantly measures cable state and compares it against adaptive thresholds, allowing the system to distinguish between genuine cable pull events and thermal expansion/contraction. This feedback mechanism maintains high detection precision while eliminating false triggers through real-time condition assessment.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent employs dynamic threshold adjustment that adapts to changing cable tension and environmental conditions. Rather than using fixed close thresholds that cause false triggers, the system dynamically modifies thresholds based on real-time monitoring, maintaining sensitive detection of cable pulls while filtering out thermal effects that would otherwise cause false alarms.

Inventive Principle:
Principle #15Dynamics

4Ease of operation

If turnbuckles or cable tensioning systems are used for tension adjustment, then the pull cable tension can be adjusted, but the technician must iteratively walk between adjustment location and switch to properly adjust tension

Engineering Contradiction:
Improvetension adjustment easeVSAvoidadjustment time
Core Design Contradiction:
Ease of operationVSLoss of time

Solution Approach 1:

The patent replaces mechanical tension adjustment with optical sensing and electronic control. The system monitors cable tension continuously and provides feedback on the actual tension state, allowing technicians to make single-pass adjustments without iterative trips between the adjustment location and switch. This substitution dramatically reduces adjustment time while improving ease of operation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements real-time feedback during tension adjustment, allowing technicians to see the actual cable tension state and switch response immediately. This feedback eliminates the need for iterative adjustment by providing clear information about whether the current tension is appropriate, reducing adjustment time from multiple trips to a single inspection and adjustment cycle.

Inventive Principle:
Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enables more accurate and adaptive tension management, reduces false triggers, and simplifies maintenance by providing real-time feedback and automatic threshold adjustments, improving the reliability and usability of cable pull switches in dynamic industrial environments.

Implementation Method 1

A sensor, such as a strain gauge, is coupled to the spring and configured to detect a tension force applied to the shaft

Methodology Applied
Scientific EffectStrain gauge measurement: Piezoresistive Effect

Implementation Method 2

The sensor may be an inductance sensor

Methodology Applied
Scientific EffectInductance sensing: Electromagnetic Induction

Implementation Method 3

The sensor may be an optical light sensor array

Methodology Applied
Scientific EffectOptical sensing: Light

Data Source

PatentEP3176799B1An improved safety switch and associated methods
Publication Date: 2021.05.19 ROCKWELL AUTOMATION TECH INC
  • EP3176799B1 patent drawingFigure 1
  • EP3176799B1 patent drawingFigure 2
  • EP3176799B1 patent drawingFigure 3~4A

AI summary

A cable pull switch comprises: a polychotomous cable pull sensor configured to provide a reading comprising at least one of a plurality of values, the reading corresponding to a tension on a pull cable or a linear displacement of a first end of the pull cable, at least one processor coupled to the polychotomous cable pull sensor. The processor configured to determine a rate of change (ROC) of the plurality of values and determine whether the plurality of values exceeds an upper pull threshold value, periodically adjust the upper pull threshold value at a fixed interval of time if the ROC of the plurality of values is below a ROC threshold, periodically adjust a lower slack threshold value at the fixed interval of time if the ROC of the plurality of values is below a ROC threshold. and determine an occurrence of a cable pull event based on the determined ROC of the plurality of values, or whether the plurality of values exceeds the upper pull threshold value.