Microprocessor Yarn Feed Control for Textile Machines
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Solution Overview
Problem
Current yarn feeding systems for textile machines fail to maintain a constant yarn length (LFA) due to mechanical wear, temperature variations, and yarn elasticity, leading to production defects, especially in high-density knitting machines, and require complex actuators or frequent adjustments.
Innovation Solution
A method and arrangement that uses microprocessor-controlled yarn feed devices to maintain constant yarn length by adjusting tension in real-time, independent of machine modifications, and applicable to all types of textile machines, including those without actuators, to intercept yarn variations and prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wheels connected to the drive shaft are used to feed yarn in constant quantity, then constant yarn quantity is provided to the machine, but mechanical wear and thermal expansion cause needle stroke variation leading to defective products
Solution Approach 1:
The patent implements a feedback control system where the actual needle stroke is measured by a sensor and compared with the target stroke. The control unit adjusts the yarn feed amount based on the detected stroke deviation, compensating for wear and thermal expansion effects. This closed-loop feedback ensures constant absorbed yarn length (LFA) despite mechanical degradation over time.
Solution Approach 2:
The patent replaces the purely mechanical yarn feeding system with an integrated system combining mechanical feed wheels, electronic sensors for stroke detection, and electronic control for dynamic adjustment. This substitution allows real-time compensation for mechanical wear and thermal effects that cannot be addressed by mechanical means alone.
2Manufacturing precision
If different yarn quantities are fed for different feed units, then each unit can be optimized, but a large number of pulleys are required exceeding space limits
Solution Approach 1:
The patent employs a universal control system where a single control unit manages all feed wheels, allowing each unit to receive optimized yarn quantities through electronic control rather than requiring separate mechanical pulley systems. The control unit can independently adjust the yarn feed amount for each needle or feed unit based on specific requirements.
Solution Approach 2:
The patent changes the control parameter from fixed mechanical pulley ratios to dynamically adjustable electronic control signals. The control unit can modify the yarn feed amount parameter for each feed unit independently, enabling optimization without adding physical pulleys.
3Stability of the object's composition
If yarn tension is controlled to be constant, then yarn leaving the device has constant tension, but friction in thread guides causes tension variation near the machine
Solution Approach 1:
The patent uses feedback control to detect actual needle stroke and calculate the required yarn feed amount, compensating for friction losses in thread guides. The system adjusts the yarn feed proactively based on detected variations, ensuring constant absorbed yarn length despite tension variations in the yarn path.
4Manufacturing precision
If actuators are added to regulate stitch formation members, then constant LFA can be controlled with precision, but machine complexity increases and compatibility with existing machines is reduced
Solution Approach 1:
The patent extracts the active regulation function from the stitch formation members (needles, cams) and places it in the yarn feed system. Instead of adding actuators to move needles or adjust cams, the system controls the yarn feed amount electronically, achieving LFA constancy without modifying the mechanical stitch formation mechanism.
Solution Approach 2:
The patent introduces an electronic control unit and sensor system as intermediaries between the mechanical yarn feed wheels and the stitch formation process. This intermediary layer enables precise LFA control through electronic measurement and adjustment without requiring direct actuation of the mechanical needle-cam system.
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
Ensures consistent yarn length across all yarns fed to the machine, reducing production defects by dynamically adjusting tension based on measured data, compatible with various textile machines, and applicable to both continuous and separate article production.
Implementation Method 1
Each yarn possesses its own elasticity resulting in yarn elongation depending on the tension to which it is subjected
Implementation Method 2
This tension can change close to the textile machine, for example a knitting machine, because of passage of the yarn through thread guides located along the path between each device and those members (needles in the latter case) which withdraw it and work it within the stitch formation cylinder. These thread guides exert friction on the moving yarn
Data Source
AI summary
A method for feeding a plurality of yarns with constant values of fed length to a textile machine (5), each yarn (2) unwinding from a spool (1) and cooperating with a usual feed device (4), arranged to maintain the tension of the yarn (2) at a predefined constant value before being directed to the textile machine (5), there being provided at least one control unit (6) for controlling the feed to said machine (5); an absorbed yarn length value to be maintained for each yarn (2) fed to the textile machine (5) is set or self-learnt, an actual value of the yarn length effectively absorbed by said machine (5) is measured, and this predefined value is compared with the actual value, to act upon one or more feed devices (4) and modify the tension value of the corresponding yarn (2) whenever this comparison indicates a deformity between said predefined values and the actual measured values, said tension modification making these absorbed yarn length values equal to the predefined value. An arrangement for implementing this method is also claimed.