Yarn Feeding Device Torque Control for Knitting Machines
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Solution Overview
Problem
Existing yarn feeding devices struggle to maintain consistent yarn tension during high-speed knitting, leading to tension peaks that can cut the yarn and result in fluctuating stitch sizes, especially when using weak or decorative yarns.
Innovation Solution
A yarn feeding device equipped with a servo-motor, torque generator, yarn speed calculator, and conversion means to apply variable torques to a rotatable buffer, controlling torque based on yarn speed changes to correct tension fluctuations, employing feedforward control to prevent delays associated with feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is used to control arm torque based on tension sensor data, then the control system can respond to tension changes, but the response is too slow to prevent high tension peaks at high speed knitting
Solution Approach 1:
The control system calculates the required arm torque in advance based on knitting data (stitch loop lengths, carrier position, knitting speed) before the actual knitting operation. This feedforward control approach prepares the torque values beforehand, eliminating the time delay inherent in feedback control systems that wait for tension sensor readings.
Solution Approach 2:
The invention replaces the mechanical feedback control system (tension sensor + feedback controller) with a computational feedforward control system that uses knitting data and mathematical calculations to determine torque requirements, achieving faster and more precise control.
2Productivity
If the yarn feeding speed is increased prior to sharp increases to store excess yarn in the arm, then the yarn tension lowers and the yarn becomes loose
Solution Approach 1:
The arm torque is made dynamically adjustable through feedforward control, allowing the system to optimize yarn tension at each moment based on calculated requirements from knitting data, rather than using fixed spring bias or excessive pre-feeding that causes tension instability.
3Productivity
If simply control the amount of yarn to be fed at high speed knitting, then the yarn feeding is synchronized with carrier motion, but high tension peaks occur that can cut the yarn
Solution Approach 1:
The control system calculates the required arm torque in advance based on knitting data (stitch loop lengths, carrier position, knitting speed) before the actual knitting operation. This feedforward control approach prepares the torque values beforehand, eliminating the time delay inherent in feedback control systems that wait for tension sensor readings.
Solution Approach 2:
The invention changes the control parameter from simple yarn amount feeding to dynamic torque control of the buffer arm, using calculated values from knitting data to adjust torque in real-time, thereby preventing tension peaks while maintaining high-speed 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 maintains almost constant yarn tension during high-speed knitting, preventing yarn cutting and stitch size fluctuations, ensuring uniform loop lengths and reliable operation with weak or decorative yarns.
Implementation Method 1
a torque generator (38) for applying a variable torque to the buffer
Implementation Method 2
the arm is biased by a spring so as to provide a substantially constant tension to the yarn
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A yarn feeding device (4) for a knitting machine comprises a motor (32) for driving a roller (34) from which a yarn (14) is fed out, and a rotatable arm (40) which intermediately stores the yarn (14) fed out from the roller (34), and the yarn (14) is fed from the arm (40) to a knitting machine body (2). A torque generator (38) is provided to apply a variable torque to the arm (40). A yarn speed is obtained from a loop length of a stitch for each knitting needle and a knitting speed calculated on the basis of knitting data (22) used in the knitting machine body (2). The yarn speed is converted into a torque to be applied to a buffer using a conversion table (50) at each knitting section in a knitting course so as to correct a yarn tension fluctuation caused by the yarn speed, and the torque generator (38) is controlled in accordance with the torque thus obtained. The yarn tension fluctuation is reduced so that high-speed knitting and knitting using a weak yarn can be facilitated.