Knitting Machine Needle Monitoring via Dynamic Time Interval Analysis
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Solution Overview
Problem
Existing needle monitoring methods for knitting machines are insensitive to speed fluctuations and often generate false alarms, and they require multiple machine revolutions to detect bent or broken needles, which delays error detection.
Innovation Solution
The method involves registering time intervals between optical signal pulses and setting dynamic limit factors (e.g., 1.2 and 0.8) to tolerate speed fluctuations, allowing immediate detection of bent or broken needles by comparing current intervals to previous ones, and optionally counting signal pulses per revolution to ensure accurate monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the monitoring method is set to be sensitive to detect bent needles or broken hook parts, then detection precision is improved, but false alarms increase due to speed fluctuations
Solution Approach 1:
The patent applies dynamics by making the evaluation criteria adaptive rather than fixed. The system dynamically adjusts the expected time interval based on the actual machine speed during operation. By continuously adapting the reference value to current operating conditions, the system maintains high detection precision while avoiding false alarms caused by speed variations.
Solution Approach 2:
The patent changes the parameter used for evaluation from absolute time interval to relative deviation from expected interval. Instead of comparing against a fixed time value, the system compares the actual time interval against an expected interval that accounts for speed fluctuations. This parameter transformation allows the system to tolerate speed variations while still detecting genuine needle defects.
2Reliability
If the monitoring method waits for a full machine revolution to detect errors, then speed fluctuations are tolerated, but detection time increases
Solution Approach 1:
The patent applies self-service by using the actual machine speed during operation to determine the expected time interval, rather than relying on preset values based on nominal speed. The system serves itself by adapting to its own operating conditions in real-time, enabling immediate detection without waiting for complete machine revolutions while maintaining tolerance to speed variations.
Solution Approach 2:
The patent performs preliminary action by calculating the expected time interval based on current speed conditions before the actual needle passage is evaluated. This allows the system to have the reference value ready immediately, enabling real-time comparison and detection without delay, while still accounting for speed fluctuations that occur during operation.
3Speed
If optical sensors are used for immediate needle detection, then detection speed is improved, but false detection increases due to needle vibrations
Solution Approach 1:
The patent applies partial action by not requiring perfect signal conditions for detection. Instead of demanding exact signal matching, the system evaluates whether the time interval deviation exceeds acceptable thresholds. This approach allows immediate detection using optical sensors while tolerating the effects of needle vibrations that cause minor signal variations, as long as the overall time interval pattern remains consistent with normal 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 approach enables reliable detection of bent or broken needles independently of speed fluctuations and reduces the time required for error detection, providing immediate alerts and minimizing waste production.
Implementation Method 1
individual signal pulses are generated by optical monitoring whenever a needle or hook moves through the field of view of the optical sensor
Data Source
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AI summary
The method according to the invention for monitoring needles of a knitting machine is based on dynamic fixing of the monitored time intervals between individual needle pulses. The time duration of at least one or more preceding time periods between individual signal pulses is taken as a measure of the time interval which is currently to be assessed. Dynamic fixing of the switching thresholds for generating the signal pulses can likewise be performed. In turn, the amplitude of preceding pulses is analysed, a trend is determined and the switching thresholds for generating the current signal pulse is stipulated from this trend. The pulses which are generated at all needle positions can be assessed by way of this method. If the needle cylinder is deliberately fitted only partially, individual needle positions can be indicated correspondingly and removed from the assessment. This results in a dependable, robust and reliable monitoring method.