Dual Loop Yarn Tension Control for Textile Machines
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Solution Overview
Problem
Existing methods for feeding yarn to textile machines, especially at large distances from the spool, fail to maintain constant and homogeneous tension due to friction and direction changes, leading to production defects and inefficiencies, particularly in diaper production machines where 'rolling takeoff' systems provide constant velocity but not tension, and 'over end takeoff' methods are limited in tension control.
Innovation Solution
A dual yarn tension control system with two sensors and a microprocessor-controlled motor unit, where one sensor regulates tension near the spool and another near the machine, adjusts yarn tension in real-time to maintain constant tension, using a first control loop with rapid intervention for immediate adjustments and a second loop with longer intervention to stabilize tension, allowing for automatic adaptation and alarm systems to prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single tension control system is used near the spool, then the yarn tension can be regulated close to the source, but the tension becomes non-uniform by the time the yarn reaches the machine due to friction and direction changes over long distances
Solution Approach 1:
The patent divides the yarn path into multiple control zones by placing tension sensors at different locations: one near the spool (first sensor) and another near the machine (second sensor). Each zone has its own control loop that independently regulates tension, ensuring uniformity throughout the entire yarn path despite the long distance and multiple guide members.
Solution Approach 2:
The patent implements dual feedback control loops where tension measurements from both sensors are continuously fed back to their respective control units. The first control loop adjusts the spool drive based on tension near the spool, while the second control loop adjusts a brake or clutch near the machine based on tension measurements there, creating a distributed feedback system that maintains uniform tension across the entire yarn path.
2Speed
If a 'rolling takeoff' system is used to unwind the spool, then constant velocity feed is achieved, but constant tension cannot be maintained due to the rotational nature of the system
Solution Approach 1:
The patent employs a feedback control loop where a tension sensor near the spool measures actual yarn tension and feeds this information to a control unit. The control unit then adjusts the spool motor's rotational speed dynamically to compensate for tension variations, allowing the system to maintain both constant velocity feed and constant tension simultaneously through active control.
Solution Approach 2:
The patent transitions from a static rolling takeoff system to a dynamic controlled system where the spool rotation is actively regulated. The control unit continuously adjusts the spool motor's operational parameters based on real-time tension feedback, enabling the system to adapt its rotational characteristics to maintain both velocity and tension constancy under varying operating conditions.
3Device complexity
If tension control is implemented only near the spool, then the system is simpler to implement, but tension variations occur over long yarn paths due to friction and guide member interactions
Solution Approach 1:
The patent segments the tension control function into two independent but coordinated control loops. The first loop handles tension regulation near the spool with simpler components, while the second loop handles tension regulation near the machine. This segmentation allows each control system to be relatively simple individually while achieving overall tension homogeneity through their coordinated operation.
Solution Approach 2:
The patent introduces a second tension sensor and control loop as an intermediary control mechanism between the yarn path and the final processing point. This intermediary control system compensates for tension variations introduced by friction and guide members along the yarn path, ensuring that tension reaches the machine in a homogeneous state without requiring excessive complexity in either individual control loop.
4Productivity
If the spool rotates about its axis for unwinding, then 'rolling takeoff' is enabled, but 'head-tail' feed method cannot be accommodated and operational continuity is lost
Solution Approach 1:
The patent implements a dynamic control system that can adapt the spool's rotational behavior based on the selected feed method. When head-tail feed is required, the control unit adjusts the spool motor to rotate the spool in the appropriate direction and at the appropriate speed, enabling the system to accommodate different feed methods dynamically rather than being fixed to a single operational mode.
Solution Approach 2:
The patent enables parameter changes in the spool drive system to accommodate different feed methods. By programmably controlling the spool motor's rotational direction, speed, and acceleration parameters, the system can switch between rolling takeoff and head-tail feed methods, thereby maintaining operational continuity and adapting to different production requirements without physical reconfiguration.
Data Source
AI summary
A method for feeding a yarn (F) under constant tension to a yarn processing point of a textile machine (T) distant from spool (2) or equivalent support from which the yarn (F) unwinds, the tension of said yarn (F) being controlled in proximity to the spool (2) such that this parameter is monitored and controlled immediately after the yarn (F) has been unwound from the spool (2), the yarn (F) fed to the textile machine (T) cooperating, before reaching said processing point on the machine (T), with a series of thread guide elements (8) which modify the tension of the regulated tension. A second tension control is effected in proximity to the textile machine (T), said control being used for further adjustment of the tension of the yarn (F) in proximity to the spool (2) to hence regulate the tension of the yarn (F) entering the machine (T) to a predetermined constant value.