Inductive Sensor Nested in Compression Spring for Belt Tension

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Solution Overview

Problem

Existing sensor arrangements for monitoring chain or belt drive tension face challenges in detecting variable tension over longer travel distances, as their detection range is often smaller than the travel path, making it difficult to reliably assess changes due to vibrations, wear, and temperature fluctuations.

Innovation Solution

A sensor arrangement featuring a compression spring with an inductive sensor placed inside, where the sensor's detection range is extended by considering the compression of the spring coils, allowing non-contact measurement of the distance between spring coils, and an oscillating circuit with damping proportional to the tension, providing precise and reliable tension monitoring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an inductive sensor is used to monitor chain or belt drive tension, then tension changes can be detected, but the detection range is smaller than the travel path, making it difficult to reliably assess changes over longer distances

Engineering Contradiction:
Improvetension detection precisionVSAvoiddetection range
Core Design Contradiction:
Measurement precisionVSLength of stationary object

Solution Approach 1:

A spring element is introduced as an intermediary between the chain/belt drive and the inductive sensor. The spring element translates the movement of the chain or belt into a corresponding compression or extension that the inductive sensor can detect within its limited range, thereby enabling monitoring over the entire travel path.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The inductive sensor is positioned inside the spring element, with the sensor nested within the coils of the spring. This nested arrangement allows the sensor to monitor the compression of the spring coils, which corresponds to the tension in the chain or belt drive, effectively extending the detection capability beyond the sensor's direct range.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Reliability

If the inductive sensor is positioned to monitor the entire travel path, then complete tension monitoring is achieved, but the device complexity increases

Engineering Contradiction:
Improvetension monitoring reliabilityVSAvoidsensor arrangement complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The spring element serves multiple functions simultaneously: it acts as a mechanical component to absorb tension variations, as a transmission element to convert movement into measurable compression, and as a structural element to position the inductive sensor. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Length of stationary object

If the detection range is extended to cover the entire travel path, then complete tension assessment is possible, but the space required for the sensor arrangement increases

Engineering Contradiction:
Improvedetection rangeVSAvoidsensor arrangement volume
Core Design Contradiction:
Length of stationary objectVSVolume of moving object

Solution Approach 1:

The inductive sensor is placed inside the spring element, utilizing the internal space of the spring coils. This nested configuration allows the sensor to be positioned within the existing structural envelope of the spring, thereby extending the detection range without proportionally increasing the overall volume of the sensor arrangement.

Inventive Principle:
Principle #7Nested doll (Nesting)

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

Enables reliable detection of tension changes over longer distances, reduces space requirements, and allows for precise monitoring of vibrations, facilitating timely maintenance and operational assessment of conveyor systems, with the option to integrate an acceleration sensor for service life monitoring.

Implementation Method 1

an inductive sensor (10), which non-contactly detects a distance between spring coils (11) of the compression spring (8)

Methodology Applied
Scientific EffectInductive sensing: Electromagnetic Induction

Implementation Method 2

an oscillating circuit with damping proportional to the tension

Methodology Applied
Scientific EffectDamped oscillation: Damping

Data Source

PatentEP3483094B1Sensor arrangement for determining a variable tension of a circumferentially moved chain or belt drive
Publication Date: 2020.04.15 SICK AG
  • EP3483094B1 patent drawingFigure 1
  • EP3483094B1 patent drawingFigure 2a~2c
  • EP3483094B1 patent drawingFigure 3a~3c

AI summary

The invention relates to a sensor arrangement for determining a variable tension of a rotating chain or belt drive, comprising a spring element (8) attached to a base body (9) which is operatively connected to the chain or belt drive, and an inductive sensor (10) which monitors voltage-dependent changes in the spring element (8). In a sensor arrangement in which the variable tension can also be reliably detected when a travel distance is significantly greater than the detection range of the inductive sensor, the inductive sensor (10) for detecting a variable distance between several spring coils (11) of the spring element (8), which is designed as a metallic compression spring, is arranged directly opposite these spring coils (11).