Drive Sprocket Side-Slot Speed Sensing for Clean Escalator Signals
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Solution Overview
Problem
Existing passenger transport devices, such as escalators and moving walks, face issues with detecting the rotational speed of drive sprockets due to exposure to lubricants and metallic abrasion, leading to erroneous signals and reliability concerns.
Innovation Solution
The use of slot-shaped recesses on the drive sprocket's ring-shaped side face, which generate a rectangular signal profile as they rotate, allowing for reliable rotational speed detection with reduced exposure to contaminants and incorporating air flow for self-cleaning of sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are positioned to scan the teeth or tooth gaps of the drive sprocket, then rotational speed detection is achieved, but the sensors are exposed to lubricants and metallic abrasion causing erroneous signals
Solution Approach 1:
The detection feature (slot-shaped recesses) is extracted from the drive chain interaction zone and placed on the ring-shaped side face of the drive sprocket. This separates the sensing function from the contaminated area where lubricants and metal abrasion occur, allowing sensors to detect rotational position without direct exposure to harmful contaminants.
Solution Approach 2:
The slot-shaped recesses serve as an intermediary detection mechanism. Instead of sensors directly scanning teeth or tooth gaps in the contaminated zone, the recesses on the side face act as a clean intermediary feature that still provides rotational position information through air flow modulation when exposed to the sensor beam.
2Productivity
If sensors are exposed to the drive chain area for detection, then rotational speed can be detected, but dust, dirt, and grease adhere to sensor heads causing erroneous signals
Solution Approach 1:
The detection functionality is extracted from the contaminated drive chain area and relocated to the clean ring-shaped side face of the drive sprocket. The slot-shaped recesses are positioned in a zone free from direct lubricant spray and metal particulate generation, eliminating the source of sensor contamination while preserving detection capability.
Solution Approach 2:
The slot-shaped recesses create localized air flow patterns that generate a self-cleaning effect on the sensor head. The air flow, induced by the rotating recesses passing through the sensor beam, creates a wiping action that removes accumulated dust and dirt from the sensor surface, maintaining detection accuracy without external cleaning mechanisms.
3Reliability
If slot-shaped recesses are arranged on the ring-shaped side face, then sensor exposure to contaminants is reduced, but additional structural features are added to the drive sprocket
Solution Approach 1:
The slot-shaped recesses serve multiple functions simultaneously: they act as structural stiffening elements for the drive sprocket web, provide the detection features for rotational speed measurement, and generate the air flow for sensor head cleaning. This multi-functionality adds minimal structural complexity while achieving multiple beneficial effects.
Solution Approach 2:
The slot-shaped recesses are positioned locally on the ring-shaped side face of the drive sprocket, specifically in the region that provides optimal detection geometry for the sensors. This localized feature addition minimizes overall structural complexity while concentrating the functional benefits where needed for reliable operation.
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
This solution provides a cost-effective and reliable method for detecting rotational speed with reduced disturbances and improved sensor cleanliness, enhancing the accuracy and longevity of the detection system.
Implementation Method 1
The air flow loosens dust and dirt from the sensor head and, with the help of centrifugal force, removes it from the sensor's detection area.
Data Source
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Figure 5
AI summary
The invention relates to a person-transporting apparatus (1), which has at least one drive sprocket (17) for driving and deflecting a transport belt (26) and at least one sensing apparatus (20) for sensing the rotational speed of the drive sprocket (17). Slit-shaped cut-outs (37) are arranged on at least one annular side surface (35) of the drive sprocket (17), wherein the longitudinal extent of the slit-shaped cut-outs (37) extends over the annular side surface (35) in the radial direction with respect to the center of rotation of the drive sprocket (17). By means of the sensing apparatus (20), a signal representing the rotational speed of the drive sprocket (17) can be produced by scanning the slit-shaped cut-outs (37), which can be moved relative to the sensing apparatus (20), and scanning the elevations (36) present between the slit-shaped cut-outs (37).